Method and apparatus for sorting coins

Abstract: A coin to be judged is passed near an oscillation coil excited by an exciting signal containing a plurality of harmonic components, that is nonsinusoidal alternating current, and the coin is sorted in accordance with a signal produced by a receiving coil electromagnetically coupled with the oscillation coil and containing at least two harmonic components. The signal induced in the receiving coil may be a composite signal of at least two harmonic components. This signal may consist of a first signal of a composite of at least two harmonic components and a second signal of a composite of at least two other harmonic components.

Description: This invention relates to a method and apparatus for sorting coins utilized in automatic vending machines, money exchange machines; service devices, etc., and more particularly to an electronic coin sorting apparatus which sorts coins by electronic means. There have been used two types of coin sorting apparatus. The first type is mechanical sorting apparatus in which the characteristics of coins are mechanically examined or judged for sorting, and the other type is electrical sorting apparatus in which the characteristics of the coins are detected by electronic means and the coins are sorted according to the detected outputs. Since the electronic coin sorting apparatus has a high sorting accuracy and can be miniaturized, this type of the sorting apparatus have been used widely. An electronic coin sorting apparatus generally constructed such that a primary coil excited by a signal of a definite frequency is disposed on one side of a coin passage, a secondary coil electromagnetically coupled with the primary coil is disposed on tile other side of the coin passage, an attenuatting voltage signal generated by the secondary coil which is generated at the time of passing the coin is used to judge whether the coin is genuine or counterfeit, and the reliability of the coin is examined according to a result of judgment. It has also been proposed an electronic coin sorting apparatus wherein a plurality of pairs of coin detecting coils each comprising a primary oscillation coil and a secondary receiving coil are provided for detecting the material, thickness, external diameter or the like of the coin. Further, according to one method, signals of different frequencies are applied to different primary coils while in another method the primary coil itself acts as an element of an oscillation circuit so as to constitute a self-oscillation circuit. In both methods, a plurality of discrete driving circuits or oscillation circuits are provided for exciting respective primary coils. US-A- 3870137 discloses a coin sorting apparatus, wherein at least two electromagnetic fields having different frequencies are provided for judging the characteristics of the coin by the action of these electromagnetic fields. Respective electromagnetic fields have different oscillation circuits to be applied with different check frequencies so as to check whether the diameter and thickness of the coin are included in predetermined ranges by using the interaction between the coin and the different check frequencies. When the coin satisfies the check standard at least two different frequencies, the coin is judged acceptable. With these prior arts, however, to improve the coin sorting accuracy, it is necessary to use plurality of oscillation circuits and oscillation coils, so that the number of component parts and hence the manufacturing cost are increased. Moreover, since respective oscillation coils are excited by different frequencies, interference between these coils are liable to occur. To avoid the interference, it is necessary to increase the distance between the coils which makes long the coin passage. In the prior art coin sorting apparatus, for example, that described in US-A- 3870137, for the purpose of providing interaction with the coin, a plurality of exciting coils respectively excited by low and high frequencies are used. Consequently where clad coins are to be examined wherein this sheets of nickel and copper are superposed as in 10 cent, 25 cent and 50 cent coins, for the purpose of checking characteristics of respective materials, it is necessary to use a plurality of oscillation circuits and oscillation coils. As a consequence, the sorting circuit also become complicated. Furthermore, for the purpose of judging the material and thickness of the coin, independent low frequency oscillation circuit and high frequency oscillation circuit are necessary for obtaining discrete mutual reactions so that the judging means becomes complicated in construction. Moreover, such judging means can be used for only specific type of coins. The precharacterizing parts of claims 1 and 3 refer to a method and an apparatus as disclosed in GB-A-2 096 211. Adjacent to a coin path, an inductor coil is positioned which is excited by two oscillators one of which oscillates with a low frequency and one of which oscillates with a high frequency, each of said frequencies being discrete frequencies. A receiving inductor coil is positioned at the other side of the coin path. The output signals of the receiving conductor coil are simultaneously fed to a high pass filter and to a low pass filter. By comparing the attenuation produced by a coin under test, both frequencies with ranges of values for particular denominations of acceptable coins, a coin test as to coin material and thickness is performed. The two exciting frequencies may cause interference, whereby the liability of evaluation of coins may be affected. Independent low frequeny and high frequency oscillation circuits are needed and, furthermore, there is a need of very specific and complicated band pass filters. GB-A-2 160 689 discloses a coin detection apparatus wherein an exciting coil positioned adjacent the coin path is excited by a square-wave. The evaluation of coins is based on the positive and negative peak values of a signal produced by a detection coil. Though the exciting signal is a multi-frequency signal, in the evaluation circuit the different frequencies are not evaluated separately. What is evaluated is only the amplitude of the composite received signal. It is an object of the present invention to provide a method and an apparatus for sorting coins which can be realized with a small-sized and inexpensive simple construction and present a high liability. This object is solved, according to the invention, with the features of claims 1 and 3, respectively. The exciting signal may be a rectangular wave or another nonsinusoidal wave. A resonance circuit or a bandpass filter selectively passing a signal in a specific frequency bandwidth may be provided. A judging circuit may be connected to the receiving coil for judging whether the coil is genuine or counterfeit, and the type of coins and the material, configuration and the outer diameter of the coin. The coin is sorted by the output of the judging circuit. The oscillation coil may be a single coil and one or two receiving coils may be electromagnetically coupled therewith. Alternatively two oscillation coils are connected in series and two receiving coils coupled with two oscillation coils respectively can be used. In the accompanying drawings: Fig. 1 is a block diagram showing one embodiment of this invention; Fig. 2 is a view showing the general construction of the coin sorting apparatus according to this invention; Fig. 3 shows the arrangement of the primary or oscillation coil and the receiving coil of the apparatus shown in Fig. 2; Fig. 4 is a perspective view of a coin useful to explain an eddy current loss; Fig. 5 is a diagram for explaining a skin effect; Fig. 6 shows one example of a rectangular wave; Fig. 7 is a spectrum diagram showing the harmonic components of the rectangular wave; Fig. 8 shows one example of a triangular wave; Fig. 9 is a spectrum diagram showing the harmonic components of the triangular wave shown in Fig. 8; Fig. 10 shows one example of a saw tooth wave; Fig. 11 is a spectrum diagram showing the harmonic components of the saw tooth wave shown in Fig. 10; Fig. 12 shows the waveform of a voltage impressed across the oscillation coil utilized in this embodiment; Fig. 13 is a spectrum diagram showing the harmonic components of the voltage shown in Fig. 12; Fig. 14 is a block diagram showing the detail of this embodiment; Fig. 15 is a spectrum diagram useful to explain the operation of the circuits shown in Fig. 14; Fig. 16, 17 and 18 are waveforms useful to explain the operation of the circuits shown in Fig. 14; Fig. 19 is a vertical sectional view of a coin that can be judged according to this invention; Fig. 20, 21 and 22 are graphs showing the effect of judgment; Fig. 23 is a block diagram showing another embodiment of this invention; Fig. 24 is a block diagram showing one example of a bandpass filter utilized in the embodiment shown in Fig. 23; Fig. 25 is a block diagram showing still another embodiment of this invention; Fig. 26 is a vertical sectional view showing one example of the coil arrangement of the embodiment shown in Fig. 25; Fig. 27 is a block diagram showing yet another embodiment of this invention; and Fig. 28 is a vertical sectional view showing one example of the coil arrangement of the emboidment shown in Fig. 27. An embodiment of this invention shown in Fig. 1 comprises a rectangular wave oscillation circuit 1, a primary or oscillation coil L 1 and two receiving or secondary coils L 2 and L 3 . The output of the rectangular wave oscillation circuit 1 is applied to the oscillation coil L 1 through an amplifier 2. The oscillation coil L 1 is disposed on one side of a coin passage 4 while receiving coils L 2 and L 3 are disposed on the other side to oppose the oscillation coil L 1 . The oscillation coil L 1 is excited by a rectangular wave signal outputted by the rectangular wave oscillation circuit 1 to vary the mutual inductance M 1 between the oscillation coil L 1 the receiving coil L 2 and the mutual inductance M 2 between the oscillation coil L 1 and the receiving coil L 3 caused by the passage of a coin 3 to be judged through the coin passage 4, so that signals for judging whether the coin is genuine or counterfeit are induced in the receiving coils L 2 and L 3 . The outputs of the receiving coils L 2 and L 3 are applied to a coin judging circuit 5 which in response to the outputs of the receiving coils L 2 and L 3 judges whether the coin 3 is genuine or counterfeit as well as the type of the coin 3. Thus, when the coin 3 is genuine the coin judging circuit 5 produces coin signals A, B, C or D representing the type of the coin 3 whereas when the coin is counterfeit, the circuit 5 produces a counterfeit coin signal. The detail of the coin judging circuit 5 will be described later. In Fig. 2, the coin 3 inserted into a slot 30 drops on a rail 4a and then passes through the coin passage 4 between the oscillation coil L 1 and the receiving coils L 2 and L 3 while rolling downward along the inclined rail 4a. While passing through the passage 4 between coils L 1 , L 2 and L 3 , the material, thickness and the outer diameter of the coin 3 are judged by the coin judging circuit 5 and a gate 32 for separating genuine coins from counterfeit coins is controlled by a solenoid coil 31. Thus, when the coin 3 is counterfeit, the solenoid coil 31 is energized by the counterfeit coin signal outputted from the coin judging circuit 5 such that the gate 32 will guide the coin 3 to a counterfeit coin passage, not shown, whereas when the coin 3 is genuine, the gate 32 is controlled to guide the judged coin 3 onto a rail 33. The genuine coins guided on rail 33 are classified into coins A, B, C, and D by a classifying solenoid coil 34 energized by a signal outputted by the coin judging circuit 5 and representing the type of the coins. Although the coin sorting apparatus described above is designed to sort genuine coins of four types, the apparatus can be constructed to judge coins of any number of types. As shown in Fig. 3, the oscillation coil L 1 is disposed on one side of the coin passage 4, and the receiving coils L 2 and L 3 are disposed on the opposite side to oppose the oscillation coil L 1 . In this embodiment, the receiving coil L 3 is mainly used to judge the material of the coin and the receiving coil L 3 is disposed near the center of the genuine coin having the smallest outer diameter. The other receiving coil L 2 is mainly used to judge the outer diameter of the coin. Therefore the receiving coil L 2 is located near the periphery of the coin where the effect of the outer diameter of the genuine coin is significant. Although the oscillation coil L 1 uses a core of pot shape, it is possible to use a drum shaped core like receiving coils L 2 and L 3 . The principle of judging the coin according to this invention will now be described. As shown in Fig. 4, when varying flux  produced by the oscillation coil L 1 passes through the coin 3 made of electric conductor, eddy current i is induced in the coin 3. The eddy current causes an eddy current loss in the form of Joule heat due to resistance of the coin. Denoting the rate of variation of flux  linking the coin 3 by f and the maximum density of the flux  by Bm, the magnitude of the electromotive force e induced in the coin 3 is expressed by e = Δ  Δ t ∞ Bm · f The eddy current i caused by the electromotive force e is expressed by i = e R ∞ Bm·f R when R represents the resistance of a current path. Consequently, the eddy current loss P can be expressed by the following equation P = i 2 · R ∞ Bm 2 ·f 2 R This equation shows that the eddy current loss is proportional to the square of the frequency of the varying flux . Due to this eddy current loss, the flux produced by the oscillation coil is attenuated when the flux links the receiving coils. The degree of loss of flux  caused by the eddy current loss differs dependent upon the material, that is, the specific resistance of metal used to proper coins. For example, the specific resistance at 20°C of copper, aluminum, nickel and iron are 1.673, 2.6548, 6.84 and 9.71 microohm cm, respectively. The eddy current causes a skin effect. Fig. 5 is an enlarged sectional view of a portion of the coin 3 and diagrammatically shows the skin effect. In Fig. 5, the eddy current produced by the flux  flows in the direction from the front side to the reverse side. When a direct current flows in the coin 3, an electric current flows though the coin 3 uniformly with respect to the section thereof. When an alternating current flows in the coin 3, an electric current does not flow uniformly through the coin 3 with respect to the section thereof, but flows more in the surface and decreases toward the center. This phenomenon is called the skin effect. Referring to Fig. 5, in which a section of the coin is divided into small segments, from electric current i'n flowing each segment, magnetic flux 'n caused by the current i'n and the number of flux linkage of 'n, it is found that the number of flux linkage is increased toward the center of the section of the coin. Therefore, increased electromotive force is great and the electric current is difficult to flow in the center. This phenomenon is more conspicuous when the frequency of the applied alternative current is higher. When the frequency is very high, most of the electric current flows in the surface of the coin. On the other hand, there is a magnetic shielding effect. When a coin of magnetic substance such as iron passes between the oscillation coil L 1 and the receiving coils L 2 and L 3 , the magnetic flux produced by the oscillation coil L 1 is absorbed in the coin, and the receiving coils L 2 and L 3 receive reduced flux. It is known that the skin effect and the magnetic shielding effect occur simultaneously and these effect cooperate. This invention is based on a unique utilization of this phenomenon. More particularly, the oscillation coil L 1 is excited by a rectangular wave consisting of a fundamental wave and a plurality of harmonic waves and the judgment of the coin is made by utilizing these harmonic waves. Fig. 7 is a frequency spectrum showing theoretical magnitudes of various harmonic components contained in a rectangular wave shown in Fig. 6 also containing a fundamental wave having a frequency of 20 kHz. In addition to a rectangular wave pulse, such non-sinusoidal waves as a triangular wave and a saw tooth wave also contain many harmonic components. Fig. 9 is a frequency spectrum showing theoretical magnitudes of harmonics components contained in a triangular wave shown in Fig. 8 and having a fundamental wave having a frequency of 20 kHz. In the same manner, Fig. 11 shows a frequency spectrum of a saw tooth wave shown in Fig. 10. The harmonic components of the rectangular wave, the triangular wave and the saw tooth wave which are not sinusoidal can be explained by Fourier series. Comparing Figs. 7, 9 and 11 with each other, the maximum value of the harmonic waves contained in a non-sinusoidal alternating current decreases as the order of the harmonic becomes higher but the rate of attenuation is great as the degree of discontinuation of the waveform is small. The waveform useful to this invention is one whose degree of discontinuation is large. Accordingly, comparison of Figs. 7, 9 and 11 shows that a rectangular wave shown in Fig. 6 is most effective. From experiment, it was found that with the configuration shown in Fig. 1, the voltage waveform across the oscillation coil L 1 is the waveform shown in Fig. 12. The frequency spectrum of the voltage induced in the receiving coils L 2 and L 3 is shown in Fig. 13 which contains harmonic components useful to this invention. Fig. 14 shows the detail of the configuration of the embodiment shown in Fig. 1. In Fig. 14, a resonance circuit constituted by a resistor R 1 and a capacitor C 1 is connected across the receiving coil L 2 and a similar resonance circuit including a resistor R 2 and a capacitor C 2 is connected across the receiving coil L 3 . These resonance circuits have filter effects having resonance points f 01 and f 02 shown in Fig. 15. As shown in Fig. 15, the resonance point f 01 is located between the fundamental frequency 20 kHz and the third harmonic 60 kHz and effective composite compositions corresponding to respective frequencies are derived out. The resonance point of frequency f 02 is located between the frequencies of 9th harmonic 180 kHz and the 11th harmonic 220 kHz so that effective composite components corresponding to respective frequencies are derived out. The composite composition corresponding to the frequency f 01 is used to examine or judge the material and thickness of the coin to be judged, whereas the composite component corresponding to the frequency f 02 is used to judge the outer diameter of the coin. When the coin 3 passes through the coin passage between the coils L 1 , L 2 and L 3 the resultant wave form appearing across receiving coils L 2 and L 3 is as shown in Fig. 16. By the action of the resonance circuit R 1 , C 1 , a composite wave as shown in Fig. 16 which is a resultant of the fundamental wave (low frequency) and the third harmonic (high frequency) appears across the receiving coil L 2 . In the same manner, a composite wave corresponding to the resultant of the 9th and 11th harmonics appears across the receiving coil L 3 . Composite waves appearing across the receiving coils L 2 and L 3 by the actions of the resonant circuits R 1 , C 1 and R 2 , C 2 are applied to low pass filters LPF(A) and LPF(B) respectively via amplifiers A 2 and A 3 . Each of the signals passed through the low pass filters is an envelope signal shown in Fig. 18 obtained by demodulating (that is by removing carrier wave) modulated wave shown in Fig. 17. After passing through the low pass filters LPF(A) and LPF(B), the signals are temporary stored in hold circuits HOLD(A) and HOLD(B) and then applied to comparators COM (A 1 -A 4 ) and COM (B 1 -B 4 ) respectively set with threshold values of respective coins produced by reference voltage circuits REF(A) and REF(B). When the coin 3 is judged as genuine, a comparator corresponding to this coin produces a signal which is applied to one input of one of AND gate circuits AND(1-4), the other input being supplied with a gate signal outputted from a judging signal circuit 51. AND gate circuits AND(1-4) which produce genuine coin signals A, B, C and D. These signals control the genuine and counterfeit sorting solenoid coil 31 through a suitable control unit, for example, a central processing unit, so as to guide genuine coin to the genuine coin passage. As above described according to this embodiment, a single oscillation coil L 1 is excited by a nonsinusoidal alternating current generated by the rectangular wave oscillation circuit 1, the oscillation coil is coupled with two receiving coils L 2 and L 3 , resonance frequencies thereof being selected to suitable frequencies by resonance circuits R 1 , C 1 and R 2 , C 2 , and the coin is judged by the output voltages of the receiving coils L 2 and L 3 . Thus it is possible to judge the material, thickness and outer diameter of the coin 3 by using only one oscillation circuit and a single oscillation coil. When a prior art apparatus utilizing a single frequency is used to judge US 5c, 10c and 25c coins each comprising a core of copper and outer layers of nickel as shown in Fig. 19 (that is so-called a clad coin), and a coin made of copper only, the characteristic of copper appears as shown in Fig. 21 thus failing to discriminate mere copper coins from clad coins. With the apparatus of this invention, the judged characteristics of the coins become as shown in Fig. 22. Thus the difference between two curves becomes larger than that shown in Fig. 21 which makes accurate judging. More particularly, a clad coin 60 comprising a core 61 made of copper and nickel clads 62 and a copper coin having the same diameter and thickness as the clad coin 60 are taken as examples. Suppose now that the frequency of the fundamental wave is set in a range of 15-30 kHz and that the frequencies of the harmonic waves are set in a range of 45-90 kHz. Then in the low frequency range of 15-30 kHz, the flux mainly interacts with the copper comprising the core of the clad coin and the percentage of attenuation resembles a curve of copper shown in Fig. 20. However, the harmonic waves result in a skin effect. By the resultant function of these effects identification of a clad coin and a copper coin can be made readily as shown in Fig. 22. As the frequency of the AC exciting field generated by the oscillation coil L 1 increases, the skin effect caused by the eddy current loss becomes remarkable. In the case of a coin as shown in Fig. 19 the skin effect concentrates in the clads, which is different from that appearing in the surface of copper. As a consequence the copper coin can be discriminated from the clad coin as shown in Fig. 22. Another embodiment of this invention is shown in Fig. 23. In this embodiment, oscillation coil L 1 is excited by a rectangular wave oscillation circuit 1, and receiving coils L 2 and L 3 are connected to bandpass filters BPF(A) and BPF(B), respectively, constructed to pass frequencies f c1 , f c2 and f c3 , f c4 shown in Fig. 15. Signals outputted from these filters BPF(A) and BPF(B) have waveforms as shown in Fig. 16, from which a composite wave can be derived out. As above described, this modification operates in the same manner as the embodiments shown in Figs. 1 and 14. Fig. 24 shows a bandpass filter generally used. Fig. 25 shows still another embodiment of this invention in which two oscillation coils L 1 and L 1 ' are excited by the same nonsinusoidal alternating current. As shown, oscillation coils L 1 and L 1 ' are connected in series to be excited by the output of the rectangular wave oscillation circuit 1 via an amplifier 2. Receiving coils L 2 and L 3 are provided to couple with the oscillation coils L 1 and L 1 ' respectively. Receiving coils L 2 and L 3 and capacitors C 1 and C 2 form resonance circuits and provide filter effects having resonance points f 01 and f 02 shown in Fig. 15 in the same manner as in the embodiment shown in Fig. 14. As a consequence signals produced by the receiving coils L 2 and L 3 are composed as shown in Fig. 16, meaning that the modification shown in Fig. 25 operates in the same manner as the embodiment shown in Figs. 1 and 14. An actual construction of the oscillation coils L 1 and L 1 ', the receiving coils L 2 and L 3 and the coin passage 4 are shown in Fig. 26. Still another embodiment shown in Figs. 27 is constituted by a single oscillation coil L 1 and a single receiving coil L 2 opposing thereto. As shown in Fig. 27, a plurality of bandpass filters BPF(1-n) are connected to the receiving coil L 2 and the outputs of the bandpass filters BPF(1-n) are derived out through amplifiers A(1-n) respectively. The arrangement of the oscillation coil L 1 , the receiving coil L 2 and the coin passage 4 is shown in Fig. 28. In the foregoing embodiments a rectangular wave oscillator is used to excite one or more primary coils, but nonsinusoidal waves other than the rectangular wave can be used so long as the nonsinusoidal wave contains desired harmonics of sufficient levels. It should be understood that the invention is not limited to specific embodiments described above, and that many changes and modification can be made within the true spirit and scope of the invention as defined in the appended claims.

Claims: A method of sorting coins comprising the steps of: passing a coin to be sorted near an oscillation coil (L 1 ) excited by an exciting signal containing a plurality of harmonic components; generating a received signal (e1,e2) in a receiving coil (L 2 ,L 3 ) electromagnetically coupled with said oscillation coil (L 1 ); deriving out by filtering from said received signal at least two deriving signals with each deriving signal containing a different frequency component; judging whether the coins are genuine or counterfeit and type of said coins based on said deriving signals; and sorting said coins in accordance with the performance of said judging step, characterized in that said exciting signal has a non-sinusoidal waveform comprising a fundamental wave and a plurality of harmonics, said filtering is carried out so that a first of said at least two deriving signals is a first composite signal of the fundamental wave and an adjacent harmonic component and a second of said at least two deriving signals is a second composite signal of an harmonic component of higher frequency and an harmonic component adjacent to said harmonic component of higher frequency, and in that in said judging, the amplitude level of each of the first and second composite signals is evaluated separately. A coin sorting apparatus comprising: an oscillation coil (L 1 ) excited by an exciting signal containing a plurality of frequency components; a receiving coil (L 2 ,L 3 ) electromagnetically coupled with said oscillation coil; a coin passage (4) for passing coins near said oscillation coil; means (5) deriving at least two deriving signals by filtering from the received signal generated in said receiving coil as a result of passing said coin near said receiving coil; and means (AND) for sorting said coins based on said signal extracted by said deriving means characterized in that said exciting signal has a non-sinusoidal wave form comprising a fundamental wave and a plurality of harmonics, and that said deriving means (5) comprises means for filtering whereby a first of said at least two deriving signals is a first composite signal of a fundamental wave component and at least one harmonic component adjacent to said fundamental wave component, and a second of said at least two deriving signals is a second composite signal of an harmonic component of higher frequency and at least one harmonic component adjacent to said harmonic component of higher frequency, and judging means evaluating the amplitude levels respectively of the first and second composite signals. The coin sorting apparatus according to claim 2 wherein said deriving means (5) comprises for filtering at least two resonance circuits (R 1 C 1 ), each resonating on a signal in a specific frequency bandwidth. The coin sorting apparatus according to claim 2 wherein said deriving means (5) comprises a band-path filter (BPF) selectively passing a signal in a specific frequency band width. The coin sorting apparatus according to claim 2 wherein said oscillation coil (L 1 ) is disposed on one side of said coin passage (4), said receiving coil comprises first and second receiving coils (L 1 ,L 2 ) disposed on the other side of said coin passage and electromagnetically coupled with said oscillation coil, said deriving means (5) comprises first deriving means (REF(A);HOLD(A); COM(A);COM(B)) connected to said first receiving coil (L 1 ) for deriving said first composite signal and second deriving means (REF(B);HOLD(B);COM(A); COM(B)) connected to said second receiving coil (L 2 ) for deriving said second composite signal and said sorting means comprises judging means (AND) responsive to amplitude levels respectively of the first and second deriving signals for judging whether coins are genuine or counterfeit and type of said coins passing through said coin passage. The coin sorting apparatus according to claim 2 wherein said oscillation coil comprises first and second oscillation coils (L 1 ,L 1 ') disposed on one side of said coin passage (4) and excited by the same non-sinusoidal alternating current, said receiving coil comprises first and second receiving coils (L 2 ,L 3 ), disposed on the other side of said coin passage and magnetically coupled with said first and second oscillation coins respectively, said deriving means comprises first deriving means connected to said first receiving coil (L 2 ) for deriving said first composite signal and second deriving means connected to said second receiving coil (L 3 ) for deriving said second composite signal and said sorting means comprises judging means responsive to amplitude levels respectively of the first and second deriving signals for judging whether coins are genuine and counterfeit and type of said coins passing through said coin passage. The coin sorting apparatus according to claim 2 wherein said oscillation coil comprises a single oscillation coil (L 1 ) disposed on one side of said coin passage (4) and excited by a non-sinusoidal alternating current, said receiving coil comprises a single receiving coil (L 2 ) disposed on the other side of said coin passage and electromagnetically coupled with said oscillation coil, and said deriving means is connected to said receiving coil.

Inventors: FURUYA ICHIRO, FURUYA YONEZO, ISHIDA TAKESHI, YOSHIZAWA GENZO, FURUYA, ICHIRO, FURUYA, YONEZO, ISHIDA, TAKESHI, YOSHIZAWA, GENZO
Applicants: NIPPON CONLUX CO LTD, NIPPON CONLUX CO., LTD.
Application year: 1988
Main classification: G07D5
IPC codes: G07D5, G07D3