WO2012045489A2

WO2012045489A2 - Device for the monoaxial or biaxial stretching of film sections (stretching frame)

Info

Publication number: WO2012045489A2
Application number: PCT/EP2011/061153
Authority: WO
Inventors: Heinrich Collin
Original assignee: Dr. Collin Gmbh
Priority date: 2010-10-08
Filing date: 2011-07-01
Publication date: 2012-04-12
Also published as: DE102010038076B4; WO2012045489A3; DE102010038076A1

Abstract

The invention relates to a device for the monoaxial or biaxial stretching of film sections, preferably by means of a stretching frame, for films made substantially of polymers, wherein a square or rectangular section of such a film is held on 4 sides by at least two grippers in each case, wherein with a view to an improved process said device is configured and modified in such a way that both the lower fixed gripper and/or the upper movable gripper can be heated preferably independently of the heating of the film by at least one, preferably each heating system.

Description

Device for mono- or biaxial stretching of film sections (stretching frame)

The invention relates to a device for mono- or biaxial stretching of film sections, which consist essentially of polymers, wherein a square or rectangular section of such a film is taken on 4 sides by at least two clips, with a solid lower clip part forms the support and a from above, perpendicular to the film plane, lowered upper clasp part clamps the film at the peripheral edge.

Advantageously, the lowering of the upper clasp part and the structure of the clamping force by z. B. pneumatic or hydraulic cylinders are effected.

In a further advantageous manner, after heating the clamped film by, for. B. hot air or IR rays, the 4 groups of clips apart on all 4 sides apart to perform a stretching process.

The clips are each guided in guide rails, which z. B. by

Geared motors or hydraulic cylinders are moved.

The clips are synchronized by a pantograph system (a system of crosswise arranged parallel strips which are hinged together) in their movement to ensure a uniform stretching process on all sides (schematic diagram see sheet 1, Fig. 1).

Implemented devices of this type, use z. B. for clamping a square film pattern in sizes of 100 x 100 mm on each of the 4 pages per 5 clips with the widths of 10 to 12 mm (see Fig. 1)

The arrangement of the clamping cylinder is according to the prior art vertically from top to bottom for movement of the upper clamp in the direction of the lower, fixed flap. A rather small width of the clips, but a larger number of clips, is required to ensure a uniform stretching of the film.

The limited width of the clip also limits the size of the incorporated pneumatic or hydraulic cylinder for applying the clamping force. For high temperature applications in particular, the use of air or N _{2 is} required for actuating the cylinders, whereby the specific pressures are limited. The use of hydraulics is not recommended due to the risk of fire.

This means that with larger film thicknesses and resulting higher stretching forces applied by the pneumatic clamping cylinder clamping force is insufficient and the slides can slip out of the clip.

According to another patent application DE 10 2009 003 751 of the Applicant, the content of which is hereby made the content of the present application, the upper clip part is located on an outside of the film to be stretched

Rotary axis hinged and in such a way that the lower, fixed clip part carries the joint, while the upper clip part upwards

is performed pivotally and that at least one cylinder for applying the clamping force to a vertical web of the lower, fixed

Turned part of the cleat rotated by 90 °, arranged horizontally and fastened and thus applies the clamping force on the upper, pivotable clip part.

Further, a plurality of horizontally juxtaposed clamping cylinder are arranged axially offset on the respective bracket, whereby the clamping cylinder can be made substantially larger in diameter and much larger pressure forces can be built (at the same pneumatic

Maximum pressure).

The device according to the prior art still has the following disadvantages:

In order to introduce the necessary stretching temperature into the film as well as into the clips themselves, according to the prior art, the heating medium air or IR radiation is used both for heating the film and the clips. This is good for films of about 0.1 mm up to about 1.5 mm thickness

working method.

With increasing foils or plate thicknesses of e.g. 2 mm to 5 mm or even stronger, it becomes more and more difficult with the foil / plate also to heat the clips to stretching temperature. However, if the clips are not heated enough, the plastic areas between the upper and lower clips will not or too slowly heat up. Likewise, the narrow surfaces of the film are heated only too slowly laterally between the individual pairs of clips.

The result of this slow heating is a very prolonged heating process until a uniform stretching temperature in the free film surfaces and within the clips is achieved. This long heat up time does the whole thing

Stretching method uneconomical and also leads to potential adverse

Changes in the structure of the stretched film / plate.

It is known that, before clamping the film into the stretching frame, at first only the clips are heated with the heating medium hot air or IR radiation. Thereafter, the heating system is driven off, or the stretching frame moved out of the hot air oven. The slides are inserted, the clips

closed, the heating system closes again, or the stretching frame is retracted again in the hot air oven and now heats both the film and the clips. Also in this method, the initially reached temperature drops rapidly in the clips and can not be achieved by prolonged reheating, together with the film.

This effect becomes more and more pronounced as the thickness of the film / plate increases and makes easy stretching at thicknesses above 2 mm and temperatures above approximately 150 (200) ° C very difficult and very time-consuming.

Another disadvantage is the insufficient transfer of attacking at an angle of 90 ° to the clamping surface stretching force on the surface of the

compressed clips.

Since a smooth surface has too low coefficients of friction, the

Surface of the clips are shaped appropriately to the at an angle transferred to 90 ° to the clip surface attacking stretching force on the plastic film can.

The light fluting used in the prior art

Clip surface in parallel but also arrow-shaped form is suitable for thin films to initiate a lower stretching force in the film.

For thicker films, e.g. between 2 mm and 5 mm thick, much higher stretching forces would have to be transferred into the film. As a rule, the films slip out of the clips despite the fine ribbing.

Object of the above invention is to overcome the existing disadvantages.

The object is achieved by the features of claim 1. According to the invention, it is thus possible that each lower, fixed clip as well as each upper, movable clip are heated independently of the heating of the film individually, preferably by each

at least one heating system, which allows the setting and / or regulation of any temperature or a common temperature control with pre-selectable ramps and temporal changes for at least one, more preferably all heated clips.

A concrete embodiment provides that in each individual clip an electric heater, preferably a resistance heater is installed, for example, with at least one associated temperature sensor and / or a suitable flexible power supply and / or each a separate

Temperature controller, which is preferably installed in a separate cabinet.

The problem of insufficient transfer of the stretching force over the surface of the compressed clips is inventively achieved by the features of claim 2. Advantageously, the lower fixed and / or the upper movable clip are not each a part with a firmly machined grip surface, but consist of one each

Kluppengrundkörper and preferably easily interchangeable, attached clip caps, these clip caps with transverse grooves,

Saw teeth or other form-fitting surfaces could be provided, which can be adapted to the thickness of the stretched films / plates as well as to the corresponding thermoplastic material and / or after heating of Klappenkappen and foil / plate under the pressure of e.g.

deep pneumatic cylinder, for example, penetrate in a range of tenths to half or more of the film / plate in the thermoplastic material, whereby the intimate interlocking of clip cap and foil is formed and can transmit particularly high stretching forces in this way.

This embodiment allows, e.g. with very fine grooves (teeth) of only 0.1 mm depth, a foil of e.g. 0.2 mm thick to about 1 mm thick, but not cut. With significantly deeper grooves (teeth) of approx. 0.5 mm deep, a 2 mm thick foil / plate can be gripped securely and many larger stretching forces can be transferred safely. With deeper teeth of approx. 0.8 mm depth, even thicker plates with a thickness of approx. 2.5 mm to 4 mm can be gripped safely.

A further advantageous embodiment of the invention provides that the electric heater and / or the temperature sensor are installed directly in the clip cap. This can be the highest possible temperatures in the grip area of the clip cap can be achieved. This variant is advantageous when highest

Temperatures must be driven. The effort is slightly higher because when changing the dome cap and the electrical connections must be disconnected.

A further advantageous embodiment is the installation of electrical

Resistance heating in the Kluppengrundkörper, preferably flush with the support side of the Kluppenkappe. This guarantees good heat transfer from the heated clip body to the clip cap. Thus, a simpler replacement of the clip cap for use with thinner or thicker sheets or plates is possible without the radiator and

Temperature sensor must be disconnected. Such a device constructed according to the measures of the invention has the following advantages:

By this arrangement is achieved for the first time that up to the highest

Stretching temperatures of about 450 ° C all individual clips or

Kluppengrundkörper and Klappenkappen an absolutely same and

have reproducible temperature.

The heating of the clips is independent of the heating system for heating the film, e.g. Hot air or IR radiation.

The heating of the clips is also guaranteed if the clips are not arranged close to each other in the primary clamping state when clamping the still unstretched specimen, but also if the clips are driven far apart after the stretching process and, for. an annealing process is followed.

Another advantage is the enormous shortening of the trial period, since the clips are heated again immediately after removal of the stretched pattern separately and very quickly to the target temperature, so that even when inserting the film in the open state of the stretching frame no temperature is lost.

Another advantage is that parallel to the temperature program for the heating of the film another, e.g. slightly higher or lower temperature profile can be controlled for the edge.

It can be safely gripped in accordance with the invention thus thicker sheets or plates, with adapted to the thickness of the film handle cutting to transfer the high stretching forces on the material to be stretched, and it can in a much shorter time and with much higher security and uniformity the Klappenkappen and thus all gripping surfaces between the clips are heated to the appropriate temperature of up to 450 ° C to allow immersion of the heated gripping surfaces in the plastic and also heat the plastic in the space between the clips and the side of the clips enough for the stretching process , The advantages and features of the invention will become apparent from the

following description of an embodiment in conjunction with the drawings and the statements. Show it:

Fig.1

A plan view of a known per se stretching frame for mono- or biaxial stretching of film sections.

Fig. 2

A sectional view through the stretching group according to FIG. 1

Fig. 3

A sectional view through a tensioning clamp of FIG. 2 with 2 variants of the above invention.

Fig. 4

A sectional view with incorporated in the clips radiators.

Fig. 5

A sectional view with interchangeable clip caps and heating the

Kluppengrundkörper.

Fig. 6

A sectional view with directly electrically heated interchangeable

Kluppenkappen.

In Fig. 1 is a plan view of a known per se stretching frame for mono- or biaxial stretching of film sections shown. The section on the bottom left shows the initial situation in which an unstretched, square film section 1 is taken by five clips on each side and clamped at the edges. The clips 2 are each guided in guide rails 3 and 4 respectively.

The Pantograph System 6 synchronizes the movement of the individual clips to ensure a uniform stretching process on all four sides of the film.

The side right and above shows the stretch frame in apart driven state after stretching with the stretched film 7. The drive for the

Stretching is effected by one (or two separate, synchronously running) Geared motors or hydraulic cylinders, which move the right guide rail 3 to the right. Likewise, the upper rail 4 is moved upwards. In a particularly advantageous manner, the cylinder for applying the

Clamping force on a vertical web of the lower, preferably fixed clip part rotated by 90 °, arranged horizontally and fastened and so apply the clamping force on the upper, preferably pivotable clip part, as shown in DE 10 2009 003 751.

FIG. 2 shows a sectional view through the stretching group according to FIG. 1. The

Primary film 1 is clamped by the vertically arranged clips 2 with bottom fixed support and from above in the vertical direction movable clamping bolt 18 and clamping cylinder 19 constructed above. The clips 2 are guided in the guide rail 3 and the movement of the individual clips synchronized by the pantograph system 6.

The heating of the film and the film-engaging clips is carried out jointly by hot air 17 from above and below or e.g. by IR radiation.

The installation situation shows that uniform heating of the clamped film is difficult even in the mid-free area, but very difficult in the area in the clips.

The film to be clamped is inserted below in a slot in the clip holder. This completely covers the edge area from above and below.

Fig. 3 shows a sectional view of the stretching group of FIG. 2 with the

innovations according to the invention.

The right side of the image shows that the lower support side of the clip 2 is heated directly by an electrical resistance heater 21. A temperature sensor can be integrated into the radiator or installed separately.

A flexible connecting cable leads to the electrical control and regulation system.

In the same way, the moving through the clamping cylinder from top to bottom

Clamping bolt 20 with an electrical resistance heater 22 close to the

Heated clamping surface. This makes it possible independently of the heating system for heating the film each clasp part to heat independently and to temper the clamped between the clip halves film section 1 very accurately.

The grip side of the clips is usually not smooth, but with a den

Friction increasing surface, e.g. with grooves milled in 90 ° to the pulling direction. However, these grooves must be adapted to the thickness of the stretched film, as well as to the polymer, so the clip can only be used for a narrower thickness range.

How this problem can be corrected, the left side of Fig. 3. Here, an easily replaceable clip cap 23 is placed on the lower fixed side of the clip 2 and secured by a screw 27. A resistance heater 25 with integrated temperature sensor heats the clip cap directly. Similarly, the adjustable from above clamping bolt 18 with a light

replaceable clip cap 24 provided; a resistance heater 26 with integrated temperature sensor heats the upper clip cap directly.

With this combination, it is now possible to cover a wide temperature range between 20 ° C and 450 ° C Kluppentemperierung, as well as a wide range of thickness, even over 1, 5 mm, cover the clamped films by simply replacing the Klappenkappen, which with different depths Gripping geometries are equipped.

Fig. 4 shows a section through two clamping clips, as these are known from DE 10 2009 003 751.

The left half of the figure shows that the upper cleat part 1 1 hereby articulated to a rotational axis 12 lying outside of the film to be stretched but approximately in the plane of the film, the lower stationary cleat part 13 carrying the joint. The cylinder for applying the clamping force 14 is fixed to a vertical web of the lower fixed clip part, rotated by 90 degrees, arranged horizontally and thus brings the clamping force on the upper pivotable clip part.

It is easy to see that the clip parts and the clamped raw foil with z. B. 1 10 mm width better warm air or the IR radiation are exposed to allow optimum heating. For larger to be stretched film thickness over 1, 5 mm and at high

Temperatures, the common heating of film and clips by hot air or IR radiation is not enough to heat the clips sufficiently high and sufficiently evenly.

According to the invention, the lower, stationary clip half 13 with a built-in tight under the grip surface electric resistance heater 28 with

integrated temperature sensor directly heated. A flexible connection cable leads to the electrical control and regulation system.

Likewise, the upper pivotable clip part 1 1 is heated directly by an electrical resistance heater 28.

The right side of the drawing shows a division of the pivotable upper cleat part 1 1, such that the front cleat part 15 is mounted separately and height adjustable on the base lever 1 1 in order to adapt the cleat surface optimally to different film thicknesses.

Also in this variant, both the lower solid clip half 13 as well as the upper pivotable and height-adjustable clip member 15 are heated separately by built-in tightly under the handle surface electrical resistance heater 28.

Fig. 5 shows a section through two clamping clips, as they are basically known from DE 10 2009 003 751. In contrast to the installation of resistance radiators described in Figure 4 directly into the clips, here additionally easily removable and exchangeable clip caps 29 are used. These Kluppenkappen 29 are each placed on the lower fixed bracket 13 or the upper pivotable clip part 1 1 and by means of

Bolts 30 attached.

In the fixed lower clip parts 13 or the movable upper clip parts 1 1 and 15 each electrical Widerstandsheizköper 31 are installed so that the flush rest on the screwed Kluppenkappen 29 and thus good heat transfer is ensured.

Quick couplings 32 also allow easy removal of a

Resistance heater 31 in case of a defect.

Shrouds 33 and 34 protect the cables from mechanical damage and overheating by the hot air or IR radiation. FIG. 6 shows a section through two tensioning clips, as these are basically known from DE 10 2009 003 751. In this variant will be

Kluppenkappen 35 used in which radiator 36 with integrated

Temperature sensors are used directly. The Kluppenkappen 35 are screwed with the screws 37 to the main body of the clips 13 and 1 1 and 15 respectively. This variant is used for highest temperatures, since the

Heat transfer in the stretched films is best and heat dissipation can be reduced through the Kluppengrundkörper.

Claims

PATEN TA NSPR CHE

1 . Apparatus for mono- or biaxial stretching of film sections

preferably by means of a stretching frame, for films substantially of polymers, wherein a square or rectangular section of such a film is taken on four sides by at least two clips, characterized in that:

that both the lower fixed clip and / or the upper movable clip can preferably be heated independently of the heating of the film by at least one heating system, preferably in each case.

2. Device according to claim 1, characterized in that the

Heating system, the adjustment and / or regulation of any temperature preferably in the range of 20 to 450 ° C allowed and / or that the heating system via a suitable control system compliance with a common temperature and / or a common temperature sensing with pre-selectable ramps and changes over time for the heated Cleats allowed.

Device according to claim 1 or 2, characterized in that:

that both the lower fixed and / or the upper movable clip each consist of a staple body and thereon preferably easily interchangeable, patch Klappenkappen.

Device according to claim 3, characterized in that:

that the clip caps are provided with transverse grooves, saw teeth and / or other form-fitting surfaces which are adaptable to the thickness of the sheets / plates to be stretched as well as to the corresponding thermoplastic material and / or which after heating the

Clip caps and / or foil / plate under the pressure of e.g.

pneumatic cylinder penetrate into the thermoplastic material, whereby such a resulting toothing of clip cap and foil high stretching forces are transferable.

Device according to one of claims 1 to 4, characterized in that in each individual clip an electric heater, which is preferably designed resistance heater is installed with associated temperature sensor, and / or a suitable flexible power supply and / or is provided in each case a separate temperature controller, which is preferably installed in a separate cabinet.

Device according to claim 5, characterized in that:

that the electric heater and / or the temperature sensor are installed directly in the clip cap, so that the highest possible temperatures can be achieved in the grip area of the clip cap.

Device according to claim 5, characterized in that:

that the electric heater and / or the temperature sensor in the Kluppengrundkörper, preferably flush with the support side of the

Clip cap, is installed.