WO1998037995A1

WO1998037995A1 - Reduced gauge steel can end

Info

Publication number: WO1998037995A1
Application number: PCT/US1997/013126
Authority: WO
Inventors: Martin Mark Hubball
Original assignee: Buhrke Tech International, Inc.
Priority date: 1997-02-27
Filing date: 1997-07-25
Publication date: 1998-09-03

Abstract

A steel can end (10) for beer and beverage cans has a reduced thickness (t) and a reduced panel depth (Z) from an aluminum can end, resulting in a reduced unit depth (Y). Such reduction in the size and gauge of a can end without compromising acceptable limits of buckle pressure, rivet formation considerations, and 'pop and tear' force considerations results in substantial savings on material costs. The steel can end (10) also resists thinning in panel wall (14) and counter sink radius (18) and can thus be formed from a circular or round blank (95). A single action press apparatus and method is used to reverse form the steel can end (10).

Description

REDUCED GAUGE STEEL CAN END

The present invention relates to can ends and a method and apparatus of forming the same, and in particular, can ends of the type utilized for brewed beverage, carbonated beverage, and non-carbonated beverage cans. Specifically, a reduced gauge steel can end for aluminum and steel beer and beverage cans having reduced dimensions resulting in an improved can end with a reduction in material costs, production costs, etc.

Background Art It has long been the industry standard to form two piece (can and end) beer and beverage cans from aluminum. However, the can industry in parts of the world has recently begun to form such beverage cans from steel . Aluminum can ends are utilized on such steel cans creating bi-metal cans which raise recycling concerns. As such, over the past few years, there has been a need for a steel can end for beer and beverage cans . However, all prior attempts to create a steel can end have failed for several reasons. Primarily, the use of steel in the existing aluminum can end technology has resulted in a non- acceptable end. For example, due to the structural strength of steel, significant problems occur in the formation of the can end. Further, problems occur in the formation of the tab and rivet for the can end as well as in the scoring of the can end to allow for acceptable "pop and tear" force standards in the opening of the can end. Such limitations with respect to the aluminum can end technology when applied to steel have prevented the formation of an acceptable steel can end of the type utilized for twelve ounce beverage cans. As such, the industry has maintained its long time use of the aluminum can end.

Over the past few decades there have been many advances in the design of aluminum can ends for beer and beverage cans resulting in a reduction in the size, e.g. diameter, gauge, etc., of the can ends. The smaller the can end can be made, the more economical such can ends become due to a decrease in the amount of material needed to form the can end, thus saving on manufacturing costs of materials. However, downsizing and downgauging are limited by buckle pressure and tab/rivet structural formations in the can ends. Initially, aluminum can ends of the type used on twelve ounce beverage cans were of a 211 diameter. This means that the can end would measure 2" and 11/16 inches (6.826 cm) -in diameter from end to end. Through many advances, the industry has progressed through the 209 (6.509 cm) and 207.5 (6.271 cm) diameters to 206 (6.033 cm) and 204 (5.715 cm) diameters to today where most aluminum can end sizes have been reduced to 202 (5.398 cm) and 204 (5.715 cm) diameters. For pressure vessels such as cans, as the end diameter decreases, the thickness of the can end required to hold a specific pressure also decreases. As a result the decrease in diameter over time has made it possible to take the material gauge of the aluminum can end to a minimum thickness of 0.0083 inches (0.2108 mm). At this thickness, the performance of the end becomes close to the low end of the acceptable limits of buckle pressure. Also, the formation of the rivet is more difficult to achieve resulting in the rivet cracking when the tab is assembled to the can end. Such limits have led to a halt of any further gauge reductions. Accordingly, there is a need in the industry to further reduce in dimension can end size while at the same time maintaining acceptable buckle pressure and adequate structural strength for tab/rivet formation as well as acceptable scoring considerations .

Referring now to Figure 1 which illustrates a perspective view of a prior art can end 10, generally comprising a panel 12 having a panel radius 14 leading into a panel wall 16 which in turn is connected to a counter sink radius 18. The counter sink radius 18 leads into a chuckwall 20 which in turn leads into a seaming panel radius 22 attaching a seaming panel 24 thereto and terminating in a curl 26. Attached to panel 12 is a tab 30 held thereto by a rivet 32. Also panel 12 includes score lines 34 forming a flap/tongue 36 upon which lifting of tab 30 breaks the flap or tongue 36 at the score lines 34 to open the beverage container .

As can be seen along lines 2-2 of Figure 1, Figure 2 illustrates generally a partial cross sectional view of the prior art can end 10 defining the panel 12, the panel radius 14, the panel wall 16, the counter sink radius 18, the chuckwall 20, the seaming panel radius 22, the seaming panel 24 and the curl 26.

Figure 3 illustrates an enlarged cross-sectional portion of the prior art can end having a profile or shape which has become the industry standard as providing the most desirable strength characteristics combined with the smallest can end size and gauge. Such a can end shape, commonly known as a B64 can end, has been used in the industry for over 20 years and is disclosed in U.S. Patent No. 3,417,898 to Bozek et al . , U.S. Patent No. 4,031,837 to Jordan and U.S. Patent No. 4,735,863 to Bachmann et al . One method of forming such a shape is disclosed in U.S. Patent No. 4,109,599 issued on August 29, 1978 to Schultz and assigned to the Aluminum Company of America (Alcoa) , and described in Alcoa's prior art B64 Reformed Shell Forming Process Report .

For ease of illustration the various sections of a can end have been distinctly marked in Figure 3. As can be seen, can end 10 includes a panel 12, a radius 14, a panel wall 16 essentially perpendicular to panel 12, a counter sink radius 18, a chuckwall 20, a seaming panel radius 22, a seaming panel 24 and a curl 26. The unit depth Y of can end 10 is measured from the top of seaming panel 24 to the lowest portion of the counter sink radius 18. Unit depth Y is defined by the summation of a panel depth Z indicating the dimension of the can end from the bottom of the panel 12 to the lowest portion of the counter sink radius 18 and a panel height X defined from the panel 12 to the top of the seaming panel 24. As such, panel height X and panel depth Z together determine the unit depth Y of the can end 10. The thickness of the can end 10 is indicated by reference character (t) . The current industry standard can end comprises a unit depth Y measuring 0.270 inches (6.858 mm) and a panel depth Z measuring 0.090 inches (2.286 mm) resulting in a panel height X of 0.180 inches (4.572 mm) . Further, this industry standard can end has a standard thickness (t) of 0.0083 inches (.2108 mm) .

Various methods and apparatus have been used to form these industry standard aluminum can ends. For example, U.S. Patent No. 4,808,052 issued to Bulso, Jr. et al . on February 28, 1989 discloses a double press action method and apparatus of forming container end panels. However, such a double action press apparatus and method is not readily adaptable to form the steel can end of the present invention and is relatively more complicated and results in higher manufacturing costs than the method and apparatus of the present invention.

As previously stated, can ends for beer and beverage cans have been reduced to this industry standard size and has become close to the low end of acceptable limits of buckle pressure and tab/rivet and score formation considerations. Such considerations have prevented the industry from further reducing the size and thickness of the can end. The present invention however, solves the problems of further reducing in size and thickness the can end for a beer and beverage container and fulfills a long felt need to do the same.

Disclosure of the Invention The present invention comprises a novel can end and method and apparatus of manufacturing a can end for beverage cans being formed of steel rather than the current industry standard aluminum and being reduced in dimensions resulting in a reduction of the material costs in manufacturing such can ends. The can end of the present invention is capable of reducing the thickness to 0.0071 inches (0.1803 mm) and further reduces the unit depth of the can end to 0.260 inches (6.604 mm) by making the panel depth 0.080 inches (2.032 mm) and maintaining the standard panel height of 0.180 inches (4.572 mm) . As a result of such reduction the blank size cut from the coil stock is smaller thus saving on material costs. The use of steel in carbonated and non-carbonated beverage style ends, such as beer and soda pop can ends, will allow further gauge reduction and even greater savings . Further the steel end also resists thinning in the panel wall and the counter sink radius. As a result, the steel can end blank can be cut round or circular since steel will not stretch during forming, unlike an aluminum can end blank which must be cut convolute or oval to accommodate for stretching. The steel can end of the present invention is formed by reverse forming the panel using a single action press apparatus. Such a novel method and apparatus allows for the formation of a steel can end capable of meeting the required buckle pressure standards, while at the same time allowing for adequate structural strength to form the rivet/tab of the can end, and further to allow proper scoring to meet the required "pop and tear" force standards.

Accordingly, it is the principal object of the present invention to provide a can end having reduced dimensions and thus reduced overall material costs.

It is a further object of the present invention to provide a steel end for beer and beverage cans .

It is also an object of the present invention to provide a can end having a reduced overall thickness from the industry standard aluminum can end.

It is an additional object of the present invention to provide a can end having a reduced panel depth from the industry standard aluminum can end.

It is another object of the present invention to provide a steel can end allowing for gauge reduction, increased material savings and cost savings and resistance in thinning of the panel wall and counter sink radius while still maintaining the required buckle resistance.

It is yet another object of the present invention to teach a method of forming a steel can end of the type utilized for twelve ounce beverage cans and characterized by having greater strength characteristics without exceeding required standards for "pop and tear" force.

It is still another object of the present invention to disclose an apparatus to form the steel can end of the present invention.

It is a further object of the present invention to provide a steel can end which will not create a problem with- respect to bi-metal recycling.

Numerous other advantages and features of the present invention will become readily apparent from the detailed description of the preferred embodiment of the invention, from the claims, and from the accompanying drawings in which like numerals are employed to designate like parts throughout the same .

Brief Description of the Drawings A fuller understanding of the foregoing may be had by reference to the accompanying drawings wherein:

Figure 1 is a perspective view of a prior art can end; Figure 2 is a partial cross sectional view of the can end as seen from lines 2-2 of Figure 1 ;

Figure 3 is an enlarged partial cross sectional view of a prior art industry standard can end;

Figure 4 is a cross sectional view of the present invention having a reduction in dimensions from the industry standards;

Figure 5 is a cross sectional view of the apparatus used in the method of forming the can end of the present invention;

Figure 6 illustrates a partial cross sectional view of the apparatus used in the method of forming the can end of the present invention at the initial step thereof;

Figure 7 is an enlarged view of the circular window labeled F7 in Figure 6 ;

Figure 8 illustrates a partial cross sectional view of the apparatus used in the method of forming the can end of the present invention at a step subsequent to the step in Figure 6;

Figure 9 is an enlarged view of the circular window labeled

F9 in Figure 8 ; Figure 10 illustrates a partial cross sectional view of the apparatus used in the method of forming the can end of the present invention at a step subsequent to the step in Figure 8;

Figure 11 is an enlarged view of the circular window labeled Fll in Figure 10;

Figure 12 illustrates a partial cross sectional view of the apparatus used in the method of forming the can -end of the present invention at a step subsequent to the step in Figure 10; and Figure 13 is an enlarged view of the circular window labeled F13 in Figure 12.

Mode(s) of Carrying Out the Invention While the present invention is susceptible to embodiment in many different forms, there are shown in the drawings and will be described herein in detail, a preferred embodiment of the invention. It should be understood however that the present disclosure is to be considered an exemplification of the principals of the invention and is not intended to limit the spirit and scope of the invention and/or claims of the embodiment illustrated.

Figure 4 illustrates the novel and unobvious and improved can end of the present invention 10 made from the method and apparatus disclosed herein and described in detail below. The can end includes a panel 12, a panel radius 14, a panel wall 16, a counter sink radius 18, a chuck wall 20, a seaming panel radius 22, a seaming panel 24, and a curl 26. The improved can end 10 of the present invention illustrated in Figure 4 is preferably formed from steel, which prior to the teachings of present invention has not been practical or possible from a manufacturing standpoint. As such, it has been found that the thickness of the can end can be reduced from the industry standard of 0.0083 inches (0.2108 mm) for the aluminum can end to a thickness (t) of 0.0071 inches (0.1803 mm) for the steel can end, resulting in a gauge reduction of 0.0012 inches (0.0305 mm) in the can end. The steel can end having the thickness of 0.0071 inches (0.1803 mm) adequately allows for the formation of the rivet without having the rivet crack when the tab is assembled to the panel 12. Additionally, it has been found that the steel can end allows for a reduction in the unit depth of the steel can end 0.01 inches^" (0.254 mm) from the industry standard 0.270 inches (6.858 mm) for the aluminum can end, to the- unit depth of the present invention 0.260 inches (6.604 mm) for the steel can end. Such a reduction preferably is achieved by reducing the panel depth from the industry standard 0.090 inches (2.286 mm) to the panel depth of the present invention 0.080 inches

(2.032 mm) . Such a significant reduction in the panel depth and unit depth, as well as in the thickness, still allows for the can end to adequately maintain the required buckle pressure of at least 95 psi (34.48 KPa) (i.e., if the end can will not buckle at a pressure of up to 95 psi (34.48 KPa), the end is acceptable) . Various can ends made from the novel and unobvious method and apparatus of the present invention were subjected to a buckle test to determine the optimum type of steel and thickness to achieve the desired result. The following chart sets forth the can end material tested (type or grade of steel), its thickness, and the highest pressure (measured in psi (parenthetical in KPa) ) applied to each sample can end tested (five of each) . With respect to the type or grade of material, e.g. T-65, the letter "T" stands for tempered and the number is an industry designation of the hardness of the steel. The higher the number, the harder the steel, resulting in greater strength, but at the same time becoming harder to form. T-65 and T-61 steel are the most common and are readily available. Other types or grades of steel are available but at higher costs. Also, T-65 and T-61 are European standards roughly corresponding to the American standard grades of T-5 and T-4 respectively. Material Thickness End #l End #2 End #3 End #4 End #5

T-65 0.2184mm 105 110 110 105 118

(0.0086 in) (724) (758) (758) (724) _. (814)

T-65 0.2108mm 112 106 116 110 110

(0.0083 in) (772) (731) (800) (758) (758)

T-61 0.2184mm 116 118 116 118 112

(0.0086 in) (800) (814) (800) (817) (772)

T-4 0.2007mm 106 110-B 112-B 112-B 112-B

(0.0079 in) (731) (758) (772) (772) (772)

T-61 0.2007mm 104-B 102-B 104-B 103-B 104-B

(0.0079 in) (717) (703) (717) (710) (717)

T-61 0.1905mm 104-B 104-B 103-B 104-B 104-B

(0.0075 in) (717) (717) (710) (717) (717)

T-61 0.1803mm 98-B 98-B 98-B 98-B 98-B

(0.0071 in) (677) (676) (676) (676) (676)

The letter "B" following the psi value denotes that the sample end buckled at that pressure. Where the letter "B" is not present following the psi value, that psi value was the highest pressure achieve by the testing system during the test run and the can end did not buckle. As can be seen, all of the tested can ends were able to withstand the 95 psi (34.48 KPa) buckle pressure limit. However the sample can ends formed of T-61 steel having a thickness of 0.0071 inches (0.1803mm) allowed for the lowest acceptable buckle pressure and are thus preferred. Further such can ends allow for acceptable rivet/tab formation as well as proper scoring meeting acceptable "pop and tear" force standards . As a result of the principles of the present invention, the overall material needed to form a can end has been reduced from 2.856 cubic inches (46.801 cubic centimeters) of aluminum to 2.776 cubic inches (45.490 cubic centimeters) of steel. As a result it has been found that the average manufacturing price of a standard industry aluminum can end of approximately $21,000,000 per one billion can ends has been reduced to an average manufacturing cost for each can end of the present invention of $18,000,000 per one billion can ends. Thus, the overall savings in the production of one billion can ends results in substantial savings totaling $3,000,000. Today, the industry produces approximately 233 billion can ends annually, worldwide .

Referring now to Figures 5-13, the inventive method and apparatus for forming the improved can end of the present invention is disclosed. Generally, the can end of the present invention is formed by the single action press apparatus 50 illustrated in Figure 5, comprising a punch assembly 60 and a die assembly 75.

Punch assembly 60 is comprised of a punch cut edge member 62 having a contact surface 62a, an upper clamp ring 64 having a contact surface 64a, and an inner form punch 66 having a contact surface 66a. Punch cut edge member 62 and inner form punch 66 are suitably mounted to a punch holder 68 which can be selectively moved toward and away from die 75 by any suitable drive means 70 such as a motorized system of pulleys and belts selectively moving punch holder 68 via telescoping guide bars slidable along a series of roller pins. Upper clamp ring 64 is positioned in a cavity 69 between punch cut edge member 62 and inner form punch 66 and is free to move vertically within cavity 69 by a suitable force means such as by a spring or pressurized air supplied to cavity 69 via air conduit 72, as will be described in more detail below.

Die assembly 75 is comprised of a die cut edge member 80 having a contact surface 80a, a lower draw ring 82 having a contact surface 82a, a lower form die 84 having a contact surface 84a, and a panel form die 86 having a contact surface 86a. Lower form die is suitably mounted to a die holder 88. Die cut edge member 80 is positioned upon a shoulder portion of lower form die 84. Lower draw ring 82 is positioned in a cavity 90 between die cut edge member 80 and lower form die 84 and is free to move vertically within cavity 90 via a suitable force means such as air pressure supplied through air conduit 91, as will be described in more detail below. Panel form die 86 is positioned in a cavity 92 inside lower form die 84 and is free to move vertically within cavity 92 via a suitable force means such as air pressure supplied through air conduit 93, as will be described in more detail below. Figures 6 and 7 illustrate the initial step in forming the can end of the present invention wherein the can end blank 95 is cut from a sheet of steel 97. Sheet of steel 97 is positioned over die assembly 75 upon contact surface 80a of die cut edge member 80, whereupon punch assembly 60 is lowered until contact surface 62a of punch cut edge member 62 contacts blank 95. As the punch assembly continues its downward movement, blank 95 is cut from sheet 97 at Zone 1 (Figure 7) . The punch assembly 60 continues downward to clamp blank 95 between contact surface 62a of punch cut edge member 62 and contact surface 82a of lower draw ring 82 at Zone 2 (Figure 7) .

Figures 8 and 9 illustrate the subsequent step in the formation of the can end of the present invention wherein the chuckwall 20 and seaming panel 24 are formed. Punch assembly 60 continues moving downward. As a result, punch cut edge member 62 forces lower draw ring 82 downward in cavity 90, and inner form punch 66 forces panel form die 86 downward in cavity 92. As inner form punch 66 is lowered, the panel 12 of blank 95 gets pressed downward between contact surface 66a and 86a, pulling seaming panel 24 out from between contact surfaces 62a and 82a, and into its illustrated position between contact surfaces 64a and 84a. Also, lower form die 84 prevents upper clamp ring 64 from moving downward, thus causing upper clamp ring 64 to have an upward movement in cavity 69 relative to punch cut edge member 62 and inner form punch 66 (as indicated by arrows) . This above described movement results in the blank taking the form shown in Figure 9, having a chuckwall 20 and a seaming panel 24.

Figures 10 and 11 illustrate the subsequent step in the formation of the can end of the present invention wherein the panel wall 16 and countersink radius 18 are formed. Punch assembly 60 begins to recede or move back, upwards and away from die assembly 75. Upper clamp ring 64 remains m place to clamp seaming panel 24 with lower form die 84 at Zone 3 (Figure 11) . Panel form die 86 is moved upward in cavity 92 by a suitable force means such as by a spring or pressurized air supplied in cavity 92. As panel form die 86 rises, the blank 95 is reverse formed to create the panel wall 16 at Zone 4 (Figure 11) , as well as the countersink radius 18. Blank 95 remains clamped between inner form punch 66 and panel form die 86 at Zone 5 (Figure 11), resulting in the formation of panel 12. The desired panel depth Z is reached when panel form die 86 is stopped by lower form die 84 at Zone 6 (Figure 10) . The can end of the present invention is now formed.

Figures 12 and 13 illustrates the final step wherein the can end is ejected from the tooling area. Punch assembly 60 continues to move back upwards and away from die assembly 75 until the entire can end is completely clear from the die assembly. The seaming panel 24 of the can end remains held against the contact surface 64a of upper clamp ring 64 by light air pressure applied from a source below the can end, until an air blast from an air supply at the side of the can end separates the seaming panel from the upper clamp ring and ejects the can end from the tooling area.

After being formed, the formed steel can end will continue to other stages in the manufacturing process to achieve a finished product, such as the forming of the curl 26, an electro-coating process, and the compound lining (gasketing) of the curl on the can end to prevent leakage in the seam between the can end and can. Once finished, the can end is ready to be seamed to the sidewall of a can, such as a beer or beverage can. It should be understood that the can end of the present invention could be utilized on any can of any material. It is to be understood that the embodiments herein described are merely illustrative of the principals of the present invention. Various modifications may be made by those skilled in the art without departing from the spirit or scope of the claims which follow. For example, it is foreseen that the can end of the present invention could be reduced in diameter as well, resulting in further downsizing and downgauging of the can end and greater material costs savings. Further, other grades of steel could be used according to the principles of the present invention which may result in the ability to further downsize and downgauge the can end while maintaining the required pressure and structural considerations.

Industrial Applicability The can end 10 of the present invention and the method of formation thereof may be employed by industry to replace the current industry standard aluminum can end. The present invention facilitates a can end 10 which requires less material to manufacture than an aluminum can end and which is capable of withstanding the pressures and rigors applied to a can end 10. The can end 10 of the present invention presents particular advantages for cans constructed from steel in that the efforts required for recycling of the can end 10 and an associated can are greatly reduced by constructing each component of steel. The need to separate the can from the can end 10 prior to recycling is eliminated by the present invention 10.

Claims

What Is Claimed Is:

1. A can end for a beverage can comprising: a panel; a panel wall connected to said panel via a panel radius; a chuckwall connected to said panel wall via a countersink radius ; a seaming panel connected to said chuckwall vi-a a seaming radius; wherein said can end is formed from steel .

2. A can end for a beverage can, said can end having a gauge, comprising: a panel; a panel wall connected to said panel via a panel radius; a chuckwall connected to said panel wall via a countersink radius; a seaming panel connected to said chuckwall via a seaming radius ; wherein said gauge is less than 0.2108 mm.

3. The can end of Claim 2, wherein said gauge is 0.1803 mm.

4. The can end of Claim 2, wherein said can end is formed from steel .

5. A can end for a beverage can, said can end defining a panel depth and a panel height equating to a unit depth, said can end comprising: a panel; a panel wall connected to said panel via a panel radius; a chuckwall connected to said panel wall via a countersink radius; a seaming panel connected to said chuckwall via a seaming radius ; wherein said panel depth is less than 2.286 mm.

6. The can end of Claim 5, wherein said panel depth is 2.032 mm.

7. The can end of Claim 5, wherein said unit depth is less than 6.858 mm.

8. The can end of Claim 7, wherein said unit depth is 6.604 mm.

9. The can end of Claim 5, wherein said can end is formed from steel .

10. An improved can end of the type for a beverage can and having a panel, ^"a panel wall connected to said panel via a panel radius, a chuckwall connected to said panel wall via a countersink radius, and a seaming panel connected to said chuckwall via a seaming radius, said can end having a unit depth defined by a panel height and a panel depth, and said can end being formed from a blank defining a gauge, said improved can end being formed from steel and characterized as being reduced in size from an industry standard aluminum can end having a gauge of 0.2108 mm and a unit depth of 6.858 mm.

11. The improved can end of Claim 10, wherein said improved can end is reduced in size by having a gauge of less than 0.2108 mm.

12. The improved can end of Claim 11, wherein said improved can end is reduced in size by having a gauge of 0.1803 mm.

13. The improved can end of Claim 10, wherein said improved can end is reduced in size by having a unit depth of less than 6.858 mm.

14. The improved can end of Claim 10, wherein said improved can end is reduced in size by having a unit depth of

6.604 mm.

15. A method of forming a can end of the type for a beverage can, comprising the steps of: providing a sheet of steel having a gauge less than 0.2108 mm; cutting a steel blank from said sheet of steel; forming said steel blank into a can end defining a unit depth of less than 6.858 mm and having a panel, a panel wall connected to said panel via a panel radius, a chuckwall connected to said panel wall via a countersink radius, and a seaming panel connected to said chuckwall via a seaming radius.

16. The product formed by the process of Claim 15.

17. An apparatus for forming a can end comprising: a single action punch assembly including a punch cut edge member, an upper clamp ring, and an inner form punch; and a die assembly including a die cut edge member, a lower draw ring, a lower form die, and a panel form die.