US2471437A - Method and apparatus for producing sapphire hollow articles - Google Patents

Description

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5 ma Tn mi Vwn mi i K Z Patented May 31, 1949 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR PRODUCING SAPPHIRE HOLLOW ARTICLES Application April 19, 1945, Serial No. 589,250

Claims. 1

This invention rel-ates to the making of annular articles of high-melting refractory materials such as aluminum oxide, spinel, and the like.

It has long been known that boules may be made from such materials by employing an oxyhydrogen flame and introducing a fine fluffy pow der of the refractory into the flame, so that the powder is melted to form droplets at very high temperature, and then the droplets are projected onto a support so that the successive droplets adhere and a boule is grown, usually with a retraction of the support in the direction of the axis of and away from the oXy-hydrogen flame.

Such boul'es are formed essentially without predetermination of the direction of the crystal axes. Since the strength and optical characteristics difier for different directions relative to the crystal axes, it has been necessary to determine the specific orientation of each boule before it could be cut to give an optimum behavior.

In the copending application of Lester, Cannon and Alexander, Serial No. 484,946, filed April 28, 1943, is described a procedure by which rods may be grown of closely regulated cross-section and having a predetermined orientation of the crystal axis relative to the length of the rod.

When it is desired to make annular articles such as annular guides, nozzles, etc., a large part of the mechanical work is that of forming the hole through the unperforated blank. These refractory materials are of great advantage because of their hardness and resistance to wear, but these same qualities make mechanical working a matter of great difiiculty, as diamond dust drills must be used and great care observed.

It has now been found that annular bodies may be made directly by depositing molten particles in an annular ring upon a support while maintaining the center clear of deposit: and that the procedure may be performed by an adaptation of the apparatus described in the aforesaid. application.

A practice of the invention is illustratively shown on the accompanying drawing, in which:

Figure 1 is an axial sectional view through an annular body prepared for forming the tip of a high temperature injector nozzle.

Figure 2 is a similar section through a tubular body.

Figure 3 is an apparatus for producing such bodies, being conventionalized in part.

Figure 4 is a horizontal section on line 4-4 of Fi ure 3.

Figure 5 is a perspective view indicating the relation of the lower end of the burner assembly, the support and starter ring, the article being formed, and the flame.

In these drawings, Figure 1 shows a body i l grown in the form of a crater with a central aperture II and a sloping flank surface 12. The procedure of producing the body, as described dash lines G, in Figure l, for preparing the body for service as an injecting nozzle tip for a Diesel engine, fuel burner, as a thread guide, as high temperature insulation for spark plugs, radio tubes, as dies for drawing wires, extruding plastics, etc.

Figure 2 shows a tubular body 13 of essentially uniform cross-section having a central aperture 5 i extending throughout its length. Such a body can be finished as a tube of uniform wall thickness by reaming and lapping the interior, and then grinding'the exterior. Such bodies or disks sawed therefrom provide long-wearing bearing sleeves or rings, female gages, etc.

The apparatus shown in Figure 3 comprises a base 28 and a standard 2! adjustably connected therewith. The base supports the columns 22 which are connected by webs 22a, 22b in which are guided the depending legs 24 of a vertically movable frame having the cross-bridge or platform 25. One of the webs, 22b, has an internally threaded portion 25 to receive a threaded revoluble spindle 2? which is journaled in the Web 22a and the bridge 25. A worm wheel 28 is fixed to the spindle 21 and can be rotated by a worm 28w connected by flexible shaft '28s to a motor 23, whereby to raise or lower the frame. The bridge 25 has a vertical bearing to support a hollow shaft 3! which has a deflector plate 32 at its upper end and at its lower end is sealed for rotary movement in a housing 33 which provides a gas chamber supplied with gas under pressure through the flexible connection 34 and supply pipe 35. A gage 36 permits close observation of the gas thus delivered. A worm wheel 37 is fixed to the shaft 38 and is rotated by a worm 38 (Fig. 4) driven through a flexible shaft 39 by a motor 40.

A gas burner 45 may be of the form shown in the aforesaid. application; and has the upper chamber it in which is suspended a basket 4! of fine mesh netting and containing the powdered refractory mate-rial. A solenoid 48 causes impact blows to be delivered whereby the basket releases the powder, at a regular rate, into the gas admitted to the chamber A5 from a supply pipe d9. This mixture of gas (for example, dry oxygen) and powder passes downwardly in the main body of the burner assembly, receives secondary gas '(such as dry oxygen) from the pipe 5!; and comes to the lower end of the burner where a combustion gas (such as dry hydrogen) is admitted from an annular chamber :52, which in turn is supplied from the pipe 53. The flame F is illustrated as being projected vertically downward. The axis of the flame F and the rotation axis of the shaft iii are offset relative to one another, so that the deposit of molten particles occurs at a restricted deposit zone eccentric to the axis of rotation: the offset or relative eccentricity of these axes may be varied by moving the standard 2! on the base 2%; the parts 2!, are retained in the adjusted position by the bolts 18 threadedly engaged with the base 28 and passing through the slots H) in the plate 21a connected to the standard 2!.

A heat-insulating jacket til surrounds the flame and the rotating support to prevent rapid loss of heat by radiation, and prevent the flame from being blown out of position by air currents.

The procedure of preparing an annular body of fused refractory, such as synthetic sapphire, from powdered aluminum oxide, may be as follows:

The burner 55 is supplied with gases and ignited. The basket ll of powdered refractory is rapped by blows excited by the solenoid d8, so that the powder enters the flame and is fused therein, and passes downward as a jet whose size and temperature can be controlled by regulating the gas supplies for a given size of burner. A starting ring R is secured to the hollow support S secured to the plate 32, this ring normally being of the same refractory material. a single crystal and carefully selecting the crystal axes directions in this starting ring, the successive deposition of the molten refractory particles will occur with an orientation of the molecules, in cooling, so that they coordinate with the molecular structure of the material already present in solid crystalline form, wherewith the final result is that the starting ring grows by de- By employing posit efiected above the dash lines X in Figs. 1

and 2, at a rate determined by the delivery of axis eccentric to the jet, so that the jet successively impacts the starting ring throughout its periphery: for the portion of the ring where the jet is not delivering molten particles, the heat insulating jacket, the heat radiated from the flame, and the heat of deflected portions of the flame serve to keep the material hot; and the speed of the motor M is regulated so that the surface remains molten during its revolution. Thus, the orienting forces existent at the alreadysolid parts act upon the slowly-cooling lower part of the molten material to cause the deposition in regular layers having the same crystalline arrangement as the starting ring.

During the deposition, some of the heat-plasticized particles do not adhere to the molten mass forming the surface of the growing ring, but scatter within the heat jacket, and others tend to enter and close the central aperture. The effect of the gas current moving from the conduit 3'5 is to minimize this latter effect. The advantage of this central expulsion current is especially great when the orifice is small.

The crystallization from the molten surface mass causes a gradual axial lengthening or growth of the starter ring; and this is compensated by downward movement of the support S by controlled energization of the motor 29, for example, by the automatic means set out in the aforesaid copending application and operating by photo-electric observation of the height of the molten upper surface. v

When the growth has progressed for the desired axial distance, the powder supply can be cut off and the flame gradually reduced to effect slow cooling of the annular article which has been made. It then is cut or broken through, for example, at the plane aa of Figure 1 or Figure 2, and a starting ring portion returned to service for making a further article. It will be noted that the starter ring need not have a truly plane upper surface, as the molten surface mass acts to deposit in regular fashion; much as broken seed crystals in a saturated aqueous solution attain a perfect shape so long as crystallizing material and space is afforded them.

Bodies of uniform cross-section, as in Figure 2, are produced by maintaining constancy of all conditions: including the size, length and temperature of the flame; the rate of delivery of powdered refractory, the rate of rotation of the support and the rate of its downward movement, the pressure and volume of the gas from the conduit 35, etc.

Bodies of varying cross-section, such as those with sloping flanks as in Figure 1, may be procluced by initially having a large hot flame and a slow speed of the motor 29, wherewith a larger quantity of powder is fused and caused to deposit over a large area, and thereafter gradually reducing the flame and relatively increasing the motor speed.

In the finished articles the upper end or lip is usually smoothly rounded, as shown in the drawings.

In visual observation of the operation, it is noted that the downward flame and particle jet, and the upward central gas current interact on one another, so that the proper position for intersection of the axis of the jet with the molten end surface is not at the top of the latter, that l is, at about half the width of the annulus being formed; but somewhat farther from the axis of the starter ring and article. The deflecting action upon the central gas current causes it to be directed away from the flame jet and to mingle with portions thereof and carry the fused particles therein upwardly away from the annulus. The gas is preheated so that it has essentially the same temperature as the justdeposited molten mass: whereby no cooling strains are produced. Preheating may be accomplished at the chamber 33 by a heating flame directed thereagainst from burner M, but it has been found in practice that heat from particles being deposited is conducted along the article and the starting ring R so that these are at temperatures and have heat contents adequate to bring the gas to the proper temperature condition during its upward movement from chamber 3i to the deposit region, when the aperture is small, as.- for example, in forming an annulus having an outside diameter of about three-eighths of an inch and an internal diameter of about oneeighth of an inch.

As examples of practice, for preparing a tubular article having an outside diameter of about threesixteenths of an inch, an inside diameter of about one-sixteenth of an inch, and a length of about one inch, the offset or eccentricity of the ax o: the burner (and of the flame F) from t of rotation of the support S (and of being formed) was between one-sixte inch and one-eighth of an inch. The axes were parallel. Oxygen and hydrogen were used for the torch at a pressure of 3 to 5 pounds per square inch, and hydrogen was supplied through the conduit 35 at a pressure below that of the torch gases, being around 2 or 3 pounds per square inch. These gases were controlled to assure essentially constant pressure at the selected level. The pressure of the gas passing through the central hole should be adjusted so that no marked or irregular distortion of the flame F is produced.

Various materials which are rendered molten or plastic by heat may be worked in the described way to produce annular bodies. Monolithic single-crystal rings and tubes may thus be made of synthetic sapphire, ruby, and other corundums, of spinel, etc.

It Will be understood that the illustrative form of practice is not restrictive, and that the invention may be practiced in many ways within the scope of the appended claims.

We claim:

1. The method of making an annular article of refractory material which comprises forming a high temperature jet containing molten particles of the refractory material and directing the same along a first axis, rotating an annular mass of the molten refractory material about its axis, said axes being substantially parallel and said mass having a minor part of its annular form in the path of the directed jet whereby the molten particles impact said mass and wherewith during the rotation the entire peripheral extent of the mass is subjected to such impact, and delivering gas through the central aperture of the mass and along the axis thereof in a direction substantially opposite to that of the particles in the jet whereby to prevent deposit of the particles adjacent the axis of said annular mass.

2. The method of making an annular article of refractory material which comprises forming a high temperature jet containing molten particles of the refractory material and directing the same along a first axis, rotating an annular mass of the molten refractory material about its axis, said axes being substantially parallel and said mass having a minor part of one face of its annular form in the path of the directed jet whereby the molten particles impact said mass and wherewith during the rotation the entire peripheral extent of the mass is subjected to such impact, delivering gas through the central aperture of the mass and along the axis thereof in a direction substantially opposite to that of the particles in the jet whereby to prevent deposit of' the particles adjacent the axis of said annular mass, and subjecting the part of the mass which is momentarily out of the path of the directed jet to a limited cooling whereby to maintain the major portion thereof in molten form while effecting solidification of the portion of the mass at the opposite face thereof.

3. The method of forming a mono-crystal article of annular form from crystalline refractory material which comprises rotating a mono-crystal starting ring of the refractory material about its axis, forming a high temperature jet containing molten particles of the refractory material and directing said jet along an axis substantially upon a restricted portion of one face of the rotating ring whereby to produce and maintain a molten annular mass upon the ring, effecting a limited cooling of the mass at portions thereof outside the said restricted portion whereby the mass solidifies adjacent the starting ring in mono-crystal relationship to the crystalline structure of said starting ring and thereby effects growth of the ring, and delivering a current of hot gas through the central aperture of the ring in a direction substantially opposite to that of the particles in the jet whereby to prevent closure of said aperture by the particles.

l. An apparatus for making an annular article of refractory material, which comprises a base, a member rotatably supported on said base and having a refractory portion and means whereby to rotate the same about an axis, a blast burner supported on said base and positioned to deliver a jet in the direction substantially parallel to said axis with said jet impacting the member at a limited region eccentric to said axis, means associated with the blast burner for supplying the same with combustible gas and particles of refractory whereby the jet is a high temperature flame and contains molten particles of the refractory which are deposited upon said refractory portion at said limited region for producing the annular article as the member rotates, said member having an axial aperture, and means whereby to deliver a gas into said aperture so that the gas flows in the direction substantially opposite to the direction of movement of said molten particles in the jet and through the member and the article as the latter is deposited.

5. An apparatus for making an annular article of refractory material, which comprises a base, a member rotatably supported on said base and having a refractory portion and means whereby to rotate the same about an axis, a blast burner supported on said base and positioned to deliver a jet in the direction substantially parallel to said axis with said jet impacting the member at a limited region eccentric to said axis, means associated with the blast burner for supplying the same with combustible gas and particles of refractory whereby the jet is a high temperature flame and contains molten particles of the refractory which are deposited upon said refraetory portion at said limited region for producing an annular mass of the molten refractory as the member rotates, said member having an axial aperture, means whereby to deliver a gas into said aperture so that the gas flows in the direction substantially opposite to the direction of movement of said molten particles in the jet and through the member and the article as the latter is deposited, and a heat-insulating jacket mounted on said base and surrounding the flame and effective to maintain a molten annular mass of the refractory material for successive presentation to said jet as the member and mass rotate and to permit solidification of parts of the mass adjacent to said member whereby to form the annular article.

RAYMOND HOLMES LESTER. MELVIN CROXALL CANNON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,597,293 Ruff Aug. 24, 1926 1,605,073 Ruff Nov. 2, 1926 2,272,342 Hyde Feb. 10, 1942 FOREIGN PATENTS Number Country Date 241,544 Great Britain Apr. 1, 1926

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