FR2570324A1 - Processing of a plastic with a view to its extrusion, especially in the form of a calibrated bead intended to act as seal and insert in multi-glazed articles - Google Patents

Abstract

The invention relates to the dispensing of a plastic of the butyl rubber type, and more especially to its processing and to its transfer from a storage container, where it is hard, viscous and at a relatively low temperature, to an extrusion nozzle, where it has to possess a viscosity and a hardness which are very much less than those which it had initially. The invention provides for processing in several stages, combining heating and application of pressure so as to supply a nozzle, which is possibly movable, at the desired rate and with the required quality of plastic. The invention applies to the production of a bead serving as seal and insert in multi-glazed articles.

Description

PREPARATION OF A PLASTIC MATERIAL FOR ITS EXTRUSION
ESPECIALLY IN THE FORM OF A CALIBER CORD FOR A
SERVE AS A JOINT AND INTERLAYER IN
MULTIPLE WINDOWS
The present invention relates to the distribution of a plastic material of the butyl rubber type, in particular with a view to the extrusion of the bead intended to serve as a seal and interlayer in multiple glazings and it relates more particularly to the preparation. of said plastic material and its routing from a tank where it is hard, viscous and at a relatively low temperature to an extrusion nozzle, possibly movable relative to the tank, THAT it must have a viscosity and a hardness much lower than those that it originally had in the tank, as well as a higher temperature.

 It is known from French patent 2,211,413 to prepare a plastic material of the butyl rubber type for the extrusion of a bead intended to be deposited on a sheet of glass to produce multiple glazing, to work from quantities reduced in material, easily and quickly reheatable, to obtain the viscosity and hardness characteristics satisfactory on the one hand for the extrusion of the bead, on the other hand for the bonding of the bead thus extruded on a glass sheet. In addition, according to this prior patent, the extrusion assembly is fixed and it is the glass sheets which move in order to receive successively along all their edges the extruded bead.

 This prior technique is satisfactory, however with a view to increasing the production rates on the one hand, with a view to increasing the dimensions of the extruded cords on the other hand, it has been thought to no longer work from reduced quantities of material, which would require too frequent refeeding stops, but from large quantities of material, especially directly from drums of raw material delivered by the supplier.

 These large quantities are more difficult to heat than small quantities which penalizes the flow rates and the rates when in fact we are trying on the contrary to increase said rates and said rates.

 To obtain at the outlet of the extrusion nozzle a material which is suitable, with the desired flow rate, at the suitable temperature, various stages of preparation of the material are therefore to be created, which requires circuits to supply these various stages.

 In addition, it has also been thought to implement a technique of laying the bead on the glass sheets in which the nozzle providing the bead would no longer be fixed, but would move, at least in one direction. Therefore the circuits leading from the raw material to the nozzle necessarily have a relatively large length and cannot be fixed. To convey the material along these circuits, it is, on the one hand, as already said, impossible to reheat it sufficiently in order to lower its viscosity, on the other hand not desirable either to reheat it too much, so as not to not degrade it. It is therefore necessary during the various stages of preparation of the plastic to combine moderate heating and pressurization.

 It is known to transport plastics in possibly sheathed flexible pipes, but our material is, at certain times in its path, at pressures of more than 300 bars and temperatures above 1000C and known pipes are unable to resist both at this temperature and at this pressure.

 The present invention aims to avoid the drawbacks of the prior techniques, namely essentially a fixed nozzle, frequent refueling stops due to the use of reduced amounts of base material.

 It plans to allow the distribution of a plastic material at high flow rate and continuously when necessary, through at least one movable nozzle, said plastic material coming from a reservoir of great importance or it is available with a viscosity and a high hardness, much higher than that which it is necessary that it has at its exit through the nozzle.

 For this, it proposes a process for the preparation of a plastic material of the type based on butyl rubber, from a mass of said material in the raw state, having in particular a high viscosity and hardness, with a view to its extrusion through an outlet nozzle, in particular in the form of a calibrated bead having a viscosity and a hardness lower than that of the raw material, process in which a reduced volume of the mass is heated of material, material is continuously extracted from this volume by subjecting it to a pressure, this material is put under a higher pressure to propel it to the outlet nozzle, this material is continuously admitted into a store with variable volume likely to increase when the quantity of material it receives is greater than the quantity of material it delivers and on the contrary likely to reduce under the opposite conditions, we extract from this variable volume store quantities of material n necessary, at the desired flow rate, within the limit, however, of the volume of material stored in the variable-volume magazine and the continuous flow that feeds said magazine.

It also offers an installation for preparing a plastic material of the butyl rubber type comprising
a reservoir of said material having a wall, in particular cover applied with pressure against the material, this wall or this cover pierced with an outlet orifice, being of a shape such that the section of the volume of material which it encloses is 'as much smaller as it is closer to the outlet orifice, and being provided on its face oriented towards the material with heating appendages which immerse in said material.

 - a pump placed at the outlet of the tank providing a continuous flow of plastic material under high pressure.

a magazine with variable volume consisting of a cylinder and a piston returned inside the cylinder with a constant force less than the force exerted by the material supplying said magazine,
- an outlet nozzle attached to the magazine # with variable volume.

 According to a particular embodiment, the tank cover is of conical shape.

 According to the invention, the variable volume magazine and the outlet nozzle are able to move, said magazine and the pump then being connected by rigid pipes joined by rotary couplings.

 Advantageously, a positive displacement pump is arranged at the outlet of the variable volume store upstream of the outlet nozzle.

The invention will now be described in more detail with reference to the accompanying figures which represent
- Figure 1: a diagram of the entire plastic distribution installation,
- Figure lA: in top view, - Figure 1B: in envy profile view,
FIG. 2: a more detailed view of the reservoir with a cover applied to the material, of conical shape,
- Figure 3: a detail view of a seal of the cover applied to the reserve,
- Figure 4: a detailed top view of an internal gear pump disposed at the outlet of the tank,
FIG. 5: a detailed view of the variable volume magazine placed downstream of the pump according to FIG. 4,
FIG. 6: a section at the level of the rotary connections fitted to the transfer means connecting the pump of FIG. 4 to the store of FIG. 5.

 FIGS. 1A and 1B give an overview of the installation for preparing a plastic material for the supply of a bead intended to serve as a seal and as an interlayer in multiple glazing.

 This cord 1 is intended to be deposited on a glass sheet 2, arranged vertically or substantially vertically against a wall 3, in particular with the insertion of a gas cushion between said wall 3 and the glass sheet 2, and resting on the rollers 4 a vertical conveyor.

 The installation for preparing the plastic material is mounted on a frame comprising a base 5 and a vertical console 6 on which the various elements of the installation rest or are fixed.

 This installation essentially comprises a reservoir 7 of the raw material 8 to be prepared and distributed in the form of the cord 1, equipped with a heated cover 9, of particular shape detailed below, a pump 10 at the outlet of this reservoir 7, a variable volume magazine 11, a positive displacement pump 12, a steerable nozzle 13, means 14 for translating the nozzle 13 and the magazine 11 in a direction different from that of movement of the glass sheets 2, and in this case following a vertical direction, orthogonal to the direction of movement of the glass sheets 2 and parallel to the plane of said glass sheets and of the wall 3, and means 15 for transferring the raw material from the pump 10 to the variable volume store 11 .

 The reservoir 7 has an enlarged base 16 by which it is fixed to the base 5 by means of a bracket 17. This reservoir 7 is generally constituted by the barrel in which the plastic, for example based on butyl rubber, is delivered by the provider.

As more particularly visible in FIG. 2, it is covered with a cover 9 capable of being inserted therein in the manner of a piston under the pressure of two lateral jacks 18 and 19 (also visible in FIG. 1A) acting on it by means of a gantry 20. This cover 9 forming a piston is provided with at least two annular seals 21 and 22 rubbing against the walls of the barrel so as to achieve sealing despite the annular undulations which are generally provided the barrels. These seals 21 and 22 have an outside diameter slightly greater than that of the inside of the barrel; they are solid, solid, hard (Shore hardness of the order of 70), made of a rubber-like material, without seams and as shown in detail in FIG. 3, they are each embedded in a groove 23, 24 of the cover 9 .

 Advantageously, to allow the centering of the cover 9 on the reservoir 7 and its evolution inside said reservoir, both in the direction of insertion and in the opposite direction, each seal 21, 22 has a profile provided with two sides cut 25, 26 at an angle of about 200 with the direction parallel to the side wall of the tank 7 against which they rest, separated by a flat portion 27 whose surface is at least 1/3 of the surface total out of the groove 23, 24 oriented towards the side wall of the reservoir 7.

 This cover 9 forming a piston is of a shape such that it delimits a volume whose section is all the more reduced the closer it is to an outlet 28 which equips it.

 It may have the shape of a conical surface, in particular either a cone or a pyramid depending on whether the reservoir 7 is cylindrical or prismatic, the outlet 28 being disposed at the tip of the cone or of the pyramid.

 Generally, the tanks 7 are cylindrical drums and the cover 9 is then conical in shape and in particular a straight cone with a circular base.

 The surface of this piston cover 9 is equipped with heating means such as electric resistors 29.

 The face directed towards the inside of the tank 7 is further provided with appendages 30 which are also heated.

 These appendages 30 can have variable lengths. Preferably, they are all the longer as they are located closer to the axis of the cone or of the pyramid formed by the cover 9.

 Advantageously, to facilitate the housing of the piston cover 9 in the tank 7, in particular when it reaches the end of the race, these appendages 30 are contained inside the volume delimited by said piston cover 9.

 The outlet 28 through the piston cover 9 of the reservoir 7 directly supplies the pump 10.

 Advantageously, taking into account the high viscosity and hardness of the material based on butyl rubber, even after the extraction of the reservoir 7, taking into account the continuity of flow required, the importance of the flow required, it it is a rotary pump 10 with internal gears.

 Preferably, to avoid the drawbacks due to too high resistance to operation, in particular at the time of starting, this pump 10 is hydraulically driven. This pump is shown diagrammatically in FIG. 1A and shown in more detail in top view in FIG. 4.

 This rotary pump 10 with internal gears has a pump body 31 enclosing a circular toothed crown 32, a rotor 33 also toothed, whose teeth are of shape complementary to the shape of those of the crown 32. This rotor 33 is off-center with respect to to the crown 32 by a decentering core 34. This rotor 33 is pierced in its center with a housing 35 with keying groove 36 to receive a motor shaft and a locking key not shown here, intended to drive the rotor 33 in rotation.

 The teeth 37 of the rotor 33 and those 38 of the crown 32 are spaced from each other in the area 39 which surrounds the decentering core 34, thus creating large spaces 40 between them.

 As we move away from this zone 39, the teeth 37 and 38 are increasingly nested one inside the other, which leads to a progressive restriction of the spaces 40.

 The spaces 40 are practically nonexistent and the teeth 37 and 38 perfectly nested one inside the other in the zone 41 diametrically opposite the decentering core 34.

 Advantageously, as can be seen in FIG. 4, the teeth 37 and 38 have a trapezoidal shape, which increases their mechanical resistance and makes it possible to have larger spaces 40 than with another shape of teeth, in particular triangular.

 Advantageously, to allow better feeding of the spaces 40 by the material extracted from the reservoir 7, the latter is brought opposite said spaces 40, in the region 39 where they are the largest, both from above and from below by a double pipe not shown in the figures, resulting from the division of a pipe 42 connected to the outlet 28 through the cover 9. A pipe 43 for pump outlet, visible only in Figure 1A is provided substantially vertically -from zone 41 or spaces 40 are the most reduced. This pipe 43 passes through the pump body 31 in a direction substantially perpendicular to the plane of the crown 32 and of the rotor 33. Advantageously, the mouths of the supply pipes and of the discharge pipe 43 cover several spaces 40.

 As can be seen in FIGS. 1A and 1B, the material from the pump 10 is transmitted to the elements of the installation located downstream, by the transfer means 15 made up of a plurality of rigid pipes 44, 45, 46 resistant to pressure and heat, connected to each other and to the upstream and downstream devices by rotary couplings 47, 48, 49, 50, an example of which is shown in section in FIG. 6.

 Such a rotary coupling, for example 49, comprises a male element 51 fitted into a female element 52, each of these two elements 51 and 52 being connected by welding to the upstream 45 and downstream 46 pipes.

 The seal between these two elements 51 and 52 is obtained using annular seals 53 and 54 and the rotation of the male part 51 in the female part 52 is facilitated using series of balls 55 and 56 rolling in toric grooves 57 and 58 partly bored in the male element 51 partly in the female element 52.

 Advantageously, to facilitate the rolling of the balls 55 and 56 on the one hand and their exchange when they are worn on the other hand, these balls are mounted resiliently, inside cavities 59, 60, on bearings 61, 62 removable from the outside of the female element 52.

 Such connections with a single axis of rotation are preferable, with regard to the high pressure tightness, to rotary ball-and-socket systems with multiple axes of rotation.

 Movements in all directions of space are made possible by the juxtaposition of a plurality of such fittings with a single degree of freedom, these fittings being joined by rigid bent pipes.

 The transfer means 15 described above are advantageously heated. They are intended to connect the outlet pipe 43 of the pump 10, capable of changing in height since it is clear of the piston cover 9 which sinks into the reservoir 7, to the variable-volume store 11 secured to the nozzle 13, also susceptible to translational movements in a vertical direction in order to be able to deposit a bead 1 over the entire height of glass sheets 2. To avoid blocking of the pipes 45 and 46 in the aligned position when the piston cover 9 is in the extreme high position and the nozzle 13 in the extreme low position or vice versa, said pipes 45 and 46 have a length such that there always remains an angle between them less than 1800.

 The plastic material conveyed by the transfer means 15 is introduced continuously at a regular rate inside the variable volume magazine 11. This magazine 11 is visible in top view in FIG. 1A, in side view in FIG. 1B and in a more detailed view in FIG. 5. It comprises a cylinder 63 provided with an inlet opening 64 and an outlet 65 supplying the positive displacement pump 12. Inside this cylinder 63 can move a piston 66 crossed over its entire length by a channel 67 for supplying the plastic, which opens into the interior of the cylinder 63, this channel 67 being connected on the side of its upstream end to the last rotary connector 50 of the transfer means 15.

The piston 66 is recalled inside the cylinder 63 by a system exerting a constant force, in particular one or more cylinders, and as in the example shown, two cylinders 68 and 69 each connected on the one hand to the cylinder 63 by a flange 70, on the other hand to the piston 66 by a plate 71. The return force of the jacks 68 and 69 is less than the force exerted by the plastic material penetrating # into the magazine 11 to avoid any backflow against the normal direction of pro # gression. The end of the piston 66 pressed into the cylinder 63 is equipped with annular scraping segments. End stops 72, 73 for the end of stroke of the piston 66 inside the cylinder 63, in each of the two possible directions of movement of said piston 66 are also provided. These stops 72, 73 are urged by contact elements 74, 75 belonging to piston 66 and arranged, one 74 determining the maximum driving position, on the rear part of the piston, the other 75
ending the maximum withdrawal position, so the maximum volume at
inside the cylinder 63, on the front end of the piston. An element
intermediate 90 intended to come into contact with the stop 72 is pre
seen on the body of the piston 66, this element determining the low level of
filling the cylinder 63 and triggering the actuation of the means
upstream of plastic supply.

The contact between the stops 72 and 73 and the corresponding elements 74, 75 controls the stopping of the injection of plastic material at the
through the outlet 65 and respectively the stopping of the supply of material to the cylinder 63.

 Advantageously, to avoid the cooling of the plastic material and possibly to perfect its heating so that it reaches the desired consistency, the walls of the cylinder 63 as well as those of the channel 67 are heated.

 This variable-volume magazine 11 delivers its plastic material with a constant pressure in the conventional positive-displacement pump 12, the speed of rotation of which is variable on demand.

 At the outlet of the pump 12, the plastic material is supplied to an extrusion head 76 essentially comprising the nozzle 13. This extrusion head 76 is mounted on a carriage 77 biased by means such as jacks and an actuated worm by an electric motor not shown making it possible to approach or move the nozzle 13 away from the glass sheet 2. The electric motor and the worm screw make it possible to finely adjust the advance of the carriage 77 carrying the nozzle 13, in particular by depending on the thickness of the glass sheets 2, while the jacks allow movements of predetermined importance.

This extrusion head is mounted on a crown 78 rotating about an axis perpendicular to the plane of the wall 3 vertical or substantially vertical so as to correctly orient the nozzle 13 with respect to the glass sheets as a function of the relative direction of movement of said nozzle and said glass sheets. Indeed, as taught in French Patent No. 2,294,313, the nozzle must make an angle between the glass sheet between 15 and 450 and preferably between 25 and 350
To block the crown 78 in predetermined positions, a blocking punch 79 engages in notches provided for this purpose in the crown 78, notches not shown in the figures.

 The variable volume magazine assembly 11, positive displacement pump 12, extrusion head 76, carriage 77 is movable in translation relative to the glass sheets 2 under the action of the means 14 detailed below. For this, this assembly is mounted on a plate 80 able to move along two slides 81-, 82 parallel to the wall 3 and therefore to the plane of the glass sheets 2, in a direction different from that of the movement caused by the conveyor. vertical with rollers 4 and in particular in a direction orthogonal to that printed on the glass sheets 2 by this roller conveyor 4. The movement along these two slides 81, 82 is caused by a motor 83 which rotates a screw without end 84 parallel to the slides 81 and 82, this worm 84 being engaged in non-figured ball bushings, integral with the plate 80. The slides 81 and 82 as well as the worm 84 are fixed along the vertical console 6 .

 As known per se, the nozzle 13 is also equipped with a system for adjusting the height of the extruded cord 1, as well as a cord cutter, not shown.

 As also known per se from the French patent document 2 20i 799, a system known per se capable of creating a vacuum in the circuit for supplying the plastic material is arranged in bypass immediately upstream of the nozzle 13. This system is also not shown in the figures.

The installation described above works as follows:
The plastic 8, for example, based on butyl rubber, is supplied in a barrel 7. This is fixed to the base 5 by the bracket 17 which encloses its base 16. The cover 9 in the form of a cone is arranged on this barrel then pressed against the material contained therein by the jacks 18 and 19. Under the action of this pressure and also of the heating produced by the heating appendages 30 and by the wall of this conical piston, the material capped by the piston cover 9 is gradually softened and extracted from the barrel 7 through the outlet 28. The pressure under which the plastic is extracted is however insufficient to transport it through the entire distribution circuit to the outlet nozzle 13. This pressure is however sufficient to force-feed the pump 10, especially since the force-feeding can be done on both sides of the pump 10 by the two supply lines. This pump due to this double supply, due to the particular shape of its teeth, can restore in its outlet pipe 43, a regular flow of plastic material under a pressure much higher than that which it had before said pump.

 This pressure in the outlet pipe may be of the order of 300 or 350 bars. With this high pressure, it is not necessary to overheat the material to convey it to the nozzle 13, and there is therefore no risk of degrading it.

 At the outlet of this pump 10, the plastic material under high pressure, however at a temperature of the order of 100 C, is introduced into the pipes and the rotary connections of the transfer system 15. Thanks to this transfer system 15, generally made of steel , the high pressures, as well as the relatively high temperature, can be tolerated without leaks.

 The plurality of rigid pipes 44, 45, 46 and rotary fittings 47, 48, 49, 50, despite the unique degree of freedom of each of said fittings, allows the plastic material to be transferred from pump 10 which descends strictly vertically into the barrel 7, to the variable-volume magazine 11 which also evolves along the slides 81, 82 in a slightly different direction, namely generally inclined by about 50 relative to the vertical. Thus, thanks to these possible movements, the piping 46 and the rotary connector 50 can take the position indicated in dotted lines in FIG. 1B, with a view to feeding the nozzle 13 arranged towards the top of the glass sheet 2 as shown in dotted lines on this same figure.

 Whatever the relative positions of the piston cover 9 and the nozzle 13 or of the variable volume magazine 11, the material 8 is always conveyed and under the same conditions.

 The magazine 11 is therefore supplied continuously with a flow which is sometimes too low to continuously extrude certain very high cords 1, of the order of 15 mm and more, on glass sheets 2 of large dimensions, which may have perimeters of almost 15 m. Thanks to this magazine 11 an intermediate reserve of material can be constituted in particular by taking advantage of the extrusion stops through the nozzle 13, between two glass sheets 2 or even at the corners of said glass sheets. During these stops the piston 66 moves back into the cylinder 63 thus increasing the capacity of the magazine 11.

 On the contrary, during the extrusion of a very high bead and in general of large section, if the continuous flow supplied by the conical heating piston 9 and the rotary pump with internal gears 10 is less than the flow exiting through the nozzle 13, the additional flow required is obtained by gradually emptying the reserve formed in the magazine 11. In this case the piston 66 advances on the contrary inside the cylinder 63. Thus, for example, when to manufacture a cord 1 of significant height we need 2.8 kg of material per minute, thanks to the reserve accumulated in the variable volume magazine, we can be satisfied with a supply of material by the conical heating piston 9 and the gear pump 10, 1.3 kg per minute continuously. This variable-volume magazine 11 also makes it possible, by the action of the lateral jacks 68 and 69, to regulate the pressure of the plastic material, regulation which is particularly important for feeding the positive displacement pump 12.

 The positive displacement pump 12 whose output flow is adjusted by acting on the motor which controls it, supplies the plastic material at the desired flow for the extrusion of a bead of a determined section. The extrusion nozzle 13 is positioned correctly with respect to the glass sheets 2, in distance and in orientation in the direction of relative movement of the nozzle 13 and the glass sheet 2. Once the nozzle 13 is correctly oriented by rotation of the crown 78 which carries it, the punch 79 comes to block said crown.

 If the bead 1 is to be placed along a parallel to the direction of movement provided by the roller conveyor 4, the nozzle 13 remains fixed, and extrudes from the bead while the glass sheet passes in front of it.

 If on the contrary the cord 1 must be deposited along a parallel to the slides 81, 82, the roller conveyor 4 remains stationary and the plate 80 moves regularly, under the action of the motor 83 acting on the screw endless 84 and on ball bushings.

The nozzle is thus driven in a regular translational movement and it deposits the cord 1 on the glass sheet? motionless.

  It is also possible by simultaneously controlling the movement of the plate 80 and that of the roller conveyor 4 to obtain a deposition of the cord along lines other than vertical and horizontal.

 It is therefore possible, thanks to this installation for preparing a plastic material, to obtain continuously, using several combined steps, the outlet from a possibly mobile nozzle 13, a bead 1 of said plastic material at a temperature, at a desired flow rate, pressure, viscosity and hardness while at the origin of the installation, the material is at a much lower temperature, the viscosity and the hardness are much higher, while also qu 'heating alone would be much too long to soften the initial material according to the desired consistency and would even risk degrading said material.

Claims (20)

 1. Process for the preparation of a plastic material of the butyl rubber type from a mass of said material to  the raw state, in particular having a high viscosity and hardness,  with a view to its extrusion through an outlet nozzle, in particular under  the shape of a calibrated bead having a viscosity and a hardness lower than that of the raw material, characterized in that it consists in heating a reduced volume of the mass of material and in continuously extracting from the material of this volume by subjecting it to a pressure, to put this extracted material under a higher pressure so as to propel a continuous flow of said material in a circuit to the outlet nozzle, to continuously admit this material in a store with variable volume likely to enlarge when the quantity of material it receives is greater than the quantity of material it delivers, and on the contrary likely to be reduced under the opposite conditions, to be extracted from this variable volume store quantities of material necessary, at the desired flow rate, within the limit however of the volume of material stored in the variable-volume magazine and of the continuous flow rate which feeds said magazine, to extrude these quantities of material extracted from the magazine n through the nozzle.  2. Method according to claim 1, characterized in that the plastic material is propelled into the circuit which leads it to the outlet nozzle under a pressure of the order of 300 bars.  3. - Installation for preparing a plastic material, of the type based on butyl rubber, from a mass of said raw material, having in particular a high viscosity and hardness, with a view to its extrusion through an outlet nozzle, in particular in the form of a calibrated bead having a viscosity and a hardness lower than that of the raw material, characterized in that it comprises upstream of said outlet nozzle  a reservoir containing the raw plastic material having a wall, in particular its cover, applied with pressure against the material, this wall or this cover pierced with an outlet orifice being of a shape such that the section of the volume of material which it the enclosure is all the more reduced the closer it is to the outlet orifice, this wall or this cover also being provided on its face oriented towards the material, with heating appendages which immerse in said material, a pump arranged at the outlet of the wall or cover applied with pressure against the material of the tank, providing a continuous flow of plastic material under high pressure,  a magazine of variable volume disposed downstream of the pump with continuous flow of material under pressure, consisting of a cylinder and a piston returned inside the cylinder with a constant force such that it is less than the force exerted by the plastic material supplying said store.  4. Installation according to claim 3, characterized in that it also comprises a positive displacement pump in particular of the electric type and with internal gears, arranged immediately before the outlet nozzle and downstream of the variable volume store.  5. Installation according to any one of claims 3 or 4, characterized in that the wall and in particular the cover applied with pressure against the material contained in the tank is a conical surface.  6. Installation according to any one of claims 3 to 5, characterized in that the wall and in particular the cover applied with pressure against the material contained in the tank is a straight cone with a circular base.  7. Installation according to one of claims 3 to 6, characterized in that the wall or the cover applied with pressure to the material of the tank is equipped with at least two peripheral seals engaged in grooves of said wall or of said cover, these seals having on the part of their profile not engaged in the grooves, a flat portion parallel to the wall of the tank along which the wall or the cover applied with pressure on the material evolves, this flat portion being framed by two cut sides promoting centering and sliding along the tank.  8. Installation according to claim 7, characterized in that the cut sides form an angle of the order due ~ 20 "with the flat portion.  9. Installation according to claims 7 or 8, characterized in that the flat portion represents approximately 1/3 of the surface without groove.  10. Installation according to one of claims 7 to 9, characterized in that the material of the peripheral seals, of the rubber type, has a Shore hardness of the order of 700.  11. Installation according to one of claims 3 to 10, characterized in that the outlet nozzle and the variable volume magazine are mounted on slides, thus allowing their translation.  12. Installation according to claim 11, characterized in that the variable volume magazine and the pump disposed at the outlet of the wall or of the cover applied with pressure against the material of the tank, are connected by a plurality of rigid pipes resistant to pressure and heat, in particular in steel, joined by rotary unions with a single degree of freedom.  13. Installation according to claim 12, characterized in that the rotary connections consist of a male element and a female element each welded to the pipes or to the upstream and downstream devices, fitted one inside the other, and turning one in the other thanks to ball bearings.  14. Installation according to one of claims 11 to 13, characterized in that the movement of the variable volume magazine and the nozzle along the slides is obtained by mounting said magazine and said nozzle on a plate driven in translation along sliding rails by an endless screw rotating in ball bushings integral with the plate.  15. Installation according to one of claims 3 to 14, characterized in that the pump disposed at the outlet of the wall or the cover is a rotary pump with internal gears having supplies on its two faces.  16. Installation according to one of claims 3 to 15, characterized in that the pump disposed at the outlet of the wall or of the cover applied with pressure against the material of the tank is a rotary pump with internal gears with trapezoidal teeth.  17. Installation according to one of claims 3 to 16, characterized in that the pump disposed at the outlet of the wall or of the cover applied with pressure against the material of the tank is a rotary pump with internal gears hydraulically driven.  18. Installation according to one of claims 3 to 17, characterized in that the outlet nozzle is preceded by a system known per se capable of creating a vacuum in the supply circuit of the plastic, this system being mounted in bypass on this circuit.  19. Installation according to one of claims 3 to 18, characterized in that the outlet nozzle is orientable and adjustable in distance with respect to the support on which it must deposit the extruded material.  20. Application of the method and the device according to the preceding claims to the extrusion of a calibrated bead of a material based on butyl rubber for the production of multiple glazing, this calibrated bead being arranged on the edge of a face of a sheet of glass to serve as a seal and interlayer between this sheet and another sheet subsequently applied to the bead parallel to the first.