WO1994024398A1

WO1994024398A1 - Insulating panel

Info

Publication number: WO1994024398A1
Application number: PCT/CA1993/000197
Authority: WO
Inventors: Kenneth R. Parker; W. Daniel Taylor
Original assignee: Parker Kenneth R; Taylor W Daniel
Priority date: 1990-09-27
Filing date: 1993-04-21
Publication date: 1994-10-27
Also published as: CN1094474A; AU4055493A

Abstract

A sealed insulated panel has a first sheet (C), or a spacer member, sandwiched between two second sheets (A, B). Small spacer elements are sandwiched between the sheets to maintain their spacing and provide a long conductive path. A seal is formed in such a manner as to encompass the whole of the panel to form at least one hermetically sealed chamber (23, 25). Each chamber is under partial vacuum whereby external pressure urges the sheets together in a cohesive unit. The spacer members on either side of the first, central panel are staggered, to maximise the conductive path length, and hence to reduce heat and sound transmission.

Description

Title; INSULATING PANEL

FIELD OF THE INVENTION

This invention relates to an evacuated insulating panel, and more particularly relates to a glazing unit.

DESCRIPTION OF THE PRIOR ART

The dewar flask is well known to be one of the most efficient insulating structures and makes use of two concentric shells sealed at the lip to form an evacuated chamber. The partial vacuum virtually eliminates conductive and convective heat transfer while a low emissivity surface on the inner shell greatly reduces heat transfer by radiation.

Numerous efforts have been made to apply the principles of the dewar flask to planar insulating structures including windows, wall sections and solar collectors. This involves the use of two sheets which must be maintained a certain distance apart. The peripheries of the sheets must then be sealed and evacuated. Successful techniques are now available in the art to provide low emissivity coatings and to provide long term seals. However, an effective means to maintain the spacing of the sheets, while keeping the insulating effect, has not been achieved. Conventional methods of maintaining the spacing between the sheets has involved the use of pillars, spheres, honeycomb structures or more recently aerogels and fiberglass. These supports are either too highly conductive, too thick or, in the case of glazings, detract from the optical qualities of the glazings.

Known proposals for evacuated panels have two panels held apart by spacers. The spacers must be relatively strong and frequently spaced to support external atmospheric pressure. Consequently, they provide a significant conduction path impairing the insulating effect.

Multi-panel glazing units are described in the

Canadian Building Digest, put out by the Division of

Building Research, National Research Council of Canada, October 1963 in an article "Factory-Sealed Double-Glazed

Units" by Solvason and Wilson.

The structure described in the above mentioned article is a typical insulating glass unit having two panes spaced apart by a hollow metal spacer containing a desiccant surrounded by one or two sealants between the frame and the pane. One disadvantage of this type of structure is that the air in the space between the panes readily conducts heat and sound. Another disadvantage is that the glass panes pump, i.e. they bow in and out with barometric or temperature changes. This interferes with the aesthetic qualities of the structure since reflections are distorted. It is also destructive to the seal and predisposes the units to breakage.

Another problem with a metal spacer is that heat is transferred at the edges causing interior perimeter condensation and thermal stresses which also predisposes the unit to breakage. Further, the desiccants are expensive and tend to affect the internal air pressure of the unit. At low temperature, the desiccant can absorb nitrogen from the air causing the glass to bow in. At high temperatures, the reverse takes place.

In an attempt to overcome these problems, very expensive glazing designs are used with sophisticated sealants with movement capabilities to contain the glass edges.

The types of structure described represent nearly all the production of insulating glass units in the world.

It is therefore an object of the present invention to provide an improved insulating panel. SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided: a spacer member; a pair of continuous outer sheets, with the spacer member located between the outer sheets; and two sets of spacer elements, with one set being located between the spacer member and one outer sheet, and the other set located between the spacer member and the other outer sheet, to maintain the outer sheets spaced apart from the spacer member, and the spacer elements of the one set being staggered with respect to the spacer elements of the other set; sealing means between the outer sheets hermetically sealing the outer sheets to define a chamber within the panel; and a partial vacuum within the chamber, whereby the spacer elements and spacer member support the outer sheets against atmospheric pressure. The spacer member has two functions, namely transferring loads between the staggered spacer elements, and increasing the thermal resistance, i.e. decreasing the conduction, between the second sheets. As such, the spacer member could be discontinuous, and need not have a uniform thickness. Preferably, it is a continuous sheet; the spacer elements may be integrally formed with it.

The seal could be provided by any appropriate material, such as an epoxy adhesive, which forms an impermeable seal to both air and moisture. As such, the seal is preferably bonded to facing surfaces of the panels around their peripheries. Where the load transfer sheet is continuous, it is not necessary for the seal to contact that sheet to define two separate chambers. The seal could be formed by bonding or fusing similar or identical in composition to the material of the second sheets.

The provision of a central spacer member provides another advantage; the spacing between the two outer sheets can be minimised. Unlike the known art, a long conductive path can be maintained of small cross- section, i.e. providing high thermal resistivity, even with close spacings of the outer sheets. This is because the major part of any conductive path can be along the spacer member. Thus, the spacing between the spacer member and each sheet can be much less than the thickness of each sheet. This further reduces risks due to accidental implosion as the volume of the chamber is reduced.

The present invention also provides an enclosure, comprising a panel shaped to define either a container, such as a box, or a tube structure.

The present invention further provides a method of assembling the panel.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the invention, it will be described in more detail by reference to the accompanying drawings, which illustrate a preferred embodiment, and in which:

Figure 1 is a fragmentary perspective view of a glazing unit, according to the invention, with the peripheral sealing means partly removed;

Figure 2 is a cross-section along the line 2-2 of Figure 1;

Figure 3 is a fragmentary perspective view showing the construction in which a corner of the central pane is cutaway to provide a communication between the respective vacuum chambers; Figure 4 is a fragmentary cross-section as along the line 5-5 of Figure 1 in which an epoxy cap is used;

Figure 5 is a view similar to Figure 4 in which solder is used as the capping material and showing a sealable tube; Figure 6 is a view similar to Figure 5, including a pump and valve for controlling internal pressure; and

Figures 7-11, 12a-c, 13, and 14a, b show further variants of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings show both a glazing unit and a non- transparent panel. First the unit of Figures 1 to 4 will be described.

The glazing unit has a central glass pane A, providing a spacer member, flanked on one side by companion pane B, and on the other by a companion pane C of the same configuration.

Thin flat spacing discs 21 intervene the pairs of panes A and B, and A and C, respectively, holding them apart in parallel relationship, to provide a thin space 23 between the panes A and B, and a similar space 25 between the panes A and C. A sealing cap D₁ spanning the periphery of the assembly provides a gas-tight seal about the periphery of the assembly of panes A, B and C, so that the spaces 23 and 25 become hermetically sealed chambers. The chambers 23 and 25 are provided with a permanent partial vacuum.

A preferred way of manufacturing the unit is as follows. With the pane A horizontal, the discs 21 are appropriately placed on its surface and the pane B is stacked on the discs. Then, discs are placed on the pane B and pane C stacked on the discs, so that an assembly is formed with the panes A, B and C juxtaposed and the discs between them.

An hermetic seal D is formed from any suitable material, such as an epoxy adhesive. As Figure 4 shows, to minimise the size of the seal, it is provided between facing peripheral surfaces of the panes B, C without adhering to the central pane A, to form two separate chambers. An assembly is formed from the panes A, B and C, sandwiching between them the spacing discs and enclosing the hermetically sealed chambers 23 and 25.

An alternative construction, according to the invention, is shown in Figures 5 and 6. Here the sealing cap is a continuous layer D₁ of solder or suitable material which extends around the periphery of the unit. In applying the layer D₁ a thin priming film 29 of copper is first applied to the edge of the glass. For the purpose of drawing a vacuum, a tube 31 is employed, extending through seal. As shown in Figure 3, sheet A could be cut back to ensure that the chambers 23, 25 are joined together, and would not require separate evacuation. In Figure 6, vacuum may be drawn through the tube 31 and it is then pinched off and sealed. COMPONENTS

The nature of the preferred components making up the glazing unit are as follows.

Glass The nature of the glass is not critical. Any suitable glass including tinted and/or coated glass can be used. However, the structure of the invention does lend itself to the use of thin glass from about 2mm to about 6mm, preferably 4mm thick. Desirably, tempered or heat strengthened glass is employed. Low emissivity glass is of particular advantage because it can give extremely high insulation values. However, this should not be used for the central pane A, as it has no way to eliminate a large amount of heat.

Spacers The spacers are preferably made of thin transparent plastic material, such as vinyl or polycarbonate. Preferred materials are plasticized polyvinyl chloride and polycarbonate containing ultraviolet inhibiters. Desirably, the spacers are discs from 1.5 mm to 6.5 mm in diameter. The discs may be punched out of a flat sheet of the material and are clear and transparent. Preferably, the spacers have an initial thickness from about 0.5 mm to 1 mm so as to set the spacing between the panes accordingly, i.e. so the spacing is substantially less than the thickness of each individual pane. The spacers are preferably spaced-apart from, about 12 mm to about 75 mm centre to centre with 50 mm centres preferred. The distance between centres is partly limited by the capability of the spacers to withstand the applied pressure and by the atmospheric pressure induced bowing of the glass that could cause visual distortion or touching. The spacers are staggered to substantially increase the conductive path through the insulating panel.

The effective conductive path is through one spacing element, through the elongate dimension of the first pane to the next nearest spacing element.

The spacers may or may not be bonded to the surface of the glass and in the instance of unbonded spaces may be only held in place by the pressure of the atmosphere. In such a circumstance if the vacuum fails, the spacers, in a vertically placed glazing unit, act as tell-tales and fall to the bottom of the unit.

The spacers are preferably non-rigid and are compressed slightly between the panes, in the range of 2- 20%. The resiliency of the spacer material permits the spacing elements to perform several functions, namely: i) damping and/or reflecting vibrations (thereby inhibiting sound transmission through the panel); ii) accommodating movement between the panes that could be caused by shock, wind loads or temperature differences; and iii) conforming to the glass surface under compression thereby providing improved optics.

Glazing Unit A preferred range of permanent partial vacuum within the chambers 23 and 25 is from about 10^"3 to 10^"12 torr, preferably 10"⁴. The chambers 23 and 25 may be partially filled with other gases other than air.

A glazing unit of the invention has a structural strength beyond that of conventional units, which permits the glazing of large surface areas. As the structure is under compression, enhanced strength is provided by the laminated construction in which pressures are distributed to all the panes. For example, by reason of the special spacers of the invention, wind load on a glazing unit of the invention is carried by all the panes. The glazing unit will have a very high resistance to thermal heat transfer. By combining low emissivity with evacuated volumes, the three common modes of heat transfer: conduction, convection and radiation are effectively eliminated, or at least substantially reduced.

The use of spacing elements in the above manner can be employed in insulating panel having a variety of shapes, including a curved edge shown at 30 in figure 7. Figure 8 illustrates a insulating panel 32 having a first sheet 33, a pair of internal second sheets 34a, 34b and a third sheet 36. Two sets of spacing elements, namely those shown at 38, 40 are provided between the first sheet 32 and the second sheets 34a, 34b. One additional set of spacing elements, namely those shown at 42 are provided between the second sheet 34b and the third sheet 36.

Each of the spacing elements in the set 38 is staggered from its neighbouring spacing elements in the set 40, and similarly each of the spacing elements the set 40 is staggered from its neighbouring spacing elements in the set 42. The sets 38, 42 could be aligned.

Figure 9 illustrates an insulating panel 50 which is identical to insulating panel 40 with the exception that sheets of insulating panel 50 are curved. All the foregoing constructions are applicable to panels formed either as transparent glazing units from glass sheets, or as non-transparent sheet from other materials, e.g. metal. The following embodiments include those with sheets or panels having integrally formed dimples, projections, etc. As such, it is expected that other non-transparent materials will be used, although for some purposes, glass or other transparent materials could be formed into the sheet or panel profiles shown.

Figure 10 illustrates another insulating panel 60 having a first sheet 62, as a spacer member, and a pair of second sheets 64. In this case, the staggered spacing elements are integrally formed with the first sheet 62. The staggered spacing elements may be formed by dimpling a thin plate to form alternating dimples 62a and 62b.

Figure 11 illustrates another insulating panel 70 having a first panel 72 and a pair of second panels 74. In this case, the staggered spacing elements are staggered formations on opposing surfaces of the first panel 72.

The spacing elements shown in figure 10 and 11 are hemispherical to provide a point contact to reduce conductivity through the spacing element. However, this point contact may be provided by other shapes as shown in Figure 12, which identifies the panels by the reference numerals of Figure 11. For example, the spacing elements may be formed on the second sheets 74 as shown in figure 12a and shaped as cones 75 with the point contact against the first sheet 72. Figures 12b and 12c illustrate the use of spheres 76 and cylinders 77.

The spacers are provided separately from or integrally with the panels. For separate spacers, they can be joined by a fine mesh to facilitate quick and accurate location for large panels. This technique is most applicable where the panel is intended to have substantial thickness, for example, to increase its strength, and is non-transparent. Then, the mesh can be dimensioned to have a thickness much less than the panel spacing, to prevent or at least minimize contact therewith. The edges of the second panels 74 can then be dished to bring them close to the panel 72, so that t'he edge sealing strip has the smallest width possible, to facilitate maintaining the partial vacuum.

It will be further realised that the central panel 72 need not be continuous, as the various chambers can be connected together (Figure 3). One of its functions is to act as a spacer member to transfer loads between the two sets of spacers. Thus, the spacers and central panel 72 could be moulded or otherwise formed while providing spaces or openings between the spacers. To assist in registering spacers, and panels where spacers are integrally moulded with them, the panels can be provided with coupling formations engaging the spacers. Thus, the spacers could comprise complementary spacer parts formed on two facing panels, which couple to both form the spacers and properly locate the panels.

Figure 13 illustrates an insulating panel in the form of solar collector 80 having a first panel 82 and second panels 84 and 85. As with the earlier embodiments, two sets of staggered spacing elements, namely those shown at 86 and 88, are provided between the first and second panels. An insulated panel 90 is spaced from the second panel 85 to form a heat trap 92, which typically would include a conduit for a heat absorbing fluid. The panel 90 could also be insulated in accordance with the invention. The first and second panels 82, 84 are transparent to transfer radiant heat directly to the heat trap 92. The second panel 85 is provided with an low emissivity coating 93 to prevent radiant heat loss to the exterior. The second panel 85 may instead be formed from any suitable opaque material to absorb the radiant heat entering the collector and to conduct the absorbed heat to the heat trap 92.

Referring to figures 14a and 14b, an enclosure is shown at 100 having insulating panels 102 including a floor 104 integrally formed by nesting two cubic structures 106 and 108. The insulating panels have a common periphery 112. Each cubic structure is formed essentially of a five sided box. Separating the panels of the boxes 106, 108 is a spacing means in the form of a spacing member or panel 110 with two sets of staggering spacing elements 110a, 110b on opposite sides thereof; again panel 110 need not be continuous. In this case, the spacing elements are integrally formed with the spacing panel as in figure 11. A perimeter seal is formed at the periphery 112 as described above.

The enclosure 100 is significant in that there are no excessive edge losses at the unsealed edges and a single evacuated chamber can be formed to ease manufacture. The spacer sheets or panels need not be joined at the lower edges since the ambient pressure, as before, maintains them in contact with one another. Any sided structure can be assembled in this manner, such as a pentagon or similar shapes, a cone, or a hemisphere. In addition, the enclosure my be constructed without a floor, i.e. as a tube, in which case, a perimeter seal would be provided at both upper and lower peripheral edges of the insulating panels. For more complex shapes, more panels may be required, but it would still be possible to attach a series of panels together, to form, for example, the interior of an object, without providing a direct, conductive connection to the exterior except at each opening.

While the spacing elements have been described above as being formed from transparent resilient materials, they may also be formed of virtually any other suitable material, that is capable of withstanding the ambient pressures and has substantially no outgassing characteristics. They need only be transparent where intended.

Any suitable materials that have the strength to withstand the ambient pressures, are gas impermeable and have substantially no outgassing characteristics, in order to maintain the partial vacuum in the insulating panel, can be employed. While the invention has been described in terms of a unit having three or four sheets, the number of panes can be five or more, and internal sheets can be discontinuous. In the applicant's unit, there will be little movement between the panes and little stress at the bonding interface.

As ambient pressure or temperature changes, conventional insulating panels either breathe if they are vented to the exterior or flex if they are sealed. Breathing allows moisture entrapment which results in reduced insulation and degradation. Flexing also reduces the insulation value, weakens the panel and distorts the appearance. Perimeter seals in conventional insulating panels function as structural members. On the other hand, the perimeter seal in the present insulating panel is needed primarily to maintain the partial vacuum.

Conventional panels rely on trapped air for insulation, the insulation value increasing with greater quantities of trapped air. Increased quantities of air result in thicker panels. This exaggerates the breathing or flexing while increasing weight and cost. On the other hand, there need only be sufficient gap between the sheets in the insulating panel 10 to prevent them from touching. The resulting laminate is a thin, economical and strong insulating panel.

To vary the insulation, or even induce significant conduction, a pump 120 and valve 122 can be connected to the chamber, as indicated in Figure 6. Air, or other suitable gas can be admitted and removed as desired. For gas other than air, the pump 120 is also connected to a suitable gas vessel.

For high vacuums, baking and gettering can be provided, to control residual gas, vapour, etc.

Claims

1. An insulating panel comprising: a spacer member; a pair of continuous outer sheets, with the spacer member located between the outer sheets; and two sets of spacer elements, with one set being located between the spacer member and one outer sheet, and the other set located between the spacer member and the other outer sheet, to maintain the outer sheets spaced apart from the spacer member, and the spacer elements of the one set being staggered with respect to the spacer elements of the other set; sealing means between the outer sheets hermetically sealing the outer sheets to define a chamber with the panel; and a partial vacuum within the chamber, whereby the spacer elements and spacer member support the outer sheets against atmospheric pressure.

2. An insulating panel as claimed in claim 1, wherein each of the second sheets and the spacer member is substantially planar.

3. An insulating panel as claimed in claim 1, which is non-planar.

4. An insulating panel as claimed in claim 1, which includes an additional sheet and an additional set of spacer elements between the other outer sheet and the additional sheet, with the other second set of spacer elements being staggered from the additional set of spacer elements.

5. An insulating panel as claimed in claim 4, wherein the said one set and said additional set of spacer elements are aligned with one another.

6. An insulating panel as claimed in any one of claims 1 to 5, wherein the spacer elements are formed from a resilient material.

7. An insulating panel as claimed in any one of claims 1 to 5, wherein all of the individual sheets, the spacer member and the spacer elements are formed from transparent material.

8. An insulating panel as claimed in claim 6 or 7, wherein the spacer elements comprise discs of vinyl or polycarbonate material.

9. An insulating panel as claimed in claim 1, wherein the spacer elements are integrally formed with at least one of the spacer member and the outer sheets.

10. An insulating panel as claimed in claim 9, wherein the spacer elements are integrally formed with the spacer member.

11. An insulating panel as claimed in claim 10, wherein the spacer member comprises a first sheet of generally uniform thickness, and the spacer elements are formed by dimpling of the first sheet.

12. An insulating panel as claimed in claim 10, wherein the spacer elements are integrally moulded with the spacer member.

13. An insulating panel as claimed in claim 9, wherein the spacer elements are integrally formed with the outer sheets.

14. An insulating panel as claimed in any one of claims 9 to 13, wherein each spacer element comprises a main spacer element part integrally formed with one of the spacer member and a respective outer sheet, and a complementary, coupling formation, on the other of the spacer member and the respective outer sheet.

15. An insulating panel as claimed in any preceding claim, wherein at least one of the outer sheets has a low- emissivity coating, to reduce radiant heat transfer.

16. An insulating panel as claimed in claim 1, which includes an additional sheet, located facing the other second sheet, and spaced therefrom, to define a heat trap.

17. An insulating panel as claimed in claim 16, wherein the spacing between the third sheet and the other second sheet is substantially greater than the spacing between the first and second sheets.

18. An insulating panel as claimed in claim 16 or 17, wherein the third sheet comprises a first layer and two second layers, with the first layer located between the two second layers, a first group of spacer elements located on one side of the first layer and a second group of spacer elements located on the other side of the first layer, a second sealing means between the three layers, and a partial vacuum within the third sheet, with the spacer elements supporting the second layers against atmospheric pressure.

19. An insulating panel as claimed in any one of claims 1 to 14, wherein the panel is shaped to form, and comprises an enclosure.

20. An enclosure as claimed in claim 19, wherein the spacer member and the outer panels comprise a plurality of nested structures.

21. An enclosure as claimed in claim 20, wherein the enclosure is generally cubic and defines a base, and side and end walls, spaced from one another, with each of the spacer member and the outer sheets being continuous through the base, side and end walls with a sealing means being provided around the distal edges of the side and end walls, remote from the base, to seal the spacer member and the outer sheets.

22. A method of forming an insulating panel comprising the steps of:

(1) providing a spacer member and a pair of outer sheets;

(2) locating a set of first spacing elements between the spacer member and one second sheet; (3) locating a second set of spacing elements between the spacer member and the other second sheet, with the first set of spacing elements being staggered from the second set of spacing elements;

(4) providing a sealing means between the outer sheets to seal a chamber within the panel;

(5) at least partially evacuating the panel to reduce the conductivity thereof, whereby the spacer elements support the outer sheets against ambient atmospheric pressure.

23. An insulating panel as claimed in any one of claims 1 - 18, in combination with a pump and a valve connected to the chamber of the panel, for controlling gas pressure in the chamber.