Dock leveler hydraulic circuit
AssigneeThe Serco Corporation
InventorJames C. Alexander
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Abstract
A dock leveler having a deck assembly, a first hydraulic cylinder to power said deck assembly to a raised position, lip mounted to said deck assembly, and a second hydraulic cylinder for powering said lip into an extended position. An hydraulic power circuit is coupled to the first and second hydraulic cylinders to control movement of said deck and lip. The hydraulic power circuit includes a pump to deliver fluid under pressure, a first valve operatively coupled to the pump to control fluid flow to the first hydraulic cylinder. A second valve is operatively coupled to the second hydraulic cylinder. An adjustable relief valve is coupled to the second valve to prevent a reduction of fluid pressure to the second hydraulic cylinder after the pump has supplied fluid under pressure through the second valve to extend the lip.
Claims7
A hydraulic circuit for a dock leveler having a deck powered by a first hydraulic cylinder and lip powered by a second hydraulic cylinder, said hydraulic circuit comprising:
- a source of hydraulic fluid, an hydraulic power circuit coupled between said source of hydraulic fluid and said first hydraulic cylinder and said second hydraulic cylinder to control movement of said deck and said lip, said hydraulic power circuit including a pump to deliver fluid under pressure from said source of hydraulic fluid, first valve means operatively coupled to said pump to control fluid flow between said source and said first hydraulic cylinder and said second hydraulic cylinder, second valve means operatively coupled to said first valve means to control fluid flow between said source and said second hydraulic cylinder, a check valve operatively coupled to said second valve means to control fluid flow from said second valve means to said source, and a pressure relief valve coupling said check valve to said source of hydraulic fluid, said pressure relief valve controlling the rate of flow from said second hydraulic cylinder through said check valve as said deck raises and said lip retracts, and said pressure relief valve preventing a flow of fluid from said second hydraulic cylinder as said check valve closes to prevent said lip from drooping after said pump has supplied fluid under pressure through said second valve means to extend said lip.
A hydraulic circuit for a dock leveler having a deck powered by a first hydraulic cylinder and lip powered by a second hydraulic cylinder comprising:
- a source of hydraulic fluid, a hydraulic power circuit coupled between said source of hydraulic fluid and said first hydraulic cylinder and said second hydraulic cylinder to control movement of said deck and lip, said hydraulic power circuit including a pump to deliver fluid under pressure from said source of hydraulic fluid, first valve means operatively coupled to said pump to control fluid flow between said source and said first hydraulic cylinder and said second hydraulic cylinder, second valve means operatively coupled to said first valve means to control fluid flow between said source of hydraulic fluid and said second hydraulic cylinder, a first check valve operatively coupled to said second valve means to control fluid flow from said second valve means to said source, a pressure relief valve coupling said first check valve to said source of hydraulic fluid, said pressure relief valve controlling the rate of flow from said second hydraulic cylinder through said first check valve as said deck raises and said lip retracts, and preventing a flow of fluid from said second hydraulic cylinder as said first check valve closes to prevent said lip from drooping after said pump has supplied fluid under pressure through said second valve means to extend said lip, and a second check valve coupled between a return path of said second valve means and said first hydraulic cylinder to permit said lip to fall by gravity after the fluid pressure has decreased in said first hydraulic cylinder.
Dependencies are inferred from the claim text.