Patent GB-1160708-A (GB)
Title: Improvements in or relating to Anti-Skid Brake Mechanisms
IPC: B64C25/46
Filed: 1966-11-10
Abstract: 1,160,708. Internal shoe-drum brakes; antiskid brakes. JAWA NARODNI PODNIK. 10 Nov., 1966 [18 Nov., 1965], No. 50368/66. Heading F2E. In a mechanical anti-skid shoe-drum brake, a brake drum 1 and an effective frictional surface consisting of two truncated-conical faces 8, 10, a flywheel 23 is partially rotatable, within certain angular limits, relative to the brake drum against the action of a retraction spring 28, the flywheel being provided with a surface forming one member of a spreading mechanism the angular rotary motion of the flywheel being limited by peripheral projections 26, one of the truncated-conical frictional surfaces 8 being formed on an insert 5 which is rigidly connected to the brake drum 1 while the second truncatedconical frictional surface is disposed on a ring 9 connected non-rotatably but axially movable in relation to the brake drum incapable of moving against action of thrust springs 14 arranged in the body of the brake drum, the ring 9 being rigidly connected to a disc which is adapted to be provided with the second member of the spring mechanism and an operating lever 9 of an expander mechanism 18 is provided with an abutment located between stops 21 arranged on a back plate 15 of the brake drum. In operation, when the expander mechanism 18 is operated, brake shoes 16 are expanded to allow their linings 17 to be applied to the truncated-conical friction surfaces 8 and 10. This action opens the ring 9 and shifts the latter axially in grooves 6 against the action of the thrust springs 14. The brake shoes 16 are adapted to be open until the stop rigidly connected to the lever 19 of the expander rests on a stop 21 arranged on the brake back plate 15 (Fig. 4). Further movement of the ring 9 occurs by the action of the spreading mechanism in the form of spiral shaped surfaces on the flywheel 23 and the disc 11. Balls 25 may be inserted between the two spiral shaped surfaces 13 and 24. The peripheral projection 26 provided on the flywheel 23 enter into one or more arc-shaped stop holes 27 arranged in the disc 11 such that, upon sudden stopping of the brake drum 1 as occurs when the wheel commences to skid on the road surface, the rotating flywheel 23 will continue its rotary motion until one or more of the projections 26 bear against the end of one or more of the arc-shaped stop holes 27 arranged in the disc 11 and the latter is moved to the right, as shown in the drawing, against the force of the thrust springs 14 by the interengagement of the spreading mechanism to release the disc from the shoes 16 and the brake ceases its braking effect momentarily until the brake drum commences to rotate again whereupon the thrust springs 14 press the ring 9 on to the frictional lining 17 to commence the braking cycle. This action is repeated continuously until there is a change in the intensity of braking or in the nature of the road surface. In a modification (Fig. 2, not shown) the disc 11 is separate from the ring 9 and is adapted to move axially against the ring 9 under the influence of the thrust springs 14. As an alternative to the spreading spiral mechanism, the latter may be replaced by a spreading mechanism consisting of spacers 29 with joints 30 and 31 inserted in bushes 32 incorporated in the flywheel 23 and in the bushes 33 incorporated in the disc 11, as shown in Fig. 5.