Abstrict A flow meter is provided for measuring the flow rate of fluid through
a conduit having an inlet and an outlet, which includes a measuring
chamber having a float disposed therein for movement in response
to fluid flow, and a detector for detecting the movement of the
float in the measuring chamber. Various devices are provided for
controlling the path of fluid flow from the conduit outlet to the
conduit inlet, which includes apparatus for allowing fluid to flow
from the outlet through the measuring chamber in a first direction
so as to move the float in the first direction past the detector,
and for also allowing fluid to flow from the outlet through the
measuring chamber in a second direction so as to move the float
in the second direction past the detector. Apparatus is connected
to the detector for measuring the rate of fluid flow in response
to the movement of the float in the first and second directions.
Claims What is claimed is:
1. A flow meter having an inlet and an outlet for measuring the
flow rate of fluid through a conduit, comprising:
first and second flow paths connected to said inlet, third and
fourth flow paths connected to said outlet;
a measuring chamber including a first port and a second port and
including a float disposed therein for movement in first and second
directions in response to fluid flow;
a detector for directly detecting the movement of said float while
said float is moving in said first direction or in said second direction
in said measuring chamber, so that the time it takes said float
to pass said detector while said float is moving in said first direction
or said second direction may be measured; and
means for controlling the path of fluid flow from said inlet to
said outlet including operating means movable between first and
second positions, whereby in said first position said operating
means fluidly connects said first port to said first flow path and
fluidly connects said second port to said fourth flow path, and
in said second position said operating means fluidly connects said
first port to said third flow path and said second port to said
second flow path whereby when said operating means is in said first
position said fluid is permitted to flow from said inlet through
said first and fourth flow paths through said measuring chamber
in said first direction so as to move said float in said first direction
past said detector, and when said operating means is in said second
position said fluid is permitted to flow from said inlet through
said second and third flow paths through said measuring chamber
in said second direction so as to move said float in said second
direction, opposite to said first direction, past said detector.
2. A flow meter in accordance with claim 1 wherein the specific
gravity of said float is substantially equal to the specific gravity
of the fluid being measured.
3. A flow meter in accordance with claim 1 wherein said float is
of a cylindrical shape.
4. A flow meter in accordance with claim 1 wherein said float includes
a core and a shell, each having different specific gravities.
5. A flow meter in accordance with claim 1 wherein said measuring
chamber is formed from a transparent tube.
6. A flow meter in accordance with claim 1 further including stop
members disposed at each end of said measuring chamber to retain
said float for a short period of time before the direction of movement
of said float is changed.
7. A flow meter in accordance with claim 1 wherein the cross-sectional
area at the ends of said measuring chamber is greater than the cross-sectional
area at the center of said measuring chamber.
8. A flow meter in accordance with claim 1 wherein said inlet is
connected by a Y-junction to said first and second flow paths, and
wherein said outlet is connected by a Y-junction to said third and
fourth flow paths.
9. A flow meter in accordance with claim 1 wherein said conduit
is connected to a four-way valve which is connected to said measuring
chamber by said first, second, third, and fourth flow paths.
10. A flow meter having an inlet and an outlet for measuring the
flow rate of fluid through a conduit, comprising:
a measuring chamber including a float disposed therein for movement
in response to fluid flow;
a detector for detecting the movement of said float in said measuring
chamber;
means for controlling the path of fluid flow from said inlet to
said outlet including means for allowing fluid to flow from said
inlet through said measuring chamber in a first direction so as
to move said float in said first direction past said detector, and
for allowing fluid to flow from said inlet through said measuring
chamber in a second direction so as to move said float in said second
direction, opposite to said first direction, past said detector;
said means for allowing fluid to flow including first and second
flow paths connected to said inlet, third and fourth flow paths
connected to said outlet, and a first port and a second port in
said measuring chamber;
said controlling means including operating means for alternately
fluidly connecting said first port to one of said first and fourth
flow paths and for alternately fluidly connecting said second port
to one of said second and third flow paths;
said flow paths being formed of compressible tubes, said operating
means operating to compress said tubes to prevent the flow of fluid
therethrough; and
means connected to said detector for measuring the rate of fluid
flow in response to the movement of said flow in said first and
second directions.
11. A flow meter in accordance with claim 10 wherein said operating
means for compressing said tubes is an eccentrically-mounted member
which is mounted such that it alternately compresses the first and
third flow paths and then the second and fourth flow paths against
corresponding seats.
12. A flow meter in accordance with claim 11 wherein said operating
means further includes lever arms arranged between said eccentric
member and said seats to compress said tubes, such that compression
takes place substantially at right angles to the axis of said tubes.
13. A flow meter in accordance with claim 10 wherein said operating
means is in the form of a rocker arm, the ends of which are movable
between two pairs of seats, said rocker arm operating to simultaneously
compress the first and third flow paths or the second and fourth
paths to prevent the flow of fluid therethrough.
14. A flow meter in accordance with claim 10 wherein said operating
means are two members eccentrically mounted and disposed between
two seats, said eccentrically-mounted members each operating at
the same time to compress one tube against each seat.
15. A flow meter having an inlet and an outlet for measuring the
flow rate of fluid through a conduit, comprising:
a measuring chamber including a float disposed therein for movement
in response to fluid flow;
a detector for detecting the movement of said float in said measuring
chamber;
means for controlling the path of fluid flow from said inlet to
said outlet including means for allowing fluid to flow from said
inlet through said measuring chamber in a first direction so as
to move said float in said first direction past said detector, and
for allowing fluid to flow from said inlet through said measuring
chamber in a second direction so as to move said float in said second
direction, opposite to said first direction, past said detector;
said means for allowing fluid to flow including first and second
flow paths connected to said inlet, third and fourth flow paths
connected to said outlet, and a first port and a second port in
said measuring chamber;
said controlling means including operating means for alternately
fluidly connecting said first port to one of said first and fourth
flow paths and for alternately fluidly connecting said second port
to one of said second and third flow paths;
said first and second flow paths being formed in a first duct and
said third and fourth flow paths being formed in a second duct,;
and
means connected to said detector for measuring the rate of fluid
flow in response to the movement of said float in said first and
second directions.
16. A flow meter in accordance with claim 15 wherein said measuring
chamber is an elongated housing with flexible end walls which are
moved by said operating means against the ends of said first and
second ducts.
17. A flow meter in accordance with claim 16 wherein said operating
means includes pusher elements for pushing the flexible end walls
against the respective end openings of said first and second ducts.
18. A flow meter in accordance with claim 17 wherein said pusher
elements are attached to said flexible end walls.
19. A flow meter in accordance with claim 17 wherein said pusher
elements are arranged in pairs on said operating means.
Description FIELD OF THE INVENTION
The present invention relates generally to flow meters and to an
improved flow meter which includes a measuring chamber having a
float disposed therein for movement in response to fluid flow, which
float is caused to move in opposite directions in order to determine
the rate of fluid flow.
BACKGROUND OF THE INVENTION
Flow meters for measuring the rate of fluid flow are well known
in the art. However, some of such flow meters are dependent on their
position, that is, they must be placed horizontally or vertically
in order to obtain a reading. In addition, some flow meters do not
have the desired measuring accuracy. Further, in particular applications,
it is desirable that a portion of the flow meter be disposable,
especially in medical applications.
Accordingly, it is an object of the present invention to provide
an improved flow meter which overcomes one or more of the aforesaid
problems. Specifically, it is within the contemplation of the present
invention to provide an improved flow meter which is not dependent
upon its position to obtain a reading and is, at the same time,
highly accurate.
It is a further object of the present invention to provide an improved
flow meter which is simple to manufacture and has the advantage
of being disposable so that it can be used in medical applications.
SUMMARY OF THE INVENTION
Briefly, in accordance with the principles of the present invention,
an improved flow meter is provided for measuring the flow rate of
fluid through a conduit, wherein the conduit has an inlet and an
outlet. First and second flow paths are connected to the conduit
outlet, and third and fourth flow paths are connected to the conduit
inlet. In addition, a measuring chamber is provided having a float
disposed therein for movement in response to fluid flow between
first and second ports, and a detector is also provided for detecting
the movement of the float in the measuring chamber. Operating means
are also provided for alternately fluidly connecting the first port
to the first and fourth flow paths and for alternately fluidly connecting
the second port to the second and third flow paths. The present
invention also includes means for controlling the path of fluid
flow from the outlet to the inlet, which includes a device for actuating
the operating means to a first position for allowing fluid to flow
from the outlet through the first and third flow paths via the measuring
chamber, while at the same time preventing the flow of fluid from
the second flow path to the fourth flow path so as to move the float
in a first direction past the detector. In addition, the device
also actuates the operating means to a second position for preventing
the flow of fluid from the first flow path to the third flow path,
while at the same time allowing fluid to flow through the second
and fourth flow paths via the measuring chamber so as to move the
float in a second direction past the detector. Finally, apparatus
is connected to the detector for measuring the rate of fluid flow
in response to movement of the float in the first and second directions.
In a preferred embodiment, the fluid flow paths are formed of compressible
tubes, with the operating means being employed to compress these
tubes in order to control the path of fluid flow. Advantageously,
compression of the fluid tubes avoids the introduction of any contamination
into the system. This is especially important when the flow meter
of the present invention is being used for medical applications,
and it is desired to work under sterile conditions.
In the present invention, a particularly high degree of measuring
accuracy is obtained if the specific gravity of the float is made
to be substantially equal to that of the specific gravity of the
liquid or fluid being measured. For example, this can be achieved
by providing the float with a cylindrical shape with a core and
shell having different specific gravities. In addition, the cylindrical
shape of the float is particularly advantageous when the apparatus
for reading the movement of the float is adapted to measure the
time which it takes for the float to pass a point of measurement.
In such case, at each end of the measuring chamber, stops may be
provided so as to retain the float or measuring element for a short
period of time before the movement of the float is reversed. Preferably,
in the vicinity of the stops, the measuring chamber is provided
with a larger cross-sectional area as compared to the cross-sectional
area of the measuring chamber in the region where the actual measurement
takes place. This insures that the liquid or fluid can flow past
the float, so that the risk of having the float stick in the measuring
chamber is reduced.
In a preferred embodiment, the measuring chamber is formed of a
transparent tube which is provided with two end pieces with connectors
for the first and second ports. Thus, the construction is very simple
to manufacture. In addition, in obtaining the measurement, a simple
photocell device can be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects, features, and advantages of the present invention
will become apparent upon the consideration of the following detailed
description of presently preferred embodiments when taken in conjunction
with the accompanying drawings, wherein:
FIG. 1 illustrates a first embodiment of the present invention
in the form of a simple outline diagram;
FIG. 2 illustrates a second embodiment of the present invention;
FIGS. 2a to 2c illustrate cross-sectional views taken along the
line A--A in FIG. 2 in three different operating positions;
FIG. 3 illustrates a third embodiment of the present invention;
FIG. 4 illustrates a double eccentric type of operating means which
can be used instead of the operating means illustrated in FIGS.
2 and 3;
FIG. 5 shows another embodiment of the present invention;
FIG. 6a illustrates a still further embodiment of the present invention;
and
FIG. 6b shows a modification of the embodiment of FIG. 6a.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
In the outline diagram according to FIG. 1 the conduit in which
the rate of flow is to be measured is designated 1 2. The part
of the conduit 1 is connected via a distributing point 3 to lines
4 and 5 respectively, which contain shut-off valves 6 and 7 respectively,
and which are connected to the two inlets 8 and 9 respectively,
of a measuring chamber 10. This measuring chamber contains a measuring
element 11. The inlets 8 and 9 are connected further to lines 12
and 13 comprising shut-off valves 14 and 15 respectively, and which
via a junction 16 are connected to the part of the conduit 2. When
measurement is to take place, the shut-off valves 7 and 14 for
example, are closed, while the valves 6 and 15 are kept open. The
float 11 is then caused to float towards the right in FIG. 1 past
a light source 17 and a photocell device 18 the output of which
is supplied to suitable apparatus for measuring the rate of fluid
flow. The photocell device 18 and such apparatus may measure, for
example, the time it takes for the measuring element 11 to pass
it. Directly after the measurement has been carried out, the direction
of flow in the measuring chamber 10 is reversed by closing the valves
6 and 15 while at the same time, the valves 7 and 14 are opened.
The movement of the measuring element 11 is thereby reversed so
that it will be directed towards the left in FIG. 1. The float 11
again passes the light source 17 and the photocell device 18 and
the measurement can be repeated.
The embodiment of the flow meter in accordance with the invention
shown in FIG. 2 differs from that shown in FIG. 1 mainly in that
it is made up of a number of single tubes, some coupling components
and a measuring element in the form of an expendable part which
may be discarded after use. In FIG. 2 the same reference designations
have been used as in FIG. 1 for corresponding parts, but with the
addition of a prime sign. Thus, the conduit wherein the velocity
of flow is to be measured is designated 1', 2'. The part of conduit
1' is connected via a simple Y-junction 3' to tubes 4' and 5'. These
tubes, in turn, are connected via junction pieces 19' and 20', respectively,
to tubes 4a' and 5a'. These, in turn, open into the inlets 8' and
9', respectively, in a measuring chamber 10'. A measuring element
11' is movable between two stops 21' and 22', respectively.
The part of conduit 2' is connected via a Y-shaped junction piece
16' to tubes 12' and 13', respectively. These tubes are connected
via junction pieces 20' and 19' to the tubes 4a' and 5a' and thus
also to the inlets 8' and 9' of the measuring chamber 10'. The valves
6 7 14 and 15 in the construction in FIG. 1 are replaced here
by an eccentric 23' and two seats 24' and 25', respectively. With
the help of this eccentric 23', the tubes 4', 5', 12 and 13' can
be compressed in pairs in such a manner as can be seen in detail
in FIGS. 2a to 2c. In FIG. 2a, a position is shown in which both
the tubes 4' and 12' are closed, while the tubes 5' and 13' are
open. FIG. 2b shows a position wherein all four tubes are open.
FIG. 2c finally shows a position in which the tubes 5' and 13' are
closed, while tubes 4' and 12' are kept open. As shown in the drawings,
any suitable apparatus may be utilized for actuating the eccentric
23'.
The function of the construction in accordance with FIG. 2 is substantially
the same as that of the construction in accordance with FIG. 1.
Thus, a reversible movement between the stops 21' and 22' is imparted
to the float 11' by the eccentric 23'. At the stop 21', the measuring
chamber 10' is provided with a widened part 26'. This allows the
liquid measured to flow past the measuring element during a short
period before the movement is reversed. A correspondingly widened
part also exists at the other end of the measuring chamber 10' adjoining
the stop 22'. This part, however, is not shown in the figure. Numerals
17' and 18', respectively, designate a schematically-indicated measuring
arrangement in the form of a light source 17' and a photocell device
18'. It will be clear though to those versed in the art that other
types of measuring arrangements can of course also be used for measuring
the movement of the float.
As can best be seen from FIGS. 2a to 2c, the opening and closing
of the tubes 4', 5', 12', and 13' takes place in such a manner that
the total pressure drop through the tubes is practically constant.
In FIG. 3 a third embodiment of the subject of the invention is
shown. This too is built up substantially according to the same
principles as the constructions according to FIGS. 1 and 2. Corresponding
parts have therefore been given the same reference designations
but with the addition of a double prime sign. The liquid which is
to be measured is thus introduced via a conduit section 1"
and withdrawn via a conduit section 2". These conduit sections
are connected to a coupling part 27" with internal ducts 28"
to 33". These ducts are connected to compressible tubes 4",
5", 12", and 13", respectively, which can be clamped
together with the help of a rocker arm 23" against four seats
6", 7", 14", and 15". In this way, precisely
the same effect is achieved as with the help of the schematically-indicated
valves 6 7 14 and 15 in the construction according to FIG. 1.
Thus, a reversible movement can be imparted to a measuring element
11" (not shown) in the measuring chamber 10" between its
inlets (outlets) 8" and 9". These inlets and outlets may
be provided with stops 21" and 22" corresponding to the
stops 21' and 22' in the construction according to FIG. 2. The movement
of the measuring element can be measured with the help of any type
of a known measuring device, e.g., with the help of a light source
and a photocell device in the same manner as in the constructions
according to FIGS. 1 and 2. These details have not been marked,
however, in FIG. 3. The contstruction in accordance with FIG. 3
has the advantage over that according to FIG. 2 however, that the
layout of the lines can be done in a simpler manner. Certain crossing
tubes, for example, are not needed.
FIG. 4 shows a double eccentric 23"' which can replace the
eccentric 23' according to FIG. 2 or the rocker arm 23" according
to FIG. 3. With the help of the double eccentric 23"', the
tubes 4"' and 12"' can thus be clamped together, while
at the same time, the tubes 5"' and 13"' are kept open.
The compression takes place against the seat 24"' and 25"',
respectively.
FIG. 5 finally shows a further embodiment in accordance with the
invention. Here too the details substantially correspond to the
constructions according to FIGS. 1 to 3. For corresponding parts,
the same reference designations have therefore been used but with
the addition of the letter a. In the figure, the measuring element
is thus marked 10a, and its two inlet or outlet parts are designated
8a and 9a. The flow which is to be measured arrives through an inlet
part 1a and is conducted through either of the tubes 4a and 5a,
either to the inlet part 8a or the inlet part 9a. After passing
through the measuring chamber 10a, the flow is conducted via one
of the tubes 12a and 13a to an outlet part 2a. With the help of
an eccentric 23a and two lever arms 34a and 35a, either the lines
4a and 12a are shut off, as shown in the figure, or the lines 5a
and 13a. Thanks to the lever arms 34a and 35a, a shut-off movement
is obtained which is substantially at right angles to the longitudinal
direction of the tubes. In this way, a pumping effect is avoided,
which otherwise would be brought about owing to the eccentric 23a.
In the position shown in FIG. 5 with the tubes 4a and 12a closed,
the liquid measured flows through the tube 5a and causes the float
11a to move towards the left in the figure. The liquid flows further
through the duct 36a and the tube 13a up to the outlet part 2a.
If, instead, the tubes 5a and 13a are closed and the tubes 4a and
12a are open, the liquid flows instead through the tube 4a, the
inlet part 8a, the measuring chamber 10a, and back through the duct
37a, which is connected to the tube 12a, which finally conducts
the liquid to the outlet part 2a. Numerals 38a and 39a designate
two O-rings between the end part 9a and the measuring chamber 10a.
Corresponding O-rings are of course found also in the end part 8a,
even though they are not shown in the drawing. The shut off of the
different tubes takes place against the seats 24a and 25a, respectively.
It will be clear to those versed in the art that the construction
in accordance with FIG. 5 functions in principle in the same manner
as those according to FIGS. 1 to 4. The advantages rest in a certain
simplification of the tube layout. A further simplification may
be achieved if the tubes above the eccentric 23a are joined to a
coupling piece corresponding to the coupling piece 27" in FIG.
3.
FIG. 6a illustrates a further simplification of the subject of
the invention. In this embodiment, once more the same reference
designations have been used as in the earlier figures but with the
addition of the letter b. Numeral 1b thus designates an inlet and
2b an outlet. From the inlet 1b, the liquid supplied is introduced
into a duct 36b. This duct 36b, together with a corresponding duct
37b on the outlet side, is connected in parallel with the measuring
chamber itself. The two ducts and the measuring chamber are arranged
jointly to pass through an elongated housing or casing which, as
a whole, is designated 10b. This housing is closed at its ends by
flexible end walls 8b and 9b. These end walls can be pressed with
the help of clamping elements 40b and 41b so as to form a seal against
the end openings of the ducts 36b and 37b. This pressing together
takes place with the help of four pusher elements 6b, 7b, 14b, and
15b, which thus correspond to the valves 6 7 14 and 15 in the
embodiment according to FIG. 1.
The function of the embodiment in accordance with FIG. 6a will
be substantially the same as the function of the above-described
embodiments. It should not be necessary therefore to describe it
in greater detail.
FIG. 6b illustrates a modification of the construction according
to FIG. 6a. In this figure, the same reference designations have
been used as in FIG. 6a but with the addition of a prime sign. In
this case, the pusher elements 6b' and 14b' are attached to the
flexible end wall 8b so that in this manner, they positively govern
the closing and opening of the end openings on the ducts 36b' and
37b'. As a result, the construction can operate independently of
the pressure in these ducts, i.e., at low pressure, as well as at
high pressure.
Another possible modification of the construction according to
FIG. 6a would be to let the pusher elements 6b, 7b, 14b, and 15b
be designed so as to originate from the end walls 8b and 9b. In
such a construction, the insertion and/or withdrawal of the measuring
chamber housing 10b with its end walls 8b and 9b would be facilitated.
In the above embodiments, constructions have been shown and described
in which the time is measured by one photocell device which is measuring
the time it takes for the float to pass the photocell, i.e., to
travel a certain distance. Of course, it is also possible to use
two photocell devices for the measuring of the time it takes for
the float to pass the distance between the two photocells.
In the embodiments which have been described, it is the movement
of the eccentric or the movement of the rocker arm which decide
when the float is to be reversed. Alternatively, the float itself
can be made to govern this movement. When the float passes the measuring
cell, the voltage in the cell increases, that is to say, a positive
slope is obtained which marks the start of measurement. The voltage
then remains constant during the further movement of the float.
When the float leaves the measuring cell, the voltage in the cell
drops and gives rise to a negative slope which marks the finished
measurement. Now this negative slope can be made to start a time
cycle, which can be fixed or variable, and which influences the
movement of the eccentric or of the rocker arm in such a manner
that the float is reversed into the desired position. This brings
the advantage, among other things, that the space 26' for allowing
the liquid to pass by, as shown in FIG. 2 is no longer required.
Moreover, the shock pressure, which occurs when the float moves
against its stop, or the pressure increase, which occurs when the
float comes to a halt in its end position and brakes the liquid,
are eliminated.
The invention is intended mainly to be used in connection with
the measurement of very small flows, e.g., on the order of magnitude
of 1 ml/min. In practice, there is nothing, however, to prevent
the principles described to be applied also to the measurement of
larger flows.
Naturally, the invention is not limited exclusively to the embodiments
described above but may be varied within the scope of the following
claims. Different constructions can be obtained, for example, if
parts from the different embodiments are exchanged against one another.
A latitude of modification, change, and substitution is intended
in the foregoing disclosure, and in some instances, some features
of the invention will be employed without a corresponding use of
other features. Accordingly, it is appropriate that the appended
claims be construed broadly and in a manner consistent with the
spirit and scope of the invention herein.
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