Set of Brake Pads for Floating-Caliper Disc Brake

The present invention relates to brakes and more particularly relates to a set of brake pads for a floating-caliper disc brake.

A floating-caliper disc brake including a generic set of brake pads is disclosed in German patent application No. DE 38 15 733. The known set of brake pads comprises a first brake pad with a first retaining spring made of resilient sheet metal for clamping engagement on the brake piston and a second brake pad with a second retaining spring for clamping engagement on an external housing leg of the floating caliper. The first and second retaining springs have an identical design. Also, the bore in the brake piston provided for engagement of the first retaining spring has the same diameter as the recess in the external housing leg, which recess has the shape of part of a circle and is provided for engagement of the second retaining spring.

Preferably, the two brake pads have an identical design in the prior art disc brake, and interchanging the two brake pads will not cause any problems. If, however, for functional reasons, a different form of friction lining is provided for use on the first brake pad than for the second brake pad, the two brake pads must not be interchanged during the assembly. If, on the other hand, the backplates of the two brake pads do not differ from each other and, further, the guide surfaces of the disc brake for support of the backplates on the axially inner side and the axially outer side are equally arranged, the first brake pad intended for use on the axially inner side would easily allow being mounted on the axially outer side, and vice-versa. The result of such an occurrence would be functional deficiencies of the disc brake. An object of the present invention is to provide a set of brake pads made up of different brake pads for a floating-caliper disc brake, permitting a first brake pad to be fitted only on the axially inner side and a second brake pad to be fitted only on the axially outer side of the floating caliper.

Principally, the solution involves simply making the retaining spring, which is already provided for attachment of the brake pad, a distinctive feature by configuring it differently for the first brake pad and for the second brake pad. When the set of brake pads is mounted correctly, each spring is retained in its associated opening in the. brake piston or the external housing leg. When the brake pads are interchanged, however, the large retaining spring does not permit insertion in the small opening, and the small retaining spring does not permit clamping engagement in the large opening. Wrong assembly with mixed up sets of brake pads is, thus, impossible with the set of brake pads according to the present invention. Another advantage is that the present invention does not cause higher manufacturing costs for the set of brake pads or the associated disc brake.

In a preferred embodiment, the dimensions of the first retaining spring are smaller than those of the second retaining spring. A further preferred embodiment permits clamping engagement of the two opposed resilient tongues. The force components directed in parallel to the brake disc will compensate each other, and only a force component directed in parallel to the axis of the brake piston remains for application of the brake pad on the brake piston.

A third resilient tongue is arranged vertically to the other two resilient tongues and has no partner so that it exerts a force that is generally directed to the axis of the brake piston to apply the brake pad to the guide surfaces of the disc brake and prevent rattling. It is preferred that the portion of the third resilient tongue, that is used for application, generally has the same distance to the axis of the brake piston as the other two resilient tongues.

In a preferred embodiment, the two retaining springs have an identical design, with the exception of the distances between the resilient tongues. Preferably, the dimensions of the two retaining springs differ by 10% approximately. This provides a great degree of distinction, without causing functional problems for the retaining springs. The present invention is especially favorable when the brake pads have identical backplates which may easily be interchanged during the assembly. On the other hand, the friction linings are different in shape and must not be mixed up under any circumstances.

The present invention for use on a floating-caliper disc brake intended for using a set of brake pads and having a bore in the brake piston that is adapted to the first retaining spring and a recess in the external housing leg that is adapted to the second retaining spring. Advantages are achieved for the manufacture of the floating caliper when the bore in the brake piston is narrower than the recess in the external housing leg because the cylindrical bore in the floating caliper provided for the brake piston is machined by a tool which reaches through the recess in the external housing leg. Because the drilling tool has a round cross-section, preferable to configure the recess in the external housing leg as part of a circle. The three resilient tongues of the first retaining spring are correspondingly arranged for engagement in the round bore in the brake piston. Preferably the second retaining spring intended for engagement into the recess, that is shaped like part of a circle, may principally be designed exactly like the first retaining spring, with the exception of the different distances of the resilient tongues from the axis of the brake piston. It is favorable that the diameters of the recess and the bore differ by roughly 10% in conformity with the dimensions of the retaining springs.

FIG. 1 is a side view of a brake pad, according to the present invention, in the correct mounting situation including a brake piston on the axially inner side, shown in a partial sectional view, and an external housing leg, shown in a partial sectional view.

FIG. 2 is a situation corresponding to FIG. 1, however, with interchanged brake pads.

The set of brake pads, according to the present invention, illustrated in the Figures and provided for use in a floating-caliper disc brake comprises a first brake pad 1 and a second brake pad 2. The first brake pad 1 includes a first friction lining 3 which is attached to the front side of a backplate 4. The second brake pad 2 includes a second friction lining 5 which is attached to a backplate 6. While the two backplates 4, 6 have an identical design, the first friction lining 3 has a smaller surface than the second friction lining 5. Further, the first brake pad 1 has a first retaining spring 7 which is attached to the rear side of the backplate 4. The second brake pad 2 has a second retaining spring 8 which is attached to the backplate 6.

The retaining springs 7, 8 serve to mount the brake pads 1, 2 on the floating caliper of the disc brake. The floating caliper has a hollow brake piston 9 on its axially inner side. The retaining spring 7 of the first brake pad 1 is intended for engagement in the hollow brake piston 9 in order to mount the brake pad 1 on the floating caliper and retain it in constant abutment with the brake piston 9. For this purpose, the first retaining spring 7 has two opposed resilient tongues 10, 11 which are engaged in an annular groove 12 in the interior of the hollow brake piston 9. The second retaining spring 8 also has two opposed resilient tongues 13, 14 for clamping engagement in a recess 15 of an external housing leg 16. Recess 15 has a step 17, and the resilient tongues 13, 14 are locked on the step. The hollow interior of the brake piston 9 takes the shape of a bore 18 having a circular cross-section and a diameter 19. The recess 15 of the external housing leg 16 is partly semicircular with a diameter 20. Diameter 19 is slightly smaller than diameter 20. According to the present invention, the distance between the two resilient tongues 10, 11 of the first retaining spring 7 is conformed to the diameter 19, and the distance between the two resilient tongues 13, 14 of the second retaining spring 8 is conformed to the diameter 20. That is to say, the resilient tongues 10, 11 are closer to each other than the resilient tongues 13, 14 which are more remote from each other. The shape of the two retaining springs 7, 8 is identical, with the exception of the distances between the resilient tongues 10 and 11, and 13 and 14, respectively. Exactly as the diameters 19 and 20, the distances of the resilient tongues differ in their size by roughly 10%.

In addition to the resilient tongues 10, 11 and 13, 14, respectively, which are arranged at an angle of 180.degree., each of the retaining springs 7, 8 has a third resilient tongue 21, 22 which is arranged at an angle of 90.degree. in relation to the other springs.

Initially, the third resilient tongue 21, 22 extends away from the backplate 4, 6 of the brake pad 1, 2 and, after a deflection, reaches towards the backplate 4, 6 again. The end of the third resilient tongue 21, 22, proximate the backplate 4, 6, abuts on the wall of the bore 18 in the brake piston 9 or the wail of the recess 15 in the external housing leg 16 and retains the respective brake pad 1, 2 in an anti-rattle manner in its guides in the disc brake (not shown). With respect to the circular cross-section of the bore 18 or the semicircular cross-section of the recess 15, the portion 23 or 24 of the third resilient tongue 21, 22, which is intended for abutment, has generally the same distance to the axis of the brake piston as the other two resilient tongues 10, 11 or 13, 14, respectively.

The situation shown in FIG. 2 occurs when the first brake pad 1 and the second brake pad 2 are interchanged. In this event, the first retaining spring 7 will be positioned in the recess 15 of the external housing leg 16. However, as the distance between the resilient tongues 10, 11 is considerably smaller than the diameter of the recess 15, the first retaining spring 7 cannot become locked in the recess 15 so that attachment of the first brake pad 1 is impossible. Matters are vice-versa with the second brake pad 2. The distance between the resilient tongues 13, 14 is considerably larger than the internal diameter of the bore 18 so that the second spring 8 cannot be inserted into the bore 18 of the brake piston 9. Therefore, it is impossible to mount the second brake pad 2 on the wrong axial side of the floating caliper.