Anti-stall pilot pressure control system for open center systems
AssigneeTimberjack Inc.
InventorsCalin Raszga, Jeffrey Girard, Ulf Bergquist
Life of this patent
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Abstract
A hydraulic control system has a pilot pressure supply circuit that applies a pressure differential dependent on engine speed to opposite sides of an anti-stall valve to turn off the pilot flow when the pressure differential falls below a certain value, resulting in holding the positions of the hydraulic devices being controlled until engine speed recovers.
Claims19
In a hydraulic control system that has hydraulic pilot pressure operated valves for controlling hydraulic work devices and a prime mover that drives a hydraulic pump that supplies hydraulic fluid under pressure to the devices through the pilot pressure operated valves, the improvement comprising an orifice in a hydraulic line in which the fluid flow is dependent on prime mover speed and a spring return pilot pressure operated anti-stall valve in a pilot pressure fluid supply line, the anti-stall valve having opposed pilot pressure ports, one of said ports being connected to one side of said orifice and the other said port being connected to the other side of said orifice, such that a sufficient reduction in the speed of the prime mover causes the pressure drop across the orifice to diminish to a point that the anti-stall valve reduces the pilot pressure fluid flow through the anti-stall valve to the pilot pressure operated valves of the hydraulic control system and relieves the pilot pressure from the pilot pressure operated valves.
In a hydraulic control system that has hydraulic pilot pressure operated valves for controlling hydraulic work devices and a prime mover that drives a hydraulic pump that supplies hydraulic fluid under pressure to the devices through the pilot pressure operated valves, the improvement comprising an anti-stall valve in a pilot pressure fluid supply line that supplies pilot pressure fluid to the pilot pressure operated valves, the anti-stall valve being responsive to a reduction in speed of the prime mover such that at full speed of the prime mover the anti-stall valve directs pilot pressure fluid flow to at least one control valve that controls at least one pilot pressure of the pilot pressure operated valves and at a reduced speed of the prime mover the anti-stall valve reduces the flow of pilot pressure fluid directed to the control valves and relieves the pilot pressure from the control valves.
Dependencies are inferred from the claim text.