Patent GB-1206833-A (GB)
Title: Vehicle brake apparatus
Inventor: PARFITT NORMAN LESLIE CYRIL
IPC: B60T13/58
Filed: 1968-02-02
Abstract: 1,206,833. Fluid-released brake systems for rail vehicles. COAL INDUSTRY (PATENTS) Ltd. 23 Jan., 1969 [2 Feb., 1968], No. 5466/68. Heading F2F. Vehicle brake apparatus comprises a first hydraulic pump manually operable to apply hydraulic pressure to release a vehicle brake, a valve openable to reduce hydraulic pressure to permit application of the brake, a second hydraulic pump operable in response to vehicle movement to apply hydraulic pressure to open the valve, a device by which opening of the valve by the second pump is prevented at relatively low vehicle speeds, and means for rendering the second pump ineffective in response to connection of the apparatus to a locomotive brake system. Preferably the above-mentioned device comprises a bleed valve 90, Fig. 1, connected between the outlet of the second pump 60 and a storage tank 18 for hydraulic fluid. Preferably the means for rendering the second pump ineffective is a bell-crank lever 80, Fig. 2, one end of which is pivotally connected eccentrically to a jockey-wheel 84 engageable with the hub 86 of one wheel of the vehicle, so that, on rotation of the wheel, movement of the lever causes a piston-rod 76, Figs. 1 and 2, pivotally connected to the other end of the lever, to reciprocate within the second pump 60. A spring 74 is wound around the piston-rod and abuts the piston 66 so as to bias the jockeywheel into engagement with the hub, and is compressible to allow sufficient movement of the piston-rod 76, when sufficient pressure is applied to the piston, to cause the jockey-wheel to disengage the hub. The apparatus provides for the following situations. When the mine-car is standing disconnected from a locomotive, the parts are as shown in the drawings; the air pressure in conduits 30, 72 is atmospheric; the brakes are automatically held "on" by the springs (not illustrated). To move the mine-car manually, hand-pump 14 is operated to compress the brake-operating springs by introduction of hydraulic fluid into lines 12 leading to wheels 10 from storage tank 18; the brakes are thereby released. When the mine-car is in motion, jockey-wheel 84, Fig. 2, is rotated by wheel-hub 86, whereby piston-rod 76 is reciprocated by bell-crank lever 80 (the closed end of the pump cylinder being pivoted to the back-plate 88 of the brake assembly). Pump 60, Fig. 1, thereupon withdraws hydraulic fluid through one-way valve 64 and discharges it through one-way valve 62 to the lower end of the housing of valve 40 where it acts on piston 52; at the same time, some fluid is returned to tank 18 through an adjustable bleed device 90. At speeds below, e.g., 2 m.p.h., valve 40 remains unopened, and the brakes remain off. If the mine-car speed increases unduly, e.g. on a downgradient, sufficient pressure builds up under piston 52 to open valve 40, whereupon fluid lines 12 are connected directly to tank 18 and the brake springs re-apply the brakes. Stopping of the mine-car stops pump 60, the pressure beneath piston 52 decays, and valve 40 re-closes. If the mine-car with brakes applied is coupled to a locomotive, the air pressure in the locomotive brake system provided at 32 reaches air chamber 68, Fig. 1, moving piston 66 rapidly to the right; valve 40 opens, but pressure beneath piston 52 quickly decays, allowing valve 40 to reclose. At the same time, air pressure in a booster device 26 moves the piston to the right in hydraulic cylinder 24, whereby the brake springs are compressed and the brakes consequently released. If the brakes are off on coupling to the locomotive, the apparatus functions to keep the brakes off. If now the locomotive driver applies the brakes by reducing the air pressure in the air system, the air piston in booster device 26 is withdrawn to the left, and with it the hydraulic piston; the increase in volume in the hydraulic system permits the brake springs to expand and the mine-car brakes are consequently applied. In an emergency, a relief valve (not illustrated) and provid d for another purpose between fluid lines 12 and tank 18 may be quickly released manually to apply the brakes. If the apparatus is used with a locomotive having a two-pipe brake system in which the locomotive brakes are applied by an increase in air pressure in the locomotive brake pipe, an inverse air-proportioning valve is required to interchange and pass on to the mine-car the pressures in the locomotive brake system. The large piston of the booster device 26 has a one-way valve actuated at a relatively high pressure difference to allow air to pass from the working side to the back of it; it also has a low-pressure-actuated one-way valve to allow air to pass in the other direction.