Abstract:
A dock leveler includes a vehicle-engaging pivotal lip extending from the front end of a pivotal deck, wherein the lip has one or more unique features that provide a smooth transition for forklifts traveling between the lip and a trailer bed upon which the lip is resting. The smooth transition minimizes jolting and vibration of the forklift and its driver as the forklift wheels pass over the leading edge of the lip. The special features of the lip may include one or more of the following: a curved traffic-bearing surface terminating at a sharp or blunt leading edge, a traffic-bearing surface that includes both flat and curved sections, a multifaceted traffic-bearing surface that approximates a curved surface, a rubber or plastic shock absorbing element, an articulated nose piece at the lip&#39;s leading edge, and a main lip plate that is coplanar with the deck&#39;s traffic surface (i.e., zero crown angle).

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The subject disclosure generally pertains to dock levelers and more specifically to a transitional lip extending from the deck of a dock leveler. 
       BACKGROUND OF RELATED ART 
       [0002]    A typical 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 loading dock platform and an adjacent bed of a truck or trailer. A dock leveler usually includes a deck that is hinged along its back edge 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 or trailer bed. 
         [0003]    In addition, usually a front hinge pivotally connects 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 trailer 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 trailer during loading and unloading operations. 
         [0004]    Often, the leading edge of the lip that rests upon the trailer bed is beveled to create a miniature ramp that minimizes physical shock to material handling equipment as their wheels travel over that leading edge. Nonetheless, the lip&#39;s leading edge and the rest of the lip can still jar the moving equipment and its driver. The magnitude of the jolt is a function of numerous factors including, but not limited to, the lip&#39;s thickness, the geometry of the lip&#39;s leading edge, the lip-to-deck crown angle (angle between the upper surfaces of the lip and the deck), angle between the upper surfaces of the lip and the trailer bed, height differential between the trailer bed and the loading dock&#39;s elevated platform, the hardness and diameter of the material handling equipment&#39;s wheels, the material handling equipment&#39;s suspension, the speed of the material handling equipment as it passes over the lip&#39;s leading edge, the combined weight of the material handling equipment and the load it is carrying, and the suspension of the trailer being loaded or unloaded of its cargo. 
         [0005]    Some of the shock occurring at the lip might be reduced by providing a dock leveler with a crown angle that varies as a function of the deck&#39;s angle of inclination. Such a dock leveler is disclosed in US published patent application 2006/0150348A1. Although varying the crown angle might reduce the mechanical shock caused by the height differential between the truck bed and the dock&#39;s elevated platform, there are still many other shock-causing factors that could be addressed. 
         [0006]    Consequently, a need exists for a better dock leveler that provides a smooth transition between the dock leveler&#39;s lip and a trailer bed upon which the lip is resting. Preferably, the dock leveler addresses a broad range of often uncontrollable factors that can reduce the smooth traveling of material handling equipment as the equipment travels between the dock leveler&#39;s lip and the trailer bed. 
       SUMMARY 
       [0007]    In some examples, a dock leveler lip includes a curved leading edge to smoothen the transition between the lip and the top surface of a trailer bed. 
         [0008]    In some examples, a dock leveler lip includes a shock absorbing polymeric element that minimizes mechanical shock and vibration to material handling equipment traveling over the lip. 
         [0009]    In some examples, the shock absorbing polymeric element includes an interlocking feature that helps hold the element in place. 
         [0010]    In some examples, a dock leveler includes an articulated lip. 
         [0011]    In some examples, a dock leveler lip includes a plurality of flat, inclined surfaces that approximate a curved surface. 
         [0012]    In some examples, a dock leveler lip includes a combination of flat and curved surfaces. 
         [0013]    In some examples, a dock leveler lip includes a curved traffic-bearing surface so that the lip can terminate at a generally sharp leading edge without the lip being too thin at that area of the lip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view of a vehicle backing toward a dock leveler whose deck is at a stored, cross-traffic position. 
           [0015]      FIG. 2  is a side view similar to  FIG. 1  but showing the vehicle having already backed into the dock with the dock leveler moving into an operating position. 
           [0016]      FIG. 3  is a side view similar to  FIG. 2  but showing the dock leveler lowering its deck upon the vehicle&#39;s trailer bed. 
           [0017]      FIG. 4  is a side view similar to  FIG. 3  but showing the dock leveler in an operative position with a forklift traveling over the lip of the dock leveler. 
           [0018]      FIG. 5  is a side view similar to  FIG. 4  but showing the dock leveler engaging a higher trailer bed. 
           [0019]      FIG. 6  is a side view similar to  FIG. 4  but showing the dock leveler engaging a lower trailer bed. 
           [0020]      FIG. 7  is a side view a dock leveler lip according to one embodiment. 
           [0021]      FIG. 8  is a side view of a dock leveler lip according to a second embodiment. 
           [0022]      FIG. 9  is a side view of a dock leveler lip according to a third embodiment. 
           [0023]      FIG. 10  is a side view of a dock leveler lip according to a fourth embodiment. 
           [0024]      FIG. 11  is a side view of a dock leveler lip according to a fifth embodiment. 
           [0025]      FIG. 12  is a side view of a dock leveler lip according to a sixth embodiment. 
           [0026]      FIG. 13  is a partially exploded perspective view of the dock leveler and lip of  FIG. 12 . 
           [0027]      FIG. 14  is a side view of a dock leveler lip according to a seventh embodiment. 
           [0028]      FIG. 15  is a side view similar to  FIG. 14  but showing the lip engaging a higher trailer bed. 
           [0029]      FIG. 16  is a side view similar to  FIG. 14  but showing the lip engaging a lower trailer bed. 
           [0030]      FIG. 17  is a side view similar to  FIG. 14  but showing an alternate embodiment. 
           [0031]      FIG. 18  is a side view similar to  FIG. 11  but showing an alternate embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIGS. 1-6  show a loading dock  10  with a dock leveler  12  for facilitating the loading and unloading of cargo on a trailer bed  14  or some other vehicle or truck bed. Dock leveler  12  includes a deck  16  that due to a rear hinge  18  can pivot about a rear edge  20  to adjust the height of its front edge  22  so that trailer bed  14  and the deck&#39;s front edge  22  can be at about the same height. Deck  16  can pivot over a range of positions including, but not limited to, a raised position ( FIG. 2 ), a cross-traffic position ( FIG. 1 ), and a below-dock position ( FIG. 6 ). 
         [0033]    To bridge the gap between the deck&#39;s front edge  22  and the rear edge of trailer bed  14 , a front hinge  24  pivotally couples a lip  26  to the deck&#39;s front edge  22 . Lip  26  can pivot between an extended position ( FIG. 3 ) and a pendant position ( FIG. 1 ). Together, deck  16  and lip  26  provide a bridge over which a forklift  28  and other material handling equipment can travel between trailer bed  14  and an elevated platform  30  of dock  10 . 
         [0034]    As the forklift&#39;s wheels roll between trailer bed  14  and lip  26 , forklift  28  and its driver may experience some jolting and vibration because the upper surface of trailer bed  14  and a traffic-bearing surface  32  of lip  26  are not perfectly coplanar. To minimize this vibration, a leading edge  34  of lip  26  includes one or more novel features that provide a smooth transition between trailer bed  14  and deck  16 . These features have been designed while carefully considering the typical operation of a dock leveler. 
         [0035]    In operation, trailer bed  14  is backed into the loading dock, as shown in  FIG. 1 . At this point, deck  16  is at its stored, cross-traffic position where a driveway surface  36  of deck  16  is generally flush with platform  30 , and lip  26  is at its pendant position. In some cases, edge  34  of lip  26  rests upon a set of lip keepers  38  so that lip  26  can help support the weight of the deck at its cross-traffic position. In cases where the dock leveler does not include lip keepers, a pedestal installed underneath the deck can be used for supporting the deck&#39;s weight. An example of such a pedestal is disclosed in U.S. Pat. No. 3,530,488. 
         [0036]    Next, referring to  FIG. 2 , deck  16  rises and lip  26  swings out to extend edge  34  of lip  26  out over the top of trailer bed  14 . Then, in  FIG. 3 , deck  16  descends to place the extended lip  26  upon trailer bed  14 . The movement of lip  26  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  26  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. 
         [0037]    Once lip  26  is resting upon trailer bed  14 , as shown in  FIG. 4 , forklift  28  can readily travel between platform  30  and trailer bed  14 . The actual inclination of deck  16  and the angle between the upper surfaces of bed  14  and lip  26  is partially determined based on the relative heights of bed  14  and platform  30 .  FIG. 4 , for instance, shows the deck&#39;s inclination when dock leveler  12  engages a trailer bed of moderate height,  FIG. 5  shows dock leveler  12  engaging a relatively high trailer bed  14   a,  and  FIG. 6  shows a relatively low trailer bed  14   b.  Leading edge  34  being able to lie directly against trailer bed  14   a  even though bed  14   a  is higher than platform  30  is because the upper traffic-bearing surfaces of lip  26  and deck  16  are at a slightly positive crown angle  40  (about 5-degrees). 
         [0038]    Although crown angle  40  ensures that the lip&#39;s leading edge  34  is resting directly upon trailer bed  14 , the transition between edge  34  and bed  14  can still cause some vibration and jolting of forklift  28  and its driver. To minimize this vibration, a lip  26   a  can be provided with a smoothly curved or contoured traffic-bearing surface  42 , as shown in  FIG. 7 . In this example, lip  26   a  has a leading edge  34   a  that is a substantially sharp line, which helps minimize any impact as a forklift wheel rolls from trailer bed  14  onto lip  26   a.  Traffic-bearing surface  42 , which lies between leading edge  34   a  and a hinged edge  44 , comprises a first approach surface  46 , a second approach surface  48 , and a final approach surface  50 . 
         [0039]    Due to the continuous curvature of the leading portion of bearing-surface  42 , first approach surface  46  and second approach surface  48  are at an incline relative to each other. A tangent line  52  to first approach surface  46 , for instance, lies at an angle (not parallel) to a line  54  that lies tangent to second approach surface  48 , yet the two surfaces  46  and  48  smoothly blend due to a curved surface  56  between surfaces  46  and  48 . In some cases, surfaces  46 ,  48  and  56  have the same radius and center of curvature. 
         [0040]    In an alternate example, shown in  FIG. 8 , a lip  26   b  includes a more blunt leading edge  34   b  that might be more durable than a sharp edge. Leading edge  34   b  is a generally flat surface that lies at an angle (greater than zero degrees) relative to the lip&#39;s first approach surface  58 . In this example, lip  26   b  has a traffic-bearing surface  60  that extends between leading edge  34   b  and hinged edge  44 . Traffic bearing surface  60  comprises first approach surface  58 , second approach surface  48 , and final approach surface  50 . Except for the slight difference between leading edges  34   a  and  34   b,  traffic bearing surfaces  42  and  60  are substantially the same. 
         [0041]    Because a curved surface can be more difficult to machine than a flat surface,  FIG. 9  shows an alternate lip  26   c  that includes a traffic-bearing surface  62  comprising a plurality of flat surfaces, which approximate the curved surfaces of lips  26   a  and  26   b.  Lip  26   c  includes a leading edge  34   c  similar to edge  34   b  (or similar to edge  34   a ). Traffic-bearing surface  62  of lip  26   c  extends from leading edge  34   c  to hinged edge  44 . Surface  62  comprises a first approach surface  66 , a second approach surface  68 , and final approach surface  50 . Each surface  66 ,  68  and  50  is substantially flat and lies at an incline relative to the others. 
         [0042]    In another example, shown in  FIG. 10 , a lip  26   d  includes a leading edge  34   d  similar to edge  34   c  (or similar to edge  34   a ). A traffic-bearing surface  70  of lip  26   d  extends from leading edge  34   d  to hinged edge  44 . Traffic bearing surface  70  comprises a substantially flat first approach surface  72 , a curved second approach surface  74 , and substantially flat final approach surface  50 . Second approach surface  74  provides a smooth tangential transition between first approach surface  72  and final approach surface  50 . 
         [0043]    To create a more shock absorbing lip and/or to achieve a curved traffic-bearing surface without having to machine such a surface, a lip  26   e  can comprise a metal plate  76  to which a formed polymeric element  78  can be attached, as shown in  FIG. 11 . Element  78  can be attached in any suitable manner including, but not limited to, an adhesive  80 , a threaded fastener  82 , a rivet, and/or a mechanically interlocking feature (e.g., tongue-and-groove, plug-and-hole, etc.). Element  78  can be of any desired shape. In this particular example, element  78  is of a shape that provides a traffic-bearing surface  84  that is similar to surface  60  of  FIG. 8 . Element  78  can also be of any desired material, including but not limited to, neoprene rubber or polyurethane. Any suitable manufacturing process including, but not limited to, extrusion, plastic injection molding, and machining can produce element  78 . Element  78  can be one continuous piece that extends the full width of deck  16 , or element  78  can comprises a plurality of segments. The phantom lines of  FIG. 11  illustrate the flexure of element  78  as a strong lower edge  83  of lip  26   e  rests firmly upon trailer bed  14 . In addition to flexibility, element  78  may advantageously have shock or vibration absorption or dampening properties. Such properties would serve to minimize or eliminate vibration transmitted from the leveler to the forktruck operator resulting from contact therebetween and/or movement of the forktruck over the leveler, or at least the lip. 
         [0044]    When a formed polymeric element or insert is used, the leading edge of the lip might be more durable if the underlying metal plate of the lip extends all the way to the tip of the lip.  FIGS. 12 and 13 , for example, show a lip  26   f  comprising a formed polymeric element  86  attached to a metal plate  88 . Plate  88  extends fully to a leading edge  34   f  of lip  26   f  so that the strength of edge  34   f  is sufficient to support the weight of deck  16  when lip  26   f  is in its pendant position held by lip keepers  38  ( FIG. 1 ). Element  86  can be comprised of a series of segments  90 , which might make lip  26   f  easier to manufacture, ship and assemble. Moreover, worn segments could be replaced with new ones or their positions could be interchanged as some segments  90  in high traffic areas wear faster than others. Although element  86  could be attached in any suitable manner, such as those mentioned with reference to element  78  of  FIG. 11 , each segment  90  could include a plurality of plugs  92  that press-fit into a corresponding plurality of holes  94  in plate  88 . 
         [0045]    In another embodiment, shown in  FIGS. 14 ,  15  and  16 , an articulated lip assembly  26   g  comprises a metal or polymeric nose piece  98  that is pivotally attached to a metal plate  100  (main piece). A hinge  102  or pivotal connection between nose piece  98  and plate  100  allows piece  98  to lie generally flat against trailer bed  14  regardless of whether the trailer bed&#39;s elevation is high as shown in  FIG. 15 , low as shown in  FIG. 16 , or at an intermediate elevation as shown in  FIG. 14 .  FIGS. 14 ,  15  and  16  generally correspond to  FIGS. 4 ,  5  and  6  respectively. In this example, lip  26   g  includes a generally sharp leading edge  34   g,  and a traffic-bearing surface  96  extends between leading edge  34   g  and hinged edge  44 . Although edge  34   g  is shown as a sharp edge, leading edge  34   g  could by of any shape including, but not limited to the shapes illustrated in  FIGS. 7-13 . Nose piece  98  can be one continuous piece that extends most of the full width of deck  16 , or piece  98  can comprises two or more segments (plurality of leading edge pieces) that are distributed along plate  100  in a manner similar to the distribution of segments  90  of  FIG. 13 . 
         [0046]    In some examples, as shown in  FIG. 17 , an articulated lip assembly  26   h  comprises nose piece  98 , an intermediate link  104 , and a main piece  106 . The articulation of assembly  26   h  allows a leading edge  108  of nose piece  98  to rest upon trailer bed  14  even when bed  14  is higher than deck  16 . Unlike many other dock levelers, this design does not require a crown angle where main piece  106  abuts the front edge of deck  16  (see crown angle  110  of  FIG. 4 ). Instead, a main traffic surface  112  of main piece  106  is substantially coplanar with deck traffic surface  36  of deck  16 . This is a significant advantage because crown angles can be difficult to produce and maintain. 
         [0047]    Alternatively,  FIG. 18  shows a lip assembly  26   k  where the articulated portion of assembly  26   h  of  FIG. 17  is basically replaced by a flexible leading edge piece  114  similar to element  78  of  FIG. 11 . When trailer bed  14  is higher than deck  16 , as shown in  FIG. 18 , a relatively stiff main piece  116  can rest solidly upon bed  14 , while a wheel  118  from a forklift or other type of material handling equipment can deflect leading edge piece  114  down against bed  14 , thereby providing wheel  118  with a generally smooth path to travel between bed  14  and deck  16 . Again, this design does not require a crown angle where main piece  116  abuts the front edge of deck  16 , thus a main traffic surface  120  of main piece  116  can be substantially coplanar with deck traffic surface  36  of deck  16 . 
         [0048]    It should be noted that leading edge piece  114  ( FIG. 18 ), nose piece  98  ( FIG. 17 ), and element  90  ( FIG. 12 ) are all deflectively coupled to a main piece. The term, “deflectively coupled” refers to a connection between two pieces where some localized or total relative movement can occur between the two. Examples of such movement include, but are not limited to, resilient bending, resilient deformation, resilient localized compression, and pivotal movement. 
         [0049]    Although the invention is described with respect to various examples, modifications thereto will be apparent to those of ordinary skill in the art. The scope of the invention, therefore, is to be determined by reference to the following claims.