US3052199A

US3052199A - Method and apparatus for making tube

Info

Publication number: US3052199A
Application number: US818483A
Authority: US
Inventors: George S Wiley
Original assignee: Bundy Tubing Co
Current assignee: Bundy Tubing Co
Priority date: 1959-06-05
Filing date: 1959-06-05
Publication date: 1962-09-04
Anticipated expiration: 1979-09-04

Description

Sept. 4, 1962 a. s. WILEY METHOD AND APPARATUS FOR MAKING TUBE 2 SheetsSheet 1 Filed June 5, 1959 INVENTOR. 650/265 5. W/LEY q) BAL ATTORNEYS Sept. 4, 1962 G. s. WILEY METHOD AND APPARATUS FOR MAKING TUBE 2 Sheets-Sheet 2 Filed June 5, 1959 INVENTOR. GEORGE S. WILEY 5 M,WM

ATTOQNEVS United States Patent Michigan Filed .Iune 5, 1959, Ser. No. 813,483 7 Claims. (Q1. 113-33) This application is a continuation in-part of my copending application Serial No. 511,281 filed May 26, 1955, now abandoned. This invention relates to the manufacture of tubing which is formed from strip metal stock. It has to do particularly with the making of tube where the interfaces of the strip stock are joined by the application of molten metal.

The invention is applicable to tube structure where the strip is fashioned to provide a wall of single thickness with edge portions of the stock disposed in interfacing relationship thus forming a seam. The edges may be disposed in abutting relationship thus forming what is ordinarily called a butt seam, although the edge portions may be formed to provide varieties or variations of the seam, as, for example, by shaping them to provide a greater interfacial area.

The invention is also applicable to tube structure wherein one or more strips of stock are fashioned to provide a tube wall :having plural plies in interfacial engagement and wherein interfacing portions of the stock provide an external seam.

In accordance with the invention, after the strip has been fashioned to tubular form and while the interfacing portions of the strip are tightly interengaged, the molten sealing metal is applied to the seam area only of the tube under conditions of very slight hydrostatic pressure. The sealing metal penetrates the interfaces by capillarity alone. This insures that none of the sealing metal will be forced into the tube interior beyond the internal seam boundary. Except for the region of the tube immediately adjacent the seam, the exterior of the tube remains uncoated so that only a minimum of the sealing metal is used.

FIG. 1 is a general view illustrating the method and showing one form of apparatus for making the tubing.

FIG. 2 is an enlarged cross sectional view taken sub stantially on line 2-2 of FIG. 1 showing pressure rolls.

FIG. 3 is an enlarged cross sectional view taken on line 3-3 of FIG. 1 showing the application of molten sealing metal.

FIG. 4 is a cross sectional view showing a tube with a modified form of se'am.

FIG. 5 is a cross sectional view of a tube showing a further form of seam.

FIG. 6 is a cross sectional view showing a tube having a two ply wall.

FIG. 7 is a sectional view of having a two ply wall.

FIG. 8 is a generally diagrammatic illustration of another form of apparatus for making the tubing.

FIG. 9 is an enlarged sectional view on line 9-9 of FIG. 8.

As illustrated in FIG. 1 the strip metal stock 1 may be pulled from a coil 2. The strip is preferably steel although other metals may be used with appropriate bonding metal. The strip is moved with longitudinal movement through a tube mill generally illustrated at 5. Such a mill is known to those versed in the art and comprises suitably formed rollers for fashioning the strip transversely into hollow cross sectional form. The mill 5, however, contrary to the conventional procedure, fashions the tube so that the seam is on the under side a different type of tube vof the tube. The mill is provided with pressure rollers at or near its outlet end and these may be disposed on vertical axes as shown in FIG. 2. The pressure rollers are indicated at 7 and 8 and are grooved to engage the tube T. It will be seen by reference to FIG. 2 that the edges of the strip are disposed at the lower portion of the tube and the edges are brought together in abutting relationship, as at 10.

The pressure applied by the rolls 7 and 8 is preferably such as to strongly force the interfaces of the edges together. This pressure may be sufiicient to slightly coin the edges as they are pressed against each other. It will be understood that certain of the rollers of the forming mill are driven by suitable means, thus to propel the strip longitudinally, and the pressure rolls 7 and 3 are preferably driven because the throat formed thereby is somewhat restrictive in order to apply pressure to the tube,- and it is preferable to drive the rollers 7 and 8 at a slightly higher peripheral speed than some of the rolls in the forming mill. The tube in the forming mill may be disposed substantially horizontally.

The tube mill is preferably disposed at an angle to the horizontal so that the strip stock and the tube fashioned therefrom moves lengthwise downwardly and angularly. The purpose of this, as will presently appear, is to position the tube for the application of the molten sealing metal.

The tube is heated preparatory to receiving the molten sealing metal and to this end is advantageously heated by electrical resistance. As shown, there is a roller electrode with a cooperating back up roller 21, another roller electrode 22 with a back up roller 23, while the third electrode is in the form of a molten body of sealing metal. The molten metal as at 25 may be retained in a suitable vessel 26. The primary of a transformer is shown at and the secondary at 31 for providing low voltage, high amperage, alternating electric current. The secondary 31 is connected by a lead 33 to the electrode 25 and by a lead 34 to the electrode 20. The other side of the secondary is connected by a lead 35 to the intermediate roller electrode 22. In this way the current is divided from one side of the secondary to the two outside electrodes and this arrangement facilitates simplifying the matter of electrically insulating the machine and the tube.

The molten metal 25 may be maintained in molten condition by heating means, shown herein as electrical resistance elements 37 with conductors 38 which are to be connected to suitable source of electrical current.

Positioned over the vessel 26, which is open at its top, is a grooved roller or wheel 40'. This roller may be comprised of inner and outer parts, as shown at 41 and 42 with electrical insulating material between the parts as shown at 43. The wheel is mounted upon an axis 44 and is driven to impart thereto a peripheral speed substantially corresponding to the lineal speed of the tube.

The downwardly and angularly extending run of tube engages in groove 45 of the roller 40. The roller is so located with reference to the level of the molten metal that the under side of the tube is caused to dip into the molten metal as the tube traverses that segment or are of the roller at the lower portion thereof. This is indicated in FIG. 3. The groove 45 preferably has a depth approximately equal to the outside radius of the tube so that the tube is snugly engaged in the groove and the abutting edges 10 thus held against each other. As the tube traverses the under side of the wheel 40 it partakes of the arcuate form of the wheel, in sort of a bight, and then the tube passes upwardly and angularly through a set of rolls 46. At least some of these rolls are driven, at such speed as to pull the tube and place a tension thereon so as to maintain the night of the tube in contact with the roller 40.- The rolls 46 also serve as cooling rolls from the standpoint of cooling the work to a temperature sufficient for the solidification of the sealing metal. As

the tube leaves the cooling and pulling rolls 46 it passes into a cooler 48 which may be an elongated jacketed tubular structure having an outer jacket 49 and an inner jacket 50. Cooling medium, such as water, may be introduced between the jackets through pipes 51 and 52 and the finished tube passes out through the end of the cooler as indicated.

The guide wheel or guide roller 40 is so positioned that the projecting lower portion of the bight of the tubes dips into the molten metal as indicated in FIG. 3. The tube has been preheated to a temperature adequate for the application of the bonding metal, and the metal flows rapidly in between the interfaces thus thoroughly and uniformly effecting a bonding film therebetween. This is due to capillarity. The seam area of the tube dips only slightly below the surface of the molten metal and the hydrostatic pressure at the seam area is insignificant. Thus, as a practical matter, penetration of the sealing metal is by capillarity alone and the sealing metal will not penetrate into the tube interior beyond the inner boundary of the seam.

The invention is particularly applicable to the formation of steel tube sealed with copper. Thus the body of metal is of copper and may be substantially commercially pure copper. Of course, brazing metals, copper in this instance being considered as a brazing metal, other than pure copper may be employed with steel. A tube can be made in accordance with the invention where steel strip is used with the interfaces bonded together by a form of soft solder, such as a tin and lead alloy, or by a form of one the so-called hard solders which may contain silver. Also, other metals may be used such as copper of Monel strip in which case the solder or bonding metal will be suitably selected for use with copper or Monel, such, for example, as a lead and tin alloy, or for that matter, a hard solder, provided the hard solder melting point is below the melting point of the metal of the strip.

The heating of the tube, especially where copper is employed for bonding steel, may be such as to raise the temperature to a point Where the elasticity of the metal of the tube diminishes or may be entirely lost, but in this event, since the tube is already formed with the interfaces closely together, the loss of elasticity does not cause an opening or spreading of the interfaces. Therefore, as the heated tube leaves the guiding roller and passes to and through the pulling and cooling rolls 46, the interfaces, with the film of bonding metal therebetween, remain in close interfacial relationship and by the time the tube passes through the set of rolls 46 the bonding metal has solidified so that the slight bend formed as the tube passes into the cooler does not deleteriously affect the bonded seam.

It is preferable to maintain the heated tube and molten metal in a non-oxidizing or reducing environment. To this end, a suitable housing 55 is placed around the roller electrodes 20 and 2 2 as well as the space between them, and this housing joins to and connects into a housing 56 surrounding the guide wheel 40 and vessel 26 of molten metal. A housing 57 joins with housing 56 and encloses the pulling rolls, and the housing 57 connects into the cooler as by a tubular housing element 58. The housing 56 serves as a cooler to lower the temperature to solidify the sealing metal and rolls 46 aid in this action. A suitable reducing or non-oxidizing gas maybe entered through the inlet pipe 60. Some of this gas may flow out through the inlet end of the housing 55 as indicated by the arrows and some may pass out through the end of the cooler. The tube is preferably cooled to the point so that when it finally passes into the atmosphere its temperature has been reduced so that no deleterious oxidation occurs.

The invention is applicable to the making of tubes with a variety of seams. The one described is where the edges of the stock'directly abut each other and this is kn n as a butt seam. A different variety of seam is 41 shown in FIG. 4 where the work piece T1 has its edges formed to overlap each other as at 65.

Although this is a form of lap seam, the edges of the overlapping parts are abrupt and the seam can thus be subjected to compression before the interfaces have been bonded together. A still further form of seam is shown in FIG. 5 where the work piece T2 has one edge formed with converging faces which meet substantially at an apex While the opposite edge is correspondingly grooved so that the edges interfit with each other to form a seam 66. This type of scam can also be subjected to pressure before the edges are bonded together.

The advantages of the invention can probably be Well appreciated by considering, as an example, the making of a tube having an outside diameter of about of A2", from strip steel stock having a thickness of about .028 and bonded with copper. The interfacial area is very small and the amount of material is small. The amount of copper needed to make the best joint is so small that it is not feasible to supply the copper in solid form. A foil strip of the correct amount of copper could not be supplied to the tube because it would be too small, delicate and weak to be handled. Any strip or wire large enough to be handled would supply a great excess of copper resulting in a weakened seam and perhaps accumulated spots or droplets of copper along the tube. To supply the seam with wire or strip in solid form would necessitate making some deformation in the edges to provide a cavity to accommodate the same, and this would result in weakening the seam. By supplying the copper in molten form, after the tube is formed and heated, the space between the interface acquires by capillarity just the amount of copper needed to fill in between the interfaces, and the material of the strip in the vicinity of the seam is not deformed in any way.

Only the portion of the tube exterior immediately adjacent the seam is coated with the sealing metal. Therefore, a minimal amount of the sealing metal is used in making the tubing and the tubing can be relatively inexpensively manufactured.

The tube T3 illustrated in FIG. 6 is made from two strips of stock, one forming the outer ply 7t} and the other forming the inner ply 71, ply 74) having abutting side edges 72 and inner ply 71 having abutting side edges 73. The plies are in interfacial engagement as at 74. This type of tube can also be made on a conventional tube mill known to those versed in the art. When this tube is passed under roller 4b, the interspaces at 7274 are held at capillary dimension so that the bonding metal enters seam 72, flows around interfaces 74 and penetrates into seam 73.

FIG. 7 shows another form of tubing T4 having a twoply Wall and this tube is formed from a single strip of stock double wrapped in a conventional tubing mill. This tube has an external longitudinal seam 75, interfaces 76 between the plies and an internal seam 77. The seams and interfaces are maintained at capillary spacing when this tube is passed under roller 40 and the sealing metal penetrates from outer seam to interior seam 77 by capillary. In both this type of tube and the type shown in FIG. 6 the sealing metal penetrates only to the in ternal boundary of the inner seam and not to the tube interior. In each of these two cases the seam area only of the tube exterior is coated.

The apparatus shown in FIGS. 8 and 9 is generally similar to the apparatus described above except that after tube T emerges from tube mill 5 and passes through the resistance heater, it is passed upwardly through the groove 45 of a pressure roll 40. Apposed to the pressure roll is a small vessel or crucible 80 having shoe portion 31 pressed into sliding engagement with portions of tube T adjacent seam 10 by a spring 82 supported on a suitable mount 83. Crucible 80 is hollowed out as at 84 and the hollow is open at its side adjacent the tube. Shoe portions 81 of the crucible and the bottom unhollowed portion cooperate with portions of the tube engaged thereby to provide a reservoir for containing a small pool 86 of molten bonding metal which may be continuously replenished through a feed pipe 87. Crucible 80 is maintained in heated condition by suitable means such as heater coils 88 having electrical leads 89. The crucible preferably has a movable mount provided by such means as lug 90 thereon slidably engaging a support 91 so that the crucible can move toward and away pressure roller 40 with irregularities in tube T.

In use, as tube T moves upwardly between roll 40 and crucible 80, its interengaged portions are held in tight interfacial relation so that sealing metal enters seam from pool 86 by capillarity. Pool 86 has a depth so slight that the hydrostatic pressure at the pool is insignificant in comparison to the capillary force tending to draw the sealing metal into the seam. Consequently, none of the sealing metal will penetrate to the tube interior beyond the inner boundary of the seam.

After tube T leaves roller and crucible 80, it may be passed between pulling and cooling rollers 46 and into cooler 48 as in the illustration of FIG. 1. Any one of tubes T1-T4 may be made by the use of apparatus shown in FIGS. 8 and 9.

I claim:

1. The method of making tube which comprises, moving strip metal stock lengthwise, fashioning the strip transversely to tubular form and bringing the side edges of the strip into interfacial relationship so that interfacing portions which intersect the outer periphery of the tube are located on the under side of the tube, passing the tube lengthwise in a downward direction, then through a bend, and then in an upward direction, applying pressure to the outer sides of the portion of said tube passing through said bend, said pressure being applied in a direction transverse to the longitudinal extent of said tube and being sufiicient to hold said side edges of the tube in tight interfacial relation to provide interspaces therebetween of capillary dimension, maintaining a body of sealing metal in molten condition, and dipping the under side of said tube at the lower portion of said bend into said sealing metal whereby the sealing metal flows between the interfaces by capillarity and substantially none of the metal enters the tube beyond said interspaces, and then cooling the sealing metal to solidify the same and unite said interfaces.

2. Apparatus for making tube comprising, a mill for fashioning strip metal stock transversely to tubular form so oriented that the strip edges meet at the under side of the tube as it moves in a lengthwise direction, means operable to pass said tube so oriented in a downward direction, then through a bend, and then in an upward direction, said means including a roller having portions extending lower than said mill and positioned to overlie the tube at said bend, said roller having a groove with a depth and a radius substantially equal to the radius of the tube exterior so that as tube enters said groove the same exerts pressure on the outer sides of the tube sufficient to force the side edges of the tube tightly together whereby to form interspaces of capillary dimension between the interfacing portions of the tube, a vessel containing a body of molten bonding metal, the lower peripheral portions of said roller being spaced above the surface of the molten bonding metal a distance less than the radius of the tube exterior, whereby the under side of the tube at its bend dips into and passes through the molten metal so that the bonding metal flows between the interfaces by capillarity and substantially none of the metal enters the tube beyond the interfaces, and means downstream from said roller operable to cool the tube and solidify the bonding metal to unite the interfaces.

3. Apparatus for making tube comprising, a mill for fashioning strip metal stock transversely to tubular form so oriented that the strip edges meet at the under side of the tube as it moves in a lengthwise direction, roller means spaced from the downstream end of said mill and having portions extending lower than said mill for receiving tube so oriented emerging from said mill, and driven friction rolls on the opposite side of said roller means from said mill for receiving tube passing away from said roller means, said friction rolls being positioned generally higher than said lower portion of said roller means, said lower portions of said roller means being positioned and mounted to overlie a portion of a tube for depressing said portion downwardly of said tube mill and friction rolls, said roller means being operative to exert pressure on outer sides of a tube engaged thereby and exert lateral pressure on the tube sufiicient to force the side edges of the tube tightly together whereby to form interspaces of capillary dimension between the interfacing portions of the tube, a vessel containing a body of molten bonding metal, said lower portions of said roller means being spaced above the surface of the molten bonding metal a distance less than the outer radius of tube with which said apparatus is adapted to be used so that in passing beneath said roller means the under side of the tube dips into and passes through the molten metal, and means downstream from said roller means operable to cool the tube and solidify the bonding metal to unite the tube interfaces.

4. The method of making tube which comprises, moving strip metal stock lengthwise, fashioning the stock transversely into tubular form and bringing portions of the stock into interengagement to form at the tube exterior a longitudinal sea-m located on the under side of the tube, passing the tube lengthwise in a downward direction, then through a bend, and then in an upward direction, applying pressure to the outer sides of the portion of said tube passing through said bend, said pressure being applied in a direction transverse to the longitudinal extent of said tube and being sufficient to hold the interengaged portions of said stock in tight interfacial relation to provide interspaces therebetween of capillary dimension, maintaining a body of sealing metal in molten condition, and dipping the under side of said tube at the lower portion of said bend into said sealing metal whereby the sealing metal flows between the interfaces by capillarity and substantially none of the metal enters the tube beyond said interfaces, and then cooling the sealing metal to solidify the same and unite said interfaces.

5. The method defined in claim 4 wherein said stock is fashioned to tubular form having a plural ply wall.

6. Apparatus for making tube comprising, a mill for fashioning strip metal stock transversely to tubular form with portions of the stock interengaged at the tube exterior to form a longitudinal seam with the tube oriented so that the seam is located on the under side of the tube, means operable to pass said tube so oriented in a downward direction, then through a bend, and then in an upward direction, said means including a roller having portions extending lower than said mill and positioned to overlie the tube at said bend, said roller having a groove with a depth and a radius substantially equal to the radius of the tube exterior so that as tube enters said groove the same exerts pressure on the outer sides of the tube sufficient to force the interengaged portions of said stock tightly together whereby to form. interspaces of capillary dimension between the interfacing portions of the tube, a vessel containing a body of molten bonding metal, the lower peripheral portions of said roller being spaced above the surface of the bonding metal a distance less than the radius of the tube exterior whereby the under side of the tube at its bend dips into and passes through the molten metal so that the bonding metal flows between the interfaces by capillarity and substantially none of the metal enters the tube beyond the interfaces, and means downstream from said roller operable to cool the tube and solidify the bonding metal to unite the interfaces.

7. The combination defined in claim 6 wherein said References Cited in the file of this patent UNITED STATES PATENTS Heine Oct. 14, 1919 Pritchard Aug. 14, 1923 8 Kennedy Jan. 8, 1952 Abramson et a1 July 31, 1956 Mautone et a1 Aug. 13, 1957 FOREIGN PATENTS Great Britain Feb. 26, 1925 Great Britain Feb. 26, 1925 Great Britain Feb. 21, 1929