DRUM BRAKES

摘要

A drum brake has a pair of brake shoes (40) moveable radially outwardly into contact with an associated brake drum to provide a handbrake function by a cross strut (100) which acts between the brake shoes or between pivoting brake operating levers (14) which actuate the brake shoes. A handbrake lever (18) is pivoted on one brake shoe or brake operating lever (14) and contacts one end of the strut to displace the other brake shoe or brake operating lever towards the drum to apply the associated shoe against the drum and by reaction through the strut to also force the other brake shoe or brake operating lever toward the drum to apply the other shoe against the drum. The strut (100) is in two parts (101,102), one part being connected for movement with each respective brake shoe or operating lever, the strut parts having inter-engageable formations in the form of teeth (103, 104) which when engaged allow the strut (100) to transmit axial force between the shoes or operating levers. Bias means (105,106) are provided for biasing the strut parts apart to disengage the inter-engageable formations to disable the strut, the inter-engageable formations (103, 104) being engaged when the handbrake lever (18) is operated to connect the strut parts (101,102) to allow the brake to be applied and being disengaged when the handbrake lever is released so that the strut parts can disengage and move apart with the brake shoes or brake operating levers to adjust the effective length of the strut as the brake shoes wear.