Patent Application
20160169525
The present application claims priority to Canadian Application filed in the Canadian Patent Office on Dec. 8, 2014. The disclosure of the application is hereby incorporated by reference in its entirety herein.
This invention relates generally to gas fired heating appliances, and in particular to such an appliance incorporating a safety release door mechanism.
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 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.
One aspect of 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.
Another aspect of the invention 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 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.
Another aspect of the invention 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.
Further aspects of the invention will become apparent from the following description taken together with the accompanying 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:
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
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
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
In
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
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 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
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 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 fireplace. The door will then be returned to its original position and the potentially dangerous delayed ignition condition will have been safely dealt with.
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 à 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 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.
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
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 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.
