Concentric mold cooling

Abstract

The invention relates to a moulding device (1) for moulding a container (2) from a preform (3), the moulding device (1) comprising a base (4) and having a central axis (5), the base (4) having a bottom (6), which is generally centered on the central axis (5) and in which a cavity (7) is arranged, against which the preform (3) can be pressed in order to form a base (8) of the container (2), the bottom (6) having an outer edge (9) and comprising a channel (10), the channel extends entirely transversely to the central axis (5) between the central axis and the outer edge (9) in order to circulate a fluid that controls the temperature of the moulding device (1) in the channel. The moulding device is characterized in that the channel (10) has a first portion (11) having, on the one hand, a first inlet region (12) offset from the central axis (5) for receiving the fluid, and an arc away from the central axis (5), which follows the first inlet region, on the other hand, which causes the fluid to flow close to the central axis (5), preferably, the flow is close to the central axis after the arc-shaped part. The invention further relates to an implementation method.

Description

Technical Field

[0001] The invention relates to the field of blow-molded containers made of plastic, in particular PET, polyethylene terephthalate, more particularly from smaller blanks or preforms which undergo expansion in a mould by injection of pressurised gas until they conform to the shape of a hollow cavity provided in the mould. The subject of the invention is a device and a method for producing containers by blow-molding. Background Art

[0002] In the field of blow-moulding of containers in a mould, it is necessary to control the temperature of said mould. In fact, in order to allow its deformation, the preforms are heated and they transfer part of their thermal calories to the blow mould. If these calories are not discharged from the mould, the latter will continue to heat up with each blow-moulding cycle until a temperature is reached that prevents production, in particular because of serious production defects such as deformation. It is then necessary to provide a circulation of a cooling liquid inside the mould, usually providing an exchanger to release again the heat from the mould absorbed by the liquid.

[0003] The cooling circuit within the mold is generally opened at least in the bottom of the mold.

[0004] Typically, the preform is in the form of a cylindrical tube with an open portion with a neck at one end and a closure, usually with a hemispherical shape, at the other end. This hemispherical portion is thus stretched to help form the bottom of the bottle, pressing at this point against the cavity presented by the bottom of the mold. Before the blow molding step, the preform is made by injection, and at the outer end of this hemispherical shape it usually shows the trajectory of the injection point.

[0005] Patent document US7025584 discloses the implementation of the classical cooling principle, namely the arrangement of flow circuits in the mold bottom. More specifically, the patent proposes circuits for a petaloid bottom, which therefore has a raised bottom separated by hollow recesses, the circuits following the surface of the recesses more closely thanks to the hollow sections elongated in the axial direction and the cleverly spaced arrangement in the middle of these hollow longitudinal sections.

[0006] Document CN202037856 shows a serpentine in the form of a diverging spiral. The cooling liquid enters the base of the mold from the peripheral surface of the base and also leaves the base at this surface. The cooling liquid enters the cooling tube in the center and gradually deviates to the periphery of the mold.

[0007] Finally, CN203381178 discloses a cooling tube obtained by providing walls in the form of ribs spaced apart from one another.

[0008] Cooling in the mould in the central region of the preform is particularly important, taking into account its thickness and stretching, and its importance in the mechanical resistance of the container subsequently obtained.

[0009] The object of the present invention is to improve the cooling of the bottom of the mould and more particularly of the bottom of the container obtained, to improve the mechanical strength of the container obtained and possibly to increase the productivity. Summary of the invention

[0010] The invention therefore proposes a molding device and a corresponding method which better distribute the cooling of the base of the container. To this end, the invention proposes that the cooling starts at a ring around the central axis of the mold, continues in a convergent manner towards the center, and then, after the cooling of the central part, continues to the parts outside the ring, preferably in a divergent manner, that is to say towards the periphery of the mold.

[0011] In doing so, it is ensured that the cooling is maximized, by avoiding the heating of the cooling liquid that would be caused by an initial circulation close to the cavity and towards the central axis, since it is obtained by the liquid starting to circulate under the cavity at the region of the ring. Thus, the liquid starts its cooling action by circulating along a complete or almost complete ring at a certain distance from the central axis, between the central axis and the outer edge, then gradually approaches the central axis and then, for a second time, acts in the portion between said ring and the outer edge. Thus, the cooling power decreases from the ring around the central axis towards the center and then from the ring to the periphery, along a correspondingly shaped channel path.

[0012] Therefore, according to the invention, it is proposed to organize the circulation of the liquid in the bottom of the mold by appropriate channels, first from the middle zone towards the center of the mold, and then between the middle zone and the outer edge of the mold. Thus, the most intense cooling occurs in the middle zone, around and away from the center of the mold, where the top of the preform usually reaches, i.e. its injection point.

[0013] The subject of the invention is therefore a molding device for molding a container from a preform, the molding device comprising a base and having a central axis, the base having a bottom, the bottom being generally centered on the central axis and in which a cavity is arranged, the preform being able to be pressed against the cavity so as to form the base of the container, the bottom having an outer edge and comprising a channel, the channel extending as a whole transversely to the central axis between the central axis and the outer edge so as to circulate a fluid for controlling the temperature of the molding device in the channel.

[0014] The channel 10 extends generally transversely to the central axis 5 at a distance short enough from the central axis to have a significant thermal effect. In the case of a significantly uneven bottom of the container, the channel 10 may at least partially follow the contour of the cavity 7 and thus have portions slightly offset from each other along the central axis 5. In general, the channel 10 extends within the bottom 6 between two planes perpendicular to the central axis 5, which allows the fluid circulating in the channel to perform its thermal regulation function. Typically, the plane farthest from the cavity 7 is about five millimeters away, while the plane closest to the cavity 7 is about two millimeters away.

[0015] According to the invention, the channel 10 has a first portion 11 which, on the one hand, has a first inlet zone 12 offset from the central axis 5 for receiving the fluid, and an arc away from the central axis 5, the arc following the first inlet zone, which, on the other hand, brings the fluid closer to the central axis 5, preferably after the arc, so that the cooling effect is greater at the ring around the central axis 5 than at the central axis 5 itself. The first inlet zone 12 forms the arrival of the coolant in the area where cooling takes place and is located less than about four centimeters from the central axis 5, preferably less than three centimeters. The arc from which the fluid circulates, from its action, extends over at least three quarters of a turn or even a full turn before the portion of the channel 10 that brings the fluid closer to the central axis 5. This arc can be circular or have a different profile, thus ensuring a first cooling at least part of the effective angular range of the ring around the central axis 5 or such a ring representing at least half a turn, preferably at least three quarters of a turn. Only after circulating in this initial portion around and at a distance from the central axis 5 and thus exerting a first cooling effect on the circumference around and at a distance from the central axis 5 , does the channel 10 direct the fluid towards the central axis 5 .

[0016] Thus, the first portion 11 , where the cooling effect of the cooling fluid begins, converges towards the central axis 5 after an initial portion which goes around the entire or at least three quarters of a circle at a distance from the central axis 5 .

[0017] According to a possible additional feature, the channel 10 has a second portion 13, which is located between the first portion 11 and the outer edge 9, downstream of the first portion 11, so that the fluid first flows into the first portion 11 and then into the second portion 13, which makes it possible to provide cooling beyond the base of the ring delimiting the first portion 11. As will be described further later, the second portion 13 is located after the first portion 11 in the flow direction of the fluid. The second portion 13 thus extends between the ring and the outer edge 9 of the bottom 6, the first portion 11 being located inside the ring, that is to say the outer surface of the bottom being substantially cylindrical.

[0018] The first portion 11 and the second portion 13 may be in the same plane perpendicular to the central axis 5, or may be slightly offset, for example if the bottom of the bottle is not flat.

[0019] According to another possible additional feature, the base 4 comprises a distributor 14 arranged against the bottom 6 at the central axis 5 and provided inside the distributor with a passage 15 for the fluid, the passage 15 having an inlet 16 for receiving the fluid leaving the first part 11, and an outlet 17 for supplying said fluid to the second part 13, in particular at a second inlet zone 19 of the second part 13, which makes it possible to bring the cooling liquid from the downstream end of the first part 11 to the upstream end of the second part 13, further away from the central axis 5, with a simple structure. The distributor is thus housed in a groove provided for this purpose in the bottom 6 and / or in the cover 20. More precisely, the first and second parts in the form of grooves form a wall between them at the bottom 6. The cover is in contact with a part of these walls, another part of these walls being in contact with the distributor at one of these faces, the other face of which is housed in the cover.

[0020] As will be described later, this circulation of the ring moving away from the central axis 5 to provide the first cooling beyond the channel 10 may be carried out in a plane further away from the cavity than the plane in which the first portion 11 of the channel 10 is located.

[0021] Thus, the inlet opening 16 is particularly located at the central axis 5, facing the first outlet zone forming the outlet end of the first part 11, and the fluid moves from the first part 11 through the distributor along the central axis 5, and the outlet opening 17 is particularly offset relative to the central axis 5 and away from the central axis, opposite the second inlet zone 19, and the fluid circulates in the second part 13 from the second inlet zone 19, and the circulation of the fluid at the outlet opening 17 and the second inlet zone 19 occurs approximately transversely to the central axis 5.

[0022] The base 4 thus takes the form of a stack obtained in sequence from the cover 20 , the dispenser 14 and the bottom 6 .

[0023] According to another possible additional feature, the distributor 14 has an axial hole 18 extending at least partially along the central axis 5 and offset from it, opening at the first inlet zone 12 in order to introduce the fluid into the first portion, which makes it possible to bring the cooling fluid to the beginning of the channel 10. This axial hole 18 is close to the central axis 5, but slightly away, and ends at a ring which delimits the cooled inner portion after the outer portion.

[0024] According to another possible additional feature, the second portion 13 has, on the one hand, a second inlet zone 19 at which it receives the fluid and, on the other hand, allows the fluid to flow away from the central axis 5 towards the outer edge 9, which makes it possible to cool the molded portion of the cavity 7, such as the petal-shaped base foot.

[0025] According to another possible additional feature, the base 4 comprises a cover 20 in which a path 22 is provided for bringing the fluid towards the channel 10 by moving it at least partially in the direction of the central axis 5 from the entry point 21, the channel 10 taking the form of, for example, a groove bored in the base 4, the cover closing the groove. The path 22 opens, for example, at the axial hole 18 of the distributor 14. Where appropriate, as Figure 2 and 8 As shown, the cover 20 also comprises an exhaust duct 23 which communicates on one hand with the outlet of the channel 10 to receive the fluid and on the other hand with the outside of the base 4 to send the liquid out of the molding device. The cover 20 generally has the shape of a cylinder of revolution.

[0026] According to another possible additional feature, the molding device 1 also comprises side shells extending along the central axis 5 against which the preform 3 can be pressed so as to form the sides of the container 2 during blow molding, which allows the final package to be formed. Thus, the molding device 1 not only comprises a base 4 that will define the base of the container 2, but also at least one and preferably two side shells that are opposite to each other during blow molding to define the sides of the container 2.

[0027] The invention also relates to a method for realizing the above-mentioned molding device. Therefore, the subject of the invention is a method for manufacturing a plastic container 2 by blow-molding a preform 3, wherein the preform 3 is placed in a molding device 1 having a central axis 5 and comprising a base 4 with a bottom 6, and then pressurized gas is injected into the preform 3 so that it conforms to the internal contour of the molding device 1 until the container 2 is formed, and the method also includes controlling the temperature of the molding device 1 with the help of a fluid.

[0028] According to the invention, the temperature is controlled by circulating a fluid in the molding device 1 at the base 4 along a path substantially transverse to the central axis 5, wherein in a first stage the fluid starts circulating in a ring around the central axis 5 at a distance from the central axis and the outer surface of the base 4, and then moves towards or away from the central axis 5.

[0029] The ring delimits a portion located inside the ring, including the central axis 5, and a portion located outside the ring, together with the outer edge 9. Cooling starts at the ring, then continues in the inner portion close to the central axis 5, preferably not away from it again, then continues from the ring, but in the direction of the outer edge 9, thus in the outer portion, preferably further away from the cavity 9 than the first portion 11 of the channel 10 extending for the inner portion and the second portion 13 of the channel 10 extending for the outer portion, after communication between the two portions in an offset plane.

[0030] According to a possible characteristic of the method, the preform 3 has a vertex 24 and is placed in the molding device 1 so that its vertex 24 is generally at the level of the central axis 5 after stretch blow molding, in such a way that the strongest cooling, that is to say when the fluid begins to circulate in the base 4, does not take place at the top 24 of the preform 3, but at the ring or the portion of the ring surrounding the top 24. Unlike the usual cooling techniques, the cooling fluid is therefore not heated when it approaches the cavity 7 by advancing along the central axis 5 until the channel 10, and the cooling does not start from the tip or top 24 of the preform, and therefore not from the center of the container 2, since the cooling gradually moves away from it, nor from the outer edge 9, since the cooling starts from the central ring close to the central axis 5, but before any convergence towards the central axis 5. In the first portion 11, the fluid is at a certain distance from the central axis 5, then approaches the central axis and does not move away from it.

[0031] According to a possible characteristic of the method, after a first phase of circulation of the fluid in the base 4, the fluid circulates close to the central axis 5. Thus, after a first phase in which the fluid acts on the ring away from the central axis 5, the fluid is gradually brought to the level of the central axis 5. The cooling effect is therefore the most important, since it is the first area of ​​effective heat exchange, at the ring, then towards the center and therefore towards the central axis 5. The circumferential circulation in the first portion 11 then converges close to the cavity 7, that is to say, in particular closer to the cavity than the communication between the first and second portions.

[0032] According to a possible characteristic of the method, the circulation of the fluid in the base 4 comprises, after the first stage, a stage during which the fluid circulates from outside the ring away from the central axis 5, in particular up to the outer edge 9 of the base 4. The fluid then circulates from the second inlet zone in the second portion 13 of the channel and moves away from the central axis 5, substantially perpendicular to the central axis 5. The second portion 13 of the channel 10 may take the form of a spiral running in a divergent direction, or simply of a succession of circular arcs connected by radial segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other advantages and characteristics will become more apparent from the following description of a single embodiment variant of the device according to the invention, given by way of non-limiting example, with reference to the accompanying drawings, in which:

[0034] [ Figure 1 ] shows a cross-sectional view of a molding apparatus with the lid, dispenser and base stacked together.

[0035] [ Figure 2 ] shows the cover and the dispenser contained therein.

[0036] [ Figure 3 ] is a cross-section showing the cover and dispenser.

[0037] [ Figure 4 ]The stack of base, dispenser and cover is shown in cross section in a plane deviating from the main axis.

[0038] [ Figure 5 ] shows a channel thus excavated in the bottom of a base, having two separated parts.

[0039] [ Figure 6 ] shows the channel thus excavated, with the distributor in its working position.

[0040] [ Figure 7 ] shows a dispenser within a cover, particularly having a groove that allows fluid to flow from the dispenser to a second portion of the channel.

[0041] [ Figure 8 ] shows a cross section along a plane perpendicular to the main axis, at the rib defining the channel, with the distributor located between the rib and the cover.

[0042] [ Fig. 9 ] shows a preform.

[0043] [ Fig.10 ] shows a container.

[0044] [ Fig.11 ] shows a spiral profile.

[0045] [ Fig.12 ] shows the spiral profile of the distributor. DETAILED DESCRIPTION

[0046] The molding device 1 according to the invention is intended to receive a preform 3 into which a pressure fluid is injected in order to press the preform against a cavity 7 provided by said molding device 1. This molding device 1 comprises at least one base 4 intended to form a generally lower portion of the future container 2, in other words its bottom, by which the container 2 then rests vertically on a horizontal surface.

[0047] The moulding device 1 may also comprise side shells which will shape the side surfaces of the container 2. The moulding device 1 is thus at least a mould bottom, but may comprise other parts making it a complete blow mould.

[0048] In any case, the molding device 1 has a central axis 5 which corresponds in practice to the axis along which the container 2 formed by it extends, and the preforms 3 are moreover aligned inside the molding device 1 around this central axis 5. The molding device 1 generally has a cylindrical shape around this central axis 5 and has a length which, as mentioned above, obviously depends on the other components that the molding device may comprise.

[0049] The molding device 1 thus comprises a base 4 , the housing being, if necessary, in extension of the base.

[0050] This base 4 has a stack along a central axis 5 consisting of a bottom 6, against which the preform 3 will rest, and a cover 20, against which the cover 20 rests on the other side. The bottom 6 has, at its outer edge 9, a circumference of revolution of a substantially cylindrical shape around the central axis 5, which bears the surface of the cavity 7 to form the shape of the container 2. On the side opposite to the cavity 7, the bottom 6 has a channel 10, for example in the form of at least one groove. Figure 5 This portion of the bottom 6 is shown, which has a channel 10 made of two grooves, each of which is integral. Of course, more than two different grooves can be imagined. At least one groove and therefore the channel 10 has a shape consisting, on the one hand, of an arc centered on the central axis 5 and having its own radius, and, on the other hand, of a straight line portion perpendicular to the central axis 5 and allowing an arc of a first radius to be connected to an arc of a second radius. It is also conceivable that the channel 10 has at least one spiral, that is, a profile whose distance relative to the central axis 5 varies over a circumference that is less than or even greater than a full turn.

[0051] Typically, the channel 10 is arranged substantially perpendicular to the central axis 5 and its function is to receive a cooling liquid which allows the temperature of the molding device 1 to be regulated at this location by absorbing the thermal calories of the preform 3 which has been previously heated to facilitate shaping.

[0052] The channel 10 of the bottom 6 , in particular when it is implemented in the form of at least one groove, has a rear portion, which is therefore a proximal portion, the position of which along the central axis 5 can substantially follow the shape of the cavity 7 in order to maximize heat exchange.

[0053] A channel in the form of at least one groove naturally has walls between successive sections of the groove in the form of ribs complementary to the groove, the cover 20 resting on the ends of at least some of these ribs, thus contributing to the sealing closure of the channel 10 .

[0054] In addition to this, the cover 20 allows the fluid that must subsequently cool the bottom 6 to be brought in and thus brought into the channels 10 in the bottom 6. It also makes it possible to allow the fluid to be discharged after it has circulated in the channels 10. The cover 20 receives cooling liquid along the central axis 5 from an element not shown, the bottom 6 and then the cover 20, said element being located outside the cover 20 in the stacking sequence. The movement of the cooling liquid to be brought into the channels 10 of the bottom 6 is therefore arranged within the cover 20. To this end, the cover 20 has a path 22 for circulating the cooling liquid towards the bottom 6 and this path 22 is located near the central part of the molding device 1, that is to say, the path 22 is kept less than 5 cm, preferably less than 3 cm from the central axis 5. This makes it possible in particular to ensure that the liquid entering the bottom 6 is close to the center, that is to say close to the central axis 5, possibly only slightly deviating from the central axis, as described below, so as to cool more intensively the substantially central part of the bottom 6 than the part close to the outer edge 9, which is the case when the fluid reaches the bottom 6 close to the outer edge 9.

[0055] Figure 3 A path 22 is shown inside the cover 20, of which a portion is aligned on the central axis 5. This embodiment also shows the possibility of an interruption of the path 22 perpendicular to the central axis 5 and then a portion again parallel to the central axis 5, offset relative to this axis. In practice, this interruption is obtained by drilling from one edge of the molding device, thus drilling from the outer edge 9 until reaching the portion of the path 22 aligned with the central axis 5 and beyond it to form the interruption. We understand that the portion of the drilling on the other side of the central axis 5 relative to the interruption is not used for the circulation of the fluid towards the bottom 6, but forms a dead end in the path of the fluid and is therefore not part of the path 22, and in general, the portions of the holes used to create said path 22 but in which the fluid cannot circulate are not part of the path 22 because they form a dead end.

[0056] In the embodiment shown here, the molding device 1 also comprises a distributor 14. This distributor 14 is mounted so as to be sandwiched between the bottom 6 on one side and the cover 20 on the other side. As will be explained, this distributor 14 participates in bringing the fluid from the path 22 of the cover 22 into the channel 10 of the bottom 6, and in bringing the fluid between successive different parts of said channel 10.

[0057] The distributor 14 generally has the shape of a disk or a small ball and is positioned at the central axis 5, between the bottom 6 and the cover 20. On the one hand, it allows the incoming liquid to be directed into the channel 10 and, on the other hand, allows two consecutive parts of the channel 10 to be connected together.

[0058] More precisely, especially Figure 3As shown, in a possible embodiment, the distributor 14 has an axial hole 18 extending parallel to the central axis 5 but spaced therefrom. This axial hole 18 is located opposite the outlet of the path 22 bored in the cover 20 for the circulation of the liquid towards the channel 10. Therefore, this axial hole 18 is also close to the central axis 5, less than about 3 cm, and helps to bring the incoming liquid as close as possible to the cavity 7 due to the flow substantially parallel to the axis. This axial hole 18 allows the cooling liquid to pass through the distributor 14 in the direction of the central axis 5, so that the cooling liquid begins its cooling action close to the central axis 5, but slightly offset from the central axis, that is to say closer to the central axis 5 than to the outer edge 9.

[0059] The distributor 14 also comprises a passage 15 for circulating the liquid, more specifically from an inlet 16 of said passage 15 located at the central axis 5 to an outlet 17 of said passage 15 located away from the central axis 5, see Figure 6 This passage 15 makes it possible to put two successive parts of the channel 10 in fluid communication, as will be described later. The inlet 16 communicates with the downstream end of the first part 11 of the channel 10, simply situated facing each other, and the outlet 17 communicates with the upstream end of the second part 13 of the channel 10, also simply facing each other.

[0060] The circulation of the fluid therefore proceeds as follows.

[0061] The fluid is initially received by the cover 20 at the central axis 5, more precisely at the hole of the channel presented by the path 22 bored therein, see Figure 3 . This path 22 allowing the fluid to circulate inside the cover 20 towards the bottom 6 extends less than 3 centimeters from the central axis 5, which makes it possible to increase the cooling effect at the portion of the central disc. In fact, this path 22 passes out from the cover 20 by being slightly away from the central axis 5. Therefore, the fluid circulates in this path 22 and leaves the cover 20 without leaving the central axis 5 by more than 3 centimeters, or at least a maximum of 5 centimeters. The fluid then continues to enter the axial hole 18 provided by the distributor 14, which is located in the extension of the downstream end of the path 22, parallel to the central axis 5. Therefore, the fluid initially received in the cover 20 in the area close to the central axis 5 advances along the central axis 5 by first passing through the path 22 bored in said cover 20 and then through the axial hole 18, all of which is closer to the central axis 5 than the outer edge 9 but does not coincide with the central axis 5.

[0062] The axial hole 18 of the distributor 14 is slightly offset from the central axis 5 so as to bring the fluid into the channel 10 at a ring present around the central axis 5 .

[0063] Thus, after passing through the axial bore 18, the fluid continues in the first portion 11 of the channel 10 to begin its function of cooling the cavity 7. Thus, the channel 10 extending substantially perpendicularly to the central axis 5 has an entry point for the fluid to enter which is slightly offset from the central axis 5. This entry point forms a first inlet region 12 for the first portion 11 of the channel 10, see Figure 5 Once carried by the cover 20 and then by the distributor 14, the fluid thus reaches the cooling channel 10, slightly away from the central axis 5. The fluid thus then circulates perpendicularly to the central axis 5 in a first portion 11, which starts away from the central axis 5 and ends closer to the central axis 5, preferably at the central axis 5. Figure 5 As shown, the first portion 11 extends at least 180 degrees and preferably includes an arc-shaped portion extending at least half a circle or even at least three quarters of a circle. This arc-shaped portion may be followed by a radial linear portion to bring the fluid to the central axis 5. Of course, we can envision more complex shapes for the first portion 11, such as a spiral shape, or even a plurality of arc-shaped portions with different radii for each, the arc-shaped portions being connected by radial portions, etc. It can be seen that the first portion 11 is such that the fluid circulates there from an area eccentric to the central axis 5 and gradually approaches the central axis 5. We can envision that the end of the first portion 11 is at the central axis 5, as in Figure 5 In this case, the first portion 11 extends over all or part of a disk centered on the central axis 5; we can also imagine that the first portion 11 also ends away from the central axis 5, but closer to it than the first entry zone 12, in which case the first portion 11 extends over all or part of a ring centered on the central axis 5, the first portion 11 preferably extending 360 degrees and, at least, extending over three quarters of a turn or even at least half a turn, and this preferably before approaching the central axis 5. This allows the most powerful cooling, i.e. the first cooling, to be organized at a ring that is gradually concentric around the central axis 5.

[0064] exist Figure 5 and Figure 6 In the embodiment shown, in the first section 11, once the fluid has completed its circulation around the central axis 5, it converges towards the central axis and the fluid is redirected further away from the central axis 5 than the first inlet area 12. The fluid then circulates in the distributor 14 in a passage 15 that starts at the central axis 5, has an input port 16, moves away from the cavity 7 through a hole along the central axis 5, and then continues in a divergent section, as shown in FIG. Figure 6As shown. The divergent portion starts from a radial portion, followed by an arc-shaped portion, and then a portion leading to the outer surface of the distributor 14, such as a portion of the side surface. Therefore, the passage 15 that leads the fluid to circulate in the distributor 14 includes a portion extending perpendicular to the central axis 5, which makes it possible to move the fluid away from the central axis 5 and which is farther away from the cavity 7 than the portion of the first portion 11 that brings the fluid closer to the central axis 5. The two portions are at the central axis 5, but are offset from each other along the axis. Therefore, the passage 15 includes a conduit that diverges from the central axis 5, the conduit of the passage being at a certain distance from the cavity, and the passage includes a conduit that converges toward the central axis 5, the conduit of the passage being closer to the cavity, and the two conduits are on different planes perpendicular to the central axis 5, so that the converging is closer to the cavity 7 than the diverging.

[0065] After the fluid enters the distributor 14 at the central axis 5 at the inlet opening 16 facing the outlet of the first part 11, it leaves the distributor 14 at the outlet opening 17 opposite the inlet of the second part 13 of the channel 10, that is, at the second inlet area 19 located away from the central axis 5, see Figure 7 . Figure 5 and 6 It is shown that the second inlet region 19 is slightly further from the central axis 5 than the first inlet region 12 .

[0066] More precisely, if Figure 4 and Figure 7 As can be seen in the figure, the outlet of the passage 15 is substantially perpendicular to the central axis 5. A cavity 25 is bored in the cover 20 to receive the fluid flowing out of the passage 15 into the cavity and to convey the fluid to the second inlet zone 19. This cavity 25 thus forms a fluid connection between the passage 15 and the second inlet zone 19 in the distributor 14, where the fluid circulates substantially parallel to the central axis 5. In fact, the outlet of the passage 15 is located in a plane slightly further away from the cavity 7 than the channel 10, and the cavity 25 in the cover allows it to rise to the channel 10, parallel to the central axis 5, at the second inlet zone 19.

[0067] As described above, the circulation of the fluid in the first portion 11 of the channel 10 occurs in a convergent manner in the direction of the central axis 5 ; in the second portion 13 , the circulation of the fluid occurs in a divergent manner away from the central axis 5 from the second inlet zone 19 .

[0068] The second portion 13 then includes an arc-shaped portion and a radial portion connecting them. Then, considering the profile of the channel 10, the fluid meanders in a region substantially perpendicular to the central axis 5 while leaving the central axis 5. Therefore, the fluid circulates to its position farthest from the central axis 5 and then connects with the discharge duct 23 provided in the cover 20 and extending parallel to the central axis 5, so that the fluid again leaves the region where cooling is organized by flowing along the central axis 5. Therefore, we understand that, in general, cooling is organized in a region extending perpendicular to the central axis 5, the fluid arrives there by following a path close to the central axis 5, then slightly separates from the central axis 5, so as to start cooling in the channel 10 from a region away from the central axis 5 and move toward the central axis, then, due to the circulation at the parallel layer, further away from the cavity 7, further away from the central axis 5 again as before, but then continues cooling from this distant region, but away from the central axis 5. Therefore, the first cooling occurs at a ring around the central axis 5, which may be a ring around the central axis 5 or a ring on most of the full circle, followed by cooling of the portion included in the ring, and then cooling of the portion outside the ring.

[0069] Of course, several such sequences are conceivable: multiple convergent coolings and / or multiple divergent coolings.

[0070] Therefore, the present invention implements a method, which can be described as follows.

[0071] The cooling of the molding device 1 is carried out by bringing a cooling liquid, usually water or glycol, into channels 10 arranged in a serpentine manner, arranged, i.e. bored, at a short distance from the cavity 7 against which the preheated preform 3 will come to bear. Cooling is thus carried out by circulating the liquid close to the cavity 2 and, previously, by circulating the fluid along the central axis 5, close to the central axis. Thus, in the cooling sequence, the fluid begins to cool the base 4 at a distance slightly from the central axis 5, circulates around the central axis 5, then approaches the central axis until it reaches it when necessary. After the first cooling step carried out due to the first portion 11 of the channel 10, the cooling liquid continues its cooling from an area approximately at the same distance from the central axis 5 as the area where the cooling begins, towards the outer edge 9, and therefore towards the outer contour of the molding device 1, the channel 10 allowing cooling, which is thus organized on either side of a circle centered on the central axis 5. Initially, the fluid cools the inside of the circle, starting from the part forming at least the majority of the circumference of the circle, by circulating in a first portion 11 arranged inside the circle, and then continues towards the central axis 5. The fluid then cools the outside of the circle by circulating in a second portion 13, starting from the vicinity of the circle and moving gradually away from the circle towards the outer edge. The circle, which thus defines a first cooling cycle inside and a second cooling cycle outside, is located between the central axis 5 and the outer edge 9. By first circulating at least half or even three quarters of a turn along the circumference of the circle before proceeding towards the central axis 5, the cooling thus starts from a ring or loop at a distance from the central axis 5 and then continues inwards to the central axis 5. In the inner part of the circle, there is no movement of the fluid directed from the center to the outside, which ensures that the areas of the cavity 7 at the periphery of the circle are indeed the areas that undergo the most important cooling.

[0072] In particular, in the case where the cavity 7 has a petaloid shape, and therefore has hollows extending substantially radially and distributed along a circumference, extending around a central portion from which they extend, the circle delimiting the first portion 11 on the inside and the second portion 13 on the outside is located close to the transition zone between the central portion and the hollow for the petaloid bottom. This circle, and therefore the first cooling ring defined by its circumference, is therefore such that the hollows formed by the petaloids are largely outside the circle. We therefore first cool the ring, outside which are the hollow ends, which subsequently form the base of the petaloid bottom. The cooling of the petaloid parts takes place after the cooling of the central portion, which itself takes place after the cooling of the entire or nearly the entire loop. The cooling thus takes place over a circle, then in a convergent manner, then in a divergent manner from the same circle.

[0073] When the preform 3 is blown, the top 24 is stretched at least in a direction perpendicular to the central axis 5, since the diameter and length of the preform 3 are significantly smaller than those of the container 2. The base 8 of the container 2 then has a slightly stretched amorphous central zone, which is radially followed by a oriented peripheral zone, which itself has been subjected to a much greater stretching. Advantageously, the circle delimiting the first portion 11 on the inside and the second portion 13 on the outside is located at the transition between the amorphous central zone and the oriented peripheral zone of the base 8 of the container 2 subsequently obtained. Therefore, the cavity 7 is first cooled at the end of the amorphous central zone and the beginning of the oriented peripheral zone, rather than at the central axis 5 or the outer edge 9.

[0074] Thus, advantageously, the first portion 11 may extend inside a circle whose radius is between one third and half of the distance of the lowest point of the cavity 7 relative to the central axis 5, which thus contributes to forming the seat of the container 2 at its base 8. Thus, the arc of the first portion 11 may be positioned relative to the central axis 5 at a distance between one third and half of the distance relative to the central axis 5, at these points being the deepest points of the cavity 7, which points then form the seat of the container 2.

[0075] Fig.11 and Fig.12 A spiral profile is shown. Fig.11 Thus, the first portion 11 of the channel 10 is shown to have a bottom 6 in the shape of a spiral. Thus, the first portion 11 starts, as already explained, at a first inlet zone 12 away from the central axis 5 and then gradually approaches the central axis 5. Here, the arc of the first portion 11 thus also gradually approaches the central axis 5. In other words, in general, the arc of the first portion 11 also allows the fluid to approach the central axis 5 while rotating around said central axis 5. As shown in the figure, the downstream end of the first portion 11, and therefore the inlet opening 16, is also at the central axis 5 here. In general, the first portion 11, from its upstream end, and therefore the inlet zone 12, in the case of a spiral, rotates around the central axis 5 at least half a turn or even three quarters of a turn or even more than one turn before arriving at said central axis 5, and therefore at the inlet opening 16.

[0076] Fig.12 A distributor 14 is shown, whose passage 15 has a spiral shape, through which the liquid passes in a divergent direction. Fig.11 The first spiral portion 11 of the embodiment of the present invention converges in a circular motion.

[0077] Fig.12The arrangement of the outlet ports 17 at the periphery of the distributor 14 with a spiral configuration, the arrangement of the inlet ports 16 at the central axis 5, and the offset arrangement of the axial bores 18 relative to the central axis are shown. The spiral configuration of the passage 15 allows the cooling fluid or cooling liquid to flow continuously from the inlet ports 16 to the outlet ports 17 while avoiding flow disturbances that would otherwise be caused by right angles.

[0078] Preferably, the direction of flow of the fluid is opposite between the substantially convergent flow occurring in the first portion 11 on the one hand and the substantially divergent flow occurring in the passage 15 on the other hand, and whether the profile is curved and continuous like a spiral, or discontinuous like a right angle. More precisely, the first portion 11 may allow the fluid to approach the central axis 5 by circulating around the central axis 5 in a clockwise direction, while the passage 15 may move the fluid away from the central axis 5. Preferably, the direction is opposite between the path in the first portion 11 close to the cavity 7 on the one hand and the path on the layer away from the cavity 7 on the other hand, where the passage 15 is located, as this allows a better distribution of the cooling forces.

[0079] Although the present invention has been described with reference to preferred embodiments, it is possible to combine all or part of the features identified herein.

Claims

1. A molding device (1) for molding a container (2) from a preform (3), the molding device (1) comprising a base (4) and having a central axis (5), the base (4) having a bottom (6) which is generally centered on the central axis (5) and in which a cavity (7) is arranged, the preform (3) can be pressed against the cavity in order to form a base (8) of the container (2), the bottom (6) having an outer edge (9) and comprising a channel (10) which extends generally transversely to the central axis (5) between the central axis and the outer edge (9) in order to circulate a fluid for controlling the temperature of the molding device (1) in the channel, The molding device is characterized in that The channel (10) has a first portion (11), which, on the one hand, has a first inlet area (12) deviating from the central axis (5) for receiving a fluid, and an arcuate portion away from the central axis (5), the arcuate portion following the first inlet area, and on the other hand, allows the fluid to flow close to the central axis (5), preferably close to the central axis after the arcuate portion.

2. Moulding device according to the preceding claim, characterised in that The channel (10) has a second portion (13) located between the first portion (11) and the outer edge (9) and downstream of the first portion (11) so that the fluid first flows into the first portion (11) and then into the second portion (13).

3. The molding device according to claim 2, characterized in that The base (4) comprises a distributor (14) arranged against the bottom (6) at the central axis (5) and provided with a passage (15) for the fluid inside the distributor, the passage (15) having an inlet (16) for receiving the fluid leaving the first part (11), and an outlet (17) for supplying the fluid to the second part (13).

4. The molding device according to claim 3, characterized in that The distributor (14) has an axial bore (18) extending at least partially along the central axis (5) and offset from the central axis, the axial bore (18) opening into the first inlet area (12) for introducing the fluid into the first portion.

5. The molding device according to any one of claims 2 to 4, characterized in that The second part (13) has, on the one hand, a second inlet region (19) at which the second part receives the fluid and, on the other hand, allows the fluid to flow away from the central axis (5) towards the outer edge (9).

6. The molding device according to any one of claims 1 to 5, characterized in that The base (4) comprises a cover (20) in which a path (22) is provided for bringing the fluid to a channel (10) by moving the fluid at least partially in the direction of the central axis (5) from an entry point (21), the channel (10) for example being in the form of a groove bored in the base (4), the cover (20) closing the groove.

7. The molding device according to any one of claims 1 to 6, characterized in that The molding device (1) also comprises a side shell extending along a central axis (5) against which the preform (3) can be pressed in order to form the side of the container (2) during blow molding.

8. A method for producing a plastic container (2) by blow-molding a preform (3), wherein: The preform (3) is placed in a molding device (1) having a central axis (5) and comprising a base (4) having a bottom (6), and then a pressurized gas is injected into the preform (3) so that it conforms to the internal contour of the molding device (1) until a container (2) is formed, the method also comprising controlling the temperature of the molding device (1) by means of a fluid, The method is characterized in that Temperature control is achieved by circulating a fluid in the molding device (1) at the base (4) along a path roughly transverse to the central axis (5), in a first stage the fluid begins to circulate in a ring around the central axis (5) at a certain distance from the central axis and the outer surface of the base (4), and then the fluid moves towards or away from the central axis (5).

9. The molding method according to claim 8, characterized in that The preform (3) has an apex (24) and is placed in the molding device (1) so that its apex (24) is approximately at the center axis (5) after stretch blow molding.

10. The method according to claim 8 or 9, characterized in that: After a first phase of circulation of the fluid in the base (4), the fluid circulates close to the central axis (5).

11. The method according to any one of claims 8 to 10, characterized in that The circulation of the fluid in the base (4) includes a phase after the first phase during which the fluid circulates outside the ring away from the central axis (5).

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