Automatic adjuster for drum brake.

摘要

An automatic adjuster for an internal shoe drum brake comprises a spacer element (22) having: a wedge shaped portion (23) which forms a link between the rigid strut (19) of a hand brake mechanism and an abutment (34) on one brake shoe (11); and a screw threaded portion (26) which engages a correspondingly threaded portion of a ratchet wheel (29). The ratchet wheel (29) is mounted between the posts of the trunnion (27) which is pivotally mounted with respect to the shoe (11). A pawl assembly (30, 36) is mounted for movement with respect to the shoe (11) and has means (35) for engagement of the spacer element (22). Spring means (39) maintains engagement between the pawl assembly (30, 36) and spacer element (22) and between the spacer element (22) and strut (19). A pawl formation (39) engages the ratchet wheel (39), so that upon pivotting of the spacer element (22) the pawl formation (38) will rotate the ratchet wheel (29) to advance the wedge shaped portion (23) between the strut (19) and abutment (34).