(19)
(11) EP 0 500 367 A2

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:
26.08.1992 Bulletin 1992/35

(21) Application number: 92301401.3

(22) Date of filing: 20.02.1992
(51) International Patent Classification (IPC)5G07D 5/08, G07F 3/02
(84) Designated Contracting States:
AT BE CH DK ES FR GB LI

(30) Priority: 20.02.1991 ZA 911248

(71) Applicant: TELKOR (PROPRIETARY) LIMITED
Sandton, Transvaal (ZA)

(72) Inventors:
  • Variawa, Omar Farouk
    Lichtenburg, Transvaal (ZA)
  • Simmonds, Edward Shane
    Sandton, Transvaal (ZA)
  • Botha, Jacobus Theron
    Pretoria, Transvaal (ZA)
  • Chinneck, Edgar Herbert
    Johannesburg, Transvaal (ZA)
  • Kowalczyk, Piotr Leonard
    Krugersdorp, Transvaal (ZA)

(74) Representative: Leale, Robin George 
FRANK B. DEHN & CO. Imperial House 15-19 Kingsway
London WC2B 6UZ
London WC2B 6UZ (GB)


(56) References cited: : 
   
       


    (54) Coil arrangement and static measuring device


    (57) s7 The invention relates to an inductive coil arrangement (18) for measuring the physical characteristics of a token (26). The coil arrangement (18) comprises a plurality of inductors (12,14,16), each inductor being formed out of at least two superposed planar spiral tracks (28,46,52,58,61,61A,62,70) separated by an insulating layer (72A,74A,76A,78A,80A,82A,84A,86A) of a multi-layer electrical device (72,74,76,78,80,82,84,86), such as a plurality of printed circuit boards which are laminated together. Conductive paths (92) extend axially between the tracks. The invention extends to a method of manufacturing the inductive coil arrangement, as well as a to token validation device (10) incorporating the inductive coil arrangement.




    Description


    [0001] This invention relates to a coil arrangement, as well as to a static measuring device employing such an arrangement.

    [0002] Most conventional coin validators rely on dynamic measurement of coins for assessing the validity thereof. Usually, an array of coils is spaced along a passage through which the coin passes, for measuring one or more of the properties thereof. The extended coil arrangement, as well as the physical dimension of the coils, generally make for a coin validator which is relatively bulky. In addition, dynamic coin validators are prone to coin bounce, arising from burrs and bumps in the coins, as well as from dirt accumulating on the runway.

    [0003] According to the invention there is provided an inductive coil arrangement for measuring at least one physical characteristic of an object, the coil arrangement comprising at least one inductor formed out of at lest two superposed planar spiral tracks separated by an insulating layer of a multilayer electrical device and having a conductive path extending between the tracks.

    [0004] Preferably, the inductive coil arrangement comprises a plurality of superposed inductors, each inductor being arranged to measure different physical characteristics of an object.

    [0005] Each spiral track is is conveniently etched from a conductive layer on one face of an insulating substrate wafer, and each inductor preferably comprises a plurality of alternating insulating substrate wafers and the spiral tracks laminated together.

    [0006] The conductive path between the tracks may extend through the insulating layer from a centre terminal of one track to the centre terminal of the superposed track.

    [0007] The conductive path may also extend through the insulating layer from an outer peripheral terminal of one spiral track to an outer peripheral terminal of the superposed spiral track.

    [0008] In one from of the invention, the inductive coil arrangement comprises first, second and third superposed inductors forming part of a token validation apparatus, the first inductor being arranged to measure the core resistivity of a tocken, the second inductor being arranged to measure the surface resistivity of the token, and the third inductor being arranged to measure the size of the token.

    [0009] The invention extends to a method of manufacturing an inductive coil arrangement comprising the steps of:

    a) providing a plurality of planar insulating substrate wafers, each wafer carrying a conductive layer on one side thereof;

    b) printing a spiral pattern onto the conductive layer of each wafer with an etchant-resistive material;

    c) etching the unprinted portion of the conductive layer away so as to form spiral tracks on each substrate;

    d) aligning the wafers and laminating them together in the correct order so as to form a multi-layer device, and

    e) forming conductive paths between at least two of the superposed spiral tracks so as to provide at least one multi-layer inductor.



    [0010] Preferably, the step of forming the conductive paths includes the steps of providing conductive terminals at the ends of each spiral track, aligning the conductive terminals, forming holes through successive conductive terminals, and filling the holes a conductive material.

    [0011] According to a further aspect of the invention, there is provided a token validation device for statically measuring one or more physical characteristics of a token comprising a coil arrangement having at least two superposed planar spiral tracks which are separated by an insulating layer of a multi-layer electrical device, a signal generator for generating a signal having a predetermined magnitude and frequency for receipt by the inductor, and signal processing means for receiving from the inductor a signal representative of the physical characteristics of the token.

    [0012] Preferably, the token validation device includes comparator means for comparing the signal processed by the signal processing means with a reference signal, for assessing the validity of the token being measured.

    [0013] Conveniently, the token validation device includes at least two superposed inductors, and sequential switching means for selectively energising the inductors one at a time, for static measurement of at least two physical characteristics of the token.

    [0014] The token validation device preferably comprises three superposed inductors arranged to measure sequentially the respective core resistivity, the surface resistivity and the size of the token.

    [0015] The invention includes a token validation device which is fitted with a coil arrangement of the type described above.

    [0016] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings:

    Figure 1 shows a schematic circuit diagram of a coin validator circuit

    Figures 2A to 2D show the respective overlying spiral track layouts of a multi-layer printed circuit board which together constitute a single inductor;

    Figures 3 and 4 show a further two overlying spiral track layouts of the printed circuit board making up a further inductor; and

    Figure 5 shows an exploded perspective view of a plurality of printed circuit boards which make up an inductive coil arrangement



    [0017] Referring now to Figure 1, a coin validator circuit 10 has first, second and third respective measuring inductors, or coils 12, 14 and 16 having respective inductances of 15wH, 5f..lH and 85wH. The inductors 12,14 and 16 together constitute an inductive coil arrangement 18 formed on a series of multi-layer printed circuit boards, details of which will be described further on in the specification.

    [0018] The first, second and third inductors 12, 14 and 16 form part of respective LC oscillators 20, 22 and 24. The oscillator 20, which includes the first coil 12 and an appropriately sized separate capacitor 20A, operates at a resonant frequency of approximately 100kHz, and energises the first coil at this frequency in order to measure the core resistivity of a coin 26 which is held in a stationary position adjacent the inductive coil arrangement 18 by means of a coin validator mechanism. The second LC oscillator 22, which includes a capacitor 22A, energises the second coil 14 at a frequency of approximately 1 MHz in order to measure the resistivity of the coin plating. The third oscillator 24, which has an associated capacitor 24A, energises the third coil 16 at a frequency of approximately 1,1 MHz for measuring the size of the coin 26. Operation of the coin validator circuit 10 is controlled by means of central signal processing and interface unit 28. A RAM or EEPROM memory module 30 is linked to the central processing unit 28, and stored within it is data relating to the physical characteristics of various standard coin types and configurations.

    [0019] Once the coin 26 has been brought to a halt adjacent the coil arrangement 18, the three LC oscillators 20,22 and 24 are activated sequentially for coin data measurements. The first oscillator 20 is activated first, and energises the first coil 14. The core resistivity of the coin 26 causes the peak-to-peak signal level from the first oscillator to drop. The attenuated signal from the coil 12 is rectified and smoothed by means of a rectifier 32, and is subsequently digitised by means of an A/D converter 34 for reception at the CPU 28.

    [0020] After the first oscillator 20 has been disabled, the second oscillator 22 is enabled to measure the coin plating resistivity. The second coil 14 is energised, and the resulting signal is smoothed and rectified by the rectifier 32, is digitised at the A/D converter 34, and is subsequently received by the CPU 28. The second oscillator is turned off and the third oscillator 24 then energises the coil 16 for measuring the size of the coin 26 on the basis of the coin 26 causing a change of inductance in the coil 16, thereby altering the frequency of the oscillator 24. The return frequency is measured by means of a counter 36 which is enabled for a predetermined period. The CPU in turn reads a digital value from the counter 36.

    [0021] Once they have been received and stored at the CPU 28, the three digital values are compared with corresponding digital values representative of valid coin types, which have been stored in the RAM or EEPROM memory module 30. If the stored and measured values correspond, this indicates that the coin 26 is valid and a signal from the CPU energises a mechanical gate or other steering means for accepting the coin 26. On the other hand, if the various values do not coincide, then a rejection signal is transmitted to the coin validation apparatus, causing the coin 26 to be rejected. The entire token validation measuring process takes approximately 150ms.

    [0022] Referring now to Figures 2A to 2D, the first inductor 12 is formed from four superposed printed circuit boards 72 to 78, comprising respective insulating substrate wafers 72A to 78A carrying respective spiral tracks 38, 46, 52 and 58 which are etched from conductive copper carried on the upper surfaces of the substrate wafers 72A to 78A.

    [0023] The top spiral track 38 of the first inductor 12 has an output which is linked to an output terminal 40. The top spiral track 38 spirals inwardly to a centre terminal 42 from where it is plated through to a centre terminal 44 provided in the following spiral track 46 on the wafer 74A. The spiral track 46 whorls outwardly in a clockwise direction, and terminates at an outer peripheral terminal 48 which is plated through to a corresponding terminal 50 in the following spiral track 52. The spiral track 52 whorls inwardly to a centre point 54, from where it in turn passes to a corresponding centre point in the next spiral track 58, which spirals outwardly and terminates at an output terminal 60. By etching the various spiral tracks out of the alternating conductive layers of a series of printed circuit boards, and by subsequently superposing the printed circuit boards, a single extremely compact inductive coil arrangement may be provided, having a number of measuring inductors with a relatively high inductance.

    [0024] The second inductor 14 in the inductive coil arrangement is illustrated schematically in Figure 5, and comprises a pair of overlapping spiral tracks 61 and 61A carried on respective substrate wafers 80A and 82A. The next two printed circuit boards 84 and 86 form the third coil 16, which comprises two spiral tracks, which are illustrated in respective Figures 3 and 4. The spiral track 62 illustrated in Figure 3 has an input terminal 64 which spirals inwardly towards a centre terminal 66. The centre terminal 66 is plated through to a corresponding centre terminal 68 in the spiral track 70.

    [0025] Turning now to Figure 5, an exploded perspective view illustrating the manner in which the coil arrangement is assembled is shown. Eight separate printed circuit boards 72 to 86 are provided for forming the three aforementioned inductors 12, 14 and 16. Each printed circuit board 72 to 86 has a respective insulating substrate wafer 72A to 86A with a conductive copper cladding on its upper face. Each of the eight spiral tracks are printed onto the copper cladding using an etchant resistant material, and the unprinted areas are removed by a photosensitive or other etchant.

    [0026] The eight suitably prepared printed circuit boards 72 to 86 are then arranged in the correct sequence, together with an uncladded insulating end wafer 88, are aligned, and are laminated or bonded together to form a multi-layer device. Holes, such as those illustrated at 90 in Figure 2D, are then drilled through the multi-layer device at the various terminals, and a conductive solder is injected through the holes so as to provide the appropriate conductive paths, such as the paths extending between the centre terminals 42 and 44, between the outer peripheral terminals 48 and 50 and between the centre terminals and 54 and 56. The end wafer 88 ensures that the spiral tracks remain unaffected while through-plating is taking place. The internal connections between the spiral tracks are illustrated schematically at 92 in Figure 5. Blind or buried vias may be used in place of holes and solder in order to effect connections between adjacent spiral tracks.

    [0027] The inductive coil arrangement 18 may take a variety of forms. Several single-layer inductors may be etched out of successive conductive layers of a multi-layer printed circuit board. Alternatively, a single coil may comprise three or more overlapping spiral tracks of three or more single printed circuit boards which have been sandwiched together. In the specific embodiment described above, the eight double layered printed circuit boards 72 to 86 may be replaced by four triple layered pcb's having conductive layers on opposite faces of the wafer substrate. Spiral tracks are etched onto the conductive layers, and the four pcb's are then sandwiched between five insulating wafers. Any other multi-layer electrical device, in which conductive and insulating layers alternate, may be utilised.


    Claims

    1. An inductive coil arrangement (18) for measuring at least one physical characteristic of an object (26), characterised in that the coil arrangement (18) comprises at least one inductor (12,14,16) formed out of at least two superposed planar spiral tracks (38, 46, 52, 58, 61, 61 A, 62, 70) separated by an insulating layer (72A, 74A, 76A, 78A, 80A, 82A, 84A, 86A) of a multi-layer electrical device (72, 74, 76, 78, 80, 82, 84, 86) and having a conductive path (92) extending between the tracks.
     
    2. An inductive coil arrangement as claimed in claim 1 characterised in that it comprises a plurality of superposed inductors (12,14,16), each inductor being arranged to measure different physical characteristics of an object (26).
     
    3. An inductive coil arrangement as claimed in either one of the preceding claims characterised in that each spiral track (38, 46, 52, 58, 61, 64, 62, 70) is etched from a conductive layer on one face of an insulating substrate wafer (72A, 74A, 76A, 78A, 80A, 82A, 84A, 86A), and each inductor (12,14,16) comprises a plurality of alternating insulating substrate wafers and spiral tracks laminated together.
     
    4. An inductive coil arrangement as claimed in any one of the preceding claims characterised in that the conductive path (92) between the tracks extends through the insulating layer from a centre terminal (42,54) of one spiral track (38,52) to a centre terminal (44,56) of the superposed spiral track (46,58).
     
    5. An inductive coil arrangement as claimed in any one of claims 1 to 3 characterised in that he conductive path extends through the insulating layer (76A) from an outer peripheral terminal (50) of one spiral track (52) to an outer peripheral terminal (48) of the superposed spiral track (46).
     
    6. An inductive coil arrangement as claimed in any one of the preceding claims characterised in that it comprises first, second and third superposed inductors (12,14,16) forming part of a token validation apparatus (10), the first inductor (12) being arranged to measure the core resistivity of a token (26), the second inductor (14) being arranged to measure the surface resistivity of the token, and the third inductor (16) being arranged to measure the size of the token.
     
    7. A method of manufacturing an inductive coil arrangement (18) comprises the steps of:

    a) providing a plurality of planar insulating substrate wafers (72A, 74A, 76A, 78A, 80A, 82A, 84A, 86A), each wafer carrying a conductive layer on one side thereof;

    b) printing a spiral pattern onto the conductive layer of each wafer with an etchant-resistive material;

    c) etching the unprinted portion of the conductive layer away so as to form spiral tracks (38, 46, 52, 58, 61, 61 A, 62, 70) on each substrate;

    d) aligning the wafers and laminating them together in the correct order so as to form a multi-layer device (18), and

    e) forming conductive paths (92) between at least two of the superposed spiral tracks so as to provide at least one multi-layer inductor (12,14,16).


     
    8. A method of manufacturing an inductive coil arrangement as claimed in claim 7 characterised in that the step of forming the conductive paths includes the steps of providing conductive terminals (40, 42, 44, 48, 50, 54, 56, 64, 66, 68) at the ends of each spiral track, aligning the conductive terminals, forming holes (90) through successive conductive terminals, and filling the holes with a conductive material.
     
    9. A token validation device for statically measuring one or more physical characteristics of a token, characterised in that it comprises a coil arrangement (18) having at least one inductor (12,14,16) formed from at least two superposed planar spiral tracks (38, 46, 52, 58, 61, 61A, 62, 70) which are separated by an insulating layer (72A, 74A, 76A, 78A, 80A, 82A, 84A, 86A) of a multi-layer electrical device (72, 74, 76, 78, 80, 82, 84, 86), a signal generator (20,22,24) for generating a signal having a predetermined magnitude and frequency for receipt by the inductor, and signal processing means (28,32,34,36) for receiving from the inductor a signal representative of the physical characteristics of the token.
     
    10. A token validation device as claimed in claim 9 characterised in that it includes comparator means (28,30) for comparing the signal processed by the signal processing means with a reference signal, for assessing the validity of the token being measured.
     
    11. A token validation device as claimed in either one of claims 10 or 11 characterised in that it includes at least two superposed inductors (12,14,16), and sequential switching means (28) for selectively energising the inductors one at a time, for static measurement of at least two physical characteristics of the token.
     
    12. A token validation device as claimed in claim 11 characterised in that it includes three superposed inductors (12,14,16) arranged to measure sequentially the respective core resistivity, the surface resistivity and the size of the token.
     
    13. A token validation device as claimed in any one of claims 9 to 12 characterised in that in includes an inductive coil arrangement (18) as claimed in any one of claims 1 to 5.
     




    Drawing