Patent GB-1045548-A (GB)
Title: Two way automatic slack adjuster
Inventor: RAUGLAS GERARD
IPC: B61H15/00
Filed: 1964-07-13
Abstract: 1,045,548. Brake slack adjusters. CARDWELL WESTINGHOUSE CO. July 31, 1984, No. 30365/64. Heading F2E. A two-way automatic slack adjuster for railroad car brake rigging comprises a pair of elongated parallel members, one forming a screw portion carrying a single nut and the other a stop clutch assembly including seats on either side of said nut, resilient means biasing the members to move in a slack take-up direction which motion holds the nut against one of said seats, resilient let-out means operatively acting between said other member and the nut to rotate the nut to a predetermined position when the nut is intermediate the said seats, and take-up control means for rotating said nut in the take-up direction when the nut is intermediate the seats. In the embodiment shown, slack adjuster 10A is incorporated in the centre rod structure 12, Fig. 1 (not shown), of a conventional airoperated brake rigging arrangement 14 to provide controlled slack let-out and take-up under substantially all braking conditions thereby restricting the brake cylinder stroke to a required 7". The adjuster comprises a rod part 84, having a non-self-locking thread 85 at one end mounting a single nut assembly 100 and a coupling to centre rod 12 at the other, and a concentric housing 80 formed by parts 304, 300, 328, 410, 330, 108 and 114, the latter being pivoted at 82 to a cylinder lever 20. A compression spring 92, disposed between the housing end 304 and a rod shoulder 94, biases the rod 84 inwards of the housing to seat the nut against the outer 98 of two stop clutch housing rings 98, 99, i.e. in the slack take-up direction. Slack let-out means comprises a compression spring 120 disposed between the end 122 of the housing member 300 and a race 104 of the nut assembly. The slack take-up control means 128 comprises a telescoping, spring-loaded assembly 126, having thrust pins 124 guided in housing member 330 and adapted to engage the other race 102 of the nut assembly, carried by a cylindrical member 408 slidably arranged on the housing members 410 and 108 and mounting a rod 130 which is coupled to and abutted by a control lever 140, said lever being pivoted at one end to the lever 20 and fulcrumed to the car structure at the other as illustrated in Figs. 3, 4 and 5 (not shown). Initial slack adjuster installation and operation.-With new brake shoes fitted, the adjuster is fitted in the fully contracted position, and the control lever 140 arranged to bias the nut assembly 100 through the control means 128 when the shoes contact the wheels. On initial application of the brake, the compressive force of the spring 92 holding the nut against seat ring 98 is overcome and the nut moves towards the seat ring 99. Due to the slack take-up assembly by virtue of its arranged position not counteracting the slack-let spring 120, said spring immediately rotates said nut to the right until engagement with said assembly occurs. The adjuster is then fully extended and set to provide a brake stroke of 7". Continuation of the stroke draws nut 100 against seat 99 so that brake thrust forces are transmitted therethrough in the usual manner. Normal operating conditions.-Under normal conditions, the adjuster operates thereafter to accommodate brake wear. On brake application, parts 84 and 80 move axially apart against the bias of spring 92 thereby disengaging the nut 100 from ring 98 and seating it against ring 99 with little or no rotation of the nut. Compression of the slack .take-up, assembly: 128 against the seated nut; is. then effected.: by continued movement  of the control lever corresponding to the brake shoe wear occurring. On release of the brake, tension: in the rigging ceases and the spring 22 starts to retract the rod 84 into the housing 80, thereby unseating the nut from seat 99 and permitting rotation thereof by the compressed take-up assembly in a direction to the left prior to seating the nut against ring 98. General rigging slack and the spacing of seats 98, 99 permit the necessary clearance for the replacement of worn shoes. The adjuster on said replacement then functions similarly as previously' described to ensure adequate slack let-out to ensure the 7" brake stroke required. The slack take-up assembly can accommodate the loss of two brake shoes but in the event of greater shoe loss, the telescopic cylinders of assembly 126 go solid under the differential movement imposed by the lever 140 through rod 130, further movement of the lever thereafter applying direct thrust during the brake stroke to the nut to cause its separation from seat 98. The spring assembly 126 then rotates the nut in the normal manner on release of the brake. In a modified embodiment, Fig. 10 (not shown), the slack let-out means comprises springs 214 biasing thrust member 224 against race 226 to induce let-out movement of the nut assembly on separation of said nut from the outer 486 of two stop-clutch seats 486, 488 on application of the brake. The slack take-up means 216 comprises a disc 230 slidably mounted on the housing extension 188 and carrying a thrust rod 234 telescopically received in a tubular member 236 housing a compression spring 238. The adjuster functions substantially as described in respect of the prior embodiment.