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US3656199A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Safety mechanism for a hydraulically operated dockboard
Assignee: KELLEY CO Inc
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Filing: 1970-11-02
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Granted: 1972-04-18
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Expires: 1990-11-02
Abstract
Abstract A safety mechanism to be incorporated with a hydraulically operated dockboard for preventing free descent of the ramp if a carrier pulls away from the dock when a load is on the ramp. The dockboard includes a ramp having its rear edge hinged to the dock and adapted to be raised upwardly to an inclined position by a hydraulic cylinder unit. The safety mechanism is located in the hydraulic supply line that supplies hydraulic fluid to the cylinder unit from a pump and the mechanism includes a pair of valves, one of which is biased to a normally closed position and the second valve is biased to a partially open position. To raise the ramp, the pump is operated and the pressurized fluid acts to move both valves to the fully open position. When the ramp is lowered in normal operation, the hydraulic fluid being displaced from the cylinder unit passes through the partially open second valve to provide a slow rate of descent from the ramp. If a truck or carrier pulls away from the dock when a load is on the ramp, the combined weight of the ramp and the load will increase the force of the hydraulic fluid flowing from the cylinder to the pump, thereby overcoming the spring force on the second valve and moving the second valve to a fully closed position. The closing of the second valve will prevent descent of the ramp and will retain the ramp in that position until the load is removed from the ramp.
Inventors
- 👤 Robert R Bregantini
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:54
CPC Classifications
B; B65; B65G; B65G69/00; B65G69/28; B65G69/2805; B65G69/2811; B65G69/2817; B65G69/2823; B65G69/287; B65G69/2876
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
235 words
In a dockboard, a supporting structure, a ramp mounted for movement on the supporting structure between a storage position and an upper position, hydraulic means for moving the ramp between the storage position and the upper position, said hydraulic means including a hydraulic power unit interconnecting the ramp and the supporting structure and said hydraulic means including a pump and conduit means connecting the discharge side of the pump and said power unit, valve means located in said conduit means, and biasing means for biasing said valve means toward an open position, said biasing means being arranged so that fluid being discharged from the pump to the power unit to raise the ramp will act in conjunction with said biasing means to move the valve means to a fully open position, said biasing means being arranged so that the force of the fluid being displaced from the power unit as the ramp is lowered under normal conditions will not overcome the force of said biasing means so that said valve means will be in a partially open position, and said biasing means being arranged so that the force of the fluid being displaced from the power unit when the ramp descends with an additional predetermined load applied thereto will overcome the force of said biasing means so that the valve means will be moved to a closed position and prevent further descent of the ramp.
Claim 2
Dependent Claim
235 words
In a dockboard, a supporting structure, a ramp mounted for movement on the supporting structure between a storage position and an upper position, hydraulic means for moving the ramp between the storage position and the upper position, said hydraulic means including a hydraulic power unit interconnecting the ramp and the supporting structure and said hydraulic means including a pump and conduit means connecting the discharge side of the pump and said power unit, valve means located in said conduit means, and biasing means for biasing said valve means toward an open position, said biasing means being arranged so that fluid being discharged from the pump to the power unit to raise the ramp will act in conjunction with said biasing means to move the valve means to a fully open position, said biasing means being arranged so that the force of the fluid being displaced from the power unit as the ramp is lowered under normal conditions will not overcome the force of said biasing means so that said valve means will be in a partially open position, and said biasing means being arranged so that the force of the fluid being displaced from the power unit when the ramp descends with an additional predetermined load applied thereto will overcome the force of said biasing means so that the valve means will be moved to a closed position and prevent further descent of the ramp.
Claim 3
Dependent Claim
78 words
The dockboard of claim 1, wherein said biasing means comprises a pair of resilient members with a first of said resilient members urging said valve means toward an open position and a second of said resilient members urging said valve means toward a closed position, the force of said first resilient member being greater than the force of said second resilient member whereby said valve means is biased to a partially open position under no-load fluid pressure conditions.
Claim 4
Dependent Claim
35 words
The dockboard of claim 2, wherein said valve means comprises a valve seat and a generally spherical ball valve, said resilient members being coil springs disposed in engagement with opposite portions of said ball valve.
Claim 5
Dependent Claim
35 words
The dockboard of claim 1, and including means for adjusting the force of said biasing means to thereby regulate the amount of said additional load necessary to move said valve means to the closed position.
Claim 6
Dependent Claim
147 words
The dockboard of claim 1, wherein said valve means comprises a casing having a passage comprising a part of said conduit means and defining a valve seat, said valve means also including a valve member adapted to engage the valve seat, said biasing means comprises a pair of resilient members with a first of said resilient members urging said valve member toward an open position and a second of said resilient members urging said valve member toward a closed position, the force of said first resilient member being greater than the force of said second resilient member whereby said valve member is biased to a partially open position under no-load fluid pressure conditions, and adjusting means for adjusting the force of at least one of said resilient members to thereby regulate the amount of said additional load necessary to move said valve member to the closed position.
Claim 7
Dependent Claim
17 words
The dockboard of claim 5, wherein said adjusting means is located on the exterior of said casing.
Claim 8
Dependent Claim
46 words
The dockboard of claim 1, and including check valve means disposed in said conduit means in parallel arrangement with said first valve means for permitting flow of fluid in a direction from the pump to the power unit and for preventing flow in the opposite direction.
Claim 9
Dependent Claim
64 words
The dockboard of claim 5, wherein said casing defines a second passage disposed in parallel arrangement with said first passage and constituting a part of said conduit means, said second passage defining a second valve seat, said dockboard also including a second valve adapted to engage said second valve seat, and second biasing means for urging said second valve member to the closed position.
Claim 10
Dependent Claim
13 words
The dockboard of claim 1, wherein said power unit is a hydraulic cylinder.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-04-18 | 1975-10-18 | 1976-04-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-18 | 1979-10-18 | 1980-04-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-18 | 1983-10-18 | 1984-04-18 | $7700.00 | Window Closed / Lapsed |