US3600778A

US3600778A - Method of manufacturing the focusing grids of color television tubes

Info

Publication number: US3600778A
Application number: US794597*A
Authority: US
Inventors: Andre Martin
Original assignee: Thomson CSF SA
Current assignee: Thales SA
Priority date: 1968-02-01
Filing date: 1969-01-28
Publication date: 1971-08-24
Anticipated expiration: 1988-08-24
Also published as: GB1223652A; NL6901423A; DE1904720A1; FR1566330A

Abstract

A method of manufacturing focusing grids for color television tubes, consisting in first producing a sheet of wires having the desired accuracy in terms of pitch and flatness, on a prismatic drum the corners of which are constituted by precision screws in the threads of which the wires are laid. The wires are then preliminary fixed to channel irons carried by the side members of a precision frame. A substantial economy is achieved by using the same frame for manufacturing a great number of grids. Only the channel iron need to be changed.

Description

Qniied States Patent 921 Inventor mm M-Ill 211113.213 11/1957 (tamer 313178 Plight-x 1130.757 4/l964 Schcllack 140/7115 TI Appl in 79597 3357,45) l2/l967 (ahen l40/7l S 22 Filed 1-. 28. I969 3.489366 1/1970 Bradum 1 313/283 X 4 Pnemcd Primary Examiner-John F Cam bell I Assugnee liaison-(SF p Pnom Feb I 1% Assistant Examiner-Richard Bernard Lazarus t s U w l 1 3] m Attorney Cushman Darby & (,ushman ll l LSJS m1 mzmon or MANUFACTURING ms rocusmc (nuns OF COLOUR TELEVISION 'ITBES 1 5 win; 3hhs' on m ABSTRACT: A method of manufacturing focusing grids for l Us l 29/2514, color television tubes, consisting in first producing a sheet of 29/2 i I40 1 140/71 5 wires having the desired accuracy in terms of pitch and flat- 1 I 1 Int, Cl. [101 9/00 mass on a prismatic drum the corners of which are constituted l 1 Field Search. 140/71 by precision screws in the threads of which the wires are laidv 7161905 H 2. I3 25 I4. 2 I5. 25 17 The wires are then preliminary fixed to channel irons carried g by the side members of a precision frame. h I Cited A substantial economy is achieved by using the same frame UNITED STATES PA TENTS for manufacturing a great number of grids Only the channel 2 H0186 IO/1957 pru zyn l |4OHL5X iron needtobechangedi l YD The present invention relates to a method of manufacturing the focusing grids of color television tubes.

Certain kinds of color television tubes comprise a two-part envelope, namely the front wall carrying the screen and the flared envelope portion or cone, in the neck of which the electron-guns are located. The focusing grid is clamped between these two parts at the time that the tube is sealed.

This grid, which is generally in the form of a flat sheet of parallel wires, must satisfy a variety of conditions relating in particular to the mutual parallelism of the wires of which it is made, the wire pitch, that is to say the spacing between two successive wires, and the overall flatness of the grid. The tolerance in these respects is no more than a few hundredths of mm. In order to keep within these tolerances, generally the grid is produced by stretching the wires over a frame which itself is manufactured to the said tolerances, the grid, thus tensioned in position on the frame, than being located between the two sections of the tube envelope at the time of the sealing of the latter.

This method means that the cost of the finished product is high, because of the necessity to manufacture a precisionmachined frame for each grid.

The present invention relates to a method of manufacturing the grid, which overcomes this drawback.

According to the invention there is provided a method of manufacturing focusing grids for color television tubes comprising the steps of preparing a sheet of parallel wires on the sides of a prism-shaped drum, whose edges are formed by screws of high precision whose pitch is that of the desired grid, said wires being positioned in the threads of said screws, and fixing the wires of a sheet on a frame on which the grid remains until the grid is clamped between the front wall and the flared portion of the tube envelope, the same frame being thus used for forming a plurality of grids.

For a better understanding of the invention and to show how the same may be carried into effect reference will be made to the drawing accompanying the ensuing description and in which:

FIG. 1 schematically illustrates, in section, the relative disposition of the elements of a color television tube concerned with the invention;

FIG. 2 shows in perspective a grid stretched on its frame;

FIG. 3 is a perspective view of a color television tube ready for sealing;

FIG. 4 is a schematic view, in section, of an arrangement for the manufacture of color television tube grids, in accordance with the invention; and

FIG. 5 is a sectional view of the frame-grid assembly, as it appears after the attachment of the grid to the frame, in the arrangement ofFIG. 4.

In all these figures, similar reference symbols designate similar elements.

FIG. 1 schematically illustrates, in section, the front wall F of the tube envelope carrying the screen E, its flared portion C, in the neck c of which there are located the electron-guns CE. A grid G is clamped between the two parts of the tube envelope. This grid is shown in perspective in FIG. 2. It is made up of parallel wires 3, stretched on a frame D.

In FIG. 3, the aforementioned elements can again be seen, in perspective, the tube being ready for sealing. Stops I0 keep the grid in the desired position in relation to the front wall F,

during the sealing operation.

FIG. 4 schematically illustrates, in section normally to its axis 1 a drum 1 in the shape of a regular prism, the edges of which are constituted by precision screws 2 and which is associated with a reel 3, the axis 3 of which is parallel to the screws 2. The axis 3' of the reel is fixed to the same frame as the drum 1. I

The drum I is made to rotate about its axis 1' in the direction of the arrow so that it picks up on the screws 2 a sheet of wires g running off the reel 3, the wires 3 seating in the threads of the screws 2. The drum sides are larger than the frame D.

The drum 1 is then halted and opposite each of its faces, i.e. between two successive screws 2, inside the drum 1, frames D are brought in position at a distance of some few tenths of mm. from the sheets of wires g.

FIG. 5 illustrates in section an embodiment of the frame D.

The

side members

11 and 11 of the frame D carry removable channel irons 20 and 20', enabling the same frame to serve many times.

The frame D being in position in relation to the wires 3, as shown in FIG. 5, the grid wires g are preliminarily fixed at 30 and 30' to the

channels

20, 20 respectively, by means of any suitable adhesive such as an organic resin or cement, this over the whole of their height.

The object of this preliminary fixing is to ensure correct positioning of the grid wires g during the final fixing operation which is preferably carried out by application of a metal to each of the two channels, using a metallizing torch such as a Shoop pistol, the metallizing being applied at 50 and 50'.

Subsequently, the grid wires g are cut at each extremity at 40 and 40', between the frame D and the screws 2. It goes without saying that prior to the cutting of the wires 3, it is necessary, in order to prevent the destruction of the wire sheet which they form, to fix them preliminarily at least to the frames at the adjacent faces.

This leaves a grid ready for sealing, the pitch of the grid wires being that of the screws 2 and its flatness being that of the faces of the prismatic drum used.

The winding of the grid wires 3 onto the drum 1 may possibly be carried out in two stages, the odd number wires being wound on during one of the stages and the even number ones during the other.

The drum 1 may have different numbers of sides, for example between 4 and 30.

Of course the invention is not limited to the embodiments described and shown which were given solely by way of example.

I claim:

1. A method of manufacturing focusing grids for color television tubes comprising the steps of preparing a sheet of parallel wires on the sides of a prism-shaped drum, whose edges are formed by screws of high precision whose pitch is that of the desired grid, said wires being positioned in the threads of said screws, preparing a frame, mounting, on two opposite side members of said frame, two removable channel irons, and fixing the wires of a sheet on said channel irons on which the grid remains until the grid is clamped between the front wall and the flared portion of the tube envelope, the same frame being thus used for forming a plurality of grids.

2. A method as claimed in claim 1, wherein said fixing on said frame is performed by means of a metallizing torch.

3. A method as claimed in claim 1, wherein prior to fixing said grid on said frame, it is preliminarily fixed by means of an adhesive.