Sheet metal container making – Apparatus to form container closure
Reexamination Certificate
1995-05-31
2001-09-18
Vo, Peter (Department: 3721)
Sheet metal container making
Apparatus to form container closure
C072S348000
Reexamination Certificate
active
06290447
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the forming of can ends for seam joining to can bodies. In the art of can making, can ends have been made over 100 years in substantially the same way, by cutting a blank and forming a can end and curling inward the peripheral portion for subsequent assembly to a can body in a seaming machine. The punching and forming of the can end are accomplished in one operation, and then a second operation is required to curl the peripheral portion of the can end inward.
The curling is not an expensive procedure, and many machines are available which perform the curling step. However, the curling step is one additional step which adds expenses and potential problems to can end making. Moreover, the curling for over 100 years has compressed the peripheral material of the can end inward, thus increasing thickness and raising the potential of wrinkling or otherwise deforming the inward curl, which may cause imperfections in the seam and result in a less than perfect seal.
In large can ends, such as used for example in pretzel tins or cookie tins, the curling machines are large and expensive, adding an additional problem which has existed in the prior art.
In the present invention can ends refers to all ends including closure ends. In the beverage industry, for example, there are 2-piece and 3-piece cans. A can body has either one or two can ends. One end usually has a pull tab.
A special problem exists which requires curling of the can ends.
Can ends and cans are formed in high speed equipment. It is necessary to stack can ends together and to be able to separate them quickly and without error when rapidly feeding them to automated down-stream equipment. If there are no curls, the ends would tend to stick together. The peripheral curls aid the separation of the can ends in rapid unstacking operations.
In making can ends, it is conventional to punch and form the can ends in one step, and then to chute the can ends to conventional curling machines to curl the ends and then to stack the ends for transfer to automated down-stream equipment.
The seaming panels have the same diameter increments on small diameter can ends as on large diameter can ends. In large can ends, the seaming area may be a small percentage of the total area of the ends. In small can ends, the seaming panel may be a large percentage of the total end area and material.
In the United States, about 100 billion beverage and beer cans are made out of aluminum annually. One company alone makes about 20 billion cans a year in the U.S., and about an additional billion worldwide.
It can be appreciated that a saving of a single step in the production of can ends for the beverage industry, even while saving only a small amount of money per can end, would be multiplied by a number of ten to the eleventh power through the entire beverage industry, and would amount to substantial savings.
If a savings of metal, for example 1%, could be realized in the manufacture of can ends for the beverage industry, that would be equivalent to the metal used in one billion can ends and would result in a substantial saving.
The saving of metal in can ends is the reason that can bodies are necked-in, which is a common practice, at the present time of this invention.
Long standing needs continue for reducing steps, tooling and machines required for the manufacture of can ends. Long standing needs exist for the reduction of metal used in the manufacture of can ends.
SUMMARY OF THE INVENTION
The present invention solves problems of long standing in the prior art by forming curls on can ends in the same station in which the end blank is punched from a sheet and the end is formed. The can end is blanked, formed and curled in a single station. Thereafter the finished can end is chuted to an accumulator, collector or stacker, which stacks the can ends for transfer to automated down-stream equipment, including but not limited to compound lining and easy opening can end conversion equipment, with the last step being in-seaming equipment use.
The present invention saves additional steps and the application of additional machines to curl the peripheral parts of the can ends.
Uniquely, the present invention curls can ends by moving metal outwardly. The moving of the metal outwardly stretches and thins the metal, reducing thickness of the metal in peripheral flanges and curls, and thus reducing the amount of metal used in can ends.
The present invention tensions and stretches rather than compresses the outer portion of the end during formation, resulting in a savings of metal. The savings of metal is especially significant in small diameter ends. The seaming panels have the same diameter increments on small cans as on large cans. Thus the seaming panels are larger percentages of end areas in small can ends than in large can ends.
The present invention cuts, forms, stretches, tensions and curls the edge and ejects the end at high speed. Before the end comes out of the tool, the upward movement of the outer edge puts tension on the metal and moves the metal outward, stretching and thinning the metal. Because the outward moved metal is stretched, there can be savings in the “blank diameter” or cut edge diameter of a can end. That reduction of the diameter, even by a small amount, can result in a large amount of savings considering the larger number of ends that are made. The present invention makes a better quality end. The conventional curl-forming machine compresses and rolls the metal inwardly, resulting in weakening of the ends and by forming miniature ripples in the curls. That creates the potential for imperfect seams. When tensioned as in the present invention no wrinkles or ripples are formed, because the material expands and flows outward rather than compresses inward as in the prior art.
The invention has four unexpected advantages. The thinning of metal and outward movement to form the curl provide reduction in metal cost. The outward stretching avoids forming compression ripples and results in improvement of the quality of the resulting seam. Doing away with the requirement for conventional curling machines and the conventional added steps of transfer in inserting, curling and removing save production costs and time.
A can end is punched from a sheet of material, formed and curled in a single station with a single movement of the punch. An intermediate axial peripheral wall is formed by the blanking punch and a cooperating die core ring. A pressure sleeve surrounding the die core ring has a chamfered inner edge which engages a peripheral edge of the blank at the lower end of the axial peripheral wall. While the formed end is held between the punch and the die, the pressure sleeve moves upward, forcing the peripheral wall outward into a recess, either in the blank punch or the die pressure sleeve, moving the metal outward into the curl, which is thus expansion formed rather than compression formed. The formed and curled end is removed from the assemblies by a knockout ring.
A preferred can end has a central end panel surrounded sequentially by a reinforcing bead, an annular reinforcing rim, a countersink base, a countersink wall, a flange, a curl having an inward extending portion and a peripheral edge. The curl is formed by moving material outwardly between an outer edge of the cover flange and the peripheral edge.
One preferred can end has a flat central end panel surrounded by a raised bead. A sloping wall extends outward from the bead. A first radius is formed at the end of the sloping wall. A planar wall extends outwardly from the first radius. A second radius is formed at the outer end of the planar wall, and a countersink wall slopes outward from the second radius. A third radius is formed at the outer end of the countersink wall. A flange extends outward from the third radius. A cover hook extends inwardly from the flange and has a peripheral edge at an inner edge of the cover hook. The cover hook and the peripheral edge are formed in a single station by cutting the peripheral edge, moving the perip
Nelson Donald
Siemonsen Frederik A.
Huynh Louis K.
James Creighton Wray
M.S. Willett, Inc.
Narasimhan Meera P.
Vo Peter
LandOfFree
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