| 摘要 |
905,796. Drum brakes. BENDIX CORPORATION. March 10, 1961 [May 6, 1960], No. 8906/61. Class 103 (1). An internal-expanding drum brake has two shoes 16, 18 carried on a torque plate 30 by levers 36 at each end of each shoe, the levers acting to apply the shoes when rotated by an actuating device 80 and to act as anchors when their non-pivoting ends are held against rotation and providing a floating abutment surface for the shoes bearing against them. The levers 36 are pivoted at 38 to the torque plate and have shoe abutment surfaces 50 so shaped to result in the maximum shoe engagement pressure being located substantially midway between the shoe ends, the linings 24 being thickened at this point to provide even wear. Anchoring forces on the levers are taken by the pivots 38 and by projections 46 formed from the torque plate. Adjustment is provided by a screw and nut adjuster between the shoe and a lever manually-operated from outside the drum by a gear 68. In the form shown in Fig. 1, the two double-acting hydraulic actuators 80 provide on the leading shoe brake for both directions of drum rotation. In the form shown in Figs. 6, 7, the shoes 16a, 18a are applied by a pneumatic diaphragm motor actuating a wedge 124 to rock cam followers 170 to spread the levers 36a pivoting on members 160 secured to the torque plate which also provides abutments 46a. The other ends of the shoes abut, through adjusters 56a on levers 36a engaging a servo linkage 100 transmitting proportioned forces from one shoe to the other. The shoes are retracted by flat springs 102 anchored at one end to the torque plate and by springs 104 which hold adjustors 56a against the abutment surfaces 50a of the levers 36a. In another embodiment, two pneumatic actuators are employed. In simplified embodiments only one hydraulic actuator is used and the levers may abut either projections from the torque plate, or a spring- centred force transfer strut. |
