Abstract:
A dock leveler includes a lip that not only pivots between an extended operative position and a pendant position relative to a deck but also translates in its pendant position between blocking and non-blocking positions. A fastener connects the lip to a hinge in such a way as to minimize the stress between the fastener and the lip. The hinge includes a lip-facing surface into which the fastener is anchored, wherein the fastener is tilted out of perpendicularity to the lip-facing surface. The head of the fastener is held parallel to the lip even though an angled gap may exist between the lip and the lip-facing surface of the hinge.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The subject invention generally pertains to dock levelers and more specifically to a reduced-stress connection between a hinge and a lip of a dock leveler.  
         [0003]     2. Description of Related Art  
         [0004]     A typical truck loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles such as trucks and trailers. Many loading docks have a dock leveler to compensate for a height difference that may exist between the floor of the loading dock platform and an adjacent bed of a truck or trailer. A typical dock leveler includes a deck that is hinged along its back edge at or near the elevation of the floor so that the deck can pivotally adjust the height of its front edge to an elevation that generally matches the height of the rear edge of the truck bed to provide a ramp for material handling equipment.  
         [0005]     In addition, a front hinge may pivotally connect an extension plate or lip to the front edge of the deck. The front hinge allows the lip to pivot between a stored, pendant position and an extended, operative position. In the extended position, the lip can rest upon the truck bed to form a bridge between the deck and the bed. This allows personnel and material handling equipment, such as a forklift truck, to readily move on and off the truck during loading and unloading operations.  
         [0006]     With some dock levelers, the lip is connected to the deck in such a way that the lip can be used as a barrier to help prevent material handling equipment from accidentally driving off the edge of the deck while the deck is in its stored, cross-traffic position and no truck is parked at the dock. An example of such a dock leveler is disclosed in U. S. Pat. No. 4,920,598. With the &#39;598 dock leveler, the lip includes a series of slots through which a corresponding series of bolts extend to fasten the lip to a deck hinge. The slots plus clearance between the underside of the lip and the hinge allow the lip to slide between a normal operating position and a raised barrier position.  
         [0007]     When the lip is in its normal operating position and is extended to rest atop the back edge of a truck bed, tremendous stress can develop between the lip and the heads of the bolts that fasten the lip to the hinge when loads move over the dock leveler. The stress is concentrated along just a portion of the bolt head because the clearance between the lip and the hinge allow the lip to cock at a slight angle relative to the contact face of the bolt head.  
         [0008]     With the design disclosed in the &#39;598 patent, the resulting stress concentrations require the use of heavier and/or stronger materials than would otherwise be needed.  
       SUMMARY OF THE INVENTION  
       [0009]     In some embodiments, a dock leveler includes a lip that not only pivots between an extended, operative position and a pendant position relative to a deck but also translates from a non-blocking pendant position to a blocking pendant position. A fastener connects the lip to a hinge in such a way as to minimize the stress between the fastener and the lip.  
         [0010]     In some embodiments, the hinge includes a lip-facing surface into which the fastener is anchored, wherein the fastener is tilted out of perpendicularity to the lip-facing surface.  
         [0011]     In some embodiments, the head of the fastener is held parallel to the lip even though an angled gap may exist between the lip and the lip-facing surface of the hinge. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a side view of a truck backing into a loading dock, wherein the dock includes a dock leveler whose lip is in a blocking pendant position.  
         [0013]      FIG. 2  is side view similar to  FIG. 1  but showing the dock leveler&#39;s deck rising and the lip extending.  
         [0014]      FIG. 3  is a side view similar to  FIGS. 1 and 2  but showing the deck having lowered the lip upon the bed of the truck, wherein the lip is at an extended operative position.  
         [0015]      FIG. 4  is a side view of the dock leveler in a below-dock end-loading position with the lip at a non-blocking pendant position.  
         [0016]      FIG. 5  is a cross-sectional side view taken along a centerline of a slot that is in the dock leveler lip while the lip is in the extended operative position.  
         [0017]      FIG. 6  is a cross-sectional view similar to  FIG. 5  but showing the lip in its blocking pendant position.  
         [0018]      FIG. 7  is a front view of  FIG. 6  but with a portion of the lip cut away.  
         [0019]      FIG. 8  is an enlarged cross-sectional view similar to  FIG. 5 .  
         [0020]      FIG. 9  shows the head-to-lip contact area of a prior art design.  
         [0021]      FIG. 10  is similar to  FIG. 9  but showing a more broadly distributed head-to-lip contact area of the current design.  
         [0022]      FIG. 11  is a cross-sectional view similar to  FIG. 5  but showing another embodiment of the dock leveler.  
         [0023]      FIG. 12  is a cross-sectional view similar to  FIG. 6  but showing the lip of the dock leveler of  FIG. 11  in a blocking pendant position.  
         [0024]      FIG. 13  is a front view of  FIG. 12  but showing a portion of the lip cut away. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]     Referring to  FIGS. 1-8 , in order to compensate for a height differential that may exist between a loading dock platform  10  and the bed of a truck  12 , a dock leveler  14  includes a ramp or deck  16  that can pivot about its back edge  18  to adjust the height of its front edge  20 . To bridge the gap between the deck&#39;s front edge  20  and the rear edge of truck  12 , a front hinge  22  pivotally connects a lip  24  to the deck&#39;s front edge  20 . Deck  16  is movable to a cross-traffic position ( FIG. 1 ), a raised position ( FIG. 2 ), an operative position ( FIG. 3 ), and a below-dock end-loading position ( FIG. 4 ). Lip  24  can pivot between a pendant position ( FIG. 4 ) and an extended operative position. Lip  24  can also translate between a blocking position ( FIG. 1 ) and the non-blocking pendant position ( FIG. 4 ).  
         [0026]     In operation, truck  12  backs into the loading dock, adjacent to platform  10 , as shown in  FIG. 1 . At this point, deck  16  is at its stored, cross-traffic position where a driveway surface  26  of deck  16  is generally flush with the floor of platform  10 , and a tip  28  of lip  24  rests upon a set of lip keepers  30 , thereby supporting the deck to allow incidental traffic across the deck. To prevent items such as a forklift and other material handling equipment from accidentally falling over the deck&#39;s front edge  20 , a back edge  32  of lip  24  protrudes above the deck&#39;s driveway surface  26  to create a barrier. This is accomplished by providing hinge  22  and lip  24  with a sliding connection  34  between the two, which will be explained later.  
         [0027]     Next, in  FIG. 2 , deck  16  rises and lip  24  swings out to extend the tip  28  of lip  24  out over the top of the truck bed. The movement of lip  24  and deck  16  can be carried out in any of a wide variety of ways that are well known to those of ordinary skill in the art. The movement, for example, can be powered, manually driven, or a combination of the two. Mechanisms for moving deck  16  or lip  24  include, but are not limited to, hydraulic cylinder or bladder, pneumatic cylinder or bladder, mechanical linkage, drive screw, rack and pinion, winch, mechanical spring, gas spring, and various combinations thereof. Regardless of how deck  16  and lip  24  are moved, prior to extending the lip, deck  16  lifts lip  24  off keepers  30  where the sliding connection between hinge  22  and lip  24  allows the lip&#39;s weight to urge the lip&#39;s back edge  32  downward to where edge  32  is below the deck&#39;s driveway surface  16 .  
         [0028]     Then, in  FIG. 3 , deck  16  descends to place the extended lip  24  upon the bed of truck  12 . Dock leveler  14  is now in its operative position where truck  12  can be loaded or unloaded of its cargo. In the operative position, it should be noted that lip  24  and the deck&#39;s traffic surface  26  create a crown  36  having a defining angle  38  of about 5-degrees. Crown  36  ensures that the lip&#39;s tip  28  engages the bed of truck  12  even when the truck bed is higher than dock platform  10 .  
         [0029]      FIG. 4  illustrates an end-loading position where the non-blocking pendant lip is lowered in front of and below lip keeper&#39;s  30 . With lip  24  not resting atop the truck bed, loads can be added and removed from the very back end of the truck without interference from lip  24 .  
         [0030]     The sliding connection between lip  24  and hinge  22  can be as described in U.S. Pat. No. 4,920,598, which is specifically incorporated by reference herein; however, an improved, reduced stress sliding connection  34  is illustrated in  FIGS. 5-8 , and  10 . In particular, connection  34  evenly distributes the contact stress between a head-engaging surface  42  ( FIG. 8 ) of lip  24  and a lip-engaging surface  40  underneath a head  44  of a fastener  46 , wherein fastener  46  connects lip  24  to a lip-hinge member  48 , which, in turn, helps pivotally connect lip  24  to deck  16 .  
         [0031]      FIGS. 9 and 10  show a comparison of the contact stress areas of the old and new designs respectively. For the dock leveler of the &#39;598 patent,  FIG. 9  shows a shaded crosshatched stress area  45  where the head of the fastener engages the lip. For the new design,  FIG. 10  shows that dock leveler  14  has a more broadly distributed contact stress area  47 , which greatly enhances the longevity of the crown defining angle  38  and reduces the fatigue of the material of the head engaging surface  24 .  
         [0032]     Although the actual hinge structure for connecting lip  24  to deck  16  may vary, in some embodiments, hinge  22  comprises a hinge pin  50  that pivotally joins a series of spools or deck-hinge members  52  to the series of lip-hinge members  48 . Deck-hinge members  52  are disposed about pin  50  and can be welded (depicted by numeral  54 ) or otherwise attached to a header  56  of deck  16 . Lip-hinge members  48  also include spools  58  disposed about pin  50 , whereby pin  50  pivotally connects spools  58  of the lip-hinge members  48  to the series of deck-hinge members  52 .  
         [0033]     To create sliding connection  34 , lip  24  includes a series of slots  60  along which fasteners  46  can slide. In some embodiments, fastener  46  is a shoulder screw that includes head  44  and a shank  62 . A threaded end of shank  62  screws into lip-hinge member  48 , and head  44 , and an upper portion of shank  62  slides within slot  60 . To ensure sliding clearance between lip  24  and a lip-facing surface  64  of lip-hinge member  48 , a gap  66  may exist between the two. Gap  66  defines an acute angle  68  when lip  24  and lip-hinge member  48  are in the extended operative position as shown in  FIGS. 5 and 8 .  
         [0034]     To evenly distribute the circumferential contact stress between head  44  and lip  24  when lip  24  is in its extended operative position of  FIG. 3 , lip-engaging surface  40  of head  44  lies squarely on the integral head-engaging surface  42  of slot  60 , as shown in  FIG. 8 . This is accomplished by having a longitudinal centerline  70  of fastener  46  be tilted out of perpendicularity with lip-facing surface  64  and by having lip-engaging surface  40  of head  44  be perpendicular to centerline  70 . So that lip-engaging surface  40  is substantially coplanar with head-engaging surface  42 , the amount of tilt (i.e., an angle  73 ) between centerline  70  and a line  75  perpendicular to surface  64  is substantially equal to acute angle  68 . Since lip-engaging surface  40  is parallel with head-engaging surface  42 , a head-to-hinge angle  72  is created between lip-engaging surface  40  and lip-facing surface  64 , wherein the head-to-hinge angle  72  substantially equals acute angle  68 .  
         [0035]     In another embodiment, shown in  FIGS. 11-13  (which correspond to  FIGS. 5-7  respectively), a lip-hinge member  74  replaces lip-hinge member  48 , and a deck-hinge member  76  replaces deck-hinge member  52 . Deck-hinge member  76  is a formed metal plate that partially wraps around hinge pin  50  and is welded to a series of deck-support beams  78  or otherwise attached to a deck  80 . Deck-hinge member  76  has a series of openings  82  through which lip-hinge members  74  extend. In this example, each lip-hinge member  74  comprises a U-shaped piece  84 , an upper plate  86 , and a lower plate  88 . U-shaped piece  84  extends from upper plate  86  and wraps partially around hinge pin  50  so that pin  50  pivotally couples lip-hinge member  74  to deck-hinge member  76 . Lower plate  88  underneath upper plate  86  provides a threaded hole for holding fastener  46 .  
         [0036]     To ensure sliding clearance between lip  24  and a lip-facing surface  90  of lip-hinge member  86 , a gap  94  may exist between the two. Gap  94  defines an acute angle  92  when lip  24  and lip-hinge member  86  are positioned in the extended operative position as shown in  FIG. 11 .  
         [0037]     To evenly distribute the circumferential contact stress between head  44  and lip  24  when lip  24  is in its extended operative position, lip-engaging surface  40  of head  44  lies squarely on the integral head-engaging surface  42  of slot  60 , as shown in  FIG. 11 . This is accomplished by having centerline  70  of fastener  46  be tilted out of perpendicularity with lip-facing surface  90  and by having lip-engaging surface  40  of head  44  be perpendicular to centerline  70 . The amount of tilt is substantially equal to acute angle  92  so that lip-engaging surface  40  is substantially coplanar with head-engaging surface  42 .  
         [0038]     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. A annular shim or conventional washer, for instance, could be placed underneath the head of the fastener, in which case the fastener would comprises the head, shank and washer (or shim), and the washer or shim would be considered as being part of the head. Therefore, the scope of the invention is to be determined by reference to the following claims: