GB1192337A - Improvements in Vehicle Brake-actuating Devices - Google Patents

Abstract

1,192,337. Spring-applied brakes; automatic brake adjusters. SVENSKA A.B. BROMSREGULATOR. 5 Nov., 1968, No. 52266/68. Headings F2E and F2F. In a vehicle brake-actuating device a main piston 15 is loaded by a main compression spring 8 and movable in a cylinder 2 by compressed air in a chamber 30 in opposition to the main spring for releasing the brake, and automatic axially-acting slack adjusting means is provided through which the main piston is connected through the vehicle brake rigging. The adjusting means includes a tubular part 17 rigidly secured to the main piston 15, a screwthreaded spindle 26 extending telescopicallyadjustably within the tubular part, a nut 23 rotatable with a non-self-locking thread meshing with the screw thread on the spindle and arranged for limited axial motion between the axially extending tapered locking surfaces 22, 20 on sleeves 21 and 19 respectively secured to a tubular part 17. The spindle 26 is provided with an auxiliary piston 27 axially movable in the tubular part 17, the latter having adjacent to its connection to the main piston an opening, in the form of a restricted passage 29, to allow compressed air to act on the auxiliary piston on the direction tending to move the auxiliary piston and spindle away from the main piston. A compression spring 34 constantly tends to drive the nut 23 in the direction away from the main piston 15 and a spring-loaded movable abutment 43 tends to limit and resist axial motion of the nut in the direction away from the main piston. In operation, when compressed air is introduced into chamber 30, via inlet 1a, and into chamber 31, via restricted passage 29, the device takes up the brake-release position shown in the drawing. The piston 27 is acted upon in the forward direction by the compressed air in the chamber 31, but movement of the piston 27 and the spindle 26 in this direction is prevented by the locking surfaces 22 and 24 which are engaged to prevent axial movement of the nut 23 and thus of the spindle 26. When the brake is to be applied, the pressure of compressed air in the chamber 30 is decreased to allow the main spring 8 to expand and move the main piston 15 forwardly to apply the brakes. In the event of excessive slack in the brake rigging a spring-loaded movable abutment tubular part 43 will contact the front needle bearing 32 of the nut 23, while air pressure in chamber 31 is still sufficient to keep the surfaces 22 and 24 engaged, and as soon as the brakeapplying force provided by the spring 8 is sufficient to overcome the force offered by the springs 38 and 39 acting on the tubular part 43, the piston-rod 17 and spindle 26 will make continued forward movement while compressing the springs 38 and 39. As the air pressure in the chamber 31 decreases, the locking surfaces 22 and 24 become disengaged and the nut 23 will start rotating on the spindle 26 to take up adjustment until the resistance in the brake rigging is sufficient to halt the spindle 26, whereas the main piston 15 and the tubular part 17 continue to move to bring the locking surfaces 20 and 25 into engagement. After the adjustment has been taken up the application of the brakes is completed with the piston 15, the tubular part 17, the nut 23 and the spindle 26 moving forwardly in unison. Instead of providing a restricted opening 29, a simple flap valve or resilient tongue may be provided at the opening 29 to restrict or throttle the air flow from the chamber 31 to the chamber 30, but to allow relatively free and rapid flow of air into the chamber 31. The main compression spring 8 may be adjusted by means of a screwthreaded sleeve 10 provided in the end of the cylinder cover 2 on which is provided a non- rotatable spring support 9 provided at its inner periphery with a screw-thread co-operating with the screw-thread on the sleeve 10 but prevented from rotational movement by means of a fixed pin 14 such that adjustment of the spring 8 may be effected by rotation of the sleeve 10 by means of a wrench acting on an hexagonal protruding portion 12, the adjusted position being locked by means of a locking nut 13.