GB2262599A - Safety device for a pressurised fuel lamp - Google Patents

Abstract

A pressurised fuel lamp has a fuel reservoir 1 in its base with a filler opening 2. A vapour port from the head space of the reservoir 1 is provided to assist ignition of the lamp. In order to prevent liquid fuel being expelled through the vapour port, the maximum filling level A-A is controlled by providing an inlet port 19 which extends in a downwardly inclined direction from the filler opening 2. <IMAGE>

Description

TITLE: SAFETY DEVICE The present invention relates to a safety device, notably to an overfill prevention device for a pressurised fuel lamp and to a lamp incorporating such a device. The lamp may be fuelled by paraffin, by petrol or by any other suitable fuel.

BACKGROUND TO THE INVENTION: In one form of paraffin lamp, the paraffin or other liquid fuel is held in a basal reservoir under pressure and is fed via a heated coil or the like to a mantle upon which the vaporised fuel burns to cause the mantle to become incandescent. Typically, the reservoir is pressurised by means of a pump mounted in the side wall of the base of the lamp. The pump pressurises the air space above the fuel.

The pump may be demountable from the lamp base for servicing.

Such lamps operate by pressurising the fuel in the reservoir so causing the fuel to be forced up to the burner where it is vaporised and burns. The fuel is heated in the fuel line in its path to the burner. Once the lamp is operating, the fuel line is maintained at a sufficiently high temperature for the fuel to vaporise. However some means has to be provided initially to heat the fuel line during the ignition of the lamp. This can be achieved by a separate heating tray or collar carrying methylated spirits which is located adjacent the fuel line and which is removed or allowed to burn out once the main fuel line is hot enough to vaporise the fuel.

An alternative to such ignition means is an arrangement where fuel from the main fuel reservoir is used. This typically comprises a second fuel line from the reservoir which feeds pressurised fuel to a venturi device formed by a spray nozzle which mixes air with the fuel spray. The air/fuel mixture is directed at the main fuel line so that when the mixture is ignited the flame heats the main fuel line to vaporise the fuel in the main fuel line.

The second fuel line incorporates a flow shut off device so that the ignition device can be operated independently of the main fuel supply to the mantle. The intensity of illumination from the lamp can be regulated by a valve in the main fuel line to the mantle. However, when the lamp is to be extinguished, the pressure in the reservoir must be released and this can be done by bleeding air and vapour from the head space in the reservoir above the fuel.

However, we have found that problems arise when such lamps are required to meet current safety standards in that liquid fuel can escape when the pressure in the reservoir is released to extinguish the lamp. The problem is further aggravated when the user of the lamp tilts the lamp to facilitate access to the bleed screw as this may put the bleed port of the reservoir beneath the surface of the liquid paraffin in the reservoir.

In order to reduce this problem, it is preferable for lamp manufacturers to form the reservoir with a generally semispherical top and to mount the bleed port at the highest point of the dome. The present invention provides an additional safety measure to ensure that the level of the surface of the fuel in the reservoir is well below the bleed port by trapping an appreciable volume of air above the fuel.

The invention needs to guard against those lamp users who tilt the lamp on its side when filling with fuel so as to get more fuel into the reservoir. If the lamp is depressurised with the liquid fuel above the vent port, liquid fuel is discharged in addition to vapour.

There is a safety check applied to such lamps to ensure that if the lamp is inclined at 25 to the vertical no liquid fuel is vented when the pressure is released.

The present invention seeks to provide lamps which pass the safety test and prevent overfilling of the reservoir.

SUMMARY OF THE INVENTION According to the present invention there is provided a pressurised fuel lamp comprising a fuel reservoir which has a tubular inlet port for filling the reservoir with fuel and which extends into the reservoir at a downwardly inclined angle to stop at the recommended level of the fuel so as to limit the filling of the reservoir to said level.

A pressure gauge may be used to monitor the pressure in the reservoir and may be mounted on the inlet port to seal it after filling. A vent valve may be set directly in the wall of the reservoir or, preferably, set in a second fuel line one end of which is coupled to the pressurised vapour above the fuel.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a pressurised paraffin fuel lantern; Figure 2 shows schematically a cross section through the lantern to illustrate the main functional features; and Figures 3a and 3b shows the filling and testing attitudes of the lantern.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Referring now to the drawings Figure 1 shows a paraffin fuel lantern or lamp comprising a fuel reservoir 1; a filler port 2 sealed by a pressure gauge 3 and mounted in the upper wall of the reservoir 1; a pump 4; a main fuel line 5 leading from the upper wall of the reservoir 1 to a mantle 7; a flame control valve 6 in the fuel line 5; a second fuel line 8 for supplying fuel to an ignition tube 9; a pressure release valve 10; a lantern glass 11 supporting a cowl 12 and, a carrying handle 13 pivotally coupled to the cowl 12.

The lantern glass 11 is supported on the shoulder of a collar 14, which is provided with two rows of air holes 15.

The air holes 15 allow air to the mantle 7 but prevent draughts or wind from significantly affecting the flow of air through the lantern and out through exhaust ports 16 immediately below a cap 17 on the cowl 12. The second fuel line 8 provides a venturi device drawing air through a port 18 through which the air and paraffin vapour may be ignited so that the flame from the ignition tube 9 plays on the fuel line 5 just below the mantle.

The operation of the lantern will now be described, particularly with reference to Figure 2 which shows schematically the functional aspects of the invention. The reservoir 1 is filled with paraffin by firstly removing the pressure gauge 3 from the filler port 2 so that the fuel may be poured into a duct 19which extends into the reservoir 1 to a level A-A. The level A-A is the safe level for filling the reservoir 1 so that if the reservoir 1 is tilted to 25 it will still operate safely. The duct 19 is inclined into the reservoir 1 so that its lower end is not only below the level A-A but also substantially central within the reservoir.This enables the lantern to be tilted during the filling process without substantially changing the maximum level to which the reservoir can be filled with fuel 26 (see levels A-A and A'-A' in Figure 3a), leaving a head space 27 filled with an air/vapour mixture.

When the reservoir has been filled and the pressure gauge 3 replaced the pump 4 is operated until the desired pressure is obtained as indicated by the gauge 3. Typically the pressure may be 2 Kg/cm2. The lantern may now be lit.

There are two methods of lighting the lantern. The first method (the rapid preheating method) employs the venturi device on the second fuel line 8 and the ignition tube 9.

When using this method, a snap closure cap 22 is opened to allow fuel to be forced up the line 8 to a nozzle where it is vapourised and mixed with air. The fuel is ignited and a flame 21 from the ignition tube 9 plays on the main fuel line 5 to heat the fuel in the line. The flame is extinguished by closing the closure cap 22 to seal the end of the second fuel line 8 in the venturi device. The cap 22 is operated by a spring loaded lever 23.

The second method uses methylated spirits which is introduced into the tray 20 with the aid of a filler can (not shown) having a long fine nozzle which is inserted through one of the holes 15 adjacent the tray 20. When this method is used the spirits in the tray 20 is allowed to burn itself out and no action is necessary to put it out.

When the main fuel line 5 adjacent to the mantle 7 has been heated sufficiently to vaporise the paraffin, the fuel control valve 6 is slowly opened and the vaporised fuel in the mantle lights so that the mantle 7 will glow brightly.

When the second fuel line 8 is used, once the mantle 7 is glowing brightly the lever 23 is released and the cap 22 closes the second fuel line 8 and is held in place by a pretensioned spring 28.

The stability of the lantern may be improyed by adding a weighted ring in the base 2 A of the reservoir 1.

When it is desired to finally extinguish the lantern the pressure is released through the valve 10 which opens into a short length of tube 25 surrounding the fuel line 8 and in communication with only the vapour space 27 of the reservoir. No more paraffin is then fed to the mantle.

Figure 3a shows the lamp held on its side in a position for filling with liquid paraffin fuel. As the fuel enters the reservoir 1 the level rises until it covers the lower end of the duct 19 and rises then within the duct 19 to indicate that the reservoir is full. Figure 3b shows the lamp inclined at 25C in the test position to ensure that in this position the second fuel line 8 is still immersed in the fuel 26 well below the liquid level in the reservoir while the lower end of the tube 25 is above the liquid level, so that operation of the pressure release valve 10 will vent only vapour with no fear of liquid being vented.

It will be appreciated that other modifications: may be made to lanterns to improve their safety. In some cases existing lanterns or lamps that can be over-filled may be modified by removing the pressure gauge and inserting a duct to extend the filling point below the level A-A, or, if appropriate the pump may be ducted according to the invention to below the level A-A so that if the pump is removable for filling, the maximum level in the reservoir will not exceed a safe level as a result of tipping or tilting the lantern for filling. The length of the duct may need to be adjusted so that its lower end lies just below the level of liquid which when tilted at an inclination of 25 is at least just below the outlet through which excess pressure is vented.

The lantern may be adapted so that access ports to the reservoir are provided with a valve which senses whether such ports are under the level of liquid in the reservoir and closes access to the ports to prevent liquid being vented under pressure.

It will be appreciated that the vessel 2 need not be a domed cylinder but could of any suitable shape.

Claims (6)

Claims

1 A pressurised fuel lamp comprising a fuel reservoir which has a tubular inlet port for filling the reservoir with fuel, the tubular inlet port extending into the reservoir at a downward inclined angle to stop at the desired maximum fuel level, so as to limit the filling of the reservoir to said level.

2 A lamp as claimed in Claim 1, wherein the lower end of the tubular inlet port is located at the centre of a horizontal plane containing the maximum desired fuel level.

3 A lamp as claimed in Claim 1 or Claim 2, wherein a pressure gauge is mounted at the top of the inlet port, to close the inlet port.

4 A lamp as claimed in any preceding claim, including a vent opening from the reservoir, the vent being above the maximum fuel level in the tank whenever the lamp is in its normal, upright position or is tilted in any direction at up to 25 to the vertical.

5 An overfill prevention device for a pressurised fuel lamp comprising a tubular inlet port adapted to be inserted in a filling opening of a fuel reservoir of the lamp and to extend in a downwardly inclined direction within the reservoir, and means for sealing the tubular inlet port to the filling opening so that the position of the lower end of the inlet port determines the maximum possible filling level of the reservoir.

6 A pressurised fuel lamp substantially as herein described with reference to the accompanying drawings.