Patent GB-326178-A (GB)
Title: Improvements in automatic slack adjusters for brakes on railway cars and the like
IPC: B61H15/00
Filed: 1928-12-05
Abstract: 326,178. Svenska Aktiebolaget Bromsregulator. Dec. 5, 1928. Addition to 300,120. Compensating for wear. -The automatic slackadjuster of the parent Specification is modified by the provision of means for preventing the rotatable part of the screw connection from being rotated in a direction opposite to the direction of rotation imparted by the driving means, for diminishing slack. In one modification the spindle 11, Fig. 1, is extended and a spring 24 arranged between a flange at the end of the extension and an antifriction bearing abutting against the flange 6<b>. When the pressure of the spring 13 between the flange 12 and the abutment 6<a> is relieved the spring 24 maintains pressure between these surfaces to prevent rotation of the casing 6 and one clutch member 15, when the clutch member 22 is rotated in the direction for releasing the clutch i.e. on brake release. In a modified form the pawl device 17, Fig. 2, connects the nut 20 and the clutch member 22a. The member 17 and the nut 20 are slidably but non-rotatably connected. The reverse rotation of the clutch members and the casing 6 are prevented as they are held by the spring 13 against a friction ring 26 slidably and non-rotatably connected to the spindle 11 and bearing against the nut 20. A pawl device may be substituted for the ring 26 in order not to offer resistance to movement of the member 22a for diminishing the slack. In a further modification a positive axial displacement of the clutch member 22<a> on disengagement of the clutch is obtained by means of a sleeve-shaped extension of the nut 20 having a collar engaging over a plunger on the member 22<a> and the one-way driving means between the nut and this clutch member comprises a helical spring fitting in borings in the nut 20 and the part 22<a>. A ball bearing is'interposed between the ring 26 and the nut 20 to elimate resistance to the rotation of the latter. A further modification shown in Fig. 4 is arranged so that the pressure of the spring 13 is relieved from the threads controlling the clutch during clutch engagement and thus no power is taken from the brake for this purpose. The spring 13 is contained inside the tube 3 which is extended so that a cap 30 on the end can abut against an inner face of the eye 5 to lock the tube 3 against rotation. The spring abuts on a washer 32 having pins 32a extending outside the tube 3 and engaging a ring 34, a bearing 14, a friction ring 26<b> and a clutch member 22<b>. The nut 20 moves on threads 36 and has a sleeve 20<a> carrying an abutment flange 38 for limiting axial movement of the clutch member 22b in the direction of the spring-pressure transmitted to it by the spring 13. On brake application the nut 20 moves on the threads 36 so that the flange 36 moves away from the clutch member 22b which is forced by spring 13 into engagement with the clutch member 40 fixed to the tube 3. Unless the slack is correct when the breaking stress prevents it the continued rotation of the nut 20 turns the tube 3 by means of the clutch and a one-way driving means comprising a helical spring 27 and a ring 37 splined to the clutch member 22b, until the tube 3 is locked by the engagement 'of the collar 30 with a face 31a on the eye 5. If the slack is too small and the adjusting-screw non- self-locking the tube 3 turns on the bearing 14 when the cap 30 is pulled away from the eye 5. Reverse rotation of the tube 3 is prevented by the ring 26<b> which is splined to an extension of the eye 5. In order normally to relieve the pressure of the spring 13 from the threads 36 the apparatus may be arranged so that the clutch is normally engaged and the cap 30 out of contact with the eye 5, diminishing of the slack begins as soon as the nut 20 is rotated. Also a braking stress arising too early disengages the clutch thus freeing the apparatus for lengthening of the pull rod. A pin 30<b> on the cap 30 is arranged, so that the apparatus may be manually adjusted, to engage the bottom of a recess 5<a> by means of its end which is convex so that there is only small friction. The operating-arm 21 of the nut 20 is disconnected and the nut turned until the pin 30<b> engages the bottom of the recess and the clutch is disengaged, when the tube 3 may be turned on the ball bearing 14 and the end of the pin 30b. In a further modification abutments on the extension 35 and the ring 34 engage before the engagement of the cap 30 and the abutment 31a. When the braking stress disengages the clutch the tube 3 will rotate until these former abutments engage, and stop the rotation and compress the spring 13 so that the spring pressure is relieved from the threads 36. The abutments 30, 30a finally engage to lock the tube. The surfaces of the abutments on the parts 34, 35, 30 and 31a may be of conical shape or corrugated to give a stronger locking action. The threads 36 may be substituted by oblique collars tending to push the nut 20 in the direction of the eye 5 at the release of the brake. The moment at which the clutch engages in the modifications shown in Figs. 1 and 2 may be varied by adjusting the position of the abutment 9. The abutment is mounted on a sleeve 42 screw threaded to the casing 7 and locked by a set screw 44 and a locknut 46. In Fig. 4 the nut 20 is formed of two parts 20<a>, 20<b> connected by screw threads by means of which the position of the abutment 38 is adjusted.