U.S. patent application number 10/145312 was filed with the patent office on 2002-09-26 for ignition inhibiting gas water heater and controller.
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 | 20020134320 10/145312 |
Document ID | / |
Family ID | 27507447 |
Filed Date | 2002-09-26 |
United States Patent
Application |
20020134320 |
Kind Code |
A1 |
Valcic, Zoran ; et
al. |
September 26, 2002 |
Ignition inhibiting gas water heater and controller
Abstract
A water heater including a water container having an inlet and
an outlet; a main burner positioned to heat water in the water
container; a pilot burner positioned to supply flame to the main
burner; and a control valve to supply fuel to the main and pilot
burners. The control valve includes a fuel inlet adapted to connect
to a supply of fuel; at least one fuel outlet adapted to connect to
the main burner; a conduit for fuel flow between the inlet and
outlet; a closure associated with the conduit to control flow of
fuel from the inlet to the outlet; a circuit associated with the
valve and including a thermally actuated device connected to the
closure, the switch, when heated by the pilot burner providing a
signal to the closure to open or close said closure; and a
combustion sensitive fuse connected to the electrical circuit and
positioned to be exposed to extraneous sources of flame and heat
external to and adjacent the control valve.
Inventors: |
Valcic, Zoran; (Chatswood,
AU) ; Whitford, Geoffrey Mervyn; (Dundas, AU)
; Bourke, Brendan Vincent; (Gordon, AU) |
Correspondence
Address: |
SCHNADER HARRISON SEGAL & LEWIS, LLP
1600 MARKET STREET
SUITE 3600
PHILADELPHIA
PA
19103
|
Assignee: |
SRP 687 PTY, LTD.
|
Family ID: |
27507447 |
Appl. No.: |
10/145312 |
Filed: |
May 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10145312 |
May 13, 2002 |
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08742587 |
Oct 28, 1996 |
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08742587 |
Oct 28, 1996 |
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08626844 |
Apr 3, 1996 |
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5797355 |
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Current U.S.
Class: |
122/14.31 ;
122/13.01; 122/17.1 |
Current CPC
Class: |
F23D 14/72 20130101;
F24H 9/2035 20130101; F24H 1/205 20130101; F23D 2209/10
20130101 |
Class at
Publication: |
122/14.31 ;
122/13.01; 122/17.1 |
International
Class: |
F22B 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 1996 |
AU |
PO 0786 |
Apr 4, 1995 |
AU |
PN 2136 |
Sep 22, 1995 |
AU |
PN 5591 |
Claims
What is claimed is:
1. A control valve for supplying fuel to a water heater containing
a main burner and a pilot burner comprising: a fuel inlet adapted
to connect to a supply of fuel; at least one fuel outlet adapted to
connect to the main burner; a conduit for fuel flow between the
inlet and outlet; a closure associated with the conduit to control
flow of fuel from the inlet to the outlet; a circuit associated
with the valve and including a thermally actuated device associated
with the closure, said device, when heated by the pilot burner
providing a signal to the closure to open or close the closure; and
a combustion sensitive fuse connected to the circuit and positioned
to be exposed to extraneous sources of flame and/or heat external
to and adjacent the control valve.
2. The control valve defined in claim 1 further comprising an
externally accessible socket in the circuit into which the fuse is
removably insertable.
3. The control valve defined in claim 2 wherein the socket is
adapted to receive the fuse independently separate from the
thermally actuated device.
4. The control valve defined in claim 2 wherein the socket is
accessible from an underside of the valve.
5. The control valve defined in claim 1 wherein the fuse is
positioned at an underside of the valve.
6. The control valve defined in claim 1 wherein the closure
comprises a member located in a portion of the conduit and is
normally resiliently biased in a closed position.
7. The control valve defined in claim 1 wherein the circuit further
comprises a solenoid associated with the closure, the solenoid
being capable of receiving an electrical signal from the thermally
actuated device and opening said closure in response.
8. The control valve defined in claim 1 wherein the fuse is
temperature sensitive.
9. The control valve defined in claim 1 wherein the circuit further
comprises an over temperature energy cut out switch associated with
a temperature sensitive thermostat probe, said energy cut out
switch being capable of interrupting gas flow through said control
valve to the main burner and the pilot burner.
10. The control valve defined in claim 1 wherein the thermally
actuated device is a thermocouple.
11. The control valve defined in claim 1 wherein the circuit
further comprises a manual switch connected to the thermally
actuated device and having on, off and pilot positions, said pilot
position causing the closure to open until such time as the
thermally actuated device is capable of providing a signal to open
the closure.
12. A control valve for supplying fuel to a water heater containing
a main burner and a pilot burner comprising: a fuel inlet adapted
to connect to a supply of fuel; at least one fuel outlet adapted to
connect to the main burner; a conduit for fuel flow between the
inlet and outlet; a closure associated with the conduit to control
flow of fuel from the inlet to the outlet, said closure comprising
a member located in a portion of the conduit and which is normally
resiliently biased in a closed position; and a circuit associated
with the valve comprising a thermocouple associated with the
closure, said thermocouple, when heated by the pilot burner
providing a signal; a solenoid associated with the closure, the
solenoid being capable of receiving output from the thermocouple
and maintaining open said closure in response to output indicative
of a flame at said pilot burner; an energy cut out switch
associated with a temperature sensitive thermostat, the energy cut
out switch being associated with a temperature sensitive thermostat
probe, said energy cut out switch being capable of interrupting gas
flow through said control valve to the main burner and the pilot
burner; and a combustion sensitive fuse positioned to be exposed to
extraneous sources of flame and/or heat external to and adjacent
the control valve.
13. A water heater comprising: a water container having an inlet
and an outlet; a main burner positioned to heat water in the water
container; a pilot burner positioned to supply flame to the main
burner; and a control valve to supply fuel to the main and pilot
burners, said control valve comprising: a fuel inlet adapted to
connect to a supply of fuel; at least one fuel outlet adapted to
connect to the main burner; a conduit for fuel flow between the
inlet and outlet; a closure associated with the conduit to control
flow of fuel from the inlet to the outlet; a circuit associated
with the valve and including a thermally actuated device associated
with the closure, said device, when heated by the pilot burner
providing a signal to means associated with the closure to maintain
open the already opened closure or to release it to a closed
position; and a combustion sensitive fuse connected to the circuit
and positioned to be exposed to extraneous sources of flame and/or
heat external to and adjacent the control valve.
14. A water heater comprising: a water container; a combustion
chamber located adjacent said tank; a main burner and a pilot
burner located inside said combustion chamber; and a flame trap
positioned at an opening in 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, said flame trap being positioned below and adjacent said
pilot burner.
15. The water heater defined in claim 14 further comprising a
venturi extending into said combustion chamber to supply combustion
air to said main burner.
16. The water heater defined in claim 14 further comprising a lint
trap positioned exteriorly of said flame trap and across said
opening.
17. The water heater defined in claim 14 further comprising a
blocking plate positioned within said combustion chamber and
adjacent said opening.
18. A water heater comprising: a water container; a combustion
chamber located adjacent said tank, said combustion chamber having
a floor portion with an opening; a conduit extending upwardly from
and being substantially sealed to said opening; a burner located
inside said combustion chamber; and a flame trap positioned across
said conduit, said flame trap permitting ingress of air and
extraneous gases, if present, into said combustion chamber and
prevent egress of flames from said structure.
19. The water heater defined in claim 18 further comprising a lint
trap positioned exteriorly of said flame trap and across an upper
portion of said conduit.
20. The water heater defined in claim 18 further comprising a lint
trap positioned across said opening.
21. The water heater defined in claim 18 further comprising a
blocking plate positioned within said combustion chamber and
adjacent an upper portion of said conduit.
Description
FIELD OF INVENTION
[0001] The present invention relates to ignition inhibiting gas
fired water heaters, particularly to improvements to gas fired
water heaters and controllers adapted to render them safer for
use.
BACKGROUND OF 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 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
common 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] Vapors from spilt or escaping flammable liquid or gaseous
substances in a space in which an ignition source is present
provides for ignition potential. "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, kerosene,
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 leads to ignition. These factors include,
among other things, the quantity, 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 about 3% and 8% gasoline with air,
for butane between about 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 (e.g., propane and butane) or liquids which
form fumes having a density close to that of air, (e.g., 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. 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 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 invention aims to substantially lower the probability of
ignition in typical fuel spillage circumstances.
SUMMARY OF INVENTION
[0009] The invention provides a gas water heater including a water
container adapted to be heated by a gas burner. An enclosure
surrounds the burner and the water container. The water heater has
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] In another aspect, the invention 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 includes 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.
[0011] 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 includes 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
includes 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.
[0012] In yet another aspect, the invention provides a gas control
valve of the type used to supply a main burner in a combustion
chamber of a water heater which has an electrical circuit
associated with the valve powered by a thermocouple heated by a
pilot burner flame. The resulting electrical potential maintains a
solenoid valve open which keeps the pilot supplied with gas for
combustion. The valve closes down the gas supply for safety if the
pilot flame blows out. The valve of the invention includes an
over-temperature fuse in the electrical circuit specifically
located to be exposed to extraneous sources of flame and heat in
the immediate surroundings of the valve. The valve has an
externally accessible socket in the electrical circuit such that
the thermal fuse can be removably inserted in such a way that if
the thermal fuse opens the electrical circuit by being heated above
a predetermined temperature, then the fuse can be subsequently
independently and separately replaced without having to interfere
with other parts of the electrical circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Selected embodiments of the invention will now be described,
by way of example only, by reference to the accompanying drawings
in which:
[0014] FIG. 1 is a schematic partial cross-sectional view of a gas
water heater embodying aspects of the invention.
[0015] FIG. 2 is a schematic partial cross-sectional view of a gas
water heater similar to FIG. 1, with additional safety
features.
[0016] FIG. 3 is a cross-sectional view of the water heater of FIG.
2 taken through the line III-III.
[0017] FIG. 4 is a schematic partial cross-sectional view of a gas
water heater similar to that of FIG. 2.
[0018] FIG. 5 is a cross-sectional view of the water heater of FIG.
4 taken through line V-V.
[0019] FIG. 6 is a schematic partial cross-sectional view of a gas
water heater with a safety feature in accordance with aspects of
the invention.
[0020] FIG. 7 is a schematic partial cross-sectional view of a gas
water heater of another embodiment of the invention.
[0021] FIG. 8 is a schematic partial cross-sectional view of a gas
water heater of yet another embodiment of the invention.
[0022] FIG. 9 is a schematic partial cross-sectional view of still
another embodiment of the invention.
[0023] FIG. 10 is a cross-sectional view of the water heater of
FIG. 9 taken through the line X-X.
[0024] FIG. 11 is an upright elevational view taken from the rear
of a gas valve according to the aspects of invention.
[0025] FIG. 12 is an upright elevational showing the left side of
the gas valve shown in FIG. 11.
[0026] FIG. 13 is an upright perspective view of the valve of FIGS.
11 and 12.
[0027] FIG. 14 is a schematic partial cross-sectional view of a
water heater with the gas valve as shown in FIGS. 11-13.
[0028] FIG. 15 is an electrical circuit embodied in the gas valve
shown in FIGS. 11-13.
[0029] FIG. 16 is a cross-sectional view of the gas valve shown in
FIGS. 11-13.
DETAILED DESCRIPTION OF THE DRAWINGS
[0030] It will be appreciated that the following description is
intended to refer to the specific embodiments of the invention
selected for illustration in the drawings and is not intended to
define or limit the invention other than in the appended
claims.
[0031] FIG. 1 illustrates 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. Water tank 6 is preferably of mains
pressure capability and capable of holding heated water. Water tank
6 is preferably insulated by foam insulation 8. Alternative
insulation may include fiberglass or other types of fibrous
insulation and the like.
[0032] Located underneath water tank 6 is main burner 14 which
preferably uses natural gas or other gases such as LPG, for
example. Main burner 14 combusts a gas and air mixture and the hot
products of combustion resulting rise up through flue 10. Flue 10,
in this instance, contains a series of baffles 12 to better
transfer heat generated by main burner 14. Near 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 pilot burner 49 the gas
control valve 48 shuts off the gas supply.
[0033] The products of combustion pass upwardly and out the top of
jacket 4 via flue outlet 16 after heat has been transferred from
the products of combustion. Flue outlet 16 discharges
conventionally into a draught diverter 17 which in turn connects to
an exhaust duct 19 leading outdoors.
[0034] Close to the height of the top of jacket 4 and flue outlet
16 is an air inlet 18 through which air is drawn down duct 22 to
main burner 14. Duct 22 is preferably 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 jacket
4.
[0035] Water heater 2 is preferably mounted on legs 24 to raise the
base 26 off the floor. In 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. 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.
[0036] 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. The mesh layers are most preferably in contact with one
another. 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.
[0037] Where base 26 meets jacket 4, mating surfaces 32 (made up
from surfaces of base 26 and jacket 4) can be sealed thoroughly to
prevent ingress of air or flammable gas or vapor. In FIG. 1, mating
surfaces 32 extend upwardly from base 26 around jacket 4. The
cylindrical wall of jacket 4 (the majority of gas water heaters are
cylindrical; however, a cubic or other 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 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 jacket 4 or duct 22
need not be sealed airtight providing they are designed and
constructed to have 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.
[0038] 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 49 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 water heater operation.
[0039] During normal operation, water heater 2 operates in the same
fashion as conventional water heaters except that most air for
combustion enters at air inlet 18 and a small proportion through
flame trap 30. However, if spilt fuel is in the vicinity of water
heater 2 then some gas or vapor from the spilt fuel may be drawn
through 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 jacket 4 or duct 22. The
spilt fuel is burned within combustion chamber 15 and exhausted
either through flue 10 via outlet 16 and duct 19 or through duct 22
and inlet 18 (which in this case will act as an outlet). Because
flame does not pass outwardly through flame trap 30, spilt fuel
external to water heater 2 will not be ignited.
[0040] 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 gas control valve 48, a flame sensitive
switch 50 which may be inserted in the same circuit as pilot flame
detecting thermocouple 51.
[0041] Flame sensitive switch 50 may be substituted by a light
detector or a heat detector. The flame sensitive switch can also be
substituted by a gas, fume or vapor detection switch which closes
off gas control valve 48 when a flammable fume is detected.
[0042] With reference to the cross section depicted in FIG. 3, duct
22 contains gas control valve 48 and flame trap 30 is shown forming
a bottom end of the duct. In fact, flame trap 30 may be positioned
spanning the bottom end of duct 22 and an adjacent portion of base
26. An advantage from such a positioning of 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
positioning of flame sensitive switch 50 (FIG. 2) directly below
gas control valve 48 which is also an ideal position to detect
flame spillage from combustion chamber 15 which can occur if, for
example, 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.
[0043] As shown in FIGS. 2 and 3, opening 28 and flame trap 30
(including a lint trap device as mentioned above) are at the base
of duct 22 below 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 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 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 water heater 2.
[0044] 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.
[0045] 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 combustion air passes through a flame quenching surface 21 and
the height of duct 54 need not be as high as jacket 4 nor need it
necessarily extend upwardly. As evident in FIG. 5, it is preferably
composed of separated layers 21a and 21b of metallic mesh. This two
layer construction avoids a layer of lint, deposited externally,
providing a possible combustion path through the mesh, as
previously explained.
[0046] Lint deposition in the openings of the mesh may be a cause
of gradual blockage. In due course such linting 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 duct 54 to become occluded with lint
and for providing an adequate path for free induction of the air
normally required for combustion.
[0047] The positioning of gas valve 48 in its preferred position is
shown in FIG. 5 outside of duct 54. The entry of the gas pipe and
thermocouple sheath into 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.
[0048] The preference for gas valve 48 outside duct 54 is that it
provides one way of providing user access to the control knob and
any buttons on gas control valve 48. It would be equally applicable
in cases where duct 22 is made of imperforate sheet metal 20 as
shown in FIGS. 1 and 2.
[0049] For ease of construction one option is that the gas pipe and
thermocouple sheath can enter water heater 2 via an opening in
jacket 4, completely bypassing duct 54. This opening can then be
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 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 flame trap 30 so that the relative
positions co-operate in the event that a flame from spilt fuel
forms on the flame trap.
[0050] 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 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. Flap 42 is connected by hinge 44 either to the inside of
passage 22 or to a flange 46.
[0051] Flange 46, if it is utilized, can have a sealing medium (not
illustrated) around it so that when flap 42 makes contact with it,
an air tight seal or a flame trap is formed. If flange 46 is not
utilized, 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. 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, flap 42 can be constructed from mesh, as
described above to act as a flame trap.
[0052] In the embodiment of FIG. 6, when fumes from split fuel
passing through the flame trap 30 are ignited, the heat of ignition
breaks nylon line 36, which is heat sensitive and frangible,
thereby causing flap 42 to move to a closed position, shutting off
the air supply to main burner 14. This leaves no path down duct 22
for air or combustible fumes which may have built up around water
heater 2 to sufficiently gain access to main burner 14 and so pilot
burner 49 and main burner 14 may not have enough air available
through flame trap 30 to continue burning in which case flame
detection thermocouple 50 will cut off the gas supply until manual
intervention can restore it when a safe atmosphere is restored.
[0053] In FIGS. 7 and 8 are illustrated a gas water heater 2
constructed similarly to that illustrated in FIG. 1. Water 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, unsealed gas paths are fine (small)
enough to act as flame traps. In this instance, when completely
sealed, air for combustion is drawn in from the air inlet 18, and
there is no means present to ignite spilt fuel at the lower
portions of water heater 2.
[0054] 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 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, should be at least about 500 millimeters
(20 inches) from base 26 (if 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.
[0055] The more frequently used typical flammable fumes of spilt
liquid fuels are far less likely to be available to a gas water
heater flame by providing an air inlet 18 at a high position above
base 26.
[0056] If base 26 and jacket 4 has small gaps or openings limited
in their size 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 base 26 and jacket 4 are scaled. 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 nylon line 36 in the vicinity of
main burner 14. 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 passage 22. The distance between nylon line 36 and flap 42
is sufficiently long to close passage 22 before a flame travelling
back up passage 22 reaches flap 42. If flap 42 is hinged so that
its closing motion is in the direction that flame would have to
travel to exit passage 22, the hinging arrangement may be aided in
closing by the movement of flame in a closing direction.
[0057] A further improvement to the above embodiments shown in
FIGS. 1-6 is to provide a snorkel 60 as shown in FIG. 8 extending
the air inlet upwardly. Snorkel 60 allows air to be drawn to main
burner 14 but, by taking air from a height above the top of jacket
4, will further reduce the risk of water heater 2 being an ignition
source of flammable gases or vapors from spilt fuel. If the height
of jacket 4 is not greater than about 500 millimeters (20 inches)
above base 26, snorkel 60 can be used to draw combustion air from a
more appropriate height, depending upon the spillage which may
occur.
[0058] 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 50 or thermocouple 51. Such a thermocouple is preferably
located just inside of the flame trap 30 where ever it appears.
Flame sensitive switches may also be used in circuit with the
thermocouple (e.g., thermocouple 51 of FIG. 1) 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.
[0059] Flame sensitive switches may be 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
flame sensitive switches, the heat sensor is externally positioned
and in some embodiments of the invention a flame sensitive switch
50 is positioned above flame trap 30 to sense flame heat input
resulting from spilt flammable vapor burning on the inside of 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 flame sensitive switch (not illustrated) is
immediately above the flame trap and it is preferred that a small
heat shield (not shown) be placed above the flame sensitive switch
to shield it from the normal radiant heat associated with the main
burner 14. In FIG. 2, the flame sensitive switch 50 is positioned a
short way above flame trap 30.
[0060] An additional level of safety is provided by the addition of
an oxygen depletion sensor in conjunction with pilot burner 49.
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 air supply duct 22 and
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 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. An element sensitive to oxygen depletion is also located in
the pilot air duct.
[0061] With these features added to the embodiments of FIGS. 1 to
7, use of the oxygen depletion sensor reduces the risk of ignition
of flammable vapor in particular when pilot burner 49 is alight but
main burner 14 is not, by sensing oxygen depletion in the incoming
pilot air supply if a flammable component 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 pilot burner 49 of gas and the
arrangement would behave safely even with extraneous flammable
fumes remaining near water heater 2. An oxygen depletion sensor can
be used alternatively in place of or in conjunction with the
previously described flame sensitive switch 50, and can be located
similarly.
[0062] 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 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 water heater 2 and be
consumed safely, conceivably until all residual risk of fire and
explosion is avoided by dissipation of the spillage.
[0063] 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 flammable gases
and vapors outside of the enclosure or jacket regardless of the
density of those gases and vapors relative to air.
[0064] In its most preferred forms water heater 2 contains at least
some of the following features:
[0065] the opening includes an aperture which is covered by a flame
trap, which prevents the burner from igniting extraneous fumes
outside of the enclosure, and an air inlet through which air for
combustion purposes is drawn;
[0066] the opening is remote from the burner and includes a duct
for passage of air to the burner;
[0067] the opening and the aperture are collocated or are a single
item;
[0068] the at least one opening is covered by a flame trap;
[0069] the aperture is in the enclosure;
[0070] the aperture is positioned close to a lower end of the
enclosure;
[0071] the aperture is positioned in a lower end of the
enclosure;
[0072] the aperture is positioned below the burner;
[0073] the aperture is positioned to allow air and fumes outside of
the water heater to enter into an air passage leading to the
burner;
[0074] the aperture allows air and fumes to enter the lowest point
of the air passage;
[0075] 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;
[0076] the 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;
[0077] the 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;
[0078] a snorkel device is provided to extend the at least one
opening to a height above the highest point of the enclosure;
[0079] the flame trap includes a heat resistant permeable material
having high thermal capacity;
[0080] the flame trap includes a screen selected from either woven
or knitted mesh;
[0081] the flame trap is made of metal;
[0082] the flame trap is made from a metal selected from the group
consisting of: steel, stainless steel, copper and aluminum;
[0083] a lint trap is included to wholly cover the aperture and the
flame trap;
[0084] the lint trap is formed by mesh placed in the path of lint
or dust travelling to the flame trap means;
[0085] 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;
[0086] the gas shut off means includes a heat sensitive means;
[0087] the gas shut off means includes a flame sensitive
switch;
[0088] the gas shut off means includes an oxygen depletion
sensitive means;
[0089] the enclosure comprises a separable jacket and base;
[0090] 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;
[0091] 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;
[0092] the flame trap has been added to the joining area or is
deliberately incorporated as part of the joining area;
[0093] the flame trap is a layer of metallic mesh cooperating with
the joining area to achieve the flame quenching or arresting
function;
[0094] the flame trap is inside of the water heater; and
[0095] the gas shut off means includes a light detection means.
[0096] One advantage provided by the invention is the provision of
a barrier to 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.
[0097] 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.
[0098] 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.
[0099] By providing an extended air intake, the risk of lint or
dust affecting the efficiency of the water heater is reduced.
[0100] Still further advantages of the invention are provided by
the structure shown in FIGS. 9 and 10. FIGS. 9 and 10 show water
heater 2 wherein aperture 28 having flame trap 30 across its mouth
and positioned below pilot burner 49, pilot burner 49 being located
adjacent one edge of main burner 14. Aperture 28 is positioned
immediately underneath pilot burner 49, preferably the closer the
better to assist in achieving smooth ignition. Aperture 28 is
connected to the lower end of the enclosure by an upwardly
extending tube 70, the upwardly extending portion of tube 70 being
preferably impermeable to air, gas or fumes. Tube 70 is preferably
constructed of sheet metal, although other suitable materials may
be substituted. Locating flame trap 30 above base 26 minimizes the
possibility of water condensate occluding the pores or openings in
flame trap 30 or water splashing from, for example, hosing the
floor near base 26 of water heater 2. Thus, the length of tube 70
is not especially critical so long as it performs the function of
preventing pore occlusion. In FIG. 9, a horizontal blocking plate
74 is located above flame trap 28 to prevent water condensate or
particulate matter such as steel scale flakes falling on the flame
trap, thereby reducing the chance of occluding it.
[0101] It has also been discovered that a two layer construction of
flame trap 30 with a lint filter is highly advantageous. FIG. 9
illustrates a lint filter 72 in addition to a double layer flame
trap 30. Filter 72 may be a different material from flame trap 30.
The potential for accumulation of lint over time has been a
concern. However, it has been unexpectedly discovered that
structure such as that shown in FIGS. 9 and 10 is surprisingly free
of lint accumulation problems. It is believed that the horizontal
and very close positioning of flame trap 30 to main burner 14
results in small pressure pulses associated with main burner 14
igniting on each occasion. Apparently, the pulses blow away any
lint from the face of flame trap 30. This appears to provide a
repeating self-cleaning effect.
[0102] Another significant advantage of the water heater of the
invention is its improved gas control valve. In conventional gas
valves, the thermocouple and over-temperature fuse have been
inconveniently located in an integrated structure sheathed in a
copper capillary tube with significant thermal inertia. If either
the thermocouple or the temperature fuse require replacement then
it is not immediately apparent which one has failed and, because
both are replaced as an integrated unit, unnecessary cost is
involved. The thermal fuse is a relatively low cost item compared
to the entire integrated structure and, therefore, it is
advantageous to be able to test the circuit by merely removing the
suspect fuse and replacing it. This test does not involve removal
of the thermocouple which requires awkward access into the water
heater combustion chamber. Thus, there can be a considerable
reduction in the time a water heater serviceperson needs to
identify and correct a problem in the many cases where an open
circuit is related to the fuse rather than the thermocouple.
Therefore, the reason for replacement being necessary can be
ascertained more directly and, thus, safe operation resumed more
certainly.
[0103] FIGS. 11-14 show a gas control valve 48 supplying main
burner 14 having an adjacent pilot burner 49 in water heater 2 with
combustion chamber 15, including a gas inlet 120 for connection to
a supply (not shown) of combustible gas. Valve 48 has a gas outlet
124 for connection to a conduit (not shown) leading to main burner
14 and an outlet 126 to connect to pilot burner 49. Internal
components of the valve include an orifice or conduit 127 for gas
flow between the inlet 120 and outlet 124 and a closure 154
normally resiliently biased to close the orifice to prevent or
permit flow of gas from the inlet 120 to the outlet 124 as
required.
[0104] Incorporated in valve 48 is an electrical circuit 128 such
as shown in FIG. 15, including thermocouple 51 connected to a
solenoid 132. Thermocouple 51 provides an electrical potential,
sometimes hereinafter referred to as "signal," when heated by a
flame established at pilot burner 49, typically 12 to 15 mV, to
solenoid 132 which is sufficient to maintain solenoid 132 open
against the normally closing bias of a spring 156 associated with
closure 154. Specifically, the electrical potential is provided to
solenoid 32, creating a magnetic force which, via an armature
connected to closure 154, maintains closure 154 open. It should be
noted that the electrical potential is not sufficient to open
closure 154 from its closed position except when valve passage 127
is first opened by manual switch 142 being manually positioned in
the "pilot" or "on" positions and the potential is adequate to
maintain closure 154 in its open position.
[0105] When a flame is absent at pilot burner 49, valve 48 remains
shut except during a start up procedure. The circuit has a manual
switch 142 with three positions, "off", "pilot" and "on". In the
"pilot" position the switch may be depressed to hold open valve 48
while thermocouple 51 heats sufficiently to power circuit 128.
Manual switch 142 is depressed in the "pilot" and "on" on positions
to lift closure 154 off its seat against the closing bias force of
spring 156. In the open position, an electrical current passing
through the coil of solenoid 158 generated by the thermocouple 51
when heated by the flame of the pilot burner 49 (FIG. 4) is
adequate to maintain closure 154 in the open position during normal
use of water heater 2. Normal use of water heater 2 involves pilot
burner 49 being alight at all times.
[0106] An over-temperature energy cut out 144 is installed inside a
temperature sensitive thermostat probe 146 (shown in FIG. 12) which
interrupts all gas flow through the valve in the event that an
unsafe temperature develops inside the tank.
[0107] As best seen in FIGS. 11 and 15, valve 48 has a fuse 134
connected in electrical circuit 128 and exposed at the bottom
surface of valve 48 to be sensitive to extraneous sources of flame
and heat external to and in the region of the valve, particularly
underneath it.
[0108] Valve 48 features an externally accessible socket 136 in
electrical circuit 128 in which thermal fuse 134 is removably
inserted. Socket 136 is positioned to receive thermal fuse 134
independently and separate from thermocouple 51.
[0109] Socket 136 and fuse 134 are accessible from the underside of
valve 48 as shown in FIGS. 11 and 14 wherein valve 48 is mounted on
an external vertical wall of water heater 2. This leads to the
advantage of rapid response time since the underside is most likely
to be impinged upon by extraneous flame because valve 48 is also
vertically above access point 138 to main burner 14 and pilot
burner 49 such as for lighting, inspection and combustion air
entry. Extraneous flame and heat within water heater 2 may result
from accidental combustion of a flammable substance near water
heater 2, the flame being likely to establish itself firstly
adjacent to access point 138.
[0110] Another advantage of mounting fuse 134 to be accessible at a
downward facing surface of valve 48 is that fuse 134 would not be
as noticeable upon a casual inspection of water heater 2 and valve
48 and, therefore, not so likely to invite removal by personnel
unaware of its safety-motivated purpose. Water heater 2 will not
continue to function if it were removed and not replaced.
[0111] Despite the preferred downward facing position of fuse 134,
positions on other faces of valve 48 are possible. Fuse 134 has
minimal thermal inertia and to that end involves minimal mass and
is not enclosed in a copper or similar sheath. A preferred fuse 134
is one encapsulated only in a small quantity of organic polymer
resin. One presently preferred form of thermal fuse 134 is
manufactured by Therm-O-Disc, Inc., Mansfield, Ohio, USA. The
radial lead type is the most suitable for insertion into a socket
136 and a model available with a maximum rated opening temperature
of 102.degree. C. has a suitably rapid response time.
[0112] 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.
[0113] 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.
[0114] In a further construction the flame trap is positioned above
the height of entry to the combustion chamber and the flame
sensitive switch 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 flame
sensitive switch also positioned to be sensitive to flame roll out
from flue blockage or combustion air starvation.
[0115] It is also possible that tube 70 as shown in FIG. 9 can be
made either partially or completely from flame trap materials,
especially the upper portion.
[0116] 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.
[0117] 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.
[0118] 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.
[0119] It should also be understood that utilization of the flame
sensitive switch or similar devices may be used with all types of
gas fired water heaters, including those not equipped with flame
traps. Further, devices other than thermocouples 51 providing
electrical potentials may be employed so long as they are capable
of converting heat energy to assist in actuating closure 154. Heat
to mechanical, heat to optical, heat to magnetic and the like types
of conversions are all within the scope of the invention.
Accordingly, "signal" as used in the claims refers not only to
"electrical potential" but to any means whereby closure 154 is
actuated/deactuated as a result of detection of heat energy.
[0120] 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 applications
08/333,871 and 08/113,618, for example, the subject matter of which
is incorporated herein by reference.
* * * * *