| 摘要 |
<p>A wheel cylinder assembly (10) has a body (12), pistons (16,18), boots (52,54) and seals (24,26). A screw assembly (88) positioned between the two pistons holds the pistons apart to maintain the specified clearance between the brake linings (44,46) and the brake drum (50) while the drum brake is released. If a predetermined amount of outward movement of the pistons occurs during brake actuation, the screw rotates with further piston outward movement. When the drum brake is released, the pistons return inwardly, and the screw is locked against reverse rotation by means of an adjuster clutch (78), preventing the pistons from returning more than the prior predetermined amount of outward movement before screw rotation began. A clutch seal (130) on an extension (104) of one clutch member (100) seals in a piston recess (64). The other clutch member is formed in that piston recess next to one end of a section (74) thereof. That section axially beyond the seal is vented (80) to atmosphere. A cross pin (114) extends across a recess (108) in the one clutch member, is mounted in slots (94,110,112) formed in the one clutch member and in the screw, and permits limited movements of the cross pin axially of the wheel cylinder assembly to control relative adjusting movement of the screw. <IMAGE></p> |
