Title:
SAFETY LOCK MECHANISM FOR A DOCKBOARD
United States Patent 3858264


Abstract:
A safety lock mechanism for a dockboard to prevent lowering of the ramp and eliminating the possibility of gaining access to a building through the space between the lowered ramp and a closed overhead door. The dockboard includes a ramp hinged at its rear edge to the loading dock and a lip is hinged to the front edge of the ramp and is movable between a downwardly hanging, pendant position and an extended position. Cross traffic legs are pivoted to the under surface of the front edge of the ramp and engage fixed legs on the supporting structure of the dockboard to support the ramp in either a dock level position or in a series of below dock level positions. The cross traffic legs are coupled to the lip so that on movement of the lip from the pendant to the extended position, the cross traffic legs will be retracted. The safety lock mechanism includes a flange or stop which is pivotally connected to each fixed leg, and when the cross traffic leg is supported on the fixed leg the flange extends vertically to the rear of the cross traffic leg, to thereby prevent the cross traffic leg from being retracted when the ramp is at a dock level position. In the event that the ramp is just slightly above dock level when a truck pulls away from a dock, the lip will fall to its pendant position and the cross traffic legs will pivot forwardly into engagement with the stop, thereby pivoting the stop forwardly and enabling the cross traffic legs to engage the fixed legs.



Inventors:
Kuhns, Robert C. (Elm Grove, WI)
Metro, Robert D. (Brookfield, WI)
Application Number:
05/420446
Publication Date:
01/07/1975
Filing Date:
11/30/1973
Assignee:
KELLY COMPANY, INC.
Primary Class:
International Classes:
B65G69/28; (IPC1-7): B65G11/00
Field of Search:
14/71,72
View Patent Images:
US Patent References:
3606627N/A1971-09-21Potter
3530488DOCKBOARD1970-09-22Beckwith
3368229Adjustable mechanical dockboard with improved safety legs1968-02-13Pfleger
3299456Dockboard1967-01-24Dieter
3203002Adjustable dockboard with counterbalancing extension lip1965-08-24McGuire
3137017Adjustable dockboard1964-06-16Pfleger



Primary Examiner:
Byers Jr., Nile C.
Attorney, Agent or Firm:
Andrus, Sceales, Starke & Sawall
Claims:
We claim

1. In a dockboard having a supporting structure and a ramp structure with the rear end of the ramp structure being hinged to the supporting structure, a lip hinged to the forward edge of the ramp structure and movable between a downwardly hanging pendant position and an outwardly extending position in which the lip forms an extension of the ramp structure, a movable leg mounted for movement on one of said structures between a supporting position and a non-supporting position, a fixed leg connected to the other of said structures and adapted to be engaged by said movable leg when the movable leg is in the supporting position to thereby support the ramp structure at a given inclination, the improvement comprising a safety stop member pivotally connected to the fixed leg and having an obstructing position wherein said stop member prevents movement of the movable leg to the non-supporting position, pivotal means for mounting said stop member for forward pivotal movement from said obstructing position to a non-obstructing position where the stop member will not obstruct movement of said movable leg to the supporting position, and means to bias the stop member rearwardly to the obstructing position, said stop member when in the obstructing position preventing rearward movement of the movable leg to the non-supporting position when the ramp structure is in a generally horizontal dock level position and thereby preventing lowering of the ramp structure, said stop member being disposed to be engaged by the movable leg as the movable leg moves from the non-supporting position toward the supporting position with the ramp structure slightly above dock level, whereby said movable leg pivots the stop member to said non-obstructed position to enable the movable leg to move to the supporting position.

2. The dockboard of claim 1, and including stop means to prevent rearward pivotal movement of said stop member beyond said obstructing position.

3. The dockboard of claim 1, wherein the stop member when in the obstructing position is located to the rear of the movable leg.

4. The dockboard of claim 1, wherein the movable leg is pivotally connected to the ramp structure and the fixed leg is secured to the supporting structure.

5. The dockboard of claim 3, wherein said pivotal means is connected to the upper end portion of the fixed leg.

6. The dockboard of claim 2, wherein the stop member is generally L-shaped and includes a first flange and a second flange, said first flange being located to the rear of the movable leg when the stop member is in the obstructing position, said stop means comprising an abutment on said fixed leg and disposed to be engaged by said second flange to provide a stop and prevent rearward movement of the first flange beyond the obstructing position.

7. The dockboard of claim 1 and including means for coupling the movable leg to the lip whereby movement of the lip from the pendant to the extended position will move the movable leg from the supporting position to the non-supporting position.

8. In a dockboard having a supporting structure and a ramp with the rear end of the ramp being hinged to the supporting structure, a lip hinged to the forward edge of the ramp and movable between a downwardly hanging pendant position and an outwardly extending position in which the lip forms an extension of the ramp, a movable leg mounted for pivotal movement on the ramp between a supporting position and a retracted non-supporting position, a fixed leg connected to the supporting structure and adapted to be engaged by said movable leg when the movable leg is in the supporting position to thereby support the ramp at a given inclination, means for coupling the movable leg to the lip whereby movement of the lip from the pendant to the extended position will move the movable leg from the supporting position to the retracted non-supporting position, the improvement comprising a safety stop member pivotally connected to the fixed leg and having a generally vertical obstructing position wherein said stop member prevents pivotal movement of the movable leg to the non-supporting position, hinge means for mounting said stop member for forward pivotal movement from said obstructing position to a generally horizontal non-obstructing position where the stop member will not obstruct movement of said movable leg to the supporting position, and means to bias the stop member rearwardly to the obstructing position, said stop member when in the obstructing position being located to the rear of the movable leg and preventing rearward movement of the movable leg to the non-supporting position when the ramp is in a generally horizontal dock level position and thereby preventing lowering of the ramp, said stop member being disposed to be engaged by the movable leg as the movable leg pivots from the retracted non-supporting position toward the supporting position with the ramp slightly above dock level, whereby said movable leg will pivot the stop member to said non-obstructed position to enable the movable leg to move to the supporting position.

Description:
BACKGROUND OF THE INVENTION

An adjustable mechanical dockboard, as shown in U.S. Pat. No. 3,137,017 includes a ramp which is hinged at its rear edge to the dock and a lip is hinged to the front edge of the ramp and is movable between a downwardly hanging, pendant position and an outer extended position where it forms an extension to the surface of the ramp.

Mechanical dockboards can also include cross traffic legs, as shown in U.S. Pat. No. 3,137,017 which are hinged to the undersurface of the forward edge of the ramp and are adapted to engage fixed supports or legs mounted on the supporting structure to support the ramp in either a dock level position or a series of below dock level positions. The cross traffic legs can be coupled to the extension lip in a manner that pivotal movement of the lip from the pendant to the extended position will cause the cross traffic legs to move to a retracted position.

In many cases the dockboards are installed in a dock located within a doorway in a building which is adapted to be closed by an overhead door, which when closed, will engage the upper surface of the ramp. If the lip is coupled to the cross traffic legs, pivoting the lip manually outwardly toward the extended position will cause the cross traffic legs to retract and the ramp can then be lowered below the closed overhead door. By this method access can be obtained to the building through the space between the lowered ramp and the closed overhead door.

To prevent the ramp from being lowered when the ramp is at a dock level position, it has been proposed, as disclosed in U.S. Pat. No. 3,137,017 to attach downwardly extending flanges or stops to the lower ends of the cross traffic legs, and when the ramp is in the dock level position, the flanges overlie the front faces of the fixed supports or legs, thereby restraining the cross traffic legs against rearward displacement and making it impossible to lower the ramp unless the ramp is first raised high enough to permit the flanges to clear the top of the fixed supports, and this cannot be done with the overhead door in the closed position.

While the use of the safety flanges prevents lowering of the ramp and unauthorized access into the building, it has been found that if a truck or carrier pulls away from the dock when the ramp is at a dock level position or just slightly above dock level, the flanges will not clear the fixed supports and will engage the rear surface of the supports thereby preventing the cross traffic legs from moving to the upright supporting position and engaging the fixed supports. This condition may present a hazard. To an operator the ramp may appear to be supported by the cross traffic legs, but when a lift truck or other load is imparted to the ramp, the ramp can fall and damage either the dockboard or the lift truck.

SUMMARY OF THE INVENTION

The present invention is directed toward an improved safety locking mechanism for a dockboard which prevents lowering of the ramp from the dock level position when the overhead door is closed and eliminates the possibility of an intruder gaining access to the building through the space between the lowered ramp and the closed overhead door. In accordance with the invention, the safety lock mechanism includes a stop member which is pivotally connected to the fixed support or leg and the stop member extends vertically and is located to the rear of the respective cross traffic leg when the leg is supported on the fixed support in the dock level position. The stop member is mounted for pivotal movement between the vertical stop position and a forward horizontal position, and when in the vertical position, the stop member will prevent the cross traffic leg from being retracted, thereby preventing the ramp from being lowered unless the ramp is first raised high enough to permit the cross traffic legs to clear the top of the flange.

In normal operation of the dockboard, if the ramp is at dock level or slightly above dock level when the truck pulls away from the dock, the lip will fall to its pendant position and the cross traffic leg will be pivoted forwardly against the stop, thereby pivoting the stop forwardly to a generally horizontal position to enable the cross traffic legs to seat on the fixed supports and thereby support the ramp against further downward movement.

The safety lock mechanism prevents the ramp from being lowered from the dock level position unless the ramp is initially raised high enough to permit the cross traffic legs to clear the top of the stop. As the ramp cannot be raised with the overhead door in the down or closed position, the safety mechanism thereby will prevent lowering of the ramp when the overhead door is closed.

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

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a dockboard incorporating the safety lock mechanism of the invention.

FIG. 2 is a side elevation showing the cross traffic legs resting on the fixed support and the ramp in a dock level position.

FIG. 3 is a view similar to FIG. 2 showing the safety stop being pivoted forwardly on return movement of the cross traffic legs;

FIG. 4 is a section taken along line 4--4 of FIG. 2; and

FIG. 5 is an enlarged side elevation of the safety stop.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a dockboard 1, similar to that disclosed in U.S. Pat. No. 3,137,017, which is adapted to be mounted in a pit or depression in a loading dock. The dockboard 1 includes a frame 2 or supporting structure and a ramp 3 is hinged at its rear edge to the frame 2. The ramp 3 is adapted to be biased upwardly to an inclined position by a spring assembly 4. One end of the spring assembly 4 is connected to the supporting structure 2, while the opposite end of the spring assembly is connected to a lever arm 5. The upper end of the lever arm carries a roller that rides on a cam plate 6 mounted on the lower surface of the ramp 3.

The force of the spring assembly 4, if unrestrained will act to pivot the lever arm 5 rearwardly, causing the upper end of the arm to ride against the cam plate 6 to thereby pivot the ramp to the upwardly inclined position, as shown in FIG. 1.

The ramp can be held in any desired position by means of a holddown mechanism 7, as disclosed in U.S. Pat. No. 3,137,017. The holddown mechanism 7 is a uni-directional device which prevents the upward movement of the ramp unless released, while permitting free downward movement of the ramp.

As illustrated in FIG. 1, an extension lip 8 is pivoted to the forward edge of the ramp. The lip 8 and ramp 3 carry an aligned hinge tube 9 which receives a hinge pin 10. With this construction the lip can be pivoted from the downwardly hanging pendant position to an extended position in which the lip is an extension to the surface of the ramp 3. Engagement of the rear edge of the lip with the forward surface of the ramp prevents the lip from moving beyond the extended position in which it is generally flush with the ramp.

The dockboard 1 also includes a lip lifting and latching mechanism 11 similar to that disclosed in U.S. Pat. Nos. 3,137,017 and 3,177,332. The lifting and latching mechanism serves to automatically move the lip from the pendant or downwardly hanging position to the extended position as the ramp is moved upwardly from the horizontal to the upwardly inclined position. The lip lifting and latching mechanism 11 also serves to latch or hold the lip in the partially extended position.

In normal operation the upper surface of the ramp 3 will be generally horizontal or flush with the upper surface of the dock. As a truck backs toward the dock the operator will release the hold down mechanism 7 through operation of a manually operated cable, thereby enabling the spring assembly 4 to pivot the ramp to the upwardly inclined position. As the ramp moves upwardly, the lip lifting and latching mechanism 11 will move the lip 8 to the partially extended position and latch the lip in this position. With the ramp 3 in the inclined position, as shown in FIG. 1, the operator then walks outwardly on the ramp and the weight of the operator in combination with the weight of the ramp will overcome the force of the spring assembly 4, thereby enabling the ramp to lower slowly until the lip 8 engages the bed of the truck or carrier, the lip will move to the fully extended position thereby releasing the lip latching mechanism and enabling the lip to freely pivot downwardly to the pendant position when the truck moves away from the dock.

The dockboard 1 also includes a pair of cross traffic legs 12 as disclosed in U.S. Pat. No. 3,137,017. Each of the cross traffic legs 12 is pivotally supported at the underside of the ramp and biased to a supporting or operating position by means of a torsion spring 13 which is wound around the hinge pin 14 that hinges the leg to the ramp. The cross traffic legs 12 are adapted to engage fixed supports 15 which are mounted on the frame 2.

As disclosed in U.S. Pat. No. 3,137,017, the cross traffic legs 12 can be provided with a series of notches 16 each of which is adapted to engage the upper end of the supports 15 to thereby support the ramp at various inclinations or elevations. For example, when the lower ends of the cross traffic legs 12 are engaged with the supports 15, the ramp 3 will be supported in a generally horizontal, cross traffic position, and when the notches 16 are engaged with the supports 15, the ramp will be supported at one of a number of below dock level positions.

As disclosed in U.S. Pat. No. 3,137,017, the cross traffic legs are adapted to be moved rearwardly to a retracted position in consequence of the lip 8 being moved from the pendant to the extended position. To retract the legs, a wiper arm 17 is secured to the forward surface of each of the legs 12 and is adapted to be engaged by roller 18 carried by a bracket 19 secured to one of the lip hinge tubes 9. When the lip is pendant, the roller 18 extends through an opening in the front header 20 of the ramp. As the lip 8 is pivoted upwardly to the extended position, the rollers 18 will act against the wiper arms 17 to pivot the cross traffic legs 12 to the retracted or rearward position.

The dockboard is normally installed in the dock 21 beneath an opening or doorway in the building, and an overhead door 22 is utilized to close off the doorway during non-loading periods. In normal operation the lower edge of the door 22 will be in engagement with the upper surface of the ramp 3, to provide a weather tight joint.

In the case where the cross traffic legs 12 are coupled to the extension lip 8, it is possible, when the ramp is at the cross traffic position, unless a locking mechanism is employed, to retract the cross traffic legs by manual elevation of the lip. In other cases where the cross traffic legs are not coupled to the lip and are manually retracted through use of an operating cable, it is also possible to retract the legs by lifting the lip and pushing the legs to the rear. With the cross traffic legs retracted, the ramp can then be manually lowered until it bottoms out on the supporting structure, thereby leaving a gap or space of approximately 8 or 9 inches between the upper surface of the ramp and the lower edge of the closed door 22. Access can be obtained through this clearance into the building.

In accordance with the invention, a safety mechanism is utilized which prevents the ramp, when in the dock level position, from being lowered, thereby eliminating the possibility of an intruder gaining access to the building through the space between the lowered ramp and the overhead door. The safety lock mechanism of the invention comprises a generally L-shaped bracket 23 and in the normal operating position, as shown in FIG. 5, it includes an upright vertical flange 24 and a generally horizontal flange 25. The central portion of bracket 25 carries a pivot pin 26, the ends of which are mounted for rotation within lugs 27 attached to the sides of the safety leg 15.

To bias the flange 24 to an upright position, a pair of torsion springs 28 are wound around the ends of the pin 26 and one end of each spring bears against the edge of the bracket 23, while the opposite edge of the torsion spring bears against the respective fixed leg 15. The force of the torsion springs will act to urge or bias the flange 24 to the upright or vertical position.

To prevent the flange 24 from moving rearwardly beyond the vertical position, a stop 29 is secured to the under surface of the upper portion of the fixed leg 15 and the horizontal flange 24 is adapted to engage the stop to limit further rearward pivotal movement of the bracket.

During periods of non-loading, the upright cross traffic legs 12 will rest on the fixed legs 15 and the overhead door 22 will be closed and be in engagement with the upper surface of the ramp 3. Under these circumstances, the flange 24 of the bracket 23 will prevent rearward displacement of the cross traffic legs 12, thereby making it impossible to lower the ramp 3 unless the ramp is first raised high enough to permit the leg 12 to clear the top of the flange 24, and this, of course, cannot be done with the door 22 in the closed position. Thus, the bracket 23 prevents the lowering of the ramp when the ramp is in a dock level position and thus eliminates the possibility of an intruder gaining access to the building through the space between the lowered ramp and the door 22.

In the event the ramp is at dock level or slightly above dock level during the loading operation, and the carrier pulls away from the dock after the loading is completed, the lip 8 will swing downwardly toward the pendant position and the cross traffic legs 12 will move under the force of the torsion springs 13 to the vertical supporting position. Under these circumstances, the lower edge of the leg 12 will engage flange 24 of the bracket 23, pivoting the bracket forwardly as shown in FIG. 3. Thus, the bracket will not interfere with movement of the cross traffic leg to its vertical supporting position. The cross traffic leg will thus seat on the fixed leg to provide support for the ramp. In this condition, the flange 24 will be horizontal and will be sandwiched between the leg 12 and support 15. As the ramp is raised for the next loading operation, the flange 24 will be free to pivot to the rear to the upstanding position under the force of springs 28.

The safety lock mechanism of the invention not only prevents lowering of the ramp from the dock level position unless the ramp is first raised high enough to permit the cross traffic legs 12 to clear the top of the flange 22, but also enables the cross traffic legs to return to their upright supporting position when the truck pulls away from the dock with the ramp at dock level or slightly above dock level.

While the description has shown the locking member or safety member to be in the form of an angle-shaped bracket 23, this configuration is not critical and the locking member can take various shapes. Similarly, the description has shown the biasing means for the locking member to be a torsion spring 28, but it is contemplated that the locking member can be biased to the locking position by any resilient member or by a counterweight system.

The safety lock mechanism, while illustrated with a dockboard in which the cross traffic legs 12 are coupled to the lip, can also be used with a dockboard having cross traffic legs which are manually retractable, as for example, through use of an operating cable.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.