WO1999022555A1

WO1999022555A1 - The manufacture of gaskets

Info

Publication number: WO1999022555A1
Application number: PCT/GB1998/003162
Authority: WO
Inventors: Gary Burns
Original assignee: Linear Limited
Priority date: 1997-10-23
Filing date: 1998-10-22
Publication date: 1999-05-06
Also published as: GB2330629A; GB9722451D0

Abstract

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

Description

TH MANUFACTURE 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

manufactured, 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 v ew 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 semi-

circular 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

1. A method of manufacturing an EMI gasket (10) comprising

forming a length of gasket (10), attaching the length of

gasket (10) to a flexible backing strip (13) as the length of

gasket (10) is formed and then cutting the gasket (10) into

shorter lengths, the cutting step also cutting the backing

strip (13) without separating the backing strip (13) into

shorter lengths.

2, A method according to claim 1 and further comprising,

after the cutting step, winding the gasket (10) and the

backing strip (13) on to a reel.

3. A method according to claim 1 or claim 2 wherein the

backing strip (13) is a strip of plastics material.

4. A method according to any one of claims 1 to 3 wherein

the gasket (10) is attached to the backing strip (13) by

gluing.

5. A method according to any one of claims 1 to 4 wherein

the gasket (10) is of semi-circular cross-section.

6. A method according to any one of claims 1 to 5 wherein

the backing strip (13) has spaced side edges, the cutting step

cutting the backing strip (13) between said edges.

7. A method according to any one of claims 1 to 5 wherein

the backing strip (13) 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 (10)

substantially as hereinbefore described with reference to the

accompanying drawings.