GB258260A - Improvements in and relating to brake controlling devices - Google Patents

Abstract

258,260. Compagnie Internationale des Freins Automatiques, Soc. Anon. Sept. 10, 1925, [Convention date]. Fluid-pressure.-A device for maintaining a predetermined clearance between brake shoes and the wheels to which they applied, comprises a reservoir containing liquid under pressure which is adapted to be connected to the cylinder of an auxiliary piston connected to the brake transmitting mechanism, by a valve or valves controlled by the movement of a main pressure-applying piston whereby adjustment of the quantity of liquid in the cylinder is effected. The main piston may be directly connected to the transmitting mechanism or may apply the braking pressure through the liquid and the auxiliary piston. The system shown in Fig. 1 comprises a switch 15 adapted simultaneously with or somewhat later than the opening of the pressure fluid supply to the cylinder b<1> of the main piston a, b to effect the opening of a valve 11 to connect a reservoir 10 containing liquid under pressure with a cylinder 6, whereby the brake shoe 3 is applied to the wheel 4 by the piston 5. The main piston a, b, however, returns liquid from the cylinder 6 to the reservoir until having travelled a distance d, a contact 16 in the circuit of the valve 11 is broken by the piston and the valve thereby closed. Pressure is then applied to the brake shoe by the main piston a, b. Thus in release, the shoe 3 will be moved away from the wheel a distance proportional to the distance d. Fig. 2 shows an arrangement in which main and auxiliary pistons 19, 31 are pivoted to levers 32. 32<1> connected by a tie-rod 34 and to brakes by rods 33, 33<1>. When the valve 22 is opened to apply the brakes, liquid under pressure is supplied from the reservoir 24 to the cylinder 25 of the main piston 19, which thereupon opens by a pawl 20 and lever 26, a valve 27 by which the liquid is admitted also to the cylinder 30 of the piston 31. Continued movement of the piston 19 after the brakes have thus been applied effects reverse movement of the piston 31 and consequent return of liquid from the cylinder 30 until disengagement of the lever 26 by the pawl 20 and closure of the valve 27. The piston 19 then applies the full pressure to the brakes. The pawl 20 is free to turn on the piston rod 18 so that it is unable to open the valve 27 during release. The clearance of the brakes is substantially proportional to the distance travelled by the piston 19 while the valve 27 is open. Fig. 3 shows a further arrangement, in which during the initial movement of the piston a, b a cam 37 on a rod 36 connected thereto opens a valve 38 in a pipe 39 leading from the reservoir 10. which pipe contains also a non-return valve 40 whereby liquid is returned to the reservoir if the shoes are applied before the completion of the predetermined stroke. When the cam 37 has left or is about to leave the rod of the valve 38, a second cam 41 opens a valve 42 to permit flow of liquid to the cylinder if the brake shoes are not already in contact with the wheel. In a modification of this arrangement, the valve 42 is dispensed with and a non-return valve arranged in a similar position to the valve 40 is adapted to be lifted by a cam such as 41.