Patent ID: 12220857

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout this text, indications of orientation such as “left”, “right”, “top”, “bottom”, “side” refer to the transport direction MD or to the film100, unless otherwise stated. The film is said to be oriented with its surface horizontal. The above information in the text refers to this, unless otherwise stated there.

FIGS.4to12illustrate basic principles of the invention. The basic structure1according to the embodiment of a device for transporting film100has (cf. in particularFIG.4andFIG.8): an upper guide unit60and a lower guide unit50, wherein the upper guide unit60is configured to guide an upper movable rope10-3and the lower guide unit50is configured to guide a lower movable rope10-1, wherein the upper rope10-3and the one lower rope10-1are arrangeable to clamp and entrain the film100at its side edge at least locally therebetween, wherein at least one guide unit50,60of the guide units50,60is configured to press the film100via the rope10-3guided by the guide unit50,60against the rope10-1guided by the other guide unit50. Furthermore, the base structure1comprises a holding portion13and a web portion12. The holding portion13carries the two guide units50,60, which are each hinged to it via legs16, and the web portion12provides the connection to the adjacent base structure1, cf.FIG.10. This connection can allow rotation relative to the adjacent base structure1, preferably, up to a defined maximum angle (in the horizontal). The base structures of each side are identical to each other.

The lower guide unit50may be configured to support the upper guide unit60.

The film100rests on the lower rope10-1and is clamped by the lower rope10-1and the upper rope10-3. In this way, the film100can be transported with the movable ropes in the transport direction MD.

The upper guide unit60is the one whose rope10-3touches the upper side of the film100, and the lower guide unit50is the one whose rope10-1touches the lower side of the film100.

The respective upper guide unit60or a part thereof is designed to be vertically movable. The bearing of the roller elements of the upper guide unit is thus designed in such a way that the pressure may be measured and adjusted.

Each guide unit50,60comprises a respective roller element20,30, which is designed to guide the respective at least one rope10-1,10-3. The lower guide unit50is designed to be movable, and the upper guide unit60is also50movably fixed.

According toFIG.4, the upper guide unit60has exactly one roller element30, which is arranged above the rope10-3guided by the upper guide unit. The lower guide unit50has exactly one further roller element20, which is arranged below the rope10-1guided by the lower guide unit.

Pressure may be applied to the respective rope from above and/or below.

A base structure1with its guide units50,60is fixedly connected to an adjacent base structure1via the holding section13or is rotatably connected if a deflection in TD is to be realized.

The upper guide unit60is thus horizontally movable with the lower guide unit50and also offers the possibility of influencing the pressure on the upper rope10-3and thus the clamping force on the film100. Preferably, the upper guide unit60has the same length as the lower guide unit50. The guide units or their roller elements20,30are arranged vertically one above the other with respect to their roller pivot points. Preferably, the two roller elements have one and the same diameter.

With a plurality of base structures1according to this disclosure, one or more areas are realized. The guide units50,60in one area may be different from the guide units50,60in another area. The areas may—but do not have to—correspond to the areas I to IV explained at the beginning.

The clamping force on the film100is generated by the pressure of one rope10-3against the other rope10-1. The clamping force on the film100is adjusted by means acting on one or both of the guide units50,60or parts thereof (e.g. the roller elements). These means may include, in addition to the gravitational force of the guide units60and the upper rope10-3, devices which exert pressure on the guide units60or parts thereof (e.g. the roller elements), which they transmit via the rope10-3. These devices may act, for example, pneumatically, hydraulically, and/or electrically. In addition, devices may be provided that detect the pressure of the clamping and adjust the pressure on the respective guide units50,60or parts thereof depending on the sensed pressure.

It is also possible to influence the clamping force of the ropes somewhat via the rope tension, especially in the areas where pressure is not applied directly via the rope pulleys.

Here, each rope10-1,10-3is an endless rope, in particular, a rope made from steel. Such an endless rope may be made, for example, by splicing the ends of a rope.

The ropes may also have a core made from plastic or, for example, have a rough surface and/or a plastic sheath around a metal or plastic rope.

Also, the ropes may be pure plastic ropes or made of a mixture of steel and plastic. These ropes may also have a smooth surface or be appropriately covered with a plastic sheath.

At least one rope may have (e.g., in its core) devices for measuring process data such as temperatures and/or data lines and for transmitting the process data or data derived therefrom to outside the rope.

The choice of materials for the ropes may influence the clamping effect as well as the temperature of the ropes. For example, a rope with a plastic content is easier to keep at a low temperature and therefore, can be cooled better because it absorbs less heat. A rope that is at a lower temperature compared to the film may be more effective in terms of adhesion of the relatively warmer film to the rope. Ropes may be cooled very efficiently with air. If at all necessary, this can be done in a simple manner at the return end of the ropes, i.e. where the ropes are not normally guided by the guide units according to the disclosure. This is also an advantage compared with the clip system, where the very strongly heating clips together with the chains can only be cooled with difficulty due to the large moving masses—and in particular at high transport speeds. The chain return may then no longer be sufficient for this purpose.

The guide elements1are static, so they may be enclosed, for example, in order to be cooled from the side facing away from the film (i.e. from behind), for example with cold air. The enclosure may be provided separately for individual guide elements or for several guide elements together, e.g. in the heating zone (area I).

In addition, the roller elements20,30may be cooled via their axles.

The condition of the surface of the ropes also plays a role in clamping, stretching and transporting the film. For example, roughening of the surface or a very smooth surface can influence the adhesion of the film, irrespective of the clamping. By means of a directionally anisotropic nature (roughness, smoothness) of the ropes, for example, a certain slippage of the film in one direction (e.g. in MD) may be favored, while slippage in the other direction (e.g. TD) is reduced or prevented altogether. This could be used to compensate for pathway differences of the ropes when staggered at the transition between area I and area II.

To minimize or completely prevent slippage, the rope surfaces may be sheathed, e.g. made from plastic.

Also, the upper rope10-3may have a different (in particular opposite) direction of lay than the lower rope10-1. In addition to the direction of lay, the type of lay may also be considered to be a constant lay or a cross lay. In this case, the strands of the upper rope10-3and of the one lower rope10-1may come to lie better in each other with an additional effect with regard to slip and clamping of the film100.

Furthermore, the ropes may have different thicknesses. For example, the lower rope10-1may be thicker than the upper rope10-3. Preferably, however, both ropes are of the same nature.

The guide units50,60or their roller elements20,30may also be offset from each other in TD or in MD for even better clamping of the film. When offset in MD, the axes of rotation of the roller elements20,30are no longer vertically above one another. When offset in MD, the roller elements20,30do not rotate in the same plane.

The running surfaces of the roller elements20,30may grip the ropes to a greater or lesser extent and thus also guide them.

At least two rows of base structures1together form a device for transporting film100in a transport direction MD, in particular, for a stretching plant, wherein one row of base structures1is arranged on the left in the transport direction MD and the other row of base structures1is arranged on the right in the transport direction MD, wherein the at least two rows of base structures are designed to guide the ropes that may be guided by them at the same speed.

Thus, the left row of base structures1is arranged to clamp the film100at its left edge, and the right row of base structures1is arranged to clamp the film100at its right edge. In accordance with the different requirements in areas I to IV (cf.FIG.1B) for guiding the ropes, the rows of base structures there may be designed differently in each case. Different variants are described below.

In the following, different configurations of rows of base structures1are further described with reference toFIGS.5to12. The terms base structure1and guide element1(as distinct from guide unit50,60) are used synonymously. The deflection or backward deflection of the ropes (and of the film there over) is also effected by lateral displacement or rotation of a straight running base structure consisting of a number of such guide units at its end, as seen in TD. Here, the guide elements50,60carrying the roller elements20and30, respectively, are mechanically fixed and thus do not allow any opening or closing angle between the adjacent guide units1.

In the area51inFIG.5of a deliberate or possible deflection or backward deflection, the individual guide elements1are connected to each other so that they can rotate relative to each other. The first guide element1at the beginning of this zone, in which the individual guide elements1are rotatably connected to each other, and the last guide element1at the end of this zone are also fixedly connected to the upstream or downstream fixedly connected guide elements1, cf.52and52inFIG.5.

If the angle is now changed via a lateral displacement of the downstream fixed guide elements1, this is reproduced via the number of rotatably connected guide elements in such a way that it is distributed evenly over the individual rotatable guide elements. Example: A stretching angle of 12 degrees is set by shifting/rotating the fixed guide elements1. In the case of 10 rotatably connected guide elements, this stretch angle is now distributed evenly over these guide elements with an angle of 1.2 degrees between every two adjacent guide elements. Therefore, the sum of the angles between two guide elements in each case gives the stretching angle.

The number of rotatably connected guide elements1, the determination of a maximum angle between these guide elements1allow a very flexible setting of the stretching angle as well as the radius in which this is implemented.

The number of rotatably connected guide elements1also allows very flexible settings by designing the system for a larger number of rotatably connected guide elements1, e.g.20with a deflection range of then approx. 1.2 meters. This would now distribute a stretching angle of 12 degrees over 20 rotatably connected guide elements of 0.6 degrees each and perform the deflection over the full 1.2 meters.

Up to the maximum adjustment angle between the rotatably connected guide elements, 1 more of these rotatably connected guide elements may now be mechanically connected to the fixed guide elements before or after them in order to achieve a smaller deflection radius for the desired 12 degrees. In this case, with a maximum angle of 1.5 degrees in this example, 8 of the 20 guide elements must be rotatably connected to each other between the rotatably connected guide elements, and a correspondingly smaller deflection radius results. However, the maximum angle could in principle be up to 4 degrees.

If desired with respect to the process, some guide elements within these e.g. 20 rotatably connected guide elements51inFIG.6may also be fixedly connected straight, whereby the radius is distributed e.g. over 2 radii, cf.61inFIG.6. A connection representing a fixed negative stretching angle in this zone is also possible.

These fixedly connected guide elements1distribute the set extension or retraction angle correspondingly linearly and may rotate freely relative to each other in the fixed frame, if not fixed. In order to avoid vibration effects on the guide elements and/or the cables at high speeds, it is intended to install so-called braking devices (i.e. a damping device) in the form of springs or the like between these guide elements. The stretching angle once set by the lateral displacement may be freely distributed between these rotatably connected guide elements1, but then remains fixed until another setting of the stretching angle.

Advantages of the embodiments of the invention: The variable adjustment possibility of the stretching angle and the radius in which this is implemented. This is very advantageous in film production, because certain properties of the film can be influenced by the setting of the stretching angle or the stretching angle and the radius. In order to achieve certain properties of the film, it is often necessary to set a high initial angle with a small radius, then ease off a little, i.e. set a negative angle, and then stretch again to achieve the desired stretch ratio.

There is no unwanted longitudinal stretching.

The distribution of the forces in the deflection and stretching phase: Unlike in the case of the clip systems as described above, the lateral forces72occurring in the stretching phase and in particular in the deflection phase are distributed much better, seeFIG.7.

Due to the permanent clamping by the ropes, there is no unwanted longitudinal stretching with the corresponding forces acting on the system.

The lateral forces that shift backwards in TD in the course of the deflection according to the deflection angle do not have the same negative effect as on the clips that tilt as a result.

On the contrary, the ropes and the pulleys guiding them are less stressed by the ropes being pulled forward when the direction of the lateral force is shifted backward relative to the running direction.

In addition, the lateral forces acting on the inside of the pulleys on the film side are balanced by those acting on the outside of the pulleys on the film side via the deflection of the ropes.

The rope tension may be used to compensate for and adjust these forces.

Holding and releasing the film: In contrast to clip systems, which always hold the film in place and cannot release it, which as described above can also lead to breakage of the entire chain track system if the stretching forces become too high, the pressure of the upper and lower guide units on the respective ropes may be adjusted variably for each guide unit.

This means that in the zones without lateral forces, the pressure will be just sufficient to hold the film in place, and in the zones with higher lateral forces, which vary according to the thickness of the film, the pressure will be increased accordingly, but only by a certain percentage above the required holding force.

This system may also open all or certain guiding elements on command or automatically by means of set parameters and thus release the film if, for example, a temperature drop occurs in front of the stretching zone which causes the stretching forces to increase.

The low overall height: This system allows a much lower overall height compared to known chain track and clip systems.

This low overall height makes it possible to bring the heating devices (nozzle boxes) and thus the blowing of hot air onto the film much closer to the film.

This makes it possible to reduce the air velocity and thus the amount of hot air needed for heating, or even the temperature of the air. At the same time, it is also possible to reduce the length of the heating zone, in particular, with the corresponding savings in energy and investment costs. Also, when converting existing lines, it is possible to bring them closer to the film by correspondingly converting the nozzle boxes, thus increasing the film output of such lines accordingly.

The individual guide elements1are mounted on a track which extends over the respective zone but may also be shorter.

Where the ropes are to be guided straight, the guide elements1are connected straight. However, this may be decided freely. If now at the end of such a fixed connecting portion, e.g. after the 4 meters, the angle is adjusted on the next support (e.g. a stretching angle is set to 12 degrees), then this is mapped over the non-fixed guide elements at the beginning of these fixed guide elements. This can be called the “snake effect”. A snake, when it creeps around the curve, does not do this from one vertebra to another, it distributes the curvature to a certain number of its vertebrae in the curve, and there, evenly. The ropes and the forces on the bearings allow an angle between the respective guiding elements of up to 4 degrees maximum. This means that if the fixed track is deflected by 12 degrees, then with 10 non-fixed guide elements between these fixed tracks, these 12 degrees would be distributed over 11 interstices, i.e. 1.09 degrees per interstice. The same works for deflecting back at the end of the stretching zone. This saves further guide elements for the respective deflections, which are absorbed by the upper and lower bearings.

The rotatable guide elements, which together form the stretching angle, are freely rotatable and do not have to be fixed to each other in order to realize the stretching angle. It has been found that the constant angular changes of two adjacent guide elements are self-adjusting if only the fixed base structures (or the rails supporting the rows of base structures), between which the rotatable base structures are arranged, are arranged at the desired stretching angle to each other.

A particular disadvantage of clip systems is that there the bearing or sliding shoe layout is dimensioned from the straight run, which means that when the film is running straight, the forces are distributed evenly over the bearings or sliding shoes. However, when the film is deflected, the lateral forces of the stretching and the so-called unwanted longitudinal stretching are added, and these shift backwards in relation to the individual clip according to the set stretching angle from the 90 degree position. This means that the clip receives greater forces on the bearings and sliding elements, and these are no longer optimally distributed. Now, the forces primarily are exerted to the front rear and rear front bearings and sliding elements and lead to wear there.

The rope system has to live with the same forces in the deflection, as far as the lateral forces of the film stretching are concerned, but the forces from an unwanted longitudinal stretching are not added here, since such a stretching does not take place. The forces are distributed to the bearings at the top and bottom and move from the optimum pressure point at the top and bottom in the middle to the walls of the bearings.

But the shifting of the stretching forces to the rear during deflection is positive here, since forces are shifted from the bearings to the pulling rope as a result.

In addition, the forces on the inner wall of the bearings facing the film due to the stretching forces and on the inner wall of the bearings facing away from the film due to the deflection of the rope partially cancel each other out and this may also be influenced/optimized via the rope tension.

The system according to the embodiments of the invention with an overall height of approx. 180 mm has an overall height reduced by approx. 50% compared to known roller chain systems and approx. 40% compared to known sliding chain systems and thus a corresponding improvement in the heat transfer coefficients due to the possibility of bringing the air nozzles closer to the film.

Depending on the requirements, the base structures may be designed to fix the ropes in transverse direction TD to the transport direction MD and in vertical direction. For this purpose, roller elements may be provided, which contribute to the fixing.

For maintenance purposes, the roller elements may be replaced individually from the outside by removing the relevant axles. Easy inspection and exchangeability of the roller elements increase the productivity of the system because the downtimes are reduced.

The guide elements50,60may be designed in such a way that they may be replaced as a whole from each other.

There are numerous other variations on the design of the guide units50,60, e.g. to optimize the guidance of the ropes.

The guide units50,60are made from metal, the roller elements20,30likewise. Other materials are also possible if they have sufficient mechanical and thermal stability.

Film threading and deflection: There are the two deflectors at the inlet and at the outlet. If necessary, the inlet may also be used as a brake to increase the rope tension.

For this purpose, the film is allowed to move in between the two deflection wheels of the two ropes.

Advantageously, the main drive of the ropes is arranged in front of or behind the deflection itself. The deflection by means of a deflection roller element provides the necessary rope tension on the forward run, whereas the rope tension on the return run of the ropes is of secondary importance. Additional drives may be added to the main drive, which are located elsewhere on the rope.

The ropes are driven so that they all run at the same speed.

In addition to driving the ropes, a drive may also be provided which acts directly on the film100.

Advantageously, the film transport device allows the tracks to be moved together along the entire length of the furnace and also at the outlet. This is done by moving all guide rails and the entire deflection at the outlet with all drives.

The degree of stretching of the film100in area II may be made variable in a simple manner, in that the rope deflection and the drive wheels are fixed in the outermost position in the outlet. By positioning a small roller element82for deflection on a track behind the last opening section, this may be moved along with this track. Only the respective rope length must be compensated for at the return end of the rope, which may be done, for example, by means of further roller elements for deflection.

A similar function, albeit to a much lesser extent, is performed by the roller element81at the inlet; it compensates for the slight horizontal displacements of the film usually measured there and reacts together with the purchasing unit and the corresponding measuring device.

The rope return may take place inside the stretching furnace parallel with the inlet or outside the stretching furnace at the same height or via deflection rollers above the stretching furnace or also in the floor in front of it and a straight return track. Additional devices for tensioning, cooling, checking and cleaning the ropes10-1,10-3may be arranged on the return path.

FIG.11illustrates areas I to IV of the plant, realized with the base structures according to embodiments of the invention. The larger distances between the base structures in the straight areas I and IV and the smaller distances in the stretching area II and in area III are clearly visible.FIG.12illustrates the inlet/outlet at the ends of the system.

The entire arrangement of the rope cycle may be effected via horizontally but also vertically arranged drive and deflection wheels.