GB518795A - Improvements in or relating to compressed air operated trailer brakes - Google Patents

Abstract

518,795. Fluid-pressure brakes. KNORR BREMSE AKT.-GES., and JANDER, H. Sept. 5, 1938, No. 25915. [Class 103 (i)] Compressed air brakes on a trailer vehicle are controlled by the pressure in a hydraulic brake system on the tractor vehicle by a valve which releases compressed air from 'the trailer' brake pipe to apply the brakes, the application being graduated in dependence on the hydraulic pressure. The system shown comprises hydraulic brakes on the tractor applied by a pedal operated master cylinder and a trailer brake valve, Fig. 2, connected to the hydraulic pipe line at 11, 12, to the compressed air trailer brake pipe at 14 and to a compressed air reservoir at 13. The valve comprises a piston 23 connected through a lever 22 and spring 21 to a piston 19 subject to the pressure in the brake pipe 14, and to that of a spring 24. The valve 16 by which the reservoir supplies the brake pipe is normally open as shown. When the hydraulic pressure on the piston 23 is initially increased the piston 19 is moved to the right seating the valve 16 and moving away from the valve 17 to connect the, pipe 14 to atmosphere through the piston bore 18 thus applying the trailer brakes. When the pressure in the pipe 14 has fallen to a value corresponding to the hydraulic pressure the piston 19 moves to seat the valve'17 without re-opening the valve 16 The piston 23 has a relatively large area and the resistance to movement of the piston 19 is small so that the trailer brakes are 'initially applied before the tractor brakes. The resistance to movement of the piston 23 subsequently increases by the engagement of a tappet 25 with a spring-urged plate 28 and the tractor brakes are then applied. The position of the plate 28 and the pressure of the spring 29 are adjustable.