WO2018134429A1 - Method for producing plastics vessels with base regions which are movable relative to one another, and corresponding deformation device - Google Patents

Abstract

A method for deforming plastics parisons to form plastics vessels (10), wherein the plastics parisons are expanded to form the plastics vessels (10), by being subjected to a flowable medium, within a cavity (28) formed by a blow mold (20), wherein the blow mold (20) has a base part (22) which delimits the cavity (28), wherein the base part (22) has at least one first region (24) and one second region (26), wherein the second region (26) of the base part has at least one segment (261, 262) which extends in a radial direction along the base part, and the second region (26) is moved relative to the first region (24) during the expansion process.

Description

 METHOD FOR MANUFACTURING PLASTIC CONTAINERS WITH FIXED FLOOR AREAS AND CORRESPONDING FORMING DEVICE

description

The present invention relates to a method and apparatus according to the preambles of claims 1, 6 and 10.

Methods and apparatus for blow molding plastic containers have long been known in the art. In this case, heated plastic preforms are usually subjected to compressed air in order to be converted into plastic containers in this way. For this purpose, the plastic preform is introduced into a blow mold and expanded against an inner wall of this blow mold. In this case, side parts are usually closed around the preform and the blow mold is completed by adding a bottom part downwards. Subsequently, the application of compressed air and in this way the expansion of the preform begins. The blow mold corresponds to the negative of the plastic container to be manufactured.

The bottom part is usually formed in one piece in known embodiments and can - depending on the design - give the expanded plastic container different floor designs.

Recently, in the manufacture of plastic containers, efforts have been made to reduce material consumption further and further to save costs. This leads to the fact that the walls and the bottom of these containers are always made thinner walls. In order to make the bottom of a container with low weight pressure stable, it is known to provide drawstrings that run from the injection point to the bottle outside. This special bottom molding ensures that the plastic container stands on the feet and does not tip over.

In order to mold such a base in plastic containers, the usual base parts of blow molds are provided with rib geometries which form the draw bands during expansion of the plastic preform.

However, this has the disadvantage that these rib geometries first come into contact with the heated plastic preform and freeze the material at these contact points. This results in most of the material hanging on the drawstrings. In contrast, the material thins out in the area of the feet. As a result, both the expression and the wall thickness of the feet on which the plastic container stands deteriorate. In addition, due to the inhomogeneous material distribution, white feet can occur.

The invention is therefore based on the object to provide a method and an apparatus available to provide an improved material distribution in the ground area. In this way, on the one hand, a higher wall thickness can be achieved in the feet of the plastic container and white feet can be avoided. On the other hand, less cooling is required with better stretching and the blow mold is optimally vented. In addition, an increased strength of the plastic containers is achieved because the drawstrings can be stretched higher.

This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

In a method according to the invention for forming plastic preforms into plastic containers, the plastic preforms are expanded within a cavity formed by a blow mold by applying a flowable medium to the plastic containers. In this case, the blow mold has a bottom part which delimits the cavity, the bottom part having at least a first region and a second region. According to the invention, the second region of the bottom part has at least one segment which extends in the radial direction along the bottom part, and during the expansion process the second region is moved relative to the first region. Preferably, the segment which extends in the radial direction along the bottom part, at least in a projection plane is rectilinear. In particular, this is a projection plane which is perpendicular to a longitudinal direction of the plastic preforms to be expanded. The course of the segments in the three-dimensional, however, preferably has a curvature. The course of the segments is preferably continuous.

Advantageously, the first and the second region of the bottom part are mutually movable.

Preferably, the second region of the bottom part forms the drawstrings of the plastic containers. By contrast, the first region of the bottom part preferably forms the feet on which the plastic container stands.

In a preferred embodiment, the second region of the bottom part is moved in particular in the longitudinal direction of the blow mold.

Advantageously, both the first and the second region of the bottom part each have at least two segments which extend in the radial direction along the bottom part. Preferably, both the first and the second region have the same number of segments. In an advantageous embodiment, the segments are arranged in particular rotationally symmetrical. The individual segments are preferably designed so that they expand outward in the radial direction from the central region of the bottom part.

Advantageously, the first region of the bottom part remains immobile in the longitudinal direction during the expansion process relative to a side part of the blow mold. In a preferred embodiment, the second region of the bottom part is located at the beginning of the expansion process in a lowered position with respect to the longitudinal direction of the plastic containers (S1). In another preferred embodiment, the second region of the bottom part is moved to this lowered position (S1) at the beginning of the expansion process. By "lowered" is meant that the distance to the mouth region of the blower form is enlarged. The central region of the bottom part preferably remains unmoved during the expansion process with respect to a side part of the blow mold in the longitudinal direction. However, it is also conceivable that the central area is also moved during the expansion process.

In a preferred method, the second portion of the bottom portion in the lowered position (S1) is farther from the plastic preform to be expanded than the first portion of the bottom portion. In this way it can be achieved that the plastic preform to be expanded can expand unhindered at the beginning of the blowing process, without coming into contact with the second region of the bottom part.

It is preferably achieved in the context of the expansion process that the plastic preform first comes into contact with the first region of the bottom part and only then in contact with the second region of the bottom part. In this way it can be prevented that the plastic material first comes into contact with the blow mold in the region of the tension bands and freezes at these contact points. In a preferred method is achieved instead that the material first rests in the foot area of the blow mold and solidifies. Thus, the feet can be molded very stable, without too much material in the range of drawstrings "hang".

In an advantageous method, the expansion of the plastic preform is carried out with at least two different pressures. In a first expansion phase (also: pre-blowing phase), the pressure (p1) is preferably lower than the pressure (p2) in a second expansion phase (also: production phase). Between the pre-blowing phase and the production phase, the expansion can advantageously take place at a second pressure p 1 (also: intermediate blow phase). The pressure p, is preferably between the pressure p1 and the pressure p2. The beginning and end of the respective expansion phases are preferably defined by the switching of valves. Thus, for example, a first valve can be closed and a second valve can be opened substantially at the same time in order to switch over from a pre-blowing pressure p1 to the intermediate-blowing pressure pi

At the beginning or during the second expansion phase, the second region of the bottom part is preferably moved from the lowered position (S1) into a position (S2) raised with respect to the longitudinal direction of the plastic containers. A "raised" position is understood to mean that the distance to the mouth region of the blow mold is reduced becomes. This means that the second area of the bottom part approaches the material bubble during the expansion phase.

 The drawstrings of the material bladder advantageously only move against when the plastic material has already come into contact with the first region of the bottom part during the preblowing phase. The material bubble is thus formed evenly during pre-blowing and lays down first in the area of the feet. In a particularly advantageous method, the material bubble is therefore first in the foot and solidifies; only then are the drawstrings of the material bubble countered and the soil thus completely formed. In this way, a particularly homogeneous material distribution can be achieved. This in turn means that it prevents the feet of the plastic container are white. This also ensures that the feet are optimally pronounced. Due to the better stretching, less cooling is also necessary. In addition, the optimal ventilation of the soil is achieved during the expansion process.

The present invention is further directed to a forming device for forming plastic preforms into plastic containers. The forming device has at least one blow mold which, in a closed state, forms a cavity within which the plastic preforms can be expanded by being exposed to a flowable medium to the plastic containers. The blow mold in turn has a bottom part which delimits the cavity, wherein the bottom part has at least a first region and a second region.

According to the invention, the second region of the bottom part has at least one segment which extends in the radial direction along the bottom part. According to the invention, the second region of the bottom part is movable relative to the first region during the expansion process.

In this case, this conversion device is set up in particular and provided for carrying out the method described above, i. that all the features carried out for the method described above are also disclosed for the forming device described here, and vice versa.

In an advantageous embodiment, the transformation station has two side parts. Preferably, the first side part is arranged on a first Blasformträgerteil and the second side part of a second Blasformträgerteil, these two Blasformträgerteile with respect to each other for opening and closing the blow mold with respect to at least one predetermined pivot axis are pivotally.

 In a further advantageous embodiment, the forming device has a so-called stretch rod or generally a rod-like body, which serve to stretch the plastic preforms in the longitudinal direction thereof.

Advantageously, the forming station has a blowing nozzle, via which the blow mold and in particular the plastic preform a flowable medium and in particular a gaseous medium and in particular compressed air can be fed to expand this plastic preform.

The forming station is advantageously arranged on a movable carrier, in particular a rotatable carrier. Preferably, a plurality of forming stations is arranged on this movable support.

The first and the second region of the bottom part can be separated from one another by a gap, for example. In particular, in an advantageous embodiment, the second region of the bottom part is surrounded by a gap. Advantageously, both the first and the second region of the bottom part each have at least two segments which extend in the radial direction along the bottom part. Preferably, at least two of the segments meet in the central region of the bottom part. Advantageously, the first and the second region of the bottom part have the same number of segments. Each region preferably has between 3 and 1 1 segments, more preferably between 3 and 9 segments and more preferably between 4 and 8 segments.

In an advantageous embodiment, the segments are arranged in particular rotationally symmetrical. The individual segments are preferably designed so that they expand outward in the radial direction from the central region of the bottom part. The course of the segments is preferably continuous.

Preferably, the feet of the plastic containers can be formed by the first region of the bottom part. By the second region of the bottom part are preferably the drawstrings the plastic containers ausformbar. The second region of the bottom part thus preferably corresponds to the drawstring geometry.

In a particularly preferred embodiment, the second area of the bottom part is further away from the plastic preform to be expanded than the first area of the bottom part in a lowered position (S1) with respect to the longitudinal direction of the plastic containers.

The bottom part is preferably designed as a two-part bottom cup, in which the Zugbandgeo- geometry can be sunk.

In an advantageous embodiment, the forming device also has a drive device to move the second region of the bottom part. The drive is preferably a pneumatic drive. However, it may also be a hand crank, an electric motor or another drive such as a hydraulic drive.

The present invention is further directed to a bottom portion for a blow mold for expanding plastic preforms into plastic containers by exposure to a flowable medium. The bottom part defines the cavity of the blow mold, in which the plastic preform is expanded, and has at least a first region and a second region.

According to the invention, the second region has at least one segment which extends in the radial direction along the bottom part, and according to the invention the second region of the bottom part is movable relative to the first region during the expansion process.

In this case, this bottom part is especially adapted and intended to serve as the bottom part of the above-described forming device.

Further advantages and embodiments will be apparent from the attached drawings, in which: Fig. 1 is a plastic container, as is advantageous from the present invention

Way can be made;

Fig. 2 is a schematic representation of a blow mold according to the invention;

Fig. 3 is an illustration of the bottom part according to the invention, in which the second

 Area is in lowered position S1;

4 is a sectional view of the bottom part according to the invention, in which the second area is in the lowered position S1;

Fig. 5 is an illustration of the bottom part according to the invention, in which the second

 Area is in the extended position S2;

Fig. 6 is a sectional view of the bottom part according to the invention, in which the second region is in the extended position S2.

The present invention makes it possible to expand plastic preforms into plastic containers in a particularly advantageous manner. FIG. 1 shows a possible embodiment of a finished plastic container. This plastic container 10 has an orifice 12 and a base body 14 adjoining this orifice. A base section 2 adjoins this base 14.

The reference character L refers to a longitudinal direction of the plastic container 10, the reference numeral R to a radial direction of the container bottom. 2

It can be seen that the bottom portion 2 has a plurality of feet 4, with which the plastic container 10 can stand upright on a straight surface. Between the individual feet 4, the bottom portion grooves, so-called drawstrings 6, on. The drawstrings also serve the stability of the soil.

Fig. 2 shows a schematic representation of the blow mold 20 according to the invention. The reference numeral 30 denotes a side part of the blow mold 20. The second side part of the blow mold is not shown in order to enable a better representation of the invention essential features. In a closed state of the blow mold, the second side part would be arranged symmetrically on the illustrated side part 30, so that a cavity 28 is formed between the side parts. In this cavity, the Kunststoffvoi ormling is expanded by exposure to a flowable medium to a plastic container.

The cavity 28 is limited except by the side parts of the bottom part 22. The bottom part 22, in turn, consists of two separate regions 24 and 26. The design of the bottom part 22 is shown in more detail in FIGS. 3 and 4. On the side opposite the bottom part 22 of the blow mold 20 is the mouth region 34 which receives the mouth 12 of the plastic container. For the purposes of this patent application, the term "top" means the blowing region of the mouth region 34. Accordingly, "lifted" means a position closer to the mouth region 34 and "lowered" means a position further away from the mouth region 34.

3 and 4 show the bottom part 22 at a time when the second area 26 of the bottom part is in a lowered position S1. The first region 24 of the bottom part includes the entire region, which extends in a star-shaped manner radially outwards starting from the central region 32 of the bottom part and is in a position raised in relation to the region 26. The first region 24 has a plurality of recesses in which the second region 26 is located (in the lowered position). Since the second region 26 in FIGS. 3 and 4 is in the lowered position, edges (251, 252) can be seen between the first and the second region. The arrangement is basically also conceivable in reverse, i. that the first area is raised.

The first region 24 has a plurality of segments 241, 242. For reasons of clarity, only two segments have been labeled, even if, in the exemplary embodiment illustrated in FIG. 3, the first region 24 actually has five segments. Of course, depending on the desired bottle shape, any other number of segments is also possible.

The second region 26 also has a plurality of segments 261, 262. Again, for reasons of clarity again only two (instead of the existing five) segments were labeled. In the illustrated embodiment, both the segments 241, 242 of the first region 24 and the segments 261, 262 of the second region 26 coincide in the center of the bottom portion 22. However, the invention also relates to such soil forms in which not all segments meet in the middle of each other. For example, in particular the segments of the second region 26 can be made significantly smaller so that these segments end already at a greater radial distance from the central region 32 of the bottom part. Also, the individual segments 241, 242 and 261, 262 need not all be identical. For example, the second region 26 could have segments of different sizes and shapes.

Figs. 3 and 4 show the bottom part 22 in the state in which it is preferably at the beginning of the expansion process, or in which it is brought. When the plastic preform is expanded toward the plastic container, the plastic preform expands and the plastic material first strikes the first region 24. The feet 4 of the plastic container 10 are formed from this region 24. Only during the blowing process, the second area 26 is moved upwards.

Figs. 5 and 6 illustrate the bottom part in this state, in which the second area 26 has been moved upwards to the position S2. Here, too, the areas 24 and 26 can be recognized, each area again having a plurality of segments. Again, not all segments have been labeled for clarity.

It can be seen in FIGS. 5 and 6 that the regions 24 and 26 abut one another in this state so that no edge is formed between the regions 24 and 26, but a smooth transition is given. In this position of the second region 26, the blow mold 20 forms the negative of the plastic container 10 to be produced. In particular, the bottom portion 2 of the plastic container 10 should be formed continuously and without edges. A part of the second region 26 protrudes in this raised position S2 in the longitudinal direction L of the blow mold 20 further upwards than the first region 24. As a result, at these points the plastic preform is pressed inwards during the expansion process. In this way, the drawstrings 6 of the plastic container 10 are formed by the second region 26. The Applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided that they are novel individually or in combination with respect to the prior art. It is further pointed out that features have also been described in the individual figures, which in themselves can be advantageous. The person skilled in the art immediately recognizes that a particular feature described in one figure can also be advantageous without taking over further features from this figure. Furthermore, the person skilled in the art recognizes that advantages can also result from a combination of several features shown in individual or in different figures.

LIST OF REFERENCE NUMBERS

2 floor section

 4 stand

6 drawstring

 10 plastic container

 12 estuary

 14 basic body

 20 blow mold

22 bottom part

 24 first area of the bottom part

 26 second area of the bottom part

 28 cavity

 30 side panel

32 central area of the bottom part

 34 mouth region of the blow mold

 241, 242 segments of the first region of the bottom part

 251, 252 edges between the first and second region of the bottom part

 261, 262 segments of the second region of the bottom part

L longitudinal direction of the plastic container / blow mold

 R Radial direction of the bottom section / bottom section

 51 lowered position

 52 raised position

Claims

claims 1 . A method of forming plastic preforms into plastic containers (10), wherein the plastic preforms are expanded within a cavity (28) formed by a blow mold (20) by applying a flowable medium to the plastic containers (10), the blow mold (20) forming a bottom part (22), which delimits the cavity (28), wherein the bottom part (22) has at least a first region (24) and a second region (26), characterized in that  the second region (26) of the bottom part has at least one segment (261, 262) extending in the radial direction along the bottom part, and during the expansion process the second region (26) is moved relative to the first region (24). 2. Method according to the preceding claim,  characterized in that  the first region (24) of the bottom part during the expansion process remains unmoved relative to a side part (30) of the blow mold (20) in the longitudinal direction and the second region (26) of the bottom part at the beginning of the expansion process in a with respect to the longitudinal direction of the plastic containers ( 10) lowered position (S1) or is moved to the beginning of the expansion process in this lowered position (S1). 3. Method according to at least one of the preceding claims,  characterized in that  the plastic preform first comes into contact with the first portion (24) of the bottom portion during the expansion process and only thereafter in contact with the second portion (26) of the bottom portion. 4. The method according to at least one of the preceding claims, characterized in that the expansion of the plastic preform is performed with at least two different pressures, wherein the pressure (p1) in a first expansion phase is lower than the pressure (p2) in a second expansion phase. 5. Method according to the preceding claim,  characterized in that  the second region (26) of the bottom part is moved at the beginning or during the second expansion phase from the lowered position (S1) into a position (S2) raised with respect to the longitudinal direction of the plastic containers (10). 6. forming device for forming plastic preforms Kunststoffbe conditions (10) with at least one blow mold (20) which forms a cavity (28) in a closed state, within which the plastic preforms by applying a flowable medium to the plastic containers (10) expandable wherein the blow mold (20) has a bottom part (22) which delimits the cavity (28), the bottom part (22) having at least one first region (24) and a second region (26),  characterized in that  the second portion (26) of the bottom portion has at least one segment (261, 262) extending radially along the bottom portion (22) and the second portion (26) of the bottom portion is movable relative to the first portion (24) during the expansion operation is. 7. Forming device according to the preceding claim,  characterized in that  both the first (24) and the second region (26) of the bottom part each have at least two segments (241, 242, 261, 262) which extend in the radial direction in a straight line along the bottom part (22) and at least two segments ( 241, 242, 261, 262) in the middle of the bottom part (22) meet. 8. Forming device according to at least one of the preceding claims, characterized in that  the feet (4) of the plastic containers (10) can be formed by the first region (24) of the bottom part. 9. Forming device according to at least one of the preceding claims, characterized in that  the second region (26) of the bottom part in a position (S1) lowered in relation to the longitudinal direction of the plastic containers (10) is further away from the plastic preform to be expanded than the first region (24) of the bottom part. 10. Bottom part (22) for a blow mold (20) for expanding plastic preforms to plastic containers (10) by applying a flowable medium, which limits the cavity (28) of the blow mold (20) in which the plastic preform is expanded, and having at least a first region (24) and a second region (26),  characterized in that  the second region (26) has at least one segment (261, 262) extending in the radial direction along the bottom part (22), and the second region (26) of the bottom part is movable relative to the first region (24) during the expansion process ,