Modulating inching valve with automatic pressure control

Abstract

Inching valves for providing controlled slow movement of a vehicle normally have a valve mechanism therein to control the pressure level of the fluid being directed to the driving clutch of the vehicle. Upon release of the pedal, a sudden jerk of the vehicle may occur. The modulating inching valve of the subject arrangement provides a housing having a valving mechanism slidably disposed therein and operative to selectively block communication between an inlet port and an outlet port. The modulating inching valve further includes an input actuator mechanism operative to selectively control the valve mechanism in response to the position of the operator's inching pedal. Through a portion of a predetermined travel distance of the input mechanism the operator controls the rate of pressure being supplied to the fluid actuated device and during the remaining portion of the predetermined travel distance the modulating relief valve automatically controls the rate of pressure rise. The modulating inching valve provides a compact arrangement allowing selective control of the pressure level to the fluid actuator device at lower torque levels within the clutch but inhibits the operator'3 s ability to control the rate of pressure rise to the clutch during higher torque levels. This eliminates undue heat and abnormal wear of the elements and further eliminates the tendency of the vehicle to jerk if the inching pedal is fully released quickly.