IL30355A - Process and apparatus for the continuous production of glass paste - Google Patents

Description

PROCESS AND APPARAillS FOB (EHE CONTINUOUS PRODUCTION OF GLASS PASTE , - paste, and it is concerned more psrticulsrly with a roems for the continuous production of glass paste and 'apparatus' v .for carrying out the process, for example with a .view to. mosaic making.

■ The material which technologists call,!glass paste" ,is , generally obtained by. melting in pets glass which is .

. . . I rendered opalescent to some degree by the addition of/ calcium / or phosphate oreh ' fluorspar or^phosphate , for by adding to the molten glass -furtheri a \ six?O*L quantit of sand v/hile limiting the time and/or temperature of treatment in such a way as to prevent <· complete fusion and thus complete vitrification. of the'/ grains of sand added. Such a "glass paste" obtained in trsamsform i . this way is then pressed or rolled oT5e¾e?©¾iit into mosaics of. varied colours, · The present invention is based on the principle of opacifying the glass paste by - e continuous, uniform -incorporation of sand into the molten glass* According to the invention, there is provided a procs for the continuous production of. lass paste wherein sand, wit or without any farther additions, is introduced continuously into the interior of a continuous tubular stream of molten glass, the resulting composite stream is inti a c mixed to form a homogeneous · glass paste, and this is rolls and formed into the desired shape. includes; an/ The inve t!on. /«sfce«&e-4:« apparat s for the continuous production of glass paste,' comprising means for i-orising mc en glass into a tubular stream, means for discharging sa d •into the interior of said tubular stream with or' without . other additives which it may be desired to incorporate ' in the mixture, end a mini g chamber positio ed to receive tr composite, stream of molten glass and sand and provided wit • be described later in detail, the intimate mixing of, the molten glass with the sand is carried out within a conditioning kiln, by subjecting the composite stream\ of glass and sand initially to a kneading action, by . ■ passing it, for example, between two grinding wheels or\ rollers rotating at different peripheral speeds, and then by applying a further kneading action. to the resultant \ mixture by passing this, for example, between a grinding \ wheel, which may be one of the two wheels jus mentioned, \ and the floor of the kiln. Further homogenisation can ·, be obtained by stirring the mix thus produced, for example with the aid of slow-running mechanical agitators of the cylindrical type used for stirring optical glass.

The production of mosaics from the mass of molten glass paste thus obtained can be carried out ' advantageously by rolling out the paste and then passing the sheet material . between two cylinders, at least one of which contains appropriate cavities round its periphery. In an improved form of the invention, the sheet of glass paste is supported by a cushion of gas between the rollers used for the rolling proper and those used for shaping, as well as beyond the latter rollers. ! Two embodiments of the invention will now be described by way of. example, as applied to the ' I. manufacture of( glass paste mosaics, reference being made to the accompanying drawings, in which: Fig. 1 is a general diagrammatic sectional view of ' one form of apparatus used for preparing the glass paste; I . Fig. la shows a detail of Fig. 1., drawn to a larger scale; .is a plan view of. the -conditioning kiln .in which..·'·.'."· the molten glass and sand are mixed together; ■ Fi s. 3 a d are diagrammatic views, in elevation and plan respectively, of an improved version of this kiln.; and Fig. 5 is a diagrammatic elevation of the apparatus for rolling out the glass paste and for shaping the mosaics.

Referring first of all to Figs, iand 2 of the drawings, a feeder 1 filled with molten glass 2\has mounted above it a vertical tube 3> into which a' storage .. container 4- pours sand 6,. along with any other additives used, through a diaphragm 5· ^ tube 3 is positioned directly over an aperture ia he bottom ?' Qf the of glassj feeder, so that a tubular stream (or "bulb") 8} filled with sand runs continuously from the aperture 7.· Surrounding the base of this tube 3 concentrically is a fixed tube 9» which dips more deeply than the tube *> into the bath of glass 2, so as to protect the bottom end of the tube 3 from direct contact with the mass of molten glass, thereby eliminating the risk of the bottom opening in the tube 3 becoming blocked by glass, while ·■· at the same time providing a seal to hold back any fines in the sand, which might tend to rise within the empty .. annular space existing between the concentric tube 9 and the tube 10, which latter is concentric with and larger . in diameter than the tube · ' This second concentric tube 10 is rotated slowly (at a speed of 10 r.p.m., for example), so as to stir the molten glass 2 and thus keep it at a uniform temperature throughout. The tube 10 ca also be raised and lowered for -regulating the flow of molten glass passin between the tube and a collar 11 surrounding the aperture 7· Any other conventional method might equally well be used, of course, for producing a uniform temperature throughout the molten glass and for regulating its rate of flow.

The composite, stream 8 of sand and glass passes into a conditioning kiln 12, within v/hich the molten glass and sand, which have already undergone a preliminary mixing by virtue of the formation of the composite stream 8, are now mixed intimately and homogeneously.

In the crown 15 of. the kiln is an opening 1 , directly opposite the aperture 7, for. the admission of the stream of glass.8.

As it enters the kiln, the tubular stream 8, the temperature of which is relatively low because of the sand having been introduced at approximately ambient temperature into the molten 'glass* is heated by a series . of burners 1¾ of. t;-.@ eu&fffoo Q0»¾Ui0¾-i o¾ t pe. Ano er set of burners 15b is fitted along the length of the conditioning kiln, above the bath of glass paste.' The composite stream 8 runs on to a roller or grinding wheel 15 which is rotating in the direction of the arrow Ε^· This wheel dips into the bath of molten glass paste 16 contained in the kiln 12 and is positioned close to the floor 17 of the kiln. A second such roller or wheel 18, turning the opposite, way to the wheel 15, in the direction of the arrow i^ at a different peripheral speed from that of the wheel 15, lies above the bath 16, in such a position that the stream 8 received by the wheel 15 passes between both wheels.

Two contra-rotating cylindrical agitators 19a and 19b , rotating in the direction of arrows F, and F^ respectively, stir the bath with their arms, which dip into the bath, beyond the wheel 15 but in front of the sill 20. \ An atmosphere screen 21 separates the conditioning kil • · ■ V from the zone in which the glass paste is shaped. \ The homogenisation of the glass paste within the kiln takes place as follows: The stream 8 of molten glass and sand first runs on to the wheel 15 and is then rolled between the wheels 15 and 18, between which, because of the difference in their peripheral speeds, it undergoes a kneading or shearing action. In this way, most of the sand is incorporated into the molten glass, and any sand that remains free falls on to that part of the surface of the bath 16 lyingcupstream of the wheel 15 · ' This is carried in a downstream direction ' by the wheel 15, along with the mixture lying upstream.

Because of the small distance between the lowermost point of the wheel 15 and the kiln floor, 17 , a further pronounced shearing action is exerted on the mix and this is driven past the wheel, so 'that the sand and the molten glass are 1 ' intimately mixed in this part of the kiln. An inclined plane 22 , below the wheel 18, assists the movement of the bath of glass paste towards the other side of the wheel 15. The difference i level of the bath on each side of this wheel should also be noted.

The homogeneity of the resultant mix is already satisfactory, but further homogenisation is produced by agitation of the bath by the agitators 19 and 19b .

Figs. 5 and- show an improved forjn of the kiln 12.

In these figures, the parts already described have been -< given the same reference numerals. This kiln differs from that shown in Pigs. 1 and 2 in that the 'inclined plane 22 has been replaced by a curved portion 3 having a concave surface facing the wheels 15 and 18, so .as to facilitate the movement of the bath of glass paste past the wheel 15. Moreover, the! sides 24 and 25 of the kiln converge towards the sill 20, beyond the agitators 19a and 19b , in order to eliminate any dead zone in the bath of glass paste.

The shaping of glass paste mosaics is carried out Very simply, at the exit from the kiln, by rolling the paste with one set of two rollers 26 and 2.7, . and then with a second set of two rolls 28. and.29, the periphery of one of which,, numbered 28, contains cavities, so that the surface of the sheet of paste can be deeply impressed, enabling the sheet to be readily divided subsequently into single mosaic pieces In accordance with one advantageous feature of the invention, the sheet of glass is supported, between the two sets of rollers and as it emerges from the rolls 28 i and 29, on a cushion of gas blown below the sheet through nozzles 30. The sheet of glass paste is thus, not subject to undesirable friction; and,, since the gas used can be pre-heated, the sheet can thus be maintained at a suitable temperature.

To vitrify the surface of the sheet at the end of the line, without markedly altering its appearance , ..all that is necessary is to fire it again after it has passed through the final rolls,. with the aid of, for example, an oxy-acetylene or oxy-propane fuel mixture. This stage renders the surface of the sheet of glass. paste so treated completely self-cleaning. ■ .

An example will now be given of the 'continuous production of glass paste mosaics carried out in . ' -accordance with the invention, using apparatus such as described in the foregoing. i · ' ' '' .· The composition (parts by weight) of the molten glass taken from the feeder 1 was as follows: • . · . , ■ ' ' i ■ ■ .

Si02 - 72.60% ; A12°3 - . 1.25% ' - CaO - .7.90% MgO - 3.75% Na20 - 14.20% .

Other mattear - 0.30$ • Any clear glass could equally well .have been used.

The temperature of the glass in the feeder 1 was between 1 , 200°C. and 1 , 250°C. and the feeder was equipped with a temperature regulating system so as to maintain that temperature constant. ' The sand mixed with the molten glass had a mean particle size of 200 microns* The sand content of the total weight of glass and sand/making up the glass paste was between 15% and 16%. Tests have shown, in fact, that the opacity of the glass paste due to the sand was not sufficient when the sand content was below 14%, so that the colour of the mosaic backing was apt to; show through; and when the sand content was more than 20%, the product became rough-surfaced and was more fragile . ' sufficient to give a temperature of 1,20Q°C.: in the paste situated in the production zone, and for this, in addition to the provision of burners as already mentioned the floor required to be heat-insulated. The heat energy put in on the upstream side of the grinding wheels vwas large, so as to raise the paste temperature quickly.

• \ One quarter of all the heat energy put into the conditioning kiln was made available in this zone. \ The temperature at the entry to the first rollers was \ approximately 1,160°C. and lay between 760°0. and 790°C. at the entry to the final rolls. , \ Under these conditions, glass paste mosaics could be produced in different colours, both easily and cheaply

Claims (1)

1. form homogeneous glass and is rolled formed into the desired A process according to wherein the intimate mixing is carried out subjecting the composite stream to a kneading action in conditioning A process according tc wherein kneading action is carried by passing the of molten glass and sand between rollers at different peripheral A proeess according to claim wherein a further kneading action carried out by passing the mixture of molte glass and sand between the floor of the conditioning kiln and a lowermost part close to the of the A process according to claim wherein the roller which i conjunction with the floor of the kiln provides the further kneading action is one of the ing rollers which provide the first kneading A process according to any one of claims 2 to wherein the mixture of molten glass and sand which has been subjected to kneading is further homogenised by being A process according to any one of the preceding applied to the manufacture of glass paste wherein the glass paste produced is rolled initially between a first pair of rollers then between a second pair of the periphery of one of the rollers of the second p ir being provided rto deeply surface of the sheet of With Suitably shaped cavities acilitate the subsequent division of the sheet into separate mosaic A process according to claim wherein the sheet of glass paste is supported a cushion air during its passage between the first second pairs of rollers and also on emerging from the second pair of process according to claim 7 or the impressed face of the mosaic sheet is passed through a flame after leaving the second pair of Apparatus for the continuous production of glass comprising means forming molten into a tubular for discharging sand into the interior of said tubular with or without other additives which it may be desired to incorporate in the and a mixing chamber positioned to receive the composite of molten and sand and provided with means for intimately mixing the molten glass and Apparatus according to claim wherein the mixing chamber is a conditioning kiln which the composite stream of molten glass and sand runs through an opening in the kiln roof contains rotating rollers rotating about horizontal axes different peripheral speeds the glass and Apparatus according to claim wherein one of the rollers is mounted so that the lowermost part of its periphery is close to floor of the Apparatus according to claim wherein part of the floor of the kiln lying upstream of the roller mounted close the floor is inclined to assist the flow of the glass and sand mixture mixing of the glass and Apparatus according to claim wherein the sides of the kiln converge towards each other on the downstream side of the said cylindrical A proces for the continuous production glass substantially as herein described with reference to the accompanying Apparatus for the continuous production substantially as herein reference to Figures 1 and or Figures 1 and to of the accompanying drawings Glass paste products when produced by the process claimed in any one of claims 1 to claim insufficientOCRQuality