Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to loading dock equipment and in particular to dock levelers that are used to span the distance between a loading dock and the bed of a vehicle. Specifically, it deals with a configuration for bumpers for use with a wider lip for a dock leveler that still protect the lip and the deck of the leveler from damage. 
     2. Prior Art 
     A conventional loading dock for transport vehicles typically has a dock leveler with a dock bumper placed on each side of the lip at a fixed position on the dock face. The width of the dock leveler is usually limited to a maximum width of seven feet because if the bumpers are placed wider apart then there is a risk that the vehicle may miss the bumper and strike the dock leveler when it backs into position. Some specialty dock levelers are wider than seven feet to provide space for wider than normal cargo. Examples of these devices are shown in U.S. Pat. Nos. 5,881,414 and 6,070,203. A dock leveler with the bumpers mounted rigidly on the front as described in U.S. Pat. No. 6,070,203 may be unable to raise and extend the lip. A transport vehicle may be positioned against the bumpers with sufficient force to prevent the dock leveler from raising, or the top of the bumpers may strike a door hinge or other protrusion beyond the rear of the transport vehicle. By retracting the bumpers there is no interference to raising the dock. The bumper mounting shown in U.S. Pat. No. 6,070,203 could potentially have utility with the lip that extends linearly such as shown in U.S. Pat. No. 6,081,954. The hypothetical reason is that since the lip does not rotate down in front of the leveler there is no requirement for the lip and the bumpers to occupy the same space. However if the bumpers cannot be retracted they may interfere with the transport vehicle and prevent the leveler from raising to extend the lip. Consequently such a theoretical structure still has significant shortcomings. 
     U.S. Pat. No. 4,420,849 shows a dock leveler with bumpers that fold away to accommodate wide loads, but with all of these devices the width of lip is limited by the space between the dock bumpers. 
     U.S. Pat. No. 6,081,954 describes a dock leveler with a lip that extends linearly rather than rotating in the conventional manner. However the distance between the bumpers would still limit the width of the leveler. 
     SUMMARY OF INVENTION 
     Given the shortcomings of the prior art, there is a need for a dock leveler which has a lip that is wider than the distance between the dock bumpers yet still provides protection to both the vehicle and the dock equipment as the vehicle backs into position. Additionally, the traditional “bridge” function of the leveler lip must be maintained to eliminate any gap between the vehicle and the dock leveler deck. One method of shipping cargo has two rows of wheeled carts on a transport vehicle. When a row of carts is pulled from the transport vehicle onto the loading dock, the outer wheels of the carts will extend beyond the seven foot span of a conventional dock leveler lip. Thus the wheels of the cart may fall into the gap between the back of the transport vehicle and the front of the dock bumper, and the movement of the carts may be impeded. 
     This invention is a dock leveler that has a lip that is wider than the space between the dock bumpers. The dock bumpers protrude through openings in the lip plate to provide protection at the same location as conventional bumpers. The protruding portion of the bumper is preferably segmented so that width of each opening in the lip is narrower than the width of the wheels of the carts. Thus the lip may be almost as wide as the opening in the back of the transport vehicle and all the wheels of the cart may roll easily from the bed of the transport vehicle over the lip and onto the dock leveler. Another feature of the bumpers is that they are retractable to allow the dock leveler to raise and extend the lip. 
     While a specific object of this invention is to define a leveler having a wider lip, it is also apparent that another compatible object of this invention is to define a dock leveler system with improved bumper protection for the assembly. That is, the assembly may be a conventional width. 
     The first preferred embodiment of this invention is described as follows. A dock leveler is mounted in a recessed pit of conventional construction. The dock leveler may be as wide as necessary to provide access to the transport vehicle. A lip is mounted to the front of the deck of the leveler and pivoted in a conventional manner. The lip may be of conventional configuration where the back edge of the lip abuts the front of the deck when extended. It may also be of the “barrier lip” configuration where the rear of the lip is extended above the top of the deck to provide a run-off guard when the lip is pendent. While either lip configuration may be used with this invention, the “barrier lip” configuration will provide greater strength for the lip. A series of slotted holes is cut through the lip at each bumper. The width of each opening is preferably narrower than the width of the wheels travelling over the lip. A dock bumper of special configuration is mounted under each side of the deck and has segments which protrude through the slotted holes in the lip. Thus the front of the bumpers will contact the back of the transport vehicle to provide a space in front of the lip. The bumpers are mounted so that the front face of the bumper segments may be retracted behind the front of the lip so the leveler and lip may be raised without interference with the back of the transport vehicle. 
     The second preferred embodiment is similar to the first except that the dock leveler has a lip that retracts linearly rather than by rotation. Because the lip does not rotate down in front of the leveler there is no requirement for the bumpers to pass through the lip in the stored position. However the leveler must still be able to raise to extend the lip onto a transport vehicle that is higher than the dock floor. The bumpers are mounted so that they may be retracted to allow the leveler to raise without interference with the back of the transport vehicle. 
     The third preferred embodiment has conventional bumpers fastened to a carriage which is mounted for vertical motion along guide tracks fastened to the dock wall. The bumper carriage is constructed with vertical support plates so that a wide lip with slotted openings may fit between the vertical support plates and store behind the bumpers. 
     Thus the bumpers do not limit the width of the lip. Because the bumpers are always under the lip when the dock leveler is in the operative position, the bumpers may be spring biased toward the upper position. This would eliminate the need of a hydraulic positioning system such as that described by in U.S. Pat. No. 6,006,389. When the transport vehicle height is at or above the height of the dock then the lip will reach over the bumpers. When the transport vehicle is lower than the dock floor, the lip will contact the top of the bumpers and force them down to the proper height. This embodiment would also work with low docks where the upper position of the bumper is higher than the dock floor. As with the first preferred embodiment, the lip may be a conventional one or a run-off guard configuration. 
     The fourth preferred embodiment is similar to the third except that the bumper mounting brackets are fixed to the dock wall at a height that does not exceed the height of the bed of the transport vehicle. Transport vehicles lower than the height of the bumpers may be lifted to the desired height by the use of a truck leveler or wheel riser ramps, which are well known in the industry. 
     The fifth preferred embodiment has conventional dock bumpers mounted directly to the dock face. As in the fourth preferred embodiment transport vehicles lower than the height of the bumpers may be lifted to the desired height by the use of a truck leveler or wheel riser ramps. A wide dock leveler of conventional construction but with a longer lip is mounted in a pit formed behind the dock wall. In the operative position the lip would reach over the dock wall and the bumpers to rest on the bed of the transport vehicle. When in the stored position the lip of the dock leveler is placed in a cavity formed in the pit behind the bumpers. This embodiment will work with dock levelers of other configurations including vertically stored with rigid or hinged lip, and horizontally stored linearly retracting lip. 
     This invention will be described in greater detail by referring to the attached drawing and the description of the preferred embodiment that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional side view of the first preferred embodiment of this invention illustrating the dock configuration and the hydraulic cylinders that operate the leveler and the lip. 
     FIG. 2 is a sectional side view of the first preferred embodiment of this invention with the leveler stored and the bumpers extended to limit the position of the transport vehicle. 
     FIG. 3 is a partial sectional side view of the first preferred embodiment of this invention with the leveler stored and the bumpers retracted to allow the leveler to raise unimpeded by the transport vehicle. 
     FIG. 4 is a perspective view of a bumper illustrating the beam and the bumper segments. 
     FIG. 5 is a sectional side view of the first preferred embodiment of this invention with the leveler raised and the lip partially extended. 
     FIG. 6 is a sectional side view of the first preferred embodiment of this invention with the leveler lowered so that the extended lip is resting on the bed of the transport vehicle, and the bumpers extended to limit the position of the transport vehicle. 
     FIG. 7 is a perspective view of the first preferred embodiment of this invention with the leveler stored and illustrating the bumper segments extended through the lip to limit the position of the transport vehicle. 
     FIG. 8 is a perspective view of the first preferred embodiment of this invention with the lip resting on the bed of the transport vehicle. 
     FIG. 9 is a sectional side view of the second preferred embodiment of this invention with the leveler in the operative position and the lip resting on the bed of the transport vehicle. 
     FIG. 10 is a sectional side view of the third preferred embodiment with bumpers mounted for vertical motion and a dock leveler having a hinged lip that stores within the bumper mounting brackets. 
     FIG. 11 is a sectional side view of the dock leveler of FIG. 10 with the dock leveler in an operative position resting on the bed of a transport vehicle that is not lower than the dock floor. 
     FIG. 12 is a sectional side view of the dock leveler of FIG. 10 with the dock leveler in an operative position resting on the bed of a transport vehicle that is lower than the dock floor. 
     FIG. 13 is a front view of the dock leveler in FIG.  10 . 
     FIG. 14 is a sectional side view of the dock leveler in FIG. 10 with the bumpers higher than the dock floor. 
     FIG. 15 is a sectional side view of the fourth preferred embodiment with fixed bumpers and a dock leveler having a hinged lip that stores within the bumper mounting brackets. 
     FIG. 16 is a sectional side view of the fourth preferred embodiment with fixed bumpers and an edge-of-dock leveler having a hinged lip that stores within the bumper mounting brackets. 
     FIG. 17 is a sectional side view of the fourth preferred embodiment with fixed bumpers and a dock leveler having a hinged lip that stores in a recessed cavity behind the bumpers. 
     FIG. 18 is a side view of fixed bumpers with a dock leveler having a lip that extends linearly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 through 6 the essential components of the first preferred embodiment of this invention will be described, it being understood that a typical dock leveler has other constructional features which need not be illustrated here. A loading dock is shown with a driveway approach  1 , a dock face  2 , and a dock floor  3  with a recessed pit  4 . A transport vehicle  5  is shown positioned in front of the dock. The dock leveler  10  is typically mounted in the pit  4 . It will be understood that this invention is not limited to any particular type of dock leveler, whether pit or vertically storing, or the mode of powering the deck and lip. The pit type is most common and will be used for purposes of explanation. 
     A frame  12  has horizontal members  13  and a vertical brace  14  both of which rest in the pit. The leveler frame also has stop blocks  15  and lip keepers  16  at the forward end of the horizontal members  13 . The leveler  10  has a deck  20  which has a top plate  21 , a bar  22  that forms a front header and a bar  23  that forms a rear header. A recessed ledge is formed at the front of the deck by a plate  24  and a spacer bar  25 . Beams  26  attached to the top plate, ledge and header bars provide structural strength to the assembly. The deck  20  is pivoted to the frame at pivot  27 . 
     A lip assembly  30  having a lip plate  31  and hinge tubes  32  is pivoted to the deck on a pin  28  inserted in hinge tubes  29  attached to the front header bar  21  and hinge tubes  32  attached to the lip plate  31 . The leveler is held horizontal in the stored position with the lip  30  in the pendant position and retained in the lip keepers  16 . The lip illustrated is of a configuration known in the industry by various names such as “Barrier Lip”, “Safety Lip”, “Run-Off Guard” Or “Post Office Lip”. The characteristic feature of each is that lip  31  has an upper portion  33  which extends above the deck  20  when the lip is pendent. The purpose is to prevent wheeled vehicles from inadvertently running off the edge of an open dock. When the lip  30  is extended, the “Run-Off Guard” portion  33  of the lip rests in the recess of the deck  20  formed by the plate  24  as shown on FIG.  6 . While preferred, the lip need not be a barrier type but may be simply one hinged at one end to the end of the deck, as is also conventional in loading docks. 
     As illustrated in FIGS. 7,  8  and  9 , slotted holes  34  are cut through the lip plate  31 . These will be explained herein for the first embodiment of this invention. 
     FIG. 1 illustrates the configuration of a typical hydraulic system used to operate the dock leveler. An arm  34  is attached to the lip  30 . Mounting brackets  36  and  39  are attached to the deck  20 , and mounting brackets  17  are attached to the frame  12 . A main cylinder  37  is pinned at one end to the brackets  36  and at the other end to the brackets  17 . When hydraulic fluid is supplied to the cylinder the deck  20  will be lifted. Similarly the lip cylinder  38  is pinned at one end to the lip arm  33  and at the other end to the deck bracket  35 . When hydraulic fluid supplied to either port of the cylinder  37  the lip  30  will be extended or retracted. A hydraulic system suitable for controlling the dock leveler of this type is described in U.S. Pat. No. 4,641,388. 
     FIG. 2 illustrates the configuration of the retractable dock bumpers when the dock leveler is in the stored position. A bumper assembly  40  has a beam  41  and bumper segments  42 . A plate  43  and mounting brackets  44  are attached to the rear of the bumper assembly. A resilient member  45  is attached between the front and rear sections of the bumper assembly  40  to absorb the impact force of the transport vehicle  5  backing into the dock. FIG. 4 illustrates a perspective view of the bumper assembly  40 . 
     Referring now to FIGS. 2 and 3, the bumper assemblies  40  are mounted for linear axial movement in the deck  20 . An opening for each bumper is cut into the front header bar  22  and guide brackets  50  and  51  are attached to the deck  20 . As illustrated in FIG. 2, the bumpers  42  are extended outward and project through the lip to block rearward movement of the vehicle even when the lip is in the pendant position. A cylinder anchor bracket  53  is also attached to the deck  20 . A hydraulic cylinder  55  having an extendable rod  56  is pinned at one end to the anchor bracket  53  and at the other end to the brackets  44  on the bumper assembly  40 . The rod  56  can be extended or retracted by supplying hydraulic fluid to either of the two ports on the cylinder  55 . 
     FIGS. 3,  5  and  6  show the condition of the bumpers at different phases of leveler deployment. FIG. 3 illustrates the leveler stored and the bumpers  42  retracted to allow the leveler to raise unimpeded by interference with the transport vehicle. FIG. 5 illustrates the deck  20  raised with the lip  30  partially extended. FIG. 6 illustrates the leveler in the operative position with the lip  30  extended and supported by the bed of the transport vehicle. The bumpers  40  are extended to limit the position of the transport vehicle  5 . 
     Alternatively, the bumper can be mounted to the end of the deck to always protrude through the slots in the lip whenever the lip is in the pendant position such as illustrated in FIGS. 2 and 7. This will protect the deck and the lip. When the lip is raised the bumper will still protrude beyond the end of the deck as shown in FIG. 6 to protect the deck when the lip is supported by the bed of the parked vehicle. This is a modification of the first preferred embodiment to simplify the structure yet still protect the deck and lip at various stages of operation. In this configuration, the bumper may be resiliently mounted to the deck to absorb shock loads. 
     FIGS. 7 and 8 are perspective views of the first preferred embodiment which better illustrate the relationships of the bumper segments  41  and the slotted openings  34  in the lip plate  31 . The hydraulic circuit that controls the extension and retraction of the bumper beams will preferably be designed so that when hydraulic pressure is applied to the main cylinder  37  then it is also applied to the retract port of the bumper cylinder  55 . Thus whenever the weight of the deck  20  is supported by the hydraulic cylinder  37 , the bumpers will then be retracted. When there is no hydraulic pressure applied to the main cylinder  37  then the deck must be supported either in the stored position by the lip keepers  17  or in the operative position by the lip resting on the bed of the truck. Therefore the bumpers may be extended whenever there is no hydraulic pressure exerted on the main cylinder  37 . Such an hydraulic circuit is not shown but will be readily understood by those skilled in this art as easily implemented. 
     FIG. 9 illustrates a second preferred embodiment of this invention. The dock leveler  210  is of a similar configuration to the first embodiment except that the deck assembly  220  does not have hinge tubes to carry a pivoting lip. The lip  60  is mounted to extend and retract linearly along the top of the deck  220 . The dock leveler is shown with the lip  60  is fully extended and supported by the bed of the transport vehicle  5 . The bumpers  40  are extended to limit the position of the transport vehicle  5 . 
     A third preferred embodiment of this invention is illustrated by FIGS. 10 through 14. FIG. 10 shows a dock leveler  110  mounted in a conventional pit  4 . The deck  120  has a conventional hinged lip  130  supported by lip keepers  16 . A guide track  90  is mounted to the dock face  2  and may be supported by a bracket  91  attached to the floor of the pit  4 . A bumper carriage  95  is mounted in the guide track  90 . The bumper carriage  95  has vertical plates  96  that carry conventional a dock bumper  98 . The bumper carriage  95  is biased upward by springs  97  so that the top of the bumper  98  is at a suitable height for the highest transport vehicle. The lip  130  has a lip plate  131  with slotted openings  134  that allow the lip to fit in the cavities formed by the vertical support plates  96 . This is illustrated by FIG. 13, a partial front view of the dock with a section cut through the left bumper to show the vertical plates  96  and slotted openings  134 . Thus the lip  130  can be stored behind the bumpers and the width of the lip is not limited by the spacing of the bumpers. A transport vehicle may impact the bumpers with very high force when the dock leveler is stored. The bumper carriage may be constructed so that excessive force on the bumper will cause the bumper carriage to deflect until it contacts the dock leveler and transfer force through the dock leveler to the dock floor. 
     FIG. 11 illustrates the dock leveler with the lip  130  extended and supported by the bed of the transport vehicle  5  which is higher than the top of the bumper  98 . FIG. 12 shows a transport vehicle with a bed height lower than the dock floor  3 . When the lip  130  is resting on the bed of the transport vehicle it also rests on top of the bumper  40  and depresses it to the proper height. Thus this embodiment will accommodate transport vehicles of varying heights. FIG. 14 shows the dock leveler installed in a low dock with the top of the bumpers  98  above the dock floor  3  to accommodate transport vehicles that are higher than the dock floor. This configuration of bumper mounting will work with dock levelers of all configurations including vertically stored with rigid lip, horizontally stored with pivoting lip or linearly retracting lip. 
     A fourth preferred embodiment of this invention is illustrated in FIGS. 15 and 16. It is similar to the third preferred embodiment except that the dock bumpers  98  are mounted to vertical plates  97  that are mounted directly to the dock face  2 . FIG. 15 shows the bumpers with a pit leveler and FIG. 16 shows the bumpers with an edge-of-dock leveler mounted directly to the dock face  2 . With this embodiment a dock leveler with a lip of any width may be used to service transport vehicles that are not lower than the top of the bumpers  98 . Lower transport vehicles may be raised to floor level with a truck leveler or wheel ramps. 
     A fifth preferred embodiment of this invention is illustrated by FIGS. 17 and 18. FIG. 17 shows conventional dock bumpers  98  mounted directly to the dock face  2 . A pit  100  formed behind the dock face forms a wall  101  to provide structural support to the bumpers. A recessed cavity is formed in the front of the pit to store the lip when it is retracted. A dock leveler  110  of conventional construction is mounted in a recessed pit and in the operative position the end of the lip plate  130  is supported by the bed of the transport vehicle  5 . As in the case of the fourth embodiment, this embodiment allows a dock leveler with a lip of any width to be used to service transport vehicles that are not lower than the top of the bumpers  98 . Lower transport vehicles may be raised with a truck leveler or wheel ramps. 
     FIG. 18 shows a dock of the same configuration as FIG. 17 except the dock leveler  210  has a lip  60  which is retracted and extended linearly. Thus the pit does not require the deep recess to store the lip. 
     While this invention has been described with respect to the preferred embodiments, it will be apparent to those skilled in this art that modifications of this invention may be practiced without departing from the scope of the invention. For example the bumpers may be extended and retracted by mechanical linkages or electric or pneumatic actuators rather than hydraulic cylinders. Similarly, the function of the resilient member  45  may be achieved by fitting a relief valve to the bumper cylinder  55  so that the energy of impact is dissipated through the hydraulic fluid.

Technology Category: 7