DE10359563A1 - Thermoforming equipment for plastic film or sheet has prestretching plug fixed to and moving with one tool part to preform film during tool closure and final product is formed by pressure difference across film - Google Patents

Abstract

The two part(2,3) tool has a prestretching plug(6) fixed to the first part. The plug position in the tool(4) is such that the plastic film or sheet(7) is preformed by the plug as the tool closes. Final forming of the film is achieved by creating a pressure difference across the film when the tool is completely closed. Film(7) is placed between the tool parts(2,3) and the second tool part(3) is guided over the prestretching plug(6), thereby guiding the film into a cavity(5) between both tool halves. The free end of the prestretching plug extends beyond the face of the first tool half(2) and during tool closure moves into a predetermined position. Pressure difference across the film is created by a compressed air flow from the first tool half onto the preformed film. Venting bores(10) in the cavity(5) formed by second tool half release trapped air. The free end of the plug is shaped to suit the final shape of the finished product. An independent claim is included for a process for thermoforming a thermoplastic film in which: a) a film is heated and introduced into the tool(4); b) the tool is closed and the film preformed by the prestretching plug so that when the tool is fully closed the film reaches a predetermined position; c) pressure is applied to one side of the film to force it into the cavity and the final shape; and d) the film is cooled.

Description

The Invention relates to an apparatus for thermoforming thermoplastic, preferably sheet-like semi-finished products according to the preamble of claim 1 closer defined type and a method for thermoforming thermoplastic, preferably sheet-like semi-finished products according to the preamble of claim 7 closer defined type.

at thermoforming processes known from practice become film-like and substantially flat semi-finished products or plastic films between a first molded part and a second molded part of a shape of a Tool clamped. Subsequently, a so-called Vorstreckstempel in the deformation direction of the semifinished product in an interior of the mold, the is limited by the two mold parts, so moved that the heated Semifinished product is brought into a defined Vorverformungslage and is also held in this Vorverformungslage. Subsequently, will the preformed semi-finished product with compressed air introduced into the mold or over a vacuum in a conventional manner in its defined Forming spent or formed, with the introduced compressed air or the vacuum on the preformed semi-finished product in a deformation direction acting pressure gradient is applied to the semi-finished product.

there However, it is disadvantageous that the tool for thermoforming with one for the movement of the pre-stretching die constructively complex drive accomplished which must be undesirable high tooling costs. Next is a disadvantage that such deformed semi-finished products so-called Have quenching marks, by the movement of the Vorstreckstempels and while The deformation of the semifinished product caused material expansion in the semifinished product caused.

Of the The present invention is therefore based on the object, a device and a method of thermoforming thermoplastic, preferably to provide sheet-like semi-finished products, by means of which a thermoforming process can be improved and simplified.

According to the invention this Task with a device according to the features of claim 1 and a method according to the features of claim 7.

Advantages of invention

With the device according to the invention as well as the method according to the invention for thermoforming of thermoplastic, preferably sheet-like Semi-finished products thereby improve and simplify a thermoforming process that a pre-deformation of the semifinished product by means of one with the first Form part of the mold of a tool firmly connected Vorstreckstempels when open Form takes place and the semi-finished by means of closed form a pressure gradient applied to the preformed semifinished product in his final Shape is spent.

The means that, for example, on a structurally complex drive for the Vorstreckstempel, which in known from practice devices is required for thermoforming, can be dispensed with. Thereby on the one hand, a control and regulatory effort in the inventively running device with fixed pre-stretch stamp in comparison to out of practice known devices reduced because only a movement of a or both moldings of the device for closing and opening the mold controlled and must be regulated. On the other hand, reduce without the drive for the Vorstreckstempel the tooling costs, so that the production costs decline.

In addition exists the possibility, during the Vorverformungsprozesses of the semi-finished by the pre-stretch die, which during a closing movement the shape, d. H. at least partially when the mold is open, is performed, u. U. a tightening of further semi-finished material in the interior allow the shape, so that a change in the thickness of the semifinished product while the pre-deformation process compared to conventional thermoforming processes is reduced.

This offers the possibility, Semi-finished products with lower material thickness than conventional thermoforming processes which, inter alia, during an upstream of the deformation process warming up of the semifinished product a lower energy input for heating the Semi-finished product is required.

Further Advantages and advantageous embodiments of the subject to The invention are the description, the drawings and the claims removed.

drawing

An embodiment of the erfindungsge The device for thermoforming sheet-like semi-finished products is shown in the drawing during various process phases and will be explained in more detail in the following description. Show it

1 the device according to the invention during a first process phase with the mold open;

2 the device according to 1 during a second process phase, during which a semifinished product to be deformed is introduced between the two molded parts of the device;

3 the device according to 1 during a third process phase or a pre-deformation phase of the semifinished product;

4 the device according to 1 at the end of the pre-deformation phase, when the shape of the device is closed;

5 the device according to 1 at the end of a molding phase, when the semi-finished product has its final shape; and

6 the device according to 1 at the end of the thermoforming process, when the mold is fully opened and the formed semi-finished product is removable from the mold.

description of the embodiment

Referring to 1 is a device 1 for thermoforming of thermoplastic, preferably sheet-like semi-finished with one of a first molded part 2 and a second molded part 3 existing form 4 in which the thermoplastic and in 2 detailed semifinished product 7 is brought from a substantially planar shape in a desired deformation position.

In this case, the device according to the invention 1 as well as the inventive thermoforming process for the production of cup-like containers, preferably with round, oval or similar shapes, particularly suitable. Such containers are used, for example, for packaging pharmaceutical products, such as tablets, capsules or the like.

So is the subject of the invention for the manufacture of products suitable, in which a pressure gradient applied to the semi-finished product alone is not is sufficient to the desired final form to be able to produce.

The two molded parts 2 and 3 limit in the closed state of the form 4 an interior 5 the form 4 in which one with the first molding 2 or the mask of the form 4 firmly connected pre-stretch stamp 6 is arranged. The second molding 3 or the mold bottom of the mold 4 is in relation to the first molding 2 slidably disposed such that the second molded part 3 in the in the 2 to 6 shown positions can be brought. The required drive is well known from practice, which is why dispense with a more detailed description of the drive.

Furthermore, of the second molding 3 the part of the interior 5 limited, the final shape of the semifinished product 7 represents negative at the end of the thermoforming process.

The second molding 3 facing end of Vorstreckstempels 6 is essentially hemispherical in shape and in other applications may also be of any other shape. It is of course at the discretion of the expert, the second molding 3 facing end of Vorstreckstempels run with an optimized to achieve the final shape of the semi-finished mold.

That means the shape of the second molding 3 facing end of Vorstreckstempels 6 depending on the desired final shape of the semi-finished product to be deformed 7 adapted so that the semifinished product 7 during a Vorverformungsphase of the semifinished product 7 by means of the pre-stretching punch 6 is brought into a defined Vorverformungslage that the semifinished product 7 during a subsequent deformation phase, during which the semi-finished product is brought into its final deformation position, is particularly easy to bring in its desired shape.

Referring to 2 is the device 1 for the thermoforming of thermoplastic semi-finished products still shown in the open state, wherein the film-like, thermoplastic semifinished product 7 between the two moldings 2 and 3 introduced in a conventional manner. The semi-finished product 7 is before putting in the mold 4 to its forming temperature, in the material-dependent thermoelastic temperature range of the semifinished product 7 lies, has been heated.

The semi-finished product 7 is per per container to be generated in each case in a circular area 8th with a diameter c in not shown and in the process of the mold 4 heated upstream of several heating stations, the heating stations, for example, designed with Kontaktheizplatten tempering. After heating the semifinished product 7 this will be in the in 2 illustrated manner between the two mold halves 2 and 3 the form 4 brought in. In the device 1 finds itself kei ne further heating of the semifinished product in the circular area 8th instead of.

The semi-finished product 7 is doing with such a distance a to the first molding 2 between the two moldings 2 and 3 introduced that contact between the semifinished product 7 and the pre-stretch stamp 6 is avoided. This means that the distance a of the semi-finished product 7 from the second molding 3 facing side of the first molded part 2 is greater than the dimension b to which of the pre-stretch stamp 6 from the first molded part 2 in the direction of the second molded part 3 cantilevered.

Subsequently, the second molded part 3 in the direction of the first molded part 2 moved, with the semifinished product 7 in the in 3 and 4 shown manner of the second molding 3 in the direction of the first molded part 2 is guided and in a heated annular area 9 of the circular area 8th , which is a circular ring segment with the width e or with the outer diameter c and the inner diameter d, on the lower mold part 3 rests. This is the semi-finished product 7 during the closing process of the mold 4 increasingly over the Vorstreckstempel 6 guided and brought into a predefined state of deformation.

Because the semifinished product 7 during the closing process of the mold 4 the device 1 for thermoforming of thermoplastic semi-finished products not yet between the two moldings 2 and 3 is clamped, can from the tempered annular area 9 during the Vorverformungsphase of the semi-finished material of the semifinished product 7 about the diameter d of the molding 3 in the interior 5 the form 4 to be pulled. The ses during the Vorverformungsprozesses of the semi-finished product 7 tracked material of the semi-finished product 7 in the interior 5 is in addition to the original in the area of the interior 5 arranged material of the semifinished product 7 deformed, whereby a smaller reduction or constriction of the thickness of the semifinished product 7 in the now deformed area of the semifinished product 7 occurs, resulting in a higher strength of the deformed semi-finished product 7 or the molding leads.

In order to Advantageously, there is generally the possibility for the thermoforming process Use semi-finished products with lower material thicknesses, which on the one hand a lower use of materials and on the other hand a reduced Energy input when heating of the semi-finished product before and during the thermoprocess is required.

In the 4 The illustrated process phase of the thermoforming process shows the shape 4 the device 1 in the closed state, the semifinished product 7 through the interior 5 protruding pre-stretch stamp 6 brought into its predefined Vorverformungslage.

Subsequently, the preformed semi-finished product 7 with between the pre-stretch stamp 6 and the first molded part 2 in the interior 5 the form 4 acted upon in such a manner known per se compressed air such that on the semifinished product 7 a pressure gradient is applied. This pressure gradient causes that due to the heating elastic and preformed semi-finished 7 further deformed and to the through the second molding 3 predetermined contour of the interior 5 conforms to the shape and to the walls of the second mold part 3 invests. The semi-finished product 7 points in the in 5 position shown its final shape.

The second molding 3 is at the first molding 2 opposite end of the interior 4 with several vent holes 10 executed, so that between the semifinished product 7 and the second molded part 3 during the application of the preformed semifinished product 7 with compressed air no the final molding process of the semi-finished product 7 can build up counteracting pressure.

In a variant of the method according to the invention for thermoforming of thermoplastic, preferably sheet-like semi-finished products, it is provided that during the final deformation process of the semifinished product 7 on the semifinished pressure gradient over a in the interior 5 the form 4 in the area between the semifinished product 7 and the second molded part 3 over the ventilation holes 10 generated vacuum on the semifinished product 7 is applied to the semifinished product 7 in the in 5 and 6 to bring shown final shape.

The admission of the semifinished product 7 with the compressed air and the contact of the semifinished product with the walls of the second molding 3 leads to a cooling of the semifinished product 7 under pressure to a temperature at which the semifinished product 7 or the molding is dimensionally stable. When this temperature is reached, the final molded semi-finished product 7 in the in 6 illustrated manner by opening the mold 4 demolded and can be removed from the device 1 be removed.

This is the second molding 3 such from the first molding 2 moved away that shaped semi-finished product 7 without contact with the moldings 2 . 3 or with the pre-stretch stamp 6 from the device 1 can lead.

The above-described thermoforming process according to the invention, wherein the thermoplastic film-like semi-finished product 7 in non-jammed condition on the pre-stretch stamp 6 is guided, bie tet also has the advantage that in the Vorverformungsprozess the semifinished product 7 occurring gliding of the semifinished product 7 around the pre-stretch stamp 6 takes place in a more favorable for the manufacturing quality of the desired molding as the manner during the Vorverformungsprozesses already clamped semi-finished products is the case.

The higher production quality results u. a. from the fact that by the thermoforming process according to the invention produced moldings have significantly less quenching marks as molded parts, which according to conventional Thermoforming be adjusted.

Especially in the preparation according to the invention of coffee cream cups with longitudinal ribs presents a significantly better shape of the cup, in particular in the area of the longitudinal ribs, compared to conventional Thermo-processed products. Furthermore, according to the invention are produced Coffee cream mug characterized by a more stable cup shape, there while the Vorverformungsprozesses of the semifinished product continuously material of the semifinished product was carried out in the manner described above and the coffee cream cups produced only little quenching marks exhibit.

Claims (8)

Contraption ( 1 ) for thermoforming of thermoplastic, preferably sheet-like semi-finished products ( 7 ) with one of a first molded part ( 2 ) and a second molded part ( 3 ) existing form ( 4 ) and with a pre-stretch stamp ( 6 ), wherein the second molded part ( 3 ) with respect to the first molded part ( 2 ) for opening and closing the mold ( 4 ) is movable, and wherein the semifinished product ( 7 ) in the heated state via the pre-stretch punch ( 6 ) deformable and over a on the preformed semi-finished ( 7 ) applied pressure gradient can be brought into its final form, characterized in that the Vorstreckstempel ( 6 ) with the first molded part ( 2 ) and is positioned in the mold such that the semifinished product ( 7 ) during a closing movement of the mold ( 4 ) by the pre-stretch stamp ( 6 ) is deformable, wherein the semifinished product ( 7 ) when the mold is closed ( 4 ) by the applied pressure gradient in its final form ( 4 ) can be brought. Apparatus according to claim 1, characterized in that the semifinished product ( 7 ) with the mold open ( 4 ) between the first molded part ( 2 ) and the second molded part ( 3 ) can be arranged that the semifinished product ( 7 ) during the closing of the mold ( 4 ) of the second molded part ( 3 ) over the pre-stretch stamp ( 6 ), wherein during the pre-stretching process of the semifinished product ( 7 ) increasingly semi-finished products ( 7 ) in one of the first molded part ( 2 ) and the second molded part ( 3 ) limited interior space ( 5 ) the form ( 4 ) is feasible. Apparatus according to claim 1 or 2, characterized in that a second molded part ( 3 ) facing end of Vorstreckstempels ( 6 ) a the second molded part ( 3 ) facing side of the first molded part ( 2 ) in such a way that the semifinished product ( 7 ) during the closing of the mold ( 4 ) can be brought into a predefined deformation state. Device according to one of claims 1 to 3, characterized in that the pressure gradient by means of a starting from the first molded part ( 2 ) on the semi-finished product ( 7 ) applied compressed air flow to the preformed semi-finished product ( 7 ) is created. Device according to one of claims 2 to 4, characterized in that in the region of the second molded part ( 3 ) limited part of the interior ( 5 ) the form ( 4 ) several vent holes ( 10 ) are provided. Device according to one of claims 1 to 5, characterized in that a second molded part ( 3 ) facing end of Vorstreckstempels ( 6 ) with a to the material of the semi-finished product ( 7 ) and to a final embodiment of the semifinished product ( 7 ) adapted form is executed. Process for the thermoforming of thermoplastic, preferably sheet-like semi-finished products ( 7 ) with a device ( 1 ) characterized by the following method steps: a) heating of the semifinished product ( 7 ) to its forming temperature, before introduction of the semifinished product ( 7 ) to the shape ( 4 ) to a predefined circular area ( 8th ); b) insertion of the semifinished product ( 7 ) between the first molded part ( 2 ) and the second molded part ( 3 ); c) closing the mold, wherein the semifinished product ( 7 ) from that in the direction of the first molded part ( 2 ) moving second molded part ( 3 ) in such a way over the Vorstreckstempel ( 6 ), that the semi-finished product ( 7 ) when the mold is closed ( 4 ) has a defined Vorverformungslage; d) applying the preformed semifinished product ( 7 ) with a pressure gradient when the mold is closed ( 4 ), so that the semifinished product ( 7 ) is further deformed; e) cooling the deformed semifinished product ( 7 ) under forced forming to a temperature at which the deformed semifinished product ( 7 ) is dimensionally stable. A method according to claim 7, characterized in that at least during the closing operation of the mold ( 4 ) and the drawing of the semifinished product ( 7 ) over the pre-stretch stamp ( 6 ) Material of the semi-finished product ( 7 ) from the support area ( 8th ) of the semifinished product ( 7 ) on the second molded part ( 3 ) in the interior ( 5 ) the form ( 4 ) to be led.