GB1403103A - Faceted coin selection method and apparatus - Google Patents

Abstract

1403103 Testing coins MARS Inc 25 May 1973 [25 May 1972] 24738/72 Heading G4V Apparatus for testing the anthenticity of faceted edge conductive coins comprises a coin track 30 along which coins roll, two electromagnetic sensors 60, 80, the primarily responsive regions of the sensors being located equidistantly above said track at a distance greater than the diameter of the inscribing circle of the coin and separated in a direction parallel to said track by a distance D substantially equal to an odd integral multiple of one half of the length of a facet and means for examining the signals produced by the sensors as the coin passes. In the embodiment shown the sensors comprise inductors having E-shaped metal cores 64, 64 and windings 62, 82 the primarily responsive regions of the sensors being the centre poles of the cores (see also Figs. 2, 3, not reproduced). The sensors are mounted on one side of a laterally inclined non-conductive side wall 40 against the other side of which the coins lean when rolling down the track. The height of the lower face of the centre pole of the core is approximately equal to the diameter of a circle circumscribing the coin and the spacing of the outer poles approximately equal to the length of one facet, the cores having cylindrical upper and lower surfaces generally concentric with a coin positioned between the inductor and the track. The inductances of the sensors on the passage of a genuine coin will lie in a range L 1 to L 2 (Figs. 4 to 6, not shown). A suitable intermediate value L INT is chosen so that if the inductance of sensors lies in the range L 1 to L INT the other inducatnce will be L INT to L 2 . The inductors are connected to respective oscillators 70, 90 the frequencies of which will be changed to f 1 , f INT or f 2 , for the respective values of the inductances L 1 , L INT or L 2 . Two narrow band detectors are connected to each of the osisllators, the detectors 72, 92 being tuned to the range f 1 to f INT and the detectors 74, 94 to the range f INT to f 2 , each detector producing one or two pulses according to whether the frequency of the oscillator enters or passes through the corresponding range with flip-flops 76, 78, 96 and 98 being set or reset appropriately. AND gates 100, 102 and EXCLUSIVE OR gate 104 analyse the outputs of the flip-flops to determine whether the frequency of one oscillator has moved into but not through one of the ranges f 1 to f INT or f INT to f 2 and the frequency of the other oscillator has moved into but not through the other frequency range. In another embodiment (Fig. 8, not shown) only the detectors 72, 92 connected to a four stage counter (108) are used, a coin being deemed genuine if the frequency of one oscillator moves into the range f 1 to f INT and the frequency of the other oscillator moves through this range.