GB2139537A - Process and apparatus for manufacturing a soldered glazing unit - Google Patents

Abstract

Soldered glazing units 1 comprise sheets of glass 2 having metallised margins which are held in spaced relation by one or more spacer members 4 soldered to the metallised margins. Such a solder joint may be formed by locating an assembled unit on a conveyor support 5, heating the spacer 4 using heating means 7 and progressively feeding heated solder into the joint region using solder feed means 8 where the spacer is still heated. The spacer is heated using inductive heating means 7 and may be reheated inductively at 9 after the application of solder. <IMAGE>

Description

SPECIFICATION Process and Apparatus for Manufacturing a Soldered Glazing Unit This invention relates to a process and apparatus for manufacturing a glazing unit comprising sheets of glass having metallised margins which are held in spaced relation by one or more spacer members soldered to such metallised sheet margins wherein the or at least one such solder joint is at least in part formed by progressively feeding heated solder into the joint region while the spacer member at that joint region is in heated condition and while the work and the source of solder are relatively displaced substantially parallel with the course of such joint part.

Such a process and apparatus are disclosed in for example Glaverbel-Mecaniver's British Patent specification No. 1 411 854. In one embodiment of the process described in that specification, the spacer member and metallised sheet margin to be joined are pre-heated by flames of burning gas so that the joint region is at elevated temperature when the solder is applied. Such pre-heating is difficult to control and this presents certain disadvantages.Amongst possible disadvantages of excessive heating are: the metallised margin and/or the spacer are oxidised thus giving poor wettability by solder metal; the spacer member is thermally expanded to such an extent that when it contracts on cooling undesirable stresses are frozen in - this can lead to early failure of even a wellformed joint so that the useful life of the glazing unit formed is reduced; damage to the glass due to thermal shock.

Even when the pre-heating is well controlled, there is a further disadvantage present in that when using ordinary gas supplies, water vapour arises as a combustion product and this can enter the panel. The presence of water vapour within a glazing panel is disadvantageous since it will condense on the glazing sheets and so mar the appearance of the unit. The effects of such water vapour can be eliminated by incorporating a desiccant into the panel, but even then it is necessary to limit the original humidity of the atmosphere within the glazing unit.

It is an object of the present invention to provide a process and apparatus for manufacturing a glazing unit in which these disadvantages are reduced.

According to the present invention, there is provided a process for manufacturing a glazing unit comprising sheets of glass having metallised margins which are held in spaced relation by one or more spacer members soldered to such metallised sheet margins wherein the or at least one such solder joint is at least in part formed by progressively feeding heated solder into the joint region while the spacer member at that joint region is in heated condition and while the work and the source of solder are relatively displaced substantially parallel with the course of each joint part, characterised in that such spacer member is inductively heated.

By making use of such process, direct heating is confined to the metallic parts to be joined, that is, the spacer and metallising strips at the margins of the sheet of glass and direct heating of the glass is avoided. Also heating is easier to control and it is possible to avoid subjecting the joint region to such high temperatures and would be encountered by passing a flame over it.

Furthermore the risk of adding to the humidity of the atmosphere within the panel by water vapour arising from gas combustion is eliminated. The invention is especially useful in the manufacture of glazing units incorporating leaden spacer strips, in view of the proximity of the melting point of lead and the liquidus temperatures of many solder alloys.

Accordingly the disadvantages associated with the use of pre-heating by flame can be substantially avoided and an improved glazing unit can result.

The spacer member(s) leading around the entire periphery of the glazing unit may be preheated, but it is more efficient for such inductive heating to be localised to a region which is about to be fed with solder. However such region should not be so small that the work is subjected to high thermal shock.

Inductive heating means and solder supply means may be moved progressively around the assembly to be bonded into the glazing unit, but the apparatus required is simplified if, as is preferred, the work is conveyed past fixed inductive heating means and adjacent solder supply means.

Advantageously, the spacer member or members is or are formed into a spacer frame intervening between each successive pair of sheets. This facilitates handling between assembly and jointing.

The solder may be fed to the joint region as a heated solid, for example as a wire, but it is preferably fed to the joint in molten condition so that it is not necessary to supply latent heat of melting to the solder.

Preferably, said molten solder is discharged from a nozzle in a continuous stream. This promotes the formation of a continuous joint.

Advantageously, the spacer member and applied solder are reheated inductively after the feeding of said solder. Such reheating can be caused to ensure that the applied solder is fully molten in situ in the joint region so that on subsequent cooling a well formed solder fillet joint will result.

During the induction heating it is preferred that the margin of work and the induction heating means are spaced apart by less than 5 mm. This promotes efficiency.

The invention extends to apparatus suitable for performing the process of the invention and accordingly provides apparatus for manufacturing a glazing unit comprising sheets of glass having metallised margins which are held in spaced relation by one or more spacer members soldered to such metallised sheet margins comprising a support for the work, means for heating a said spacer member in the region of the joint to be formed, means for progressively feeding heated solder into the joint region while the spacer member there is in heated condition, and means for effecting relative displacement of the work and the source of such solder in a direction substantially parallel to that of the course of such joint region, characterised in that such spacer member heating means is inductive heating means.

The use of such an apparatus avoids the disadvantages referred to above involved in the use of gas heating means.

Preferably said support is constituted as a conveyor for conveying the work past fixed inductive heating means and adjacent solder supply means.

Advantageously said solder supply means comprises a nozzle for feeding molten solder to the joint region, and preferably such solder supply means further comprises a reservoir for feeding molten solder to the nozzle.

Said inductive heating means preferably comprises one or more windings on the limbs of at least one generally U- or horseshoe-shaped core. This enables the field produced to be concentrated at the ends of the core(s) and the spacer member can readily be moved in that region of concentrated field so promoting efficiency. The core may be for example of ferrite.

Preferably, second inductive means is provided for heating the spacer member after the feeding of solder thereto.

The invention will now be described in greater detail with reference to the accompanying diagrammatic drawings in which: Figure 1 is a schematic side elevation of an apparatus according to the invention; Figure 2 is a cross-section on the line Il-Il of Figure 1; Figure 3 is a plan view of the detail shown in Figure 2; Figure 4 is a cross-section on the line lV-lV of Figure 1; and Figures 5 and 6 illustrate an alternative, preferred form of heating unit.

In Figure 1, a glazing unit assembly 1 comprises two sheets of glass 2 having metallised margins (indicated at 3 in Figures 2, 4 and 6) which are held in spaced relation by a spacer member 4 in the form of a frame which is in course of being soldered to one of those margins (3). The unit is carried on a conveyor support 5 in the direction of arrow 6 successively past an inductive heating means 7, diagrammatically represented as a coil, and a solder supply means 8. An optional second inductive heating mean 9 is provided downstream of the solder supply means 8.

Part of an embodiment of the inductive heating means 7 is shown in Figures 2 and 3 and comprises a continuous conductor 10 wound at 1 1 around two ferrite bars 12, 13 which are linked at their ends remote from the glazing unit assembly 1 by two further ferrite bars 14, 1 5 to form a generally horseshoe-shaped core for the windings 11. The field produced is thereby concentrated on the spacer member 4.

Figure 2 illustrates the spacer member 4 being soldered to a first glass sheet. The work 1 is suitably conveyed past the heating means within 5 mm of the ends of the ferrite bars 12, 13 of the heating means 7.

A plurality of the horseshoe-shaped heating units shown in Figure 3, as many as necessary to achieve the desired heating effect, is arranged alongside the conveyor 5 to constitute the heating means 7 shown in Figure 1. The conductor 10 may be continuous along all these heating units. The conductor 10 is preferably constituted as a pipe so that cooling fluid can be circulated therein. The second inductive heating means 9, when present, may be of identical construction.

Figure 4 illustrates one way of applying solder to the region of the joint between the spacer strip 4 and the lower glass sheet 2. A reservoir 15 contains molten solder 16 and is formed with a nozzle 17 through which the solder 16 can flow as a continuous jet 18. Solder flows through the nozzle 17 and is controllable by a needle valve 19 adjustable by a mechanism 20. Heating means 21, preferably thermostatically controlled, is located in the reservoir 15 for maintaining the solder 16 at a suitable temperature. A tray 22 is provided for catching excess solder 23.

Figures 5 and 6 show a preferred alternative embodiment of inductive heating means 7, this view of the heating means in Figure 6 being along the line VI-VI of Figure 5. In Figure 5, a plurality of U-shaped ferrite elements 24, in fact five are shown, are lined up side-by-side and a continuous conductor 25 is interwoven between their limbs.

Like the conductor 10 shown in Figures 2 and 3, the conductor 25 is preferably constituted as a pipe so that cooling fluid can be circulated therein.

The heating means is arranged adjacent and preferably within 5 mm of the path of a glazing unit assembly as shown in Figure 6. As will be noted from Figure 6, the spacer member 4 has previously been joined to the upper glazing sheet 2 by a solder fillet 26, and the heating means 7 is arranged to heat particularly the lower edge of the spacer member 4 prior to the application thereto of solder (e.g. using the apparatus illustrated in Figure 4) to form a similar solder fillet joining the spacer member 4 to the lower glass sheet.

As an alternative to feeding solder from a reservoir of molten solder, solder in wire form may be passed to a nozzle where it is melted in situ, for example inductively, so that it can issue as a continuous molten stream.

In a specific practical example, glazing units have been manufactured using leaden spacer strips having the composition: Antimony 3%, Bismuth 0.1%, Tin 0.1% and lead 96.8% (by weight). This leaden alloy has a melting point of about 3270C. The leaden strip was tinned with a solder alloy having the composition Tin 23%, Bismuth 37%, lead 40% (by weight) which has a liquidus temperature of 1 300C. The thickness of the layer of solder alloy formed on the spacer strip was about 25 ym on the side to face the outsides of the unit and about 10 ym on the other side.

The metallised margins of the glass sheets were also tinned to a thickness of about 40 ym. The work was assembled and conveyed past heating means such as that illustrated in Figures 5 and 6 at a speed of 15 m/minute while the heating means was using about 2 k W of power. The total length of the heating means was 50 cm. The spacer strip was heated to above 1 000C in this way. The heating was controlled so that the temperature of the space strip was kept below the liquidus temperature (13000) of the solder alloy used to tin it. A stream of a different solder alloy (Tin 30%, Bismuth 10%, lead 60% by weight) having solidus and liquidus temperatures of 13700 and 21400 repsectively was then caused to flow into the joint region to form the solder joint.

Claims (16)

1. A process for manufacturing a glazing unit comprising sheets of glass having metallised margins which are held in spaced relation by one or more spacer members soldered to such metallised sheet margins wherein the or at least one such solder joint is at least in part formed progressively feeding heated solder into the joint region while the spacer member at that joint region is in heated condition and while the work and the source of solder are relatively displaced substantially parallel with the course of such joint part, characterised in that such spacer member (4) is inductively heated.

2. A process according to Claim 1, wherein the work (1) is conveyed past fixed inductive heating means (7) and adjacent solder supply means (8).

3. A process according to Claim 1 or 2, wherein the spacer member or members (4) is or are formed into a spacer frame intervening between each successive pair of sheets (2).

4. A process according to any preceding claim, wherein said solder (16) is fed to the joint region in molten condition.

5. A process according to Claim 4, wherein said solder is discharged from a nozzle (17) in a continuous stream (18).

6. A process according to any preceding claim, wherein the spacer member(s) (4) and applied solder are reheated inductively (9) after the feeding of said solder (8).

7. A process according to any preceding claim, wherein during said inductive heating the margin of the work (1) and the inductive heating means (7) are spaced apart by less than 5 mm.

8. Apparatus for manufacturing a glazing unit comprising sheets of glass having metallised margins which are held in spaced relation by one or more spacer members soldered to such metallised sheet margins comprising a support for the work, means for heating a said spacer member in the region of the joint to be formed, means for progressively feeding heated solder into the joint region while the spacer member there is in heated condition, and means for effecting relative displacement of the work and the source of such solder in a direction substantially parallel to that of the course of such joint region, characterised in that such spacer member (4) heating means (7) is inductive heating means.

9. Apparatus according to Claim 8, wherein said support is constituted as a conveyor (5) for conveying the work (1) past fixed inductive heating means (7) and adjacent solder supply means (8).

10. Apparatus according to Claim 8 or 9, wherein said solder supply means comprises a nozzle (1 7) for feeding molten solder to the joint region.

1 Apparatus according to Claim 10, wherein said solder supply means further comprises a reservoir (15) for feeding molten solder (1 6) to the nozzle (17).

12. Apparatus according to any of Claims 8 to 11, wherein said inductive heating means (7) comprises one or more windings (11, 25) on the limbs of one or more generally U- or horseshoeshaped cores (121 5, 24).

13. Apparatus according to any of Claims 8 to 12, wherein second inductive heating means (9) is provided for heating the spacer member (4) after the feeding of solder thereto.

14. A process for manufacturing a glazing unit substantially as herein described with reference to the accompanying drawings.

1 5. Apparatus for manufacturing a glazing unit substantially as herein described with reference to the accompanying drawings.

16. A glazing unit manufactured by a process according to any of Claims 1 to 7 and Claim 14.