GB2156711A

GB2156711A - Method of making a gapped contact/electrode assembly

Info

Publication number: GB2156711A
Application number: GB08509033A
Authority: GB
Inventors: Denis William Tuckwood
Original assignee: Pressac Ltd
Current assignee: Pressac Ltd
Priority date: 1984-04-05
Filing date: 1985-04-09
Publication date: 1985-10-16
Also published as: GB2156711B; GB8509033D0

Abstract

A method of making a gapped contact/electrode assembly e.g. a spark gap for a CRT socket, comprises applying an insulation element to a contact/electrode preform 1 so that the insulation element holds the preform, and severing the preform intermediate spaced positions to form air gaps. <IMAGE>

Description

SPECIFICATION Method of making a gapped contact/electrode assembly This invention relates to a method of making a gapped contact/electrode assembly.

Examples of prior contact assemblies can be found, for example, in the specifications for United Kingdom Patent No. 2,023,947 and United States Patent Nos. 3,865,452 and 4,1 1 9,878.

According to the present invention there is provided a method of making a gapped contact/electrode assembly comprising applying an insulation element to a contact/-electrode preform so that the insulation element holds the contact/electrode preform at a pair of spaced positions, and severing the contact/ electrode preform intermediate said spaced positions to form a gapped contact/-electrode assembly.

Advantageously support means is provided for supporting the contact/electrode preform before the insulating element is applied.

Preferably the support means and preform are moved to severing means where the support means is severed from the preform, and where the preform is severed intermediate said spaced positions. The preform may be severed from the support means at the same time as the preform is severed intermediate said spaced positions In one embodiment the preform may be severed before the insulation element is applied.

In another embodiment the insulation element is applied before the support means is severed from the preform.

The insulation element may conveniently be moulded onto the preform Advantageously the insulation element is applied to a plurality of said preforms so that the insulation element holds each preform at a pair of spaced positions, and each preform is severed intermediate said spaced positions.

Preferably the support means comprises a substantially continuous inner member secured to one end of each preform, and a substantially continuous outer member secured to another end of each preform. The preforms may extend radially outwardly between the inner and outer members. The inner and outer members are conveniently substantially ring-shaped.

The insulating element may be applied over the entire inner member and over a portion of each preform.

Preferably the support means is severed from the preforms by severing the outer member from each preform. Preferably also the inner member is not severed from any preform A plurality of said inner and outer members may be provided, each supporting a plurality of said preforms, in the form of a continuous strip. The strip may be fed to the severing means and where the support means is severed from the preforms, thereby severing adjacent outer members from one another.

Reference is now made to the accompanying drawings, in which: Figure 1 is a plan view showing one stage in a method according to the invention; Figure 2 is a plane view showing another stage in a method according to the invention; Figure 3 is a plan view of a further stage in a method according to the invention; and Figure 4 is a perspective view of a gapped contact/electrode assembly made in accordance with the invention.

In Fig. 1 a continuous flexible metallic strip generally designated 1 includes support means in the form of two frames 2. The frames 2 are interconnected by interconnecting members 4 and 5.

Each frame 2 comprises an outer ringshaped member 6, which is connected to the interconnecting members 4 and 5, and an inner ring-shaped member 7. The frames 2 support a plurality of electrical contact or electrode preforms 8 which extend radially outwards from the inner member 7 to the outer member 6. When.one of the frames 2 is arranged in a substantially flat plane, the longitudinal axes of the preforms 8 intersect at a point lying in said plane. Each preform 8 includes a widened portion 8a the purpose of which is explained below.

Each frame 2 is provided with an earth preform 9, which does not have a widened portion.

The strip 1 may be provided on a reel (not shown) from which it is unwound. After a predetermined length of the strip 1 has been unwound, an insulation element 10 is moulded to one or more of the frames 2 (see Fig. 2).

In Fig. 2 part of the strip 1 is shown in ghost so that the inner member 7 and the portion of the preforms 8 and the earth connection 9 within the insulation element 10 can be seen.

Each insulation element 10 comprises a ring-shaped block of plastics material, and is provided with a plurality of apertures 11 each of which is aligned with one of the preforms 8. Each aperture 11 is aligned with the portion of the preform 8 which lies between the inner member 7 and the widened portion 8a.

The insulating element 10 holds each preform 8 at two spaced positions one on each side of the aperture 11.

The assembly shown in Figs. 3 and 4 has been subjected to the final stage of the method, in order to produce a contact/eiectrode assembly or "earth ring" generally designated 20.

The arrangement shown in Fig. 2 is moved to severing means (not shown) where the preforms 8 are severed from the outer member 6, and hence from the interconnecting members 4 and 5. In this way adjacent frames 2 are disconnected from one another and from the strip 1. In addition each preform 8 is severed intermediate the two spaced positions i.e. in the part which is aligned with the apertures 11, in order to produce a spark gap 1 2. The insulation element 10 acts as a support member for the preforms 8 after they have been severed from the strip 1.

In Figs. 3 and 4 a portion 8b of each preform 8 and a portion 9b of the earth preform 9 extends radially outwardly from an outer rim 1 0a of the insulating element 10.

The portions 8b may be connected to contacts provided on, for example, a CRT (cathode ray tube) socket. Further details of such sockets can be found in our copending United Kingdom patent application ''Improvements in Electrical Sockets" of even date.

The widened portion 8a of each preform 8 is provided in order to make the profile irregular between the insulation element 10 and the preform 8, thereby increasing the captive strength of the bond between the two. Since the earth preform 9 is bonded to the insulation element 10 at all parts except for the portion 9b, there is no need to provide a widened portion for this preform.

A portion 8c of each preform 8, which extends between the inner member 7 and the spark gap 12, is electrically connected to the inner member and hence to the earth connection 9.

In use, the spark gap device 20 is arranged in, for example, a CRT socket so that each of the portions 8b of each preform 8 is in electrical communication with a corresponding contact in the CRT socket. The earth preform 9 is electrically connected to a contact of the CRT socket which is connected to earth.

If the voltage applied to one of the portions 8b of the preforms 8, from any one of the contacts of the CRT socket, exceeds a predetermined value then a spark will jump the spark gap 1 2. This enables the excess current to be drained to earth through the portion 8c of the preform 8, through the inner member 7, and through the earth preform 9 from where the current passes to earth through the earth contact of the CRT socket.

In this way, the spark gap device 20 provides a safety mechanism which prevents damage to the CRT and accompanying circuit components by excess voltage.

It will be appreciated that the predetermined value which the voltage must exceed in order to produce a spark may be varied by varying the size of the spark gap 1 2.

In a modification, the strip 1 may be fed to the severing means before the insulation element 10 is applied.

Claims

1. A method of making a gapped contact/electrode assembly comprising applying an insulation element to a contact/electrode preform so that the insulation element holds the contact/electrode preform at a pair of spaced positions, and severing the contact/electrode preform intermediate said spaced positions to form a gapped contact electrode assembly.

2. A method according to Claim 1 in which support means is provided for supporting each preform before the insulation element is applied.

3. A method according to Claim 2 in which the support means and preform is moved to severing means where the support means is severed from the preform and the preform is severed intermediate said spaced positions.

4. A method according to Claim 3 in which the support means is severed from the preform and the preform is severed intermediate said spaced positions simultaneously.

5. A method according to any preceding claim in which the preform is severed before the insulation element is applied.

6. A method according to Claims 3 or 4 in which the insulation element is applied before severing the support means from the preform.

7. A method according to any preceding claim in which the insulation element is moulded onto the preform.

8. A method according to any preceding claim further comprising applying the insulation element to a plurality of said preforms so that the insulation element holds each preform at a pair of spaced positions, and severing each preform intermediate said spaced positions.

9. A method according to Claim 8 when dependent on Claim 2 in which the support means comprises a substantially continuous inner member secured to one end of each preform, and a substantially continuous outer member secured to the other end of each preform.

10. A method according to Claim 9 in which each preform extends radially outwardly between the inner and outer members.

11. A method according to Claims 9 or 10 in which the insulation element is applied over the entire inner member and over a period of each preform.

1 2. A method according to Claim 9, 10 or 11 in which the outer member is severed from each preform.

1 3. A method according to any of Claims 9 to 1 2 in which a plurality of inner and outer members are provided, each supporting a plurality of said preforms, in the form of a continuous strip.

1 4. A method according to Claim 1 3 in which the strip is fed to severing means where the support means is severed from the strip, thereby severing adjacent members from one another.

1 5. A method of making a gapped contact/electrode assembly substantially as herein described with reference to and as shown in the accompanying drawings.