Patent GB-888283-A (GB)
Title: Improvements relating to brake slack adjusters
IPC: B61H15/00
Filed: 1959-11-16
Abstract: 888,283. Automatic slack adjusters in brake rigging. WESTINGHOUSE AIR BRAKE CO. Nov. 16, 1959 [Nov. 17, 1958], No. 38710/59. Class 103 (1). An automatic double-acting brake slack adjuster having a tube 3 in screw-threaded engagement with a rod 4 whereby slack is varied by rotating tube 3, in which ratchet nuts 21, 22 engage sets of oppositely handed non-self-locking screw threads 19, 20 on tube 3, and a non-rotatable runner 23-27 movable relative to housing 2 during brake application over a distance corresponding to the slack and arranged to move nuts 21, 22 with pawls 56, 71, Figs. 2, 3, carried by runner 23-27, forward and back over threads 19, 20 the runner 23-27 carrying cam means controlling the engagement and disengagement of pawls 56, 71 with the teeth of nuts 21, 22 and being set automatically relative to the runner in dependance on the extent of forward movement of the runner to determine, during the backward movement, whether one or other or neither of pawls 56, 71 engage nuts 21, 22. The cam means comprises respectively, members 52, 67 engaged by rollers 51, 66 carried by pins 50, 65 on crank levers 46, 61, Figs. 2, 3, pivoted at 49, 64 to runner part 25, the levers also carrying pawls 56, 71 biased by springs 55, 70 towards nuts 21, 22, the member 67 having an extension 75 slidable in member 52 and an extension 78 normally abutting the end-plate 2a, of housing 2 fixed through member 6 and clevis 7 to a lever 5, Fig. 1, a spring 80 abuts a ring 81 on extension 78 and part 25. A pin 84 and a nut 86 are biased to the ends of a slot 82 in member 52 by a spring 83. A push-rod 87 or nut 86 projects from member 52 toward an adjustable stop in housing end 2b. The tube 3 is attached by collar 90 and clamp 91 to a brake rod 93, Fig. 1, and lever 5 is connected to brake cylinder piston-rod 109. On braking, lever 5 rocks clockwise relative to a link 107 to move housing 2 and tube 3 (through a nut 9 in member 6) rightward against spring 110 mounted between housing end 2b and-flange 111 of part 25; lever 97 rocks anti-clockwise to shift rod 93 and runner 23-27 leftward also against spring 110. Movement of housing 2 and tube 3 relative to runner 23-27 corresponds to the slack in the rigging. During initial movement, spring 80 maintains member 67 in contact with end 2a until wall 79 of part 25 engages member 67. The roller 62 drops into the widening gap 72 between members 67, 52 and pawl 71 engages nut 22 which continues to spin counterclockwise, Fig. 3, due to the pawl riding up faces 59. If slack is sufficient, then rod 87 will not engage stop 89 and on brake-release spring 110 moves housing 2, tube 3 and assembly 23-27 to the shown position; pawl 71 prevents clockwise rotation of nut 22 which, through threads 20, rotates tube 3 counterclockwise to displace rod 4 outwardly and increase slack. Toward the end of brake release member 67 abuts end 2a to close gap 72 and force roller 66 on to surface 67 to disengage pawl 71 from nut 22. Meanwhile spring 83 prevents movement of member 52 relative to roller 51 to maintain pawl 56 disengaged from nut 21. If the rigging slack is within desired limits, then rod 87 abuts stop 89 causing rightward movement of member 52; roller 51 engages in a groove 114 in member 52 to check the premature operation of pawl 56 due to vibration; member 52 moves sufficiently for roller 66 to roll on to surface 115 of member 52 to disengage pawl 71 from nut 22; hence both pawls are disengaged and no adjustment of rod 4 takes place. If slack is excessive, rod 87 engages stop 89 to move member 52; roller 51 drops into notch 57 to allow pawl 56 to engage nut 21 whilst roller 66 rolls on to surface 115 as before. The nut 21 continues clockwise rotation, Fig. 2, due to pawl 56 riding up faces 44. On brake release nut 21 is prevented from counterclockwise rotation and causes, through threads 29, the rotation of tube 3 to draw rod 4 into tube 3 to take up slack. Due to spring 83, member 52 and assembly 23-27 move rightward together to maintain pawl 56 engaged until member 67 (by contact with end 2a) shifts leftward to successively close gap 72 and then move member 52 to force roller 51 out of notch 57 to disengage pawl 56 from nut 21. Both nuts 21, 22 then rotate freely during the final stage of brake release. The tube 3 can be rotated manually by means of a wrench on part 16 to reset the rigging after the fitting of new shoes, and rod 4 can screw directly into tube 3 whose external threads 19, 20 may be integral with or attached to the tube.