GB1327820A - Method for checking coins and apparatus for the performance of the aforesaid method - Google Patents

Abstract

1327820 Coin testing G PRUMM 24 Aug 1970 [22 Aug 1969 18 Sept 1969] 40614/70 Heading G4V A method of testing coins comprises the steps of subjecting a coin to two measuring operations, at least one of which is a damping measurement, i.e. the measurement of the attenuation of oscillations induced in one coil by oscillations in another when a coin moves between them or the effect of a coin on free oscillations in a single coil, and logically coupling information derived by said two measuring operations to provide an indication of the validity of the coin. The damping amplitude is preferably analysed by double threshold devices as described in U.S. Specification 3,682,286 which give a signal only when the amplitude lies in a predetermined "window". The method may be applied in either single type or multitype coin testers. The first measurement may be a diameter test performed by contact switches (Figs. 1 to 3, not shown) and if the coin is of correct diameter signals from damping measurement device (16) are allowed to proceed to an evaluation circuit. A separate coin channel and measuring device may be provided for each coin type, but the coin channels are preferably arranged so that they can be monitored by one measuring probe (Figs. 10 and 13, not shown). The positioning of the various coin channels from the measuring probe (118) may be arranged so that the coins with the greatest damping qualities are situated furthest from the probe, so that the damping effect of all the coins is equal (Figs. 11 and 12, not shown) thus permitting one double threshold device to be used for analysing all the coins. Alternatively two coins of almost identical damping properties may be so positioned that they can be more readily distinguished (Figs. 14 and 15, not shown). In a further arrangement (Fig. 4, not shown) separate coin entry slots (23) to (26) each provided with a diameter testing switch (34) to (37) lead to common damping measurement coils (32) and (33), alternatively, Fig. 5, a single coin entry slot 11 may be provided with a slider 39 which actuates one of switches 44 to 47 depending on the diameter of the coin inserted. Actuation of one of the switches (34) to (37) or 44 to 47 permits the evaluation of the signal from the damping measurement device characteristic of the corresponding coin size. The coin diameter may also be measured using circular rotating members. In one embodiment, Fig. 8, an inserted coin is carried in recess 71 of rotating disc 70, past a measuring probe 16, where the coin displaces a slide 74 to make contact with one of the diameter switches 79 to 82. In another embodiment (Fig. 9, not shown) the rotating disc (88) has a stepped recess into which inserted coins fall. The angular rotation (96) required to bring a coin to probe (16) is therefore a function of its diameter, a contact strip (95) fixed to the disc closing a corresponding diameter switch (98), (99). In another embodiment, Fig. 6, induction proximity switches 48 to 51 are used to determine the diameter of a coin 15 inserted into channel 14, before the coin reaches the damping measurement device 16, and the switches are so arranged that the actuation of one switch blocks the actuation of all the succeeding switches, thus ensuring that only one diameter switch is actuated. The coin channel may be inclined so that the coins lean against the wall opposite the switch, ensuring that only coins of a certain thickness will actuate them. In a further embodiment (Fig. 7, not shown) a single photoelectric device (52) is provided for sensing the largest coin and a pair of photo-electric devices for example (55), (56) is provided for each other coin diameter, one device (56) being positioned just within the required diameter limit and the other device (55) positioned just outside. Actuation of the device (56) closes the corresponding diameter switch but actuation of device (55) almost instantaneously re-opens the switch. A further device (59) checks the coins for a central bore. A device may also be included to test the coin faces for embossment. The damping measurement device may be situated centrally in the coin channel or displaced towards the top of the channel, (Fig. 20, not shown) in the latter "diameter-oriented" position, at which the smallest coin (150) just enters the field of influence of the device (149), the effect of the coin diameter on the overall damping properties of the coins is greatly increased over the former, 'metal-oriented" position at which the coin material is the most important factor (Figs. 21 and 22, not shown). An alternative arrangement of measurement device, with two coils wound transversely to the axis of the coin (Fig. 23, not shown) also increases the relative importance of the diameter of the coin. Circuitry.-The circuits are designed so that there is a number of similar parallel measuring and evaluation circuits, one for each coin type, and a common coin accept/reject circuitry means for all coin types. In one embodiment, Fig. 25, there is a common coin channel for all coin types, and two pairs of measuring coils, the first 201 and 202 are "diameter-oriented" and the second "metal-oriented". When a coin 203 moves between the coils the signal from coil 202 is amplified and relayed to double threshold devices 251, 252, 253 with associated flip-flops 261, 262, 263. When one of the flip-flops receives only one pulse from the threshold device, indicating that the damping amplitude lies within the prescribed "window" a signal is sent to one of AND gates 301, 302 or 303. At the second measuring location the signal from coil 221 is amplified and directed to all three AND gates at one of which the input conditions are satisfied, allowing passage of the signal to one of the resistors 341, 342 or 343 which are designed to reduce all the expected genuine signals to the same level. The modified signal is then directed to double threshold device 205 which has an associated flip-flop 206. When only one pulse is received by the flip-flop, indicating a genuine coin, and a signal is present on line 281 indicating that the testing operation is complete, the input conditions of AND gate 208 are fulfilled and a signal is sent to the coin accept/ reject circuitry 209.