Patent ID: 7210376

Claim:
A device for transmitting torque between two rotatable, coaxial shaft members, the device containing a clutch between the two shaft members and engageable to counteract rotational speed differential between the shaft members by means of a hydraulic piston under the control of an electrically controlled throttle or pressure valve, and a clutch pump for supplying hydraulic pressure to the hydraulic piston, wherein the clutch pump is a differential pump driven by the rotational speed differential between the two shaft members, wherein the hydraulic piston, the valve, and the clutch pump are connected in a hydraulic system also containing a feeder pump for maintaining a certain base pressure in the system, characterized by means in the hydraulic system for conditionally allowing flow from the feeder pump past the valve and to the hydraulic piston to actuate the clutch irrespective of the flow from the clutch pump.