Extrusion blow-moulding machine and method for producing a hollow body

Abstract

An extrusion blow-moulding machine and a method for producing hollow bodies, in particular bottles (20), are disclosed. The extrusion blow-moulding machine comprises an extruder head (30), a blow mould (40) with a cavity (41), and a blowing mandrel (70). In order to cool the hollow body which has been blown, the extrusion blow-moulding machine has a cooling mould (60) with a cavity (61) corresponding to the finished hollow body.

Description

[0001] Extrusion blow molding machine and method for producing a hollow body

[0002] The present invention relates to an extrusion blow molding machine and a method for producing a hollow body according to the preamble of the independent claims.

[0003] Various devices and methods for producing a hollow body are known from the prior art.

[0004] Single- or multi-layer plastic containers, for example made of polyolefins, are often manufactured using an extrusion blow molding process, particularly a tube blow molding process. This process involves continuously extruding a plastic tube, which may be single- or multi-layered, using an extrusion head, also known as an extruder head. The plastic tube is inserted section by section into a mold cavity, also known as a mold cavity, of a blow molding tool, shaped into the desired form using a blowing medium introduced under excess pressure, cooled, and demolded. The blow molding tool typically consists of two blow mold halves, each of which forms one half of the mold cavity. The blow mold halves are periodically opened, closed, and reopened to insert a tube section into the mold cavity and, after inflation, demold the finished container.For inflation, a blowing mandrel is inserted into the extruded tube. This allows the container to be inflated while simultaneously creating a defined opening.

[0005] Polyolefins are typically introduced into the blow mold at a temperature of 180° Celsius, with a deviation of up to 20° K. At the end of the blow molding process, before demolding the finished plastic container, the blow molding tool must be cooled sufficiently to ensure that the shaping of the plastic material is largely complete and that no undesirable deformation can occur during further processing of the plastic container.

[0006] Polyolefins are typically demolded at approximately 60° to 80° Celsius, with the temperature at the neck and bottom still being approximately 80° to 100° Celsius.

[0007] Blow molds are typically constructed in several parts and are usually made of aluminum, steel, or even non-ferrous metals. The two mold halves of a blow mold each have a mold body in which at least one mold cavity is formed. The mold body is mounted on a base plate, usually made of steel, which is part of the closing unit of the blow molding machine. Due to the pressures that occur during the blow molding process, the base plates and the mold bodies must be relatively solid.

[0008] Considering the relatively good thermal conductivity of the individual components in blow molding tools, it is immediately apparent that a very significant effort must be put into the periodic heating and cooling of the blow molding tools in order to achieve reasonably acceptable cycle times while simultaneously producing high-quality products. It is known that the heating and cooling of the blow molding tool can be achieved using a suitable fluid, such as water, which is circulated under pressure through the channels, milled recesses, and bores of the blow molding tool. To achieve the shortest possible cycle times, the heating / cooling fluid is passed through the channels, milled recesses, and bores at relatively high pressure. To withstand these high pressures, the blow molding tool must be designed to be even more solid.However, combined with the good thermal conductivity of the materials used for the blow molding tool, this results in even greater effort for the periodic heating and cooling of the blow molding tool. Furthermore, the more massive design of the blow molding tool also increases the effort required for the periodic opening and closing of the blow mold halves.

[0009] A generic device and method are known from WO 2004 / 078457 A1. To shorten cycle times, it is proposed to use two blow mandrels and to arrange them independently of the extruder head. However, this only results in minor improvements in cycle time.

[0010] It is therefore an object of the invention to remedy at least one or more disadvantages of the prior art. In particular, an extrusion blow molding machine, also called an extrusion blow molding machine, for producing hollow bodies and preferably a corresponding method is to be provided, which enables the cycle times in the blow mold to be reduced.

[0011] This object is achieved by the devices and methods defined in the independent patent claims. Further embodiments emerge from the dependent patent claims.

[0012] An extrusion blow molding machine according to the invention for producing hollow bodies, in particular bottles, comprises an extruder head, a blow molding tool with a cavity, and a blow mandrel. For cooling the blown hollow body, the extrusion blow molding machine has a cooling mold with a cavity corresponding to the finished hollow body. In other words, the cooling mold has a contour that corresponds to the complete contour of the finished hollow body, i.e., is a negative of the finished container body.

[0013] The cooling mold is designed in particular so that the container can be subjected to a final shaping by blowing pressure. In other words, the cooling mold must completely enclose the container and also withstand increased internal pressure.

[0014] The cooling mold is intended for the final shaping of the hollow body.

[0015] The blow molding tool can also have multiple cavities, in which case the cooling mold also has multiple cavities. Accordingly, a blow mandrel is provided, which is constructed in several parts, meaning it engages multiple cavities simultaneously.

[0016] This arrangement makes it possible to divide the cooling process of the container after it has been inflated into several sections or phases. In particular, it is possible to carry out part of the cooling process outside the blow mold, namely within a separate cooling mold. Accordingly, the time during which the blow mold is occupied by the inflated hollow body can be shortened. This shortens the cycle time, allowing the blow mold to be used sooner to form another hollow body.

[0017] A separate cooling mold can also be constructed much more simply than a blow mold. This is due, on the one hand, to the fact that lower blowing pressures are required within the hollow body during cooling, meaning the cooling mold has to absorb fewer forces. Accordingly, it can be designed more easily. On the other hand, only cooling channels need to be provided on the cooling mold. Other complex equipment is eliminated.

[0018] Separate cooling is particularly advantageous because the hollow body can be removed from the blow mold before it has cooled down. This allows the blow mold to remain at a higher average temperature, reducing downtime caused by prolonged cooling or heating. Smaller temperature differences between the individual states also make the device more economical and energy-efficient.

[0019] Within the cooling mold, the warm and still soft container can be subjected to a relatively low blowing pressure so that it maintains or regains its final shape. This blowing pressure can be lower than the blowing pressure during the blowing process itself. This can be up to 10 bar, in particular 8 bar. The blowing pressure during the cooling process within the cooling mold is usually only half as high and amounts to a maximum of 6 bar, preferably only 4 bar, in particular less than 4 bar.

[0020] It can be provided that at least one further blow mandrel is provided.

[0021] If a first and a second blow mandrel are provided, hollow bodies can be inflated alternately. The blowing process is thus no longer dependent on the occupancy of the blow mandrel, but can be started independently of the occupancy of the first blow mandrel. Since a corresponding waiting time is eliminated, the provision of at least one additional blow mandrel also shortens the cycle time.

[0022] Additionally, the extrusion blow molding machine may be provided with at least one additional cooling mold. This is essentially identical to the first cooling mold.

[0023] Such an arrangement enables a further reduction in cycle time. In particular, if the cooling, or the second cooling phase in the cooling mold, takes longer than the blowing and the first cooling phase of a hollow body, a second blown hollow body can be cooled in the second cooling mold even though the first cooling mold is still occupied.

[0024] Preferably, the cooling mold, or each cooling mold, is radially movable relative to a longitudinal axis of the extruder head. The cooling mold can thus be removed from the working area relative to the extruder head. Accordingly, the hollow body can be parked at a distance from the working area for the period in which it needs to be cooled. The working area is thus free to blow another hollow body and / or to provide a second cooling mold to accommodate a second hollow body.

[0025] The longitudinal axis of the extruder head is typically defined by the extrusion direction of the extruded tube. In particular, the extruder head can be moved along the longitudinal axis. In typical use, the extruder head can therefore move up and down.

[0026] Alternatively, it can be provided that the cooling mold, or each cooling mold, is arranged to be rotatable about an axis of rotation parallel to the longitudinal axis.

[0027] The cooling mold or molds can be arranged on a rotation axis similar to a carousel, so that by rotating the carousel or the cooling molds around the rotation axis by a certain angle, a new cooling mold is located in the work area.

[0028] For example, a hollow body can be transferred to a first cooling mold, then the carousel can be moved until a second cooling mold is in the position of the former first cooling mold. A second hollow body can then be transferred to the second cooling mold.

[0029] It is also conceivable to provide two arrangements of cooling molds, each rotatable about a separate axes of rotation. In other words, the cooling molds can be arranged on two carousels, which mesh with each other like gears. The area of ​​engagement is typically located in the working area of ​​the extruder head. By synchronously rotating both carousels, a cooling mold from the first carousel and a cooling mold from the second carousel can be brought alternately into the working area. The cooling molds can then each be equipped in the working area with a blown hollow body that requires cooling.

[0030] Additionally or alternatively, it can be provided that the blowing mandrel, or each blowing mandrel, is arranged to be pivotable about a horizontal axis.

[0031] In other words, the blowing mandrel can be pivoted about an axis arranged at right angles to the longitudinal axis.

[0032] This allows the blowing mandrel to be aligned along the longitudinal axis on the one hand, and pivoted at right angles to it on the other. Accordingly, the blowing mandrel, or rather the end of the blowing mandrel, can be pivoted out of the working area.

[0033] This allows the cooling mold(s) to be statically arranged outside the work area. For example, in typical use, one cooling mold can be positioned on either side of the extruder head. By simply pivoting the blow mandrel by -90° or +90°, either of the two cooling molds can be loaded.

[0034] Additionally or alternatively, it can be provided that the cooling mold and / or the blowing mandrel, or each cooling mold and / or each blowing mandrel, is axially movable relative to the longitudinal axis of the extruder head.

[0035] This arrangement allows the cooling mold to be inserted between the open blow mold halves of the blow molding tool, and the finished blown hollow body, which requires subsequent cooling, to be transferred to the cooling mold on site. The blow molding tool is preferably designed in several parts and, in particular, has two blow mold halves. These are typically designed symmetrically. This is particularly true when the hollow body to be blown is designed rotationally symmetrically. In the case of hollow bodies that are designed asymmetrically, the blow mold halves are typically designed mirror-symmetrically.

[0036] The bottom area of ​​blow-molded hollow bodies is often curved inward at least in some areas and / or has undercuts. In such cases, the blow molding tool can have, in addition to two mold halves, an additional removable bottom, which is typically movable in the longitudinal direction, i.e., axially, so that the hollow body can be demolded without damage. However, particularly with bottles, it is possible to dispense with a movable bottom and remove bottles with only slight undercuts from the tool using so-called forced demolding.

[0037] Similarly, and for the same reasons, the cooling mold is constructed in several parts and, in particular, has two cooling mold halves. If the blow molding tool has a separate base area, a corresponding base area is also provided on the cooling mold.

[0038] A separate base area is also advantageous for hollow bodies that have been forcibly demolded, because otherwise the corresponding edges of the tool could damage the molded body when the cooling mold halves are brought together.

[0039] A further aspect relates to a method for producing a hollow body, in particular a bottle, in particular with an extrusion blow molding machine as described here. The method comprises the steps of: - extruding a tube from an extruder head,

[0040] - Inserting this extruded tube into a blow molding tool,

[0041] - Inserting a blow mandrel into the extruded tube in the blow molding tool,

[0042] - Inflating the tube into a hollow body,

[0043] - demoulding of the hollow body, characterized in that the hollow body is introduced into a cooling mould after demoulding.

[0044] This process allows the cycle time in the blow mold to be shortened. By placing the material in a separate cooling mold, part of the cooling process can be performed outside the blow mold. This frees the mold sooner, allowing another hollow body to be blown into the mold more quickly.

[0045] Preferably, the hollow body is placed into the cooling mold together with the blowing mandrel. This ensures that the neck area of ​​the hollow body is not deformed but remains dimensionally stable.

[0046] After the hollow body has been inserted into the cooling mold, it can be moved radially to its longitudinal axis. This radial movement allows the working area of ​​the extruder head to be released again. The cooling mold(s) can be moved linearly out of the working area or, for example, pivoted out of the working area around a separate rotational axis.

[0047] Additionally or alternatively, it can be provided that after the hollow body has been introduced into the cooling mold, the cooling mold is moved along its longitudinal axis. This sequence of movements also allows the cooling mold to be removed from the immediate working area of ​​the extruder head. Preferably, after the hollow body has been removed from the blow mold, another extruded tube is introduced into the blow mold and inflated to form another hollow body. This results in a corresponding reduction in cycle time.

[0048] It can be provided that at least one further cooling form is provided at the same time.

[0049] This makes it possible for the second blown hollow body to be demolded from the blow molding tool, even though the cooling process in the first cooling mold has not yet been completed and the first cooling mold is still occupied by the first blown hollow body.

[0050] Accordingly, in a further step, the second blown hollow body can be demoulded and placed into the further cooling mold.

[0051] During or after the further hollow body is blown again, the first blown hollow body can be removed from the first cooling mold and the mold can be made available again to receive a hollow body.

[0052] This measure also shortens the cycle time.

[0053] The invention is explained below with reference to schematic figures. It shows:

[0054] Figure 1 : A blow molding tool;

[0055] Figure 2 : a cooling form;

[0056] Figures 3A to 3D : individual process steps ;

[0057] Figures 4A to 4C: an alternative embodiment and the associated method steps. Figure 1 shows a blow molding tool 40 to explain the basic structure of such a blow molding tool. The blow molding tool, designated overall by the reference numeral 40, has a first blow mold half 42 and a second blow mold half 43. These are laterally displaceable relative to one another in order to periodically open and close the blow molding tool 40. Each blow mold half 42, 43 comprises a base plate 44, which forms part of a closing unit of a blow molding machine. Mounted on the base plate 44 is a molded body 45, in which one or more cavities 41 are formed as mold cavities. According to the illustrated embodiment, the molded body 45 has two mold cavities, each of which defines one half of the shape of a body of a plastic container.Since the mold cavities correspond, for the sake of clarity not both mold cavities are provided with all reference symbols, although the explanations apply to both mold cavities.

[0058] A head plate 46 is equipped with a cavity 47 for defining a neck portion of the plastic container. In the case of a blow molding tool for an extrusion blow molding machine, neck knives 48, which are only indicated in Figure 1, are also provided on the head plate 46 of the blow molding tool according to the prior art for severing an extruded plastic tube inserted into the blow molding tool 40.

[0059] A base part 49 closes off the mold cavities at the lower end of the blow molding tool 40. Venting slots 52 can be formed on the mutually facing surfaces 50, 51 of the blow mold halves 42, 43, which define a parting plane of the blow molding tool 40. Guide pins 53 are formed on one of the blow mold halves 40, which slide into guide bushings 54 of the other blow mold half 42 when the blow mold halves 42, 43 are closed. The molded body 45 has a wall surface, i.e., an inner wall 55, which forms part of the mold cavity.

[0060] The blow molding tool 40 shown in Figure 1 is configured as typically used in the prior art. A blow molding tool 40 for an extrusion blow molding machine as described herein and a corresponding method is preferably configured as described in WO 2004 / 078457 A1.

[0061] The blow molding tool is used in a position that is rotated 180° upside down from the position shown in Figure 1. An extruded tube is inserted accordingly from above through the base toward the head plate.

[0062] The blown hollow body is removed from the blow molding tool together with the blow mandrel according to the method described here. Accordingly, no neck knives 48 are provided on the head plate, but rather separate cutting knives arranged downstream of the blow molding tool 40 in the extrusion direction, so that they can be operated independently of the blow molding tool.

[0063] Figure 2 shows a cooling mold 60 with a cavity 61 corresponding to the cavity 41 of the blow mold 40. It should also be noted here that in generic use, the cooling mold is used in a position that is rotated 180° upside down from the position shown in Figure 2. The cooling mold 60 has a first cooling mold half 62 and a second cooling mold half 63, which together form the corresponding cavity 61. As can be seen, the cooling mold 60 is relatively simple in construction compared to the blow mold 40 from Figure 1 and only has cooling channels (not shown in detail here). The cooling mold 60 according to Figure 2 can also be significantly less solid, since the forces acting on the cooling mold 60 are significantly lower than the forces acting on the blow molding tool 40.

[0064] Figures 3A to 3D now show process steps for producing a hollow body as described here.

[0065] Figure 3A shows an extruder head 30 from which a tube 21 is extruded. The extruder head 30 has a longitudinal axis 31 that extends in the extrusion direction of the tube 21. The blow molding tool 40 is arranged downstream and below the extruder head 30. The blow molding tool 40 has two blow mold halves 42 and 43 and is closed in the present case. Within the blow molding tool 40 there is already a finished blow-molded hollow body in the shape of a bottle 20. Downstream of the blow molding tool 40 is a cooling mold 60 with two cooling mold halves 62 and 63, which is shown open. Between the cooling mold halves 62 and 63 there is arranged a blow mandrel 70, the end of which extends into the bottle 20. However, this is not shown in detail in the present figures.

[0066] Also shown is a second cooling mold 60' with two cooling mold halves 62' and 63', which are moved laterally and radially, respectively, relative to the longitudinal axis 31. Also visible is a second bottle 20', which is demolded from the second cooling mold 60' in this step, since it is completely cooled.

[0067] In the following figures, only the basic elements are provided with reference numerals. Accordingly, the elements mentioned in the description but not designated can be found in Figure 3A.

[0068] Figure 3B now shows the next step. The bottle 20, which has not yet completely cooled, is removed from the blow mold 40 together with the blow mandrel 70. For this purpose, the blow mold halves 42 and 43 are opened. The blow mandrel 70, together with the bottle 20, is then moved axially along the longitudinal axis 31. The cooling mold 60 is opened accordingly, so that the bottle 20 can be inserted into the cooling mold 60, or between the cooling mold halves 62 and 63.

[0069] Simultaneously with the blow mandrel 70, the extruder head 30 including the already extruded tube 21 (see Figure 3A) also moves in the axial direction along the longitudinal axis 31, so that the further extruded tube 21 can be introduced between the blow mold halves 42 and 43 of the blow molding tool 40.

[0070] Subsequently, the extruded tube 21 is severed from the container 20 with knives (not shown here), and the cooling mold 60 is closed. The cooling mold 60, together with the container 20 located therein and the blowing mandrel 70, is then displaced radially relative to the longitudinal axis 31. Simultaneously or subsequently, a second cooling mold 60', together with a second blowing mandrel 70', is brought into the working area of ​​the extruder head 30, i.e., below the blow molding tool 40.

[0071] This situation is illustrated in Figure 3C. Simultaneously with the displacement of the cooling mold 60, a low blowing pressure can be applied by the blowing mandrel 70. This blowing pressure is typically lower than the blowing pressure required for blowing the hollow body. In this case, the blowing pressure is in the range of 4 bar. This is maintained until the bottle 20 has cooled. This also gives the bottle its final shape. This step applies equally to all embodiments.

[0072] At the same time, the blow mold halves 42 and 43 of the blow molding tool 40 are closed. Before this, however, a second blow mandrel 70' is inserted into the extruded tube 21, so that a corresponding neck is formed on the container during the closing of the blow molding tool 40. With the blow molding tool 40 closed, a blowing pressure is applied by the second blow mandrel 70', so that another bottle 20' is inflated. As can be seen, a second cooling mold 60' is already positioned below the blow molding tool 40.

[0073] Figure 3D now shows the next step. A tube 21 is still being extruded in the extruder head 30. The extruder head 30 must move upwards along the longitudinal axis 31, i.e., away from the blow mold 40. Within the blow mold 40, the second bottle 20' has already partially solidified; a first phase of a cooling process has therefore already been completed. During this process, the first finished bottle 20 can be demolded from the first cooling mold 60. The process has thus essentially returned to the status described for Figure 3A, with the difference that the second cooling mold 60' is now located below the blow mold 40 and the finished container is demolded from the first cooling mold 60. The process is now continued as described for Figure 3A, only with a reversed initial configuration of the cooling molds 60 and 60'.

[0074] Figures 4A to 4C show an alternative device for carrying out the method and the corresponding method steps. The devices are essentially constructed from the same components as already described in Figure 3A. For the sake of clarity, only Figure 4A is provided with all reference numerals.

[0075] In the following figures, only the basic elements are provided with reference numerals. Accordingly, the elements mentioned in the description but not designated can be found in Figure 4A.

[0076] Figures 4A to 4C show an extrusion blow molding machine having a blow mandrel 70 pivotable about a horizontal axis. The horizontal axis is thus arranged substantially perpendicular to the longitudinal axis 31. It extends out of the plane of the page. The blow mandrel 70 can thus move to the left and right, or pivot left and right, relative to the illustration in Figure 4A.

[0077] Figure 4A shows the blow molding tool 40. This tool has two blow mold halves 42 and 43 and is closed in this case. Within the blow molding tool 40 is a fully blown hollow body in the shape of a bottle 20. A blow mandrel 70 is arranged below the blow molding tool 40, the end of which extends into the bottle 20. However, this is not shown in detail in the present figures.

[0078] Above the blow molding tool 40 is the extruder head 30 with an already extruded tube 21.

[0079] On both sides of the blow molding tool 40 there is a cooling mold 60, 60' with two cooling mold halves 62, 62' and 63, 63', which is shown open.

[0080] The bottle 20 from Figure 4A has already partially cooled. In the next step, the blow mold halves 42 and 43 are opened and the bottle 20 is removed from the blow molding tool together with the blow mandrel 70. To do this, either the blow molding tool 40 can be moved away from the blow mandrel or the blow mandrel 70 can be moved away from the blow molding tool 40. The extruded tube 21 is then severed from the container 20 using knives (not shown here), and then the blow mandrel 70 and the horizontal axis are rotated and the partially cooled bottle 20 is transferred to the cooling mold 60. This situation is shown in Figure 4B. At the same time or subsequently, the extruder head 30 is moved along the longitudinal axis 31 in the direction of the blow molding tool 40 so that the extruded tube 21 can be received between the blow mold halves 42 and 43. Subsequently, the blow mold halves 42 and 43 of the blow molding tool 40 are closed.Beforehand, however, the blow mandrel 70 is inserted into the extruded tube 21, so that a corresponding neck is formed on the container during the closing of the blow molding tool 40. With the blow molding tool 40 closed, the blow mandrel 70 applies blowing pressure, inflating another bottle. As can be seen, the second cooling mold 60' is already open and ready to receive the additional bottle.

[0081] After the additional bottle has partially cooled, the blow mold halves 42 and 43 are opened and the additional bottle is removed from the blow molding tool 40 together with the blow mandrel 70. For this purpose, either the blow molding tool 40 can be moved away from the blow mandrel or the blow mandrel 70 can be moved away from the blow molding tool 40. The extruded tube 21 is then severed from the container 20 using knives (not shown here), and the blow mandrel 70 is subsequently rotated about the horizontal axis in the opposite direction to that previously described, and the partially cooled bottle is transferred to the second cooling mold 60'. This situation is shown in Figure 4C. Simultaneously or subsequently, the extruder head 30 is moved along the longitudinal axis 31 in the direction of the blow molding tool 40 so that the extruded tube 21 can be received between the blow mold halves 42 and 43.

[0082] The first bottle 20 is then removed from the first cooling mold 60, so that it can accommodate a new bottle. The process can now begin again.

[0083] For industrial production, it is preferable to provide the individual process steps or plant components, molds in multiple versions in order to manufacture a plurality of products in one work cycle.

Claims

Patent claims 1. Extrusion blow molding machine for producing hollow bodies, in particular bottles (20), comprising an extruder head (30), a blow molding tool (40) with a cavity (41) and a blow mandrel (70), characterized in that the extrusion blow molding machine has a cooling mold (60) with a cavity (61) corresponding to the finished hollow body for cooling the blown hollow body.

2. Extrusion blow molding machine according to claim 1, characterized in that at least one further blow mandrel (70) is provided.

3. Extrusion blow molding machine according to claim 1 or 2, characterized in that at least one further cooling mold (60) is provided.

4. Extrusion blow molding machine according to one of claims 1 to 3, characterized in that each cooling mold (60) is radially movable relative to a longitudinal axis (31) of the extruder head (30).

5. Extrusion blow molding machine according to one of claims 1 to 3, characterized in that each cooling mold (60) is arranged to be rotatable about an axis of rotation parallel to the longitudinal axis (31).

6. Extrusion blow molding machine according to one of claims 1 to 3, characterized in that each blow mandrel (70) is arranged to be pivotable about a horizontal axis.

7. Extrusion blow molding machine according to one of claims 1 to 5, characterized in that each cooling mold (60) is axially movable relative to a longitudinal axis (31) of the extruder head (30).

8. Extrusion blow molding machine according to one of claims 1 to 7, characterized in that the blow molding tool (40) has two blow mold halves (42, 43).

9. Extrusion blow molding machine according to one of claims 1 to 8, characterized in that the cooling mold (60) has two cooling mold halves (62, 63).

10. A method for producing a hollow body, in particular a bottle (20), comprising the steps: - extruding a tube (21) from an extruder head (30), - introducing this extruded tube (21) into a blow moulding tool (40), - Inserting a blow mandrel (70) into the extruded tube (21) in the blow molding tool (40), - Inflating the tube (21) to a hollow body, - demoulding the hollow body, characterized in that the hollow body is introduced into a cooling mold (60) after demoulding.

11. Method according to claim 10, characterized in that the hollow body is introduced into the cooling mold (60) together with the blowing mandrel (70).

12. Method according to claim 10 or 11, characterized in that the cooling mold (60) is moved radially to the longitudinal axis after the introduction of the hollow body.

13. Method according to one of claims 10 to 12, characterized in that after demolding of the hollow body from the blow molding tool (40), another extruded tube (21) is introduced into the blow molding tool (40) and inflated to form a further hollow body.

14. The method according to claim 13, characterized in that a further cooling mold (60) is provided at the same time.

15. The method according to claim 14, characterized in that the further hollow body is demolded and introduced into the further cooling mold (60).

16. Method according to one of claims 13 to 15, characterized in that during or after the renewed inflation of the further hollow body, the cooling mold (60) is demolded and made available for receiving a hollow body.

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