Pinning device, casting unit and machine

Abstract

A pinning device (32) for electrostatically attaching a film (F) to a chill roll (28) has a first fastening unit (36), a second fastening unit (38), an attachment region (A) between the fastening units (36, 38), a high-voltage source (42), an electrode (34), at least one insulation device (46), and at least one vibration absorber (44). The at least one insulation device (46) extends from the associated fastening unit (36, 38) to a film section (B). The electrode (34) extends in the attachment region (A) from the first fastening unit (36) to the second fastening unit (38) and through the at least one insulation device (46), and the electrode (34) is subjected to a high voltage provided by the high-voltage source (42). The vibration absorber (44) is fastened to the at least one insulation device (46) and is designed to absorb vibrations of the electrode (34). A casting unit (14) and a machine (10) for producing the film (F) are also provided.

Description

Technical Field

[0001] The present invention relates to a pinning device for electrostatically attaching a film to a cooling roller, a corresponding casting unit, and a machine having such a casting unit. Background Technology

[0002] When producing thin plastic films, the molten plastic film is first deposited onto a cooling roller, where it cools and solidifies. To ensure uniform cooling and therefore uniform material properties, the film must be placed uniformly across its entire width and continuously along its length on the cooling roller.

[0003] To prevent the membrane from deforming due to the mechanical solutions used in its application, it is known to use electrodes to generate an electric field with high strength near the surface of the cooling roller, through which the membrane must pass. Due to the electric field, the polar molecules of the membrane align. This generates an electrostatic attraction between the membrane and the cooling roller, causing the membrane to adhere evenly and automatically to the cooling roller.

[0004] However, generating such a strong electric field requires a very high voltage of 8 kV or higher at the electrodes, which can cause sparks between the electrodes and the cooling roller. These sparks damage the surface of the cooling roller and also reduce the quality of the produced film. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a spark-reducing pinning device, casting unit, and machine.

[0006] This objective is achieved by a pinning device for electrostatically attaching a film to a cooling roller, the device comprising a first fastening unit, a second fastening unit, an attachment region located between the fastening units, a high-voltage source, electrodes, at least one insulating device, and at least one vibration absorber. The at least one insulating device extends from the associated fastening unit to the film section. At least one electrode travels in the attachment region from the first fastening unit to the second fastening unit and through the at least one insulating device, and the electrode is subjected to a high voltage via the high-voltage source. The vibration absorber is fastened to the at least one insulating device and is designed to absorb vibrations from the electrode.

[0007] Because of the vibration absorber, the vibration of the insulation device, and therefore the vibration of the electrodes (which occurs invariably during machine operation), is rapidly absorbed, causing this vibration to decay quickly and with a low amplitude. This avoids the distance between the electrode and the cooling roller becoming too low, which would lead to arcing, and also makes it virtually impossible for the electrode to be immersed in the melt plume from the nozzle. Furthermore, this avoids large variations in the distance between the electrode and the cooling roller, which would be transferred to adhesion and negatively impact the visual and / or quality properties of the film.

[0008] In one respect, the vibration absorber has a natural frequency corresponding to the natural frequency of the electrode, particularly the natural frequency corresponding to the lowest natural frequency of the electrode, so that the vibration absorber can absorb the vibration of the electrode particularly efficiently.

[0009] Similarly, it can be envisioned that the vibration absorber has several natural frequencies, one, several, or all of which correspond to the natural frequencies of the electrodes.

[0010] In this context, "corresponding" is understood to mean that the natural frequency of the vibration absorber is the same as the natural frequency of the electrode, or within a range of ±10% of the natural frequency of the electrode.

[0011] In one embodiment, the vibration absorber has a base, at least one absorber mass block, and at least one spring connector, wherein the absorber mass block is movably fastened to the base by means of the spring connector, and in particular, wherein the base is fastened to an insulating device. In this way, a simple and reliable vibration absorber is realized.

[0012] The weight of the absorber mass block and the distance between the absorber mass block and the base are selected such that the vibration absorber has a natural frequency corresponding to the natural frequency of the electrodes.

[0013] The vibration absorber may have two absorber mass blocks and two spring connectors, wherein the two absorber mass blocks are the same or different and / or are fastened to the base at the same or different distances from the base by means of the corresponding spring connectors, thereby allowing one or more natural frequencies of the vibration absorber to be set in a simple manner.

[0014] Each absorber mass block is fastened to the base by means of a corresponding one in a spring connector. In particular, the absorber mass blocks and the base are aligned in a straight line, with the base positioned between the two absorber mass blocks.

[0015] Vibration absorbers can have two different natural frequencies, for example, when the absorber mass blocks are arranged with the same weight at different distances from the base.

[0016] To further simplify the construction, the at least one absorber mass block may be a weight block and / or at least one spring connector may be a resilient rod.

[0017] In one embodiment, the fastening device has two insulating devices that extend from each of the opposing fastening units toward each other. Due to the insulating devices, electric arcing on the cooling rollers can be reliably prevented.

[0018] The insulating device may extend only outside the membrane segment, or overlap with the membrane or membrane segment in an overlap area of ​​2 mm to 15 mm.

[0019] For example, insulating devices are insulating tubes, insulating covers, and / or insulating sleeves.

[0020] For particularly effective absorption, the vibration absorber, especially the base, can be fastened to an insulating device.

[0021] For example, vibration absorbers, especially bases, are threaded to, clamped to, coupled to and / or plugged into insulation devices.

[0022] In one aspect, the at least one electrode is strip-shaped or wire-shaped, particularly wire-shaped, whereby the electric field can be specifically shaped. In particular, the use of strip-shaped electrodes results in a particularly uniform electric field, thereby reducing high voltage (with the same adhesion effect) and thus reducing electric arcing.

[0023] In one embodiment, the at least one electrode is movable in its longitudinal direction between a first fastening unit and a second fastening unit. Specifically, at least one rotatable coil is provided in both the first and second fastening units, on which the at least one electrode is partially wound. Therefore, deposits on the electrode that affect the quality of the electric field can be removed.

[0024] In one aspect, the adhesion region has a film segment that corresponds in the axial direction to a segment of the cooling roller in which the film is deposited, wherein at least one vibration absorber is arranged outside the film segment. This arrangement eliminates the risk of damage to the film from the vibration absorber.

[0025] To absorb vibrations reliably, two vibration absorbers can be present for each electrode, with the vibration absorbers arranged on different sides of the membrane segment.

[0026] To make the electric field more uniform, the pinning device may have at least two electrodes, at least two insulating devices, and at least two vibration absorbers, wherein the vibration absorbers are fastened to the insulating devices of different electrodes, and in particular, the vibration absorbers for different electrodes are arranged on the same or different sides of the membrane segment.

[0027] The first electrode can be strip-shaped or wire-shaped, especially wire, and / or the second electrode can be strip-shaped or wire-shaped, especially wire.

[0028] For example, the electrodes travel parallel to each other and / or each has two side surfaces, wherein the electrodes face each other with their respective side surfaces.

[0029] In one embodiment, the first fastening unit and / or the second fastening unit have a damping device configured to dampen vibrations of the electrodes in the attachment region. The damping device causes vibrations to decay more quickly.

[0030] In one aspect, the damping device has a damping roller whose axis of rotation is perpendicular to the longitudinal direction of the electrode and perpendicular to the width direction of the electrode, wherein the damping roller is movably mounted in the width direction and located on the edge of each of the electrodes, particularly on the edge opposite to the cooling roller.

[0031] For example, the damping device has a damping roller for each electrode, the axis of rotation of which is perpendicular to the longitudinal direction of the electrode and parallel to the width direction of the electrode, and in particular, each of the electrodes rests on one of the damping rollers.

[0032] The insulating device can be fastened to the damping device by means of at least one damper made of elastic material.

[0033] This objective is also achieved by a casting unit having a slit mold, a cooling roller and a pinning device as described above, particularly wherein the cooling roller is grounded.

[0034] This objective is also achieved by a machine for producing films, which has a casting unit as described above and a stretching machine, particularly a transverse, longitudinal and / or synchronous stretching machine, which has a furnace.

[0035] The features and advantages described for the pinning device are similarly applicable to the casting unit and / or machine, and vice versa. Attached Figure Description

[0036] Further features and advantages of the present invention are derived from the following description and the accompanying drawings, in which:

[0037] Figure 1 A schematic diagram of a machine according to an embodiment of the present invention is shown, having a cooling roller unit according to an embodiment of the present invention;

[0038] Figure 2 A schematic perspective diagram is shown based on Figure 1 The cooling roller unit has a pinning device according to an embodiment of the present invention.

[0039] Figure 3 It shows that according to Figure 2 A schematic diagram of the pinning device is shown.

[0040] Figure 4 It shows that according to Figure 2 A perspective view of the insulation device of the pinning device, wherein a vibration absorber is fastened thereto;

[0041] Figure 5 The perspective view shows the results based on Figure 4 Vibration absorber,

[0042] Figure 6A vibration absorber according to the second embodiment is shown in a side view.

[0043] Figure 7a , Figure 7b Two graphs are shown showing the deflection of the electrodes in the vertical and horizontal directions after excitation on pinning devices with or without a vibration absorber (top) in each case.

[0044] Figure 8 Showing according to Figure 2 A perspective view of one of the fastening units.

[0045] Figure 9 Showing according to Figure 8 The damping device of the fastening unit,

[0046] Figure 10 A vibration absorber of a pinning device according to a third embodiment of the present invention is shown, and

[0047] Figure 11 A cross-section of the electrode and insulating device according to a fourth embodiment of the present invention is shown. Detailed Implementation

[0048] exist Figure 1 The image shows, in a highly schematic manner, a machine 10 for producing membrane F, which includes several different machines and devices.

[0049] Machine 10 is, for example, a sequential membrane production machine. Based on this, the invention is explained by way of example without limiting the scope of protection.

[0050] In the example shown, machine 10 has an extrusion machine 12, a casting unit 14, at least one longitudinal stretching machine 16 (MDO, "machine orientation oriented"), a transverse stretching machine 18 (TDO, "transverse orientation oriented"), a processing device 20, and a winding device 24.

[0051] The extruder 12 has an extruder and is configured to produce a melt from at least one starting product.

[0052] For example, one or more extruders are (one or more) single-screw extruders, (one or more) cascade extruders and / or (one or more) twin-screw extruders.

[0053] Other mixing and processing components, such as busbar extruders or planetary roller extruders, could also be considered.

[0054] The melt is deposited onto the cooling roller 28 of the casting unit 14 by means of the slit mold 26, thereby producing film F.

[0055] Similarly, a melt can be generated by polymerization. For this purpose, monomers (and optional additives, such as catalysts) are mixed and polymerized in the reactor and / or extruder of extruder 12. The resulting polymerized melt can then be deposited directly onto the cooling rollers 28 of casting unit 14 via nozzle 26, thereby producing film F.

[0056] The resulting membrane F can have one or more layers. For multilayer membranes, it is conceivable that one extruder produces several or all layers, or that one extruder produces each layer.

[0057] Subsequently, membrane F is fed to longitudinal stretching machine 16 and stretched in the longitudinal direction there.

[0058] For example, a transverse stretching machine 18, as described in DE 10 2021 128 332 A1, has a furnace 30 with different zones for temperature control of the membrane F along the typical movement or extraction direction of the machine 10.

[0059] In furnace 30, membrane F is heated in a known manner and stretched in the transverse direction by transverse stretching machine 18, thereby producing a uniaxially oriented or biaxially oriented membrane as in the exemplary embodiment.

[0060] Optional processing device 20 is, for example, a device for activating the surface of film F by corona treatment in order to achieve, for example, improved metal adhesion. Corona treatment can be performed on one side or both sides.

[0061] The winding device 24 is used to wind up the produced film F and is the last device in the extraction direction. It has a winding sleeve on which the film F is wound.

[0062] exist Figure 2 The enlarged schematic diagram shows the casting unit 14 (also known as the cooling roller unit).

[0063] The casting unit 12 shown here includes a slit mold 26, a cooling roller 28, and a pinning device 32. Figure 3 A schematic diagram of the pinning device 32 is shown.

[0064] The cooling roll 28 is cooled, hence it is also called a "chill roll".

[0065] A slit mold 26 is positioned above a cooling roller 28 and is designed to continuously deposit the plastic melt forming film F onto the cooling roller 28. The plastic used is, in particular, polyethylene terephthalate (PET). Similarly, the use of other plastics is conceivable.

[0066] Then, the film F is uniformly attached to the cooling roller 28 using the pinning device 32. The cooling roller 28 is then... Figure 2 The film is rotated counterclockwise in the view. In the exemplary embodiment shown, after the cooling roller 28 has rotated approximately three-quarters of the way, the film F produced in this way is finally removed from the cooling roller 28, and further cooled and fed to the longitudinal stretching machine 16 if necessary.

[0067] The pinning device 32 is an electrostatic pinning device and has at least one electrode 34, two fastening units, specifically a first fastening unit 36 ​​and a second fastening unit 38, an optional low voltage source 40, a high voltage source 42, at least one vibration absorber 44, and at least one insulating device 46.

[0068] In the exemplary embodiment shown, the low voltage source 40 and the high voltage source 42 are designed as a single device. The low voltage source 40 and the high voltage source 42 may also be designed as separate devices.

[0069] Fastening units 36 and 38 are arranged in the axial direction of the cooling roller 28, either in front of or behind it. An adhesion region A is designed between the two fastening units 36 and 38. Similarly, the adhesion region A, viewed in the axial direction of the cooling roller 28, has a segment called film segment B, which corresponds to the region of film F on the cooling roller 28. For example, film segment B is the segment of adhesion region A corresponding to the axial segment of the cooling roller 28, where film F is deposited on the cooling roller 28.

[0070] The membrane segment B is specifically spaced apart from the fastening units 36 and 38, such that the attachment area A has two external segments C, which are arranged between the membrane segment B and one of the fastening units 36 and 38 in each case.

[0071] Electrode 34 is fastened to each of fastening units 36 and 38 respectively and extends between the two fastening units 36 and 38, that is, it also passes through the attachment area A.

[0072] For example, as in the exemplary embodiment shown, electrode 34 is strip-shaped, meaning its width is much longer than its thickness, specifically by an order of magnitude. Additionally, in its longitudinal direction, its length is several orders of magnitude greater than its width.

[0073] Therefore, electrode 34 has two side surfaces and two edges extending in its longitudinal direction and its width direction. One edge faces the cooling roller 28, and the other edge faces away from the cooling roller 28. The direction between the edges of the same electrode 34 is referred to as the width direction of electrode 34. In particular, the width direction of electrode 34 corresponds to the radial direction of cooling roller 28.

[0074] Electrode 34 has a width, for example, between 3 mm and 15 mm, particularly a width greater than or equal to 4 mm and less than 13 mm. For example, a width of 12.7 mm is conceivable.

[0075] It is conceivable that electrode 34 is not designed as a strip, but as a line, i.e., circular, or in particular a line. Additionally, almost any other cross-section of electrode 34 is conceivable.

[0076] Electrode 34 is arranged behind slit mold 26 in the direction of rotation of cooling roller 28. For example, the distance between electrode 34 and cooling roller 28 is at least equal to the thickness of film F on cooling roller 28, for example, at least 2 mm. The distance between electrode 34 and cooling roller 28 is at most 20 mm.

[0077] Electrode 34 is subjected to a high voltage via a high voltage source 42. The high voltage is, for example, between 5 kV and 10 kV, and particularly between 7 kV and 9 kV.

[0078] The cooling roller 28 is grounded, which generates a strong electric field in the attachment area A, and the film F is guided through the strong electric field.

[0079] Additionally, a low current, known as pinning current, is generated. For example, at a high voltage of 20 kV, the current is approximately 30 mA. At a high voltage of 9 kV, a current of approximately 12 mA can be generated.

[0080] If electrode 34 breaks, the high-voltage source is cut off. The possibility of electrode 34 breaking due to the high-voltage source is identified by edge detection.

[0081] Similarly, electrode 34 can withstand a low voltage from a low voltage source 40. The low voltage is, for example, less than 150 V, particularly between 60 V and 130 V, such as 120 V. The high and low voltages are cascaded accordingly.

[0082] In addition to electrode 34, a second hollow insulating device 46 is provided, which is fastened to fastening units 36, 38 relative to each other.

[0083] For example, as in the illustrated embodiment, the insulating device 46 extends toward each other from the fastening units 36, 38.

[0084] The insulating device 46 extends through the outer section C of the attachment area A to the film section B. The insulating device 46 thus covers the entire outer section C to prevent arcing on the cooling roller 28, which could damage it, and the insulating device 46 specifically extends only to the outside of the film section B. Alternatively, the insulating device 46 may overlap with the film section B, for example, with an overlap of 2 mm to 15 mm for each of the insulating devices 46.

[0085] Similarly, it is conceivable that the insulating device 46 does not cover the entire outer section C, but is spaced apart from the membrane section F.

[0086] Electrode 34 travels successively through two insulating devices 46 in the region between fastening units 36 and 38, i.e., in attachment region A. More specifically, electrode 34 enters the insulating device 46 originating from the first fastening unit 36 ​​and travels within the outer section C of the insulating device 46. At the end of the insulating device 46, electrode 34 exits the insulating device 46 and then travels bare through membrane section B.

[0087] In another external section C, at the beginning of another insulating device 46, the electrode 34 extends into the other insulating device 46 and travels therein until it reaches the fastening unit 38.

[0088] It is also conceivable that electrode 34 can move in its longitudinal direction between the two fastening units 36, 38. For this purpose, as described in the following embodiments, a rotatable coil is provided in the first fastening unit 36 ​​and the second fastening unit 38, on which electrode 34 is partially wound. In this context, it may also be referred to as a coil unit rather than a fastening unit.

[0089] Electrode 34 is mechanically tensioned between fastening units 36 and 38 with a force of, for example, 200 N. Depending on this mechanical tension, the width of electrode 34, and the length of attachment area A, electrode 34 has a specific inherent frequency.

[0090] exist Figure 4 The diagram shows a perspective view of one of the insulating devices 46 and the electrode 34 by way of example, with a similar illustration of one of the vibration absorbers 44. For clarity, the corresponding fastening units 36 and 38 are omitted.

[0091] Electrode 34 is arranged to be free to move within insulating device 46 and to move through insulating device 46.

[0092] As can be seen, the insulating device 46 is, for example, an insulating tube, an insulating cover, and / or an insulating sleeve. It has an approximately rectangular longitudinal cross-section. For example, the corners are rounded or the short sides are formed by curved sections.

[0093] The inner diameter of the insulating device 46 in its longitudinal direction corresponds to the width of the electrode 34, so that the electrode 34 can be guided in the insulating device 46.

[0094] In the exemplary embodiment shown, each insulating device 46 completely surrounds the receiving electrode 34 along the circumference of the electrode 34.

[0095] However, it is also conceivable that electrode 34 is not completely sealed, as long as the side facing the cooling roller 28 is sealed by the corresponding insulating device 46.

[0096] The insulating device 46 is made of plastic, particularly polyetheretherketone (PEEK). Specifically, the PEEK is tempered PEEK. The insulating device 46, composed of tempered PEEK, has proven to be particularly durable. Other materials for producing the insulating device 46 are also conceivable, such as polytetrafluoroethylene (PTFE), polyphthalamide (PPA), or polyetheretherketone (PEK), provided they have sufficiently high dielectric strength and are dimensionally stable at temperatures above 150°C.

[0097] Vibration absorber 44 is fastened to insulation device 46. Figure 5 The vibration absorber 44 is illustrated in perspective view.

[0098] The vibration absorber 44 is fastened in such a way that the vibration absorber 44 is firmly located on the insulating device 46, but the mobility of the electrode 34 in the insulating device 46 is not affected.

[0099] For example, as shown in the exemplary embodiment, the pinning device 32 has two vibration absorbers 44 that are identical in design.

[0100] The vibration absorber 44 has a base 48, two absorber mass blocks 50 and two spring connectors 52.

[0101] Like the insulating device 46, the base 44 can be made of plastic, particularly polyetheretherketone (PEEK). Specifically, the PEEK is tempered PEEK. Other materials for producing the base 44 are also conceivable, such as polytetrafluoroethylene (PTFE), polyphthalamide (PPA), or polyetherketone (PEK), provided they have sufficiently high dielectric strength and are dimensionally stable at temperatures above 150°C.

[0102] The base 48 has a fastening section 54 and a connecting section 56, on which the spring connector 52 is fixed.

[0103] The fastening section 54 and the connecting section 56 can be designed as a single piece, so that the base 48 is a single piece.

[0104] For example, base 48 is an injection-molded part or 3D-printed element made of plastic. Using other materials, such as metal or blends of plastic and metal, is similarly possible.

[0105] The fastening section 54 is used to fasten to the insulating device 46 and is designed as a clamp in the illustrated exemplary embodiment.

[0106] In the tightened state, the tightening section 54 engages around the insulating device 46, thereby tightening the vibration absorber 44.

[0107] For example, the fastening section 54, designed as a clamp, can be reliably closed by means of a screw.

[0108] It is conceivable that the base 48 is threaded onto the insulating device 46 or plugged into the insulating device 46.

[0109] Similarly, it is conceivable that the vibration absorber 44 has only one absorber mass block 50 or more than two absorber mass blocks 50, or has only one spring connector 52 or more than two spring connectors 52.

[0110] In the exemplary embodiment shown, the absorber mass block 50 is designed as a heavy block, such as a cylinder made of solid material. The material of the absorber mass block 50 can be, for example, lead, steel, plastic, aluminum, or a mixture of these materials.

[0111] Similarly, one can imagine the weight having any other shape, such as a cuboid, cone, or circle or sphere.

[0112] In the exemplary embodiment shown, the spring connector 52 is a resilient rod.

[0113] Each of the absorber mass blocks 50 is fastened to the connection section 56 of the base 48 by means of a spring connector 52.

[0114] The spring connector 52 extends in the axial direction, that is, it also extends parallel to the electrode 34.

[0115] For example, the spring connectors 52 extend in opposite directions, such that the absorber mass blocks 50 are similarly opposite to each other relative to the base 48. Thus, the base 48 is located between the absorber mass blocks 50 in the axial direction.

[0116] The absorber mass block 50 and the base 48 are located on the straight line along which the spring connector 52 extends.

[0117] Therefore, the absorber mass block 50 is spaced apart from the base 48 and is movably mounted because the spring connector 52 enables the absorber mass block 50 to move.

[0118] In the exemplary embodiment shown, one of the absorber mass blocks 50 is arranged at a first distance a1 away from the base 48, and the second absorber mass block 50 is arranged at a second distance a2 away from the base 48.

[0119] The vibration absorber 44 has at least one natural frequency, which depends on the weight of the absorber mass block 50 and its distances a1, a2 from the base 48. The vibration absorber 44 may also have several natural frequencies, such as two natural frequencies, as shown in the exemplary embodiment.

[0120] In the exemplary embodiment shown, the absorber mass blocks 50 have the same weight, but different distances a1 and a2, thereby generating two different natural frequencies of the vibrating absorber 44.

[0121] Similarly, it can be envisioned that the two absorber mass blocks 50 and the distances a1 and a2 of the absorber mass blocks 50 from the base 48 are the same, so that the vibrating absorber 44 has only one natural frequency.

[0122] One or more natural frequencies of the vibration absorber 44 are selected such that it or one of them corresponds to the natural frequency of the electrode 34. For example, in this context, "corresponds" means that the natural frequencies corresponding to each other are the same or differ from each other by at most ±10%.

[0123] Specifically, the natural frequency of the vibration absorber 44 corresponds to the lowest natural frequency of the electrode 34.

[0124] For example, for electrode 34 with a width of 12 mm, a length of 4.2 m, and a mechanical voltage of 200 N, the natural frequency is approximately 24.8 Hz.

[0125] It is also conceivable that electrode 34 has several natural frequencies. In particular, it has the highest harmonic of the lowest natural frequency as its natural frequency.

[0126] For example, one of the natural frequencies of the vibration absorber 44 is 24.8 Hz, thereby matching the aforementioned example of the electrode 34.

[0127] exist Figure 6 The image shows a vibration absorber 44 of a second embodiment of the pinning device 32. This embodiment's vibration absorber 44 has only one natural frequency because the absorber mass blocks 50 have the same weight and are both arranged at the same distance from the base 48, i.e., a1 = a2.

[0128] As in Figure 3 As can be seen from the illustration, the two vibration absorbers 44 of the pinning device 32 in the illustrated embodiment are arranged on different sides of the membrane segment B.

[0129] During the operation of the stretching machine 10, a high-voltage electric field is generated between the electrode 34 and the cooling roller 28 by means of the pinning device 32, with the electrode 34 being subjected to a high voltage. Due to the rotational motion of the cooling roller 28, the membrane F passes through the electric field.

[0130] Due to the electric field, the surface of the cooling roller 28 becomes charged, and the polar molecules of the plastic material in the film F align. Therefore, an electrostatic attraction is generated between the cooling roller 28 and the film F. Because of this attraction, the film F adheres uniformly to the cooling roller 28.

[0131] During operation of machine 10, electrode 34 may vibrate, for example, due to an electric arc, melt inhomogeneity, unequal distribution of pinning additives, stretching, or other effects due to its length. Then, electrode 34 vibrates at its natural frequency.

[0132] Since the vibration absorber 44 is fastened to the insulating device 46, the vibration is transmitted to the vibration absorber 44, and similarly causes the absorber mass block 50 to move, causing the vibration absorber 44 to vibrate at its natural frequency. Since the natural frequency of the vibration absorber 44 corresponds to the natural frequency of the electrode 34, and the phase of the vibration of the vibration absorber 44 is opposite to the phase of the vibration of the electrode 34, the vibration in the electrode 34 is greatly reduced.

[0133] For example, Figure 7a The figure shows two graphs illustrating the vertical vibration of electrode 34 after excitation. The lower graph shows the deflection or amplitude of electrode 34 of pinning device 32 with vibration absorber 44, and the upper graph shows the deflection of electrode of pinning device without vibration absorber.

[0134] In a similar way, Figure 7b The figure shows two graphs illustrating the horizontal vibration of electrode 34 after excitation. The lower graph shows the deflection or amplitude of electrode 34 of pinning device 32 with vibration absorber 44, and the upper graph shows the deflection of electrode of pinning device without vibration absorber.

[0135] It can be clearly seen that, in the case of the pinning device 32 with vibration absorber 44, the amplitude of the deflection or vibration of electrode 34 is reduced or absorbed significantly faster than in the case without vibration absorber. For example, vibration attenuation is achieved three times faster.

[0136] Therefore, the electric arc between electrode 34 and cooling roller 28 is reliably reduced, and electrode 34 extends into the melt plume from slit mold 26 less frequently.

[0137] Additionally, if provided, during operation, electrode 34 is continuously moved along its longitudinal direction, i.e., unwound in the first fastening unit 36 ​​and wound up in the second fastening unit 38, or vice versa. In this way, deposits generated by the evaporation of the plastic material of the membrane F are removed, thereby increasing or maintaining the uniformity of the electric field.

[0138] Deposition is also reduced by applying a low voltage to the electrodes 34. The current, also known as the heating current, is generated by the low voltage passing through each of the electrodes 34, from the first fastening unit 36 ​​to the second fastening unit 38 (or vice versa), and has an ampere number between 1 A and 8 A.

[0139] For example, the amperage of electrode 34, designed as a 3 mm strip, is between 2 and 2.5 A, and the amperage of electrode 34, designed as a 12.7 mm strip, is approximately 7 A. When a wire is used as electrode 34, the current is lower.

[0140] The electrode is not grounded, which causes the current to be interrupted due to the breakage of electrode 34.

[0141] Due to the current, electrode 34 becomes hot, and thus the evaporation of the plastic material of membrane F is deposited less strongly on electrode 34 as condensate.

[0142] Therefore, the quality of the produced membrane F can be significantly improved and machine downtime can be significantly reduced.

[0143] exist Figure 8 and Figure 9 The fastening unit 38 of the pinning device 32 is described in the text, wherein... Figure 8 The second fastening unit 38 is shown in the open state, and Figure 9 The fastening of the corresponding insulating device 46 on the second fastening unit 38 is shown.

[0144] The first fastening unit 36 ​​was therefore designed for this purpose.

[0145] exist Figure 8 In the diagram, the second fastening unit 38 is shown open. The second fastening unit 38 is relative to... Figure 2 It is located on the upper left side of the cooling roller 28.

[0146] The first fastening unit 36 ​​on the right side of the cooling roller 28 has essentially the same construction, except that it is a mirror image.

[0147] The second fastening unit 38 has a housing 58, a rotatable coil 60, a voltage supply device 62, a first guide roller 64, a mechanical tensioning device 66, and a damping device 70.

[0148] Electrode 34 is partially wound around rotatable coil 60 and extends from rotatable coil 60 to voltage supply device 62.

[0149] The voltage supply device 62 is electrically connected to the high voltage source 42 and has a roller 72.

[0150] Roller 72 guides electrode 34 and subjectes electrode 34 to a high voltage supplied by high voltage source 42 in the process.

[0151] Subsequently, electrode 34 travels to the first guide roller 64 and from there leaves the fastening unit 38 to reach the attachment area A.

[0152] In the first fastening unit 36, the electrode 34 travels in the reverse order described in the second fastening unit 38 and eventually onto the rotatable coil.

[0153] The two rotatable coils 60 of the fastening units 36 and 38 can be driven. In this way, the electrode 34 can move between the first fastening unit 36 ​​and the second fastening unit 38. For example, the electrode 34 can unwind from the rotatable coil of the first fastening unit 36, travel through the attachment region A into the second fastening unit 38, where the electrode 34 is wound up by the rotatable coil 60 of the second fastening unit 38.

[0154] Additionally, the tension or mechanical stress of electrode 34 and thus its inherent frequency can be set by means of driven rotatable coil 60.

[0155] It is also conceivable that several electrodes in electrode 34 are wound on the same rotatable coil 60. In this case, for example, a common rotatable coil 60 is provided, which has different regions for the different electrodes 34. The mechanical stress and therefore the natural frequency of the different electrodes 34 can then be set by tensioning devices for each of the electrodes 34.

[0156] Damping device 70 represents the outlet of fastening units 36 and 38.

[0157] A damping device 70 is provided on an arm 62, which extends from the housing 58 of the corresponding fastening units 36, 38 in the direction of the attachment area A.

[0158] In particular, the length of the cantilever 62 can be adjusted, for example, by means of a motor and a rack and pinion mechanism.

[0159] Insulating device 46 is fastened to damping device 70 by means of fastening device 80, such as in Figure 9 It can be seen in the image.

[0160] For example, the fastening device 80 has vibration damping elements 82, such as dampers made of elastic material, with insulating devices 46 clamped between the vibration damping elements 82. The clamps can be adjusted, for example, by means of screws.

[0161] exist Figure 9 The enlarged illustration shows the damping device 70.

[0162] The damping device 70 has two damping rollers 84, each of which is fastened to the mounting block 86.

[0163] Each mounting block 86 is resiliently mounted perpendicular to the side surface of the electrode 34, so that the damping roller 84 is also resiliently mounted.

[0164] Each of the damping rollers 84 is rotatable about an axis of rotation that is perpendicular to the longitudinal direction of the electrode 34 and parallel to the width direction of the electrode 34. In other words, the axis of rotation extends parallel to the side surface but perpendicular to the longitudinal direction of the electrode 34.

[0165] Electrode 34 is guided between two damping rollers 84, each of which contacts the side surface of electrode 34.

[0166] The damping device 70 dampens the vibration of the electrode 34, and thus the vibration of the electrode 34 decays even faster.

[0167] Other damping devices are also conceivable, such as those described in DE 10 2022 118 971 A1.

[0168] In another embodiment, two electrodes 34 may be provided, each electrode 34 traveling through at least one insulating device 46. However, preferably, each of the electrodes 34 travels through two insulating devices 46.

[0169] In the case of two electrodes 34, at least two vibration absorbers 44 are provided, wherein, in each case, one vibration absorber 44 is fastened to one of the insulating devices 46 of each of the electrodes 34 and has the inherent frequency of the corresponding electrode 34.

[0170] Vibration absorbers 44 of different electrodes 34 can be arranged on the same side of the membrane segment B, for example, adjacent to each other, or arranged on different sides of the membrane segment B, for example, opposite each other.

[0171] If the two natural frequencies of the two electrodes 34 are different, and if the two natural frequencies of the vibration absorber 44 correspond to the different natural frequencies of the two electrodes 34, then the same vibration absorber 44 as described in the first embodiment can still be used.

[0172] It is also conceivable that if two electrodes 34 are used, four vibration absorbers 44 can be used, with one vibration absorber 44 provided for each insulating device 46 in each case.

[0173] Figure 10 and Figure 11 Further embodiments of the invention are shown, which substantially correspond to the first or second embodiment. Therefore, only the differences will be addressed thereafter, and identical and functionally equivalent parts are given the same reference numerals.

[0174] The description of other embodiments relates to the first or second embodiment, but the features of all embodiments can be easily combined together.

[0175] exist Figure 10 The vibration absorber 44 of the pinning device 32 according to the third embodiment is illustrated in perspective view.

[0176] In this embodiment, the absorber mass block 50 is designed in a U-shape, with the apex of the U-shape fastened to the connector 52. The legs of the U-shape extend to the base 48 and may be thicker at their ends.

[0177] This vibration absorber 44 has four inherent frequencies and is therefore suitable for many different electrodes 34 and / or mounting conditions, especially different mechanical stresses.

[0178] exist Figure 11 The image shows a cross-section of the electrode 34 and associated insulating device 46 according to a fourth embodiment. In this embodiment, the electrode 34 is a line with a circular cross-section. Therefore, the insulating device 46 is adapted to the cross-section of the electrode 34. The insulating device 46 has an annular cross-section, in which the electrode 34 travels within the annulus.

Claims

1. A pinning device for electrostatically attaching a membrane (F) to a cooling roller (28), comprising a first fastening unit (36), a second fastening unit (38), an attachment area (A) located between the fastening units (36, 38), a high voltage source (42), an electrode (34), at least one insulating device (46) and at least one vibration absorber (44). The at least one insulating device (46) extends from the associated fastening unit (36, 38) to the membrane section (B). in, The electrode (34) extends from the first fastening unit (36) to the second fastening unit (38) in the attachment region (A) and passes through the at least one insulating device (46), and the electrode (34) is subjected to a high voltage provided by the high voltage source (42), and The vibration absorber (44) is fastened to the at least one insulating device (46) and is designed to absorb the vibration of the electrode (34).

2. The pinning device according to claim 1, characterized in that, The vibration absorber (44) includes a natural frequency that corresponds to the natural frequency of the electrode (34), particularly the lowest natural frequency of the electrode (34).

3. The pinning device according to claim 1 or 2, characterized in that, The vibration absorber (44) includes a base (48), at least one absorber mass (50) and at least one spring connector (52), wherein the absorber mass (50) is movably fastened to the base (48) by means of the spring connector (52), and in particular, wherein the base (48) is fastened to the insulating device (46).

4. The pinning device according to claim 3, characterized in that, The vibration absorber (44) includes two absorber mass blocks (50) and two spring connectors (52), wherein the two absorber mass blocks (50) are the same or different and / or are fastened to the base (48) at equal (a) or different (a1, a2) distances from the base (48) by means of the respective spring connectors (52).

5. The pinning device according to claim 3 or 4, characterized in that, The at least one absorber mass block (50) is a weight block and / or the at least one spring connector (52) is a resilient rod.

6. The pinning device according to any one of the preceding claims, characterized in that, The pinning device (32) includes two insulating devices (46) that extend toward each other from each of the opposing fastening units (36, 38).

7. The pinning device according to any one of the preceding claims, characterized in that, The at least one electrode (34) is strip-shaped or wire-shaped, especially wire.

8. The pinning device according to any one of the preceding claims, characterized in that, The at least one electrode (34) is movable in its longitudinal direction between the first fastening unit (36) and the second fastening unit (38), and in particular, at least one rotatable coil (60) is provided in the first fastening unit (36) and the second fastening unit (38), and the at least one electrode (34) is partially wound around the at least one rotatable coil (60).

9. The pinning device according to any one of the preceding claims, characterized in that, The attachment area (A) includes a film section (B) corresponding to the section of the cooling roller (28) where the film is attached, wherein at least one vibration absorber (44) is arranged outside the film section (B).

10. The pinning device according to claim 9, characterized in that, The pinning device (32) includes two vibration absorbers (44), wherein the vibration absorbers (44) are arranged on different sides of the membrane segment (B).

11. The pinning device according to any one of the preceding claims, characterized in that, The pinning device (32) includes at least two electrodes (34), at least two insulating devices (46) and at least two vibration absorbers (44), wherein the vibration absorbers (44) are fastened to the insulating devices (46) of different electrodes (34), and in particular, the vibration absorbers (44) for different electrodes (34) are arranged on the same or different sides of the membrane segment (B).

12. The pinning device according to any one of the preceding claims, characterized in that, The first fastening unit (36) and / or the second fastening unit (38) include a damping device (70) configured to dampen vibrations of the electrode (34) in the attachment area (A).

13. A casting unit having a slit mold (26), a cooling roller (28) and a pinning device (32) according to any one of the preceding claims, wherein the cooling roller (28) is grounded.

14. A unit for producing a film, having a casting unit (12) and a stretching unit (16, 18) according to claim 13, particularly a transverse, longitudinal and / or synchronous stretching unit, the stretching unit having a furnace (30).

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