GB2156925A

GB2156925A - Wear indicator

Info

Publication number: GB2156925A
Application number: GB08507963A
Authority: GB
Inventors: Klaud-Uwe Brodersen
Original assignee: Textar GmbH
Current assignee: Textar GmbH
Priority date: 1984-03-31
Filing date: 1985-03-27
Publication date: 1985-10-16
Also published as: GB8507963D0; FR2562187A1; DE8410070U1; SE8501271L; FR2562187B1; IT8521128V0; NL8500612A; IT8519934A0; IT1185074B; SE8501271D0; GB2156925B

Abstract

A wear indicator for insertion in the lining (3) of a brake shoe (1) comprises an electric conductor surrounded by a synthetic casing (6). Securing of the synthetic casing in the lining is effected by gluing or cementing. The outer surface of end (7) of the synthetic casing is profiled to provide a surface pattern of at least one projection and/or recess providing discontinuities in the axial direction to assist retention. This pattern may consist of grooves or channels running in the shape of rings, screw-lines or spirals; or intersecting spirals. Pattern may be interrupted by areas (12) with reduced diameter. Pattern may arise as a result of localised indentation (see Fig. 7a). Production of pattern may be by means of heated die plates and can be carried out at same time as injection moulding. <IMAGE>

Description

SPECIFICATION Wear indicator This invention relates to a wear indicator, for example for disk brake coatings and the like.

One form of such wear indicators have an electric conductor surrounded by a synthetic coating or casing and having an end to be inserted in a bore hole of the friction lining of a brake shoe. The coating can be fastened in the bore hole of the friction lining by cementing or gluing. The use of such wear indicators is described in German Auslegeschrift No.2010816.

In the case of these wear indicators, whose insulated conductor ends are inserted and cemented into a bore hole of the friction lining, the user requires definite adhesive qualities for these bonds. The bonds must be capable of sustaining a given force without the danger of the glued or cemented bond disconnecting. Where the outer insulating coating is covered by a twisted plait or mesh, for example of fibre-glass, or the like, generally sufficient values of strength would be obtained for the bond. However, such twisted plaits are complex and therefore expensive to manufacture. In the case of wear indicators with synthetic coatings and which do not have a plaited outer layer, their smooth surfaces give bonding values which are not, or only rarely, satisfactory.

According to one aspect of the present invention, there is provided a wear indicator, suitable for insertion into the lining of a brake shoe, comprising a continuous synthetic casing in which there is disposed an electric conductor and which has an end region for such insertion, wherein an outer surface of said end region has been profiled to provide at least one projection and/or recess to form a surface pattern providing discontinuities in the axial direction to assist in retaining the end region in a brake lining.

According to another aspect of the present invention there is provided, in combination, a brake shoe having a lining and secured in the lining, a wear indicator according to said one aspect of the present invention.

According to another aspect of the present invention there is provided a method of manufacturing a wear indicator suitable for insertion in a lining of a brake shoe, the method comprising: forming a continuous synthetic casing around an electric conductor; and forming in the outer surface of a region of the casing, by a moulding process carried out under pressure, at least one projection and/or recess forming a surface pattern providing discontinuities in the axial direction.

The moulding process could also be carried out at elevated temperatures, that is at temperatures at which the casing is softened to facilitate the moulding process.

Embodiments of the invention provide simple, and therefore, relatively cheap synthetic casings with secure anchorage possibilities for the conductor end to assist in providing a firm fit of the wear indicator in the friction lining. Thus, according to one aspect, the synthetic casing of the conductor end region possesses, on its circumferential surface, a profiling.

By means of such a surface pattern on the synthetic casing at the conductor end region, an increase in the effective surface area for adhesion follows in a simple way, as well as a better distribution and anchorage of the cement or glue.

The pattern on the synthetic casing at the conductor end region can be in the form of grooves, channels, or similar, running in the shape of rings, screw-lines or intersecting screw-lines. After the cement or adhesive has hardened, its mass, which is greater in the grooves, channels, or similar, forms a type of back-gripping anchor, which effectively opposes disconnection of the conductor end region from the friction lining.

The pattern can be interrupted in the axial direction, to provide areas with a smooth circumferential surface and having an outer diameter which is less than the diameter of the pattern, which areas serve to provide an increased area for the acceptance of cement.

According to a further embodiment of the invention, the pattern of the synthetic casing can be fashioned in such a way that it is formed by channels running in an axial direction and interrupted in a transverse direction, whereby an effective axial anchorage follows. Further, the pattern can consist of localised indentations distributed on the circumference of the casing, e.g.

cup-shaped or rectangular indentations.

For better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which: Figures 1 and 2 show a front and side view respectively of a brake shoe with inserted wear indicator; and Figures 3 to 7b portray, diagrammatically and on an increased scale, various profile patterns for the end of the synthetic casing.

The brake shoe 1 shown in Figures 1 and 2 has a carrying plate 2 with a friction lining 3, into which the wear indicator 4 may be inserted and bonded by gluing or cementing, using a suitable adhesive. The wear indicator consists of an electric conductor 5 (Fig. 7b), an insulating outer coating or casing 6 of synthetic material with one end 7 for insertion and bonding into the friction lining 3, and another end 8 providing an electric connector 8.

In the case of the embodiment in Figure 3, the profiling or surface pattern on the synthetic casing 6 at the end 7 (providing an insertion end region) consists of grooves, channels 9, or similar, running in the shape of rings. The bottom surface of the grooves could be orientated so as to extend obliquely. In the case of the embodiment in Figure 4, a helical groove 10 on the synthetic casing of the conductor end extends in the shape of screw-lines or spirals.

In the example in Figure 5, two grooves in the shape of spirals are provided, which run in opposite directions and intersect, for example at 11.

In the embodiment of Figure 6 a ring-groove pattern such as 9 (Figure 3) is interrupted by areas 12 with reduced diameter. As is shown here, the interrupted ring-surface areas 12 can possess a smooth bottom surface.

In the embodiment shown in Figure 7a and 7b, the anchorage of the bond between the synthetic casing 7 of the conductor end region and the bore hole in the friction lining 3 arises as a result of localised indentations 13 distributed on the circumference of the casing. In the case illustrated, the localised indentations are in the form of rectangles running in an axial direction. From Figure 7b the radial distribution of the localised indentations on the casing circumference can be seen.

The production of the profiling or surface pattern on the casing end region of the wear detecting element (indicator) can be effected conveniently by means of heated die plates and can be carried out at the same time as the injecting of the connector formed piece. Practice has shown that the stress capacity of the cemented bond is substantially increased using a surface pattern since the effects of adhesion and mechanical anchorage augment one another. The aim is for highly stressable bonds between the conductor end region and the friction lining.

The casing can be formed by any suitable method, for example injection moulding or extrusion.

Claims

1. Wear indicator, suitable for insertion into the lining of a brake shoe, comprising a continuous synthetic casing in which there is disposed an electric conductor and which has an end region for such insertion, wherein an outer surface of said end region has been profiled to provide at least one projection and/or recess to form a surface pattern providing discontinuities in the axial direction to assist in retaining the end region in a brake lining.

2. Wear indicator according to claim 1, wherein the surface pattern comprises projections and/or grooves extending with a circumferential component.

3. Wear indicator according to claim 2 in which said projections and/or grooves extend perpendicularly to an axis of the casing.

4. Wear indicator according to claim 2, in which said projections and/or grooves extend obliquely to an axis of the casing.

5. Wear indicator according to claim 4, in which ones of said grooves intersect others of said grooves.

6. Wear indicator according to any preceding claim, wherein the surface pattern is interrupted in the axial direction by areas having a smooth circumferential surface and with an outer diameter less than that of the greatest diameter of the pattern.

7. Wear indicator according to claim 1, wherein the surface pattern comprises localised indentations distributed circumferentially.

8. Wear indicator according to claim 1, wherein the surface pattern comprises axially extending grooves, interrupted to provide said projections.

9. A wear indicator substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

10. In combination, a brake shoe having a lining, and secured in the lining, a wear indicator as claimed in any preceding claim.

11. A method of manufacturing a wear indicator suitable for insertion in a lining of a brake shoe, the methods comprising: forming a continuous synthetic casing around an electric conductor; and forming in the outer surface of a region of the casing, by a moulding process carried out under pressure, at least one projection and/or recess forming a surface pattern providing discontinuities in the axial direction.