Patent GB-1442738-A (GB)
Title: Load-dependent vehicle braking system
IPC: B60T13/38
Filed: 1974-03-29
Abstract: 1442738 Loud dependent braking system KNORR-BREMSE GmbH 29 March 1974 [3 April 1973] 14179/74 Heading F2F A load-dependent braking system utilizing a fluid pressure medium (particularly compressed air but alternatively other gases or hydraulic oils) comprises a spring-loaded brake cylinder 5 operable by fluid pressure to move to a release position and a loaddependent valve means 1 comprising pistons 6, 7 cooperable with a balance beam 16 having a fulcrum roller 17 movable as a function of vehicle load by a load dependent pressure generated by a relay valve and supplied to a chamber 22; a pressure medium control reservoir 43 communicates with chambers 11, 13 provided on one side of each of the pistons 6, 7 to supply a datum pressure thereto, a chamber 12 on the other side of the piston 7 communicates with the brake cylinder 5 and a chamber 10 on the other side of piston 6 is arranged to receive fluid medium at a pressure dependent on the setting of a brake control means (e.g. a driver's braking valve) from a main supply of pressure medium (e.g. reservoir 40) through an electrically controlled reducer valve arrangement 47, 52, 53, 54 whose output is variable in response to electrical operation. In the compressed air railway vehicle braking system illustrated a main air line 46 controlled by a driver's brake valve connects via a non- return valve 45 with chambers 11, 13 and with reservoir 43 an air-overload device may be provided in a by-pass to the non-return valve 45. The line 46 connects with three separate chambers 49, 50, 51 of a pressure reducing valve 47 via electromagnetic valves 52, 53, 54. A control piston 48 defines, opposite chambers 49, 50, 51, a chamber 55 connected by means of line 56 with chamber 10 and a double valve 57 controls the pressure in chamber 55 by connection either with atmosphere or with reservoir 40. The load dependent pressure supplied to chamber 22 acts on a piston 21 and movement of the piston 22 is transmitted to the fulcrum roller 17 via a sliding crank gear 19. At the side of the roller 17 there bears on the balance beam 16 a pusher 25 carrying a valve disc 26 received in a sleeve 27. The disc 26 defines with the sleeve 27 an outlet valve 26, 28 to atmosphere, the inner chamber 31 of the sleeve 27 being connected to the cylinder 5 via a connection 3. The sleeve 27 also has a base part 37 defining with a valve seat 36 an inlet valve 36, 37 from a chamber 38 connected with reservoir 40 to connection 3. In the operative condition, with the brakes released, as illustrated, the line 46 is charged to its full pressure and the pressure in chambers 10, 12 are equal to the datum pressure in chambers 11, 13. As the vehicle load increases the roller 17 moves towards a central position decreasing the length of lever arm associated with piston 6. Thus if braking is triggered when the vehicle is fully loaded with roller 17 in the central position the pressure decrease in line 46 is communicated to chamber 10 by actuation of the pressure reducing valve 47. The piston 6 then moves to pivot the beam 16 clockwise to open valve 26, 28 and reduce the pressure in cylinder 5 to give braking by action of the spring(s) therein and also reduce the pressure in chamber 12 to the level of that in chamber 10 whereupon equilibrium is restored. With a partial vehicle load, the pressure in chamber 12 does not have to be reduced totally to the level of that in chamber 10 before equilibrium is restored. For electrically triggered braking one or plurality of valves 52, 53, 54 (is) are triggered to disconnect the respective chambers 49, 50, 51 from line 46 and connect to atmosphere. The double valve 57 is thereby actuated and the pressure reduced in chamber 55 and chamber 10 to cause braking. Instead of the digitalelectrically triggered arrangement the reducing valve arrangement may be electrically operable in infinitely variable manner. If the vehicle is braked by means of an electrical brake (not shown) a solenoid valve 58 is simultaneously actuated to bridge the pressure reducing valve 47 and connect line 46 directly to chamber 10 so that the pressure in cylinder 5 is then controlled directly by the pressure in line 46.