Abstract:
A dock leveler for a truck loading dock includes a pivotal deck that is raised by an inflatable actuator. The actuator includes a pliable upper section that when inflated has a generally vertical cylindrical shape that can provide a heavy deck with substantial columnar support. The actuator also includes a relatively rigid base that is sealingly joined to the pliable upper section such that upper section and the rigid base define an inner chamber of air. A blower for inflating the actuator can be installed inside or outside the actuator. In some embodiments, a valve system reverses the airflow so that the blower can forcibly deflate and compress the actuator up against the bottom of the deck so that the area underneath the actuator can be cleaned.

Description:
TECHNICAL FIELD  
       [0001]     The subject invention generally relates to dock levelers, and more specifically to a dock leveler whose deck is raised by an inflatable member.  
       BACKGROUND  
       [0002]     Loading docks often include a dock leveler to facilitate the loading or unloading of a truck&#39;s cargo. The dock leveler provides a bridge that material handling equipment and personnel can use to travel between a loading dock platform and the bed of the truck. Dock levelers usually include a deck or ramp that can pivot about its rear edge to raise or lower its front edge. Often a lip plate extends from the front edge of the deck and is adapted to engage the rear of the truck bed. The lip plate is usually movable between a stored, retracted position and an extended, vehicle-engaging position. The pivotal movement of the deck enables the dock leveler to set the lip plate on or remove it from the truck bed.  
         [0003]     To pivot a deck, a dock leveler usually includes some type of actuator that extends, expands or otherwise moves to force the deck upward. Downward movement of the deck may be achieved by relying on the weight of the deck (biased down dock leveler) or by physically pushing the deck back down with an external force or weight (biased up dock leveler), such as the weight of a person standing on the deck.  
         [0004]     There are a wide variety of well-known actuators available today. Some common ones include, hydraulic cylinders, pneumatic cylinders, coil springs, high-pressure air springs, linear motors, and inflatable actuators. The subject invention pertains to inflatable actuators, which comprise an inflatable chamber disposed underneath a deck. To raise the deck, a blower discharges pressurized air into the chamber, which causes the chamber to expand and lift the deck. Upon de-energizing the blower, the weight of the deck forces the air within the chamber to backflow through the blower, whereby the chamber controllably collapses to lower the deck.  
         [0005]     Although inflatable actuators are effective at raising a deck, the blowers of such actuators can be particularly loud. Moreover, a pit in which a dock leveler is installed can become quite dirty from the traffic across the deck and by debris infiltration from the adjacent driveway. An inflatable chamber, its blower and various other dock leveler components underneath the deck can be difficult to clean due to the limited space of a typical dock leveler pit.  
         [0006]     Consequently, a need exists for an inflatable actuator that is quieter and easier to clean and whose blower is protected from debris.  
       SUMMARY  
       [0007]     In some embodiments, an inflatable actuator for a dock leveler has an internal volume of air contained between a pliable upper section a more rigid base.  
         [0008]     In some embodiments, the inflatable actuator is substantially cylindrical.  
         [0009]     In some embodiments, the more rigid base includes an upwardly extending flange joined to which the pliable upper section is joined.  
         [0010]     In some embodiments, the inlet and/or outlet of the blower passes through the more rigid base to maintain the integrity of the pliable upper section.  
         [0011]     In some embodiments, the blower is installed inside the inflatable actuator.  
         [0012]     In some embodiments, the blower is mounted to the base of inflatable actuator.  
         [0013]     In some embodiments, the inflatable actuator includes an access opening.  
         [0014]     In some embodiments, an inflatable actuator includes a valve system that enables a blower to selective inflate or forcibly deflate the actuator.  
         [0015]     In some embodiments, a blower can forcibly collapse an inflatable actuator while the dock leveler deck remains elevated and substantially stationary.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a side view of a dock leveler whose deck, shown in a cross-traffic position, can be raised by an inflatable actuator.  
         [0017]      FIG. 2  is a cross-sectional side view similar to  FIG. 1  but with the actuator inflated to lift the deck.  
         [0018]      FIG. 3  is similar to  FIG. 1  but with the actuator deflated and the lip of the dock leveler resting upon the rear of a truck bed.  
         [0019]      FIG. 4  is similar to  FIG. 2  but showing another embodiment where the blower is inside the actuator.  
         [0020]      FIG. 5  is similar to  FIG. 4  but showing the blower installed at another location inside the actuator.  
         [0021]      FIG. 6  is similar to  FIGS. 4 and 5  but showing an inflatable actuator with various access openings that are covered or otherwise closed.  
         [0022]      FIG. 7  is cross-sectional side view showing an inflated actuator with an internal blower and valve system, wherein the valve system is schematically illustrated.  
         [0023]      FIG. 8  is a side view of the actuator of  FIG. 7  but with a portion cut away to show the inside of the actuator when forcible deflated up against the underside of the deck.  
         [0024]      FIG. 9   a  is a schematic diagram showing one embodiment of an inflated actuator, a valve system in an inflate configuration, and a blower.  
         [0025]      FIG. 9   b  is a schematic diagram similar to  FIG. 9   a  but showing the valve system in a deflate configuration, wherein the blower forcibly deflates the actuator.  
         [0026]      FIG. 10   a  is a schematic diagram showing a second embodiment of an inflated actuator, a valve system in an inflate configuration, and a blower.  
         [0027]      FIG. 10   b  is a schematic diagram similar to  FIG. 10   a  but showing the valve system in a deflate configuration, wherein the blower forcibly deflates the actuator.  
         [0028]      FIG. 11   a  is a schematic diagram showing a second embodiment of an inflated actuator, valve system in an inflate configuration, and a blower.  
         [0029]      FIG. 11   b  is a schematic diagram similar to  FIG. 11   a  but showing the valve system in a deflate configuration, wherein the blower forcibly deflates the actuator. 
     
    
     DETAILED DESCRIPTION  
       [0030]      FIGS. 1-3  show various operating positions of a dock leveler  10  and its inflatable actuator  12  which are installed within a pit  14  of a loading dock  16 . To facilitate loading or unloading cargo from a vehicle  19  (e.g., truck trailer, etc.), dock leveler  10  includes a pivotal deck  18  and a lip  22  that provide a path for personnel and material handling equipment to travel between a platform  24  of the dock and vehicle  19 . To selectively raise and lower a front edge  26  of the deck, inflatable actuator  12  can pivot deck  18  about a hinge  28  that couples a rear edge  30  of the deck to a supporting frame  32 . This enables dock leveler  10  to set lip  22  on or remove it from the truck bed. Lip  22  extends from deck  18  to bridge the gap between front edge  26  and a rear edge  34  of vehicle  19 .  
         [0031]     To raise deck  18 , a blower  36  or some other source of pressurized air forces air through an inlet  38  to expand inflatable actuator  12 . To lower deck  18 , blower  36  is de-energized, which allows the deck&#39;s weight to controllably collapse actuator  12  by forcing air to backflow through blower  36 .  
         [0032]     The sequence of operation at dock  16  typically begins with dock leveler  10  at its stored, cross-traffic position of in  FIG. 1 . In this position, inflatable actuator  12  is deflated, lip  22  is at its pendant position supported by a set of lip keepers  40 , and the top surface of deck  18  is generally flush with platform  24 . Arrow  42  represents vehicle  19  backing the rear edge of its truck bed toward a bumper  44  of dock  16 .  
         [0033]     Next, in  FIG. 2 , blower  36  is energized to inflate actuator  12  with relatively low-pressure air (preferably less than 10 psig.). A centrifugal blower is just one example of such a source of low-pressure air. As inflatable actuator  12  expands, it forces deck  18  upward. Lip  22 , which a hinge  46  pivotally couples to the deck&#39;s front edge  26 , pivots outward to extend out over the truck bed of vehicle  19 . Arrow  48  schematically represents any actuator capable of moving lip  22  (e.g., by acting upon a lug  50  extending from lip  22 ). Examples of such a lip actuator include, but are not limited to, pneumatic cylinders, low-pressure air actuator, coil springs, high-pressure air springs, linear motors, mechanical linkages responsive to the movement of deck  18 , and various combinations thereof.  
         [0034]     After lip  22  extends out over rear edge  34  of vehicle  19 , it is selectively locked or otherwise held in this position and blower  36  is de-energized to deflate actuator  12 . This allows deck  18  to descend to lower lip  22  upon the truck bed of vehicle  19 , as shown in  FIG. 3 . In this position, cargo can be readily added or removed from vehicle  19 .  
         [0035]     To enable inflatable actuator  12  to raise and lower deck  18  in such a manner, actuator  12  comprises a pliable upper section  52 , such as a nylon fabric tube, bladder, bag, or the like. An upper panel  54  of section  52  seals the upper end of actuator  12 . To seal a lower end of the actuator, upper section  52  can be bonded, fused, welded, or otherwise attached to a more rigid base  56 . Together, the side portion of pliable upper section  52 , upper panel  54 , and base  56  define an expandable chamber that contains an internal volume of air  58 . A tube  60  places inlet  38  of actuator  12  in fluid communication with a discharge outlet  62  of blower  36 , so blower  36  can force air into the chamber to expand actuator  12 . When blower  36  is de-energized, the weight of deck  18  can force the air out of the chamber in reverse flow through blower  36 , as deck  18  descends.  
         [0036]     Although the structural details of actuator  12  may vary, in some embodiments, pliable upper section  52  is made of a nylon fabric and base  56  is made of ABS (Acrylonitrile Butadiene Styrene). Actuator  12  is generally cylindrical when inflated. In some cases, base  56  includes an upwardly extending flange  64  that adds rigidity to base  56  and provides a generally strong, stationary wall through which tube  60  can extend. The rigidity of base  56  and joining the base in direct sealing relationship to upper section  52  at a circumferential joint  66  may provide several benefits. First, a rigid base may be less likely to bulge under pressure, thus actuator  12  maintains a generally constant area of contact between the bottom of actuator  12  and a floor  68  of pit  14 . With a constant area of contact, debris in the pit is less likely to work itself underneath actuator  12 . Second, a rigid base may be more durable and less likely to be punctured by debris on pit floor  68 . Third, a smooth, rigid base may be easier to clean. Fourth, having upper section  52  sealingly joined to base  56  at joint  66  eliminates the need for an additional internal sealing member just to seal off the bottom of actuator  12 .  
         [0037]     Referring to  FIGS. 4 and 5 , in some cases blower  36  may be installed somewhere inside the inflatable actuator to provide quieter operation and help keep the blower clean. In  FIG. 4 , for example, blower  36  is mounted to base  56 , and an inlet tube  70  extending from the suction opening of blower  36  and passing through flange  64  or through upper section  52  places the internal volume of air  58  in fluid communication with the exterior air. A suitable air filter can be connected in series with tube  70  and installed outside of the inflatable actuator so that the filter can be readily serviced.  
         [0038]     In  FIG. 5 , an upper section  72  of an inflatable actuator  74  supports blower  36 . Tube  76  (e.g., a flexible hose) extending from the suction opening of blower  36  and passing through an upper panel  78  of upper section  72  places the internal volume of air in fluid communication with the exterior air. Although tube  76  is shown extending thorough upper panel  78 , alternatively tube  76  could also be routed through upper section  72 , a base  75  or any other part of inflatable actuator  74 .  
         [0039]     In this example, base  75  is shown to include a drain plug  81  for draining condensation  87  or any other fluid that may happen to collect at the bottom of base  75 . Base  75  may also include a raised central portion  83  that creates a trough  85  for collecting the fluid and directing it toward drain plug  81 . Bases  56 ,  64  and  86  can be modified to also include such a drain plug and trough.  
         [0040]     Referring to  FIG. 6 , to provide service access to an internally mounted blower, an inflatable actuator  80  may include an access opening, which may be selectively closed by some appropriate device, such as a zipper  82  or a removable cover  84 . Zipper  82  is preferably installed horizontally as shown because the bursting stress in an upper section  85  is greater in the circumferential direction than vertically, thus a horizontal zipper is less likely to pull apart. Moreover, a horizontal zipper avoids being creased at multiple locations when upper section  85  folds as actuator  80  collapses.  
         [0041]     Referring to  FIGS. 7 and 8 , it may be desirable to elevate deck  18  and lift a base  86  of an inflatable actuator  88  off the dock pit floor  68  for the purpose of cleaning the pit area or for other service reasons. To raise base  86  as shown in  FIG. 8 , actuator  88  first lifts deck  18  to the position of  FIG. 7 , and a prop  90  is installed to keep it there. Once prop  90  supports the weight of deck  18 , blower  36  in conjunction with a valve system evacuates the air from within actuator  88 , whereby the reduced air pressure inside actuator  88  draws base  86  up to its position of  FIG. 8  because the top of actuator  88  is secured to the underside of deck  18 . Once base  86  is elevated, a retainer system  92  such as a chain, hook, latch, strap, cable, or the like can hold the base  86  in its raised position even after blower  36  is de-energized.  
         [0042]     Referring further to  FIGS. 9   a ,  9   b ,  10   a ,  10   b ,  11   a , and  11   b , to selectively pressurize actuator  88  to raise deck  18  or to depressurize actuator  88  to lift base  86  for servicing, a valve system  94   a ,  94   b , or  94   c  determines whether blower  36  inflates or deflates actuator  88 . Valve system  94   a , for example, includes a 2-position, 4-way valve  96  that could be actuated electrically, manually, or otherwise. Valve  96  in the position shown in  FIGS. 7 and 9   a  allows blower  36  to draw in exterior air through a first line  98  and discharge the air through a second line  100  into actuator  88 , thereby pressurizing actuator  88  to raise deck  18 . A filter  102  can be added to help keep the interior of actuator  88 , valve  96 , and blower  36  clean. To lift base  86 , valve  96  can be positioned as shown in  FIGS. 8 and 9   b , whereby valve  96  allows blower  36  to evacuate air from within actuator  88  via line  100  and discharge the air through line  98 .  
         [0043]     It should be noted that one or more subcomponents of valve system  94   a , blower  36  and filter  102  can be installed inside actuator  88  as shown in  FIGS. 7 and 8 , or valve system  94   a  can be installed outside of actuator  88  as shown in  FIGS. 9   a  and  9   b  (also similar to  FIGS. 1-3 ). The same applies to valve systems  94   b  and  94   c , which are alternatives to valve system  94   a.    
         [0044]     Valve system  94   b  of  FIGS. 10   a  and  10   b  includes two 2-position, 3-way valves  104  and  106  that can be actuated electrically, manually, or otherwise. Valves  104  and  106  in their positions shown in  FIG. 10   a  allow blower  36  to draw in exterior air through a first line  108  and discharge the air through a second line  110  into actuator  88 , thereby pressurizing actuator  88  to raise deck  18 . To lift base  86 , valves  104  and  106  can be positioned as shown in  FIG. 10   b , whereby valves  104  and  106  allow blower  36  to evacuate air from within actuator  88  via line  110  and discharge the air through a discharge line  112 .  
         [0045]     In another embodiment, a valve system  94   c  of  FIGS. 11 and 11   b  includes four 2-position, 2-way valves  114  that can be actuated electrically, manually, or otherwise. Valves  114  in their positions shown in  FIG. 11   a  allow blower  36  to draw in exterior air through a first line  116  and discharge the air through a second line  118  into actuator  88 , thereby pressurizing actuator  88  to raise deck  18 . To lift base  86 , valves  114  can be positioned as shown in  FIG. 11   b , whereby the valves allow blower  36  to evacuate air from within actuator  88  via line  118  and discharge the air through a discharge line  120 .  
         [0046]     Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art. Therefore, the scope of the invention is to be determined by reference to the following claims: