This invention relates to necking dies for beverage container and aerosol container production.
Beverage cans for various soft drinks or beer are generally formed by drawn and iron technology (i.e., the DI can), in 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.
An alternative to conventional DI cans include bi-oriented molded container made of a polyethylene terephthalate resin (i.e., the PET bottle). However, PET bottles are considerably less recyclable than their aluminum DI can counterparts.
Therefore, it has been investigated to utilize drawn and iron technology to provide containers having the geometry of PET bottles composed of a recyclable metal. One disadvantage of forming metal bottles using DI technology is the time and cost associated with the necking process. Necking typically includes a series of necking dies and knockouts that progressively decrease the diameter of the bottle's neck portion to a final dimension. Typically, the necking process for a 53 mm bottle style can requires on the order of 28 necking dies and knockouts to reduce the can diameter from approximately 53 mm to a final opening diameter of approximately 26 min.
The manufacturing cost associated with the production of 28 necking dies and knockouts is disadvantageously high. In each of the prior necking dies the necking surface is typically polished to a very smooth finished surface (i.e. Ra 2-4 μin) adding to the cost of the necking system. Additionally, the time required to neck the can bodies through 28 or more necking dies can be considerable also contributing to the production cost of the aluminum bottles. Finally, additional necking stations may require a substantial capital investment.
In light of the above comments, a need exists for a method of manufacturing aluminum bottles having a reduced number of necking dies, hence having a decreased production cost.
Generally speaking, the present invention provides a necking die design allowing for more aggressive reduction per necking die for necking metal bottles.
Broadly, the necking die includes at least a partially non-polished necking surface and a non-polished relief following the necking surface.
The at least partially non-polished necking surface includes a non-polished land, polished neck radius portion and polished shoulder radius portion. The non-polished land has a geometry and a surface finish that provides for necking without collapse of the structure being necked.
For the purposes of this disclosure, the term “polished” represents that the surface has a smooth machined surface finish, wherein the surface roughness (Ra) ranges from about 2-6 μin. For the purposes of this disclosure, the term “non-polished” denotes that the surface has a rough surface, wherein the surface roughness (Ra) is greater than about 8 μin.
In another aspect of the present invention, a necking system is provided incorporating the above described necking die. Broadly, the necking system includes:
a plurality of necking dies each necking die having an at least partially non-polished necking surface and a non-polished relief following the necking surface.
The reduction in the necking dies having an at least partially non-polished surface in accordance with the present invention is higher than the degree of reduction employed with conventional polished necking dies.
For the purposes of this disclosure, the term “reduction” corresponds to a geometry of the necking surface in the die that reduces the diameter of the can body at its neck end. In the system of dies, the reduction provided by each successive die results in the final dimension of the bottle neck.
In another aspect of the present invention, a necking method is provided using a necking die system, as described above, in which the necking system employs necking dies including a level of reduction that was not possible with prior systems.
Broadly, the necking method includes:
providing a metal blank;
shaping the metal blank into a bottle stock; and
necking the bottle stock, wherein necking comprises at least one necking die having an at least partially non-polished necking surface.
The following detailed description, given by way of example and not intended to limit the invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, wherein like reference numerals denote like elements and parts, in which:
a represents a magnified view of the contact angle.
One aspect of the present invention is a necking die design in which a partially non-polished necking surface 10 reduces surface contact between the necking surface and the bottle stock being necked in a manner that reduces the force that is required to neck the bottle (hereafter referred to as “necking force”). It has unexpectedly been determined that a necking surface having a rougher surface provides less resistance to a bottle stock being necked than a polished surface. As opposed to the prior expectation that a smooth surface would provide less resistance and hence require less necking force, it has been determined that a smooth surface has greater surface contact with the bottle being necked resulting in greater resistance and requiring greater necking force. In the present invention, the increased surface roughness reduces the surface contact between the necking surface and the bottle being necked, hence reducing the required necking force.
Reducing the necking force required to neck the bottle stock allows for necking dies having a more aggressive degree of reduction than previously available in prior necking dies.
In one embodiment, a non-polished surface has a surface roughness average (Ra) ranging from more than or equal to 8 μin to less than or equal to 32 μin so long as the non-polished necking surface does not disadvantageously disrupt the aesthetic features of the bottle stock's surface (coating) finish in a significantly observable manner. In one embodiment, a polished surface has a surface roughness average (Ra) finish ranging from 2 μin to 6 μin.
Referring to
The non-polished land portion 13 in conjunction with the knockout (not shown) provide a working surface for forming an upper portion of the bottle stock into a bottle neck during necking. In one embodiment, the non-polished land 13 extends from tangent point of neck radius portion 12 of the die wall parallel to the center line of the necking die. The non-polished land portion 13 may extend along the necking direction (along the y-axis) by a distance Y1 being less than 0.5″, preferably being on the order of approximately 0.0625″. It is noted that the dimensions for the non-polished land portion 13 are provided for illustrative purposes only and are not deemed to limit the invention, since other dimensions for the land have also been contemplated and are within the scope of the disclosure, so long as the dimensions of the land are suitable to provide a necking action when employed with the knockout.
Another aspect of the present invention is a relief 20 positioned in the necking die wall following the necking surface 10. The dimensions of the relief 20 are provided to reduce frictional contact with the bottle stock and the necking die, once the bottle stock has been necked through the land 13 and knockout. Therefore, in some embodiments, the relief 20 in conjunction with the partially non-polished necking surface 10 contributes to the reduction of frictional contact between the necking die wall and the bottle stock being necked, wherein the reduced frictional contact maintains necking performance while reducing the incidence of collapse and improving stripping of the bottle stock.
In one embodiment, the relief 20 extends into the necking die wall by a dimension X2 of at least 0.005 inches measured from the base 13a of the land 13. The relief 20 may extend along the necking direction (along the y-axis) the entire length of the top portion of the bottle stock that enters the necking die to reduce the frictional engagement between the bottle stock and the necking die wall to reduce the incidence of collapse yet maintain necking performance. In a preferred embodiment, the relief 20 is a non-polished surface.
In another aspect of the present invention, a necking system is provided in which at least one of the necking dies of the systems may provide an aggressive reduction in the bottle stock diameter. Although
In one embodiment, the introductory die has a reduction of greater than 5%, preferably being greater than 9%. The inside diameter of the top portion of the die is one dimension that is measured in determining the degree of reduction provided. The level of reduction that is achievable by the dies of the necking system is partially dependent on the surface finish of the necking surface, necking force, bottle stock material, bottle stock, required neck profile, and sidewall thickness. In one preferred embodiment, an introductory necking die provides a reduction of greater than 9%, wherein the initial necking die is configured for producing an aluminum bottle necked package from an aluminum sheet composed of an Aluminum Association 3104, having an upper sidewall thickness of at least 0.0085 inch and a post bake yield strength ranging from about 34 to 37 ksi.
In one highly preferred embodiment, a necking system is provided in which the plurality of necking dies include an introductory necking die having a reduction greater than 9%, 12 intermediate dies having a reduction ranging from 4.1 to 6.1%, and a final necking die having a reduction of 1.9%.
In another aspect of the present invention, a method of necking bottles, utilizing a necking system as described above, is provided including the steps of providing an aluminum blank, such as a disc or a slug; shaping the blank into an aluminum bottle stock; and necking the aluminum bottle stock, wherein necking comprises at least one necking die having an at least partially non-polished necking surface.
The present invention provides a necking system including a reduced number of dies and knockouts, therefore advantageously reducing the machine cost associated with tooling for necking operations in bottle manufacturing.
By reducing the number of necking die stages, the present invention advantageously reduces the time associated with necking in bottle manufacturing.
It is noted that the above disclosure is suitable for beverage, aerosol or any other container capable of being necked. Additionally, the above disclosure is equally applicable to drawn and iron and impact extrusion necking methods.
Although the invention has been described generally above, the following examples are provided to further illustrate the present invention and demonstrate some advantages that arise therefrom. It is not intended that the invention be limited to the specific examples disclosed.
Table 1 below shows the reduction provided by a 14 stage die necking schedule, in which the necking die geometry was configured to form an aluminum bottle necked package from an aluminum bottle stock having a upper sidewall sheet thickness of approximately 0.0085 inch and a post bake yield strength ranging from about 34 to 37 Ksi. The aluminum composition is Aluminum Association (AA) 3104. As indicated by Table 1, the bottle stock is necked from an initial diameter of approximately 2.0870″ to a final diameter of 1.025″ without failure, such as wall collapse.
As depicted in Table 1 the necking system includes a first necking die that provides a reduction of approximately 9%, 12 intermediate dies having a reduction ranging from approximately 4.1 to 6.1%, and a final necking die having a reduction of 1.9%.
Referring to
Having described the presently preferred embodiments, it is to be understood that the invention may be otherwise embodied within the scope of the appended claims.
The present application is a continuation of U.S. patent application Ser. No. 11/383/515, entitled “MANUFACTURING PROCESS TO PRODUCE A NECKED CONTAINER”, filed May 16, 2006, now U.S. Pat. No. ______, which is incorporated herein by reference in its entirety. The present application is also related to PCT Patent Application No. PCT/US2007/11549 entitled “MANUFACTURING PROCESS TO PRODUCE A NECKED CONTAINER”, filed May 14, 2007, which is also incorporated herein by reference in its entirety.
Number | Date | Country | |
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Parent | 11383515 | May 2006 | US |
Child | 12767190 | US |