HEAT-INSULATING WINDOW GLASS

Abstract: A heat-insulating window glass comprising at least one cavity which has no communication with the external faces of the glass and which is evacuated to a gas pressure below 0.1 mbar, and bridging members in said cavity, which members extend transversely relative to the external faces of the glass. The window glass is easy to handle and its transparency properties are good because the cavity extends approximately to the marginal portions of the glass and covers less than 20% of the total volume of the glass sheet and the total area of the bridging members in a lengthwise section through the glass covers less than 10% of the total area of the glass.

Description: Heat-Insulating Window Glass The subject invention is concerned with heat -insulating window glass having at least one cavity therein which has no communication with the external faces of the glass and which is evacuated to a gas pressure below 0.1 mbar, and comprising bridging members in the cavity extending transversely relative to the external faces of the glass. It is known to provide supporting elements between the glass panes of a window and to evacuate the gap therebetween. As a result of such evacuation, the transmittance of heat through the window is greatly reduced. On account of the risk of implosion it has hitherto been necessary to dimension the glass as well as the support elements with considerable safety margins and as a consequence such windows are difficult and cumbersome to handle. For the same reason this type of windows are expensive to manufacture and their transparency properties are not particularly good. The purpose of the subject invention is to provide a heat-insulating window glass which possesses high transparency properties, which is no more difficult or inconvenient to handle than is conventional window glass, and which is not exceptionally expensive to manufacture. The window plate glass in accordance with the ivention is characterised in that the cavity extends approximately to the marginal edges of the glass and covers less than 20% of the total volume of the glass sheet, and in that the total area of the bridging members in a longitudinal section through the glass covers less than 10% of the total area of the glass. Because heat transfer through conductivety or convection in a gas at low pressure is insignificant the cavity in the glass sheet may be very narrow. Since the delimiting walls of the cavity are closely spaced, the bridging members between the two walls may be of reduced dimensions. Thus, the evacuated volume of the cavity is small, for which reason the risks of damages from shattered glass in thetcase of an implosion are negligible. The bridging members are small and cover only a small percentage of the surface of the glass, and for this reason the transparency of the glass is effected only to a very small extent. The invention will be described in closer detail in the following with reference to the accompanying drawings, wherein Fig. 1 is a broken plan view of a window glass in accordance with the invention, Figs. 2 and 3 show the window glass in a cross-sectional view in accordance with a first embodiment in views before and after interconnection of the various components, Figs. 4 and 5 and Figs. 6 and 7 are similar views to Figs. 1 and 2 but show a second and a third embodiment of the glass in accordance with the invention. The glass sheet 1 in Fig. 1 is provided with marginal portions 2 and internally thereof are provided bridging elements 3. The latter have but a very small extension in the surface of vision but their number is considerable. One embodiment of the glass sheet in accordance with the invention is shown in Figs. 2 and 3. The window pane is formed by the application on two glass sheets 4 and 5 of thermosetting plastics or glass having a comparatively low melting point in the form of small droplets 3' in a predetermined array of dots, whereafter the two glass sheets 4, 5 are brought close together with the droplets in facing relationship. The droplets on each sheet may rise above the sheet level by e.g. 0.1 - 0.15 millimeters. When the droplets are brought together concave bridging elements 3 are formed, the cross-sectional size of which varies from a maximum value closely adjacent the sheet to a minimum value halfway therebetween. When the plastics has set, alternatively the glass has solified, the cavity 6 intermediate the sheets 4, 5 is evacuated and sealed, for instance by fusing edge strips 7 of glass with the edge faces of the glass sheets. The thermosetting plastics, alternatively the glass, in the droplets could be mixed with e.g. crushed silica which increases the strength of the bridging elements. By admixture of carbon black or some other similar colouring agent the occurrence of light refractional phenomena in the bridging elements 3 is avoided. In this manner the glass may be "tinted" to the desired degree of ligbt transmission. In accordance with the second embodiment shown in Figs. 4 and 5 the bridging elements 3 consist of protuberances formed in the glass sheets 4' and 5'. Protuberances or bumps of this kind may be produced during the manufacture of the glass sheets through rolling one face of the sheet. The sheets are then interconnected in a heating process during which the two sheets are joined together to one single unit, whereupon the cavity between the two slabs is evacuated. The protuberances could be tinted in the same manner as the plastics and glass in accordance with the preceding embodiment to eliminate the generation of light reflexes in the window pane. The third embodiment concerns a translucent but not transparent plate glass in accordance with the invention. Just like in accordance with the previous embodiments the glass comprises two layers 4" and 5" which are joined together into one glass with a cavity 6 between the layers. In this embodiment one face of the glass is exposed to a rolling operation during which a wavy pattern is imparted to the glass face and when the two glass layers are brought together with the wavy patterns in opposite relationship, the waves of the pattern form the desired supporting or bridging elements 3 and the cavities 6. The two glass layers are interconnected in the manner described previously. The projections formed in a t-ranslucent but not transparent glass could also have the shape of ridges forming a striped or square pattern extending over the inner faces of the glass layers. In this manner the glass may be given decorative light-refractional properties while at the same time cleaning of the glass panes is just as easy as in case of ordinary plate glass since the external faces of the window are even and smooth. The window glass in accordance with the invention may also be dome-shaped. When this is the case fewer bridging elements are required, since the dome-shape as such improves the structural strength and durability of the glass. The glass in accordance with the invention may be manufactured with an average gap of 0.3 millimeters between the layers 4 and 5. As a consequence, the total volume of the enclosed cavity/cavities is quite small and therefore the risk of damages from shattered glass is negligible in case of an implosion. A glass sheet of this kind may replace ordinary window glass in normal window frames and can be mounted by means of known technique. When the glass is provided with bridging elements 3 between the glass layers 4, 5 having a thickness of 0.1 millimeters and in a number of between 30 and 100 per cm2 the human eye cannot discern their presence at a distance exceeding 1 meter, provided the bridging elements are tinted in a mat black. Since the internal supporting elements between the two layers of the glass cover only a few percent of the total volume of the glass the heat transfer from the external face 8 of the glass to the internal face 9 will amount to a few percent only of the heat transfer in window panes of homogeneous plate glass. The invention is not limited to the embodiments described above but a variety of modifications are possible within the scope of the appended claims. The edges of the glass sheet may, for instance, have a different shape than the ones shown. Also other materials than glass are conceivable,

Claims: Claims 1. A heat-insulating window glass having at least one cavity therein which has no communication with the external faces of the glass and which is evacuated to a gas pressure below 13.1 mbar, and comprising bridging members in the cavity, which members extend transversely relative to the external faces of the glass, c h a r a c t e r i s e d i n t h a t the cavity extends approximately to the marginal edges of the glass and covers less than 20% of the total volume of the glass sheet, and in that the total area of the bridging members in a longitudinal section through the glass covers less than 10% of the total area of the glass. 2. A heat-insulating window glass as claimed in claim 1, c h # r a c t e r i s e d i n t h a t the number of bridging members in the cavity exceeds one per square centimeter. 3 A heat-insulating window glass as claimed in claim 1, wherein the glass surface is dome-shaped, c h a r a c t e-r i s e d i n t h a t the number of bridging members in the cavity is less than one per square centimeter. 4. A method of manufacturing heat-insulating window glass having at least one cavity therein which has no communication with the external faces of the glass and which is evacuated to a gas pressure below 0.1 mbar, and comprising bridging members in said cavity, said members extending transversely relative to the external faces the glass, the number of said bridging members in the cavity exceeding one per square centimeter, c h a r a c - terised by applying droplets in a dot-screen pattern on one of the sides of at least one of the two glass layers, said droplets consisting of a thermosetting resin, alternatively of glass having a comparatively low melting point, bringing the glass sheets together with the droplets abutting the opposite glass sheet and thereafter pulling the sheets slightly apart until the desired gap between the sheets is obtained, evacuating the cavity between the sheets after setting of the plastics, alternatively solidifying of the glass, and sealing the cavity. 5 A method as claimed in claim 4, c h a r a c t e r i s e d by the sealing of the cavity by means of a border strip which extends in the shape of an arch towards the cavity and which is interconnected with the glass sheets by fusion.

Inventors: ASSARSSON, TORSTEN
Applicants: ASSARSSON, TORSTEN
Application year: 1981
Main classification: C03B23
IPC codes: E06B3, C03B23