GB2365619A

GB2365619A - Picture tube with production-optimised and weight-reduced funnel

Info

Publication number: GB2365619A
Application number: GB0112486A
Authority: GB
Inventors: Volker Knoche; Stefan Hergott; Dr Peter Elfner
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 2000-05-26
Filing date: 2001-05-22
Publication date: 2002-02-20
Also published as: DE10025780A1; DE10025780C2; HK1045908A1; GB0112486D0

Abstract

A screen funnel 2, suitable for use in a picture tube, comprises a soldering edge 6 and a parabolic region 2.1 wherein the wall thickness d of the funnel 2 decreases from the soldering edge 6 to the start of the parabolic region 2.1. It is provided that the wall thickness d along the plane of the large axis C-C of the screen 1 is greater than the wall thickness d along the plane of the diagonals A-A of the screen 1. This advantageously reduces the required overall wall thickness d and hence the weight of the funnel 2 as compared to the state of the art, while at the same time requiring only low moulding pressures during manufacture.

Description

2365619 Picture tube with production-optimised and weight-reduced funnel

The invention relate--- to a picture tube with a screen and a funnel. The front face of the screen facing the observer is substantially rectangular.

Such picture tubes operate according to the cathode ray principle. The above-mentioned glass parts - screen and funnel - enclose an evacuated space. The picture tube also comprises parts which serve to produce pictures, in particular an electron beam gun, an electron beam deflector, a shielding image and a mask.

When the glass television funnel is pressed the glass drop falls into the mould and is subsequently shaped by the downward travelling die. During this process the glass rises in the constantly decreasing gap between mould and die until the enclosed region is completely filled. At the same time, the glass cools, so the contour of the glass is retained after the die has been withdrawn from the mould. The viscosity of the glass is reduced during cooling and therefore becomes so hard that it retains the inner contour.

The moulding pressure which is required in order to fill the region between mould and die is dependent on a plurality of factors. The viscosity of the glass and therefore the temperature determine the resistance to a change in shape. The warmer the glass the more easily it can be shaped. The wall thickness is also influential, a thinner wall and therefore lower heat capacity allows the glass to cool quickly. When the 2 glass is in a cold state it has a high resistance and only a small amount of material can then flow.

Previously the wall thickness was largely proportional to the length of the respective axis of intersection of the glass television funnel, i.e. as the diagonal axis of intersection had the greatest dimension the glass television funnel had the greatest wall thickness along this axis. The wall thickness along the large axis came after and the wall thickness along the small axis was the smallest.

In order to produce funnels with reduced weight it was hitherto attempted to reduce the wall thickness based on the, as then known, wall thickness cha. racteris tics. This proved to be disadvantageous as the moulding pressure required rose disproportionately.

The object of the present invention is to provide a weight reduced glass television screen funnel which can be produced with a moulding pressure which is reduced with respect to known processes.

According to one aspect of the present invention there is provided a picture tube screen funnel suitable for connection to a screen of the picture tube, said screen funnel comprising a soldering edge and a parabolic region, wherein the wall thickness of the funnel decreases from the soldering edge to the start of the parabolic region. It is also provided that the wall thickness along a section C-C, which is defined by the direction of a large axis of the screen, is greater, as a function of the height above the soldering edge, by more than 50% of the height above the soldering edge than the wall 3 thickness along a section A-A which is defined by the direction of the diagonals of the screen.

Accordir.: to a second aspect of tile present invention there is provided a process for producing a screen funnel as above described, comprising the following steps: causing a hoL glass drop to fall into a mould; shaping the glass drop by a downward travelling die, wherein the glass rises in the constantly decreasing gap between the mould and the die until the region enclosed by the mould and die is completely filled, and allowing the glass to cool, so that the contour of the glass is retained after the die is withdrawn from the mould.

The invention may be understood more readily, and various other aspects of the invention, may become apparent from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 shows a picture tube in side view in a section, cut through the picture axis.

Fig. 2 shows the subject of Fig. 1 in a plan view of the front face of the screen with the respective sections.

Fig. 3a -- 3c show the sections AA, B-B, C-C of Fig. 2.

4 Fig. 4 shows the wall thickness characteristic along the sections of Fig. 3a - 3c according to the state of the art. Fig. 5 shows the wall thickness characteristic along the sections of Fig. 3a - 3c according to the invention.

The picture tube shown in Fig. 1 has a screen 1 and a funnel 2. In this case, the electronic and electrical details are not to be described further.

The two above-mentioned parts, screen 1 and funnel 2, are joined together along a plane 3 which extends perpendicularly to the axis 4 of the picture tube. This plane is also designated as soldering edge 6 for the funnel 2. The neck 2.1, which is also designated as the parabolic region of the picture tube, is also shown. The transition from the funnel 2 to the neck 2.1 is given the reference numeral 8.

The screen 1 has a front face 1.1 and flank faces, of which only the two flank faces 1.2, 1.4 opposing one another can be seen in this case.

Fig. 2 shows the front face of a picture tube according to the invention. As can be seen, the front face is designed as a geometric rectangle formed by the edges 1.10, 1.11, 1.12 and 1.13. In a preferred embodiment a radius of curvature can be provided at the four corners.

The sections through the funnel 2 are also shown in Fig. 2. Section A-A designates the section along the diagonals, section B-B the section along the so-called small axis and section C-C the section along the large axis of the front face of the screen 1.

Fig. 3a - 3c show the thickness characteris tics along,3ectioil A-A in Fig. 2, i.e. along the so-called diagonals, the section B-B in Fig. 2, i. e. the section along the so-called small axis, and section C-C in Fig. 2, i.e. the section along the so-called large axis of the funnel 2 from the soldering edge 6 to the neck region 2.1.

According to the invention. the thickness decreases continuously from the soldering edge 6 to the neck, for example from 10 mm to 4 mm.

This applies to the characteristic of the thickness along all sections AA, B-B and C-C.

A coordinate system is also shown in Fig. 3a - 3c. In this case, x designates the distance from the soldering edge 6 and z the so-called height above the soldering edge 6.

The wall thickness d along the sections A-A, B-B and C-C for a television funnel 2 produced by a conventional method is shown in Fig. 4 as a function of the height above the soldering edge. The wall thickness d for a television funnel 2, as produced according to the invention, is shown in Fig. 5 as a function of the height above the soldering edge 6.

As can be seen from Fig. 4, the wall thickness of television funnels produced according to the state of the art was largely proportional to the 'Length of the respective axis or the 6 respective section. This meant that the greatest wall thickness was in the diagonals, section A-A, followed by the wall thickness along the large axis, i.e. along the section CC and finally, the wall thickness along the small axis, i.e. along the section B-B. The thickness characteristic along section A-A is designated by the reference numeral 100 in Fig. 4, the characteristic along the large axis, i.e. the section C-C, by 110 and the characteristic along the small axis, i.e. the section B-B, by reference numeral 120.

In order to reduce overall wall thicknesses and to thereby achieve a reduction in weight according to the invention, it is provided that the greatest wall thickness occurs not along the diagonals but along the large axis, i.e. along the section C-C, the wall thickness along the section A-A, i.e. the diagonals, comes after and the smallest wall thicknesses occur along the so-called small axis, i.e. the section B-B. The thickness characteristic, starting from the soldering edge 6 up to the start of the parabolic region 8 as a function of the height above the soldering edge 6, i.e. along the z axis in Fig. 3a - 3c, is shown in Fig. 5. The thickness characteristic along the section A-A is again denoted by 100, the thickness characteristic along section C-C by 110 and the thickness characteristic along the section B-B by 120.

As can be seen from Fig. 5, the thickness d of the small axis (section BB) decreases continuously with distance from the soldering edge 6. The majority of the change in thickness takes place in the vicinity of the soldering edge 6. In the region above the change in thickness up to connection to the parabolic region 8, the wall thickness stays at this low value in order to achieve a low weight.

7 In the large axis (section C-C) the wall thickness d is also reduced starting at the soldering edge 6, and the reduction is distributed uniformly over the height z.

In comparison with the known characteristic of a television funnel with high overall weight, the wall thickness d at the large axis (section CC) is unchanged. As a result, there is a wide flow channel. Owing to this flow channel the glass mass remains hot and soft even with shaping according to the invention. The soft glass can easily flow onward and even the edge regions, in particular the soldering edge 6, remote from the glass drop can be filled completely. As a result of the minimum thickness along section B-B it is ensured that the viscosity is high enough and therefore the moulding pressure is low.

A uniform reduction in the wall thickness from the soldering edge 6 up to the parabolic region 8 is produced for the diagonals (section A-A).

According to the invention the wall thickness along the large axis (section C-C) is greater by more than 50% of the height above the soldering edge than the wall thickness along the diagonals (section A-A).

As a result of the invention a television screen funnel is created which, owing to the reduced wall thicknesses, has a reduced weight in comparison with television screen funnels according to the state of the art, wherein at the same time only a low moulding pressure is required for production of such a funnel.

8 Glass material arid glass nielt energy can be saved owing to the reduction in weight of the television funnel.

9

Claims

1 A picture tube screen funnel (3) suitable for connection to a screen (1) of the picture tube, said screen funnel comprising a soldering edge (6) and a parabolic region (2.1), wherein the wall thickness of the funnel (2) decreases from the soldering edge (6) to the start (8) of the parabolic region (2.1) and the wall thickness along a section C-C, which is defined by the direction of a large axis of the screen (1), is greater, as a function of the height above the soldering edge (6), by more than 50% of the height above the soldering edge than the wall thickness (d) along a section A-A which is defined by the direction of the diagonals of the screen (1).

2. A screen funnel according to claim 1, wherein the wall thickness along the section B-B of the small axis of the screen is defined, as a function of the height above the soldering edge (6), so as to be smaller by more than 50% of the height above the soldering edge than the wall thickness along the section A-A and/or the section C-C.

3. A screen funnel according to one of claims 1 to 2, wherein the wall thickness (d) along the section B-B decreases from the value at the soldering edge (6) to less than 50% of the value at the soldering edge (6) within 50% of the height of the start (8) of the parabolic region above the soldering edge (6).

4 A screen funnel according to one of claims 1 to 3 wherein the wall thickness (d) along the section A-A decreases from the value at the soldering edge to less than 70% of the---alue at the soldering edge within 50% of the height of the start (8) of the parabolic region above the soldering edge (6).

5. A process for producing a screen funnel (1) according to one of claims 1 to 4, comprising the following steps: causing a hot glass drop to fall into a mould; shaping the glass drop by a downward travelling die, wherein the glass rises in the constantly decreasing gap between the mould and the die until the region enclosed by the mould and die is completely filled, and allowing the glass to cool, so the contour of the glass is retained after the die is withdrawn from the mould.

6. A process according to claim 5 wherein the pressure does not exceed a predetermined low value.

7. A process according to claims 5 or 6, wherein the wall thickness (d) along the section C-C is maintained throughout the process so that a flow channel is formed allowing the soft glass to also completely fill edge regions, in particular the soldering edge (6), located remote from the glass drop.

11 A Screen funnel as substantially herein described and with reference to anyone of the accompanying figures 1 to 3 and 5.