| 摘要 |
An internal shoe drum brake comprises a pair of brake shoes, an adjustable length strut extending between the shoes and having a ratchet movement of which adjusts the length of the strut, an actuating lever pivotally connected to one end of the strut and engaging one shoe, the lever being so arranged that a force acting on one end in a direction generally parallel to the drum axis rotates the lever to exert a force on one shoe and a reaction force through the intermediary of the strut on the other shoe to urge said shoes apart, and a pawl engageable with the ratchet. To reduce the number of parts the pawl is pivotally mounted on the other shoe and is rotatable about its pivot to move the ratchet and thereby adjust the length of the strut when there is excess wear of the shoes. Furthermore, the strut preferably has a portion which is engageable with a surface portion of the brake back plate, or a member secured to the back plate, to react forces to the back plate. The surface portion is preferably parallel with the strut axis to permit sliding movement of the strut thereon. |
