US2936480A

US2936480A - Method and apparatus for the attenuation of heat softenable materials into fibers

Info

Publication number: US2936480A
Application number: US585886A
Authority: US
Inventors: Kleist Dale
Original assignee: Owens Corning Fiberglas Corp
Current assignee: Owens Corning
Priority date: 1956-05-21
Filing date: 1956-05-21
Publication date: 1960-05-17
Anticipated expiration: 1977-05-17
Also published as: NL217315A; CH349379A; GB839482A; DK103908C; BE564030A; DE1081195B; FR1175351A

Description

D. KLEIST May 17, 1960 2,936,480 METHOD AND APPARATUS FOR THE ATTENUATION OF HEAT SOFTENABLE MATERIALS INTO FIBERS 2 Sheets-Sheet 1 Filed May 18, 1956 AIR STEAM 0!? GA mmvrox Da/e l1 lc-vsf RTTQRNE 71$ SUCTION BOX May 17, 1960 D. KLEIST 2,936,480

METHOD AND APPARATUS FOR THE ATTENUATION OF HEAT SOFTENABLE MATERIALS INTO FIBERS Filed May 18, 1956 2 Sheets-Sheet 2 HTTOIZNE Y5 United States Patent METHOD AND APPARATUS FOR THE ATTENUA- 113g? RgF HEAT SOFIENABLE MATERIALS INTO Dale Kleist, St. Louisville, Ohio, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware Application May 18, 1956, Serial No. 585,886

9 Claims. (Cl. 18-2.5)

This invention relates to a methodand apparatus for the attenuation of heat softenable materials into fibers and it is particularly directed to the formation of long, fine fibrous glass.

It is known that long, fine diameter glass fibers can be formed for utilization in insulating mats and blankets by centrifugally projecting streams of glass into an extremely hot blast of gases moving at high velocity.

Apparatuses and methods suitable for carrying out the just described process are shown, for examples, in I-Ieymes and Peyches Patent No. 2,624,912 and in Slayter and Stalego Patent No. 2,609,566. However, the use of extremely hot blasts of gases, particularly the products ofcombustion of gas and airin a closed chamber, creates a substantial problem from a manufacturing standpoint resulting from the volume and heat of the blast.

ltis, therefore, the principal object of this invention to provide a method and apparatus by which large volumes of glass may be attenuated into fine fibers through the use of simple attenuation blasts such as steam, air, heated air, or superheated steam where it is not necessary to have combustion take place in order to furnish the gases. While it has been suggested in the prior art that fibers may be formed by the attenuation of blasts of steam or air, it has heretofore been difficult if not impossible to produce'fibers having diameters in the order of, say, 50 hundred thousandths of an inch or less by these methods.

It is, therefore, also an object of this invention to provide a method and apparatus whereby a simple blast of air or steam in itself much cooler than the material which it is employed to attenuate, may be utilized with the use of certain auxiliary or supplemental heating means designed and employed to control the rate of heat loss of the material being attenuated.

Other and more specific objects will be better understood from the specification which follows and from the drawings in which:

Fig. 1 is a viewin vertical section, partially schematic in nature, of an apparatus designed and operated according to the invention for the formation of very fine diamcter fibers from molten glass.

Fig. 2 is an enlarged, fragmentary, vertical, sectional view of a modification of apparatus built according to the invention. r Fig. 3 is a view similar to Fig. 2 but showing yet another modification of the apparatus.

Fig. 4 is a view similar to Figs. 2 and 3 but showing still another modification of the apparatus.

Fig. 5 is a schematic illustrationof yet another modification of apparatus for practicing the invention.

rs the embodiment of the invention illustrated in Fig. l aglass melting tank is generally indicated at and shown as providing a body of molten glass 11. The tank 10 base bushing 12 with a single relatively large diameter orifice 13 through which flows a stream of molten glass 14.

A spindle generally indicated at 15 is mounted for rotation on a vertical axis by suitable bearings (not shown) and may be driven, say, at 3000 r.p.m. or more, by belts 16 also engaged with a suitable driving motor (not shown) On the lower end of the spindle 15 there is removably secured a centrifuge 17 shown in the form of a hollow cone shaped body having a generally vertical an-' nular periphery 18 and a return lower lip 19. In the embodiment of Fig. 1 the centrifuge 17 carries a centrally located distributing basket 20 which rotates with the centrifuge 17 and is centrally located therein.

The spindle 15 is hollow so that the stream of glass 14 flows downwardly through the spindle 15 and into the bottom of the basket or distributor 2 0. The glass, still at relatively high temperature, flows across the bot tom of the distributing basket 20 and is projected by centrifugal force radially outward through a plurality of distributing orifices 21 drilled in the vertical walls of the basket 20. Glass flies away from the distributing basket 20 in the form of relatively heavy streams 22 which impinge upon the periphery 18 and lip 19 of the centrifuge 17. The glass on the inner surfaces of the periphery 18 and lip 19 fiows together to form an annular body of glass generally indicated at 23 which is subjected to extremely high centrifugal forces because of the relatively large diameter of the centrifuge 17 and its relatively high speed of rotation. The centrifugal force thus created extrudes the glass through a large number of stream forming orifices 24 that are drilled in the periphery 1 8 of the centrifuge 17 The problem of control of the temperature and thus the viscosity of the glass in its travel to the inner walls of the periphery 18 and lip 19, through the orifices 24 and sub sequently until attenuation is completed is critical. The temperature of the glass at the orifices 24 must be sufiiciently high so that it will flow through the orifices 24 but sufficiently low so that it will not separate from itself in the form of droplets or slugs. It has been discovered that while the temperature of the glass in its pathway from the centrifuge should continuously decrease, it is essential that its rate of heat loss be retarded under control immediately or shortly after it has left the orifices 24 so that it can be successfully attenuated into long, fine fibers by the forces of the centrifuge and of an attenuating blast generally indicated at 25 and surrounding the periphery 18 of the centrifuge 17.

The attenuating blast 25 is emitted from an annular blower ring 26. The blast may be air, heated air, steam, or superheated steam or any other blast of gases having suificient velocity to apply traction to streams of glass 27 flowing away from the orifices 24 under centrifugal force.

if an attenuating blast is employed at high enough temperatures so that it reheats the glass beyond its refusing point, i.e., to such a temperature that the glass surfaces are softened, theintimate contact between the surfaces of the fibers being attenuated so scratches and roughens the surfaces that the resulting product is brashy and less suitable for use in end products. It is desirable, therefore, not to increase the temperature of the glass streams issuing from the centrifuge. However, it has been discovered that the blast of gases plus the assaaeo ambient air surrounding the centrifuge 17 so rapidly cools the glass streams that the attenuating lengths of the individual streams are too short to permit attenuation to very fine fibers. For this reason, it is also desirable to retard the rate of heat loss from the glass by supplying supplemental heat to the attenuating length of the streams.

As used herein, the term attenuating length is defined as meaning that length of the stream between the outer surface of the periphery 18 of the centrifuge 17 and the position in the fiber where it has reached its minimum diameter. During this attenuating length the fiber must be elongated sufficiently so as to reduce its diameter from the diameter at the orifice 24 to the final diameter. Because of the surface tension and viscosity of the glass even at elevated temperatures, it is impractical to make the orifices 24 of diameters even approximating the finished diameters of the fiber to be formed. They must, therefore, be many times as large and each fiber is formed off a molten cone of glass extruded through its particular orifice 24 by centrifugal force.

In order to control the rate of heat loss by the fibers during the attenuating length the apparatus and method the invention provide means for adding supplemental or auxiliary heat to the attenuating lengths of the fibers. In Fig. 1 this means is illustrated as a radiant burner generally indicated at 28 so positioned as to direct radiant energy at the attenuating lengths of the fibers. In Fig. 1 the radiant burner or heater 28 is illustrated as comprising a ceramic ring 29 mounted in a support ring 3% and provided with a plurality of gas inlet pipes 31 so that the gas burns adjacent the curved radiating surface of the ceramic ring 29. The gas flame is'short and hot so that it heats the radiating ceramic ring 29 and, by the high emissivity of the ceramic, radiant energy is emitted from. the burner 28 toward the periphery 18 of the centrifuge 17 and attenuating lengths of the streams 27 to be formed into elongated fine fibers 32.

In the apparatus as illustrated in Fig. l a vertical column or enclosure 33 extends downwardly beneath the centrifuge 17 in order to enclose the descending shroud or veil of fibers 34 as they are carried downwardly by the combination of gravity and the jet of air 25. A foraminous conveyor 35 is shown as moving across beneath the enclosure 33 for accumulating the mass of fibers thereon in the form of a blanket 36 carried away by the conveyor 35 and between compression rollers generally indicated at 37. A suction box 38 may be located beneath the conveyor 35 to assist in laying the fibers 32 of the veil 34downwardly on the conveyor 35.

In Fig. 2 a modified form of heat transferring means is shown for transferring energy to apply heat to the attenuating lengths of glass streams 39 that are being emitted from stream forming orifices 40 in the periphery. of a rotary centrifuge generally indicated at 41. As in the embodiment of the invention illustrated. in Fig. 1, the centrifuge 41 may be provided with a glass distributing basket 42 into which a stream of molten glass 43 flows. The glass in the stream 43 is distributed over the inner face of the distributing basket 42 by centrifugal force and emitted as coarse streams 44 which impinge upon the inner surface of the centrifuge 41. The streams 39, projected outwardly through their orifices 4%) by centrifugal force, are entrained in a downwardly moving radial blast of gas 45 which is directed parallel to and concentric with the axis of rotation of the centrifuge 41. The blast of gas 45 is discharged from an. annular blower ring 46. As explained above, the blast of gas 45 may be air or steam at relatively low temperature compared to the temperature of the molten glass forming the streams 39.

The force of the blast 45 turns the streams downwardly redirecting them to form a generally tubular veil of fibers 47 and to move the veil downwardly away from the centrifuge 41.

In order to provide for effective attenuation of the streams 39 into long, fine fibers 47, a supplemental heating means 48 is provided. The heating means 48 consists of an annular ring 49 of ceramic, or other material having a high rate of emissivity, so positioned, shaped and directed as to concentrate the radiant heat energy upon the attenuating lengths of streams 39 between their discharge from the stream forming orifices 40 and the ultimate reduction in diameter when they change from softened attenuable streams to fixed diameter fibers. A plurality of electric coils 50 is positioned in the concave face of the radiant ring 49 for generating the heat which is radiated from the heating means 48. The rings 50 are electrically connected to power input lines 51.

While the embodiments of the invention illustrated in Figs. 1 and 2 employ radiant heat energy emanating from a source external of the veil of

fibers

34 or 47, respectively, the invention also contemplates the transfer of energy from a supplemental source external of the veil and external of the blast but in a form other than radiant heat.

The embodiment of the invention illustrated in Fig. 3 is similar to that shown in Figs. 1 and 2 except for variation in the precise configuration of a centrifuge 52 and in the nature of the supplemental heat source gen erally indicated at 53. In Fig. 3 the centrifuge 52 has a frusto-conical periphery 54 with a taper that is inverted compared to the taper of the periphery of the centrifuge 41 of Fig. 2. Like the earlier embodiments of the invention, the centrifuge 52 may be provided with a glass distributing basket 55 serving to distribute a molten glass stream 56 in the form of coarse streams 57 to the interior surface of the periphery 54 whence the glass flows through stream forming orifices 58 as glass streams 59. The streams 59 are entrained in a blast of gases 60 discharged from an annular blower ring 61 and attenuated to form fibers 62 in a generally tubular, downwardly moving veil of fibers.

Supplemental heat is generated in the attenuating lengths of the streams 59 by means of induction heating coils 63 carried by a frusto-conical mounting plate 64.

Because of the chemical constituents of the glasses" known in the art and suitable for centrifugal fiber forming procedures, such glasses usually containing considerable proportions of alkali, the electrical characteristics of the glass streams 59 are such that the induction field created by the induction coils 63 generates heat within the bodies of the streams 59 at their attenuating lengths.

In the embodiments of the invention illustrated in Figs. 1, 2 and 3, the blasts of

gases

25, 45 and 60 are emitted from blower rings 26, 46 or 61, respectively,

which are located at levels above the peripheries of the centrifuges 17, 41 and 52, respectively. In these figures the attenuating blasts are so directed as to impinge upon the

streams

27, 39 or 59 at their attenuating lengths to apply traction to the streams as they cool for attenuating them into fine fibers.

In the embodiment of the invention illustrated in Fig. 4 attenuation of glass streams 65 to form fine fibers 66 is accomplished by transferring the attenuating force along the fibers 66 back to the attenuating lengths of the streams 65. In this embodiment of the invention a centrifuge 67, similar to the earlier described centrifuges and, if desired, having a glass distributor basket 68, has a generally annular periphery 69 through which a plurality of stream forming orifices 70 are drilled. A stream of molten glass 71 is flowed into the distributing basket 68 and through its orifices 72 discharged as coarse streams 73 onto the interior of the periphery 69 of the centrifuge 67. Centrifugal force then flows the glass through the stream forming orifices 70 as streams 65. The decrease in temperature of the glass streams 65 in their attenuating lengths produces the fibers 66 of sulficient mechanical integrity to be entrained in an annular, downwardly moving blast generally indicated at 74 which is emitted from an annular blower 75 located at a level below the stream forming orifices 70 of the centrifuge 67. The blower 75 has a downwardly extending skirt 76 and the orifice of the blower 75 is so designed that the blast 74 hugs the surface of the skirt 76, entraining and carrying the fibers 66 downwardly therewith.

In this embodiment of the invention supplemental heat is transferred to the attenuating lengths of the stream 65 to reduce their rate of heat loss from an annular radiant heat source generally indicated at 77 and comprising a radiant emitting ring 78 heated by gas flames burning in ports 79 fed from a gas line 80.

By employing a supplemental heat source to retard the rate of heat loss from the glass streams issuing from the centrifuge and an attenuating blast emitted from a separate source, better control of the fiber forming process is made possible. The amount of supplemental heat supplied from the external source is completely independent of the blast. In contrast, where a blast is relied upon for both force and supplemental heat, a change in either force or heat of the blast also affects the other.

In all or" the embodiments shown in Figs. 1-4 inclusive, the supplemental heat not only is applied to or generated 7 in the attenuating lengths" of the glass streams but it also is effective at least on the peripheral area of the centrifuges as well. The heat or energy transferring means which surround the centrifuges are all capable of transferring the energy through the blasts of gas to the streams and to the centrifuges themselves. Radiant heat strikes the outer surfaces of the centrifuges 17, 41 and 67 of Figs. 1, 2, and 4 respectively. In Fig. 3 the inductive field from the coil 63 encompasses the centrifuge 52 as well as the streams 59. Thus in all four figures heat is also applied to the centrifuges for retarding their loss of heat as well as retarding the loss of heat from the streams.

The embodiment of the invention illustrated in Fig. 5 comprises a centrifuging basket 81 into which there is fed a stream of molten glass 82. The molten glass is spread over the inner surface of the basket 81 and projected as streams 83 from orifices 84 into the path of a blast of gases 85 from an annular blower 86. In this embodiment, supplemental heat is generated in the attenuating lengths of the streams by di-electric heating. The centrifuge 81 is connected as one plate of a system also including an annular plate 87 exterior of the blast 85 and both are connected to a high frequency electrical generator 88.

As used in the following claims the phrases electrical energy field or electrical energy apparatus" are intended to include, respectively, fields of electrical energy produced by both electromagnetic or induction apparatus and capacitive or di-electric apparatus and apparatus of either type.

I claim:

1. In a method for attenuating fibers from streams of glass being projected radially outward from a centrifuge into an annular blast of gas having high kinetic energy and that is moving generally parallel and concentrio to the axis of the centrifuge for attenuating said streams into fibers and for redirecting said fibers as a generally tubular veil moving longitudinally of such axis, the improvement comprising transferring energy inwardly through said blast from a supplemental source other than said blast and external of said moving veil and said blast to supply heat to the attenuating lengths of all of said streams in sufiicient quantity for retarding the rate of heat loss therefrom but not in suflicient quantity for increasing the temperature thereof.

2. A method for attenuating fibers from streams of glass being projected radially outward from a centrifuge, said method comprising directing an annular blast of gas generally parallel and concentric to the axis of the centrifuge for attenuating said streams into fibers and redirecting said fibers as a generally tubular veil" moving longitudinally of such axis, and transferring radiant heat inwardly through said blast from a supplemental source external of and substantially surrounding said moving veil in sufiicient quantity for retarding the rate of heat loss from the attenuating lengths of all of said streams.

3. A method for attenuating long fine fibers from streams of glass being projected horizontally radially outward from a centrifuge, said method comprising, directing an annular blast of gas having a temperature less than the temperature of said streams downwardly across the paths of movement of said streams away from said centrifuge for entraining and attenuating said streams into fibers and for carrying said fibers downwardly as a generally tubular veil, and applying heat inwardly through said blast from a source radially external thereof to the attenuating lengths of all of said streams in quantities sufficient for retarding the rate of heat loss from said streams in said attenuating lengths but not sufficient for increasing the temperature thereof.

4. A method according to claim 3 in which the heat is applied by directing radiant heat inwardly through said blast onto the attenuating lengths of said streams.

5. Apparatus for attenuating fibers from streams of heat softenable material being projected radially outward from the periphery of a centrifuge comprising an annular blower concentric with the axis of the centrifuge and having an annular orifice for emitting a blast of gases for attenuating said streams into fibers and redirecting said fibers as a generally tubular veil moving axially away from said centrifuge, and an annular radiant energy source mounted radially external of said moving veil and of said blower and having its energy emitting means directed inwardly toward the periphery of said centrifuge for applying supplemental heat to the attenuating lengths of said streams.

6. A method for attenuating fine fibers from streams of glass that are projected outwardly by centrifugal force from orifices in the periphery of a centrifuge, said method comprising directing an annular high velocity blast of gaseous medium generally parallel to and concentric with the axis of said centrifuge for applying kinetic energy to said streams for redirecting said streams as a generally tubular veil moving longitudinally of said axis and for attenuating said streams into fibers, and creating an electrical energy field from a source radially external of said blast, said field encompassing the periphery of said centrifuge and the attenuating lengths of said streams and having sufiicient strength for generating heat in and retarding the rate of heat loss from the attenuating lengths of said streams.

7. A method according to claim 6 in which the elec trical field is capacitive.

8. Apparatus for attenuating fine fibers from streams of glass that are projected outwardly by centrifugal force from orifices in the periphery of a centrifuge, said apparatus comprising an annular blower concentric with said centrifuge and closely spaced radially thereof for directing a high velocity blast of gaseous medium generally parallel to and concentric with the axis of said centrifuge for applying kinetic energy to said streams for redirecting said streams as a generally tubular veil moving longitudinally of the axis of said centrifuge and for attenuating said streams into fibers, an annular radiant energy apparatus concentric with and spaced radially externally of said annular blower and means for energizing said apparatus for creating an energy field encompassing the periphery of said centrifuge and the attenuating lengths of said streams for generating heat therein sufficient for retarding the rate of heat loss therefrom but not sufiicient for increasing the temperature thereof.

9. Apparatus according to claim 5 in which the annular radiant energy source is a radiant heater.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS 7 France July 2, 1956 (Corresponding to Belgian Pat. No. 545,632.) France Dec. 28-, 1936 Great Britain Dec. 13, 1939 OTHER REFERENCES Abstract of Belgian Patent No. 545,632, found in Recueil des Brevets dInvention, 1956, vol. 2, page 252.