US3504687A - Safety device for liquid fuel burner - Google Patents

Description

April 7, 1970 J. M. DUNSTON SAFETY DEVICE FOR LIQUID FUEL BURNER 2 Sheets-Sheet 1 Filed Aug. 23, 1968 Q m 2 ii I h l/ll/f ///////////I///// W\ mm mm.

0 0 0 0 n.r\ x SiFE-- c @x April 7, 1970 J. M. DUNSTON SAFETY DEVICE FOR LIQUID FUEL BURNER 2 Sheets-Sheet 2 Filed Aug. 23, 1968 United States Patent 3,504,687 SAFETY DEVICE FOR LIQUID FUEL BURNER James M. Dunston, Natick, Mass., assignor to the United States of America as represented by the Secretary of the Army Filed Aug. 23, 1968, Ser. No. 754,885 Int. Cl. F16k 17/14; F23n ]/00 US. Cl. 13768 Claims ABSTRACT OF THE DISCLOSURE A safety device for a liquid fuel burner having a reservoir capable of being filled with liquid fuel under pressure up to a predetermined level providing a vapor space above the liquid fuel in the reservoir comprising a fuel feed tube for conducting liquid fuel from the reservoir to the burner, the fuel feed tube being mechanically rupturable at a predetermined point within the vapor space upon deformation of the reservoir wall caused by pressure within the reservoir to cut off the flow of liquid fuel from the reservoir to the burner.

The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a safety device for liquid fuel burners, particularly gasoline burners, to prevent excessive pressure buildup in the fuel tanks thereof and to minimize the possibility of explosion.

In outdoor camping activities and military field operations, pressurized liquid fuel burners are often used for heating and cooking purposes. Such burners range in size from very compact stoves having a capacity of about 2,500 B.t.u. per hour for use by individuals or small groups to relatively large and complex burner units used by the military in cooking and baking for large groups, such as the Burner Unit, Gasoline Field Range Outfit described in Military Specification MlLB 40098C dated July 12, 1967, which has a capacity of about 55,000 B.t.u. per hour. All of these burners have certain common characteristics including a closed fuel tank or reservoir, means for creating a pressure greater than atmospheric with the tank and a fuel filling device which prevents complete filling of the tank. The latter device insures a minimum vapor space above the level of the liquid fuel in the tank at all times. This vapor space provides for safe expansion of the fuel under normal operating conditions as the temperature of the fuel rises due to the proximity of the burner where combustion is occurring.

When the unit is operating, fuel is drawn from the lower portion of the tank through a fuel feed tube to a generator or vaporizer wherein the liquid fuel is converted to vapor prior to being fed to the burner in order to provide for more efficient combustion. Because of the requirement for portability of such equipment, the fuel tanks, the generator and the burner are usually arranged in close proximity to one another to provide a compact unit. In this arrangement, considerable heat is reflected or radiated from the burner and the container being heated above the burner and heat is conducted from the generator and other parts of the unit to the fuel tanks. The resulting increase in the temperature of the liquid fuel and fuel vapors in the tank causes an increase in the pressure within the tank. When a burner unit is used at or near its heating capacity for heating a large container and to an even greater extent when the unit is used within a field range cabinet or field oven, the danger of excessive pressure buildup in the tanks with the possibility of explosion is a recognized problem. Close surveillance of the burner may permit corrective ice action by reducing the rate of combustion in the burner. However, such surveillance is not always possible in actual operation since distraction or, in the case of military operations, operating conditions may not permit close attention.

It is therefore an object of the present invention to provide a means for the prevention of explosions of fuel tanks in gasoline fired field range burner units.

Another object of the invention is to provide a safety device which will automatically cut off the supply of liquid fuel from a fuel tank to a burner unit in a gasoline field range when the pressure in the fuel tank reaches a predetermined level.

A further object of the invention is to provide a safety device which will automatically reduce the pressure within the fuel tank of a pressurized gasoline burner by discharging combustible vapors from within the tank through the burner for normal combustion.

A still further object of this invention is to provide a safety device for pressurized gasoline burners which is tamper-proof in that it cannot be by-passed or rendered inoperative.

A still further object of this invention is to provide a safety device which may be simply and inexpensively replaced after it functions.

Various other objects and advantages derived from the invention will be apparent from the following description of one embodiment of the invention and from the appended claims.

The foregoing objects are accomplished by providing a fuel feed tube which is mechanically rupturable at a predetermined point thereon above the level of liquid fuel in the tank and means mounted within the fuel'tank for rupturing the fuel feed tube upon the occurrence of a predetermined pressure within the fuel tank. The supply of liquid fuel to the generator is cut off when the fuel feed tube is ruptured and the fuel rich vapors in the upper part of the fuel tank are passed through the generator to the burner where they are safely consumed.

The present invention may be more fully understood by reference to the accompanying drawing showing one embodiment of the invention, wherein like reference characters designate like parts in the various views, and in which:

FIGURE 1 is a vertical plan view, partially in section, of a gasoline burner unit of the type covered by the abovementioned Military Specification MIL-B-40098C, modified in accordance with the present invention.

FIGURE 2 is a partial horizontal section of the fuel tank and fuel feed tube of the gasoline burner unit shown in FIGURE 1, with portions of the fuel tank broken away, along the plane 22 of FIGURE 1; and

FIGURE 3 is an enlarged vertical sectional view, with portions broken away, of the fuel feed tube, the indented portion of the sidewall of the fuel tank, and the fuel feed tube connecting member, as seen in FIGURE 1 with the position of these elements after operation of the safety device being shown in broken lines.

Referring more particularly to FIGURE 1, the burner unit comprises a generally tubular frame 4, a fuel tank 5 supported by clamps (not shown) attached to the tubular frame, a generator assembly 6, a fuel feed tube 7, a burner head 8, a mixing chamber assembly 9, a needletype control valve 10, an air valve 11, a pressure indicating gage 12, and a top shield assembly 13. In addition, such units are generally provided with preheater means and an air pump, which have been omitted from the drawings for purposes of clarity. The generator assembly 6 extends over the burner head 8 such that the heat from the flame at the burner head serves to vaporize the liquid fuel passing through the generator assembly prior to its being introduced into the mixing chamber 14 and thence to the burner head.

The fuel tank 5 is preferably generally U-shaped and has a generally cylindrically shaped cross-section except through a portion of the bight of the U-shaped tank. One arm of the U-shaped fuel tank has a filling device comprising a filler tube (not shown) extending therethrough to the interior of the fuel tank. The configuration of the filler tube provides a means for introducing liquid fuel into the fuel tank up to a predetermined maximum level which assures a minimum air space in the tank above the level of the fuel. The filler tube is closed by a filler cap assembly (not shown). As shown in FIGURES 1, 2 and 3, an indented portion is formed in the sidewall of the fuel tank at the bight of the U. This indented portion is conformed to expand or deform outwardly when the pressure within the fuel tank increases to a level which is substantially above normal operating levels but safely below pressure levels which would cause the tank to rupture. For example, in the burner unit described in Military Specification MILB-40098C, which has a normal operating pressure of 30 p.s.i.g., outward movement of the indented portion of the tank occurs between 90-125 p.s.i.g. while rupture of the tank would occur at about 350 p.s.i.g.

The generator assembly 6 is composed of an elongated tubular member 16 which is preferably filled with chopped steel wool fiber which serves as both a heat transfer and filtering medium, whereby the liquid fuel passing through the generator assembly is vaporized and some fuel additives, particularly tetraethyl lead, are filtered out.

The front end of the elongated tubular member 16 is provided with a downwardly extending tube 17 which connects the generator assembly to the control valve 10. The rear end of the elongated tubular member 16 is provided with a downwardly extending tube 18 including a flanged lower end portion 19 which cooperates with nut 20 to attach the generator assembly to the fuel feed tube 7 and the fuel tank 5 at bushing 21.

The fuel feed tube 7 is comprised of a flanged upper end portion 22 and an elongated cylindrical tube 23 joined to flanged upper end portion 22 and extending downwardly to a point near the bottom of the fuel tank. The fuel feed tube cooperates with bushing 21, flanged lower end portion 19, and nut 20 to connect the fuel feed tube with downwardly extending tube 18. The elongated cylindrical tube 23 is preferably cut or formed at an oblique angle at its lower end and has a weakened portion 24, preferably formed by a V-shaped cut, which extends substantially completely around the circumference of tube 23 at a level which is above the normal maximum level of the liquid fuel in the fuel tank and, therefore, within the vapor space 25 above the liquid fuel. The weakened portion 24 in the form of a V-Shaped cut has a depth such that, if the tube 23 is bent appreciably, it will rupture at the weakened portion 24. A cut having a depth of approximately half the thickness of the sidewall of tube 23 has been found suitable for this purpose.

As shown in FIGURES 1, 2, and 3 a connecting member 26 in the form of a flat piece of metal bent to form an angle is welded or otherwise attached to the sidewall of the fuel tank at the interior surface of indented portion 15. Arm 27 of the connecting member extends inwardly of the fuel tank and has a bore 28 through which tube 23 passes in a snugly fitting relation. Connecting member 26 is attached to indented portion 15 at such a level that arm 27 will be appreciably below weakened portion 24 of tube 23. As a result of this arrangement, when the indented portion of the fuel tank expands outwardly due to excessive pressure within the fuel tank, as discussed above, the connecting member 26 pulls and bends tube 23 until the latter ruptures at weakened portion 24, as discussed above. This automatically stops the flow of liquid fuel from the fuel tank through the fuel feed tube into the generator assembly, only the fuel vapors in the vapor space 25 above the liquid fuel being able to flow through the ruptured fuel feed tube into the generator assembly and thence to the burner head. This has the immediate effect of reducing the pressure within the fuel tank to a safe level and very soon thereafter the flame is extinguished because of lack of sufficient fuel vapors passing through the burner to maintain operation thereof.

In the operation of the burner unit described, the fuel tank 5 is filled with gasoline to the level permitted by the filling device, leaving vapor space 25 in the fuel tank. The filling device and the control valve 10 are then closed. The fuel tank is pressurized by means of an air pump (not shown) connected to air valve 11 to a pressure of about 25 p.s.i.g. The front portion of the generator assembly is heated by the preheating means (not shown). When sufficient preheating has taken place, control valve 10 is opened, permitting liquid fuel to flow from fuel tank 5 upwardly through fuel feed tube 7 into generator assembly 6 where it is vaporized, the fuel vapors passing through control valve 10 into mixing chamber 14 where air is mixed with the fuel vapors. The mixture of fuel vapors and air then passes upwardly into burner head 8, emerging therefrom through burner head slots 29, at the exterior ends of which it burns. The preheating means may also serve as a pilot for igniting the mixture of fuel vapors and air emerging from the burner head slots in starting the burner operation. The control valve 10 is used to establish the desired rate of combustion at the face of the burner head. Heat produced by the combustion of the mixture of fuel vapors and air in most cases will be conducted away sufficiently rapidly by Whatever equipment is being heated to prevent excessive buildup of heat and pressure in the fuel tank. The top shield assembly 13 assists in preventing excessive buildup of pressure in the fuel tank. However, enough heat passes back to the fuel tank to maintain suflicient pressure therein to maintain flow of liquid fuel into the generator assembly without requiring air pressure once the burner is in operation.

If the burner unit should be operated within the confines of a field range cabinet or field oven or the like or under other conditions whereby the temperature, and therefore the pressure, increases in the fuel tank to dangerous levels, i.e. levels substantially in excess of normal, as described above, the indented portion 15 of the fuel tank expands or deforms outwardly to a position shown in broken lines as 15' in FIGURE 3. This movement of the indented portion causes the connecting member 26 to move to a position shown in broken lines as 26' in FIGURE 3, arm 27 of the connecting member taking the new position shown in broken lines as 27'. This movement of connecting member 26 and arm 27 causes the fuel feed tube 23 to bend toward indented portion 15 to a position shown in broken lines as 23 in FIGURE 3. If the pressure is sufiiciently great in the fuel tank, tube 23 ruptures at weakened portion 24 before rupture of the fuel tank occurs. Reduction of the pressure in the fuel tank begins immediately upon rupture of the fuel feed tube and the resulting cessation of flow of liquid fuel from the fuel tank into the generator assembly. The flame is not instantaneously extinguished since under the high temperature condition some vapors of the fuel will continue to flow from the vapor space above the liquid fuel in the fuel tank through the ruptured fuel feed tube, the generator assembly, and the mixing chamber assembly to the burner head and will burn for a short time. However, after a short time, the flame will be extinguished due to lack of sufficient fuel passing through the burner unit to maintain operation thereof. Thus the danger of explosion of the fuel tank is greatly reduced.

Resumption of use of the burner unit after rupture of the fuel feed tube requires replacement of the damaged fuel tank and fuel feed tube with a new fuel tank having its indented portion and connecting member properly disposed to cooperate with a new fuel feed tube having a weakened portion, as described above. Replacement of the fuel tank and fuel feed tube is much less costly than the replacements which would be required if the fuel tank exploded, not to mention the potential savings in terms of lives or personal injuries which are accomplished by the safety device of the invention.

The safety device of the invention has the additional significant advantage of being substantially tamper-proof. It cannot be readily by-passed or rendered inorperative since the indented portion of the fuel tank and the connecting member are built into the interior of the tank, out of reach of potential tamperers. Once the fuel feed tube is connected to the fuel tank, the connecting member and the fuel feed tube passing therethrough are enclosed by the fuel tank, only the automatic operation of the safety device under excessive pressure conditions, as described above, will bring about any change in the arrangement of the several parts of the safety device.

While the present invention is particularly useful in conjunction with the gasoline fired field range burner units herein described, it can also be used as a safety device in other types of burners or heaters employing liquid fuels, such as gasoline, kerosene, or other volatile fuels, whenever there is a possibility of an excessive build-up of temperature and pressure of fuel vapors in the fuel tank of such equipment as the result of heat being reflected, radiated, or conducted back to the fuel tank and fuel feed tubefrom the burner or generator or objects being heated.

It will be understood that various changes in details, materials of construction, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A safety device for a liquid fuel burner having a reservoir capable of being filled with liquid fuel under pressure up to a predetermined level providing a vapor space above said liquid fuel in said reservoir comprising a fuel feed tube for conducting liquid fuel from said reservoir to said burner, said fuel feed tube being mechanically rupturable at a predetermined point within said vapor space, and means mounted within said reservoir for movement against said tube to rupture same upon the occurrence of a predetermined pressure within said reservoir whereby the flow of liquid fuel from said reservoir to said burner is cut off upon the occurrence of said predetermined pressure within said reservoir.

2. A safety device as in claim 1 wherein said fuel feed tube has a weakened portion in its sidewall at a point within said vapor space at which point said fuel feed tube ruptures on being deformed a predetermined amount.

3. A safety device as in claim 2 wherein said weakened portion in the sidewall of said fuel feed tube comprises a V-shaped circumferential cut in the exterior surface thereof.

4. A safety device as in claim,1 wherein said means mounted within said reservoir comprise an arm having one end attached to the wall of said reservoir and having an opening in the other end thereof for receiving the portion of said fuel feed tube lying below said predetermined point thereon whereby upon predetermined deformation of said reservoir wall under the influence of internal pres sure, movement of said arm will cause said tube to rupture at said predetermined point thereon.

5. A safety device as in claim 4 wherein a portion of the wall of said reservoir is indented, said one end of said arm being attached to said indented portion.

References Cited FOREIGN PATENTS 555,283 1/1957 Italy.

WILLIAM F. ODEA, Primary Examiner R. GERARD, Assistant Examiner US. Cl. X.R.

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