Abstract:
An extendible shield for sheltering the pit area below a dock leveler of a loading dock. The shield is especially suited for dock levelers having a ramp of pivotally adjustable height with a lip extension for providing a traffic path between the rear of a vehicle and a loading dock platform. The shield includes a curtain wrapped around a roller, which provides the shield with a vertical span that can vary to match the up and down movement of the ramp. Various embodiments include features such a flexible seal that seals against the rear of a vehicle and cutouts for accommodating a vehicle restraint and lip keepers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention generally pertains to loading docks, and more specifically to a shield system for shielding an area below a dock leveler. 
     2. Description of Related Art 
     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. To compensate for height differences between the loading dock platform and an adjacent bed of a truck or trailer, many loading docks have a dock leveler. A typical dock leveler includes a deck, also known as a ramp or dockboard, which is pivotally hinged along its back edge to vary the height of its front edge. An extension plate, or lip, extends outward from the deck&#39;s front edge to span the gap between the rear of the truck bed and the front edge of the deck. The lip is usually moveable between a stored position to an extended, operative position. In the extended, operative position, the lip extends from the deck&#39;s front edge and rests upon the truck bed to form a bridge between the two. This allows personnel and material handling equipment to readily move on and off the vehicle during loading and unloading operations. 
     To help shield against weather while a vehicle is being serviced at the dock, usually some type of seal is installed around the perimeter of the doorway. Such seals are usually installed along the upper and side edges of the doorway to help seal any air gaps that may otherwise exist between the face of the building and the rear of the vehicle. The dock leveler lip resting upon the rear of the vehicle is often relied upon to seal most of the doorway&#39;s lower edge. 
     However, the area or pit underneath a dock leveler&#39;s ramp is usually exposed to outside air. This can create problems, especially when there is a significant temperature differential between the indoor and outdoor air. For example, warm outside air may condense underneath a relatively cool ramp of a dock leveler used in a cold storage warehouse. The condensation can promote corrosion of various parts of the dock leveler. Conversely, a heated building during the winter may loose a significant amount of heat by thermal conduction through the ramp, as cold outside air cools the ramp from underneath. Thus, regardless of whether the outside air is colder or warmer than the inside air, it may be beneficial to shield the underside of a dock leveler from outside air, as proposed in U.S. Pat. No. 4,682,382. 
     The &#39;382 patent suggests using a rectangular panel to help shield the area underneath a dock leveler. A lower edge of the panel is coupled to the dock, while the panel&#39;s upper edge has a resilient sealing strip for sealing against the rear of a vehicle. The effectiveness of that seal, however, may depend on how squarely a vehicle backs into the dock and may further depend on the shape or contour of the vehicle&#39;s rear surface. Moreover, in the absence of a vehicle, it appears that the dock leveler lip, rather than the rectangular panel, is relied upon to shield the underside of the ramp from the outside air. Also, to move the lip from a stored, pendant position to an extended, operative position, the ramp apparently must lift the lip up and over the upper edge of the panel before the lip can be set back down atop the truck bed. As the lip travels over the top of the sealing strip, the underside of the ramp may be momentarily exposed to an inrush of outside air. 
     SUMMARY OF THE INVENTION 
     To help shield a pit area below a dock leveler, a shield system includes a shield having a lower edge adjacent the pit area and an upper edge coupled to the ramp. The upper edge moves with the ramp, while the lower edge remains below the dock. Thus, the shield provides a weather-shielding span whose vertical length varies with movement of the ramp. 
     In some embodiments, the vertical length of the weather-shielding span varies by virtue of a roller about which the shield is wrapped. 
     In some embodiments, the upper edge of the shield can be coupled to the ramp by being attached to a dock leveler&#39;s lip extension. 
     In some embodiments, the upper edge of the shield can be coupled to the ramp by being attached directly to the ramp. 
     In some embodiments, the upper edge of the shield can be coupled to the ramp by being attached to a hinge that connects the lip extension to the ramp. 
     In some embodiments, the shield includes notched out areas to accommodate various loading dock related items such as a vehicle restraint or lip keepers. 
     In some embodiments, the shield includes a compliant seal capable of sealing against the rear of a vehicle. 
     In some embodiments, a shield includes several loops of fabric to create a seal that is compliant without the drawbacks of foam. Foam generally has relatively low wear resistance and tends to absorb moisture and hold dirt. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a dock leveler with portions removed to show a weather shield that helps shelter an area below the dock leveler. 
     FIG. 2 is similar to FIG. 1, but with the dock leveler in a raised position. 
     FIG. 3 is similar to FIG. 1, but with the dock leveler in an operative position. 
     FIG. 4 is a front view of FIG.  2 . 
     FIG. 5 is a front view of FIG.  1 . 
     FIG. 6 is similar to FIG. 5, but showing another embodiment of a dock leveler shield. 
     FIG. 7 is similar to FIG. 1, but showing yet another embodiment of a dock leveler shield. 
     FIG. 8 shows the dock leveler shield of FIG. 7, but with the dock leveler in a raised position. 
     FIG. 9 shows the dock leveler and shield of FIG. 1 in an end loading position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a vehicle  10 , such as a truck or trailer, backing into a loading dock  12 . Once vehicle  10  is parked and in position to be loaded or unloaded of its cargo, a dock leveler  14  moves its ramp  16  and lip extension  18  through their positions of FIGS. 1,  2  and  3  sequentially to create a traffic path between vehicle  10  and a platform  20  of dock  12 . Whether dock leveler  14  is at its stored position of FIG. 1, an intermediate position of FIG. 2, or at its operative position of FIG. 3, a shield system  22  having a flexible shield, such as a curtain  24 , helps shelter an area  26  underneath ramp  16  from outside air  28 . 
     Although the actual structure of dock leveler  14  may vary, in some embodiments, ramp  16  is hinged along a rear edge  30 . This allows an actuator  32 , such as a hydraulic cylinder, to pivotally adjust the height of a front edge  34  of ramp  16 , so edge  34  can be placed at approximately the same height as the truck or trailer bed  36  of vehicle  10 . 
     To bridge the gap between front edge  34  and the rear of vehicle  10 , lip  18  is coupled to edge  34  for movement between a stored position (FIG.  1 ), and an extended, operative position (FIG.  3 ). Lip  18  is schematically illustrated to represent the wide variety of lip extensions that are known to those skilled in the art. One example of lip  18  is disclosed in U.S. Pat. No. 4,920,598, which is specifically incorporated by reference herein. Even though in some embodiments lip  18  both pivots and translates in moving between its stored and operative positions, other lip extensions that only pivot or only translate are also well within the scope of the invention. 
     In some cases, the pivotal motion of lip  18  is provided by a hinge  38  having one series of leaf segments  40  attached to front edge  34  of ramp  16  and another series of leaf segments  42  staggered axially relative to segments  40  and coupled to lip  18 . Segments  40  and  42  are welded to alternate spools  44  that allow relative rotational movement about a central hinge pin  46 . An actuator  48  (e.g., hydraulic, pneumatic, mechanical, electrical, etc.) between one of the lip segments  42  and a fixed point  50  on ramp  16  is able to extend and retract to pivot lip  18  about pin  46 . 
     Translation of lip  18  allows a rear edge  52  of lip  18  to protrude above ramp  16  when dock leveler  14  is in its stored position of FIG.  1 . This offers the benefit of having an obstruction that helps prevent material handling equipment from accidentally driving off the front edge of ramp  16  when lip  18  in not engaging a vehicle. Relative translation between lip  18  and ramp  16  can be provided by attaching a stud  54  to each hinge segment  42  (i.e., the segments that pivot with lip  18 ), and having a head of each stud  54  slide within a slot  56  of lip  18 , as shown in FIG.  5 . 
     Hinge segments  42  also provide a convenient location to couple an upper edge  58  of curtain  24  to ramp  16 . For example, in some embodiments, screws  59  attach curtain  24  to a metal strip  61  that is mounted to hinge segments  42 , as shown in FIG.  4 . To attach strip  61  to segments  42 , a series of tabs  63  extending from the backside of strip  61  can be welded to segments  42 . 
     The structure of curtain  16  or its method of mounting is preferably such that curtain  24  provides a weather-shielding span  60  whose vertical length varies with movement of ramp  16 . One way of accomplishing this is to wrap a lower edge  62  of curtain  24  around at least one roller. In some cases, lower edge  62  of curtain  24  is preferably held by two rollers  64  and  66  with a lower central portion of curtain  24  defining a notch  68  that fits around a vehicle restraint  70 , as shown in FIGS. 4 and 5. Vehicle restraint  70  can be used to engage a rear impact guard  72  of vehicle  10  to help prevent vehicle  10  from accidentally pulling away form dock  12 . Restraint  70  is schematically illustrated to represent the wide variety of vehicle restraints that are known to those skilled in the art. One example of restraint  70  is disclosed in U.S. Pat. No. 6,116,839, which is specifically incorporated by reference herein. 
     By using a roller, then, as front edge  34  of ramp  16  rises, the roller (or rollers) pays out curtain  24  to maintain an appreciable amount of weather-shielding coverage in front of pit area  26 . Providing the rollers with a spring return helps keep curtain  24  taut and allows the rollers to automatically take up curtain  24  as ramp  16  descends. An example of a two-roller system with a vehicle restraint is illustrated in FIGS. 4 and 5, and an example of a single roller  74  without a vehicle restraint is shown in FIG.  6 . 
     However, it should be appreciated that with some rearrangement of the components, a single roller  76  with a vehicle restraint is also well within the scope of the invention. If space permits, roller  76  can be mounted anywhere between an upper surface of ramp  16  and a lower surface of pit area  26 . For example, in FIGS. 7 and 8, roller  76  is mounted at an intermediate position between an upper edge  78  of a curtain segment  80  and a lower edge  82  of curtain  84 . A lower edge  86  of curtain segment  80  is attached to a housing of roller  76 , and an upper edge of curtain  84  wraps around roller  76 . Lower edge  82  of curtain  84  is mounted just above vehicle restraint  70 . With this arrangement, the housing of roller  76  is sheltered behind the curtain and a cutout for vehicle restraint  70  may not be needed. 
     In some cases, curtain  24  may include openings  88  to accommodate what is known as lip keepers  90 . Lip keepers  90  engage a lower edge of lip  18  to help support the weight of lip  18  and ramp  16  when dock leveler  14  is in its stored position of FIGS. 1 and 5. To maximize the curtain&#39;s ability to shield against outside air, fabric flaps  92  may be installed over at least a portion of holes  88 . Such flaps can be attached to curtain  24  along any edge of holes  88 , or may simply be the result of only cutting partially around the perimeter of holes  88  (analogous to a hanging chad). However, holes  88  without flaps can be used, as shown in FIG.  6 . And if a curtain is mounted above the lip keepers, as in FIGS. 7 and 8, such holes may not be needed. 
     To minimize drafts that may blow up from underneath lip  18 , a resilient seal  94  can be installed along upper edge  58  of curtain  24 . Seal  94  preferably seals against the rear of vehicle  10 , as vehicle  10  backs up against a dock bumper  96 . Seal  94  is schematically illustrated to encompass a wide variety of resilient seals including, but not limited to, foam, flexible panels, and brushes. In some embodiments, seal  94  is a series of fabric loops sewn or otherwise attached to curtain  24 . The fabric used for seal  94  can be the same as that used for curtain  24 , or may be of a completely different material. Some examples of materials that can be used for curtain  24  or seal  94  include, but are not limited to, vinyl; canvas duck; rubber impregnated fabric; nylon; and HYPALON, which is a registered trademark of Dupont. 
     A typical operating sequence begins with dock leveler  14  in the stored position, as shown in FIG.  1 . Ramp  16  is generally flush with platform  20 , and lip keepers  90  support lip  18  in its generally vertical position. As vehicle  10  backs against bumpers  96  of dock  12 , vehicle restraint  70  engages the vehicle&#39;s rear impact guard  72 . To place lip  18  atop the bed of vehicle  10 , actuator  32  first lifts ramp  18 , and actuator  48  then extends lip  18 , as shown in FIGS. 2 and 4. As ramp  16  rises, rollers  64  and  66  pay out curtain  24  to help keep pit area  26  sheltered. Next, ramp  16  descends to place the extended lip  18  down against the bed of vehicle  10 . Upon doing so, rollers  64  and  66  draw in curtain  24 , and seal  94  seals against the rear surface of vehicle  10 . Vehicle  10 , restraint  70 , and dock leveler  14  are now in a position for most loading or unloading operations, as shown in FIG.  3 . 
     However, lip  18  overlaying vehicle  10  may interfere with placing or removing cargo from the very end of the vehicle. So, for some end loading operations, lip  18  may need to be removed from vehicle  10 , and ramp  16  may need to be lowered below platform  20  (known as “below dock operation”). A forklift truck operating on ramp  16  may then extend its forks to place or remove the last load from vehicle  10 . In placing leveler  14  in below dock operation, ramp  16  lowers lip  18  below lip keepers  90 . To do this, actuator  48  needs to slightly extend lip  18  so the lower edge of lip  18  misses keepers  90  as ramp  16  descends, as shown in FIG.  9 . To prevent lip  18  from striking and thus damaging the roller housing during below dock operations, a sturdy wedge  98  installed above rollers  64  and  66  can be used to guide the lower edge of lip  18  around the roller housing. 
     Upon completing the loading or unloading of vehicle  10 , lip actuator  48  allows lip  18  to hang pendant, and ramp actuator  32  moves ramp  16  first up and then back down to place the pendant lip  18  back into lip keepers  90 , as shown in FIG.  1 . 
     Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those skilled in the art. Therefore, the scope of the invention is to be determined by reference to the claims, which follow.