GB262510A - Improvements in or relating to friction brakes - Google Patents

Abstract

262,510. Hopkins, B. L. Sept. 9, 1925. Blocks acting on drums; compensating for wear.-An internal expanding drum brake comprises a plurality of box-like shoes 7, radially guided upon saddle pieces 5 carried upon an anchorage member, and racking cams 14 which are pivoted on bearings 15 disposed between the adjacent ends of the shoes and provided with levers 22 set at an angle to the radial direction of the drum and slotted to engage pins 24 on an angularly movable ring 25. The toe pieces of the shoes, engaged by the cams lie upon a chord of the drum circle. The contacting points of each cam lie on a circle having its centre at the pivot point of the cam. The brake-operating lever 20 is fixed to a shaft on which is fixed one of the cams or it may be pivoted on a cam shaft and provided with a lever engaging the pin engaged by the lever of the cam. The saddle pieces may be U-shaped, and springs 11 engaging bosses on the saddle pieces and the shoes normally seat the shoe on the saddle piece. The inner face of the shoe bearing on the saddle piece is provided with ribs to prevent collection of dirt interfering with the operation of the brake. For purposes of adjustment, a lug provided on the brake-operating lever 20 is adapted to engage an adjustable screw stop, or an arcuate slot may be provided in the ring 25 engaging a pin adapted to be locked in different positions in a slot in the anchorage member. The angular movement of the cams gives movement to the shoes equal to the thickness of the brake lining. The ring 25 may be operated by mechanism driven by rotating parts of the vehicle, or the ring 25 may be fixed and the anchorage member rotated. The sets of shoes may be duplicated in each drum. A brake having lour shoes is arranged with the toe pieces lying on chords forming a square.