Patent GB-530658-A (GB)
Title: Improvements in automatic slack adjusters for brakes
IPC: B61H15/00
Filed: 1939-06-28
Abstract: 530,658. Adjusting brake mechanism. SVENSKA AKTIEBOLAGET BROMSREGULATOR, and BROWALL, B. H. June 28, 1939, No. 18875. [Class 103 (i)] An automatic slack-adjuster comprises a twopart connecting rod or link, one part having a quick-pitch thread and carrying a nut which is held against rotation to couple the rod parts for transmitting the brake pressure. In the event of excessive slack a second nut is displaced along the screwed rod part and during its return movement in release, its rotation is prevented by a friction device so that it takes the screwed rod part with it and thus contacts the rod as a whole; the first nut rotating to permit this. The adjustment is unaffected by elastic yielding of the brake rigging. The device may act both to reduce excessive and to increase insufficient slack. The screwed rod part 1 carrying nuts 3, 4 is slidable in the rod part 2. A casing 5 is slidable on the part 2 against the action of a spring 6. A spring 11 seated on a collar 18 on the nut 4 urges an annular disc 15 into frictional engagement with flanges 9, 10 on the casing 5 and the nut. Anti-friction bearings 16<SP>1</SP>, 16<SP>11</SP> are interposed between the spring and disc 15 and between the collar 18 and the part 14 of the casing. In applying the brake the pressure is at first transmitted from part 2 through the spring 6, casing 5 and nut 4 to rod 1, rotation of the nut being prevented by the friction of the disc 15. If there is insufficient slack, the brake shoes are applied before the engagement of a projection 7 on the casing with a stop, the spring 11 yields, the parts 10, 15 are disengaged and both nuts being thus free to turn, the rod 1 is pulled outwardly from the part 2. When the projection 7 engages the stop, rotation of the nut 3 is prevented by its engagement with a flange 13 on the part 2 and this nut thus couples the parts 1, 2 to transmit the brake pressure. If the slack is excessive, the projection engages the stop before the brake shoes are applied, the casing 5 is moved relatively to the left compressing the spring 6, taking with it along the rod 1, by the flange 14, the nut 4, rotation of which is permitted by disengagement of the parts 9, 15. At the beginning of the brake release movement, while the brake pressure is reducing the spring 11 yields so that the friction device 10, 15 slips permitting rotation and displacement of the nut 4 on the rod 1 but when the pressure ceases the nut is held against rotation thus coupling the rod 1 to the casing 5 which under the action of the spring 6 slides this rod into the part 2. The nut 3 may engage the flange 13 during the whole of the application movement and the device then acts only to reduce excessive slack. The anti-friction bearing 16<SP>11</SP> may be disposed between spring 11 and the bearing 16<SP>1</SP>. the flange 14 being arranged to engage a collar between the two bearings. In a further modification, Fig. 5, the initial application movement is transmitted from the part 2 to the part 1 by a third nut 21 which is arranged with a spring 23 and slipping friction clutch 22 in a similar manner in relation to the part 2 as is the nut 4 in relation to the part 5. Rotation of the disc 15 in the slack increasing direction may be positively prevented by a oneway clutch spring 33.