Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02330214 2002-12-02
PORTABLE GROUND THAWING APPARATUS
BACKGROUND OF THE INVENTION:
The present invention relates to an improvement in a ground heater and more
particularly to a portable apparatus used to defrost a small portion of frozen
ground to
a certain depth for ease in excavation. In cold climates the ground can often
be
frozen to a depth of three feet or more. This frozen ground can be extremely
difficult
to excavate, as the moisture in the soil freezes producing a barrier similar
to
concrete. It is often necessary to place utility lines such as gas, water or
electricity
several feet below the surface of the earth. In order to service these lines
it is
necessary to excavate. The frozen ground can make this excavation similar to
digging through cement. Heavy equipment is available to perform this task, but
such
can be extremely dangerous near gas or other lines making it necessary to dig
manually. Several devices are known which may be used to thaw a small section
of
ground prior to excavation. These devices defrost and thereby soften the
ground
aiding so that the manual excavation of dirt may be possible.
U.S. Patent number 5,441,038 issued to Ohmann discloses a ground thaw
device using a chamber with sidewalls and a roof made of an insulating
material.
The chamber has a port that is substantially airtight to the outside and made
to
receive a
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burner. As the port is substantially closed, large amounts of heat can build
in this
area creating problems. The device may also be fitted with a fan which may be
used
to dissipate this heat, adding to the complexity of this device.
U.S. Patent number 5,033,452 issued to Carriere also discloses a thawing
device with a thermally insulated housing. This device uses a burner mounted
inside
a fire tube. The housing in this device uses a pitched roof with a steam vent
at its
apex. This vent allows for the escape of steam and thus, heat. It has been
found that
steam may greatly aid in thawing the ground as it penetrates and softens the
earth.
U.S. Patent number 4,349,010 issued to Bentham generally discloses a frost
removal
system which uses a series of heating pipes. These pipes are placed on the
ground
for thawing.
As can be seen from this discussion it would be desirable to have a highly
portable device for thawing a portion of earth and order to allow for its
excavation.
This device should be light enough to allow a single person without assistance
to
transport setup and use. This device should be able to run for extended
periods of
time on small amounts of gas and be safe to operate.
SUMMARY OF THE INVENTION:
It is the primary objective of the present invention to provide a method by
which
a defined area of ground can be thawed to a depth of three feet during the
cold winter
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months which will allbw individuals to evacuate soil from previously hard
frozen earth
to gain access to buried cables, water lines, gas lines, or other similar
utilities that are
commonly placed below the surface of the earth. It should be stated at this
point that
this device should be useful for defrosting a small portion of ground any time
as
necessary to aid in its excavation. Further the user may incorporate more than
one
device at a time if necessary to thaw a larger area.
It is an additional objective of the present invention to provide such a
method of
thawing frozen earth that does not require the use of a great deal of heating
fuel and
therefore operates in an efficient manner. It is a further objective of the
present
invention to provide such a method of thawing frozen earth that is extremely
portable
and is designed and constructed in a manner that allows a single person to
easily and
effectively to both operate the device and transport it from place to place.
These objectives are accomplished by the use of a shallow rectangularly
shaped box-like apparatus (or thaw body) that is open-ended on the side that
would
normally form the floor of the thaw body. This open-ended box is constructed
with a
high degree of insulating value and is designed to trap heat against the
surface of
frozen ground. The insulating qualities of the thaw body are accomplished by
building
the walls of the box in a double-walled fashion. This means that all the walls
will have
both an inner and outer wall which leaves an open space between them. This
space
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may then be filled with a commonly available insuiation material such as
fibergiass
or foam insuiation. This method of construction ensures that the interior of
the
thaw body retains the maximum amount of any heat that is directed into it and
enables the present invention to operate in the most efficient manner possible
whtle being empioyed to thaw frozen ground during the winter months. The
heating requirements of the present invention are supplied by the use of an
extemaily mounted radiant propane heater that is commonly available in the
marketplace today. One such heater is sold under the name MR. HEATER~m or
commonly referred to as sunflower heads. This attachment is built into one of
the
short verticai waiis on the end of the thaw body by placing the burner eiement
of
the radiant heater In the most outward opening of the vented heat transfer
tube.
The vented he8t transfer tube is a cylindrical opening that passes from the
outside
of the thaw body to the inner body cavity and which is made up of an inner and
outer tube. The outer tube Is a cylindrical opening of the thaw body wall
while the
inner tube is a separate and relatively short seeWn of a tube that Is somewhat
smaiier in its outside diameter than the inside diameter of the outer tube.
Additionally, the inner tube Is permanently attached to the most outer end of
the
outer tube and extends outward therefrom in a manner so that it extends beyond
the outer wall of the thaw body. The attachment of the inner tube to the outer
tube
is also made in such a manner so that its orientation is offset with respect
to the
position of the outer tube. This offset of the Inner tube is critical to the
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spirit of the invention as it leaves a gap between the inner and outer tubes
that
allows for the free flow of air to the radiant heater. This free flow of air
to the
heater enhances the efficiency of the radiant heater and therefore increases
the
operational effectiveness of the invention. Once the radiant heat is channeled
into the thaw body of the present invention, it encounters the reflector
shield that
is attached to the upper inside surface of the thaw cavity. The reflector
shield is a
reflective plate attached to the thaw cavity by the use of a plurality of
bolts and
wing-nuts. The reflector shield serves the purpose of directing the heat
generated
by the radiant heater in a downward manner which forces it to encounter the
earth. Further, all inner surfaces of the thaw body may be coated with a
reflective
surface to reflect the radiant heat toward the ground. Thus, this design
transfers
the heat generated by the radiant heater into the internal cavity of the thaw
body
and then directs it in a downward manner where it contacts and effectively
thaws
frozen ground.
According to a first aspect of the invention, there is provided a portable
ground thawing apparatus, comprising:
a portable insulated thaw body defining an enclosed inner cavity said thaw
body having a top section, side sections and an open bottom thawing section;
a thaw body opening having a first diameter on said thaw body wherein one
of said side walls defines therein said thaw body opening;
a radiant type heater having a fuel inlet, a radiant burner and a burner
control; and
a tube section having a first and second end and a diameter less than said
first diameter of said thaw body opening, said first end fixedly attached to
said
portable insulated thaw body such that said first end extends into said thaw
body
opening and defines a vent gap section for the free passage of gases between
said tube section and said thaw body opening, said second end of said tube
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section being fixedly attached to said radiant type heater so as to completely
encompass said radiant burner such that said tube section directs heat from
said
radiant burner into said inner cavity of said thaw body said second end and
said
radiant type heater being positioned outside of said thaw body.
According to a second aspect of the invention, there is provided a portable
ground thawing apparatus, comprising:
a thaw body defining an inner cavity having side walls and a top section
said thaw body having an inner and an outer surface with a center insulating
layer
between said inner and outer surface;
an opening having a first diameter on said thaw body defined by one of
said side walls said opening having an inner surface, an outer opening defined
by
said outer surface of said thaw body and an inner opening defined by inner
surface of said thaw body;
a radiant type heater having a fuel inlet, a radiant burner and a burner
control; and
a tube section having a first and second end and a diameter less than said
first diameter of said opening, said first end fixedly attached to said
portable
insulated thaw body such that said first end extends into said thaw body
opening
past said outer opening and defines a vent gap section for the free passage of
gases between said inner cavity and the outside said vent gap being between
said tube section and said thaw body openings inner surface, said second end
of
said tube section being fixedly attached to said radiant type heater so as to
completely encompass said radiant burner such that said tube section directs
heat
from said radiant burner into said inner cavity of said thaw body said second
end
and said radiant type heater being positioned outside of said thaw body.
According to a third aspect of the invention, there is provided a portable
ground thawing apparatus, comprising:
a thaw body defining an inner cavity having side walls and a top section
said thaw body having an inner and an outer surface;
a reflector shield removably attached in said inner cavity so as to
substantially cover said top section while leaving an air space between said
top
section and said reflector shield;
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an opening on said thaw body defined by one of said side walls said opening
have an inner surface, an outer opening defined by said outer surface of said
thaw body and an inner opening defined by inner surface of said thaw body and
a
first diameter;
a radiant type heater having a fuel inlet, a radiant burner, a conical
reflector
section and a burner control; and
a tube section having a first and second end and a diameter less than said
first diameter of said opening, said first end fixedly attached to said
portable
insulated thaw body such that said first end extends into said thaw body
opening
past said outer opening and defines a vent gap section for the free passage of
gases between said inner cavity and the outside said vent gap being between
said tube section and said thaw body openings inner surface, said second end
of
said tube section being fixedly attached to said radiant type heater so as to
completely encompass said radiant burner such that said tube section directs
heat
from said radiant burner into said inner cavity of said thaw body said second
end
and said radiant type heater being positioned outside of said thaw body.
For a better understanding of the present invention, reference should be
made to the drawings and the description in which there are illustrated and
described preferred embodiments of the present invention.
DESCRIPTION OF THE DRAWINGS:
FIG. 1 is a perspective view of the present invention illustrating its general
design
characteristics and the orientation of its major components in relation to one
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another and the body of the invention.
FIG. 2 is also a perspective view of the present invention as shown in FIG. 1
and illustrates the configuration of the underside of the body of the
invention.
FIG. 3 is a front elevation cross-sectional view of the present invention with
the
cross-section being taken along the line 3-3 of FIG. 2 and which details the
construction of the bottom side of the invention.
FIG. 4 is a side elevation cross-sectional view of the present invention with
the
cross-section being taken along line 5-5 of FIG. 2 and which illustrates the
placement
of the radiant heater in the body of the invention.
FIG. 5 is a close-up and cross-sectional view of the radiant heater component
of the present invention which details the manner of construction of the heat
transfer
tube and its orientation to the radiant heater.
FIG. 6 is a close-up top elevation view of the radiant heater component of the
present invention and further details its major parts and the manner in which
they
interact with the body of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT:
Referring now to the drawings, and more specifically to FIGS. 1 and 2, the
portable ground thawing apparatus 10 is primarily made up of the radiant
heater 14
and the thaw body 12. The thaw body 12 is a generally shallow rectangularly
shaped
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box-like apparatus that is open-ended on the side that would otherwise form
the floor
of the thaw body 12. Additionally, the thaw body 12 contains a plurality of
body
handles 36 which are attached in convenient locations on the outer surfaces of
the
thaw body 12 which allow the invention to be easily lifted and carried during
its use.
This enables the present invention to be easily moved from place to place
which
greatly expands its thawing capabilities.
The thawing function of the invention is enhanced by its method of
construction
by which the walls are built in a double walled configuration which creates an
open
space between them. This space is then filled with an insulating material such
as
fiberglass or closed cell foam which greatly increases the thaw body's 12
ability to
retain heat. This method of construction ensures that the interior of the thaw
body 12
retains the maximum amount of any heat that is directed into it enabling the
present
invention to operate in the most efficient manner, while also keeping the
external
temperature at a safe level to prevent burns to the user.
The heating requirements of the present invention are supplied by the use of
an externally mounted radiant propane heater 14 that is commonly available in
the
marketplace today. This attachment is made in one of the end short vertical
walls of
the thaw body 12 by placing the radiant heater 14 in the most outward opening
of the
vented heat transfer tube 18. The vented heat transfer tube 18 is essentially
a
cylindrical opening that passes from the outside of the thaw body 12 to the
inner
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body cavity 28. On the exterior of the present invention, the radiant heater
14 is
covered with the heater cage 16 which keeps things such things as human hands
and flammable materials from coming into contact with the high heat generated
by
the radiant heater 14 thereby lessening the risk of serious injury or the
unintentional
starting of fires.
Once the radiant heat is channeled into the thaw body 12 of the present
invention, it encounters the reflector shield 30 that is attached to the upper
inside
surface of the thaw cavity 28. The reflector shield 30 is a reflective plate
that is
attached to the thaw cavity 28 by the use of a plurality of bolts 32 and wing-
nuts and
which serves the purpose of directing the heat generated by the radiant heater
14 in a
downward manner which forces it into contact with the earth. Thus, the design
of the
present invention transfers the heat generated by the radiant heater 14 into
the
internal cavity 28 of the thaw body 12 and then directs it in a downward
manner where
it contacts and effectively thaws frozen ground.
The fuel source necessary for the radiant heater 14 is supplied by the use of
a
portable propane tank 38 that is commonly used in such articles as outdoor
grills and
other cookers and which supplies gas to the heater through the propane hose 40
which runs from the tank 38 to the back side of the heater 14. The propane
hose 40
also contains the gas flow controls and other critical safety features that
will be more
fully discussed in conjunction with other features of the present invention
below.
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Additionally, the propane hose is also commonly fitted with a excess flow
restrictor
valve 42 which, in the event that there is an uncontrolled free flow of gas
within the
propane hose 40, will shut off the flow of gas from the propane tank 38 to the
heater
14 thereby avoiding any potential hazards created from the accumulation of
unburned
gas.
The manner of construction of the thaw body 12 and its outer walls is further
detailed in FIGS. 3 and 4. These illustrations clearly show the manner in
which the
dual walls of the thaw body 12 form an interior cavity which allows for the
use of the
body insulation 34. As previously discussed, the use of the body insulation 34
greatly
increases the thaw body's 12 ability to retain heat which increases the
invention's
thawing capabilities and also increases the efficiency of performing this
role. The dual
wall of the thaw body 12 is constructed by the use of an inside wall 27 and an
outside
wall 29 over the entire length of the invention's exterior. This manner of
construction
produces a box-like apparatus that is very proficient at retaining heat within
a confined
area which forms the ideal environment for the thawing of frozen earth. These
drawings also further illustrate the manner in which the reflector shield 30
is attached
to the thaw body 12 and its location therein.
The location and manner of construction of the vented heat transfer tube 18 is
also further illustrated in these two drawings. The vented heat transfer tube
18 is
made up of an outer tube 20 and an inner tube 22. The outer tube 20 is a
cylindrical
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opening of the thaw body 12 wall that extends entirely through the wall while
the inner
tube 22 is a separate and relatively short section of a tube that is somewhat
smaller in
its outside diameter than the inside diameter of the outer tube 20 and which
is
permanently attached to it. The attachment of the inner tube 22 is made to the
most
outer end of the outer tube 20 and extends outward therefrom in a manner so
that it
extends beyond the outer wall of the thaw body 12. This extension of the inner
tube
22 forms the base to which the radiant heater 14 is attached and this aspect
will be
more further discussed below.
The attachment of the inner tube 22 to the outer tube 20 is made in such a
manner so that its orientation is offset with respect to the position of the
outer tube 20.
This offset of the inner tube 20 is critical to the spirit of the invention as
it leaves a
vent gap 24 between the inner and outer tubes that allows for the free flow of
air to
the radiant heater 14. This free flow of air to the heater enhances the
efficiency of the
radiant heater 14 and therefore increases the operational effectiveness of the
invention.
The orientation of the vented heat transfer tube 18 within the thaw body 12 is
further detailed in FIG. 3 which also illustrates the positioning of the inner
tube 22
within the outer tube 20 of the heat transfer tube 18. This drawing also
clearly shows
the manner by which the inner tube 22 is attached on one side to the inside
diameter
of the outer tube 20. This method of attachment leaves a vent gap 24 around
the
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edges of the inner tube 22 that are opposite to its point of attachment to the
outer
tube 20. The creation of this gap 24 is a result of the fact that the outer
dimension of
the inner tube 22 is smaller than the inside diameter of the outer tube 20.
Additionally, the radiant heater 14 is attached to the body of the invention
in a manner
which creates a reflector gap 62 between the body of the heater 14 and the
outer wall
of the thaw body 12. This reflector gap 62 allows air to freely flow around
the radiant
heater 14 and so works in conjunction with the vent gap to ensure that the
heater's
burner 58 located within the inner tube 22 is always supplied with a
sufficient amount
of oxygen in the burning process.
The manner in which the radiant heater 14 is attached to the thaw body 12 is
further illustrated in FIGS. 4 and 5. As previously stated, the radiant heater
14 is
attached to the thaw body 12 of the present invention by the use of the
extending
nature of the inner tube 22 of the vented heat transfer tube 18. The most
outward
end of the inner tube 22 is equipped with a heater attachment flange 26 which
matches exactly in dimensions and configuration to the most inner surface of
the
reflector 56 of the of the radiant heater 14. The attachment is made by
passing a
plurality of bolts though the most rearward surface of the reflector 56 and
into the
heater attachment flange 26. Again, the orientation of the most rearward
portion of
the inner tube 22 holds the heater reflector 56 in a position which leaves a
reflector
gap 62 between the leading edge of the reflector 56 and the outer wall of the
thaw
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body 12 which allows for the free passage of air to the heater 14.
The basic configuration of the radiant heater 14 and a further detail of its
orientation with regard to the body of the present invention is illustrated in
FIGS. 5 and
6. The radiant heater 14 is commonly made up of a burner 58 which is
surrounded by
an outwardly expanding cone shaped reflector 58 which has the purpose of
evenly
dissipating the heat generated by the burner 58. Gas is delivered to the
burner 58 by
means of the propane hose 40, which attaches to the body of the heater 14
through
the control valve 60. The control valve is the component which is used to
regulate the
quantity of gas being delivered to the heater 14 and is itself attached to the
most
outward end of the heater vent tube 54.
The most outward end of the vent tube 54 is also equipped with the thermal
coupler 48 which serves to shut off the flow of gas to the burner 58 in the
event that
the flame goes out. The thermal coupler 48 works in conjunction with a heat
sensor
50 which is embedded in the heater reflector 56 in a location so that it can
constantly
monitor the temperature of the burner 58 and to which it is attached by means
of the
heat sensor wire 52. Finally, the vent tube 54 also contains a burner vent 44
which
allows air to enter the radiant heater 14 during operation to ensure the
proper air/fuel
mixture is achieved for proper burner 58 operation. The present invention also
employs a vent wind guard 46 which is an open ended cylinder that fits over
and
around the vent tube 54 in a location so that it limits the amount of air that
can enter
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the burner vent 44. This is an essential component of the present invention as
it is
often used in the open where it may be exposed to high winds. Without the use
of the
vent wind guard, 46 these high winds would be able to enter the vent tube 54
and
disrupt the flow of gas to the burner 58 causing flame blow outs. The open
ended
nature of the vent wind guard 46 allows sufficient air to enter the burner
vent 44 for
normal operation but also keeps large volumes of air out and thereby avoids
flame
blowouts.
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Although the present invention has been described in considerable detail with
reference to certain preferred versions thereof, other versions are possible.
Therefore,
the spirit and scope of the appended claims should not be limited to the
description of
the preferred versions contained herein.
