GB542724A - Improvements in or relating to pawl and ratchet devices particularly for brakes of motor vehicles - Google Patents

Abstract

542,724. Pawl and ratchet mechanism. OHLSON, G. E. Dec. 22, 1939, No. 32806. Convention date, Jan. 2, [Class 80 (iii)] [Also in Group XXXIV] A ratchet and pawl device of the type comprising a screw-threaded ratchet bar so that the pawl may be displaced along the bar by rotating the bar as well as by a sliding action comprises a carrier having a tubular part 5 slidable on the screw-threaded ratchet bar 1 and a tubular guide 6 in which the toothed pawl 2 is slidable. The angle v between the guide and the bar is such that the pawl and carrier are self-locking relatively to the bar as regards movement in the direction of the arrow s. The device is particularly suitable for automatic slack adjusting mechanism for brakes. The Specification as open to inspection under Sect. 91 describes also automatic slack adjusting mechanism for, brakes comprising a pair of pawl devises 10, 12, such as above described adapted to engage the threaded bar 14 which is connected at one end 40 to the brake. The pawl 12 is pivoted at 30 to the forked end of a rod 28 connected to a pedal 26 and a pawl 10 is secured to a rod 16 provided with stops 22, 24 for co-operation with a fixed stop 20. In applying the brake the fall on the rod 28 is transmitted to the bar 14 and the brake by the pawl 12 and the pawl 10 and rod 16 are carried along by the bar 14. If the clearance between the brake shoes and the brake drum is excessive, the stop 22 engages the stop 20 so that the bar 14 slides relatively to the pawl 10. During release, the bar returns the distance determined by re-engagement of the stops 24, 20 and the pawl 12 slides on the bar under the action of the springs 36 until it abuts the pawl 10 as shown. The effective length of the bar and the rod 28 is thus shortened. The pawl 12 has a pin 60 that runs in a slot in the pawl 10. The stop 22 may be clamped to the rod 16 so as to yield under excessive force. Manual adjustment may be effected by rotating the bar 14, the connection 40 between the bar and a rod 38 connected to the brake permitting the rotation. In a modification, the bar 14 and rod 28 operate under pressure instead of in tension and the effective length thereof is lengthened to reduce the brake clearance. This subject-matter does not appear in the Specification as accepted.