Sauer Gmbh

William L Welscher

William J Akins

In a wheeled vehicle propelled by a hydrostatic transmission which has a variable displacement pump fluidly connected to a motor in a closed circuit for propulsion and a hydraulically-released brake for stopping the vehicle, a return to neutral and brake release circuit including: a system reservoir for holding fluid; a charge pump for drawing fluid from the reservoir and providing pressurized flow of same; a hydraulically-released brake operatively attached to the wheels of vehicle and the charge pump; a displacement control for providing differential pressure command signals to a servo piston for varying hydrostatic transmission displacement; a solenoid valve for interrupting the flow of fluid to the brake and displacement control, thus braking the vehicle and returning the variable pump to neutral; and a set of drain passages fluidly connecting the solenoid, displacement control and brake (through the solenoid) to the system reservoir so that the components may be immediately drained to allow the engagement of the hydraulically-released brake and return of the variable pump to neutral. Interrupting the fluid flow and draining the residual pressure, as described above, stops the vehicle quickly.

Displacement override/brake control circuit

A control assembly for hydrostatic transmission having a valve controlling the flow of fluid to the pump includes a pump body member having a cavity with a moveable valve element mounted in the body and connected to a fluid pressure source, and having a neutral position. Linkage including an upstanding pin interconnects the pump to the valve element. A cover extends over the body and is secured thereto. A control shaft extends through the cover having an exterior end with a manual control lever mounted thereon, and an interior end to which a cam plate having an elongated cam slot therein is secured. A detent portion in the cam slot opposite to the upstanding pin defines a neutral position for the pin. A screw adjusts the valve element into a neutral position. A torsional spring in the cover yieldingly holds the control shaft, the control lever, the cam plate, the valve element, and the remainder of the linkage in a neutral position. The method of assembling the control assembly involves placing an elongated alignment tool on the upstanding pin and moving the tool into a prepositioned cam slot detent, placing the cover on said body and extending said tool through an aperture in the cover; securing the cover to the body, and removing the tool.

Method of assembling a control having a body member and a cover member

A manual control for hydrostatic transmission has a body member having a first cavity exposed to hydraulic pressure into which a manually operated input shaft extends. The body member has a second cavity with a passage intersecting the first cavity and a shaft and O-ring seal in therebetween. The second cavity is free of hydraulic pressure and has an electrical switch extending thereinto. Switch has an actuating member cable of electrically and individually actuating at least two separate circuits. Cam are operatively connected to the input shaft and positioned to contact the electrical switch such that a first of the cam caused by the input shaft will open one of the circuits and a second increment of movement of the cam will close the other of the circuits. Switches normally in a neutral and closed position with respect to one circuit. The method of assembling the aforementioned structure involves providing a torsional spring to interconnect the body member, the cam, and the shaft to normally maintain the switch in a neutral position wherein one circuit is closed and the other is opened. The cam plate of the cam is released from spring connection to the shaft. The cam plate is devised so that it will maintain the switch in its neutral position. The cam plate is then fixed in a position with respect to the input shaft and the switch.

Neutral start switch and backup alarm switch, and method of assembling

A control assembly, for hydrostatic transmissions equipped with a pump and a valve element to control flow of hydraulic fluid to the pump, including a pump body member having a cavity with a movable valve element mounted in the body and connected to a source of pressurized hydraulic fluid and having a neutral position. A cover member is secured over the body member and a control shaft having interior and exterior ends extends therethrough. A manual control lever is mounted on the exterior end of the control shaft, and a cam plate with an elongated cam slot therein is secured to the interior end of the control shaft. Linkage, including an arm pivotally connected to the pump body and having a first upstanding pin thereon, interconnects the pump and the valve element. A second arm pivotally mounted on the first upstanding pin and a second upstanding pin mounted offset from the first upstanding pin on the second arm interconnects the control lever and valve element via control shaft and cam plate. A detent portion located in the cam slot opposite the second upstanding pin defines a concurrent neutral position for the pin. A resilient torque spring in the cover yieldingly holds the control shaft, the control lever, the cam plate in the concurrent neutral position and simultaneously holds the valve element and the remainder of the linkage in a neutral position. A method of assembling this control assembly is also disclosed.

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Ankeny, IA, United States of America

William L Welscher