Dock leveler with automatic vehicle barrier

Abstract: A dock leveler assembly (I,II) is provided having an automatic barrier (230;330) actuated in response to movement of the lip for preventing accidental runoff of material handling vehicles from the loading dock. The assembly includes a ramp for pivotal movement between a stored first position wherein an exposed surface thereof is coplanar with the loading dock platform surface (212;312), an upwardly inclined second position, and a declining third position. The lip is operatively connected to a front edge portion of the ramp for movement from a depending position to an outwardly extended cantilevered position. The assembly includes a barrier unit (230;330) movable between operative and inoperative modes. When in the operative mode, a portion of the barrier unit automatically projects above the ramp exposed surface and forms a vehicle safety barrier of optimum height.

Description: This invention relates to a dock leveler according to the preamble of claim 1 and more particularly to a dock leveler assembly which when in one mode automatically provides a barrier to prevent material handling equipment from accidentally running off the exposed front end of the loading dock. Loading dock levelers, sometimes called dockboards, are used to facilitate the loading and unloading of variously sized vehicles which are parked adjacent to a loading dock that has a working surface above the roadway adapted to adjoin the bed of a parked vehicle. Examples of loading dock leveler assemblies are disclosed in US-AS 3,583,014, 3,699,601, 3,728,753, 4,110,860, 4,257,137, 4,531,248, 4,570,277 and 4,744,121. Such dock levelers compensate for height variations between the bed of the parked vehicle and the working sometimes referred hereafter as platform surface, surface of the dock since they are typically disposed in a pit or recess at the front of the loading dock and include a ramp pivotal between a raised position above the working surface of the dock and a below dock level position. An extension plate or lip is hinged to the front edge of the ramp and is movable to an extended position to span the gap between the bed of the parked vehicle and the front edge of the ramp. When such dock levelers are not in use, they are stored in a cross-traffic position having the an exposed upper surface of ramp flush with the working surface of the dock and the lip disposed in a depending position. In the practical implementation of such dock levelers certain safety problems may arise. Loading dock personnel may accidentally drive or push fork lift trucks or related material handling equipment off the exposed front end of the dock leveler when there is no vehicle parked adjacent the loading dock and the dock leveler is stored in the cross-traffic position. Dock levelers have heretofore been provided to minimize the risk of such accidental run off. Such dock levelers utilize a lip pivotally fixed to the front edge of the ramp wherein the pivot axis of the lip is set outwardly, or forwardly, a substantial distance from the rear edge of the lip. Such a design allows the rear section of the lip between the pivot axis and the lip rear edge to project above the ramp surface and form a barrier when the lip is not in its fully extended cantilevered position. When such a lip is in positions between the stored depending position and the fully extended cantilevered position, the rear section of the lip still forms a barrier by projecting angularly to a varying degree above the ramp surface. Thus, the continued projection of the lip rear section might seriously obstruct loading and unloading operations. Another type of dock leveler having an automatic vehicle barrier is disclosed in US-A-4,920,598 representing the closest prior art and thus being the base for the above referenced preamble of claim 1. The dock leveler assembly disclosed therein relies on a portion of the lip to form a barrier. There are circumstances where it is desirable to provide an automatic barrier to prevent accidental material handling equipment runoff when the dock leveler assembly is in a stored cross-traffic position and loading and unloading equipment is being utilized. Such circumstances include situations where material must be loaded onto or unloaded from the extreme rear of the bed of the vehicle parked adjacent the loading dock and the placement of the material interferes with the use of the dock leveler with the lip thereof in a fully extended position resting on the rear of the vehicle bed. It is also advantageous to avoid the pinching area developed in levelers which utilize a lip having a barrier forming rear section which overlaps the ramp under certain operating conditions since a potential for entrapping equipment or personnel exists in such levelers. Thus, it is a general object of the present invention to provide an improved loading dock leveler which automatically raises a substantial safety barrier or stop to prevent fork lift trucks and related material handling equipment from accidentally running off the front end of the loading ramp when the latter is in stored position. This object according to the present invention is accomplished by means of a dock leveler of the type indicated above and being characterized by the features of the characterizing clause of claim 1. It is an advantage of the present invention that it provides an improved loading dock leveler which is readily operable and has maximum safeguards for the safety of loading dock personnel and equipment. It is a further advantage of the present invention that it provides an improved loading dock leveler which allows loading and unloading operations involving the rear bed portion of a parked vehicle. Further and additional objects and advantages will appear from the following description, accompanying drawings, and appended claims. In accordance with one embodiment of the invention, a dock leveler is provided having a ramp hingedly mounted to a frame mountable in a pit formed in a loading dock. The ramp is mounted for movement between a stored first position wherein an exposed upper surface of the ramp is substantially coplanar with the loading dock platform surface, an upwardly inclined second position, and a declining third position. Operatively connected to the front edge portion of the ramp is a lip which is movable between a depending position when the ramp is in the stored first position, and an outwardly extended cantilevered position. The dock leveler includes a barrier means movable between an operative mode and an inoperative mode in response to movement of the lip to and from the lip depending position. In the operative mode, a predetermined portion of the barrier means projects above the upper surface of the ramp and forms a vehicle safety barrier of optimum height when the lip is in the depending position and the ramp is in the stored first position. In the inoperative mode, the barrier means does not project above the ramp surface when the lip is in an outwardly extended cantilevered position. For a more complete understanding of the present invention reference should now be made to the accompanying drawings wherein: Fig. 1 is a fragmentary perspective, sectional view of a first embodiment of the improved dock leveler showing a barrier means in the inoperative mode and an actuator means for raising and lowering the barrier means; Fig. 2 is similar to Fig. 1 but showing the barrier means in an operative mode; Fig. 3 is a fragmentary top plan view of a second embodiment of the improved dock leveler showing the spacing between post-like members comprising a barrier means therefore and Fig. 4 is an enlarged, fragmentary vertical sectional view taken along line 4-4 of Fig. 3 showing an actuator means for raising and lowering the post-like member of the barrier means. Figs. 1 and 2 illustrate a first embodiment of the improved dock leveler assembly I wherein a plate section 230 is provided which is disposed proximate the front edge of the ramp and spans the entire width thereof. In an inoperative mode, or unraised position, plate section 230 is supported in coplanar relationship with the exposed ramp surface by depending side guards 212b and reinforcing channels 212c arranged in parallel relation and affixed to the underside of the ramp and projecting outwardly from the rear edge of the ramp. The plate section 230 has affixed to the underside thereof a plurality of depending laterally spaced reinforcing extensions 236 arranged so as to interfit between the reinforcing channels 212c. A fixed center bracket 238 depends from the underside of plate section 230 and is connected to an exposed upper end of a piston 250 forming a component of a vertically mounted hydraulic cylinder assembly 252. The cylinder 251 of the assembly is supported by a depending U-shaped member 254 affixed to the underside of the two centrally located ramp reinforcing channels 212c, see Fig. 1 or 2. The hydraulic cylinder 251 is connected to a suitable source of hydraulic pressure, not shown, and is adapted to actuate the piston 250 to raise plate section 230 above the ramp surface as shown in Fig. 2, or to retract the piston to lower the plate section to a flush position with respect to the exposed ramp surface 212, as shown in Fig. 1. The activation of the hydraulic cylinder assembly 252 is synchronized with the movement of the lip through a suitable switching control array, not shown, which also controls the mechanism that extends and retracts the lip. Thus, when the lip is moved to the depending position, the switching control array is preset to activate the assembly 252 to raise the plate section 230; and when the lip is moved to the extended cantilevered position, the switching control array is preset to activate the assembly 252 so as to return the plate section 230 to a coplanar relation with the ramp upper surface. The hydraulic cylinder assembly 252 may also be actuated by a limit switch positioned in one of the lip keeper brackets not shown. The limit switch may be preset to activate the assembly to raise the plate section 230 when the lip assumes a stored position within the keeper brackets and to lower the plate section when the lip is disengaged from the keeper brackets. It will be apparent that the hydraulic cylinder assembly 252 and its associated piston 250 illustrated in the embodiment of Figs. 1 and 2 may be replaced by suitable electromechanical devices. Figs. 3 and 4 illustrate a second embodiment of an improved dock leveler assembly II that utilizes a plurality of vertically adjustable post-like members 330 to form a barrier. As shown in Fig. 4, each post-like member 330 is disposed in an aligned opening 312b formed in the ramp 312. The opening may be reinforced by a depending circular guide collar 312c. The top surface 330a of the post-like member forms a closure for the ramp opening when the member is in the inoperative mode. The lower end 330b of each member 330 has a depending finger 332 fixedly secured thereto. Pivotally connected to the finger is one leg 262a of an L-shaped lever 262. A second leg 262b of the lever 262 is pivotally connected to the exposed end of a hydraulically activated piston 260a, the latter forming a component of a hydraulic cylinder assembly 260. The assembly cylinder 260b is pivotally suspended from a bracket 264 affixed to the ramp underside. A lug 266 projects laterally from the lever 262 at the junction of the legs 262a and 262b and is slidably disposed within an elongate slot 268a formed in a depending bracket 268 affixed to the underside of the ramp. The longitudinal axis of the slot is substantially parallel to the exposed upper surface of the ramp and transverse to the direction of movement of each post-like member. Retraction of the piston 260a into the cylinder 260b causes relative movement of the lug 266 forwardly with respect to the slot 268a and counter-clockwise movement of lever 262 about the lug 266 whereby the upper end 330a of the post-like member is moved from the raised position, shown in phantom lines in Fig. 4, to the inoperative, lowered position. Extension of the hydraulic cylinder piston slides the lug 266 rearwardly in slot 268a causing clockwise movement of lever 262 about the lug and raising the post-like member surface 330a above the ramp exposed surface. As heretofore described, activation of the hydraulic cylinder assembly 260 is synchronized with the movement of the lip between the cantilevered and depending positions by a suitable switching control array, not shown, which also operates the mechanism for pivotally rotating the lip. The hydraulic cylinder assembly 260 may also be actuated by a limit switch positioned in one of the lip keeper brackets as previously described. The raising and lowering of the post-like member 330 may be accomplished by alternative electromechanical or hydraulic devices that directly drive the post-like member 330. Although a plurality of post-like members 330 may be disposed in a parallel line proximate the front edge of the ramp, Fig. 3 shows an optional spacing of three post-like members wherein two of the members 330A, 330B are positioned adjacent the side edges and the front edge of the ramp and a third member 330C is positioned rearwardly along the longitudinal centerline of the ramp. Thus, the three members form the vertices of an isoceles triangle. The distance, approximately two and one half feet, between the members forming the equal sides of the triangle is limited to a length narrower than the width of conventional material handing equipment. When utilizing the triangular arrangement of the barrier members, the latter may be operated between an inoperative mode and an operative mode only when the lip is in the depending stored position. The first and second embodiments illustrated in Figs. 1 to 4 may have the barrier controlled to move between an operative mode and an inoperative mode in an alternate manner. For example, plate section 230 of assembly I may be raised and lowered independently of the movement of the lip. This alternative manner may be accomplished by having a suitable switching control array preset to activate the hydraulic cylinder assembly 252 to lower or raise the plate section 230 in response to signals generated by operation of associated loading dock equipment such as vehicle restraints. The hydraulic cylinder 252 can also be activated by providing a control unit operable by loading dock personnel through suitably coded keys or buttons. The raising and lowering of the post-like members of assembly II may be controlled in similar alternate manners.

Claims: A dock leveler for a loading dock having a substantially horizontal platform surface, said dock leveler comprising: a frame having a rear section; a ramp having a rear edge portion hingedly connected to the frame rear section, said ramp being movable between a stored substantially horizontal first position and a predetermined upwardly inclined second position; a lip operatively connected to a front edge portion of the ramp and movable between a stored position and an outwardly extended cantilevered position when said ramp assumes said second position; and barrier means (230; 330) movable between an operative mode and an inoperative mode, said barrier means (230; 330) being in an operative mode when said ramp is in the first position and said lip is in the stored position, whereby a predetermined portion of said barrier means (230; 330) and projects above the exposed surface (212; 312) of the ramp and forms a safety barrier, while when said barrier means (230; 330) is in an inoperative mode it assumes a non-projecting position relative to the exposed surface (212; 312) of the ramp, said barrier means being in said inoperative mode when said lip is in the outwardly extended cantilevered position, characterized by actuator means (252; 260) for raising said barrier means (230; 330) to an operative mode when said lip is moved to the stored position, and for lowering said barrier means (230; 330) to an inoperative mode when said lip is moved to the outwardly extended cantilevered position, the actuator means (25) being also capable of raising and lowering said barrier means (230; 330) independently of the angular position of the ramp. The dock leveler of claim 1 wherein said barrier means comprises an intermediate plate section (230) extending substantially across the width of said ramp. The dock leveler of claim 1 wherein said barrier means comprises a plurality of relatively spaced post-like members (330). The dock leveler of claim 3 wherein said actuator means (260) is operatively connected to said member (330) and effects controlled endwise movement thereof between operative and inoperative modes.

Inventors: HAHN NORBERT, SWESSEL MICHAEL A, HAHN, NORBERT, SWESSEL, MICHAEL A.
Applicants: RITE HITE CORP, RITE-HITE CORPORATION
Application year: 1991
Main classification: B65G69
IPC codes: B65G69