Abstract: A specific type of hydraulic fan drive system is provided for engine drive machines, such as on road and off road machines, such as buses, construction equipment, agricultural equipment, and so on. The hydraulic fan drive systems turn a cooling fan (39) which provides airflow to cool the engine on such machines. This system uses a proportional pressure reducing valve (34) (or combination of valves providing a pressure reducing function) between the pump (12) and the fan motor (38). This valve (34) or (combination of valves) controls the pressure drop across the fan motor (38) based on a control signal from an electronic controller (50). The valve allows as little or as much flow to pass as is required to maintain this pressure drop at the load (the fan motor (38)).

Abstract: An X-Y shifting mechanism (25) is disclosed for controlling the shifting of a shift rail (17) in a first (Y-Y) transverse direction. The mechanism includes a shift finger assembly (39) including a shift finger (23). A lever member (57) is pivotable about the axis (A) of rotation. When the lever member (57) is pivoted, the movement is transmitted through a spring (91) to rotate a spring seat member (73), thus causing pivotal movement of the shift finger (23). During a non-synchronous engagement, kick-out movement causes pivotal movement of the shift finger in the opposite direction, compressing the spring (91) rather than damaging the shifting mechanism. The disclosed mechanism also enables preselection of neutral, compressing the appropriate one of the springs (91), such that the preloaded spring will move the shift finger and shift rail to the neutral position as soon as a torque break occurs.

Abstract: A pressure override control which utilizes pump output flow for destroking of a variable displacement pump to minimize loss of power and generation of heat and which includes modifications to the displacement control valve for the pump and, particularly, the cross connection of displacement-controlling servo motors when the displacement control valve is in a neutral position with blocking of communication of said servo motors to a displacement control pressure and drain whereby the pump cannot be positioned in a maximum displacement position in response to certain system malfunctions in the power override control circuitry.

Abstract: A synchronous control system for a pair of hydrostatic transmissions and more particularly a drive for a vehicle using a pair of hydrostatic transmissions with each driving a propulsion member and a straight tracking control therefor, with the system having a pair of pressure-responsive displacement controls, associated one with each transmission and pressure lines connected thereto for providing a control pressure signal which is applied to a displacement control.

Abstract: An overspeed protection control for an engine which drives at least one pump and having valve means selectively operable to cause an increase in pressure in a circuit supplied by said pump and a resulting increase in load torque on the engine. Means responsive to the engine speed exceeding a predetermined value causes operation of the valve means, and includes a control valve positionable either in response to a pressure differential across an orifice in the circuit supplied by the pump with the pressure differential being an indication of flow rate and, therefore, engine speed, or operable by a control circuit including means for detecting engine speed.