Title of Invention

A SAFETY VALVE FOR PRESSURE STOVES

Abstract

This invention provides a pressure stove working on a liquid fuel such as kerosene comprising a metal pressure tank R capable of being hermetically closed, a rigid outlet tube D extending from near the bottom of the tank to a burner U, a rigidly fitted air pump provided on the equipment for raising the pressure inside the tank R, and a safety valve S provided towards the top of said pressure tank, said safety valve comprising an opening E provided towards the top of said tank and a cap P made of a heat and pressure sensitive nonmetallic material such as plastic or rubber dimensioned to press fit on to the said opening E.

Full Text

This invention relates to a safety valve for pressure stoves. Stoves, pertomaxes or blowlamps having a metal pressure tank inflated by a rigidly fitted air pump are popular because of their portability and efficiency. But accidents for the users of these appliances are common as the pressure tank occasionally bursts due to increased pumping and/or heating of the lank. Spring biased safety valves for the pressure tank already exist. The spring biased safety valve comprises a metal disc provided on an opening at fee top of the pressure tank, said metal disc being held down on to the said opening by a spring. Under routine working pressures of the appliance the disc is not lifted up, but when the pressure inside the tank reaches near bursting levels the disc is lifted up to release the pressure. But in spite of the availability of this safety valve accidents continue to occur. The reasons for this are that the stove with the spring biased safety valve is costly so that people tend to purchase the cheap stove (without a safety valve) and that the spring biased valve itself gets stuck occasionally. Most pressure stoves and petromaxes have a hard rubber washer provided under the metal cap that is opened for filling the lank with kerosene. This rubber washer is held down by the threaded metal cap so as to provide an aitight pressure chamber. However this rubber washer cannot give way before an explosion as it is held down by the threaded metal cap. The object of this invention is to propose an economical and unfailing safety valve for the above appliances. Accordingly this invention provides a pressure stove, petromax or blowlamp working on a liquid fuel such as kerosene comprising a metal pressure tank R capable of being hermetically closed, a rigid outlet tube D extending from near the bottom of said tank to a bumer U, an air pump fitted rigidly on to the equipment for raising the pressure inside the tank, and a safety valve S provided towards the top of the pressure tank, said safety valve comprising an opening E provided towards the top of said tank and a cap P made of a heat and pressure sensitive nonmetallic material such as plastic or rubber dimensioned to press fit on to the said opening E. In the preferred embodiments the safety valve opening on the said tank is formed by the mouth at the top of a tubular projection extending upwards from the said tank. An outer metal cap is provided for covering the said heat and pressure sensitive cap. In some embodiments means are provided for positioning the caps spaced from each other and further means are also provided in others for the space between the two caps to communicate with the exterior. The outer metal cap besides shielding the inner synthetic cap from the heat and flames also helps to retrieve the inner cap once tt has been pushed out by high pressure within the tank. The sensitive inner cap is preferably cup shaped and dimensioned to press fit into the mouth of the safety valve. The size of the inner cap can be varied according to the sensitivity required. It has to be noted that in the stove according to the invention the outer metal cap does not restrict the movement of the inner synthetic cap. Also as the inner synthetic cap is press fitted on to the safety valve mouth it is free to be ejected out. An inner press fitting cap made of most materials would be ejected out and can act as a safety valve but in the stoves of the prior art this is not possible as threaded caps are being invariably used. The invention limits itself to nonmetallic materials and that too heat and pressure sensitive materials such as plastic or rubber. A separate mouth capable of being closed by a cap is preferably provided towards the top of said tank (but below the safety valve) for filling the tank with liquid fuel. Means for regulating the flow of liquid fuel to the burner is also preferably provided along with the appliance. The body of the air pump is conveniently housed within the pressure tank. The invention will now be described with reference to the accompanying drawings, wherein: Fig. 1: is a diagrammatic representation of a pressure stove fitted with the safety valve according to the invention; Fig.2: is the sectional elevation of an embodiment of the safety valve according to the invention fitted on the pressure tank of the stove. The invention is illustrated and explained with reference to a pressure stove but it is equally applicable to petromaxes or blowlamps and other devices employing a metal pressure tank and a burner. As shown in the figures the pressure stove working on kerosene has a pressure lank R made from metal sheet, a rigid outlet tube D made of metal extending from near the bottom of the tank to a burner U through a vertical tube J, and a pipe valve V for regulating the flow of kerosene. All these parts are fitted together through a flame F. A rigidly fitted air pump (not shown in the figure) is provided along with the equipment, the body of the pump being housed within the pressure tank R. M is the mouth capable of being closed by a threaded metal cap (with a sealing disc below) for filling the tank with kerosene. S is the safety valve provided towards the top of the pressure tank. The mouth M is provided a little below the safety valve S so that air is enclosed within the tank even when it is full. The safety valve is shown in detail in Fig.2 and this has an outwardly extending tubular projection N of the pressure tank, said projection made of metal being externally threaded towards the top. The mouth E of this tubular projection is engaged by a resilient cup shaped cap P made of plastic or rubber, said cap being dimensioned to press fit into the said mouth so as to provide an air tight fitting. A resilient cap made of low-density polythene is preferred. The resilient cap that is tightly fitted would provide a leak proof closure. For the ordinary working pressures of the pressure stove this cap would remain in place due to the friction between the sidewall of the cap and the neck of the said tubular projection. Due to increased manual pumping or due to accidental flame heating of the pressure tank the pressure within the tank will reach a high value and would lift up the cap P. Even in cases where the cap is not lifted up due to a functional failure the plastic or rubber cap under the high temperature and pressure that is generated would get damaged and would leak before the metal tank can burst. The diameter and resilience of the cap P can be adjusted so that the cap will not be lifted up during the routine working of the pressure stove but would be lifted up under the near bursting pressure within the tank. The tubular projection N usually has a diameter ranging between 1 and 4 cm and in the embodiment illustrated it has a diameter of 1.75 cm The metal cap C has an internally threaded skirt dimensioned to fit over the externally threaded projection N. The skirt of the fitted cap C touches the rim Q so that the base of the metal cap is positioned spaced from the synthetic cap P in the fully fitted position of the caps. The base of the cap C is provided with an caning G that allows the air to escape out. The cap C acts as a retriever of the synthetic cap P that might otherwise be thrown off to a distance by the near bursting pressure within the tank. In the routine working of the stove the metal cap C also prevents burning of the synthetic cap by the flames on the tank that at times occur due to kerosene spilling over and catching fire. The metal cap does not restrict the dislodgement of the inner synthetic cap from the safety valve mouth E. I claim: 1. A pressure stove working on a liquid fuel such as kerosene comprising a metal pressure tank R capable of being hermetically closed, a rigid outlet tube D extending from near the bottom of said tank to a burner U, an air pump fitted rigidly on to the equipment for raising the pressure inside the tank, and a safety valve S provided towards the top of the pressure tank, said safety valve comprising an opening E provided towards the top of said tank and a cap P made of a heat and pressure sensitive nonmetallic material such as plastic or rubber dimensioned to press fit on to the said opening E. 2. The appliance as claimed in claim 1, wherein said heat and pressure sensitive cap is resilient so as to provide an airtight closure. 3. The appliance as claimed in claims 1 to 2, wherein said safety valve opening E on the tank R is formed by the mouth at the top of a tubular projection N extending upwards from the said tank, said tubular projection having a diameter ranging between 1 to 4 cm. 4. The appliance as claimed in claims 1 to 3, wherein an outer metal cap C is provided for covering the said heat and pressure sensitive nonmetallic cap P. 5. The appliance as claimed in claim 4, wherein means are provided for positioning the said caps such that their bases are spaced from each other and further means provided for the space between the two caps to communicate with the exterior. 6. The appliance as claimed in claims 1 to 5, wherein said heat and pressure sensitive cap P is cup shaped and is capable of press fitting into the mouth E of the safety valve. 7. A pressure stove substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Documents:

2258-mas-1998 abstract duplicate.pdf

2258-mas-1998 abstract.pdf

2258-mas-1998 claims duplicate.pdf

2258-mas-1998 claims.pdf

2258-mas-1998 correspondence others.pdf

2258-mas-1998 correspondence po.pdf

2258-mas-1998 description (complete) duplicate.pdf

2258-mas-1998 description (complete).pdf

2258-mas-1998 drawing duplicate.pdf

2258-mas-1998 form-1.pdf

2258-mas-1998 form-19.pdf

2258-mas-1998 form-3.pdf

2258-mas-98 claims-duplicate.pdf

2258-mas-98 description (complete)-duplicate.pdf

2258-mas-98 drawings-duplicate.pdf