GB2066768A

GB2066768A - Front-of-dock dockboard

Info

Publication number: GB2066768A
Application number: GB8100245A
Authority: GB
Original assignee: KELLEY CO Inc
Current assignee: KELLEY CO Inc
Priority date: 1980-01-07
Filing date: 1981-01-06
Publication date: 1981-07-15
Also published as: MX151567A; BR8100055A; DE3100240A1; AU6601481A; FR2473023A1; NL8100035A; ZA8112B; AU526234B2; NL183932C; FR2473023B1; DE3100240C2; CA1141904A; GB2066768B; JPS56103660A; NL183932B; AR223749A1

Abstract

A dockboard to be attached to the front of a loading dock includes a plate (24), side edges of which are pivotally connected to guide bars (21) that are movable vertically within guideways (20). The bars are mounted for vertical movement within guides (14), and the bars and deck plate (24) are partially counterbalanced to an upper position by a counterweight mechanism (28) that is connected to the bars through a chain drive. The deck plate is stored in a vertical position below deck level and, is lifted to a raised position above dock level, pivoted to a substantially horizontal position and then lowered into engagement with the bed (3) of a carrier located in front of the dock. The pivotal connection between the deck plate and the guide bars enables the deck plate to tilt diagonally as a load moves across the deck plate. <IMAGE>

Description

SPECIFICATION Front-of-dock dockboard This invention relates to a dockboard to be mounted on a loading dock.

United States Patent 3,596,303 is directed to a dockboard to be mounted on the front of a loading dock. As described in that patent, a deck plate or ramp is normally stored in a vertical position in front of the loading dock and the side edges of the deck plate are pivotally connected to guide bars which are mounted for movement within uideways on the front surface of the dock.

When a truck or carrier pulls into position in front of the loading dock, the deck plate or ramp is manually lifted upwardly to an above-dock-level position, is pivoted about the guide bars to a substantially horizontal position and then is lowered downwardly until it engages the dock and the bed of a carrier.

As shown in the aforementioned patent, to aid in manually lifting the deck plate to the upper vertical position, a counterweight system is employed in which a series of weights are connected to the lower ends of the guidebars through a cable-pulley arrangement.

As the deck plate or ramp in the abovedescribed dockboard is relatively short in a frontto-rear dimension, and as the ramp is normally provided with a hump or ridge which extends from side-to-side, the deck plate is relatively rigid and inflexible.

In most loading operations, the bed of the truck will not be parallel with the upper surface of the loading dock, but instead will normally be slightly tilted relative to the dock due to an uneven distribution of the load in the truck or the slope of the drive, etc. Thus, the entire forward edge of the ramp, in most cases, will not be seated on the truck bed. When a lift truck passes over the deck plate in travelling between the dock and the truck bed, the deck plate, due to its relatively stiff and inflexible nature, will not bend or deflect under the weight of the lift truck passing thereon, with the result that the deck plate can be subjected to severe stress.

The invention is directed to an improved frontof-dock dockboard which has a smooth and reliable operating action and includes a mechanism to enable the deck plate or ramp to tilt to compensate for non-alignment between the truck bed and the upper surface of the dock. More specifically, the dockboard of the invention includes a deck plate or ramp having its side edges pivotally connected to guidebars which are slidable within guideways formed in the upper edge portion of a generally rectangular frame. The frame, in turn, is mounted for vertical movement within guides mounted on the front surface of the dock.

To aid in manually lifting the deck plate from the lower vertical storage position to an upper position, a counterbalancing system is utilized in which a series of counterweights are connected to the frame through a synchronized sprocket and chain drive.

The deck plate is normally stored in the vertical position below dock level and after a truck or carrier pulls into position in front of the dock, the deck plate is manually lifted to a raised position above dock level, then pivoted to a substantially horizontal position and lowered by gravity into engagement with the bed of the truck and the loading dock. When the truck moves away from the dock after the loading operation is completed, the deck plate will swing to a generally vertical position and the frame will lower by gravity to move the deck plate to the lower storage position.

As the deck plate is pivoted to the guide bars which are mounted for sliding vertical movement with respect to the rectangular frame, the deck plate can tilt in a diagonal direction, as a lift truck passes over the deck plate, to compensate for misalignment between the truck bed and the upper surface of the dock. Because the deck plate is capable of tilting, the forward edge of the deck plate, if not in continuous contact with the truck bed, will be moved into continuous contact with the truck bed, as the weight of the lift truck is applied to the forward edge. This substantially reduces the stress to which the deck plate, and its supporting structure, is subjected during service.

The synchronized chain and sprocket drive, which connects the counterbalancing weights with the rectangular frame, prevents the frame from cocking or racking as it is moved vertically within the guides, thereby providing smoother vertical movement and enabling the deck plate to be more easily lifted to the upper position.

Other objects and advantages will appear in the course of the following description.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which; Fig. 1 is a front elevation of the dockboard of the invention as mounted on a loading dock with parts broken away in section; Fig. 2 is a vertical section of the dockboard as mounted on the loading dock and showing the deck plate in the lower storage position; Fig. 3 is a view similar to Fig. 2 showing the deck plate in the upper raised position; Fig. 4 is a view similar to Fig. 2 showing the deck plate in the horizontal cross traffic position where it spans the gap between the loading dock and the truck bed; Fig. 5 is an enlarged fragmentary top view of the dockboard with parts broken away; Fig. 6 is an enlarged horizontal section showing the shaft mounting for the counterbalancing mechanism; Fig. 7 is a view taken along line 7-7 of Fig. 6; and Fig. 8 is a fragmentary enlarged front elevation showing the mounting of the rectangular frame to the guide structure.

The drawings illustrate a dockboard 1 which is secured to the front surface of a loading dock 2, and in use, is adapted to span the gap between the upper surface of the loading dock and the bed 3 of a truck or carrier located in front of the dock.

The dockboard 1 includes a supporting structure 4 which is mounted in the front wall 5 of the dock 2. The supporting structure consists of a pair of generally rectangular vertical beams 6 which are located along the sides of the dockboard and the upper ends of the beam 6 are connected together by a horizontal angle 7. As best shown in Fig. 2, the horizontal leg of the angle 7 is mounted flush with the upper surface 8 of the dock, while the vertical leg of the angle 7 is mounted to the vertical front face 5 of the dock.

Bumpers 9 are mounted on the forward faces of the vertical beams 6 and upper plates 10 are bolted to the upper surface 8 of the dock and extend forwardly over the upper ends of the respective beams 6. Plates 10 are provided with downwardly bent edge portions 11 which overhang the upper portion of the respective bumper 9 and prevents the truck bumper from overriding and hanging up on the bumpers 9.

The supporting structure 4 also includes a pair of supports 12 which extend downwardly from the beams 6, and a front plate 13 is secured between the supports 12.

A pair of spaced vertical guide members 14 are secured to the inner surface of each beam 6 and the corresponding supports 12 and each pair of guide members 14 defines a vertical guideway 15.

A generally rectangular frame 16 is mounted for vertical movement within the guideway 1 5, and as best illustrated in Figs. 1 and 8, the frame includes an upper generally rectangular beam 17, a lower horizontal, generally rectangular beam 18 and a pair of side bars 19, which connect the ends of the beams 17 and 18. The side bars 19 are mounted for sliding movement within the guideways 1 5 to thereby permit the frame 16 to move vertically relative to the loading dock 2.

As best illustrated in Fig. 5, generally boxshaped guide members 20 are mounted in the upper beam 17 adjacent the side edges of the rectangular frame 16, and guide bars 21 are mounted for sliding vertical movement within the guides 20. To limit the downward movement of the guide bars 21 with respect to the guides 20, a stop block 22 is mounted on the upper end of each guide bar and is adapted to engage the upper end of the guide 20 to limit the downward movement of the guide bar 21 relative to the guide 20. Similarly, upward movement of each guide bar 21 within the guide 20 is limited by a pin 23 which extends through an opening in the lower end of the guide bar.

A generally rectangular deck plate or ramp 24 is pivotally connected to the upper ends of the guide bars 21. To provide the pivotal connection, each side edge of the deck plate is provided with a pair of lugs 25 which are connected to the upper end of the respective guide bar 21 by pins 26. This pivotal connection permits the deck plate 24 to be pivoted relative to the rectangular frame 16.

The forward edge of the deck plate is biased downwardly so that the deck plate will normally assume a generally vertical storage position, as shown in Fig. 2. The deck plate can be most conveniently biased to this position by locating the pivotal connection between the lugs 25 and the pins 26 at a position to the rear of the fore-to-aft center of gravity of the deck plate. Thus, when unrestrained, the deck plate falls by gravity to the generally vertical storage position, as shown in Fig. 2. Alternately, springs or other biasing means can be used to urge the deck plate to the vertical position.

To aid in manually lifting the deck plate from the vertical storage position shown in Fig. 2, to the raised or elevated position shown in Fig. 3, a hand hole 27 is formed in the rear edge of the deck plate.

A ccarinterbalancing system is incorporated to partially counterbalance the weight of the deck plate 24 and frame 16, in order to reduce the manual force necessary to raise the deck plate. In this regard, a series of counterbalancing weights 28 are located adjacent the front wall of the dock, and chains 29 are connected to the ends of the weights 28 and pass upwardly over sprockets 30 and are dead-ended on lugs 31 located adjacent the ends of the lower beam 18 of the rectangular frame 16. With this construction the weights 28 will serve to partially counterbalance the weight of the frame 16 and deck plate 24 to enable the deck plate to be lifted with a lesser force.

The chains 29 which connect the counterweights and the deck plate are synchronized so that they operate in unison to thereby prevent the rectangular frame from jamming within the guideways 15, as it is raised and lowered. As best illustrated in Fig. 6, each sprocket 30 is mounted on a horizontal shaft 32 and each shaft 32 is journalled for rotation within a pair of bearings 33. Each bearing 33 is mounted within a V-shaped recess 34 in a bearing plate 35 and the bearing plates 35 are sandwiched between plates 36 and 37 which extend forwardly from the horizontal leg of the angle 7. The plates 35, 36 and 37 are connected together by bolts 38.

In addition, spacer sleeves 39 and 40 are mounted on the shaft and maintain the sprockets 30 in proper position on the shafts 32.

To drive the chains 29 in synchronization, the inner ends of the shafts 32 are connected within the respective ends of a tube 41 by pins 42. With this construction, the shafts 32 will rotate in synchronization as the counterweights move vertically relative to the dock. The pins 42 extend through aligned slots 43 formed in the respective ends of the tube 41, and collars 44 are secured around the ends of the tube to prevent expansion of the slots. The slots permit limited longitudinal movement of the shafts 32 and compensate for possible misalignment in the installation of the dockboard.

To aid in moving the frame 16 vertically in the guideways 15, rollers 45 are mounted on roller shafts 46 attached to the lower portions of the side bars 19 and the rollers are adapted to ride against the front surfaces of the respective rear guides 14. As the center of gravity of the deck plate is located forwardly of the plane of the frame 16, the gravity moment will tend to pivot the frame forwardly about the lower ends of bars 19, and the rollers 45 thereby function to provide a smooth non-jamming movement of the frame 16 within the guideways 1 5.

The ramp or deck plate 27 is stored in the vertical position, as shown in Fig. 2, with the rear or, upper edge of the deck plate located slightly below the upper surface of the dock. The truck 3 or other carrier, backs toward the dock until the bed of the truck engages the bumpers 9. To place the deck plate in operation position, the operator pulls upwardly on the deck plate through use of the hand hole 27, moving the deck plate to an upper vertical position, as shown in Fig. 3. In this position, the lower edge of the deck plate is located above the bed of the truck, so that the deck plate can then be pivoted to a generally horizontal position.After pivoting the deck plate to the horizontal position, the deck plate falls by gravity, with the side members 19 of the rectangular frame 1 6 sliding downwardly within the guideways 1 5, until the rear edge of the deck plate engages the upper surface of the dock and the forward edge of the deck plate engages the bed of the carrier 3.

As previously mentioned, the bed of the carrier, in many instances, will not be parallel to the upper surface of the dock, but will be slanted or tilted relative thereto. Thus, when the deck plate moves by gravity to the cross traffic position, only a portion of the forward edge of the deck plate may be engaged with the bed 3 of the carrier.

During the loading operation, a lift truck may move across the deck plate causing a forward-torear impact. When the weight of the lift truck moves over the forward edge of the deck plate, which is on the bed of the carrier, the sliding connection between the guide bars 21 and the guides 20 will permit the deck plate to tilt in a diagonal direction to bring the entire forward edge of the deck plate into engagement with the bed of the carrier, as the lift truck passes thereover. This pivotal action substantially reduces the stress on the deck plate which would occur if a portion of the deck plate is out of contact with the bed as the lift truck moves thereover.

The sliding connection between the frame 16 and the dock permits the deck plate 27 to accommodate substantial variances in height between the upper surface of the dock and the bed 3 of the carrier. For example, if the truck is unloading, the bed of the carrier may raise substantially as the load is removed from the truck bed, while in the other case, the bed of the truck may lower due to a lift truck moving across the bed or as additional load is applied to the bed. In either case, the sliding connection will enable the plate or ramp to follow these variations in relative height between the bed and the dock.

When the loading operation has been completed, the truck pulls away from the dock and due to the fact that the deck plate 24 is nose heavy, the forward edge of the deck plate will pivot downwardly. To cushion the impact, a pair of resilient bumpers 47 are mounted through bolts 48 and spacers 49 to the upper beam 17 of frame 1 6. As the weight of the deck plate is greater than the counterbalancing force of weights 28, the deck plate and the frame will move downwardly by gravity until the lower ends of the guide bars 19 bottom out in the guideways 15.

The dockboard of the invention is an inexpensive unit which can be installed on the front surface of the dock without alteration of the dock.

The sliding connection between the guide bars 21 and the guides 20 permit the deck plate or ramp to pivot diagonally to compensate for tilting misalignment between the truck bed and the upper surface of the dock. By permitting the deck plate to tilt as a lift truck or other load passes thereon, stresses in the deck plate are substantially reduced.

The use of the rectangular sub-frame 1 6 maintains accurate alignment between the sides of the deck plate to provide a smoother operation.

The chain and sprocket drive provide synchronization between the counterbalancing forces at opposite sides of the frame and aids in preventing cocking or jamming of the frame within the guideways. In addition, the rollers 45 also function to insure smooth vertical movement of the rectangular frame.

Claims

1. A dockboard to be mounted on a loading dock having an upper surface and a front wall, comprising a generally rectangular frame disposed adjacent the front wall of the dock, guide means for mounting the frame for vertical movement relative to the dock, a pair of guideways disposed on said frame adjacent the sides thereof, a guide member mounted for sliding vertical movement within each guideway, and a deck plate pivotally connected to the upper ends of the guide members, said deck plate being liftable vertically from a first vertical lower storage position in which the deck plate is disposed generally vertically along the front wall of the dock to a second higher vertical position whereat the lower end of the deck plate is above the deck of a carrier disposed adjacent the front wall of the dock so that the deck plate can be pivoted about said guide members to a generally horizontal position and lowered to a cross traffic position to span the distance between the dock and the bed of said carrier with the rear end of the deck plate supported on the dock and the forward end of the deck plate supported on the carrier, the forward end of the deck plate being biased downwardly so that the deck plate will assume a generally vertical position when the carrier is removed from its location adjacent the front wall of the dock and said deck plate will descend by gravity to said storage condition, the pivotable connection of said deck plate to the guide members permitting the deck plate to tilt as a load passes over the deck plate when in the cross traffic position.

2. The dockboard of claim 1 , wherein said guideways are disposed along the upper edge of said frame.

3. The dockboard of claim 1 , wherein said frame includes an upper frame member, a lower frame member and a pair of side members connecting said upper and lower frame members, said guide means comprising a pair of vertical tracks mounted on said dock, said side members being slidable within the respective tracks.

4. The dockboard of claim 1, and including counterbalancing means connected to the frame for partially counterbalancing the weight of the deck plate.

5. The dockboard of claim 4, wherein said counterbalancing means comprises a weight, and a pair cf chains interconnecting the weight and the side edges of said frame.

6. The dockboard of claim 5, and including a pair of rotatable sprockets mounted in spaced relation adjacent the upper edge of the dock, each sprocket being engaged with a chain, one end of each chain connected to said weight and the opposite end of each chain connected to the lower portion of said frame.

7. The dockboard of claim 6, and including a shaft to carry each sprocket, and means for interconnecting the shafts to provide synchronous movement of said chains as the weights move vertically.

8. The dockboard of claim 3, wherein each track is composed of a pair of vertical walls spaced in a front-to-rear direction, said dockboard including a guide roller mounted on each side of the frame and disposed to ride against the forward surface of the rear vertical wall of each pair.

9. A dockboard to be mounted on a loading dock having an upper surface and a front wall, comprising a supporting structure mounted on the front wall of the dock, a generally rectangular frame disposed along the front wall of the dock, guide means on the supporting structure and disposed adjacent the front wall of the dock for mounting the frame for vertical movement, said frame comprising an upper frame member, a lower frame member and a pair of side members connecting said upper and lower members, said side members mounted for sliding movement in said guide means, a generally rectangular deck plate having a forward edge and a rear edge, and means for pivotally connecting the side edge portions of the deck plate to the upper portion of said frame, said deck plate being liftable vertically from a first vertical lower storage position in which the deck plate is disposed generally vertically along the front wall of the dock to a second higher vertical position whereat the lower end of the deck plate is above the deck of a carrier disposed adjacent the front wall of the dock so that the deck plate can be pivoted about said guide members to a generally horizontal position and lowered to a cross traffic position to span the distance between the dock and the bed of said carrier with the rear end of the deck plate supported on the dock and the forward end of the deck plate supported on the carrier, the forward end of the deck plate being biased downwardly so that the deck plate will assume a generally vertical position when the carrier is removed from its location adjacent the front wall of the dock and said deck plate will descend by gravity to said storage condition, the pivotal connection of said deck plate to the guide members permitting the deck plate to tilt as a load passes over the deck plate when in the cross traffic position.

10. The dockboard of claim 9, and a guide element mounted on the lower portion of each side member of the frame, said guide means including a guideway defined by a pair of vertical walls disposed in spaced forward-to-rear direction on said dock, each element disposed to ride against the forward surface of the rear vertical wall of each pair.

1 The dockboard of claim 10, wherein said guide elements are rollers.

12. A dockboard to be mounted on a loading dock, said dock having an upper surface and a front wall, comprising a supporting structure mounted on the front wall of the dock, a generally rectangular frame disposed adjacent the front wall of the dock, guide means for mounting the frame for vertical movement on said supporting structure, a deck plate having a front edge and a rear edge and a pair of side edges, means for pivotally connecting the side edge portions of the deck plate to the upper portion of the frame, counterweight means disposed along the front wall of the dock, a pair of chains, a pair of sprockets mounted at the upper end of the supporting structure and engaged with the respective chains, one end of each chain being connected to said counterweight means and the opposite end of each chain being connected to the lower portion of said frame, a shaft to carry each sprocket, said shafts being in general axial alignment, and a connecting member connecting the adjacent ends of the shafts together whereby the chains will operate in synchronization as the counterweight means moves vertically ta prevent skewing of said frame in said guide means.

13. The dockboard of claim 12, and including means for permitting limited relative axial movement between each shaft and the connecting member.

14. A dockboard to be mountea on a loading dock, substantially as hereinbefore described, with reference to, and as shown in the accompanying drawings.