CA1074562A - Stream feeder with increased heat transfer capacity - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An electrically heated stream feeder for producing glass filaments comprising a chamber having an opening for supplying glass marbles for conversion to a molten body, a bottom wall for the chamber having orifices for discharging molten glass as streams, upstanding sidewalls for the chamber where the interior surface of at least one of the upstanding walls has raised portions to provide increased surface area for heat transfer, and a perforated heating strip extending across the chamber in spaced relation above the bottom wall, such heating strip including at least a portion inclined downwardly to one of the upstanding walls to urge unmelted marbles towards such wall.

Description

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One type of glass filament forming process uses an electrically heated stream feeder that is fed glass marbles.
The heated feeder melts these marbles into a body of molten glass primarily by ~onduction and radiation and discharges the molten glass as streams. Mechanical or fluid means attenuates the streams into glass filaments.
Competition in glass filament products demands a great deal from marble melting stream feeders. Economic conditions call for marble melting stream feeders that provide increased molten glass throughput to increase glass filament production.
Further a moredemanding communityof glassfilament productusers calls for filament size uniformity in products.
The goals of both increased production rates and filament size uniformity from marble melt stream feeders conflict with each otherO Of course, more feeders will increase glass filament production, but these feeders are normally made from expensive platinum alloys. Therefore greater melting capacity for smaller conventional sized stream feeders presents a more attractive choice.
Melting glass marbles by a stream feedex is a complex and sensitive operation that directly affects the quality of glass filaments produced, especially at higher production rates.
For example, introduction of glass marbles to a feeder has a chilling effect that disturbs the temperature pattern of molten qlass in the feeder. This disturbance causes viscosity vari-ations in the molten glass streams discharged from the feeder.
These viscosity differences produce glass filaments having undesirable nonuniform diameter variations along their lengths.
These nonuniformities tend to become even more pronounced with attempts at higher production rates.

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It is an object of the present invention to obviate or mitigate the above disadvantages.
According to the present invention there is provided a feeder forsupplying moltenheat softenedmineral materialin streams toproduce filamentscomprising, abottom wallhaving at least oneopening throughwhich moltenmaterial inthe feederis discharged asa streamthe feederincluding opposedwalls, atleast one ofwhich hasa corrugatedregion toprovide anincreased surface area insuch region for heat transfer; the feeder being adapted for connection to means for heating the same.
An embodiment of the invention will now be described by way of example only with reference to the accompanying draw-ings, in which: -Figure 1 is an isometric view of a glass marble melt-ing stream feeder. The feeder is illustrated with an internal melting strip or element sloping downwardly towards the end walls and with sidewalls having corrugated upper portions.
Figure 2 is an end elevation of the feeder shown in Figure 1. Below the feeder is a blower that directs gaseous blasts to attenuate glass filaments from molten glass streams emitted from the feeder. The blower is shown in section.
Figure 3 is a front elevation of the feeder and blower of Figures 1 and 2.
Figure 4 is a section of the heating element in the feeder of Figures 1-3. The size of the element is compared with one of the marbles supplied to the feeder.
Figure 5 is a showing of the general marble and molten glass movement at the heating element in the feeder shown in Figures 1-3 during marble melting in filament forming operations.
Figure 6 is a front elevation of glass marble melting stream feeder like the one shown in Figures 1-3 except for the

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1074~;62 heating element. The feeder of Figure 6 has a sloplng heating ele~
ment formed b~ two perforated flat planar portions.

Figure 7 is an end elevation of a glass marble melting stream feeder like the one shown in Figures 1-3 except for the heating element. The feeder of Figure 7 has a perforated flat heating element.
Figure 8 is an isometric view of a glass marble melting stream feeder like the one shown in Figures 1-3 except for the sidewall construction. The feeder of Figure 8 has vertical sidewalls that are fully corrugated.
Figure 9 is an isometric view of a glass marble melting stream feeder like the one shown in Figures 1-3 except for the end walls. In Figure 9 each of the end walls of the feeder has an upper corrugated portion.
Figure 10 is an isometric view of a glass marble melting stream feeder like the feeder shown in Figures 1-3 except for the sidewall construction. The feeder of Figure 10 includes sidewalls each having a lower corrugated portion below the heating element or strip. The corrugated portions have rounded ridges and grooves running vertically.
Figure 11 is a front elevation of a stream feeder like the one shown in Figure 7 except for the sidewall con-struction. The feeder of Figure 11 has sidewalls with small corrugated temperature control patches.
Figure 12 is an isometric view of a portion of a feeder wall.
Figure 13 is an isometric view of a portion of another feeder wall.
Figure 14 is an isometric view of a portion of a feeder wall and heating element.

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Figure 15 is an isometric Yiew of a portion of still another feeder wall.
The method and apparatus of the irlvention are particularly ~aluable in processes for forming filaments of heat-softenable mineral material such as glass, but the inven-tion is also useful in operations for forming filaments from other thermoplastic filament forming material such as nylon, polyester and polyethylene.
Figures 1-3 show a glass filament forming operation including an electrically heated glass marble melting stream feeder 10 including a heating element or strip 12 and upstand-ing sidewalls 14.
The stream feeder 10, which is made of electri-cally conductive and high temperature resistant material such as an alloy of platinum, discharges molten glass as streams 16. Gaseous blasts from a slotted blower 18 imme-diately below the feeder 10 attenuates the molten glass streams 16 downwardly into glass filaments 20.
A chute 24 guides glass marbles 26 to the feeder 10 for melting through a supply passageway or opening 28 in the roof or top wall 30 of the feeder 10. As shown in Figures 1-3 an upstanding tubular member 32 on the roof 30 defines the marble supply opening 28.
The chute 24 connects to a suitable source of marbles, such as marble holding hoppers, which are not shown in the figures.
The feeder 10 includes: the top wall 30, vertical sidewalls 14,converging sidewalls36, a bottom wall 38 and ~ 4 11)7456Z

vertical end walls 40. These walls define a generally rectangular chamber 42 within the feeder.
The bottom wall 38 has orifice openings or passage- -ways for delivering the streams 16 of molten glass from the feeder 10. As shown one straight row of depending orificed projections or tubular members 44 form the orifice openings.
Electric terminals 46 are on the end walls 40 of the feeder 10. These terminals connect to a source of electrical energy effective to heat the feeder 10 by conventional resistance heating. The electrically heated feeder 10 melts glass marbles 26 supplied to it to form a body of molten glass.
The molten glass is discharged through the orificed projections 44 of the feeder 10 as the streams 16.
The slotted blower 18 is an assembly that includes opposed blower halves 50 and 52. Each of these halves includes a row of jet or nozzle openings which are supplied withsuitable fluidunder pressure (for example, steam, air or other gaseous blowing media) from a source through a supply tube (such as supply tube 56 shown in Figure 3). The blower 18 xeleases the blowing fluid as downwardly directed blasts effective to attenuate the streams 16 downwardly into the filaments 20. U.S. Patent 2,206,060 describes a suitable blower for use in attenuating the streams 16.
In practice refractory material surrounds the feeder 10 to reduce heat loss during filament forming operations~ but for ease of discussion and illustration the figures do not show the refractory.
The heating strip 12 is joined to the walls within the feeder 10 and is for melting the glass marbles. The heating strip 12 extends across the interior of the feeder 10 in spaced ,.,; .

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relation above the bottom wall 38. Therefore the strip 12 divides the chamber 42 of the feeder into an upper space or region 60 and a lower space or region 62. The upper region 60 is a melting chamber; the lower region 62 is a reservoir chamber for molten glass. Molten glass in the lower chamber 62 leaves the feeder through the orificed projections 44 to emerge as the streams 16.
The heating strip 12, like the walls of the feeder 10, is normally made of an alloy of platinum. The strip is dimen- t 10 sioned relative to the walls of the feeder so that when the feeder 10 is electrically energized, the heating strip 12 becomes hotter than the feeder walls.
The heating strip 12 rests on support members 64 and hanger 66 provides support for the heating strip 12 from above.
The heating strip 12 is spaced a sufficient distance below the outlet orifice 68 of the marble supply opening 28 that the marbles 26 can accumulate in stacked relationship above the strip 12. Normally this distance is from 3-5 marble diameters below the marble outlet orifice 68.
The shape of the heating strip 12 is formed to define two side-by-side parallel extending elongated channels 70 and 72 of the same dimensions running lengthwise within the feeder 10. The heating strip 12 includes two portions 74 and 76, each sloping downwardly away from each other from the strip's mid-region 78 tdirectlY under the marble outlet orifice 68) to the end walls 40 60 that the elongated channels 70 and 72 each include two inclined sections, sections 80 and 81 and sections 82 and 83 respectively. The downwardly sloped or inclined portions of the heating strip 12 urge the glass marbles 26 along the channels 70 and 72 away from the center region 78 10745~;~

of the strip 12 towards the end walls 40 during melting.
The strip 12 is perforated to have small openings 86 so thatmolten glassfrom meltingmarbles abovethe strip12 can flow downwardly into the lower reservoir section 62. The openings 86 are small enough so that molten glass moving through them is at desired filament attenuation viscosities (temperatures). The smallness of the openings 86 discourages higher viscosity portions of the marbles 26 from moving downwardly into the lower reser-voir section 62. Normally the openings 86 are in the range of from 1/16 to 1/32 of an inch for a normal operating temperature range of from 2350 to 2450 degrees F used in most blower attenuation processes.
The channels 70 and 72 are curved at their bottom regions. As shown the bottom regions are formed with a hemi-spherical curve having a diameter substantially equal to the diameter of the marbles 26 supplied to the feeder 10. This relationship is shown in Figure 4. As shown the channels become progressively larger towards their upper regions. The width dimension of the channels is denoted by the reference letter M. M is normally from 15-25 percent larger than the diameter of the bottom regions of the channels. In practice, it has been found useful at times to make the diameter of the curved bottom region a little larger than the diameter of the marbles 26 supplied to the feeder 10; preferably the diameter is not more than 15 percent larger than the diameter of the marbles.
The depth or height H (Figure 4) of the channels 70 and 72 is shown larger than the diameter of the marbles supplied to the feeder.
Since the marbles 26 accumulate in stacked relation .;

1074S~2 above the heating strip 12 during melting, marbles nearer the bottom of the stack (closer to the heating strip 12) are hotter, Therefore they melt before the marbles higher in the stack. The marbles become hotter and hotter as they move progressively down-wardly in the stack. Fusin~ or merging of adjacentmarbles begins to occurunder the intense heatin the feeder. Therefore theytake on more the form of a molten body of glass with regions of higher and lower viscosities. Finally a homogenous refined body of molten glass forms in the region immediately above the lower regions of the channels 70 and 72 of the heating strip 12 and the molten glass flows through the strip 12 to the reservoir section 62 below.
As the nonhomogenous body of glass moves into the channels 70 and 72, it comes under the concentrated influence of radiation from the strip 12. The surface portions defining each of the channels combine to concentrate their radiation in their respective channel so that refinement of the glass occurs.
Also, the curved channel shape and dimensions of the heating strip 12 promotes melting that provides a molten glass body of uniform viscosity.
The inclined disposition of the heater strip 12 (portions 74 and 76) urges marbles towards the hotter melting regions nearer the end walls 40. As the unmelted marble portions in and immediately adjacent the channels continue to melt, they move lengthwise of the channels 70 and 72 towards the end walls 40. The weight of marbles in the stack above the heating strip 12 assists marble movement lengthwise of its chan-nels. The unmeltedmarble portionsbecome smallerand smalleras they move towards the end walls 40. Thus a substantial portion of final glass refinement occurs at the lower ends of the channels ~, ~

~--)74S62 70 and 72 nearer the end walls 40. Figure 5 indicates with arrows general marble and molten glass movement in the feeder 10 during melting.
The inclination of the heating strip 12 is preferably such that it effects small marble shifts in the stack during melting that occur at closely spaced intervals. This gradual, ~athe~ substantially continuous, movement of marbles downwardly during melting effects a slow introduction of marbles 26 into the feeder 10. This results in increased thermal stability throughout the entire feeder 10. This means that molten glass of substantially the same viscosity (temperature) is provided during filament forming operations.
A slope of from 10 to 12 degrees below the horizontal (Angle A in Figure 2) has given good results for feeders like the one shown in Figures 1-3 having: a depth between 7 and 8 inches (D in Figure 2); a length between 7 and 8 inches (L in Figure 2) and a width of between 2 and 3 inches (W in Figure 2).
The slope (Angle A) generally needs to be larger for ~igger feeders requiring longer inclined heating strip portions.
It is preferred that a feeder including a heating strip has at least a portion of the heating strip sloping downwardly to an upstanding wall of the feeder to urge mineral material, such as unmelted glass portions, towards the upstanding wall. For example, Figure 6 shows another embodiment of the invention. A glass marble melting stream feeder 90 has a heating strip 92 in spaced relation above the bottom wall 94. The strip 92 includes two perforated planar portions 96 and 98 each inclined downwardly away from the .-~
other portion to the end walls of the feeder.
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The embodiment shown in Figure 6 might be modified to include a heating strip comprising two perforated planar portions each inclined downwardly awayfrom theother portion to the sidewalls of a feeder (see Figure 9) or a heating strip might be used having two generally opposed pairs of perforated members where each of the pairs is inclined downwardly from an apex region away from its generally opposed portion to an up-standing wall (sidewall or end wall). Such a heating strip would have a pyramid-like shape.
Referring again to Figures 1-3, the sidewalls 14 of the feeder 10 each includes a corrugated portion 100 above the heating strip 12 to provide increased heat transfer surfaces for the melting region 60. The corrugated portions 100 have corrugations that include elongated curved ridges 102 and grooves 104 oriented to extend between the end walls 40. The ridges 102 and grooves 104 are shown ex~ending in a direction parallel to the bottom wall 38.
The lower portions 108 of each of the sidewalls 14 are straight or planar.
The corrugated portions 100 of the sidewalls 14 draw more electric current during energization of the feeder 10.
This occurs because the cross sectional area of the corrugated portions 100 is larger in the direction of current flow twhich is between the terminals 46) than the noncorrugated lower portions 108. Since a conductor (or conductor portion) that has a greater cross sectional area provides less resistance per unit length, more electric current flows through the corrugated portions 100 than the lower portions 108 during operation of the feeder 10.

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~074562 The thickness of the sidewalls below the heating strip 12 is shown uniform throughout but it may be advantageous to vary the thickness of the wall in this region to obtain a desired heat pattern. For example, the wall 14 may be pro-gressively thicker at its lower regions below the heating strip 12.
In practice the corrugated portions 100 of the side-walls 14 are heated by electric current to substantially the same temperature as the lower planar portions 108, but provide more heat to the upper marble melting chamber 60. The interior heat transfer surfaces of the corrugated portions 100 are larger than the interior surface of the planar portions 108 because of the ridges 102 and grooves 104 and so more heat is transferred to the glass in the melting chamber 60 by the corrugated portions 100. The amount of heat can be con-trolled by the size and number of the ridges 102 and grooves 104. In practice grooves having a depth h (Figure 2) of from 1/8 to 1/2 inch have given good results where the ridges are spaced apart a distance d (Figure 2) of from 1/2 to 1 inch and the wall thickness is about .030 of an inch Figure 6 shows the feeder 90, which is like the feeder 10 except for the heating element 92.
Figure 7 shows a glass marble melting stream feeder 120 that is like the feeder 10 except for its hèating strip.
Feeder 120 has a perforated flat heating strip 122 disposed parallel to the bottom wall 124. The uniformly thick sidewalls 126 each have an upper corrugated sidewall portion 127 that extends from the top of the feeder 120 downwardly to the upper surface of the heating strip 122. The elongated ridges and grooves of the corrugated portions 127 extend between the end . JJ

walls 128 in a direction parallel to the bottom wall 124, Figure 8 shows another feeder, feeder 130~ Feeder 130 is like the feeder 10 except for its upstanding sidewalls 132. These sidewalls, which have a uniform thickness, are corrugated their entire height, Its rounded ridges 134 and grooves 136 run parallel to the botto~ wall 138 just like the ridges 102 and grooves 104 of feeder 10, The corrugations provide a greater heat transfer surface for both the upper melting region and the lower reservoir region of the feeder 130. Therefore for the same wall temperature ~ore heat is transferred to glass in the feeder 130 than would occur with a feeder having planar upstanding sidewalls.
Figure 9 illustrates another glass marble melting stream feeder, feeder 140. This feeder includes uniformly thick vertical sidewalls 142 that are like the sidewalls 14 of the feeder 10. That i5 the upstanding sidewalls 142 each have an upper corrugated portion 144 for the upper marble melt-ing chamber or region just like the feeder 10. Additionally, the feeder 140 has end walls 146 each with an upper corrugated portion 148 for the melting region. The corrugated portions 144 and 148 are from the top wall 149 downwardly along their respective sidewalls and end walls to the upper surface of the feeder's perforated heating strip 150. The corrugated por-tions 144 and 148 have elongated rounded ridges 152 and 154 respectively separated by elongated grooves 156 and 158 res~
pectively; these corrugations are the same size and extend parallel to the bottom wall 160.
The heating strip 150 includes two inclined portions 162 and 164. These portions ~re inclined downwardly to the ~ 12 . .. : ~,,, . . ". ~, , .

sidewalls 142.
Terminals 166 are on the end walls 168.
The corrugated portions 144 draw more electric current than the lower remainder and planar portions of the sidewalls 142 because the corrugated shape of the wall provides a larger cross sectional area in the direction of current flow. The ridges 154 and grooves 158 of the corrugated portions 148 extend across the direction of current flow between the terminals 166 and across the top wall 149. Therefore the corrugated 10 configuration presents increased conductor length (not increased .
cross section). Sinceincreased lengthincreases resistancethere is consequently, less electric current flow between the terminals 166 through the top wall 149 than between the terminals 166 through the portions 144.
It canbe seentherefore thatfeeder wallscan be configured to control flow of electric current and to provide an increased internal heat transfer surface.
Figure 10 shows still another glass marble melting stream feeder, feeder 180. Feeder 180 has uniformly thick planar end walls 182 with terminals 184 and uniformly thick vertical side-.walls 186,each having a corrugatedportion 188. The elongatedrounded ridges 190and grooves 192 of the corrugatedportion 188 run in a directionnormal (vertical) to the bottom wall 194 of the feeder 180, so that the corrugated portions 188 like the corrugated endwall portions148,discourage flow of electriccur-rent between the terminals 184. Hence the upper planar wall por-tions 196Of the sidewalls186 drawmore current;therefore,they are heated to a higher temperature than the corrugated portions 188.

-~74S62 The feeder 180 is shown with a planar heating strip 198 that extends in a plane parallel to the bottom wall 194.
Figure llillustrates another glass marble melting stream feeder. A mar~lemelting streamfeeder 200is shown having: upstanding sidewalls 202, terminals 204 on the end walls and a perforated flat horizontal heating strip 206. The sidewalls 202 each have a corrugated patch or region 208 below the heating strip 206.
The rounded ridges 210 and grooves 212 of the corrugated patches 208 extend in an oblique fashion, that is more vertically oriented than horizontal. Therefore the patches 208 present a greater resistance to electric current flowing between the terminals 204 through the sidewalls 202. Hence, during filament forming operations the patches 208 would tend to be cooler than the surrounding regions of the sidewalls 202. Of course, the amount of slope for the ridges ~10 and grooves 212 can be modified to obtain the degree of resistance desired for current flowing between the terminals 204 through the sidewalls 202.
For example, ridges 210 and grooves 212 can be disposed horizon-tally to minimize resistance, under this disposition of thecorrugations the patches 208 would tend to become hotter than the surrounding regions of the sidewalls 202.
Hence, it is apparent that wall portion patches can be used to make minor temperature variations at desired regions of a stream feeder to control glass temperature.
Figure 12 illustrates a wall portion 220 for a stream feeder like those shown in the figures. The portion 220 has a planar exterior surface 222 and a corrugated interior surface 224 with elongated rounded ridges 226 and grooves 22~.
Like the other corrugated wall portions of stream feeders .,' ' ''~

10 7~S~;2 discussed herein, a wall configured like the portion 220 provides a larger heat transfer surface,but unlike the other corrugated wall portions the thickness of the wall varies.
Figure 13 illustrates a wall portion 230 for a stream feeder like those discussed. The portion 230 has a planar exterior surface 232 and an interior surface 234 having spaced apart tapered blade-like ridges 236 and grooves 238.
The ridges and grooves of the wall portions 220 and 230 can be oriented as discussed in relation to the corrugated wall portions of the stream feeders discussed herein.
Figure 14 illustrates a wall portion 240 and a heating strip 242 for a stream feeder like those discussed. The wall portion has a uniform thickness and is corrugated, but the corrugations 244 (ridges and grooves) above the heating strip 242 are larger than the corrugations 246 (ridges and grooves) below the strip 242. This type of wall can be used on a stream feeder like the feeder 130 shown in Figure 8. The corrugations below the heating strip are associated with the reservoir region of the feeder and the corrugations above are associated with the 20 marble melting region. Therefore more heat is transferred to `
material in the melting region of the feeder.
Figure 15 shows a wall portion 250 for a stream feeder like those disclosed herein. The portion 250 has a planar exterior wall surface 252 and an interior wall surface 254 having discrete raised portions 256 shown as cube-like projections.
These projections provide a greater heat transfer surface.
A stream feeder including walls with raised portions provides increased surface area for heat transfer, which is extremely important in converting mineral material, such as glass marbles, to a heat-softened condition. Cold mineral ~ 15 -~074562 f material in the form of marbles can send thermal shudders through a bushing. But increased heat transfer capacity from increased interior surface areas can in a real sense overcome these tendencies to thermal changes. More uniform temperatures, and hence viscosities, are kept throughout filament forming operations.
While the apparatus disclosed herein has shown feeders for melting glass marbles other forms of material might be supplied. For example, glass portions such as cullet or raw batch material might be supplied to feeders.

Claims (23)

The embodiments of the invention in which an exclusive property or privilege is claimed are de-fined as follows:-

1. A feeder for supplying molten heat softened min-eral material in streams to produce filaments comprising, a bottom wall having at least one opening through which molten material in the feeder is discharged as a stream said feeder including opposed walls, at least one of which has a corrugated region to provide an increased surface area in such region for heat transfer; said feeder being adapted for connection to means for heating the same.

2. A feeder for supplying molten heat softened min-eral material in streams to produce filaments comprising, a bottom wall having openings through which molten material in the feeder is discharged as streams for attenuation into filaments, joined together opposed walls extending generally normally away from the bottom wall, at least one of the walls having a corrugated region to provide an increased surface area in such region for heat transfer; said feeder being adapted for connection to means for heating the same.

3. A feeder for supplying heat-softened mineral material in a filament forming condition com-prising: a chamber having an opening for supplying un-melted mineral material for conversion to a flowable heat-softened body; a bottom wall for the chamber having at least one orifice for discharging the heat-softened material as a stream; opposed end walls and sidewalls for the chamber at least a portion of one of which has a corrugated region extending bet-ween the end walls to provide an increased surface area for heat transfer,said feeder being adapted for connection to means for heating same.

4. A feeder for supplying heat-softened min-eral material in a filament forming condition comprising:
a chamber having an opening for supplying unmelted mineral material for conversion to a flowable heat-softened body; a bottom wall for the chamber having at least one orifice for discharging the heat-softened material as a stream; joined together upstand-ing opposed end walls and sidewalls for the chamber ex-tending generally normally away from the bottom wall, at least a portion of one of the opposed sidewalls having a corrugated region extending between the end walls to provide an increased surface area for heat transfer; and means for heating the feeder.

5. The apparatus of claim 4 further including a perforated heating strip extending across the interior of the feeder in spaced relation above the bottom wall and wherein said at least one corrugated region is located in spaced rela-tion further above the bottom wall than the heating strip.

6. An electrically heated feeder for supplying streams of molten heat softened mineral material comprising an electrically conductive bottom wall having orifices for dischar-ing molten material as streams; a first pair of spaced apart opposed electrically conductive walls, each of the walls extending generally normally away from the bottom wall;
a second pair of spaced apart opposed electrically con-ductive walls, each of the second pair of walls extend-ing generally normally away from the bottom wall and joined to the first pair of walls; and a terminal for electric current attached to each of the first pair of walls, at least one of the second pair of walls having a corrugated portion of uniform wall thickness extending between the first pair to provide an increased surface area for heat transfer.

7. The feeder of claim 6 in which the cor-rugations extend in a direction parallel to the bottom wall.

8. The feeder of claim 6 in which the cor-rugations extend in a direction generally normal to the bottom wall.

9. The feeder of claim 6 in which at least one of the first pair of walls includes corrugations extending between the second pair of walls in a direc-tion generally parallel to the bottom wall.

10. An electrically heated feeder for supply-ing streams of molten glass comprising: opposed spaced apart electrically conductive sidewalls; opposed spaced apart electrically conductive end walls that are joined to the sidewalls; an electrically conductive bottom wall joined to the sidewalls and the end walls, the bottom wall having orifices for discharging molten glass as streams; an electrically conductive top wall joined to the side and end walls, the top wall including a supply opening through which glass marbles are provided to the interior of the feeder; a perforated electrically con-ductive heating strip extending across the interior of the feeder in spaced relation above the bottom wall to divide the interior into an upper marble melting region and a lower reservoir region for holding molten glass formed from the marbles; and electric terminals on the end walls through which electric current is supplied to the feeder, the sidewalls being uniformily thick through-out and each having an internal corrugated surface of spaced apart elongated ridges and grooves extending in a direction generally parallel to the bottom wall above the heating strip to provide increased internal heat transfer surface for glass in the upper glass melting region of the feeder.

11. The feeder of claim 10 in which the elon-gated ridges and grooves are rounded.

12. The feeder of claim 10 in which the elon-gated ridges and grooves extend the entire distance be-tween the end walls.

13. The feeder of claim 10 further including end walls each having above the heating strip an internal corrugated surface with spaced apart elongated ridges and grooves extending in a direction generally normal to the bottom wall.

14. The feeder of claim 13 in which the elon-gated ridges and grooves on the internal surfaces of the sidewalls and end walls are the same size.

15. The feeder of claim 10 in which the side-walls below the heating strip each have an internal corrugated surface with spaced apart elongated ridges and grooves extending between the end walls and in a direction generally parallel to the bottom wall.

16. The feeder of claim 15 in which the elon-gated ridges below the heating strip are smaller than the elongated ridges above the heating strip.

17. Apparatus for producing filaments of heat softened mineral material comprising: a feeder for supplying streams of molten material including opposed spaced apart electrically con-ductive sidewalls, opposed spaced apart electrically conductive end walls that are joined to the sidewalls, an electrically conductive bottom wall joined to the sidewalls and end walls, the bottom wall having orifices for discharging molten material as streams, an electrically conductive top wall joined to the side and end walls, the top wall including a supply opening for supplying marbles of material to the interior of the feeder, a perforated electrically conductive heating strip extending across the interior of the feeder above the bottom wall dividing the interior into an upper melting region and a lower reservoir region for holding molten material formed from the marbles, electric terminals on the end walls through which electric current is supplied to the feeder, the sidewalls being corrugated above the heating strip with elongated ridges and grooves extending between the end walls in a direc-tion parallel to the bottom wall to provide increased heat to material in the upper material melting region of the feeder during heating of the feeder; and means for attenuat-ing the streams into filaments.

18. The apparatus of Claim 17 in which the means for attenuating the streams into filaments is a blower for releasing blasts of fluid media.

19. A feeder for supplying heat-softened mineral material in filament forming condition compri-sing: a chamber having an opening for supplying un-melted mineral material for conversion to a flowable heat-softened body; a bottom wall for the chamber having at least one orifice for discharging the heat-softened material as a stream; joined together upstand-ing opposed end walls and side walls for the chamber extending generally normally away from the bottom wall, the interior surface of at least one of the opposed sidewalls having elongated blade-like raised portions extending in a direction generally parallel to the bottom wall to provide an increased surface area for heat transfer; and means for heating the feeder.

20. A feeder for supplying heat-softened mineral material in a filament forming condition com-prising: a chamber having an opening for supplying un-melted mineral material for conversion to a flowable heat-softened body; a bottom wall for the chamber having at least one orifice for discharging the heat-softened material as a stream; opposed end walls and sidewalls for the chamber at least a portion of one of which has a corrugated region extending bet-ween the end walls to provide an increased surface area for heat transfer, and a perforated heating strip extending across the interior of said feeder in spaced relationship above said bottom wall.

21. A feeder as claimed in claim 20 in which said perforated heating strip is inclined relative to said bottom wall so that the distance thereof above said bottom wall varies.

22. A feeder as claimed in claim 21 in which said heating strip is at a maximum distance from said bottom wall at a point opposite said opening for supply-ing unmelted mineral material.

23. A feeder as claimed in claim 20, 21 or 22 in which said heating strip is formed as a pair of parallel channel members.