Centrifugal clutch with overspeed relief valve

Claim 1

In a clutch for transmitting torque from an engine to the input shaft of a transmission, said clutch including a rotatable input member having means for connection to said engine and having means defining an annular fluid retaining chamber whereby centrifugal force generates fluid pressure in said chamber which is a function of engine speed and thereby the rate of rotation of said input member, a driven hub disposed coaxially with respect to said input member and being drivingly coupled to said transmission input shaft, a clutch pack of annular input clutch plates disposed coaxially with respect to said input member, said pack having at least one driving plate constrained for rotation with said input member and having at least one driven plate constrained for rotation with said driven hub, an annular pressure plate disposed coaxially with respect to said clutch plates for exerting a force thereon tending to engage said driving and driven plates, an annular clutch capacity modifying member disposed in said chamber of said input member and exposed to said fluid pressure therein, said input clutch capacity modifying member being movable axially in response to changes of said fluid pressure, at least one engagement spring acting between said capacity modifying member and said pressure plate for exerting a force on said pressure plate tending to engage said input clutch plates, at least one disengagement spring acting on said capacity modifying member in opposition to the force of said fluid pressure thereon whereby said engagement spring is ineffective to engage said input clutch plates until said fluid pressure reaches a first predetermined level, and further including centrifugal overspeed relief means for automatically disengaging said clutch when engine speed has reached a second, higher predetermined level and for automatically re-engaging said clutch when speed drops below said second level whereby damage due to overspeeding is prevented.