GB2476481A

GB2476481A - Electronic device for measuring and monitoring the amount of liquefied gas remaining in a gas bottle

Info

Publication number: GB2476481A
Application number: GB0922471A
Authority: GB
Inventors: Graham Anthony
Original assignee: GASLO INNOVATIONS Ltd
Current assignee: GASLO INNOVATIONS Ltd
Priority date: 2009-12-23
Filing date: 2009-12-23
Publication date: 2011-06-29
Also published as: GB0922471D0

Abstract

A monitoring device, for monitoring the condition of a bottle or canister containing liquefied gas, comprises a support platform 13; means for detecting the weight of a bottle (19, figure 3) positioned on the platform 13; a display device 39; and an electronic control device (37, figure 4) programmed to compare the detected bottle weight with a lower threshold value and to cause the display device 39 to indicate the quantity of liquefied gas remaining in the bottle. The device may also compare the detected bottle weight and indicate the fraction or percentage of gas remaining on a bar chart 18. The device may also comprise a battery operated leak detector (49, figure 3) and trigger an alarm 45,47 when a leak is detected or when the weight of the gas bottle falls below a predetermined threshold. The device may be solar powered 41 and may have a foot operated kick switch 43 to bring the display 39 from a sleep or standby mode into an operating mode.

Description

Monitoring Device for Monitoring the Condition of A Bottle Containing Liquefied Fuel Gas

FIELD OF THE INVENTION

This invention relates to a device for monitoring the condition of a bottle containing liquefied fuel gas, particularly but not exclusively where the fuel is liquefied petroleum gas (LPG), to indicate the quantity of liquefied fuel gas remaining in the bottle.

BACKGROUND TO THE INVENTION

Where for example town gas is unavailable, bottled LPG is commonly used for cooking, heating, and running other appliances. Petroleum gas is created as part of the process of refining crude oil -it is collected and compressed into a liquid before being bottled. The LPG will remain in its liquid form for as long as it is held under sufficient pressure. If that pressure is lowered (i.e. some gas is drawn off) an amount of the liquid will boil into gas until the pressure is restored.

In use, the bottle will be fitted with a regulator, and a pipe leading from the regulator to an appliance, the regulator serving to define a maximum flow rate for gas leaving the bottle along the pipe. Typically a filled bottle of LPG will last for between 2 and 3 weeks, depending on the extent of its use.

Various types of LPG are generally available -propane, butane or a mixture of the two. A commonly used commercially available LPG, "Butano" is a liquefied gas composition of butane (60%), propane (9%), isobutane (30%) and ethane (1%).

It is desirable for the user to know how much fuel is present in the bottle, so as to accurately predict when it will become empty and to replace it with a full bottle at a convenient moment.

Most gas bottles have an empty weight stamped somewhere on the bottle.

It has been proposed simply to weigh the bottle on bathroom scales and subtract the empty bottle weight to determine how much gas is left. However, due to the need for strength, gas bottles can easily weigh as much as the gas that they contain. Typically, an empty bottle may weigh about 13 kg and be capable of containing about the same weight of LPG when full. This method is therefore not usually convenient, and cannot indicate the condition of the bottle while it is in use.

We are aware of European patent publication EP 0 955 529 (Truma Gerätetechnik GmbH & Co), which describes a filling level measuring device which has at least one ultrasonic transducer incorporated in a carrier for the bottle and coupled to a coupling layer for transmission of the ultrasonic waves made of a hard elastic material, which is pressed into contact with the bottle by a pressure mechanism, e.g. a conical coil spring, when the bottle is positioned on the carrier.

Such a device is complicated and costly to construct and furthermore relies upon the bottle being in an exactly vertical orientation to give an accurate reading.

Also, determining the level of liquid in the bottle does not, by itself, indicate how much fuel remains to be used.

We are also aware of European patent publication EP 0052609 (Energy Innovation Enterprises Limited), which describes an apparatus for indicating the quantity of liquefied gas contained in a storage bottle for supplying gas to a consuming appliance. The apparatus includes a pressure sensing means for sensing gas pressure within the bottle and is arranged to operate an indicator means which gives a desired indication, the indicator means being calibrated to indicate the quantity by weight or volume of liquefied gas contained in said bottle.

The pressure gauge system proposed in the 609 document relies upon the relationship between pressure and content of the bottle under dynamic conditions, i.e. as gas is being taken from the bottle. The pressure gauge is unable to indicate the degree of filling of the bottle under static conditions, and furthermore the pressure vs content relationship varies according to the flow rate of gas from the bottle, so that accurate indications are only given when gas is being drawn off at a given flow rate. In any event, in some countries legislation prevents the interposition of any device between the bottle and the regulator, making such a system commercially unavailable.

There is therefore a need for a simple device for determining the condition of a bottle containing liquefied fuel gas, in a safe, convenient and accurate manner.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a monitoring device for monitoring the condition of a bottle containing liquefied fuel gas, the monitoring device comprising: -a support platform; -means for detecting the weight of a bottle positioned on the platform; -a display device; -an electronic control device programmed to compare the detected bottle weight with a lower threshold value related to a predetermined empty condition of the bottle and to cause the display device to indicate the quantity of liquefied fuel gas remaining in the bottle.

In a preferred embodiment, the electronic control device is further programmed to compare the detected bottle weight with an upper threshold value related to a predetermined full condition of the bottle and to cause the display device to indicate the proportion of liquefied fuel gas remaining in the bottle.

The control device may be solar powered. The display device may be in sleep mode as a default condition. The monitoring device may have a kick switch positioned to be foot operated and being adapted to cause the control device to bring the display device from a sleep mode into an operating mode.

The control device may be programmed to cause the display device to indicate one or more of: (i) the weight of liquefied fuel gas remaining in the bottle; or (ii) the fractional amount of liquefied fuel gas remaining in the bottle; or (iii) the percentage amount of liquefied fuel gas remaining in the bottle.

Further, but less preferred possibilities include the display of indications of the calorific value of liquefied fuel gas remaining in the bottle or the remaining time of supply of liquefied fuel gas remaining in the bottle at a predetermined flow rate.

The indication displayed on the display device may be in the form of a multi-element bar chart or a pie chart.

The device may further comprise a visible and/or audible alarm device, the control device being programmed to trigger the alarm device when the detected weight of a bottle positioned on the platform falls below a further threshold value, such as a visual alarm device triggered as the percentage of fuel remaining in the bottle falls below 25% and an audible alarm device triggered as the percentage of fuel remaining in the bottle falls below 10%, typically representing about 1 hour of continued use.

As with any flammable gas, there is a serious risk of explosion in the event of an LPG leak, and indeed in some parts of the world explosions from arising from leaks from LPG fuel apparatus are unfortunately too common. Leaks may arise where the regulator is connected to the bottle or to a pipe leading to a gas-powered appliance, or more commonly as a result of the material of such a connecting pipe perishing as a result of long-term exposure to the gas. In rare occasions, a leak might arise from the bottle itself. As propane and butane themselves are colourless and odourless, a small amount of stenching agent' is sometimes added to the commercial LPG products so that the leak is likely to be detected by smell. Nevertheless, LPG is heavier than air, and a leak will result in a dangerous build-up of gas if there is not adequate floor-level ventilation.

The device may therefore further comprise at least one leak detector (otherwise known as a gas sniffer) located adjacent the platform and having a gas inlet positioned below the level of the upper bottle supporting surface of the platform. A visible and/or audible alarm device may be provided, which incorporates means to trigger the alarm device when the leak detector detects a leakage of fuel gas from a bottle positioned on the platform. The leak detector may be battery powered. The leak detector may be adapted to operate periodically in order to save battery power, such as to be in operative mode for 15 to 60 seconds, such as about 30 seconds every 15 to 60 minutes, such as every minutes, save for the operation of the kick switch which would bring the leak detector into operation immediately. The or each leak detector should be sensitive to at least the presence of whichever fuel is expected to contained within the bottle used with the device, for example sensitive to propane and/or butane in the case is LPG fuel. A suitable leak detector is, for example, obtainable from Ningbo DSW Industry Co. Ltd of Zhejiang, China.

The platform preferably includes one or more windows providing a gas flow path to the leak detector(s). In a preferred embodiment, the platform is supported by a plurality of ground engaging legs, positioned to provide a space between the platform and the ground of, for example, about 5 mm to 30 mm, such as about 14 mm. In this case the or each window ideally opens to the space between the platform and the ground.

The means for detecting the weight of a bottle positioned on the platform may take the form of one or more weight sensors, e.g. compression gauges, conveniently positioned in the legs supporting the platform. Suitable compression gauges include, for example, those typically used in electronic bathroom scales, preferably modified with thermostatic control, to avoid inaccurate readings in conditions where the ambient temperature may be variable. A suitable such weight sensor is available from Circatron Ltd, Tonbridge, Kent.

The platform may have a generally circular upper bottle supporting surface, thereby to match the bottle shape, preferably with a tolerance to allow for bottles that may become misshapen in use. Thus, in a preferred embodiment the platform has a generally circular cross-section. It is however advantageous for the solar panel, display device and the kick switch to be located outside the circle defined by the platform. Thus in a preferred embodiment, the device has a configuration including a generally circular part comprising the platform, and an extension part, extending from the generally circular part and comprising the display device. This construction is of particular value where the bottle in use is located within a cabinet, for example, the cabinet of an LPG fueiJed boiler, so that the extension part extends outside the periphery of the cabinet. The display device can then be observed, the kick switch can be operated and the solar panel can be exposed to day light without the need to open the cabinet.

The upper bottle supporting surface of the platform may be shaped to retain a bottle placed thereon in a predetermined position, for example wherein the upper bottle supporting surface includes concentric ridges to retain a bottle placed thereon in the predetermined position. If the ambient temperature is cool enough, and gas has been drawn from the bottle continuously for some time, condensation may form on the outside of the bottle. The ridges may include at least one notch positioned to allow any condensation dripping from the outside surface of a bottle to drain away off the platform, and consequently not add to the detected weight of the bottle.

The upper and/or lower threshold values are preferably adjustable, to allow for bottles of different volumes and weights. Thus, the control device may be pre-programmed with one or more empty bottle weights, a user-operable selection device being provided where two or more empty bottle weights are pre-programmed. It is also possible to arrange for the control device to set the lower threshold value at the detected bottle weight when an empty bottle is positioned on the platform, thereby to set the lower threshold value for the use of a next bottle of similar weight.

In a similar manner, the control device may be programmed to set the upper threshold value at the detected bottle weight when a full bottle is positioned on the platform.

Where in use, the bottle will be fitted a regulator, and a pipe leading from the regulator to an appliance, the set or pre-programmed lower threshold value should take account of the weight of the regulator and the pipe.

The invention also provides a method of monitoring the condition of a bottle containing liquefied fuel gas, using the device described herein.

INTRODUCTION TO THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying illustrative drawings, in which: Figure 1 is a top view of a monitoring device according to the invention for monitoring the condition of a bottle containing liquefied fuel gas; Figure 2 is a bottom view of the monitoring device shown in Figure 1; Figure 3 is a cross section taken on the line Ill -III in Figure 1, with an LPG bottle shown partly in section; and Figure 4 is a circuit diagram for the control device of the monitoring device of Figures 1 and 2.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, it will be seen that the monitoring device has a configuration including a generally circular part 11 including a support platform 13, and an extension part 15, extending from the generally circular part 11. The platform 13 has a generally circular upper bottle supporting surface 17, shaped to retain a bottle 19 placed thereon in a central position. The bottle 19 (not shown in Figures 1 and 2) contains LPG 20 and is fitted a regulator 21, and a pipe 23 leading from the regulator to an appliance not shown, the regulator 21 serving to define a maximum flow rate for gas leaving the bottle 19 along the pipe.

The upper bottle supporting surface 17 includes concentric ridges 25, 27 to retain the bottle 19 in a central position. The ridge 27 includes a notch 29 positioned to allow any condensation dripping from the outside surface of a bottle 19 to drain away from the platform 13. The platform 13 is supported by a plurality of spring-loaded ground engaging legs 31, positioned to provide a space 33 between the platform 13 and the ground 35. The springs of the spring-loaded ground engaging legs 31 are formed of a plastic material, to avoid any temperature effects which might result from the use of metal springs. Within each leg there is a compression gauge not shown which, in a known manner senses the weight of the platform and the bottle 19. The compression gauges are connected to a solar-powered electronic control device 37 (see Figure 4) located in a suitable position.

The extension part 15 houses an LCD display device 39, a solar panel 41 and a non-locking foot or kick switch 43 positioned to be foot operated. Two visible and audible alarm devices 45 and 47 are located, one on either side of the display device 39. The display device 39, solar panel 41, kick switch 43 and the two alarm devices 45 and 47 are connected to the control device 37. The kick switch 43 is adapted to cause the control device 37 to bring the display device 39 from a sleep mode into an operating mode for 30 seconds.

The electronic control device 37 is programmed to compare the detected bottle weight WD with a pie-set lower threshold value WL related to a predetermined empty condition of the bottle and with a pre-set upper threshold value WH related to a predetermined full condition of the bottle and to cause the display device 39 to indicate the proportion of liquefied fuel gas remaining in the bottle, when the display device is in its operating mode. The upper and lower threshold values WL and WH take account of the weight of the regulator 21 and the pipe 23.

The percentage P of gas remaining in the bottle is given by the equation: P = 100 (WD -WL) I (WH -WL).

The indication displayed on the display device 39 is in the form of a four element bar chart 18, each element representing 25% of the bottle capacity.

The control device 37 is programmed to trigger the visible element of alarm device 45 when P falls below 25% and to trigger the audible element of alarm device 45 when P falls below 10%.

A battery powered leak detector 49, sensitive to the presence of propane or butane, is located centrally under the platform 13 and has a gas inlet in the form of a grilled window 51 positioned below the level of the upper bottle supporting surface of the platform 13. The window 51 opens to the space 33 between the platform 13 and the ground 35 to provide a gas flow path to the leak detector 49.

The leak detector 49 is programmed as a default condition to operate for 10 seconds every 2 to 3 hours (as indicated in Figure 4) or, for example, for 15 seconds every 30 minutes. The visible and audible alarm device 47 is triggered when the leak detector 49 detects a leakage of fuel gas from a bottle positioned on the platform 13. The kick switch 43 is adapted to bring the leak detector from a sleep mode into an operating mode, between its default operating phases. The circuitry of the leak detector 49 is also adapted to cause the alarm device 47 to be triggered in the event of a low battery power.

Referring to Figure 4, it will be seen that the solar panel 41 is arranged to charge a back-up battery 42, which supplies power to illuminate the LCD display 39 in the event of darkness. An on/off switch 44 for the circuit is triggered when a weight above 10 kg is sensed on the platform 13. An automatic set zero control 48, connected to the control device 37, ensures that the detected weight is set to zero when a bottle is removed from the platform 13. -10-

Claims

CLAIMS1. A monitoring device for monitoring the condition of a bottle containing liquefied fuel gas, the monitoring device comprising: 5.asupportplafform; -means for detecting the weight of a bottle positioned on said platform; -a display device; -an electronic control device programmed to compare the detected bottle weight with a lower threshold value related to a predetermined empty condition of the bottle and to cause said display device to indicate the quantity of liquefied fuel gas remaining in the bottle.
2. A monitoring device according to claim 1, wherein said lower thresholdvalue is adjustable.
3. A monitoring device according to claim 1 or 2, wherein the electronic control device is further programmed to compare the detected bottle weight with an upper threshold value related to a predetermined full condition of the bottle and to cause said display device to indicate the proportion of liquefied fuel gas remaining in the bottle.
4. A monitoring device according to claim 3, wherein said upper thresholdvalue is adjustable.
5. A monitoring device according to claim 4, wherein said control device is programmed to set said upper threshold value at the detected bottle weight when a full bottle is positioned on said platform.
6. A monitoring device according to any preceding claim, wherein said control device is solar powered.
7. A monitoring device according to any preceding claim, wherein said control device is programmed to cause said display device to indicate either or both of the fractional amount of liquefied fuel gas remaining in the bottle; or the percentage amount of liquefied fuel gas remaining in the bottle.
8. A monitoring device according to any preceding claim, wherein the indication displayed on said display device is in the form of a multi-element bar chart.
9. A monitoring device according to any preceding claim, further comprising a visible and/or audible alarm device, said control device being programmed to trigger said alarm device when the detected weight of a bottle positioned on the platform falls below a further threshold value.
10. A monitoring device according to any preceding claim, further comprising at least one leak detector located adjacent said platform and having a gas inlet positioned below the level of the upper bottle supporting surface of said platform.
11. A monitoring device according to claim 10, further comprising a visible and/or audible alarm device, the leak detector incorporating means to trigger said alarm device when said leak detector detects a leakage of fuel gas from a bottle positioned on the platform.
12. A monitoring device according to claim 11, wherein said leak detector is battery powered.
13. A monitoring device according to any one of claim 10 to 12, wherein said leak detector is adapted to operate periodically.
14. A monitoring device according to any one of claims 10 to 13, wherein said at least one leak detector is sensitive to at least the presence of propane and/or butane. -12-
15. A monitoring device according to any preceding claim, wherein said platform includes a window providing a gas flow path to said at least one leak detector.
16. A monitoring device according to any preceding claim, wherein the platform is supported by a plurality of ground engaging legs, positioned to provide a space between the platform and the ground.
17. A monitoring device according to claim 15 and 16, wherein the window opens to the space between the platform and the ground.
18. A monitoring device according to any preceding claim, wherein said platform has a generally circular upper bottle supporting surface.
19. A monitoring device according to any preceding claim, wherein the upper bottle supporting surface of the platform is shaped to retain a bottle placed thereon in a predetermined position.
20. A monitoring device according to claim 19, wherein the upper bottle supporting surface includes concentric ridges to retain a bottle placed thereon in said predetermined position.
21. A monitoring device according to claim 20, wherein said ridges include at least one notch positioned to allow any condensation dripping from the outside surface of a bottle to drain away from the platform.
22. A monitoring device according to any preceding claim, having a kick switch positioned to be foot operated and being adapted to cause the control device to bring the display device from a sleep mode into an operating mode.
23. A monitoring device according to claims 13 and 22, wherein said kick switch is adapted to bring the leak detector from a sleep mode into an operating mode. -13-
24. A monitoring device according to any preceding claim, having a configuration including a generally circular part comprising said platform, and an extension part, extending from the generally circular part and comprising the display device.
25. A monitoring device according to claim 24, wherein said control device is solar powered and a solar panel is located is said extension part.
26. A monitoring device according to claims 22 and 24, wherein said kick switch is located in said extension part.
27. The combination of a monitoring device according to any preceding claim and a bottle containing a liquefied gas mixture comprising propane and butane.
28. The combination according to claim 17, wherein the bottle is fitted a regulator, and a pipe leading from the regulator to an appliance, the regulator serving to define a maximum flow rate for gas leaving the bottle along said pipe, wherein said lower threshold value takes account of the weight of said regulator and said pipe.
29. A method of monitoring the condition of a bottle by use of a device according to any preceding claim.