IL105194A - Coin blank - Google Patents

Abstract

The invention relates to a bimetallic blank for coins, medallions, tokens, gaming chips and the like, consisting of an inner disc (1) of a first metal or of a metal alloy which is pressed into the central aperture of an outer ring (2) of a second metal or of a second metal alloy, the disc (1) being provided with obliquely extending indentations (5) on its outer edge (4). <IMAGE>

Description

Coin blank Krupp VDM GmbH C. 89372 COIN BLANK The invention relates to a two-part blank for coins, medals, tokens,, gambling chips and the like, comprising an inner disc of a first metal or a metal alloy, which is pressed into the central opening of an outer ring of a second metal or a second metal alloy.

In the past, coins have mainly been produced from one solid piece of metal of uniform composition. Coins are also produced from different metals and metal alloys. These are mainly laminated materials such as are produced, for example, by the roll-bonding of a steel core with a brass layer on both sides. In the more recent past the production of coins has increasingly also used laminated materials consisting of an inner disc of one metal, which is enclosed by an outer ring of another metal or of another metal alloy. For example, the Italian 500 lira coin consists of an inner disc of a gold-coloured copper alloy. An outer rim of a silver-grey chromium steel having a bluish lustre is pressed concentrically around said inner disc. The production of the components of such a concentric laminated material requires special attention in view of the present-day technology of highspeed coining machines by means of which these composite materials can be produced even in large numbers at a justifiable expense. Special steps are therefore needed to achieve a satisfactory adhesive bond between the inner disc and the outer ring during coining.

US-A- 3 499 739 suggests that the outer ring should be made somewhat thicker than the inner disc. The intention is that during the coining operation the outer rim should be pressed over the edges "of the inner disc, to achieve a positive bonding between the disc and the ring. JP-A- 58-3743 suggests that the inner disc or alternatively the outer ring should be formed with a circularly extending edge groove. For assembly the two components are placed in one another, whereafter material of the inner disc is pressed into the groove' in the outer ring, or vice versa, using a special tool.

EPA-A-0 080 437 discloses a construction in which the inner edge of the outer ring is wedge-shaped, the inner disc being formed with an edge bead. During the coining operation, material can then flow from said bead over the tapered inner edge of the outer ring. At the same time, the inner edge of the outer ring is formed with a number of projecting teeth which are forced into the inner disc during coining. This makes it impossible for the outer ring and inner disc to rotate in relation to one another after coining.

EP-A- 0 160 343 takes up this idea, using a very similarly shaped outer rim. In the case of the coin known from EP-A- 0 280 615, a ball is introduced into the outer ring, the ball then being plastically reshaped to form the inner disc. According to EP-A-0 415 892 the inner edge of the outer ring is formed with an interrupted peripheral groove into which material of the inner disc then flows during the coining operation.

While the teaching of US-A- 3 499 739 has proved to be inadequate for practical application, and the teaching of the aforementioned JP-A requires a special tool for assembly, the teachings of EP-A 0 08.0 437, 0 160 343 and 0 415 892 have the disadvantage that the inner side of the outer ring must be given a complicated geometrical shape.

It has now been surprisingly found that any rotation of the two parts and the dropping of the inner disc out of the outer ring following coining is reliably prevented by a suitable shaping, which can be simply performed, of the outer edge of the inner disc. To this end it is enough to form the outer edge of the inner disc with depressions arranged directed obliquely in relation to one another. The depressions can also take the form of a winding groove. As a result, the material of the outer part is prevented from flowing into the depressions of the inner part.

According to a further feature of the invention, the outer ring and the inner disc of- the concentric composite material forming the coin have very different electric conductivities. This is best achieved by using for the part of good electric conductivity a copper coin material having a specific electric resistance of 25 μΩ-cm at the most. A chromium steel or a chromium magnetic steel having a specific electric resistance of at least 70 μΩ.οπι should be selected for the part having poor electric conductivity. The part having poorer electric conductivity can also be a laminate of layers of ferritic and austenitic steel. As a result, the following is achieved: The present-day electronic coin testing apparatuses make different use of the principle of. electromagnetic interaction between electromagnetic fields of different frequency and the metals of the coin. As the coins are passing through the coil systems of coin testing apparatuses, the coins can deliver characteristic double signals if the outer ring of the laminated material is the part of considerably better conductivity, or alternatively a single of characteristic curved shape is delivered if a part of considerably better conductivity forms the inner disc.

The invention will be explained with reference to the drawings, wherein: Fig. 1 shows the outer ring of the coin in perspective, Fig. 2 is a perspective view of one construction of the inner disc, and Fig. 3 shows an embodiment which is a variant of that shown in Fig. 2.

A coin comprises an outer ring 2 (Fig. 1) formed with a central opening whose outline so corresponds to that of the inner disc 1 (Figs. 2 or 3) that the inner disc 1 is non-positively connected to the outer ring 2 by being pressed into the central opening thereof .

To improve the cohesion of the two parts 1, 2, according to the invention the outer edge 4 of the inner disc 1 (Fig. 2) is formed with a number of oblique depressions 5. In the embodiment illustrated in Fig. 3 the depressions are combined into a winding groove 5a extending around the outer edge 4 of the inner disc 1. When the parts 1, 2 are compressed, material flows into the recesses 5, 5a, thus producing a positive connection of the parts 1, 2 in addition to a non-positive connection.

Due to the oblique position of the depressions 5, 5a according to the invention the flowing in of the material during the compression of the two parts 1, 2 is appreciably facilitated, since the depressions 5, 5a become gradually filled with the material of the other part, in which there are no depressions.

Claims (4)

1. A two-part blank for coins, medals, tokens, gambling chips and the like, comprising an inner disc of a first metal or a metal alloy, which is pressed into the central opening of an outer ring of a second metal or a second metal alloy, characterized in that the outer edge M) of the disc is formed with obliquely extending depressions.

2. A blank according to claim 1, characterized in that the oblique depressions form a winding groove extending around the outer edge («H of the inner disc (*^·

3. A blank according to claims 1 or 2, characterized in that the materials of the inner disc and the outer ring f*) differ in specific electric resistance by at least 45 μΩ.οιη.

4. A blank according to claim 3, characterized in that the. part of poor electric conductivity consists of chromium steel or chromium/nickel steel or is a laminate of an austenitic steel and a ferritic rustproof steel. n C0HN AND p^m