Abstract: This disclosure deals with a drive for a fan of an internal combustion engine, the drive including a clutch connected between the engine and the fan blades. A piston is movable to actuate the clutch, and an actuating fluid is employed to move the piston. The fan drive is connected to the engine lubricating system so that the engine lubricant acts as the actuating fluid. An engine temperature responsive circuit actuates the clutch to engage and disengage at certain engine temperatures. The fan drive includes a fluid feed path, return path and control path, but only two fluid connections to the clutch are necessary. When the temperature responsive circuit operates to disengage the clutch, a valve releases the pressure in order to quickly disengage the clutch.

Abstract: Disclosed is a fluid-pressure operated mechanism such as a clutch having radial walls defining a fluid-receiving and exhausting chamber between them. The clutch is of the hydraulic-apply, spring-release type, fluid pressure being supplied to engage the clutch and fluid pressure being exhausted to release the clutch. Fluid pressure release is often not rapid enough to enable quick release of the clutch and relief valve means of the centrifugal type is provided to accelerate fluid release. The improvement resides in spring means in combination with the centrifugal valve to prevent operation of that valve during rotation of the clutch at speeds below a predetermined value, whereby to prevent complete dumping of fluid, so as to enable the released clutch to retain a volume of fluid consistent with rapid re-engagement of the clutch when fluid pressure is applied.

Abstract: A pressure responsive relief valve closing responsive to clutch actuating pressure and opening responsive to centrifugal forces and a spring force to relieve residual pressure in the hydraulic actuator of a rotating clutch to avoid clutch drag.

Abstract: There is disclosed a relief valve apparatus for an oil pressure operated clutch having an oil pressure operation chamber, the apparatus comprising a weight in combination with a leaf spring wherein the weight, during rotation of the clutch, is subjected to a centrifugal force and, under the influence thereof, promotes a valve opening force of the leaf spring itself to permit the discharge or dumping or oil contained within the chamber.

Abstract: A relieve valve in a hydraulically operated clutch for the residual pressure caused by centrifugal force on the hydraulic fluid tending to produce limited engagement of the clutch.

Abstract: A fluid pressure operated clutch which transmits torque from an engine output shaft to a transmission input shaft, including a rotatable flywheel connected to the output shaft, an adapter connected to the flywheel for rotation with the flywheel, the adapter having a first annular plate with a fluid passage near the inner periphery of the plate, and a centrifugal piston which defines with the adapter a fluid chamber supporting a rotatable torus of hydraulic fluid. The piston has a second annular plate, slideable with respect to the first plate, and a second fluid passage near the outer periphery of the second plate. The first and second plates, at their inner peripheries, provide a controlled clearance to vary the rate of hydraulic fluid into the first fluid chamber as the second plate slides.

Abstract: A hydraulically operated friction clutch wherein a spring-urged piston is provided to effect engagement of the friction elements, received in a casing mounted on the driving shaft for axial reciprocation relative to this casing and defining with this casing two coaxially arranged variable volume chambers communicating with each other, adapted to receive liquid under pressure the first one of said chambers is in permanent communication with a pressure liquid supply passage, while the other chamber is communicable via a valve means with a drain passage and the pressure liquid supply passage. The pressure liquid supply passage and the drain passage have a portion common to both of them, wherein the valve means is mounted so that the movable valve member thereof can reciprocate in a direction substantially perpendicular to the axis of rotation of the clutch, by which reciprocation it selectively connects the other chamber with the drain passage and with the pressure liquid supply passage.

Abstract: A rotating annular piston is hydraulically actuated to engage a rotating friction device, such as a clutch or brake, by introducing fluid pressure to an apply chamber for the piston. Disengagement is subsequently effected by exhausting fluid from the chamber, after which a centrifugal pressure head release valve in a wall of the chamber releases any residual entrapped fluid from the chamber in order to prevent undesired false actuation of the rotating piston that may otherwise occur due to centrifugal force acting on the residual fluid. The valve comprises a metallic ball subject to centrifugal force tending to move it radially outward from the piston axis but held in a tapered or conical seat of an exhaust port, thereby blocking the port, by fluid pressure supplied to the apply chamber. In the absence of that fluid pressure, however, the centrifugal force exerted on the ball unseats it and opens the port.

Abstract: A multi-disc hydraulically operated friction clutch is provided with valve means in the form of longitudinally split plugs received in the drain openings of the plunger and varying the flow passage area of these openings, depending on the position of the plunger. Said plugs of the valve means are displaced, on the one hand, by the contact thereof with the pressure disc of the clutch, and, on the other hand, by their abutting against the housing of the clutch. By selecting the ratings of the valve means, i.e., the dimensions of the drain slit in the plugs, it is possible to ensure any required degree of smoothness of engagement of the clutch, the pressure disc acting upon the package of the friction discs with a gradually varying effort, proportional to the rate of draining of the working fluid through the plunger.