GB2139684A - Method of manufacturing a sealed hollow glazing unit - Google Patents

Abstract

A seal hollow glazing unit 1 may be made by assembling glazing sheets 2,3 with metallised margins 4,5 and one or more intervening metallic spacer members 6 and bonding the spacer member 6 to the metallised sheet margins using solder 7,8. The gas content of an inter-sheet space 9 may be conditioned via one or more punctures 10 in a spacer member 6 whereafter the puncture 10 is sealed by applying heat and solder to the site of the puncture. Heat is applied to the spacer member 6 by inductive heating means 11 located in the vicinity of the puncture 10. <IMAGE>

Description

SPECIFICATION Method of manufacturing a sealed hollow glazing unit This invention relates to a method of manufacturing a sealed hollow glazing unit comprising glazing sheets held in spaced relation by one or more metallic spacer members solderbonded to metallised marginal portions of the sheets in which the gas content of the or at least one inter-sheet space is conditioned via one or more punctures in one or more spacer members whereafter heat and solder metal are applied to a said spacer member at the or each such puncture to effect sealing.

Glazing units of the aforementioned type are of course extremely well known. Such conditioning may take various forms with the object of improving one or more properties of the glazing unit. Amongst conditioning techniques which may be used are the following: removal of atmospheric moisture (e.g. by flushing with dry air), to avoid the appearance of condensation within the unit; nodification of the composition of the gas mixture within the unit, to promote heat and/or sound insulation and/or to facilitate testing of the integrity of the sealing of the unit e.g. by detecting the escape of any foreign gas which has been introduced; evacuation of the inter-sheet space(s), to promote heat and sound insulation; zither modification of the gas-pressure within the unit.

One reason for modifying the gas-pressure within the unit is to achieve planeity of the sheets of the unit at the location where it is to be installed. Such planeity is especially desirable in the case where such units are to be installed as a large building facade. When viewed from outdoors, such facades often reflect an image of their environs and an objectionable aspect is afforded if the outer sheets of the units are dished inwardly or outwardly. One possible reason for such nonplaneity is a difference in atmospheric pressure due to a difference in altitude between the site of the factory where the unit was made and the site of the building in which it is to be installed. Another possible reason is that such units are usually manufactured while the sheets are lying horizontally on a support. The top sheet tends to sag under gravity.These effects can be reduced or eliminated by appropriate modification of gas-pressure within the unit.

The conditioning could in some cases be effected by manufacturing the unit within a chamber in which the required atmospheric conditions were maintained, but this is extremely inconvenient. Accordingly it is general practice to bond the units together and then to condition them. This entails placing each inter-sheet space in communication with a pump or source of the required gas or gases to be introduced and subsequently sealing the unit. The usual practice is to puncture the or a spacer member for the or each inter-sheet space either before or after bonding the unit together, and then after bonding to condition the space or spaces and seal the puncture using solder.In order that the solder should bond satisfactorily to the spacer around a puncture, it is necessary that the spacer should be heated, but methods of heating the spacer which have hitherto been employed using a soldering iron have entailed a considerable risk of softening the solder joint between the spacer and one or both of the sheets which it holds apart..Since the glazing unit is likely to be stressed in use by wind gusts which flex one sheet of the unit and thus cyclically stress the spacer attached to that sheet and the joints of that spacer to its adjacent sheets, this can lead to a shortening of the life of the seal at those joints so that the benefit afforded by conditioning the gas content of a said inter-sheet space may soon be lost. For consistent satisfactory results this procedure requires very careful control of sealing temperatures and higly skilled labour.

It is an object of the present invention to provide an alternative method of effecting such sealing which is simpler to perform and readily lends itself to automation.

According to the present invention, there is provided a method of manufacturing a sealed hollow glazing unit comprising glazing sheets held held in spaced relation by one or more metallic spacer members solder-bonded to metallised marginal portions of the sheets in which the gas content of the or at least one inter-sheet space is conditioned via one or more punctures in one or more spacer members whereafter heat and solder heat are applied to a said spacer member at the or each such puncture to effect sealing, characterised in that the heat is applied to such spacer member by inductive heating means located in the vicinity of the puncture.

Such a method is simpler to perform and readily lends itself to automation. Inductive heating of the spacer member is more easy to control as to temperature than other methods of heating and can easily be localised around the puncture to be sealed so that there is less risk of having a deleterious effect on the spacer-sheet joints.

The heating must of course be sufficient to bring the spacer member surrounding the puncture to a suitable temperature for acceptable bonding with the applied solder and of course the solder must be molten for bonding to occurs. The requirement for such heating is accordingly reduced when said solder metal is heated prior to its contact with the spacer member as is preferred.

In some preferred embodiments of the invention, said solder metal is molten prior to its said contact.

In other preferred embodiments of the invention, the solder metal is fed to the puncture as a wire which may be preheated or not.

Solder wire is very easy to feed.

The heated solder may be fed to the puncture from a store or reservoir of hot solder, but it is found convenient to heat the solder during its passage from such a store to the' puncture and in preferred embodiments of the invention, such preheating of the solder metal is effected by the means used for inductively heating the spacer member.

In some preferred embodiments of the invention said solder metal is fed to the puncture as a pellet. Such a pellet may be cold, but is preferably heated or molten as aforesaid. When using a molten pellet (or droplet) there is ecomony in the use of solder as compared with feeding e.g. a stream of molten solder to the puncture.

Such a solder pellet may be fed or projected mechanically towards the puncture, or it may be allowed to fall under gravity if the glazing unit is appropriately oriented, but in preferred embodiments of the invention, said solder pellet is inductively propelled towards said puncture.

In preferred embodiments of the invention, said conditioning includes the step of introducing a foreign gas into the or a said inter- sheet space. The expression "foreign gas" is used herein to denote any gas other than water vapour, oxygen and nitrogen which is introduced in an amount such that its escape form the unit is readily detectable in the atmosphere. This is a very simple and reliable way of checking the air-tightness of the unit after sealing. It is of course desirable that such a foreign gas should be non-toxic, nonexplosive and non-combustible, and effectively colourless in the amounts used. Sulphur hexafluoride is a particularly preferred example of a gas fulfilling these requirements.

Preferred embodiments of the invention will now be described in greater detail with reference to the accompanying diagrammatic drawings in which: Figure 1 is a plan view of a glazing unit being treated with certain upper parts removed and the view being along the line I-I of Fig. 2, Figure 2 is a sectional elevation along the line Il-Il of Fig. 1, and Figure 3 is a sectional elevation of a second glazing unit being treated.

In Figs. 1 and 2 a glazing unit 1 comprises two sheets of glass 2, 3 each of which has a metallised margin respectively 4, 5. A channel form spacer member 6, for example of tinned copper is bonded to the metallised margins 4, 5 by solder fillets 7, 8 to define an inter-sheet space 9. The spacer member 6 is punctured at 10 to allow communication with the intersheet space 9 so that the gas content of the latter can be conditioned.

After conditioning it is required to seal the puncture 10 with solder.

To this end, an inductive heating device 11 is provided. This inductive heating device comprises a generally horse-shoe shaped core whose limbs 12, 13 are formed of ferrite bars which are linked at their base by two further ferrite bars 14, 15. The limbs 12, 13 are each surrounded by an inductance coil formed from a continuous conductor 16 suitably in the form of a copper tube which can be cooled with water in known manner.

The free ends of the ferrite bars 12, 13 are located symmetrically to either side of the puncture 10 and as close as possible to the spacer member 6 in order that the heating may be as rapid as possible.

In a specific practical example, in order to seal a puncture such as 10 having a diameter of about 1 mm, such an inductive heater is brought to the work so that the free ends of the ferrite bars 12, 13 (spaced apart by about 10 mm) are within 1 mm of the spacer member.

Solder in wire form having liquidus temperature below 190on is fed to the puncture and the inductive heating coil is energised by a high frequency generator operating at about 35 kHz with a maximum power output of 3 kW for a period of less than 2 seconds. At the end of that time it was found that the puncture was sealed with no perceptible deterioration in the quality of the sheet-spacer joints.

In a variant, a pellet of solder was applied to the puncture.

Fig. 3 shows a second type of hollow glazing panel 17 comprising two sheets 18 of glass each having metallised margins 19. The sheets 19 are held spaced apart by a leaden spacer strip 20 bonded to the metallised sheet margins 19 by solder fillets 21. The leaden spacer strip 20 is punctured at 22 so that the inter-sheet space 23 is in communication with the atmosphere so that its gas content can be conditioned. After conditioning, it is required to seal the puncture 22 with solder.

To this end, a wire of solder metal 24 is fed to the puncture 22 through an inductive heating coil diagrammatically shown at 25. The end of the coil 25 is brought close to the puncture 22 and serves both to pre-heat the solder 24 and to heat the spacer 20 in the inter-mediate vicinity of the puncture 22.

A method according to the present invention presents particular advantages in sealing a lead-spacer type of hollow glazing unit in view of the low melting point of lead and the consequent risk of damaging the spacer when operating a previously known method involving the use of a soldering iron.

A specific example of solder alloy inevitable for use in sealing and said puncture has the following composition: Tin 50%, Lead 32% and Cadmium 18% by weight. This is a eutectic mixture with a liquidus temperature of 146 C.

Claims (10)

1. A method of manufacturing a sealed hollow glazing unit comprising glazing sheets held in spaced. relation by one or more metallic spacer members solder-bonded to metallised marginal portions of the sheets in which the gas content of the or at least one inter-sheet space in conditioned via one or more punctures in one or more spacer members whereafter heat and solder metal are applied to a said spacer member at the or each such puncture to effect sealing, characterised in that the heat is applied to such spacer member by inductive heating means located in the vicinity of the puncture.

2. A method according to Claim 1, wherein said solder metal is heated prior to its contact with the spacer member.

3. A method according to Claim 2, wherein such preheating of the solder metal is effected by the means used for inductively heating the spacer member.

4. A method according to Claim 2 or 3 wherein said solder metal is molten prior to its said contact.

5. A method according to any of Claims 1 to 3, wherein said solder metal is fed to the pUncture as a wire.

6. A method according to any of claims 1 to 4 wherein said solder metal is fed to the puncture as a pellet.

7. A method according to Claim 6, wherein said solder pellet is inductively propelled towards said puncture.

8. A method according to any preceding claim, wherein said conditioning includes the step of introducing a foreign gas e.g. sulphur hexafluoride into the or a said inter-sheet space.

9. A method of manufacturing a sealed hollow glazing unit according to Claim 1 and substantially as herein described.

10. A hollow glazing panel manufactured by a method according to any preceding claim.