U.S. patent application number 16/575851 was filed with the patent office on 2020-01-09 for method for testing switch in advance pneumatic detector.
The applicant listed for this patent is Kidde Technologies, Inc.. Invention is credited to Aaron Stanley Rogers, Dharmendr Len Seebaluck.
Application Number | 20200011752 16/575851 |
Document ID | / |
Family ID | 60021887 |
Filed Date | 2020-01-09 |
United States Patent
Application |
20200011752 |
Kind Code |
A1 |
Seebaluck; Dharmendr Len ;
et al. |
January 9, 2020 |
METHOD FOR TESTING SWITCH IN ADVANCE PNEUMATIC DETECTOR
Abstract
A method for testing a switch in an advance pneumatic detector
with a pressure tube includes moving a piston within the pressure
tube with a magnet. A pressure of a gas in a portion of the
pressure tube is adjusted in response to moving the piston. A state
of the switch is monitored.
Inventors: |
Seebaluck; Dharmendr Len;
(Wake Forest, NC) ; Rogers; Aaron Stanley; (Surf
City, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kidde Technologies, Inc. |
Wilson |
NC |
US |
|
|
Family ID: |
60021887 |
Appl. No.: |
16/575851 |
Filed: |
September 19, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15383390 |
Dec 19, 2016 |
10466124 |
|
|
16575851 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G08B 17/04 20130101;
G01L 19/0015 20130101; H01H 37/40 20130101; G01L 19/14 20130101;
G01L 9/0041 20130101; H01H 37/36 20130101; G08B 13/20 20130101 |
International
Class: |
G01L 9/00 20060101
G01L009/00; G01L 19/00 20060101 G01L019/00; G01L 19/14 20060101
G01L019/14 |
Claims
1. A method for testing a switch in an advance pneumatic detector
with a pressure tube, the method comprising: moving a piston within
the pressure tube with a magnet; adjusting a pressure of a gas in a
portion of the pressure tube in response to moving the piston; and
monitoring a state of the switch.
2. The method of claim 1, wherein monitoring the state of the
switch comprises setting the switch in a test phase in response to
the pressure adjustment of the gas in the pressure tube.
3. The method of claim 2, wherein setting the switch in a test
phase comprises activating a diaphragm located in the switch in
response to the pressure adjustment of the gas in the pressure
tube.
4. The method of claim 3 further comprising activating an
electrical signal to indicate the state of the diaphragm.
5. The method of claim 1 further comprising setting the switch into
a normal operational phase.
6. The method of claim 1 further comprising attaching the magnet to
the pressure tube of the advance pneumatic detector.
7. A method of assembling an advance pneumatic detector, the method
comprising: placing a piston within a pressure tube of a switch of
the advance pneumatic detector; charging the switch with gas;
hermetically sealing the switch; calibrating the advance pneumatic
detector; and attaching a magnet to a portion of the pressure tube,
wherein the magnet is slidably engaged with the pressure tube.
8. The method of claim 7 further comprising installing the advance
pneumatic detector onto an aircraft.
9. The method of claim 7, wherein calibrating the advance pneumatic
detector comprises adjusting a pressure of an inert gas inside the
switch.
10. The method of claim 7, wherein charging the switch comprises
inserting an inert gas into the switch and the pressure tube.
11. The method of claim 7, wherein attaching the magnet comprises
placing the magnet at an axial location of the pressure tube such
that a portion of the magnet is axially aligned with a portion of
the piston.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. application Ser.
No. 15/383,390 filed Dec. 19, 2016 for "IN-SITU FUNCTIONALITY TEST
FEATURE FOR ADVANCE PNEUMATIC DETECTOR" by D. L. Seebaluck and A.
S. Rogers.
BACKGROUND
[0002] The present disclosure relates to an advance pneumatic
detector ("APD"). In particular, the disclosure relates to an APD
with a test feature for detecting the state of the APD.
[0003] An APD is typically comprised of both an alarm switch and a
fault switch. APDs can utilize a pressure tube that contains a gas
that will expand as it is heated, thus increasing the pressure in
the pressure tube. An alarm switch is used to indicate overheat or
fire situations. An alarm switch includes a deformable diaphragm
that is at a normal state when the system is at a normal pressure.
As the pressure increases in the pressure tube, the diaphragm
deforms and closes an electrical circuit, indicating that there is
an alarm condition in the system. A fault switch is used to
indicate whether there are leaks, disconnects, or other problems in
the APD. A fault switch includes a deformable diaphragm that is
deformed when the system is at a normal pressure. If the pressure
drops below normal, the diaphragm of the fault switch resumes its
normal state and opens an electrical circuit, indicating that there
is a fault condition in the system.
[0004] APDs utilizing both an alarm switch and a fault switch are
used on aircraft to detect alarm and fault conditions. The pressure
tubes for the alarm and fault switches can typically run anywhere
from one foot long to fifty feet long, and can be placed in systems
that are prone to overheating or fires. With existing APDs used in
aircraft applications, such as in the engine or wing, there are no
current designs that allow for in-situ testing to verify and
confirm whether a switch of the APD is still functioning.
Currently, to determine whether the APD is functional, the APD must
be removed from the aircraft and subjected to high heat or extreme
cold (e.g., liquid nitrogen bath) in order to reset the switch
and/or provide indication for a low-pressure state or latent
failure mode.
SUMMARY
[0005] An advance pneumatic detector to indicate pressure changes
in an environment includes a switch, a pressure tube, an endcap, a
piston, and a magnet. The pressure tube is connected to the switch.
The endcap is disposed on an end of the pressure tube opposite from
the switch. The piston is disposed within and forms a seal against
the pressure tube. The piston is slidably engaged with the pressure
tube. The magnet is slidably attached to and surrounds a portion of
the pressure tube. The magnet is configured to control the
positioning of the piston within the pressure tube.
[0006] A method for testing a switch in an advance pneumatic
detector with a pressure tube includes moving a piston within the
pressure tube with a magnet. A pressure of a gas in a portion of
the pressure tube is adjusted in response to moving the piston. A
state of the switch is monitored.
[0007] A method of assembling an advance pneumatic detector
includes placing a piston within a pressure tube of a switch of the
advance pneumatic detector. The switch is charged with gas. The
switch is hermetically sealed. The advance pneumatic detector is
calibrated. A magnet is positioned to surround a portion of the
pressure tube such that the magnet is slidably engaged with the
pressure tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side cross-sectional view of an APD with a
switch, a pressure tube, and a piston.
[0009] FIG. 1A is a side cross-sectional view of the APD of FIG. 1
with the switch in a first position.
[0010] FIG. 1B is a side cross-sectional view of the APD of FIG. 1
with the switch in a second position.
[0011] FIG. 1C is a side cross-sectional view of the APD of FIG. 1
with the switch in a third position.
[0012] FIG. 2A is a side cross-sectional view of the APD of FIG. 1
with the piston in a first position.
[0013] FIG. 2B is a side cross-sectional view of the APD of FIG. 1
with the piston in a second position.
[0014] FIG. 2C is a side cross-sectional view of the APD of FIG. 1
with the piston in a third position.
[0015] FIG. 3 is a flowchart illustrating a method of assembling
the APD of FIG. 1.
DETAILED DESCRIPTION
[0016] In general, the proposed APD incorporates a pressure tube
with a magnetic piston element, the position of which is controlled
by a magnet external to the pressure tube. Without needing to
remove the APD from the aircraft, the magnet can be moved
longitudinally along to the pressure tube in order to move the
piston and change the pressure in the pressure tube thereby
tripping the switch. The benefit of the proposed APD is the
elimination of the requirement of removing the APD from the
aircraft thereby saving large amounts of time during routine
inspections of the aircraft.
[0017] FIG. 1 shows a side cross-sectional view of APD 10. APD 10
includes switch 12, housing 14 (including first retainer portion 16
and second retainer portion 18), contact pin 20, fault diaphragm
22, alarm diaphragm 24, insulator 26, insulator 28, cavity 30,
pressure tube 32 (including first chamber 34, second chamber 36,
internal stops 38, and external stops 40), endcap 42, piston 44
(including passage 46), magnet 48, power source 50, and electronic
controller 52. APD 10 also includes path A, path B, path C, and
path D. Similar configurations are disclosed in U.S. patent
application Ser. Nos. 13/836,675, 14/287,969, and 14/515,886 by
Applicant Kidde Technologies, Inc., which are incorporated herein
by reference in their entirety.
[0018] APD 10 is a linear thermal sensor with integrated alarm and
fault switches. Switch 12 is a discrete pressure switch configured
to detect changes in pressure within switch 12 due to temperature
changes external to switch 12. Housing 14 is a rigid casing that
encloses switch 12. First retainer portion 16 and second retainer
portion 18 are portions of housing 14. First retainer portion 16
and second retainer portion 18 are constructed out of a refractory
metallic material that is capable of conducting an electrical
signal. Refractory materials are used so that first retainer
portion 16 and second retainer portion 18 can maintain their
strength when first retainer portion 16 and second retainer portion
18 are subject to high temperatures. Contact pin 20 is a rod of
solid, electrically conductive material. In one non-limiting
embodiment, contact pin 20 is formed of metallic material.
[0019] Fault diaphragm 22 and alarm diaphragm 24 are semi-rigid
deformable sheets of solid electrically conductive material. Fault
diaphragm 22 and alarm diaphragm 24 can be constructed out of
refractory metallic materials. Fault diaphragm 22 and alarm
diaphragm 24 can have any thickness that allows fault diaphragm 22
and alarm diaphragm 24 to deform. Fault diaphragm 22 has a smaller
thickness in the embodiment shown so that it deforms at lower
pressures than alarm diaphragm 24. This allows switch 12 to be used
to indicate different pressure levels corresponding to alarm and
fault conditions. Insulator 26 and insulator 28 are pieces of solid
material. Insulator 26 and insulator 28 can be made of any material
that is capable of acting as an electrical insulator. Cavity 30 is
a space within housing 14 that is in communication with pressure
tube 32.
[0020] Pressure tube 32 is a tube of solid material containing an
inert gas such as helium or hydrogen. In one non-limiting
embodiment, pressure tube 32 includes a metallic material such as
stainless steel 321. Pressure tube 32 can have a typical length
between 0.305 meters (1 foot) and 15.24 meters (50 feet) depending
on where APD 10 will be used. A diameter of pressure tube 32 can
include approximately 0.063 inches (1.600 millimeters). First
chamber 34 and second chamber 36 are hollow portions of pressure
tube 32 on opposite sides of piston 44. Internal stops 38 are
pieces of solid material extending radially inward form pressure
tube 32. External stops 40 are pieces of solid material extending
radially outward from pressure tube 32. Endcap 42 is a cover
including a solid material that seals the outer end of pressure
tube 32.
[0021] Piston 44 is a disk or cylinder of solid material. In one
non-limiting embodiment, piston 44 includes a material that is
metallic and/or magnetized such as a permanent magnet or an
electromagnet. Passage 46 is channel configured to communicate a
fluid (the gas within pressure tube 32) between first chamber 34
and second chamber 36. Magnet 48 is a piece of solid material that
is magnetized and is longitudinally movable along the exterior of
pressure tube 32. Magnet 48 can include a permanent magnet or an
electromagnet. In one non-limiting embodiment, magnet 48 includes a
series or combination of permanent magnets and/or electromagnets
disposed along pressure tube 32. Magnet 48 can include a cuff or
cylindrical shape. Power source 50 is any power source capable of
supplying electric power to switch 12. Electronic controller 52 is
a controller for sending and receiving electrical signals.
Electronic controller 52 is configured to alert the pilot of a
thermal or fire condition.
[0022] In one non-limiting embodiment, APD 10 is installed on an
aircraft in one of the main landing gear wheel wells, the main
engine, or the auxiliary power unit. Switch 12 includes housing 14
that is constructed of first retainer portion 16 and second
retainer portion 18. First retainer portion 16 and second retainer
portion 18 are connected to one another with insulator 26
positioned between them so that retainer portions 16 and 18 are
electrically isolated from one another. Housing 14 includes cavity
30 that is bound by first retainer portion 16, second retainer
portion 18, and insulator 26. First retainer portion 16 contains
contact pin 20 with insulator 28 running between first retainer
portion 16 and contact pin 20. Second retainer portion 18 contains
pressure tube 32.
[0023] Contact pin 20 is held in first retainer portion 16 with
insulator 28 running between contact pin 20 and first retainer
portion 16. Fault diaphragm 22 and alarm diaphragm 24 are held
between first retainer portion 16 and second retainer portion 18 in
cavity 30. Fault diaphragm 22 is held in switch 12 between
insulator 26 and second retainer portion 18. Alarm diaphragm 24 is
held in switch 12 between first retainer portion 16 and insulator
26. Insulator 26 is located between first retainer portion 16 and
second retainer portion 18 to insulate the two portions and to
prevent electrical signals from being passed between them.
Insulator 28 is located between first retainer portion 16 and
contact pin 20 to insulate them and to prevent electrical signals
from being passed between them. Cavity 30 is positioned between
first retainer portion 16 and second retainer portion 18.
[0024] Pressure tube 32 runs through second retainer portion 18 and
fluidly connects to cavity 30. Pressure tube 32 also extends into
cavity 30. Pressure tube 32 is capped on an end opposite from
switch 12 by endcap 42. First chamber 34 and second chamber 36 are
located within pressure tube 32 and are separated by piston 44.
First chamber 34 and second chamber 36 are fluidly connected via
passage 46. First chamber 34 is fluidly connected to cavity 30 of
switch 12. First chamber 34 is disposed between housing 14 and
piston 44. Second chamber 36 is disposed between piston 44 and
endcap 42. Internal stops 38 are connected to an inner surface of
pressure tube 32 and extend into a pathway of piston 44. External
stops 40 are connected to an external surface of pressure tube 32
and extend into a pathway of magnet 48. In a non-limiting
embodiment, external stops 40 can be integrally formed with
pressure tube 32. In another non-limiting embodiment, external
stops 40 can be removably attached onto pressure tube 32. Endcap 42
forms a mechanical and hermetic seal with an end of pressure tube
32 opposite from switch 12.
[0025] Piston 44 is disposed within and forms a seal against
pressure tube 32. Piston 44 is slidably engaged with pressure tube
32. Piston 44 divides pressure tube 32 into first chamber 34 and
second chamber 36. Passage 46 extends through piston 44 and fluidly
connects first chamber 34 and second chamber 36 of pressure tube
32. Magnet 48 extends around at least a portion of pressure tube
32. Magnet 48 is slidably attached to and surrounds a portion of
pressure tube 32. Magnet 48 is configured to control the
positioning of piston 44 due to a magnetic field of magnet 48
interacting with piston 44 and applying a magnetic force, which
causes piston 44 to move within pressure tube 32. In one
non-limiting embodiment, magnet 48 is attached to pressure tube 32
after APD 10 is installed onto the aircraft. In another
non-limiting embodiment, magnet 48 is attached to pressure tube 32
before APD 10 is installed onto the aircraft.
[0026] Power source 50 is connected to fault diaphragm 22 along
path A. Electronic controller 52 is connected to alarm diaphragm 24
along path B and to contact pin 20 along path C. Path D exits
electronic controller 52 to send a signal to an electronic
component that will indicate what type of pressure conditions are
present in switch 12. These electronic components can include
electrical equipment in the cockpit of an aircraft.
[0027] Pressure tube 32 contains a gas that expands as it is
heated, therefore as pressure tube 32 is heated the pressure in
pressure tube 32 will increase. As the pressure in pressure tube 32
increases, the pressure in cavity 30 will also increase. The
pressure in cavity 30 can cause fault diaphragm 22 and alarm
diaphragm 24 to deform. In the embodiment shown in FIG. 1, there is
no pressure in switch 12 and fault diaphragm 22 and alarm diaphragm
24 are in their normal configuration (for example, occupying a
convex shape towards pressure tube 32). Pressure tube 32 will be
placed next to aircraft components that are capable of overheating
or components where a fire could occur, such as the landing gear
wheel well, the engine, or the auxiliary power unit.
[0028] The state of switch 12 is tested by activating switch 12 due
to a change in pressure in pressure tube 32 caused by movement of
piston 44 by magnet 48. As magnet 48 is moved in longitudinal
direction (right to left in FIG. 1) relative to pressure tube 32,
the magnetic field of magnet 48 interacts with piston 44. Movement
of magnet 48 causes piston 44 to move linearly within pressure tube
32. As piston 44 is moved, pressure of a gas within first chamber
34 of pressure tube 32 is adjusted in response moving piston 44.
The gas in first chamber 34 becomes compressed which in turn
increases the pressure of the gas within first chamber 34 and
cavity 30. At least one of fault diaphragm 22 and alarm diaphragm
24 can be activated in response to the pressure adjustment of the
gas in pressure tube 32 and cavity 30. An electrical signal is
activated to indicate the state of fault diaphragm 22 and alarm
diaphragm 24.
[0029] Internal stops 38 protrude into the pathway of piston 44 and
prevent piston 44 from moving too close to housing 14. Internal
stops 38 mechanically prevent piston 44 from moving past a certain
point in pressure tube 32. Likewise, external stops 40 protrude
into the pathway of magnet 48 and prevent magnet 48 from moving too
close to housing 14. External stops 40 mechanically prevent magnet
48 from moving past a certain point along pressure tube 32.
[0030] For example, as magnet 48 is moved towards housing 14,
piston 44 also moves towards housing 14 in response to the moving
magnetic field of and corresponding change in magnet force from
magnet 48. As piston 44 moves towards housing 14, the pressure
within first chamber 34 and cavity 30 increases which deforms at
least one of fault diaphragm 22 and alarm diaphragm 24. Conversely,
as magnet 48 is moved away from housing 14, piston 44 also moves
away from housing 14 in response to the moving magnetic field of
and corresponding change in magnet force from magnet 48. As piston
44 moves away from housing 14, the pressure within first chamber 34
and cavity 30 decreases which causes at least one of fault
diaphragm 22 and alarm diaphragm 24 to form back into its original
un-deformed convex shape.
[0031] Passage 46 provides a restricted orifice, weep hole, or
bleed passage, which allows the gas pressure within pressure tube
32 to equalize across piston 44, for example as between first
chamber 34 and second chamber 36. Passage 46 acts as a pressure
relief mechanism by permitting piston 44 to move and overcome the
counter-acting pressure of cavity 30. Passage 46 permits a time
delay for testing to satisfy an alarm or fault persistence filter
of electronic controller 52. During operation of the aircraft,
passage 46 allows a small amount of time during the change state of
piston 44 so that the controller in the cockpit can observe the
fault/alarm state of APD 10.
[0032] In one non-limiting embodiment, a first mechanic monitors an
engine fire panel in the cockpit while a second mechanic activates
piston 44 with magnet 48 and moves piston 44 to one of internal
stops 38. Depending on the direction of activation (movement) of
piston 44, the pressure in cavity 30 increases or decreases as a
step function, then decays as the seepage via passage 46 equalizes
the pressure in pressure tube 32 on both sides of piston 44. Thus,
the first mechanic in the cockpit observes the engine fire panel
alarm light go from OFF to ON to OFF, which indicates that switch
12 was activated into both states. The first mechanic then tells
the second mechanic to move piston 44 with magnet 48 to another
stop and the process is repeated for to indicate an integrity or
fault condition.
[0033] With existing APDs, once they are bolted onto the aircraft
they may never change state and can be attached to the aircraft for
25+ years with no means for checking the state of the switch.
Existing APDs require complete removal of the APD from the aircraft
in order to assess the states of the diaphragms in the switch.
Existing APDs must be removed completely from the aircraft and
inserted into a high temperature oven or kiln to exercise the alarm
switch and then introduced into dry ice or liquid nitrogen to lower
the gas pressure sufficiently to exercise the fault switch. This
process is undesirable for the aircraft service and maintenance due
to the large amount of time it takes to remove the APD assembly
from the aircraft.
[0034] With piston 44 and magnet 48, a state of APD 10 can be
tested without the need for removing APD 10 entirely from the
aircraft. Piston 44 and magnet 48 provide a non-invasive means of
going out onto the aircraft, opening up an area of the aircraft
containing APD 10, and charging the gas pressure in first chamber
34 of pressure tube 32 with piston 44, and modulate the pressure in
pressure tube 32 to activate switch 12 into different test, alarm,
fault, or normal states. Additionally, pre-installing magnet 48
onto pressure tube 32 helps to limit the amount of ground support
equipment necessary during servicing of the aircraft.
[0035] FIG. 1A is a side cross-sectional view of switch 12 in
system 40 at normal pressure conditions during operation of the
aircraft. In the embodiment shown, normal pressure conditions exist
under normal operating temperatures. Normal operating temperatures
exist between a pre-set fault temperature and a pre-set alarm
temperature. The pre-set fault temperature defines a lower limit of
the normal operating temperatures and is the point at which
pressure conditions will drop below normal. Fault diaphragm 22 will
deform when the temperature rises above the pre-set fault
temperature. The pre-set alarm temperature defines an upper limit
of the normal operating temperatures and is the point at which
pressure conditions will rise above normal. Alarm diaphragm 24 will
deform when the temperature rises above the pre-set alarm
temperature. Normal pressure conditions thus exist between the
pre-set fault temperature and the pre-set alarm temperature. At
normal pressure conditions, fault diaphragm 22 deforms and comes
into contact with alarm diaphragm 24.
[0036] Under normal pressure conditions, an electronic signal is
being sent through fault diaphragm 22 from power source 50. When
fault diaphragm 22 comes into contact with alarm diaphragm 24 under
normal pressure conditions, an electrical circuit between the two
is closed and the electrical signal from power source 50 will
travel through fault diaphragm 22 to alarm diaphragm 24. This
electrical signal can then travel through alarm diaphragm 24 and
along path B to electronic controller 52. Electronic controller 52
will register this electrical signal and will send out a signal
along path D indicating that there are normal pressure conditions
in switch 12.
[0037] Utilizing switch 12 in pneumatic detectors is advantageous,
as switch 12 can send a signal that indicates a system is at a
steady state. This allows a user to verify that the pneumatic
detector is operable and that the system is functioning
normally.
[0038] FIG. 1B is a side cross-sectional view of the integrated
switch of FIG. 1A at a higher than normal pressure conditions
during operation of the aircraft. Above normal pressure conditions
exist at temperatures above the pre-set alarm temperature. In the
embodiment shown, the pre-set alarm temperature of the sensor is
316 degrees Celsius (600.00 degrees Fahrenheit). Temperatures above
the pre-set alarm temperature of the sensor will cause above normal
pressure conditions. In alternate non-limiting embodiments, the
pre-set alarm temperature of the sensor can vary based on the
thickness of alarm diaphragm 24 in switch 12 and the quantity of
gas contained in pressure tube 32. At above normal pressure
conditions, both fault diaphragm 22 and alarm diaphragm 24 will
deform. This will cause fault diaphragm 22 to come into contact
with alarm diaphragm 24 and it will cause alarm diaphragm 24 to
come into contact with contact pin 20.
[0039] In operation, an electronic signal is being sent through
fault diaphragm 22 from power source 50. When fault diaphragm 22
comes into contact with alarm diaphragm 24 under normal pressure
conditions, an electrical circuit between the two is closed and the
electrical signal from power source 50 will travel through fault
diaphragm 22 to alarm diaphragm 24. When alarm diaphragm 24 comes
into contact with contact pin 20, an electrical circuit between
them is closed and the electrical signal will travel through alarm
diaphragm 24 to contact pin 20. This electrical signal can then
travel through contact pin 20 and along path C to electronic
controller 52. Electronic controller 52 will register this
electrical signal and will send out a signal along path D
indicating that there are above normal pressure conditions in
switch 12.
[0040] Above normal pressure conditions can occur when there is a
fire or overheat condition in a component, such as an engine,
landing gear wheel well, or auxiliary power unit. Pressure tube 32
can run along these components. As the heat rises in or around the
components, the pressure in pressure tube 32 will increase, which
will increase the pressure in cavity 30 of switch 12. If the
temperatures get above the pre-set alarm temperature, the pressure
will get high enough to cause alarm diaphragm 24 to deform and come
into contact with contact pin 20. This closes the circuit between
alarm diaphragm 24 and contact pin 20 and causes an electrical
signal to travel between the two. This signal will be sent to
electronic controller 52. Electronic controller 52 can then send a
signal indicating that there is an alarm condition in switch
12.
[0041] FIG. 1C is a side cross-sectional view of the integrated
switch of FIG. 1A at a lower than normal pressure condition during
operation of the aircraft. Below normal pressure conditions exist
at temperatures below the pre-set fault temperature of the sensor.
In the embodiment shown, the pre-set fault temperature of the
sensor is -54 degrees Celsius (-65 degrees Fahrenheit), which is
the temperature at a lower limit of the normal operating
temperatures. Temperatures below the pre-set fault temperature of
the sensor will cause below normal pressure conditions. In
alternate embodiments, the pre-set fault temperature of the sensor
can vary based on the thickness of fault diaphragm 22 in switch 12.
At below normal pressure conditions, both fault diaphragm 22 and
alarm diaphragm 24 will be in their normal configuration and they
will not be touching.
[0042] In operation, an electronic signal is being sent through
fault diaphragm 22 from power source 50. Because fault diaphragm 22
is not in contact with alarm diaphragm 24 when there are below
normal pressure conditions, an electrical circuit between the two
is open. The electrical signal from power source 50 will not travel
through fault diaphragm 22 and alarm diaphragm 24 to electronic
controller 52. Electronic controller 52 will register that there is
no electrical signal coming in and will send out a signal along
path D indicating that there are below normal pressure conditions
in switch 12.
[0043] Below normal pressure conditions can occur when there is a
leak, disconnect, or other problem in pressure tube 32 or switch
12. If there is a leak or disconnect, the pressure in pressure tube
32 and cavity 30 of switch 12 will decrease. As the pressure
decreases, both alarm diaphragm 24 and fault diaphragm 22 will
retain their normal configurations and will not be touching. This
will open the circuit between alarm diaphragm 24 and fault
diaphragm 22 and will prevent a signal from traveling along path B
to electronic controller 52. The lack of a signal entering
electronic controller 52 will indicate that there is a fault
condition in the system. Electronic controller 52 can then send a
signal along path D indicating that there is a fault condition in
switch 12.
[0044] FIG. 2A shows a side cross-sectional view of APD 10 with
piston 44 in a first position. FIG. 2A depicts switch 12 at normal
pressure conditions with piston 44 in a first position. In the
embodiment shown, normal pressure conditions exist under normal
operating temperatures. Normal operating temperatures exist between
a pre-set fault temperature and a pre-set alarm temperature. The
pre-set fault temperature defines a lower limit of the normal
operating temperatures and is the point at which pressure
conditions will drop below normal. Fault diaphragm 22 will deform
when the temperature rises above the pre-set fault temperature. The
pre-set alarm temperature defines an upper limit of the normal
operating temperatures and is the point at which pressure
conditions will rise above normal. Alarm diaphragm 24 will deform
when the temperature rises above the pre-set alarm temperature.
Normal pressure conditions thus exist between the pre-set fault
temperature and the pre-set alarm temperature. At normal pressure
conditions, fault diaphragm 22 deforms and comes into contact with
alarm diaphragm 24.
[0045] Under normal pressure conditions, electrical power is being
sent to fault diaphragm 22 from power source 50. When fault
diaphragm 22 comes into contact with alarm diaphragm 24 under
normal pressure conditions, an electrical circuit between the two
is closed and the electric signal from power source 50 will travel
through fault diaphragm 22 to alarm diaphragm 24. This electric
signal can then travel through alarm diaphragm 24 and along path B
to electronic controller 52. Electronic controller 52 will register
this electric signal and will send out a signal along path D
indicating that there are normal pressure conditions in switch
12.
[0046] In FIG. 2A, piston 44 and magnet 48 are occupying positions
along pressure tube 32 where piston 44 and magnet 48 were
positioned when APD 10 was assembled. Under normal operating
conditions, piston 44 and magnet 48 can remain un-moved along
pressure tube 32. Throughout the life cycle of the aircraft, piston
44 and/or magnet 48 may oscillate due to vibrations in APD 10 from
the aircraft. As piston 44 oscillates or is jostled within pressure
tube due to aircraft vibrations, passage 46 allows gas pressure to
pass through passage 46 thereby equalizing a pressure differential
between first chamber 34 and second chamber 36, which prevents
switch 12 from activating. Without passage 46 in piston 44, small
oscillations of piston 44 could cause an abrupt pressure change
within cavity 30 and potential activation of at least one of fault
diaphragm 22 and alarm diaphragm 24 indicating a false fault or
alarm condition. Passage 46 permits piston 44 to oscillate in small
linear movements if one of internal stops 38 breaks. Therefore, by
not having piston 44 be so reactive to the normal pressure
fluctuations experienced during a typical flight cycle, the risk of
false fire warnings or false failure indications is minimized.
[0047] Utilizing the combination of piston 44 and magnet 48 with
pressure tube 32 in APD 10 is advantageous because switch 12 can
now send a signal that indicates which state switch 12 currently
occupies without the need for completely removing APD 10 from the
aircraft. This allows a user to verify that switch 12 is operable
and that APD10 is functioning normally.
[0048] FIG. 2B shows a side cross-sectional view of APD 10 with
piston 44 in a second position. Piston 44 has been moved towards
housing 30 (to the left in FIG. 2B) in response to moving magnet 48
towards housing 30. In response to moving piston 44, the pressure
of the gas within first chamber 34 and cavity 30 has increased. In
response the increased pressure of the gas in first chamber 34 and
cavity 30, both fault diaphragm 22 and alarm diaphragm 24 will
deform. This will cause fault diaphragm 22 to come into contact
with alarm diaphragm 24 and it will cause alarm diaphragm 24 to
come into contact with contact pin 20.
[0049] In operation, electrical power is being sent through fault
diaphragm 22 from power source 50. When fault diaphragm 22 comes
into contact with alarm diaphragm 24 in response to piston 44
moving closer to housing 14, an electrical circuit between the two
is closed and the electric signal from power source 50 will travel
through fault diaphragm 22 to alarm diaphragm 24. When alarm
diaphragm 24 comes into contact with contact pin 20, an electrical
circuit between them is closed and the electric signal will travel
through alarm diaphragm 24 to contact pin 20. This electric signal
can then travel through contact pin 20 and along path C to
electronic controller 52. Electronic controller 52 will register
this electric signal and will send out a signal along path D
indicating that switch 12 occupies a first test phase, which under
normal operating conditions would indicate an alarm condition.
[0050] As piston 44 is moved closer to housing 14, the pressure in
pressure tube 32 will increase, which will increase the pressure in
cavity 30 of integrated switch 12. If the pressure gets above a
pre-set alarm pressure of switch 12, the pressure will get high
enough to cause alarm diaphragm 24 to deform and come into contact
with contact pin 20. This closes the circuit between alarm
diaphragm 24 and contact pin 20 and causes an electric signal to
travel between the two. This signal will be sent to electronic
controller 52. Electronic controller 52 can then send a signal
indicating that switch 12 occupies the first test phase (e.g., an
alarm condition).
[0051] FIG. 2C shows a side cross-sectional view of APD 10 with
piston 44 in a third position. Piston 44 has been moved away from
housing 30 (to the right in FIG. 2B) in response to moving magnet
48 away from housing 30. In response to moving piston 44, the
pressure of the gas within first chamber 34 and cavity 30 has
decreased. In response the decreased pressure of the gas in first
chamber 34 and cavity 30, both fault diaphragm 22 and alarm
diaphragm 24 will form back into a non-deformed state. This will
cause both fault diaphragm 22 and alarm diaphragm 24 to come back
into in their normal non-deformed configuration and they will not
be touching.
[0052] In operation, an electrical signal is being sent through
fault diaphragm 22 from power source 50. Because fault diaphragm 22
is not in contact with alarm diaphragm 24 when piston 44 is moved
away from housing 44, an electrical circuit between the two is
open. The electric signal from power source 50 will not travel
through fault diaphragm 22 and alarm diaphragm 24 to electronic
controller 52. Electronic controller 52 will register that there is
no electric signal coming in and will send out a signal along path
D indicating that switch 12 occupies a second test phase, which
under normal operating conditions would indicate an fault
condition.
[0053] When piston 44 is moved away from housing 14 and towards
endcap 42, the pressure in first chamber 34 and cavity 30 of
integrated switch 12 will decrease. As the pressure decreases in
first chamber 34 and cavity 30, both alarm diaphragm 24 and fault
diaphragm 22 will retain their normal configurations and will not
be touching. This will open the circuit between alarm diaphragm 24
and fault diaphragm 22 and will prevent a signal from traveling
along path B to electronic controller 52. The lack of a signal
entering electronic controller 52 will indicate that switch 12
occupies the second test phase (e.g., fault condition). Electronic
controller 52 can then send a signal along path D indicating that
there is a fault condition in integrated switch 12.
[0054] FIGS. 2A-2C provide examples of a method of testing switch
12 in APD 10. The method of testing switch 12 in APD 10 can include
attaching magnet 48 to pressure tube 32 of APD 10. Piston 44 is
moved within pressure tube 32 with magnet 48 surrounding a portion
of pressure tube 32. A pressure of a gas in a portion of pressure
tube 32 is adjusted in response to moving piston 44. A state of
switch 12 is monitored. Switch 12 is set in a test phase in
response to the pressure adjustment of the gas in pressure tube 32.
Setting switch 12 in a test phase includes activating at least one
of fault diaphragm 22 and alarm diaphragm 24 located in switch 12
in response to the pressure adjustment of the gas in pressure tube
32. An electrical signal is activated to indicate the state of at
least one of fault diaphragm 22 and alarm diaphragm 24. Switch 12
is set into a normal operational phase.
[0055] FIG. 3 shows a flowchart illustrating method 300 of
assembling APD 10. Method 300 includes steps 302 through 318. Step
302 includes placing piston 44 within pressure tube 32 of switch 12
of APD 10. Step 304 includes charging switch 12 with gas. Step 304
also includes step 306 of supplying an inert gas into switch 12 and
pressure tube 32. The inert gas can be supplied into switch 12
through at least one of
[0056] Step 308 includes calibrating APD 10. Calibrating APD 10
includes various additional steps. For example, computational fluid
dynamics are used to model the engine of the aircraft. Functional
hazard analysis of fire threats are completed in regions of the
engine that need heat and/or fire protection. A fire threat is
determined based on a maximum allowable temperature. The maximum
allowable temperature is then cross-referenced with the design
capabilities of APD 10. Some additional steps can be performed
including determining a maximum ambient safe operating temperature,
determine the full length of the alarm that is needed to fit into
the aircraft element being monitored, and determine which length of
alarm provides adequate localized fire detection. These steps are
used to determine the temperature threshold of APD 10 as well as a
sufficient length of pressure tube 32. Once the temperature
threshold and length of pressure 32 are determined, a pressure of
the inert gas inside switch 12 is adjusted (step 310) such that
switch 12 is activated at temperatures matching the maximum ambient
safe operating temperature of the location in the aircraft of
pressure tube 32. Calibrating APD 10 can also include setting fault
diaphragm 22 and alarm diaphragm 24 at a predetermined distance
from each other (or from contact pin 20) that corresponds to a
distance of travel of fault diaphragm 22 and/or alarm diaphragm 24
when pressure tube 32 reaches a predetermined pressure.
[0057] Step 312 includes hermetically sealing switch 12 by
attaching endcap 42 onto the end of pressure tube 32. Step 314
includes attaching magnet 48 to a portion of pressure tube 32 such
that magnet 48 is slidably engaged with pressure tube 32. Step 316
includes placing magnet 48 at an axial location of pressure tube 32
such that a portion of magnet 48 is axially aligned with a portion
of piston 44. Step 318 includes installing APD 10 onto an
aircraft.
[0058] Assembling APD 10 with method 300 allows APD 10 to function
as discussed above and provides the benefits discussed above of
being able to test the state switch 12 of APD 10 without needing to
completely remove APD 10 from the aircraft.
Discussion of Possible Embodiments
[0059] The following are non-exclusive descriptions of possible
embodiments of the present invention.
[0060] An advance pneumatic detector to indicate pressure changes
in an environment includes a switch, a pressure tube, an endcap, a
piston, and a magnet. The pressure tube is connected to the switch.
The endcap is disposed on an end of the pressure tube opposite from
the switch. The piston is disposed within and forms a seal against
the pressure tube. The piston is slidably engaged with the pressure
tube. The magnet is slidably attached to and surrounds a portion of
the pressure tube. The magnet is configured to control the
positioning of the piston within the pressure tube.
[0061] The advance pneumatic detector of the preceding paragraph
can optionally include, additionally and/or alternatively, any one
or more of the following features, configurations and/or additional
components.
[0062] The switch can further comprise a housing with a cavity
between a first retainer portion and/or a second retainer portion,
wherein the cavity is in fluid communication with the pressure tube
and the piston, a contact pin can be held in the first retainer
portion, a fault diaphragm can be held in the cavity of the housing
near the second retainer portion, and/or an alarm diaphragm can be
held in the cavity of the housing near the first retainer
portion.
[0063] At least one of the piston and the magnet can comprise a
permanent magnet and/or an electromagnet.
[0064] The piston can comprise a passage that can extend through
the piston.
[0065] The piston can divide the pressure tube into a first chamber
and/or a second chamber, the first chamber can be between the
housing and the piston and the second chamber can be between the
piston and the endcap, and the passage can fluidly connect the
first chamber and the second chamber.
[0066] A method for testing a switch in an advance pneumatic
detector with a pressure tube can include moving a piston within
the pressure tube with a magnet. A pressure of a gas in a portion
of the pressure tube can be adjusted in response to moving the
piston. A state of the switch can be monitored.
[0067] The method of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components.
[0068] Monitoring the state of the switch can comprise setting the
switch in a test phase in response to the pressure adjustment of
the gas in the pressure tube
[0069] Setting the switch in a test phase can comprise activating a
diaphragm located in the switch in response to the pressure
adjustment of the gas in the pressure tube.
[0070] An electrical signal to indicate the state of the diaphragm
can be activated.
[0071] The switch can be set into a normal operational phase.
[0072] The magnet can be attached to the pressure tube of the
advance pneumatic detector.
[0073] A method of assembling an advance pneumatic detector can
include placing a piston within a pressure tube of a switch of the
advance pneumatic detector. The switch can be charged with gas. The
switch can be hermetically sealed. The advance pneumatic detector
can be calibrated. A magnet can be positioned to surround a portion
of the pressure tube such that the magnet can be slidably engaged
with the pressure tube.
[0074] The method of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components.
[0075] The advance pneumatic detector can be installed onto an
aircraft.
[0076] Calibrating the advance pneumatic detector can comprise
adjusting a pressure of an inert gas inside the switch.
[0077] Charging the switch can comprise inserting an inert gas into
the switch and/or the pressure tube.
[0078] Attaching the magnet can comprise placing the magnet at an
axial location of the pressure tube such that a portion of the
magnet can be axially aligned with a portion of the piston.
[0079] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *