DE102007044323A1 - External guide for film tube in blown film line, has guide plates with guiding surfaces aligned with respect to longitudinal axis, where guiding surfaces have base with uprising raised to axis for swirling air stream to flow along film tube - Google Patents

Abstract

The guide has guide plates (6, 7) with guiding surfaces aligned with respect to a longitudinal axis (4), where the guiding surfaces have a base with an uprising (8) raised to the axis for swirling the air stream to flow along a film tube (3). One of the plates comprises an angular sheet, and the guide is aligned for radial adjustment. The uprising includes spherical elevation, spherical recess, rack, bead form, circular form, semicircular form, polygon form and/or rhombus form. A blower blows air in a longitudinal direction between the tube and one of the guiding surfaces.

Description

The The invention relates to a blown film plant and an external guide for a Foil tube in a blown film line.

at the production of foil hoses at a blown film plant, the liquid film rises, solidifies on the way and enters before the upper end of the plant in a calibration one. This leads the Foil hose controls to the top of the plant where usually the film is deflected and laid flat.

The Exterior guide, the For this purpose, accesses the film tube, often has a calibration with roles.

A alternative embodiment lies in the fact that the film tube provided between the outside Sheet metal led becomes.

Such Sheets are essentially flat, but usually with a curvature arranged around the film tube around. Most are numerous roles or sheets provided.

Around To avoid sticking of the film, the sheet can, for example be set in rotation. An alternative is to use holes in the To provide sheet metal and from the outside actively air through the holes towards the film towards bubbles.

Of the Invention is based on the object, the existing technology improve.

To In a first aspect of the invention, this object solves an external guide for a Foil tube in a blown film plant, with the outer guide a guide element with one to a longitudinal axis directed guide surface, wherein the guide surface one Reason with one to the longitudinal axis has raised structuring.

Conceptual be first explains a blown film plant has a longitudinal axis. This one does not have to be an exact axis of rotation of the entire system. Rather, it is the longitudinal axis the direction in which the film rises. Usually stands the longitudinal axis vertical.

Regarding the guide surface is explained further, that these to the longitudinal axis should be directed. Again, this does not necessarily require that a normal on the surface mathematically exactly the longitudinal axis meets. Rather, it is sufficient if one intended for guiding the film area is provided, which is essentially so that the scope of the film tube on the surface support can, especially with a cushion flow. So be special to a pure guide plate not a leadership role, because a leadership role has no aligned guide surface.

The "reason" of the guide surface is understood to be a practically arbitrarily shaped surface can, which at a radially from the longitudinal axis directed outward Looking towards the guide element farther away than the structuring arising from the ground. The reason may be, for example, in the form of radially outward surfaces present or consist of furrows, grooves, channels or hollows. Essential is that concerning it the longitudinal axis there are two differently spaced two-dimensional courses. Not under the chosen formulation So smooth sheets fall with pure holes, because in a hole a "reason" does not exist is. On the other hand, that's the extra Presence of holes for a reason with increased structuring quite conceivable.

Advantageous arises in an embodiment of the described type a guide element for the Foil, which by the simplest means, namely ideally with metal sheets, can be produced. The raised structuring is suitable an airflow flowing along the film tube swirl, so they for the film tube acts as a cushion flow with respect to the guide surface. This will be a Adhesion of the film to the guide surface safely avoided. With suitable design and suitable process parameters It is even expected that not even a touch between the ascending film tube and the guide surface of the guide element takes place.

To In a second aspect of the invention, the stated object solves a Exterior guide, in which the guide surface one Structuring in the form of a Strömungsverwirbelerhebung and / or a Strömungsverwirbelvertiefung having.

Also such elevations and depressions are suitable, one along the film flowing air flow so to swirl that forms a cushion flow.

To In a third aspect of the invention, the stated object solves a Blown film system with an external guide for one Foil tube, with the outer guide a guide element with one to a longitudinal axis having directional guide surface, wherein the guide surface a Having structure and wherein a fan is provided, which in a leadership area a longitudinal flow on the outside of the Foil tube produced.

Other than according to the first two aspects presented the invention may for the third Aspect of the invention even be used a flat guide element, which has only holes. It can even be used such a sheet, through which conventionally air is blown from the outside approximately radially to the film. Also, such a sheet can be successfully converted to an embodiment of the invention, when a fan is provided, which blows the air for the cushion flow along the film tube under the guide surfaces. In a suitable design and with a sufficiently large flow, the existing perforations of conventional sheets can also lead to a cushion flow for the film, as compared with the conventional embodiment variant, the supply of air for the cushion flow is much simpler.

To a fourth aspect of the invention solves the problem posed a External guide for a film hose in a blown film plant, wherein the outer guide is a guide element with a a longitudinal axis directed guide surface and a fan for introducing air as a cushion flow between the film tube and the guide surface, being the blower the air is introduced under the foil tube under the guide surface.

This fan For example, that of an already existing cooling fan on Blaskopf or a separate blower be.

Also in this aspect of the invention, conventional perforated sheets may be used be used.

It It should be understood that the features of the above four aspects of the invention can be combined with each other, each advantageous Forms of the invention can be obtained.

Prefers the guide surface is airtight. So was especially thought to use sheets as guide surfaces, the only on its surface carry a macroscopic structuring. In a conventional, perforated sheet metal can be a conversion be done by the air supply from the outside of the guide elements is disconnected and the openings to be locked there. An air-tight guide surface tends to lead to stronger ones upholstery currents as air-permeable Guide surfaces.

The Outside guide points preferably several guide elements in axial, radial or tangential different arrangement.

The Film tubes, those of the guide elements guided are to be, are essentially circular. Thus, the should guide one also possible have round shape. In many embodiments of the invention, in particular When using sheet metal, round shapes can be significantly cost-effective shape or at least approximate, if numerous individual guide elements are provided.

at an axially different positioning of the guide elements the hose is over a certain axial distance safely supported.

at a radially different positioning of the guide elements can the leadership to enter different diameters of the hose.

A Tangentially different arrangement, so a tangential resolution of Guide elements, allows the assembly of a guide ring from several individual elements. This is for example in handling much more practical when setting up and maintaining the system.

Prefers is the outside guide in a calibration region of the film tube arranged, in particular attached to a calibration basket. The calibration area on one Film plant is the area in which usually one from the outside guide is applied to the already solidified film.

It It is suggested that the outer guide for a radial Adjustability is set up. This allows the use for different Diameter of foil tubes. It is envisaged that such radial adjustability take place dynamically can, so while the current system. A radial adjustability caused by a Variety of tangentially differently arranged outer guide elements, that these are each radially adjusted individually, ie in their Distance to the longitudinal axis the system are adjusted. This can easily over the rear, so arranged radially outward Carrying structures for the individual guide elements respectively.

The Outside guide points prefers a casting on. If on the guide surface, so the hose directed surface the guide element, a relatively complex and / or relatively deeply contoured structure should be provided a corresponding guide element very reasonably priced and high precision produce as a casting.

The Structuring preferably has a spherical elevation, a spherical depression, a bridge, a drop shape, a polygon shape and / or a diamond shape on.

Preferably, a plurality of Strö vortex surveys with channels bounding sides.

Conceptual be explained, that as a "turbulence survey" a macroscopic Elevation of at least 1 mm, preferably of at least 3 mm, in particular of at least 5 mm or 10 mm, which is thus quite clear inwardly, so for example radially, projecting on the guide surface. Such a survey leads in that the padding flow flowing along in the operation of the blown film installation is swirled there. In particular, it can be characterized by a laminar flow in go over a turbulent flow, or the turbulence can be increased become.

By a skilled distribution of the plurality of Strömungsverwirbelierhebenungen is created a fairly stable air cushion, so through the scheme temperature, throughput of the extruder, air flow and material very accurately It can be determined whether and where the film comes into contact with the outer guide can. The strongly swirling air flow provides for a right vigorous Upholstery for the blown film tube.

If Connecting to the sides of the surveys channels will cause an excessive back pressure bolstering stream avoided. Rather, with a suitable design, a network of interconnected channels through which the cushion flow with relatively low flow resistance, but still big Turbulence, can flow.

It is alternatively and cumulatively suggested that a variety from turbulence surveys in the form of re the longitudinal axis inclined Rhombus is provided.

above has already been explained that the turbulence surveys to a strengthening of the Cushioning effect of the blown air lead can. Independently of it, whether channels exist and in what form these channels are designed, has become In experiments by the inventor, it was found that the flow swirl elevations formed particularly advantageous as diamond-shaped elevations are. This means that in a settlement of the guide surface the Contour of the survey is handled as a rhombus. A rhombus has four corners, which is considered as "slanting", if the connection between two opposite corners of the rhombus only shortened, not punctiform, on the longitudinal axis to project.

at some experiments by the inventor have been shown to be coaxial as well to the longitudinal axis lying elevations, especially in the form of squares, especially in the form of diamonds, to a good upholstery with at the same time great possible Lead throughput can. In other experiments, it has been shown that by a low Turning the squares or generally the geometric body, which the elevations form, a very good cushioning effect can be achieved could.

It be explicit pointed out that the beneficial effects are not only show with diamonds. In total, circles, part circles and / or other circular geometries as well as polyhedra as advantageous geometries for the Elevations and / or depressions observed. In particular, were surfaces with triangles, with squares, with pentagons or with hexagons worked out as particularly advantageous. The boundary edges between can the corners, have to but not be straight. Rather, also convex and in particular concave edge configurations between the corners proved to be advantageous.

alternative and cumulatively, a plurality of fluidizing surveys are proposed, which in rows around the longitudinal axis in more than ten or more than twenty Rows over a length the outer guide, preferred in more than thirty Rows, more preferably in more than forty rows.

It has just proven in prototype measurements by providing a certain minimum number of rows of elevations and / or depressions of the upholstery effect especially becomes stable. When the air flows along the guide surface or when flowing along Guide surfaces only a small number of rows of turbulence surveys happens has been shown that the cushioning effect may not yet is sufficiently stable, especially with very flat elevations. As soon as However, more rows are provided, the stability of the cushion flow at jumps appropriate design enormously.

Prefers has the guide surface Area ratio between stream whirling and re one outside These enfolded mantle envisions provided by at most 5: 1, preferably at most 2: 1, more preferably of at most 1: 1, up.

Conceptually, it should be explained that in particular the ratio between the crests of the elevations and the intermediate surface should have this ratio. In a preferred embodiment, the peaks of the Strömungsverwirbelerhebungen on a surface which corresponds at least substantially to an inner circumference of the guide surfaces, which can thus be traversed almost by a circular ring perpendicular to the longitudinal axis. Also a little from the Circular ring deviating surface contour at the survey can be considered as a dome. In this case, particular consideration should be given to those areas of the tip surfaces which deviate from the circular ring, for example, only at most 5 mm radially inwards or outwards. Alternatively and cumulatively, those regions of the crest surface can also be understood here, which deviate from the circular ring, for example, only at most a quarter, preferably at most one tenth, of the radius difference between the largest increase and the lowest channel.

It It should be noted that in most cases the inner contour is not corresponds to an ideal circle, but a polygon to different bubble diameter approach well to be able to. In this case, the above statements are analogous to a polygonal geometry transferred to.

The Guide surface is according to this thought, divided into hilltops of the elevations and themselves Intermediate channels. Between the sums of these two surfaces are given ratios be valid.

It has been shown in experiments on prototypes that specified ratios to a very stable cushion flow at the same time not too much elevated flow resistance being able to lead. at such conditions is the surface of the guide element rather than such a surface to understand in which from a surface Strömungsverwirbelerhebungen radially to protrude inward, as such, in which furrows in a surface are retracted.

It has already been explained above, that turbulence surveys on a macroscopic scale, in particular of at least 1 mm, 3 mm, 5 or 10 mm in height with respect to a between them formed bottom, with suitable design for a stable bolstering stream for the blown film tube can provide. The transition between the bottoms and the crests of the eddy hillocks be formed almost arbitrarily, for example, with angular transitions, with Throats, with bigger or smaller radius of curvature or smoothly flowing. It is essential, however, that flow paths are radially outside the imagined around the knolls inside surface area result, so that the blowing air mostly flow freely can, but at the same time by the flow vortex surveys a Turbulence in the flow is introduced, an existing turbulence is increased, or at least the Reduced degree of laminarity becomes.

Prefers are the crests of the eddy currents quite pronounced. It has proven to be advantageous if the Strömungsverwirbelerhebungen an inner circumferential surface define edges having a maximum radius of curvature 3 mm at a transition from the crests to channels lying between them. In such a Design the peaks of Strömungsverwirbelerhebungen are identical with the lateral surface or only with slight deviations from this, with a rather sharp curved transition edge from the crests to the side walls of the Surveys leads, So into the flow channels.

The Bottoms of the flow channels can be very be designed freely. In particular, they can be U-shaped, V-shaped, with rectangular cross-section or any other shapes configured be.

at Attempts of the inventor, such forms have been found to be particularly suitable exposed, a cushion flow to create.

It it is suggested that the guide element has an angle plate. In prototype experiments of the inventor Angle plates have a very low cost option proved to carry out the invention.

The Invention will be described below with reference to second embodiments with reference closer to the drawing explained.

It demonstrate

1 roughly schematically a section through a blown film plant with a rising from a blow head film tube and an outer guide and

2 roughly schematically a view of the outer guide according to marking II-II in 1 ,

The blown film plant 1 in 1 extruded by means of the blow head 2 the film tube 3 from a melt-shaped polymer. The film tube 3 rises along a vertically aligned longitudinal axis 4 up and frozen on the way up. In the middle area is a calibration 5 provided, which the film tube 3 leads to a deflection and a flattening (not shown).

In the calibration area 5 has the blown film plant 1 various guide plates 6 . 7 (exemplified) on. These surround the area that is provided for the film tube during operation of the system.

The guide plates 6 . 7 are each slightly angled sheets with stamped or cast surveys 8th (marked by example). These surveys 8th each have the form ei ner rhombus, with a longitudinal extension 9 the rhombuses 8th at least approximately parallel to the longitudinal axis 4 the entire facility is aligned. The surveys 8th are arranged regularly to each other and cover an entire surface 10 the sheets 6 . 7 ,

Every survey 8th consists of a dome surface 11 (marked as an example) with a relatively steep base 12 the sheets 6 . 7 running edges.

The sheets 6 . 7 In particular, straight plates, curved plates or angle plates can be. The sheets may as well be arranged in the calibration area as in a higher or lower area on the system 1 ,

It is essential that a fan (not shown) is provided, which along a direction of cushion flow 13 Air or another gas between the sheets 6 . 7 and the film tube 3 blows. Because of the surveys 8th on the sheets 6 . 7 , where the surveys 8th inward towards the longitudinal axis 4 are directed, the incoming air is swirled, and there is a stable cushion flow for the film tube 3 during operation of the plant 1 , As a blower, a blower of a cooling ring 14 can be used, or it can be used a separate blower.

Claims (13)

External guide for a film tube ( 3 ) in a blown film plant ( 1 ), wherein the outer guide is a guide element ( 6 . 7 ) with one to a longitudinal axis ( 4 ) directed guide surface ( 11 . 12 ), characterized in that the guide surface ( 11 . 12 ) a reason ( 12 ) with one to the longitudinal axis ( 11 . 12 ) structuring ( 8th ) having. Exterior guide for one Foil tube in a blown film plant, wherein the outer guide is a guide element with one to a longitudinal axis having directional guide surface, in particular according to claim 1, characterized in that the guide surface a Structuring in the form of a Strömungsverwirbelerhebung and / or a Strömungsverwirbelvertiefung having. Blown film plant with an outer guide for a film tube, wherein the outer guide a guide element with one to a longitudinal axis having directional guide surface, in particular according to claim 1 or 2, characterized in that the guide surface one Has structuring and that a blower is provided, which in a leadership area a longitudinal flow on the outside of the Foil tube produced. Exterior guide for one Foil tube in a blown film plant, wherein the outer guide is a guide element with one to a longitudinal axis directed guide surface as well a fan for introducing air as a cushion flow between the film tube and the guide surface, in particular according to claim 1 or 2, characterized in that the fan is the air along the foil tube under the guide surface initiates. Blown film system or external guide to one of the preceding claims, characterized characterized in that the guide surface is airtight is. Blown film system or external guide to one of the preceding claims, characterized characterized in that the outer guide more guide elements having in axially different arrangement. Blown film system or external guide to one of the preceding claims, characterized characterized in that the outer guide more guide elements having radially different arrangement. Blown film system or external guide to one of the preceding claims, characterized characterized in that the outer guide more guide elements has tangentially different arrangement. Blown film system or external guide to one of the preceding claims, characterized characterized in that the Au ßenführung in one Calibration range of the film tube is arranged, in particular attached to a calibration basket. Blown film system or external guide to one of the preceding claims, characterized characterized in that the outer guide for a radial Adjustability is set up. Blown film system or external guide to one of the preceding claims, characterized characterized in that the outer guide is a casting having. Blown film system or external guide to one of the preceding claims, characterized characterized in that the structuring comprises a spherical elevation, a spherical depression, a bridge, a drop shape, a circular shape, a partial circle shape, has a polygonal shape and / or a diamond shape. Blown film system or external guide according to one of the preceding claims, characterized in that the guide element has an angle plate.