A drum brake which comprises two brake shoes, an actuator situated between two first adjacent ends of the shoes and a fixed fulcrum block situated between the other two ends of the shoes. An adjuster is designed to increase the distance between the first ends of the shoes automatically as a function of the wear on the lining of the shoes. The adjuster comprises a lever pivoted at one end on a first of the shoes in the vicinity of the actuator. A pawl is pivoted on the first shoe and biased by a resilient member into engagement with a toothed sector formed on the other end of the lever. An operating member is responsive to an increase in the distance between the first ends of the shoes, so as to pivot the lever in the direction corresponding to adjustment of the brake. The resilient member comprises a spring of which at least part cooperates with the surface of the lever remote from the first shoe irrespective of the position of the adjuster.
The invention relates to a drum brake for an automotive vehicle, comprising two brake shoes (18, 20) adapted to be moved apart by a wheel cylinder (14), one (18) of said shoes carrying an adjuster including a lever (40) having a free end (48) defining a toothed sector (52) cooperating with a pawl (44) also carried by said one shoe (18), a strut (50) being provided between the other shoe (20) and the lever (40) to automatically control pivoting of the latter. A link (74) disposed between the pawl (44) and the lever (40) to prevent pivoting of the latter through more than a predetermined angle relative to the position occupied by the lever (40) when the lining carried by the shoes (18, 20) are new.
The invention relates to a drum brake in which the strut (32, 132, 232) is maintained at an approximately constant distance relative to the brake motor (20, 120, 220). The brake comprises a strut (32, 132, 232) disposed between two brake shoes (12, 112, 212; 14, 114, 214) and maintaining the brake shoes in spaced-apart relationship through a wear compensating device (38, 137, 138, 237, 238). The strut includes an inclined plane (60, 160, 260) cooperating, in proportion to wear of the friction elements (16, 116, 216; 18, 118, 218), with a projection (64, 164, 264) carried by one shoe, the inclined plane approximating an arc of a circle centered on the center of rotation of the associated shoe during wear of the associated friction elements. The invention may be applied to brakes for automotive vehicles.
An internal shoe drum brake incorporates an automatic adjuster which includes and adjuster element carried by one of the brake shoes, a strut extending between the shoes and engaged by the adjuster element and a rotary adjuster cam mounted on the same shoe as the adjuster element, or a parking brake lever pivoted on the shoe, the cam engaging the adjuster element in a non-rotatable manner. When the shoes are separated for braking, excess shoe separation causes the adjuster element to be disengaged from the cam so that the cam is rotated by a spring to re-engage the adjuster element and thereby establish a retracted position of the shoes.
A recentering device for a drum brake is provided in an opening of the strut placed between the shoes and includes a spring placed between two cups which are capable of sliding in the opening and both engage a fixed bearing element on the brake support plate and are supported by one of the shoulders formed in the opening. During braking, the strut compresses the spring through one of the two cups by way of the corresponding shoulders. On termination of braking, the spring recenters the strut, driving it back until one of the cups regains its bearing on the associated fixed bearing element, thus recentering the shoes bearing on the strut.
An internal drum brake of the kind including a strut between a hand brake lever pivoted on one shoe and the other shoe, has a wear adjuster comprising a pair of screw-threaded members with a pawl and pawl wheel for relative rotation thereof on operation of the service brake system, the axis of the screw-threaded members intercepting the line of action between the shoe and an abutment which limits return movement of the shoe to a brake-released position, one of the members having a spacer between the shoe and the abutment, the spacing effect of the spacer being changed on relative rotation of the screw-threaded members.
