Abstract: Double-acting hydraulic clutches. In a double-acting hydraulic clutch of the type having a pair of oppositely movable pistons for effecting engagement of clutch plates there is provided a resilient partition separating the chambers occupied by each of said pistons. Such resilient partition yields sufficiently upon the supplying to a given cylinder of energizing fluid whereby without slowing the entry of such fluid the shock of the in-rushing fluid is softened and undesired suddenness, or grab, in clutch engagement is minimized.

Abstract: A fluid pressure actuated friction clutch assembly includes rotatable driving and driven members adapted to be coupled frictionally together by a clutch pack as the pack is compressed by two pistons movable between advanced and retracted positions relative to the driving member. The pistons are moved between their advanced and retracted positions by a non-compressible pressure fluid as the latter is filled and emptied from a main chamber located behind the pistons. Secondary chambers containing pressure fluid urge the pistons toward their retracted positions with one of the pistons being urged rearwardly with a greater force than the other. Accordingly, as the main chamber is filled, the other piston advances to engage and partially compress the clutch pack before the one piston engages the clutch pack to fully compress the clutch pack and thereby complete clutch engagement.

Abstract: A transmission control apparatus for a vehicle having a transmission with fluid actuated clutch means and hydraulic brake means wherein a first fluid conduit, having a fluid flow constricting means interposed therein, connects a fluid pressure source with the clutch means, with an inching valve means being fluidically connected in parallel with the first conduit by second and third conduits upstream and downstream respectively, from the fluid flow constricting means, for regulating the pressure of the pressure fluid supplied to the clutch means, with the inching valve means also being operatively connected with the brake means and responsive to the degree of actuation of the brake means and actuatable between a first and a second position, whereby in the first position, the pressure fluid can freely flow into, through and out of the inching valve toward the clutch means so as to effectively bypass the fluid flow constricting means, however in the second position, the fluid flow through the second conduit is b

Abstract: A fluid pressure regulating apparatus in which a conduit means connects a source of pressure fluid to a fluid pressure operated clutch for actuating the latter and in which a valve means is interposed for controlling the pressure of fluid passing therethrough in such a manner so that the fluid pressure increases from a minimum to a maximum value within a predetermined interval of time initially at the same rate as the source pressure, then at a lesser rate than the source pressure, and finally again at the same rate as the source pressure to assure shock free engagement of the clutch.

Abstract: The power train of a crawler tractor comprises a hydraulically operated modulating main clutch (operated by a clutch control valve) for transmitting motive power from the tractor engine to a hydraulically operated reversible multi-speed range power shift transmission (operated by a shift selector valve) for varying the speed at the output shaft of the transmission. A control lever assembly at the tractor operator's station comprises a manually operable gear selector lever and a manually operable safety lever. The gear selector lever is pivotally mounted on an oscillatable shaft and movable laterally in opposite directions from a centered neutral position to rotate the oscillatable shaft and thereby operate the shift selector valve (connected to the oscillatable shaft) and shift the transmission to either first or second speed ranges in either forward or reverse direction.

Abstract: A device for gradually increasing hydraulic pressure in a hydraulic fluid supply control circuit for respective hydraulically operated cylinder-piston assemblies of clutches provided in a transmission, which has an inlet connected to a source of hydraulic pressure, an outlet connected to each of the cylinder-piston assemblies, a passage for communicating said inlet with said outlet, a quick return valve provided in said package and having a large diameter land portion and a plurality of small diameter land portions, means for gradually increasing hydraulic pressure including a cylindrical valve and a pressure regulating valve, wherein said pressure regulating valve is shut off from the main hydraulic circuit until the cylinder chamber of said clutch brake cylinder-piston assembly is filled with hydraulic fluid, whereby peak pressure is not produced immediately before the hydraulic pressure is started so as to permit the hydraulic pressure to be gradually increased.

Abstract: A hydraulic transmission control circuit includes a hydraulically responsive modulating valve for modulating a first fluid pressure and a differential valve for establishing a second fluid pressure communicated to a master clutch, the control circuit also including a manually controlled modulating valve for precisely adjusting the second pressure and for selectively adjusting the first fluid pressure during regulation of the second fluid pressure, the manual modulating valve also being adapted for selectively communicating the hydraulically responsive modulating valve with a drain in order to assure a proper rate of modulation for both the first and second fluid pressures.

Abstract: In a control system for a vehicle having a transmission with fluid actuated frictional engaging means and brake means wherein a first hydraulic passage means interconnects a fluid pressure source with the frictional engaging means, a regulating valve is disposed in the first hydraulic passage means, for regulating the pressure of the pressure fluid supplied to the frictional engaging means, with the regulating valve means also being operatively connected with the brake means and responsive to the degree of actuation of the brake means and actuatable between a first and a second position, whereby in the first position the pressure fluid can freely flow into, through and out of the inching valve toward the frictional engaging means, however in the second position, the fluid flow through a first set of radial apertures is blocked by a regulating spool and thereafter further radial apertures are progressively opened by the regulating spool means so as to regulate the force of the pressure fluid acting on the fric

Abstract: An accumulator structure for use in a hydraulic control system for controlling an hydraulic motor utilized to engage a friction device in a transmission including an accumulator piston mounted in a housing, a source of fluid pressure, a valve connected between the source and the motor. A first conduit connects the valve and motor, the first conduit including a fluid restriction, and a second conduit connects the valve and the accumulator. A third conduit is provided between the accumulator and the first conduit. The accumulator includes a counter-bored portion defining together with a reduced land portion on said piston, a passage which connects the second conduit to the third conduit when the piston is in the inactive position to provide a rapid fluid fill of the motor initially.

Abstract: A control system for a vehicular drive train including a slipping clutch for proportioning power from a prime mover to implements and a primary output shaft of the vehicle including a manual control conditioned by a manual selector to vary engagement of the slipping clutch through a regulating valve in a first mode of vehicle operation and to regulate acceleration of the prime mover in a second mode of vehicle operation.

Abstract: Hydraulic mechanism in a transmission for engaging a clutch for forward or reverse before a clutch for first, second, or third speed. Flow of pressure fluid to the latter clutch is by way of a quick fill spool having a large orifice, a rate of rise spool, and a poppet therein having a small orifice. A restricted orifice of appreciable, helically turned length is used in connection with the spools and the poppet in such a way that, after the power unit for the clutch for first, second, or third speed is filled with fluid, pressure of the fluid in the power unit is raised at controlled rate to its maximum.

Abstract: A system for controlling pressure of a fluid, specifically the pressure of servo oil delivered to a clutch which determines the torque transmitted by the clutch. The system includes a pump, a pressure regulating valve to provide servo oil at constant pressure from the pump, and a pilot valve controlled by a solenoid responsive to electric current to vary the pressure in a pilot fluid line supplied from the constant pressure line. The oil is delivered from the fixed pressure line to the clutch by a throttling flow control servo valve which can open for rapid filling of the clutch cylinder. This valve is biased to close by the delivered pressure and biased to open by the pilot pressure. It may also be biased to close by a spring, and in this case be restrained from completely closing, so that the valve assumes its minimum area when the delivered pressure is slightly less than the pilot pressure.

Abstract: Hydraulic double clutch comprising a tractor-driving clutch unit and a power takeoff clutch unit accommodated in a clutch housing serving also as an oil tank. Hydraulic pumps disposed in the housing have gears respectively meshing with a gear on the drive disk assembly of the double clutch to force the working oil into the clutch units through individual oil passages and to push the pistons of the units. Each of the oil passages is provided with a poppet valve at an intermediate portion thereof. The poppet valves are opened or closed to disengage or engage the clutch units independently of each other for interruption or transmission of the torque of engine. Each of the valves is automatically opened when the pressure on the piston builds up to excess and is therefore serviceable also as a pressure control valve. The valve is operable to bring the clutch unit into substantially semi-engaged state.

Abstract: A power shift transmission having a torque converter with a lock-up clutch for locking the impeller to the turbine of the torque converter to provide direct drive from the engine to the input end of the transmission includes a flow-limiting pressure-reducing valve, between the source of pressurized fluid for actuating the clutches of the system, for reducing the pressure and flow of the fluid to the pressure-actuated lock-up clutch below the pressure for the actuation of the remainder of the clutches in the system. This system provides a smoother operation of the lock-up clutch as well as prevents the creation of a high pressure drop within the actuating fluid system.

Abstract: A dual hydraulic clutch with two operating positions and an intermediate neutral position receives pressure fluid through a three-position selector valve communicating with a pair of piston cylinders which are alternately under high and low fluid pressure in operation and are both under low pressure in neutral. Shifting the control valve partly unloads one of the cylinders into a throttled discharge line with generation of a pressure drop therein to actuate a bypass valve for instantly lowering the pressure in a supply line; the disappearance of this pressure drop upon termination of shifting gradually recloses the bypass valve for progressively raising the supply pressure to its operating level.

Abstract: Clutch controlling apparatus which may be utilized in industrial-type vehicles, such as for example, forklift trucks, for controlling the vehicle during inching operations includes a source of fluid pressure, a fluid pressure-type clutch fluidically connected to the pressure source, an inching valve disposed within the fluid circuit connecting the fluid pressure source and the clutch mechanism which controls the degree to which the clutch mechanism is actuated and which in turn is actuated to a degree which is dependent upon the depression of the vehicle brake pedal, and limitng means for selectively inactivating the inching valve such that the inching valve is inoperative independent of the brake pedal.In this manner, when the vehicle is being operated on level ground, the inching operation is performed by intermittently depressing the brake pedal which actuates the inching valve which in turn deactivates the clutch mechanism thereby terminating driving torque to the vehicle transmission.

Abstract: Disclosed herein is a hydraulic modulator valve for a control system of a hydraulically operated mechanism having a casing with a bore therein, a stepped spool axially and slidably engaged within the bore to form an annular fluid throttle passage against the circumference of the bore between a first and a second ports drilled through the casing, and spool actuator for controlling axial displacement of the spool. The stepped spool comprises a large diameter portion to be hermetically engaged within the bore, a small diameter portion and a medium diameter portion in sequence, the throttle passage being formed by the bore and the medium and small portions of the spool.

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.

Abstract: An "inching" valve for use in vehicles such as an industrial lift truck for controlling the operation of separate pressurized fluid actuated clutches for driving the vehicle forwards or backwards wherein rotary and axial movements of a single cylindrical valve piston within its cylinder control respectively clutch selection for forward or reverse drive and the "inching" movement in the drive direction selected in functional relation with actuation of the brake pedal.

Abstract: A vehicle or vessel having a forward and rearward clutch has, according to the invention, a single lever clutch control system whereby an operator may select a forward or rearward clutch and, simultaneously "inch" the vehicle or vessel using one and the same control lever.

Abstract: A hydraulic pressure regulating system for a vehicle having a regulator valve, a shift valve and a plurality of fluid actuated clutch means, wherein an accumulator being provided between the regulator valve and the shift valve is so designed as to control the fluid pressure to keep it relatively low when the fluid actuated clutch means is in its initial engagement condition and communicates with the regulator valve so as to increase the fluid pressure sufficiently to provide for the full engagement of the fluid actuated clutch means when the clutch means becomes substantially fully engaged.