Patent GB-406518-A (GB)
Title: Improvements in or relating to brake mechanism
IPC: F16D65/56
Filed: 1933-05-15
Abstract: 406,518. Brakes. NAPIER & SON, Ltd., D., 211, Acton Vale, Acton, and SEWELL, C. W., 2, Holly Park Road, Finchley, both in London. May 15, 1933, No. 14110. [Class 103 (i).] Brake mechanism comprises the combination with hydraulic operating means of stops for determining the normal position of the brake shoes that are adjustable by means adapted to move the stops first a predetermined amount corresponding to the desired clearance of the shoes then sufficiently to apply the shoes to the drum and finally to retract them the predetermined amount. The adjusting means may be combined with means for equalising the clearance of a pair of brake shoes as described in Specification 406,517 and it may serve as an alternative means for applying the brake. Figs. 1, 2 and 4 show a mechanism in which brake shoes B can be applied by a hydraulic cylinder B<3> and also by mechanical means which includes the means for equalizing the clearance of the two shoes from the drum A and also for reducing the clearance of both shoes to a predetermined amount. A cam C engaging projections B<4>, B<5>, on the shoes B can slide with frictional restraint on the flat end D of the operating spindle D<x>, which is mounted in the fixed bearing E. The frictional restraint is provided by disposing the cam C between a flange D<1> formed on the spindle and a spring washer D<3> threaded on it. The arm F of the spindle Dx is connected by links H<2>, to a bell-crank G<2> mounted concentrically at G<1> with a hand-lever G operatively connected to the bell-crank by a screwed rod J<1>. A winged handle J<4> pivoted at J3 to the rod J<1> has a cam surface J<6> for engagement with the lever G. The rod J<1> is normally locked against rotation by the engagement of its non-circular head J<2> with a corresponding recess in the lever G. A locking pawl and rack G<5>, G<6> is provided for the lever G. The brake shoes B may thus be applied by the lever G through the cam C and if one shoe is applied before the other the cam slides on the spindle D against the frictional restraint so that when the shoes are released the clearance is equalised. To reduce the clearance of both shoes, the handle J' is turned on the pivot J<3> to a vertical position and by the action of the cam surface J<6> the rod J<1> is lifted and the shoes are thus moved towards the drum. The rod J<1> can then be rotated until the shoes are actually applied. Upon returning the handle J<4> to the position shown the shoes are spaced from the drum to a predetermined extent. Fig. 6 shows shoe adjusting means which do not form part of operating means for the brake. A pair of cams K<1>, K<2> serving as stops for the shoes B are connected to a lever L pivoted on a screwed rod M similar to the rod J<1>, Fig. 1, and slidable in a fixed tub N against which the cam surface on the lever J<4> is adapted to abut. Movement of the lever L about its pivot is restrained by friction washers. By turning the lever J<4> on its pivot J<3>, the cams K<1>, K<2> are operated to move the shoes B towards the drum. The screwed rod is then turned until the shoes are applied, the lever L turning about its pivot if the clearance of the shoes is unequal so that when the lever J<4> is returned to the position shown, the shoes are spaced from the drum by an equal and predetermined amount.