VENTILATION MODULE FOR A FILM STRETCHING SYSTEM AND SUCH A FILM STRETCHING SYSTEM

Description

[0001] The invention relates to a ventilation module for a film stretching system and to such a film stretching system. Such a film stretching system can be, for example, a longitudinal stretching system, a transverse stretching system, a sequential stretching system with a longitudinal stretching stage and a transverse stretching stage, or a simultaneous stretching system.

[0002] Such film stretching systems, which are used to produce plastic films, are divided into different zones in which different temperatures prevail. Ventilation modules are necessary to regulate the temperature of the plastic film, which can also be referred to as a film. On the one hand, this temperature control serves to generate or adjust certain film properties. On the other hand, by controlling the temperature of the plastic film web, it can also be stretched (longitudinally and / or transversely). Such a film stretching system comprises several such ventilation modules, which are arranged at a distance from one another in the transport direction of the plastic film web, i.e. in the pull-off direction. The ventilation modules comprise ventilation nozzles, which serve to regulate the temperature of the plastic film web. The ventilation nozzles are also referred to as blow-out nozzles or blow-out nozzle arrangements.

[0003] Generally, the goal is to position the ventilation nozzles as close as possible to the plastic film web to ensure optimal heat transfer. In practice, however, this option is limited by the transport system, which transports the plastic film web between the blow-out nozzles. The transport system height and a suitable safety margin then determine the distance between the blow-out nozzles and the plastic film web.

[0004] One way to bring the blow-out nozzles closer to the plastic film web is to use telescopic nozzle attachments. However, this solution is expensive and therefore rarely implemented. Since the transport system must also be adjustable in width (the stretching width must be adjustable), these nozzle attachments must also be adjusted. Such nozzle attachments are mechanically complex and therefore costly.

[0005] Various ventilation modules are known from the prior art. DE 196 23 471 C1 describes a ventilation nozzle constructed in the form of a perforated nozzle. A large number of holes arranged in a row, offset both in the discharge direction and transversely to the discharge direction, are permeated by a volume flow of air. This volume flow of air is supplied to the holes via a multi-chamber system (feed chamber, additional chamber, distribution chamber).

[0006] In addition, EP 2 692 508 A1 discloses a device for stretching a thermoplastic film in the width direction, wherein an air blowing nozzle provided therein blows heated air onto a film running along a film passage surface.

[0007] A temperature control device for coated fabrics is known from US Pat. No. 3,199,224. A plurality of blow-out nozzles are arranged on both sides of a conveyor belt through which the fabrics are conveyed. These blow-out openings are located within return suction openings. The discharged air jet strikes the material web, bounces off it, and is then sucked back in through the return suction openings.

[0008] A disadvantage of US 3,199,224 is the unclear airflow conditions. In principle, the airflow to be discharged can be described as a chaotically fluctuating flow, meaning that no temporally stationary flow state is established. In this specific case, this means that the free jets oscillate chaotically back and forth. They either only briefly touch the surface of the material web or briefly tip directly into the adjacent return openings. These chaotically fluctuating flows then lead to temporally and spatially uneven heating or cooling of the material web. This results in the uneven mechanical properties of the material web.

[0009] This problem is even greater if, instead of a material to be coated, a plastic film web is to be produced, as proposed in US 3,199,244. In this case, it is important that the mechanical properties (e.g. flatness, haze, Gurley, porosity or shrinkage) are introduced evenly. The strong oscillation and tilting of the free jets, which can also be referred to as impact jets, is very disadvantageous here because it leads to very different heat transfer across the film. For example, it is possible that part of the plastic film web always runs over the impact jets due to the feed movement when these are just tilted away. This part of the plastic film web therefore only experiences a lower heat input. On the other hand, another part of the plastic film web could always happen to run over the impact jets, which hit it favorably and ensure a high heat input.In this case, areas with high heat transfer would alternate with those with low heat transfer. The plastic film web would thus be heated at different temperatures.

[0010] In abstract terms, the unstable flow conditions of existing aeration modules and film stretching systems cause uneven heat input. Due to the movement of the plastic film web in the draw-off direction, its temperature is subjected to different locations and times. Thus, heat treatment steps or process engineering operations in the plastic film web take place at different times and locations. As a result, crystallization, for example, begins or ends at different times or in different positions, which negatively impacts the properties of the plastic film web, such as transparency or similar.

[0011] The object of the present invention is therefore to create a ventilation module for a film stretching system and a corresponding film stretching system that enables simultaneous temperature control of the plastic film web. In particular, more stable flow conditions are to be created. The free jets are therefore no longer allowed to oscillate and tilt as much, thus ensuring more uniform temperature control over time and space.

[0012] The object is achieved by the ventilation module according to the invention according to independent claim 1 and by the film stretching system according to the invention according to claim 14. Claims 2 to 13 contain further developments of the ventilation module according to the invention, and claim 15 contains a further development of the film stretching system according to the invention.

[0013] The ventilation module according to the invention serves to heat or cool plastic film webs, which can have a wide variety of layer thicknesses and compositions. The ventilation module can be used in different zones of a film stretching system. The ventilation module comprises a film feed zone, into which the plastic film web is fed, and a film outlet zone, from which the plastic film web exits again, appropriately tempered. The plastic film web is moved in the withdrawal direction within the ventilation module in a transport plane from the film feed zone toward the film exit zone. Between the film feed zone and the film exit zone, at least one first blow-out nozzle arrangement is provided, which is designed to blow air toward the plastic film web for heating or cooling.The at least one first blow-out nozzle arrangement comprises at least one blow-out nozzle, wherein the at least one blow-out nozzle extends with its longitudinal direction transversely or perpendicularly to the pull-off direction of the plastic film web and is aligned parallel to the transport plane. Furthermore, at least one first suction back system with at least two suction channels is provided. The suction back system comprises two suction areas and is designed to suck air through the suction areas and the suction channels. The suction back system is also arranged between the film feed area and the film outlet area. The at least two suction areas are spaced apart from one another in the pull-off direction and aligned parallel to the transport plane, wherein the at least two suction areas extend with their longitudinal direction transversely or perpendicularly to the pull-off direction of the plastic film web.The at least one blow-out nozzle of the at least one first blow-out nozzle arrangement is arranged (immediately adjacent) between the first and second suction regions, wherein the at least one blow-out nozzle of the at least one first blow-out nozzle arrangement and the at least two suction regions are arranged on the same side of the transport plane. The at least one first suction region is arranged exclusively upstream of the at least one blow-out nozzle in the pull-off direction of the plastic film web, and the at least one second suction region is arranged exclusively downstream of the at least one blow-out nozzle in the pull-off direction of the plastic film web.The at least one first blow-out nozzle arrangement comprises a plurality of nozzle boxes, wherein between two nozzle boxes or at a distance from two nozzle boxes there is a predominantly or completely air-impermeable cover plate arrangement which preferably runs parallel to the transport plane, whereby two adjacent suction areas of different blow-out nozzles are limited in their extension.

[0014] It is particularly advantageous that the suction areas are arranged exclusively in front of and behind the discharge nozzle in the draw-off direction. This creates an impact jet across the entire width of the plastic film web, which oscillates less back and forth and no longer bends. This results in a very constant heat input into the plastic film web. In contrast to US 3,199,224, the discharge nozzle is free of a suction area in the longitudinal direction. Thus, the individual discharge nozzles in US 3,199,224 are each surrounded on all sides by a corresponding suction area. The suction areas are preferably arranged less than 50 cm, 40 cm, 30 cm, 20 cm, 15 cm, 10 cm, or less than 5 cm from the discharge nozzle.The reason for this stabilization can be seen in the fact that the discharge velocity (impulse) is so high that the free jet (impact jet) cannot be drawn immediately into the intake area and is forced to travel a longer distance (via reflection from the plastic film web). Another possibility is that the recirculation vortices support the free jet (impact jet) laterally, thus stabilizing it.

[0015] In a further development of the invention, it was surprisingly discovered through extensive simulation that particularly good results are achieved when the total, i.e., combined intake opening area of ​​both intake areas in the overlap area of ​​the transport plane is 8 to 14 times larger than the total nozzle opening area of ​​the discharge nozzle flanked by the intake areas. This leads to significantly less oscillating impact jets. These jets tilt significantly less to the side than those of the prior art.

[0016] Particularly preferably, the air volume flow that is blown out of the blow-out nozzle in a certain time corresponds to the air volume flow that is fed to the return suction system through the two suction areas in the same time.

[0017] An analysis of the average heat transfer coefficient from the blow-out nozzle to the plastic film web has shown that the novel aeration module according to the invention has a significantly higher average heat transfer coefficient than previously known aeration modules. Furthermore, the heat transfer coefficient of the aeration module according to the invention is significantly more stable or constant over time on the plastic film web, meaning it does not fluctuate as much. The measured temperature fluctuations of the plastic film web after leaving the aeration module are also significantly lower.

[0018] In a preferred embodiment, the at least one blow-out nozzle is designed as a slot nozzle, wherein the nozzle opening area is formed by a fully or partially open slot running in the longitudinal direction of the blow-out nozzle. Alternatively, the blow-out nozzle can also comprise a hole nozzle, wherein the nozzle opening area is formed by a plurality of holes arranged in series in the longitudinal direction of the blow-out nozzle (in the withdrawal direction and / or transversely to the withdrawal direction) and separated from one another in the form of a grid arrangement. In the context of the invention, the nozzle opening area is understood to be the surface area of ​​the at least one blow-out nozzle through which an air mass volume flow can pass. The advantage of a fully or partially (includes e.g.The advantage of a slot opened (i.e. the arrangement of connecting struts at regular intervals) is that a heat transfer coefficient can be achieved which is very stable over time and the temperature fluctuations of the plastic film web after leaving the ventilation module are lower. However, the structure is somewhat more complex, particularly if the ventilation module extends over a very long length in the longitudinal direction and the dimensions of the slot (e.g. slot width) have to be kept constant. Therefore, the slot can also be interrupted at regular intervals by corresponding connecting struts which are only a few millimeters or a few centimeters thick for stabilization. In another exemplary embodiment, the exhaust nozzle comprises a grid arrangement which has a large number of holes arranged in a row and spaced from one another.Such a grid arrangement can be manufactured very easily and offers very high mechanical stability. If the holes are very close together (spacing e.g. less than 20mm, 15mm, 12mm, 10mm, 8mm, 6mm or less than 5mm), then these holes do not act as individual holes with a multitude of individual free jets, but rather a (common) impact jet can be created in the longitudinal direction of the exhaust nozzle. More than one row of holes can also be provided. In particular, two to eight rows can be provided, which are arranged at a distance from one another in the withdrawal direction. Some or all of these holes can, for example, be elongated holes, with their greater extent running either longitudinally or transversely to the withdrawal direction. In principle, it would also be possible for the at least one exhaust nozzle to comprise a mixture of a slot nozzle and a perforated nozzle.In this case, both shapes would alternate along the length of the discharge nozzle. The area where the discharge nozzle is designed as a perforated nozzle (in the form of a grid arrangement) could serve to mechanically stabilize the discharge nozzle. The other areas could then be designed as slotted nozzles.

[0019] Preferably, the first and second intake regions are also formed by a plurality of holes arranged in series in the longitudinal direction of the respective intake region and separated from one another in the form of a corresponding first or second grid arrangement. This ensures high mechanical stability of the intake region. Here, too, more than one row of holes can be provided. In particular, two to eight rows can be provided, which are arranged spaced from one another in the withdrawal direction. Some or all of these holes can, for example, be elongated holes, with their greater extent running either longitudinally or transversely to the withdrawal direction.

[0020] Preferably, the at least one first blow-out nozzle arrangement comprises a separate nozzle box for each blow-out nozzle. In principle, however, several blow-out nozzles could also be arranged in a common nozzle box. The nozzle box comprises corresponding first and second side walls, which are arranged at a distance from one another in the withdrawal direction and which extend in the longitudinal direction of the at least one blow-out nozzle and are arranged transversely or perpendicular to the transport plane. The at least one nozzle box also comprises, opposite the blow-out nozzle, a rear wall which extends in the longitudinal direction of the at least one blow-out nozzle and connects the side walls to one another. The at least one blow-out nozzle is arranged between the side walls. The nozzle box surrounds a corresponding air intake or air guidance chamber, which is preferably open towards the transport plane only in the region of the blow-out nozzle.The nozzle box can be constructed as described in DE 196 23 471 C1. The side walls can be arranged parallel to each other, resulting in a rectangular or square cross-section of the nozzle box. They can also converge at least partially in the direction of the transport plane, resulting in the at least one nozzle box having an at least partially conical cross-section.

[0021] In particular, the corresponding first and second suction channels are formed on the outer area of ​​the side walls, or the first and second suction channels run along the respective side wall.

[0022] A further improvement of the ventilation module occurs when the suction system also includes a corresponding suction box, which extends transversely, in particular perpendicularly, to the pull-off direction of the plastic film web and is aligned parallel to the transport plane. This can be achieved, for example, by arranging the suction box at a greater distance from the transport plane than the at least one nozzle box, with both boxes being arranged on the same side of the transport plane.

[0023] Preferably, however, the at least one first suction system is integrated into the at least one nozzle box of the at least one first blow-out nozzle arrangement.

[0024] The suction box also comprises an intake slot extending in the longitudinal direction of the suction box and / or a plurality of intake openings arranged in series in the longitudinal direction of the suction box and separated from one another. The suction box is preferably open in the longitudinal direction only within the scope of its intake slot or openings. Otherwise, it is closed by corresponding side or rear walls.

[0025] In the course of further intensive investigations and simulations, attempts were made to further support the impact jet emerging from the at least one blow-out nozzle of the at least one first blow-out nozzle arrangement by means of simple geometries or to bring it closer to the plastic film web without having to use complex nozzle attachments. As already explained at the beginning, telescopic nozzle attachments usable for this purpose are mechanically complex to construct and therefore correspondingly expensive because the construction must be able to be pushed into one another due to the width adjustment of the transport system. In a further development according to the invention, it was discovered that it is advantageous if a guide plate arrangement is attached to one side of the at least one blow-out nozzle, which guide plate arrangement protrudes further in the direction of the transport plane than the at least one blow-out nozzle, wherein the guide plate arrangement, like the blow-out nozzle, also extends in the longitudinal direction.This guide plate arrangement can consist of one or more guide plates extending longitudinally. Plastic plates can also be used. In this case, the impingement jet is supported on only one side, whereby the impingement jet is sucked onto the lateral guide (Coanda effect) and thus brought closer to the film. This also prevents premature tipping or oscillation of the impingement jet. The result is more uniform temperature control. The guide plate arrangement or guide plate can also be referred to as a Coanda guide plate.

[0026] The ventilation module preferably also comprises at least one second blow-out nozzle arrangement and at least one second suction-back system. These are constructed in a similar manner to the first blow-out nozzle arrangement and the first suction-back system. The second blow-out nozzle arrangement can therefore comprise one or more blow-out nozzles whose longitudinal direction is aligned transversely or perpendicularly to the pull-off direction of the plastic film web and which extend parallel to the transport plane. However, the first blow-out nozzle arrangement and the at least one first suction-back system are arranged on a first side of the transport plane, whereas the at least one second blow-out nozzle arrangement and the at least one second suction-back system are arranged on a second side of the transport plane, which is opposite the first side. As a result, the plastic film web is temperature-controlled from two sides.

[0027] The film stretching system according to the invention is used to produce plastic film webs and is equipped with at least one aeration module or several of the described aeration modules. If multiple aeration modules are used, these can all be identically constructed. It is of course also possible to use different aeration modules. For example, aeration modules can be used in which the at least one blow-out nozzle is formed from a perforated nozzle, and in which the at least one blow-out nozzle is formed from a slotted nozzle. The same applies to the intake areas. Even within a aeration module, if multiple blow-out nozzles are used, these and the associated intake areas can be designed differently (holes or slots, or size, shape, orientation (angular position), etc.).In the event that at least two ventilation modules differ in the number of exhaust nozzles in their at least one first exhaust nozzle arrangement, the total nozzle opening area of ​​all exhaust nozzles in the at least one first exhaust nozzle arrangement of one ventilation module is preferably approximately the same size as the total nozzle opening area of ​​all exhaust nozzles in the at least one first exhaust nozzle arrangement of the other ventilation module. This always ensures a uniform heat input.

[0028] The ventilation module preferably comprises at least one further exhaust nozzle, which is flanked by further first and second intake regions. The structure and arrangement are the same as for the at least one exhaust nozzle. In this case, the at least one first exhaust nozzle arrangement comprises further nozzle boxes, with each further exhaust nozzle being arranged in a further nozzle box. At least between two nozzle boxes or spaced apart from two nozzle boxes there is a predominantly or completely air-impermeable cover plate arrangement which runs parallel to the transport plane, whereby two adjacent intake regions of different exhaust nozzles are limited in their extent. This means that air can only be extracted in the intake regions, whereby the flow conditions can be adjusted very precisely and reproducibly.

[0029] Various embodiments of the invention are described below by way of example with reference to the drawings. Like objects have the same reference numerals. The corresponding figures of the drawings show in detail: Figure 1: a view of a film stretching system; Figures 2A, 2B: a cross-section through different embodiments of the ventilation module according to the invention; Figure 3: a representation illustrating an overlap area of ​​the suction areas and the blow-out nozzle of the ventilation module according to the invention above a transport plane for a plastic film web; Figures 4A, 4B: various representations of a nozzle box of a first blow-out nozzle arrangement of the ventilation module according to the invention; Figure 5: a cross-section through an embodiment of the ventilation module according to the invention with blow-out nozzle arrangements and suction systems arranged on both sides of the transport plane; Figure 6: a plan view of the blow-out nozzle arrangement comprising several blow-out nozzles separated from one another by a cover plate arrangement, each blow-out nozzle being flanked by two suction areas;Figures 7, 8A, 8B: a cross-section through different embodiments of the ventilation module according to the invention; Figure 9: a cross-section through different embodiments of the ventilation module according to the invention, wherein the embodiments differ in the number of exhaust nozzles and recirculation nozzles; Figure 10: a spatial representation of an embodiment of the ventilation module according to the invention, wherein the exhaust nozzles comprise perforated nozzles; Figure 11: a spatial representation of an embodiment of the ventilation module according to the invention, wherein the exhaust nozzles of the first exhaust nozzle arrangement are designed as twin nozzles; and Figures 12A, 12B: various diagrams comparing exemplary profiles of the temperature and the average heat transfer coefficient of a ventilation module according to the invention and a ventilation module from the prior art.

[0030] Figure 1shows a plan view of a film stretching system 1 according to the invention. This film stretching system 1 can be designed as a longitudinal stretching system or transverse stretching system or sequential stretching system with a longitudinal stretching stage and a transverse stretching stage or as a simultaneous stretching system. The film stretching system 1 serves to stretch a plastic film web 2 and is divided for this purpose, for example, into different zones 1a, 1b, 1c, 1d and 1e. Of course, not all of these zones 1a to 1e actually have to be present. In the different zones 1a to 1e, the plastic film web 2 is exposed to different temperatures in order to generate or adjust certain film properties. The first zone 1a is also referred to as the preheating zone. The second zone 1b is referred to as the stretching zone, whereas the third zone 1c is referred to as the further heating zone. The fourth zone 1d is also referred to as the neutral zone and the fifth zone 1e as the cooling zone.In principle, there can be further neutral zones between the individual zones 1a to 1e to ensure separation of the zones 1a to 1e, so that the individual zones 1a to 1e influence each other less (the air flows from one zone 1a to 1e to the other).

[0031] A zone 1a to 1e comprises a ventilation module 3 according to the invention or several of the ventilation modules 3 according to the invention. These ventilation modules 3 extend in the withdrawal direction 4 of the plastic film web 2 with a length of approximately more than 1 m, 1.5 m, 2 m, 2.5 m, 3 m, 3.5 m, 4 m, 4.5 m or more than 5 m, but preferably less than 6 m, 5 m, 4 m, 3 m, 2 m, 1 m. They also comprise an extension in the longitudinal direction 5, i.e. transversely or perpendicularly to the withdrawal direction 4 of the plastic film web 2, with a length of more than 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 9 m, 10 m, 11 m, 12 m, 13 m or more than 15 m, but preferably less than 17m, 16m, 15m, 14m, 13m, 12m, 11m, 10m, 9m, 8m, 7m, 6m, 5m, 4m, 3m or less than 2m.

[0032] A ventilation module 3 can comprise a fan device (not shown) and a corresponding heating and / or cooling device (not shown). Thus, the ventilation modules 3 can heat or cool the plastic film web 2 depending on which zone 1a to 1e they are located in. If the plastic film web 2 is to be heated, the air blown towards the plastic film web 2 is heated by the at least one heating and / or cooling device. In the cooling zone 1e, for example, the plastic film web 2 is cooled. For this purpose, the ambient air is usually sucked in from outside the ventilation module 3 and blown onto the plastic film web 2. However, it would also be possible for the air sucked in from outside to be additionally cooled.The basic, particularly internal, structure of a ventilation module 3, preferably with several deflection chambers to achieve the most homogeneous air flow possible, is described, for example, in DE 196 23 471 C1, the disclosure of which is incorporated into this application. It is also shown that the plastic film web 2 is introduced into the first zone 1a and removed from it after the fifth zone 1e.

[0033] The Figure 2A and 2Bshow a cross-section through different embodiments of the ventilation module 3 according to the invention. The border of the ventilation module 3 is chosen only as an example. The ventilation module 3 could also have a different shape. The ventilation module 3 comprises a film feed area 6a and a film outlet area 6b. The plastic film web 2 is moved in the pull-off direction 4 within the ventilation module 3 in a transport plane 7 from the film feed area 6a in the direction of the film outlet area 6b. Between the film feed area 6a and the film outlet area 6b there is at least one first blow-out nozzle arrangement 8 which is designed to blow air for heating or cooling in the direction of the plastic film web 2. The at least one first blow-out nozzle arrangement 8 comprises at least one first blow-out nozzle 8a.The at least one first blow-out nozzle 8a extends with its longitudinal direction transversely or perpendicularly to the withdrawal direction 4 of the plastic film web 2 and is aligned parallel to the transport plane 7. The longitudinal direction of the at least one blow-out nozzle 8a runs parallel to the longitudinal direction 5 of the ventilation module 3. In the embodiment of the . Figure 2A and 2B The at least one first blow-out nozzle arrangement 8 also comprises at least one additional blow-out nozzle 8b. This is arranged offset from the at least one blow-out nozzle 8a in the withdrawal direction 4.

[0034] Furthermore, at least one first suction system 9 is provided with at least two suction channels 10a, 10b, each having a suction area 11a, 11b. The at least one first suction system 9 is designed to suction air through the suction channels 10a, 10b, wherein the at least one first suction system 9 is also arranged between the film intake area 6a and the film outlet area 6b.

[0035] The at least two suction areas 11a, 11b are spaced apart from one another in the withdrawal direction 4 and aligned parallel to the transport plane 7. The at least two suction areas 11a, 11b extend with their longitudinal direction transversely or perpendicularly to the withdrawal direction 4 of the plastic film web 2. The longitudinal direction of the two suction areas 11a, 11b preferably runs parallel to the longitudinal direction 5 of the ventilation module 3.

[0036] The at least one blow-out nozzle 8a of the at least one first blow-out nozzle arrangement 8 is arranged between the first and second suction areas 11a, 11b. The at least one blow-out nozzle 8a of the at least one first blow-out nozzle arrangement 8 and the at least two suction areas 11a, 11b are arranged on the same side of the transport plane 7.

[0037] The two suction areas 11a, 11b have a total suction opening area 12 in the overlap area of ​​the transport plane 7 (see Figure 3 ) which is 8 times to 14 times larger than the nozzle opening area 13 at the blow-out area of ​​the at least one blow-out nozzle 8a in the overlap area to the transport plane 7. The total suction opening area 12 is the sum of the suction opening area 12a of the first suction area 11a and the suction opening area 12b of the second suction area 11b.

[0038] Furthermore, at least one additional blow-out nozzle 8b is shown, which extends with its longitudinal direction 5 also transversely or perpendicularly to the pull-off direction 4 of the plastic film web 2 and is aligned parallel to the transport plane 7, wherein the further blow-out nozzle 8b each has its own nozzle opening surface 13 at the blow-out area. Both blow-out nozzles 8a, 8b of the at least one first blow-out nozzle arrangement 8 are arranged at a distance from one another in the pull-off direction 4. The nozzle opening surface 13 of the further blow-out nozzle 8b is arranged between a first and a second further suction area 11a, 11b. The respective further first and second suction areas 11a, 11b are also connected to the at least one first return suction system 9 via a first and second suction channel 10a, 10b, respectively.The respective further first suction area 11a is arranged in the withdrawal direction 4 of the plastic film web 2 exclusively before and the respective further second suction area 11b is arranged in the withdrawal direction 4 of the plastic film web 2 exclusively after the further blow-out nozzle 8b.

[0039] In Figure 3 It is shown that the two suction areas 11a, 11b extend further in the longitudinal direction 5 than the transport plane 7. In plan view, the suction areas 11a, 11b partially protrude beyond one or both ends of the transport plane 7. The transport plane 7 indicates the area over which the plastic film web 2 can move or extend. For the presented size analysis, however, only those parts of the entire suction opening area 12 that lie in the overlap area of ​​the transport plane 7 are relevant. The same applies to the nozzle opening area 13.

[0040] The intake opening area 12 refers only to the (open) area through which an air mass flow can flow. The same applies to the nozzle opening area 13.

[0041] The at least one blow-out nozzle 8a extends in the longitudinal direction 5 preferably the same distance as the two suction areas 11a, 11b.

[0042] In order to achieve the most constant possible air mass volume flow (in terms of quantity and shape), which is output in a specific time interval through the first and the optional second blow-out nozzle 8a, 8b in a specific time interval, it is important that the at least one first suction area 11a is arranged exclusively upstream of the at least one blow-out nozzle 8a in the withdrawal direction 4 of the plastic film web 2 and the at least one second suction area 11b is arranged exclusively downstream of the at least one blow-out nozzle 8a in the withdrawal direction 4 of the plastic film web 2.

[0043] As explained above, the air mass volume flow that is emitted by the at least one exhaust nozzle 8a in a specific time interval essentially corresponds to the air mass volume flow that is sucked in through the two intake areas 11a, 11b in the same time interval. In order to create the impact jet 15 (see Figure 2A , 2B) as best as possible, the total intake opening area 12 (sum of the two (partial) intake opening areas 12a, 12b) in the overlap area of ​​the transport plane 7 should be 8 times or more than 8 times, 9 times, 10 times, 11 times, 12 times or more than 13 times as large as the total nozzle opening area 13 of the at least one blow-out nozzle 8a in the overlap area of ​​the transport plane 7. At the same time, the total intake opening area 12 of both intake areas 11a, 11b can be 14 times as large or less than 14 times, 13 times, 12 times, 11 times, 10 times or less than 9 times as large as the total nozzle opening area 13 of the at least one blow-out nozzle 8a in the overlap area of ​​the transport plane 7.

[0044] With regard to Figure 3It is shown that the intake opening area 12a of the first intake region 11a is approximately the same size as the intake opening area 12b of the second intake region 11b. It could, of course, also be the case that the intake opening areas 12a, 12b of the two intake regions 11a, 11b differ from one another. They preferably differ by less than 30%, 25%, 20%, 15%, 10%, or less than 5%.

[0045] The at least one first blow-out nozzle arrangement 8 comprises at least one nozzle box 20a, in which the at least one blow-out nozzle 8a is arranged. The nozzle box 20a comprises a first and a second side wall 21a, 21b, which are arranged spaced apart from one another in the withdrawal direction 4 and extend in the longitudinal direction 5 of the at least one blow-out nozzle 8a and are arranged transversely or perpendicularly to the transport plane 7. The at least one nozzle box 20a also comprises a rear wall 21c arranged opposite the blow-out nozzle 8a, which extends in the longitudinal direction 5 of the at least one blow-out nozzle 8a and connects the side walls 21a, 21b to one another. The at least one blow-out nozzle 8a is arranged between the two side walls 21a, 21b. In the illustrated embodiment of the Figure 2A and 2BThere is also at least one additional nozzle box 20b, in which the at least one additional blow-out nozzle 8b is arranged. The structure is the same as that of the at least one nozzle box 20a already described. Preferably, exactly one blow-out nozzle 8a, 8b is arranged in each nozzle box 20a, 20b.

[0046] A portion of the first suction channel 10a extends along an outer side of the first side wall 21a of the at least one nozzle box 20a. A portion of the second suction channel 10b extends along an outer side of the second side wall 21b of the at least one nozzle box 20a. A suction channel 10a, 10b is not defined by the fact that it must also be guided through additional wall sections that extend transversely or perpendicularly to a base section. A suction channel 10a, 10b can also be formed by the air flow being guided only along one side wall 21a, 21b of the at least one nozzle box 20a due to the at least one first suction system 9.

[0047] In Figure 2AIt is shown that the two side walls 21a, 21b, which are offset from one another in the withdrawal direction 4, converge at least partially toward one another in the direction of the transport plane 7, whereby the at least one nozzle box 20a comprises an at least partially conical cross-section. The at least one blow-out nozzle 8a is formed or arranged at the end regions of the side walls 21a, 21b that conically converge toward one another.

[0048] In Figure 2BIn contrast, it is shown that the side walls 21a, 21b run approximately parallel to one another and are closed on their side facing the transport plane 7 by a front wall 21d, wherein the at least one exhaust nozzle 8a protrudes from the front wall 21d arranged adjacent to the transport plane 7 and divides the front wall 21d into two parts. The at least one first suction channel 10a extends along the first part of the front wall 21d, and the second suction channel 10b extends along the second part of the front wall 21d.

[0049] Referring to the Figure 2A and 3 An air-impermeable cover plate arrangement 25 is also shown, which is arranged between two nozzle boxes 20a, 20b and which runs parallel to the transport plane 7. The respective suction areas 11a, 11b are preferably defined by a distance between the blow-out nozzle 8a and the cover plate arrangement 25. In Figure 2BIt is shown that the cover plate arrangement 25 is arranged at a distance from the nozzle boxes 20a, 20b. Here, too, two adjacent intake areas 11a, 11b of different exhaust nozzles 8a, 8b are limited in their extent by the cover plate arrangement 25.

[0050] In Figure 2BIn a configuration in which the nozzle boxes 20a, 20b also comprise a front wall 21d aligned parallel to the transport plane 7, the cover plate arrangement 25 is, in the simplest case, designed as a simple two-dimensional plate. This extends parallel to the transport plane 7 and is preferably held spaced from the front wall 21d by spacers 29. The cover plate arrangement 25 is preferably screwed to the spacers 29. In particular, the at least two nozzle boxes 20a, 20b are arranged adjacent to one another, forming a spacing space 28. The suction channels 10a, 10b run from a suction area 11a, 11b arranged on each nozzle box 20a, 20b through the spacer space 28, wherein the cover plate arrangement 25 is fastened to two nozzle boxes 20a, 20b by means of the spacers 29 and protrudes in the direction of the transport plane 7.

[0051] The cover plate assembly 25 comprises at least one cover plate, which is preferably flat and consists of a (flat) element or (cover) sheet. The cover plate assembly 25 can have various shapes (e.g., rectangular, square, etc.).

[0052] The cover plate arrangement 25 can also be attached to the nozzle boxes without the use of corresponding spacers 29.

[0053] In Figure 2AIn contrast, the cover plate arrangement 25 is adapted to the conically converging side walls 21a, 21b. The cover plate arrangement 25 comprises at least one side wall (in this exemplary embodiment, there are two side walls) arranged parallel to the transport plane 7. Another beveled side wall of the cover plate arrangement 25, which connects the two parallel side walls, runs approximately parallel to at least one side wall 21a, 21b of the at least one nozzle box 20a, which tapers conically toward the other side wall 21b, 21a of the at least one nozzle box 20a. The respective suction channel 10a, 10b is formed between this side wall of the cover plate arrangement 25 and that side wall 21a, 21b of the at least one nozzle box 20a.

[0054] The cover plate arrangement 25 can also have a trapezoidal cross-section. In principle, it would also be possible for at least two nozzle boxes 20a, 20b to be arranged adjacent to one another, forming a spacing space 28, with the corresponding suction channel 10a, 10b extending from a suction area 11a, 11b arranged on each nozzle box 20a, 20b through the formed spacing space 28.

[0055] Preferably, all blow-out nozzles 8a, 8b of the at least one first blow-out nozzle arrangement 8 are equally spaced from the transport plane 7. It would also be possible for one blow-out nozzle 8a of the at least one first blow-out nozzle arrangement 8 to be arranged closer to the transport plane 7 than another blow-out nozzle 8b of the at least one first blow-out nozzle arrangement 8.

[0056] Preferably, the following applies to the embodiments of the Figure 2A and 2Bthat the cover plate arrangement 25 is spaced approximately equally far from the transport plane 7 as the at least one adjacent blow-out nozzle 8a, 8b, 8c, 8d, 8e, 8f.

[0057] In the Figure 2A and 2B An exemplary path of the impact jet 15 is shown. This jet strikes the plastic film web 2 and is then deflected in a roller-like manner in the withdrawal direction 4 and counter to the withdrawal direction 4, before being sucked away via the respective suction areas 11a, 11b.

[0058] In the Figure 2A and 2BAlso shown is the at least one first suction system 9, which comprises at least one suction box 26a, which extends with its longitudinal direction transversely, in particular perpendicular to the pull-off direction 4 of the plastic film web 2 and is aligned parallel to the transport plane 7. Its longitudinal direction runs in particular parallel to the longitudinal direction 5 of the ventilation module 3. The at least one suction box 26a is further spaced from the transport plane 7 than the at least one nozzle box 20a. However, the at least one suction box 26a and the at least one nozzle box 8a are arranged on the same side of the transport plane 7. The at least one suction box 26a comprises a continuous suction slot 27 extending in the longitudinal direction of the at least one suction box 26a or a plurality of suction openings arranged in series in the longitudinal direction of the suction box 26a and separate from one another.This continuous longitudinal slot 27 or the suction openings point in the direction of the transport plane 7 and thus in the direction of the at least one nozzle box 20a. The at least one return suction box 26a preferably sucks in air only or predominantly via the suction slot 27 or the corresponding suction openings.

[0059] In the Figure 2A and 2B It is shown in dotted lines that in addition to the first blow-out nozzle arrangement 8 and the first suction system 9, there may also be a second blow-out nozzle arrangement 30 and a second suction system 31. In this context, Figure 5 There, it is shown that the at least one second blow-out nozzle arrangement 30 and the at least one second suction-back system 31 are arranged on the opposite side of the transport plane 7, compared to the at least one first blow-out nozzle arrangement 8 and the at least one first suction-back system 9.

[0060] The at least one second blow-out nozzle arrangement 30 comprises one or more blow-out nozzles 8a, 8b, each with a nozzle opening surface 13. The at least one blow-out nozzle 8a or the plurality of blow-out nozzles 8a, 8b extend with their longitudinal direction transversely or perpendicularly to the pull-off direction 4 of the plastic film web 2 and extend parallel to the transport plane 7. The at least one second suction-back system 31 likewise comprises a plurality of suction regions 11a, 11b, which extend with their longitudinal direction transversely or perpendicularly to the pull-off direction 4 of the plastic film web 2. The nozzle opening surface 13 of the at least one blow-out nozzle 8a or the plurality of blow-out nozzles 8a, 8b of the at least one second blow-out nozzle arrangement 30 are arranged between a first and a second suction region 11a, 11b of the at least one second suction-back system 31.The at least one second blow-out nozzle arrangement 30 and the at least one second suction-back system 31 correspond in terms of their structure to the first blow-out nozzle arrangement 8 and the first suction-back system 9, respectively, to which reference is hereby made.

[0061] Preferably, the at least one blow-out nozzle 8a of the first blow-out nozzle arrangement 8 is arranged congruently in plan view with the at least one blow-out nozzle 8a of the second blow-out nozzle arrangement 30. The same preferably also applies to the corresponding intake areas 11a, 11b.

[0062] In Figure 5The course of the air flow is also shown. The impact jet 15 exits the at least one first blow-out nozzle 8a and strikes the plastic film web 2. There, it is redirected in a cylindrical manner and sucked away via the suction areas 11a, 11b, which are arranged directly adjacent to the at least one blow-out nozzle 8a. The corresponding first and second suction channels 10a, 10b are formed by a part of the front wall 21d of the nozzle box 20a and by the corresponding side wall 21a, 21b of the nozzle box 20a.

[0063] Figure 5shows that the two nozzle boxes 20a, 20b are arranged adjacent to each other, forming a spacing space 28. This spacing space 28 is formed by the side walls 21b of the two adjacent nozzle boxes 20a, 20b. An air mass volume flow flows through this spacing space 28 and is extracted through the two second extraction channels 10b of the intake areas 11a, 11b. Therefore, preferably, no separate guide device for the air mass volume flow is necessary.

[0064] In Figure 5It is also shown that the cover plate arrangement 25 protrudes in the direction of the transport plane 7 from the corresponding nozzle box 20a or 20b. In this case, the cover plate arrangement 25 is arranged closer to the transport plane 7 than the respective front walls 21d of the nozzle boxes 20a, 20b. The cover plate arrangement 25 is fastened, in particular screwed, to both nozzle boxes 20a, 20b by means of spacers 29. In a plan view of the cover plate arrangement 25, it is arranged in an overlap with the front wall 21d. The respective suction channel 10a, 10b therefore runs through a space 28 between the front wall 21d and the cover plate arrangement 25. The cover plate arrangement 25 is preferably spaced the same distance from the transport plane 7 as the adjacent exhaust nozzles 8a, 8b.

[0065] In the event that the ventilation module 3 comprises only one exhaust nozzle 8a, the two adjacent intake areas 11a, 11b are nevertheless delimited by a corresponding cover plate arrangement 25. The term "cover plate arrangement" encompasses the use of one or more plates, which are particularly flat and can be rectangular or square in shape, for example.

[0066] The Figure 4A and 4Bshow various representations of such a nozzle box 20a, 20b, as used, for example, in the first blow-out nozzle arrangement 8. The front side of such a nozzle box 20a, 20b is at least partially open because air is blown in through it. As already explained, the ventilation module 3 according to the invention or the film stretching system 1 according to the invention provides for the use of a heating and / or cooling device which is designed to heat or cool a specific amount of air to a specific temperature in a specific time. The at least one heating and / or cooling device comprises an air outlet which is connected to the at least one first blow-out nozzle arrangement 8. This air outlet is connected in particular to the open front side of the corresponding nozzle box 20a, 20b of the first blow-out nozzle arrangement 8. The at least one heating and / or cooling device also comprises an air inlet.This can either be connected to the at least one first recirculation system 9, allowing the ventilation module 3 to operate as a recirculation module. Preferably, the air inlet is also connected to an at least partially open end face of the at least one recirculation box 26a of the at least one first recirculation system 9. Alternatively, the air inlet can also be connected to an area outside the ventilation module 3, allowing fresh air to be drawn in. This fresh air can be additionally heated or cooled. "Cooling" also means that the fresh air is merely drawn in and blown through the at least one discharge nozzle 8a toward the plastic film web 2.

[0067] In the Figure 4A and 4BIt is also shown that the first intake area 11a is formed by a plurality of holes arranged in series in the longitudinal direction 5 of the first intake area 11a and separated from one another in the form of a first grid arrangement 40a. The same applies to the second intake area 11b. This is also formed by a plurality of holes arranged in series in the longitudinal direction 5 of the second intake area 11b and separated from one another in a second grid arrangement 40b.

[0068] At least one hole or all holes of the first and / or second suction region 11a, 11b preferably comprise or comprise a greater extension in the withdrawal direction 4 than in the longitudinal direction 5 of the first and / or second suction region 11a, 11b.

[0069] At least one hole or all holes of the first and / or second intake area 11a, 11b comprise in cross section, i.e. in plan view (see Figure 4B) have a square, round, oval or n-polygonal shape or are approximate to such a shape.

[0070] It can also be seen that the cover plate arrangement 25 and the first grid arrangement 40a are connected to one another, preferably by screwing. A one-piece design could also be possible. For example, the individual holes can be created by punching or lasering the cover plate arrangement 25. The same applies to the cover plate arrangement 25 that extends towards the other side wall 21b of the nozzle box 20a. This cover plate arrangement 25 is also preferably firmly connected to the second grid arrangement 40b, preferably by screwing or formed as a single piece therewith. The respective grid arrangement 40a, 40b is therefore arranged in particular in one plane with the corresponding cover plate arrangement 25. This plane is preferably parallel to the transport plane 7. In principle, the respective grid arrangement 40a, 40b could also be screwed to the corresponding nozzle box 20a, 20b.

[0071] The corresponding first or second grid arrangement 40a, 40b preferably extends as far in the longitudinal direction 5 as the plastic film web 2 extends.

[0072] The at least one nozzle box 20a, as well as preferably the corresponding grid arrangements 40a, 40b and the cover plate arrangement 25, consists of a metal.

[0073] Figure 4B shows that the at least one blow-out nozzle 8a of the at least one first blow-out nozzle arrangement 8 comprises a slot nozzle, wherein the nozzle opening surface 13 is formed by a slot running in the longitudinal direction 5 of the blow-out nozzle 8a. This slot is completely open in the exemplary embodiment. It could also be partially open, with interruptions being provided, for example, by connecting struts (for mechanical stabilization).

[0074] In Figure 6A top view of the first blow-out nozzle arrangement 8 is shown. In the exemplary embodiment, four nozzle boxes 20a, 20b, 20c, 20d are arranged spaced apart from one another in the withdrawal direction 4. Each nozzle box 20a to 20d contains a blow-out nozzle 8a, 8b, 8c, 8d. Each of these blow-out nozzles 8a to 8d is flanked by a first and a second intake area 11a, 11b. The individual intake areas 11a, 11b of the various nozzle boxes 20a to 20d are spaced apart from one another by a cover plate arrangement 25.

[0075] In Figure 7A cross-section through a further embodiment of the ventilation module 3 according to the invention is shown. This comprises four nozzle boxes 20a to 20d. Two nozzle boxes 20a, 20b or 20c, 20d are assigned to a return suction box 26a, 26b. This means that each return suction box 26a or 26b draws in the air from two exhaust nozzles 8a, 8b or 8c, 8d. A cover plate arrangement 25 is arranged at a distance from each of the two nozzle boxes 20a, 20b or 20b, 20c or 20c, 20d. A cover plate arrangement 25 is also arranged on the outer walls of the ventilation module 3, extending in the direction of the outermost nozzle boxes 20a and 20d and thus defining the corresponding extraction areas 11a, 11b.

[0076] Furthermore, an additional partition wall 50 can be provided, which ensures that no air circulation takes place between the at least one return suction box 26a with the two associated nozzle boxes 20a, 20b and the at least one further return suction box 26b with the two associated nozzle boxes 20c and 20d.

[0077] To the impact jet 15 (not shown in Figure 7 ), a guide plate arrangement 60 is preferably arranged on the at least one blow-out nozzle 8a or on all blow-out nozzles 8a, 8b, 8c, 8d of the at least one first blow-out nozzle arrangement 8, which protrudes further in the direction of the transport plane 7 than the at least one blow-out nozzle 8a or than all of the blow-out nozzles 8a, 8b, 8c, 8d. The guide plate arrangement 60 preferably extends in a closed manner in the longitudinal direction 5 of the at least one blow-out nozzle 8a or of the respective blow-out nozzle 8a, 8b, 8c, 8d.

[0078] Such a guide plate arrangement 60 can of course also be arranged on the blow-out nozzles 8a to 8d of the second blow-out nozzle arrangement 30.

[0079] Such a guide plate arrangement 60 makes it possible to bring the impact jets 15 closer to the plastic film web 2 in order to achieve a more uniform heat transfer coefficient. This eliminates the need for complex, particularly telescopic, nozzle attachments, which would increase manufacturing costs. The guide plate arrangement 60 allows the impact jet 15 to be supported (only) on one side. Simulations have produced the surprising result that the impact jet 15 is sucked onto the lateral guide (Coanda effect) and can thus be brought closer to the plastic film web 2. At the end of the guide plate arrangement 60, the laterally guided impact jet 15 detaches and strikes the plastic film web 2. Tipping or swinging of the impact jet 15 is thus reduced. The result is a more uniform temperature control of the plastic film web 2.

[0080] In principle, the guide plate assembly 60 can be designed more cost-effectively than conventional nozzle attachments. For example, the guide plate assembly 60 could fold away in or against the withdrawal direction 4 like a hinged sheet. Alternatively, the guide plate assembly 60 could also be designed as a solid attachment, which, however, is arranged only on one side and not formed as a box with a slot like a nozzle attachment.

[0081] Figure 8Ashows a cross-section through another exemplary embodiment of the ventilation module 3 according to the invention. This exemplary embodiment shows that the at least one first suction system 9 is integrated into the at least one nozzle box 20a, 20b, 20c, 20d of the at least one first exhaust nozzle arrangement 8. The corresponding at least one nozzle box 20a therefore again comprises a separate suction receiving area, which is preferably completely closed with the exception of the suction areas 11a, 11b in the longitudinal direction 5 of the corresponding nozzle box 8a, wherein the air sucked in by the first suction system 9 can be sucked out via the end face of the corresponding nozzle box 20a. It can be said that the suction boxes 26a, 26b, 26c, 26d are integrated into the nozzle boxes 20a to 20d. This allows a particularly compact design of the ventilation module 3 according to the invention to be realized.

[0082] Figure 8Bshows a further embodiment of the ventilation module 3 according to the invention from Figure 8A For a better overview, only the nozzle boxes 20a, 20b, 20c and 20d are shown. In contrast to Figure 8A The spacing space 28 between two nozzle boxes 20a, 20b or 20b, 20c or 20c, 20d is closed by a cover plate arrangement 25 at least in the direction of the transport plane 7. Therefore, an air flow cannot form from the transport plane 7 into the spacing space 28. The cover plate arrangement 25 is preferably screwed to two nozzle boxes 20a, 20b or 20b, 20c or 20c, 20d. It extends at least over the width of the spacing space 28 (in the withdrawal direction 4) and over the width of the plastic film web 2. It can be flat or as in Figure 8Bshown protruding in the direction of the transport plane. It can comprise one or more plates. This ensures that the air is extracted predominantly (more than 80% of the air) or exclusively at the respective intake areas 11a, 11b. The cover plate arrangement 25 can be attached with a spacer 29 or placed directly onto the respective nozzle boxes 20a, 20b or 20b, 20c or 20c, 20d, or screwed to them or firmly connected.

[0083] Figure 9shows a cross-section through a plurality of ventilation modules 3 according to the invention, which are shown one above the other. The individual ventilation modules 3 have a different number of exhaust nozzles 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h. In the first embodiment, there are eight exhaust nozzles 8a to 8h. In the second embodiment, there are six exhaust nozzles 8a to 8f. In the third embodiment, there are four exhaust nozzles 8a to 8d. In the fourth embodiment, there are three exhaust nozzles 8a to 8c. According to the invention, however, the total nozzle opening area 13 of all exhaust nozzles 8a to 8h of the first exhaust nozzle arrangement 8 is constant. This means that with many exhaust nozzles 8a to 8h, the respective nozzle opening area 13 of the corresponding exhaust nozzle 8a to 8h is smaller than with only a few exhaust nozzles 8a to 8c. Overall, the heat input into the plastic film web 2 is therefore constant. The same also applies to the entire intake opening area 12.This is composed of the intake opening area 12a of the respective first intake area 11a and the intake opening area 12b of the respective second intake area 11b.

[0084] Overall, the size of the entire intake opening area 12 of the first exhaust nozzle arrangement 8 is constant. This means that in the case of a plurality of intake areas 11a, 11b (as in the first example in Figure 9 ), the respective intake opening areas 12a, 12b of the respective first and second intake areas 11a, 11b are smaller than in the case where there are only a few intake areas 11a, 11b, as in the last example of the Figure 9 is shown.

[0085] Such a design is advantageous if the film stretching system 1 according to the invention includes at least two ventilation modules 3 which differ in the number of their blow-out nozzles 8a, 8b, ... etc. In this case, the total nozzle opening area 13 of all exhaust nozzles 8a, 8b, ... etc. of the at least one first exhaust nozzle arrangement 8 of one ventilation module 3 is approximately as large as the total nozzle opening area 13 of all exhaust nozzles 8a, 8b, ... etc. of the at least one first exhaust nozzle arrangement 8 of the other ventilation module 3. The same also applies to the total intake opening area 12 of all intake areas 11a, 11b of the first exhaust nozzle arrangement 8 of one ventilation module 3 compared to the total intake opening area 12 of all intake areas 11a, 11b of the first exhaust nozzle arrangement 8 of the other ventilation module 3.

[0086] Of course, this also applies to the Figure 9second blow-out nozzle arrangement 30 (not shown) and the second suction system 31.

[0087] Investigations have shown that when using three or four nozzle boxes 20a to 20d, a more uniform air flow can be achieved within the ventilation module 3 than when five, six, seven, eight or more than eight nozzle boxes 20a to 20h are used.

[0088] Figure 10shows a further embodiment of the ventilation module 3 according to the invention in a spatial representation. The ventilation module 3 here again comprises eight exhaust nozzles 8a to 8h, whereby these exhaust nozzles 8a to 8h do not comprise a continuous slot nozzle in this embodiment. Rather, at least one exhaust nozzle 8a, in this case all exhaust nozzles 8a to 8h of the at least one first exhaust nozzle arrangement 8, is formed by a perforated nozzle or comprises such a perforated nozzle. The entire nozzle opening area 13 of an exhaust nozzle 8a to 8h is formed by a plurality of holes arranged in series in the longitudinal direction 7 of the respective exhaust nozzle 8a to 8h and separated from one another in the form of a grid arrangement.

[0089] The at least one hole or all holes of the nozzle opening surface 13 comprise a square, round, oval or n-polygonal shape in cross section or are approximated to such.

[0090] Figure 11shows a cross-section through a further embodiment of the ventilation module 3 according to the invention. In this embodiment, there are four exhaust nozzles 8a to 8d, which are arranged at a distance from one another in the withdrawal direction 4. At least one exhaust nozzle 8a, in this case all exhaust nozzles 8a to 8d, of the at least one first exhaust nozzle arrangement 8 comprise a twin nozzle with two outlet chambers separated and spaced from one another in the withdrawal direction 4. As a result, the nozzle opening area 13 is composed of two partial nozzle opening areas separated from one another in the withdrawal direction 4. In this case, too, the at least one exhaust nozzle 8a is flanked by two suction areas 11a, 11b each.

[0091] In principle, the temperature uniformity increases when fewer blow-out nozzles 8a, 8b, ... etc. are used. In contrast, however, the local load on the plastic film web 2 also increases, since the heat is introduced over very short sections (high heat transfer coefficient). In addition, the air hits the plastic film web 2 at a high air velocity. For thermally and mechanically sensitive film types (e.g., PA, PET), this would be critical because such a plastic film web 2 could be deformed (stretched) by the strong impact jet 15, for example, or damaged by the strong temperature input. Thus, the number of blow-out nozzles 8a, 8b, ... etc. is selected according to the material of the plastic film web 2. The same applies to the size of the nozzle opening area 13 and the entire intake opening area 12 of the intake areas 11a, 11b that flank the nozzle opening area 13.

[0092] Preferably, the individual nozzle boxes 20a, 20b, ... etc. can be inserted into a holding device (not shown) in the longitudinal direction 7. This allows for easy replacement of the respective nozzle boxes 20a, 20b, ... etc. with nozzle boxes 20a, 20b, ... etc. with a modified exhaust nozzle 8a, 8b, ... etc. The same preferably also applies to the return suction boxes 26a, 26b, ... etc.

[0093] All statements made for the blow-out nozzle arrangement 8 and the first suction-back system 9 also apply to the at least one second blow-out nozzle arrangement 30 and the at least one second suction-back system 31.

[0094] In Figure 12ATwo curves of an averaged temperature of the plastic film web 2 over time are shown. The curves can be determined by measurements or simulations (= calculation of the measured values). The temperature is averaged over the width of the plastic film web 2 at the respective point in time at the film outlet area 6b of the ventilation module 3. The temperature is averaged over the width of the plastic film web 2 and is recorded by several sensors (between 2 and 30 sensors) that are arranged at a distance across the width of the plastic film web 2. For example, their measured values ​​are added together and divided by the number of measured values. The measurement curve marked with dots results from the use of the ventilation module 3 according to the invention. The measurement curve marked with crosses is achieved from the use of ventilation modules from the prior art.It can be seen that the temperature fluctuations over time are significantly lower when using the ventilation module 3 according to the invention and the film properties can therefore be kept more constant.

[0095] Figure 12B shows the average heat transfer coefficient of an entire ventilation module 3 under consideration to the plastic film web 2 over time, which is to be equated with the temporal progression of the areal mean heat transfer coefficient of the ventilation module 3. The measurement curve marked with dots results from the use of the ventilation module 3 according to the invention. The measurement curve marked with crosses is achieved using ventilation modules from the prior art. It can be seen that fluctuations in the average heat transfer coefficient over time are significantly smaller when using the ventilation module 3 according to the invention, and the film properties can therefore be kept more constant.

[0096] The invention is not limited to the described embodiments. Within the scope of the invention, all described and / or illustrated features can be combined with one another in any way.

Claims

1. A ventilation module (3) for a film stretching system (1) for heating or cooling plastic film webs (2) having the following features: - the ventilation module (3) comprises a film entry region (6a) and a film exit region (6b), the plastic film web (2) being movable in the withdrawal direction (4) within the ventilation module (3) in a transport plane (7) from the film entry region (6a) in the direction of the film exit region (6b); - at least one first outlet nozzle arrangement (8) is provided between the film entry region (6a) and the film exit region (6b) and is designed to blow air in the direction of the plastic film web (2) for the purpose of heating or cooling; - the at least one first outlet nozzle arrangement (8) comprises at least one outlet nozzle (8a), the at least one outlet nozzle (8a) extending with its longitudinal direction (5) transverse or perpendicular to the withdrawal direction (4) of the plastic film web (2) and being oriented in parallel to the transport plane (7); - at least one first return system (9) having at least two extraction channels (10a, 10b) is provided, which extraction channels each have an intake region (11a, 11b), the at least one first return system (9) being designed to extract air via the extraction channels (10a, 10b); - the at least one first return system (9) is arranged between the film entry region (6a) and the film exit region (6b); - the at least one outlet nozzle (8a) of the at least one first outlet nozzle arrangement (8) and the at least two intake regions (11a, 11b) are arranged on the same side of the transport plane (7); - the at least two intake regions (11a, 11b) are distanced from one another in the withdrawal direction (4) and are oriented in parallel to the transport plane (7), the at least two intake regions (11a, 11b) extending with their longitudinal direction (5) transverse or perpendicular to the withdrawal direction (4) of the plastic film web (2); - the at least one outlet nozzle (8a) of the at least one first outlet nozzle arrangement (8) is arranged between the first and the second intake region (11a, 11b) in such a way that the at least one first intake region (11a) is arranged in the withdrawal direction (4) of the plastic film web (2) exclusively before the at least one outlet nozzle (8a), and the at least one second intake region (11b) in the withdrawal direction (4) of the plastic film web (2) is arranged exclusively after the at least one outlet nozzle (8a), characterized in that the at least one first outlet nozzle arrangement (8) comprises a plurality of nozzle boxes (20b, 20c, 20d, 20e, 20f); and - a predominantly or completely air-impermeable cover plate arrangement (25), which runs in parallel to the transport plane (7), is situated between two nozzle boxes (20a, 20b, 20c, 20d, 20e, 20f) or at a distance from two nozzle boxes (20a, 20b, 20c, 20d, 20e, 20f), whereby two adjacent intake regions (11a, 11b) of different outlet nozzles (8a, 8b, 8c, 8d, 8e, 8f) are delimited in respect of their extent.

2. The ventilation module (3) according to claim 1, characterised by the following feature: - the two intake regions (11a, 11b) in the region of overlap with the transport plane (7) have a total intake opening area (12) which is 8 times to 14 times greater than the nozzle opening area (13) at the outlet region of the outlet nozzle (8a) in the region of overlap with the transport plane (7).

3. The ventilation module (3) according to claim 2, characterised by the following features: - the total intake opening area (12) of the first and second intake region (11a, 11b), in the region of overlap with the transport plane (7), is 8 times or more than 8 times, 9 times, 10 times, 11 times, 12 times or more than 13 times greater than the total nozzle opening area (13) of the outlet nozzle (8a) in the region of overlap with the transport plane (7); and / or - the total intake opening face (12) of the first and second intake region (11a, 11b) is 14 times or less than 14 times, 13 times, 12 times, 11 times, 10 times or less than 9 times larger than the total nozzle opening area (13) of the outlet nozzle (8a) in the region of overlap with the transport plane (7).

4. The ventilation module (3) according to any one of the preceding claims, characterised by the following features: - the at least two intake regions (11a, 11b) are arranged in the withdrawal direction (4) of the plastic film web (2) at a distance before and after the at least one outlet nozzle arrangement (8) which is less than 100 cm, 90 cm, 80 cm, 70 cm, 60 cm, 50 cm, 40 cm, 30 cm, 20 cm or less than 10 cm; and / or - the at least one first return system (9) is designed to extract, via the at least two intake regions (11a, 11b), at least 80%, 85%, 90% or 95% of the air volume flow that is extractable via the at least one first outlet nozzle arrangement (8).

5. The ventilation module (3) according to any one of the preceding claims, characterised by the following features: - the intake opening area (12a) of the first intake region (11a) is approximately the same size as the intake opening area (12b) of the second intake region (11b); or - the intake opening area (12a, 12b) of the first and second intake region (11a, 11b) differ by less than 30%, 25%, 20%, 15%, 10% or by less than 5% from one another.

6. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature; - a guide plate arrangement (60) is mounted on the at least one outlet nozzle (8a) of the at least one first outlet nozzle arrangement (8), which guide plate arrangement protrudes in the direction of the transport plane (7) further than the at least one outlet nozzle (8a), with the guide plate arrangement (60) extending in the longitudinal direction (5) of the at least one outlet nozzle (8a).

7. The ventilation module (3) according to any one of the preceding claims, characterised by the following features: - two nozzle boxes (20a, 20b, 20c, 20d, 20e, 20f) are arranged adjacently to one another so as to form a gap (28); - an extraction channel (10a, 10b) runs from an intake region (11a, 11b) arranged on each nozzle box (20a, 20b, 20c, 20d, 20e, 20f), through the gap (28), the cover plate arrangement (25) being secured to two nozzle boxes (20a, 20b, 20c, 20d, 20e, 20f) by means of spacers and protruding in the direction of the transport plane (7).

8. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the cover plate arrangement (25) is distanced from the transport plane (7) by the same distance as the adjacent outlet nozzles (8a, 8b, 8c, 8d, 8e 8f).

9. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the respective intake regions (11a, 11b) are defined by a distance between the outlet nozzle (8a) and the cover plate arrangement (25).

10. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the cover plate arrangement (25) is mounted to two nozzle boxes (20a, 20b) by means of a spacer (29) and protrudes in the direction of the transport plane (7).

11. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the cover plate arrangement (25) can include one or more plates.

12. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the cover plate arrangement (25) is attached with a spacer (29) or is placed directly on the various nozzle boxes (20a, 20b or 20b, 20c or 20c 20d), or screwed or fixedly connected thereto, respectively.

13. The ventilation module (3) according to any one of the preceding claims, characterised by the following feature: - the cover plate arrangement (25) extends at least over the width of the gap 28 and over the width of the plastic film web 2, so that the air is extracted largely predominantly, namely more than 80% of the air or exclusively at the intake regions (11a, 11b).

14. A film stretching system (1) for producing plastic film webs, comprising one ventilation module (3) or a plurality of ventilation modules (3) which is or are constructed in accordance with one of the preceding claims.

15. The film stretching system (1) for producing plastic film webs (2) comprising a plurality of ventilation modules (3) according to claim 14, characterised by the following features: - all ventilation modules (3) are constructed identically; or - at least two ventilation modules (3) differ in respect of the number of outlet nozzles (8a to 8h) of their at least one first outlet nozzle arrangement (8), the entire nozzle opening area of all outlet nozzles (8a to 8) of the at least one first outlet nozzle arrangement (8) of one ventilation module (3) corresponding to approximately the entire nozzle opening area of all outlet nozzles (8a to 8c) of the at least one first outlet nozzle arrangement (8) of the other ventilation module (3).