US3463907A - Ticket-checking machines - Google Patents

Description

Aug. 26, 1969 E. LEWIS TICKET-CHECKING MACHINES 5 Sheets-Sheet 1 Filed Jan. 27, 1966 @Sh @A ESS sr o Vqzwr H:

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Aug. 26, 1969 E. L Ewls 3,463,907A

TICKET-CHECKING MACHINES Filed Jan. 27. 1966 5 Sheets--SheefI 2 5E C UNDAR Y C UNNE C TONS Aug. 26, 1969 E. L Ewls 3,463,907

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United States Patent O 3,463,907 TlCKET-CHECKING MACHINES Eric Lewis, Malmesbury, England, assigner to The Plessey Company Limited, Ilford, England, a British company Filed Jan. 27, 1966, Ser. No. 529,169 Claims priority, application Great Britain, Feb. 11, 1965, 5,97 8/ 65 Int. Cl. Gtk 7/08 U.S. Cl. 23S- 61.11 7 Claims ABSTRACT OF THE DISCLGSURE A device controlling the automatic cutoff of a singlejourney section, containing a magnetic deposit, from an inserted ticket comprises three parallel ferromagnetic cores, each having a winding, which are arranged at the three corners of an equilateral triangle. When the ticket is in its check position, its deposit aiiects the coupling between two cores. The windings of one of these and of the third core are so fed from a common A.C. source that, in the absence of a ticket deposit the voltage induced in the winding of the remaining core supplemented if desired by a supplement voltage derived from the same A.C. source constitutes a small bias voltage in antiphase to the output voltage produced by a magnetic deposit, and the resultant biased output is rectified and compared with a reference voltage, also derived from the same A.C. source and rectified to produce a D.C. output of one polarity in the presence of a magnetic deposit between given limits of magnetic conductance and of the opposite polarity in all other cases. This D.C. comparator output is utilized to operate a guillotine and printer via a trigger circuit and a logic circuit, the latter controlled by a front microswitch opened by the presence of a ticket and a rear microswitch opened by abutment of the ticket against the stop, to prevent operation of the guillotine and printer until the ticket rests against the stop and to prevent reoperation until the front microswitch has been cleared.

DISCLOSURE This invention relates to apparatus for this detection of a magnetic or conductive deposit on a carrier and is more particularly intended for, though not exclusively applicable to, machines for checking tickets having a magnetic imprint and more particularly for the checking and automatic part-cancellation of magnetic (or if desired electroconductive) imprints arranged in a uniformly spaced series from one end of a ticket form towards the other, each imprint representing a journey, fare stage, or the like.

According to the present invention the device includes means for locating the carrier with the deposit in a predetermined position, and a magnetic bridge in which three magnetic cores, each having a winding, are magnetically coupled by their fluxes and so arranged with reference to the deposit when the carrier is in said predetermined position, that this deposit discriminatively iniiuences the flux that couples one of the cores with one of the other two cores, means for feeding the winding of one of the cores with alternating current, preferably of radio-frequency, to form a transformer primary winding, while the winding of a second core is utilised as a secondary winding, the winding on the third core being connected in series with either of the two windings referred to in such manner as to oppose the effect of the same, thus in the case of series connection with the primary winding, producing in the secondary winding a flux which is opposite and approximately equal to the flux produced by the said primary Winding, or in the case of series connection with 3,463,907 Patented Aug. 26, 1969 BCC the secondary winding, to produce, as a result of the ux passing through the third core from the primary winding, a voltage which is opposite and approximately equal to the voltage produced in the said secondary winding. It will be appreciated that with this arrangement a secondary-voltage output is obtained which, from a predetermined low value occurring in the absence of any deposit, will, in the case of a magnetic deposit, be either substantially in phase or substantially in antiphase with the source, according to the direction of the residual unbalance, and will increase in one direction, for example in a positive direction relating to the in-phase voltage, in accordance with the amount of the deposit, while the presence of an electroconductive nonmagnetic deposit will produce a variation opposite to the first-mentioned variation, i.e., in the example a variation in antiphase to the input voltage. It will also be appreciated that the magnitude of the variation will depend on the permeability or electroconduction qualities of the deposit.

Preferably the arrangement is such that in the absence of a deposit there is a residual secondary voltage in antiphase to the variation produced by the presence of a magnetic deposit. In this case a magnetic deposit of a permeability value not exceeding a predetermined value will reduce the absolute value of the output voltage, since the variation produced is in phase opposition to the residual voltage mentioned. For very small permeability values `the resultant output will thus be of the same phase as the residual output but of smaller value, and for somewhat greater permeability values the resultant output will pass through zero and with increasing permeability a resultant voltage will appear which is in phase opposition to the residual voltage, but up to the predetermined value of permeability is still smaller in value than the residual Voltage (or a desired fraction thereof); when however the permeability is above the permitted value, the resultant output voltage will rise to a value (in phase opposition to the residual voltage) which is greater than the residual voltage. A conductive deposit will produce variation in phase with the residual voltage and will therefore always produce a resultant voltage output higher than the residual voltage. Thus, if the absolute value of the output voltage is utilised to produce an acceptance response if the residual voltage is reduced below a predetermined limit, and a rejection response or no response if the residual Voltage is left unaltered, or reduced less than to the predetermined limit, a device has been achieved which will accept only deposits of magnetic material within predetermined magnetic-conduction limits.

Preferably the magnetic bridge comprises three cores extending parallel to each other at the corners of an equilateral hiangle and embedded with their windings in a molding of insulating material. According to a further preferred feature tof the invention, the magnetic bridge is fed from an oscillator, and the voltage output of the bridge in the absence of a deposit is arranged, either by the construction of the bridge, or by superposition of a suitable Voltage derived from the same Oscillator, to be in antiphase with the voltage variation produced by the presence of the acceptable deposit, and this output as well as a reference voltage also derived from the same oscillator are each rectified, the rectified voltages being supplied to a comparator which produces a D.C. output of one given polarity when the voltage of the biased bridge output is greater, and of the opposite polarity when the biased bridge output is smaller than the reference voltage. The output of the comparator is then fed to a trigger or gate circuit which becomes 'operative to produce an acceptance response only in the latter case and subject further to a logic circuit which has two other inputs respectively controlled by two microswitch feelers each controlled by the presence of a ticket in the device, one feeler being arranged to be operated only when a ticket is fully inserted against a stop determining the checking position, and the other being arranged at a point on the path of the ticket from an insertion opening to the stop so as to be operated whenever a ticket has been inserted beyond an intermediate point of this path. The logic circuit is arranged to permit an acceptance response only when both microswitches have been operated, and then to prevent a further ac ceptance response until both, or at least the last-mentioned one, of the microswitches has been closed and reopened after the preceding acceptance response. In the preferred embodiment the response consists in the issue of a pulse which is utilized for initiating the operation of a mechanical device including a guillotine which cuts off an end porton of the ticket including the deposit nearest to this end, the length of such portion being equal to the spacing of the individual deposits; preferably the acceptance pulse also causes a printing device to print identification marks on the opposite face of the remainder of the ticket, near the end of this remainder.

It will be readily appreciated that the provision of the llogic circuit not only ensures that the mechanism is not operated until the ticket has reached the appropriate position in which the first remaining deposit is in the correct position, and that the guillotine cut will be so positioned that the remainder of the ticket will be operative at the next insertion if any deposit is left, but that the logic circuit also prevents accidental cutting oft of more than one deposit at a time due to the users maintaining pressure on the ticket after the first operation of the guillotine.

IOne embodiment of the invention as applied to such ticket checking machines will now be described in more detail with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic block diagram of the circuit employed.

FIGURE 2 is a schematic perspective View of the magnetic bridge constituting the sensing element.

FIGURE 3 is an enlarged perspective view 'of a practical embodiment of a sensing element including the magnetic bridge.

FIGURE 4 is a diagram of a suitable rectifier and comparator arrangement.

FIGURE 5 shows a half-wave voltage doubler and rectifier circuit, of which two are combined in the circuit of FIGURE 4.

FIGURE 6 is a circuit diagram of 'the trigger circuit for response to negative voltage output from the comparator.

FIGURE 7 is a similar trigger circuit suitable for alternative use when response to positive output signals is required.

FIGURE 8 is a circuit diagram of a suitable transistorized oscillator circuit.

FIGUR-E 9 is a diagram indicating the output of the comparator circuit plotted over the magnetic (positive) or electric (negative) conduction qualities of the deposit under test, assuming a .G5-volt response overlap in the trigger circuit between the on and off states, and

FIGURE l0 is a circuit diagram of a logic circuit which serves to apply the acceptance response of the trigger circuit of FIGURE 6 to a guillotine and printing mechanism when a ticket has been fully inserted into the machine, and then to prevent reoperation of the mechanism until the ticket has been withdrawn.

Referring now rst to FIGURE 1, the device according to the invention will be considered as applied to an automatic imprint checking and cancelling machine for tickets having imprints of a magnetic deposit, each representing a journey or part-journey, arranged at one end of the ticket, in uniformly spaced `succession from that end. The device comprises an oscillator for a radio-frequency of approximately 1.6 megacycles/sec. which produces three output voltages in phase with each other and has therefore been represented as three generators 1, 2 and 3, driven by a common shaft 4. The output voltage of gern erator 1 feeds two series-connected primary windings 11 and 12 of a sensing element 5 which in addition includes a secondary winding 13. The three windings 11, 12 and 13 are respectively wound on cores 14, 15 and 16 which, as shown in FIGURES 2 and 3, extend parallel to each other and are arranged, at the corners of an equilateral triangle 17, in an insulating body 18 encased in a brass sleeve 19. Means 22 are provided for guiding a ticket 10 to, and locating it in, the position shown in FIGURE 3, in which the magnetic imprint 6 nearest to the end of a valid ticket forms a magnetic shunt reducing the magnetic reluctance of the flux path coupling cores 14 and 16, while the magnetic reluctance of the paths coupling core 15 with either of the two cores 14 and 16 is left substantially unaltered. The two primary windings 11 and 12 are so arranged on the cores 14 and 15 that the fluxes respectively produced by them in core 16 due to magnetic coupling are opposite and, in the absence of a deposit-carrying ticket, substantially equal.

Referring now once more to FIGURE 1, the secondary winding 13 is connected in series with a voltage RVl, derived from generator 2 by la voltage divider 7, which is in antiphase to such voltage as is induced in winding 13 by the primary windings 11 and 12 in the presence of a ticket having a magnetic deposit in the appropriate position. The resultant composite voltage A will, therefore, in absence of a ticket, be in such antiphase position and be equal to the value RVl. When a ticket having a magnetizable deposit is in position, the value of this cornposite antiphase voltage will decrease with increasing amounts of deposit to become Zero at a predetermined amount of deposit, and with further increasing amounts of deposit the composite voltage will change to the inphase position and progressively increase in valve as the amount of deposit increases. When on the other hand a ticket carrying an electroconductive nonmagnetic deposit is presented, the antiphase voltage derived from the winding 13 is added to the antiphase voltage RV1, and an increased antiphase output will appear at A. The said resultant composite voltage A is supplied via an amplifier S and a rectifier 9a to one input of a comparator 9 to a second input of which the voltage output o of the generator 3 is supplied via a second rectifier 9b the voltage RVl being adjusted to be equal in value to this voltage output o. It will be readily appreciated that with this arrangement in the absence of a deposit-carrying ticket the two input voltages of the comparator 9' are equal, resulting in zero output, and that in the presence of a ticket having an electroconductive deposit the rectified input voltage A will exceed the rectified votlage o, a condition which will produce a positive D.C. output of the comparator 9. Similarly a ticket having a magnetic deposit exceeding a certain amount will produce an in-phase resultant output of greater absolute value than the bias voltage RVl, and will thus likewise produce a positive comparator output. On the other hand a magnetic deposit of less than this amount will result in lowering the value of the voltage A below the value of voltage o and will thus produce a negative comparator output. This negative output is utilized to produce, via a logic system 23, an acceptance response when this negative output exceeds a predetermined minimum value sufficient to operate a trigger 22 while ensuring a rejection of magnetic deposits below a predetermined minimum amount as well as of magnetic deposits exceeding a predetermined maximum amount somewhat lower than the above-mentioned certain amount.

The combined rectifier and comparator circuit is shown in FIGURE 4. The amplified output of the sensing element, constituting the first input of the circuit, is represented by a generator 20 producing an A.C. voltage V1, while the second input is represented by a generator 3 producing an A.C. votlage V2. The circuit of FIGURE 4 can be considered as a combination of two half-Wave voltage-doubler rectifier circuits, each as shown in FIG- URE 5, to which the outputs of generators 20 and 3 are respectively supplied, and whose outputs are connected in opposition by a cross-connection 21. It will be observed that since each of the voltages from sources and 3 is rectied individually, and the rectified output voltages are connected in opposition, the comparator and subsequent parts of the circuit are not phase-sensitive but only responsive to the absolute values of the two voltages V1 and V2, and that the output voltages of the comparator will be positive when the voltage V1 of source 20, that is to say the amplified vector sum of the output from sensing element 11, 12, 13 and the bias voltage from divider 7 is greater than the reference voltage from source 3, and negative in the converse case.

In FIGURE 9 the resultant output voltage of the cornparator has been plotted as a function of the presence of magnetic coating material to the right of the zero line and of the presence of electroconductive coating material to the left of the zero line. The iigure shows that the comparator will produce no output in the absence of any coating and a negative output in the presence of a moderate amount of magnetic coating, while with progressively greater amounts of magnetic coating the negative output first drops to zero and is eventually replaced by a positive output, which is also present in the case of any electrically conducting nonmagnetic coating material.

The comparator output is fed to a trigger circuit as indicated at 22, FIGURE 1. A suitable trigger circuit using a p-n-p silicon transistor VT1 in the rst stage and n-p-n germanium transistors VT2 and VT3 in the second and third stages is shown in FIGURE 6, while FIGURE 7 illustrates an alternative trigger circuit which is intended for use when response to positive, instead of negative output signals is required, and in which the lirst-stage transistor VT1 is an n-p-n silicon transistor and the secondstage and third-stage transistors VT2 and VT3 are p-n-p germanium transistors. In each case the values of resistors R1, R2 and R4 are so chosen that R1 R2 R.1, and the current in resistor R4, or if desired the voltage drop across R4, or part of this voltage drop, can be utilized as output of the circuit.

In the embodiment illustrated in FIGURE 1, a logic control circuit 23 is interposed between this trigger output and the mechanism which serves to cutoi the first available deposit on the ticket and to provide the ticket with an imprint. A suitable logic circuit is illustrated in FIGURE 10. This logic circiut comprises a irst microswitch M1 which is interposed between resistor R4 of the trigger circuit and the positive terminal marked -l-Ve, and which is so arranged as to be normally closed but to be opened by a ticket when upon full insertion into the machine the ticket strikes an insertion-terminating stop, and a further microswitch M2 which is arranged to remain closed until the ticket passes an intermediate point of its insertion into the machine. For easier distinction the microswitch M1 will be referred to as the rear microswitch and microswitch M2 as the front microswitch. The illustrated logic circuit may be said to comprise .a trigger circuit constituted by two transistors I1 and J8 which is utilized as a memory device and is arranged to have a wide voltage differential of, for example, 2.0 volt. The first-stage transistor I1 is biased by a potential divider constituted by two resistors R23 and R24 connected across a iixed voltage of, for example, 16 volt, to bias the transistor J1 to the midpoint of the trigger-circuit characteristic, so that the bias voltage is adequate to hold transistor I7 in its switched-on condition after it has been switched on by the application of an additional voltage, but insuicient to overcome the voltage which is developed at the emitter of transistor J1 across a resistor R21 when the second transistor I8 conducts. C13 in an electrolytic capacitor of high capacitance, for example 2 pif. The circuit is illustrated in the condition occurring when no ticket is in the machine, and both microswitch M1 and M2 are accordingly closed. In this condition the front microswitch M2 shunts by a low-value resistor R25 the bias that is fed to transistor I1 thereby rendering transistor J7 nonconducting and causing transistor J8 to conduct. At the same time the rear microswitch M1 connects one end of resistor R4 to the positive line, causing any output current which may be coming from the preceding trigger circuit via transistors VT3, to bypass the logic circuit. On the other hand, a blocking diode D1 prevents the closing of microswitch M1 from affecting the bias voltage for transistor J1 developed across resistor R21. Accordingly transistor I is off and transistor I 8 is on (conducting) when no ticket is in the machine.

When a ticket is now inserted, it will rst open the front microswitch M2, thereby allowing the bias voltage developed across resistor R21 to rise to its normal level, `since the still closed rear microswitch M1 is prevented by the blocking diode D7 from short-circuiting this resistor. Since, however, the bias voltage, as explained above, is insufficient in itself to overcome the emitter voltage of transistor I7 when transistor J8 conducts, the transistor I7 remains nonconductive. The ticket then proceeds to its checking position, where its validity is determined by the sensing system. Since the presence of a valid deposit is intended to operate a guillotine cutting the end portion of a ticket, it is important to prevent this opertaion from taking place until the ticket rests against a stop exactly determining the desired position. To ensure this the rear microswitch M1 has been provided, which remains closed to prevent an output from the logic circuit from affecting the transistor I7 until, on reaching the stop, the ticket opens this rear microswitch. In addition the rear microswitch M1 is utilised to supply, when open, current to a terminal H. This current produces a warning signal when at the time the microswitch M1 is open due to the presence of a ticket or other object, the output of the trigger transistor VT3 is a rejection response, while as will be explained below, in the case of an acceptance response microswitch M1 is reset within a few microseconds to its closed position due to the guillotine operation, thus preventing the appearance of the warning signal.

When a valid ticket has been inserted so that an acceptance response is obtained from the transistor VT2, the output current from transistor VT3 is caused to by-pass the base of transistor J1 via the closed rear microswitch M1 until the ticket when it is fully inserted, opens the switch, thus allowing the trigger output current to act on the base of transistor I f1 which, when switch M2 is open, is biased in the conducting direction. The flow of current from transistor VT3 through resistor 24 will increase the voltage drop in resistor R21 suiciently to switch on transistor J7, and as a consequence to switch olf transistor J2. The switching-off of transistor J8 is utilized in a manner to be described below, to operate a guillotine and printing mechanism to cut off an end portion of the ticket and apply an imprint to the main portion of the ticket. At the same time the cessation of the current through transistor I 8 and the resistor 29 of relatively low Value compared to resistor 28, considerably reduces the voltage drop in resistor R27, thereby making the emitter of transistor I 7 more positive than before.

When, as the result of the switching off of transistor I 8, the end of the ticket has been cut ofr, the rear microswitch M1 will return to its closed position and cause the trigger output of the sensing system in the collector circuit of transistor VT3 to bypass the network controlling the base voltage of transistor I1. The voltage across resistor R21 therefore returns to its original bias level; but since, due to the switching 01T of transistor I8, the emitter of transistor I7 has, as mentioned above, become much more positive than the bias voltage, the transistor I7 remains in its on condition. This fact prevents any unintended repeat operation of the guillotine even if pressure on the ticket is maintained so that the ticket, after the cutting-off of is original end portion, once more opens the rear microswitch M1, since the transistor I7, being already in its on condition, will not again be affected Iby the resulting increase in current through the resistor R24.

When the ticket is now withdrawn, not only rear microswitch M1 but also front microswitch M2 will close. The closing of the front switch M2 reduces the base bias of transistor J, :sufficiently to cause transistor J1 to return to its olf condition, thereby causing transistor J8 to be switch on, and resetting the logic circuit.

As mentioned before, the switch-off of transistor I8 is utilized to operate the guillotine and printing mechanism. This is effected by a relay S which is controlled by a further transistor J9 connected as shown in FIG- URE 10. The operation is as follows:

As long las transistor J8 conducts, the voltage ldrop in resistor R29 causes the collector voltage of transistor J8 to be considerably more positive than a voltage which is applied to the positive terminal of a diode D9, which latter therefore is nonconducting and the charge of a coupling capacitor C11 will correspondingly be low. Now base current will flow through transistor J9, which is a germanium transistor whose emitter circuit includes a forward-biased silicon diode D11. When now, after insertion of a valid ticket, transistor J8 becomes switched olf, its collector voltage grows more negative, causing base current to flow in transistor J9, which thus becomes switched on, and condenser C14 will at the same time be charged. The resulting collector current of transistor I9 is utilized to operate the relay S controlling the guillotine and printing mechanism. As capacitor C11 approaches its full charge, the charging current, which is also the base current of transistor J9, will rapidly be reduced, causing transistor I9 to be switched olf again after a short period, thereby releasing the ticket after minimum of time. When the ticket has Ibeen removed from the machine, causing transistor .T8 to become conducting again, the base of transistor J9 becomes positive by the forward voltage of a shunt diode D10, thus restoring the initial condition.

What I claim is:

1. Apparatus for detecting the presence on a carrier of an amount of magnetic or electroconductive deposit between a predetermined maximum and a predetermined minimum which comprises in combination: a magnetic bridge in which three magnetic cores, each having a winding, are mechanically coupled by their fluxes, means for locating such carrier with the deposit in a predetermined position relative to said cores, the cores being so arranged with reference to the deposit when the carrier is thus located, that such deposit discriminately influences the flux that couples one of the three cores with One of the other two cores, means for feeding the winding of one of the cores with alternating current to form a transformer primary winding, while the winding of a Second core is utilised as a secondary winding, the winding of the third core being so connected in series with either of the two windings referred to as to oppose the field effect thereof, means for providing a residual unbalance in such manner that in the absence of a deposit there is a residual secondary-voltage output in antiphase to the Variation produced by the presence of an acceptable deposit, means for feeding the magnetic bridge with -current from an alternating-current source, means for rectifying the resultant voltage output, means for deriving from said source a reference voltage and for rectifying said reference voltage, and a voltage comparator having a first input to which the rectified said resultant voltage is applied and a second voltage input to which the rectified said reference voltage is supplied to produce a comparator output whose polarity l1s determined by the algebraic sign of the diiference of said rectified voltages.

2. Apparatus as claimed in claim l, wherein the means providing a residual unbalance are so constructed that this unbalance is in antiphase to the voltage variation produced by a magnetizable deposit.

3. Apparatus as claimed in claim 1 wherein the magnetic bridge comprises three cores arranged side by side to extend parallel to each other to the same side of a common end surface at the corners of an equilateral triangle and all jointly embedded with their windings in a molding of insulating material.

4. Apparatus as claimed in claim 1, including an oscillator feeding the magnetic bridge, and means for deriving a reference voltage from the same oscillator.

5. Apparatus as claimed in claim il, wherein the means providing a residual unbalance include a potentiometer supplied with current derived from said source, the voltage output of the potentiometer being connected in series with the said secondary winding.

6. Apparatus as claimediin claim 4, further comprising a trigger or gate circuit to which the comparator output is fed, and which is arranged to become operative to produce an acceptance response only when the biased bridge output is maller than the reference voltage and subject further to a logic circuit which has two other inputs respectively controlled by two microswitch feelers each controlled `by the presence of a ticket in the device, one feeler being arranged to be operated only when a ticket is fully inserted against a stop determining the checking position, and the other being arranged at a point on the path of the ticket from an insertion opening to the stop so as to be operated whenever a ticket has been inserted beyond an intermediate point of this path.

7. Ticket checking apparatus as claimed in claim 6, wherein the logic circuit is arranged to permit an acceptance response only when both microswitches have been operated, and then to prevent a further acceptance response until at least the last-mentioned one, one of the microswitches has been closed and reopened after the preceding acceptance response.

References Cited UNITED STATES PATENT-S 2,513,745 7/1950 Reynolds 324--41 2,858,505 10/1958 Shawhan 324-41 2,915,699 12/1959 Mierendorf et al 324-41 MAYNARD R. WILBUR, Primary Examiner THOMAS J. SLOYAN, Assistant Examiner U.S. Cl. XR. 324-34

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