Backplate and a method of making a backplate

Abstract

A backplate supports friction material of a disc brake pad. The backplate includes a substantially planar portion of sheet metal and a stiffening flange extending around at least a portion of the periphery of the planar portion.

Description

The present invention relates to a backplate and a method of making a backplate. More particularly, the present invention relates to a backplate and a method of making a backplate for supporting friction material of a disc brake pad, in particular, but not exclusively, for use on heavy vehicles such as trucks.

Backplates of vehicle disc brake pads essentially perform two functions: they provide a solid support for slidably mounting the friction material within the brake carrier in such a way to transmit shear loads induced on the friction material during braking to the carrier, and they transmit and distribute the pressure applied by brake tappets during braking evenly to the surface of the friction material to ensure even wear of the friction material over its service life.

In order to perform the former of these two functions it is common for resilient means such as a leaf-type spring to hold the pad radially in the carrier whilst permitting movement towards and away from an associated brake disc thereby prevent rattling of the pad in use. To ensure that the friction material is securely attached to the backplate, some form of positive location is usually provided on the backplate, such as holes or recesses into which the material can extend or steel mesh welded on to the backplate around which the friction material may be formed.

Each brake is generally provided with one or more tappets that apply the braking force over a small area relative to the total area of the backplate. In order to perform the function of distributing the pressure from the brake tappet(s) it has hitherto been necessary to provide a relatively thick solid steel backplate that is punched or otherwise cut from steel sheet and is resistant to bending, or alternatively to provide an intermediate spreader plate in order to distribute the load over a thinner, although still substantial backplate. If a thick backplate is used, this constitutes a substantial proportion of the overall mass of the pad when unworn (e.g. approximately 30%). Once the friction material has been worn away in use, the backplate is usually thrown away.

This means that any reduction in the mass of the backplate that can be achieved will result in environmental benefits and a reduction in the cost of materials. A lower backplate mass additionally means that a lower strength, and therefore lower mass (and a potentially lower cost) pad spring may be sufficient to hold the backplate in place.

A further disadvantage of prior art backplates for heavy vehicles is that high capacity stamping machines are required in their manufacture, with a consequential high capital investment being required to set up a manufacturing plant.

The present invention seeks to overcome, or at least mitigate, the problems of the prior art.

One aspect of the present invention provides a backplate for supporting friction material of a disc brake pad, the backplate comprising a substantially planar portion of sheet metal and a stiffening flange extending around at least a portion of the periphery of the planar portion.

A second aspect of the present invention provides a backplate for supporting friction material of a disc brake pad, the backplate being provided with an integral spring arranged so as to resiliently resist movement in a direction in a plane as defined by the backplate, in use.

A third aspect of the present invention provides a backplate for supporting friction material of a brake pad for use in a heavy vehicle disc brake, the backplate comprising sheet metal, having a thickness in the range of 1 mm to 3 mm and wherein a stiffening feature is provided in the backplate to impart sufficient strength thereto.

A further aspect of the present invention provides a method of making a backplate for supporting friction material of a disc brake pad comprising the steps of:

• • i) cutting a blank from a metal sheet;
  • ii) drawing the blank in a press so as to form a backplate having a substantially planar portion and a stiffening flange extending around at least a portion of the periphery of the planar portion.

Embodiments of the present invention will be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of the rear face of a disc brake pad incorporating a backplate according to one embodiment of the present invention;

FIG. 2 is a cross-sectional view of line X-X of FIG. 1; and

FIG. 3 is a perspective view of the front of a disc brake pad according to second embodiment of the present invention.

Referring to FIGS. 1 and 2, a disc brake pad 10 comprises a steel backplate 12 and sacrificial friction material 14. The friction material may be of any suitable known type, and does not form part of the invention. The backplate 12 is formed of relatively thin sheet metal material, typically sheet steel. Backplates according to the present invention for use with heavy vehicles are formed from sheet steel having a thickness of between approximately 1 mm and 3 mm, preferably approximately 2 mm. This contrasts with prior art backplates, which generally have a thickness of 8 mm to 9 mm.

It can be seen that the backplate comprises a substantially planar body portion 18 and a peripheral flange portion 16 arranged at substantially 90° to the body and extending away from the friction material 14.

In this embodiment, the backplate 12 is further provided with a pair of raised bosses 20 and 22 positioned so as to be contacted by tappets (not shown) of an actuating portion of the disc brake and thereby urge the friction material 14 into contact with a brake disc (not shown) to effect braking. The bosses are substantially circular in shape and comprise two raised tappet contacting faces 30 that are substantially parallel to the plane of the body portion 18 and are interconnected therewith by skirt portions 32. In this embodiment, the skirt portions 32 are substantially perpendicular to the planes of body portion 18 and faces 30. In another embodiment, the skirt portions may be angled relative thereto, however.

In other classes of embodiment, the number of projections 20 and 22 may be adjusted according to the number of tappets provided on the brake actuating portion, or a single projection may be provided for two or more tappets. The shape and depth of the bosses may be adjusted as required. It may appreciated by those skilled in the art that the bosses 20 and 22 serve to stiffen the backplate and distribute the load applied by the brake tappet(s) more evenly over the friction material 14, thereby reducing the tendency of the backplate 12 and friction material to bend. The bosses 20 and 22 advantageously assist in the positive location of the friction material 14 to the backplate 12, thus reducing the risk of the friction material detaching under sheaf loads.

In a preferred embodiment of the invention, radially outwardly extending ribs 24 may be formed around the base circumference of the bosses 20 and 22 that serve to further enhance the load spreading characteristics thereof. It can be seen that in FIG. 1, four ribs 24 are provided for each boss, but this may be adjusted according to the particular requirements and characteristics of a backplate.

It can be further seen from FIG. 1 that the upper portion of flange 16 is provided with a pair of recesses 26 and 28 that are shaped so as to locate an appropriately dimensioned pad spring (not shown). The shape of recesses 26 and 28 may be altered so as to accommodate various shapes of pad spring.

The backplate 12 is preferably manufactured from a blank of relatively thin sheet steel that is formed between appropriately contoured dies in a press so as to form the peripheral flange 16 and/or bosses 20 and 22. The backplate is preferably cold formed although hot forming is also envisaged. Some localised thinning of the material may occur during pressing but this is largely restricted to the corners where flanges formed on the radial edges and circumferential edges intersect, and to the boss areas.

Turning now to FIG. 3, in which an alternative embodiment of backplate is shown and is which like numerals have, where possible been used to designate like parts, with the addition of the prefix “1”. It can be seen that in this embodiment, a pad spring 134 is formed integrally with the backplate again preferably using the press forming process described above. One advantage of providing an integral pad spring 134 is that the need for a separate spring component to be manufactured is negated. This may provide additional cost and weight savings.

It should be understood that numerous changes may be made within the scope of the present invention. For example, the backplate may be manufactured from materials other than steel, such as aluminium, provided the materials have appropriate strength and drawing characteristics. Alternative manufacturing methods may be employed such as drop forging, fabrication, or die casting. Stiffening features other than a flange may be provided in the backplate and the flange may not necessarily extend around the entire periphery of the backplate. For example, a flange may be provided on one or more of the radial or circumferential edges of the backplate only. The backplate may be used in relation to pads intended for fitment to other vehicles such as cars and the like.

An integral pad spring may be provided in backplates manufactured using alternative methods to the drawing methods described above. The volume defined by the peripheral flange may be at least partially filled with insulating material so as to inhibit the transfer of friction induced heat to the brake tappet(s), whose seals may otherwise be damaged by such high temperatures.

Claims

1. A backplate for supporting friction material of a disc brake pad, the backplate comprising: a substantially planar portion of sheet metal including a first face that receives the friction material and a second face: and a stiffening flange extending around an entire periphery of the substantially planar portion of sheet metal, wherein the stiffening flange extends from the second face and away from the first face.

2. The backplate according to claim 1 wherein the stiffening flange is disposed substantially perpendicular to the substantially planar portion of sheet metal.

3. The backplate according to claim 1 further including an inner circumferential edge and an outer circumferential edge, wherein the stiffening flange is provided on at least one of the inner circumferential edge and the outer circumferential edge of the backplate.

4. The backplate according to claim 1 wherein the stiffening flange is provided on a radial edge of the backplate.

5. (CANCELLED)

6. The backplate according to claim 1 wherein the stiffening flange is press formed.

7. The backplate according to any of claim 4 wherein the stiffening flange is provided with recess that receives a pad spring.

8. The backplate according to claim 1 wherein the backplate includes an integral pad spring.

9. A backplate for supporting friction material of a disc brake pad, the backplate comprising: a substantially planar portion of sheet metal; a stiffening flange extending around at least a portion of a periphery of the substantially planar portion of sheet metal; and a boss arranged to transmit a load induced by a brake actuator to the friction material.

10. The backplate according to claim 9 wherein the boss is press formed.

11. The backplate according to claim 9 wherein the boss includes a face and a stiffening rib extending from the face.

12. The backplate according to claim 11 wherein the stiffening rib extends radially from the face.

13. The backplate according to claim 1 wherein the substantially planar portion of sheet metal has a thickness between 1 and 3 mm.

14. A backplate for supporting friction material of a disc brake pad, the backplate comprising: a flange extending around at least a portion of a periphery of the backplate; and an integral spring arranged to resiliently resist movement in a direction substantially in a plane defined by the backplate.

15. The backplate according to claim 14 wherein the integral spring is press formed.

16. (CANCELLED)

17. The backplate according to claim 14 further comprising a press formed boss arranged to transmit a load induced by a brake actuator to the friction material.

18. (CANCELLED)

19. A disc brake pad comprising: friction material; and a backplate for supporting the friction material, the backplate comprising: a substantially planar portion of sheet metal including a first face that receives the friction material and a second face; and a stiffening flange extending around an entire periphery of the substantially planar portion of sheet metal, wherein the stiffening flange extends from the second face and away from the first face.

20-21. (CANCELLED)

22. A method of making a backplate for supporting friction material of a disc brake pad comprising the steps of: cutting a blank from a metal sheet; drawing the blank in a press to form a backplate having a substantially planar portion with a first face that receives the friction material, a second face and a stiffening flange extending around at least a portion of a periphery of the substantially planar portion, and the stiffening flange extends from the second face and away from the first face; and securing the friction material to the first face of the substantially planar portion.