Patent GB-400614-A (GB)
Title: Improvements in and relating to braking apparatus
IPC: B61H15/00
Filed: 1932-03-21
Abstract: 400,614. Brakes. COMPAGNIE INTERNATIONALE DES FREINS AUTOMATIQUES, 34, Rue Gachard, Brussels. March 21, 1932, No. 8369. Convention date, March 19,1931. [Class 103 (i).] A device for adjusting the slack in brake mechanism which is operative as regards decreases as well as increases in the slack comprises a member adjustably connected to the brake piston and which acts to arrest the piston after a predetermined release stroke, this member being adjusted to correct a decrease in the slack by a device which becomes operative when in the application of the brakes the pressure rises in the system at the moment of engagement of the brake shoes &c. with the wheels, increases in play being corrected by the engagement of the member with a fixed stop at the end of the application stroke. The adjustable member may limit the release stroke of the piston by closing an outlet valve for the cylinder or by engaging a stop. In Fig. 1, liquid is supplied to and returned from the brake cylinder 3 by a main control valve 9 through conduits 7a, 8a respectively, non-return valves 7b, 8b being provided. An arm 5 pivoted at 5a and frictionally connected to the piston rod 2a is connected by a rod 6 to a valve 6a. When the brakes are applied this valve is moved by the piston and if the piston stroke is excessive the valve engages the fixed part 6b and by the continued movement of the piston, the arm 5 is adjusted on the piston rod. In the release movement, the piston can only return until the conduit 8a is closed by the return of the valve 6a. When by the application of the brake shoes to the wheels the pressure in the cylinder rises, a piston 10 is moved against the action of a spring 10a and if due to the stroke being too short, the valve 6a has not reached the normal position, it is moved to this position and the arm 5 thereby adjusted with respect to the piston rod 2a by the rod of the piston 10. The valve 6a may be dispensed with, the arm 5 engaging a stop in the release position. In Fig. 4, the brakes are applied by placing the main switch 11 in position F so as de-energise a supply valve 7f and are released by de-energising the spring- closed valve 8f by moving the switch to position D. The arm 5 is in this case connected to the sliding element 6d of a switch in the circuit of the release valve 8 f so that this circuit is broken and the piston thereby arrested when it has made a predetermined release stroke. The arm 5 is adjusted in relation to the piston rod by the engagement of the member 6d with a stop 6b if the application stroke is excessive and by the piston 10 if the stroke is too short. In order that the piston 10 may be returned relatively quickly, the release passage 8b for the main cylinder is restricted. In another arrangement the piston 10 is replaced by the core of a solenoid the circuit of which is closed by a manometer connected to the brake cylinder. In Fig. 7, the adjustment of the arm 5 when the application stroke is too short is effected by a member of the transmitting mechanism. The levers 14, 15 carrying brake shoes 14a, 15a, are connected together by the link 16 and respectively to the piston rod 2a and to a sliding rod 15b which normally abuts on a stop 19. A spring 17 is interposed between the rod 15b and a fixed part such as the cylinder 3. When the brakes are applied, the reaction of the braking pressure transmitted by the lever 15 to the rod 15b moves this rod against the spring action and if the piston and parts 5, 6 have not already moved to the normal position the parts 5, 6 are moved to this position by the lever 18. The engagement of a projection 6m on the rod 6 with a stop 6b effects the adjustment, when the stroke is greater than normal. The engagement of the rod 6 with the lever 18 and thus with the stop 19 determines the release movement of the piston. The adjustment of the arm 5 by the compression of the spring 17 may be effected through electric or hydraulic means.