Patent GB-1440120-A (GB)
Title: Hydraulically operated friction brakes
IPC: F16D65/18
Filed: 1974-03-08
Abstract: 1440120 Full-face disc brakes; fluid-friction brakes; cooling FERODO Ltd 27 Sept 1974 [29 Sept 1973 11 Oct 1973 22 Oct 1973 2 Nov 1973 5 Dec 1973 8 March 1974 9 March 1974 25 April 1974] 47653/73 49149/73 51054/73 56362/73 10423/74 10660/74 18082/74 and 45668/73 Heading F2E An hydraulically-operable friction brake (for a vehicle) of the kind wherein the hydraulic liquid also constitutes the medium for removing the heat generated during operation of the brake comprises (i) a casing 1, (ii) a rotary member 2 mounted in the casing, (iii) a pressure-operable retarding device 12, 13, 13<SP>1</SP> for acting on the rotary member 2, (iv) a pump (e.g. a gear pump 16, 17 driven by rotary member 2) for circulating hydraulic liquid, (v) two separate fluid circuits provided between the pump and the retarding device one for operating the retarding device, the other for cooling the liquid, and (vi) valve means comprising (a) a valve member 33, Fig. 2, (b) a first valve element 36 secured to the valve member, (c) a second valve element 40 slidable on the member, the second valve element being urged away from the first valve element by a spring 39 and constituting pressure-sensitive means for controlling distribution of flow of liquid between the two circuits, and (d) means (e.g. passage 37) for equilibrating hydraulic pressure across the valve means. The right-hand half of Fig. 2 is a half-section on line Z-Z of Fig. 1, and the upper and lower left-hand quadrants are quarter sections on lines X-X and Y-Y respectively. Friction plates 13 with linings 13<SP>1</SP> are splined to a hub 14 secured to shaft 2 while counter-plates 12 are slidable on pins 11, the assemblage being compressed during operation by annular piston 10. The hub 14 incorporates scoops 49 to facilitate circulation of hydraulic fluid in the cooling circuit. In the inoperative phase (right-hand-half position of valve apparatus 33 &c., Fig. 2) oil discharged by pump 16, 17 into its outlet port 21 flows into port 25 then partly through pipes 27, through the external cooling part, Fig. 9, and returns through conduit 28, Fig. 1, whence it passes outwards between plates 12, 13 and then through opening 23, Fig. 2, to pump inlet passage 22; the remainder passes directly through inlet port 24 to passage 22. In the operative phase, (left-hand-half position, Fig. 2) flow through port 24 is cut-off, flow through port 25 and pipe 27 is restricted, and some oil passes through an orifice 48, Fig. 2, leading to annular piston 10. The position of the valve apparatus, and hence the degree of retarding torque on shaft 2 is governed by an actuating rod 35. Internal passage 37 may be replaced by an external fixed by-pass governed by valve position. Piston 10 may be replaced by a bellows piston. In Fig. 9, pipe 27 and conduit 28 are connected by heat-exchanger tubing 89, optionally finned, and cooled by a shrouded fan 87. In Fig. 8 (not shown) tubing 89 is replaced by four spaced heat exchangers, and in Fig. 10 (not shown) by a heat exchanger through which passes water for anti-freeze from and to the vehicle's engine-cooling system.