GB1487972A - Pressure imbalance indicators - Google Patents

Abstract

1487972 Brake fluid pressure imbalance indicator SOC ANON AUTOMOBILES CITROEN 15 Jan 1975 [22 March 1974] 1817/75 Heading F2F In a pressure imbalance indicator comprising a easing 4 with two supply ducts 13, 14 of independent fluid pressure circuits 2, 3 intersecting a bore 5 for a resiliently centred spool 6 with end faces co-operating with the easing to define chambers 11, 12 connected by ducts a, b to respective supply ducts 13, 14 and indicators 21 actuated by displacement of the spool from its central position, grooves 7, 8 of the spool are aligned with the ducts 13, 14 in its central position and at least one duct a, b includes a flow restrictor d, e. The spool may be stepped or the centring springs 15, 16 may be of different stiffness so that the indicator is responsive to different imbalance thresholds for faults in circuits 2 and 3. The spool lands may be disposed to close the supply duct to the faulty circuit when displaced (Fig. 3), and a by-pass duct 40 (Fig. 3) may be provided which is normally closed but on failure in front circuit 3 by-passes a rear brake pressure regulator L. Movement of the spool illuminates a lamp 21 and preferably also actuates a solenoid 41 or 42 (Fig. 3) to retain the spool in its displaced position when the pressure falls in both circuits. In Fig. 8 the spool movement operates a switch 19a or 19b to illuminate a lamp 21 and energize a solenoid 64a or 64b to move a valve spool 67 to cut off the faulty circuit upstream of a pressure accumulator 52 or 53 and a pressure distributor E which may be integral with the casing of the indicator 1. The restrictor is preferably one or several spaced discs 35 with apertures 36 (Fig. 5) held in the duct a or b by a hollow plug 32a.