Patent GB-487461-A (GB)
Title: Improvements in automatic slack adjusters for vehicle brakes, especially railway carbrakes
IPC: B61H15/00
Filed: 1937-07-12
Abstract: 487,461. Automatic adjusters for brakes. SVENSKA AKTIEBOLAGET BROMSREGULATOR. July 12, 1937, No. 19319. Convention date, April 7. [Class 103 (i)] Relates to automatic slackadjusters especially for railway car brakes both for reducing and increasing slack, the increase taking place due to stresses arising too early in the brake rigging when applying the brakes. A locking device for locking the adjuster against slack increasing is rendered operative at the commencement of brake release and inoperative at the commencement of brake application so that it is locked during the whole release and will thus be locked even if the brakes do not completely release. The lock may also be rendered operative during brake application at the point where the desired brake clearance has been taken up and thus take the place of the usual locking means for this purpose which prevents slack increases due to stress in the brake rigging. The invention is applied to pawl-and-ratchet wheel adjusters or adjusters of the toothed rod type. The usual nut 1, Fig. 1, engaging the screw 2, carries a ratchet wheel 13, Figs. 1 and 2, adapted to be engaged by a pawl 14 which carries a spring-pressed friction shoe 22 adapted to engage the usual adjuster operating sleeve 10 actuated by movement of the brake rigging. The sleeve 10 is rotated on brake application in the direction of the arrow A and tilts the pawl out of engagement with the ratchet wheel 13 thus unlocking the nut 1 for slack increasing movement. On the initial movement of the sleeve in the opposite direction, the pawl is re-engaged and locks the nut 1. The usual screw-threads 18, 19 guide locking faces 20, 21 into engagement during brake applicationso that the adjuster is locked at a certain stage of the brake application. In a modification, this latter function may be performed by the pawl 14. For this purpose a groove is provided in the casing 10 opposite the shoe 22 at the end of its travel so that the pawl 14 is released into engagement with the ratchet wheel 13 for the latter stage of the brake application. In Fig. 5, the adjuster comprises a rod 43 having teeth in the form of a screw-thread with which co-operates a nut 38 comprising resiliently connected sectors. On brake application, a toothed rod 31 connected to the actuator 37 of the slack adjuster, by means of a lever 35 engages a sleeve 34 with the nut 38, which is moved away from its seat 39 and released from the rod 43, the parts 43, 40 of the adjustable brake rod can now move relatively for increase of the brake shoe clearance. Movement of the rod 31 past the lever 35 is allowed by teeth 32. When the actuator 37 engages' the ear 36 of the housing 33, the nut 38 is again locked by the seat 39. At the commencement of the release movement, the lever 35 and the sleeve 38 are moved in the opposite direction and allow the nut 38 to remain in locking engagement with the rod 43, during the whole releasing movement and until the commencement of another brake application. In an adjuster of the screw and nut type in which the lock is combined with the adjuster actuating means, the actuating sleeve 10, Fig. 7, is pivoted at 50. On brake application, the pawl is moved in the direction of the arrow A and the pawl 11 is swung away from the ratchet wheel 53. On the commencement of brake release, the pawl 11 is swung into engagement with the ratchet wheel 53 which with the adjusting nut 7 is locked against slack increasing rotation and then is rotated in slack reducing direction. The nut 7 is prevented from rotation with the sleeve 10 by a spring- pressed friction shoe engaging a fixed part. In the modification shown in Fig. 8, a disc 68 is moved axially by screw-thread 67 when the adjuster actuating arm 11 is turned on brake application until a pawl 70 is disengaged laterally from a circular fixed ratchet 73 and teeth 69 are disengaged whereupon the disc 68 is allowed to turn with the arm 11 until the pawl 70 is opposite a cut-away portion of the ratchet. A spring 75 then moves the disc 68 on the thread 67 so as to re-engage the teeth 69 and lock the sleeve 7 against slack increasing rotation. This stage occurs when the desired brake shoe clearance has been taken up. On release, the teeth 69 remain engaged and the arm 11 turns the sleeve 7 in slack reducing direction, the pawl 70 running over the ratchet 73. Specification 421,759 is referred to.