The invention relates to a cartridge for storing liquefied gas under pressure, such as butane or propane - LPG and a method for producing such a cartridge. These cartridges may be connected to combustion devices and are used for preparing coffee, boiling various decoctions and roasting food.

Known cartridges are disposable rather than refillable; they have various dimensions and capacity ranging from 190 gr. to 500 gr. One known type of cartridge is connected to the combustion devices by perforation. Other known cartridges for storing gas include a storage container for storing the gas and a valve, which connects the cartridge to the combustion device. In operation the cartridges provide through their valve evaporated gas to the combustion devices, which are safely connected therewith. Such known cartridges are provided with a thread in order to screw the cartridges to combustion devices which are provided with complementary thread, or they receive combustion devices clasping thereon.

The object of the present invention is a cartridge and a method for the production of a cartridge with high safety level with regard to liquefied gas leakage and to the robustness and strength of the valve, whereby any improvement is made in an economical and efficient manner. The invention is defined in independent claims 1 and 10.

A cartridge for storing liquefied gas according to the invention includes a container for storing liquefied gas and a valve. The valve comprises a jacket, which has a first almost cylindrical wall, a second almost cylindrical wall and an annular bottom, the first wall and the second wall being almost coaxial and the first wall being situated almost within the cylindrical space defined by the second wall. The jacket comprises two layers, and protrusions are formed on the jacket. According to the invention the protrusions are formed on both said layers and each protrusion formed on the one of the two layers penetrates a complimentary protrusion formed on the other of the two layers. The protrusions may be formed on the second wall and protrude within the cylindrical space defined by the second wall. Alternatively or in addition to the protrusions formed on the second wall, the protrusions may be formed on the annular bottom. The protrusions that are formed on the annular bottom may protrude inwards, i.e. within the cylindrical space defined by the second wall, or outwards, i.e. in the opposite direction of the cylindrical space. The cartridge may further comprise a cap, which cap fits to the jacket. The cap has a non-flat ring-shaped bottom edge that cooperates with the protrusions formed on the second wall. Means may also be formed on the second wall, which means receives complementary locking means that may be formed on the cap to lock the cap to the valve of the cartridge. The non- flat ring-shaped bottom edge of the cap may have a wavelike shape. In one embodiment the second wall has four protrusions of almost conical shape protruding within the cylindrical space defined by the second wall The protrusions, when the cap is mounted on the valve, are situated inside troughs formed on the non-flat ring-shaped bottom edge of the cap. When turning the cap on the valve, the protrusions cooperate with the bottom edge of the cap to insert or withdraw the locking means that are formed on the cap to the means formed on the second wall. The locking means that are formed on the cap may comprise flaps and the means formed on the second wall may be a groove.

One way to attach the cartridge to a combustion device is via a threaded connection. For such a connection a thread is formed on the first wall of the jacket. A method for the production of a cartridge for storing gas including a container for storing gas and a valve comprises the steps of providing two layers of material to produce the jacket of the valve, inserting the one layer into the other of the two layers, simultaneously forming protrusions on both layers, so that the protrusions formed on the one layer that is inserted to the other layer lock the protrusions formed on the other layer so that the two layers are attached together. Finally, after forming the protrusions and attaching the two layers together the valve is attached to the container.

Preferably the attachment of the valve to the container includes the step of forming a groove in the jacket of the valve. The method may be used to produce any cartridge in accordance with the present invention.

The protrusions formed on the jacket of the valve render possible the production of a double layer jacket in an efficient and economical manner.

Embodiments of the invention are described below, with reference to figures 1 to 9:

Figure 1 shows a cartridge and a combustion device according to the invention.

Figure 2 shows a safety valve before adhering it to the storage container.

Figure 3 shows the safety valve after its adherence to the storage container. Figure 4 shows a further embodiment of the safety valve after its adherence to the storage container.

Figure 5 shows a cartridge with a cap to seal it.

Figure 6 shows a cap with clasping details.

Figure 7 shows a section of a cartridge with a cap. Figure 8 shows the valve attached to the storage container of the cartridge.

Figure 9 shows a top view of the valve fitted to the cartridge with four protrusions.

Figure 1 shows the cartridge 60 and the combustion device 70. The cartridge comprises a storage container 30 made of tinplate and a safety valve 10. Components of the safety valve 10 are a jacket 1 , a cylinder 3, a piston 8 and a spring 2.

The jacket 1 of the valve 10 has an almost flat annular bottom 11 with an internal perimeter and an external perimeter, a first almost cylindrical wall 12 and a second almost cylindrical wall 13. The first and the second walls are almost coaxial, and the bottom diameter of the first wall and the second wall are equal to the diameter of the internal perimeter and the external perimeter of the annular-shaped bottom respectively. The second cylindrical wall 13, i.e. the cylindrical wall with the larger diameter, defines in its interior an almost cylindrical space. As shown in figure 2, the first wall is situated within the cylindrical space defined by the second wall.

The first cylindrical wall 12, namely the cylindrical wall with the smaller diameter, defines in its interior an almost cylindrical space 14. The valve cylinder 3, the spring 2 and a piston 8 are mounted in the cylindrical space 14. A thread 15 is formed on the exterior surface of the cylindrical wall 12 with the smaller diameter. The thread 15 is formed on the end of the cylindrical wall, which is spaced from the annular bottom. Below the thread 15 there are means, such as an annular groove, which holds the cylinder 3 within the cylindrical space 14. When the user wants to attach a combustion device to a cartridge 60, the user screws the combustion device 70 to the thread 15. With the combustion device 70 screwed on the storage device, the valve 10 allows the gas to flow to the combustion device 70. When the user unscrews the combustion device 70 from the cartridge 60, the valve 10, through the action of the spring 2 and the piston 8, does not allow the gas to escape from the cartridge 60, even when the cartridge is full and under pressure.

The second almost cylindrical wall 13, namely the cylindrical wall with the larger diameter, is limited on its one end by the annular bottom 11. A rim 29 is formed on its other end of the cylindrical wall 13. The rim 29 fits on the container 30, as shown in figure 3 and in figure 7. At a short distance from the rim 29, the wall has a groove 31, which is formed when, during the production of the cartridge 60, the valve 10 is adhered to the container 30. The groove 31 secures connection between the storage container 30 and the valve 10 and achieves waterproof attachment between the two items. Protrusions 35 are formed on the second wall 13. In the example shown in figures 8 and 9 there are four protrusions 35 of almost conical shape.

During production the cartridge 60 is sealed with a cap 40. The cap 40 has an almost flat head 43 and a ring-shaped and non-flat bottom edge 44. As the user turns the cap 40 the protrusions 35 present on the second wall guide the cap 40. In the example of figures 5, 6 and 7 the perimeter of the bottom edge of the cap 40 has a wavelike form and has troughs 41 which receive the protrusions 35 so that, when the cap 40 is mounted to the jacket 1 , its removal is not possible unless the user removes it by turning the cap 40. The cap 40 covers and protects the valve thread from possible shocks and accidental impacts with any foreign item. It also protects the valve from the accession of foreign elements, such as dust, water, oils, etc. , that might clog the valve hole and affect the proper and efficient functioning thereof.

The cap has means 48, 49 which means, when the cap 40 is mounted to the valve 10 interlock in the groove 31. In the example of figures 6 and 7, the cap has four cuts 49 that form four flaps 48 which, when the cap 40 is mounted on the valve 10, the flaps 48 are securely locked in the groove 31. In the particular example the flaps have an extension at their free ends to lock within the groove 31. The means 48, 49, such as the flaps 48, could be resilient to facilitate locking within the groove 31. The protrusions 35, the ring- shaped bottom edge 44 of the cap 40 and the flaps 48 are formed in such a way that, when the user turns the cap 40, the protrusions 35 interact with the non-flat bottom edge 44 of the cap 40 in order to facilitate the insertion or removal of the flaps 48 in the groove 31 and consequently the locking or unlocking of the cap 40 to the valve 10, respectively. Thus, the protrusions 35 support, on one hand, the cap 40 so as to clasp on the groove 31 of the valve 10 and on the other hand, they serve as guide for the cap to be easily clasped or removed.

The jacket 1 of the valve is dual and consists of two metal layers 17 and 18 that abut on each other almost throughout their surface. The production of the jacket is effected by inserting one layer 18, i.e. the inner layer, into the other layer 17, i.e. the outer layer. The protrusions 35 are formed by a metal device that presses by pushing or hammering at selected locations the outer layer 17 against the inner layer 18. Thus, the protrusions 35 are formed simultaneously on both layers 17, 18 and lock firmly the two layers together. After production of the valve 10 with the two layers 17, 18 and the protrusions 35, the valve 10 is fitted to the container 30 and subsequently the groove 31 is formed. Cartridges with valves having double layer jackets offer higher safety level compared to the ones made of a single layer. In another embodiment of the invention further protrusions that hold the two layers together are formed in the annular bottom 11 - see figure 4, item 351. If protrusions are formed in the annular bottom, they may project inwards, i.e. within the cylindrical space defined by the second wall as the protrusions 351 outwards. The protrusions 351 formed in the annular bottom may be formed in addition to the protrusions 35 formed on the second circular wall 13 or instead of them.

The protrusions formed on the jacket of the valve are an efficient and economical mean to improve safety because they render possible the production of a double layer jacket and facilitate the locking of the cap to the valve.