Patent GB-189434-A (GB)
Title: Improvements in or relating to friction brakes
IPC: B61H13/30
Filed: 1922-10-14
Abstract: 189,434. Durand, P. Nov. 23, 1921, [Convention date]. Addition to 187,240. No Patent granted (Sealing fee not paid). Band; force - transmitting mechanism; blocks acting on drums. - Relates to brake mechanism of the kind described in the parent Specification, in which the pressure applied to the friction members so as to keep the braking effect constant irrespective of the variation of coefficient of friction with the speed. The present improvements consist (1) in rendering the maximum braking effect dependent upon the load carried by the wheel to which the brake is applied; (2) in rendering the regulation effective for both directions of rotation of the drum or wheel. As shown in Fig. 2, the spring 12 which is connected at one end to the rotatable member 8 which carries the braking element 3, and the cam 6 instead of being attached at its other end to the fixed member 13<1> is attached to a lever 34 pivoted upon the member 13<1> and to the seating 37 which supports the load. Thus when the retarding effect of the brake acting through the member 8 and spring 12 tends to turn the lever 34 and to lift the load the member 8 will turn about the fixed axle 1 and so effect an adjustment of the angle of the cam lever 9 with respect to the member 8 and thereby reduce the pressure applied to the member 3 and the retarding effect produced thereby. Fig. 4 shows a modification of another arrangement described in the parent Specification, the pull rod 20 being connected to a bell-crank lever 38 pivoted at 36 to the load seating 37 and linked at 40 to the member 8. When a pull is applied to the rod 20, the member 8 is moved in a clockwise direction so that the cam lever 17 engaging the fixed pin 18 expands the brake member 3, until the friction drag on this member bv the drum 2 counterbalances the force applied by the rod 20. The maximum force that can be exerted by the rod 20 is limited however by the downward force of the load on the seating 37 which is merely raised if the pull on the rod exceeds this value. Fig. 5 shows an arrangement in which the regulation of the brake is effective for both directions of rotation of the drum 2. The blocks 43, have pins 44, which slide in slots 45 in the member 8, and by which they are connected to links 57 connected to levers 47, 49. The lever 49 is linked at 50 to the fixed member 59 and the lever 47 is connected to the pull rod 10. The pins 55 on the levers 47, 49 slide in slots as shown in the fixed member 59. A pair of springs 58, 58<1> are attached at one end to the member 59 and have the other end arranged to slide in slots 62 in the member 8. Assuming the drum to be rotating in a clockwise direction and the blocks 43 to be applied by a pull on the rod 10, the spring 58 becomes effective to counteract the drag of the blocks in a similar manner to that described with reference to Fig. 2. If the drum is rotating in the opposite direction, the spring 58<1> is effective. Abutments may be provided to limit the movement of the member 8. To render the braking effect dependent upon the load with this arrangement, the pin 60 to which the springs are attached may slide in a vertical slot in the fixed member 59 and be attached to a vertically slidable member which carries the load. Fig. 8 shows an arrangement similar to Fig. 5, modified for external blocks.