CA1162121A - Heat control systems - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Improvements in fireplace systems include several features some of which are separably usable in other heating apparatus. The features include a barometric damper adaptor, a grate structure, a manner of mounting hollow grate tubes in a fireplace assembly, an improved combustion chamber assembly, a combined damper and ducting system, a revised plenum system for a fireplace or the like and a tempering system cooperative with such a unit.

Description

SPECI}ICATI0~
The presenl invention pertains to heat control systems.
More ~)articulally, it relates to the i~provements in prior such systems and to adaptations therefrom.
U. ~. Patent No 4,026,26~ descr:lbes and claims a flreplace system, with modifications and alternatives, that well serves to enable a user to obtaln beneficial results over those afforded by predecessor firepl3ces. While the systems described in that patent have been and continue to be succes fully incorporated into use, it has become a~,arent that still f`urther improvements may be de~irable ln some circumstances.
Moreover, c~onti~nued research into the arec1 o~
alterrl~tive ~leat sources for the typLcal residence or buslness has revealed the need for inc~reased erficiency in performance of all kinds of different sources of heat. For cer-ta~n, conser~ation of ener~y has becorne the name of the ~rame It ls, accordingl-r, one general obJect of ~-he present invent;ion to provide new and lmproved apparatus usabLe in connection with the practice o~ the teachin~s of the cl~orec;ald patent.

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1~&21~

Another general ob~ect of the present in~ention is to provide new and lmproved apparatus usable not only with that specific kind of equipment but also readily adaptable to a wide variety of other such apparatus.
A further ob~ect of the present invention is to provide heating system improvements ~hich enhance both safety and efficiency of fuel consum~tlon.
It is a related ob,~ect of the present invention to provide new and improved apparatus of the foregoing character that is capable of being produced and sold in an economical manner.
In accordance with one feature o~ the present invention, a weighted damper is disposed in a conduit which opens laterall~ througn the wall Or an outer tube coupled into a stack at its outlet end and encircling an inner tube which connects with a combustion chamber. One or more aspects of the structure include those of the inner tube extending upwardly above the conduit, means defining a wall substantially closing the space between the inner and outer tubes at a location between the conduit and the combustion chamber~ the inner tube pre~erably but n~ot necessarily having a width less than the width of the stack and sensing means responsive to temperature cooperative with locking means that hold the damper in a closed position with control enabled by the sensing means for operating the locking means in correspondence with activity within the combustion chamber.
Another aspect of the invention pertains to the inclusion of a door assembly spaced forwardly from 1,he combustion chamber together with a closure assembly spaced between the door i29 and the combustion chamber. The closure assembly further features one or more of a gate openable into the chamber and a damper selectively openable and disposed to permit the passage of air through the door assembly over and upwardly away from the primary combustion area in the chamber.
A further aspect of the present invention is directed to the use of a tube-type grate within which a plurality of assembled bars are seated, with those bars being conformed to seat above a manifold associat;ed with the tubes and also having a shield that closes spaces between the forward end portions of the bars. Also involved is a multiply-secured clamping assembly for such tubes.
In its system aspect, the invention is particularly related to an arrangement wherein outside air is supplled for use in the combustion chamber and which includes means for circulating air in heat-exchànge relationship with the combustion chamber but exclusive of the combustion air. The clrculating means lncludes a plenum chamber together with an intake Or air from outside the space being heated. A damper, disposed between the intake and the plenum chamber, is normally closed to prevent a back flow of warmed air to the outside but automatically admits the outside air into the plenum chamber upon demand.
Another aspect related to the same type pf heating system involves the use of a duct that leads from the plenum chamber and outlets into the space tc be heated. A normally-closed damper is disposed between the plenum chamber and the duct.
That damper op~ns automatically in response to operation of a fan in the circulacion system. Qlso with regard to the same basic 1%~

approach in a heating system, stlll another aspect involves the inclusion of a duct that leads from the space being heated into the circulation system. A fan moves air in the circulation system, and a normally-open damper is located between the duct and the circulation system, this damper automatically closing in response to operation of the fan. A feature also desirably included with the foregoing, but usef`ul separately-in itself`, embodies a duct that leads from a portion of such a plenum chamber, disposed above a discharge opening into the space being heated, to an entrance located in the vicinity of the bottom of the combustion chamber and opening into such space.
The features of the present invention which are believed to be patentable are set forth with particularity in the appended claims. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like numerals identify like elements, and in which:
Figure 1 is an exploded p~rspective view of a fireplace system;
Figure 2 is a fron~ elevational view of fl portion of the system of Figure l;
Figure 3 is a cross-sectional view taken along the line 3~3 in Figure 2;
Figure 4 is a fragmentary cross-sectional view of a component desirably used in the system of Figure l;
Figure 4a is a somewhat schemati( and side-elevational view of an adaptation of the component of Figure 4;

Figure 5 is a view similar to Figure 4 but with a different orientation and arrangement of the elements;
Figure 6 is a cross-sectional view of an improved grate assembly for use in the apparatus of Figures 1-3;
Figure 7 is a fragmentary cross-sectional view taken ~long the line 7-7 in Figure 6 and with certain components removed;
Figure 8 is a fragmentary cross-sectional view taken similarly to Figure 3 but show~ng improvements included in the apparatus thereof;
Figure 9a is a fragmentar~ and enlarged cross-sectional view taken along the line 9a-9a in Figure 6;
Figure 9b is a fragmentary and e~ploded side-elevational view of components shown in Figures 6 and 9a;
Figure 10 is a somewhat schematic rear-elevational view of a damper and duct system added to the fireplace system of Figure l;
Figure 11 is a similar front-elevational view of the system of Figure 10;
Figure 12 is a similar side-elevational view of the system of Figure 10; ~ ~
Figure 13 is a similar top plan View of the system of Figure 10;
Figure 14 is a fra~mentary isometric view of a portion of the system of Figure 10; and Fi~ure 15 is an isometric view of a system similar to that shown in Figure 1 but with the inclusion of a further component .

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The improvements to be described are herein presented relative to the apparatus described in the afore-sald U. S. patent 4,026,2~3. Accordingly, that patent is incorporated herein by reference. Moreover, Figures 1-3 of this patent application correspond, with one exception, to Flgures l, 2 and lO of` that patent. In order to gain an understanding o~ the overall aspects, this description proceeds first with what, therefore, may be a redundant discussion of the sub~ect matter of that pa1;ent.
A fireplace system includes a firebox 20 formed of a heat-conductive material such as sheet steel. Firebox 20 confines a region of combustion of burnable products such as firewood. In itself, firebox 20 inc]udes a front wall 22 bridging sidew~lls 24 and di'sposed vertically over its lower 15 portion but slanting lnwardly and upwardly over its upper portion 26. A rear wall 28 is vertlcally disposed over its lower portion and is formed to slant upwardly and ~orwardly throughout its upper portion 32. Additional wall sections serve to defin~ a smoke shelf 42, Opening upwardly from smoke shelf' 42 is an exhaust 20 outlet 44 for conveying th~e combustion products on through the usual chlmney or stack 45. Slanting upwardly and forwardly through the region of` shelf 42 are a plurality of conduits 46.
A baffle sheet 48 slants upwardly and generally alongside the uppermost surface of conduits 46. Another baffle 50 projec~s 25 upwardly but has its margins spaced from the sidewalls so as to permit upwardly rising smoke to egress through outlet 44 around the edges of this particular baff'le. Baffle 50 chokes off` the central region of the smoke path, preventing backward eddy currents.

Defined in front wall 22 is an opening 52 through which fuel to be consumed is inserted and ignited. Opening 52 is aligned with an opening in an o~ter ~acket 54 that encloses firebGx 20. A collar 55 has an out~turned flange which is fastened and sealed around aild to the margins of the latter opening, while defining a door holder flange 56. A
door frame 58, carrying a pair; of sliding fire doors 60 that preferably are composed of transparen'~ glass, is secured to flange ~6. As illustrated, frame 58 is spaced by collar 55 from ~a~ket 54 by a'distance to accommodate the brick or stonework that forms the aesthetically attractive wall through which the fireplace opens.
In the manner shown, collar 55 is removably affixed to ~acket 54. This reduces'the clearances necessary to move the main part of the fireplace unit :Lnto a given enclosure.
Both its front and rear flanges enable alr-tight sealing to associated surfaces, for reasons better to be appreciated in connection with the descriptlon of operation included in the aforementioned patent. Flange 56 also defines out-turned surfaces that serve as a guide for the laying of brick or stone.
A baffle 59 pro~ects downw~ardly and rearwardly of the top panel of collar 55 for the purpose ~f preventing an internal circulating current of smoke toward fire doors 60. Desirably, collar 55 may ~e circumscribed by a ~leeve of insulating material.
A plurality of laterally-,paced tubes 61 are oriented so as to open at one end 62 through t,he lower portion of rear walls 28 and emerge at the other end into a manifold 63 ~ ~2~1 which rllns crosswise along the bottom of opening 52. Also running transversely to opening 52~ generally along lts lower portion and spaced somewhat inwardly thereof, is a pipe 64 through the back surface ~f which is defined a plurality of longltudinally-spaced combustion air ~utlets. A strut 66 extends between the front-top edge of pipe 64 and the upper wall of manifo]d 63 for both strength!giving and appearance purposeF. A series of small aperture~ are spaced along the upper surfaces of pipe 64 so clS, in u~e, to form an air screen.
Successively spaced indi~idually between different ones of tubes ~1, and orlented near the lower portions thereof, are a plurality of bars 68 which serve to collect i~nited coals and retain the same in a position ad~acent to the tubes.
Bars 68 are suspended by a plurallty of straps that depend from a palr of rods 70 disposed transversely across the top of tubes 61 respectively near the ~ront and rear thereof.
Bars 68 each so fill the space between adJacent ones of tubes 61 as to hold embers untll they are reduced at least substantially to ashes.
As herein conte~plated, the entire area beneath the grate defined by tubes 61 is opened to an underlying ashpit, although that is not necessary, The desirability of using such an open ashpit is described more fully in the aforementioned patent.
Outer Jacket 54 encloses firebox 20. ~acket 54 is in itself a similar metallic enclosure the walls of which are generally spaced from the walls o~ firebox 20. Jacket 54 defines or accommodates front opening 53, outlet 44, manifold Z~2~

63, plpe 64, an air return inlet 71 and a heated-air plenum opening 72. However, Jacket 54 may be constructed during installation of a fireplace so as to be composed of brick or stone materials. In any event, a variety of heat-conductive spaced-apart fins preferably project outwardly from firebox 20 and into the s~ace defined by ~acket 54. Thc)se fins, such as 78 herein shown and otners ill.ustrated in the patent, increase heat exchange with air circulated within Jacket 54. Also.in accordance with the di3cussion in the aforesaid patent, one mode of adaptation of the present invention involves use of baffles 82 and 83, deflector assembly 84, with its vanes 85 and 86 and web 88, and the related apparatus described in that patent.
As also described~in the prior patent, firebox 20 rests on a baseplate 89 that has a member across its front and two rearwardly extend~ng legs at either sidè. IJpturned edge margins accommodate Jacket 54~ The central open space within baseplate 89 is above the ashpit. During lnstallation, all exposed marginal joints are sealed with asbestos cement. That same structural approach may be continued in connection with the present improvements.
Also secured on th~ interior surfaces of sidewall.s 24 and rear wall 28 are pairs of spaced vertlcal brackets 93 from which project upwardly slanting posts 94. Lending protection to those walls are respective fireplates 95 that have apertures to receive posts 94 and wnich are so located as to position th6 fireplates at the corresponding ends and the back of burnin~ logs.
That approach is retained hereinafter. However~ and as will be further described, fireplates g5 desirably are revised so as to serve additional purposes.

~iZl~.

Pro~ecting la~erally from stack 45, as shown in Figure 1, is a barometric damper 96 which, in itself in the patent~ was conventional. That is, it has an internal valve flap 97 that is counterweighted so as normally to enable ~ust enough stack suction from the firebox to remove the combustion products. Flap 97 opens further to let in additional air when high wind across the top of the stack increases the updraft.
In the system of the patent, damper 96 communicates with a source o~ air from outside th~ enclosure or space being heated.
As is to be descrlbed below, that damper arrangement is herein improved upon.
The aforesaid prior patent also teaches use of thermostat means within the enclosure being heated for enabling and disabling certain control means in response to temperature change. Such control means serve to govern the conveyance of air frcm an outside source to the firebox itself`, to the circulation system for heated air or to both. Basically, those features preferably are retained in connection with what yet is to be described. On the other hand, the improvements connected with the discussion hereinafter also find utility in systems that may be quite different from those which derive from the aforesaid patent.
In ~igure 4, an inner tubo 100 has its inlet or lower end 102 leading or secured to the combustion chamber de~ined in principal part by firebox 20. An outer tube 104 encircles tube 100 and is coupled at its upper or outlet end into a stack 106 by a connection section lQ8. A conduit 110 opens laterally through the wall of outer tube 104. A weignted damper 112 is secured by a pivot at 114 within conduit 110 and in the path of air inletted through the outer end 116 of the conduit. In itself, damper 112 is a vane whichg in the conventional manner, i3 eccentrically weighted so as to open normally just enough to accommodate upwardly-directed suction forces within stack 106 that exceed those desirable for maintaining adequate and proper combustion within firebox 20.
As illustraGed, the outlet or upper end 118 of tube 100 extends upwardly above conduit 110, so as to dispose its upper end 118 at an elevation greater than the elevation of the uppermost side of conduit 110. At the same time, outlet end 118 is disposed below outlet end 120 of outer tube 104.
Moreover, outlet end 11~ in this case preferably has a width which is less than the width of stack 106. As accommodated by the inclusion of coupling or transitional section 11~8, the outlet or upper end of outer`tube 104 has a width which is greater thàn the width of stack 106.
At a location between conduit 110 and firebox 20, in this case phys.ically below the elevation of the lowermost portion of conduit llQ, is a wall 122. Thus, the o~ly air that can be drawn through the space between tubes 100 and 104 upwardly into stack 106 has to be inletted through Gonduit 110.
As used on a sy~stem of the kind depicted in Figures 1-3 installed to serve as the primary source of heating that served a residence having approximately 1200 square feet of floor area, an arrangement in accordance with Figure 4 was such that i~ner tube 100 had a diameter of 10 inche~, stack 106 (the flue ln the chimney) had a diameter of 12 inches, conduit 110 also had a diameter of 12 inches, and outer tube 104, correspondingly, had a d:iameter of 14 inches. The weight upon damper 112 was aclJusted in position so that, in the absence of significant wind across the top of stack 106, combustion within firebox 20, without the additional forced input of outside air, there is Just enough draft to avoid smoking with the door to the firebox open.
The altern~tive shown in Figure 5 adapts the principles implementecl in the arrangement of Figure 4 to the receipt of gases from firebox 20 delivered in a horizontal, rather than a vertical, direction. Thus, inner tube 100l receives the ihput frcm the combustion chamber`at an inlet end 102' from whicn the inner tube turns, in an L-shaped manner, so as to again proJect; its outlet end 118 in an upward direction. Correspondingly, outer tube 104 is conformed in an L-shaped manner so as to have horizontal and vertical legs.
The outlet end of conduit la4' once again connects through a coupling 108 to stack 106. Conduit 110' connects into the upright leg of conduit 104'.` Included in the upright leg portion of inner tube 100' i5 a removable closure 124 that is accessible through conduit 110 upon the disengagement of dam~er 112. That may serve as a convenient cleanout for the removal of deposits within the horizontal leg of inner tube 100'.
A damper arrangement as shown in either of Figures 4 and 5 contributes greatly to efficient and safe operation. The suction or draft effected within the stack by chimney action depends upon prevailing temperatures and the size of the st~ck.
Those parameters are subject to extreme variation even in normal operation. Appliances, that use woocl or a similar solid fuel, are controlled as to the amount of draf~ by usi~g dampers e`ither in the flue or at the point at which air entors into the firebox. That control requ:ires a degree o~ knowledge ~L~621~1 and Judgment from proper use, Even under the best of conditions, there often is an improper venting in the chimney. As a result, there frequently is a buildup of soot and creosote on the internal walls of the stack. Such materials have led to the occurrence of a fire within the stack.
The con~entional barometric damper, as illustrated in ~igure 1, is lntended to ad~ust the amount of draft through the stack so a~ automatically to accommodate the air flow needs within the firebox while yet allowing sufficient draft through the stack. Even in the case of the occurrence of a fire within the stack, the damper arrangemellt is supposed to open in order to allow a burning-out of the soot or creosote without lncreasing draft through the firebox. However, in order to provide a stack, for an appliance that burns wood or the like, large enough to vent the smoke from the burning of a fire at full capacity, conventional design calls for assigning a size to the stack of about twice as large as that needed for more normal burning condltions. On the other hand, that excess capacity often allows a portion of the alr that enters the stack to circulate down to the fire and undesirably interfere with proper oper~ation.
ln the embodiment of ~igures 4 and 5, the use of the smaller-diameter inner tube 100, that extends beyond conduit 110, inhibits such undesired downward flow. The larger size of outer tube 104 serves to allow damper 112 b~tter to ad~ust the amount of suction through the entire assembly. The illustrated arrangement allows air to enter the stack i~ order to increase the decomposition of combustible material i~ the smoke originating from the firebox, while still automatically compensating i2~2~

for increased chimney action. Should the desired combustion within the firebox be reduced, even deliberately, to a point that causes the emission of an increased quantity of unburned particles, the action of ~low through conduit 110 is such as to assist in the proper venting of those unburned particles without affecting the action within the firebox its~lf. Air entering through conduit 110 soon dissipates the additional heat that deve]ops as a result of any burning of soot or creosote within the stack. As a result, temperatures within the stack tend to retllrn soon to normal temperature.
Stated another way, the flow up the stack contributed through conduit 110, when the combustion within firebox 20 is purposely throttled down, is sufficient to carry any creosote on outwardly from the stack in most circumstances and yet also serves, should there be ignition of a collection of such substance within the stack, ~o ailow the increased draft to complete that ignitlon at an early stage and without affecting draft upon the firebox itself. Furthermore, the new barometric damper arrangement shown tends to result in a saving of fuel supplied to firebox 20, because it reduces the amount of heat lost up the stack.
It is to be noted that the barometric damper systems of Figures 4 and 5 find utility as used on any heating unit, stove or the like that burns a solid fuel such as wood. In use, it serves well t~ separate the functions of control of draft through the firebox, on the one hand, and the control of the provision of adeqvrate air through the stack or chimney, on the other hand.

~1~121 In Figure 4a, a barometric adaptor 130 is in itself constructed in the manner of Figure 4 and is adapted to a free-standing stove 132. Included in conduit 110 and located near inner tube 100, or otherwise dlsposed so as to sense the temperature in the vicinity of tubes 100 and 104, i~ a high-~
limit electric switch 134. Switch 134 is wired in series with an electromagnet 136 t~ a source of operatlng power. Magnet;
136 is disposed within conduit 110 in a location to attract, and lock into its closed position, pivoted damper v~ne 112 when the magnet is energized through switch 134. S~-itch 134 has normally-closed contacts that open when the sensed temperature rises to a pre-selected limit. When the fire is out inside stove 132, therefore, switch 134 remains closed and damper vane 112 is held.~n a closed condition so as to prohib~t the undesired loss of heat up stack 106. After the fire has been started, and the ~lue temperature warms up to the pre-selected value, switch 134 breaks the circuit to electromagnet _36. It will also be noted that, if the supplied electrical power ceases, the damper is automatically released.
In the particular embodiment of Figure Lla, a shroud 138 partially encircles and is spaced from the rear and sidewalls of stove 132. A pipe 140 is coupled at one end through shroud 138 and at its other end r-?ceives air from outside the space being heated by stove 132. Included ln the inlet of pipe 140 is an electromechanically-ope,ated damper 142. Also disposed within pipe 1~0 is an electrically-operated fan or blower 14ll.
When fan 144 is energized to draw air through damper 142, that air is caused to circulate around and outwardly into the space being heated f`rom stove 132. As a result, the overall heating system features the addition to the space o~ fresh air and a 11~212~L

positi~e pressure is created within that space. As explained in the aforesaid patent, the production of heated air so as to create a positive pressure within ~he space serves to prevent leakage into the space of unheated outside air around doors, windows or other cracks.
In the pre~erred arrangement of the system of Figure 4a, damper 142 is also powered through switch 134 so that damper 142 is maintained in a closed position until the flue or stac~ temperature reaches tihe pre--selected value at whic~ ~
switch 134 opens. Similarly, fan 144 preferably also is powered in response to operation of switch 134. In that case, however, switch 134 additionally includes a pair of normall~-open contacts in series to the source of electrical power with fan 144. ~hus, fan 144 is energi~ed to draw outside air through pipe 140 only when the flue or stack temperature reaches the activation level`of switc~ 134.
In case of power ~ailure, fan 144, of course, is inoperable. At the same time~ nevertheless~ damper 142 automatically opens so that outlet air is inletted by gravity flow. If desired, a manually-operated disconnect may be included in series with the w~ring of fan 144 so as to preclude the powered drawing of outside air at such times as it may be desired to recirculate, or heat by convection only, the air already contalned within the space being heated. In addition, a manually-operated override control may be included on damper 142, so as to force that damper to remain in an open condition during times of power failure or when it otherwise is desired to insure the admission of outside air.

~6Z~

In the original embodiment of the heating system as depicted in Figures 1-3 3 grate ~ubes 61 were welded at the rear ends into openings provided in rear wall 28 and at the front ends into corresponding openings formed in a wall of manlfold 63. ~uring ordinary operation with conventional wood fuels, the flexibllity of the connecting walls adequately accommodated the effects of thermal expansion and contraction in grate tubes 61. At the same time, the bars 68 of the additional drop-in grate assembly, which ser~re to catch live coals and hold tnem ad~acent to tubes 61, efiected what was a rather substantial barrier to the free flow of air in and around tubes 61. In time~ and particularly when uslng pieces of wood for fuel that burned at very high temperatures and when the system was operated.at maximum burning capacity, some failures occurred at the point o~ welding of tube 61 into the corresponding walls. ~his is believed to have been a result of diversion of the combustion ai.r stream from the burning fuel back onto and down the front of manifold 63. In addition, that air stream channeled itself under the burning fuel and rose upwardly alongside rear wall 28 and behind fi.rewal.l 95.
The new embodiments for the drop~in grate bars as shown in ~igures 7 and 8 overcome those deficien$ies.
As shown in Figures 6 and 7, bars 68a again are ~oined into an assembly by supports 70a so that the bars are seated individually between corresponding ones of tubes 61. However, bars 68a are conformed at their forward end portions to seat above manifold 63. In additlon, a shield 150 closes the spaces between all of the forward end portions of bars 68a and is so positioned as to block the flow of combusticn air onto manifold 63. An additional crosswise bar 152, latera.lly connecting the 1~621Z~L

forward ends of all of bars 68a and dlsposed above manifold 63 and pipe 64, serves additionally as a ba~rier to the flow of hot combustion àir downwardly and back to the rear toward rear wall 28. At the same time, bar 152 also serves, in cooperation with an andiron 154 to be described further, the purpose of preventing the drop-in grate assembly, that inc.udes bars 68a, from sliding too far to the rear and thereby exposing a grea'er portion of pipe 64 and manifold 63.
In the original embodiment of ~igures 1-3, a pr'mary purpose of glass doors 60 is to separate combustion air, supplied from the outside, from air circulating within the space being heated. It has been found, unfortunately, that at least most conventionally-available glass door assemblies permit an undesirable degree of leakage. That leakage allows air to be supplied to the process of combustion from the space being heated. It also tends undesirably to create a circulation of air f`rom the combustion area back toward the glass doors. The result has been an interference with proper control of the process of combustion and also the creation of excessive heat near the top of the glass doors.
In the modification illustrated in Figure 8, such problems are prevented, or at least largely overcome, by the inclusion of a gate 160 and a damper 162 both of which are spaced inwardly from glass doors 60 at the rear of frame 55 and preferably Just sliKhtly further to the rear behind front wall 22 of the firebo~. Gate 160 and damper 162 together serve as an enclosure assembly located between sliding door assembly 60 and the combustion chamber. Gate 160 is hingedly affixed along its lower portion at 164 from the assembly of manifold 63 and so as to be swingable to a more-forward and open position as shown by a dashed l ne in ~igure 8.

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Laterally spaced andirons 154 are secured to the rear slde of gate 160 by struts 166. Gate 160 thus is openable to permlt the lnsertion of fuel through doors 60 and into the primary burning portlon of chamber 20. When gate 160 is in its opeh position, the andiron structure pro~ects upwardly so as to assist in the laading of fuel, such as logs, into the combustion chamber.
Damper 162 is hinged along its upper edge at 168 to front wall 22 at the rear of frame 55. That permits damper 162 to be swung outwardly and upwardly. Damper 162 slightly overlaps gate 160 so as to complete ~n inner-door assembly.
Being located above gate 160, damper 162 is disposed to prohibit the passage of air, through leakage in the door assembly, over and upwardly ~away from the p~imary combustion area in chamber 20. ~ simple latch, not shown, preferably is included to permit holding damper 162 in an open position.
Damper 162 serves to prevent inner circulation when it is in the closed position and also tends to prevent the build-up of excessive heat, whether closed or open, from being transmitted to the upper portion of frame 55.
In the original embodiment of Figures 1-~, the basic combustion chamber and overlyin`g plenum area was in the form of a rigid shell composed of front wall 22, rear wall 28 and sidewalls 24. Firewalls 95 were disposed in spaced position inside that rigid shell to absorb the effects of the highest temperatures produced within the primary co~ibustion area. In the embodiment of Figure 8, that principle is retained. In addition, howe-~er, plates 95a, along the sides of the primary combustion are~, are extended forwardly, toward door 60, so ~ gL6ZlZ~

as to define a forward margin 170 spaced closely adjacent to the rear edge margin of gate 160. That relationship serves to form a shield or channel that di~erts any air, that is drawn in or around the lateral edge margins of gate 160, upwardly toward the plenum area instead of into the primary combustion area. In lieu of extending fire~alls 95a so far forward, a channel may be formed with respect to an~ pro~ect from the respective ones of sidewalls 24 so that any air, which tends to leak around the sides of gate 160, is directed upward]y toward the plenum chamber instead of feeding the fire.
Whe~ electrical power is lost for operating the various blowers described in connectlon with the heating system of Fig~res 1 and 3, and that system has been modified to include the features o~ Figure 8, the opening of gate 160 may be accompanied by the placing o~ damper 162 in the closed position while leaving glass door 60 o~pen. Damper 162 then serves to direct the air entering the unit from the space being heated down into the primary combustion area in order to obtain adequate burning in the absence of blower operation. Deslrably, a tempered glass panel 172 is centrally located within gate 160 so that the user may view the flames of combustion through glass door 60.
As mentioned above, a few of the original heating systems constructed in accordance with ~igures 1-3 have encountered difficulty with a fractu~e of welds at ends of grate tubes 61. In addition, the long-term operation of any form of conven'ional grate tube entails a gradual deterioration of the walls of the tube. Eventually, therefore, such tubes need replacement. Whether retrofitting existing unlts or employed in the fabrication of new units, the arrangement particularly illustrated in Figures 9a and 9b is advantageous.
~n that approach, a pair of facing U-shaped clamps 180 and 182 are sized to grip an end portion of a tube 61. A flrst pair of holes 184 and 186 are defined in the respective legs of each clamp 180 to face the mating clamp l8?. A fastener 188 is engageable through holes 184 and 186 so as to secure the clamps together. In t;his case, fasteners 188 are bolts that fit through holes 184 and 186 into correspondlng threaded holes 190 provided in th~ matin~ clamp. Other forms ol known fastening elements may, of cour~e, be substituted.
In any case, there also is a retalner 192 disposed on the side of the securing wall opposite at least one of clamps 180 and 182. Additional, l~ngitudinally-directed, holes 194 in the cla~ps receive bolts 196 that are threaded through the securing wall into threaded holes 198 provided in retainer 192.
Regardless of the specific manner of fastening as between the three different basic parts, the ob~ective secured is that of removably securing the respective end portions of tubes 61 to 20 the upright walls at the respective opposing ends of the grate tubes.
As described in the aforesaid patent, the heating system of Figures 1-3 was adaptable for use in a variety of different applications, including modification of an existing fireplace system, installation as a discrete fireplace unit associated with nearby air ou~lets that circulated heated air into the room within which the unit was located or &S tied into a duct system that supplied the heated air to all or part of an entire building as in the manner of a conventional furnace. In 1~21;~1 adapting the system of the patent for the supply of heat to a single room, the manner of installation is similar to that of installing a number of known prior fireplace units that employ an enclosing shell which includes the formation of heat-exchanging passages for circulating heated air, from externally of the firebox, into the r~om. As in those prior units, the exchange of heat m~y be accelerated by includlng a blower in the system. At the same time, the location of any outlet duct above a return colder-air duct allows such a system to operate by gravity flow in the absence of a blower or in the failure of operation of an included blower by reason of power failure.
When, however~ a system of the positive-air supply kind, as above descrik,ed in~connection with Figures 1-3 or as modified in accordance with the improvements of the further description above, is employed wlth an external ductwork system that leads throughout the enclosure, problems of proper air flow may be encountered. A particular problem is encountered whenever power is lost so as not to be available for operation of blowers or :it otherwise is desired to operate the heating system by gravity flow.
In general~ a safe installation requires that circulating heated air should not be able to get into the duct-work, at least throughout the total enclosure, without the use of blowers. Otherwise, an excessively "hot spot" might be developed. That has been assured in the past, when ductwork leads outwardly from such a unit, either level with or above the combustion chamber, by in;talling a conventional back-draft clamper. That serves to prevent hot air from entering ~i2~

the ductwork by gravity flow. A more severe situation may be presented when the ductwork is installed so as to lead down the side of and to a point below the heating unit. That arrangement may create an alr trap that prevents hot air from flowing into the ductwork. In that case, th~ heating system itself may encounter the creation of dangerously high temperatures, because of the fact that the h~ated air may be unable to escape. The connecting ductwork arrangements of Figures 10-14 obviate such deficiencies, difficulties and problems.
This new system preferably, although not necessarily, includes a fireplace system constructed in the manner of the system of Figures 1-3 modified to include the improYements of Figures 4-9. It thus inc~ludes a fireplace unlt ~00 that has an outer Jacket 202 spaced from but enclosing a firebox 204 above which is a smoke snelf 206 and a hot-air plenum chamber 208. A stack 210, provided with a barometric damper 212, proJects upwardly from smoke shelf 206 as a chimney.
Opening into one side of plenum chamber 208 is an inlet damper 2i4. Damper 214 leads from a plenum 216 provided with an air entrance controlled by another damper 218. Damper 218 communicates, either directly or indirectly, with air supplied from outside the space being heated. To force the introduction o~ that outside air, a blower 220 may be included within plenum ~16 ~here the mode of installation permits, however~ an equipment or furnace room is disposed behind fireplace unit 200, houses all blowers, and is separated with respect of air circulation from the space being heated. That room then includes an inlet opening to the exterior of the ZlZ~I, building for admitting outside air which may become somewhat warmed as it travels through this furnace room. In that case, damper 218 may be relocated so as actually to govern the control of air from the outside of the buildlng into such a furnace room.
Lea~ing outwardly from the other side of plenum chamber 208 is a duct 222 which supplles the overall ductwork system 'hat leads to the hot-air registers distributed throughout the different rooms of the interior space to be heated. At that outlet from plenum chamber 208, which supplles air to duct 222, there is a damper 224 just beyond which, into duct 222, is a temperature sensitive switch control 226.
Pro~ecting outwardly from the front of plenum chamber 208 is a grill 228 b~ehind which is another damper 230.
In this case, grill 228 is spaced outwardly by a collar 232 that accommodates masonary work or the like for aesthetically completing the fireplace installation in the conventional manner.
Leading into one side of the lower portion of jacket 202 is a gravity air return duct 234 which extends from a grill 236 mounted on or near the floor in the room of the interior space in which unit 200 is located or, alternatively, in a similar location in some other portion of the total interior space to be heated that affords good circulation for gravity flow. Duct 234 outlets through a damper 238 and through jacket 202 into the space between the latter and firebox 204.
At the other side of the lower portion of unit 200 is a plenum 239 which feeds circulating air through a collar 240 and the wall o~f Jacket 202 again into the interior space between jacket 202 and firebox 204 Plenum 239 leads from the normal cold-air return ductwork system 242 distribu'ed throughout the different rooms of which the interior space to be heated is _ 24 -~l~iZlZ~

compose~. Although it may be located elsewhere, a circulation blower 244 for the overall interior circulation system is indicated as herein ~ncluded conveniently within plenum 239.
In the illustrated system, blower 244 corresponds in function to circulation-air fan 108 of the aforesaid patent.
Analogously, blower 220 corresponds to fan 134 of that referenced patent. Moreover, the same thermostatically controlled system, as explained in connection with E~igure 9 of that patent, advantageously may be employed in connection with the operation of the herein heating system of ~igures 10-14.
Dampers 21LI, 224, 230 and 238 all may be constructed in the æame manner. That is, each is composed of a vertically-spaced æuccession of horizon~tally-oriented longitud~nal slats each Or which is in turn pivot,ed to rotate about a horizontal axis, with all of the slats i`n a given damper being ganged together. The slats are so spaced vertically that, when all are pivoted to a vertical orientation, they mutually overlap sufficiently to close the opening, Upon pivoting of the slats into a near-horizontal position, on the other hand, the damper is opened. For automatic self-actuation in response to air movement, each gang of slats is limited in movement to short of a full horizontal position, Thus, those dampers which are normally open, in the absence of the flow of air in a forward direction, are so arranged that their inlet margins swing upwardly to a closed position under air pressure, while the slat gang falls downwardly and outwardly to an open position in the absence of the air. A reverse mode of operation is obtained simply by inverting such an assembly. That is, in -~1~;2lZ~

absence of flowing air, the downstream and outermost margins swing downwardly so as to dispose the slat gang in a closed orientation. On the other hand, a flow of air from the rear of the ælat assembly serves to open these slats.
In the illustrated embodiment, dampers 214 and 224 are norr;lally in a closed position. On the other hand, damper 230 and 238 are normally in an open position; any movement of air developed by a corresponding blower serves automatically to close the normally-open dampers.
Damper 214 serves the primary purpose of acting as a check v~lve to prevent the backrlow of warm air from escaping to outs-~de the space being heated. Damper 224 prevents air from flowing into ductwork 222 unless blower 244 is operating so as to cause intentional clrculation throughout the entire space being heated. ~eing normally open, ~amper 230 permits heated air to flow into the room in which unit 200 is located under gravity rlow, but that damper closes when circulation blower 244 begins to operate. Damper 238, wllich ls normally open, allows a greater flow of air to enter the unit and be circulated than otherwise would be the case when circulation blower 244 is de-energized so that all heat is by virtue of gravity flow. That increased flow of air occurs by reason of the fact that blower 244 is in itself a restriction in the return-air ductwork. It also bypasses the blocking effect of the usual back-draft damper installed in the return air duct when the overall heating system is installed in parallel with some kind of conventional furnace. It may be noted that damper 224 also serves as a back-dra:~t damper with respect to the paralleled conventional furnace when the latter unit is operating instead Or unit 200.

Damper 218 is normally open and is located on the suction side of the outside air blower supply system and ahead of damper 214. Thus, damper 218 allows make-up or pressurizing air to enter the furnace-room-type of installation unless the . 5 ultimate outside air blower is turned on, in which case that latter blower furnishes the make-up air.
When a fire is first ignited and heat begins to be produced, air is clrculated through damper 238 from within the space being heated. ~hat ci~culated air passes through unit 200 and back into the interior space through damper 230. In the absence of availa~le electrical power, that mode of operation would continue. With power avallable, however, thls gravlty-flow mode of operatio.n continues only until the heat produced brings unit 200 up to a pre-selected temperature, such as 150F, at which point clrculation blower 2411 automatically is energized in accordance with the teachings of the aforesaid patent.
The pressure of air forced to circulate by blower 244 automatically effects the closing of dampers 230 and 238, while damper 224 automatically opens so that air returned through ductwork 242 is fed through unit 200 in heat-exchanging relationship and distributed throughout the interior by way of ductwork 222. Thermal sensitive switch 226 pre~erably is adjusted so that when the heated air temperature, as measured at the entrance to ductwork 222, exceeds a value of approximately 180F, outside air supply blower 220 is energized to operate at a lower speed. Upon the beginning of operation o~ blower 220, damper 230 automatically closes and damper 214 opens itself to allow cooler air to enter plenum 208 Preferably, thermal-switch 226 is of a two~stage variety~ including a second pair o~ switch contacts that automatically activate air blower 200 into a still higher speed o~ operatlon when the sensed temperature exceeds a yet higher value such as 200F.
5 In the manner of the system of the prior patent, and although not shown in Flgures 10-14, operation of the circulation air system also contemplates operation of the combustion air supply system which also has an outside source. Thus, the signal. representing temperature as sensed by switch 226 may be incorporated in the combustion air supply system in order to shut off that air blower after interior space temperature has been reached, so as thereby to enable the rate of combustion to subside.
When firebox 204.has cooled suf~iciently that the temperature is back to the exemplary value of 150F, circulation blower 244 is de-energized, damper 224 thereupon closes, and dampers 230 and 238 open so that unit 200 operates under a gravity-flow condition. If` that is insufficient to maintain interior space temperature, the thermostatically-controlled system of' the prior patent serves to energize the combustion air blower and achieve a repeat of the heating cycle.
It may be noted that jacket 202 and plenum chamber 208 are so constructed as to permlt the different systems to be connect.ed to either side of the unit as is most convenient for a given installation. That is, damper 224 and ductwork 222 may be exchanged in position with damper 214 and plenum 216.
Similarly, damper 232 and its duct 234 may be interchanged in location with adaptor 240 ~nd plenum 23~ In this connection, adaptor 240 desirably may include adjustable air-directing vanes that may be set, regardless of which side Or unit 200 is ~6:~Zl connected to the adaptor~ for directing the circulated air most favorably to spread over the exposed surfaces of firebox 204.
Also supporting su_h interchangeably, as between opposite sides of unit 200~ is a deflector 250 pivoted centrally at 252 and located in the space behind firebox 204 and yet inside ~acket 202. Generally,` deflector 250 serves the same purpose as deflector assembly 84 shown in the aforesaid patent and in Figure 3. In this case, however, deflector ~50 may be ad~usted about pivot 252 so a!~ to be ln the most appropriate position dependlng upon which side of unit 200 is fed from plenum 208. Otherwise, deflector 250 may be structured in the same manner as deflector asse~bly 84 of the patent.
As shown in Figure 12, a shield or cover 256 preferably is included to enclose door extension or frame 55 on both sides and the top and then extend on up the front of the unit into plenum 208 Shield 256 serves to gather heat from the door-frame area and discharge it into the room through the front opening of the plenum.
As shown only in ~igure 11 for clarity, an additional duct 260 preferably is included to lead from another floor register 262 and continue into the region above plenum 208 and at a location above the discharge opening of the plenum through damper 214. Duct 260 provides a layer of room temperature air between the heated air being discharged from plenum 208 and the overlying ceiling of the room. When operating on gravity flow, particularly when that operation is the only mode available during lack of electrical power, the additional layer of room ~ 29 ~

air above the plenum assists in p~eVenting excesSi~e heat from rising into the ceilin~ area. Duct 260 also serves to create a circular movement of air from the region of the ceiling toward the floor are2~ and that seeks to warm the latter. The same principle may be enlarged upon so that duct 260 also serves to pull down more highly-heated alr that tends to collect toward the top of rooms with very high ceilings.
In Figure 15, chi~neys 270 and 271 are secured on the outside of firebo~{ 204 ad~acent to respective sides of opening 20. At its bottom end, chimney 270 is coupled into one end of manifold 6;'. Similarly, the bottom of chimne~ 271 is coupled into the other end of the manifold. Chimneys 270 and 271 serve to increase the draft of air through grate tubes 61 while the heating uni.t system is operating under a gravity-flow condition of air circulation. Chimneys 270 and 271 are installed in the space betweèn firebox 204 and ~acket 202. The upper ends of chimneys 270 and 271 are open so as to exhaust that air into the plenum area above firebox 204.
~s also indicated in Figure 15, a double-sided baffle 274 preferably is included interiorly intermediate the length of manifold 63. Baffle 274 serves to lessen turbulence of the air exiting from hollow grate tubes 61 and thereby to increase the gravity flow of air into the chimney.
With reference again to ~igure 3 an apertured plate 276 preferably spans the distance between upper wall 32 of the primary combustion area and upper wall port~ron 26. Plate 276 serves as a spark arrester, inhibiting the upward flowing of course sparks, such as from burning paper, and preventing them from escaping up the stack and onto the rool' of the building.

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Such materials simply fall back into the primary combustion area.
~ arious modifications, of course, may be made at many different points in the structure. ~or example, the primary combustion area may be enlarged by extending rear wall 28 to a higher level and bringlng the upper portion 32 of the rear wall more forwardly to form a throat. A series of tubes or chambers then may extent into the present plenum area sc that the arrangement forms a dome or heat-chamber effect in the top o~ the unit, with the room air passing around those tubes or chambers. Such an arrangement should be even more efficient because of the trapping of heat from above the chimney out~et.
The system lends`itself well to cooperation with an underground tempering system. As is well known, the temperature in the ground, below the frost line, remains rather constant, a representative value being around 59F. In a manner analogous t;o that employed in o~her known heating systems, that ground temperature can be used to temper outside air, warming it in the winter and cooling it ln the summer. Such an arrangement can be employed in cor~Junctio~ with the aforedescribed outside air blower by cooling room air and adding Just enough outside air for make up.
Such a tempering system may be located beneath the aforementioned furnace room The structure of a suitable tempering system need not be complicated nor expensive. A
row of cement blocks may be used to form one or more multi-celled air chambers. In one example, outside air is inletted through a duct to such a chamber. Air also is inletted through 2iZl , a duct from the interior space of the building under control by the unit. ~nother duct leads outwardly from the thus-formed air chamber and is connected to the outside air blower already discussed, such as blo-~er 220.
When blower 220 is inoperative, make-up air ente~s through the outside a~r duct, travels through the interiors of the blo,-ks, and is warned. That warmed air then ls conveyed by ductwork so as to enter through damper 218 of the system of Figure 10. When a cooler make-up air supply is called for, blower 220 is energized and both room air through one duct and outside air is drawn through the tempering unit. In normal operation, such operation lnhibits the build-up of frost in the intake of the tempering system. If necessary~
however, an additional exhau'st farl ma;y be included for the supply of further ventilation by automatically letting more outside air into the tempering system.
The inclusion of a tempering system in the overall heating arrangement enables the user to increase the supply of fresh air during cold weather while reducing the amount of additional fuel needed to accommodate that fresh air. In the manner of known underground ternpering systems, operation of only the circu'~ation system in the summer, wlth the admission of outside air through the tempering unit, performs the functlon of air conditioning.
It will be observed that the varlous additions depicted and described afford, at th~ outset, a number of improvements to the baslc heating system of the prior patent.
Even though the approach of that patent ~as been successfully employed in a number of installations, significant advancement 1~i2121 , has been disclosed. In addition, a variety of specific lmprovements are of such a nature as to admit of utility in connection with still different heating systems.
In many cases, manufacture is facilitated by permitting reversibility of points of connection of different ductwork and other conponents. Moreover, the interconnection of adapting parts is ~;uch that essentially all operating portions of the system may be factory pre-assembled. All that is then required durir.g field installation is the setting of the unit and the coupling thereto of conventionally-distributed ductwork.
Several aspects of the new disclosure contribute to increased safety. Moreover, automatic use of gravity-flow air circulation, when suffi~ient, has been af`forded in a way which is safe even when the heatLng system is connected into a building ductwork system that also may be supplied with heat from a conventional furnace. Of course, the use of gravity flow when appropriate serves to reduce energy costs in operating blowers or fans.
While particular embodiments of the invention have been shown and described, and numerous modifications and alternatives have been suggested, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall wilhin the true spirit and scope of theinvention

Claims (14)

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

1. For use in a heating system which includes a com-bustion chamber in which hot gases are delivered into a stack and which has a venting control system that includes:
an inner tube communicating at its inlet and with said chamber for receipt of said gases;
an outer tube encircling said inner tube and coupled into said stack at its outlet end;
a conduit opening laterally through the wall of said outer tube;
and a weighted damper disposed in said conduit in the path of air inletted through the outer end of said conduit;
said inner tube extending upwardly above said conduit, disposing the outlet end of said inner tube at an elevation greater than the elevation of the uppermost side of said conduit.

2. A venting control system as defined in claim 1 in which said outlet end of said inner tube is disposed below the outlet end of said outer tube.

3. A venting control system as defined in claim 2 in which said outlet end of said inner tube has a width less than the width of said stack.

4. A venting control system as defined in claim 3 in which the outlet end of said outer tube has a width greater than the width of said stack.

5. The venting control system as defined in claim 1 further including means defining a wall substantially closing the space between said inner and outer tubes at a location be-tween said conduit and said combustion chamber.

6. A venting control system as defined in claim 5 in which said inner tube has a width less than the width of said outer tube.

7. A venting control system as defined in claim 1 in which said inner tube has a width less than the width of said stack.

8. A venting control system as defined in claim 7 in which said inner tube terminates below said stack.

9. A venting control system as defined in claim 7 in which said outer tube has a width greater than said width of said stack.

10. A venting control system as defined in claim 1 further including:
sensing means responsive to the temperature in the vicinity of said tubes;
locking means for holding said damper in a closed position;
and means controlled by said sensing means for opera-ting said locking means in correspondence with activity within said combustion chamber.

11. A venting control system as defined in claim 10 in which said controlled means effects closing of said damper automatically in response to the absence of significant com-bustion in said chamber.

12. A venting control system as defined in claim 10 in which said combustion chamber is fed with air from outside the space to which heat is supplied by said system, and which includes means for interrupting the supply of said air in response to reduction of said temperature below a pre-selected amount.

13. A venting control system as defined in claim 1 wherein both of said inner and said outer tubes are generally of an L-shape with one leg of each projecting toward said stack and the other leg of each being disposed generally horizontally, said conduit being generally horizontally disposed and opening into an intermediate portion of said outer tube.

14. A venting control system as defined in claim 13 in which said inner tube includes a selectively openable door facing said conduit and accessible therethrough.