Patent Publication Number: US-6655971-B2

Title: Lever-type connector with a peak operation resistance shortly before complete connection

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a lever-type connector and to a method for assembling such a connector. 
     2. Description of the Related Art 
     Lever-type connectors facilitate the mating of two connector housings, and are used in multi-contact connectors and other situations where a large connecting force is required. A known lever-type connector has male and female housings configured for mating with one another. A lever is mounted pivotally on the male housing and is formed with a cam groove. The female housing is formed with a follower configured for engagement in the cam groove at the beginning of the mating process. The cam groove has a side surface that pushes the follower as the lever is pivoted and moves the housings into a fully mated condition. A locking mechanism is provided between the lever and the mating housing to lock the housings in a fully mated condition. 
     The pivoting movement of the lever may be interrupted before the housings are connected properly. U.S. Pat. No. 5,562,465 shows a connector that attempts to avoid such a problem. This connector has a lever with an integral spring piece, and a mating housing with a striking portion disposed for engagement by the spring piece near the end of the pivotal movement of the lever. Thus, pivoting movement of the lever deforms the spring piece as the housings approach a fully connected condition. The locked engagement of two properly connected housings resists the resilient restoring forces of the spring piece. However, the restoring force of the spring piece pushes the lever back, if the housings are not locked together. In this way, partial connection of the housings is identified. 
     Connection can be detected satisfactorily in the prior art connector. However, the spring piece is left resiliently deformed after the housings are connected properly and locked together. Thus, the spring piece may experience a permanent set and may fatigue over time. As a result, the spring piece cannot be expected to display a connection detecting function when the two housings are reconnected after being separated for maintenance or other reason. Therefore, there has been a demand for a new means. 
     The present invention was developed in view of the above problem, and an object thereof is to allow two housings of a lever-type connector to be connected properly with high reliability. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a lever-type connector with first and second housings that are connectable with each other. A lever is supported pivotally on the first housing and has at least one curved cam surface that gradually approaches the center of rotation of the lever. At least one follower is provided on the second housing and is engageable with the cam surface so that the housings are connected as the lever is pivoted. A resistance means is provided for giving a peak operation resistance to the lever when the lever is pivoted to a position immediately before the housings are connected properly. 
     A locking mechanism may be provided between the lever and the second housing to lock the housings together when the housings reach a properly connected state. The peak operation resistance preferably is larger than a resistance that acts when the housings are locked. 
     The housings are connected gradually as the lever is pivoted, and the operation resistance is peaked by the resistance means immediately before the housings are connected properly. The peak operation resistance is larger than the resistance that acts when the housings are locked. Thus, an inertial force pushes the second housing as the lever is pivoted to overcome the peak operation resistance. Consequently, the housings are connected properly and locked together with high reliability due to the inertial locking mechanism. 
     The resistance means preferably comprises a portion of the cam surface where a distance from the center of rotation decreases at a higher rate. More particularly, portions of the cam surface that contact the follower immediately before the housings are connected properly are inclined more steeply than other portions of the cam surface. Accordingly, the peak operation resistance is higher as the lever approaches the end of its pivotal movement. The peak operation resistance is obtained merely by changing the shape of the cam surface, and without providing a special resistance member. Thus, the resistance means is simple and inexpensive. 
     The resistance means preferably achieves the peak operation resistance when the housings have moved by a connection stroke larger than about 80%, preferably larger than 85%, and most preferably larger than 90% of a connection stroke needed to properly connect the housings. However, the resistance means preferably achieves the peak operation resistance when the housings have moved by a connection stroke less than 95% of a connection stroke needed to reach proper connection. 
     At least one starting position locking means may be provided on the lever, the first housing and/or the second housing to lock the lever temporarily in a starting position where the housings can be connected. Additionally, at least one releasing means may be provided for releasing the starting position locking means when the housings are to be mated so that the lever can pivot. 
     The invention also is directed to a method of assembling a lever-type connector. The method comprises partly mating first and second housings, and pivoting a lever on the first housing to connect the housings by the function of a cam means. An operation resistance of the lever is set to comprise a peak operation resistance when the lever is pivoted to a position immediately before the housings are connected properly connected. 
     The method may further comprise locking the two housings together with a locking mechanism when the housings reach a properly connected state. 
     Preferably, the peak operation resistance is larger than a resistance that acts when the housings are locked. 
     The method may comprise reaching a peak operation resistance when the housings have moved by a connection stroke larger than about 80%, preferably larger than 85% and most preferably larger than 90% of a connection stroke that properly connects the housings. However, the connection stroke for peak operation resistance preferably is less than 95% of a connection stroke needed to connect the housings properly. 
    
    
     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 plan view showing a connection initial state of male and female housings according to one embodiment of the invention. 
     FIG. 2 is a section along  2 — 2  of FIG. 1 showing a state before the housings are connected. 
     FIG. 3 is a section similar to FIG. 2, but showing an initial connection state of the two housings. 
     FIG. 4 is a section similar to FIG. 2, showing a state where the lever experiences a peak operation resistance. 
     FIG. 5 is a section similar to FIG. 2, but showing a state where the two housings are connected properly. 
     FIG. 6 is a graph showing characteristics of a connecting force and a lever operating force. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A connector according to the invention has a male housing  10  and a female housing  20  that are connectable with each other. Sides of the housings  10 ,  20  that are to be connected are referred to herein as the front. 
     The male housing  10  is made e.g. of a synthetic resin and has a main body  11  and a receptacle  12  formed on the front surface of the main body  11 . Male terminal fittings (not shown) are inserted from behind into cavities in the main body  11  and have tabs that project into the receptacle  12 . Shafts  14  extend from lateral surfaces of the receptacle  12 . 
     The female housing  20  also is made of synthetic resin, and is configured to fit into the receptacle  12  of the male housing  10 . Female terminal fittings (not shown) are inserted into cavities in the female housing  20 . 
     A synthetic resin lever  30  is mounted pivotally on the male housing  10 . The lever  30  has two arms  31  and an operable portion  32  that extends between ends of the arms  31 . A shaft hole  33  is formed in the middle of each arm  31 , and the shafts  14  of the receptacle  12  extend through the shaft holes  33 . Thus, the lever  30  is pivotable between a starting position shown in FIG.  2  and an end position shown in FIG.  5 . 
     Each arm  31  of the lever  30  has a cam groove  35  at one side of the shaft hole  33 . Each cam groove  35  is curved so that a distance from the shaft hole  33  gradually decreases from a starting end  35 A toward a terminus  35 B. In other words, the cam groove  35  has a substantially spiral shape so that its radial distance from the shaft hole  33  decreases in an azimuthal direction. An entrance  36  is open in the leading end edge of the arm  31  and communicates with the starting end  35 A. 
     Cam follower pins  22  project from the lateral surfaces of the female housing  20  for engaging the cam groove  35 . A longitudinally aligned entrance groove  16  is formed in the lateral surfaces of the receptacle  12  of the male housing  10  and allows the follower pin  22  to enter. As described later, each follower pin  22  move from the starting end  35 A to the terminus  35 B of the cam grooves  35  as the lever  30  is pivoted, and reaches the terminus  35 B when the female housing  20  connects to the back end of the receptacle  12 . It should be noted that a play is provided at the back of each terminus  35 B. 
     A resiliently deformable partial lock  38  is cantilevered from the leading end of the arm  31  of the lever  30  at a side substantially opposite from the cam groove  35 , and a forwardly open guide groove  17  extends forward and backward in each of the lateral surfaces of the receptacle  12 . As shown in FIG. 2, the partial locks  38  fit resiliently into the guide grooves  17  to hold the lever  30  temporarily at the starting position and to prevent further pivoting. The entrances  36  of the cam grooves  35  align with the entrance grooves  16  and open forward when the lever  30  is at the starting end. 
     A rib  24  is formed on each of the lateral surfaces of the female housing  20  and can enter the corresponding guide groove  17 . As the ribs  24  enter the guide grooves  17 , the partial locking pieces  38  undergo a forced resilient deformation and exit the guide grooves  17 . As a result, the pivoting movement of the lever  30  is permitted. 
     A lever-side lock  40  is provided in the widthwise center of the operable portion  32  of the lever  30  for locking the lever  30  at the end position. The lever-side lock  40  includes a resiliently deformable lock  41  that is formed with a lock groove  42 . 
     A housing-side lock  25  is provided in the widthwise center at the rear of the upper surface of the female housing  20 , and is dimension for contact by the lever-side lock  40 . The housing-side lock  25  has a projection  26  engageable with the lock groove  42  of the lock  41 . More specifically, as shown in FIG. 5, the lever-side lock  40  strikes against the housing-side lock  25  when the female housing  20  is fit properly into the receptacle  12  of the male housing  10  and the lever  30  is pivoted to the end position. Thus, the lock  41  moves beyond the projection  26  and deforms resiliently. Consequently, the projection  26  fits into the lock groove  42  to lock the housings  10 ,  20 . 
     The distance from the shaft hole  33  decreases at a higher rate in a specified area  45  of each cam groove  35  located slightly before the terminus  35 B than in other areas. Hence, the specified area  45  has a curved shape with a steep inclination. In other words, the derivative of the function that describes the shape of the cam groove  35  is higher in the specified area  45  as compared to other areas thereof. Preferably, the derivative increases in the specified area  45  shortly before the terminus  35 B and then decreases again. Thus, operation resistance to the pivotal movement peaks and then decreases when the follower pins  22  pass the specified area  45 . 
     A connecting force necessary to connect the male and female housings  10 ,  20  is shown in the characteristic curve K of FIG. 6, The operation resistance to the pivotal movement of the lever  30  has been set conventionally to peak substantially at a middle stage of the pivotal movement corresponding to less than about 70% of the full pivotal movement of the lever or of the connection stroke of the two housings, as shown in a characteristic curve s of FIG.  6 . However, the operation resistance to the pivotal movement of the lever  30  peaks immediately before the housings  10 ,  20  are connected properly with each other, as shown in a characteristic curve S of FIG.  6 . This pivoting occurs when the lever  30  has been pivoted by more than about 80%, preferably more than about 85%, most preferably by more than about 90% of its full pivotal movement to connect the two housings  10 ,  20 . 
     The peak operation resistance force is set larger than a resistance that acts when the lever  30  is locked. Thus, a sum of a resistance to engage the lock  41  and the projection  26  for locking and a resistance acting between the two housings  10 ,  20  being connected at this time. 
     The female housing  20  fits into the receptacle  12  of the male housing  10 , as shown by an arrow of FIG. 2, with the lever  30  held at the starting position. In an initial fitted state, the follower pins  22  of the female housing  20  enter the entrance grooves  16  and are located at the entrances  36  of the cam grooves  35  as shown in FIG.  3 . 
     A finger is placed on the operable portion  32  to pivot the lever  30  in clockwise direction of FIG. 3 in this state. Thus, the follower pins  22  enter the starting ends  35 A of the cam grooves  35  through the entrances  36 , and the female housing  20  is pulled gradually into the receptacle  12  of the male housing  10  while the follower pins  22  are pressed toward the shafts  14  mainly by the outer surfaces (upper surfaces in FIG. 3) of the cam grooves  35 . 
     The lever  30  is pivoted further to reach a state immediately before the housings  10 ,  20  are connected properly, and the steep surface areas  45  of the cam grooves  35  press the follower pins  22 , as shown in FIG.  4 . The peak operation resistance given to the lever  30  is shown in the curve S of FIG.  6 . 
     The peak operation resistance is larger than a sum of the resistance required to engage the lock  41  and the projecting portion  26  for locking and the resistance acting between the two housings  10 ,  20  being connected. If the lever  30  is pivoted against the peak operation resistance, then the female housing  20  is pushed by an inertial force by way of the engagement of the cam grooves  35  and the follower pins  22 . Consequently, the two housings  10 ,  20  are connected properly and lock together by the engagement of the lock  41  and the projection  26 , as shown in FIG.  5 . 
     As described above, the two housings  10 ,  20  can be connected properly with high reliability due to the inertial locking mechanism. Thus, the corresponding male and female terminal fittings can be connected precisely. 
     The steep surface area  45  whose distance from the center of rotation decreases at a higher rate, as compared to the other areas, is formed at the specified side surface of the cam groove  35  as a means for giving a high resistance to the lever  30  to form an inertial lock. Such a means can be simple. 
     The invention is not limited to the above described and illustrated embodiment. For example, the following embodiment also is embraced by the technical scope of the invention as defined in the claims. Beside the following embodiment, various changes can be made without departing from the scope and spirit of the present invention as defined in the claims. 
     Depending on the shape and other factors of the connector, the lever may be mounted on the female housing and the follower pins may be on the male housing unlike the foregoing embodiment. 
     Even though the lever  30  for assisting or performing the connection of the male and female housings  10 ,  20  is pivotal, the lever may move along another path, such as a substantially linear path, and cam means assist the connection of the male and female connector housings  10 ,  20  when moved.