US3816087A - Method of interconnecting glass parts by passing through electric current - Google Patents

Abstract

In sealing glass parts to each other by passing electric current through the preheated glass edges, the electric current is supplied to the glass edges via a stream of rare gas.

Description

United States Patent 1191 Van Duuren et al.

1 111 3,816,087 1 June 11, 1974 METHOD OF INTERCONNECTING GLASS PARTS BY PASSING THROUGH ELECTRIC CURRENT [75] lnventors: Kars Van Duuren; Adrianus Cornelis Johannes Verhoeven, both of Emmasingel, Eindhoven,

Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Oct. 12, 1971 [2]] App]. No.: 188,614

Related US. Application Data [63] Continuation of Ser. No. 8,325, Feb. 3, I970,

abandoned.

[30] Foreign Application Priority Data Netherlands 6902027 Feb. 8, 1969 [52] [1.8. CI. 65/40, 65/152, 219/121 P [51] Int. Cl C031) 29/00 [58] Field of Search 65/40, 152; 219/121 P [56] References Cited UNITED STATES PATENTS 12/1942 Guyer 65/40 10/1958 Gage 219/121 P x Primary Examiner-Robert L. Lindsay, Jr. Attorney, Agent, or FirmFrank R. Trifari [57] ABSTRACT In sealing glass parts to each other by passing electric current through the preheated glass edges, the electric current is supplied to the glass edges via a stream of rare gas.

3 Claims, 2 Drawing Figures 1 METHOD OF INTERCONNECTHNG GLASS PARTS BY PASSING THROUGH ELECTRIC C 1:

This application is a continuation of application Ser. No. 8,325, filed Feb. 3, 1970, now abandoned.

The invention relates to a method of interconnecting glass parts by fusing their edges together, in which the joined, preheated edges are heated and caused to fuse together by the passage of electric current with the aid of current supply points arranged along the outer circumference.

It is known, for example, from British Pat. specification No. 885,195 to use the flames of gas burners as current supply points. It has been found, however, that a few disadvantages may be involved. It may occur that the arc is unsteady so that a broader strip of glass is heated than required. Moreover, the arc may stand still for some time at a given point of the glass surface, although the glass surface is moved relatively to the current supply point. This gives rise to local overheating and decomposition of the glass.

In order to avoid these disadvantages British Pat. specification No. 985,422 proposes to surround the gas flame conveying the electric current by flow of nonionized gas, for example, cold air, However, this method is complicated.

It has been found that said disadvantages can be completely obviated by using in accordance with the invention as a current supply point a stream of a rare gas. It is preferred to use argon as a conductive gas for the electric current.

The invention will be described more fully with reference to an embodiment and to the drawing, in which FIG. 1 is a schematic cross sectional view and H6. 2 is a schematic longitudinal sectional view of an assembly for interconnecting glass parts of the bulb of an electron tube.

In the drawing reference numeral 1 designates the glass cone of an electron tube, to which a flat glass window 2 has to be sealed. The cone 1 is clamped in a holder and the glass plate 2 in a holder 111, which holders can be caused to rotate.

After the edges of the bulb parts 1 and 2 to be sealed together have been heated by means of gas burners 3 and tat about 600C, a rare gas, in this case argon is supplied to the copper tubes 5 by means of the hoses 6 of insulating material, while an alternating voltage is applied to the tubes 5 by means of the conductors 9. The tubes 5 are adjusted previously by means of the clamping connection 8 so that their mouthpieces are at a distance of about 0.5 to 2 cm from the glass edges of the bulb parts 1 and 2 to be sealed. The argon stream is sufficiently conductive in the cold state for conveying the electric current to the pre-heated glass edges. By this electric current the argon gas is rapidly heated so that an arc 12 is struck as in the case of the current supply via a gas flame in the known methods. In the embodiment shown, the bulb 1 has a wall thickness of 2 mm, the window 2 has a thickness of 4 mm. The alternating voltage is initially about 7,000 V.cm with an arc length of about 0.5 cm on either side of the window 2 and after heating of the argon stream and the glass it drops to about 1,500 V. These values correspond approximately with those involved in the use of a gas flame for current supply. The argon stream has in this case a sectional area of 1 mm, whilst about 2 litres of argon are consumed per minute at each supply point.

In contrast to the known methods, in which the are passed along a gas flame reciprocates unsteadily, the arc struck via an argon stream is almost completely already and does not tend to stick to given points of the weld so that burned-in dots in the weld are avoided.

The current strength through the arcsand the glass edges is initially 8 Amp. but it is afterwards raised to about 14 Amp. at which the glass becomes thin liquid. After the edges of the bulb parts 1 and 2 have fused together, the electric current as well as the supply of argon are interrupted in order to avoid that a cold stream of argon strikes the hot weld, after which the weld is after-heated in a conventional manner by means of the burners 3 and 4 and is subsequently cooled slowly. The holder 11, in which the window plate 2 is held, for example, by subatmospheric pressure, can be moved up and down in a conventional manner so that during the preheating process the glass edges of the parts 1 and 2 can be held at a given distance from each other and heating of the outer and inner sides is more uniform. For sealing the edges together, they are simply brought into contact with each other.

The invention is suitable both for sealing together thick glass wall parts, for example, the window and the cone of television display tubes and for interconnecting thin-walled parts, for example, the neck and the cone of such a display tube. The length of the arc and the current strength are, of course, adapted to the thickness of the glass as well as the diameter and the rate of flow of the argon if necessary.

Although only argon is mentioned herein, the other rare gases: neon, helium, krypton and xenon may also be employed. However, argon is found to provide the best results.

Instead of using two current supply points three or more supply points may be used in a conventional manner, in which case threeor multi-phase alternating current is used. If desired, the glass parts may be sealed together whilst they are standing still with respect to the current supply points,

The ignition voltage and the arc voltage may be reduced by producing an auxiliary discharge in the gas supply duct or closely in front of the gas outlet aperture so that the gas stream is pre-ionized.

What is claimed is:

1. A- method of interconnecting glass parts by sealing their edges to each other comprising the steps of:

preheating the edges of the glass parts;

bringing the preheated edges in contact with each other;

passing an electric current through at least two streams of ionized rare gas, said streams being arranged circumferential to the edges to be sealed and directed at said edges;

and rotating said edges relative to the streams to uniformly heat said edges by said current to provide an evenly fused glass seal between said edges.

2. A method as claimed in claim 1, wherein said rare gas is argon.

3. A method as claimed in claim 2 wherein the gas stream is pre-ionized by an auxiliary discharge.

Claims (3)

1. A method of interconnecting glass parts by sealing their edges to each other comprising the steps of: preheating the edges of the glass parts; bringing the preheated edges in contact with each other; passing an electric current through at least two streams of ionized rare gas, said streams being arranged circumferential to the edges to be sealed and directed at said edges; and rotating said edges relative to the streams to uniformly heat said edges by said current to provide an evenly fused glass seal between said edges.

2. A method as claimed in claim 1, wherein said rare gas is argon.

3. A method as claimed in claim 2 wherein the gas stream is pre-ionized by an auxiliary discharge.

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