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US 4,065,921 AGranted
Hydraulic control means, particularly for vehicle steering means
AssigneeDanfoss A/S
InventorsJohannes Vagn Baatrup, Thorkild Christensen
Life of this patent
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AssigneeDanfoss A/S
InventorsJohannes Vagn Baatrup, Thorkild Christensen
Estimating the term…
The invention relates to a hydraulic control unit for a servomotor of the type used for vehicle steering systems. The unit has a control circuit with a power operated pump and a hand operated metering motor and an operating circuit with a power operated pump. The two circuits intersect upstream from the servomotor. A pressure comparison, throttling and proportioning valve is disposed between the outlets of the two pumps of the control and operating circuits. The proportioning valve is controlled by a differential pressure applied by the pumps and a spring which supplements the operating pump pressure. In the normal operating mode the proportioning valve allows a minor fractional flow of the pressurized fluid generated by the control pump to flow through the valve to the operating circuit. Under varying conditions when either of the pumps become wholly or partially inoperative the proportioning valve provides for an increased flow from the unaffected circuit to the disabled circuit to maintain a degree of operation until such time that the breakdown has been cured.
A hydraulic control unit for a servomotor comprising a control circuit having a pump and a hand operated metering motor, and operating circuit having a pump, said control and operating circuits intersecting upstream of said servomotor, a pressure comparison throttling and proportioning valve having first and second ports, connected respectively to said control and operating pumps and a third port connected to said metering motor, said proportioning valve being controlled by a differential pressure applied to said first and second ports and having a normal operating mode in which there is a major fractional flow of fluid from said first port to said third port and a minor fractional flow of fluid from said first port to said second port.
A hydraulic control unit for a servomotor comprising a control circuit having a pump and a hand operated metering motor, an operating circuit having a pump, said control and operating circuits intersecting upstream of said servomotor, a pressure responsive throttling and proportioning valve having a casing with a bore, a valve element having first and second spools at opposite ends slidably disposed in said bore, spring means biasing said valve element in one direction, said valve element having differential forces on said valve element which are control pump pressure at one end and operating pump pressure at the other end supplemented by the action of said spring means, a first transverse port in said casing connecting said control pump to said bore, second and third spaced apart transverse ports in said casing straddling said first port and connecting said operating pump to said bore, said valve having a normal operating mode in which there is a major fractional flow of fluid from said control pump to said control circuit and a minor fractional flow of fluid from said first port to said third port.
Dependencies are inferred from the claim text.