Patent ID: 6611415
Filing Date: 2003-08-26
Classification: B62D

Abstract:
A fail-safe circuit comprising:a supply source of pressure oil; an actuator; and a plurality of solenoid type control valves provided between the supply source and the actuator and connected to said actuator in parallel, said control valve being provided with a centering spring to maintain at a neutral position in normal times, and with a supply port, a return port and two actuator ports, configured to communicate said supply port and said return port with each other and not to communicate said supply port and said return port with said respective actuator ports at the neutral position, a supply port of a control valve located at the most upstream end of said control valves being connected to said supply source, a return port of a control valve located at the most downstream end of the said control valves being connected to a tank while said each return port of said control valves is connected a supply port of a control valve located downstream from and adjacent to the connected valve, wherein the driving of said actuator is controlled while only a specified control valve of said plurality of control valves is selected and other control valves are maintained at the neutral position.