Master cylinder with externally adjusted secondary compensation

Abstract

The master cylinder (10) with externally adjusted secondary compensation comprises a tandem master cylinder (10) having primary and secondary piston assemblies (20, 30) disposed within a stepped bore (12). The portion of the bore containing the secondary piston assembly (30) has an enlarged diameter bore section (14) such that an end member (50) may be threadedly received within a bore opening (13) of the master cylinder (10). The end member (50) includes a longitudinal portion (55) having therein at least one outlet opening (60) and one compensation opening (58), each opening (58, 60) communicating with an interior opening (56) receiving slidably the secondary piston assembly (30) and a resilient spring (34) seated at one end of the interior opening (56) and biasing the secondary piston assembly (30). In order to adjust the position of the compensation opening (58) relative to a preferred position of the secondary piston assembly (30), the primary piston assembly (20) is held by a rod member (21) at a maximum at-rest position corresponding to a maximum at-rest booster output rod (43) position, while pressurized medium is transmitted to a secondary chamber outlet port (16) and flows to the reservoir (18). The end member (50) is threadedly advanced until the compensation opening (58) is closed off by a seal (32) of the secondary piston assembly (30) and pressurized medium flow blocked, and then rotated to retract the end member (50) a predetermined distance equal to the diameter of the compensation opening (58) so that flow is re-established. Finally, the threaded end member (50) is fixed relative to the master cylinder (10) by mechanical swaging (56) or other appropriate attachment methods.