USRE13504E - Sig-koiis to the thermal syndicate limited - Google Patents

Description

,J. P. BOTTOMLEY, R. S. HUTTON & R. A. S. PAGET.

MANUFACTURE OF SILICA cuss.

1121101111011 FILED 111111: 10, 1911.

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Beissued Jan. 7, 1913.

WIT/asses J. F. BOTTOMLEY, R. S.-'HUTTON & R. A. S. PAGET.

MANUFACTURE OF SILICA GLASS. APPLICATION I ILED JUNE 10 1911.

Baissued Jan. 7,1913.'

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Baissued Jan. 7, 1913.

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'40 or molded in situ into the desired form.

UNITED sTArns ATE T FFIC Q JAMES FRANCIS BOTTOMLEY, or WALLSEND,

ROBERT SALMON HUTTON, OF MAN- CHESTER, AND RICHARD ARTHUR SUIRTEES PAGET. F LO1 TDO1J,'ENGLAND, AS-' SIGNORS TO THE THERMAL SYNDICATE LIMITED, OE \VALLSEND, ENGLAND.

MANUFACTURE OF SILICA GL ASSQ.

Speoiilca tion of Reissued Letters latent. Reissucd Jan. '7; 1913."

Original No. 812,399, dated February 13, 1906, Serial No. 251,321. Application for reissue filed June 10,

To all whom it ma 3 COl'tt'aZTl'I I Be it known that we,-Jl\;\rns Fnimcis BorronLnr, touaa'r SALMON II'UT'TON, and RICHARD Au'rnua Sirmnas liwn'r, baron'et, 5 the last named formerly being known and si ling as Ali rmrn Pacer, all subjectsof His i ajest-y the King of Great Britain, residing at lVallsemLon-Tyne, in the county of Northumberland; Manchester, in the county [0 of Lancaster, and London, England, (for- --merly of North Gray, in the county of Kent,) respectively, have invented a certain nevi and useful Improvement in the Mannfacture of Silica. Glass, of which the follow- 15. ingis a specification. i

' This invention relates to improvements in the manufacture of silica glass from quartz I 01; practically pureglass-makers sand, by

" which is meant a silica glass the fusingpoint of which is above the temperature ob-- tainable in'gas or' fuel furnaeesyas used in glass manufacture.

We have observed that the conditions of working are limited by the fact that by heating quartz or glass-makers sand unmixed with other substances it is only possible to get it into a plastic state and that further heating produces volatilization before a really fluid condition is obtained: In order,

therefore, to produce articles of any desired shape, we heat amass of quartz,;sa1id, or other-suitable form of silica by conduction and (or) radiation from materialfor example, carbon or graphiteshaped so as to give the desired heating area and brought to the required temperature by the passage of an electric current; and we provide a means whereby when the mass has reached a plastic condition it may be directly shaped The methods of heating by conduction include passage of an electric current through acore formed of arod or tube embedded in a granulated or pulverized mass of the ma- 'terial to be fused, or through a plate either embedded in or supporting the material to be fused, or through the wall or Walls of the receptacle containing the material.

The methods of heating by radiation incdude the passage of an electric current "through a ,core formed of a plate or number Serial No. 632,523.

i with the material to be heated and forming, in effect, a'coyer for the furnace. v

The methods of working the plastic ma- 6 teria'l may include molding by pressure of a die or mold into thc'nlass contained in a corresponding receptacle, or by pressing,be tween corresponding molds, or by blowing the material upward or downward freely or into molds. For examplepa tubular and perforated heating-core {fixed between tvvo carbon terminals or electrodesflmaybe emr bedded in a mass of, sand or other ,forin of silica, one or both of the eIectrodeS being cored out's o to form a passage, whereby. airor other gas under pressure may be introduced at will; Sufiicient current is passed through the core to raise, it to the requisite temperature and is' maintained until a suiliciont quantity of the material immediately surrounding the heated zone is brought into a plastic state. In, this condition the fused material forms a gas-tight joint around the ends of the core. By intro- (lacing into and throughthe coreat the required moment a supply of gas under .pressure and by regulating the-same by means of a gas-tap or other device.attached to the gas-passage "the plastic mass may be freely expanded or caused to assume any desired shape by blowing into :inexternal mold, the external unagglomerat ed material being removed Where necessary to allow of greater freedom of expansion. r.

In order to give seci-irityagainst blowing out at the joints between the resistance material and the plastic silica,means may be provided for mechanically compressing or cooling or compressing and, cooling suitable portions of the plastic mass before subjecting it to gaseous pressure;

It willbe evident that for the passage of gas it is unnecessary to make use of the actual heating material or electrodes themselves but that an independent tube can be inserted for this purposeat any col'wenient Instead of using a rodor lobe a%iat plate or rod or tube flattened at the c nter and heated by the passage of an'electric current may be utilized for obtaining a more extended surface of the plastic mass,

of plates so situated as to be out of contact It will besuflicient in many cases ,to use in series or in parallel, as desired.

one side only of the heated resistance, a highly-refractory material, such as magnesia or alumina, being placed on the other side.

Where a more extended heating-surface is required, .a number of plates may be employed, which may be connected electrically On account of the impossibilit of obtaining tion the methods used in the molding and shaping. of' glass on a large scale cannot be directly applied. By the use of our invention, however, and by obtaining the plastic .material in the desired form and position it is possible to adopt a suitable modification of the processes used in the molding of the mold being provided with an air-out et at some suitable position.

The material produced by' the methodsdescribed is for the. most art glazed on the 'nnerv surface only, whi e the outer is covcredwith a thin layer of agglomerated sand; The roduction of a material glazed on both si' es may be brought about by limiting the amount of material'within' the heated zone, so that the whole is rendered plastic. For example, the heat from a resistance-core may be made to radiateonto Q a mass of silica in an inclosed chamber till the whole is made plastic, care being taken to render the heat losses through external radiation small. Suitable gas-passages are provided whereby the plastic material may be blowniz'n situ, either freely or into super imposed molds, suitable rrangements being made. for removing the sistance-core from above;the fused mass, oivice versa.

In the alternativethel silica ma be inclosed in a crucible or 0t} er suitable receptacle which may, if desired, form one part of a mold and which m y be heated b the passage of the electric riurrent throng the walls of'the' same, or th ough a suitable resistance material surrounding it, or through both, the plastic material being shaped either by blowing from the receptacle into an exterior mold or by pressure of a mandrel or the like into theplastic mass. i

It will be evident that in fusing sililza by the heat generated by 'the passage of the electric current throughga resistance forthe 1 purposes of this. vention other materials quartz in asuflicl'ently fluid condi-.

electric current the silica in .in the act of expansion under pressure.

transverse sections, respectively,

' tively, of a furnace,

than carbon of sufiiciently high melting or volatilizing point and not liable to react with silica within the range of temperature of plastic silica might be used as the heating media.

In order to obtain a proper distribution of i the mass prior to blowing, the natural flow of such .-mass when in a viscous state may be utilized. For example, in heating a rod or the like surrounded by sand the fused mass will gradually flow so as to be thickest1 at the center of the under side of the re t I Provision may be made for allowing the mass during the blowing to expand upward or downward at will or for rotatin it so as to bring the thickened portion to the top. In the case of the shaping of a plastic mass surrounded by unfused sand by blowing it'into an external mold the mold-may be perforated, so as to allow of the escape of the send as the plastic mass ex ands during blowing, an external. mold ing used where necessary to close the perforations until the escape of the sand is desired or a single large opening may be substituted for the perforations closed as before by a cover of any desired form.

Referring now to the drawings, Figures 1 and 2 are longitudinal and transverse sections, respectively, of a furnace exemplifyin a method of heating by conduction through a tubular core. Fig. 3 shows a pair of tongs suitable for mechanically pressing the fused mass in order to secure the joint between the core and the plastic material. Fig. 4 is a detail of Fig. 1 after blowing. 5 is a transverse section showing heating by conduction through a plate embedded in sand, with an independent tube for introducing gas underipressure ,into the interior of the fused mass and with a mechanical device for pressing the edges to secure a joint, the material. being shoF'wn 1g. 6 is a perspectlve view of the clamping device. Fig. 7 is an alternative clamping device to that shown in Figs. 5 and 6. Figs. 8 and 9 are longitudinal and transverse sections, respectively, of the furnace, showing a method of heating by a resistance-plate supporting the materiallto be fused.

Figs. 1.0 and 11 are longitudinal andof a furnace, showing a method of heating the material in a receptacle through the walls of which the heating current passes, the material to be fused being limited, so that it is fused throughout. Figs. 12 and '13 are longitudinal and transverse sections, respecshowing a method of heating by radiation from a resistance-plate heated by the passage of a current with means for separating the source of heat and the portion of the furnace containing the Figs. 14, 15 and 16 are die, and molded product,

sists ofa cored-outrodiof graphite or agripheral perforations, plugged t e center of the fused mass 6.

' cored or a glom'erated, carbon havin one or more pewhlch may be lightly to prevent choking, through which air introduced into the core may'pass into The tubular core is fixed between terminals or electrodes 0 of phiteor carbon, one of which is gas-passage and is connected, by means ofa gas-tap d, with a source of compressed air or other s. E,

'3. The method of lea ing the current to t e terminals not shown, but can bedone in a'ny convenient way.

0 is an iron plate, to which the molds f v can be fixed, and serves as the bed of the.

furnace. Loose brickwork may be built up all around to retain the material to be fused.

In order to remove the sand prior to blowing the lower mold is fittedwith a sliding dit" I Fig.

ingt e tongs in position door g, through which the sand contained within,the molds may flow out, the door beingclosed after the escape of the sand.

The upper mold may conveniently be provided with a removable cover, as shown, to "facilitate filling in sand prior to fusion.

3. shows'a form of tongs h for presscure a. gas-tight joint.

' 4; is a detailed view of Fig. 1, showand the fused-mass blown out, so as to fill the mold.

I The following is an example of a method of operation: Using a graphite core twenty inches long and one and three eighths inches 'external diameter with I walls tl1rce-'*':- teenthl of an inch thick embedded in gla makcrs sand, a current at about twelve Illindred ampcres at about seventeen volts is passed through the corefo'r one hour. The fusion beingthen', effected the clamps are closed around the ends, so as to secure the.

joints. The unfusedz sand in the furnace is removed through the slidin door 9 and compressed air gradually a mitted, so as to. force the plastic material into the molds j, which may be made of any materialcapable of standing the temperature of the exterior of the fused mass. The blown-out product is then removed and finished as de sired.

In the. drawings the molds are shown as fixed 'in but it willbeevidcnt that they could be put in position immediately prior to blowing, in which case the edges of the mo ds may be brought. close to the fuscd mass without fear 66 of overheating.

the carbon and the silica wi of carbornndum and evolution of carbonic fused. mass at each end, so as to se-' place prior to fusion being cllectcd In carrying out the experiments of heating by conduction it is important to obtain'suita le materials for the heating-core, as want' of homogeneity in the core might result,ip

considerable reaction taking place between oxid owing to local overheating. \Vith. asutliciently homogeneous material for the. core it is possible by the proper regulation of the temperature and length of heating to reduce the formation of gas due to local action to a negligible amount.

In Fig. 5 the heatingcore consists of a carbon or graphite plate a, which is embedded in the material to be fused. It is fixed between terminal blocks 1 as shown in Fig. 8, into which the electrodes 0 pass. The plate is perforated about its center to admit an independent tube j, formed of some suitable material, such as carbon or graphite, and preferably flanged at the head, so as to prevent leakage during blowir'ig. On completion of the fusion the clamp (shown in perspective inFigfi) is tightened, so as to compress the edges of the fused material onto, the plate to prevent leakage durin blowing. Compressed air is then admittetfi so as to expand the fused muss freely, as shown, or into an inverted mold, which may be secured by lugs to the clamp In Fig. 7 the clamping device consists of corresponding rings of the required shape fixed on the jointed arms- For example, using an agglomerated carbon plate eighteen by six inches by fivc-sixteenths ol an inch, a current of about one thousand ampercs at about twenty-two volts is passed through the plate until suliicicnt material has been fused. The figures, l1o\v1-vcr,(tan on] be taken as indicating average values ant will be different for different kinds of carbon. It is of importancc that the heating should not be done too rapidly, as reaction between he carbon or graphite and the silica is liable to take place. If the heating is prolonged, this may also be the case, and it .may be advantageous gradually to decrease the amount of current when prolonged heating is required. When the fusion is complete, theclamps are tightened around the edges of the fused mass and compressed air introduced," as before described.

In Figs. 8 and 9 the carbon-plate a is fixed between terminal blocks 6, into which tl c electrodes 0 pass, the plate being supported by a thick plate of refractory mate-' rial Z, which, an electrical conductor, is separated from the heated plate by an interposed layer of some refractory non-conducting material, such magnesia. The material to be fused is placed on the heating-plate, which is perforated to admit an independent gas-tube j of carbon or the the formation like. When the fusion is complete, the shaping of the material is brought about by pressing a mold onto the fused mass and forcing the latter into it with compressed air or gas, leakage being prevented by the pressure of the m dld on the fused material. "The current requirements are of the same order. as described with reference to Fig. 5.

In Figs. 10 and 11 the quantity of material to be fused is limited by inclosing it in a receptacle composed of plates a and ter-. minals 2', through one or more of which thecurrent passes, heat losses at. the .surface'being prevented by a'suitable cover of plates, preferably of carbon or graphite, supportmg a mass of some heatinsulating material. YVhen the inclosed material is fused throughout, the cover is removed and the material shaped b blowing into molds, as go-described with reference to Figs. 8 and -9, the product produced by this method being glazed on both sides.

In Figs. 1 and 13 the plate a is fixed between graphite terminal blocks 71, into which 25 the electrodes pass, and forms, in effect, a cover-over the material to be fused, which-is placed immediately below it in a shaped receptacle-such, for example, as m, (shown in Fig. 14),so as to be heated by radiation from it. As in the case of heating by conduction, as described with reference to Figs. 8 and 9, one side only of the plate is used, a refractory material, such as magnesia, being placed on the other. The shaped receptacle 3a m is surrounded by some heat-insulating material contained in an outside vessel 6, the whole being mounted one bogie and forming the lower half of the furnace. then the fusion is completed, the bogie is withdrawn, so as to separate the heatingplates fromthe' lower portion of the furnace, and the plastic material brought into a position where it may be shapedbythe pressure of a die, such a. (Shown in Fig. 15.) Heat losses are prevented by a cover of carbon or graphite supporting a thicli layer of heat-insulating material. For example, using an agglomerated carbon late eighteen by six inches by five-sixteent s of aninch, a cur rent of, about fifteen hundredamperes at twenty-two volts is passeduntil the whole of the material is brought to a plastic condition. The molding is then carried out as above described. v

In Fig. 17 a similar methodof heating is shown to' that described with reference to Figs. 12 and 13. In this case -theshaping of the material is brought about by introducing below the fused material an independent gas tube j, connected to a supply of air or gas, as before described. When the 'fusion is completed, the lower portion of the furnace is separated fromthe heatingplate and shaping brought about'by blowing the plas- In the case of fusing. by radiation it vious that as the mat'enalisnot in contact with the heating-surface there is no 'riskof chemical reaction taking lace between this surface and the surface 0 the plastic mass, and, further, that where the plastic mass is contained in a carbon rece tacle the temperature of the receptacle wil not be above that of the molten silica, and consequently the reaction is reduced to a, minimum. Y It follows that it is possible by the use of this method to continue the heating for a a longer period than would otherwise be feasible and that larger masses may be dealt with. It will be evident that the methods above described for the treatment of pure silica. may also be applied to silica lasses containing so high a percentage of si ica as tobe infusible in gas or fuel furnaces as used in glass manufacture without departingfrom the scope of this invention. I Prior to the present invention two processes of making silica articles had been suggested. One principally developed by Shenstone, consisted in a buildin up process by which small pieces of roc crystal were fused in an oxyhydrogen blow pipe flame and further pieces being fused and added a. transparent tube bulb or the like was gradually produced and drawn or blown. The other suggestion by Thompson and Hutton was to fuse silica around a carbon resistance shaped to correspond to the article it was desired to produce and when the particles of silica had joined or-adhered to each other to allow the mass to cool in situ after which the carbon was removed. The material thus produced is practically a ,cast" material and physically this may be identified by the fact that it consists of vitreous silica uniformly permeated with small spherical air bubbles due to the air spaces existing between thegrains of sand prior to fusion. According to this invention the process is not complete at the point of fusion where the particles cohere but remain friable for the" current is so regulated as before'described that the fused mass becomes plastic throughout and while in this condition is extended say by blowing with the result that the article or material produced has a fibrous or laminated structure due to the distortion of the-air bubbles in the direction of strain appliedduring the process of plastic working, the eventual article produced being practically of wrought as distinguished from cast materiahthis result necessarily following from using the process as described.

= What is claimed is l. The improved process of manufacture 12 8 mg articles of silica. glass which cdhsists in" heating/the crude material by means; of-the heat generated by a resistance suohas can; bon placed in an electric circuit until/the;

0! tie material into molds pressed into the mass.

requisitemass is in a plastic conditiim, then articles of silica while still nal blowin r i 2. The improved process of manufacturing articles of silica glass which consists in heating the crude material by means of the heat generated by a gesistance such as carbon placed in an electric circuit and out of contact with the material to be fused un til the requisite mass is in a plastic condition, then while still plastic shaping the mass by internal blowing.

3. The improved process of manufacturing articles of silica glass which consists fusing the crude material by means of the heat generated b a hollow perforated resistance-core placed? in an electric circuit, then securing the fused mass to the extremities of the core and then passing compressed air or gas through said core so as to effect the shaping of the fused mass in 852314.

4. The improved process of manufacturing glass-which consists in fus mg the crude materialby means 'of the heat generated by a resistance placedin an electrio circuit, thensecuring the extremities of the fused mass, then blowing the and effecting the shaping in situ.

5. As an article of manufacture silica ware made from powdered or granulated to plasand so manipulated while plastic as to give a product of a laminated or fibrous aracter. i

6. As-zan article of manufacture silica fused mass raw material which has been fused ticity were having a laminated or fibrous characplastic shaping the mass by interter and having elongated air spaces distribner surface being glazed and the outer surface being agglomerated.

In testimony whereof We have hereunto the presence of the subset our hands in scribing Witnesses.

JAMES FRANCIS BOTTOMLEY. ROBERT SALMON. HU'ITON. RICHARD ARTHUR SURTEES PAGET.

Witnesses to the signature of James F rancis Bottomley:

WILLIAM CRAIG, ROBERT MORRISON. Witnesses to the mon Hutton:

LUTHER J. PARK, J. G. SLESSOR. Witnesses to the signature of Richard Arthur Sui-tees Pa et: 4

RIPLEY WILSON, C. P. LIDDON.

signature of Robert Sal-

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