Abstract:
A dock leveler includes a pivotally extendable lip coupled to a pivotal deck by way of a front hinge, wherein the structure in the area of the front hinge optimizes the torsional flexibility of the deck; provides a well supported, durable crown (apex angle between an extended lip and the deck); and reduces the part count of the dock leveler. The front hinge includes a deck-hinge member that extends approximately the full width of the deck and is preferably formed from a single sheet of material. A particularly narrow front header or flange disposed along the front edge of the deck reinforces the relatively thin deck plate so that the plate&#39;s rigidity more closely matches that of the thicker lip, yet the flange is sufficiently small to allow the deck to twist so that the deck can place the tip of the lip squarely upon a sideways inclined truck bed.

Description:
[0001]    This Application is a Divisional of U.S. patent application Ser. No. 10/902,458, filed on Jul. 29, 2004, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The subject invention generally pertains to dock levelers and more specifically to the structure around a hinge that pivotally connects a lip extension plate to the deck of a dock leveler. 
         [0004]    2. Description of Related Art 
         [0005]    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 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 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. 
         [0006]    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 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 vehicle during loading and unloading operations. 
         [0007]    The design of the front hinge and the adjoining structure determines some key features of the dock leveler. These features include the crown, openness of the front hinge, flexibility of the deck, and part count. 
         [0008]    First, the crown is the angle or apex created between the upper surfaces of the deck and an extended lip. The crown angle is usually about two or three degrees less than 180 degrees, and it becomes an important feature when the truck bed is higher than the platform from which the deck extends. When the truck bed is higher than the platform, the deck must lie at an incline to elevate the deck&#39;s front edge. If the lip were coplanar with the deck, whereby no crown existed, the lip would project its distal edge (tip of the lip) a little above the truck bed. This would create a detrimental step between the tip of the lip and the truck bed, wherein the step might trip dockworkers or jar forklifts. A crown eliminates this step by pointing the tip of the lip back down against the truck bed. 
         [0009]    It can be difficult, however, to maintain a desired crown as the weight of a forklift repeatedly carrying loads over the front hinge area of the dock leveler generates tremendous forces that tend to flatten the crown over time. Numerous hinge and lip structures have been devised to counter such forces; however, many of them rely on a single abutment subjected to high stress concentrations. A common example of such an abutment would be the back edge of the lip abutting the front edge of the upper deck plate. With such a design, high stress concentrations can eventually wear down the abutment to diminish or eliminate the crown. Other dock levelers, such as disclosed in U.S. Pat. No. 5,815,871, involve assemblies having intricate cross-sectional shapes that can be expensive to produce. 
         [0010]    The second mentioned feature of the dock leveler pertains to the openness of the front hinge, which connects the lip to the deck. The openness refers to any gaps that may exist at the hinge when the lip is at its pendant position. U.S. Pat. No. 3,587,126 provides an example of a dock leveler whose front hinge is of an open design, while U.S. Pat. No. 6,370,719 shows a hinge of a more closed design. Although either style may function well, some believe that a closed-style hinge looks cleaner, provides less of a pinching hazard, and prevents items from accidentally falling between the pendant lip and the deck. 
         [0011]    Third, torsional flexibility of the deck or the ability of the top surface of the deck to twist out of its normal plane of flatness is another important feature of a dock leveler. Such flexibility allows the deck to twist so that the front edge of the deck and the lip extending from it can align themselves to the plane of the truck bed. For instance, if the dock platform is level but the truck bed lies at an angle from the right to left side of the truck, the deck can twist accordingly. 
         [0012]    The deck&#39;s torsional flexibility is partially determined by the existence or absence of a front header. When present, the front header usually lies just behind the front hinge and extends generally perpendicular to a series of beams that support the upper plate of the deck. These beams are typically welded or other wise affixed to the header—which thus serves to structurally tie the beams together. Often, the front hinge is mounted directly to the front header. U.S. Pat. No. 6,370,719 shows an example of a dock leveler with a front header, and U.S. Pat. No. 3,587,126 shows one without a header. Some decks with headers are torsionally too stiff, while other decks without headers can be too flexible. Without a header, the top plate of the deck may be so flexible and unsupported that the weight of forklifts may deform the plate in the areas between its supporting beams, whereby the plate becomes permanently dished down in those areas. 
         [0013]    Fourthly, the part count of a front hinge assembly can have a direct affect on the cost of a dock leveler. Generally, the number of parts is preferably kept to a minimum, which can be difficult to do when the hinge assembly comprises a series of spaced-apart hinge segments that are pivotally connected by a hinge pin. 
         [0014]    Consequently, a need exists for a front header and hinge assembly that provides a dock leveler with a minimal number of parts, a long lasting crown, a generally closed hinge, and a deck with appropriate flexibility. 
       SUMMARY OF THE INVENTION 
       [0015]    In some embodiments, a dock leveler includes a front hinge that pivotally connects a lip to a deck of the leveler, wherein the front hinge includes a formed deck-hinge member that extends between at least two of the deck&#39;s support members. 
         [0016]    In some embodiments the formed deck-hinge member extends along most of the deck&#39;s width. 
         [0017]    In some embodiments, the front hinge of the dock leveler closes most of the gap between the lip and the deck when the lip is at the pendant position. 
         [0018]    In some embodiments, the front hinge comprises a deck-hinge member pinned to a plurality of lip-hinge members, wherein the plurality of lip-hinge members extend into a corresponding plurality of apertures in the deck-hinge member. 
         [0019]    In some embodiments, the deck-hinge member has a plurality of slits for engaging a plurality of support beams underneath the top plate of the deck. 
         [0020]    In some embodiments, the lip in an extended position engages a front edge of the deck and an upper surface of the deck-hinge member to ensure that a crown or apex exists where the lip and deck meet. 
         [0021]    In some embodiments, the deck includes a narrow front header or flange that provides the deck with a desired amount of torsional flexibility while supporting the deck plate at it&#39;s free edge to help prevent deformation in the areas between the deck&#39;s support beams. 
         [0022]    In some embodiments, the front header provides the front edge of the deck&#39;s top plate with a level of flexibility that is comparable to that of the lip even though the average material thickness of the lip is greater than that of the top plate. 
         [0023]    In some embodiments, the bottom edge of the front header is above the longitudinal centerline of the front hinge pin. 
         [0024]    In some embodiments, the bottom edge of the front header is above the front hinge pin. 
         [0025]    In some embodiments, the bottom edge of the front header is above the deck-hinge member. 
         [0026]    In some embodiments, the deck-hinge member engages the hinge pin along a curved surface that extends less than 360-degrees around the hinge pin. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a side view of a truck at a loading dock, wherein the dock includes a dock leveler whose deck and lip are at their stored positions. 
           [0028]      FIG. 2  is side view similar to  FIG. 1  but showing the deck rising and the lip extending. 
           [0029]      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. 
           [0030]      FIG. 4  is a perspective view of the dock leveler of  FIG. 3 . 
           [0031]      FIG. 5  is a perspective view of a deck-hinge member used in the dock leveler of  FIG. 1 . 
           [0032]      FIG. 6  is a close-up side view of the dock leveler of  FIG. 3  but with a side plate of the deck removed to show details of the front hinge. 
           [0033]      FIG. 7  is similar to  FIG. 6  but showing the lip in a pendant position as also shown in  FIG. 1 . 
           [0034]      FIG. 8  is a perspective view of another embodiment of a dock leveler. 
           [0035]      FIG. 9  is close-up side view similar to  FIG. 6  but for the dock leveler of  FIG. 8 . 
           [0036]      FIG. 10  is close-up side view similar to  FIG. 7  but for the dock leveler of  FIG. 8 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0037]    Referring to  FIGS. 1-3 , 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 between a raised position ( FIG. 2 ) and a lowered position ( FIG. 1 ), and lip  24  can pivot between an extended position ( FIG. 3 ) and a pendant position ( FIG. 1 ). 
         [0038]    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 platform  10 . Also, lip  24  is shown at its pendant position where, in some embodiments, a tip  28  of lip  24  rests upon a set of lip keepers  30 . 
         [0039]    Next, referring to  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. 
         [0040]    Then, in  FIG. 3 , deck  16  descends to place the extended lip  24  upon the bed of truck  12 . 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. 
         [0041]    Regardless of how deck  16  and lip  24  are moved, an important aspect of the invention pertains to front hinge  22  and its surrounding structure. It is this part of dock leveler  14  that helps determine the crown (angle between deck surface  26  and extended lip  24 ), openness of hinge  22 , and the torsional flexibility of deck  16 . In this first embodiment, hinge  22  is of a closed design and is mounted adjacent to a narrow front header or flange  32  ( FIGS. 6 &amp; 7 ). Hinge  22  and flange  32  are purposefully designed to increase the strength of the crown, optimize the torsional flexibility of the deck, and minimize total part count of the dock leveler. 
         [0042]    Hinge  22 , for instance, includes a deck-hinge member  34  cut and formed from a single sheet of material (see  FIG. 5 ) and welded or otherwise attached to deck  16 . Preferably, that attachment to deck  16  is accomplished by deck-hinge member  34  having several slits  36  for engaging a series of central support members or beams  38  to which deck hinge member  34  is welded and that support a deck plate  40  of deck  16 . Deck-hinge member  34  may also be welded or otherwise attached to side support members  39 . Accordingly, deck-hinge member  34  serves to structurally tie together the support members (both central and side) in a similar manner to a conventional front header—while also serving the function of creating the deck portion of the hinge structure. In the embodiment shown  FIGS. 4-7 , the deck-hinge member is a unitary piece connecting all of the deck support members and thus extending along most of the width of the deck  16 . Alternatively, individual deck-hinge members could extend between and structurally tie together less that all of the deck support members—such as a pair of deck support members. Either form of deck-hinge members would perform both their hinge function as well as the function of extending between and thus structurally tying together two or more deck support members. Deck-hinge member  34  may be provided with pin-retaining bars  41  that help maintain the radial position of hinge pin  50  relative to deck-hinge member  34 . If needed, one or more sections  42  of deck-hinge member  34  can be notched out to provide operating clearance for a lip actuator. Deck-hinge member  34  defines a plurality of apertures  44  for receiving an equal plurality of lip-hinge members  46 . 
         [0043]    Referring to  FIGS. 6 and 7 , lip-hinge members  46  according to this illustrative embodiment are U-shaped pieces that are welded or otherwise attached to a lower surface  48  of lip  24 . With lip-hinge members  46  extending into apertures  44  of deck-hinge member  34 , a hinge pin  50  can be inserted between members  34  and  46  to pivotally couple lip  24  to deck  16 , whereby lip  24  can pivot about a longitudinal centerline  52  of pin  50 . 
         [0044]    For simplicity, less frictional contact area, and ease of manufacturing, deck-hinge member  34  has a curved pin-engaging surface  54  that contacts pin  50  over an area of less than 360 degrees, as indicated by arc  56  of  FIG. 6 . Likewise, lip-hinge member  46  also has a curved pin-engaging surface  58  that contacts pin  50  over an area of less than 360 degrees, as indicated by arc  60  of  FIG. 7 . 
         [0045]    To maximize the strength and minimize the part count of the front hinge assembly, deck-hinge member  34  preferably extends seamlessly along most if not all of its length, or the width of deck  16 , or the length of pin  50 . The term “seamlessly” refers to a part made from one continuous piece and/or along which a straight or winding path can be traced generally lengthwise without encountering a seam or joint. 
         [0046]    To establish a crown  62  ( FIGS. 3 and 6 ) that can withstand heavy, repeated loading, the upward movement of lip  24  is limited by a back edge  64  of lip  24  abutting front edge  20  and/or lower surface  48  of lip  24  engaging an upper surface  66  of deck-hinge member  34 . The crown angle  68  or apex between an upper lip surface  70  of lip  24  and the driveway surface  26  of deck  16  is typically about 5-degrees (angle  72 ) less than 180-degrees. Ideally, lip  24  abuts front edge  20  and upper surface  66  simultaneously to form crown angle  68 , thereby creating a two-point crown control which aides in the longevity of maintaining a desired lip crown by distributing the repeated load of a traversing fork truck. 
         [0047]    To provide deck  16  with an appropriate amount of torsional flexibility, flange  32  ( FIGS. 6 &amp; 7 ) is made particularly narrow. The deck-hinge member  34  performs some of the function of a conventional header by structurally tying two or more deck support members together, such that the addition of flange  32  provides the appropriate amount of torsional rigidity allowing deck  16  to twist so that the tip  28  of lip  24  can lie squarely atop the bed of truck  12  even when the truck bed and platform  10  are at an angle to each other (as measured from the left to right side of the truck). 
         [0048]    Since deck plate  40  is supported by beams  38  and side supports  39 , plate  40  may be thinner than lip  24 . So, to prevent plate  40  from permanently deflecting or bowing downward in the areas between beams  38  and between beams  38  and side supports  39 , or at least to prevent front edge  20  from deflecting much more than lip  24 , flange  32  preferably provides front edge  20  of deck  16  with a level of rigidity that is comparable to that of lip  24 . Because deck-hinge member  34  performs some of this function itself, flange  32  can be smaller than a conventional header, such as being of a height that places a lower edge  74  of flange  32  at an elevation that is above the lower extremity  51  of the hinge pin  50 . As shown here, the lower edge  74  is above the hinge pin&#39;s centerline  52  and preferably higher than pin  50  itself. Although flange  32  is shown as a separate piece that is welded or otherwise attached to deck plate  40 , alternatively, the front edge of plate  40  could be formed or bent downward to create a flange that extends integrally from plate  40 , whereby deck plate  40  and flange  32  would be a unitary piece. It should be noted that flange  32  is disposed vertically between the bottom of front edge  20  and the upper surface  66  of the deck-hinge member  34 . This position of flange  32  allows it to transfer loads applied to the free front edge  20  (particularly the length thereof between the support members or beams) into the deck-hinge member  34  and thus to the support members or beams to which member  34  is attached. 
         [0049]    The relatively narrow flange  32  can also be used on a dock leveler  76  that has a front hinge  78  of a more open design, as shown in  FIGS. 8-10 . In this case, hinge  78  comprises a series of lip-hinge members  80  connected to a lip  82  and a series of deck-hinge members  84  attached to a deck  16 ′. Hinge pin  50  joins members  80  and  84  to render lip  82  pivotal relative to deck  16 ′. 
         [0050]    To establish a crown  86  (similar to previously mentioned crown  62 ) that can withstand heavy, repeated loading, the upward movement of lip  82  is limited by a back edge  88  of lip  82  abutting a front edge  90  of deck  16 ′ and/or a lower surface  92  of lip  82  engaging an upper surface  94  of deck-hinge member  84 . Ideally, lip  82  abuts front edge  90  and upper surface  94  simultaneously to form crown  86 , thereby creating a two-point crown control which aides in the longevity of maintaining a desired lip crown. Again, flange  32  is compressed between the free front edge of the deck and the deck hinge members  84  for applied loads. This facilitates the transfer of those loads to the support members or beams to which deck-hinge members  84  are attached thereby reinforcing the free front edge of the deck. 
         [0051]    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. Therefore, the scope of the invention is to be determined by reference to the following claims: