GB1567400A - Friction pads for disc brakes - Google Patents

Description

(54) IMPROVEMENTS IN AND RELATING TO FRICTION PADS FOR DISC BRAKES (71) We, TOKICO LTD., a Japanese body corporate of 6-3, Fujimi 1-Chome, Kawasaki-ku, Kawasaki-shi, Kanagawa-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to friction pads for disc brakes.

There have been proposed and practically employed a great variety of friction pads for disc brakes and in one of the most commonly employed disc brake friction pads, a backing plate having opposite plain sides secured thereto by any conventional moulding or other method. When the friction pad of this type is secured to the caliper of the disc brake, a set screw is screwed from the outer side of the caliper through the caliper into a female tapped hole in the backing plate to thereby secure the caliper and friction pad together. Therefore, the backing plate is required to have the function of holding the friction pad flat and also the function of receiving the pad securing set screw when the friction pad is to be secured to the caliper.

For the latter purpose, the conventional friction pad has the following serious disadvantages. One of the disadvantages is that the pad securing set screw extends through the female tapped hole in the backing plate into the friction material so that the engaging length of the pad and set screw can be increased and as a result, the set screw tends to come into contact with the brake disc before the friction pad has worn away completely resulting in damage to the disc. It is therefore not possible to use the full thickness of the friction pad and the friction pad has to be discarded while it still has an otherwise serviceable portion remaining. The second disadvantage is that since the backing plate and friction pad are secured together on their plain surface, the contacting surfaces of the backing plate and friction material have to be provided with a plurality of convex-concave engaging means so that the two members are prevented from separating from each other in the direction of the plane of the interface between the backing plate and friction pad. The third disadvantage is that since the backing plate has the function of receiving the set screw therethrough, the backing plate is required to have a thickness greater than would be necessary solely for its function as a backing plate. This results therefore in a waste of material.

A feature of the present invention is to provide an improved friction pad for a disc brake which can effectively eliminate the disadvantages inherent in the conventional disc brake friction pad.

Another feature of the present invention is to provide a disc brake friction pad in which the extending amount of the set screw into the backing plate is small so that the friction pad can be used for its intended purpose until the friction material of the pad has worn away completely without contact between the set screw which secures the friction pad to the caliper of the brake disc and the brake disc to thereby provide an economical disc brake having a relatively long service life.

Another feature of the present invention is to attain a firm joint between the backing plate and friction material in a friction pad by minimizing the loss of material.

A still further feature of the present invention is to make it possible to employ a relatively thin material for the backing plate to thereby prevent waste of the material for the backing plate and to reduce the overall weight of the friction pad.

In accordance with the present invention, there is provided a friction pad for a disc brake comprising a pad of friction material one side of which is secured to one side of a backing plate in which a part-spherical convex portion formed on said one side of the friction material projects therefrom and is received in a complementary shaped partspherical concave portion formed in said one side of the backing plate, and a tapped hole is formed in the backing plate at the centre of the part-sperical concave portion for receiving a set screw for securing said friction pad to the caliper of a disc brake.

The invention is described further hereinafter, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross sectional view of one preferred form of friction pad constructed in accordance with the present invention; Fig. 2 is a right-hand elevation of the friction pad as shown in Fig. 1; Fig. 3 is a left-hand elevation of the friction pad as shown in Fig. 1; and Fig. 4 is a cross section through a disc brake incorporating a friction pad constructed in accordance with the invention.

Fig. 1 shows the friction pad in a cross sectional view. As is most clearly shown in Fig. 1, the friction pad 1 generally comprises a pad of friction material 2 and a backing plate 3 which is secured on one side to the adjacent side of the pad of friction material 2.

The backing plate 3 has a part-spherical convex portion 4 in the centre of its side remote from the friction material. The backing plate 3 also has a projection 3a at the lower end which extends downwardly and outwardly at an angle less than 90" with respect to the vertical plane of the major portion of the backing plate and to the vertical plane of the interface between pad 2 and plate 3. The projection 3a functions as a guide and positioning means when the pad 1 is secured to the caliper 10 of a disc brake (see Fig. 4) or a detent in the application of the disc brake in which the friction pad 1 is incorporated. The backing plate 3 is generally formed by pressing as a unitary construction and therefore, when the backing plate is pressed, a partspherical concave portion 4', is formed on the side of the backing plate 3 adjacent to the friction material 2 in opposing relationship to the convex portion 4. A convex partspherical portion 6 of pad 2 is complimentarily shaped to plate concave portio 4' and is accommodated therein.

The conventional friction material 2 is secured to the adjacent side of the backing plate 3 by any conventional manner, such as moulding, so that the friction material can be firmly secured to the said side of the backing plate 3 with uniform strength.

After the friction material 2 has been secured to the backing plate 3, a through bore 5 is formed in the centre of the convex portion 4 of the backing plate 3 from the convex side through to the concave side thereof and is extended into a blind bore in the convex portion 6 of the friction material 2 which has been formed and inserted into the concave portion 4' during the moulding of the friction pad 1. Thereafter, the bore 5 is tapped for receiving a set screw 16 (see Fig. 4). The blind bore in portion 6 is of such a length that the leading or inner end thereof terminates substantially in the interface 7 which coextends with the plane which is defined by the portions surrounding the concave portion 4' in the backing plate 3 and the convex portion 6 of pad 2.

While the friction pad 1 may have any shape other than the circular shape as shown in Figs. 2 and 3 (oval or rectangular shape, for example) depending upon the shape of the actual disc to which the friction pad is applied, and when the friction pad has an oval or rectangular shape, two or more convex portions 4 (and also concave portions 4') may be provided on the backing plate 3 and friction pad 2, respectively, as apparent to those skilled in the art.

Fig. 4 shows a disc brake in which a friction pad 1 in accordance with the invention is incorporated. As shown in Fig. 4, the caliper 10 has two opposite and spaced legs 10a, 10b disposed on the opposite sides of the disc D and supported by a support member 12 by means of a bolt 11 for slidable movement, the support member being in turn fixedly secured to a vehicle body not shown). One of the caliper legs 10a receives a cylinderpiston mechanism 13 which is adapted to effect braking operation in a conventional manner by applying a movable friction pad 14 received in the support member 12 against the disc D and the other leg 1 0b of the caliper has the friction pad 1 in accordance with the invention secured thereto. The friction pad 1 is disposed in a suitable position with respect to the other caliper leg 1 0b by means of the projection 3a and fixedly secured to the caliper leg 1 0b against rotation by screwing the set screw 16 which is abutted by a plate 15 interposed between the caliper leg and friction material 2 and which terminates short of the plane 7 into the tapped bore 5.

With the above construction and arrangement of the parts of the friction pad 1, even if the friction material 2 of the friction pad 1 has worn away, since the leading end of the set screw 16 is precluded from abutting against the disc D before the plane 7 of the backing plate 3 comes into contact with the disc D, there is no opportunity for interference between the screw and disc whereby the pad can be used until the friction material has worn away completely.

As the backing plate 3 is provided on one side with the convex portion 4 to form the concave portion 4' in the other side thereof, a portion of the friction material projects into the concave portion 4' to form a convex portion 6 of pad 2 and this co-operates with the concave portion 4' to increase the connection between the two parts. Furthermore, as compared with the conventional friction pad in which the backing plate is provided with a plurality of through holes into which the friction material 2 projects to increase the connection between the backing plate and friction material, the present invention is advantageous in that the friction pad can be processed easier and with less loss of material.

Furthermore, since the thickness of the backing plate 3 in the axial direction of the disc brake becomes greater at the convex area than the thickness of the remaining portion of the backing plate, the length of the tapped hole 5 can be increased accordingly.

WHAT WE CLAIM IS: 1. A friction pad for a dise brake comprising a pad of friction material one side of which is secured to one side of a backing plate, in which a part-spherical convex portion formed on said one side of the friction material projects therefrom and is received in a complementary shaped part-spherical concave portion formed in said one side of the backing plate, and a tapped hole is formed in the backing plate at the centre of the part-spherical concave portion for receiving a set screw for securing said friction pad to the caliper of a disc brake.

2. A friction pad as claimed in claim 1, in which a blind hole, constituting an extension of the tapped hole in the backing plate, is formed in the convex portion of the pad of friction material.

3. A friction pad as claimed in claim 2 or in which the blind hole in the convex portion of the pad of friction material terminates at the interface between the plain surfaces of the backing plate and pad which are defined by the areas surrounding said concave portion of the of the backing plate and the convex portion of the friction material pad, respectively.

4. A friction pad for a disc brake as claimed in claim 1, 2 or 3 in which the backing plate has a generally circular shape in elevation with a lug or protection, extending radially outward and at an angle to the interface between the plate and the pad of friction material, for guiding and positioning the friction pad and preventing rotation thereof when it is secured to the caliper of a disc brake.

5. A friction pad for a disc brake, substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 1,2 and 3 of the accompanying draw ings.

6. A disc brake incorporating a friction pad as claimed in claim 1 and constructed substantially as hereinbefore particularly described with reference to and as illustrated in Fig. 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. between the two parts. Furthermore, as compared with the conventional friction pad in which the backing plate is provided with a plurality of through holes into which the friction material 2 projects to increase the connection between the backing plate and friction material, the present invention is advantageous in that the friction pad can be processed easier and with less loss of material. Furthermore, since the thickness of the backing plate 3 in the axial direction of the disc brake becomes greater at the convex area than the thickness of the remaining portion of the backing plate, the length of the tapped hole 5 can be increased accordingly. WHAT WE CLAIM IS:

1. A friction pad for a dise brake comprising a pad of friction material one side of which is secured to one side of a backing plate, in which a part-spherical convex portion formed on said one side of the friction material projects therefrom and is received in a complementary shaped part-spherical concave portion formed in said one side of the backing plate, and a tapped hole is formed in the backing plate at the centre of the part-spherical concave portion for receiving a set screw for securing said friction pad to the caliper of a disc brake.

2. A friction pad as claimed in claim 1, in which a blind hole, constituting an extension of the tapped hole in the backing plate, is formed in the convex portion of the pad of friction material.

3. A friction pad as claimed in claim 2 or in which the blind hole in the convex portion of the pad of friction material terminates at the interface between the plain surfaces of the backing plate and pad which are defined by the areas surrounding said concave portion of the of the backing plate and the convex portion of the friction material pad, respectively.

4. A friction pad for a disc brake as claimed in claim 1, 2 or 3 in which the backing plate has a generally circular shape in elevation with a lug or protection, extending radially outward and at an angle to the interface between the plate and the pad of friction material, for guiding and positioning the friction pad and preventing rotation thereof when it is secured to the caliper of a disc brake.

5. A friction pad for a disc brake, substantially as hereinbefore particularly described with reference to and as illustrated in Figs. 1,2 and 3 of the accompanying draw ings.

6. A disc brake incorporating a friction pad as claimed in claim 1 and constructed substantially as hereinbefore particularly described with reference to and as illustrated in Fig. 4 of the accompanying drawings.