BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a connector set applied to electrical connection between electrical terminals. 
   2. Description of the Related Art 
   Various connectors in practical use are provided with locking means for preserving a locking state. A combination of a resilient arm with a locking projection and a stopper for engaging with the locking projection is exemplified as the locking means. The resilient arm is in general formed as sort of a cantilever and projects rearward and oblique to an axis of the connector so as to smoothly deform in accordance with insertion movement of the connector. 
   SUMMARY OF THE INVENTION 
   According to such connectors of prior arts, in the course of insertion movement of the connector, a degree of deformation of the resilient arm increases depending on progress of the insertion. Thereby the insertion must be accomplished against increasing repulsive force. 
   The present invention is achieved in view of the above problem and is intended for providing a connector set, repulsive force of which is kept substantially constant throughout the insertion. 
   According to an aspect of the present invention, a connector set is provided with a first member including a locking device having a proximal portion formed as a protrusion ranging in parallel with an axis of the first member, a resilient beam extending from the proximal portion and being elastically swingingly deformable along the proximal portion, and a locking projection projecting from the resilient beam; and a second member configured to receive the first member in a direction of the axis of the first member, the second member including an engaging portion configured to latch the locking projection. 
   Preferably, the locking device is provided with means for regulating repulsive force of the locking device. More preferably, a front end of the locking device includes a chamfered bevel. Further preferably, the means for regulating repulsive force of the locking device is a slit formed at a rear end of the locking device, the slit partially separating the proximal portion and the resilient beam. Still preferably, the means for regulating repulsive force of the locking device is a slit separating the proximal portion and the resilient beam around a rear end of the locking device. Alternatively preferably, the means for regulating repulsive force of the locking device is a slot formed around the locking projection. Further preferably, the second member is configured to house the first member. Still further preferably, the resilient beam is repulsively supported in an inner surface of the second member. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a connector set in accordance with an embodiment of the present invention; 
       FIG. 2  is a top view of a first connector housing and a locking device of the connector; 
       FIG. 3  is a front view of the locking device; 
       FIG. 4  is a sectional view of the connector set under a connection process; and 
       FIG. 5  is a sectional view of the connector set in a connection state. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An embodiment of the present invention will be described hereinafter with reference to  FIGS. 1 through 5 . Throughout the specification and claims, front and rear are defined in accordance with a direction where a first connector housing  10  is inserted into a second connector housing  20 . 
   As shown in  FIGS. 1 through 5 , a connector set  1  in accordance with the present embodiment is provided with a first connector housing  10  and a second connector housing  20 . The second connector housing  20  is configured to house the first connector housing  10 . When the first connector housing  10  and the second connector housing  20  are engaged, terminals (not shown) housed therein are mutually connected. Terminal housings  11  and  21  are respectively formed at substantially central portions of the connector housings  10  and  20 . The terminal housing  21  is formed so as to receive the terminal housing  11 . When the terminal housing  21  receives the terminal housing  11 , the terminals housed therein are mutually connected. 
   A top wall  12  of the first connector housing  10  is provided with a locking device  30 . The locking device  30  is provided with a locking projection  31  around a distal end thereof, which is configured to engage with and disengage from an engaging portion  40  of the second connector housing  20 . When the first connector housing  10  is inserted in the second connector housing  20 , the locking projection  31  latches the engaging portion  40  so as to preserve a connection state between the first connector housings  10  and  20 . 
   The locking projection  31  is further configured to be capable of disengaging from the engaging portion  40  so that a user can extract the first connector housing  10  out of the second connector housing  20 . 
   The locking device  30  is made of any resilient material and formed in a unitary body with the first connector housing  10 . The locking device  30  ranges along the top wall  12  of the first connector housing  10  in parallel with an axis thereof along which the first connector housing  10  is inserted in and extracted from the second connector housing  20 . The locking device  30  is composed of a proximal portion  32  formed as a protrusion ranging along the top wall  12  and a resilient beam  33  bending from the proximal portion  32  about a resilient connection  32   a  with the proximal portion. The resilient connection  32   a  extends in a direction generally parallel to the axis of the connector housing  10  as illustrated, for example, in  FIG. 2 , and over-hanging the top wall  12 . The resilient beam  33  is provided with a rib  33   a  projecting therefrom, on which the locking projection  31  is projectingly formed. Because of resilience, the locking device  30  is elastically inwardly deformable along the proximal portion  32  and outwardly repulsive toward an inner surface, namely a sliding surface  22 , of the second connector housing  20  when the first connector housing  10  is connected with the second connector housing  20 . 
   A front end of the locking device  30  has a chamfered bevel  34 , which slips onto an inner surface  41  of the engaging portion  40  in the course of insertion of the first connector housing  10  into the second connector housing  20 . A rear end of the locking device  30  has a slit  36  as means for regulating repulsive force of the locking device  30 , which partially separates the proximal portion  32  and the resilient beam  33  and hence allows the rear portion of the locking device  30  to further inwardly deform. 
   The engaging portion  40  is formed on an open end  23 , into which the first connector housing  10  is inserted, of the second connector housing  20 . The engaging portion  40  spans and is supported by right and left sides of the open end  23 . The engaging portion  40  is provided with an engaging surface  42  as opposed to the open end  23 , which a locking surface  35  of the locking projection  31  latches when the first connector housing  10  is connected to the second connector housing  20 . Thereby the first connect housing  10  and the second connector housing  20  are preserved in the connection state and prevented from displacing. 
   The first connector housing  10  and the second connector housing  20  come into the connection state in a manner as described hereinafter. As shown in  FIGS. 1 through 5 , a front end of the terminal housing  11  of the first connector housing  10  is first inserted into the terminal housing  21  of the second connector housing  20 . In this occasion, the locking device  30  elastically deforms and abuts the inner surface  41  of the engaging portion  40  to slip therein. 
   When the terminal housing  11  is further inserted into the terminal housing  21 , the locking device  30  further deforms around the slit  36 . Further a contact spot where the locking device  30  touches the inner surface  41  of the engaging portion  40  moves from the chamfered bevel  34  toward a sliding slope  37  of the locking projection  31 . When the terminal housing  11  is further inserted, the inner surface  41  gets over the locking projection  31 . Accompanying this movement, any excessive force is not necessary because the slit  36  allows partial deformation of the locking device  30 . Then, the engaging surface  42  of the engaging portion  40  latches the locking projection  31 . 
   After the locking projection  31  latches the engaging surface  42 , the repulsive force of the locking device  30  preserves a rib sliding portion  38  to be repulsively supported in the inner surface  41 . 
   In accordance with the present embodiment described hereinbefore, the locking device  30  ranges in parallel with the axis along which the first connector housing  10  is inserted into the second connector housing  20  so as to deform perpendicularly to the axis about resilient connection  32   a.  A degree of deformation of the locking device  30  does not change so much depending on progress of the insertion of the first connector housing  10 . Thereby, force for the insertion against the repulsive force of the locking device  30  is kept substantially constant throughout the insertion. 
   Instead of providing the locking device  30  with the slit  36 , slots around the locking projection  31  may be formed as means for regulating repulsive force of the locking device  30 . This provides a similar effect to the above embodiment. 
   Although the invention has been described above by reference to an embodiment of the invention, the invention is not limited to the embodiment described above. Modifications and variations of the embodiment described above will occur to those skilled in the art, in light of the above teachings.
A connector set is provided with a first member including a locking device having a proximal portion formed as a protrusion ranging in parallel with an axis of the first member, a resilient beam extending from the proximal portion and being elastically deformable along the proximal portion, and a locking projection projecting from the resilient beam; and a second member configured to receive the first member in a direction of the axis of the first member, the second member including an engaging portion configured to latch the locking projection.