Blowing head for shaping a melt into a foil tube and set for converting a blowing head.

Abstract

Blowing head (10) for forming a melt (16) into a film tube for a blown film plant, with the following features: a. the blow head (10) has an annular nozzle with an annular gap (14) from which the melt (16) emerges in a ring shape, and b. the annular nozzle has an internal mandrel (18) which defines an inner diameter of the melt (16), and c. the annular die has an internal mandrel (20) which serves to fine-tune the annular gap (14) by defining an inner edge of the annular gap (14), and which follows the pre-mandrel (18) in an extrusion direction (22), and d. the mandrel (20) is placed on the front mandrel (18), and e. the blow head (10) has a heating element (32) for heating the mandrel (20), and f. the mandrel (20) is detachably connected to the front mandrel (18) for the purpose of cleaning or maintenance, characterized in that g. the heating medium (32) is a component separate from the mandrel (20), so that the heating medium (32) can remain on the blow head (10) when the mandrel (20) is removed from the front mandrel (18).

Description

[0001] The invention relates to a blow head for forming a melt into a film tube for a blown film line and a set for converting a blow head.

[0002] Such a die is used to expel a plastic melt in an annular shape and further process it into a film tube. The invention relates in particular to improving the design and handling of the die of a die to ensure precise control of the annular gap and uniform extrusion under optimal thermal conditions.

[0003] A die head, as known in the prior art, has an annular nozzle with an annular gap through which the melt exits in a ring-shaped configuration. The annular nozzle usually includes an internal mandrel that defines the inner diameter of the melt. An internal mandrel that defines the inner edge of the annular gap and follows the mandrel in the direction of extrusion is usually used to fine-tune the annular gap. The mandrel is placed on the mandrel, enabling the mechanical connection between these two components. To bring the melt to the required temperature and ensure uniform extrusion, the die head has a heating medium that heats the mandrel. The mandrel is also usually connected to the mandrel via a detachable connection to facilitate maintenance.

[0004] However, known prior art designs present specific challenges. A key problem is that the heating medium is often integrated into the mandrel and must be removed during mandrel disassembly. This increases the complexity of maintenance and makes cleaning the annular gap time-consuming. Furthermore, mechanical damage to the heating medium can occur if it is removed during disassembly. The heating medium is often connected to the power supply via a connector, the position of which inside or outside the die head also presents challenges. Internal connector designs are limited to low voltages and heating outputs due to space constraints, while external connector solutions require complex disassembly work, as the internal piping of the die head must be removed to insert the connector.

[0005] In addition, the alignment of the heating means in the state of the art does not always lead to a uniform heating of the annular gap, which can negatively affect the quality of the melt and thus the produced film.

[0006] The objective of the present invention is to provide a die head that facilitates cleaning and maintenance of the annular gap without having to remove the heating medium. At the same time, the design should ensure uniform heating of the melt to ensure reliable extrusion and avoid mechanical damage to the heating medium.

[0007] According to the invention, a die head is proposed that has an annular nozzle with an annular gap through which the melt emerges in a ring shape. The annular nozzle comprises an internal mandrel, which defines the inner diameter of the melt, and an internal mandrel, which serves to finely adjust the annular gap by defining an inner edge of the annular gap and following the mandrel in the extrusion direction. The mandrel is mounted on the mandrel, and the die head has a heating means for heating the mandrel to bring the melt to the required temperature and ensure uniform extrusion. The mandrel is detachably connected to the mandrel.

[0008] It is proposed that the heating medium be a separate component that can remain on the blow head when the mandrel is removed from the front mandrel.

[0009] The heating medium serves to bring the melt to the required temperature to ensure uniform extrusion. It is preferably arranged so that its defined radiation direction is specifically directed at a so-called ironing zone and the exit gap. The ironing zone usually refers to the area immediately at the exit of the annular gap of the ring die, in which the melt, after leaving the annular gap, is transformed into its final geometry by external influences such as cooling and mechanical shaping. It plays a decisive role in the stability and quality of the extruded film tube. In the ironing zone, the temperature of the melt is specifically controlled to ensure that no cracks or inhomogeneities occur. At the same time, the melt is mechanically guided so that the thickness and diameter of the film tube are precisely defined.The ironing zone also forms the transition from melt extrusion to bubble formation, which gives the film tube its final shape. In the context of the invention, the ironing zone is specifically heated by the defined radiation direction of the heating medium to prevent melt fractures and ensure the consistent quality of the extruded melt.

[0010] This targeted heating prevents possible melt fracture, which could otherwise negatively affect the quality of the extruded melt and thus of the film tube.

[0011] Melt fracture describes an undesirable phenomenon that can occur during the extrusion process when the melt becomes unstable upon exiting the annular gap of a ring die or during further processing. It is an irregularity in the material flow that leads to visible and structural defects in the extruded material, such as cracks, roughness, or waves.

[0012] Melt fractures often occur due to uneven temperature distribution in the melt, excessive extrusion speed, insufficient material homogeneity, or mechanical stresses in the ironing zone. Such defects can significantly impair the quality of the extruded film tube and lead to material loss or scrap.

[0013] Within the scope of the invention, targeted heating of the ironing zone and precise control of the melt temperature and flow ensure that melt fractures are avoided and uniform extrusion is guaranteed.

[0014] The proposed design offers several advantages. Since the heating medium is a separate component, it remains on the die head when the mandrel is disassembled, reducing the risk of mechanical damage to the heating medium. Maintenance of the annular gap is significantly simplified because no electrical connection in the mandrel needs to be removed. At the same time, the heating medium can be positioned to ensure uniform heating of the melt. This helps prevent melt fractures and improves the quality of the produced film. The design can reduce line downtime and, preferably, does not require special tools or skilled electricians for maintenance.

[0015] The ring nozzle of the blow head usually has an external attachment mouthpiece, which is arranged opposite the attachment mandrel and defines the outer diameter of the melt.

[0016] The die attachment thus contributes significantly to the shaping of the extruded melt. Following the die attachment in the extrusion direction is an external die, which serves to finely adjust the annular gap. The external die defines the outer edge of the annular gap and thus contributes to precise melt control. The die is mounted on the die attachment and, together with it, forms a detachable unit.

[0017] The external die allows for fine adjustment of the annular gap by defining the outer edge of the annular gap. Between the mandrel and the die, a gap is formed through which the melt can be conveyed and which defines the annular gap.

[0018] This gap forms the annular gap through which the melt exits in the desired annular shape. The geometry of the annular gap is crucial for the quality and uniformity of the extruded melt and can be precisely adjusted by fine-tuning the positions of the mandrel and die.

[0019] The heating medium is positioned to heat the mandrel. Its preferably defined radiation direction ensures heating of the ironing zone or the exit gap to prevent melt fractures. Heat transfer is preferably uniform to bring the melt to the required temperature and ensure consistent extrusion.

[0020] The structural separation between the mandrel and the heating medium allows the heating medium to be designed as a separate component that can remain on the die head when the mandrel is removed. This ensures a robust and durable design that facilitates maintenance while increasing energy efficiency.

[0021] The arrangement of the components is usually designed to precisely define the annular gap. The inner mandrel and the outer die act as fine-tuning elements for the inner and outer edges of the annular gap. This precise geometry enables uniform extrusion of the melt and contributes to the high quality of the resulting film tube.

[0022] In one embodiment, the blow head has an internal heat ring arranged between the mandrel and the heating means.

[0023] The internal heat ring is a component that, in the described embodiment, is located between the mandrel and the heating medium. Its function is to optimize heat transfer from the heating medium to the mandrel. The heat ring forms a thermal connection between the heating medium and the mandrel, ensuring that heat is transferred evenly and efficiently.

[0024] With regard to the previously described elements of the die head, the heat ring has a functional relationship to the mandrel and the heating medium. It ensures that the heat generated by the heating medium is transferred to the mandrel with minimal losses. At the same time, the heat ring preferably serves as a separate component that is mechanically detachable and does not cause additional complexity when disassembling the mandrel.

[0025] The shape of the heat ring can be used to either create or prevent a temperature gradient on the outer surface of the mandrel. Depending on the application, this could be achieved by a specific shape of the heat ring, for example, by varying the wall thickness or by special arrangements of the contact surfaces. One possibility is to arrange the heating medium at an angle to the heat ring to enable targeted control of the temperature distribution.

[0026] In principle, however, the shape of the heat ring is not crucial as long as the following criteria are met: The heat ring should be detachable from the mandrel to facilitate maintenance and cleaning of the mandrel. Furthermore, it should ensure reliable and uniform heat transfer between the heating medium and the mandrel. These properties make the heat ring a key element for the thermal efficiency and process reliability of the die head.

[0027] Integrating the heat ring into the die head enables precise temperature control at the mandrel, improving uniform melt extrusion and preventing melt fractures. At the same time, the design remains robust and easy to maintain, increasing the plant's operating efficiency.

[0028] In one embodiment, the blow head has a protective element for the heating medium in order to protect the heating medium from damage during disassembly and / or assembly of the mandrel.

[0029] The protective element is a component specifically designed to mechanically protect the heating element during assembly or disassembly of the mandrel. It prevents the heating element from being damaged by accidental contact, impact, or other impacts that may occur during these operations.

[0030] The protective element has a direct functional relationship to the heating medium, the mandrel, and the heat ring (if present). It is preferably arranged to preserve the integrity of the heating medium without compromising heat transfer to the mandrel. At the same time, the protective element ensures that maintenance and assembly work on the mandrel and surrounding components can be carried out unhindered.

[0031] In terms of its structural design, the protective element can be designed, for example, as a mechanical cover or a protective ring. It could be made of a material that provides sufficient mechanical stability while simultaneously providing thermal insulation to prevent overheating of the heating medium. Alternatively, it could be made of a thermally conductive material that promotes heat transfer, provided this supports the function of the heating medium.

[0032] The protective element preferably fulfills several functions: Firstly, it protects the heating element from external influences during disassembly or assembly of the mandrel. Secondly, it contributes to ensuring the longevity of the heating element by reducing mechanical stress and preventing damage due to accidental handling errors.

[0033] The integration of a protective element makes the blow head even more robust and easier to maintain, as the likelihood of heating element failure or repair due to mechanical damage is minimized. This improves the operational reliability of the entire system without compromising the functionality of other components, such as the mandrel or heat ring.

[0034] In one embodiment, the blow head has a carrier on which the heating medium can be fixed.

[0035] The carrier is a component that serves to mechanically hold the heating medium and fix it in a defined position within the die head. This fixation ensures that the heating medium always remains optimally aligned with the ironing zone and the exit gap, ensuring precise heating of the melt.

[0036] The relationship between the support and the other components of the die head is functionally designed to efficiently support heat transfer from the heating medium to the mandrel and, if applicable, to the internal heat ring. At the same time, the support prevents the heating medium from changing its position due to movement or vibration during operation or maintenance, thus increasing process stability.

[0037] In a further embodiment, the carrier is combined with the internal heat ring and / or the protective element to form a single component. This preferred design allows for a reduction in the number of separate components in the blow head, thus simplifying assembly and disassembly.

[0038] When the carrier, the internal heat ring and the protective element form a common component, heat transfer is optimized because the components are in uniform thermal contact.

[0039] The shape of the support, especially if it is part of a common component, can vary depending on the design. For example, it could be flat to provide extensive support for the heating element, or it could be designed as a ring-shaped element that specifically transfers heat to an internal heat ring. In principle, the shape of the support remains flexible as long as the fixation of the heating element and the requirements for thermal and mechanical stability are met.

[0040] The integration of the support further increases the operational reliability of the blow head, as the heating medium remains firmly fixed regardless of external influences. The preferred combination with the heat ring and / or the protective element also results in a robust and maintenance-friendly overall design that is both thermally efficient and mechanically resilient.

[0041] The option of designing the carrier as a separate component or as part of a combined component offers flexibility in adapting the design to specific requirements. This design thus contributes to the versatility and functionality of the die head.

[0042] In one embodiment, the blow head has a contact surface between the heating means and the mandrel or between the heat ring and the mandrel which is conical in shape so that the mandrel can be detached from the attachment mandrel regardless of its temperature.

[0043] The conical contact surface ensures thermally and mechanically stable mechanical connection between the mandrel and adjacent components, such as the heating element or the heat ring. At the same time, the conical shape allows for easy separation of the mandrel from the attachment mandrel, even when the die head is still at operating temperature. This is particularly advantageous during maintenance or cleaning work, as no additional cooling time is required.

[0044] The conical contact surface is designed so that the base of the conical surface lies on the mandrel and the tip of the conical surface points toward the mandrel. This arrangement ensures that the mechanical connection does not create additional resistance as the temperature rises, but can be easily released due to the geometry. At the same time, the conicity ensures optimal thermal contact, maximizing heat transfer between the components.

[0045] Compared to the previously described elements of the die head, the conical contact surface enables efficient and uniform heat transfer from the heating medium or heat ring to the mandrel. This design reduces thermal stresses and prevents components from jamming or accidentally coming loose due to temperature changes.

[0046] The conical contact surface also contributes to holding the mandrel precisely in its position, which is crucial for fine-tuning the annular gap and thus for the quality of the extruded melt. Its design ensures that the mandrel is fixed in exactly the same position even during repeated assembly and disassembly, without compromising the geometry of the annular gap.

[0047] This design makes the die head both easier to maintain and more thermally and mechanically robust, as the connecting elements function reliably even at high operating temperatures. This contributes to the overall service life of the design and process stability.

[0048] In one embodiment, the blow head has at least one thermal sensor for detecting an actual temperature in the area of ​​the mandrel.

[0049] The thermal sensor measures the current temperature in the mandrel area and ensures that the temperature control of the heating medium can be precisely adjusted to the requirements of the extrusion process. The thermal sensor is positioned so that the measured temperature reflects the actual temperature at the mandrel as accurately as possible, without being influenced by other heat sources or the melt.

[0050] In a preferred embodiment, the thermal sensor is integrated into the carrier, the internal heat ring, and / or the protective element. This arrangement allows for mechanical protection of the thermal sensor while ensuring proximity to the heat source to ensure precise temperature measurement.

[0051] For optimal positioning of the thermal sensor, it is preferably placed adjacent to the heating medium's support ring, preferably close to the internal gap heater, provided heat transfer is functioning properly. This position ensures that the measured temperature serves as the control variable for controlling the heating medium and is not directly influenced by the melt temperature. The goal is to establish a control loop between the heating medium and the thermal sensor without the properties of the melt directly interfering with the measurement.

[0052] Multiple thermal sensors distributed around the circumference of the mandrel are conceivable to enable more uniform temperature monitoring. The temperature measurement location remains variable and could be adapted as needed to meet specific requirements.

[0053] The thermal sensors or a connected system can be designed to measure only a temperature and not a temperature profile. This keeps the design simple and robust, while the measured values ​​are sufficient to reliably record the actual temperature in the area of ​​the mandrel.

[0054] This arrangement helps ensure efficient temperature control of the die head and precise heating of the mandrel without external influences distorting the measurement. At the same time, the integration of the thermal sensor into the carrier, heat ring, or protective element ensures additional mechanical stability and protection. This leads to improved operational reliability and an extended service life of the die head components.

[0055] In one embodiment, the mandrel of the blow head has at least one centering aid on which the mandrel can be placed so that it can be placed on the mandrel without offset.

[0056] The centering aid serves to ensure precise alignment of the mandrel on the pre-mandrel. This prevents the mandrel from moving into an incorrect position during assembly or operation, which could compromise the quality of the melt and the uniformity of the annular gap. The centering aid could, for example, be designed as a conical or flat guide element that holds the mandrel in the correct position before it is fixed. The centering aid has a direct functional relationship to the previously described elements of the die head, especially the mandrel and the pre-mandrel, and contributes to the stability and precision of the overall design.

[0057] In one embodiment, the blow head is designed for the assembly of differently shaped mandrels. The heating means and / or the heat ring are each preferably designed for use with several different mandrels.

[0058] This design allows for increased flexibility of the die head, as it can be adapted to different requirements without having to replace fundamental components such as the heating element or the heat ring. Differently designed mandrels could, for example, differ in geometries or dimensions adapted to specific extrusion processes. The heating element and the heat ring are designed to ensure efficient heat transfer and precise function regardless of the mandrel variant.

[0059] In one embodiment, the heating means is designed to be applied to the mandrel in the assembled state.

[0060] The heating medium is designed to establish a direct thermal connection to the mandrel during assembly of the die head. This ensures efficient heat transfer without loss. The heating medium can be attached to the mandrel by a fixed position within the die head or by a mechanical spring that presses the heating medium against the mandrel during operation. In the simplest case, one or more tightening screws are provided to attach the heating medium and / or the heat ring to the mandrel.

[0061] In one embodiment, the mandrel has at least one forcing bore by means of which it can be separated from the attachment mandrel before disassembly.

[0062] The forcing hole serves as a mechanical aid to release the mandrel from the attachment mandrel during disassembly in a controlled and damage-free manner. Such a hole could, for example, be used to insert a tool attachment that pushes the mandrel off. This function significantly simplifies maintenance and reduces the risk of mechanical damage to the components.

[0063] In one embodiment, the heating means has a heating output of more than 3 kW, in particular more than 3.6 kW. Alternatively or additionally, the heating means is designed for a voltage of more than 250 V.

[0064] This design implies that the heating medium is fundamentally designed for operation with more than one phase, thus enabling higher power density and more efficient heating.

[0065] The values ​​mentioned are based on the power grids commonly used in Europe, with a voltage of approximately 230 V per phase. In countries with different power grids, such as the USA, where a mains voltage of approximately 110 V is common, these values ​​must be adjusted accordingly. In these countries, the heating element could be designed to achieve the required heating output using more than one phase. This ensures functionality regardless of regional mains voltages, while maintaining the heating element's performance efficiency.

[0066] The specified heating power is provided for the heating medium, preferably per segment. However, the segmented design of the heating medium is optional, and in a preferred embodiment, the heating medium is operated with a single power supply. The high heating power and voltage allow efficient heating even in demanding extrusion processes, while the simple power supply keeps the design robust and easy to maintain.

[0067] In one embodiment, the heating means has multiple segments in the extrusion direction to vary the temperature segment by segment in the extrusion direction. Alternatively or additionally, the heating means has multiple circular segments to vary the temperature segment by segment along individual circular segments of the annular die.

[0068] The heating medium can also be designed as a single ring. During heating, this ring is stretched against the heating ring and the contact with the outer part. However, the heating is preferably operated uniformly across the circumference. Optionally, multiple sensors can be provided to enable more precise control. A segmented design allows the temperature to be varied in specific areas of the ring, for example, to meet different melt requirements.

[0069] In one embodiment, the blow head, in particular the attachment mandrel, has at least one cable guide to guide cables for the heating medium and / or the thermal sensor out of the blow head.

[0070] The difference from the state of the art is that no connectors are required. The heating cables are preferably routed continuously without interruption by plug connections. The thermal sensors preferably remain on the mandrel during removal, which facilitates maintenance and eliminates the need for sensor realignment.

[0071] Another aspect of the invention relates to a kit for converting a blow head for forming a melt into a film tube for a blown film line. The kit comprises the following features: The die head to be converted has a ring nozzle with an annular gap through which the melt exits in a ring shape. The ring nozzle has an internal mandrel that defines the inner diameter of the melt. The set includes an internal mandrel that can be placed on the mandrel and serves to finely adjust the annular gap by defining an inner edge of the annular gap and following the mandrel in the direction of extrusion. The mandrel is detachably connected to the mandrel for cleaning purposes.

[0072] The set also includes a heating element for heating the mandrel. The heating element is designed as a separate component, allowing it to remain on the blow head when the mandrel is removed from the front mandrel.

[0073] The mandrel is preferably included in the conversion kit, while the heating fluid is not required. Existing ring nozzles can be converted by replacing the mandrel, as the mandrel remains compatible with the existing design thanks to its detachable connection to the attachment mandrel.

[0074] However, it should be noted that in existing systems, the cables of the current solution may be too short to connect a new multi-phase heater. A new heater also typically requires new cables and additional accessories, which could be particularly challenging in older systems. Upgrading to higher heating outputs is often not feasible in existing systems because the cross-section of the blow head may be too small for larger cable dimensions.

[0075] The ability to convert the old ring nozzles to the new mandrel design nevertheless offers significant advantages, as the new mandrel connection and the retention of the heating medium at the die head significantly reduce maintenance requirements.

[0076] In a preferred embodiment, the heating means contained in the set is designed according to the type described.

[0077] The heating medium preferably remains on the blow head during mandrel disassembly, thus ensuring the mechanical stability and functionality of the system. It is designed to ensure the required heat transfer to the mandrel without the need to replace the heating medium during conversion.

[0078] The design of the heating element preferably enables precise and uniform heating of the mandrel, which improves extrusion quality. This design contributes to making the conversion of existing die heads efficient and compatible with the requirements of modern extrusion processes without having to completely change the basic design of the die head.

[0079] Further advantages and aspects of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Fig. 1 shows a cross-sectional view of a blow head according to the invention in an overview view. Fig. Figure 2 shows a detailed view of the internal elements within the melt, in particular the mandrel and the mandrel.

[0080] In Fig. Figure 1 shows the overall layout of the blow head 10, with all essential components visible at a glance. The annular melt 16 is shown in section. Fig. Figure 2 shows a detailed view of the internal elements within the melt 16, with only one side of this sectional view shown here. The detailed view illustrates the precise arrangement and functional interaction of these components, which are crucial for the adjustment of the annular gap 14 and the thermal efficiency of the die head 10.

[0081] At the blow head 10, the processing of the annular melt 16 begins, which is formed into the desired diameter by the annular gap 14. This function is initially implemented by the internal mandrel 18, which defines the inner diameter of the melt 16, and the corresponding external die 26, which initially defines the outer diameter of the melt 16.

[0082] Subsequently, the fine adjustment of the annular gap 14 is achieved by the mandrel 20 and the nozzle 28. The mandrel 20 can be placed on the auxiliary mandrel 18 and defines the inner edge of the annular gap 14, while the nozzle 28 is mounted on the auxiliary nozzle 26 and defines the outer edge of the annular gap 14. The annular gap 14 is arranged between the auxiliary mandrel 18 and the mandrel 20, as well as between the auxiliary nozzle 26 and the nozzle 28, enabling the conveyance of the melt 16 and the definition of the annular gap 14 in the extrusion direction 22.

[0083] A centering aid 42 is arranged between the mandrel 20 and the auxiliary mandrel 18, enabling secure and precise positioning of the two parts. The mandrel 20 is releasably connected to the auxiliary mandrel 18 by means of a clamping screw 52 and a clamping sleeve 54. The auxiliary mandrel 18 has a separate clamping screw 56 for connecting it to other components of the die head 10 arranged opposite to the extrusion direction 22.

[0084] A cable guide 50 is inserted through the attachment mandrel 18, which serves to securely accommodate the cables 48 of the thermal sensor 44 and to lead them out of the blow head 10.

[0085] At the level of the mandrel 20, a support 34 is arranged within the blow head 10, on which the heating means 32 is mounted. In this embodiment, the support is combined with the internal heat ring to form a single component. A conical contact surface 38 is formed between the support 34 and the mandrel 20. The base of the conical contact surface 38 lies on the front mandrel 18, while the tip points toward the mandrel 20. This geometry enables reliable heat transfer and facilitates the removal of the mandrel 20, regardless of the actual temperature.

[0086] The mandrel 20 has a forcing bore 40 which serves to pull the carrier 34 towards the mandrel 20 or to push it off the carrier 34 in a controlled manner in order to disassemble the blow head 10.

[0087] In the center of the blow head 10, a space 58 is provided for internal air piping through which the blow air is guided. An IBC (Internal Bubble Cooling) system featuring a centering device 60 can be mounted on the mandrel 20. In this version, the IBC system is attached to the mandrel 20 with a bayonet lock 62. List of reference symbols 10 Blow head 14 Annular gap 16 Melt 18 Attachment mandrel 20 thorn 22 Extrusion direction 26 Attachment mouthpiece 28 Mouthpiece 32 heating agents 34 carriers 38 Conical contact surface 40 Forcing hole 42 Centering aid 44 Thermal sensor 48 Thermal sensor cable 50 cable routing 52 clamping screw for mandrel 54 clamping sleeve for mandrel 56 Separate clamping screw for attachment mandrel 58 Space for internal air piping 60 Centering for IBC system 62 Bayonet lock of the IBC system

Claims

[1] Blow head (10) for forming a melt (16) into a film tube for a blown film line, having the following features: a. the blow head (10) has an annular nozzle with an annular gap (14) through which the melt (16) emerges in a ring shape, and b. the ring nozzle has an internal mandrel (18) which defines an inner diameter of the melt (16), and c. the annular nozzle has an internal mandrel (20) which serves for fine adjustment of the annular gap (14) by defining an inner edge of the annular gap (14) and which follows the attachment mandrel (18) in an extrusion direction (22), and d. the mandrel (20) is placed on the attachment mandrel (18), and e. the blow head (10) has a heating means (32) for heating the mandrel (20), and f. the mandrel (20) is detachably connected to the attachment mandrel (18), for example for the purpose of cleaning or maintenance, characterized by, that g. the heating means (32) is a separate component from the mandrel (20) so that the heating means (32) can remain on the blow head (10) when the mandrel (20) is dismantled from the attachment mandrel (18). [2] Blow head (10) according to claim 1, with the following further feature: the blow head (10) has an internal heating ring which is arranged between the mandrel (20) and the heating means (32). [3] Blow head (10) according to one of claims 1 or 2, with the following further feature: the blow head (10) has a protective element for the heating medium (32) in order to protect the heating medium (32) from damage during disassembly and / or assembly of the mandrel (20). [4] Blow head (10) according to one of the preceding claims, in particular according to claim 2 or claim 3, with the following further feature: a. the blow head (10) has a support (34) on which the heating means (32) can be fixed, preferably with the additional feature: b. the carrier (34), the internal heat ring and / or the protective element are a common component. [5] Blow head (10) according to one of the preceding claims, with the following further feature: a contact surface (38) between the heating means (32) and the mandrel (20) or between the heat ring and the mandrel (20) is conical, so that the mandrel (20) can be detached from the attachment mandrel (18) regardless of its temperature. [6] Blow head (10) according to one of the preceding claims, with the following further feature: a. the blow head (10) has at least one thermal sensor (44) for detecting an actual temperature in the area of ​​the mandrel (20), preferably with the following additional feature: b. the thermal sensor (44) is integrated in the carrier (34), the internal heat ring and / or in the protective element. [7] Blow head (10) according to one of the preceding claims, with the following further feature: the attachment mandrel (18) has at least one centering aid (42) on which the mandrel (20) can be placed so that it can be placed on the attachment mandrel (18) without offset. [8] Blow head (10) according to one of the preceding claims, with the following further features: a. the blow head (10) is designed for the assembly of differently shaped mandrels (20), and b. the heating means (32) and / or the heat ring are each designed to use the plurality of different mandrels (20). [9] Blow head (10) according to one of the preceding claims, with the following further feature: the heating means (32) is designed to be applied to the mandrel (20) in the assembled state. [10] Blow head (10) according to one of the preceding claims, with the following further feature: the mandrel (20) has at least one forcing bore (40) by means of which it can be separated from the attachment mandrel (18) before disassembly of the mandrel (20). [11] Blow head (10) according to one of the preceding claims, with at least one of the following further features: a. the heating means (32) has a heating power of >3 kW, in particular >3.6 kW, and / or b. the heating medium (32) is designed for a voltage >250 V. [12] Blow head (10) according to one of the preceding claims, with at least one of the following further features: a. the heating means (32) has a plurality of segments in the extrusion direction (22) in order to vary the temperature in the extrusion direction (22) segment by segment, and / or b. the heating means (32) has several circular segments in order to vary the temperature segment by segment along individual circular segments of the ring nozzle. [13] Blow head (10) according to one of the preceding claims, with the following further feature: the blow head (10), in particular the attachment mandrel (18), has at least one cable guide (50) for leading cables (48) for the heating means (32) and / or the thermal sensor (44) out of the blow head (10). [14] Set for converting a blow head (10) for forming a melt into a film tube for a blown film line, having the following features: a. the blow head (10) has an annular nozzle with an annular gap (14) through which the melt (16) emerges in a ring shape, and b. the ring nozzle has an internal mandrel (18) which defines an inner diameter of the melt (16), and the set includes: c. an inner mandrel (20) which can be placed on the attachment mandrel (18), which serves for a fine adjustment of the annular gap (14) by defining an inner edge of the annular gap (14), and which follows the attachment mandrel (18) in an extrusion direction (22), and d. the mandrel (20) is detachably connected to the attachment mandrel (18) for cleaning purposes, and the set further comprises: e. a heating means (32) for heating the mandrel (20), wherein f. the heating means (32) is a separate component from the mandrel (20), so that the heating means (32) can remain on the blow head (10) when the mandrel (20) is dismantled from the attachment mandrel (18). [15] Set according to claim 14, with the following further feature: the heating means (32) is designed according to one of claims 1 to 13.

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