DE102008054544B4 - Method for producing a plastic film tube and a corresponding plastic film tube - Google Patents

Abstract

Method for producing a plastic film tube (1) with a target cross section (5, 6) that deviates from a round cross section, with the following method steps: includes, so that its circumference is greater than the circumference of the cross section of the semi-finished tube (2); - Applying a predetermined force (F1, F2) to the mounted semi-finished tube (2) for pressing the semi-finished tube (2) to the core cross-section (8) of the core tool (7), wherein when the semi-finished tube (2) is subjected to the force (F1, F2) folds (17) are produced in the longitudinal direction of the semi-finished tube (2), which extend into a respective cut-out (9) in order thereby to tighten the semi-finished tube (2); - Heating the semi-finished tube (2) to a predetermined forming temperature for a predetermined period of time to produce the plastic film tube (1) with the target cross section (5, 6); and - pulling off the plastic film tube (1) shaped and cooled in this way from the core tool (7).

Description

The present invention relates to a method of manufacturing a plastic film tube and to a plastic film tube made by such a method.

According to the current state of the art, the production of hoses with a deviating from a circular cross-section, z. B. rectangular, square u. Like., With the production methods used so far not or only with strong restrictions regarding. The formation of the cross-sectional geometry, the wall thickness tolerance and the surface training possible. However, such hoses are needed, for example, for the production of hollow fiber composite components in order to achieve a better design of the inner surface.

As a method of manufacturing plastic film tubes in particular the Blasextrusionsverfahren is used in which liquid plastic, for. As polymers or polyamides are extruded from an annular nozzle in an air jet. With this method, the production of thin-walled Kunststofffolienschläuchen with a deviating from the circular cross-section and simultaneous demand for a high manufacturing accuracy with respect. The dimensional and shape retention is not possible.

Another method for producing hoses is the profile extrusion of plastics through a die. With this manufacturing technology, it is possible to produce hoses with a geometry other than circular. However, this means that only a limited number of tubes with a small wall thickness can be produced. Certain plastic films can be z. B. do not produce at all due to their molecular structure with this technology.

Another problem with hoses with a different cross section of the cross section is the transport of the hoses to the place of use, as in the production of certain geometries or cross sections, larger wall thicknesses, the use of plastics with a high modulus of elasticity, as well as due to the higher area moment of inertia Cross sections, the conventional Aufwickelverfahren on a drum, reel o. Ä. May be connected to damage the hose.

The US Pat. No. 6,793,871 B1 discloses a method of making a large volume, cup or trough-type container of thermoplastic material in which a tubular preform made of compact plastic is extruded in a predetermined length and then deformed into the container, the extruded preform being expanded by a predetermined amount and from below a core is moved into the expanded preform and the expanded preform is clamped at its lower free end sealing against the core and then the preform is molded by means of molding air to the container.

The US 2,837,121A discloses a flexible hose and method of making the same. The molded hose has a laminated body made up of layers of a structure having an intermediate elastomeric material, the hose having cylindrical attachment portions at each end and a spiral corrugation extending therebetween. Furthermore, the tube has a shaped outer surface and a helical spring covered with elastomeric material and having spaced turns surrounding the body and having its ends attached to the attachment portions. The turns of the spring are attached to the outer surface of the tip of the turns.

Against this background, the present invention has the object to provide a method for producing a plastic film tube having a deviating from a circular cross-section target cross-section.

According to the invention, this object is achieved by a method having the features of patent claim 1.

Accordingly, a method is provided for producing a plastic film tube having a target cross section deviating from a round cross section:
Mounting a semi-finished tube on a core tool having a core cross section, which has cutouts, so that its circumference is greater than the circumference of the cross section of the tube blank; Impinging the drawn up semi-finished tube with a predetermined force for pressing the semi-finished tube to the core cross-section of the core tool, wherein wrinkles are generated in the longitudinal direction of the semi-finished tube when applying the semi-finished tube with the force, which hineinerstrecken into a respective cut, thereby tightening the tube stock; Heating the semi-finished tube to a predetermined forming temperature for a predetermined period of time to produce the plastic film tube having the target cross-section; and peeling the thus formed and cooled plastic film tube from the core tool.

Thus, the present invention over the approaches mentioned above has the advantage that the inventive method a production of plastic film tubes with a deviating from the circular cross-section with a high accuracy of geometry, sharp formation of corners with small radii, defined wall thickness, dimensional stability at low cost and large hose length allows. Due to the various steps of the method according to the invention, it is possible to produce tubes with a cross-sectional geometry optimized for the respective application if production in the extrusion process is not possible due to insufficient wall thickness, material or transport.

By applying the drawn semi-finished tube with the force for generating the folds, so-called oversize folds, in the longitudinal direction of the semi-finished tube variations in cross-section can be compensated by manufacturing tolerances or local reinforcements, for example in the manufacture of fiber composite components (for example, in Blasschlauchtechnik).

The size of the cutouts in the core tool is to be determined as a function of the coefficient of friction of the core and tubing material as well as the circumference of the foil tube to be produced (eg of a polymer).

The cutouts are needed to tighten the tube blank to the circumference of the core by means of a force generated, for example, by applying a pressure differential (vacuum) or a forming tool, for example special tensioning bars, to the cross section of the core tool, i , H. the core cross-section, adapt.

The application possibilities of such a plastic film tube are manifold and make it possible to make better use of space available in certain applications than in the prior art and thereby save weight through reduced use of material. For example, the use of these plastic film tubes in the manufacture of composite components is possible in which such hoses, the production of components is possible with the hitherto possible round cross-hoses and the resulting resin accumulation, local underpresses and overpressions, material overstresses and resulting Leakage, sometimes not at all or only with restrictions regarding the quality of the manufactured components was possible.

In the present case, a "semi-finished tube product" is understood as meaning a tube produced in the normal extrusion or blown-extrusion process with a round or circular cross-section which is provided wound up.

The term "target cross-section" is understood to mean a hose cross-section which is to be achieved. A first target cross-section is formed by means of the core tool. A second target cross-section can optionally be obtained by means of a further method step.

In the dependent claims are advantageous embodiments and improvements of the present invention.

The thus pressed to the core cross-section of the core tool tube blank is then heated to a predetermined forming temperature, corresponding to the tube blank material, and on this for a predetermined period of time, for. B. held for a short time to reduce the stresses caused by the forming and pressing in the material of the tube semi-finished product. This achieves a first target cross section.

The term "plastic film tube" is to be understood as meaning the semi-finished tube formed on the target cross-section.

To remove the molded plastic film tube after cooling from the core tool, the plastic film tube with a medium, for. B. compressed air are applied. Short term for detachment from the core section or for the entire duration of the demolding process. A further facilitation of the peeling as well as the winding up results from the fact that the material of the core tool has a low frictional resistance.

The plastic film tube can then be cut to a required final size.

The plastic film tube produced in this way with a cross section deviating from the round cross section is also characterized in particular by the fact that it has a thin-walled construction. The wall thicknesses are in the range of about 30 microns ... 4 mm, in particular in the range of 0.2 ... 0.3 mm.

In an optional method step, the molded and stripped plastic film tube can be introduced into a mold having a second target cross-section in a negative mold and subjected to pressure and heat for shaping onto the second target cross-section. In this case, the folds of the first target cross section disappear inside the outer contour. A direct forming of a flat wound Semi-finished hose on a geometry with sharp outer edges is not possible without the core tool.

It may also be possible that the plastic film tube for a continuous forming on this second target cross section through the negative mold, which is designed for this purpose as a die, is pulled through at a predetermined speed.

"Semi-finished fiber" means fabrics, scrims and fiber mats, rovings and semi-finished products made from them. These are provided with a matrix, for example an epoxy resin, and then cured to a fiber composite component, for example by means of an autoclave.

Preferably, a release layer can be additionally applied to the plastic film tube, which reduces adhesion of the cured fiber composite component. This facilitates removal of the plastic film tube after the at least curing of the fiber composite component.

The term film tube thin-walled hoses are to be understood. These hoses are made for example of polymers such. As polyamides or alternative plastics. These hoses may be single-layered or multi-layered as a combination of multiple layers of these materials or with an additional layer of release agent. The wall thicknesses of these hoses are in the range of about 30 microns ... 4 mm, in particular in the range of 0.2 ... 0.3 mm.

The invention will be explained in more detail with reference to the embodiment shown in the schematic figures of the drawing. It shows:

1 a semi-finished tube with a round cross section and in a transport folding;

2 an exemplary target cross section;

3 Forming steps of the semi-finished tube after 1 in target cross sections according to an embodiment of a method according to the invention;

4 a core cross section of an exemplary core tool;

5 a cross-section of the drawn up on the core tool tube blank;

6 Applying a force for forming the arrangement according to 5 by means of a vacuum;

7 Applying a force for forming the arrangement according to 5 by means of a forming tool;

8th a perspective view from the perspective of another core tool;

9 a cross-sectional view of a plastic film tube having a target cross section created by the method according to the invention;

10 a sectional view of a plastic film tube in a negative mold for forming on another target cross-section; and

11 a sectional view of the plastic film tube in a negative mold with the further target cross-section.

In all figures of the drawing the same or functionally identical elements - unless otherwise stated - have been provided with the same reference numerals.

1 shows a cross section of a conventional thin-walled hose as a semi-finished tube 2 with round cross section 4 or circular cross-section after the production in Blasextrusionsverfahren, which can be folded flat for transport 3 , This hose serves as a semi-finished tube 2 for the production of a plastic film tube 1 with a target cross-section 6 which is in the in 2 example shown is trapezoidal. This target cross section 6 will be referred to as a second target cross section 6 designated.

3 shows schematically forming steps of the semi-finished tube 2 to 1 in a first target cross-section 5 and the second target cross section 6 according to an embodiment of a method according to the invention.

With the method according to the invention, hoses can be used as semi-finished hose products 2 referred to, which were prepared by extrusion or blown extrusion process (see 1 ) into other geometries with corresponding target cross sections.

The process can be divided into two forming steps.

In the following, the inventive method for the production of a plastic film tube 1 with a trapezoidal cross section (see 2 ) as a second target cross-section 6 exemplified. The production of other target cross sections is possible analogously to this example with minor modifications.

The aim is to produce a thin-walled plastic film tube 1 with the second target cross section 6 , The use of such a plastic film tube 1 as an aid for the production of components made of fiber composites requires such a hose with additional oversize folds in order to compensate for any fluctuations in the cross section of a fiber composite component by manufacturing tolerances or local reinforcements.

In a first process step, the semi-finished tube 2 provided in a wound-up form and in a second process step on a core tool 7 , whose core cross-section 8th in 4 shown, reared what was in 5 is shown schematically in a cross-sectional view.

The core cross section 8th is similar to the second target cross section 6 as a trapeze, but with side cutouts 9 , which are arranged symmetrically here, formed. It is easy to imagine that the core tool 7 is perpendicular to the plane of the drawing and expands in this direction in a certain length. Also run the cutouts 9 along this direction. Through the cutouts 9 results in a web arranged in the middle 10 , with its lower end on a foot section 7 is vertical and at its upper end at right angles with a head section 12 connected is. The cutouts 9 have a cutout height S. Through the cutouts 9 is a circumference of the core cross-section 8th increased. It is preferred that this circumference is longer or larger than a circumference of the tube half-blank section. The ratio of the core cross section 8th To the extent of the tube semi-finished product cross section is to be determined depending on the coefficient of friction of the core and tube material and the circumference of the film tube to be manufactured. The core tool may be made of plastic, for. As PA, PTFE, or metal or consist of a combination of these or other materials. The hose can z. B. consist of a polymer plastic.

How out 5 is apparent, is the core tool 7 inside an interior 14 of the semi-finished tube 2 ,

In a second production step, the medium from the interior 14 of the semi-finished tube 2 sucked off and the semi-finished tube 2 to the core cross section 8th pressed. By the appropriate design of the cutouts 9 in size, position, number and shape as well as a corresponding design of the core surface and the choice of the excess of the semi-finished tube circumference this is possible. 6 shows this applying an application of a force F1 for forming on the arrangement 5 by means of a vacuum. The force F1 is equal to the product of a pressure difference Δp from an ambient pressure p0 and an internal pressure p1 in the interior 14 of the semi-finished tube and a product of the cutting height S and a length of the cutout 9 ,

After pressing the tube semi-finished product 2 to the core cross section 8th becomes the semi-finished tube 2 for the unmolding process to a predetermined forming temperature (indicated here as t1) heated and held thereon briefly for a predetermined period of time.

Alternatively, a force F2 by means of a forming tool 13 , as 7 schematically illustrated, applied. The forming tool 13 consists in the example shown of two clamping rails, which on both sides of the semi-finished tube 2 in the cutouts 9 with simultaneous heating to the core cross-section 8th press and so a transformation of the tube semi-finished product 2 cause.

8th shows a vanishing point perspective of the core tool 7 , from which the longitudinal extension of the cutouts 9 between the foot section 11 and the head section 12 is clarified.

After cooling of the thus shaped tube semi-finished product 2 can do this in a further step from the core tool 7 subtracted from. It can support a medium, for. B. compressed air, for a short time or for the duration of the Entformprozesses in the interior 14 be directed. The thus shaped semi-finished tube 2 is now the plastic film tube 1 with the first target cross section 5 which is in 9 is shown cut to a predetermined final dimension in a perspective cross-sectional view. Here are clearly sharp edges in the corners at foot section 11 and head section 12 to recognize.

10 shows a sectional view of the plastic film tube 1 in a negative form 21 a mold 20 for forming on another, namely the second target cross-section 6 ,

First, wrinkles on the plastic film tube 1 explained. At the bottom has the plastic film tube 1 Fußfalten 15 with a sharp edge. In the area of the pages are in the interior 14 To identify protruding areas, which by pressing into the cutouts 9 of the core tool 7 were generated. These areas have lower cutouts 16 and top section folds 18 , as well as in the interior 14 protruding section rounded inner cutout folds 17 , Sharp-edged head folds 19 are in the upper area of the plastic film tube 1 arranged.

The negative form 21 in the mold 20 has a cross-section corresponding to the second (in this example trapezoidal) target cross-section 6 (please refer 2 ). The interior of the plastic film tube 1 here still has the ambient pressure p0, but in the next step, a pressure p1 is applied, which causes the in the interior 14 protruding areas on the walls of the negative mold 21 create as in 11 is illustrated. At the same time the arrangement is at a predetermined forming temperature of the plastic film tube 1 heated. This will make the plastic film tube 1 plastically on the second target cross-section 6 reshaped.

This second, optional forming step in the negative mold is used inter alia to remove the in the first forming step on the core tool 7 generated wrinkles 15 ... 19 , A direct transformation of the flattened tube semi-finished product 2 ( 1 and 3 ) on a geometry with sharp outer edges is not possible without the first forming step.

The mold 20 for this second forming step is also conceivable for a continuous process in which the plastic film tube 1 at a predetermined speed through the negative mold 21 , which is designed here as a template, pulled and thereby on the second target cross-section 6 is transformed.

• • Gute Wiedergabe von Kanten und Ecken mit geringen Radien
• • Möglichkeit zur Herstellung angepasster Schläuche vor Ort, dadurch geringe Transportkosten
• • Das erfindungsgemäße Verfahren ist für eine große Bandbreite von Geometrien, Querschnitten, Materialien und Wandstärken (ca. 30 μm...4 mm, insbesondere im Bereich von 0,2...0,3 mm) verwendbar.
• • Das erfindungsgemäße Verfahren ist teilautomatisierbar.
• • Das erfindungsgemäße Verfahren bietet außerdem eine Möglichkeit zur Herstellung kostengünstiger und qualitativ hochwertiger Faserverbundbauteile, zum Beispiel für Luft- oder Raumfahrt.

In the following, further advantages of the method according to the invention are mentioned in a nutshell:

• • Good reproduction of edges and corners with small radii
• • Possibility of producing adapted hoses on site, thus low transport costs
• The method according to the invention can be used for a wide range of geometries, cross sections, materials and wall thicknesses (about 30 μm to 4 mm, in particular in the range of 0.2 to 0.3 mm).
• The method according to the invention is semi-automatic.
• The method according to the invention also offers a possibility for producing cost-effective and high-quality fiber composite components, for example for aviation or aerospace.

The invention is not limited to the illustrated in the figures, special method for producing a fiber composite component in aerospace.

The geometry of the target cross sections can be modified in many ways. You can create more than two target cross sections, for example in several forming steps.

In addition, applications are conceivable in which plastic film tubes 1 with respective target cross-section 5 . 6 be used for the transport of liquid or gaseous media, but only a certain space is available for the integration of the hoses. Due to the possibility of producing hoses with an adapted cross-section of the available space can be better utilized.

The invention relates to a method for producing a plastic film tube 1 with a deviating from a circular cross-section target cross-section 5 . 6 It has the following process steps: mounting a semi-finished tube 2 on a core tool 7 ; Applying the mounted semi-finished tube 2 with a predetermined force F1, F2 for pressing the tube semi-finished product 2 to a core cross-section 8th of the core tool 7 ; Heating the tube semi-finished product 2 to a predetermined forming temperature for a predetermined period of time to produce the plastic film tube 1 with the target cross section 5 . 6 ; and peeling off the thus formed and cooled plastic film tube 1 from the core tool 7 ,

LIST OF REFERENCE NUMBERS

1

Plastic film tube

2

Tube semis

3

transport fold

4

Round cross-section

5

First target cross section

6

Second target cross section

7

core tool

8th

Core cross-section

9

neckline

10

web

11

foot section

12

header

13

forming tool

14

inner space

15

feet Folding

16

Lower detail fold

17

Inner detail fold

18

Upper detail fold

19

head fold

20

mold

21

negative form

F1 ... 2

force

p 0 ... 1

print

S

cutting height

t1

temperature

Claims (8)

Method for producing a plastic film tube ( 1 ) with a target cross-section deviating from a circular cross-section ( 5 . 6 ), with the following process steps: - mounting a semi-finished tube ( 2 ) on a core tool ( 7 ) with a core cross-section ( 8th ), which excerpts ( 9 ), so that its circumference is greater than the circumference of the cross section of the tubular semi-finished product ( 2 ); - applying the mounted semi-finished tube ( 2 ) with a predetermined force (F1, F2) for pressing the tubular semi-finished product ( 2 ) to the core cross-section ( 8th ) of the core tool ( 7 ), wherein when applying the semi-finished tube ( 2 ) with the force (F1, F2) folding ( 17 ) in the longitudinal direction of the tube semi-finished product ( 2 ), which are in a respective section ( 9 ), thereby forming the semi-finished tube ( 2 ) to streamline; - heating of the semi-finished tube ( 2 ) to a predetermined forming temperature for a predetermined period of time for the production of the plastic film tube ( 1 ) with the target cross-section ( 5 . 6 ); and - removing the thus formed and cooled plastic film tube ( 1 ) from the core tool ( 7 ). A method according to claim 1, characterized in that the loading of the mounted semi-finished tube ( 2 ) with the force (F1) by applying a pressure difference. A method according to claim 1, characterized in that the loading of the mounted semi-finished tube ( 2 ) with the force (F2) by means of at least one forming tool ( 13 ) he follows. Method according to at least one of the preceding claims, characterized in that for drawing off the molded plastic film tube ( 1 ) from the core tool ( 7 ) the plastic film tube ( 1 ) is pressurized with a medium. Method according to at least one of the preceding claims, characterized in that the molded and withdrawn plastic film tube ( 1 ) in a mold ( 20 ), which determines the target cross section ( 6 ) in a negative form ( 21 ) and introduced with pressure and heat for shaping on the target cross-section ( 6 ) is applied. A method according to claim 5, characterized in that the plastic film tube ( 1 ) for a continuous forming on the target cross-section ( 6 ) through the negative mold ( 21 ), which is designed for this purpose as a die, is pulled through at a predetermined speed. Method according to at least one of the preceding claims, characterized in that the core tool ( 7 ) from one with a for the predetermined forming temperature of the tube blank ( 2 ) temperature resistant material is made with a low frictional resistance. Method according to at least one of the preceding claims, characterized in that the semi-finished tube product ( 2 ) is formed in one or more layers and / or the molded plastic film tube ( 1 ) is coated with one or more layers.

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