Patent GB-284935-A (GB)
Title: Improvements in vehicle brake mechanism
IPC: F16D65/60
Filed: 1927-07-15
Abstract: 284,935. Clark, D'A. M., (Bendix Brake Co.). July 15, 1927. Compensating for wear: force-transmitting mechanism; blocks acting on drums. - Vehicle brake-operating mechanism comprises a brakeapplying device swivelling in steering with the wheel, a brake-operating device not swivelling with the wheel and universallying engaging the brake-applying device approximately at the swivelling axis and means for automatically adjusting one of said devices to preserve as the brake wears the position of said device with respect to the swivelling. axis. An arm 80, Figs. 1 and 6, splined and clamped on the brake camshaft 58 is enclosed in a casing 84 which encloses the adjusting-mechanism and is operated on by a lever 88 to apply the brake. A worm 90 has a bearing at each end in the casing and passes through a notch in the end of the arm 80. A nut 94 threaded on the worm, is slidably engaged by the sides of the casing 84 to prevent it turning and adjustably engages the arm 80 to apply the brake. The adjustment is brought about when the brake is applied, by a pawl 104 which engages a fixed or adjustabe stop 106 exterior to the casing, and turns the worm by a ratchet wheel 96. The pawl 104 is returned by a leaf spring which may have formed on it a holding-tooth for the ratchet wheel. In a modification the adjustment is made when the brake is released and the teeth on the ratchet wheel are reversed and the pawl is formed as a hook which on its return movement under spring pressure turns the wheel. The brake comprises a central shoe on a fixed pivot and two end shoes acted on by the cam and connected to the central shoe by floating pivots. The clearance of the central shoe is determined by a fork straddling one of the floating pivots with a certain clearance and pivoted on a stem frictionally clamped to the brake backing-plate. The casing 84 is sleeved on the shaft 58 and may be filled with lubricant. The bracket 60 carrying the cam and its shaft and a plate 110 carrying the stop 106 are lightly clamped against the brake backing-plate so that they can shift to allow the cam to centre itself. In a modification of the ratchet mechanism the ratchet wheel is held by one end of a leaf spring 128, Fig. 10, the end of which forms a pawl operated by a separate plunger 130. In another form a lever operated by the stop 106 is pivoted on the pivot of the holding pawl and carries an arm on which is mounted the operating-pawl; the pawls are connected by a tension spring urging them against the ratchet. In a further form the lever engaging the stop is secured to a cap 144, Fig. 16, forming a journal for the end of the worm 90 and having an arm 146 carrying the operating pawl 148. In a further modification the clearance of the shoes is determined by frictionally-held forked stops embracing pins carried by the shoes and the shaft 58, Fig. 19, is formed with worm-gear teeth engaging a worm 162 carried by a crank arm 164 engaged by the lever 88. A torsion spring 166 tends to turn the cam to apply the brake and when adjustment is necessary turns the arm 164 to engage a fixed stop 168.