CA2302730A1 - A portable/transportable campsite or patio heater - the 'otpot - Google Patents

Abstract

The subject invention describes a portable/transportable Patio or Camp-site Heater, or Fire-pot, in which the preferred embodiment uses a partially manufactured, new or discarded propane cylinder modified by the addition of a chimney and metal stand. Ventilation holes are cut into the base of the cylinder so as to provide primary combustion air to the fuel inside the cylinder. An oval hole cut into the front lower half of the cylinder is designed to provide secondary combustion air to the fire, and to allow the user to see the conflagration. It is designed to consume relatively small amounts of fuel in a manner which creates intense heat inside the 'OTPOT. This heat is transferred to the walls of the pot and its chimney so as to raise the temperature of the metal to the point at which it radiates significant amounts of heat to the surrounding seated persons. The design enables the fire to consume smoke particles (so that little smoke is emitted from the chimney), and also ensures that the combustion products released from the chimney are at a high temperature, so that they rise rapidly into the atmosphere and minimize inconvenience to the surrounding seated persons. The preferred embodiment of this invention uses solid fuel - wood, charcoal, or briquettes. The 'OTPOT
can also be used to cook food (e.g.roast potatoes or corn), roast marshmallows or other tid-bits, or to boil liquids or fry food. The design has a low centre of gravity and a stable stand, and it can be fitted with spark guards to minimize risks of fire in adjacent property. It can stand on open ground or in a metal tray depending upon local needs, and it is easily portable. The 'OTPOT is expected to have a useful lifetime of several years.

Description

Field of the Invention This invention relates to a design for a portable and transportable Patio, or Camp-site Heater, herein called the " 'OTPOT"
Background of the Invention People all over the world sit in front of camp fires or bonfires when spending time outdoors.
The activity is encouraged by the need for additional warmth when sitting outdoors on a cool evening, and by the hypnotic feeling of relaxation induced by looking into the dancing flames of a campfire.
In our modern societies the open fire is considered a potential fire hazard, particularly in forested areas and in urban or cottage areas where the fire may be located next to a wooden building, or sited on a wooden deck. For these reasons many designs of outdoor fireplaces, patio heaters, or camp-site heaters, which burn fuel wood, are available in the marketplace. These outdoor fireplaces may consist of the simple cast concrete fire pit, or circular metallic enclosures embedded in the ground, (as seen in many provincial parks).
In cottage country, many outdoor fireplaces are designed to sit on a wooden deck, in which case the fire is placed on a steel base, usually raised on legs about 30 cm. above the level of the deck, and it is enclosed by a moderately fine steel mesh whose function is to contain burning embers which may be released from the fire by the combustion process. Most of these fireplaces can be used for simple roasting of tid-bits of food (e.g. roasting of marshmallows) but some incorporate facilities for grilling food. Virtually all of these designs suffer from the same major limitations; they are not designed to concentrate and radiate heat and warmth to the persons seated around the fire, other than direct radiation from the flames. Therefore, to receive any significant warmth from the fire, it has to be relatively large.
Consequently these patio heaters usually consume large volumes of fuel wood, and tend towards creating the fire hazard that they were intended to control. Also drifting smoke released from the fire can be a major nuisance to those seated around the fire.
A recently marketed patio heater is the traditional Mexican ceramic "Fire Pot", or 'Chiminea' which is an attractively shaped, ceramic, 'pot-bellied' object having an incorporated chimney, and a round or oval, moderately large opening in the front face of the pot. This opening has the purpose of making the fire visible; radiating heat to those sitting in front of it and facilitating the addition of fuel to the fire. Some heat is also radiated from the surfaces of the ceramic pot, but this is somewhat minimal because the ceramic wall of the pot is a relatively poor conductor of heat. This fire pot usually stands on (but is not firmly attached to) a metal stand which raises the ceramic base of the pot 10 to 20 cm above the deck. Other disadvantages of this ceramic pot are its initial high cost, and its tendency to fracture due to uneven heat, or to repeated heating and cooling. Alternatively, it may crack if it is used after it becomes wet (e.g.after exposure to rain). The pot is sold without guarantee as to its useful lifetime.
A patent search and a review of commercially available literature did not reveal any inventions or commercially available patio/campsite heaters with characteristics similar to those described in the following patent application other than the Mexican Chiminea described above.
The subject invention is derived from the shape and function of the Mexican Chiminea, but has the advantage that it can be constructed from partially manufactured, new or discarded propane cylinders, in various sizes, The concept offers a new product line for the manufacturers of propane cylinders. The propane cylinder is modified by the addition of a chimney, a hole cut into its side to allow the fire to be seen, and the addition of a stable base. Primary combustion air inlet holes are cut into the base of the propane cylinder. Suitably sized pieces of fuel wood or charcoal may be dropped down the chimney into the fire , or placed through the front opening. It is designed to consume relatively small amounts of fuel in a manner which creates intense heat inside the 'OTPOT. This heat is transferred to the walls of the pot and its chimney so as to raise their temperature to the point at which they radiate significant amounts of heat to the surrounding seated persons. The design enables the fire to consume smoke particles so that little smoke is emitted from the chimney. The design also ensures that combustion products are released from the chimney in a controlled manner, at a reasonable height above the ground, and they are at a high temperature, so that they rise rapidly into the atmosphere and minimise inconvenience to the surrounding persons.
It is known that this design can also be copied by persons skilled in the art, in sheet metal, using standard sheet metal fabrication techniques.in a variety of geometrical (triangular, square or polygonal) cross sections.
The fuel used in this invention may be solid, or, with the aid of suitable high temperature burners of conventional design, liquid or gaseous, but the preferred embodiment would burn fuel wood or charcoal /briquettes. Because the front opening of the 'OTPOT may be covered by a spark-guard which can be movable or permanently installed, it is intended that the fire should be lit by dropping ignited paper 'sticks' down the chimney, followed by kindling sticks. When the kindling is burning more fuel, either charcoal/briquettes or fuel wood may also be dropped down the chimney. Further additions of fuel can be made in the same way, as necessary, to maintain the intensity of the fire inside the 'OTPOT. It can also be used to cook food (e.g. roast potatoes or corn) with the aid of an accessory placed around the base of the chimney; roast marshmallows or other tid-bits with the aid of a long fork or skewer, or boil liquids or fry food in a container supported on a ring (or trivet) positioned above the top of the chimney. The design has a low centre of gravity and is fitted with a stable stand. The preferred embodiment mounts the 'OTPOT at a 15 to 20 degree slope, front to back, with the front opening looking upwards, so as to enable the persons sitting in front of the 'OTPOT to see into the body of the fire. The 'OTPOT
can be fitted with a spark guard to minimise risks of fire in adjacent property. It can stand on open ground or in a metal tray depending upon local needs, and it is easily portable and transportable. It is expected to have a useful lifetime of several years and that it may be retailed at a reasonable cost.
Basic Description of the Invention The attached drawing illustrates a preferred embodiment of the invention.
Figure 1 shows a modified, 13.5 kg. capacity propane cylinder (1) having an attached chimney (2) (15 cm.
diameter and 30 cm.length) and a rectangular or oval hole (3) (30 cm.long and 12.5 cm high) cut into its side.
A spark-guard and /or a pair of doors may be fitted over this hole if it is considered desirable to ensure that embers can not be ejected from the fire. A square (45 cm per side), geometrically stable base (4) is attached to the bottom of the cylinder by means of four legs which support the base of the cylinder about 20 cm. above the ground. A
bowl (5) may be placed below the ventilation holes in the base of the cylinder (shown in Fig.2) to catch embers which fall through the holes. A trivet or hob, constructed from suitably sized angle iron, permanantly installed over the top of the chimney, may be used to boil a can of water, or fry food in a frying pan, using the heat issuing from the chimney. It can also be used to support a spark-guard (6) which may be placed over the top of the chimney. A ring installed on the spark guard may be used to lift the spark guard on or off the top of the chimney when adding fuel, of cooking etc.
Figure 2 shows an arrangement of ventilation holes (20 to 25 holes, each approximately 19 mm diameter) in the base of the cylinder.
Principles of Operation:
This invention incorporates a combination of basic principles, non of which is new or novel in itself, except that in combination they work to overcome the limitations of known, existing patio/camp-site heaters. These principles include:
i) Utilisation of a commercially available object as the base, or starting point, on which to construct a new device having an application which is not related to that of the commercially available object.

ii) Containment of the hot gases of combustion from solid, liquid, or gaseous fuels in a metal container fitted with a chimney, so as to heat the wall and chimney surfaces to a high temperature, which then become a 'hot radiating body'.
iii) Use of the 'chimney effect' to induce flows of both primary and secondary combustion air, both to contain and consume noxious smoke emissions.
iv) The principle of creating a small intense fire by means of an adequate supply of both primary and secondary combustion air, so as to minimise the production of visible smoke and fully combust small burning embers.
v) The principle of 'maximum utility' in the form of accessories and attachments which facilitate the cooking of food or 'tid-bits' for the entertainment of the user and possible guests.
vi) The principle of a low centre of gravity combined with geometrically stable construction, so as to maximize the stability and safety of the hot radiating container.
vii) The principle of fire safety by incorporating a component to arrest sparks .
While one embodiment of this invention has been described and illustrated in the accompanying drawings which is based on an existing product (a propane cylinder) it will be evident that those skilled in the art may make changes and modifications to the design described herein without departing from the essence of this invention. All such modifications or variations are believed to be within the sphere and scope of the invention as described in the claims appended hereto.

Claims (15)

1) In a preferred embodiment, a propane cylinder is modified, by means of an attached chimney of approximately one half of the diameter of the cylinder, and a height of not more than the length of the cylinder, centred on the top end of the cylinder, and a rectangular, or oval hole having a major dimension of about one third of the circumference and a minor dimension of about one third of the height of the cylinder, is cut into the lower half of the vertical surface of the cylinder. An arrangement of twenty to twenty five ventilation holes, each about 2 cm.
diameter is cut into the base of the cylinder. A square (approximately 1.5 times the diameter of the cylinder, per side,) geometrically stable base is attached to the bottom of the cylinder by means of four legs which support the base of the cylinder about 15 to 20 cm above the ground. The whole assembly is arranged to slope from front to back at an angle of 15 to 20 degrees so as to facilitate the viewing of the fire inside the cylinder. After igniting the fire inside the cylinder, by means of conventional techniques, suitably sized pieces of fuel wood, charcoal or briquettes may be dropped down the chimney into the fire, or it may be inserted through the open hole in the side of the cylinder from which the spark guard is temporally removed. A spark arrester is placed on a swivelling hob or permanantly installed hob or trivet, over the top of the chimney. Embers which fall through the ventilation holes in the base of the cylinder are caught in a metal bowl placed below the base of the cylinder. A metal tray (say 60 cm.square) having 5 cm. deep walls is placed beneath the base of the cylinder to diffuse the heat radiated from the bottom of the cylinder when it is standing on a wooden deck. The oval opening in the front of the cylinder is covered by a spark-guard. A sheet metal collar to facilitate the roasting of food (such as potatoes) is fitted around the base of the chimney, The spark guard on the swivelling hob may be replaced by a pan in which water may be boiled or food cooked.

2) A propane cylinder is modified, by means of an attached chimney of approximately one half of the diameter of the cylinder, and a height of not more than the length of the cylinder, located on the top end of the cylinder, and a round, rectangular, or oval hole having a major dimension of about one third of the circumference and a minor dimension (in the case of rectangular or oval holes) of about one third of the height of the cylinder, is cut into the lower part of the vertical surface of the cylinder.
An arrangement of ventilation holes, having a total surface area of about two thirds of the area of the chimney are cut into the base of the cylinder. A square, circular or polygonal geometrically stable base is attached to the bottom of the cylinder by means of four legs(in the case of a square base) or 3 or more legs in the case of a circular or polygonal base, which support the base of the cylinder about 15 to 20 cm above the ground. The whole assembly may be vertical or may be arranged to slope from front to back at an angle of 10 to 20 degrees so as to facilitate the viewing of the fire inside the cylinder. After igniting the fire inside the cylinder, by means of conventional techniques, suitably sized pieces of fuel wood, charcoal or briquettes may be dropped down the chimney into the fire, or it may be inserted through the open hole in the side of the cylinder. A
spark arrester may be placed on a swivelling or permanently installed hob or trivet (which may also be used to support a container of water etc., over the top of the chimney. Embers which fall through the ventilation holes in the base of the cylinder are caught in a metal bowl placed below the base of the cylinder. A sheet metal collar to facilitate the roasting of food (such as potatoes) is fitted around the base of the chimney,

3) A propane cylinder or a sheet metal fabrication of circular, triangular, square or polygonal shape has an attached chimney of approximately one half of the diameter of the fabrication, and a suitable height, located on the top end of the cylinder, and an oval or alternate shape hole having a major dimension of about one third of the circumference and a minor dimension of about one third of the height of the fabrication, is cut into the lower part of the front vertical surface of the fabrication, leaving an integrated fire containment tray, or barrier, below the open hole, having a depth of not less than 5 cm. fronting the base of the fabrication..Alternatively a number of secondary combustion air inlet holes having a total area at least equal to that of the cross section of the chimney may be cut into the top half of the walls of the cylinder An arrangement of ventilation holes, each about 2 cm. diameter is cut into the base of the fabrication, or alternatively, a single hole of larger diameter, covered by expanded mesh whose function is to support the burning fuel inside the fabrication. A
circular or square base is attached to the bottom of the fabrication by means of three or four legs respectively, which support the base of the fabrication about 15 to 20 cm above the ground. The whole assembly may be arranged to stand vertically, or it may be arranged to tilt, from front to back, at an angle suitable for the viewing of the enclosed fire through the open hole in the front of the assembly. After igniting the fire inside the cylinder, by means of conventional techniques, suitably sized pieces of fuel wood, charcoal or briquettes may be inserted through the open hole in the side of the fabrication or dropped down the chimney into the fire. Embers which fall through the base of the fabrication are caught in a metal bowl placed below the base of the fabrication. One or more doors may be placed so as to cover the open hole in the front face of the assembly so as to completely enclose the fire, when considered necessary.

4) A container, set on a stable base, in which primary combustion air is admitted through holes in its lower surfaces so as to promote vigorous combustion of solid fuel, placed and ignited in the lower part of the container, and in which secondary combustion air is admitted to the container via one or more holes in its upper surface, so as to allow the further combustion of smoke, particles or combustible gases, so as to produce hot gases which are contained inside the container for a time period long enough to efficiently heat the internal walls of the container, so as to make the external surface of the container a heat radiating body suitable for the comfort and warming of persons who may be seated around the container. Simultaneously, the generated hot gases are released from a chimney located on the top surface of the container at a height above the ground such that they are encouraged to rise up into the atmosphere by natural forces, where they are diluted and cause minimum discomfort to persons who may be seated around the container.

5) A metallic surface, (supported above the ground) which may be cylindrical or other suitable geometric shape, raised to a temperature sufficient to radiate heat to the surrounding space by means of an internal fire; the temperature of the surface(s) to be sufficiently high so as to radiate heat for the comfort of sedentary persons sitting around the radiating surface

6) A form of smoke control, achieved by the fact that the hot gases from the vigorous combustion of the solid fuel are contained inside a container, in close conjunction with a supply of secondary air, for a period long enough to cause almost complete combustion of smoke particles and small embers generated by the combustion process. An optional detachable spark arrester is available to provide additional security against the risk that a spark or glowing ember could be emitted from the patio heater and cause a local conflagration

7) A form of smoke and noxious fume control, achieved by the fact that the combustion gases leaving the chimney are:
a) released to the atmosphere at approximately head height of the persons sitting around the heater, from a small diameter chimney, and b) very hot, and are caused to rise quickly into the atmosphere.

8) A portable and transportable patio or camp-site heater which combusts solid, liquid or gaseous fuels in a manner which effectively heats the internal surfaces of the cylinder so as to create a hot radiating body.

9) A patio or camp-site heater having a supporting structure attached to the external surface of the heater which may be used for the purposes of roasting food placed into it.
Alternatively or simultaneously, edible tid-bits may be cooked by inserting the food carried on a suitable spit, or long fork, into the heat emanating from the chimney of the assembly, or alternatively into the front opening in the wall of the assembly so as to gain direct access to the heat from the source of combustion.

10) A patio or camp-site heater which may be used for the heating of water or the cooking of food by placing a suitable container on a swivelling or permanently installed hob, or trivet, positioned directly over the heat rising from the chimney.

11) A patio or camp-site heater which is designed for the efficient combustion of solid fuel which incorporates a chimney having an internal diameter large enough to allow the solid fuel to be dropped down the chimney for the purpose of sustaining the longevity of the fire contained in the device.

12) A patio or camp-site heater having sliding or hinged doors on its outer surface, which, when open, to allow persons sitting around the fabrication to see the enclosed fire and its associated flames.
The opening may also be used for the insertion of solid fuel, or for the purpose of roasting, cooking or heating food or edible tid-bits. When not used for viewing the fire, the doors may be closed so as to enclose the fire in a safe and effective manner.

13) A patio or camp-site heater having a means by which gaseous or vaporized fuels may be mixed with primary combustion air and ignited, so as to burn with a high temperature flame which is directed so as to swirl around the internal surfaces of the device. Secondary combustion air being supplied by means of an air inlet in the under surface of the assembly in order to facilitate the complete and efficient combustion of the gaseous fuel, so as to generate a high temperature inside the container. Also a mechanism whereby the volume of fuel supplied to the burner per unit of time may be controlled.

14) A patio or camp-site heater which is both portable and transportable.

15) A patio or camp-site heater which can be manufactured in different sizes, whilst maintaining the desirable properties described herein.