US3538874A

US3538874A - Compressive stress forming of container flanges

Info

Publication number: US3538874A
Application number: US695471A
Authority: US
Inventors: Walter Sawert
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1968-01-03
Filing date: 1968-01-03
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10
Also published as: GB1212773A

Description

United States Patent ms l CONTAINER FLANGES 18 Claims, 6 Drawing Figs. a .v

US. (l 113/120, 220/74 Int Cl. B21d 51/00 Field ofSearch 220/67, 66;

Primary ExaminerCharles W Lanham Assistant Examiner- Michael J. Keenan Att0rn eyDiller, Brown, Ramik and Holt ABSTRACT: This disclosure is directed to a novel method of cold forming metallic container flanges by subjecting a peripheral end portion of a tubular metallic body to multiaxial compressive stresses which progressively axially lengthen the peripheral end portion and reduce the wall thickness thereof during the radial outward guiding of the peripheral end portion to thereby transform the peripheral end portion into a radially outwardly directed peripheral flange. The peripheral end portion is subjected to the compressive stresses by forcing the peripheral end portion between opposed working surfaces ,which define a progressively diminishing gap which over at least a part of its length is narrower than the initial wall thickness of the peripheral end portion.

Patented Nov. 10, 1970 SEE INVENTOR COMPRESSIVE STRESS FORMING OF CONTAINER FLANGES According to present can making technology, it is common to form a flange at one or both ends of a can body for subsequently seaming thereon a can cover. Flanging is presently done with a die having a widening contour which when forced into a can body deflects the metal at the end over the widening contour of the die to extend the metal outwardly and generally normal to the die body contour. This flanging method, called die flanging or dynamic flanging, produces a circumferential flange of approximately 0.1 inch length or more.

Die flanging or dynamic flanging subjects the entire circumference of the can body edge to tension forces which tend to crack the circumferential flange during the formation thereof. This tendency of cracks developing is lessened when the can bodies are made of materials which are fairly ductile. However, dynamic flanging cannot be used to flange metallic can bodies which are made of certain hard and/or brittle materials such as double reduced" or hard rolled" metallic plate. Certain aluminum alloys of hard tempers are not susceptible to die flanging because these materials are so brittle that the edges of the can bodies crack during the flanging operation. This is especially true with tube welded can bodies which, of necessity, are made from ll-grain" metal, i.e., the metal rolling direction being parallel to the height of the can body. Dynamic flanging of welded can bodies produces cracks which are numerous, severe and frequently extend well down into the can cylinder.

In lieu of dynamic flanging can bodies have been flanged by what is generally termed spin flanging. In such cases a spinning flanging head carrying a plurality of rotatable or stationary elements is introduced into the interior of a can body during relative rotation between the spinning head and the can body. During the progressive introduction of the spinning head, the peripheral edge of the can body is subjected to progressive tensile stresses which direct the peripheral edge radially outwardly and transform the same into a flange. However, here again the tensile stressing of the peripheral edge results in flange cracking.

In keeping with this invention, it is a primary object to provide a novel method which avoids the disadvantages inherent in dynamic flanging and spin flanging methods by subjecting a peripheral end portion of a metallic can body to miltiaxial compressive stresses which, during the radial outward guiding of the peripheral end portion, transform the latter into a peripheral flange in the absence of cracks or undesirable distortions.

A further object of this invention is to provide a novel method of flanging can bodies wherein the multiaxial compressive stresses are produced by forcing the peripheral edge portion of the can body between opposed working surfaces which define a progressively diminishing gap which over at least a portion of its length is narrower than the initial wall thickness of the peripheral end portion which causes the end portion to progressively axially lengthen and tangentially expand while the wall thickness is reduced solely under the influence of compressive stresses and in the absence of tensile stresses.

Another object of this invention is to provide a novel apparatus for practicing the flanging method heretofore described, as well as the novel flanged can body produced in accordance with the method of this invention.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawing.

[N THE DRAWING FIG. 1 is a fragmentary elevational view with parts broken away for clarity of an apparatus for-flanging can bodies in accordance with this invention, and illustrates an end of the can body being initially introduced between a plurality of pairs of working surfaces which subject the edge to multiaxial compressive stresses;

FIG. 2 is a highly enlarged fragmentary view of the encircled portion of FIG. 1, and illustrates the can body edge being subjected to axial and radial compressive stresses;

FIG. 3 is a fragmentary view looking from right-to-left in FIG. 2, and illustrates circumferentially directed compressive stresses;

FIG. 4 is a view similar to FIG. 2, and illustrates the completion of the can body flange; and

FIG. 5 and 6 are fragmentary sectional views similar to FIG. 2, and illustrate two different embodiments of the invention.

As was heretofore noted, both dynamic flanging and spin flanging subjects the entire peripheral edge of a can body to tensile stresses which cause the elongation of the can body edge and, as an example, the edge of a number 211 can body having a 2 11/16 inch body diameter is elongated approximately 8 percent. High strength double reduced and full hard plate cannot be elongated by conventional methods more than 1 to 1.5 percent, thus indicating that the flanging of can bodies from these high strength materials by conventional methods without producing cracks would be an impossibility.

However, in accordance with this invention which is to be immediately described hereafter, the can body edges are not subjected to tensile stresses but are subjected only to multiaxial compressive stresses and cracking is virtually precluded. The phrase multiaxial compressive stresses" may be considered to define the forming of the flanges whereby all of the principal stresses involved are compressive stresses (of the same and/or different magnitudes), or two of the principal stresses are compressive stresses and the third one is or approaches zero. As an example, the penetration of a ball or pyramid of a hardness tester into the surface of metallic material causes the hardest material to flow under a threedimensional compressive stress field without cracking.

The invention will be best understood if described by first referring to FIG. 1 of the drawing which illustrates an apparatus 10 for flanging a substantially tubular, metallic can body 11 having an upper peripheral edge or edge portion 12 and a lower peripheral edge 13. The can body 11 includes a longitudinal welded seam 14, but it is to be understood that the method as performed by the apparatus 10 is equally applicable to seamless or soldered or glued can bodies.

The apparatus 10 includes a lower plate or support member I 15 having an upwardly directed centering boss 16. The base or plate 15 is freely rotatable about its axis and the axis of the can body 11, and means (not shown) are provided for reciprocat ing the plate 15 and the can body 11 carried thereby in upward and downward directions as viewed in FIG. 1.

The apparatus 10 further includes a die member 17 having a shaft 18 which is rotated by conventional means (not shown) to impart rotation to the die member 17. A periphery of the die member 17 is contoured to define a working surface 20 which, as viewed in FlG. 2, is directed progressively axially up wardly and radially outwardly. I

A pair of

identical split rings

21, 22 surround the die member 17 in the operative position shown in FIG. 1, and conventional means (not shown) are provided for moving the

split rings

21, 22 from the closed position shown in FIG. 1 to an open position at which the flanged can body 11 can be removed from the apparatus 10, as will be more apparent hereafter.

The

rings

21, 22 are identical and each includes a radially inwardly and upwardly directed bore 23 in which is received a member 24 which can be locked in a desired position of adjustment by means of a screw 25 in a conventional manner readily apparent from FIG. 1. Each member 24 carries at its end a freely rotatable ball-shaped element 26 having an outermost spherical surface 27 which with the working surface 20 defines a guide or passage 28 which progressively decreases in size from an entrance opening 30. While only one member 24 and its associated ball-shaped element 26 is illustrated as being associated with each of the

split rings

21, 22, it is to be understood that additional members and ball-shaped elements carried thereby may be positioned about the inner circumference of the

split rings

21, 22 to define as many passageways 28 as may be found necessary to flange a particular can end portion.

The can body 11 is flanged by the apparatus by first positioning the can body 11 in the manner illustrated in FIG. 1. of the drawing. The plate 15 is, of course, initially lower than that illustrated in FIG. l to enable the can body ill to be positioned thereupon after which the plate 15 is moved vertically upwardly to present the peripheral edge portion 12.0f the can body 11 to the entrance portion 30 of the passage 28. The

split rings

21, 22 are suitably held stationary in the position illustrated in FIG. 1 and the die member 17 is rotated in either a clockwise or a counterclockwise direction.

As is best illustrated in FIG. 2 of the drawing, the entrance portion 30 of the passage 28 is of a lesser dimension than the initial wall thickness T of the can body edge l2. As the edge 12 is progressively urged into each of the passages 28, the

working surfaces

20, 27 subject the peripheral edge 12 to compressive stresses Sa, Sr and Sc. The compressive stresses Sa are directed in general parallelism with the can body axis in a downward direction as indicated by the downwardly directed unnumbered headed arrows in FIG. 2. The compressive stresses Sr are directed generally transverse to the can body axis, while the compressive stresses Sc are imposed upon the flange 12 in generally a circumferential direction, as illustrated in FIG. 3. Thus, as the die member 17 rotates the multiaxial compressive stresses 50, Sr and Sc cause the material of the peripheral edge to cold flow in the absence of tensile stresses upwardly tangentially and radially outwardly to the position shown in FIG. 4 to form a flange F. The

working surfaces

20, 27 cause the metal of the edge 12 to progressively extrude into the passage 23 causing a reduction in the initial thickness T and the resultant flange F.

At the completion of the formation of the flange F, the

split rings

21, 22 are separated to remove each ball-shaped element 26 from beneath the formed flange F to permit the now flanged can body to be removed by the downward movement ofthc plate IS.

The method just described was experimentally practiced by mounting a die member, corresponding to the die member B7 in the chuck of a conventional lathe and supporting a corresponding member 24 carrying a ball-shaped element 26 on the tool holder of the lathe cross-slide. The ball-shaped element was of a 0.150-inch diameter, and was positioned adjacent a corresponding working surface in such a way that the passage 2% formed an entrance opening 30 which was appropriately .0005 inch less than the initial thickness T of the can body, and progressively narrowed axially upwardly and radially outwardly, as is shown in FIG. 2. A welded can body was centered upon the lathe tail stock and hand fed at .020 inch per revolution into the passage 28 during relative rotation (18 revolutions per minute) between the die member 17 and the ball-shaped element 26. Satisfactory uncracked flanges were repetitively formed in this manner.

A razor was used to form deep notches in the ends of the can body edges. both in the unwelded material and in the welded seam l4, and during the flanging of the notched can bodies by the apparatus just described the notches did not progress deeper into the flange, while similar tests of notched can bodies which were conventionally die flanged caused the notches to progress completely through the length of the formed flanges.

In standard conventional die flanging, the can body thickness at the very tip of the finished flange is reduced by about 3 to 4 percent compared to the initial thickness thereof. For example, in the case of 55-lb. base weight sheet metal the initial undeformed thickness of the can body peripheral edge or tip is approximately .006 inch and the tip of the flange is approximately between .0057 to .0058 inch. However, in the practice of the method of this invention, the reduction between initial and final tip thickness ranges betweem 15 to 20 percent. For the same SS-Ib. base weight sheet the tip of the flange F ranges between .0043 to .005 2 inch. If this flange were straightened the cross section would be very much like that of a right-angled trapezoid where the base line is the original undeformed thickness of the metal (here about .006 inch) and the opposing line at the tip is about 15 to 20 percent shorter (here about .0048 to .0052 inches).

In accordance with the experiments performed and the apparatus l0 illustrated in FIG. 1, both the die member 317 and the ball-shaped elements 26 are freely movable and relatively rotatable. However, neither the particular shape of the ballshaped elements 26 nor the relative movement thereof is significant. The significant feature of the method is the particular size and shape of the passages 28 such that the edge l2 of each can body is subjected to the compressive stresses Sa, Sr and Sc. For example, in accordance with a modification of the apparatus 10 shown in FIG. 5 the perfectly spherical ball-shaped elements are each replaced by a roll 35 having a working surface 36 which in conjunction with the working surface 20 of the die member 17 forms the upwardly and outwardly tapering passage 28. Experiments were carried out in the manner heretofore described by employing a 1-inch diameter roll, corresponding to the roll 35, having an axial radius of .075 inch. Successful uncracked flanges were produced by the compressive stresses generated by the working surfaces 20, an.

In lieu oftwo movable working surfaces 20, 27 and 20, 36 as in FIGS. 2 and 5 respectfully, the invention can be practiced by supporting a stationary immovable member d0 having a working surface 41 adjacent the working surface 20 of the die member 17, as shown in FIG. 6. The member 430 can, for example, be supported by a housing as the die l7 rolls along the member 40 maintaining all the way the necessary passage 23 and the can body end is transported along with the die 17 by conventional means. The forming process is performed in the manner heretofore fully described.

From the foregoing, it will be seen that novel and advantageous provisions have been made for carrying out the desired end. However, attention is again directed to the fact that additional variations may be made in this invention without departing from the spirit and scope thereof as defined in the appended claims.

I claim:

I. A method of cold forming a tubular metallic body in the absence of tensile stresses comprising the steps of subjecting a peripheral end portion of the body to multiaxial compressive stresses and simultaneously progressively axially and tangentially lengthening the peripheral end portion and reducing the wall thickness thereof, and guiding the peripheral end portion in a radial direction during the compressive stressing to transform the peripheral end portion into a radially directed peripheral flange.

2. The method as defined in claim ll wherein the peripheral end portion is guided radially outwardly during the compressive stressing to form a radially outwardly directed peripheral flange.

3. The method as defined in claim 1 wherein the peripheral end portion is subjected to the compressive stresses by forcing the peripheral end portion of the body between opposed working surfaces which define a progressively diminishing gap which over at least a portion of its length is narrower than the initial wall thickness of the peripheral end portion.

4. The method as defined in claim ll wherein the peripheral end portion has a terminal end of an initial wall thickness, and the wall thickness is reduced more than 5 percent during the cold forming thereof.

5. The method as defined in claim 2 wherein the peripheral end portion has a terminal end of an initial wall thickness which is between 10 to 20 percent greater than the thickness of a terminal end of the peripheral flange.

6. The method as defined in claim 3 including the step of imparting relative rotation between the opposed working surfaces during the compressive stressing of the peripheral end portion.

7. The method as defined in claim 3 including the step of imparting relative rotation between at least one of the opposed working surfaces and the body, and relative axial movement between the tubular body and the opposed working surfaces during the compressive stressing of the peripheral end portion.

8. The method as defined in claim 3 wherein the tubular body has a longitudinal side seam weld.

9. The method as defined in claim 3 wherein the peripheral end portion has a terminal end of an initial wall thickness which is between 5 to 25 percent greater than the thickness of a terminal end of the peripheral flange.

10. The method as defined in claim 3 wherein the peripheral end portion is guided radially outwardly during the compressive stressing to form a radially outwardly directed peripheral flange.

11. The method as defined in claim 3 wherein one of the working surfaces is immovable.

12. A flanged can body comprising a metallic tubular member having a main body portion and axially opposite end portions, said main body portion being of a predetermined wall thickness, at least one of said axially opposite end portions includes a radially directed compressive stress-formed peripheral flange, and a terminal end of said flange has a wall thickness which is between to percent less than the wall thickness of said main body portion.

13. The flanged can body of claim 12 wherein said tubular member has a longitudinal side seam weld.

14. Apparatus for transforming a peripheral end portion of a metallic tubular body into a peripheral flange comprising means defining a pair of generally radially directed opposed working surfaces which form a progressively diminishing gap which over at least a portion of its length is narrower than the initial wall thickness of the peripheral edge portion, means for rotating the body relative to at least one of said working surfaces, means for progressively introducing the peripheral end portion of the body into said gap whereby said opposed working surfaces apply multiaxial compressive stresses against said peripheral end portion and simultaneously progressively axially and tangentially lengthening said end portion, reducing the wall thickness thereof, and transforming said end portion into a radially directed peripheral flange.

15. The apparatus as defined in claim 14 wherein one of said working surfaces is a rotatable element positioned radially outwardly of the remaining working surface.

16. The apparatus as defined in claim 14 wherein one of said working surfaces is maintained immovable during the forming process, and is positioned radially outwardly of the remaining working surface.

17. The apparatus as defined in claim 14 wherein said gap is directed generally radially outwardly from an entrance opening thereof whereby during the compressive stressing the end portion is transformed into a radially outwardly directed flange.

18. The method as defined in claim 1 wherein the step of subjecting the peripheral end portion of the body to multiaxial compressive stresses is performed by applying a force to the body, the application of the force resulting in no tensile stresses being applied to the body.