Patent GB-329277-A (GB)
Title: Improvements in and relating to the actuation of flexible band brakes
IPC: F16D49/10
Filed: 1929-02-12
Abstract: 329,277. Wilson, W. G. Feb. 12, 1929. Band or coil.-A flexible band brake system adapted to control a number of rotary elements comprises a primary brake band superimposed upon a secondary brake band and arranged so that whether the rotary elements rotate in the same or different directions, a lapping brake action is obtained for each element and the several controls are all arranged on and operated from one side. Figs. 1 and 5 show a lapping brake for counter-clockwise rotation of a reversing drum of an epicyclic driving gear in which the actuating gear is on the same side as those of the clockwise rotating drums described in Specification 220,021. One or more secondary brake bands a extends around the brake drum and has superimposed thereon a primary band brake b which contacts with half its width on the drum, forming a direct brake. The ends of each brake band are near one another, but the ends of one band are displaced 180‹ from those of the other. A block c on one end of the primary brake b is pivoted by a link e to the frame and is connected by a pull rod h to a toggle-lever system, the other end of the band brake being free. The secondary brake band a has at one end a lug i which passes through a slot in the band band is anchored to the casing by a link k, the other end of the band being free. The free end of the band b is provided with a block l lying on the band, one end m being the point of application of the brake and the other n being forked to accommodate a wear adjustment rod o pivoted to a lug p on the band b. The toggle-lever system comprises a bar q pivoted at r, a strut t pivoted at s to the bar and at u to a thrust pad v. the hooked end w of which engages the block m, and the pull rod h at a pivot y. To release the brake the bar q is turned into the position shown in dotted line by the downward pressure of a pedal, the strut t then descends and the pad v turns about its fulcrum u, and the rod h through its fulcrum y swings about the pivot g, the hooked end w of the thrust pad being lifted away from the hooked end m of the block l. When the brake is applied the block l, through the toggle levers, moves circumferentially towards the anchored end of the primary band in a counterclockwise direction and is also radially applied, thus causing its movement to be imparted to both primary and secondary bands which are tightened on the brake drum in a counter-clockwise direction. In a modification, Fig. 2, a lap braking action of the kind described in Specification 220,021 is effective for either direction of rotation of the drum. The primary brake band is in two parts 1, 2, the part 2 being pivoted at 3 to a link 4 connected to the casing and the part 1 being pivoted at 9 to the link. The secondary brake band is in two parts 10, 11, the adjoining ends on each side being connected by lugs 12, 13 to a yoke 14 pivoted to a link 16 connected to the casing. The lugs 12, 13 pass through slots 18, 19 in the free ends of the primary brake band and the free ends of the secondary brake bands lie on the opposite side of the drum to the lugs 12, 13. A lug 20 on the free end of the lower half 2 of the primary band is engaged by the hooked end 21 of a double link 22 which is connected at the upper ends by an automatic brake adjustment mechanism and pivoted at 23 to one arm of a lever 24, the other arm being connected to the primary band at 25. The lever 24 is pivoted at 26 to a fixed bracket 27 and is supported by a spring 28. The toggle lever mechanism comprises lever 30 operated by a cam 31, the lever supporting a strut 33 which supports one end 35 of a thrust lever 36 the other end 37 of which engages at 38 with the free end 39 of the upper primary band. A strut 43 is placed between the end 37 of the thrust lever and an arm 40 pivoted at the upper part of the link plate 22. The off position of the brake is shown in full lines and when the cam 30 is raised to apply the brakes the strut 33 is raised and the end 37 of the lever 36 depressed as it pivots about the strut 43. The strut 43 thus exerts an upward force on the arm 40 and also on the links 22 to apply a circumferential and radial pressure on the primary band 2 and a similar downward pressure on the primary band 1. The band 1 thus tightens onto the brake drum and slides counter-clockwise over the upper half 10 of the secondary brake band. Similarly the lower half 2 of the primary band is tightened onto the drum and slides over the lower half 11 of the secondary brake drum in a clockwise direction. Thus for a clockwise rotation of the drum the braking effort is transmitted through the lower half of the primary brake band and the upper half of the secondary brake band, whilst for a counter-clockwise rotation the braking effort is obtained through the upper half of the primary brake band and the lower half of the secondary brake band.