GB520874A - Improvements in or relating to fluid pressure brakes for vehicle trailers - Google Patents

Abstract

520,874. Fluid-pressure brakes. BOSCH GES. R. Dec. 1, 1938, No. 34969. Convention date, Dec. 1, 1937. Addition to 518,506. [Class 103 (i)] The invention of the parent Specification, comprising an auxiliary valve 16 operated by the draught coupling of a trailer vehicle against the action of a pre-tensioned spring 22 and controlling the supply of pressure fluid to a trailer brake cylinder 41, is now applied to a trailer brake system having a pressure controlled secondary valve 40 between an auxiliary reservoir 44 and the brake cylinder. According to the invention the auxiliary valve 16 is located between the secondary valve 40 and the brake cylinder 41. Fig. 2 shows the construction of the secondary valve 40 and the positions of the parts with the brakes released pressure being maintained in the control pipe 18<SP>1</SP> leading to the driver's valve on the towing vehicle. Spaces 49, 50, 51, and 52 within the cylindrical body of valve 40 are defined by a stationary partition 48 and a pair of pistons 46 and 47 carried by a tubular element 45. The air under pressure'in pipe 18<SP>1</SP> is applied to chamber 50 and passes through a charging valve 54 to chamber 51 and the auxiliary reservoir 44. The outlet of reservoir 44 is connected with a chamber 55 normally shut off from chamber 52, which is connected by means of a pipe 18 and through auxiliary valve 16 with the brake cylinder, by a valve 59. Chamber 49 is permanently open to atmosphere. Upon venting pipe 18<SP>1</SP> to apply brakes, pistons 46 and 47 move downwards, and tubular element 45 unseats valve 59 so that air passes from reservoir 44 and chamber 55 past valve. 59 to chamber 52 and thence through the auxiliary valve 16 to the brake cylinder 41. When pressure is applied to pipe 18' and chamber 50 to release the brakes, pistons 46 and 47 rise. Valve 59 consequently closes to cut off the reservoir 44 from the brake cylinder pipe 18 and, moreover, the tubular element 45 lifts off the valve 59 so that chamber 52 and the brake cylinder are vented through the bore in element 45 and chamber 49. The auxiliary valve 16 may be mounted on the bogie frame of the trailer instead of, as shown, on the yoke 10. The pivotal connection between the draw-bar 11 and valve rod 15 is then situated on the pivotal axis of yoke 10 so that the valve is not operated when the yoke is uncoupled and lowered to the ground. The arrangement of the auxiliary valve 16 between the secondary valve 40 and the brake cylinder enables both valves to operate simultaneously when the driver releases the accelerator and depresses the brake pedal, and avoids delay in application of the trailer brakes which would arise if valve 40 operated in succession to valve 16, owing to valve 16 being interposed between 18<SP>1</SP> and valve 40.