Method for manufacturing a container

Abstract

A method for manufacturing a container, which is composed of an outer container and an inner bag, has a container opening and at least one wall opening in the outer container, wherein in the bottom region of the container excess material is squeezed out and forms a squeeze joint, which has a bottom tab, the welded bottom joint of the inner bag is clamped in and held in the bottom tab in the axial direction, and the parison is blown by a pressure medium to lie against the walls of a blow mold and is removed from the blow mold, the method comprising the following steps: a) removing a section of the bottom tab of the outer container so that a section of the bottom joint of the inner bag is exposed outwardly; b) lifting the exposed section of the bottom joint into the outer container so that an opening between the bottom joint of the inner bag and the outer container is created; c) introducing a pressure medium into the opening, thereby separating the inner bag on both sides from the outer container; d) supplying the pressure medium into the container opening so that the inner bag lies again against the outer container.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a container comprising a substantially rigid outer container and a readily deformable inner bag, the outer container and the inner bag being made of thermoplastics which do not form a welded connection with one another, wherein the container has a container opening and the outer container has at least one wall opening through which pressure equalization in the intermediate space between the inner bag and the outer container is achieved when the inner bag contracts as a result of the discharge of its contents. In the method, a parison composed of at least two layers is co-extruded and arranged between the open halves of a blow mold, wherein the blow mold is closed when the parison has the length required for producing the container. Here, excess material is extruded in the bottom region of the container to be produced and an outwardly projecting tab composed of 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. The parison is then blown with a pressure medium, usually compressed air, to lie against the walls of the blow mold and to be removed from the blow mold. BACKGROUND

[0002] Although the different types of thermoplastics of the outer container and the inner bag do not form a welded connection with one another, if the container is produced in a co-extrusion process according to the above-described method, the different types of thermoplastics will be attached to one another with considerable attachment forces. Before such a container can be used, i.e. filled with a liquid or for example a container content in gel-like form which is then gradually discharged, for example by means of a gasless pump or in the case of a squeeze container by pressing it, the inner bag must be separated from the wall of the outer container and then again lie against it.

[0003] This can be achieved in such a way that a negative pressure is applied to the inner bag through the container opening, whereupon the inner bag suddenly contracts. Here, the inner bag with its bottom seam clamped in the bottom tab of the outer container is more or less detached from the outer container in an uncontrolled manner, wherein it is also possible that the inner bag detaches only at one side. A pressure medium, usually compressed air, is then introduced into the inner bag through the container opening in order to again lie against the outer container, so that the inner bag can take up the preset filling volume.

[0004] A method for separating the inner bag from the outer container is known from DE 10 2006 012 487 B4, in which at least one wall opening is formed by drilling through or piercing the wall of the outer container with a drill bit or a piercing needle, wherein compressed air is introduced into the intermediate space between the container and the inner bag after the wall of the outer container has been completely penetrated. Thereby, the inner bag is detached from the wall of the outer container, wherein the supply of compressed air into the intermediate space between the inner bag and the outer container is only continued until a predetermined pressure value is measured at the container opening previously sealed in the inner bag. Even with this behavior, it is not ensured that the inner bag is detached from the outer container uniformly on both sides.

[0005] If the inner bag does not separate from the wall of the outer container to a large extent uniformly, a relatively high underpressure can arise in the inner bag as a result of the discharge of the filling material, despite the pressure equalization openings in the wall of the outer container. The greater this underpressure, the greater the penetration through the very thin wall of the inner bag and the greater the risk of the inner bag not sealing. If the underpressure in the inner bag is too great, this can also lead to functional problems of the pump, which is provided in most cases, so that the entire container contents cannot be discharged. SUMMARY

[0006] It is an object of the application to specify a method in which the inner bag can be separated from the outer container more uniformly and again be applied to the outer container.

[0007] Furthermore, a device can be specified by means of which the method can be carried out.

[0008] The object is achieved according to the application by the features of the technical solutions 1 and 8.

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

[0010] The method according to the application provides for a first step, in which a small section of the base web of the outer container is removed, so that a section of the base seam of the inner bag, which is clamped in the base web, is exposed outwardly.

[0011] It is preferred here that the section of the base web is cut off, for which the use of a ring-shaped knife is particularly advantageous. The section that is cut off can be located in the middle region of the extrusion seam, viewed in the longitudinal direction of the extrusion seam. Here, the cutting is carried out transversely through the extrusion seam and only to a depth at which the inner bag does not become unsealed.

[0012] The next method step is to lift or press the exposed section of the base seam into the outer container, whereby an opening is produced between the base seam of the inner bag and the outer container. An opening is thus formed on both sides of the base seam of the inner bag, into which opening a pressure medium is introduced during or after the lifting of the base seam, which flows from both sides of the inner bag to the neck region of the container and separates the inner bag from the outer container on both sides here.

[0013] It is preferred that compressed air is used as the pressure medium.

[0014] The exposed section of the base seam can be lifted by any suitably shaped tool, wherein it is particularly advantageous to use a pin-shaped blowing core as the tool, by means of which the pressure medium can be blown into the opening at the same time.

[0015] In the method according to the application, the inner bag is completely separated on both sides in the shortest cycle time without damage, such as Weiβbruch or disadvantageous crease formation, arising here at the inner bag.

[0016] The last step of the method according to the application consists in supplying a pressure medium into the container opening in a manner known per se, so that the inner bag re- adheres at the outer container, more precisely without the inner bag remaining deformed, i.e. without a fold formation, and without a gas pocket (Lufteinschluss) between the inner bag and the outer container, upon separation.

[0017] The outer container and the inner bag can each consist of one or more layers, which do not form a welded connection with one another upon co-extrusion. The outer container usually comprises an oxygen diffusion barrier. In the method according to the application, this oxygen diffusion barrier is cut away only at a small portion of the extrusion seam, at which the container has its highest material density. This results in only a very small diffusion of oxygen into the inner bag.

[0018] Since only a small central section of the extrusion seam of the container is cut away, and this region is precisely defined, especially in use, by the annular knife, the inner bag remains with its welded bottom seam reliably anchored in the unimpaired region of the outer container's bottom tab on both sides, so that the inner bag is fixed in the outer container in the axial direction and can only contract in the radial direction upon emptying the container contents.

[0019] The method according to the application is carried out with the following preferred data at a bottle-shaped container with a volume of 12.5 cm 3 : In a single cut carried out perpendicular to the extrusion seam, the extrusion seam is cut away in the middle over a length of about 4 mm with a cut depth of about 3 mm by means of an annular knife about 27 mm long. The separating tool has a pin-shaped blow core about 7 mm long, wherein the core is introduced by about 2.5 mm. The diameter of the gas pressure nozzle at the core is between 0.5 mm and 1.5 mm, depending on the adhesion of the inner bag.

[0020] The complete, uniform separation of the inner bag from the outer container and the smooth re-adhesion of the inner bag are thus achieved in a significantly shortened work step.

[0021] In other bottle types, the cut-away extrusion seam length and the cut depth can be changed accordingly. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figures 1 to 3 Only the schematic steps of the method according to the application are shown. DETAILED DESCRIPTION

[0023] Figure 1A central vertical section of the container is shown, which comprises a rigid outer container 1 and a tight inner bag 2. The vertical section extends centrally in the longitudinal direction through the bottom squeeze joint 3, at which the welded bottom joint 4 of the inner container 2 is clamped into a bottom tab 5 made of the welding material of the outer container 1.

[0024] In Figure 2 the section 6 of the bottom tab 5 is cut off with a ring knife not shown, so that a section 7 of the bottom joint 4 of the inner bag 2 is exposed outwardly.

[0025] Figure 3 It is shown that the exposed section 7 of the bottom joint 4 is lifted by a core rod 8 into the container, whereby an opening is created between the bottom joint 4 of the inner bag 2 and the outer container 1 into which compressed air is introduced, whereby the inner bag 2 is separated from the inner wall of the outer container 1 on both sides of the squeeze joint 3.

[0026] The device for carrying out the method according to the invention comprises a receiving device for the containers to be processed, a cutting device with a ring knife which removes the section of the squeeze joint of the container fixed in the receiving device in a single cut, and a separating device which comprises a separating pin which is connected to a source of compressed air and is pushed forward and presses the squeeze joint into the container here.

Claims

1. A method for producing 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 thermoplastics which do not form a welded connection with one another, the container having a container opening and at least one wall opening in the outer container, through which wall opening 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 halves 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 excess material is extruded and a press seam is formed, which press seam has a bottom tab made of the welded material of the outer container, the welded bottom seam of the inner bag is clamped in and held in the bottom tab in the axial direction, 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, Its characteristics include the following steps: a) Remove a section of the bottom flap of the outer container, so that a section of the bottom seam of the inner bag is exposed outward; b) Lifting the exposed section of the bottom seam into the outer container, thereby creating an opening between the bottom seam of the inner bag and the outer container; c) A pressure medium is introduced into the opening, thereby separating the inner bag from the outer container uniformly on both sides; d) Supply the pressure medium into the container opening so that the inner bag re-attaches to the outer container.

2. The method of claim 1, wherein, Cut off the section of the bottom tab.

3. The method according to claim 2, characterized in that, Use a circular cutter to cut off the section of the bottom tab.

4. The method according to any one of claims 1 to 3, characterized in that, Remove the centered section of the bottom patch.

5. The method according to claim 4, characterized in that, Cut off the centered section of the bottom patch.

6. The method according to any one of claims 1 to 3, characterized in that, Compressed air is used as the pressure medium.

7. The method according to any one of claims 1 to 3, characterized in that, The exposed section of the bottom seam is lifted by a tool.

8. The method according to claim 7, characterized in that, The air-blowing mandrel is used as a tool to blow the pressure medium into the opening.

9. An apparatus for performing the method according to any one of claims 1 to 8, characterized in that, The device includes: a receiving device in which a container to be processed is fixed; and a cutting device having an annular blade arranged in a forward-advancing manner. A separation device having an air-blowing core rod that is held in a forward-moving manner and connected to a compressed air source.

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