GB545907A - Improvements in brakes - Google Patents

Abstract

545,907. Drum brakes. BENDIX AVIATION CORPORATION. Oct. 29, 1940, No. 15836. Convention date, Nov. 24, 1939. [Class 103 (i)] In a brake of the kind.in which the friction means such as a pair of linked shoes anchors at one end or the other according to the direction of rotation of the drum, the hydraulic brake application cylinder is adapted to have a dash-pot action to cushion the shock of a change of anchorage and automatic adjustment means is provided comprising a member carried by the friction means and movable relatively thereto by contact with the drum. A pair of shoes 14, 16 pivotally connected by a member 30 and arranged to anchor on a post 18 are applied by a hydraulic cylinder 50 containing a baffle 58 provided with grooves 60, 62 adjacent the bleeder and inlet passages 66, 64. A light pressure is maintained in the pipe lines when the brake is released and springs 70 are compressed between the pistons 52 and the baffle so that the piston rods 54 engage the shoes irrespective of the setting of the shoe adjustment means. The release spring 40 attached to shoe 16 which anchors during forward braking is stronger than the spring 42 attached to shoe 14. Thus in forward braking only the shoes 14 leaves the anchor but in reverse braking this shoe initially leaves the anchor but on application is returned by the frictional action of the drum and this movement is cushioned by the liquid being forced through the restricted passages 60, 62. The shoe webs are provided with part cylindrical recesses for engagement with the. anchor and with extensions 20 to position the shoe ends in a radial direction. Alternative mechanical means for applying the brake comprises a lever 80 pivoted to the shoe 16, connected to shoe 14 by a link 82 and operated by a cable 86. An automatic adjuster for the shoes comprises a block 90 of hard material slidably mounted on the shoe web between guides 108 and extending through the friction lining 22 so as to be flush with the surface thereof. A lever 100 has a disc 98 secured thereto by which it is pivotally mounted on the shoe web and is frictionally clamped to the web by a spring 102. The lever normally contacts a stop 110 mounted on the back plate and thus determines the release position of the shoe. As the lining wears the block 90 is moved inwardly relatively to the shoe and adjusts the lever by engagement of a cam slot 92 in the block with a pin 96 projecting from the part 98 of the lever. The stop 110 is mounted on the back plate by an eccentric pin 114 for manual setting. The member 30 comprises parts secured together for manual adjustment. Specification 535,131 is referred to.