GB2539918B

GB2539918B - Refurbishing glazing units

Info

Publication number: GB2539918B
Application number: GB1511497.8A
Authority: GB
Inventors: Jason Hwozdyk Lee
Original assignee: WINDOW DOCTOR SERVICES Ltd
Current assignee: WINDOW DOCTOR SERVICES Ltd
Priority date: 2015-06-30
Filing date: 2015-06-30
Publication date: 2019-09-25
Anticipated expiration: 2035-06-30
Also published as: GB201511497D0; GB2539918A

Description

REFURBISHING GLAZING UNITS

Field

The present invention relates to methods of refurbishing pre-formed sealed glazing units. In particular, the present invention is directed to a method of replacing desiccant in the spacer bars of the sealed glazing units.

Background

Modern glazing units typically comprise sheets of glass separated by one or more spacer bars generally located around the periphery of the unit. The glazing unit is constructed such that the inferior volume between the glass sheets is sealed and can be filled with, for example, low-pressure air or an inert gas. The spacer bar is generally hollow and has a cavity in which desiccant material is contained. The desiccant material Is used to help prevent the build-up of moisture within the unit, An interior wall of the spacer bar is porous to the gases and moisture inside the unit allowing the desiccant materials to absorb moisture from the interior volume of the unit, thus aiding in the prevention of condensation inside the unit.

Condensation appearing on the interior surface of glass sheets in glazing units is a well-known problem, which can lead to decreased insulation performance and can adversely affect the visual appearance and transparency of the unit. In addition to this, moisture in the atmosphere of the interior volume of the unit results in a loss of insulating performance even when no condensation has formed.

Over time, the seal on the unit will typically degrade such that it allows moisture from the surroundings to enter the interior of the unit. As a result, the desiccant materials in a glazing unit become Increasingly saturated with water and can become ineffective for the removal of moisture from the interior volume of the glazing unit. This leads to loss of performance and can result in condensation forming inside the unit.

Document US 2007/0033887 describes a system where a hole is drilled through the glass surface of a glazing unit and the condensation is removed by flushing the interior of the unit with a cleaning fluid. The unit is then re-sealed with a particular valve system to modulate pressure within the unit. However, this system will result in the unit still containing water-saturated desiccant material and therefore the desiccant material will not prevent future ingress of moisture into the unit, and therefore prevent the formation of condensation. It is also disadvantageous to drill through the glass surface of a glazing unit. Drilling into a pane of glass may cause the glass sheet to crack or shatter, and will not work with some types of glass (in particular when drilling through tempered glass, as may be used in glass doors). Forming holes in the glass surface is also undesirable due to the transparency and visual appeal of the glass being deteriorated by the sealing of the hole after regeneration of the unit. Decorations on the internal surface of the glass panel, for example stained glass or leaded glass effects, may also be damaged by the process of forming holes in the glass sheet.

Document US 2005/0144863 describes a system where moisture is allowed to escape from the interior of a glazing unit by placing a filter in a hole created through the glass sheet or frame into the internal space of the unit. The filter allows moisture to escape from the internal space to the surroundings whilst inhibiting the flow of moisture into the unit. As with document US 2007/0033887, this system will leave the unit with water-saturated desiccant material that cannot effectively protect against future ingress of moisture into the unit, and thus formation of condensation. Drilling a hole through the desiccant containing frame into the internal space of the glazing unit also allows desiccant material to enter the internal space between the panes of glass, worsening the transparency and visual appeal of the glazing unit. A glazing unit is disclosed in document US 4,394,806 that features a replaceable desiccant-containing element. It is noted, however, that this approach only allows the desiccant to be replaced by a user or technician for glazing units having such a replaceable desiccant-containing element on original installation. The glazing unit additionally requires a particular frame surrounding the glazing unit to house the desiccant-containing element. The teaching of this document is therefore specific to glazing units having, on original installation, a replaceable desiccant-containing element and a specific frame. For a glazing unit without this construction, installing the disclosed system would necessarily involve complete replacement of the glazing unit and frame, which would be expensive and time consuming.

Document WO 2008/000084 describes a glazing unit featuring replaceable desiccant tubes located within the frame that houses the glazing unit. The teaching of this document is therefore specific to glazing units having, on original installation, replaceable desiccant tubes and having a specific frame to house the desiccant tubes. Without replacement of the entire glazing unit and frame, this approach may not be used to refurbish glazing units of different construction.

As a result, there remains the problem of existing glazing units degrading over time such that the existing desiccant is no longer able remove interior moisture nor prevent future build-up of moisture in the unit.

Summary of the Invention

Aspects of the invention are set out in the independent claims, optional features are set out in the dependent claims. A first aspect presents a method for existing glazing units to be refurbished by replacement of the deteriorated desiccant material in the unit, without needing to deconstruct or replace the glazing unit itself.

In accordance with a first aspect, there is provided a method of refurbishing a pre-formed sealed glazing unit formed from more than one spacer bar and at least two sheets of glass, wherein a spacer bar is situated along each edge of the glazing unit, with the spacer bars connected by corner keys at their ends, the method comprising the steps of: drilling at least one hole through an edge-facing wall of more than one of the spacer bars, wherein the hole is formed so as only to penetrate the edge-facing wall of the spacer bars; draining pre-existing desiccant from the spacer bars using the at least one hole through an edge-facing wall of the spacer bars; refilling new desiccant into the spacer bars using the at least one hole through an edge-facing wall of the spacer bars; and resealing the glazing unit; wherein sealant is removed from the spacer bars of the glazing unit prior to the drilling step. A sealed glazing unit generally has at least two sheets of glass separated by spacer bars. The spacer bars are typically situated along the edges of the unit such that the spacer bars and the glass sheets define the boundaries of the sealed interior of the glazing unit. The glazing unit may comprise two glass sheets separated by the spacer bars (i.e. double-glazed), or may comprise more than two glass sheets with spacer bars separating each sheet from the next (such as triple-glazed).

It will be understood that the spacer bars referred to herein refer to hollow bars, which in use, usually contain a desiccant material. Spacer bars are typically made from steel or aluminium, although they may be made from any other suitable material (such as plastic composite and fibre-glass reinforced materials known generally as ‘Warm Edge’ (RTM) technology), and will be porous with respect to gases and moisture flowing between the interior space of the glazing unit and the space inside the spacer bar. For example, the spacer bars may have perforations or holes on their inner surface, which allow the passage of moisture and gases into the spacer bar but do not allow a desiccant to flow into the space between the glass sheets. In this regard, and by way of example, reference is made to spacer bars from Swisspacer (RTM), Alu Pro (RTM) or Thermoseal (RTM).

The term “moisture” as used herein and throughout the description will be understood to refer to water in any form, for example water in the form of condensation, droplets dispersed in the atmosphere, or gaseous water vapour. A glazing unit will usually comprise straight and/or curved sections of spacer bar arranged around the perimeter of the glazing unit and connected by one or more keys, such as at the corner portions, which may include corner keys or bent sections of a spacer bar. A glazing unit in accordance with the present invention will comprise one spacer bar situated along each edge of the glazing unit, with the spacer bars connected by corner keys at their ends. Corner keys typically connect spacer bars by inserting into the ends of two adjoining spacer bars, plugging the ends of the two spacer bars and holding them together. Corner keys may additionally have a flexible portion in between the attached spacer bars such that the spacer bars can be arranged at a variable angle relative to each other. Corner keys may be made from any suitable material, for example corner keys may be made from a rigid plastic or a metal. The material the corner keys are made from may depend on the material the spacer bars are made from. More than one bent or crimped spacer bar which has been shaped to follow the outline of the glazing unit may be used in conjunction with corner keys. Where a spacer bar has been bent or crimped, the bent section of the spacer bar and an adjacent straight section of the spacer bar will not have a continuous internal volume. In this way, desiccant will not be able to flow from the straight section of the spacer bar into or through the bent section. It will therefore be understood that whether corner portions comprise corner keys inserted into the spacer bars or a bent section of spacer bar, the corner portions of the spacer bars will contain substantially no desiccant.

All of the spacer bars in a glazing unit may contain desiccant or, in some cases, only some of the spacer bars may contain desiccant depending on how the unit has been constructed. The glazing unit may be a substantially rectangular unit having four edges and a spacer bar containing desiccant situated along each edge; however the glazing unit may be any shape and have any suitable number of spacer bars, provided that more than one are present. The glass sheets referred to herein may be any suitable glass sheets. For example, the thickness of the glass sheet will vary depending on the purpose of the glazing unit and may be any thickness. The specific composition and physical properties of the glass sheets will also vary according to the use of the glazing unit. In particular, the present invention allows the refurbishment of a glazing unit comprising any type of glass, while previous methods of drilling through the glass would be incompatible with tempered glass for example.

Drilling a hole through a spacer bar may be achieved by any suitable method, for example by drilling a substantially circular hole through the wall of the spacer bar. The hole may be circular or may have any other suitable shape, and it will be understood that the hole will have dimensions sufficient for desiccant to flow out, or for desiccant to be inserted using the hole.

In accordance with the present invention, sealant is removed from the glazing unit before drilling the hole through the wall of a spacer bar.

In some embodiments a hole may be drilled by low speed drilling in order to help avoid causing damage to the glazing unit. In other embodiments standard or high speed drilling may be used. Optionally, the hole will be formed by drilling perpendicularly to the wall of the spacer bar and in some embodiments, additional tools or guides may be used to ensure the direction of drilling and/or the extent of the hole drilled is as required and to avoid damaging the glazing unit

According to the embodiments described herein a hole is drilled through an edgefacing wall of more than one spacer bar of a glazing unit. An edge-facing wall as referred to herein and throughout the description will be understood to refer to a wall on the outer side of a spacer bar with respect to the interior volume of the unit, the edgefacing wall being perpendicular to the surface of the glass sheets such that the glass sheets do not cover the edge-facing wall.

Draining deteriorated desiccant from the spacer bars and refilling the spacer bars with new desiccant means that a glazing unit will not only have existing condensation, along with moisture in the atmosphere within the unit, substantially removed but will be able to remove substantially any future ingress of moisture into the unit. In this way, a glazing unit can have increased longevity and may not need to be replaced by a new glazing unit. It will also be understood that that the glazing unit may be refurbished in this way without dismantling the glazing unit, which would be time consuming and would be more likely to result in damage to the glazing unit.

The methods of the embodiments described herein additionally allow the avoidance of any steps of flushing the interior of the unit with cleaning fluids to wash out the condensation, which may themselves damage the unit or leave residues on the inner wall of the glass sheets.

The deteriorated desiccant may be drained from a spacer bar using at least one hole through an edge-facing wall of a spacer bar under gravity, or alternatively may be manually assisted by applying suction or flushing a gas through the spacer bar for example. If flushing or suction is used this may also have the benefit of helping to remove moisture in the atmosphere inside the unit. In other embodiments where the desiccant will not flow out of a spacer bar easily, a tool may be used to break up the desiccant and help to remove it, for example a rod may be inserted into the hole to break up the desiccant. In some embodiments, two holes may be formed through an edgefacing wall of a spacer bar and a flexible rod used in a “flossing” motion to remove the desiccant.

The hole is drilled so as only to penetrate the edge-facing wall of the spacer bars of the glazing unit. Only penetrating the edge-facing wall means that desiccant and/or dust formed during drilling the hole may not enter the interior volume of the glazing unit between the glass sheets. This dust and/or desiccant is difficult and time consuming to retrieve and will affect the transparency and visual appeal of the glazing unit if not removed. Penetrating more than just the edge-facing wall would also leave the unit with additional holes that would need to be sealed in order to ensure new desiccant does not enter the interior volume of the glazing unit.

According to embodiments of the present invention, only one hole is drilled in each spacer bar where desiccant is replaced. Alternatively, more than one hole may be drilled in a single spacer bar where necessary. In some embodiments, the step of drilling at least one hole through an edge-facing wall of more than one spacer bar comprises drilling at least one hole through each separate spacer bar of the glazing unit. Alternatively, only some of the spacer bars present in the glazing unit may have holes drilled in them. In some embodiments, where a single spacer bar spans multiple sides of the glazing unit, or where a separate spacer bar is provided along each side of the glazing unit, at least one hole may be drilled in the spacer bar or bars along each side of the glazing unit.

The glazing unit may be resealed by any suitable method known in the art. The resealing of the glazing unit may comprise applying a sealant to the glazing unit. In some embodiments a plug or patch is applied to the hole drilled in a spacer bar over which an additional sealant may then be applied. In other embodiments, a single sealant may be used to plug the hole and to seal the unit. In some embodiments a sealant is applied around the circumference of the glazing unit. It will be understood that where a glazing unit has allowed moisture to enter into the interior of the unit, the existing seal is likely to be damaged. In this way, applying new sealant to the glazing unit will help to inhibit any future ingress of moisture into the interior of the unit. The glazing unit may also originally comprise an outdated sealant and applying a higher quality modern sealant will provide a significant improvement to the glazing unit’s longevity. In some embodiments the original sealant is removed from the glazing unit and a new sealant is applied around the circumference of the unit.

Any suitable sealant may be used according to the present invention. In some embodiments the sealant may comprise a two part chemically-curing sealant. In other embodiments the sealant may comprise a hot-melt adhesive. The sealant may comprise a butyl rubber sealant, a polysulfide sealant, a polyurethane sealant, or a silicone sealant. Suitable sealants, by way of example, can be purchased from ECI (RTM) (European Chemjcai Industries), Eenzi. Bostik (RTM), Tremco (RTM), Kommeriing (RTM), Η B Fuller (RTM) and EuroSeal (RTM).

The new desiccant with which a spacer bar Is refilled according to some embodiments may comprise any suitable desiccant known in the art. It will be understood that the desiccant will be In a form such that if cannot pass through the Inner wall of the spacer bar info the Interior of the glazing unit between the glass sheets. In some embodiments the desiccant may be in the form of pellets of grains. A suitable desiccant may comprise for example, silica gel, calcium chloride, or molecular sieves. In some embodiments the desiccant with which the spacer bar is refilled may be of a higher quality than the desiccant that was removed from the spacer bar such that the same; amount of desiccant can provide a glazing unit with increased longevity compared to the original unit. Suitable dessicants include those sold by Glasmoi (RTM), Grace (RTM) and Ruroslv (RTM),

The term “new desiccant” as used herein and throughout the description is intended to refer to desiccant having substantially less water absorbed in the desiccant than in the desiccant removed from a glazing unit during refurbishment (l,e, the new desiccaht has a, substantially greater capacity for absorbing Water than the deteriorated desiccant which is being replaced).

In certain embodiments, the method further comprises the step of replacing a gas within the sealed glazing unit. It is commonly understood that glazing units may also have an insulating atmosphere, for example an argon atmosphere, within the unit that increases its insulation properties. ,A damaged or ineffective seal will slowly allow the Insulating gas to flow out of the unit and moist air to How Into the unit, reducing insulation performance.

According to some embodiments of the present invention, replacing a gas within the sealed glazing unit comprises the stops of: forming a bole through an edge-facing wall of a corner portion of the glazing unit; replacing the gas inside the sealed glazing unit with an Insulating gas using the hole through an edge-facing wall of a corner portion of the glazing unit; and resealing the glazing unit.

As previously described herein, corner portions may include corner keys or bent sections of a spacer bar and will contain substantially no desiccant. Forming a hole in through an edge-facing wall of a corner portion of the glazing unit allows a hole to be formed into the interior volume of the glazing unit between the glass sheets without allowing desiccant to enter the space between the glass sheets. The gas within the unit may then be replaced with an insulating gas without the need for forming holes through the glass sheets and without allowing desiccant to enter the space between the glass sheets. Forming a hole in through an edge-facing wall of a corner portion of the glazing unit also allows the gas inside the unit to be replaced without drilling through the glass sheets.

Where a corner key has a sealed pre-formed hole that was used for filling the unit with an insulating gas during production, the aforementioned hole through an edge-facing wall of a corner portion of the glazing unit can be formed through the seal of the existing hole.

The term “insulating gas” as used herein is intended to refer to a gas that provides greater thermal insulation than an equivalent volume of air. For example, an insulating gas atmosphere between the glass sheets of a sealed glazing unit can result in a reduced level of thermal conduction through the unit compared to an atmosphere of air. In some embodiments, the insulating gas can be argon, although any other suitable insulating gas may be used, for example krypton or xenon.

Optionally, replacing the gas inside a sealed glazing unit with an insulating gas comprises pumping the insulating gas into the unit using the hole through an edge-facing wall of a corner portion of the glazing unit. It will be understood that the gas to be replaced inside the unit can be flushed out of the unit upon pumping the insulating gas into the unit. In some embodiments the gas to be replaced can be flushed out of the unit through the same hole used for pumping in the insulating gas. Alternatively, one or more additional holes may be formed, optionally through an edge-facing wall of a corner portion of the glazing unit, and the gas to be replaced flushed out through the one or more additional holes. The gas can be pumped into the unit using any suitable equipment, for example a tube or nozzle connected to a source of the insulating gas may be inserted into the hole and the insulating gas then pumped into the unit through the tube or nozzle.

When flushing the gas out from the interior of the glazing unit, the glazing unit can be orientated such that the hole through which the gas is being flushed out is on the upper edge of the glazing unit. As the insulating gas is usually denser than the gas being replaced, the replacement gas will therefore sink to the bottom of the unit and push the gas to be replaced towards the upper edge of the glazing unit.

It will be understood that a hole formed through an edge-facing wall of a corner portion of the glazing unit may be sealed substantially as described previously herein in relation to a hole through an edge-facing wall of the more than one spacer bars. In some embodiments a black sealant is used to plug and seal the hole through an edge-facing wall of a corner portion of the glazing unit. Using a black sealant means that the sealant can be distinguished from the surrounding material more easily, and therefore it is possible to verify that the sealant has filled a hole being sealed by examining the inner side of the hole through the glass sheets. Alternatively, the hole may be sealed using plugs of a type known in this field such as from Swisspacer (RTM) or Alu Pro (RTM).

In some embodiments, the sealant which is used to seal the hole in a spacer bar or a corner portion of the unit is the same sealant as a sealant applied around the entire circumference of the glazing unit. In this way, the glazing unit as a whole may be sealed at the same time as a hole in a spacer bar or a corner portion of the unit, saving time and the cost of using multiple sealant materials.

The optional, additional step of forming a hole for replacing gas through an edgefacing wall of a corner portion of the glazing unit may be conducted by any suitable method. For example, the hole could be formed by drilling a substantially circular hole through a corner key or a bent section of a spacer bar. The hole may be circular or may have any other suitable shape, and it will be understood that the hole can have dimensions sufficient for the gas inside the glazing unit to be replaced using the hole, for example to allow the insertion of a tube or nozzle into the hole whilst still allowing the displaced gas to escape through the hole. In some embodiments a hole for replacing gas is drilled through a section of a spacer bar which has a corner key inserted into it such that a hole for replacing gas is formed through the outer wall of the spacer bar, the corner key inside the spacer bar, and the inner wall of the spacer bar. In some embodiments the corner key has a sealed pre-formed hole which was used during the original manufacturing process to introduce an insulating gas into the unit and a new hole can optionally be formed through the sealant in the pre-formed hole.

In some embodiments the hole for replacing gas may be formed by low speed drilling in order to help avoid causing damage to the glazing unit. In other embodiments high speed drilling may be used. Optionally, the hole can be formed by drilling perpendicularly to the wall of the spacer bar or corner key surface and in some embodiments, additional tools or guides may be used to ensure the direction of drilling and/or the extent of the hole drilled is as required to avoid damaging the glazing unit. In other embodiments the hole for replacing gas is formed by drilling at a nonperpendicular angle to the spacer bar or corner key surface, for example a hole for replacing gas may be drilled directly through the corner of a corner key into the interior volume of the glazing unit.

As mentioned previously herein, in some glazing units not all of the spacer bars may contain a desiccant, or the spacer bars may not be completely filled with desiccant. It is therefore possible to upgrade a glazing unit by adding additional desiccant to empty or partially filled spacer bars in the unit using the method of the present invention.

In a second aspect, there is provided a method of upgrading a pre-formed sealed glazing unit formed from more than one spacer bar and at least two sheets of glass, wherein a spacer bar is situated along each edge of the glazing unit, with the spacer bars connected by corner keys at their ends, the method comprising the steps of: drilling at least one hole through an edge-facing wall of more than one of the spacer bars, wherein the hole is formed so as only to penetrate the edge-facing wall of the spacer bars; filling the spacer bars with desiccant using the at least one hole through an edgefacing wall of the spacer bars; and resealing the glazing unit, wherein sealant is removed from the spacer bars of the glazing unit prior to the drilling step.

It will of course be appreciated that where the spacer bar already comprises desiccant material, it will be necessary to remove the existing desiccant before filling with new desiccant.

The term “active desiccant” as used herein is intended to refer to a desiccant which substantially retains its maximum water absorption capacity, i.e. the desiccant has not yet absorbed significant amounts of water.

In some embodiments, the sealed hole through an edge-facing wall of the spacer bar is sealed using the same sealant as a sealant applied around the entire circumference of the glazing unit

As described previously herein, a gas within a sealed glazing unit may be replaced by using a hole formed through an edge-facing wall of a corner portion of the glazing unit. This allows a hole to be formed into the interior volume of the glazing unit between the glass sheets without allowing desiccant to enter the space between the glass sheets. The gas within the unit may therefore be replaced with an insulating gas without the need for forming holes through the glass sheets and without allowing desiccant to enter the space between the glass sheets.

Brief Description ofthe Drawings

Embodiments will now be described, by way of example only and with reference to the accompanying drawings having like-reference numerals, in which:

Figure 1 is a sectional view of a typical sealed glazing unit.

Figure 2 is a cross-sectional view of a typical sealed glazing unit along the axis of a spacer bar.

Figure 3 is a cross-sectional view of a glazing unit, wherein a hole has been formed through an edge-facing wall of the spacer bar.

Figure 4 is a cross-sectional view of a glazing unit, wherein the desiccant has been removed from the spacer bar through a hole in an edge-facing wall of the spacer bar.

Figure 5 is a cross-sectional view of a glazing unit, wherein the spacer bar has been refilled with desiccant and sealed.

Figure 6 is a cross-sectional view of the corner of a glazing unit along an axis perpendicular to the surface of the glass sheets.

Figure 7 (not of the invention) is a cross-sectional view of the corner of a glazing unit, wherein a hole has been formed through the corner key and spacer bar into the interior volume ofthe glazing unit.

Figure 8 (not of the invention) is a cross-sectional view of the corner of a glazing unit, wherein a hole has been formed diagonally through the corner key into the interior volume of the glazing unit.

Figure 9 is a cross-sectional view of the corner of a sealed glazing unit, wherein holes have been formed through the spacer bar and corner key to replace desiccant and to replace the gas inside the unit.

Specific Description

Referring to Figure 1, a sectional view of a typical glazing unit 1 is shown. Glazing unit 1 comprises glass sheets 3 separated by spacer bar 5, which is usually made from aluminium or steel but may be made from any suitable material such as described above. The boundaries of the interior volume of the glazing unit 13 are defined by the glass sheets 3 and the spacer bars 5. Although not shown, a primary sealant is usually applied between the spacer bar 5 and glass sheets 3. The primary sealant is usually a thermosetting polyisobutylene or other butyl compound. The spacer bar 5 contains desiccant 7 and is covered on its edge-facing wall 9 by sealant 15 (which is generally known in the art as a secondary sealant). Suitable materials include polysulfides, polyurethane, silicone, hot melt butyl or epoxy based systems. Spacer bar 5 is shown schematically as a rectangular prism, however the spacer bar may be any shape. The desiccant may be any suitable sealant as described herein.

Referring to Figure 2, a cross-sectional view of glazing unit 1 along the axis of spacer bar 5 is shown. Now referring to Figure 3, a hole 17 is drilled through only the edge-facing wall 9 of spacer bar 5 so as to allow desiccant 7 to drain out of the spacer bar but not allowing desiccant or drilling dust to enter the interior volume of the glazing unit 13. Desiccant 7 may flow out through hole 17 only under gravity or a tool could be used to aid removal of the desiccant.

Now referring to Figure 4, a spacer bar 5 is shown having an interior volume 19 containing no desiccant. Desiccant 7 may have been removed through a hole 17 as shown in Figure 3, or the glazing unit shown in Figure 4 could have been originally manufactured with an empty spacer bar. Spacer bar 5 is filled with fresh desiccant 8 through hole 17 using desiccant tube or funnel 21, although any means for filling the spacer bar with desiccant could be used. A glazing unit with a spacer bar 5 having been refilled with fresh desiccant 8 is shown in Figure 5. Hole 17 has been sealed by applying a new sealant 27, although any means of sealing the hole could be used as described herein.

Referring to Figure 6, a cross-sectional view of the corner of a glazing unit 1 along an axis perpendicular to the surface of the glass sheets 3 is shown. Two spacer bars 5 are connected at their ends by a corner key 12 inserted into the ends of the spacer bars 5. The spacer bars contain desiccant 7 and are covered on their edgefacing surface 9 by sealant 15.

Now referring to Figure 7 (not of the invention), a hole 23 is drilled through the sealant 15, the edge-facing wall of the spacer bar 9, the corner key 12, and the inner wall of the spacer bar 11. The hole 23 defines a channel between the interior volume of the glazing unit 13 and the environment outside the unit. In this example the sealant 15 is drilled through during the formation of hole 23, however sealant 15 may alternatively be removed prior to drilling. The hole 23 being formed through corner key 12 means that the desiccant 7 is separated from the hole 23 by the corner key 12 and so the desiccant 7 cannot flow into the interior volume of the glazing unit 13.

In Figure 8 (not of the invention) an alternative example is shown in which a hole 25 is drilled through the sealant 15 and through the corner of corner key 12, avoiding the spacer bars 5 altogether. In the case of either of the examples of Figures 7 and 8, an insulating gas, which can be argon, is pumped into the unit through hole 23 or 25, flushing the gas inside the unit out though the same hole. The gas can be pumped into the unit using any suitable equipment, for example a tube or nozzle connected to a source of the insulating gas may be inserted into the hole 23 or 25 and the insulating gas then pumped into the unit through the tube or nozzle. In this way the gas inside the unit is replaced with the insulating gas, improving the thermal insulation properties of the unit.

Referring to Figure 9, a hole 23 in the corner key 12, which was used to replace the gas inside the unit, has been sealed with new sealant 27. In this embodiment, the sealant 27 is black such that when observing the inner side of hole 23, it can be determined whether the sealant 27 has filled the hole 23. As shown in Figure 9, a hole 17 was formed for replacing the deteriorated desiccant 7 with fresh desiccant 8 in the same unit, and has also been sealed with new sealant 27.

While the Figures referred to herein only show embodiments where one spacer bar is drilled into to replace desiccant, it will be understood that in accordance with the present invention, the same method is applied to more than one spacer bar and could be applied to any number of spacer bars in a glazing unit, or to form more than one hole in a single spacer bar as required. Optionally, the desiccant can be replaced by the methods described herein in all spacer bars of a glazing unit where the desiccant is deteriorated.

Claims

1. A method of refurbishing a pre-formed sealed glazing unit formed from more than one spacer bar and at least two sheets of glass, wherein a spacer bar is situated along each edge of the glazing unit, with the spacer bars connected by corner keys at their ends, the method comprising the steps of: drilling at least one hole through an edge-facing wall of more than one of the spacer bars, wherein the hole is formed so as only to penetrate the edge-facing wall of the spacer bars; draining pre-existing desiccant from the spacer bars using the at least one hole through an edge-facing wall of the spacer bars; refilling new desiccant into the spacer bars using the at least one hole through an edge-facing wall of the spacer bars; and resealing the glazing unit; wherein sealant is removed from the spacer bars of the glazing unit prior to the drilling step.

2. A method of upgrading a pre-formed sealed glazing unit formed from more than one spacer bar and at least two sheets of glass, wherein a spacer bar is situated along each edge of the glazing unit, with the spacer bars connected by corner keys at their ends, the method comprising the steps of: drilling at least one hole through an edge-facing wall of more than one of the spacer bars, wherein the hole is formed so as only to penetrate the edge-facing wall of the spacer bars; filling the spacer bars with desiccant using the at least one hole through an edge-facing wall of the spacer bars; and resealing the glazing unit; wherein sealant is removed from the spacer bars of the glazing unit prior to the drilling step.

3. A method according to any one of the preceding claims, wherein the step of drilling at least one hole through an edge-facing wall of the spacer bars comprises drilling at least one hole through each separate spacer bar of the glazing unit.

4. A method according to any one of the preceding claims, wherein the method further comprises the step of replacing a gas within the sealed glazing unit.

5. A method according to Claim 4, wherein replacing a gas within the sealed glazing unit comprises the steps of: forming a hole through an edge-facing wall of a corner portion of the glazing unit; replacing the gas inside the sealed glazing unit with an insulating gas using the hole through an edge-facing wall of a corner portion of the glazing unit; and resealing the glazing unit.

6. A method according to any one of Claims 1 to 2, wherein resealing the glazing unit comprises applying a sealant to the glazing unit.

7. A method according to Claim 5 , wherein the insulating gas is argon.