Abstract: A particularly compact planetary gear mechanism includes an axially shiftable ring gear to provide either a direct drive mode or a speed reduction ratio mode between an input sun gear thereof and an output planet carrier thereof. In a first embodiment, the ring gear is urged in a first direction by a compressible spring apparatus to a conjoint coupled relationship with the sun gear for direct drive. In a less frequently used mode the ring gear is urged by a hydraulically actuated annular piston closely encircling it into a fixed relationship with a stationary coupling in opposition to the compressible spring apparatus. A second embodiment has no spring apparatus so that the annular piston is hydraulically biased in either axial direction for positively shifting the ring gear.

Abstract: Inching valves for providing controlled slow movement of a vehicle normally have a valve mechanism therein to control the pressure level of the fluid being directed to the driving clutch of the vehicle. Upon release of the pedal, a sudden jerk of the vehicle may occur. The modulating inching valve of the subject arrangement provides a housing having a valving mechanism slidably disposed therein and operative to selectively block communication between an inlet port and an outlet port. The modulating inching valve further includes an input actuator mechanism operative to selectively control the valve mechanism in response to the position of the operator's inching pedal. Through a portion of a predetermined travel distance of the input mechanism the operator controls the rate of pressure being supplied to the fluid actuated device and during the remaining portion of the predetermined travel distance the modulating relief valve automatically controls the rate of pressure rise.

Abstract: Fluid systems for controlling clutch engagement normally have modulating pressure relief valves to aid in smooth clutch engagement. It is also desired in such systems to ensure that the system pressure is reduced to a low level so that the load piston is fully reset prior to initial engagement of the newly filled clutch. In this arrangement, in order to ensure that the load piston is fully reset, a mechanism is provided which establishes a ratio between the pressure of the fluid being directed to the clutch and the pressure of the fluid acting on the load piston of the modulating pressure relief valve so that the pressurized fluid acting on the load piston during the filling of the clutch is vented to the reservoir to reset the load piston even though the pressure of the fluid available to the clutch is still at a higher pressure level.

Abstract: A fluid control system (10) for selectively controlling two independent actuators or clutches (12, 14) has a pair of normally opened solenoid valves (62, 64) for controlling fluid pressure in a pair of actuating chambers (40, 42). This controls actuation of a pair of directional spools (36, 38) which in turn controls engagement and disengagement of the clutches (12, 14) such that failure of one of the solenoid valves to close properly would not allow engagement of the clutches. A common actuating chamber (44) is provided between the directional spools (36, 38) and in fluid communication with the first and second actuating chambers (40, 42) through orifices (58). The abutment of the first and second directional spools prevents simultaneous engagement of both clutches.

Abstract: Fluid systems having modulating pressure relief valves are normally needed in systems having clutches that require smooth engagement. It is also desired in many systems to maintain a difference in pressure levels between the fluid in different clutches, such as, speed and directional clutches during initial engagement in order to ensure that only one of the clutches absorbs the initial load. In order to reduce power losses and improve system efficiency, it is desirable to reduce the pressure level of the higher clutch once the clutches are fully engaged. The present modulating pressure relief valve assembly provides a valve device that is effective to limit the maximum pressure in the system and change the pressure difference between the clutches upon full engagement thereof. The valve device is located in a single bore thus reducing total valve size and manufacturing costs.

Abstract: A fluid control system (10) for two independent actuators or clutches (11,12) has a pair of normally open solenoid valves (44,46) for controlling fluid pressure in a pair of actuating chambers (31,32). This controls actuation of a pair of directional spools (26,27) which in turn controls engagement and disengagement of the clutches (11,12) such that failure of one of the solenoid valves to close properly would not cause unexpected engagement of the associated clutch. A shuttle spool (59) is movable in response to pressurization of one of the actuating chambers (31,32) to a position for venting the other actuating chamber (31,32) thereby preventing simultaneous engagement of both clutches.

Abstract: A pressure modulating and reducing valve (10) communicates pressurized hydraulic fluid from a pump (11) to a hydraulically actuated clutch of a transmission at a modulated rate of pressure rise and at a reduced pressure. In order to provide a compact valve, the valve (10) has a pressure reducing valve spool (61) slidably nested within a sleeve member (46) of a load piston to provide a valving action therebetween for controlling fluid flow between an inlet port (24), a load port (26) and a drain port (27) in a body (19). Movement of the sleeve member (46) causes an increase in the pressure at the load port (26) which causes the pressure reducing valve spool (61) to move against a spring (77,78) to establish a pressure in the load port (26) proportional to the travel distance of the sleeve member (46).

Abstract: A pressure modulating valve 28 has a principal use for retrofitting into an original hydraulic system (10) to modulate the fluid pressure from a source (11) of hydraulic fluid to hydraulic clutches (50, 52) in a transmission (54). In prior art valves, the routing of hydraulic fluid from the original system to the valve involved the connection of many lines. The present invention is connected to the source (11) at only one location and discharges fluid to the clutches from said location. The valve (28) is operated by the fluid provided at the one location without the need to route fluid around the valve (28) to the various components thereof. The valve (28) also modulates the fluid supplied to the clutches from a low pressure to a high pressure to provide smooth clutch engagement.

Abstract: A hydraulic system responsive to movement of a shift lever energizes selected pairs of drive engaging devices in a vehicle transmission by applying a gradual rise in pressure to the selected speed drive engaging device and by applying a delayed and a lesser gradual pressure rise to a selected directional drive engaging device. The circuit neutralizes the transmission by blocking fluid pressure from at least one of the devices if the vehicle engine is started with the shift lever at a position other than neutral and also neutralizes the transmission when the vehicle brakes are applied while still maintaining full fluid pressure to other vehicle components. These functions are accomplished by a combination of a pair of selector valves, a pressure modulation valve assembly and a greatly simplified and compact spool differential check and safety valve.

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: A modulating valve in a hydraulic control system of a vehicle transmission for communicating fluid under pressure to a load at a gradually increasing rate or for venting fluid under pressure at a gradually decreasing rate from the load.