Danfoss A/s

Danfoss Power Solutions Aps

Kjeld Ravn

Carl Christian Dixen

Harry S Nissen

Dirk Wroblewski

Flemming Thomsen

An electrohydraulic control valve () comprising a control valve element () displaceable in a first direction by a pressure in a first pressure chamber () and in a second direction by a pressure in a second pressure chamber (). Each pressure chamber () is connected to a line between a high pressure port (PP) and a low pressure port (PT) via a magnetic valve (). Each magnetic valve () is a three-way valve and comprises a first valve seat () and a second valve seat (). A space () between the first valve seat () and the second valve seat () is connected to the pressure chamber () and a first valve element () positioned outside the space () cooperates with the first valve seat () and a second valve element () positioned outside the space () cooperates with the second valve seat ().

Electrohydraulic control valve

An electrohydraulic control valve comprising a valve element that is displaceable in a first direction by a pressure in a first pressure chamber and in a second direction by a pressure in a second pressure chamber. The first pressure chamber is connectable to a high pressure supply and a low pressure supply. The second pressure chamber is connectable to the high pressure supply and the low pressure supply. A first magnetic valve is connected to the first pressure chamber and a second magnetic valve is connected to the second pressure chamber. A third magnetic valve is connected to the high pressure supply and to the first magnetic valve and to the second magnetic valve. It is intended to provide an electrohydraulic control valve that is both reliable and less complex than previous valve arrangements. To this end the first magnetic valve and the second magnetic valve are three-way valves.

Disclosed is an arrangement that includes a piston cylinder unit having pressure chamber in which fluid acts in opposition to a spring piston combination, a pressure generator and a fluid conduit extending between a tank and the tank. A first and a second valve are connected in series between the pressure generator and tank with the pressure chamber being in fluid communication with the connection between the valves. In known arrangements of the above type there is dead play wherein not every control signal corresponds to a defined position of the piston in the cylinder. However as disclosed herein the setting accuracy is improved by a throttle in parallel with valve that is fluidly connected between the pressure chamber and the piston cylinder unit. Also third and fourth valves may be connected in series between the pressure generator and tank and have a fluid connection between the third and fourth valves to the unit pressure chamber that is opposite the first chamber to provide a bridging circuit.

Fluid-controlled servo-arrangement

A control system for a two way acting hydraulic servomotor wherein the servomotor is connected in the diagonal of a bridge circuit that includes four magnetic valves with a pair of the valves being normally open in a non-energized condition being connected to the one end of the servomotor and to the container and a second pair of the valves being normally closed in a deenergized condition being connected to the opposite end of the servomotor and to a pressure source. Circuitry provides pulse trains that are modulatable to control the operation of the magnetic valves and thereby the application of pressurized fluid to the opposite ends of the servomotor.

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Sydals, Denmark

Kjeld Ravn