U.S. patent application number 10/892678 was filed with the patent office on 2004-12-23 for electrical/visual differential pressure indicator with solid state sensor.
This patent application is currently assigned to PTI TECHNOLOGIES, INC.. Invention is credited to Moscaritolo, Daniel K., Mouhebaty, Bijan, Sandoval Diaz, Fermin Alejandro.
Application Number | 20040255684 10/892678 |
Document ID | / |
Family ID | 32507373 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040255684 |
Kind Code |
A1 |
Mouhebaty, Bijan ; et
al. |
December 23, 2004 |
Electrical/visual differential pressure indicator with solid state
sensor
Abstract
A method of determining fouling of a filter includes the use of
a differential pressure indicator which has a housing with at least
two ports in the housing. One port receives a first pressure, and
the second port receives a second pressure. A pressure resistive
device is placed between the first port and the second port, and
changes its position when the first pressure exceeds the second
pressure by a predetermined amount. A magnet is coupled to the
pressure resistive device. A digital displacement sensor senses the
position of the magnet and is in communication with an electronic
indicator. The electronic indicator activates when the first
pressure exceeds the second pressure by a predetermined amount,
thus allowing determination of filter fouling.
Inventors: |
Mouhebaty, Bijan; (Westlake
Village, CA) ; Sandoval Diaz, Fermin Alejandro;
(Camarillo, CA) ; Moscaritolo, Daniel K.;
(Thousand Oaks, CA) |
Correspondence
Address: |
Keyvan Davoudian
PILLSBURY WINTHROP LLP
Suite 2800
725 South Figueroa Street
Los Angeles
CA
90017-5406
US
|
Assignee: |
PTI TECHNOLOGIES, INC.
|
Family ID: |
32507373 |
Appl. No.: |
10/892678 |
Filed: |
July 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10892678 |
Jul 16, 2004 |
|
|
|
10334085 |
Dec 30, 2002 |
|
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Current U.S.
Class: |
73/723 |
Current CPC
Class: |
G01L 9/0089 20130101;
G01L 19/12 20130101; G01L 19/14 20130101 |
Class at
Publication: |
073/723 |
International
Class: |
G01L 009/00 |
Claims
What is claimed is:
1. A method of determining a fouling status of a filter,
comprising: measuring a differential pressure between a flow
upstream from the filter and a flow downstream from the filter;
causing, by means of a solid state digital displacement sensor, an
electronic indicator to activate when the differential pressure is
higher than a set value; and determining the fouling status of the
filter based on the activation of said electronic indicator.
2. The method of claim 1, wherein the electronic indicator is a
light emitting diode (LED).
3. The method of claim 1, wherein the electronic indicator is an
auditory alert.
4. The method of claim 1, wherein said differential pressure is
measured by a measurement device comprising: a housing having a
first port to which the upstream flow pressure is ported and a
second port to which the downstream flow pressure is ported; a
pressure resistive device located between the first port and the
second port, wherein the pressure resistive device changes its
position when the upstream pressure exceeds the downstream pressure
by a predetermined amount; and a magnet coupled to the pressure
resistive device.
5. The method of claim 4, wherein the electronic indicator is
activated based on a position of the magnet as detected by the
solid state digital displacement sensor.
6. The method of claim 4, wherein the electronic indicator is
located remotely from the housing of the measurement device.
7. The method of claim 4, wherein the measurement device further
comprises a control module, said module being electrically coupled
to the solid state digital displacement sensor and in communication
with the electronic indicator, said electronic indicator being
activated based on a position of the magnet as detected by the
solid state digital displacement sensor.
8. The method of claim 7, wherein the control module is an
electronic circuit.
9. The method of claim 7, wherein the control module is a
microcontroller.
10. The method of claim 9, wherein the measurement device includes
a plurality of electronic indicators sequentially activating
according to a schema based on temporal measurements of signals
from the solid state digital displacement sensor.
11. The method of claim 4, wherein the pressure resistive device
includes a piston assembly having a piston and a spring coupled to
a first end of the piston, said magnet being coupled to a second
end of the piston.
12. The method of claim 4, wherein the pressure resistive device
includes a diaphragm assembly having a diaphragm and a connecting
rod, wherein a spring is coupled to a first end of the connecting
rod and the magnet is coupled to a second end of the connecting
rod, and the connecting rod is coupled to the diaphragm at a
location between the first end and the second end of the connecting
rod.
13. A method of determining a fouling status of a filter,
comprising: (a) measuring a differential pressure between a flow
upstream from the filter and a flow downstream from the filter; (b)
causing, by means of a solid state digital displacement sensor, a
plurality of electronic indicators to become sequentially activated
at predetermined intervals when the differential pressure is higher
than a set value; (c) correlating said intervals to the amount of
time for which said differential pressure remains higher than said
set value; and (d) determining the fouling status of the filter
based on the number of said plurality of electronic indicators that
are activated.
14. The method of claim 13, wherein the electronic indicator is a
light emitting diode (LED).
15. The method of claim 13, wherein the electronic indicator is an
auditory alert.
16. The method of claim 13, wherein the electronic indicator is
located remotely from the filter.
Description
RELATED APPLICATION DATA
[0001] This is a divisional of application Ser. No. 10/334,085,
filed Dec. 30, 2002, now U.S. Pat. No. ______.
FIELD OF INVENTION
[0002] The present invention is directed generally to a
differential pressure indicator, and more specifically, to a
differential pressure indicator incorporating the use of a digital
displacement sensor, and to a method of using same to determine
filter fouling.
BACKGROUND
[0003] Many attempts have been made in the past to provide a
mechanism for monitoring the condition of a filter in either a
fluid or gaseous environment and to detect whether a filter element
must be replaced or reconditioned before continuing operation.
These devices are, for example, used in hydraulic systems to
provide a visual or electrical signal (or a combination of both)
when differential pressures across a filter element exceed a set
value. Devices of this nature have been fashioned in electrical
forms, mechanical forms, or a combination of both. However,
problems have arisen with the said devices.
[0004] The most cost-efficient indicators to date utilize a
combination of mechanical and electrical elements. In these hybrid
indicators, a mechanical micro switch is used to provide a signal
by opening or closing an electrical circuit. However, the use and
reliability of a micro switch is limited when low currents (less
than 0.5 amp) are required. Additionally, many applications require
hermetically sealed switches, which in turn increase the size,
weight, and cost of the indicator.
[0005] Thus, there is a need for reliable, small, inexpensive
differential pressure indicators that can work with low currents
and a broad range of temperatures, especially for applications
involving hydraulic systems in aircraft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 depicts a cut-away view of a differential pressure
indicator in a non-actuated state according to an embodiment of the
present invention;
[0007] FIG. 2 depicts an electrical schematic of a control module
incorporating a circuit board according to an embodiment of the
present invention;
[0008] FIG. 3 depicts a cut-away view of a differential pressure
indicator in an actuated state according to an embodiment of the
present invention;
[0009] FIG. 4 depicts a cut-away view of a differential pressure
indicator in a non-actuated position according to an alternative
embodiment of the present invention;
[0010] FIG. 5 depicts an electrical schematic of a control module
incorporating a microcontroller according to an embodiment of the
present invention.
DETAILED DESCRIPTION
[0011] Embodiments of the present invention are directed to
differential pressure indicators incorporating pressure-resistive
devices and digital displacement sensors to measure filter
performance characteristics. Various pressure-resistive devices may
be used depending on the relevant pressures involved in the
application. Similarly, various electrical indicators may be used
depending on the relevant application of the differential pressure
indicator. Embodiments of the present invention may be used in
either gas pressure or fluid pressure applications.
[0012] The differential pressure indicator presented herein
replaces the mechanical micro switch of previous designs with a
solid state digital displacement sensor. The use of a
non-mechanical electrical switch and electronic indicator
significantly reduces the part count compared with existing
differential pressure indicator designs. The reduction in part
count also has an immediate impact on assembly component cost and
has the added benefit of improving reliability in both low and high
differential pressure applications regardless of the system
pressure. Differential pressure indicators are less susceptible to
shock and vibration, smaller in size and more suitable to low
current applications. Furthermore, digital displacement sensors
provide a significant cost savings over micro switches.
[0013] The reduction of moving parts along with the robustness of
solid state electronics enhances the reliability and capability of
the indicator. Additionally, with this approach, the operating and
release points can be maintained within a few pounds per square
inch differential ("PSID"), even over a wide range of voltage
inputs. According to the preferred embodiment of the invention, the
differential pressure indicator can work with voltages ranging from
3.8 to 30 VDC and can operate with a current supply as low as 10
mA. Additionally, this indicator can work within operating
temperatures ranging from -40.degree. F. to +302.degree. F.
[0014] FIG. 1 depicts a cut-away view of a differential pressure
indicator in a non-actuated state according to a preferred
embodiment of the present invention. The differential pressure
indicator, according to this embodiment, includes a housing 10, a
high pressure port 20, a low pressure port 30, a spring 40, a
chamber 110 housing a piston 50, a magnet 60, a digital
displacement sensor 70, a control module 80, a light-emitting diode
("LED") 90, and leads 100. According to the embodiment of FIG. 1, a
pressure upstream from a filter element is ported to the high
pressure port 20 that is ported through the housing 10, and the
upstream pressure pushes on one end of the piston 50, which resides
in a chamber 110 in the housing 10. A pressure downstream from a
filter is ported to the low pressure port 30, also ported through
the housing 10, and the downstream pressure pushes on the opposite
end of the piston 50. The piston 50 is coupled to the spring 40 at
one end, and the permanent magnet 60 at the other. The magnet 60
provides a magnetic field that affects the digital displacement
sensor 70. The digital displacement sensor 70 is coupled to the
control module 80, and the magnetic field of the magnet 60 causes
the digital displacement sensor 70 to output a different digital
signal to the control module 80 than it would otherwise if the
magnetic field were not present. The control module 80 is
electronically coupled to the LED 90, and the leads 100. The leads
100 allow for remote sensing, such as coupling the leads to an LED
located some distance from the differential pressure indicator, for
instance, in an instrument panel in the cockpit of an airplane.
[0015] When the differential pressure indicator is in a
non-actuated state as shown in FIG. 1, the magnet 60 is in the
presence of the digital displacement sensor 70, and the magnetic
field produced by the magnet 60 causes the digital displacement
sensor 70 to produce a certain digital signal to the control module
80.
[0016] FIG. 2 depicts a control module according to an embodiment
of the present invention wherein the control module is an
electronic circuit. In FIG. 2, a voltage regulator 200 is in
electrical communication with the digital displacement sensor 70.
The voltage regulator 200 receives power from an external supply,
for instance, from an airplane's battery or alternator. The
incorporation of the voltage regulator increases the life of the
electrical components and allows the differential pressure
indicator to work across a broad range of voltage inputs. The
voltage regulator changes the voltage input it receives to a
voltage output that can be specifically used by the circuit. For
example, the voltage regulator 200 accepts 30 VDC from the power
source and drops the voltage to 5 VDC. The regulator 200 operates
to maintain the output supply voltage at 5V, for example, even if
the load which it is supplied changes.
[0017] In FIG. 2, when the differential pressure indicator is in a
non-actuated state, the digital displacement sensor 70 is in the
magnetic field of the magnet 60 and is producing a digital signal
of "1" (voltage=5VDC), so that no voltage potential exists across
the LED 90. When the digital displacement sensor is not within the
magnetic field of the magnet 60, the digital displacement sensor 70
produces a digital signal of "0" (voltage.noteq.1V), this allows
the voltage from the regulator to be applied across the LED 90,
energizing the LED 90. In a preferred embodiment, if the primary
power source is removed, as when the aircraft is turned off when
parked, for example, the electronic indicator remains activated by
an embedded power source. The embedded power source is a secondary
power source to a primary power source that powers the circuit. In
FIG. 2, the embedded power source is depicted as a capacitor 210,
according to one embodiment of the present invention. According to
another embodiment, the embedded power source may be a battery.
[0018] In an embodiment of the invention using an electronic
circuit as a control module, C1 is a 1 .mu.F 100V capacitor, C2 is
a 1500 nF 50V capacitor, C3 and C5 are 2.2 .mu.F 10V capacitors, C4
is a 1.0 Farad Gold CAP capacitor, D1-D3 are Schottky 30 V 30 mA
diodes, D4 is a 3MM LED, R1 is a 43.2K.OMEGA. resistor, R2 is a
12.1K.OMEGA. resistor, R3 is a 2K.OMEGA. resistor, and the DDS is
the digital displacement sensor PTI P/N 7594207-101. The present
invention is not limited to the illustrated embodiment, and one
skilled in the art may easily modify this circuit and/or its values
to accomplish the same goals with different configurations.
Furthermore, while this schematic depicts an embodiment where the
digital displacement sensor 70 produces a digital value of "1" in
the presence of a magnetic field and "0" otherwise, one skilled in
the art could easily manipulate this schematic such that the
digital displacement sensor 70 produces a digital value of "0" in
the presence of a magnetic field and "1" otherwise.
[0019] FIG. 5 depicts a control module according to a preferred
embodiment of the present invention wherein the control module is a
microcontroller. In FIG. 5, a voltage regulator 200 is in
electrical communication with a microcontroller 500, a digital
displacement sensor 70, and the secondary power source, in this
case, a capacitor 510. In FIG. 5, when the differential pressure
indicator is in a non-actuated state, the digital displacement
sensor 70 is in the magnetic field of the magnet 60 and is
outputting a digital signal of "1" (voltage=5VDC), to the
microcontroller 500. When the digital displacement sensor is not
within the magnetic field of the magnet 60, the digital
displacement sensor 70 outputs a digital signal of "0"
(voltage.noteq.1V) to the microcontroller 500. The microcontroller
500 determines the amount of time that the digital displacement
sensor 70 has been outputting a digital signal of "0." If the
digital displacement sensor 70 outputs a digital signal of "0" for
less than two (2) seconds, then LED1 520 is activated. If the
digital displacement sensor 70 outputs a digital signal of "0" for
more than two (2) seconds, but less than five (5) seconds, then
LED2 530 is activated. If the digital displacement sensor 70
outputs a digital signal of "0" for more than five (5) seconds, but
less than ten (10) seconds, LED3 540 is activated. And if the
digital displacement sensor 70 outputs a digital signal of "0" for
more than ten (10) seconds, LED4 550 is activated.
[0020] The addition of multiple LED's that sequentially activate
based upon a signal's temporal measurement alert to the possibility
of "false positives" caused by pressure spikes. That is,
occasionally a system experiences a pressure spike that is not
caused by the fouling of a filter, but rather by some other
anomaly. These pressure spikes characteristically only occur for a
short period of time, for example a period of three or four
seconds. The use of a microcontroller alerts to the presence of a
pressure spike as opposed to the fouling of a filter and saves
needless examination or replacement of the filter. However, if the
differential pressure surpasses the actuation differential pressure
for longer than ten (10) seconds (thus causing the digital
displacement sensor 70 to output a digital signal of "0" for longer
than ten (10) seconds), the cause is most likely due to a fouled
filter and not a pressure spike. Thus, if LED4 520 activates, it
alerts that the filter is most likely fouled and needs examination
or replacement.
[0021] In a preferred embodiment of the differential pressure
indicator incorporating the use of a microcontroller, if the
primary power source is removed, as when the aircraft is turned off
when parked, for example, the electronic indicator remains
activated by an embedded power source. In FIG. 5, the embedded
power source is depicted as a capacitor 510, according to one
embodiment of the present invention. According to another
embodiment, the embedded power source may be a battery.
[0022] In an embodiment of the present invention incorporating the
use of a microcontroller as a control module, the microcontroller
is Microchip PIC12C Family Part Number PIC12C509A, the digital
displacement sensor is Honeywell Digital Position Sensor Model No.
SS449A, C1 is a Resin Dipped Solid Tantalum, 35 VDC 0.1 mF
capacitor, C2 is a Ceramic Disc, 25 V 0.1 mF capacitor, R1 is a
Metal Film, 0.25W 100K.OMEGA. resistor, R2 is a Metal Film, 0.25W
33K.OMEGA. resistor, R3-R6 are Metal Film, 0.25W 1K.OMEGA.
resistors, and LED1-LED4 are Amber 1.5 VDC 20 mA Light Emitting
Diodes. The present invention is not limited to the illustrated
embodiment, and one skilled in the art may easily modify this
circuit and/or its values to accomplish the same goals with
different configurations. Furthermore, while this schematic depicts
an embodiment where the digital displacement sensor 70 produces a
digital value of "1" in the presence of a magnetic field and "0"
otherwise, one skilled in the art could easily manipulate this
schematic such that the digital displacement sensor 70 produces a
digital value of "0" in the presence of a magnetic field and "1"
otherwise.
[0023] FIG. 3 depicts a differential pressure indicator in an
actuated state according to a preferred embodiment of the present
invention. In the actuated state, the pressure flowing upstream of
a filter, ported through the high pressure port 20, is higher than
the pressure flowing downstream and ported through the low pressure
port 30. This difference in pressure tends to push the piston 50
towards the low pressure port 30. If the upstream pressure being
ported through the high pressure port 20 exceeds the downstream
pressure being ported through the low pressure port 30 by a
specified value (the actuation differential pressure), then the
piston/magnet combination will move far enough away from the
digital displacement sensor 70 such that the magnetic field no
longer engages the digital displacement sensor 70. When the digital
displacement sensor 70 is no longer engaged by the magnetic field,
it causes the power flowing through the circuit 80 to pass through
the LED 90, activating it.
[0024] The specific actuation differential pressure, that is, the
difference in pressure between the upstream pressure and the
downstream pressure that causes the LED 90, or other suitable
electronic indicator, to activate may be set by varying the
strength and tension of the spring 40.
[0025] FIG. 4 shows a cut-away view of a differential pressure
indicator with a diaphragm assembly as its pressure resistive
device. For applications involving low differential pressures,
i.e., differential pressures below 15 PSID, a preferred embodiment
utilizes a diaphragm assembly. FIG. 4 is similar to FIG. 1 except
that the piston assembly has been replaced with a diaphragm
assembly. In this embodiment of the invention, upstream pressure is
ported through the high pressure port 20 such that the upstream
pressure presses against one side of the diaphragm 400. Downstream
pressure is ported through the low pressure port 30 and pushes
against the opposite side of the diaphragm 400. A connecting rod
410 passes through the diaphragm 400 and is coupled to the spring
40 at one end and a magnet 60 at the other. When the upstream
pressure exceeds the downstream pressure, the differential pressure
pushes the diaphragm 400 towards the low pressure port 30. The
movement of the diaphragm 400 causes the connecting rod 410 to move
towards the low pressure port 30 as well, withdrawing the magnet 60
from the presence of the digital displacement sensor 70. When the
differential pressure exceeds the actuation differential pressure,
the magnet 60 will have moved far enough away from the presence of
the digital displacement sensor 70 so that the magnetic field of
the magnet 60 no longer engages the digital displacement sensor 70.
When the digital displacement sensor 70 is no longer engaged by the
magnetic field, the digital placement senor 70 causes power to pass
through the LED 90, activating it.
[0026] Another embodiment of the present invention utilizes any
suitable pressure resistive device or module in the place of the
piston assembly or diaphragm assembly.
[0027] In another embodiment of the present invention, any suitable
type of electronic indicator may be utilized, replacing the
light-emitting diode present in FIGS. 1, 2, and 3. The purpose of
the electronic indicator is to provide a visual or auditory alert
indicating that a filter may require cleaning, replacement, or
examination.
[0028] In another embodiment of the present invention, no light
emitting diode or other electronic indicator is present in the
differential pressure indicator itself. Instead, a set of leads are
used to electronically couple the differential pressure indicator
to an electronic indicator located some distance away from the
differential pressure indicator, for example, to a light-emitting
diode located in the cockpit of the airplane. Another embodiment of
the present invention may only have the electronic indicator, for
instance an LED, electronically coupled to the circuit, leaving the
leads off completely. In still another embodiment of the present
invention, both the on-board light emitting diode, or other
electronic indicator, and leads are present. This design has the
added benefit of having an alert located some distance away from
the actual differential pressure indicator, for example, in the
cockpit of an airplane, and an alert at the actual site of the
indicator so that when maintenance is required, the specific
differential pressure indicator may be easily identified.
[0029] In one embodiment of the present invention, the housing 10
is made of metal. In another embodiment of the invention, the
housing 10 is made of plastic or other suitable material.
[0030] In one embodiment of the present invention, the digital
displacement sensor outputs a digital signal of 1 when the magnetic
field of the magnet is present, and a digital signal of 0 when it
is not. In another embodiment, the signals are reversed and when
the magnetic field is present, the digital displacement sensor
outputs a digital signal of 0 and when it the magnetic field is
removed, it outputs a digital signal of 1.
[0031] While the description above refers to a particular
embodiment of the present invention, it will be understood that
many modifications may be made without departing from the spirit
thereof. The accompanying claims are intended to cover such
modifications as would fall within the true scope and spirit of the
present invention. The presently disclosed embodiments are
therefore to be considered in all respects as illustrative and not
restrictive, the scope of the invention being indicated by the
appended claims, rather than the forgoing description, and all
changes that come within the meaning and range of equivalency of
the claims are therefore intended to be embraced therein.
* * * * *