US3326265A - Radiant heating means - Google Patents

Description

June 20, 1967 PAULlN 3,326,265

RADIANT HEATING MEANS Filed March 16, 1965 ZSheets-Sheet 1 INVENTOR RAY J. PAULIN BY 7/02, .1 v (j/ ATTORNEYS June 20, 1967 I R. J PAULIN 3,326,265

RADIANT HEATING MEANS Filed Marqh 16, 1965 2 Sheets-Sheet 2 Fig. 2

INVENTOR RAY J. PAULIN ATTORNEYS United States Patent 3,326,265 RADIANT HEATING MEANS Ray J. Paulin, 1359 Yellowstone Road, Cleveland Heights, Ohio 44118 Filed Mar. 16, 1965, Ser. No. 440,158 1 Claim. (Cl. 158-99) This application is a continuation-in-part of my copending application, Ser. No. 279,247, filed May 9, 1963 now abandoned.

This invention relates to heating devices and, more particularly, to a device for mixing fuel gas and air and burning the mixture to convert the chemical energy of the m1xture to radiant energy.

The invention is particularly concerned with, although not limited to, small, portable, infrared emitting gas burners for heating land/or cooking purposes. Conventlonal devices for these purposes include a source of pressurized gas, such as bottled propane, and range type burner units. These conventional units, although satisfactory ifOl' some purposes, produce heating and/ or cooking flames that are inefficient and expensive with regard to fuel consumption. Moreover, the improper operation of these conventional units in confined areas, such as tents and cabins, may produce products of incomplete combustion such as carbon monoxide. Those unfamiliar wlth flame characteristics which indicate incomplete combustion or the improper use of primary and/ or secondary air would not be forewarned as to the production of this lethal gas.

The present invention, on the other hand, relies on the emission of infrared or radiant heat as an energy source for heating and/or cooking purposes. The device does not produce a visible flame but produces a characteristic lnfrared glow that indicates a proper fuel: air ratio and substantially complete combustion that results in maximum fuel economy and little or no toxicity of combustion products.

Gas fueled, infrared emitting heaters are in use today primarily as industrial space heaters. These heaters, however, may be ineflicient in that the maximum heat absorptive and emissive surface of the unit may not be utilized because the device does not sufficiently uniformly mix the gas fuel and air prior to combustion, or does not deliver this mixture at a substantially uniformly constant pressure to the combustion chamber, zone, or face of the device.

Other conventional devices include a perforated ceramic burner plate. The ceramic burner plates were intended to solve the problems of flashback and incomplete combustion but it has been found that such burner plates overcome these problems only if they are provided with perforations having a consistently uniform cross sectional opening. Even if the quality of these ceramic plates is carefully maintained, the perforations tend to become clogged with lint and/ or carbon. Furthermore, ceramic burner plates are expensive and easily broken.

In order to overcome the deficiencies of heat generators having ceramic burner plates, infrared generators have been proposed which include screens as the burner grid means. Exemplary of such infrared generators are the generators set forth in the US. patents to Lambert (3,040,805) and Mentel et al. (3,084,736). These patentees effectively overcame the problem of providing an infrared generator without an expensive ceramic burner plate by replacing such an element with wire mesh screens. These patentees, however, provide burner screen units which comprise a plurality of superposed mesh screens. It was believed by these patentees that, in addition to a single Patented June 20, 1967 burner screen, other screen or screens were necessary to prevent flashback or combustion in the bodyof the generator. In fact, one patentee found that incandescence would not, as a practical matter, be possible in the absence of additional screening means.

The foregoing prior art infrared generators produced a desirable, even blanket of flame across the burner screen. However, the additional screening material employed increases the unit cost of each infrared generator. Furthermore, the provision of a plurality of screens as a burner screen means proportionately increases the tendency for the burner screen to become clogged with lint and/ or carbon and necessitates an additional screen or filter across the primary air inlet.

According to the present invention, a grid or burner screen means is provided which consists of a single screen. A reverberatory screen is spaced a uniform distance from the single burner screen and the problem of flashback or combustion within the generator body is eliminated by providing the single burner screen with a concave surface with respect to the interior of the generator.

It is, therefore, an object of this invention to overcome many of these prior art problems.

It is a more specific object of the present invention to provide a radiant heater having means for intimately mixing primary air and fuel gas and for delivering this mixture to a combustion chamber at a substantially uniformly constant pressure, and having a single burner screen that is shaped to eliminate flashback or combustion within the body of the heater.

It is a further object of this invention to provide a radiant energy emitting device that may be utilized either as a space heater or as a cooking device.

It is another object of this invention to provide a method of maximizing the conversion to radiant energy of chemical energy of a hydrocarbon containing fuel gas.

Other objects and advantages of the invention will become more readily apparent when the same is considered in connection with the following detailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a radiant heating device according to this invention;

FIG. 2 is a fragmentary elevational view of the device shown in FIG. 1 with portions broken away for clarity;

FIG. 3 is a fragmentary view of the device, the plane of the view being indicated by the line 33 in FIG. 2; and

FIG. 4 is a fragmentary sectional view of the device, the plane of the section being indicated by the line 44 in FIG. 2.

Referring now to the drawings, a radiant heating device 10 is illustrated. The heating device 10 includes a cylinder 11 containing pressurized fuel gas such as propane, a fuel gas tube 12, a fuel delivery pipe 13, a body portion or conduit 14, a reflector pan 15, and a shroud or cover 16.

A suitable flow control valve 17 is fixed to the mouth of the cylinder 11 and the volume of fuel gas admitted to the system may be regulated by a thumbscrew 18. The tube 12 is in fluid communication with the flow control valve 17 and has a venturi nozzle 19 formed on its other end. The venturi nozzle 19 extends into the pipe 13 and is retained therein by a nut 20. The pipe 13 is provided with primar air inlet openings 23 so that fuel gas flowing through the venturi nozzle 19 draws air through the openings 23 and provides a maximum entrainment of air in the fuel gas stream with a minimum gas pressure.

The fuel gas and entrained air flow through the fuel delivery pipe 13 to a fuel delivery chamber 24 at the end of the pipe 13. From the fuel delivery chamber 3 24, the fuel gas and air enter the conduit 14 to which the pipe 13 is fixed. As may be seen in FIG. 2, the conduit 14 comprises a lower plenum chamber 25 and an upper plenum chamber 26. The lower plenum chamber 25 is defined by'a substantially cylindrical sidewall 27 and the upper plenum chamber 26 is defined by a substantially cylindrical sidewall 28 which has a larger diameter than the sidewall 27. The sidewall 27 and/or the sidewall 28 may be frustrums of right circular cones, but any normal section of the sidewall 27 must have a smaller area than the area of any normal section of the sidewall 28. Moreover, the fuel delivery chamber 24 has a smaller diameter than the diameter of the sidewall 27.

The plenum chambers 25 and 26 are separated by a baffle screen 29 which is spot-welded to an annular shoulder 30 between the sidewalls 27 and 28. The baffle screen 29 comprises a lattice defining a multiplicity of diamondshaped openings 31.

As the fuel gas and air stream flows from the fuel delivery chamber 24 to the lower plenum chamber 25, the stream is expanded and the pressure rises. As the stream flows through the baffle 29 to the upper plenum chamber 26, the fuel gas and air are intimately mixed and the intimate mixture is further expanded and is increased in pressure substantially simultaneously with the intimate mixing. The fuel gas and air are not only intimately mixed in this manner, but the substantially simultaneous expansion of the mixture induces the equalization of fuel gas and air pressure throughout the transverse extent of the upper plenum chamber 26.

The top of the upper plenum chamber 26 is closed by a burner screen means comprising a single grid screen 32. The grid screen 32 has a relatively fine mesh, such as 40 x 60, and may be fabricated from a heat resistant material such as Inconel.

The openings in the grid screen 32 comprise a multiplicity of burner ports and the fuel-air mixture flowing through these burner ports at substantially constant pressure over the entire surface of the screen 32 may be ignited by a match inserted through an opening 33 in the reflector pan 15. Since the access of secondary air to these burner ports is somewhat restricted, the majority of the air necessary for complete combustion of the fuel "gas is admitted as primary air through the air inlet openings 23. The size of the openings 23 is selected to prevent an excessively high or an excessively low primary airzgas ratio. If this ratio is too low, the flame lengthens unduly and carbon monoxide may be produced. Furthermore, the flame tips will turn yellow and smoke or carbon will result. If this ratio is too high, strikebacks may result, with the consequent production of carbon monoxide.

The airzfuel ratio is adjusted so that the flame is confined to a combustion chamber 34 and appears therein as a blue sheet. The combustion chamber 34 is defined by the grid screen 32 and by a reverberatory screen 35 which is mounted in closely spaced relationship to the grid screen 32.

The reverberatory screen 35 has a relatively coarse mesh, such as x 10, and may be fabricated from a heat resistant material such as Inconel.

The screen 35 absorbs heat from the flames in the combustion chamber 34 and emits this absorbed heat as radiant energy. The screen 35, therefore, is spaced from the screen 32 so that the absorptivity of the screen 35 substantially corresponds to its emissivity. Since the flame is intended to be confined entirely within the combustion chamber 34, the presence of flames above the screen 35 is a convenient indicator as to improper operation of the device 10.

As may be seen most clearly in FIG. 2, the screens 32 and '35 are spaced a uniform distance apart across the upper mouth of the plenum chamber 26. The screens 32 and 35, moreover, are shaped so that they each have a concave surface with respect to the interior of the body portion 14. It has been found that such concavity and d uniform spacing are essential to the efficient operation of the burner and it has been found further that such concavity substantially eliminates flashback or combustion in the body portion 14.

The screen 35 is preferably formed as a cone having a fiat, annular rim 35a and the screen 32 is spot-welded to the rim 35a and extends across the base of the cone formed by the screen 35. As was previously stated, the screens 32 and 35 are spaced a uniform distance apart across the upper mouth of the plenum chamber 26 and, therefore, have similar shapes. However, since the screen 32 is a relatively fine mesh screen and mechanical forming operations would tend to alter the total open area of the screen 32 by stretching and/or flattening some of the wires, it has been found that, if the screen 32 is spotwelded across the base of the screen 35 while the screen 32 is flat (as is indicated in phantom outline in FIG. 2), the screen 32 will bulge upwardly by its own expansion and by the pressure of the gas on its bottom surface during the initial operation of the device. Thus, the screen 32 is seasoned to conform to its operable shape prior to efficient use of the device. Since the screen 32 is peripherally fixed to the screen 35, any tendency of the screen 32 to expand in a flat plane or to return to its flat condition is obviated.

The screen assembly comprising the screens 32 and 35 is peripherally pressed between a flange 28a formed at the upper mouth of the plenum chamber 26 and a flange 15a formed at the lower rim of the reflector pan 15. A plurality of screws 38 extend through the flanges 15a and 28a and through the screen assembly and the cover 16.

If the device 10 is to be used for cooking purposes, a grate 39 may be snapped over the rim of the pan 15 as is shown in FIG. 1. Even if the device 10 is tobe used as a space'heater, however, the grate 39 may be employed to prevent accidental contact with the reverberatory screen 35.

The grate 39 includes a plurality of depending legs 39a. The grate 39 may be removed from the reflector pan 15, inverted, and replaced on the pan 15 so that the legs 39a extend away from the pan 15. The entire unit may then be inverted so that it is supported by the legs 39a. In such a position the heat may be directed downwardly and food placed under the pan 15 may be cooked without dripping into the unit.

As is shown in FIGS. 2 and 4, the device 10 is mounted on a tripod 40 by a clamp 41 which is welded to the bottom of the plenum chamber 25. For pot or pan cooking purposes, the tripod 40 may support the device 10 in the illustrated upright position. For use as a radiant heater, or for indirect side broiling, the tripod 40 may be tipped so that a handle 41 and two tripod legs rest on the ground to support the device 10. If the device 10 is tipped or inverted, the tank 11 should be reoriented by loosening the nut 20 so that the tank is in a substantially upright position during operation.

The scope of the invention is not limited to the slavish imitation of all the structural and operative details mentioned above. These have been given merely by way of an example of a presently preferred embodiment of the invention.

What is claimed is:

A radiant heater comprising a cylindrical conduit, a fuel delivery chamber fixed to one end of said conduit, said conduit including a first plenum chamber having a cross sectional area which is greater than the cross sectional area of said fuel delivery chamber, said conduit including a second plenum chamber adjacent said first plenum chamber and having a cross sectional area that is greater than the cross sectional area of said first plenum chamber, said heater having altogether three screens, said screens consisting of a single baflle screen peripherally fixed within said conduit and spaced from said fuel delivery chamber to define said first plenum chamber Within said conduit, a single grid screen Within said conduit and spaced from said baffie screen to define said second plenum chamber within said conduit, and a single reverberatory screen within said conduit and spaced from said grid screen a uniform distance, said uniform distance being substantially less than the distance between said baflie screen and said grid screen to define a combustion chamber Within said conduit, said reverberatory and grid screens being fixed to each other at their peripheries and being fixed as a unit to the conduit, said reverberatory screen and said grid screen having concave surfaces with respect to the interior of said conduit, said grid screen being originally planar with respect to the interior of said conduit and assuming said concave surface upon the application of gas pressure and heat.

References Cited UNITED STATES PATENTS 3,084,736 4/1963 Mentel et al. 3,114,411 12/1963 Dadas 158-116 3,139,879 7/1964 Bauer et al.

FOREIGN PATENTS 239,274 12/ 1960 Australia.

673,616 11/1963 Canada. 1,129,123 9/1956 France.

494,087 10/ 1938 Great Britain.

893,554 4/1962 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

H. B. RAMEY, Assistant Examiner.

Dedication 3,326,265.R0y J. Paulz'n, Cleveland Heights, Ohio. RADIANT HEATING MEANS. Patent dated June 20, 1967. Dedication filed Mar. 4, 1977, by the assignee, Paulin Products ompcmy. Hereby dedicates to the Public the remaining term of said patent.

[Ofiicial Gazette May 3, 1.977.]

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