| 摘要 |
<p>In the control lever of an expanding shoe brake is freely journaled a wormwheel engageable with the driving shaft of an operating cam of a shoe brake. The worm wheel (12) being angularly fastened by engagement with a worm screw (16). A sprocket (40) coaxial with the worm screw is in unidirectional engagement with it through a freewheel mechanism (36, 38, 42, 44) and is displaced forward and backward by a rack (54) driven by a pawl integral with the brake carrier for causing a corresponding rotation of the worm wheel (16) when the displacement of the control lever exceeds a predetermined value. According to the invention, the rotation of the worm wheel (16) causes successive incremental displacements of an abutment (20) of said freewheel mechanism up to a terminal position of disengagement. <IMAGE></p> |
