Hydraulic brake pressure control valve unit

Claim 1

A pressure control valve unit for insertion in a brake system extending from a hydraulic pressure source, comprising in combination: a. a main valve housing having a liquid flow passage formed therein, one end of said flow passage being connected through part of said brake system to said pressure source and the other end of said flow passage being connected to said rear wheel cylinders; b. a control chamber formed in said main valve housing and being fluidally separated from said flow passage; c. a piston, one end thereof being fitted with a valve member adapted for on-off control of said fluid passage, one end of said piston being exposed to said liquid flow passage and the other end of said piston being exposed to said control chamber; d. a tightly movable separating wall fitted in said control chamber; e. a liquid pressure conveying means adapted for conveying liquid pressure prevailing in said liquid flow passage to one side of said movable separating wall and to said piston end exposed to said liquid flow passage; f. an inertia valve adapted for interruption of said liquid pressure conveying means upon establishment of a predetermined deceleration of said vehicle; g. a first spring arranged between said valve housing and said movable separating wall, said spring becoming effective upon movement of said separating wall; and h. a second spring arranged between said movable separating wall and said piston which becomes effective only after lapse of a predetermined time period upon initiation of the movement of either said separating wall or said piston or both.