GB2330629A

GB2330629A - The manufacture of gaskets

Info

Publication number: GB2330629A
Application number: GB9722451A
Authority: GB
Inventors: Gary Burns
Original assignee: Linear Ltd
Current assignee: Linear Ltd
Priority date: 1997-10-23
Filing date: 1997-10-23
Publication date: 1999-04-28
Also published as: GB9722451D0; WO1999022555A1

Abstract

An EMI gasket 10 is manufactured in a continuous length and as the length is produced the EMI gasket is glued to a flexible backing strip 13. The EMI gasket is simultaneously cut 14 with the cut extending partially through the backing strips so that the backing strip maintains its continuity. The backing strip is then wound on to a reel for transport and subsequent use.

Description

THE MANUFACTITRE OF GASKETS The invention relates to the manufacture of gaskets and particularly to the manufacture of electromagnetic interference gaskets (EMI gaskets) EMI gaskets are widely used to prevent leakage of radiation into and out of enclosures. They are used, for example, in mobile telephones to seal joints between casing parts and prevent the ingress/egress of radiation. A typical gasket comprises a resilient core surrounded by an outer portion that is conductive.

These EMI gaskets are formed in lengths. They are difficult to transport in such lengths and, in any event, they are often used in much shorter lengths than the lengths in which they are manufactured. In order to overcome this problem, the gasket is currently produced in lengths, a number of lengths are adhered side-by-side but parallel to one another on a sheet of plastics material and the lengths of EMI gasket are then sliced at, say, 30mm intervals. The sheet of shorter gasket lengths is then transported for use.

The adhesion of the EMI gasket lengths on to the sheet is labour intensive and time-consuming. In addition, the sheets are not necessarily convenient to handle and transport.

According to the invention, there is provided a method of manufacturing an EMI gasket comprising forming a length of gasket, attaching the length of gasket to a flexible backing strip as the length of gasket is formed and then cutting the gasket into shorter lengths, the cutting step also cutting the backing strip without separating the backing strip into shorter lengths.

By attaching the length of gasket to a backing strip as it is manufacturea, the speed and cost of manufacture is reduced and the gaskets on the backing strip are easier to handle.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which Figure 1 is a cross-sectional view of an EMI gasket, Figure 2 is a plan view from above of a part of a length of a gasket of the kind shown in Figure 1 attached to a backing strip in a first disposition and cut into shorter lengths, and Figure 3 is a plan view from above of a part of a length of a gasket of the kind shown in Figure 1 attached to a backing strip in a second disposition and cut into shorter lengths.

Referring first to Figure 1, the EMI gasket 10 is of semicircular cross-section (but can be any other shape). It includes an inner core 11 of resilient foamed material such as a foamed plastics material and an outer cover 12 which is of electrically conductive material.

The EMI gasket 10 is produced by extruding the core 11 and simultaneously applying the cover 12.

As the EMI gasket 10 is formed, it is continuously and simultaneously attached to a backing strip 13 (see Figure 2).

The backing strip 13 is wider than the EMI gasket and is formed from a flexible plastics material. The gasket 10 is attached to the backing strip 13 by gluing.

The gasket is then cut into required lengths which may, for example, be 30mm, by the use of knives (not shown). The cuts produced by the knife are shown in Figure 2 and have the reference numeral 14. As will be seen, each cut 14 is normal to the length of the backing strip 13 and the cuts 14 are equi-distantly spaced apart along the gasket.

It will also be seen that the cuts do not extend across the whole width of the backing strip 13 but have ends spaced inwardly of the side edges of the strip 13. Accordingly, the backing strip 13 is not separated into shorter lengths but maintains a continuity and strength along its length.

As a result, the backing strip 13 carrying the cut lengths of EMI gasket 10 can be wound on to a reel (not shown) for transport and subsequent use.

In the alternative arrangement shown in Figure 3, the EMI gasket 10 is, as it is formed, attached along the edge of the backing strip 13. The gasket 10 is then cut into shorter lengths with the backing strip 13 being partially cut across its width from one side edge towards the centre of the strip so that the backing strip 13 remains continuous along its length and can be wound onto a reel (not shown).

It will be appreciated that the EMI gasket 10 can be easily and inexpensively attached to the backing strip 13 as it is manufactured. The process is quick and not labour intensive.

The backing strip 13 can be readily reeled up.

It will be appreciated that there are many modifications that could be made to the proposal described above with reference to the drawings. The EMI gasket 10 may have any convenient profile; it need not have the profile described above with reference to the drawings. The cuts 14 could be at any convenient spacing. They need not be regularly spaced; they could be irregularly spaced as required.

Where two or more EMI gaskets 10 are produced simultaneously, they may be simultaneously attached to a single strip 13, cut as described above and then wound on to a reel. The backing strip 13 need not be of a plastics material; it could be of any convenient material. The EMI gasket 10 need not be attached to the backing strip 13 by gluing; it could be attached in any convenient way such as welding.

Claims

CLAIMS 1. A method of manufacturing an EMI gasket comprising forming a length of gasket, attaching the length of gasket to a flexible backing strip as the length of gasket is formed and then cutting the gasket into shorter lengths, the cutting step also cutting the backing strip without separating the backing strip into shorter lengths.
2. A method according to claim 1 and further comprising, after the cutting step, winding the gasket and the backing strip on to a reel.
3. A method according to claim 1 or claim 2 wherein the backing strip is a strip of plastics material.
4. A method according to any one of claims 1 to 3 wherein the gasket is attached to the backing strip by gluing.
5. A method according to any one of claims 1 to 4 wherein the gasket is of semi-circular cross-section.
6. A method according to any one of claims 1 to 5 wherein the backing strip has spaced side edges, the cutting step cutting the backing strip between said edges.
7. A method according to any one of claims 1 to 5 wherein the backing strip has spaced side edges, the cutting step cutting the backing strip from one side edge towards the centre of the strip.
8. A method of manufacturing an EMI gasket substantially as hereinbefore described with reference to the accompanying drawings.