Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Reexamination Certificate
2001-04-30
2002-12-31
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
C072S356000
Reexamination Certificate
active
06499329
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for manufacturing a bottle-shaped can, of which a can trunk, a shoulder portion and a neck portion having a threaded portion are integrally formed, of a metallic sheet having a thickness of 0.1 to 0.4 mm, and a tool for use in the method.
More particularly, the invention relates to a forming method for forming especially the shoulder portion into a smooth and beautiful slope not in a step shape or a shape having a step mark left, when the bottle-shaped can is to be manufactured by working the bottom side of the can formed into a bottomed cylindrical shape, to form the shoulder portion having an inclined annular face and a diametrically small cylindrical neck portion integrally, and a tool for use in the method.
BACKGROUND ART
As beverage cans for various soft drinks or beer, there are generally employed the DI cans (Drawn and Ironed cans), of which the can trunk (or side wall portion) and the can bottom are integrally formed by drawing and ironing a metallic sheet such as an aluminum alloy sheet or a surface-treated steel sheet.
Specifically, this DI can has its body formed by integrally forming the bottom portion having a shape of a high pressure resistance and a trunk portion thinned by the drawing and ironing workings and by necking in the open upper end of the trunk portion to reduce a diameter of the open upper end. The can body is filled with a drink such as a soft drink or beer, and the diametrically reduced open upper end is seamed with an easy open end (i.e., an end sheet having an easy opening) having a smaller diameter than that of the trunk. These cans are shipped as canned drinks.
As disclosed in WO 81/01259, on the other hand, there is also practiced the bottomed cylindrical can which is formed to have a thinner trunk wall than a bottom wall by drawing and re-drawing (or bending and extending at the re-drawing time) the surface-treated steel sheet laminated on its two sides with a thermoplastic resin film. The can thus manufactured is necked in like the DI can so that it may be used as the beverage can.
As the containers for various soft drinks, on the other hand, there have been employed in recent years the bi-oriented molded container made of a polyethylene terephthalate resin (i.e., the PET bottle). Accordingly, there have been manufactured various beverages contained in the PET bottles which can be repeatedly sealed with threaded caps.
These beverage PET bottles have an advantage over the above-described can containers for beverages in that the PET bottles can be repeatedly sealed with the caps. However, the PET bottles are in considerably lower states than those of the can containers in the recycling ratio for collecting and recycling the resources. Therefore, it has been investigated to enhance the conveniences of the can containers by adding re-sealing function to the can containers having the high resource recycling ratio.
In the prior art, there are disclosed in Japanese Patent Laid-Open No. 10-509095 (WO96/15865) several types of bottle-type DI cans having shapes similar to those of the PET bottles, i.e., the DI cans which have threaded neck portions to be screwed and closed with the threaded caps.
These DI cans are classified into: the type in which an end sheet to be seamed on the open upper end of a can trunk is formed integrally with a threaded neck portion; the type in which the threaded neck portion is integrally formed by reducing the diameter of the open upper end side of the can trunk stepwise by the neck-in working; and the type in which the diametrically small neck portion and the shoulder portion having a slope are formed by drawing the bottom portion side (or the end wall portion) of a cup at multiple steps, in which the trunk portion of the cup is then ironed into a thin trunk portion and in which a threaded portion is formed in the neck portion whereas the can end is seamed on the open end of the trunk portion. In the above-specified Laid-Open, there are disclosed not only the structures of the bottle-shaped cans of the individual types but also the forming methods.
According to the disclosure of Japanese Patent Laid-Open No. 58-47520, on the other hand, at the time of drawing the can trunk, the bottom portion is drawn into a convex stepped shape, and this convex stepped shape is re-drawn at a subsequent ironing time, to form a convex stepped portion having a diametrically small cylindrical neck portion and a square shoulder portion in the bottom portion (or the end wall portion) of the DI can. This neck portion is threaded and sealed with the threaded cap. After this DI can was filled with beverage from the end opening of the trunk portion, this end opening is sealed by seaming the can end.
In Japanese Patent Laid-Open No. 64-62233, moreover, there is disclosed that the DI can drawn and ironed is pressed (or drawn) at its bottom to form a diametrically small cylindrical neck portion and a frusto-conical shoulder portion (having a shape of a frustum of a cone) and that a thread is then formed in or a threaded cylindrical portion is mounted on the neck portion.
Of the aforementioned bottle-shaped cans which can be sealed again with the threaded cap, the can of the type in which the threaded neck portion is formed integrally with the end sheet is formed at its body into the DI can or a bottomed can such as the DTRD can (Drawn, Thin and Re-Drawn) formed by being drawn and bent/extended (or stretched) or the can formed by being bent/extended (or stretched) and ironed. The can trunk is filled with a content such as beverage, and then the open upper end of the can trunk is seamed and sealed with the end sheet having the threaded neck portion formed integrally therewith. According to the bottle-shaped can of this type, therefore, the can body has a shape substantially identical to that of the existing general can, and enjoys an advantage that few changes are required in the filling facilities to suppress the cost for the facilities.
In the bottle-shaped can of this type, however, the end sheet seaming portion is located in the upper portion of the can to raise problems that dust is liable to accumulate in the concave portion inside of the seamed portion, and that the seamed portion itself protrudes to deteriorate the appearance.
In the bottle-shaped can of the type in which the neck portion is formed not at the end sheet but integrally at the upper end portion of the can body, on the other hand, the upper end portion is stretched thin by a similar working as the can body is drawn and ironed or bent and extended. Considering the later step of working the neck portion, therefore, the upper end portion of the can body may be worked so relatively thick as to make the extension of the material less than the lower portion. Since the neck portion has a considerably smaller diameter than that of the can body, however, the diametrical reduction ratio for forming the neck portion is so large that the neck portion is difficult to constrict all at once by enlarging one drawing rate. In addition, it is desirable to reduce the cap size so as to lower the cost for the material and accordingly to reduce the diameter of the neck portion more than the external diameter of the can body. In order to satisfy these desires, it is necessary to make the diametrical reduction ratio more for forming the neck portion by drawing the open upper end of the can body, and this necessity requires multiple steps of neck-in workings.
For example, the can to be relatively frequently used as the drink can for beer has a trunk diameter of 66 mm (of 211 diameter), and twenty to thirty necking steps are required if the neck portion of such can is to be necked in to a diameter of 25.4 mm. Thus, in the bottle-shaped can having the neck portion formed by constricting the open upper end of the can body, a number of necking machines are required to raise the cost for the facilities, and the increase in the number of working steps makes it frequent to damage or deform the can thereby to lower the quality of the can.
In the bottle-sh
Enoki Yasushi
Moriya Satoru
Ogawa Yukio
Daiwa Can Company
Larson Lowell A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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