Figure 7-13. - Self-adjusting mechanisms.
cable then is passed up and over the anchor and attached to the secondary shoe. Operation is as follows:
1. Brakes are applied and the shoes expand and contact the drum.
2. The primary shoe self-energizes, and, through servo action, applies the secondary shoe.
3. The heel of the secondary shoe is lodged against the anchor pin.
4. The movement of the primary shoe tightens the cable by shifting the cable guide outward and in the direction of rotation.
5. The cable then moves the adjusting lever upward. If enough shoe-to-drum clearance is available, the adjusting lever will engage the next tooth on the star wheel. The brake shoes retract and the cable slackens, as the brakes are released. The return spring then helps force the adjusting lever downward, rotating the star wheel, which expands the brake shoes. In the reverse direction, the toe of the primary shoe is forced against the anchor, and the secondary shoe moves around to tighten the adjusting cable. The adjusting process is then completed.
Link type - The link type self-adjusting system (fig. 7-13) uses solid linkage rods to connect the adjusting lever to the stationary anchor point. The two linkage rods, connected together by a bell crank that pivots on the secondary brake shoe, operate the adjuster. One rod attaches to the anchor point and the bell crank,Continue Reading