Abstract:
The shut-off device is intended for refillable gas cylinders. In order to be sure that only authorized persons can refill the cylinder, the filling device comprises a non-return valve element ( 16 ) which prevents filling and which can only be neutralized using a special magnet ( 18 ).

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application, Ser. No. 09/350,722, filed Jul. 9, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an automatic shut-off device for a valve for compressed or liquefied gases comprising a valve body designed to be mounted on a gas cylinder and provided with an internal passage that allows the cylinder to be filled with pressurized gas. 
     BACKGROUND OF THE INVENTION 
     Although not restricted thereto, the invention is more specifically aimed at a valve of the type described in Kerger, U.S. Pat. No. 5,282,496, the entire disclosure of which is hereby incorporated by reference in its entirety. This patent relates to a valve for refillable cylinders and which comprises a level-regulating valve to prevent it from being possible for the cylinder to be filled beyond a certain limit, for example 80% of its maximum capacity, so as to avoid potential risks of an accident. 
     However, there are still risks of an accident either if the cylinders are refilled by non-specialists and do not have level-regulating valves as proposed in the aforementioned patent, or if they are refilled with an inappropriate gas or if the user manages to neutralize the level-regulating valve, or even for other reasons. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a simple and effective automatic shut-off device for a valve like the one described in the preamble and which prevents a gas cylinder from being filled by a non-specialist or unauthorized individual who does not possess special equipment. 
     In order to achieve this object, the invention provides an automatic shut-off device as described in the preamble which is characterized in that the internal passage has a widened cross section containing a ball sensitive to a magnetic field and of a diameter greater than the diameter of the passage and which acts as a non-return valve element by blocking the passage in the direction of filling, and in that said valve element can be neutralized by shifting the ball sideways under the effect of a magnetic field generated by a magnet placed on the outside of the valve. 
     In consequence, any attempt at filling the cylinder is bound to fail given that the ball, under the effect of its own weight and the pressure of the filling gas, is pressed against its seat which is formed by the upper edge of the passage and closes the passage toward the inside of the cylinder. Only somebody who knows how to open the passage and is in possession of an appropriate magnet will be able to carry out filling once he has moved the ball off its seat using this magnet. 
     Any attempt at filling the cylinder with the cylinder lying on its side is also bound to fail. Admittedly, by lying the cylinder down the passage can be opened because the ball, under the effect of its own weight, moves off its seat, but the pressure of the filling gas returns the ball onto its seat and automatically closes the passage. 
     According to one preferred embodiment, there is a tube made of synthetic material inside the axial passage. The upper edge of this tube serves to form the seat for the ball. 
     It is also possible to envisage a niche in the region of the ball in the exterior wall of the valve body and which is intended to accommodate a magnet of complementary shape. It is therefore necessary not only to have a magnet available to open the device but, in addition, this magnet has to have a special shape adapted to suit that of the niche. 
     The valve may also comprise means for preventing the ball from obstructing the upper passage above the widened cross section. These means may consist of a polygonal cross section of this passage or of a spring provided between this passage and the ball. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other specific features of the invention will emerge from the description of an advantageous embodiment, presented below by way of an illustration, with reference to the appended drawings in which: 
     FIG. 1 depicts a partial section view through the body of a valve provided with a first embodiment of an automatic shut-off device according to the present invention in the shut off position; 
     FIG. 2 is a view similar to that of FIG. 1 but during the neutralization phase; 
     FIG. 3 depicts a partial section view through the body of a valve provided with a second embodiment of an automatic shut-off device according to the present invention, in the shut off position; 
     FIG. 4 depicts a view similar to that of FIG. 3, but during the neutralization phase; 
     FIG. 5 shows a view similar to that of FIG. 3, while gas is being withdrawn from the gas cylinder; 
     FIG. 6 is a cross section on the section plane VI—VI of FIG. 5, and 
     FIG. 7 is a partial section view of a third embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The reference  10  denotes part of a valve designed to be mounted on a refillable gas cylinder. The reference to a gas cylinder is not restrictive and extends to cover all kinds of reservoir. This may be a valve as described in Kerger, U.S. Pat. No. 5,282,496 or any other device allowing the cylinder to be refilled, with or without a level-regulating valve, operating as a two-way valve or a one-way valve. Reference can be hade to Kerger, U.S. Pat. No. 5,282,496 for an exemplary application of the invention. 
     The body  10  has an axial passage  12  communicating with the inside of the cylinder, not depicted. At a certain point, this passage ends in a widened portion  14  containing a spherical metallic ball  16 , preferably made of special steel. This ball normally rests on its seat which is formed by the upper edge of the passage  12  and therefore prevents filling gas from entering the cylinder. 
     FIG. 2 shows the neutralizing of the device using a powerful magnet  18  which is brought up close to the body  10  of the valve in the region of the ball  16  and whose field is powerful enough to move the ball  16  off its seat and open the passage to the filling gas. The magnet  18  may be a simple permanent magnet. 
     In order to further complicate the task of anybody wishing to discover how to neutralize the shut-off system and who may avail himself of a magnet in order to be able to fill the cylinder, it is possible to provide a niche in the wall of the body  10  into which niche the magnet has to be introduced. This niche could extend as far as close to the widened portion  14 , and would also then have the further advantage of bringing the magnet even closer to the ball  16 . 
     FIGS. 3 and 4 show one such embodiment with a cut-out or niche  22  in the wall  10  in the region of the widened portion  14 . The niche  22  may be cylindrical or frustoconical as shown in the figures. In vertical section, in the figures, the niche  22  may have a round or polygonal cross section, for example a triangular cross section. In order to be able to move the ball  16  away from its seat and uncover the passage  12 , it is therefore necessary to have use of a magnet  24  (FIG. 4) which has a shape that complements that of the niche  22 . 
     In order to further complicate the task of people who are not authorized to fill the gas cylinder, it would be possible, at the bottom of the niche, to provide an axial stem, so that the magnet to be introduced into the niche would have to have a corresponding bore in its head so that it could be introduced into the niche  22 . 
     In the case of a niche  22  and of a magnet  24  which are cylindrical, it would also be possible to provide these with complementary screw threads, possibly a special thread type, so that the magnet would have to be screwed into the body  10  of the valve. It would therefore be impossible for the shut-off to be neutralized with a magnet that could be sourced on the open market. 
     In the embodiment of FIGS. 3 and 4, the widened cross section  14  does not need to extend over 360° and may be restricted to a lateral notch in the region of the niche  22 . However, for reasons of ease of manufacture, it may be preferable for the widening  14  to also be provided, in the case of FIGS. 3 and 4, across the entire circumference. 
     FIGS. 3 and 4 also show, by way of a variation, a tube  26  provided in the passage  12  and the upper edge of which it intended to form the seat for the ball  16 . This tube may be made of synthetic substance, for example nylon, and its purpose is to ensure better shut-off at the ball  16  by comparison with metal-to-metal contact. 
     If, as is generally the case, the passage  12  is used for the passage of gas when filling the cylinder with gas and withdrawing gas there from, a problem may arise when withdrawing gas. Specifically, as FIG. 5 shows, when withdrawing gas, the gas pressure is enough to lift the ball  16  and hold it against the lower edge of the upper passage  28  which leads to the seat  30  of the non-depicted shut-off member of the valve, which would close the passage  28  and prevent the gas from being withdrawn. To solve this problem it is possible, in the lower part of the passage  28 , to provide an obstacle, for example in the form of a diametral stem which prevents the ball  16  from obstructing the passage  28 . 
     It is also possible to convert the circular cross section of the passage  28 , at least in the lower region  28   a , into a polygonal cross section, for example a square cross section as shown in FIGS. 3 to  5  and more particularly in the view in cross section that is FIG.  6 . Thus, when the ball  16  is forced against the lower end of the passage  28  there remain several, in this particular instance, four, passages  28  for the gas in the four corners. 
     FIG. 7 shows another means intended to prevent the passage  28  from being obstructed by the ball  16  when gas is being withdrawn. In this embodiment, there is a spring  34  provided between the ball  16  and the passage  28  which is, for reference, extended downwards by a circular axial flange  32  to ensure that the spring is held. The force of this spring  34  is great enough to keep the ball  16  in a floating state away from the flange  32  during a normal operation of withdrawing gas. 
     In one advantageous embodiment, it is possible to benefit from the presence of this spring  34  to design it as a flow limiter or safety valve. Such limiters are known per se and are used to shut off the flow of gas when the flow rate or the pressure exceeds a predetermined limit. This may, in particular, arise in the event of an accident, for example if the valve should break. All that is then required is simply for the force of the spring  34  to be rated such that it prevents the passage  28  from being shut off by the ball  16  under normal gas pressure and flow rate conditions but allows shut-off in the event of abnormal operation.