HK1032573B - Tube shoulder and process for its manufacture - Google Patents

Description

The present invention relates to a multilayer tube-shell for a tube and a method for manufacturing such tube-shells according to the general terms of the independent claims.

The state of the art has given rise to various tube-shoulders, which are now made almost exclusively of thermoplastic plastic by injection molding and welded in a further step with the tubular tube body.

Certain plastics, such as polyethylene (PE), have a high permeability to oxygen, carbon dioxide, and odorant and aromatic substances. In the case of tube acultem made from these materials, diffusion causes unwanted substances to enter the tube into the environment or from the environment into the tube, which affects the filling material. To prevent this harmful permeability, tube shoulders usually have a two-layer structure consisting of an outer forming layer and an inner barrier layer.

The material for the forming layer is usually polyethylene (PE) and the material for the barrier layer is polyethylene terephthalate (PET).

The use of multilayer tube casts made of PE and PET has become widespread today. From the state of the art, therefore, various attempts are known to produce multilayer tube casts rationally and economically, e.g. as revealed in US-4,185,757. None of the known solutions fully satisfies. Since tube casts are a mass-produced product, the price is primarily determined by two factors: firstly, the material consumption and, secondly, the cycle time for manufacturing.

The problem of non-adhesive materials has led to inefficient or even impracticable solutions in the current state of technology. These are based, for example, on US-4,185,757, on delicate intersections and cross-sections designed to provide a formless connection between the inner barrier layer and the outer, forming layer of a tube shoulder. These intersections and cross-sections consist, for example, of corresponding grooves and ribs, which are usually attached to the symmetry axis of the tube shoulder and are designed to be forcibly deformed.

Another multilayer tube-shell is described in the European patent application EP 0 130 239. This arrangement is based on the fact that an inner barrier layer adheres to an outer forming layer by friction. This arrangement is unsatisfactory for several reasons: first, the two layers must be assembled in a separate step, second, no secure hold between the two parts is possible, and third, the parts require increased manufacturing precision, which takes into account, inter alia, the curing behaviour of the materials.

US-3,565.293 is a folding tube, consisting of a multilayer tube shell with a barrier layer and an outer layer, with protruding grooves and intersections, may be made of plastic or metal and is manufactured separately.

The parts of the tube-shaped frames described above can generally only be further processed after they have been completely cooled. In addition, it is necessary to connect the individual parts, which are now usually produced separately, in a separate process (also manually).

The present invention is intended to avoid the disadvantages discussed above in connection with the state of the art, on the one hand, by means of the disclosed invention, drastic reductions in material costs are possible and, on the other hand, the manufacturing time is massively reduced and optimized, which results in a better use of the resources invested.

In contrast to the state of the art, which is generally based on forced deformation of cooled parts, the present invention does not wait for the material of the first component to cool, but is further processed in the uncured state, which, on the one hand, significantly saves time and, on the other hand, greatly reduces material consumption, since the layers of the tube shells described here are produced significantly thinner than the conventional tube shells.

The possibility of further processing the first component before the material has been completely cured is made possible by the inventive, manufacturing-optimized design of the tube shoulder, which, unlike the designs known from the state of the art, does not have a unified effect on the manufacturing cycles. Back cuts or delicate slices that are poorly malleable or even have to be deformed are specifically avoided. Large-sized contact surfaces are sought between the individual parts of the tube shoulder, arranged so that no deformation is necessary and resulting in the simplest possible construction of the spray mold. The design is thus optimized so that no negative impact is made on the manufacturing activity, which is compensated for by the deformation of the material.

The invention makes it possible for the first time to inject a first material component into a first cavity of an injection moulding machine and to remove that first material component from the first cavity before the material is cured, in order to inject it, after release, into a second cavity of the first injection moulding machine or a second injection moulding machine with a second component of another material in such a way as to result in a solid mechanical connection between the first and second phase. The first material component is placed in the first cavity on a support. This support is designed to transport non-plastic material. After the first phase is injected, the support is removed from the first cavity and the plastic component is inserted into the second cavity.before the material of the second component is injected, a release of the material of the first component takes place. This is a mechanical process in which a slide or a functionally equivalent element releases a certain area or surface of the first material component, so that the material of the second component in this area encircles the material of the first component after the injection process. The welded mechanical impact results in a formless connection between the first material component and the second material component.This exemption shall preferably be as large as possible.

The invention has two major advantages over the present state of the art: on the one hand, it greatly reduces the material consumption of a two-layer tube-shell and, on the other, it drastically reduces the cycle time during manufacture.

The present invention is also suitable for the further step of integrating a tube body with the tube shoulder, which can be supplied as an external part to the processing process, preferably in a further cavity or combined with one of the steps in which the first or second material component is produced.

The following figures provide a detailed discussion of the invention in a preferred embodiment. Figure 1 shows a schematic of a preferred embodiment of a tube shoulder in a perspective cross-sectional view. Figure 2 shows the schematic of the manufacturing process of a tube shoulder.

The outer layer 2 is composed of polyethylene (PE) and the outer layer 3 is composed of polyethylene terephthalate (PET). The outer layer 2 is primarily used to shape the tube shelf 1, with the outer layer 3 serving to measure the density of the tube shelf 1. The two materials of the outer layer 2 and the outer layer 3 are typically not melted together. However, to achieve a mechanical connection, the outer layer 2 uses the outer layer 3 to form a large liquid layer, which is used in the first step of the application. The outer layer 2 is used in the first step of the application process to avoid the formation of a large liquid layer.

The design of the tube shoulder 1 according to the invention, in which all the mechanical connections between the outer layer 2 and the barrier layer 3 are designed to have the largest possible area, makes it possible to release the barrier layer 3 in a tool 10 only while the material of the barrier layer 3 is still partially plastic. This is not possible for delicate or poorly deformable back cuts (e.g. back cuts requiring forced deformation). The disclosed invention is therefore based on a design of tube shoulders that allow an optimal area and free of forced deformation without back cuts. The individual steps of manufacture are shown in Figures 2a) and 2b).

The injection mold 10 consists of a base 11 with two openings 20 and 21. Two identical rotationally symmetrical cores 12.1 and 12.2 and two identical ring-shaped free elements 14.1 and 14.2 press tightly into the openings 20 and 21 from below, forming a first cavity 22 and a second cavity 23. The first cavity 22 corresponds to the negative of a barrier layer 3 as shown in Figure 1. The second cavity 23 corresponds to the negative of a barrier layer 3 and an outer layer 3.

A first channel 25 is used to inject molten plastic from a first material component, preferably PET, into the first cavity 22 to form a barrier layer 3 as shown in Figure 1.Before the plastic of this barrier layer 3 is hardened, the core 12, the free-falling layer 14 and the partial plastic barrier layer 3 are pulled out of the opening 20 and this process is illustrated by an arrow 30.

As shown in Figure 2b), the release 14 is then moved (arrow 37) to release a lower area 4 of the barrier layer 3.

The core 12, the free-falling core 14 and the barrier layer 3 are then pushed tightly into the second opening 21 of the injection mold 10 (Figure 2a). This is shown schematically by an arrow 31. A second channel 26 is used to inject a second material component around the barrier layer 3 formed by the first material component, thus creating a solid mechanical connection. At least one surface, preferably a ring-shaped surface 4, 5 (see Figure 5), serves as a mechanical attachment. The second material component forms an outer layer 1, 2 according to Figure 1.

The whole process is shown here in a very schematic way and is in practice advantageously incorporated in a turning tool with typically two cavities 20 and two cores 14.1 and 14.2. Both cores 14.1 and 14.2 are used simultaneously.

At the end of a production cycle, the free-runner 14 is used as an additional exhaust support for the finished tube shell 1.

To achieve a better sealing of cavities 22 and 23, the interacting surfaces of free-standing elements 14.1, 14.2 and cavities 22, 23 are advantageously conical.

The very fast manufacturing process described here is additionally controlled, depending on the dimensions of the tube-shoulder 1 to be manufactured, by cooling the core 14 and the injection mould 1.

For aesthetic reasons, different coloured or transparent plastics may also be used to achieve special optical effects. This may be advantageous, for example, if the barrier layer 3 is placed in the area of an outlet 6 (see Figure 1) so that it is visible from the outside to the user.

Claims (10)

1. Method for the manufacture of multilayer tube shoulders (1) made of plastic, characterized in that

   a) an inner layer (3) is manufactured by means of injecting a first material component through a first runner (25) into a first cavity (22) onto a support (12.1, 12.2) with a release element (14.1, 14.2);

   b) the inner layer (3) is removed from this first cavity (22) together with the support (12.1, 12.2) and the release element (14.1, 14.2);

   c) an area (4) of the inner layer (3) arranged on the support (12.1, 12.2) is released forming an undercut by means of shifting the release element (14.1, 14.2);

   d) the inner layer (3) with the support 12.2) and the release element (14.1, 14.2) is introduced into a second cavity (23);

   e) in this second cavity (23) the inner layer (3) arranged on the support (12.1, 12.2) is surrounded by an outer layer (2) in a positively engaging manner by means of injection of a second material component through a second runner (26).
2. Method for the manufacture of multilayer tube shoulders according to claim 1, characterized in that the inner layer (3) is a barrier layer (3).
3. Method for the manufacture of multilayer tube shoulders according to claims 1 or 2, characterized in that on injecting the second material component (2) a tube body is integrally connected to the tube shoulder (1).
4. Mould (10) for the facture of multilayer tube shoulders according to the method according to one of claims 1 to 3, characterized by a first opening (20) and a second opening (21) in which openings (20, 21) a first and a second support (12.1, 12.2) and a first and a second release element (14.1, 14.2) are arranged, such that a first and a second cavity (22, 23) for manufacture of an inner layer (3) and an outer layer (2) of a multilayer tube shoulder (1) are formed.
5. Mould (10) for manufacture of multilayer tube shoulders (1) according to claim 4, characterized in that the support is a core (12.1, 12.2) and the release element (14.1, 14.2) is of annular shape.
6. Mould (10) for manufacture of multilayer tube shoulders (1) according to one of claims 4 or 5, characterized in that the first and second core (12.1, 12.2) are applied simultaneously.
7. Tube shoulder (1), manufacturable according to the method according to one of claims 1 to 3, characterized in that the contact areas between the inner layer (3) and the outer layer (2) are of a design without undercut, such that a forceless demoulding is possible.
8. Tube shoulder (1) according to claim 7, characterized in that the inner layer (3) is designed in a rotation-symmetrical manner.
9. Tube shoulder (1) according to claim 7 or 8, characterized in that the contact areas between the inner layer (3) and the outer layer (2) are designed to be consequently diminishing.
10. Tube shoulder (1) according to one of claims 7 to 9, characterized in that the inner layer (3) consists of polyethylene terephthalate (PET) and the outer layer (2) consists of polyethylene (PE).