CA1055609A - Liquid fuel blending dispensing pump - Google Patents

Abstract

ABSTRACT

A liquid fuel blending dispensing pump which has advantageous operating characteristics over known types of pumps utilizing a mechanical computer. The disclosed pump-includes a mixer valve for mixing the fuel from two lines to give a desired blended grade. A pulse generator is associated with each fuel line to give a pulse output for each unit quantity of respective base grade dispensed.
A pulse rate adjuster is connected to the output of one of the pulse generators and is settable in accordance with the blend grade selected so that a first pulse train is given from the pulse rate adjuster and a second pulse train is given from the other pulse generator. The pulse trains are of equal frequency when the respective flow rates are correct, and a comparator is provided for comparing the frequencies of the pulse trains and giving an error signal representative of any discrepancy. A servo-control is res-ponsive to the error signal to drive the mixer valve so as to tend to reduce the error signal to zero.

Description

~L055609 - - -The invention relates to a liquid fuel blclldins dispensing pultlp. Such pumps operate by blending two base $rades of fuel in selectable proportions to give the required grade. The cost of the fuel dispensed depends upon the unit cost of the base grades, the selected proportions of the base grades in the blend and the volwne dispensed. Hitherto, it .. . . .
has been customary to provide a mechanical computer in the dispensing pump having input drives from volume meters coupled in the supply lines for the respective base grades, there being displays giving a running indication of ~olume and cost of fuel dispensed and adjustable gearing which is set in accordance with the grade of blend required. The cornputer is e~fective, by differential action, to control a blend mixer valve ~hich determines ~he blend ratio. Mechanical computers of the Icind described are inflexible in that in order to provide for a different pattern of available base grades it is necessary to provide a differènt set of gears. Also, the manual effort required to select a grade by changins the inter-meshing gears , is relatively difficult. Furthermore, the mechanical computer , ' 20 su~fers from wear and requires rei~ular attention and servicing.
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The present invention seeks to provide an improved liquid ~uel blending dispensing p~np.
According to the invention there is provided a liquid fueI blending dispensing pump comprising two fuel lines for 25 carrying respective base grade-q of fuel, a mixer valve for ~, mixing the fuel from the two lines to give a desired blended grade, a pulse generator associated with each fuel Line to give a p~ls~ output for each unit quantity of respective base , ~ - . , :

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grade dispensed, a pulse rate adjuster at the dispensing pump connected to the output of one of the pulse generators and settable in accordance with the blend grade selected so that a first pulse train is given from the pulse rate adjuster and a second pulse train is given from the other pulse generator, the pulse trains being of equal frequency w~en the respective flow rates are correct, a comparator at the dispensing pump comparing the frequencies of the pulse trains and giving an error signal representative of any discrepancy, and a servo-control responsive to the -: . : .
error signal to drive the mixer valve so as to tend to reduce the error signal to zero. The adjuster may be a - frequency divider, but in a preferred embodiment of the .
invention it is a fre~uency multiplier having an adjustable .j, .
multiplication ratio.
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The comparator is preferably a reversible countex having a first input which receives the first pulse train .~; : . . , to count the pulses forwardly and a second input which receives the second pulse train to coun~ the pulses backwardly, the error signal being the cumulative count in the counter. Such a counter is regarded as a frequency or rate comparator in this context since the cumulative count represents the frequency difference between the r~ pulse trains taken over the total and progressively ~ increasing time since the start of the count.
'.5 Preferably there is provided a combining circuit for combining the two pulse trains to give a pulse output I representative of the total flow of fuel. Preferably there ¦ is provided a cost multiplier having a multiplication factor which is adjustable in accordance with the unit cost of the fuel blend grade selected, the cost multiplier being supplied ., .

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witll the pulse output ~rom the combining circuit and thus beins effective to sivc a pulse output reprcsentative o~ the total price of the fuel dispensed.
The pulse outputs representative of total ~olume -and total price may be applied directly to respective cumul- -ative pulse counters which drive displays to indicate volume and cost. In addition, a display may be driven by the unit .
price input to the cost multiplier to give an indication of the unit price of the blend grade selected. The displays are prefcrably disital displays which may be electro-luechanical, but lYhich are preferably electronic - for example, seven-seg-ment solid state displays.
'~ In a proferred embodiment of the invention volume o~
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price information i8 represented as parts of a serial binary digital data word which which continuously recirculates in a ;, . . . . .
, ~register associated with the pump. With this arransement the respective volume and price parts of the word are up-dated 1 .
' as they appear cyclically in accordance with whether an ,,1 , . . .
additional volume or price pulse was or was not generated in ! 20 that cycle. The part~ of the word are routed to the displays At ~he appropriate times in the cycle~. Such an arrangement is particularly suitab}e for use in multiplex data system s~-here-, ~ . . . ~
by information may be transmitted to a central control where paymen* is effeoted.
The invention will ~urther be described with reference to the accompanying drawings, of which :-isura l is a sche.natic dras~ing o~ a fuel dispensing ,' pump in accordance with the invention; and .~ ~ . . ..

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~isurc 2 i5 ~ schematic block diasram of another fuel dispensing pWIlp in accordance with the invention.
Referrins to Figure 1 there is sho~ a fuel dispensins pump which comprises two fuel lines 1 and 2 ~hich carry respective base grades o~ fuel. Line 1 carries a lo~ base grade and line 2 carries a high base grade. The srades fronl ;~ ;
~- lines 1 and 2 are mixed by a mixer valve ~ and passed through an outlet conduit ll to the dispensing nozzle of the pump. In line 1 there is a pulse generator 5 ~rhich gives a pulse output for each unit quantity of fuel passing throush the line. In line 2 there is a similar pulse generator 6~ The unit of fuel : .
correspondi~$ to each pulse i9, in this example, 0.005 sallons.
The operator sets A blend control 7 in accordance with the grad~ of blend requirod frotll the pump. The blend control givos an output to a divider circuit 8 which adjusts the ratio of ~;~ division which the circuit effects.
'1 Pulses from pulse generator 6 are passed throush the , ~ divider circuit 8 and the number of pulses siven from the ou~-'I
' put 9 of the divider circuit is the number of input pulses ;~ ~0 applied divided by the preset ratio. If the blend selected is such that there are n unlts of low grade ~uel toa m units ,~ o~ high g~ade fuel, then the ratio to which the divider 8 is , ~ set is m/n. This means that the trains from pulse generator 5 and from the divider circuit 8 should contain the same nu;nber ,:
25~ ~ of ~ pul9es provided that the mixer valve 3 is set appropriately.
The pulse train from pulse generator 5 is applied to A first input lO of a reversible pulse counter :ll and the ;pulse train frolll output 9 of circuit 8 is applied to a second :i . : : . :

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~ ` ` 1055f~09 input 12 from the pulse countcr. The pulses applied to input 10 are counted in a forward direction and the pulses applied to input 12 are counted in the reverse d-rection. Therefore, since the pulse rates at the two inputs should be equal the cumulative count in counter 11 should be zero. ~ny error is represented by the actual count registered in the counter. This error signal is applied to an amplifier 13 ~Yhich controls a servo-motor 14 lYhich, in turn, drives the valve 3. The arrange-ment is such that the valve 3 is driven in such a sense as to -~
compensate for the error and reduce the error signal to zero.
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In this way the blend is continuously adjusted to the correct `
value.
In order to derive indications of the total ~olume disponsed, the total cost of the fuel dispensed, and the unit price o~ the ~uel bcins dispensed, three indicators 15, 16 and 17 are provide~. These are seven-segment solid state electronic numerical indicato~s. Indicator 15 is the volume indicator -. .. .
and this is drivcn by a store 18 which receives an input ~om a pulse combinins circuit 19. The combining circui-t 19 receives both pulse trains from generator 5 and divider circuit 8 and ., . ~. . .
;Z combines the trains so as to give an additive pulse output repre~entative of the total volume o~ fuel dispe~sed. The output from circuit 19 is applied to a multiplier circuit 20 which has an adju~stable multiplication factor which is se* by an output from unit 7. This output is representative of the ~ . . - :
unit pri¢o Or the grade of fuel l~hich has been selected. Thus, ~ -the total pulse output from circuit 19 is multiplied by a 1 , .
jZ fnctor correspondin~ to the unit price of the fuel beins 1: ' ':.

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dispensed and thc Illultiplied output is representative of the total cost of the fual dispensed. This is ~pplied to a - store 21 the output of which is fed to the cost indicator 16.
The unit price inforlllation iS applied from the illpUt ~.
to circuit 20 to be displaycd directly on the unit price indicator 17.
Referring now to Figurc 2 there is shown a block diagram of another embodiment of the invention. In Yigure 2 the fuel lines l and 2, the Illixer ~alve 3 and the output line 4 are not shown specifically but it is to be understood that ,~ they are similar to the arrangement of Figure l. The pulse generators 5 and 6 are sho1Yn ~n Fisure 2~ InstoAd o~ the output from pulse generator 6 being applicd to a dividins circuit, th~ output ~rom the pulso generator 5 is applied to a pulse multiplier 23. The multiplication factor of the ~;' multiplier 23 is set by a random access memory 24 which is -~ controlled in accordance with the blend chosen ~rolll an input 'i llne 25. If the blend chosen is n units of low grade fuel to j m units of hiSh ~rade ~uel, then the multipIication factor set i9 m/n. The ~ulse train output fro~n multiplier 23 and ~rom pulse generator 6 are applied as opposing inputs to the roversible counter ll as in the Figure l arrangement. The output from the counter ll is applied to amplifier 13 and servo-control l~ ~o as to control the mixer valve to reduce the error signal, which is the output from eounter l1.
Another rando.~access memory 26 receives an input from Iine 25 and g1ve~ an output according to the blend 1 ' selectod which is representative of the uni* price of the .
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i ' ' ' '' . , ~a)55609 selccted blend. This output is applicd to a multiplicr circuit 20 which receiveq a combined pulse train froln an adder circuit 19 as in the Fisure 1 arransement. The output from the adder circuit is representative of the total volume of fuel dispensed and is applied, as is the output from multiplier Z0, to an input of a binary coded decimal addins and subtracting circuit 27. The output from memory 26 is applied to illwninate a display (not shown) ~rhich corresponds -- to the display 17 of Fi~ure 1, sivinS an indication of the unit price of the blend selected.
The arranselllent of ~lgure 2 differs from that o~
Fisure 1 in that direct totalis~tion of the volume and cost pulses is not made. Instead, information concerning the running volume and cost dispensed as well as other factors is stored as a binary decimal data word in a recirculatin register. The register comprises a store 28 of 100 bit - capacity and a subsidiary store 29 of k bit capacity. The output from store 29 is fed baclc to the input of store 28. I~
~his way, the data word, which includes the runninS volume and cost information, is continuously recirculated in the two :.......... . . .
otoxes 28 and 29. The word is recorded in serial form and ;~ -includcs parts representative of each of the current ~olume and cost. The timing of the circulation of the word is controlled by a multiplex unit 30 which receives an input ~rom a decoder unit 31. As the appropriate part of the word, ~
say the volume, reaches the store 29 it may be up-dated to a ~; -new value dep~nding upon whether a volume pulse has been received from the addins circuit 19 in the last cycle. The .~~ . . .. ..
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additional pulso, if any, iq received over a line 32 from the unit 27 and is applied to n1ultiplex unit 30. The data word has a duration o~ 5 milliseconds, so that each cycle lasts for this time. Thus, each cycle of 5 milliseconds the ~Yord may be up-dated in respect of volume and cost as appropriate.
In addition to volume and cost information the data ;; word includes information concerning the amount o~ a~ailable ;~ .
eredit left in the transaction. The initial credit is set by the operator in accordance with a preset cost ~hich is the re~luired value Or fuel to be dispensed. This preset cost ,is set in a cost store 33. The multiplex unit 30 is effective by virtue o~ cost signal~ applied o~or line 32, to reduce the ; eurrent eredit balanoe in the word as appropriate ~n each cycle.
; Thu~, the reeireulating ~ord ineludes infornlation concerning eurrent eost, eurrent volwne and current eredit balance ~ which is applied over a data link 34 to a eentral control l~here ,~ the information~is used by a eashier who receives payment.
~ ~ Also, the information concerning current eost and current '1 ~ vol~ne is applied to eost and volume storos such as 16 and lS
of Figure 1.
Ineoming eontrol data is reeeived from the eentral oontrol on a line 35 and is effeetive to issue control instruetions for starting the pump motors and other control ; functions. Also, the control informatioIl ineludes~current unit priee signals~hieh, via a random aeeess memory 36, '~ governs the unit prlee lrhich is set by the mentory 26. In thisway, ourrent unit priee ean be up-dated e~ery cyele and ean ~ there~ore be eontrolled remotely from the eentral eontrol to ',~' . ~. ' : , 9- .

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$ive changing unit prices from time to time as appropriate.
This may be useful to chanse the price according to the time of day, for example. ~ogic means is effective to stop up-datin~ of the current unit price during a dispensins cycle.
The timin~ of the control is governed by a counter 37 which receives an input from a central cl~ck and which controls a counter 38 effective to set the decoder unit 31.
At the end of a dispensing operation it is necessary to stop the flow of fuel. If this operation is achieved too suddenly there will be unacceptable strain on the dispensing mechanism. Therefore, it is desirable to reduce the flow ., rate shortly before cut-off. It is convenient to effect this control by reference to the amount of fuel remaining to be dispensed. Thus, it is convenient to make use o~ the remaining credit information in the data word. Ho~ever, if the slow-do~m o~ the fuel rate is controlled in accordance with the remaining - credit, the actual voi~ne of fuel rémaining to be dispensed will depend upon the unit price of the blend chosen. Thus, the slol~-ç dol~n of the flolr rate may take place when there is an appreciable volume of ~uel to be dispensed. In order to avoid this, the . ~ , . .
credit balance information is applied to a comparator 39 as well as in~ormation from the unit price menlory 26. The comp-j arator is e~ective to divide the credit balance by the unit . . .
~ price and therefore achieve a volume indication. This volume ~ -.. ~ . . ..
indication is co!npared with the preset level and l~hen the ;~
~¦ - co~.parison indicates that a predetermined volume remains to be dispensed a control~si5nal ls issued to slow the pump motors.
~, ; Similarly, ~hen the credit b~lance has reduced to zero, a control signa3 is issued ~rom the comparator 39 to cut off the ! flow completely.
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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A liquid fuel blending dispensing pump comprising two fuel lines for carrying respective base grades of fuel, a mixer valve for mixing the fuel from the two lines to give a desired blended grade, a pulse generator associated with each fuel line to give a pulse output for each unit quantity of respective base grade dispensed, a pulse rate adjuster at the dispensing pump connected to the output of one of the pulse generators and settable in accordance with the blend grade selected so that a first pulse train is given from the pulse rate adjuster and a second pulse train is given from the other pulse generator, the pulse trains being of equal frequency when the respective flow rates are correct, a comparator at the dispensing pump comparing the frequencies of the pulse trains and giving an error signal representative of any discrepancy, and a servo-control responsive to the error signal to drive the mixer valve so as to tend to reduce the error signal to zero.

2. A liquid fuel blending dispensing pump as claimed in claim 1 wherein the adjuster is a frequency multiplier having an adjustable multiplication ratio.

3. A liquid fuel blending dispensing pump as claimed in either of the preceding claims wherein the comparator is a reversible counter having a first input which receives the first pulse train to count the pulses forwardly and a second input which receives the second pulse train to count the pulses backwardly, the error signal being the cumulative count in the counter.

4. A liquid fuel blending dispensing pump as claimed in claim 1 or claim 2 wherein there is provided a combining circuit for combining the two pulse trains to give a pulse output representative of the total flow of fuel.

5. A liquid fuel blending dispensing pump as claimed in claim 1 or claim 2 wherein there is provided a cost multiplier having a multiplication factor which is adjustable in accordance with the unit price of the fuel blend grade selected, the cost multiplier being supplied with the pulse output from the combining circuit and thus being effective to give a pulse output representative of the total cost of the fuel dispensed.

6. A liquid fuel blending dispensing pump as claimed in claim 1 or claim 2 wherein there is provided a digital register and means for repetitively and cyclically feeding to the register a serial binary digital data word having parts representing respectively the current volume and the current cost of the fuel as it is dispensed, the volume and cost parks of the word being up-dated as they appear cyclically in accordance with whether an additional volume or cost pulse was generated in that cycle.