EP0349396A1 - Method for vacuum-packaging liquids and pastes in soft tubes provided with a dispenser valve or pump, and apparatus for carrying out this method - Google Patents

Abstract

In order to benefit from all the advantages offered by dispenser valves comparable to precompressed metering pumps 10 when they are arranged on flexible tubes 12 which contain a more or less fluid paste 13, it is valuable to be able to create an air vacuum in the tube when its base 14 is being welded. <??>For this purpose, a packaging method is proposed which comprises at least the following stages: 1) the introduction of the paste through the base of the tube already equipped with its valve 2) the drawing off, through the said base, of the air remaining in the said tube above the said product, then closure of the said tube leaktight by welding its base. <??>Advantageously, an intermediate stage consists in firstly partially welding the base of the tube filled with paste. During stage 2, the air is drawn off through the non-welded part of the base of the tube and this is followed by the completion of the welding of this base. <??>According to this preferred embodiment of the present method, stage 2 is advantageously implemented in its entirety by virtue of a device 50 comprising two groups of pieces which slide relative to each other which can be mounted on a press 90 and connected to a vacuum pump 91. When its lower notch 51 covers the prewelded base 14 of a tube 12 which is placed in a support 20 serving as a stop for the lower unit 52, the driving-in of the upper unit formed by the cylinders 70, 75 and 80, which is caused by the press, in fact triggers, by means of a cam 72 and balls 63, the opening of the valve 57 followed rapidly by the tightening of the jaws 54. <IMAGE>

Description

The present invention relates to tubes of more or less fluid paste used for dispensing cosmetic or pharmaceutical products such as toilet milks, sun creams, toothpaste, balms, etc. These tubes are provided with a valve distribution comparable to those which are usually arranged on perfume vaporizers for example. They are made of a rather flexible plastic material and the bottom of the tube is closed by the welding of this envelope, giving the tubes a very conventional appearance. They differ from comparable packaging, however, by the air vacuum created in the tubes when they are welded. The invention relates more specifically to the method for performing this welding while removing air from the tube. It also relates to a device useful for implementing this method.

The flexible tubes currently used to present pasty products generally do not include a dispensing valve. However, this association can be very advantageous, especially if special valves, called precompression dosing pumps, are used. A particularly advantageous embodiment of the latter was improved in 1975 (see French patent 2,305,241) so that it can operate whatever their position relative to the vertical. An example of these improved pumps of the prior art is shown in different positions in Figures 1 to 3.

The vertical section shown schematically in these figures highlights six different pieces. Three of them are fixed relative to each other. These are the crimping cup 1 which makes it possible to tightly associate the assembly of the valve 10 with the container containing the dough (not shown), the turret 2 intended to be placed on the side from the outside of the container and the body 3, the lower end of which is surrounded by the dough in reserve. The other three parts can slide vertically in the body 3: the hollow piston rod 5, the double valve 4 and the return spring 6. In FIG. 1, their configuration corresponds to the rest position, valve closed. Without going into all the details of operation of this pump, let us only remember that the depression of the piston rod 5 causes the compression of the fluid trapped in the pump chamber 7. It is only when this compression is greater than the resistance of the spring 6 that the fluid manages to open the passage 8 and escapes. The different parts then have respective positions in accordance with those of FIG. 3 which presents the open valve.

Such a valve confers on the tube of dough which carries it three qualities. As a pump, it ensures that the product reserve is used up to at least 95%. The dosing function is particularly valuable for pharmaceutical products, but can also be useful in other applications. Finally, precompression is fundamental vis-à-vis safety or more simply cleanliness of use. Indeed the pressure which must be reached in the chamber 7 so that the passage 8 opens, is much higher than the pressure which could be created in the tube by pressing it with the hand. There is therefore a risk of unintentionally causing a dough emission.

However, the use of these precompression dosing pumps for the emission of paste encounters the problem of priming them. When the valve has just been crimped onto the dough tube, its chamber 7 contains air. During the first depression of the piston rod 5, this air is compressed. But the properties of the gas do not allow it to reach a pressure sufficient to escape through the passage 8. This is why the body 3 is usually provided with a gadroon 9. The skirt of the valve 4 can then be caused to come off the inner cylinder slightly, thus opening a passage for compressed air towards the interior of the container (see fig 2). If this system properly primers the pump in the presence of gas or liquid, it is in no way suitable for pasta because of its more viscous consistency. Indeed, the air expelled into the pulp reserve remains near the chamber 7 in the form of a bubble. When the piston rod 5 and the valve 4 go back up, it is then air which is returned to the chamber 7 of pump and not the expected paste. Thus it becomes practically impossible to prime the pump.

French patent application 2,625,729 which discloses a tube fitted with a precompression metering pump, but having a semi-rigid wall, overcomes this drawback by ensuring an initial pressure inside the container. This however leads to the use of specially shaped vial tubes. From an economic point of view, it is more advantageous to keep the flexible tubes commonly used. The present invention therefore aims to solve the problem of priming the pumps used for the distribution of pasty products in combination with flexible tubes.

It is based on the idea of creating a vacuum inside the tube containing the dough. In fact, the known methods for achieving this vacuum in containers intended to be closed by a dispensing valve apply essentially to rigid bottles. They consist in effect in capping the bottle with its valve by a device which bears on the walls of the container and thus isolates a sealed chamber. The air can then be sucked out of this chamber while the valve immediately put in place on the bottle is crimped in a following operation. Regarding flexible tubes, no method has yet been proposed except to weld them through the product they contain. This process used for example in order to "dick" a cylinder filled with bleach in individual cartons, is however not feasible in the presence of greasy pastes.

• 1°)introduction dudit produit dans ledit tube par son fond,
• 2°)aspiration par ledit fond de l'air subsistant dans ledit tube au-dessus dudit produit, puis fermeture étanche dudit tube par soudure de son fond.

The present invention rather discloses a method of packaging a liquid or pasty product in the form of a flexible tube comprising a bottom and a head provided with a dispensing valve, characterized in that it comprises at least the following steps:

• 1) introduction of said product into said tube through its bottom,
• 2) aspiration by said bottom of the air remaining in said tube above said product, then sealing of said tube by welding its bottom.

The dispensing valve is advantageously a precompression dosing pump. It is preferably mounted on a neck welded to the tube by crimping or by overmolding.

For the industrial implementation of this process, a support can be provided to receive the tube placed upside down. It advantageously comprises means for maintaining the dispensing valve in a position such that it contains the least amount of air possible. The tube can thus be transported from one station to another from a machine capable of automatically carrying out the various stages of the process of the invention. The step of introducing said product is then carried out using a spout integral with said machine and the lower end of which is moved relative to the tube as the quantity of product introduced increases so that said end remains permanently above the surface of the product.

Advantageously, said method further comprises an intermediate step consisting in partially welding the bottom of said tube filled with paste, the aspiration of air in the last step of said process taking place by the non-welded part of said bottom and being followed by completion of the welding of the bottom of said tube. The partial welding step of the bottom of the tube is then preferably carried out, after preheating, by means of jaws comprising in their center a recess so that they press the bottom of said tube along its entire length except at level d 'a small duct located in the middle of said bottom. During the last step of the process, the air is sucked in through said duct left in the middle of the partially welded bottom of said tube while said duct is in turn welded. Advantageously, the welding of the duct is carried out between 1/10 and 1 second after the start of the suction of the air. The conduit can be welded by ultrasound or thermomechanically by heating the bottom of said tube before the implementation of the last step.

In order to automatically carry out the last step of the method of the invention when it uses an intermediate partial welding step, a device is proposed. It comprises two groups of parts which can undergo vertical translation with respect to each other when a vertical force is exerted against elastic means placed between them:
- The first group of parts comprising a cylindrical part with a vertical axis provided, in the upper part, with a hollow cylinder with the same axis as that of the part and having a throttle acting as a valve seat, in the lower part, with a symmetrical cut relative to a horizontal axis intersecting the axis of said part cylindrical and serving to guide the bottom of a tube and, approximately halfway between the upper and lower parts, of two horizontal cylindrical reserves symmetrical with respect to the axis of said notch, passing right through said cylindrical part and can receive two jaws protruding into said notch, each jaw being tightly connected to said cylindrical piece and being able to slide relative to it under the combined effect of a return spring and a ball.
- The second group of parts comprising a skirt, the internal surface of which adapts to the external vertical surface of said cylindrical part in order, on the one hand, to provide it with a limit stop and, on the other hand, allow the progressive engagement by means of a cam, of said balls in said reserves of said cylindrical part and also comprising, rigidly connected to said skirt, a cylinder provided with a central channel ending in a needle which can engage so tight in the throttle of said hollow cylinder of said cylindrical part and thus open said valve,
the first group of parts being able to collaborate with said support to form with it a sealed chamber from which the air is evacuated, the second group being compatible with a head of said automatic machine transmitting said vertical force and pumping air.

As this rapid description of the invention suggests, the tubes thus produced can also contain liquids or include less sophisticated valves than the metering pumps mentioned above. In all cases, the problem of priming the valves is resolved by the air vacuum created. The atmospheric pressure applied to the flexible tube in fact supplies the energy necessary for filling the pump chamber with the same pasty product. Another advantage is the absence of contamination of the liquid or the paste contained in the tube in contact with polluted air or the oxygen it contains.

In terms of its implementation, the advantage of the intermediate partial welding step is clear. It significantly reduces the amount of air that must then be pumped. For the same purpose, the device of the invention provides for placing the valve communicating the air pumping system with the bottom of the tube as close to the latter as possible.

• -la figure 1 est une coupe verticale d'une pompe-doseuse à précompression de l'art antérieur qui peut être placée sur les tubes souples qui sont ensuite soudés sous vide d'air conformément au procédé de l'invention. Sur cette figure, la pompe-doseuse est montrée dans sa position fermée de repos,
• - la figure 2 correspond à une coupe similaire lorsque la pompe-doseuse est actionnée en vue de son amorçage,
• - la figure 3 illustre toujours cette coupe, mais l'actionnement de la pompe-­doseuse aboutit en l'occurrence à l'émission de la pâte,
• - la figure 4 montre, selon une coupe verticale, un tube muni de sa pompe-­doseuse en cours de remplissage selon un mode de réalisation du procédé de la présente invention,
• - la figure 5 illustre, à l'aide d'une coupe verticale similaire à celle de la figure 4, la phase de présoudure du fond d'un tube selon un mode de réalisation du procédé de la présente invention,
• - la figure 6 est une coupe horizontale passant par le plan I-I de la figure 5,
• -la figure 7 représente, à l'aide d'une coupe verticale comparable à celles des figures 4 et 5 la dernière phase de soudure d'un mode de réalisation du procédé de l'invention,
• -la figure 8 est une coupe horizontale suivant le plan II-II de la figure 7,
• - la figure 9 montre, en coupe verticale, l'ensemble d'un dispositif permettant de mettre en oeuvre le procédé de la présente invention.

The method and the device of the present invention are described on the following pages with the aid of drawings. Their essential role is to help understanding and cannot fix their modes or their forms of realization. In particular we have already pointed out that the dispensing valve placed on the flexible tube may very well be of another type than that mentioned so far. Likewise the invention applies equally well to liquids. However, we will illustrate this with a precompression dosing pump delivering a paste in accordance with the spirit of origin. In the drawings:

• FIG. 1 is a vertical section of a precompression dosing pump of the prior art which can be placed on the flexible tubes which are then welded under vacuum in accordance with the method of the invention. In this figure, the dosing pump is shown in its closed rest position,
• FIG. 2 corresponds to a similar section when the dosing pump is actuated with a view to priming it,
• FIG. 3 still illustrates this section, but the actuation of the dosing pump in this case results in the emission of the paste,
• FIG. 4 shows, in a vertical section, a tube fitted with its dosing pump during filling according to an embodiment of the method of the present invention,
• FIG. 5 illustrates, using a vertical section similar to that of FIG. 4, the phase of pre-welding of the bottom of a tube according to an embodiment of the method of the present invention,
• FIG. 6 is a horizontal section passing through the plane II of FIG. 5,
• FIG. 7 represents, using a vertical section comparable to those of FIGS. 4 and 5, the last welding phase of an embodiment of the method of the invention,
• FIG. 8 is a horizontal section along the plane II-II of FIG. 7,
• - Figure 9 shows, in vertical section, the assembly of a device for implementing the method of the present invention.

The welding process with establishment of the air vacuum in the dough tube will now be described with the aid of FIGS. 4 to 8. It in fact presupposes the use of a machine automatically carrying out the different stages of the process. To facilitate this automation, a cylinder 12 of flexible plastic is first cut to the desired length. It is then welded to a part 11, generally cylindrical, forming the neck of the future dough tube. On this neck 11, a precompression metering pump 10 can then be fixed in a sealed manner like that described above. Figures 4, 5 and 6 show a metering pump 10 provided with a metal cup crimped on the neck 11. An attachment of the pump 10 by molding the neck 11 is however also possible. The assembly formed by the pump 10 and the cylinder 12 is then placed on a support 20 forming part of the machine mentioned above. This support 20, metallic or plastic, has an interior housing that can receive the assembly, the pump 10 being arranged downward while the cylinder 12 opens upward. This housing is also provided with means 21 suitable for securing the valve in the low position of the metering pump 10 (cf. FIG. 2). These means 21 consist, for example, of metal tongues which can slide over a length of travel defined inside horizontal reserves formed in the support 20 and comprising a return spring. When the pump-cylinder assembly is introduced inside the support, the pump 10 is then advantageously pressed against the bottom of the housing so that its piston rod rises. The tongues 21, which had automatically retracted into the support 20 when the pump passed, come out under the pressure of their spring and consequently block the pump. In this position, the chamber 7 is reduced to a minimum so that the valve contains the least amount of air possible. However, we will see below that it is not imperative to maintain the pump in this way as long as the pump-cylinder assembly cannot easily escape from the support 20.

The first phase of the process then consists in filling the cylinder 12 with paste 13. This is preferably carried out using an injection system 30 provided with a fairly long spout 31. During filling, the lower end of the spout is kept close to the surface of the dough so as to avoid trapping air bubbles. This implies a relative displacement of the spout relative to the cylinder 12 as the amount of dough placed in the cylinder 12 increases. For example the beak goes up.

Then the support 20 is translated relative to the injection system 30. According to a first particularly advantageous embodiment of the present method, the support 20 is then placed under a welding station. During this movement, the upper edge 14 of the cylinder 12 remains, if necessary, near a heating ramp not shown in the figures. Its role is to maintain the plastic at a temperature related to the welding operation. The latter is carried out according to a traditional method using jaws 40, preferably metallic, which pinch the cylinder 12 horizontally at its upper edge 14 and press the two lips thus created against each other as indicated on the Figure 5. Optionally, the jaws 40 are themselves provided with heating resistors in order to perform the welding of the lips in a thermo-mechanical manner. It is then possible to do without an intermediate heating ramp. According to this preferred embodiment of the present invention, the jaws 40 here have a fairly deep recess 41. This is preferably located in the middle of their length (see fig 6) and concerns their entire thickness. It follows that the welding of the bottom of the tube remains partial: a conduit 17, although small, still allows the interior of the tube to communicate with the atmosphere. This is why this phase of the process is rather called the presoldering step.

• 1°)l'air est aspiré par le canal 55 si bien qu'il est évacué aussi bien de la chambre 16 que de l'espace résiduel 15 intérieur au tube,
• 2°)les mâchoires sont pressées l'une contre l'autre et referment le conduit 17 en achevant la soudure du fond 14 du tue.

Again the support 20 is translated relative to the pre-welding station 40 while the edge 14 of the cylinder 12 which has become the bottom of the tube is still advantageously maintained near a heating ramp. The whole is then positioned under a device 50 specially designed to complete the welding of the bottom of the tube and evacuate the air that the interior of the tube still contains (cf. space 15). Before describing this device more precisely, we can explain using Figures 7 and 8 how it works. The bottom 14 of the tube is first of all engaged in a guide 51 presented by the lower part 52 of the device 50 until the latter abuts on the surface of the support 20. A seal 53 therefore ensures the insulation of the room 16 thus created. At the same time the bottom 14 of the pre-welded tube is at the height of two jaws 54. The device 50 is designed so that it performs consecutively, but at close time intervals (between 1/10 and 1 second of beat), the following two operations:

• 1) the air is sucked in through the channel 55 so that it is evacuated both from the chamber 16 and from the residual space 15 inside the tube,
• 2) the jaws are pressed against each other and close the conduit 17 by completing the welding of the bottom 14 of the killer.

It should be noted that the jaws could also correspond respectively to an anvil and to a sonotrode in order to achieve rather a welding by ultrasound. Anyway, the dough 13 is thus found under vacuum inside a flexible tube made perfectly tight. When the means 21 are actuated to allow the release of the tube (by means of an electromagnet for example), the piston rod of the pump comes out while the chamber 7 of the pump automatically fills with paste. In other words, the precompression dosing pump is already primed.

Note that in the absence of means 21 for keeping the pump in the low position throughout the process of the present invention, priming can still be carried out. In fact, the atmospheric pressure surrounding the flexible tube transmits the pressure necessary for filling the pump chamber to vacuum. Moreover, this pressure can theoretically dispense with the use of a pump as a dough distribution member. And a simple valve could suffice subject to a fairly high vacuum and not to be too demanding in terms of final exhaustion of the tube. Finally, nothing prevents the process from being applied to a liquid product.

An embodiment of the device 50 making it possible to carry out the last welding step is now described with the aid of FIG. 9. Two groups of parts, preferably metallic, can undergo a relative movement of vertical translation. In the absence of effort, they are kept at a maximum distance from each other by means of a spring 60. The group of lower parts essentially consists of a cylindrical part 52 comprising interior recesses of fairly complex shape . In the upper part, there is a hollow cylinder 55 of the same axis as the axis of the cylindrical part 52. This hollow cylinder 55 has a variable cross section. It has in particular a throttle 56 which acts as a valve seat. Indeed, a ball 57 rests on the throttle 56 while a spring 58, introduced at the base of the hollow cylinder 55 and held by a nut 59, pushes the ball 57. A cylindrical channel pierced in the center of the nut 59 allows the hollow cylinder 55 to communicate with a horizontal cut made in the lower part of the cylindrical part 52. The cut has a shape allowing engagement of the bottom of the tube to be welded. This is guide 51 mentioned above. At the top of the guide 51 and under the nut 59, two horizontal jaws 54, placed symmetrically with respect to the guide, protrude. They are mainly housed inside cylindrical reserves 64 formed in the thickness of the part 52 (cf. fig. 8). They each have a shoulder allowing the support of a spring 61. The latter has a return function tending, in the absence of force, to cause the retraction of the jaws inside the part 52. Each jaw 54 is also provided with a seal 62 ensuring a tight connection of the jaws and the cylindrical part 52. At the periphery of the part 52, a ball 63 is engaged in each of the reserves 64 so that it provides a stop for the jaws 54 and s opposes the springs 61. On the underside of the part 52, a seal 53, of the same axis as the axis of the part, is finally maintained thanks to a removable ring 65.

The other group of parts has two main elements. First of all, a skirt 70 adapts to the external vertical wall of the cylindrical part 52. If the external surface of the skirt 70 is smooth, its internal surface is more worked. First of all, it has a shoulder 71 intended to cooperate with a flange 66 projecting from the cylindrical part 52 with a view to a stop. Then, approximately at the height of the jaws 54, the interior of the skirt gradually widens by a cone serving as a cam 72. Thus when the skirt 70 slides on the part 52, the ball 63 engages under the action of the cam 72 more or less in the reserves 64 and the jaws 54 emerge more or less inside the guide 51.

Furthermore, a cylinder 75 can engage vertically in the hollow cylinder 55 of the cylindrical part 52. The corresponding connection is sealed by means of a seal 76. In order to adapt to the constriction 56 mentioned above, the cylinder 75 in fact ends at its lower part with a needle 77. The sliding of the cylinder 75 in the part 52 therefore results in the depression of the ball 57 which is then pushed back towards the nut 59 thanks to the needle 77. Note that the entire cylinder 75 has a narrow internal channel 78.

The cylinder 75 and the skirt 70 are rigidly linked with respect to each other thanks to a third part 80 in the form of a hollow cylinder threaded along its internal surfaces and external. If the external thread 81 allows the skirt 70 to be fixed, the internal thread 82 has the role of promoting the mounting of the entire device 50 on the machine ensuring the automatic implementation of the welding process of the invention. FIG. 9 shows in front view a part of the head 90 of this machine which thus ensures the connection with a vacuum pump 91. The latter can operate continuously throughout the various phases of the process of the invention. It does not need to be particularly efficient, negative pressures of the order of 0.5 bar being sufficient.

The head 90 is also secured to a jack or a mechanical control allowing its movement along a vertical axis. When the device is pressed in this way on the pre-welded bottom 14 of a tube contained in a support 20, the seal 53 soon meets the upper surface of this support. The part 52 is therefore pressed against it and thus closes the chamber 16 in a sealed manner.

When the head 90 descends further, thus opposing the resistance of the spring 60, the skirt 70 and the needle 77 slide relative to the cylinder part 52. This has the primary effect of pushing the ball 57 back into the hollow cylinder 55. The chamber 16 and the interior 15 of the tube (cf. FIGS. 5 and 7) are then placed in communication with the vacuum pump 91 and the air is expelled therefrom. The second effect is the driving in of the balls 63 according to the mechanism described above. Consequently, the two jaws press against each other through the bottom 14 of the tube and weld it at the location of the conduit 17 (cf. fig. 6). These two effects can occur with a more or less long beat time depending on the length of the needle 77 relative to the progression of the change in internal section of the skirt 70. When the head rises, it firstly drives the skirt and the needle 77 so that the jaws retract, then the valve 57 closes. Finally, the part 52 lifts up and releases the tube which is now sealed and ready to undergo other finishing operations (for example fitting a pusher, packaging, etc.).

• 1/le bord supérieur 14 du tube, qui admet tout d'abord une forme circulaire, est déformé de sorte que deux lèvres apparaissent et sont rapprochées l'une de l'autre,
• 2/l'air est aspiré par la fente subsistant entre les deux lèvres du bord 14 déformé,
• 3/les deux lèvres sont soudées ensemble.

According to another embodiment of the present method, the presoldering step does not exist. As soon as the tube held upside down in the support 20 is full of dough 13, the tube-support assembly is directly arranged in a station capable of creating a vacuum in the tube and, immediately after, of welding all from its bottom. As before, a ramp system can heat the bottom of the tube during its passage from the filling station to this new final welding station. Then the latter consecutively performs the following operations:

• 1 / the upper edge 14 of the tube, which first of all assumes a circular shape, is deformed so that two lips appear and are brought together,
• 2 / the air is sucked in through the gap remaining between the two lips of the deformed edge 14,
• 3 / the two lips are welded together.

The device allowing the implementation of these three operations at very close time intervals is not shown in the drawings. In fact, it can be designed in many ways. However, in order to convince ourselves of the possibility of developing it, we will describe a possible principle. This is similar to the device 50 illustrated in FIG. 9 and proposed in the context of the first embodiment of the present method developed above. Indeed, it is essentially the lower part 52 of the device 50 that should be adapted. For example, the notch 51 takes a more flared shape while the sealing ring 53 has a larger diameter. Thus it is possible to present the lower part 52 of the device directly above the support 20 so that the cylinder initially formed by the edge 14 of the tube is entirely covered by the notch 51. By engaging in it as the device descends on the support 20, the walls of the notch then contribute to the progressive deformation of the edge 14 of the tube. When the device finally comes into contact with the support 20, the edge 14 has two lips facing each other.

At the same time, a room comparable to the room 16 in Figure 7 is then isolated from the ambient air. It is now possible to create a vacuum there in a similar manner to the first embodiment presented here thanks to the mechanical opening of a valve 57 disposed between the chamber and a vacuum pump 91. For this, the new device may include all the parts provided on the device 50 which are located above the jaws 54. Then, the opening of the valve is obtained by further depressing the head 90 on the support 20.

The new device should also be provided with welding means capable of welding the two lips formed in the edge 14 over their entire length. These means are not necessarily mechanical. Their actuation will then triggered by a signal (electronic for example) emitted after an appropriate period of time since the instant of the opening of the previous valve. In order to operate more reliably, mechanical actuation also conditioned by further depressing the head 90 is preferable. It could also use jaws moved by a cam system. However, these would apply here on the whole of each of the lips of the edge 14.

Claims (16)

1.- Method for packaging a liquid or pasty product in the form of a flexible tube comprising a bottom (14) and a head provided with a dispensing valve (10), characterized in that it comprises at least the following steps: 1) introduction of said product (13) into said tube through its bottom (14), 2) suction by said bottom (14) of the air remaining in said tube above said product (13), then sealing of said tube by welding its bottom (14). 2.- A method of packaging a liquid or pasty product according to claim 1, characterized in that said method further comprises an intermediate step consisting in partially welding the bottom of said tube filled with paste, the aspiration in the last step of said process taking place by the non-welded part of said bottom and being followed by the completion of the welding of the bottom of said tube. 3.- A method of packaging a liquid or pasty product according to claim 2, characterized in that said dispensing valve (10) is a precompression dosing pump. 4. A method of packaging a liquid or pasty product according to any one of claims 2 or 3, characterized in that said dispensing valve (10) is fixed to said tube by crimping or by overmolding on a neck (11) welded to said tube. 5. A method of packaging a liquid or pasty product according to any one of claims 2 to 4, characterized in that the tube is first of all placed upside down on a support (20) forming part of a machine capable of automatically implementing the process. 6. A method of packaging a liquid or pasty product according to claim 5, characterized in that said support (20) comprises means (21) for maintaining said dispensing valve (10) in a position such that it contains as little air as possible. 7.- A method of packaging a liquid or pasty product according to any one of claims 5 or 6, characterized in that the step of introducing said product is carried out using a spout (31) integral with said machine and the lower end of which is moved relative to the tube as the quantity of product introduced increases so that said end remains permanently above the surface of the product. 8. A method of packaging a liquid or pasty product according to any one of claims 5 to 7, characterized in that the partial welding step is carried out, after preheating the bottom (14) of said tube, thanks to jaws (40) having in their center a recess (41) so that they press the bottom of said tube along its entire length except at a small conduit (17) located in the middle of said bottom (14). 9. A method of packaging a liquid or pasty product according to claim 8, characterized in that, during its last step, the air is sucked in through said conduit (17) left in the middle of the bottom (14) partially welded said tube while said conduit (17) is in turn welded. 10.- A method of packaging a liquid or pasty product according to claim 9, characterized in that the welding of said conduit (17) is carried out between 1/10 and 1 second after the start of the aspiration of the air. 11.- A method of packaging a liquid or pasty product, according to any one of claims 9 or 10 characterized in that the conduit (17) is welded by ultrasound. 12.- A method of packaging a liquid or pasty product according to any one of claims 9 or 10, characterized in that the conduit (17) is thermomechanically welded by heating the bottom (14) of said tube before the implementation of the last step. 13.- Device for the automatic implementation of the last step of the method according to any one of claims 5 to 12, characterized in that it comprises two groups of parts which can undergo a vertical translation one relative to the 'other when a vertical force is exerted against elastic means (60) placed between them:
- The first group of parts comprising a cylindrical part (52) of vertical axis provided, in the upper part, with a hollow cylinder (55) of the same axis as that of the part (52) and having a throttle (56) acting as a valve seat (57), at the bottom, of a notch (51) symmetrical with respect to a horizontal axis intersecting the axis of said cylindrical piece (52) and serving to guide the bottom (14) of a tube and, approximately halfway between the upper and lower parts, of two horizontal cylindrical reserves (64) symmetrical with respect to the axis of said notch (51), traversing right through said cylindrical piece (52) and capable of receiving two jaws (54) projecting into said notch (51), each jaw (54) being tightly connected to said cylindrical piece (52) and able to slide relative to it under the combined effect of a return spring (61) and a ball, (63),
the second group of parts comprising a skirt (70), the internal surface of which adapts to the external vertical surface of said cylindrical part (52) in order, on the one hand, to offer it a limit stop (71) and , on the other hand, allow the progressive engagement using a cam (72) of said balls (63) in said reserves (64) of said cylindrical part (52) and also comprising, rigidly connected to said skirt ( 70), a cylinder (75) provided with a central channel (78) ending in a needle (77) which can engage in a sealed manner in the constriction (56) of said hollow cylinder (55) of said cylindrical part (52) and thus open said valve (57),
this first group of parts being able to collaborate with said support (20) to form with it a sealed chamber (16) from which the air is evacuated, the second group being compatible with a head (90) of said automatic machine transmitting said vertical force and pumping air. 14.- Device according to claim 13, characterized in that the various parts of the two groups are metallic. 15.- Device according to any one of claims 13 or 14, characterized in that said cylindrical part (52) of the first group of parts comprises on its underside a seal (53) held by a ring (65) screwed. 16.- Device according to any one of claims 13 to 15, characterized in that said valve (57) is provided by a ball held by a spring (58) which is placed in said hollow cylinder (55) and rests on a hollow nut (59) screwed to the top of said notch (51).

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