GASOLINE PUMP MULTIPLEXER SYSTEM FOR REMOTE INDICATORS FOR SELF-SERVICE GASOLINE PUMPS

• US 3,641,536 A
• Filed: 04/14/1970
• Issued: 02/08/1972
• Est. Priority Date: 04/14/1970
• Status: Expired due to Term

• Current Assignee: Frank B. Prosprich
• Original Assignee: Frank B. Prosprich
• Inventors: Prosprich, Frank B.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Mooney, Robert J.
• Application Number:
  US05/028,379
• Time in Patent Office: 665 Days
• Field of Search: 340/203,206,310,182,184 222/26,23,76 235/92FL,92AC,151.34 73/194E
• US Class Current: 340/870.15
• CPC Class Codes: B67D 7/228 using digital counting

Abstract

A multiplexer system employing a form of pulse width modulation and detection. The system is particularly adapted to use in a telemetering system for remote indicators. The system operates in connection with a self-service gasoline pump and transmits via a 60 Hz. powerline gallons and dollars information. A modified form of the system transmits only dollars or only gallons information for a plurality of pumps. The system can be further adapted for inventory control purposes. Variants include signal forcing and totalizing circuits for a plurality of independent information sources providing absolute accuracy.

Claims

1. In a dispensing system having at least one dispensing apparatus which is capable of generating separate triggering pulses corresponding to fractional parts of at least two different units of measurement related to the dispensed product, a multiplexer system comprising:

a pulse width modulator responsive to one of said triggering pulses for generating a series of pulses having a first duration separated by intervals having a second duration, said pulse width modulator also being responsive to another of said triggering pulses for generating a series of pulses having said second duration separated by intervals having said first duration, and said pulse width modulator further being responsive to the simultaneOus occurrence of the two triggering pulses for generating a series of pulses having said first duration separated by intervals having said first duration, a gated carrier frequency oscillator connected to said pulse width modulator and providing a pulse modulated output, transmission means receiving said pulse modulated output from said gated carrier frequency oscillator for transmitting the modulated signal to a central point, receiver means at said central point for receiving the transmitted signal and providing a detected output, pulse sorter means connected to receive the detected output from said receiver for providing a first output in response to a series of pulses having said first duration and a second output in response to a series of pulses separated by intervals having said first duration, and indicator means connected to each of said first and second outputs of said pulse sorter means for providing an indication at the central point whenever either of said triggering pulses occur.

2. A multiplexer system as recited in claim 1 wherein said pulse width modulator comprises:

an astable multivibrator, and switching means responsive to said triggering pulses for selectively changing the time constants of said astable multivibrator. 3. A multiplexer system as recited in claim 2 wherein said astable multivibrator includes a plurality of timing resistors and said switching means further comprises;

a first one-shot triggered by one of said triggering pulses for producing a pulse output having a fixed duration substantially longer than both said first and second durations, a second one-shot triggered by another of said triggering pulses for producing an output pulse having a duration equal to that of the output of said first one-shot, a first electronic switch connected to the output of said first one-shot and operable to connect a first combination of said timing resistances to said astable multivibrator, a second electronic switch connected to said second one-shot and operable to connect a second combination of timing resistances to said astable multivibrator, an AND gate receiving as its inputs the outputs of both said first and said second one-shots and providing an output only when the outputs from said first and second one-shots are coincident, and a third electronic switch connected to said AND gate and operable to connect a third combination of timing resistances to said astable multivibrator.

4. A multiplexer system as recited in claim 1 wherein said pulse sorter means comprises:

first and second pulse width discriminators each operable to detect a pulse having said first duration, one of said pulse width discriminators receiving the detected output from said receiver means and the other of said pulse width discriminators receiving the inversion of the detected output from said receiver means, and first and second integrating one-shots connected to the output of said first and second pulse width discriminators, respectively.

5. A multiplexer system as recited in claim 1 wherein said dispensing apparatus is a gasoline pump and said units of measurement are dollars and gallons, respectively, and said indicator means provides numerical readouts of the number of gallons dispensed and the dollar value thereof.

6. A multiplexer system comprising a pulse width modulator responsive to a first data pulse for generating a series of pulses having a first duration separated by intervals having a second duration, said pulse width modulator also being responsive to a second data pulse for generating a series of pulses having said second duration separated by intervals having said first duration, and said pulse width modulator further being responsive to the simultaneous occurrence of said first and second data pulses for generating a series of pulses having said first duration separated by intervals having said first duration, a gated carrier frequency oscillator coNnected to said pulse width modulator and providing a pulse modulated output, transmission means receiving said pulse modulated output for transmitting the modulated signal to a remote point, receiver means at said remote point for receiving the transmitted signal and providing a detected output, pulse sorter means connected to receive the detected output from said receiver for providing a first output in response to a series of pulses having said first duration and a second output in response to a series of pulses separated by intervals having said first duration, and indicator means connected to each of said first and second outputs of said pulse sorter means for providing an indication at the remote point whenever either of said first or second data pulses occur.

7. A multiplexer as provided in claim 6 wherein said pulse width modulator comprises:

an astable multivibrator, and switching means responsive to said first and second data pulses for selectively changing the time constants of said multivibrator.

8. A multiplexer system as recited in claim 7 wherein said astable multivibrator includes a plurality of timing resistances and said switching means comprises a first one-shot responsive to said first data pulse for generating an output pulse having a duration substantially longer than either said first or second durations, a second one-shot responsive to said second data pulse for generating an output pulse equal to that generated by said first one-shot, a first electronic switch connected to said first one-shot and operable to connect a first combination of said timing resistances to said astable multivibrator, a second electronic switch connected to said second one-shot and operable to connect a second combination of said timing resistances to said astable multivibrator, an AND gate connected to both said first and said second one-shots and producing an output when the outputs of said first and said second one-shots are coincident, and a third electronic switch connected to the output of said AND gate and operable to connect a third combination of said timing resistances to said astable multivibrator.

9. A multiplexer system as recited in claim 8 wherein said receiver means comprises:

an input tank circuit resonant at the carrier frequency, a logarithmic amplifier connected to said input tank circuit and providing an amplified output which emphasizes smaller signal amplitudes, a tuned amplifier connected to the output of said logarithmic amplifier, and a threshold detector connected to said tuned amplifier providing an output substantially identical to the modulation envelope.

10. A multiplexer system as recited in claim 9 wherein said pulse sorter means comprises:

first and second pulse width discriminators each operable to detect pulses having said first duration, one of said pulse width discriminators being connected to receive the output of said threshold detector and the other of said pulse width discriminators being connected to receive the inversion of the output of said threshold detector, and first and second integrating one-shots connected to respective ones of the outputs of said pulse width discriminators for providing output pulses having durations equal to the duration of the outputs of said first and second one-shots.

11. In a self-service gasoline dispensing system having a plurality of gasoline pumps each of which are capable of generating trigger pulses corresponding to fractional parts of units of measurement related to the dispensed gasoline, a remote indicator system comprising a sender for each pump responsive to the trigger pulses produced thereby and producing a modulated signal characteristic of its particular pump, each of said senders being connected to a common powerline, a receiver for each sender located at a central station and also coupled to said common powerline, each of said receivers being responsive tO the characteristic modulated signal produced by its corresponding sender, and output means connected to each receiver for producing an indication of the amount of gasoline dispensed, said output means comprising:

a plurality of one-bit memories, each of said memories being connected to a respective receiver corresponding to one of said plurality of gasoline pumps, strobing means for strobing the outputs of each memory at least twice between two consecutive trigger pulses generated by its related pump, and accumulating means connected to said strobing means for totalizing the total number of trigger pulses generated by all of said plurality of gasoline pumps.

12. A remote indicator system as recited in claim 11, wherein said strobing means comprises:

a plurality of AND gates each connected to a respective one of said plurality of one-bit memories, a clock oscillator, and a counter connected to said clock oscillator and operative to strobe each AND gate in succession.

13. A remote indicator system as recited in claim 12 wherein said accumulating means comprises:

a flip-flop connected to be toggled back and forth by the combined outputs of said AND gates and the output of said clock oscillator, a stepping motor driven by the outputs of said flip-flop, and a totalizing counter driven by said stepping motor.

14. A remote indicator system as recited in claim 11 wherein said strobing means comprises:

a plurality of AND gates each associated with a respective one of said plurality of one-bit memories, said AND gates each having three inputs, the first of said inputs connected to receive a signal from its associated one-bit memory, the second of said inputs connected to receive the input signal to said one-bit memory, and the third of said inputs connected to said strobing means whereby an input signal to said one-bit memory prevents said AND gates from passing a signal.

15. In a self-service gasoline dispensing system having a plurality of gasoline pumps each of which are capable of generating trigger pulses corresponding to fractional parts of units of measurement related to the dispensed gasoline, a remote indicator system comprising a sender for each pump responsive to the trigger pulses produced thereby and producing a modulated signal characteristic of its particular pump, each of said senders being connected to a common powerline, a receiver for each sender located at a central station and also coupled to said common powerline, each of said receivers being responsive to the characteristic modulated signal produced by its corresponding sender, and output means connected to each receiver for producing an indication of the amount of gasoline dispensed, each sender being connected to the powerline by a coupling network comprising:

a coupling transformer having primary and secondary windings, said primary winding receiving the output of said sender, a capacitor connected across said primary winding to form a tank circuit resonant at the signal frequency, at least one coupling capacitor connected in series with the secondary winding of said coupling transformer and the powerline for blocking the powerline frequency, and at least one current forcing resistor connected in series between said coupling capacitor and said secondary winding.