Patent Description:
In the prior art, thermoplastic containers are used as packaging for various consumer goods, including detergents, food, for example in the form of liquids (such as beverages), solids (such as butter) or powder (such as chocolate flakes), and other objects, such as toys, kitchen utensils or parts for vehicles (e.g. parts of the engine). Depending on the desired application, containers are required over a whole variety of different dimensions with a wide range of different materials. Accordingly, various methods are known for manufacturing such containers depending on the application.

In a first known application, a container is made by thermoforming. A flat sheet of a thermoplastic is heated, for example by an infrared radiation source, until the thermoplastic has reached its thermoforming temperature, which is normally located between its glass transition temperature and its melting temperature. The flat sheet is then deformed locally by an external force, for example by deep drawing with a press or plug, in order to obtain the desired shape of the container. Typically, but not always, the sheet is also blown against the mould after deep drawing. This desired shape is then retained after the thermoplastic has cooled. Materials suitable for this process comprise, among others, polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS) and polypropylene (PP). A typical example of a container made in this way is a butter tub.

A disadvantage of this method is that the relative dimensions of the container are limited. In particular, in practice, the depth of the container can almost never be greater than, or at least not significantly greater than, the length and/or the width of the container (i.e. its footprint). In addition, the ratio of the length to the width is often also limited such that, typically, the length is at most about twice the width.

Furthermore, the dimension of the upper opening of the container depends on the size of the press. Namely, the upper opening of the container must be large enough to allow the press to be removed. This also makes it impractical to provide an undercut.

Furthermore, deep drawing leads to the side walls being very thin and, in particular, thinner than the bottom. In other words, the container has no uniform thickness. These thin walls also limit the extent to which the container can further be inflated, since inflating the container too much can cause the already thin walls to become too thin, thereby compromising the integrity of the container.

Labels can be applied to the container by applying so-called 'in-mould labelling' or by applying the label after manufacturing of the container or by printing with ink after cooling of the container.

In a second known application, a container is made by injection moulding. Here, a thermoplastic in a liquid state is injected under high pressure into a die whose cavity is the shape of the desired container. The plastic solidifies by cooling. Materials suitable for this method comprise, among others, PE, PA, and PP. A typical example of a container made in this way is a reusable container, such as a bottle caps, reusable storage boxes, dustbins, etc..

A disadvantage of this method is that the entire container must be made out of the same thermoplastic polymer material. This makes it difficult to provide an odour and/or moisture barrier.

It is also practically impossible to provide shapes with an undercut as such moulds are very expensive. Namely, it is necessary that the central part of the die is then adjustable to a diameter that is smaller than the smallest diameter of the container, which is mechanically complex. In addition, the outer shape of the die must also consist of at least two halves. Such dies are, because of their high cost price, not economically applicable for the production of disposable containers, for example.

Furthermore, the container wall thickness should be large enough since the plastic, in its liquid state, must flow through the die. This also leads to a limitation of the relative dimensions of the container. In particular, the following rule of thumb applies, namely, the larger the volume of the container, the thicker the walls should be. However, the time required for the container to cool, i.e., harden, in the die increases rapidly depending on the thickness of the walls. In other words, the production of large containers takes considerably more time and is therefore less economically interesting.

In addition, it is theoretically possible to apply a print to the container by providing the corresponding shape on the die, but with every change in the shape of the pre-print, the die must be replaced, which is excessively expensive. Applying a label during the production of the container is also very cumbersome and usually requires the use of a vacuum installation to prevent liquid plastic from getting between the label and the die. Also, a new label design often leads to stocks of previous labels being discarded and/or a new device being required to manufacture the new labels.

In a third known application, a container is made by blow moulding, also known as extrusion blow moulding. Here, a thermoplastic is first extruded into a continuous preform (a so-called 'parison'), for example a hollow tube. Immediately afterwards, the preform, which is still warm and semi-liquid, is placed in a mould and is blown against the mould with the aid of a gas, for example compressed air in order to obtain the desired shape of the container. This desired shape is then retained after the formed thermoplastic has cooled. This type of blow moulding is therefore an almost continuous process. Materials suitable for this method comprise, among others, PE and PP. A typical example of a container made in this way is a bottle for fabric softener or detergent.

A disadvantage of this method is that the PET material is difficult to use in practical applications. In general, extrusion blow moulding is very sensitive since the parison is almost liquid, so that the preform can deform undesirably even in the case of small air disturbances, such as the opening of an outside door in a production hall. Since PET is even more liquid compared to other materials (such as PE or PP), undesired deformation can even lead to a collapse of the parison, a so-called drawdown.

Furthermore, the blowing causes different parts of the preform to expand differently, so that the thicknesses of the different walls of the container are not uniform. The wall must also be relatively thick so that the parison is formed sufficiently firmly. Labels can be applied to the container by applying so-called 'in-mould labelling' or by applying the label after the container has been made or by printing it on the container afterwards.

Blow moulding can also be used, in modified form, for the manufacture of containers (e.g. bottles) for water or soft drinks based on PET. This is known as injection blow moulding or also injection stretch blow moulding. A preform is obtained by injection moulding. The preform is then heated and subsequently blow moulded to a larger form. When blow moulding is assisted by the mechanical stretching by means of a stretching rod, the process is called injection stretch blow moulding. This type of preform is used after it has cooled down and is typically completely solid and, in particular, much more solid compared to a parison, making the PET material usable when compared to extrusion blow moulding. On the other hand, since the preform is the result of injection moulding, it is not possible to add a layer for moisture or odour barrier, and pre-printing is also not feasible here. Injection stretch blow moulding also results is low wall thickness, which renders undercuts and anisotropic shapes rather hard to achieve. Undercuts can be provided during blow moulding, but this causes a local thinning of the walls of the container, which is undesirable.

Also, an installation for injection blow moulding is relatively expensive.

<CIT>, <CIT>, <CIT>, <CIT> disclose methods and systems for deforming a thermoplastic tube into a container, which methods make use of stretching the tube.

<CIT> discloses a system for stretching a thermoplastic tube where cylindrical members are inserted in opposing ends of the tube and pins are moved radially outwards to grip the ends. Afterwards, the cylindrical members are pulled apart.

It is an object of the present disclosure to provide a method for manufacturing a thermoplastic container wherein there is less limitation on the relative dimensions of the container.

This object is achieved by means of a method for manufacturing a thermoplastic container, the method comprising: a) providing a thermoplastic tube with an inner wall, an outer wall, a longitudinal direction, a first end, a second end, a middle zone, a first zone and a second zone, the first zone extending from the middle zone to said first end and the second zone extending from the middle zone to said second end; b) gripping said first zone and said second zone; c) locally heating said middle zone to the thermoforming temperature of the thermoplastic; d) pulling said first zone and said second zone apart along said longitudinal direction thereby narrowing the middle zone; e) closing a closing portion of the middle zone to obtain a closure; f) cutting through the closed-off middle zone at the location of the closing portion to obtain two separate tubular parts; g-ii) placing at least one of the tubular parts in a mould; h-ii) heating said tubular part in the mould to the thermoforming temperature of the thermoplastic; and i-ii) deforming said tubular part against the mould to obtain said container, said deforming preferably comprising at least one of: blow moulding, vacuum forming and pressing.

In step a) a thermoplastic tube is provided with a middle zone, a first zone and a second zone. Already in this step the dimensions of the container have already been substantially determined. After all, they are chosen such that, during the blow moulding in step i), the tubular part only needs to deform minimally. Hence, the final footprint of the container substantially corresponds to the cross-section of the tube and the depth of the container substantially corresponds to the height of the first and second zone, respectively. The dimensions of the tube can in particular be chosen such that they are just small enough to be placed in the mould.

The method also makes it possible to obtain relatively large absolute dimensions of the container with relatively thin walls. This is partly because with this method there is no need for injection moulding, which would entail thick walls, and also because there is no need for a parison, which is often too liquid to manufacture sufficiently large containers without having relatively thick wall.

There are also fewer limitations to applying undercuts. Namely, in no step in the process is there any need for a plug or similar element to be arranged within the tube or container for deformation thereof. Hence, the wall thickness of the container before the blow moulding can be much thicker compared to the existing methods, leaving sufficient material for the locally high deformation required for an undercut.

Furthermore, there is also no need to use a parison such that this method is also suitable for manufacturing PET containers and other materials that are typically too sensitive for extrusion blow moulding.

In addition, this method allows an ink-print to be applied directly to the thermoplastic tube, in particular to the first and/or second zone, since the deformation is minimised during blow moulding as described in more detail below.

Also, the final container, at least the side walls thereof, has a more uniform wall thickness as compared to containers made with the existing methods since the tube initially has a uniform thickness and it is only deformed to a relatively small extent.

In practice it has been found that when applied to certain thermoplastics, the method described above can lead to the bottom of the container being fairly brittle. This is because the bottom of the container that emerges from the middle zone is normally heated at least twice during the process, namely during the pulling apart of the tube and later during blow moulding. However, it is known that such successive heating cycles are detrimental to the integrity and/or resilience of certain thermoplastics.

It is an alternative object of the disclosure to provide a method for manufacturing a thermoplastic container, wherein there is less limitation on the relative dimensions of the container and wherein there is less limitation on the choice of the thermoplastic material.

This alternative object of the disclosure is achieved by an alternative method for manufacturing a thermoplastic container, the method comprising: a) providing a thermoplastic tube with an inner wall, an outer wall, a longitudinal direction, a first end, a second end, a middle zone, a first zone and a second zone, the first zone extending from the middle zone to said first end and the second zone extending from the middle zone to said second end; b) gripping said first zone and said second zone with the aid of retaining members, each of said retaining members having a mould surface which is substantially perpendicular to said longitudinal direction and is located along said middle zone; c) locally heating said middle zone to the thermoforming temperature of the thermoplastic; d) pulling said first zone and said second zone apart along said longitudinal direction thereby narrowing the middle zone by moving said retaining members away from each other; e) closing a closing portion of the middle zone to obtain a closure; f) cutting through the closed middle zone at the location of the closing portion to split the middle zone into a first portion and a second portion so that said tube is split into a first and a second tubular part, the first tubular part comprising said first zone and a first bottom portion, which first bottom portion is formed by said first portion of the middle zone and the second tubular part comprising said second zone and a second bottom portion, which second bottom portion is formed by said second portion of the middle zone; g-i) arranging, for at least the first tubular part, a bottom moulding member opposite a respective one of said retaining members such that said first bottom portion is located between the bottom moulding member and the respective retaining member, each bottom moulding member being provided with a counter mould surface which is substantially perpendicular to said longitudinal direction and is oriented towards its respective mould surface; and h-i) deforming said first bottom portion into a bottom by pressing the bottom moulding member and its respective gripping organ against each other.

The same advantages are retained in this alternative method, for example that the dimensions of the container have already been predominantly determined in step a). Moreover, the dimensions of the container may even be completely determined in step a) in case the container is no longer deformed after step h-i).

This alternative method further has the advantage that after splitting the tube there is no need to reheat each tubular part before blow moulding in a mould. On the contrary, after splitting, the bottom is immediately formed by the bottom portions created from the split of the middle zone.

According to the disclosure of the alternative method, step h-i) comprises venting gas from a space between said mould surface and said first bottom portion, each retaining member preferably being provided with a gas venting opening for this venting.

This prevents an overpressure from being created between a retaining member and a bottom portion during the pressing of the mould surface and the counter mould surface against each other.

According to the disclosure of the alternative method, steps d), e), f), g-i) and h-i) are carried out without allowing said middle zone to cool to below the thermoforming temperature of the thermoplastic.

This alternative object is also achieved by an another method for manufacturing a thermoplastic container, the method comprising: a) providing a thermoplastic tube with an inner wall, an outer wall, a longitudinal direction, a first end, a second end, a middle zone, a first zone and a second zone, the first zone extending from the middle zone to said first end and the second zone extending from the middle zone to said second end; b) gripping said first zone and said second zone with the aid of retaining members, each of said retaining members having a mould surface which is substantially perpendicular to said longitudinal direction and is located along said middle zone; c) locally heating said middle zone to the thermoforming temperature of the thermoplastic; d) pulling said first zone and said second zone apart along said longitudinal direction thereby narrowing the middle zone by moving said retaining members away from each other; e) closing a closing portion of the middle zone to obtain a closure; f) cutting through the closed-off middle zone at the location of the closing portion to split the middle zone into a first portion and a second portion so that said tube is split into a first and a second tubular part, the first tubular part comprising said first zone and a first bottom portion, which first bottom portion is formed by said first portion of the middle zone and the second tubular part comprising said second zone and a second bottom portion, which second bottom portion is formed by said second portion of the middle zone; and g-iii) for at least the first tubular part, sucking gas away from a space between said mould surface and said first bottom portion for the purpose of deforming said first bottom portion until it abuts said mould surface.

The same advantages are retained in this other method, for example that the dimensions of the container have already been substantially determined in step a). Moreover, the dimensions of the container may even be completely determined in step a) in case the container is no longer deformed after step g-iii).

This other method also has the advantage that after splitting the tube there is no need to reheat each tubular part before blow moulding in a mould. On the contrary, after splitting, the bottom is immediately formed by the bottom portions created from the split of the middle zone by the vacuum moulding of the bottom portion.

Obtaining the closure in step e) can be done in various ways.

According to a first disclosure, step e) comprises the further heating of at least the closing portion of said middle zone to above the melting temperature of the thermoplastic before pushing the inner walls against each other so that the pushed against one another inner walls fuse to obtain the closure.

According to a second disclosure, step a) comprises co-extruding the tube with an inner layer formed by a low-density polyethylene, a linear low-density polyethylene or another thermoplastic having a low melting temperature and step e) comprises the further heating of at least the closing portion of said middle zone to above the melting temperature of the low-density polyethylene or the linear low-density polyethylene before pushing the inner walls against each other so that the pushed against one another inner walls fuse to obtain the closure.

According to a third disclosure, step a) comprises applying an adhesive layer on the inner wall of said middle zone at least at the location of said closing portion and step e) comprises, after the inner walls have been pushed against each other, curing the adhesive layer to obtain the closure.

These alternative options make it possible to manufacture the closure in different ways depending on the desired application. For example, certain thermoplastics are less suitable for the manufacture of a closure by melting (i.e. heat sealing), while a co-extrusion increases the cost price, which is not always desirable.

Obtaining the thermoplastic tube in step a) can be done in various ways.

According to a first disclosure, step a) comprises extruding the tube.

According to a second disclosure, step a) comprises co-extruding the tube.

According to a third disclosure, step a) comprises injection moulding the tube.

These alternative options make it possible to manufacture the thermoplastic tube in different ways depending on the desired application. The desired thickness of the tube can therefore be taken into account before deciding which process is used.

According to the second disclosure, the co-extrusion can be used to produce at least one layer that forms an odour barrier and/or a moisture barrier. Optionally, the inner layer can also be made of low-density polyethylene or linear low-density polyethylene for the closure of step e).

The methods according to the disclosure are suitable for a wide variety of thermoplastics, including polyethylene terephthalate, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile butadiene styrene, polyethylene and biopolymers, in particular polylactic acid.

According to the disclosure, step a) comprises applying an ink pre-print to an outer wall of the tube. Here, the ink pre-print has, preferably, a design that takes into account the deformation by blow moulding in step i-ii).

The ink pre-print can be used to convey information to the consumer, such as the brand name, characteristics of the container, etc. In other words, the ink pre-print can serve as a substitute for a label to be applied with an in-mould process or afterwards. Such ink pre-prints are also difficult to remove, unlike a label. Moreover, such an ink pre-print is also more environmentally friendly than a label since the ink pre-print is applied directly to the container, while the label may be made of a material other than the container, which makes recycling more difficult. This enables making single material containers.

According to the disclosure, step g-ii) comprises placing a label between the tubular part and the mould.

This makes it possible to apply a label to the container via an in-mould labelling process.

According to the disclosure, step a) comprises providing said tube with, at its first end and at its second end, a protruding portion which is integrally manufactured with the tube and the method further comprises step j) deforming said protruding portion into a lid for the container.

By providing an integrally manufactured protruding portion at the ends, which ends form the top of the container, these portions can be used to form the lid of the container.

According to the disclosure, step e) comprises pushing the inner wall of said closing portion against each other to obtain said closure.

According to an alternative disclosure, step e) comprises rotating, around said longitudinal direction, said first zone and said second zone in the opposite direction relative to each other to obtain said closure.

These alternatives allow the closure to be obtained in various ways.

It is a further object of the present disclosure to provide a system for pulling apart a tube.

This further object is achieved by means of a system for pulling apart a tube, which tube has an inner wall, an outer wall, a longitudinal direction, a first end, a second end, a middle zone, a first zone and a second zone, wherein the first zone extends from the middle zone to said first end and the second zone extends from the middle zone to said second end, the system comprising: a first retaining member which is provided for insertion into the first zone via the first end; a second retaining member provided for insertion into the second zone via the second end, each retaining member being adjustable between a first position in which the retaining member fits inside the tube and a second position in which, in use, the retaining member exerts a pressure on the inner wall of the tube; and actuation means configured to: insert the retaining members in their first position into their respective zone of the tube; subsequently bring the retaining members into their second position so that they exert a pressure on the inner wall of the tube to obtain a temporary fixed connection between a retaining member and its respective zone; and then move the retaining members away from each other to move the first zone and the second zone of the tube away from each other, wherein the actuation means are further configured to insert the first retaining member in the first zone of the tube as close as possible to the middle zone and to insert the second retaining member in the second zone of the tube as close as possible to the middle zone and moving the retaining members away from each other to move the first zone and the second zone of the tube away from each other narrows the middle zone.

By using such a system it is possible to make a temporary fixed connection between a retaining member and its respective zone so that movement of the retaining members leads to the zones moving away from each other. Furthermore, placing the retaining members close to the middle zone reduces the risk of deformation of the first and second zone during the subsequent pulling apart of the zones.

According to the disclosure, each retaining member is provided with an inflatable annular element that has a deflated position in which the annular element fits inside the tube and has an inflated position in which the annular element, in use, exerts a pressure on the inner wall of the tube.

The deflated position of the annular element corresponds to the first position of the retaining member and the inflated position of the annular element corresponds to the second position of the retaining member. The use of inflatable means has the advantage that the pressure is applied more evenly to the tube, in contrast to mechanical means, so that there is less chance of damage to the tube. Inflatable means are also relatively inexpensive compared to mechanical means.

Preferably, the annular element is located in a groove provided on the retaining members. According to the disclosure, the groove is formed between two plate-shaped elements that each have a shape corresponding to a cross-section of the tube. It is advantageous if one of the plate-shaped elements, typically the outermost, is mounted on a movable arm that is configured to be actuated by the actuation means. According to the disclosure, each retaining member is integrally manufactured.

The tube can be made from various materials, including metal, glass or a thermoplastic, such as the ones described above in relation to the methods according to the disclosure.

According to the disclosure, the system further comprises heating means which are provided to heat said middle zone and wherein the actuation means are further configured to actuate the heating means to heat said middle zone before the retaining members are actuated to move away from each other.

The heating means make it easier to move the first and second zones away from each other with a limited force.

According to the disclosure, a length of the middle zone is selected depending on a desired thickness of a bottom of the container.

Namely, stretching the middle zone locally reduces the wall thickness. By making the middle zone sufficiently long, it is possible to minimise the local deformation of the wall during stretching so that the bottom of the container, said bottom being formed by a portion of the middle zone, is sufficiently thick.

According to the disclosure, the tube is made of a thermoplastic and the system further comprises splitting means that are movable substantially transversely with respect to said longitudinal direction to split the middle zone into a first portion and a second portion so that said tube is split into a first and a second tubular part, wherein the first tubular part comprises said first zone and a first bottom portion, which first bottom portion is formed by said first part of the middle zone and wherein the second tubular part comprises said second zone and a second bottom portion, which second bottom portion is formed by said second part of the middle zone, and wherein the actuation means are further configured, after the retaining members have moved away from each other, to move the splitting means transversely, in particular towards each other, to split said tube into said tubular parts.

This system allows not only the thermoplastic tube to be pulled apart but also this tube to be divided into two tubular parts.

According to the disclosure, each of said retaining members comprises a mould surface configured to be positioned substantially perpendicular to said longitudinal direction and along said middle zone, the system further comprising: a first bottom moulding member provided to cooperate with said first retaining member to deform said first bottom portion; a second bottom moulding member provided to cooperate with said second retaining member to deform said second bottom portion, each bottom moulding member comprising a counter mould surface corresponding to its respective mould surface and is configured to be positioned primarily perpendicular to said longitudinal direction and oriented towards its respective mould surface, and wherein the actuation means are further configured to, after the splitting means have split the tube: position the first bottom moulding member opposite the first retaining member and the second bottom moulding member opposite the second retaining member; and then press the first bottom moulding member and the first retaining member against each other to deform said first bottom portion into a bottom and press the second bottom moulding member and the second retaining member against each other to deform said second bottom portion into a bottom.

This system makes it possible, after the tube has been split into tubular parts, to deform the bottom portion of each tubular part into a bottom without having to make use of an additional blow moulding step. Hence also avoiding two successive heating phases.

According to the disclosure, each retaining member is provided with a gas venting opening configured to vent a gas from a space formed between said mould surface and said first bottom portion. This gas venting opening is in particular formed by making the movable arm hollow.

As above, such a gas venting opening prevents an overpressure from arising between the mould surface and the bottom portion of the tubular part.

According to an alternative disclosure, each of said retaining members comprises a mould surface configured to be positioned substantially perpendicular to said longitudinal direction and along said middle zone, each retaining member being provided with a plurality of gas venting openings configured to vent a gas from a space formed between said mould surface and said first bottom portion, which system is further provided with extraction means configured to extract gas from a space between said mould surface and said first bottom portion via said gas venting openings.

This system allows, after the tube has been split into tubular parts, the bottom portion of each tubular part to be deformed into a bottom without having to use an additional blow moulding step and without having to use one or more bottom moulding members.

The object of the disclosure is also achieved by the use of a system as described above for performing steps c) and d) of the methods described above.

The alternative object of the disclosure is also achieved by using a system as described above for performing steps g-i) and h-i) of the method as described above and also by using a system as described above for performing step g-iii) of the method as described above.

According to the disclosure, the disclosure provides a method for manufacturing a thermoplastic container, the method comprising: a) providing a thermoplastic tube with an inner wall, an outer wall, a longitudinal direction, a first end, a second end, a middle zone, a first zone and a second zone, the first zone extending from the middle zone to said first end and the second zone extending from the middle zone to said second end; b) gripping said first zone and said second zone; c) locally heating said middle zone to the thermoforming temperature of the thermoplastic; d) pulling said first zone and said second zone apart along said longitudinal direction, thereby narrowing the middle zone; e) closing a closing portion of the middle zone to obtain a closure; f) cutting through the closed-off middle zone at the location of the closing portion to obtain two separate tubular parts; and g-iv) deforming at least one of said tubular parts into a container.

Details about steps a) to f) are already described above. According to the disclosure, steps g-iv) comprise steps g-i) and h-i), which have already been described above. According to the disclosure, steps g-iv) comprise steps g-ii), h-ii) and i-ii), which have already been described above. According to the disclosure, steps g-iv) comprise steps g-i), h-i), g-ii), h-ii) and i-ii), which have already been described above. According to the disclosure, steps g-iv) comprise steps g-iii), which have already been described above. According to the disclosure, steps g-iv) comprise steps g-iii), g-ii), h-ii) and i-ii), which have already been described above.

At least the advantage relating to the dimensions of the container is achieved by this method. Moreover, other advantages described above may also be applicable depending on the nature of step g-iv).

The disclosure will hereafter be further explained in detail by way of the following description and the accompanying drawings.

Although the present disclosure will hereinafter be described with reference to certain drawings, the disclosure is not limited thereto and is only defined by the claims. The drawings shown here are merely schematic representations and are not limiting. The dimensions and the relative dimensions do not necessarily correspond to actual practical implementations of the disclosure.

In addition, terms such as 'first', 'second', 'third', and the like are used in the description and in the claims in order to make a distinction between similar elements and not necessarily in order to indicate a sequential or chronological order. It is to be understood that the terms in question are interchangeable under appropriate circumstances and that the disclosure described herein is capable of operation in other sequences than described or illustrated herein.

Moreover, terms such as 'top', 'bottom', 'above', 'under' and the like in the description and the claims are used for descriptive purposes. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the disclosure described herein is capable of operation in other orientations than described or illustrated herein.

It is to be noted that the term 'comprising', or its derivatives, used in the claims, should not be interpreted as being restricted to the means listed thereafter; the term does not exclude other elements or steps. Thus, the scope of an expression such as 'a device comprising means A and B' should not be limited to devices consisting only of components A and B. It means that with respect to the present disclosure, the only relevant components of the device are A and B.

As used herein, the term 'container' means a typically thin-walled, volume-containing object. Examples are reusable boxes for storing goods, packaging, car parts, etc..

<FIG> shows a flowchart of a method <NUM> for manufacturing a thermoplastic container. In step <NUM>, a thermoplastic tube <NUM> is provided with an inner wall <NUM>, an outer wall <NUM>, a longitudinal direction <NUM>, a first end <NUM>, a second end <NUM>, a middle zone <NUM>, a first zone <NUM> and a second zone <NUM>, the first zone <NUM> extending from the middle zone <NUM> to said first end <NUM> and the second zone <NUM> extending from the middle zone <NUM> to said second end <NUM> as shown in <FIG>.

Each of the zones <NUM>, <NUM> will be deformed into a container. This container <NUM> can, as shown in <FIG>, be provided with a lid <NUM>. However, the container <NUM> does not necessarily have to have a lid <NUM>. It is sufficient that the container <NUM> is provided with a bottom <NUM>, side walls <NUM> (of which only two are indicated by a reference numeral) and a top opening <NUM>. The wall of the tube <NUM> in the zones <NUM>, <NUM> forms the side walls <NUM> of the container <NUM> and the middle zone <NUM> will serve to manufacture the bottoms <NUM> of the containers <NUM>, i.e. the middle zone <NUM> serves to produce two separate bottoms <NUM>. The tube <NUM> shown in <FIG> is not provided to form a container <NUM> with lid <NUM>, but to form a container around an open top <NUM> (as shown in <FIG>), while the tube <NUM> shown in <FIG> is provided for this purpose by the additional portions <NUM> at the ends <NUM>, <NUM>, which additional portions <NUM> will form the cover <NUM>.

According to the disclosure, the tube <NUM> is extruded. This can be done by introducing solid pellets of the thermoplastic into a extrusion machine that heats them up so that they become liquid and then pressing them through the die to produce the hollow tube <NUM>. Suitable thermoplastics are polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polypropylene (PP) and biopolymers such as polylactic acid.

The extrusion process is carried out continuously. In addition, a co-extrusion can also be used to obtain a multi-layered tube <NUM>. In this way, an odour barrier and/or a moisture barrier can be formed. An inner layer can also be made from a low-density polyethylene, a linear low-density polyethylene or other heat sealable materials, which, as described below, is advantageous for obtaining the closure of the middle zone <NUM>.

According to the disclosure, injection moulding is used to manufacture the tube <NUM>.

The dimensions of the tube <NUM>, in particular the cross-section, are determined by the final desired shape of the container. In particular, the cross-section is ideally chosen which corresponds as closely as possible to the ground surface, i.e. the footprint, of the container.

In step <NUM>, an ink pre-print can optionally be applied to the outer wall <NUM>, for example by means of rollers, pads, inkjet printing, offset printing, etc. When designing the ink pre-print (i.e. the effective design), account should preferably be taken of the deformation, although it is minimal, which the wall of the tube <NUM> will undergo in the blow moulding step (step <NUM>). Being able to form the ink pre-print directly in the tube <NUM> has the advantage that, after manufacturing the container, no additional label needs to be provided and/or applied, which additional label is typically made from a material other than the container, whereby the recycling of the container becomes more difficult. The ink pre-print is preferably applied before the tube <NUM> is cut into pieces, which pieces serve for the manufacture of two containers. This makes it possible to apply the ink pre-print in-line with during the extruding of the tube.

In step <NUM>, the zones <NUM>, <NUM> are gripped as described in more detail below. In step <NUM>, the middle zone <NUM> is locally heated to the thermoforming temperature of the thermoplastic, which is typically above the glass transition temperature and below the melting temperature. This heating can be done in various ways, including the use of infrared lamps or heating air flows. The purpose of this step is to make the middle zone <NUM> locally deformable. To this end, care should be taken to ensure that the temperature remains lower than the melting temperature of the thermoplastic to prevent the middle zone <NUM> from collapsing altogether.

In step <NUM>, the first and second zones <NUM>, <NUM> are pulled apart along the longitudinal direction <NUM>. One of the two zones <NUM>, <NUM> can remain stationary, but both zones <NUM>, <NUM> can also undergo a translation. It will be appreciated that due to the stretching out of the middle zone the wall thins locally, which thinning can be minimised by making the middle zone sufficiently long as already described above.

Preferably, a system <NUM> according to the present disclosure is used to perform step <NUM>. As shown in <FIG>, the system <NUM> comprises a frame <NUM> on which two movable arms <NUM>, <NUM> are provided, which arms <NUM>, <NUM> are provided with retaining members <NUM>, <NUM> at their ends. As shown in <FIG>, the retaining members <NUM>, <NUM> are provided with an inflatable annular element <NUM> that is clamped or fitted between two plates <NUM>, <NUM> and supported on a support plate <NUM>. In other words, the plates <NUM>, <NUM>, <NUM> together form a groove in which the annular element <NUM> is placed. The different plates <NUM>, <NUM>, <NUM> are, in the drawings shown, connected to each other by bolts <NUM>, but other connecting means, for example glue, are also possible. The plates <NUM>, <NUM>, <NUM> can also be manufactured as an integral part provided with a groove in which the annular element <NUM> is located.

As shown in <FIG>, a first retaining member <NUM> is inserted into the first zone <NUM> as close as possible to the middle zone <NUM>, which middle zone <NUM> may already be heated but may also be cool. Positioning the retaining member <NUM> close to the middle zone <NUM> reduces the risk of the first zone <NUM> deforming under the influence of the tensile force to be applied to the retaining member <NUM>. Analogously, a second retaining member <NUM> is inserted into the second zone <NUM>. This insertion is done by actuating the arms <NUM>, <NUM> under the control of actuation means (not shown) provided as part of the system <NUM>. Both arms <NUM>, <NUM> can be inserted sequentially or simultaneously.

Preferably, the middle zone <NUM> is not heated before the retaining members <NUM>, <NUM> grip their respective zones <NUM>, <NUM> so that, as described below, the annular element <NUM> can perform its role as a thermal insulator.

As shown in <FIG>, it is possible to insert the retaining members <NUM>, <NUM> when their annular element <NUM> is in the lowered position. After the retaining members <NUM>, <NUM> are inserted, the annular elements <NUM> are inflated. This can be done, for example, by supplying compressed air, or another gas or liquid, via opening <NUM>. By inflating the annular elements <NUM>, these will exert a pressure on the inner wall <NUM> of the tube <NUM>. Such a contact causes the tube <NUM> to no longer be locally displaceable relative to the retaining members <NUM>, <NUM> due to the friction between the annular elements <NUM> and the inner wall <NUM> of the tube <NUM>. In other words, the retaining members <NUM>, <NUM> provide a temporary fixed connection to the first and second zone <NUM>, <NUM>, respectively, so that these zones can be displaced.

After inflation, one or both retaining members <NUM>, <NUM> are translated so that they are pulled away from each other in the longitudinal direction <NUM>. As a result, the zones <NUM>, <NUM> are also moved away from each other, as a result of which the middle part <NUM> becomes smaller in diameter as shown in <FIG>, in other words the middle part <NUM> narrows. According to the disclosure, the annular element <NUM> is made of a rubber.

The shape of the retaining members <NUM>, <NUM> (i.e. the shape of the cross-section almost perpendicular to the longitudinal axis <NUM>) typically corresponds to the shape of the tube <NUM> so that the annular element <NUM> must be inflated as little as possible before it comes into contact with the inner wall <NUM> of the tube <NUM>. In case the annular element <NUM> has to bridge a relatively large amount of space to come into contact with inner wall <NUM>, the compressed air must be supplied under a relatively high pressure, which possibly results in the wall of the tube <NUM> deforming due to the pressure of the annular element <NUM>. It will be appreciated that, in case the tube <NUM> has a rectangular, triangular, or other cross-section, the annular element <NUM> has a corresponding shape.

An additional advantage of the annular element <NUM> is that it partially functions as a thermal insulator, as a result of which the first and second zones <NUM>, <NUM> remain relatively cool relative to the heated middle zone <NUM>. This further reduces the risk of deformation of the first and/or the second zone <NUM>, <NUM>. In addition, the annular element <NUM> in this way prevents the heating of the middle zone <NUM> from having an effect on the crystal structure of the first and/or the second zone <NUM>, <NUM>. In other words, the heat applied to the middle zone <NUM> does not propagate to the <NUM>, <NUM> zones due to the thermal insulator <NUM>. Such a heating would modify the crystalline structure of <NUM>/<NUM>, and subsequent heating of these zones would render them brittle. In an alternative, it is also possible to replace the inflatable annular element <NUM> with mechanical means, for example one or more bars which slide outwards in order to thus push against the wall of the tube <NUM>. Such mechanical means are especially advantageous if the tube is made of a metal, since the mechanical means can generate a greater frictional force, so that the zones <NUM>, <NUM> can be pulled away from each other in the case of a metal tube, in contrast to a rubber annular element <NUM> that could slip.

It will be apparent to a person skilled in the art that the system <NUM> is suitable for both thermoplastic tubes and metal tubes. In addition, the system <NUM> is also suitable for pulling apart a glass tube.

In step <NUM>, the most central part of the middle zone <NUM>, which part will hereinafter be referred to as the closing part <NUM>, is pushed in such that opposing inner walls <NUM> come into contact with each other so that the middle zone <NUM> is closed. This pushing against each other can be done by means of two bars (not shown) that are pushed towards each other and between which the closing part <NUM> is situated. According to the disclosure, these bars can also be mounted on the frame <NUM> of the system <NUM> and can also be actuated by the same actuation means. According to another disclosure, there is no need for bars, but the retaining members <NUM>, <NUM> are rotated in the opposite direction relative to each other about the longitudinal axis <NUM> so that the middle zone <NUM> and, in particular, the closing part <NUM>, rotates until the inner walls of the closing part <NUM> come into contact with each other. The closing of the closing part <NUM> can be achieved in various ways.

According to a first disclosure, the closing part <NUM> is further heated, for example by infrared lamps or heated air or by heating the bars themselves. In particular, the temperature is raised above the melting point, as a result of which the inner walls <NUM> melt together and thus make the closure.

According to a second disclosure, the tube <NUM> is formed by a co-extrusion with an inner layer of a low-density polyethylene, a linear low-density polyethylene or other heat sealable materials.

The further heating of the closing part <NUM> is now only necessary to the extent that the melting temperature of the inner layer of the tube <NUM> is to be reached. The fusion, i.e. melting, of the inner layers creates the closure.

According to a third disclosure, an adhesive layer is applied locally in the middle zone <NUM> at least at the location of the closing part <NUM>. By pushing the inner walls <NUM> against each other, the layers of glue come into contact with each other, so that they harden and form the closure.

In step <NUM>, the first and second zones <NUM>, <NUM> are separated from each other by cutting through the closure. In this way, two closed-off tubular parts are obtained. This cutting can be done by a knife (not shown), a water jet, a laser, etc. which may optionally also be mounted on the frame <NUM> of the system <NUM> and which can also be actuated by the same actuation means. It is clear here that the middle zone <NUM> thus splits into a first bottom part <NUM> and a second bottom part <NUM> (shown in <FIG>). The first bottom part <NUM> together with the first zone <NUM> thus forms a first tubular part <NUM> and the second bottom part <NUM> together with the second zone <NUM> forms a second tubular part <NUM>.

Each of these tubular parts <NUM> is transformed into the final desired container in the following steps. In particular, in step <NUM>, at least one of the two tubular parts <NUM> is placed in a mould <NUM>. In the mould <NUM>, the tubular part <NUM> is heated, for example by infrared lamps <NUM>, heated air, electric heating <NUM>, in step <NUM>. Since the tubular part <NUM> already closely matches the shape of the mould <NUM>, the required deformation is small, so that, as described above, the walls <NUM> have a relatively uniform thickness. In step <NUM>, the tubular member <NUM> is blow moulded against the mould <NUM>, for example by supplying compressed air or another gas. In this way the final container is obtained which, after cooling, can be removed from the mould <NUM>. Alternatively, step <NUM> may use vacuum forming and/or press forming to deform the tubular member <NUM> against a mould. In general, step <NUM> comprises deforming the tubular member <NUM> against a mould.

In case the container has an undercut, it is advantageous if the mould <NUM> consists of two separate halves. This allows, after the container has cooled sufficiently, the two halves to be moved away from each other in order to remove the container from the mould <NUM>.

It is optionally possible, before placing the tubular part <NUM> in the mould <NUM>, to place a label (not shown) in the mould <NUM> so that the final container is provided with a label. This is known as applying an in mould labelling.

In step <NUM>, a lid is manufactured for the container. This lid can be manufactured in various ways which are known to a person skilled in the art. However, advantageously, the lid is integrally manufactured with the container. This is described in more detail with reference to <FIG>.

<FIG> shows a tube <NUM> of which, unlike the tube in <FIG>, additional portions <NUM> are provided at the ends <NUM>, <NUM>. These portions <NUM> form an integral part of the tube <NUM> and are obtained by cutting certain parts away from the tube <NUM>. This cutting away can for instance be done by a knife, a laser jet, a water jet or a counter mould. In the drawings shown, each of the portions <NUM> forms an almost flat portion, but it may also be that these portions <NUM> are curve-shaped, for example in case the tube <NUM> has a cross-section which is not rectangular but rather circular. It will be appreciated that the dimensions of the additional portions <NUM> are large enough to form the lid <NUM>.

Steps <NUM> to <NUM> are identical for tube <NUM> with additional portions <NUM>. In this way one obtains after step <NUM> the container with the additional portion <NUM> still connected thereto. This portion is deformed to make the lid in step <NUM>, for example by blow moulding against a mould half or by thermoforming with a press. Preferably, the blow mould steps <NUM> and <NUM> occur simultaneously.

A flowchart of an alternative method <NUM> for manufacturing a thermoplastic container is shown in <FIG>. Steps <NUM> to <NUM> correspond to respective steps <NUM> to <NUM> already described above. In short, these steps therefore comprise the following: manufacturing a thermoplastic container in step <NUM>, optionally applying an ink pre-print in step <NUM>, gripping the zones <NUM>, <NUM> in step <NUM>, locally heating the middle zone <NUM> in step <NUM>, pulling apart the zones <NUM>, <NUM> in step <NUM>, closing the most central part of the middle zone <NUM> in step <NUM> (as shown in <FIG>), and separating the first and second zones <NUM>, <NUM> from each other in step <NUM>.

In step <NUM>, at least for one tubular part <NUM> but preferably for both tubular parts simultaneously (as illustrated in <FIG>), a bottom moulding counterform <NUM>, <NUM> is positioned opposite each retaining member <NUM>, <NUM> as shown in <FIG>. Preferably, this positioning is done during the outward movement of the retaining members <NUM>, <NUM> (indicated by arrows <NUM>) in order to save time. In particular, each bottom moulding member <NUM>, <NUM> is transversely displaced so that they are slid between the separate tubular parts <NUM>. This can be done, for example, by positioning the bottom moulding members <NUM>, <NUM> on a movable arm (not shown), which arm in turn is mounted on the frame <NUM>.

A retaining member <NUM>, <NUM> for use in method <NUM> is shown in more detail in <FIG>. The main difference with the retaining member of <FIG> is that plate <NUM>, on its outward-facing side (i.e. the side substantially perpendicular to the longitudinal direction <NUM> and facing the middle zone <NUM>), is a mould surface that has a shape corresponding to the desired shape of the bottom. A further difference is that the retaining member <NUM> of <FIG> is provided with a gas venting opening formed by making the arm <NUM> hollow such that gas, i.e. air, can escape from the hollow space between the mould surface and the bottom part <NUM>. The bottom moulding members <NUM>, <NUM> are then in turn provided with a counter mould surface that has a shape corresponding to the mould surface.

In step <NUM>, the retaining members <NUM>, <NUM> and the bottom moulding members <NUM>, <NUM> are moved towards each other in the longitudinal direction <NUM> (indicated by arrows <NUM>) until they exert pressure on each other, whereby the bottom members <NUM>, <NUM> are deformed until they have the desired shape and thus form a bottom <NUM>, <NUM>. During this deformation, the gas venting opening allows air which would otherwise be trapped between the mould surface and the bottom part <NUM>, <NUM> to be released.

Although two bottom moulding members <NUM>, <NUM> have been described above, namely one bottom moulding member for each tubular part, it will be appreciated that only one integrally formed bottom moulding member can be provided with a counter mould surface on either side (as shown in <FIG>). In such a variant, the bottom moulding member remains static while, by the movement of the retaining members <NUM>, <NUM> to the static bottom moulding member, the bottom portions <NUM>, <NUM> of both tubular parts <NUM>, <NUM> are deformed.

In an alternative method (not shown), steps <NUM> and <NUM> are replaced by one joint step, namely vacuum moulding of one or both bottom portions <NUM>, <NUM>. For this purpose, use is preferably made of retaining members <NUM>, <NUM> as shown in <FIG>, namely with a plurality of gas venting openings <NUM> which are connected with pipes <NUM> to the hollow arm <NUM>, which in turn is connected to extraction means (not shown). It will be appreciated that each of the gas venting openings <NUM> can also be directly connected, via pipes <NUM>, to the extraction means. In this alternative method there is no need for bottom moulding counterforms.

The extraction means are configured to suck away the gas located between a retaining member <NUM>, <NUM>, in particular the mould surface thereof, and the bottom part <NUM>, <NUM> via the gas venting openings <NUM>. By sucking this gas away, i.e. creating a vacuum in the space between the retaining member <NUM>, <NUM>, in particular the mould surface thereof, and the bottom part <NUM>, <NUM>, the bottom part <NUM>, <NUM> will deform until it is sucked against its respective mould surface. In other words, the bottom part <NUM>, <NUM> is vacuum formed against the mould surface of the retaining member <NUM>, <NUM> until they have the desired shape and thus form a bottom <NUM>, <NUM>.

Claim 1:
System (<NUM>) for pulling apart a tube (<NUM>), which tube has an inner wall (<NUM>), an outer wall (<NUM>), a longitudinal direction (<NUM>), a first end (<NUM>), a second end (<NUM>), a middle zone (<NUM>), a first zone (<NUM>) and a second zone (<NUM>), wherein the first zone extends from the middle zone to said first end and the second zone extends from the middle zone to said second end, the system comprising:
- a first retaining member (<NUM>) which is provided for insertion into the first zone via the first end;
- a second retaining member (<NUM>) provided for insertion into the second zone via the second end, each retaining member being adjustable between a first position in which the retaining member fits inside the tube and a second position in which, in use, the retaining member exerts a pressure on the inner wall of the tube; and
- actuation means configured to:
- insert the retaining members in their first position into their respective zone of the tube;
- subsequently bring the retaining members into their second position so that they exert a pressure on the inner wall of the tube to obtain a temporary fixed connection between a retaining member and its respective zone; and
- then move the retaining members away from each other to move the first zone and the second zone of the tube away from each other,
characterized in that the actuation means are configured to insert the first retaining member in the first zone of the tube as close as possible to the middle zone and insert the second retaining member in the second zone of the tube as close as possible to the middle zone, and in that moving the retaining members away from each other to move the first zone and the second zone of the tube away from each other narrows the middle zone.