Abstract:
A dock leveler including a ramp having a rear edge movably interconnected with a loading dock, an intermediate member movable relative to the ramp, and an inflatable assembly positioned to cause relative movement between the ramp and the intermediate member upon inflation of the inflatable assembly, thereby resulting in movement of the ramp. The intermediate member is movably mounted to a pit floor, a support structure, or the ramp. A roller member is mounted to an end of the intermediate member. The inflatable assembly can be operatively associated with a vacuum device to allow for selective removal of gas from the inflatable assembly. Alternatively, a hydraulic assembly and a support frame may replace the inflatable assembly and intermediate member. The dock leveler includes hook-type bracket members and mounting bores to accommodate either powering arrangement.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119 of U.S. Provisional Application No. 60/162,691, entitled DOCK LEVELER, filed on Nov. 1, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a dock leveler used to bridge the gap between a loading dock and the bed of a truck or carrier parked adjacent the loading dock, and more particularly to improvements in dock levelers incorporating an airbag or other inflatable member for raising the ramp of the dock leveler. 
     A dock leveler typically includes a frame or supporting structure mounted in a pit or depression in the loading dock. The rear end of a ramp or deck plate is pivotally mounted to the supporting structure so that the ramp is movable from a horizontal position to a position within the working range of the ramp (e.g., between an upwardly inclined position and a downwardly declined position). An extension lip is pivotably mounted to the forward end of the ramp, and is movable between a downwardly hanging pendant position and an extended position in which the lip forms an extension to the ramp. 
     After a truck has parked in front of the loading dock in preparation for a loading or unloading operation, the ramp of the dock leveler is raised to its upwardly inclined position. The lip is then pivoted outwardly to its extended position. As the ramp is lowered, the lip engages the bed of the truck to support the ramp, such that the ramp and the lip in combination bridge the gap between the loading dock and the truck bed. After the loading or unloading operation is completed, the ramp is raised and the lip falls by gravity to its pendant position. The ramp is then lowered to its horizontal position, and the truck can then pull away from the loading dock. 
     In the past, the ramp has been pivoted to its upward position in response to operation of a mechanical or hydraulic mechanism. However, recent developments in the dock leveler art disclose an inflatable member or bag utilized to pivot the ramp to its upwardly inclined position, such as is illustrated in U.S. Pat. No. 5,802,650. This patent discloses a bag inflated with low-pressure air by an inflating device such as a fan or blower, and is hereby incorporated by reference in its entirety. 
     Dock leveler users have different preferences as to size and power units for their dock levelers, necessitating a dock leveler distributor to carry a wide variety of stock items to match a large number of combinations. 
     SUMMARY OF THE INVENTION 
     The present invention relates to improvements to the above-noted dock levelers incorporating an inflatable member. In one aspect, the dock leveler of the present invention is adapted to be mounted to a loading dock having an upper dock surface and a pit disposed in the upper surface. The dock leveler includes a supporting structure positionable within the pit, the pit having a floor, the supporting structure including at least two vertical members, each vertical member having therethrough at least one horizontally-oriented bore. The dock leveler also includes a ramp having a rear edge movably interconnected with the supporting structure at a pivot point; at least two hook-type bracket members affixed to the rear edge of the ramp; and a power unit positioned to cause relative movement between the ramp and the pit floor upon operation of the power unit, thereby resulting in movement of the ramp relative to the supporting structure. 
     In one embodiment, the power unit is an inflatable assembly and can include an intermediate member pivotably mounted to the hook-type bracket members. The intermediate member includes a roller member mounted to an end of the intermediate member. In another embodiment, the inflatable assembly includes a blower device operatively connected to the inflatable assembly. In yet another embodiment, the power unit is a hydraulic assembly having a hydraulic cylinder and can include a support frame removably mounted to the at least two vertical members using attachment devices in the bores. The support frame can be affixed to the pit floor, and the hydraulic cylinder can be pivotably attached to the support frame and to the ramp. Finally, the hydraulic assembly can include a hydraulic pump operatively connected to the hydraulic cylinder. 
     In yet another embodiment, the dock leveler includes structure to accommodate both hydraulic and pneumatic power units, allowing the same dock leveler structure to be used with either power unit, thus reducing the number of stock keeping units that need to be manufactured and carried. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal section view of a dock leveler constructed according to the invention, illustrating the ramp in its upwardly inclined raised position. 
     FIG. 2 is a partial section view of the dock leveler of FIG. 1, with portions broken away, showing a portion of the inflatable member, the support and the inflating device subassembly. 
     FIG. 3 is a bottom plan view of the subassembly illustrated in FIG.  2 . 
     FIG. 4 is an isometric view of a lifting tool for raising the forward end of the lifting device support above the supporting surface to a raised position. 
     FIG. 5 is a schematic view of the dock leveler of FIG. 1 showing the lifting tool of FIG. 4 in an engaged, inoperative position. 
     FIG. 6 is a view similar to FIG. 5, showing the lifting tool in its operative lifting position for raising the forward end of the lifting device support and showing mounting of the auxiliary wheels to the lifting device support. 
     FIG. 7 is a view similar to FIGS. 5 and 6, showing removal of the lifting device support, the inflatable member and the inflating device using the auxiliary wheels mounted to the support. 
     FIG. 8 is a partial section view taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is a perspective view of alternative embodiment of the dock leveler of FIG. 1 illustrating a hydraulic power unit with the present invention. 
     FIG. 10 is a partial section view taken along line  10 — 10  of FIG.  9 . 
     FIG. 11 is a partial perspective view of another embodiment of the dock leveler of FIG. 1 illustrating an alternative mounting arrangement of the hydraulic power unit with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a dock leveler  10  is mounted in a pit or depression  12  in a loading dock  14 . The lower surface or floor  16  of pit  12  preferably slopes downwardly and forwardly. Dock leveler  10  is adapted to bridge the gap between the upper surface of loading dock  14  and the bed of a truck or carrier parked in front of loading dock  14 , to facilitate loading or unloading of the truck or carrier. 
     Dock leveler  10  includes a frame or supporting structure  18 , which is mounted in pit  12 , and the rear end of a ramp or deck plate  20  is pivotably mounted to the upper end of frame  18  via one or more pins  22 , again in a conventional manner. Ramp  20  is movable between a generally horizontal stored, dock-level position, in which ramp  20  is flush and substantially co-planar with the upper surface of dock  14 , and an upwardly inclined position, as shown in FIG.  1 . 
     To pivotably mount ramp  20  to frame  18 , a series of lugs  24 , interconnected with ramp  20 , are mounted to the upper ends of vertical members  19  of frame  18  through pins  22 . Each vertical member  19  includes two horizontal bores  21  therethrough. The bores  21  are provided, although not employed in this embodiment, to accommodate an alternative embodiment as described below and as illustrated in FIGS. 9 and 10. 
     An extension lip  26  is hinged to the forward end of ramp  20  by means of hinge pins  28 . Extension lip  26  is pivotable from a downwardly hanging pendant position, as illustrated in FIG. 1, to an outwardly extending position (not shown), via a conventional lip extension mechanism which is actuated when ramp  20  is moved from its raised position to a lowered position. When lip  26  is moved to its outwardly extending position, lip  26  is generally co-planar with ramp  20 , forming an extension to ramp  20 . Lip  26  can be moved from its pendant position to its extended position and held in its extended position by various mechanical, hydraulic or pneumatic mechanisms, in a manner as is known, and the lip lifting and latching mechanism is not, in itself, a part of the present invention. 
     Frame  18  further includes a pair of spaced, forwardly-extending side members  30  located adjacent the sides of pit  12 , and a pair of front support pads  32  mounted to the forward ends of side members  30 . The support pads  32  are designed to support dock level supports  33 . Side members  30  are preferably in the form of angle members, each defining an outer vertical section and lower horizontal sections spaced slightly above pit floor  16 . A lifting subassembly, shown generally at  34 , is located in pit  12  beneath ramp  20 . Lifting subassembly  34  consists of an inflatable member or bag assembly  36  including vertically superimposed upper and lower bags  38 ,  40 , respectively. The construction of bag assembly  36  is illustrated and described in U.S. Pat. No. 5,446,938, which is hereby incorporated by reference in its entirety. The bags  38 ,  40  are preferably formed of any satisfactory air-impervious material, such as fabric coated with a thermoplastic resin, and have contiguous horizontal surfaces joined together via an annular seal enclosing an opening providing communication between bags  38 ,  40 . It should be appreciated that one or more bags could be used. 
     The upper surface of bag assembly  36 , defined by the upper extent of upper bag  38 , bears against a pressure plate  39  mounted to the underside of the deck plate  20  by a series of C-shaped pressure plate brackets  41 . The pressure plate brackets  41  are welded to the underside of the deck plate  20 , and the pressure plate  39  is riveted to the pressure plate brackets  41 . A deck bracket  198  is also welded to the underside of the deck plate  20 , as is described in more detail below. 
     Bag assembly  36  is mounted to a bag support assembly  44  (FIGS.  1  and  3 ), which as shown consists of three side-by-side sections  46 ,  48  and  50  (FIG.  3 ). Sections  46 ,  48  and  50  include upper support plates  52 ,  54  and  56 , respectively, which have downturned side flanges  58 ,  60 ;  62 ,  64 ; and  66 ,  68 , respectively. Front bumpers  70 ,  72 , in the form of inverted L-shaped sections, are mounted to the forward ends of support sections  46  and  50 . 
     A pin  74  extends through aligned openings located adjacent the rearward ends of flanges  58 - 68 , and an axle  76  extends through aligned openings located toward the forward ends of flanges  58 - 68 . Pin  74  and axle  76  function to secure support sections  46 ,  48  and  50  together. 
     Referring to FIGS. 1-3, pin  74  is removably engageable within upwardly facing slots formed in depending hook-type bracket members  78  mounted to a rear transverse angle member  79  located at the rearward ends of beams  42  below ramp  20 . Each bracket member  78  includes an upwardly extending lip  80  at its lower, forward end defining the slot within which pin  74  is received. With this construction, the rearward end of support  44  is removable from engagement with brackets  78  via an upward movement of the rearward end of support  44 . 
     A series of wheels  82  are mounted to axle  76 . An outer pair of wheels are located adjacent flanges  58  and  68 , and an inner pair of wheels  82  are located one between sections  46  and  48  adjacent flanges  60  and  62 , respectively, and the other between sections  48  and  50  adjacent flanges  64  and  66 , respectively. The wheels  82  are engageable with pit floor  16  so as to enable rolling movement of support  44  thereon. As shown in FIG. 1, when wheels  82  are engaged with pit floor  16  and when pin  74  is mounted within the slots in brackets  78 , the rearward end of support  44  is elevated relative to the forward end. It should be appreciated that one or more wheels could be used. 
     A fan or blower assembly  84  is mounted to the lower surface of one of the plates, preferably to plate  54  of central section  48 . Fan assembly  84  consists of an upper housing  85   a  and a lower housing  85   b  (FIG.  2 ). A fan unit including a mounting ring  86  having a series of bosses  87  is secured between upper housing  85   a  and lower housing  85   b , with the fan itself being disposed within upper housing  85   a  and its inlet and a filter being disposed within lower housing  85   b . Fan assembly  84  is electrically operated, and includes a conventional cord engageable with an electrical outlet (not shown) for providing power to fan assembly  84 . 
     As shown in FIG. 2, an air pipe assembly  88 , consisting of a fan outlet section  90  formed integrally with ring  86 , a flexible elbow  92  and a discharge section  94 , is mounted between the fan assembly  84  and the interior of lower airbag  40 . Fan outlet section  90  receives pressurized air from fan assembly  84 , which is then transferred through elbow  92  and discharge section  94  into lower airbag  40  and subsequently into upper airbag  38 . 
     While fan assembly  84  is shown mounted to support  44 , it is understood that fan  84  could be mounted in any other location, such as between beams  42 . Alternatively, it is understood that air from a pressurized, regulated air source, such as compressed shop air, could be used in place of fan assembly  84 . 
     Referring to FIG. 2, a flexible elastomeric reinforcing ring  96  is secured, such as by heat sealing or gluing, to the lower wall  98  of lower airbag  40 , and ring  96  includes a central opening overlying the inlet opening formed in airbag lower wall  98 . A nipple  100  having barbs  102  is connected to the end of discharge section  94  and extends through the aligned openings formed in plate  54 , bag lower wall  98  and ring  96 . Barbs  102  are engageable with reinforcing ring  96  so as to securely mount bag assembly  34  to discharge pipe assembly  88 . 
     Bag assembly  34  is secured to support sections  46 , 48 , 50  using a clamp bar  106  (FIG.  2 ), which is secured via bolts  108  and associated nuts to plates  52 ,  54  and  56 , after bag reinforcing ring  96  is secured to nipple  100  using a downward push-on motion forcing ring  96  over the barbs  102  of the nipple  100 . 
     With the construction as illustrated in FIGS. 1-3, lifting assembly  34 , consisting of bag assembly  36 , bag support  44  and fan assembly  84 , is removable as a unit from dock leveler  10 , to facilitate servicing and/or replacement of such components. This arrangement substantially simplifies construction of dock leveler  10  by enabling the airbag, support and fan subassembly to be assembled separately from the other components of dock leveler  10 . Further, a very short run of piping is necessary to communicate pressurized air from fan assembly  84  to airbag assembly  36 , which again simplifies manufacture and minimizes the mount of pressure loss through the piping. 
     A lifting tool  110  (FIG. 4) is adapted for use in raising the forward end of airbag support  44 . Lifting tool  110  includes a lower lifting section  112  and a lever or lifting handle section  114 . Lower lifting section  112  includes a pair of lifting members  116  and a forward mounting member  118  in the form of an angle section mounted between the forward ends of lifting members  116 . The lower flange of forward mounting member  118  is disposed in a plane parallel to the plane of the lower surfaces defined by lifting members  116  and is spaced there below, so as to define a pair of slots  120 . Lever section  114  includes a pair of tube handle sections  122  connected at their upper ends via a crossbar  124 . The lower ends of tube handle sections  122  and the rearward ends of lifting members  116  are welded together. An axle  126  extends through aligned openings formed in tube handle sections  122  and lifting members  116 , and wheels  128  are mounted to the ends of axle  126 . 
     Lifting section  112  and lever section  114  cooperate to define an acute angle therebetween, preferably 70 degrees to 80 degrees. 
     Referring to FIGS. 5 and 6, lifting tool  110  is used to lift the forward end of airbag support  44  when the maintenance strut  130  of dock leveler  10  is in its operative position in which ramp  20  is raised upwardly to a maintenance position from its conventional at-rest position, in accordance with conventional operation of a maintenance strut of this type. Lifting tool  110  is moved to an engaged position in which axle  76  is received within slots  120 , with the lower flange of angle  118  being located below axle  76  and the forward bottom edges of lifting members  116  being located over axle  76 . While maintaining such engagement of lifting section  112  with axle  76 , the user exerts a downward and rearward force on handle section  114  by grasping upper cross-bar  124  and bringing handle section  114  to its FIG. 6 position in which the upper end of handle section  114  engages pit floor  16 . During such movement of handle section  114 , wheels  128  roll rearwardly on pit floor  16  to the position as shown in FIG. 6, in which the axle  126 , to which wheels  128  are mounted, is located rearwardly of axle  76 . This movement results in lifting members  116  raising axle  76 , and thereby the forward end of support  44 , to a raised position as shown in FIG.  6 . 
     The geometry of lifting tool  110 , in which axle  76  is located forwardly of lifting tool axle  126  when lifting tool handle section  114  is engaged with pit floor  16 , enables the operator to leave lifting tool  110  in its FIG. 6 position to maintain the front end of support  44  in its raised position. The weight of support  44 , airbag assembly  34  and fan  84  exerts a downward force on wheels  128  and the forward end of handle section  114  to maintain lifting tool  110  in its operative lifting position, without assistance from the operator. The operator is then free to clean the rearward portion of pit  12  below support  44 , such as by using a broom or by spraying water, or by another other satisfactory method. After use, lifting tool  110  is returned to its FIG. 5 position and removed for subsequent operation of dock leveler  10   
     Alternatively, while lifting tool  110  is in its operative lifting position of FIG. 6, and if the operator desires to remove support  44  for servicing of airbag assembly  34 , fan assembly  84  or support  44 , the operator mounts a pair of auxiliary wheel assemblies  134  to flanges  58  and  68 . Each auxiliary wheel assembly  134  consists of a mounting plate  136  having a wheel  138  rotatably mounted to its lower end, and having an upper clamping plate  139  mounted to its upper end. Clamping plate  139  includes a threaded opening that receives the threaded shank of a bolt  140  (FIG.  8 ). Bolt  140  engages flange  58  of support  52  to clamp flange  58  between the end of bolt  140  and the upper end of mounting plate  136 . In this manner, auxiliary wheel assemblies  134  are temporarily secured to flanges  58 ,  68 . 
     Mounting plate  136  of each auxiliary wheel assembly  134  is constructed such that each auxiliary wheel  138  is located at an elevation below that of support wheels  82  when auxiliary wheel assemblies  134  are mounted to support  44 . In this manner, when lifting tool  110  is moved from its operative lifting position of FIG. 6 back toward its engaging position of FIG. 5, auxiliary wheels  138  engage a rolling surface, which in this case is the lower flange of frame side members  30 , and support wheels  82  are located above pit floor  16  and frame side members  30 . Alternatively, it is understood that auxiliary wheels  138  may be constructed so as to engage pit floor  16 . 
     The user then removes lifting tool  110 , and exerts a downward force on the forward end of support  44  to pivot the rear end of support assembly  44  upwardly, as shown in FIG. 7, while maintaining engagement of auxiliary wheels  138  with frame side members  30 . This downward movement of the forward end of support  44  and raising of the rearward end of support  44  disengages pin  74  from the slot in brackets  78 . Engagement between dock leveler  10  and lifting subassembly  34  is then released, and the operator exerts a forward force in the direction of arrow  142  (FIG. 7) cause auxiliary wheels  138  to ride on frame side members  30  to withdraw subassembly  34  forwardly from below ramp  20 . After the subassembly  34  has been serviced as required or if pit  12  has been serviced as necessary upon removal of subassembly  34 , subassembly  34  is replaced by reversing the above steps. That is, subassembly  34  is moved rearwardly while maintaining auxiliary wheels  138  in engagement with frame side members  30 , until pin  74  engages the forward surfaces of brackets  78 . The operator then employs lifting tool  110  to raise the forward end of support  44  as shown in FIG. 6, wherein pin  74  rides on the forward surfaces of brackets  78  until pin  74  is received within the slot formed in brackets  78 . While support  44  is in its raised position, auxiliary wheel assemblies  134  are removed from support  44 , and lifting tool  110  is thereafter moved back to its FIG. 5 position and then withdrawn from below ramp  20 . Ramp  20  is then once again moved to its raised position by operation of fan  84 , and maintenance strut  130  is then replaced to its inoperative position as shown in FIG.  1 . Dock leveler  10  is then again ready for operation. 
     It is understood that lifting tool  110  and auxiliary wheel assemblies  134  could be employed in connection with any type of lifting device support, and are not limited to use in connection with an airbag-type lifting arrangement. It is also understood that lifting tool  110  and auxiliary wheel assemblies  134  could be employed in an airbag-operated dock leveler in which fan  84  is in a location other than mounted to support  44 . 
     FIGS. 9 and 10 illustrate an alternative embodiment of the dock leveler  10  illustrated in FIG.  1 . In this embodiment, a hydraulic assembly  150  has replaced the airbag lifting subassembly  35  without the need for cutting or welding additional mounting locations. 
     As shown in FIG. 9, the hydraulic assembly includes a hydraulic cylinder  152  positioned within a support frame  158 , which is positioned directly on the pit floor  154 . The hydraulic cylinder  152  is pivotably attached to the proximal end  166  of the support frame  158 . The proximal end  166  of the illustrated support frame  158  is removably anchored to the pit floor  154  using bolts. The distal end  170  of the support frame  158  is removably attached to the vertical members  19  using bolts  174  or other attachment devices in the bores  21  (see also FIG.  10 ). A hydraulic piston  178  moves within the hydraulic cylinder  152 , and is pivotably attached to the lip hinge pins  28  at the center of the lip  26 . A hydraulic pump  182  and a hydraulic fluid reservoir  186  are also mounted within the support frame  158 . In operation, the hydraulic piston  178  is extended and retracted to pivot the deck plate  190  upward and downward, respectively. As used herein, “extend” and “retract” are relative terms and should not be interpreted as requiring that the hydraulic piston  178  be completely extended and completely withdrawn, respectively. 
     As shown in FIGS. 9 and 10, the hook-type bracket members  78  are provided, although not used in this embodiment, to make the dock leveler  10  identical to that illustrated in the previous embodiments. Pressure plate brackets  41  are mounted to the underside of the deck plate  190 . A pressure plate and the pressure plate brackets  41  are also not used in this embodiment. Providing hook-type bracket members  78 , bores  21 , and pressure plate brackets  41  in every embodiment of a dock leveler allows for a reduction in the number of stock keeping units (SKUs) carried by the manufacturer and the distributors. Rather than carrying different dock levelers for different power units, the same dock leveler can be used whether the dock leveler has a pneumatic or a hydraulic power unit, because the same dock leveler is designed to accommodate either power unit. Because the dock levelers are identical except for the power unit, the dock leveler may be completely manufactured except for the power unit and stored for later sale. Likewise, a consumer who purchases a dock leveler with a hydraulic power unit can later convert to a pneumatic power unit in a simple process that involves no cutting or welding. 
     FIG. 11 illustrates another embodiment of the dock leveler  10  illustrated in FIG.  1 . This embodiment is substantially identical to the embodiment illustrated in FIG. 9, with the exception of the attachment between the hydraulic piston  178  and the deck plate  190 . In this embodiment, the hydraulic piston  178  is pivotably attached to a piston bracket  194 , which is removably attached to a deck bracket  198 . The illustrated deck bracket  198  is welded to the underside of the deck plate  190 , and the piston bracket  194  is bolted to the deck bracket  198 . Two threaded members or nuts (not shown) are welded to the back side of the deck bracket  198  facing the deck plate  190  to accommodate bolting the piston bracket  194  to the deck bracket  198 . This embodiment allows a longer deck plate  190  to be used with the same hydraulic cylinder  152  illustrated in the embodiment of FIG.  9 . To further accommodate a reduction in SKUs, the deck bracket  198  can be present in all embodiments of dock levelers of ten feet in length or greater whether they use a bag lifting subassembly or a hydraulic assembly. The piston bracket  194  is added with the hydraulic system when a hydraulic system is used in a dock leveler. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain best modes known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.