US 4,284,309 AGranted

Brake control valve having operator feedback

AssigneeCaterpillar Tractor Co.

InventorWayne A. Hoefer

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Abstract

PCT No. PCT/US79/00595 Sec. 371 Date Aug. 13, 1979 Sec. 102(e) Date Aug. 13, 1979 PCT Filed Aug. 13, 1979 PCT Pub. No. WO81/00386 PCT Pub. Date Feb. 19, 1981 Conventional fluid control circuits for service brakes and the like do not always provide an operator with "pedal feel" to indicate the degree of brake engagement. Such "pedal feel" is particularly desirable in braking systems wherein the brakes thereof are spring-engaged and released by hydraulic fluid pressure. This invention provides a control valve (18) having an inlet (20), an outlet (21), a valve member (19) movable betweeen closed and open position, and a first spring (30) for urging the valve member (19) toward its closed position. An operator input (36) is adapted to apply variable input force to the valve (18) to reduce the closing force of the first spring (30) and a second spring (33) is provided for applying a progressively increased opposing force to the operator's input force to provide the operator with "pedal feel" to indicate the degree of engagement of the brakes (15). A pair of passages (24,39) communicate the inlet (20) with opposite ends of the valve member (19) to aid in providing such "pedal feel."

Claims17

Dependent claims

In a fluid control circuit (10) having pump means (11) for discharging pressurized fluid therefrom, fluid actuated coupling means (15) for being actuated upon communication of pressurized fluid to the actuating chamber (14) thereof from said pump means (11), said coupling means (15) having an actuating chamber (14), and valve means 18 for selectively venting pressurized fluid from the actuating chamber (14) of said coupling means (15) to control actuation thereof, said valve means (18) including an inlet (20) connected to said pump means (11), an outlet (21) connected to a reservoir, a valve member (19) movable between a closed position blocking communication between said inlet (20) and said outlet (21) and an open position communicating said inlet (20) with said outlet (21), first means (23) for applying an opening force to said valve member (19) to urge it towards its open position, including first passage means (24) for communicating fluid pressure from said inlet (20) to act on said valve member (24), and second means (29) for applying a closing force to said valve member (19) to urge it towards its closed position, the improvement comprising said valve means (18) further including

third means (36) for applying a variable input force to said valve means (18) to reduce the closing force of said second means (29), and
fourth means (42) for applying a progressively increased opposing force to said input force in response to actuation of said third means (36) to indicate the degree of engagement of said coupling means (15), including second passage means (39) for communicating fluid pressure from said inlet (20) to act on said valve member (24).

Dependencies are inferred from the claim text.