Note: Descriptions are shown in the official language in which they were submitted.
CA 02873760 2014-12-08
TITLE
Gas Fired Heating Appliance With Safety Release Door Mechanism
FIELD
This invention relates generally to gas fired heating appliances, and in
particular to
such an appliance incorporating a safety release door mechanism.
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BACKGROUND
Due to their convenience, energy efficiency, and reduced hydrocarbon
emissions,
natural gas and propane burning fireplaces, stoves and other similar heating
appliances have, to a large extent, displaced wood burning appliances in many
geographic locations. Over the years, gas and propane burning appliances have
become common in both residential and commercial settings.
A significant
percentage of gas burning appliances that are installed are of the direct vent
type,
wherein the firebox is sealed from the room within which it is installed and
combustion air is drawn from an outside environment into the firebox.
Direct vent appliances offer a number of advantages, the most significant of
which
is an increase in overall efficiency. However, a sealed firebox can also
present
particular dangers that should be recognized and accounted for in the
appliance
design. One such danger involves a delayed ignition that can occur when an
individual attempts to light the appliance after natural gas or propane has
accumulated within the firebox. Igniting a significant volume of accumulated
gas
can effectively cause a small explosion. In certain instances these explosions
can
result in the front door of the appliance being blown into the room within
which the
appliance is installed. Since the doors of the appliances are often
manufactured
largely from glass, the glass can break, with fragments being expelled
outwardly
and potentially damaging individuals and property. Even where the door glass
does
not shatter upon being exposed to the pressure of the gas ignition, the door
can be
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forced into the room, potentially damaging the door, breaking the glass,
damaging
property in the immediate vicinity of the fireplace and/or causing personal
injury.
To help avoid the possibility of appliance doors shattering and/or being blown
into a
living space under delayed ignition situations, others have suggested
installing relief
dampers within the firebox that can relieve the over-pressure in the event of
delayed ignition.
The use of relief dampers can result in varying degrees of
effectiveness. If the internal resistance of the damper is too great, the
dampers
will not open and will not provide an effective means to release internal
pressure.
On the other hand, should the resistance of the dampers be too low, the
dampers
may tend to open when internal pressures within the firebox are well below the
pressures that may cause safety concerns, resulting in a loss of heating
efficiency
and combustion performance. Further, the mechanical nature of current relief
dampers is such that they warp or become deformed due to exposure to high
temperatures, can become corroded, or over time they can react sluggishly with
their ability to properly function slowly diminished.
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SUMMARY
The invention therefore provides a gas fired heating appliance comprising a
chassis,
a firebox having an interior cavity having a gas burner, said firebox
including an
opening communicating the interior of the firebox with an environment external
to
the appliance; a door for enclosing the opening; at least one track member,
said
track member having a retracted position and an elongated extended position,
said
track member having a first end secured to said chassis or said firebox and a
second end engaging said door, when in said retracted position said track
member
positioning said door to enclose and seal said opening, when in said extended
position said track member retaining said door in a position outwardly off-set
from
the firebox adjacent said opening.
The invention also provides a gas fired heating appliance comprising a
chassis, a
firebox having an open front enclosed by a door, the door including a viewing
window and a frame; a gas burner; and one or more track members, said track
members having a retracted position and an elongated extended position, said
track members having first ends secured to said chassis or said firebox and
second
ends engaging said frame of said door, when in said retracted position said
track
members positioning said door so as to enclose said front of said firebox,
when in
said extended position said track members retaining said door in a position
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outwardly off-set from said firebox, said track members movable from said
retracted position toward said extended position through the application of
firebox
pressure, elevated beyond a pre-determined value, to said door.
The invention further provides a gas fired heating appliance comprising a
chassis, a
firebox having a pressure release openings therein; a door associated with
said
pressure release opening, said door having a closed position wherein it
effectively
seals said pressure release opening to prevent or limit the flow of gases
through
said pressure release opening, said door having a displaced position wherein
gases
from within said firebox are allowed to flow through said pressure release
opening;
one or more track members associated with said door, said track members having
a
retracted position and an extended position, said track members having a first
end
secured to said chassis or said firebox and a second end engaging said door,
when
in said retracted position said track members positioning said door such that
said
door encloses said pressure release opening, when in said extended position
said
track members retaining said door in a position outwardly off-set from said
firebox,
said track members comprising two or more telescoping members that telescope
when said track members are moved between said retracted and said elongated
positions; and
biasing means to bias said track members to said retracted position.
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Further aspects of the invention will become apparent from the following
description
taken together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to show more clearly
how
it may be carried into effect, reference will now be made, by way of example,
to the
accompanying drawings which show exemplary embodiments of the present
invention in which:
Figure 1 is a side perspective view of a gas fireplace exemplifying an
embodiment
of the present invention.
Figure 2 is a side perspective view similar to Figure 1 wherein the exterior
side and
top panels of the fireplace have been removed.
Figure 3 is view similar to Figure 2 wherein the fireplace door has been
displaced
outwardly from the front of the fireplace.
Figure 4 is an enlarged detail view of the attachment of the fireplace door to
track
members.
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Figure 5 is a view similar to Figure 3 wherein the fireplace door has been
removed
from the track members and wherein the door does not include a decorative
screen
attached thereto.
Figure 6 is an outer side view of one of the track members shown in Figure 3
in a
retracted position.
Figure 7 is an outer side view of one of the track members shown in Figure 3
in an
extended position.
Figure 8 is an inner side view of one of the track members shown in Figure 3
in an
extended position.
Figure 9 is a view similar to Figure 3 wherein the fireplace door is in the
process of
being returned to its position sealed against the front of the firebox and
includes an
alternate form of decorative screen.
Figure 10 is an alternate embodiment of the invention to that shown in Figure
1.
Figure 10A is an enlarged detail view of portion A of Figure 10.
Figure 11 is a view similar to Figure 10 wherein the fireplace door has been
displaced outwardly from the front of the fireplace.
Figure 12 is an alternate embodiment of the invention to that shown in Figures
1
and 10.
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Figure 12A is an enlarged detail view of portion A of Figure 12.
Figure 13 is an upper side perspective view of the fireplace shown in Figure
12.
Figure 14 is an alternate embodiment of the invention to that shown in Figures
1,
and 12.
Figure 14A in an enlarged detail view of portion A of Figure 14.
Figure 15 is a view similar to Figure 14 wherein the fireplace door has been
displaced outwardly from the front of the fireplace.
Figure 15A is an enlarged detail view of portion A of Figure 15.
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DESCRIPTION
The present invention may be embodied in a number of different forms. The
specification and drawings that follow describe and disclose some of the
specific
forms of the invention.
The attached drawings depict an exemplary embodiment of the invention wherein
the gas heating appliance is shown as a gas fireplace. It will, however, be
appreciated from a thorough understanding of the invention that although a gas
fireplace has been shown, various other heating appliances are embodied within
the
invention. For example, the appliance could equally be a gas wall heater or a
free-
standing gas stove.
In Figures 1 through 5 there is shown a relatively standard gas fireplace that
generally comprises an outer housing or chassis 1, a removable door 2 (with or
without a decorative screen 11), a firebox 3 having a generally open front
that is
enclosed by door 2, a gas burner 4 and an intake/exhaust port 5. In this
instance
the fireplace is a direct-vent fireplace where the intake and exhaust are
concentric
ducts. Door 2 may be in any one of a wide variety of forms. In the embodiment
shown, the door is comprised of a glass viewing window 6 surrounded and held
by a
frame 7. Here, the door is generally rectangular having two side portions 8, a
top
portion 9 and a bottom portion 10. The door encloses the front of the firebox
to
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present a sealed fire chamber so as to limit the possibility of the intrusion
of
flammable or noxious gases into the room within which the fireplace is
situated.
Where the fireplace includes a decorative screen 11, the screen would
typically
include a number of rearwardly extending arms 12 that hook into mounts or
slots
26 on door frame 7 so that the screen may be effectively hung from the door.
With reference to Figure 2, the appliance may include one or more latches 13
that
releasably engage door 2. When engaged with the door, the latches releasably
secure the door about the open front of the firebox. That is, the latches
serve the
function of holding the door tightly in place, maintaining the seal between
the
firebox and the door, and permitting the door to be removed for servicing the
gas
burner and cleaning the interior of the firebox.
In accordance with an embodiment of the invention there is further provided
one or
more track members 14 comprised of two or more telescoping members. Track
members 14 may be telescoping and/or pneumatic cylinders and/or hydraulic
cylinders. In the particular embodiment shown in Figures 2 through 5 the track
members comprise telescoping inner, middle and outer rails (15, 25 and 16
respectively). While three nested or telescoping rails have been shown, other
combinations and numbers of rail components could also be used. Track members
14 have first ends 17 that are secured to the chassis, the firebox or other
fixed or
structural portion of the fireplace, and second ends 18 that engage door 2.
The
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track members have a retracted position (where the rails substantially overlap
one
another) and an elongated extended position (where the degree of overlapping
of
the rails is less than in the case of the retracted position). With the first
ends 17 of
track members 14 secured to the chassis or the firebox, and with second ends
18 of
the track members secured to door 2, when the track members are in their
retracted position the door will be positioned to enclose front of the
firebox.
Similarly, when the track members are in their extended position the door will
be
held outwardly off-set from the front of the firebox, generally parallel to
the front of
the appliance and in a generally vertical plane (see Figure 3). It will
further be
noted that where door frame 7 has mounted thereto a decorative feature (for
example, a screen) the displacement of the door to an outwardly off-set
position
will cause a corresponding displacement of the decorative feature. Preferably,
track
members 14 include one or more stoppers 19 that prevent separation of the
component rails when the track members are moved to their extended position.
It
will be appreciated by one of skill in the art that a very wide variety of
different
stoppers could be utilized to perform the intended function.
In Figures 2 through 5 the depicted fireplace is shown as including a pair of
track
members 14, one mounted on each side of the fireplace and engaging opposite
sides of door frame 7. Other configurations of track members could also be
incorporated within the design of the appliance. For example, there could be
multiple track members running along each respective side of the fireplace,
track
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members could be mounted on the top and bottom of the fireplace such that they
engage the top and bottom portions of the door frame, or track members could
be
mounted on all four sides of the chassis or the firebox and engage all four
sides of
the door frame.
In a further embodiment, a single track member could be used to engage the
door.
In such cases it is expect that the track member and the frame of the door
will
need to be sufficiently rigid to enable the door to be effectively supported
from a
single point. In addition, the track member may be in the form of a series of
wide,
nested, plates that engage the door over a significant portion of a side or
the top
portion of the door frame.
With reference once again to Figures 3 and 4, in one embodiment of the
invention
second ends 18 of track members 14 include hooks 20 that receive complimentary
shaped pins 21 on frame 7. Hooks 20 are preferably oriented in an upward
direction so that the pins on the door frame can be lowered into the hook
bowls to
effectively hang the door from the track members. Other ways to mount the door
to the track members are possible (including other configurations and
variations of
hooks; pins and other releasable mounts; and screws, bolts and other
fasteners,
etc.) without significantly affecting the overall functionality of the
invention.
Through mounting the door to the ends of the track members in this fashion the
door can easily be lifted from the track members and removed completely from
the
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fireplace to allow unobstructed access to the interior of the firebox for
service
and/or cleaning.
Having in mind the above described structure, the operation of track members
14
and latches 13 will now be described in further detail with reference to a
situation of
delayed ignition. If for any reason there should be a delayed ignition of gas
within
the firebox when the appliance is fully assembled and the door held tightly in
place,
the increased pressure within the firebox will bear directly against door 2.
If the
pressure is low enough, it will be simply vented through the exhaust without
any
noticeable affect. However, where the pressure is significant (to the point
where it
could cause damage to the appliance or its surroundings) latches 13 will
disengage,
permitting door 2 to be pushed outwardly from the front of the appliance,
thereby
allowing for the dissipation of internal pressure from within the firebox. As
the door
is pushed outwardly, track members 14 will move from their retracted to their
extended position, while at the same time holding the door firm and
maintaining
the door in a position that is generally parallel to the front of the
appliance and
generally vertical.
Track members 14 may include one or more biasing members 30, which may be
one or more springs, hydraulic or pneumatic cylinders, and/or one or more
friction
inducers that retard the movement of the track members from their retracted to
their extended position. Biasing members 30 will effectively help to "absorb"
some
of the pressure from the delayed ignition within the firebox, and will also
help to
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reduce the likelihood of the door being blown outwardly at a velocity that
could
result in damage to the door and/or the track members. In one embodiment,
springs, having one end secured to the outer rail 16 of the track member and
their
opposite end secured to either the inner rail 15, chassis 1, firebox 3 or the
outer
housing 1 of the fireplace, may be used. In an alternate embodiment, friction
inducers (made from rubber or other friction inducing material) may be
positioned
between the inner and outer rails. Further, a friction inducing coating may be
applied to portions (for example, see areas 27 in Figure 7) of the rails. In
yet a
further embodiment the dimensional tolerances of the inner and outer rails may
be
such that there is sufficient inherent friction between the respective rails
to help
"control" the rate of movement of the track members to their extended
position.
To permit both a release of internal pressure from within the firebox, and to
also
help to prevent the door from being blown outwardly at an excessive rate, the
biasing means can be designed to only retard the rate of extension of the
rails once
the seal between the door and the firebox has been broken and internal gases
have
been given an opportunity to escape.
In instances where biasing means 30 are utilized, their function could also
extend
to retaining the door in place within the front opening of the firebox. In
such
instances biasing means 30 may effectively remove the need for the use of
latches
13. That is, the biasing means could be positioned (and their biasing force
chosen)
such that they draw door 2 into contact with the front of the fireplace to
hold the
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door in position and to effectively seal the front of the firebox. In the case
of an
over-pressure situation within the firebox the biasing means would still
permit the
door to extend outwardly to relieve the excess internal pressure.
In embodiments where latches 13 are utilized, to "release" the door from the
firebox, and to allow over-pressure within the firebox to dissipate without
damaging
the appliance, it will be understood that latches 13 must be designed to
disengage
(or at least partially release) the door upon the pressure within the firebox
exceeding a predetermined value. While a variety of mechanisms could
accomplish
that goal, it is expected that in most instances latches 13 will frictionally
engage
door 2 so that when the pressure within the firebox exceeds the frictional
force
holding the door in place, the door will be allowed to be moved outwardly from
the
front of the firebox. To that end latches 13 may include springs 22 so that
the
release of the latch requires a force exceeding that applied by the spring. In
such
instances the spring constant of the springs can be chosen to permit the door
to
move outwardly via track members 14 when internal pressure exceeds a pre-
determined value (ie it exceeds the force applied by the springs). As the door
moves outwardly following a delayed ignition, it will be held parallel to the
front of
the fireplace by track members 14 as described above. Once the seal between
the
door and the fireplace has been broken, excess pressure will vent into the
surrounding room until the internal fireplace pressure is reduced to the point
where
the springs of the latches draw the door back into contact with the front of
the
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fireplace. The door will then be returned to its original position and the
potentially
dangerous delayed ignition condition will have been safely dealt with.
Figures 10, 10A and 11 show an alternate embodiment of the invention. Here,
track members 14 have been replaced with pneumatic or hydraulic cylinders 52.
Cylinders 52 will largely function similar to track members 14 with the body
53 of
the cylinders mounted to the side surface of the firebox or the chassis, and
the end
of the cylinder rod 54 fixed or otherwise secured to door 2. It is expected
that in
most instances the end of the rod will be releasably secured to the door to
allow the
door to be completely removed from the fireplace if desired. Pneumatic or
hydraulic cylinders 52 are normally biased to its retracted position such that
they
cause the door to be drawn inwardly, thereby sealing the open front of the
firebox.
Since cylinders 52 will provide a positive force drawing the door into contact
with
the front of the fireplace, in most cases it is expected that there will be no
need for
the utilization of separate latches to retain the door in place. Cylinders 52
thus
perform the dual function of securely holding the door in place and sealing
the
firebox, and providing a pressure release mechanism by which the door can be
displaced outwardly from the front of the firebox to release built up internal
pressure if such pressure were to exceed a predetermined level. Once the
internal
pressure has dissipated, cylinders 52 will draw the door back into contact
with the
fireplace and re-seal the firebox.
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Figures 14, 14A, 15 and 15A show a different embodiment of the invention
wherein
track members 14 have been replaced by a single cylinder 55 mounted at the top
of
the fireplace. As in the case of cylinder 52, it is expected that cylinder 55
will be a
hydraulic or pneumatic cylinder, however, it will be appreciated that a spring
activated cylinder could also be utilized for either cylinder. In this case,
cylinder 55
includes a cylinder body 56 and a cylinder rod 57. Body 56 will generally be
mounted along the central portion of the upper surface of the fireplace and at
an
angle of approximately 900 to the fireplace door. Rod 57 may include a lateral
support member 58 that extends outwardly from either side of rod 57 at 900
such
that support member 58 is generally parallel to fireplace door 2. Support
member
58 may then be releasably secured to the upper or top portion of fireplace
door 2 to
thereby effectively releasably secure the door to the fireplace.
The function of cylinder 55 will essentially be the same as that of cylinder
52, in
that the cylinder will perform the dual function of retaining the fireplace
door tightly
against the front of the fireplace in order to maintain an airtight seal,
while at the
same time permitting the dissipation of internal pressure that exceeds a
predetermined value. With the use of a single cylinder 55, lateral support
member
58 assists in securely holding fireplace door 2 in place and maintaining it in
a
proper orientation and position vis a vis the front of the fireplace. Body 56
and/or
rod 57 and/or support member 58 may include elements to prevent rotation of
rod
57 such that the fireplace door is at all times maintained in a proper
orientation
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that will allow the door to move outwardly and then be retracted back inwardly
while remaining "square" and sealed with the front of the fireplace. It will
also be
appreciated that while not shown in the attached drawings, multiple cylinders
55
could be used if desired (and in particular for exceedingly heavy or wide
doors).
Further, in some instances cylinder or cylinders 55 may be positioned on the
sides
of the fireplace.
Figures 15 and 15A depict an embodiment of the invention shown in Figure 14
wherein the fireplace door has been displaced outwardly on account of the
build up
of excessive firebox pressure, resulting in an extension of rod 57 from body
56
thereby presenting an opening in the front of the fireplace through which
excess
firebox pressure can dissipate. Of course, it will be appreciated that when
servicing
or cleaning of the firebox is necessary, an individual merely need to grasp
the door
and pull it outwardly with sufficient force to off-set that of cylinder 55.
Once the
door has been moved outwardly from the front of the fireplace, a cylinder lock
(which could comprise a pin, snap ring, etc.) can be inserted about rod 57 in
order
to prevent it from being drawn back into body 56 so that the door may be
removed
from lateral support member 58 to provide full access to the interior of the
firebox.
Alternately, a mechanical lock or brace could be positioned on the surface of
the
fireplace such that it engages one or both of rod 57 and lateral support 58 to
retain
the rod in an extended position.
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In still a further alternate embodiment of the invention the firebox includes
a
pressure release opening 50 through which gases from within the firebox can
escape upon internal firebox pressure exceeding a predetermined level. The
pressure release opening is a separate opening in the firebox, distinct from
the
open front, and may be located in the top, back, bottom or side surfaces.
Multiple
pressure release openings may be utilized. For illustration purposes, in
Figures 12
and 13 pressure release opening 50 is located in the back surface of the
firebox. In
this embodiment, a door 51 is used to normally enclose pressure release
opening
50 and to seal and prevent the escape of gases from within the firebox through
the
opening. Door 51 maybe secured to the firebox through the use of one or more
track members 14 that are configured to function essentially the same as the
track
members secured to door 2. The track members will serve to position door 51
about pressure release opening 50, while permitting door 51 to be offset from
the
surface of the firebox upon the internal pressures within the firebox
exceeding a
predetermined level. Track members 14 may include one or more biasing means to
both help retard the movement of the track members from their retracted to
their
extended positions, and to return door 51 to its position enclosing pressure
release
opening 50 upon the dissipation of the internal pressure within the firebox.
As in
the case of the embodiment described above, the biasing means could be any
combination of one or more springs, hydraulic or pneumatic cylinders,
belleville
washers, etc. It will be appreciated by those of ordinary skill in the art
that if
desired, firebox 3 may include one or more pressure release openings 50
enclosed
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by doors 51 mounted on track members 14, as well as a primary door 2, also
mounted on separate track members. Further, as shown in Figures 12 and 13,
door 51 may alternately be secured to the firebox through the use of one or
more
hydraulic or pneumatic cylinders 52, with or without the use of separate
latches.
It will thus be appreciated that the described structure provides a safety
release
door mechanism that helps to prevent damage to the appliance and the
surroundings in the room within which the appliance is situated, and that
helps to
prevent personal injury in the case of delayed ignition within the firebox. In
an
over-pressure situation the door is allowed to move outwardly from the firebox
in a
controlled manner in order to dissipate the internal pressure, while at the
same
time preventing the door from being blown into the room and minimizing
twisting
or distorting (which can cause breakage of the glass). The structure further
presents service personnel with a simplified manner of removing the appliance
door. Where for service purposes it is necessary to access the interior of the
firebox, where latches 13 are present they can be manually disengaged from
door
2, at which point the door can be grasped and pulled outwardly from the front
of
the appliance. Track members 14 will thus support the weight of the door and
hold
it securely in position adjacent to the front of the fireplace. At that point
the door
can be lifted from hooks 21 on the ends of the track members and fully removed
from the appliance, thereby exposing the entire front of the firebox.
Replacing the
door merely requires engaging pins 21 with hooks 20, sliding the door back
into
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place in the front of the firebox and re-engaging the latches. If latches 13
are not
utilized and the door is retained solely by track members 14 and biasing means
30,
moving the door outwardly for servicing will require a disengagement of the
biasing
means from the latches or the application of a force that exceeds that applied
by
the biasing means.
It is to be understood that what has been described are the preferred
embodiments
of the invention. The scope of the claims should not be limited by the
preferred
embodiments set forth above, but should be given the broadest interpretation
consistent with the description as a whole.
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