Patent GB-240155-A (GB)
Title: Improvements in or relating to brakes
IPC: F16D51/50
Filed: 1925-09-12
Abstract: 240,155. Flanigan, E. B. Sept. 20, 1924, [Convention date]. Blocks acting on drums; compensating for wear.-An internal expanding brake comprises two shoes 18, 19, pivoted by means of adjustable links 24, 25 on pins 28, 29 carried by a link 22 pivoted at 21 to the cover plate 17, and adapted to be expanded into engagement with the brake drum 16 by a cam 39 carried by a shaft 40 mounted in a swinging bracket so that it is free to move vertically in a slot 41 in the cover plate. A. floating toggle may replace the cam. When the shoes are engaged with the drum, the frictional reaction on one of them, depending on the direction of rotation, is transferred to the other through the links 24, 25, the shoe, the application of which is thus assisted, bearing on a fixed stop 44. A screw stop 35 may be provided to limit the downward movement of the link 22 and to take the weight of the upper shoe when the brake is released. The stop also prevents the frictional reaction on the shoe 19 being transferred to the shoe 18 when the drum is rotating in an anticlockwise direction, so that the braking action obtained is less than when the drum is rotating in a clockwise direction. By arranging the pivot 28 of the link 24 further from or nearer to the pivot 21 than the pivot 29 of the brake 25, the effort applied to the shoe 19 by the shoe 18 when the drum rotates in a clockwise direction may be increased or decreased. As shown in Fig. 7, the cam 45 may be carried by a shaft 46 journaled in a fixed bearing and the fixed stop 44 be dispensed with by forming the heel 47 of the cam as a circular sector struck from the axis of the shaft 46. In a brake application, the cam acts only on the shoe 18, and the shoe 19 bears against the heel 47. To prevent wedging of the end of the shoe 19 against the drum, it may be provided with a guiding lug 49 bearing against the heel 47, or the heel may be received in an arcuate slot in the end of the shoe, the upper face of the cam being then cut away to receive the right-hand wall of the slot. The arrangement shown in Fig. 7, in which the cam shaft does not float in a slot, is suited for use with a brake having two pairs of shoes arranged side by side in a common drum and adapted for independent actuation by a pair of cams, since the cam shafts may comprise respectively a shaft and a sleeve surrounding the shaft. If, as shown in Fig. 9, the supporting- stop 35 is replaced by a spring 57 adjustably anchored at 59, the brake shown in Fig. 1 will be equally effective for either direction of rotation of the drum. In the modification shown in Fig. 9, the shoe 52 is longer than the shoe 53, the upper link includes a threaded sleeve 55 whereby its length may be adjusted without removing the shoe pivot pin, and the floating shaft 61 which operates the shoes is provided with forked ends 64, 65 rotatably mounted in the ends of the shoes. The end of the shoe 52 is provided with a guiding lug 69 engaging a fixed stop 68. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a further modification in which the end of the upper shoe remote from the link 25 is anchored on the cover plate and the lower shoe is expanded by a link carried by a brake-operating shaft mounted in a fixed bearing, the brake being suited for front wheels of vehicles, where only a light braking action is required when the vehicle is backed. This subject-matter does not appear in the Specification as accepted.