A symmetrical mass flow meter for placement within a defined fluid
stream or pre-existing pipe line which defines an axial line. The
flow meter including a single conduit tube which forms two substantially
symmetrical and free floating loops between the inlet and the outlet
of the flow meter. The flow meter conduit directs the fluid through
the first loop and crosses the axial line substantially perpendicular
to this line. The second loop directs the fluid from the crossing
point and returns it into the defined fluid stream. The conduit
is deflected perpendicular to the direction of flow at the crossing
of the axial line along the axial line. Sensors are positioned on
the periphery of each loop to measure the Coriolis reaction force
created by the fluid in response to the central deflection of the
conduit. The reaction forces are measured without reference to a
specific axis of rotation or a fixed position. External vibrational
effects on the sensor measurement unrelated to the Coriolis reaction
forces are physically and electronically minimized by the conduit
1. In a Coriolis mass flow meter of the type imparting an oscillation
transverse to the direction of flow therein and having sensors located
symmetrically with respect to and on opposite sides of the impartation
of the oscillation and means for determining mass flow from the
sensor signals due to the reaction of the flow in response to the
imparted oscillation, comprising: a conduit having an inlet and
an outlet rigidly fixed with respect to one another and a continuous
flexible flow tube communicating with the inlet and the outlet at
respective ends thereof, said flow tube formed symmetrically about
a substantially straight line between the inlet and the outlet and
substantially free of restrictions or constraints along its length
offset from said straight line the flow tube having two successive
loops, the first and second loop communicating with one another
and adapted to direct the flow through the flow tube at the communication
between said loops so as to cross the line between the inlet and
the outlet substantially perpendicular thereto, the flow tube adjacent
the inlet end having an inlet connecting portion adapted for deflecting
the flow from the inlet to a position spaced from the line between
the inlet and and the outlet end directing the flow into the first
loop, and an outlet connecting portion adapted to direct the flow
from the second loop from a position spaced from the line between
the inlet and the outlet and directing the flow into the outlet
of the conduit.
2. In a Coriolis mass flow meter as claimed in 1 further comprising:
means for oscillating said flow tube in a direction along the line
between the inlet and the outlet of the conduit, said oscillating
means positioned substantially at the crossing of the flow tube
with the line between the inlet and the outlet and at the communication
between said first loop and said second loop.
3. In a Coriolis mass flow meter as claimed in claim 2 wherein
said oscillating means further comprises a coil winding and a bar
magnet extending within said coil winding, said coil being subject
to an oscillating current such that said bar magnet is alternately
driven through said coil, said bar magnet attached to said flow
tube at the crossing of the line between the inlet and the outlet
of the conduit.
4. In a Coriolis mass flow meter conduit as claimed in claim 1
further comprising a second, substantially indential flow tube positioned
adjacent to the first described flow tube, said inlet end of said
conduit adapted to divide the flow entering the inlet end and feed
equivalent flows into both said first and second flow tubes and
said conduit outlet adapted to converge the flow from both said
flow tubes into a single flow stream.
5. In a Coriolis mass flow meter as claimed in claim 1 wherein
the inlet connecting portion and the outlet connecting portion are
formed as part of said flow tube.
6. In a Coriolis mass flow meter as claimed in claim 1 wherein
said first and second loops are formed in a single plane transverse
to the line between the inlet and outlet ends of the conduit.
7. In a Coriolis mass flow meter as claimed in claim 1 wherein
said first and second loops are formed in substantially parallel
8. In a Coriolis mass flow meter as claimed in claim 1 wherein
the first and second loops substantially form a FIG. "8"
when viewed along the line between the inlet and outlet ends of
9. In a Coriolis mass flow meter as claimed in claim 8 wherein
the first and second loops are formed substantially in a single
plane transverse to the line between inlet and outlet of the conduit.
10. In a Coriolis mass flow meter as claimed in claim 9 wherein
the plane of said first and second loops is substantially perpendicular
to the line between the inlet and outlet of the conduit.
11. In a Coriolis mass flow meter as claimed in claim 1 wherein
the first and second loops form a "B" shape when viewed
along the line between the inlet and outlet of the conduit.
12. In a Coriolis mass flow meter as claimed in claim 1 wherein
said first and second loops further comprise an inlet arm portion,
a first radial portion, a substantially linear central arm portion,
a second radial portion and an outlet arm portion, the central arm
portion forming the communication between the first and second loops,
and the inlet arm portion and the outlet arm portion adapted to
direct the flow substantially parallel to the flow within the central
13. In a Coriolis mass flow meter of the type imparting an oscillation
transverse to the direction of flow therein and having sensors located
symmetrically with respect to and on opposite sides of the imparted
oscillations and means for determining mass flow from the sensor
signals due to the reaction of the flow in response to the imparted
oscillation, comprising: a conduit having an inlet and outlet rigidly
fixed with respect to one another and a continuous flow tube mounted
between said inlet and outlet and being substantially free-floating
from said mounting, said flow tube adapted to direct the flow through
two successive loops, the communication between the two loops positioned
along a substantially straight line formed between the inlet and
the outlet of the conduit and substantially perpendicular thereto,
the oscillation of the flow tube imparted in a direction substantially
along a line between the inlet and outlet of the conduit.
14. In a Coriolis mass flow meter of the type receiving an imparted
oscillation transverse to the flow therein and having sensors positioned
on opposite sides of the imparted oscillation, the sensors producing
signals representative of the reaction of the flow on opposite sides
of the imparted oscillation, comprising: a conduit having an inlet
and an outlet fixed with respect to one another, a continuous flow
tube mounted at opposite ends to said inlet and said outlet and
being substantially free-floating between said ends,said flow tube
forming a B-shape when viewed along the line formed between the
inlet and the outlet of the conduit, the B-shape adapted to directed
the flow through two successive loops, whereby the flow being directed
through said flow tube is in the same radial direction substantially
through its length.
15. An apparatus for measuring the mass flow of a fluid moving
through a defined fluid stream by measuring the Coriolis reaction
forces of the fluid in response to an imparted oscillation, comprising:
means defining a conduit having an inlet and an outlet, the inlet
and the outlet defining a straight line between their respective
positions, two substantially free floating loops connected to form
a FIG. "8" design when viewed along the straight line,
a first portion of said conduit means adapted to direct flow from
said inlet to said first loop, a second portion adapted to direct
flow from said second loop to said outlet, a central portion connecting
said first loop and said second loop and passing through the straight
line defined by the inlet and the outlet such that a fluid flowing
through said central portion is directed substantially perpendicular
to the straight line at said line passing; means imparting an oscillating
deflection perpendicular to the central portion of said conduit
means, said deflection means positioned substantially along the
straight line; and means for individually sensing the movement of
said first and second loops due to the reaction of the fluid in
said conduit means to said deflection means, said sensing means
positioned adjacent to the periphery of said first and second loops.
16. An apparatus as claimed in claim 15 wherein said sensing means
comprises a piezo-electric transducer.
17. An apparatus as claimed in claim 16 wherein said transducer
is mounted directly to said conduit means.
18. An apparatus as claimed in claim 15 wherein said sensing means
is an accelarometer type sensor.
19. An apparatus as claimed in claim 15 wherein said deflection
means is mounted on a bracket which is connected at its opposite
ends adjacent to the inlet and the outlet of said conduit means.
BRIEF SUMMARY OF THE INVENTION
This invention relates to the measurement of mass flow within an
existing or defined fluid stream by the use of what is known as
a Coriolis flow meter. Typically, Coriolis type flow meters comprise
a tube or conduit which is oscillated in an alternating mode, transverse
to the flow within the tube. The transverse oscillation of the tube
causes a repetitive reaction force by the fluid against the tube
in opposite directions on opposite sides of the applied transverse
vibration. The repetitive reaction of the tube can be correlated
to the mass flow rate within the tube. This type flow meter should
be compared to the simple torsional bending of a tube created by
a rotational or DC mode system.
Various conduit designs have been proposed in order to measure
the mass flow by this Coriolis method. Sipin in U.S. Pat. No. 3329019
teaches a linear or straight tube design which directly measures
the force of the reaction couple caused by the fluid. Further Sipin
U.S. Pat. Nos. 3355944 and 3485098 disclose the transverse
oscillation of a tube having a curvature within the line of flow.
This design variation (over the '019 patent) is intended to increase
the measurability of the reaction force couple. The curvature of
the tube in these two later patents is restricted to a maximum of
180.degree., such that the fluid within the flow meter does not
reverse its direction of flow in the line of the fluid stream. Additionally,
the curved portion of the tube is essentially cantalevered such
that oscillation of the tube causes an effective partial rotation
of the curved end of the tube about a fixed axial line (e.g. the
line defined by the fluid stream).
In Cox et al., U.S. Pat. No. 4127028 the curvature of the tube
is increased over the 180.degree. limitation of Sipin '098 with
reversals in the direction of flow being desired. Cox increases
the deflection arm of the opposite reaction forces on the tube about
the position of the oscillatory motion to increase the measurability
of the tube deflection. Additionally, Cox intendeds to utilize the
resonant frequency of the vibrating tube to limit unwanted vibrational
influences during the sensing of the reaction force against the
tube. The Cox tube is cantalevered (similar to the '944 and '098
patents) about a, desirably, fixed rotational axis.
The Cox patent ('028) recognizes that noise created by the mechanical
oscillation of the tube and other external vibrational influences
greatly effect the sensitivity of the flow meter. To limit the effect
of these unwanted vibrational influences, Cox teaches a second identically
curved cantalevered tube which is provided adjacent to the first
tube. The second tube is oscillated in the opposite vibrational
mode from the first tube. The intent being that, since the identical
tubes vibrate at substantially the same resonant frequency, the
external vibrational effects on the reaction force sensing should
A number of more recent patents propose various structural changes
over the Cox '028 designs for producing a similar effects as the
dual tube of this patent. These further developments in flow meters
of this type include the use of velocity-type sensors to measure
the phase difference between the repetative reaction on the opposite
sides of the imparted oscillation. (See Roth U.S. Pat. No. 3087325.)
Additionally, in Cox et al., U.S. Pat. No. 4192184 velocity sensors
are used on the dual tube design similar to that disclosed in the
'028 patent. In Smith, U.S. Pat. No. 4422338 velocity sensors
are used in conjunction with linear sensors for measurements of
a single cantilivered U-shaped tube. The velocity sensors vary the
position of the reference or zero plane of the tube to eliminate
vibrations unrelated to the reaction force couples from the measurements.
The sensing of the tube reaction in all of the designs in the above
referenced patents is affected by external mechanical vibrations
of the tube. These vibrational influences are created by the tube
oscillation means, the machinery within the process line and other
external environmental influences. Most of these flow meter designs
use cantilevered tubes having a fixed spring constant which resists
the bending or motion of the tube due to the fluid reaction force.
This cantalevered tube is oscillated about a, supposedly, fixed
rotational axis. However, the internal and external vibrational
influences affect the positioning of this axis such that the reference
line of the sensors is not fixed during sensing. These sensor reference
fluctuations greatly affect the sensitivity of this type mass flow
Commonly assigned, copending U.S. application No. 809658 titled
"Mass Flow Meter" teaches a flow meter tube formed into
a loop which is spiraled about the axis of the fluid stream. The
direction of the imparted oscillation to this loop is substantially
parallel to the axial line. Thus, the deflection are imparted into
a transverse plane with respect to the piepline of the defined fluid
stream and not transverse to the flow within the pipeline. The transverse
oscillation imparted to the flow meter tube causes only the reaction
force couples on this tube and does not substantially effect the
flow in the defined fluid stream. Another improvement proposed by
this copending application is the measurement of the fluid reaction
on the flow meter tube without reference to a specific rotational
or fixed axis. Additionally, the spiraled loop is substantially
free floating and, thus, has a significantly reduced spring constant,
which increases the sensitivity of the meter.
It should be appreciated that as long as there is an increase in
the effective transverse velocity of the fluid from the entrance
of the flow meter tube to a point of maximum velocity (at the oscillation
or deflection means) and a decrease in the transverse velocity gradient
from the maximum point to the outlet of the flow meter, there should
be a transverse reaction force in one direction on the inlet portion
of the flow meter tube and in an opposite direction on the outlet
portion of the flow meter tube. This principle is described in Sipin
'019 for a vibrating straight tube and in Sipin '098 for a U-shaped
Assuming that the point of maximum transverse velocity is the mid-point
of the flow meter tube (and the point of oscillation), the inertial
reaction of a single fluid particle to the oscillatory motion on
the flow meter tube in the transverse direction will decrease from
the inlet of the conduit while approaching this maximum point from
the input end of the flow meter conduit. This reaction force will
be directed in the negative direction between this midpoint and
increase in magnitude to a maximum (or effectively decrease since
it is in the relatively negative direction) as it approaches the
outlet of the conduit. In flow meter tubes which have reversals
in the direction of flow, the transverse reaction of the fluid particle
will reach a maximum magnitude at symmetrically located positions
on opposite sides of the maximum vibration point along the input
and output legs of the tube. The integrated reaction force due to
the combined reaction of all fluid particles between the tube entrance
and its mid-point can be expresed as a single reaction force, as
can the integrated force due to the deceleration of the fluid particle
between the midpoint and the outlet. These resulting reaction forces
create an oscillating motion of the tube which is measured as an
indication of the fluid mass flow.
The nature of the motion of the tube due to the reaction of the
fluid in the direction perpendicular to the axial line on either
side of the mid-point is not necessarily material to the determination
of the mass flow within the tube since the integrated force is a
point force and proportional to the maximum value of the transverse
velocity and not the velocity gradient (unlike the case for an elementary
Additionally, the location of this resulting reaction force is
not necessarily required since the relative reaction of the input
and output legs of the flow meter conduit are to be sensed rather
than measuring the actual magnitude of this deflection. However,
the point of maximum Coriolis reaction is the ideal location for
the reaction force sensor since the magnitude of the reaction force
will be easier to separate from other external vibrations being
sensed at this location on the tube.
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention includes a flow
meter conduit which is centrally driven directly along the axial
line of the pre-existing defined fluid stream. A loop or couple
arm is formed for both the incoming and outgoing fluid flow with
each loop symmetrical about a central oscillatory means. The loops
are not cantilevered with respect to any specific fixed rotational
axis and are, each, substantially free-floating, i.e., substantially
free of restrictions of constraints along its length. The sensing
of the fluid reaction force on each loop is made independently.
Preferably, each loop provides a large deflection arm with respect
to the point of central oscillation.
Deficiencies in known flow meter designs relate to their sensing
technique and the effect of the vibrational influences on the reaction
force measurement. The present invention drives the flow meter conduit
directly along the line of the defined fluid stream of the existing
piping system. Additionally, the fluid reaction force against the
flow meter conduit is preferably sensed without reference to a specific
axis of rotation. The conduit is, also, substantially free-floating
and has effectively reduced the spring constant of the tube and
the resistance of the conduit in responding to the fluid reaction
force. All of these factors act to increase the sensitivity of the
mass flow measurement in the present invention.
The preferred embodiment of this invention includes a conduit or
tube which is placed within the line of a defined fluid stream.
The first loop of the conduit is formed with its outlet crossing
this axial line, substantially perpendicular thereto. The inlet
into the loop redirects the flow of the stream 90.degree. with respect
to the axial line. The inlet portion of the conduit redirects the
flow approximately 180.degree. relative to at least two planes which
are perpendicular to this axial line. An outlet portion of the flow
meter conduit, beginning at the outlet of the first loop or the
crossing point of the conduit with the axial line, redirects the
flow similar to that of the inlet portion, only in mirror image,
such that the flow returns into of the pre-existing pipeline of
the defined fluid stream. The second loop of the flow meter conduit
and the outlet portion of the flow meter are substantially identical
in size and shape to the first loop and inlet portion of the conduit.
The two loops are, preferably, positioned symmetrically about the
center point of the meter (or crossing point of the axial line).
An oscillating driver is positioned at the axial crossing and between
the two loops. The driver imparts a deflection to the conduit which
is substantially perpendicular to the flow at this point. This imparted
oscillation is, also, directed substantially along the axial line
of the pre-existing pipeline and at the most rigid point with respect
to the defined fluid stream. Thus, the effect of this oscillation
on the fluid flow up and down the stream from the flow meter is
Each loop is provided with at least one sensor or pick-up which
independently measures the oscillatory motion of its corresponding
loop due to the transverse acceleration of the fluid created by
the driver motion. The phase differential of the deflection of each
loop due to the opposite reaction force gradients is the preferred
reference characteristic of the sensors. The preferred sensor is
a piezo self-referencing transducer which is an accelerometer-type
sensor. This type sensor converts the mechanical vibratory energy
of the tube into a electrical pulse where the relative motion becomes
proportional to the acceleration of the tube. The piezo transducer
is generally used together with a low pass filter to electrically
eliminate unwanted vibrational frequency components. This type transducer
may also be directly mounted to the tube wall at the point of maximum
deflection of each loop and does not require a pre-set reference
to any specific fixed position of the loop. Thus, the output of
the sensor is related only to the oscillatory motion of the loop
created by the fluid reaction force.
By driving the conduit at a central point between the loop and
along the axial line of the existing fluid stream the effect of
the driver on the sensativity of the flow meter is substantially
increased. Additionally, the vibratory effect on the fluid flow
by the driver oscillation is substantially eliminated up and down
stream from the flow meter. This elimination is because the driver
motion is directly along the line of the fluid stream and not perpendicular
By positioning the sensors on a substantially freefloating loop
without requiring a fixed reference location, the loop motion may
be sensed without the inclusion of errors related to vibrations
of a fixed reference position. The vibrational effects on the flow
meter conduit not related to the fluid reaction force are substantially
eliminated from the sensor output by this invention. The use of
accelerometer-type sensors provide a means for rejection of unwanted
noise in the conduit reaction measurements since signals which do
not represent deflection due to the fluid reaction may be electronically
eliminated. By reducing the unwanted vibrational effects on the
flow meter conduit measurements, the accuracy and sensitivity of
the flow meter is substantially increased.
"In line" mounting of the transversely placed flow meter
conduit brings the inlet and the outlet of the flow meter closer
together. This structure substantially reduces the size of the meter
castings, such as its cover and mounting brackets. Also, the portion
of the process line which is displaced by the flow meter is minimized.
Additionally, since the flow meter is symmetrical about its center
position, the center of gravity of the meter does not effect its
motion in response to the reaction forces.
Further objects and advantages of this invention will become apparent
to those skilled in the art by particularly pointing out and describing
the preferred embodiments of this invention. For the purpose of
illustrating the invention, there is shown in the drawings a number
of forms which are presently contemplated; it being understood,
however, that this invention is not limited to the precise arrangements
and instrumentalities shown.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a perspective view of one embodiment of the invention
with reference to an axial coordinate system.
FIG. 2 shows a top view of the embodiment shown in FIG. 1.
FIG. 3 shows a front view of the embodiment in FIGS. 1 and 2 with
reference to dimensional parameters.
FIGS. 4a and 4b show an enlarged view of the preferred sensor embodiment
utilized in the invention.
FIG. 5 shows a perspective view of a second embodiment of the invention.
FIG. 6 shows a dual tube variation of the embodiment of the invention.
FIG. 6a shows a partial view of the flow meter tube shown in FIG.
FIG. 7 shows a side view of an additional embodiment of the invention.
FIG. 8 shows a perspective view of the embodiment shown in FIG.
FIG. 9 shows a perspective view of an additional embodiment of
the contemplated invention.
FIG. 10 shows a perspective view of an additional embodiment of
DETAILED DESCRIPTION OF THE DRAWINGS
In the first embodiment of the invention as shown in FIGS. 1 2
and 3 the flow meter conduit is referred generally to by the reference
numeral 10. The flow meter 10 is positioned substantially along
the axial line formed by the existing pipe line or defined fluid
stream. This axial line will be generally referred to as the X-axis
12. The vertical or Y-axis in the drawings will be referred to by
the reference numeral 14 and the Z-axis will be referred to by the
reference numeral 16. This coordinate reference system is particularly
shown in the perspective view in FIG. 1 with respect to this first
The conduit 10 has an inlet 18 and an outlet 20 which are positioned
substantially on the Z-axis 16 or within the plane formed by the
Y-axis 14 and the Z-axis 16. The connection to the conduit 10 from
the defined fluid stream to the inlet 18 and from the outlet 20
to the defined fluid stream is made through connecting portions
22 and 24 respectively.
Beginning at the inlet 18 the flow meter conduit 10 generally
forms an inverted S-shape, when viewed perpendicular to the Y-Z
plane and substantially defines two loops or deflection arms (see
FIG. 3). The first loop 40 of the conduit 10 extends from the inlet
18 through an inlet arm portion 30 curves through a first radial
portion 32 and extends through a central arm portion 34. The central
arm portion 34 passes through the X-axis 12 crossing substantially
perpendicular to this axis, such that the flow within the conduit
10 is perpendicular to the X-axis 12 at this crossing. Central arm
poriton 34 connects to a second radial portion 36 which in turn
connects to an outlet 20 through an outlet arm poriton 38. These
portions of the conduit 34 36 and 38 define the second loop 42.
The relative length of central arm poriton 34 as can be seen in
FIG. 3 is preferably twice the length of the inlet arm portion
30 or outlet arm poriton 38 of either the first 40 or second loop
42. This design minimizes the size of the flow meter and reduces
the spring constant of the flow meter conduit as compared to known
designs. It should be noted that each of these portions may be varied
in length considering the properties of the fluid within the flow
meter conduit 10. The diameter of the tubing of the conduit and
its construction material will also vary depending on the temperature,
pressure and fluid in the stream. The first loop 40 and the second
loop 42 are substantially identical such that the flow meter is
symmetrically about the X-axis 12 and the crossing point of this
axis. Additionally, in this first embodiment (FIGS. 1-3) the conduit
10 from the inlet 18 to the outlet 20 is substantially formed within
a single plane which is defined by the Y-axis 14 and the Z-axis
Since the flow of the pre-existing defined fluid stream is substantially
along the X-axis 12 the flow into and out of the flow meter conduit
10 must be deflected away from the X-axis 12 to connect with the
inlet 18 or outlet 20 which are positioned along the Z-axis 16.
This deflection of the flow is performed by connecting portions
22 and 24 which are positioned on respectively opposites sides of
the X-axis 12 for connection to the inlet 18 and the outlet 20.
These connecting portions 22 24 direct the fluid flow into the
first loop 40 which directs it in substantially a circular fashion
through the X-axis 12 and returns it from the second loop 42 to
the outlet 20 returning then to the defined fluid stream.
The preferred embodiment of the driver 48 is a mechanical feedback
multivibrator which operates at the resonant frequency of the mass
being driven. The driver generally comprises a bar magnet which
is attached to the flow meter conduit 10 (in FIGS. 1-3). The driver
48 in all embodiments shown deflects the flow meter conduti substantially
along the X-axis 12. An opposing current coil is positioned on either
side of the conduit 10 for alternately attracting and repelling
the bar magnet to cause the desired vibratory motion of the conduit
10 at the mid-point or X-axis 12 crossing. In typical circuitry
for the driver, a MOSFET bridge drives the coil which in turn drives
the magnets and the conduit 10. Conventional coil accelerometer
feedback or a combination of piezo/coil or a piezo/crystal may be
used to eliminate some of the electomagnetic common mode noise created
by the driver 48 which may effect the sensor and the flow rate determination.
Shown in FIG. 4a and 4b is a mechanical section of the preferred
embodiment of the sensor 56. This type sensor 56 is generally known
as an accelerometer and consists of a ceramic piece 58 having a
film or surface mounted center positioned mass 60. This sensor 56
can be attached directly to the conduit tube 10 onto each of the
loops or may be positioned by means of a mechanical clip (not shown).
Thin, typically, capton encapsulated wires are hung from the flow
meter tube 10 and are attached to the electronics box (not shown)
of the flow meter to provide the electrical signals from the sensor
Since mechanical noise effects the sensing of the fluid reactions
on the conduit 10 it is desirable to include a means for producing
a sensor signal having a narrow band so that unwanted electrical
noise caused by the vibration of the driver or other external influences
may be eliminated easily from the signal. This vibrational reaction
will be in addition to a differential noise cancellation between
the sensors 56 and the driver 48. Narrow band filters may be used
along with the output of the piezo X-tal preamp, on which is mounted
the central mass 60 being very tightly meshed in characteristics
and physically tied together with the sensor for temperature tracking
so that any phase shift of the filters will be substantially identical
to that of the sensors. Therefore, the integrity of the desired
mechanical phase shift is maintained.
The vibrations of the driver 48 create an increase in the transverse
momentum of the fluid which causes a reaction force against the
conduit wall 10. This reaction force creates a motion of the loops
40 or 42. The sensors 56 are positioned on opposite sides of the
central oscillation of the driver 48 to record this loop motion.
The sensors 56 produce serial information related to each loop's
motion which may be correlated in a microprocessor in any convenient
manner to provide an accurate determination of the corresponding
mass flow rate.
The embodiment of the flow meter conduit 110 shown in FIG. 5 is
a variation of the inverted "S" form shown in FIGS. 1-3.
This conduit 110 substantially forms a figure "8" design
such that the inlet arm portion 130 and the outlet arm portion 138
are formed in a radial fashion similar to their respective radial
portions 132 and 136. In this embodiment the inlet connecting portion
122 and outlet connecting portion 124 will still deflect the fluid
stream away from the X-axis 12 prior to joining with the inlet 118
and outlet 120 which are positioned along the Z-axis 16.
The embodiment shown in FIGS. 7 and 8 include an offset of the
flow meter conduit 210 away from the single plane defined by the
Y-axis 14 and the Z-axis 16. The inlet 218 and the outlet 220 are
positioned at a point adjacent to the X-axis 12 and are connected
through an inlet bend 222 and an outlet bend 224 respectively,
to position the inlet 18 and the outlet 20 away from the Z-axis
In FIG. 6 a dual tube design is shown. The conduit 110' form is
basically the same as that shown in FIG. 5 except that a second,
adjacent conduit 110" is provided. Inlet bend portion 122 divides
the flow from the defined fluid stream into the two conduits while
outlet bend portion 124' converges the flow from the outlets 120'
of the two conduits into the pipeline of the defined fluid stream.
Sensors 56 may be utilized to measure the deflection of each conduit
110' and 110" individually or may measure the comparative motion
of the adjacent loops 140' and 142' of each conduit to determine
the deflection signature.
FIG. 6A shows a partial view of the embodiment in FIG. 6 including
its driver 48. The two adjacent conduits 110' and 110" are,
preferably, used as a mounting reference for the coil 52 and bar
magnet 50 of the driver 48. This structure shows the coil 52 mounted
to conduit 110' by bracket 53. The bar magnet 50 is attached to
the adjacent conduit 110" at one end and positioned within
the coil 52 windings at its opposite end. When the coil 52 is excited
in the alternating mode, the two conduits will be alternatly repelled
or attracted to one another (depending on the mode of the coil).
Thus, the direction of drive oscillation is opposite in each conduit
at any one point in time. Therefore, the corresponding deflections
of the loops 140' and 142' of each conduit will be opposite to its
adjacent loop. Therefore, the sensed deflection will be essentially
twice that of a single tube design. Dual tube deflection and sensing
are discussed in Cox et al, U.S. Pat. No. 4127028 and Smith et
al, U.S. Pat. No. 4491025.
In FIG. 9 an alternate embodiment of the invention is shown having
two substantially circular or oval shaped loops 340 342 positioned
adjacent to one another. The loops are substantially parallel with
their central connection point provided along the X-axis 12. The
driver 48 is positioned at this central point. The reaction forces
of the fluid causing motion of each loop are sensed individually
on each loop with the comparative signature information being correlated
substantially the same as in previous designs.
In the embodiment of FIG. 10 a symmetrical conduit flow meter
410 is formed where the loops 440 and 442 are not formed in a circular
or oval shape. In this particular design, the inlet bend and outlet
bend portions utilized in the previously discussed conduit designs
are not required. The flow meter attaches at the inlet 418 and directly
deflects the flow of the fluid in a direction perpendicular to the
X-axis. A first radial portion 432 arcs from the inlet 418 position
to a point substantially along the Z-axis 16. A central arm portion
434 extends substantially along the Z-axis 16 crossing the X-axis
12 substantially perpendicular thereto. A second radial portion
436 arcs to return the flow towards the X-axis 12. The outlet 420
is positioned along the X-axis 12 at a position away from the Z-axis
16 and return the flow into the defined fluid stream.
Many variations on the invention may be designed such that the
driver deflects the conduit at a position where the flow meter crosses
the X-axis, substantially along the X-axis and perpendicular the
line of flow through the flow meter conduit at the point of oscillation.
The loops should have a curvature in excess of at least 180.degree.
and, preferably, in excess of 270.degree., and should also be symmetrical,
both, in and out of this deflection point such that the oscillatory
vibrations related to the fluid reaction forces are substantially
equivalent. The measurement of the reaction forces will be measured
with respect to their phase oscillation rather than their specific
location. Therefore, the symmetrical nature of the conduit design
is desired only to produce a uniform reaction force and spring constant
relative to the fluid flow.
The present invention, may be embodied in other specific forms
without departing from the spriit or essential attributes thereof
and, accordingly, reference should be made to the appended claims,
rather than to the foregoing specification, as indicating the scope
of the invention.