U.S. patent application number 09/808059 was filed with the patent office on 2001-08-09 for ignition inhibiting gas water heater.
This patent application is currently assigned to SRP 687 Pty. Ltd.. Invention is credited to Bourke, Brendan Vincent, Valcic, Zoran, Whitford, Geoffrey Mervyn.
Application Number | 20010011529 09/808059 |
Document ID | / |
Family ID | 25644893 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010011529 |
Kind Code |
A1 |
Bourke, Brendan Vincent ; et
al. |
August 9, 2001 |
Ignition inhibiting gas water heater
Abstract
A gas water heater including a water container adapted to be
heated by a gas burner; and an enclosure surrounding the burner,
the enclosure having at least one entryway adapted to allow air and
fumes to enter the enclosure without igniting flammable gases or
vapors outside of the enclosure.
Inventors: |
Bourke, Brendan Vincent;
(Gordon, AU) ; Valcic, Zoran; (Chatswood, AU)
; Whitford, Geoffrey Mervyn; (Dundas, AU) |
Correspondence
Address: |
IP Department
Schnader Harrison Segal & Lewis
36th Floor
1600 Market Street
Philadelphia
PA
19103
US
|
Assignee: |
SRP 687 Pty. Ltd.
|
Family ID: |
25644893 |
Appl. No.: |
09/808059 |
Filed: |
March 14, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09808059 |
Mar 14, 2001 |
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09243710 |
Feb 3, 1999 |
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09243710 |
Feb 3, 1999 |
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09138359 |
Aug 21, 1998 |
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6138613 |
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09138359 |
Aug 21, 1998 |
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08626844 |
Apr 3, 1996 |
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5797355 |
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Current U.S.
Class: |
122/17.2 |
Current CPC
Class: |
F23D 14/72 20130101;
F23D 14/725 20130101; F24H 1/205 20130101; F23D 2209/10 20130101;
F24H 9/2035 20130101; F23L 1/02 20130101 |
Class at
Publication: |
122/17.2 |
International
Class: |
F24H 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 1995 |
AU |
PN2136 |
Sep 22, 1995 |
AU |
PN5591 |
Claims
What is claimed is:
1. A gas water heater comprising a water container adapted to be
heated by a gas burner; and an enclosure surrounding said burner,
said enclosure having at least one entry means adapted to allow air
and extraneous fumes to enter said enclosure without igniting
extraneous fumes outside of said enclosure.
2. A water heater as claimed in claim 1 wherein said entry means
includes an aperture which is covered by a flame trap which
prevents said burner from igniting extraneous fumes outside of said
enclosure; and an air inlet through which air for combustion is
drawn.
3. A water heater as claimed in claim 1 wherein said entry means is
remote from said burner and includes a duct for passage of air to
said burner.
4. A water heater as claimed in claim 2 wherein said entry means
and said aperture are collocated or are a single item.
5. A water heater as claimed in claim 1 wherein said entry means is
covered by a flame trap.
6. A water heater as claimed in claim 2 wherein said aperture is in
the enclosure.
7. A water heater as claimed in claim 2 wherein the aperture is
positioned proximate to a lower end of the enclosure.
8. A water heater as claimed in claim 2 wherein said aperture is
positioned in a lower end of the enclosure.
9. A water heater as claimed in claim 2 wherein said aperture is
positioned below said burner.
10. A water heater as claimed in claim 2 wherein said aperture is
positioned to allow air and said extraneous fumes outside of said
water heater to enter into an air passage leading to said
burner.
11. A water heater as claimed in claim 2 wherein said aperture
allows air and said extraneous fumes to enter the lowest point of
said air passage.
12. A water heater as claimed in claim 2 wherein one or a
combination of: a light detection or sensitive device; a flame
detecting or sensitive device; a temperature sensitive or detecting
device; a heat detecting or sensitive device; and an oxygen
depletion sensitive or detection device, is located in said water
heater to detect flame from said extraneous fumes if they have been
ignited inside said enclosure.
13. A water heater as claimed in claim 1 wherein said entry means
includes an air inlet which is not covered by a flame trap, said
air inlet having its lowest opening at a height of not less than
about 500 millimeters (20 inches) from a bottom portion of said
enclosure.
14. A water heater as claimed in claim 1 wherein said entry means
is located at or adjacent to the highest point of said enclosure,
if said enclosure has a height of about 500 millimeters or greater,
from a bottom portion of the enclosure.
15. A water heater as claimed in claim 1 wherein a snorkel device
extends said entry means to a height above the highest point of
said enclosure.
16. A water heater as claimed in claim 5 wherein said flame trap
includes a heat conductive permeable material.
17. A water heater as claimed in claim 5 wherein said flame trap
includes a screen made from woven or knitted mesh.
18. A water heater as claimed in claim 5 wherein said flame trap is
made of either steel or stainless steel.
19. A water heater as claimed in claim 5 wherein a lint trap is
included to wholly cover said aperture and said flame trap.
20. A water heater as claimed in claim 19 wherein said lint trap is
formed by mesh placed in the path of lint or dust travelling to
said flame trap.
21. A water heater as claimed in claim 1 further including a gas
shut off means which shuts of gas supply to said burner and or a
pilot burner if said air and extraneous fumes are ignited after
entering said enclosure.
22. A water heater as claimed in claim 21 wherein said gas shut off
means includes a heat sensitive means.
23. A water heater as claimed in claim 21 wherein said gas shut off
means includes a flame sensitive switch.
24. A water heater as claimed in claim 21 wherein said gas shut off
means includes an oxygen depletion sensitive means.
25. A water heater as claimed in claim 5 further comprising a
jacket surrounding said water container and said enclosure and a
base located beneath said enclosure.
26. A water heater as claimed in claim 25 wherein said flame trap
is provided at or as part of the construction of joining areas of
said base of said water heater to said jacket of said water heater,
or said jacket to other components of said water heater or said
base to other components of said water heater or at any location
where said extraneous fumes could enter said enclosure.
27. A water heater as claimed in claim 5 wherein said flame trap is
formed by a joining area of components of said water heater
including either only gaps or apertures of a size small enough to
act as a flame trap.
28. A water heater as claimed in claim 26 wherein said flame trap
has been added to the joining area or is deliberately incorporated
as part of said joining area.
29. A water heater as claimed in claim 28 wherein said flame trap
is a layer of metallic mesh cooperating with said joining area to
achieve a flame quenching or arresting function.
30. A water heater as claimed in claim 29 wherein said flame trap
is inside of said water heater.
31. A water heater as claimed in claim 21 wherein said gas shut off
means includes a light detection means.
32. A water heater having a burner adapted to combust gas to heat a
water container above the burner within an outer enclosure having
an opening means to admit air required to combust the gas; and
including air and fume flow means cooperative with said opening to
reduce or eliminate a possibility of fumes adjacent the enclosure
being ignited outside said enclosure by a gas flame associated with
said burner.
33. A water heater as claimed in claimed in claim 5 wherein a fume
detecting device is located in said water heater to detect said
extraneous fumes after they have entered said enclosure.
34. A water heater as claimed in claim 1 wherein said entry means
is positioned close to a lower end of the enclosure.
35. A water heater as claimed in claim 1 wherein said entry means
is positioned in a lower end of the enclosure.
36. A water heater as claimed in claim 1 wherein said entry means
is positioned below said burner.
37. A water heater as claimed in claim 1 wherein said entry means
is positioned to allow air and said extraneous fumes outside of
said water heater to enter into an air passage leading to said
burner.
38. A water heater as claimed in claim 37, wherein said entry means
allows air and said extraneous fumes to enter the lowest point of
said air passage.
39. A water heater as claimed in claim 37, wherein one of or a
combination of: a light sensitive device; a flame detecting device;
a temperature detecting device; a heat detecting device; and an
oxygen depletion measurement device, is located in said water
heater to detect flame from said extraneous fumes after they have
been ignited.
40. A water heater as claimed in claim 5 wherein said flame trap is
a flame quenching or arresting means.
41. A water heater as claimed in claim 12, wherein said device or
said devices are included in a gas shut off device.
42. A water heater as claimed in claim 1, wherein one of or a
combination of: a light detection or sensitive device; a flame
detecting or sensitive device; a temperature sensitive or detecting
device; a heat detecting or sensitive device; and an oxygen
depletion sensitive or detection device, is located in said water
heater to detect flame from said extraneous fumes if they have been
ignited inside said enclosure.
43. A water heater as claimed in claim 42, wherein said device or
said devices are included in a gas shut off device.
44. A water heater comprising a burner adapted to combust gas to
heat a water containment and flow means above the burner within an
outer enclosure having an opening means to air required to combust
the gas; and air and fume flow means cooperative with said opening
means to reduce or eliminate a possibility of fumes adjacent the
enclosure from being ignited outside the enclosure by a gas flame
associated with said burner; said water heater including gas shut
off means having a flame detecting or sensing device located in a
path of flame external to a combustion chamber of said water heater
and also located in any path of flame of said fumes ignited in the
enclosure.
45. A water heater as claimed in claim 44 wherein said flame
external to said combustion chamber is caused by flame spillage
from said burner caused by a blockage of an exhaust flue connected
to said combustion chamber.
46. A water heater as claimed in claim 44 wherein said flame
external to said combustion chamber is caused by air starvation in
said combustion chamber.
47. A water heater comprising: means for storing or containing
water; means forming a chamber adjacent said storing or containing
means; a burner located in said chamber; and a flame trap
associated with said chamber means permitting combustion air and
extraneous gases, if present, into said chamber and capable of
preventing ignition of extraneous gases outside said chamber.
48. A water heater as claimed in claim 47 further comprising a
separate opening in said means forming a chamber for ingress of
combustion air.
49. A water heater as claimed in claim 47 wherein said flame trap
comprises a barrier selected from the group consisting of woven or
knitted mesh, ported ceramic tile and heat resistant permeable
materials of high thermal capacity.
50. A water heater as claimed in claim 47 further comprising a lint
trap positioned to hinder contact of blocking materials with said
flame trap.
51. A water heater comprising: a water tank; a combustion chamber
located below said tank; a burner located inside said combustion
chamber; a flame trap positioned in a portion of structure
associated with said combustion chamber, said flame trap permitting
ingress of air and extraneous gases, if present, into said
combustion chamber and prevent egress of flames from said
structure.
52. A water heater as claimed in claim 49 further comprising a
separate opening in said structure for ingress of combustion air
into said combustion chamber.
53. A water heater as claimed in claim 51 wherein said flame trap
comprises a barrier selected from the group consisting of woven or
knitted mesh, ported ceramic tile and heat resistant permeable
materials of high thermal capacity.
54. A water heater as claimed in claim 51 further comprising a lint
trap positioned to hinder contact of blocking materials with said
flame trap.
55. A water heater as claimed in claim 44 wherein said aperture is
positioned above the height of said burner and in communication
with a downward path of combustion air toward said burner.
56. A water heater as claimed in claim 55 wherein a flame sensitive
sensor is positioned between said flame trap and an opening to said
combustion chamber to detect flame external to said combustion
chamber caused by one of: flame spillage from said burner caused by
a blocked exhaust flue connected to said combustion chamber; air
starvation in said combustion chamber; and extraneous fumes
combusting between said flame trap and said combustion chamber.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to arrangements to make gas
fired water heaters safer for use.
BACKGROUND OF THE INVENTION
[0002] The most commonly used gas-fired water heater is the storage
type, generally comprising an assembly of a water tank, a main gas
burner to provide heat to the tank, a standing pilot burner to
initiate the main burner on demand, an air inlet adjacent the
burner near the base of the jacket, an exhaust flue and a jacket to
cover these components. Another type of gas-fired water heater is
the instantaneous type which has a water flow path through a heat
exchanger heated, again, by a main burner initiated from a pilot
burner flame. For convenience, the following description is in
terms of storage type water heaters but the present invention is
not limited to this type. Thus, reference to "water container,"
"water containment and flow means," "means for storing or
containing water" and similar such terms includes water tanks,
reservoirs, bladders, bags and the like in gas-fired water heaters
of the storage type and water flow paths such as pipes, tubes,
conduits, heat exchangers and the like in gas-fired water heaters
of the instantaneous type.
[0003] A particular difficulty with many locations for water
heaters is that they are also used for storage of other equipment
such as lawn mowers, trimmers, snow blowers and the like. It is a
common procedure for such machinery to be refueled in such
locations.
[0004] There have been a number of reported instances of spilled
gasoline and associated fumes being accidently ignited. There are
many available ignition sources, such as refrigerators, running
engines, electric motors, electric light switches and the like.
However, gas water heaters have sometimes been suspected because
they often have a pilot flame.
[0005] Any vapors from spilt or escaping flammable liquid or
gaseous substances in a space in which an ignition source is
present, provides a potential for ignition. "Fumes," "extraneous
gases" or "extraneous fumes" is sometimes hereinafter used to
encompass gases, vapors or fumes generated by a wide variety of
liquid volatile or semi-volatile substances such as gasoline,
kerosine, turpentine, alcohols, insect repellent, weed killer,
solvents and the like as well as non-liquid substances such as
propane, methane, butane and the like. Many inter-related factors
influence whether a particular fuel spillage does lead to ignition.
These factors include, among other things, the quantity, the nature
and physical properties of the particular type of spilt fuel. Also
influential is whether air currents in the room, either natural or
artificially created, are sufficient to accelerate the spread of
fumes, both laterally and in height, from the spillage point to an
ignition point yet not so strong as to ventilate such fumes
harmlessly, that is, such that air to fuel ratio ranges capable of
enabling ignition are not reached given all the surrounding
circumstances.
[0006] One surrounding circumstance is the relative density of the
fumes. When a spilt liquid fuel spreads on a floor, normal
evaporation occurs and fumes from the liquid form a mixture with
the surrounding air that may, at some time and at some locations,
be within the range that will ignite. For example, that range for
common gasoline vapor is between 3% and 8% gasoline with air, for
butane between 1% and 10%. Such mixtures form and spread by a
combination of processes including natural diffusion, forced
convection due to air current draughts and by gravitationally
affected upward displacement of molecules of one less dense gas or
vapor by those of another more dense. Most common fuels stored in
households are, as used, either gases with densities relatively
close to that of air (eg. propane and butane) or liquids which form
fumes having a density close to that of air, (eg. gasoline, which
may contain butane and pentane among other components is very
typical of such a liquid fuel).
[0007] In reconstructions of accidental ignition situations, and
when gas water heaters are sometimes suspected and which involved
spilt fuels typically used around households, it is reported that
the spillage is sometimes at floor level and, it is reasoned, that
it spreads outwardly from the spill at first close to floor level.
Without appreciable forced mixing, the air/fuel mixture would tend
to be at its most flammable levels close to floor level for a
longer period before it would slowly diffuse towards the ceiling of
the room space. The principal reason for this observation is that
the density of fumes typically involved is not greatly dissimilar
to that of air. Combined with the tendency of ignitable
concentrations of the fumes being at or near floor level is the
fact that many gas appliances often have their source of ignition
at or near that level.
[0008] The present invention aims to substantially lower the
probability of ignition in typical fuel spillage circumstances.
SUMMARY OF THE INVENTION
[0009] The invention provides a gas water heater including a water
container adapted to be heated by a gas burner; an enclosure
surrounding the burner and the water container, the water heater
being characterized by having at least one opening adapted to allow
air for combustion or extraneous fumes to enter the enclosure
without igniting flammable extraneous fumes outside of the
enclosure.
[0010] Preferably the at least one opening includes an aperture
which is covered by a flame trap, which prevents the burner
igniting extraneous fumes outside of the enclosure; and an air
inlet through which air for combustion purposes is drawn.
[0011] Preferably the opening is remote from the gas burner and
includes a duct for passage of air to the burner.
[0012] Preferably the opening and the aperture are collocated or
are a single item.
[0013] Preferably the at least one opening is covered by a flame
trap.
[0014] Preferably the aperture is in the enclosure.
[0015] Preferably the aperture is positioned close to a lower end
of the enclosure.
[0016] Preferably the aperture is positioned in a lower end of the
enclosure.
[0017] Preferably the aperture is positioned below the burner.
[0018] Preferably the aperture is positioned to allow air and fumes
outside of the water heater to enter into an air passage leading to
the burner.
[0019] Preferably the aperture allows air and fumes to enter the
lowest point of the air passage.
[0020] Preferably one of or a combination of: a light detection or
sensitive device; a flame detecting or sensitive device; a
temperature sensitive or detecting device; a heat detecting or
sensitive device; and an oxygen depletion sensitive or detection
device, is located in the water heater to detect flame from the
fumes if they have been ignited inside the enclosure.
[0021] Preferably the at least one opening includes an air inlet
which is not covered by a flame trap, the air inlet having its
lowest opening at a height of not less than about 500 millimeters
or about 20 inches or more from the bottom of the enclosure.
[0022] Preferably the at least one opening is located at or
adjacent to the highest point of the enclosure, if the enclosure
has a height of about 500 millimeters or greater, from the bottom
of the enclosure.
[0023] Preferably a snorkel device is provided to extend the at
least one opening to a height above the highest point of the
enclosure.
[0024] Preferably the flame trap includes a heat resistant
permeable material having high thermal capacity.
[0025] Preferably the flame trap includes a screen selected from
either woven or knitted mesh.
[0026] Preferably the flame trap is made of metal.
[0027] Preferably the flame trap is made of one of: steel,
stainless steel, copper and aluminum.
[0028] Preferably a lint trap is included to wholly cover the
aperture and the flame trap.
[0029] Preferably the lint trap is formed by mesh placed in the
path of lint or dust to travelling to the flame trap means.
[0030] Preferably the water heater includes a gas shut off means
which shuts off the gas supply to the burner and or a pilot burner
if the air and fumes are ignited after entering the enclosure.
[0031] Preferably the gas shut off means includes a heat sensitive
means.
[0032] Preferably the gas shut off means includes a flame sensitive
switch.
[0033] Preferably the gas shut off means includes an oxygen
depletion sensitive means.
[0034] Preferably the enclosure comprises a separable jacket and
base.
[0035] Preferably the flame trap is provided at or as part of the
construction of joining areas of the base to the jacket, or the
jacket to other component or the base to other component or at any
location where the fumes could enter the enclosure.
[0036] Preferably the flame trap is inherent in or is formed by the
joining areas including either only gaps or apertures of a size
small enough to act as a flame trap.
[0037] Preferably the flame trap has been added to the joining area
or is deliberately incorporated as part of the joining area.
[0038] Preferably the flame trap is a layer of metallic mesh
cooperating with the joining area to achieve the flame quenching or
arresting function.
[0039] Preferably the flame trap is inside of the water heater.
[0040] Preferably the gas shut off means includes a light detection
means.
[0041] The invention further provides a water heater having a
burner adapted to combust gas to heat a water container above the
burner within an outer enclosure having an opening to admit air
required to combust the gas; and including air and extraneous fume
flow means co-operative with the opening to reduce or eliminate a
possibility of extraneous fumes adjacent the enclosure being
ignited outside the enclosure by a gas flame associated with the
burner.
[0042] Preferably a fume detecting device is located in the water
heater to detect fumes after they have entered the enclosure.
[0043] Preferably the at least one opening is positioned close to a
lower end of the enclosure.
[0044] Preferably the at least one opening is positioned in a lower
end of the enclosure.
[0045] Preferably the at least one opening is positioned below the
burner.
[0046] Preferably the at least one opening is positioned so as to
allow air and fumes outside of the water heater to enter into an
air passage leading to the burner.
[0047] Preferably the at least one opening allows air and fumes to
enter the lowest point of the air passage.
[0048] Preferably one of or a combination of: a light sensitive
device; a flame detecting device; a temperature detecting device; a
heat detecting device; and an oxygen depletion measurement device,
is located in the water heater to detect flame from fumes after
they have been ignited.
[0049] Preferably the flame trap is a flame quenching or arresting
means.
[0050] Preferably the device or devices are included in a gas shut
off device.
[0051] Preferably one of or a combination of: a light detection or
sensitive device; a flame detecting or sensitive device; a
temperature sensitive or detecting device; a heat detecting or
sensitive device; and an oxygen depletion sensitive or detection
device, is located in the water heater to detect flame from fumes
if they have been ignited inside the enclosure.
[0052] Preferably device or devices are included in a gas shut off
device.
[0053] The invention also provides a water heater having a burner
adapted to combust gas to heat a water container above the burner
within an outer enclosure having an opening to air required to
combust the gas; and including air and extraneous fume flow means
cooperative with the opening to reduce or eliminate a possibility
of fumes adjacent the enclosure being ignited outside the enclosure
by a gas flame associated with the burner; the water heater
including gas shut off means which has a flame detecting or sensing
device located in a path of flame external to a combustion chamber
of the water heater and also located in any path of flame of fumes
ignited in the enclosure.
[0054] Preferably the flame external to the combustion chamber is
caused by flame spillage from the burner caused by a blockage of an
exhaust flue.
[0055] Preferably the flame external to the combustion chamber is
caused by air starvation in the combustion chamber.
[0056] One advantage of the invention is the provision of a barrier
to the unprotected entry, at the lower end of the jacket or
enclosure, of flammable extraneous fumes. In alternative
embodiments it provides a protected entry means for such fumes near
or at the base of the enclosure in which case these extraneous
fumes are consumed in a controlled manner. The protected entry is,
in the most preferred form, a flame trap preventing ignition of the
remaining fumes in the surrounding atmosphere or of any liquid
remaining nearby.
[0057] An advantage of locating the air intake for combustion
purposes above the midpoint of the gas water system is that it
reduces the chance of extraneous fumes entering the heater via the
air intake because generally such flammables are heavier than air,
which in the main do not attain dangerous levels at the air intake
level.
[0058] The use of air close-off means and gas shut-off means
activated by a trigger provides the advantage of suffocating any
flame in the heater, or switching off the gas supply, or preventing
uncontrolled or undirected ignition of gases or vapors from exiting
the heater environment.
[0059] By providing an extended air intake, the risk of lint or
dust affecting the efficiency of the water heater is reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] An embodiment of the present invention will now be
described, by way of example only, by reference to the accompanying
drawings in which:
[0061] FIG. 1 is a cross section through a gas water heater
embodying aspects of the present invention;
[0062] FIG. 2 is a cross section through a gas water heater similar
to FIG. 1, with additional safety features (of flame trap and
TSS);
[0063] FIG. 3 is a cross section taken through the line 111-111 of
FIG. 2;
[0064] FIG. 4 is a cross section through a gas water heater similar
to that of FIG. 2;
[0065] FIG. 5 is a cross section taken through line V-V of FIG.
4;
[0066] FIG. 6 is a cross section through a gas water heater with a
safety feature (of air close-off means);
[0067] FIG. 7 is a cross section through a gas water heater of
another embodiment of the present invention.
[0068] FIG. 8 is a cross section through a gas water heater of yet
another embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0069] Illustrated in FIG. 1 is an assembly of a storage type gas
water heater 2 including jacket 4 which surrounds a water tank 6, a
main burner 14 in a combustion chamber 15. The water tank 6 is
preferably of mains pressure capability and is capable of holding
heated water. The water tank 6 is preferably insulated by foamed
insulation 8. Alternative insulation may include fiberglass or
other types of fibrous insulation and the like.
[0070] Located underneath the water tank 6 is the main burner 14
which uses natural gas or other gases such as LPG, for example. The
main burner 14 combusts a gas and air mixture and the hot products
of combustion resulting rise up through flue 10, possibly with
heated air. Near the pilot burner 49, is a sheath 52, preferably
made of copper, containing wires from a flame detecting
thermocouple 51 which is a known safety measure to ensure that in
the absence of a flame at the pilot burner 49 the gas control valve
48 shuts off the gas supply. Passing through the center of the tank
6 is a flue 10, in this instance incorporating a series of baffles
12 to better transfer heat generated by the main burner 14.
[0071] The products of combustion pass upwards and out the top of
the jacket 4 via the flue outlet 16 after heat has been transferred
from the products of combustion. The flue outlet 16 discharges
conventionally into a draught diverter 17 which in turn connects to
an exhaust duct 19 leading outdoors.
[0072] Close to the height of the top of the jacket 4 and the flue
outlet 16 is an air inlet 18 through which air is drawn down the
duct 22 to the main burner 14. The duct 22 is suitably constructed
from sheet metal 20. In a non-illustrated alternative construction,
a part or all of duct 22 may be inside the external cylindrical
envelope of the jacket 4.
[0073] The heater 2 is preferably mounted on legs 24 to raise the
base 26 off the floor. In the base 26 is an aperture 28 which is
closed, but not gas tightly, by a flame trap device 30 (which
operates on a flame quenching principle). The flame trap 30 is
preferably made from two parallel sheets of mesh each about 0.010
inch diameter metal wire strands woven into mesh having about 30 to
40 strands per inch. Mild steel or stainless steel wire are
suitable. Alternatively a ported ceramic tile of the SCHWANK type
(registered trade mark) can be utilized although the recognized
flame quenching ability of metallic woven or knitted mesh together
with its robustness and ease of forming generally commends its use.
The tile type functions as a flame quenching trap as long as the
porosity is suitable.
[0074] A single layer of mesh or a porous ceramic tile may be
susceptible to clogging by lint or other "blocking" materials such
as dust or the like. Lint caught in the openings of a single mesh
or a tile might act as a wick which may allow flame, which would
not otherwise pass through the flame trap, to do so. In this
situation the flame trap device would tend not to function as
efficiently. To prevent this tendency, the flame trap is preferably
constructed with either two layers of mesh or a layer of mesh and a
tile. In this way the layer of mesh further from the source of
fumes acts as a flame trap and the layer closer to the source of
fumes acts as a lint trap.
[0075] Where the base 26 meets the jacket 4, the mating surfaces 32
(made up from surfaces of base 26 and jacket 4) can be sealed
thoroughly to prevent ingress of air or any flammable gas or vapor.
In FIG. 1, the mating surfaces 32 extend upwardly from the base 26
around the jacket 4. The cylindrical wall of jacket 4 (the majority
of gas water heaters are cylindrical; however, a cubic shaped
jacket 4 may be utilized) can be sealed gas tightly so no openings
or breaks remain upon assembly and installation. In particular gas,
water, electrical, control, or other connections, fittings or
plumbing, wherever they pass through the jacket 4 or base 26, can
be sealed airtight. The joining area (or mating surfaces 32) of
base 26 to jacket 4 and all service entries or exits to the jacket
4 or duct 22 need not be sealed airtight providing they are
designed and constructed being only minor surface to surface
clearances or gaps, each of which is capable of acting as flame
quenching traps. The structure of such service entries or exits are
known in the art and not described herein. It is preferred,
however, that the space around the burner be substantially air/gas
tight except for means to supply combustion air.
[0076] Pilot flame establishment can be achieved by a
Piezo-electric igniter. A pilot flame observation window can be
provided which is sealed. Alternatively, if the pilot is to be lit
by removing or opening an access, safety interlocks (not
illustrated) are included to ensure complete closure against
unprotected fume access during heater operation.
[0077] During normal operation, the heater 2 operates in the same
fashion as conventional heaters except that most air for combustion
enters at air inlet 18 and a small proportion through flame trap
30. However, if a spilt fuel is in the vicinity of the heater 2
then some gas or vapor from the spilt fuel is drawn in through the
flame trap 30 before it builds up to a level to enter via air inlet
18. Flame trap 30 allows the combustible gas or vapor and air to
enter but prevents flame escaping the jacket 4 or duct 22. The
spilt fuel is burnt and exhausted either through the flue 10 via
outlet 16 and duct 19 or through the duct 22 and inlet 18 (which in
this case will act as an outlet). Because flame cannot pass
outwardly through the flame trap 30, any spilt fuel external to the
heater 2 will not be ignited.
[0078] FIGS. 2 and 3 show an embodiment similar to that of FIG. 1.
Like parts use the same reference numbers as those of FIG. 1. In
FIG. 2 there is, adjacent the gas control valve 48, a flame
sensitive switch 50 which may be inserted in the same circuit as
the pilot flame detecting thermocouple 51.
[0079] The flame sensitive switch may be substituted by a light
detector or a heat detector. The flame sensitive switch can also be
substituted by a gas, fume vapor detection switch which will close
off gas control valve 48 if a flammable fume is detected.
[0080] With reference to the cross section depicted in FIG. 3, the
duct 22 contains gas control valve 48 and the flame trap 30 is
shown forming a bottom end of the duct. In fact, the flame trap 30
may be positioned spanning the bottom end of the duct 22 and an
adjacent portion of the base 26. An advantage from such a
positioning of the flame trap 30, including that shown in FIGS. 2
and 3, by comparison with the center position of base 26 shown in
FIG. 1, is that it permits the positioning of a flame sensitive
switch 50 (FIG. 2) directly below the gas control valve 48 which is
also an ideal position to detect flame spillage from the combustion
chamber 15 which can occur if, for example, the flue 16, or exhaust
duct becomes blocked. Similarly it is ideally positioned to detect
flame spillage such as would occur due to air starvation if inlet
18 were inadvertently blocked.
[0081] As shown in FIG. 3, opening 28 and flame trap 30 (including
a lint trap device as mentioned above) are at the base of the duct
22 below the gas control valve 48 and flame detecting thermocouple
50 (see FIG. 2). In this way, should fumes which enter through
flame trap 30 be ignited, a flame forms and burns on the inside
surface of the flame trap and the flame detecting switch 50
actuates the gas control valve 48 to shut off the gas supply, thus
removing it as a continuing source of ignition. After the pilot and
main flames have been extinguished, any vapors of spilt fuel
continuing to enter through the flame trap 30 may continue to burn
because of the initial ignition and resulting suction of air and
may continue to burn until there is insufficient flammable vapor
remaining to be drawn in from the vicinity of the heater assembly
2.
[0082] By providing an air inlet 18 at a high position above the
base 26, the more commonplace liquid fuels, the flammable gases and
vapors are far less likely to be available to a gas water heater
flame.
[0083] In the water heater 2 of FIGS. 4 and 5, the path for air
entry to main burner 14 is provided by a combined flame trap and
duct 54 fabricated of metallic mesh 21. This arrangement provides
that all combustion air passes through a flame quenching surface 21
and the height of the duct 54 need not be as high as the jacket 4
nor need it necessarily extend upwardly. As evident in FIG. 5, it
is preferably composed of the separated layers 21a and 21b of
metallic mesh. This two layer construction avoids any layer of
lint, deposited externally, providing a possible combustion path
through the mesh, as previously explained.
[0084] Lint deposition in the openings of the mesh may be a cause
of gradual blockage. In due course such Tinting may cause
starvation of combustion air. Therefore an extended surface area
(along the full height of water heater 2 as depicted for instance)
of the combined flame trap and air duct 54 may be of advantage for
prolonging the time taken for the duct 54 to become occluded with
lint and for providing an adequate path for free induction of the
air normally required for combustion.
[0085] The positioning of gas valve 48 in its preferred position is
shown in FIG. 5 outside of the duct 54. The entry of the gas pipe
and thermocouple sheath into the duct 54 is effected so that if a
hole is left it is small enough either to be totally sealed or to
act as a flame quenching trap.
[0086] The preference for the gas valve 48 outside the duct 54 is
that it provides one way of providing user access to the control
knob and any buttons on the gas control valve 48. It would be
equally applicable in cases where the duct 22 is made of
imperforate sheet metal 20 as shown in FIGS. 1 and 2.
[0087] For ease of construction one option is that the gas pipe and
thermocouple sheath can enter the water heater 2 via an opening in
the jacket 4, bypassing completely the duct 54. This opening can be
then sealed or if a gap is left, the gap is sized to act as a flame
trap. However, whichever way the thermocouple sheath passes to
enter the combustion chamber, if it includes the flame sensitive
switch 50 or other equivalent sensor, then it is greatly preferred
that the flame sensitive switch 50 or other sensor is located in
relation to the position of the flame trap 30 so that the relative
positions co-operate in the event of a flame from spilt fuel forms
on the flame trap.
[0088] Illustrated in FIG. 6 is a another embodiment of the present
invention, similar to that of FIG. 1, with like parts like
numbered. This embodiment includes an anchor 34 which anchors a
nylon line 36 which is a heat sensitive frangible member. The nylon
line 36 passes close to the upper surface of the flame trap 30 and
around a lower pulley 38 then continues on to an upper pulley 40
around which it passes through 180 degrees, to make connection with
a flap 42. The flap 42 is connected by hinge 44 either to the
inside of passage 22 or to a purpose built flange 46.
[0089] The flange 46, if it is utilized, can have a sealing
medium(not illustrated) around it so that when the flap 42 makes
contact with it, an air tight seal or a flame trap is formed. If
the flange 46 is not utilized, the flap 42 can carry a seal so
that, when released to move to a closed position, it will seal the
inside of duct 22 to air tight quality or, in the alternative to
form a flame trap. The flap 42 can be biased towards the closed
position by a spring, which is a preferred method, or alternatively
the biasing can be by means of gravity. If desired the flap 42 can
be constructed from mesh, as described above to act as a flame
trap.
[0090] In the embodiment of FIG. 6, when fumes from split fuel
passing through the flame trap 30 are ignited, the heat of ignition
breaking the nylon line 36, which is heat sensitive and frangible
causing the flap 42 to move to a closed position, shutting off air
supply to the main burner 14. This leaves no path down the duct 22
for air or combustible fumes which may have built up around the
heater 2 to sufficiently gain access to the main burner 14 and so
the pilot burner 49 and the main burner 14 may not have enough air
available through the flame trap 30 to continue burning in which
case the flame detection thermocouple 50 will cut off the gas
supply until manual intervention can restore it when a safe
atmosphere is restored.
[0091] In conjunction with any form of the invention as shown in
FIGS. 1 to 6, a gas shut down facility similar to the above
mentioned gas shut down ability can be provided. In another form,
the gas shut down facility can be initiated by a flame sensitive
switch (FSS) or a thermocouple. Such a thermocouple is preferably
located just inside of the flame trap 30 where ever it appears.
FSS's are also used in water heaters in circuit with the
thermocouple (eg 50 of, FIG. 1) normally provided for confirming
the establishment and retention of a pilot flame by raising an
electric current flow to a level capable of keeping open a gas
supply to the pilot burner.
[0092] FSS's are used to reduce fire hazards in circumstances where
flame of the burner can "spill" through an air access opening
adjacent the main and pilot burners. In known FSS'S, the heat
sensor is externally positioned and in the present invention a FSS
50 is positioned above the flame trap 30 in order to sense flame
heat input resulting from spilt flammable vapor burning on the
inside of the flame trap 30 after having entered the combustion
chamber through a possible entry path. In the embodiment of FIG. 1
the preferred position of the FSS (not illustrated) is immediately
above the flame trap and it is preferred a small heat shield (not
shown) be placed above the FSS to shield it from the normal radiant
heat associated with the main burner 14. In FIG. 2, the FSS (50) is
positioned a short way above the flame trap 30.
[0093] In FIGS. 7 and 8 are illustrated a gas water heater 2
constructed similarly to that illustrated in FIG. 1. The heater 2
includes a base 26 and jacket 4 which are either completely sealed
(not illustrated) to air tight and flammable gas or vapor tight
quality or alternatively, any gas paths unsealed are fine enough to
act as flame traps. In this instance, when completely sealed, all
air for combustion is drawn in from the air inlet 18, and there is
no means present to ignite any spilt fuel at the lower portions of
the heater 2.
[0094] The embodiments shown in FIGS. 7 and 8 have no flame trap 30
or opening 28. However, an appreciable time delay will occur before
gases or vapors from spilt fuel rise to the elevated level of air
inlet 18. Only then could the gases or vapors be drawn down passage
22 to the main burner 14. Many spillages, nevertheless are quite
minor in terms of volume of liquid spilt and in such cases the
embodiment of FIG. 7 would tend to provide an adequate level of
protection and that of FIG. 8 even more so. The air inlet 18, if it
does not include a flame trap 30, would need to be at least about
500 millimeters (20 inches) from the base 26 (if the base 26 is
near to the ground), in the presence of gasoline fumes (a different
height may be required for other fumes). However, for added
protection a greater distance is preferred.
[0095] By providing an air inlet 18 at a high position above the
base 26, the more frequently used typical flammable fumes of spilt
liquid fuels, are far less likely to be available to a gas water
heater flame.
[0096] If the base 26 and jacket 4 has small gaps or openings
limited in their size in order to act as flame traps, then its
operation will be similar to the embodiment of FIG. 1. The features
of FIG. 6 can be incorporated also with the embodiments described
in FIGS. 7 and 8 when the base 26 and jacket 4 are sealed. In this
instance, because the water heater now includes a heat sensitive
frangible member 36 located in an air passage in the vicinity of
the main burner 14, if gases or vapors ignite having flowed down
the passage 22 (which would indicate that the volume of gases or
fumes had risen to the level of air entry of the air inlet 18), the
resulting flame would melt a frangible member such as the nylon
line 36 in the vicinity of main burner 14. The nylon line 36 can be
connected in turn to a non-flammable and non-frangible section
which in turn makes connection with a spring biased flap similar to
flap 42 capable of sealing the passage 22. The distance between the
nylon line 36 and the flap is sufficiently long to close the
passage 22, before a flame travelling back up the passage 22
reaches the flap. If the flap is hinged so that its closing motion
is in the direction that flame would have to travel to exit the
passage 22, the hinging arrangement may be aided in closing by the
movement of flame in a closing direction.
[0097] A further improvement to any of the above embodiments in the
previous paragraph is to provide a snorkel 60 as shown in FIG. 8
extending the air inlet upwardly. The snorkel 60 allows air to be
drawn to the main burner 14 but, by taking air from a height above
the top of the jacket 4, will further reduce the risk of the heater
2 being an ignition source of flammable gases or vapors from spilt
fuel. If the height of the jacket 4 is not greater than about 500
millimeters (20 inches) above the base 26, the snorkel 60 can be
used to draw combustion air from a more appropriate height,
depending upon the spillage which may occur.
[0098] An additional level of hazard reduction is provided by the
addition of an oxygen depletion sensor in conjunction with the
pilot burner (not illustrated). This makes available the entire air
requirement for the pilot flame to the pilot burner only through a
pilot air duct (not illustrated), gas tightly separate from the air
supply duct 22 and the combustion chamber 15. The pilot air duct
has an air intake external to the remainder of the water heater
assembly, preferably low to floor level where water heaters are
generally installed, standing upright on a floor. At any convenient
location in the pilot air duct between the air intake end and the
pilot burner is a flame quenching insert, composed of one or more
of a variety of high thermal capacity gas porous heat resistant
materials such as described in relation to the flame trap 30.
Locating the flame quenching insert at or near the air intake end
is advantageous to make it accessible for cleaning of lint or dust
that may accumulate in it. In the pilot air duct is also located an
element sensitive to oxygen depletion in the pilot air duct.
[0099] With these features added to any of the embodiments of FIGS.
1 to 7, the use of the oxygen depletion sensor reduces the risk of
ignition of escaping flammable vapor in particular when the pilot
burner is alight but the main burner is not, by sensing oxygen
depletion in the incoming pilot air supply if a flammable component
it ignites in which case it would cause a gas control valve 48 of
the type referred to in FIG. 1 to shut down gas flow to the pilot
burner. The shut down provides a time period for flammable vapor to
safely ventilate. Resumption of normal operation of the water
heater requires human intervention but, even if done ill-advisedly,
in any event the oxygen depletion sensor would continue to deny the
pilot burner of gas and the arrangement would behave safely even
with extraneous flammable fumes remaining near the water heater. An
oxygen depletion sensor can be used alternatively in place of or in
conjunction with the previously described flame sensing sensor 50
(FSS), and can be located similarly.
[0100] The invention thus far described can function at three
levels of safety. The embodiment, as illustrated in relation to
FIGS. 7 and 8, adds height and distance that fumes from spilt fuel
must travel to reach the main burner 14 or pilot burner 49. The
second embodiment, as illustrated in FIGS. 1, 2, 3 and 6, adds not
only height and distance but also allows some and advantageously
all the extraneous fumes to enter the base of the heater 2 and be
consumed safely, conceivably until all residual risk of fire and
explosion is avoided by dissipation of the spillage.
[0101] The third level, as illustrated in FIGS. 4 and 5, adds a
further level of confidence by protecting all air entry with a
flame arrestor, recognizing that high levels of airborne lint or
other dust may tend to block the air intake and starve the burner
of air for combustion if the air entry were not periodically
cleared of that lint or other dust. The embodiment of FIGS. 4 and 5
can be constructed to protect against ignition of all flammable
gases and vapors outside of the enclosure or jacket regardless of
the density of those gases and vapors relative to air.
[0102] Whilst the above embodiments are directed to room or indoor
installed gas water heaters, the improvements described will
function in an outdoor environment, if spillages occur nearby and
fumes enter the gas water heater.
[0103] The foregoing describes embodiments of the present invention
and variations thereof and modification by those skilled in the art
can be made thereto without departing from the scope of the
invention. For example, the flame trap may be located at various
positions other than those shown in the drawings and described
above. One alternative position is in the side of the combustion
chamber opposite the gas supply. In such a construction the flame
trap would be located in an opening in the skirt below the water
tank and extending through the corresponding portion of
insulation.
[0104] In a further construction the flame trap is positioned above
the height of entry to the combustion chamber and the FSS is
positioned above that height of entry in the flow path of
combustion air toward the burner. The aperture covered by the flame
trap is in radiant heat communication with a FSS also positioned to
be sensitive to flame roll out from flue blockage or combustion air
starvation.
[0105] Further, the flame trap may be made from a variety of
materials such as those described above, but can be fabricated from
others not specifically identified so long as they permit passage
of air and fumes in one direction but prevent flames from
travelling in the opposite direction.
[0106] Suitable flame trap materials include those being porous,
gas permeable and possessing sufficiently high thermal capacity to
quench flame under typical conditions of use. Metallic structures
having small holes, made from, for example, mild steel, stainless
steel, copper or aluminum are suitable and porous ceramics
including glass or mineral wool woven or non-woven constructions
are also suitable. Fibre matrix ceramic is suitable as is flexible
or rigid constructions.
[0107] Also, the air passage for combustion air, such as in the
structure labelled 22 in FIG. 1, can be located between water tank
6 and jacket 4. The passageway can be of a variety of shapes and
sizes and can be formed in and bounded by the insulation or can be
formed by tubes, pipes conduits and the like.
[0108] Finally, main burner 14 and combustion chamber 15 can have
different constructions such as those described in U.S. Pat. Nos.
4,924,816; 5,240,411; 5,355,841; and co-pending application Ser.
Nos. 08/333,871 and 08/113,618, for example, the subject matter of
which is incorporated herein by reference.
* * * * *