GB2266252A - Damping cover - Google Patents

Abstract

A damping cover for use on the rear of a carrier plate of a friction lining comprises a metal plate provided with a cold- setting self-adhesive damping layer on one side thereof. The free surface of the damping layer is coated with an antiblocking agent which is solid at room temperature but melts at a temperature of 50 to 150 DEG C. The blocking agent is preferably a styrene-acrylate copolymer or a copolymer of vinyl chloride and vinyl acetate.

Description

Damping Cover The present invention relates to a damping cover comprising a metal sheet and a damping layer, which is preferably applied to the rear of a carrier plate of a friction lining and which damps noises arising during braking.

Damping covers are commercially available. They comprise, for example, a thin steel sheet; one side of the steel sheet is provided with an anticorrosive coating and the other side is provided with a cold-setting self-adhesive damping layer. The damping layer is covered with silicone paper as protection against sticking, which must be removed when the cover is applied to the carrier plate. To simplify this, devices have been developed which are designed to blow off the paper with compressed air. However, these devices do not always work reliably, so that faults often occur during the automated application of the damping cover to the carrier plate. Furthermore, the silicone paper needs to be disposed of.

Damping covers are also known consisting of gummed steel sheet with a Novolak adhesive, which are applied at around 150'C and do not stick at room temperature.

These damping covers can therefore be stacked in a magazine without covering paper. However, a disadvantage is the low dissipation factor of 0. 04 and less in the range of 20 to 80'C. In contrast, the dissipation factor of damping covers with a cold-setting self-adhesive damping layer based on silicon adhesives or polyacrylate copolymers reaches values of up to 0. 20 in this range.

An object of the invention is to provide a damping cover with a surface which is non-adhesive at room temperature, but whose acoustic properties are as good as damping covers having a cold-setting self-adhesive damping layer.

The invention provides a damping cover as claimed in claim 1.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a cross-sectional view through a damping cover in accordance with the invention, and Figure 2 is a graph of dissipation factor against temperature for two Examples in accordance with the invention.

In Figure 1, a damping cover comprises a metal sheet 1, one side of which is provided with a cold-setting self-adhesive damping layer 2. The free surface of the damping layer 2 is coated with an antiblocking agent 3 which is solid at room temperature but melts at temperatures of 50 to 150it.

As the antiblocking agent 3, it is preferable to use a copolymer of styrene and acrylate or an unplasticised copolymer of vinyl chloride and vinyl acetate. These damping coatings can then be stuck to the carrier plate of the friction coating at 90'C or at a higher temperature.

The metal sheet 1 preferably consists of an iron alloy, e.g. steel. It is also possible to use other metal alloys e.g. based on aluminium or copper. The sheet thickness is 0.2 to imam.

As the damping layer 2, it is preferable to use a 0.05 to 0. 5mm layer of a cold-setting adhesive based on a silicone or a polyacrylate copolymer, whose free surface is provided with a 0. 03 to 0. imam thick layer of the antiblocking agent 3.

The free surface of the metal sheet 1 may be provided with the usual corrosion protection e. g. a zinc layer or a varnish.

Surprisingly, it has been established that the antiblocking agents of the invention impair neither the dissipation factor nor the adhesion to a carrier plate.

The invention will now be explained in more detail with reference to the following two Examples, the structure of the damping coating being as shown in Fig. 1. The test results in Fig. 2 show the dissipation factor in the resonant range of the second order for lcm wide and 20cm long fixed strips of the damping covers of the Examples; the damping layer was selected so that the maximum loss factor of the second order was in the region of 20'C in one Example and in the region of 80'C in the other.

Example 1 The silicon paper covering the damping layer 2 is removed from a commercial damping cover consisting of a 0. 5mm thick steel sheet 1 of cold rolled strip St2, one side of which is coated with an anticorrosive varnish 4 and the other side of which is coated with a 0. 075mm thick cold-setting self-adhesive damping layer 2 based on a polyacrylate copolymer. A dispersion of a styrene-acrylate copolymer is applied to the exposed surface using a roller. After drying, this layer of antiblocking agent 3 has a thickness of approximately 0.05mm. It starts to become sticky at approximately 90'C.

Test strips are punched from the thus produced damping coating, for which the dissipation factor of the second order is determined as a function of the temperature.

The results are shown in Fig. 2.

Example 2 Another commercial damping cover similar to that in Example 1, but with a damping layer 2 based on a silicon adhesive, is treated as in Example 1 and coated with a dispersion of a copolymer of vinyl chloride and vinyl acetate. After drying, this layer of antiblocking agent 3 has a thickness of approximately 0.05mm. It starts to become sticky at 90'C.

As in Example 1, strips are punched from the thus produced damping cover and tested. The results are likewise shown in Fig. 2.

Comparative tests with corresponding damping cover without a coating of antiblocking agent show that the coating of antiblocking agent has no effect on the dissipation factor.

Furthermore, it has been established that the shear strength of the damping covers in accordance with the invention, which are stuck to a steel plate at at least 90'C, is higher than that of the corresponding damping covers with no coating of antiblocking agent, which are stuck on at room temperature.

Claims (5)

Claims:

1. A damping cover comprising a metal sheet provided with a cold-setting self-adhesive damping layer on one side thereof, wherein the free surface of the damping layer is coated with an antiblocking agent which is solid at room temperature but melts at a temperature of 50 to 150-C.

2. A damping cover according to Claim 1, wherein the antiblocking agent is a styrene-acrylate copolymer.

3. A damping cover according to Claim 1, wherein the antiblocking agent is a copolymer of vinyl chloride and vinyl acetate.

4. A damping cover according to any one of Claims 1 to 3, wherein the layer of antiblocking agent is 0.03 to O.lmm thick.

5. A damping cover substantially as herein described with reference to the accompanying drawing and any of the Examples.