Method and apparatus for manufacturing a coin formed from two different materials and coin

Description

[0001] The present invention relates to a method, according to the preamble of Claim 1, for manufacturing a coin, medal, or similar formed from two different materials.

[0002] The invention also relates to an arrangement intended to implement the method and a product manufactured with its aid.

[0003] Coins manufactured from at least two different materials have been in use for a long time. The best-known examples in Europe are the one and two-euro coins. Because metals and metal alloys shape plastically under load, the components made from different alloys can be attached to each other by compression, in such a way that either the ring forming the hole, or the centre to be placed in the hole in the centre of the coin shapes radially under pressure. Because, when compressed, a plastically shapable material tends to flow to fill the space reserved for it, the compression can take place from the upper or lower surfaces of the coin, so that the ring and centre tighten against each other as the mould becomes filled. If it is wished to make a coin or medal from a material that cannot be shaped plastically, it becomes more difficult to attach the centre to the ring, because such a material, for example stone, ceramic, or glass, which cannot be shaped plastically, will not flow in the mould, but instead fractures under load. The danger of fracturing is increased by the fact that the coins, medals, and similar planar pieces are generally quite thin. Thus, particularly when loaded radially the cross-sectional area receiving the load is small, so that even quite low loads can lead to the material's ultimate stress limit being exceeded and the centre being damaged.

[0004] Publication CN 1236584 discloses a method for manufacturing a bimetal coin. In it, a tongue and groove combination is formed in the ring and centre made form different metals, and the pieces are pressed together.

[0005] The present invention is intended to create a method for manufacturing a coin formed from at least two different materials, in which the centre of the coin is manufactured from a material that cannot be shaped plastically, such are stone, ceramic, or glass.

[0006] The invention is based on a ring of a plastically shapable material being stamped and pressed using a mandrel stamp, in such a way that the ring is shaped to a set dimension and an opening equipped with a bevel is formed in the middle of it. The centre, which is of a material that cannot be shaped plastically, is pressed into this bevelled opening, in such a way that the centre is wedged tightly into the opening by the bevel of the opening.

[0007] More specifically, the method according to the invention is characterized by what is stated in the characterizing portion of Claim 1.

[0008] The arrangement according to the invention is, in turn, characterized by what is stated in the characterizing portion of Claim 7.

[0009] The coin according to the invention is characterized by what is stated in the characterizing portion of Claim 10.

[0010] Considerable advantages are gained with the aid of the invention.

[0011] With the aid of the invention, it is possible to manufacture coins, medals, and various commemorative medals and decorations using new materials. The medal, coin, or commemorative medal being made can be of proof quality or with a normal polish and it can have a hole of precisely the desired shape. The hole can be, for example, shaped like the map of Finland. This will make such medals very distinguished and dignified. With the aid of a suitable selection of materials, a symbolism linking a coin or medal to a specific place or event can be attached to it. Thus, for example by making the centre of a coin from the stone symbolizing each province in Finland, i.e. it so-called provincial stone, it is possible for each province to obtain its own typical commemorative coin or medal. Similarly, it is possible to use glass or ceramic, for instance as the raw material for a commemorative medal for localities known for these sectors of industry. With the aid of the invention, even a brittle material can be attached reliably to a coin and the metal ring surrounding the centre will at the same time protect the thin and brittle centre. Even though the coin or medal according to the invention is intended as a commemorative or collector's item, or even as an object for investment, it must, of course, also withstand a reasonable amount of handling.

[0012] With the aid of centres made from various minerals, coins can be made very dignified and stylish. In addition, because the combination of materials is demanding in terms of manufacturing technique, it also, for its part, adds to the value of the object. If desired, various methods can be used to make patterns in stone or ceramic materials, and even further settings of other materials.

[0013] In the following, the invention is examined with the aid of examples and with reference to the accompanying drawings.

[0014] Figure 1 shows one ring blank and centre for a coin according to the invention.

[0015] Figure 2 shows a mandrel stamp for manufacturing a ring blank according to the invention.

[0016] Figure 3 shows the ring blank during compression in the mandrel stamp of Figure 2.

[0017] The term plastic shaping refers to the material's yielding in such a way that permanent deformations arise in it, without the material breaking. The yield limit of plastic materials is lower than their ultimate limit, i.e. the material can be shaped without fracturing. Brittle materials, i.e. materials than cannot be plastically shaped, do not have a yield limit that appears before the ultimate limit, but instead breaking occurs without substantial permanent deformation, once the ultimate limit is exceeded. A piece made from the material will then break. One definition of a material that is brittle or cannot be plastically shaped can thus be that a piece manufactured from the material will break before yielding.

[0018] In the following description and in the Claims the name coin is used for a product according to the invention, for reasons of simplicity. However, the invention relates to all similar reasonably thin objects, in which there are two relatively extensive faces oriented opposite to each other, and an edge that rounds around them. The names of these can be, for example, coins, medals, and commemorative medals or decorations.

[0019] Figure 1 shows schematically a centre 1 made of a brittle material being placed in a ring 2 shaped for it. The outer edge 5 of the centre is straight. The ring 2 is shaped in the manner described above to correspond to the dimensions of the coin and in it is also formed the desired stamped patterns. In the outer edge of the ring 2 there is a raised edging 3. The hole 4 in the ring 2 is shaped at an angle, in such a way that its greatest diameter is slightly greater than the diameter of the centre 1 and its smallest diameter is correspondingly smaller than the diameter of the centre 1. In this embodiment, both the centre 1 and the ring 2 are symmetrical around their axis of rotation.

[0020] In terms of the invention, it is essential that the ring 1 made of a shapable material and forming the outer circumference of the coin is shaped beforehand to set dimensions and it is stamped prior to the attachment of the centre 1. Because the ring 2 cannot be shaped after, or during the attachment of the centre, no great stresses act on the brittle centre and the centre 1 can be attached in place without damage. The ring 1 is formed by stamping from a ring blank from a suitable metal alloy, or possibly from an unalloyed metal, using a mandrel stamp according to Figure 2. In particular, the ring can be made from available coinage alloys. The mandrel stamp comprises the actual mandrel stamp 6, inside which a mandrel 7 is fitted. Between the mandrel 7 and the mandrel stamp 6 is an elastomer piece 8. The edges 9 of the cup part of the mandrel stamp 6 form a stamp for the side of the coin that comes first and in it there is the desired pattern for the stamp. On the sides of the cup part there is a stamp ring 10, in the inner edge of which there is a pattern according to the pattern that is desired in the outer edge of the ring 1 of the coin. The above construction includes an upper stamp 11, which closes mould formed by the edges 9 of the mandrel stamp 6, the stamp ring 10, and the mandrel 7.

[0021] The pressing of the ring of the coin to the set dimensions and the stamping are shown schematically in Figure 3. The ring 2 is preferably manufactured from a normal numismatic ring blank. The stamping of the ring takes place, for example, using a numismatic stamping machine, using the mandrel stamp described above. As such, the blank can be stamped using some other device as a mandrel stamp, but using a numismatic stamping machine will ensure the quality of surface and pattern necessary for valuable and collectors' coins. The ring blank is placed in the mandrel stamp, when its first side comes against the edge 9 of the mandrel stamp. The hole in the centre of the blank is now greater than the diameter of the mandrel 7, so that the point of the mandrel 7 will fit into the hole in the blank. When the upper stamp is pressed against the second, in this case the upper surface, the blank forms into the shape of the mould space of the mandrel stamp, according to Figure 3. The bevel 4 according to the point 12 of the mandrel is formed in the hole in the blank, and the patterns, for example a text and shield, according to the stamps 6, 11 are formed in the upper and lower surfaces. The pattern, for example milling, according to the stamp ring 10 is formed in the outer edge.

[0022] When the upper stamp 11 is pressed against the blank, the mandrel moves down as the elastomer 8 flexes and its height from the upper surface of the ring 9 of the mandrel stamp becomes the same as the distance between the ring 9 of the mandrel stamp and the upper stamp. At the same time, the bevel of the point 12 of the mandrel always settles to the same point when pressed by the upper stamp, so that the hole in the blank is always shaped in the same way and the shape of the hole will be precise. This is of primary importance, because if the shape and size of the hole vary, it will not be possible to attach a centre made of brittle stone or other similar material without breaking it. If, for example, stone, ceramic, or glass with a thickness of about 2 mm is used as the centre, and if its diameter is about 25 mm, the largest diameter of the hole in the ring will be 25.50±0,05 mm and the smallest 25.20±0,05 mm. The precise dimensions of the centre would then be 25.35±0.05 mm. As can be seen on the basis of the tolerance in the example, the shape of the metallic blank must be quite precise. To achieve the precision of the hole, the use of the elastomer 8 is essential, because the point of the mandrel is then always guided in the same way according to the upper stamp and the blank can easily be shaped, because the point of the mandrel 7 does not determine the position of the upper stamp. It is obvious that the mandrel can also be made fixed, but in that case the very high precision requirements may become a problem, which will increase the manufacturing costs of the ring blank. However, more important is the fact that the flexing of the elastomer prevents the ring blank from catching on the point of the mandrel and the stamping ring and permits it to be removed from the mandrel stamp. When the upper stamp 11 is raised after stamping, the elastomer 8 or spring arrangement stretches and pushes the mandrel upwards and detaches the stamped ring blank 2 form the lower stamp 6.

[0023] Once the ring 2 is ready, the centre 1 is attached to it by pressing it into the hole of the ring 2 using a hand press, when it will become attached to the ring by a wedged joint, with the aid of the compressive forces created. A simplified description is that the manufacture of the coin takes place in such a way that a centre 1, with a precisely defined diameter dimension, is made from a brittle materials. A ring blank is made and is pressed to a defined dimension in such a way that the hole is given a precisely dimensioned conical shape. Finally, the centre 1 is pressed into the ring 2, when it is attached in place by the friction forces of the wedged joint and by the compressive effect caused by the flexibility of the ring.

[0024] Within the scope of the invention, it is also possible to envisage solutions differing from the embodiments described above. The manufacture of coins that are symmetrical around their axis of rotation can be more easily implemented with the aid of our invention. However, it can be envisaged that the inner or outer edge of the ring is not a circle, but, for example, a polygon, or even a map image, or a corresponding even more complex pattern. However, it will then be more difficult to stamp and shape the ring. Depending on the purpose of coin, all, or only one or two of the surfaces of the ring blank can be stamped. The centre can be pressed into the ring mechanically too, if the numbers being manufactured are sufficient to justify the investment in equipment.

[0025] Instead of an elastomer, the mandrel using is shaping the ring can be attached to a dual-action cylinder. In that case, the upward movement of the cylinder will place the mandrel against the upper stamp during stamping and the return movement will pull the mandrel out of the hole of the ring. When using a dual-action cylinder, the mandrel is pulled after stamping to the lower dead point, when the stamped ring will also detach reliably from the mandrel. This solution is, however, more expensive to implement than a simple elastomer piece. Alternatively it is possible to envisage the use of, for example, a diaphragm spring or some other spring for controlling the movement of the mandrel.

Claims

1. Method for manufacturing a coin of at least two different materials, in which method:

- a centre (1) is made,

- a ring blank with a hole in the centre is made,

- the ring blank is stamped using a stamp from at least one surface, in order to form a ring (2),

- the centre (1) is attached to the ring (2) by fitting it to the hole in the ring (2),

characterized in that

- the ring blank is stamped using a mandrel stamp and shaped to a set dimension, in such a way that a dimensionally precise and bevelled (4) opening is formed in the hole,

- the centre (1) is manufactured from a material that cannot be plastically shaped, and

- the centre (1) is pressed into the hole in the ring (2), in order to form a wedged joint between the ring (2) and the centre (1).

2. Method according to Claim 1, characterized in that a bevel (4) is formed in the ring, in such a way that the greatest diameter of the hole is greater than the diameter of the centre and the smallest diameter of the hole is smaller than the diameter of the centre.

3. Method according to either Claim 1 or Claim 2, characterized in that the bevelled opening is formed in the ring by a mandrel (7), which is supported at one end by an elastomer piece.

4. Method according to either Claim I or Claim 2, characterized in that the bevelled opening is formed in the ring by a mandrel (7), which is supported at one end by a double-acting cylinder.

5. Method according to any of Claims 1 - 4, characterized in that the centre (1) is manufactured from stone, ceramic, or glass.

6. Method according to any of Claims 1 - 5, characterized in that the ring (2) is manufactured from a metal alloy or a metal.

7. Arrangement for manufacturing a coin formed from at least two different materials, which arrangement comprises:

- a mandrel stamp for shaping a ring (2) with a hole, forming the outer circumference of the coin, from a ring blank, and

- a press for pressing a centre (1), made from a brittle material, into the hole in the ring (2),

characterized in that

- in the point of the mandrel (7) of the mandrel stamp there is a bevel (12) which is arranged to make contact with the ring blank, in such a way that, when stamping the blank, a bevel (4) defined by the shape (12) of the mandrel (7) is formed in the hole in the ring (2).

8. Arrangement according to Claim 7, characterized in that the mandrel (7) of the mandrel stamp is supported on elastomer (8) at the end of the mandrel opposite to the bevelled end.

9. Arrangement according to Claim 7, characterized in that the mandrel (7) of the mandrel stamp is supported on a double-acting cylinder at the end of the mandrel opposite to the bevelled end.

10. Coin formed from at least two different materials, which comprises a metal ring (2) and a centre fitted to a hole in the ring, characterized in that the centre is manufactured from a plastically inelastic material.

11. Coin according to Claim 10, characterized in that the centre (1) is manufactured from stone, ceramic, or glass.