Hydraulic arrangement for dockboards

Claim 2

A dockboard installation including a base structure, a dockboard hinged at a rearward edge to said base structure, and a hydraulic arrangement for raising and lowering the dockboard, comprising: a. a hydraulic cylinder and piston combination for raising the dockboard when the cylinder is supplied with pressurized fluid; b. a pump for supplying pressurized fluid to said cylinder from a reservoir; c. a pressure operated control valve connected by conduit means to the pump outlet, the cylinder, and the reservoir, said valve having a valve member movable from a first position, in which the valve member allows flow of fluid from the hydraulic cylinder to the reservoir, to a second position in which it prevents flow of fluid from the hydraulic cylinder to the reservoir, said valve member being directly responsive to fluid pressure at the pump outlet so as to move to its second position when the pump is delivering fluid at normal working pressure and biased so as to return to its first position when the pressure at tHe pump outlet is substantially reduced, whereby the position of the valve member is dependent on the fluid pressure at the pump outlet, so that the dockboard may be raised by operating the pump to supply hydraulic fluid to the cylinder with the valve member in its second position and whereby when the pump is stopped pressure reduction at the pump outlet allows the valve member to return to its first position, so that fluid may flow from the cylinder to the reservoir allowing the dockboard to lower, the arrangement also comprising d. a relief valve in the hydraulic cylinder circuit said relief valve being arranged to relieve pressure from said hydraulic cylinder circuit to said reservoir; and e. valve actuating means arranged to operate said relief valve to relieve pressure to said reservoir as the piston nears the end of its stroke, said relief valve thus operating to reduce pressure at the pump outlet at the stage when the pump is stopped thus facilitating the return of the valve member to its first position to allow lowering of the dockboard.

Claim 3

A dockboard installation according to claim 1, wherein the valve member is urged towards its first position by spring means mounted between the valve member and retaining means adjustable by screw means for altering the compression in the spring means.

Claim 4

A dockboard installation according to claim 1, wherein the control valve has a bore in which the valve member is slidable, said bore having two aligned portions of small and large diameter respectively, the valve member having portions of corresponding diameters slidable in said bore portions, and wherein the small diameter portion of the bore has its outer end in communication with the pump outlet whereby the smaller end of the valve member is at all times subject to pressure in said pump outlet to move towards its second position, said control valve also including a first port connected to said hydraulic cylinder, said first port being so positioned in the side of said smaller diameter bore portion as to be uncovered by the valve member when in its second position, said control valve also having a second port also connected to said hydraulic cylinder, said second port being so positioned in the large diameter bore portion as to be uncovered by the valve member when in its said first position, said valve also having an outlet connected to the reservoir and communicating with said second port when the valve member is in its first position.

Claim 5

A dockboard installation including a base structure, a dockboard hinged at a rearward edge to said base structure, a lip hinged to the forward edge of said dockboard and movable between a collapsed position to an extended position in which the lip forms an extension of the dockboard, and a hydraulically operated mechanism for raising the dockboard and extending the lip, said hydraulically operated mechanism including a hydraulic cylinder and piston combination for raising the dockboard when the cylinder is supplied with hydraulic fluid and said mechanism also including lip operating means operable to raise the lip from the collapsed position to the extended position on movement of the dockboard between intermediate and raised positions, said lip operating means imposing forces on said cylinder and piston combination additional to those imposed by the weight of the dockboard while the lip is being moved to its extended position, and wherein the said hydraulic cylinder is connected to a hydraulic circuit including: a. a pump for supplying pressurized fluid to said cylinder from a reservoir; b. a pressure operated control valve connected by conduit means to the pump outlet, the cylinder, and the reservoir, said valve having a valve member movable from a first position, in which the valve member allows flow of fluid from the hydraulic cylinder to the reservoir, to a second position in which it prevents flow of fluid from the hydraulic cylinder to the reservoir, said valve member being directly responsive to fluid pressure aT the pump outlet so as to move to its second position when the pump is delivering fluid at normal working pressure and biased so as to return to its first position when the pressure at the pump outlet is substantially reduced, whereby the position of the valve member is dependent on the fluid pressure at the pump outlet, so that the dockboard may be raised by operating the pump to supply hydraulic fluid to the cylinder with the valve member in its second position and whereby when the pump is stopped pressure reduction at the pump outlet allows the valve member to return to its first position, so that fluid may flow from the cylinder to the reservoir allowing the dockboard to lower, the arrangement also comprising c. a relieve valve in the hydraulic cylinder circuit said relief valve being arranged to relieve pressure from said hydraulic cylinder circuit to said reservoir; and d. valve actuating means arranged to operate said relief valve to relieve pressure to said reservoir as the piston nears the end of its stroke, said relief valve thus operating to reduce pressure at the pump outlet at the stage when the pump is stopped thus facilitating the return of the valve member to its first position to allow lowering of the dockboard.

Claim 6

A dockboard installation including a base structure, a dockboard hinged at a rearward edge to said base structure, a lip hinged to the forward edge of said dockboard and movable between a collapsed position to an extended position in which the lip forms an extension of the dockboard, and a hydraulically operated mechanism for raising the dockboard and extending the lip, said hydraulically operated mechanism including a hydraulic cylinder and piston combination for raising the dockboard when the cylinder is supplied with hydraulic fluid and said mechanism also including lip operating means operable to raise the lip from the collapsed position to the extended position on movement of the dockboard between intermediate and raised positions, said lip operating means imposing forces on said cylinder and piston combination additional to those imposed by the weight of the dockboard while the lip is being moved to its extended position, and wherein the said hydraulic cylinder is connected to a hydraulic circuit including: a. a pump for supplying pressurized fluid to said cylinder from a reservoir; b. a pressure operated control valve connected by conduit means to the pump outlet, the cylinder, and the reservoir, said valve having a valve member movable from a first position, in which the valve member allows flow of fluid from the hydraulic cylinder to the reservoir, to a second position in which it prevents flow of fluid from the hydraulic cylinder to the reservoir, said valve member being directly responsive to fluid pressure aT the pump outlet so as to move to its second position when the pump is delivering fluid at normal working pressure and biased so as to return to its first position when the pressure at the pump outlet is substantially reduced, whereby the position of the valve member is dependent on the fluid pressure at the pump outlet, so that the dockboard may be raised by operating the pump to supply hydraulic fluid to the cylinder with the valve member in its second position and whereby when the pump is stopped pressure reduction at the pump outlet allows the valve member to return to its first position, so that fluid may flow from the cylinder to the reservoir allowing the dockboard to lower, the arrangement also comprising c. a relieve valve in the hydraulic cylinder circuit said relief valve being arranged to relieve pressure from said hydraulic cylinder circuit to said reservoir; and d. valve actuating means arranged to operate said relief valve to relieve pressure to said reservoir as the piston nears the end of its stroke, said relief valve thus operating to reduce pressure at the pump outlet at the stage when the pump is stopped thus facilitating the return of the valve member to its first position to allow lowering of the dockboard.

Claim 7

A dockboard installation according to claim 4, wherein the valve actuating means is adjustable to allow for adjustment of the stroke of the piston.