Importance

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Abstract

A fluid control valve for controlling the flow of hydraulic fluid at a high pressure from a primary pump and the flow of the hydraulic fluid at a low charge pressure from a charge pump to cam-lobe type hydraulic motors which are used to assist in driving a vehicle. When energizing the motors, charge pressure is first delivered to the motors. Thereafter, all of the supply and return lines leading to the motors and to the primary pump and the charge pump are connected together to further increase the pressure delivered to the motors. Finally, the charge pressure line is disconnected and the supply and return lines leading to the motors are connected to the high pressure supply and return lines leading to the primary pump. When the supply and return lines leading to the motors are disconnected from the primary pump, the lines leading to the motors are drained into a reservoir. An accumulator is provided within the motors to absorb sudden pressure delivered thereto. Notches are placed on the spool for further gradually introducing the high pressure fluid to the supply and return lines of the motors. The flow of charge pressure fluid which controls the shifting of the spool is restricted by an orifice to control the rate of shifting and to provide sufficent time for gradually introducing the high pressure to the motors.

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First Claim