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BACKGROUND OF THE INVENTION AND RELATED-ART STATEMENT  
       [0001]     The present invention relates to a lock mechanism, and a latch device, which has a moving member that is capable of approaching and moving away from a main body, and holds said moving member to be immovable in the locked position and enables movement in the unlocked state.  
         [0002]     In vehicle compartment internal accessories such as cup holders and ashtrays, and audio devices., and the like, some have latch devices in order to close an opening-and-closing lid. For example, in Japanese Patent No. 3126992, a pair of circulating cam grooves having mutually different shapes is formed on both sides of a latch body  16 . Also, the base part of a trace member is fixed on a housing, and a pair of trace parts formed on a trace part of the trace member is made capable of tracing respectively following the pair of circulating cam grooves.  
         [0003]     These trace parts are pushed by the groove wall surface of the circulating cam groove in each pushing-in operation of the latch body, but because the shapes of the circulating cam grooves differ between the front side and the back side of the latch body, twisting is caused in the trace member. The trace parts are made to circulate in a fixed direction by the recoil force of the trace member against this twisting force.  
         [0004]     Also, the latch body becomes in a state being locked to the housing in a state in which the trace parts are coupled respectively in recessed parts formed respectively on the circulating cam grooves. By this, the lock strength can be made higher compared with the case of one trace part.  
         [0005]     However, in Japanese Patent No. 3126992, because the trace parts are made to circulate by twisting force on the trace member, the durability of the trace member is not good.  
         [0006]     The present invention, in consideration of the above circumstances, aims to provide a lock mechanism, and a latch device, in which the trace member can be made to circulate following the circulating cam groove without utilizing twisting force on the trace member.  
         [0007]     Further objects and advantages of the invention will be apparent from the-following description of the invention.  
       SUMMARY OF THE INVENTION  
       [0008]     In a first aspect of the invention, a lock mechanism has a moving member that is capable of approaching and moving away from a main body, and holds the moving member to be immovable in the locked position and enabling movement in the unlocked state. The lock mechanism comprises a circulating cam groove, which is formed on said main body; a trace member, which is formed roughly in an angle bracket shape and is provided to be capable of swaying on said moving member, and of which one trace part circulates following said circulating cam groove in each approaching and moving away operation of said moving member and locks the moving member in a state having coupled with a coupling part provided in the circulating cam groove; and-a wall surface, which is provided in a different position from said circulating cam groove on said main body, and another trace part of said trace member becomes able to contact it only in the locked state of said moving member.  
         [0009]     Furthermore, the circulating cam groove is formed on the main body. Meanwhile, the roughly bracket-shaped trace member is provided on the moving member, which is capable of approaching and moving away from the main body. Of this trace member, one trace part circulates following the circulating cam groove in each approaching and moving away operation of the moving member. Also, the one trace part locks the moving member in a state having coupled in the coupling part provided in the circulating cam groove.  
         [0010]     Also, on the main body, the wall surface is provided in a different position from the circulating cam groove, and the other trace part of the trace member becomes able to contact it only in the locked state of the moving member.  
         [0011]     That is, when the one trace part of the trace member circulates following the circulating cam groove, because the other trace part does not contact the wall surface, it comes to circulate in the same form as the circulating cam groove together with the one trace part. Therefore, there is no occurrence of twisting force on the trace member.  
         [0012]     Because it is not the case that the trace part is made to circulate by causing twisting force on the trace member, there is no requirement for high measurement precision in the circulating cam groove, and the mold expense can be reduced. Also, because twisting force is not caused on the trace member, the durability of the trace member can be improved.  
         [0013]     Also, by making it such that a gap is provided at least between the other trace part and the main body, the sliding resistance caused in circulation of the trace part of the trace member comes to be caused only between the one trace part and the wall surface of the circulating cam groove. Therefore, because only roughly the same sliding resistance as in the case when only one trace part is used is caused, regardless of the fact that two trace parts are being used, smooth operation can be obtained.  
         [0014]     Furthermore, in the locked state of the moving member, because the locked state of the moving member can be held by two trace parts, not only with the one trace part of the trace member coupling with the coupling part of the circulating cam groove, but also with the other trace part contacting the wall surface, the lock strength can be improved compared with the case when the locked state is held by one trace part.  
         [0015]     In a second aspect, the lock mechanism includes a moving member that is capable of approaching and moving away from a main body, and holds the moving member to be immovable in the locked position and enabling movement in the unlocked state. The lock mechanism comprises a circulating cam groove, which is formed on said moving member; a trace member, which is formed roughly in an angle bracket shape and is provided to be capable of swaying on said main body, and of which one trace part circulates following said circulating cam groove in each approaching and moving away operation of said moving member and locks the moving member in a state having coupled with a coupling part provided in the circulating cam groove; and a wall surface, which is provided in a different position from said circulating cam groove on said moving member, and another trace part of said trace member becomes able to contact it only in the locked state of said moving member.  
         [0016]     Still referring to the second aspect, the circulating cam groove and the wall surface are provided on the moving member and the trace member is provided on the main body to obtain approximately the same effect as the lock mechanism of the first aspect.  
         [0017]     In a third aspect of the lock mechanism, the other trace part of said trace member contacts said wall surface when a force is further applied toward a direction moving said moving member away from said main body from the locked state of the moving member.  
         [0018]     Further regarding the lock mechanism of the third aspect, in the normally locked state of the moving member, the other trace part of the trace member does not contact the wall surface, but when a force is further applied toward a direction moving the moving member away from the main body from this state, the other trace part contacts the wall surface so as not to allow the moving member to move away from the main body.  
         [0019]     That is, by making the lock strength in two levels, during normal use the lock strength of the moving member can be made lighter.  
         [0020]     In a fourth aspect of a lock mechanism, the circulating cam groove is roughly heart shaped, and the coupling part of the circulating cam groove is a recessed part.  
         [0021]     In a fifth aspect of a lock mechanism, the trace member is an elastically deformable metal pin.  
         [0022]     In a sixth aspect, a latch device has a latch body that is inserted into a roughly box-shaped housing and is forced toward the pulling-out direction. The latch device comprises a circulating cam groove, which is formed on one side of said latch body; a trace member, which is formed roughly in an angle bracket shape and is provided to be capable of swaying on said housing, and of which one trace part circulates following said circulating cam groove in each pushing-in operation of said latch body and locks the latch body in a state having coupled with a coupling part provided in the circulating cam groove; and a wall surface, which is formed on another side of said latch body, and another trace part of said trace member becomes able to contact it only in the locked state of said latch body.  
         [0023]     The circulating cam groove of the sixth aspect is formed on one side of the latch body. Meanwhile, the roughly angle bracket-shaped trace member is provided to be capable of swaying on the housing into which the latch body is inserted. Of this trace member, the one trace part of the trace member circulates following the circulating cam groove in each pushing-in operation of the latch body. Also, the one trace part locks the latch body in a state having coupled with the coupling part provided in the circulating cam groove.  
         [0024]     Furthermore, the wall surface is provided on the other side of the latch body, and the other trace part of the trace member becomes able to contact it only in the locked state of the latch body, and an effect similar to that of the first aspect can be obtained.  
         [0025]     A seventh aspect of the latch device is similar to the sixth aspect, wherein the other trace part of the trace member contacts the wall surface when a force is further applied toward the pulling-out direction of the latch body from the locked state of the latch body. By this, roughly the same effect as the effect recited in the second aspect can be obtained.  
         [0026]     An eighth aspect of the latch device is similar to the sixth or seventh aspect, wherein the circulating cam groove is roughly heart shaped, and the coupling part of the circulating cam groove is a recessed part.  
         [0027]     The ninth aspect of the latch device may be similar to the sixth through eighth aspects, wherein the trace member is an elastically deformable metal pin.  
         [0028]     In a tenth aspect, a lock mechanism comprises: a locking claw, which is provided on the housing of the latch device recited in any of sixth to ninth aspects, and is locked in a hole part formed on a first member; gripping parts, which are provided to be capable of approaching and moving away from each other on the front end part of the latch body of said. latch device, and become in a closed state being housed inside the housing in the locked state of the latch body, and become in an open state during unlocking of the latch body; a second member, which relatively approaches and moves away from said first member; and a gripped part, which is provided on said second member, and is gripped by said gripping parts in the locked state of the latch body, and is released from the gripped state of the gripping parts during unlocking.  
         [0029]     In the tenth aspect, the locking claw is provided on the housing of the latch device, and it is locked in the hole part formed on the first member. Also, the gripping parts which become capable of approaching and moving away from each other are provided on the front end part of the latch body of the latch device, they become in the closed state housed inside the housing in the locked state of the latch body, and they become in the open state during unlocking of the latch body.  
         [0030]     Meanwhile, the gripped part is provided on the second member which relatively approaches and moves away from the first member, it is gripped by the gripping parts in the locked state of the latch body, and it is released from the gripped state of the gripping parts during unlocking.  
         [0031]     Because the present invention is made of the above constitution, when the one trace part of the trace member circulates following the circulating cam groove, the other trace part does not contact the wall surface, and therefore there is no occurrence of twisting force on the trace member, there is no requirement for high measurement precision in the circulating cam groove, and the mold expense can be reduced. Also, because twisting force is not caused on the trace member, the durability of the trace member can be improved. Furthermore, because only roughly the same sliding resistance as in the case when only one trace part is used is caused, regardless of the fact that two trace parts are being used, smooth operation can be obtained. Also, because the locked state of the moving member can be held by two trace parts, the lock strength can be improved compared with the case when the locked state is held by one trace part. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1  is a perspective view showing the state in which the latch device and striker pertaining to a mode of working of the present invention are respectively attached;  
         [0033]      FIG. 2  is a perspective view showing the latch device and striker pertaining to a mode of working of the present invention;  
         [0034]      FIG. 3  is an exploded perspective view showing the latch device and striker pertaining to a mode of working of the present invention;  
         [0035]      FIG. 4 (A) is a sectional view showing the unlocked state of the latch body of the latch device pertaining to a mode of working of the present invention;  
         [0036]      FIG. 4 (B) is a sectional view showing the locked state of the latch body;  
         [0037]      FIG. 5  is a perspective view from the underside of the housing of the latch device pertaining to a mode of working of the present invention;  
         [0038]      FIG. 6  is a plan view showing the coupled state of the circulating cam groove and the trace part of the latch device pertaining to a mode of working of the present invention;  
         [0039]      FIG. 7  is a plan view showing the coupled state of the circulating cam groove and the trace part of the latch device pertaining to a mode of working of the present invention;  
         [0040]     FIGS.  8 (A) and  8 (B) are sectional views showing the coupled state of the circulating cam groove and the trace part of the latch device pertaining to a mode of working of the present invention;  
         [0041]     FIGS.  9 (A)- 9 (H) are operational drawings for explaining the coupled state of the circulating cam groove and the trace part of the latch device pertaining to a mode of working of the present invention;  
         [0042]      FIG. 10  is a perspective view showing a modified example of the circulating cam groove and the trace member pertaining to a mode of working of the present invention; and  
         [0043]      FIG. 11  is a perspective view showing another modified example of the circulating cam groove and the trace member pertaining to a mode of working of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0044]     A latch device pertaining to a mode of working of the present invention is now explained.  
         [0045]     As shown in  FIG. 1  through FIGS.  4 (A) and (B), the latch device  10  has a box-shaped housing  12 , and an opening  14  is formed on one end in the lengthwise direction. The latch body  16  is made capable of being housed inside this housing  12 , and the latch body  16  is inserted from the opening  14 .  
         [0046]     A gripping piece  30  sticking outward is provided on the front end part of the latch body  16 , and a hinge part  32  is provided on the base part of the gripping piece  30  so that it is made capable of elastic deformation. By this, the gripping piece  30  becomes capable of approaching and moving away from itself.  
         [0047]     Also, the base part  34  of the latch body  16  is roughly parallelepiped-shaped, and in  FIG. 4 (A), a circular hole  36  is formed on the left side of the base part  34  following the lengthwise direction from the bottom surface of the base part  34 . A compression coil spring  38  is made capable of being received inside this circular hole  36 .  
         [0048]     One end part of the compression coil spring  38  contacts the back wall of the circular hole  36 , and the other end of the compression coil spring  38  is made capable of contacting the bottom part of the housing  12 . A bar-shaped spring bearing  40  is placed upright on the bottom part of the housing  12 , and the compression coil spring  38  is received inside the circular hole  36  in a state having been fitted around the outside of the spring bearing  40 . By this, the latch body  16  becomes in a state regularly being forced toward the direction of pulling out from the housing  12  by the compression coil spring  38  while in a state being housed inside the housing  12 .  
         [0049]     Here, as shown in  FIG. 3 , a bump  42  is placed protruding on the left side surface of the base part  34 . Meanwhile, a long hole  44  capable of coupling with the bump  42  is formed on the wall surface  12 A of the housing  12 . The bump  42  after coupling with the long hole  44  becomes capable of moving following the long hole  44 . By this, movement of the latch body  16  against the housing  12  is allowed, while the latch body  16  is prevented from being completely pulled out from the housing  12 .  
         [0050]     Meanwhile, a rectangular frame  18  is provided on the opening  14  side of the housing  12 , and it sticks out from a wall surface  12 A of the housing  12  and a pair of wall surfaces  12 B orthogonal to the wall surface  12 A. From the wall surface  12 B, as shown in FIGS.  4 (A) and  4 (B), a locking claw  22  is placed protruding, and it is made capable of elastic deformation toward the inside of the wall surface  12 B.  
         [0051]     The housing  12  is made capable of attachment to opening-and-closing lids of audio devices, and the like, and cup holders and ashtrays inside vehicle compartments, and the like, and here, as one example it is made to be attached on the back surface of a box-shaped attachment member  24  (see  FIG. 1 ).  
         [0052]     A receiving recessed part  26  into which the housing  12  is capable of being received is provided on the back surface of this attachment member  24 , and it is made such that the rectangular frame  18  contacts the perimeter part of the receiving recessed part  26 . Also, a locking hole  28  into which the locking claw  22  is capable of locking is formed inside the receiving recessed part  26 , and the housing  12  is fixed to the attachment member  24  in the locked state of the locking claw  22 .  
         [0053]     Incidentally, as shown in  FIG. 5  ( FIG. 5  is a drawing viewing  FIG. 4 (A) from a direction rotated 90° ), an insertion hole  46  is formed on the bottom part of the housing  12 , and a locking part  48  constituted by locking pieces  48 A and  48 B which protrude in mutually different manners is provided on the perimeter part of the insertion hole  46 .  
         [0054]     A coupling recessed part  49  is formed on the base part of this locking piece  48 A, and it is made capable of coupling with a roughly angle bracket-shaped trace member  50  having a shape as if having cut out a part of a side composing the rectangular shape. The trace member  50  is formed with elastically deformable metal, and it is held to be capable of swaying in the direction of arrow A with the coupling part  48  as fulcrum. The front end part of this trace member  50  is made as trace parts  50 A and  50 B, and they are formed so that the front end surfaces face each other.  
         [0055]     Meanwhile, as shown in  FIG. 2  and  FIG. 3 , on the right side of the base part  34  of the latch body  16 , there is provided a thin part  52 , having been made thin by providing a stepping from the plane level of the left side surface of the base part  34 , and the trace parts  50 A and  50 B are made capable of facing it. Here, a pair of inclined parts  52 A is provided on the end surface of the thin part  52  so that the end surface of the thin part  52  becomes thin tipped whereby the trace parts  50 A and  50 B become easier to couple.  
         [0056]     Also, a roughly heart-shaped cam part  54  is placed protruding on the side that the trace part  50 A faces, and on the side that the trace part  50 B faces, as shown in  FIG. 6 , there is placed a roughly heart-shaped protruding part  58 , being positioned inside the cam part  54  viewing as a plane and being made smaller than the external shape of the cam part  54 .  
         [0057]     Also, on the thin part  52 , a stopper wall  62  facing opposite the cam part  54  is placed upright on the side of the gripping piece  30  (see  FIG. 4 (A)),. and a cam wall  64  protruding from the stopper wall  62  leaving the two ends (stopper parts  62 A,  62 B) of the stopper wall  62  is provided in a position facing opposite the recessed part  54 A of the cam part  54 . The cam surface  64 A of this cam wall  64  facing opposite the recessed part  54 A is formed in a state being inclined against the stopper wall  62 , and it guides the trace part  50 A.  
         [0058]     As shown in FIGS.  4 (A) and  4 (B), when the latch body  16  is pressed in a direction opposing the force of the compression coil spring  38  and is pushed into the housing  12 , the pair of gripping pieces  30  contacts the inner surface of the rectangular frame  18  of the housing  12 , and they are elastically deformed toward the direction of approaching each other (closing). At this time, the trace part  50 A moves while swaying following the shape of the circulating cam groove  56  constituting the cam wall  54 . At this time, the trace part  50 B does not contact the protruding part  58 .  
         [0059]     Meanwhile, as shown in  FIG. 8 (A), the trace member  50  is open slightly toward the direction of moving away from itself going toward the sides of the trace parts  50 A and  50 B, and the side of the trace parts  50 A and  50 B of the trace member  50  contacts the inner surface of the wall surface  12 A of the housing  12  so that the trace parts  50 A and  50 B do not come off from the thin part  52 .  
         [0060]     Here, the distance of separation between the outer surfaces on the side of the trace parts  50 A and  50 B of the trace member  50  is made larger than the distance of separation between the inner surfaces of the wall surface  12 A of the housing  12 , and the trace member  50  is in contact with the inner surface of the wall surface  12 A of the housing  12  in a state having elastic force accumulated.  
         [0061]     By this, during swaying of the trace member  50 , a suitable degree of elastic force comes to be applied to the trace member  50  and movement of the trace member  50  is restricted so that the trace part  50 A can assuredly circulate following the shape of the circulating cam groove  56 .  
         [0062]     Also, the interval between the front end surfaces of the trace parts  50 A and  50 B is made larger than the thickness of the thin part  52  so that the front end surfaces of the trace parts  50 A and  50 B do not contact the surface of the thin part  52 . Therefore, the trace part  50 A comes to move in circulation contacting the inner surface of the wall surface  12 A of the housing  12  and the wall surface of the circulating cam groove  56 , so that sliding resistance is not caused between the front end surfaces of the trace parts  50 A and  50 B and the surface of the thin part  52 .  
         [0063]     Also, as shown in  FIG. 4 (B), when the trace part  50 A reaches the recessed part  54 A of the cam part  54 , the trace part  50 A couples with that recessed part  54 A and movement is stopped. This state is the locked state of the latch body  16 , and the compression coil spring  38  comes to be held in a state having elastic force accumulated.  
         [0064]     Incidentally, as shown in  FIG. 6 , a slight gap t (here 0.15 mm) is provided between the recessed part  54 A of the cam part  54  and the recessed part  58 A of the protruding part  58  corresponding to that recessed part  54 A viewing as a plane, and when a force toward the pulling-out direction is further applied to the latch body  16  in the locked state of the latch body  16 , the trace member  50  is elastically deformed slightly, and as shown in  FIG. 7  and  FIG. 8 (B), the trace part  50 B contacts the recessed part  58 A of the protruding part  58  so that the lock strength by the trace member  50  is increased.  
         [0065]     Also, as shown in  FIG. 4 (A), when the locked state of the latch body  16  is released, the compression coil spring  38  having elastic force accumulated returns, the latch body  16  is pushed out from the housing  12 , the gripping pieces  30  return, and they move away from each other (open).  
         [0066]     Next, the operation of the latch device  10  pertaining to the mode of working is explained.  
         [0067]     As shown in  FIG. 4 (A) and  FIG. 9 (A), when the latch body  16  is in the state having been pushed out from the housing  12 , the trace part  50 A of the trace member  50  is positioned in the entrance of the circulating cam groove  56 , and the gripping pieces  30  provided on the front end part of the latch body  16  are in the expanded-diameter state apart from each other.  
         [0068]     Meanwhile, as shown in  FIG. 1 , the attachment member  24  is received inside a box-shaped receiving body  60  to be capable of drawing out, and a striker  66  having an expanded-diameter part  66 A formed on the front end part is provided toward the back of the receiving body  60 . When the front surface of the attachment member  24  is pressed, the expanded-diameter part  66 A presses the middle part between the gripping piece  30  and the gripping piece  30 , and the latch body  16  is pushed into the housing  12 . Thus, when the latch body  16  is pushed into the housing  12  (when it is pushed toward the direction opposing the force of the compression coil spring  38 ), the gripping pieces  30  are elastically deformed toward the direction of approaching each other, and the trace part  50 A contacts the perimeter wall of the cam part  54 , and as shown in  FIG. 9 (B), the trace part  50 A comes to move while swaying inside the circulating cam groove  56  constituted by the perimeter wall of the cam part  54  and the inner surface of the housing  12 .  
         [0069]     Here, the trace member  50  is in contact with the inner surface of the wall surface  12 A of the housing  12  in a state having elastic force accumulated, and a suitable degree of frictional force is applied to the trace member  50  during swaying of the trace member  50 . By this, the movement of the trace member  50  is restricted, and the trace part  50 A comes to circulate assuredly following the shape of the circulating cam groove  56 . That is, the trace member  50  does not swing about freely.  
         [0070]     Also, as shown in  FIG. 9 (C), when the trace part  50 A contacts the stopper part  62 A of the stopper wall  62 , the latch body  16  comes to be restricted in movement, and the latch body  16  cannot be moved further toward the back of the housing  12 .  
         [0071]     In this state, when the pressing force on the latch body  16  is released, the latch body  16  is pressed toward the direction of being pulled out from the housing  12  by the returning force of the compression coil spring  38 . By this, the trace part  50 A contacts the perimeter wall of the cam part  54  facing opposite the stopper part  62 A, and it is guided to the recessed part  54 A following the shape of the perimeter wall. Also, as shown in  FIG. 9 (D), when the trace part  50 A couples with the recessed part  54 A, the latch body  16  becomes in the locked state.  
         [0072]     Meanwhile, regarding the gripping piece  30 , as shown in  FIG. 4 (B), the outside of the gripping piece  30  hits the rectangular frame  18 , and the gripping piece  30  rotates toward the direction of approaching itself with the hinge part  32  as fulcrum. By this, the expanded-diameter part  66 A of the striker  66  is gripped by the gripping piece  30 , and it becomes in a state with the attachment member  24  being received inside the receiving body  60 .  
         [0073]     In this state, as shown in  FIG. 6 , a gap t is provided between the trace part  50 B and the recessed part  58 A of the protruding part  58 . From this state, when a force toward the direction of pulling the attachment member  24  out from the receiving part  50  is applied (when a force toward the direction of pulling the latch body  16  out from the housing  12  is applied), the trace part  50  is elastically deformed, and as shown in  FIG. 9 (E) and  FIG. 7 , the trace part  50 B couples with the recessed part  58 A of the protruding part  58 , and it is held in a state with the latch body  16  being locked by the trace part  50 A and the trace part  50 B.  
         [0074]     Next, when the front surface of the attachment part  24  is pressed, the latch body  16  is pushed into the housing  12  by the expanded-diameter part  66 A of the striker  66 , and the locked state of the latch body  16  is released. Also, the trace part  50 A contacts the cam wall  64 , and is guided to the stopper part  62 B following the cam surface  64 A, and as shown in  FIG. 9 (F), the latch body  16  is restricted in movement in a state having the trace part  50 A contacted to the stopper part  62 B.  
         [0075]     In this state, when the pressing force on the attachment part  24  is released (when the pressing force on the latch body  16  is released), the latch body  16  is pressed toward the direction of being pulled out from the housing  12  by the returning force of the compression coil spring  38 , and as shown in FIGS.  9 (G) and  9 (H), the trace part  50 A moves while swaying following the circulating cam groove  56  formed on the surface of the thin part  52 , and as shown in  FIG. 9 (A), it returns to the entrance of the circulating cam groove  56 , and as shown in  FIG. 4 (A), it becomes in a state having the latch body  16  pulled out from the housing  12 .  
         [0076]     At this time, the gripping pieces  30  of the latch body  16  become in a state expanded in diameter being apart from each other by the returning force of the hinge part  32 , the gripping state on the expanded-diameter part  66 A of the striker  66  is released, and the receiving body  60  can be pulled out from the attachment member  24 .  
         [0077]     Here, although it is not illustrated, a compression spring is provided between the receiving body  60  and the attachment member  24 , and by making it so that the attachment member  24  is pressed, it can be made so that the attachment member  24  is automatically pushed out from the receiving body  60  by the returning force of the compression spring when the locked state of the latch body  16  is released.  
         [0078]     Incidentally, in this mode, as shown in  FIG. 6  and  FIG. 7 , by placing the protruding part  58  that can be contacted by the trace part  50 B inside the cam part  54  and making it smaller than the external shape of the cam part  54  viewing as a plane, when the trace part  50 A is circulating following the shape of the circulating cam groove  56 , it is made such that the trace part  50 B does not contact the protruding part  58 , so that the trace part  50 B is made to circulate in the same form as the circulating cam groove  56  together with the trace part  50 A. Therefore, there is no occurrence of twisting force on the trace member.  
         [0079]     Thus, because it is not the case that the trace part  50 A is made to circulate by causing twisting force on the trace member  50 , there is no requirement for high measurement precision in the shape of the cam groove  54 , and the mold expense can be reduced. Also, because twisting force on the trace member  50  is not caused, the durability of the trace member  50  can be improved.  
         [0080]     Furthermore, when the trace part  50 A circulates following the shape of the circulating cam groove  56 , because the trace part  50 B does not contact the protruding part  58 , it becomes that only roughly the same sliding resistance as in the case when only one trace part is used is caused, regardless of the fact that two trace parts  50 A and  50 B are being used.  
         [0081]     Therefore, smooth operation can be obtained. Here, the groove width of the circulating cam groove  56  is made larger than the outer diameter measurement of the trace part  50 A, and the sliding resistance acting on the trace part  50 A is made smaller compared with the case when the groove width of the circulating cam groove  56  is made roughly the same as the outer diameter measurement of the trace part  56 A.  
         [0082]     Also, as shown in  FIG. 7  and  FIG. 8 (B), in the locked state of the latch body  16 , because the locked state of the latch body  16  can be held by the two trace parts  50 A and  50 B, by making it such that not only is the trace part  50 A coupled with the recessed part  54 A of the cam part  54 , but also the trace part  50 B is coupled with the recessed part  58 A of the protruding part  58 , the lock strength can be improved compared with the case when the locked state is held by one trace part.  
         [0083]     As shown in  FIG. 6 , a gap “t” is provided between the recessed part  54 A of the cam part  54  and the recessed part  58 A of the protruding part  58 .  FIG. 7  illustrates the latch body  16  when a force, toward the direction of pulling the attachment member  24  out from the receiving body  60 , is further applied from the normally locked state of the latch body  16 . The trace part  50 B couples with the recessed part  58 A of the protruding part  58 , and the locked state of the latch body  16  is held by the trace part  50 A and the trace part  50 B. In some embodiments, a gap “t” may not be provided. Therefore, it also may be made such that the locked state of the latch body  16  is held by the trace part  50 A and the trace part  50 B in the state having normally locked the latch body  16 .  
         [0084]     Also, the protruding part  58  was made roughly heart shaped, but it is not limited to this shape. Because it is &#39;sufficient if the trace part  50 B becomes capable of contact only in the state having the trace part  50 A coupled in the recessed part  54 A, it is sufficient if a recessed part  58 A being positioned inside the cam part  54  viewing as a plane and being capable of coupling with the trace part  50 B is formed, for example, it also may be crescent shaped. Also, here, the trace member  50  was formed with metal, but it is not absolutely necessary to be metal.  
         [0085]     Furthermore, in this mode, a latch device  10 , having a latch body  16  inserted inside a housing  12  and is forced toward the pulling-out direction, is attached to the attachment member  24 . However, the latch device  10  may, in other embodiments, be, attached to the receiving body  60 , and the striker  66  may be attached to the attachment member  24 .  
         [0086]     Furthermore, although one embodiment of the lock mechanism may comprise a circulating cam groove  56  and a trace member  50 , other embodiments are contemplated.  
         [0087]     For example, as shown in  FIG. 10 , the trace member  50  may be attached directly to the attachment member  24  to be capable of swaying, and the a cam body  68  having a cam part  54  and a protruding part (not illustrated) formed may be provided on the receiving body  60 . Also, although it is not illustrated, the cam body  68  may be provided on the attachment part  24 , and the trace member  50  may be provided on the receiving body  60 .  
         [0088]     Here, in the case when the trace member  50  is not received inside the housing  12  (see  FIG. 8 (A)) and it in a state being exposed to the outside, the coupling state between the coupling part  48  holding the trace member  50  to be capable of swaying and the trace member  50  is made tighter so that frictional force is applied to the trace member  50  during swaying of the trace member  50 . By this, the movement of the trace member  50  is restricted.  
         [0089]     Furthermore, in this mode, the cam part  54  was placed protruding on one face of the thin part  52 , and the protruding part  58  was placed protruding on the other face of the thin part  52 , but as shown in  FIG. 11 , the cam part  54  and the protruding part  58  also may be placed in parallel.  
         [0090]     In this case, a roughly U-shaped trace member  70  is used, and it is held by a holding member  72  so that it becomes capable of swaying toward the direction of arrow B. A boss  74  is provided on the holding member  72 , and an arc-shaped arc rib  76  is provided roughly concentrically to the boss  74  with a gap between it and the outer perimeter of the boss  74 . Although trace member  70  is coupled in the gap between this arc rib  76  and boss  74 , the coupling state is made tighter so that frictional force is applied on the trace member  70  during swaying of the trace member  70 . By this, the movement of the trace member  70  is restricted.  
         [0091]     Also, the front end parts of the trace member  70  are bent and made as trace parts  70 A and  70 B. The distance of separation between the trace part  70 A and the trace part  70 B is held constant, the trace part  70 A circulates following the cam part  54 , and the trace part  70 B moves accompanying the movement of the trace part  70 A. Also, the trace part  70 B first contacts with the protruding part  58  and becomes capable of coupling with the recessed part.  58 A in the state with the trace part  70 A coupled with the recessed part  54 A of the cam part  54 .  
         [0092]     The disclosure of Japanese patent application No. 2005-141721 filed on May 13, 2005 is incorporated herein as a reference.  
         [0093]     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.

Summary:
A lock mechanism holds a moving member on a main body immovably in a locked state and allows movement in an unlocked state. The lock mechanism includes a circulating cam groove formed on the main body or the moving member, and a trace member having an angle bracket shape with one and the other trace parts to sway on the main body or moving member. The one trace part circulates along the circulating cam groove in each approaching and moving away operation of the moving member, and locks the moving member in a state having coupled with the coupling part. A wall surface is formed on the main body or moving member to be disposed in a different position from the circulating cam groove so that the other trace part of the trace member is operable to contact the wall surface only in the locked state of the moving member.