Alliedsignal Inc.

William F Dillon, Jr

Robert F Gaiser

Donald A Crumb

Richard A Zander

A master cylinder (12) having a switch (70) which is activated by either a magnet (78) carried by a float (76) in a reservoir (40) or a pin (66) moved by a differential area piston (52). The switch (70) had a first blade (82) connected a source of electrical current (106) through an indicator light (124) and a second blade (88) connected to an electrical ground (114). A reed switch (100) is connected to the first (82) and second (88) blades and responds to the magnet to close an electrical circuit to operate the indicator light (124) if a low fluid level is present in the reservoir (40). A first contact (96) on the first blade (82) is positioned in switch 70 by a non-electrical conductive actuation pin (66) that extends through the housing (22) of the master cylinder (12). A second contact (94) on the second blade ( 88) has a projection (92) that engages the housing (22) of the master cylinder (12) to define a fixed location for the first contact (94) and establish a fixed gap between the first (94) and second (96) contacts. If a pressure differential is created in the master cylinder (12) between the fluid pressure supplied to operate the wheel brakes (18) and (20), the differential area piston (52) moves and brings the second contact (96) into engagement with the first contact (94) to close the electrical circuit and activate the indicator light (124).

Master cylinder with fluid level and pressure failure detection

The proportioning valve assembly (40, 140) may be screwed into a complementary-shaped opening in a master cylinder (10). The valve assembly (40, 140) includes a differential area piston (50, 150) biased by a spring (70, 170) toward the outlet (21, 121) which communicates with the rear brakes. The master cylinder (10) includes a pair of passageways (16, 18) which communicate primary fluid pressure and secondary fluid pressure directly to the differential area piston (50, 150) of the proportioning valve assembly (40, 140) to displace the piston (50, 150) to a balanced position. If there is a failure of pressure in the primary brake circuit, the proportioning valve assembly (40, 140) actuates the differential area piston (50, 150) to permit fluid flow to bypass the piston (50, 150) and be communicated directly to the rear brakes of the vehicle.

Primary and secondary pressure-balanced proportioning valve

The proportioning valve assembly may be screwed into a complementary-shaped opening in a master cylinder. The valve assembly includes a differential area piston biased by a spring toward the outlet which communicates with the rear brakes. The master cylinder includes a pair of passageways which communicate primary fluid pressure and secondary fluid pressure directly to the differential area piston of the proportioning valve assembly to displace the piston to a balanced position. If there is a failure of pressure in the primary brake circuit, the proportioning valve assembly actuates the differential area piston to permit fluid flow to bypass the piston and be communicated directly to the rear brakes of the vehicle. Upon failure, a differential area sleeve surrounding the piston moves to actuate an electrical failure warning switch.

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South Bend, IN, United States of America

William F Dillon, Jr