There is a requirement to reduce the weight of vehicle components in general for reasons of performance and economy. This requirement is particularly strong for relatively weighty components such as disc brake calipers. There is also a requirement to provide a disc brake caliper which is free from jamming of brake pads in the caliper due to the building up of dust and dirt between the pads and the caliper and which is also free from noise and vibration problems which can arise when the disc brake is applied and any sliding clearances between the pads and the caliper are taken up. This clearance take-up can result in the well known"clunk" noise.

It is an object of the present invention to provide a disc brake caliper which meets the above requirements.

Thus according to the present invention there is provided a disc brake caliper comprising : - a caliper body formed in aluminium; - a pair of disc brake pads supported in the body for sliding movement towards each other under the action of actuator means carried by the body to engage an associated brake disc when the caliper is mounted in its operation position in a vehicle ; - two pairs of support surfaces on the body, one pair of surfaces supporting each respective pad against circumferential movements relative to the body when the brake is applied and the associated disc is engaged; - biasing means supported by the body to bias each pad into contact with its respective pair of support surfaces; - the support surfaces being formed as inserts from a metal which is harder than the body and being curved in a radial sense so that when the brake is applied each pad tends to rotate slightly about an axis parallel to the axis of rotation of the associated disc; - the biasing means tending to reverse this slight pad rotation when the brake is released to clear dust and dirt from between each pad and its associated pair of support surfaces.

A disc brake caliper in accordance with the present invention thus meets the above requirements by reducing weight due to the use of an alloy body with harder metal support surface inserts, by including a self-cleaning action in the caliper due to the slight rotation of the pads on each brake application followed by the re-rotation of the pads when the brake is released, and by eliminating any clearance between the pads and the body since the pads are biased into contact with the support surfaces so there is no clearance to take up when the brake is applied and thus the well known"clunk"noise is also avoided.

The support surfaces may be formed as separate inserts which are mechanically secured to the body by screws, bolds, rivets or any other suitable means.

The support surfaces may alternatively be formed as inserts which are cast into the body. Each such cast insert may include formations which are enveloped by the body casting to retain the insert in position.

In yet a further alternative the support surfaces may be formed from spring steel and may be clipped in position in the body.

The biasing means may conveniently comprise spring steel clips which bias the pads radially inwardly against the support surfaces. These clips may conveniently act on pins which extend across a pad replacement aperture in the caliper body.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a disc brake caliper in accordance with the present invention; Figure 2 shows a view of half of the body of the brake of Figure 1 which separates on the plane X-X of Figure 1; Figure 3 shows a section on the line Y-Y of Figure 2; Figures 4,5 and 6 show details of a support insert used in the brake of Figure 1; Figures 7,8 and 9 show details of a spring clip used to radially inwardly bias the pads of the brake of Figure 1; Figure 10 shows a pad retention pin used in the brake of Figure 1; Figures 11 and 12 show details of a disc brake pad used in the brake of Figure 1, and Figures 13,14 and 15 show view of an alternative form of support insert designed to be cast into the caliper body.

Referring to the drawings, the disc brake caliper comprises a two-piece body 10 of aluminium and a pair of disc brake pads 11 and 12 supported within the body for sliding movement towards each other under the action of two pairs of interconnected piston and cylinder assemblies 13 and 14 respectively to engage a brake disc (not shown) between the pads.

Each pad (see Figure 2) is supported within its respective part 10a or 10b of the body 10 between a pair of curved support inserts 15 and 16 respectively. These support inserts (see Figures 4 to 6) are machined from steel (e. g. stainless steel) and secured in respective recesses 15a and 16a in the caliper body by screw studs 17 and 18 respectively which extend through ears 19 and 20 on the inserts. Each insert has its own curved support surface 20,21, which is curved in a radial sense relative to the caliper body. The distance D (see Figure 2) between the radially outer ends of the inserts 15 and 16 is equal to approximately twice the radius N of curved support surfaces 20 and 21.

The pads 11,12 (see Figures 11 and 12) each comprise a backing plate 11a, 12a, a friction material member 11b, 12b and an anti-squeal layer 11c, 12c. The backing plates each have curved contact surfaces 11 d, 11 e ; 12d, 12e which correspond with curved support surfaces 20 and 21 of inserts 15 and 16.

Each disc brake pad is radially inwardly biased by a biasing means in the form of a pair of spring clips 23 which react against a pair of pad retention pins 24 which extend across a pad replacement aperture 25 formed in the caliper body.

Each spring clip 23 (see Figures 7,8 and 9) has a pair of limbs 23a, 23b, which bear down on the top edge of the respective disc brake pads 11 and 12. A bridging portion 23c of each clip partially embraces the reduced diameter central portion 24a of each pin. The length"W'of each clip (see Figure 8) is approximately the same as the width'W1'of the pad replacement aperture 25 (see Figure 1) and the length 'W2'of the central portion 24a between end portions 24b of each pin (see Figure 10). Thus, the clips not only radially bias the pads inwardly but also hold the end portions 24b of the pins 24 in position in bores 27 in the body 10.

Referring to Figure 3, which shows a section through half 10a of the caliper body it will be appreciated that the actuating fluid enters the caliper via an inlet port 30 and flows directly to piston and cylinder assemblies 13 and via a drilling 31 and a connecting pipe 32 to the other pair of piston and cylinder assemblies 14 in the other half 10b (not shown in Figure 3) of the caliper body. Alternatively the piston and cylinder assemblies 13 and 14 could be interconnected by internal drilling with the caliper halves. Each pair of piston and cylinder assemblies has its own bleed nipple 33,34 respectively (or a single bleed nipple in the top of the body could be used).

The two halves 10a, 10b of the caliper body are held together by bolts extending through bores 35 in the body halves. In an alternative construction the caliper body is a one piece casting. The caliper as a whole is supported on a suspension structure of the vehicle by bolts extending through bores 36.

Referring to Figure 2, the caliper is mounted with the co-operating disc (not shown) rotating in the direction of the arrow'F'of Figure 2 when the vehicle is moving in the forward direction of travel. When the brake is applied, the contact between the curved contact surfaces 11d and 12d at the leading edge of pads 11 and 12 and the curved support surfaces 20 of the inserts 15 resist circumferential pad movement. This contact also tends to cause the pad 11, for example, to slightly rotate as indicated by the arrow'R'in Figure 2. When the brake is released, the force applied to the pad 11 by the forward spring clip 23 tends to reverse this rotation of the pad relative to its support surface. This rotation and counter-rotation clears any dirt or dust which may have gathered between each pad and its active support surface.

As will be appreciated, if the vehicle is travelling in the reverse direction, the other curved contact surfaces 11e and 12e co-operate with the corresponding curved surfaces 21 of inserts 16 to cause rotation of the pads 11 and 12 in the opposite direction to the arrow'R'when the brake is applied. This rotation is again reversed by the other spring clip 23 when the brake is released. Thus the cleaning action occurs when the brake is applied both in the forward and reverse drive directions.

As will be apparent from the above, the disc brake caliper in the present invention does provide a lighter caliper due to the use of an aluminium body with harder metal support inserts and a cleaning action is generated when the brake is applied both in the forward and reverse drive directions. Also, since both brake pads are biased into contact with their respective support surfaces in the caliper there is no clearance between the pads and the caliper body so that when the brake is applied there are no clearances to be taken up in the circumferential sense and hence the common 'clunking'noise is avoided.

Figures 13 to 15 show an alternative form of support insert 40 which is designed to be cast into the caliper and provided with a flange 41 which is enveloped within the caliper body 10a as indicated in Figure 15. Again, this insert has a curved support surface 42 which co-operates with the corresponding curved surface on the contacting pad to generate the previously described cleaning effect etc. A threaded blind bore 43 is provided into which a removable handling device can be screwed to hold the insert in the correct position during casting etc.