Caterpillar Tractor Co.

Caterpillar Inc.

James P Mueller

Howard A Marsden

Weldon L Phelps

Willard J Haak

David G Johnson

Clutch-brake steering systems are known to operate on track vehicles which are highly reliable and cost effective, but lacked the fine degree of controllability found in the more expensive differential steering. An electronically controlled clutch-brake steering control apparatus provides control signals to electrohydraulic proportional valves for accurately modulating the control pressures of a set of steering clutches and brakes. A pair of sensors deliver signals, which are indicative of track speed, to the control apparatus. The apparatus acts to adaptively adjust selected ones of the valves to maintain a desired track speed differential. Thus, the controllability of the clutch-brake steering system is enhanced to effectively compete with more expensive and complex systems.

Clutch brake steering control

A high pressure hydraulic system, including a bidirectional fluid motor having two ports, a pair of normally closed, pilot operated poppet valves, each connected to an associated port, a fluid reservoir, a flow sensor having a flow path interconnecting each of the poppet valves and the reservoir and having an output for providing a signal representing the flow rate, along the flow path, a pair of metering valves each connected to the pilot of an associated poppet valve for controlling the flow of fluid through the associated poppet valve, control signal inputs for each of the metering valves, and flow rate signal inputs connected to the output of the flow sensor for each of the metering valves so that each poppet valve is ultimately controlled by both control signals and the flow rate through the flow sensor.

High pressure hydraulic system

A brake modulation valve includes a spool reciprocable in a body to provide application and release of the brakes of a vehicle through movement of a pedal, the movement of the pedal providing application of the brakes being resisted by resilient means in the form of primary, secondary and tertiary springs brought into play in series fashion so that the operator of the pedal is aware of varying pedal feel during application of the brakes.

Brake modulation valve for pedal-applied brakes

A digital positioner for remote actuation of a control valve includes a double-acting actuating piston connected to the control valve and a plurality of fluid-responsive stop means disposed to either side of the actuating piston. A plurality of remotely controlled pilot valves are operatively connected to respectively control the actuating piston and selected ones of the stop means. The system is especially adapted for remotely controlling hydraulic systems having a control valve for modulated control of the system for different speeds of the system.

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East Peoria, IL, United States of America

James P Mueller