DESCRIPTION

This invention relates to a security system and has particular but not exclusive application to tokens for use in coin validators.

It is well known to use both coins and tokens in coin operated amusement machines, the tokens being typically minted from brass or similar materials. Many unsecure tokens of similar dimensions are in circulation and are sometimes undesirably being used in machines to which they do not belong, at great loss to the machine owner.

In order to improve security, the tokens have been provided with a groove in a characteristic position and machines belonging to a particular owner are provided with a token entry opening covered by a plate which includes a slot having a shape corresponding to that of the grooved token. Two types of grooved tokens have been used hitherto. The first type of token has a

groove that extends across a circular face of the token in a predetermined chordal position. The groove needs to align with a corresponding projection in the slot of the cover plate to be acceptable. This type of token is inconvenient to use because it must be manually aligned with the projection in the cover plate slot and must be slid into the opening, with a possibility of sticking at coin entry.

The second type of grooved token is formed with a profiled rim to cooperate with a correspondingly formed entry slot in the cover plate. However, the registration between the token and the entry slot can be defrauded by using tokens which are slightly thinner or of smaller diameter than the true token.

With both of these mechanically keyed tokens, it has been necessary to provide two entry slots on the amusement machines, one for normal coins and one fitted with a cover plate to accept the token. Conventionally, this has required the fitting of two coin validators, one for coins and one for the tokens. With the increasing use of electronic coin validation, it has been necessary to retain two coin entry slots

each fitted with detection means prior to the main electronic validator. An example of such an arrangement is described in our application No. 8631054 filed 31st December 1986.

It has in the past been proposed to use a code on a token and an example of such an arrangement is disclosed in US Patent 3 926 291. However the manufacture of the token is complicated and expensive.

The present invention provides an improved security system having particular application to tokens, in which manufacture of the token can be readily achieved from a blank of metal, in a simplified manner.

In accordance with the present invention, an identification device such as a token is produced by cold forming a metal in such a manner as to form a pattern of regions of relatively high and low magnetic permeability so as to define a characteristic code to identify the device.

Certain metals, such as stainless steel exhibit a change in magnetic permeability when subjected to cold working and thus by selectively cold working portions of an identification device such as a token, it is possible to provide a characteristic code therein. It has been found that paramagnetic austentitic stainless steel is partially transformed to ferromagnetic martensitic by cold working and a particular preferred composition is Ni 8%, Cr 18% (balance Fe) . However other stainless steels exhibit the same property and also other metals such as manganese steel and to some extent cast iron also exhibit the property. Reference is directed to Kaye and Laby 13th Edition page 106.

Thus, in one aspect the present invention provides a token for use in a coin validator, cold formed of a metal in such a manner as to include a pattern of relatively high and low magnetically permeable regions that define a characteristic code.

Preferably, the token is disc shaped and said regions are formed concentrically thereof.

In another aspect, the invention provides a method of forming a token for use in a coin validator, comprising cold forming a blank of metal which exhibits relatively low magnetic permeability, so as to provide selectively a pattern of relatively high permeability regions, thereby to define a characteristic code. Conveniently, the regions of high permeability are formed by stamping.

The process may include prior to said cold forming, the step of forming the token with upstanding portions corresponding to the regions of high permeability and thereafter forming the token with a planar surface by cold forming thereby to form said regions of high magnetic permeability. The advantage of forming the token with a planar surface is that the pattern of high permeability and low permeability regions is not visible, which improves protection against fraudulent copying.

Preferably, the cold forming is performed at a temperature of less than 30°C.

The invention also includes a security system including the aforesaid identification device with said pattern of relatively high and low permeability regions, and detector means for detecting the code defined by said regions and providing a predetermined output signal if the detected code corresponds to a stored value thereof.

The detector means may include means for applying a magnetic field to the identification device, and means for detecting the level of flux which permeates through said regions upon passage of the device past the detector means whereby to provide an electrical signal corresponding to said code.

The magnetic field may be produced by a permanent magnet or by an electromagnet which may be AC or DC driven.

The field coupled through said regions may be detected by means of a Hall effect transducer. Alternatively, a single AC coil may be provided in a resonant circuit to produce the field. The effect of passage of the relatively high and low permeability regions past the

coil is to alter both the Q and the frequency of the resonant circuit. Either of these effects may be detected in order to determine the characteristic code.

The invention has the advantage that a coin validator can be provided with a single entry slot for both coins and tokens. Moreover, the invention can be incorporated into a conventional coin validator so that signals from the detecting means, indicative of the characteristic token code, can be fed to the microprocessor of a conventional coin validator for comparison with stored values thereof to determine whether the token is acceptable. Moreover, the coin validator may, by use of its conventional coils, perform a test upon the metallic material and diameter of the token in order to confirm further that it is of acceptable type. Thus, a single device can be provided according to the invention, to process both coins and tokens.

In order that the invention may be more fully understood, examples thereof will be described with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a first embodiment of a token in accordance with the invention;

Figure 2 is an enlarged partial section taken along the diameter of the token shown in Figure 1 along the line X-X;

Figures 3 to 5 are sectional views illustrating process steps used to form another embodiment of token according to the invention;

Figure 6 is a plan view of a detector for use in detecting a token according to the invention;

Figure 7 is a sectional view of the detector shown in Figure 6, taken along the line Y-Y; and

Figure 8 is a schematic sectional view of a coin validator incorporating a token acceptor, in accordance with the invention.

Referring firstly to Figures 1 and 2, a token 1 of stainless steel is formed from a discoidal blank having planar surfaces by stamping so as to form a series of

concentric grooves 2 to 6 on each disc shaped face thereof.

Under normal conditions, stainless steel is a paramagnetic austentitic material. The present invention makes use of the fact that upon cold working, stainless steel is partially transformed into a ferromagnetic martensitic material. Thus, in the regions of the grooves 2 to 6, regions of relatively high permeability are formed whereas the remainder of the token 1 remains of a relatively low permeability.

A number of metallic materials exhibit this property such as cast iron, manganese steel and others but it is believed that stainless steel produces the greatest change in permeability in response to cold working. The composition of the stainless steel has a bearing on the degree of permeability change produced by cold working as can be seen from Table 1

TABLE 1

Ni 12, Cr 18 Austenized 1.003

50% cold reduction 1.11

90% cold reduction 1.7

Ni 12, Cr 25 Austenized 1.003

90% cold reduction 1.005

The permeability change does not occur at elevated temperatures and the cold working should preferably be performed below 30°C to achieve maximum effect.

The formation of the grooves 2 to 6 produces a deformation in a surface region of the token so as to provide accompanying high permeability regions in the vicinity of the grooves. Thus, in order to achieve the effect, it is not necessary to deform the entire thickness of the disc.

The configuration of the grooves 2 to 6 define a characteristic code on the token 1. This code is read by means of a magnetic detector 7 when the token moves past it in the direction of arrow A. Thus, the radially outermost groove 2 can be used to define a "start bit" and the innermost groove 6 defines a "stop bit" for the code. The presence or absence of grooves between the start and stop bits defines the characteristic code for the token. It will be appreciated that as the token moves past the dectector arrangement 7, the code will be read on a first occurrence for the leading sector of the disc shaped token, and for a second occurrence for the trailing sector of the token, in an opposite sense. After appropriate processing, the two outputs of the detector arrangement 7 can be compared with one another for error checking purposes.

One possible disadvantage with the token shown in Figure 2 is that the grooves 2 to 6 identify the disc position of bits in the code. This problem is overcome by the process shown in relation to Figures 3 to 5, which forms a disc shaped token having planar surfaces.

Initially, a disc shaped blank 8 is placed between stamping members 9, 10. Figure 3 shows the result of stamping the disc. A number of projections 11 to 15 are produced by corresponding recesses 11a to 15a formed in the stamping member 10. This stamping is carried out at a high temperature i.e. sufficiently high not to produce a transformation of the low permeability stainless steel into its high permeability state. Consequently, the entire stamped disc 8 remains paramagnetic, i.e. of relatively low permeability.

The disc 8 is then placed between stamping members 16, 17 which have planar stamping surfaces 16a, 17a. As a result, the disc shaped faces of the token 8 are stamped into a planar condition such that the projections 11 to 15 are deformed downwardly into the disc. This stamping is carried out at below 30°C and the resultant cold working of the stainless steel in

the regions of the projections 11 to 15 produces localised partial transformations of the metal into its ferromagnetic martensitic form, thereby producing regions of high magnetic permeability; these regions are referenced lib to 15b in Figure 5. As a result, concentric regions of higher permeability are formed in the disc 8. The regions lib to 15b correspond to the regions associated with the grooves 2 to 6 shown in Figure 2.

Also, the stamping members 16, 17 may impart indicia (not shown) onto the surfaces of the token to indicate the machine owner and their value.

The detector arrangement 7 will now be described with reference to Figures 6 and 7. An annular soft iron pole piece 19 is formed with a central post 19a and a surrounding annular yoke 19b. An energising coil 20 formed on an annular former 21 surrounds the post 19a. A Hall effect device 22 is mounted on the tip of the post 19a.

As the token 8 moves past the detector arrangement 7, it receives a magnetic field, primarily from the annular yoke 19b. As one of the concentric high permeability regions e.g. region 12b, becomes aligned with the central post 19a, the region 12b provides a high permeability flux path bridging the gap between the yoke 19b and the post 19a, as can be schematically in Figure 6. Consequently, output of the Hall effect device 22 may be processed to indicate the occurrence of the low permeability region 12b. It will thus be appreciated that as the token moves past the detector arrangement 7 in the direction A, the Hall effect device will be switched sequentially in a manner corresponding to the magnetic code defined by the low permeability region lib to 15b.

Referring now to Figure 8, a schematic realisation of a coin validator incorporating a coin acceptor, in accordance with the invention, is shown wherein a coin rundown path has a coin inlet opening 24 and leads to a coin acceptor chute for acceptable coins and tokens and a coin reject chute 26. Acceptable coins are detected by means of inductive sensing coils 27 to 29. Coil 27 is of a relatively small diameter and disposed on one

side of the coin rundown path. Coil 28 is of a larger diameter and is disposed on the opposite side of the coin rundown path to coil 27. Coil 29 surrounds the coil rundown path 23. The coils 27 to 29 are driven as respective different frequencies by validation and drive circuitry 30. An example of a suitable form of coin validator is described in our UK-A-2 169 429 to which reference is directed. Broadly, the coils are energised to form an inductive coupling with a coin as it passes along the rundown path 23 and the degree of interaction is compared with stored values corresponding to acceptable coins by means, of a microprocessor in the circuitry 30. Upon detection of an acceptable coin, the microprocessor commands a solenoid operated gate 31 to open and allow the coin to pass down the passageway 25; otherwise the coin is rejected along passageway 26. In accordance with the invention, the validation and drive circuits additionally are arranged to energise the detector coil 20 of the detector arrangement 7. Also, the microprocessor in the circuitry 30 is responsive to conditioned of the Hall effect device 22. Thus, for tokens, the microprocessor receives a digital code produced by the hall effect switch 22, corresponding to

the code formed on the token 8. This code is compared with stored values thereof by means of the microprocessor and the solenoid operated gate 31 is controlled either to reject or accept the token in dependence upon the comparison carried out by the microprocessor. Thus, a single coin entry opening 24 can be provided both for tokens and coins i.e. without the need for separate entry slots as in the prior art.

The stored value of the code canm be programmed into the memory circuits associated with the microprocessor by a software deriven arrangement used for setting acceptable coin values. Alternatively, a much simpler arrangement can be used wherein DIL switches 32 are connected to the circuitry to define a digital code corresponding to the token. This allows a very simple form of re-programming in the field, for different token codes Also, it will be appreciated that the token detection system need not be incorporated into a conventinal validator but could instead comprise a separate modulator unit for use with a conventional validator.

Many modifications and variations of the above described embodiments are possible. For example, the coil 20 can be replaced by a permanent magnet; however this has the disadvantage that magnetic coins would be attracted to the sensor arrangement 7 and also, a build up of magnetic material from coins may occur on the magnet. In contrast, with an electromagnet, it can be switched off to release any build up of magnetic material and to release fraudulent wasters etc which might stick to the magnet and block the coin passageway. It will be appreciated that the coil 7 can be energised either by an AC or a DC field. Furthermore, instead of using a Hall effect device, other magnetic sensors can be used.

In another technique, the sensing arrangement 7 comprises a single inductive coil arranged to produce an inductive coupling with the token, the coil being arranged in a resonant circuit. The passage of the regions lib to 15b on the token 8 past the coil produce a change in the resonant frequency and the Q of the coil and this may be sensed in order to sense the code on the token.

Also, it will be appreciated that two sensors 7 could be utilised, one on each side of the coin path so that two sets of data would be obtained from opposite sides of the token, which could be compared for error checking purposes.

Also, although the invention has been described hereinbefore in relation to tokens for coin validators, it may have other applications. In particular, the invention could be used for a key for use in a lock, the lock having a detector arrangement corresponding to the arrangement 7 described above.