WO2003055665A1

WO2003055665A1 - Method and device for tempering preforms

Info

Publication number: WO2003055665A1
Application number: PCT/DE2001/004714
Authority: WO
Inventors: Peter Rose
Original assignee: Sig Corpoplast Gmbh & Co. Kg
Priority date: 2001-12-13
Filing date: 2001-12-13
Publication date: 2003-07-10
Also published as: AU2002226293A1; DE10197198D2

Abstract

Disclosed are a method and a device for tempering preforms (1) made of a thermoplastic material. After being tempered inside a blowing mould (34, 37, 51), the preforms (1) are reshaped into a container (13) by means of a pressurized medium. The preforms are impinged upon at least temporarily by electromagnetic radiation having a frequency ranging from 1 MHz to 100 GHz. The preforms are guided past an electrode generating the electromagnetic radiation during at least part of the tempering time. An electrode-shaped heating element is arranged at least in some areas next to a transport path of the preforms.

Description

Method and device for tempering preforms

The invention relates to a method for tempering preforms made of a thermoplastic material which, following their tempering within a blow mold, are shaped into a container by the action of a medium under pressure, in which the preforms are at least temporarily exposed to electromagnetic radiation which has a frequency in the range of 1 MHz to 100 GHz.

The invention further relates to a device for tempering preforms made of a thermoplastic material, which is provided with at least one heating element that as a Radiation generator is formed, the radiation of which at least partially has electromagnetic waves with a frequency in the range from 1 MHz to 100 GHz.

In the case of container molding by the action of blowing pressure, pre-tempered preforms made of a thermoplastic material, for example preforms made of PET (polyethylene terephthalate), are fed to different processing stations within a blow molding machine. Typically, such a blow molding machine has a heating device and a blowing device, in the area of which the pre-tempered preform is expanded into a container by biaxial orientation. The expansion takes place with the aid of compressed air, which is introduced into the preform to be expanded in a controlled manner. The procedural sequence for such an expansion of the preform is explained in DE-OS 43 40 291.

The basic structure of a blow molding station for container formation is described in DE-OS 42 12 583. Options for tempering the preforms are explained in DE-OS 23 52 926.

The preforms and the blown containers can be transported within the blow molding device with the aid of different handling devices. The use of transport mandrels on which the preforms are attached has proven particularly useful. The preforms can also be handled with other support devices. The use of gripping pliers for handling preforms and the use of expanding mandrels that are used to hold them in one Mouth area of the preform are also included in the available designs.

The handling of the preforms, which has already been explained, takes place on the one hand in the so-called two-stage process, in which the preforms are first produced in an injection molding process, then stored temporarily and only later conditioned in terms of their temperature and blown into a container. On the other hand, it is used in the so-called one-step process, in which the preforms are suitably tempered and then inflated immediately after their injection molding manufacture and sufficient solidification.

Different embodiments are known with regard to the blowing stations used. In the case of blowing stations which are arranged on rotating transport wheels, a book-like opening of the mold carriers can often be found. However, it is also possible to use mold carriers which are displaceable relative to one another or guided in a different manner. In the case of stationary blow molding stations, which are particularly suitable for accommodating a plurality of cavities for forming containers, plates which are arranged parallel to one another are typically used as mold carriers.

The preforms are heated in a two-stage process and the corresponding temperature profiling is carried out when the one-stage process is carried out, using infrared emitters. With such infrared emitters, relatively high amounts of energy can be introduced into the preforms in a short time. Due to the efficiency of the infrared emitter however, a considerable amount of energy is released to the environment of the temperature control device or the blow molding machine. The resulting greatly reduced efficiency leads to relatively high energy costs.

It is also already known to carry out heating of the preforms at high frequency, since with such heating a much better efficiency can be achieved. A device for performing high-frequency heating is described, for example, in EP-OS 0 849 067. However, the implementation of high-frequency heating leads to a number of technical problems. On the one hand, care must be taken to ensure that an environment is adequately shielded from high-frequency radiation. According to the prior art, sleeve-like electrodes are therefore used, in which the preforms are inserted. Counter electrodes are formed by a metal rod that is inserted into the preforms. This construction, which is also described, for example, in EP-OS 0 849 067, enables a very effective shielding of an environment from high-frequency radiation, but the required handling means that only a relatively small number of preforms are tempered per unit of time can. For this reason, heating devices of this type have so far not been usable for use in connection with high-performance blow molding machines.

The object of the present invention is therefore to improve a method of the type mentioned in the introduction in such a way that the temperature control of a large number of preforms per unit of time is supported.

This object is achieved in that the preforms are guided past an electrode generating the electromagnetic radiation for at least part of the duration of their temperature control.

Another object of the present invention is to construct a device of the type mentioned in the introduction in such a way that a high production capacity is provided.

This object is achieved in that the heating element is arranged at least in some areas next to a transport path of the preforms.

The arrangement of the heating element next to the transport path of the preforms and the resulting bypassing of the preforms to the electrode generating the electromagnetic radiation enables both good shielding and the heating of a relatively large number of preforms per unit of time to be achieved. It is not necessary to insert the preforms into a heating device by means of a lifting movement and to remove them again, the heating device can instead be arranged in a stationary manner and the preforms can be easily guided past. The heating of the preforms is determined by coordinating the transport speed, the length of the temperature control section and the radiation energy provided per unit area.

In particular, it is thought of using the heating

High frequency in a range from 10 MHz to 3 GHz. A frequency range from 10 MHz to 100 MHz is particularly preferred. To support a high production rate, it is proposed that the preforms be continuously moved past the electrode.

When implementing devices with lower production output, it is also possible for the preforms to be moved past the electrode step by step.

To avoid complicated positioning devices for the electrodes, it is proposed that an electrode inserted into at least one of the preforms is moved together with the preform.

A highly effective shielding with a simple geometric design is provided in that the preforms are enclosed in a tunnel-like manner by the electrode-like heating element during at least part of their transport path.

To support the gentle transport of the preforms, it is proposed that the preform be held by a support element.

In particular, it proves to be expedient for the preform to be placed on a support element.

Another variant is that the preform is held like a pair of pliers by the support element.

To avoid mechanical stress on the outside of the preform, it is also possible for the support element to be inserted at least in regions into an opening of the preform. A uniform and intensive heating of the preforms is supported in that a counterelectrode can be positioned within the preform, at least in some areas.

A simplified drive system with electrodes movably guided in the direction of the transport path can be achieved in that the counterelectrode is arranged to be movable together with the support element along at least part of the transport path of the preform.

A simple path of movement of the preforms along their transport path can be provided in that the electrode-shaped heating element is designed like a tunnel.

A temperature profile of the preforms in the direction of their longitudinal axis can be supported by the fact that for the heating of the preforms along at least part of the transport path, stick electrodes are arranged which are arranged opposite one another.

An advantageous design for generating electromagnetic fields is that the stick electrodes are cylindrical.

A simple temperature profiling of the preforms in the direction of their longitudinal axis is supported in particular by the fact that at least two stick electrodes are arranged one above the other in the region of electrode holders transversely to their longitudinal direction.

To support an optimal material distribution during a blow deformation of the preforms proposed that the preforms are provided with a temperature profile in the direction of their preform longitudinal axis before they are fed to the tunnel-like heating element.

Temperature profiling is supported in that a temperature profiling of the preforms is carried out using stick electrodes.

High field strengths in temperature profiling and the resulting short heating times can be achieved by inserting a rod-shaped counterelectrode into the preforms when performing the temperature profiling.

An advantageous geometrical arrangement consists in the fact that when performing temperature profiling of the preforms, rod electrodes and counter electrodes which are positioned in a crossed manner relative to one another are used.

To specify an intensity of the field strength acting, it is proposed that the stick electrodes be positioned relative to a longitudinal axis of Vorfor to specify a respective profiling field strength.

To specify a temperature profile to be achieved, it is proposed that at least two stick electrodes be controlled differently relative to one another.

An equalization of the electromagnetic field and an increase in the field strength can be achieved in that transverse electrodes are transported through the tunnel-shaped electrodes together with the preforms. To support continuous heating of the preforms, it is proposed that the transverse electrodes be positioned so that they can be positioned.

To simplify mechanical control, it is proposed that the transverse electrodes be positioned together with the counter electrodes.

Exact adherence to specified movement profiles can be achieved by positioning the transverse electrodes in a curve-controlled manner.

Another possibility for specifying a temperature profile ■ is that an uneven profiling field is generated by using a profiled counterelectrode.

Exemplary embodiments of the invention are shown schematically in the drawing. Show it:

1: A perspective view of a blow molding station for the production of containers from preforms,

2 shows a longitudinal section through a blow mold in which a preform is stretched and expanded,

3: a sketch to illustrate a basic structure of a device for blow molding containers,

4: a vertical section through a preform within a tunnel electrode and with an inserted counter electrode, 5: a vertical section through a preform, which is positioned between two heating units, each of which is equipped with stick electrodes,

6 shows a perspective illustration of a preform in the region of a tunnel-shaped electrode, a counterelectrode being introduced into the preform shown cut in the vertical direction,

7: a diagram to illustrate the dependence of a heating time for PET preforms when exposed to high frequency within a tunnel electrode without temperature compensation,

8: a diagram to illustrate the course of a heating time for PET preforms following the heating with the tunnel electrode when exposed to high frequency when using parallel stick electrodes without carrying out temperature compensation,

9: a diagram to illustrate the dependence of the field strength and distance in the case of parallel stick electrodes without dielectric,

10: a representation similar to FIG. 5, but in which, however, a rod inserted into the preform is used as the counter electrode, 11: a side view of a profiled inner electrode

and

Fig. 12: a schematic representation of a tunnel electrode, in which transverse electrodes are transported together with the preforms.

The basic structure of a device for shaping preforms (1) into containers (13) is shown in FIG. 1 and in FIG. 2.

The device for forming the container (13) essentially consists of a blow molding station (33) which is provided with a blow mold (34) into which a preform (1) can be inserted. The preform (1) can be an injection molded part made of polyethylene terephthalate. In order to enable the preform (1) to be inserted into the blow mold (34) and to enable the finished container to be removed, the blow mold (34) consists of mold halves (35, 36) and a base part (37) which is lifted by a lifting device (38). is positionable. The preform (1) can be held in the area of the blowing station (33) by a transport mandrel (39) which, together with the preform (1), passes through a plurality of treatment stations within the device. However, it is also possible to insert the preform (1) directly into the blow mold (34), for example using pliers or other handling means.

A connection piston (40) is provided below the transport mandrel (39) to enable a compressed air supply line. arranged, which supplies the preform (1) with compressed air and at the same time seals relative to the transport mandrel (39). In the case of a modified construction, it is in principle also conceivable to use fixed compressed air supply lines.

The preform (1) is stretched using a stretching rod (41) which is positioned by a cylinder (42). In principle, however, it is also conceivable to carry out a mechanical positioning of the stretching rod (41) via cam segments which are acted upon by tapping rollers. The use of curve segments is particularly expedient when a plurality of blowing stations (33) are arranged on a rotating blowing wheel. The use of cylinders (42) is expedient if there are blowing stations (33) arranged in a fixed position.

In the embodiment shown in Fig. 1, the stretching system is designed such that a tandem arrangement of two cylinders (42) is provided. The stretching rod (41) is first moved from a primary cylinder (43) to the area of the bottom of the preform (1) before the actual stretching process begins. During the actual stretching process, the primary cylinder (43) with the stretching rod extended is positioned together with a slide (44) carrying the primary cylinder (43) by a secondary cylinder (45) or via a cam control. In particular, it is contemplated to use the secondary cylinder (45) in a cam-controlled manner in such a way that a respective stretching position is specified by a guide roller (46) which slides along a cam track while the stretching process is being carried out. The guide roller (46) is pressed against the guideway by the secondary cylinder (45). The carriage (44) slides along two guide elements (47).

After one. The mold halves (35, 36) arranged in the region of supports (48, 49) are closed

Locking the carrier (48, 49) relative to each other with

With the help of a locking device (50).

To adapt to different shapes of the mouth section, according to FIG. 2 the use of separate thread inserts (51) in the area of the blow mold (34) is provided.

In addition to the blown container (13), FIG. 2 also shows the preform (1), drawn in broken lines, and schematically a developing container bladder (14).

Fig. 3 shows the basic structure of a blowing machine, which is provided with a rotating heating wheel (52) and a rotating blowing wheel (53). Starting from a preform input (54), the preforms (1) are transported by transfer wheels (55, 56) into the area of the heating wheel (52). Along the heating wheel (52) are radiant heaters (57) and blowers

(58) arranged to temper the preforms (1). After the preforms (1) have been adequately tempered, they are transferred to the blowing wheel (53), in the area of which the blowing stations (33) are arranged. The finished blown containers (13) are transferred from a transfer line by further transfer wheels

(59) fed.

In order to be able to form a preform (1) into a container (13) in such a way that the container (13) has material properties that make it possible to use foodstuffs filled in the container (13), in particular beverages, for a long time. guarantee, special procedural steps must be followed when heating and orienting the preforms (1). In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

Different plastics can be used as the thermoplastic material. For example, PET, PEN or PP can be used.

The preform (1) is expanded during the orientation process by compressed air supply. The compressed air supply is divided into a pre-blowing phase in which gas, for example compressed air, is supplied at a low pressure level and a subsequent main blowing phase in which gas is supplied at a higher pressure level. Compressed air with a pressure in the interval from 10 bar to 25 bar is typically used during the pre-blowing phase and compressed air with a pressure in the interval from 25 bar to 40 bar is fed in during the main blowing phase.

Fig. 4 shows a longitudinal section through a preform (1) which is held by support elements (39) and arranged within a tunnel-shaped heating element (57). The heating element (57) forms an electrode of a high-frequency heating. High frequency is understood here to mean all electromagnetic waves with a frequency above the visible light. In particular, the term high frequency thus also includes microwaves.

A counter electrode is in the preform (1)

(2) positioned together with the preform (1) and the support element (39) through the tunnel-shaped

Electrode of the heating element (57) transported through becomes. In the embodiment shown, the support element (39) consists of a transport mandrel on which the preform (1) is attached. In principle, however, it is also conceivable to implement the support element (39), for example, as a tong-shaped holding element.

The electrical field that heats the preform (1) forms between the counter electrode (2) and the tunnel-shaped heating element (57). It has proven to be particularly advantageous to arrange the tunnel-shaped heating element (57) and the counter electrode (2) at a relatively small distance from one another.

• Fig. 5 shows an embodiment in which the

Heating element (57) consisting of two radiation devices arranged opposite one another

(3, 4) is formed, each of stick electrodes

(5) and electrode holders (6, 7).

FIG. 6 shows the arrangement according to FIG. 4 in a perspective illustration. In the embodiment illustrated here, the tunnel-shaped heating element (57) extends in a curved manner along the circumference of the heating wheel (52) shown in FIG. 3. In principle, however, it is also possible to design the tunnel-shaped heating element (57) with a linear extension or aas linear segments. If linear segments of the heating element (57) are used, it is also possible, for example, to position individual ones of these linear segments at an angle relative to one another. Such a design proves to be expedient, for example, if a chain-like drive for the support elements (39) is used instead of the heating wheel (52). Such chain-like or linked drives can be Transport along a movement path that can be specified within a wide free space.

7 shows the dependence of the heating time in seconds on a set temperature in degrees Celsius generated by high frequency when using a tunnel electrode and without temperature compensation. The lower course shows the temperature in the area of an inside of the preform (1), the upper course shows the temperature in the area of an outside of the preform (1) and the middle course shows the temperature in a middle of the wall of the preform (1). The diagram shows the time required to reach a given temperature at a given radiant power.

The diagram in FIG. 8 shows the dependence of the heating time for PET preforms in the case of exposure to high frequency after heating with the tunnel electrode as a function of a temperature to be achieved when using parallel cylinder electrodes and without temperature compensation. The left curve illustrates the temperature of an outside of the preform (1), the right curve shows the temperature in the area of an inside of the preform (1) and the middle curve shows the temperature in the area of a center of the wall of the preform (1).

From FIG. 9 it can be seen how, in the case of parallel rod-shaped electrodes without dielectric, the field strength results as a function of the distance of the respective location from the electrodes. A radiation device (3) is in the area of the distance with the value "0" and the radiation device (4) is in the area of the distance "42" arranged. The distance between the radiation devices (3, 4) is thus 42 mm. The radius chosen was 4 mm, the voltage between the radiation devices (3, 4) is 15,000 volts.

To support uniform heating of the preforms (1) in the circumferential direction, provision is made for the preforms (1) to rotate at least temporarily during their heating. When producing rotationally symmetrical containers (13), the preforms (1) are rotated at least during the predominant time of heating. In the production of containers (13) which have a cross-sectional configuration that deviates from a circular contour, it can also prove advantageous to rotate the preforms (1) only temporarily or to provide a stepwise rotation in order to produce a defined temperature profile in the circumferential direction.

Shielding an environment against escaping high-frequency radiation is of particular importance when carrying out heating using high frequency. Basically, for example, it is contemplated to provide the entire blow molding machine with a shield which, similar to a Faraday vision cage, prevents high-frequency radiation from escaping. In the area of the machine's transparent covers, fine metal grids can be used, similar to the doors of microwave ovens.

According to another embodiment, it is envisaged to carry out a complete shielding in the area of the heating device. It also proves to reduce the shielding effort it is sufficient to provide only a narrow area of the electrodes with shields. In particular, it is contemplated to arrange a shield in the area of the entrance and the exit of the tunnel-shaped electrode. It is also contemplated to place a shield below the tunnel-shaped electrode.

According to a further embodiment, the electrode-shaped tunnel can be surrounded by a further metallic tunnel, the outer metallic tunnel being grounded. In this way, very effective shielding can be provided.

When using chain-shaped or chain-like transport elements for holding the preforms (1) in the area of the heating device, it is also contemplated to provide the tunnel-shaped electrode with a circumferential, closed profile. Such a profile preferably has side walls that run parallel to one another and curved upper and lower regions with a constant transition into the parallel side faces. Such a design considerably reduces parasitic radiation from high-frequency radiation and the effort for separate shielding devices can be reduced.

According to a further embodiment, the tunnel-shaped electrode (57) is also intended to be formed from individual segments. The segmentation can take place, for example, in the vertical or in the horizontal direction. It is also possible to perform a segmentation by separating the upper bulge area of the tunnel-shaped electrode. The arrangement described in Fig. 5 is preferably used to carry out a heat profile of the preform (1) in the direction of a longitudinal axis Vorfor (8). For example, it is possible to either control the individual stick electrodes (5) differently or to change the spacing of the electrodes opposite one another relative to one another.

10 shows an embodiment in which the electromagnetic field for profiling the preform (1) is not generated between the rod electrodes (5) of the electrode holders (6, 7) lying opposite one another, but instead as a counter electrode (2) into the interior of the preform (1) inserted rod is used. Such a process sequence has the advantage that there is only a relatively small distance between the rod electrodes (5) and the counterelectrode (2), so that high field strengths can be achieved and in which an effective focusing of the radiation is also supported in order to achieve a precisely defined one To achieve temperature profiling.

According to FIG. 10, there is a crossed electrode arrangement between the counter electrode (2) and the stick electrodes (5). The specification of an effective field strength can also be specified in this embodiment either by controlling the individual stick electrodes (5) or by changing the distance of the stick electrodes (5) relative to the counter electrodes (2). With regard to the control of the stick electrodes (5), a heating intensity specification can be achieved both via the applied voltage and via the generated frequency. 11 shows a further variant in which a counterelectrode (2) profiled with respect to its contour is used to carry out temperature profiling. The counter electrode (2) has an electrode base (9), an electrode head (10) and an electrode shaft (11). In the embodiment shown, the electrode shaft (11) is provided with a waist-like taper. In principle, however, it is also possible to implement several successive tapering areas and thickening areas. The different areas are preferably merged into one another via a continuous surface contour. In principle, however, step-like or ramp-shaped transitions can also be implemented.

13 shows, in a highly simplified manner, a plan view of a horizontally cut tunnel-shaped electrode (57). A plurality of preforms (1), into which counter electrodes (2) are inserted, are arranged within the tunnel. To increase a field strength acting on the preforms (1) and thus to shorten the heating time, transverse electrodes (14) are transported through the tunnel-shaped heating elements (57) together with the preforms (1). In particular, it is contemplated to connect both the tunnel-shaped heating element (57) and the transverse electrodes (14) to the high-frequency generator.

A preferred embodiment consists of a length (15) and a width (16) of tunnel segments (17), which are relative by the transverse electrodes (14) are delimited from each other, about the same dimensions. This provides square tunnel segments (17) with respect to their cross-sectional area, the electromagnetic field heating the preforms (1) being generated between these walls of the tunnel segments (17) and the counterelectrode (2).

A positioning of the transverse electrodes (14) can, for example, together with the lifting movement of the counter electrodes (2) when entering the preforms

(1) and when lowering after heating has ended. The positioning of both the counter electrodes (2) and the transverse electrodes (14) is preferably carried out in a curve-controlled manner. However, other positions are also possible, for example using servo drives.

According to a further embodiment variant, it is possible to use electrodes opposite one another for carrying out the HF heating, which electrodes are, for example, plate-like or rod-like and are arranged for shielding within a tunnel-shaped shielding electrode. Such an arrangement avoids inserting counter electrodes into the preforms.

It is also contemplated that only a uniform basic temperature control of the preforms is carried out in the area of the high-frequency heating and a temperature profile is carried out after this uniform basic temperature control. Temperature profiling can also be carried out with high-frequency emitters like basic temperature control, but it is also possible for them Temperature profiling of IR emitters or others

Use heating elements.

Claims

P a t e n t a n s r u c h e

Process for the tempering of preforms made of a thermoplastic material, which, following their tempering within a blow mold, are converted into a container by the action of a medium under pressure, in which the preforms are at least temporarily exposed to electromagnetic radiation which has a frequency in the Has a range from 1 MHz to 100 GHz, characterized in that the preforms (1) are added to an electrode (2, 5, 57) generating the electromagnetic radiation for at least part of the duration of their temperature control.

2. The method according to claim 1, characterized in that the preforms (1) are continuously moved past the electrode (2, 5, 57).

3. The method according to claim 1, characterized in that the preforms (1) are gradually moved past the electrode (2, 5, 57).

4. The method according to any one of claims 1 to 3, characterized in that an electrode (2) introduced into at least one of the preforms (1) is moved together with the preform (1).

5. The method according to any one of claims 1 to 4, characterized in that the preforms (1) are enclosed in a tunnel-like manner by an electrode-like heating element (57) during at least part of their transport path.

6. The method according to any one of claims 1 to 5, characterized in that the preforms (1) before being fed to the tunnel-like heating element

(57) can be provided with a temperature profile in the direction of their preform longitudinal axis (8).

7. The method according to any one of claims 1 to 6, characterized in that a temperature profile of the preforms (1) is carried out using stick electrodes (5).

8. The method according to any one of claims 1 to 7, characterized in that in the implementation the temperature profile, a rod-shaped counter electrode (2) is inserted into the preforms (1).

9. The method according to any one of claims 1 to 8, characterized in that when performing a temperature profiling of the preforms (1) cross-positioned rod electrodes (5) and counter electrodes (2) are used.

10. The method according to any one of claims 1 to 9, characterized in that the rod electrodes (5) are positioned relative to a longitudinal axis of the preform (8) for specifying a respective profiling field strength.

11. The method according to any one of claims 1 to 10, characterized in that at least two stick electrodes (5) are controlled differently relative to each other.

12. The method according to any one of claims 1 to 11, characterized in that transverse electrodes (14) are transported through the tunnel-shaped electrodes (57) together with the preforms (1).

13. The method according to any one of claims 1 to 12, characterized in that the transverse electrodes

(14) can be positioned.

14. The method according to any one of claims 1 to 13, characterized in that the transverse electrodes

(14) are positioned together with the counter electrodes (2).

15. The method according to any one of claims 1 to 14, characterized in that the transverse electrodes

(14) can be positioned under cam control.

16. The method according to any one of claims 1 to 15, characterized in that an uneven profiling field is generated by using a profiled counter electrode (2).

17. Device for tempering preforms made of a thermoplastic material, which is provided with at least one heating element which is designed as a radiation generator, the radiation of which at least partially has electromagnetic waves with a frequency in the range from 1 MHz to 100 GHz, characterized in that the heating element is arranged at least in regions next to a transport path of the preform (1).

18. The apparatus according to claim 17, characterized in that the preform (1) is held by a support element (39).

19. The apparatus according to claim 17 or 18, characterized in that the preform (1) is placed on a support element (39).

20. The apparatus according to claim 17 or 18, characterized in that the preform (1) is held like pliers by the support element (39).

21. The apparatus according to claim 17 or 18, characterized in that the support element (39) is at least partially inserted into an opening of the preform (1).

2. Device according to one of claims 17 to 21, characterized in that a counter electrode

(2) is at least partially positioned within the preform (1).

23. Device according to one of claims 17 to 21, characterized in that the counter electrode (2) together with the support element at least along part of the transport path of the preform (1)

(39) is movably arranged.

24. Device according to one of claims 17 to 23, characterized in that the electrode-shaped heating element (57) is tunnel-like.

25. The device according to any one of claims 17 to 24, characterized in that for heating the preforms (1) along at least part of the transport path relative to each other arranged electrode electrodes (5) are positioned.

26. The apparatus according to claim 25, characterized in that the stick electrodes (5) are cylindrical.

27. The device according to one of claims 17 to 26, characterized in that at least two stick electrodes (5) in the region of electrode holders (6, 7) are arranged one above the other transversely to their longitudinal direction.

28. Device according to one of claims 17 to 27, characterized in that the electrodes (2, 5, 57) as part of a device for performing a two-stage blowing process.

29. Device according to one of claims 17 to 27, characterized in that the electrodes (2, 5, 57) are designed as part of a device for carrying out a one-stage blowing process.

30. Device according to one of claims 17 to 29, characterized in that for the preforms (1) in the region of the heating element (57)

Rotational drive is provided.

31. The device according to claim 30, characterized in that the rotary drive has a control for specifying a stepwise rotation.

32. Device according to one of claims 17 to 31, characterized in that a shield is arranged in the region of an input of the electrode-shaped heating element (57).

33. Device according to one of claims 17 to 32, characterized in that in the region of an output of the electrode-shaped heating element

(57) a shield is arranged.

34. Device according to one of claims 17 to 33, characterized in that a shield is arranged below the tunnel-like heating element (57).

35. Device according to one of claims 17 to 34, characterized in that the tunnel-like heating element (57) at least in some areas is double-walled and that the outer wall of the heating element (57) is designed as a shield.

36. Device according to one of claims 17 to 35, characterized in that the tunnel-like heating element (57) is designed as a closed hollow profile that is equipped with substantially parallel side walls.

37. Device according to one of claims 17 to 36, characterized in that stick electrodes (5) are arranged substantially crossed to counter electrodes (2) which can be inserted into the preforms (1).

38. Device according to one of claims 17 to 37, characterized in that at least two of the stick electrodes (5) are connected to a control device for separate electrode control.

39. Device according to one of claims 17 to 38, characterized in that at least one of the stick electrodes (5) is arranged so that it can be positioned transversely to a longitudinal axis of the counter electrode (2).

40. Device according to one of claims 17 to 39, characterized in that a plurality of movable transverse electrodes (14) are arranged within the tunnel-like heating element (57).

41. Device according to claim 40, characterized in that the transverse electrodes (14) can be moved together with the preforms (1) through the tunnel-like heating element (57).

42. Device according to one of claims 17 to 41, characterized in that the transverse electrodes

(14) can be positioned together with the counter electrodes (2).

43. Device according to one of claims 17 to 42, characterized in that the transverse electrodes

(14) are connected to a cam control.

44. Device according to one of claims 17 to 43, characterized in that the counter electrode (2) is provided with a cross-sectional profile.