Patent Publication Number: US-7594830-B2

Title: Joint connector

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is a divisional application of U.S. patent application Ser. No. 12/026,644, filed Feb. 6, 2008, the entire contents of which are incorporated by reference. The Ser. No. 12/026,644 application is a divisional application of the earlier filed U.S. patent application Ser. No. 10/665,833, filed on Sep. 18, 2003, priority to which is claimed herein and the contents of which are incorporated herein by reference. The 10/665,833 application claimed the benefit of the dates of the earlier filed Japanese Patent Application Nos. JP2002-273842, filed Sep. 19, 2002; JP2003-027650, filed Feb. 4, 2003; JP2003-032805, filed Feb. 10, 2003; JP2003-035346, filed Feb. 13, 2003; and JP-2003-130386, filed May 8, 2003; the entire contents of each of which are incorporated herein by reference, and priority to each of which is hereby claimed. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to joint connectors used for, for example, branching a wire harness (electric wires) wired in an automobile, and particularly to a joint connector that can achieve cost reduction and exhibit excellent workability in connecting electric wires. 
   2. Description of the Prior Art 
   Hereinbelow, a first prior art and its problems to be solved are discussed. 
   In recent years, electrical components incorporated in, for example, automobiles have increasingly been diversified. This has created the necessity of branching wire harnesses in complex manners, and accordingly, there has been a greater use of joint connectors. 
   Here, an example of prior-art joint connectors is described. One example of the terminal in a first prior-art joint connector of this kind has a male terminal portion and a female terminal portion provided in one piece of terminal and an electric wire press-fit portion partially provided so as to be connected with an electric wire by press-fitting. In a stacking direction of one-stage parallel-line-shaped connectors, that is, in a vertical direction, the male terminal portions are extended from a housing so as to straddle the housings to make connection. By stacking the press-fit joint connectors, the male terminal portions are inserted into female terminal portions of another joint connector terminal to be connected, which has the same shape. In addition, a terminal-linking portion is used to make connection in the terminals&#39; juxtaposed direction (lateral direction) within a single one-stage parallel-line-shaped connector using terminal-linking portions. 
   This structure is described with reference to the drawings. As shown in  FIG. 1 , joint connector terminals  110  have male terminal portions  111  protruding upwardly, female terminal portions (not shown), and electric wire press-fit portions  112 . By stacking one-stage parallel-line-shaped press-fit joint connectors  100  in which a plurality of joint connector terminals  110  are juxtaposed, a lower stage male terminal portion  111  is fitted and connected with an upper stage female terminal portion, and electrical connection is achieved between the upper and lower one-stage parallel-line-shaped press-fit joint connector terminals. 
   The continuity in the terminal&#39;s lateral direction (terminal&#39;s juxtaposed direction) is made through a terminal-linking portion, which is not shown in the figure, so that electrical connection is made in the one-stage parallel-line-shaped press-fit joint connector (see, for example, Japanese Unexamined Patent Publication No. 2001-291567). 
   In another prior-art joint connector, which is a second prior-art joint connector, a terminal  210  itself has, as shown in  FIGS. 2 and 3 , a female terminal portion  211  (see  FIG. 3 ) and a male terminal portion  212 , as the above-described first prior-art joint connector  100 . Specifically, the female terminal portion  211  is formed at a front portion of one terminal, and a portion thereof that extends further forward from the female terminal portion  211  is bent back to form the male terminal portion (joint portion)  212 . In addition, a plurality of the terminals  210  are arranged in a juxtaposed condition, these terminals  210  are formed in a shape such that they are linked through a carrier  201  in a lateral direction, and the male terminal portions  212  formed to be bent backward are inserted into the female terminal portions  211  that are stacked thereon and have the same configuration (see, for example, Japanese Unexamined Patent Publication No. 2001-307816). 
   The male terminal portions  212  are bent 180 degrees in the front of the press-fit joint connector having a one-stage parallel shape, and, as shown in  FIG. 2B , a joint connector  200  is stacked on another joint connector  200  while being slid on the other joint connector  200 , which lies underneath, whereby the terminals in the joint connector  200  having a vertically one-stage parallel shape are electrically connected. Although connector differing in their terminal configurations, this connector basically has a similar connection principle to that of the first prior-art joint connector  100 , which was introduced first. 
   It should be noted that this case requires an operation in which the terminal joint portions (male terminal portions) are bent with two manufacturing steps after the terminals connected to electric wires are inserted into a housing. 
   Another prior-art joint connector, which is a third joint connector is provided with, as shown in  FIGS. 4 and 5 , a terminal  310  having on one end an electric wire-crimped portion  311 , and on the other end a press-fit blade  312  in both the terminals&#39; juxtaposed direction and the terminal housings&#39; stacking direction. Then, the terminals  310  are inserted into a joint connector housing  300  having a one-stage parallel-shape, and after the connector housing  300  is stacked on another one and electric wires are wired in desired paths passing through the terminal press-fit portions, an electric wire supporting member is assembled with the connector housing  300 . This produces a configuration in which predetermined press-fit terminals are conductively connected to each other through electric wires  320 ,  330 , . . . etc. (see, for example, Japanese Unexamined Patent Publication No. 2001-229989). 
   In this case, connection can be made with a certain freedom with respect to the housings&#39; stacking direction or the juxtaposed direction, but the electric wires  320 ,  330 , . . . etc. need to be wired correspondingly. 
   The problems to be solved in the above-described first prior art are as follows. 
   The first prior-art joint connector  100 , which was described first, has a special connection structure between its terminals, and therefore, the terminals that are necessary to be connected in the stacking direction (vertical direction) require a step of standing the male terminal portion  111  upwardly after inserting the terminals. In addition, because a terminal-linking portion is provided to make a connection in the direction of terminals&#39; juxtaposed (lateral direction), it is necessary to cut off the terminal-linking portion for each wiring pattern by specifying the cut-off position. For this reason, in the use of the joint connector  100 , cumbersome manufacturing steps such as bending-back of the terminals and cutting-off of the linking portion are required, which reduce efficiency in electric wire connecting operation by the joint connector. 
   In the case of the second prior-art joint connector  200 , which was described next, as well as the case of the first prior-art joint connector  100 , connection between the terminals is achieved by bending back portions of the terminals, and therefore, efficiency improvement in electric wire connecting operation cannot be made by the joint connector  200 , as with the first prior-art joint connector  100 . 
   Also, the third prior-art joint connector  300 , which was described last, has a drawback in that it is provided with a press-fit blade for the stacking direction and a press-fit blade for the juxtaposed direction within one terminal and therefore the size of the terminal itself becomes large to a certain extent, accordingly increasing the size of the joint connector itself. Moreover, after the terminals  310  are inserted and the one-stage parallel-line-shaped connectors  300  are stacked, electric wires need to be wired and fixed into a desired circuit, which reduces efficiency in the connection operation for the joint connector  300 . 
   Apart from these problems, the first prior-art joint connector  100  and the second prior-art joint connector  200  in particular have a drawback in that, because they have a structure in which one terminal has both a female terminal portion and a male terminal portion, the terminal itself has a complex configuration, which requires a complex molding in manufacturing the terminal, and quality control for the terminals becomes difficult. 
   Furthermore, since both of the male terminal portion and the female terminal portion are manufactured from one sheet of metal plate, the electrical resistance is high in the male-female contacts or the like and accordingly heat generation becomes great due to the requirement for types of material and thickness that matches the spring characteristics of the female terminal portion (for example, brass having a thickness of 0.25 mm) Therefore, a limitation in use arises in that a sufficiently large current cannot pass. 
   Next, a second prior art and its problems to be solved are discussed below. 
   A fourth prior-art joint connector, which relates to the second prior art, comprises an inserting-side connector portion and a receiving-side connector portion in which the inserting-side connector portion is inserted, and the inserting-side connector portion is guided by the receiving-side connector portion while being inserted so that the inserting-side connector portion and the receiving-side connector portion are fitted and connected with each other. The inserting-side connector portion is provided with a plurality of connector housings in which a plurality of terminal-accommodating compartments are juxtaposed in a lateral direction for accommodating connecting terminals, and a connector housing-locking means having an interlocking recess portion provided on the connector housing and an interlocking protrusion portion interlocked therewith, for stacking and combining the connector housings into a plurality of stages. The receiving-side connector portion is provided with a connector case having an inserting-side connector portion-receiving compartment for receiving and holding the inserting-side connector portion, and a circuit-forming unit mounted to the connector case and having a plurality of connection pins protruding in the inserting-side connector receiving compartment so as to be connected to the connecting terminals of the inserting-side connector portion (see Japanese Unexamined Patent Publication No. 2001-39239). 
   The problems to be solved in the above-described second prior art are as follows. 
   In the fourth prior-art joint connector, the inserting-side connector portion is normally configured by stacking a plurality of connector housings into a plurality of stages, and thereafter tightly inserting the interlocking protrusion portion into the interlocking recess portion of the connector housing-locking means by way of press-fitting after to combine them. Thus, it has a rigid structure such that the connector housings do not shift relatively to each other even when an external force is applied to the inserting-side connector portion. 
   Accordingly, in fitting and connecting such an inserting-side connector portion into the inserting-side connector portion-receiving compartment of the receiving-side connector portion, it is desirable to insert and fit the inserting-side connector portion into the inserting-side connector portion-receiving compartment of the receiving-side connector portion in a proper posture such that the axis of the inserting-side connector portion and the axis of the receiving-side connector portion are aligned to be parallel to each other. However, in the work of fitting and connecting the connector, the inserting-side connector portion is often inserted into the receiving-side connector portion in an inclined state, and it is difficult to insert the inserting-side connector portion in a proper posture. Since the inserting-side connector portion has a rigid structure, its insertion accordingly requires a great force. In addition to this, there is a risk of causing poor electrical connection in the connector because the insertion might become impossible halfway or the connector housings or the connecting terminals might be deformed by an excessive force applied thereto. 
   Moreover, in many cases, the thickness of each of the connector housings does not become a uniform dimension since there is a dimensional tolerance. In particular, in case of the minimum value within the dimensional tolerance, pitch between the connecting terminals when the connector housings which are stacked sometimes becomes smaller than a predetermined pitch, and thus does not match the pitch of the connection pins of the circuit-forming unit in the mating receiving-side connector portion. Thus, there is also a risk of causing poor electrical connection in the connector since the connection pins of the receiving-side connector portion cannot be properly inserted into the connecting terminals of the inserting-side connector portion when inserting the inserting-side connector portion into the receiving-side connector portion. 
   Next, a third prior art and its problems to be solved are discussed below. 
   A fifth prior-art joint connector, which relates to the third prior art, is provided with: an inserting-side connector portion (stacked connector) in which connector housings, each having a plurality of terminal-accommodating compartments juxtaposed in a single layer for accommodating female terminals, are stacked into a plurality of stages and are combined by a connector-coupling means; and a receiving-side connector portion (electrical connection box) having a connector case (upper case) for accommodating the inserting-side connector portion inserted from one opening thereof, and a plurality of male terminals protruding in the connector case and connected to the female terminals of the connector housing in the inserting-side connector portion (see Japanese Unexamined Patent Publication No. 2001-39239). 
   Meanwhile,  FIG. 6  shows an inserting-side connector portion  601  provided with connector housings  603 , each having a plurality of terminal-accommodating compartments  602  juxtaposed in a single layer for accommodating female terminals (not shown), are stacked into three stages (see  FIG. 6  (A)), and these connector housings  603  are each combined by engaging an engagement recess portion  605  with an engaging protruding portion  606  of a connector-coupling means  604  (see  FIG. 6  (B)). In addition, an upper face of a cover  607  attached above the connector housing  603  stacked in the uppermost stage of the inserting-side connector portion  601  is provided with a locking arm  609  of a connector-locking means  608  for locking the inserting-side connector portion  601  and the receiving-side connector portion with each other when the inserting-side connector portion  601  is inserted into the receiving-side connector portion (not shown) On the upper face of the locking arm, an engaging protrusion  610  is protruded so that it engages with the engagement recess portion (not shown) provided on the upper wall of the connector case in the receiving-side connector portion. Reference character W denotes electric wires constituting a wire harness, and their terminals are connected to the female terminals accommodated in the terminal-accommodating compartments  602  of the connector housings  603  (see Japanese Unexamined Utility Model Publication No. 5-65073). 
   The problems to be solved in the above-described third prior art are as follows. 
   In the fifth prior-art joint connector, the connector-locking means  608  for locking the inserting-side connector portion  601  and the receiving-side connector portion with each other is provided at a location in the uppermost end side so that it locks the uppermost portion of the inserting-side connector portion and the uppermost portion of the connector case in the receiving-side connector portion. 
   Meanwhile, in the connector-coupling means  604  used for combining the connector housings  603 , backlash (play gap or clearance) is not easily caused between the engagement recess portion  605  and the engaging protruding portion  606  since the engaging force in the direction of stacking the connector housings  603  is large; however, backlash is easily caused between the engagement recess portion  605  and the engaging protruding portion  606  since the engaging force in the direction along the surfaces of the connector housings  603 , that is, in the direction in which the connector housings  603  are pulled out of the receiving-side connector portion is smaller than that in the stacking direction. 
   Accordingly, if a tensile force is applied to the electric wires W in such a manner as to pull out the connector housings  603  from the mating receiving-side connector portion, the backlash is accumulated more as the number of stacked stages of the connector housings  603  increases, and the connector housing  603  located in the lower shifts in the direction in which it is pulled out of the receiving-side connector portion. As a result, the connector housings  603  may be lifted and loosened, and the fitting between the female terminals of the inserting-side connector portion-side and the male terminals of the receiving-side connector portion-side can become insufficient. This degrades the connection state between both connector portions, and thus, there is a risk of degrading performance and reliability of the joint connector. 
   Next, a fourth prior art and its problems to be solved are discussed below. 
   A sixth prior-art joint connector in this prior art is generally provided with: a connection case in which an external connector for accommodating a plurality of female terminals is inserted; and a circuit-forming unit mounted to a base wall of the connection case and having a plurality of male terminals protruding in the connection case through a plurality of male terminal piercing holes formed in the base wall and a holder composed of a circuit board for supporting the male terminals. The male terminals of the circuit-forming unit are inserted into the female terminals of the external connector inserted in the connection case, whereby the joint connector is connected to the external connector (see Japanese Unexamined Patent Publication No. 2001-39239). 
   The problems to be solved in the above-described fourth prior art are as follows. 
   The joint connector of this type, used for wire harnesses, has had an increasing number of terminals in recent years, and the number of male terminals in the circuit-forming unit also tends to increase. As the number of male terminals increases, variations occur in dimensions and assembling accuracy of male terminals in the circuit-forming unit. This causes difficulty in smoothly passing these male terminals through male terminal piercing holes formed in the base wall of the connection case, making troubles in manufacturing (assembling) of the joint connector. In addition to this, there is a risk of degrading performance and quality of the joint connector when passing male terminals through male terminal piercing holes, as the male terminals may be deformed or damaged. For these reasons, the male terminal piercing holes formed in the base wall of the connection case are usually formed to have a bore diameter larger than the outer diameter of the male terminals with some margin so that the male terminals of the circuit-forming unit smoothly pass through the male terminal piercing holes. 
   When the bore diameter of the male terminal piercing holes is thus allowed to have some margin, it becomes easy to mount the circuit-forming unit to the base wall of the connection case. Nevertheless, this increases the clearance (gap) between the male terminals and the male terminal piercing holes, making it difficult to accurately position the circuit-forming unit against the base wall of the connection case. As a result, when mounting the circuit-forming unit to the base wall, the male terminals protruding in the connection case easily dislocate from predetermined locations, causing difficulty in aligning the male terminals and the female terminals when inserting the external connector into the joint connector; this may produce contact failures between both terminals. 
   In order to solve such a problem, a joint connector as shown in  FIG. 7  is suggested and used. This joint connector is, as in the above-described connection box, provided with: a connection case  702  in which an external connector  701  for accommodating a plurality of female terminals is inserted; and a circuit-forming unit  705  mounted to a base wall  703  of the connection case  702 , and having a plurality of male terminals  706  protruding in the connection case  702  through a plurality of male terminal piercing holes  704  formed in the base wall  703  and a holder  707  composed of a circuit board for supporting the male terminals. The male terminals  706  of the circuit-forming unit  705  are inserted into the female terminals of the external connector  701  inserted in the connection case  702 , whereby the joint connector is connected to the external connector  701 . In this configuration, a positioning protrusion  708  is protruded in the central area of the base wall  703  of the connection case  702 , and in the holder  707  of the circuit-forming unit  705 , a positioning hole  709  is formed, into which the positioning protrusion  708  is inserted with a small clearance so as to be attached and fitted thereto. Thus, when mounting the circuit-forming unit  705  to the base wall  703  of the connection case  702 , the positioning protrusion  708  of the base wall  703  side is attached and fitted to the positioning hole  709  of the circuit-forming unit  705  side, whereby the circuit-forming unit is positioned so that the male terminals  706  protruding in the connection case  702  are held in predetermined locations without being dislocated. 
   In the seventh prior-art joint connector of this type, the positioning protrusion  708  is attached and fitted to the positioning hole  709  with no clearance, and therefore, when mounting the circuit-forming unit  705  to the base wall  703  of the connection case  702 , the circuit-forming unit can be accurately positioned. However, it is necessary to provide a space for providing the positioning protrusion  708  on the base wall  703  of the connection case  702  in a protruding manner, and a space for forming the positioning hole  709  in the holder  707  of the circuit-forming unit  705  exclusively. In addition, the shape of the circuit pattern of the holder  707  needs to be wired in such a manner that it extends outwardly to get around the positioning hole  709 . As a result, a problem arises in that the shapes of the connection case  702  and the circuit-forming unit  705  become large, increasing the size of the joint connector; moreover, since the shapes of the connection case  702  and the circuit-forming unit  705  becomes large and the positioning protrusion  708  is provided in a protruding manner, the material cost increases, and accordingly the cost of the connector increases. 
   Next, a fifth prior art and its problems to be solved are discussed below. 
   An eighth prior-art joint connector is discussed as a joint connector related to a fifth prior art. The eighth prior-art joint connector is provided with: a plurality of connector housings each having a plurality of terminal-accommodating compartments juxtaposed therein for accommodating connecting terminals connected to electric wires constituting a wire harness or the like by crimping or the like; a connector housing-locking means composed of an interlocking recess portion and an interlocking protrusion portion for stacking and combining the connector housings into a plurality of stages, provided respectively at a front and a back of each of the connector housings on both side portions thereof, so that an interlocking recess portion or an interlocking protrusion portion provided on one of the connector housings is engaged with an interlocking protrusion portion or an interlocking recess portion provided on another one of the connector housings that is stacked thereon; and an interlocking protrusion protruding on the other stacked connector housing so as to engage with the connecting terminal accommodated in the terminal-accommodating compartment of the one of the connector housings, for preventing disengagement of the connecting terminal and detecting an incomplete insertion. 
   In the connector housing-locking means that is provided at the front of the connector housing on both side portions thereof, its interlocking recess portion is formed of a recessed groove opened upwardly above the connector housing, and having an extended-diameter stepped portion in its lower inner bottom portion, whereas its interlocking protrusion portion is a linear interlocking piece protruding downwardly below the connector housing and having a claw for engaging with the extended-diameter stepped portion at its fore-end. 
   In the connector housing-locking means that is provided at the rear of the connector housing on both side portions thereof, as opposed to the connector housing-locking means provided at the front, the interlocking recess portion formed of a recessed groove opened downwardly below the connector housing and having an extended-diameter stepped portion having its upper inner bottom portion, whereas the interlocking protrusion portion is formed of a linear interlocking piece protruding upwardly above the connector housing and having a claw for engaging with the extended-diameter stepped portion of the interlocking recess portion at its fore-end (see Japanese Unexamined Patent Publication No. 2002-246127). 
   The problems to be solved in the above-described fifth prior art are as follows. 
   The eighth prior-art joint connector is generally configured to be assembled by stacking the connector housings into a plurality of stages and combing them by the connector housing-locking means in a state where the connecting terminals are accommodated in the terminal-accommodating compartments of the connector housings. Also, when the connector housings are stacked, by the configuration of the connector housing-locking means, the connector housings are stacked by shifting and overlaying them in a direction perpendicular to the inserting direction of the connecting terminals. If the connecting terminals are accommodated in the terminal-accommodating compartments of the connector housings in an incompletely inserted state, the interlocking protrusion protruding on a connector housing to be stacked hits the wall or the like of the connecting terminal and does not engage with the engaging portion. This can be utilized to detect an incompletely inserted state of the connecting terminals. 
   The connector housings are generally formed by plastic molding and therefore have the advantages of being lightweight, inexpensive, and easy to manufacture; however, their strength is not sufficient, so they can be easily deformed by an applied external force. For this reason, even if such inconvenience arises that the connecting terminals are accommodated in the terminal-accommodating compartments in an incompletely inserted state and the interlocking protrusion does not engage with the connecting terminals, the interlocking protrusion tends to slide aside by the partial deformation of the terminal-accommodating compartments, which is the same condition as if the interlocking protrusion engages with the connecting terminals. Thus, a proper detection for the incomplete insertion of the connecting terminals becomes impracticable, and there is a risk of combining the stacked connector housings in the condition where the connecting terminals are accommodated in terminal-accommodating compartments in an incompletely inserted state. This causes a problem of degrading performance and reliability of the connector. 
   In order to resolve such a problem, it is conceivable that by increasing the wall thickness of the terminal-accommodating compartment in the connector housing and thereby increasing its mechanical strength, deformation of the connector housings in stacking the connector housings is prevented and an incompletely inserted state of the connecting terminals is reliably detected to prevent combining a connector housing with a connecting terminal being in an incompletely inserted state. Nevertheless, this causes the connector housing to have a larger outer dimension, and therefore, as the number of stacked stages of connector housings increases, the size of the joint connector accordingly becomes larger, causing inconvenience in assembling it in various equipment or the like, which is another problem. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a joint connector that is inexpensive and improves working efficiency in electric wire connection. 
   It is another object of the present invention to provide a joint connector that solves the problem in the second prior art, which makes it possible to fit and connect its inserting-side connector portion and receiving-side connector portion together easily and to prevent poor electrical connection in the connector reliably. 
   It is further another object of the present invention to provide a joint connector that solves the problem in the third prior art, which makes it possible to maintain good connecting state between its inserting-side connector portion and receiving-side connector portion even with an increased number of stacked stages of the connector housings in its inserting-side connector portion, and to improve performance and reliability of the joint connector. 
   It is still another object of the present invention to provide a joint connector that solves the problem in the fourth prior art, which makes it possible to position its circuit-forming unit accurately in mounting the circuit-forming unit to the base wall of the connection case without additionally providing a positioning protrusion and a positioning hole so that poor connections can be prevented in the joint connector and its performance and reliability be improved, and to achieve size and weight reduction and cost reduction of the joint connector. 
   It is yet another object of the present invention to provide a joint connector that solves the problem in the fifth prior art, which makes it possible to straighten connecting terminals in its terminal-accommodating compartment in a desired normal inserted state quickly even if the connecting terminals are accommodated in its terminal-accommodating compartment in an incompletely inserted state when stacking connector housings, thus improving performance and reliability in connection, and to be small-sized and be assembled in various equipment or the like with high efficiency, without causing cumbersome work. 
   In order to accomplish the foregoing and other objects, the present invention provides, in accordance with a first aspect, a joint connector in which a male connector and a female connector are fit, comprising: a male connector having a circuit board and male terminals provided on the circuit board at a predetermined interval and standing in one direction and in a direction intersecting therewith, the male terminals being conductively connected selectively with each other by a circuit pattern on the circuit board; and a female connector in which connector housings each having a plurality of female terminals are stacked. 
   Because the male connector is composed of a plurality of male terminals provided on a circuit board and standing in a matrix form and the circuit pattern for selectively connecting the male connectors selectively with each other is formed on the circuit board, branching of electric wires can be freely carried out merely by fitting the male connector to the female connector. Therefore, it is not required to perform such additional and cumbersome operations as bending the terminals and wiring special electric wires for connections in the connector in connecting the connector as were necessary in conventional joint connectors, and the branching operation of wire harnesses can be carried out efficiently. 
   Moreover, an excellent heat dissipation is attained since a circuit board is used in a portion of the male connector, and consequently, high-density implementation of the terminals and size reduction in the connector itself can be achieved. 
   In accordance with a second aspect, the present invention also provides a male connector for a joint connector in which a male connector and a female connector are fit, comprising: a circuit board; and male terminals provided on the circuit board at a predetermined interval and standing in one direction and in a direction intersecting therewith; wherein the male terminals are conductively connected selectively with each other by the circuit pattern on the circuit board, and the male terminals are interlockable with female terminals in a female connector in which one-stage parallel-line-shaped connector housings each having female terminals inserted and interlocked therein are stacked. 
   A joint connector in accordance with a third aspect of the invention is the joint connector as set forth in the first aspect, wherein the circuit pattern on the circuit board is composed of a copper foil circuit, and the copper foil circuit is formed using a rolled material. 
   By forming the copper foil circuit using a copper plate of a rolled material, it is possible to support a large electric current, and further size reduction of the joint connector itself can be achieved together with the use of the circuit board in a portion of the male connector. 
   A male connector for a joint connector in accordance with a fourth aspect of the invention is the male connector for a joint connector as set forth in the second aspect, wherein the circuit pattern on the circuit board is composed of a copper foil circuit, and the copper foil circuit is formed using a rolled material. 
   In accordance with a fifth aspect, the present invention provides a joint connector including an inserting-side connector portion and a receiving-side connector portion in which the inserting-side connector portion is inserted, the inserting-side connector portion and the receiving-side connector portion being fitted and connected to each other, comprising: an inserting-side connector portion including a plurality of connector housings each having a plurality of terminal-accommodating compartments juxtaposed along a lateral direction for accommodating connecting terminals, an interlocking recess portion provided on at least one of the connector housings, an interlocking protrusion portion interlocking therewith, and a connector housing-locking means for combining the connector housings stacked into a plurality of stages; and a receiving-side connector portion including a connector case having an inserting-side connector portion-receiving compartment for receiving and holding the inserting-side connector portion, and a circuit-forming unit being mounted to the connector case and having a plurality of connection pins protruding in the inserting-side connector portion-receiving compartment to be connected with the connecting terminals in the inserting-side connector portion; wherein a clearance is provided between respective interlocking surfaces of an interlocking recess portion and an interlocking protrusion portion constituting the connector housing-locking means so that the interlocking protrusion portion is loosely interlocked with the interlocking recess portion, whereby the plurality of connector housings are loosely combined so as to be shiftable relative to each other. 
   Thus, the stacked connector housings, which constitute the inserting-side connector portion, are loosely combined to be shiftable relative to each other, forming a flexible structure capable of expansion, contraction, slide, bend, and so forth, like an accordion. For this reason, even when the inserting-side connector portion is inserted into the receiving-side connector portion in an inclined state, the connector housings shift relative to each other quickly, changing their shape, and the inserting-side connector portion is aligned with the receiving-side connector portion to be quickly straightened in a proper posture. Therefore, insertion of the inserting-side connector portion does not require a great force and, in addition, the insertion does not become difficult midway, making the insertion of the inserting-side connector portion easy. Moreover, no excessive force is applied to the connector housings and the connecting terminals, so these are not easily deformed. 
   Moreover, even if the pitch between the connecting terminals when the connector housings have been stacked deviates from the pitch between the connection pins of the receiving-side connector portion because of the dimensional tolerance of the connector housings, the connector housings expand one another in the stacking direction and it becomes easy to match the pitch between the connecting terminals with the pitch between the connection pins of the receiving-side connector portion. Consequently, the connection pins of the receiving-side connector portion can be inserted smoothly and not forcibly into the connecting terminals of the inserting-side connector portion when the inserting-side connector portion is inserted into the receiving-side connector portion. As a result, fitting and connection between the inserting-side connector portion and the receiving-side connector portion become easy, and the connector&#39;s poor electrical connection can be prevented reliably. 
   A joint connector in accordance with a sixth aspect of the invention is the joint connector as set forth in the fifth aspect, wherein a plurality of protruding guide portions for forming a guide groove in which a side portion of a connector housing in the inserting-side connector portion are juxtaposed on an inner side wall of the inserting-side connector portion-receiving compartment in the receiving-side connector portion, and a width of the protruding guide portions gradually narrows toward an entrance of the inserting-side connector portion-receiving compartments while a width of the guide groove gradually widens. 
   With this configuration, when inserting the inserting-side connector portion into the receiving-side connector portion, the side portions of the connector housings in the inserting-side connector portion are guided by the guide grooves of the receiving-side connector portion, the entrances of which are widened. Therefore, the inserting-side connector portion is not likely to be inserted in an inclined state against the receiving-side connector portion, and the inserting-side connector portion is easily inserted in a proper posture aligned with the receiving-side connector portion; thus, both of the connector portions and can be more smoothly fitted and connected to each other. 
   A joint connector in accordance with a seventh aspect of the invention is the joint connector as set forth in the fifth aspect, wherein a lance is provided on one wall of each of the terminal-accommodating compartments in each of the connector housings in the inserting-side connector portion, the lance having a straddle structure in which its base line end is supported by the wall though a pair of slits formed in a longitudinal direction of the terminal-accommodating compartments and being composed of an elastic interlocking piece in which a thick-walled built-up portion is formed on its back side and an interlocking protrusion interlocked with the connecting terminal is formed on its inner side, and a lance-receiving portion is provided at a corresponding location on another wall opposite to the lance, for receiving the built-up portion of the lance provided on a terminal-accommodating compartment in an adjacent connector housing when inserting the connecting terminals into the terminal-accommodating compartments, to permit displacement of the lance bending outwardly. 
   With this configuration, the elastic interlocking piece constituting the lance can attain strong support since it has a straddle structure even in cases where the wall thickness of the terminal-accommodating compartments in the connector housings of the inserting-side connector portion is reduced. In addition, since the built-up portion is provided and the strength becomes greater with the reinforcement, a retention force for the connecting terminals can be sufficiently ensured. Therefore, it is possible to reduce the wall thickness of the terminal-accommodating compartments and accordingly make the connector housings thin, so the height of the inserting-side connector portion in which the connector housings are stacked becomes small, thus reducing the size of the joint connector. Additionally, the pitch between the connecting terminals along the stacking direction becomes small, minimizing wasted spaces. 
   A joint connector in accordance with an eighth aspect of the invention is the joint connector as set forth in the seventh aspect, wherein a double interlocking rib for the connecting terminals is protruded on an outer side of the other wall located rearward of the lance provided on each of the terminal-accommodating compartments in each of the connector housing in an inserting-side connector portion, and an interlocking hole is provided at a corresponding location to the double interlocking rib on the one wall, for interlocking with a double interlocking rib protruding on a terminal-accommodating compartment of an adjacent connector housing. 
   With this configuration, the connecting terminals accommodated in the terminal-accommodating compartments in the connector housings in the inserting-side connector portion are interlocked doubly with the double interlocking rib and the lance. Therefore, disconnection of the connecting terminals from the terminal-accommodating compartments can be prevented more reliably. 
   When the connecting terminal is not inserted deeply to the predetermined location but is in an unfinished, incompletely inserted state in inserting a connecting terminal into a terminal-accommodating compartment, the fore-end of the double interlocking rib collides with the rear end of a connecting terminal, preventing insertion of the double interlocking rib even if the double interlocking rib protruding on the terminal-accommodating compartment of one of the connector housings is attempted to be inserted into the interlocking hole provided in the terminal-accommodating compartment of an adjacent one of the connector housings when stacking the connector housings to form a plurality of stages. For this reason, the double interlocking rib cannot be inserted into the interlocking hole to a predetermined depth, making the stacking of the connector housings difficult. In view of this, this configuration makes it easy to detect an incompletely inserted state of the connecting terminals in the terminal-accommodating compartments without using complex mechanisms. 
   In accordance with a ninth aspect, the present invention provides a joint connector in which an inserting-side connector portion and a receiving-side connector portion are locked with each other by a connector-locking means, comprising: an inserting-side connector portion having a plurality of connector housings, in each of which a plurality of terminal-accommodating compartments for accommodating female terminals are juxtaposed in a single layer, the connector housings stacked in a plurality of stages and combined; and a receiving-side connector portion having a connector case in which the inserting-side connector portion is inserted, and a plurality of male terminals protruding in the connector case and being connected to the female terminals of the connector housings in the inserting-side connector portion; wherein the connector-locking means is provided at a lateral side location when viewed from the inserting direction so as to lock a side portion of the connector housing in the inserting-side connector portion and a side wall of the connector case in the receiving-side connector portion. 
   Since the connector-locking means are provided at side positions of both connector portions, one or a plurality of lock supporting points for locking the connector housings vertically stacked into a plurality of stages shifts/shift from the uppermost end locations of both connector portions to arbitrary midway locations vertically, and the distance from the lock supporting points of the connector-locking means to free ends, such as the uppermost end and lowermost end locations of both connector portions, is shortened. 
   As a result, the number of connector housings stacked between the lock supporting point of the connector-locking means and the respective free ends becomes less, so that the accumulated amount of backlash caused between the connector housings is reduced, and the connector housings are prevented from shifting and loosening in the direction in which it is removed from the receiving-side connector portion due to the effect of the foregoing tensile force. 
   Therefore, even when the number of stacked stages of the connector housing is increased in the inserting-side connector portion, a good connecting state between the inserting-side connector portion and the receiving-side connector portion is maintained and the performance and reliability of the joint connector can be improved. 
   A joint connector in accordance with a tenth aspect of the invention is the joint connector as set forth in the ninth aspect, wherein the connector-locking means is provided at both side locations so as to lock both side portions of at least one of the connector housings in the inserting-side connector portion and both side walls of the connector case in the receiving-side connector portion. 
   With this configuration, even if a tensile force pulling the connector housings out of the receiving-side connector portion acts on the connector housings of the inserting-side connector portion, the connector housings are firmly held by the connector-locking means at both side ends and are stabilized and the joint connector becomes strong. 
   A joint connector in accordance with an eleventh aspect of the invention is the joint connector as set forth in the ninth aspect, wherein the connector-locking means comprises an engagement recess portion and an engaging claw portion composed of an elastic piece having at its fore-end a claw for engaging the engagement recess portion, the engagement recess portion being provided on a side portion of at least one of the connector housings in the inserting-side connector portion and the engaging claw portion being provided in a cantilevered fashion on a side wall of the connector case in the receiving-side connector portion. 
   With this configuration, the engaging operation in the connector-locking means becomes smooth and the engagement failure becomes infrequent, so connection of the inserting-side connector portion with the receiving-side connector portion is made more reliable. In addition, the engagement recess portions having generally a simple shape and structure is provided on the side portions of the connector housings in the inserting-side connector portion and the engaging claw portions having a more complex shape and structure than the engagement recess portion is provided on the connector case side of the receiving-side connector portion. As a consequence, manufacture of the joint connector becomes easier and less expensive, and in addition, size reduction can be achieved. 
   A joint connector in accordance with a twelfth aspect of the invention is the joint connector as set forth in the ninth aspect, wherein the connector-locking means comprises an engagement recess portion and an engaging claw portion composed of an elastic piece having at its fore-end a claw for engaging with the engagement recess portion and a curved tab diagonally extending outwardly with respect to the claw so as to be in a substantially Y-shape. 
   With this configuration, the claw of the engaging claw portion can be easily disengaged from the engagement recess portion by pressing the inclined inner side face of the curved tab in the engaging claw portion in the axis direction of the engaging claw portion, releasing the lock by the connector-locking means quickly. Consequently, the inserting-side connector portion can be easily pulled out and separated from the receiving-side connector portion without using complex and expensive jigs, and replacement, repair or the like for the connector can be made conveniently. 
   In accordance with a thirteenth aspect, the present invention provides a joint connector to be connected to an external connector, in which male terminals of a circuit-forming unit are inserted into female terminals of the external connector inserted in a connection case, comprising: a connection case into which the external connector for accommodating a plurality of female terminals; and a circuit-forming unit mounted to a base wall of the connection case, the circuit-forming unit having a plurality of male terminals protruding in the connection case through a plurality of male terminal piercing holes formed in the base wall, and a holder for supporting the male terminals, wherein among plurality of male terminal piercing holes formed in the base wall of the connection case, a fraction of the male terminal piercing holes is/are reference holes formed to be smaller than the other male terminal piercing holes. 
   With this configuration, the reference holes and the male terminals passing through the reference holes can be utilized as the conventional positioning hole and the conventional positioning protrusion, respectively. Consequently, when mounting the circuit-forming unit to the base wall of the connection case, the male terminals are passed through the reference holes at small clearances so that the circuit-forming unit can be quickly guided and held in a predetermined location. Thereby, the circuit-forming unit can be accurately positioned without additionally providing the positioning protrusions and the positioning holes that have been required conventionally. As a result, when the circuit-forming unit is mounted to the base wall, the male terminals protruding in the connection case do not deviate from predetermined locations, and when the external connector is inserted into the joint connector, the male terminals and the female terminals are aligned so that poor connections between both terminals can be prevented. Thus, performance and reliability of the joint connector can be improved. 
   Moreover, it becomes unnecessary to provide a space for providing the positioning protrusion in the base wall of the connection case and a space for forming the positioning hole in the holder of the circuit-forming unit, and in addition, it is unnecessary to form the shape of the circuit pattern on the holder so that the wiring greatly extends outwardly to get around the positioning hole. As a result, the shapes of the connection case and the circuit-forming unit become smaller, thus making the joint connector small and lightweight. Furthermore, since the shapes of the connection case and the circuit-forming unit become smaller and the positioning protrusion is eliminated. As a result, cost of the materials can be reduced and accordingly the cost of the joint connector can be reduced. 
   A joint connector in accordance with a fourteenth aspect of the invention is the joint connector as set forth in the thirteenth aspect, wherein the reference hole(s) is/are formed to be smaller out of the male terminal piercing holes formed in a central area of the base wall of the connection case. 
   With this configuration, the reference hole(s) is formed at a location in the vicinity of the center of gravity of the circuit-forming unit. Thus, the circuit-forming unit can be positioned in a well-balanced manner, and the circuit-forming unit can be easily mounted to the base wall of the connection case. 
   A joint connector in accordance with a fifteenth aspect of the invention is the joint connector as set forth in the thirteenth aspect, wherein the reference holes are formed to be smaller out of the male terminal piercing holes formed at a plurality of positions radially spaced from a central area of the base wall of the connection case. 
   With this configuration, even when the number of male terminals of the circuit-forming unit is increased, the circuit-forming unit can be positioned in a well-balanced manner and the accuracy in the positioning can be improved. 
   A joint connector in accordance with a sixteenth aspect of the invention is the joint connector as set forth in the fifteenth aspect, wherein the reference holes are male terminal piercing holes that are formed at a plurality of locations radially spaced from a central area of the base wall of the connection case, and are formed to be small by making an axis diametrical size with respect to a Y-axis of the male terminal piercing holes formed at locations spaced along an X-axis and an axis diametrical size with respect to the X-axis of the male terminal piercing holes formed at locations spaced along the Y-axis shorter than respective axis diametrical sizes with respect to corresponding axes of the male terminal piercing holes other than the reference holes. 
   With this configuration, the reference holes formed on the X-axis have a smaller clearance with the male terminals with respect to the Y-axis and the reference holes formed on the Y-axis have a smaller clearance with the male terminals with respect to the X-axis; therefore, it is possible to suppress side-to-side rattling (backlash) in the X-axis direction and the Y-axis direction of the male terminals inserted in the reference holes, enabling the circuit-forming unit to be positioned accurately. 
   In addition, because the axis diametrical size with respect to the X-axis of the reference holes formed on the X-axis and the axis diametrical size with respect to the Y-axis of the reference holes formed on the Y-axis are not different from the corresponding axis diametrical sizes of the foregoing other male terminal piercing holes, some margin is created in the clearance between the reference holes formed on the X-axis and the male terminals with respect to the X-axis and in the clearance between the reference holes formed on the Y-axis and the male terminals along the Y-axis. There are cases where pitch variations with respect to the X and Y axes between the male terminal piercing holes and the male terminals are accumulated as they are spaced farther from the respective central areas of the base wall of the connection case and the circuit-forming unit in the X and Y direction. In such cases, a positional deviation, i.e., a mismatch (misalignment) in their centers, is caused between opposing male terminal piercing holes and male terminals with respect to the X and Y axis directions. Even if this occurs, there is some margin in the clearances with respect to the X and Y directions as described above. For this reason, when mounting the circuit-forming unit to the base wall of the connection case, the male terminals of the circuit-forming unit can be passed through the reference holes not forcibly, and the mounting of the circuit-forming unit becomes easy, improving efficiency in manufacturing (assembling) the joint connector. 
   In accordance with a seventeenth aspect, the present invention provides a joint connector comprising: a plurality of connector housings each having a plurality of terminal-accommodating compartments juxtaposed therein for accommodating connecting terminals, wherein: each of the connector housing includes a connector housing-locking means composed of an interlocking recess portion and an interlocking protrusion portion provided respectively at a front and a rear of each of the connector housings on both side portions thereof, for stacking and combining the connector housings into a plurality of stages, such that an interlocking recess portion or an interlocking protrusion portion provided on one of the connector housings is respectively engaged with an interlocking protrusion portion or an interlocking recess portion provided on another one of the connector housings that is to be stacked; each of the connector housing further includes an interlocking protrusion protruding on the other connector housing so as to engage with the connecting terminals accommodated in the terminal-accommodating compartments of the one of the connector housings, for preventing disengagement of the connecting terminals and detecting an incomplete insertion; and in the connector housing-locking means provided at the front of each of the connector housings on both side portions thereof, the interlocking recess portion has a recessed groove opened in a lateral direction, and the interlocking protrusion portion has a lateral interlocking piece, extending forward and rearward, for being loosely inserted relatively into the recessed groove of the interlocking recess portion and engaging therewith, and a vertical interlocking piece capable of contacting the interlocking recess portion, the interlocking protrusion portion being formed in a substantially L shape by the lateral interlocking piece and the vertical interlocking piece. 
   With this configuration, in stacking the connector housings, even when connecting terminals are accommodated in terminal-accommodating compartments in an incompletely inserted state, those connecting terminals can be quickly straightened in a desired normal inserted state to accommodate them in a predetermined location. Thus, connection performance and reliability in the connector can be improved, and in addition, being small-sized, being assembled for various equipments can be carried out efficiently without cumbersome work. 
   A joint connector in accordance with an eighteenth aspect of the invention is the joint connector as set forth in the seventeenth aspect, wherein a guiding recessed groove and a guide rib fitted thereto, for restricting a relative shift between stacked connector housings, are provided between the connector housing-locking means provided at the front and rear of the connector housing on both side portions thereof, and respective rear portion of the guiding recessed groove and the guide rib are formed into an inclined surface widening toward their bottom. 
   With this configuration, relative shifting between the stacked and combined connector housings is more reliably constrained by the guide ribs, and in addition, backlash is suppressed by the contact between the inclined surfaces of the guiding recessed groove and the guide rib. Moreover, when stacking a connector housing from an inclined posture, the guide ribs do not hit the inner periphery of the guiding recessed grooves, and they can be smoothly fitted; thus, workability in stacking the connector housings can be improved. 
   A joint connector in accordance with a nineteenth aspect of the invention is the joint connector as set forth in the seventeenth aspect, wherein a terminal-guiding slope portion projecting downwardly is provided on a lower wall near an terminal insertion hole in the terminal-accommodating compartment in the connector housing, and a corresponding upper portion of both side walls near the terminal insertion hole is provided with an undercut for engaging with the terminal-guiding slope portion. 
   With this configuration, the connecting terminal can be easily inserted into the terminal-accommodating compartment of the connector housing by being guided by the terminal-guiding slope portion at the terminal insertion hole without causing an electric wire to be compress-buckled or bent-deformed, even when it is connected to such an electric wire easily bent-deformed or compress-buckled due to its small size and diameter. 
   A joint connector in accordance with a twentieth aspect of the invention is the joint connector as set forth in the seventeenth aspect, wherein a rear portion of the terminal-accommodating compartment of the connector housing is opened upwardly, a stopper member is provided on upper portions of both side walls of the terminal-accommodating compartment above the terminal insertion hole to cover the opening above the terminal insertion hole, and a corresponding lower portion of the terminal-accommodating compartment on both side walls is provided with a cut-out for receiving the stopper member. 
   With this configuration, the electric wire is not lifted in an upward direction even when a tensile force acts on the electric wire in an upward direction after the connecting terminal are inserted and accommodated in the terminal-accommodating compartment, and the rear side of the lance and the connecting terminal in the connector housing can be prevented from breakage. Furthermore, the stopper member restricts the inserting direction of the connecting terminal from the terminal insertion hole. Therefore, it becomes possible to detect upside-down insertion of the connecting terminal into the terminal-accommodating compartment quickly, and thus the connecting terminal can be prevented from being accommodated in the terminal-accommodating compartment upside down. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a first prior-art joint connector concerning the present invention; 
       FIG. 2  shows a perspective view ( FIG. 2A ) showing a process step for forming a male terminal of a second prior-art joint connector, which is different from the one shown in  FIG. 1 , and a perspective view ( FIG. 2B ) showing a step of assembling the joint connector; 
       FIG. 3  is a cross-sectional view showing the conventional joint connector of  FIG. 2  in a stacked condition; 
       FIG. 4  is a cross-sectional view taken along a direction of terminals&#39; stacking of a third prior-art joint connector, which is different from those shown in  FIGS. 1 and 2 ; 
       FIG. 5  is a cross-sectional view taken along a direction of terminals&#39; juxtaposition of the prior-art joint connector shown in  FIG. 4 ; 
       FIG. 6  show an inserting-side connector portion of a fourth prior-art joint connector, wherein (A) is a perspective view showing connector housings in a condition before they are stacked and (B) is a perspective view showing the connector housings in a condition in which they are stacked and combined; 
       FIG. 7  is a partially-omitted cross-sectional view showing the way in which an external connector is inserted into a fifth prior-art joint connector, corresponding to a cross section taken along line S-S in  FIG. 39 ; 
       FIG. 8  is a perspective view showing a joint connector according to a first embodiment of the present invention in a disassembled condition; 
       FIG. 9  is a perspective view showing the joint connector of  FIG. 8  in an assembled condition; 
       FIG. 10  is a perspective view showing a female connector element of the joint connector of  FIG. 8 ; 
       FIG. 11  is a perspective view showing a male terminal assembly of the joint connector of  FIG. 8 ; 
       FIG. 12  is a view showing a circuit board face of the male terminal assembly shown in  FIG. 11 , viewed from an opposite side of  FIG. 11 ; 
       FIG. 13  is a cross-sectional view for illustrating the thickness of a copper foil circuit pattern; 
       FIG. 14  is an exploded perspective view showing a joint connector according to a second embodiment of the present invention, adapted to a multi-pin connector for automobile wire harnesses; 
       FIG. 15  is an enlarged perspective view showing the joint connector in an assembled condition, in which the component parts of  FIG. 14  are combined; 
       FIG. 16  shows a connector housing constituting an inserting-side connector portion of  FIG. 14 , wherein  FIG. 16A  is a perspective view thereof viewed from its obverse side and  FIG. 16B  is a perspective view thereof viewed from its reverse side; 
       FIG. 17  shows the connector housing of  FIG. 16 , wherein  FIG. 17A  is a top plan view thereof and  FIG. 17B  is a bottom plan view thereof; 
       FIG. 18  an enlarged cross-sectional view showing an interlocking condition between an interlocking recess portion and an interlocking protrusion portion of a connector housing-locking means; 
       FIG. 19  shows a lance portion of a connector housing, wherein  FIG. 19A  is a perspective view showing the way in which a lance is provided in a terminal accommodating compartment,  FIG. 19B  is an enlarged perspective view of the lance, and  FIG. 19C  is an enlarged perspective view showing an interlocking protrusion of the lance; 
       FIG. 20  shows an interlocking protrusion portion of a lance provided in a terminal accommodating compartment of a connector housing, wherein  FIG. 20A  is a longitudinal sectional view and  FIG. 20B  is a transverse cross-sectional view; 
       FIG. 21  a longitudinal sectional view showing a condition before a double interlocking rib is interlocked, which protrudes in a terminal accommodating compartment of a connector housing adjacent to an interlocking hole of a terminal accommodating compartment of a connector housing that accommodates a connecting terminal in a condition before it is interlocked; 
       FIG. 22  is a longitudinal sectional view showing the way in which the double interlocking rib is interlocked into the interlocking hole from the state of  FIG. 21 ; 
       FIG. 23  is a longitudinal sectional view showing a double interlocking rib in a condition before it is interlocked, which is provided in a terminal accommodating compartment of a connector housing adjacent to an interlocking hole of a terminal accommodating compartment of a connector housing into which a connecting terminal is accommodated in an incompletely inserted condition; 
       FIG. 24  is across-sectional view showing a modified example of the double interlocking rib; 
       FIG. 25  shows an inserting-side connector portion made up of connector housings stacked and combined, wherein  FIG. 25A  is a left-side view and  FIG. 25B  is a front view; 
       FIG. 26  is a cross-sectional view taken along line X-X in  FIG. 25  A; 
       FIG. 27  shows a receiving-side connector portion, wherein  FIG. 27A  is an elevational vertical cross-section and  FIG. 27B  is a cross-sectional view taken along line Y-Y in  FIG. 27A ; 
       FIG. 28  is an elevational vertical cross-section showing a modified example of the receiving-side connector portion of  FIG. 27 ; 
       FIG. 29  shows the way in which the inserting-side connector portion is inserted into the receiving-side connector portion, wherein  FIG. 29A  illustrates a condition in which the inserting-side connector portion and the receiving-side connector portion are opposed and the inserting-side connector portion is inserted in a proper posture,  FIG. 29B  illustrates a condition in which the inserting-side connector portion is inserted with its right inclined side downward, and  FIG. 29C  illustrates a condition in which the inserting-side connector portion is inserted with its right inclined side upward; 
       FIG. 30  is a schematic view showing the inserting-side connector portion is inserted into the receiving-side connector portion with the use of a connector retainer; 
       FIG. 31  is an exploded perspective view showing a joint connector according to a third embodiment of the present invention, adapted to a multi-pin connector for an automobile wire harness; 
       FIG. 32  is a schematic enlarged view showing a connector-coupling means in the inserting-side connector portion of  FIG. 31 ; 
       FIG. 33  a schematic cross-sectional view showing the way in which the inserting-side connector portion is inserted in the receiving-side connector portion shown in  FIG. 31 ; 
       FIG. 34  is a schematic cross-sectional view showing the way in which a locked state of the inserting-side connector portion and the receiving-side connector portion is released; 
       FIG. 35  is an illustration showing the way in which a claw of an engaging claw portion is disengaged from an engagement recess portion using a connector lock-releasing jig in  FIG. 34 ; 
       FIG. 36  is a perspective view showing a modified example of the engaging claw portion in a connector-locking means; 
       FIG. 37  is a schematic cross-sectional view showing the way in which a locked state between the inserting-side connector portion and the receiving-side connector portion is released using a commercially available screw driver; 
       FIG. 38  is an exploded perspective view showing a joint connector according to a fourth embodiment of the present invention, into which an external connector is inserted; 
       FIG. 39  is a front view of the joint connector of  FIG. 38 , viewed from a side from which an external connector is inserted, where its male terminals are not shown; 
       FIG. 40  is a partially-omitted cross-sectional view showing the way in which an external connector is inserted into the joint connector, taken along line S-S in  FIG. 39 ; 
       FIG. 41  is a front view showing another embodiment of the joint connector according to the present invention, viewed from a side from which an external connector is inserted; 
       FIG. 42  is a perspective view showing a connector housing of a joint connector according to a fifth embodiment of the present invention; 
       FIG. 43A  is a perspective view of the connector housing of  FIG. 42 , viewed from its reverse side, and  FIG. 43B  is a perspective view of the connector housing of  FIG. 43A , viewed from its back; 
       FIG. 44  is a cross-sectional view taken along line X-X in  FIG. 42 ; 
       FIG. 45  is a cross-sectional view showing the way in which tensile force in an upward direction acts on an electric wire whose connecting terminal is properly accommodated in a terminal accommodating compartment of the connector housing shown in  FIGS. 42 through 44 ; 
       FIG. 46  is a cross-sectional view showing the way in which a connecting terminal is inserted upside down into a terminal accommodating compartment of the connector housing shown in  FIGS. 42 through 44 ; 
       FIG. 47A  is a side view showing the way in which, when combining connector housings by stacking, one of the connector housings is arranged to be in an inclined state relative to the other one of the connector housings so that its front is lowered diagonally downward, and  FIG. 47B  is a cross-sectional view of  FIG. 47A ; 
       FIG. 48A  is a side view showing the way in which, from the state shown in  FIG. 47 , the other one of the connector housings is brought close to the one of the connector housing side so that a transverse interlocking piece of an interlocking protrusion portion in a connector housing-locking means provided in a front of the other one of the connector housing to be stacked is loosely inserted into an interlocking recess portion in a connector housing-locking means provided in its front of the one of the connector housing, and  FIG. 48B  is a cross-sectional view of  FIG. 48A ; 
       FIG. 49A  is a side view showing the way in which, from the state shown in  FIG. 48 , the other one of the connector housings is rotated to be in parallel to the one of the connector housings while being shifted forward so that an interlocking protrusion provided protruding on the other one of the connector housings is engaged in an engaging portion of the connecting terminal accommodated in the terminal accommodating compartment of the one of the connector housing in an incompletely inserted state to push the connecting terminal in forward, and  FIG. 49B  is a cross-sectional view of  FIG. 49A ; 
       FIG. 50A  is a side view showing the way in which the other one of the connector housings is shifted forward further from the state shown in  FIG. 48  until a vertical interlocking piece of the interlocking protrusion portion makes contact with a recessed groove of an interlocking recess portion of the connector housing-locking means in the front, to stack on the one of the connector housings, so that the interlocking recess portion of the connector housing-locking means is engaged with the interlocking protrusion portion at its front and back to combine the two adjacent connector housings, and  FIG. 50B  is a cross-sectional view of  FIG. 50A ; 
       FIG. 51  is a partial side cross-sectional view showing the way in which a joint connector assembled by repeating stacking and combining the connector housings shown in  FIG. 50  is aligned with a mating connector so that their centerlines are matched, to fit with the mating connector; and 
       FIG. 52A  is a partial side cross-sectional view showing the way in which the joint connector is fitted and connected with the mating connector from the state shown in  FIG. 50 ,  FIG. 52B  is an enlarged illustration showing the way in which an interlocking tab of a connector housing in the joint connector is engaged in a groove width-widened portion of a guide groove of a connector case in the mating connector, and  FIG. 52C  is a cross-sectional view taken along line Y-Y in  FIG. 52B . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinbelow, joint connectors according to first through fifth embodiments of the present invention are described with reference to the drawings. 
   As shown in the exploded perspective view of  FIG. 8  and the assembled view of  FIG. 9 , a joint connector  1  according to a first embodiment of the present invention is provided with a female connector  2  having a large number of female terminals F, and a housing  35  in which the female connector  2  can be accommodated. It is also provided with a large number of male terminals M (see  FIG. 11 ) for connecting the female terminals F (see  FIG. 10 ) of the female connector  2 , and a male connector  3  having a cover  36  attached on a side opposite to the side of the housing  35  into which the female connector is inserted. 
   As shown  FIG. 10 , the female connector  2  has a structure in which female connector elements  20 , comprising a rectangular thick-plate-like female terminal holder (one-stage parallel-line-shaped connector housing)  21  and female terminals F juxtaposed in the female terminal holder  21 , are stacked in a vertical direction. The female connector elements  20  correspond to each one of sub-harnesses, which are not shown in the figure, and each of the female connector elements  20  is configured so as to be attached with a different sub-harness. It should be noted that the female terminal holder  21  of the female connector element  20  is made of a resin material such as PBT (polybutylene terephthalate) and PP (polypropylene), and a plurality of female terminal-accommodating groove portions  21   a  (see  FIG. 10 ) are formed in its upper face overall-widthwise at a predetermined gap. Each of the female terminal-accommodating groove portions  21   a  and one side  21   b  (front side face shown in  FIG. 10 ) of each female terminal holder  21  are connected by a male terminal piercing hole (not shown). 
   An engaging portion, not shown in the figure, that is latched and engaged with the female terminal F is formed in a portion of the female terminal-accommodating groove portion  21   a  shown in  FIG. 10 , so that, by inserting the female terminal F into the female terminal-accommodating groove portion  21   a , the female terminal F is accommodated and retained inside the groove. The female terminal holder  21  also has a claw portion  21   c  for stacking at both ends of the holder. It should be noted that the structure for stacking the female connector elements  20  may be any kind of structure insofar as the elements  20  can be stacked and fixed, and it is not limited to the claw shape shown in the figure. 
   Each female connector element  20  is provided with an element-locking means  21  for stacking and combining the female connector elements  20  a plurality of stages (10 stages in the example shown in the drawings). It should be noted that the element-locking means  21  is also made of a resin material such as PBT (polybutylene terephthalate) and PP (polypropylene) and is formed by a plastic molding process. 
   It also should be noted that in the present embodiment, the crimp type female terminal F as shown in  FIG. 10  such as 025 terminal, 040 terminal, or 090 terminal is appropriately employed as needed, but this is not restrictive and a press-fit type female terminal may be used for the female terminal. 
   In  FIG. 8 , a large number of female connector elements  20  as shown in  FIG. 10  are stacked to constitute the female connector  2 . During a producing operation of sub-harness, which is one of the producing steps of wire harness, a female terminal F that is required to connect with the same sub-harness or another sub-harness are inserted into each of the female connector elements  20 . 
   On the other hand, the male connector  3  shown in  FIG. 8  is provided with a rectangular tubular housing  35 , a male terminal assembly  30  that can be inserted into the housing  35 , and a cover  36  that is attached to the housing  35 . The housing  35  is made of, for example, a resin material such as PBT (polybutylene terephthalate) and PP (polypropylene). The cover  36  has a rectangular plate-like shape, is attached to a side of the housing  35  on which the male terminal assembly  30  is mounted, and serves as a case cover for protecting the male terminal assembly  30 . It should be noted that the cover  36  is also made of, for example, a resin material such as PP (polypropylene) and PBT (polybutylene terephthalate) and is formed by a plastic molding process. 
   Meanwhile, on a side face of an inner wall of the housing  35 , a plurality of engaging groove portions  35   a  for engaging with the female connector  2  and accommodating it inside the housing, when it being inserted, are formed so as to be juxtaposed. 
   It should be noted that the housing  35  of the male connector  3  serves not only to hold the male terminal assembly  30  but also to guide the female connector  2  to an appropriate position relative to the male connector  1  so that the male terminal M and the female terminal F are engaged well. 
   The male terminal assembly  30  comprises, as shown in  FIG. 11 , a circuit board  31 , and a large number of male terminals M perpendicularly provided over one surface of the circuit board  31  in a matrix. An end of each individual male terminal M is press-inserted into a terminal insertion hole (not shown) formed in the circuit board  31  in a matrix, and it is solder-joined to the circuit board  31 . Here, in  FIGS. 11 and 12 , the male terminals M are juxtaposed along one direction on the circuit board  31  and in a direction perpendicular thereto, but they may be arranged in intersecting directions in a matrix except the one direction on the circuit board  31  and the direction perpendicular thereto, insofar as the female terminals F and the male terminals M are engaged each other. 
   The male terminals M are press-inserted in and fixed to the circuit board  31  by general hammering, and thereafter solder-joined to copper foil circuit patterns  31   a ,  31   b , . . . , etc. (see  FIG. 12 ). Conceivable pitches for the male terminals M include pitches of 040 specification, 025 specification, or 090 specification. 
   The male terminals M used here are made of brass, but this is not restrictive and they may be made of pure copper. 
   As shown in  FIG. 12 , copper foil circuit patterns having a thickness of about 0.2 mm is formed on the circuit board  31  in advance, and the copper foil circuit patterns  31   a ,  31   b , etc. are formed so as to connect between specific terminal insertion holes selectively. 
   It should be noted that the copper foil circuit patterns  31   a ,  31   b , . . . , etc. on the circuit board  31  may be formed, for example, to have identical patterns on both faces of the circuit board. This can ensure conductive characteristic and reduce the amount of generated heat. 
   The heat dissipation property of the circuit board  31  itself and the low resistance owing to the sufficient thickness (0.2 mm) of the copper foil circuit patterns  31   a ,  31   b  . . . , etc. together achieve reduction in the amount of generated heat and efficient heat dissipation of the generated heat even when a considerable electric current is passed through the joint connector  1 ; as a result, it is possible to achieve high-density implementation of the male terminal M and side reduction of the joint connector  1 . 
   Thus, by forming a thick copper foil on a surface of the circuit board  31 , the width of the circuit can be narrowed and the size of the circuit board itself can be reduced. Here, it is not always necessary that the copper foil circuit patterns be formed on both faces of the circuit board, and a circuit necessary to connect between the male terminals may be formed by etching only on a circuit board face that is opposite the portion on which male terminals are perpendicularly provided. 
   The male terminals M used here meet a specification that corresponds to the female terminal F, which engage therewith. That is, in the case of the female connector  2  having 025 female terminals, 025 male terminals are perpendicularly provided on the circuit board  31 ; in the case of the female connector having 040 female terminals, 040 male terminals are perpendicularly provided on the circuit board  31 ; in the case of the female connector having 090 female terminals, 090 male terminals are perpendicularly provided on the circuit board  31 . 
   Since the joint connector according to the first embodiment of the present invention is configured as described above, the male connector  3  can be easily assembled by accommodating the male terminal assembly  30  in the housing  35  and attaching the upper cover  36 . The female connector  2  can also be easily assembled by stacking female connector elements  20  in which a plurality of female terminals F are inserted in the female terminal holder  21 . In addition, connection of the joint connector  1  is completed merely by inserting the female connector  2  from an opening on the male terminal side of the male connector  3  to engage them together. That is, a female terminal F( 1 ) inserted in a certain female terminal holder  21  is electrically connected to another female terminal F( 2 ) that is in the same sub-harness circuit, or to further another female terminal F( 3 ) inserted in another female terminal holder  21  that is in another sub-harness circuit, through the male terminals M and the copper foil circuit patterns  31   a ,  31   b , . . . , etc. on the circuit board. Thus, electric wires in a wire harness can be branched in a desired shape with the use of the joint connector  1 . 
   Therefore, unlike conventional type joint connectors, additional and cumbersome processes are unnecessary, such as folding and bending the fore-end of a terminal of a connector to engage it with an upward terminal&#39;s female hole portion having a matching shape, or selectively cutting terminals laterally adjacent thereto, when fitting a male connector and a female connector together. 
   In addition, such a cumbersome operation is also unnecessary that after terminals are inserted into the connector housing, an electric wire is arranged between terminals that are to be connected to each other and an electric wire&#39;s sheath portion is cut through with a blade-shaped portion of a terminal&#39;s fore-end to press-fit it with the electric wire&#39;s conductor portion. 
   As described above, the joint connector  1  according to a first embodiment of the present invention can use terminals used as standards including terminals with 025 form, terminals with 040 form, or terminals with 090 form. Consequently, it is advantageous in terms of cost since terminals with special shapes are not necessary. 
   Moreover, unlike conventional cases, it is not necessary to process the male terminal portion after the terminals are inserted, and therefore, workability in connection of the joint connector  1  improves. 
   Furthermore, circuit patterns of the circuit board  31  can be easily changed by changing transfer film patterns, and therefore, design changes become easy. For this reason, the joint connector can be adapted to many kinds of harness circuit patterns. Further, since copper foil circuit patterns  31   a ,  31   b , . . . , etc. are collectively formed on the circuit board  31 , special terminals or electric wires for connecting terminals are not necessary, and size reduction of the joint connector itself is possible. 
   Moreover, because the wiring pattern is composed of the copper foil circuit patterns  31   a ,  31   b , . . . , etc. having a certain thickness, a sufficient sectional area for continuity is ensured. In addition to this, since a circuit board is used for a part of the joint connector, heat dissipation property improves and heat generation is less than that in conventional type joint connectors. Consequently, it is possible to pass an electric current with a degree that is permitted in a wire harness. 
   It should be noted that in the foregoing embodiment, the female connector has a form in which one-stage parallel-line-shaped connector housings each having female terminals inserted and interlocked therein are stacked; however, this embodiment is not limited thereto, and any forms may be employed as far as the female connector is such that connector housings each having a plurality of female terminals are stacked. Accordingly, in place of the one-stage parallel-line-shaped connector housings, it is possible to employ a form in which two-stage parallel-line-shaped connector housings are stacked. Alternatively, it is possible to employ a form in which connector housings constructed in an arc shape are stacked, or a form in which connector housings having a plurality of female terminals arranged in a V-shape are stacked. 
   It should be noted that the thickness of the copper foil circuit patterns  31   a ,  31   b , . . . , etc. is determined from a cross-sectional view of the wire harness connected to the joint connector and terminals&#39; pitch. When a 0.5 mm 2  wire harness is connected to the joint connector of the present invention constituted by 025 terminals, an appropriate thickness of the copper foil thickness is 0.2 mm. If the thickness is greater than that, manufacturing becomes difficult, whereas if less, the copper foil&#39;s sectional area becomes insufficient and the wire harness&#39;s permissible current cannot be passed through. 
   The above-discussed point is specifically explained with reference to  FIG. 13 . The concept of pattern designing is to strike the balance between dimensions of the width of the copper foil circuit pattern ( 3 ) including a pattern slope ( 6 ) and an inter-wire gap ( 5 ) within the 025 terminal&#39;s inter-terminal pitch ( 2 ), which is 2.2 mm, and the 2.2 mm pitch, and further the width of a land for soldering ( 9 ) after press-fitting the male terminal within the copper foil pattern width ( 3 ). 
   The inter-wire gap ( 5 ) is necessary for ensuring the insulation between two opposing copper foil circuit patterns, and a gap of at least 0.5 mm is necessary, for example, in a 12-V automobile power supply. The pattern slope ( 6 ) is caused due to etching characteristics of circuit patterns, and when the copper foil thickness ( 1 ) is 0.2 mm including its variation, the slope ( 6 ) is about 0.1 mm. In that case, the minimum width of the copper foil circuit pattern ( 3 ) is 1.5 mm, and the gap ( 5 ) in that case is 0.7 mm. Accordingly, the minimum sectional area ( 7 ) that can be ensured is ( 7 )=0.28 mm 2  when ( 3 )=1.5 mm. This circuit board pattern sectional area corresponds to twice the sectional area of the wire harness since the circuit board is superior in heat dissipation property, so it can cover a wire harness area of approximately 0.5 mm 2 . 
   It should be noted that by further varying the thickness of the copper foil, it becomes possible to ensure a sufficient permissible current while using 090 terminals, which are different from 040 terminals or 025 terminals. 
   Now, a joint connector according to a second embodiment of the present invention is described in detail with reference to the drawings. 
     FIG. 14  is an exploded perspective view showing a joint connector according to the second embodiment of the present invention, adapted to a multi-pin connector for automobile wire harnesses.  FIG. 15  is an enlarged perspective view showing the joint connector in an assembled condition, in which the component parts of  FIG. 14  are combined.  FIG. 16  shows a connector housing constituting an inserting-side connector portion of  FIG. 14 , in which  FIG. 16A  is a perspective view thereof, viewed from its obverse side and  FIG. 16B  is a perspective view thereof, viewed from its reverse side.  FIG. 17  shows a connector housing of  FIG. 16 , in which  FIG. 17A  is a top plan view thereof, and  FIG. 17B  is a bottom plan view thereof. 
   A joint connector according to the second embodiment of the present invention comprises, as shown in the above-mentioned figures, an inserting-side connector portion (female connector)  511 , and a receiving-side connector portion (male connector)  513  into which the inserting-side connector portion  511  is inserted. The inserting-side connector portion  511  comprises a plurality of ten-terminal connector housings  515  (10 housings in the example shown in the figures) in a rectangular plate-like form having a plurality of terminals in which a plurality of terminal-accommodating compartments  517  (10 compartments in the example shown in the figures) are juxtaposed in a lateral direction for accommodating connecting terminals  519  (see  FIGS. 21 through 23  and  26 ), an interlocking recess portion  523  provided on the connector housing  515 , and a connector housing-locking means  521  that has an interlocking protrusion portion  525  that interlocks therewith and is for stacking and combining the connector housing  515  in a plurality of stages (10 stages in the example shown in the figure). These connector housings  515  and the connector housing-locking means  521  are formed by a plastic molding process. It should be noted that each individual connector housing  515  corresponds to each one of the sub-harnesses, and different sub-harnesses are attached to respective connector housings  515 . 
   The receiving-side connector portion  513  has a rectangular box-like shaped connector case  527  and a circuit-forming unit  531 . The rectangular box-like shaped connector case  527  is formed by a plastic molding process, and has a rectangular shaped, inserting-side connector portion-receiving compartment  529  on its one side for receiving and holding the inserting-side connector portion  511 . The circuit-forming unit  531  is attached to the other side of the connector case  527 , and has a plurality of connection pins  533  (100 bars in the example shown in the figures) that protrude in the inserting-side connector portion-receiving compartment  529  so as to be connected to connecting terminals  519  in the inserting-side connector portion  511 . The inserting-side connector portion  511  and the receiving-side connector portion  513  are configured to fit and connect to each other. Reference numeral  535  designates a rectangular plate-like shaped case cover for protecting the circuit-forming unit  531  that is provided on a side of the connector case  527  on which the circuit-forming unit  531  is attached, and it is formed by a plastic molding process. 
   More specifically, all the ten connector housings  515  that constitute the inserting-side connector portion  511  have the same structure so that they can be easily and reliably stacked and combined, and at the rear ends of both its side portions  537  in each of them, ear portions  539  that serve as grip portions when inserting the inserting-side connector portion  511  into the receiving-side connector portion  513  are provided in a protruding manner. 
   As shown in  FIGS. 16 through 18 , the total of four interlocking recess portion  523  of the connector housing-locking means  521 , each of which is made up of an angular C-shaped recessed groove opened in a lateral direction, are provided, on outer side walls of both of the endmost terminal-accommodating compartments  517 , and in each of the side portions  537  of each connector housings  515  constituting the inserting-side connector portion  511 , so that two of each are spaced apart from each other along the front-and-back direction (a longitudinal direction of the terminal-accommodating compartment  517 ). 
   Two of the interlocking protrusion portions  525 , the total of four, are provided in the downward positions that correspond to the interlocking recess portions  523  so that they project downwardly in a hook-like shape from the side portions  537 ; thus, in two adjacent connector housings  515 , the interlocking protrusion portions  525  provided on one of them are inserted into interlocking recess portions  523  provided on the other one to interlock with each other. 
   Further, as is clear from  FIG. 18 , under the condition in which the interlocking protrusion portions  525  are interlocked with the interlocking recess portions  523 , a clearance  524  is provided between interlocking surfaces  523   a  and  525   a  of the interlocking recess portion  523  and the interlocking protrusion portion  525 . It is preferable that the gap (play) of the clearance  524  be about 0.1 mm to 0.2 mm. 
   The connector housing-locking means  521  also comprises, in each of the side portions  537  of each connector housing  515 , a rectangular inserting recessed groove  541  protruding on each of outer side walls of the endmost terminal-accommodating compartments  517  so as to be sandwiched between the interlocking recess portions  523 , and a rectangular plate-like guide rib  543  protruding directly below the corresponding inserting recessed groove  541  from the side portion  537 . Accordingly, inserting recessed groove  541  provided on one of the adjacent connector housings  515  is loosely attached and fitted to the guide rib  543  provided on the other one. Thus, the distance of relative shift (move distance) in the connector housings  515  stacked in a plurality of stages along the horizontal direction (the direction along the contact surfaces) is constrained so that it does not become excessively large. 
   It should be noted that the numbers of the interlocking protrusion portions  525  (the interlocking recess portions  523 ) and the guide ribs  543  (the inserting recessed grooves  541 ) are not limited to those in the above description. Also, it is preferable to vary the shapes and locations of the guide ribs  543  and the inserting recessed grooves  541  appropriately for each connector housing  515  because mistakes in the stacking order of the connector housings  515  become less frequent and workability in stacking can be improved. 
   Further, as shown in  FIGS. 16A ,  17 A, and  18 , a rectangular recessed groove  545  is provided on an upper face of the side portion  537  that corresponds to each of the interlocking recess portions  523 . By sticking the fore-end of a rod-like disengaging jig  547  into the recessed groove  545  and rotating it in the direction indicated by the arrow shown in  FIG. 18  (in an upward direction), the upper connector housing  515  is slightly lifted and the connector housing-locking means  521  is unlocked to release the combination between the stacked connector housings  515 , so that the connector housings  515  can be disassembled into individual pieces. 
   In the joint connector according to the second embodiment of the present invention, the clearance  524  is, as described above, provided between the interlocking surfaces  523   a  and  525   a  of the interlocking recess portion  523  and the interlocking protrusion portion  525 , which constitute the connector housing-locking means  521 , and the interlocking protrusion portion  525  is loosely interlocked with the interlocking recess portion  523 . As a consequence, the stacked connector housings  515  that constitute the inserting-side connector portion  511  are loosely combined so as to be shiftable relative to each other, forming a flexible structure capable of expansion, contraction, slide, bend, and so forth, like an accordion. For this reason, even when the inserting-side connector portion  511  is inserted into the receiving-side connector portion  513  in an inclined state, the connector housings  515  shift relative to one another quickly, changing their shape, and the inserting-side connector portion  511  is aligned with the receiving-side connector portion  513  to be quickly straightened in a proper posture. 
   Therefore, insertion of the inserting-side connector portion  511  does not require a great force and, in addition, the insertion does not become difficult midway, making the insertion of the inserting-side connector portion  511  easy. Moreover, no excessive force is applied to the connector housings  515  and the connecting terminals  519 , so these are not easily deformed. 
   Moreover, even when the pitch between the connecting terminals  519  in case that the connector housings  515  have been stacked deviates from the pitch between the connection pins  533  of the receiving-side connector portion  513  because of the dimensional tolerance of the connector housings  515 , the connector housings  515  expand one another in the stacking direction and it becomes easy to match the pitch between the connecting terminals  519  with the pitch between the connection pins  533  of the receiving-side connector portion  513 . Consequently, the connection pins  533  of the receiving-side connector portion  513  can be inserted smoothly and not forcibly into the connecting terminals  519  of the inserting-side connector portion  511  when the inserting-side connector portion  511  is inserted into the receiving-side connector portion  513 . As a result of the foregoing, fitting and connection between the inserting-side connector portion  511  and the receiving-side connector portion  513  become easy, and the connector&#39;s poor electrical connection can be prevented reliably. 
   Furthermore, as shown in  FIGS. 16A ,  17 A, and  19 A, a lance  551  is provided on one wall, that is, an upper wall  517   a , of each terminal-accommodating compartments  517  in each connector housing  515  of the inserting-side connector portion  511 . The lance  551  has a straddle structure in which its base line end is supported by the above-mentioned wall  517   a  through a pair of slits  549  formed in the longitudinal direction of the terminal-accommodating compartments  517 . The lance  551  is composed of an elastic interlocking piece made of plastic in which a thick-walled built-up portion  553  (see  FIGS. 19A and 19B ) is formed on its back side and an interlocking protrusion  555  (see  FIG. 19C ) interlocked with one of the connecting terminals  519  is formed on its inner side. 
   On the other wall that is opposite the terminal-accommodating compartment  517  corresponding to the location of the lance  551 , that is, on the lower wall  517   b , a lance-receiving portion  557  is provided, as shown in  FIGS. 16B ,  17 B,  20 A, and  20 B. When the connecting terminal  519  is inserted into the terminal-accommodating compartment  517 , the lance-receiving portion  557  receives the built-up portion  553  of the lance  551  provided on the terminal-accommodating compartment  517  of the adjacent connector housings  515  to permit displacement of the lance  551  bending outwardly. The lance-receiving portion  557  is composed of a slit-shaped thin hole. Although the lance-receiving portion  557  shown in the figures is a thin hole, it may be composed of a recessed groove (closed-end hole), not a hole, when the strength of the lance  551  can be ensured sufficiently and the built-up portion  553  can be made small. 
   When the lance  551  with such a structure is employed, the elastic interlocking piece constituting the lance  551  can attain strong support since it has a straddle structure even in cases where the wall thickness of the terminal-accommodating compartments  517  in the connector housings  515  of the inserting-side connector portion  511  is reduced. In addition, since the built-up portion  553  is provided and the strength becomes greater with the reinforcement, a retention force for the connecting terminals  519  can be sufficiently ensured. Therefore, it is possible to reduce the wall thickness of the terminal-accommodating compartments  517  and accordingly make the connector housings  515  thin, so the height of the inserting-side connector portion  511  in which the connector housings  515  are stacked becomes small, reducing the size of the joint connector. Additionally, the pitch between the connecting terminals  519  along the stacking direction becomes small, minimizing wasted spaces. Thus, it is preferable to use the lance  551  with such a structure. 
   Furthermore, as shown in  FIGS. 16B ,  17 B, and  21  through  23 , a double interlocking rib  559 , for example, in a rectangular shape for the connecting terminal  519  is protruded on an outer side (lower portion) of the lower wall (the other wall)  517   b  located rearward of the lance  551  provided on each terminal-accommodating compartment  517  in each connector housing  515  of the inserting-side connector portion  511 . Meanwhile, on the upper wall  517   a  (the one wall) corresponding to the location of the double interlocking rib  559 , an interlocking hole  561  is provided for interlocking with a double interlocking rib  559  protruding on a terminal-accommodating compartment  517  of an adjacent connector housing  515 . 
   When the connector housings  515  are stacked to form a plurality of stages (10 stages in the example shown in the figures), as shown in  FIG. 21 , the connecting terminal  519  (electric wire is not shown) is inserted from its entrance side (the right side in  FIG. 21 ) to the terminal-accommodating compartment  517  of each connector housing  515  in advance before the stacking and is accommodated therein. In doing so, a tab-like interlock receptor portion  519   a  protruding on an upper portion of the fore-end of the connecting terminal  519  comes into contact with the interlocking protrusion  555  of the lance  551 , bending the lance  551  upwardly from the slit 549 portion to interlock with the interlocking protrusion  555 , so that disconnection of the connecting terminal  519  is prevented. In this state, the connector housings  515  are stacked and combined. 
     FIG. 21  is a longitudinal sectional view showing a condition before a double interlocking rib  559  protruding on a terminal-accommodating compartment  517  in one of the connector housings  515  is interlocked with an interlocking hole  561  provided in a terminal-accommodating compartment  517  of another one of the connector housings  515  adjacent thereto, when the connector housings  515 , in which the connecting terminals  519  are accommodated in the terminal-accommodating compartment  517 , are stacked to form a plurality of stages.  FIG. 22  is a longitudinal sectional view showing a condition in which the connector housings  515  are stacked and the double interlocking rib  559  is interlocked with the interlocking hole  561  after the condition shown in  FIG. 21 . 
   As illustrated here, in stacking the connector housings  515 , when the double interlocking rib  559  protruding on the terminal-accommodating compartment  517  is interlocked with the interlocking hole  561 , the connecting terminals  519  accommodated in the terminal-accommodating compartments  517  in the connector housings  515  are interlocked doubly with the double interlocking rib  559  in addition to interlocking with the interlocking protrusion  555  of the lance  551 . This is preferable in that disconnection of the connecting terminals  519  from the terminal-accommodating compartments  517  can be prevented more reliably. 
   Moreover, as shown in  FIGS. 21 ,  22 , and so forth, it is preferable to provide a projection  559   a  at the rear portion of the double interlocking rib  559  since the projection  559   a  is caught on the edge of the interlocking hole  561  after the double interlocking rib  559  is interlocked with the interlocking hole  561 , making it difficult to disengage from the interlocking hole and thus disconnection of connecting terminals  519  is prevented further strongly. The projection  559   a  may be provided for all the double interlocking ribs  559 ; however, in the case where the width of the connector housing  514  is large, it may be provided for those double interlocking ribs  559  located at its center, since there is a possibility that the center portion may be lifted. 
     FIG. 23  is a longitudinal sectional view of the connector housing  515  showing a condition before a double interlocking rib  559  protruding on the terminal-accommodating compartment  517  of one of the connector housing  515  is interlocked with an interlocking hole  561  provided in a terminal-accommodating compartment  517  of an adjacent one of the connector housings  515  in which a connecting terminal  519  is accommodated in the terminal-accommodating compartment  517  in an incompletely inserted state. 
   As illustrated here, when the connecting terminal is not inserted deeply to the predetermined location but is in an unfinished, incompletely inserted state in inserting the connecting terminal  519  into the terminal-accommodating compartment  517  before stacking the connector housings  515 , the fore-end of the double interlocking rib  559  collides with the rear end of the connecting terminal  519 , preventing insertion of the double interlocking rib  559  even if the double interlocking rib  559  protruding on the terminal-accommodating compartment of one of the connector housings  515  is attempted to be inserted into the interlocking hole  561  provided in the terminal-accommodating compartment  517  of an adjacent one of the connector housings  515  when stacking the connector housings  515  to form a plurality of stages. For this reason, the double interlocking rib  559  cannot be inserted into the interlocking hole  561  to a predetermined depth, making the stacking of the connector housings  515  difficult. In view of this, it is preferable to provide the double interlocking rib  559  since the incompletely inserted state of the connecting terminal  519  in the terminal-accommodating compartment  517  can be detected easily without using complex mechanisms. 
   It should be noted that, as shown in  FIG. 24 , the double interlocking rib  559  may be formed in such a shape that its lower portion is sloped toward the lance-receiving portion  557 , that is, the fore-end of the connecting terminal  519 . Such a shape is preferable since it easily makes contact with the housing if the insertion condition of the connecting terminal  519  is incomplete, and sensitivity of detecting the incompletely inserted state of the connecting terminal  519  increases. 
   In addition, it is preferable to appropriately vary the shapes and locations of the double interlocking rib  559  and the interlocking hole  561  for each connector housing  515 , as in the case of the above-described guide rib  543  and the inserting recessed groove  541 , since mistakes in the stacking order of the connector housing  515  become less frequent and workability in stacking can be improved. 
   Reference numeral  563  designates a connection pin insertion hole formed by piercing through a front wall  517   c  of the terminal-accommodating compartments  517  so that, when the inserting-side connector portion  511  is inserted in the receiving-side connector portion  513 , the connection pins  533  of the receiving-side connector portion  513  can be inserted in the connecting terminals  519  accommodated in the terminal-accommodating compartments  517  of the connector housings  515  to achieve electrical connection. Reference numeral  565  denotes lock grooves provided on both side portions  537  at the locations near the fore-ends in each of the connector housings  515 . After inserting the inserting-side connector portion into the receiving-side connector portion and fitting it thereto, the lock grooves are interlocked with claws  573   a  (see  FIG. 27 ) of lock claw portions  573  provided in the receiving-side connector portion so that the inserting-side connector portion is fixed so as not to come out of the inserting-side connector portion-receiving compartment  529  of the receiving-side connector portion  513 . It should be noted that in the example shown in the figures, both the side portions  37  of the connector housing  515  are provided with the lock grooves  565 , but only one of the side portions  537  may be provided therewith. 
     FIGS. 25A and 25B  are a left-side view (front-side view) and a front view, respectively, showing the inserting-side connector portion  511  in which ten of the connector housings  515  are stacked and combined vertically to form 10 stages, and  FIG. 26  is a cross-sectional view taken along line X-X in  FIG. 25A . To assemble the inserting-side connector portion  511  of this kind, the connecting terminals  519  connected to electric wires A that constitute a sub-harness are inserted and accommodated in advance in the terminal-accommodating compartments  517  of the connector housing  515  before stacking the connector housings  515 , as shown in  FIG. 26 , and thereafter, the connector housings  515  are stacked and combined using the connector housing-locking means  521 . In this process, the operation of inserting the connecting terminals  519  inside the terminal-accommodating compartments  517  of the connector housing  515  may be carried out before any of the ten connector housings  515  are stacked, or may be performed sequentially each time a connector housing  515  for an upper stage is stacked over a connector housing  515  for a lower stage. 
   It should be noted that, above the connector housing  515  stacked to be the uppermost stage of the inserting-side connector portion  511 , a rectangular plate-shaped cover  567  is attached (see  FIGS. 25 and 26 ), which is provided with ten double interlocking ribs  559  (not shown) in a protruding condition at corresponding locations on its lower portion such that the connecting terminals  519  accommodated in its terminal-accommodating compartments  517  can be doubly interlocked, and also provided with four interlocking protrusion portion  525  for the connector housing-locking means  521 , two guide ribs  543 , and a lance-receiving portion (recessed groove)  557  (not shown). 
   Next, the configuration of the receiving-side connector portion  513  is described further. As shown in  FIGS. 15 ,  27 A, and  27 B, on both inner side walls the inserting-side connector portion-receiving compartment  529  in the connector case  527  constituting the receiving-side connector portion  513 , a plurality of protruding guide portions  571  (only those on one side are shown in the figure) having, for example, a substantially angular cross-sectional shape are juxtaposed to form guide grooves  569  having, for example, a substantially angular C-shape for guiding both side portions  537  of each connector housing  515  in the inserting-side connector portion  511  to be inserted therein. The protruding guide portions  571  are provided along the longitudinal direction of the inserting-side connector portion-receiving compartment  529  and vertically at predetermined intervals, that is, at a pitch size that matches the pitch of the connecting terminals  519  accommodated in the terminal-accommodating compartments  517  of the inserting-side connector portion  511  with respect to the connector housing stacking direction. 
   In the example shown in the figures, the guide grooves  569  are formed by recessing both inner side walls of the inserting-side connector portion-receiving compartment  529 , and for this reason, the height level of each protruding guide portion  571  provided on the inner side walls is at the same level of the inner side wall surface of the inserting-side connector portion-receiving compartment  529 , so it does not project inward beyond the inner side wall surface. As for the guide grooves  569 , in the example shown in the figures, 11 grooves are provided so that the respective side portions  537  of the inserting-side connector portion  511  side and the side portion  537  of the cover  567  can be inserted, and accordingly, ten protruding guide portions  571  are provided. In addition, the width of each of the protruding guide portions  571  is so formed as to be narrowed and tapered toward the entrance of the inserting-side connector portion-receiving compartment  529 , while the width of each of the guide grooves  569  is gradually widened. It should be noted that the protruding guide portions  571  may be juxtaposed so as to project inwardly from both inner side walls of the inserting-side connector portion-receiving compartment  529 , and in this case, the guide grooves  569  are formed between the protruding guide portions  571  that project. It also should be noted that in the example shown in the figures, the guide grooves  569  are formed on both inner side walls of the inserting-side connector portion-receiving compartment  529  in the receiving-side connector portion  513 , but they may be formed only on one of the inner side walls. 
   On both side walls of the inserting-side connector portion-receiving compartment  529 , lock claw portions  573  each made of an elastic interlocking piece are provided, which interlock with the lock grooves  565  provided on the connector housings  515  when the inserting-side connector portion  511  is inserted into the receiving compartment  529 , so that the inserting-side connector portion  511  is fixed so as not to come out of the inserting-side connector portion-receiving compartment  529  of the receiving-side connector portion  513 . The lock claw portions  573  can sufficiently fix the inserting-side connector portion  511  even if the number thereof is not as many as the corresponding number (20 in the example shown in the figure) of the lock grooves  565  provided in the connector housings  515 . For this reason, in cases where the connector housings  515  of the inserting-side connector portion  511  are stacked to form ten stages as shown in the figures, the total of four lock claw portions  573  are provided on both side walls of the inserting-side connector portion-receiving compartment  529 , two at each of locations at which the third-stage and eighth-stage connector housings  515 , from the bottom, of the inserting-side connector portion  511  are inserted, for example. It should be noted that in the example shown in the figures, the lock claw portions  573  are provided on both side walls of the inserting-side connector portion-receiving compartment  529 , but they may be provided only on one of the side walls. 
   Meanwhile, in the example shown in the figures, the circuit-forming unit  531  is formed as follows. An insulating substrate  532  is provided with, on one surface (reverse surface) thereof, a circuit pattern formed by printing or the like and made of a conductive material such as a copper foil or the like. On the other surface thereof (obverse surface), a plurality of connection pins  533  (100 pins in the example shown in the figures) composed of good conductive pin contacts and made of a copper material or the like are provided so that one ends of them are connected to the circuit pattern while the other ends of them pierce the insulating substrate  532  and protrude therefrom. This circuit-forming unit  531  is accommodated and held in a circuit-forming unit-accommodating compartment  575  formed opposite the inserting-side connector portion-receiving compartment  529  of the connector case  527 , separated therefrom by a partition wall  529   a , and the connection pins  533  pierce the partition wall  529   a  and protrude inside the inserting-side connector portion-receiving compartment  529  so as to be inserted into and connected to the connecting terminals  519  of the inserting-side connector portion  511 . It should be noted that the circuit-forming unit  531  may be a bus bar type (not shown) in which the circuit pattern and the connection pins  563  are formed of bus bars, in place of the circuit board type as described above. 
   It is preferable to use the receiving-side connector portion  513  having such a configuration for the following reason. When inserting the inserting-side connector portion  511  into the receiving-side connector portion  513 , the side portions  537  of the connector housings  515  in the inserting-side connector portion  511  are guided by the guide grooves  569  of the receiving-side connector portion  513 , the entrances of which are widened. Therefore, the inserting-side connector portion  511  is not likely to be inserted in an inclined condition against the receiving-side connector portion  513 , and the inserting-side connector portion  511  is easily inserted in a proper posture aligned with the receiving-side connector portion  513 ; thus, both of the connector portions  511  and  513  can be more smoothly fitted and connected to each other. 
   A receiving-side connector portion  577  shown in  FIG. 28  shows a modified example of the foregoing receiving-side connector portion  513 . The receiving-side connector portion  577  is different from the foregoing receiving-side connector portion  513  as follows. In comparison with the receiving-side connector portion  513 , the length of one or a plurality of (two in the example shown in the figure) protruding guide portions  572  that is/are located in the middle of the protruding guide portion  571  is formed longer than the other ones by a predetermined length toward the entrance of the inserting-side connector portion-receiving compartment  529 , projecting along the longitudinal direction of the inserting-side connector portion-receiving compartment  529 . Also, extension portions  579  are formed on both upper and lower ends of the entrance of the inserting-side connector portion-receiving compartment  529 , such that they extend longer than both side ends by a predetermined length and their inner wall surfaces are inclined outwardly toward the entrance to form a funnel-like shape. The rest of the configurations are the same as the foregoing receiving-side connector portion  513 . 
   It is preferable that the protruding guide portions  572  located in the middle region are formed to have a longer length in this way, because the axis deviation in inserting the inserting-side connector portion  511  into the receiving-side connector portion  577  reduces further, and the insertion can be made in a proper posture. It is also preferable to provide the extension portions  579  since the advantageous effect of correcting the axis deviation caused at the time of inserting the inserting-side connector portion  511  into the receiving-side connector portion  577  becomes greater. It should be noted that, naturally, even when either one of the above-described two means is omitted, insertion performance of the inserting-side connector portion  511  can be improved more than that in case of the receiving-side connector portion  513 . In addition, in the case of providing the protruding guide portions  572  in the middle region, it is preferable to increase the number of the protruding guide portion  572 , that is, to lengthen the vertical distance in which they are provided, since insertion of the inserting-side connector portion  511  becomes easy even when the number of stacked stages of the connector housings  515  in the inserting-side connector portion  511  is increased. 
   The joint connector according to the present invention is assembled as follows. As shown in  FIG. 29A , the inserting-side connector portion  511  and the receiving-side connector portion  513  are opposed, and in a proper posture in which the axes of both connector portions  511  and  513  are aligned to be parallel, the inserting-side connector portion  511  is inserted into the inserting-side connector portion-receiving compartment  529  of the receiving-side connector portion  513  so that the connection pins  533  of the receiving-side connector portion  513  are inserted inside the connecting terminals  519  accommodated in the terminal-accommodating compartments  517  of the inserting-side connector portion  511 ; thus, the inserting-side connector portion  511  and the receiving-side connector portion  513  are fitted and connected to each other. 
   Incidentally, in inserting the inserting-side connector portion  511  into the receiving-side connector portion  513 , the axis of the inserting-side connector portion  511  often does not become parallel to the axis of the receiving-side connector portion  513 . For example, there are many cases in which, as shown in  FIG. 29B , the axis of the inserting-side connector portion  511  rotates clockwise relative to the axis of the receiving-side connector portion  513 , so that the inserting-side connector portion  511  is inserted in a condition in which it inclines downward to the right, or as shown in  FIG. 29C , the axis of the inserting-side connector portion  511  rotates anti-clockwise relative to the receiving-side connector portion  513 , so that the inserting-side connector portion  511  is inserted in a condition in which it inclines upward to the right. 
   When the inserting-side connector portion  511  is inserted in an inclined condition as described above, the connector housings  515  quickly shift relatively to each other since the inserting-side connector portion  511  has a flexible structure as described above, and the axis of the inserting-side connector portion  511  aligns parallel to the axis of the receiving-side connector portion  513 , quickly straightening the inserting-side connector portion  511  into a proper posture. Thus, the inserting-side connector portion  511  can be inserted smoothly and not forcibly with a relatively small force, and both of the connector portions  511  and  513  can be quickly fitted and connected to each other. 
   In assembling the joint connector, it is possible to use connector retainers  581  and  582  as shown in  FIG. 30  to fit and connect the inserting-side connector portion  511  and the receiving-side connector portion  513  together. In this case, the support-retaining portions  581   a  of the connector retainer  581  is made to support the ear portions  539  of the connector housing  515  in the inserting-side connector portion  511 , and support-retaining portions  582   a  of the connector retainer  582  are made to hold chuck portions  583  provided on the connector case  527  of the receiving-side connector portion  513  in a protruding condition. By operating the connector retainers  581  and  582 , the inserting-side connector portion  511  is inserted into the receiving-side connector portion  513 . It is preferable to use such connector retainers  581  and  582  since shifts of both of the connector portions  511  and  513  in vertical and lateral directions are suppressed, and the inserting-side connector portion  511  can be easily inserted into the receiving-side connector portion  513 . 
   In addition, when inserting the inserting-side connector portion  511  into the receiving-side connector portion  513 , if the number of stacked stages of the connector housings  515  in the inserting-side connector portion  511  is small, a free space is sometimes created inside the inserting-side connector portion-receiving compartment  529  of the receiving-side connector portion  513  in which the inserting-side connector portion  511  is to be inserted, making it difficult to insert the inserting-side connector portion  511 . When this is the case, it is preferable to insert dummy plates in the guide grooves  569  of the inserting-side connector portion-receiving compartment  529  in which such free spaces are created in order to fill the free spaces because not only insertion of the inserting-side connector portion  511  becomes easy but also the inserted inserting-side connector portion  511  is prevented from becoming wobbly by vibrations or the like and made stable. 
   Next, a joint connector according to a third embodiment of the present invention is described in detail with reference to the drawings.  FIG. 31  is an exploded perspective view showing a joint connector according to the third embodiment of the present invention, adapted to a multi-pin connector for an automobile wire harness 
   A joint connector according to the third embodiment of the present invention is, as shown in the foregoing figure, configured as follows. The joint connector is provided with an inserting-side connector portion (stacked connector)  611  and a receiving-side connector portion (electrical connection box)  613 . The inserting-side connector portion (stacked connector)  611  is provided with ten-terminal connector housings  617  that are stacked and combined in a plurality of stages (10 stages in the example shown in the figures), each of the connector housings having a plurality of terminal-accommodating compartments  619  (10 compartments in the example shown in the figure) for accommodating female terminals (not shown). The receiving-side connector portion (electrical connection box)  613  has a connector case (upper case)  621  in which the inserting-side connector portion  611  is inserted from an opening thereof and is accommodated, and a plurality of male terminals  623  (10 terminals vertically and 10 terminals horizontally, the total of 100 in the example shown in the figures) that are provided in the case  621  in a protruding condition and are to be connected to the female terminals in the connector housings  617  in the inserting-side connector portion  611 . The inserting-side connector portion  611  is inserted into the receiving-side connector portion  613 , and the inserting-side connector portion  611  and the receiving-side connector portion  613  are interlocked by a connector-locking means  615 . 
   More specifically, the connector housings  617  that constitute the inserting-side connector portion  611  are formed by a plastic molding process in a plate-like shape having the same shape, structure, and size so that they can be easily and readily stacked and combined, and be easily inserted into the receiving-side connector portion  613 . In their terminal-accommodating compartments  619 , female terminals connected to the terminals of electric wires (not shown) constituting a wire harness are accommodated. The connector housings  617  are stacked into 10 stages in the present embodiment and are combined with each other by connector-coupling means  625 . 
   The connector-coupling means  625  each have, as shown in  FIGS. 31 and 32 , an angular C-shaped engagement recess portion  627  and a hook-like engaging protruding portion  629  for interlocking therewith, which form a vertical pair and are provided on both side portions (only one of the side portions is shown in the example shown in the figure) of each connector housings  617 . The engaging protruding portion  629  of an adjacent one of the connector housings  617  is engaged with the engagement recess portion  627  so that the connector housings  617  are connected and combined with each other. It should be noted that, although not shown in the figures, the connector-coupling means  625  is also provided with, near the engagement recess portion  627  and the engaging protruding portion  629 , engaging protruding/recessed portions for restricting the relative shift of the connector housings  617  in the direction along the stacking surface. Reference numeral  631  denotes a cover that is attached on the uppermost connector housing  617  after the connector housings  617  are stacked and combined into 10 stages. 
   The connector case  621  of the receiving-side connector portion  613  is formed into a squared box-shape by a plastic molding process, and is provided with a first accommodating space  633  for receiving and accommodating the inserting-side connector portion  611  that is inserted from an opening on one side. On both inner wall faces of the connector case  621  provided with the first accommodating space  633 , guide grooves  635  are provided, by which both side portions of the connector housings  617  of the inserting-side connector portion  611  are guided when inserted. The guide grooves  635  are juxtaposed along the longitudinal direction of the connector case  621 , that is, along the inserting direction of the inserting-side connector portion  611 , so as to have a predetermined gap in the vertical direction, that is, at a pitch size that matches the pitch of the female terminals accommodated in the terminal-accommodating compartments  619  of the inserting-side connector portion  611  in the connector housing stacking direction. 
   The male terminals  623  provided in the first accommodating space  633  of the connector case  621  in a protruding condition are, as shown in  FIGS. 31 and 33 , composed of pin-shaped connecting members made of a good conductive material such as copper, copper alloy materials, or the like. Their base ends pierce through, and are supported by, a circuit board  637  in which a circuit pattern formed of a conductive material such as a copper foil is formed on one surface (back surface) of an insulating plate of plastic or the like by printing or the like, and they are connected at the other surface (obverse surface) of the circuit board  637  to the circuit pattern by soldering. 
   The circuit board  637  is, as shown in  FIG. 33 , configured as follows; it is accommodated and held in a second accommodating space  639  provided in the opposite side of the first accommodating space  633  of the connector case  621  and separated by a partition wall  621   a ; also, the male terminals  623  protrude in the first accommodating space  633  from through holes  621   b  formed in the partition wall  621   a  so that they are inserted into and are connected with the female terminals of the inserting-side connector portion  611 . It should be noted that the male terminals  623  and the circuit board  637  may be composed of a bus bar made of a good conductive material such as copper and a copper alloy material. Reference numeral  641  denotes, as shown in  FIG. 31  and  FIG. 33 , a case cover (lower case) attached to an opening portion of the second accommodating space  639  of the connector case  621 , which is for supporting and protecting the circuit board  637  accommodated in the second accommodating space  639 . 
   As shown in  FIG. 33 , the connector-locking means  615 , which are for interlocking the inserting-side connector portion  611  and the receiving-side connector portion  613  each other by inserting the inserting-side connector portion  611  into the receiving-side connector portion  613 , are provided on both side positions according to the present embodiment so that both side portions of the connector housings  617  in the inserting-side connector portion  611  interlock with both side walls of the connector case  621  in the receiving-side connector portion  613  in which the first accommodating space  633  is provided. 
   More specifically, the connector-locking means  615  is composed of, as shown in  FIGS. 33 through 35 , an engagement recess portion  643  and an engaging claw portion  645 . The engagement recess portion has a substantially angular C-shape, and it is provided on both side portions of each of the connector housings  617  in the inserting-side connector portion  611  and at locations relatively near the fore-end with respect to the inserting direction of the inserting-side connector portion. The engaging claw portion  645  is composed of an elastic piece having, at its fore-end, a claw  647  for engaging with the engagement recess portion  643  and a curved tab  649  diagonally extending outwardly against the claw so that it forms a substantially Y shape (substantially forked shape). 
   The engaging claw portions  645  are provided in a cantilevered fashion so that the claws  647  are located near the bottom side (the partition wall  621   a  side) of the first accommodating space  633  and lined with the direction in which the inserting-side connector portion  611  is inserted, and that its base ends are provided on both side walls of the connector case  621  of the receiving-side connector portion  613  provided with the first accommodating space  633  and at locations where there are the guide grooves  635  in which the third and eighth stage connector housings  617  are guided and inserted when the receiving-side connector portion  613  is inserted into the inserting-side connector portion  611  (see  FIG. 31 ). 
   When the inserting-side connector portion  611  is inserted into the receiving-side connector portion  613  and accommodated in the first accommodating space  633  of the connector case  621 , the claws  647  of the engaging claw portions  645  of the connector-locking means  615  are engaged with the engagement recess portions  643 , locking the inserting-side connector portion  611  and the receiving-side connector portion  613  with each other, and the male terminals  623  of the receiving-side connector portion  613  are inserted into the female terminals of the inserting-side connector portion  611 , so that both connector portions  611  and  613  are electrically connected (see  FIG. 33 ). 
   The joint connector according to the third embodiment of the present invention is assembles as follows. In the terminal-accommodating compartments  619  of the connector housings  617 , the female terminals connected to the terminals of the electric wires constituting a wire harness are accommodated, and the connector housings  617  are stacked, and are combined by the connector-coupling means  625 , to obtain the inserting-side connector portion  611 . Next, this inserting-side connector portion  611  is opposed to the receiving-side connector portion  613 , the centers (axes) of both connector portions  611  and  613  are aligned, and the inserting-side connector portion  611  is inserted into the first accommodating space  633  of the connector case  621  in the receiving-side connector portion  613 . Then, the claws  647  of the engaging claw portions  645  of the connector-locking means  615  are engaged with the engagement recess portions  643  to lock both connector portions  611  and  613 , and the male terminals  623  of the receiving-side connector portion  613  side are inserted into the female terminals of the inserting-side connector portion  611  side to electrically connect both connector portions  611  and  613 . 
   It should be noted that although in the above-described embodiment, the connector-locking means  615  are provided at positions on both sides so as to lock both side portions of the connector housings  617  in the inserting-side connector portion  611  with the both side walls of the connector case  621  in the receiving-side connector portion  613 , it is possible that they are provided on one of the sides so that one of the side portions of the connector housings  617  in the inserting-side connector portion  611  is locked with one of the side walls of the connector case  621  in the receiving-side connector portion  613  that opposes the one of the side portions. 
   Since the connector-locking means  615  are provided at side locations when viewed in the inserting direction so that the side portions of the connector housings  617  of the inserting-side connector portion  611  are locked with the side walls of the connector case  621  in the receiving-side connector portion  613 , one or a plurality of lock supporting points for locking the connector housings  617  vertically stacked into a plurality of stages shifts/shift from the uppermost end locations of both connector portions  611  and  613  to arbitrary midway locations vertically, and the distance from the lock supporting points of the connector-locking means  615  to free ends, such as the uppermost end and lowermost end positions of both connector portions  611  and  613 , is shortened. 
   As a result, the number of connector housings  617  stacked between the lock supporting point of the connector-locking means  615  and the respective free ends becomes less, so that the accumulated amount of backlash caused between the connector housings  617  is reduced and the connector housings  617  are prevented from shifting and being lifted in the direction in which it is removed from the receiving-side connector portion  613  due to the effect of the foregoing tensile force. 
   Therefore, even when the number of stacked stages of the connector housing  617  is increased in the inserting-side connector portion  611 , a good connecting state between the inserting-side connector portion  611  and the receiving-side connector portion  613  is maintained and the performance and reliability of the joint connector can be improved. 
   In addition, it is preferable to provide the connector-locking means  615  at the positions on both sides so that both side portions of the connector housings  617  of the inserting-side connector portion  611  are locked with both side walls of the connector case  621  in the receiving-side connector portion  613  because, if a tensile force such as to pull the connector housings  617  out of the receiving-side connector portion  613  acts on the connector housings  617  of the inserting-side connector portion  611 , the connector housings  617  are firmly held by the connector-locking means  615  at both side ends and are stabilized and the joint connector becomes strong. 
   It is also preferable that the connector-locking means  615  is made of the engagement recess portion  643  and the engaging claw portion  645  composed of an elastic piece having at its fore-end the claw  647  for engaging with the engagement recess portion  643 , since the engaging operation in the connector-locking means becomes smooth and their engagement failure becomes infrequent, so connection of the inserting-side connector portion with the receiving-side connector portion is made more reliable. 
   The connector-locking means  615  may be configured such that, as opposed to the above-described embodiment, its engagement recess portions  643  are provided on the side walls of the connector case  621  in the receiving-side connector portion  613 , and the engaging claw portions  645  are provided on the side portions of connector housings  617  of the inserting-side connector portion  611 . 
   As in the foregoing embodiment, it is preferable to provide the engagement recess portions  643  having generally a simple shape and structure on the side portions of the connector housings  617  in the inserting-side connector portion  611  and to provide the engaging claw portions  645  having a more complex shape and structure than the engagement recess portion  643  on the side walls of the connector case  621  in the receiving-side connector portion  613  in a cantilevered fashion, since manufacture of the joint connector becomes easier and less costly and, in addition, size reduction can be achieved. 
   The engaging claw portions  645  of the connector-locking means  615  may be provided so as to correspond to the engagement recess portions  643  provided on the respective connector housings  617  of the inserting-side connector portion  611 ; however, as in the foregoing embodiment, even if they are provided at positions on the side walls of the connector case  621  that correspond to the third and eighth stage connector housings  617 , any stages of the connector housing  617  are not loosened or lifted when a tensile force such as to pull out the connector housings  617  acts thereon after locking the inserting-side connector portion  611  and the receiving-side connector portion  613 , and a good connecting state can be maintained. 
   Accordingly, the locations of and the number of the engaging claw portions  645  to be provided are not limited to the foregoing embodiment and may be appropriately changed according to the number of stacked connector housings  617 , the environment and conditions in which the joint connector is used, or the like. Generally, the number of the engaging claw portions should be increased when the number of stacked stages of the connector housings  617  is large, but be reduced when the number of stacked stages thereof is small. When the number of the engaging claw portion  645  provided on the side wall of the connector case  621  is one, it is preferable to provide it at the center position that is the intermediate point along the vertical direction of the connector case  621 . Meanwhile, the engagement recess portions  643  are provided for each of the connector housings  617  since it is desirable that the connector housings  617  are formed to have the same shape, structure, and size so that they can be easily stacked and combined, or inserted into the receiving-side connector portion  613 ; however, they may be provided only on the side portions of the connector housings  617  corresponding to the engaging claw portions  645 , and the number thereof is not limited to that described in the present embodiment. 
   To release the locked state of the inserting-side connector portion  611  and the receiving-side connector portion  613 , a simple connector lock-releasing jig  651  as shown in  FIGS. 34 and 35  is used, in which a four rod-like pushing members  655  the fore-ends of which are formed in a tapered shape are protruded from a support member  653  made of a rectangular plate at positions corresponding to the positions in the connector-locking means  615  at which the engaging claw portions  645  are provided. 
   The four pushing members  655  of the connector lock-releasing jig  651  are passed through four piercing holes  641   a  formed in the case cover  641  in the receiving-side connector portion  613  and through holes  621   c  provided in the connector case  621 , and are pushed in the axis direction of the engaging claw portions  645  by pressing the fore-ends of respective pushing members  655  onto inclined inner side faces  649   a  of the curved tabs  649  of the engaging claw portions  645 . By doing so, the curved tabs  649  are deformed outwardly and bent away from the side walls of the connector case  621  against the elasticity of the elastic piece, and the claws  647  are easily disengaged from the engagement recess portions  643 ; thus, the connector-locking means  615 , that is, the locked state of both connector portions  611  and  613  is released, and the inserting-side connector portion  611  can be easily and readily pulled out and separated from the receiving-side connector portion  613 . After the locked state being released, the engaging claw portions  645  quickly return to their original positions because of their elasticity. 
   It should be noted that there may be cases where the fore-end portions of the pushing members  655  or the curved tabs  649  are caused to slide aside when pressing the fore-ends of the pushing members  655  of the connector lock-releasing jig  651  against the inner side faces  649   a  of the curved tabs  649  of the engaging claw portions  645 , and the claws  647  of the engaging claw portions  645  do not easily come off from the engagement recess portions  643 , inhibiting a quick release of the locked state between both connector portions  611  and  613 . If this is the case, it is preferable that, as shown in  FIG. 36 , the inner side face  649   a  of the engaging claw portion  645  is provided with a recessed groove  649   b  having, for example, a U-shaped cross-sectional shape in which the fore-end of the pushing member  655  enters along its longitudinal direction of the curved tab  649 . When the recessed groove  649   b  is provided, the pushing member  655  is pressed in the axis direction of the engaging claw portion  645  (the direction indicated by the arrow) while it is being guided by the recessed groove  649   b , and therefore, the relative slide (sideway drift) of the pushing member  655  or the curved tab  649  is prevented reliably. 
   In addition, in cases where the connector lock-releasing jig  651  is not available (for example, in cases where the locked state needs to be released at a small-scale garage in a town), a small, flat head screwdriver driver  657  as shown in  FIG. 37  is passed through four inclined holes  621   d  formed diagonally in the vicinity of the locations at which the curved tabs  649  of the engaging claw portions  645  of the connector case  621  are provided, one at a time. Then, its fore-end is pressed against the curved tab  649 , and the screwdriver  657  is tilted until the side face of the shaft of the screwdriver  657  hits the slope and the entrance edge of the inclined hole  621   d , so that the curved tab  649  is deformed outwardly and the claw  647  is set free and disengaged from the engagement recess portion  643 . This operation is repeated four times to release the locked state between both connector portions  611  and  613 . 
   Thus, it is preferable to use the engaging claw portion  645  having the curved tab  649 , since the inserting-side connector portion  611  can be easily and readily pulled out and separated from the receiving-side connector portion  613  merely using the simple connector lock-releasing jig  651  or the commercially available driver  657  and replacement, repair, or the like of the connector can be made conveniently. 
   Next, a joint connector according to a fourth embodiment of the present invention is described in detail with reference to the drawings. 
     FIG. 38  is an exploded perspective view showing one embodiment of a joint connector  711  according to the fourth embodiment of the present invention, into which an external connector  713  is inserted.  FIG. 39  is a front view of the joint connector of  FIG. 38 , viewed from a side from which the external connector is inserted.  FIG. 40  is a partially-omitted cross-sectional view taken along line S-S in  FIG. 39 , showing the joint connector  711  in which an external connector  713  is inserted. 
   The joint connector according to the fourth embodiment of the present invention is used as a multi-pin connector for an automobile wire harness. As shown in  FIGS. 38 through 40 , it is provided with a connection case (upper case)  715  in which an external connector  713  for accommodating a plurality of female terminals (not shown) is inserted (including external insertion), and a circuit-forming unit  721  attached to a base wall  717  of the connection case  715  and having a plurality of male terminals  723  (100 terminals in the example shown in the figures) and a holder  725  for supporting them, the male terminals  723  protruding in the connection case  715  through a plurality of male terminal piercing holes  719  (100 holes in the example shown in the figures) formed in the base wall  717 . 
   As shown in  FIG. 38 , the external connector  713  is configured by a stacked connector having 10 connector housings  727  each having a plurality of terminal-accommodating compartments  729  (10 compartments in the example shown in the figures) that are for accommodating female terminals (not shown) connected to terminals of electric wires (not shown) for a wire harness and are juxtaposed into a single layer. The connector housings  727  are formed in a plate shape by a plastic molding process so as to have the same structure and size, and are stacked into a plurality of stages (10 stages in the example shown in the figures). The connector housings  727  are combined by connector-coupling means (not shown), and on the uppermost stage connector housing  727 , a cover  731  is attached. 
   Reference numeral  733  denotes substantially angular C-shaped engagement recess portions provided on both side portions of the connector housings  727  near their fore-ends to detachably lock (fix) the external connector  713  inserted in the joint connector  711  so that it does not come out of the joint connector  711 , and they engage with the later-described engaging claw portions  735  provided on the connection case  715  to lock the external connector  713  when the external connector  713  is inserted into the joint connector  711 . It should be noted that various other types than the stacked connector may be used for the external connector  713 , and for example, one in which a plurality of terminal-accommodating compartment  729  are provided in a connector block formed of plastic may be used. 
   The connection case  715  is, as shown in  FIG. 38 , formed by processing a plastic material into a squared box shape and is provided with a connector accommodating compartment  737  for receiving and accommodating the external connector  713  inserted from one opening thereof. On both inner wall faces of the connection case  715  provided with the connector accommodating compartment  737 , guide grooves  739  by which both side portions of the connector housings  727  in the external connector  713  are guided and inserted are juxtaposed along the longitudinal direction of the connection case  715 , that is, along the inserting direction of the external connector  713 , and at intervals that match the stacking intervals of the connector housings  727  of the external connector  713 . 
   Engaging claw portions  735  (see  FIGS. 38 and 40 ) are provided in a cantilevered fashion on both side walls of the connection case  715  provided with the connector accommodating compartment  737  and at locations where there are the guide grooves  739  into which, for example, the third and eight stage connector housings  727  of the external connector  713  are guided and inserted when the connector  713  is inserted into the connection case  715 . Each of the engaging claw portions  735  is composed of an elastic piece and has on its fore-end a claw  736  for engaging with an engagement recess portion  733  provided on the connector housings  727  of the external connector  713 . 
   The 100 male terminals  723  protruding in the connector accommodating compartment  737  of the connection case  715  are, as shown in  FIGS. 38 and 40 , are each composed of a pin-shaped connecting member made of a good conductive material such as copper and a copper alloy material. These male terminals  723  are formed to have, for example, a squared cross-sectional shape and to have the same width, height, and length. The shape of the male terminals  723  may be a rectangular cross-sectional shape, a circular cross-sectional shape, or the like. The holder  725  is composed of a circuit board in which a circuit pattern formed of a conductive material such as a copper foil is provided on one surface (reverse surface) of an insulating plate of plastic or the like. Base ends of the male terminals  723  are supported on another surface (obverse surface) of the holder  725  by passing through holder  725  and are connected to the circuit pattern. It should be noted that the male terminals  723  and the holder  725  constituting the circuit-forming unit  721  may be composed of a bus bar made of a good conductive material such as copper and a steel alloy material. 
   The circuit-forming unit  721  is, as shown in  FIG. 40 , configured as follows. It is accommodated in a circuit-forming unit-accommodating compartment  741  provided in the opposite side to the connector-accommodating compartment  737  of the connection case  715  and separated by a base wall  717 , and is attached on the base wall  717  of the connection case  715 , and the male terminals  723  of the circuit-forming unit  721  protrude inside the connector accommodating compartment  737  through the male terminal piercing holes  719  formed in the base wall  717  so that they are inserted into the female terminals of the external connector  713  and connected therewith. Reference numeral  743  is, as shown in  FIGS. 38 and 40 , a case cover (lower case) attached to the opening of the circuit-forming unit-accommodating compartment  741  of the connection case  715 , for holding and protecting the circuit-forming unit  721  accommodated in the circuit-forming unit-accommodating compartment  741 . 
   Meanwhile, among the plurality of male terminal piercing holes  719  (100 holes in the example shown in the figures) formed in the base wall  717  of the connection case  715 , some of the male terminal piercing holes  719  are made into reference holes  720  smaller than the other male terminal piercing holes  719  so that the circuit-forming unit  721  can be accurately positioned and mounted when the circuit-forming unit  721  is mounted to the base wall  717  of the connection case  715 . 
   More specifically, for example, in the example shown in  FIG. 39 , among the 100 male terminal piercing holes  719 , five male terminal piercing holes  719  are made to have a smaller shape than the other male terminal piercing holes  719 , whereby reference holes  720   a ,  720   b , and  720   c  are formed. That is, the reference hole  720   a  is formed by making smaller the male terminal piercing hole  719  that is formed in the vicinity of the center of the base wall  717  of the connection case  715 . The reference holes  720   b  are formed by making smaller two male terminal piercing holes  719  that are at a plurality of positions radially spaced from the reference hole  720   a , the vicinity of the center of the connection case, each one of which is respectively in the left and right peripheral portions (left and right side end portions) spaced along the X-axis in the example of the figure. In addition, the reference holes  720   c  are formed by making smaller two male terminal piercing holes  719  that are at a plurality of positions radially spaced from the reference hole  720   a , the vicinity of the base wall of the connection case, each one of which is respectively in the upper and lower peripheral portions (upper and lower end portions) spaced along Y-axis in the example of the figure. 
   The male terminal piercing holes  719  and reference holes  720  are formed to have an angular cross-sectional shape, and except the reference holes  720   b  and  720   c , the male terminal piercing holes  719  and the reference hole  720   a  are formed to have a squared cross-sectional shape. Except for the reference hole  720 , the male terminal piercing holes  719  are formed in a squared cross-sectional shape with a size having a gap such that the male terminals  723  can be easily inserted therein. 
   Although the reference hole  720   a  has a squared cross-sectional shape, its axis diametrical size along the X-axis and its axis diametrical size along the Y-axis are made shorter than those of the other male terminal piercing holes  719  except the reference hole  720 , so it is formed smaller. This reduces the vertical and horizontal clearances of the male terminal  723  that passes through the reference hole  720   a , suppressing side-to-side rattling (backlash) of the male terminal  723  in the X-axis direction and the Y-axis direction. 
   Likewise, the two reference holes  720   b  on the right and left are formed small such that their axis diametrical size along the Y-axis is smaller than the axis diametrical size along the corresponding axis (Y-axis) of the other male terminal piercing holes  719  except the reference holes  720 ; this reduces the clearances with the male terminals  723  along the Y-axis, thereby suppressing side-to-side rattling (backlash) of the male terminals  723  that are inserted in the reference holes  720   b  more reliably, with respect to the Y-axis direction. On the other hand, their axis diametrical size with respect to the X-axis is not different from the axis diametrical size of the male terminal piercing holes  719  other than that of the reference holes  720  with respect to the corresponding axis (X-axis). Therefore, these reference holes  720   b  have a rectangular shape with long sideways, and some margin is created in the clearances between the reference holes  720   b  and the male terminals  723  with respect to the X-axis. For this reason, the male terminals  723  can be easily passed through the reference holes  720   c  even when a positional deviation with respect to the X-axis is caused between the male terminal piercing holes  719  and the male terminals  723  opposed to each other as the amount of pitch variation with respect to the X-axis between the male terminal piercing holes  719  and the male terminals  723  is accumulated as they are spaced farther from the respective central areas of the base wall  717  of the connection case  715  and the circuit-forming unit  721  in the X-axis direction. 
   Moreover, the reference holes  720   c  at the top and bottom are formed small such that their axis diametrical size with respect to the X-axis is shorter than the axis diametrical size of the other male terminal piercing holes  719  except the reference holes  720  with respect to the corresponding axis (X-axis); this reduces the clearance with the male terminals  723  with respect to the X-axis, thereby suppressing side-to-side rattling (backlash) of the male terminals  723  inserted into the reference holes  720   c  more reliably with respect to the X-axis. On the other hand, their axis diametrical size with respect to the Y-axis is not different from the axis diametrical size of the male terminal piercing holes  719  other than the reference holes  720  with respect to the corresponding axis (Y-axis). Therefore, these reference holes  720   c  have a vertically long rectangular shape, and some margin is created in the clearances between the reference holes  720   c  and the male terminals  723  with respect to the Y-axis. For this reason, the male terminals  723  can be easily passed through the reference holes  720   c  even when a positional deviation with respect to the Y-axis is caused between the male terminal piercing holes  719  and the male terminals  723  that are opposed to each other since the amount of pitch variation with respect to the Y-axis between the male terminal piercing holes  719  and the male terminals  723  is accumulated as they are spaced farther from the vicinity of the centers of the base wall  717  of the connection case  715  and the circuit-forming unit  721  in the Y-axis direction. In this way, when mounting the circuit-forming unit  721  to the base wall  717  of the connection case  715 , the circuit-forming unit  721  can be accurately positioned. In addition, mounting of the circuit-forming unit  721  can be made easily, and efficiency in manufacturing (assembling) the joint connector  711  can be improved. It should be noted that the shapes of the male terminal piercing holes  719  and the reference holes  720  may be such shapes as a circular cross-sectional shape and an elliptic cross-sectional shape, other then the angular cross-sectional shape such as a squared cross-sectional shape, a rectangular cross-sectional shape, and a triangular cross-sectional shape. 
   The reference holes  720  may be such a hole/holes as formed small only among one or a plurality of the male terminal piercing holes  719  that are formed in the vicinity of the center of the base wall  717  of the connection case  715 , other than those shown in  FIG. 39 . In addition, they may be such a hole/holes formed small out of only one or a plurality of the male terminal piercing holes  719  that are spaced radially (along the X-axis, the Y-axis, or the X and Y axes) from the vicinity of the center of the base wall  717  to arbitrary positions. Further, they may be such a hole/holes formed small out of the male terminal piercing holes  719  formed in the vicinity of the center and the male terminal piercing holes  719  formed at one or a plurality of positions that are spaced to arbitrary positions along the X-axis, the Y-axis, or the X and Y axes. 
   When one reference hole  720  is formed to be small out of the male terminal piercing holes  719 , it is desirable to make its axis diametrical size with respect to the X-axis and its axis diametrical size with respect to the Y-axis smaller than those of the male terminal piercing holes  719  other than the reference hole  720 . Even in cases where a plurality of reference holes  720  are arranged spaced from each other, if they are arranged only on the X-axis or on the Y-axis, their axis diametrical size with respect to the X-axis and their axis diametrical size with respect to the Y-axis are made smaller than those of the male terminal piercing holes  719  other than the reference holes  720 , as in the case of only one reference hole. 
   Thus, by forming some of the male terminal piercing holes  719  to be reference holes  720 , which are smaller than the other male terminal piercing holes  719  among the plurality of male terminal piercing holes  719  formed in the base wall  717  of the connection case  715 , the reference holes  720  and the male terminals  723  passing through the reference holes  720  can be utilized as the conventional positioning hole and the conventional positioning protrusion, respectively. Consequently, when mounting the circuit-forming unit  721  to the base wall  717  of the connection case  715 , the male terminals  723  are passed through the reference holes  720  at small clearances so that the circuit-forming unit  721  can be quickly guided and held in a predetermined location. Thereby, the circuit-forming unit  721  can be accurately positioned without additionally providing the positioning protrusions and the positioning holes that have been required conventionally. As a result, when the circuit-forming unit  721  is mounted to the base wall  717 , the male terminals  723  protruding in the connection case  715  do not deviate from predetermined locations, and when the external connector  713  is inserted into the joint connector  711 , the male terminals  723  and the female terminals are aligned so that poor connections between both terminals are prevented. Thus, performance and reliability of the joint connector  711  can be improved. 
   Moreover, it becomes unnecessary to provide a space for providing the positioning protrusion in the base wall  717  of the connection case  701  and a space for forming the positioning hole in the holder  725  of the circuit-forming unit  721 , and in addition, it is unnecessary to form the shape of the circuit pattern on the holder  725  so that the wiring greatly extends outwardly to get around the positioning hole. Therefore, the shapes of the connection case  715  and the circuit-forming unit  721  become smaller, thus making the joint connector  711  small and lightweight. Furthermore, since the shapes of the connection case  715  and the circuit-forming unit  721  become smaller and the positioning protrusion is eliminated, cost of the materials can be reduced and accordingly the cost of the joint connector  711  can be reduced. 
   Further, because the reference hole  720  is formed to be small out of the male terminal piercing holes  719  formed in the vicinity of the center of the base wall  717  of the connection case  715 , the reference hole  720  is formed at a location in the vicinity of the center of gravity of the circuit-forming unit  721 . Therefore, the circuit-forming unit  721  can be positioned in a well-balanced manner, and the circuit-forming unit  721  can be easily mounted to the base wall  717  of the connection case  715 . 
   In addition, since the reference holes  720  is formed to be small out of the male terminal piercing holes  719  formed at a plurality of positions radially spaced from the vicinity of the center of the base wall  717  of the connection case  715 , the circuit-forming unit  721  can be positioned in a well-balanced manner and the accuracy in the positioning can be improved even when the number of the male terminals  723  in the circuit-forming unit  721  is increased. 
   Moreover, the reference holes  720  ( 720   b  and  720   c ) are the male terminal piercing holes  719  formed at a plurality of positions radially spaced from the vicinity of the center of the base wall  717  of the connection case  715 , and they are formed to be small by making their axis diametrical size with respect to the Y-axis of the male terminal piercing holes  719  formed at locations spaced along the X-axis and their axis diametrical size with respect to the X-axis of the male terminal piercing holes  719  formed at locations spaced along the Y-axis shorter than the respective axis diametrical sizes with respect to the corresponding axes of those male terminal piercing holes  719  other than the reference holes  720 . Therefore, side-to-side rattling (backlash) of the male terminal  723  inserted into the reference holes  720  ( 720   c  and  720   c ) can be suppressed with respect to the X-axis direction and the Y-axis direction, and the circuit-forming unit  721  can be accurately positioned. 
   Furthermore, since the axis diametrical size with respect to the X-axis of the reference holes  720   b  formed on the X-axis and the axis diametrical size with respect to the Y-axis of the reference holes  720   c  formed on the Y-axis are not different from the corresponding axis diametrical sizes of the other male terminal piercing holes  719 , some margin is created in the clearance between the reference holes  720   b  and the male terminals  723  with respect to the X-axis and in the clearance between the reference holes  720   c  and the male terminals  723  with respect to the Y-axis. Thus, even when a positional deviation is caused between the male terminal piercing holes  719  and the male terminals  723  in the X-axis or Y-axis direction, the male terminals  723  of the circuit-forming unit  721  can be passed through the reference holes  720  ( 720   b  and  720   c ) not forcibly in mounting the circuit-forming unit  721  to the base wall  717  of the connection case  715 ; thus mounting of the circuit-forming unit can be made easy. 
   The joint connector  711  of the present invention has such a configuration as described above. When using the joint connector  711 , the external connector  713  is opposed to the connector accommodating compartment  737  of the connection case  715  in the joint connector  711 , then the centers of the joint connector  711  and the external connector  713  are aligned, and the external connector  713  is inserted into the connector accommodating compartment  737  of the joint connector  711 . Then, the claws  736  of the engaging claw portions  735  on the joint connector  711  side are engaged with the engagement recess portions  733  on the external connector  713  side to lock the external connector  713  with the joint connector  711 , and meanwhile, the male terminals  723  on the joint connector  711  side are inserted into the female terminals on the external connector  713  side to make connection. 
     FIG. 41  shows, in the joint connector  711  of the embodiment depicted in, for example,  FIGS. 38 through 40 , guide grooves  745  having, for example, a V-shaped cross-sectional shape provided along the direction in which the external connector  713  is inserted and at four locations on the outer peripheral surface of the connection case  715 , that is, at respective four locations on both side faces along the X-axis and on the top and bottom faces along the Y-axis direction. These guide grooves  745  are provided for smoothly inserting a continuity testing jig (not shown) into the joint connector  711  while aligning their center axes, and the continuity testing jig is provided with guiding projections having a V-shaped cross-sectional shape that fits to the guide grooves  745 . 
   It should be noted that guiding projections may be provided in place of the guide grooves  745  and the continuity testing jig may be provided with guide grooves. Also, the shapes of the guide grooves and the guiding projections are not restricted to the V-shaped cross-sectional shape, and may be such a shape as a semi-circular cross-sectional shape, a U-shaped cross-sectional shape, a T-shaped cross-sectional shape, an angular C-shaped cross-sectional shape, a dovetail groove-shaped cross-sectional shape. Moreover, the number of the guide grooves  745  and the guiding projections may be only one or more than one (may be other than four as described above). The other configurations are the same as illustrated in  FIGS. 38 through 40  and are not further elaborated on. 
   Thus, by providing the guide grooves  745  or the guiding projections, a continuity testing jig can be smoothly and accurately inserted when inserting the testing jig to test the continuity of the joint connector  711 , and the testing accuracy for the joint connector  711  can be improved. 
   Next, a joint connector according to a fifth embodiment of the present invention is described in detail with reference to the drawings. 
     FIG. 42  is a perspective view showing a connector housing  812  constituting a joint connector  810  (see  FIG. 51 ) according to the fifth embodiment of the present invention.  FIG. 43A  is a perspective view of the connector housing  812  of  FIG. 42 , viewed from its reverse side, and  FIG. 43B  is a perspective view of the connector housing  812  of  FIG. 43A , viewed from its back.  FIG. 44  is a cross-sectional view taken along line X-X in  FIG. 42 . 
   The joint connector  810  according to the fifth embodiment of the present invention is a stacked joint connector provided with a plurality of connector housings  812  and connector housing-locking means  814  and  816  for stacking and combining these connector housings  812  into a plurality of stages in a vertical direction. 
   The connector housing  812  is provided with, as specifically shown in  FIGS. 42 and 43 , a plurality of terminal-accommodating compartments  822  (10 compartments in the example shown in the figures) juxtaposed in a single layer in a lateral direction, which are for accommodating a plurality of female connecting terminals  820  (10 terminals in the example shown in the figure) connected to electric wires  818  constituting a wire harness or the like by crimping or the like (see  FIGS. 45 and 46  etc.). The housing is formed into a thick-walled rectangular plate-like block by a plastic molding process. Both side portions thereof are provided with flange portions  824  (including such flange portions  824  formed of both of the side portions themselves) for smoothly inserting and guiding the joint connector  810  into a mating connector  811  (see  FIG. 51 ) in a protruding manner. Each of the flange portions  824  is provided with a lock groove  826  for locking the joint connector  810  with the mating connector  811  to prevent their disengagement. 
   At the rear of the flange portion  824 , an interlocking tab  825  projecting in a vertical direction is formed so that, when the joint connector  810  is fitted to a later-described mating connector  811  (see  FIGS. 51 and 52 ), it engages with a groove width-widened portion  866   a  formed at the entrance side of a guide groove  866  in a connector case  864  of the connector  811 , whereby the rear portion of the connector housing  812  of the joint connector  810  do not become wobbly. The joint connector  810  is assembled, as shown in  FIG. 51 , in such a manner that the connector housings  812  having the same structure and size are stacked, for example, into 10 stages in a vertical direction and are combined, and a rectangular plate-like cover  828  having a matching size to the size of the connector housing  812  is attached on the uppermost stage connector housing  812 . It should be noted that both side portions of the cover  828  is also provided with flange portions  824  in a protruding manner, and a lock groove  826  is provided thereon. 
   The connector housing  812  is as follows. The rear of the terminal-accommodating compartments  822  is opened upwardly. On one wall at the front of the terminal-accommodating compartment  822 , that is, on an upper wall  822   a , a lance  832  is provided, which, for example, has a straddle structure in which its base end is supported on the upper wall  822   a  by a pair of slits  830  (see  FIG. 42 ) formed along the longitudinal direction of the terminal-accommodating compartments  822 . The lance  832  also has a built-up portion  834  (see  FIGS. 44 through 46  etc.) thick-walled and formed on the back side, and an interlocking claw  836 , formed on the inner side, for engaging with a tab-like interlock receptor portion  820   a  (see  FIG. 45 ) protruding on the upper portion of the fore-end of the connecting terminal  820 . The lance  832  is composed of an elastic interlocking piece made of plastic. 
   As shown in  FIGS. 44 through 46  etc., on the other wall opposite to the terminal-accommodating compartment  822  corresponding to the location of the lance  832 , that is, on the lower wall  822   b , a lance-receiving portion  838  is provided. The lance-receiving portion  838  receives the lance  832 &#39;s built-up portion  834  that is slightly lifted upwardly by the interlocking claw  836  brought into contact with the interlock receptor portion  820   a  of the connecting terminal  820 , when a connecting terminal  820  is inserted into a terminal-accommodating compartments  822  of another adjacent (lower stage) connector housing  812  (see  FIG. 45 ), to permit the lance  832  to dislocate outwardly. The lance-receiving portion  838  is formed of a slit-like thin hole. Since the interlock receptor portion  820   a  of the connecting terminal  820  engages with the interlocking claw  836  of the lance  832 , the built-up portion  834  of the lance  832  is lowered, and thus, the connecting terminal  820  is engaged and fixed with the lance  832  so as not to disengage from the terminal-accommodating compartment  822 . Although the lance-receiving portion  838  is described as a thin hole in the example shown in the figures, it may be formed of a recessed groove (closed-end hole), not a hole, if a sufficient strength of the lance  832  is maintained and the size of the built-up portion  834  can be reduced. In addition, the configuration and the location of the lance  832  to be provided are not limited to those described above. 
   As shown in  FIGS. 43A ,  43 B, and  44  through  46 , in the connector housing  812 , an interlocking protrusion  840  having, for example, an angular shape is protruded on an outside (lower side) of the lower wall  822   b  that is located further rearward of the lance  832  of the terminal-accommodating compartment  822 . Since the interlocking protrusion  840  comes into contact and engages with the engaging portion  820   b  of a connecting terminal  820  accommodated in another (lower stage) connector housing  812  stacked on the connector housing  812 , it is made possible to prevent disengagement of the connecting terminal  820  from the terminal-accommodating compartment  822  (double interlocking function is achieved together with the disengagement prevention by the lance  832 ), and to detect an detecting incomplete insertion. 
   As shown in  FIG. 44  through  FIG. 46 , a terminal-guiding slope portion  842  projecting downwardly is provided on the lower wall  822   b  of the terminal-accommodating compartment  822  and in the vicinity of the terminal insertion hole  823  formed at the rear of the terminal-accommodating compartment  822  of the connector housing  812 . Each of the corresponding upper portions of both side walls  822   c  in the vicinity of the terminal insertion hole  823  is provided with an undercut  844  for engaging with the terminal-guiding slope portion  842 . Thus, when stacking connector housings  812 , an undercut  844  of one of the connector housings  812  is engaged with a terminal-guiding slope portion  842  of another (upper stage) connector housing  812  to be stacked thereon. 
   By providing such a terminal-guiding slope portion  842  and an undercut  844 , a connecting terminal  820  can be easily inserted into the terminal-accommodating compartment  822  of the connector housing  812  by being guided by the terminal-guiding slope portion  842  of the terminal insertion hole  823  without causing an electric wire  818  to be compress-buckled or bent-deformed, even when it is connected to such an electric wire  818  easily bent-deformed or compress-buckled due to its small size and diameter. 
   In addition, a stopper member  846  formed of a laterally-long piece is provided so as to cover an upper opening of the terminal insertion hole  823  in the connector housing  812  and straddle over the upper portions of both side walls  822   c  of the terminal-accommodating compartments  822  that are above the terminal insertion holes  823 . The corresponding lower portions of both side walls  822   c  of the terminal-accommodating compartment  822  is provided with a cut-out  848  for receiving the stopper member  846  so that the cut-out  848  of one of the connector housing  812  is engaged with the stopper member  846  of another (lower stage) connector housing  812  to be stacked when stacking the connector housings  812 . 
   Thus, by providing the stopper member  846  over the opening of the terminal insertion hole  823 , as shown in  FIG. 45 , the electric wire  818  is not lifted in an upward direction even when a tensile force acts on the electric wire  818  in an upward direction after the connecting terminal  820  are inserted and accommodated in the terminal-accommodating compartment  822 , and the rear side of the lance  832  and the connecting terminal  820  in the connector housing  812  can be prevented from breakage. Furthermore, the stopper member  846  restricts the inserting direction of the connecting terminal  820  from the terminal insertion hole  823 . Therefore, even if the connecting terminal  820  is, as shown in  FIG. 46 , inserted upside down into the terminal-accommodating compartment  822 , the inserting direction shifts diagonally upwardly in the figure by the stopper member  846  and thus the fore-end of the connecting terminal  820  comes into contact with the rear portion of the lance  832 , which makes the insertion impossible. Therefore, it becomes possible to detect upside-down insertion of the connecting terminal  820  into the terminal-accommodating compartment  822  quickly to reliably prevent the connecting terminal  820  from being accommodated in the terminal-accommodating compartment  822  upside down. It should be noted that reference numeral  850  denotes a small diameter terminal insertion hole formed on a front wall  822   d  of the terminal-accommodating compartment  822 , for inserting connecting terminals  870  of a mating connector (see  FIG. 51 ). 
   The connector housing-locking means  814  comprise, as shown in  FIGS. 42 through 44 , interlocking recess portions  852  provided at the front of both side portions in the connector housing  812 , for example, on upper portions of the flange portion  824 , and corresponding interlocking protrusion portions  854  provided, for example, on lower portions of the flange portions  824 . It is configured so that the interlocking recess portions  852  provided for one of (lower stage) connector housings  812  are engaged with interlocking protrusion portions  854  provided for another one of (upper stage) connector housings  812  to be stacked thereon. More specifically, each interlocking recess portion  852  has an angular C-shaped recessed groove  852   a  opened in a lateral direction. The interlocking protrusion portion  854  has a lateral interlocking piece  854   a  extending forward and rearward, for being loosely inserted in the recessed groove  852   a  of the interlocking recess portion  852  and engaging therewith, and a vertical interlocking piece  854   b  capable of contacting the interlocking recess portion  852 ; and it is formed into a substantially L-shape by the lateral interlocking piece  854   a  and the vertical interlocking piece  854   b . The fore-end of the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  is disposed facing forward so as to oppose the recessed groove  852   a  of the interlocking recess portion  852 . 
   The connector housing-locking means  816  comprise, as shown in  FIG. 42  through  FIG. 44 , interlocking recess portions  856  provided at the rear of on both side portions of the connector housing  812 , for example, on upper portions of the flange portion  824 , and corresponding interlocking protrusion portions  858  provided, for example, on lower portions of the flange portions  824 . It is configured so that the interlocking recess portions  856  provided for one of (lower stage) connector housings  812  are engaged with the interlocking protrusion portions  858  provided for another one of (upper stage) connector housings  812  to be stacked thereon. More specifically, the interlocking recess portions  856  each has an angular C-shaped recessed groove  856   a  opened in a lateral direction. The interlocking protrusion portions  858  are each composed of a linear interlocking piece  858   a  projecting downwardly from the flange portion  824 , and a claw  858   b  formed at its fore-end and facing inward, for engaging with the recessed groove  856   a  of the interlocking recess portion  856 . 
   Play gaps are provided between interlocking surfaces of the interlocking recess portion  852  and the interlocking protrusion portion  854  engaging therewith in the connector housing-locking means  814 , and between interlocking surfaces of the interlocking recess portion  856  and the interlocking protrusion portion  858  engaging therewith in the connector housing-locking means  816 , to loosely engage them with each other. Thus, a plurality of connector housings  812  are relatively shiftable and loosely combined to form an accordion structure. 
   Further, as shown in  FIGS. 42 ,  43 A, and  43 B, rectangular guiding recessed grooves  860  for constraining a relative shift between the stacked connector housings  812  are provided, for example, on upper portions of the flange portions  824  and between the connector housing-locking means  814  and  816  provided at the front and the back of the both side portions of the connector housing  812 . Also, the corresponding lower portions of the flange portions  824  are provided with rectangular plate-shaped guide ribs  862  protruding downwardly so as to be fitted to the guiding recessed groove  860 . Respective rear portions of the guiding recessed grooves  860  and the guide ribs  862  are formed into inclined surfaces  860   a  and  862   a  widening toward their bottoms. The guiding recessed grooves  860  of one of connector housings  812  are engaged with the guide ribs  862 , which are inserted therein, of another one of (upper stage) connector housings  812  to be stacked thereon. 
   By providing the guiding recessed grooves  860  and the guide ribs  862 , relative shifting between the stacked and combined connector housings  812  is more reliably constrained by the guide ribs  862 , and in addition, backlash is suppressed by the contact between the inclined surfaces  860   a  and  862   a  of the guiding recessed groove  860  and the guide rib  862 . Moreover, when stacking a connector housing  812  from an inclined posture, the guide ribs  862  do not hit the inner periphery of the guiding recessed grooves  860 , and they can be smoothly fitted; thus, workability in stacking the connector housings  812  can be improved. 
   When the connector housings  812  are stacked into a plurality of stages, for example, into 10 stages and combined by the connector housing-locking means  814  and  816  to assemble the joint connector  810 , the connecting terminals  820  connected to the electric wires  818  are inserted and accommodated in advance from the terminal insertion holes  823  into the terminal-accommodating compartments  822  of the connector housing  812  that is disposed at the lowermost stage. In the present embodiment, the connecting terminals  820  are not inserted deeply to a predetermined location in the terminal-accommodating compartments  822  and are accommodated in an incompletely inserted state, so a condition in which they are not engaged with the lances  832  is shown. Then, a connector housing  812  to be stacked for the second lowermost stage (upper stage) is arranged in an inclined state while being shifted slightly rearward so that its front side is lowered diagonally downwardly with respect to the lowermost stage (lower stage) connector housing  812  (see  FIGS. 47A and 47B ). 
   Next, in this state, the upper stage connector housing  812  is lowered while being maintained to be in the inclined state and brought closer to the lower stage connector housing  812 , so that the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  in the connector housing-locking means  814  provided on the front side of the upper stage connector housing  812  to be stacked is loosely inserted into the recessed groove  852   a  of the interlocking recess portion  852  in the connector housing-locking means  814  provided on the front side of the lower stage connector housing  812 , to loosely engage the interlocking recess portion  852  and the interlocking protrusion portion  854  with each other in the connector housing-locking means  814  (see  FIGS. 48A , and  48 B). 
   Subsequently, the upper stage connector housing  812  is shifted forward and at the same time is rotated so as to be parallel to the lower stage connector housing  812  (clockwise in  FIG. 49 ), using the connector housing-locking means  814  as a supporting point. In that process, the interlocking protrusion  840  protruding on the upper stage connector housing  812  is brought into contact and engaged with the engaging portion  820   b  of the connecting terminal  820  accommodated in the terminal-accommodating compartment  822  in an incompletely inserted state, and by this interlocking protrusion  840 , the connecting terminal  820  is pushed deeply into the terminal-accommodating compartment  822 , accompanying the shift of the upper stage connector housing  812 . Meanwhile, a portion (fore-end portion) of the guide rib  862  provided for the upper stage connector housing  812  is inserted into the guiding recessed groove  860  provided for the lower stage connector housing  812 , and at the rear, the interlocking recess portion  856  of the connector housing-locking means  816  and the interlocking protrusion portion  858  are brought into a semi-engaged state (see  FIGS. 49A , and  49 B). 
   Next, from the state described above, the upper stage connector housing  812  is further shifted forward until the vertical interlocking piece  854   b  of the interlocking protrusion portion  854  comes into contact with the recessed groove  852   a  of the interlocking recess portion  852  in the connector housing-locking means  814  at the front, so as to be stacked on the lower stage connector housing  812 . At the front, the interlocking recess portion  852  is engaged with the interlocking protrusion portion  854  in the connector housing-locking means  814  at the front, while at the rear, the interlocking recess portion  856  is engaged with the interlocking protrusion portion  858  in the connector housing-locking means  816 , whereby the adjacent upper and lower stage connector housings  812  are combined with each other. With the completion of stacking the connector housings  812 , the connecting terminal  820  is inserted to a predetermined designed location in the terminal-accommodating compartment  822  and accommodated therein, and the interlock receptor portion  820   a  of the connecting terminals  820  engages with the interlocking claw  836  of the lance  832 , fixing the connecting terminal  820  so as not to be disengaged from the terminal-accommodating compartment  822 . At the same time, the terminal-guiding slope portion  842  engages with the undercut  844 , the stopper member  846  engages with the cut-out  848 , and the guide rib  862  engages with the guiding recessed groove  860  (see  FIGS. 50A and 50B ). 
   When the stacking operation finishes for the second lowermost stage (upper stage) connector housing  812  against the lowermost stage connector housing  812  in the manner described above, another set of connecting terminals  820  are inserted into the terminal-accommodating compartments  822  of the upper stage connector housing  812 , and thereafter, the third lowermost connector housing  812  is stacked on the upper stage connector housing  812  and is combined by connector housing-locking means  814  and  816  in a similar manner. Subsequently, similar operations are repeated and the connector housings  812  are stacked and combined into 10 vertical stages to assemble the joint connector  810  as shown in  FIG. 51 . 
   It should be noted that in the foregoing embodiment, each time one layer of connector housing  812  is stacked, connecting terminals  820  are inserted in the terminal-accommodating compartments  822  of the connector housing  812  stacked on the upper stage; however, it is possible to accommodate connecting terminals  820  in advance in the terminal-accommodating compartments  822  of the upper stage connector housing  812  before stacking an upper stage connector housing  812  on a lower stage connector housing  812 , and to stack the upper and lower stage connector housings  812  each other in which connecting terminals  820  have been accommodated, in assembling the joint connector  810 . This way of assembling is preferable, since the stacking operation of the connector housings  812  becomes easy and work efficiency improves, and moreover, especially when it is necessary to insert connecting terminals  820  connected to such electric wires  818  having a small diameter and being easily bent into the terminal-accommodating compartments  822  of a connector housing  812 , the terminals can be inserted while being guided by the terminal-guiding slope portions  842  provided for the terminal insertion holes  823 , which reduces cumbersome work necessary for inserting the connecting terminal  820 . 
   In the foregoing embodiment, the interlocking recess portion  852  of the connector housing-locking means  814  provided at the front on both side portions of the connector housing  812  is provided on an upper portion of the housing  812 , and the corresponding lower portion is provided with the interlocking protrusion portion  854 ; however, it is possible to provide the interlocking recess portion  852  on an lower portion of the housing  812  and to provide the corresponding upper portion of the housing  812  with the interlocking protrusion portion  854 . In this case, the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  is disposed facing rearward so as to oppose the recessed groove  852   a  of the interlocking recess portion  852 . When stacking the connector housings  812 , the recessed groove  852   a  of the interlocking recess portion  852  of the connector housing-locking means  814  in the upper stage connector housing  812  that is disposed in an inclined state in which its front is lowered diagonally downwardly is relatively loosely inserted into the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  of the connector housing-locking means  814  in the lower stage connector housing  812 . The upper stage connector housing  812  is shifted forward and is rotated so as to be parallel to the lower stage connector housing  812 , using the connector housing-locking means  814  as a supporting point. Thus, the housings are stacked in a similar way. 
   Thus, the interlocking recess portion  852  of the connector housing-locking means  814  provided at the front of both side portions of the connector housing  812  has a recessed groove  852   a  opened in a lateral direction, and the interlocking protrusion portion  854  has a lateral interlocking piece  854   a  extending forward and rearward, for being loosely inserted in the recessed groove  852   a  of the interlocking recess portion  852  and engaging therewith, and a vertical interlocking piece  854   b  capable of contacting the interlocking recess portion  852 , the interlocking protrusion portion being formed into a substantially L-shape by the lateral interlocking piece  854   a  and the vertical interlocking piece  854   b . When stacking the connector housings  812  into a plurality of stages and combining them by the connector housing-locking means  812  and  814  to assemble the joint connector  810 , with respect to one of the connector housings  812 , the other one of the connector housings  812  to be stacked is disposed in an inclined state such that its front is lowered diagonally downwardly while being shifted slightly rearward. In a posture of such an inclined state, the other one of the connector housings  812  is brought closer to the one of the connector housings  812 , and the recessed groove  852   a  of the interlocking recess portion  852  or the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  in the connector housing-locking means  814  that is provided at the front of the one of the connector housings  812  is relatively loosely inserted into the lateral interlocking piece  854   a  of the interlocking protrusion portion  854  or the recessed groove  852   a  of the interlocking recess portion  852  of the connector housing-locking means  814  in the connector housing-locking means  814  that is provided at the front of the other one of the connector housings  812 . Then, the other one of the connector housings  812  is shifted forward and is rotated so as to be parallel to the one of the connector housings  812 , using the connector housing-locking means  814  at the front as a supporting point, and to be overlapped with the one of the connector housings  812 . 
   In that process, the interlocking protrusion  840  protruding on the other one of the connector housings  812  is engaged with the engaging portion  820   b  of the connecting terminal  820  accommodated in the terminal-accommodating compartment  822  of the one of the connector housings  812  in an incompletely inserted state. By this interlocking protrusion  840 , the connecting terminal  820  can be inserted deeply into the terminal-accommodating compartment  822 , accompanying the shifting of the other one of the connector housings  812 . As a result, in stacking the connector housings  812 , even when connecting terminals  820  are accommodated in terminal-accommodating compartments  822  in an incompletely inserted state, those connecting terminals  820  can be quickly straightened in a desired normal inserted state to accommodate them in a predetermined location. Thus, connection performance and reliability in the connector can be improved, and in addition, being small-sized, assembling for various equipment can be carried out efficiently without cumbersome work. 
   To connect the above-described joint connector  810  with a mating connector  811 , as shown in  FIG. 51 , the joint connector  810  and the mating connector  811  are opposed to each other and disposed so that their centerlines match. Next, the flange portions  824  protruding on both side portions of the connector housings  812  and the cover  828  constituting the joint connector  810  are made to support by a plurality of substantially angular C-shaped guide grooves  866  formed in both inner side walls of the connector case  864  of the mating connector  811 , and, while slide-guiding along the guide grooves  866 , the joint connector  810  is inserted and fitted into the connector case  864  of the mating connector  811 . Then, elastic interlocking claws  868  formed at, for example, the third and eighth stages among the guide grooves  866  of the mating connector  811  are engaged with two corresponding lock grooves  826  provided on the flange portions  824  of the joint connector  810 , to fix the joint connector  810  so as not to disengage from the mating connector  811  (see  FIG. 52A ). 
   With the fitting of the joint connector  810  to the mating connector  811 , a plurality of pin-shaped (male) connecting terminals  870  mounted to the mating connector  811  and protruding in the connector case  864  are inserted into connecting terminals  820  accommodated in the terminal-accommodating compartments of the connector housings  812  in the joint connector  810 , establishing electrical contact with the terminals  820 . Thus, the joint connector  810  is connected to the mating connector  811 . 
   It should be noted that, as shown in  FIG. 52B  and  FIG. 52C , an interlocking tab  825  formed at the rear of a flange portion  824  of a connector housing  812  in the coupling joint connector  810  engages with a groove width-widened portion  866   a  formed near the entrance of the guide groove  866  in the connector case  864  of the mating connector  811  when the joint connector  810  is fitted to the mating connector  811 , so that the rear portion of the connector housing  812  in the joint connector  810  does not become wobbly. Thus, it is preferable that the interlocking tab  825  is made to engage with the groove width-widened portion  866   a  in this way since the backlash of the connector housings  812  can be prevented in the joint connector  810  fitted to the mating connector  811 , and reliability in the connector&#39;s connection can be further improved even when the joint connector  810  has an accordion structure in which the connector housings  812  are loosely combined to be shiftable relative to each other. 
   Only selected embodiments have been chosen to illustrate the present invention. To those skilled in the art, however, it will be apparent from the foregoing disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention is provided for illustration only, and not for limiting the invention as defined by the appended claims and their equivalents.