DE69303458T2 - Improvements to LPG bottles - Google Patents

Description

The invention relates to cylinders for liquid gas or liquefied petroleum gas (LPG) for domestic purposes.

In areas without a gas distribution network, fuel gas for domestic purposes, especially for cooking, is supplied to households in the form of LPG in appropriate cylinders. These cylinders are designed in such a way that they can be transported relatively easily by means of a transport vehicle to the consumer's connection installation; a standard size containing 12.7 kg of LPG is usually used. The cylinders are refillable, so they are provided with a shut-off valve that acts as a non-return valve, but which opens when connected to the connection unit at the consumer.

As long as there is still liquid in the cylinder, the gas pressure is equal to the vapor pressure of the liquid; the gas pressure therefore does not give an indication of the amount of liquid still in the cylinder, this amount can only be determined by precise weighing. However, when almost all of the gas has been used up so that there is no liquid left, the pressure of the remaining gas drops very rapidly during use. The consumer therefore has almost no warning when the cylinder contents are used up and must be replaced with a new, filled cylinder.

Apart from the space required for a storage cylinder, filled LPG cylinders pose a fire and explosion hazard; and often laws limit the amount of combustible material that can be stored in or near homes. It is therefore undesirable and often impractical or illegal for the consumer to always have a filled storage gas cylinder on hand to replace when the cylinder currently in use runs out. The consumer must therefore purchase and have a new cylinder delivered each time in order to be able to use fuel gas again. This of course has unfortunate results if a cylinder suddenly runs out, for example, in the middle of preparing a meal.

It is an object of the invention as defined in the appended claims to provide means for avoiding these difficulties. This object is achieved by providing a reserve supply of liquefied gas in a reserve cylinder contained in the main gas cylinder, to which (the reserve cylinder) the (household) gas supply connection can be transferred when a drop in pressure indicates that the main cylinder is almost empty.

Patent specification EP 244 590 does show a system in which an outer cylinder contains a large gas cylinder. In this case, however, the inner cylinder is a high-pressure cylinder and is provided with a pressure reducing valve. This system enables the outer cylinder to be of a lighter construction, for example made of cold-welded metal. However, such a cylinder would not be acceptable for external purposes for safety reasons.

The invention is described below with reference to the drawings:

Figure 1 shows a liquid cylinder according to the invention in perspective, broken open;

Figure 2 shows a partial perspective view of a modification of the arrangement according to Figure 1; and

Figure 3 is a longitudinal section, partially exploded, of another embodiment of the invention.

The LPG cylinder 1 according to Figure 1 is of welded construction and is provided with a base or base plate 2 on which the cylinder stands upright during use and with a valve 3 through which the cylinder is filled and also connected to the consumer's gas system. During filling and storage the valve 4 is provided which is depressed when the cylinder is connected to the consumer's distribution system, thereby opening the valve so that fuel gas can flow from the cylinder into the consumer's distribution system. A handle 5 (shown removed for clarity) surrounds the valve and serves for handling, i.e. carrying the cylinder during transport and at the same time protecting the valve against damage or accidental depression.

According to the embodiment of the invention according to figures 1 and 2, the cylinder is provided during manufacture with an inner reserve cylinder 6 which is connected, through the wall of the outer cylinder 1, to a second valve 7 of a similar (or the same) type as the valve 3.

For consumption, both cylinders are filled with LPG according to their volume through the appropriate valves. Preferably, the total capacity of the main cylinder is 12.7 kg of LPG and between 4% and 55% of the gas is contained in the reserve cylinder 6. At the consumer, the cylinder 1 is connected to the consumer's system by means of the valve 3. The gas is then gradually consumed until the outer cylinder 1 is exhausted and the pressure drops rapidly as the remaining gas in the main cylinder 1 is consumed. The consumer then leads its connection from the valve 3 to the valve 7 and is thus able to consume the gas from the reserve cylinder 6. for the operation in progress until a replacement cylinder can be obtained from the supplier. In the arrangement shown in Figure 1, the gas supplier must connect the filling device to both valve 3 and valve 7 in order to fill the master cylinder and the reserve cylinder. Figure 2, on the other hand, shows an embodiment in which the filling of the cylinders is simplified. In this case there is a check valve 8 (inside the master cylinder 1) through which gas can flow from the master cylinder 1 into the reserve cylinder 6, but not vice versa. In this arrangement both cylinders can be filled with LPG through the valve 3 of the master cylinder, the gas flowing from the master cylinder 1 into the reserve cylinder 6 through the check valve 8. There must of course be no direct outlet from the inner cylinder to the outer cylinder, since such an outlet would prevent the aforementioned drop in pressure which warns of the imminent consumption of the contents of the outer cylinder.

In the embodiment according to figure 3, the reserve cylinder 6 is removable from the main cylinder and can be replaced when service and replacement are required. Furthermore, the user or the service company can service or replace the check valve 8 on the removed reserve cylinder 6.

The exchangeability or removal of the replacement cylinder 6 is achieved by a collar or projection 1A formed on the main cylinder 1 and provided with an internal thread and a corresponding threaded head 6A on the reserve cylinder 6. Furthermore, the main cylinder is cast or otherwise formed in two parts 1C and 1D to facilitate manufacture, which are welded together as shown.

Claims (3)

P1. A liquid gas cylinder comprising a master cylinder (1) with a master cylinder outlet valve (3) and an internal reserve cylinder (6), characterized in that the internal reserve cylinder (6) has a separate outlet outside the master cylinder (1) for connection to the connection system of a consumer, and that a check valve (8) is provided between the reserve cylinder (6) and the master cylinder (1), whereby both cylinders can be filled through the outlet valve (3) of the master cylinder (1). 2. A liquid gas cylinder according to claim 1, wherein the capacity of the reserve cylinder (6) is between 4% and 55% of the total content of the cylinder. 3. A LPG cylinder according to claim 1 or 2, wherein the inner reserve cylinder (6) is detachable from and replaceable with respect to the main cylinder (1).