US20080302351A1

US20080302351A1 - Gas-Fired Portable Heater

Info

Publication number: US20080302351A1
Application number: US11/758,889
Authority: US
Inventors: Donald O. Hunter; Clancy Holt; Ronald Holt
Original assignee: DYNAMIC OUTDOORS LLC
Current assignee: DYNAMIC OUTDOORS LLC
Priority date: 2007-06-06
Filing date: 2007-06-06
Publication date: 2008-12-11
Also published as: CA2634782A1

Abstract

A portable gas fired heater includes a combustion chamber having an air inlet and an air outlet. A low DC voltage (optionally AC voltage) fan or blower directs air through the combustion chamber so that the air is heated. Preferably, a vortex generator is located between the fan or blower and the combustion chamber such that air entering the combustion chamber swirls. The heater is designed to have a low center of gravity and thus difficult to tip-over. Nevertheless, several safety features are provided including a tip-over switch, thermal coupler, temperature limit switch, and a manual shutoff.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates broadly to gas-fired portable heaters. More particularly, this invention relates to propane fired portable heaters useful for heating small boats.
2. State of the Art
Outdoor portable heaters are typically gas-powered and are adapted to force heated air from a combustion chamber through an outlet into an open area. These heaters include a combustion chamber to ignite a source of fuel and generate heat. Air is drawn into the combustion chamber to permit combustion. The resulting heated air which is not needed for combustion is blown outward to provide heat in a direction predefined by the outlet.
The fuel source for most outdoor portable heaters is a gaseous hydrocarbon such as propane because of its relative availability and efficiency. The volatility of propane requires that a safe portable heater be equipped with sufficient safety systems such that propane does not become hazardous to the user.
Additionally, outdoor portable heaters should be stable when placed on a surface so that the heaters do not easily tip-over as a result of external forces. Numerous structural features have been used to provide structural stability for these heaters.
Despite the availability of outdoor portable heaters, various aspects of the commercially available portable heaters make them generally unsuitable for use on small boats (e.g., fishing and guide boats), as small boats pose various issues not otherwise generally encountered in the use of outdoor heaters. For example, small boats typically have very limited space and thus certain portable heaters which are not sufficiently small are not useful for the small boat application. In addition, because different small boats have different architectural features, a single portable heater is generally unable to direct its heat at desired heights or in desired directions so that it may be usable on different boats. Further, electrically fired heaters are not feasible on most small boats because the electrical power supply on a small boat is limited. Also, because most gas fired portable heaters are intended for stationary use, most gas powered portable heaters cannot safely and reliably supply heat in a strong wind which results from forward movement of a boat. Similarly, most gas fired portable heaters cannot safely and reliably supply heat when subjected to unpredictable motion due to waves or due to sudden boat movements.
Thus, there remains a need in the art to provide an adaptable portable heater which can supply sufficient heat in outdoor applications such as on small boats, and which can be safely operated despite being subjected to relatively extreme conditions.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a portable heater that can be used safely outdoors on the deck of a small boat.
It is another object of the invention to provide a portable heater that has a moveable hot air outlet that can change the direction of the heated air outflow without physical movement of the entire portable heater.
It is a further object of the invention to provide a portable heater that is extremely stable.
It is still another object of the invention to provide a portable heater that has a low center of gravity.
It is yet another object of the invention to provide a portable heater that includes a plurality of safety mechanisms directed to potential boat-related situations.
It is another object of the invention to provide a portable heater that has an adjustable footing.
It is a further object of the invention to provide a portable heater that has improved combustion.
It is still another object of the invention to provide a portable heater that can heat a relatively large area relative to the heater's relatively small size.
It is yet another object of the invention to provide a gas fired portable heater which is relatively quiet.
In accord with these objects, which will be discussed in detail below, a portable gas fired heater is provided for outdoor use, and is particularly suitable for, although not limited to, use on a small boat. The portable heater is used in conjunction with a separate gaseous fuel supply (such as propane gas, LPG, etc.) which is connected to the heater by a hose. The heater itself includes a combustion chamber having an air inlet, an air outlet and a low voltage electric fan or blower which is arranged to cause air to flow into the air inlet, through the combustion chamber and exit the air outlet. A burner tube assembly is located inside the combustion chamber and is fluidly coupled to the aforementioned hose through an electrically operated valve at a location outside the combustion chamber. A piezoelectric igniter extends into the combustion chamber and is located so that it can ignite gas flowing out of the burner tube assembly. According to the presently preferred embodiments, the combustion chamber is isolated by two perforate walls which allow air to pass into and out of the chamber but which limit the likelihood that combustible solid material will enter the chamber. In the preferred embodiments, the fan is located at the air inlet and a thermal coupler and thermal limit switch are located near the burner tube assembly. The thermal coupler senses when there is or is not a flame in the combustion chamber and the thermal limit switch senses the temperature.
The presently preferred combustion chambers are cylindrical and are mounted in a heater housing which is provided with an adjustable air flow director adjacent to the air outlet of the combustion chamber and/or an adjustable footing. The housing is dimensioned and the combustion chamber is so located such that the heater, overall, has a low center of gravity. The bottom of the housing is preferably provided with one or more adjustable feet and a tip-over switch. The top of the housing is preferably provided with a handle. In some embodiments, the fan is located inside the housing and the housing is provided with an air inlet adjacent to the fan. In other embodiments, the fan is attached to but external of the housing.
According to one embodiment, the low voltage fan is a squirrel cage blower driven by a DC motor and a vortex generating cone with vanes is located between the blower and the combustion chamber. When the motor is running, air is pulled into the squirrel cage and directed over the cone with vanes, thereby causing a turbulent airflow to reach the combustion chamber. The turbulent airflow increases the efficiency of the combustion and the distance that hot air is projected out of the combustion chamber is increased. According to an alternate embodiment, an AC motor is used.
According to another embodiment, a directional adjusting means is provided to allow a user of the portable heater to change direction of the out-flowing hot air without moving the entire portable heater. The directional adjusting means may take the form of an adjustable outlet or an adjustable foot.
In accord with another embodiment, the portable heater housing has a stable base which prevents the heater from tipping over. The stable base may take the form of a wide foot which is perpendicular to the direction of air flow through the combustion chamber in conjunction with a housing element which is in line with the combustion chamber and is located at the air entry end of the heater. Alternatively, the stable base may take the form of providing the housing with a larger footprint than the combustion chamber. In either case, the portable heater also maintains a low center of gravity so that the heater is maintained in an operable position on unstable surfaces such as on the deck of a moving boat.
According to another aspect, the portable heater contains multiple safety systems to guard against operational failures. First, a manual power switch to the fan can be turned off in the event of an emergency. Second, a temperature limit switch is provided that restricts fuel flow to the combustion chamber when the temperature of the portable heater exceeds a predetermined threshold. Third, a tip-over switch stops fuel flow if the portable heater tilts more than approximately 15 degrees from its resting position so that the heater may be used in unstable environments such as on the deck of a boat. Fourth, a thermal coupler is provided adjacent to the burner tube so that the supply of gas is automatically cut off if the flame goes out.
According to another embodiment, the housing is equipped with a control panel for activation of the heater and management of safety systems.
In accord with another embodiment, the hot air outlet of the portable heater is equipped with a noise reduction plate.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of first embodiment of an outdoor portable heater according to the invention;

FIG. 1 a is a side elevation view of an alternate first embodiment of the heater;

FIG. 2 is transparent side elevation view of the outdoor portable heater of FIG. 1;

FIG. 3 is a broken perspective view of the burner tube assembly;

FIG. 4 is an exploded perspective view of the combustion chamber, burner tube, fan, and associated components;

FIG. 5 is a simplified schematic block diagram illustrating the electrical components of the heater;

FIG. 6 is a side elevation view of a second embodiment of a heater according to the invention;

FIG. 6 a is a perspective view of a portion of the base of the heater of FIG. 6;

FIG. 7 is a cut away broken perspective view of the combustion chamber, vortex generating cone with vanes, and squirrel cage blower of the second embodiment;

FIG. 8 is a top plan view of the vortex generating cone with vanes; and

FIG. 9 is a perspective view of the air outlet of the second embodiment illustrating the sound dampening plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to FIGS. 1 and 2-4, a first embodiment of a portable gas fired heater 10 is shown. The heater 10 includes a combustion chamber 12 having an air inlet 14, an air outlet 16 and a low voltage electric fan or blower 18 is arranged to cause air to flow into the air inlet, through the combustion chamber and exit the air outlet. A burner tube assembly 20 is located inside the combustion chamber and is fluidly coupled to a hose 22 through an electrically (and manually) operated valve 24 at a location outside the combustion chamber 12. Those skilled in the art will appreciate that the hose 22 is similar to those used to couple LPG tanks to gas fired grills and it is provided with standard fitting 26 which readily couples to standard LPG tanks.
The burner tube assembly 20 is mounted on a perforate combustion chamber wall 28 at the air inlet 14 of the combustion chamber 12. A piezoelectric igniter 30 is also mounted on the wall and extends into the combustion chamber 12 and is located so that it can ignite gas flowing out of the burner tube assembly 20 into the combustion chamber 12. According to the presently preferred embodiments, the combustion chamber is isolated by the perforate wall 28, described above, and a second perforate wall 32. The perforate walls allow air to pass into and out of the chamber but limit the likelihood that combustible solid material will enter the chamber. In the preferred embodiments, a thermal coupler 34 and thermal limit switch 36 are located near the burner tube assembly. The thermal coupler 34 senses when there is or is not a flame in the combustion chamber 12 and the thermal limit switch 36 senses the temperature. As described in more detail below with reference to FIG. 5, the heater is turned off if gas is flowing into the combustion chamber but is not burning or if the temperature reaches a predetermined limit such as 87° F.
As seen best in FIGS. 1 and 2, all of the components are mounted in a housing 11 which has a relatively large base 11 a defining a relatively large footprint. According to the illustrated embodiment, the base is eighteen inches long, seven and one quarter inches wide in the front and six and one half inches wide in the rear. A carry handle 11 b is preferably located on the top of the housing 11 over the heater's center of gravity (i.e. between the fan 18 and the combustion chamber 12). A tip-over switch 38 (described in detail below with reference to FIG. 5) is advantageously centrally located in the base 11 a of the housing 11. As seen best in FIG. 1, the housing 11 is provided with an adjustable air director 42 which is pivotable about the point 44 so that the hot air output can be directed somewhat up or down relative to the housing 11 as indicated by the phantom lines in FIG. 1.
Referring now to FIG. 1 a, an alternate first embodiment of a heater 10′ according to the invention is shown with similar reference numerals with added ′ refer to similar parts. There are three differences between the heater 10 and the heater 10′ and they all relate to the housing 11′. The first difference is that the air director 42′ is not adjustable in this embodiment. The second difference is that an adjustable drop down leg 11′d is provided at the front of the base 11′a and is adjusted by thumbscrew 11′c. Loosening the thumbscrew allows the leg to drop down (or be pushed up) and fastening the thumbscrew secures the position of the leg. This arrangement provides a different way of directing hot air flow up or down. The third difference is that the tip-over switch 38′ has been moved to the back of the base so that the lowering of the adjustable foot does not trigger the tip-over switch. The switch is centrally located relative to the longitudinal axis of the heater however since a sideways tip-over is more likely than a longitudinal tip-over.
As seen best in FIG. 4, the fan 18 of the first embodiment includes fan blades 18 a which are coupled to an electric motor 18 b which is mounted on a fan guard 18 c and is selectively coupled to a power source (not shown) via an electrical cable 18 d. The power source may be a DC power source such as a battery or the DC output of an AC to DC converter which is coupled to an AC power source. The fan guard is used to mount the fan in the housing 11. The burner tube assembly includes a nozzle 20 a and an L-shaped tube 20 b. The perforate wall 28 is coupled to the combustion chamber via four flanges 28 a-28 d which are coupled to four similarly located flanges 12 a-1 d at the air intake end of the combustion chamber 12. It will be appreciated that, though not shown, the perforate wall 32 is coupled to the combustion chamber 12 in a similar manner. Screws, rivets, or the like are used to coupled the flanges of the perforate walls to the flanges of the combustion chamber. The piezoelectric igniter 30 includes the spark head 30 a, an electrical cable 30 b and a pushbutton piezoelectric transducer 30 c.
Referring now to FIG. 5, the above described fan/blower 18 and gas valve 24 are coupled to a DC power source 1 via a manual switch 40. (According to an alternate embodiment, an AC motor and an AC power source are used.) The coupling to the power source is interrupted by any one of the thermal coupler 34, temperature limit switch 36 and tip-over switch 38. The thermal coupler shuts off the supply of gas if the flame goes out. The temperature limit switch is preferably set to shut off the heater if the temperature exceeds a predetermined value, e.g. 87° F. If the fan shuts off, the temperature sensed by the temperature limit switch will shut down the burner after a short period of time. The tip-over switch is a spring loaded normally off switch (sometimes known as a dead man's switch). In the presently preferred embodiment, if the housing of the heater tips fifteen or more degrees, the circuit completed by the tip-over switch is broken.
Turning now to FIGS. 6-9, a second embodiment of a heater 110 according to the invention is shown with similar reference numerals (increased by 100) referring to similar parts, The housing 111′ in this embodiment is generally cylindrical and is provided with a lower base 111′a and an upper handle 111′b. The base 111′a has a thumb screw release 111′c for lowering an L-shaped leg/foot 111′d (FIG. 6 a) as in the embodiment described above with reference to FIG. 1 a. The inlet to the housing (and the combustion chamber therein) is supplied by a squirrel cage blower 118 which also acts as a third point of tripod-like support in conjunction with the base 111′a and/or foot 111′d. A control panel 119 is mounted above the blower 118 and supports the piezoelectric pushbutton 130c, electrical switch 140 as well as a manual gas valve control 145 which is connected to a manually and electrically controlled gas valve (not shown) via a linkage 146. The outlet of the housing (and the combustion chamber contained therein) is provided with a “chimney reducer” 142′ which increases the velocity of the air exiting the combustion chamber by way of a venturi-like effect.
As seen best in FIG. 7, a vortex generator 150 is located between the blower 118 and the combustion chamber 112. The combustion chamber 112 and its associated parts are identical to the combustion chamber 12 and its associated parts described above with reference to FIGS. 2-4. The vortex generator 150 is comprised of a cone 152 and a plurality of substantially triangular vanes 154. These are arranged to cause the air exiting the blower to swirl as it enters the combustion chamber 112. The swirling air results in better heat transfer as the air passes through the combustion chamber.
As seen best in FIG. 8, the vortex generator 150 of the presently preferred embodiment has a conical portion 152 such that some air from the blower is directed to the periphery of the combustion chamber. Four generally triangular blades or vanes 154 are arranged as shown. The blades and the conical portion direct the air into a swirling cylinder as the air enters the combustion chamber. The air is thus exposed to the combustion chamber in a substantially uniform way so that the air is substantially uniformly heated. According to the presently preferred embodiment, the base of the conical portion has a diameter of about six inches.
As seen best in FIG. 9, a sound dampening plate 156 is placed after the second perforate wall 132 of the combustion chamber. As illustrated the sound dampening plate is provided with six large perforations 158. According to the presently preferred embodiment, the perforations are each about two inches in diameter. The sound dampening plate reduces noise by approximately 33%.
The embodiment of FIGS. 6-9 is even more compact than the embodiments of FIGS. 1-4. The cylindrical housing is approximately eight inches in diameter and approximately twenty-three inches long, including the four inch long chimney reducer. The squirrel cage blower adds an additional seven to eight inches to the overall length of the heater.
The fan/blower motor is preferably a 12 or 24 VDC motor that consumes approximately 5.1 amperes and produces about 1/35 HP at a speed of approximately 1,875 rpm. The fan/blower preferably produces a hot air output of approximately 175 cfm. The overall weight of the heater is approximately 12 lbs and it produces a thermal output of approximately 30,000 btus.
There have been described and illustrated herein several embodiments of a portable gas fired heater. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.

Claims

1. A portable gas fired heater, comprising:

a combustion chamber having an air inlet and an air outlet;

a burner tube located in the combustion chamber;

a gas flow tube coupled to the burner tube and adapted to be coupled to a source of burnable gas;

means for propelling a stream of air into the air inlet; and

a vortex generator located between the air inlet and the means for propelling a stream of air, said vortex generator including a substantially conical part and a plurality of stationary vanes extending outward from said substantially conical part which cause the stream of air to be turbulent as it enters the air inlet.

2. A heater according to claim 1, further comprising:

an adjustable air flow director adjacent to said air outlet.

3. A heater according to claim 1, wherein:

said means for propelling a stream of air is an electric fan.

4. A heater according to claim 3, wherein:

said fan is a low voltage DC fan.

5. A heater according to claim 3, wherein:

said fan is an AC fan.

6. A heater according to claim 1, wherein:

said means for propelling a stream of air is a squirrel cage blower.

7. A heater according to claim 6, further comprising:

a relatively wide foot, said relatively wide foot and said squirrel cage blower together forming a support for said heater.

8. A heater according to claim 6, wherein:

said blower is a low voltage DC blower.

9. A heater according to claim 6, wherein:

said blower is an AC blower.

10. A heater according to claim 1, wherein:

said heater has a low center of gravity.

11. A heater according to claim 1, further comprising:

sound dampening means adjacent said air outlet.

12. A heater according to claim 11, wherein:

said sound dampening means includes a perforated plate.

13. A heater according to claim 1, further comprising:

a safety device selected from the group consisting of a tip-over switch, a thermal coupler, and a temperature limit switch.

14. A portable gas fired heater, comprising:

a gas combustion chamber having an air inlet and an air outlet;

a burner tube located in said combustion chamber;

a gas supply tube coupled to said burner tube and adapted to be coupled to a source of burnable gas;

means for propelling a stream of air into the air inlet; and

a plurality of safety devices including a tip-over switch, a thermal coupler, and a temperature limit switch each of which is automatically operable to turn off said gas fired heater.

15. A heater according to claim 14, wherein:

said tip-over switch is centrally located underneath said heater, and said thermal coupler and temperature limit switch are located inside said combustion chamber.

16. A heater according to claim 14, further comprising:

a gas valve operatively coupled to said safety devices.

17. A heater according to claim 14, wherein:

said temperature limit switch prevents said heater from operating at a temperature of at least 87° F.

18. A heater according to claim 14, wherein:

said tip-over switch prevents said heater from operating if the heater tips at least 15 degrees.

19. A portable gas fired heater, comprising:

a gas combustion chamber having an air inlet and an air outlet;

a burner tube located in the combustion chamber;

means for propelling a stream of air into the air inlet;

a vortex generator located between the air inlet and the means for propelling a stream of air, said vortex generator including a substantially conical part and a plurality of stationary vanes extending outward from said substantially conical part which cause the stream of air to be turbulent as it enters the air inlet; and

20. A heater according to claim 19, further comprising:

a supporting foot wider than said combustion chamber.

21. A heater according to claim 20, wherein:

said heater has a low center of gravity.