US3198871A

US3198871A - Westeren etal rotary furnace

Info

Publication number: US3198871A
Authority: US
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03

Description

Aug. 3, 1965 H. w. wl-:sTEREN ETAL 3,198,871

ROTARY FURNACE Filed June 26, 1961 2 Sheets-Sheet 1 BYJH.

Aug. 3, 1965 Filed June 26. 1961 lll 95 l H. w. wEsTi-:REN TAL 3,198,871

ROTARY FURNAGE 2 Sheets-Sheet 2 iftarrzey- United States Patent O 3,198,871 RGTARY FURNACE Herbert W. Westeren, Barrington, and William C. Diman, Warwick, Rl., assignors to C. I. Hayes, Inc., Cranston, 2.3i., a corporation of Rhode Island Filed .lune 26, 196i, Ser. No. 119,475 tl Claims. (Cl. 13-21) The present invention relates to a rotary furnace. More particularly the present invention relates to a furnace construction having a rotary drum that it is adapted to receive articles thereon from an inlet station, the articles being transferred by the rotary drum to a heating station for the heat treatment thereof.

The furnace construction embodied herein may be utilized to transfer various types of articles to a heating station wherein the article is preferably formed in a cylindrical configuration. One form of such an article is a small cylindrical rod or wire that is adapted to be heated and reshaped into a sphere for use as an electrical contact or the like. ln moving the cylindrical rods or wires to the heating station it has been found that a rotary drum assembly is particularly efficient in this respect and has the advantage of being speed controlled and further is able to discharge the heat treated article to a work collection station by the mere rotation thereof.

Accordingly, it is an object of the present invention to provide a rotary furnace having a drum therein that is adapted to transfer articles to a heat treating station, the articles being heat treated and then discharged to a collection station due to the rotary movement of the drum.

Another object of the invention is to provide a furnace construction that is adapted to heat treat cylindrical articles for transforming them into spherical elements.

Still another object is to provide apparatus for heat treating articles that includes a rotatable drum defined by a plurality of arcuate shaped segments covered by a graphite cloth, the cloth defining the peripheral surface of the drum.

Still another object is to provide a rotatable drum for use in the heat treatment of articles in a furnace construction, the drum including a plurality of segments covered by a graphite cloth in surrounding relation, and the graphite cloth being provided for absorbing the high temperatures in the furnace when the articles are located thereon.

Still another object is to provide a rotatable drum for use in a furnace that includes a hub member to which a plurality of segments are interconnected, the segments being radially movable to engage a surrounding cloth that defines the peripheral surface of the drum.

Still another object is to provide apparatus for forming small spherical elements that includes a drum that is removably mounted in the apparatus and that is adapted to be withdrawn from the apparatus by means of a track construction.

Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

In the drawings which illustrate the best mode presently contemplated by us for carrying out our invention:

FIG. 1 is a vertical sectional view of the furnace construction embodied in the present invention showing the relative position of the rotatable drum mounted therein, and a heating element vertically disposed above the drum at the furnace heating station.

FIG. 2 is a top plan View of the furnace construction illustrated in FIG. l;

FIG. 3 is a perspective view of one of the arcuate segments that form a part of the rotatable drum;

FIG. 4 is a perspective view of the arcuate segment to which a mounting element is attached, the mounting element being adapted to interconnect the segment to the hub member of the drum;

FIG. 5 is a perspective view of the hub member of the rotatable drum;

FIG. 6 is a sectional view taken along lines 6-6 in FIG. l;

FIG. 7 is a perspective view of the graphite cloth that surrounds the segments of the drum and that denes the peripheral surface thereof;

FG. S is an enlarged fragmentary perspective view of one of the segments showing the grooved peripheral surface thereof;

FIG. 9 is an enlarged fragmentary perspective view of the rotatable drum showing the relative position of the drum with respect to the furnace heating element that is illustrated in dotted lines, a plurality of articles being shown in cylindrical form on the drum periphery prior to deformation thereof by the heating element, and a JCC plurality of spherical elements being shown on the drum periphery after transfer out of the heating station and after the spherical formation thereof from their cylindrical configuration;

FG. 10 is a perspective view of one of the small cylindrical articles prior to the introduction thereof to the heating station of the furnace construction; and

FIG. ll illustrates the spherical form of a cylindrical article after it has been moved to the heating station and then melted and reformed due to the heat generated by the heating element.

Referring now to the drawings, and particularly to FIGS. l, 2, and 6, the furnace construction embodied in the present invention is illustrated and is generally indicated at It). The furnace construction 10 includes a base 12 on which the furnace unit is mounted, the furnace unit being defined by a housing generally indicated at 13 formed with a front Wall 14, a rear wall 15,

side Walls

16 and 17, a bottom wall 18 and a curved top wall 19. End caps 2li and 21 are secured to the uppermost ends of the front and

rear walls

14 and 15 respectively and define enclosed chambers therewith for receiving the ends of an electric heating element to the be described hereinafter. Also mounted on the base 12 is a control panel 22 on which suitable electrical controls, recording and indicating means are mounted for observing and controlling the heating cycle of the furnace construction.

The furnace construction may be utilized for heat treating various types of articles and is not limited to receiving and heat treating an article having any particular design, shape or configuration. However, for purposes of the description herein, the furnace construction 10 will be confined to the heat treatment of small metallic cylindrical rods or wire pieces that are adapted to be reformed into small spherical elements. In addition to the novel features of the furnace, the method of forming the small spherical elements is considered to be one of the novel aspects of the invention embodied herein.

In carrying out the sphere-forming operation it is necessary that the cylindrical wire pieces, one example of which is indicated at 25 in FlG. l0, be moved to a heating station where they are heated to the melting point, whereupon they immediately reform into small spheres. In order to transfer the Small wire pieces into the heating station, a work drum, generally indicated at 26, is provided and is mounted for rotation within the housing 13. The worlr drum 26 is mounted on a shaft 28 that extends through the front and rear walls 14 and 1S of the housing 13 and that is journalled in suitable bearings 30 and 32 that are mounted on the front and

rear walls

14 and 15 respectively. As will be described hereinafter, the Work drum 26 is keyed or splined to the shaft 21S so as to be slidable with respect thereto,

collars

34 and 36 being provided and being mounted on the shaft 23 for locating the bearings 39 and 32 in position with respect to the shaft. Secured to the left end of the shaft 2S, as seen in FIG. 6, is a pulley 3S with which a chain 4t) engages. A pulley 42, driven by a motor 44 through a speed reducer 46, is also engaged by the chain 4G and transfers the drive from the speed reducer 46 to the shaft 26. As will be described the work drum is rotated at a relatively slow speed, which is accomplished by interconnecting the speed reducer 46 to the motor 44 through a gear train 48 and increasing the diameter of the pulley 38 with respect to the pulley 42.

Although the work drum 26 is constructed as a unitary assembly, it includes a plurailty of elements that may bc removed from the assembly for replacement or repair. The central portion of the work drum Z6 is defined by a hub member illustrated generally in FIG. at Si), the hub member 5t? including a disc S2 having pairs of elongated openings S4 spaced around the surface thereof. Spaced radially inwardly from the periphery of the disc 52 is a circular flange 5S that is concentric with a central opening formed in the disc 52, the central opening receiving an elongated sleeve 66 therein that is secured to the disc 52. As illustrated in FGS. 5 and 6, the elongated sleeve 6G projects outwardly approximately the same distance on both sides of the disc 52, and is secured thereto by oppositely positioned triangular shaped plates 62, the right angles of which abut the disc 52 and the periphery of the sleeve 60. As best seen in FIG. 6, the shaft 28 extends through the sleeve 6), while cooperating suitably formed splines or keyways are formed in the sleeve 60 and on the shaft 28 for interconnecting the shaft and the sleeve for rotation, and for providing for relative axial movement therebetween when the work drum is to be removed from the furnace construction.

Forming the outer peripheral portion of the work drum 26, are a plurality of arcuate shaped segments 64 to the inner surfaces of which are suitably secured in some convenient manner curved or arcuate plates 66. The arcuate configuration of the segments 64 are such that the segments when placed in abutting relation form a continuous peripheral surface for the work drum. The segments 64 which are formed of a refractory material are adapted to be mounted in position on the hub member 5t) by means of the arcuate plates 66 to each of which is joined a radially extending plate 68 having an inturned flange 70 formed thereon. Formed in each of the radially extending plates 68 are spaced elongated openings 72 that are adapted to coincide with the openings 54 in the disc 52, While each flange 76 has a threaded hole 74 formed therein that receives an adjusting bolt 76 in threaded engagement therein. In the assembly of the work drum 26, securing bolts 78 are located in the aligned,

elongated openings

54 and 72 and secured therein by nuts 79, thereby mounting the arcuate segments 64 on the hub member Si). As shown in FIG. l, the adjusting bolts 76 are located in the threaded openings 74, the end of the bolts 76 bearing against the circular ange 5S that is formed on the disc 52. It is seen that the arcuate segments 64 may be forced outwardly through their plates 66 and 63 by rotating the adjusting bolts 76 in the appropriate direction. With the securing bolts 78 loosened, turning of the adjusting bolts 76 causes the flanges 7tl and the plates 68 and segments 64 interconnected thereto to walk outwardly thereby radially adjusting the position of the arcuate segments 64. As will be described below, this radial adjustment of the arcuate segments 64 is required for producing an accurate fitting for the peripheral surface of the work drum that is defined by a continuous web or piece of woven graphite cloth St). The graphite cloth Sil is positioned in surrounding relation with respect to the arcuate segments 64 and as illustrated, defines the peripheral surface of the work drum 26. With the cloth 80 located in surrounding relation around the arcuate segments 64, the adjusting bolts 76 are rotated so as to move the segments 64 radially outwardly, thereby causing the cloth Sti to be stretched tightly in engagement around the segments. When the segments 64 have been adjusted to the required position by the adjusting bolts 76, the securing bolts 7S are tightened to firmly secure the radially extending plates 68 to the disc 52 whereupon the arcuate segments 64 and the cloth Si) are retained in their tight fitting relation. As illustrated in FIG. 8, the outer surface of each arcuate segment 64 is formed with a plurality of laterally extending spaced grooves indicated at 81. The grooves Si define a plurality ot lateral edges that cooperate with the tightly stretched cloth 89 to prevent the web from wrinlding or forming uneven spots or Waves therein. In effect, the edges of the grooves 81 act to straighten any undulations or wrinkles that tend to form in the cloth surface, the resulting smooth cloth surface being essential during the sphere forming operation, as will be described hereinafter.

The peripheral surface of the work drum 26 that is defined by the cloth and the segments 64 forms a moving bed for a heating station which is indicated in FiGS. l and 6 at 82. The heating station 32 is further defined by an upper insulating slab S4 of refractory material in which an inverted trough 85 is formed, the sides of the trough S5 being bordered by marginal insulating slabs 86 and 3S that are also formed of a refractory material. The marginal insulating slabs 6 and 83 are mounted against the front and rear walls 14 and 1 5 respectively of the housing 13 on

brackets

90 and 92 respectively that are secured to said front and rear walls, the marginal insulating slabs 86 and 3S cooperating to support the upper insulating slab 84 thereon. The work drum 26 is mounted in the housing 13 such that the periphery thereof, defined by the arcuate segments 64 extend between the marginal insulating slabs 86, SS, the marginal insulating slabs being spaced apart sufficiently to provide for free movement of the work drum 26 therebetween.

Extending through the heating chamber 82 is an electrode or resistance-heating element 94, preferably formed of silicon carbide, .and being of sufficient length and diameter to produce the heat that is essential during the sphere forming operation. The silicon carbide heating element -94 is adapted to be electrically controlled in the operation of the `furnace, and may be heated up to temperatures as high as 2400 F., it lbeing understood that the heating element 94 will be externally controlled from the control panel 22. Although only one form of a heating element is illustrated it is further understood that other forms may be utilized in the furnace construction 10 for producing the necessary heat in the sphere forming operation. Referring again to FIG. 6, it is seen that the outer ends of the heating element 94 extend through the front and rear walls `14 and 1S of the housing 13 and are enclosed by the end caps 20 and 21, collars 93 4and 95 being secured to the Iheating element for positioning it in the trough 85 at the heating station 82.

Referring again to FIG. 1, the upper insulating slab 84 is shown formed with a passage 96 that communicates with the heating station 82 and an opening 98 formed in the curved top wall 19 of the cover 13. Secured in the `opening 98 and communicating with the passage 96 is a sight port 100 that projects outwardly of the cover 13 and provides for convenient viewing of the heating station 82.

In order to introduce the small cylindrical wire pieces lZ5 into the furnace construction, a Work entry chute 102 is provided and extends through an opening in the curved top wall 19 and through a corresponding passage 104 in the upper insulating slab 82 for communication with the periphery of the work drum `26 on the downstream side of the heating station 82. As shown in FIGS. l and 2, the Work entry chute y102 projects `outwardly from the curved top wall `19 and has a width substantially equal dieser/1 to the width of the work drumd for introducing a plurality of the wire pieces 25 onto the Work drum periphery. The chute 1l2 is further inclined to permit `gravitation of the Wire pieces downwardly onto the Work drum periphery and is also formed with a curved lower end 196 that acts to properly direct the gravitating wire pieces onto the periphery of the work drum.

Formed in the side wall 17 of the housing 13 is a discharge opening ltl through which a discharge chute 110 extends, the discharge chute 11@ Ibeing conveniently secured within the housing 13 and being located so as to receive the newly Vformed spheres thereon that have been formed at the heating station and are moved therefrom by the work drum 26 during the normal rotation thereof. As the newly formed spheres gravitate downwardly due to the rotation of the work drum in a clockwise direction as seen in FIG. 1, they fall onto the discharge chute 11i? which then directs them through the discharge opening 108 into a work collector 112 from which the spheres are removed for further handling. Oftentirnes it is nec- H essary to remove the work drum 25 from the housing l1? for maintenance or repair of the .parts thereof, 'However, since the surface of the graphite cloth 3ft must be maintained free of uneven spots or undulations, care must be taken to avoid rolling the Work drum 26 from the housing 13 on its periphery. For this purpose L-sbape tracks 114 .and 11.6 are provided and are secured to the inside sur-face of the front and

rear walls

14 and 15 respectively of the housing 13 and are disposed just below the mounted position `of the shaft ZS. As illustrated more clearly in FIG. 6, the L-shape tracks 11112 and 116 underlie the outer ends of the sleeve 6h and are adapted to support the work drum 26 through the sleeve 6ft when the work drum 26 is removed from the housing 13. In carrying out the removal operation of vthe work drum, the shaft ZS is first disengaged from the sleeve e@ by moving it longitudinally with respect thereto. Since the shaft 2S and the sleeve 6@ are interengaged only through a spline connection, longitudinal movement of the shaft with respect to the sleeve is permitted. It is understood that prior to removing the shaft 2S from engagement with the sleeve 60, the belt 4l), pulley 33 and

collars

34 and 36 are removed from their assembled position so as to permit longitudinal movement of the shaft 2S. Upon removal of the shaft 28 from engagement with the sleeve 6i) and withdrawal thereof from the housing 13, the work drum 26, through the sleeve 60, is supported by the tracks 1.14, 116. Fastening bolts 11S are next released so that the side wall K16 can be removed from the housing 13. The work drum 26 is then free for removal from the housing 13 on the tracks 114, 116. It is seen that by this technique the cloth St) will be prevented from contacting a surface and will thereby be protected from disgurement.

During the sphere-forming operation, it is necessary to provide an atmosphere Within the furnace unit that will prevent oxides from forming on the wire pieces 25. It is also necessary to prevent the graphite cloth Sti from oxidizing, and for this purpose an exothermic atmosphere is introduced into the furnace housing `13 through a port 12@ that is located in the lowermost end of the side wall 13 thereof. The exothermic atmosphere continuously circulates through the housing 13 and conditions the graphite cloth Sti and the metal pieces 2:7 to prevent the oxidation thereof, It is understood that 4other suitable treatment atmospheres may be utilized depending `upon the conditions and material treated.

In operation of the apparatus, the small metallic wire pieces or rods 25 are lintroduced into the housing 13 by way of the work entry chute 102. With the work drum 26 rotating at a relatively slow speed, the Wire pieces are directed onto the graphite cloth il@ by the curved end `106 of the work entry chute. The wire pieces are then slowly moved into the heating station 82 and underneath the heating element 94 which is spaced vertically above the periphery of the `work drum 2e. As the wire pieces Z5 move into the heating station 82, the high temperatures generated by the heating element causes them to reach the melting point thereof, whereupon, due to surface tension they are immediately reformed int-o spheres, one of which is indicated at 124 in FIG. 11. As the work drum 26 continues to rotate, the newly formed spheres are carried therewith until they reach a point whereby the weight thereof causes them to roll downwardly onto the discharge chute 110 and then into the work collector 112.

Since the wire pieces 2S are normally of such a small dimension, having a length of about 1/s of an inch, a plurality of them may be simultaneously introduced into the work entry chute 102 for deposit on the graphite cloth Sil. The wire pieces arrange themselves in rows, generally, as illustrated in FIG. 9, and as many as 14 to 16 pieces may constitute a single row. When the Work pieces are conveyed to the heating station 82, they are immediately brought to the melting point thereof due to the high temperatures present at the heating station. It is critical, at this point, that the base upon which the wire pieces rest, in this case the graphite cloth, be of such a material that will not rise in temperature as fast as the wire pieces. The idea is to prevent the surface on which the Wire pieces rest from reaching the melting point before the wire pieces, since should the surface on which the wire pieces rest be distorted by the heat, at spots would appear on the spheres as they are formed. The graphite cloth has a high emissivity with respect to that of the metallic wire pieces and will absorb heat fast but still has good insulating characteristics. This quality combined with the arcuate segments which are also formed of an insulating material prevents the graphite cloth from reaching the melting point thereof as quickly as the wire pieces` The low mass of the graphite cloth in addition to the insulating backing therefor causes the small wire pieces to heat partly by conduction and partly by radiation, which results in the Wire pieces heating rapidly and reaching the melting point thereof immediately after introduction into the heating station.

As the small Wire pieces reach the melting point, the surface tension of the material causes them to immediately reform in globule or spherical form. As the work drum 26 continues to rotate, the newly-formed spheres 124 are conveyed just beyond the heating station 82 which in effect causes the temperature of the spheres to lower. The spheres, then, in effect, freeze in their spherical form, and further rotation of the work drum causes them to roll into the work collector 112. It is also seen that the graphite cloth 80 must be relatively smooth and free of depressions or undulations that would tend to distort the spheres as they are formed from the wire pieces.

The small wire pieces are formed of a metal material, the characteristics of which will be determined by the end use of the spherical elements. It is contemplated that wire pieces of a gold-silver alloy will be utilized in the apparatus described herein although other alloys and eleents may be used as desired without departing from the spirit of the invention, the only limiting characteristics being that the metal material used cannot be fluid at ambient temperatures and small pieces thereof will reform into spheres when heated to the melting point thereof.

While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

We claim:

1. In apparatus for fabricating small spherical elements, a furnace construction including a housing having a work drum mounted for rotation therein, heating means located in said furnace and vertically spaced above said work drum, means for feeding small metallic pieces in elongated form into said housing and onto said work drum, means for rotating said work-drum for carrying said elongated pieces into close proximity to said heating means, wherein the heat generated by said heating means causes said elongated pieces to reach the melting point thereof and form into small spheres, means for collecting the newly formed spheres after they are discharged from said work drum, said work drum including a hub and a plurality of imperforate segments mounted on said hub and defining the periphery of said drum, and a heat absorbing cloth covering said segments and dening the outer peripheral surface of said drum for receiving the small elongated pieces thereon, said cloth absorbing the heat from said heating means so that the surface thereof is not distorted by the heat generated by said heating means, wherein said elongated pieces located on said cloth form into spherical elements when brought to the melting point thereof by said heating means.

2. In apparatus as set forth in claim 1, each of said segments having a plurality of laterally extending grooves formed on the outer surface thereof over which the heat absorbing cloth is positioned, said grooves acting to stretch the cloth so as to provide a perfectly smooth and uninterrupted surface for receiving said small metallic pieces thereon.

3. In apparatus for forming small metallic spheres, a furnace construction including a housing having a rotatable member mounted therein, heating means located in said housing for supplying heat therein and disposed in spaced relation with respect to said rotatable member to dene a heating station therebetween, means for feeding small metallic pieces in cylindrical form into said furnace and onto said rotatable member, means for rotating said rotatable member for moving said cylindrical metallic pieces to said heating station, wherein the heat generated by said heating means causes said cylindrical pieces to reach the melting point thereof and then form into small spheres and means for collecting the newly formed spheres after they are discharged from said rotatable member, and said rotatable member including a plurality of imperforate arcuate shaped segments formed of an insulating material around which a heat absorbing cloth is located in surrounding relation, said cloth forming the outer peripheral surface of said rotatable member for receiving said cylindrical pieces thereon.

4. In apparatus as set forth in claim 3, said heat absorbing cloth being formed of graphite.

5. In apparatus as set forth in claim 3, each of said arcuate segments being formed with a plurality of laterally extending grooves in the outer surface thereof that underlie said cloth, said grooves acting to stretch said cloth so as to form a smooth and uniform surface for receiving said metallic pieces thereon.

6. In apparatus as set forth in claim 3, said arcuate segments being joined to a central hub through intermediate connectors, and means for radially adjusting said connectors to force said segments into firm contact with the cloth that is located in surrounding relation with respect thereto.

7. In a rotary furnace, a housing having a rotatable member mounted therein, a heating element located in said housing for supplying heat therein and disposed in spaced vertical relation with respect to said rotatable member to dene a heating station therebetween, said rotatable member including a plurality of imperforate arcuate segments that are interconnected to a hub member and cooperate therewith to define a cylindrical drum construction, a web of material formed of graphite cloth disposed around said segments in surrounding relation and defining the outer peripheral surface of said rotatable member, means for radially moving said segments with respect to said hub member to tension said graphite cloth surrounding said segments, means for introducing work pieces to be heat treated into said furnace and onto the outer peripheral surface of said rotatable member, means for rotating said rotatable member for moving said work pieces to said heating station, wherein the heat generated by said heating element causes said work pieces to reach the melting point thereof and then form into small spheres, and means for collecting the newly formed spheres after they are discharged from said rotatable member.

S. In apparatus as set forth in claim 7, means mounted on said housing for removing said rotatable member from said furnace including a trackway for receiving and retaining said hub member therein during the removing operation, whereby the peripheral surface of said rotatable member is prevented from making Contact with a surface during said removing operation.

References Cited by the Examiner UNITED STATES PATENTS 849,141 v4/07 Ladd 34-115 1,728,371 9/29 Shelton et al 13--21 2,038,251 4/36 Vogt 18-48 2,404,986 7/46 Roth 13-21 2,793,282 5/ 57 Steigerwald 18-2.2

` 2,867,000 1/59 Huszar.

3,019,485 2/ 62 Diamond 18-48 RICHARD M. WOOD, Primary Examiner. MAX L. LEVY, Examiner.

Claims

1. IN APPARATUS FOR FABRICATING SMALL SPHERICAL ELEMENTS, A FURNACE CONSTRUCTION INCLUDING A HOUSING HAVING A WORK DRUM MOUNTED FOR ROTATION THEREIN, HEATING MEANS LOCATED IN SAID FURNACE AND VERTICALLY SPACED ABOVE SAID WORK DRUM, MEANS FOR FEEDING SMALL METALLIC PIECES IN ELONGATED FORM INTO SAID HOUSING AND ONTO SAID WORK DRUM, MEANS FOR ROTATING SAID WORK DRUM FOR CARRYING SAID ELONGATED PIECES INTO CLOSE PROXIMITY TO SAID HEATING MEANS, WHEREIN THE HEAT GENERATED BY SAID HEATING MEANS, SAID ELONGATED PIECES TO REACH THE MELTING POINT THEREOF AND FORM INTO SMALL SPHERES, MEANS OR COLLECTING THE NEWLY FORMED SPHERES AFTER THEY ARE DISCHARGED FROM SAID WORK DRUM, SAID WORK DRUM INCLUDING A HUB AND A PLURALITY OF IMPERFORATE SEGMENTS MOUNTED ON SAID HUB AND DEFINING THE PERIPHERY OF SAID DRUM, AND A HEAT ABSORBING CLOTH COVERING SAID SEGMENTS AND DEFINING HE OUTER PERIPHERAL SURFACE OF SAID DRUM FOR RECEIVING THE SMALL ELONGATED PIECES THEREON, SAID CLOTH ABSORBING THE HEAT FROM SAID HEATING MEANS SO THAT THE SURFACE THEREOF IS NOT DISTORTED BY THE HEAT GENERATED BY SAID HEATING MEANS, WHEREIN SAID ELONGATED PIECES LOCATED ON SAID CLOTH FROM INTO SPHERICAL ELEMENTS WHERN BROUGHT TO THE MELTING POINT THEREOF BY SAID HEATING MEANS.