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This invention relates to an improved price calculating and indicating
circuit useful in motor fuel dispensing apparatus of the electronic type,
such as that disclosed in copending application Ser. No. 455,476, filed
Mar. 27, 1974 now U.S. Pat. No. 3,934,756. Although the dispensing
apparatus disclosed in the aforementioned application is of the so-called
blending type (wherein two different fuel components are blended in
different proportions to give different grades of liquid fuel for
dispensing), the circuit of the present invention is applicable also to
non-blending-type or single-product dispensers. It will be described
herein in connection with blending-type dispensers merely for the sake of
convenience.
The price calculating circuit disclosed in the previously-mentioned
application operates well, and appeared to meet the requirements of
governmental regulatory (Weights and Measures) bodies. However, it was
later found that there were unique values of both pricing and gallonage
wherein the Weights and Measures requirements were not met.
An object of this invention is to provide a novel price calculating and
indicating circuit for dispensers.
Another object is to provide a price calculating and indicating circuit
which obviates the difficulties experienced in prior circuits.
A further object is to provide a price calculating and indicating circuit
which fully meets the Weights and Measures requirements.
A detailed description of the invention follows, taken in conjunction with
the accompanying drawings, wherein:
FIG. 1 is a block diagram (logic diagram) of a circuit according to this
invention; and
FIG. 2 is a set of waveforms useful in explaining the invention.
Referring now to the drawings, a continuously-operating square wave
generator (clock) 1 of 100 KHz is the basic signal source for the system.
The generator 1 is preferably in the form of an integrated circuit (IC).
The output 2 of generator 1 is represented by waveform C, FIG. 2. A
portion of the output of generator 1 is divided by 10 in a frequency
divider 3, and then by 10 again in another frequency divider 4, to provide
at 5 a clock signal of 1 KHz, which is used for certain purposes in the
logic system of the complete or overall dispensing apparatus disclosed in
the aforementioned application. The dividers 3 and 4 form no part of the
price circuit of the present invention, but are illustrated herein only in
order to provide a more complete disclosure.
Another portion of the output of generator 1 is coupled to one input of an
AND with logic negation (i.e., a NAND) 6, whose output 7 is coupled to the
toggle input T of a single shot or one shot 8 which, when activated,
provides an output pulse of one microsecond duration at its output 9. When
NAND gate 6 is not inhibited, the 100 KHz square wave output of generator
1 is fed through this gate to the single shot 8 to activate the latter,
producing at 9 square pulses of 1 microsecond duration occurring at a
repetition rate of 100 KHz.
A signal representative of the total flow of the liquid or liquids being
dispensed is supplied at 10 as one of the inputs to an EXCLUSIVE OR 11.
This signal represents equal fractional parts of a unit volume (typically,
0.01 gallon) of the liquid being dispensed. In a blending-type liquid
dispensing apparatus, as disclosed in the aforementioned application, the
flows of the two blending components are separately measured by meters
which operate pulsers producing 1000 pulses per gallon, and the outputs of
the two pulsers are added and then divided by 10, resulting in the
production of pulses at the rate of 100 pulses per gallon of total or
combined liquid flow. These latter pulses are used at 10 for the circuit
of this invention. Although pulses have been described for flow
representation, for convenience and ease of illustration the waveform at
10 is illustrated at A in FIG. 2 as a square wave wherein each complete
cycle corresponds to 0.01 gallon of flow of the liquid or liquids being
dispensed. With one square wave cycle for each 0.01 gallon, the frequency
at 10 would be 20 Hz at 12 gallons per minute of liquid flow.
The 0.01 gallon square wave which appears at the output of the IC 11 is fed
to the toggle input T of a single shot or one shot 12 which, when
activated, provides an output pulse of 1 microsecond duration at its
output 13. The IC 12 is edge triggered by the square wave applied to its T
input, resulting in output pulses at 13 which are represented by waveform
B, FIG. 2.
Alternatively, it would be possible to make the input 10 comprise short
pulses, rather than the 20 Hz square wave previously mentioned. (This
could be done, for example, by causing such square wave to toggle a
one-shot). In this case, the one shot 12 would not be needed, and the
output 13 would be coupled directly to the logic device 11. (The waveform
B of FIG. 2 would then be that of the output of logic device 11.)
The pulses at 13 are applied to the reset or clear (C) input of an IC
flip-flop 14, resulting in the production at its output 15 of the
positive-going portions F.sub.1 of waveform, F, FIG. 2. (How the
negative-going portions F.sub.2 of this waveform are developed will be
explained hereinafter.) Thus, at the leading edge or onset of each cycle
of the 0.01 gallon square wave A, a pulse B is produced at 13, resulting
in the production of a positive-going signal F.sub.1 at 15 which activates
gate 6 to start the feeding of the clock signal from generator 1 (waveform
C) to the IC 8, as illustrated by waveform D, FIG. 2.
The output 9 of the IC 8 is applied to a divide-by-N circuit 16 of IC type,
and also to a series of three decade-related counters 17, 18, and 19.
Gating of the pulses (derived from generator 1, through the single shot 8)
to the counters 17-19 (again of IC type) is effected by the circuit 16.
The division N corresponds digitally to the price per gallon of the liquid
being dispensed, and is set by three or four price per gallon switches
(BCD switches) 20, depending upon whether the price per gallon is a three
or four digit number (four switches are indicated). The switches 20 are
associated with the circuit 16 in a known manner, to carry out the
described function.
Assume (for example) that a price of 75.2 cents per gallon has been
established, which means that the switches 20 would be set to 0752. The
circuit 16 functions in the manner of a counter. Beginning at the instant
when the clock signal is gated into the IC 8, the circuit 16 begins to
count the pulses from 8 reaching such circuit. After the number of pulses
(assumed to be 752) which correspond to the price per gallon have entered
the IC 16, a pulse (waveform E, this pulse occurring at the time of the
752nd cycle of waveform D) is generated on the output connection 21 of the
IC 16. This E pulse is coupled to the toggle input T of a single shot or
one shot 22 which, when activated, provides an output pulse of 1
microsecond duration at its output 23. This latter pulse is applied to the
set (S) input of the IC 14, setting this flip-flop (as illustrated by the
negative-going portions F.sub.2 of waveform F, FIG. 2), which stops the
pulses (on 9) from entering the IC 16 and the counters 17-19, by
inhibiting gate 6.
The process previously described is repetitive. After 752 pulses have been
gated to the counters 17-19, the system so far described is quiescent
(except, of course, for the generator 1, which operates continuously)
until the next B pulse arrives at the flip-flop 14 (in response to the
onset of the next cycle of the 0.01 gallon square wave A). When this
occurs, 752 pulses are again gated to the counters 17-19, and so on for
each following cycle of the 0.01 gallon square wave A.
The IC counters 17-19 are divide-by10 counters connected in a series, to
provide an overall division factor of 1000. The binary-coded outputs of
these counters are connected in a more or less standardized
OR-AND-amplifier arrangement denoted generally by numeral 24, in such a
manner as to provide on the common output lead 25 an initial pulse after a
predetermined number (e.g., 501) pulses have entered this set of counters
(from connection 9, to which the input of the "unit" counter 17 is
coupled), and subsequent pulses after each additional 1000 pulses (since
the counters are divide-by10 counters). Thus, from the beginning of the
pricing operation, pulses are produced at the output 25 (see waveform G,
FIG. 2) after (for example) 501, 1501, 2501, 3501, etc. pulses supplied to
the initial counter 17 (these pulses supplied being represented time-wise
by waveform D). The circled numerals on the IC blocks 17-19 denote the
"501" setting of these counters.
Prior to starting a delivery from the dispensing apparatus, all of the
counters in FIG. 1 are reset to zero (as will later be described in more
detail), and under these conditions, the first pulse which appears on line
25 from the ICs 17-19 (see waveform G) occurs after 501 pulses have
entered this set of counters. See pulse number 501 on waveform G, during
the first 752-pulse count of waveform D. Every subsequent pulse on 25
occurs after an additional 1000 pulses have entered counters 17-19 (from
8); pulse number 1501 is shown on waveform G, FIG. 2, near the end of the
second 752-pulse count of waveform D.
The circuit of this invention causes the calculation of total sales
(represented by the pulses G on lead 25) to be correct to the nearest 1/2
cent. The pulses G on lead 25 are supplied to a series of four
decade-related dollar counters 26, 27, 28, and 29, which are divide-by10
counters arranged in a series and which drive, respectively, the 1 cent,
10 cent, 1 dollar, and 10 dollar digits of a four-digit total dollar sale
display 30. The circuit described operates repetitively, and the digits in
the total dollar sale display 30 continuously increase as the number of
0.01 gallon pulses (corresponding to waveform A) continue.
If the price exceeds 1 dollar per gallon, it would be possible for two
pulses to occur on line 25 during a single 0.01 gallon cycle (of waveform
A). However, this presents no particular problem, since all pulses which
occur on this line are counted in the dollar display 30, and the digits of
this display change so rapidly that there will be no visual confusion.
Resetting of the counters 17-19 and 26-29 to zero is effected prior to each
delivery of fluid (i.e., prior to each gasoline dispensing operation) by
the application of a relatively long (100 milliseconds) reset pulse to the
connection 31, from which connection the reset bus 32 extends to all of
the mentioned counters. The reset connection 31 normally is in the
0-state, but goes to the 1-state during reset.
The reset signal on connection 31 is coupled to the toggle input T of a
single shot or one shot 33 which, when activated, provides an output pulse
of 1 microsecond duration at its output 34. Output 34 is coupled as the
other input to the EXCLUSIVE OR 11. Upon reset, the pulse on 34 goes
through the IC 11 and activates the single shot 12. producing a single B
pulse (referring to FIG. 2) on 13. This single B pulse results in the same
action as in a normal dispensing operation, activating gear 6 to cause the
circuit 16 to go through one cycle of operation (i.e, to cause it to count
the number of pulses which have been set on the switches 20). However,
since this cycle of operation is so short (it would be only 15
milliseconds, for example, even at a price of $1.50 per gallon) compared
to the 100 millisecond reset signal being applied to the counters 17-19
and 26-29 at this same time, the counters 17-19 and 26-29 will not count
this cycle, and the display 30 will remain at zero.
On the other hand, this pseudo B pulse (meaning a B pulse not
representative of liquid flow) will effect a complete resetting of the IC
16, which latter is particularly important if the price setting of
switches 20 has been changed between the end of one delivery and the
beginning of the next.
* * * * *
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