Danfoss A/s

Niels G Karlberg

Poul H Pedersen

The invention relates to a priority valve for a hydraulic installation having a main circuit and an auxiliary circuit. The priority valve has a slide member which primarily has a controlled throttle for dividing the supply fluid between the main and auxiliary circuits in accordance with the priority demands of the main circuit. The priority valve has a flow path leading to the auxiliary circuit which has throttle elements in series which provide pressure drops in steps to minimize cavitation when there is a rapid flow of fluid in the auxiliary circuit.

Priority valve for hydraulic installations

The invention relates to hydraulic steering apparatus of the type having valve gear for selectively directing pressurized fluid to and from opposite sides of a servomotor connected to vehicle wheels to be steered. This type of steering apparatus only requires pressurized fluid when actuated and may provide an auxiliary circuit with pressured fluid at times when it is not being actuated. Priority valves give priority to the steering apparatus. During extended intervals when pressured fluid is supplied to an auxiliary circuit, parts of the steering apparatus are subjected to substantial cooling. Then when the priority valve diverts hot pressurized fluid from the auxiliary circuit to the cooled steering apparatus the temperature differential causes an adverse effect on the steering apparatus by creating a tendency for binding of parts due to the unequal expansion of valve sleeves. A heat exchanger is provided having passages through which hot pressurized fluid to and from the priority valve is passed and the housing of the heat exchanger is in contact with the housing of the steering apparatus in the vicinity of the inlet and outlet ports of the steering apparatus. The heat exchanger prevents the steering apparatus parts from extensive cooling and the harmful uneven expansion of valve sleeve is avoided.

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Nordborg, Denmark

Niels G Karlberg