US20080038495A1

US20080038495A1 - Plastic tube bodies, and method for producing them

Info

Publication number: US20080038495A1
Application number: US11/767,216
Authority: US
Inventors: Hans Kuhn; Anton Demarmels
Original assignee: Individual
Current assignee: SIG Combibloc Services AG
Priority date: 1997-04-30
Filing date: 2007-06-22
Publication date: 2008-02-14

Abstract

A method for producing a tube preform using an injection molding method. An injection molding method is used to produce tube preforms which can be constructed with either one layer or a plurality of layers. The preform subsequently is heated and biaxially expanded by compressed air. A tube can be obtained which, on the one hand, has a tube shoulder with the strength provided by an industrial thread and, on the other hand, has a side wall which exhibits the softness desired for a tube.

Description

This application is a continuation-in-part of U.S. patent application Ser. No. 10/716,167 filed Nov. 18, 2003, which is a divisional of U.S. patent application Ser. No. 09/171,965 filed Oct. 30, 1998, which is a 371 of International Application No. PCT/EP97/02224 filed Apr. 30, 1997, all of which are hereby incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to plastic tube bodies and to a method for producing them. In particular, the present invention relates to a method for producing plastic tube bodies, in accordance with which, so-called tube preforms are produced and then formed into the final tube shape at a later point in time.
The invention also relates to a device for the production of a tube body, which has an input mechanism for the admission of a blow-formed thermoplastic container and an output mechanism for withdrawal of the tube body.
Finally the invention concerns a tube body, which is designed as part of a blow-formed and biaxially oriented container made from a thermoplastic material.

BACKGROUND

Various methods for producing plastic containers, for example from a thermoplastic, are known in the prior art. Prior art methods have included injection molding, blow molding, laminating methods, polyfoil and coextrusion methods.
An appropriate selection of material is made on the basis of the various properties of the component(s) with which the container is later to be filled. In addition to the control and obvious parameters such as strength, etc., criteria for selecting the material also include the aggressivity or the volatility of the component, or a desired inert behavior between the component and container, as is mostly necessary with medical active substances.
Diffusion of one or more active substance components through a wall of the container is extremely undesirable particularly in the case of containers for medical or pharmaceutical components, since the loss of the volatile components means that the percentage of quantitative composition no longer corresponds to the original data, with the result that a medically prescribed dosage, which is based on the original composition of the substance, is no longer assured.
Furthermore, when volatile components serving as solvents diffuse out, a resultant change in consistency can lead to more rapid ageing, drying out or poorer application properties.
Since a single material is often unable to fulfill all desired requirements (such as, for example, good compatibility with the component(s) and impermeability for specific volatile constituents thereof), consideration heretofore has been given to multi-layer containers (in particular tubes) in which the various layers can be formed from different materials. For example, such multi-layer containers have been produced by calendering methods in which the various materials are extruded and calendered in a roll configuration, that is to say rolled to form films or multi-layer films. The films produced in this way can then be welded to shoulder pieces and/or sealing/closure pieces, which are produced, for example, by means of an injection molding method. The shoulder pieces or sealing/closure pieces, however, do not have the properties of the multi-layer film, since they have been produced in a conventional way by means of injection molding and consist of only one material layer.
A further possibility for achieving complete protection against diffusion is to provide high cost metal containers, which are complicated to produce but do provide a natural diffusion barrier because of the molecular density of metal. These metal containers can be provided with an additional layer in the interior, in order to ensure an inert behavior between the fluid and container wall. The production of metal containers, however, is much more complicated than the fabrication itself because of the many individual steps (rolling, coating with plastic, forming the containers, folding and flanging the longitudinal seam, etc.). In addition, fabrication times and material costs are substantially higher.
For these reasons, consideration has been given to producing multi-layer plastic containers by using a multi-layer injection molding method. Such a method is disclosed, for example, in EP 0 537 346 A. The first step in this method is to inject a so-called enveloping layer into the injection mold, followed by, or simultaneously with a so-called core layer that has previously been formed by using a forming agent. The result is a container with a two-layer wall with the layers formed by different materials.
A further problem to be considered in producing plastic containers is the transportation size of the containers. More particularly, the plastic containers usually are not produced at the location where they are later filled with the component, but instead by a supplier at a different location. Since plastic containers for some applications may be of considerable size, yet light in weight, a transportation problem arises to the extent that in relation to the weight of the goods to be transported, the freight charges are also calculated in part on the basis of the volume of the goods. Consequently, with large-volume (empty) containers, transportation is relatively costly since, for example, a truck is essentially transporting “air”.
For this reason, it has already been proposed to supply plastic containers to the consumer not in their final form, but in the form of so-called preforms. EP 0 374 247 A1 and EP 0 325 440 A2 are examples in this regard. Injection molding methods for producing multi-layer container preforms are described in these documents.
An example of plastic containers are tubes that are presently widely used, for example, in the field of medicine, in cosmetics, for dental care agents and in nutrition. The tubes comprise tube body and a tube closure, such as a cap, usually produced by injection molding. The tube body should desirably have a firm shoulder region provided with a screw thread having sufficient strength to seal the tube reliably with the tube closure. It is to be kept in mind here that, by contrast with plastic bottles, tubes typically use industrial threads that are not positively disengaged from a mold but instead are turned out of the mold. Moreover, the tube body should have a side wall that gives the user the required “feeling of a tube”, specifically a sufficiently soft consistency which permits the mostly highly viscous component to be completely dispensed by squeezing the tube.
To date, tube bodies have been produced in two different ways which are known in the prior art as the “KMK” method and the “AISA” method. These two methods are described below with reference to FIGS. 13 and 14.
The “KMK” method is shown diagrammatically in FIG. 13. As may be gathered from the representation, a cylindrical tube 600, which corresponds to the later formed tube side wall, is introduced into a mold cavity 500. The tube 600 may be formed from a (multi-layer) film which has been produced using the calendering method explained above, and thus has a welded seam 610. After the tube 600 has been moved into the cavity 550 of the mold 500, plastic 510, for forming the tube shoulder, is introduced into the mold cavity 550 as a “sausage” in the shape of a circle. In a subsequent step, the tube shoulder is then formed by a punch 520 which is lowered into the mold cavity 550 of the mold 500.
In accordance with the “AISA” method shown diagrammatically in FIG. 14, a tube side wall 600 (which can be produced as previously described in connection with the KMK method) is introduced into an already prefabricated tube shoulder 550′.This tube shoulder 550′ can have been produced previously by injection molding. The elements of tube shoulder 550′ and tube side wall 600 thus assembled are then welded, for example by means of high frequency or hot air.
Both of the previously mentioned methods ensure that the tube body produced meets the various requirements made of the tube shoulder and tube side wall. Disadvantages of these production methods include a relatively complicated and cost-intensive manner to produce the tubes, and the tubes having to be moved in their final size to a customer's location where the tubes are filled, whereby the full size tubes occupy a substantial volume for transportation and storage.
Such tube bodies can be referred to, for example, as tubes according to general linguistic usage, with a neck section provided with a thread or a resilient cam and/or a relief, on which a turning catch is provided. The tube has a shoulder section between the neck or closure section and a main part of the tube.
Usual production procedures for the production of such tubes are, for example, the production of tube section preforms from a foil material, which is welded afterwards with a injection molded closure section provided with a shoulder section. Likewise, so-called deep-drawing procedures exist, with which the tube bodies from injection molded preforms are produced.
In WO 97/40972, the production of a tube body is described, with which a first container body is blow formed, and afterwards an end region of the container is cut open.
For the blow formed production of containers from preforms, different procedures and devices are well known for spraying and pouring before blow forming.
The preform is blow formed into a container after a thermal conditioning, using a blow tube. Stretch pins are positioned by pneumatic cylinders or a circulating control.
During blow molding of a container, preforms made of a thermoplastic material, such as PET (polyethylene terephthalate), are positioned at respective work stations in a blow molding machine. A blow molding machine typically includes a heating mechanism as well as a blowing mechanism. The preform is heated to and kept at a moderate temperature before biaxially expanding the preform to form a container. The expansion takes place by compressed air, which is introduced into the preform. The process engineering operational sequence with an expansion of the preform is explained in DE-OS 43 40 291.
An exemplary container blow molding station is described in the DE-OS 42 12 583. Possibilities for keeping the preform at a moderate temperature are explained in the DE-OS 23 52 926.
Within the blow molding device, the preform as well as the blown containers can be transported with the help of different handling mechanisms, such as those wherein the preform is retained by use of transportation elements. In addition, the preform can be handled with other carrying mechanisms. The use of grippers for the handling of preforms and the use of expanding mandrels are also known.
The handling of the preform can take place using a so-called two-stage procedure, with which the preform is manufactured first in an injection molding procedure, stored temporarily afterwards and later heated and blow molded to form a container. Alternatively, the preform may be kept at a moderate temperature immediately after injection molding thereof and a sufficient solidification, and then thereafter blown to form a container.
Various types of blow molding stations are well-known. The blow molding stations may be located on rotary wheels, and book-like hinged preform carriers may be used. In addition, preform carriers may be differently arranged relative to one another.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for producing and/or filling fillable plastic tube bodies and/or containers in a simple, cost-effective and/or space-saving manner.
In a general sense, the invention provides a method for producing a tube preform using an injection molding method.
The inventor of the present invention has found that in the case of producing tube preforms using an injection molding method and of subsequent extension, in particular by heating the preform and biaxial expansion, a tube can be obtained whose tube shoulder, on the one hand, has the strength required for an industrial thread, and whose side surface, on the other hand, exhibits the softness desired for a tube.
In accordance with a first preferred embodiment, a first step is advantageously to produce a tube body preform which has a shoulder region, open towards the interior of the tube body preform, and a closed end region. The tube body preform produced in such a way can then be transported to the filler, where it is first heated in a first method step, and then brought into its final shape and size with the aid of biaxial expansion. Finally, in a subsequent method step, the closed end region of the tube body is cut open in order to permit the plastic tube to be filled with the desired component. The use of biaxial expansion (by contrast with the axial expansion in the case of cold stretching, for example) renders it possible to use transparent tube materials that exhibit a glass-like transparency even in the expanded state.
The biaxial expansion of the tube body preform may be advantageously performed by means of compressed air in a blowing method, only the tube side wall being expanded while the tube shoulder stays in its original shape. The biaxial expansion thus effected renders it possible to produce a tube with a side wall that is characterized to a particular extent by the desired “feeling of a tube”, that is to say the softness of a squeezable tube. Furthermore, the tube side wall produced in such a way has particular strength.
The tube body preform may be advantageously produced using an injection molding method. This permits the tube body preform to be produced in an extremely cost-effective way and with a high quality.
If the biaxial expansion of the tube preform is performed with compressed air, prior heating of the preform can advantageously be performed using infrared light.
If a plastic tube produced in accordance with the invention is, for example, to be printed with a product designation, this may take place after the expansion of the preform, and advantageously after the closed end region of the tube body has been cut open.
The plastic body preform has a closed end region that enables blow molding of the tube body, as by biaxial expansion.
According to another aspect of the invention, the tube preform may be of a multi-layer configuration. For this purpose use may be made of an injection molding line having at least two feeding containers, with different materials being introduced into the feeding containers. After the materials have been plasticized, they may be forced through an annular nozzle with concentrically arranged annular nozzle gaps, and the delivery rates of the materials may be substantially the same in terms of direction and magnitude, with the result that the homogeneity of the first and second materials is maintained after they leave the nozzle. The materials thus plasticized are then injected into a mold cavity of an injection mold, it being the case here, as well, that the homogeneity of the material layers may be maintained in the mold cavity. A tube preform produced in this way is then formed into the final tube in a subsequent method step, use advantageously being made for this purpose of the herein described blow molding method. One advantage of these multilayer tube preforms is the possibility of producing tubes with already integrated closure and shoulder regions, which are distinguished by being completely multilayered.
The invention also provides a method of the kind specified wherein high production rates are supported with good product quality.
More particularly, the invention provides a method of forming a container comprising the steps of:

- a) injection molding a preform from a thermoplastic material,
- b) placing the preform into a blow mold,
- c) biaxially expanding the preform to form a container through stretching and supplying of a pressurized blowing gas,
- d) removing the containers from the blow mold,
- e) cutting off the containers end region to form an open end,
- f) pressing together the open end, and
- g) welding the open end.

Air may be used as the blowing gas.
According to another aspect of the invention, there is provided a device for carrying out one or more of the above method steps. Such a device may have a container input mechanism, a container output mechanism, and a cutting mechanism located between the input and output mechanisms for cutting off an end region of the container opposite the closure section of the container.
According to a further aspect of the invention, there is provided a tube body of the kind specified that can be industrially produced. A final section of the tube body, which is opposite a closure section, is welded to close an open end formed by a separation of a end region from the balance of the container from which the tube is formed.
More particularly, an end region of the container is completely separated from the balance of the container. The end region that is severed preferably extends into the typically cylindrical side wall region of the container that extends from the closed end of the container to the closure region. The exact location of the cutting plane can determined as desired for a particular application. The separation of the end section need not necessarily be along a plane or along a plane perpendicular to the center axis of the container, but instead may extend at an incline to the center line. Preferably the open end is bounded by a smooth edge, but this may be varied with the nature of the edge being determined in part by the cutting tool. In addition, the outline of the edge can be adapted to different production requirements or to a particular product design. For example, the edge may be configured to provide a wave-like appearance suggesting a cooling effect.
High production rates are supported in particular by the fact that the production of the container can be accomplished in a two-stage procedure.
In order to provide a desired strength, a stretch pin or pins may be used during blow molding of the container.
The container may be made from a preform with a single-layer structure or from a preform with a multi-layer structure. With a multi-layer structure, a layer can be prepared as a barrier layer inhibiting permeation of gases through the side wall of the container that might otherwise occur for the given component to be contained within the finished tube. An innermost layer may also be selected to facilitate filling and/or dispensing of a product, as by minimizing adherence of the product to the side wall of the container/tube.
A production procedure may be accomplished in such a manner that a flask-shaped container is manufactured.
In accordance with a particular application, the tube body is manufactured as a tube, and particularly a tube formed from a bottle K.
In accordance with another embodiment, welding the open end is accomplished before filling the tube container.
In accordance with another embodiment, welding of the open end is accomplished after the tube/container is filled.
A compact production plant may be made available by the fact that the input mechanism of the cutting mechanism is coupled with a blow molding apparatus.
An integrated plant concept may also involve the output of the assembly used to cut the ends of the containers may be coupled to the input of a filling assembly.
Additionally, the cutting mechanism may be coupled with welding equipment.
The tubes produced from the tube preforms are suitable for a variety of uses such as, for example, tubes for cosmetic, medical, pharmaceutical and hazardous media or foodstuffs, etc.; and semi-rigid tubes for cleaning agents, chemicals, biological materials or consumer articles, etc.
Tube preforms according to the invention may provide one or more of a number of advantages. One advantage resides in very low production costs, since the steps, otherwise required, of inserting shoulder pieces and welding the parts to one another, for example, are no longer required. Furthermore, in the case of multi-layer tube preforms, the specific dosing of the individual thermoplastic materials renders it possible for cost-intensive constituents to be optimally set, something which can have a substantial effect on the production costs.
The foregoing may be explained using an example. Consideration is given to a previously known tube whose wall consists of three material layers, the middle layer being an expensive diffusion-inhibiting material. This layer makes up approximately 80-90% of the tube volume; only 10-20% of the tube volume is due to the cost-effective inner and outer layers. If, for example, PE is used as a cost-effective outer or inner material (approximately 1.60 DM/kg) and EVOH as the expensive middle material (approximately 12 DM/kg), this would mean material costs of approximately 10.96 DM/kg for an average tube. A reduction in cost to approximately 2.64 DM/kg can be achieved with the method according to the invention by optimizing the use of materials.
A further advantage resides in the fast injection technique for producing preforms, since previous containers have had to be produced by extrusion, a technique which requires equipment which is more cost-intensive and has longer production cycles.
A further advantage consists in the possibility of being able to operate a plurality of injection molds, specifically up to 144, in parallel.
Other advantageous developments of the invention will become apparent from the following description of exemplary embodiments of the present invention that are explained below in detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings:
FIG. 1 is a perspective representation of a blowing station for the production of containers from preforms;
FIG. 2 is a profile of a blow mold, in which a preform is expanded and strained;
FIG. 3 is a schematic illustration of a device for blow molding containers;
FIG. 4 is a modified heating area with increased heating capacity;
FIG. 5 is a side view of a container with separated end region;
FIG. 6 is a schematic representation of a production plant for the production and filling of tube bodies;
FIG. 7 is a perspective view of a tube body prepared as a bottle;
FIG. 8 is schematic illustration of an injection molding apparatus for producing the preforms according to the invention;
FIG. 9 is a cross-sectional view of a blown multilayer bottle, together with the detail K;
FIG. 10 is an enlargement of the layered structure of detail K of FIG. 9;
FIG. 11 are schematic illustrations showing a number of possible layer designs for a multilayer preform according to the present invention;
FIG. 12 is a perspective view, partly broken away in section, of an injection-molding apparatus for use in multilayer injection molding method; and
FIGS. 13 and 14 are schematic illustrations of methods for producing tube preforms according to the prior art.

DETAILED DESCRIPTION

FIGS. 1 and 2 disclose exemplary blow molding equipment for manufacturing intermediate product containers. The principal components of the equipment for the shaping of preforms 1 into containers 2 are shown.
The device for the molding of the container 2 essentially comprises a blow molding station 3, where a blow mold 4 is provided and into which a preform 1 is placed. The preform 1 can be formed, for example, in whole or in part from polyethylene terephthalate, polypropylene, mixtures thereof, or other suitable materials.
To allow for insertion of the preform 1 into the blow mold 4 and for removal of the finished container 2, the blow mold 4 if formed by half- molds 5, 6 and a floor part 7, which are positionable by an actuating device 8. The preform 1 can be delivered to the blow molding station 3 by a transport element 9, which together with the preform 1 moves through a plurality of treatment stations within the device. In addition, it is possible to insert the preform 1, for example, by the use of a gripper or other handling means directly into the blow mold 4.
A blow rod 10 is arranged underneath the transport element 9, for use in supplying compressed air to the interior of the preform 1, and at the same time insulating the transport element 9. In a modified construction, compressed air supply lines may be used.
Stretching of the preform 1 can be completed with the help of a stretch pin 11, which is positioned by a cylinder 12. In another embodiment, a mechanical positioning of the stretch pin 11 may be accomplished by use of guide rollers riding on a curvilinear surface of cam segments. The use of curved cam segments is appropriate, in particular, if a plurality of blowing stations 3 are arranged on a rotary blowing wheel.
In the embodiment shown in FIG. 1, the stretch pin system has a tandem arrangement made available by two cylinders 12. The stretch pin 11 may be driven first by a primary cylinder 13 before beginning the actual stretching of the body 14 of the preform 1. During the actual stretching procedure, the primary cylinder 13 is positioned together with the stretch pin by a carriage 15 that is moved by a secondary cylinder 16 over a reciprocating control. In particular, using the secondary cylinder 16 in such a manner, a cam controlled by a guide roller 17, which protects the procedure of driving the stretch pin along a course along slides is given. The guide roller 17 is driven along the path by the secondary cylinder 16. The carriage 15 slides along two driving elements 18.
After getting within the range of the mold carriers 19, 20 the arranged half- molds 5, 6 are secured by a mold latch 40 near the mold carriers 19, 20, which takes place with the help of a bolting device.
To use preforms with closure sections 21 different than the preform 1 in accordance with FIG. 2, the use of separate neck clamps 22 within the blow mold 4 is contemplated.
Additionally, FIG. 2 shows a container 2, a developing blown container 23, and also a preform 1.
FIG. 3 shows the fundamental structure of a blowing machine, which is provided with a heating area 24 as well as a rotary blowing wheel 25. The preform enters from the preform input 26, then the preform 1 is transported by delivery wheels 27, 28, 29 into the heating area 24. Along the heating area 24 a heating emitter 30 as well as a blower 31 are arranged, in order to keep the preform 1 at a moderate temperature. While keeping it at a moderate temperature, the preform 1 is transferred to the rotary blowing wheel 25, in which the blow molding stations 3 are arranged. The finished blown containers 2 are transported by additional delivery wheels to a distribution area 32.
In order to be able to transform a preform 1 into a container 2 in such a manner where the container 2 exhibits material properties ensuring a long life of substances within the container 2, in particular beverages, the heating and orientation of the preform 1 is maintained. Beyond that, favorable effects can be obtained by adherence to dimension specifications. The use of the tubes and/or bottles according to the invention makes possible, for example, the packing of medical, cosmetic, pharmaceutical and chemical contents, in particular, adhesive materials.
In addition to thermoplastic material, different plastics can be used. For example PET, PEN, Pa or PP are operational.
The present invention refers to, in particular, the new use of tubes and/or bottles for the packing or handling of the below mentioned products.
The expansion of the preform 1 according to the procedure takes place via admission of compressed air. A gas (e.g. compressed air) is supplied during an initial blowing phase at a low pressure, and is supplied at a higher pressure level during a main blowing phase. During the initial blowing phase, typically, compressed air with a pressure in the interval from 10 bar to 25 bar is used and during the main blowing phase compressed air with a pressure in the interval from 25 bar to 40 bar is supplied.
In the embodiment illustrated in FIG. 3, the heating area 24 is composed of a plurality of chain-like transport elements 33, which are guided by a chain trained over wheels 34. In particular, the chain-like arrangement is an essentially rectangular shape or outline. When the shown embodiment is within the range of where the delivery wheel 29 and an input wheel 35 are located, the heating area 24 should be expanded to the area within the range of where the largely dimensioned returning wheel 34 and the two comparatively smaller dimensioned returning wheels 36 are used. In addition, in principle, arbitrary other guidances are conceivable.
The illustrated arrangement proves relative to making as close an arrangement of the delivery wheel 29 and the input wheel 35 as possible to each other as particularly appropriate, since in the range of the appropriate expansion of the heating area 24 three returning wheels 34, 36 are encompassed. In each case the smaller returning wheels 36 are within a linear range of the transition of the heating area 24 and the larger returning wheel 34 is in an area opposite the delivery wheel 29 and to the input wheel 35. Alternatively, in the use of chain-like transport elements 33, it is also possible to use a rotary heating wheel.
After completion of the blowing operation, the containers 2 are led out by a removal wheel 37 from the blowing stations 3 to the delivery wheel 28, then to the distribution wheel 38 and then to the distribution area 32.
In FIG. 4 a modified heating area 24 is shown, which can be kept at a moderate temperature by the larger number of heating emitters 30, and a larger quantity of preforms 1 can be processed for the same amount of time. The blowers 31 introduced here blow air into cooling air channels 39, which are opposite the heating emitters 30, and in each case discharge the cooling air through openings in the delivery system. A direction of flow for the cooling air is realized by releasing it in the direction transverse to a transport direction of the preform 1. The cooling air channels 39 can be made available within the area of the heating emitters 30, opposite the surface reflectors for the heating radiation. It is likewise possible that the delivered cooling air could cool the heating emitters 30.
The production steps were explained in detail for the production of the container 2. FIG. 5 provides an explanation of the production of the further production steps. For the production of a tube container 41 an end region 42 is separated from the container 2. This can take place mechanically or under employment of other suitable separation processes. The end region 42 is removed from the tube container 41 and can form a further closure section, where, for example, a recycling material can be used.
In FIG. 6 a production plant is shown, with which all production steps are locally accomplished. Granulate-like raw material 43 is driven to an injection molding mechanism 44 and transformed to the preforms 1. The preform 1 is driven to a blower 45 and transformed into the container 2. The containers 2 are supplied afterwards to a cutting mechanism 46, which separates the end regions 42 of the remainder of the container 2 and thereby makes the tube containers 41 available. The tube containers 41 are supplied in a further production step of a filling mechanism 47, which brings a filling material into the tube container 41. With a procedure as such, the one closure section 21 of the tube container 41 is first sealed. This can take place for example via screwing on or lifting up a cover and/or applying a closure sealing. The filling procedure is thus accomplished by the open end opposite the closure section 21 in the tube container 41, which was produced before by cutting the end region 42 off.
In a locking production step of the filled tube container 41, welding equipment 48 is supplied, which welds the still open closure section 21 for an opposite range of the tube container 41 in the range of an open end 49.
Deviating from the production concept in FIG. 6, different variants can be realized. In particular it is not necessary to operate all illustrated components in common. For example it is possible to operate the injection molding mechanism 44 locally, separately from the blower 45 and to temporarily store and/or transport the manufactured preform 1. Likewise it is possible to combine the injection molding mechanism 44 and the blower 45 into a common single-step plant.
The presented order of filling the tube body 41 in a first step and of welding the open end in a second step can alternatively be accomplished by, first welding the open end and then filling the tube container through the closure section 21. The actually selected sequence of the production steps only takes place as a function of the defaults of a respective user and on the characteristics of the product which can be filled up.
In accordance with FIG. 6, the cutting mechanism 46 is at the input side provided with an input mechanism 50 and at the output with output equipment 51. Between the input mechanism 50 and the output equipment 51 a separator 52 is provided.
In accordance with a special process step, it should also be remembered to work on the open end again after the execution of the welding procedure in order to reach an optimally arranged edge outline. In particular it should be remembered to be completed after the execution of the welding procedure by cutting of the edge along the welding seam. Thereby a flat edge is made available, which avoids sharp and/or rough upper edges. The cutting process can be accomplished for example mechanically or using another method in the described cutting or separation processes.
As a function of respective application and production conditions, the cutting process can take place in the area of the welding edge both at an empty tube body and after the execution of a filling procedure.
FIG. 7 shows, an example of the invention, in accordance with the procedure, a manufactured bottle. Such bottles can be filled with different products, for example with silicone materials. Other uses concern chemical products such as fats, adhesives or foam-end substances. During the production of such a bottle, in contrast to the described production sequence, there is no welding of the tube containers 41 in the range of the open end 49, but the closure section 21 opposite the open end of the tube container 41 by a floor part 53 is welded. The floor part 53 is arranged here opposite the inside of the tube container 41.
After filling the bottle through the open area provided by the floor part 53 into a suitable device, for example a bottle pistol, the floor part 53 can be moved in the direction of the closure section 21 by applying a force on the floor part 53, and the product filled up thereby from the one closure section 21, which was closed before.
In accordance with the invention, during the production of a tube container can be varied by shaping the wall ranges within a wider range. To make certain that the production of a bottle with tube containers 41 along the floor part 53 is at least in the range of the tube containers 41, it is arranged in an essentially cylindrical shaping processes. The cylindrical shaping currently supported is easily shifted to the floor part 53 and avoids leakages. A sufficient tightness can be supported beyond that by a suitable sealing rim or different shapes at the edge of the floor part 53.
As already explained above, from the widest point of view the invention consists of the idea of firstly using an injection molding method to produce blown tube preforms instead of finished tubes. These preforms (or blanks) have the advantage that they can be produced with large savings in material. The reason for this resides in the wall thickness of the tube side wall, which is important for the desired softness of the later side wall. To be precise, because of the material-specific viscosity of plasticized polymers, it is impossible to inject thermoplastics with less than a specific minimum wall thickness, particularly if multilayer tubes need to be injected.
This problem is solved by the injection molding of inventive preforms, because the side wall of the preform is not injected with the final dimensions of the later tube (only the tube shoulder is injected with the final dimensions). The final dimensions of the preformed side wall are reached only by later secondary finishing methods, which are usually carried out only by the consumer of the tube preforms.
The aim below is to describe, with reference to FIG. 8, the principle of the design of an injection molding apparatus which can be used to produce the inventive tube preforms. It is important here to note that the injection molding apparatus shown in FIG. 8 is suitable both for producing simple (that is to say single-layer) preforms and for producing the particularly preferred multilayer preforms as will be explained below.
FIG. 8 represents a multiplicity of feeding devices 60 a, 60 b, . . . 60 i, . . . 60 n, which in each case represent integrated devices for conveying, plasticizing and metering thermoplastic materials. The number 60 i of the feeding devices is determined by the number of plastics to be used, and by the number of the material layers to be produced. Thus, for example, the production of a single-layer tube requires the use of only one feeding device 60 i, which can be filled with a desired material. A two-layer tube (in which the outer layer consists, for example, of PP, and the inner layer of PA) requires the use of two feeding devices 60 i in which, respectively, PP or PA are conveyed, plasticized and metered. However, in the case of a three-layer tube, which is to have a further layer made from PP, for example, as inner layer, there is no need to use a further feeding device 60 i, it is possible instead to undertake an appropriate subdivision (not shown) of the mass flows inside the lines 100, 200, 300, . . . to the nozzle 70, for example by means of a suitable valve arrangement.
Inside the feeding devices 601, the material is made available by being introduced into the accumulators 63 a, 63 b, . . . , 63 i, . . . , 63 n, and is conveyed by screws 22 into regions 21, in which it is plasticine by the influence of heat.
The plasticized material is fed into a line network 100, 200, 300, in which it continues to be held plasticized by control mechanisms (not shown), with the result that when they reach the injection nozzle 10 the thermoplastic materials are in a state which is optimum for injection molding methods.
The plasticized materials are introduced into the mutually “separated annular gaps 120, 220, 320 (compare FIG. 12) of the nozzle 70 through the inlets which are arranged in the nozzle and communicate directly with the respective lines 100, 200, 300.
The inlet rate and the conveying pressure depend on the respective nozzle geometries, it being necessary inside the nozzle to take account of the shear forces and compressive forces which arise, in such a way that the delivery rate of the individual materials and layers are essentially the same in terms of direction and latitude.
It is possible, through ensuring this feature, for the homogeneity of the various layers to be maintained after they leave the annular gaps, since the layers do not mix with one another, that is to say the spatial unit of the individual layer components (for example PA, PET, EVOH, etc.) is essentially maintained in a layered fashion, with the result that continuous component layers are to be found.
The material, which is still plasticized, is injected into an injection mold 80 (compare FIG. 8 ), it being possible to construct the latter in different ways corresponding to the preform to be produced. In the mold 80 shown in FIG. 8, it is to be borne in mind that it permits the production of tube preforms 80 which have an open end region 95 (compare FIG. 10, a tube preform 90 being shown here which has a closed end region 95). The production of a tube preform 90 with an open end region is advantageous to the extent that the later filling of the finished tube is performed via the end region 95 of the tube 90, the result being an already appropriately open tube. A disadvantage of a tube preform 90 with an open end region 95 consists, however, in that monoaxial expansion methods such as cold-stretching methods are, in particular, the ones which come into consideration for the secondary finishing step to produce the final tube dimensions. These methods have the disadvantage that they place extreme loads on the plastic, and lead to increased brittleness of the later tube. Moreover, they have the effect that the side wall becomes milky, and thus unattractive, at least for tubes to be used in cosmetics. Consequently, according to the invention, it is regarded as particularly advantageous to produce tube preforms 90 with a closed end region 95 (as shown in FIG. 10), which can be brought to their final size with the aid of biaxial expansion methods (compare further below in this regard).
The solidification phase, which can be supported by a cooling system in the injection mold 80, begins as soon as the mold 80 is fed the plasticine material.
Since, as a rule, the mold 80 consists of a plurality of parts, opening the mold releases the workpiece such that it can easily be ejected.
Injection molding technology can be used to connect a multiplicity (up to approximately 40 of injection molds 80 to the conveying devices 60 i, with the result that a high rate of production can be achieved. The number of tube layers to be produced depends on the individual material characteristics, on their various physical properties, and on the specifications of the tubes respectively to be produced.
FIG. 10 shows in cross-section an inventive tube preform which is constructed as a preferred embodiment in three layers. The preform 90 shown has a shoulder region 93 (consisting of the actual tube shoulder 91 and a closure region 92, as well as a side wall region 96 which is provided with a closed end part 95. Instead of the thread design shown in the closure region 92, it is also possible to provide another possible closure, for example a hooded cap or a hinged lid.
Common to the shoulder regions and side wall regions 93,96 in the multilayer tube preform shown is the enlarged region shown in the detail K which reproduces the cross-section of the container wall. The detail K shown in FIG. 10 shows a 3-layer wall, but equally possible are double walls or multilayer walls of which a few exemplary combinations are shown in FIG. 11. What is decisive is that the number of layers is identical in all regions, the container thus being formed in one piece in one production operation.
Different variations of layers are shown in FIG. 11, the different shadings corresponding to different materials. Only a few possible combinations are presented as material combinations.
The thermoplastic materials which can preferably be used for the method are generally polymers such as polyethylene (PE) or polyethylene terephthalates (PET), polyethylene glycol terephthalates or polypropylene (PP). Polyamide (PA) or ethylenevinyl alcohol (EVOH) can be used for possible further layers situated between the inner or outer edge layers. However, it is also possible to use any other plastics which are melt processable.
FIG. 12 is a diagrammatic perspective representation of an injection molding nozzle 70 according to the invention, by means of which three-layered tube preforms can be produced. The injection molding nozzle 70 has three annular gaps 120, 220, 320 which in each case inject a layer of the tube preform into the mold 30 (compare FIG. 8). The annular gaps 120, 220 and 320 are arranged concentrically and radially spaced from one another.
In addition, the annular gaps can have an axial spacing (not shown).
The annular gaps are connected by bores to a line system 100, 200 and 300 which is connected to the conveying devices 60 i (compare FIG. 8). Of course, the number of feed lines, and thus of annular gaps is not limited to the number shown, but depends, as already described, on the number of layers desired. In the diagrammatic representation, the nozzle 70 is to be seen in one piece, but unipartite production can be very complicated, with the result that a multipartite design, for example through screwed or welded joints, can be more favorable for production.
After an inventive preform 90 (which can be either of single-layer or multilayer design and can have an open or closed end part 95 has been produced, the preform is advantageously moved to the filler, where the side wall region 96 is brought to its final dimensions using a secondary finishing method.
There is a particularly advantageous secondary finishing method for preforms with a closed end region 95 which can consist of any thermoplastic and, in particular, of PET, PP and Grivery (amorphous polyamide). In this method, the preform is heated in the region of the side wall, preferably using infrared radiation, until the side wall becomes soft. The preform is then introduced into a mold which with regard to the tube shoulder region, surrounds the preform in a self-closed fashion, and with regard to the lateral region prescribes the final shape of the later tube. Then, preferably with the aid of an air mandrel, compressed air is blown into the heated preform until the side wall has reached its final size and shape. Of course, in this case the wall thickness of the individual layers is reduced. It is possible using this method for the wall thickness of the layers, which consist of cost-intensive materials, to be greatly reduced (to below 50 μm), with the result that a substantial cost component can be saved (up to 50% by comparison with conventional tubes). Furthermore, the reduction in wall thickness renders the tube containers softer and thus easier to handle.
Finally, in the last operation, the closed (as before) end region of the now finished tube is cut open perpendicular to the tube longitudinal axis (compare the line of section S in FIG. 9) in order to provide the filling opening.
An alternative secondary finishing method in accordance with a further preferred embodiment of the present invention is a monoaxial expansion method, which is suitable for tube preforms with an open end region 95 (compare FIG. 10). An example of such a method is a cold-forming method in which the tube preform 90 is stretched cold in its longitudinal direction. In this case, the side wall of the preform 90 is stretched to about 3.5 times or more of its length.
Since no molding methods and cold stretching methods are sufficiently known to the average person skilled in the art, no attempt will be made here to consider them in detail.
Finally, it is pointed out that the examples shown above are merely explanatory and are not to be construed in a way which limits the extent of protection. The latter is to be defined only by the attached claims.
Appended hereto is an Appendix from which the foregoing description was derived, which Appendix is hereby incorporated herein by reference in its entirety. The Appendix refers to the same drawings annexed to the present application.

Claims

1. A method for producing fillable plastic tube bodies, comprising the steps of:

a. injection molding a tube body preform which has a shoulder region that open towards the interior of the tube body preform, and a closed end region;

b. heating the tube body preform;

c. biaxially expanding the tube body preform in order to form a tube body; and

d. cutting open a closed end region of the tube body to form a cut-open end of the tube body.

2. The method according to claim 1, wherein step c includes blow molding the tube body from the preform.

3. The method according to claim 1, wherein step b includes heating the tube body preform by means of infrared radiation or hot air.

4. The method according to claim 1, comprising the step of printing the biaxially expanded tube body with a desired tube inscription.

5. The method according to claim 1, comprising the steps of:

e. filling the biaxially expanded tube body with desired contents via the cut-open end of the tube body; and

f. closing the cut-open end of the tube body by means of welding.

6. The method according to claim 1, wherein step a comprises:

g. filling at least two feeding containers, respectively, with first and second thermoplastic materials;

h. plasticizing the first and second thermoplastic materials in the respective feeding containers;

I. injecting the first and second thermoplastic materials through an annular nozzle having at least two concentrically arranged annular nozzle gaps at essentially the same delivery rate in terms of direction and magnitude for the first and second materials, with the result that the homogeneity of the first and second materials is maintained after they leave the annular gaps; and

j. directing the plasticized materials into a mold cavity of an injection mold as they leave the annular nozzle with the homogeneity the materials being maintained in the mold cavity, the mold cavity defining the shape of the tube body preform.

7. The method according to claim 6, wherein thermoplastic material injected through an outer one of the annular gaps can be welded.

8. The method according to claim 6, wherein the thermoplastic material which is injected through an inner one of the annular gaps is selected to be compatible with the substance to be contained in the tube body.

9. The method according to claim 6, where at least one further material layer in injected through a respective annular gap of the nozzle disposed between the annular gaps through which the first and second materials are injected, which material is selected to have a diffusion-inhibiting effect on the substance to be contained in the tube body.

10. The method according to claim 9, the thermoplastic material which is injected through the outer one of the annular gaps comprising polyethylene (PE), polyethylene glycol terephthalates or polyalkylene terephthalates (PET) or polypropylene (PP).

11. The method according to claim 9, the thermoplastic material which is injected through the inner one of the annular gaps comprising polyethylene (PE), polyethylene glycol terephthalates or polyalkylene terephthalates (PET) or polypropylene (PP).

12. The method according to claim 9, wherein the thermoplastic material of the further layer comprises polyamide (PA) and/or (PE) and/or (PET) and/or (PP) and/or ethylenevinyl alcohol (EVOH) and/or PEN and/or PVDC and/or polyethylene glycol terephthalates.

13. The method according to claim 6, wherein the tube preforms are cold-stretchable.

14. A tube body preform, wherein the tube body preform is injection molded with a shoulder region that open towards the interior of the tube body preform, and a closed end region.

15. A tube body produced using a method according to claim 1.

16. A procedure for the production of a tube body, comprising the steps of:

a. injection molding a preform from a thermoplastic material;

b. putting the preform into a blow mold;

c. biaxially expanding the preform to form a container by stretching and supplying pressurized blowing gas;

d. removing the containers from the blow mold;

e. cutting off a closed end region of the container to form an open end;

f. pressing the opposite open end and a closure section together; and

g. welding the open end.

17. The procedure according to claim 16, wherein the production of the containers is accomplished in a two-stage procedure.

18. The procedure according to claim 16, wherein the production of the container is accomplished in a classifying procedure.

19. The procedure according to the requirements of claim 16, wherein the procedure is accomplished using a stretch pin.

20. The procedure according to the requirements of claim 16, wherein the container is made of a preform with a single-layer structure.

21. The procedure according to the requirements of claim 16, wherein the container is made of a preform with a multilayer structure.

22. The procedure according to the requirements of claim 16, wherein the container is manufactured as a flask-shaped container.

23. The procedure according to the requirements of claim 16, wherein the tube body is manufactured as a tube.

24. The procedure according to the requirements of claim 16, wherein the tube body is manufactured as a bottle.

25. The procedure according to the requirements of claim 16, wherein welding the open end is accomplished before a filling of the tube container.

26. The procedure according to the requirements of claim 16, wherein separating the closed end region and welding the open end is accomplished in a processing step.

27. The procedure according to the requirements of claim 16, wherein the welding of the open end is accomplished after filling the tube container.

28. The procedure according to the requirements of claim 16, wherein the open end is treated after welding.

29. The procedure according to the requirements of claim 28, characterized in that the treatment is accomplished before the filling.

30. The procedure according to the requirements of claim 28, wherein the treatment is accomplished after the filling.

31. A device for the production of a tube body, comprising an input mechanism for the admission of a blow-formed container from a thermoplastic material; output mechanism for the removal of the tube body; and a cutting mechanism located between the input mechanism and the output mechanism, the cutting mechanism being operative to cut off a closed end region of the container opposite a closure region of the container.

32. The device according to claim 31, wherein the input mechanism is coupled to the outlet of a blow mold that in turn in coupled to the outlet of an injection mold.

33. The device according to claim 31, wherein the output mechanism is coupled to a drop mechanism.

34. The device according to claim 31, wherein the cutting mechanism is provided with our coupled to welding equipment.

35. The device according to the requirements of claim 31, characterized in that preparing the production of tubes is realized.

36. The device according to the requirements of claim 31, for producing bottles.

37. A tube body, which is designed as a separated part of a blow-formed and biaxial oriented container made of a thermoplastic material, wherein a final section of the body, which is arranged opposite a closure section, is joined by welding an open end of the container formed by separating an end region of the container.

38. A tube body, which is designed as a separated part of a blow-formed and biaxial oriented container from a thermoplastic material, characterized in that a final section of the body, is welded for a closure section opposite a floor part, which is relative to a side wall of the movable and sealed body.