US3785311A

US3785311A - Method for producing a metallic container or can

Info

Publication number: US3785311A
Application number: US00147073A
Authority: US
Inventors: T Yoshikawa
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 1970-06-04
Filing date: 1971-05-26
Publication date: 1974-01-15
Anticipated expiration: 1991-01-15
Also published as: GB1320061A; DE2127603A1

Abstract

A metal blank or tin plate is drawn to form a cup, said cup is then subjected to ironing, trimming and flanging to produce a metallic container or can. However the final ironing is not effected at all on the upper part of the can body wall. For this purpose, a punch core is used which has the upper portion of smaller diameter and the rest portion of larger diameter, the latter constituting a substantial part of the core. The container thus produced has a thin walled center portion constituting a greater part of the body wall and a thick walled upper portion constituting a smaller part of the body wall.

Description

Yoshikawa METHOD FOR PRODUCING A METALLIC CONTAINER OR CAN [451 Jan.15,1974

FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Charles W. Lanham Assistant Examiner-M. J. Keenan Attorney-Watson, Leavenworth & Kelton [57] ABSTRACT A metal blank or tin plate is drawn to form a cup, said cup is then subjected to ironing, trimming and flanging to produce a metallic container or can. However the final ironing is not effected at all on the upper part of the can body wall. For this purpose, a punch core is used which has the upper portion of smaller diameter and the rest portion of larger diameter, the latter constituting a substantial part of the core. The container thus produced has a thin walled center portion constituting a greater part of the body wall and a thick walled upper portion constituting a smaller part of the body wall.

1 Claim, 4 Drawing Figures [75] Inventor: Tatsumi Yoshikawa, Tokyo, Japan [73] Assignee: Daiwa Can Co., Ltd., Tokyo, Japan [22] Filed: May 26, 1971 [21] Appl. No.: 147,073

[30] Foreign Application Priority Data June 4, 1970 Japan 45/54468 [52] US. Cl. 113/120 H, 72/348 [51] Int. Cl B21d 22/30 [58] Field of Search 72/348; 113/120 H [56] References Cited UNITED STATES PATENTS 3,406,554 10/1968 Frankenberg 72/348 3,029,507 4/1962 Gaggini 72/348 1,295,430 2/1919 Carlson 72/348 3,556,032 l/1971 Fraze 113/120 H 1,944,527 1/1934 Pfaendler 72/367 2,980,993 4/1961 Lyon 72/348 1 l A l ,i

PATENTEDJAH 15 I974 FIG. 2a

FIG. 2b

FIG.3

METHOD FOR PRODUCING A METALLIC CONTAINER OR CAN BACKGROUND OF THE INVENTION It is known that a metal blank or tin plate is drawn to form a cup, which is then subjected to ironing to form an incomplete tubular can with an end, thereafter it is stripped off the punch core, and the upper zig-zag part of said cup is trimmed, then a part of the trimmed upper part is subjected to flanging and double seaming with a cover to form a can. In order to keep costs down, it has been a desideratum to make the body wall of the can as thin as possible and to elevate the can making speed as high as possible. On the other hand, however, it has been considered to be impossible to fulfil the above two items for the following reason.

The cup as formed by drawing does not have the same thickness all around the body wall. Thus, when the cup is subjected to ironing, the thick portion is elongated more than the thin portion, which results in that the upper edge of the body wall is rendered zigzag. As the can is stripped off the punch core after completion of ironing, the outermost projected tip ofsaid zigzag portion butts first against the finger of the stripper. If the outermost projected tip has a substantial thickness and/or the depth of said zig-zag portion is shallow, it will not be bent even when it butts against the finger of the stripper at a high speed. If said tip is thin, however, it will be bent unless it butts against the finger of the stripper at a low speed.

It has been thought that when the punch core is stripped of the can after ironing, the punch core should take an inverted truncated conical form having a greater diameter in the upper part or a cylindrical form having substantially identical thickness throughout the vertical length. The can body which has been subjected to ironing by the use of a punch core in the form of an inverted truncated cone has a wall thicker in the lower part and thinner in the upper part. When a punch core in a cylindrical form is used for ironing of the can body, it has a wall having the same thickness throughout the vertical length. In any case, when it is intended to make the can wall thin to decrease the amount of material to be used for the can, the upper end of the body wall becomes so thin that it will easily be bent when the core is stripped.

In this invention, the upper part of the can body wall is so thick and a zig-zag portion of said part is so shallow that it will not be bent even when it butts against the finger of the stripper at a production velocity of at least 200 cans per minute. The central part of the can body wall has a very small thickness after ironing. The punch core used in this invention is such that it will produce the above structure of the can body wall.

U.S. Pat. No. 3,029,507 indicates that a disc made of aluminum is formed into a tubular can with an end, which is then subjected to ironing so as to elongate the body wall thinly. A can formed by impact extrusion as shown in said U.S. Patent has the same wall thickness with respect to a section perpendicular to the axis of the can, as is different from a can made by drawing. Thus the can made by impact extrusion will hardly produce any zigzag portion in the upper body edge after ironing of said body wall, and there are fewer cases of being bent by the stripper finger than with the can made by drawing when the thickness of the upper end is equal. Accordingly there is no consideration in said U.S. Patent about the zigzag problem of the upper edge of the can, and thus no description therein about a technical idea of imparting little or no ironing upon the upper part of the can body in the last step, which will distinguish the present invention from that shown in said U.S. Patent.

SUMMARY OF THE INVENTION This invention relates to a method for producing a metallic container or can with the upper edge of the body wall having a thickness enough to maintain its original form even when it butts against the stripper finger at high speed. For the purpose, the final ironing is not effected on the upper part of the product after the first ironing. Thus the finished product has a thin walled center portion constituting a greater part of the body wall and a thick walled upper portion constituting a smaller part of the body wall.

It is another object of the invention to provide a can with a thick walled upper edge of the can having such thickness as not to be bent even when it butts against the finger of the stripper, the other part than the upper edge of said can having an extremely thin thickness so as to curtail the amount of material to be used for the can.

It is a further object of the invention to provide a can which has been subjected to drawing, ironing, trimming and flanging and which has in the upper part a thickness enough to double seam a metal end thereupon, while in the other part an extremely thin thickness.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view out along a plane containing an axis of a tubular can of this invention.

FIG. 2a is a vertical sectional view of a cup as formed by drawing.

FIG. 2b is a vertical sectional view of a cup of FIG. 2a after the first ironing.

FIG. 3 is a front view of a punch core of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The word drawing used herein is meant by a process in which a circular metal blank or tin plate is held under suitable pressure between a die plate and a pressure plate, said plate is then caused to pass with a punch core drawing die ring, and a cup is formed thereby. In this case, the difference between the outside diameter of said punch core and the inside diameter of said die ring being at least twice the thickness of the tin plate.

The word ironing used herein is meant by a process in which the wall of the cup body is thinly elongated when the cup is caused to pass with the punch core through an ironing die ring since the difference between the outside diameter of the punch core and the inside diameter of the ironing die ring is less than twice the thickness of the wall of the cup body.

A cup A shown in FIG. 2a is one as formed by the above drawing. The bottom end wall thickness is substantially equal to that of a tin plate. The body wall thickness is nearly equal to that of the tin plate, but does not have the same thickness for the reasons that the pressure for holding the tin plate does not substantially uniformly act upon the tin plate, that the tin plate itself does not have the uniform thickness and that the material of the tin plate is not uniform, etc. This cup A is subjected to ironing by the use ofa punch core shown in FIG. 3 (the ironing die ring used is not shown). The punch core shown in FIG. 3 has a lower zone 4? in the lower part thereof which is progressively enlarged in upward direction, a central zone which rests on the zone 4P and has an equal diameter, an upper zone 9 which rests thereon and has progressively smaller diameters in upward direction and an uppermost zone thereon having a small diameter. As the cup is caused to pass with the punch core through the ironing die ring, the part of the cup which has contacted the zone 4P of the punch core is shown as 4a in FIG. 2b showing a product after the first ironing is over. It is the lower part of the body wall of the cup having a thickness which is progressively smaller in upward direction. The central part 511 and the upper part 6a in FIG. 2b are those having contacted the central zone of the punch core with an equal diameter. Therefore, an open end of said product remains within the central zone.

As set forth hereinabove, since the wall of the cup body does not have the same thickness, the elongation by the above stated ironing of the body wall is not uniform with respect to the entire circumference thereof. Accordingly, the open end of the body wall will become zigzag as indicated by the reference numeral 8 in FIG. 2b. The open end of the body wall after the first ironing is positioned below the upper zone 9 of the punch core. When the final ironing is effected to the product as shown in FIG. 2b which has been subjected to the first ironing, the central part of the body wall of the product is thinly elongated successively from the lower part 4a thereof and the upper part 6a including the open end of the product will reach within the uppermost zone of the punch core. In this ironing step, the rate of reduction of the thickness in the part 6a will not occur at all. After this product has been past through the final ironing die ring, it is stripped off the punch core. The product after the final ironing subjected to trimming is shown in FIG. 1. As compared with the product of FIG. 2b, the can shown in FIG. I has the bottom end 2 made concave internally, the parts 4 and made thinner then the

parts

4a and 5a and the upper part 6 not made thinner, than the part 6a. Thus the depth of the zig-zag portion of the upper part of this product is not deeper than that of the product of FIG. 2b. In FIG. 1, the part 7 represented by a dotted line shows an outwardly, radially bent portion by flanging of the upper edge of the part 6 after trimming. In the can in FIG. 1, the bottom end 2 has the same thickness as that of the tin plate and the arc plate 3 connecting the end 2 with the body wall has the thickness extremely slightly smaller than that of the tin plate. The lower part 4 has the progressively smaller thickness in upward direction and the successive central part 5 constituting a greater part of the body wall has the smallest thickness. The successive part thereon is made progressively thicker which leads to the uppermost part having such thickness as not to be bent when it butts against the finger of the stripper. Examples of thickness of each part are 0.35 to 0.30 mm for the end 2 and the are part 3, 0.30 to 0.10 mm for 10 mm of the lower part 4, about 0.10 mm for the central part5, 0.10 to 0.20 mm for about 5 mm of the upper part 6 and about 0.20 mm for the upper edge of the body wall.

The can was made of tin plate but other material such as aluminum can be used. The rate of production was 250 cans per minutes but there was substantially no bending of the upper edge of the can. For the purpose of double seaming, it is preferable to have the upper part with the thickness of 0.2 mm extended in 5 mm or so below the upper edge after trimming.

The above description is only one embodiment of the invention. After drawing, the ironing can be effected once or several times. In any case it is possible to produce a can in which the upper part of the body wall has the thickness greater than that of the central part thereof as shown.

The thickness of the tin plate, the rate of reduction of the thickness of the lower part 4 of the body wall and the rate of increase of the thickness of the upper part 6 may vary with the material used and not confined to the figures used the above examples. However, since it is an object of the invention to reduce the amount of material used, it is obviously desirable to made the central body wall as thin as possible by sharply decreasing or increasing in drawing or ironing the thickness of the other parts of the body wall without destroying thereof. The thickness of the central part may thus be made 0.1 mm or less. When the thickness of the upper edge of the body wall is 0.18 to 0.28 mm according to the particular material used, it is not bent as it butts against the stripper finger even at the production rate of 250 cans/- min and a metal cover can be double seamed by the use of an ordinary double seamer. When the second ironing or the subsequent ironings are conducted by means of the punch core, the omission of ironing of the upper part of the body wall in the last ironing will result in fewer zigzag portions of the upper edge. This is because the thickness of the body wall is made equal after the first ironing with respect to a plane perpendicular to the axis of the can and thus the zigzag portion of the upper edge resulting from the first ironing will not be exaggerated any longer so long as it is not elongated. For the reason above, there is few distances in this invention between the projected part and the recessed part in the zigzag portion of the upper edge of the wall of the can body, which will cause advantages of preventing the projected part from bending as it butts against the finger of the stripper.

It is thought that the invention and its attendant advantages will be understood from the foregoing description and it will be apparent that various changes and modifications may be made without departing from the spirit and scope of the invention.

I claim:

1. A method for producing a metallic container comprising drawing a metal blank to form therefrom a cup which includes a bottom wall and a side wall extending upwardly from said bottom wall and terminating in an opening at the top of said cup, said cup bottom wall and side wall having substantially the same thickness,

providing an elongated punch core having an end segment which progressively enlarges in diameter in the direction of its other end and which merges with a second segment of substantially uniform diameter, a third segment adjacent said second segment and having progressively smaller diameter in the direction of said other end, and a fourth segment adjacent said third segment and having a substantially uniform diameter not larger than the smallest diameter of said third segment,

6 positioning said core punch vertically with said end location in said core punch second segment,

segment at the bottom and receiving said core then effecting the further ironing of said product by punch in said cup through said opening, elongating the central part of the body wall without then effecting a first ironing of said cup with said elongating the upper portion thereof and while punch core by elongating the body wall including 5 maintaining said cup opening positioned at a locathe upper part thereof and reducing the thickness tion in the fourth zone of said punch core, and of the lower part of the body wall in a degree in then stripping the container off the punch core and which said thickness becomes progressively smaller thereafter effecting trimming and flanging the end in a direction upward from said bottom wall, and of the container. while maintaining said cup opening positioned at a 10

Claims

1. A method for producing a metallic container comprising drawing a metal blank to form therefrom a cup which includes a bottom wall and a side wall extending upwardly from said bottom wall and terminating in an opening at the top of said cup, said cup bottom wall and side wall having substantially the same thickness, providing an elongated punch core having an end segment which progressively enlarges in diameter in the direction of its other end and which merges with a second segment of substantially uniform diameter, a third segment adjacent said second segment and having progressively smaller diameter in the direction of said other end, and a fourth segment adjacent said third segment and having a substantially uniform diameter not larger than the smallest diameter of said third segment, positioning said core punch vertically with said end segment at the bottom and receiving said core punch in said cup through said opening, then effecting a first ironing of said cup with said punch core by elongating the body wall including the upper part thereof and reducing the thickness of the lower part of the body wall in a degree in which said thickness becomes progressively smaller in a direction upward from said bottom wall, and while maintaining said cup opening positioned at a location in said core punch second segment, then effecting the further ironing of said product by elongating the central part of the body wall without elongating the upper portion thereof and while maintaining said cup opening positioned at a location in the fourth zone of said punch core, and then stripping the container off the punch core and thereafter effecting trimming and flanging the eNd of the container.