Note: Descriptions are shown in the official language in which they were submitted.
~ 1 75~5~
--1--
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
I 175256
- 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.
31 1 75256
--5--
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
