Abstract: A rotary control valve includes a directional control valve having a rotatable valve element for controlling the direction of fluid flow from an input passage to a pair of control ports and from the control ports to a drain passage. A pressure regulating valve is connected to a source of pilot pressure and has a valve spool for controlling the regulated pressure level of pilot fluid in the input passage. A cam is connected to the valve element for unitary rotation therewith. A spring and a plunger are disposed between the valve spool and the cam so that the valve spool is mechanically moved in a rectilinear direction by the cam in either direction from a neutral position to increase the level of the regulated pressure in the input passage proportional to the degree of rotation of the rotatable valve element.

Abstract: A vehicular steering mechanism of overly complex construction is known which displaces a left turn control valve or a right turn control valve through separated cams in response to the rotation of a steering wheel. The subject steering mechanism is simpler, more economical and more compact by including an input shaft and a single actuating cam which are conjointly rotatable away from a neutral position in either direction. The actuating cam defines a profiled guide slot of a substantially spiral shape, and a cam follower assembly is cooperatively associated therewith including a cam following roller wheel that is received in the profiled guide slot. The cam follower assembly includes a bellcrank supporting the roller wheel and indirectly connected to a left turn control valve and a right turn control valve. The vehicle is steered by the controlled rotation of the bellcrank and the subsequent displacement of the control valves and. The steering mechanism also includes an effective centering and stop assembly.

Abstract: A track adjusting flow controlling mechanism sets the optimum tension or "controlled sag" in the endless track of a track type vehicle. A piston and associated valve assembly control flow of pressurized fluid to a track adjusting clyinder. Movement of the piston tensions the track with substantially no sag ("S") and subsequent retraction of the piston provides correct track tension with an optimum track sag ("S"). Supply of pressurized fluid to the piston and valve assembly is controlled by the vehicle operator from the operator's station. Conventional track adjusting operations require considerable time and effort and are often an undesirable task. In view of this, the adjusting task is often neglected with the resulting rapid wear of the track and related components. The subject track adjusting mechanism provides a quick and simple operation to provide proper track adjustment.

Abstract: An underspeed actuator (18) is connected to the displacement control (17) for controlling the displacement of a variable displacement pump (11) of a hydrostatic transmission (10) in response to the pressure differential between low and high pressure control signals (A,B) wherein the pressure differential is directly proportional to the engine speed. An overspeed control valve means (41) is connected to the low and high pressure signals and decreases the pressure level of the high pressure signal received by the underspeed actuator (18) in response to the pressure differential exceeding a predetermined magnitude. This reduces the displacement of the variable displacement pump (11) thereby controlling the amount of engine overspeed caused by the hydrostatic transmission (10) driving the engine when the vehicle is descending a steep hill.

Abstract: A control arrangement comprises a pivotal control member having a pair of arms and a pivotal lever disposed between the arms. The stop member is secured on the lever to engage a snubber upon relative pivoting between the control member and lever. The control arrangement is adapted for connection to a control valve to alert the operator when the control lever has over-travelled a "run" condition of operation when the stop member engages the snubber.

Abstract: A fluid control circuit includes a source of pressurized fluid (10) adapted for connection to a hydrostatic transmission (23) upon actuation of a vent control valve (16). The vent control valve (16) is connected to a control and preconditioning valve (17) which functions to ensure that a control lever (14) is in its "vent" position upon starting of an engine and provides for the continuous preconditioning of the control circuit subsequent to such start-up. The control circuit is relatively non-complex in structure and function and does not require positioning of the control lever (14) in a special reset position upon shifting thereof between its "run" and "vent" positions.

Abstract: A fluid control cirucit for selectively varying the displacement of a variable displacement pump (P), such as the type employed in a hydrostatic transmission, comprises a primary control circuit connecting a pressurized fluid source (10) with the pump (P) and adapted to be actuated to selectively vary the displacement of the pump (P) between minimum and maximum values. A separate override control circuit is connected to the primary control circuit to override it to selectively vary the displacement of the pump (P).

Abstract: A control circuit comprises pressurized fluid source (11), a two-position directional control valve (14) and an actuator (13), such as the pump of a hydrostatic transmission, connected to the fluid source and the control valve to be selectively actuated thereby.

Abstract: A control circuit (10) for the variable displacement pump (18) of a hydrostatic transmission (16) or the like comprises an underspeed actuator (31) connected to the servo system (19) of the pump (18), a venturi (15) interconnected between a source of pressurized working fluid (11) and the pump (18) and a pressure regulating valve (36) interconnected between a downstream side of the venturi (15) and the pump (18). A throat (29) and upstream side of the venturi (15) are connected to the underspeed actuator (31) for communicating a differential fluid pressure signal thereto to automatically control the displacement of the pump (18) under certain operating conditions of an engine of a vehicle.

Abstract: A hydrostatic unit of the type contemplated by the present invention includes one or more pump and motor combinations interconnected by means of a conventional closed loop. Controls for the hydrostatic unit include a speed control and vent valve assembly as well as a venturi manifold which functions to normally establish a selected pressure differential in a pair of supply conduits for determining instant operating conditions for the transmission. In order to automatically regulate displacement of each pump unit in response to prime mover speed, an underspeed actuator valve unit includes a piston which is hydraulically responsive to the differential pressure in order to adjust operation of a lever which controls displacement of the pump unit. A part throttle control valve prevents the underspeed actuator from reducing displacement of the pump unit when speed of the prime mover is reduced by a manual throttle control.