Patent GB-1212170-A (GB)
Title: Brake slack adjuster
IPC: B61H15/00
Filed: 1969-05-20
Abstract: 1,212,170. Brake rigging slack adjusters. CARDWELL WESTINGHOUSE CO. 20 May, 1969 [24 June, 1968], No. 25625/69. Heading F2E. In a brake slack adjuster for the brake rigging of a railway vehicle of the kind including slacktake-up controlling means comprising an actuator including overtravel spring means, thrust pin means interposed between the overtravel spring means and a nut on a threaded rod, a sliding member mounted on the adjuster housing for longitudinal sliding movement relative to it; and means for moving the sliding member against the overtravel spring means in response to brake cylinder overtravel to bias the thrust pin means against the nut to bias the nut to rotate in a slack-take-up direction, the overtravel spring means comprises a first canister member received over the housing and interposed between the slidably mounted member and the thrust pin means, a compression spring housed in the first canister member, the slidably mounted member operatively engaging the compression spring for compression against the thrust pin means on the movement in response to brake cylinder overtravel, and a second canister member received over the first canister member and fixed to the housing, the slidably mounted member extending into the second canister member for operative engagement with the compression spring. In normal operation, piston-rod 18, Fig. 1, is forced outwards by admission of air to brake cylinder 16, to apply the brakes. Live lever 20 is thereby turned slightly counter-clockwise, pulling connecting rod 26 to apply rail bogie brake apparatus (not illustrated) on the right. Adjuster 10 and rod component 160 are thereafter placed under tension by lever 20, pulling connecting rod 64 to apply further brake apparatus (not illustrated) on the left. The adjuster 10 is connected to lever 20 by a pin 82 and a clevis 81, Fig. 3, the clevis 81 being screwed to a tubular housing extension 87 threaded, at its other end, into a ring member 178, Fig. 4, the ring member 178 being threaded, in turn, into a sleeve 170 forming part of the main part, 80, of the housing. When slack in the rigging is to be taken up, in consequence of brake shoe wear, the slack adjuster is automatically shortened for this purpose in the manner to be described. The adjuster includes arod 84 whose left-hand end 136, Fig. 3, is connected through rod 131 with rod component 160, Fig. 1; right-hand end 85 of rod 84 is screw-threaded,- Fig. 4, and extends through a spin nut 86 and through the housing extensicn 87. While clevis 81 is being pulled by live lever 20 during brake application, a trigger rod 190, Fig. 3, is being pushed against a trigger lever 66 to which it is pivoted at 66. Trigger lever 66 is pivoted at 27, Fig. 1, to connecting rod 26 while its other end is accommodated in a fixed bracket structure 68. Consequently, trigger rod 190 is pushed to the left, taking with it a sleeve 212, Fig. 4, to which it is connected at 214. Sleeve 212 compresses a spring 224 via retainer 244, and the spring, via the end wall 218 of a first canister member 216, Fig. 5, pushes thrust pins 105 to displace nut 86 from seat 98 and force it against seat 99. At this stage, springs 322, 324, Fig. 3, surrounding rod 84, are being compressed between housing end ring 310, Fig. 3, and spring seat 94, Fig. 4, fixed to the rod. When the brakes are released by release of air from cylinder 16, tension in adjuster 10 is relieved, whereupon rod 84 moves to the right in housing 80, pushing nut 86 off seat 99 and against pins 105. Because of the energy already stored in compression spring 224, nut 86 rotates around rod 84 in a "slack take-up" direction to shorten the adjuster. When all the brake shoes are new, and the slack adjuster is first being applied to the brake rigging, it is applied in its fully contracted condition. In these circumstances there is insufficient slack in the rigging to permit the required 7 inch brake piston stroke; but once the power stroke (the first power stroke to be applied after fitting the adjuster) has proceeded to the point where nut 86 is freed from seat 98, a let-out spring 104, Fig. 4, forces nut 86 to rotate around rod 84 in the "slack let-out" direction. Within the first canister member 216, Figs. 4 and 5, there is located a stop sleeve 250 to define the limit of contraction of spring 224. Movement of the first canister member leftwards is limited by the limited movement of nut 86 and pin members 105, and rightwards by a ring 228 welded to the end of a second canister member 260, Figs. 4 and 6. This second canister member is screwed into sleeve 170 at 266. The second canister member 260 has a sealing element 286, and sleeve 212 has a sealing element 298. A locking ring 306 retains sleeve 212 on housing extension 87. The apparatus may be slightly modified for application to a "top rod" arrangement instead of to a "central" rod arrangement as shown.