Sundstrand Corporation

Sauer-danfoss Inc.

Stanley W Crull

Frederic W Pollman

Mark A Peterson

Donald J MacIntosh

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 (,) which provides airflow to cool the engine on such machines. This system uses a proportional pressure reducing valve (,) (or combination of valves providing a pressure reducing function) between the pump (,) and the fan motor (,). This valve (,) or (combination of valves) controls the pressure drop across the fan motor (,) based on a control signal from an electronic controller (,). 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 (,)).

Hydraulic fan drive system having a non-dedicated flow source

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.

Pressure override control

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. A rotary valve with a pair of relatively rotatable valve members connected one to each of the two transmissions for rotation proportional to the output speed of the transmissions and connected into said pressure lines and having port means which have their relation varied, dependent upon a displacement in the position of one valve member with respect to the other to connect a pressure line to a sump and thereby modify the control pressure in said last-mentioned pressure line, to result in modifying the speed of one transmission and bring the two transmissions back to synchronized speed.

Synchronous control system

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.

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Ames, IA, United States of America

Stanley W Crull