Stretching device and method for uniaxially stretching film web in conveying direction thereof

Abstract

The invention relates to a stretching device for uniaxially stretching a film web in the conveying direction thereof, comprising: a first roller (holding roller), by means of which the film web can be guided and which is rotated at a first circumferential speed; a second roller (stretching roller) arranged downstream of the first roller, by means of which the film web can be guided and which is rotated at a second circumferential speed, the second circumferential speed being greater than the first circumferential speed, and wherein at least one pressure roller is provided, by means of which the film web can be pressed against one of the rollers. At least one holding assembly is provided, with respect to which the pressure roller can be rotated about its axis of rotation. The pressure roller is supported on the holding assembly by a support point extending over a part of the axial length of the pressure roller, in particular over a quarter of the axial length of the pressure roller, or by a plurality of support points distributed over the axial length of the pressure roller and / or over the circumferential direction of the pressure roller. According to the invention, a first movement device is provided, by means of which the support point or the plurality of support points can be moved relative to the pressure roller in a direction parallel to the axis of rotation of the pressure roller.

Description

Technical Field

[0001] The present invention relates to a stretching apparatus for uniaxially stretching a film sheet along its conveying direction according to claim 1, and the method according to claim 9. Background Technology

[0002] Stretching devices, of various types, are typically arranged in series, particularly within or downstream of blown film or flattening film equipment. These stretching devices include at least one first roller, also referred to as a holding roller, through which the film web is guided, and the first roller rotates at a first circumferential speed. A second roller, also referred to as a stretching roller, is located downstream of the first roller and guides the film web after it has left the first roller. The second roller rotates at a second circumferential speed, which is greater than the first circumferential speed. In the stretching section where the film web has left the first roller but has not yet reached the second roller, the film is stretched, i.e., elongated, along its transport direction. This stretching section is also commonly referred to as the stretching gap. Furthermore, the first and second rollers typically have opposite directions of rotation, so that the film web is guided through each roller with the largest possible containment angle. Overall, the described stretching is used to specifically modify important characteristics of the film web.

[0003] However, undesirable necking can also occur during this stretching process, where the film width narrows relative to its original width. Additionally, the edges of the film width thicken, resulting in an uneven thickness distribution along the lateral direction. Therefore, these edges must be separated, thus reducing the usable width of the film width. The separated edges are unusable and therefore incur undesirable costs. To mitigate these effects, numerous improvements have been proposed in the past. One measure is to incorporate at least one pressure roller, which can compress the film width against one of the rollers. In the past, reducing the stretching gap has also been an improvement.

[0004] However, if a pressure roller is used, the stretch gap cannot be reduced to the desired extent in conventional stretching equipment. Unpublished patent application PCT / EP2022 / 081608 discloses a pressure roller with a reduced diameter, which is supported by a support portion to reduce deflection. This measure can reduce the stretch gap, resulting in a larger usable portion of the film width. However, because the support portion has an interruption, there is a risk that this interruption, as a defect, will always appear at the same location on the film width when viewed laterally, leading to a decrease in film width quality. Summary of the Invention

[0005] Therefore, the aim is to propose a stretching device and a method that can reduce the disadvantages mentioned above.

[0006] The aforementioned objective is achieved by a stretching apparatus having the features of claim 1 and a method having the features of claim 9. Further features and details of the invention are derived from the dependent claims, the description, and the drawings. Herein, the features and details described in conjunction with the method according to the invention also apply to the stretching apparatus according to the invention, and vice versa, so that mutual reference or reference is always possible in respect of the disclosures regarding various aspects of the invention.

[0007] The key feature of the tensioning device according to the present invention is that, • At least one retaining component is provided, and the pressure roller is rotatable relative to the retaining component about its axis of rotation. • The pressure roller is supported at the retaining assembly by a support portion extending over a portion of its axial length, particularly more than a quarter of it, or by multiple support portions distributed over the axial length and / or circumferential direction of the pressure roller. • A first motion device is provided, which enables the one or more support parts to move relative to the pressure roller in a direction parallel to the rotation axis of the pressure roller.

[0008] This invention is particularly based on the understanding that, although the support portion, especially the support roller, reduces the deflection of the pressure roller, it always abuts against the same position on the pressure roller. Because the pressure roller typically has an elastic circumferential surface, the area abutted by the support portion is pressed in more strongly than other areas. The pressed area typically has not yet returned to its original position before reaching the film surface, resulting in uneven pressure from the pressure roller onto the film surface. Furthermore, the pressed area can be pressed in more and more strongly, exacerbating the described effects. Additionally, different levels of contamination can occur depending on whether the surface area of ​​the pressure roller is in contact with the support portion.

[0009] The contact area between the pressure roller and the support part can be changed by the relative movement of the support part relative to the pressure roller. In particular, this can be done periodically. The advantage here is that the aforementioned effects no longer occur at the same position and are not transmitted to the same position on the film web. Because the increasingly larger pressing part of the pressure roller is also avoided, the overall quality of the film web is improved.

[0010] Furthermore, according to the invention, at least one retaining component is provided, the clamping roller being rotatable relative to the retaining component, wherein the clamping roller is supported on the retaining component by a support portion extending over a portion of the axial length of the clamping roller, particularly more than a quarter of the axial length, or by a plurality of support portions distributed over the axial length and / or circumferential length of the clamping roller.

[0011] These measures allow the force acting on the pressure rollers to be received by a retaining assembly, which is located radially away from the first and / or second rollers. The available space here can then be used to design a retaining assembly with high bending stiffness. This results in a more uniform thickness across the film width and thus improved quality.

[0012] Conversely or additionally, the diameter of the pressure roller can therefore be reduced relative to the prior art. The reduced diameter of the pressure roller makes the tension gap smaller, or even smaller, and thus positions the pressure roller on the separation or collision line. The smaller tension gap is advantageous because it further reduces the necking effect. It is advantageous that at least one of these rollers is equipped with multiple pressure rollers.

[0013] Furthermore, the present invention also enables the film web to pass over the pressure roller at an enclosing angle. In this case, the force exerted on the pressure roller by the film web can be easily compensated by the structure according to the invention, while simultaneously avoiding possible streaking on the film web. Advantageously, the film web winds around the pressure roller at an enclosing angle between 0° and 90°. This enclosing angle is particularly between 0.1° and 90°, preferably between 0.5° and 90°. The foregoing measures further reduce the stretch gap, thereby minimizing necking.

[0014] In an advantageous embodiment of the invention, the retaining assembly includes at least one support extending parallel to the axis of rotation and arranged immobile relative to the first and / or second rollers. The support extends particularly along the entire length of the pressure roller and thus provides the necessary reaction force to compensate for the deflection of the pressure roller. The support then provides the necessary support force for the supporting portion and therefore for the pressure roller. Here, the support can be constructed integrally, or it can be assembled from individual support pieces. This allows for a modular structure of the support, wherein the support can be assembled from different numbers of support pieces depending on the working width of the stretching device, which in particular reduces the manufacturing cost of the stretching device. The support is designed in a way that is independent of the support itself, such that the forces acting on the pressure roller do not cause deflection of the support. The support and the roller to which the support is distributed are preferably arranged immobile relative to each other. This means that with the adjustment movement for adjusting the roller, the distributed support is also adjusted together, so that no shift in the forces acting on the pressure roller occurs.

[0015] To achieve easy mobility of the support parts relative to the pressure roller, the first motion device is advantageously configured to include a frame, with each support part resting on the frame, wherein the frame is movable relative to the pressure roller and, more particularly, relative to the support. Thus, a simple movement drive mechanism acting on the frame can be provided. In particular, this results in a stable device that is movable but has only a minor impact on the force acting on the pressure roller.

[0016] In another design, the frame is supported on a bracket and is particularly movable relative to the bracket by means of a sliding or rolling mechanism. Here, the sliding mechanism can be a rail-slider combination, which achieves a low-cost structure. The rolling mechanism can be, for example, a raceway, in which multiple rollers are arranged at the bracket or the frame. Using a raceway minimizes friction between the bracket and the frame.

[0017] Advantageously, the first motion device includes at least one drive mechanism, which enables each support portion and / or, in particular, the frame, to move alternately along a first direction and along a second direction opposite to the first direction. The drive mechanism can be, for example, a linear motor or a servo motor. A drive mechanism implemented as a dual-function piston-cylinder unit is also conceivable. Alternatively, a rotary drive mechanism can be provided, whose rotational motion can be converted into linear motion by a transmission mechanism element. With the drive mechanism, the support elements can be positioned, in particular, in periodic motion. Particularly advantageously, the amplitude of the motion can be set. In particular, it is advantageous that the motion along the first and second directions is greater than 0 mm and less than 300 mm, especially less than 200 mm.

[0018] Particularly advantageous is the provision of support portions for a first column and at least one second column, wherein the columns extend along the longitudinal direction of the pressure roller, and wherein, in particular, the first and second columns are movable relative to each other. Thus, it is possible to execute the movement of each column independently of each other. In this case, it is possible to provide a separate drive for each column, or, when a single drive is provided, to achieve relative mobility of the two columns through coupling. In particular, it is possible to set the relative movement of the two columns, and especially to set it independently of each other. Therefore, it is possible to provide as much settling as possible in the operating parameters, even with different film widths, in order to obtain the best possible quality for the film width. Furthermore, it is advantageous that the support portions for each column are arranged in their own frames, thus enabling a simple structure. Mobility of each frame relative to the support can be achieved, as described above in conjunction with the individual frames.

[0019] Advantageously, at least two rows of support portions or at least two support portions are provided, each arranged at different angular positions along the circumferential direction of the pressure roller. The pressure roller operates in this way within a groove-shaped recess, which can also be referred to as a roller bed. Therefore, by supporting the pressure roller at different positions, the clamping force provided by the holding assembly is better distributed circumferentially on the pressure roller. Furthermore, this measure makes it easier to hold the pressure roller in its position.

[0020] To further mitigate the aforementioned drawbacks, a second motion device is provided, which moves the pressure roller along its axial direction. Therefore, the pressure roller can move relative to the first roller or relative to the second roller, thereby further homogenizing the force acting on the film web, which in turn leads to improved film web quality. The second motion device may include a second drive unit arranged at the holding assembly. As the second drive unit for the second motion device, a piston-cylinder unit that performs a dual function and is operated by compressed air is employed. A continuously rotating motor, whose rotational motion is converted into linear motion, for example, via gears and coupling rods, is also conceivable. Finally, a servo motor or a linear motor is also conceivable.

[0021] To enable such movement of the pressure roller, it is configured such that the pressure roller is connected to a retaining assembly via at least one retainer or at least one attachment, wherein, in particular, the pressure roller can move relative to the retainer or attachment using a second motion device, or the retainer or attachment can move together with the pressure roller relative to the retaining assembly. Thus, it is possible to configure the retainer or attachment to move relative to the retaining assembly, particularly relative to its support, wherein the pressure roller can also be moved accordingly. Alternatively or additionally, the pressure roller can also be movably supported in a sliding bearing, for example, relative to the retainer or attachment.

[0022] Advantageously, each pressure roller is rotatably supported at its end in a retainer or accessory of the retaining assembly, wherein, in particular, the pressure roller is also provided with relative mobility of the pressure roller relative to the retainer or accessory along the radial direction of the pressure roller.

[0023] Preferably, each pressure roller is equipped with a retaining component.

[0024] The retaining assembly is preferably supported on the frame, and the first roller and / or the second roller are also supported in the frame.

[0025] In an advantageous embodiment of the invention, the at least one support portion includes at least one roller (also referred to as a support roller) on which the pressure roller rolls along the circumferential surface. In particular, each support portion includes multiple rollers. The rollers themselves are supported on a retaining assembly. Such rollers reduce friction on the pressure roller, thereby keeping the surface of the pressure roller as undamaged as possible.

[0026] In one improved embodiment, the at least one support portion includes at least one support roller supported on a shaft by at least one bearing. The shaft is secured to a retaining assembly, particularly to a movable frame of the retaining assembly, by means of shaft supports or retainers. Specifically, the roller is rotatably supported on the shaft by ball bearings, roller bearings, or needle roller bearings. Such bearings can withstand the large forces necessary to support the pressure roller in the stretching device. Each shaft is secured to the retaining assembly, particularly at both ends, by means of shaft supports. Here, the shaft supports can be common shaft supports for two adjacent shafts, respectively. Furthermore, the shaft supports can be distributed along the axial length of the shaft. Each roller can have its own shaft; however, it is advantageous to have at least two rollers on each shaft. Alternatively, elongated rollers with an axial length greater than their outer diameter can be used instead of multiple rollers.

[0027] As an alternative or supplementary solution, it is advantageous that the at least one support portion includes at least one roller, wherein each roller is fastened to the drive shaft (Welle), wherein the drive shaft is rotatably supported on a drive shaft bearing, which itself is fastened to the frame of the retaining assembly. The design scheme described above with respect to the shaft (Achse) can be meaningfully transferred to the drive shaft assembly.

[0028] The rollers disclosed in the aforementioned embodiments can be configured in different designs. Thus, to reduce friction between the rollers and the pressure roller, the rollers can be provided with a smooth circumferential surface, i.e., the surface on which the pressure roller rolls. This can be achieved, for example, by chrome plating the roller surface. In this regard, it is advantageous to make the circumferential surface hard or rigid to avoid damage, which is particularly advantageous by making the circumferential surface metallic. If the pressure roller includes a soft circumferential surface, then a hard or rigid circumferential surface and / or a smooth circumferential surface are particularly advantageous. Therefore, it is possible to prevent excessive wear or even damage to the pressure roller even when there is relative movement between the pressure roller and the support element.

[0029] Furthermore, it is possible to configure at least one roller to include a structure on its circumferential surface. A structure means that a recess exists on the circumferential surface. Such a structure can be regular, i.e., including, for example, grooves and / or drilled holes. Such a regular structure is then produced, particularly by machining or manufacturing the circumferential surface using tools, especially by contact machining. As a supplementary or alternative, an irregularly structured portion of the circumferential surface of the at least one roller can be provided. Such an irregularly structured portion can be achieved, particularly by blasting the circumferential surface with projectiles, such as in sandblasting or glass bead blasting. The structure with recesses primarily serves to receive air introduced into the roller gap / roller gap by the pressure roller and thereby prevents interruption of contact between the roller and the pressure roller.

[0030] Typically, the circumferential surface characteristics can be determined by the circumferential surface characteristics of the rollers, i.e., the holding rollers and / or the stretching rollers. If the rollers include a flexible circumferential surface, particularly due to a coating of at least part of an elastomer, then the associated clamping rollers can include a very hard circumferential surface if the clamping rollers, for example, comprise polished steel. In this case, it is preferable that the support rollers at least partially include a flexible circumferential surface.

[0031] The at least one roller can be concavely shaped on its circumferential surface, that is, the at least one roller has a larger diameter at its edge than at its center along its axis of rotation. Alternatively, the circumferential surface can be convex. Concave or convex circumferential surfaces can reduce the contact area between the pressure roller and the roller and thereby reduce surface wear. However, a convex shape is particularly advantageous because it improves the mobility of the roller relative to the pressure roller.

[0032] Within the scope of this invention, "roller" can also refer to a sleeve, wherein, in particular, the axial length is greater than the diameter.

[0033] In another advantageous embodiment of the invention, the support portion includes at least one concave groove element in which the pressure roller is located, wherein the inner surface of the groove element has an opening through which fluid under overpressure can be guided to the area between the groove element and the pressure roller. This fluid is preferably a gas, particularly air. Thus, with this measure, the pressure roller can be held in place by the support portion without contact and guided during rotation. A “floating support” exists for the pressure roller. The groove element can be an elongated shell made of plastic, fiber-reinforced plastic, or metal. The opening on the inner surface (the radius of which is preferably only slightly larger than the outer radius of the pressure roller) can be connected to an inlet conduit, such as a through-hole fluid connection, thereby enabling the easy external delivery of fluid under overpressure (pressure higher than ambient pressure). To achieve better fluid distribution between the inner and outer surfaces of the pressure roller, the inner surface of the groove element can be covered or coated with a porous material, such as sintered plastic and / or sintered metal. The groove element can also be constructed using only sintered material.

[0034] To apply a force toward at least one support to the pressure roller, at least one tensioning device is provided. This device provides a force that acts on the pressure roller in the direction of the holding assembly, and particularly in the radial direction of the pressure roller. Even with end supports provided for the pressure roller as described above, such a tensioning device is advantageous in holding the pressure roller at or within at least one support along its entire length. This is especially important when the unrotated pressure roller is in contact with the already rotated first and / or second rollers or with the film web. The tensioning device is also used to prevent the pressure roller from popping out of or tilting with the support.

[0035] Particularly advantageous is the provision of at least one pulling device capable of applying a force directed toward the holding assembly to the pressure roller, wherein the pulling device comprises at least one magnet and at least one magnetizable element. Here, the magnet is arranged within or at the holding assembly, and the magnetizable element is arranged within or at the pressure roller and / or within or at the holding assembly. In other words, to generate an attractive magnetic force, the element must be partially magnetizable, and the second element must carry at least one magnet. The magnet is preferably a permanent magnet, but can also be a switchable electromagnet.

[0036] As an alternative or supplementary solution, it is advantageous to provide at least one traction device that can act on the pressure roller with a force pointing towards the holding assembly. This traction device includes at least one suction device arranged on the holding assembly, which can apply a suction force to the pressure roller acting towards the holding assembly. Here, the suction device can be, for example, a drilled hole, hose, pipe, etc., with one end in the direct environment relative to the pressure roller and the other end connected to a negative pressure generator, such as a blower or negative pressure pump. The advantage of using such a suction device for generating traction force is that the magnitude of the traction force can be varied.

[0037] Furthermore, it is advantageous that at least one cleaning element is arranged on the retaining assembly, particularly on the support of the retaining assembly, by means of which the outer surface of the pressure roller can be cleaned. Such a cleaning element can be, for example, a piece of cloth, felt, etc., extending at least partially along the length of the pressure roller, which makes particularly long-lasting contact with the pressure roller. However, the cleaning element can also be a wiping element fastened to a slider. The slider can move along a guide portion preferably fastened to the support in the axial direction of the pressure roller. Thus, the surface of the pressure roller can be cleaned by the continuous or as-needed movement of the slider. The slider can also move beyond at least one end of the pressure roller so that the wiping element itself can be replaced or cleaned. Wiping the pressure roller also has the advantage of not forming deposits or dirt that could damage the film web.

[0038] Furthermore, it is preferable that the pressure roller has a coating, particularly a rubber coating, on its outer surface. The coating is advantageously made of a compressible material, thereby providing sufficient static friction to the film web.

[0039] Furthermore, it is advantageous that the pressure roller can be driven to rotate using a drive device. In other words, a drive device is provided that allows the pressure roller to be placed in rotation or held in place. This drive device can be a known electric motor or a pneumatic motor. The advantage is that the pressure roller is already in rotation before being placed onto the already moving film web. This reduces wear on the pressure roller and avoids damage to the film web during placement.

[0040] Advantageously, the pressure roller is capable of pressing against the roller within an angle range of up to + / - 30 degrees around the following line defined by a common tangential plane of the two rollers. For this purpose, the retaining assembly is provided with movable support relative to the rollers, wherein the retaining assembly is capable of movement at least along the circumferential direction of at least one roller. Particularly advantageously, the pressure roller is capable of moving across the line when viewed along the conveying direction of the film web. In this case, the film web leaves or contacts the roller not at the separation line or collision line, but after or before them. Specifically, this means that in the case of the retaining roller, the film web initially runs on the pressure roller, and in the case of the stretching roller, the film web initially runs on the pressure roller before contacting the stretching roller. In this case, the stretching gap can be shortened again, thereby further reducing the necking.

[0041] In another embodiment of the invention, at least two retaining assemblies are provided for holding the roller and / or for the stretching roller, wherein the two retaining assemblies are connected to each other by a connecting element. Thus, generally, each roller can have two retaining assemblies, wherein the two retaining assemblies are fastened to a connecting element. The connecting element is sized such that the pressure roller of the first retaining assembly presses the film web onto the roller in the region of its collision line, and the pressure roller of the second retaining assembly presses the film web onto the roller in the region of its separation line. The connecting element can be moved relative to the associated roller in the circumferential and / or radial directions by means of at least one adjusting mechanism, so that the pressure roller can also move with the movement of the connecting element. To enable the movement of the connecting element, the adjusting element preferably includes at least one air-operated piston cylinder unit. Preferably, the connecting element is supported on a frame, and the associated roller is also supported on the frame. If the two retaining assemblies connected to each other by the connecting element can be adjusted at different lines of the associated roller, an amplified adjustment force is thus achieved, because the particularly bending-resistant connecting element also contributes to the normal force along the radial direction of the roller. Overall, this allows the film web to be pressed more firmly onto the rollers again with a given adjustment force, thereby further reducing necking. Particularly preferred is that both the holding roller and the stretching roller are also provided with two holding assemblies and one connecting element.

[0042] The aforementioned stretching equipment and its advantageous design can be installed in any film manufacturing or film processing equipment. In particular, the stretching equipment according to the invention can be installed in series within a blown film equipment or a flattening film equipment. In a blown film equipment, the stretching equipment can, for example, be installed between the flattening device and the reversing device along the conveying direction of the film web, or downstream of the reversing device but before the winding device. In a blown film equipment, the film web can also be a double-layered film web, formed by combining blown films (folienblase). The two layers of the film web can then be connected to each other at two side edges or only at one side edge, or separated from each other by a previous cut on both sides.

[0043] The aforementioned objective is further achieved by a method for uniaxially stretching the film web along its transport direction. • The film web is guided by a first roller (holding roller) rotating at a first circumferential speed. • The film width is guided by a second roller (stretching roller) located downstream of the first roller and rotating at a second circumferential speed. • Wherein, the second circumferential velocity is greater than the first circumferential velocity. • The film web is pressed toward one of the rollers using at least one pressing roller. The key feature of the method according to the invention is that at least one retaining assembly is provided, the pressure roller rotating relative to the retaining assembly, wherein the pressure roller is supported on the retaining assembly by a support portion extending over a range of more than one-quarter of the axial length of the pressure roller, or by a plurality of support portions distributed over the range of the axial length and / or the circumferential range of the pressure roller, wherein the one support portion or the plurality of support portions move relative to the pressure roller in a direction parallel to the rotation axis of the pressure roller by means of a first motion device.

[0044] This allows for the acquisition of the same advantages as those described above in conjunction with the stretching apparatus according to the invention.

[0045] In the design scheme of the method according to the invention, the pressure roller also moves along its axis of rotation. The movement of the support portion and / or the pressure roller can be performed periodically. In particular, the movement directions of the pressure roller and the support portion are arranged in opposite directions. Here, it is possible to set the speed distribution of the movement of the pressure roller and the support portion to be the same. However, different speed distributions can also be set, especially in conjunction with the different strokes traversed by the pressure roller and the support portion respectively. Using the measures mentioned above, it is possible to adapt the movement to the characteristics of the film web. In particular, when the stretching equipment according to the invention is arranged in series, the movement can also be adapted to the method and operating parameters of the film web manufacturing equipment. Attached Figure Description

[0046] Other advantages, features, and details of the invention will become apparent from the following description, in which different embodiments are explained in detail with reference to the accompanying drawings. Here, features mentioned in the claims and in the specification are important to the invention individually or in any combination of the mentioned features. Throughout the disclosure, the features and details described in conjunction with the method according to the invention are of course applicable in conjunction with the stretching device according to the invention, and vice versa, so that mutual reference or reference is always possible in relation to the disclosure of various aspects of the invention. The various drawings are shown below: Figure 1 A schematic diagram of the stretching device according to the invention is shown. Figure 2 Illustrations showing further details of the stretching device according to the invention are provided. Figure 3 Showing from Figure 4 View III-III, Figure 4 Showing from Figure 2 View IV-IV, Figure 5 An illustration shows an improvement of the stretching device according to the invention. Detailed Implementation

[0047] Figure 1 A schematic diagram of the stretching apparatus according to the invention is shown. A film web 101 enters the stretching apparatus 100 along the conveying direction T. The film web first runs onto a preheating roller or successively onto multiple preheating rollers, wherein only one preheating roller 102 is shown. The task of the preheating roller is to bring the film to a predetermined temperature. For this purpose, the preheating roller is typically temperature-controlled, wherein a temperature-controlled fluid is typically introduced into the preheating roller.

[0048] After exiting one or more preheating rollers 102, the film web 101 reaches a first roller 110, which can also be referred to as a holding roller 110. This holding roller can be connected to a drive device (not shown), such as its own electric motor, which drives the roller 110 to rotate at a first circumferential speed. As a supplement or alternative, a braking device can be provided.

[0049] The first roller 110 is preferably equipped with a first pressure roller 111, which, together with the first roller 110, provides an inlet gap for the film. Preferably, the inlet gap or running path of the film web 101 is configured such that the film web 101 runs tangentially with the rollers 110, 111 within the inlet gap. The roller gap is used to minimize the air gap between the roller 110 and the film.

[0050] Furthermore, the first roller 110 is provided with a second pressing roller 112, which forms an exit gap with the roller 110. The second pressing roller 112 is adjustable along the circumferential direction and / or along the radial direction of the first roller 110. The second pressing roller 112 is used to cause the film to exit the first roller 110 along a line extending parallel to the axial direction of the first pressing roller 110.

[0051] Viewed along the conveying direction T of film 101, a second roller 120, which can be referred to as stretching roller 120, is arranged downstream. The stretching roller 120 is connected to another drive device (not shown), such as its own electric motor, which drives the roller 120 to rotate at a second circumferential speed. The rotation direction R1 of roller 110 is opposite to the rotation direction R2 of roller 120. This achieves the goal of having the largest possible containment angle around each roller 110, 120. Here, the second circumferential speed is greater than the first circumferential speed, thus the stretching roller 120 has a larger circumferential speed than the holding roller 110. This causes film 101 to be stretched proportionally to its conveying direction between the exit gap of the first roller 110 and the inlet edge of the second roller 120. The distance between the exit gap and the inlet edge is also commonly referred to as the stretching gap.

[0052] It is feasible that the first roller 110 and the second roller 120 can move relative to each other. This can affect the stretching gap. The change in the stretching gap can affect the properties of the film. Preferably, the stretching gap is as small as possible, that is, the shortest possible distance between rollers 110 and 120, within which the film width is freely guided.

[0053] Preferably, the second roller 120 is provided with a third pressure roller 121, which, together with the second roller 120, provides a second inlet gap for the film. Preferably, the inlet gap or running path of the film 101 is configured such that the film 101 runs tangentially with the rollers 120, 121 within the inlet gap. The roller gap serves to minimize air between the stretching roller 120 and the film, thereby minimizing friction between the film web and the roller 120.

[0054] When the tension gap is set to be very small, the third pressing roller 121 will collide with the roller 110, and thus the third pressing roller will inevitably deflect in this case.

[0055] Furthermore, the second roller 120 may optionally be equipped with a fourth pressure roller 122, which forms an exit gap with the roller 120. The fourth pressure roller 122 is also adjustable along the circumferential direction of the second roller 120. The fourth pressure roller 122 is used to cause the film to exit the second roller 120 along a line extending in a direction parallel to the axial direction of the roller 120.

[0056] In principle, one or more pressure rollers can be omitted in the stretching apparatus according to the invention. However, the inlet gap or outlet gap can be discussed. This should refer to the line along which the film adheres to the holding roller or stretching roller, or at which the film detaches from the holding roller or stretching roller.

[0057] It is also possible to provide other rollers, especially rollers with one or two pressure rollers, wherein two rollers arranged directly in succession are driven such that the roller arranged downstream has a higher circumferential speed than the roller in front.

[0058] At least one cooling roller 130 is arranged downstream of rollers 110 and 120, which can be used to cool the film web 101 again, thereby enhancing the new molecular orientation within the film web achieved by the stretching.

[0059] Figure 2 Further details of the stretching apparatus 100 according to the invention are shown. The second pressure roller 112 and the third pressure roller 121 are shown alongside the holding roller 110 and the stretching roller 120. Here, embodiments of the invention are explained in conjunction with the pressure roller 112; however, additional or all pressure rollers, especially the pressure roller 121, can be combined with embodiments of the invention.

[0060] The second pressure roller 112 and / or the third pressure roller 121 are preferably supported on a support 140, particularly a transverse support, extending transversely to the conveying direction of the film width. The support 140 is, in turn, directly or indirectly supported on a frame, on which the one or more rollers are also supported. The support 140 itself can be composed of multiple interconnected single pieces. Because the one or more rollers 110, 120 are movable relative to the frame, adjusting devices, such as pivot bearings or slider-track combinations, can be provided between the frame and the rollers 110, 120. The support 140 can also be supported on these adjusting devices, wherein the support 140 and thus the pressure roller are movable independently relative to these adjusting devices, so that the pressure roller can be moved relative to the first roller and / or the second roller 110, 120. The following description, by means of an embodiment, illustrates how the pressure roller is supported on the support, wherein the invention is not limited to this embodiment.

[0061] Another preferred design for the retaining assembly 113 of the pressure roller is now described, exemplarily for the pressure roller 112; however, this is certainly effective for all other pressure rollers as well. Figure 3 and Figure 4 Other views of the retaining component are shown below, and these views are also referred to in the following description.

[0062] Multiple retainers 141 are connected to a frame 146, and the retainers are distributed in the longitudinal direction of the frame and thus in the axial direction of the pressure roller 112. This axial direction is illustrated by the diagram of the rotation axis 142 of the pressure roller. Each retainer 141 carries a shaft 143, wherein a separate shaft 143 can be provided between each pair of retainers 141, or the shaft 143 can extend through multiple retainers 141. Alternatively, a drive shaft can be provided instead of a shaft, which is then rotatably supported in the retainer, such that the following description of the shaft 143 also applies to the drive shaft. The shaft 143 between two retainers 141 is hereinafter also referred to as the shaft section.

[0063] The frame 146 is supported on a support 140, where a track 147 is preferably fixedly mounted. The frame is particularly capable of being movably supported on the track by means of a sliding element or slider. The mobility of the pressure roller 112 parallel to the axis 142 is indicated by a double arrow 149. To enable back-and-forth movement along the double arrow, a movement drive 148 is provided, which is fixed directly or indirectly to the support 140, for example. The movement drive 148 is connected to the frame, for example, via a push rod 151. The components described in this paragraph, especially the track 147, frame 146, movement drive 146, and / or push rod 151, can be components of a motion device in the sense of claim 1. Figure 4 The frame 146 can only be seen from these components.

[0064] A first shaft and at least one second shaft 143, or a first shaft row and at least one second shaft row 143, are provided, extending parallel to each other and parallel to the axial direction of the pressure roller 112. Each shaft 143 carries one or more rollers 144 rotatably supported on the shaft. In the case of a drive shaft, these rollers 144 can be securely connected to the drive shaft. Thus, the rollers 144 are also distributed on the pressure roller along the axial direction of the pressure roller using the shaft 143. The pressure roller 112 rolls on these rollers 144 during operation, and thus these rollers are part of the support device, by which the pressure roller 112 is supported on the retaining assembly 113. Each shaft 143 or shaft segment can be provided with a separate set of rollers 144. Advantageously, the shaft segments of the first shaft or shaft row are arranged axially offset from at least one shaft segment of the second shaft or shaft row to avoid point-by-point contamination or wear that would otherwise occur due to uneven rolling of the rollers on the pressure roller.

[0065] Two parallel shafts, or shaft rows, together with their rollers 144, form a groove-shaped recess in which the pressure roller 112 is located, thereby preventing any form of movement other than intentional rotational and / or traversal motion. The pressure roller 112 itself can be rotatably supported by a retainer 141 or an accessory 150 of the retainer at its end via a rotary bearing. The rotary bearing can be movably arranged in the retainer or accessory to reduce the radial force that may act on the rotary bearing when the clamping force changes. This movability can be achieved, for example, by means of an elongated hole in the accessory 150 in which the rotary bearing is movably arranged. Additionally, a movement drive 152 for the pressure roller 112 can be arranged at the accessory 150, allowing the pressure roller to move back and forth along its axis 142, i.e., in the direction of the double arrow 153.

[0066] To ensure that the pressure roller remains in constant contact with the roller 144, a plurality of magnets 145 can be arranged directly or indirectly on the support along the axial direction within the length of the pressure roller 112. In this embodiment, the pressure roller includes at least one magnetizable element, preferably an iron core extending along the axial direction, in its body. This magnetizable element or iron core is attracted by magnetic force, preferably as a permanent magnet. The magnetizable element within the pressure roller is not shown.

[0067] In summary, through the aforementioned combination Figures 2 to 4 The described arrangement reduces the deflection of the pressure roller. Therefore, it is possible to increase the clamping force of the pressure roller on rollers 110 and / or 120 and / or shorten the stretching gap. Both of these feasible solutions result in a reduction of the necking effect and thus lead to more cost-effective production of marketable film widths. Furthermore, rollers 144 and / or the pressure roller can be moved to avoid ultimately creating marks on the film width 101.

[0068] Figure 5 An advantageous improvement to the stretching device according to the invention is now shown. An embodiment for preferably conforming to... Figures 2 to 4The roller has two retaining assemblies for two pressing rollers, one of which is associated with the collision line of the film web on the roller, and the second pressing roller is associated with the separation line. The two retaining assemblies are connected to each other by a connecting element 160. The connecting element provides the advantage that the two retaining assemblies, together with the pressing rollers, can be moved relative to the roller 112 using a common adjusting device 161. The adjusting device can, for example, include a piston cylinder unit operated by compressed air, by which the connecting element can be adjusted along the radial direction of the roller 112 (shown by double arrows 162). For adjustment along the circumferential direction of the roller 112, the connecting element 160 can be movably arranged on the adjusting device 161. It is also conceivable that the adjusting device can be pivotally arranged on a frame or on a bracket carrying the roller 112.

[0069] List of reference numerals in the attached diagram: 100 stretching equipment 101 Film width 102 Preheating Roller 110 First roller; holding roller 111 First pressing roller 112 Second pressure roller 113 Retaining Components 120 Second roller; stretching roller 121 Third pressure roller 122 Fourth pressure roller 130 Cooling Roller 140 supports 141 Retainer 142 Rotation axis 143 axis 144 Roller 145 Magnet 146 Frame 147 orbits 148 Motion drive for frame 146 149 Double Arrow 150 Attachments 151 putter 152 Moving drive for pressure roller 112 153 Double Arrow 160 Connecting elements 161 Adjustment device 162 Double arrow used to indicate the radial direction T conveying direction Rotation direction of roller 110 (R1) The rotation direction of roller 120 (R2).

Claims

1. A stretching apparatus for uniaxially stretching a film web along its conveying direction, comprising: • A first roller (holding roller) guides the film width, and the first roller rotates at a first circumferential speed. • A second roller (stretching roller) is arranged downstream of the first roller, which guides the film width, and the second roller rotates at a second circumferential speed. • in, The second circumferential velocity is greater than the first circumferential velocity. • The device includes at least one pressure roller, which is used to press the film web towards one of the rollers. Its features are, The pressure roller is provided with at least one retaining component, and is rotatable about its axis of rotation relative to the retaining component. The clamping roller is supported at the retaining assembly by a support portion extending over a portion of the axial length of the clamping roller, particularly more than a quarter of its length, or by a plurality of support portions distributed over the axial length and / or circumferential length of the clamping roller. A first motion device is provided, which enables the one or more support parts to move relative to the pressure roller in a direction parallel to the rotation axis of the pressure roller.

2. The stretching device according to the preceding claims, characterized in that, The retaining assembly includes at least one support that extends parallel to the axis of rotation and is arranged in a non-movable manner relative to the first roller and / or the second roller.

3. The stretching device according to any one of the preceding claims, characterized in that, The first motion device includes at least one frame, with each support portion resting on the frame, wherein the frame is movable relative to the pressure roller and, in particular, relative to the support.

4. The stretching device according to the preceding claims, characterized in that, The frame is supported on the support and is particularly movable relative to the support by means of a sliding or rolling device.

5. The stretching device according to any one of the preceding claims, characterized in that, The first motion device includes at least one drive device, and each support portion, and in particular the frame, is capable of moving alternately along a first direction and a second direction opposite to the first direction using the drive device.

6. The stretching device according to any one of the preceding claims, characterized in that, The pressure roller is provided with a second motion device, which enables it to move along its axial direction.

7. The stretching device according to any one of the preceding claims, characterized in that, The pressure roller is connected to the retaining assembly via a retainer, wherein, in particular, the pressure roller can move relative to the retainer using the second motion device, or the retainer can move relative to the retaining assembly together with the pressure roller.

8. The stretching device according to any one of the preceding claims, characterized in that, The support portions are provided with a first column and at least one second column, wherein the columns extend along the longitudinal direction of the pressure roller, and wherein, in particular, the first column and the second column are movable relative to each other.

9. A method for uniaxially stretching a film web along its conveying direction. • in, The film width is guided by a first roller (holding roller), which rotates at a first circumferential speed. • The film width is guided by a second roller (stretching roller) arranged downstream of the first roller, the second roller rotating at a second circumferential speed. • Wherein, the second circumferential velocity is greater than the first circumferential velocity. • In this process, at least one pressure roller is used to press the film web toward one of the rollers. The feature is that it is provided with at least one retaining component, and the pressure roller rotates relative to the retaining component. The clamping roller is supported at the retaining assembly by a support portion extending over a portion of its axial length, particularly more than a quarter of it, or by a plurality of support portions distributed over the axial length and / or circumferential direction of the clamping roller. The one or more support parts move relative to the pressure roller in a direction parallel to the rotation axis of the pressure roller using a first motion device.

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