CA1175256A - Compound liquid flow meter - Google Patents
Compound liquid flow meterInfo
- Publication number
- CA1175256A CA1175256A CA000395687A CA395687A CA1175256A CA 1175256 A CA1175256 A CA 1175256A CA 000395687 A CA000395687 A CA 000395687A CA 395687 A CA395687 A CA 395687A CA 1175256 A CA1175256 A CA 1175256A
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- Canada
- Prior art keywords
- flow
- meter
- cover
- wall
- casing
- Prior art date
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Abstract
Abstract of the Disclosure A compound liquid flow meter comprises a casing which is open along one side and has at one end an inlet adapted for connection to a supply conduit and at its opposite end an out-let adapted for connection to a discharge conduit, A cover closes the open side of the casing and a main flow path is provided through the casing including a turbine meter supported by the cover and having a characteristic of accuracy over a first range of flow rates greater than a predetermined rate and of rapid acceleration in response to increasing flow; and a main valve controlling the flow through the turbine meter;
an auxiliary flow path extends from the inlet to the outlet and includes a low flow measuring meter supported by the cover and having a characteristic of accuracy over a second range of flow rates lower than and overlapping said first range of flow rates; an auxiliary valve supported by the cover and controlling the flow through said low flow meter; wherein the improvement comprises a transverse wall in the casing between the inlet and the outlet, said wall having an aperture therein; spring means biasing the main valve to closed position; means supporting said main valve and said spring means on the down-stream side of the wall so that the main valve controls the flow through the aperture, a transverse wall in the cover abutting the transverse wall in the casing, said cover trans-verse wall having an aperture therethrough forming part of said auxiliary flow path; and means sealing the downstream end of the turbine meter to the upstream side of the wall at the periphery of the aperture.
an auxiliary flow path extends from the inlet to the outlet and includes a low flow measuring meter supported by the cover and having a characteristic of accuracy over a second range of flow rates lower than and overlapping said first range of flow rates; an auxiliary valve supported by the cover and controlling the flow through said low flow meter; wherein the improvement comprises a transverse wall in the casing between the inlet and the outlet, said wall having an aperture therein; spring means biasing the main valve to closed position; means supporting said main valve and said spring means on the down-stream side of the wall so that the main valve controls the flow through the aperture, a transverse wall in the cover abutting the transverse wall in the casing, said cover trans-verse wall having an aperture therethrough forming part of said auxiliary flow path; and means sealing the downstream end of the turbine meter to the upstream side of the wall at the periphery of the aperture.
Description
~ 1 75~5~
This invention relates to the measurement of liquid flow in elosed conduits, where the Elow is sub-ject to a wide ranc3e of variations.
Compound liquid flow meters have parallel flow paths, one of which includes a turbine me-ter accurate over a wide range of relatively high flow ra-tes, but inaecurate below a known minimum rate~ The other flow path includes a meter accurate at low flow rates, but having a narrow range with a low maximum rate o~
15 flow greater than the minimum flow rate of the turbine meter. It is essential tha-t the flow pa-th throucJh the turbine meter be closed by a valve during the low ran~3e of flow rates where that meter is inaccurate.
It has previously been considered neeessary to have the valve quiek-acting in response -to the rate of flow, so that it opens cluickly when the flow rate exceeds the minimum aecurate flow rate of the turbine meter, and so tha-t it eloses quic]cly when the flow rate falls below that minimum.
Many quiek-acting valve meehanisms have been proposed in the prior art. See for example Masson et al U.S. Patent 3,677,804 and Pelt U.S. Patent 4,100,800. The prior art quiek-aeting valve mechanisms are complex. Masson et al. uses a combined cam and toggle mechanism. Pelt us~s a complex mechanism involviny two cams and an in-clined plane. The prior ar-t compound meters including quick-acting valve mechanisms have reduced accuracy duriny the crossover range of flows during whlch the valve is openil~g or closiny. This lack o~ accuracy is 35 recoyllized in the standard for such meters published .~
1 1 7~256 by The American Water Works i~ssociation and identified as their Standard C-702-78. That standard allows compound meters to have a minimum accuracy as low as 90~ i~ the crossover range where the va:Lve is opening or closing, but requires that the total crossover range of flow rates where accuracy is below 97% be limited (e.g. 20 gals. per min. for a 3 in. meter).
The present invention provides a compound liquid flow meter which comprises a casing open along one side and having at one end an inlet adapted for connection to a supply conduit and at its opposite end an outlet adapted for connection to a discharge conduit, a cover closing the open side of the casing; a main flow path through the casing including a turbine meter supported by the cover and having a characteristic of accuracy over a first range of flow rates greater than a predetermined rate and of rapid acceleration in response to increasing flow; and a main valve controlling the flow through the turbine meter;
an auxiliary flow path extending from the inlet to the outlet and including a low flow measuring meter supported by the cover and having a characteristic of accuracy over a second range of flow rates lower than and overlapping the first range of flow rates; an auxiliary valve supported by the cover and controlling the flow through the low flow meter; wherein the improvement comprises a -transverse wall in the casing between the in.let and the outlet, the wall having an aperture therein; means supporting the main valve on the downstream side of th.e wall so that the main valve controls the flow through the aperture; spring means bias-ing the main valve to closed. position; means sealing the downstream end of the turbin.e meter to the upstream side of the wall at the peripher~ of the aperture; and a trans-verse wall in the cover abut.ting the transverse wall in the casing, the cover transverse wall having an aperture therethrough forming part of the auxiliary flow path.
In a preferred emhodiment, the compound liquid
This invention relates to the measurement of liquid flow in elosed conduits, where the Elow is sub-ject to a wide ranc3e of variations.
Compound liquid flow meters have parallel flow paths, one of which includes a turbine me-ter accurate over a wide range of relatively high flow ra-tes, but inaecurate below a known minimum rate~ The other flow path includes a meter accurate at low flow rates, but having a narrow range with a low maximum rate o~
15 flow greater than the minimum flow rate of the turbine meter. It is essential tha-t the flow pa-th throucJh the turbine meter be closed by a valve during the low ran~3e of flow rates where that meter is inaccurate.
It has previously been considered neeessary to have the valve quiek-acting in response -to the rate of flow, so that it opens cluickly when the flow rate exceeds the minimum aecurate flow rate of the turbine meter, and so tha-t it eloses quic]cly when the flow rate falls below that minimum.
Many quiek-acting valve meehanisms have been proposed in the prior art. See for example Masson et al U.S. Patent 3,677,804 and Pelt U.S. Patent 4,100,800. The prior art quiek-aeting valve mechanisms are complex. Masson et al. uses a combined cam and toggle mechanism. Pelt us~s a complex mechanism involviny two cams and an in-clined plane. The prior ar-t compound meters including quick-acting valve mechanisms have reduced accuracy duriny the crossover range of flows during whlch the valve is openil~g or closiny. This lack o~ accuracy is 35 recoyllized in the standard for such meters published .~
1 1 7~256 by The American Water Works i~ssociation and identified as their Standard C-702-78. That standard allows compound meters to have a minimum accuracy as low as 90~ i~ the crossover range where the va:Lve is opening or closing, but requires that the total crossover range of flow rates where accuracy is below 97% be limited (e.g. 20 gals. per min. for a 3 in. meter).
The present invention provides a compound liquid flow meter which comprises a casing open along one side and having at one end an inlet adapted for connection to a supply conduit and at its opposite end an outlet adapted for connection to a discharge conduit, a cover closing the open side of the casing; a main flow path through the casing including a turbine meter supported by the cover and having a characteristic of accuracy over a first range of flow rates greater than a predetermined rate and of rapid acceleration in response to increasing flow; and a main valve controlling the flow through the turbine meter;
an auxiliary flow path extending from the inlet to the outlet and including a low flow measuring meter supported by the cover and having a characteristic of accuracy over a second range of flow rates lower than and overlapping the first range of flow rates; an auxiliary valve supported by the cover and controlling the flow through the low flow meter; wherein the improvement comprises a -transverse wall in the casing between the in.let and the outlet, the wall having an aperture therein; means supporting the main valve on the downstream side of th.e wall so that the main valve controls the flow through the aperture; spring means bias-ing the main valve to closed. position; means sealing the downstream end of the turbin.e meter to the upstream side of the wall at the peripher~ of the aperture; and a trans-verse wall in the cover abut.ting the transverse wall in the casing, the cover transverse wall having an aperture therethrough forming part of the auxiliary flow path.
In a preferred emhodiment, the compound liquid
- 2~ -flow meter has a principal fLow path including a wide range turbine meter which is accurate for a range of flows greater than a predetermined minimum flow. The meter also includes a parallel auxiliary flow palh through a conventional meter such as a positive displacement meter, which is accurate over a lower range of flow rates. The upper end of that lower range overlaps the low end of the accurate range of flow rates of the turbine meter.
The compound meter includes a casing open along a portion of one side and having an inlet at one end and an outlet at the opposite end. The casing has a trans-verse wall between the inlet and the outlet, and an aper-ture in the wall is part of the principal flow path.
A main valve, which is disclosed as a simple poppet valve, controls the flow through the aperture.
That valve is mounted on a stem extending through a valve guide which also serves as a retainer for a spring which biases the valve to closed position.
When there is no flow through the valve, the total pressure difference between the upstream and downstream sides of the compound meter acts on the valve in a valve-opening direction. The valve assembly including the valve, stem, guide and spring, is mounted on the .
~3~ ~ 75256 downs-tream side of the~ transverse wall in the casincJ.
~ cover for the open side oE the casiny supports the turbine meter within the casinCJ on the upstrcam side of the -transverse wall~ The -turbine meter has a highly accurate characteristic, i.e., one which attains a high and constant accuracy at a rate of Elow just sliyh-tly above l:he minimum rate which starts rotation of the turbine. rl~he lowex ran~e me-ter is supported by the cover~ which contains the parallel flow ~ath.
Thc auxiliary flow path includes a fixed orifice of carefully selected size~, which determines the pressure drop across the compound mcter when the main valve is closed, and hence deterrnines the rate of flow at which -the main valve starts -to open.
The auxiliary flow path may also include a secondary flow respollsive valve which is biased open and closes in response to a predetermilli-~d pressure difference across the meter,. This flow responsive val~e has a minimwn openiny, so that there is always some flow throu~h the positive displacernent meter.
This compound meter proYides an improved accuracy durilliJ tlle crossover betwee]l the closed main valve position, where only the lower range meter is function-~5 iniJ, and the open main valve~ position, wherein bo-th meters are functioniny. The main valve structure opens smoothly to turn the turbine meter on when -the flow is i3reat enougll and closes smoothly to turn the turbine me-ter off when the flow is below the minimum accurate flow for that meter.
This smooth action starts to open the main valve at a predetermined pressure difference equa] to the sum of the pressure dif~erellces across the orifice, the secondary valve and the low ranye meter. As the ~ ~75256 flow rate increases~ the accoml~anying increase in pressure diffexence across the rnain valve opens i-t farthcr and this pressure difference plus the head due to the stream velocity closes the secorldary flow re-sponsive valve, thereby reducing the speed of thc- low ~low me-ter~to a value determined by t~le minimum opening of that valve. As -the flow rate deereases, the second-ary valve opens before the main valve closes so that the low xate meter is running at about 50% of i-ts max-imum capaeity when the mair, valve closes, after whichall flow down to zero is then measured only throucJh the low rate meter.
Embodiments of the invention are shown by way of example in the drawings, in which:-Fig. 1 is a diagral~natie view of a compound meteren~odyin~ the invention.
FicJ. 2 is a diacJrammclt:ie illustration of an altern-ative register arranCJement for the outputs of the two rneters in Fig. 1.
Fig. 3 is an elevatiorlal view of a eompound meter embodyin~ the inventionO
FicJ. 4 is a plan view of the me-~er of FicJ. 3.
FicJ. 5 is a eross~seet:ional view, on a greatly enlar~ed scale, taken on the line 5~5 of Fig. 4.
Fig. 5a is a frac~nentclry eross-seetional view taken on the line 5a-5a of FicJ. 'j.
FiCJ. 6 i5 a graphieal view illustrating a typical aeeuraey eharaeteristie of a prior art eompound meter.
30~iCJ. 7 is a~graphieal view showing the flow char-aeteristies of a prior art low flow rneter when used in a eompound meter.
~ig. 8 is a graphical view similar to Fig. 6, showing an aeeuracy eharaeleristie of a eompound meter embodying the present invention.
Fi(J. 9 is a cJraphical view similar to Fiy. 7, show~
ing the flow characteristic of the low flow meter whe~n used in th~ compound meter of the present invention, Fig. 10 is a~cross-sectional view showin~ a tur-bine meter suitable Eor use in -the compound ~neter of the presen-t inven-tion.
Fi~. 11 is a~raphica] view illustratin~ an accuracy characteristic of the turbine meter o:E Fig, 10.
DEl'~ILED DESCR~[Pl'XON
Fi c~ . 1 This figure diayra~ at:ically illustra-tes a compound flow meter embodying the present invention. The compound meter includes a con-duit l,carryinc~ liquid whic:ll flows either throu~h a principal Elow path including a wide ranc3e turbine meter 2 and a valve mechanism 3 or throu~h a parallel ~ auxiliary flow path 10 includincJ a low flow range meter 8. ~Le turbine meter 2 operates an indicatox 5 and the low ranye meter 8 operates an indicator 9.
Tlle total ~low through the compourLd meter is obtained by takincJ readings from both the indicators 5 and 9 and adding them.
The valve mecllanism 3 includes a poppet valve 4 mounted on a stem ~a and biased to closed position by a spring 6. rrhe stem ~a is slidably moun-ted in an aperture in a~wall 7 haviny other apertures 7a to 30 permit the passac3e of liquid.
In the auxiliary flow path 10 there is provided, pre~erably upstream from the m*~er 8, a valve 15 shown as a leaf sprin~ fixed at orle end on a wall 17 havincJ
an aperture 17a. ~alve 15 is sel~-biased to an open 35 position and movable to closed position by the pressure dif~erence across -the valve. The valve 15 is pro-Yided Witll an aperture 15a,~which serves to allow a ~ j -6 ~1 75256 minim~n flow through the meter ~, even when the valve 15 is closed.
Downstream from the meter ~, there is provided a fi~ed orifice 16 whose diameter is selected so that the pressure drop across it is coordinated with the sprin~ rate of spring 6 to determine the flow rate at which the valve 4 opens.
The press~re drop between the inlet and the out-let of the compound meter is divided in the main flow path between the pressure drop across the main meter 2 and that across the main valve 4. In the auxiliary flow path~ the pressure drop between inlet and outlet is the sum of the pressure drops across the valve 15, the meter 8 and the orifice 16.
The principal function of the valve 15 is to re-duce the flow through the low flow meter 8 after the turbine meter 2 reaches the constant portion of its accuracy characteristic (Fig. 11). It is desirable to reduce the speecl of the meter 8 at such times in order to reduce wear by preventing it from running continu-ously at hi~h speed. On the other hand, it is alsodesirable to keep it opera-ting at low speed, because the turbine meter in some installations ~ay operate for lon~ periods at high speeds. If the low flow meter is allowed to~stop dl~rin~ those periods, it mi~ht con-ceivably become fixed in position and fail to star-t a~ain when the flow through -the turbine nleter is re-duced.
For those installations where the func-tions just described are not required, the valve 15 could be omitted.
When there is no flow throu~h -~he corlduit 1, the valve 4 is subjected to the pressure difference be-tween the inlet and the outlet of the compound meter, and the valve is held closed by the sprin~ 6. As _7_ ~l 7~255 -the flow increases, -that pressure difference increases.
At a predetermined rate o~ flow es-tablished by -the force of the sprin~ 6 and by the characteris-tics of the orifice 16 and the low flow meter ~, the pressure difference becomes sufEicien-tly grea-t to initiate an opening movement of the valve 4.
i~. 2 lQ This flgure illustrates diagrammatically an altern-ative appara-tus for determining the sum of the ~lows througll the turbine meter 2 and the positive displace-ment meter 8. The turbine meter 2 operates a trans-mitter 11 and the positive displacemen-t meter 8 oper-ates a transmitter 12. The transmitters 11 and 12 drive an adder 13 which in turn drives a register 14.
The register 14 indicates the sum of the readings of the two meters. ~ recorder may be used in place of the register.
F_gs. 3~5 These figures illustrate in detail a preferred em-bodiment of the present invention. This compound 25 meter includes a casing 20 open at the top, as shown at 2Qa in ~ig. 5~ and closed by a cover 21 held in place b~ holts 22. A gasket 18 seals the connection between casing 20 ancl cover 21, The casing 20 has an inlet 20b at the righ-t~hand end, as it appears in the 30 drawing, and an outlet 20c at the left-hand end~ ~
transverse wall 23 extends across the casing 20 midway between the inlet 20b and the outlet 20c and is pro-vided wi-th a central aperture 23a.
Mounted on the transverse wall 23 is a valve 35 assembl~ 24 including a valve seat 25 extending through the aperture 23a and having a~flange 25a engaging the i 175256 upstre~n ~ace o~ the wall 23. A seal riny 26 is pro-vided between the flange 25a and the wall 23. The seat 25 projects through the wall 23. ~ ring 27 is threaded onto the projecting end o~ the seat 25. The ring 27 carries a plurality o~ peripherally spaced studs 30 projecting downstream frorn the wall 23. A guide and retainer 31 has a flange 31a apertured to enyage shoulders on the studs 30. The flange 31a is held in place on the studs 30 by means of nuts 32. The guide and re-tainer 31 has a deeply dished configuration with a reentrant central cone 31b which serves as a guide for a valve stem 33 supporting a valve 34 which cooper-ates with the seat 25. A coil spring 35 is held in compression between the valve 34 and -the guide and retainer 31.
The cover 21 supports within the casing 20 a tur- ¦
bine meter 36 located on the upstream side of the wall 23. The meter 36 must have sensitivity to low flows, similar to that o~ the prior art turbine meter 74 illustrated in Fig. 10~ with its accuracy charac-ter-istic at low flow shown in Fig. 11. The meter 36 drives an upwardly extending shaft 37 carrying at its upper end a rotating permanent bar magnet 38 which drives an indicator 40 (Fig. 3~ of conven-tional con-struction. The downstream end of meter 36 is sealedto the flange 25a by a molded seal rin~ 39.
The cover 21 also carries a low flow meter 41 which may be a conventional positive displacement meter of the nutating disc type. The meter 41 drives another permanent maynet 42 which in turn drives an indicator 43 (Fig, 3). The low flow meter 41 is located entirely within the cover 21~ being retained in a ch~mber whose lower~end is closed by a plate 44 held in place by screws 45.
A stud 46 pro~ects downwardly ~rom the cover 21 -~ 3 1~5256 A bar ~7 is fix~d on the top of the turbine meter 36 and is at-tached to the stud ~6 by means of bolts 48.
The parallel auxiliary flow path Erom the inlet 20b through the positive displacement me-ter ~1 may be traced through a narrow space (arrow 50 in the drawin~) a-t the upstream end of the turbine meter 36, thence throuyh a valve 52 mounted on the under side of the cover 21.
Valve 52 is best seen in Fig. 5a, and is shown as a simple leaf spring~valve self~biased to the open posi~
tion shown in that figure. The leaf sprin~ valve 52 is provided with an opening 52a aligned with an open-ing 51a in a transverse wall 51 of the cover 21. As the pressure drop across the valve 52 increases, the valve closes smoothly, whereupon the opening 52a be-comes an operative restric-tion limiting the ma~imum flow through the meter 41. Transverse wall 51 ex-tends across the cover ~1 and is aligned with the transverse wall 23 in casing 20. The auxiliary flow path extends -throulJh opening 51a into a chamber containing the pos~
itive displacement meter 41. The auxiliary ~low path extends from that meter throu~h an e~it passage 21b and a restriction 53 o~ selected dimensions to the out-let 20c.
In assembling -the compound meter, the valve assembly ~5 2~ is mounted on the transverse wall 23 of casing 20.
The meters 36 and 41 are mounted on the cover 21. The assembly consisting of~the cover and the two meters may then be put in place on the casing 20. The meter 36 passes through the opening 20a in the top of the casing 20 with adequate clearance on all sides. The cover assembly is then fastened in place with the bolts 22 and the compound meter is comple-te.
, 10-~ 1~5256 _gs. 6-7 These figures illustrate the ~ccuracy o~ typical prior ar~ compound flow meters. The phrase "percent accurac~" as used in this ar-t means a low reading if the figure is below 100% and a high reading i~ the readin~
is over 100~.
~ eferring to Fig. 6, the solid line 61 illustrates the acceptable low reading accurac~ limit for compound meters as established by the American Water Works Association Standard C~702-78. The straight line 6 shows the acceptable high reading accuracy limit as established by the same standar~ here is a region in line 61 between about 6 gallons per minute and 33 gallons per minute where the acceptable low reading accuracy is lowered to ~0~, whereas it is maint~ined elsewhere at ~7~ except for the very low end of the range, This is the crossover re~ion where the meter is changing from the positive displacement meter to the condition where both meters are functioning. The dotted line curve 62 shows the accuracy charac-teristics of a typical prior art compound flow mete:r-under con-ditions of increasing flow and the solid line curve 63 shows the accuracy characteristics of the sa~e meter under conditions o~ decreasing flow.
The dotted line curve 65 shows the variation with increasin~ flow of the head loss across the prior art compounA meter. The solid line curve 66 shows the head loss for the same meter during decreasing flow.
In Fig. 7, there is illustrated b~ dotted line 67 the variation in flow through the positive displacement meter under conditions of increasing flow. The full line 68 shows the corresponding flow rate through the positive displacement meter under conditions of decreas in~ flow~
I .1 75256 Figs._8~ll Figs. 8 and 9 correspond to Figs. 6 and 7 respect-tively, bu-t show the characteristics o~ a compound meter of the present inven-tion. In Fiy. 8, the lines 61,64 are the same as the lines similarly n~mbered in Fiy. 6, showing the acceptable accuracy limits Eor a compound meter. The curve 71 shows the accuracy of a me-t~r constructed in accordance with the present inven-tion. That curve is the same for~either increasing ordecreasing flow. The curve 72 shows the variation with flow of the head loss across a compound meter con-structed in accordance with the present invention.
The curve 73 in Fig. 9 shows the variation in flow through a low flow meter such as 8 or ~1~ which may be a positive displacemen-t meter of the nutating disc type, over the whole range of flow to the complete compound meter. The disc meter measures most of the flow up to about 15 gallons per minute, after which the valve 4 or 34 starts to open and flow rate through the disc meter decreases due to the closure of the valve 52 in Fig. 5 or 15 in Fig. 1.
Fig. 10 shows a turKine meter 74 a type known in the art~ and is particularly sùitable for use in compound meters constructed in accordance with the present inYention. The turbine meter 74 of Fig. 10 includes an impeller 75~ fixed on a shaft 76 journaled in bearings 77 and 78. The shaft 76 has its ends facing two thrust inserts 81 and 82. The end play of the shaft may be adjusted by a nut 83 which turns on a stud 84 carrying the thrust insert 81. The shaft 76 carries a pinion gear 85 cooperating with a larger gear 86 forming part of a gear train 87 (not shown in detail) which drives a vertical sha~t 88 carry--1.2~ 75256 in~ ~-t i-ts u~per end a ma~net 91 eoopera-ting with another macJn~t 92 on the opposite side o~ a fixcd wall ~3.
The macJnets 91 and 92 may be arr~nged as a ma~n~-tie eoupling.in aceordanee wi-th the U.S. Patent to Southall, 5 No. 3,~4~ . The turbine meter 74 aecelerates rapicl-ly~ onee its minimum rate o~.flow is exeeeded, as shown by~the steep slope on ~he lcw flow portion of the curve ~3 in Fig. 11. This rapid aceeleration eharact~ristie is aehieved by suppor-ting th.e rotor 75 on a live shaft a turning.in the spaced ~earïngs 77 and 78, w;th.adjus-t-able end play to limit the endwise load. The reduetion ~ear train be-tween the turbine 75 and the shaft 88 of the maynet 91 gives the impel].er 75 a substanti~l meehanieal advantacJe over the magne-t 30 ancl thus eon-15 tributes to the high ra-te o~ aceele~ration. Furthermore, al~y thrust due to the macJnet is support~d on the bear-ings which earry the sha:et 88, and is not transmitted baek to the impeller 75.~ The macJnet 91, shaft 88 and gt?ar train 77 run in clean liquid supplied through a 20 capillary seal so as to reduce fur-ther -the friction Thus, the impeller 75 starts easily and aceelerates ~uickly to speeds where its aeeuracy is about 100%, as shown by the curve ~3~in Fig. 11.
The disc meter flow eurve 73 in Fi~. ~ inereaces 25 ~radually from zero flow and reaches a~maximum as shown at 73a ;Eollowed by a sharp decrease in :Elow as shown a-t 73b.~ This sharp decrease is caused by the elosure of the valve 52 in Fig. 5 or the valve 15 in Fig. 1.
~fter that valve is elosed, the dise meter is maintain-30 ed runnincl at a low rate for all higher rates of flowthrough the eompound meter. This low rate of flow throu~h the disc meter~is for the purpose of preventing i.t from sticking, possibly from the deposit of minerals from the licIuid bein~ measured, which might occur iE it -13~ ~ 175256 were to remain stationary for a long period of time.
Referring to Fi~. 8~ it may be seen that the initial portion 71a o~ the accuracy curve 71 is due to the low flow meter but that approximately at point 71b, the curve of the turbine meter becomes substantially ~reater than that through the disc meter and the portion 71c of the curve 71 i.s substantially all due to the turbine meter.
It is essential, in orde.r to secure the sustained high accuracy characteristic of ~ig. 8 in a compolmd meter, that the turbine meter employea have a charac-teristic of~rapid acceleration in response to increas-in~ flow. It is also essential to use a simple main valve mechanism which opens ~radually, as shown at 3 .
in Fig. 1 or at 34 in Fig. 5.
The auxiliar~ valves 15 of F:i~. 1 and 52 of ~i~. 5 axe bo-th located upstream from -the low flow meter and the restricti~e orifices 16 of Fi~. 1 and 53 of Fig. 5 are located downstream from the low flow meter. It is possible to locate the auxiliary valve either up-stream or do~Jnstream from the low flow meter. However, any orifice closely upstream from a meter tends to increase the turbulence of flow t~rough the meter, and may disturb its accuracy. The valves 15 and 52 are shown upstream o~ their respective meters for reasons o~ convenience.
While the 10~J flow meter has been described as a positive displacement meter of the nutating disc type, other suitable types of low flo~ meters could be sub-stituted in a compound meter of the present invention.
-14- 3 l 7 5 2 5 6 The particular scales and flow rates clted above and shown in Figs. 6~ 7, 8, 9 and 11 are de-te.nnined by the size of the meter and are no-t to be considered as limitations of the invention~
.0
The compound meter includes a casing open along a portion of one side and having an inlet at one end and an outlet at the opposite end. The casing has a trans-verse wall between the inlet and the outlet, and an aper-ture in the wall is part of the principal flow path.
A main valve, which is disclosed as a simple poppet valve, controls the flow through the aperture.
That valve is mounted on a stem extending through a valve guide which also serves as a retainer for a spring which biases the valve to closed position.
When there is no flow through the valve, the total pressure difference between the upstream and downstream sides of the compound meter acts on the valve in a valve-opening direction. The valve assembly including the valve, stem, guide and spring, is mounted on the .
~3~ ~ 75256 downs-tream side of the~ transverse wall in the casincJ.
~ cover for the open side oE the casiny supports the turbine meter within the casinCJ on the upstrcam side of the -transverse wall~ The -turbine meter has a highly accurate characteristic, i.e., one which attains a high and constant accuracy at a rate of Elow just sliyh-tly above l:he minimum rate which starts rotation of the turbine. rl~he lowex ran~e me-ter is supported by the cover~ which contains the parallel flow ~ath.
Thc auxiliary flow path includes a fixed orifice of carefully selected size~, which determines the pressure drop across the compound mcter when the main valve is closed, and hence deterrnines the rate of flow at which -the main valve starts -to open.
The auxiliary flow path may also include a secondary flow respollsive valve which is biased open and closes in response to a predetermilli-~d pressure difference across the meter,. This flow responsive val~e has a minimwn openiny, so that there is always some flow throu~h the positive displacernent meter.
This compound meter proYides an improved accuracy durilliJ tlle crossover betwee]l the closed main valve position, where only the lower range meter is function-~5 iniJ, and the open main valve~ position, wherein bo-th meters are functioniny. The main valve structure opens smoothly to turn the turbine meter on when -the flow is i3reat enougll and closes smoothly to turn the turbine me-ter off when the flow is below the minimum accurate flow for that meter.
This smooth action starts to open the main valve at a predetermined pressure difference equa] to the sum of the pressure dif~erellces across the orifice, the secondary valve and the low ranye meter. As the ~ ~75256 flow rate increases~ the accoml~anying increase in pressure diffexence across the rnain valve opens i-t farthcr and this pressure difference plus the head due to the stream velocity closes the secorldary flow re-sponsive valve, thereby reducing the speed of thc- low ~low me-ter~to a value determined by t~le minimum opening of that valve. As -the flow rate deereases, the second-ary valve opens before the main valve closes so that the low xate meter is running at about 50% of i-ts max-imum capaeity when the mair, valve closes, after whichall flow down to zero is then measured only throucJh the low rate meter.
Embodiments of the invention are shown by way of example in the drawings, in which:-Fig. 1 is a diagral~natie view of a compound meteren~odyin~ the invention.
FicJ. 2 is a diacJrammclt:ie illustration of an altern-ative register arranCJement for the outputs of the two rneters in Fig. 1.
Fig. 3 is an elevatiorlal view of a eompound meter embodyin~ the inventionO
FicJ. 4 is a plan view of the me-~er of FicJ. 3.
FicJ. 5 is a eross~seet:ional view, on a greatly enlar~ed scale, taken on the line 5~5 of Fig. 4.
Fig. 5a is a frac~nentclry eross-seetional view taken on the line 5a-5a of FicJ. 'j.
FiCJ. 6 i5 a graphieal view illustrating a typical aeeuraey eharaeteristie of a prior art eompound meter.
30~iCJ. 7 is a~graphieal view showing the flow char-aeteristies of a prior art low flow rneter when used in a eompound meter.
~ig. 8 is a graphical view similar to Fig. 6, showing an aeeuracy eharaeleristie of a eompound meter embodying the present invention.
Fi(J. 9 is a cJraphical view similar to Fiy. 7, show~
ing the flow characteristic of the low flow meter whe~n used in th~ compound meter of the present invention, Fig. 10 is a~cross-sectional view showin~ a tur-bine meter suitable Eor use in -the compound ~neter of the presen-t inven-tion.
Fi~. 11 is a~raphica] view illustratin~ an accuracy characteristic of the turbine meter o:E Fig, 10.
DEl'~ILED DESCR~[Pl'XON
Fi c~ . 1 This figure diayra~ at:ically illustra-tes a compound flow meter embodying the present invention. The compound meter includes a con-duit l,carryinc~ liquid whic:ll flows either throu~h a principal Elow path including a wide ranc3e turbine meter 2 and a valve mechanism 3 or throu~h a parallel ~ auxiliary flow path 10 includincJ a low flow range meter 8. ~Le turbine meter 2 operates an indicatox 5 and the low ranye meter 8 operates an indicator 9.
Tlle total ~low through the compourLd meter is obtained by takincJ readings from both the indicators 5 and 9 and adding them.
The valve mecllanism 3 includes a poppet valve 4 mounted on a stem ~a and biased to closed position by a spring 6. rrhe stem ~a is slidably moun-ted in an aperture in a~wall 7 haviny other apertures 7a to 30 permit the passac3e of liquid.
In the auxiliary flow path 10 there is provided, pre~erably upstream from the m*~er 8, a valve 15 shown as a leaf sprin~ fixed at orle end on a wall 17 havincJ
an aperture 17a. ~alve 15 is sel~-biased to an open 35 position and movable to closed position by the pressure dif~erence across -the valve. The valve 15 is pro-Yided Witll an aperture 15a,~which serves to allow a ~ j -6 ~1 75256 minim~n flow through the meter ~, even when the valve 15 is closed.
Downstream from the meter ~, there is provided a fi~ed orifice 16 whose diameter is selected so that the pressure drop across it is coordinated with the sprin~ rate of spring 6 to determine the flow rate at which the valve 4 opens.
The press~re drop between the inlet and the out-let of the compound meter is divided in the main flow path between the pressure drop across the main meter 2 and that across the main valve 4. In the auxiliary flow path~ the pressure drop between inlet and outlet is the sum of the pressure drops across the valve 15, the meter 8 and the orifice 16.
The principal function of the valve 15 is to re-duce the flow through the low flow meter 8 after the turbine meter 2 reaches the constant portion of its accuracy characteristic (Fig. 11). It is desirable to reduce the speecl of the meter 8 at such times in order to reduce wear by preventing it from running continu-ously at hi~h speed. On the other hand, it is alsodesirable to keep it opera-ting at low speed, because the turbine meter in some installations ~ay operate for lon~ periods at high speeds. If the low flow meter is allowed to~stop dl~rin~ those periods, it mi~ht con-ceivably become fixed in position and fail to star-t a~ain when the flow through -the turbine nleter is re-duced.
For those installations where the func-tions just described are not required, the valve 15 could be omitted.
When there is no flow throu~h -~he corlduit 1, the valve 4 is subjected to the pressure difference be-tween the inlet and the outlet of the compound meter, and the valve is held closed by the sprin~ 6. As _7_ ~l 7~255 -the flow increases, -that pressure difference increases.
At a predetermined rate o~ flow es-tablished by -the force of the sprin~ 6 and by the characteris-tics of the orifice 16 and the low flow meter ~, the pressure difference becomes sufEicien-tly grea-t to initiate an opening movement of the valve 4.
i~. 2 lQ This flgure illustrates diagrammatically an altern-ative appara-tus for determining the sum of the ~lows througll the turbine meter 2 and the positive displace-ment meter 8. The turbine meter 2 operates a trans-mitter 11 and the positive displacemen-t meter 8 oper-ates a transmitter 12. The transmitters 11 and 12 drive an adder 13 which in turn drives a register 14.
The register 14 indicates the sum of the readings of the two meters. ~ recorder may be used in place of the register.
F_gs. 3~5 These figures illustrate in detail a preferred em-bodiment of the present invention. This compound 25 meter includes a casing 20 open at the top, as shown at 2Qa in ~ig. 5~ and closed by a cover 21 held in place b~ holts 22. A gasket 18 seals the connection between casing 20 ancl cover 21, The casing 20 has an inlet 20b at the righ-t~hand end, as it appears in the 30 drawing, and an outlet 20c at the left-hand end~ ~
transverse wall 23 extends across the casing 20 midway between the inlet 20b and the outlet 20c and is pro-vided wi-th a central aperture 23a.
Mounted on the transverse wall 23 is a valve 35 assembl~ 24 including a valve seat 25 extending through the aperture 23a and having a~flange 25a engaging the i 175256 upstre~n ~ace o~ the wall 23. A seal riny 26 is pro-vided between the flange 25a and the wall 23. The seat 25 projects through the wall 23. ~ ring 27 is threaded onto the projecting end o~ the seat 25. The ring 27 carries a plurality o~ peripherally spaced studs 30 projecting downstream frorn the wall 23. A guide and retainer 31 has a flange 31a apertured to enyage shoulders on the studs 30. The flange 31a is held in place on the studs 30 by means of nuts 32. The guide and re-tainer 31 has a deeply dished configuration with a reentrant central cone 31b which serves as a guide for a valve stem 33 supporting a valve 34 which cooper-ates with the seat 25. A coil spring 35 is held in compression between the valve 34 and -the guide and retainer 31.
The cover 21 supports within the casing 20 a tur- ¦
bine meter 36 located on the upstream side of the wall 23. The meter 36 must have sensitivity to low flows, similar to that o~ the prior art turbine meter 74 illustrated in Fig. 10~ with its accuracy charac-ter-istic at low flow shown in Fig. 11. The meter 36 drives an upwardly extending shaft 37 carrying at its upper end a rotating permanent bar magnet 38 which drives an indicator 40 (Fig. 3~ of conven-tional con-struction. The downstream end of meter 36 is sealedto the flange 25a by a molded seal rin~ 39.
The cover 21 also carries a low flow meter 41 which may be a conventional positive displacement meter of the nutating disc type. The meter 41 drives another permanent maynet 42 which in turn drives an indicator 43 (Fig, 3). The low flow meter 41 is located entirely within the cover 21~ being retained in a ch~mber whose lower~end is closed by a plate 44 held in place by screws 45.
A stud 46 pro~ects downwardly ~rom the cover 21 -~ 3 1~5256 A bar ~7 is fix~d on the top of the turbine meter 36 and is at-tached to the stud ~6 by means of bolts 48.
The parallel auxiliary flow path Erom the inlet 20b through the positive displacement me-ter ~1 may be traced through a narrow space (arrow 50 in the drawin~) a-t the upstream end of the turbine meter 36, thence throuyh a valve 52 mounted on the under side of the cover 21.
Valve 52 is best seen in Fig. 5a, and is shown as a simple leaf spring~valve self~biased to the open posi~
tion shown in that figure. The leaf sprin~ valve 52 is provided with an opening 52a aligned with an open-ing 51a in a transverse wall 51 of the cover 21. As the pressure drop across the valve 52 increases, the valve closes smoothly, whereupon the opening 52a be-comes an operative restric-tion limiting the ma~imum flow through the meter 41. Transverse wall 51 ex-tends across the cover ~1 and is aligned with the transverse wall 23 in casing 20. The auxiliary flow path extends -throulJh opening 51a into a chamber containing the pos~
itive displacement meter 41. The auxiliary ~low path extends from that meter throu~h an e~it passage 21b and a restriction 53 o~ selected dimensions to the out-let 20c.
In assembling -the compound meter, the valve assembly ~5 2~ is mounted on the transverse wall 23 of casing 20.
The meters 36 and 41 are mounted on the cover 21. The assembly consisting of~the cover and the two meters may then be put in place on the casing 20. The meter 36 passes through the opening 20a in the top of the casing 20 with adequate clearance on all sides. The cover assembly is then fastened in place with the bolts 22 and the compound meter is comple-te.
, 10-~ 1~5256 _gs. 6-7 These figures illustrate the ~ccuracy o~ typical prior ar~ compound flow meters. The phrase "percent accurac~" as used in this ar-t means a low reading if the figure is below 100% and a high reading i~ the readin~
is over 100~.
~ eferring to Fig. 6, the solid line 61 illustrates the acceptable low reading accurac~ limit for compound meters as established by the American Water Works Association Standard C~702-78. The straight line 6 shows the acceptable high reading accuracy limit as established by the same standar~ here is a region in line 61 between about 6 gallons per minute and 33 gallons per minute where the acceptable low reading accuracy is lowered to ~0~, whereas it is maint~ined elsewhere at ~7~ except for the very low end of the range, This is the crossover re~ion where the meter is changing from the positive displacement meter to the condition where both meters are functioning. The dotted line curve 62 shows the accuracy charac-teristics of a typical prior art compound flow mete:r-under con-ditions of increasing flow and the solid line curve 63 shows the accuracy characteristics of the sa~e meter under conditions o~ decreasing flow.
The dotted line curve 65 shows the variation with increasin~ flow of the head loss across the prior art compounA meter. The solid line curve 66 shows the head loss for the same meter during decreasing flow.
In Fig. 7, there is illustrated b~ dotted line 67 the variation in flow through the positive displacement meter under conditions of increasing flow. The full line 68 shows the corresponding flow rate through the positive displacement meter under conditions of decreas in~ flow~
I .1 75256 Figs._8~ll Figs. 8 and 9 correspond to Figs. 6 and 7 respect-tively, bu-t show the characteristics o~ a compound meter of the present inven-tion. In Fiy. 8, the lines 61,64 are the same as the lines similarly n~mbered in Fiy. 6, showing the acceptable accuracy limits Eor a compound meter. The curve 71 shows the accuracy of a me-t~r constructed in accordance with the present inven-tion. That curve is the same for~either increasing ordecreasing flow. The curve 72 shows the variation with flow of the head loss across a compound meter con-structed in accordance with the present invention.
The curve 73 in Fig. 9 shows the variation in flow through a low flow meter such as 8 or ~1~ which may be a positive displacemen-t meter of the nutating disc type, over the whole range of flow to the complete compound meter. The disc meter measures most of the flow up to about 15 gallons per minute, after which the valve 4 or 34 starts to open and flow rate through the disc meter decreases due to the closure of the valve 52 in Fig. 5 or 15 in Fig. 1.
Fig. 10 shows a turKine meter 74 a type known in the art~ and is particularly sùitable for use in compound meters constructed in accordance with the present inYention. The turbine meter 74 of Fig. 10 includes an impeller 75~ fixed on a shaft 76 journaled in bearings 77 and 78. The shaft 76 has its ends facing two thrust inserts 81 and 82. The end play of the shaft may be adjusted by a nut 83 which turns on a stud 84 carrying the thrust insert 81. The shaft 76 carries a pinion gear 85 cooperating with a larger gear 86 forming part of a gear train 87 (not shown in detail) which drives a vertical sha~t 88 carry--1.2~ 75256 in~ ~-t i-ts u~per end a ma~net 91 eoopera-ting with another macJn~t 92 on the opposite side o~ a fixcd wall ~3.
The macJnets 91 and 92 may be arr~nged as a ma~n~-tie eoupling.in aceordanee wi-th the U.S. Patent to Southall, 5 No. 3,~4~ . The turbine meter 74 aecelerates rapicl-ly~ onee its minimum rate o~.flow is exeeeded, as shown by~the steep slope on ~he lcw flow portion of the curve ~3 in Fig. 11. This rapid aceeleration eharact~ristie is aehieved by suppor-ting th.e rotor 75 on a live shaft a turning.in the spaced ~earïngs 77 and 78, w;th.adjus-t-able end play to limit the endwise load. The reduetion ~ear train be-tween the turbine 75 and the shaft 88 of the maynet 91 gives the impel].er 75 a substanti~l meehanieal advantacJe over the magne-t 30 ancl thus eon-15 tributes to the high ra-te o~ aceele~ration. Furthermore, al~y thrust due to the macJnet is support~d on the bear-ings which earry the sha:et 88, and is not transmitted baek to the impeller 75.~ The macJnet 91, shaft 88 and gt?ar train 77 run in clean liquid supplied through a 20 capillary seal so as to reduce fur-ther -the friction Thus, the impeller 75 starts easily and aceelerates ~uickly to speeds where its aeeuracy is about 100%, as shown by the curve ~3~in Fig. 11.
The disc meter flow eurve 73 in Fi~. ~ inereaces 25 ~radually from zero flow and reaches a~maximum as shown at 73a ;Eollowed by a sharp decrease in :Elow as shown a-t 73b.~ This sharp decrease is caused by the elosure of the valve 52 in Fig. 5 or the valve 15 in Fig. 1.
~fter that valve is elosed, the dise meter is maintain-30 ed runnincl at a low rate for all higher rates of flowthrough the eompound meter. This low rate of flow throu~h the disc meter~is for the purpose of preventing i.t from sticking, possibly from the deposit of minerals from the licIuid bein~ measured, which might occur iE it -13~ ~ 175256 were to remain stationary for a long period of time.
Referring to Fi~. 8~ it may be seen that the initial portion 71a o~ the accuracy curve 71 is due to the low flow meter but that approximately at point 71b, the curve of the turbine meter becomes substantially ~reater than that through the disc meter and the portion 71c of the curve 71 i.s substantially all due to the turbine meter.
It is essential, in orde.r to secure the sustained high accuracy characteristic of ~ig. 8 in a compolmd meter, that the turbine meter employea have a charac-teristic of~rapid acceleration in response to increas-in~ flow. It is also essential to use a simple main valve mechanism which opens ~radually, as shown at 3 .
in Fig. 1 or at 34 in Fig. 5.
The auxiliar~ valves 15 of F:i~. 1 and 52 of ~i~. 5 axe bo-th located upstream from -the low flow meter and the restricti~e orifices 16 of Fi~. 1 and 53 of Fig. 5 are located downstream from the low flow meter. It is possible to locate the auxiliary valve either up-stream or do~Jnstream from the low flow meter. However, any orifice closely upstream from a meter tends to increase the turbulence of flow t~rough the meter, and may disturb its accuracy. The valves 15 and 52 are shown upstream o~ their respective meters for reasons o~ convenience.
While the 10~J flow meter has been described as a positive displacement meter of the nutating disc type, other suitable types of low flo~ meters could be sub-stituted in a compound meter of the present invention.
-14- 3 l 7 5 2 5 6 The particular scales and flow rates clted above and shown in Figs. 6~ 7, 8, 9 and 11 are de-te.nnined by the size of the meter and are no-t to be considered as limitations of the invention~
.0
Claims (4)
a. a casing open along one side and having at one end an inlet adapted for connection to a supply conduit and at its opposite end an outlet adapted for connection to a discharge conduit;
b. a cover closing the open side of the casing;
c. a main flow path through the casing including:
1. a turbine meter supported by the cover and having a characteristic of accuracy over a first range of flow rates greater than a predetermined rate and of rapid acceleration in response to increasing flow; and 2. a main valve controlling the flow through the turbine meter;
d. an auxiliary flow path extending from the inlet to the outlet and including:
1. a low flow measuring meter supported by the cover and having a characteristic of accuracy over a second range of flow rates lower than and overlapping said first range of flow rates;
2. an auxiliary valve supported by the cover and controlling the flow through said low flow meter;
wherein the improvement comprises:
e. a transverse wall in the casing between the inlet and the outlet, said wall having an aperture therein;
f. means supporting said main valve on the downstream side of the wall so that the main valve controls the flow through the aperture;
g. spring means biasing the main valve to closed position;
h. means sealing the downstream end of the turbine meter to the upstream side of the wall at the periphery of the aperture; and i. a transverse wall in the cover abutting the transverse wall in the casing, said cover transverse wall having an aperture therethrough forming part of said auxiliary flow path.
2. an auxiliary valve supported by the cover and controlling the flow through said low flow meter;
wherein the improvement comprises:
e. a transverse wall in the casing between the inlet and the outlet, said wall having an aperture therein;
f. means supporting said main valve on the downstream side of the wall so that the main valve controls the flow through the aperture;
g. spring means biasing the main valve to closed position;
h. means sealing the downstream end of the turbine meter to the upstream side of the wall at the periphery of the aperture; and i. a transverse wall in the cover abutting the transverse wall in the casing, said cover transverse wall having an aperture therethrough forming part of said auxiliary flow path.
2. A compound liquid flow meter as in claim 1, including:
a. a cylindrical seat extending through said aperture, having a flange abutting the upstream side of the transverse wall and a threaded end downstream from said wall;
b. a ring threaded on said end of said seat;
c. an array of peripherally spaced rods projecting downstream from said ring, each said rod having a shoulder facing downstream;
d. a spring retainer abutting the shoulders on said rods;
e. means holding the spring retainer against the shoulders; and f. said main valve being located within the array of rods and facing the downstream end of said seat;
g. said spring means being compressed between the retainer and the main valve and biasing the main valve against the seat.
a. a cylindrical seat extending through said aperture, having a flange abutting the upstream side of the transverse wall and a threaded end downstream from said wall;
b. a ring threaded on said end of said seat;
c. an array of peripherally spaced rods projecting downstream from said ring, each said rod having a shoulder facing downstream;
d. a spring retainer abutting the shoulders on said rods;
e. means holding the spring retainer against the shoulders; and f. said main valve being located within the array of rods and facing the downstream end of said seat;
g. said spring means being compressed between the retainer and the main valve and biasing the main valve against the seat.
3. A compound meter as in claim 1, in which the accuracy characteristic is within 3% of being 100% accurate over the entire range of flow within the meter capacity.
4. A compound meter as in claim 2, in which the accuracy characteristic is within 3% of being 100% accurate over the entire range of flow within the meter capacity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000395687A CA1175256A (en) | 1982-02-05 | 1982-02-05 | Compound liquid flow meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000395687A CA1175256A (en) | 1982-02-05 | 1982-02-05 | Compound liquid flow meter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175256A true CA1175256A (en) | 1984-10-02 |
Family
ID=4121990
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000395687A Expired CA1175256A (en) | 1982-02-05 | 1982-02-05 | Compound liquid flow meter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1175256A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10863667B2 (en) | 2015-09-28 | 2020-12-15 | Precision Planting Llc | Systems and devices for controlling and monitoring liquid applications of agricultural fields |
-
1982
- 1982-02-05 CA CA000395687A patent/CA1175256A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10863667B2 (en) | 2015-09-28 | 2020-12-15 | Precision Planting Llc | Systems and devices for controlling and monitoring liquid applications of agricultural fields |
| US11337366B2 (en) | 2015-09-28 | 2022-05-24 | Precision Planting Llc | Systems and devices for controlling and monitoring liquid applications of agricultural fields |
| US11350562B2 (en) | 2015-09-28 | 2022-06-07 | Precision Planting Llc | Systems and devices for controlling and monitoring liquid applications of agricultural fields |
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