DOUBLE GLAZING

Abstract: Double glazing sheeting suitable for glazing a green­ house includes two glass panes (1, 2) secured together along opposite peripheral margins (3, 4, 5, 6). At least one of the panes (1, 2) has a bend extending along or parallel to its edge (3, 4, 5, 6) to define an air space between the panes (1, 2). The bend is defined between two adjacent portions of the same pane having a maximum inclination relative to each other of up to approximately 30°. A shaped pane for producing double glazing can be made by applying shaping tools to a glass ribbon having a viscosity of 10 7.4 to 10 9.6 poises to produce an off-set in the ribbon. The ribbon is then cut to produce the shaped pane.

Description: DOUBLE GLAZING The present invention relates to double glazing sheeting suitable for glazing a greenhouse, and a method of producing a shaped glass pane for use in the production of that double glazing sheeting. Double glazing for normal architectural applications is known in which the peripheral margins of the flat glass panes of a unit are spaced apart by separate spacer elements to define an air space between the panes. Such units may be sealed or unsealed but, in either case, have the disadvantage that the use of these spacer elements adds to the cost of production. The requirements for double glazing a greenhouse are simpler because it is not necessary for the glazing to be of high optical quality, although it is desirable to keep light transmission levels high. Nor is it very important, for horticultural glazing, to avoid temporary deposits e.g. of condensation or dust, on the panes, provided these are removable. GB-A-429,751 describes the production of insulating panels in which two glass sheets of dished formation have flanges all the way round their margins, which flanges are fused or cemented together. GB-A-734,922 discloses double glazing which comprises plates of glass welded together around their margins to provide a sealed air space between the plates. Although the use of spacer elements for providing the air space is obviated the welding operation is expensive. GB-A-816,495 describes a method of rolling glass into a desired shape and then supporting the glass until it is cool enough to retain its shape unsupported. A disadvantage of this method is that the glass needs to be shaped at two separate locations, beginning as the glass ribbon is formed from the molten glass, for example at about 0 1000 C, and then the ribbon is supported after it has attained the desired shape. GB-A-854,154 describes a process for producing angular sections of glass in which a ribbon of glass is shaped ard the shaped glass is then conveyed to an annealing apparatus. As in the method described in GB-A-816,495 shaping is begun whilst the glass is still very hot, and the shaped glass is not produced in a single stage forming operation. It is an object of the present invention to provide double glazing suitable for use in glazing a greenhouse in which two panes of glass are secured together so as to define therebetween an air space, without the need to provide spacer elements. It is another object of the present invention to provide a method of producing a shaped glass sheet for use in the production of double glazing, in which method a glass ribbon can be shaped in a forming operation carried out at a relatively low temperature so avoiding or at least alleviating the need to support the formed glass and thus facilitating the maintenance of high production speeds. According to the present invention there is provided double glazing sheeting suitable for glazing a greenhouse, comprising two discrete panes of glass secured together along opposite peripheral margins thereof, at least one of the panes having a bend extending along or parallel to the peripheral margins to define an air space between the panes, wherein the bend is defined between two adjacent portions of the same pane having a maximum inclination relative to each other of up to approximately 300. Each pane may be formed with two of said bends each extending along a respective peripheral margin, which bends are stepped to form flanges secured to the corresponding flanges of the other pane. One pane may be formed with two of said bends each extending along a respective peripheral margin, which bends are stepped to form flanges secured to unbent peripheral margins of the other pane. Each pane may be formed with one said bend extending along a peripheral margin, which bend is stepped to form a flange secured to an unbent peripheral margin of the other pane. The bends may be formed along one pair only of opposite peripheral margins of the sheets. The panes may be secured together by aadhesive which may comprise an ultra-violet curing adhesive or a butyl cord, or may be secured together mechanically for example by clamping. The air space may be in the range 4 to 30 mm wide. Also according to the present invention there is provided a method of producing a shaped glass pane for use in the production of double glazing sheeting of the invention, in which shaping means is applied to an advancing glass ribbon, characterised by applying shaping tool means to the glass ribbon whilst the viscosity of the glass is in the range 107-4 to 109.6 poises to produce an off-set ribbon portion along the glass ribbon, and cutting the ribbon to produce a shaped glass pane having a bend extending along or parallel to a peripheral margin of the pane, which bend comprises at least a part of the off-set portion and is defined between two adjacent portions of the pane having a maximum inclination relative to each other of up to approximately 300. At least the off-set portion may be cooled during or immediately after the formation thereof. The shaping tool means may be applied to the lateral margin so that the raised portion has a stepped crosssection transversely of the ribbon and comprises a flange. The shaping tool means may be applied to each lateral margin of the ribbon to produce two said off-set portions each along a respective lateral margin so that each of the off-set portions has a stepped cross-section transversely of the longitudinal direction of the ribbon and comprises a flange. The shaping tool means may be applied to a central region of the ribbon to produce the off-set portion along the central region, and thereafter the cutting operation is performed longitudinally along the off-set portion to produce two said shaped panes each having a stepped peripheral margin comprising a respective flange formed from the off-set portion. The shaping tool means may be applied at each lateral margin and at the central region of the ribbon. Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows schematically, part of an embodiment of double glazing sheeting according to the present invention, comprising two panes of glass each having bent peripheral margins at opposite sides thereof, Figure 2 shows in cross-section the double glazing sheeting illustrated in Figure 1, connected to adjacent double glazing sheeting means of glazing bars and glazing caps, Figure 3 shows schematically, part of a second embodiment of double glazing sheeting according to the present invention comprising one pane of glass having bent peripheral margins at opposite sides and a flat pane of glass, Figure 4 shows schematically, part of a third embodiment of double glazing sheeting according to the present invention comprising two panes of glass each having one bent peripheral margin, Figure 5 shows schematically, part of a fourth embodiment of double glazing sheeting according to the present invention, comprising one pane of glass bent along a central region thereof and one flat pane of glass, Figures 6 and 7 show in cross-section shaped glass sheets for use in producing double glazing sheeting according to the present invention, Figure 8 shows an apparatus, viewed in the longitudinal direction of the ribbon, for producing a shaped glass ribbon, and Figure 9 shows a plan view of the apparatus illustrated in Figure 8. Referring to the drawings, Figure 1 shows an embodiment of double glazing sheeting suitable for use in glazing a greenhouse, comprising two panes of glass 1, 2 each having bent peripheral margins 3, 4, 5, 6 at opposite sides thereof which are stepped to form flanges extending along the sides of the panes. These bent margins define an air space 7 between the panes. Figure 2 shows the double glazing sheeting illustrated in Figure 1 connected to adjacent double glazing sheeting by means of conventional glazing bars 8 and clamped down by means of the glazing caps 9. Figure 3 shows double glazing sheeting in which one pane of glass 1 has bent peripheral margins 3 and 4 at opposite sides thereof and the other pane of glass 2 is flat, the bent margins 3 and 4 of the pane 1 are stepped to form flanges which are secured to the unbent peripheral margins of the pane 2, thereby defining the air space 7 between the panes. Figure 4 shows double glazing sheeting in which each pane of glass 1, 2 has one bent peripheral margin 4, 6 and one unbent peripheral margin 3, 5. Each bent margin is stepped to form a flange which is secured to an unbent peripheral margin of the other pane. Figure 5 shows double glazing sheeting in which one pane of glass 1 is bent along its central region 10 so as to be roof-shaped and the other pane of glass 2 is flat. For lightness and economy the glass used to produce the double glazing sheeting preferably has a thickness in the range 2 to 4 mm. The thermal insulation provided by double glazingincreaseswith the air space until an air space of approximately 50 mm is reached and thereafter the increase in insulation diminishes. In the double glazing sheeting according to the present invention the air space is preferably at least 4 mm and for convenience of manufacture and handling of the panes is preferably not greater than 30 mm. The air space may be in the range of 6 to 30 mm. In the embodiment of Figures 1 to 4 the bent portions of the peripheral margins can be considered to be inclined at a specific angle to the plane of the pane of glass. The bend is defined between two adjacent portions of the same pane having an inclination relative to each other of @.8. From practical consideration and in order to produce useful results the minimum angle for g 0 is 2 although it is theoretically possible to have lower angles. The practical upper limit for the angle 8 is 0 approximately 30 since the formation of larger angles could complicate the shaping and cutting process. The preferred range of angles is from 30 to 200 since this provides the best compromise between exigencies of production and the desirability of obtaining air space of at least 10 mm in panes of suitable width for use#in standard horticultural glazing systems. In the embodiments shown in Figures 1 to 4 the peripheral margins 3 and 4 of the pane 1 can be secured to the peripheral margins 6 and 5 respectively of the pane 2 by for example a glue between the margins. A suitable glue is LOCTITE 385 adhesive which after assembling of the glass panes 1, 2 as shown in Figure 1 is cured under ultra-violet light for approximately 30 seconds by the use of for example PHILIPS MBU400V lamps. If a butyl cord is used it can be placed along the peripheral margins of one pane and the other pane then pressed onto the cord. The panes of the double glazing sheeting shown in Figures 1 to 5 are secured together along two opposite margins only and the other two margins are open. This can be tolerated if the sheeting is to be used for glazing a greenhouse since the temporary deposit of small amounts of foreign matter such as wind-blown soil, on the panes does not particularly matter. However, when used for glazing a greenhouse it may be preferable to have a barrier at the upper end of the sheeting to prevent direct entry of falling dust and rain into the air space. Nevertheless, it is preferable to provide some form of access so that for example a spray can be used to remove any substantial accumulation of for example algae on the glass surfaces. The sheeting shown in Figures 1 to 5 each comprise two panes of equal plan area, exactly in register. However, the edge of one pane can be made to extend beyond the edge of the other pane to provide a marginal area having the thickness of one pane. This may be desirable if, for example, the glazing system used is able to accommodate only a single thickness of glass. In each embodiment there may be a protective strip of plastics material, for example polyvinyl chloride along the peripheral edges of one of the panes to cushion the contact between the panes. For manufacturing a shaped glass pane for use in producing the double glazing sheeting, the apparatus shown in Figures 8 and 9 may be employed. This apparatus comprises three scissor jacks 11, 12, 13 mounted on a floor 14 under a roller glass production line just upstream of an annealing lehr. The jacks are spaced from one another transversely of the direction of advance of a ribbon of glass 15. Each jack 11, 12, 13 carries at its upper end a carbon shaping tool 16, 17, 18, which is located beneath the ribbon 15, and with means 19, 20, 21 for individually raising each shaping tool 16, 17, 18 above the plane of the ribbon. Above the ribbon 15 and above each shaping tool 16, 17, 18 is located a polished carbon shaping roller, 22, 23, 24 respectively, which are idler rollers and are each mounted on a beam 25 which has water passages for cooling the beam. The beam is fixed to stanchions 26, 27 at each side of the production line. In front of and behind the j#acks 11, 12, 13 and shaping rollers 22, 23, 24, are further rollers 28, 29 which extend across the production line and which support the glass ribbon 15 in the region of the j#acks and shaping rollers. The surfaces of the shaping tools and rollers may be of other suitable material. Certain metals, for example steel, may be used to constitute the shaping tools or rollers. Example 1 To produce a shaped glass pane having the cross-section shown in Figure 6 a rolled ribbon of soda-limesilica glass having a thickness of 4 mm and a width of 1440 mm was advanced through the apparatus shown in Figures 8 and 9. The central shaping tool 17 was in a raised position above the plane of the ribbon 15 and the two lateral shaping tools 16, 18 were maintained below the plane of the ribbon 15. None of the shaping rollers 22, 23, 24 were employed to shape the ribbon. The shaping tool 17 was located at a position where the glass had a viscosity in the range 108 to 109 poises, the temperature being in the range of 6800C to 7200C for soda-lime-silica glass. As the ribbon was advanced through the line the shaping tool 17 formed a raised off-set portion 30, Figure 6, which progressively extended longitudinally along the central region of the ribbon. As the raised off-set portion was being formed air jets were directed onto the top surface of the ribbon to cool it and "freeze" the raised off-set position thereby obviating any need for subsequently supporting the ribbon provided with the raised off-set portion. The ribbon was thereafter cut transversely and longitudinally along its centre line so as to produce two shaped panes having a cross-section of each of the panes shown in Figure 4. The angle O8 of the bend produced by the raised off-set portion can be varied by controlling the height of the shaping tool 17 above the plane of the ribbon 15. The minimum angle O for a useful gap of 4 mm was approximately 30 For a gap of 20 mm the angle O was approximately 10.30. Example 2 To produce shaped glass having the cross-section shown in Figure 7 a rolled ribbon of soda-lime-silica glass having a thickness of 3 mm and a width of 1440 mm, was advanced through the apparatus shown in Figure 8 and 9 at a speed of 400 m/hr. The three shaping tools 17, 18, 19 were all in a raised position above the plane of the ribbon 15 and the shaping rollers 22, 23, 24, were located to co-operate with the shaping tools. As in the Example 1 the shaping tools were located at a position where the viscosity of the glass was in the range 108 to 109 poises and the temperature was in the range of 6800C to 7200C. As the ribbon 15 was advanced through the line the shaping tools 16, 17, 18 formed a raised off-set portion 31 which progressively extended along the central region of the ribbon 15 and a further raised off-set portions 32, 33 at each lateral margin of the ribbon 15. Each shaping roller 22, 23, 24 co-operated with its respective shaping tool to assist in forming the shape of the raised offset portions. The ribbon was thereafter cut longitudinally along its centre line and transversely so as to produce shaped panes having the cross-section of each of the panes shown in Figure 1. In the two examples of the present invention described above the angle e was kept relatively low. This avoids the substantial problems which arise when cutting a moving ribbon of glass of channel-shaped cross-section in which the sides of the channel are steeply inclined to the base of the channel. It was found that when the shaping process is begun when the glass viscosity has increased to 107-4 poises, it is likely to be difficult to achieve values of g 0 significantly greater than 30 C. To achieve higher angles, it would be necessary to shape the ribbon in a number of successive stages, starting at a glass viscosity below 107-4 and supportingthe shaped portions when these are formed. Such a multistage process begun at high temperature, for example the process described in GB-A-816,495 does permit such high production speeds as the present process. In the two examples described above the shaping tools were positioned where the ribbon viscosity was in the range 108 to 109 poises and the temperature was in the range 6800C to 720 0C, in order to form the bends in a single forming operation. The forming operation could be carried out 6 at a viscosity in the range 107-4 to 109-6 and at a temperature in the range 6500C to 7500C. Some support may be provided to maintain the shape of the ribbon after forming the off-set portions, particularly if the off-set portions are formed when the glass is at the upper end of the viscosity range and the off-set portions are cooled on or immediately after formation. Although the working range has been described in terms of both viscosity and temperature, for general application of the present invention to various types of glass it is the viscosity of the glass rather than the temperature which is important. For the standard soda-lime-silica glass compositici used the temperature quoted correspond to the following viscosities: Temperature: Or Viscosity: poises 650 109.6 680 109 720 108 750 The examples given above refer to the shaping of a rolled ribbon of glass. In appropriate circumstances, the method of the invention may be applied to glass ribbon formed in other ways, for example, a float glass ribbon, or a sheet glass ribbon formed by a vertical drawing process, especially a sheet glass ribbon that has been turned so that it is advancing horizontally. The present invention is particularly directed to double glazing sheeting for the double glazing of greenhouses, and is also applicable to the double glazing of roof lights, e.g. of patent glazing, if the not too stringent conditions similar to those for the double glazing of greenhouses are acceptable.

Claims: Claims: 1. Double glazing sheeting suitable for glazing a greenhouse, comprising two discrete panes of glass (1, 2) secured together along opposite peripheral margins (3, 4, 5, 6) thereof, at least one of the panes having a bend extending along or parallel to the peripheral margins to define an air space between the panes, characterised in that the bend is defined between two adjacent portions of the same pane having a maximum inclination (@) relative to each other of up to approximately 300. 2. Sheeting according to Claim 1, characterised in that each pane is formed with two of said bends each extending along a respective peripheral margin, which bends are stepped to form flanges secured to the corresponding flanges of the other pane. 3. Sheeting according to Claim 1, characterised in that one pane is formed with two of said bends each extending along a respective peripheral margin, which bends are stepped to form flanges secured to unbent peripheral margins of the other pane. 4. Sheeting according to Claim 1, characterised in that each pane is formed with one said bend extending along a peripheral margin, which bend is stepped to form a flange secured to an unbent peripheral margin of the other pane. 5. Sheeting according to any one of Claims 2 to 4, characterised in that said bends are formed along one pair only of opposite peripheral margins of the sheets. 6. Sheeting according to any one of Claims 1 to 5, characterised in that the panes are secured together by adhesive. 7. Sheeting according to Claim 6, characterised in that the adhesive is an ultra-violet curing adhesive. 8. Sheeting according to Claim 6, characterised in that the adhesive is a butyl cord. 9. Sheeting according to any one of Claims 1 to 8, characterised in that the air space is in the range 4 to 30 mm wide. 10. A method of producing a shaped glass pane for use in double glazing sheeting according to Claim 1, in which shaping means is applied to an advancing glass ribbon, characterised by applying shaping tool means to the glass ribbon whilst the viscosity of the glass is in the range to to 109.6 poises to produce an off-set ribbon portion along the glass ribbon, and cutting the ribbon provided with the off-set portion to produce a shaped glass pane having a bend extending along or parallel to a peripheral margin of the pane, which bend comprises at least a part of the off-set portion and is defined between two adjacent portions of the pane having a maximum inclination (g) relative to each other of up to approximately 300. 11. A method according to Claim 10, characterised in that at least the off-set portion is cooled during or immediately after the formation thereof. 12. A method according to Claim 10 or Claim 11, characterised by applying the shaping tool means to the lateral margin of the ribbon to produce the off-set portion along the lateral margin so that the off-set portion has a stepped cross-section transversely of the ribbon and comprises a flange. 13. A method according to Claim 10 or Claim 11, characterised by applying the shaping tool means to each lateral margin of the ribbon to produce two said off-set portions each along a respective lateral margin so that each of the off-set portions has a stepped cross-section transversely of the longitudinal disection of the ribbon and comprises a flange. 14. A method according to Claim 10 or Claim 11, characterised by applying the shaping tool means to the central region of the ribbon to produce the off-set portion along the central region, which off-set portion has a generally flat top, and thereafter cutting the off-set portion longitudinally to produce two said shaped panes each having a stepped peripheral margin comprising a respective flange. 15. A method according to Claim 13 and Claim 14, characterised in that the shaping tool means is applied at each lateral margin and at the central region of the ribbon. 16. A method according to any one of Claims 10 to 15, characterised in that the off-set portion is a raised portion.

Inventors: DUNNING, MALCOLM JOHN, MELDING, ANDREW DAVID, STEERE, ROBIN CHARLES
Applicants: PILKINGTON BROTHERS P.L.C.
Application year: 1982
Main classification: A01G9
IPC codes: A01G9, E06B3, C03B23, E04D3