STRETCHING AND COOLING ROD FOR CONTAINER FORMING
Patent Information
- Authority / Receiving Office
- MX · MX
- Patent Type
- Patents
- Current Assignee / Owner
- SIDEL PARTICIPATIONS SAS
- Filing Date
- 2023-04-12
- Publication Date
- 2026-05-19
AI Technical Summary
Existing stretch/blow molding processes face issues with poor material distribution and uneven cooling, particularly in the container bottom, leading to defects like deformation and unsatisfactory wall thickness, especially when using recycled PET which has varying heat absorption properties.
A stretching rod with a cylindrical body, a distal end featuring a tip and an annular skirt, and internal channels for controlled gas injection, ensuring precise cooling and uniform material distribution by directing cooling gas towards the container bottom.
Improves cooling control and material distribution, reducing deformation and enhancing the quality of the container bottom, allowing for faster production with reduced defects and gas consumption.
Smart Images
Figure MX434023B0
Abstract
Description
STRETCHING AND COOLING ROD FOR CONTAINER FORMING Field of Invention The present invention relates to the field of manufacturing containers by blow molding or stretch blow molding from thermoplastic preforms, such as polyethylene terephthalate (PET). More particularly, the invention relates to a stretching and cooling rod intended for use in a stretch blow molding technique for container forming. The invention also relates to a method for manufacturing containers using the stretching and cooling rod according to the invention. Background of the Invention The formation of thermoplastic containers by stretching and blowing of preforms previously heated to a temperature sufficient to soften the walls is already known. For this purpose, a forming device is used, comprising a mold with a cavity shaped like the footprint of the container to be produced. The preheated preform is placed in the cavity. Its walls then undergo biaxial stretching to conform to the mold's shape. Rezfrnn / eznz / B / YiAi Ref. 343915 is axially stretched using a stretching rod to cause axial expansion of the preform. Simultaneously with this stretching operation, a pressurized fluid is injected into the preform to cause radial expansion of the wall. This forming process is well-known. For the final container to have a perfectly molded bottom, it is preferable that the stretching rod be adjusted to ensure a satisfactory container wall thickness. Poor material distribution is a recurring defect observed in containers produced by a stretch blow molding process. It is not necessarily a matter of ensuring a constant container wall thickness, as in certain cases it may be desirable to thicken specific areas, particularly those subject to significant stress (especially near the bottom). Rather, it is a matter of ensuring that the material thickness corresponds to the container specifications, defined according to its shape and intended use. A material defect located in the center can also create hotter areas that are more prone to sagging. To refine the blown bottom structure and secure the material to the mold cavity, an additional internal cooling stage can be very useful. This stage involves cooling the bottom through the Rezfrnn / eznz / B / YiAi stretching rod, at the end of the blowing phase, for a very short time, in very localized places at the bottom. Thus, processes have been developed to promote a distribution of material adapted to demanding specifications. Furthermore, recycled PET is increasingly used in the field of container manufacturing by stretch blow molding and stretching / blow molding for environmental reasons. This material further exacerbates the problem of material distribution because it has different heat absorption properties; therefore, controlling the cooling of the resulting container is even more crucial. Furthermore, despite the improvements made to the drawing-blowing processes, there are still problems with bottom deformation after demolding the bottle, particularly due to the lack of control of the cooling phase. Document JP2001088202 proposes a stretching and cooling rod with holes specifically designed for cooling the bottom of a preform. These holes are located in the rod's body, above the tip formed at its end. The tip is designed to make contact with the bottom of the preform. Rezfrnn / eznz / B / YiAi during drawing, then slightly retracted during the cooling phase, to allow gas to escape through the holes and, by this effect, cool the bottom at the end of the blowing phase. However, in this configuration, the cooling gas escapes in a poorly controlled manner and is not precisely directed to the bottom of the resulting vessel. Summary of the Invention Current solutions are unsatisfactory and there is a need to further improve the cooling stage to obtain better quality packaging. The invention aims to solve this problem and proposes, for this purpose, a stretching rod that ensures the stretching of the preform along its axis, preventing undesirable contact between the outside of the rod and the inside of the preform body, while improving the distribution of the cooling gas, particularly on the bottom of the resulting vessel. The path of the cooling gas is controlled and verified by the use of a stretching rod according to the invention. For this purpose, the invention relates to a stretching rod for a molding unit for manufacturing a container from a preform, such stretching rod extending longitudinally, parallel to a main Y axis, comprising - a body of cylindrical or tubular shape; Rezbnn / eznz / B / YiAi - a distal end extending from such a body; at least one internal channel to allow the circulation of a cooling gas to such distal end; - a peak located at the distal end of the extension rod; - a point protruding from such a summit and a plurality of holes, such holes being in fluid communication with such an inner channel and being distributed around the point on such a summit. Such an extension rod is characterized in that it comprises an annular skirt in the extension of such a body, at the height of the distal end, such skirt having a height lower than the height of the tip. Advantageously, the edges of the skirt and / or the end of the protruding tip of the stretching rod are rounded. According to some models, the outer body and the skirt are a single piece. Advantageously, the tip of the stretching rod is conical in shape. In some modalities, the peak extends orthogonally to the main Y axis. In some models, the holes are oriented outwards in the direction of the main Y axis, and this at an angle between 1 and 50 degrees, preferably in Rezfrnn / eznz / B / YiAi an angle of 30 degrees. Advantageously, the annular skirt of the stretching rod has a toothed shape. In some forms, the annular skirt of the stretching rod has a toothed shape with rounded and convex ridge edges and concave channel edges. Advantageously, the top of the stretching rod features a recess in the shape of an inner rosette. The invention also relates to a method for manufacturing a container by stretch blow molding using the stretch rod according to the invention, comprising at least the following steps: - placing a preheated preform in a blow mold which, in the closed position, has a mold cavity that forms the footprint of the container to be blown; - close such a blow mold; - blowing such a preform into the blow mold through a blow nozzle and, substantially simultaneously, a stage of stretching such a preform by inserting the stretching rod inside such a preform, supporting it against the bottom of such a preform to facilitate the axial elongation of such a preform; - cooling the interior of such a formed container by injecting air through such a stretching rod, provided with such a plurality of provided holes Rezfrnn / eznz / B / YiAi for this purpose. - lift such a stretching rod; - extract such a blown container by opening such a blow mold. Brief Description of the Figures The invention will be better understood thanks to the following description, which is based on possible embodiments, explained in an illustrative and in no way limiting manner, with reference to the attached figures, in which: Figure 1 schematically represents a simplified top view of one modality of a rotary-type molding machine, illustrating in particular the molding units (without the blowing and stretching means) distributed around a carousel, such blowing units, depending on their relative position with respect to the inlet or outlet of the machine, being in the open position or in the closed position; Figure 2 schematically represents a partial perspective view of one of the molding units of the machine according to the modality of Figure 1, illustrating in particular, outside the unit in the open position, an exploded view of a mold made in three parts, especially two mold halves and a mold bottom; Figure 3 schematically represents a view through a vertical median longitudinal section of a unit Rezfrnn / eznz / B / YiAi of machine molding, during a first stage of a cycle for blowing a container, showing in particular the insertion of the distal end of the rod into a preform enclosed within a mold; Figure 4 schematically represents a view similar to Figure 3, during a further stage after the end of the blowing cycle, showing in particular the distal end of the rod inserted into the blown container and extending to the bottom of such blown container; Figure 5 schematically represents a view similar to Figure 3, during a later stage of the blowing cycle at the time of cooling, showing in particular the protruding tip of the stretching rod; Figure 6 schematically represents a detailed view of Figure 3, with the stretching rod positioned at the level of the bottom of the preform; Figure 7 schematically represents a perspective view of a modality of the distal end of the stretching rod, showing in particular an annular skirt that has rounded edges; Figure 8 schematically represents a view according to a median longitudinal cut of the first modality of Figure 7; Figure 9 schematically represents a view Rezfrnn / eznz / B / YiAi according to a median longitudinal cut of a second modality of the distal end of the stretching rod, showing in particular the annular skirt having holes emerging through the top with a direction according to an angle relative to the longitudinal axis of such rod, and also the annular skirt with straight and beveled edges; Figure 10 schematically represents a view according to a median longitudinal cut of a third modality of the distal end of the stretching rod, showing in particular the annular skirt which has a toothed shape with rounded and convex ridge edges and concave hollow edges; Figure 11 schematically represents a view according to a median longitudinal cut of a fourth modality of the distal end of the stretching rod, showing in particular the annular skirt with a convergent profile from the body of such rod towards its distal end. Figure 12 schematically represents a side view of a modality of the distal end of the stretching rod, showing in particular a skirt with an annular edge inscribed in the same plane, as well as the tip and the top with dotted lines; Figure 13 schematically represents a side view of yet another modality, showing a skirt with straight, serrated edges, with ridges and valleys; Rczbnn / cznz / B / YiAi Figure 14 schematically represents a side view of a modality, showing a skirt with rounded serrated edges; and Figure 15 schematically represents a perspective view of a modality of the distal end of the stretching rod, showing in particular a rosette-shaped recess at the level of the top. Detailed Description of the Invention In the rest of the description, elements with identical structure or analogous functions will be designated with the same reference. The invention is designed to be implemented in a container manufacturing facility 2. Such facility normally comprises a molding machine as shown in Figure 1, comprising at least molding units 18, each molding unit 18 carrying at least blowing means incorporating a stretching rod 1, such mold 14 comprising at least two half-molds 140 each comprising an inner molding face and respectively mounted on supports 142 movable about a Y axis, between at least an open position and a closed position of the molding unit 18, wherein such inner faces of such at least two joined half-molds 140 delimit from each other a molding cavity 15 of the container 2. In practice, the blow molds 14 are distributed circularly, in the form of a carousel 170, as shown Rezfrnn / eznz / B / YiAi is shown in Figure 1, and they are topped by respective blow molding installations. In practice, as can be seen in Figure 2, the body of the blow molding installation always extends substantially vertically above the mold and substantially coaxial with the molding cavity 15 of the blow mold 14. Figure 2 schematically represents a perspective view of one of the molding units 18 of the machine according to the modality of Figure 1, illustrating in particular, outside the unit in the open position, an exploded view of a mold 14 made in three parts, especially, two half-molds 140 and a bottom of the mold 141. All these elements are well known to experts in the art and are not described in detail for a better understanding of the invention. Reference is made to Figure 3, which shows a first embodiment of a rod 1 according to the invention, in partial longitudinal section, which is implemented with a preform 3 of PET or recycled PET, intended to be stretched and blown in the blow molds 14 of an installation briefly described above, to form a container 2, such as a bottle. In Figure 3, the stretching rod 1 is in the high position and in the process of being inserted into the preform 3. Rod 1 is designed to be mounted on the body of the Rezfrnn / eznz / B / YiAi blow molding installation also mentioned above. Such a stretching rod 1 extends longitudinally, parallel to the main Y axis. The stretching rod 1 according to the invention is a hollow stretching rod, which then performs a dual function: a stretching function on one hand and a container cooling function on the other. To do this, it has a first end called the proximal end (not shown) that can be fixed to a displacement device inside the manufacturing installation. As can be seen in Figure 6, the preform 3 conventionally comprises an elongated tubular body, on the Y axis, limited by a wall 31 attached at the top to a threaded neck 32 and at the bottom to a substantially hemispherical bottom 30. Between the neck 32 and the body of the preform, a radial collar 33 protrudes outwards from the preform 3. In general, the preform 3 illustrated in figure 6 has a symmetry of revolution around its Y axis. When the preform is placed in the blow molding installation, the Y-axis of rod 1 is substantially coincident with the axis of revolution of preform 3. In what follows, the axis of rod 1 or that of preform 3 will be designated in the same way. What follows will be described as vertical Rezfrnn / eznz / B / YiAi any direction parallel to the axis of revolution of the rod and as transverse any direction perpendicular to the axis of revolution of the rod. As shown in Figure 3 or Figure 4, the stretching rod 1 comprises a cylindrical or tubular body 4. In some embodiments, the body 4 of the stretching rod 1 may have a shoulder, i.e., two longitudinal sections with two different diameters. This is particularly advantageous for blowing small-diameter preforms. The body 4 also comprises a central internal channel 6 extending axially and communicating with a plurality of orifices 9 through which a cooling gas 10, in particular air, is injected into the interior of the fabricated container 2 for cooling purposes. The orifices 9 are therefore in fluid communication with the internal channel 6. In the extension of the body 4, at the level of the distal end 5, the stretching rod 1 comprises a peak 7. A tip 8 projects from this peak 7. As shown in Figure 7, the stretching rod 1 further comprises an annular skirt 11 in the extension of its body 4. Figure 4 schematically represents another stage of a blowing cycle, in which the draw rod 1 is in the lowered position and therefore placed in the Rezfrnn / eznz / B / YiAi bottom of preform 3 during the blowing stage. During this stage, preform 3 becomes a container 2. Figure 5 schematically represents one modality of another stage of a blowing cycle, in which the draw rod 1, still in the lowered position, performs the cooling stage, called the sweep phase, of the vessel 2 thus formed by injecting the cooling gas 10. The cooling gas 10 will then pass through the internal channel 6 of the draw rod 1 to diffuse locally and precisely at the bottom of the vessel 2. The injection of the cooling gas 10 is shown as arrows in Figure 5. In some embodiments, and as shown in Figure 7, the diameter of the annular skirt 11 is equal to the diameter of the body 4 of the stretching rod 1. In this advantageous configuration, the cooling gas 10 is directed in a very localized manner. In some versions, the outer body 4 and the annular skirt 11 are obtained as a single piece. In other words, they form one and the same piece. According to other models, the outer body 4 and the annular skirt 11 are two separate parts. The structural modifications of the draw rod 1 have the advantage of directing the cooling gas 10 towards the bottom of the vessel 2, throughout its Rezfrnn / eznz / B / YiAi lower surface, and thus improve the cooling stage. Figure 7 shows an embodiment in which the orifices 9, communicating with the internal channel 6, are arranged and distributed on the top 7, around the point 8. The orifices 9 allow the injection of the cooling gas 10 into the bottom of the blown vessel. The orifices 9 are arranged on the top 7, and around its entire circumference, thus allowing the injection of the cooling gas 10 from the internal channel 6 into the interior of the blown vessel 2. The holes 9 are, for example, cylindrical in shape and preferably have a diameter of between 0.3 and 3 millimeters (mm). They can also have another shape, for example, an oblong shape. According to a preferred embodiment, the injection surface area is between 3 and 6 square millimeters (mm²) and does not exceed 20 square millimeters (mm²). The injection surface area corresponds to the sum of the diameters of the holes 9. This represents the amount of cooling gas 10 that can be injected thanks to the configuration of the rod 1, which comprises holes 9 that act as restriction holes. Thus, thanks to the invention, it is possible to achieve internal cooling of the formed vessel 1 while minimizing the consumption of cooling gas 10. The stretching rod 1, in fact, has a very low dead volume and an optimized design for the Rezfrnn / eznz / B / YiAi internal cooling of a blown container 2. The stretching rod 1 therefore has a plurality of holes 9 arranged at the top 7. The protruding point 8 can have any shape. In particular, such a point 8 can be conical, rounded conical, ovoid, hemispherical, etc. According to a preferred embodiment, as depicted in Figure 7, the peak 7 is perpendicular to the body 4 of the draw rod 1. This allows for better distribution and control of the cooling gas 10, which then escapes uniformly through the holes 9. Figure 8 schematically represents a midsectional view of one embodiment of the distal end of the stretching rod 1, showing in particular an annular skirt 11 with rounded edges and a cylindrical tip 8. In this embodiment, the edges 12 of the annular skirt 11 are rounded. This is particularly advantageous because it prevents any risk of breakage if these edges 12 come into contact with the wall of the preform 3, for example, during the stretching phase. This variant of rounded edges 12 of the skirt 11 can also be applied to other embodiments of the invention. In this configuration, the annular skirt 11 has the same diameter as the diameter of the body 4 of the extension rod 1. On the top 7 are arranged, around Rezfrnn / eznz / B / YiAi the protruding tip 8, five holes 9. Furthermore, as shown in Figure 8, the annular skirt 11 has a height 110 less than the height 80 of the tip 8, such that the tip 8 protrudes from the annular skirt 11. In other words, the distal end of the extension rod 1 is formed by the tip 8, and the annular skirt 11 is an extension of the body 4 outwards with respect to the top 7. This allows the controlled direction of the cooling gas 10 as it exits the inner channel 6 through the orifices 9. In a preferred embodiment, the height 110 of the annular skirt 11 is less than the height 80 of the tip 8 by a value between 0.5 and 4 millimeters (mm), even more preferably by a value of 1 mm. In some forms, the height 110 of the annular skirt 11 varies around its circumference. For example, the annular skirt 11 may have serrated or scalloped edges, and therefore have gaps and ridges, as shown in Figure 13. However, in this case, the height 110 remains less than the height 80 of the tip 8. Figure 8 schematically represents a view according to a mid-longitudinal section of the first modality of Figure 7. The inner channel 6 is divided into different sections to flow into the holes 9. The cooling stage is an additional stage in Rezfrnn / eznz / B / YiAi describes a manufacturing process for PET and recycled PET (rPET) containers. The cooling gas flow 10 is shown schematically in Figure 5 using arrows. This cooling stage specifically reduces the internal temperature of the resulting container and is intended to limit heat transfer from the inside to the outside after the container 2 has exited the mold. This also helps limit bottom collapse, which generally has a negative impact on stress, increasing the risk of rejects. In fact, a bottom with too high a temperature will tend to sag during the exit stage. The resulting container 2 may then potentially have leaks or other defects.The presence of the annular skirt 11 according to the invention has the advantage of considerably improving the cooling stage by amplifying the action of the injected cooling gas 10, which is directed precisely where its presence is required. This allows for a considerable improvement in the cooling stage of the resulting vessel 2, and thus achieves optimal cooling, even when, for speed reasons, the duration of the cooling stage must be very short. In some modalities, as shown in the figure 9, the holes 9 are oriented obliquely, outwards in the direction of the main Y axis, towards the bottom Rezbnn / eznz / B / YiAi of the preform with a deviation of 1 to 50 degrees. In a preferred embodiment, the 9 holes are turned outwards in the direction of the main Y axis, with a deviation of 30 degrees. The orientation of the holes allows the cooling gas 10 to be distributed evenly towards the bottom of the preform 3 and therefore towards the bottom of the resulting container 2, i.e., over its entire surface. Furthermore, this further improves the cooling of the bottom, where the highest temperatures are found, and where stress zones can develop due to its sagging. In a preferred embodiment, the skirt 11 has rounded edges and the rod holes 9 are oriented at an angle. In some versions, the annular skirt 11 of the extension rod 1 has straight and beveled edges. This version is illustrated in Figure 9. In a modality illustrated in Figure 10, the annular skirt 11 has a toothed shape with rounded, convex crest edges and concave hollow edges. In some embodiments where the annular skirt 11 has ridges and valleys, the holes 9 may be aligned with either a valley or a ridge. According to a preferred embodiment, the holes 9 are aligned with a ridge, so Rezfrnn / eznz / B / YiAi concentrate the cooling gas at the bottom of container 2. In another variant, as illustrated in Figure 11, the annular skirt 11 has a converging diameter from the body 4 of the rod 1 towards the protruding tip 8. In other words, its diameter decreases towards the free end, and therefore the annular skirt 11 has a narrow shape. The annular skirt 11 has a cross-section that decreases from the peak 7 to its distal free end. According to another variant, not shown, the diameter of the annular skirt 11 is greater than the diameter of the body 4 of the extension rod 1. The annular skirt 11 then has a flared shape. By flared shape is meant a shape whose cross-section increases. Thus, a flared free end of the annular skirt 11 means that the end of such a skirt has a cross-section that increases from the top 7 to its free end. Figure 12 shows another view of rod 1 according to the invention, with a skirt 11 having an annular edge inscribed in the same plane, as well as the tip 8 and the top 7 with dotted lines. Figures 13 to 15 show variations of a type of annular skirt 11, which features gaps and ridges. Figure 13 shows a skirt 11 with straight edges Rezfrnn / eznz / B / YiAi dentatos, con crestas y valles, con una altura de la fladón siempre menos al altura de la punta 8. Figure 14 shows a modality in which skirt 11 has serrated rounded edges. Figure 15 shows an embodiment where the skirt 11 has smooth edges of constant height, but where the peak 7 has a recess in the shape of an inner rosette. The inner rosette is centered in the recess of peak 7 with respect to point 8 and extends over the recess of peak 7 to the edges of the skirt 11. Advantageously, it can be hollow at peak 7. According to other embodiments, the inner rosette has edges. In this way, the skirt 11 and the edges of the inner rosette form a double wall. According to some embodiments, the edges of the inner rosette have a height less than or equal to the height 110 of the skirt 11. According to one variant, the edges of the inner rosette have a height less than the height 80 of the tip 8. This embodiment advantageously allows the cooling gas 10 to be channeled and further improves its direction towards the bottom of the vessel 2. Advantageously, each hole 9 is located at the level of a top portion of an inner rosette branch. The invention also relates to a method for manufacturing a container 2 by stretch blow molding using the stretch rod 1 described above. The manufacturing process according to the invention Rezfrnn / eznz / B / YiAi comprises at least the following stages: - place a preheated preform 3 in a blow mold 14 which, in the closed position, has a mold cavity 15 that forms the footprint of the container 2 to be blown; - close such blow mold 14; - blowing such preform 3 into the blow mold 14 through a blow nozzle 16 and, substantially simultaneously, a stage of stretching such preform 3 by inserting the stretching rod 1 into the interior of such preform 3, supporting it against the bottom 30 of such preform 3 so as to facilitate the axial elongation of such preform 3; - cooling the interior of such a container 2 thus formed by injecting a cooling gas 10, normally air, through such a stretching rod 1, provided with a plurality of holes 9 provided for this purpose; - raise such a stretching rod 1; secure the blown container 3 by external securing means; - open such a blow mold 14. Figure 1 shows a top view schematically representing one type of rotary molding machine, illustrating the molding units 18 (without the blowing and stretching means) distributed circumferentially on the carousel 170, and which, depending Rezfrnn / eznz / B / YiAi of their relative position with respect to the machine's entrance or exit, are in the open or closed position. A container 2 is manufactured by blowing a hot preform 3 into a mold 14 of a molding unit 18 of the facility using at least one pressurized fluid, usually air. In one exemplary embodiment, the manufacture of the containers 2 is carried out by draw-blow molding. The blow molding means advantageously incorporate at least one draw rod 1. The extension rod 1 is axially driven, along the Y axis, in displacement by the associated drive means (not shown). The stretching rod 1 is therefore mounted to slide axially to be inserted into the interior of the preform 3 through the opening radially delimited by its neck 32, leaving an annular space free between the neck 32 and the rod 1 to allow the passage of the blowing fluid. The extension rod 1 is mounted axially between at least a first high position and a second low position. In the first position, rod 1 extends out of mold 14, and in the second position, called the low position, rod 1 moves downwards to stretch Rezfrnn / eznz / B / YiAi axially the preform 3 inside the mold 14, when the blowing is carried out. Figures 3 to 5 illustrate some of the stages in the manufacture of a vessel 2 and the different positions of the stretching rod 1 during these stages. Therefore, a first stage, as seen in Figure 3, refers to the introduction of a preform 3 into a blow mold 14. The preform 3 has been preheated to a temperature above the glass transition temperature of the material (which is around 80 °C in the case of PET). Once preform 3 is in position and mold 14 is closed, as shown in figure 4, the stretching rod 1 is inserted into the inside of preform 3, until it reaches the lower position, i.e., it is placed at the bottom of preform 3. In a preferred embodiment, the low position of the stretching rod 1 corresponds to a position where the tip 8 touches the bottom of the preform 3. In other modalities, the low position of the stretching rod 1 corresponds to a position in which the tip 8 is slightly behind the bottom of the preform 3. Substantially simultaneously with the insertion of the stretching rod 1 into the preform 3, comes the blowing, or blow-stretching, stage, during which Rezfrnn / eznz / B / YiAi injects a fluid (for example, air) into the preform 3, first at an average pressure called pre-blowing pressure, between 5 bar and 15 bar, while moving the stretch rod 1 from its high position to its extended low position. The blow molding stage ends with a momentary increase in pressure to a high pressure, higher than the pre-blow pressure, to press the material firmly against the cavity 15 of the blow mold 14 and thus imprint the shape of the container 2 on it, as shown in figure 4. The blow pressure is greater than or equal to 15 bar, and for example from around 35 to 40 bar. The stretching rod is held in the extended position to prevent any unintentional slippage of the material on the bottom of the mold until the pressure in the container has reached the blowing pressure. This is followed by a cooling stage carried out by injecting a cooling gas 10 into the bottom of the vessel 2 thus formed. The stretching rod 1 is then in the lowered position, as shown in Figure 5. According to some embodiments, the cooling stage, also called the sweeping stage, consists of accelerating the cooling of vessel 2 from the inside. In one embodiment illustrated in Figure 5, the draw rod 1, in the lowered position, performs the cooling stage. Rezbnn / eznz / B / YiAi gas outlet 10 is represented by arrows. In some embodiments, the stretching rod 1 moves axially within the molding cavity 15 during the cooling stage to perform an axial sweep of the molding cavity 15, for example from top to bottom and vice versa, following a predetermined course. In some variants, the stretching rod 1 is selectively driven in rotation to perform a circular sweep of each molding cavity 15 of the molds 14 cooled by means of at least one cooling gas 10. The extension rod 1, for example, is continuously actuated on itself to perform a 360° sweep or, alternatively, sequentially. Advantageously, the rotary drive of the stretching rod 1 occurs in combination with the axial displacement of such rod, the assembly being controlled by selective control of the drive means. Finally, at the end of the cooling stage, mold 14 is opened and the formed container 2 is removed, thus completing the cycle. A new cycle can then begin with the introduction of a new preform 3. The use of a stretching rod 1 according to the Rczbnn / cznz / B / YiAi invention allows for better control of the cooling stage. Thanks to this improved control, it is possible to increase blowing rates while limiting heat diffusion from the inside to the outside. Furthermore, the improved cooling of the bottom of vessel 2 helps to limit the risk of sinking. Furthermore, the use of such a stretching rod 1 offers greater flexibility in the use of preforms, particularly those whose shape does not perfectly match that of a bottle. Finally, it has been verified that the use of the stretching rod 1 according to the invention allows for accelerated cooling of the bottom 30 of the preform 3, while simultaneously reducing the number of unsatisfactory quality containers 2. This is directly related to the design of the stretching rod 1, which now comprises an annular skirt 11, enabling the precise and controlled direction of the cooling gas 10 towards the bottom of the container 2 thus formed. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.
Claims
CLAIMS Having described the invention as above, the following claims are claimed as property: 1.A stretching rod for a molding unit for manufacturing a container from a preform, the stretching rod extending longitudinally, parallel to a principal Y-axis, comprising: - a cylindrical or tubular body; - a distal end in the extension of said body; at least one internal channel to permit the circulation of a cooling gas to said distal end; - a peak located at the distal end of the stretching rod; - a tip projecting from said peak; and - a plurality of holes, said holes being in fluid communication with the internal channel and distributed around the tip at said peak; characterized in that it comprises an annular skirt in the extension of said body, at the level of the distal end, the skirt having a height less than the height of said tip.
2. The extension rod according to claim 1, characterized in that the edges of said skirt and / or the end of said tip are rounded. Rezfrnn / eznz / B / YiAi 3. The extension rod according to claim 1 or 2, characterized in that the outer body and the skirt are of a single piece.
4. The stretching rod according to any of claims 1 to 3, characterized in that the tip has a conical shape.
5. The extension rod according to any of claims 1 to 4, characterized in that the top extends orthogonally with respect to the main Y axis.
6. The stretching rod according to any of claims 1 to 5, characterized in that the holes are oriented outwards in the direction of the main Y axis, and this from an angle between 1 and 50 degrees, preferably an angle of 30 degrees.
7. The extension rod according to any of claims 1 to 6, characterized in that the annular skirt has a toothed shape.
8. The stretching rod according to claim 7, characterized in that the annular skirt has a toothed shape with rounded, convex ridge edges and concave hollow edges.
9. The stretching rod according to any of claims 1 to 8, characterized in that the top has an inner rosette-shaped recess.
10. A method of manufacturing a Rezfrnn / eznz / B / YiAi container by stretch blowing using the stretch rod according to claims 1 to 9, characterized in that it comprises at least the following steps: - placing a preheated preform in a blow mold having, in the closed position, a mold cavity forming the footprint of the container to be blown; - closing such blow mold; - blowing such preform into the blow mold through a blow nozzle and, substantially simultaneously, a step of stretching such preform by inserting the stretch rod into such preform, bearing it against the underside of such preform to facilitate axial elongation of such preform; - cooling the interior of such container thus formed by injecting air through such stretch rod, provided with such a plurality of holes provided for this purpose;- lift such a stretching rod; - extract such a blown container by opening the Rezfrnn / eznz / B / YiAi blow mold.;