Electric and fluid controls for clutch and transmission

Claim 1

In an apparatus comprising a gear-box having driven members, driving members and members to be moved to selectively engage a driven member with a driving member, and hydraulic means for moving said members to be moved, means for driving said driven members comprising an input shaft, an engine, a friction clutch for coupling the shaft to the engine and means for actuating the clutch comprising a cylinder having a piston slidably disposed therein and connected to a movable part of the clutch, a source of fluid under pressure, a fluid return reservoir, a hydraulically operated main valve for actuating the piston, said main valve being connected to the cylinder, the fluid source and the fluid return reservoir, an electromagnetically operated primary valve of smaller volume than that of the main valve for actuating the main valve, said primary valve being in fluid connection with the main valve, the fluid source and the fluid return reservoir, means comprising an electrical control unit for actuating the primary valve, and a fluid flow restriction means having a one-way valve parallel thereto effective only to allow fluid flow towards the piston-cylinder assembly from said valve arrangement.