GB2029882A - Secondary glazing comprising plastic film - Google Patents

Abstract

The marginal edge of plastic film 17 is held and gripped by a resilient retaining strip 18 in a channel 11 extending around a frame formed from frame members 10. Frame members 10 may be connected together by corner cleats 13, providing continuous channel 11 around the frame, and mullion and transom elements 19, 26 can be mounted on the frame. The secondary glazing can be applied to a sliding system with the transom elements 19 being received within upper and lower rails or slideways 30, 31. The secondary glazing is especially arranged to provide a kit of parts which can easily be assembled or disassembled and cover a wide range of glazing areas by simply cutting the frame members to size. <IMAGE>

Description

SPECIFICATION Secondary glazing This invention relates to secondary glazing for windows, doors, and other lights.

Secondary glazing is used to improve insulation from thermal losses, and is fitted adjacent to an existing primary frame and located either on such frame or within the same aperture, reveal or other surrounding structure. Conventionally, the secondary glazing comprises a frame which carries the glazing, and this frame must be made to accurate dimensions for fitting and assembly to the primary frame. Additionally, as the conventional glazing material is glass, this must also be provided and mounted in the secondary frame after cutting accurately to size.

Sometimes, secondary glazing may comprise two or more of such glazed frames.

According to this invention we provide secondary glazing including a frame assembled from elongate members, a channel extending around the frame and opening to the face adapted in use to extend in a plane substantially parallel but spaced from the plane of a primary frame, glazing material comprising a plastic film stretched across the secondary frame with the marginal edge secured within the channel by a resilient retaining strip pushed into the channel and adapted and arranged to hold and grip the marginal edge of the film within the channel.

We have found that plastics material in the form of a thin film is most satisfactory as a secondary glazing material. It is much cheaper than glass and can be cut to size simply. It is also light-weight and permits the use of a lower load bearing frame assembly than that possible with glass. It is also safer since it will not crack or shatter, this being paricularly important in domestic installations where accidental impact may occur.

Preferably, the elongate frame members are of like cross-section and are connected at their ends by corner cleats which form part of the secondary frame and include a contiguous portion of said channel extending around each corner of the secondary frame.

This construction provides versatility in sizes of frame that can be assembled from frame members, as frame members can be cut to the desired size from a standard kit designed to include a range of glazing sizes. Additionally, as the glazing material can be rolled, folded or otherwise packed to small size, the secondary glazing according to this invention can be supplied to the user in the form of a flat-packed kit of parts.

Preferably, the resilient retaining strip is of a constant cross-section and may be made of any suitable elastomeric material such as a plastic or rubber based extrusion. It is preferably adapted and arranged for wedging engagement within the open top of the channel, and thus holds the plastics film secured in retention within the channel. The strip can be such as to be capable of cutting to the correct or desired length of the channel which is defined by the contiguous channel portions provided by the frame members and the corner cleats.

The elongate frame members may be extrusions of plastics or aluminium, and the corner cleats may be mouldings or die-castings. Preferably, the corner cleats are substantially rigid to ensure that the corners of the frame are relatively strong and will resist bending or buckling on assembly of the frame.

In a preferred construction according to this invention, the secondary glazing includes a pair of transom elements and a pair of mullion elements. These elements surround the elongate frame members and are also located at their adjacent ends. Conveniently, the elongate frame members include a lengthwise formation adapted to engage within a complementary formation in both the transom and mullion elements. Preferably, the formations are such that the elongate frame member can be slidden along the length of the associated transom or mullion element but is interengaged against lateral displacement. For example, a T-shape, dove-tail or key-hole section may be suitable.

The transom elements may have a constant cross-section and also comprise extrusions. The mullion elements may be extrusions as well. Accordingly, in providing the secondary glazing according to this invention in kit form, the transom and mullion elements can be provided for cutting to the desired size.

The transom elements can be adapted for engagement with either a header rail or sill rail respectively depending on the fixing and location required for the secondary glazing. Where two or more secondary glazing frames are used in combination, the frames can abut one another extending in a common plane. However, preferably the header or sill rails and the transom elements are adapted for relative sliding movement of the frames so that at least one of the secondary glazing frames can be slid along to overlie the adjacent frame. The header and sill rails and the transom elements may also be adapted to permit the removal of a secondary glazing frame by a simple lifting action. This can be achieved by providing clearance between the header rail and the upper transom element.

One or both of the mullion elements may carry along an outer edge a seal of the pile or brush type. Similar seals may be carried by the header and sill rails to engage the transom elements.

These seals can also be provided in strip form which is flexible and can be rolled or folded to compact size and which can be cut to the desired length.

Preferably, the mullion elements include an upstanding rib or flange which extends lengthwise and can be used as a handle for moving or holding the secondary frame.

The glazing material may be selected from a wide range of plastic films that are available.

Different weights of film may be used, and variations in colour and translucency can be provided to give a wide range of choice. Indeed, in the use of the secondary glazing according to this invention, a significant advantage is that the plastics film is so cheap that it can be changed as often as necessary, and in some instances can be used as a solar shield to reduce ultra-violet penetration.

An exemplary embodiment of this invention as applied to a slidable secondary glazing scheme is depicted in the accompanying drawings wherein: Figure 1 is a perspective view, partly sectioned, of an adjacent pair of secondary glazing frames mounted for sliding movement; Figure 2 is a sectional view on line Il-Il of Fig. 1; Figure 3 is a perspective view, partly exploded, of an alternative detail for the transom elements; Figure 4 is a perspective view of a corner cleat; and Figure 5 is a perspective view to an enlarged scale of a limit stop and seal carrier indicated by arrow V in Fig. 1.

With reference to the embodiments depicted in the drawings, the secondary glazing frame comprises four elongate members 10 formed with a lengthwise channel 11 open to one face, and a T-head rib 12 extending lengthwise along one side.

As is best shown in Fig. 3 and 4, the adjacent ends of the members 10 are connected together by a corner cleat 13. The cleat 13 has short T-head ribs 14 matching the ribs 12 of the members 10 and has a short channel portion 15 of which the open ends align with channels 11 of adjoining member 10. The cleat 13 is provided with two limbs 16 extending normally to each other which engage within the bottom of the respective channel 11 of the adjoining member 10. The channel portion 15 extends obtusely to the right-angled corner to prevent a sharp angular change in the corner extent of the channel.

The glazing material 17 comprising a selected piece of plastics film which may be oversize initially, is extended across the frame formed from the members 10 and corner cleats 13 as just described. The plastic material 17 is secured to the frame by a retainer strip 18. The retainer strip 18 is made of a resilient material which can be deformed so as to be forced into the open mouth of the channel 11 of each member 10 and bent around each corner cleat 13 and be received within the channel portion 15 of the respective cleat. The retainer strip 18 is of square or rectangular section, but may be trapezoidal providing a narrow wedging angle.The film is laid over the open mouth of the channel prior to the retainer strip 18 being pushed into the channel so that when the strip is entered into the channel, the marginal edge of the film is gripped and pulled down into the channel with the strip. This wedging action serves to tension the film especially as the strip is progressively entered into the channel. As there is no sharp angle at the corner of the frame, the film will not tend to crease or fold at the corners but be smoothly extended and tensioned over the frame. As will be appreciated, any excess of film protruding outwards from the channel can be trimmed by scissors or a knife.

The secondary frame also includes opposed mullion elements 19 which extend on opposed sides of the secondary frame. Each mullion element 19 is formed with a T-slot 20, and this is complementary to the T-head rib of the member 10. Accordingly, the mullion element 19 can be cut to size and mounted on an associated frame member 10 by a simple sliding movement and held against transverse pulling apart by the interengagement of the T-head rib 12 with the T-slot 20.

A length of self-adhesive pile seal 21 is secured to the one face of the mullion element 19 which is opposed to an upstanding rib or flange 22 that is arranged to provide a handle for sliding or holding the secondary glazing frame in use. It will be understood that the flange 22 may also serve as a stop to prevent two frames crashing together in case of sliding movement of two frames in the same direction. For instance, as shown in Fig. 1, to prevent the left-hand outer frame being moved behind the right-hand inner frame.

The disposition of the mullions 19 in a secondary glazing system is chosen so that the flanges 22 are so arranged, and the seal 21 is adhered or bonded to the correct face of the mullion so that the pile seals of adjacent secondary glazing frames lie in adjacent contact with each other.

If desired, self-adhesive pile seals need not be used, but the mullion elements may be provided with T-shaped slots into which the base of a similar type of seal is received and held.

As best shown in Fig. 2, the mullions at opposed ends of the secondary glazing frames are adapted in use to abut against the reveal face of the window or primary frame 23. This structure 23 carries an elongate element 24 to which a double finned section 25 is secured. The section 25 is designed to provide a pair of flexible fins or leaves which will be engaged by the mullion 19 and which will provide for a wide range of tolerances should the reveal or primary frame, or even the secondary frame be out-of-square. Conveniently, such angle element 24 and the finned section 25 may be formed as an integral flexible gasket strip which can be cut to size and fixed as appropriate to the structure.

The secondary frame further includes upper and lower transom elements 26 which are of like constant cross-section and may be extrusions. One side of each transom element is formed with a T-slot 27 mating with the T-head rib of the frame member 10, and the other side is formed with a deep channel 28. As with the mullion elements 19, the transom elements 26 are arranged for slidable inter-engagement on the upper and lower frame elements 10 once cut to size.

In order to maintain the mullion and transom elements 19, 26 in position on the frame members 10 once assembled with the corner cleats 13, a screw 29 is arranged to extend through the base of the T-slot to bite into and on the T-head of each corner to locate and tension the assembly.

In this embodiment, the secondary glazing frames are mounted between a head rail 30 and sill rail 31, each of which would be secured and fixed to the structure or primary frame by suitable fixings such as screws 32. The head and sill rails are of slightly different configuration but they provide a double track. The sill rail 31 has two rails each of which engages within a respective deep channel 28 of a transom element 25. The head rail 30 provides two slideways, each of which receives a respective upper transom element 25 and each of these slideways is bounded by lengthwise T-slots carrying pile seals which are received in the T-slots in a manner as afore-described.

In a known manner, a head clearance is provided within the box section of the head rail 30 to permit the secondary frame to be lifted clear from the lower track 31 for removal or assembly.

As detailed in Fig. 5, a special limit stop and seal carrier 33 is secured to the lower corner of the slidable inner frame by means of a screw 34 and holds the adjacent mullion in position. The carrier 33 provides a stop face 35 which can be arranged to abut on the lower edge of the opposed rib or flange 22 of the other frame to prevent the two frames crashing together on relative sliding movement. The carrier 33 has a short T-head lug 36 which locates in the bottom of a T-slot in the transom element 26. A short end of pile seal 37 is located in the bottom face of the carrier 33 and is arranged to wipe the bottom of the sill rail 31. The carrier 33 is an assembly of two or more parts which enable it to be right-handed or left-handed as required.

With reference to Fig. 3, this depicts a slight variation of the transom element wherein a Tslot 38 is formed integrally to carry a pile seal.

From the foregoing description with reference to the drawings, it should be understood that the whole secondary glazing system can be assembled from kit form provided that the various parts are cut to the required size.

Although the fitting of the glazing material is referred to as an initial stage in the assembly after the frame members 10 and corner cleats 13 have been connected together, the glazing film can be fitted last as the channel is not obstructed by any other parts after assembly of the frame. Indeed this is an advantage for handling the parts during fitting and assembly. It is another advantage that the user can quickly and easily change the glazing material as desired, and where the user may wish only to use the secondary glazing system for a limited period of the year, it can be disassembled and stored away without any problems associated with sheets of glass.

Furthermore, simpler or more complex installations can be based on the principle parts as just described. In a simple fixed glazing system, provision could be made for securing the frame elements 10 or the corner cleats 13 to a sub-frame arranged for fixing to, or adjacent to a primary frame or surround. Additionally, in some installations, two or more frames may be supported merely to lie adjacent to one another without any provision for relative sliding movement. In such installation suitable lengths of pile seals would extend along the edges of the abutting mullions. The head and sill supports may be selected as desired.

Extensive tests have been carried out on the secondary glazing system according to the preferred embodiment as described and illustrated herein the determine the thermal transmittance and conductance (U-Value) by means of test apparatus designed to satisfy the criteria of ASTMC-236-66 (Thermal Conductance and Transmittance of Built-up Sections by means of the Guarded Hot-Box). These tests were made to evaluate the U-Value of the secondary glazing system using plastic film, and in accordance with this invention.

Tests were carried out on a standard single glazed window with the glazing being of 4mm glass sheet, and this provided a Norm or Standard from which variations in the U-Value introduced by secondary glazing could be shown. One of the secondary glazing installations tested for comparison included a glazed system in which the glass sheet was of 6mm thickness.

In these tests a large number of experiments were carried out and the results were averaged with a tolerance spread. As a result of these tests it was found as follows: Single glazing (4mm glass) U-Value 5.30 i 0.01 Primary glazing 4mm glass and Secondary glazing (plastics film) U-Value 3.58 + 0.04 Primary glazing 4mm glass and Secondary glazing (6mm glass) U-Value 3.13 i 0.03 It can be calculated from the above U-Values that as expected the thermal transmittance for secondary glazing using 6mm glass is superior to that of the plastics film by a small ratio of 100:11 7. However, the U-Value for the plastic film is significantly superior than that of the single glazing with 4mm glass, this being in a ratio of 117: :169. This is surprisingly a far better result than would be expected having regard to the thinness of the plastic film and that the seal to the frame in only through the resilient sealing strip.

Accordingly, it is considered that the low cost of the secondary glazing system using a cheap plastic film provides substantial practical and cost-effective advantages which enable such system to compete with the glazed equivalent.

Claims (11)

1. Secondary glazing including a frame assembled from elongate members, a channel extending around the frame and opening to the face adapted in use to extend in a plane substantially parallel but spaced from the plane of a primary frame, glazing material comprising a plastics film stretched across the secondary frame with the marginal edge secured within the channel by a resilient retaining strip pushed into the channel and adapted and arranged to hold and grip the marginal edge of the film within the channel.

2. Secondary glazing according to claim 1 wherein the elongate frame members are of like cross-section and are connected at their ends by corner cleats which form part of the frame and include a contiguous portion of said channel extending around each corner of the secondary frame.

3. Secondary glazing according to claim 1 or claim 2 wherein the resilient retaining strip is of a constant cross-section and is made of an elastomeric material and adapted for wedging engagement within the open top of said channel.

4. Secondary glazing according to claim 2 or claim 3 wherein said elongate frame members receive the limbs of a corner cleat which extend normally and engage within the channel of the frame members.

5. Secondary glazing according to any one of the preceding claims wherein the elongate frame members include a lengthwise formation adapted to mount a transom or mullion element thereon.

6. Secondary glazing according to claim 5 wherein a pair of opposed mullion elements are mounted on respective opposed elongate frame members, and a pair of opposed transom elements are mounted on respective other opposed elongate frame members.

7. Secondary glazing according to claim 6 wherein said lengthwise formation comprises a Tshaped head which engages in a T-shaped slot in the transom or mullion element mounted thereon.

8. Secondary glazing according to claim 7 wherein said mullion elements are adapted to carry seals on at least one face.

9. Secondary glazing according to claim 8 wherein said mullion elements are provided with an upstanding flange or rib providing a handle.

10. Secondary glazing according to claim 9 wherein said frame with the mullion and transom elements is mounted for sliding movement between a head and sill rail system adapted for securing to a structure or window frame.

11. Secondary glazing substantially as hereinbefore described with reference to the accompanying drawings.