Patent Publication Number: US-6699079-B2

Title: Electric connector permitting testing of electric conductivity of terminals in provisional locking position

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. Ser. No. 09/868,064, filed Aug. 30, 2001, pending; which is a U.S. national phase application of international application No. PCT/JP99/07075 filed Dec. 16, 1999, which application was not published in English. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an electrical connector, which may be used for a wire harness in automobiles, and more particularly relates to an electrical connector, in which connecting terminals contained in a housing are locked by a rear holder which is engaged with a rear portion of the housing. 
     (2) Description of Related Art 
     In conventional electrical connectors for use in a wire harness, connecting terminals installed within a housing are locked in position by means of flexible locking arms. In general, the locking arms are formed integrally with the housing. Therefore, the housing including the locking arms is liable to be complicated in construction, and a mold for manufacturing the housing becomes very complicated and expensive. Since each locking arms are formed within respective connecting terminal accommodating holes, a width of a locking arm has to be much smaller than a width of a connecting terminal accommodating hole and a sufficiently large locking force could not be attained. 
     In order to improve the difficulty in manufacturing the housing as well as to increase a size of the locking arms, there has been proposed to form locking arms in a separate rear holder as illustrated in FIGS. 1 and 2. In this known electrical connector, a rear holder c is inserted into an opening b formed in a housing a such that the rear holder is clamped at two positions with respect to the housing a by means of locking means not shown. A first position is a provisional locking position in which the rear holder c is halfway inserted into the housing a, and a second position is a complete locking position in which the rear holder c is completely inserted into the housing a. 
     At the provisional locking position, a connecting terminal e having an electric wires d connected thereto is inserted into a rectangular hollow portion f of the rear holder c such that a projection i of a locking arm h is engaged with an opening g formed in the connecting terminal e. When the rear holder c is further inserted into the housing up to the complete locking position, front ends j of the locking arms h ride over guide portions k of the housing a and a locking force of the locking arms h is increased. 
     However, in the known electrical connector, since the rear holder c includes the rectangular hollow portions f, a structure of a mold or tool for manufacturing the rear holder could not be simplified sufficiently. That is to say, the mold must be constructed to have one or more bushings and still has a complicated structure. When it is required to release a locking condition between a locking arm h and a connecting terminal e, a special tool has to be inserted into a rectangular hollow portion f from a rear end of the rear holder c, and thus the rear holder c and connecting terminal e might be injured by the tool. 
     Similarly, in the known electrical connector having the locking arms integrally formed with the housing, when it is required to remove a connecting terminal from the housing, a special tool has to be inserted into the housing from a rear end of the housing along an electric conductor or from a front end through an opening into which connecting terminals of a corresponding electrical connector have to be inserted, and the locking arm is resiliently bent by the tool to release a locking condition between the locking arm and the connecting terminal. Then, the electrical conductor is pulled to remove the connecting terminal from the housing. 
     Moreover, each of the above mentioned known electrical connectors is composed of a number conductors connected to a wire harness, connecting terminals and housing, and therefore in order to prevent an erroneous connection of wire harnesses, it is necessary to perform an electrical conduction test. Upon conducting the electrical conduction test, after all the connecting terminals have been inserted into the housing, an electrical conduction testing tool is inserted into the housing from the front side opening through which connecting terminals of a corresponding electrical connector are to be inserted into the housing, and the testing tool is engaged with the connecting terminals. 
     As explained above, in case of releasing a locking condition between a connecting terminal and a locking arm, since the releasing tool must be inserted into the housing from the front side opening of the housing, the inserting operation is liable to be difficult and the housing and connecting terminals might be damaged by the tool. Furthermore, upon performing the electrical conduction test, the testing tool must be inserted into the housing from the front side opening such that the tool is engaged with the connecting terminals, it is required to insert the testing tool with a relatively large force. Furthermore, if connecting terminals of a corresponding electrical connector have been inserted into the housing, it is necessary to remove them before conducting the electrical conduction test. 
     SUMMARY OF THE INVENTION 
     The present invention has for its object to provide an electrical connector which can mitigate the above mentioned drawbacks and locking arms can be manufactured easily. 
     It is another object of the invention to provide an electrical connector, in which a clamping force of a locking arm can be improved. 
     It is another object of the invention to provide an electrical connector, in which a locking condition between a connecting terminal and a locking arm can be easily released through a window formed in a housing. 
     It is still another object of the invention to provide an electrical connector, an electrical conduction test for a connecting terminal inserted into a housing can be performed easily by means of a window formed in the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal cross sectional view showing a part of a known electric connector; 
     FIG. 2 is an exploded perspective view of the known connector, while a part of the electric connector is cut out; 
     FIG. 3 is a perspective view illustrating a first embodiment of the electric connector according to the invention in the assembled condition; 
     FIG. 4 is an exploded perspective view of the connector of FIG. 3, while connecting terminals are removed; 
     FIG. 5 is a longitudinal cross sectional view of the electrical connector shown in FIG. 4; 
     FIG. 6 is a longitudinal cross sectional view showing a condition in which a rear holder is locked at a provisional locking position; 
     FIG. 7 is a longitudinal cross sectional view illustrating a condition in which connecting terminals have been inserted into the housing; 
     FIG. 8 is a longitudinal cross sectional view showing a condition in which the rear holder is pushed into a complete locking position; 
     FIG. 9 is a schematic view illustrating a condition in which a connecting terminal is inserted halfway; 
     FIG. 10 is an explanatory view depicting a condition in which the rear holder is further inserted from the condition shown in FIG. 9; 
     FIG. 11 is an explanatory view illustrating a condition in which the connecting terminals are inserted up side down; 
     FIG. 12 is an explanatory view illustrating a condition in which the connecting terminals are inserted up side down; 
     FIG. 13 is an explanatory view representing an operation for releasing a locked condition between the connecting terminal and the rear holder; 
     FIG. 14 is a schematic view showing an electrical conduction test; 
     FIG. 15 is a view depicting the electrical conduction test; 
     FIG. 16 is a view showing a step after the electrical conduction test; 
     FIG. 17 is a view for explaining the electrical conduction test wherein a locking arm is not in a locked condition; 
     FIG. 18 is a perspective view showing a second embodiment of the electric connector according to the invention in an assembled condition; 
     FIG. 19 is an exploded perspective view of the electrical connector shown in FIG. 18 while connecting terminals have been removed; 
     FIG. 20 is an exploded perspective view depicting a condition in which a rear holder locked at a provisional locking position; 
     FIG. 21 is a longitudinal cross sectional view showing a condition in which the connecting terminals are inserted into the housing; 
     FIG. 22 is an explanatory view illustrating a condition in which the insertion of the connecting terminals has been interrupted; 
     FIG. 23 is an explanatory view depicting a condition in which the connecting terminals are inserted up side down; 
     FIG. 24 is an explanatory view for releasing a locked condition between the connecting terminal and the rear holder; 
     FIG. 25 is a view illustrating the electrical conduction test; 
     FIG. 26 is a view depicting the electrical conduction test; 
     FIG. 27 is a view showing a step after the electrical conduction test; and 
     FIG. 28 is an explanatory view showing the electrical conduction test under a condition in which the locking arm is not in the locked condition. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to the invention, an electrical connector including a housing containing one or more connecting terminals having electric cables connected thereto, a rear holder engaged with a rear portion of the housing such that the connecting terminals are held within the housing, and a locking means for locking said housing and rear holder with each other, characterized in that said rear holder is formed by a substantially plate-like member which comprises a main portion which is inserted into slits formed in the housing and is engaged with said locking means such that said main portion is engaged with the housing, and locking arms provided at a front end of said main portion and are inserted into respective connecting terminal accommodating holes formed in the housing such that the connecting terminals are locked. 
     According to another aspect of the invention, an electrical connector a housing containing one or more connecting terminals having electric cables connected thereto, a rear holder engaged with a rear portion of the housing such that the connecting terminals are held within the housing, and a locking means for locking said housing and rear holder with each other, characterized in that said rear holder comprises a main portion which is inserted into slits formed in the housing and is engaged with said housing by means of said locking means, and locking arms provided at a front end of said main portion and are inserted into respective connecting terminal accommodating holes formed in the housing such that the connecting terminals are locked, and that windows are formed in upper and lower walls of the housing at positions near locking portions between said connecting terminals and said locking arms such that said connecting terminal accommodating holes are communicated with external through said windows. 
     Now the present invention will be explained in detail with reference to embodiments shown in the drawings. 
     FIG. 3 is a perspective view showing a first embodiment of the electrical connector according to the invention in an assembled form. Male type connecting terminals  2  having electric conductors  1  connected to rear portions thereof are accommodated within a housing  3 , and the connecting terminals  2  are locked by a rear holder  4  which is engaged with a rear portion of the housing  3 . FIG. 4 is an exploded perspective view of the electrical connector from which the connecting terminals  2  are removed, and FIG. 5 is an exploded perspective view corresponding to FIG.  2 . 
     The connecting terminal  2  is formed from a single electrically conductive metal plate and includes a terminal main body  11  formed in a shape of a rectangular hollow member and a terminal connecting portion  12  provided at a front end of the terminal main body, said terminal connecting portion  12  being formed in a flat blade which can be connected to a female type connecting terminal of a corresponding electrical connector not shown. At a rear portion of the terminal main body  11 , there are further provided a core conductor clamping portion  13  for clamping a core conductor of the electric wire  1  and a sheath clamping portion  14  for clamping a sheath of the electric wire  1 . The terminal main body  11  further includes a stabilizer  15  for keeping a stable posture of the connecting terminal  2  and a locking hole  16  which is engaged with an engaging portion of a locking arm of the rear holder as will be explained later. 
     The housing  3  is made of an electrically insulating synthetic resin material and accommodates a plurality of connecting terminals  2  aligned in upper and lower rows. The housing  3  includes upper and lower outer walls  21 , right and left side walls  22 , a front end surface  23  and a rear end surface  24 . At the frond end surface  23 , there is provided a tubular portion  25  into which a housing of a corresponding electrical connector is to be inserted. A space within the housing  3  is divided by a horizontal partition  26  and a plurality of vertical partitions  27  to form a plurality of terminal accommodating portions  28  for accommodating the connecting terminals  2 . On inner surfaces of the upper and lower walls  21 , there are formed slits  28  such that these slits are communicated with the terminal accommodating holes  28  through the vertical partitions  27  and the rear holder  4  can be inserted into the housing  3  through said slits  28 . 
     At the front portion of the terminal accommodating holes  28  there is formed an end wall  31  having openings  30  through which the terminal connecting portions  12  of the connecting terminals  2  can project. In an inner surface of the opening  30 , there is formed a guide surface  31   a  for guiding the terminal connecting portion  12  toward the opening  30 . The terminal accommodating hole  28  includes a main body accommodating portion  32  for accommodating the terminal main body  11  of the connecting terminal  2  in a tight manner, a clamping portion accommodating portion  33  for accommodating the sheath clamping portion  14  of the connecting terminal  2 , stabilizer guiding recesses  34  for guiding the stabilizers  15  of the connecting terminal  2 , and an arm accommodating portion  35  for accommodating a locking arm of the rear holder  4 . 
     In the upper and lower outer walls  21  there are formed locking holes  36  which are engaged with locking projections formed in the rear holder  4  as will be explained later, and windows  37  through which the terminal accommodating holes  28  are communicated with the external. Some locking holes  36  and windows  37  are communicated with each other by removing parts of the partitions. A tool for releasing a locking condition between a locking arm and a connecting terminal  2  as well as probes of an electrical conduction testing device can be inserted through the windows  37 . On a side of the front end surface  23 , a part of a window  37  constitutes an outer wall of the arm accommodating portion  35  and a stopper wall  38  for restricting the movement of the locking arm is provided. A vertical portion  38   a  and a horizontal portion  38   b  of a stopper wall  38  are urged against a front surface and a outer surface of a locking arm, respectively which is not resiliently bent. The horizontal portion  38   b  is urged against the front surface of a locking arm which is resiliently bent. 
     The rear holder  4  is manufactured in a substantially plate-like shape by means of an injection molding machine having a double-plate mold using an electrically insulating synthetic resin material. The rear holder  4  comprises a holder main body  41  which is inserted into the slits  29  of the housing  3  without play. On an outer surface of the holder main body  41  there are formed a plurality of locking projections  42  which are urged against the rear end surface  24  of the housing  3  and are engaged with the locking holes  36 . On right and left sides of a locking projection  42  there are formed slits  43  and  44  which extend in a back and forth direction such that a portion of the holder main body  41  situating between these slits can be bent resiliently. At a front end of the holder main body  41  there are formed a plurality of resilient locking arms  45  for locking the connecting terminals  2  in position, each of said locking arms being inserted into respective terminal accommodating holes  28  of the housing  3 . A locking arm  45  has a width which is slightly smaller than that of the terminal accommodating hole  28 , and includes a locking portion  45   a  which is engaged with a locking hole  16  formed in a connecting terminal  2 . On an outer surface of the rear end of the holder main body  41 , there is provided a flange  46  which serves to limit the forward movement of the rear holder  4  by engagement with the rear end surface  24  of the housing  3 . 
     FIGS. 6-17 show configurations, positions and operations of various portions of the connecting terminals  2 , housing  3  and rear holder  4 . FIG. 6 illustrates a provisional locking position in which the rear holder  4  has been inserted midway into the housing  3 . In this condition, connecting terminals  2  are inserted into the housing  3  one by one. The locking projections  42  of the rear holder  4  are urged against the rear end surface  24  of the housing  3 , and the locking portions  45   a  of the locking arms  45  of the rear holder  4  are situated at a substantially mid position of the terminal accommodating holes  28  viewed in the back and forth direction. 
     When a connecting terminal  2  is further inserted into a terminal accommodating hole  28 , a locking portion  45   a  of a locking arm  45  is pushed outwardly by means of a terminal main body  11  of the inserted connecting terminal  2 . In this manner, the connecting terminal  2  is moved forwardly while the locking arm  45  is resiliently bent outwardly. When the locking hole  16  of the connecting terminal  2  has passed through the locking portion  45   a  of the locking arm  45 , the locking arm  45  is returned into their initial posture and the locking portion  45   a  is engaged with the locking hole  16  as depicted in FIG.  7 . 
     After inserting all the necessary connecting terminals  2 , the rear holder  4  is further inserted forwardly. During this operation, the locking projections  42  of the rear holder  4  are inserted into the slits  29  of the housing  3  while the portions between the slits  43  and  44  are deformed inwardly. By this operation, the rear holder  4  is moved into the complete locking position together with the connecting terminals  2 , and the terminal main bodies  11  of the connecting terminals  2  are inserted into the main body accommodating portion  32  of the housing  3  and are urged against the end wall  31  as illustrated in FIG.  8 . Furthermore, the locking arms  45  are inserted into the arm accommodating portion  35  and the front ends of the locking arms  45  are urged against the vertical portion  38   a  of the stopper wall  38 . At the same time, the locking projections  42  are engaged with the locking holes  36  and the flange  46  is brought into contact with the rear end surface  24 . In this case, the outer surfaces of the locking arms  45  are pushed by the horizontal portions  38   b  of the stopping wall  38  such that the locking force of the locking arms  45  for the connecting terminals  2  can be improved. 
     When the rear holder  4  is situated at the provisional locking position with respect to the housing  4  and the connecting terminals  2  are inserted halfway, the locking arms  45  that remained to be resiliently bent outwardly by the terminal main bodies  11  of the connecting terminals  2  as depicted in an upper portion of FIG.  9 . When the rear holder  4  is further inserted into the housing toward the complete locking position, the front ends of the locking arms  45  are urged against the horizontal portions  38   b  of the stopper wall  38  as shown in an upper portion of FIG. 10, and the rear holder  4  could not be moved further in the forward direction. By this condition, an operator can recognize that the in a way I and no when it at a connecting terminals  2  have not been inserted correctly. It should be noted that lower portions of FIGS. 9 and 10, show conditions in which the connecting terminals  2  has been correctly accommodated in the housing  3 . 
     If one or more connecting terminals  2  are inserted up side down, the terminal main bodies  11  of the connecting terminals  2  are urged against the front walls of the clamping portion accommodating portions  33  of the terminal accommodating holes  28 , and the connecting terminals  2  could not be inserted into the given positions as illustrated in an upper portion of FIG.  11 . If the connecting terminals  2  are further inserted, the connecting terminals  2  are advanced without being engaged with the locking arms  45  and the front ends of the terminal connecting portions  12  are urged against the end wall  31  of the housing  3  as shown in a lower portion of FIG.  11 . Alternatively, as depicted in FIG. 12, the front ends of the terminal connecting  12  are urged against the end wall  31  and the sheath clamping portions  14  of the connecting terminals  2  are urged against the inner surface of the holder main body  41  of the housing  4 . Then, the operator can recognize that the connecting terminals  2  have been inserted up side down. 
     When the connecting terminals  2  which have been inserted correctly are to be removed from the housing  3 , the rear holder  4  is moved backward from the complete locking position into the provisional locking position as shown in FIG.  13 . Then, a tip of a tool  51  is inserted through a window  37  under a front end of a locking arm  45  and the locking arm is resiliently bent outwardly to release locking between the connecting terminal  2  and the locking arm  45 , and a electrical wire  1  is pulled in a direction A. 
     When the electrical conduction test for preventing erroneous wiring of the electrical wires  1  is to be performed, the connecting terminals  2  are inserted into the housing  3  at the provisional locking position of the rear holder  4  and conduction test tools  53  having probes  52  are situated in opposition to the upper and lower outer walls  21  as depicted in FIG.  14 . Since a plurality of connecting terminals  2  are aligned in a direction perpendicular to a plane of the drawing, a plurality of corresponding probes  52  are also aligned in the same direction. The upper and lower conduction test tools  53  are coupled with each other into a single unit by means of an electrically insulating member not shown and are arranged to be opened and closed. 
     When the conduction test tools  53  are closed to clamp the housing  3  therebetween as depicted in FIG. 15, the probes  52  are brought into contact with the terminal main bodies  11  of the connecting terminals  2  through the windows  37 . In this manner, the electrical conduction test can be performed. That is to say, the wire harness circuit can be tested by means of a test circuit connected to the conduction testing tools  53 . 
     After the electrical conduction test, as shown in FIG. 16, the rear holder  4  is pushed by means of a pushing tool  54  with a given force such as about 1 kgf. In this case, when the connecting terminals  2  and locking arms  45  are not correctly engaged with each other as illustrated in FIG. 17, the locking arms  45  are remained in a outwardly bent condition, but a normal result of the electrical conduction test is obtained. However, the rear holder  4  could not be inserted into the complete locking position owing to the engagement of the front ends of the locking arms  45  with horizontal portions  38   a  of the stopper wall  38  when the rear holder  4  is pushed forward, and the operator can recognize the condition that the connecting terminals  2  have not been inserted correctly. 
     FIG. 19 is a perspective view showing a second embodiment of the, electrical connector according to the invention in an assembled condition, while parts of the connector are cut off. In this embodiment, female type connecting terminals  6  having electric wires  5  connected to their rear ends are accommodated within a housing  7  and are locked in position by means of a rear holder  8  engaged with the rear portion of the housing  7 . FIG. 19 is an exploded perspective view showing the connector while the connecting terminals  6  are removed, and FIG. 20 is an exploded perspective of the connector with the connecting terminals  6 . At a rear portion of a rectangular hollow terminal main body  61  of a connecting terminal  6  there are provided a core wire clamping portion  62  and a sheath clamping portion  63 . Within the terminal main body  61  there are provided a fixed contacting member  64  which can be urged against a male type connecting terminal of a corresponding connector not shown, and a movable contact  65 . On an outer surface of the terminal main body  61 , there is formed a stabilizer  66  which is locked by the rear holder  8 . The housing  7  comprises upper and lower outer walls  71 , right and left side walls  72 , a front end surface  73  and a rear end surface  74 , and a space within the housing  3  is divided by a horizontal partition  75  and vertical partitions  76  to form a plurality of terminal accommodating portions  77 . On inner surfaces of the upper and lower walls  71 , there are formed slits  78 . At the front portion of the terminal accommodating holes  77  there is formed and end wall  81  having openings  80  and in an outer surface of the end wall  81 , there is formed a guide surface  81   a . The terminal accommodating hole  77  includes a main body accommodating portion  82  for accommodating the terminal main body  61  of the connecting terminal  6  as well as a part of a locking arm in a tight manner, a clamping portion accommodating portion  83  for accommodating the sheath clamping portion  63  of the connecting terminal  6 , an arm accommodating portion  84  for accommodating the other portion of the locking arm, and a lock stopping recess  85  which is engaged with a lock stopping projection of the rear holder  8 . In the upper and lower outer walls  71 , there are formed windows  86  through which the terminal accommodating holes  77  are communicated with the external, and a stopper wall  87  is provided at front end surfaces  73  of the windows  86 . The stopper wall  87  includes a vertical portion  87   a  and a horizontal portion  87   b  and constitutes an outer wall of the arm accommodating holes  84 . 
     The rear holder  8  is formed in a substantially plate-like shape and comprises a holder main body  91 , lock stopping projection  92  and slits  93 ,  94  formed in the outer surface of the holder main body  91 , and a plurality of resilient locking projections  95  provided at a front end of the holder main body  91 . A locking arm  95  has a width which is slightly smaller than that of the terminal accommodating hole  77  of the housing  7 , and includes a first locking portion  95   a  which is engaged with a rear portion of a terminal main body  61  of a connecting terminal  6 , a second locking portion  95   b  which locks a rear portion of a stabilizer  66  of the connecting terminal  6 , and first and second holding portions  95   c  and  95   d  which hold a side portion and a front portion of the stabilizer  66 , respectively, said portions being formed as an integral body. At a rear portion of the holder main body  91 , there is formed a flange  96 . 
     FIGS. 21-28 illustrate the functions of the second embodiment of the electrical connector according to the invention. In a provisional locking position of the rear holder  8 , when a connecting terminal  6  is inserted into the housing  7 , the terminal main body  61  of the connecting terminal  6  is moved forward while a locking arm  95  is resiliently bent outwardly. When the terminal main body  61  of the connecting terminal  6  has passed through the first locking portion  95   a  of the locking arm  95 , the locking arm  95  is returned and the rear end of the terminal main body  61  is locked by the first locking portion  95   a  as shown in FIG.  21 . At the same time, the rear end of the stabilizer  66  is locked by the second locking portion  95   b , and first and second holding portions  95   c  and  95   d  push the side wall and front wall of the stabilizer  66 , respectively. 
     When the rear holder  8  is further inserted forwardly into the complete locking position, as depicted in a lower portion of FIG. 22, the terminal main bodies  61  of the connecting terminals  6  are inserted into the main body accommodating portion  82  of the housing  7  and are urged against the end wall  81 . Simultaneously, the first and second holding portions  95   c  and  95   d  of the locking arms  95  are inserted into the main body accommodating portion  82  and the second locking portion  95   b  is inserted into the arm accommodating portion  84  and are urged against the vertical portion  87   a  of the stopper wall  87 . At the same time, the lock stopping projections  92  of the rear holder  8  are engaged with the lock stopping holes  85  of the housing  7  and the flange  96  of the rear holder  8  is brought into contact with the rear end surface  74  of the housing  7 . In this condition, the outer surfaces of the second locking portions  95   b  of the locking arms  95  are pushed by the horizontal portions  87   b  of the stopper wall  87  of the housing, and this results in that the locking force for the connecting terminals  6  can be maintained sufficiently. 
     When the rear holder  8  is in the provisional locking position, if the connecting terminals  6  are inserted halfway, the locking arms  95  are resiliently bent outwardly by means of the stabilizers  66  as depicted in an upper portion of FIG.  22 . Therefore, when the rear holder  8  is further inserted toward the complete locking position, the second locking portions of the locking arms  95  are brought into contact with the horizontal portions  87   b  of the stopper wall  87 . Therefore, the rear holder  8  could not be moved further in the forward direction and an operator can recognize that the connecting terminals  6  have not been inserted correctly in the provisional locking position. 
     If one or more connecting terminals  6  are inserted up side down as shown in FIG. 23, the terminal main bodies  61  of the connecting terminals  6  are urged against the rear portions of the locking arms  95  of the rear holder  8  and the stabilizers  66  of the connecting terminals  6  are brought into contact with the partition  75  of the housing  7 . Furthermore, the core wire accommodating portions  62  of the connecting terminals  6  are brought into contact with the holder main body  91  of the rear holder  9 , and therefore, the connecting terminals  6  could not be inserted any more. 
     When the connecting terminals  6  which have been inserted correctly are to be removed from the housing  7 , at first the rear holder  8  is pulled out of the complete locking position and is moved into the provisional locking position as shown in FIG.  24 . Then, a tip of a tool  51 ′ is inserted through a window  86  of the housing  7  under a front end of a second locking portion  95   b  and the locking arm  95  is resiliently bent outwardly to release locking between the connecting terminal  6  and the locking arm  95 , and an electrical wire  5  is pulled in a direction A. 
     When the electrical conduction test for preventing erroneous wiring of the electrical wires  5  is to be performed, as illustrated in FIG. 25, the connecting terminals  6  are inserted into the housing  7  at the provisional locking position of the rear holder  8  and conduction test tools  53 ′ having probes  52 ′ are situated in opposition to the upper and lower outer walls  71  of the housing  7 . Next, the upper and lower conduction test tools  53 ′ are coupled with the housing  7  as depicted in FIG. 26 such that the probes  52 ′ are brought into contact with the stabilizers  66  of the connecting terminals  6  through the windows  86  of the housing  8 . In this manner, the electrical conduction test can be carried out. 
     After the electrical conduction test, as shown in FIG. 27, the rear holder  8  is pushed by means of a pushing tool  54 ′ with a force like as the first embodiment. Also in the second embodiment, when the connecting terminals  6  and locking arms  95  are not correctly engaged with each other as illustrated in FIG. 28, the locking arms  45  are remained in a outwardly bent condition, but the electrical conduction test shows a normal result. However, since the second holding portions  95   d  of the locking arms  95  are brought into contact with the vertical portions  87   a  of the stopper wall  87  when the rear holder  4  is pushed forward, the rear holder  8  could not be inserted into the complete locking position. In this manner, the operator can recognize the condition that the connecting terminals  6  have not been inserted correctly. 
     As stated above, in the first and second embodiments, since the rear holder  4 ,  8  is formed as a substantially flat plate, it can be manufactured by means of a simple mold of a double-plate structure. Therefore, a width of the locking arm  45 ,  95  can be close to that of the terminal accommodating hole  28 ,  77 , a plurality of the locking portions  95   a ,  95   b  can be provided, and the first and second holding portions  95   c ,  95   d  can be provided. Furthermore, the locking arms  45 ,  95  can be held by the stopper wall  38 ,  87 . In this manner, the locking force of the locking arms  45 ,  95  can be improved. 
     Moreover, since the housing  3 ,  7  does not include the locking arms, a mold for manufacturing the housing can be simple and a cost for manufacturing the housing  3 ,  7  can be reduced. The guide surfaces  31   a ,  81   a  can be provided in the end wall  31 ,  81  of the housing  3 ,  7 , and therefore an operation of inserting the connecting terminals  2  and an operation of coupling a corresponding connector can be performed easily. Furthermore, since the connecting terminal  3 ,  6  can be inserted in a direction parallel to an axis of the housing  3 ,  7 , an operation of inserting the connecting terminals  2 ,  6  becomes easy and undesired insertion of connecting terminals  2 ,  6  such as halfway insertion and up-side-down insertion can be effectively prevented. In this manner, a reliability of the electrical connection can be improved. 
     The locking condition between the connecting terminals  2 ,  6  and the rear holder  4 ,  8  can be released from the windows  37 ,  86  provided in the upper and lower outer walls  21 ,  71  of the housing  3 ,  7 , and therefore the locking release operation can be performed without difficulty. Moreover, the connecting terminals  2 ,  6  can be removed from the housing  3 ,  7  by means of the tool  51 ,  51 ′ without injuring the housing  3 ,  7  and connecting terminals  2 ,  6 . Since the condition of the connecting terminals  2 ,  6  inserted into the housing  3 ,  7  can be monitored through the windows  37 ,  85 , erroneous insertion of the connecting terminals  2 ,  6  can be prevented. 
     The probes  52 ,  52 ′ of the electrical conduction test tool  53 ,  53 ′ can be brought into contact with the connecting terminals  2 ,  6  through the windows  37 ,  86  formed in the outer walls  21 ,  71  of the housing  3 ,  7 . In the known electrical connectors, the probes  52 ,  52 ′ of the electrical conduction test tool must be connected to the connecting terminals  2 ,  6  by inserting them into the housing through the opening  30 ,  80  of the housing  3 ,  7  with a large force. 
     In the first and second embodiments of the electrical connector according to the invention, the connecting terminals  2 ,  6  are arranged in two rows, but according to the invention, they may be aligned in a single row. When the connecting terminals  2 ,  6  are arranged in more than two rows, windows are formed in the partition  26 ,  27  at positions corresponding to the windows  37 ,  86 , and after removing the upper and lower connecting terminals  2 ,  6 , the tool  51 ,  51 ′ may be inserted through these windows and the locking between the connecting terminals  2 ,  6  and the locking arms  45 ,  95  may be released. Positions and size of the windows  37 ,  86  of the housing  3 ,  7  are set such that both the lock releasing tool  51 ,  51 ′ and the electrical conduction tool  53 ,  53 ′ can be inserted through the windows, but if it is not necessary to insert the lock releasing tool  51 ,  51 ′, the windows may be small such that only the electrical conduction test tool  53 ,  53 ′ can be inserted through the windows. 
     As explained above, in the electrical connector according to the invention, since the rear holder is formed in a substantially flat plate-shape, the rear holder can be manufactured by a simple double-plate mold and the locking arms can be formed easily. Since the locking arm has a width which is slightly smaller than that of a terminal accommodating hole, the locking arm can have a larger width than the known connector, and a locking force of the locking arm can be increased. 
     In the electrical connector according to the invention, since the windows are formed in the outer wall of the housing, the locking condition between the connecting terminal and the locking arm can be released by inserting the tool through the windows. Therefore, it is no more necessary to insert the tool from the front opening or rear opening of the housing, and thus the housing and connecting terminals can be prevented from being injured by the tool. 
     Furthermore, since the probes of the electrical conduction test tool can be brought into contact with the connecting terminals through the windows formed in the outer wall of the housing, it is no more necessary to insert the probes of the electrical conduction test tool from the front opening of the housing into which a corresponding connector is to be inserted, and the electrical conduction test can be performed easily.