Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Patent
1983-09-26
1989-12-12
Spruill, Robert L.
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
72102, 72111, B21D 5126
Patent
active
048859249
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of forming containers, and more particularly but not exclusively to a method of reshaping a container which has been drawn from sheet metal.
U.S. Pat. No. 3,730,383 describes and claims a light weight metal container body comprising a side wall and a bottom end wall which is substantially thicker than the side wall, said bottom wall having an upwardly domed central portion therein with a substantially vertical wall section extending downward from the periphery of the domed portion to an outwardly and upwardly flaring frustoconical shoulder leading into the side wall of the container body. The bottom end wall includes small bend radii connecting the vertical wall section to the central domed portion and to the flaring shoulder. A further bend radius connects the flaring shoulder to the side wall. The thinner side wall extends a substantial distance within the flaring shoulder. Such prior art cans are made from aluminium alloy and are wall ironed to create the relatively thin side wall and a thick bottom having a hollow central portion. The interior of the cans is coated with a protective coating and the bottom end wall is pressed to final shape between a punch engaging the external surface of the hollow portion of the bottom end and a hollow die entered in the can to support an annulus of bottom end material around the hollow portion so that co-operation of the punch and die pulled the end material to conform to the punch and die profiles and create a bottom end wall having a domed portion supported by the vertical wall section.
However it is in the nature of materials such as tinplate and certain aluminium alloys to springback after cold work so that even if the punch and die are close fitting on the metal the so-called "vertical" wall of the bottom end wall will not be vertical when it is removed from the tools and the structural benefit of the wall being vertical or nearly vertical is not practically and reliably achieved.
Furthermore, it is current practice to draw a bottom wall with an open profile to permit the spraying of lacquer onto the internal surfaces of the container. If the punch and die used to reform the bottom wall are a tight fit on the metal to obtain as upright a wall as possible, there is a risk that the internal lacquer may be damaged by abrasion.
The resistance of the bottom wall to flexure is also dependent upon the radius of the outwardly convex bead on which the container stands. The production of the vertical annular wall in conjunction with a small radius stand bead is limited by the nature of the forming operation by which a bead of this type is produced between a punch and die.
To produce a bead of small radius, the convex radius of the nose of the punch is limited to that which will not penetrate the container material during forming. A profile requiring a small radius in conjunction with a steep annular wall will give rise to a tool section of insufficient strength to support the stresses imparted to the punch during the forming operation.
An object of the present invention is to provide a method of reshaping a container in which the problems described above are reduced.
According to the invention there is provided a method of reshaping a container having a side wall and a bottom wall, the side wall extending substantially axially to a free edge defining a mouth of the container, the bottom wall comprising a central panel around which a hollow support surface for the container extends, the hollow support surface being incorporated in a transitional portion connecting the periphery of the central panel to the side wall, characterised in that the method comprises the steps of applying first support means to the mouth of the container and second support means to the bottom wall of the container, and applying a roll to the transitional portion of the bottom wall, the second support means and the roll being arranged such that at least a part of the transitional portion is therebetween, and causing relative displacement of the roll and the second
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Ball Martin F.
Claydon Paul C.
Metal Box p.l.c.
Spruill Robert L.
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