U.S. patent application number 10/042984 was filed with the patent office on 2003-07-10 for flue pipe control.
Invention is credited to Gerich, Richard L., Hudson, Christine M., Kempf, Douglas J., Khadkikar, Prasad S., Prather, Douglas E., Rose, Derek J., Welch, Richard E., West, Jeffrey A..
Application Number | 20030127061 10/042984 |
Document ID | / |
Family ID | 21924825 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030127061 |
Kind Code |
A1 |
Khadkikar, Prasad S. ; et
al. |
July 10, 2003 |
FLUE PIPE CONTROL
Abstract
An improved flue pipe construction particularly adapted for a
fuel fired water heater is disclosed which serves to reduce or
minimize heat loss when the water heater is in a standby mode. The
flue pipe construction comprises inner and outer concentric flue
pipes which define an air space therebetween and one or more valve
arrangements associated therewith to selectively restrict air flow
through such air space. The valve arrangements include a thermally
responsive actuator operative to open and close the valve member in
response to heat generated by firing of the burner assembly without
the need for any external power supply or interlocks.
Inventors: |
Khadkikar, Prasad S.;
(Seville, OH) ; Gerich, Richard L.; (Mansfield,
OH) ; Hudson, Christine M.; (Hudson, OH) ;
West, Jeffrey A.; (Bellville, OH) ; Rose, Derek
J.; (Mansfield, OH) ; Kempf, Douglas J.;
(Mansfield, OH) ; Prather, Douglas E.; (Jackson,
MI) ; Welch, Richard E.; (Lexington, OH) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
21924825 |
Appl. No.: |
10/042984 |
Filed: |
January 9, 2002 |
Current U.S.
Class: |
122/18.3 |
Current CPC
Class: |
F24H 9/0026 20130101;
F23M 9/003 20130101; F24H 1/205 20130101 |
Class at
Publication: |
122/18.3 |
International
Class: |
F24H 001/12; F24H
001/34; F24H 001/38; F24H 001/40 |
Claims
We claim:
1. An improved flue pipe assembly for selectively promoting and
inhibiting heat transfer between a fluid flowing through the
interior of a flue pipe and a fluid surrounding the exterior of
said flue pipe, said flue pipe assembly comprising: a generally
elongated flue pipe having an inner surface and an outer surface,
said flue pipe being adapted to conduct a flow of a first fluid
through the interior thereof, and a second fluid surrounding said
outer surface and being in heat transfer relationship therewith;
and apparatus within said flue pipe for selectively promoting and
inhibiting heat transfer between said first fluid and said second
fluid through said flue pipe.
2. A flue pipe assembly as set forth in claim 1 wherein said
apparatus operates to promote heat transfer from said first fluid
to said second fluid and to inhibit heat transfer from said second
fluid to said first fluid.
3. A flue pipe assembly as set forth in claim 1 wherein said
apparatus is operative to provide an insulating layer along said
inner surface when said first fluid is below a predetermined
temperature to inhibit heat transfer from said second fluid to said
first fluid.
4. A flue pipe assembly as set forth in claim 3 wherein said
insulating layer comprises a substantially non-flowing layer of
said first fluid.
5. A flue pipe assembly as set forth in claim 4 wherein said
apparatus includes an inner flue pipe supported within said
elongated flue pipe and spaced therefrom to define an annular flow
path therebetween and a valve assembly selectively operable to
allow and inhibit flow of said first fluid through said annular
flow path.
6. A flue pipe assembly as set forth in claim 5 wherein said valve
assembly is self powered.
7. A flue pipe assembly as set forth in claim 1 wherein said valve
assembly is thermally actuated from a closed position in which flow
of said first fluid through said annular flow path is inhibited to
an open position to allow flow of said first fluid through said
annular flow path.
8. A flue pipe assembly as set forth in claim 7 wherein said valve
assembly is actuated to said open position in response to an
increase in the temperature of said first fluid.
9. A flue pipe assembly as set forth in claim 8 wherein said valve
assembly is located at one end of said flue assembly.
10. An improved flue pipe assembly for effecting heat transfer from
a first fluid flowing through an interior of said flue pipe
assembly to a second fluid surrounding an outer surface of said
flue pipe assembly and for resisting heat transfer from said second
fluid to said first fluid, said flue pipe assembly comprising: a
first outer flue pipe having an inner surface and an outer surface,
said outer surface being adapted to be in contact with said second
fluid; a second inner flue pipe positioned within said first flue
pipe and having an inner surface defining an interior space adapted
to allow flow of said first fluid therethrough and an outer surface
positioned in spaced opposed relationship to said inner surface of
said first flue pipe to define a fluid flow space therebetween; and
a valve assembly associated with said flue pipe assembly, said
valve assembly being movable between a first open position in which
said first fluid may flow through said fluid flow space and a
second closed position in which fluid flow through said fluid flow
space is restricted.
11. A flue pipe assembly as set forth in claim 10 wherein said
valve assembly is self powered to move between said open and closed
position.
12. A flue pipe assembly as set forth in claim 11 wherein said
valve assembly includes a thermally responsive actuator, said
actuator being operable to move said valve assembly to said open
position in response to an increase in the temperature of said
first fluid above a predetermined temperature.
13. A flue pipe assembly as set forth in claim 10 wherein said
inner flue pipe includes a plurality of spaced openings therein
whereby said first fluid may flow from said interior space into
said fluid flow space when said valve assembly is in said open
position.
14. A flue pipe assembly as set forth in claim 13 further
comprising a flange member projecting into said interior space
adjacent at least some of said openings.
15. A flue pipe assembly as set forth in claim 14 wherein said
flange member projects at an angle into the direction of flow of
said first fluid.
16. A flue pipe assembly as set forth in claim 10 wherein said
valve assembly is positioned adjacent one end of said flue pipe
assembly.
17. A flue pipe assembly as set forth in claim 16 further
comprising a second valve assembly positioned adjacent the other
end of said fluid pipe assembly.
18. A flue pipe assembly as set forth in claim 16 wherein said
valve assembly includes a valve member movable into and out of
engagement with said inner and outer flue pipe.
19. A flue pipe assembly as set forth in claim 18 wherein said
valve member is pivotably supported adjacent said outer flue
pipe.
20. A flue pipe as set forth in claim 10 wherein said valve
assembly includes a thermally responsive actuation assembly.
21. A flue pipe as set forth in claim 20 wherein said thermal
actuator assembly includes a thermally responsive member positioned
in overlying relationship to said interior space and operative to
open said valve assembly in response to a temperature of said first
fluid in excess of a predetermined temperature.
22. A flue pipe as set forth in claim 21 wherein said thermally
responsive member is made from a shape memory alloy.
23. An improved flue pipe assembly for use in a fuel fired hot
water heater comprising: an outer flue pipe adapted to form part of
a reservoir of water to be heated by said water heater and having
one end adapted to be positioned in overlying spaced relationship
to a burner assembly of said water heater; an inner flue pipe
positioned within said outer flue pipe and cooperating therewith to
define an annular space between said inner and outer flue pipes,
said annular space being open at opposite ends of said inner flue
pipe; at least one opening adjacent said one end of said flue pipe
assembly, said opening being adapted to allow combustion gases from
said burner assembly to flow into said annular space; and a valve
assembly positioned adjacent the other end of said flue pipe
assembly, said valve assembly being operative to selectively open
and close said open annular space at said other end of said flue
pipe assembly to thereby resist air flow through said annular space
when said burner assembly is in a standby mode.
24. A flue pipe assembly as set forth in claim 23 wherein said
valve assembly includes a thermally responsive actuator operative
to open said valve assembly in response to heat generated by said
burner assembly.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates generally to an improved flue
pipe assembly particularly adapted for improving the efficiency of
hot water heaters and more specifically to such apparatus which is
designed to inhibit heat loss from the hot water within the water
heater storage tank of a water heater.
[0002] Conventional gas fired water heaters in use today
incorporate a center flue pipe which extends upwardly through the
water storage tank and which is generally cylindrical in shape. Hot
combustion gases from a gas fired burner assembly positioned below
the water storage tank are directed upwardly through this center
flue pipe which serves to transfer heat therefrom to the stored
water surrounding the outer surface of the flue. In many cases the
flue will include a device operative to induce turbulence into the
flowing hot gases to improve heat transfer to the surrounding
water. Such devices are commonly referred to as baffles and
typically comprise an elongated zig zag or spiral shaped member
suspended in the center of the flue. The combustion gases typically
exit the top of the water heater and are directed out of the
building within which the water heater is located via a vent or
smoke pipe.
[0003] When the burner assembly is not firing, ambient air will
flow through this flue pipe and cool the heated water in the
storage tank thus reducing the overall efficiency of the water
heater. In recent years increasing emphasis has been placed on
improving the ability of such water heaters to efficiently heat the
stored water and to reduce the heat loss therefrom when in a
standby mode (i.e. burner assembly in an off condition) to thereby
improve the overall operating efficiency.
[0004] Various types of insulation have been added to the outer
surface of the water storage tank which have greatly reduced heat
loss through these outer walls. Additionally, various types of
damper arrangements have been incorporated into the external vent
pipe to reduce air circulation through the flue pipe during standby
periods. However, these damper arrangements generally require a
power supply for operating same as well as safety interlocks to
insure they are opened before the burner is fired. In some cases
these devices may incorporate an arrangement that insures they are
in an open position in the event of a power supply failure.
Nevertheless, such devices are complex and costly to manufacture
and because they require an external power supply, they also result
in increased installation costs. Further, gas fired water heater
manufacturers generally prefer to avoid the need for an external
power supply for operation of their products. Additionally, because
these devices are commonly incorporated in the external vent pipe
and the internal flue pipe of the water heater is open to the
surrounding environment via the vent hood, such dampers are not
totally effective in preventing air flow through the flue pipe.
[0005] The present invention, however, overcomes the problems
associated with the prior art devices by providing an effective
insulating barrier between the wall of the flue and any air flow
through the flue pipe thereby greatly reducing heat loss when the
heater is in the standby mode while still ensuring good effective
heat transfer through the flue pipe to the water when the water
heater is firing. The primary objective of the present invention is
to provide an arrangement which is highly efficient in transferring
heat from the combustion gases to the water when the burner is
firing but minimizes heat transfer from the water to gases flowing
through the flue pipe when the water heater is in a standby
mode.
[0006] In one embodiment an open cylindrical member of a diameter
less than that of the flue pipe is positioned concentrically within
the flue pipe and includes a plurality of openings in the sidewalls
thereof with radially inwardly extending flanges positioned above
the respective openings. A self powered thermally responsive valve
assembly operates to selectively open and close the annular space
between the inner cylindrical member and the flue pipe at the upper
end thereof in response to firing of the burner assembly. Because
the center of the cylindrical member is continuously in open
communication with the water heater venting system there is no need
for costly and complex interlocks with the burner control system.
Further, the system does not require any external power supply for
operation thus avoiding any increased installation expenses by the
end user of the water heater.
[0007] In another embodiment, a similar valve assembly is also
provided to open and close off the annular space between the
cylindrical liner and flue pipe at the lower end thereof to further
isolate the air volume in this annular space from convection air
currents.
[0008] Each of these embodiments offer the advantage of effectively
restricting heat loss from the heated water in the tank to air
currents flowing through the center of the water heater while in a
standby mode and yet also ensures good heat transfer to the tank
water from the combustion gases when the burner is firing. For each
case the path from burner assembly to the external venting system
is continuously open thus eliminating the need for any complicated
safety interlocks with the burner controls. Further because the
system is self activating, there is no need for any external or
auxiliary power supply which would increase installation costs or
require periodic maintenance.
[0009] Additional advantages and features of the present invention
will become apparent from the subsequent description and the
appended claims taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a conventional gas fired hot
water heater with portions thereof broken away;
[0011] FIGS. 2 and 3 are schematic views of a portion of a flue
pipe assembly for a water heater illustrating a preferred
embodiment of the present invention in a standby mode and firing
mode respectively;
[0012] FIG. 4 is a fragmentary section view of an upper portion of
a water heater incorporating the embodiment of FIGS. 2 and 3 and
showing the valving arrangement utilized therein in a closed
position, all in accordance with the present invention;
[0013] FIG. 5 is viewed similar to that of FIG. 4 but showing the
valving arrangement in an open position;
[0014] FIG. 6 is a plan view of the valving arrangement shown in
FIG. 4;
[0015] FIG. 7 is a view of the valve assembly of FIG. 6 as seen
looking in the direction of arrow 7 and with portions of the water
heater shown in section;
[0016] FIG. 8 is a plan view of one of the valve members
incorporated in the valving arrangement of FIG. 6;
[0017] FIGS. 9 and 10 are elevational views of the valve member of
FIG. 8, the respective views being taken at right angles to each
other;
[0018] FIGS. 11, 12 and 13 are side, plan and front views
respectively of an actuator bracket forming a part of the valve
assembly of FIG. 6;
[0019] FIGS. 14 and 15 are side and plan views of a mounting
bracket forming a part of the valve assembly of FIG. 6;
[0020] FIG. 16 is a view similar to that of FIG. 4 but showing an
alternative valving assembly in accordance with the present
invention;
[0021] FIG. 17 is a plan view of the valving assembly of FIG.
16;
[0022] FIG. 18 is a view similar to that of FIG. 16 but showing the
valving assembly rotated by 90.degree.;
[0023] FIG. 19 is a view similar to that of FIG. 2 but showing the
inclusion of a second thermally actuated valve at the lower ends of
the inner and outer flue pipes; FIGS. 20 and 21 are fragmentary
sectional views of another valving arrangement in accordance with
the present invention with the valving arrangement shown in open
and closed positions respectively;
[0024] FIG. 22 is a section view of the embodiment shown in FIGS.
20 and 21, the section being taken along lines 22-22 of FIG.
21;
[0025] FIG. 23 is an elevational view of a bimetallic valving
member forming a part of the embodiment of FIGS. 20 and 21; and
[0026] FIGS. 24 and 25 are enlarged fragmentary section views of
yet another embodiment of the present invention with the valving
shown in closed and open positions respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Referring now to the drawings and more specifically to FIG.
1, there is shown a conventional gas fired water heater indicated
generally at 10. Water heater 10 includes an outer housing 12
within which is disposed a water storage tank 14 surrounded by a
layer of insulation 16 and a gas fired burner assembly 18.
[0028] Water storage tank 14 has a generally elongated cylindrical
shape, is positioned above burner assembly 18 and includes an outer
shell 20, a generally conically shaped hood portion 22 sealingly
secured to a lower portion of shell 20 and overlying the burner
assembly and an axially elongated flue pipe 24 which is sealingly
secured to hood portion 22 at its lower end and which projects
outwardly through outer housing 12 at the upper end 26 thereof.
Flue pipe 24 is connected to a smoke or vent pipe not shown via a
draft hood 28. In operation, combustion gases generated by the
firing of burner assembly 18 are directed upwardly through flue
pipe 24 via hood 22 and serve to transfer heat to the water
contained within storage tank 14. In many cases, a spirally shaped
or zig zag baffle member 30 is supported within flue pipe 24 and
serves to create a mixing of the combustion goods as they flow
upwardly through flue pipe 24 to improve heat transfer to the water
by reducing any thermal boundary layer that may form along the
sidewalls of flue pipe 24.
[0029] Water heater 10 also includes suitable fittings 32 and 34
for connection to a supply of water and a water distribution system
with water inlet 32 being provided with a dip tube 36 which serves
to direct the inflow of cold water to the bottom of the tank
14.
[0030] Additionally, water heater 10 includes a control assembly 37
for controlling the supply of gas to burner assembly 18 in response
to the sensed temperature of the water within tank 14. A drain
spigot and valve assembly 39 is also provided for enabling the user
of the water heater to periodically flush debris from the bottom of
tank 14 as well as to drain same should this be desired.
[0031] As thus far described, water heater 10 is of a construction
typical for gas water heaters currently in use.
[0032] As noted above, such water heaters are relatively efficient
in transferring heat from the combustion process to the water
within tank 14. Additionally, great care has been taken in the
design of such systems to reduce heat loss to the environment
through the outer walls of the tank 14. Such efforts include
surrounding the outer wall 20 with insulating materials and
minimizing the size and number of penetrations through such
insulating material 16. However, the flue pipe 24 is in continuous
open communication with the environment at both the upper and lower
ends thereof. As a result, when the water heater is in the standby
mode, air within flue pipe 24 will absorb heat from the hot water
in tank 14 via flue pipe 24 and create a convection draft
therethrough resulting in more frequent firing of the burning
assembly to maintain the desired water temperature. The heat loss
occasioned by this convection draft may result in a significant
reduction in the overall operating efficiency of the water
heater.
[0033] In order to minimize this convection draft heat loss while
maintaining or perhaps even improving heat transfer to the water
from the combustion gases, the present invention incorporates a
modified flue pipe assembly 38 which, as shown in FIGS. 2 and 3,
includes an elongated generally cylindrically shaped outer flue
pipe 40 and a smaller diameter inner flue pipe 42 of substantially
equal length. Inner flue pipe 42 is preferably supported
concentrically within outer flue pipe 40 so as to define an annular
space 41 therebetween and includes a plurality of circumferentially
and axially spaced openings 44 therein. A louver 46 extends
generally radially inwardly immediately above each of the openings
44 and is angled axially somewhat in a downward direction toward
burner assembly 18. Annular space 41 is in open communication with
the burner assembly 18 at its lower end and is closed off at the
upper end of flue pipes 40 and 42 by a temperature responsive valve
assembly 48. Valve assembly 48 includes a thermally responsive
actuator 50 centrally positioned over the open upper end of inner
flue pipe 42 and oppositely moveable valves 52 and 54. When burner
assembly is in a standby mode (i.e. not firing), valve assembly 48
will be in a closed position effectively sealing off the upper end
of the annular space 41 between inner and outer flue pipes 42 and
40. As a result, annular chamber 41 will effectively create a dead
air space thereby insulating outer flue pipe 40 and the heated
water radially outwardly thereof from air circulation through inner
flue pipe 42. When burner assembly 18 is fired, the hot combustion
gas will initially flow upwardly through inner flue pipe 42 and
heat actuator 50 of valve assembly 48 which will operate to move
valve members 52 and 54 into an open position thereby opening the
upper end of chamber 41 and allowing flow of hot combustion gases
into intimate contact with the inner surface of outer flue pipe 40.
Heat from the combustion gases will then be transferred through
outer flue pipe 40 to heat the water.
[0034] It is believed that the combination of the openings 44 in
inner flue pipe 42 and the angled louvers 46 will cooperate to
enhance flow of hot combustion gases into annular chamber 41
thereby enhancing heat transfer to the surrounding water when valve
assembly 48 is in an open position. However, when the water heater
is in a standby mode, it is believed that inner pipe 42 with
louvers 46 will assist in reducing air circulation into and out of
annular chamber 41 as well as the air flow velocity therethrough
thus enhancing the insulating effort of the "dead" air space
provided between the two flue pipes. It should also be noted that
because valve assembly 48 only closes off annular chamber 41, the
entire area within inner flue pipe 42 is continuously open to the
vent system. Thus there is no need to provide any interlocks with
the controls for burner assembly 18 because should valve assembly
48 fail to open on firing of burner 18, the hot combustion gases
will still be vented via inner flue pipe 42. It should be noted
that modeling analysis has indicated that the use of an inner flue
pipe 42 without the inclusion of a valve assembly reduces the fluid
flow velocity in the gap between the inner and outer flue pipes and
thus reduces standby heat loss even without the inclusion of valve
assembly 48.
[0035] Thermally actuated valve assembly 48 is shown in greater
detail and will be described with reference to FIGS. 4 through 15.
With reference to FIGS. 4 and 5, valve assembly 48 includes a pair
of valve members 52 and 54 pivotably supported on an upper surface
56 of hot water heater 58 via brackets 60 and 62 and suitable
support members 64 and 66. Additionally thermal actuator 50 extends
between valve 52 and 54 and includes a pair of actuator brackets 68
and 70 and an interconnecting rod 72 extending therebetween. A pair
of compression springs 74 and 76 are provided on rod 72 adjacent
opposite ends thereof and serve to bias brackets 68 and 70 toward
each other. A center thermally responsive opening member 78 is also
provided on rod 72 positioned between brackets 68 and 70 and acting
in opposition to respective springs 74 and 76.
[0036] Valve members 52 and 54 are substantially identical in
construction and hence only valve member 52 will be described in
detail with corresponding portions of valve member 54 being
indicated by the same reference numbers primed. As best seen with
reference to FIGS. 6-10, valve member 52 includes a substantially
planar semicircular portion 80 from which a supporting flange 82
extends upwardly from a location substantially equidistant from the
opposite ends thereof. Supporting flange 82 includes an elongated
center portion 84 having a laterally extending slot 86 positioned
adjacent the upper end thereof and a pair of laterally spaced
outwardly extending pivot flanges 88, 90 adjacent the planar
portion 80. Aligned openings 94 are provided in respective pivot
flanges 88 and 90 and are sized to receive a pivot pin 96 by which
valve member 52 may be pivotably supported via bracket 60 and
support member 64. A suitable heat resistant resilient sealing
material 98 is suitably secured to lower surface 100 of planar
portion 80 and is suitably sized so as to matably engage the upper
edges of inner and outer flue pipes 40 and 42 when valve member 52
is in a closed position.
[0037] Actuator bracket 68 is also substantially identical to
actuator bracket 70 and hence only bracket 68 will be described, it
being understood that corresponding portions of bracket 70 will be
indicated by the same reference numbers primed.
[0038] As best seen with reference to FIGS. 11, 12 and 13, actuator
bracket 68 includes an elongated substantially planar portion 102
having an upstanding flange portion 104 provided at one end
thereof. A reduced width tab portion 106 is provided at the
opposite end of planar portion 102 from flange 104 and is adapted
to be received within slot 86 of valve member 52. Preferably, tab
106 will have a width and thickness so as to be relatively loosely
fitted within slot 86. Flange portion 104 includes an opening 108
therein suitably sized to slidingly receive rod 72
therethrough.
[0039] Bracket 60 is substantially identical to bracket 62 and
hence only bracket 60 will be described in detail it being
understood that corresponding portions of bracket 62 will be
indicated by the same reference numbers primed. As shown in FIGS.
14 and 15, bracket 60 is generally rectangular in shape and
includes an upstanding portion 110 through which bore 112 extends.
Bore 112 is suitably sized to receive pivot pin 96 so as to thereby
enable valve member 52 to be pivotably supported therefrom in
cantilevered relationship. As noted above, bracket 60 is suitably
fixedly supported on water heater 10 by a suitable support member
64 affixed to the upper surface 56 of water heater 10.
Alternatively, bracket 60 may be directly secured to water heater
10 if desired.
[0040] Referring once again to FIGS. 4 through 7, valve members 52
and 54 are pivotably supported with opposite ends 114, 116 and
114', 116' of semicircular portion 80 in opposed relationship and
sealing material 98, 98' provided thereon in sealing engagement
with the upper end of flue pipes 40 and 42. Respective tabs 106,
106' of actuating brackets 68 and 70 are loosely received within
respective slots 86, 86' of valve members 52 and 54 and
interconnecting rod 70 extends through openings 108, 108' of
upstanding flange portions 104, 104'. As noted above, flange
portions 104, 104' are acted on opposite sides by respective
compression springs 74 and 76 and thermally responsive opening
member 78.
[0041] In operation, as thermally responsive opening member 78 is
heated by combustion gas flowing upwardly through inner flue pipe
42, it will operate to exert oppositely directed forces on
respective actuator brackets 68 and 70 thereby causing them to
overcome the biasing forces of springs 74 and 76 and to move
outwardly along rod 72. As actuator brackets 68 and 70 are biased
outwardly along rod 72, the opposite ends thereof will operate
against flange portion 82, 82' thereby causing respective valve
members 52 and 54 to pivot about respective rods 96 and move
sealing members 100, 100' out of engagement with flue pipes 40, 42
and open the upper end of chamber 41. Thereafter, the hot
combustion gases will be directed through openings 44 into intimate
heat transfer relationship with outer flue pipe 40 to heat the
water within tank 14 and then exhausted via the open upper space
between flue pipes 40, 42.
[0042] Once the water temperature has reached the preset
temperature, controller 37 will shut down burner assembly 18
thereby discontinuing the supply of heat to thermally responsive
opening member 78 and allowing same to cool. As thermally
responsive opening member 78 cools and contracts, the biasing
action of springs 74 and 76 will cause actuator brackets 68 and 70
to move along rod 72 toward each other thereby allowing valve
members 52 and 54 to move into a closed position as shown in FIG. 4
in which convection draft air flow through annular chamber 41 is
effectively resisted. The thus confined "dead" air space will then
serve as an insulating layer against heat loss to air that may
circulate through inner flue pipe 42.
[0043] In a presently preferred embodiment, it is contemplated that
thermally responsive opening member 78 will be in the form of a
helical coiled spring fabricated from a shape memory alloy
material. Such materials are known in the art and exhibit the
ability to rapidly change from a given shape to a "remembered"
shape upon being heated to a predetermined temperature and to
return to a deformed shape upon cooling below the predetermined
temperature. In the particular embodiment described, the
"remembered" shape would be a longer helical coil and the "deformed
shaped" would be a shortened helical coil.
[0044] It should be noted that because thermally responsive opening
member 78 is centrally disposed above the open inner flue pipe 42
it will be immediately subjected to heating by the combustion gases
upon firing of burner assembly 18 and will thus be quickly
responsive to same to open valve members 52 and 54. Further,
because the center of inner flue pipe 42 is continuously open to
the vent system, combustion gas will always be free to flow to and
through the associated vent system and exhausted to the outside
even in the event valve assembly 48 should fail to open. Thus, it
is not necessary to incorporate any interlock system between valve
assembly 48 and control 37 although this could be done if desired.
It should also be noted that while a shape memory alloy material is
presently preferred, other types of thermally responsive opening
devices could be substituted therefor, the only requirements being
that the device be capable of generating a sufficient force to move
valve members from a closed position to an open position in
response to an increase in temperature thereof.
[0045] Referring now to FIGS. 16-18, there is shown another
embodiment of a valve assembly 118 in accordance with the present
invention. In this embodiment, valve assembly 118 comprises a valve
member 120 in the form of an annular ring having an open center
portion 122 aligned with the open center of inner flue pipe 42 and
a pair of diametrically opposed radially outwardly projecting
extensions 124, 126. A suitable heat resilient sealing material 128
is secured to the lower surface 130 of valve member 120 and serves
to sealingly engage the upper ends of inner and outer flue pipes
40, 42 in the same manner as material 98 when valve member 120 is
in a closed position.
[0046] In order to retain valve member 120 in position with respect
to inner and outer flue pipes 40 and 42, as well as to guide
opening and closing movement thereof, an elongated generally
U-shaped guide member 132 is provided which includes a pair of leg
portions 134, 136 extending through suitable openings provided in
respective extensions 124, 126 with the terminal ends thereof being
secured to upper surface 138 of hot water heater 10'.
[0047] An actuator assembly 140 is also provided which includes a
second generally U-shaped elongated member 142 having a pair of leg
portions 144, 146 and an interconnecting portion 148. As shown,
member 142 is positioned substantially perpendicular to member 132
with interconnecting portion 148 being affixed to member 132 at the
point of intersection. Legs 144 and 146 each project through valve
member 120 and are secured to outer flue pipe 40. A pair of
thermally responsive opening members 150, 152 are provided on leg
members 144, 146 each having one end fixedly secured to an annular
flange member 154, 156 each of which are in turn fixedly secured to
respective leg portions 144 146 adjacent the upper end thereof. The
opposite ends of thermally responsive opening member 150,152 are
secured to the upper surface 158 of valve member 120.
[0048] In operation, when burner assembly 18 is fired, the hot
combustion gas flowing through inner flue pipe 42 will operate to
heat thermally responsive opening members 150, 152. Once the
temperature of thermally responsive opening member 150, 152 exceeds
a predetermined temperature, they will contract thereby lifting
valve member 120 upwardly away from inner and outer flue pipes 40,
42 and allowing the hot combustion gases to flow through annular
chamber 41 in the same manner as described with respect to valve
assembly 48. When burner assembly 18 is shut down, thermally
responsive opening members 150, 152 will cool and thus return to
their elongated state thereby moving valve member into a closed
position as shown.
[0049] Preferably, as with valve assembly 48, thermally responsive
opening members 150, 152 will be in the form of helical coils of
shape memory alloy material although in this embodiment, the
"remembered" hot shape will be a shorter helical coil. Again, it
should be noted that other devices having the ability to move valve
member 120 upwardly in response to an increased temperature may be
substituted therefor.
[0050] While the above embodiments have been described with the use
of only a single thermally responsive valve assembly positioned at
the upper end of flue pipes 40, 42, it may in some applications be
desirable to incorporate a second valve assembly at the lower end
of flue pipes 40, 42. Such an embodiment is illustrated
schematically in FIG. 19 in which both upper 160 and lower 162
valve assemblies are incorporated to close off annular space 41
between inner and outer flue pipes 40, 42 during the standby mode.
Either valve assemblies 48 or 118 may be used for either of valve
assemblies 160, 162 or alternatively one or both may be of the type
described below with reference to FIGS. 20 and 21. Further, if
desired, a single valve assembly may be provided at the lower end
of flue pipes 40, 42.
[0051] FIGS. 20-23 illustrate yet another embodiment of the present
invention. In this embodiment, a valve assembly 164 is secured to
the upper end of inner flue pipe 166 and operates to selectively
open and close off the annular area 168 between inner and outer
flue pipes 166 and 170. Valve assembly 164 comprises first and
second substantially identical elongated bimetal strips 172, 174
each of which includes a plurality of upwardly projecting fingers
176 separated by notches 178 extending laterally inwardly from the
upper edge thereof. As shown, the lower edges of first and second
strips 172 and 174 are secured to the upper edge of inner flue pipe
166 in any suitable manner such as by a plurality of
circumferentially spaced rivets 180. Preferably, second strip 174
is circumferentially offset from first strip 172 such that fingers
176 of one strip overlie notches 178 of the other strip. Strips 172
and 174 are fabricated from a suitable bimetal material having the
ability to resist the by-products of combustion contained in the
combustion gases passing through flues 166,170.
[0052] When the water heater is in a standby mode, the ends of
fingers 176 will extend axially and radially outwardly into
engagement with outer flue 170. The overlapping arrangement of the
respective fingers and notches 176, 178 will enable the bimetal
strips to effectively close off the upper end of annular space 168
thereby resisting cooling convection gas currents and reducing the
resulting standby heat loss. When the water heater burner assembly
is actuated, the hot combustion gases traveling through the flue
pipe will heat respective first and second bimetal strips 172, 174
and, as a result of the differential in the coefficient of
expansion between the layers of the bimetal strips, fingers 176
will move radially inwardly to the position shown in FIG. 21
thereby opening the upper end of annular space 168 thus enabling
the flow of gases therethrough.
[0053] Once the water has been heated to the desired temperature,
the water heater burner assembly will be shut down and bimetal
strips 172, 174 will cool thus causing fingers to return to the
closed position as shown in FIG. 20. It should be noted that strips
172 and 174 may alternatively be fabricated from a shape memory
alloy if desired.
[0054] Referring now to FIG. 24, a further embodiment of the
present invention is shown. This embodiment is similar to that of
FIGS. 2 and 3 with the exception that fixed louvers 46 have been
replaced with thermally actuable louvers 182. As shown, louvers 182
are preferably fabricated from a suitable bimetal material and are
secured to inner flue pipe 184 in overlying relationship to
respective openings 186 provided therein thus closing off
communication between annular space 188 disposed between inner and
outer flue pipes 184, 190 and the open interior space 192 defined
by inner flue pipe 184 when the water heater is in a standby mode.
When the burner assembly fires, the hot combustion gases traveling
through space 192 will heat bimetal valves 182 in response to which
they will move into a position similar to that of louvers 46 shown
in FIGS. 2 and 3. Upon a return of the burner assembly to a standby
mode, bimetal valves 182 will cool and return to their respective
closed positions as shown in FIG. 24.
[0055] It should be noted that while it is believed preferable to
utilize one of the valve assemblies described above to close off
the upper and/or lower openings between inner and outer flue pipes
184 and 190 in combination with valves 182, valve assemblies 182
could be used alone although it is believed the resulting
improvements in operating efficiency for the water heater will not
be as great. Also, as mentioned above, valves 182 may be fabricated
from a shape memory alloy in lieu of a bimetal material if
desired.
[0056] It should be noted that with respect to all of the
embodiments above, the diameter of inner flue pipe 42, 166, 184
must be selected relative to the size of the burner assembly so as
to provide adequate flue area for proper venting of the combustion
gases. Further, the number and positioning of the louvers should be
such that they do not prevent the proper venting of the combustion
gases even when the valve assembly is in a closed position. Also
the number and positioning of the openings 44, 186 as well as the
shape and angulation of the louvers and the spacing between the
inner and outer flue pipes 40, 42; 166, 170; 184, 190 will be
selected so as to maximize the heat transfer to the surrounding
water when burner assembly 18 is being fired and yet minimize the
cooling effect of convection drafts on the heated water while the
water heater is in a standby mode.
[0057] As may now be appreciated, the present invention provides a
relatively inexpensive easily fabricated flue pipe assembly which
is highly effective in reducing standby heat losses for water
heaters. Because the present invention enables full flow of
combustion gas even when the valve assemblies are in a closed
position, no interlocks are required. Further, the present
invention achieves these objectives without requiring any
additional external connections upon installation of the water
heater such as for auxiliary power.
[0058] While it will be apparent that the preferred embodiment of
the invention disclosed is well calculated to provide the
advantages and features above stated, it will be appreciated that
the invention is susceptible to modification, variation and change
without departing from the proper scope or fair meaning of the
subjoined claims.
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