US3594894A - Method of forming cartridges - Google Patents

Abstract

A cylindrical container has each end partially integral formed with a final separate closure piece restrained against outward pressure by the integrally formed portion and is formed by a method comprising the steps of inserting an end disc and a neck portion in a length of seamless steel tubing; heating the two ends of the tubing to an accurately controlled temperature which is slightly above the recrystallization temperature of the steel tubing and forming the spherical ends of the tubing in two heated dies which are held at a temperature below the recrystallization point.

Description

I United States Patent [1113,594394 [72] Inventor Carl H. Mayer. Jr- 2,200,162 5/1940 De Vulitch 29/479 Northbrook, [11. 2,246,123 6/1941 Bruun 29/479 X [21] Appl. No. 777,266 2,374,771 5/1945 Needham 29/479 X [22] Filed Nov. 20,1968 2,687,142 8/1954 Lan 29/479 X [45] Patented July 27, 1971 2,459,316 1/1949 Gramelspacher .1 33/479 X [73 1 A i G n ral Fire Extinguisher Corporation 3,274,678 9/1966 Andrews 29/479 X Nmhbmk Primary Examiner-John F. Campbell Assistant ExaminerRichard Bernard Lazarus Atl0rneyHill, Sherman, Meroni, Gross & Simpson [54] METHOD OF FORMING CARTRIDGES 13 Claims, 2 Drawing Figs.

ABSTRACT: A cylindrical container has each end partially in- [52] 0.8. CI 29/471-1, tegral formed with a final Separate dosure piece restrained 29/475' 29/479' 29/498' 1 13/120 against outward pressure by the integrally formed portion and [51] ID. Cl 823k 31/02 is formed y a method comprising the Steps of inserting an end [50] Fleld 0f Search 29/479, disc and a neck portion in a length of Seamless steel tubing; 482; 113/ 20 S heating the two ends of the tubing to an accurately controlled temperature which is sli htl above the recr stallization tem- [56] References, Cited perature of the steel tubi ng ind forming the :pherical ends of UNlTED STATES PATENTS the tubing in two heated dies which are held at a temperature below the recrystallization point.

METHOD OF FORMING CARTRIDGES BACKGROUND OF THE INVENTION 1. Field of the lnvention This invention generally relates to a cartridge and to a method and apparatus for forming the same. More particularly it includes the method and apparatus for forming a highpressure cylinder from a length of seamless steel tubing by the use of localized heating and forming in closing the ends of the tubing.

2. Description of the Prior Art As those skilled in the art of container manufacturing are aware, high-pressure containers made of steel have been manufactured a long time. However, with the advent of modern chemicals and packaging technology, especially in the areas of fire extinguishers and spray containers, the demand for very low-cost, lightweight and efficient high-pressure containers, has increased greatly. The need has thus arisen for a high-pressure cartridge container having sufficiently high strength, low cost and adaptability to satisfy these new needs.

in spite of these increased needs almost all cylinders heretofore have been produced by a method known as "spinning. Spinning is accomplished by machine, which in principle is a lathe with a hollow spindle provided with a grip for holding the tube in correct position for spinning. In carrying out the process, the end of the tube to be spun is heated by acetylene torch to approximately 1,800" F. This nearly white-hot metal is then placed in the machine, and the spindle is rotated at a high speed (600 to l, 5OO r.p.m.) in an oxygen-laden atmosphere. A spinning tool traveling on an are repeatedly forces the hot metal and mill scale towards the centerline of the tubing, exposing clean and extremely hot metal to the whirlwind around the tube on each backstroke. When enough metal is gathered, a second acetylene torch is often brought to bear on the centerline of the gathered metal, bringing this mix ture of overheated steel and mill scale practically to the melting point. A few more passes of the spinning tool then completes the spinning of the closure. The spun tube is then usually placed in a rack with other recently spun and very hot cylinders thereby impeding the lowering of the temperature to the recrystallization point of the steel below which point no more harm can come to the steel from the spinning process.

It is recognized by metallurgists that carbon steel deteriorates when held at high temperature because these high temperatures produce a change of state in the carbon in the steel. The longer the steel is held at temperatures above the recrystallization temperature, the more this effect is produced. When such steel is stressed, it will weaken and "internally corrode with the passage of time. The catalytic force within the cylinder as well as the catalytic reaction of salt spray and industrial gases can speed this process.

Recognizing the deterioration of the steel in the heated spun end sections, industry specifications require that the closures at the end portions be at least twice as thick as the sidewalls. The magnitude of this weakening is emphasized by an appreciation of the fact that because of the spherical shape of the end closures an undeteriorated uniformly thick steel wall would be twice as strong as the cylindrical portion of the container body. Thus, doubling the thickness of the closure portion would, with steel not subject to deterioration, provide a closure with a strength four times that of the sidewalls.

SUMMARY OF THE INVENTION in dies heated to a temperature below the recrystallization temperature of the material being worked. Application of pressure to the tubing to force 'it into the die results in the progressive hotand cold-working of the tubing to reach the desired configuration. This close control of the heat being applied practically eliminates the problems presented in the prior art. There is thus produced an end closure which need only be of uniform thickness and yet provide greater strength than the container main body portion. There is thus inherent in my method a greater flexibility of manufacture to suit varying needs.

Another aspect of the method of my invention is the formation of the end closures with an end disk and neck portions trapped therein. Under the disclosed embodiment in my invention the end closures are formed as semispheres having an opening therethrough. This opening will generally be less than half the diameter of the body portion and will have resulted from the partial formation of the semisphere during forming. Both end closures of the container may be formed simultaneously to trap an end disk and neck portion inside the container. After the end closure portions are formed the end disk, being of a diameter larger than the end closure opening, is brought to bear on the inner surface of the end closure surrounding the periphery of the opening and secured in place. The securement of the end disk may be accomplished from outside the container and may be by a method such as welding. With one end of the container closed, the neck member, in the form of a tubular structure having an outwardly extending peripheral flange about one end, is positioned with a portion thereof protruding through the remaining openings in the container so that the flange of the neck member bears against the inner surface of the container in the area surrounding the opening. The neck member is secured in position to complete the container save for application of any desired valve means.

With the end disk and neck portions bearing against the inner surfaces of the container it follows that very little stress is put on the joining weld, thereby increasing their sealing effectiveness.

An important advantage of the new cartridge here disclosed is that in the event the welds joining the slug and the bushing or fitting become ruptured, it is not physically possible for the slug or the bushing to be blown out through the holes at the opposite ends of the cartridge.

The apparatus of my invention for making a container comprises a pair of spaced cavity dies whose cavity openings oppose each other. The cavities may be semispherically shaped and have their openings configured to conform generally to the outer dimensions of the tubing stock of which the container will be made. One of the dies may be anchored against movement and the other of the opposing dies may have a power means attached thereto to move it toward the opposing die. The dies are spaced apart a distance greater than the length of the tubing stock necessary to form it. The tube lies on a cradle which serves to align it for the application of the deforming force. Surrounding the opening of each cavity but spaced therefrom, is a heating means which may comprise an induction coil. This heating means will completely surround the end of the tubing material adjacent to the opening and allow accurate control of the tubing temperature to a temperature slightly above its recrystallization temperature. A heating means is also supplied to each of the dies so that the forming surfaces may be accurately heated to a temperature below the recrystallization point of the tubing material.

The method of making a container with the apparatus heretofore described comprises the steps of inserting an end disk and a neck portion into the length of tubing prior to the deformation of the tube ends, deforming the ends of the length of tubing in a die in one continuous progressive initially hotand finally cold-working of the tubing to form the ends of the tubing into a generally semispherical end closure configuration. This occurs when the tubing material heated to a temperature slightly above the recrystallization temperature of the tubing is continuously moved into the die cavity heated to a temperature below the recrystallization temperature of the tubing and formed into a semispherical shape. Hot-working of the tubing material takes place while the temperature of the tubing material is above thereerystallization temperature and cold-working takes place as the tubing material is worked at a temperature below its recrystallization point.

Formation of the end closures traps the end disk and neck portion inside the partially formed container. By orienting the end disk into a position overlapping and closing one opening joining is easily effected from the exterior of the container. The neck portion may be ofa tubular configuration with a circumferential portion of a size larger than the opening so that when the neck portion is in position in the opening the larger circumferential portion bears against the inner surface of the tubing in the area surrounding the opening. Joining in this case may also be easily effected externally of the container. The joint may be made in the area between the outer circumference of the neck portion and in the inner surface of the end opening.

The resultant container is especially adapted for high pressures. Advantageously it includes a main cylindrically shaped body portion having semispherically formed end portions. Each 'end portion has an opening therethrough which may be circular and may have a center coinciding with the axis of the cylindrical tube. An end disk of a size larger than one of said openings closes the opening. A neck member in the form of a tubular structure has an outwardly extending peripheral flange about one end and has its opposite end extending through the opening in the end of the container opposite the end closed by' the end disk. The neck portion may have external and internal threads thereon and is adapted to support the container valve or closure means.

In the construction of the container by my method the thickness of the container main body and end portion material may be uniform The thickness of the end disk may be varied to suit design conditions although I have found an end disk having a thickness greater than the thickness of the container to provide the maximum versatility. Recognizing that various codes may still require the spherical end portions to have increased thickness it is contemplated in my invention that the spherical end portions may increase in thickness in direct relation to their distance from the main cylindrical body portion to a maximum thickness in the area of the end opening.

Containers of my invention produced by the apparatus and method of my invention are stronger and safer than containers of the prior art because the maximum strength of the material is preserved'and deterioration with age accompanying other methods is practically eliminated. Less material is required because of the increased effective strength of the tubular material thereby making the containers lighter with all the advantages that accrue thereto. My method and construction makes maximum use of the material. Thus for example, seamless, electric or open hearth steel, of D.O.T. 3-l800 quality may be used for the container main body and end portions with maximum utilization. in these areas while the end disk may be made of the same high-quality steel plate costing less than half as much. Likewise the neck portion may be made from much less expensive bar stock. My invention thus allows the use of much less expensive material in the container end construction and does this at a cost much less than that required to form the expensive tubing material.

Not only does this design and construction reduce material costs but the more efficient manufacturing process allows them to be produced in less time. With the joining means for the end disk and the neck portion external of the container and operating primarily in a sealing capacity the structural integrity of the container is greatly increased with the result that defective containers are practically eliminated. Manufactur' ing the cylinders as I do, the end spheres are almost as polished as the forming dies, rather than being rough and grooved. Thus joining preparation is minimized. Also mill scale is virtually eliminated through the rapid heating, shielding by the dies and coiling by the dies. The cylinder thus formed may be produced in less time than heretofore thereby increasing the efficiency of the manufacturing process. This efficiency is further heightened by the fewer number of rejects resulting from my efficient design.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view of a cartridge construction of the present invention; and

FIG. 2 is a cross-sectional elcvational view through the manufacturing apparatus-as it would appear in an initial stage of the manufacturing process.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a cylinder 10 constructed in accordance with the present invention comprises a main cylindrical body portion 12 having semispherically formed end portions 14 and 15. The end portions 14 and 15 have circular openings 18 and 19 respectively, extending therethrough. The thickness of the semispherical end portions 14 and 15 in this case is shown as progressively increasing from the area of intersection of the semispherical portions with the main cylinder body 12, to an area of greatest thickness adjacent the openings 18 and 19. An edge 18a and 19a surrounds the openings-18 and 19 respectively. A bottom disk 20 having a thickness greater than that of the cylindrical body portion 12 and a diameter of about half of that of the main body member 12 is positioned centrally over the opening with its outer edges 20a overlapping the opening 18 and bearing against the thickest portion of the spherical end 14. A weld 22 or other equivalent means extends about the edge 18a of the opening 18 and secures the bottom disk 20 to the spherical end 14. The weld or joining means 22 takes the form of a fillet which has its maximum thickness generally in the area of the intersection of the opening and the bottom disk. In one form of my invention the tubular portion 12 has an outside diameter of about 2 inches and has a wall of No. 1020 steel having a thickness of about seventy-two thousandths of an inch. The bottom disk 20 is also formed out of No. I020 steel and has an outside diameter 1% inches with a thickness of about one-eighth inch.

A generally cylindrically configured neck member 30 protrudes through the opening 19 except for an interior flange 31 formed integrally therewith which is of a diameter larger than the opening 19. The flange portion 31 has a surface area 310 which bears against an area of the spherical portion 15 surrounding the opening 19. l have found that by providing an inwardly tapering bevel to the edge of the spherical portion 15 surrounding the opening 19, a neat pocket is formed surrounding the protruding portion of the neck member 30 in which a weld fillet 32 may be deposited to give an efficient and neat appearing joint with the neck member 30.

Having the flange member 31 bearing against the thickened portion, the spherical portion 15 adjacent the opening 19 provides a barrier to prevent the neck member or bushing 30 from being blown through the opening in the event of a cracking or rupture of the weld. With this construction, the joining weld or means 32 carries little or no pressurization stress but functions to hold neck member 30 in place and prevents the leakage of gas from the interior of the cylinder. Again it is emphasized that the fillet weld or means 32 will have its upper surface substantially on an arc the center of which is near the point of intersection of the neck member 30 and the opening 19. This results in maximum sealing effectiveness.

The neck member 30 may have an interior opening 33 in the flange 31 and an opening 34 in the protruding portion 30a. Further, threads'35 may be formed in the outer cylindrical surface of the protruding portion 30a so that a container closure and/or valve means may be readily and conveniently attached thereto.

The neck member is conveniently formed of bar stock having a cost of less than half of the cost of the tubing which forms the container body. Also the formed plate on the bottom of the completed cylinder may be purchased of the same highquality steel as the original tubing for much less than half of the per pound cost of the tubing. This substitution of the lowcost materials for portions of the cylinder which heretofore have been expensively formed of the high-cost tubing material is an important advantage of my invention.

Referring to FIG. 2 the elements and the apparatus which are used to make up the cylinder as heretofore described with regard to FIG. I are shown in their disassembled positions. Thus a cartridge [0' formed of a tubular member l2 and having a bottom disk 20 and neck member 30' is shown on a cradle having a first cradle member 40 and a second cradle member 42. The first cradle member 40 is fixedly attached to a first die holder means 52 and in turn to a fixed support 50 by a bracket 41. The second cradle member 42 includes rollers 44 on which the tube 12 rests so that the second roller member may move with respect or relation to cartridge A bracket 43 secures the second cradle member 42 to a movable second holder die 60.

A water cooled induction heating coil 70 surrounds a first or what containerwise would ordinarily be the bottom end 14' of the tube 12. A number of insulating mounting brackets 75 are attached by means 76 to the induction heating coil 70 and support said coil in spaced relation to the tube end 14'. The brackets in turn are secured to a first die holder member 52. The induction heating coil 70 functions to heat the tube end 14 to a very closely controlled temperature slightly above the recrystallization point of the material from which the tube 12 is formed. The coil 70 will thus possess the required capacity to produce the necessary heat and will be spaced at the requisite distance from the tube 12 to produce the required heat distribution over the end area 14.

Directly adjacent the end of the tube 12' is a heated die member 77 having a generally semispherically shaped die cavity 79. A centrally located circular die member 78 has a portion thereof 78a projecting into the cavity 79. The projection 781: may assume the configuration of a conical frustum whose inclined conical surface will provide a forming surface that determines the configuration of the opening 18 in the completed structure.

A circumferentially positioned die holder means 52 surrounds the die 77 and carries the die heating means 55. As shown, this heating means takes the form of a General Electric Company Cal-Rod heater which is wrapped around the die holder 52 and which may conveniently be recessed in grooves, It is important that the heating means allow accurate control of the die temperature and the exact form of the heating means is not critical. The die support member 50 serves to secure the die assembly against movement during forming where forming is accomplished by applying an outside force in one direction such as shown in the preferred embodiment A heat-insulating barrier 53 is positioned between the die assembly 52, 77, 78 and the support member 50 to prevent heat loss from the dies and allow close temperature regulation of the dies. We have found the Martinite" inorganic board insulation manufactured by the Johns-Manville Company to be particularly suited for the barrier material because of its incompressibility and thermal qualities. According to the manufacturer's specifications, Martinite" is identified as having a thermal conductivity range of from 0.76 to 0.86 b.t.u. inches per square foot per Fahrenheit degree per hour over the range of from 100 F. to l,000 F., respectively. 7

A similar but oppositely directed die construction is pro-- vided for the tube end and the description of the corresponding elements is incorporated herein to avoid duplication. Again a water cooled induction heating coil 90 completely surrounds the tube 12' in the area of the end 15. Similarly, a heated die member 97 having a generally semispherically configured die cavity 99 therein will serve to form the end 15. A series of insulating mounts 95 secure the induction heating coil 90 to the die holder means 60. A heating means 68 surrounds the holder means 60. The die member 97 also contains a circular die member 98 having a portion 98a in the shape of a frustum of a cone projecting beyond and into the cavity 99, where it serves to present a forming edge for defining a configuration of the opening 19. A heat-insulating barrier 69 provides a backing for the die assembly 60, 97, 98.

A guide means 62 having one end riding in a groove not shown and its other end attached to the barrier 69 may be provided to assure die alignment. A die power means takes the form of a power cylinder 64 which is coupled by adjustable means 65 to the support 60 whereby the die 97 may be moved forward against the tube 10 to exert the required forming pressure. In practice I have found that a hydraulic cylinder having a 10 ton capacity is sufficient to provide quick and accurate operation. The power cylinder 64 is anchored by a means 66 to a support base 51. The support member 50 may also be anchored to this base.

Summarizing the apparatus as shown in FIG. 2, it may be seen that a pure simplicity of design and function will allow the manufacturing process to be carried out quickly, accurately, and economically.

OPERATlON Operation of the apparatus as described in FIG. 2 to produce an end product such as is shown in FIG. 1 takes place in the following manner. The tubular member 12' having an end disk 20 and a neck member 30 inside is placed on the cradles 40 and 42 with one end of the tube 14 adjacent the mouth of the die cavity 79 and surrounded by the induction coil 70. At this point, the die member 97, until now in a retracted position, is moved toward the end 15'. During movement of the die and heating assembly toward the end 15', the tube 12 is supported by the rollers 44. Accuracy and alignment of the die assembly movement is assured by the guide 62. When the die assembly has moved to a position where the area of the end 15 is surrounded by the induction the movement may cease temporarily and the induction coils 70 and 90 are energized to rapidly heat the ends of the tube 14 and 15 to an accurately controlled temperature only slightly above the recrystallization point of the steel in the tube 12'. This localized heating of the ends 14 and 15 may be very accurately controlled through the use of electrical energy in a watercooled coil. The water provides coolant for the coil.

The dies 77 and 97 are themselves heated by the means 55, 68 to a temperature less than the recrystallization temperature of the steel tube 12'. l have found in practice that forming the dies 77 and 97 of a material known as Stellite 06" which has a coefficient of friction against steel of only half that of bronze against steel, facilitates forming and greatly reduces tool wear.

With the tube ends 14' and 15' heated, the die assembly including the die 97, is moved toward the stationary die 77 thereby simultaneously beginning the forming of both ends initially as the heated end areas 14 are formed they are at a temperature above the recrystallization of the steel and therefore are what may be termed hot formed.

Since movement of the ends 14' and 15' into the forming dies 77 and 97 respectively moves the ends away from the heat of the induction coil 79 and 90 and into the lower temperature dies, the temperature in the tube ends 14 and 15 changes from the temperature just above the crystallization point of the steel to a temperature below this point so that any further forming takes place under what is commonly known as coldforming process. Thus, the initial forming of the tube always begins as hot forming and ends as cold forming.

The power cylinder continues to extend until the tube is formed and each end of the tube reaches and abuts the shoulder 78a, 98a in its respective forming die. After forming the power cylinder then retracts to its initial position easily releasing the formed tube.

Thus forming process has many advantages. Thus, for example, the ductility and rapidity of hot forming is complemented by the cold-forming process which utilizes compressive forces rather than the tensile forces to produce a better surface finish, higher mechanical properties and closer tolerances. Furthermore, the minimum time above recrystallization temperature does not allow the deterioration which takes place at temperatures above the level. If steel which has been allowed to deteriorate is stressed, it will weaken and age" or internally corrode" with the passage of time. The catalytic process within the cylinder as well as the catalytic reactions of salt spray and industrial gases can speed this process. It can be understood that in high-pressure containers such as fire extinguisher cartridges, for which this process is particularly adapted, any reduction in the ability of the cartridge to withstand stresses" is to be avoided. It is because of this weakening that occurs in steel which has been held or formed at high temperatures above the recrystallization point, that specifications for high-pressure cylinders specify that the ends of the cylinders be of double thickness. This is so in spite of the fact that if the ends of the cylinders were formed of material the same thickness as the remainder of the cylinder they would be twice as strong. 1 am thus able to produce a container having end portions of a uniform thickness which will actually withstand twice the stress of the sidewalls. However, it is recognized that recognition and acceptance of my process in the specifications may take time.

At this point the cartridge 10' has its ends 14 and 15 formed as is shown for example in FIG. 1 with the bottom disk and the necked member 30'trapped inside. The tube is removed from the forming machine and the edges of the end openings are cleaned or machined to bright steel, thereby preparing these edges 18g and 19a for the next welding step. This welding step is accomplished by placing the tube over a conventional mandrel which orients the bottom disk 20' so that its outer periphery overlaps the interior area of the end portion 14' around the opening 18. By a shielded arc weld or brazing the bottom disk is secured to the formed tube in an efficient and gas tight manner. If required to meet spccifications, the bottom disk may be of a thickness greater than the material forming the cylindrical sidewalls. As was noted in the description of the cylinder, this construction is very efficient in manufacture and design. Thus, the weld is easily applied between the clean edge 18a and the disk 20 and the bead which is formed is extremely effective in sealing the resulting joint.

The steel neck member 30' is now oriented as may be best seen in FIG. 1 so that it protrudes through the opening and brings a pressure flange such as 31 1 into bearing relation with the interior surface of the end around the opening 19. In this case the opening edge 190 may also have been prepared by bright cleaning or machining to present the clean joining surface. The neck member serves to center itself in the opening 19 thereby allowing quick, accurate, and efficient welding or brazing to secure ii in place. The above end closing steps are given by way of example and are not to be construed as limiting. Thus for example it is possible to machine the opening 19 so that the neck section may be press fitted into the opening rather than being welded or brazed.

From the foregoing description of the cylindrical container and its method of formation, the many and important advantages of my invention over the prior art may readily be seen. Although the highly technical terminology and explanations have not been used in the interests of brevity and ease of understanding by those not so technically oriented, these matters may be more fully elaborated and explained in the United States Steel Corporation publication entitled The Making, Shaping and Treating of Steel, which has been published since 1919 and is a well-known reference of the art.

While I have illustrated and described one preferred form of the invention, it will now be apparent to those skilled in the art that other changes, substitutions, additions and omissions may be made in the exemplary form shown without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

l. A rnethod of making a container comprising the steps of heating the end of a predetermined length of tubing above the recrystallization temperature of the tubing material and moving the heated end in one continuous progressive movement into a die having a temperature below the recrystallization temperature of the tubing to deform the end into a generally semispherical end closure configuration by initially hot-working and finally cold-working of the tubing.

2. A method of making a container according to claim 1 wherein the two ends of the tubing are heated to an accurately controlled temperature which is slightly above the recrystallization temperature of the tubing material prior to forming l the ends in the die.

' 3.'A method of making a container according to claim 2 wherein the dies in which the ends are formed are heated to a temperature below the recrystallization temperature of the tubing to thereby effect the hotand cold-working of the tubing upon the continuous movement of the tubing into the die.

4.'A method of making a container according to claim 1 in cluding the steps of inserting an end disk and a neck portion into the length of tubing prior to the deformation of the tube ends whereby the end disk and neck portion are trapped inside the container forming the end closures with an opening thcrcthrough and orienting and joining the end disk and neck portion to complete the container.

5. A method of making a container according to claim 3 including the step of preparing the openings in the spherical ends of the tubing to facilitate joining of the end disk and neck portions thereto and wherein said tubing material is steel and said joining is accomplished by welding.

6. A method of making a container comprising the steps of positioning a metallic tubular member with a first end in alignment with the mouth of a first die cavity, said first dic cavity having a first localized heating means adjacent to the mouth of said first die cavity, said first heating mouth having an effective heating range within which the temperature may be closely controlled, moving said first end into the range of said first heating means, heating said first tube end to an accurately controlled temperature only slightly above the recrystallization temperature of said metallic tubular member material, moving said first heated. end away from said first heating means into the lower temperature die cavity whereby the heated first end remains for a period of time at a temperature above the recrystallization temperature of the metallic material to be initially hot formed and then cools below the recrystallization temperature to thereafter be cold formed.

7. A method of making a container according to claim 6 wherein said movement of said first end pauses in the range of said-first heating means to allow heating of said metallic material before continuing to move into said die cavity.

8. A method of making a container according to claim 6 wherein said first end is moving substantially continuously into said die cavity during the forming of said first end above and below the recrystallization temperature of said metallic tube material.

9. A method of making a container according to claim 6 wherein said metallic tubular member also has a second end in alignment with the mouth of a second die cavity, said second die cavity having a second localized heating means there adjacent, said second heating means having an effective range within which the temperature may be closely controlled and wherein both said first and second ends are moved into the range of their respective heating means to heat both the first and second tube ends to an accurately controlled temperature only slightly above the recrystallization temperature of said metallic tubular member material, locating said first and second heated ends from the range of their respective heating means into their respective lower temperature die cavities whereby the heated first and second ends remain for a period of time at a temperature above the recrystallization temperature of the metallic material to be initially hot formed and then cooled below the recrystallization temperature to thereafter be cold formed.

10. A method of making a container according to claim 9 including the steps of supporting the tubular member prior to forming and wherein said first and second die cavities open toward each other and are of a size conforming to the crosssectional configuration of said tubular member, said first die cavity being fixed in position and said second die cavity moving toward said first die cavity to provide the movement of said tubular member.

11. A method of making a container according to claim 9 including the steps of inserting an end disc and a neck portion into the tubular member prior to the formation of the first and second tube ends, said first and second tube ends being formed to leave a central opening therein, smallerin diameter than said end disc and said neck portion, said end disc and neck portion being thereby trapped inside said container. said end disc and neck portion being each joined to said tubular member over one of said end openings to complete the container.

12. A method of forming a container according to claim 6 wherein said die cavity includes a generally circular abutment therein and wherein said movement of said first end continues until the peripheral edges of said first tubular end contact said abutment.

13. A method of making a container according to claim 6 wherein the temperature of said die cavity may be closely controlled to allow a ready change in temperature thereof and to assure that the tubular members is initially hot formed and subsequently cold formed.

Claims (13)

1. A method of making a container comprising the steps of heating the end of a predetermined length of tubing above the recrystallization temperature of the tubing material and moving the heated end in one continuous progressive movement into a die having a temperature below the recrystallization temperature of the tubing to deform the end into a generally semispherical end closure configuration by initially hot-working and finally coldworking of the tubing.

2. A method of making a container according to claim 1 wherein the two ends of the tubing are heated to an accurately controlled temperature which is slightly above the recrystallization temperature of the tubing material prior to forming the ends in the die.

3. A method of making a container according to claim 2 wherein the dies in which the ends are formed are heated to a temperature below the recrystallization temperatUre of the tubing to thereby effect the hot- and cold-working of the tubing upon the continuous movement of the tubing into the die.

4. A method of making a container according to claim 1 including the steps of inserting an end disk and a neck portion into the length of tubing prior to the deformation of the tube ends whereby the end disk and neck portion are trapped inside the container forming the end closures with an opening therethrough and orienting and joining the end disk and neck portion to complete the container.

5. A method of making a container according to claim 3 including the step of preparing the openings in the spherical ends of the tubing to facilitate joining of the end disk and neck portions thereto and wherein said tubing material is steel and said joining is accomplished by welding.

6. A method of making a container comprising the steps of positioning a metallic tubular member with a first end in alignment with the mouth of a first die cavity, said first die cavity having a first localized heating means adjacent to the mouth of said first die cavity, said first heating mouth having an effective heating range within which the temperature may be closely controlled, moving said first end into the range of said first heating means, heating said first tube end to an accurately controlled temperature only slightly above the recrystallization temperature of said metallic tubular member material, moving said first heated end away from said first heating means into the lower temperature die cavity whereby the heated first end remains for a period of time at a temperature above the recrystallization temperature of the metallic material to be initially hot formed and then cools below the recrystallization temperature to thereafter be cold formed.

7. A method of making a container according to claim 6 wherein said movement of said first end pauses in the range of said first heating means to allow heating of said metallic material before continuing to move into said die cavity.

8. A method of making a container according to claim 6 wherein said first end is moving substantially continuously into said die cavity during the forming of said first end above and below the recrystallization temperature of said metallic tube material.

9. A method of making a container according to claim 6 wherein said metallic tubular member also has a second end in alignment with the mouth of a second die cavity, said second die cavity having a second localized heating means there adjacent, said second heating means having an effective range within which the temperature may be closely controlled and wherein both said first and second ends are moved into the range of their respective heating means to heat both the first and second tube ends to an accurately controlled temperature only slightly above the recrystallization temperature of said metallic tubular member material, locating said first and second heated ends from the range of their respective heating means into their respective lower temperature die cavities whereby the heated first and second ends remain for a period of time at a temperature above the recrystallization temperature of the metallic material to be initially hot formed and then cooled below the recrystallization temperature to thereafter be cold formed.

10. A method of making a container according to claim 9 including the steps of supporting the tubular member prior to forming and wherein said first and second die cavities open toward each other and are of a size conforming to the cross-sectional configuration of said tubular member, said first die cavity being fixed in position and said second die cavity moving toward said first die cavity to provide the movement of said tubular member.

11. A method of making a container according to claim 9 including the steps of inserting an end disc and a neck portion into the tubular member prior to the formation of the first and second tube ends, said first and second tube ends being formed to leave a centRal opening therein, smaller in diameter than said end disc and said neck portion, said end disc and neck portion being thereby trapped inside said container, said end disc and neck portion being each joined to said tubular member over one of said end openings to complete the container.

12. A method of forming a container according to claim 6 wherein said die cavity includes a generally circular abutment therein and wherein said movement of said first end continues until the peripheral edges of said first tubular end contact said abutment.

13. A method of making a container according to claim 6 wherein the temperature of said die cavity may be closely controlled to allow a ready change in temperature thereof and to assure that the tubular members is initially hot formed and subsequently cold formed.

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