Head assembly for liquid fuel catalytic beater
United States Patent Hefling et al. Apr. 8, 1975 [54] HEAD ASSEMBLY FOR LIQUID FUEL 3,240,256 3/l966 Binkley el al 431/328 CATALYTIC BEATER 3,343,586 9/1967 Berchtold et a] 431/350 3,457,02I 7/1969 Gladden et al. .r 431/350 [75] Inventors: Dennis Very! g; Richard 3,734,682 5/1973 May 431 329 Douglas Curtis; Floyd 0. Cruver, Jr., all of Wichita, Kans; David J. FOREIGN PATENTS R APPLICATIONS Gladden, Dearbom- Mlchl,095,865 I2/l954 France 431/328 [73] Assignee: The Coleman Company, Inc.,  
  wlch&#39;mi Kans- Primary Examiner-Carroll B. Dority, Jr. 22 Filed; No 5 1973 mmiey, Agent, or FirmDawson, Tilton, Fallon &amp;  
  un mus [2l] Appl. No.: 412,585 g Related U.S. Application Data [63] Continuation of Ser. No. 221,327. Jan. 27. 1972, [57} ABSTRACT uhurdoned A liquid fuel catalytic heater has a head assembly including a catalytic element having outer wall portions 431/329 25 5 4 3 which are straight and generally upright in the direc- 5 i B 431/350 tion of combustion air flow over to percent of 0 can 43&#39;l/326 328 the combustion area to effect more efficient heating and to radiate heat laterally of the catalytic element [56] References Cited through a guard canopy UNITED STATES PATENTS 6 Claims, 2 Drawing Figures 3,217.70l ll/l965 Weiss 43l/329 HEAD ASSEMBLY FOR LIQUID FUEL CATALYTIC HEATER RELATED APPLICATION This is a continuation application of copending application Ser. No. 221,327, filed Jan. 27, 1972 and now abandoned.  
 BACKGROUND AND SUMMARY This invention relates to catalytic heaters; and more particularly, it relates to an improved head assembly for a portable catalytic heater which operates on a refillable liquid fuel charge.  
  Portable liquid fuel catalytic heaters have been known in the art for some time. Typically, a porous catalytic element having a catalyst impregnated on its outer surface partially defines a fuel vapor chamber wherein fuel is vaporized. The fuel is fed to the chamber by a wick which conducts liquid fuel from a tank located beneath the head assembly. Such portable liquid fuel catalytic heaters characteristically have a catalytic element in the form of a hemisphere or dome which is surrounded by a guard canopy having a cylindrical side skirt of metal which directs room air for combustion onto the catalytic element. The primary heat transfer mechanism in this type of catalytic heater is through convention currents. One such heater is disclosed in the Berchtold, et al., re-issue US. Pat. No. 26,976.  
  In the present invention. a portable liquid fuel catalytic heater has a head assembly wherein the catalytic element is formed, preferably by molding, into a shape having a generally upright side wall of frusto-conical shape and a slightly domed top. Preferably, the inclination of the side wall forms an angle in the range of 3-l5 with the vertical, and the height of the slightly domed top is less than about one-fourth the height of the side wall portion. A canopy is provided in the heater which covers the head assembly and it includes a generally cylindrical skirt portion; however, the skirt portion of the canopy contains large windows laterally of the side wall of the catalytic element.  
  It has been found with the improved head construction of the present invention, that most of the combustion takes place at the side wall of the catalytic element and that a relatively minor portion of combustion occurs at the top. Because of the straight shape of the side wall parallel to its axis, combustion air traveling upwardly along the side wall tends to have a reduced velocity, and this has been found to significantly enhance the efficiency of combustion of the vapor passing through the side wall of the porous catalytic element. Further, lateral heating by radiation is greatly enhanced with the present construction because most of the combustion takes place at the side wall and there is a relatively unimpeded radiation path laterally of the side wall. This is of particular advantage in a tent, for example, wherein persons gathered around the heater can be warmed through radiation. As has already been mentioned, lateral radiation heating with previous catalytic heaters has been minimal.  
  It is also preferable to have a slight dome shape at the center of the top portion of the catalytic element in order to facilitate lighting of the heater in a wind.  
  Normally, portable liquid fuel catalytic heaters having a domed catalytic element exhibit an area at the very top where combustion is reduced. This is caused by the upward flow of combustion air at this point, away from the surface of the catalytic elements. This is sometimes referred to as the dead area.&#34; It has been found that with the shape of the catalytic element of the present invention, the dead area at the top center of the catalytic element is greatly reduced.  
  Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing.  
 THE DRAWING FIG. 1 is an upper perspective view of a liquid fuel catalytic heater constructed according to the present invention with a portion of the head assembly and its support tube cut away; and  
  FIG. 2 is a vertical cross sectional view of the catalytic element of the heater of FIG. 1.  
 DETAILED DESCRIPTION Referring then to the drawing, FIG. 1 shows a portable liquid fuel catalytic heater including an upper head assembly generally designated by reference numeral supported on a tube 11 which, in turn, is secured by means of a bayonet lock generally designated 12 to a collar 13 mounted to the top ofa fuel tank or reservoir 14 wherein liquid fuel is stored. The fuel tank 14 is, of course, refillable.  
  A canopy generally designated by reference numeral 15 encompasses the head assembly 10, and a snuffer (not shown) is also provided for covering a catalytic element 16 in the head assembly 10 when it is desired to stop combustion.  
  The catalytic element I6 includes a frusto-conical side wall 17 and a domed top 18 integral with the side wall 17. An outwardly extending foot flange I9 is formed at the bottom of the side wall 17.  
  The catalytic element 16 is preferably formed from non-combustible fibers such as ceramic fibers which are vacuum formed into the shape that has been illustrated. A slurry ofthe fibers together with a binder such as a starch adhesive or colloidal silicone is drawn into a die of the desired shape by means of a vacuum. This forms a porous, felt-like base through which fuel vapor is transmitted. The surface of the base is then impregnated with a catalyst, such as platinum, according to conventional means. The present invention is not limited, however, to any particular base material nor to a specific catalyst; but, rather, this invention relates to improvements in the shape of the catalytic element and the advantages resulting therefrom.  
  The catalytic element 16 may also be provided with an exterior wire mesh screen designated 20 in FIG. 1. The catalytic element 16 partially defines a fuel vapor chamber generally designated 21 at the center of which there is a wick 22. The wick 22 is surrounded at its intermediate section with a vertically slidable tube 23 to which there is attached a wick-adjustment mechanism generally designated by reference numeral 24 and including a yoke 25 which is adjustable upwardly and downwardly from a position outside of the support tube 11 to move the adjustment tube 23 to cover more or less of the portion of the wick 22 within the fuel vapor chamber 21. The bottom portion of the wick 22 extends downwardly into the reservoir 14 and conducts liquid fuel upwardly into the fuel vapor chamber 21. The fuel then vaporizes from the exposed portion of the wick 22 and passes through the catalytic element 16, combustion occurring at the outer surface thereof.  
  A head bottom 27 is attached to the top of and supported by the support tube 11. The bottom 27 includes a peripheral recess 28 for receiving the outwardly extending foot portion 19 of the catalytic element 16. As best seen in FIG. 1. the catalytic element and the screen 20 are held in place by crimping the outer portion of the head bottom 27 over the top of the foot flange 19.  
  Resting on top of the head bottom 27 and secured to it as with spot welding is a head support 29 which extends inwardly to form a central aperture 30 through which the adjustment tube 23 is raised and lowered. The head support 29 forms a pan which is filled with Fiberglas insulation material 31 which, in turn, is covered with a sheet of tin foil 32. The tin foil 32 and insulation material 31 are held in place by means of tabs 34 which are formed in the head bottom and extend upwardly through the insulation material and tin foil and then crimped over to hold them in place.  
  The canopy is secured to the top of the reservoir 14 in a suitable manner permitting it to be pivotally moved to uncover the catalytic element 18 for starting. The canopy 15 includes a plurality of upwardly extend ing windows 38 which extend upwardly from a lower skirt 39 to provide at least 50 percent free space later ally of the side wall 17 of the catalytic element 16. Since most of the combustion takes place at the side wall 17 in this construction, as will be explained more fully below, the placement of the windows 38 and the large openings provided thereby greatly facilitate the radiation of heat from the surface ofthe side wall 17 so that persons gathered around the heater may be warmed by radiation. The top of the canopy 15 includes a screen 40 through which heated room air and combustion products move.  
  Turning now to HQ. 2, the frusto-conical shape of the side wall 17 of the catalytic element 16 can be better appreciated. An angle, indicated as .r, is formed between the outer surface of the side wall 17 and a verti- :al line. This inclination is primarily to facilitate removal of the vacuum-formed catalytic element from its mold; the primary function of the upright shape of the side wall is to promote lateral heating through radia- Zion. Thus, the angle .r may be varied within the range 1 5, although for the reason mentioned, it is prefera- Jly greater than about 3.  
  Combustion air is drawn in beneath the lower skirt 39 )fthe canopy 15, in the direction ofthe arrows 43, and :ombustion takes place primarily at the outer surface )f the upright side wall 17. Because the combustion iurface is straight in the direction of flow of combus- :ion air and it is generally parallel to the flow lines. the noting combustion air tends to cling to the outer surace and reduce its velocity. This promotes a more :omplete combustion. and significantly contributes to he improved burning efficiency of the heater. Tests no on heaters constructed according to the present inention demonstrate that fuel vaporizing from the wick l2 flows primarily outwardly in a radial direction, hereby indicating that most of the combustion takes ilace at the side wall 17 of the catalytic element. Furher, after the heater has heated sufficiently, the outer urface of the side wall 17 glows with a much brighter ight than does the top 16. Thus, heating by lateral radittion, as diagrammatically illustrated by the sinusoidal arrows 44 is significant and can be felt by persons located beside the heater.  
  It has been found that significant radiant heating to the side of the heater is best achieved if the total surface area of the side wall 17 is in the range 50-75 percent of the total exposed area of the catalytic element 16, and preferably within the range to percent. Another design parameter that has been found important is the ratio of the height of the side wall 17 (as indicated by the arrow 1 in FIG. 2) to the height of the slightly domed top 18. The dead area at the center of the top 18 surprisingly has been found to be minimized when the ratio z/y is maximized; however, if the top 18 were perfectly flat even though the dead area would be at a minimum, a difficulty arises in lighting the heater, Normally, lighting is accomplished by swinging the canopy 15 to uncover the catalytic element 16 and placing a small amount of fuel on the center portion of the top 18 and lighting it, It has been found that if the top 18 is perfectly flat, lighting of the heater in the wind becomes difficult because the wind tends to blow the flame out. However, by a slight doming of the type shown in FIG. 2, lighting is facilitated while keeping the dead area to a minimum, Preferably, the ratio of the height of the side wall to the height of the top 2/ is less than about 4/].  
  Another advantage of the present invention is that the time between starting and attaining normal operating temperature for the catalytic element is reduced, and this is due at least in part to the reduced mass of the element. The need for an interior wire screen, as prior elements required, has been eliminated because the inventive element is molded into its shape and retains it without such screen,  
  Thus, with the present invention, a portable liquid fuel catalytic heater has been found to exhibit a more efficient burning of fuel than occurs in heaters with conventional hemispherical catalytic elements. Further, by maintaining a major portion of the combustion area in a generally upright side wall wherein the shape of the side wall is straight along the direction of flow of combustion air, most of the combustion takes place at the side wall and may be radiated through a protective canopy provided with large openings to heat persons gathered around the heater by radiation.  
  Having thus described in detail the preferred embodimerit of the invention, persons skilled in the art will be able to modify certain of the structure which has been illustrated and to substitute equivalent elements for those which have been disclosed, while continuing to practice the principle of the invention; and it is, therefore, intended that all such modifications and substitutions be covered as they are embraced within the spirit and scope of the appended claims.  
 We claim:  
  1. ln a portable liquid fuel catalytic heater, the improvement comprising: a catalytic element having an upright frusto-conical side wall defining a vertical axis of symmetry and a top integral therewith for partially defining said fuel vapor chamber, the outer surface of said side wall being substantially straight along upright paths defining the direction of combustion air flow and comprising between 50 and percent of the total combustion surface of said catalytic element and lines on the outer surface of said side wall extending parallel to said axis defining an included angle with the vertical in the range between 0 and 15, the combustion per unit area being appreciably greater on said side wall than on said top; a protective canopy over said catalytic element and spaced outwardly therefrom to provide a space for the flow of combustion air, said canopy defining a plurality of apertures extending along substantially the entire height of and spaced about the circumference of the side wall portion of said catalytic element, the total area of said apertures comprising at least 50 percent of the area of said canopy adjacent said side wall element to facilitate lateral heating by radiation; and means including a wick for supplying liquid fuel to said chamber where said fuel is vaporized.  
  2. The heater ofclaim 1, wherein said included angle is approximately 3 with the vertical 3. The heater of claim 1, wherein said apertures in said canopy comprise a plurality of vertically elongated apertures spaced about the periphery of said canopy and each extending from a point above the sidewall portion of said catalytic element to a point below said sidewall portion.  
  4. The system of claim 1, wherein the top of said catalytic element is slightly domed to facilitate lighting of said element in a wind, the height of said side wall being at least four times greater than the height of said domed top.  
  5. The heater of claim 1, wherein said catalytic element includes non-combustible fibers molded to form a porous element impregnated at its surface with a catalyst.  
  6. The heater of claim 1 further comprising a wire mesh on the exterior of said catalytic element for covering the same, said element being free of any interior support to thereby reduce the mass thereof and facilitate rapid starting.