Wheel Brake Assembly

The invention relates to a wheel brake assembly, and more particularly to a drum brake arrangement wherein a thin wall mounting plate having a strength character incapable of taking the brake torque is utilized to mount the brakes shoes and the wheel cylinder. The backing plate is secured to a mounting flange which in turn is fixed to an axle support member such as an axle housing. The anchor pin for the brake shoes is secured to the flange and also acts as a backing plate mounting bolt. This arrangement permits a substantial decrease in brake assembly weight as compared to conventional current production drum brakes of a similar size. The anchor pin is assembled directly to the mounting flange, eliminating torque transfer through the backing plate assembly. This provides for a more precise anchor pin location than is the case when a backing plate is mounted on a support member and the anchor pin is then mounted on the backing plate. This eliminates the provision of a separate reinforcement plate at the anchor pin as well as the use of two mounting bolts which are commonly used generally adjacent the anchor pin to mount the backing plate. By providing the wheel cylinder mounting on the thin backing plate and requiring no torque to be transmitted through the backing plate, a simple wheel cylinder casting can be utilized, with the wheel cylinder being retained on the backing plate with a wire clip instead of the commonly used wheel cylinder mounting bolts. The brake adjusting mechanism, parking brake linkage, brake shoe tie downs, and brake shoe retracting springs are assembled as a part of the brake unit mounted on the backing plate in a manner similar to that in current use. When the brake is used as a front wheel brake, the parking brake mechanism is not required and the mounting flange is secured to a fixed support which may be a part of the steering knuckle or other front axle support.

FIG. 1 is an elevation view of a wheel brake assembly embodying the invention with arts in section.

FIG. 2 is a cross section view taken in the direction of arrows 2--2 of FIG. 1 and having parts broken away.

FIG. 3 is an elevation view of the other side of the wheel brake assembly of FIG. 1, taken in the direction of arrows 3--3 of FIG. 2 and having parts broken away and in section.

The wheel brake assembly 10 is illustrated as including a wheel brake unit 12, an axle support member or housing 14, and a wheel brake unit mounting flange 16. The brake drum, which is also a part of the wheel brake assembly, is not illustrated for simplicity. However, the brake drum is provided in a manner well known in the art. FIG. 1 is an outer side view of the wheel brake assembly with the drum removed, while FIG. 3 is an inner side view of the assembly. The wheel brake unit 12 includes a backing plate 18, brake shoes 20 and 22, a wheel cylinder 24 positioned between the upper end of brake shoes 20 and 22, an adjuster screw 26 positioned between the lower ends of the shoes 20 and 22, an adjuster actuating mechanism 28, and an anchor pin 30. If the wheel brake unit is for the vehicle wheels having a parking brake mechanism, it will also include a brake shoe spreader bar 32 and appropriate parking brake linkage 34. The brake shoe retracting springs 36 and 38, the shoe hold down mechanisms 40 and 42, and adjuster screw spring 44 are also parts of the wheel brake unit 12.

The backing plate 18 has a centrally formed axle-receiving opening 46 and an anchor pin-receiving opening 48 which is positioned radially outward of opening 46. The axle housing or support member 14 extends through opening 46 as shown in FIG. 2. The axle 50, which is a rear axle for the wheel of the particular brake assembly illustrated, is suitably mounted in the housing 14. The mounting flange 16 is secured to axle housing 14 by suitable means such as weld 52. The backing plate 18 is secured to the mounting flange 16 on one side of opening 46 by the anchor pin 30, which thus acts as a backing plate circumferential locating and mounting means. Two mounting bolt assemblies 54 and 56, on the generally opposite side of opening 46 from the anchor pin 30, also fasten the backing plate to the flange.

The brake assembly construction has been found to permit an assembly weight decrease of approximately twenty-five percent as compared to conventional brake assemblies of the same capacity. This results in vehicle weight savings and cost and leads to better fuel economy. It is advantageous to have the anchor pin assembled directly to the mounting flange, eliminating torque transfer through the backing plate assembly. Since the backing plate only needs to support but not take stresses from the wheel cylinder and the brake shoes, its thickness is reduced to approximately half that of conventional backing plates and is a thin wall of material. The arrangement eliminates the anchor pin reinforcement plate otherwise needed, as well as two of four backing plate mounting bolts, nuts and lock washers. A more simple wheel cylinder casting is used, and the wheel cylinder needs only to be mounted for retention. The brake assembly has been found to function as well as conventionally designed brake assemblies.