CA1239084A - Portable gas heater - Google Patents

Abstract

ABSTRACT

Portable, gas-fired heaters are known to consist of an outer casing, a gas burner, a gas supply pipe, a gas-flow valve, and they have the convective draft of combustion air enter the heater along the lower sides or through a perforated bottom.
In this invention greater compactness, portability, reliability and safety are achieved by a combination of a central-ly-located flue and a rounded, closed bottom to the heater. The flue is so disposed as to create a reverse-draft inlet at the top of the heater, thus cooling the outer walls of the heater casing.
A rounded lid permits emergency extinguishing of the flame, and dust free storage for the burner. A retractable wire grill and a heat diffuser serve to keep the temperature of the heater's external top surface below a desirable maximum value during heater operation.

Description

I
BACKGROUND OF THE INVENTION

This invention relates to a gas-fired heater or furnace.
Previous construction-type gas heaters, for use during construction or repair of buildings, or during repair of permanent furnaces, have had, variously, the disadvantages of being bulky in relation to their heat output, of lacking convenience in portability and storage, or of being sensitive during operation to wind currents and drafts which cause flame instability and difficulties in ignition 10 They also lack the capability of positive, swift extinguishing of flame and quick containment of all overheated surfaces should inflammable materials fall onto or be blown onto heated, external surfaces of the heater during operation, or if these materials come directly into contact with the flame and are ignited. During storage con ventional heaters luck protection for the burner jets from dust which could clog them Camping-type gas heaters, for use in tents or in small shelters, and other types of small, portable gas heaters have the same disadvantages as the construction-type heaters. Both camp-Z0 ing-type and construction-type heaters are also ordinarily unable to operate in standing surface water of more than a fraction of an inch or so, because of their bottom-draft or lower-side draft openings In the present invention, these disadvantages are overcome, and numerous positive advantages are provided. For example, we have achieved great compactness by cooling the outer walls of the heater with the draft inlet air; the configuration of the invention also achieves great ignition reliability, flame stability, infrared shielding of the container walls, smaller overall dimensions in net-anion to the burner output, and a closed bottom to the heater.

~9(~34 DESCRIPTION OF PREFERRED EMBODIMENT
The invention will now be described in detail with rev-erroneous to the drawings.
Figure l is a side view of the heater with the top lid open and the wire grill raised ready for heater operation.
Figure 2 is a back view of the heater with the lid open Figure 3 is a side view showing the grill retracted into the casing, when the lid has been closed for transportation or storage of the heater Figure 4 is a view of the heat diffuser disc showing the arrangement of perforations.
As shown in Figures 1 and 2, the heater in the preferred embodiment consists of a cylindrical, upright, outer casing l, having a semi-elliptical closed bottom 23, and a separate cover or lid 2 of the same shape as the casing bottom 23 The lid 2 is hinged at a hinge 3, arranged to permit the lid to be swung open during heater operation, and to be clamped shut by a latch 4 during storage or transportation The outer casing 1 is mounted on feet 5 which are bolted 20 or welded to the casing 1, and are also bolted or welded to an open, cylindrical metal base 6 made of heavy gauge metal of slight-lye larger diameter than the outer casing 1 and of such a height as to provide desired ground clearance for the bottom of the casing 1 in operation; this base 6 also provides the proper weight and shape to ensure tip-over stability for the heater in case of accidental jolting of the unit during operation The casing 1 houses a gas burner 10, with gas jets 101 having air-inlet orifices 102, and a gas line assembly 11, leading to an externally-mounted gas-flow valve 12, anal to a thermostatic 30 flow-control 13 and thermostatic sensor 14 associated wit the gas-flow valve 12 The casing 1 also houses, attached to the burner, pilot light 15 and a pilot light thermocouple 16 which are, respectively, I
attached to a pilot light gas line 17 and thernlocouple wires 40 leading to the gas-flow aloe lo The gas-flow valve 12 is connected via a gas-cock 25 to a gas-regulator hose 24, which is connected to a standard gas-pressure fog-ultra on a gas tank or other suitable fuel gas supply The gas-flow valve 12 is mounted on a valve bracket 32 and a bracket support 33 both made of metal and welded or bolted to the cylindrical base 6 Also inside the casing 1, above the gas burner, is an open, upright, cylindrical flue 18 This flue serves simultaneously as an 10 inlet-draft director, a wall cooling duct, and an infrared heat shield for the outer casing walls, as will be described in more detail later.
The flue 18 is attached to the casing 1 by four support-spacer rods 19, which support the flue in position but at the same time cause only minimum thermal conductive contact between the flue 18 and the outer casing 1 The flue is positioned centrally in the casing 1, and at such a height that its bottom-opening end is near the level of the air inlet orifices 102 in the burner jets, preferably being one to two inches above them The flue 18 has a minimum diameter equal to the diameter of the gas burner, and is suitably smaller than the diameter of the outer 20 casing 1 so as to form between the flue and the walls of the casing 1 an annular-shaped draft inlet passage 100, whose horizontal surface area is sufficient to pass adequate primary draft air to the jet orifices 102, and secondary draft air to the combustion zone, so as to ensure come plate combustion of the fuel gas, for example propane. The purpose of the flue 18 is fourfold: first, it conducts the flue gases and heated air from the burner combustion zone upward into the space which is to be heated by the heater; second, it shields the walls of the casing 1 from direct infrared radiation emitted by the gas flame in the combustion zone, and this aids in maintaining a cooler wall temperature of the casing 1 during heater operation;
30 third, it forms the inner boundary of a draft-inlet passage 100 which directs the inlet draft air towards the semi-elliptical bottom 23, and thence inward-lye towards the gas burner jets 101 and the combustion zone; fourth, it I
forces the cooler inlet draft air to first circulate downward along the walls of the casing 1 so as to cool them during heater operation, The semi-elliptical bottom I has the shape to properly redirect the downward moving draft-inlet air inwardly above the bottom 23 towards the gas jets 101 and thence to the combustion zone .
The draft air flow in the present invention is the reverse of the conventional bottom-draft inlet, where the air first enters a heater through orifices in the heater's bottom or through the lower 10 side walls. In the present invention, the air first enters the top of the heater casing. This has many advantages, It ensures perfect ignition of the gas flame by the pilot light because it prevents cross drafts from entering the combustion zone during ignition, whereas conventional bottom draft inlets or lower side draft inlets cause convective turbulence plumes in the combustion zone and irregular ignition. The present arrangement of the draft prevents overheating of the container walls because the draft is also automatically a wall-cooling flow since the cooler draft flows down along the inside walls of the casing 1 before entering the combustion zone. The invention also 20 provides great flame stability during ignition and during operation under windy conditions as compared with conventional bottom or side draft inlets. The arrangement of the invention permits a closed bottom for the outer casing 1, It also permits greater compactness because of the cooler walls in relation to the thermal output of the heave r, The carrying ring 8 serves in several ways; it forms a handle for opening the lid 2 in preparation for lighting the heater;
it provides a carrying handle for the heater when the lid 2 is closed and clamped shut; it projects backwards when the lid is swung open 30 during operation so as to automatically provide advantageous protect-ivy clearance between the valve assembly 12 and surrounding objects or wall; it serves as a heat sink to more quickly dissipate heat from V8!~
the lid 2 during heater operation, when the lid it closed soon after operation, or immediately after any emergency closing of the lid to extinguish the flame; it supports a retainer clip 9 which holds the gas pressure regulator 26 securely in place during transport-anion or storage of the heater; it partially surrounds and protects the pressure regulator 26 from accidental blows or impact during storage or transportation.
A cylindrical wire grill or cage 29, supported above the flue 18 during heater operation, has a diameter slightly smaller 10 than the diameter of the casing 1, and has vertical sides, an open bottom, and a semi-elliptical top. The surface of the grill is cooled by air flowing In through its sides to mix with the hot rising plume from the flue. The grill is of such a height as to keep the top surface of the grill always below some specified maximum tempt erasure, for example, 400 OF is preferred, this temperature being below the ignition or charring temperature of paper or inflammable fabrics which might accidentally contact the outer heated surface of the grill during heater operation The grill has a top of semi-elliptical shape which approximately matches the contours of the 20 dome of the plume of heated rising air at the desired maximum i50-therm, e.g. 400 OF, and also matches the inner surface shape of the lid 2 The grill 29 is supported and held up firmly in place during heater operation by four detent fasteners 31, which in turn are fastened by welding to the underside of the four support-spacer rods 19.
When it is desired to transport or store the heater, the grill 29 is pushed downwards to free its bottom ring 36 from the four detent fasteners 31; the grill then drops down to rest on the top of the four support-spacer rods 19 with the grill sides nesting in the annular 30 draft space 100. From Figure 3 is can be seen that the lowering of the grill permits the lid 2 to close down completely over the top of the lowered grill, and to seal the burner compartment and the gas jets 101 from any dust or debris during transportation or storage.
Additionally, in the event of anything inflammable falling into the burner during operation, a sharp rap on the top of the grill will lower it at once into the casing l; the lid 2 can then be swung sharply shut to extinguish all flame and to seal the hot interior compartment of the burner completely from the outside space, This closing of the lid shuts off the gas burner by shutting off the draft of external air into the burner When the burner flame is thus extinguished, so is the pilot flame also; the pilot thermocouple then cools and shuts off lo the main gas-flow valve 12.
It will be obvious to those skilled in the art how to make a grill higher than the height of the casing 1, if desired, and to still be able to store the grill completely within the heater when the lid is closed by making the grill as a multi-section, telescoping assemblage, for example.
The semi-elliptical form of the lid 2 is advantageous for two reasons. First, it matches the top shape of the grill 29, and this permits storage of the grill inside the heater body when the lid is closed; second, it permits quick extinguishing of all flame when desired, since when the grill is lowered, the top lid can at once be closed closely over the semi-elliptical top of the grill to completely seal off the interior from all air draft, and with a minimum volume of enclosed oxygen-containing air in the top to support undesirable residual combustion This ensures that the flame goes out with minimum delay.
Attached to the top of the flue 18 by two or more metal struts 34 is a circular, perforated metal diffuser disc 35 ( see Figure 4), having a flared outer edge; this disc 35 is installed, flared side down, preferably one to two inches above the level of the flue top. This diffuser 35 serves to deflect sideways, and outwardly/ the hot air and flue gases rising from the flue, thereby creating a narrow, rapid flow of the hot air and gases up around the outer edge of the diffuser, between it and the adjacent sides of the grill 29 This rapid flow creates a pressure drop which in turn draws in cool air from outside the grill, cooling the grill and the hot rising plume This permits the surface of the grill to remain below the desired maximum surface temperature, for example 400 OF, while still keeping the height of the grill no higher than can fit into the closed lid when the grill has been retracted, dropped, or telescoped downward into the casing 1 for transportation or storage.
The desired compactness of the heater is thus achieved in the invention by a combination of a closed-bottom cylinder and a 10 top-draft, that is by a downward, reverse draft, channeled by the flue 18. This results in a cooler, outside wall and a smaller, overall heater size relative to the thermal output The manner in which the draft is achieved keeps the casing wall 1 from overheating, permitting a compact foreign. The snowily size relative to the thermal output permits ready portability, permits installation, if necessary, in a small space, and facilitates storage. The reverse draft and shielding of the combustion zone give reliable ignition, along with freedom from flame instability and ignition problems, while still ensuring complete combustion.
In the operation of the heater, the lid 2 is opened and swung back, the grill 29 is pulled up and its bottom ring 36 is locked into place by the detent fasteners 31. The gas pressure regulator 26 is connected to a suitable gas supply. The gas supply is then turned on and the gas cock 25 is opened. The control knob 38 on the gas-flow valve 12 is depressed, releasing gas to the pilot light 15, and then the pilot light is lit by a pushbutton lighter, taper, or snatch When the pilot flame has heated the pilot thermocouple 16 sufficiently, the main control knob 38 is then turned to allow the gas to flow to the burner, where it is then lighted by the pilot flame. The thermostatic control 30 13 on the valve 12 is set to any desired ambient space temperature;
the burner will then operate automatically to shut off and relight so as to maintain the desired space temperature It will be obvious to those skilled in the art that various standard heater accessories can be attached to the preferred embodiment, if desired, within the spirit of the invention For example, a tip over switch can be attached to the base ring 6, so as to automatically shut off the gas-flow valve 12 and stop the gas flow to the burner by an electric signal when the burner is tipped more than a few degrees from the vertical during operation; a high-heat sensor and sensor switch can be installed to monitor the temperature of any surface of the heater, and to act to shut off the burner via the valve 12 should the desired surface temperature limit of the sensor be exceeded. A push-button piezoelectric lighter can be installed to light the pilot f laze, if desired. The grill 29 can be made in two or more sections so as to rise to any desired height above the heater top during operation, and then to telescope down and nest into the annular draft space 100 for storage.
It will also be obvious that, while the semi-elliptical bottom 23 is preferably closed, so that all of the draft inlet air is drawn in only through the annular space 100 as described, the presence of some small openings in the bottom 23 for pipe inlets, or even for some small supplementary draft air for any reason, will still be within the spirit of the invention, since the main draft flow will still be downwards through the opening 100, and the draft will thus function to cool the outer walls and stabilize the ignition and flame, as desk c robe d in the prey e rued embodime nut .
Various configurations of the flue 18 other than cylindrical, such as sections of a cone, can be used within the spirit of the in-mention. Various shapes, configurations and combinations of dill-user plates other than that shown in Figure 4 can also be used to accomplish the desired quick dilution and cooling of the hot air plume from the flue Also, obviously, without the presence of a heater lid

2, the heater could be used for other purposes than for space heating, such as, for example, heating a chemical or metallurgical vat, I

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heating a crucible, heating a barbecue hearth, and so on. It will also be obvious that, while the heater of the present invention is portable, it could also be employed as a fixed heater in situations where its cool wall temperature and compactness would be ad-vintages, for instance.
The dimensions of the heater and its components are basic-ally set by the But output chosen, For example, with a burner of 40, 000 But per hour, we have found that a heater having an outer casing of 12 inches diameter, a flue of 10 inches diameter, a dill-user disc of 8 inches diameter, and a grill of overall height of 22 inches as measured from the bottom of the base ring 6, can be operated in an ambient space held at 900F without any of the ox-posed surfaces of the heater exceeding 4000F, and with the heater casing never exceeding Z50F Other thermal outputs, and other limiting outer surface temperatures can be accommodated within the invention by suitably altering the component dimensions, as will be obvious to those skilled in the art from the description. The gas-flow valve 12 should be chosen to have a maximum capacity not less than the But output chosen for the burner.
Z0 It will be obvious to those skilled in the art how to adapt the present invention to forced-draft heaters as opposed to the natural convection draft described specifically in the preferred embodiment .
It will be obvious that a top lid of shape other than semi-elliptical could be employed, for example hemispherical or even cylindrical; but these other shapes will all add unnecessary and undesirable residual oxygen-containing air, and this will prolong the time required for extinguishing the interior combustion upon closing the lid in an emergency I

The semi-elliptical shape of the bottom also serves to minimize the residual oxygen-containing air in the bottom of the heater in the event of emergency extinguishing of the flame being necessary by closing the lid The valve 12 can be surrounded by a metal shield or casing if desired for additional protection from blows or contact during storage.
A supplementary carrying handle, attached for example to the hinge 3, can be added if desired.

It will be obvious that the gas burner 10, which is shown as being circular in Figures 1, 2 and 3, can be of other shapes pro-voided that its longest horizontal dimension is never greater than the diameter of the flue 18.

Claims (4)

(Claim 1 as amended)

1. A heater comprising an outer casing having a closed bottom and sides and an open top, said casing containing a burner, an oxygen-combustible fuel supply means and a flue, said burner being centrally located near the bottom of the outer casing, said fuel supply means communicating externally to a fuel supply, said flue being a vertical, open-ended flue-pipe installed within the casing above the burner and attached to the casing for placement and support solely by the minimum number of support-spacer rods needed for said support, thereby also providing only minimum thermal conductive con-tact between the flue and the casing, said flue extending vertically to surround the flame combustion zone, with the open top of said flue ox-tending to at least the height of the open top of the outer casing, said flue having its bottom horizontal dimensions at least as large as the horizontal dimensions of the burner and sufficiently smaller than the horizontal dimensions of the casing to thereby form, between the flue and the outer casing, a draft passage serving to direct substantially all of the inlet draft of combustion air or oxygen-containing gas to flow at first inward over the lip of the outer casing, then between the flue and the outer casing, then permitting it to flow centrally inward beneath the flue to the centrally located burner, thence upward to the combustion zone and into the flue.

2. A heater as in Claim 1, in which the burner is a gas burner, said gas burner being connected to a gas supply pipe communicating to an externally mounted gas-flow valve supplying gas to the burner, said gas burner having a gas pilot light and pilot light thermocouple connected to the externally mounted gas-flow valve, said gas-flow valve being controlled by a thermostat connected to an ambient temperature sensor.

(Claim 3 as amended)

3. A gas heater comprising a cylindrical, vertical, metal outer casing having a closed, semi-elliptical bottom and an open top, said casing containing a centrally located gas burner near the casing bottom, said casing also containing a flue, said casing ex-tending vertically to at least the height of the top of the combustion zone, said gas burner being connected to a gas supply pipe commun-icating to an externally mounted gas-flow valve, said burner having attached to it a gas pilot light and a pilot light thermocouple each connected to the external gas-flow valve, said gas-flow valve being connected to a gas supply, said gas-flow valve being thermostatically controlled by an ambient temperature sensor, said flue being a vertical, open-ended, cylindrical, metal flue-pipe centrally install-ed above the burner so as to laterally surround the flame combustion zone and extending further vertically to at least the height of the open top of the outer casing, said flue being attached to the outer casing walls for positioning and support solely by the minimum number of support-spacer rods needed to support and connect the flue to the casing, thereby also minimizing the thermal conductive contact between the flue and the casing, said flue having its bottom diameter at least as large as the diameter of the gas burner and sufficiently smaller than the diameter of the outer casing to thereby form, between the flue and the outer casing, a vertical, draft-passage inside the casing, serving to direct a sufficient volume of inlet draft air or oxygen-containing gas to supply the burner by directing the draft flow at first inward over the top rim of the outer casing, then downward between the flue and the casing, then permitting the draft to flow centrally inward beneath the flue to the centrally located burner, thence upward to the combustion zone and out through the flue

4. A gas heater as in Claim 3 having a top grill-cage and a heat diffuser, said grill comprising a cylindrical, vertical cage of metal, openwork rods attached to a bottom, circular support ring having a diameter slightly less than the inside diameter of the heater's outer casing, said vertical grill rods extending straight for a height not exceeding the interior depth of the outer casing, and then tapering centrally inward to form a semi-elliptical, openwork cage top, the whole said grill cage being held up above the flue by the bottom support ring being clamped to the flue support-spacer rods which attach the flue at its top end to the outer casing wall, said heat diffuser com-prising one or more circular, perforated, metal discs having a flared outer edge and of diameter approximately the diameter of the flue, said discs being attached by mounting struts to the top of the flue, so as to position the discs horizontally and centrally at a distance above the flue not exceeding the interior, vertical depth of the semi-elliptical top of the grill cage.
A gas heater as in Claim 4 having a metal, grill cage and a metal lid with a handle, said grill being retractable downward for storage when the heater is not in operation by detaching the bottom support ring of said grill from clamps on the flue support-spacer rods, thereby allowing it to drop so that when thus retracted the grill's bottom support ring and vertical metal sides are enclos-ed in the annular draft passage between the flue and the outer casing, leaving the grill's semi-elliptical top protuding up above the flue top, said metal lid being hinged to the outer casing's top and with attached means for clamping said lid down over the top of the heater, said metal lid being of a semi-elliptical shape to accomodate the semi-elliptical top of the retracted, stored metal grill and to enclose it completely when the lid is closed, said handle on the lid consist-ing of a right, metal cylinder, or major section thereof, said cylinder diameter being smaller than the diameter of the lid and at least three inches in length, said cylindrical handle being welded to the lid with the longitudinal axis of the cylinder being at right angles to the lid's outer surface, said handle having at least one perforation in its side of sufficient size and smooth shape to serve as a hand-grasp hole adapted for carrying the heater when said lid is clamped shut, said lid having centrally attached to its outer surface a metal clamp adapted to grasp and hold a gas pressure regulator for storage.