GB2383619A

GB2383619A - Brake shoe or pad made using a room temperature curing adhesive

Info

Publication number: GB2383619A
Application number: GB0130644A
Authority: GB
Inventors: Richard David Maitland Cooke
Original assignee: AP TMF Ltd
Current assignee: AP TMF Ltd
Priority date: 2001-12-21
Filing date: 2001-12-21
Publication date: 2003-07-02
Also published as: GB0130644D0

Abstract

A brake drum shoe 10 or disc brake pad has a friction member 11 bonded to a backing support 12 by an adhesive 13 which cures at room temperature. The adhesive (which may be silicone based and sold by the trade name Rhodorsil in two-part form) may then have performance improved by heating. Backing plate 12 may be metal with spikes or projections (21, fig 1A) and/or an abutment or flange (20, fig 1A). Methods of ensuring the correct curvature of the friction surface using a former (18, fig 6) thus avoiding grinding, and adhesive bead or spot patterns (figs 4a-4f) are also disclosed.

Description

BRAKE SHOES AND PADS This invention relates to the manufacture of brake shoes for using in drum brakes and brake pads for use in disc brakes. Such shoes or pads conventionally comprise a friction material member secured to a metal backing support.

One of the problems associated with the manufacture of such shoes or pads is that the friction material is preferably bonded to the metal backing support but this bonding process expends large amounts of heat and is therefore expensive.

It is an object of the present invention to at least mitigate the above problem.

Thus according to the present invention there is provided a brake shoe or pad comprising a metal backing support member and a friction material member bonded to the backing support by an adhesive which cures at room temperature.

The invention also provides a method of manufacturing a brake shoe or pad comprising the steps of :-

- providing a metal backing support ; - providing a friction material member ; apply a room temperature curing adhesive to the metal backing support and/or the friction material member; - uniting the metal backing support and friction material member, and - allowing the adhesive to cure to adhere the friction material member to the metal support.

A suitable adhesive is the silicone based RTV (Room Temperature Vulcanising) adhesive sold under the trade name Rhodorsil by the French Company Rhône-Poulenc.

Such an adhesive in two part form will vulcanise within 25 to 30 minutes from the mixing of the adhesive parts at room temperatures. The performance of the adhesive may be improved by applying heat during curing. This may provide even quicker curing thus reducing the time before which the shoe or pad can be handled without risk to the bond between the friction material member and the metal backing support. For example, the temperature could be raised to temperatures of up to 200 C for a period from a few minutes up to say 3 hours.

Typically the adhesive layer may be of the order of 0.3 mm in thickness. The adhesive is also non-resilient.

The required volume of adhesive may be applied to the backing support member in, for example, extruded beads or by spot application, and the friction material member then applied to squash the adhesive to form a layer between the friction material member and backing support member of the desired thickness.

A wide range of adhesive bead extrusion or spot application patterns may be employed to give the desired adhesive thickness when squashed between the friction material member and the backing support member.

The backing support member may be provided with one or more abutments or flanges which engage the edge of the friction material member to help to resist the shear forces acting on the adhesive during use of the shoe or pad. Additionally or alternatively one or more projections (e. g. barbs or spikes) may be provided on the backing support member which partially penetrate into the friction material member when this member is applied to the support member.

When the invention is used in relation to arcuate brake shoes for drum brakes the curvature of the outer friction surface of the shoe can be arranged to correspond with the curvature of the brake drum within which the shoe will be used. Conveniently any differences in the curvature of the friction material member and the metal support member of the shoe can be accommodated by variations in the thickness of the adhesive layer. This technique avoids the

necessity for the grinding of the friction surface to fit its associated drum.

Such a curvature match can be achieved, for example, by pressing the metal support member, adhesive and friction material member of the shoe against a former having the same curvature of the drum within which the brake shoe is to operated. This causes the outer friction surface of the shoe, which is pressure against the curvature of the former, to conform to the desired curvature.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which :- Figure 1 is a diagrammatic view of a brake shoe in accordance with the invention; Figure 1A shows details of one end of the shoe of figure 1 on a larger scale; Figure 2 is a diagrammatic view of a brake pad in accordance with the present invention; Figure 3 is an enlarged view of part of the brake shoe of figure 1; Figures 4 (a) to 4 (f) show different adhesive bead and spot application patterns for use in the manufacture of the brake shoe in accordance with the present invention; Figure 5 show diagrammatically the use of a nozzle to apply the adhesive to a metal backing support when manufacturing a brake shoe in accordance with the present invention, and Figure 6 show diagrammatically the method of ensuring that the curvature of the outer friction surface of the brake shoe corresponds with the curvature of a brake drum in which the shoe is to be used.

Referring to figure 1, this shows that a brake shoe 10 in which a friction material member 11 is bonded onto a metal support member 12 by an adhesive layer 13. The metal support

member 12 comprises the conventional table 14 and web 15. In accordance with the invention the adhesive used to bond the friction material member to the metal backing support is a room temperature vulcanising adhesive such as that sold under the trade name Rhodorsil by the French Company Rhône-Poulenc.

This adhesive is of a two-part form which typically vulcanises within 25 to 30 minutes of mixing of the parts of the adhesive at room temperature. The performance of the adhesive may be improved by heating the brake shoe up to 2000 C for a period of up to 3 hours but this is not essential.

Typically the adhesive layer 13 will have a thickness of the order of 0.3 mm and is none resilient in order to avoid any loss of braking effect.

The adhesive is applied to the brake shoe 10 via a nozzle 16, as shown diagrammatically in figure 5. Either the metal support may be moved relative to the nozzle or the nozzle may be moved relative to the metal support in order to apply the adhesive to the metal support either as a bead in a pattern of, for example, the form shown in figures 4 (a) to 4 (d) or as a spot application using a pattern of the form shown in 4 (f). Figure 4 (e) shows a further application pattern in which the adhesive is spread out to a block formation before the placing in position of the friction material member 11.

Clearly the adhesive may be applied either to the metal support 12 or to the underside of the friction material member 11 using any of the patterns described above or any other suitable pattern which can easily be devised. The volume of adhesive required to give the necessary thickness layer of adhesive can be easily calculated and this volume is then applied by using the bead pattern or spot application pattern etc. as discussed above.

The outer friction surface 17 of the brake shoe is preferably shaped to have the same curvature as the curvature of the internal surface of the brake drum within which the brake shoe is to be used.

This curvature can be obtained by, for example using a former 18, see figure 6, which has a surface 19 of the same curvature as the intended inside of the associated brake drum. During curing of the brake shoe, pressure is applied to the metal support 12 as indicated by arrow X in figure 6 thus forcing the metal support, adhesive and friction material member against the former 18 so that the outer friction surface 17 of the brake shoe conforms to the desired curvature and any differences in the curvature of the friction material member and the metal support member are accommodated by variations in the thickness of the adhesive layer 13.

This method of achieving the required curvature of the external friction surface of the brake shoe avoids the necessity for the grinding of the surface which normally increases the cost of brake shoes.

Figure 1A shows a modified form of metal backing support 12 which is provided with an abutment or flange 20 against which one or both ends of the friction material member 11 abut. This flange helps to react the shear forces acting on the adhesive during use of the brake shoe and thereby lowering the stresses within the adhesive. Additionally, or alternatively, the metal backing support may be provided with small spikes or other projections 21 which partially penetrate the friction material member when the member is adhered to the metal backing support and also assist in resisting any shear forces acting between the friction material member and the metal backing support.

As will be appreciated the method of manufacturing the brake shoes shown in the above

referred to figures comprises the steps of : - providing the metal backing support 12 ; - providing the friction material member 11; applying the room temperature curing adhesive layer 13 to the metal backing support and/or the friction material member; - uniting the metal backing support and the friction material member, and - allowing the adhesive to cure to adhere the friction material member to the metal support.

As indicated above the performance of adhesive may be improved by heating the brake shoe up to a temperature of approximately 200 C to speed the curing process and hence reduce the time before the shoe or pad can be handled without risk to the bond between the friction material member and the metal backing support Although the invention has been described above in relation to the manufacture of a brake shoe for use in a drum brake it is clear that the same inventive concept could be used to manufacture a brake pad for a disc brake, as shown diagrammatically in figure 2, in which the disc brake pad 30 comprises a friction material member 31 bonded to a metal backing support 32 by an adhesive 33 which cures at room temperature. All the details regarding the application of adhesive to the metal backing support, the nature of the adhesive itself and the use of stress relieving flanges 20 etc. could also be applied to a disc brake pad.

Claims

CLAIMS 1) A brake shoe or pad comprising a metal backing support member and a friction member bonded to the backing support by an adhesive which cures at room temperature.
2) A shoe or pad according to claim I in which the adhesive is of the silicone based room temperature vulcanising type.
3) A shoe or pad according to claim 1 or 2 in which the adhesive if of the order of 0.3 mm in thickness.
4) A shoe or pad according to any one of claims 1 to 3 in which the adhesive is subjected to the application of additional heat to improve the performance of the adhesive.
5) A shoe or pad according to any one of claims 1 to 4 in which the backing support member is provided with one or more abutments or flanges which engage the edge of the friction material member to help to resist the shear forces acting on the adhesive during use of the shoe or pad.
6) A shoe or pad according to any one of claims 1 to 5 in which one or more projections are provided on the backing support member which partially penetrate into the friction material member when this member is applied to the support member.
7) A method of manufacturing a brake shoe or pad comprising the steps of :- providing a metal backing support; providing a friction material member; apply a room temperature curing adhesive to the metal backing support and/or the

<Desc/Clms Page number 8>

friction material member; uniting the metal backing support and friction material member, and allowing the adhesive to cure to adhere the friction material member to the metal support.
8) A method according to claim 7 in which the adhesive is of the silicone based room temperature vulcanising type.
9) A method according to claim 7 or 8 in which the adhesive is subjected to the application of additional heat to improve the performance of the adhesive.
10) A method according to claim 9 in which the adhesive is heated to a temperature of up to 200 C for a period of up to 3 hours.
11) A method according to any one of claims 7 to 10 in which the required volume of adhesive is applied to the backing support member in extruded beads or by spot application, and the friction material member then applied to squash the adhesive to form a layer between the friction material member and backing support member of the desired thickness.
12) A method according to any one of claims 7 to 11 in which one or more abutments or flanges are formed on the backing support member prior to the adherence thereto of the friction material member, the abutments or flanges being provided for engagement by the edge of the friction material member to help resist the shear forces acting on the adhesive during use of the shoe or pad.
13) A method according to any one of claims 7 to 12 in which during curing of the adhesive the metal support, adhesive and friction material member are pressed against a former having a curvature the same as that of the drum within which the brake shoe is to be operated, thus causing the outer surface of the friction material member which is pressed against the curvature of the former, to conform to the desired curvature and

<Desc/Clms Page number 9>

any differences in the curvature of the friction material member and the metal support member of the shoe to be accommodated by variations in the thickness of the adhesive layer.
14) A brake shoe or pad constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
15) A method of manufacturing a brake shoe or pad substantially as hereinbefore described with reference to and as shown in the accompanying drawings.