EP0532435B1 - Device and process for closing carbondioxide containers - Google Patents

Abstract

The device and the method relate to the closing of containers for liquid carbon dioxide used, for example, as propellant in fire extinguishers. The device comprises a filling head (3) into which is inserted the neck (2) of the container (1) provided with a partially-fitted closing element (5). After the container has been filled through the closing element, the latter is pushed in by means of a metal rod (25) through which an internal current is then passed which welds the closing element onto the neck of the container in a fraction of a second. <IMAGE>

Description

The device and method which are the subject of the invention relate to carbon dioxide bottles, used for example as a propellant in fire extinguishers.

There are known such bottles with metal walls comprising a threaded neck provided with a screwed shutter.

The filling of these bottles is, for example, carried out using the method described in patent FR 22 57 549.

According to this method, the end of the bottle to be filled, fitted with a nut and a closure cap, is introduced into a filling head, to which it is connected by screwing, then, after filling, the screw is screwed. 'nut by means of a screwing means, driven for example by a geared motor, housed outside this filling head, the nut thus tightening the seal which closes the bottle.

Such bottles are refillable and can, after use, be refilled and closed with a new closure cap tightened by a nut.

Furthermore, there is a tendency at least in small capacity bottles to use now instead of refillable bottles such as those described above non-refillable bottles.

The patent FR 1478959 describes a process for filling and then closing a small metal bottle capable of containing a fluid such as carbon dioxide under pressure. According to this method, the end provided with a neck of the bottle is engaged in a filling chamber. An annular seal enables a tight connection to be made between the wall of the bottle and that of the filling chamber. At the upper part of the chamber thus formed, an orifice is closed by a portion of a metal strip capable of running transversely above the neck of the bottle. Above the strip, in the axis a metal electrode is placed on the neck, playing the role of a punch which, after filling the small bottle, makes it possible to cut a disc in the strip, this punch cooperating with an annular matrix placed just below the strip. The electrode is then moved in the direction of the neck so that it presses the edge of the disc against that of the neck.

Resistance welding of the disc is then carried out on the neck. For the metal of the electrode, a metal or alloy must be chosen which has sufficient mechanical characteristics for punching and sufficient conductivity for welding.

Document WO 90/11233 describes an oxygen-containing bottle in which a capsule is welded to the end of the neck, oxygen being kept under pressure inside the bottle by a valve. The capsule here does not provide a sealing role but only protects the control of the valve. Furthermore, this capsule, once placed on the neck, is opposed by its shape to the entry of a pressurized gas into the bottle, its annular edge coming to be pressed against the neck, the shape of the wall connected to this annular edge. being such that the capsule fully penetrates the neck. Such a capsule cannot therefore be used to fill bottles.

We looked for the possibility of developing a process making it possible to quickly and safely carry out the successive operations of filling carbon dioxide bottles.

We have also sought the possibility of producing shutters which are not liable to leak as a result of aging of the seals, temperature variations, overpressures or various other causes. Finally, we sought a method allowing the implementation, under the best conditions of the shutter according to the invention.

Attempts have also been made to develop a shutter capable of closing the bottle by itself, after welding, and which can be used positioned on the bottle during the filling phase of the latter.

The process according to the invention achieves these results. In particular, it enables rapid filling with liquid carbon dioxide of metallic bottles and, as soon as filling is completed, sealing of these bottles is perfectly sealed and durable with a very high speed. very high security.

The method according to the invention relates to a method for closing a metal bottle for non-refillable carbon dioxide which is filled and then closed by means of a filling head.

According to the method of the invention, the end of the bottle comprising a neck is introduced and maintained inside a filling head so that the wall of this bottle is in leaktight support, by means of a seal, against the inlet wall of the filling head. After filling the bottle with carbon dioxide, the bottle is closed by pressing the edge of a shutter against the edge of the neck then the two annular edges are welded by resistance against each other by means of 'An electrode abutting against the shutter, the return of electric current being effected by at least one contact piece abutting against the side wall of the bottle. The interior space between the wall of the filling head and that of the bottle engaged inside the filling head is a closed, sealed space and placed before the introduction of the bottle inside of the filling head, on the neck of the bottle, by partial fitting, a shutter so as to leave a gap between its annular edge and the annular edge of the neck. This shutter has a side wall connected to its annular edge and capable of cooperating with the corresponding side wall of the neck by means of guide edges distributed around the axis of the neck and inclined relative to the generatrices of the wall of the neck. to come over part of their length in elastic support against this wall of the neck. This shutter also has passages formed between its side wall and the corresponding wall of the neck in the areas between the guide edges, these passages joining the annular passage formed between the annular edges of the shutter and the neck and making it possible to penetrate inside the bottle carbon dioxide in a determined amount, by means of introduction of carbon dioxide. After filling the bottle, the shutter is pushed in using a metal rod so that the annular edge of the shutter comes in support against the edge of the neck by means of a thrust acting on the metal rod or on the bottle after pressing against the side wall of the bottle at least two metal rods distributed around the axis of the neck in order to make it coaxial with the axis of the filling head, connect the metal rod in contact with the shutter to a pole of an electrical energy source, the other pole of which is connected to the two rods, pressing against the wall from the bottle. A very high current is passed through the circuit thus produced for a very short time, the passage of this current ensuring the melting of the metal of the annular edges in a thin contact zone and thus producing a sealed weld capable of resisting the pressure of the carbon dioxide contained in the bottle.

Advantageously, the low-voltage and high-intensity electric power source includes electrical means, such as thyristors, making it possible to obtain a maximum current density in the welding zone, of at least 50 amperes per mm2 the electric power source being arranged so as to cause the welding zone to pass through at least two separate current pulses, each lasting less than half a period, successively passing through the welding zone in opposite directions.

Preferably, the thrust means, allowing the annular edge of the shutter to bear against one another against the annular edge of the neck, is a means connected to the axial rod which makes it possible to move the latter along the axis of the filling head until the end of this rod comes to bear against the shutter, then presses the two annular edges in order to allow their welding by current flow. It is also possible to achieve this thrust, also after filling the bottle, by moving it in the direction of the axial rod in a fixed position, using the means of displacement of the support means of the bottle, in order to come to bear. the annular edge of the neck against that of the shutter itself pressing against the end of the axial rod.

At least one insulating passage means is provided for the electrical connection between one of the two poles of the electrical energy source and the welding zone of the two annular edges, at the level of the crossing of the metal wall of the head of filling. Preferably this insulating passage means is formed around the rod axial when it crosses this wall; preferably also a dynamic seal allows this axial rod to slide through this insulating passage means itself connected to the wall of the filling head by a seal. Advantageously, the lateral retractable metal rods are slidably mounted through insulating passage means by means of watertight dynamic seals and these insulating passage means are themselves connected to the wall of the filling head by a watertight seal.

Preferably, the carbon dioxide contained in the filling head is purged after welding the shutter; the purge means is a passage through the wall of the filling head provided with a purge valve.

Also preferably, the wall of the filling head is made of a non-magnetic metal or alloy.

The bottle is made of any metallic material which can be used, such as, for example, non-alloyed or low-alloyed drawing steel. It is the same for the shutter.

The invention also relates to the shutter for a carbon dioxide bottle which allows the implementation of the process according to the invention thanks to the possibility that it offers a fitting on the neck of the bottle in partial interlocking, this position not obstructing the filling and then allowing the bottoming and welding thanks to the device according to the invention.

The shutter according to the invention comprises at its upper end an annular edge capable of coming to bear against the annular end edge of the neck of the bottle, in order to allow the closure thereof by welding and a male side wall or female, connected by its upper end to the annular edge and able to cooperate with the corresponding internal or external lateral wall of the neck. The male or female side wall has guide edges distributed around the axis of this neck and inclined with respect to the generatrices of the corresponding wall of the neck so as to come into resilient abutment against this wall in the partially nesting position. Between the guide edges the side wall is shaped so as to move away from the corresponding wall of the neck so as to form passages which join the annular passage formed between the annular edges of the shutter and the neck, when this shutter is in partial interlocking, thus allowing the penetration of liquid carbon dioxide inside the bottle. The shutter has a bottom connected directly or indirectly to its annular edge, bottom which extends transversely to the axis of the neck and ensures the closure of the bottle after welding of the annular edge with the end of the neck and which is suitable for being drilled in service by suitable means.

Preferably, the lower part of the shutter is a male part whose section of the wall in a plane perpendicular to the axis of the shutter is not circular, the guide edges being slightly inclined relative to the generatrices of the inner wall facing the neck so as to approach it from bottom to top to come into elastic abutment against it in the partial nesting position. Passages are provided between the wall of this male part and the interior wall of the neck between the guide edges. These passages join the annular passage formed between the annular edges facing the shutter and the neck.

Advantageously, the male part has the shape of a truncated pyramid, the rounded edges of which constitute the guide edges, the sides of the pyramid constituting the passages for liquid carbon dioxide and the small base of the pyramid, engaged inside the neck. constituting the opening wall of the bottle in service by a piercing means such as a punch.

The shutter may include a female lower part, the guide edges of which cooperate with the external side wall of the neck, the passages for the liquid carbon dioxide being formed between the guide edges by means of an adapted shape of the side wall of the shutter. between these guide edges, or even through holes through this side wall.

Advantageously, the bottles are produced from seamless tubes of revolution, for example from non-alloy steel with low carbon content, the neck and the end opposite to it being produced by forming preferably cold. The end opposite the neck is preferably given a rounded shape closed, for example, by a welded obturator.

Many variations or modifications can be made which do not depart from the scope of the invention.

The figures and example below describe, without limitation, a particular embodiment of the invention.

Figure 1 is an elevational and sectional view of the filling head according to the invention in which is engaged the neck of a bottle to be filled.

FIG. 1A is a view of an insulating passage for a current supply rod through the wall of the filling head of FIG. 1.

Figure 2-1 is an elevational and sectional view of the shutter according to the invention in partial partial nesting position in the neck of the bottle.

Figure 2-2 is a view of the shutter of Figure 2-1 in the closed position.

Figure 2-3 is a top view of the shutter in Figures 2-1 and 2-2.

We see in Figure 1 a metallic bottle 1 of revolution whose end provided with the neck 2 is engaged in the filling head 3. The bottle of this example was produced by forming a section of non-alloy steel tube, suitable for stamping, seamless. The neck 2 was produced by necking as well as the bottom, at the opposite end, which is closed by a disc 4 of the same metal, welded.

Before introduction into the head 3, the obturator 5 is partially fitted onto the neck 2. This obturator 5 comprises at the upper part an annular edge 6 whose dimensions are determined so that it can come to bear against the annular front edge 7 of the neck 2 when the male lower part 8 is fully inserted into this neck 2.

As shown in Figures 2-1, 2-2 and 2-3 the male lower part 8 of the shutter 5 produced by stamping has three guide edges such as 9 distributed around the axis X1-X1 slightly inclined at least over part of their length, relative to the generatrices of the inside wall of the neck. As shown in Figures 2-1 and 2-2 these guide edges come over part of their length in elastic abutment against the inner wall of the neck 2 already in the partially nesting position. We see in Figure 2-3 that the male part 8 has a section in the shape of an equilateral triangle in a plane perpendicular to the axis X1-X1 the vertices such as 9-1 which correspond to the guide edges such as 9 being rounded. We also see that when the annular edges 6, 7 of the shutter 5 and the neck 2 are not in contact there are three passages such as 10 which can allow the filling of the bottle with liquid carbon dioxide. It is noted that this male part 8 has approximately the shape of a trunk of a pyramid whose small base 11 constitutes the opening zone which, in use, must be perforated by a punching means.

As shown in Figure 1, the bottle 1 has been introduced into the head 3 provided with its shutter 5 in the partial nesting position. This bottle 1 rests on a support means 12 adjustable in height along the axis X2-X2 of the filling head 3. This height is adjusted so that the current supply rods 15A and 15B, capable of sliding along the transverse axis X3-X3 can come to bear against the wall 16 of the neck 2 in an area thereof without a more or less insulating protective layer. The rods 15A and 15B pass through the wall 17 of the filling head 3 through insulating passages such as 18 provided with dynamic seals allowing the rods 15A and 15B to slide without excessive loss of carbon dioxide despite the filling pressure of around a hundred bars.

At the upper part of the head 3 the current supply rod 25 is slidably mounted like the rods 15A and 15B through an insulating passage such as that of FIG. 1A (insulating passage 18).

FIG. 1A is an enlarged view of the means ensuring the passage of the 3 rods 15A, 15B and 25 for supplying the welding current. We see that the rod 25, of axis X2-X2, passes through an insulating part 18 inserted in a housing 19 formed in the metal wall 17 of the filling head 3. This insulating part can be made of a ceramic or, preferably, of a material plastic, such as for example a polytetrafluorethylene. This insulating part 18 allows the passage of a rod such as 25 with little play and has a good sliding coefficient. A static seal, such as the O-ring 20, provides a tight connection between the part 18 and the wall 17. A dynamic seal, such as the lip seal 21, ensures a tight sliding connection between the part insulator 18 and the current supply rod 25. A flange 22 of polytetrafluoroethylene is screwed into the wall 17 according to the holes indicated in X4 and X5 to maintain the insulating part 18 in its housing with tightening of the O-ring 20 and maintenance of the seal dynamic 21.

The rods 15A and 15B not only provide an electrical connection but also, thanks to a synchronized drive means not shown, the centering of the neck 2 whose axis is placed in coincidence with that X2-X2 of the filling head 3. The tubular passage 26 is connected to a pipe, not shown, for injecting liquid carbon dioxide under a pressure of the order of one hundred bars. The amount thus injected is precisely determined to ensure the introduction into the bottle of the desired amount of this liquid carbon dioxide through the passages such as 10 in a very short time of the order of a second. Part of the carbon dioxide remains in the interior cavity of the head 3. It is noted that the dynamic lip seal 27 housed in a groove in the interior wall of the head 3, at the entry edge thereof, in pressing against the wall of the bottle 1, prevents significant losses of carbon dioxide. As soon as the bottle is filled, a pushing means (not shown) lowers the current supply rod 25 until it presses against the annular edge 6 of the shutter 5 and the male part 8 is completely engaged in the neck 2. Thus the two annular edges 6, 7 of the shutter 5 and of the neck 2 are pressed against each other. The diameter of the rod 25 is determined to correspond substantially to the outside diameter of the annular edges 6 and 7. Welding is then carried out by means of an electrical energy source comprising two thyristors capable of each controlling the flow of current during a half period of at least one cycle of an AC power supply. One of the two poles of the electric power source is connected to the axial current supply rod 25 and the other is connected to the two lateral rods 15A, 15B in parallel. Then the passage of two consecutive unidirectional discharges and of opposite directions is controlled through the contact zone of the two annular edges 6, 7, these two discharges of low voltage and very high intensity, each having a duration of less than one hundredth of a second, suffice to ensure fusion welding of these two annular edges over a small thickness in their contact zone. The current density, greater than 50 A / mm2 preferably reaches 100 to 300 A / mm2. The current supply rods 15A, 15B and 25 are preferably made of copper or a high conductivity alloy based on copper. They are advantageously cooled by an internal water circulation, not shown.

After welding, the filling head 3 is purged of the carbon dioxide it contains by opening a not shown purge valve which is connected, also not shown, to the tubular passage 28. The bottle 1 is then extracted from the head filling 3 by lowering the support means 12.

Preferably, the wall 17 of the filling head 3 is made of a metal or non-magnetic alloy to avoid disturbances in the distribution of the welding current. For example, an austenitic steel or an aluminum alloy or the like is used.

Although a shutter 5 is advantageously used provided with a male part 8 which fits inside the neck, it is also possible to use a shutter comprising a female lower part inside which fits the neck 2 In one case as in the other, the guide edges allow a partial nesting by coming into elastic support on the wall opposite the neck.

Although the bottle 1 is advantageously made from a steel tube, it can also be done by forming a steel sheet. It can also be made of any other suitable metal.

Claims (9)

1. A process for closing a metal bottle (1) for liquid carbon dioxide, filling and then closing of which is effected by introducing the end of the bottle comprising a neck (2) into the interior of a filling head (3) and holding it therein in such a way that the wall of said bottle is in sealing contact by way of a seal (27) against the entrance wall of the filling head, in which process, after the bottle is filled with carbon dioxide, the bottle is closed by causing the edge (6) of a closure member (5) to bear against the edge (7) of the neck (2), then the two annular edges are welded against each other by resistance welding by means of an electrode (25) which comes to bear against the closure member, the return of the electric current being effected by at least one contact portion (15A, 15B) which comes to bear against the side wall (16) of the bottle, characterised in that the internal space between the wall of the filling head (3) and that (16) of the bottle (1) which is engaged in the interior of the filling head is a closed sealed space and that prior to the introduction of the bottle (1) in the interior of the filling head (3) a closure member (5) is placed on the neck (2) of the bottle (1) by partial engagement into same, so as to leave a gap between its annular edge (6) and the annular edge (7) of the neck, the closure member comprising a side wall connected to its annular edge (6) and capable of co-operating with the corresponding side wall of the neck by virtue of guide edges (9) which are distributed around the axis of the neck and which are inclined with respect to the generatrices of the wall of the neck, so as to come to bear resiliently against said wall of the neck, over a part of their length, the closure member also comprising passages (10) provided between its side wall and the corresponding wall of the neck in the zones between the guide edges (9), said passages communicating with the annular passage between the annular edges of the closure member and the neck and permitting carbon dioxide to pass into the interior of the bottle in a given amount, by virtue of means for introducing carbon dioxide, then after filling of the bottle the closure member (5) is pushed in by means of a metal bar (25) so that the annular edge (6) of the closure member comes to bear against the edge (7) of the neck (2) by virtue of a thrust means acting on the metal bar (25)or on the bottle (1) and after at least two metal bars (15A, 15B) distributed around the axis of the neck are brought to bear against the side wall (16) of the bottle (1) so as to make the neck coaxial with the axis (X2-X2) of the filling head (3), the metal bar (25) which is in contact with the closure member (5) is connected to a pole of an electrical energy source of which the other pole is connected to the two bars (15A, 15B) bearing against the wall (16) of the bottle (1) and a current of very high strength is passed for a very short time through the circuit provided in that way, the flow of said current causing fusion of the metal of the annular edges (6, 7) in a thin contact zone which thus provides a sealed weld capable of withstanding the pressure of the carbon dioxide contained in the bottle.
2. A process according to claim 1 characterised in that the operation of welding the annular edges (6, 7) of the closure member (5) and the neck (2) against each other is effected by passing through the electric circuit at least two consecutive unidirectional discharges in opposite directions, at low voltage and of very high strength, which pass through the welding zone, each being of a duration of less than a hundredth of a second.
3. A process according to claim 2 characterised in that the electrical energy source of low voltage and high current strength comprises electric means for obtaining a maximum current density in the welding zone of at least 50 amperes/mm².
4. A process according to one of claims 1 to 3 characterised in that after welding of the annular edges (6, 7) of the closure member (5) and the neck (2), which are in contact with each other, the carbon dioxide contained in the filling head (3) is purged prior to withdrawal of the bottle.
5. A closure member (5) comprising an annular edge (6) capable of coming to bear against the annular end edge (7) of the neck (2) of the bottle (1) so as to permit closure thereof by welding and an end portion as well as a male or female side wall connected by its upper end to the annular edge and capable of co-operating with the corresponding internal or external side wall of the neck (2) characterised in that the male or female side wall comprises guide edges (9) which are distributed around the axis of said neck and which are inclined with respect to the generatrices of the corresponding wall of the neck so as to cane to bear resiliently against said wall in a position of partial engagement in the neck, and that between the guide edges (9) the side wall is so shaped as to extend away from the corresponding wall of the neck (2) so as to form passages (10) which communicate with the annular passage between the annular edges (6, 7) of the closure member (5) and the neck (2) when said closure member is in a position of partial engagement therein, thus permitting the liquid carbon dioxide to pass into the interior of the bottle, and that the end portion (11) is directly or indirectly connected to its annular edge (6), which end portion extends transversely with respect to the axis of the neck and provides for closure of the bottle after welding of the annular edge (6) to the end (7) of the neck (2), and which is capable of being pierced in service by a suitable means.
6. A closure member according to claim 5 characterised in that it comprises a male side wall connected by its upper end to the annular edge (6) and by its lower end to the end portion.
7. A closure member according to claim 6 characterised in that the male part (8) is in the approximate shape of a truncated pyramid whose rounded edges (9-1) constitute the guide edges, between each side of the pyramid, the small base (11) of the pyramid constituting the end portion of the closure member.
8. A closure member according to claim 5 characterised in that it comprises a female side wall connected by its upper end to the annular edge (6) and that it comprises an end portion connected directly to the annular edge.
9. A closure member according to one of claims 5 to 8 characterised in that it is formed by a single plate of metal sheet formed by stamping.

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