Abstrict A new and improved fluid flow meter which is suitable for a variety
of industrial and mechanical applications. The fluid flow meter
includes a fluid flow sensor that detects fluid flowing at low rates
and a fluid oscillation sensor that detects fluid flowing at high
rates through the sensor. The combined use of a fluid flow sensor
and a fluid oscillation sensor enables the fluid flow meter to measure
fluid flow rates over a broad range.
Claims 1. A fluid flow meter comprising: a housing for receiving a flowing
fluid; a fluid flow sensor provided in said housing; an oscillation
chamber provided in said housing for receiving the fluid; an outlet
flow channel provided in said housing in non-obstructed relationship
to said oscillation chamber; and an oscillation sensor provided
in said housing.
2. The fluid flow meter of claim 1 further comprising at least
one feedback fluid flow channel provided in said housing for receiving
the fluid from said oscillation chamber and wherein said oscillation
sensor is provided in said at least one feedback fluid flow channel.
3. The fluid flow meter or claim 2 wherein said oscillation chamber
narrows in configuration from an upstream end to a downstream end
of said oscillation chamber.
4. The fluid flow meter of claim 2 further comprising an inlet
mouth provided on said at least one feedback fluid flow channel.
5. The fluid flow meter of claim 1 wherein said fluid flow sensor
has a capability to formulate and display a flow rate of the fluid
in the form of a "yes/no" answer, with "yes"
indicating positive flow of the fluid and "no " indicating
no flow of the fluid.
6. The fluid flow meter of claim 5 further comprising at least
one feedback fluid flow channel provided in said housing for receiving
the fluid from said oscillation chamber and wherein said oscillation
sensor is provided in said at least one feedback fluid flow channel.
7. The fluid flow meter of claim 6 wherein said oscillation chamber
narrows in configuration from an upstream end to a downstream end
of said oscillation chamber.
8. The fluid flow meter of claim 6 further comprises an inlet mouth
provided oil said at least one feedback fluid flow channel.
9. The fluid flow meter of claim 1 wherein said said flow sensor
comprises a housing having an inlet end and an outlet and, a heating
element provided in said housing adjacent to said inlet end, and
a plurality of thermal sensor wires provided in said housing in
spaced-apart relationship to said heating element.
10. The fluid flow meter of claim 9 further comprising at least
one feedback fluid flow channel provided in said housing for receiving
the fluid from said oscillation chamber and wherein said oscillation
sensor is provided in said at least one feedback fluid flow channel.
11. The fluid flow meter of claim 10 wherein said oscillation chamber
narrows in configuration from an upstream end to a downstream end
of said oscillation chamber.
12. The fluid flow meter of claim 10 further comprising and inlet
mouth provided on said at least one feedback fluid flow channel.
13. A fluid flow meter comprising: a housing for receiving a flowing
fluid; an oscillation chamber provided in said housing; a fluid
flow sensor provided in said housing upstream of said oscillation
chamber for measuring low flow rates of the fluid; at least one
feedback fluid flow channel provided in said housing for diverting
arid re-distributing a portion of the fluid from said oscillation
chamber and back to said oscillation chamber; an outlet flow channel
provided in said housing in non-obstructed relationship to said
oscillation chamber; and all oscillation sensor provided in at least
one of said feedback fluid flow channels for measuring high flow
rates of the fluid.
14. The fluid flow meter of claim 13 wherein said oscillation chamber
narrows from an upstream end to a downstream end of said oscillation
chamber.
15. The fluid flow meter of claim 13 wherein said at least one
feedback fluid flow chamber comprise a pair of feedback fluid flow
channels.
16. The fluid flow meter of claim 15 wherein said oscillation chamber
narrows from an upstream end to a downstream end of said oscillation
chamber.
17. A fluid flow meter comprising: a housing for receiving a flowing
fluid; an oscillation chamber provided in said housing; a fluid
flow sensor provided in said housing upstream of said oscillation
chamber for measuring low flow rates of the fluid; at least one
feedback fluid flow channel provided in said housing for diverting
and re-distributing a portion of the fluid from said oscillation
chamber and back to said oscillation chambers said at least one
fluid flow channel having an inlet mouth; and an outlet flow chamber
provided in said housing in non-obstructed relationship to said
oscillation chamber; and an oscillation sensor provided in said
at least one feedback flow channel for measuring high flow rates
of the fluid.
18. The fluid flow meter of claim 17 wherein said oscillation chamber
has subs substantially parallel chamber walls.
19. The fluid flow meter of claim 17 wherein said at least one
feedback fluid flow channel comprises a pair of feedback fluid flow
channels.
20. The fluid flow meter of claim 19 wherein said oscillation chamber
has substantially parallel chamber walls.
Description FIELD OF THE INVENTION
[0001] The present invention relates to flow meters for measuring
the rate of flow of a fluid through a vessel. More particularly,
the present invention relates to a new and improved fluid flow meter
which includes both a fluid oscillation sensor and a fluid flow
sensor to provide fluid flow measurement capabilities over a broad
range while minimizing loss of fluid pressure.
BACKGROUND OF THE INVENTION
[0002] Flow meters are widely used in a variety of industries for
measuring the rate of flow of fluids through a vessel. For example,
breathing devices used in hospitals, car air conditioners, and household
gas meters utilize gas meters. However, most fluid flow meters known
in the art are capable of measuring fluid flow rates only over a
narrow range. Moreover, these fluid flow meters are not suitable
for measuring the rate of flow of fluids through a micro-sized channel.
There currently exists no wire-type sensor fluid flow meter which
is capable of measuring fluid flow rates over a dynamic range of
10000:1.
[0003] Flow meters having various structures and designs are known
in the art. U.S. Pat. No. 4224230 discloses a fluidic oscillation
flow meter. The flow meter exploits the Coanda effect, in which
a main fluid jet collides with a concave wall or sink, producing
an unstable or turbulent fluid oscillation effect. Thus, the oscillation
effect is directly proportional to the flow resistance, and this
requires a substantial pressure drop between the inlet and outlet
ends of the meter for proper functioning of the meter.
[0004] Another flow meter which operates under the Coanda effect
is disclosed in U.S. Pat. No. 5396809. That flow meter includes
an array of sensors disposed in an oscillation sink that is placed
in direct contact with the flowing fluid. The flow meter improves
and enhances measurement accuracy for fluids having a low rate of
flow.
[0005] U.S. Pat. No. 5363704 discloses a flow meter which includes
converging flow channels with a central oscillation sink disposed
in direct contact with the flowing fluid. When the rate of flow
of the fluid through the flow channels increases, the oscillation
effect is improved although the turbulence of the fluid in the oscillation
sink increases. To remedy this effect and increase the signal/noise
ratio of the signals measured by oscillation sensors in the oscillation
sink, channels extend from the oscillation sink and communicate
with the separate flow channels to permit flow of the fluid from
the oscillation sink to the channels. This increases the signal/noise
ratio of the sensor signals.
[0006] U.S. Pat. No. 5157974 discloses a fluidic flow meter which
is suitable for mini-microcomputer technologies. In the flow meter,
a flow sensor is placed at the outlet of the flow channel. When
fluid flows through the channel, the fluid oscillates. A signal
amplifier measures the signal and calculates flow speed and then
converts the flow speed to flow volume. While this configuration
prevents a decrease in the signal/noise ratio when oscillation of
the fluid occurs, the oscillation signal is attenuated.
[0007] Japanese Pat. no. JP44-262209 discloses a flow meter having
a design which is similar to that of U.S. Pat. No. 5157974 except
that an oscillation frequency sensor is placed at the inlet of an
oscillation chamber to increase the sensor oscillation frequency.
However, the sensor has a tendency to inaccurately interpret the
oscillation signal when the upstream fluid pressure changes.
[0008] Japanese Pat. no. JP2001-208575 discloses another flow meter
which operates according to the Coanda effect. The fluid inlet channel
of the flow meter gradually narrows to accelerate the fluid, then
passes through a short channel and into an oscillation chamber having
an oscillation sensor. Like the flow meter of JP44-262209 the sensor
has a tendency to inaccurately interpret the oscillation signal
when the upstream fluid pressure changes.
[0009] An object of the present invention is to provide a new and
improved fluid flow meter which avoids the drawbacks of conventional
fluid flow meters.
[0010] Another object of the present invention is to provide a
new and improved fluid flow meter which has broad mechanical and
industrial application.
[0011] Still another object of the present invention is to provide
a new and improved fluid flow meter which combines a fluid oscillation
sensor and a fluid flow sensor to impart fluid flow rate measurement
capability over a broad range.
[0012] Yet another object of the present invention is to provide
a new and improved fluid flow meter which enhances fluid oscillation
while preventing or substantially minimizing drop in fluid pressure
through the fluid flow meter.
[0013] A still further object of the present invention is to provide
a new and improved fluid flow meter which is capable of accurate
measurement over prolonged use.
[0014] Yet another object of the present invention is to provide
a new and improved fluid flow meter which is self-cleaning.
[0015] A still further object of the present invention is to provide
a new and improved fluid flow meter which may include an oscillation
chamber and one or a pair of fluid flow feedback channels which
extend from the downstream end to the upstream end of the oscillation
chamber to enhance oscillation of a fluid in the oscillation chamber.
SUMMARY OF THE INVENTION
[0016] In accordance with these and other objects and advantages,
the present invention is generally directed to a new and improved
fluid flow meter which is suitable for a variety of industrial and
mechanical applications. The fluid flow meter includes a fluid flow
sensor that detects fluid flowing at low rates and a fluid oscillation
sensor that detects fluid flowing at high rates through the sensor.
The combined use of a fluid flow sensor and a fluid oscillation
sensor enables the fluid flow meter to measure fluid flow rates
over a broad range.
[0017] The fluid flow meter may include an oscillation chamber
and at least one feedback fluid flow channel which has an inlet
end at the downstream end of the oscillation chamber and an outlet
end at the upstream end of the oscillation chamber. The oscillation
sensor may be a single-wire flow oscillation sensor that is placed
in the feedback flow channel.
[0018] The oscillation chamber of the fluid flow meter may gradually
narrow from the outlet end to the inlet end of the feedback fluid
flow channel, or from the upstream end to the downstream end of
the oscillation chamber. This tapered configuration of the oscillation
chamber facilitates oscillation of the flowing fluid at a relatively
low fluid flow rate. Alternatively or in addition, the inlet end
of the feedback fluid flow channel may be enlarged to enhance oscillation
of the fluid flowing through the oscillation chamber.
[0019] The oscillation sensor may be a single-wire oscillation
sensor, whereas the fluid flow sensor may be a multiple-wire fluid
flow sensor. The fluid flow sensor may include a sensor housing,
a heating element provided in the sensor housing adjacent to an
inlet end, and multiple, spaced-apart thermal sensors provided in
the sensor housing downstream of the heating element. The fluid
flow sensor utilizes a "time of flight" method to determine
the rate of flow of the fluid through the sensor housing. Electric
energy is intermittently applied to the heating element, which heats
the fluid flowing against the heating element. Flow rate of the
fluid is calculated by dividing the distance between the heating
element and the sensors by the time which elapses between heating
of the fluid at the heating element and thermal detection by the
thermal sensors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will now be described, by way of example,
with reference to the accompanying drawings, in which:
[0021] FIG. 1 is a side view of an illustrative embodiment of the
fluid flow meter of the present invention;
[0022] FIG. 2 is a longitudinal sectional view, taken along section
lines 2-2 in FIG. 1 of the fluid flow meter;
[0023] FIG. 2A is a sectional view of a portion of another embodiment
of the fluid flow meter of the present invention;
[0024] FIG. 3 is a longitudinal sectional view illustrating interior
elements of a fluid flow sensor component of the fluid flow meter;
[0025] FIG. 4 is an exploded, perspective view of the fluid flow
meter;
[0026] FIG. 5 is a longitudinal sectional view illustrating interior
elements of a typical fluid-flow oscillation sensor component of
the fluid flow meter;
[0027] FIG. 6 is an enlarged view of the oscillation chamber, feedback
fluid flow channels, and sensor elements of the fluid flow meter,
more particularly detailing a typical flow path of a fluid through
those elements of the fluid flow meter in operation of the invention;
and
[0028] FIG. 7 illustrates an alternative configuration for the
feedback fluid flow channels and oscillation chamber of the fluid
flow meter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Shown throughout the drawings, the present invention is
generally directed to a new and improved fluid flow meter which
is capable of measuring rates of flow of fluids across a broad flow
rate range. The fluid flow meter includes a fluid flow sensor that
detects fluid flowing at low rates and a fluid oscillation sensor
that detects fluid flowing at high rates through the sensor. The
fluid flow meter is suitable for a variety of industrial and mechanical
applications, including but not limited to gas meters or other fluid
meter system tools, medical devices, vehicle air controllers, mass
flow controllers or micro-flow controllers in micro device technologies.
[0030] Referring initially to FIGS. 1-5 an illustrative embodiment
of the fluid flow meter of the present invention is generally indicated
by reference numeral 10. The fluid flow meter 10 includes a housing
12 which may have a base portion 14 to which is mounted a top portion
16 as shown in FIG. 4. Alternatively, it is understood that the
housing 12 may have a unitary construction. As shown in FIG. 2
a fluid flow inlet 18 and a fluid flow outlet 20 are provided at
respective ends of the housing 12. As further shown in FIG. 2 the
fluid flow inlet 18 may communicate with an inlet chamber 22 in
which is typically provided a fluid flow sensor 24 the details
of which will be hereinafter described. An oscillation chamber 32
in the housing 12 communicates with the inlet chamber 22. At least
one, and preferably, two feedback fluid flow channels 36 further
extend through the housing 12 on opposite sides of the oscillation
chamber 32. The inlet end 37 of each feedback fluid flow channel
36 is located at the downstream end of the oscillation chamber 32.
Each channel 36 arcs back through the housing 12 and the outlet
end 38 of each channel 36 communicates with the upstream end of
the oscillation chamber 32. In a preferred embodiment, as shown
in FIG. 2 the chamber walls 34 of the oscillation chamber 32 gradually
narrow or taper inwardly from the outlet end 38 to the inlet end
37 of each channel 36. In an alternative embodiment, shown in FIG.
2A, the chamber walls 34 may be substantially parallel and the inlet
end of each channel 36 is enlarged to define an inlet mouth 36a.
In each embodiment, a fluid oscillation sensor 40 the details of
which will be hereinafter described, is provided in one or both
of the channels 36 for purposes which will be hereinafter described.
[0031] As further shown in FIG. 2 an outlet chamber 48 may communicate
with the downstream end of the oscillation chamber 32 through an
outlet flow channel 46 which extends through the housing 12. The
fluid flow outlet 20 extends from the outlet chamber 48 through
the housing 12 and communicates with the exterior of the housing
12.
[0032] As shown in FIG. 3 the fluid flow sensor 24 of the fluid
flow meter 10 is preferably a multi-wire type of micro flow sensor
and includes a sensor housing 26 having an inlet end 27a and an
outlet end 27b. A heating element 28 spans the interior of the housing
26 adjacent to the inlet end 27a, and multiple thermal sensor wires
30 likewise span the interior of the housing 26 at selected spacings
with respect to each other and with respect to the heating element
28. The heating element 28 is preferably a polysilicon heater/thermistor.
Each of the thermal sensor wires 30 is connected to a flow rate
calculating device 31 which includes a fluidic flow meter logic
circuit to calculate the flow rate of the fluid, as hereinafter
described. The circuit may include the capability to formulate and
display the flow rate of the fluid in the form of a "yes/no"
answer, with "yes" indicating positive flow of the fluid
and "no" indicating little or no flow of the fluid. In
operation of the fluid flow meter 10 as hereinafter described, a
fluid 50 flows through the sensor housing 26 from the inlet end
27a to the outlet end 27b. An electrical current is intermittently
applied to the heating element 28 which heats the flowing fluid
50. The heated fluid 50 then successively contacts the respective
thermal sensors 30. Accordingly, the flow rate calculating device
31 calculates the flow rate of the fluid 50 by dividing the distance
between the heating element 28 and each successive thermal sensor
wire 30 by the time required for the heated fluid 50 to traverse
the distance between the heating element 28 and the corresponding
thermal sensor wire 30. It is understood that the fluid flow sensor
24 heretofore described represents just one example of a fluid flow
meter which is suitable for implementation of the present invention,
and that any type of fluid flow meter which is capable of measuring
the flow rate of a fluid flowing therethrough may be used instead.
[0033] As shown in FIG. 5 the fluid oscillation sensor 40 of the
fluid flow meter 10 is preferably a single wire-type fluid oscillation
sensor. Such a sensor may be conventional and includes an enclosure
42 having a single oscillation wire 44 which spans the interior
of the housing 42 in multiple passes. Accordingly, a turbulent or
oscillating fluid 50 flowing through the enclosure 42 contacts and
oscillates the oscillation wire 44 which provides this information
to an oscillation measuring device 45 connected thereto to determine
the degree of oscillation or turbulence of the fluid 50 as is known
by those skilled in the art. The oscillation measuring device 45
includes flow calculation logic circuit which converts the period
oscillation frequency of the oscillation wire 44 under influence
by the oscillating fluid 50 to instant flow speed of the fluid
50 as is known by those skilled in the art.
[0034] Referring next to FIGS. 2 4 and 6 in operation the fluid
flow meter 10 is installed in a fluid flow line 66 by connecting
a fluid inlet conduit 62 to the fluid flow inlet 18 and a fluid
outlet conduit 64 to the fluid flow outlet 64 of the housing 12.
As shown in FIG. 6 a fluid 50 which may be a gas or a liquid,
flows from the fluid inlet conduit 62 through the fluid flow sensor
24 in the inlet chamber 22 of the housing 12 into the oscillation
chamber 32 through the outlet flow channel 46 and outlet chamber
48 and from the housing 12 through the fluid flow outlet 20 and
fluid outlet conduit 64 of the fluid flow line 66 respectively.
[0035] When the fluid 50 flows at a relatively low flow rate of
typically about 1.5 m/s or less, little or no fluid oscillation
occurs in the oscillation chamber 32 or feedback fluid flow channels
36. Accordingly, the fluid flow sensor 24 rather than the fluid
oscillation sensor or sensors 40 is used to measure the flow rate
of the fluid 50 at these relatively low flow speeds. An electrical
current is intermittently applied to the heating element 28 thereby
heating the flowing fluid 50. As the heated fluid 50 flows into
contact with the respective thermal sensors 30 the flow rate calculating
device 31 calculates the flow rate of the fluid 50 by dividing the
distance between the heating element 28 and each successive thermal
sensor wire 30 by the time required for the heated fluid 50 to
flow from the heating element 28 and each thermal sensor wire 30.
This information may be displayed on a suitable display screen (not
shown), for example, connected to the flow rate calculating device
31 as desired.
[0036] When the fluid 50 flows at a relatively high flow rate of
typically greater than about 1.5 m/s, the fluid oscillation sensor
or sensors 40 rather than the fluid flow sensor 24 is used to
determine the flow rate of the fluid 50. Accordingly, at such relatively
high fluid flow rates, some of the fluid 50 flowing through the
oscillation chamber 32 enters the inlet end 37 of the feedback fluid
flow channel or channels 36 and is distributed through the fluid
oscillation sensor or sensors 40 therein. Each channel 36 distributes
the fluid 50 back around to the upstream end of the oscillation
chamber 32 where the fluid 50 exits the outlet end 38 of the channel
36 and pushes against the main stream of fluid 50 flowing from the
inlet chamber 22 into the oscillation chamber 32. This causes oscillation
of the fluid 50 in the oscillation chamber 32 and channels 36. The
oscillation frequency of the oscillation sensor wire 44 produced
by the oscillating fluid 50 is measured by the oscillation measuring
device 45 (FIG. 5) connected to the fluid oscillation sensor 40.
The oscillation measuring device 45 uses the period oscillation
frequency produced by the oscillation sensor wire 44 to calculate
instant flow speed via the flow calculation logic circuit, as is
known by those skilled in the art. Accordingly, the fluid flow sensor
24 and the fluid oscillation sensor or sensors 40 are capable of
detecting and measuring fluid flow rates over a broad range (on
the order of about 10000:1).
[0037] An alternative fluid flow configuration for a fluid flow
meter 52 in another embodiment of the invention is shown in FIG.
7. The fluid flow meter 52 includes a housing 54 into which extends
a fluid flow inlet 56 which receives the flowing fluid 50. An oscillation
chamber 60 in the housing 54 gradually broadens from the fluid flow
inlet 56 to a pair of outlet channels 58 which diverge from the
oscillation chamber 60. At least one, and preferably, two feedback
fluid flow channels 57 extend through the housing 54 from each
outlet channel 58 to the upstream end of the oscillation chamber
60. A fluid oscillation sensor 40 is provided in one or both of
the channels 57 and a fluid flow sensor 24 is provided typically
in the fluid flow inlet 56. Accordingly, some of the flowing fluid
50 flows through the channels 57 and re-enters the oscillation chamber
60 thus causing oscillation of the main stream of fluid flowing
from the fluid flow inlet 56 into the oscillation chamber 60. The
fluid flow sensor 24 is used to calculate relatively low fluid flow
rates (typically about 1.5 m/s or less), whereas the fluid oscillation
sensor or sensors 40 are used to calculate relatively high fluid
flow rates (typically greater than about 1.5 m/s), as heretofore
described with respect to the embodiment of FIGS. 1-6.
[0038] While the preferred embodiments of the invention have been
described above, it will be recognized and understood that various
modifications can be made in the invention and the appended claims
are intended to cover all such modifications which may fall within
the spirit and scope of the invention. |