US3319947A - Portable space heaters - Google Patents

Description

May 16, 1967 Filed Dec.

IOI

FIG 7 M. R. TRUESDELL PORTABLE SPACE HEATERS 2 Sheets-Sheet 1 INVENTOR.

MERLYN R. TRUESDELL ATTORNEY y 1937 M. R. TRUESDELL 3,319,947

PORTABLE SPACE HEATERS Filed Dec. 14, 1964 2 Sheets-Sheet 2 IN VENTOR.

ME RLYN R. TRUE SDE L L iiiksfu,

ATTORNEY United States Fatent C) 3,319,947 PORTABLE SPACE HEATERS Merlyn R. Truesdell, Marion, Iowa, assignor to Century Engineering Corporation, Cedar Rapids, Iowa, a corporation of Iowa Filed Dec. 14, 1964, Ser. No. 417,987 1 Claim. (Cl. 26319) This invention concerns space heaters of the portable, non-vented type employing air aspirating nozzles and is particularly directed to several novel features for the larger capacity sizes of such heaters providing increased combustion efficiency, reliability and at the same time lower cost and ease of maintenance.

Interest in the utility of air aspirating liquid fuel burners has been revived by recent developments in this area by the Gulf Research & Development Company of Pittsburgh, Pa. Generally speaking, it has proven easy to adapt the air aspirating principle to portable space heaters, especially of the non-vented type. However, certain practical difficulties have arisen in the case of such heaters of larger capacity, say in the neighborhood of 140,000 B.t.u.s or so. When available air aspirating nozzles have been enlarged to the extent necessary for the increased heater capacity, difiiculties have arisen in maintaining good control and evenness of combustion. For example, flow rates through such nozzles tend to become less even and aspiration of the fuel less thorough. Furthermore, since economics presently demand use of carbon type vanes in the eccentric vane type air compressors used in connection with such nozzles, an air output filter is absolutely vital in order to prevent carbon dust clogging the nozzles. At the same time the filter must be of suificient capacity and kept clean or diminution of the air supply to the nozzles, with consequent reduction in performance of the heater, will occur. Much trouble has arisen, particularly in the field, with such heaters simply because their air output filters have clogged, the rate of such clogging tending often to be erratic, so that prescribed regular cleaning periods have not always been sufiicient to keep the filters functioning properly.

The primary objects of present invention, therefore, are to provide solutions to the foregoing difiiculties. Briefly described, the present invention utilizes two conventional air aspirating nozzles of lower capacity, the sum of their capacities equaling that of the heater, and twin ignition systems mounted side by side in a single burner head, the latter providing supplies of supplementary air to the nozzles in two distinct directions in order to assure clean and thorough combustion. In addition to supplementary air admitted generally radially inwards just downstream of the nozzle orifices, the burner head of the present invention admits additional supplementary air from the rear thereof axially of and between the nozzles. The latter assures sufiicient air for complete combustion at the critical point where the spray cones of the two nozzles overlap. The use of ignition systems, of course, also insures functioning of the heater even should one ignition system become disabled. The air output filter, in turn, is constructed with a permanent filter element of the sintered type of sufiicient capacity and is enclosed by a transparent housing or bowl so that a constant visual check can be maintained as to the cleanliness of the filter element. Finally, the fuel tank itself is formed with its longitudinal seam at the top, rather than at the bottom as has often been the practice, so that leakage resulting from a defective seam is prevented, the formation of the seam also providing a mount for the cylindrical jacket, spacedly surrounding the combustion chamber and other components, horizontally located above the fuel tank.

3,319,947 Patented Mary 16, 1967 Other and further objects, features and advantages of the present invention will become apparent from the detailed description of the preferred form thereof read in conjunction with the following drawings, in which:

FIGURE 1 is a side elevation of a portable space heater incorporating the features of the present invention, certain portions being broken away;

FIGURE 2 is an end elevation view of the heater of FIGURE 1;

FIGURE 3 is a sectional view along line 33 of FIGURE 1;

FIGURE 4 is an elevational view illustrating the front face of the burner head;

FIGURE 5 is a vertical section along the line 55 of FIGURE 6 through the axis of the air outlet filter employed in the heater of FIGURE 1;

FIGURE 6 is a view of the lower face of the filter head of FIGURE 5; and

FIGURE 7 is a schematic diagram of the electrical circuitry employed in the heater of FIGURE 1.

In the drawings, the space heater of the present invention, designated generally by the reference numeral 10, utilizes a squat, horizontally disposed elongated fuel tank 11 having rounded sides, a flattened bottom and top, and fiat ends, one of which at the upstream end of heater 10 is inset as at 12 in order to provide a transformer compartment 13 which in turn is closed by a suitable cover 1 The body of fuel tank 11 is rolled from a single piece suitable sheet metal joined at its edges to form a centrally disposed seam 15 running longitudinally of tank 11 along its top. The ends of seam 15 are turned upwardly, suitably secured at 16 as by welding, and thereabove bent outwardly in opposite lateral directions to form flanges 17 providing a mount for a hollow cylindrical heater shell or jacket 18 thereabove. Heater jacket 18 is split longitudinally to provide a fixed lower half 19, suitably secured to flanges 17 at 20, and an upper half 21 overlapping the lower half 19 and providing a cover removably secured thereto at 22. The downstream end of heater jacket 18 is provided with a nose piece 23 fixed to the lower half 19 of jacket 18 and rounded off to form a downstream opening 24 of reduced cross-sectional area. Heater 10 is further equipped with two pairs of legs 25, 26 straddling tank 11 and heater jacket 18 at spaced locations therealong Each pair of legs 25, 26 is secured to tank 11 at 27 within the open ends of one of a pair of channels 28 passing transversely under fuel tank 11 and upwardly part way along each of its sides. Above the ends of channels 28 legs 25, 26 are bent around and against the upper portions of the sides of fuel tank 11 and then rise upwardly and divergingly outwards to embrace heater jacket 18, being joined above cover 21 to form a pair of hand grips 29. The lower ends of legs 25 abut the ground while the lower ends of legs 26 are provided with wheels 30 carried on an axle 31 therebetween.

Concentrically within and spacedly from the inner wall of the downstream half or so of heater jacket 18 is mounted a cylindrical combustion chamber 35 by means of suitable brackets 36, secured to the lower, fixed half 19 of jacket 18, in order to form an annular passage 37 communicating at its upstream end with the upstream end of heater jacket 18 and at its downstream end with opening 24 in nose piece 23. Combustion chamber 35 is preferably formed of suitable stainless steel and closed at its upstream end by an end wall 38 provided with a rounded, laterally elongated symmetrical opening therein 39 axially aligned with combustion chamber 35. The downstream end of combustion chamber 35, in turn, is partially closed by an outwardly disposed nose cone 40 mounted on suitable brackets 41 to provide a restricted annular opening 42 between the rim of nose cone 40 and a small annular end wall 43 of combustion chamber 35 disposed just upstream of nose cone 40. The opening 39 through the combustion chamber end wall 38 is in turn closed by a burner assembly which will be hereinafter described in detail.

Suitably spaced upstream of combustion chamber 35 is a fan and pump assembly 50 for supply both of the air required for aspirating the fuel and of the supplementary air required for complete combustion, as well as the air to be heated. Assembly 50 employs a fan motor 51 of conventional design located concentrically within heater jacket 18 and upstream of combustion chamber 35 by means of a suitable wire formed cage 52 secured both to motor 51 and to the walls of the fixed lower half 19 of heater jacket 18. The downstream end of a double ended motor shaft 53 carries a propeller type fan 54 of a diameter only slightly less than the interior diameter of heater jacket 18, while the other or upstream end of motor shaft 53 drives a conventional air compressor 55 'of the eccentric vane type, employing carbon vanes, contained within a housing bolted as at 56 to the upstream end of fan motor 51. The intake air to compressor 55 is drawn through a suitable air intake filter 57 and the air output therefrom is passed through an air outlet filter assembly 58.

Outlet filter assembly 58 comprises a generally circular, die cast head 59 having a lower face which is axially inwardly stepped to provide an annular seat 60. The latter receives an annular gasket 61 therein against which the upper edge of a transparent, cylindrical filter bowl 62 is maintained by an appropriate bolt 63 extending upwardly axially through bowl 62 and threadedly engaging an axial bore 64 in head 59. The lower face of the latter inwardly of bowl 62 is annularly recessed at 65, which recess communicates with an angled passage 66 opening through a fiange 67 formed integrally with and tangentially of head 59 by which outlet filter assembly 58 is secured to the rear face of compressor 55 over the air outlet opening thereof. The lower face of head 59 inwardly of recess 65 is still further counterbored to provide a seat 68 to receive an annular gasket 69 against which is seated the open end of a hollow cylindrical filter element 70 of the sintered type. The lower end of filter element 70 is closed and provided with an axial bore through which bolt 63 extends. Filter element 70 is maintained against gasket 69 by virtue of a boss 71 formed integrally with bowl 62 about bolt 63 and extending upwardly to engage the lower end face of filter element 70, being sealed thereto by virtue of a resilient washer 72. Tightening of bolt 63 thus maintains both bowl 62 and filter element 70 in tight engagement with their respective gaskets 61 and 69. Finally, the remainder of the lower face of head 59 inwardly of filter element 70 is provided with a C-shaped recess 73 communicating with an outlet passage 74 extending radially outwardly therefrom and threadedly receiving at its outer end an appropriate pipe elbow 75. A passage 76 is bored upwardly through the roof of recess 73 opening in turn through the top of head 59 and is closed thereat by a threaded plug 77. The remaining area of the lower face of housing 59 Within filter element 70 is provided with a relief passage 73 also opening upwardly through the top of head 59. Relief passage 78 is counterbored downwardly to provide a tapered, annular seat 79 which receives a loose fitting ball relief valve 80 resiliently maintained thereagainst by a suitable helical spring 81 adjustably compressed by a headed screw 82, axially bored at 83, threaded into the upper end of relief passage 78 against spring 81 and maintained in selected positions by means of locknut 84. The purposes of passages 76 and 78 will be hereafter more fully explained.

The burner assembly closing opening 39 in combustion chamber end wall 38 includes a burner head or housing 90, preferably a dished casting having the rim of its open face of the same contour, but somewhat larger, as opening 39 in combustion chamber end wall 38 so that it overlaps the same. The margin thereby formed between opening 39 and the rim of burner housing 90 serves to threadedly receive bolts 91 from the rear face of housing 90 through laterally protruding bosses 92 cast integrally therewith on the inner wall thereof, thus fixing housing 90 to combustion chamber end Wall 38. The rim of housing 90 is also formed with a plurality of semicircular or scalloped air inlet ports 93 therein abutting end wall 38 and providing access for the supplementary air supplied by fan 54 to combustion chamber 35. The rear wall of burner housing 90 is provided with a pair of integrally cast bosses equally and horizontally spaced from the axis of housing 90 and combustion chamber 35 and are axially bored to receive a pair of air aspirating nozzles 94 of conventional design. For a heater having a capacity of 140,000 B.t.u.s a pair of nozzles each havin sufficient capacity for a heater of 75,000 B.t.u.s have proved very satisfactory. Such nozzles are manufactured, for instance, by Delavan Manufacturing Company of West Des Moines, Iowa, and are readily available stock items. Nozzles 94 project inwardly from the rear wall of burner housing 90, terminating just upstream of end wall 38, their axes being thus parallel to and horizontally equally disposed from the axis of combustion chamber 35.

Just below and between nozzles 94 the rear wall of housing 90 is further bored to provide an air port 95 so that the supplementary air may enter combustion chamber 35 generally axially thereof and in the overlap area between the spray cones of nozzles 94. Aspirating air for each nozzle 94 enters the same axially thereof from its rear end through a suitable branched air supply line and fittings 96 which at its upstream end is connected into elbow of air outlet filter 58. Fuel for each nozzle is supplied laterally of the nozzle through a branched fuel line and fittings 97 which at its upstream end is connected to the outlet end of a fuel strainer assembly comprising a fuel riser tube 93 angling downwardly within fuel tank 11 midway therealong, tube 98 incorporating an in-line, sintered fuel filter 99 within its upper end. Preferably, tank 11 is also equipped with a suitable drain plug 100.

Above and between nozzles 94 a laterally elongated boss on the rear wall of housing 90 carries a pair of ignition electrodes 101, one for each nozzle. The remaining electrode 102 for each nozzle 94 is carried in its own boss on the rear wall of housing 90 below and outboard of its respective nozzle. Each pair of electrodes 101, 192 are energized, through suitable line connections 103, by means of one of two transformers T1 and T2 which in turn are supplied by a power line and plug 104 and 105, respectively, to which fan motor 51 is connected in parallel by supply lines 106.

During operation of heater 10, air from compressor 55 supplied to nozzles 94 through air outlet filter 58 draws the fuel from tank 11 up through fuel filter 99 and fuel line 97 in quantities proportionate to the air supplied by compressor 55. The proper amount of air for nozzles 94 may be adjusted by screw 82, which varies the tension of spring 81 against ball relief valve in air outlet filter 58, so that air pressures in excess of those required will be bled oil through the axial relief bore 83 in screw 82.

Achievement of the proper air supply to nozzles 94 is greatly aided by use of an air pressure gauge which may be easily inserted in the air line 96 simply by removing plug 77 of air outlet filter 58 replacing it with the air pressure gauge. Air outlet filter 58 not only insures the necessary cleanliness of the air supplied to nozzles 94 but in addition the transparent bowl 62 thereof permits quick and constant surveillance of the condition of the exterior surface of filter element 70 which receives the output from compressor 55 and thus is contaminated with carbon dust from the vanes of the compressor. If filter element 70 is allowed to become clogged, reduction in the air supplied to nozzles 94 will result with obvious consequent reduction in the efiiciency and capacity of heater 10.

Fan 54 supplies the supplementary or remaining air to combustion chamber 35 needed for complete combustion of the fuel supplied thereto by nozzles 94. Such air strikes the combustion chamber end wall 38 and is deflected generally radially inwardly through the ports 93 of burner head 90 past the downstream ends of nozzles 94 where the mixture of fuel and air is ignited by electrodes 101, 102 which operate continually. The general radially inward direction of the supplemental air through ports 93 tends to spread the flame and to maintain it as much as possible in the upstream portion of combustion chamber 35 in order that combustion take place as evenly throughout combustion chamber 35 as is possible; if the supplementary air were brought in wholly axially of nozzles 94 the tendency would be for the entire combustion to occur in the downstream end of combustion chamber 35. In addition, nose cone 40, restricting the egress from combustion chamber 35 to that provided by the annular opening 42, additionally contributes to maintaining combustion as evenly as possible throughout combustion chamber 35. The great bulk of the air driven by fan 54 is of course passed over the heated outer surface of combustion chamber 35 through the annular passage 37 between it and heater jacket 18 and expelled from nose piece 23 at which point it joins the products of combustion issuing from combustion chamber 35 through passage 42. The size and number of scalloped ports 93, the size of supply port 95 and the proper sizes of nozzles 94 can be readily determined by conventional methods Well known to those skilled in the art.

Though the present invention has been described with reference to a particular embodiment and detailed descriptive language has been employed, it is not so limited. Instead, the following claim is to be read as encompassing all modifications and adaptations falling Within the spirit and scope thereof.

I claim:

In a portable space heater including a cylindrical heater jacket open at each end and horizontally disposed above a fuel container therebelow, a cylindrical combustion chamber disposed within a downstream portion of said jacket effective to provide an air heating passage between said chamber and jacket and having a centrally disposed burner inlet opening in its upstream end, a motor driven fan in a portion of said jacket upstream of said burner inlet opening effective to draw air in the open upstream end of said jacket and propel it both toward said opening and out the downstream end of said jacket through said passage, said fan motor being provided with and driving an air compressor, said compressor being of the eccentric vane type and having carbon formed vanes, and a burner head assembly mounted to said combustion chamber, said assembly including a burner housing enclosing said burner inlet opening and having a plurality of supplementary air inlet ports adjacent said openin receiving therethrough a portion of the air propelled by said fan, said ports directing said air into said combustion chamber through said burner inlet opening transversely With respect to the axis of said chamber, the improvement comprising: said fuel container having an elongated, horizontally disposed tank with end walls and its bottom, top and side walls formed from a single piece of sheet material, the abutting ends of said sheet material forming a seam extending longitudinally of said tank along the top wall thereof, said seam including upwardly turned portion of said abutting ends disposed in face to face contact with and secured to each other, heater jacket supporting portions thereabove extending laterally outward in opposite directions from the upper end of said upwardly turned portions effective to form an elongated seat providing a mount for said jacket extending longitudinally along and beneath the outer wall of said jacket, a pair of air aspirating nozzles operatively connected to said fuel container and said compressor, said nozzles being mounted in said burner housing to discharge into said combustion chamber through said burner inlet opening, the supplementary air entering said combustion chamber through said supplementary air ports passing across the spray patterns of said nozzles, the axes of said nozzles being laterally spaced so that said spray patterns overlap in an area lying within said combustion chamber and between said nozzle axes, an additional air inlet port in the rear of said burner housing between said nozzle axes effective to direct a further portion of the air supplied by said fan into said combustion chamber generally axially thereof through said burner inlet opening and thence into the aforesaid overlap area of the spray patterns of said nozzles, ignition means including a pair of spaced electrodes adjacent each of said nozzles effective to maintain continuous ignition of the air-fuel mixture supplied to said combustion chamber, and an air filter for the aspirating air supplied by said compressor to said nozzle, said filter comprising a permanent air filtering element having an outer visible filter surface to which air upstream of said element is supplied by said compressor and a transparent housing enclosing said surface effective to permit visual ascertainment of the cleanliness of said element.

References Cited by the Examiner UNITED STATES PATENTS 2,174,663 10/ 1939 Keller. 3,073,583 1/1963 Woollen 26319 3,101,193 8/1963 Varvel 263-19 3,148,956 9/1964 Hetherwick et al. 34-88 X 3,256,003 6/1966 Briggs 26319 FOREIGN PATENTS 902,893 8/ 1962 Great Britain.

FREDERICK L. MATTESON, Jr., Primary Examiner. D. A. TAMBURRO, Assistant Examiner.

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