US 7,320,335 B2
Electrohydraulic control device
Martin Heusser, Munich (Germany); and Georg Neumair, Thalhausen (Germany)
Assigned to HAWE Hydraulik GmbH & Co. KG, Munich (Germany)
Filed on Feb. 18, 2005, as Appl. No. 11/62,051.
Claims priority of application No. 20 2004 003 749 U (DE), filed on Mar. 10, 2004.
Prior Publication US 2005/0199295 A1, Sep. 15, 2005
Int. Cl. F16K 31/06 (2006.01)
U.S. Cl. 137—596.17  [137/625.65] 10 Claims
OG exemplary drawing
 
1. Electrohydraulic control device for a hydro-motor operating in a portable working device, the electrohydraulic control device comprising a control system,
first and second working lines connected to the hydro-motor, a pressure source and a return system,
a first main directional solenoid seat valve connected between the first working line and both the pressure source and the return system,
a second main directional solenoid seat valve connected between the second working line and both the pressure source and the return system,
each of the first and second main directional solenoid seat valves being designed for being switched by the control system between two switching positions for either connecting the connected working line with the return system and separating the working line from the pressure source, or connecting the connected working line with the pressure source and separating the working line from the return system,
a first load holding valve connected between the second working line and the return system,
a second load holding valve connected between the first working line and the return system,
each of the first and second load holding valves being designed to be selectively switched by the control system between two switching positions for either connecting the connected working line with the return system or separating the connected working line from the return system without leakage to maintain the working pressure of the hydro-motor in the connected working line,
the first load holding valve being switched to connect the second working line with the return system at the same time that the first main directional solenoid seat valve is switched to connect the first working line with the pressure source,
the second load holding valve being switched to connect the first working line with the return system at the same time that the second main directional solenoid seat valve is switched to connect the second working line with the pressure source,
a circulation switching assembly connected between the pressure source and the return system so that a pressureless circulation is allowed from the pressure source into the return system when the first and second working lines are both separated from the pressure source, and
a respective one of first and second backflow preventing valves being provided between the first main directional solenoid seat valve and the first working line and between the second main directional solenoid seat valve and the second working line,
wherein the first and second load holding valves are 2/2-directional solenoid seat valves each of which is designed for selectively being switched into the switching position for connecting the connected working line to the return system either by a routine or by a selective actuation of the control system by a short electric switching pulse after the electrohydraulic control device has been switched off, for intentionally relieving pressure from the connected working line into the return system which pressure is trapped in the connected working line between the hydro-motor and the respective backflow preventing valve when the electrohydraulic control device has been switched off.