Method for adjusting film blowing device and film blowing device

Abstract

The invention relates to a method for post-controlling the temperature of a film tube extruded by means of a film blowing device, comprising the following method steps: ejecting a film tube (1) of plasticized thermoplastic material in a drawing direction along a longitudinal axis (L) of the film blowing device by means of a film blowing die (6), a cooling gas flows downstream of the film blow mold (6) in the drawing direction onto the film tube (1) by means of at least one cooling gas ring (10) such that the film tube (1) hardens at the frost line (14) under the action of the cooling gas, a post-control of the temperature of the film tube (1) is carried out by means of a post-temperature control unit (20) downstream of the frost line (14), the post-temperature control unit (20) has a plurality of adjustable blowing elements (22) for blowing a temperature control gas onto the film tube (1), the blowing elements forming a through-opening for the film tube (1),-by adjusting the blowing elements (22), the diameter (D) of the through-opening formed by the blowing elements (22) is adapted to the diameter of the film tube (1), and-the film tube (1) is formed by adjusting the blowing elements (22). Measuring the actual temperature of the film tube downstream of at least one of the blowing elements (22), and adjusting the temperature of the film tube (1) downstream of the at least one blowing element (22) to a target temperature by blowing a temperature control gas onto the film tube (1) by means of the post temperature control unit (20).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a film tube from plasticized thermoplastic material in a winding direction along the longitudinal axis of a blown film line by means of a blow head and a blown film line. By means of at least one cooling gas ring downstream of the blow head in the winding direction, cooling gas is blown onto the film tube such that the film tube solidifies at the frost line under the action of the cooling gas. BACKGROUND

[0002] EP 1491319 A1 shows a blown film line which comprises a gas suction device which surrounds the film tube downstream of the correction basket with essentially ring-shaped arranged suction nozzles for extracting monomer vapor containing evaporations. Directly above (i.e. downstream) of the gas suction device, on the outside of the film tube, a post-conditioning unit in the form of a further cooling gas ring is arranged which is designed as a rigid ring with a fixed and unchangeable inner diameter for the film tube to pass through.

[0003] Above or downstream of the additional cooling ring, the film tube enters a flattening unit which flattens the film tube. By means of a winding unit, the film tube is pulled away downstream of the flattening unit. The flattened film tube is then wound onto a reel.

[0004] The film tube can be cooled with an additional cooling gas ring before it enters the flattening unit still relatively warm, so that the risk of the film layers blocking (sticking to each other) in the winding unit after the film tube has been folded is less. This means that the film layers cannot or can hardly be separated from each other when the film layers are wound onto a plurality of reels or during the subsequent handling.

[0005] During the extrusion of the film tube, certain formulations and products cause so-called flatness errors in the produced film. Such flatness errors are, for example, waviness with any distribution, sagging in the edge region and so-called camber.

[0006] Such errors are clearly visible when the film is unrolled from the finished reel and un-stretched on the floor. Simply put, flatness errors are local length deviations of individual film regions over the web width.

[0007] These defects can usually be visually detected in the film web in the stretch from the winding to the winder or in the winder.

[0008] Known measuring devices measure the flatness of the web in the transverse direction on the way from the winding to the winder or in the winder. Furthermore, the known measuring devices record the geometric quality of the reel as the reel is formed. This is intended to ensure that poor flatness quality is detected at an early stage.

[0009] A control loop is also proposed in which such a measuring device is coupled with a stretching unit which intends to improve the flatness by heating and stretching the film tube after winding up.

[0010] In the region of the still circular film tube, it is known to use an infrared radiation heater arranged at a fixed diameter above the frost line to reheat the film tube again in order to improve the flatness quality of the subsequently collapsed film. This exploits the effect that the uneven stress distribution due to the different molecular orientation on the circumference of the film tube and the resulting local length differences are reduced again by the re-heating so that flatness errors in the collapsed film are significantly reduced or completely prevented.

[0011] The uneven stress distribution is mainly caused by flow effects in the extrusion die of the blow head, for example by a flow channel design which does not optimally match the raw material, by an unsuitable heating profile of the extrusion die, or by an uneven circumferential temperature distribution and / or circumferential volume distribution of the melt inside the extrusion die and at its outlet.

[0012] Furthermore, flatness errors are also caused by an excessive contact pressure (filling level) in the calibration basket which is arranged at a height which does not match the frost line of the film tube, or by a slight off-centering of the calibration basket relative to the extrusion die.

[0013] Flatness errors which occur during the collapsing process itself are secondary if the film tube enters the collapsing process as free as possible from any already occurring flatness errors.

[0014] The transverse cross-section control systems known in the prior art intervene in the bubble cooling in the tube forming zone between the calibration extrusion die and the frost line, which can significantly improve the aforementioned problems, but cannot completely avoid such problems for many flatness-sensitive products.

[0015] A disadvantage of the heating tunnel is the rigid arrangement of the radiation heaters, since usually various different bubble diameters are produced. The variable distance between the film and the heating tunnel is an additional influencing parameter which coexists with the actual production parameters, which makes it difficult to set up an automatic control loop.

[0016] US 3930781 A shows a post-cooling device attached to the calibration basket. The post-cooling device has a cooling air ring arranged on the other side of the film solidification line, which has air outlet openings directed at the film tube, which consist of a plurality of individual blowing elements which are pairwise connected to each other at their adjacent ends in such a way that they can be pivoted about a horizontal axis and can be adjusted radially with respect to the tube axis and form a regular polygon with each other. SUMMARY

[0017] It is an object of the present invention to provide a blown film production line which has as effective and variable a post-tempering unit downstream of the frost line as possible.

[0018] This object is achieved by a method for post-tempering a film tube extruded by means of a blown film production line, having the following method steps:

[0019] - pushing out a film tube of plasticized thermoplastic material in the winding direction along the longitudinal axis of the blown film production line by means of a blowing head,

[0020] - blowing cooling gas onto the film tube downstream of the frost line with respect to the winding direction by means of at least one cooling gas ring, so that the film tube solidifies at the frost line under the action of the cooling gas,

[0021] - post-tempering the film tube by means of a post-tempering unit downstream of the frost line, the post-tempering unit having a plurality of adjustable blowing elements for blowing tempering gas onto the film tube, which blowing elements form a passage opening for the film tube,

[0022] - adapting the diameter of the passage opening formed by the blowing elements to the diameter of the film tube by adjusting the blowing elements,

[0023] - measuring the actual temperature of the film tube downstream of at least one of the blowing elements, and

[0024] - adjusting the temperature of the film tube downstream of at least one blowing element to a target temperature by blowing tempering gas onto the film tube by means of the post-tempering unit.

[0025] The actual temperature of the film tube can be measured at any point downstream of at least one of the blowing elements, i.e. in a region of the film tube which is circular, or in a region of the film tube which is no longer circular, for example in or downstream of a flattening unit, i.e. in or downstream of a winding unit. This means that the actual temperature can also be measured in a region which is no longer in line with the longitudinal axis of the blown film production line.

[0026] By precisely adjusting the temperature of the film tube, excessive subsequent cooling or heating can be avoided, so that the energy efficiency can be improved.

[0027] This also ensures a high degree of consistency of the process. Changes in environmental conditions, for example the ambient temperature and / or the humidity of the ambient air, can lead to significant variations in the temperature of the film tube under the same machine parameters. In the worst case, this can lead to blockages or defects in the film. However, fluctuations in the machine parameters, such as the output quantity and / or the output speed of the plasticized material, also lead to variations in the temperature of the film tube. The adjustment of the target temperature of the film tube makes the process more consistent and thus the quality of the film tube produced higher.

[0028] The post-conditioning unit can have a plurality of guide elements adjustably hinged on the frame for guiding the film tube and forming a guide opening for guiding the film tube therethrough, the diameter of the guide opening being adapted to the diameter of the film tube by adjusting the guide elements.

[0029] The actual temperature profile of the film tube can be measured in the circumferential direction, at least over at least one circumferential region of the film tube, whereby the temperature and / or the volume flow of the conditioning gas of the blow-off elements arranged in the circumferential distribution are each set in accordance with the difference between the actual temperature of the film tube in the respective circumferential region of the respective blow-off element and the target temperature in the respective circumferential region of the film tube.

[0030] In order to avoid blocking, the film tube can be cooled downstream of the frost line, at least in certain regions in the circumferential direction. In order to improve the flatness quality, the film tube can be heated downstream of the post-conditioning unit, at least in certain regions in the circumferential direction.

[0031] The actual temperature of the film tube can be measured in an outlet region of the post-conditioning unit, through which the film tube exits the post-conditioning unit.

[0032] The temperature and / or the volume flow of the conditioning gas can be set in accordance with the difference between the measured temperature of the film tube and the target temperature of the film tube. The target temperature can be a specific absolute temperature value. Alternatively, it is also possible to calculate the target temperature by means of a difference value on the basis of the actual temperature of the film tube before the film tube passes through the post-conditioning unit. In this case, the target temperature is calculated from the actual temperature of the film tube before the film tube passes through the post-conditioning unit, plus or minus a fixed temperature difference value, if applicable.

[0033] The temperature sensor for measuring the temperature of the tubular film can be located anywhere downstream of the post-conditioning unit, for example on the flattening unit. The temperature sensor can also be part of the post-conditioning unit, in which case the temperature sensor is arranged in an outlet region of the post-conditioning unit.

[0034] In special applications, it can be necessary to influence the temperature profile differently in the circumferential direction, for example to set a constant temperature profile in the circumferential direction starting from a non-uniform temperature profile in the circumferential direction on the basis of local conditions. It can also be necessary to set a non-uniform temperature profile in the circumferential direction. To this end, it can be provided that the temperature profile of the film tube downstream of the post-conditioning unit, in particular in a region of the outlet of the post-conditioning unit through which the film tube exits the post-conditioning unit, is measured in the circumferential direction, and the temperature and / or the volume flow of the conditioning gas of the blow-off elements arranged in the circumferential distribution are each set in accordance with the difference between the temperature of the film tube in the respective circumferential region of the respective blow-off element and the target temperature in the respective circumferential region of the film tube.

[0035] The temperature of the tempering gas can be between 5°C and 150°C, in particular between 8°C and 110°C. The target temperature of the film tube downstream of the post-tempering unit can be between 35°C and 110°C, in particular between 45°C and 80°C.

[0036] Furthermore, an annular gas curtain can be blown substantially parallel to the longitudinal axis and around the flow of tempering gas. The gas curtain thus surrounds the tempering gas flow and protects it from external influences and does not mix excessively with ambient air having a different temperature than the tempering gas.

[0037] The film tube can be guided downstream of the at least one cooling gas ring and upstream of the frost line by means of a correction basket having a plurality of correction elements configured to enclose the film tube and form a correction opening, the correction elements being adjustable to set the diameter of the correction opening.

[0038] The object is also achieved by a blown film production line having a blowing head for pushing out a film tube of plasticized thermoplastic material in a winding direction along a longitudinal axis of the blown film production line, at least one cooling gas ring downstream of the blowing head in the winding direction for blowing cooling gas onto the film tube in order to allow the film tube to solidify at the frost line under the action of the cooling gas. A post-tempering unit for post-tempering the film tube is configured and intended to be arranged downstream of the frost line. The post-tempering unit has a plurality of blowing elements for blowing tempering gas onto the film tube, the blowing elements being configured to enclose the film tube and form a passage opening for the film tube, and the blowing elements being adjustable for setting the diameter of the passage opening. A temperature sensor for detecting the temperature of the film tube is arranged downstream of at least one of the blowing elements, the blown film production line having a control unit which is set to adjust the temperature of the film tube downstream of the at least one blowing element to a target temperature by blowing tempering gas onto the film tube by means of the post-tempering unit.

[0039] The at least one cooling gas ring can form a central opening for the film tube to pass through and have at least one internal outlet nozzle for the cooling gas.

[0040] The post-tempering unit can have a plurality of guide elements configured to enclose the film tube and form a guide opening for guiding the film tube, the post-tempering unit having a frame to which the guide elements are adjustably hinged for setting the diameter of the guide opening.

[0041] The diameters of the correction opening, the guide opening and the passage opening are to be understood as the maximum possible diameter of an imaginary circle within the adjustable elements, i.e. the correction elements of the correction basket and the guide elements and the blowing elements of the post-tempering unit.

[0042] If the rear tempering unit has both a blowing element and a guiding element, it is ensured that the film tube is fed to the downstream unit, for example the collapsing unit, as centrally as possible. The combination of blowing element and guiding element in one unit also allows a high flow rate of the tempering gas to the film tube without excessively influencing the position of the film tube or causing vibrations in the film tube. This also prevents the film tube from contacting the blowing element. Furthermore, the combination of blowing element and guiding element in one unit makes the installation height of the rear tempering unit lower.

[0043] The possible high flow rate also improves the temperature control effect. In particular when cooling the film tube, an effective rear cooling is achieved by blowing in the tempering gas at a high flow rate, so that the rear cooling distance required for convective cooling after the at least one cooling gas ring is shorter. The longer the rear cooling period, the longer the rear cooling section must be. This leads to a correspondingly high blown film production line. A more effective temperature control effect during cooling means that the required rear cooling section can be shorter. Thus, the blown film production line has a more compact design and a lower overall height.

[0044] Furthermore, by the blowing element being adjustably articulated to the frame to set the diameter of the passage opening, an efficient and variable rear tempering is achieved. This ensures that the blowing element always maintains a constant distance from the film tube, regardless of the diameter of the film tube produced.

[0045] The rear tempering unit can also be designed to heat and / or cool the film tube. To this end, the rear tempering unit can have a cooling unit for cooling the tempering gas and / or a heating unit for heating the tempering gas. In order to reduce or prevent the film from sticking together when folding (blocking), the film tube can be rear-cooled. This means that the blown film production line can be operated at a higher output, i.e. at a higher film tube winding speed, without there being a risk that the film tube is fed to the collapsing unit when it is too hot and there is a risk of blocking. Thus, the output rate, i.e. the amount of film produced per unit of time, can be increased. Furthermore, the use of additives in the plastic material to reduce the tendency to block can be reduced or even avoided. In addition to cost savings, the reduction of additives can also have a positive effect on the service life of the screw of the extruder or the extruder. Additives for reducing the tendency to block usually include mineral fillers, which can lead to increased wear of the extruder components, in particular the screw.

[0046] However, in order to improve the flatness of the film tube, the film tube can be reheated to reduce the uneven stress distribution in the molecular structure. This improves the flatness and uniformity of the film tube.

[0047] One specific advantage here is that the same post-conditioning unit is equally suitable for cooling tubular films made of a material sensitive to blocking and for heating tubular films made of a material sensitive to flatness. This means that no post-conditioning unit needs to be exchanged when switching between a material sensitive to blocking and a material sensitive to flatness.

[0048] In order to blow the conditioning gas onto the film tube, the blowing elements can each have at least one inwardly facing blowing nozzle. The at least one nozzle can be designed as a circumferential slot around the film tube. A plurality of short slots or openings can also be arranged one behind the other or next to each other in the circumferential direction. The at least one blowing nozzle should be designed or arranged in such a way that a uniform flow of the conditioning gas onto the film tube is possible.

[0049] In one embodiment of the blown film production line, the blowing elements and / or the air distribution ring arranged radially outside the blowing elements and supplying them with conditioning gas can each have at least one outlet nozzle pointing radially to the radially outer side of the at least one blowing nozzle at least substantially parallel to the longitudinal axis in order to generate a curtain of gas flowing around the longitudinal axis in an annular manner parallel to the axis. It is also conceivable to provide separate rings to generate the curtain of gas. The curtain of gas surrounds the conditioning gas flow and protects it from external influences and does not mix excessively with ambient air of a different temperature.

[0050] It can be advantageous for the blowing elements to be arranged downstream of the guiding elements. The conditioning gas hits the film tube after leaving the at least one blowing nozzle and is drawn along the take-up direction of the film tube. If the blowing elements are arranged downstream of the guiding elements, at least a part, preferably the largest part, of the conditioning gas does not hit the guiding elements and is therefore not deflected or swirled. This achieves the longest possible distance of the conditioning gas acting on the film tube without being influenced.

[0051] In an exemplary embodiment, the blowing elements and the guiding elements can be adjusted synchronously. This ensures that the blowing elements are always kept at a constant distance from the film tube, regardless of the diameter of the film tube, or that the blowing elements are set back radially from the guiding elements by a constant amount.

[0052] In order to achieve the synchronous adjustment of the blowing elements and the guiding elements, the post-conditioning unit can have, for example, a plurality of carriages distributed circumferentially, which are adjustably articulated to the frame. At least one of the blowing elements and at least one of the guiding elements can then be attached to each of the carriages.

[0053] When the blowing elements are arranged set back radially from the guiding elements, the diameter of the guiding openings of the post-conditioning unit formed by the guiding elements is smaller than the diameter of the through openings of the post-conditioning unit formed by the blowing elements.

[0054] According to an exemplary embodiment, the blown film production line includes a flattening unit located downstream of the post-temperature control unit for flattening the film tube. Here, the area between the post-temperature control unit and the flattening unit contains no components that affect the film tube.

[0055] An annular baffle device can be positioned downstream of the post-temperature control unit, through which the diaphragm tube passes for feeding. The baffle device can consist of individual baffles, each connected to a bracket of the blowing or guiding element. The baffles are arranged circumferentially adjacent to each other and together form a ring. The baffle device serves to maintain the temperature-controlled gas along the diaphragm tube for a certain length and protect it from external influences, preventing excessive mixing with ambient air at different temperatures.

[0056] The post-temperature control unit may also include a suction unit for at least partially extracting the temperature-controlling gas. If the blowing element blows as far as possible along the winding direction, the suction unit can be positioned downstream of the blowing element. If the blowing element blows substantially in the opposite direction to the winding direction, the suction unit can be positioned upstream of the blowing element. The suction unit can be fluidly connected to the temperature-controlling gas supply source for the blowing element. Under certain conditions, this allows for a reduction in the amount of energy required to pre-temperature control the gas. Specifically, a control system can be provided that uses the suction unit to regulate the volumetric flow rate of the recirculated temperature-controlling gas to achieve the highest possible energy recovery.

[0057] In one embodiment, at least one temperature sensor for detecting the temperature of the thin-film tube is arranged circumferentially around the longitudinal axis upstream of the blowing element.

[0058] The blown film production line can also be equipped with a temperature sensor for detecting the temperature of the temperature-regulating gas.

[0059] This allows the temperature of the film tube to be determined and controlled downstream of the blowing element. For this purpose, the temperature sensor can be placed on a bracket for the blowing element or guide element, or on a frame in the outlet area of ​​the post-temperature control unit, or on any other element of the blown film production line downstream of the post-temperature control unit.

[0060] In one embodiment, the temperature of the film tube can be determined by means of a temperature sensor upstream of the blowing element. For this purpose, the temperature sensor can be arranged on a bracket for the blowing element or guide element, or on a frame in the inlet area of ​​the post-temperature control unit, or on any other element of the blown film production line upstream of the post-temperature control unit.

[0061] The temperature and / or the volumetric flow or pressure of the temperature control gas can be adjusted depending on the temperature of the film tube upstream and / or downstream of the blowing element, or the temperature difference between the temperature of the film tube upstream and downstream of the blowing element, and the difference between the target temperature and the actual temperature of the film tube downstream of the blowing element.

[0062] To this end, the blown film production line can further comprise a pressure sensor and / or a volumetric flow sensor for detecting the pressure or the volumetric flow of the temperature control gas. The pressure can be used to infer the volumetric flow of the temperature control gas. The sensor is preferably located within the production line system for supplying the blowing element with temperature control gas. This means that the sensor can be located anywhere between the blower for generating the pressure and the blowing nozzle of the blowing element. BRIEF DESCRIPTION OF DRAWINGS

[0063] Example embodiments will be described in more detail below with reference to the accompanying drawings. In the drawings,

[0064] Figure 1 is a general view of a blown film production line with a post-temperature control unit of a first embodiment,

[0065] Figure 2 is an enlarged view of the blown film production line in the area of a second embodiment of the post-temperature control unit,

[0066] Figure 3 is an enlarged view of the blown film production line in the area of a third embodiment of the post-temperature control unit,

[0067] Figure 4 is an enlarged view of the blown film production line in the area of a fourth embodiment of the post-temperature control unit,

[0068] Figure 5 is a top front view of a post-temperature control unit according to Figure 1

[0069] Figure 6 is a side view of a post-temperature control unit according to Figure 5

[0070] Figure 7 is an enlarged top view of a post-temperature control unit according to Figure 5 DETAILED DESCRIPTION

[0071] Figure 1 ​​​is a partial longitudinal sectional side view of a blown film production line for producing a thin-film tube 1 along a longitudinal axis L. An extruder 3 is arranged on a machine base 2, on which two feed hoppers 4, 5 for thermoplastic material can be seen. The thermoplastic material fed in granular form via the feed hoppers 4, 5 is plasticized and homogenized in the screw of the extruder 3 by means of pressure and additional heating means and is pressed into a blow head 6 adjacent to the extruder 3, the vertical axis of which runs along the longitudinal axis L of the blown film production line. The blow head 6 has a schematically illustrated annular nozzle 7 on its upper side, from which the inflated, axis-symmetrical thin-film tube 1, which is initially still composed of plasticized film material, is extruded. After the film material has solidified, the thin-film tube 1 essentially retains its diameter. The thin-film tube 1 is flattened in a flattening unit 8 and pulled upward away by a winding-up unit 9. The flattened thin-film tube 1 is then wound onto a roll (not shown here). In the direction from the blow head 6 to the winding-up unit 9, the functional terms "front" and "downstream" are used in the sense of indicating "below" and "above" in spatial terms.

[0072] Above the blow head 6, a cooling gas ring 10 is shown with a partially schematically illustrated gas supply line 11. The gas supply line 11 is connected at the inlet side with a blower 12, via which cooling gas, usually air, is delivered to the cooling gas ring 10. For this purpose, ambient air is drawn in by the blower 12. Other cooling gases or cooling gas mixtures can also be used. The cooling gas ring 10 has an inner outlet nozzle 13 from which the cooling gas flows out and onto the thin-film tube 1, which is under an increased internal pressure and is guided in an annular shape essentially parallel to the wall through a central opening 19 of the cooling gas ring 10. The cooling gas flowing from the blower 12 to the thin-film tube 1 is indicated by arrows. The diameter of the plasticized thin-film tube 1 in this region initially expands under the above-mentioned overpressure inside until it solidifies under the action of the cooling gas and assumes a constant diameter. The transition point from plasticized material to hardened material is referred to as the "frost line" and is indicated as 14. The frost line 14 does not have to be a clear line, but can extend over a limited area in the direction of the longitudinal axis L. In order to generate the internal overpressure, an internal cooling tower 15 is centrally mounted on the blow head 6, via which the cooling gas is introduced into the interior of the thin-film tube 1. The introduced cooling gas is discharged via a gas extraction line 16 in such a way that the defined internal pressure is maintained.

[0073] Above, i.e. downstream, the frost line 14 in the winding direction along the longitudinal axis L there is a correction basket 17 which contains correction elements 18 with superimposed roller arrangements which are arranged essentially as a ring around the film tube 1. In order to be able to adapt to different diameters of the film tube 1, the roller arrangements are located on pivoting sections which form individual partial circumferences, by means of which the diameter of the correction opening of the correction basket 17 through which the film tube 1 is guided along the longitudinal axis L can be changed. In cross section, these sections form a polygonal correction opening. In the example shown, the correction opening has a diameter K.

[0074] The cross section of the still relatively warm film tube 1 is stabilized and guided by the correction basket 17. The correction basket 17 can be arranged in a height-adjustable manner with respect to the blow head 6 in order to always be able to be in the optimum height position with respect to the frost line 14.

[0075] A post-conditioning unit 20 is arranged downstream of the correction basket 17 and serves for post-conditioning the film tube 1. The post-conditioning unit 20 has a plurality of guide elements 21 with roller arrangements, although other guide elements can also be provided instead of the roller arrangements. The guide elements 21 enclose the film tube 1 and form a guide opening with a diameter F. In the present design example, the diameter F of the guide opening is identical to the diameter K of the correction opening. The guide elements 21 serve, inter alia, for centrally guiding the film tube 1 along the longitudinal axis L so that the film tube 1 is guided centrally into the flattening unit 8 in order to avoid creases or edge misalignments. As will be explained in detail below, the guide elements 21 are adjustably articulated to the frame of the post-conditioning unit 20 in order to be able to change the diameter F of the guide opening.

[0076] Furthermore, the post-conditioning unit 20 has a plurality of blowing elements 22 which enclose the film tube 1 and form a through-opening for the film tube 1 with a diameter D. As will be explained in more detail below, the blowing elements 22 are also adjustably articulated to the frame of the post-conditioning unit 20 in order to set the diameter D of the through-opening. The blowing elements 22 blow the conditioning gas diagonally upwards onto the film tube 1 in the winding direction. However, it is also conceivable in principle to blow the conditioning gas horizontally, i.e. in a plane perpendicular to the longitudinal axis L, onto the film tube 1.

[0077] The diameters K, F and D are each defined as the maximum possible diameter of an imaginary circle within the adjustable elements, i.e. the correction elements 18 of the correction basket 17 and the guide elements 21 and the blowing elements 22 of the post-conditioning unit 20.

[0078] A suction unit 23 is arranged downstream of the blowing elements 22, through which the film tube 1 is centrally guided by the suction unit 23. The suction unit 23 comprises one or more suction elements 24 for extracting the tempering gas. In order to extract as much tempering gas as possible before it enters the environment, a baffle device with a plurality of baffles 25 is provided downstream of the at least one suction element 24, which is designed in a circular shape and arranged transversely to the longitudinal axis L and has a comparatively small distance to the film tube 1 compared to the distance to the at least one suction element 24. The individual baffles 25 are each attached to one of the blowing elements 22, but can also be arranged on the carriage 47 to which the blowing elements 22 are attached. The suction elements 24 can be designed as a rigid circumferential ring. As an alternative, it is also possible to arrange a plurality of suction elements 24 circumferentially, whereby, similar to the blowing elements 22, these are pivotably arranged in order to change the inner diameter of the suction unit 23 and to enable it to adapt to different film tube diameters.

[0079] The blowing elements 22 are supplied with tempering gas by means of a blower 26. The blower 26 sucks in ambient air and guides it to the blowing elements 22. For this purpose, a feed line 27 is used, which connects the blower 26 to an air distribution ring 28 of the rear tempering unit 20. The air distribution ring 28 is arranged in the form of a ring that surrounds the film tube 1 and, in the example shown, also the guide element 21, and serves to distribute the tempering gas circumferentially uniformly. The air distribution ring 28 is fluidically connected to the individual blowing elements 22 via supply lines 29.

[0080] A cooling unit in the form of an air cooler 30 and a heating unit in the form of an air heater 31 are arranged in the feed line 27, whereby an external cooling or heating source can also be used. This means that the tempering gas can be cooled or heated as required before it is supplied to the blowing elements 22. Alternatively, it is also possible to provide only the air cooler 30 or only the air heater 31. The arrangement order of the blower 26, the air cooler 30 and the air heater 31 can be selected as required.

[0081] It should be noted that the blower 26, the air cooler 30 and the air heater 31 are shown at the level of the rear tempering unit 20. For this purpose, these components can be arranged in the tower frame of the blown film production line. However, they can also be provided on the machine base.

[0082] The at least one suction element 24 is fluidically connected to the blower 26 via an exhaust line 32. This means that the tempering gas can be conveyed upstream of the air cooler 30 and the air heater 31 via the blower 26 for energy recovery, thereby reducing the required heating or cooling capacity.

[0083] The blown film production line also has a control unit 33, which is connected to the blower 26, the air cooler 30 and the air heater 31 in order to control them. Furthermore, the control unit 33 is connected to the control flap 34 in the exhaust line 32 in order to control the volume flow of the recirculated temperature control gas in the exhaust line 32. Signals from a plurality of sensors are processed in order to control the system. The control unit 33 is equipped with a temperature sensor 35 for detecting the temperature of the temperature control gas in the feed line 27, with a pressure sensor 36 for detecting the pressure in the air distribution ring 28 on the air distribution ring 28, with a temperature sensor 37 for detecting the temperature of the film tube 1 before it enters the post-temperature control unit 20 upstream of the post-temperature control unit 20 and with a temperature sensor 38 for detecting the temperature of the film tube 1 after it leaves the temperature control unit 20 downstream of the post-temperature control unit 20.

[0084] Figure 2 An enlarged view of the blown film production line in the region of a second embodiment of the post-temperature control unit 20 is shown. Components which correspond to components of the blown film production line shown in Figure 1 are marked with the same reference signs and are explained.

[0085] Unlike the post-temperature control unit 20 according to the first embodiment, the post-temperature control unit 20 of the second embodiment has no suction unit and no baffle device. One or more air curtains can be blown in order to ensure that the temperature control gas flowing from the blowing element 22 is as laminar as possible along the surface of the film tube 1. For example, an inner air curtain 39 flowing in the take-up direction can be blown, which flows out through openings not shown in detail in the blowing element 22, thereby enclosing the temperature control gas between itself and the film tube 1. Alternatively or additionally, an outer air curtain 40 flowing in the take-up direction can be blown, which flows out through openings not shown in detail in the air distribution ring 28.

[0086] Likewise, alternatively or additionally, an inner air curtain 41 flowing against the take-up direction can be provided, which is blown out of openings not shown in detail in the blowing element 22. Furthermore, alternatively or additionally, an outer air curtain 42 flowing against the take-up direction can be provided, which is blown out of openings not shown in detail in the air distribution ring 28.

[0087] Additionally or alternatively, a lower air curtain 43 flowing radially can be blown out of openings not shown in detail in the air distribution ring 28.

[0088] Figure 3 An enlarged view of the blown film production line in the region of a third embodiment of the post-temperature control unit 20 is shown. Components which correspond to components of the blown film production line shown in Figure 1 and Figure 2The components of the blown film production line that correspond to components of the rear temperature control unit 20 according to the first embodiment are provided with the same reference numerals and are explained.

[0089] Unlike the rear temperature control unit 20 according to the second embodiment, no air curtain is provided. Instead, the rear temperature control unit 20 has a baffle device consisting of a plurality of baffles 25 arranged downstream of the blowing elements 22. Each baffle 25 is attached to one of the blowing elements 22, but can also be arranged on the carriage 47 to which the blowing elements 22 are attached. In the example shown, the baffles 25 form a truncated conical baffle device and a narrow annular slot between each baffle 25 and the film tube 1 for the passage of the temperature control gas.

[0090] Figure 4 An enlarged view of the blown film production line in the region of a fourth embodiment of the rear temperature control unit 20 is shown. The components of the blown film production line that correspond to components of the rear temperature control unit 20 according to the first embodiment are provided with the same reference numerals and are explained. Figures 1 to 3

[0091] Unlike the rear temperature control unit 20 according to the first three embodiments, in the fourth embodiment the blowing elements 22 are arranged upstream of the guide elements 21. Furthermore, the blowing elements 22 do not blow diagonally upwards in the take-up direction, but rather diagonally downwards against the take-up direction.

[0092] Figure 5 A top view of the rear temperature control unit 20 according to the fourth embodiment is shown, wherein the components of the blown film production line that correspond to components of the rear temperature control unit 20 according to the first embodiment are provided with the same reference numerals and are explained. Figure 1 Figure 1 The rear temperature control unit 20 has a frame 44 to which the movable elements described below are attached and which, if necessary, is arranged to be height-adjustable relative to the blown film head. Furthermore, the air distribution ring 28 is attached to the frame 44.

[0093] The frame 44 forms a central passage through which the film tube 1 is guided parallel to the longitudinal axis L shown. Six adjustment units 45 are distributed circumferentially. The adjustment units 45 serve to adjust the guide elements 21 in a direction radial relative to the longitudinal axis L.

[0094] The frame 44 forms a central passage through which the film tube 1 is guided parallel to the longitudinal axis L shown. Six adjustment units 45 are distributed circumferentially. The adjustment units 45 serve to adjust the guide elements 21 in a direction radial relative to the longitudinal axis L. Figure 1

[0095] The adjustment units 45 each comprise a pivot arm 46 that is pivotably attached to the frame 44. In this case, the pivot arm 46 is pivotable about a pivot axis arranged parallel to the longitudinal axis L.

[0096] ​​​Furthermore, the adjustment units 45 each have a carrier 47 which, in the shown embodiment, carries two guide elements 21 in the form of rollers which are spaced apart from each other in the direction of the longitudinal axis L and which are arranged to overlap in a V-shape when seen in the direction of the longitudinal axis L. The carriers 47 are pivotably connected to the pivot arms 46. In this case, the carriers 47 are pivotably connected to the pivot arms 46 about a pivot axis which is arranged parallel to the longitudinal axis L.

[0097] Furthermore, the adjustment units 45 each comprise a coupling lever 48 which is pivotably connected to the carrier 47.

[0098] Finally, the adjustment units 45 each comprise an actuation mechanism by means of which the coupling lever 48 is pivotably connected to the frame 44.

[0099] In order to represent the actuation mechanism, the coupling levers 48 of the adjustment units 45 are each connected to the frame 44 in a pivotable and displaceable manner via a coupling element (not shown). The coupling element is rotatably connected to the frame 44. The coupling lever 48 is slidably coupled to the coupling element. Furthermore, a cam follower 49 is attached to each of the coupling levers 48 and is guided for translational movement along a guide 50 on the frame 44. In the shown embodiment, the guide 50 is a groove in a plate 51 which is fixedly attached to the frame 44. However, other guide systems are also conceivable. The shape of the guide 50 is curved and adapted such that the carrier 47 is always centrally aligned with respect to the longitudinal axis L, independent of the distance from the longitudinal axis L or the film tube 1. This ensures an exact central alignment of the guide elements 21 in the form of two rollers with respect to the film tube 1, so that the two rollers always remain in contact with the film tube 1.

[0100] In principle, other actuation mechanisms are also conceivable, for example parallelogram arrangements, so that at least an adjustment of the carrier 47 radially with respect to the longitudinal axis L as far as possible should be ensured.

[0101] The blowing elements 22 are also attached to the carriers 47, whereby they are radially slightly behind the guide elements 21. In the shown embodiment example, the blowing elements 22 are each arranged to axially overlap one of the guide elements 21.

[0102] In the shown illustration, the guide elements 21 have not yet been guided completely to the film tube 1 in order to guide it. For the sake of clarity, the guide elements 21 are shown at a slight distance from the film tube 1. Figure 5

[0103] Figure 6 A view from radially outward of the longitudinal axis of the film tube 1 according to the application is shown in Fig. 3. Figure 5 ​Figure 6 shows a side view of a rear tempering unit according to the application. Four guide elements 21 and two blowing elements 22 are firmly mounted on a carrier 47. The guide elements 21 in the form of rollers are arranged in pairs, one above the other, in a V-shape. The two pairs of guide elements 21 are arranged one above the other in a matching arrangement.

[0104] The two blowing elements 22 are arranged above, i.e. downstream of, the guide elements 21. Like the guide elements 21, the blowing elements 22 are also arranged one above the other in a V-shape. The blowing elements 22 have blowing openings 52 on the inner side, i.e. in the direction towards the film tube. The tempering gas escapes through the blowing openings 52 and flows against the surface of the film tube. In the shown example embodiment, the blowing openings 52 are arranged in such a way that, in contrast to the embodiment according to Figures 1 to 4 the tempering gas is not blown at an angle with respect to the longitudinal axis in the direction of winding or against the direction of winding, but is blown horizontally, i.e. in a plane perpendicular to the longitudinal axis L, onto the film tube.

[0105] Figure 7 Figure 7 shows an enlarged top view of a rear tempering unit according to the application in another embodiment. The shown embodiment of the rear tempering unit is essentially the same as the one shown in Figure 5 Figure 6, corresponding components have the same reference numerals. In contrast to the embodiment shown in Figure 5 Figure 6, the blowing elements 22 have outlet nozzles 53 which are aligned parallel to the longitudinal axis L. The outlet nozzles 53 blow the tempering gas upwards parallel to the longitudinal axis L, thereby forming a curtain of gas which travels around the longitudinal axis L. However, they can also be additionally or alternatively arranged on the bottom side of the blowing elements 22 and blow the curtain of gas downwards. Figure 5 In addition, in the shown embodiment, outlet nozzles 54 are also provided on the air distribution ring 28, which are aligned parallel to the longitudinal axis L. The outlet nozzles 54 blow the tempering gas upwards parallel to the longitudinal axis L, thereby forming a further curtain of gas which travels around the longitudinal axis L. They can also be additionally or alternatively arranged on the bottom side of the air distribution ring 28 and blow the curtain of gas downwards.

[0106] It is also conceivable that the outlet nozzles 53, 54 are arranged only on the blowing elements 22 or only on the air distribution ring 28. In addition, a separate distribution ring can also be additionally or alternatively provided, which is designed to have outlet nozzles to generate one or more curtains of gas. Radially aligned outlet nozzles can also be provided. In addition, a separate supply of gas from the tempering gas can be provided to form one or more curtains of gas.

[0107]

[0108] ​The inlet nozzles 52 and the outlet nozzles 53, 54 can have any shape, for example in the form of holes or slots. For example, the blowing element 22 can have in each direction a single blowing nozzle 52 and / or a single outlet nozzle 53 which extends at least approximately over the entire length of the blowing element 22. It is also possible to provide a plurality of slot-shaped inlet nozzles 52 or outlet nozzles 53 which are arranged to overlap and / or at an angle to a plane perpendicular to the longitudinal axis L.

[0109] List of reference signs

[0110] 1 film tube

[0111] 2 machine base

[0112] 3 extruder

[0113] 4 feed hopper

[0114] 5 feed hopper

[0115] 6 blowing head

[0116] 7 annular nozzle

[0117] 8 flattening unit

[0118] 9 winding unit

[0119] 10 cooling gas ring

[0120] 11 gas supply line

[0121] 12 blower

[0122] 13 outlet nozzle

[0123] 14 frost line

[0124] 15 internal cooling tower

[0125] 16 gas extraction duct

[0126] 17 correction basket

[0127] 18 correction element

[0128] 19 central opening of the cooling gas ring

[0129] 20 post-conditioning unit

[0130] 21 guide element

[0131] 22 blowing element

[0132] 23 suction unit

[0133] 24 suction element

[0134] 25 baffle

[0135] 26 blower

[0136] 27 feed line

[0137] 28 air distribution ring

[0138] 29 supply line

[0139] 30 air cooler

[0140] 31 air heater

[0141] 32 exhaust line

[0142] 33 control unit

[0143] 34 control flap

[0144] 35 temperature sensor in the feed line

[0145] 36 pressure sensor in the air distribution ring

[0146] 37 temperature sensor before the post-temperature control unit

[0147] 38 temperature sensor after the post-temperature control unit

[0148] 39 inner air curtain flowing in the winding direction

[0149] 40 outer air curtain flowing in the winding direction

[0150] 41 inner air curtain flowing against the winding direction

[0151] 42 outer air curtain flowing against the winding direction

[0152] 43 lower air curtain flowing radially

[0153] 44 frame

[0154] 45 adjustment unit

[0155] 46 pivoting arm

[0156] 47 bracket

[0157] 48 coupling rod

[0158] 49 cam follower

[0159] 50 guide

[0160] 51 plate

[0161] 52 blowing nozzle

[0162] 53 outlet nozzle

[0163] 54 exit nozzle

[0164] D diameter of the through opening

[0165] F diameter of the guide opening

[0166] K diameter of the correction opening

[0167] L longitudinal axis

Claims

1. A method for post-temperature conditioning of a film tube extruded by means of a blown film production line, comprising the following steps: -A film tube (1) of plasticized thermoplastic material is pushed out in the winding direction along the longitudinal axis (L) of the blow molding film production line by means of a blow molding head (6). -Cooling gas is blown onto the film tube (1) downstream of the blow molding head (6) relative to the winding direction by means of at least one cooling gas ring (10), so that the film tube (1) solidifies at the frosting line (14) under the action of the cooling gas. - The film tube (1) is post-temperature regulated by means of a post-temperature regulation unit (20) downstream of the frost line (14), the post-temperature regulation unit (20) having a plurality of adjustable blowing elements (22) for blowing temperature regulating gas onto the film tube (1), the blowing elements forming through openings for the film tube (1). - By adjusting the blowing element (22), the diameter (D) of the through opening formed by the blowing element (22) is adapted to the diameter of the film tube (1). -Measure the actual temperature of the film tube (1) downstream of at least one of the blowing elements (22), and - By blowing the temperature-regulating gas onto the thin film tube (1) using the post-temperature-regulating unit (20), the temperature of the thin film tube (1) downstream of the at least one blowing element (22) is adjusted to the target temperature.

2. The method according to claim 1, Its features are, The post-temperature control unit (20) has a plurality of guide elements (21) which are adjustablely hinged to the frame (44) for guiding the thin film tube (1) and forming a guide opening for guiding the thin film tube (1) through which it passes. The diameter (F) of the guide opening is adapted to the diameter of the thin film tube (1) by adjusting the guide element (21).

3. The method according to claim 1 or 2, Its features are, The actual temperature of the thin film tube (1) is measured over at least one circumferential region of the thin film tube (1), and The temperature and / or volumetric flow rate of the temperature-regulating gas arranged in at least one blowing element (22) in the at least one circumferential region is set according to the difference between the actual temperature in the corresponding circumferential region of the corresponding circumferential region of the corresponding blowing element (22) and the target temperature in the corresponding circumferential region of the corresponding blowing element (22).

4. The method according to any one of claims 1 to 3, Its features are, The film tube (1) is cooled or heated downstream of the frost line (14), at least in certain areas along the circumference, by means of the temperature-regulating gas.

5. The method according to any one of claims 1 to 4, Its features are, The actual temperature of the thin film tube (1) is measured in the region where the thin film tube (1) emerges from the outlet of the post-temperature control unit (20).

6. The method according to any one of claims 1 to 5, Its features are, The temperature and / or volumetric flow rate of the temperature-regulating gas are set based on the difference between the measured actual temperature of the membrane tube (1) and the target temperature of the membrane tube (1).

7. The method according to any one of claims 1 to 6, Its features are, An annular air curtain is blown out substantially parallel to the longitudinal axis and around the flow of the temperature-regulating gas.

8. The method according to any one of claims 1 to 7, Its features are, The thin film tube (1) is guided downstream of the at least one cooling gas ring (10) and upstream of the frost line (14) by means of a correction basket (17) having multiple correction elements (18), the correction elements (18) being configured to enclose the thin film tube (1) and form a correction opening, the correction elements (18) being adjusted to set the diameter (K) of the correction opening.

9. Blown film production line, including: A blow molding head (6) is used to eject a plasticized thermoplastic film tube (1) along the longitudinal axis (L) of the blow molding film production line in the winding direction. At least one cooling gas ring (10), the cooling gas being downstream of the blow molding head (6) in the winding direction, is used to blow the cooling gas onto the film tube (1) so that the film tube (1) solidifies at the frosting line (14) under the action of the cooling gas, and A post-temperature control unit (20) is used to perform post-temperature control on the thin-film tube (1), and the post-temperature control unit is constructed and intended to be arranged downstream of the frost line. Its features are, The post-temperature control unit (20) has a plurality of blowing elements (22) for blowing temperature-controlled gas onto the thin film tube (1), the blowing elements being configured to enclose the thin film tube (1) and form a through opening for the thin film tube (1), and the blowing elements (22) being adjustable to set the diameter (D) of the through opening. A temperature sensor (38) for measuring the actual temperature of the thin film tube (1) is arranged downstream of at least one of the blowing elements (22), and The blown film production line has a control unit (33) configured to regulate the temperature of the film tube (1) downstream of the at least one blowing element (22) to a target temperature by blowing the temperature regulating gas onto the film tube (1) by means of the post-temperature regulating unit (20).

10. The blown film production line according to claim 9, Its features are, The post-temperature control unit (20) has a plurality of guide elements (21) configured to enclose the thin film tube (1) and form a guide opening for guiding the thin film tube (1). The post-temperature control unit (20) has a frame (44) to which the guide elements (21) are adjustablely hinged to in order to set the diameter (F) of the guide opening.

11. The blown film production line according to claim 10, Its features are, The blowing element (22) is arranged downstream of the guiding element (21).

12. The blown film production line according to claim 10 or 11, Its features are, The blowing element (22) and the guiding element (21) can be adjusted synchronously.

13. The blown film production line according to any one of claims 10 to 12, Its features are, The diameter (F) of the guide opening of the rear temperature control unit (20) is smaller than the diameter (D) of the through opening of the rear temperature control unit (20).

14. The blown film production line according to any one of claims 9 to 13, Its features are, The post-temperature control unit (20) has a cooling unit (30) for cooling the temperature control gas and / or a heating unit (31) for heating the temperature control gas.

15. The blown film production line according to any one of claims 9 to 14, Its features are, Each of the blowing elements (22) has at least one inward blowing nozzle (52) for blowing the temperature-controlled gas onto the diaphragm tube (1).

16. The blown film production line according to claim 15, Its features are, The blowing element (22) or the air distribution ring (28) arranged radially outside the blowing element (22) and supplying the temperature-regulating gas to it each has at least one outlet nozzle (53, 54), which is radially pointed at least substantially parallel to the longitudinal axis to the radial outside of the at least one blowing nozzle (52) in order to create an air curtain flowing out in an annular manner parallel to the longitudinal axis (L).

17. The blown film production line according to claim 16, Its features are, The post-temperature control unit (20) has multiple brackets (47) arranged circumferentially and adjustablely hinged to the frame (44). At least one of the blowing elements (22) and at least one of the guiding elements (21) are fastened to each of the brackets (47).

18. The blown film production line according to any one of claims 9 to 17, Its features are, The blown film production line includes a flattening unit (8) located downstream of the post-temperature control unit (20) for flattening the film tube (1), and The area between the post-temperature control unit (20) and the flattening unit (8) has no components that affect the thin film tube (1).

19. The blown film production line according to any one of claims 9 to 18, Its features are, The annular baffle device (25) through which the thin film tube (1) passes is arranged downstream of the rear temperature control unit (20).

20. The blown film production line according to any one of claims 9 to 19, Its features are, The post-temperature control unit (20) has a suction unit (23) for at least partially extracting the temperature-controlling gas, and The suction unit (23) is fluidly connected to the temperature-controlled gas supply source of the blowing element (22).

21. The blown film production line according to any one of claims 9 to 20, Its features are, At least one temperature sensor (37) for detecting the temperature of the thin film tube (1) is arranged circumferentially around the longitudinal axis (L) upstream of the blowing element (22).

22. The blown film production line according to any one of claims 9 to 21, Its features are, The blown film production line includes a temperature sensor (35) for detecting the temperature of the temperature-regulating gas.

23. The blown film production line according to any one of claims 9 to 22, Its features are, The blown film production line includes a pressure sensor (36) for detecting pressure and / or a volumetric flow sensor for detecting the volumetric flow rate of the temperature-regulating gas, for supplying the temperature-regulating gas to the blowing element (22).

24. The blown film production line according to any one of claims 9 to 23, Its features are, A calibration basket (17) is arranged downstream of the at least one cooling gas ring (10) and has a plurality of calibration elements (18) configured to enclose the membrane tube (1) and form a calibration opening for guiding the membrane tube (1). The calibration elements (18) are adjustable to set the diameter (K) of the calibration opening.

Images