WO2000027734A1

WO2000027734A1 - Loading dock seal having variable hardness

Info

Publication number: WO2000027734A1
Application number: PCT/US1999/026535
Authority: WO
Inventors: Charles J. Ashelin; Thomas J. Boffeli; David J. Hoffman; Jason D. Miller; Gregory J. Thill
Original assignee: Rite-Hite Holding Corporation
Priority date: 1998-11-09
Filing date: 1999-11-09
Publication date: 2000-05-18
Also published as: AU1815900A

Abstract

A dock seal that can be installed around a doorway or loading dock of a building includes a resiliently compressible foam core protected by a tough, water-resistant cover. The foam core easily compresses to readily and sealingly conform to the rear contour of a vehicle backed up against the seal. Yet the foam core exerts a sufficient restorative force to fully and repeatedly recover its original decompressed form. Low compressive forces that provide overall sufficient restorative forces is accomplished by providing the foam core with localized soft zones at selected areas beneath the cover. The soft zones can be created by voids in the core or by using foam with different degrees of compressibility. The soft zones are generally placed at areas where the cover is especially susceptible to wear, e.g., where the back edges and hinges of the vehicle usually engage and tend to gouge into the cover. To further enhance the compressibility and recovery of the foam, venting sheltered from rain and dirt is provided along the sides and back of the seal. Mounting plates with unique profiles promote venting, ease installation, and allow thicker foam cores within a limited projected distance from the face of the building.

Description

LOADING DOCK SEAL HAVING VARIABLE HARDNESS

Background of the Invention

Field of the Invention

The subject invention generally pertains to loading dock seals and more specifically to a resiliently compressible foam seal.

Description of Related Art

Trucks typically back up against a loading dock or doorway of a building to facilitate loading and unloading of the vehicle. A dock seal or shelter usually installed along the top and lateral edges of the doorway is often used to seal an air gap that might otherwise exist between the outer wall of the building and the back of the vehicle. If left unsealed, the gap might allow the outside weather to increase the building's heating or cooling load, allow rain and snow to enter the interior of the building or simply subject the inside dock workers to an uncomfortable draft while they service the vehicle.

In sealing the air gap, a dock seal should accommodate vehicles of various size; accommodate out of parallelism between the back of the vehicle and the building wall; flex around surface irregularities of the vehicle, such as hinges; yield to repeated vertical movement of the truck caused by weight being loaded or unloaded from the truck; resist wear; and readily recover its original shape after the vehicle departs.

Some of these objectives are accomplished to a limited extent by a conventional dock seal having a resiliently compressible foam pad. As the truck backs against the seal, the foam pad compresses to conform to the contour of the rear edges of the truck. The compressibility of foam is partially due to its porosity, which, unfortunately, is also the very property that tends to make foam absorb moisture, hold dirt, and be less wear resistant. Thus, foam dock seal pads are often protected by a strong outer fabric cover that is water-resistant. However, problems are created when the cover encases a foam core that is especially soft. After repeated compressions, soft foam pads tend to take a set and not fully recover their original decompressed form. This not only degrades the seal's original full range of compression (thus reducing its ability to seal), but also causes the outer fabric to sag which provides a poor appearance along the exterior of the building.

A firmer foam pad is less susceptible to taking a set; however, harder foams create other problems. The harder or stiffer the foam pad, the less it conforms to the contour of the truck, and thus it provides a less effective seal. Also, a harder pad exerts a higher restorative force when compressed that pushes the outer cover against the back surface of the truck. The higher force becomes a problem, as the back end of a truck usually moves an inch or so (up to three inches) up and down repeatedly in reaction to being loaded or unloaded. The movement creates abrasive friction between the pad and the truck. Since the magnitude of friction is generally a function of the normal force (i.e., restorative force) times a coefficient of friction, the higher normal force from a stiffer pad creates higher friction, which in turn promotes wear along the front face of the cover, especially in certain areas. Areas of high wear are predominantly found where the upper and lower edges of most trucks engage and tend to gouge into the seal. Also, hinges and other protrusions extending from the back of many trucks tend to abrade the cover at other locations.

Since soft foam and hard foam each have their own drawbacks, it becomes difficult to provide a foam having an intermediate level of hardness or softness without some compromise.

Summary of the Invention

In order to provide a dock seal that easily compresses to readily conform to the rear contour of a vehicle, yet exerts a sufficient restorative force to fully recover its original decompressed form without creating areas of high wear, there is provided a seal that includes a resiliently compressible foam core within an outer protective cover. The foam core has localized soft zones beneath the cover preferably at areas that would otherwise have a greater tendency to wear. The soft zones can be created by voids in the core or by using foam with different degrees of compressibility.

In some embodiments the foam is able to vent to a sheltered air passageway disposed along the side of the seal.

In some embodiments the foam's ability to breathe can be enhanced by aligning voids in the foam directly to vents.

In some embodiments, the foam core vents towards the back: opposite the front that faces the vehicle. In some embodiments, the covered foam and a separate mounting plate can be manually handled separately to facilitate installation and replacement of the seal.

Brief Description of the Drawings

Figure 1 is a side view of one embodiment of an inventive dock seal showing a vehicle backing towards a dock seal.

Figure 2 is a front view of a loading dock showing a partial cut-away view of an inventive dock seal. Figure 3 is a cross-sectional side view taken along line 3-3 of Figure 2.

Figure 4 is a cross-sectional top view taken along line 4-4 of Figure 3.

Figure 5 is the same cross-sectional view as Figure 3, but with the seal being compressed.

Figure 6 is cross-sectional side view similar to that of Figure 3, but of alternate embodiment.

Figure 7 is cross-sectional side view similar to that of Figure 3, but of another embodiment of an inventive dock seal.

Figure 8 is cross-sectional side view similar to that of Figure 3, but of another embodiment of an inventive dock seal. Figure 9 is cross-sectional side view similar to that of Figure 3, but of yet another embodiment of an inventive dock seal. Figure 10 is a cross-sectional top view similar to that of Figure 4, but of another embodiment of an inventive dock seal.

Figure 11 is a cross-sectional top view similar to that of Figure 4, but of another embodiment of an inventive dock seal. Figure 12 is a cross-sectional top view similar to that of Figure 4, but of yet another embodiment of an inventive dock seal. -

Figure 13 is cross-sectional side view similar to that of Figure 3, but of an embodiment having two layers of foam.

Figure 14 is the same cross-sectional side view as Figure 13, but with the seal being compressed.

Description of the Preferred Embodiment

Figures 1 and 2 show a vehicle 10, such as a trailer 12 of a truckl4, backing up to a loading dock 16. Loading dock 16 is basically a doorway 18 or an opening in a wall 20 of a building, and may be associated with a dock leveler 22, bumpers 24, or other peripheral items to facilitate loading and unloading of the trailer's cargo. One peripheral item in particular, which is the subject of this application, is a dock seal 26. When vehicle 10 is backed against dock seal 26, seal 26 helps seal the air gap that might otherwise exist between the outer face of wall 20 and an upper 30 and lateral edges 32 of the rear of vehicle 10. Much of the gap between the doorway and a lower rear edge 34 of vehicle 10 can be blocked off by a conventional dock leveler which usually has a retractable lip 36 that can extend outward to bridge the gap. However, the gap at the upper and lateral edges of vehicle 10 typically requires additional sealing, and the shape of the gap in these areas can be quite unpredictable. Therefore, in one exemplary embodiment of the an inventive dock seal, seal 26 includes two vertically elongated side-sealing members 38 that resiliently compress to fill the irregular gap along the back lateral edges of vehicle 10. Dock seal 26 also includes an upper-sealing member 40, such as a head curtain 42; however, side seals 38 will be discussed first. For the embodiment shown in Figures 3, 4 and 5, side seal 38 includes a core 44 that provides the desired properties of resilience and compressibility. Compressibility allows seal 38 to conform to the contour of the vehicle's back surface to effectively seal against outside air, and resilience allows seal 38 to substantially recover its original decompressed shape. In one embodiment, core 44 consists of a resilient, compressible foamed polyurethane or foamed polyester, such as, for example, an L24 open-cell polyurethane foam provided by Leggett & Platt of Carthage, Missouri. However, it should be appreciated by those skilled in the art that a wide variety of other synthetic or natural foams may also work well. Moreover, mechanical springs or bellows may also accomplish the desired functions otherwise provided by foam.

Since the inherent porosity of foam tends to absorb moisture, hold dirt, and make core 44 less wear resistant, a tough, flexible, water-resistant protective cover 46 covers the most exposed areas of core 44. One example such a cover would be a 3022_MFRLPC_DC7 material provided by the Seaman Corporation of Wooster, Ohio. Other examples of cover materials would include, but not be limited to, hypalon, canvas duck, rubber impregnated fabric and coated nylon fabric. For some embodiments, cover 46 wraps around core 44 and is joined at a seam 48 to cover the core's front 50 and two sides, while leaving some areas uncovered to allow core 44 to breathe, i.e., expel air from within the cellular structure of the foam as core 44 is compressed and draw in air as it decompresses. Thus, a bottom 52 and/or a top portion 54 of core 44 can be left uncovered. If desired, additional breathing can be provided by having cover 46 include several side vents 56, such as slits or holes, distributed along the core's length. The additional breathing can reduce the overall impedance to airflow, so the foam core can compress and decompress more freely. To help prevent moisture and dirt from being drawn into side vents 56, side flaps 58 can be added for at least partially sheltering the vents. One edge 60 of each flap can be sewn or attached by some other conventional means to cover 46, while an opposite edge 62 can be attached to a mounting plate 64. Attachment of flap 58 to mounting plate 64 can be accomplished by way of a touch and hold fastener 66, such as VELCRO; however other methods of attachment would also include, but not be limited to, screws, adhesive, snaps, zipper, hooks, clamps, or even press fitting an elongated bead of the cover into a long groove of the mounting plate. Together, flap 58, cover 46, and mounting plate 64 define a sheltered air passageway 68 that, in conjunction with vents 56, places the cellular pores of foam core 44 in fluid communication with the outside atmosphere, while helping prevent the ingress of moisture, dirt and other particulate.

With the exemplary design just described, core 44, cover 46, and flaps 58 could be considered as one subassembly, while mounting plate 64 with anchors 70 could be considered as another. Having two separately installable subassemblies eases the installation and replacement of seal 38. First, mounting plate 64 can be attached to wall 20 by way of anchors 70, and then the covered core (items 44 and 46) can be readily attached afterwards by way of touch and hold fasteners 66.

Forming mounting plate 64 from sheet metal, which is not as thick as a conventional wood mounting board, provides more room for foam 44 within a same projecting distance 72 from the face of wall 20 (see Figure 4). With all other factors being the same, a longer projection of foam reduces the compressive forces 71 (or the foam's generally equal and opposite restorative force 73) of vehicle 10 against seal 38 (see Figure 5), since a greater quantity of foam is being compressed within the same distance. A lower normal force 71 and 73 results in lower frictional forces 75 between cover 46 and vehicle 10, as the frictional force is generally a function of the normal force multiplied by the coefficient of friction for vehicle 10 against cover 46. Lower frictional forces 75 reduce wear and abrasion to prolong the life of protective cover 46.

Certain localized high-wear areas 74 and 76 of the cover, e.g., where the upper and lower edges of many vehicles meet the cover's front face 50', can be protected by providing a soft zone 78 at these areas and/or by providing a compressible core having variable hardness from front to back. The terms "soft," "softness" and "soft zone" (in contrast to "hard," "hardness" and "hard zone") refers to portions of the seal that are more easily compressed (i.e., exerts less resistance to external pressure) than other areas. A soft zone 78 can be created by any one of a variety of ways; however, in one embodiment, it is produced by a collapsible V-shaped cavity 80 traversing a back face 82 of foam core 44. Cavity 80 results in less foam in a localized area, which makes core 44 easier to compress there, as shown in Figure 5. Consequently, cover 46 at soft zone 78 is subjected to a lower restorative force than what is exerted at adjacent harder zones 84, such as, for example, directly above and below the soft zone. As a further enhancement, venting of foam core 44 may be improved by aligning vent 56 directly to cavity 80. This might allow the numerous small pores of the foam that naturally line the surface of the cavity to effectively "spill into" and draw from a wide open cavity 80 essentially unrestricted, as opposed to being partially obstructed by a close fitting cover. Otherwise, upon decompressing, air being drawn back into the foam may tend to suck cover 46 tightly up against itself, thereby sealing off many of the surface pores, and thus slowing down the core's recovering its decompressed shape.

The high- wear area 76 near the top of seal 38 can be further protected from wear by providing upper-sealing member 40 with a head curtain 42 that overlaps area 76. Although a primary purpose of head curtain 42 is to provide a seal along upper rear edge 30 of a vehicle 10, head curtain 42 can also serve other functions as well. Allowing head curtain 42 to slide vertically relative to side seal 38 while staying somewhat fixed relative to vehicle 10 as vehicle 10 intermittently raises and lowers slightly can especially protect area 76 from wear. Reduced wear at area 76 is not only achieved by having a coefficient of friction between cover 46 and curtain 42 being less than that between cover 46 and vehicle 10, but also by having curtain 42 more broadly distribute the vehicle's compressive forces against the front face of cover 46. In one embodiment, head curtain 42 is rendered moveable in a vertical direction upon being supported by a flexible frame 88, such as, for example, a pair of spring steel arms 90 cantilevered outward from a baseboard 92 at each lateral side of doorway 18. Curtain 42 extends from baseboard 92 and drapes over a crossbar 94 that extends between arms 90. A flexible foam pad 96 can be added between baseboard 92 and crossbar 94 to provide the curtain above it with additional support and provide frame 88 with additional spring-back. It should be appreciated by those skilled in the art that the use of head curtain

42 is just one example of an upper-sealing member 40. Another example of an upper sealing member would include a resiliently compressible foam pad similar to the one disclosed in U. S. Patent 4,799,341, which is specifically incorporated by reference herein. Another example would be to use one of the side seals disclosed herein and simply install it horizontally above and straddled across two vertically installed side seals.

As alternatives to cavity 80 being V-shaped, other cavity shapes can also create a soft spot 78, such as the various cavity shapes shown in Figures 6, 7, 8, and 9. For example, a rectangular cavity 98 open to a back 100 of a foam core 102 fully traverses the width of the core 102 and is open to a vent 56, as shown in Figure 6. Another cavity 104, shown in Figure 7, is a bore 106 interposed between a front 108 and back 110 of a foam core 112. Cavity 104 has a longitudinal centerline 114 traversing the width of the core, e.g., the bore's longitudinal centerline 114 is generally perpendicular to the compressive forces 71 (Figure 5) exerted by the vehicle 10. In this example, cavity 104 is not directly aligned to a side vent, thus venting might occur at a lower 118 and/or upper end 120 of seal. In Figure 8, a cavity 122 has a conical shape that is open to a back 124 of a core 125, but not necessarily open to either side, i.e., conical cavity 122 does not necessarily traverse the full width of core 125 (although it could). The embodiment of Figure 9 is similar to that of Figure 8; however, a cavity 126 is semispherical as opposed to conical and is open to a face 128 rather than a back 130 of foam core 132.

In another exemplary embodiment, shown in Figure 10, a seal 144 has a cavity 134 that extends vertically a full length (or portions thereof) of a foam core 136. Although cavity 134 might not necessarily provide a discrete localized soft spot at a predetermined elevation, it does provide foam core 136 with an overall restorative force that is lower than it would be if core 136 were solid without cavity 134.

Consequently, the lower restorative force creates less friction and less wear along its cover 138. In addition, side flaps 140 are an integral extension of cover 138; thus cover 138 requires less material to make. Flaps 140 extend from a front face 142 of seal 144 and attaches to mounting plate 64 by way of touch and hold fastener 66, or some other comparable fastener as discussed earlier. Since much of the foam core's sides are fully exposed to an air passageway 146 (which in turn is open to atmosphere), separate side vents might be omitted.

Figure 11 shows another embodiment similar to that of Figure 7, but with a unique mounting plate 148. Plate 148 includes one or more air passageways 150 that run along its length and are open to atmosphere at an upper 152 and lower end 154 (see Figure 13). Vent holes 156 extending from passageway 150 to a back surface 157 of a foam core 158 allows the core to breathe, as well as provide access to install anchor bolts 70. The cross-sectional shape of plate 148 lends itself well to extrusion processes (e.g., aluminum or plastic) with cross-holes readily drilled in a subsequent operation for anchor bolts 70 and vents 156. As with other embodiments, a touch and hold fastener 66 removably attaches a protective cover 160 to plate 148, and a cavity 104' (e.g., one similar to bore 106 of Figure 7) creates a soft spot where desired.

The embodiment shown in Figures 12 -14 shows a seal 168 with a mounting and cover design similar to that of Figure 11 ; however, a dual-compressibility foam core 162 having variable hardness from front to back replaces core 158. Core 162 includes a relatively soft (typically lower density) back layer of foam 164 that reduces the overall compressive forces to minimize friction and wear of cover 160. Core 162 also includes a front layer of foam 166 that is not quite as soft, so its restorative forces allow seal 168 to substantially recover its original decompressed shape. Additional localized soft areas can be provided by any one of the cavities already discussed, such as a V-shaped notch 170 as shown.

It should be appreciated by those skilled in the art, that the embodiments just disclosed encompass a variety of features including but not limited to cavity shape, venting, mounting plates, dual-compressibility, upper-sealing member, head curtain, and integral nonintegral side flaps all of which can be combined and interchanged in a variety of combinations that fall well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the claims, which follow: We claim:

Claims

1. A dock seal disposed adjacent a wall with a doorway includes an elongated seal adapted to provide a compressive seal against a vehicle, the elongated seal comprising:

a compressible core having a front face and a rear face and having a variable hardness therebetween, the rear face being adapted to generally face the wall in a substantially fixed relationship thereto; and

a protective cover disposed along the front portion of the compressible core and adapted to be engaged by the vehicle, with the front face moving towards the back face in response to the vehicle compressing the compressible core.

2. The dock seal of claim 1, wherein the compressible core includes a foam front portion adjacent the front face and a foam back portion adjacent the rear face with the foam front portion being harder than the foam back portion.

3. The dock seal of claim 1, wherein the protective cover includes a side flap that is spaced apart from the foam core to define a sheltered air passageway that places the foam core in fluid communication with air outside the protective cover.

4. The dock seal of claim 3, wherein the protective cover includes a vent at least partially sheltered by the side flap.

5. The dock seal of claim 1, wherein the variable hardness is by virtue of a void defined by the compressible core.

6. The dock seal of claim 5, further comprising a plurality of voids that are spaced apart vertically.

7. The dock seal of claim 5, wherein the void is open to the rear face.

8. The dock seal of claim 5, wherein the void is open to the front face.

9. The dock seal of claim 5, wherein the void is an elongated V-shaped notch that traverses the back face of the compressible core.

10. The dock seal of claim 5, wherein the void is conical.

11. The dock seal of claim 5, wherein the void is a bore having a longitudinal centerline with a component extending horizontal and perpendicular to the restorative force exerted on the vehicle.

12. The dock seal of claim 5, wherein the protective cover includes a vent aligned in open fluid communication to the void to facilitate compression and decompression of the compressible core.

13. The dock seal of claim 3, wherein the protective cover includes a vent at least partially sheltered by the side flap, wherein the vent places the compressible core in fluid communication with the air passageway.

14. The dock seal of claim 3, further comprising a mounting plate adapted to couple the compressible core to the wall and being attached to the side flap to further define the air passageway.

15. The dock seal of claim 14, wherein the side flap is attached to the mounting plate by way of a touch and hold fastener.

16. The dock seal of claim 1, further comprising a mounting plate with an air passageway, wherein the mounting plate is adapted to couple the elongated seal to the wall with the air passageway placing the compressible core in fluid communication with air outside the protective cover.

17. A dock seal disposed adjacent a wall with a doorway includes an elongated seal adapted to provide a compressive seal against a vehicle, the elongated seal comprising:

a compressible core having a front face and having a soft zone at a predetermined elevation between an adjacent harder zone both above and below the soft zone; and

a protective cover disposed along the front face of the compressible core and adapted to be engaged by the vehicle, whereby upon the compressible core being compressed by the vehicle, the soft zone exerts a restorative force that is less than that of the adjacent harder zone to help alleviate wear of the protective cover at the predetermined elevation.

18. The dock seal of claim 17, wherein the restorative force of the soft zone is less

than that of the adjacent harder zone by virtue of the compressible core having a

cavity behind the soft zone.

19. The dock seal of claim 18, wherein the compressible core includes a back

adapted to face the wall with the cavity being open to the back.

20. The dock seal of claim 17, wherein the protective cover includes a side flap that is spaced apart from the compressible core to define a sheltered air passageway

that places the compressible core in fluid communication with air outside the protective cover.

21. The dock seal of claim 20, further comprising a mounting plate adapted to

couple the compressible core to the wall and being attached to the side flap to further

define the air passageway.

22. The dock seal of claim 21 , wherein the protective cover includes a vent at least

partially sheltered by the side flap.

23. The dock seal of claim 21, wherein the side flap is attached to the mounting

plate by way of a touch and hold fastener.

24. The dock seal of claim 17, further comprising a mounting plate with an air

passageway, wherein the mounting plate is adapted to couple the elongated seal to the wall with the air passageway placing the compressible core in fluid communication with air outside the protective cover.

25. The dock seal of claim 17, wherein said front face includes a plurality of vertically spaced apart soft zones to help alleviate wear of the protective cover at a corresponding plurality of predetermined elevations.

26. A dock seal disposed adjacent a wall with a doorway includes an elongated seal adapted to provide a compressive seal against a vehicle, the elongated seal comprising:

a foam core including a front portion and a back portion both of which are resiliently compressible but with the back portion being softer than the front portion; and

a protective cover disposed along the front portion of the foam core and adapted to be engaged by the vehicle, whereby the back portion being softer helps alleviate wear of the protective cover by readily yielding in response to the vehicle compressing the foam core, and the front portion readily recovering itself and the protective cover to a substantially restored shape in response to the vehicle departing.

27. The dock seal of claim 26, wherein the protective cover includes a side flap that is spaced apart from the foam core to define a sheltered air passageway that places the foam core in fluid communication with air outside the protective cover.

28. The dock seal of claim 27, wherein the protective cover includes a vent at least partially sheltered by the side flap.

29. The dock seal of claim 27, further comprising a mounting plate adapted to couple the foam core to the wall and being attached to the side flap to further define the air passageway.

30. The dock seal of claim 29, wherein the side flap is attached to the mounting plate by way of a touch and hold fastener.

31. The dock seal of claim 26, further comprising a mounting plate with an air passageway, wherein the mounting plate is adapted to couple the elongated seal to the wall with the air passageway placing the foam core in fluid communication with air outside the protective cover.