Abstract:
A shield system for shielding the area underneath a dock leveler allows a gap to be created either above or below the shield when the deck rises, whereby a shield of a given height dimension can used on dock levelers of various lift heights. In some embodiments, the shield is a pliable curtain that a tensioner holds taut during some operations of the dock leveler, yet the curtain can collapse for below-dock operation. The shield system can be used on horizontally storing dock levelers or vertically storing ones. In some cases, the system includes a pliable web that extends between a front face of the deck and a lip extending from the deck. The web can help seal the area adjacent to a pair of dock bumpers.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a divisional of U.S. patent application Ser. No. 11/268,945, filed Nov. 8, 2005, now U.S. Pat. No. 7,146,673, entitled “Weather Shield for Underneath a Dock Leveler,” and incorporated herein by reference in its entirety. 

   FIELD OF DISCLOSURE 
   The subject disclosure generally pertains to loading docks and more specifically to a shield system for sheltering an area underneath a dock leveler. 
   BACKGROUND 
   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 or ramp that 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 deck and lip are usually moveable between a stored position and an operative position. When in the stored position, the deck may be either vertical or horizontal, depending on the style of dock leveler. U.S. Pat. No. 6,502,268 shows an example of a horizontally storing deck, and U.S. Pat. No. 5,396,676 discloses a dock leveler with a vertically storing deck. In either case, the lip in the operative position 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, some type of seal is usually installed around the perimeter of the doorway. Such seals are typically 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. 
   The area or pit underneath a dock leveler&#39;s deck, however, is usually exposed to outside air. This can create problems, particularly when there is a significant temperature differential between the indoor and outdoor air. Warm outside air, for example, may condense underneath a relatively cool deck 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 deck, 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 and the abovementioned &#39;268 and &#39;676 patents. These patented shields, however, have their limitations. 
   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. 
   The &#39;268 patent discloses a shield that is connected to both the underside of the deck and the foundation surrounding the pit. Although such a design works well for new dock leveler installations, such a shield can be difficult to custom fit to an already-existing dock leveler. The shield, for instance, may need to be sized for the deck&#39;s degree of opening and may need special cutouts to accommodate various components and operating mechanisms of the dock leveler. 
   The &#39;676 patent discloses a shield that flexes inward or farther underneath the deck as the deck descends. Since dock levelers typically have a lip actuator and/or other operating mechanisms near the front edge of the deck, a shield flexing inward may interfere with such mechanisms. Moreover, the &#39;676, &#39;268, and &#39;382 patents fail to disclose an effective way of sealing the area between the underside of an extended lip and adjacent dock bumpers, which are often installed at the dock to establish a predetermined minimum distance between the rear edge of a truck and the face of the building or front edge of the dock leveler. 
   Consequently, a need exists for an under leveler seal system that overcomes the limitations of current systems. 
   SUMMARY 
   In some embodiments, a shield system includes a curtain that can be maintained in vertical tension without the curtain having to span the entire vertical gap between a fully raised deck and the pit. 
   In some embodiments, the curtain is attached to the deck and can lift away from the pit. 
   In some embodiments, the curtain is attached to the pit and the deck can lift away from the curtain. 
   In some embodiments, the curtain is held in tension by way of a tensioner that is attached to the deck. 
   In some embodiments, the curtain is held in tension by way of a tensioner that is coupled to the pit. 
   In some embodiments, the tensioner includes a spring. 
   In some embodiments, the tensioner includes a pliable elongate member, such as a cable, strap, cord, chain, or the like. 
   In some embodiments, the tensioner includes a wheel such as a pulley, sheave or the like. 
   In some embodiments, a seal system includes a flexible web suspended from a lip of a dock leveler, wherein the web can seal against a front edge of the deck and/or the side a dock bumper. 
   In some embodiments, a seal system includes a curtain supported by the toe guards of a dock leveler. 
   In some embodiments, the sealing curtain is closer to the upper end of the toe guard than the lower end so that curtain can remain generally planar. 
   In some embodiments, the sealing curtain and the toe guard can both collapse to facilitate below-dock end loading. 
   In some embodiments, a collapsible sealing member is supported in a generally fixed orientation relative to the deck, so that as the deck pivots the seal avoids interfering with operating mechanisms underneath the deck. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a loading dock with shield system for shielding the area underneath a dock leveler. 
       FIG. 2  is a side view of the shield system of  FIG. 1 , wherein the dock leveler is at a stored position. 
       FIG. 3  is side view similar to  FIG. 2  but with the deck raised and the lip partially extended. 
       FIG. 4  is a side view similar to  FIG. 2  but with the lip resting on the truck bed. 
       FIG. 5  is a side view similar to  FIG. 2  but with the dock leveler in a below-dock position. 
       FIG. 6  is similar to  FIG. 1  but showing another embodiment of a shield. 
       FIG. 7  is similar to  FIG. 2  but showing the embodiment of  FIG. 6 . 
       FIG. 8  is similar to  FIG. 3  but showing the embodiment of  FIG. 6 . 
       FIG. 9  is similar to  FIG. 4  but showing the embodiment of  FIG. 6 . 
       FIG. 10  is similar to  FIG. 5  but showing the embodiment of  FIG. 6 . 
       FIG. 11  is similar to  FIG. 2  but showing another embodiment of a shield system. 
       FIG. 12  is similar to  FIG. 3  but showing the embodiment of  FIG. 11 . 
       FIG. 13  is similar to  FIG. 4  but showing the embodiment of  FIG. 11 . 
       FIG. 14  is similar to  FIG. 5  but showing the embodiment of  FIG. 11 . 
       FIG. 15  is similar to  FIG. 2  but showing another embodiment of a shield system. 
       FIG. 16  is similar to  FIG. 3  but showing the embodiment of  FIG. 15 . 
       FIG. 17  is similar to  FIG. 4  but showing the embodiment of  FIG. 15 . 
       FIG. 18  is similar to  FIG. 5  but showing the embodiment of  FIG. 15 . 
       FIG. 19  is similar to  FIG. 2  but showing another embodiment of a shield system. 
       FIG. 20  is similar to  FIG. 3  but showing the embodiment of  FIG. 19 . 
       FIG. 21  is similar to  FIG. 4  but showing the embodiment of  FIG. 19 . 
       FIG. 22  is similar to  FIG. 5  but showing the embodiment of  FIG. 19 . 
       FIG. 23  is similar to  FIG. 2  but showing another embodiment of a shield system. 
       FIG. 24  is similar to  FIG. 3  but showing the embodiment of  FIG. 23 . 
       FIG. 25  is similar to  FIG. 4  but showing the embodiment of  FIG. 23 . 
       FIG. 26  is similar to  FIG. 5  but showing the embodiment of  FIG. 23 . 
       FIG. 27  is a perspective view similar to  FIG. 1  but showing another embodiment of a seal system. 
       FIG. 28  is a partial cutaway perspective view similar to  FIG. 1  but showing another embodiment of a seal system. 
   

   DETAILED DESCRIPTION  
     FIGS. 1-5  show a loading dock  10  with a shield system  12  that includes a pliable curtain  14  for shielding a pit area  16  underneath a dock leveler  18 . By blocking out weather and other elements, curtain  14  helps protect pit area  16 . By using a pliable curtain rather than a thicker, more rigid structure, shield system  12 , and alternate embodiments thereof, can be readily adapted to fit a wide variety of dock levelers and pits. A curtain, for instance, can be custom cut to size at the installation site, and various cutouts can be made so that the curtain does not to interfere with the operation of the dock leveler. 
   Such trimming is not readily accomplished with thicker foam seals, especially if they are encased within a fabric covering. Moreover, a thick foam seal takes up more space underneath a dock leveler than does a relatively thin curtain. 
   A pliable curtain, however, is not self-supporting, so shield system  12  and various other embodiments herein include some sort of tensioner or supporting structure that helps support the curtain. Although such supporting structure consumes additional space, the supporting structure can be installed wherever it is most convenient. 
   With the versatility of curtain  14  and its supporting structure, shield system  12  can be applied to a wide variety of dock levelers, such as those whose structure and operation are described in U.S. Pat. Nos. 6,502,268; 3,137,017; 4,293,969, 5,396,676; 4,776,052; and 6,205,606; all of which are specifically incorporated by reference herein. 
   For example, dock lever  18  may include a deck  20  that can pivot about its rear edge  22  to raise and lower its front edge  24 . A lip  26  can be pivotally attached to front edge  24 , as explained in the “Background.” The deck of some dock levelers store horizontally, as shown in  FIGS. 2 ,  11  and  15  and disclosed in U.S. Pat. Nos. 6,502,268; 3,137,017; and 4,293,969. Other decks store vertically, as shown in  FIGS. 19 and 23  and disclosed in U.S. Pat. Nos. 5,396,676; 4,776,052; and 6,205,606. The mechanisms for pivoting deck  20  and lip  26  have not been shown so as to not interfere with the illustration of other features of the dock leveler  18 . However, such mechanisms are well known in the industry. 
   The operating sequence of dock leveler  18  and shield system  12  may begin with deck  20  in its stored, cross-traffic position, as shown in  FIG. 2 . In this position, lip  26  may be supported by a set of lip keepers  28  so that lip  26  and keepers  28  can help hold deck  20  in its generally horizontal position. With dock leveler  18  in its stored position, a vehicle  30 , such as a truck, trailer, or the like, can back into dock  10  until the rear end of vehicle  30  engages or is adjacent to a set of bumpers  32 . 
   To help shield pit area  16 , curtain  14  has a lower edge  34  attached to the loading dock&#39;s front face  36 , just below pit  16 . A tensioner  38  attached to an upper edge  40  of curtain  14  applies vertical tension to curtain  14 . The tension helps keep curtain  14  generally upright in front of pit area  16 , i.e., between an upper surface  42  of pit  16  and a lower surface  44  of deck  20 . Curtain  14  can be made of any pliable or semi-flexible material including, but not limited to, nylon, canvas, HYPALON (Dupont trademark), canvas duck, rubber impregnated fabric, foam, etc. Curtain  14  may include various notches  46  or cutouts  48  to accommodate lip keepers  28 , vehicle restraints, or other components. 
   Tensioner  38  represents any structure that can create vertical tension in curtain  14 . In one example, tensioner  38  comprises one or more pliable elongate members  50  (e.g., cable, strap, chain, cord, etc.) extending between the curtain&#39;s upper edge  40  and an anchor point  52  on deck  20 . In some embodiments, a spring  54  (e.g., helical spring, elastic cord, gas spring, etc.) coupled to member  38  can be used to maintain tension in member  38  as deck  20  pivots up and down, and a wheel  56  (e.g., pulley, sheave, etc.) allows the tension to be applied to curtain  14  in a generally vertical direction. In other embodiments, a deadweight or counterbalance can be used for creating the vertical tension in curtain  14 . 
   After vehicle  30  engages or is sufficiently close to bumpers  32 , a vehicle restraint  58  may raise its barrier  60  to engage the vehicle&#39;s ICC bar  62 , thereby helping hold vehicle  30  in position. The use of a vehicle restraint to engage a vehicle&#39;s ICC bar is well known in the industry and is disclosed in U.S. Pat. Nos. 4,560,315; 5,702,223; and 6,106,212; all of which are specifically incorporated by reference herein. 
   Once vehicle  30  is in the position shown in  FIG. 3 , deck  20  rises so that lip  26  can be extended and subsequently lowered back down to rest upon the vehicle&#39;s truck bed, as shown in  FIG. 4 . When deck  20  is raised, as shown in  FIGS. 1 and 3 , upper edge  40  of curtain  14  and lower surface  44  of deck  20  define a gap  64  therebetween. Gap  64  has a height  66  that varies with the pivotal movement of deck  20 . Being able to create gap  64  while still maintaining tension in curtain  14  allows a curtain of a given height to fit various dock levelers even though their decks may rise to different levels. Moreover, being able to create gap  64  means that curtain  14  does not have to extend fully up to the maximum lift height of deck  20 , thus curtain  14  can be shorter than if upper edge  40  were directly attached to deck  20 . 
   In comparing  FIGS. 2 and 3 , it should be noted that as deck  20  rises, spring  54  stretches to accommodate the increased distance between wheel  56  and the curtain&#39;s upper edge  40 . 
   With dock leveler  18  in the position of  FIG. 4 , vehicle  30  can be loaded and unloaded of its cargo while curtain  14  provides an effective barrier that helps keep pit area  16  clean and dry, as the height of gap  64  is now minimal or nonexistent. 
   For end-loading or other below-dock operations, dock leveler  18  can be positioned as shown in  FIG. 5 . In this position, deck  20  lowers lip  26  below its lip keepers  28 . Even though the vertical distance between the deck&#39;s lower surface  44  and the upper surface  42  of pit  16  is less than the full height of curtain  14 , below-dock operation is still possible due to the flexibility of curtain  14 , which allows curtain  14  to collapse under pressure from deck  20 . 
     FIGS. 6-10  illustrate an alternate shield system  140  where pliable curtain  14  is supported by a collapsible supporting structure  142 . With this design, curtain  14  can be trimmed at the installation site to fit any pit, dock leveler and associated hardware. Once cut to size, any number of supporting structures  142  can be mounted to the pit floor or other anchor point and attached to curtain  14  at any suitable location that does not interfere with the operation of dock leveler  18 . Structures  142  can be fastened to curtain  14  by any suitable means including, but not limited to, threaded fasteners, VELCRO, adhesive, straps, rope, and clamps. Structure  142  is schematically illustrated to represent any body that can be collapsed under pressure and later resiliently recover its original shape. Examples of structure  142  include, but are not limited to, a foam block or column, a helical or leaf spring, a telescoping member (e.g., piston/cylinder, air spring, shock absorber, etc.), rubber or other polymeric rod, and various combinations thereof. In some cases, structure  142  may be encased within a protective fabric jacket. 
   The operation of shield system  140  is comparable to that of system  12  with  FIGS. 6 ,  7 ,  8 ,  9  and  10  corresponding to  FIGS. 1 ,  2 ,  3 ,  4  and  5  respectively. When deck  20  is in a cross-traffic position, as shown in  FIG. 7 , the upper edge of curtain  14  and supporting structure  142  is adjacent to the lower surface of deck  20 . Supporting structure  142  holds curtain  14  relatively taut in front of pit  16  so that system  140  can effectively shelter the area under deck  20 . Since deck  20  is not attached to system  140 , deck  20  is free to pivot to a raised position, as shown in  FIG. 8 . The collapsibility of curtain  14  and structure  142  allows deck  20  to descend to a below-dock position, as shown in  FIG. 10 . 
     FIGS. 11-14  illustrate an alternate shield system  68  that includes curtain  14 . Shield system  68  is similar to system  12  with  FIGS. 11 ,  12 ,  13  and  14  corresponding to  FIGS. 2 ,  3 ,  4  and  5  respectively. Shield system  68  has a curtain tensioner  70  comprising a spring  72 , an elongate member  74 , and a wheel  76  that are similar to corresponding items of tensioner  12 . However, wheel  76  and an anchor point  78  can be attached to any convenient point of the loading dock rather than having to be attached to deck  20 . Wheel  76 , for instance, could be attached to a sidewall of pit  16 , and anchor point  78  could be attached to the floor of the pit. By allowing the separation of tensioner  70  and deck  20 , tensioner  70  can be shorter because the tensioner  70  does not have to span the maximum lift distance of the deck  20 . The flexibility of curtain  14  still allows below-dock operation as shown in  FIG. 14 . Although curtain tensioner  70  comprises spring  72 , elongate member  74  and wheel  76  to apply vertical tension in curtain  14 , a wide variety of other spring loaded mechanisms mounted within pit  16  and separated from deck  20  could be used for holding curtain  14  taut. 
   In another embodiment, shown in  FIGS. 15-18 , a shield system  80  includes a flexible curtain  82  suspended from deck  20 . Curtain  82  is held vertically taut by way of a tensioner  84  that includes two spring-loaded arms  86 , an upper arm  86   a  and a lower arm  86   b . Each arm  86   a  and  86   b  has a distal end attached to curtain  82 , and the two arms are joined at a central pivot point  88 . A torsion spring can be used to urge the distal ends of arms  86   a  and  86   b  apart so that they impart vertical tension in curtain  82 .  FIGS. 15 ,  16 ,  17  and  18  correspond to  FIGS. 2 ,  3 ,  4  and  5  respectively. The flexibility of curtain  82  and arms  86  being able to pivot about point  88  under the urging of the torsion spring allow below-dock operation as shown in  FIG. 18 . 
   In another embodiment, shown in  FIGS. 19-22 , a shield system  90  includes a flexible curtain  92  suspended from a vertically storing pivotal deck  94  and supported by one or more foam blocks  96 .  FIGS. 19 ,  20 ,  21  and  22  correspond to  FIGS. 2 ,  3 ,  4  and  5  respectively. Although shield system  90  is shown mounted to a vertically storing dock leveler  98 , system  90  could also be installed on horizontally storing dock levelers, such as dock leveler  18 . In  FIGS. 19-21 , foam block  96  helps keep curtain  92  in a generally fixed orientation relative to deck  94 . In  FIG. 22 , however, the flexibility of curtain  92  and foam block  96  allow below-dock operation. 
   Shield system  90  also includes flexible webs  100  that help seal the gap that may otherwise exist between lip  26  and bumper  32 . In some installations, web  100  has one edge  102  ( FIG. 21 ) attached to the underside of lip  26  and another edge  104  attached to curtain  92  and/or deck  94 . Web  100  is sufficiently flexible to collapse as lip  26  pivots toward deck  94 , as shown in  FIGS. 19 ,  20  and  22 .  FIG. 21  shows how web  100  can deform in reaction to vehicle  30  backing into the dock. Although web  100  is shown installed to dock leveler  98 , web  100  could be installed on a wide variety of dock levelers including, but not limited to, all of the dock levelers disclosed in  FIGS. 1-28 . Moreover, web  100  could be installed on dock levelers that have additional seals other than those disclosed herein or installed on dock levelers that have no additional seals whatsoever.  FIG. 27  shows a perspective view of two webs  100  installed on a dock leveler  106 . 
     FIGS. 23-26  show a shield system  108  similar to shield system  90  with  FIGS. 23 ,  24 ,  25  and  26  corresponding to  FIGS. 19 ,  20 ,  21  and  22  respectively. With shield system  108 , curtain  92  is held taut by one or more leaf springs  110  (e.g., bands of spring steel) instead of being supported by foam blocks  96 . Otherwise, shield systems  108  and  90  operate in a similar manner. 
     FIG. 27  shows a shield system  118  that includes a curtain  120  or flexible shield attached to a right toe guard  122  and a left toe guard  124  of dock leveler  106 . Curtain  120  has an upper edge  126  attached to deck  20 . A lower edge  128  can be directly attached to toe guards  122  and  124 , as shown in  FIG. 27 , or an extension bracket  130  can couple lower edge  128  of curtain  120  to a lower segment of the toe guards, as shown in  FIG. 28 . The toe guards help prevent someone from accidentally getting their foot pinched between the deck and the dock as the deck moves down to a cross-traffic position. As the deck descends, the toe guards can collapse, for each toe guard  122  and  124  comprises a plurality of segments  132  and  134  that can move relative to each other. Although their actual structure may vary, some examples of toe guards and how they function are disclosed in U.S. Pat. Nos. 3,456,274; 4,928,340; 4,557,008; and 4,110,860; all of which are specifically incorporated by reference herein. 
   Referring to  FIG. 28 , flexible fingers or tabs  136  can be attached to web  100  to improve the sealing between web  100  and bumper  32 . 
   Although the invention is described with respect to various embodiments, modifications thereto will be apparent to those of ordinary skill in the art. The various curtains, for example, are shown as being attached to the pit and separated from the deck or vice versa; however, it is conceivable and well within the scope of the invention to have a split curtain comprising two curtain sections with one section attached to the deck and the other section attached to the pit. With a split curtain design, the two sections would separate as the deck rises and would overlap or come together when the deck returns to its lowered position. Therefore, the scope of the invention is to be determined by reference to the following claims.