Commercial Intertech Limited

David E Frye

Frederick W Cords

Jeffrey S Swanson

A hydraulic control system configured for use with a towed vehicle hydraulic brake system controls the pressure of the hydraulic fluid provided to the brake as a function of an operator-selected input. A hydraulic pressure control manifold is coupled between a pump and the towed vehicle brake and controls the pressure of the hydraulic fluid supplied to the brake with a plurality of pressure relief check valves interconnected in a parallel hydraulic circuit between the pump and the brake. A plurality of on-off valves are connected in a series hydraulic circuit with the check valves. The pressure relief levels of the check valves correspond to a plurality of towed vehicle braking forces. An operator of a towing vehicle chooses a desired one of the plurality of braking forces through a selector switch. When a desired braking force is chosen, appropriate on-off valves in the hydraulic pressure control manifold are closed or opened, thereby enabling or disabling appropriate check valves and controlling the pressure of the hydraulic fluid supplied to the brake and the corresponding towed vehicle braking force.

Towed vehicle brake system

A power-assisted hydraulic steering system for use in connection with a vehicle having a steering linkage which couples a steering wheel to a vehicle steering actuator, an electrically actuated hydraulic pump, and a tank of hydraulic fluid. The steering system includes a boost cylinder connected to the steering actuator, a hydraulic spool valve fluidly coupling the pump and tank to the boost cylinder, and a switch coupled to the pump. A spool which is mechanically coupled to the steering actuator is mounted within the valve for reciprocal motion between neutral, extended and retracted positions, and is biased to the neutral position by a centering spring which establishes a power-assist threshold. The switch senses the position of the spool, and switches the pump on when the spool is in the extended and retracted positions. When steering forces applied to the steering actuator by rotation of the steering wheel are less than the power-assist threshold, the spool will remain in the neutral position with the pump switched off and the valve fluidly isolating the pump and tank from the boost cylinder. When steering forces applied to the steering actuator by rotation of the steering wheel are greater than the power-assist threshold, the linkage housing forces the spool to the retracted or extended position depending on the direction of the rotation, thereby switching the pump on and driving the boost cylinder and steering actuator through a power-assist retraction or extension stroke.

Power-assisted hydraulic steering system

A brake system for use in connection with a vehicle including a hydraulic internally boosted master cylinder, a hydraulic pump, and hydraulic brakes wherein the master cylinder controls hydraulic fluid pressure to the brakes and has a primary or sensing piston, a modulator stem, and a secondary pistons, with the sensing piston responsive to a mechanical input force to urge the secondary piston forwards increasing the hydraulic fluid pressure applied to the brakes. In a second embodiment, the internally boosted master cylinder further includes a tertiary piston movable by hydraulic pressure between retracted and extended positions and biased toward the retracted position by a tertiary piston return spring. The tertiary piston controls hydraulic pressure applied to one or more brakes independent of the brakes controlled by the secondary piston.

Internally boosted master cylinder

A brake system with a hydraulic pilot brake valve for use in connection with a vehicle requiring finite brake control with high volume pressure control. The brake system includes the hydraulic pilot brake valve, a main hydraulic system, a control hydraulic system, and hydraulic brakes. The main hydraulic system includes a belt-driven hydraulic pump, a tank of hydraulic fluid, and an accumulator. The control hydraulic system includes an electrically actuated hydraulic pump and a tank of hydraulic fluid. The pilot brake valve is designed to control the flow of hydraulic fluid from the main hydraulic system to the hydraulic brakes, and includes a modulator chamber and a primary chamber. The modulator chamber houses a modulator piston valve, and the primary chamber houses a primary input piston which extends into a sleeve chamber of a sleeve. The modulator piston valve controls a modulating fluid flow from the control hydraulic system to generate amplified input forces on the input piston in the primary chamber. These input forces urge the input piston and sleeve toward extended positions, which controls the flow of hydraulic fluid from the main system to the brakes. The modulator piston valve is comprised of a modulator piston and a primary control piston, both being movable between retracted and extended positions and biased toward the retracted position, and a secondary control piston, which is capable of motion between extended and retracted positions.

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North Mankato, MN, United States of America

David E Frye