Parking brake of a drum brake

摘要

A parking brake (10) having a drum containing first and second brake shoe portions (11, 12), a handbrake lever (18) pivoted (19) adjacent one end on one (11) of the brake shoe portions and a strut (20) extending between a first abutment on the handbrake lever and a second abutment (21) on the other (12) of the brake shoe portions. Pivoting of the handbrake lever relative to said one brake shoe portion (11) moves the strut (20) which in turn moves the other brake shoe portion (12) away from said one brake shoe portion to bring the shoe portions into contact with the drum thus applying the parking brake. One of the abutments is in the form of a biased wedging means (21) which acts on the strut (20) to take up all play in the thrust path between the handbrake lever (18) and the other brake shoe portion (12) via the strut. A clamping member (27) is provided for disabling the wedging means (21) from operating except when initial manufacturing or assembly clearances are being taken up in the strut or when a subsequent manual adjustment of shoe clearance is being made. Alternative snail-cam type wedging means (21) are also disclosed as in an electrically actuated parking brake system with an automatic clearance adjustment device.