GB1604068A

GB1604068A - Metal container ends

Info

Publication number: GB1604068A
Application number: GB2390578A
Authority: GB
Original assignee: National Can Corp
Current assignee: National Can Corp
Priority date: 1977-07-29
Filing date: 1978-05-30
Publication date: 1981-12-02
Also published as: IE46997B1; GR60707B; IE781206L

Description

(54) IMPROVEMENTS IN AND RELATING TO METAL CONTAINER ENDS (71) We, NATIONAL CAN CORPORA TION, a Corporation organised under the laws of the State of Delaware, United States of America, of 8101 West Higgins Road, Chicago, Illinois 60631, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates generally to container ends and more particularly to ends that are utilised in containers that are used for packaging products under high pressure, such as beer and carbonated beverages. The invention relates to container ends and to apparatus for and methods of producing such ends.

In recent years, many of these products have commonly been packaged in metal containers formed either of aluminium or of tinplated steel. Since the beer and carbonated beverage industry utilises many millions of containers annually, it is essential that the containers be formed of a minimum thickness of metal so that the container can be marketed at the lowest possible price. The cost of the container is extremely important since, for many products, the cost of the container approaches or exceeds the cost of the product being packaged therein. As much, any cost reduction in manufacturing finished containers is extremely desirable.

Because of the large market for metal containers, particularly those formed of aluminium, a very small saving in the amount of material for a single container can substantially affect the overall cost considerations.

For example, a reduction in metal thickness of approximately 0.001 inches can result in many thousands of pounds in savings for a manufacturer of cans.

In recent years, many beverages have been packaged in what is commonly referred to as a two-piece container. In this container, the bottom wall and side wall are formed as an integral unit by drawing and ironing a flat blank to produce a container body open at one end. The open end of the body then has an end panel secured thereto by a conventional seaming process.

When these types of containers are utilised for packaging beer or carbonated beverages, the containers must be capable of withstanding minimum pressures of 90 psi before the container end will "buckle" and also be capable of withstanding minimum pressures of 60 psi before the container will "rock".

The term "rock" is related to the deflection of the centre panel portion of the end panel, which normally has a tab connected thereto by a rivet, and the term identifies the pressure at which any given portion of the centre of the end panel projects above the upper peripheral edge or chine of the container. The term "buckle" pressure is the pressure that an end is capable of withstanding without any notable distortion of the end and/or rupture of any portion of the end.

Quite recently the present applicants developed a drawn and ironed container that can be manufactured from thin gauge metal and still be capable of withstanding the pressures indicated above. This drawn and ironed container is described in United States Patent No. 3,942,673 issued to Seung W. Lyu et al. While this drawn and ironed container has found a remarkable degree of commercial success, the end panel utilised in connection therewith still of necessity must be formed from a metal blank having a thickness of approximately 0.0135 inches to withstand the desired buckle and rock pressures.

Various proposals have been suggested for reducing the metal thickness of an end panel.

One example of such proposal is described in Cospen et al. United States Patent No.

3,843,014. This patent discloses a particular configuration for the countersink portion of an end panel between a peripheral curl and a centre flat panel portion. The patentees of this patent indicate that the particular configuration of the one end panel will allow a panel to be formed from metal having a thickness of the order of 0.0115 inches.

Actual tests were conducted with sample end panels constructed in accordance with the teachings of Cospen et al. disclosure and it was found that, while the container end panel was capable of withstanding the minimum buckle pressures required, the particular configuration resulted in the end being bulged outwardly sufficiently at approximately 30 psi to produce a "rocker" container. Thus, such a proposal has not been accepted as a commercially feasible alternative to the present commercial ends.

Accordingly the present invention provides a circular, metal container end having a thickness not greater than 0.0120 inches and including a peripheral curl and a substantially flat central panel with a countersink between the curl and the central panel and extending below the central panel, the countersink having inner and outer flat walls interconnected by a first arcuate portion having a radius less than three times the thickness of the metal, the fiat inner wall being integral with the central panel through a second arcuate portion which does not extend above the central panel and which has a radius approximately twice the thickness of the metal and the inner flat wall having a length to locate a lower edge of said first arcuate portion at least 0.075 inches below a lower peripheral edge of the central panel, the outer flat wall having a length sufficient to locate its upper end above a plane extending through the lower peripheral edge of the central panel, and the outer flat wall defining an angle of less than 5" with respect to a second plane extending perpendicular to the said plane, the peripheral curl being integral with the upper end - and extending above the central panel, the container end being capable of resisting at least 90 psi buckle pressure and at least 60 psi rock pressure.

According to a second aspect of the present invention, apparatus for use in prpducing a container end as defined above comprises co-operating lower and upper (as hereinafter defined) annular dies mounted for movement relative to each other along a path, the lower die including a centre die member, an inner annular die member surrounding the centre die member and having a peripheral vertical surface and an arcuate portion on the upper end of the vertical surface which has a radius of less than 0.030 inches, and an outer annular die member having a substantially vertical surface defining an angle of less than 5- with the saId peripheral vertical surface of the said inner annular die member, the surfaces being spaced from each other to define a recess therebetween, and the upper die including an annular punch having a lower arcuate surface circumscribing an arc of 180" and having a radius of less than 0.035 inches, the punch having a length of at least twice the radius so that both the walls of the countersink are substantially vertical with the outer wall of the countersink defining an angle less than 5, with respect to a vertical plane and a lower edge of the countersink being spaced from a lower edge of the centre panel portion by a vertical dimension of more than 0.075 inches.

The terms "upper" and "lower" as used above and hereinafter, together with other terms of orientation, are to be understood as being used purely for convenience as a way of defining the orientations of various parts relative to other parts and not absolutely.

Preferably the punch has an outer flat wall portion, the length of which is such as to locate the juncture between the flat wall portion of the countersink and the peripheral curl of the container end above the peripheral lower edge of the central portion, and to produce an arcuate portion having a radius of less than 0.030 inches between the inner flat wall and the central portion.

Preferably, the upper die element has an inwardly directed generally horizontal surface on the upper inner edge of the punch and the inner die member is positioned so that the spacing between the generally horizontal surface and the arcuate surface on the inner die member is less than the thickness of the metal when the die elements are in a closed position and the arcuate portion between the inner flat wall and the central portion is reduced in thickness. There is thus a coining operation performed in the said arcuate portion.

Preferably there are provided means for doming the central portion during movement of the die elements towards each other.

The invention may be carried into practice in various ways but one container end embodying the invention, the apparatus of forming the end and the method of forming the end in accordance with the invention will now be described by way of example with reference to the accompanying drawing in which Figure 1 shows a plan view of a metal container end constructed in accordance with the present invention; Figure 2 is a fragmentary sectional view of the tooling utilised for forming the countersink walls of the end shown in Figure 1; and Figure 3 is an enlarged fragmentary sectional view of the peripheral portion of the container end shown in Figure 1.

Figure 1 of the drawings illustrates a container end, generally designated by reference numeral 10, having a peripheral curl 12 which is adapted to be seamed on to a container body utilising a conventional double seaming process. The container end 10 has a generally flat central panel portion 14 which has a score 16 produced therein to define a removable section. A tab 18 is connected to the removable section 16. As is conventional in ends of this type, the container end 10 has a countersink 20 located between the peripheral curl 12 and the central flat panel portion 14.

The opening means includes the score 16 and the tab 18 are shown for purposes of illustration only and any other type of opening means may be incorporated into the end being described. For example, the opening means may be of the "button" or any other "ecology" type end. Also, the end being described can be used on either a two piece or a three piece container.

In accordance with the present invention, the countersink 20 is specifically configured so that the container end panel may be formed from a flat blank of aluminium having a thickness of 0.0120 inches or less and having the same diameter as blanks previously used for making ends, while being capable of resisting buckle pressures of more than 90 psi and rock pressures of more than 60 psi. Furthermore, this can be accomplished with a minimum modification of the existing tool normally utilised for converting an end panel to a finished end.

Referring to Figure 3, the countersink 20 includes an inner wall 22 and an outer wall 24 which are interconnected by an arcuate portion 26. The inner wall 22 is connected to the centre panel portion 14 through an arcuate portion 28.

The parameters or dimensions of the respective portions which form the countersink 20 are interrelated to optimise the maximum pressures that the end is capable of withstanding without buckling or rocking.

More specifically the inner flat wall 22 has a length that will locate the peripheral edge 30 of the central panel portion 14 a dimenion H above the lower edge of arcuate portion 26.

It has been determined that the angle A of the inner flat wall 22 with respect to a reference plane P, when considered in conjunction with the length of the flat wall 22, has a significant effect on the pressure resistance the container can withstand without failure. It has been determined that by having the dimension H greater than 0.075 inches and having a minimum angle A, the buckle and rock pressures are substantially increased, when compared with a present day standard 209 diameter and having the dimension H set at 0.065 inches.

Also, the length of the outer flat wall 24 and the angle thereof have an important effect on obtaining buckle pressures of more than 90 psi and rock pressures of more than 60 psi utilising an aluminium blank which has a thickness of 0.012 inches or less.

Preferably, this outer straight flat wall portion 24 is of a sufficient length that the juncture 32 between the upper end of the flat wall portion 24 and the lower end of the peripheral curl 12 is located at a height of more than 0.080 inches above the lower edge of countersink 20, more specifically, arcuate portion 26. The angle B defined between wall portion 24 and a vertical plane P extending perpendicular to the panel is preferably less than five degrees and in the illustrated embodiment is approximately four degrees.

Stated another way, the length of the flat outer wall portion 24 is such that the juncture 32 at the upper end of outer flat wall 24 is located above the peripheral lower edge of the flat panel portion 14. However, while this flat portion is preferably longer, the maximum dimension is dictated by the existing seamer tooling so as not to interfere with the double seaming of the end on to the container.

The particular dimensions of the radii R1 and R2 are also important in producing an acceptable end that meets minimum buckle pressure requirements utilising a stock material having a thickness of 0.0120 inches or less. In the embodiment illustrated, the radius R I is less than three times the thickness of the aluminium while the radius R2 is preferably approximately twice the thickness of the aluminium metal. In order further to increase the resistance of the end to buckling, the arcuate portion 28 is coined along the radius portion R2 so as to reduce the thickness of the arcuate portion and work harden the metal therein. This work hardening of the metal results in stiffening the arcuate area 28 which increases the resistance to buckling. The central panel portion also preferably has a slight upward dome having a radius R3.

The apparatus for producing the end is shown in Figure 2 and consists of an upper die 60 and a lower die 62 which cooperate with each other to form the countersink of the particular construction described above.

The lower die 62 consists of a central portion or member 64 that has a spherical upper surface 66 to produce a slight dome in the central panel portion 14. The lower die 62 also includes an inner die member 68 which has an outer peripheral surface 70 that extends parallel to the plane that extends perpendicular to the end. The upper end of the vertical surface 70 has an arcuate portion 72 which has a radius of less than 0.030 inches. The lower die 62 also has an outer die member 76 that has a surface or wall 78 which cooperates with the surface or wall 70 to define a recess 79 and which defines an angle of less than five degrees with respect to the vertical surface 70 or a plane extending perpendicular to the end 10.

The upper die 60 has an annular punch 80 which has a lower arcuate surface 82, with a radius of less than 0.035 inches, which circumscribes an arc of 180 and has flat vertical inner and outer surfaces 84 and 86 at opposite ends of the arcuate surface 82. The annular punch 80 is adapted to be received into the recess 79 that is defined between the surfaces 70 and 78. The upper die 60 also has an inwardly directed generally horizontal surface 88 located above the lower edge of the arcuate surface 82 by a predetermined dimension as will be explained later. Also, the spacing between the surfaces 70 and 78 is just slightly greater than the sum of twice the radius of the arcuate surface 82 and twice the thickness of the metal.

Thus, when the punch 80 is moved towards the lower die 62, the countersink Z0 will be formed with the inner wall 22 being substantially vertical and the outer wall 24 also being substantially vertical and the lower edge of the arcuate portion 26 being moved away from the central panel portion 14. As the upper die bottoms out with respect to the lower die 62, the arcuate surface 72 cooperates with the inwardly directed inclined surface 88 to coin the arcuate area around the periphery of the central flat panel portion 14.

The advantages of making the lower die 62 as a three-piece unit will be apparent. One significant advantage is that the inner and outer die members 68 and 76 can be moved relative to each other along the path of movement of the dies 60 and 62 to position accurately an upper edge of the flat outer wall 78 with respect to an upper edge of the arcuate surface 72 on the upper end of the inner wall 70 of the recess 79.

This arrangement allows the manufacture of ends accurately to control the specific dimensions of the countersink 20, particularly the depth thereof with respect to the central panel portion 14. Also, the three die members that define the lower die 62 can readily be adjusted to accommodate metal of varying thickness. It will be appreciated that the thickness of a coil of metal specified to have a thickness of 0.0120 inches may vary in thickness + 0.0005 inches. Thus, this variation can readily be accommodated by proper adjustment of the die members 64, 68 and 76 with respect to each other along the path of movement of the dies 60 and 62, indicated by arrows D in Figure 2.

In addition, if a slight increase in buckle pressure is desired, with a small sacrifice in rock pressure, the amount of coining of the arcuate portion 28 can be increased.

The adjustment of the die members 64, 68 and 76 relative to each other is a simple matter which can be accomplished in a short period of time. For example, the die members are normally fixed to a bed of a press by bolts (not shown). For adjusting the die members 64, 68 and 76 relative to each other, it is only necessary to select shims (not shown) of a proper thickness and position them between the respective die members and the bed of the press. The closed position of the punch with respect to the lower die 62 can be adjusted in the same manner.

Turning now to the inner flat wall portion 22 of the countersink 20, it is preferable that this wall define a minimum angle with respect to a vertical reference plane. This angle is preferably zero but practical considerations virtually prevent the angle from being zero because it would make it difficult if not impossible to remove the end from the lower die. Therefore, the annular spacing between the inner vertical surface 84 of the punch 80 and the vertical surface 70 of the inner die portion 68 is made as small as possible while still allowing for sufficient clearance for the end to be readily removed from the die. It has been found that making this space between one and one-third and one and one-half times the thickness of the metal stock will produce a minimum angle for the vertical wall 22 and still allow the end to be readily removed from the die.

The method aspect of the invention can best be understood from the further description of the apparatus shown in Figure 2. The upper and lower dies 60 and 62 are aligned with each other for relative movement along a predetermined path so that the annular punch 80 is aligned with the recess 79 and the inclined surface 88 is aligned with the inner die portion 68. A sheet of metal material having a maximum thickness of 0.0120 inches is then inserted between the die elements and the die elements are moved towards each other to force the punch into the recess and produce the countersink 20.

During this relative movement, a portion of the metal material is forced into engagement with the outer surface 78 of the recess 79 to produce a flat wall portion for the outer portion of the countersink. At the same time, the cooperation between the die portion 68 and the punch 80 produces a second or inner flat wall portion for the countersink 20 and an arcuate portion interconnecting then flat wall portion with the central panel portion.

By proper selection of the length of the annular punch 80, which is preferably more than twice the radius of its lower arcuate surface, the lower edge of the countersink is located at a depth greater than 0.075 inches with respect to the peripheral edge of the central panel portion 14. Also, by proper selection of the length of the flat wall portion 78, the juncture between the upper edge of the outer flat wall portion and the curl 12 will be located at least 0.080 inches from the lower edge of the countersink.

A specific example of the dimensions for producing a 209 diameter end will now be set forth. Radius R1 is set for 0.030 inches while radius R2 has a dimension of 0.025 inches.

Outer flat wall portion 24 defines an angle B of approximately four degrees while inner flat wall portion defines an angle A of 10 degrees. The countersink depth H has a dimension of 0.083 inches while the juncture 32 between the peripheral curl 12 and the flat wall portion 24 is located at 0.092 inches above the lower edge of the arcuate portion 26. The surface 66 has a radius of 8 inches so that R3 is 8 inches. It was determined that the doming of the central panel portion removes all excess metal and in fact stretches the metal in the central panel portion.

A blank having a peripheral diameter of approximately 3.250 inches was converted to the dimensions set forth above to produce a 209 diameter finished end. Actual tests of sample ends produced in accordance with these dimensions show that the ends were capable of withstanding a buckle pressure of approximately 96.5 psi and a rock pressure of 70 psi.

If it is desirable to increase the rock pressure with a slight sacrifice in buckle pressure, the coining of arcuate portion 28 could be eliminated. This results from the fact that when the arcuate area is coined, excess metal is developed in the central panel portion 14 which inherently will result in the domed panel portion being flexed upwardly at a lower pressure.

The significant advantage of the end described is that it can be produced with conventional conversion tooling, except for one station. Normally, such tooling has six stations with the integral rivet for connecting the tab being formed at the first and second stations, the score producing the removable section being produced at the third station, the tab being preliminarily staked by partial deformation of the rivet at the fourth station and firmly staked at the fifth station. The sixth station in present commercial tooling produces the final configuration for the central panel portion, such as producing the desired strengthening beads in the central flat panel portion as well as the necessary lettering on the end.

With the end as described above, it is only necessary to revise the tooling in the sixth station to include the punch portion 80, the domed central portion 64 and inner and outer lower die elements 68 and 76. Furthermore, the particular dimensions, specifically the location of the countersink with respect to the remainder of the end is such that conventional seaming tooling can be utilised for double tooling the present end onto a container body. There are several types of seaming tooling that are presently being used by various packagers but all of these are adapted for having the countersink located at a specific location. The existing seaming tooling requires that the diameter of the centre portion of the countersink be 2.296 inches for a 209 diameter end and 2.416 inches for a 211 diameter end. With the end described above, the diameter of the centre portion of the countersink located at the centre point for radius R 1 is 2.296 inches.

Thus, the fully converted end can readily be double seamed to a container body utilising commercial equipment that packages are presently using.

The particular configuration of the countersink wall, and particularly the depth thereof as well as the length of the outer flat wall portion of the countersink, allows the manufacturer of ends to reduce the thickness of the stock material from the present thickness of 0.0135 inches to a thickness not greater than 0.0120 inches and possibly even 0.0115 inches. Such a reduction in metal thickness substantially reduces the overall cost of manufacturing ends.

WHAT WE CLAIM IS: 1. A circular, metal container end having a thickness not greater than 0.0120 inches and including a peripheral curl and a substantially flat central panel with a countersink between the curl and the central panel and extending below the central panel, the countersink having inner and outer flat walls interconnected by a first arcuate portion having a radius less than three times the thickness of the metal, the flat inner wall being integral with the central panel through a second arcuate portion which does not extend above the central panel and which has a radius approximately twice the thickness of the metal and the inner flat wall having a length to locate a lower edge of said first arcuate portion at least 0.075 inches below a lower peripheral edge of the central panel, the outer flat wall having a length sufficient to locate its upper end above a plane extending through the lower peripheral edge of the central panel, and the outer flat wall defining an angle of less than 5 with respect to a second plane extending perpendicular to the said plane, the peripheral curl being integral with the upper end and extending above the central panel, the container end being capable of resisting at least 90 psi buckle pressure and at least 60 psi rock pressure.

2. A container end as claimed in Claim 1, in which the first arcuate portion has a radius of 0.030 inches and the second arcuate portion has a radius of 0.025 inches.

3. A container end as claimed in Claim 2 in which said second arcuate portion has a thickness less than the metal thickness of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. be located at least 0.080 inches from the lower edge of the countersink. A specific example of the dimensions for producing a 209 diameter end will now be set forth. Radius R1 is set for 0.030 inches while radius R2 has a dimension of 0.025 inches. Outer flat wall portion 24 defines an angle B of approximately four degrees while inner flat wall portion defines an angle A of 10 degrees. The countersink depth H has a dimension of 0.083 inches while the juncture 32 between the peripheral curl 12 and the flat wall portion 24 is located at 0.092 inches above the lower edge of the arcuate portion 26. The surface 66 has a radius of 8 inches so that R3 is 8 inches. It was determined that the doming of the central panel portion removes all excess metal and in fact stretches the metal in the central panel portion. A blank having a peripheral diameter of approximately 3.250 inches was converted to the dimensions set forth above to produce a 209 diameter finished end. Actual tests of sample ends produced in accordance with these dimensions show that the ends were capable of withstanding a buckle pressure of approximately 96.5 psi and a rock pressure of 70 psi. If it is desirable to increase the rock pressure with a slight sacrifice in buckle pressure, the coining of arcuate portion 28 could be eliminated. This results from the fact that when the arcuate area is coined, excess metal is developed in the central panel portion 14 which inherently will result in the domed panel portion being flexed upwardly at a lower pressure. The significant advantage of the end described is that it can be produced with conventional conversion tooling, except for one station. Normally, such tooling has six stations with the integral rivet for connecting the tab being formed at the first and second stations, the score producing the removable section being produced at the third station, the tab being preliminarily staked by partial deformation of the rivet at the fourth station and firmly staked at the fifth station. The sixth station in present commercial tooling produces the final configuration for the central panel portion, such as producing the desired strengthening beads in the central flat panel portion as well as the necessary lettering on the end. With the end as described above, it is only necessary to revise the tooling in the sixth station to include the punch portion 80, the domed central portion 64 and inner and outer lower die elements 68 and 76. Furthermore, the particular dimensions, specifically the location of the countersink with respect to the remainder of the end is such that conventional seaming tooling can be utilised for double tooling the present end onto a container body. There are several types of seaming tooling that are presently being used by various packagers but all of these are adapted for having the countersink located at a specific location. The existing seaming tooling requires that the diameter of the centre portion of the countersink be 2.296 inches for a 209 diameter end and 2.416 inches for a 211 diameter end. With the end described above, the diameter of the centre portion of the countersink located at the centre point for radius R 1 is 2.296 inches. Thus, the fully converted end can readily be double seamed to a container body utilising commercial equipment that packages are presently using. The particular configuration of the countersink wall, and particularly the depth thereof as well as the length of the outer flat wall portion of the countersink, allows the manufacturer of ends to reduce the thickness of the stock material from the present thickness of 0.0135 inches to a thickness not greater than 0.0120 inches and possibly even 0.0115 inches. Such a reduction in metal thickness substantially reduces the overall cost of manufacturing ends. WHAT WE CLAIM IS:

1. A circular, metal container end having a thickness not greater than 0.0120 inches and including a peripheral curl and a substantially flat central panel with a countersink between the curl and the central panel and extending below the central panel, the countersink having inner and outer flat walls interconnected by a first arcuate portion having a radius less than three times the thickness of the metal, the flat inner wall being integral with the central panel through a second arcuate portion which does not extend above the central panel and which has a radius approximately twice the thickness of the metal and the inner flat wall having a length to locate a lower edge of said first arcuate portion at least 0.075 inches below a lower peripheral edge of the central panel, the outer flat wall having a length sufficient to locate its upper end above a plane extending through the lower peripheral edge of the central panel, and the outer flat wall defining an angle of less than 5 with respect to a second plane extending perpendicular to the said plane, the peripheral curl being integral with the upper end and extending above the central panel, the container end being capable of resisting at least 90 psi buckle pressure and at least 60 psi rock pressure.

central panel portion.

4. Apparatus for use in producing a container end as claimed in Claim I comprising cooperating lower and upper (as herein defined) annular dies mounted for movement relative to each other along a path, the lower die including a centre die member, an inner annular die member surrounding the centre die member and having a peripheral vertical surface and an arcuate portion on the upper end of the vertical surface which has a radius of less than 0.030 inches. and an outer annular die member having a substantially vertical surface defining an angle of less than 5" with the said peripheral vertical surface of the said inner annular die member the surfaces being spaced from each other to define a recess therebetween, and the upper die including an annular punch having a lower arcuate surface circumscribing an arc of 180 and having a radius of less than 0.035 inches, the punch having a length at least twice the radius so that both walls of the countersink are substantially vertical with the outer wall of the countersink defining an angle less than 5 with respect to a vertical plane and a lower edge of the countersink being spaced from a lower edge of the centre panel portion by a vertical dimension of more than 0.075 inches.

5. Apparatus as claimed in Claim 4, in which the punch has an outer flat wall portion the length of which is such as to locate the juncture between the flat wall portion of the countersink and the peripheral curl of the container end above the peripheral lower edge of the central portion, and to produce an arcuate portion having a radius of less than 0.030 inches between the inner flat wall and the central portion.

6. Apparatus as claimed in Claim 5 in which the upper die element has an inwardly directed generally horizontal surface on the upper inner edge of the punch and in which the inner die member is positioned so that the spacing between the generally horizontal surface and the arcuate surface on the inner die member is less than the thickness of the metal when the die elements are in a closed position and the arcuate portion between the inner flat wall and the central portion is reduced in thickness.

7. Apparatus as claimed in Claim 5 or Claim 6 further including means for doming the central portion during movement of the die elements towards each other.

8. Apparatus as claimed in Claim 5 or Claim 6 or Claim 7 in which the annular spacing between the inner annular flat wall and an adjacent vertical surface ofthe punch is less than one and one-half times the thickness of the metal so that the inner flat wall of the countersink defines a minimum angle with respect to the said reference plane.

9. A metal container end substantially as described herein with reference to the accompanying drawing.

10. Apparatus for forming a metal container end substantially as described herein with reference to the accompanying drawing.