Partial opening device for pre-opening gripper

Abstract

The invention relates to a partial opening device for pre-opening a gripper, in particular a gripper of a stretching unit. The partial opening device comprises at least one partial opening disc and a driver, wherein the driver is configured to drive the at least one partial opening device. The partial opening disk has a circumferential surface including a rotating contact surface, where the contact surface is configured to engage with a blade portion of the gripper when the gripper is directed through the partial opening disk such that the gripper is pre-opened.

Description

Technical Field

[0001] The invention relates to a partial opening device for pre-opening a gripper, in particular a gripper of a stretching unit, an opening system for opening a gripper, a stretching unit comprising such an opening system and a method for opening a gripper. Background Art

[0002] Stretching units are used in particular for the production of plastic films and stretched textiles. In general, a material web to be stretched, generally a plastic film, is gripped in such a unit by means of a gripper unit or grippers and moved through the unit. The grippers are movably arranged on a revolving guide rail and are driven centrally or independently.

[0003] In particular, the material web to be stretched is clamped in the entry zone by means of grippers which are movably arranged on both sides of the material web to be stretched on revolving guide rails. The grippers are moved one after another from the entry zone via the stretching zone to the lead-out zone and then back again to the entry zone, wherein the film can be subjected to, for example, a predetermined relaxation and / or thermal post-treatment in the lead-out zone.

[0004] In order to clamp / grasp the material web in the entry zone, the gripper moves from an open position to a closed position (clamping position). Typically, the gripper comprises at least two clamping faces, which are substantially opposite to each other and serve to clamp the material web. By actuating a lever (also referred to as a blade), the clamping faces can be moved towards each other into the clamping position. In addition, the blade serves to open the gripper in order to release the material web after stretching. In particular, the gripper must be opened again after the stretching process. The opening usually occurs after the stretched film has been fed through another heating zone or cooling zone by means of the gripper. After the grippers return on the revolving guide rail, they clamp the material web again (in another position) and then move again through the stretching zone of the stretching unit. The gripper must be opened in order to be able to clamp the material web again.

[0005] In existing stretching units, in particular film stretching units, the opening of the grippers is not always reliable, so that the open position of the grippers cannot be achieved. In this case, the grippers remain in a partially open state or even close themselves again. As a result, these grippers cannot grip the material web again, with the risk of damaging the stretching unit and / or the film to be stretched. In order to prevent this, mechanical forced opening devices are often used. Known forced opening devices, such as opening wheels or opening strips, provide stops, which strike against the not completely opened grippers or the closed grippers when these grippers are guided past the forced opening device. The grippers are forced to open with the aid of the stops.

[0006] However, the impact and rapid opening of such a stopper can lead to very high mechanical stresses, which significantly shorten the service life of the gripper. If a part of the gripper, such as a blade or another part of the gripping mechanism, breaks due to the impact stress, this can also lead to damage to other parts of the film stretching unit and / or downtimes and thus to production losses.

[0007] In particular in the case of high-speed stretching units (e.g. production speeds > 500 m / min with corresponding gripper travel speeds), such as BO units, i.e. units in which the film is stretched in transverse and longitudinal direction, for example for the production of PET, PE, PP, PA films and the like, such forced opening is to be avoided. However, the opening rate of known magnetic and therefore non-impact opening devices decreases with increasing gripper travel speed. Furthermore, the opening rate of known non-impact opening devices is often insufficient if the grippers are difficult to open. This is particularly true in the case of large film thicknesses, in the case of immobilized blade sections or in the case of high transverse film tensions (i.e. in the case of high transverse tensile forces). Summary of the invention

[0008] It is therefore an object of the present invention to provide a device and a method which enable a gripper to be opened reliably even in situations where the gripper travel speed is high and / or the gripper is difficult to open.

[0009] This object is solved in particular by means of a partial opening device for pre-opening or for fully opening a gripper according to claim 1, by means of an opening system for fully opening a gripper according to claim 9, by means of a stretching unit according to claim 13 and by means of a method for opening a gripper according to claim 15. Further aspects of the invention are specified in the dependent claims and in the following description.

[0010] In particular, the object is solved by means of a partial opening device for pre-opening a gripper, wherein the gripper can be a gripper of a stretching unit, in particular a film stretching unit. However, the invention is not limited to film stretching units, but can also be used, for example, in conjunction with stretching textiles or other materials. Further fields of application are also possible.

[0011] The partial opening device according to the invention does not fully open the gripper. This means that the gripper is not moved from the closed position to the open position by means of the partial opening device. In particular, the partial opening device is configured to pre-open only such grippers that need to be pre-opened in order to be fully opened, or the partial opening device can be configured to pre-open all grippers that are guided past.

[0012] In the case of a pre-opened gripper, the gripper is only partially opened by the partial opening device. For example, the partial opening device moves the gripper from a closed position without completely opening the gripper. The additional opening process is then controlled by an opening device, preferably a contactless opening device (e.g. a magnetic opening device). In this case, the partial opening device is upstream of the opening device or is positioned in the front region of the opening device so that the opening device can take over the pre-opened gripper.

[0013] In a first application, only a portion of the gripper is to be pre-opened, in particular a portion of the gripper which is opened below a predefined opening degree when guided past the partial opening disk. In this case, the partial opening device is positioned in the (front) region of the opening device. In this case, the predefined opening degree may correspond to the opening degree to which the opening device moves the gripper in the event of a correct functioning of the opening device.

[0014] Then, when guided past, the grippers that do not have a predefined degree of opening are pre-opened by the partial opening device. The grippers that do not have a predefined degree of opening may be due, for example, to the fact that the grippers (or their blades) are hard and / or firmly adhere to the film edge of the film to be stretched. The grippers that are pre-opened by the partial opening device are then fully opened by the actual opening device (e.g., a magnetic opening device).

[0015] In the second application, all grippers are pre-opened. For this purpose, a partial opening device is positioned before the actual opening device. The grippers guided past are then opened by the partial opening device, thus pre-opened, and transferred in the pre-opened state to the actual, preferably magnetic, opening device.

[0016] In a further aspect, a partial opening device may be provided for fully opening the gripper. In this case, the partial opening device is positioned downstream of the opening device or in the region of the opening device. In this case, the partial opening device processes the gripper which has already been partially opened from the opening device and initiates a further subsequent opening process of the already partially opened gripper. When fully opening the gripper, the partial opening device may guide the gripper past a tipping point or even into a fully open position. A tipping point is understood to mean a point at which - if this point has been exceeded - the gripper or blade portion is reliably fully opened.

[0017] By means of the partial opening device, it is also possible to prevent (i) the opening device from not fully opening the clamp (in particular by means of pre-opening) and / or (ii) an already (partially) opened clamp from remaining in the partially opened state or closing again (in particular by means of full opening).

[0018] The partial opening device comprises at least one partial opening disk and a drive, wherein the drive is configured to drive the at least one partial opening device. The partial opening disk is in particular rotated by the drive.

[0019] The partially opening disc comprises a circumferential surface, wherein the circumferential surface has a rotational contact surface. This contact surface is configured to engage with a blade portion of the gripper when the gripper is guided past the partially opening disc and if the gripper has an opening degree below a predefined opening degree when guided past the partially opening disc, so that the gripper is pre-opened or optionally fully opened.

[0020] Thus, in a first application, when only a portion of the grippers is to be pre-opened, the partial opening device is positioned in the region of the opening device, preferably in the front region of the opening device (the partial opening device is therefore connected in parallel to the opening device). In this case, the predefined degree of opening can correspond to the degree of opening to which the opening device will move these grippers when these grippers are guided through the partial opening device in the case of correct functioning of the opening device. Thus, only the grippers that are guided through and are not fully opened by the opening device at that time are pre-opened by the partial opening device. After passing through the partial opening device, all grippers are then partially opened (either by the opening device when functioning correctly, or by the partial opening device), so that the opening device can take over the grippers and the rest of the opening can be implemented. Thus, the pre-opened grippers are further opened by the opening device after being guided through the partial opening device.

[0021] If all grippers are pre-opened (second application), the partial opening device can be upstream of the opening device. In this case, the predefined degree of opening can be determined so that it substantially corresponds to the closed position of the grippers. Thus, all grippers guided past are pre-opened by the partial opening device and the partially opened grippers are transferred to the opening device for full opening.

[0022] If the gripper is to be fully opened, in particular the part of the gripper which is opened to a lesser extent than a predefined degree of opening when guided past the partially opening disc, the partial opening device can be positioned in the region of the opening device (and thus connected in parallel with the opening device) or downstream of the opening device. In this case, the predefined degree of opening can correspond to the degree of opening which the gripper typically has when leaving the opening device (in case the other opening device functions correctly). Thus, the gripper which is guided past and which is only insufficiently opened by the opening device is fully opened by the partial opening device. The gripper which is insufficiently opened by the opening device is finally fully opened by the partial opening device.

[0023] For pre-opening, the predefined opening degree may be, for example, at least 1% or at least 5% or at least 10% or at least 15%, and for full opening, for example at least 85% or at least 90% or at least 95%. The predefined opening degree may in particular be set by the position of the partially opened disc.

[0024] By pre-opening, the time for opening the clamp is extended compared to conventional opening devices, so that the clamp is subjected to less mechanical stress. As a result, not only can full opening be ensured, but the service life of the clamp can also be extended. This applies similarly to full opening.

[0025] In the pre-opening, there is a mechanical contact between the contact surface of the partially opened disk and the blade part of the associated clamp. The position and / or the diameter of the partially opened disk can be selected so that only one clamp is always in contact with the rotating contact surface. Similarly, the position and / or the diameter of the partially opened disk can be selected so that several (at least two) clamps can be in contact with the rotating contact surface at the same time. However, compared to a forced opening device, the mechanical stresses are significantly reduced because the clamp is only partially opened and the relative speed between the clamp or its blade part and the partially opened disk can be reduced or even set to zero due to the driven partially opened disk.

[0026] According to one aspect of the invention, the partial opening device can pre-open the gripper with an opening degree ranging from greater than 0% up to at least 5%, preferably up to at least 10% and particularly preferably at least 15%. According to one aspect of the invention, the (or another) partial opening device can fully open the gripper from an opening degree of at least 95%, preferably at least 90%, and particularly preferably at least 85%. The percentage relates to the distance that the (one or more) clamping surfaces of the gripper move when transitioning from the closed state to the open state.

[0027] Partial opening of the gripper enables reliable opening of the gripper even when, among other things,

[0028] The clamp (or the blade part and / or at least one clamping surface) is stuck,

[0029] at least one clamping surface adheres and / or becomes stuck to the material web to be conveyed,

[0030] Residual material and / or deposits make opening the gripper more difficult, and / or

[0031] Due to the high travel speed of the gripper, the inertia of the movable parts of the gripper makes opening the gripper more difficult.

[0032] In particular, the drive can be configured to synchronize with the clamp travel speed. Synchronization of the drive with the clamp travel speed can occur so that there is essentially no slip between the clamp to be partially opened and the partially opened disk, or a desired slip can be set. For example, the drive can be synchronized so that the contact surface of the partially opened disk has a slip in the range of -10% to +10%, preferably in the range of -5% to +5%, and in particular in the range of 0% to +3% relative to the clamp to be partially opened. Therefore, the mechanical stresses that impact the clamps (or their blades) on the contact surface can be reduced, and the pre-opening (or full opening) can be guided by the partially opened disk. Therefore, the service life of the clamp and the partially opened disk can be extended.

[0033] The drive may be a direct drive or an indirect drive. For example, the drive may include a belt drive or a chain drive and / or an electric motor, such as a synchronous motor.

[0034] Furthermore, the position of the partially opened disk can be adjustable in the TD direction and / or in the MD direction. Thus, a predefined degree of opening can also be set. In order to adjust the position of the partially opened disk, the partially opening device can include at least one positioning device, or the adjustment can be performed manually. The at least one positioning device can include, for example, at least one linear motor and / or one linear guide. Similarly, the positioning device can include a transmission device, such as a trapezoidal thread spindle, which converts a rotary drive motion into a linear motion.

[0035] The term MD direction refers to "machine direction", while the term TD direction refers to "transverse direction". The MD direction relates to the direction in which a material web (particularly a plastic film) is fed through a stretching unit. It is also the main direction of travel along the length of the material web. In contrast, the TD direction relates to the direction perpendicular to the MD direction (in the plane of the material web).

[0036] Furthermore, the position of the partially open disk is adjustable in the vertical direction. The vertical direction is a direction vertical to the plane of the material web. Thus, the partially open disk can be positioned in three directions (MD, TD and vertical). The adjustment in the vertical direction can be performed manually. In particular, the vertical position can be specified once (e.g. during assembly via the elongated hole) or the vertical position can be adjusted manually. For this purpose, a positioning device can be provided.

[0037] Preferably, the position of the partially opened disc can be adjusted independently of each other in MD, TD and / or vertical direction.For this purpose, individually drivable / adjustable motion axes or positioning devices can be provided.

[0038] In particular, the partially opening device can include a control device that can change the speed of the partially opening disk. To this end, the control device can control the drive. Thus, a desired slip of the partially opening disk can be set.

[0039] The optimum position of the partially opening disc depends on the film edge thickness of the material web to be transported. The film edge thickness is here the thickness of the material web, in particular a plastic film, which can be measured between the clamping surfaces of the clamp in the closed state when the clamp has clamped the material web. As the position of the blade portion changes with the film edge thickness, the position of the contact point also changes, i.e. the point at which the blade portion first contacts the rotating contact surface of the partially opening disc. By positioning the partially opening disc in the MD, TD and / or vertical direction, the desired contact point (and therefore a predefined opening degree, below which there is a pre-opening or a full opening) can be set depending on the film edge thickness, so that the lowest possible mechanical loads occur in the pre-opening and / or the full opening, and the clamp can be opened reliably.

[0040] For an ideal pre-opening, the partially open disk is positioned so that, for example, a non-contact opening device (e.g., a magnetic opening device) has the option of subsequently reliably fully opening the pre-opened clamp. After the pre-opening, the non-contact opening device handles the pre-opened clamp and continues the opening process. The transfer of the clamp preferably occurs so that the opening process continues, i.e. before the pre-opened clamp begins to close again on its own. Similarly, for an ideal full opening, the partially open disk is positioned so that, for example, a parallel or forward non-contact opening device (e.g., a magnetic opening device) transfers a clamp that has been opened to a large extent or a clamp that has not been opened correctly to the partially open device, which then performs full opening. As described above, the partially open device can be configured to pre-open only such a clamp that needs to be pre-opened so that it is then fully opened by the opening device (first application), or the partially open device can be configured to pre-open all clamps that are guided through (second application).

[0041] For example, to position the partially opened disc, the film edge thickness may be input into the user interface of the computing device. The ideal position of the partially opened disc may then be calculated, and the partially opened disc may be manually positioned accordingly.

[0042] In particular, the contact surface of the partially opening disc may comprise a profiled cross section. This profiled cross section may be adjusted to the contact area of ​​the blade portion of the gripper to be partially opened, preferably such that the position of the contact point in the MD direction is independent of the film edge thickness of the material web (e.g. film) held by the gripper to be partially opened. The profile enables an ideal pre-opening or full opening and thus compensates for small fluctuations in the film edge thickness without the need to reposition or reposition the partially opening disc.

[0043] The partially open disk can be a polymer or metal partially open disk. For example, the partially open disk can be a high temperature polymer partially open disk, in particular a PEEK partially open disk. If the partially open disk is a metal partially open disk, its circumferential surface can optionally be at least partially coated. The coating can include, for example, a polymer coating (in particular PEEK). Therefore, wear and tear and mechanical stress on the blade sheet and the partially open disk can be further minimized.

[0044] The object is additionally solved by means of an opening system for opening a gripper, in particular a gripper of a stretching unit. The opening system comprises at least one partial opening device of the above-mentioned type and a magnetic opening device, wherein the magnetic opening device is configured to open the gripper using a magnetic force when the gripper is guided past the magnetic opening device. The magnetic force can be generated using at least one permanent magnet and / or using at least one electromagnet.

[0045] Furthermore, the at least one partial opening device may be positioned in the MD direction to perform a pre-opening of the gripper.

[0046] For the pre-opening, the partial opening device is for example positioned in front of and / or at least partially in front of the effective area of ​​the magnetic opening device, i.e. the partial opening device is positioned upstream of its area or in its area. If the effective area of ​​the magnetic opening device overlaps with the partial opening device, the pre-opened clamps can simply be transferred to the magnetic opening device, or only those clamps whose degree of opening is below a predefined degree of opening when guided past can be pre-opened. Here, the predefined degree of opening is preferably selected so that it corresponds to the degree of opening achieved by the usual opening of the clamps using the magnetic opening device. In this case, the partial opening device will thus ensure that all clamps have a certain (pre-opened) degree of opening after passing the partial opening device.

[0047] Furthermore, the partial opening device can be positioned in the MD direction to fully open the gripper. For full opening, the partial opening device is positioned, for example, after the effective area of ​​the magnetic opening device and / or at least partially in the effective area of ​​the magnetic opening device. If the effective area of ​​the magnetic opening device overlaps with the partial opening device, a gripper that is already partially opened but not fully opened can simply be transferred to the partial opening device. In this case, the predefined degree of opening is preferably selected so that it corresponds to the degree of opening that the gripper typically achieves when leaving the magnetic opening device. By means of full opening, the partial opening device can ensure that all grippers are opened after passing the partial opening device.

[0048] The effective area of ​​the magnetic opening device is the area where a magnetic force acts on the blade part of the holder, which is sufficient to actuate the blade part.

[0049] In particular, the at least one partial opening device can be positioned relative to the magnetic opening device so that the contact point of the partially opened disk is positioned in the front area in the MD direction, in particular in the front third of the magnetic opening device (relative to the length L of the effective area of ​​the magnetic opening device).

[0050] Furthermore, the at least one partial opening device can be positioned relative to the magnetic opening device so that the contact point of the partial opening disk is located at a distance d before or after the point at which the maximum magnetic force acts on the clamp to be opened. In particular, the distance d can be in the range from L to L / 2, preferably in the range from L to L / 3, and particularly preferably in the range from L to L / 5 mm, where L indicates the length of the effective area of ​​the magnetic opening device.

[0051] This distance is preferably chosen so that the partially opening disc engages in the area before / after the maximum magnetic force, since after exceeding the maximum magnetic force, no opening of the gripper by the magnetic opening device will take place. Furthermore, a partially opened gripper can be diverted or taken over by the partial opening device so that the gripper opens further, therefore before the gripper starts to close itself again, but in any case before the gripper closes again.

[0052] Furthermore, the opening system can comprise a mechanical forced opening device, wherein the mechanical forced opening device is located after the magnetic opening device and the partial opening device in the travel direction of the gripper. The forced opening device ensures that the gripper is opened without exception before it grips the material web again. In normal operation, the opening system is set up so that the opening occurs via the partial opening device and the magnetic opening device and the opening is sufficient. The forced opening device is only used as a backup solution, for example in case of failure of the partial opening device. The forced opening device can be an opening strip or a conventional opening wheel.

[0053] The opening strip is stationary. If an unopened or only partially opened gripper is guided past the opening strip, the blades rub against the opening strip and are actuated so that the gripper is forced fully open. Similarly, the opening wheel fully opens the gripper. When the gripper is guided past the stationary opening wheel, the opening wheel actuates the blades and thus fully opens the gripper.

[0054] Furthermore, the object is solved by means of a stretching unit, in particular a transverse direction orienter, a machine direction orienter and / or a simultaneous stretching unit, which comprises a plurality of grippers for gripping a material web to be stretched (e.g. a film). Furthermore, the stretching unit comprises an opening system of the aforementioned type. Typically, the grippers are guided in a rotating manner on at least two tracks, wherein the material web to be stretched is located between the tracks. An opening system can be assigned to each of these tracks.

[0055] In a machine direction orienter, the material web is stretched in the longitudinal direction (MD direction). In a transverse direction orienter, the material web is stretched in the transverse direction (TD direction). Machine direction orienters and transverse direction orienters are often combined so that longitudinal stretching is performed first and transverse stretching is then performed (or vice versa). In a simultaneous stretching unit, stretching in the machine direction and stretching in the transverse direction occur simultaneously.

[0056] The stretching unit can be a film stretching unit, in particular for stretching plastic films, such as PET, PE, PP, PA and / or the like. The thickness of the end film can be in the range from 2 to 200 μm, preferably in the range from 2 to 100 μm, and in particular in the range from 2 to 50 μm. The gripper travel speed is, for example, greater than 400 m / min, preferably greater than 500 m / min, particularly preferably greater than 600 m / min.

[0057] Furthermore, the object is achieved by a method for opening a gripper, in particular a gripper of a stretching unit, wherein the method comprises the following steps:

[0058] pre-opening of the gripper by means of at least one partial opening device as previously described, and

[0059] Open the gripper using the magnetic opening device,

[0060] - Optionally forcibly opening the gripper using a mechanical forced opening device after the gripper has been guided through the partial opening device and the magnetic opening device without successful opening.

[0061] In addition to the pre-opening, the gripper can also be fully opened. This method enables a reliable and wear-resistant opening of the gripper, thus achieving a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Additional features and advantages of the present invention can be found in the following description and in the accompanying drawings to which reference is made. In the drawings:

[0063] Figure 1 shows a schematic diagram of a stretching unit;

[0064] Figure 2 Another schematic diagram of a stretching unit is shown;

[0065] Figure 3 shows a schematic diagram of a gripper unit;

[0066] Figure 4 shows a schematic detailed view of a gripper unit;

[0067] Figure 5 A schematic diagram of the opening system is shown;

[0068] Figure 6 A schematic diagram showing a partially opened disc of a partially opened device;

[0069] Figure 7 a schematic diagram showing a partially opened device; and

[0070] Figure 8 A flow chart of a method for opening a gripper is shown. DETAILED DESCRIPTION

[0071] Figure 1 and Figure 2 An exemplary stretching unit 10 is shown in each case. The stretching unit 10 comprises an oven 14 and two drive systems 16. The drive systems 16 are positioned here mirror-symmetrically with respect to an axis of symmetry S of the stretching unit 10 and extend at least partially into the oven 14. The drive systems 16 operate outside the oven 14 in an entry zone 18 as well as in an exit zone 20, in which the material web 12 of the stretching unit 10 is fed and removed. It should be understood that the drive systems 16 can also operate completely within the oven 14.

[0072] In addition to the entry zone 18 and the exit zone 20, the stretching unit has at least three further zones 22, 24, 26. The zones 22, 24, 26 are adjacent to one another, so that, as viewed along the general travel direction and pulling direction R of the stretching unit 10, the entry zone 18 initially adjoins the first zone 22, the first zone 22 then adjoins the second zone 24, the second zone 24 then adjoins the third zone 26, and the third zone 26 finally adjoins the exit zone 20.

[0073] The drive systems 16 have a first spacing from one another in a first zone 22 of the stretching unit 10 adjacent to the entry zone 18, which is also referred to as a preheating zone. Further zones may be adjacent to the heat treatment zone 26. Similarly, further regions may be provided between the described zones 22, 24, 26. For example, a cooling zone may be provided after the heat treatment zone 26, in which the stretched and heat treated film is further cooled.

[0074] In a second zone 24 , also referred to as the stretching zone, the spacing of the two drive systems from one another increases until finally a second spacing is reached at the beginning of a third zone 26 , also referred to as the heat treatment zone.

[0075] Each of the drive systems 16 has a rail 17 on which a large number of gripper units 28 are guided. The gripper units 28 can be moved along the rail 17 by means of the drive of the corresponding drive system 16. Similarly, the grippers can also be driven directly. In this case, the rail 17 is designed, for example, as a linear motor.

[0076] exist Figure 1 and Figure 2 In FIG. 1 , only two gripper units 28 are shown symbolically for each drive system 16 . However, the stretching unit 10 comprises a large number of gripper units 28 arranged along the rail 17 .

[0077] The track 17 of the corresponding drive system 16 circulates a closed path from the entry zone 18 to the exit zone 20 and back again. The track section forming the forward stroke extends within the oven 14 between the entry zone 18 and the exit zone 20 in the intended direction of travel of the gripper unit 28.

[0078] In the illustrated embodiment ( Figure 1 ), the track section running from the exit zone 20 to the entry zone 18 in the normal operating direction and forming a return portion is also located in the oven 14. However, as described in accordance with Figure 2 In the embodiment shown in FIG. 1 , it may be located outside of the oven 14 .

[0079] To operate the stretching unit 10 , the material web 12 to be stretched is fed in the stretching direction R to an entry zone 18 of the stretching unit 10 . To this end, the material web 12 is secured by its edges running in the stretching direction R to two drive systems 16 .

[0080] More specifically, the edge of the material web 12 (eg, the edge of the film) is passed through the clamping device 30 ( Figure 3 ) is fixed in place and is therefore moved by movement of the gripper unit 28 along the track 17 of the drive system 16 in the pulling direction (MD direction).

[0081] In the entry zone 18 , the material web 12 has a width E perpendicular to the pulling direction R which corresponds approximately to the first spacing between the drive systems 16 .

[0082] The material web 12 is then fed through the first zone 22 and heated there. In the subsequent second zone 24, thus the stretching zone, the material web 12 is stretched in the TD direction and optionally in the MD direction with a continuously increasing pitch of the drive system 16. At the end of the second zone 24, the material web has a second width A.

[0083] After finishing stretching, the material web 12 passes through the third zone 26 where relaxation may occur and leaves the stretching unit 10 with a width A before the material web 12 is separated from the gripper unit 28 in the take-off zone 20 after pre-cooling.

[0084] For example, the stretching unit 10 is a cross direction orienter. It is also conceivable that the stretching unit 10 is a machine direction orienter, wherein the material web is stretched in the longitudinal direction (thus the pulling direction R).

[0085] Furthermore, the stretching unit 10 can be a simultaneous stretching unit, wherein the material web 12 can be stretched both transversely to the stretching direction R and in the stretching direction R in the second zone 24 , thus in the stretching area.

[0086] During processing of the material web 12, large tensile forces act on the gripper units 28 in a tensile direction, especially in the second zone 24, thus in the stretching zone. The tensile direction is predominantly in the main direction P of the gripper units 28 and to a lesser extent transversely thereto.

[0087] The gripper units 28 must be designed to withstand high tensile forces, in particular in their main direction P. The main direction P is a horizontal direction which therefore extends transversely to the edge of the material web 12 received in the gripper unit 28 .

[0088] In order to reliably absorb these tensile forces, the gripper unit or gripper 28 closes and grips the material web 12 in the entry region 18. In the exit region, the gripper opens again and releases the stretched material web 12. An opening system 100 is provided for opening the gripper so that the gripper arrives in the entry region 18 in an open state.

[0089] exist Figure 3 In FIG. 2 , one of the grippers or gripper units 28 is shown as an example in a perspective view. Figure 4 is a detailed view (side view) of the gripper 28. The gripper unit 28 comprises a main part 32 and two guide parts 34. The main part 32 has a basic body 36 and comprises the actual clamping means 30 which clamp the material web 12.

[0090] The side of the base body 36 on which the clamping device 30 is arranged is also referred to as the material side. The other side, i.e. the side of the base body 36 without the clamping device 30, is referred to as the guide side, because guide components 34 are fixed to this side. These guide components 34 run on rails 17 of the drive system 16. Therefore, the main component 32 includes a material side and a guide side.

[0091] In the embodiment shown, the clamping device 30 is formed in a known manner by sections of a base body 36, in particular an integrally formed lower clamping surface 37 and a blade section 38 rotatably mounted on the base body 36, said blade section 38 comprising an upper clamping surface 38. The clamping device 30 defines a fixing section 40 or a fixing opening, in which the edge of the material web 12 to be fixed can be inserted and fixed to the gripper unit 28 by means of the upper clamping surface 38.

[0092] The main direction P of the gripper unit 28 is perpendicular to the edge of the material web 12, which edge is fixed in place in the gripper unit 28. The main direction P is, for example, Figure 3 The fastening material web 12 exerts a tensile force on the gripper unit 28 in the tensile direction (mainly in the main direction P) in the second zone 24 (stretching zone).

[0093] The guide components 34 each include a base body 42 and at least one guide element 44 fixed to the base body 42. Figure 3 In the gripper unit 28 shown exemplarily in FIG, the guide part 34 further comprises a drive element 46, which is for example a chain or a part of a chain of the drive system 16. The drive element 46 can also be an engagement projection for a belt of the drive system 16 or part of a linear motor.

[0094] In the embodiment shown, the guide element 44 is formed as a roller. However, in other embodiments, the guide element 44 can also be a sliding element and / or a magnetic element, such as a permanent magnet or a ferromagnetic counterpart.

[0095] The guide members 34 define a receiving space 48 for the rail 17 (also referred to as guide rail). In particular, a recess may be provided in each of the base bodies 42 of the guide members 34, in which recess the rail 17 is received.

[0096] The receiving space 48 is located respectively in front of the body part 32 or on the leading side of the body part 32. The guide elements 44, in particular rollers and if applicable sliding elements, can project into the receiving space 48 and bear against the rail 17 and act as guides on the rail.

[0097] exist Figure 4 , the clamping device 30 of the clamp / clamp unit 28 is particularly shown. The lower clamping surface 37 is part of the base body 36 and is rigidly designed. The upper clamping surface 38 is movable and can be moved from a closed position to an open position. For this purpose, the blade piece 39 is actuated. The upper clamping surface and the blade piece in the closed position are denoted by the reference numerals 38 and 39. The upper clamping surface and the blade piece in the closed position are denoted by the reference numerals 38' and 39'.

[0098] exist Figure 5 , an opening system 100 for opening a gripper 28, in particular a gripper of a stretching unit 10, is schematically shown. The opening system 100 comprises a partial opening device 150 and a magnetic opening device 120. The magnetic opening device 120 is configured to open the gripper 28 using a magnetic force when the gripper 28 on the rail 17 is guided past the magnetic opening device.

[0099] The partial opening device 150 is positioned in the front region of the magnetic opening device 120 in the MD direction, in particular in the front third of the magnetic opening device 120 (relative to the length L of the effective region of the magnetic opening device 120 ).

[0100] As shown here, the active area of ​​the magnetic opening device 120 overlaps with the partial opening device 150, so that the pre-opened grippers can be simply transferred from the partial opening device 150 to the magnetic opening device 120. Depending on the application, the partial opening device 150 can be configured so that only those grippers that need to be pre-opened in order to then be fully opened are pre-opened by the partial opening device (first application), or the partial opening device 150 can be configured to pre-open all grippers 28 guided past (second application).

[0101] In the embodiment shown, the grippers 28 are opened in the outgoing zone 20 by means of the opening system 100 and are returned via the deflector 19 on the rails 17 to the incoming zone 18 in order to grip the material web 12 again.

[0102] If the gripper 28 cannot be successfully opened, for example due to a malfunction of the partial opening device 150 and / or the magnetic opening device 120 , a forced opening device 190 can be provided which forces the gripper to open before the access area 18 is reached again.

[0103] Figure 6 A schematic diagram of a partially opened disk 160 of a partially opened device 150 is shown, as for example in Figure 7 The partially opened disk 160 can be rotationally driven about an axis of rotation 161 .

[0104] The partially opening disk 160 has a circumferential surface 162 including a rotational contact surface 164. When the gripper 28 is guided past the partially opening disk 160, this contact surface 164 engages with the blade piece 39 of the gripper 28, so that the gripper 28 is pre-opened or fully opened. In the example shown here, the blade piece 39 of the gripper is actuated by the partially opening disk 160, so that the upper clamping surface 38 of the gripper moves from the closed position to the partially open position. Thus, the gripper is pre-opened and then transferred to the magnetic opening device 120 for further opening.

[0105] Similarly, the blades 39 of the clamp can also be actuated by the partially open disk 160 so that the upper clamping surface 38 of the clamp moves from the partially open position to the fully open position. Therefore, once the clamp is taken over by the magnetic opening device 120, the clamp is fully opened.

[0106] like Figure 6As shown in , the partially open disk is positioned in the MD and TD directions so that the blade portion 39 moves or actuates a distance X from the first contact with the partially open disk 160 at the contact point 165 until it is removed from the partially open disk 160. The distance X or position of the partially open disk 160 can be measured so that the clamp is pre-opened in a range of an opening degree of greater than 0% to at least 5%, preferably to at least 10%, and particularly preferably to at least 15%. Similarly, the distance X or position of the partially open disk 160 can be measured so that the clamp is fully opened from an opening degree of at least 95%, preferably 90%, and particularly preferably at least 85%. The percentage is related to the distance traveled by the upper clamping surface 38 of the clamp to transition from the closed state to the open state.

[0107] Figure 7 A schematic diagram of a partial opening device 150 is shown, as it can be used for pre-opening or full opening. In principle, such a partial opening device can be retrofitted into an existing opening system or be part of an opening system 100 according to the invention.

[0108] The partial opening device 150 includes a Figure 6 160 of the partially opened disc 160 of the design shown in . In addition, the partially opened device 150 includes a drive 170. The drive can be a direct drive or an indirect drive. For example, the drive can include a synchronous motor and a belt drive 172 or a chain. The drive 170 can rotatably drive the partially opened disc 160. In doing so, the drive 170 can be synchronized with the gripper travel speed so that the contact surface 164 of the partially opened disc 160 has a slip in the range of -10% to +10%, preferably in the range of -5% to +5%, and in particular in the range of 0% to +3% compared to the gripper 28 to be partially opened.

[0109] Furthermore, the partially opening device 150 shown comprises positioning devices 166, 167 which can adjust the position of the partially opened disk in the TD direction and / or in the MD direction R, for example via screw drives 168, 169. Furthermore, the position of the partially opened disk 160 can be adjustable in the vertical direction Z. For this purpose, further positioning devices (not shown) can be provided.

[0110] In particular, the partial opening device 150 may include a control device 200 that can change the speed of the partial opening disk 160.

[0111] Figure 8 A schematic diagram of a method 1000 for opening a gripper 28, in particular a gripper 28 of a stretching unit 10, is shown, wherein the method comprises the following steps:

[0112] Pre-opening 1100 the gripper by means of at least one partial opening device 150 as described above,

[0113] opening 1200 the holder using a magnetic opening device 120, and

[0114] After the gripper has been guided through the partial opening device and the magnetic opening device without successful opening, the gripper is optionally forced open 1300 using a mechanical forced opening device.

[0115] It should be understood that steps 1100 and 1200 are performed in a prescribed order during pre-opening. It is also possible to perform pre-opening first, then opening, and finally full opening. However, forced opening is downstream of steps 1100 and 1200 and is performed only in emergency situations (if implemented). If the partial opening device is configured to pre-open such a clamp that needs to be pre-opened in order to be fully opened (first application), the clamp can also be opened only by means of the magnetic opening device 120. This applies to a clamp that has achieved at least a predefined degree of opening when guided through the partial opening device and is therefore fully opened by the opening device. The present invention can certainly be designed in another way currently proposed, and the result will not impair any key features of the present invention. The present embodiment is exemplary in every respect and is not to be considered restrictive; and all modifications falling under the equivalent principle of the attached claims will be included therein.

[0116] Reference numerals list

[0117] 10 stretching unit

[0118] 12 Material web

[0119] 14 Oven

[0120] 16 Drive system

[0121] 17 Track

[0122] 18. Entrance Zone

[0123] 19 Deflector

[0124] 20 Lead-out area

[0125] 22 first zone (preheating zone)

[0126] 24 Second Zone (Stretching Zone)

[0127] 26 The third zone (heat treatment zone)

[0128] 28 Gripper unit

[0129] 30 Clamping device

[0130] 32 Main components

[0131] 34 Guide components

[0132] 36 Matrix

[0133] 37 Lower clamping surface

[0134] 38 Upper clamping surface

[0135] 39 blade part

[0136] 40 Fixed section

[0137] 42 Matrix

[0138] 44 Guide element

[0139] 46 Drive element

[0140] 48 Receiving Space

[0141] 100 Open System

[0142] 120 Magnetic opening device

[0143] 150 Partial opening device

[0144] 160 Partially opened disk

[0145] 161 Rotation axis

[0146] 162 Circumferential surface

[0147] 164 Contact Surface

[0148] 165 Contact Points

[0149] 166 Positioning device

[0150] 167 Positioning device

[0151] 168 Screw drive

[0152] 169 Screw drive

[0153] 170 Driver

[0154] 172 Belt drive

[0155] 190 Forced opening device

[0156] 200 Control device

[0157] 1000 Methods

[0158] 1100 Partial opening (pre-opening or full opening)

[0159] 1200 Open

[0160] 1300 Forced Open

[0161] A The width of the material web at the end of the stretching zone

[0162] E Width of the material web in the entry zone

[0163] P Main direction of tension

[0164] R pulling direction (MD direction)

[0165] S symmetry axis

[0166] TD TD direction

[0167] X distance

[0168] Z vertical direction

[0169] L The length of the effective area of ​​the magnetic opening device

Claims

1. A partial opening device (150) for pre-opening a gripper (28), in particular a gripper of a stretching unit (10), the partial opening device (150) comprising at least one partially open disk (160) and a driver (170), wherein the driver (170) is configured to drive the at least one partially open disk (160), and wherein The partially opening disk (160) has a circumferential surface (162) including a rotational contact surface (164), wherein the contact surface (164) is configured to engage with a blade portion (39) of a holder (28) if: The clamp (28) is guided past the partially opened disc (160) so that the clamp (28) is pre-opened if the blade piece (39) has an opening degree below a predefined opening degree when guided past the partially opened disc.

2. The partial opening device (150) according to claim 1, wherein the drive (170) is configured to be synchronized with the travel speed of the clamp so that the contact surface (164) of the partially opening disk (160) has a slip in the range of -10% to +10%, preferably in the range of -5% to +5%, and in particular in the range of 0% to +3% compared to the clamp (28) to be partially opened.

3. The partially opening device (150) according to claim 1 or 2, wherein The drive (170) is a direct drive, or wherein The drive (170) is an indirect drive which can include a belt drive or a chain drive.

4. A partial opening device (150) according to any one of the preceding claims, wherein the position of the partial opening device is adjustable in the TD direction and / or the MD direction, wherein the partial opening device (150) preferably includes at least one positioning device (166, 167) for adjusting the position of the partial opening disk (160) in the TD direction and / or the MD direction.

5. The partial opening device (150) according to any one of the preceding claims, wherein the position of the partial opening disc (160) is adjustable in the vertical direction.

6. The partial opening device (150) according to one of claims 4 or 5, wherein the partial opening device (150) further comprises a control device (200) which is capable of changing the position of the partial opening disk (160).

7. The partial opening device (150) according to any one of the preceding claims, wherein The contact surface (164) of the partially opened disk comprises a contoured cross-section, wherein the contoured cross-section is adapted to the contact area of ​​the blade portion (39) of the clamp (28) to be partially opened, preferably such that the position of the contact point in the MD direction is independent of the film edge thickness of the material web (12) held by the clamp to be partially opened.

8. The partial opening device (150) according to any one of the preceding claims, wherein the partial opening disc (160) is a polymer partial opening disc, or wherein The partially opening disk is a metallic partially opening disk, and wherein optionally the circumferential surface (162) is at least partially coated, wherein the coating can include a polymer coating.

9. An opening system (100) for opening a gripper (28), in particular a gripper of a stretching unit, the opening system comprising at least one partial opening device (150) according to any one of claims 1 to 8; and A magnetic opening device (120) wherein the magnetic opening device is configured to open the clamp (28) using a magnetic force when the clamp is guided past the magnetic opening device, and wherein The at least one partial opening device (150) is positioned in the MD direction (R) so as to perform a pre-opening of the grippers.

10. An opening system (100) according to claim 9, wherein the at least one partial opening device (150) is positioned relative to the magnetic opening device (120) so that the contact point (165) of the partial opening disk (160) is positioned in the front area of ​​the magnetic opening device (120) in the MD direction, in particular in the front third of the magnetic opening device (120).

11. An opening system (100) according to claim 9 or 10, wherein the partial opening device (150) can be positioned relative to the magnetic opening device (120) so that the contact point (165) of the partial opening disk (160) is located at a certain distance before or after the point where the maximum magnetic force acts on the clamp (28) to be opened.

12. The opening system (100) according to any one of claims 9 to 11, wherein the opening system further comprises a mechanical forced opening device (190), wherein: The mechanical forced opening device is located behind the magnetic opening device (120) and the partial opening device (150) in the travel direction of the clamp.

13. A stretching unit (10), in particular a transverse direction orienter, a machine direction orienter and / or a simultaneous stretching unit, comprising a plurality of grippers (28) for gripping a web (28) of material to be stretched, in particular a film, and An opening system (100) according to any one of claims 9 to 12.

14. The stretching unit (10) according to claim 13, in particular a film stretching unit, wherein the gripper travel speed of the stretching unit (10) is greater than 400 m / min, preferably greater than 500 m / min, particularly preferably greater than 600 m / min.

15. A method (1000) for opening a gripper, in particular a gripper (28) of a stretching unit (10), wherein the method comprises the following steps: pre-opening (1100) the gripper by means of at least one partial opening device (150) according to any one of claims 1 to 8, if the gripper (28) has an opening degree below a predefined opening degree when being guided past the partially opening disk (160), and opening (1200) the holder using a magnetic opening device (120), and After the gripper has been guided past the partial opening device (150) and the magnetic opening device (120) without being successfully opened, the gripper is optionally forced open (1300) using a mechanical forced opening device (190).

Images