Metal deforming – By use of tool acting during relative rotation between tool... – With cutting of work or product
Reexamination Certificate
1998-07-09
2001-05-22
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
With cutting of work or product
C072S115000, C072S330000
Reexamination Certificate
active
06233990
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a formed piece of aluminium or some other relatively soft metal. Especially, the present invention relates to the manufacture of such a piece of metal, which as such is suitable to be used as the bottom of a cooking utensil, such as a frying pan or a kettle, or which forms a blank which can be machined further by turning e.g. to a cooking utensil, lamp globe, a traffic sign, lid for a soft-drink can, etc.
1. Description of Related Art
Until now, frying pans and similar utensils for the preparing of food have been manufactured of a metal blank by pressure turning. In this method, the blank in form of a plate is fastened to a rotating mandrel so that the inner bottom of the pan being manufactured is placed against the support surface of the mandrel, whereafter the sides of the pan are formed by using a turning tool to bend the sides of the blank against the sides of the mandrel acting as a mould.
It is also known to manufacture kettle bottoms in the shape of a plate e.g. of aluminium; these are connected to a kettle made of another material, e.g. stainless steel, by pressing.
A drawback of the prior art manufacture of cooking utensils has been the expensiveness of the metal blank forming the utensil or its bottom. In addition, the patterning and finishing of the bottom have been done either by chipping with a lathe or by pressing in a manufacturing process including many stages, which is both expensive and time-consuming. Also waste of material has raised the costs of the process.
2. Summary of the Invention
It is thus an object of the present invention to provide a new solution for machining a piece of aluminium or some other metal which can be formed in a similar way so that the manufacturing process, e.g. when manufacturing cooking utensils, is made less expensive and simpler than the known prior art solutions. It is characteristic of the method of the present invention that a slice is cut from a raw-cast rod of said metal; it forms a blank which is roll formed by placing it on a moulding tool rotating about its axis to rotate with the tool and by forming it from its opposite side with a rolling tool rotating about its axis, the said tool being in linear rolling contact with the blank and inclined to the axis of the mould tool, thus forming the blank between the opposite rotating tools to a substantially disc-shaped piece of plate.
Roll forming is a method of cold forming, which is based on the plastic deformation of metal, and in which a roll forming tool forms and distributes metal in a way comparable with the rolling of dough. Thus, it is typical for roll forming that, on the area to be formed, the blank expands at the same time as its material thickness grows smaller. Thus, the blank can be formed to a shape corresponding to the mould surfaces of the tool in one single stage so that no waste is generated in the process.
In accordance with the present invention, the use of raw-cast metal as raw material in the roll forming process, e.g. when manufacturing cooking utensils, means a substantial saving in costs, compared with the known method of pressure turning, in which the blank to be turned to a utensil or its bottom is thin rolled metal. For example, in case of aluminium, the crude metal provided by a foundry is approximately 30% cheaper than a rolled product. The blanks to be roll formed are cut as slices e.g. from a rod cast in the shape of a cylinder so that they are easily roll formable to circular disc-shaped pieces of plate, which can form the bottom of a cooking utensil or e.g. the shield of a traffic sign finished into its final shape.
The present invention makes it possible for the piece of plate to be patterned either from its one side or both sides in connection with roll forming with the help of elevations and/or recesses occurring on the rolling surface. Thus, the patterns are produced directly during the roll forming process, and no separate turning or pressing stages are required. Roll forming places no restrictions for the patterns of the surface facing the mould tool, because the blank remains on the mould tool during forming, following completely the shapes of the surface. On the opposite side of the piece, facing the roll forming tool, it is possible to freely form annular elevations and recesses with the help of the similar shapes on the tool surface. In case of other patterning, one must be certain that the movement of the rolling surface of the roll forming tool and that of the surface of the rotating blank are synchronized e.g. within a suitable sector division of the surfaces so that corresponding surface patterns match each other all the while during the forming process. This is dependent e.g. on the cone angle of a suitably tapered roll forming tool and on the angle of deflection between the axes of the roll forming tool and the mould tool having a substantially planar mould surface, the possibilities and solutions concerning which are obvious to those skilled in the art.
For example, the following patterns can be formed by roll forming: grease pockets for the inner bottom of frying pans, markings of the manufacturer, product, etc. in the bottom of a cooking utensil, or radial reinforcing ribs used e.g. in a traffic sign or on the lid of a soft-drink can.
The blank which is cut from a raw-cast rod and which may be e.g. cylinder-shaped, does not necessarily have to be a circular, uniformly thick slice, because, irrespective of the original shape of the blank, in the forming process, the blank forms itself to the desired disc-shape like a rollable dough. However, it is of advantage, if the blank's shape resembles as much as possible the circular, disc-like shape, to which the blank is formed during the roll forming process of a piece of plate. If the blanks are formed by slicing a raw-cast metal rod so that a rod with circular cross-section is cut in a perpendicular direction, the blanks to be cut tend to deform and flatten out in the cutting direction so that they become elliptical in shape. This is a manufacturing-technical disadvantage, because, in the next roll forming stage, the piece must be returned to its circular shape which the blank would originally have had without the said deformation.
However, the problem described above can be solved in accordance with preferred embodiments of the present invention so that disc-shaped slices are cut from a metal rod of circular or elliptical cross-section by directing the cutting tool to the rod in such a way that the cut profile of the rod is elliptical in shape, but that the slice of metal detached from the rod becomes substantially circular, due to flattening occurring in the cutting direction. Then it has been achieved by simple methods that, irrespective of the deformation occurring in the metal material, the cut blank is circular and thus ideal for the next roll forming stage. In roll forming, the blank deformations occur mainly radially and evenly in various directions, and the blank is able to find the shape of the final utensil fast and with as little material transitions as possible. This accelerates the forming process, improves its profitableness and maximizes its capacity in serial production.
The simplest way to produce a substantially circular, disc-shaped blank is to cut a slice from a metal rod with circular cross-section by directing a cutting tool to the rod obliquely to its axial direction. In the invention, it is thus possible to use standard-form crude metal rods cast to the shape of a cylinder without it being in any way necessary to modify the shape of the rod. Alternatively, the metal rod may be of elliptical cross-section, and a piece or a blank is cut by directing the cutting tool to the rod perpendicularly to its axis from the direction of the great axis of the ellipse. Also combinations of these two methods are applicable within the scope of the present invention.
The angle, at which the cutting tool is directed to a metal rod of circular cross-section, may be for example about 60-80
Kässi Leena
Kassi Timo
Piispanen Ari Juhani
Altera Law Group LLC
Kässi Leena
Larson Lowell A.
Rondex Oy Ltd.
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