A hydraulic control system for a material handling vehicle, the material handling vehicle including a pump having a pump outlet, a reservoir, one or more hydraulic actuators, and a controller, the pump outlet is in fluid communication with a supply passage and the reservoir is in fluid communication with a return passage, the one or more hydraulic actuators are configured to raise and lower a fork assembly attached to a mast of the material handling vehicle, the hydraulic control system comprising: a high pressure relief valve configured to provide fluid communication from the supply passage to the reservoir when a pressure upstream of the high pressure relief valve exceeds a high pressure threshold; a low pressure relief valve arranged on a low pressure relief line, the low pressure relief line connected between the supply passage and the return passage upstream of the high pressure relief valve; and a low pressure control valve arranged on the low pressure relief line upstream of the low pressure relief valve, the low pressure control valve moveable between a control valve open position where fluid communication is provided from the supply passage to the low pressure relief valve and a control valve closed position where fluid communication is inhibited from the supply passage to the low pressure control valve, wherein the low pressure relief valve is configured to provide fluid communication from the supply passage to the reservoir when the low pressure control valve is in the control valve open position and a pressure upstream of the low pressure relief valve exceeds a low pressure threshold, the low pressure threshold is less than the high pressure threshold, and the low pressure control valve is moveable between the control valve open position and the control valve closed position when the fork assembly reaches a predetermined elevated height. 500> Controller 446 506 '422 600 --, Measure Elevation Level Above Yes Threshold No Elevation Level? Actuate or Maintain Actuate or Maintain Low Relief Control Low Relief Control Valve to Open Position Valve to Closed Position
VARIABLE HYDRAULIC PRESSURE RELIEF SYSTEMS AND METHODS FOR A MATERIAL HANDLING VEHICLE
2023-02-23
Patent
Elektronische Ressource
Englisch
IPC: | B66F HOISTING, LIFTING, HAULING, OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD , Hub-, Verhol- oder Schubvorrichtungen, soweit nicht anderweitig vorgesehen, z.B. Vorrichtungen mit unmittelbarer Krafteinwirkung auf die Last |
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