JP2011518695A - Device for stretching a film web in the transverse direction - Google Patents

Abstract

  In an apparatus for stretching a film web in a transverse direction, a tenter clip (1) travels on a guide rail (2) by a travel roller (7). Vibration, noise, wear and friction loss occur at high working speeds. In order to avoid this, a permanent magnet or an electromagnet (8) is arranged on a predetermined area of the traveling roller (7) on the tenter clip (1) or on the guide rail (2). This draws the tenter clip (1) towards the guide rail (2) in a defined direction. For this reason, traveling of the tenter clip (1) on the guide rail (2) is stabilized, and a high working speed is realized in the apparatus for stretching the film web in the transverse direction.

Description

  The present invention relates to an apparatus for transverse stretching of a film web.

  In known transverse stretching devices, a number of tenter clips are combined together to form a clip chain that circulates continuously. The clip chain is provided on both sides of the film web in the longitudinal direction. With tenter clips, the film web is conveyed at high temperature through a transverse stretching device and stretched simultaneously.

  Such a transverse stretching device is described, for example, in DE 3703097.

  The guide rail on which the tenter clip travels is generally provided with a rectangular, vertically oriented cross section. The entire guidance system for the clip chain on both sides of the film web is constructed or assembled from various parts of straight, angled or curved guide rails in the direction of travel. At the entrance of the transverse stretching device, the synthetic plastic film is gripped at the ends by each row of tenter clips on both sides of the film web and is conveyed longitudinally through the stretching device. In that regard, the guide rails for the clip chains provided on both sides are configured or embodied such that the distance between the clip chains is greater in a predetermined region of the lateral stretching device. Thereby, the film fixed and tensioned in the tenter clip is stretched transversely with respect to the traveling direction. At the exit of the transverse stretcher, the tenter clip releases the film web. A predetermined area is provided, in which the continuous clip chain is driven, deflected and returned to the starting point via a further guidance system.

  Tenter clips generally have a base body, a mechanism that firmly grips the film web, elements that link individual tenter clips into a chain, and for vertical and horizontal guidance of the tenter clips on guide rails It consists of a running roller.

  The running roller for horizontal guidance not only guides the tenter clip on the guide rail, but also withstands the tensile force of the film web. These travel rollers are typically arranged to face each other in the base body so that they can support themselves in vertical travel on two sides of the guide rail. it can. This allows the tenter clip to perform uncontrolled or uncontrolled movements with or without film tension, at high travel speeds, and in curved sections of the guide rail. It is realized that it is impossible.

  Providing a method for preventing the system of opposed running rollers and rails from becoming stuck due to unavoidable tolerances and geometrical relationships in the area of the curved part of the guide rail is required. For example, the inner method between the traveling rollers facing each other is achieved by being configured to be slightly larger than the thickness of the guide rail. That is, for example, there is play of 0.3 mm to 0.5 mm.

  In the region of the transverse stretching device, in the region where the film web exerts a tension on the tenter clip in the direction transverse to the traveling direction toward the center of the transverse stretching device, It is pushed toward the guide rail. As soon as the tenter clip releases the film, the tension of the film is lost, along with the tenter clip under its own weight as well as under the dynamic inertia forces that occur at high clip chain speeds. May be unstable.

  Such a system consisting of a tenter clip, a running roller and a guide rail is described in EP 047152B1. It describes that vibrations, noise and wear on the guide rails and running rollers occur as a result of play at high drive speeds. In order to avoid these disadvantages, in EP 0 471 522 B1, for the guidance of the tenter clip in the horizontal direction, a complex roller system is used to push the travel roller, which can be adjusted laterally with respect to the travel direction, against the guide rail. It has been proposed to do. This reduces the play that exists in the prior art to zero at any time. This lever device is mechanically complex. Furthermore, this lever device is such that all travel rollers of the tenter clip that are in opposition to each other under pre-tension contact the rail, and at the bearing of the travel roller and between the travel roller and the guide rail. This causes friction loss at the contact points.

  DE 195 15036 A1 describes a system consisting of a tenter clip with a running roller. In this case, stabilization is achieved by using a damping element.

  DE 19510141C1 discloses a tenter clip system with a linear motor drive.

DE3703097 EP0471052B1 DE19515036A1 DE19510141C1

  An object of this invention is to provide the apparatus which has a tenter clip in a horizontal extending | stretching apparatus. In this case, acceptable levels of vibration, noise, wear and friction loss in the transverse stretching apparatus are achieved at high operating speeds.

Means for Solving the Invention

  According to the invention, this object is achieved by the features listed in claim 1. Further advantageous forms of the invention arise from the dependent claims and the description.

  A fundamental feature of the present invention is an apparatus for generating a magnetic force so that the tenter clip is permanently drawn toward the guide rail in a defined direction, regardless of whether film tension is present. Includes the use of provided devices.

  A suitable direction for this purpose is the direction in which the film tension is effective during the transverse stretching process. This keeps the force relationship in the tenter clip controlled during the process interruption in the end region of the device, which stabilizes the travel of the tenter clip on the guide rail.

  For example, a magnet position is provided on the tension roller, in which a small distance, for example 1 mm, is regularly placed between the magnet and the guide rail along the guide rail during the travel of the tension roller. Existing. This interval is an air gap, and a magnetic field is generated between the guide rail and the magnet in the air gap. In the magnetic field, force pulls the tenter clip, along with the connected travel rollers, towards the guide rail. For this purpose, the guide rail must be made of a magnetically suitable material known to those skilled in the art, such as steel. Sufficient orders of magnitude can be provided by the powerful magnets available today. The orientation for the required order of magnitude of the magnetic force is given by the weight of a typical tenter clip. A typical tenter clip can weigh for example 6 kg. The magnet must overcome at least the force of weight under the influence of the tenter clip attempting to tilt on the guide rail due to the lack of film tension.

  With respect to the use of magnets in the types and methods described above, the travel roller located on the same side of the guide rail as the magnet is in constant contact with the guide rail. In this regard, the position of the component is selected such that it does not cause contact between the magnet and the guide rail. Due to the magnetic force, the tenter clip is stabilized during travel and the travel roller does not disengage. For this reason, collision and run-out of the traveling roller do not occur, thereby reducing wear of the traveling roller and the guide rail. Furthermore, the traveling roller disposed on the other side of the guide rail does not actually contact the guide rail or rarely contacts the guide rail. This reduces the friction loss of these travel rollers as compared to a configuration in which all travel rollers of the tenter clip are constantly under pre-tension. In order to be applicable, it is possible to completely omit the traveling roller on the side facing the magnet in the guide rail. Overall, the device according to the invention represents a significant advance in actuation force that allows the tenter clip to run at high production speeds in the transverse stretching device.

  In the following, advantageous exemplary forms and further details of the invention are described.

  In known tenter clips, it has become typical to provide several traveling rollers, for example a pair of traveling rollers, adjacent to each other for grip support of the tenter clip relative to the guide rail. One or more of such pairs of traveling rollers can be used. Here, the pair of traveling rollers may be arranged in an overlapping manner. With sufficient force, one magnet can be placed between the two travel rollers. If the force of one magnet is not sufficient, a plurality of magnets may be arranged in the running direction in front, behind and / or between the running rollers.

  It is also possible to arrange the magnet of the tenter clip below the guide rail so that a force directed downward in the vertical direction acts on the tenter clip perpendicular to the direction of the force of the film. As a result, the traveling roller disposed above the guide rail of the tenter clip is permanently in contact with the guide rail, whereby the traveling of the tenter clip is also stabilized in the vertical direction. Have that.

  The air gap in which the magnetic field is generated between the magnet and the guide rail decisively determines the generated magnetic force and the force that pulls the tenter clip toward the guide rail. As the magnetic force increases correspondingly, the air gap decreases. A technically relevant median or intermediate value needs to be found between the magnetically unnecessary small air gap and sufficient play between the magnet and the guide rail. This play is necessary to prevent contact between the magnet and the guide rail, even when the guide rail has curvature, tolerances or other irregularities. In order to achieve an optimal air gap, it is appropriate to be able to adjust the position of the magnet on the tenter clip. This can be achieved through a screw / nut combination and, if applicable, through an elongated slot hole in the base body of the tenter clip. However, other adjustment means for the position of such components known to those skilled in the art can also be used.

  In the operation of such a system, abrasive wear inevitably occurs in the mechanical components.

  However, the use of the magnet of the present invention reduces this abrasive wear. This is because the traveling rollers are placed in a stable state in contact with the guide rail, and are no longer placed alternately in a contact state or a non-contact state. However, even in that case, abrasion is unavoidable. Metal brush wear is left on the magnet, which may interfere with the function of the device.

  Accordingly, it is an objective to provide a device for cleaning a magnet. This device may consist, for example, of one or more brushes arranged at appropriate positions in the guidance system. This causes the magnets to be rubbed or brushed by one or more brushes during clip chain travel. This scrapes away abrasive fines that may stick to the magnet. In order to make this possible, the magnets are arranged such that the magnets meet or hit the brushes arranged in the region of the guide rails that are not rolled by the running rollers of the guide rails. The device may be perfected by a suction device integrated in the guide rail. Here, the suction device sucks dust adhering from the brush and / or magnet.

  Today, permanent magnets are available that can generate very high forces even in small structural spaces. However, an electromagnet may be utilized if the force does not need to be large enough in certain cases. In this regard, a clip chain with a tenter clip is further supplied with current from a fixed and stationary machine part, for example a guide rail, via an elastically biased slip contact, similar to a railway system. A current supply system may be provided.

  Through this system, the tenter clip magnet may be temporarily switched off by electronic control. This has the advantage that fine particles of abrasive wear that adhere to the magnet can be more easily scraped off by the brush described above.

  The reverse configuration is also conceivable. In this case, a continuous row of magnets is arranged on the guide rail, while the tenter clip simply comprises a corresponding magnetically effective counter element. This simplifies the supply of current when using electromagnets. A slip ring need not be utilized, but rather the magnet can be securely incorporated into a stationary and stationary guide rail.

  In this case, a cleaning brush that removes abrasive wear from the row of magnets may be attached to the tenter clip. The suction device is securely attached at the appropriate location in the area of the guide rail. Here, for example, a row of magnets can be disturbed during a short extension. Therefore, the brush for short stretching does not run on the magnet, but rather runs on the suction nozzle.

  With the apparatus of the present invention, high production speeds for transverse stretching devices with tenter clips are possible under acceptable levels of vibration, noise, wear and friction loss.

FIG. 1 is a partial perspective view of an apparatus of the present invention having a tenter clip and guide rails when viewed from the outside of a film web. FIG. 2 is a perspective view showing a tenter clip when viewed from the inside of the film web without a guide rail. FIG. 3 is a view showing a tenter clip having another configuration of a magnet. FIG. 4 is a view showing an apparatus having a cleaning element and a current supply unit. 4a is a cross-sectional view of FIG. FIG. 5 is a diagram showing an apparatus when a magnet is provided on the guide rail.

  Exemplary forms of the invention are described in connection with the drawings and are described in more detail below.

  1 and 2, the device of the present invention having a tenter clip 1 is shown. Here, the tenter clip 1 reinforces or supports itself by a plurality of traveling rollers 7 a, 7 b, 7 c on the guide rail 2. For this reason, the traveling roller is attached to the base body 4 of the tenter clip. The tenter clip is coupled or combined with a number of further tenter clips, not shown, via chain links or joints 6, so that the clip chain circulates or freely moves around in the transverse stretching device Form. Shown is a tenter clip having a guide rail on one side of the film web 3, which is guided in the direction of the arrow through a transverse stretching device. The structure of the tenter clip and guide rail guiding system is symmetrical with respect to the longitudinal direction of the film. This means that the tenter clip and the guide rail are similarly arranged on the other side (not shown) of the film web 3.

  In known types and methods, the film web is held or gripped by the film clamp device 5 of the tenter clip. The film clamping device 5 is not shown, but can be opened or closed by an actuating device according to the prior art. The traveling roller 7a is disposed on the side facing the outer side of the guide rail so as to withstand the tension of the film. The magnet 8 prevents the tenter clip from being inclined toward the inner side of the guide rail by its own weight in an area where there is no film tension. The vertical guidance of the tenter clip is handled by one or more traveling rollers 7c. The traveling roller 7 c is similarly attached to the base body 4. Duplicate, individual, single-row, or double-row configurations of travel rollers are dependent on additional parameters that are not deterministic in the present invention.

  In FIG. 2, the adjusting screw 9 is shown on the magnet 8. Here, the adjusting screw allows adjustment of the position of the magnet 8 in the direction towards the guide rail via a nut / counternut combination. If desired, an elongated slot hole with an additional fixing screw may be further provided in the base body below the magnet. This makes it possible to reliably withstand magnetic force. With this configuration, the air gap between the magnet 8 and the guide rail 2 is adjusted small so that no contact occurs between the magnet 8 and the guide rail 2 but still the maximum possible magnetic force is generated. Can be done.

  The configuration of the magnet according to the present invention can be adapted to the configuration of the traveling roller as shown in FIG.

  The magnet can be mounted in the direction of travel between the two travel rollers and / or in front of and behind the travel rollers.

  The attachment of the magnet below the guide rail to generate the vertical force component can be easily ascertained directly from the description by a specialist. Therefore, it is not shown separately.

  4 and 4a show a tenter clip 1 having a guide rail 2 and a brush 10 and a suction device 11. The brush is attached to a portion of the guide rail that is not rolled by the traveling roller. In this case, the magnet is disposed on the base body 4 above or below the traveling roller. Therefore, the magnet is arranged outside the contact zone extending in the longitudinal direction of the guide rail 2 between the traveling roller and the guide rail.

  FIG. 4 shows a control unit and current supply line systems 13 and 12 as an example. The current supply line system 12 conducts current to the guide rail 2 for an electromagnet used as a modification. A current is conducted from the supply line 12 to a current rail 15 that is continuous in the traveling direction of the tenter clip on the guide rail via a line inside the guide rail 2. From there, current is supplied to the electromagnet of the tenter clip via an elastically loaded slip contact, not shown in detail. The current rail 15 can be attached above or below the travel path of the travel roller 7.

  Although not shown in detail, in the control unit 13, the supply of current to the magnet is interrupted at a predetermined time. The point in time can be adjusted by the operator of the device to assist in cleaning the magnet through the brush 10 and the suction device 11.

  FIG. 5 shows the device in the opposite form. In this case, a row of magnets 8 is arranged on the guide rail 2. Instead, a magnetically effective counter element 14 is arranged in the base body of the tenter clip. Adjustment of the counter element 14 can be performed in a similar manner as described in connection with FIG. 2 for adjustment of the air gap. In this regard, the brush 10 is fixed to the base body 4 of the tenter clip, so that the brush 10 constantly hits the magnet 8, i.e. brushes the magnet 8. For example, the suction device 11 is similarly attached to the inside of the guide rail 2. For this, the guide rail is provided with a cut-out by a row of magnets 8. The magnet itself can be configured as a permanent magnet or an electromagnet. In the case of using an electromagnet, the supply of current to the magnet 8 is realized on a fixed and stationary guide rail via a current supply line system 12 connected to the control unit 13.

Claims (11)

In an apparatus for transverse stretching of a film web,
Having at least one clip chain, the clip chain being movably guided on at least one guide rail (2);
The clip chain has a tenter clip (1), the tenter clip (1) comprising a clamping device (5) for the film web (3) and a plurality of travel rollers (7) comprising a guide rail A traveling roller (7) provided so as to be able to roll along (2), and
A device for generating a magnetically effective force is provided, characterized in that it draws the tenter clip (1) towards the guide rail (2) in a defined direction. apparatus.   The device according to claim 1, characterized in that the defined direction coincides with the direction of the force the film web (3) exerts on the tenter clip as a reaction to transverse stretching. The defined direction further includes one component;
Device according to claim 2, characterized in that the component draws the tenter clip towards the guide rail (2) perpendicular to the direction of stretching of the film web (3).   Device according to any of the preceding claims, characterized in that the device for generating a magnetically effective force comprises at least one magnet (8).   Device according to claim 4, characterized in that at least one magnet (8) is attached to the base body (4) of the tenter clip (1).   The tenter clip in the apparatus according to claim 5.   5. Device according to claim 4, characterized in that at least one magnet (8) is arranged on the guide rail (2).   A guide rail in the apparatus according to claim 7.   8. The device according to claim 5, wherein the air gap in the magnet (8) is adjustable by adjusting means (9).   10. A device according to claim 5, 7 or 9, characterized in that a cleaning device (10, 11) is provided, which removes abrasive particles from the magnet.   Device according to claim 10, characterized in that the cleaning device consists of one or more brushes (10) and one or more suction devices (11).

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