U.S. patent application number 10/103540 was filed with the patent office on 2002-10-31 for gas pilot system and method having improved oxygen level detection capability and gas fueled device including the same.
Invention is credited to Deng, David.
Application Number | 20020160325 10/103540 |
Document ID | / |
Family ID | 26800576 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020160325 |
Kind Code |
A1 |
Deng, David |
October 31, 2002 |
Gas pilot system and method having improved oxygen level detection
capability and gas fueled device including the same
Abstract
A pilot system including a pilot including a nozzle and a sensor
adjacent to the nozzle. The sensor determines whether or not the
pilot flame is in a predetermined position relative to the
nozzle.
Inventors: |
Deng, David; (Chino Hills,
CA) |
Correspondence
Address: |
HENRICKS SLAVIN AND HOLMES LLP
SUITE 200
840 APOLLO STREET
EL SEGUNDO
CA
90245
|
Family ID: |
26800576 |
Appl. No.: |
10/103540 |
Filed: |
March 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10103540 |
Mar 20, 2002 |
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09844974 |
Apr 26, 2001 |
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Current U.S.
Class: |
431/76 |
Current CPC
Class: |
F23N 5/12 20130101; F23D
2207/00 20130101; F23D 2208/10 20130101; F23D 2900/00014 20130101;
F23N 5/14 20130101; F23D 14/725 20130101; F23N 5/08 20130101; F23N
2227/22 20200101 |
Class at
Publication: |
431/76 |
International
Class: |
F23N 005/00 |
Claims
I claim:
1. A pilot system for generating a pilot flame, comprising: a pilot
including a nozzle; and an electrical resistance measurement device
adjacent to the nozzle.
2. A pilot system as claimed in claim 1, wherein the electrical
resistance measurement device comprises a pair of spaced
electrodes.
3. A pilot system as claimed in claim 1, further comprising: an
ignitor positioned adjacent to the nozzle; wherein the electrical
resistance measurement device is located between the nozzle and the
ignitor.
4. A pilot system as claimed in claim 1, further comprising: a
shield adjacent to the nozzle and defining an open region through
which the electrical resistance measurement device extends.
5. A pilot system as claimed in claim 1, further comprising: a
mixing chamber located upstream of the nozzle including a gas
inlet, an air inlet and a gas/air mixture outlet in communication
with the nozzle.
6. A pilot system as claimed in claim 1, wherein the pilot is
constructed such that the pilot flame will be located in a first
position in response to a first oxygen level and a second position
in response to a second oxygen level, the second oxygen level being
less than the first oxygen level, and the electrical resistance
measurement device will measure a level of electrical resistance
indicative of an allowable oxygen level when the pilot flame is in
the first position and will not measure a level of electrical
resistance indicative of an allowable oxygen level when the pilot
flame is in the second position.
7. A gas fueled device, comprising: a burner; a pilot including a
nozzle associated with the burner; and an electrical resistance
measurement device adjacent to the nozzle.
8. A gas fueled device as claimed in claim 7, wherein the burner
comprises a ceramic plaque.
9. A gas fueled device as claimed in claim 7, wherein the
electrical resistance measurement device comprises a pair of spaced
electrodes.
10. A gas fueled device as claimed in claim 7, further comprising:
an ignitor positioned adjacent to the nozzle; wherein the
electrical resistance measurement device is located between the
nozzle and the ignitor.
11. A gas fueled device as claimed in claim 7, further comprising:
a shield adjacent to the nozzle and defining an open region through
which the electrical resistance measurement device extends.
12. A gas fueled device as claimed in claim 7, further comprising:
a mixing chamber located upstream of the nozzle including a gas
inlet, an air inlet and a gas/air mixture outlet in communication
with the nozzle.
13. A gas fueled device as claimed in claim 7, wherein the pilot is
constructed such that the pilot flame will be located in a first
position in response to a first oxygen level and a second position
in response to a second oxygen level, the second oxygen level being
less than the first oxygen level, and the electrical resistance
measurement device will measure a level of electrical resistance
indicative of an allowable oxygen level when the pilot flame is in
the first position and will not measure a level of electrical
resistance indicative of an allowable oxygen level when the pilot
flame is in the second position.
14. A gas fueled device as claimed in claim 13, further comprising:
a gas inlet operably connected to the pilot; and a control device
operably connected to the electrical resistance measurement device
that prevents gas flow from the gas inlet to the pilot when the
electrical resistance measurement device does not measure a level
of electrical resistance indicative of an allowable oxygen
level.
15. A gas fueled device as claimed in claim 13, further comprising:
a gas inlet operably connected to the burner; and a control device
operably connected to the electrical resistance measurement device
that prevents gas flow from the gas inlet to the burner when the
electrical resistance measurement device does not measure a level
of electrical resistance indicative of an allowable oxygen
level.
16. A method of monitoring a pilot flame produced by a pilot,
comprising the steps of: determining whether the pilot flame is
located in a predetermined region associated with the pilot by
sensing a property other than temperature; and preventing gas from
flowing to the pilot in response to a determination that the pilot
flame is not in the predetermined region.
17. A method as claimed in claim 16, wherein the step of
determining whether the flame is located in the predetermined
region comprises measuring electrical resistance in the
predetermined region.
18. A method as claimed in claim 16, wherein the gas pilot includes
a nozzle and an ignitor defining a region therebetween and the step
of determining whether the pilot flame is located in a
predetermined region comprises determining whether the pilot flame
is located between the nozzle and the ignitor.
19. A method as claimed in claim 16, wherein the step of preventing
gas flow from flowing to the pilot comprises closing a valve.
20. A method as claimed in claim 16, wherein the gas pilot includes
a nozzle, the method further comprising the step of: mixing gas
with ambient air to form an air/gas mixture; and providing the
air/gas mixture to the nozzle.
21. A pilot system for generating a pilot flame, comprising: a
pilot including a nozzle; and a measurement device adjacent to the
nozzle that measures a property other than temperature.
22. A pilot system as claimed in claim 21, wherein the measurement
device comprises an electrical resistance measurement device.
23. A pilot system as claimed in claim 22, wherein the electrical
resistance measurement device comprises a pair of spaced
electrodes.
24. A pilot system as claimed in claim 22, further comprising: an
ignitor positioned adjacent to the nozzle; wherein the electrical
resistance measurement device is located between the nozzle and the
ignitor.
25. A pilot system as claimed in claim 21, wherein the pilot is
constructed such that the pilot flame will be located in a first
position in response to a first oxygen level and a second position
in response to a second oxygen level, the second oxygen level being
less than the first oxygen level, and the measurement device will
measure a level of the property other than temperature that is
indicative of an allowable oxygen level when the pilot flame is in
the first position and will not measure a level of the property
other than temperature that is indicative of an allowable oxygen
level when the pilot flame is in the second position.
26. A pilot system as claimed in claim 21, wherein the measurement
device comprises a sensor that senses electromagnetic
radiation.
27. A pilot system as claimed in claim 26, further comprising: an
ignitor positioned adjacent to the nozzle that emits
electromagnetic radiation when heat by the pilot flame; wherein the
sensor senses electromagnetic radiation from the ignitor.
28. A gas fueled device, comprising: a burner; a pilot including a
nozzle associated with the burner; and a measurement device
adjacent to the nozzle that measures a property other than
temperature.
29. A gas fueled device as claimed in claim 28, wherein the
measurement device comprises an electrical resistance measurement
device.
30. A gas fueled device as claimed in claim 29, wherein the
electrical resistance measurement device comprises a pair of spaced
electrodes.
31. A gas fueled device as claimed in claim 28, wherein the burner
comprises a ceramic plaque.
32. A gas fueled device as claimed in claim 28, further comprising:
an ignitor positioned adjacent to the nozzle; wherein the
electrical resistance measurement device is located between the
nozzle and the ignitor.
33. A gas fueled device as claimed in claim 28, wherein the pilot
is constructed such that the pilot flame will be located in a first
position in response to a first oxygen level and a second position
in response to a second oxygen level, the second oxygen level being
less than the first oxygen level, and the measurement device will
measure a level of the property other than temperature that is
indicative of an allowable oxygen level when the pilot flame is in
the first position and will not measure a level of the property
other than temperature that is indicative of an allowable oxygen
level when the pilot flame is in the second position.
34. A gas fueled device as claimed in claim 28, wherein the
measurement device comprises a sensor that senses electromagnetic
radiation.
35. A gas fueled device as claimed in claim 34, further comprising:
an ignitor positioned adjacent to the nozzle that emits
electromagnetic radiation when heat by the pilot flame; wherein the
sensor senses electromagnetic radiation from the ignitor.
36. A gas fueled device as claimed in claim 31, further comprising:
a gas inlet operably connected to the pilot; and a control device
operably connected to the measurement device that prevents gas flow
from the gas inlet to the pilot when the measurement device does
not measure a level of the property other than temperature
indicative of an allowable oxygen level.
37. A gas fueled device as claimed in claim 31, further comprising:
a gas inlet operably connected to the burner; and a control device
operably connected to the measurement device that prevents gas flow
from the gas inlet to the burner when the measurement device does
not measure a level of the property other than temperature
indicative of an allowable oxygen level.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending
U.S. application Ser. No. 09/844,974, filed Apr. 26, 2001, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTIONS
[0002] 1. Field of Inventions
[0003] The present inventions relate generally to gas pilots and,
more particularly, to the oxygen level detection systems associated
with gas pilots.
[0004] 2. Description of the Related Art
[0005] Gas pilot systems are associated with a wide variety of gas
fueled devices. Such devices include, but are not limited to,
vented gas heaters, which include pipes or conduits that are used
to vent exhaust to the atmosphere, vent-free gas heaters, vented
and vent-free gas log heater, vented and vent-free fireplace
systems, water heaters, vented and vent-free stoves, and ovens. The
most common types of gas fuel are natural gas and propane. A gas
pilot system typically includes an ignition device, such as an
electrode, and a pilot having a small nozzle. A pilot flame is
formed when gas from the nozzle is ignited by the ignition device.
The pilot flame is then used to ignite the gas that is supplied to
the burner(s) of the gas fueled device during use.
[0006] The level of oxygen in the air is typically about 20.9%. It
is important that the oxygen level in a room in which a gas fueled
device is used remain at or near 20.9%, both for proper combustion
and safety purposes. An adequate supply of fresh air will maintain
the oxygen level at or near the desired level. In buildings with
loose structures, such as houses made of wood, an adequate supply
of fresh air will enter via wall spaces as well as door and window
frames. Other buildings are more tightly sealed. Here, steps should
be taken to insure that fresh air is supplied.
[0007] Unfortunately, some rooms do not receive an adequate supply
of fresh air. Thus, for safety purposes, many gas fueled devices
include an oxygen depletion sensor system ("ODS system") which will
automatically shut off the flow of gas to the pilot and burner when
the oxygen level in the air drops below a predetermined "unsafe"
level (typically below about 18.2%). The ODS systems monitor the
pilot flame because the position of the pilot flame relative to the
pilot nozzle is indicative of the oxygen level in the room.
[0008] Referring to FIGS. 1A to 1C, conventional ODS systems employ
a thermocouple TC to detect the presence of a pilot flame F when it
is in the "normal" oxygen level position (oxygen level greater than
or equal to 21%) illustrated in FIG. 1A or the "relatively low"
oxygen level position (oxygen level between 18.2% and 19.2%)
illustrated in FIG. 1B. In either case, gas will continue to flow
to the pilot and burner because the voltage generated by the
thermocouple TC, and received by the ODS system controller, will be
within an allowable range. When the oxygen level drops to an
"unsafe" level (oxygen level below 18.2%), the pilot flame F will
move to the location illustrated in FIG. 1C. Here, the pilot flame
will not be in contact with the thermocouple TC or substantially
close to thermocouple TC. As a result, the temperature of the
thermocouple TC will drop, as will the voltage produced thereby.
The voltage drop will cause the ODS system to cut off the supply of
gas to the pilot and burner. As illustrated in U.S. Pat. No.
5,807,098 to Deng, which is incorporated herein by reference, some
ODS systems also include a second thermocouple that is used to
generate a warning when the pilot flame moves to the "relatively
low" oxygen level position.
[0009] Although conventional ODS systems are generally quite
useful, the inventor herein has determined that there are also
certain disadvantages associated therewith. Most notably, when the
level of oxygen in a room is dropping, the pilot flame F will often
first bounce back and forth between the "normal" position
illustrated in FIG. 1A and the "relatively low" position
illustrated in FIG. 1B, and then bounce back and forth between the
"relatively low" position illustrated in FIG. 1B and the "unsafe"
position illustrated in FIG. 1C. This can go on for a significant
period of time. The pilot flame F will, for example, often bounce
back and forth between the "relatively low" position and the
"unsafe" position for 15 seconds and, during this time, the
temperature at the thermocouple TC will not drop to a level low
enough to cause the ODS system to cut off the supply of gas to the
pilot and burner. As a result, the inventor herein has determined
that the conventional methods of monitoring the pilot flame
introduce unnecessary delays into the operation of conventional ODS
systems.
SUMMARY OF THE INVENTIONS
[0010] A pilot system in accordance with one embodiment of a
present invention includes a pilot having a nozzle and a sensor
adjacent to the nozzle that senses or measures a property other
than temperature in the pilot area. Exemplary sensors include light
sensors and electrical resistance measurement devices. The sensor
determines whether or not the pilot flame is in a predetermined
position relative to the nozzle. In a preferred implementation, the
sensor determines when the pilot flame is not in either of the
"normal" oxygen level and "relatively low" oxygen level positions,
i.e. when the pilot flame is in the "unsafe" oxygen level
position.
[0011] There are a number of advantages associated with such a
pilot system. Most notably, non-temperature based sensors are
capable of detecting movement of the pilot flame the instant that
the pilot flame first moves to the "unsafe" oxygen level position,
even if it quickly bounces back to the "relatively low" oxygen
level position. ODS systems employing the present pilot system
will, therefore, be able to make an "unsafe" oxygen level
determination much more quickly than ODS systems that employ a
conventional thermocouple-based pilot flame monitoring arrangement.
As a result, ODS systems employing the present pilot system will
also be able to, for example, cut off the supply of gas to a pilot
and burner much faster than ODS systems that employ a conventional
thermocouple-based pilot flame monitoring arrangement.
[0012] The above described and many other features and attendant
advantages of the present inventions will become apparent as the
inventions become better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Detailed description of preferred embodiments of the
inventions will be made with reference to the accompanying
drawings.
[0014] FIG. 1A is a side view of a conventional pilot system and
oxygen depletion sensor with the pilot flame in the "normal" oxygen
level position.
[0015] FIG. 1B is a side view of the conventional pilot system and
oxygen depletion sensor illustrated in FIG. 1A with the pilot flame
in the "relatively low" oxygen level position.
[0016] FIG. 1C is a side view of the conventional pilot system and
oxygen depletion sensor illustrated in FIG. 1A with the pilot flame
in the "unsafe" oxygen level position.
[0017] FIG. 2A is a side view of a pilot system and oxygen
depletion sensor in accordance with a preferred embodiment of a
present invention with the pilot flame in the "normal" oxygen level
position.
[0018] FIG. 2B is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 2A with the pilot flame in the
"relatively low" oxygen level position.
[0019] FIG. 2C is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 2A with the pilot flame in the
"unsafe" oxygen level position.
[0020] FIG. 3 is a section view of a mixing chamber in accordance
with a preferred embodiment of a present invention.
[0021] FIG. 4 is a top view of a portion of the pilot system and
oxygen depletion sensor illustrated in FIG. 2A.
[0022] FIG. 5A is a side view of a pilot system and oxygen
depletion sensor in accordance with a preferred embodiment of a
present invention with the pilot flame in the "normal" oxygen level
position.
[0023] FIG. 5B is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 5A with the pilot flame in the
"relatively low" oxygen level position.
[0024] FIG. 5C is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 5A with the pilot flame in the
"unsafe" oxygen level position.
[0025] FIG. 6 is a top view of a portion of the pilot system and
oxygen depletion sensor illustrated in FIG. 5A.
[0026] FIG. 7A is a side view of a pilot system and oxygen
depletion sensor in accordance with a preferred embodiment of a
present invention with the pilot flame in the "normal" oxygen level
position.
[0027] FIG. 7B is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 7A with the pilot flame in the
"relatively low" oxygen level position.
[0028] FIG. 8 is a perspective view of a portion of the pilot
system and oxygen depletion sensor illustrated in FIG. 7A.
[0029] FIG. 9 is a plan view of a portion of the pilot system and
oxygen depletion sensor illustrated in FIG. 7A.
[0030] FIG. 10A is a side view of a pilot system and oxygen
depletion sensor in accordance with a preferred embodiment of a
present invention with the pilot flame in the "normal" oxygen level
position.
[0031] FIG. 10B is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 10A with the pilot flame in
the "relatively low" oxygen level position.
[0032] FIG. 10C is a side view of the pilot system and oxygen
depletion sensor illustrated in FIG. 10A with the pilot flame in
the "unsafe" oxygen level position.
[0033] FIG. 11 is a perspective view of a heater in accordance with
a preferred embodiment of a present invention.
[0034] FIG. 12 is a partially exploded view of a propane gas
heating assembly that may be used in conjunction with the heater
illustrated in FIG. 11.
[0035] FIG. 13 is a diagram of a portion of a gas fueled system in
accordance with a preferred embodiment of a present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The following is a detailed description of the best
presently known modes of carrying out the inventions. This
description is not to be taken in a limiting sense, but is made
merely for the purpose of illustrating the general principles of
the inventions.
[0037] As illustrated for example in FIGS. 2A, 3 and 4, a pilot
system 10 in accordance with a preferred embodiment of a present
invention includes a pilot 12 having a gas/air mixing chamber 14
and a nozzle 16. Gas G enters the mixing chamber 14 through a small
gas orifice 18, while air A enters the mixing chamber through a
pair of small air orifices 20. The gas/air mixture G/A exits the
mixing chamber 14 through an outlet orifice 22. Mixing continues as
the gas/air mixture G/A travels through a tube 24 to the nozzle 16.
The gas G in the gas/air mixture G/A is ignited by the L-shaped
electrode 26 of an ignitor 28 to create the pilot flame F. The
inlet and outlet orifices 18 and 22 are preferably formed from a
relatively hard material. In a preferred implementation, the
orifices are formed in a ruby or other hard precious stone that is
mounted in a copper frame.
[0038] The size of the orifices 18 and 20 depends on the fuel being
used. For example, when the fuel is natural gas supplied at a
pressure of 6 inches of mercury, the orifice 18 is approximately
0.38 mm in diameter and the orifice 18 is approximately 0.46 mm in
diameter when the natural gas is supplied at a pressure of 3 inches
of mercury. In both cases, the orifices 20 are each approximately 3
mm in diameter. The orifice 18 is approximately 0.22 mm in diameter
and the orifices 20 are each approximately 3.2 mm in diameter when
the fuel is liquid propane gas supplied at about 8 to 11 inches of
mercury. The outlet orifice 22 is approximately 4 mm. The outlet
pressure should be about 8 to 11 inches of mercury when the fuel is
liquid propane gas and about 3 to 6 inches of mercury when the fuel
is natural gas.
[0039] Mixing the gas and air in the manner described above is
advantageous because it insures that the level of oxygen in the
ambient air will be accurately represented by the position of the
pilot flame F, thereby increasing the accuracy of the ODS system
described below. Accuracy of the ODS system may also be augmented
by controlling movement of the pilot flame F through use of the
relationship between the diameter of the pilot nozzle 16, the fuel
pressure, the distance of the electrode 26 from the nozzle as well
as the location of the electrode relative 26 to the nozzle
centerline, and the level of oxygen in the air. In a pilot system
for use in conjunction with a propane gas heater such as that
illustrated in FIGS. 11-13, the diameter of the pilot nozzle 16 is
approximately 0.23 mm (.+-.0.005 mm) and the gas pressure is
between 8 and 11 inches of mercury. The downwardly extending
portion of the L-shaped electrode 26 is offset with respect to the
centerline of the pilot nozzle 16 by 3.00 mm and is spaced
approximately 3.50 mm from the nozzle. Such an arrangement reduces
the speed of gas flow, thereby increasing the duration and
effectiveness of gas/air mixing, and also reduces the tendency of
the pilot flame F to bounce around, as compared to conventional
S-shaped electrodes.
[0040] The exemplary pilot systems disclosed herein also includes
an oxygen depletion sensor that may be used in a ODS systems in the
manner described below with reference to FIGS. 11-13. The oxygen
depletion sensor is preferably a sensor that measures or senses a
property other than temperature and a variety of such oxygen
depletion sensors are described below.
[0041] The oxygen depletion sensor in the exemplary pilot system 10
illustrated in FIGS. 2A, 3 and 4 is a light sensor that senses
light from the pilot flame F. Any suitable light sensor may be
employed so long as it is capable of detecting the presence and
absence of light emitted by the pilot flame F. In one preferred
embodiment, the pilot system 10 is provided with an infrared
sensing device 30 having a sensing element 32 that is positioned
adjacent to the pilot nozzle 16 and pilot flame F. A suitable
infrared sensing device is manufactured by Shanghai Infrared
Appliances Co., located in Shanghai, China. The pilot flame F
generates infrared electromagnetic radiation (i.e. electromagnetic
radiation with wavelengths between 750 nanometers and 1 millimeter)
which is sensed by the sensing element 32 when the pilot flame is
in the "normal" oxygen level position illustrated in FIG. 2A
(oxygen level greater than or equal to 21%) and, in the illustrated
embodiment, in the "relatively low" oxygen level position
illustrated in FIG. 2B (oxygen level between 18.2% and 19.2%). The
infrared radiation causes the sensing element 32 to generate a
flame signal which indicates that the flame is in an allowable (or
"safe") position. Another example of a suitable light sensor is one
that senses visible light (not shown), such as those produced by
China Wuxi Light Appliances Co, located in Wuxi, China.
[0042] In the preferred embodiment, the instant that the pilot
flame F moves beyond the "relatively low" oxygen level position
illustrated in FIG. 2B to the "unsafe" level position (oxygen level
below 18.2%) illustrated in FIG. 2C, the sensing device 30 will
stop generating a flame signal which indicates that the pilot flame
is in an allowable position. The signal from the sensing device may
drop to zero, or simply to a level lower than the expected level,
when the pilot flame F moves from the "normal" or "relatively low"
oxygen level position to the "unsafe" oxygen level position. Thus,
even in those instances where the pilot flame F jumps back and
forth between the "relatively low" and "unsafe" oxygen level
positions, the present sensing device 30 will immediately indicate
that the oxygen level has dropped to an "unsafe" level because it
will fail to produce the expected flame signal the first time that
the pilot flame moves out beyond of the "relatively low" position
to the "unsafe" position.
[0043] As illustrated in FIGS. 2A and 4, the exemplary pilot system
10 may also be provided with a light shield 34 that is positioned
above the nozzle 16 around the area that will be occupied by the
pilot flame F when the oxygen level is "normal." The light shield
34, which is preferably opaque, non-reflective and formed from
metal, includes a slot 36 that faces the sensing element 32. The
light shield 34 prevents the sensing element 32 from being effected
by stray light that could result in the expected flame signal when
the flame is actually in the "unsafe" oxygen level position. As
such, the sensing element 32 will only be effected by the infrared
or visible electromagnetic radiation from the pilot flame F which
passes through the slot 36 when the pilot flame is in the "normal"
and "relatively low" oxygen level positions. In the illustrated
embodiment, the light shield 34 is about 7.2 mm in diameter and
about 10 mm in length, while the slot 36 is about 3.6 mm wide.
[0044] In an alternative embodiment (not shown), the components may
be reconfigured such that the sensing device 30 will stop
generating a signal which indicates that the pilot flame F is in an
allowable position the instant that the pilot flame F moves out of
the "normal" oxygen level position to either the "relatively low"
oxygen level position or the "unsafe" oxygen level position. For
example, the light shield 34 could be provided with a small hole
that faces the sensing element 32 in place of the slot 36 in order
to substantially reduce the amount of light from the pilot flame F
that will reach the sensing element when the pilot flame moves to
the "relatively low" oxygen level position.
[0045] The exemplary pilot system 10 is also provided with a
bracket system 38 that fixes the positions of the various elements
of the pilot system relative to one another. Referring more
specifically to FIGS. 2B and 2C, the exemplary bracket system 38
includes a L-shaped main bracket 40 having a first portion 42 that
is mounted on the pilot 12 adjacent to the nozzle 16. The light
shield 34 is supported by the first portion 42. The ignitor 28 and
sensing device 30 are mounted on a second portion 44 of the main
bracket 40 and are fixed in place by a clamp 46. The clamp 46 may
be secured to the main bracket 40 with a screw 48 or other suitable
fastening device. A pair of mounting apertures 50 and 52 are formed
in the main bracket 40 so that the pilot system 10 may be easily
mounted within a gas fueled device. In the illustrated embodiment,
the end of the sensing element 32 is about 20 to 22 mm from the
nozzle 16 and about 26 to 36 mm above the nozzle (measured with the
system 10 oriented such that the pilot 12 extends vertically).
[0046] Another exemplary pilot system, which is generally
represented by reference numeral 10', is illustrated in FIGS. 5A-6.
Pilot system 10' is substantially similar to pilot system 10 and
similar elements are represented by similar reference numerals.
Turning first to FIGS. 5A and 6, the pilot system 10' includes a
sensor that measures the electrical resistance of whatever gas
(e.g. pure air, pure gas or a gas/air mixture) is in the area
adjacent to the nozzle 16. Any suitable resistant measurement
device may be employed so long as it is capable of measuring the
electrical resistance of the gas in the area adjacent to the
nozzle. The exemplary pilot system 10' is provided with an
electrical resistance measuring device 54 including an sensing
device 56 that is positioned adjacent to the pilot nozzle 16 and
pilot flame F. The sensing device 56 includes a pair of generally
L-shaped electrodes 58a and 58b positioned above the nozzle 16 in
the position shown in FIG. 6. A space 60 of approximately 3 mm
separates the free ends of the L-shaped electrodes 58a and 58b,
which are located in the area that will be occupied by the outer
edge of the pilot flame F when the pilot flame in the "normal"
oxygen level position illustrated in FIG. 5A. The pilot system 10'
also includes a shield 34' with a slot 36' that accommodates the
L-shaped electrodes 58a and 58b.
[0047] Preferably, a constant current (I) is applied to the sensing
device 56 by the electrical resistance measuring device 54 and the
voltage (V) across the electrodes 58a and 58b is measured by the
measuring device. The electrical resistance (R) may then be
determined using the R=V/I formula. The measuring device 54 also
produces a signal indicative of the electrical resistance in the
area adjacent to the nozzle 16.
[0048] The high temperature at the outer edge of the pilot flame F
causes the gas in the gas/air mixture G/A to be ionized and
electrical resistance is inversely related to the level of gas
ionization. The electrical resistance of the gas in the region
adjacent to the nozzle 16 will be approximately 8-12 M.OMEGA. (i.e.
8-12.times.10.sup.6.OMEGA.) when the pilot flame is in the "normal"
oxygen level position (oxygen level greater than or equal to 21%)
illustrated in FIG. 5A. The resistance level will be significantly
lower when the pilot flame F is in the region adjacent to the
nozzle 16 (FIG. 5A) than it will be when the pilot flame F is in
the "relatively low" oxygen level position (oxygen level between
18.2% and 19.2%) illustrated in FIG. 5B. More specifically, the
electrical resistance will rise to about 20 M.OMEGA. when the pilot
flame F is in the "relatively low" oxygen level position
illustrated in FIG. 5B because the hot outer edge of the pilot
flame F will no longer be present in the region where resistance is
being measured. This results in a reduction in temperature in the
region adjacent to the nozzle 16 and a correspondingly lower level
of gas ionization. The resistance will be about 80-100 M.OMEGA.
when the pilot flame F is in the "unsafe" level position (oxygen
level below 18.2%) illustrated in FIG. 5C because the temperature
and gas ionization levels in the region adjacent to the nozzle 16
will fall even further.
[0049] The difference in resistance will be detected by the
measuring device 54 within about 1 second from the time at which
the pilot flame F moves. This is true whether pilot flame F is
moving from the "normal" oxygen level position to the "relatively
low" oxygen level position, or from the "relatively low" oxygen
level position to the "unsafe" oxygen level position. Thus, even in
those instances where the pilot flame F jumps back and forth
between the "normal" and "relatively low" oxygen level positions,
the present measuring device 54 will immediately indicate that the
oxygen level has dropped to a "relatively low" level because the
resistance measured thereby will increase beyond the 8-12 M.OMEGA.
range the first time that the pilot flame F moves out of the
"normal" oxygen level position to the "relatively low" oxygen level
position. Similarly, in those instances where the pilot flame F
jumps back and forth between the "relatively low" and "unsafe"
oxygen level positions, the present measuring device 54 will
immediately indicate that the oxygen level has dropped to an
"unsafe" level because the resistance measured thereby will
increase beyond the 20 M.OMEGA. range the first time that the pilot
flame moves out of the "relatively low" oxygen level position to
the "unsafe" oxygen level position.
[0050] Another exemplary pilot system, which is generally
represented by reference numeral 10", is illustrated in FIGS. 7A-9.
Pilot system 10" is substantially similar to pilot system 10' and
similar elements are represented by similar reference numerals. The
pilot system 10" also includes a sensor that measures the
electrical resistance of whatever gas (e.g. pure air, pure gas or a
gas/air mixture) is in the area adjacent to the nozzle 16. Here, an
electrical resistance measuring device 62 includes a sensing device
64 that is positioned adjacent to the pilot nozzle 16 and pilot
flame F. The sensing device 64 includes a first electrode that
defines an enclosed open area, such as the exemplary annular
electrode 66 that defines an open area 68, and a second electrode,
such as the exemplary L-shaped electrode 70, which has a portion
that is positioned within the open area. The L-shaped electrode 70
is also used to ignite the gas in the exemplary embodiment.
[0051] The annular electrode 66 in the exemplary embodiment is
preferably formed from stainless steel wire that is about 1 mm in
diameter. The annular electrode 66 also has an outer diameter of
about 8 mm and is positioned about 8 mm above the nozzle 16 so that
it occupies the area that will be occupied by the outer edge of the
pilot flame F when the pilot flame in the "normal" oxygen level
position illustrated in FIG. 7A. The exemplary L-shaped electrode
70 is also formed from stainless steel wire that is about 1 mm in
diameter. As such, within the open area 68, the distance D (FIG. 9)
between the L-shaped electrode 70 and the inner surface of the
annular electrode 66 is about 2.5 mm. The electrodes 66 and 70 are
preferably supported by insulative structures 72 and 74.
[0052] A constant current (I) is applied to the sensing device 64
by the measuring device 62 and the voltage (V) across the
electrodes 66 and 70 is measured by the measuring device. The
electrical resistance (R) may then be determined using the R=V/I
formula. The measuring device 62 also produces a signal indicative
of the electrical resistance in the area adjacent to the nozzle
16.
[0053] The electrical resistance of the gas in the region adjacent
to the nozzle 16 will be approximately 8-12 M.OMEGA. (i.e.
8-12.times.10.sup.6.OMEGA.) when the pilot flame is in the "normal"
oxygen level position (oxygen level greater than or equal to 21%)
shown in FIG. 7A. As noted above, the resistance level will
increase significantly when the pilot flame F moves out of the
"normal" oxygen level position adjacent to the nozzle 16 (FIG. 7A)
to the "relatively low" oxygen level position (oxygen level between
18.2% and 19.2%) illustrated in FIG. 7B or to the "unsafe" oxygen
level position (oxygen level below 18.2%). The difference in
resistance will be detected by the measuring device 62 within about
1 second from the time at which the pilot flame F moves. This is
true whether pilot flame F is moving from the "normal" oxygen level
position to the "relatively low" oxygen level position, or to the
"unsafe" oxygen level position.
[0054] Thus, even in those instances where the pilot flame F jumps
back and forth, the present measuring device 62 will immediately
indicate that the oxygen level has dropped to a "relatively low"
level because the resistance measured thereby will increase beyond
the 8-12 M.OMEGA. range the first time that the pilot flame F moves
out of the "normal" oxygen level position to the "relatively low"
oxygen level position. Alternatively, the present measuring device
62 may be used to immediately indicate that the oxygen level has
dropped to an "unsafe" level the first time that the pilot flame F
moves to the "unsafe" oxygen level position and the resistance
exceeds 20 M.OMEGA..
[0055] Another exemplary pilot system, which is generally
represented by reference numeral 10'", is illustrated in FIGS.
10A-10C. Pilot system 10'" is substantially similar to pilot system
10 and similar elements are represented by similar reference
numerals. For example, pilot system 10'" includes a pilot 12 having
a gas/air mixing chamber 14 and a nozzle 16. The gas G in the
gas/air mixture G/A is ignited by an electrode 26' of an ignitor
28, which is supported by a bracket system 38', to create the pilot
flame F. Here, however, the oxygen depletion sensor is a light
sensor that senses light associated with the ignition electrode 26'
instead of light from the pilot flame F. The electrode 26' will
glow when the flame F is in the "normal" oxygen level position
(oxygen level greater than or equal to 21%) shown in FIG. 10A or
the "relatively low" oxygen level position (oxygen level between
18.2% and 19.2%) shown in FIG. 10B, but will stop glowing (or will
fail to create a sufficiently detectable amount of light if only
glowing slightly) when the pilot flame F moves to the "unsafe"
oxygen level position (oxygen level below 18.2%) shown in FIG. 10C.
The sensed light from the electrode may be either visible or
infrared, depending on the type of sensor used.
[0056] In the illustrated embodiment, a sensing device 30 having a
sensing element 32 is positioned adjacent to the electrode 26'. Any
suitable light sensor may be employed so long as it is capable of
detecting the presence or absence of light emitted by the electrode
26'. When the pilot flame F moves beyond the "relatively low"
oxygen level position, the electrode 26' will stop glowing and the
sensing device 30 will stop generating a flame signal which
indicates that the pilot flame is in an allowable position. The
signal may drop to zero, or simply to a level lower than an
expected level. Alternatively, the electrode 26' may be
repositioned so that it will stop glowing when the pilot flame
moves beyond the "normal" oxygen level position.
[0057] Although not so limited, heaters are one example of a gas
fueled device in accordance with the present inventions. An
exemplary heater 100 is shown in FIG. 11. Such a heater may be
fueled by natural gas, propane gas or other appropriate fuels. The
exemplary heater 100 includes a housing 102 mounted on a base 104.
The housing 102 includes a heating chamber 106 which contains a
plurality of heat emitting ceramic infrared burner plaques 108 and
is covered by a grill 110. The housing 102 also includes a
plurality of air circulation vents 112 and 114. Air enters the
housing through vent 112 and exits through the heating chamber
grill 110 and the vent 114. A pair of handles (not shown) may also
be provided on the sides of the housing. The heater controls are
located on the top portion 116 of the housing 102 in the exemplary
heater 100. These controls include an on/off button 118, an
ignition/pilot button 120, and a burner control knob 122 that is
used to block/permit the flow of gas to the pilot 12 and to select
the number of burners to which fuel will be supplied. The on/off
button 118 and the ignition/pilot button 120 are part of a control
device 124 which, in the exemplary control embodiment, includes an
electronic controller 125 such as a control circuit,
microcontroller, microprocessor or other suitable control
apparatus.
[0058] As shown by way of example in FIG. 12, a propane gas-fueled
heating assembly that may be used in conjunction with the housing
102 shown in FIG. 11 includes five burners 126, each of which
consists of an infrared ceramic plaque 108 that is secured to a
corresponding burner box 128. The number of burners may, however,
be increased or decreased to suit particular applications. An upper
burner deflector bracket 130 and lower burner deflector bracket 132
are also shown. Additionally, although the propane gas-fueled
heating assembly illustrated in FIG. 12 includes the exemplary
pilot system 10'" illustrated in FIGS. 10A-10C, any of the other
pilot systems illustrated herein (i.e. systems 10,10' and 10") may
be employed in its place.
[0059] Gas enters the heating assembly in the exemplary embodiment
through a pressure regulator 134 and travels through an inlet pipe
136 to a control valve 138. No gas will pass beyond the control
valve 138 when the control knob 122 is set to the OFF position.
Propane gas is supplied to the pilot system and burners in the
following manner. Turning first to the pilot system, and referring
to FIGS. 12 and 13, the heater is placed in the pilot mode by
turning the control knob 122 from the OFF position to the PILOT
position and then depressing the knob and holding it in place. This
allows gas to flow to the pilot 12 through a gas line 139. The
on/off button 118 is then pressed to supply power to the system.
Next, when the ignition/pilot button 120 is pressed, pulses of
power will be supplied to the ignition electrode 26' by way of a
connection line 140. So long as the user continues to holds the
ignition/pilot button 120 and a pilot flame has not been lit, the
pulses will continue for 20 seconds and then cease for 10 seconds
with this pattern repeating for 5 minutes. The system will shut of
if there is no pilot flame at the end of the 5 minute period.
[0060] Once the pilot flame is lit, the pilot flame sensing device
associated with the pilot system (the sensing device 30 in pilot
system 10'", for example) will send a signal to the control 124 by
way of a connection line 142 which indicates that a pilot flame is
present. The controller 125 will then cause a magnetic valve unit
144, which is normally closed, to open so that the supply of gas to
the pilot 12 will be maintained when the user releases the control
knob 122. The opening of the magnetic valve unit 144 will also
allow the user to supply gas to the burners 126. To that end, the
exemplary heater 100 includes LOW, MEDIUM and HIGH heat output
settings which correspond to one, three or five burners 126
receiving gas. The heat output settings are selected by rotating
the control knob 122. When the control knob 122 rotated from the
PILOT position (where gas will be supplied to the pilot 12 if the
control knob is depressed) to the LOW position, gas will be
supplied to one of the burners 126 through a gas line 146. Gas will
be supplied to three of the burners 126, through gas lines 146 and
148, when the control knob 122 is in the MEDIUM position, and will
be supplied to all five of the burners, through gas lines 146, 148
and 150, when the control knob is in the HIGH position.
[0061] It should be noted that if, for example, a three burner
design is employed, then the corresponding progression could be
one, two or three burners. It should also be noted that heaters in
accordance with the present invention may also be constructed in
such a manner that all of the burners will be used whenever the
heater is in operation and the amount of gas supplied to the
burners will be controlled by a thermostat.
[0062] Turning to oxygen level detection, the flame sensing device
(the sensing device 30 in pilot system 10'", for example) and
controller 125 form an ODS system that may operate in the following
manner. As noted above, the instant that the pilot flame F moves to
the "unsafe" oxygen level position (oxygen level below 18.2%), the
sensing device 30 will stop generating a flame signal which
indicates that the pilot flame is in an allowable position. The
controller 125 will, as a result, immediately close the magnetic
valve 144 that allows gas to pass to the pilot 12 and the burners
126. The heater 100 may, if desired, be provided with an audio
and/or visual alarm that is triggered by the controller 125 when
the valve 144 is closed by the controller in response to an
"unsafe" oxygen level detection.
[0063] Although the present inventions have been described in terms
of the preferred embodiments above, numerous modifications and/or
additions to the above-described preferred embodiments would be
readily apparent to one skilled in the art. By way of example, but
not limitation, the present inventions may be incorporated in
heaters which do not have a thermostatic control system. The
"unsafe," "low" and "normal" oxygen level percentages discussed
above may be varied if desired. The exemplary pilot system may also
be incorporated into other gas fueled devices such as water
heaters, stoves, ovens and other types of heaters. The pilot,
sensing device and controller could also be reconfigured and
repositioned such that the sensing device senses the flame when it
is in the "unsafe" oxygen level position and this sensing results
in closure of the gas valve(s). It is intended that the scope of
the present inventions extends to all such modifications and/or
additions.
* * * * *