FOLDING BLADE FOR A BLOWN FILM LINE AS WELL AS BLOWN FILM LINE WITH SUCH A FOLDING BLADE

Abstract

The invention relates to a folding blade for a blown film line, as well as to a blown film line equipped therewith. Folding blades are used for laterally folding in a film bubble running to the take-off pinch rolls. If they engage deeply into the film bubble, they are provided with a fin on the rear side, and referred to as deep folding blades. The invention proposes that the rear side of a folding blade be equipped with a fin, which exhibits a collapsible element with an adjustment device. The volume of the fin can thereby be varied. In particular, the fin can be laid flat against the rear side of the folding blade.

Description

The invention relates to a folding blade for a blown film line, as well as to a blown film line with such a folding blade.

Blown film lines are used to a great extent to manufacture a variety of film webs. In a blown film line, a plastic melt is first extruded through a circular die using an extruder. The inside of the resultant molten tube is pressurized with compressed air, so that the molten tube expands with increasing distance from the die. Reference is there made to a tube formation zone. As the process continues, the melt-like film bubble is cooled, and solidifies at the so-called frost line in modern systems. It runs through a collapsing unit until reaching take-off pinch rolls. The take-off pinch rolls handle two functions: They pull up the film bubble at a preset rate on the one hand, and seal the film bubble away from the compressed air introduced into the interior on the other.

In some instances, it is desirable to feed the film bubble to the take-off pinch rolls with folded-in sides. In particular, it is conceivable in this case that the film bubble be inflated to a point where the resultant circumference would no longer have fit on the lay-flat width of the line when simply collapsed, i.e., the freely usable width of the rolls in the take-off or a reversing unit often situated above the latter, or the other downstream equipment of the line.

Folding blades are known for folding in the sides of a film bubble. In its simplest configuration, a folding blade consists of a mostly at least triangular, elongated folding surface, with the wider base being situated below, i.e., upstream in relation to the direction of extrusion. As the film gets pulled up by the take-off pinch rolls, the folding surface becomes increasingly inclined toward the vertical axis of the film bubble, i.e., into the space that a simply ascending film bubble would occupy. The excess pressure inside the film bubble presses the film surface against the folding surface. To the right and left of the folding surface, the excess pressure makes the film bubble try to occupy the entire original space of the ascending film bubble. As a result, folding flanks, i.e., sections of the film bubble extending to the rear side of the folding surface, form on both sides of the folding surface of the folding blade.

The more the film ascends and the more narrowly the folding surface of the folding blade tapers, the larger the folding flanks of the film bubble become.

If the folding blade projects into the ascending film bubble beyond a certain level perceived as critical, for example by more than 200 mm or more than 250 mm, use is normally made of a so-called deep folding blade. A deep folding blade initially consists of a folding blade with the already described folding surface. On the rear side, i.e., on the side toward which the folding flanks extend, the upper end of the folding blade is also provided with a fin, which protrudes toward the back from the folding surface. The fin ensures that the two folding flanks now extending around the folding surface will only contact each other to less of an extent, if at all.

DE 10 2007 029 794 B4 discloses a blown film line with two folding blades, wherein the folding blades can be adjusted further into or out of the ascending film bubble.

Italian Laid-Open Patent Specification C 2007A000023 discloses a blown film line with a deep folding blade, wherein the deep folding blade consists of a triangular wedge with folding surface, and wherein the rearward fin can be made to travel along the wedge, so that the wedge can be outwardly displaced. A large, movable part of the fin is now downwardly displaced. An upper, fixed part of the fin is situated above a part of the engine frame otherwise located in the path, and as a result of the displacement, the downwardly moved part of the fin is situated below the part of the engine frame otherwise located in the path.

For example, other folding blades and deep folding blades may be gleaned from DE 35 06 772 C2, Patent Specification DE 22 48 516, DE 25 10 515 C3, U.S. Pat. No. 2,955,318, EP 0 457 304 B1, U.S. Pat. No. 2,961,930, U.S. Pat. No. 3,566,756, U.S. Pat. No. 3,897,530 or U.S. Pat. No. 3,976,418.

The object of the present invention is to provide the known prior art with a folding blade, a blown film line and a method.

In one aspect of the present invention, this object is achieved with a folding blade for a blown film line, with a folding surface for folding in a film bubble running alongside, along with a fin protruding toward the back from the folding surface for preventing folding flanks projecting around the folding surface from coming into contact with each other, wherein the folding blade is characterized in that the fin exhibits a collapsible element with an adjustment device.

The following are terminological explanations:

The “folding surface” is meant to be the surface to be facing the vertical axis of the film bubble, along which the film bubble pulled by the take-off pinch rolls can thus upwardly drift, and in so doing be folded in. In a simple case, the folding blade is formed, for example, by a plate made out of wood, metal and/or provided with plastic sliding parts and shaped like a triangle, with rounded edges and a thickness normally measuring several centimeters, and the folding surface is simply a surface of this plate.

The “rearward” alignment in principle is only obtained in a situation where the folding blade has been built into a blown film line. In general, however, the folding surface should be the side with which the folding blade is to be aligned relative to the film web running alongside, so that a rear side of the folding blade facing away from the vertical axis of the film bubble comes about on the opposing side. A fin located there is to be viewed as rearward.

The “fin” can be configured in a variety of ways. The only requirement placed upon it is that the folding flanks projecting around the folding surface be guided without damage upon contact. A more or less smooth surface is therefore recommended, in particular one without any sharp, protruding elements.

The fin is usually only provided in an upper region of the folding blade, for example in an upper half or upper third.

According to the aspect of the invention described above, the fin exhibits a “collapsible element”. This must be understood to mean that the fin can reduce the size of its outer contours relative to each other. An envelope around the fin in a non-collapsed state, i.e., in the expanded state, thus has a larger volume than an envelope around the collapsed fin.

Within the meaning of the invention present here, the collapsible property only exists if the fin can be re-expanded. As known from U.S. Pat. No. 3,566,756, for example, a fin consists of wood. Therefore, while it can be reduced in terms of its volume through exposure to a destructively attacking force, it cannot be re-expanded. The inventive idea present here is not intended to encompass destructive collapsing.

While the fin from the deep folding blade in C02007A000023 has a movable position, it remains identical with respect to its volume, since both the fixed upper part of the fin and the movable lower part of the fin are each designed to be non-collapsible in terms of their volume.

The introduced aspect of the invention advantageously prevents any displacement by the fin or parts of the fin if so desired. Rather, the fin can simply be varied in terms of its size. As a result, it can not only be adjusted to various fold-in depths, but, for example when suitably configured, be laid flat so as to project toward the rear of the folding blade only very slightly or not at all. This gives the folding blade a wide variety of uses, and allows it to be implemented with simple and cost-effective technical means.

The “adjustment device” can in particular include any connecting means for applying force, air, another fluid or electrical current.

In a preferred embodiment, the collapsible element exhibits a bellows, and the adjustment device is designed as a volume adjustment device.

A “bellows” is to be understood as any component that exhibits a textile, soft, foldable and/or elastic sheath, in particular with a structural reinforcement situated therein or thereon. In particular, it must be possible to expand a bellows by filling it with a fluid, and collapse it by pumping or sucking out the fluid.

In a collapsible element designed in this way, the adjustment device acts as a volume adjustment device. This means that the adjustment device is to be set up to expand or collapse the volume of the bellows, preferably in several stages or even continuously.

It can be provided that the bellows be outwardly sealed fluid tight, except for the connection to the adjustment device.

Another embodiment can provide that the bellows be semi-permeable in design, wherein the adjustment device is connected and configured in such a way that a stream of fluid can be supplied to the bellows so as to keep the volume of the collapsible element constant.

If an adjustment device exhibits a port for guiding fluid, the collapsible element becomes especially easy to collapse and re-expand: All that need be done is to secure a line with a pump to the port. If the pump then blows a fluid, air in the simplest case, into the collapsible element, the collapsible element will expand. By contrast, if air is evacuated from the collapsible element, it will assume the collapsed state.

Let it be noted that a pump does not necessarily have to be situated outside the collapsible element. Rather, enough installation space might also be available inside the collapsible element to set up practically independent adjustment devices.

One example would be a hydraulic or pneumatic cylinder, which in the collapsible element can ensure a resizing, for example hooked up to a stabilizing framework inside the collapsible element, which then can be sheathed with material or film, turning it into a bellows.

Independently force-applying elements can also be provided, for example a return spring inside the collapsible element. In such a structural design, it may be envisaged that the return spring brings the collapsible element into a resting volume, with the volume of the fin only moving out of this state when an outer force is applied. When the force is removed, the fin once again assumes the resting volume.

It is proposed that the fin exhibit a fixed element. In such a case, the fin is composed of at least two parts, specifically at least one fixed element and at least one collapsible element.

Let it generally be noted that, within the framework of the present application, indeterminate articles or numerical values are to be understood as minimum data. A term like “one . . . ”, “two . . . ”, etc. is thus always to be understood as “at least one . . . ”, “at least two . . . ”, etc., unless it may be gleaned from the respective context that “precisely one . . . ”, “precisely two . . . ”, etc. is meant.

As a rule, a fixed element will be more cost effective and technically easier to construct than a collapsible element.

If a folding blade arranged on the blown film line exhibits regions where the rearwardly protruding fin does not hinder the variability of use, such a part can readily be fixed in place. The collapsible element can make sense in particular in a case where the folding blade might otherwise collide with the engine frame when displaced or swiveled away from the vertical axis of the film bubble, for example with a swing bearing, a bearing ring and/or a carrier ring, in particular of the kind that is often encountered for an oscillation unit at roughly the height of the take-off pinch rolls.

The fin can exhibit a guide for the collapsible element. The collapsible element can then be given a less stable design.

A guide for the collapsing element preferably is located on a fixed element of the fin. For example, it can be a short rail or slide bearing, or a stably designed component of the collapsible element is guided inside the fixed element of the fin.

The collapsing element can exhibit a swiveling edge, wherein a lower edge is preferably designed like a hinge or otherwise pivoted. A swiveling edge allows the edge to be swiveled on the folding blade flatly or as flatly as possible around the pivot bearing on the lower region of the folding blade in the collapsing process. For purposes of re-expansion, the swiveling edge can be pivoted back toward the rearward side from the folding blade, once again around the hinge-like lower edge.

In a second aspect of the present invention, the set object is achieved by means of a blown film line with a folding blade as described above, wherein the folding blade is situated between a bubble expansion zone and take-off pinch rolls, and the fin is aligned facing away from a vertical axis for the running film bubble.

It is proposed that a connection be used to hook up the adjustment device to an energy source of the blown film line, in particular to a pump.

As has already been explained, the pump is set up in a preferred embodiment of the invention in such a way that it can pump in particular air or some other fluid into the collapsible element or pump it out of the collapsible element by way of a hose or pipe.

For example, another embodiment provides that the connection be a power cable, and the energy source of the blown film line be an electrical power supply.

Alternatively or cumulatively, the connection can be a mechanical connection, for example comprised of gear wheels, knee levers or other mechanical structures.

In particular, the collapsible element is to be situated at the height of a swing bearing or another frame part of the blown film line, which would otherwise collide with the fin as the folding blade or usual two folding blades are swiveled or horizontally displaced on the line. It is precisely there where it makes the most sense to provide a collapsible element.

The blown film line can ideally be moved into at least two or three or four different folding operation modes by adjusting the collapsible element, specifically:

• • A deep folding operation mode, in which the folding surface and fin are arranged so as to engage into the ascending film bubble, and the fin protects the film bubble folded in from the folding surface against its folding flanks coming into contact with each other during operation, and/or
  • A first folding operation mode, in which the collapsible element is present in the collapsed state, and the folding flanks of the film web folded in from the folding surface still do not come into contact with each other, and/or
  • A second folding operation mode, in which the collapsible element is present in the collapsed state, and does not contact the folding flanks of the film web folded in from the folding surface, and/or
  • A non-folding operation mode, in which the folding surface of the folding blade and the fin are varyingly positioned relative to the folding operation types, so that they do not engage into the ascending film bubble, wherein the fin is preferably collapsed, so that the folding surface generates no folding flanks during operation, and the blown film line flattens out the film bubble without folding in.

In a third, independent aspect of the invention, the set object is achieved by a method for retrofitting or upgrading a blown film line, wherein a folding blade is installed as described above, if necessary accompanied by an expansion or modification of a folding blade or deep folding blade or a lateral guide.

In a fourth aspect of this present invention, the set object is achieved by a method for operating a blown film line, in which a collapsible element of a fin is brought to a desired volume with an adjustment device in order to set how deeply a folding blade or deep folding blade engages into the ascending film bubble.

The invention will be described in greater detail below based on an exemplary embodiment, making reference to the drawing. Shown on:

FIG. 1 is a schematic, spatial view of a folding blade with a collapsible fin, and

FIG. 2 is a highly schematic, spatial view of an alternative folding blade with a collapsible small fin.

From a structural standpoint, the folding blade 1 on the figure initially consists of a triangular base plate 2. The base plate 2 is made out of a wood-based material, and has rounded edges.

While facing the vertical axis of a film bubble, a front side 3 (covered on the figure) is provided for purposes of immersion at an angle into the film bubble pulled up by the take-off pinch rolls on a blown film line.

The rear side of the folding blade 1 carries a fin 7. The fin 7 essentially consists of a collapsible bellows 8 and fixed angle section 9.

The bellows 8 is composed of a rigid plate 10 and soft cloth or film on a first flank 11 and on a second flank 12 (covered), wherein the flanks 11, 12 join the rigid plate 10 with the base plate 2. The rigid plate 10 is also joined with the base plate 2 inside the bellows by an articulated mechanism 13 (not shown in detail).

In an upper region 14 of the bellows 8, the two flanks 11, 12 converge and the rigid plate 10 tapers.

Two recesses 15 on the rigid plate 10 that otherwise runs with three straight edges at a certain distance leave space for two edges 16, 17 of the angle section 9.

The rigid plate 10 is interrupted by an opening, to which a hose 19 is connected by way of a fitting 18, so that the hose 19 can communicate with the internal space of the bellows 8.

A pointed extension (covered by the leg of the angle section 9) of the rigid plate 10 projects as far as into the angle section 9.

If air is pumped into the bellows 8 through the hose 19 during operation, the excess pressure inside the bellows 8 causes the rigid plate 10 to lift from the base plate 2 in a direction of expansion 20, specifically to pivot around the articulated mechanism 13. The movement continues until the two flanks 11, 12 are tensioned. The rigid plate 10 then runs in alignment with the rearwardly averted edges of the angle section 9.

By contrast, if air is sucked out of the bellows 8 through the hose 19, the bellows 8 collapses, and the rigid plate 10 comes to lie flat on the base plate 2 along a collapsing direction 21 around the articulated mechanism 13.

In both the collapsing and expanding process, the tip of the rigid plate 10 is guided in the angle section 9.

A sealed hollow space can be provided inside the bellows 8 for the air that was forced in and sucked out. The two flanks 11, 12 should then form an essentially or hermetically tight seal with the rigid plate 10 and base plate 2.

For example, it is simpler to provide a hydraulic cylinder between the rigid plate 10 and base plate 2, which ensures the movement.

The labile flanks 11, 12 follow the movement of the rigid plate 10. If the entire internal space of the bellows 8 is exposed to a vacuum in the collapsing process, the two flanks 11, 12 are automatically retracted into the interior during the collapsing movement, and hence do not endanger the film bubble. By contrast, if the internal space of the bellows 8 is not subjected to a vacuum in the collapsing process, it is advisable that bands, e.g., rubber bands, be provided between the two flanks 11, 12, so as to reliably fold the latter into the internal space.

The alternative deep folding blade 22 on FIG. 2 has a fin 23 with a technically very similar structural design. Therefore, no detailed description will be provided at this juncture.

From at technical standpoint, the fin 23 initially differs from the one from the embodiment described on FIG. 1 in that there is no fitting 18 for compressed air. Provided instead is an electrical power line (not shown), which drives an adjustment system located inside the bellows.

However, a separate guide with a fixed part was omitted on an upper edge 24 of the fin 23. As a consequence, the collapsible element embodied by the fin 23 extends up until the upper edge 24 of the alternative deep folding blade 22.

In terms of proportions, the fin 23 is only situated in an upper region 25 of the alternative deep folding blade 22. For this reason, an articulated mechanism 26 is not located on a lower side of the deep folding blade, but rather further up, preferably above the center of the alternative deep folding blade 22. As a consequence, a base plate 27 extends with a free part 28 under the fin 23 up to a lower edge 29 of the alternative deep folding blade 22.

REFERENCE LIST

• 1 Folding blade
• 2 Base plate
• 3 Front side
• 4 Lower side
• 5 Upper edge
• 6 Rear side
• 7 Fin
• 8 Bellows
• 9 Angle section
• 10 Plate
• 11 First flank
• 12 Second flank
• 13 Articulated mechanism
• 14 Upper region
• 15 Recesses
• 16 Edge of angle section 9
• 17 Edge of angle section 9
• 18 Fitting
• 19 Hose
• 20 Direction of expansion
• 21 Collapsing direction
• 22 Alternative deep folding blade
• 23 Fin
• 24 Upper edge
• 25 Upper region
• 26 Articulated mechanism
• 27 Base plate
• 28 Free part
• 29 Lower edge

Claims

1. A folding blade for a blown film line, with a folding surface for folding in a film bubble running alongside, as well as with a fin protruding toward the back from the folding surface for preventing folding flanks projecting around the folding surface from coming into contact with each other, wherein the fin exhibits a collapsible element with an adjustment device.

2. The folding blade according to claim 1, wherein the collapsing element exhibits a bellows and/or the adjustment device is designed as a volume adjustment device.

3. The folding blade according to claim 1, wherein the adjustment device exhibits a connection for a fluid guide.

4. The folding blade according to claim 1, wherein the fin exhibits a fixed element.

5. The folding blade according to claim 1, wherein the fin exhibits a guide for the collapsing element, preferably located on a fixed element of the fin.

6. The folding blade according to claim 1, wherein the collapsible element exhibits a swiveling edge.

7. A blown film line with a folding blade according to claim 1, wherein the folding blade is arranged between a bubble expansion zone and take-off pinch rolls, and the fin is aligned facing away from a vertical axis of a film bubble.

8. The blown film line according to claim 7, wherein a connection is used to hook up the adjustment device to an energy source of the blown film line, in particular to a pump.

9. The blown film line according to claim 7, wherein the collapsible element is situated at the height of a swing bearing or another frame part of the blown film line.

10. The blown film line according to claim 7, wherein displacing the collapsible element provides two or three or four different folding operation modes to choose from, specifically:

a. A deep folding operation mode, in which the folding surface and fin are arranged so as to engage into the ascending film bubble, and the fin protects the film bubble folded in from the folding surface against its folding flanks coming into contact with each other during operation, and/or

b. A first folding operation mode, in which the collapsible element is present in the collapsed state, and the folding flanks of the film web folded in from the folding surface still do not come into contact with each other, and/or

c. A second folding operation mode, in which the collapsible element is present in the collapsed state, and does not contact the folding flanks of the film web folded in from the folding surface, and/or

d. A non-folding operation mode, in which the folding surface of the folding blade and the fin are varyingly positioned relative to the folding operation types, so that they do not engage into the ascending film bubble, wherein the fin is preferably collapsed, so that the folding surface generates no folding flanks during operation, and the blown film line flattens out the film bubble without folding in.