FR2702738A1 - Method and machine for the manufacture of plastic pouches intended to serve as flexible fluid-tight packages for pasty products - Google Patents

Abstract

Method and machine for the manufacture of plastic pouches intended to serve as flexible fluid-tight packages for pasty products, comprising a preformed head of generally cylindrical shape moulded from a rigid hot-weldable plastic material on which is added a piece of a tubular cover whose two edges have been welded to each other forming a protruding rib. The means of feeding, giving a round shape to and placing the piece of cover on the head consist of fixed (45) and moving (46) vacuum sleeves whose wall, which is perforated with holes, communicates with an annular vacuum chamber in order to be able to draw in and retain at will the film constituting the wall of the tubular cover the diameter or shape of the external perimeter of which corresponds substantially to the diameter or shape of the internal perimeter of the said sleeve (45) or (46), according to the phases of a feeding automaton actuating a moving carriage (33) with which the said sleeves are rendered integral.

Description

 The present invention relates to a method for manufacturing plastic bags intended to serve as leaktight packaging for products in pairs, such as cosmetics which can be oxidized in air, toothpastes or the like, of the type comprising a preformed head of generally shaped cylindrical molded from a rigid heat-weldable plastic material to which is attached a piece of a tubular sheath obtained from a strip of metal-plastic composite film, the two edges of which have been welded to one another forming a projecting rib external to said sheath; as well as the machine for implementing said process.

 Numerous packaging tubes of the type described above are known, made of various materials. In particular, document FR-A-2 207 794 discloses a process for the manufacture of flexible packaging tubes and describes a machine for the implementation of this process. This tube is obtained from a sheet of flexible metal composite plastic material carrying a finishing coating, a cut piece of which is rolled on itself and mechanically assembled by its lateral edges formed and superimposed so as to present a longitudinal joint which s extends over all the length of the tube produced. In the same way, this tube is assembled mechanically by wedging with a rigid preformed head of suitable shape. Such a packaging tube does not offer total security with regard to the pressures which could be exerted on the pasty product which it must contain and it can open under the effect of excessively high pressure or a malformation of the assembly or mounting folds on the head of the piece of sheet.

 To remedy the above drawbacks, the method of manufacturing plastic bags according to the present invention uses a tubular sheath obtained continuously in a known manner in 501r from a ribbon of composite metal-plastic material, the edges of which are welded to each other in a manner also known per se, a piece of this tubular sheath being itself heat welded on a rigid preformed head molded from a suitable plastic material, the welding process consisting in carrying out first a first assembly welding point between the two parts by simultaneously flattening the rib of the tubular sheath, and following this operation with a hot circular weld.

 The machine for implementing the method according to the invention is characterized by the presence of means for feeding round or shaped and for depositing pieces of tubular sheath on a rigid head, these means being constituted by sleeves with fixed and mobile voids, the latter being driven in an up-down movement by a suitable automaton preceded by a fixed entry die for rounding or shaping and followed by a cutting device to the appropriate length of the sheath tubular.

 The machine according to the invention is further characterized by its welding device for closing flat the bottom of the piece of sheath cut simultaneously with the welding of a point on the head in order to flatten the rib and fix the piece tubular sheath at this level on the rigid head.

 The machine according to 1 invention is finally characterized by its circular hot welding device of the piece of tubular sheath on the rigid head by means of a heated rotary wheel of appropriate shape and position, the welding pressure being adjustable at will.

Other advantages and particular characteristics of the method and of the machine according to the invention will appear during the detailed description which follows of a preferred embodiment provided by way of nonlimiting example and illustrated by the appended drawings in which
- Figure 1 shows a finished pocket seen in section.

 - Figure 2 shows the pocket of Figure 1 in side view.

 - Figure 3a shows a schematic view of the coiled tubular sheath.

 - Figure 3b shows a section of the coiled tubular sheath.

 - Figure 4 shows a schematic overview of the machine.

 - Figure 5 shows a schematic overview of the machine.

 - Figure 6 shows an elevational view in partial section of a plate with its carrying fingers.

 - Figure 7 shows a detail of the blocking support of the carrier fingers.

 - Figure 8 shows an elevational view of the device for feeding, removing and cutting the tubular sheath.

 FIG. 9 represents a plan view of the device of FIG. 8.

 - Figure 10 shows the device for cutting the tubular sheaths seen in elevation, closed jaws.

 - Figure 11 shows the device of Figure 10 seen in plan, jaws open.

 - Figure 12a shows a longitudinal sectional view of the suction sleeves.

 - Figure 12b shows a cross-sectional view of the suction sleeves of Figure 12a.

 - Figure 13 shows an elevational view in partial section of the flat soldering device of the bottoms and the hammer weld.

 - Figure 14 shows a plan view of the welding heads.

 - Figure 15 shows an elevational view of the rotary welding device.

 FIG. 16 represents a front view of the device of FIG. 15.

 - Figure 17 shows a detail of the assembly of the pressure adjustment device of the welding wheel.

 If we refer to Figures 1 and 2, we see in these figures a pocket consisting of two parts, namely a head 1 on which is attached the piece of sheath 2 forming the pocket itself.

 The head 1 is a rigid part preferably produced by injection molding in a suitable plastic material such as for example a polyolefin. It comprises a base 4 of generally circular cylindrical shape but may also have an oval shape, having the general shape of a plug surmounted by elongated arms 4 'facilitating the establishment of the sheath 2, as will be seen later .

 The sheath 2 is a piece of a tubular sheath obtained from a ribbon of pliable metal-plastic composite material carrying a finishing coating at least on its external face. This strip is folded back on itself and welded along a longitudinal joint where the opposite lateral edges are superimposed and assembled by an external weld in a well known manner, thus forming a projecting rib 3 on one side of the tube. As shown in FIG. 3a representing the coiled tubular sheath and FIG. 3b representing the section of this coiled sheath, the sheath 2 is delivered wound flat, the rib 3 being situated in the middle of the face of the flattened tube situated on the internal side of the coiled tube.

 As shown in FIGS. 1 and 2, when the bag is finished, a determined length of tubular sheath is assembled in a sealed manner on the head 1 forming a base, and the sheath 2 is pinched at its upper part to form a sealed weld 5 closing the pocket flat upwards. This pocket can then be filled via the head 1 before being closed in a conventional manner with the product that it must contain.

 The method of manufacturing such a bag comprises, after placing on the head 1 of the piece of tubular sheath 2 cut to the appropriate length, a two-stage assembly operation of this tubular sheath 2 on the head 1 followed by a closing operation by hot welding of the top of the tubular sheath 2.

 Due to the existence of an excess thickness of material formed by the rib 3 of the tubular sheath 2, it is essential to carry out a heat weld in two stages to obtain a sealed assembly between the head 1 and the piece of sheath tubular 2.

 A first heat welding operation makes it possible to flatten the rib 3 and punctually weld this rib against the wall of the tubular sheath 2 itself, as well as the interior of this sheath 2 against the external wall of the base 4 of the head 1.

 A second heat sealing operation carried out using the thumbwheel will then allow the sealed assembly of the tubular sheath 2 to be completed on the base 4 of the head 1.

 Finally the top of the sheath 2 is closed by a flat heat seal 5, this operation being carried out in a preferred form of the present invention simultaneously with the first point assembly operation of the sheath 2 on the head 1, but it is obvious that it can be carried out during another phase of the bag manufacturing process.

 The machine making it possible to carry out the automatic continuous mounting of the flexible sheath 2 on a rigid head 1 of plastic material is shown diagrammatically, in FIG. 4 in elevation and in FIG. 5 in plan. We see in Figure 4 that this machine has a frame 6, preferably made of mechanic welding on which is mounted a turntable 7 which supports on its periphery six plates 8 arranged at 60C from each other, on each of which are mounted four fingers carriers 9 which support the rigid heads of the bags to be assembled, it being understood that the number of carrier fingers 9 per plate 8 can vary according to the rates desired for the production of the bags. The plate 7 is rotated by an indexing automaton 7 'with six positions, schematically represented in broken lines in FIG. 5, of a well known conventional type which will not be described in more detail here.

A workstation 10 (A, B, C, D, E or F) corresponds to each of the six stop positions of the plate 7 and facing the carrying fingers 9 present after each rotation of 1/6 "of rotation of said plate ) mounted on a chassis secured to a frame 6 of the machine as shown in FIG. 4. Each of these six work stations A, B, C, D, E and F corresponds to a phase in the manufacturing cycle of the pockets, namely
- Station A is the machine loading station which here described by way of example is manual, but which could be very easily automated in a manner known per se by means of a parts distributor and a loading automat . Such a system well known to those skilled in the art could be added without difficulty to the machine described here without it being necessary to describe the detail here.

 - Station B is the rounding station, depositing the sheath 2 on the head 1 and cutting the length thereof.

 - at station C, the closing closure of the bottom of the piece of tubular sheath 2 is carried out as well as a spot of welding of this same sheath on the head I at the level of the rib 3.

 - at station D, the rotary welding of the tubular sheath piece 2 is carried out on the head 1.

 - Station E is free on the machine described here but could be used to set up a control device which will not be described here, as well known to those skilled in the art.

 - finally, station F is equipped with a manipulator provided with four or n grippers to lift the finished bags and deposit them, for example, in a carton according to a device well known to those skilled in the art which will not be described either in more detail here.

 As can be seen in Figure 6, the carrying fingers 9 of the pockets are mounted vertically and rotating on their respective plates 8. As shown in FIG. 15, these carrier fingers 9 are in fact made integral by means of a retaining nut 11, of a shaft 12 mounted to rotate thanks to the bearings 13a and 13b retained in the fixed sleeve 14 secured to the plate 8. At their upper ends, the carrying fingers 9 terminate in an end piece 15 of suitable shape for receiving the base 4 of the rigid head 1 of a pocket. A pinion 16 is fixed respectively to each lower end of each shaft 12 which drives the carrier finger 9 and is made integral with it. The elongated lower end of any one of the four or n shafts 12 mounted on the same plate 8 is further provided with a bevel wheel 17 also integral in rotation with the shaft 12 on which it is mounted. The pinions 16 or, as the case may be, all the pinions 16 and the bevel gear 17 are locked on the respective ends of the shafts 12 on which they are mounted by means of a stop washer 18 and a screw 19.

 Between the four or n shafts 12 integral with the four or n carrying fingers 9 of the same plate 8 and their associated pinions 16 are disposed each time, between two successive pinions 16, three or nl pinions 20 meshing with the two neighboring pinions 16, the axes of these pinions 20 being preferably aligned with the axes of the shafts 12, therefore of the corresponding carrying fingers 9. As shown in FIG. 7, these pinions 20 are mounted rotating on bearings 21 fitted on the axes 22 where they are retained by washers 23 and screws 24, the axes 22 being themselves made integral with the corresponding plate 8 by virtue of to nuts 25.

 It is thus obvious that by rotating the bevel wheel 17 of a plate 8, all of the four or n carrying fingers 9 of this plate 8 are driven simultaneously in the same direction and at the same speed. said bevel wheel 17 is blocked in a determined position all four or n carrying fingers 9 are locked in the same relative position relative to said plate 8. However, as shown in FIG. 7, each plate 8 bears precisely on its lower face , therefore on the side of the bevel wheel 17, a locking device in position constituted by a locking finger 26 which can be engaged between two teeth of the bevel wheel 17. This locking finger 26 is carried by a bolt 27 mounted in free tilt on a support 238 secured to the plate 8. An axis 239 allows the lock 27 to oscillate freely around it, the masses of the part 29 located on either side of this axis 239 being such that the lock 27 tends to normal nt to tilt clockwise and thereby normally engage the locking finger 26 between two teeth of the bevel wheel 17, thereby locking the latter in a determined position and thereby blocking all the fingers carriers 9 of each of the plates 8 in a determined position. We will see below how and under what circumstances the bevel wheel 17 can be released and be made to rotate and thus rotate the carrier fingers 9.

 After loading the pocket heads 1 on the carrying fingers 9 of a plate 8 and rotating 1 / 6th of a turn of the plate 7 thanks to the automatic control mechanism, the plate 8 is presented at station B where s' performs the sheath 2 and its length cutting on a mechanism shown in elevation in Figure 8. This mechanism is mounted on a suitable frame 28 secured to the frame 6 of the machine. This mechanism naturally comprises four or n similar devices arranged in parallel, each corresponding respectively to a carrier finger 9. From a roller 29 of tubular sheath wound according to FIG. 3a, that is to say with the flat weld located on the inner side on this roller 29, the tubular sheath 2 passes over a conventional unwinder shown diagrammatically at 29 ′ before engaging between the jaws of the traction jaw 31. This jaw 31, actuated by a jack 32 adjusted so as to cause the closure of the jaw 31 on the axis of the flat sheath, which also corresponds to the vertical axis of the corresponding carrier finger 9, is carried by a movable carriage vertically shown in Figure 8 at 33.

 The movable carriage 33 which carries the jaws 31 as well as the movable sleeves 45 which will be discussed later, is actuated by a motorized system with toothed belts of low ascent well known to those skilled in the art, simply shown diagrammatically in the figures. 8 and 9 and not described in more detail here. It allows this set to make an appropriate race as we will see later.

 Then the plastic sheath tape passes through a fixed inlet die 34 carried by a plate 35 secured to the frame 28. As can be seen in FIG. 9, this plate 35 naturally carries a bar 34 in which the four are machined or n input channels corresponding to the four or n devices located in parallel. As shown in FIG. 8, this generally cylindrical, circular or oval shape inlet channel, depending on the shape of the pocket to be produced, has inside, in the case of a circular cylindrical pocket, a conical passage the inlet diameter 341 is substantially equal to the width of the film 2 of the flat sheath and the outlet diameter 342 is substantially equal to the outside diameter of said sheath 2 put in the round.

 The plate 35 also carries, by means of an appropriate bearing 37, an adjustment flywheel 36 whose axis 38 engages by its threaded lower part in a nut 39 secured to a support plate 40, which, thanks to four guide columns 41 passing through four applied bearings 42 fixed on the fixed face 35, supports by means of a plate 43 carried by appropriate columns, the four or n fixed sleeves 45 carried by a bar 44 whose position in height is thus made adjustable.

 Under the bar 44 carrying the fixed sleeves 45 are arranged movable sleeves 46 carried by the bar 47 in the same way as the fixed sleeves are carried by the bar 44 secured to the carriage 35 shown diagrammatically in FIG. 8 in the high position and in the low position , the low position causing the movable sleeves 46 to be seated on the corresponding carrying fingers 9 so that their base surface coincides with the base surface of the respective supporting end pieces 15.

 The fixed sleeves 45 and the movable sleeves 46 are shown in detail in Figures 12a in longitudinal section and 12b in cross section. They are preferably made of a plastic material having a certain flexibility, such as high density polyethylene and have a generally cylindrical circular or oval shape as the case may be, their internal wall 451 having a diameter substantially equal to the outside diameter of the sheath 2 placed in the round and the external wall having three stepped zones 452, 453 and 454 corresponding respectively to three corresponding zones 442, 443 and 444 of equivalent axial length of the four or n bores of the bars 44 or 47 intended to receive said sleeves.

 As can be seen in FIG. 12a, the diameters of the zones 442 and 444 correspond respectively to the diameter of the zones 452 and 454 of the sleeve 45 or 46 which thus comes to forcibly fit into its corresponding bore of the bar 44 or 47. By against the diameter of the intermediate part 443 of this bore is greater than the external diameter 453 of the sleeve in the same zone so that an annular chamber 455 remains in this zone.

A number of lateral holes 456 formed in the intermediate zone 453 of the sleeve 45 over the entire periphery and in several rows bring the internal wall 451 into communication with this annular chamber 455. On the other hand, a bore 441 allows the installation of 'a tube connected to a suction device, not shown, making it possible to create a vacuum in the annular chamber 455. Finally a longitudinal rib 457 existing on the internal wall 451 of the sleeve makes it possible to accommodate the excess thickness due to the rib 3 tubular sheath 2 as will be seen later.

 Below the support plate 40 adjustable in height and also integral with the latter is arranged a mechanism for cutting the tubular sheaths shown in FIGS. 10 and 11, a mechanism which is therefore adjustable in height simultaneously and in the same quantity as the fixed sleeves 45. Two half jaws 48 and 49 each consisting of two parts assembled by screws forming between them a suitable slot 51 and 52, are mounted by means of two support bars 53 and 54 on two double jacks, 55a and 55b and 56a and 56b respectively, themselves suitably secured to the support plate 40 which also suitably carries two guide pins 57 and 58 of the support bars 53 and 54. A band cylinder 59 carrying a cutting blade 60 is integral with the half jaw 49 and its movement.

 We can now describe the operation of this set of feeding, removal and cutting of the plastic film. At the start of a cycle, the plastic tubular sheath tape unwound from the roller 29 with its rib 3, arranged as indicated above on the inner side, passes through the open jaw 31 then the die 34, where it opens by taking a rounded shape, then by the fixed sleeve 45 which retains it by vacuum, the rib 3 being disposed in the groove 457 provided for this purpose, then by the movable sleeve 46, not connected to the vacuum pump and in the high position, to finally hang between the cutting jaws 48 and 49 to the level of the plane of the cutting blade 60 as shown in dashed lines in FIG. 8. The automaton then actuates the movable carriage 33 to lower the jack 32 with its jaws 31 open and the movable sleeve 46 carried by the bar 47 to the low level of the tubular sheath 2, that is to say until the plane of the underside of the movable sleeve 46 is coincident with the plane of the cutting blade 60. At this i Now the jaw 31 is clamped by the jack 32 and clamps the tube 2 flat at its upper part, while the movable sleeve 46 is connected to the vacuum pump to retain the tubular sheath 2 already rounded by its passage through the die 34 and thus fully rounded at its lower part, its rib 3 being housed in the groove 457 of the sleeve and that the fixed sleeve 45 releases on its side the tubular sheath 2, its connection with the vacuum pump then being cut . The movable carriage 33 then continues its race to the low position to stop when the end of the tubular sheath 2 exactly covers the corresponding head I of the pocket to be produced, carried by the end piece 15 of the carrier finger 9 while the jaws 31 clamped on the tubular sheath 2 at the upper part ensures the unwinding of this from the roller. At this instant the movable sleeve 46 releases the tube, its connection with the vacuum pump being cut, the traction jaws 31 open again and the fixed sleeve 45 now connected to the vacuum pump then again retains of the tubular sheath 2. The mobile carriage 33 can then return to its starting position, which allows the above-described cutting device to come into action, which results in the clamping of the jaws 48 and 49 followed by 'A round trip of the cutting blade 60 actuated by the band cylinder 59, which ensures the simultaneous cutting of the four or n tubular sheaths relating to the same plate 8, then the reopening of the jaws 48 and 49. This device is visible in elevation with the jaws closed in Figure 10 and in plan with the jaws open in Figure 11. The assembly B is then ready for the next cycle.

 All this assembly is naturally controlled by an electronic automaton well known to those skilled in the art and which will not be described in more detail here. Furthermore, the adjustment flywheel 36 acting on the position of the cutting device and of the fixed sleeve 45 makes it possible to adjust the length of the cut piece of tubular sheath 2, therefore ultimately the size of the pocket to be produced.

 After rotation of the turntable 7 by a new 1 / 6th of a turn, the four or n pockets to be produced simultaneously are then presented under the device C for welding the bottoms and a point on the head, the pieces of tubular sheath 2 being fitted onto their respective heads I arranged on the end pieces 15 of the carrying fingers 9.

 The device C is mounted on a chassis 100 integral with the frame 6 of the machine on which is fixed a plate 101 which carries two bearing bearings 102 serving to guide two shafts 103 carrying a plate 104 which supports the welding assembly funds, as shown in Figure 13.

 In the middle of the plate 101 a smooth bearing 105 allows the axis 106 of a flywheel 107 to which it is integral and which engages by its threaded lower part in a nut 108 itself integral with the plate 104. In this way l assembly of this plate 104 and the welding devices of the bottoms which it supports is adjustable in height in order to allow the height position of the welding devices of the bottoms to be adjusted to the chosen length of the pieces of tubular sheath 2 during the section in device B above. For each of the four or n pockets assembled simultaneously on the same plate 8 of the machine, the bottom welding device consists of two hot welding heads 109a and 109b made of a material which is a good conductor of heat such as for example brass, suitably electrically heated by electric heating cartridges and temperature controlled in a conventional manner using thermocouples.

 As shown in Figure 13 in section and Figure 14 in top view, the welding head 109a is fixed using screws and by inserting an insulating piece 110 on a head holder 111 itself mounted slightly movable on an intermediate support plate 112 by means of a stud 113, so as to allow a slight axial movement between the two parts. In a system with four support fingers for a plate 8, there are two support plates 112 each of which carries respectively two heads 109 on their respective head carriers 111 as described above, and each of these plates 112 is at its tower mounted in the same way, by means of a stud 113, on a base head holder 114, which gives it a certain mobility with respect to this part, the head holder 14 itself mounted, always according to the same principle, by means of a stud 113 on the end plate 115 of the guide unit associated with a jack 116.

 The movable mounting of the welding heads 109a allows each of them to be oriented independently of the others with respect to the welding head 109b which faces it respectively. The welding heads 109b, similar to the welding heads 109a and heated in the same way, are all made rigidly integral with a guide assembly and an associated jack 117 slightly less powerful than the jack 116, the latter ensuring the position axial of the end of the welding head 109a when its piston is in its extreme advanced position and the head 109b which faces it abuts against the face 109a to obtain the necessary welding pressure which is then imparted by the actuator 117 adjusted in position so that its movable piston does not reach the end of its travel when the heads 109b abut against the heads 109a. The welding of the bottoms is thus quite simply hot by pinching the upper ends of the four or n pieces of respective tubular sheath 2 fitted on their corresponding heads I mounted on the support fingers 9 between the respective jaws 109a and 109b of the welding heads. , after actuation of cylinders 116 and 117.

 A welding point is also produced at the same station C between the piece of tubular sheath 2 at its rib 3 and the head 1 on which it is fitted. This operation is preferably done simultaneously with the welding of the funds described above, but it can also be slightly offset in time with respect to this welding of the fades, in which case it will preferably be done after the welding of the funds, because it ensures the holding of the piece of tubular sheath 2 on its head 1 during the welding of the bottom. As can be seen in Figures 13 and 14 this welding point is achieved by means of a welding head called hammer 118, made of a metal that is a good conductor of heat such as brass, and fixed by two screws to the door -head 119 similarly made of a metal good conductor of heat and equipped with suitable heating cartridges and a thermocouple to bring it to the temperature required for the welding operation. The front part of the hammer head 118 is provided with a nose 118a of suitable length, the front part of which ends in a concave arc of a circle having a diameter substantially equal to the outside diameter of the pocket to be produced.

 The head holder 119 with its head 118 is mounted by means of an insulator 120 on a head support 121 which carries two axes 124 sliding in two ball bearing bearings 123 secured to the plate 125. Two springs 122 mounted on the axes 124 between the plates 125 and the support 121 provides the required welding pressure when the nose 118a of the hammer 118 is in abutment against the piece of tubular sheath 2 fitted on its head 1 mounted on the corresponding support finger 9.

 The plate 115 supporting together four or n hammer welding heads is mounted on a guide unit provided with a pneumatic cylinder 126, itself rigidly fixed on the frame 6, 100 so that the height position of the four or n hammers correspond exactly to the level of the four or n nozzles 15 supports of the head pockets 1 carried by the respective fingers 9.

 As is clearly visible in FIG. 13, the piece of tubular sheath engaged on its head I is arranged so that its closing rib 3 is on the left side, so that the nose 118a of the hammer comes to flatten said rib 3 and sufficiently heats this limited area to flatten and assemble all of the film thicknesses present at this location and simultaneously ensure the welding of said tubular sheath 2 on the head 1 at this point.

 After the welding of the bottoms and the assembly points on the heads described above, the assembly of the welding heads is withdrawn and the turntable 7 can perform a new 1 / 6th of a turn. The four or n pockets being finished are then presented under the device B where the rotational welding of the sheath pieces 2 is carried out on their respective heads 1.

 This assembly is mounted on a chassis 200 integral with the frame 6 of the machine, on which is fixed by bolts a plate 201 carrying two shafts 203 each held by two flanges 202 on this plate 201. A mobile plate 206 carried by twice two ball bearings 205 sliding on the two shafts 203 can be moved by a pneumatic cylinder 204. On the movable plate 206 is welded a vertical support 207 which carries the four or n sets of drive rollers 208 and welding model 209.

 The movable plate 206 carries on its underside two positioning rollers 228 mounted with the interposition of suitable bearings on axes 229 located in the axis of the two extreme weld wheels of a set of four or n weld wheels 209 carried by the movable plate 206, being evident that each axis of the welding wheel 209 is situated in the same vertical plane as the axis of the corresponding support finger 9, plane which is parallel to the axis of the complete machine and perpendicular to the plane containing the four or n axes of the support fingers 9 of the same plate 8.

 The drive roller 208 mounted on the axis 214 is retained by means of suitable bearings in the stirrup 210, itself mounted on two support axes 211 which can slide freely in two bearing bearings 213 secured to the support 207, two compression springs 212 tending to separate the stirrup 210 from the latter.

 Furthermore, the axis 214 drives, by means of a coupling 215 of the double gimbal type allowing a slight offset of the two axes integral in rotation, the welding wheel 209, the axis of which can rotate freely in a sheath 216 itself. - even fitted into a thermally insulating part 217 secured to a table 218 mounted in the same way as the stirrup 210 on two support axes 219 which can slide freely in two bearing bearings 220. As can be seen in FIGS. 15 and 17, the axis 223 of a micrometer 222 secured to a support 221 itself secured to the support axes 211 of the stirrup 210 pushes the table 218 through a compression spring 224 housed in an appropriate guide 224 ′ secured to the table 218. The pressure exerted by the welding wheel is thus adjustable by this micrometer 222 relative to the pressure exerted by the drive roller 208 on the support finger 9.

 The table 218 also carries at its upper part a finger 225 which engages in an oblong hole 227 at the upper part of a heating block 226 made of a material which is a good conductor of heat such as the solder wheel 209 and equipped with heating elements and a thermocouple suitable for imparting to the assembly formed by said block 226 and its associated welding wheel 209 the temperature required for carrying out the welding by rotation. As can be seen in FIG. 15, the thumbwheel 209 is fitted into the base of the heating block 226 on which it can rotate while being in close thermal relation with it, the finger 225 preventing said heating block 226 from being driven in rotation by the wheel.

 Referring to FIGS. 6, 7 and 15, it can also be seen that the chassis 200 supporting the device C appropriately carries a motor 231 with incorporated encoder mounted on a support 232 itself tilted on a horizontal axis 233 integral of the fixed chassis 200. This axis 233 is disposed at one end of the support 232, the other end of which rests on a vertical pusher finger 237 which can be actuated by a jack 235 itself secured to the chassis 200. Finally, the axis of the motor 231 carries a bevel gear 234 capable of meshing with the bevel wheel 17 which as previously described drives all of the support fingers 9 in rotation. When the jack 235 pushes back the plate 232 to engage the pinion 234 with the wheel 237, a linkage 236 secured to the support 232 simultaneously pushes the lock 27 which then switches on its axis 239 and thus allows the locking fingers 26 to release the bevel wheel 17.

 The rotational weld assembly D then operates as follows: when the four or n support fingers 9 each equipped with the head 1 and the piece of tubular sheath 2 partially assembled as described above are presented in front of the assembly D after rotation of the turntable 7 by 1 / 6th of a turn, the jack 204 pushes the movable plate 206 until the positioning rollers 228 abut against the base of the two extreme support fingers 9 mounted on the plate 8. In this position the four or n drive rollers bear on a zone 230, preferably knurled, of the four or n support fingers 9 of the same plate 8, against which they bear thanks to the thrust spring 212. Simultaneously the jack 235 pushes the plate 232 of so as to engage the bevel gear 234 on the corresponding wheel 17 which is released from its locking finger 26 as just described above.

 The encoder incorporated in the motor 231 then causes all four or n carrying fingers 9 to perform one complete revolution. As a result, the drive rollers 208, which bear on the knurled zones 230 of said fingers 9 and which may optionally be fitted with an O-ring or any other suitable coating in order to improve their adhesion to said fingers, are also caused to rotate by friction and to rotate the corresponding welding wheels 209 which are connected to them by means of the couplings 215.

These welding knobs 209 bear on the base of the support end pieces 15 disposed at the end of the carrying fingers 9 and each equipped with the head I and the piece of tubular sheath 2 partially assembled as described above. The soldering temperature is adjusted by the heating device incorporated in the heating block 226 while the soldering pressure can be adjusted independently by means of the micrometer 222. It is thus seen how is carried out, in a complete rotation of the four or n bearing fingers 9, the complete weld between each of the pieces of tubular sheath 2 and the associated head 1 to complete the production of the four or n pockets to be produced.

 At the end of this operation, the turntable can redo 1 / 6th of a turn in order to bring the four or n pockets thus completed in front of the free station D on the machine thus described, but which can possibly be equipped with a device for control of finished parts. At the end of this control operation, the plate turns again by 1/6 of a turn to bring the finished and controlled bags to station F where they are released either manually or by means of an automatic device well known from skilled in the art and which will not be described in detail here.

 The control of all the operations and the operating cycle of the machine thus described is ensured by an electronic automaton, in a manner known per se and which will not be described in detail here.

 It is also obvious that the machine thus described can be the subject of numerous variants without departing from the scope of the present invention. Thus, for example, it is possible to produce the welding knobs 209 with their heating block 226 in one piece, it being understood that the current feeds must then be produced by sliding contacts.

 Furthermore, the production of pockets mounted on heads having a circular cylindrical shape has above all been described, but it is quite obvious, as has already been mentioned, that it is possible to mount pockets on heads having a shape generally oval, the carrying fingers 9 must then have a similar shape to allow the positioning rollers 228, the drive rollers 208 and the welding wheel 209 to follow this shape during the rotation of the fingers.

Claims (15)

I) Method for manufacturing plastic bags intended to serve as flexible leaktight packaging for pasty products, of the type comprising a preformed head (1) of generally cylindrical shape molded from a rigid heat-weldable plastic material to which is attached a piece of a tubular sheath (2) obtained from a ribbon of composite film of metal-plastic material, the two edges of which have been welded to each other by forming a protruding rib (3) external to the sheath (2) , characterized in that after putting the sheath (2) around, the flexible sheath (2) is assembled on the rigid head 1 by a first spot hot welding of the two parts at the rib ( 3) tubular sheath, followed by a circular hot weld between the two parts. 2) Method according to claim 1 above characterized in that the manufacturing of the pockets is carried out according to the following sequence of operations, by means of a suitable automaton annexed to a turntable (7)  - positioning of the tubular sheath (2) on the head (1) and length cut of the tubular sheath (2)  - simultaneous hot welding of the bottom to close it flat and of a point on the head at the rib (3) of the tubular sheath (2)  - hot rotary welding of the piece of tubular sheath (2) on the head (I). 3) Machine for implementing the method according to claims I and 2, characterized in that it comprises means for feeding, rounding and depositing a piece of sheath (2) on the head (1) carried by the end piece (15) of a carrier finger (9). 4) Machine according to claim 3 characterized in that the means for feeding, rounding and depositing the piece of sheath (2) on the head (1) are constituted by fixed vacuum sleeves (45) and movable (46) whose wall perforated with holes (456) is in communication with an annular vacuum chamber (455) so as to be able to suck up and retain at will the film constituting the wall of the tubular sheath (2) whose diameter or shape of the outer perimeter corresponds substantially to the diameter or shape of the inner perimeter of said sleeve (45) or (46), depending on the phases of a feeder machine actuating a mobile carriage (33) of which said sleeves are made integral. 5) Machine according to claim 3 or claim 4 characterized in that a fixed preliminary means for rounding the flat tubular sheath (2) is constituted by a die (34) whose inner cone, through which said tubular sheath (2) at the outlet of the roller (29), has an inlet diameter (341) substantially equal to the flat width of the tubular sheath (2) on its roller and the outlet diameter (342) has a diameter substantially equal to the outside diameter of the tubular sheath (2) after its shaping, or an oval inner shape similar to the oval outer shape of said tubular sheath (2) after its shaping. 6) Machine according to any one of claims 3 to 5 characterized in that the cutting device (59, 60) of the tubular sheaths (2) makes it possible to cut to length simultaneously all the tubular sheaths (2) of the n production lines pockets produced simultaneously after being clamped in a vice (48, 49). 7) Machine according to any one of claims 3 to 6 characterized in that the flat closing weld of the bottoms (5) and a weld point on the head (1) at the rib (3) of the sheath tubular (2) are produced simultaneously by means of heat sealing heads (109) and hammers (118) respectively heated and temperature controlled in an appropriate manner. 8) Machine according to any one of claims 3 to 6 characterized in that the flat closing weld of the bottoms (5) and a weld point on the head (1) at the rib (3) of the sheath (2) are produced with a slight time difference thanks to hot welding heads (109) and hammers (118) respectively heated and appropriately regulated in temperature, the operating cycle of which is controlled by the automaton control. 9) Machine according to claim 7 or claim 8 characterized in that the heat seal half-heads of the bottoms (109a) of the n pockets to be assembled simultaneously are mounted on one side on supports (111, 112, 114) articulated with one another by studs (113) so as to ensure their alignment with the fixed half-heads (109b) which face them respectively. 10) Machine according to any one of claims 3 to 8 characterized in that the peripheral welding of the pieces of tubular sheath (2) on the head (1) is provided by a heating and rotating wheel (209). 11) Machine according to claim 9 characterized in that the heating and rotating wheel (209) is driven by a roller (208) itself driven in friction by the corresponding carrier finger (9). 12) Machine according to claim 10 characterized in that means are provided for adjusting the welding pressure of the welding wheel (209) independently of the friction friction pressure of the roller (208) on the carrier finger (9) . 13) Machine according to claim 12 characterized in that the means for adjusting the welding pressure of the welding wheel (209) consist of a micrometer (222) acting on a compression spring (224). 14) Machine according to claim 9 characterized in that the soldering wheel (208) is heated by an independent heating block 1226) on which it can rotate while remaining in close thermal relationship with it. 15) Machine according to claim 10 characterized in that the connection between the axes of the welding wheel (209) and the drive roller (208) is formed by a coupling (215) of the double cardan type allowing a certain offset between said two respective axes kept parallel to each other.