Control circuit for a power transmission mechanism

Claim 1

IN A POWER TRANSMISSION MECHANISM FOR A WHEELED VEHICLE HAVING AN INTERNAL COMBUSTION ENGINE, A POWER INPUT MEMBER DRIVABLY CONNECTED TO SAID ENGINE, A POWER OUTPUT MEMBER, A GEAR ELEMENT INTERCONNECTING SAID POWER INPUT MEMBER AND SAID POWER OUTPUT MEMBER AND FORMING PLURAL TORQUE DELIVERY PATHS THEREBETWEEN, A FLUID PRESSURE OPERATED SERVO MEANS FOR CONTROLLING THE RELATIVE MOTION OF SAID GEAR ELEMENTS, A SOURCE OF FLUID PRESSURE, CONDUIT STRUCTURE INTERCONNECTING SAID SERVO MEANS AND SAID FLUID PRESSURE SOURCE, A SHIFT VALVE DISPOSED IN AND PARTLY DE FINING SAID CONDUIT STRUCTURE INCLUDING A MOVABLE VALVE ELEMENT ADAPTED ALTERNATELY TO DISTRIBUTE FLUID PRESSURE TO SAID SERVO MEANS AND TO BLOCK THE DISTRIBUTION OF FLUID PRESSURE THERETO, VALVE MEANS FOR ESTABLISHING A FLUID PRESSURE SIGNAL RELATED FUNCTIONALLY IN MAGNITUDE TO ENGINE TORQUE, A PASSAGE EXTENDING FROM SAID VALVE MEANS TO SAID SHIFT VALVE FOR DISTRIBUTING SAID PRESSURE SIGNAL TO SAID SHIFT VALVE TO ACTUATE THE SAME, AND BOOSTER VALVE MEANS DISPOSED IN AND PARTLY DEFINING SAID PASSAGE INCLUDING A VALVE CHAMBER AND A MOVABLE VALVE ELEMENT DISPOSED IN SAID CHAMBER, SAID CHAMBER COMMUNICATING WITH A HIGH PRESSURE REGION OF SAID CONDUIT STRUCTURE WHEN SAID VALVE ELEMENT IS MOVED IN ONE DIRECTION, SAID VALVE ELEMENT BEING SUBJECTED TO SAID PRESSURE SIGNAL AND URGED THEREBY IN SAID ONE DIRECTION WHEN SAID PRESSURE SIGNAL EXCEEDS A PRECALIBRATED VALVE.