Abstract:
A rotary latch mechanism is provided for securing the lid of a container in a closed position wherein a mechanical advantage is employed to facilitate latching and unlatching of a latch plate of the rotary latch mechanism.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to latching mechanisms, and, more particularly, to a rotary latch for containers such as tool boxes mounted to the bed of a pickup truck. 
       BACKGROUND OF THE INVENTION 
       [0002]    Rotary latches are routinely used on doors, chests, cabinets and other containers where a lid or door must be retained in a closed and/or locked position. One common type of rotary latch includes a latch plate moveable between a latched and unlatched position. When unlatched, the latch plate may receive a striker pin mounted to the lid of a toolbox, for example, as the lid is moved to a closed position. Once the lid is closed, the latch plate moves to the latched position to capture the striker pin and retain the lid in the closed position. The rotary latch may be provided with a lock to prevent the latch plate from releasing the striker pin except when unlocked. 
         [0003]    A number of designs have been proposed in the prior art to move the latch plate from its latched position and allow the striker pin to be released. One approach is disclosed in U.S. Pat. No. 6,973,810 in which a handle mounted to the housing of a rotary latch is pivoted to set in motion a series of components that cooperate to move the latch plate to an unlatched position. In this and similar designs, a first end of the handle is pivotally mounted to the latch housing and its opposite, second end connects to one of the components that function to open the latch plate. The latch plate is opened by moving the second end of the handle to an unlatched position thus pivoting the handle about its first end. However, a substantial amount of force is required to pivot the latch handle because, as noted above, its second end is directly connected to the series of components that cooperate to open the latch plate. 
       SUMMARY OF THE INVENTION 
       [0004]    This invention is directed to a rotary latch mechanism for securing the lid of a container in a closed position wherein a mechanical advantage is employed to facilitate latching and unlatching of the latch plate of the rotary latch mechanism with much less force than is required in prior art designs of the type described above. 
         [0005]    In one presently preferred embodiment, the latch mechanism includes a latch body and a handle having a first end, and a second end coupled to a pivot pin mounted to the latch body. The pivot pin carries a pivot arm that contacts an actuator which releasably engages a latch plate operative to capture a striker pin, such as from the lid of the truck box, when the lid is closed. The first end of the handle preferably mounts a lock cylinder which is moveable between a locked and unlocked position. With the lock cylinder unlocked, the handle may be grasped and pulled outwardly so that its first end is spaced from the latch body. Such movement of the handle rotates the pivot pin connected to the second end of the handle, which, in turn, causes the pivot arm carried by the pivot pin to engage the actuator and ultimately move the latch plate to an unlatched position to receive, or to release, the striker pin. 
         [0006]    Unlike prior art latch mechanisms of the type described above, a mechanical advantage is obtained with the rotary latch of this invention. Pulling the handle outwardly from the latch body is made easier because its first end is not connected to any components that directly or indirectly cause movement of the latch plate. Instead, the handle acts as a lever arm wherein rotation of the pivot pin coupled to the second end of the handle is created by lifting the opposite, first end of the handle. As noted above, rotation of the pivot pin, in turn, sets in motion the components operative to move the latch plate to the unlatched position. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    The structure, operation and advantages of the presently preferred embodiment of this invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a perspective view of the rotary latch of this invention in the latched and locked position; 
           [0009]      FIG. 2  is a view similar to  FIG. 1 , except with the rotary latch in the latched and unlocked position; 
           [0010]      FIG. 3  is a view similar to  FIGS. 1 and 2 , except with the rotary latch in an unlatched position; 
           [0011]      FIG. 4  is a rear view of the rotary latch in a latched and locked position; 
           [0012]      FIG. 5  is a view similar to  FIG. 4  except in the unlocked position; and 
           [0013]      FIG. 6  is a view similar to  FIG. 4  except with the rotary latch in an unlatched position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring now to the drawings, the rotary latch  8  of this invention comprises a latch body  10  having a center section  12  located between opposed end sections  14  and  16 . The center section  12  is formed with a recess  18  to receive the fingers as one grasps a handle  20  which spans the recess  18  and extends between the two end sections  14 ,  16 . 
         [0015]    A first end  22  of the handle  20  is formed with a through bore  23  within which a key cylinder  24  is mounted. The first end  22  is beveled so that it engages a correspondingly beveled seat  26  mounted on the front surface  28  of the latch body  10 . An opening (not shown) is formed in the latch body  10  through which the key cylinder  24  extends between spaced posts  30  and  32  each connected at one end to the rear surface  34  of the latch body  10 . The inner end of the key cylinder  24  is mounted to a locking plate  36  by a bolt  38 , and a coil spring  40  extends between the locking plate  36  and the rear surface  34  of the latch body  10 . As described in more detail below in connection with a discussion of the operation of the rotary latch  8  of this invention, in response to operation of the key cylinder  24  the locking plate  36  is movable between a locked position shown in  FIGS. 1 and 4  wherein it spans and contacts the ends of each post  30 ,  32 , and an unlocked position depicted in  FIGS. 2 ,  3 ,  5 , and  6  in which the locking plate  36  is rotated approximately 90° so that it may pass between the posts  30 ,  32 . 
         [0016]    The second end  42  of the handle  20 , opposite its first end  22 , is beveled to engage a second seat  44  mounted to the end section  16  of latch body  10 . The second end  42  of handle  20  is coupled to a pin  46  which is pivotally mounted to an upper bearing  48  and a lower bearing  50  each connected to the rear surface  34  of the latch body  10 . For purposes of the present discussion, the terms “upper,” “lower,” “vertically” and “laterally” refer to the orientation of the structures of the rotary latch  8  in the position depicted in the Figs. The pin  46 , in turn, is fixed to a pivot arm  52  which is movable with rotation of the pin  46  relative to an actuator  54 . As best seen in  FIGS. 4-6 , the actuator  54  is pivotally mounted on a shaft  56  connected to the rear surface  34  of the latch body  10 . The upper end of the actuator  54  is preferably formed with a locking pawl  58  formed to engage one or more gear teeth  60  in a latch plate  62  which is pivotally mounted on a shaft  64  connected to the rear surface  34  of the latch body  10 . The latch plate  62  is formed with a notch  66  adapted to receive a striker pin  63 , shown in phantom in  FIGS. 4 and 5 . The striker pin  63  may be carried by the lid of a truck tool box, for example (not shown). The latch plate  62  and actuator  54  are located between a front guide plate  68 , a portion of which is shown in  FIG. 5 , and a rear guide plate  70  a portion of which is shown in  FIG. 6 . Both the front and rear guide plates  68 ,  70  are mounted to the rear surface  34  of the latch body  10 . 
         [0017]    A spring (not shown) carried on the shaft  64  biases the latch plate  62  toward an unlatched position, illustrated in  FIG. 6 , wherein its notch  66  is oriented substantially vertically in position to receive or to release the striker pin  63 , as described below. The actuator  54  is biased by a spring (not shown) mounted to the shaft  56  in a substantially vertical orientation, as depicted in  FIG. 5 . In this position, the locking pawl  58  of the actuator  54  may engage one of the gear teeth  60  on the latch plate  62  to prevent the latch plate  62  from rotating to the unlatched position shown in  FIG. 6 . Preferably, the pivot arm  52  rests against a side edge  72  of the actuator  54  with the latch plate  62  in the latched position. 
         [0018]    The rotary latch  8  of this invention operates as follows. If the key cylinder  24  is in the locked position depicted in  FIGS. 1 and 4 , with locking plate  36  spanning and in contact with posts  30 ,  32 , a key (not shown) may be inserted into the key cylinder  24  to rotate it to an unlocked position illustrated in  FIGS. 2 and 5 . Once the key cylinder  24  is unlocked, one may grasp the handle  20  and pull its first end  22  outwardly from the front surface  28  of the latch body  10 , as shown in  FIG. 3 , thus overcoming the force exerted by coil spring  40  on the key cylinder  24  and moving the locking plate  36  toward the rear surface  34  of the latch body  10  in between the posts  30 ,  32 . Such movement of the first end  22  of handle  20  causes its second end  42  to rotate the pin  46  in bearings  48 ,  50 . The pivot arm  52 , which is fixed to the pin  46  and in contact with the side edge  72  of actuator  54 , rotates with the pin  46  and pivots the actuator  54  in a counterclockwise direction from the position shown in  FIG. 5  to that depicted in  FIG. 6 . In the course of such pivotal motion, the locking pawl  58  of the actuator  54  disengages a gear tooth  60  formed in the latch plate  62  which allows the spring acting on the latch plate  62  to rotate it from the latched position shown in  FIG. 5  to the unlatched position illustrated in  FIG. 6 . When the latch plate  62  is unlatched, the striker pin  63  may be removed from the notch  66  in the latch plate  62  so that the lid or door to which the striker pin  63  is attached may be opened. 
         [0019]    The rotary latch  8  remains in the position shown in  FIG. 6 , with its latch plate  62  oriented substantially vertically, until such time as the lid or door which mounts the striker pin  63  is closed. As the striker pin  63  approaches the latch plate  62 , it is guided into the notch  66  therein by the front and rear guide plates  68 ,  70 . The striker pin  63  engages the latch plate  62  and rotates it in a clockwise direction to the latched position, overcoming the spring force acting on the shaft  64  which mounts the latch plate  62  and urges it to the unlatched position. Since the actuator  54  is biased to the vertical position shown in  FIG. 5 , once the latch plate  62  is moved to its latched position the actuator  54  is free to rotate in the clockwise direction and assume a position wherein its locking pawl  58  contacts one of the gear teeth  60  in the latch plate  62  in order to retain the latch plate  62  in the latched position. 
         [0020]    An important aspect of this invention is the mechanical advantage realized by the handle  20  in setting in motion the operation of pivot arm  52 , actuator  54  and latch plate  62  to release the striker pin  63  from the rotary latch  8 . As noted above, the first end  22  of handle  20  is pulled outwardly from the front surface  28  of the latch body  10  causing rotation of the pin  46  which is coupled to the opposite, second end  42  of the handle  20 . The first end  22  of handle  20  does not directly act on the components that open the rotary latch, e.g. the pivot arm  52 , actuator  54  or latch plate  62 , but rather the overall length of the handle  20  is used advantageously as a lever arm to rotate pin  46 . This construction greatly reduces the effort required to open the rotary latch  8  of this invention, especially compared to prior art arrangements such as described above. 
         [0021]    While the invention has been described with reference to a preferred embodiment, it should be understood by those skilled in the art that various changes may be made and equivalents substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.