Vertically storing dock leveler

• US 5,117,526 A
• Filed: 07/02/1991
• Issued: 06/02/1992
• Est. Priority Date: 05/03/1990
• Status: Expired due to Term

• Current Assignee: 3894576 Canada, Ltd.
• Original Assignee: Serco Limited (Serco Group PLC)
• Inventors: Alexander, James
• Primary Examiner(s): Britts, Ramon S.
• Assistant Examiner(s): MULCARE, NANCY C
• Application Number:
  US07/724,626
• Time in Patent Office: 336 Days
• Field of Search: 14/71.1, 14/71.3, 14/71.7, 14/41-42, 14/46-47, 14/32, 92/85 B, 91/396, 104/31, 105/435
• US Class Current: 14/71.7
• CPC Class Codes: B65G 69/2817 with fluid-operated means

Abstract

A hydraulic lift bridge/leveler that is raised by an hydraulic cylinder and lowered primarily by gravity. A toggle mechanism is used to lock the bridge in a near vertical position. An auxiliary cylinder moves a lock-out arm assembly to release the toggle mechanism and power the bridge downward to a point where the weight moment through the pivot point is significantly large that the bridge will lower itself by gravity. The main cylinder employs a cushion mechanism that decelerates the bridge by slowly increasing hydraulic pressure in the cylinder. This allows the bridge to be raised at an initially high rate of speed and then slowed down near the end of travel at a near vertical position.

Claims

1. Apparatus for spanning a distance between spaced objects at least one of which is stationary, said device movable from a generally vertical stored position to a generally horizontal operative position comprising:

a deck hingedly connected to said stationary object,

means for raising said deck from said operative position to said inoperative position,

lock means for holding said deck in said inoperative position, and

means mounted on said deck for contacting said lock means for releasing said lock means thereby permitting said deck to be lowered said means mounted on said deck moving in contact with said locking means additionally for urging said deck to rotate toward said operative position.

2. The device of claim 1 wherein said lock means comprises a toggle arm assembly, a first arm pivotally mounted to said deck and a second arm pivotally mounted to said stationary object, said first and second arms pivotally coupled to each other, and stop means on one of said arms to lock said arms into alignment with each other.

3. The device of claim 2 wherein said means associated with said lock means comprises a kick-out arm mounted to engage said lock means and pivot one of said arms relative to the other to release said lock means, and means for moving said kick-out arm to engage one of said arms of said lock means and rotate said deck.

4. The device of claim 3 wherein said means for moving said kick-out arm comprises an hydraulic cylinder mounted to said deck and to said kick-out arm and extensible to cause said deck to rotate by movement of one of said arms of said lock means.

5. The device of claim 2 further comprising spring means to bias said lock means into alignment with each other.

6. The device of claim 1 further comprising sensor means to determine whether said lock means is engaged to hold said deck in said inoperative position.

7. The device of claim 1 wherein said means for raising said deck comprises an hydraulic cylinder and an extensible piston in a cavity of said cylinder dividing said cavity into two chambers, further including means to vary the flow rate of said hydraulic cylinder at the end of piston extension to decelerate movement of said deck as it approaches said inoperative position.

8. The device of claim 7 wherein said means to vary the flow rate comprises an extension at one end of said cylinder, an exit port, a fluid return path in said extension coupled to said exit port, means in said cylinder to close said fluid return path and an adjustable fluid bypass between said cylinder cavity and said exit port.

9. The device of claim 8 wherein said adjustable fluid bypass comprises a channel in fluidic contact with one of said chambers and a needle valve in said channel to adjust the fluid flow therein to said exit port.

10. The device of claim 7 wherein said means to vary the flow rate comprises a tapered section on said piston, a fluid return path in said cylinder and, said tapered section engaging said fluid return path as said piston extends from said cylinder to gradually reduce fluid flow and thereby decelerate movement of said piston.

11. Apparatus for spanning a distance between spaced objects at least one of which is stationary, said device movable from a generally vertical stored position to a generally horizontal operative position comprising:

a deck hingedly connected to said stationary object,

hydraulic means for raising said deck from said operative position to said inoperative position,

lock means for holding said deck in said inoperative position,

means mounted on said deck for contacting said lock means for releasing said lock means thereby permitting said deck to be lowered said means mounted on said deck moving in contact with said locking means additionally for urging said deck to rotate toward said operative position, and means in hydraulic fluid communication with said hydraulic means for hydraulically slowing movement of said deck as it approaches said inoperative position.

12. The device of claim 11 wherein said hydraulic means comprises a piston and cylinder assembly connected between said deck and said stationary object, said piston dividing said cylinder into two chambers one of which having a fluid exit port for returning fluid to a reservoir said when deck is raised.

13. The device of claim 12 wherein said means for hydraulically slowing movement of said deck comprises an extension on said cylinder, said fluid exit port in said extension and a tapered plug on said piston to gradually close said fluid exit port as said piston is extended from said cylinder to raise said deck.

14. The device of claim 12 wherein said means for hydraulically slowing movement of said deck comprises an auxiliary channel in fluid communication with said fluid exit port and a valve in said auxiliary channel whereby as said deck is raised fluid flow from said cylinder to said exit port passes through said auxiliary channel at a flow rate decreasing as said deck approaches said inoperative position.

15. The device of claim 11 further comprising lock means for holding said deck in said inoperative position and means associated with said lock means for releasing said lock means and urging said deck to rotate toward said operative position.

16. The device of claim 15 wherein said lock means comprises a toggle arm assembly having a pair of arms, one arm pivotably mounted to said deck and the other arm pivotably mounted to said stationary structure with said arms pivotably connected to each other and a stop member on one of said arms to lock said arms into alignment with each other.

17. The device of claim 16 wherein said means associated with said lock means comprises a kick-out arm mounted to engage said lock means and pivot one of said arms relative to each other to release said lock means, and means for moving said kick-out arm to engage one of said arms of said lock arms and rotate said deck.