US3090263A

US3090263A - Sealed tube

Info

Publication number: US3090263A
Application number: US646425A
Authority: US
Inventors: Martin J Laverty; Theodore F Aronson
Original assignee: Murray Manufacturing Corp
Current assignee: Murray Manufacturing Corp
Priority date: 1957-03-15
Filing date: 1957-03-15
Publication date: 1963-05-21
Anticipated expiration: 1980-05-21

Description

May 21, 1963 M. J. LAVERTY ETAL 3,090,263

SEALED TUBE Filed March 15, 1957 4 Sheets-Sheet 1 Zhwentors MA/Qr/N f 1/1 1/5/97) 45 77/500025 A A/QO/V-SO/V May 21, 1963 M. J. LAVERTY ETAL SEALED TUBE 4 Sheets-Sheet 2 Filed March 15, 1957 my g W D 5 m M5 M Z Z M A $9 y 1, 1963 M. J. LAVERTY ETAL 3,090,263

SEALED TUBE Filed March 15, 1957 4 Sheets-Sheet 3 (Ittorneg 4 Sheets-Sheet 4 SEALED TUBE M. J. LAVERTY ETAL IN V EN TORS MARI/N J LA VERTY BY THEODORE A AQUA SON Q AT T ORIVZY May 21, 1963 Filed March 15, 1957 United States Patent 3,090,263 SEALED TUBE Martin J. Laverty, West Hempstead, and Theodore F. Aronson, Glen Cove, N.Y., assignors to Murray Mann facturing Corporation, Brooklyn, NY.

Filed Mar. 15, 1957, Ser. No. 646,425 13 Claims. (Cl. 7889) This invention relates to fluid tight tubular members such as used in magnetic circuit breakers, and to novel methods and apparatus for sealing the tubular member.

The tubular member as utilized in a circuit breaker comprises generally a non-magnetic thin walled tube, pref erably integrally closed at one end and a magnetic flange member, or pole-piece, attached to that end.

The tube is substantially filled with a liquid and is therefore hydraulically sealed at both ends. It is essential for efficient operation of the circuit breaker that the tube retain the liquid without leakage. The tube also encloses a movable core member, also known as a polepiece, and a spring, urging the movable core member away from the end pole piece.

In order to understand the problems which motivated the invention, it will be helpful to have at least a general knowledge of the operation of the tube assembly. Thus, the tube is surrounded by a coil of wire which conducts the circuit current so that the electromagnetic field generated by the flow of current passes through the pole piece and core. Under conditions of normal current flow,

the reluctance of the magnetic circuit and the stiffness of,

the spring maintain the movable core against one end, which we shall call the sealed end of the tube; this end is remote from the end pole piece. If an overload condition occurs, the current which traverses the coil of wire generates an electromagnetic force of suflicient intensity to urge the core member towards the end pole piece. Thus, the desired operation of the circuit breaker depends upon the movable core reaching the end pole piece within a given time after an overload conditions occurs. The time delay varies, of course, with the magnitude of the overload, but for any conditions of overload the tube assembly is designed to provide an inversely proportional delay. For this reason, the tube assembly is known in the industry as a hydraulic-magnetic time delay tube. Therefore, it should now be apparent that in order for the tube assembly to operate efficiently, there can be no leakage of the liquid from the tube and further, there can be tolerated only minimal forces of surface tension acting between the movable pole piece and the sealed end of the tube, otherwise the mobility of the core would be almost impossible to predict.

The tube assemhbly is fabricated by attaching a pole piece to one end of the tube, filling the tube with a suitable liquid, inserting a spring and core and finally sealing the open end of the tube.

Convetionally, the tube is sealed by mounting a tightfitted disk into the open end and soldering the joint between the wall of the tube and the disk. This process is encumbered by several disadvantages, for example: the soldered joint is often defective, resulting in a large number of rejects; defective joints are extremely difiicult, if possible, to repair; the heat necessary for soldering causes expansion and vaporization of the liquid in the tube which produce an internal pressure sufiicient to cause the liquid and/ or gases to bubble through the molten solder before the solder solidifies; and the solder is expensive and the soldering operation slow.

Accordingly, it is an object of this invention to seal the tube without suffering any of the above-mentioned disadvantages.

It is a feature of our invention to close and seal the 3,090,253- Patented May 21, 1963 tube by shaping, or forming, without the application of heat.

It is a further feature of the invention to seal the tube, preferably with no additional material, and use only the wall of the tube itself.

It is a further feature of the invention to form an end wall, from the side wall of the tube, having a very small radius of curvature at the corner.

it is still a further feature of this invention to form the above-mentioned end wall concavely so that the forces of surface tension acting between the opposing surfaces of the movable pole piece and end wall are minimized.

It is a further object of our invention to provide novel spin-forming apparatus to form mechanically a hydraulic seal.

It is still a further object of our invention to provide a novel process for sealing the tube.

in accordance with a first aspect of our invention, there is provided a metallic tubular member comprising a cylindrical Wall and an end wall integral with the cylindrical wall, extending radially inwardly and cohered at the center to form a hydraulic seal.

In accordance with a second aspect of our invention, there is provided a method of sealing an end of a metallic tubular member, comprising forming an end wall by spin-forming the cylindrical wall thereof radially inwardly so that the opposite portions of the wall are brought to g-ether, and continuing the spin-forming until cohesion at the junction of the opposite portions is effected.

in accordance with a third aspect of the invention, there is provided apparatus for sealing an end of the tube comprising a spin-forming head having a pair of rotatably mounted forming rollers diametrically located on opposite sides of the tube, and means for rotating the spinning head so that the rollers revolve about the tube while gradually moving the rollers toward each other against the wall of the tube, thereby deforming the Wall radially inwardly until opposite portions of the cylindrical wall are cohered together.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction With the accompanying drawings, wherein: b1 FIG. 1 is an elevational view of the sealed tube assem FIG. 2 is a view of the tube assembly with half the tube and end pole piece cut-away;

FIG. 3 is a view taken along lines 3-3 of FIG. 2;

FIG. 4 is a vertical section partly in side elevation and partly in cross-section of one embodiment of the spinforming apparatus;

FIG. 5 is a plan view of the tube clamping device taken along lines 55 of FIG. 4;

FIG. 6 is a sectional view of the embodiment shown in FIG. 4 taken along lines 66 thereof;

FIG. 7 is a view taken along lines 7-7 of FIG. 6;

FIG. 8 is a view taken along lines 88 of FIG. 6;

FIG. 9 is a bottom view of the spin-forming apparatus;

FIGS. 10-15 are front sectional and end views showine the forming rollers and tube at different phases of the forming operation;

FIG. 16 is a side view, partly in cross-section, of a preferred embodiment of the spin-forming apparatus; and

FIG. 17 is a top view of the spinning head illustrated in FIG. 16.

FIG. 18 is a perspective view showing one of the C shaped forming members as shown in FIGURES 16 and 17.

Referring first to FIGS. l-3, there is illustrated a tube 3 assembly, adapted for use in a circuit breaker, comprising a tube 1 made of a non-magnetic material such as brass, a magnetic pole piece 2 attached at one end of the tube and a movable pole piece 3 located within the tube and urged away from the end pole piece 2 by a spring 4. The tube is filled with a liquid having a suitable viscosity and in accordance with our invention is hydraulically sealed by spin-forming. The end wall 5 of the tube ll is concave so that only a relatively small surface area contacts the pole piece. The small contact area and the lubricating effect provided by the liquid trapped in the corner of the end Wall 5 prevent the pole piece from sticking to the end wall.

The forming of the end wall 5 and the sealing of the tube assembly is effected by spin-forming apparatus illustrated in the remaining figures.

Referring first to FIGS. 4-9, there is illustrated one embodiment of our spin-forming apparatus, comprising a spinning head generally indicated at 6 (FIGS. 4, 6), rotatably mounted and axially slidable in a housing 7; the housing being adjustably supported on a post. A rotatable shaft 8 drives the spinning head 6 from a source of power (not shown), and is mounted within the housing 7 against inner races 9, to of ball bearing assemblies ll, 12 respectively; the outer races l3, 14 thereof bearing against the housing '7. The bearing assemblies l1, 12 are maintained in spaced relation by means of a sleeve 15, and clamped between a shoulder 16 formed on the lower part of the shaft. The bearing assemblies ll, 12 and shaft 8 are slidable axially Within the housing 7; the reasons for such movement will be explained in conjunction with the description of the operation of the machine.

Referring now to FIGS. 4 and 6, the shoulder '16 of the shaft 8 is extended axially for a short distance and then enlarged at 13. The enlarged portion 18 is counterbored at 19 to have a frustro-conical opening.

A centrally located hole 2% is bored into the shaft 8 to a depth approximately half-way between the shoulder 16 and bolt 18 and extends through the top of the conical counterbore 19. A shaft 21, carrying a spinning assembly is slidably mounted in the hole 2%.

As best seen in FIGS. 6 and 7, the shaft 21 is provided with a slot 23 elongated in the axial direction to accommodate a cylindrical pin 24 which is passed through a circular opening in the shaft 8. The pin is coupled directly to the shaft 8, but the elongated opening in the shaft 21 provides with the pin a yieldable driving connection between the

shafts

8 and 21.

The shaft 21 has at its lower end a conical section 25 having a surface corresponding to the surface of the conical opening 19 in the enlarged portion 18. The conical section 25 is provided with grooves 26, 27 in the shape of a T oppositely disposed relative to the axis of the shaft. A pair of T shaped

jaws

28, 29 are slidably mounted in the grooves 26, 27. A pair of forming

rollers

39, 31 are rotatably mounted to the bottom of the jaws respectively by means of stud screws 32, 33.

Referring now to FIGS. 6, 8 and 9, a peripheral circular wall 34 is provided which surrounds the enlarged portion 18 and includes

grooves

35, 36 which constitute extensions of the oppositely disposed grooves 26, 27 respectively and similarly guide the jaws Z8, 29.

The conical section 25 and part of the slidable shaft 21 are counterbored at 37 to accommodate a bearing assembly 38. A pilot pin 39 is rotatably mounted in the bearing assembly, and is instrumental in supporting and shaping the tube as will be described more fully hereinafter.

The bearing assembly 38 is locked against a shoulder 40 by a washer 41 threaded into the tapped counterbore 37. The pilot pin 39 is maintained in the bearing assembly by means of a nut 42 threaded on the upper end of the pilot pin 39.

As best seen in FIG. 4, the spinning head 6 includes a bottom surface which is substantially parallel to the plane of a tube clamping mount 43. The spinning head rotates on the surface of the tube clamping mount by means of rollers 44, mounted on axles which bridge 6 shaped

clamps

46, 47; the

clamps

46, 47 being fastened to the bottom surface of the spinning head. The rollers 4-5 are diametrically disposed on the spinning head and are adapted to race on the upper surface of the tube clamping mount 43.

Referring now to FIGS 5, 6 and 8, the tube clamping mount is supported on a table 48 and comprises a fixed jaw 49 secured to the table by means of bolts 50 and an adjustable jaw 51 supported in guide ways 52 and movable into clamping position by means of a bolt 53. The bolt 53 is rotatably attached to the adjustable jaw 51, and threadedly engages a bar '54- fixed to the table The

jaws

49 and 51 are provided with semi-circular cut-

outs

55, 56 respectively, the walls of which embrace the body of the tube 1. The contiguous surfaces of the fixed and movable jaws are complementary to permit smooth and easy adjustment.

Tubes of dilferent size diameters are accommodated by simply replacing one set of jaws by another set having appropriate semi-circular cut-outs.

The forming

rollers

39, 31 shown in FIG. 6, and in greater detail in FIGS. 1045, are free to rotate on the stud screws 32, 33 and are of equal diameter. The shape and relative positions of the rollers are essential in order to achieve the expected results. A first condition is that one roller, e.g. roller 31, have substantially a semicircular peripheral face and the other roller, i.e. 3h, have substantially a flat peripheral face with rounded corners. A second condition is that the rollers be off-set relative to the axis of the tube, preferably by half the thickness of one roller. lthough we have found by experimentation that the shape and positions of the rollers as described above produce the desired result, other equivalent shapes and dispositions of the rollers may be determined by further tests.

Utilizing the apparatus described hereinabove, a tube is hydraulically sealed by a cold-forming process as follows:

The tube 1, including the

pole pieces

2, 3, spring 4 and oil, is clamped between the

jaws

49 and 51. The drive shaft 8 is rotated which drives the spinning head 6 through the pin and

slot coupler

23, 24. The spinning head is initially in the raised or uppermost position, as shown in FIG. 4, and as it rotates, it is lowered by means not shown to the position shown in FIG. 6'. The lowering of the spinning head may be accomplished at any convenient rapid advance speed.

As seen in FIG. 6, when the race rollers 44, 4-5 just contact the upper surface of the tube mount 43, there is preferably, although not necessarily, a slight clearance between the end of the tube 1 and the pilot pin 39. As the drive shaft 8 continues to bear down on the tube mount,

jaws

23, 29 carrying forming rollers Stl, 31 are urged toward the tube as a result of the conical surfaces of the jaws riding in the conical counteribore.

Referring now to FIGS. 10-15, the action of the rollers on the tube is illustrated during different stages of the sealing operation. At the start of the operation, as mentioned above, the pilot pin 39 does not contact the end of the tube; however, as the tube is being worked by the rollers, the tube is deformed and elongates, and when spinning progresses to the stage shown in FIG. 10, the pilot pin contacts and steadies the tube.

The spinning head is then progressively lowered causing the rollers to move closer towards each other as shown in FIGS. 12 and 13, to deform the opposite portions of the cylindrical wall of the tube radially inwardly. Gradually, the head is fully lowered to produce a mechanical seal as shown in FIGS. 14 and 15. The seal is believed to be a cohesion of the opposite portions of the tube wall coming together; i.e. a cold weld.

The end of the tube extending beyond the seal is pinched-off by the apparatus and the sealing operation is completed.

The efficiency of the seal was tested by heating the tube to produce a substantial increase in the vapor pressure within the tube. It was found that the seal could withstand pressures, without rupturing, which were sufficient to cause the cylindrical wall of the tube to distend outwardly.

The vertical feed speed from the position shown in FIG. 6 to the completion of the spinning operation is at a controlled rate which, in cooperation with the angle of the conical bore 19 and complementary surfaces, advances the forming rollers from the position shown in FIG. 6 to that shown in FIG. 15; the rate being selected to produce satisfactory cold-forming. By way of example, the rollers may be moved between the two positions shown in FIGS. 6 and 15 in approximately 1 /2 to 2 /2 seconds while rotating the spinning head between 2000 and 5000 r.p.m.

As described at the outset of the specification, it is important that the end wall 5 of the tube 1 be formed to have a concave surface and turned to have a small radius of curvature with the side wall. This is achieved substantially by operation of the pilot pin limiting the upward movement of the end of the tube while the tube is being elongated, thereby causing the end wall 5 to move downwardly and form a concave surface with a small radius of curvature at the corner.

Referring now to FIGS. 16 and 17, there is illustrated a preferred embodiment of our spin-forming apparatus, comprising a rotatable shaft 60 supported in a housing 61 by

ball bearing assemblies

62, 63. The housing 61 is slidably attached to a tubular bracket 64 secured to a post 65 by means of

collar bearings

66, 67. The shaft 60 is driven by a pulley 68 splined thereto by key 69.

The lower end of the shaft 60 terminates in a flange 70 which carries a pair of diametrically disposed pins 71, 72. The pins have mounted at the lower end thereof swivel mounted shoes 73, 74 respectively.

The shaft 60 is counterbored at 75 to accommodate a shaft 76 slidably mounted in the space provided by the counterbore. The shaft 76 includes a radial extension at 77 which bears on thrust bearings (not shown) and is rotated together with the shaft 60 as a result of pins 71, 72 passing through aligned holes in the extension 7'7.

The aligned centers of the shafts 60 and 76 are hollowed to provide space for a non-rotatable shaft 78 having a pilot pin 79 and nose 80 at one end for supporting the tube being sealed.

The lower end of shaft '76 supports a spin-forming head 81, comprising a pair of oppositely disposed C shaped forming

members

32, 83 pivotally mounted to the shaft 76 by a pin 84. The forming members carry

rollers

85, 86 respectively which are disposed and shaped as described in the first embodiment.

As shown in FIG. 16, the lower end of the shaft 76 is counterbored at 87 to accommodate ball bearing assembly 38 which supports pivot pin 79 and permits rotation of shaft 76 therearound.

A spring '89 is mounted in the space between the shafts 60 and 76 to provide some resiliency in the axial direction between the two shafts, whereby when the swivel shoes 73, 74 are brought to bear against the C shaped

members

82, 83 of the spinning head, the force of impact is, to a large extent, absorbed by the spring 89.

The essential diiferences in the second embodiment are the non-rotatable pilot pin shaft 78 which is independently secured to an extending portion 90 of the post 65, the spinning head 81 and the mode of operating the spinning head.

The pilot pin shaft 78 is secured to the post extension by means of a screw 91 entering a groove 92. The groove 92 extends axially a given distance which is determined by 6 the extent of vertical travel of the shaft 60, whereby the screw 91 rides in the groove.

The vertical travel of the shaft 78 is limited in one direction by a shoulder 93 attached to a sleeve 94 surrounding the shaft 78 and in the other direction by a collar 95 attached by a screw 96 to the shaft.

In the initial position of the forming apparatus the shafts 60 and '78 are raised and the tube clamped as in the first embodiment. The shafts are then gradually lowered by suitable mechanical means (not shown) and the swivel shoes are brought to bear on the opposite C shaped members. 111 FIG. 17 the position of the shoes is shown by dash lines.

The centrifugal force produced by the rotation of the spinning head is sufficient to separate the forming members prior to the application of force by the shoes. However, if desired, the forming members may be spring urged.

The spin-forming operation is substantially similar to that described in conjunction with the first embodiment. Briefly, the apparatus is lowered to the desired position so that the rollers are located on opposite sides of the tube. Shaft 60 is then further lowered so that the swivel shoes 73, 74 are brought to bear on the respective forming members forcing the members to move towards each other about the pivot pin 84. After the rollers have reached a predetermined position, at which cohesion of the end wall at the center is effected, the shaft 60 is retracted, permitting the rollers to move outwardly away from the tube.

The concavity ofthe end wall is obtained as discussed above; and similarly, the piece of tubing extending above the seal is pinched-off by the machine and the process is completed.

In this latter embodiment, it was found essential that the pilot pin shaft be prevented from rotating. Even slight rotation caused the neck of the deformed wall to fail be fore cohesion was effected; the cause of the failure was probably due to metal fatigue.

The core at a point adjacent the tube closure is but very slightly smaller than the inside diameter of the tube. Any radius at the corners will reduce the tube diameter and permit the core end to wedge mechanically, or jam, and stick, so that it cannot move freely under the magnetic forces involved. It is obvious that the tube cannot be closed in such manner as to have zero radius at these corners. Therefore, to prevent mechanical sticking, or wedging, of the core, the end closure must bar the core from moving up far enough to reach the reduced diameter of the tube at the beginning of the corner radius. That is, the depth of concavity of the end closure must exceed the internal radius of curvature at the corners. The surface tension effects referred to in the specification are sound reasons for concavity, but the mechanical wedging explained above is a more vital reason why both a very small radius at the corners and a substantial concavity are needed.

Although our invention has been described in connection with tubes useful in magnetic circuit breakers, it is to be realized that our invention has much greater application and may be utilized wherever it is desired to seal an end of a metallic tube by forming an end wall out of the side wall.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. Apparatus for sealing one end of a tube, comprising means for fixably clamping said tube at the opposite end thereof, a spin-forming head comprising a pair of rotatably mounted and longitudinally offset forming rollers diametrically located on opposite sides of said tube where it is desired to seal said tube, means for rotating said spinning head so that said rollers revolve about said tube,

means for gradually moving said rollers toward each other against the wall of said tube thereby deforming said wall radially inwardly until opposite portions of the side wall are cohered together, and means for supporting said one end of the tube to limit the outward movement thereof during the deformation and elongation of the tube wall, the elongation being suflicient to cause the radially formed end wall to move inwardly in the form of a concavity, and the cohered wall being pinched off by said forming rollers.

2. The apparatus according to claim 1, wherein said forming rollers are mounted off-set by approximately onehalf the thickness of said rollers.

3. The apparatus according to claim 2, wherein the circumferential surface of one roller is arcuate and the circumferential surface of the other roller is substantially flat, and rounded at the edges.

4. Apparatus for sealing an end of a metallic tube, comprising a tube clamping mount for fixably supporting said tube in an upright position with the end desired to be sealed free of said tube mount; a rotatable spin-forming head comprising a pair of members pivotally mounted on a common axis, a pair of forming rollers of equal diameter rotatably mounted and longitudinally offset on said pivotal members respectively, said pivotal members being shaped so that at one extreme pivotal position said rollers are separated by a distance greater than the diameter of said tube, means for positioning said spin-forming head so that said rollers are located on opposite sides of said tube where it is desired to seal said tube, means for rotating said spinforming head, and means for applying pressure uniformly and gradually to each of said pivotal members causing said rollers to move towards each other thereby deforming the side wall of said tube radially inwardly until opposite portions of the side wall are cohered together, means for supporting the free end of said tube to limit the upward movement thereof during the deformation and elongation of the tube wall, the elongation being sufiicient to cause the radially formed end to move inwardly in the form of a concavity, and the cohered wall being pinched off by said forming rollers.

5. The apparatus according to claim 4, wherein said rollers are mounted off-set by approximately one-half the thickness of said rollers.

6. The apparatus according to claim 5, wherein the circumferential surface of one roller is arcuate and the circumferential surface of the other roller is substantially fiat with rounded edges.

7. Apparatus for sealing an end of a metallic tube, comprising a tube clamping mount for fix-ably supporting said tube in an upright position with the end to be sealed free of said tube mount; a rotatable spin-forming head comprising a pair of members pivotally mounted on a common axis, a pair of forming rollers of equal diameter rotatably mounted on said pivotal members respectively, said pivotal members being shaped so that at one extreme pivotal position said rollers are separated by a distance greater than the diameter of said tube; a first rotatable shaft coupled to and adapted to drive said spin-forming head, a second rotatable shaft coupled to drive said first shaft and having a centrally located opening adapted to slidably accommodate said first shaft, said second shaft carrying means for applying pressure to each of said pivotal members, means for operating said second shaft so that said pressure means bears against said pivotal members uniformly and gradually, causing said rollers to move towards each other thereby deforming the side wall of said tube radially inwardly until opposite portions of the side wall are cohered together.

8. The apparatus according to claim 7, and further comprising means for supporting the free end of said tube during the forming thereof.

9. The apparatus according to claim 8, wherein said means for supporting the free end comprises a non-rotatable shaft passing axially through an opening in said first and second shafts, the supporting end of said shaft limiting the upward movement of the deformed portion of the tube between the forming rollers, which deformed portion is being elongated by the action of said forming rollers, whereby the limiting action of said shaft forces the end wall of said tube downwardly to form a concave surface with the side wall thereof.

10. The apparatus according to claim 9 and further comprising a spring mounted between said first and second shafts, whereby when said pressure means is applied to said spinning head the impact is substantially absorbed by said spring.

11. The apparatus according to claim 10, wherein said pivotal members are in the shape of an L, and said rollers are mounted respectively on the transverse legs of the L shaped members extending beyond the ends thereof.

12. Apparatus for sealing an end of a metallic tube, comprising a tube clamping mount for supporting said tube in an upright position with the end to be sealed free of said tube mount; a rotatable spin-forming head provided with a frustro-conical opening, the base of the conical space being at the bottom of the spin-forming head, a conical member mounted in the conical space but symmetrically spaced from the wall thereof, the conical member having a central opening greater than the diameter of said tube and provided with diametrically disposed radial grooves, a pair of jaws slidably mounted in said radial grooves and each having a conical surface adapted to ride in said conical space against the wall thereof, a pair of forming rollers rotatably mounted on said jaws respectively and extending below the base of said spinforming head, means positioning said head so that said rollers are located on opposite sides of said tube, said tube being aligned with the central opening in said conical section, a pair of race rollers rotatably mounted to and diametrically disposed on the bottom of said spinforming head and adapted to race on a surface of said tube clamping mount, means moving said spin-forming head downwardly causing said jaws and forming rollers to move towards each other against the wall of the tube, thereby deforming the tube radially inwardly until the opposite wall portions are cohered together, and means located in the central opening in said conical section for supporting the free end of said tube during the forming operation.

13. The apparatus according to claim 12 wherein said means supporting the free end comprises a non-rotatable member limiting the upward movement of the deformed portion of the tube between the forming rollers which deformed portion is being elongated by the action of said forming rollers, whereby the limiting action of said shaft forces the end wall of said tube downwardly to form a concave surface with the side wall thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,820,823 Oster Oct. 8, 1918 2,284,210 Johnson May 26, 1942 2,330,811 Darner Oct. 5, 1943 2,406,059 Burch Aug. 20, 1946 2,568,991 Dewey Sept. 25, 1951 2,709,381 Enghauser May 31, 1955 2,754,705 Enghauser July 17, 1956 2,765,608 Ford Oct. 9, 1956 2,776,473 Dailey Ian. 8, 1957 2,792,536 Immel May 14, 1957 2,807,760 Berg Sept. 24, 1957 2,960,051 Darlington Nov. 15, 1960 FOREIGN PATENTS 598,854 Great Britain Feb. 27, 1948

Claims

1. APPARATUS FOR SEALING ONE END OF A TUBE, COMPRISING MEANS FOR FIXABLY CLAMPING SAID TUBE AT THE OPPOSITE END THEREOF, A SPIN-FORMING HEAD COMPRISING A PAIR OF ROTATABLY MOUNTED AND LONGITUDINALLY OFFSET FORMING ROLLERS DIAMETTRICALLY LOCATED ON OPPOSITE SIDES OF SAID TUBE WHERE IT IS DESIRED TO SEAL SAID TUBE, MEANS FOR ROTATING SAID SPINNING HEAD SO THAT SAID ROLLERS REVOLVE ABOUT SAID TUBE, MEANS FOR GRADUALLY MOVING SAID ROLLERS TOWARD EACH OTHER AGAINST THE WALL OF SAID TUBE THEREBY DEFORMING SAID WALL RADIALLY INWARDLY UNTIL OPPOSITE PORTIONS OF THE SIDE WALL ARE COHERED TOGETHER, AND MEANS FOR SUPPORTING SAID ONE END OF THE TUBE TO LIMIT THE OUTWARD MOVEMENT THEREOF DURING THE DEFORMATION AND ELONGATION OF THE TUBE WALL, THE ELONGATION BEING SUFFICIENT TO CAUSE THE RADIALLY FORMED END WALL TO MOVE INWARDLY IN THE FORM OF A CONCAVITY, AND THE COHERED WALL BEING PINCHED OFF BY SAID FORMING ROLLERS.