Patent Publication Number: US-7591668-B2

Title: Connector and connector assembly

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a connector and a connector assembly. 
   2. Description of the Related Art 
   U.S. Pat. No. 6,824,417 discloses a connector that has a female housing with a lock arm and a detector mounted on the lock arm. The detector is movable between a standby position and a detection position with respect to the female housing. A movement preventing means holds the detector at the standby position in the process of connecting the housing with a mating housing. However, the detector is freed from the movement preventing means and can move to the detection position as the housings are connected properly. Accordingly, the connected state of the two housings can be detected based on whether the detector can be moved. 
   The arrival of the above-described detector at the detection position is confirmed by seeing the position of the detector or hearing a locking sound given by the detector at the detection position. However, there are cases where the position of the detector cannot be confirmed clearly or the locking sound may be drowned out by noise at an operation site. Thus, there is a likelihood of forgetting to move the detector and, hence, impairing the connection detecting function of the connector. 
   Japanese Unexamined Patent Publication No. 2006-253073 discloses another connector with a connection detecting function. This connector has a first housing with a lock projection. A second housing is connectable with the first housing and includes a lock arm. A connection detector is provided in the second housing and is slidable between an initial position and a detection position in directions substantially parallel to a connecting direction of the two housings. A resilient piece is cantilevered from the connection detector and extends towards the detection position. 
   The resilient piece contacts the lock arm when the connection detector is at the initial position and prevents a sliding movement of the connection detector to the detection position. Additionally, the resilient piece is displaceable together with the lock arm. The lock arm interferes with the lock projection in the process of connecting the housings and is deformed resiliently in a direction intersecting the connecting direction of the two housings. The lock arm passes the lock projection when the two housings are connected properly. Thus, the lock arm restores resiliently and engages the lock projection to prevent separation of the two housings. Additionally, the resilient piece is disengaged from the lock arm by interference with the lock projection. Thus, the connection detector can slide to the detection position. 
   An external force could be exerted on the connection detector of the above-described connector to move the connection detector towards the detection position before the housings are connected. This force could resiliently curve an area between a base end of the resilient piece and a locking portion thereof that engages the lock arm. Excessive deformation of the resilient piece could disengage the resilient piece from the lock arm due to the resilient restoring force of the resilient piece. As a result, the connection detector can slide to the detection position even though the housings are not connected yet. 
   The invention was developed in view of the above situation and an object thereof is to improve overall operability of a connection function. 
   SUMMARY OF THE INVENTION 
   The invention relates to a connector with a housing capable of accommodating at least one terminal fitting. At least one detector is assembled with the housing and can move from a standby position to a detection position if the housing is connected properly with a mating housing. However, the detector is prevented from moving to the detection position if the housing is connected only partly with the mating housing. The detector is has at least one opening and a background color seen through the opening differs when the detector is at the standby position than when the detector is at the detection position. Thus, the arrival of the detector at the detection position can be confirmed clearly. As a result, an operator will not forget to move the detector, and the reliability of a connection detecting function is improved. 
   A part of the detector may be seen through the opening when the detector is at the standby position and a part of the housing may be seen through the opening when the detector is at the detection position. The color in the opening and the color of a part surrounding opening can be the same at the standby position. Thus, an operator knows the arrival of the detector at the detection position when the background color seen through the opening becomes different from the color of the surrounding part, and the operator need not remember the specific background colors. 
   The housing preferably includes a lock arm for holding a connected state with the mating housing, and a corresponding part of the lock arm can be seen through the opening when the detector is at the detection position. Thus, the condition of the corresponding part of the lock arm also can be confirmed. 
   The detector preferably is a first color and the housing is a color different from the first color. Thus, it is not necessary to color-separate one part and production is easier. 
   A resilient piece preferably extends from the detector towards the detection position. The resilient piece contacts the lock arm to prevent a sliding movement of the detector to the detection position and is engaged with the lock arm for displacement together with the lock arm in a state where the detector is at the initial position. The lock arm interferes with a lock projection of the mating housing in a connecting process of the housing with the mating housing and deforms resiliently in a direction intersecting the connecting direction of the two housings. The lock arm passes the lock projection when the housings are connected properly and resiliently restores to engage the lock projection in a manner to prevent separation of the housings. The resilient piece is disengaged from the lock arm by interference with the lock projection so that the detector can move to the detection position. Accordingly, the detector is prevented from moving from an initial position to a detection position in a state where the housings are not yet connected, thereby improving operability. 
   An external force could be exerted on the connection detector to move the connection detector towards the detection position before the housings are connected. This external force could curve or otherwise deform the resilient piece so that the resilient piece contacts the restriction before being disengaged from the lock arm to prevent any further curved deformation of the resilient piece. Thus, the resilient piece cannot curve sufficiently to disengage from the lock arm. Consequently, the connection detector cannot move from the initial position to the detection position before the housings are connected. 
   A restriction preferably is provided to prevent an excessive curved deformation of the resilient piece towards a side opposite to the lock when the resilient piece is engaged with the lock arm and when the connection detector is at the initial position. 
   The maximum curved deformation of the resilient piece is between the base end of the resilient piece and the lock that engages the lock arm. Thus, the restriction is formed in this area where maximum deformation will occur, and hence can prevent excessive deformation of the resilient piece. 
   The resilient piece interferes with the lock projection when the housings are connected properly and the connection detector is at the initial position. Thus, the resilient piece inclines and displaces towards the restriction. Displacement of the resilient piece is maximal at its extending end. Thus, the restriction is not formed at the extending end of the resilient piece, and there is no likelihood of hindering displacement of the resilient piece due to interference of the extending end of the resilient piece with the restriction. 
   An arcuate or tapered contact preferably is formed at an end edge of the restriction closest to the extending end of the resilient piece. The extending end of the resilient piece engages the contact end edge of the restriction when the resilient piece is displaced to approach the restriction. This contact and the resilient piece could deform if the contact was an angular edge. However, the contact is arcuate or tapered and the resilient piece will not deform. 
   The restriction preferably is integral or unitary to the connection detector. Since the restriction is formed on the connection detector as a formation base of the resilient piece, there is no likelihood of disrupting the positional relationship of the resilient piece and the restriction. 
   The connection detector preferably includes two side walls at opposite sides of the resilient piece. The restriction connects the side walls and is aligned angularly to the side walls. Thus, the deflection strength of the restriction is higher than if the restriction is a single plate, and curved deformation of the resilient piece is restricted reliably. 
   The invention also relates to a connector assembly comprising the above described connector and a mating connector connectable therewith. 
   These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view in section showing a state before two housings are connected in a first embodiment of the invention. 
       FIG. 2  is a side view in section showing a state in the process of connecting the two housings. 
       FIG. 3  is a side view in section showing a state where the two housings are properly connected to bring a detector to a detection position. 
       FIG. 4  is a plan view showing a state where the detector is held at a standby position with respect to a lock arm. 
       FIG. 5  is a plan view showing a state where the detector is held at the detection position with respect to the lock arm. 
       FIG. 6  is a front view showing the state where the detector is held at the detection position with respect to the lock arm. 
       FIG. 7  is a front view of the detector. 
       FIG. 8  is a bottom view of the detector. 
       FIG. 9  is a front view of the housing. 
       FIG. 10  is a plan view of the housing. 
       FIG. 11  is a vertical section of a second embodiment showing a state where a restriction prevents excessive curved deformation of a resilient piece. 
       FIG. 12  is a vertical section of a second housing with a connection detector located at an initial position. 
       FIG. 13  is a vertical section showing a connecting process of two housings. 
       FIG. 14  is a vertical section showing a state where the two housings are properly connected and the connection detector is at the initial position. 
       FIG. 15  is a vertical section showing a state where the two housings are properly connected and the connection detector is at a detection position. 
       FIG. 16  is a horizontal section showing a state where the connection detector is held at the initial position. 
       FIG. 17  is a plan view of the second housing. 
       FIG. 18  is a plan view showing a state where the connection detecting member is detached from the second housing. 
       FIG. 19  is a front view showing a state where the connection detector is detached from the second housing. 
       FIG. 20  is a bottom view of the connection detector. 
       FIG. 21  is a front view of the connection detector. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first embodiment of the invention is described with reference to  FIGS. 1 to 10 . A connector of this embodiment is provided with a housing  10 , one or more female terminal fittings  40  and a detector  60 . The housing  10  is connectable with a mating housing  90  and the detector  60  is movable between a standby position SP and a detection position DP with respect to the housing  10 . In the following description, ends of the housings  10 ,  90  to be connected are referred to as front ends concerning forward and backward directions. 
   The male housing  90  is made e.g. of synthetic resin and includes a terminal accommodating portion  91  for accommodating male terminal fittings  50  and a tubular receptacle  92  that projects forward from the front of the terminal accommodating portion  91 . Cavities  93  are formed in the terminal accommodating portion  91  and accommodate male terminal fittings  50 . Tabs  51  of the male terminal fittings  50  project forward from the front surface of the cavities  93  and into the receptacle  92 . A releasing piece  94  projects forward from the back of the receptacle  92  and a lock  95  projects from the upper surface of the receptacle  92 . A retainer  96  is mounted in the terminal accommodating portion  91  for retaining the male terminal fittings  50 . The retainer  96  includes terminal locks  97  for locking boxes  52  of the male terminal fittings  50 , and substantially sawtooth-shaped projections  98  for biting in the insulation coatings of wires  55  connected with the male terminal fittings  50 . The male terminal fittings  50  are retained in the cavities  93  primarily by the engagement of locking lances  54  with the inner walls of the cavities  94 . The locking lances  54  are formed in the boxes  52  by cutting and bending. Alternatively or additionally, the male terminal fittings  50  may be retained in the respective cavities  93  by locks (not shown) provided thereon. 
   The housing  10  is made e.g. of synthetic resin and includes a flat block-shaped housing main body  11 . A lock arm  12  is provided on the upper surface of the housing main body  11  and a fitting  13  surrounds the housing main body  11 , as shown in  FIG. 9 . Cavities  14  are arranged in a lateral row in the housing main body  11  and accommodate female terminal fittings  40 . As shown in  FIG. 10 , left and right receiving portions  15  project from the rear end of the housing main body  11 . Further, a communication space  16  penetrates a rear end of the housing main body  11  and provides communication between the upper surface of the housing main body  11  and the cavities  14 . A wire holder  17  can be fit in this communication space  16 . As shown in  FIG. 1 , the wire holder  17  includes substantially sawtooth-shaped or pointed projections  18  for engaging the insulation coatings of wires  41  to prevent movements of the wires  41  in forward and backward directions. 
   An accommodating chamber  19  for a shorting terminal  42  is formed in the front of the housing main body  11  and provides communication between at least two adjacent cavities  14 . The accommodating chamber  19  also opens in a side surface of the fitting  13 , and the shorting terminal  42  can be mounted through this side opening. The shorting terminal  42  contacts the female terminal fittings  40  in at least two of the cavities  14  from below to short the terminal fittings  40  (see  FIG. 1 ) until connection of the two housings  10 ,  90  is completed. The releasing piece  94  of the receptacle  92  presses the shorting terminal  42  away from the terminal fittings  40  to release the shorted state when the housings  10 ,  90  are connected properly (see  FIG. 3 ). 
   The lock arm  12  has left and right legs  21  that stand up from the upper surface of the housing main body  11 . Left and right arms  22  extend forward and back from the upper ends of the legs  21  and a lower plate  23  couples the bottom end edges of the arms  22 . A substantially rectangular upper plate  24  couples the upper end edges of the arms  22  and a lock main body  25  couples the front ends of the arms  22 . The lock arm  12  is pivotally displaceable up and down like a seesaw in a direction intersecting a connecting direction of the two housings  10 ,  90  with the legs  21  as supports. A formation area of the lower plate  23  in forward and backward directions extends from a position behind the lock main body  25  to the rear ends of the arms  22 , and the upper plate  24  is arranged at the rear ends of the arms  22 . The lower and upper plates  23  and  24  are thin and are arranged substantially horizontally in different levels. A mount space  26  is defined between the upper plate  24  and the lower plate  23  and between the two arms  22 . 
   Left and right guide ribs  27  project at opposite lateral edges of the arms  22  extend substantially in forward and backward directions. Left and right retaining projections  28  project at the opposite lateral edges of the lower surfaces. The lower surfaces of the guide ribs  27  and the upper surfaces of the retaining projections  28  are connected unitarily. 
   Left and right side walls  31  stand up from the fitting  13  at opposite sides of the lock arm  12 . A coupling wall  32  couples the front ends of the upper edges of the opposite side walls  31 . 
   The outer surfaces of the housing  10  including the lock arm  12  are formed entirely in a second color, specifically in a bright color, such as yellow, and the entire external appearance thereof is seen uniformly in the bright color before the detector  60  is assembled. 
   Each female terminal fitting  40  is narrow and long in forward and backward directions. A substantially box-shaped connecting portion  43  is formed at the front part of the female terminal fitting  40  and a wire crimping portion  44  with at least one open barrel is formed at the rear part of the female terminal fitting  40 . A locking lance  45  is formed in the connecting portion  43  by cutting and bending. The female terminal fitting  40  is inserted into the cavity  14  from behind and is retained in the cavity  14  by the resilient engagement of the locking lance  45  with the inner wall of the cavity  14 . Alternatively or additionally, the female terminal fitting  40  may be retained in the cavity  14  by a locking portion provided in the cavity  14 . 
   The detector  60  is made e.g. of synthetic resin and includes a substantially block-shaped operable portion  61  near the rear end. Left and right guide arms  62  are cantilevered forward from the opposite sides of the operable portion  61  and a cover  63  couples the upper end edges of the guide arms  62 . A detecting main body  64  is cantilevered forward from the operable portion  61  at a position below the cover  63  and between the two guide arms  62 , as shown in  FIG. 8 . As shown in  FIG. 7 , guide grooves  65  are formed in the inner surfaces of the guide arms  62  and extend in forward and backward directions. The guide grooves  65  are arranged so that openings thereof face inwardly. Left and right retaining projections  66  are provided on the inner surfaces of the guide arms  62  below the guide grooves  65 . 
   As shown in  FIG. 4 , the cover  63  is a substantially flat plate covering substantially the rear half of the housing main body  11 . Left and right contact pieces  67  project forward from the front end edge of the cover  63 . Left and right through holes  68  are formed at positions near the opposite lateral edges of the cover  63 . The through holes  68  of the cover  63  are rectangular and are longer in forward and backward directions. The corresponding retaining projections  66  can be seen through the through holes  68  in an isolated state before being assembled. The cover  63  also is formed with a window  69  at a substantially widthwise center position near the rear end edge. The window  69  of the cover  63  is a substantially round hole. The upper surface of the detecting main body  64  can be seen through the window  69  when the detector  60  is in a standby position SP and the upper surface of the upper plate  24  can be seen through the window  69  when the detector  60  is at the detection position DP. 
   The detecting main body  64  is a narrow plate that is long in forward and backward directions and is resiliently deformable up and down. A contact  71  projects down at the front end of the detecting main body  64 . A front end portion of the detecting main body  64  is thinner than a base end thereof that is connected with the operable portion  61  to enable smooth deformations of the front end and to increase the strength of the base end. The bottom end of the operable portion  61  is slightly below the lower surface of the detecting main body  64 , and the front end edge of the bottom end of the operable portion  61  defines connection detecting portions  72 . 
   The outer surfaces of the detector  60  preferably are entirely in a first color different from the second color, specifically in a darker color such as blue, so that the entire external appearance thereof is seen uniformly in the first color before being assembled with the lock arm  12 . 
   The detector  60  is assembled with the lock arm  12  of the housing  10  from behind so that the detecting main body  64  enters the mount space  26 . The guide ribs  27  engage the guide grooves  65  in this assembling process so that the detector  60  is slid forward with respect to the lock arm  12  and the guide arms  62  are deformed resiliently out in the width direction by the interference of the retaining projections  28 ,  66 . The retaining projections  66  of the detector  60  engage the retaining projections  28  of the lock arm  12  from the front when the detector  60  is assembled to the standby position SP with respect to the lock arm  12  for retaining the detector  60 . Additionally, the contact projection  71  engages the lock main body  25  from behind to prevent the detector  60  from moving any farther forward. These engaging actions hold the detector  60  at the standby position SP. At this time, the detecting main body  64  is held between the lower and upper plates  23  and  24  and between the left and right arms  22 . Furthermore, the upper plate  24  is held between the detecting main body  64  and the cover  63 . Thus, the detector  60  is united with the lock arm  12  and can be displaced like a seesaw. A sliding space  39  for the upper plate  24  is defined between the lower surface of the cover  63  and the upper surface of the detecting main body  64 , and a dimension of the sliding space  39  is substantially equal to or slightly larger than the thickness of the upper plate  24 . The lock arm  12  and the detector  60  displace in the unlocking direction when the operable portion  61  is pressed down. 
   The detector  60  is held at the standby position SP with respect to the lock arm  12 . In this state, as shown in  FIGS. 1 and 4 , the operable portion  61  projects more backward than the rear surface of the housing main body  11 . The upper surfaces of the arms  22  can be seen through the through holes  68  and the upper surface of the detecting main body  64  can be seen through the window  69  when the detector  60  is viewed from above. The detector  60  is entirely in the first color (preferably blue). Thus, a background color seen through the window  69  is the same first color (blue) as a peripheral part of the window  69 . On the other hand, a background color seen through the holes  68  is the second color (preferably yellow) as the color of the housing main body  11  and remains the second color (yellow) even when the detector  60  is moved. 
   The receptacle  92  of the mating housing  90  is inserted between the housing main body  11  and the fitting  13  when the housing  10  is connected with the mating housing  90 . In this connecting process, the lock main body  25  of the lock arm  12  moves onto the lock  95  of the mating housing  90 , as shown in  FIG. 2 . Thus, the lock arm  12  and the detector  60  are displaced to extend obliquely up towards the front and the connection detecting portions  72  of the detector  60  are displaced in to face the receiving portions  15  of the housing main body  11  from behind. The connecting operation of the two housings  10 ,  90  could be left incomplete (e.g. halfway), and then an attempt could made to move the detector  60  forward toward the detection position DP. However, the connection detecting portions  72  will contact the receiving portions  15  to prevent a forward movement of the detector  60 . The contact projection  71  is kept engaged with the lock main body  25  to prevent the forward movement of the detector  60 . 
   The lock main body  25  passes the lock  95  when the two housings  10 ,  90  are connected properly. Thus, the lock arm  12  returns resiliently towards its free state to engage the lock main body  25  with the lock  95  and to hold the housings  10 ,  90  together. At this time, the lower surface of the contact projection  71  contacts the upper surface of the lock  95  so that the detecting main body  64  is deformed up and out relative to the lock arm  12 . Further, the operable portion  61  of the detector  60  is displaced up and out together with the lock arm  12 , thereby disengaging the connection detecting portions  72  from the receiving portions  15 . As a result, the contact projection  71  and the lock main body  25  are disengaged to permit a movement of the detector  60  to the detection position DP. In this state, the background color seen through the window  69  remains the second color (yellow) since the position of the detector  60  relative to the lock arm  12  continues to be the standby position SP. 
   The detector  60  then is slid towards the detection position DP with respect to the lock arm  12 . In this sliding process, the contact projection  71  passes the lock  95  and the lock main body  25 . Thus, the detecting main body  64  restores resiliently. As this sliding movement ends, the contact projection  71  engages the lock main body  25  from the front, as shown in  FIG. 6 . The front ends of the contact pieces  67  then contact the coupling wall  32  from behind to prevent further forward movement of the detector  60 . In this way, the detector  60  is held at the detection position DP and cannot move forward and back with respect to the lock arm  12 , as shown in  FIGS. 3 and 5 . Further, front ends of both guide arms  62  slip under the coupling wall  32  and contact the lower surface of the coupling wall  32  to prevent upward displacement of the detector  60  and the lock arm  12  in the unlocking direction. Thus, the lock main body  25  and the lock  95  are kept reliably engaged to doubly lock the housings  10 ,  90 . The rear end of the detector  60  at the detection position DP and the rear end of the housing main body  11  are aligned in forward and backward directions. 
   The upper plate  24  of the lock arm  12  is displaced back with respect to the detector  60  in the sliding space  39  between the detecting main body  64  and the cover  63  as the detector  60  is moved from the standby position SP to the detection position DP. Thus, the upper plate  24  of the lock arm  12  gradually appears in the window  69  immediately before the detector  60  reaches the detection position DP. The upper plate  24  appears in the entire window portion  69  as the detector  60  reaches the detection position DP. Accordingly, if an operator looks inside the window  69  in this state, the second color (yellow color) of the upper plate  24  (housing  10 ) can be seen through the window  69 . 
   On the other hand, the upper plate  24  is located before the window  69  if the detector  60  is kept at the standby position SP. Therefore only the upper surface of the detecting main body  64  can be seen through the window  69  via the sliding space  39  and the background color seen through the window  69  is the same first color (blue color) as the peripheral part of the window  69 . Accordingly, an operator judges that the detector  60  has not been moved if there is no change in the background color seen through the window  69 , and, in this case, the detector  60  is pushed to the detection position DP anew. 
   The background color seen through the window  69  is a different color than the one seen at the standby position SP when the detector  60  is moved from the standby position SP to the detection position DP. Therefore the arrival of the detector  60  at the detection position DP is detected visually and clearly. As a result, an operator will not forget to move the detector  60 , thereby improving the reliability of the connection detecting function of the connector. 
   The color in the window  69  when the detector is at the standby position SP is the color of the upper surface of the detecting main body  64  and the color outside the window  69  at the upper surface of the cover  63  is the same (e.g. blue). Thus, the operator need not remember the background colors seen through the window  69  at the standby position SP and at the detection position DP and can judge the arrival of the detector  60  at the detection position DP by the fact that the color (yellow in this embodiment) is different from that of the peripheral part of the window  69  has appeared in the window  69 . Therefore, an erroneously confirming possibility of the operator decreases and the reliability of the connection detecting function is improved. 
   The detecting main body  64  of the lock arm  12  is seen through the window  69  at the detection position DP. Thus, a condition such as a defective state of the detecting main body  64  also can be confirmed. Therefore the quality of the lock arm  12  also can be improved. 
   The detector  60  preferably is entirely in the first color (blue) and the housing  10  preferably is entirely in the second color (yellow) different from the first color. Thus, there is no need to color-separate the upper plate  24  and the detecting main body  64  from surrounding parts, and production is easier. 
   The window  69  is at the easily detectable position of the detector  60  in the widthwise intermediate part of the outer or upper surface of the connector near the operable portion  61  and has an easily visible shape (looped opening). Thus, the visibility thereof is good. 
   The invention is not limited to the above described and illustrated embodiment. For example, the following embodiments are also embraced by the technical scope of the present invention. 
   It is sufficient that the background colors seen through the window are different at the standby position and at the detection position, and they can be any colors. Each background color may not necessarily be limited to a single color and may be a combination of colors. Of course, it is preferable to combine such colors that a color difference chromatically stands out between the standby position and the detection position. 
   The background other than the detecting main body may be seen through the window at the standby position, and the background other than the upper plate may be seen through window portion at the detection position. 
   The detector may be mounted on a movable part of the housing other than the lock arm, such as a lever in a lever-type connector. 
   The window may be a cutout at an end edge of the detector. 
   A plurality of windows may be formed in the detector. 
   A transparent or semitransparent filter may be mounted to cover the window to prevent external matter, such as dust, from entering the window. 
   A second embodiment of the invention is described with reference to  FIGS. 11 to 21 . A connector of this embodiment is provided with a first housing  110  having male terminal fittings  111  mounted therein and a second housing  120  having female terminal fittings  121  mounted therein. It should be noted that, in the following description, forward and backward directions are the same directions as those parallel to a connecting direction of the housings  110 ,  120 . 
   The first housing  110  is made e.g. of synthetic resin and includes a tubular receptacle  112  projecting forward in the same direction as the connecting direction with the second housing  120 . A lock  113  projects from the upper surface (outer surface) of the upper wall of the receptacle  112 . 
   The second housing  120  is made unitarily e.g. of synthetic resin and has a block-shaped terminal holding portion  122  and a rectangular tubular fitting  123  that surrounds a front portion of the terminal holding portion  122 . The female terminal fittings  121  are accommodated in the terminal holding portion  122 . A lock arm  124  is formed unitarily on the upper surface of the terminal holding portion  122  and extends in forward and backward directions. The lock arm  124  includes left and right arms  125  that extend in forward and backward directions, a lock  126  that connects the front ends of the arms  125 , a coupling plate  127  that couples the rear ends of the arms  125 , legs  128  that project from substantially central positions of the lower surfaces of the arms  125 , and a lower plate  129  that couples the bottom end edges of the arms  125  and is supported on the terminal holding portion  122  at the legs  128 . The lock arm  124  is in a locking posture where the arms  125  extend forward and backward in directions substantially parallel to connecting and separating directions of the two housings  110 ,  120  and are in a free state where the lock arm is not resiliently displaced. However, the lock arm  124  is resiliently displaceable like a seesaw to an unlocking posture reached by displacing a front end of the lock arm  124  up substantially orthogonal to forward and backward directions with the legs  128  as supports. Guide ribs  130  are formed at the outer lateral edges of the arms  125  extend in the length direction of the arms  125 . Stoppers  131  are formed on lower surfaces of the guide ribs  130 . The lower plate  129  extends from the rear ends of the arms  125  to a position slightly behind the lock  126  and the front ends of the arms  125 . There is an open space between the front end edge of the lower plate  129  and the lock  126  for receiving the lock projection  113 . An upper wall  123 A of the tubular fitting  123  is formed with an opening  123 B by cutting away an area excluding the opposite left and right edges and a front edge, and the lock arm  124  is exposed upward through this opening  123 B. 
   A connection detector  133  is mounted in the second housing  120  and is made unitarily e.g. of synthetic resin. The connection detector  133  has left and right long narrow side walls  134  that extend in forward and backward directions. An operable portion  135  couples the rear ends of the side walls  134 , and a bar-shaped support  136  projects forward and parallel with the side walls  134  in a space between the opposite side walls  134 . A resilient piece  137  extends farther forward from the front extending end of the support  136  and a restricting plate  138  couples the upper edges of the side walls  134 . 
   Guide grooves  139  are formed in the inner side surfaces of the side walls  134  and extend substantially parallel to the lengthwise direction of the side walls  134 . Retaining projections  140  project in from the inner side surfaces of the side walls  134  at substantially central positions in forward and backward directions. The resilient piece  137  has a smaller vertical thickness than the support  136 . The upper surface of the resilient piece  137  is substantially flush with and continuous with the upper surface of the support  136  and the lower surface of the resilient piece  137  is above the lower surface of the support  136 . A lock  141  is formed at the front end of the resilient piece  137  for engaging the lock  126  of the lock arm  124 . The lock  141  has a projecting end  142  at the front extending end of the resilient piece  137 , a touching portion  143  projecting down from a position slightly behind the projecting end  142 , and a cut-away portion  144  at the lower surface of the projecting end  142  and the front surface of the touching portion  143 . The resilient piece  137  is resiliently deformable to curve up and out between a rear base end substantially continuous with the front end of the support  136  and the lock  141  and resiliently displaceable so that the lock  141  side is displaced up and out with the base end as a support. Further, the front end of the resilient piece  137  is located behind the front ends of the side walls  134 . 
   The restriction  138  is connected with the upper end edges of the side walls  134  at right angles and extends continuously in forward and backward directions from the rear ends of the side walls  134  (front end of the operable portion  135 ) to a position slightly behind the front ends of the side walls  134 . The front end of the restriction  138  is slightly behind the front projecting end  142  of the lock  141  of the resilient piece  137  and is at substantially the same position as the touching portion  143  in forward and backward directions. In other words, a formation range of the restriction  138  in forward and backward directions includes an area corresponding to at least a lengthwise middle part of the resilient piece  137  in a curvable area from the base end of the resilient piece  137  to the lock  141 , i.e. is not an area not corresponding to the extending end or the lock  141  of the resilient piece  137 . Accordingly, the front end of the resilient piece  137  that includes the projecting end  142  and the substantially front half of the touching portion  143  of the lock  141  projects more forward than the front end of the restriction  138 . Most of the resilient piece  137 , excluding the front end, is covered by the restriction  138  from above. Thus, the resilient piece  137  is protected from interference of external matter by the restriction  138 . Further, a space for permitting upward resilient displacement and curved deformation of the resilient piece  137  is defined between the lower surface of the restriction  138  and the upper surface of the resilient piece  137 . An arcuate contact portion  145  is formed at the lower edge of the front end of the restriction  138  at the same side as the extending end of the resilient piece  137 . The restriction  138  also is formed with a single window  169  at a widthwise intermediate position near the rear end edge. The window  169  of the restriction  138  is a round hole. When the detector  133  is in a state before being assembled or in the standby position SP, the upper surface of the support  136  of the detector  133  can be seen through the window  169 . When the detector  133  is at the detection position DP the upper surface of the coupling  127  of the housing  110  can be seen through the window  169 . 
   The connection detector  133  is assembled with the lock arm  124  from behind by being slid with the guide grooves  139  engaged with the guide ribs  130 . The retaining projections  140  pass the stoppers  131  and engage the stoppers  131  from the front when the connection detector  133  reaches the stand-by position SP, as shown in  FIG. 16 . Thus, a backward movement of the connection detector  133  is prevented, and the touching portions  143  at the front end of the resilient piece  137  engage the lock  126  from behind to prevent further forward movement of the connection detector  133 . As a result, the connection detector  133  is held at the initial or stand-by position SP (see  FIGS. 12 and 17 ). In other words, the connection detector  133  has its forward movement towards the detecting position DP prevented. 
   The projecting end  142  of the resilient piece  137  is placed on the outer surface of the lock  126 , and the cut-away portion  144  is fit obliquely to the lock  126  from an upper rear side. In this state, the support  136  is held vertically between the lower plate  129  and the coupling  127 , and the coupling  127  is held vertically between the support  136  and the restriction  138 . Thus, the connection detector  133  cannot move vertically relative to the lock arm  124 . 
   The support  136  is held between the arms  125  and the left and right side walls  134  are held in contact with the left and right inner wall surfaces of the tubular fitting  123 . Thus, the connection detector  133  is prevented from moving laterally relative to the lock arm  124  and the second housing  120 . Further, with the connection detector  133  at the initial position SP, the upper surface of the restriction  138  is at substantially the same height as the upper surface of the upper wall  123 A of the tubular fitting  123 . Therefore, external matter will not collide with the restriction  138  from above. 
   The resilient piece  137  is displaced resiliently up to disengage the locks  141 ,  126 . Thus, the connection detector  133  held at the initial position SP can be moved forward substantially parallel to the connecting direction of the housings  110 ,  120  while being guided by the guide grooves  139  and the guide ribs  130 . Forward movement of the connection detector  133  is prevented when the bottom end of the touching portion  143  slides on the upper surface of the lock  126  and the front end of the restriction  138  contacts a front stop  123 D on a front edge  123 C of the tubular fitting  123 . Simultaneously, the touching portion  143  passes the lock  126 , the resilient piece  137  is restored resiliently and the touching portion  143  engages the lock  126  from the front. Thus, a backward movement of the connection detector  133  towards the initial position SP is prevented to hold the connection detector  133  at the detecting position DP. 
   The front ends of the side walls  134  contact the front edge  123 C from the lower side when the connection detector  133  is at the detecting position DP. Thus, an upward displacement of the front end of the connection detector  133 , i.e. a resilient displacement of the lock arm  124  to the unlocking posture, is prevented. External matter will not collide with the restriction  138  from above even with the connection detector  133  at the detection position DP, since the upper surface of the restriction  138  is at the same height as or slightly lower than the upper surface of the upper wall  123 A of the tubular fitting  123   
   The receptacle  112  is fit on the terminal holding portion  122  and is inserted into the tubular fitting  123  in the process of connecting the two housings  110 ,  120 . Then, as shown in  FIG. 13 , the lock  126  moves onto the lock projection  113 . Accordingly, the lock arm  124  is displaced resiliently to the unlocking posture. At this time, the connection detector  133  also inclines its posture to displace the front end side thereof up while being united with the lock arm  124 . However, the lock  141  is held engaged with the lock  126 , and the connection detector  133  cannot move to the detecting position DP. 
   The lock  126  passes the lock projection  113  as the connecting operation of the housings  110 ,  120  proceeds and the two housings  110 ,  120  become connected properly as shown in  FIG. 14 . The lock arm  124  then is restored resiliently to the locking posture so that the engagement of the lock  126  and the lock projection  113  locks the housings  110 ,  120  together. A part of the connection detector  133  except the resilient piece  137  is returned to its original posture together with the lock arm  124  when the lock arm  124  is restored resiliently. At this time, the lock projection  113  is located under the lock  141  of the resilient piece  137 . Thus, the resilient piece  137  is displaced resiliently up relative to the side walls  134  and the restriction  138 , and the touching portion  143  is placed on the upper surface of the lock projection  113 . 
   The contact  145  at the front end of the restriction  138  may collide with the upper surface of the lock  141  from above when the lock arm  124  is restored resiliently together with the connection detector  133 . This collision is at a part of the lock  141  in forward and backward directions where the thickness is largest and where the touching portion  143  is formed. Thus, the portion of the lock  141  between the restriction  138  and the lock  113  will not deform. 
   The locks  141  and  126  are disengaged from each other by an upward movement of the touching portion  143  relative to the lock  126  in the state where the two housings  110 ,  120  are connected properly and the connection detector  133  is at the initial position SP. Thus, the connection detector  133  is permitted to move forward. Further, the upper surface of the lock  113  in contact with the lock  141  and the upper surface of the lock  126  are at substantially the same height so as to be substantially flush with each other. Thus, the lock  141  can slide to move from the outer surface of the lock  113  onto that of the lock  126 . In other words, the connection detector  133  can slide from the initial position SP to the detecting position DP. 
   The touching portion  143  passes the lock  126 , as shown in  FIG. 15 , if the operable portion  135  is pushed from behind in this state to move the connection detector  133  to the detecting position DP. Therefore the resilient piece  137  is restored resiliently and the touching portion  143  is engaged with the lock  126  from the front. This engagement prevents a backward returning movement of the connection detector  133  towards the initial position SP and holds the connection detector  133  at the detecting position DP. 
   The connection detector  133  cannot be moved from the initial position SP to the detecting position DP if the two housings  110 ,  120  are not connected yet. Specifically, a strong pushing force could be exerted on the operable portion  135  from behind while the connection detector  133  is at the initial position SP. This pushing force will cause the resilient piece  137  to deform resiliently and will curve the part of the resilient piece  137  between the base end and the lock  141  up as shown in  FIG. 11 . If this resilient deformation amount increases, a forward inclined angle of the front end of the resilient piece  127  increases. Thus, the front end of the projecting end  142  could contact the upper surface of the lock  126  to displace the touching portion  143  up relative to the lock  126  and, consequently, the touching portion  143  could disengage from the lock  126 . Then, the lock  141  of the resilient piece  137  would no longer prevent a forward movement of the connection detector  133 , and the connection detector  133  could move to the detecting position DP. 
   However, in this embodiment, the restriction  138  is provided above the resilient piece  137  and prevents an excessive curved deformation of the resilient piece  137 . Thus, even if a curved deformation amount of the resilient piece  137  is maximized, the lock  141  is held engaged with the lock  126  to prevent a forward movement of the connection detector  133 . In this way, the connection detector  133  cannot move to the detecting position when the two housings  110 ,  120  are not connected yet. 
   The lengthwise intermediate part of the resilient piece  137  is displaced maximally when the resilient piece  137  is curved. Thus, the restriction  138  is formed over the range including the area corresponding to the lengthwise intermediate part of the resilient piece  137 . Therefore, the excessive curved deformation of the resilient piece  137  is prevented effectively. 
   The connection detector  133  still is at the initial position SP when the housings  110 ,  120  become properly connected. Thus, the resilient piece  137  interferes with the lock projection  113 , inclines its posture and displaces towards the restriction  138 . A displacement amount of the resilient piece  137  at this time is largest at the extending front end of the resilient piece  137 . As a result, the formation range of the restricting portion  138  excludes the extending end. Therefore, there is no likelihood of hindering the displacement of the resilient piece  137  due to the interference of the extending end of the resilient piece  137  with the restriction  138 . 
   The extending front end of the resilient piece  137  contacts the contact  145  at the front end edge of the restriction  138  as the resilient piece  137  is displaced. The contact portion  145  and the resilient piece  137  may be deformed if this contact  145  is an angular edge. However, the contact  145  is arcuate in this embodiment to prevent deformations of the contact  145  and the resilient piece  137 . 
   The restriction  138  is unitary to the connection detector  133  as a base of the resilient piece  137 . Thus, there is no likelihood of disrupting the positional relationship of the resilient piece  137  and the restriction  138 . 
   The restriction  138  is connected with the upper edges of the side walls  134  at substantially right angles. Thus, the deflection strength of the restriction  138  is higher as compared with a restriction formed as a single plate. Therefore, curved deformation of the resilient piece  137  is restricted reliably. 
   The invention is not limited to the above described and illustrated embodiment. For example, the following embodiments are also embraced by the technical scope of the present invention. 
   Although the restriction is formed on the connection detector in the above embodiment, it may be formed in the second housing. 
   Although the restriction is formed not to correspond to the extending end of the resilient piece in the above embodiment, it may correspond to the extending end of the resilient piece. 
   The restriction is in the lengthwise middle part of the resilient piece in the above embodiment. However, the restriction need not be in the lengthwise middle part of the resilient piece. In this case, a part of the resilient piece other than the middle part maximally displaced upon the curved deformation of the resilient piece contacts the restriction. 
   The restriction is reinforced by being connected with the walls in the above embodiment. However, it may be a single cantilevered plate according. 
   The restriction is plate-like in the above embodiment, but it may be a block with a large thickness in the deforming direction of the resilient piece. 
   Although the contact is arcuate in the above embodiment, it may be a tapered or angular edge according to the invention. 
   In the above embodiment, the connection detector is mounted slidably on the lock arm and is inclined together with the lock arm. However, the invention is also applicable to connectors in which a connection detector is not mounted on a lock arm, but slidably supported on a part of a second housing other than the lock arm.