329,666. Hingston, W. H., and Safety Servo Brakes, Ltd. Feb. 20, 1029. Compensating for wear.-A d-evice for automatically adjusting brake operating gear or other transmission mechanism to take up wear comprises a spring loaded control element 14 normally held in an idle position by a stop or abutment 18 arranged to release the control element at a predetermined point during every operation of the transmission mechanism, the control element being locked against movement by the increase of tension in the transmission mechanism when the load is taken up, so that it moves only if the mechanism fails to take up its load before it moves beyond the predetermined point, such movement of the element coupling the adjusting device to a relatively moving part of the mechanism so as to cause actuation of the adjusting device to reduce the clearance during the release movement of the mechanism. The device is shown connected between two sections 1, 2 of a brake operating pull rod, a pintle block 3 being mounted on the section 2 and pivoted to a yoke 4 secured to the section 1. The pintle block is also pivoted to a forked arm 5 mounted on a fixed fulcrum 6, and the rod 2 is threaded into an adjusting sleeve 7 rotatably and slidably mounted in the pintle block and bearing on a washer 8 pressed against the bottom of a recess 9 in the pintle block by a spring 10 adjusted by a nut 11. A ratchet wheel 12 mounted on the other end of the adjusting sleeve is spaced from the end face 13 of the pintle block by the control element, comprising a collar 14 which is freely rotatable on the sleeve when the washer 8 is in contact with the bottom of the recess 9. A spring 15 tends to rotate the collar in an anti-clockwise. direction and a single ratchet tooth on the collar is engaged by a pawl 16 which also engages the ratchet wheel 12. The collar 14 also carries a pin 17 adjustable by a screw 17<b> which co-operates with the spring-pressed abutment 18 mounted on the lever 5 adapted normally to prevent anticlockwise rotation of the collar. To apply the brake the rod 1 is pulled; this movement rocks the lever 5 and the abutment 18 moves downwards relatively to the pin 17. When there is no excess clearance the tension of the pull rods overcomes the spring 10 and clamps the collar between the ratchet wheel 12 and the face 13 of the pintle block before the abutment 18 clears the pin 17. When the predetermined clearance is exceeded the next operation of the brake results in the pin 17 clearing the abutment 18 before the gear takes up its load so that the collar 14 is rotated by the spring 15 and the pawl 16 permitted to engage a fresh tooth of the ratchet wheel 12. On the return movement the pawl 16 turns back the collar 14 and rotates the ratchet wheel 12 and adjusting sleeve 7 through the space of one tooth, shortening the pull rod. The device may be mounted between the pull rod and a brake operating lever which then takes the place of the lever 5. The control collar may co-operate with a fixed cam or tappet adapted to turn it when necessary.