Abstract:
A cam-type door latch assembly comprises a handle and an arm assembly terminating in a finger-like cam and pivotal to bring the cam into engagement with a conventional locking pin assembly. The arm assembly is selectively adjustable for lengthening or shortening the arm assembly, thereby adjusting the contact force between the cam and the locking pin and, consequently, the door closing force. The arm assembly comprises a sleeve enclosing a wedge nut and a cam arm having offsetting inclined faces which are tightened against each other with a threaded connector to lock the wedge nut and cam arm in position in the sleeve when the cam has been properly adjusted relative to the locking pin.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of U.S. provisional application Serial No. 60/319,457, filed Aug. 9, 2002, which is incorporated herein in its entirety.  
         BACKGROUND OF INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates generally to latches for rollup-type truck cargo doors. In one aspect, the invention relates to a cam-type door latch having an adjustable latch assembly to adjust the closing force of the door.  
           [0004]    2. Description of the Related Art  
           [0005]    Trailers for semi-tractors and delivery trucks have long used roll-up doors to control access through a rear opening of the truck or trailer. The doors are typically provided with a resilient gasket along the lower edge to provide a seal between the door and adjacent frame when the door is closed. The doors are typically secured in the closed position through a latch assembly which is mounted adjacent the lower edge of the door. One such latch assembly is known in the industry as a “cam lock.” The cam lock typically comprises a pivoting handle attached to a latch arm having a curved finger-like cam extending transverse to the arm. The cam is positioned snuggly beneath a cam retainer mounted in a catch box or latch plate mounted in the frame. Pivoting the handle downward rotates the cam into engagement with the pin, securing the door in the closed position with a downwardly-exerted force sealing the gasket against the frame. Pivoting the handle upward disengages the cam from the pin so that the door can be opened.  
           [0006]    Over time, the gasket can wear and lose its resiliency, or the door-mounting hardware can become loosened, so that the cam lock is unable to exert sufficient force against the pin to satisfactorily draw the door downward against the frame. Various methods have been proposed for addressing this problem. Replacement of the gasket and/or adjustment of the door can correct the problem but can be time-consuming and costly. Repositioning of the cam lock on the door can also be done, but this may require a costly modification to the door. Furthermore, where the cam lock should be repositioned in order to provide the desired seal may not be immediately evident, necessitating several repositioning attempts.  
           [0007]    Adjustable latches have also been developed. For example, U.S. Pat. No. 5,692,788 to Costa, issued Dec. 2, 1997, discloses a catch box with an adjustable locking pin for a cam-type door latch assembly. The locking pin is housed in a frame-mounted catch box into which the cam is received. The locking pin comprises a vertically-adjustable strike pin which can be adjusted upwardly or downwardly by turning a threaded post while the cam engages the strike pin, thereby ensuring the desired degree of sealing force between the door and the frame. However, the catch box is susceptible to the accumulation of dirt and debris which can interfere with the turning of the post and the movement of the strike pin, thereby limiting the adjustability of the locking pin.  
         SUMMARY OF INVENTION  
         [0008]    A truck has a support bed at a rear portion thereof, and a rear enclosure mounted to the support bed and defined in part by sidewalls and a top wall. A door opening is at a rear portion of the enclosure and is defined by a door frame and the support bed. Vertical tracks are mounted in the door frame adjacent to the opening, and a door is mounted in the vertical tracks for vertical movement between a closed position and an open position. A latch is pivotally mounted near the bottom of the door for movement between a latched position and an unlatched position and has a handle, a cam arm, and a cam. An opening is in the support bed beneath the door opening and is adapted to receive the cam when the handle is rotated from an unlatched position to a latched position. A cam retainer is mounted in the support bed and is adapted to engage the cam and draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. According to the invention, the cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed.  
           [0009]    According to another embodiment of the invention, the cam arm comprises a sleeve having a channelway therethrough and a shaft adapted for slidable register with the channelway. According to another embodiment, the invention further comprises a wedge nut adapted for slidable translation relative to the shaft. The wedge nut can be wedge shaped, and can have ribs to grip the channelway. According to another embodiment, the shaft and the channelway can have a wedge-shaped cross-section. According to another embodiment, the sleeve can have a lock screw to lock the shaft to the sleeve. The shaft can have notches to indicate its position relative to the sleeve.  
           [0010]    According to another embodiment of the invention, a door is adapted to be mounted in tracks in a door opening for vertical movement between a closed position and an open position. A latch is pivotally mounted near the bottom of the door for movement between a latched position and an unlatched position and has a handle, a cam arm, and a cam. The cam is adapted to engage a cam retainer mounted in an opening in a support bed beneath the door opening to draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. The cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed.  
           [0011]    According to yet another embodiment, a latch is adapted to be pivotally mounted near the bottom of a door for movement between a latched position and an unlatched position and having a handle, a cam arm, and a cam. The cam is adapted to engage a cam retainer mounted in an opening in a support bed beneath the door to draw the door against the support bed when the handle is rotated from an unlatched position to a latched position. The cam arm is longitudinally adjustable to adjust the length of the cam arm and thus adjust the force of the door against the support bed. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    In the drawings:  
         [0013]    [0013]FIG. 1 is a perspective view of the rear of a conventional truck trailer having a cam-type door latch assembly according to the invention.  
         [0014]    [0014]FIG. 2 is an exploded view of the cam-type door latch assembly shown in FIG. 1.  
         [0015]    [0015]FIG. 3 is an enlarged elevational view of the cam-type door latch assembly of FIG. 1 and a catch box mounted in a support bed of the trailer shown in phantom lines and illustrating the adjustable engagement of the cam with a cam retainer mounted in the catch box.  
         [0016]    [0016]FIG. 4 is a sectional view of a sleeve comprising a portion of an adjustable arm assembly of the door latch assembly shown in FIGS. 2 and 3 and taken along line  4 - 4  of FIG. 2.  
         [0017]    [0017]FIG. 5 is a side view of a portion of the adjustable arm assembly of the door latch assembly shown in FIG. 2.  
         [0018]    [0018]FIG. 6 is a sectional view of a portion of the adjustable arm assembly shown in FIG. 5 taken along line  6 - 6  of FIG. 5.  
         [0019]    [0019]FIG. 7 is a plan view from underneath of a portion of the adjustable arm assembly taken along lines  7 - 7  of FIG. 5.  
         [0020]    [0020]FIG. 8 is a side view of a wedge nut comprising a portion of an adjustable arm assembly of the door latch assembly shown in FIG. 2.  
         [0021]    [0021]FIG. 9 is a plan view from underneath of the wedge nut shown in FIG. 8 taken along lines  9 - 9  of FIG. 8. 
     
    
     DETAILED DESCRIPTION  
       [0022]    A cam-type latch assembly for a roll-up truck cargo door has a cam attached to an adjustable cam arm for selectively adjusting the engaging force between the cam and a cam retainer, thereby ensuring tight closure of the door.  
         [0023]    Referring to the drawings and to FIG. 1 in particular, a semi-truck trailer  10  is shown having a generally conventional rear roll-up cargo door  12  mounted in a frame  14  defining a door opening. The trailer  10  comprises a well-known support bed  16  for supporting cargo thereon, and an enclosure  17  comprising side walls  13  and a top wall  15  mounted to the support bed  16 . The frame  14  is mounted to the support bed  16 , the side walls  13 , and the top wall  15  in a well-known manner, and comprises a pair of well-known parallel, spaced-apart vertical tracks (not shown) attached to the frame  14  on either side of the door opening and adapted to support the door  12  for movement of the door  12  between an open position and a closed position. It will be apparent to a person of ordinary skill in the industry that such a door assembly can also be utilized in other vehicles having an enclosed cargo space supported on a support bed.  
         [0024]    The lower edge of the door  12  is provided with a conventional resilient gasket  126  for sealing the door  12  against the support bed  16  (FIG. 3). The support bed  16  houses a well-known catch box  128 , as shown in greater detail in FIG. 3. The catch box  128  comprises a box-like structure set into the support bed  16 , having a chamber  130  and a transversely-mounted cam retainer  132  which operably communicates with an adjustable cam-type door latch assembly  18  according to the invention.  
         [0025]    Referring now to FIG. 2, a preferred embodiment of the door latch assembly  18  has a generally conventional configuration comprising a handle assembly  20  and an attached cam arm assembly  22  pivotally mounted to a mounting plate  26  through a conventional pivot assembly  36 . The handle assembly  20  comprises a handle  30  having a generally conventional locking end  32  and a pivot end  34  comprising the pivot assembly  36 . The handle assembly  20  is adapted to pivot about the pivot assembly  36  to selectively rotate the door latch assembly  18  into a locked or unlocked position. When the door latch assembly  18  is in the locked position, the handle  30  will be in a generally horizontal orientation. The handle  30  is rotated counterclockwise to bring the door latch assembly  18  into an unlocked configuration. A well-known locking pawl assembly  24  is also pivotally mounted to the mounting plate  26 .  
         [0026]    Extending downwardly from the pivot assembly  36  at an angle to the handle  30  is the cam arm assembly  22  comprising a sleeve  38 . As shown in FIG. 4, the sleeve  38  is a hollow, elongated body comprising a major arcuate wall  42  and a minor arcuate wall  44  in spaced-apart juxtaposition connected by a first sidewall  50  and a second sidewall  52  in spaced-apart juxtaposition to define a channelway  40  having a somewhat rounded wedge shape. The inner portion of the major arcuate wall  42  forms a major arcuate surface  46 . The inner portion of the minor arcuate wall  44  forms a minor arcuate surface  48 . A threaded setscrew bore  54  extends laterally through the major arcuate wall  42  into the channelway  40  for threadably receiving a conventional setscrew  56 .  
         [0027]    Referring again to FIG. 2, the cam arm assembly  22  also comprises a wedge nut  60  and a cam arm  90  terminating in a cam  92  extending laterally from the cam arm  90 . Referring to FIGS. 8 and 9, the wedge nut  60  comprises a generally rounded wedge-shaped body having a major curved face  62  and a minor curved face  64  in spaced-apart juxtaposition connected by a first flat face  66  and a second flat face  68  in spaced-apart juxtaposition, and adapted for slidable register with the channelway  40 . The major curved face  62  is provided with a plurality of parallel, spaced-apart raised ribs  84 .  
         [0028]    Extending through the wedge nut  60  intermediate the major curved face  62  and the minor curved face  64  is an aperture  72  having a generally cylindrical narrow aperture wall  74  transitioning through an annular shoulder  78  to a generally cylindrical wide aperture wall  76  to form a narrow aperture  80  coaxial with a wide aperture  82 . The narrow aperture  80  is threaded. The wedge nut  60  also comprises an inclined face  70  transverse to the flat faces  66 ,  68 . The wedge nut  60  is slidably received in the channelway  40  with the minor curved face  64  in slidable communication with the minor arcuate wall  44 , the first flat face  66  in slidable communication with the first sidewall  50 , the second flat face  68  in slidable communication with the second sidewall  52 , and the ribs  84  in slidable communication with the major arcuate wall  42 .  
         [0029]    Referring to FIGS.  5 - 7 , the cam arm  90  is an elongated shaft having a first end  91  and a second end  93  and a generally rounded wedge-shaped cross section comprising a major curved face  96  and a minor curved face  98  in spaced-apart juxtaposition connected by a first flat face  100  and a second flat face  102  in spaced-apart juxtaposition. Preferably, the cross-sectional configuration of the cam arm  90  is the same as the cross-sectional configuration of the wedge nut  60 . A bolt head aperture  110  extends coaxially into the cam arm  90  at the second end  93 . A tapered bolt aperture  104  tapering expansively from the bolt head aperture  110  to the first end  91  extends through the cam arm  90  coaxially with the bolt head aperture  110 . The diameter of the bolt head aperture  110  is somewhat greater than the diameter of the adjoining end of the tapered bolt aperture  104  so that an annular shoulder  112  is formed at the transition from the bolt head aperture  110  to the tapered bolt aperture  104 . The minor curved face  98  is provided with a plurality of parallel, evenly spaced-apart notches  114  to form a linear scale  115 . The cam arm  90  is slidably received in the channelway  40  with the major curved face  96  in slidable communication with the major arcuate wall  42 , the minor curved face  98  in slidable communication with the minor arcuate wall  44 , the first flat face  100  in slidable communication with the first sidewall  50 , and the second flat face  102  in slidable communication with the second sidewall  52 .  
         [0030]    Extending laterally from the second end  93  is a generally conventional finger-like arcuate cam  92  having an upper arcuate surface  94 . As shown in FIG. 3, the arcuate surface  94  engages the cam retainer  132  mounted in the catch box  128  in a generally conventional manner to secure the trailer door  12  in a closed position against the support bed  16 . The first end  91  terminates in an inclined face  116  for slidable communication with the inclined face  70  of the wedge nut  60 .  
         [0031]    A threaded fastener  118 , preferably a bolt, having a bolt head  119  and a threaded portion  120 , is inserted through the bolt head aperture  110  and the tapered bolt aperture  104  to be threaded into the threaded narrow aperture  80  in the wedge nut  60 . A washer  122  is adapted to be inserted into the bolt head aperture  110  for insertion of the bolt  118  therethrough to serve as a bearing surface for the bolt head  119  during rotation of the bolt  118 . Referring again to FIG. 2, the bolt  118  is inserted through the bolt head aperture  110 , the washer  122 , and the tapered bolt aperture  104  so that the head  119  bears against the washer  122  which is seated against the annular shoulder  112  (FIG. 5). The threaded portion  120  is threaded into the wedge nut  60  to form the cam arm assembly  22  so that the inclined face  70  of the wedge nut  60  is in slidable communication with the inclined face  116  of the cam arm  90 . A cap  124 , preferably fabricated of a resilient material such as a plastic, can be inserted over the bolt head  119  and frictionally retained in the bolt head aperture  110  to protect the bolt head  119  and the bolt head aperture  110  against impact and dirt.  
         [0032]    The cam arm assembly  22  is adjusted by loosening the setscrew  56  and the bolt  118  so that the cam arm assembly  22  can be slidably moved within the sleeve  38 . The position of the cam arm assembly  22  in the sleeve  38  is manually adjusted, preferably with reference to the scale  115 , to provide the desired contact force between the arcuate surface  94  and the cam retainer  132 . As shown in FIG. 3, as the bolt  118  is turned in a tightening, i.e. clockwise, direction, the wedge nut  60  will be drawn against the cam arm  90 . Because of the inclined faces  70 ,  116 , the wedge nut  60  will translate laterally relative to the cam arm  90 . The tapered bolt aperture  104  will accommodate the lateral movement of the bolt  118  as the wedge nut  60  moves laterally. With the cam arm assembly  22  inserted into the channelway  40  in the sleeve  38 , lateral translation of the wedge nut  60  will urge the ribs  84  into frictional contact with the major arcuate surface  46  and the minor curved face  98  into frictional contact with the minor arcuate surface  48 , which will tend to “lock” the cam arm assembly  22  into the sleeve  38 . The desired degree of insertion of the cam arm assembly  22  into the sleeve  38  is assisted by reference to the scale  115 . The setscrew  56  can then be threaded against the cam arm assembly  22  to further lock the cam arm assembly  22  in position.  
         [0033]    Referring again to FIG. 3, adjustment of the adjustable door latch assembly  18  is expected to typically involve shortening the cam arm to bring the arcuate surface  94  into snug contact with the cam retainer  132 . This function is accomplished by loosening the setscrew  56  and the bolt  118  so that the cam arm assembly  22  can be slidably adjusted further into the sleeve  38 . It will be apparent from FIG. 3 that this function is accomplished with the door latch assembly  18  disengaged from the cam retainer  132  in order to provide access to the bolt  118 . However, the scale  115  can be used to guide incremental changes in the insertion of the cam arm assembly  22  into the sleeve  38  until the proper contact force between the arcuate surface  94  and the cam retainer  132  is achieved. The cam arm assembly  22  is then locked into the sleeve  38  by suitable tightening of the bolt  118  and tightening of the setscrew  56 . Over time, as the trailer door  12  again becomes loosened, the adjustment procedure can be repeated to maintain the proper door closure force between the door  12  and the support bed  16 .  
         [0034]    The novel adjustable door latch assembly  18  provides a simple and effective means of maintaining the proper closure force for a trailer door. The clamping force between the arcuate surface  94  and the cam retainer  132  can be readily adjusted by manually adjusting the length of the cam arm, guided by the scale  115 , followed by retightening of the setscrew  56  and the bolt  118 . Adjustment of the door closure force through repositioning of the entire door latch assembly on the door is eliminated. Furthermore, the adjustment mechanism described herein is not exposed to the accumulation of dirt and debris which could adversely affect the operation of the adjustment mechanism as is an adjustable cam retainer or other catch box adjustment mechanism. The simplicity of operation of the adjustment mechanism enables the iterative adjustment of the contact force between the arcuate surface  94  and the cam retainer  132  relatively quickly.  
         [0035]    While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the foregoing description and drawings without departing from the spirit of the invention.