Automatic adjustment strut for a drum brake

摘要

PCT No. PCT/FR94/01309 Sec. 371 Date Nov. 21, 1994 Sec. 102(e) Date Nov. 21, 1994 PCT Filed Nov. 9, 1994 PCT Pub. No. WO95/16864 PCT Pub. Date Jun. 22, 1995An automatic adjustment strut for a drum brake which is mounted in the vicinity of actuating member and located between a first end of first and second shoes. The first and second shoes are lined with friction pads. The strut has a body with first and second ends which bear on the first and second shoes and extension arrangement for automatically extending the body as a function of ear of the friction pads. The extension arrangement is formed by a screw-nut system and controlled by a pawl which urges toothing secured to a member of a screw-nut system. The pawl is carried by an elastic strip secured to the body of the strut. The elastic strip is separated from the body of the strut when the drum brake is in the position of rest. A lever mechanism tilts to allow the elastic strip and the body of the strut to move toward each other when the shoes are urged apart through actuating member. The lever mechanism has a first arm and a second arm with the first arm bearing on a nut in the screw-nut system. The first arm is pierced with an oblong opening through which a screw of the screw-nut system passes. The second arm which extends from the first arm with a vertex of angle greater than 90 DEG , is located between the body of the strut and the elastic strip. The strut is characterized in that when the actuating member is implemented, the first arm of the lever mechanism bears on the nut at two zones which are substantially diametrically opposite with respect to the axis of symmetry of the nut and acts on nut to rotate a screw and thereafter change the space relationship between a head and the body to provide a corresponding changed in the linear space between the first ends of the first and second shoes.