Metal deforming – By use of tool acting during relative rotation between tool... – With metal deformation of different type
Patent
1982-03-05
1985-04-23
Larson, Lowell A.
Metal deforming
By use of tool acting during relative rotation between tool...
With metal deformation of different type
72 84, 72105, 72348, B21D 1906, B21D 2200
Patent
active
045121729
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to methods of reducing the diameter of a marginal portion of a cylindrical body to produce a shoulder and neck and more particularly but not exclusively to a method of forming a can body having an outward directed flange on the neck.
BACKGROUND ART
Traditional methods of reducing the diameter of cylindrical bodies include "die necking" in which one end of the cylindrical body is forced into a conical die which exerts a compressive force to reduce the diameter and "roll necking" in which a roll is engaged with the exterior of the cylindrical body as it is rotated to generate the shoulder profile by a spinning or beading process.
U.S. Pat. No. 3,995,572 describes a method and apparatus for producing a seamless can body with a reduced diameter opening for receiving an aerosol valve. Starting with a cylindrical workpiece a truncated conical portion supporting a cylindrical portion of reduced diameter is formed by each of a sequence of dies to finally form a shoulder characterized by the curvilinear configuration imposed by each die. The disadvantage of this series of "die necking" operations is that each die only brings about a relatively small reduction in can diameter so that the expense of several press tools is incurred. Furthermore, the shoulder produced has a corrugated or stepped shape which is not always desirable.
Beverage cans are now well known in which the top of the side wall is necked in to receive an aluminium can end of diameter smaller than the outside diameter of the bulk of the can body. The objective in such cans is to use less aluminium can end material, thus the present invention also seeks to provide a method of making neck portions of reduced diameter.
These prior art cans are usually 2.585" (65.6 mm) diameter necked down to 2.462 (62.5 mm) diameter and made by one of several roll forming methods currently available.
In one known roll forming method, as described in British Pat. No. 1,330,346 (U.S. Pat. No. 3,688,538) a peripheral edge margin of the sidewall of the can body is spun on a mandrel as an external roll compresses the margin to generate a shoulder neck and flange. However, a collapsible mandrel is required to carry out this method. In another roll forming method, as described in our British Pat. No. 1,534,716, (U.S. Pat. No. 4,058,998) the can body is supported in axial compression while a marginal portion adjacent the open end of the body is deformed radially inwards by a pair of external rollers so that the combination of axial and radial forces generate a shoulder, neck and flange. This method requires only a simple solid chuck, because the neck is formed into free space.
DISCLOSURE OF THE INVENTION
Accordingly this invention provides a method of forming at least one shoulder, a neck and a flange at an open end of the cylindrical side wall of a can body said method comprising the steps (1) successively forcing a marginal edge portion defining the open end of the side wall into one or more dies of reducing diameter to make a portion of reducing diameter consisting of a corresponding number of shoulder portions supporting a cylindrical portion; and (2) applying rolls in at least one rolling operation to at least part of the portion of reducing diameter and cylindrical portion to further change the diameter of the cylindrical portion and generate at least one shoulder supporting the neck and flange.
According to a preferred embodiment of the method a pair of rolls applies a radial force in combination with an axial force on the can in a method claimed according to any of claims 1 to 9 or claim 22 of British Pat. No. 1,534,716. The method may be applied to can bodies of materials which tolerate severe cold work, the method comprising a simple die neck followed by rolling being suitable when the can body is made of aluminium or alloys thereof. When the can is made of metals which are less tolerant of cold work, extra die necking operations may be included in the method, for example when the body is made of tinplate or stiff aluminiu
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patent: 3688538 (1972-09-01), Hoyne
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patent: 4403493 (1983-09-01), Atkinson
Abbott James B.
Berry Christopher
Kohn Ernest O.
Slade Mark N.
Larson Lowell A.
Metal Box plc
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