Ground warming heater and method and system relating thereto

Abstract

A ground heater includes an insulated housing enclosing a primary fuel line within the insulation, an ambiently aspirated hollow tube running the length of the housing and extending substantially entirely through a cavity defined by an inner surface of the housing and wherein the cavity defines an opening into the housing, a torch head mounted in a torch head housing and having a fuel line thereto branched from the primary fuel line and mounted in fluid communication with an upstream end of the tube, the opposite downstream end venting to atmosphere so that a flame from the torch head extends along the interior of the tube to heat the cavity and a ground surface in registry with the opening.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Canadian Patent Application No. 2,534,488 filed Jan. 30, 2006 entitled System and Apparatus for Safely Coupling Multiple Ground Thawing Heaters.

FIELD OF THE INVENTION

The present invention relates to a ground warming heater and more particularly to a ground warming heater having an improved torch and which may be coupled together in a system comprising a plurality of such heaters fuelled from a minimum number of fuel supplies.

BACKGROUND OF THE INVENTION

It is known to thaw frozen ground so as to ease excavation such as for maintenance or repair access to buried utilities. A variety of patents discuss prior art heaters including U.S. Pat. No. 6,408,843 issued to Olson, U.S. Pat. No. 5,441,038 issued to Ohmann, and U.S. Pat. No. 5,033,452 issued to Carriere.

These prior art apparatus and others typically use propane as fuel and generally use one propane tank for each heater. A multiplicity of fuel lines are required and are exposed to vandalism and general damage.

There is a need for a safe and efficient system of ground warming heaters.

As stated in U.S. Pat. No. 6,408,843 to Olson, a ground heater is used to thaw ground to depths in the order of three feet during the cold winter months which will allow individuals to excavate soil from previously hard frozen earth to gain access to utilities.

Some of the disadvantages of the prior art heaters include convenience and safety factors. Some ground heaters utilize burners which are removably installed and which may be easily dislodged by accidental contact with the fuel lines. Multiple burners have multiple lines which add to clutter and risk of damage. Multiple burners enhance the risk of one blowing out and discharging unburned fuel while the other continues to act as an ignition source. Other heaters are poorly insulated resulting in hot surfaces.

Further, for large areas requiring thawing, multiple heaters have been provided however each being supplied with their own fuel supply, or with a header distributing a plurality of flexible lines, further elevating the risk of damage, numbers of connections and access by vandals.

SUMMARY OF THE INVENTION

In summary the present invention may be characterized in one aspect as including a ground heater for thawing or otherwise warming the ground and a method of using the heater, wherein the heater includes an insulated housing enclosing a primary fuel line within the insulation, an ambiently aspirated hollow heating tube running the length of the housing and extending substantially entirely through a cavity defined by an inner surface of the housing and wherein the cavity defines an opening into the housing, a torch head mounted in a torch head housing and having a fuel line thereto branched from the primary fuel line and mounted in fluid communication with an upstream end of the heating tube, the opposite downstream end venting to atmosphere so that a flame from the torch head extends along the interior of the heating tube to radiantly heat the cavity and a ground surface in registry with the opening.

The cavity may extend along substantially an entire length of the housing, and the opening may be in a bottom of the housing and also extend along substantially the entire length of the housing. The heating tube may extend through the cavity and along the entire length thereof so as to extend through opposite end walls of the housing. The torch head housing may be cylindrical or tubular so as to conveniently mount in registry with or to the upstream end of the heating tube in fluid communication therewith.

The primary fuel line may be mounted so as to extend along a sidewall of the housing from an upstream end wall to a downstream end wall. The branch fuel line may extend from the primary fuel line across the upstream end wall to an upstream end of the torch head housing.

The torch head may include a fuel metering orifice and a bore extending therethrough downstream of the orifice. At least one aspirating aperture may be provided in a sidewall of the torch head in fluid communication with the bore downstream of the metering orifice. The torch head may be mounted substantially concentrically in, so as to be supported by, the torch head housing. The torch head housing includes a perforated support at a downstream end thereof. A flame holder end of the torch head is mounted to the support and adjacent the downstream end of the torch head housing so as to dispose a flame seated in the flame holder end downstream along the heating tube towards the downstream end of the heating tube to thereby discharge exhaust gases of combustion therefrom and to draw an ambient airflow into the upstream end of the torch head housing, over the torch head and through the at least one aspirating aperture and through perforations or apertures in the perforated support so as to flow into the upstream end of the heating tube for improved combustion of the fuel/air mixture at the igniter immediately adjacent the flame holder end of the torch head.

In a preferred embodiment the perforated support includes at least one rigid member on which the torch head is mounted within the torch head housing, wherein the rigid member defines at least one breathing aperture, herein to include perforations or other apertures, where the at least one breathing aperture extends substantially entirely around the downstream end, that is, the flame holder end of the torch head in a plane substantially orthogonal to a direction of flow of the ambient air through the torch head housing, and wherein the torch head housing and the torch head define a substantially annular breathing channel therebetween extending in the direction of flow and in registry with the at least one breathing aperture.

In one preferred heater embodiment the at least one breathing aperture includes a pair of breathing apertures oppositely disposed on opposite sides of the downstream end of the torch head. The at least one breathing aperture may consist solely of a pair of breathing apertures. The at least one breathing aperture may include a pair of opposed facing substantially semi-circular slots disposed substantially symmetrically on the opposite sides of the downstream end of the torch head.

In one embodiment an outside diameter of the breathing channel may be substantially equivalent to an inside diameter of the heating tube. Further, the torch head housing may be cylindrical, and may include a concentrically nested pair of cylinders, wherein the torch head is mounted concentrically within an inner cylinder of the pair of cylinders. The upstream end of the heating tube may be of greater diameter than a throat and a mid-section of the heating tube extending between the upstream and downstream ends of the heating tube, so that an outer cylinder of the pair of cylinders may mate telescopically into or register against the upstream end of the heating tube.

In a preferred embodiment the at least one aspirating aperture includes a radially spaced apart array of apertures radially spaced around the longitudinal axis of the torch head for radially aspirating air radially into the bore to mix with fuel flowing under pressure through the metering orifice and into the bore. Advantageously a perforated flame holder plate is mounted across a downstream end of the bore in the flow of the mixture of fuel and air exiting the bore into the upstream end of the heating tube. The igniter may be mounted adjacent and downstream of the flame holder end of the torch head.

A system of such ground heaters may advantageously include a plurality of the ground heaters mounted one to another in series along the primary fuel line so as to be spaced apart along the primary fuel line. Further, the plurality of heaters may include at least a first plurality of the heaters mounted in series along a first primary fuel line and a second plurality of heaters mounted in series along a second primary fuel line, wherein the first and second primary fuel lines are in parallel fluid communication for operating their respective heaters in parallel.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the drawings wherein similar characters of reference denote corresponding parts in each view:

FIG. 1 is an underside perspective view from the upstream end of a heater according to one embodiment of the present invention.

FIG. 2 is the view of FIG. 1 with the lock boxes removed from both ends of the heater.

FIG. 3 is the heater of FIG. 1 in partially exploded view.

FIG. 4 is a perspective view from the upstream side of a torch head housing and torch head in a partially exploded view.

FIG. 4a is the view of FIG. 4 with the torch head installed in the torch head housing.

FIG. 5 is a perspective view from the downstream side of the torch head housing and torch head of FIG. 4.

FIG. 5a is a perspective view from the downstream side of the torch head housing and torch head of FIG. 4a.

FIG. 6 is an end elevation view of the upstream side of the heater of FIG. 2 with the heater in its operative orientation and installed on frozen ground.

FIG. 7 is a perspective view from the upstream side, partially cut away, of the heating tube and main fuel line of the heater of FIG. 3.

FIG. 8 is a partially cut away sectional view along line 8-8 in FIG. 2.

FIG. 9 is an enlarged view of the sectional view of the torch head of FIG. 8.

FIG. 10 is a sectional view along line 10-10 in FIG. 2 illustrating the heater of FIG. 2 inverted into its operative orientation and installed on frozen ground.

FIG. 11 is, in plan view, one embodiment of a system of multiple heaters according to the present invention installed in series along the main fuel line.

FIG. 12 is, in plan view, one embodiment of a system employing the heaters according to the present invention installed two parallel branches of the main fuel line wherein each branch contains multiple heaters in series.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention is an improved ground heater 10 and includes a method of using such heaters and a system of such heaters for thawing or otherwise warming large areas of ground. The system includes a plurality of heaters coupled together so as to be fuelled by a reduced number of fuel gas sources than are conventionally required. For example, each heater in the system may be coupled together along a common main or primary fuel line 12 to an adjacent heater. Connections and the main fuel line itself have improved protection from abuse, accidental or intentional. A variety of sizes of heaters may be provided and the heaters may be arranged in series and/or parallel to adapt to larger areas as well. The heaters may include those having dimensions of two feet by seven and one half feet when viewed in plan view, by one foot deep. Convenient man-handling chain, cable, or other handles (not shown) may be provided at each end of the heater housings 14.

Housings 14 are insulated and each form an elongate cavity 16 with an open bottom defined by the lower circumferential edge 14a of the housing. The housing rests on for example frozen ground 18 with the open bottom facing the ground so as to dispose the cavity downwardly. A hollow radiant heating tube 20 extends through and along the length of cavity 16 and out of each of the opposite ends of the housing, respectively upstream end 14b and downstream end 14c. Heating tube 20 delivers heat from a flame 22 (shown not to scale) supported on a flame holder plate 24 mounted in bore 26 in torch head 28. The heat from heating tube 20 radiates through the cavity and its open bottom to warm ground 18. Main fuel line 12 extends through insulation 52 in housing 14 so as to be insulated from cavity 16 and not accessible from outside the housing. Fuel line 12 supplies fuel via a branch line 32 and a conventional optional regulator 44 to the upstream or infeed end 28a of torch head 28.

In the system including multiple heaters 10, the fuel source 30 may be a single propane bottle coupled to a first heater 10 in the chain of heaters. For example, the chain of heaters may include fifty heaters 10 in series. Fuel source 30 may be coupled directly to the first heater and to main fuel line or the fuel source can be regulated at a first pressure (for example about ten psig or more) for delivering gas at a controlled pressure through the main fuel line 12 to the individual branch lines 32 feeding the individual heaters 10. While a regulator at the fuel source is not required, there is added safety should any branch lines such as coupling hoses or the main fuel line be damaged. Advantageously the sections of the main fuel line extending between the heaters may be armoured three quarters of an inch flexible hose, armoured for example by being wrapped in the wrapping used to wrap and protect hydraulic lines. The regulator 44 for each heater 10 regulates fuel at a second pressure (about eight to twelve psig) to torch head 28. In a preferred embodiment not intended to be limiting, the torch head housing 34 is mounted at the upstream end 20a, that is, the branch line end of heating tube 20 and is accessible at that end of the heater. An ambient air flow is drawn into housing 34 in direction A. The flame holder plate 24 holds a flame 22, which may be for example approximately fourteen inches long oriented down along the length of tube 20. Exhaust gases exit in direction B from the opposite end, that is, the downstream end 20b of the tube.

The torch head 28 has ambiently air inlets or apertures 28c aspirating a mixing chamber 26a in bore 26 downstream of a small feed metering orifice 26b sized to vaporize the fuel fed under pressure through the orifice into chamber 26a. Flame holder plate 24 partially closes off the downstream end of mixing chamber 26a. The flame holder plate 24 may be a press fit into the open downstream end of bore 26. Torch head 28 advantageously is mounted concentrically in torch head housing 34. Torch head housing 34 in one embodiment includes an inner cylinder 40a and an outer cylinder 40b, both concentric and nested about a longitudinal axis C of torch head 28. Flame 22 is seated so as to extend downstream substantially along axis C.

Each end of the main fuel line 12 on each heater 10 may be fitted with a manual ball-valve 40 and each torch assembly may be fitted with its own manual ball-valve 42 for quick, accessible shut-off in case of necessity or emergency. Regulator 44 may provide fuel to torch head 28 through a thermo-coupled shut-down valve safety device (not shown) which will close and terminate gas flow to the torch head if the flame is extinguished, that is, if the related temperature sensor detects a corresponding temperature drop.

In a preferred embodiment the upstream end 20a of tube 20 is five inches diameter and is mounted directly through the center of housing 14 when viewed in lateral cross section. The five inch diameter section 20c of tube 20 houses cylinder 40b snugly therein and the smaller two and one half inch diameter by three inch long cylinder 40a that itself houses torch head 28. Air flow in direction D flows through the annular breathing channel 46 formed between cylinder 40a and torch head 28 for controlled and optimized combustion so as to get the maximum or optimized length of flame 22. The diameter of tube 20 is reduced to three inches diameter at the throat or combustion section 20d of tube 20. The downstream end 20b of tube 20 extends three quarters of an inch through the insulated housing end wall 14c into a ventilated exhaust lock box 48. The open exhaust end 20b of tube 20 is covered with a baffle 50 that retains heat maximum efficiency, and also assists cooling the exhaust.

Air flowing through breathing channel 46, that is entering in direction A generally and flowing over torch head 28 in direction D, is partially entrained into and through apertures 28c. Three equally radially spaced apart apertures 28c are provided in the illustrated embodiment. Air from apertures 28c mixes in chamber 26a with fuel from orifice 26b. The fuel/air mixture exits bore 26 through apertures in plate 24 whereupon the mixture is ignited to form flame 22. Air in breathing channel 46 that is not entrained into apertures 28c continues to flow over torch head 28 and exits channel 46 through an opposed facing pair of semicircular slots 58 formed in rigid torch head supporting bracket or member 60. Slots 58 substantially completely encircle downstream end 28b of torch head 28. Although not wishing to be bound by any particular theory of operation, applicants believe that the air flow through slots 58 enhances the elongation of flame 22 downstream along tube 20, perhaps by causing a vortex or vorticity in the flow in throat 20d thus enhancing complete fuel/air mixing and an improved more complete combustion.

In a preferred embodiment the fuel for torch head 28 is propane. Torch head 28 may be fabricated from brass rod, and atomizes propane through a #80 drill bit propane orifice 26b for combustion in chamber 26a. The torch head 28 is mounted into the two and one half inch diameter tube section 20c so as to be mounted flush into torch head housing 34.

In more detail, in a preferred embodiment the heater housing 14 includes an outer and an inner protective shell 14d and 14e respectively made of galvanized steel sandwiching insulation 52 therebetween. In one embodiment, insulation includes a high temperature woven fiber ceramic insulation layer 52a such as Cerablanket (a registered trademark of Thermal Ceramics, Inc. of Augusta, Ga.) adjacent the inner shell 14e. A thickness of one inch may be employed. Outwardly of layer 52a and adjacent to outer shell 14d, is a layer 52b of mineral fiberboard insulation such as FBX Industrial Board insulation from Fiberex Insulations Inc., Sarnia, Ontario, Canada. A thickness of two inches may be employed.

In one example of a ground heating system, multiple heaters 10 are joined by a length of flexible three quarters of an inch preferably armored fuel line 54 between adjacent heaters, that is, coupled between the main fuel lines 12 of adjacent heaters 10. Flexible coupling between adjacent heaters by flexible fuel lines 54 allows for accommodating elevation and slope changes, as well as rotation of the heaters to accommodate corners. As described above, main fuel line 12 may be a three quarters of an inch pipe safely located within the outer shell 14d of housing 14 and through the fiber board insulation layer 52b so as to be wholly located within its own longitudinally extending cavity 56 formed in board insulation layer 52b. Cavity 56 extends along the entire length of outer shell 14d.

To further protect the equipment from tampering, vandalism, and general damage, the burner and exhaust ends 20a and 20b respectively of each heating tube 20 in each heater 10 are enclosed within lock boxes 48a and 48b respectively. Each lock box has a lid and openings for coupling with the burner or discharge end of an adjacent heater 10, and has holes or louvers to allow air/exhaust travel. When fastened to housing 14, for example using mechanical fasteners, lock boxes 48a and 48b are spaced above the ground level of ground 18 to allow for insulated mats or blankets (not shown) to be placed tightly and thermally efficiently around each heater 10 to increase heat radiated to the ground instead of being dissipated to atmosphere. This increases the thaw dimensions being warmed. The top of each lock box has a lockable lid to control access to the valves, torch, etc. Advantageously, the lock boxes of adjacent heaters are spaced only enough to allow for insulated mats to prevent heat loss between heaters and promote thermal efficiency.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims

1. A ground heater for warming the ground comprising:

an insulated housing having a cavity extending along substantially an entire length thereof, a bottom of said housing having an opening along substantially said entire length thereof for registry of said cavity with a ground surface to be warmed when said housing is placed thereon,

a hollow heating tube extending through said cavity along said entire length and so as to extend through opposite end walls of said housing, said tube having an upstream end and an opposite downstream end, a torch head housing mounted to said upstream end of said heating tube in fluid communication therewith,

a primary fuel line mounted in and extending along a sidewall of said housing so as to extend from an upstream end wall of said opposite end walls to a downstream end wall of said opposite end walls, a branch fuel line extending from said primary fuel line to an upstream end of said torch head housing,

a torch head having a fuel metering orifice and a bore extending through said torch head downstream of said fuel metering orifice, and at least one aspirating aperture downstream of said metering orifice in a sidewall of said torch head in fluid communication with said bore, said torch head mounted substantially concentrically in, so as to be supported by, said torch head housing, said torch head housing having opposite upstream and downstream ends and a perforated support at said downstream end of said torch head housing, a flame holder end of said torch head mounted to said support and adjacent said downstream end of said torch head housing so as to dispose a flame seated in said flame holder end downstream along said heating tube towards said downstream end of said heating tube to thereby discharge exhaust gases of combustion therefrom and to draw an ambient airflow into said upstream end of said torch head housing, over said torch head and through said at least one aspirating aperture and said perforated support,

wherein said perforated support comprises at least one rigid member on which said torch head is mounted within said torch head housing, said rigid member defining at least one breathing aperture which extends substantially entirely around said downstream end of said torch head in a plane substantially orthogonal to a direction of flow of said ambient air through said torch head housing, said torch head housing and said torch head defining a substantially annular breathing channel therebetween extending in said direction of flow and in registry with said at least one breathing aperture.

2. The apparatus of claim 1 wherein an outside diameter of said breathing channel is substantially equivalent to an inside diameter of said heating tube.

3. The apparatus of claim 1 wherein said torch head housing is cylindrical.

4. The apparatus of claim 3 wherein said torch head housing comprises a concentrically nested pair of cylinders, and wherein said torch head is mounted concentrically within an inner cylinder of said pair of cylinders.

5. The apparatus of claim 4 wherein said upstream end of said heating tube is of greater diameter than a mid-section of said heating tube extending between said upstream and downstream ends of said heating tube, and wherein an outer cylinder of said pair of cylinders mates telescopically into said upstream end of said heating tube.

6. The apparatus of claim 1 wherein said at least one aspirating aperture comprises a radially spaced apart array of apertures around said torch head for aspirating air radially into said bore to mix with fuel flowing under pressure through said metering orifice and into said bore, and wherein a perforated flame holder plate is mounted across a downstream end of said bore in the flow of said mixture of fuel and air exiting said bore into said upstream end of said heating tube.

7. The apparatus of claim 6 wherein igniter is mounted adjacent downstream of said flame holder end of said torch head.

8. A system of ground heaters comprising a plurality of ground heaters according to claim 1 in series along said primary fuel line.

9. The system of claim 8 wherein said plurality of heaters includes a first plurality of said heaters mounted in series along a first primary fuel line, and a second plurality of heaters mounted in series along a second primary fuel line, wherein said first and second primary fuel lines are in parallel fluid communication for operating in parallel said first and second plurality of said heaters.

10. The apparatus of claim 1 wherein said at least one breathing aperture includes a pair of breathing apertures oppositely disposed on opposite sides of said downstream end of said torch head.

11. The apparatus of claim 10 wherein said at least one breathing aperture consists solely of said pair of breathing apertures.

12. The apparatus of claim 10 wherein said pair of breathing apertures includes a pair of opposed facing substantially semi-circular slots disposed substantially symmetrically on said opposite sides of said downstream end of said torch head.

13. The apparatus of claim 11 wherein said pair of breathing apertures includes a pair of opposed facing substantially semi-circular slots disposed substantially symmetrically on said opposite sides of said downstream end of said torch head.

14. A method for warming the ground comprising the steps of:

a) providing an insulated housing having a cavity extending along substantially an entire length thereof, a bottom of said housing having an opening along substantially said entire length thereof and placing said housing on a ground surface to be warmed so as to register said cavity with the ground surface to be warmed by positioning said opening adjacent the ground surface to be warmed,

b) providing a hollow heating tube extending through said cavity along said entire length and so as to extend through opposite end walls of said housing, said tube having an upstream end and an opposite downstream end, a tubular torch head housing mounted to said upstream end of said heating tube in fluid communication therewith,

c) providing a primary fuel line mounted in and extending along a sidewall of said housing so as to extend from an upstream end wall of said opposite end walls to a downstream end wall of said opposite end walls, and a branch fuel line extending from said primary fuel line to said upstream end of said heating tube,

d) providing a torch head having a fuel metering orifice and a bore extending through said torch head downstream of said fuel metering orifice, and at least one aspirating aperture downstream of said metering orifice in a sidewall of said torch head in fluid communication with said bore, wherein said torch head is mounted substantially concentrically in, so as to be supported by, said torch head housing, said torch head housing having opposite upstream and downstream ends and a perforated support at said downstream end of said torch head housing, a flame holder end of said torch head mounted to said support and adjacent said downstream end of said torch head housing so as to dispose a flame seated in said flame holder end downstream along said heating tube towards said downstream end of said heating tube to thereby discharge exhaust gases of combustion therefrom and to draw an ambient airflow into said upstream end of said torch head housing, over said torch head and through said at least one aspirating aperture and said perforated support, wherein said perforated support comprises at least one rigid member on which said torch head is mounted within said torch head housing, said rigid member defining at least one breathing aperture which extends substantially entirely around said downstream end of said torch head in a plane substantially orthogonal to a direction of flow of said ambient air through said torch head housing, and wherein said torch head housing and said torch head define a substantially annular breathing channel therebetween extending in said direction of flow and in registry with said at least one breathing aperture,

e) supplying fuel under pressure to said fuel metering orifice in said torch head so as to mix metered fuel from said orifice and ambient air from said at least one aspirating aperture in said bore as said mixture flows downstream through said bore so as to exit said downstream end of said torch head, and

f) igniting said mixture exiting said downstream end of said torch head by an igniter mounted adjacent said flame holder end of said torch head.

15. The method of claim 14 further including adapting an outside diameter of said breathing channel so as to be substantially equivalent to an inside diameter of said heating tube.

16. The method of claim 14 further comprising the steps of adapting said torch head housing so as to include a concentrically nested pair of cylinders, and mounting said torch head concentrically within an inner cylinder of said pair of cylinders.

17. The method of claim 16 further including adapting said upstream end of said heating tube so as to be of greater diameter than a mid-section of said heating tube extending between said upstream and downstream ends of said heating tube, and adapting an outer cylinder of said pair of cylinders so as to mate telescopically into said upstream end of said heating tube.

18. The method of claim 14 further including adapting said at least one aspirating aperture to include a radially spaced apart array of apertures around said torch head for aspirating air radially into said bore to mix with the fuel flowing under pressure through said metering orifice and into said bore, and further including mounting a perforated flame holder plate across a downstream end of said bore in the flow of the mixture of fuel and air exiting said bore into said upstream end of said heating tube.

19. The method of claim 14 further comprising the step of providing a plurality of ground heaters according to claim 14 in series along said primary fuel line.

20. The method of claim 19 further including adapting said plurality of heaters to include a first plurality of said heaters mounted in series along a first primary fuel line, and a second plurality of heaters mounted in series along a second primary fuel line, wherein said first and second primary fuel lines are in parallel fluid communication for operating in parallel said first and second plurality of said heaters.