A PORTABLE/TRANSPORTABLE CAMPSITE OR PATIO HEATER - THE 'OTPOT

APPAREIL DE CHAUFFAGE PORTAGE DE PATIO OU DE SITE DE CAMPING - LE 'OTPOT

English 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.

Claims

The Embodiments of the invention in which an exclusive property or privilege
is
claimed are defined as follows:
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.
3

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.
4

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.
6

Description

CA 02302730 2000-03-21
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

CA 02302730 2000-03-21
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.
2

CA 02302730 2000-03-21
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.

Representative Drawing