PUMP OUT TUBE PREFORM

Abstract

A pump-out tube for evacuating a space between two sheets of glass, the pump out tube being receivable in a hole formed in at least one of the sheets of glass, the pump out tube formed as a separate element comprising a tubular member and a seal formed around the tube.

Claims

1. A method of producing a two-part pump-out tube for evacuating a space between two spaced apart sheets of glass, one of said sheets of glass having a hole for receiving the two-part pump-out tube, wherein the two-part pump-out tube is formed as a separate element prior to fitting the two-part pump-out tube to the hole, comprising the steps of: applying by forming or fitting, a preform seal first part to an end of a tubular member second part.

2. The method of claim 1, further including heating the preform seal first part to a temperature to at least partially melt the preform seal first part and secure it to the tubular member second part.

3. The method of claim 1, wherein the preform seal first part is formed around the tubular member second part by a step selected from the group of i) heat sealing a heat treated preform to the tubular member, ii) dry pressing preform material in a mould to the tubular member and iii) forming preform material and a binder into a paste, pressing the mixture into a mould and curing the preform mixture to the tubular member.

4. The method of claim 1, wherein the produced two-part pump-out tube has the preform seal first part extending outwardly from the tubular member second part to define a seat configured to support the tubular member second part in the hole.

5. The method of claim 1, wherein the tubular member second part has a diameter less than a thickness of the glass which is to be used.

6. The method of claim 1, wherein the preform seal first part is a preform of solder glass and the tubular member second part is a glass tube.

7. The method of claim 1, wherein the preform seal first part is formed with a stepped region comprising a first step having a first diameter and a second step having a second diameter, wherein the first step is located distally of the first step toward the lower opening of the tubular member second part, and the second diameter is greater than the first diameter.

8. The method of claim 7, wherein the first diameter is the same as a diameter of the hole and is at least partially receivable in the hole.

9. The method of claim 1, wherein the preform seal first part is conically shaped diverging towards a distal end of the tubular member second part.

10. The method of claim 1, wherein the preform seal first part is annular shaped with the inner diameter of the preform seal first part conforming to the outer diameter of the tubular member second part, the heated preform seal first part wets the surface of the tubular member second part to seal the preform seal first part to the tubular member second part when the heating is removed and/or the preform seal first part and tubular member second part are cooled.

11. The method of claim 1, wherein the preform seal first part is a shape selected from the group of a square, circle or any other geometric having a recess formed therein conforming to an outer diameter of the tubular member second part.

12. The method of claim 1, wherein the preform seal first part is annular shaped with the diameter of a recess in the preform seal first part conforming to an outer diameter of the tubular member second part.

13. The method of claim 1, wherein the heated preform seal first part wets the surface of the tubular member second part to seal the preform seal first part to the tubular member second part when the heating is removed and/or the preform seal first part and tubular member second part are cooled.

14. A method of installing a two-part pump-out tube in a hole in a glass sheet comprising the steps of: a. initially applying by forming or fitting, a preform seal first part to an end of a tubular member second part to form an integral two-part pump-out tube by one of the steps selected from the group consisting of: i. applying a preform of solder glass to the end of a tubular member, and then heating the preform to a temperature to at least partially melt the preform to secure the preform to the tubular member and cooling the preform and tubular member; ii. placing a glass tube in a mould and then applying into the mould an amount of solder glass dry powder, where the tube and powder are then pressed under pressure to form the desired shape and to secure the tube to the solder glass powder; and iii. placing a glass tube in a mould and then applying into the mould an amount of wet solder glass paste, where the tube and paste are then dried in air or in an oven, to solidify the solder glass to form the desired shape and to secure the tube to the solder glass powder; b. fitting the integral two-part pump-out tube to the hole; and c. heating the glass sheet and integral two-part pump-out tube to a temperature to at least soften the preform seal first part to seal the tubular member first part to the underlying glass sheet.

15. A method of forming a vacuum insulating glazing (VIG) unit comprising the steps of: a. initially applying by forming or fitting, a preform seal first part to an end of a tubular member second part to form an integral two-part pump-out tube by a step selected from the group of i. applying a preform of solder glass to the end of a tubular member, and then heating the preform to a temperature to at least partially melt the preform to secure the preform to the tubular member and cooling the preform and tubular member; ii. placing a glass tube in a mould and then applying into the mould an amount of solder glass dry powder, where the tube and powder are then pressed under pressure to form the desired shape and to secure the tube to the solder glass powder; and iii. placing a glass tube in a mould and then applying into the mould an amount of wet solder glass paste, where the tube and paste are then dried in air or in an oven, to solidify the solder glass to form the desired shape and to secure the tube to the solder glass powder; b. fitting the integral two-part pump-out tube to a hole of a first glass substrate, the first glass substrate being spaced from a second glass substrate by spacers and hermetically sealed to a second glass substrate; and c. heating the glass substrates and integral two-part pump-out tube to a temperature to at least soften the preform seal first part to seal the tubular member second part to the underlying glass substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1(a) is a photograph of the prior art approach to a pump out tube and solder glass preform, where the two components are used as individual components to be combined at the hole in the glass. FIGS. 1(b), (c) and (d) are illustrations of potential variations of the proposed invention where the component is a combined glass tube and solder glass preform;

[0032] FIGS. 2(a), (b) and (c) illustrate the formation of the pump out tube according to the invention, where the glass tube and solder glass preform were bonded by partially heating the preform to melt it and seal it to the glass tube; 2(b) shows the rear view of the combined tube and preform shown in FIG. 2(a); FIG. 2(c) is an illustration of the geometry of this form of the component as in FIG. 2(a).

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] While the following description of the invention will be described in some places with reference to a VIG unit, it would be understood by those skilled in the art that the invention can be used in other similar circumstances where a tube needs to be hermetically sealed to a glass pane, such as display panels.

[0034] Heat Sealing Method

[0035] According to the preferred embodiment, a pump-out tube for evacuating a space between planar sheets, preferably glass panes comprising a tubular member and a seal formed around the tubular member, the seal comprising a heat treated preform heat sealed, or dry pressed, or cured from paste, to the tubular member. The preform may be one of a number of geometric shapes but in the preferred embodiment is annular shaped with the inner diameter of the preform conforming to the outer diameter of the tubular member. The planar sheets are preferably paired glass panes having a hole with a diameter at least the same size as the thickness of the glass pane formed therein. The hole and annular seal is sized to receive the annular seal at least partially within the hole. The diameter of the tubular member is less than the thickness of the sheets or panes of glass and less than the diameter of the hole. The preform may be provided with a stepped region where the diameter of the stepped region corresponds to the diameter of the hole. To make the preform more universally usable, multiple stepped regions may be provided see FIG. 1 (c). Alternatively the preform may be conical shaped, see FIG. 1(d).

[0036] Solder glass or glass solder is a low melting point glass in which usually silica glass powder is mixed with materials such as organic binders, inorganic fillers and solvents are added to alter the thermal properties of the silica for binding, coating and sealing applications. There a number of commercially available solder glass materials. The solder glass may be vitreous or non-vitreous depending on whether the mixture forms a crystalline or non-crystalline structure when sintered to form a seal. The solder glass may be of a composition that is sintered with oxides, the dominant categories of which are the lead, bismuth, vanadium, tin, silver, and gold oxides. These oxides are sintered with various other oxides such as aluminium, zinc, calcium, potassium, iron, sodium, tellurium, titanium, oxides that allow for changes in thermal and mechanical properties to suit the glass onto which it is applied.

[0037] To form the pump out tube according to a first embodiment, the preform is separately fitted to the glass tubular member and the glass tubular member and solder glass preform are held together at one end of the tube. The solder glass is then heated until melting occurs. Once the solder glass wets to the tubular member surface and seals, the heating is removed or the combined tubular member and preform cooled. FIG. 2, shows a 2 mm glass pump-out tube fused at one end to a larger diameter (5 mm) preform of solder glass.

[0038] The solder glass preform can be produced at different thicknesses and diameters or formed in-situ around the tubular member. Upon heating, the solder glass partially melts to secure the preform to the tubular member and the natural flow of the solder glass produces a cone shape at the end of the tube. This simplifies locating the preform on the hole on the glass pane. Thus by separately producing the pump out tube prior to fitting to the hole in the sheet material, the invention utilises the existing components to effectively and simply solve the problem of sealing large diameter holes with a small diameter tube. There is no need for special geometries or new components. It is also possible that this product could be used in other technologies, such as flat panel displays.

[0039] The heating of the solder glass must be controlled within limits depending on the thermal properties of the solder glass. The preferred solder glass used in embodiments of the invention melts between 320-480° C. If the heating is too quick then undesirable bubbles may form in the structure leading to premature cracking of the preform and/or the solder glass will deform significantly; once the optimum temperature and time of exposure has been determined the preform can be produced with great accuracy and reproducibility. Considering other industrial technologies, this pump out tube according to the invention could be produced with great speed and at low cost.

[0040] Dry Pressing Method

[0041] The production process used in further embodiments of the invention may incorporate a process of dry pressing solder glass powder with a tubular member in a mould; or alternatively a wet paste of the solder glass with the tubular member could be cured in a mould, to produce a preform of solder glass attached to a glass tubular member. By use of the mould the solder glass geometry could be of any shape, such as annulus disk, annulus disk with an edge step, conical, square, etc.

[0042] Wet Pressing Method

[0043] Production Using Pressing Wet Paste of Glass Solder and Curing

[0044] A glass tube of diameter 2 mm is placed in a mould that has a predefined geometry. The solder paste is prepared by mixing solder glass with a binder material, e.g. ethyl cellulose, which was first dissolved in an appropriate solvent. This mixture is formed at a viscosity less than 200 Pa sec, and then injected into the mould to fill the volume surrounding the glass tube. The combined preform and tube are then cured, at room temperature or in an oven for a specific time. Once cured the glass tube will adhere to the solder glass paste and both are removed as a single complete component.

[0045] Production of Vacuum Induced Glass Panel.

[0046] In order to produce a vacuum insulating glass unit, a 4 mm hole is formed in the corner of a first glass substrate and the first and second glass substrate are positioned so that the planes of the glass are substantially parallel. An array of spacers/pillars are positioned between the substrates for spacing the substrates from one another and supporting them. Edge sealing material which is generally a solder glass is positioned around the peripheral edge of the substrates.

[0047] The edge seal may be made of or include any of the following materials: solder glass (i.e. glass frit; an oxide inclusive mixture having a melting point lower than that of normal glass), ceramic, Indalloy No. 53 available from Indium Corp. in paste or wire form having a composition of 67% Bi and 33% In (% by weight), Indalloy No. 1 from Indium Corp. in paste or wire form having a composition of 50% In and 50% Sn, Indalloy No. 290 available from Indium Corp. in paste or wire form having a composition of 97% In and 3% Ag, Indalloy No. 9 from Indium Corp. in paste or wire form having a composition of 70% Sn, 18% Pb and 12% In, Indalloy No. 281 available from Indium Corp. in paste or wire form having a composition of 58% Bi and 42% Sn, Indalloy No. 206 available from Indium Corp. in paste or wire form having a composition of 60% Pb and 40% In, Indalloy No. 227 available from Indium Corp. in paste or wire form having a composition of 77.2% Sn, 20% In and 2.8% Ag, Indalloy No. 2 available from Indium Corp. in paste or wire form having a composition of 80% In, 15% Pb and 5% Ag, Indalloy No. 3 available from Indium Corp. in paste or wire form having a composition of 90% In and 10% Ag, or any other suitable hermetically sealing material.

[0048] The substrates are then heated to a temperature to soften and form a hermetic seal around the periphery of the space between the substrates.

[0049] The pump-out tube according to the invention is fitted into the 4 mm diameter hole formed in a glass substrate. The glass substrate is heated to a temperature of 380° C.-420° C. for 15 to 30 minutes to enable the solder glass to soften and wet the interior of the hole in the glass and seal the pump-out tube into the glass pane. It is important not to heat the substrates for too long so as not to break down the structural integrity of the solder glass. If the pump out tube and glass panes are heated for too long or the temperature too high, the viscosity of the solder glass will deteriorate and the shape of the preform will soften to a level where it will not retain the tubular member in the hole. After placement on a flat sheet and upon heating, the solder glass would melt and seal to the tubular member and also seal to the flat sheet, which would be glass in most cases.

[0050] After the pump out tube has been positioned and heated, the tube of the component should not have moved from its original position, with respect to its height and vertical alignment, by an amount greater than 0.2 mm. Changes in the original position, with respect to height and vertical alignment, which are greater than 0.2 mm, will render the tube of-no-use in the desired application.

[0051] In order to evacuate the space between the glass substrates, the pump out tube is connected to a vacuum source and the gas in the space between the substrates reduced to a pressure equal to or below 0.01 hPa. The pump out tube is then sealed and the excess material above the glass substrate removed. The edge structure together with the pump-out tube eliminates the egress or outgress of gas to/from the space between the glass substrates.

[0052] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.