CA1170135A - Fireplace insert - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention relates to a fireplace insert having unique characteristics of a fiberglass insulated twin wall construction engineered to work on the principle of air convection. Cold air is drawn into a bottom inlet, circulated through channels between the firebox and an air shroud or air casing, and forced through outlets at the top of the unit back into the room. A controllable damper cuts down the heat carried up the chimney, and an air tight door controls the amount of in-house air drawn to feed the fire, and hence the amount of heat that escapes up the chimney.

Description

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PRIOR ART

It is no~ well understood ~y those skilled in the art that most fireplaces are really uneconomi-cal in that they draw healed air frQm the home intothe fireplace to help effect the combustion of the fire and then forcing a great deal of that already heated air out the chimrley. There have been many and various attempts to provicle glass firaplace doors, or the like, in order to prevent this discharge, and indeed there further have been many stoves and fire~
place inserts developed to likewise combat this pro-blem.
However, these prior art attempts have lS not provided for a good sealing relationship of the insert with respect to the face of th.e fireplace or the fireplace housing itself, and hence air still leaks from the house into the fire and up the chimney.
~urther, when the fireplace is not in use, there can be cold air leaking from around the fireplace insert down through the chimney and effec~ing adverse energy efficiency in the home.
It is further believed that these prior art fireplace insert approaches have not achieved sufficient insulation of the firebox in combination with air circulation therearound so as to obtain the most effective heat transfer from the firebox and for transmitting such heat back into the room. Further, these prior art attempts have not incorporated a good sealed relationship of the firebox itself by having an airtight door arrangement to prevent air leakage around the door.

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OBJECI'S OF l`HE I~7ENT~CON

It is the general object of the present invention to a~oid and overcome the oregoing and other problems of the prior art practice~ by providing a fireplace insert that has a firebox performing efficiently as a heat exchanger by utilizing a well insulated air shroud or casing~ and air circulation features axound the firebox of inside room air to effect the most efficient: heat transfer thereto, with the minimum of heat exiting up the chLmney. This object is achieved by providing a very efficient arrangement of a large portion of the insert extending on to the fireplace hearth in order to circulate air most efficiently with only slightl~ over hal of the insert extending into the fireplace itself.
A further object of the in~ention is to ¦ provide a unique flared front hood arrangement to achieve an excellent air seal of the fireplace insert against the fireplace face because of the flared hood and the use of thick insulation between the fireplace face and the flared hood.
A further object of the invention is to pro~ide an improved airtight door that preYents heated air from being drawn back into the fire and keep soot, smoke, and sparks from blo~ing into the room.
A further object of the invention i~ to provide a specialized baffle arrangement within the air shroud around the firebox to provide for the most efficient flow of air and heat transfer around the firebox~ and yet maintain the flared front hood in a a ~

cool condition so as to prevent being burned by coming into contact therewith.~
A ~urther object of the in~ention is to provide a fireplace insert wh~ch can optionally utilize power blowers convenientl~ associated with the intake air portion of the flared hood to achieve optimum air ~low and heat transfer from the firebox.
The aforesaid objects of the invention and other objects which will become apparent as the detailed description proceeds are ach~ved by pro-viding a fireplace insert for a fireplace having a front face surrounding the fireplace opening thereto which comprises: a firebox having a ~ront openin~;
a door select.ively closing the opaning; an air shroud surrounding the firebox and creating an air space around the sides and top of the fire~bx; an exhaust flue at the top back of the firebox and communicating in sealed relationship through the air shroud; a front hood attached to and communicating with the air shroud and defining a flat surfac~ to engaye with.the face of the fireplace when the insert is posîtioned thereinto; seal means between the hood and the fire place face to provide a substantial fluid seal ~etween the insert and the fireplace; and means to provide entrance of roQm a;r into the hood to circulate around the firebox and discharge back into the room, BRIEF DESCRIPTION OF THE~ WINGS

~or a better understanding o~ the inven-tion, reference should be had to th.e accompanying drawings wherein:

Fi~. l is a xont eleYational viaw of the fîreplace insert comprising the preferred embodiment o~ t~le invention;
Fig~ ~ is a partially broken away side ele~ational view of the fireplace ~ Fig. l;
Fig. 3 is a top broken away plan view of the firepl~ce of Fiy~ l;
Fig~. 4 i~ a top broken away plan ~iew of the door construction; and Fiy~ 5 ;s an enlarged cross-sectional view of the door construction a~ taken rom line 5-5 of Pig.. 4.

DETAILED DESCRIPTION OP TE~E PR$FER~ EMBODrMENT

With reference to the embodiment of the invention illustrated in Figs 1 through 3 of the drawings, the numeral lO indicates gene~ally a fireplace insert which comprises a firebox identified genexally by numeral 12, an air casing or shroud identified generally by numeral 14 surrounding the firebox on all three sides and t~e top, and a ~lared front hood indicated by numeral 16 mounted to the shroud 14 and providing the means for input and output air as more fully descrîbed hereinafter.
~ he firebox 12 is preferably made from welded metal pieces, but could be cast, ir desiredi and includes ceramic fire brick, preferably of about two-inch thickness on the floor, indicated by the numeral 18, ànd split ~ire brick of abou-t one and three~eighths inch thickness around the sides and back, indicatea by numeral 20. The ceramic fire . . I

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brick of t~o inches in the floor is sufficient so that no heat is transfer~ed down through the Eloor into the base, and h.ence t:he shroud 14 surrounds only the sides and the top and thereby operates in an extremely efficient manner in transferring heat generated from within the firebox, as deiined herein-after.
A ~eature of the invention is the damper indicated generally by numexal 22 which has a direc~ and sealed communication to the top rear of the firebox through a substantially rectangularly shaped opening as seen best in ~ig. 3 of the drawings.
The damper plate 24 is pivotally mounted on pins 26 so as to be actuated in pivotal ~ovement by lever arm 28 fixedly ~ounted to one side thereo~ and pivotally receiving rod 30 which is connected th~ough the front o~ ~hroud 16 to an actuating kno~ 32 so that a simple straightforward push or pull of knob 32 will cause pi~otal action of the damper plate 24 around pins 26 to effectively op~ or close the damper. It has been found that it is most efficient to operate the fireplace insert with the damper ~ery nearly closed so that only about four square inches of damper area, as opp~sed to a normal approximate llO square inches of damper iII a standard thirty-six inch ~ireplace r will be capable of allo~-ing approxLmately 40 pounds of hard ~ood to completely ~urn up o~er an eight~hourperiod, pro~iding a heat output of 38l850 BTU at this reduced four-square inch damper openi~g position~ As indicated above, the damper housing identi~ied by numeral 22a is connected in sealed relation~ip at 22~ to the firebox 12~ and likewise pa~ses in sealed rel~tîonship throu~h the shroud 14 so as to provide a direct and sealed com-munication ~rom the firebox throu~h th~ damper, and hence into the chimney wh.ell the fireplace insert is appropriately positioned into the fireplace for use as will be descrihed h.erei.nafter.
A further import:ant ~eature o~ the in~ention i~ in the flared front hood 15 wherein, as ~est seen in the top plan view o~ Fi.g~ 3, the siaes of the front hood extend at approximately a 62~ angle towards each other, indicated ~y numeral 17, to create a very pleasing aesthetic appearance in the room, as well as proYiding larger side face su~iaces 16a and 16b, which achieve a larger surface area to e~fect heat transfer, and also to att~in a cooled relationship on these surfaces, thus enhancing the safety feature of the insert to prevent ~urning of any one or anything coming into contact with.these sur~aces 16a and 16b during the use of the fireplace insert. The flaring oE face surfaces 16a and 16b also then results in large flat side surfaces 16c, d, and e, on the side and top portions outside the shroud 14, all as best seen in Fig~ 3~ Th.ese flat surfaces 16c, d, and e, : 25 cooperate with a recessed relationship of the shroud 14 at the sides, as indicated at 14a and 14h in Fig~
3 so that fiberglass-type insulation 30 can be in-serted into the recess provided there~y and stay in position to allo~ a co~pressed fluid seal when the fireplace insert is pos~tioned into the fireplace.
The same recessed rela~ionship i5 provided along the top edge of the shroud 16 to receive the -Eiherglass ~7-seal skrip aa i~ ~hown on the sides 14a and 14b in Fig. 3, Hence, the fiberglass strip 30 extends con-tinuously around the sides and top to ~orm a continu-ous perimeter ~etween the faces 16c, d, and e, and the face o~ the fireplace as t~e insert 10 is pushed into the fixeplace. Preferably, the flared front hood provides that the suraces 16c, d, and e will be four to six inches long so that a large flush com-pres~e~ relationship of the ~i~erglass 30 is achieved between the ~ace of the fireplace and the recessed relationship defined with the edges 16c, d, and e and the recessed surfaces 14a and 14~ of the shroud. This ~luid-sealed relationship of the hood 16 to the ~ire-place face is extremely important so that no cold air leaks down the fireplace and into the room, and further so that no warm air ~rom the room leaks past the fireplace insert and up the chLmney, as it will tend to be drawn by the hot gases leaving the flue 22 wh~n a fire is burning .in the fire~ox 12, and this structural arrangement very effectively achieves this desired result, particularly when the fi~erglass ~aterial 30 is pre.~erably at least four inches t~ick and is very compressed as the insert 10 is positioned into the fireplace~ The large four to six-inch over-hang ensures that the proper seal is achieYed evenwith variable widths and heights of the ~ireplace opening, and e~en against irregular brick or stone faces.
~ ~urther structural ~eature o~ the hood 16 is the provision of the inlet cold air ports indicated generally ~y numerals 32,34 on the lower s~des of the hoodO These inlets are provided of such size so as to receiye ~ ~mall electric motor and fan thereinto, hence enhancing the forced circulation o air as desired. The hood 16 has a series o~ outlet holes indicated generally ~y numeral 36 along the top edge, and al50 has a top pro;ection 16f extending out to provide a pleasing appearance and further to receive the rod 30 in sliding relationship for support there-throug~, which is open, and allows t~e dlscharge of hot air being circulated around the firebo~ in a manner more fully described hereinafter.
The structuxe of the ~ireplace insert design is then completed ~y having a ~orwardly pro-~ecting hearth sill ox bottom plate 40, and two support legs 42 in the rear which are vertically adjustable so as to allow the positioning o~ the fireplace in exactly horizontal relationship after it has been pushed into final position in the ~ireplace, The legs 42 can be reached by a screwdriver from inside the fire~ox upon simple re~oYal of a few of the fire brick, and then screwed up or down to obtain the proper horizontal level. Pre~erably/ the hearth sill 40 is about three-ei~hths inch lower than the bottom of the ~irebox 12, and hence the legs 42 will have to be adjusted downwardly to obtain the proper horizontal level. Hence, the fireplace insert 10, when fully in position, is supported on the hearth sill 40 along the full front edge and then on the two legs 42 at the rear, normally being fully pushed into position so as to compress the fiberglass as described above around the full perimeter of the hood so as to seal the brick and stone joints normally associated with the face of the fireplace.

3~.9 ~9-Th~ ~ire~Qx 12, of course, has an opening on the front thereo~ and a door ~ndicated genexally by numeral 50 i~ pro~ided which is hinged a-t 52 and has a handle 54 and three glass opening~ The door is designed to provide a sealed a~r~t~ht relationship with the firebox, and thi~ is provided as best seen in Figs. 4 and 5, wherein a ~e~d of asbestos braiding 56 extends around the full outsîde perimeter on the inside sur~ace of the door SO so that when the door is positioned and t~e handle latched, there is a pressure seal on the asbestos ~raid 56 around the full perimeter to obtain a fluid-~tight closure.
Similarly~ as indicated in Fig~ 5, as~estos braids 60 are pro~ided around the ~ull perimeter of the glass 60 as held in place ~y the frame so that there is no air leakage around the glass in t~e door 50, either.
As a decorative ~eature, the ~ace of the ~irebox ma~ ha~e colored tile.s indicated generally by numeral 70 as best seen in Fig. 1, adhesively secured thereto~ A further decorative ~eature is to add a dummy-brass knob 32a at a ~alanced opposite position rom knob 32.
The essential air flow of the in~ention is depicted primarily in Fig~ 2 which indicates input cold air throu~h the opening 32 ~hich prefera-bly will have a grill work of s~me type thereon, as shown by arrow 8Q, thence primarily deflected down and along the backsides bet~een the shroud 14 3Q and the firebox 12 as depicted by arrows 8Qa and 80b, and achie~ed by a deflection baffle 82 extending --10~

from the opening 32 to deflect the air as indicated.
In this connection, an important feature of the invention is that there ic; a small open space 84 between the structure surrounding the opening 32 and the ~a~fle 82 which allowc, a ~nall portion of the input air to pass up and along the inside surface of the side portions of hood 16 so as to effect a cooling thereof and prevent any person or thing from being burnt by coming into contact with th~s portion of the hood.
The air then, by the time it passes at about the position of arrow 80b, is directed upwardly along the back o the firebox, around the openings to either side of the damper 22, as indicated b~
arrow 80c, along the top o the fire~ox at 80d, and thence either up and out the openings 36 as indicated by arrow 8Oe, or down and out through the extension 16f of hood 16 as indicated ~y arrow 80f~ Naturally, because there is a large opening after the air passes beneath baffle 82 as indicated by arrow 80~ between the firebox 12 and the shroud 14, some air can and will pass along the side walls and up towards the position of arrow 80d and 80e, without extendi~g clear around the back and up to the position of arrow 80c. Thus, it should be clearly understood that all uniform amounts of cold air pas~ing around the fully exposed surface of firebox 12 to effect the most efficient of this air flow will in effect ha~a the desired result of hea~ transfer from the firebox 12 to the air w~ich is being discharged back into the room at 80e and 80fo 3~

As a urther enhancement to the air heat exchan~e. characteristics of the fireplace insert, it is extremely des~rable to include a s~eral inch thick layer of insula-tion around the full~ exposed surface of the air shroud 14, th.is îndicated generally by numeral 90 in Figs. 2 and 3. Preferably, this will be fiberglass insulation with an outer aluminum facing.
It should be understood -that an important feature of the invention is that the portion of the lQ fireplace insert extending into the room is 40 to 50 percent of the total depth of the fîreplacer as is evident from viewing Figs. 2 and 3 of the drawings, thus ensuring a natural air flow input from the room to openings 32, and hence a natural air flow around the firebox because of the larger portion ex~ending into the room~ The basic design is for approximately 13 1/2 inches to be the depth e~tending into the fireplace with 10 inches extending onto the fireplace hearth in order to circulate the air most efficiently.
As best seen in Fig7 1, ~all controllable opening combustion parts indicated by numeral 100 are incIuded just beldw the door 50.
The fireglass insulated twin wall con-stru~tion hence is engineered to wo.rk on the principle of convection with more rapid circulation being achieved by utilizing the independent electric blowers in the inlets 32 and 34. Hence~ the cold air drawn into the bottom inlets 32 and 34 circulates through the channels between the fire~Qx heat exchanger 12 3~ and the air shroud 14 so that warm air is forced through the outlets at the top and ront of the hood, or in opposite relationship to the inlets and back into the room~

By appropriately setting th.e damper, a slo~, even burn will be achieved achieving much ¦ greater heat efficiency than a regular fireplace, ¦ while actually consuming less wood ~n the same amount of tIme. Naturally, fireplace type glass is utilized in the door, and the ceiling o the door and the glass relatîve to the firebox prevents heated air from being drawn back into t~e fire and keeps soot, smoke, and sparks from blowing into the xo~m.
Because the ~ireplace insert is made from heavy metal and utilizes the ire brick on the floor and the ~ides, it is a hea~ unit that will effectively remain in place once positîoned sLmply by gravity, and will provide the seal around the full periphery of the hood as defined above. It should also again be stressed that the hood itself will remain cool, at least relatively so/ whereby it will not have enough temperature to burn anybody or anything, even though a lar~e portion of the hood is in an exposed relationship in the room.
~ hile in accordance with the patent statutes only the best known Qmbodiment of the inven-tion has been illustrated and descri~ed in detail, it is to be particularly understood that -the invention is not limited thereto ox thereby, but that the inventive scope is defined in the appended claims.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fireplace insert for a fireplace hav-ing a front face surrounding the fireplace opening thereto, which is characterized by:
(a) a firebox having a front opening;
(b) an air shroud surrounding the firebox and creating an air space around the sides and top of the firebox;
(c) an exhaust flue at the top back of the firebox and communicating in sealed relationship through the air shroud;
(d) a front hood attached to and communica-ting with the air shroud and defining a flat surface to engage with the face of the fireplace when the insert is positioned thereinto;
(e) seal means between the hood and the fireplace face to provide a substantial fluid seal be-tween the insert and the fireplace;
(f) means to provide entrance of room air into the base of the hood to circulate around the fire-box and discharge back into the room; and (g) baffle means in the air space to direct the major flow of air along the lower sides and to the back of the firebox, and wherein said baffle means has an opening therein adjacent the front of the firebox to direct cool air to the inside portions of the front hood.

2. A fireplace insert as defined in Claim 1 which incorporates insulation surrounding all outside surfaces of the air shroud to enhance heat transfer from the firebox to the circulating air.

3. A fireplace insert as defined in Claim 2 which incorporates a fully sealed door to the firebox, including asbestos cords held in com-pression around the full periphery thereof when the door is in a closed position.

4. A fireplace insert as defined in Claim 3 wherein the hood incorporates about a 60 degree angle on its surface thereof, converging towards the room to provide a larger exposed hood surface within the room when the fireplace insert is fully in posi-tion in the fireplace.