Method for manufacturing a container

Abstract

A method for producing a container, which consists of an outer container and an inner bag, has a container opening and an aperture in the outer container, wherein in the bottom region of the container excess material is extruded and a tab is formed, the welded bottom seam of the inner bag is clamped and held in the axial direction in the tab, and by means of a pressure medium the parison is blown against the wall of the blow mould and removed from the blow mould, then an aperture is formed in the wall of the outer container, the inner bag is separated from the wall of the outer container and is again applied thereto, at opposite locations in the wall of the outer container an aperture is formed respectively, and a pin-shaped tool pushes the inner bag from the wall of the outer container back a predetermined distance through the aperture and is separated therefrom, then a pressure medium, preferably compressed air, is introduced through the aperture into the intermediate space between the inner bag and the outer container, which substantially separates the entire inner bag from the wall of the outer container.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a container, preferably a bottle, which consists of a substantially rigid outer container and an easily deformable inner bag, which are made of thermoplastic plastics which do not form a welded connection with one another, wherein the container has a container opening and at least two wall openings in the outer container, through which a pressure equalization in the intermediate space between the inner bag and the outer container is achieved when the container contents are discharged, wherein in the method a parison consisting of at least two hoses is co-extruded and arranged between the open half-molds of a blow mold, and when the parison has the length required for producing the container, the blow mold is closed, wherein in the bottom region of the container to be produced the excess material is extruded and a tab is formed from the welding material of the outer container, the welded bottom seam of the inner bag is clamped and held in the axial direction in the tab, and wherein the parison is blown through a pressure medium to lie against the walls of the blow mold and is removed from the blow mold, then the wall openings are formed and the inner bag is separated from the walls of the outer container and lies against them again. BACKGROUND

[0002] Such a method has been known for a long time. DE 4139555 C2 discloses a container produced in this way, in which the wall openings are formed by the fact that, when the blow mold is closed, the radially protruding material of the parison is extruded in the shoulder region of the bottle-shaped container, whereby an un-welded, open opening is produced at the shoulder.

[0003] EP 0 912 420 B1 proposes that the wall openings in the outer container be formed at an angle of 90° to the plane defined by the bottom seam and the longitudinal axis of the container, so that the inner bag can be folded flat when the container contents are discharged. In this way, the container contents can be discharged with a reduced residual amount, wherein the negative pressure produced in the inner bag is also smaller.

[0004] In order to bring the container contents out as completely as possible by means of a gasless pump or by applying external pressure at the extruded bottle, it has proven to be advantageous to separate the inner bag from the walls of the outer container before the container is filled, the inner bag lying against the outer container with considerable adhesion. It has been shown here that the separation can only be carried out in an inconsistent or incomplete manner, especially in the region of the shoulder of the container, so that a small residual amount of the container contents cannot be discharged. However, a more serious problem also arises when the inner bag is deformed irregularly and partially folded, especially in the region of the transition to the shoulder region during the separation process, which in some cases can lead to a white crack in the bag material, so that it can lead to a damage to the diffusion barrier of the inner bag through the damaged site or even to a bag that is not sealed.

[0005] The applicant has found that when the parison is blown to lie against the walls of the blow mould, the inner bag has a different wall thickness in the circumferential direction, more precisely so that the inner bag is thicker in the region of the vertical plane extending through the bottom seam than in the wall region located therebetween. An explanation for this can be that when the bottom seam is pressed out, the parison is flattened together from the initially cylindrical shape, wherein the subsequent blowing produces a greater cylindrical shape with the above-mentioned greater wall thickness in the region above the end of the bottom seam.

[0006] The greater wall thickness in the mentioned peripheral region of the blown container can lead to the inner bag being deformed irregularly upon separation, wherein in particular in the transition region to the shoulder section of the container a crumpled buckling can be configured, which in turn can lead to a white crack of the inner bag, through which the vapor diffusion layer of the inner bag or even the inner bag itself can be damaged. A container damaged in this way, together with the container contents, cannot be used. SUMMARY

[0007] It is an object of the present application to give a method with which a usable container can be produced in which the above-mentioned damage is avoided.

[0008] This object is achieved according to the present application by the features of technical solution 1.

[0009] Advantageous designs of the present application are described in other technical solutions.

[0010] It is provided according to the present application that in the produced blown container, holes are formed in the wall of the outer container at oppositely located points on the intersection of the plane defined by the bottom seam and the longitudinal axis of the container with the wall of the container, and a pin-shaped tool pushes the inner bag back from the wall of the outer container through the holes by a predetermined distance and thereby separates it from the wall, and then a pressure medium, preferably compressed air, is introduced through the holes into the intermediate space between the inner bag and the outer container, which substantially separates the entire inner bag from the wall of the outer container.

[0011] Here, when the pin-shaped tool is formed as hollow, the pressure medium can be blown through the pin-shaped tool or, for example, through the pressure vessel in which the container is arranged.

[0012] The holes can be formed in the container at any height in the mentioned peripheral region. However, it is particularly advantageous to propose that when the container has a bottle shape, the holes are configured in the shoulder region of the container, wherein the holes can also be formed adjacently below or above the shoulder region.

[0013] It is also very advantageously provided that the holes are formed by ring knife cutting, as described in DE 197 37 964 C1. However, the use of a rotating tubular knife (Rohrmesser) for producing through-holes in the outer container is also within the scope of the application.

[0014] With the method according to the application, the inner bag can be smoothly separated from the wall of the outer container over its entire circumference, whereby damage to the inner bag or even its unsealing is avoided. Since the inner bag can be separated from the wall of the outer container uniformly and completely, it is also possible to avoid a large amount of residue that cannot be brought out with the contents, as is the case in the event of incomplete separation. BRIEF DESCRIPTION OF DRAWINGS

[0015] Further features of the application result from the following description of a bottle-shaped container manufactured with the method according to the application. Herein are shown:

[0016] Figures 1A to 1D Different views and vertical sections of the container are shown;

[0017] Figure 2 A container is shown, which has a punch pin for separating the inner bag from the wall of the outer container. DETAILED DESCRIPTION

[0018] The container 1 shown in the figures comprises a neck region 2, which transitions via a shoulder region 3 into a wider region 4. The container 1 is composed of a substantially rigid outer container 5 and an easily deformable inner bag 6.

[0019] A straight extrusion seam 7 is located at the bottom of the container, in which the inner bag 6 is held.

[0020] Figure 1B A side view of a hole 8 through the wall of the outer container 5 is shown, which lies in a vertical plane through the welded bottom seam 7 and the central longitudinal axis of the container 1. Figure 1C and Figure 1D It is shown that two holes 8 are formed in the wall of the outer container 6 in an opposite manner. That is, the two holes 8 are not staggered in the circumferential direction relative to the plane, as is the case in the prior art.

[0021] The two holes 8 are located in the transition region of the wide portion 4 of the container 1 to its shoulder region 3.

[0022] The figures also show that the holes 8 are not formed by a drilling tool, but by ring knife cutting, as is preferred.

[0023] Figure 2The device 9 with the punch pin 10 is shown, which presses the inner bag 6 at a distance to the interior of the container 1 through the hole 8, in order to separate the inner bag 6 in the surrounding area from the wall of the outer container 5, then the separation process is continued by the device 9 or by another device by blowing in compressed air. Figure 2 The right part of the figure shows the device 9 with the retracted punch pin 10.

Claims

1. A method for manufacturing a container, which container consists of a rigid outer container and an easily deformable inner bag, which outer container and inner bag are made of thermoplastic plastics which do not form a welded connection with one another, the container having a container opening and an aperture in the outer container, through which aperture pressure equalization in the intermediate space between the inner bag and the outer container is achieved, wherein a parison consisting of at least two hoses is co-extruded and arranged between the open half-molds of a blow mold, and when the parison has the length required for the manufacture of the container, the blow mold is closed, wherein in the bottom region of the container to be manufactured the excess material is extruded and a tab is formed from the welded material of the outer container, the welded bottom seam of the inner bag is clamped and held in the axial direction in the tab, and the parison is blown through a pressure medium to lie against the walls of the blow mold and to be removed from the blow mold, then an aperture is formed in the wall of the outer container, the inner bag is separated from the wall of the outer container and lies against it again, characterized in that, - an aperture is formed in the wall of the outer container at two oppositely situated points, which apertures lie on a plane defined by the bottom seam, which intersects the longitudinal axis of the container, and - a pin-shaped tool pushes the inner bag back through the apertures over a predetermined distance from the wall of the outer container and thereby separates it from the wall, then a pressure medium is introduced through the apertures into the intermediate space between the inner bag and the outer container, which separates the inner bag from the wall of the outer container. The container has a bottle shape with a shoulder region, the aperture is formed in the shoulder region or adjacently below the shoulder region. The aperture is formed by a ring-shaped cutter. The aperture is formed by a ring-shaped cutter. The aperture is formed by a rotating tubular cutter.

2. The method of claim 1, wherein, The aperture is formed by a rotating tubular cutter.

3. The method of claim 1, wherein, The pressure medium is compressed air.

4. The method of claim 2, wherein, The compressed air is introduced through the pin-shaped tool.

5. The method of claim 1, wherein, The aperture is formed by a ring-shaped cutter.

6. The method of claim 2, wherein, The aperture is formed by a ring-shaped cutter.

7. The method according to any one of claims 1 to 6, characterized in that, The aperture is formed by a rotating tubular cutter.

8. The method of claim 7, wherein, The aperture is formed by a rotating tubular cutter. The pressure medium is compressed air. The compressed air is introduced through the pin-shaped tool.

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