DE102004021006A1 - Thermoforming tool and method for thermoforming a film - Google Patents

Abstract

In order to obtain a thermoforming tool in which CPET deep-drawing films can be processed into moldings with hot tool, which have undercuts and avoid the disadvantages of the previously used thermoforming tools, it is proposed that the tool has a cavity with a peripheral edge and at least one on The edge about a pivot axis pivotally mounted tool part comprises a projection which can be transferred from a first pivot position to a second pivot position, wherein the projection protrudes in the first pivot position of the tool part from the edge in the direction of the interior of the cavity of the tool and wherein the projection in the second pivot position of the tool part is arranged in a position in which it no longer protrudes into the cavity in a projection parallel to the removal direction projection.

Description

The The invention relates to a thermoforming tool for the production of a shaped body a thermoforming film, in particular a CPET thermoforming film.

background The invention relates to the production of so-called snap cap closures for containers in which the lid has indentations formed in an edge region, when closing of the container engage with an edge of the container, in particular one outwards bent edge, and so on a detachable connection between the lid and the cup.

CPET materials are for Food packaging, which at the same time warming the Serve meals particularly suitable because CPET materials in the heating of Dine up to 200 ° C and tolerate more and at the same time at temperatures where the food is frozen are, still toughening are.

Such Materials need be crystallized at high mold temperatures to a sufficient To possess thermal stability. At the same time, the material becomes by holding at the crystallization temperature removed from the tool in a soft state, so only tools can be used where there are no undercuts. Otherwise, would be at the removal of the thermoformed film affects the imprinted shape and the molded body unusable.

the was so far taken into account that the thermoforming tool with Sliders is provided, which in the molding of the molding in the mold cavity protrude and before the demolding of the molding from the thermoforming mold withdrawn again so that the removed from the thermoforming tool, still warm Foil can be removed from the mold after the forming step, without the shaping suffers.

Other Materials as CPET are less problematic here because there Shaping with a hot Foil with cooled Tool can be made. The thermoformed film has so have already experienced a certain hardening after the shaping step.

at CPET materials, it is important to keep the molding in a warm condition from the hot Removing tool, the molding then often transferred into a so-called cold mold and cooled down there becomes.

Problematic in the thermoforming tools previously used is the use the slider, the elaborate one Require drive mechanism and thus the thermoforming tools expensive and make maintenance intensive.

task the present invention is to propose a thermoforming tool, at that with hot Tool in particular CPET thermoforming foils processed into moldings can be which undercuts have and which are the disadvantages of the past avoid related thermoforming tools.

These Task is in the above-mentioned thermoforming tool according to the invention thereby solved, that the tool is a cavity with a peripheral edge and at least one on the edge about a pivot axis includes pivotally mounted tool part with a projection, which can be transferred from a first pivot position into a second pivot position, wherein the projection of the tool part in the first pivot position protruding from the edge into the cavity of the tool and wherein the projection in the second pivot position of the tool part is arranged in a position in which it is in removal direction no longer seen in the cavity protrudes.

Surprised can be with a pivoting tool part, which a Advantageous to the formation of undercuts and which is pivotally mounted, in a very simple way undercuts in thermoformed moldings Made of CPET materials and the soft thermoforming film in the thermoformed form from the hot Mold demoulding without the imprinted during thermoforming of the film shape thereby impaired becomes. When removing the molding in the removal direction the mold pivot the mold part with the projection, or the Tool parts with the projections, from the first pivot position (position where the thermoforming sheet is deformed is) in a second pivot position in which they are no longer in the cavity protrude.

Thereby will be the way for released the shaped body, and demolding without impairment the shape of the molding becomes possible.

by virtue of the fact that you are working with a hot tool can and the molding if necessary, be cooled afterwards can, high treatises in the production are possible.

Preferably, the angle of pivotal movement of the tool part during pivoting of the first to the second position less than 90 °, wherein the pivoting movement with respect to the first and the second position is limited in each case by a stop.

In order to avoids that pivots the tool parts in a dead position out of which they only come out through special measures swiveled back can be. A biasing of the tool parts by means of a spring is unfavorable, since this the removal of the thermoformed foil as the tool difficult.

Remains the angle of the pivoting movement is less than 90 °, then the tool parts no later than during insertion another slide safely swung back to its first position. A review of correct position of the tool parts before the start of the next deep-drawing process can be dispensed with.

Furthermore let yourself achieve another advantage, namely, that the tool part with appropriate storage already due to its own weight falls back from the second pivot position to the first pivot position. This means that the tool parts with the protrusions at the moment, in that of the molded body taken from the thermoforming tool, currently back to the first Swing back position and thus are immediately placed back in the position in which a new deep drawing process can be performed.

the can by a corresponding arrangement of the pivot bearing of the tool part and helped a distribution of its own weight with respect to the pivot axis become.

Want one distinctively different Undercuts on the moldings With a thermoforming tool, this can be done simply by: one the distance of the pivot axis of the tool part to the edge of cavity adjustable.

A alternative or complementary Solution here may be to displaceably arrange the projection on the tool part.

Becomes such a special function is not needed, the tool part preferably integrally formed with the projection.

A Modification of the undercuts with otherwise the same thermoforming tool can then be also easy to realize when the tool part on the solvable Tool is held. Then you can the tool part itself with the projection simply against a tool part with a different shaped projection, for example stronger or less strong in the cavity protrudes, exchange.

For the beginning addressed snap-on caps are sufficient projections, which protrude in the first position about 3/10 to 10/10 mm into the cavity.

The Pivot axis of the tool part is preferably with respect to the Edge area of the cavity at which they are arranged arranged with tangential orientation.

For the snap cap closures are preferred at least two, more preferably at least three, pivotally mounted Tool parts used, in particular at uniform angular intervals on Edge of the cavity are arranged.

• a) Bereitstellen der Folie;
• b) Beheizen eines Tiefziehwerkzeugs auf eine vorgegebene Temperatur; c) Einführen der Folie in das geöffnete, beheizte Tiefziehwerkzeug;
• d) Schließen des Werkzeugs und Anlegen der Folie an das Werkzeug;
• e) Öffnen des Werkzeugs und Entnehmen der tiefgezogenen Folie aus dem beheizten Werkzeug;
• f) Abkühlen der tiefgezogenen Folie.

The invention further relates to a method for thermoforming a film, in particular from a CPET material for producing a shaped article, the method comprising the steps:

• a) providing the film;
• b) heating a thermoforming tool to a predetermined temperature; c) inserting the film into the opened, heated thermoforming tool;
• d) closing the tool and applying the foil to the tool;
• e) opening the tool and removing the thermoformed film from the heated tool;
• f) cooling the thermoformed film.

According to the invention is hereby used as a deep drawing tool a tool as described above.

The Tool is preferred when processing CPET materials heated to a temperature of 170 to 180 ° C, since in this Temperature the film is heated quickly to a temperature during the crystallization processes run sufficiently fast in the CPET material.

Around To shorten the holding time in the tool, the film is preferred preheated introduced into the tool, preferred preheating temperatures for CPET materials in the range of 100 to 120 ° C lie. The film is still easy to handle at such temperatures.

The Applying the film to the tool happens, as is well known either by vacuum or by compressed air, or combined by means of Use of negative pressure and support of compressed air.

As already described above, the thermoformed film is removed from the tool in the heated tool when hot, although the film can hold its shape, but is still soft and would damage when using a different than the deep-drawing tool according to the invention by parts that should produce an undercut.

The thermoformed film can be cooled forced, for example by blowing with cold air. Another possibility is the cooling through a chilled Support form, while the deep-drawn film is introduced into the cooled mold.

Prefers the film is held in the heated thermoforming tool for so long, until the CPET material has a degree of crystallization of about 24% or has more.

This Make sure that the CPET material is for food packaging has sufficient heat stability and, for example, heating Food in the microwave without any problems.

on the other hand the film in the heated tool is preferred only for so long held until a crystallization degree of CPET material of a maximum of 28 % is obtained. higher Crystallization grades have the disadvantage that the material becomes too brittle and the impact resistance decreases too much.

Prefers the film is provided as a continuous material, in which case preferred the deep-drawn moldings in the endless material first remain in this state then transported on to the cooled mold and only then from the supernatant punched out of the film and separated. The supernatant can be taken as endless material at the end of the process and again be wound up.

Prefers For example, the film that is provided as a continuous material is substantially guided in one plane, then the deep drawing tool and optionally the cooled mold lowered in the same cycle from a working position to a transport position so that the film in the lowered state of the thermoforming tool and optionally the cooled Form is transported and then what the thermoforming tool and optionally the cooled Form can be raised back to the working position to the next deep-drawing process carry out to be able to. At the same time, the thermoformed in the previous cycle slide in the chilled Dip the mold and let it cool down.

These and other advantages of the present invention will become apparent below closer to the drawings explained. They show in detail:

1 : A deep drawing tool according to the invention;

2 : an enlarged detail of the thermoforming tool 1 ;

3 a schematically illustrated process sequence of the deep drawing process according to the invention; and

4a ) and 4b ): shaped bodies produced according to the invention.

1 shows a total with the reference numeral 10 designated deep-drawing tool with a circular cavity 12 , which from a further receding ring area 14 is limited. In the ring area 14 are at different positions in the circumferential direction vacuum openings 16 arranged over which in the space between one on the thermoforming tool 10 applied thermoforming films (not shown) and the cavity 12 a negative pressure can be generated, due to which the thermoforming sheet is then applied to the surface of the thermoforming mold 10 is created.

In order to be able to emboss projections in the edge region in the molded body to be created, which here has the form of a so-called snap-on lid, are on the thermoforming tool 10 at regular angular intervals on the edge of three tool parts 18 arranged out of the in 1 shown first pivot position can be pivoted out into a second pivot position.

In the in 1 shown first pivot position protrude the tool parts 18 with projections arranged at a free end 20 inside the cavity 12 or its ring area 14 into and thus form undercuts.

These projections then form as in the produced snap cap inside elevations, with which the snap lid under the edge of a bottom part, for example a cup, a shell or a plate or the like can grab and engage.

These Lids serve to close of the bottom part to the packaged food when heated by means of Microwave or even in the stove from over-drying to protect. So packed Food can Therefore, inserted directly with the packaging in the microwave and warmed, or cooked.

2 shows in magnification a detail of 1 namely a tool part 18 However, now in a pivot position corresponding to a second pivot position in which the projection 20 in removal direction no longer projected into the area of the ring area 14 or the cavity 12 extends. This makes it clear that one out of the tool 10 removed molding, which is still in a hot state and is correspondingly soft, without affecting its shape from the thermoforming tool 10 can be removed because when removing the tool part 18 get along with the one by the lead 20 impressed elevation (indentation) moved together in the removal direction and the molding in the in 2 then shown position completely free, so that this unhindered by the thermoforming tool 10 removed and can be transported for cooling on.

At the in 2 shown tool part 18 is the lead 20 in one piece to the tool part 18 formed. To realize different undercuts or the lead 20 to exchange for another projection, is the tool part 18 detachable on the thermoforming tool 10 held, for example screwed. In the in 2 swung out form shown can be (not visible in the illustration) under the tool part 18 a fastener (eg screw) and thus solve the tool part 18 from the thermoforming tool 10 remove.

3 schematically shows the process sequence for the production of a shaped article according to the present invention, wherein here preferably continuous material in the form of a CPET film 22 from a wrap 24 is withdrawn and not shown guide rollers a thermoforming tool 26 is supplied. The thermoforming tool 26 is heated to a crystallization temperature of the CPET material (preferred temperature range is 170 to 180 ° C). At the top of the thermoforming tool 26 is a so-called bell 28 arranged, which is a cavity 30 of the thermoforming tool 26 spans and during the thermoforming cycle the foil outside the edge of the cavity 30 against the thermoforming tool 26 suppressed. At this stage is then on the part of the thermoforming tool 26 a vacuum is applied so that the film is in the cavity 30 deformed into it and in particular also to projections 32 from on the thermoforming tool 26 pivotally held tool parts 24 around to the surface of the thermoforming tool. The application of the film to the tool surface can be achieved by generating an overpressure within the bell 28 get supported.

In this state, the thermoforming sheet 22 for a time in which a degree of crystallinity in the CPET material is from 24 to 28%. Then the thermoforming tool 10 down from the transport plane of the film 22 lowered and the foil 22 transported by one clock, so that the previously formed snap-on lid above a so-called cold form 36 are arranged and can be absorbed by this for forced cooling.

The cold form 36 no longer has all the details of the thermoforming tool 26 in particular, the projections are missing 32 or the associated tool parts 34 ,

When lowering the thermoforming tool 26 swivel the tool parts 34 upwards, so that the projections 32 seen in the projection from the area of the cavity 30 swing out and thus release the area of the deep-drawn film in particular also the molded indentations and allow the unimpeded transport of the film.

Downstream of the cold form 36 then finds a cutting or stamping step in a cutting or punching device 40 instead, which is only symbolically indicated here with a knife edge. Here are the moldings (in particular here snap cover) punched out of the continuous film and as a stack 42 separated from a foil remainder 44 collected. The remaining film 44 can be back on a reel 46 be taken or else shredded directly to an extruder fed with the endless film 22 can produce again.

The 4a ) and 4b ) show finally produced from CPET material molded body, wherein the in 4a ) shown molding a snap lid 50 represents with a level middle area 52 to the a high vaulted edge 54 followed.

In the edge 54 are radially inwardly facing indentations 56 arranged in shape corresponding to the projections of the tool part used in the thermoforming tool in the shaping step. These indentations 36 provide a snap connection of the snap lid 50 with an associated lower part (here shell 60 ), which of an outwardly bent edge 62 is limited. When attaching the snap cover 50 on the shell 60 grab the indentations 56 under the edge 62 of the lower part 60 and thus ensure a secure hold of the lid 50 on the shell 60 , It is clear that this does not seal the shell 60 is achieved, which is not desired in the present case, because in the closed state should be in the shell 60 Developing water vapor build up pressure, but should first displace the air contained therein without the snap cap 50 detached and takes off.

The connection through the indentations 56 on the edge 62 On the one hand, they are sturdy enough and allow the formation of a small air gap between the snap-on lid 50 and the shell 60 as soon as the gas space in the shell 60 warmed, so in the shell 60 when heated no pressure is built up.

On the other hand, the forming gap is so small that most of the resulting moisture, ie water vapor, in the shell 60 is retained so that it does not lead to drying of the heated food in it.

Due to the use of the deep-drawing tool according to the invention in the manufacture of the snap lid 50 let the indentations 56 precisely on the edge 54 Arrange the lid so that it with defined geometry on the shell 60 is held.

Thereby let yourself very precise achieve the effect described above in the heating of the food. At the same time, this also provides sufficient protection against moisture loss given during the freezing of food.

Claims (18)

Thermoforming tool for the production of a molded body a thermoforming sheet, wherein the tool has a cavity with a circumferential edge and at least one pivotable about a pivot axis at the edge stored tool part comprising a projection, which consists of a first pivot position can be converted into a second pivot position, wherein the projection in the first pivot position of the tool part protruding from the edge in the direction of the interior of the cavity of the tool and wherein the projection in the second pivot position of the tool part, is arranged in a position in which it is in a direction to the removal direction seen parallel projection, no longer protrudes into the cavity. Tool according to claim 1, characterized that the angle of pivotal movement of the tool part during pivoting from the first to the second position is less than 90 °, wherein the pivoting movement with respect to the first and the second position by one stop is limited. Tool according to claim 2, characterized that the tool part is stored so that it due to its own weight falls back from the second pivot position to the first pivot position. Tool according to one of claims 1 to 3, characterized that the distance of the pivot axis of the tool part to the edge of cavity is adjustable. Tool according to one of claims 1 to 4, characterized the projection is displaceably arranged on the tool part. Tool according to one of claims 1 to 5, characterized that the tool part is detachable held on the tool. Tool according to one of claims 1 to 6, characterized that the projection in the first position about 3/10 to 10/10 mm protrudes into the cavity. Tool according to one of claims 1 to 7, characterized that the pivot axis of the tool with respect to the edge with tangential Alignment is arranged. Tool according to one of claims 1 to 8, characterized the tool comprises at least two pivotally mounted tool parts. Method for thermoforming a film, in particular from a CPET material, for producing a shaped body, comprising the steps: a) providing the film; b) Heating a thermoforming tool to a predetermined temperature; c) Introduce the slide into the open, heated thermoforming tool; d) Close the tool and apply the film to the heated tool; e) opening the tool and removing the thermoformed film from the heated tool; f) cooling the thermoformed foil; characterized in that a thermoforming tool Tool according to a or more of the claims 1 to 9 is used. Method according to claim 10, characterized in that that the film is preheated introduced into the tool is, the preheating temperature preferably in the range of 100 to 120 ° C. Method according to claim 10 or 11, characterized that the tool is heated to a temperature in the range of 170 to 180 ° C. Method according to one of claims 10 to 12, characterized that the film by means of vacuum and / or compressed air to the tool is created. Method according to one of claims 10 to 13, characterized in that the deep-drawn film is cooled in a cooled mold. Method according to one of claims 10 to 14, characterized that held the film in the heated thermoforming tool so long until the CPET material has a degree of crystallinity of 24% or more. Method according to claim 15, characterized in that that the film is held in the heated tool for so long until a crystallization degree of the CPET material of a maximum of 28% is obtained. Method according to one of claims 10 to 16, characterized that the film is provided as a continuous material. Method according to claim 17, characterized in that that the foil is guided essentially in one plane, and that the thermoforming tool and optionally the cooled mold in the same cycle from a working position to a transport position be lowered, that the film transported in the plane and that then the thermoforming tool and possibly the cooled mold again be raised to the working position.