Patent Application
20090032012
The present application is directed to an improved radiant gas burner unit, and more particularly to a shallow radiant gas burner unit with side gas inlets and improved heat distribution.
The use of radiant burners is common in connection with conventional cooking and heating systems. The radiating surface of the burner is typically a ceramic plate with densely spaced holes through which a combustible mixture of gas and air flows. The air/gas mixture is ignited at the ceramic surface and combustion takes place at the surface as well as partially in the holes. The velocity of the air/gas mixture through the holes is no less than the backward flame propagation velocity, so that the flame does not travel into the plenum behind the ceramic plate.
Past systems of the type disclosed, for example, in U.S. Pat. No. 6,012,444 provide a radiant burner which is approximately 28 inches by 12 inches. Such units disperse the air/gas mixture within a chamber adjacent to the ceramic plate. The air/gas mixture is dispersed by gas tubes of unequal length positioned longitudinally within the chamber, which dispersion attempts to provide equal gas distribution within the chamber and thus equal heating across and throughout the ceramic plate or plates.
It is important to assure equal heating across and throughout the surface of the ceramic plate to provide maximum and optimum radiation from all parts of the surface, and thus even cooking or heating. At the same time, the flammable gas under the ceramic plate must be the proper mixture of air and gas. For example, methane gas and air mixtures may have a variety of mixture ratios, but radiation efficiency, although difficult to measure, is believed to be optimal for complete combustion at ratios of approximately 10:1. For propane gas and air mixtures, radiation efficiency is more likely optimal for complete combustion at ratios of approximately 24:1.
A high velocity gas jet induces a sufficient quantity of air into the mixing tube or diffuser tube. The quantity of air/gas mixture needed to supply the entire radiating ceramic surface of the unit requires the mixing or diffuser tube to have a relatively large diameter.
In prior art burner units, the large mixing or diffuser tube diameter was responsible for the depth or thickness of the burner unit body behind the ceramic radiating surface, i.e. the overall thickness of the unit. Thus, such prior art burner units are generally thick or deep in the direction “d,” or the height or thickness of the burner unit. This height dimension limits use of the burner units to ovens and other applications of conventional size, which are of considerable bulk.
The burner unit disclosed here is an improved radiant burner that is very shallow in the direction perpendicular to the radiating surface, or a thin radiating burner unit. The decreased size of the unit is enabled by the use of multiple, smaller diameter, shorter mixing tubes, extending across the width of the burner unit, and receiving a fuel/air mixture from multiple gas sources along the side of the burner unit. Additionally, the burner unit of the present application has been shown though experimentation to provide improved heat distribution.
The burner of the present application is a shallow radiating unit that is compatible with outdoor grills which are narrow or slender, or with small sized cooking systems where limited vertical space or height is available. Ovens for boats or recreational vehicles are good examples of cooking systems requiring space limited radiant burner units. In such units, broiling may be performed from the top, over the items to be cooked, while heating may be performed from the bottom, under the items to be cooked. The present unit may be used in either position, or moved between positions. Additionally, the small size of the present improved burner unit may enable the unit to be positioned within a lid or the cover of a conventional grill to provide enhanced broiling options.
Unlike prior art cooking systems which supply or inject the air/gas mixture at the end of the unit to a large single mixing tube running along the majority of the length of the unit, the air/gas mixture is introduced to the present device via multiple inlets, but preferably 3 or more side inlets. Thus, all portions of the ceramic radiating surface are fed equally well and uniform radiation takes place, and in a smaller sized burner unit which was not previously possible.
A gas supply or gas manifold along the edge of the unit guides the gas to the appropriate gas orifice location where inlet air is then induced into the mixing tube. The multiple mixing tubes each handle only a small quantity of air/gas mixture. As a result, the diameter of the mixing tubes of the present device is much smaller. The tubes are also much shorter in length, as compared to conventional prior art radiant burner units. While the use of venturi diffuser tubes is possible, the use of single diameter mixing tubes also accomplishes the necessary air/gas mixture intake just as effectively and at lower cost and ease of manufacture. Baffles are also used in positions intermediate the ceramic plates and the mixing tubes to further enhance the dispersion of the air/gas mixture across the unit. Further, the baffles of the present application are more simple in design than those of the prior art. Thus, the smaller diameter, shorter mixing tubes, together with the more limited mixing and redirecting baffles, permit a much shallower unit. Using the geometry mentioned, the appropriate air/gas mixture is distributed for proper operation across the whole unit.
The present application provides an improved radiant gas burner unit 10. General and partial views of the present unit 10 are shown in FIGS. 2 and 4-7, while a prior art radiant gas burner unit is depicted in
The mixing tubes 14 are additionally supported spaced from a long side wall 16 within the box 12 on support members 18. The multiple mixing tubes 14 illustrated are less than approximately 6 inches in length, and more preferably between 4 and 5 inches, and have an approximate external diameter of 7/8 inches. The described dimensions in the illustrated embodiment are known to obtain the desired temperature output and efficiency from the present improved infrared gas burner unit 10, and it is likewise known that minor adjustments to such dimensions may obtain similar, but alternative desired results.
A simple baffle 20 is provided over the ends 14a of the mixing tubes 14 which are spaced from the wall of the box 12 supporting the openings 15, and through which the air/gas mixture exits the mixing tubes 14. The baffle 20 may be secured along a side wall 22 opposite the side wall 16, either by welding or other fastening means, and, either alternatively or in addition, the baffle 20 may be supported on the ends 14a of the mixing tubes 14. The simple baffle 20 may be provided as solid plate material, for example, of stainless steel as in
The second half 12b of the shallow box 12 supports an infrared ceramic burner or plate 24. As shown in
The
As shown in
High temperature felt 34 may be used as a seal against leakage again of the air/gas mixture. As shown in
During operation of the unit 12, the gas supply 36 positioned along the longest side wall of the shallow box 12, supplies the desired fuel to the mixing tubes 14 under atmospheric pressures. The desired fuel may be methane, butane, propane and/or natural gas, as well as alternate fuels. Between the gas supply 36 and an open end 14b of the mixing tubes 14, a gap 38 is required. The gap 38 enables the entering fuel to mix with air provided via the gap 38, such that the desired air/gas mixture is supplied to the interior of the shallow box 12 via the diffuser tubes 14. Among a variety of factors (such as diameter of the mixing tube opening), the size of the gap 38 is dependent on the desired air/gas mixture, for example 12:1 for methane, or 37:1 for butane, to be supplied to the unit 10 to enable the desired gas burning efficiency and the desired heat to be provided by the unit 10. Gaps 38 may be provided in the range of 0.0 to 0.5 inches.
The overall size of the present improved radiant gas burner 10 is preferably less than approximately 17 inches in length, less than approximately 6 inches in width, and less than approximately 2 inches in height. In an even more preferred embodiment, the overall dimensions of the radiant gas burner unit 10 is approximately 15 inches in length, approximately 5.5 inches in width and approximately 1.5 inches in height. In this preferred embodiment, the mixing tubes have an external diameter of approximately 1 inch and each of four (4) individual ceramic grid plates are approximately 3.75 inches wide and 5.5 inches wide and 0.5 inches thick.
Attachment flanges 28 of any type and dimension may extend from or be attached to the shallow box 12, including additional strengthening flanges F of the type shown in
Additional advantages and modifications to the present improved gas burner unit 10 will be readily apparent to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details or representative examples described. Accordingly, while care has been taken to provide details concerning the specific preferred features of the present improved gas burner unit, departures may be made from the detail described here without departing from the spirit or scope of the disclosed general inventive concept and the following claims.
