Taximeter Arrangements

Abstract

An electronic taximeter comprises a time reference pulse source, a distance travelled pulse source, a time measuring circuit, a level detector, a gate circuit and a fare indicator. When the vehicle is stopped or is running below a selected speed pulses are supplied by the time reference pulse source to actuate the fare indicator while any pulses from the distance travelled pulse source are blocked by the gate. When the vehicle is running at a speed higher than the selected speed, as determined by the time measuring circuit and level detector, the gate is opened so that pulses from the distance travelled pulse source are admitted to the fare indicator and the time reference pulse source is disabled.

Description

The invention relates to taximeter arrangements in which time and distance information in the form of electrical impulses is used, on the one hand, to calculate the fare and, on the other hand, for supervisory registration, such taximeter arrangements normally, on the one hand, comprising two impulse sources, one of which yields time reference impulses and the other one of which generates distance impulses and, on the other hand, comprising means for treating the impulse information for controlling a figure indicating unit showing the fare and the distance passed at predetermined conditions.

The fare calculation in connection with taximeter registration is based on ordinances issued by authorities, the rule being that the fare is based in part on hire time, in part on the driving distance and in part on the tariff. It is here to be noted that the calculation of the fare in practice is performed in such a way that at a speed below a certain predetermined speed in a vehicle with the fare indicator activated only time-depending forward stepping of the fare figures will take place, whereas above said speed a forward-stepping depending on distance occurs. Due to this, all taximeter constructions must comprise a device adapted to determine this speed which could be termed the critical speed.

Prior art arrangements working with time and distance information in the form of electric impulses comprise means enabling the impulse frequency of time reference impulses to be compared with the frequency of the distance impulses, the actually higher impulse frequency being determined in the comparison device and selected to feed the fare calculation means.

The general problems encountered in a comparison device for the respective impulse frequencies reside, on the one hand, in providing a definite breaking frequency and, on the other hand, in bringing about a change having no hysteresis and not involving loss of impulses.

According to the present invention there has been obtained a new taximeter construction in which the above problems have been solved in a novel and fundamental way whereby simultaneously essential advantages have been obtained due to the fact that a great flexibility is obtained in the adaptation of the device to changed tariffs. In the first line, however, it has been the purpose of the invention to provide a taximeter which is suitable of being constructed from miniature-scale digital electronic circuits. Such circuits are now generally accessible with known circuit connections for impulse information treatment of problems corresponding to the fare calculation in the present case, the use of such circuits involving an obvious natural transition from mechanical to electrical counting means for the calculation.

Also in line with the general development of the technique it is here possible to imagine new possibilities as far as fare debitation processes are concerned.

Obviously a transition to electronic counting circuits enables more complicated calculating processes to be performed than those permitted by mechanical computer means. Accordingly it is essential to obtain a flexible construction of the taximeter in order to comply with such requirements.

The characteristic features of the present invention will appear from the attached claims.

The invention will be described in greater detail in connection with an embodiment shown in the drawings in which:

FIG. 1 is a basic circuit diagram of the mutual arrangement of the electronic digital circuits,

FIG. 2 additionally shows the arrangement of the circuits in the form of schematic blocks and,

FIG. 3 illustrates a binary distance impulse generator together with a pulse sequence diagram,

FIG. 4, 5 and 6 illustrate circuits for total distance, time measuring and clock function also together with the corresponding puls sequence diagrams .

According to FIG. 1 which enables the function of the taximeter arrangement to be traced, a distance impulse generator 1 is provided with relays yielding a contact closure for every half meter passed by the vehicle. The contact closures control a pulse generator emitting a square wave having the frequency ratio of 1 period per meter. A subsequent binary computer 2 counts the square pulses and a decoder 3 yields an impulse for every 100 meters. The output pulses actuate a rotary magnet 4 adapted to step forward a counter unit indicating the total distance passed.

When the taximeter is turned on a further rotary magnet 5 is actuated. This magnet operates to step forward a counter indicating the total distance paid.

The square wave from pulse generator 1 triggers a time measuring circuit 6 yielding a voltage which decreases with increasing frequency of the square wave. When the voltage is below a predetermined boundary value a level detector 7 will react and open a gate circuit 8.

Gate circuit 8 passes the distance impulses to a distance debiting binary counter 9. Depending on the distance rate selected a number of distance impulses will be counted for every output impulse from the distance pulse generator 1.

At the same time as the level detector opens the gate circuit 8 a clock 10 is halted. The clock or time pulse generator 10 yields impulses having a frequency of 4 Hz. The clock pulses are counted in a binary counter 11 which after a number of pulses, depending on the selected time rate, yields an output pulse. The output pulses from the distance debitation and time debitation counter are fed to an output circuit 12 from which an output impulse is obtained for every second impulse. The output impulses activate a third rotary magnet 13 adapted to step forward the counter for the fare.

The distance impulse generator 1 comprises, on the one hand, two relays of reed type adapted alternately to be actuated by a magnetic field in dependence on the motion of the vehicle and, on the other hand, a pulse generator comprising a bi-stable flip-flop. The two outputs of the relays will during the alternations of the magnetic field alternately be connected to the ground of the apparatus. By a suitably chosen gearing the output pulses are standardized to two impulses for every passed distance of 1 meter or 1 yard as desired. The pulse generator in turn comprises a bi-stable flip-flop. The outputs of the distance impulse generator are connected to the collectors of the transistors in the flip-flop. If anyone of the outputs of the generators is connected to ground the flip-flop will be caused to tip over in the corresponding direction. As the outputs alternately are connected to ground any fault in any of the relays contacts will mean that no impulses are counted whereby the fault will be immediately detected. By using the double contact arrangement faults caused by contact bounces will be eliminated.

The counter 2 for the total distance comprises 8 binary counter stages, a 3-input NAND circuit and corresponding zero-setting means. On the outputs of the binary counter stages pulses corresponding to 1, 2, 4, 8, 16, 32, 64 and 128 meters, or yards respectively will be obtained. Switching over to 0.1 miles pulses is simply performed by connecting the inputs to the stages of the 16, 32 and 128 yards outputs. When the NAND circuit is receiving signals on all three inputs its output will change from 1 to 0 level. The zero signals chokes a transistor whereby the voltages on the zero-setting inputs of the counters will increase to about 4 Volts. Thereby the counters will be set to zero, the signals on the outputs on the counters will disappear, the output of the NAND circuit will be set to 1 and the transistor of the zero-setting circuit will again become conductive.

The output circuits 3 for the total distance is arranged to lengthen the negative pulse on the output of the NAND circuit. This pulse is too short to enable the rotary magnet to react. For this reason the pulse is lengthened to about 0.3 seconds in a mono-stable flip-flop comprising a NAND circuit and a transistor. The emitter of the transistor is connected to the base of the end transistor. The rotary magnet is connected between the collector of the end transistor and +12 Volts. A diode is also connected across the magnet circuit and protects the transistor against transient voltages. The circuit is dimensioned for a current of 0.5 Ampere at about 25 Ohms inductive charge.

As far as the output circuit 5 for the total distance paid is concerned, no separate counter chain is provided for this function for economic reasons so that there is no memory for accumulating distances less than 100 meters. The indicated distance may therefore deviate from the true value but in the long run the total sum will balance-out statistically. The output circuit 5 comprising transistors in PNP-NPN connection is also dimensioned for 0.5 Amperes at 25 Ohms. The circuit is switched-in by opening contact SIA.

The time measuring circuit 6 comprises two transistors, four diodes and an RCC network. Each time pulse generator 1 changes over, one of the condensers such as CL is discharged. The voltage on the other condenser C2 is then applied to a so-called super emitter follower 14. The discharge condenser C1 immediately starts recharging. When the following distance impulse arrives C2 is discharged instead and the voltage across condenser C1 is connected to emitter follower 14. When no distance impulses arrive -- the vehicle is at standstill -- the output voltage from the emitter follower amounts to about +4 Volts. On the other hand, when the distance impulses arrive at an increasing rate the voltage goes down towards zero. For every distance-time rate combination R is chosen so that the transition takes place at the most suitable speed.

The output of the emitter follower 14 is connected to level detector 7 which is a slightly fed back PNP-NPN transistor switch. The emitter of the PNP transistor is at approximately +2.5 Volts. When the output voltage from the time measuring circuits is below about 2 Volts both transistors start conducting. Thanks to the feed-back the transition from choked to saturated transistors will take place instantaneously, whereby annoying intermediate positions of the gate circuit and the clock are avoided.

At low speed the output signal from the switch is +5 Volts, at high speeds approximately 0 Volt and the switch-over takes place instantaneously. However, due to the feed-back a certain hysteresis is to be found consisting in that the switching in and switching off levels are different. However, the hysteresis is limited to the extent possible.

The gate circuit 8 can be supplied with distance signals in three different ways. A means that the signals are taken from both collectors of the two transistors of the pulse generator. Hereby a distance rate range 1-128 meters in one-meter steps is obtained. B means that the signals are taken only from the one collector of the transistors of the pulse generator which gives a distance rate range 130-256 meters in two-meters steps. Finally, C means that the signals are taken from the collectors of the first binary counter stage in the total distance counter 2. This gives the rate range 260-512 meters in four-meters steps. The distance signals are initially differentiated and the negative pulses obtained hereby yield positive pulses on the output of the NAND circuit. The signal is then applied to the one input of another NAND circuit forming the gate proper. To the other input the signal from the level detector is applied after inversion in a transistor 15. At low speeds the signal is approximately 0 Volt and gate 8 is blocked. Above the selected boundery speed the signal is +5 Volts and the gate is open. The output signal is inverted in a further NAND circuit so that positive output pulses are obtained for feeding counter 9 for distance debitation.

Distance debitation counter 9 comprises eight binary counter stages, a NAND circuit having 8 inputs and zero-setting circuits, this counter operating in the same way as the total distance counter 2. The correct distance rate is adjusted by connecting the inputs of the NAND circuit to certain of the outputs of the counter. Unused inputs are in this case connected to the plus pole of the voltage source.

The clock 10 comprises a transistor oscillator of unijunction type, a blocking transistor 16 and 2 buffer stages for the output signal. The oscillating frequency is adjusted to a value as close to 4 Hz as possible with the aid of a trimming potentiometer P of 10 Kiloohm.

At low speeds the blocking transistor 16 is choked due to the fact that no voltage appears on the output transistor 15 of the level detector. The oscillator circuit is then supplied with voltage and the oscillator is oscillating. At high speeds the transistor 16 is conductive and the voltage supplied to the charging circuit falls below the level at which the unijunction transistor is able to discharge the condenser CL of the charging circuit. By not permitting the voltage to go down to zero the first charge is performed more quickly than the following. This approximately compensates for the charge lost when the clock is halted. The output signal is reinforced in a transistor and a NAND gate, the signal also being inverted. When very long time rates are required an outer condenser not shown may be connected in parallel to CL in order to lower the frequency to 1.6 Hz.

Clock signals feed the counter 11 for the time debitation. It has exactly the same construction as the counter 9 for distance debitation. The time rate is adjusted by connecting the NAND circuit in a predetermined way with the outputs of the various binary counter stages.

The output signals from, on the one hand, the distance debitation counter 9 and, on the other hand, the time debitation counter 11 are fed to an output circuit 12 for the rotary magnet 13 of the debitation counter. The signals are here passed over a NAND circuit to a JK-flip-flop. There a frequency halving is obtained which means that one output pulse is obtained for two impulses. By this procedure two essential advantages are obtained. In the first place less than half a distance debitation unit and half a time debitation unit will be lost in the registration and in the second place a distance debitation unit and a time debitation unit cannot fall out -- almost -- simultaneously. The output pulses trigger a transistor switch which actuates rotary magnet 13 for the stepping forward of the debitation counter.

In order to stop the counting when the passenger is due to pay the debitation counters 9 and 11 are blocked by interrupting the collector voltage to the two transistors 15 and 16, one turning off gate circuit 8 and the other one halting clock 10. Hereby both distance and time pulses are prevented from entering the respective counters.

Before the vehicle is hired again the counters have to be set to zero which is performed by earthing the base of the transistors in the zero-setting circuits of the counters and by earthing the restoring input of the JK-flip-flop in the output circuit 12.

In order to guarantee stable operating conditions in electronic input circuits a voltage stabilization is provided. This is arranged with a series resistance and a parallel-connected zener diode 17. The nominal voltage is 5.1 Volts +5 percent. The stepping magnet circuits 4, 5 and 13 are fed with uncontrolled voltage of 12 to 15 Volts.

The voltage feed goes via two paths, on the one hand, via the switch key and on the other hand, via the occupied marking. Here a diode 18 is provided in order to prevent back current from flowing to the switch key.

The specific advantages obtained by the present invention consists in that the taximeter may be made independent of the absolute value of the impulse frequencies. Thus, for example, the clock itself may have a frequency which under all conditions is higher than the highest distance impulse for frequency. Thanks to the adjustable frequency divider the clock may operate on one and the same frequency all the time and its frequency may be chosen in order to achieve optimum frequency stability or to comply with certain requirements, for example, for the purpose of adapting the device to miniature scale outfit. A change of the time rate is performed simply by adjustment of the frequency divider which may be made without access to frequency measuring devices. By providing separate means for respectively time and distance impulses no systematic pulse losses will be produced which is an essential factor from the point of view of exactitude. Moreover, thanks to the separate feeding paths the mechanism of the fare price indicator can be adapted, as required, to various step lengths for respectively the time and distance impulses.

Claims

What I claim is:

1. Taximeter arrangement in which time and distance information in the form of electric impulses is used for forward stepping of a fare indicator 13, said arrangement comprising, on the one hand, two impulse sources 1, 10, 11 one of which 10, 11 produces time reference impulses where the other one 1 produces distance impulses, and on the other hand, an impulse handling member 9 controlling said fare indicator 13, said taximeter arrangement being adapted to a time-depending rate below a certain predetermined speed and to a distance-depending rate above said speed, characterized by a speed meter 6, 7 which dependent on the speed of the vehicle during transition through the predetermined speed from a lower to a higher speed, on the one hand, opens a gate 8 for the distance impulses to supply these impulses to the impulse handling member 9 and, on the other hand, stops the impulse source 10, 11 also connected to the fare indicator 13 and producing time reference impulses which then cease to feed the fare indicator 13, and vice versa, in order to bring about independently of the mutual frequency relation of the time and distance impulses the change between the time rate and the distance rate.

2. Arrangement as claimed in claim 1, characterized in that the impulse source 10, 11 comprises a frequency divider 11 which is adjustable for various time rates.