Abstract: A drum-type brake actuator provides increased force transmission efficiency and assembly simplicity. An anchor carries two pistons which are moved to apply a brake shoe by the cooperative operation of a lever and strut arrangement. The utilization of three pivot joints in a simplified mechanism results in high efficiency output.

Abstract: This invention relates to a cable actuated parking brake mechanism for a drum brake. A lever and an associated lever return spring are arranged to accommodate blind assembly of the cable to the lever. The spring guides the cable from an opening in the backing plate to the lever. The spring cooperates with the lever to indicate to an assembler that the cable is fully inserted as well as aids in directing a cable button to an engagement surface.

Abstract: A wheel cylinder has a body, pistons, boots and seals. A screw assembly positioned between the two pistons holds the pistons apart to maintain the specified clearance between the brake linings and the brake drum while the 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 brake is released, the pistons return inwardly, and the screw is locked against reverse rotation by means of a clutch, preventing the pistons from returning more than the prior predetermined amount of outward movement before screw rotation began. A clutch seal on an extension of one clutch member seals in a piston cylinder section. The other clutch member is formed on that piston next to one end of the cylinder section. The cylinder section axially beyond the seal is vented to atmosphere.

Abstract: A drum brake is provided of the leading-trailing shoe type in which a single piece spring installed as a part of the assembly holds down the brake shoe assemblies against the backing plate and also retracts the shoes after brake actuation. The single piece spring also retains the lower ends of the shoes against the anchor plate. This arrangement eliminates the need for separate shoe hold-down springs and separate upper and lower return springs, resulting in a significant reduction in parts and labor for assembly.

Abstract: In a preferred embodiment a self-adjusting vehicle wheel drum brake is provided having an adjuster strut with a threadably extending star wheel and an adjuster pawl mechanism having a dual step tip. The dual step tip allows the adjuster mechanism to move the adjuster pawl in small incremental steps, thereby lowering in half or in close approximate thereto, the amount of wear required upon a pair of brake shoes before the adjuster pawl will effectuate outward movement of the brake shoes.

Abstract: A thermal compensating self-adjusting vehicle wheel drum brake apparatus and method is provided including a wheel cylinder, a plate for mounting the wheel cylinder, an adjuster strut with a star wheel for adjustably extending a pair of brake shoes. An adjuster pawl is provided for turning the adjuster star wheel. The adjuster pawl is inserted within an aperture of one of the shoes. A thermal elongating stop extendible at a predetermined temperature contacts and wedges the adjuster pawl to prevent pivotal motion thereof whenever the temperature of the brake is above a predetermined value.

Abstract: A master cylinder assembly has a low pressure, high volume displacement quick take-up chamber and a high pressure, low volume displacement pressurizing chamber formed by a stepped bore and a stepped piston. A compensation control and blow-off valve unit has a peripheral lip seal type valve providing compensation flow on break release but preventing flow from the quick take-up chamber during brake apply. A normally closed check valve is held open while the master cylinder is in the fully released position to provide communication between both pressurizing chambers and the fluid reservoir. As the pressurizing cup for the high pressure chamber closes its compensation port, the check valve is permitted to close by camming action of a valve pin and a camming surface on the piston. Initial flow is obtained from the quick take-up chamber past the pressurizing cup into the high pressure chamber.