US3190728A - Apparatus for melting material by means of a flame of elevated temperature - Google Patents

Description

A. YUNDERINK June 1965 APPARATUS FOR MELTING MATERIAL BY MEANS, OF A FLAME OF ELEVATED TEMPERATURE Filed May 10. 1961 u AT: v ubEk/NK INVENTOR.

BY J44 Chap m m United States Patent" t 3 190 72s APPARATUS non irnrrrrro MATERIAL BY MEANS or FLAME or ELEVATED TEM- PERATURE i Ate Vunderink,'Bussurn, Netherlands, assignor to Ronette Piezo Electrische Industrie N.V., Amsterdam, Netherlands, a corporation of the Netherlands Filed May 10, 1961,5er. No. 109,068

'Claims priority, application Netherlands, Oct. 27, 1960,

256,337/60 6 Claims. or. 23-473 The present invention relates to an apparatus for melting powdered material by means 'of a flame of'elevated tem perature .and for precipitating said molten material, including a burner comprising two concentric tubes, the outermost of which is connected to a source of combustible gas and the innermost of which is connected to a source of of such apparatuses is to form a pear or rod-shaped body from powdered material having a high melting point, by

melting the particles of the powder and by precipitating saidmolten particles on a catching surface, saidv pear or rod-shaped body consisting of a monocrystal of the desired material or a polycrystalline form of said material, in which the crystallites have a specific orientation.

Said method maybe used for example for the manufacture of synthetic corund-um and spinel;

One of the most important conditions that are to be satisfied if the method is to proceedsatisfactorily, is that the rate of growth of the body to be formed is kept con stant very accurately. Said rate of growth especially depends on the amount of powder supplied to the flame and is furthermore influenced by changes, if any, in the distance between the burner-mouth and the surface on which the molten particles precipitate.

i The object of the invention is to provide an apparatus which very favourably compares with the known apparat-uses. asregards the fulfillment of the conditions just mentioned. 7

To achieve this end the apparatus according to the invention is so formed that the powder dosing device comprises a closed housing communicating with the source of oxygen, which housing contains a powder supply vessel, a powder carrier having a powder supporting face which in plan view is narrow, elongated and tapers into a sharp point,

a mean forcontinuouslyfeeding powder from the powder supply vessel to the. powder carrier and a discharg tube which passes through the wall of the housinguand connects .the interior of the housing with the innermost burner tube, the entrance of the discharget-ube and the 'powdercarrier being adjustably :displaceable relative to each other. 1

Theapparatus according to the invention may also be so designed that the powder supply vessel, the powder feeding means and the powdercarrier are formed by a vertical hollow cylinder open at the upper side having a gutter shaped recess helically provided in its innerwall, which recess begins at the bottom bf the cylinder and gradually terminates into'the upperrim of the cylinder, which rim is located in a horizontal plane. up p For elucidating the invention some embodiments will be described with reference to the accompanying drawings, in which:

FIG. 1 is aschematic showing of'a first embodiment according to the invention in which the flame is directed upwardly; 7

:FIG. 2 is a vertical section of the power vessel as shown in FIG. 1;

FIG. 3 is a plan view of the powder vessel according to FIG. 2;

FIG. 4 is a bottom view of the powder vessel according to FIGS. 2 and 3, in which more particularly the leaf springs supporting the powder vessel are shown;

FIG. 5 is an alternative embodiment in which the flame is directed downwardly. V

The burner shown in FIG. 1 comprises an inner tube 1 and an outer tube 2 that are concentrically arrangedrelative to each other. A supply tube 3 coming from a source of a combustible gas (not shown) is connected to said outer tube 2. Said conduit 3'is provided with a regulating valve 4. A conduit 5 connected to a source of oxygen (not shown) and provided with a regulating conduit 7 branches into a conduit 10 and a conduit 9. Conduit 10 leads to a chamber 6 which is in direct communication with the inner tube '1. Conduit 9 leads to a powder dosing device to be described hereinafter.

By means of the regulating valve7 the total amount of oxygen supplied can be regulated, said amount of oxygen being distributed over the conduits 9 and 10 by means of the regulating valve 8.

The powder dosing device is accommodated in an entirely closed housing 11. The oxygen conduit 9 communicates with the interior of the housing 11; In the bottom 12 of the housing 11 a circular groove 13 is provided. A round plate 14 stands with four legs 15 in the groove 13. Three obliquely arranged leaf springs 16, 17 and 18 bear with their lower ends on the plate 14 and with their upper ends carry a powder vessel 19. As appears from FIGS. 2 and 3 this powder vessel 19 is cylindrical and is provided with a bottom, but it is open at the upper side, so that this vessel can contain an' amount of powder. In the innerwall of the powder vessel 19 a helical recess 20 is provided, the lower wall of which recess is gutter-shaped. Seeing that the powder vessel 19 hasa fiat horizontal upper side it .will be clear that the gutter-shaped portion 21'at the upper side of the powder vessel gradually tapers into a curved point-shaped end shown at 22 in FIG. 3. Against the lowerside of the vessel 19 a round plate of magnet- .isable material 23 is secured, while beneath said plate an electro-magnet 24 is arranged. If the electr c-magnet 24 is energized via the leads 25 the plate 23 functioning as an armature will be pulled downwardly over a certain distance, as a result of which the powder vessel 19 likewise moves downwardly of course. The springs 16, 17 and 18 will slightly flex then which is attended by the displacement of the upper ends of said springs in horizontal direction, so that the powder vessel 19 not only moves downwardly, but in addition is rotated over a certain angleabout its vertical axis. 1

The arrow 38 in FIG. 4-which is a bottom view of the powder vessel'shows the direction in which the powder vessel 19 rotates when it moves downwardly under the influence of the electro-inagnet 24. When the energizing current is interrupted the powder vessel moves upwardly again, while simultaneously it again rotates back about its vertical axis. If the powder vessel 19 contains an amount of powdered material, said material will in the first place be subjected to a centrifugal force, so that this material will move outwardly as far as possible, i.e. towards the recess'20. As long as there is powdered material in the vessel 19 there will alwaysbe a winding of the recess 20 into which the powder will move. .Now the nature of the movements of the powder vessel 19 'is such that as a'result of said movements the :powder will be gradually moved upwardly through the helical recess 20. Preferably the mass of the powder vessel 19 and the stiff- Patenied June 22, 1965 V ness of the leaf springs 16-18 are so chosen that the natural frequency of the vibrating powder vessel is adapted to the frequency of the current through the magnet coil 24 in order to thus obtain a sufliciently large amplitude. At the upper end of the vessel 19 the recess, as has been observed hereinbefore already, tapers into a point, so that the amount of powder which can be contained in the upper end of said reces gradually decreases. Seeing that the supply of powder from below always continues and as the tapering end of the recess and notably the guttershaped portion 21 thereof will be able to contain less and less powder, the powder that cannot be contained in said recess will fall back into the vessel 19 and join the supply of powder still present therein. The result is that there is an arcnate portion of the gutter 21 in which in various places along the arch different amounts of powder are available, while all the same in each place the supply of fresh powder regularly continues.

Above the end 22 of the gutter-shaped portion 21 there is a vertical tube 25 which passes through the upper wall 26 of the housing 11 and which ends adjacent the entrance to the innertube 1. Oxygen supplied through conduit 9 can only escape from the casing 11 through tube 25. When the oxygen enters the lower end of tube 25 an amount of powder from the portion 22 of the helical recess will be entrained. How much powder will be entrained in point of fact depends on it whether a broader or a narrower portion of the gutter-shaped winding 22 is located beneath the entrance of tube 25. This depends in turn on the adjustment of the plate 14 which may be effected by turning it by means of an operating rod 27 extending from the housing 11 through the bottom 12 thereof. During the turning of the plate 14 the legs 15 on which it stands will move through the groove 13. The amount of powder entrained by the oxygen passing through tube 25 can be controlled therefore in the first place by turning the vessel 19 relative to the tube 25 and in the second place by controlling the amplitude of the energizing current passed to the electro-magnet 24, so that by unit-of-time more or less powder is passed upwardly.

The flame produced by the burner is schematically shown at 28. Said flame entrains powder particles which will deposit on a catching surface 29. Said catching surface 29 is secured to a driving means, schematically shown as comprising a toothed rack 30 which by means of a rotatable pinion 31 is adapted to be moved upwardly and downwardly in vertical direction.

The material precipitated on the catching surface 29 and gradually growing into the shape of a rod is shown at 32. Adjacent the place where the molten material precipitates an optical system is arranged, said system being schematically designated by 33. Said optical system 33 is so arranged and directed that it receives the light emitted by the molten material that has just precipitated. Said light is concentrated into a bundle by the optical system 33, which bundle falls onto a photo-electric cell 34. The electric current produced by the photo-electric cell 34 is passed through leads 35 to an electric feeding and regulating apparatus 36. The alternating current produced by said apparatus 36, which current asregards its amplitude depends on the current generated'by the photo-electric cell 34, is passed to the electro-magnet 24 by leads 25'.

The operation of the apparatus is as follows:

Powder vessel 19 contains an amount of powder. Combustible gas flows via conduit 3, the regulating valve 4 being entirely or partly open, to the outer tube 2 in which it rises upwardly. Oxygen flows through conduit 5, the regulating valve 7 being entirely of partly open and regulating valve 8 occupying a certain position, so that therefore the oxygen enters the apparatus in two places. In the first place it enters chamber 6 and in the second place it enters housing 11. From chamber 6 oxygen can escape in upward direction through the innertube 1.

In chamber 6, therefore, a weak flow in upward direction results. The oxygen which has entered housing 11 leaves this housing through tube 25. The oxygen flowing upwardly through tube 25 will continuously entrain an amount of powder from that portion of the tapering gutter 22 that is located beneath tube 25. The adjustment of a portion of gutter 22 beneath said tube is effected by manipulating the operating handle 27 so as to obtain a coarse adjustment of the amount of powder to be entrained. The accurate adjustment of the amount of powder to be entrained is effected by varying the amplitude of the energizing current of the electro-magnet 24. Said energizing current is an alternating current originating from the feeding and regulating apparatus 36.

As the material precipitates, initially on the catching surface 29 and afterwards on the material which has precipitated previously, the toothed rack 30 is gradually moved upwardly as a result of the rotation of pinion 31 according to arrow 37. Now it is the intention, as has been stated before, that the distance between the burner mouth and the place of crystal growth remains very accurately constant. Now this is achieved by means of the optical system 33 in cooperation with the photo-electric cell 34. The optical system is so arranged, that an image is obtained of the material that has precipitated most recently, as well as of the tip of the flame. As the flame emits relatively little light the total light intensity will be determined substantially exclusively by the growing crystal body. The intensity of the light received therefore is slight when the photo-electric cell 34 does not receive light from the place of growth of the crystal body and is large if such light is received. The latter case presents itself if the growing of the crystal should take place slightly too rapidly. In said case the rate of growth should be slightly decreased which can be effected by introducing less powder into the flame. This is effected because the increased intensity of the light received by the photo-electric cell 34 produces an electric current which so influences the feeding and regulating apparatus 36 that the current supplied by said apparatus for energizing the electro-magnet 24 will have a smaller amplitude. A

The result thereof is that less powdered material is moved upwardly through the helical recess 20, so that in consequence less powder is supplied to the portion of the gutter 22 above which the tube 25 is located. Seeing that a smaller amount of material is conveyed to said portion a smaller amount of powder will be entrained by the oxygen flowing through tube 25, so that also the amount of powder entering the flame 28 will be smaller. With the total oxygen supply remaining equal the powder supply will decrease. Thus the rate of growth of the crystal will be slowed down, so that the place of crystal growth will move upwardly relative to the burner mouth and this will continue until the image formed by the optical system 33 has again the right configuration. Said control of the rate ofgrowth by controlling the dosing of powder operates exceedingly accurately, so accurately in fact that'the object contemplated can be fully achieved. As a result it is no longer necessary to employ the method which has been conventionally used so far and according to which differences in the rate of growth were compensated for by moving the catching surface temporarily more rapidly or more slowly upwardly. The conventional apparatuses for varying the speed of movement of the catching surface were relatively complicated and not very accurate.

In the apparatus under consideration the catching surface is moved upwardly at a constant speed and the rate of growth itself is adjusted by means of the dosing of powder.

FIG. 5 shows a portion of a similar appartus as the one shown in FIG. 1, in which, however, the flame is direoted downwardly. This may be effected in a very simple manner by bending the powder discharge tube 25 through so that the stream of powder therefore is ultimately directed vertically downwardly. The burner may then also be arranged upside down, so that the flame is directed downwardly.

I claim:

1. In apparatus for melting powdered material by means of a flame of elevated temperature and for precipitating said molten material in the form of a rod, includ ing a burner comprising two concentric tubes, means to supply combustible gas to the outer of said tubes, means to supply oxygen to the inner of said tubes, powder dosing means including a closed chamber, conduit means having an inlet end in communication with said closed chamber and an outlet end in communication with said inner burner tube, a catching surface for precipitated material adjacent said burner and positioned in vertical axial alignment therewith, means to move said catching surface away from the burner in a vertical direction at a constant rate, means to supply oxygen under pressure to the closed chamber of the powder dosing means, powder supply means within said closed chamber, a trough-shaped powder-carrying channel means contained within said chamber and open along its length to said powder supply, said channel means terminating in a discharge portion having gradually reduced powder-carrying capacity, said discharge pontion being positioned adjacent the inlet end of said conduit means to cause powder to be injected into said conduit means by the flow of said oxygen under pressure into said inlet end to supportcombustion at said burner, means to move powder into said channel means and toward said discharge portion, rate of said injection of powder.

2. The invention as defined in claim 1, wherein means is provided to mount the inlet end of the conduit means and the discharge portion of the channel means in relatively movable relationship.

3. The invention as defined in claim 1, wherein vibra and means to vary tory mounting means is provided for the channel means to induce mevement of powder toward the discharge portion, and means is provided to vary the rate of said vibration.

4. The invention as defined in claim 1, wherein said powder supply means comprises an open-topped cylindrical vessel, and said powder-carrying channel is helically formed in the interior wall of said vessel.

5. The invention as defined in claim 4, wherein said conduit means is fixed and said vessel is mounted for relative movement about its vertical axis. a

6. The invention as defined in claim 4, wherein vibratory mounting means is provided for said vessel to induce movement of powder toward the discharge portion of the channel means, and means is provided to vary the rate of said vibration.

References Cited by the Examiner UNITED STATES PATENT Beckman 302-53 FOREIGN PATENTS 243,251 11/25 Great Britain. NORMAN YUDKOFF, Primary Examiner.

ANTHONY SCIAMANNA, MAURICE A. BRINDISI,

Examiners.

Claims (1)

1. IN APPARATUS FOR MELTING POWDERED MATERIAL BY MEANS OF A FLAME OF ELEVATED TEMPERATURE AND FOR PRECIPITATING SAID MOLTEN MATERIAL IN THE FORM OF A ROD, INCLUDING A BURNER COMPRISING TWO CONCENTRIC TUBES, MEANS TO SUPPLY COMBUSTIBLE GAS TO THE OUTER OF SAID TUBES, MEANS TO SUPPLY OXYGEN TO THE INNER OF SAID TUBES, POWDER DOSING MEANS INCLUDING A CLOSED CHAMBER, CONDUIT MEANS HAVING AN INLET END IN COMMUNICATION WITH SAID CLOSED CHAMBER AND AN OUTLET END IN COMMUNICATION WITH SAID INNER BURNER TUBE, A CATCHING SURFACE FOR PRECIPITATED MATERIAL ADJACENT SAID BURNER AND POSITIONED IN VERTICAL AXIAL ALIGNMENT THEREWITH, MEANS TO MOVE SAID CATCHING SURFACE AWAY FROM THE BURNER IN A VERTICAL DIRECTION AT A CONSTANT RATE, MEANS TO SUPPLY OXYGEN UNDER PRESSURE TO THE CLOSED CHAMBER OF THE POWDER DOSING MEANS, POWDER SUPPLY MEANS WITHIN SAID CLOSED CHAMBER, A TROUGH-SHAPED POWDER-CARRYING CHANNEL MEANS CONTAINED WITHIN SAID CHAMBER AND OPEN ALONG ITS LENGTH TO SAID POWDER SUPPLY, SAID CHANNEL MEANS TERMINATING IN A DISCHARGE PORTION HAVING GRADUALLY REDUCED POWDER-CARRYING CAPACITY, SAID DISCHARGE PORTION BEING POSITIONED ADJACENT THE INLET END OF SAID CONDUIT MEANS TO CAUSE POWDER TO BE INJECTED INTO SAID CONDUIT MEANS BY THE FLOW OF SAID OXYGEN UNDER PRESSURE INTO SAID INLET END TO SUPPORT COMBUSTION AT SAID BURNER, MEANS TO MOVE POWDER INTO SAID CHANNEL MEANS AND TOWARD SAID DISCHARGE PORTION, AND MEANS TO VARY RATE OF SAID INJECTION OF POWDER.

Images