IE43903B1 - Process and apparatus for making fibres from attenuable material,for example glass - Google Patents

Abstract

1523823 Making glass fibres SAINT-GOBAIN INDUSTRIES 2 Feb 1976 [21 Feb 1975] 03946/76 Heading C1M Glass fibres are made by generating a main gaseous blast 12A and an intersecting secondary gaseous jet (from 36) transversely of blast 12A, the jet having a smaller cross-sectional area and greater kinetic energy per unit of volume than the blast so that the jet and blast form a zone of interaction; delivering molten glass (from aperture 37) to said zone for attenuation; and contacting the resultant flow with an additional gaseous current (from 216). The additional current prevents fibres adhering to plate 209.

Description

This invention relates to a process and apparatus for making fibres from attenuable material, for example glass, in which process and apparatus a main gaseous blast and a secondary gaseous jet, are generated, the jet being directed so as to meet the blast and its kinetic energy being sufficient to cause it to enter the blast, so that a zone of interaction is established close to the path along which the jet penetrates the blast, and attenuable material being carried to the boundary of the blast into which it enters to reach the zone of interaction, as a result of which the material is attenuated and fibres are produced.

An object of the invention is to improve.this ; process and apparatus, whereby advantageous effects may be obtained which will be described herein.

According to this invention a process for making fibres from attenuable material comprises:- generating a main gaseous blast; directing a secondary gaseous jet transversely thereof, the cross-sectional area of the jet being less than that of the blast and its kinetic energy per unit of volume being greater than that of the blast so that the jet penetrates the blast so as to give rise to a zone of interaction; delivering a stream of attenuable material into the said zone in which it is attenuated; and delivering an additional gaseous current into contact with the flow resulting from the blast and the secondary jet. - 2 43903 Also according to this invention apparatus for making fibres from attenuable material comprises:- means for generating a main gaseous blast; means for directing a secondary gaseous jet of smaller size than the main blast transversely of the blast so as to penetrate it and give rise to a zone of interaction, the kinetic energy per unit of volume of the jet being greater than that of the blast; supply means for delivering attenuable material so that it will enter the said zone; and means for delivering an additional gaseous current into contact with the flow resulting from the blast and the secondary jet.

Further according to this invention apparatus for making fibres from attenuable material comprises:- means for generating a main gaseous blast; a plurality of fibre forming centres associated with the main blast and spaced from one another transversely thereof, each centre being associated with supply orifice means for the material and the centres having a structure with a common wall adjacent a boundary of the main blast and equipped with a plurality of apertures each situated, in relation to the main blast, in a position upstream of a corresponding material supply orifice; and means for directing a separate gaseous secondary jet through each aperture comprising a gas discharge tube penetrating each aperture of the said structure to introduce a secondary jet into the blast.

An object of the invention is to reduce the tendency of fibres to adhere to a plate disposed downstream of - 3 633 0 3 an outlet for delivering the stream of attenuable material. This is achieved by bringing the additional gas current, for example a current of air, into contact with the zone of interaction of the blast and the secondary jet at the level > of the upstream edge of the plate and at a point which, in relation to'the direction of flow of the blast, is situated immediately downstream of the outlet. This stream of air at the upstream edge of the plate produces a layer Of gas on the surface of the plate exposed to the resulting flow, .0 this layer having the tendency to prevent adherence and piling up of attenuable material on the surface of the plate.

In apparatus comprising a plurality of fibre forming stations or centres staggered transversely to the gas flow direction and each comprising a secondary jet entering the .5 blast and an outlet orifice for the attenuable material, the means for providing an additional gaseous current may comprise either a series of individual jets each aligned with a fibre forming station, or a slot for emitting air transversely to the flow direction. In both cases, the !0 additional supply of air' tends to create a layer of air on that surface of the downstream plate which is exposed to the resulting flow and it also tends to promote more vigorous penetration of the stream into thezone of · interaction.

The invention will now be described by way of example, with reference to the drawings,in which:4 Figure 1 is a vertical section of one embodiment; Figure 2 is a sectional plan on the plane 2-2 of Figure 1; Figure 3 is an enlarged vertical section on the plane 3-3 of Figure 4; Figure 4 is an underneath plan on the line 4-4 of Figure 3; Figure 5 is a detail section similar to Figure 3; Figure 6 is a perspective view showing means for supplying and distributing gas for the secondary jets; Figure 7 is a partly broken away, horizontal detail section through a number of fibre forming stations; Figure 8 is a perspective view of a device for mountingpipes which supply gas to the secondary jets; Figure 9 and Figure 10 are detail sections of another embodiment, Figure 9 being a section on the line 9-9 of Figure 10 and Figure 10 a section on the line 10-10 of Figure 9; Figures 11 and 12 are sections similar to Figure 3 but showing further embodiments of a device for supplying additional air; Figure 13 is a section of another embodiment; and Figure 14 is an underneath plan of part of Figure 13.

Referring to Figures 1 to 5 a crucible 200 is associated with a fore-hearth 201 from which glass is supplied. Instead of supplying glass from the fore-hearth of a glass furnace, an electrically heated melting crucible may be used for melting and supplying the glass.

The crucible has a series of glass outlet apertures 37 to deliver glass to a zone of interaction between a main gaseous blast or current and a series of secondary or carrier jets, and each secondary jet is associated with each glass outlet orifice to produce a corresponding number of fibre forming centres or stations. The main current or blast is indicated by the arrow 12A and the secondary or - 5 43803 Carrier jets are emitted from food tubes through orifices 36, These feed tubes and orifices will be described in more detail below.

The main current is supplied from a pipe 202 and is produced by the combustion of fuel in a combustion chamber 203 supplied with a mixture of gas and air through a pipe 201, A burner 205 supplied with a mixture of gas and air through a pipe 206 supplies gas which is ejected through the orifices 36 (Fig. 5)· The arrangement of these parts which make up each fibre-forming station is shown in. more detail in Figures 3 and 1. As Can be scon, the tubes 207 for the carrier jots, slightly penetrate the apertures 3f>a and omit the gas jets transversely to the main current 12A issuing from pipe 202. As shown in Figures 1 to 8, the apertures 36a are formed in a wall or shoulder 208 which is contiguous with the upper boundary of the main current 12A and is integral with the crucible 200.

Each fibi'e forming station arranged as described above operates in known manner and the parameters, including the kinetic energy of the main current and of the secondary jet in the zone of operation, the temperatures and velocities of the main current and of the jet, the temperature of the glass, the ratio between the dimensions of tlio glass orifices and the jot orifices, the distance between them, and other parameters may all correspond to those already known.

One improvement of the present invention relates to the downstream plate; it is referred to as a downstream plate because it is situated khhsc downstream of the fibre forming ·- 6 43903 station in relation to the diroction of flow of the current 12λ, that is to say, downstream of the glass outlet orifice 37 which in turn is downstream of the jet orifice 56. The downstream plate is shown more particularly in Figures 1, 3 and 5 where it is indicated by reference numeral 209. As can he seen in Figure 1, the downstream plate is mounted by adjustable supports 210 so that its position and inclination can be regulated. The plate 209 is thus positioned so that by its inclination it deflects the gas current after the latter has iC passed the glass outlet orifice.

The downstream plate (Figs. 3 and 5) contains a pipe 211 fitted with connections 212 for circulation of a cooling medium such as water through the pipe 211. The downstream plate is thus cooled by this circulation of cooling medium.

As has been indicated above, the use of a plate downstream of the fibre forming stations tends to bring about contact between the fibres and the plate and hence an accumulation of glass on the surface of the plate. This tendency is considerably reduced by virtue of the conditions under which the air is conducted, preferably in the form of a fluid layer along the undersurface of the downstream plate or along the leading edge 213 (Fig. 3) of the plate. The air or gas used for this purpose is described as additional and the jet produced is referred to as additional jet or current. fn the embodiment of Figures 1 to 8, the leading edge 213 is situated at a distance from the lower part of the crucible 200 so that a slot is formed, and the additional current can be passed through this slot into a zone downstream of the glass - 7 £3903 outlet orifices 37. The plate 209 contains a pipe 214 having couplings 215 for supply of the additional gas, which is for example air. A series of channels 216 communicates with the feedpipe 214 to carry air to the leading edge 213, this air then passing through the .slot close to the crucible. To close the gap between the crucible and. the downstream plate and ensure that the additional gas cannot escape but will pass through the slot formed by the leading edge 213, a sheet metal cover 217 (Fig. 3) is connected to supporting structure 218, and the lower edge of this cover is folded over in the region of the lower wall of the crucible so as to form a cavity containing a refractory insulating material 219 such as alumina fibres. This cover is of slightly resilient stainless steel. With this arrangement including the cover 217, the downstream plate can be positioned as described and in contact with the cover 217.

The action of the additional Jet is indicated in Figure 5, in which tho flow linos IridicaCo not only tho flow directions of tiic main current I2A and of the secondary jet. from the jet tube 207, but also of the additional current flowing through the channels 216 to the leading edge 213 of the downstream plate, where the additional current passes through the slot to enter the system at the boundary of the main current, so as to produce a current or fluid layer at the level of the undersurface of the plate 209. In addition Figure 5 shows molten glass passing down through the aperture 37 and forming a filament or stream which is carried down by the carrier jet into the main current, just downstream of the carrier jet.

The lai. tor enters the main current as show and in known manner creates a zone of interaction and a resultant gas current and the glass stream is attenuated into a fibre, as indicated in Figure 5. The additional current impinges against the upper boundary surface of the resultant current as show and· thus dynamically exerts a localised action which effects the flow of the resultant current. The apparatus Isas a number of such fibre forming stations spaced apart at intervals transversely to the main current. One channel 216 for additional gas is aligned with each secondary jet orifice 36 and the associated glass outlet orifice 37.

Wien a number of channels for additional gas is provided, the additional gas from the several channels tends to merge to form a more or less continuous sheet of gas flowing from the slot and along the undersurface of the downstream plate at the boundary of the resultant current. The glass, which is in the process of being formed into fibres, is thus prevented from coming into contact with the surface of tho downstream plate.

It should be noted that the presence of the gas pipe 214 and tho flow of additional gas over the surface of the downstream plate help to cool the plate, so that the action of the additional gas combines with the action of the cooling agent circulating through the pipe 211 to maintain the plate at a relatively low temperature. This also helps to prevent the glass from sticking to the plate.

In an installation in which a large number of fibre forming stations, for example about 80, are placed at intervals - 9 439°3 apart transversely to the current, the downstream plate is preferably divided up. This is illustrated in Figures 2 and 7, where, because of the large number of fibre forming stations, the downstream plate is in three parts, each with its own pipe 211 for cooling medium and pipe 214 for additional gas, and the corresponding pipe connections for the supply of water and air, respectively, as described above. When the plate is divided up in this way, efficient and accurate circulation of cooling'water is more easily achieved and accurate distribution of the supply of additional air is ensured. The operating conditions can therefore be kept to close tolerances. - Referring to the arrangement of secondary jets shown in Figures 1 to 8, the upstream plate 208 preferably forms an integral part of. the crucible '200. When the apparatus is used for glass compositions conventionally emptoyed in the manufacture of glass fibres, this plate is made of a platinum alloy, in order to ensure regularity of fibre formation at each fibre forming station. It is also important to observe precise upstream-downstream alignment of the secondary jet orifices 36 and the glass outlet orifices 37. This precise alignment may be automatically obtained by supplying the glass from a narrow slot rather than from a series of separately formed apertures, as indicated above. Precise alignment of tho secondary jets with the filaments of molten glass can also bo achieved by the arrangement shown in Figures 1 to 8, but in this case precision of alignment is obtained, in spite of the use of separate glass orifices, by making the upstream plate 20S an integral part ol' the crucible 200.

Since the apertures 36a for the secondary jets and the orifices for the glass are both formed in tho same piece of apparatus, precise alignment is obtained and preserved even when various parts of this piece of apparatus are subject to differing conditions of thermal expansion or contraction,.

Precision of alignment is moreover facilitated by other arrangements provided in the embodiment of Figures 1 to 8.

Ir Figures 2, 3, 4, 7 and 8 it can be seen that each secondary jet is emitted from a jet tube 207 which penetrates the aperture 36a, the diameter of the tube 207 being slightly smaller than that of the aperture 36a. The jet tubes 207 arc separated into four groups in Figure 2 and each group is mounted on a feed manifold 220 connected to a feed pipe 221.

By dividing up the total number of tubes 207 and mounting each group separately, a wider margin is allowed, for thermal expansion and contraction of the manifold 220 which supports and supplies each group, than would be possible if all the tubes were mounted on a single support for all the fibre forming stations. More margin for expansion and contraction is also allowed by using jet tubes 207 each of which penetrates a separate aperture 36a and using tubes having a slightly smaller external diameter than the diameter of the apertures. Grouping, arranging and mounting the jet tubes as described above so as to leave a margin for expansion and contraction is particularly important if, for example, the crucible 200 and upstream plate 208 are made of platinum alloy and the jet tubes and accessory parts are made of a less costly metal - ii 4SS0S such as stainless steel, since these different metals have different coefficients of thermal expansion and contraction.

As shown particularly in Figure 8, each group of jet tubes 207 together with the manifold on which it is mounted and the associated feedpipe 221 forms a unit resembling a rake which is mounted at the base of the feedpipe 221. As shown in Figures 1 and 2, the feedpipes 221 are connected to the burner 205 to produce the secondary gas jets and means are preferably provided for introducing air into the current of gas entering each feedpipe 22i. This intrcdi.ofcicn of air is achieved by an air supply unit 223 (see also Fig. 6) arranged between the combustion chamber 205 and the mounting plates 222 by which the feedpipes 221 for the groups of jet tubes are mounted. This unit 223, which dilutes the combustion gas and lowers its temperature as it leaves the burner 205 to a temperature compatible with the jet tubes, comprises air supply pipes 224 connected to tubes 225. Several of these supply pipes 224 are distributed along the whole length of the .diluter, and the tubes 225 cai'ry the air from the pipes 224 to channels 226. One channel 226 is provided for each group of secondary jet tubes. The jet tubes are thus supplied with the products of combustion from the burner 205 diluted with air from the pipes 224.

Referring now to Figures 2, 4 and 7 an additional secondary jet orifice 36 with secondary tube 207 has been provided at each end of the line of glass outlet apertures 37· This arrangement provides for uniform fibre forming action at the level of the glass outlet orifices at opposite ends of - 12 tlie line. In addition, a comparable arrangement for the channels supplying additional gas is provided. In other words, as can be seen from Figures 2, 4 and 7, a channel for supplying additional gas is placed in line with each end of the series of glass outlet apertures for reasons similar to those mentioned in connection with the supplementary orifices provided for the secondary jet.

A modified form of downstream plate and of means tor supplying the additional current are shown in Figures 1, 9 and 10. In this case, the downstream plate 227 has a conduit 228 for circulation of cooling medium, with feed connections 229, as well as with a conduit 230 for supply of air with feed connections 231. The channels 232 through which the additional air is carried from the conduit 230 are connected to the base of a slot 233 which has an edge directed towards the leading edge 234 and just above it.

This plate is mounted in the same general fashion in relation to the fibre forming stations as that described above with reference to Figure 1. The downstream plate of Figures 1, 9 and 10 is also adjustable for closing the gap between itself and the crucible, in a manner analogous to that indicated at 217 and 219 in Figures 1, 3 and 5· A slot like the slot 233 may be used to assist spreading out of the additional gas along the upstream edge of the plate and thus assist the formation of a sheet of additional gas over the lower surface of the plate which is exposed to the flow of the resultant current.

Another embodiment of the downstream plate and means of supplying additional gas is shown in Figure 11. In this £3903 ease, the lower part of the crucible 200 is of modified shape and the form of the downstream plate 234 is also modified so that it is adapted to the lower part of the crucible as will be described. The plate 234 contains a conduit 235 for cooling medium with feed connections 236. The conduit 237 for additional gas, which is supplied through feed connections 238, opens into channels 239 which communicate with a slot between the leading edges of the plate 234 and the lower part of the crucible. Fittings are provided between the plate and the crucible to ensure that the additional gas will flow in the desired direction and out through the slot.

Figure 12 shows'another embodiment foi* mounting the downstream plate, in which an upstream plate or shoulder 208 with apertures 36a, corresponding to the jet tubes 207, forms an integral part of the crucible 200, The construction of the downstream plate 209 is generally the same as that described above, The shape of the space between the plate and the crucible is different. Thus the plate is fitted with a’ metal band 240 which extends over the whole transverse length of the plate 209 and which together with the upper part of the plate forms the boundary of an elongate slot for the passage of the additional gas into the resultant current.

This arrangement is insulated against heat from tlie crucible by a layer of insulating material 241 on the wall 240. Such insulation, like the insulation 219· described eai-lier, is advantageous because it reduces heat loss from the crucible.

In all the embodiments described above, whenever jet tubes 207 are arranged in the apertures forming part of the - 14 crucible, it is desirable to provide for thermal insulation between the jet lubes and the apertures. Such insulation may be provided by covering the tubes with alumina, for example. Such insulation not only reduces the heat loss from the crucible but protects the metal of the jet tubes.

All the arrangements described above are equally applicable to an apparatus of the general type shown in Figure 1, in which the crucible is mounted under a fore-hearth 201 from which molten glass is supplied. The crucible is insulated 1C from the structure supplying the glass by a ceramic element 242 containing a tube 243 for cooling medium (Figs. 1 and 2). Insulation in the form of fibrous material may also be used as indicated at 244 to cover the lower part of contiguous surfaces of the fore-hearth to reduce heat loss in this zone.

It is advantageous in some cases to provide electric resistance elements 245, connected to the extremities of the crucible 200, as a means of heating it.

Figures 13 and 14 show another embodiment for supplying the additional air. In this embodiment, the fore-hearth for supplying the glass is 246 and the crucible with a spinneret in its lower part is 247. The glass supply apertures are indicated by 37 and in this embodiment the secondary jets are supplied through orifices formed in projections 248 extending from the manifold 249 for supplying tho jots. A feed tube 250 is connected to the manifold 249.

The main current 12A is generated by the burner 251, the upper boundary of the main current being close to the secondary jet orifices 36 and glass outlet orifices 37.

A downstream plate unit 252 is situated, downstream of the orifices 37. This unit is hollow and contains a manifold. 253 supplied by a pipe 254. The manifold has numerous extensions 255 witli orifices 256 for emission of additional air in a position which in relation to the direction of flow of the main current is downstream of the fibre forming station formed by the glass outlet ahd secondary jet orifices.

As can be seen in Figure 14, the jet orifices, glass outlet orifices and additional gas current orifices are arranged in groups and are in alifcr-me«i in the flow direction. Each group constitutes one.fibre forming station.

The additional gas current may have a pressure of the order of 0.5 to 2 bars and preferably from 0.8 to 1.2 bars.

In an apparatus having 80 fibre forming stations as shown in Figures 1 to 8, the air current used for the additional gas may be supplied at a rate of from 15 to 30 Nnr per hour and preferably between about 17 and 25 Nm.

The kinetic energy per unit volume of additional gas current is considerably lowei- than that of the secondary jet.

Under Subsection (1) of Section 14 of. the Patents Act, 1964, attention is drawn to Patent No. 39070.

Claims (33)

1. A process for making fibres from attenuable material comprising:- generating a main gaseous blast; directing a secondary a gaseous jet transversely thereof, the crosssectional area of the jet being less than that of the blast and its kinetic energy per unit of volume being greater than that of the blast so that the jet penetrates the blast so as to give rise to a zone of interaction; delivering a stream of attenuable material into the said zone in which it is attenuated; and delivering an additional gaseous current into contact with the flow resulting from the blast and the secondary jet.

2. A process according to claim 1 wherein the additional gaseous current is applied so as to reduce the tendency for attenuable material to adhere to structure adjacent the path of fibre movement.

3. A process according to claim 1 or claim 2,wherein the attenuable material is delivered in a position which, with reference to the direction of movement of the main blast, is downstream of the secondary jet.

4. A process according to any preceding claim wherein the additional gaseous current is introduced into the blast, in a position which, with reference to the blast, is downstream of the point of introduction of the attenuable material. -17 43903

5. A process according to any preceding claim wherein the additional gaseous current contacts the said resulting flow in the immediate vicinity of the stream of attenuable material.

6. A process according to any preceding claim wherein the additional gaseous current flows along a surface extending downstream of the zone of introduction of the attenuable material.

7. A process according to any preceding claim wherein 0 a plurality of secondary gaseous jets are directed transversely of the main blast to give rise to zones of interaction.

8. A process according to claim 7 wherein a plurality of streams of attenuable material, equal in number to the secondary gaseous jets, are delivered to the zones of inter5 action,

9. A process according to any preceding claim wherein the attenuable material is molten glass.

10. Apparatus for making fibres from attenuable material comprising:- means for generating a main gaseous blast; means ) for directing a secondary gaseous jet of smaller size that; the main blast transversely of the blast so as to penetrate it and give rise to a zone of interaction, the kinetic energy per unit of volume' of the jet being greater than that of the blast; supply means for delivering attenuable material so ί that it will enter the'said zone; and means for delivering an additional gaseous current into contact with the flow resulting from the blast and the secondary jet. -1843903

11. Apparatus according to claim 10 wherein the means for delivering the additional gaseous current has an outlet directing the current to the boundary of the said resulting flow downstream of the said zone with respect to the direction of movement of the blast.

12. Apparatus according to claim 10 or claim 11 wherein the means for delivering the additional gaseous current is arranged so that the latter contacts the said resulting flow in the immediate vicinity of the location where the attenuable material enters the said zone.

13. Apparatus according to any of claims 10 to 12 comprising a plate extending downstream of the location where the attenuable material enters the said zone, the plate being arranged so that the additional gaseous current flows in contact with it.

14. Apparatus according to claim 13 wherein the means for supplying the attenuable material has at least one supply orifice situated downstream of the location where the jet penetrates the blast with respect to the direction of movement of the blast, and wherein the means for delivering the additional gaseous current into the said resulting flow directs the gas downstream of the supply orifice near the upstream edge of the plate.

15. Apparatus according to claim 13 or claim 14 wherein the plate contains a gas supply pipe for the additional gaseous -193903 current provided with at least one channel or outlet directed towards the leading edge of the plate and delivering the gas in the region of the upstream edge.

16. Apparatus according to any of claims 13 to 15 includ; ing means for directing a plurality of secondary gaseous jets transversely of the main blast, wherein a plurality of spaced supply orifices each delivering a stream of the attenuable material is arranged transversely to the main blast, the means for directing secondary jets discharging.each jet -° upstream of each supply orifice, and wherein the means for delivering the additional gaseous current comprises. a slot extending along the supply orifices and directing the gas to the upstream part of the plate.

17. Apparatus according to claim 16 wherein the .5 individual channels or outlets of the plate are disposed between the gas supply pipe for the additional gaseous current and the slot, each channel or outlet being downstream of a respective supply orifice,

18. Apparatus according to any of claims 13 to 15 !0 including means for directing a plurality of secondary gaseous jets transversely to the main blast wherein a plurality of spaced supply orifices each delivering a stream of the attenuable material is arranged transversely to the main blast, the means for directing secondary jets discharging each jet :5 upstream of each supply orifice, and wherein the outlet for the additional gaseous current is near the upstream edge of the plate and comprises several spaced orifices downstream - 2043903 of each supply orifice.

19. Apparatus according to any of claims 13 to 18 wherein the plate has a conduit for circulation of a cooling fluid.

20. Apparatus according to any of claims 10 to 19 comprising a structure at one side of the main blast with a wall adjacent the boundary of the blast, the means for directing a secondary jet delivering the jet into the blast transversely through the structure.

21. Apparatus according to claim 20 having means for introducing a plurality of secondary jets through the structure into the blast and upstream of spaced supply orifices for the attenuable material which orifices are disposed transversely of the blast, and wherein the means for delivering the additional gaseous current downstream of the attenuable material includes a slot or a plurality of separate, spaced orifices.

22. Apparatus according to any of claims 10 to 21 wherein the or each secondary jet is directed from a gas discharge tube disposed within an aperture in a wall which forms a boundary to the main blast.

23. Apparatus according to claim 22 having a plurality of secondary jets, wherein the tubes are in groups, means being provided for assembling the tubes of each group and for feeding each group separately, the several assembly and feed means being expansible and contractible independently. _ 21 4 3 9 0 3

24. Apparatus according to claim 22 or 23 wherein the wall adjacent the boundary of the blast and the outlet for the attenuable material form an integral structure.

25. Apparatus for making fibres from attenuable material 5 comprising:- means for generating a main gaseous blast; a plurality of fibre forming centres associated with the main blast and spaced from one another transversely thereof, each centre being associated vzith supply orifice means for the material and the centres having a structure with a common LO wall adjacent a boundary Of the main blast and equipped with a plurality or apparfares each si euated, in rel .'iioa ts the main blast, in a position upstream of a corresponding material supply orifice; and means for directing a separate gaseous secondary jet through each aperture comprising a L5 gas discharge tube penetrating each aperture of the said structure to introduce a secondary jet into the blast.

26. Apparatus according to claim 25 wherein the supply orifice means comprises a supply orifice at each centre.

27. Apparatus according to claim 25 or claim 26 comprising !0 means for delivering at least one additional gaseous current into contact vzith the flow resulting from the blast and the secondary jets.

28. Apparatus according to any of Claims 25-27 wherein the gas discharge tubes are in groups, means being provided !5 for assembling the tubes of each group and feeding each group separately, the several assembly and feed means being capable of expanding and contracting independently.

29. Apparatus according to any of Claims 25-28 wherein the common wall and the supply orifice means for attenuable 43Sos material form an integral structure.

30. Apparatus according to any of claims 22,23 or 24 or any of claims 25 to 29 wherein each tube is enclosed in a layer of thermal insulating material at the level of 5 the apertures in the wall.

31. Apparatus according to any of claims 10 to 24 or 25 to 29, or claim 30 as dependent on any of claims 10 to 24 or 25 to 29, comprising an electric resistance heated container for supply of molten attenuable material-. 10

32. A process for making fibres from attenuable material substantially as herein described with reference to the accompanying drawings.

33. Apparatus for making glass fibres constructed and arranged substantially as herein described and shown in the 15 accompanying drawings.