GB938216A - Fluid operated braking system - Google Patents

Abstract

938,216. Pneumatic brakes. OVERLAND ANCHOR LOK Inc. March 6, 1962 [March 21, 1961], No. 8655/62. Class 103 (1). In a vehicle braking system including pneumatically operated brakes a mechanically powered alternate brake actuating means is normally held de-activated by pressurized air and is provided with control means to vent the pressurized air from the brake actuating means thereby activating the same to actuate and hold the brakes positively actuated until pressurized air is again admitted to the brake actuating means. A tractor and trailer braking system is shown in Figs. 1A and 1B, respectively, while the brake cylinders 49 and alternate brake actuating means 34 are shown in Fig. 2. A compressor 10 controlled by a governor 46 supplies storage reservoirs 12, 13 from where it passes to the emergency braking system conduits shown in solid black lines. Pressurized air passes via parking valve 17 and pressure check valve 26 to chamber 33, Fig. 2, of the alternately actuating means 34 in order to keep the springs 113, 114 normally compressed (as shown). The pressurized air also passes via a conduit 25, and valve 55 held open by the pressure in conduit 18 acting on a diaphragm 20 to the emergency line 56 on the trailer to maintain the springs 113, 114 compressed in alternate brake actuating means 34a. The brakes are normally applied by foot-operated control valve 15 to admit pressurized air into distributing line 47 leading to the front wheel brake cylinders (not shown) and simultaneously into line 48 leading to the rear wheel cylinders 49 by way of the quick release valve 50. At the same time pressurized air is admitted to conduit 53 through the lower end of double check valve 39 to conduit 40 and thence past open valve 41 to normal braking line 42 of the trailer braking system. The air depresses the piston 43 of relay emergency valve 43 to admit pressurized air from trailer reservoir 63 past open valves 44, 65 into chamber 66 from where it flows into brake cylinders 49a. The pressurized air in conduit 56 acts on the diaphragm 69 to maintain the valve 65 normally open. When the reservoir 63 needs recharging pressurized air flows past check valve 71 and through passage 72 into the reservoir. The pressurized air is admitted to cylinders 49, 49a via a port 48 (Fig. 2) and acts on a diaphragm 83 to compress the spring 95 and rotate the double cam 62 to apply the brake shoes. The trailer brakes may be actuated by a hand braking valve 37 which admits pressurized air into conduit 38 through the upper end of double check valve 39 into conduit 40 and past open valve 41 to the trailer braking system. If it is required to park the vehicle, valve member 23 of the parking valve 17 is moved to abut seat 136 and is held there by the pressurized air in conduit 16 acting on the shoulder of the valve member. Conduit 25 is vented via passage 138 and seat 135 to atmosphere by way of vent 139. In pressure check valve 26 the check valve 30 normally held against seat 27 by the pressure in conduit 25 rises to vent conduits 32 to atmosphere via vent 28. The pressure in chamber 33 falls allowing springs 113, 114 to apply the brakes. A coloured indicator 125 is provided so that it can be seen when the brakes are applied whether or not the shoes are worn. Check valves 26 26a normally have the valve 30, 30a abutting seat 27 so that air can pass via central bore 29, 29a and past elastic sleeve band 31, 31a to conduits 32, 56. This arrangement maintains the pressure in chambers 33 at the highest pressure ever existing in reservoirs 12, 13. So if the pressure in the reservoir drops after a prolonged use of the brakes but not below a predetermined value, at which value the valve 30, 30a rises to vent conduits 32, 56 to atmosphere, the springs 113, 114 do not act to apply the brakes. If the trailer came uncoupled or in the event of another emergency the pressure in emergency brake lines would fall so that springs 113, 114 could apply the brakes.