Abstract:
The present invention relates to an electrical connector with a locking mechanism which is to be locked to a counter electrical connector by insertedly connecting the connector to the counter electrical connector and then conducting a given rotating operation, and in which only a given rotation operation is required for enabling a locking state to be naturally canceled by a spring force. According to the present invention, irrespective of whether the electrical connector has a single pole or plural poles, the connectors can be connected and locked to each other without requiring an adjustment of a lock ring in the peripheral direction, only by determining the fitting position. In the electrical connector with a locking mechanism of the present invention, a lock ring at the initial position is positioned by fitting between a protruding portion disposed on a fitting portion, and a recess portion disposed in a lock ring fitted onto the fitting portion. When the lock ring is positioned by the fitting of the protruding portion and the recess portion, a fitting mechanism conducts the positioning operation and a connector is insertedly connected to the counter connector. Then, an outward projection of the counter electrical connector is fitted into a slot of the lock ring. The lock ring is always urged in the advancing direction by a spring member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector with a locking mechanism, and more particularly to an electrical connector with a locking mechanism by which a coupling state with a counter electrical connector is locked by conducting a given rotation operation after the electrical connector is insertedly connected to the counter electrical connector. The present invention relates also to an electrical connector with a locking mechanism in which only a given rotation operation is required for enabling a locking state to be naturally canceled by a spring force. 
     2. Description of the Prior Art 
     FIG. 10 diagrammatically shows a prior art electrical connector with a locking mechanism. In the connector C 3  of the figure, a cylindrical lock ring  110  is attached to the connector body  100  so as to be longitudinally movable. The connector C 3  is insertedly connected to a counter electrical connector C 4 , and a female thread  111  of the lock ring  110  is then screwed with a male thread  112  formed on the counter electrical connector C 4 . As a result, the connectors C 3  and C 4  are locked to each other so as not to drop off. 
     FIG. 11 diagrammatically shows another prior art electrical connector with a locking mechanism. When the connector C 5  of the figure is insertedly connected to a counter electrical connector C 6 , an engaging piece  210  formed on the connector body  200  is automatically engaged with an engaging portion  220  of the counter electrical connector C 6 , and the connectors C 5  and C 6  are locked to each other so as not to drop off. When a pressing portion  230  formed on the connector body  200  is pressed by a finger in the locking state so as to bend inwardly the engaging piece  210 , the locking state is canceled and the connector C 5  can be extracted from the counter electrical connector C 6 . 
     FIG. 12 diagrammatically shows a further prior art electrical connector with a locking mechanism. The connector C 7  of the figure has one pole  325 . A cylindrical lock ring  310  is attached to the connector body  300  of the connector C 7  so as to be rotatable and axially movable. The lock ring  310  is always urged toward the illustrated initial position in the retracting direction, by a spring member (not shown) which is interposed between the connector body  300  and the lock ring  310 . A slot  320  which elongates in the spiral direction is opened in the lock ring  310 . An engaging holding face  322  is sectionally formed in the hole wall face  321  of the slot  320 . When the connector C 7  is insertedly connected to a counter electrical connector C 8  and the lock ring  310  is then rotated, the entire wall face  321  of the slot  320  is engaged with an outward projection  324  disposed on the counter electrical connector C 8 , so that the lock ring  310  is moved forward, whereby the outward projection  324  is engaged with the engaging holding face  322 , with the result that the connectors C 7  and C 8  are locked to each other so as not to drop off. When the lock ring  310  in the locking state is reversely rotated, the locking state is naturally canceled by the spring force and the connector C 7  can be extracted from the counter electrical connector C 8 . 
     Among the above-described prior art connectors C 3 , C 5 , and C 7  of FIGS. 10,  11 , and  12 , the connector C 7  of FIG. 12 has excellent locking operability because a locking operation can be completed only by insertedly connecting the connector to the counter electrical connector C 8  and then slightly rotating the lock ring  310 . Furthermore, the connector C 7  has an advantage that, when the outward projection  324  of the counter electrical connector C 8  and the slot  320  of the lock ring  310  of the connector C 7  are formed in two places which are separated from each other by 180°, high locking stability is obtained wherein an offset load hardly occurs. 
     In the connector C 7  of FIG. 12, in the case where the connector has a single pole  325  as illustrated, even when the lock ring  310  at its initial position is rotatable with respect to the connector body  300 , the locking operation can be conducted by insertedly connecting the connectors C 7  and C 8  to each other at a position where the outward projection  324  of the counter electrical connector C 8  can be fitted into the slot  320  of the lock ring  310 , and then rotating the lock ring  310 . In the case where the connector C 7  is a multipolar connector having plural poles, when the connectors C 7  and C 8  are to be insertedly connected to each other, it is required to conduct a two-step positioning operation in which the fitting positions in the peripheral direction of the connectors are first determined in order to enable the poles (not shown) of the connectors to be adequately connected to each other, and the lock ring  310  is then rotated so as to adjust the position of the slot  320  in the peripheral direction to the position where the outward projection  324  of the counter electrical connector CB can be fitted into the slot. This prevents the connection work from being conducted rapidly and smoothly. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed in view of the above-mentioned circumstances. 
     It is an object of the invention to provide an electrical connector with a locking mechanism in which the basic structure of the connector C 7  of FIG. 12 that has a single pole is employed as it is, and the lock ring at the initial position can be positioned in the rotation direction. 
     It is another object of the present invention to provide an electrical connector with a locking mechanism in which, even in the case of a multipolar electrical connector with a locking mechanism, when the electrical connector with a locking mechanism is to be connected to a counter electrical connector, the connectors can be surely connected and locked to each other without requiring an adjustment of a lock ring in the rotation direction, only by determining a fitting position where poles of the connectors can be adequately connected to each other. 
     In the electrical connector with a locking mechanism according to the present invention, the presumption portion has a configuration comprising: 
     a cylindrical fitting portion which can be fitted into a cylindrical fitted portion of a counter electrical connector; 
     a cylindrical lock ring which is attached to the fitting portion so as to be rotatable and axially movable; 
     a guide face which is formed on the lock ring, which elongates in a spiral direction, and to which, when the fitting portion is fitted into the fitted portion, an outward projection disposed on the fitted portion is opposed; 
     a cam face and an engaging face which is continuous with the cam face, the cam face and the engaging face being sectionally formed in the guide face, and, when the lock ring is rotated, being engaged with the outward projection to guide the lock ring toward a lock position in an advancing direction; and 
     a spring member which always urges the lock ring toward an initial position in a retracting direction. 
     The configuration of the presumption portion is formed also in the prior art connector C 7  which has been described with reference to FIG.  12 . According to the electrical connector with a locking mechanism of the present invention having this configuration, a locking operation can be completed only by insertedly connecting the connector to the counter electrical connector and then slightly rotating the lock ring, and hence the connector has excellent locking operability. Furthermore, the connector has an advantage that, when the outward projection of the counter electrical connector and the slot of the lock ring are formed in two places which are separated from each other by 180°, high locking stability wherein an offset load hardly occurs is obtained. When the lock ring in the locking state is reversely rotated, the locking state is naturally canceled by the spring force and the connector can be extracted from the counter electrical connector. 
     The electrical connector with a locking mechanism according to the present invention has, in addition to the presumption portion, a positioning mechanism as the configuration of the characterizing portion. The positioning mechanism is formed by a protruding portion and a recess portion which is to be fitted onto and unfitted from the protruding portion, the protruding portion and the recess portion being respectively formed on the fitting portion and the lock ring. Furthermore, the positioning mechanism is configured so that it restricts the rotation angle of the lock ring at the initial position and the restriction state of the rotation angle of the lock ring which is caused by the protruding portion and the recess portion is canceled by a forward movement of the lock ring toward the lock position. 
     According to the present invention, the position in the rotation direction of the lock ring at the initial position is always determined by the positioning mechanism, and hence there arises no case where the lock ring is rotated to a position other than that which is determined by the positioning mechanism. Irrespective of whether the electrical connector with a locking mechanism has a single pole or plural poles, when the connector is to be connected to a counter electrical connector, therefore, the connectors can be surely connected and locked to each other without requiring an adjustment of the lock ring in the peripheral direction, only by determining the fitting position where the poles of the connectors can be adequately connected to each other. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, a width of the recess portion of the positioning mechanism is larger than a width of the projection of the positioning mechanism, and an idle space is formed between the projection and the recess portion. According to this configuration, the dimensional accuracy of the resin molding of the lock ring and the fitting portion on which the protruding portion and the recess portion of the positioning mechanism are respectively formed can be relaxed. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, an edge portion which protrudes toward an inner side of the lock ring is annularly formed on a rear end portion of the lock ring, the recess portion of the positioning mechanism is formed in one place in a peripheral direction of the edge portion, a trunk portion is continuously disposed on a base of the fitting portion in a stepwise manner, the trunk portion having a diameter which is larger than a diameter of the fitting portion, the protruding portion of the positioning mechanism is formed in a step portion in an interface between the trunk portion and the base, and a step face of the step portion is formed as an abutting face which restricts the initial position of the lock ring. 
     According to this configuration, the places where the protruding portion and the recess portion of the positioning mechanism are to be respectively formed can be specifically determined. Since the protruding portion is formed on the side of the fitting portion, it is not required to form the recess portion on the side of the fitting portion. This serves to easily ensure a required mechanical strength for the fitting portion which is to be fitted onto and unfitted from the cylindrical fitted portion of the counter electrical connector. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, a spring seat is formed in place of the fitting portion, the place being positioned more forward than the protruding portion, and the spring member is interposed between the spring seat and the edge portion of the lock ring. According to this configuration, the spring member is covered by the lock ring so as not to be exposed to the outside. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, a projection and a groove portion which is to be fitted onto and unfitted from the projection are respectively formed on the fitting portion and the fitted portion, the projection and the groove portion form a fitting mechanism which restricts a fitting position between the fitting portion and the fitted portion in a peripheral direction, and an introducing groove for introducing the outward projection to the cam face is formed in the lock ring, the introducing groove elongating from a front end face of the lock ring to a beginning portion of the cam face. 
     According to this configuration, the fitting position between the fitting portion and the fitted portion in the peripheral direction can be determined by positioning the projection and the groove portion of the fitting mechanism. Even when the connector is a multipolar connector having plural poles, therefore, the poles of the connector can be adequately connected to those of a counter electrical connector. In spite of the above, the position of the lock ring in the peripheral direction is determined to a given position by the positioning mechanism, and hence the connectors can be surely connected and locked to each other without requiring an adjustment of the lock ring in the peripheral direction, only by determining the fitting position where the poles of the connectors can be adequately connected to each other. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, a width of an opening of the introducing groove in the front end face of the lock ring is larger than a thickness of the outward projection, and, when the projection of the fitting mechanism is positioned with respect to the groove portion, the outward projection is always opposed to the opening of the introducing groove in the front end face of the lock ring. 
     According to this configuration, even if an idle space is formed between the projection and the recess portion of the positioning mechanism, when the connector is to be connected to a counter electrical connector, the connectors can be surely connected and locked to each other without requiring an adjustment of the lock ring in the rotation direction. 
     In the electrical connector with a locking mechanism according to the present invention, preferably, plural poles are arranged inside the fitting portion. Such a connector is used as a multipolar connector, and the plural poles are protected by the cylindrical fitting portion. 
     In the electrical connector with a locking mechanism according to the present invention, the guide face may be formed by an entire wall face of a slot which is formed in the lock ring and which elongates in the spiral direction. Preferably, a mark indicating a position of the projection of the fitting mechanism is formed on an outer face of the trunk portion. Preferably, another mark indicating a rotation direction for forward moving the lock ring is formed on an outer face of the lock ring. 
     As described above, according to the present invention, even when a connector having plural poles is to be connected to a counter electrical connector, the connectors can be surely connected and locked to each other without requiring an adjustment of a lock ring in the rotation direction, only by determining a fitting position where poles of the connectors can be adequately connected to each other. Therefore, it is possible to provide a connector having excellent connecting operability and locking operability. 
     The configuration and function of the present invention will be more apparent from the following description of embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view diagrammatically showing an electrical connector with a locking mechanism of an embodiment of the present invention; 
     FIG. 2 is a diagrammatic side view of the connector; 
     FIG. 3 is a view looking in the direction of the arrow III in FIG. 2; 
     FIG. 4 is a diagrammatic perspective view of a counter electrical connector; 
     FIG. 5 is a partially cutaway diagrammatic side view illustrating a connecting operation; 
     FIG. 6A is a diagrammatic side view of a state where the electrical connector with a locking mechanism of the present invention is connected to the counter electrical connector, and 
     FIG. 6B is a diagrammatic section view taken along the line VIb—VIb of FIG. 6A; 
     FIG. 7A is a diagrammatic side view showing an initial stage of a locking operation, and 
     FIG. 7B is a diagrammatic sectional view taken along the line VIIb—VIIb of FIG. 7A; 
     FIG. 8A is a diagrammatic side view showing an intermediate stage of the locking operation, and 
     FIG. 8B is a diagrammatic section view taken along the line VIIIb—VIIIb of FIG.  8 A; 
     FIG. 9A is a diagrammatic side view showing a locking state, and FIG. 9B is a diagrammatic section view taken along the line IXb—IXb of FIG. 9A; 
     FIG. 10 is a partially cutaway side view of a prior art example; 
     FIG. 11 is a partially cutaway side view of another prior art example; and 
     FIG. 12 is a diagrammatic perspective view of a further prior art example. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the electrical connector with a locking mechanism according to the present invention will be described. 
     As shown in FIG. 1, the electrical connector with a locking mechanism (hereinafter, referred to merely as “connector”) C 1  comprises the connector body  10 , a lock ring  30 , and a spring member  50 . 
     The connector body  10  is formed from a synthetic resin molded member. In the connector body  10 , a trunk portion  12  is continuously disposed on a base of a cylindrical fitting portion  11 . The trunk portion  12  is larger in diameter than the fitting portion  11 . Plural poles  13  are disposed inside the fitting portion  11  in a predetermined arrangement. The poles  13  are fixed to the connector body  10 . Plural conductors (not shown) of an electric cord  60  which is passed through the trunk portion  12  are connected to the poles  13 , respectively. The poles  13  may be pin poles, or strip-like poles, or have another shape. A spring seat  14  is annularly formed on the outer periphery of the fitting portion  11 . A projection  16  which extends axially from the spring seat  14  is formed on the outer periphery of the fitting portion  11  and in front of the spring seat  14 . 
     The lock ring  30  is formed from a synthetic resin molded member. An annular edge portion  31  is formed in a rear edge portion of the lock ring  30  so as to protrude into the lock ring. As shown in FIG. 5, the lock ring  30  is fitted onto a fitting portion  11  of the connector body  10 . In a state where the lock ring  30  is fitted onto the connector body  10 , the edge portion  31  is placed between the large-diameter trunk portion  12  and the spring seat  14  of the connector body  10 . A spring member  50  which is fitted into the fitting portion  11  is interposed and held between the edge portion  31  and the spring seat  14 . 
     In a step portion  15  in an interface between the trunk portion  12  and the base of the fitting portion  11 , a protruding portion  71  is disposed in one place of the peripheral direction of the step portion. By contrast, a recess portion  72  which can be fitted onto and unfitted from the protruding portion  71  is disposed in one place of the peripheral direction of the edge portion  31  of the lock ring  30 . The protruding portion  71  and the recess portion  72  constitute a positioning mechanism  70  for restricting the relative position of the lock ring  30  in the peripheral direction with respect to the fitting portion  11 . As shown in FIG. 6B, the width H 1  of the recess portion  72  of the positioning mechanism  70  is larger than the width H 2  of the protruding portion  71 . When the lock ring  30  is retracted and the recess portion  72  is fitted onto the protruding portion  71 , a gap is formed between the protruding portion  71  and the recess portion  72 . The gap serves as an idle space S so that an idling rotation of the lock ring  30  is allowed within a predetermined angle range. FIG. 6B shows a state where the protruding portion  71  is fitted into the center place in the lateral direction of the recess portion  72 . In this state, the lock ring  30  can be idly rotated in either of the rightward and leftward directions by an angle corresponding to the angle θ shown in the figure. 
     When the protruding portion  71  and the recess portion  72  of the positioning mechanism  70  are fitted to each other, the lock ring  30  abuts against the step face of the step portion  15  as shown in FIG. 5, thereby restricting the retracting position of the lock ring. The position in this state is the initial position of the lock ring  30 . The step face of the step portion  15  is formed as an abutting face  15   a  which restricts the initial position of the lock ring  30 . The lock ring  30  is always urged toward the initial position in the retracting direction by the force of the spring member  50 . 
     A slot  32  which extends in the spiral direction is formed in two places of the peripheral wall of the lock ring  30  which are separated from each other by 180°. A front hole wall face of each of the slots  32  is formed as a guide face  33 . The guide face  33  elongates in the spiral direction, and, as shown in FIGS. 1,  6 A,  7 A,  8 A, and  9 A, is sectioned into a cam face  33   a  which is inclined in the spiral direction, a chevron-shaped face  33   b  which is continuous from the end portion of the cam face  33   a , and a recessed engaging face  33   c  which is continuous from the cam face  33   a  via the chevron-shaped face  33   b.    
     As shown in FIG. 4, a counter electrical connector (hereinafter, referred to merely as “counter connector”) C 2  has a cylindrical fitted portion  21 , and the body  22  which is inside the fitted portion  21 . Plural poles are disposed in the body  22 . In the fitted portion  21 , an outward projection  23  is formed in two places of the fitted portion which are separated from each other by 180° in the peripheral direction. A groove portion  24  which extends in the axial direction is formed in a center portion between the outward projections  23 . The projection  16  shown in FIG. 1, and the groove portion  24  of the counter connector C 2  constitute a fitting mechanism  17 . The fitting mechanism  17  has the role of restricting the fitting position in the peripheral direction of the fitting portion  11  of the connector C 1  and the fitted portion  21  of the counter connector C 2 . When the projection  16  of the fitting mechanism  17  is positioned with respect to the groove portion  24  and the fitting portion  11  is fitted into the fitted portion  21 , the plural poles  13  of the connector C 1  are adequately connected to the plural poles in the body  22  of the counter connector C 2 , respectively, thereby electrically connecting the connectors C 1  and C 2  to each other. 
     As shown in FIGS. 6A,  7 A,  8 A, and  9 A, an introducing groove  34  which extends from the front end face of the lock ring  30  to the beginning portion of the cam face  33   a  is formed in the front end portion on the inner periphery side of the lock ring  30 . The introducing groove  34  has a role of, when the projection  16  of the fitting mechanism  17  is positioned with respect to the groove portion  24  and the fitting portion  11  is fitted into the fitted portion  21 , introducing the outward projection  23  of the counter connector C 2  into the beginning portion of the cam face  33   a . In the illustrated example, the width of the inlet part of the introducing groove  34 , i.e., the groove width W (FIG. 6A) in the front end face of the lock ring  30  is larger than the thickness of the outward projection  23 . Even in a state where the lock ring  30  at the initial position is idly rotated in the rightward direction or the leftward direction, therefore, the outward projection  23  of the counter connector C 2  is surely introduced via the introducing groove  34  into the beginning portion of the guide face  33  when the projection  16  of the fitting mechanism  17  is positioned with respect to the groove portion  24  and the fitting portion  11  is fitted into the fitted portion  21 . 
     In the connector C 1  described above, when the projection  16  constituting the fitting mechanism  17  and on the side of the connector C 1  is positioned with respect to the groove portion  24  on the side of the counter connector C 2  and the fitting portion  11  is then fitted into the fitted portion  21  of the counter connector C 2  as indicated by the arrow P of FIG. 5, the outward projection  23  of the counter connector C 2  is fitted via the introducing groove  34  into the slot  32  formed in the lock ring  30  of the connector C 1  as shown in FIGS. 6A and 6B, and then introduced into the beginning portion of the guide face  33 . At this time, even if the lock ring  30  at the initial position is idly rotated in the rightward direction or the leftward direction, the above-mentioned action of the introducing groove  34  enables the outward projection  23  of the counter connector C 2  to be surely introduced into the beginning portion of the cam face  33   a.    
     After the fitting portion  11  of the connector C 1  is fitted into the fitted portion  21  of the counter connector C 2  to connect the connectors C 1  and C 2  to each other, the locking operation described below is conducted. 
     In the locking operation, the lock ring  30  is rotated. Specifically, after the connectors C 1  and C 2  are connected to each other, the lock ring  30  is rotated in the direction R (the rightward direction as seen from the side of the connector C 1 ) along which the cam face  33   a  abuts against the outward projection  23 . Then, the cam face  33   a  is pushed forward by the outward projection  23 , and hence the lock ring  30  is moved forward against the force of the spring member  50  while being rotated. Therefore, the engaging position between the cam face  33   a  and the outward projection  23  is moved via the position of FIG. 7A, and the chevron-shaped face  33   b  then overrides the outward projection  23  as shown in FIG.  8 A. Thereafter, the chevron-shaped face  33   b  passes over the outward projection  23  and the engaging face  33   c  is engaged with the outward projection  23  as shown in FIG. 9A, thereby attaining a locking state. 
     In the case where the above-mentioned locking operation is to be conducted, when the lock ring  30  is located at the initial position, the recess portion  72  is fitted into the protruding portion  71  of the positioning mechanism  70 . Therefore, it is impossible to rotate the lock ring  30  so as to exceed the above-mentioned range of the idling rotation while the lock ring  30  is maintained to be located at the initial position. By contrast, when the connectors C 1  and C 2  are connected to each other, the outward projection  23  of the counter connector C 2  is introduced into the beginning portion of the guide face  33 , and, when the lock ring  30  is rotated, the cam face  33   a  is engaged with the outward projection  23  to moved forward the lock ring  30 . When the lock ring  30  is moved forward in this way, the recess portion  72  of the positioning mechanism  70  escapes from the protruding portion  71  of the mechanism as shown in FIGS. 8A and 8B and the restriction state (positioning state) of the rotation angle of the lock ring  30  is canceled. Therefore, the locking operation can be conducted only by connecting the connectors C 1  and C 2  to each other and then rotating the lock ring  30 . 
     When the locking state is to be canceled, the lock ring  30  is reversely rotated. As a result, the chevron-shaped face  33   b  overrides the outward projection  23  engaged with the engaging face  33   c , the cam face  33   a  is then engaged with the outward projection  23 , and the beginning portion of the guide face  33  reaches the outward projection  23 . This causes the locking state to be canceled. Thereafter, the connector C 1  is extracted from the counter connector C 2 . 
     In the illustrated embodiment, as shown in FIGS. 1 to  3 ,  5 , and  6 A, a triangular mark M 1  indicating the position of the projection  16  of the fitting mechanism  17  is formed on the outer face of the trunk portion  12  of the connector C 1 . By contrast, as shown in FIGS. 4 to  6 A, a triangular mark M 2  indicating the position of the groove portion  24  of the fitting mechanism  17  is formed on the outer face of the counter connector C 2 . According to this configuration, positioning of the projection  16  of the fitting mechanism  17  with respect to the groove portion  24  can be simply realized by matching only the marks M 1  on the side of the connector C 1  to the mark M 2  on the side of the counter connector C 2 . Therefore, the workability of connecting the connectors C 1  and C 2  to each other is improved. When a mark M 3  indicating the rotation direction of the lock ring  30  in the locking operation is formed on the outer periphery of the lock ring  30  as shown in FIGS. 1 and 2, there is an advantage that, when the connectors C 1  and C 2  are connected to each other and then locked by moving forward the lock ring  30  while rotating the ring, the rotation direction of the lock ring  30  can be known from the mark M 3  at a glance. As shown in FIG. 2, a rugged face  36  is formed on the outer periphery of the lock ring  30  in order to prevent fingers holding the lock ring  30  in the locking operation from slipping. 
     In the connector C 1 , the protruding portion  71  and the recess portion  72  of the positioning mechanism  70  are respectively formed on the fitting portion  11  and the lock ring  30 , and it is not always required to form the protruding portion  71  on the fitting portion  11  and the recess portion  72  on the lock ring  30 . When the protruding portion  71  is formed on the fitting portion  11  and the recess portion  72  on the lock ring  30  as in the case of the embodiment, however, the protruding portion  71  is useful for enhancing the mechanical strength of the fitting portion  11 . Even when the fitting portion  11  is wrenched in the operation of fitting or unfitting the portion to the fitted portion  21  of the counter connector C 2 , therefore, the fear that the fitting portion  11  is damaged can be reduced. 
     Also the projection  16  and the groove portion  24  of the fitting mechanism  17  are not restricted to the configuration of the embodiment. For example, the projection  16  may be disposed on the side of the counter connector C 2  and the groove portion  24  may be disposed on the side of the fitting portion  11 . When the projection  16  is disposed on the fitting portion  11  as in the case of the embodiment, however, the projection  16  is useful for enhancing the mechanical strength of the fitting portion  11 . Even when the fitting portion  11  is wrenched in the operation of fitting or unfitting the portion to the fitted portion  21  of the counter connector C 2 , therefore, the fear that the fitting portion  11  is damaged can be reduced.