For many years a standard masonry fireplace cavity whether of brick, stone, or other non-flammable materials usually required the standard dimensions of 36″ wide, 30″ high, 22″deep, and a rear dimension width of 24″. Early fireplaces had no “closure” doors and were “open” but would eventually accommodate a screen for fire prevention from flying sparks. Earlier colonial era fireplaces of two centuries ago included a one or two level height of stone or bricks on the hearth floor on each side called “hobs”. These hobs provided the several functions of a warming shelf, support to keep logs above the hearth “floor” and a more efficient way to confine and direct the draft of air more efficiently to the burning flame area by “closing-in” the space between the ends of the logs and the fireplace sides. Draft control consisted of minimal or no damper adjustment in order to control heat radiation, and the hobs helped direct draft air more effectively to the combustion flame area. In more modern days a front enclosure was employed utilizing hinged glass doors to allow easier replenishment of fuels for combustion. In recent years we have had a resurgent interest in obtaining better fireplace inserts, many looking like a smaller “Franklin-Type” design, (an iron-sided, heat-radiating, free-standing box with draft control doors).
My “improvement in the art” relates to a slide-in fireplace insert system placed into a standard residential fireplace opening and intended for burning fossil fuels such as wood, coal, charcoal, brickettes, wood pellets, etc, or related consumables to produce “room heat”. The insert system comprises three components: a control/base, a “surround” front closure and a tubing cluster.
1. Control/base—The heart of the insert system, the control/base has two plenum chambers (fixedly attached to the rear of the front control/base panel each with an axial suction fan, each plenum with a plurality of air exit holes on the top surface. The control/base has a central major hinged air draft control door said hinged air draft control also containing two fine-tuning air draft adjustments located thereon and a plurality of air exit holes located above the draft door opening. Also included are the necessary switches, controls and electric power supply cord. It is essential to point out that the ash pan and the grate, while not fixedly attached to the control/base itself are considered vital parts thereof.
At this point it seems prudent to point out that the plenum chambers and hobs are the same physical items the only difference being in function. The hobs were historically of “solid” stone and used to refer to a centuries-old use as an aid to get draft air more efficiently conducted to the flame area, whereas the plenums are asymetric rectangular hollow air chambers used to divide the intake plenum air volume into separate columns of moving air with the aid of its axial air intake fan. The generally parallel “common” side of each of the two plenum chambers not only define the walls of the hobs for air draft supply, but effectively “center” the ash pan between them.
2. Front closure—An important yet most under-developed area of all similar structures to date. Most have bifold doors, some are simple center-opening but all used to the present are most inefficient especially those with thicker ( 3/16″) tempered glass. The “R” factor is bad enough with (⅛″) clear tempered glass. In tests done to date the most efficient medium for heat radiation appears to be no glass at all.
3. The Tubing Cluster—the said five-sided box arrangement of pipes (or metal tubings) has one function; to connect the air outlets of the said plenum chambers to the said air exit outlets in the face of the control base and exposing as much as possible of their heat absorbing exterior metal surfaces in each of the five planes to the heat-radiating source in order to provide a maximum heated air volume exiting into the attendant room, the lower plane of tubing embedded within the control/base just beneath the grate.
My “improvement in the art” relates to a slide-in fireplace insert system placed into a standard residential fireplace opening and intended for burning fossil fuels such as wood, coal, brickettes, charcoal, etc, or related consumables.
The control/base contains two plenum chambers and each with a suction fan pulling air into the said chamber and a plurality of air exiting holes aligned along the top surface. It is through these exiting holes that plenum air is divided into separate generally parallel moving columns of air as they start their collective separate heating journeys, each said moving column of air in its own individual air-confining metal heat-absorbing tubing fixedly attached at each end. The said box structure has an equal number of corresponding air inlet tubes to be fixedly attached to each respective plenum air supply source outlets. From each plenum the air columns progress from the hobs up the right and left sides within the fireplace cavity. The total of the said tubing arrangements make a 90 degree bend to converge toward each other over and above the said heat-radiating source (centered in the fireplace cavity), then the said tubing begin several convergences through 90 degrees toward the rear of the fireplace cavity, down the back of the fireplace cavity, and the said tubing (fixedly attached) to finally converge arriving at the said exit openings in the control front for the said heated air columns to be exited forwardly in a horizontal plane over a fragrance strip into the attendant room between the heat-radiating grate level above, and the ash collector pan level below. When the glowing red hot coals get too small for heat radiation they fall through the mesh openings in the grate and drop into the said ash collector pan beneath. It is important to know that when this said insert is in use any draft control built into the bottom of the chimney flue is no longer needed. All draft is now controlled by the fireplace insert system flue controls on the front of the said control/base. When the said insert is installed and in use, any chimney “built-in” flue controls should be permanently set on “open”.
An unexpected benefit is realized when the fire is “low” and few glowing coals are left. Just adding new wood or combustible fuel on top of those glowing coals, and raising the major draft door slightly will divert part of the exiting air flow and redirect that said air flow back through the mesh grate thereby fanning the embers “into life”, igniting the newly added fuel.
An optional further improvement in the art also utilizes a specially configured electrical heating rod (eg. “Calrod” or equivalent) formed to be inserted into the said horizontal forwardly disposed air exiting pipes and able to supply heat into the said attendant room even when no flame-type ongoing heat-radiating source through the woven wire mesh grate is utilized.
Number | Name | Date | Kind |
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3001521 | Reilly | Sep 1961 | A |
4088114 | Johnson | May 1978 | A |
4250867 | Andersen et al. | Feb 1981 | A |
4252106 | Estes | Feb 1981 | A |
Number | Date | Country | |
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20080041361 A1 | Feb 2008 | US |