Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1999-01-25
2001-02-20
Bryant, David P. (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C040S027500, C428S579000, C428S609000
Reexamination Certificate
active
06189197
ABSTRACT:
This invention relates to products, such as bimetallic coins and medals, and a method for producing the products.
In general, a bimetallic coin or medal, formed by joining two pieces of metals of different material for preventing falsification and for producing high quality products, includes an annular ring and an insert inserted in the center of the ring.
Though the bimetallic coin is a product produced by joining two different metals, it should be inseparable even though a substantial impact is applied on the coin during the use.
Prior art methods for forming the bimetallic coin or the medal, such as European patent publication No.0415892 have disclosed an art that the ring having spaced grooves centrally formed around the inner circumferential surface thereof and the insert having spaced ridges centrally formed around the outer circumferential surface thereof in conformity with the grooves but in opposite direction, are joined together by plastic metal flow of the ridges into the corresponding grooves following compression of both the ring and the insert inserted in the ring at minting the coin.
And European patent No.0080437 has disclosed an art that the ring having an annular ridge centrally formed around the inner circumferential surface thereof and the insert in a simple disc form are joined together by causing a plastic metal flow of the insert to surround the annular ridge following compression of the insert inserted in the ring at minting the coin.
However, all of the foregoing methods requires costly and difficult forming processes due to the formation of the grooves or the ridges at the inner circumferential surface of the ring, and can not be carried out without an exclusive equipment for forming the inner circumferential surface of the ring.
Moreover, forming the grooves or the ridges at the inner circumferential surface of a small diametered coin or medal is not commercially viable.
Different from the above prior arts, Canadian patent No. 1,317,746 has disclosed an art that the ring nothing formed thereon but thicker than the insert is joined with the insert having spaced grooves centrally formed around the circumferential surface thereof by plastic metal flow of the ring into the spaced grooves of the insert at minting the coin.
However, the metal flow of the art is opposite to the natural metal flow developing at minting the coin.
That is, the natural metal flow developing in the ring at the minting is in an outward direction expanding both the inner and the outer diameters of the ring, and the natural metal flow developing in the insert at the minting is also in an outward direction reducing the width of the grooves because the grooves have been centrally formed around the circumferential surface of the insert.
Therefore, in case a bimetallic coin or medal is to be formed with the art, since the ring has to be put under a restraint at around the outer circumferential surface thereof at the minting to force the plastically deformed surplus metal of the ring(squeezed out metal of the ring by compression at minting) to flow into the grooves of the insert, the art has a problem that a high pressure should be applied for the inward metal flow of the ring and, consequently, the joining force between the ring and the insert is reduced.
SUMMARY OF THE INVENTION
The object of this invention is to provide a bimetallic coin and a method for forming the same, which is easy to form but costs low, and can assure a sufficient joining force between a ring and an insert.
This object and features of this invention can be achieved by providing a method for forming a bimetallic coin including processes for forming a ring by subjecting a first metal to blanking, annealing, and pickling, forming an insert thicker than the ring by subjecting a second metal to blanking and annealing, forming a thickened rim on each side, and an annular ridge around the circumferential surface of the insert, and pickling the insert, and joining the ring and the insert by causing plastic metal flow of the ridge of the insert into the inner circumferential surface of the ring by pressing the insert inserted in the center of the ring; and by providing a bimetallic coin with the method.
REFERENCES:
patent: 3636616 (1972-01-01), Remning
patent: 4472891 (1984-09-01), Ielpo
patent: 5094922 (1992-03-01), Ielpo et al.
patent: 5630288 (1997-05-01), Lasset et al.
patent: 5996262 (1999-12-01), Kim
patent: 1317746 (1993-05-01), None
patent: 0 080 437 (1983-06-01), None
patent: 0415892A1 (1990-08-01), None
patent: 529349 (1993-03-01), None
patent: 6-269308 (1994-08-01), None
Bryant David P.
Cozart Jermie E.
Jacobson Price Holman & Stern PLLC
Poongsan Corporation
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