Abstract:
A packaging container such as a tube, which is characterized in that the head ( 11 ) of the tube is inter alia sealed by the interior annular element ( 18 ) configured by a film material that engages with the shoulder ( 15 ) of the head. The annular element ( 18 ) is produced by pre-forming a plastic film annular element ( 18 ).

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a packaging container, particularly, a packaging tube. 
   Packaging containers, especially packaging tubes, comprise a tubular body, sometimes also referred to as pipe body, a tube head connected with the tubular body and provided with a discharge (dispenser), and a closure cap that opens and closes the discharge and is attached to the tube head, for instance, by means of a screw thread. Various methods have been developed for the production of packaging containers of the type briefly outlined hereinabove. For example, the tubular bodies may be extruded or co-extruded or, starting from a strip of sheeting, they may be produced by so-called longitudinal seam welding in which the edges of the sheeting strip are joined to each other by the application of heat and pressure and thus form the tubular body. As regards the materials for the tube body, use is made of metals, plastic materials with or without barrier layers and combinations of these materials, the actual choice of material being for the most part governed by the merchandise for which the packaging tube is intended. High-quality goods, such as pharmaceuticals, cosmetics and other body-care means—toothpaste being a case in point—that contain volatile active ingredients or react with gases, call for tubular bodies made of diffusion-resisting materials or material combinations, whereas in the case of less demanding merchandise, such as technical lubricants for example, materials without blockage effect will prove sufficient. The term diffusion is here understood as referring to the migration of volatile components from the interior of the tube towards the outside and vice versa. Once the tube bodies have been produced, they are equipped with heads. This operation can be performed by means of press moulding or injection moulding or by the application of a prefabricated head to the tube body. The plastic materials used for the heads and the tubes have to be compatible, because in each of the named methods the plastic materials of the head and the tube have to flow into each other in order to form the joint. When press moulding is employed, a blank of plasticized plastic material is transformed in a press mould and, while this process is going on, one end of the tube body is also joined to the head that is coming into being. Joining by injection moulding is characterized by the fact that one end of the tube body is joined to the head during the mould-filling process. When a prefabricated head is joined to a tube body, the tube body is attached to the shoulder of a head by means of melting and pressure. 
   In the case of packaging tubes for high-quality substances, where the tube body is rendered substantially diffusion-resistant by means of an appropriate choice of material, problems are created by the fact that the diffusion resistance of the head has to be made to match that of the tube body. When the previously named head forming and jointing methods are employed, polyolefins, preferably polyethylene (PE) and polypropylene (PP), are used as materials. When this material is used for the head and the tube consists of a laminate, the material of at least one laminate layer, i.e. of one of the cover layers, must be compatible, so that a head-tube joint can be obtained by means of melting and the application of pressure. The aforementioned polyolefins have the advantage that they can be readily jointed, but the drawback that they absorb the volatile components of the packed substances, aromatics among them, with the consequence that the packed substances suffer a quality reduction, and it can also happen that the head disintegrates, as it were, on account of the material consistency becoming soft, i.e. spongy. Gradual disintegration of the material consistency facilitates increased absorption of volatile components and endangers the strength of the joint between head and tube body. 
   Seals have been developed against this insufficient diffusion resistance. A distinction is made between external seals and internal seals, the former being applied to the external surface of the tube shoulder, the latter to the internal surface of the tube shoulder facing the interior of the tube, covering the shoulder surfaces from the dispenser neck to the joint between tube and head. Seals in the form of annular disks, with a central hole as aperture for the outlet channel, are described as external and internal annular elements according to the place where they are applied. As far as the sealing of tube heads is concerned, external annular elements have not attained the same importance as their internal counterparts. This is due to the fact that, subject to their being made of appropriate materials, they will render the passage of gases (O 2 , CO 2 , etc.) from the outside inwards more difficult or even suppress it altogether, but are not effective against the absorption of gaseous components of the packed substances (aromatics, for instance), whereas internal annular elements will perform both these sealing functions, always provided that the internal annular element covers the internal surface of the tube shoulder without jointing defects. A jointing defect is here understood as a folding or waving of the annular element, so that its open sides will not be joined to the surface of the tube shoulder. Jointing defects often lead to fractures of the seals, i.e. the annular elements, in which case there will be no blockage effect at all. 
   As material for the annular elements, which are produced from film strips, consideration may be given to monofilms (monofilms of plastics or metals), plastic-plastic laminates and plastic-metal laminates. To all intents and purposes, however, only plastic-metal laminates have proved successful among these films, and this for the reason that only annular elements made of this material combination can be joined to the shoulder of a head without jointing defects, while in the case of annular elements made of plastic films, inclusive of plastic laminate films, lack of jointing defects cannot be attained with certainty. 
   Plastic-metal laminates consist of an aluminium film that is sheathed, i.e. covered on both sides with a polyolefin film. In most cases so-called adhesion promoters are also to be found between the aluminium layer and the polyolefin layers. The aluminium layer or aluminium film serves as barrier layer, and constitutes a highly effective barrier layer against migrations any kind, whereas one polyolefin layer serves as means for joining the annular element to the shoulder surface, the other polyolefin layer as separation of the aluminium layer from the packed material. Though they have the advantages of the defect-free mounting on the head and considerable diffusion resistance, annular elements made of plastic-metal laminates are also associated with disadvantages. The elements are cut or, more precisely, punched from a strip of material. At the cutting or punching edge the metal will be bared and remain uncovered. In the built-in position of the annular element, given a difference between the outer diameter of the element and the inner diameter of the tube body, this metallic part of annular element will not be protected against the packed substance and, depending on the type of substance involved, the metal may lead to contamination of the packed material or the packed material can cause corrosion of the metal layer starting from the metallic cutting edge. Further, films of the type described above are prone to become delaminated between the two covering layers and the intermediate metal layer, starting from the cutting edge. Annular elements made of plastic material do not have the drawbacks of contamination and delamination, but their marked tendency to become folded and wavy constitutes an equivalent disadvantage. 
   Bearing in mind this prior art, the inventor set himself the object of developing an annular element (i.e. an internal annular element) with which the disadvantages of the known annular elements will be avoided. 
   SUMMARY OF THE INVENTION 
   The foregoing object is achieved by the present invention by providing a packaging tube comprising a tubular tube body and a tube head arranged on the tube body, said tube head consisting of a shoulder and a discharge and an internal annular element that is arranged on the side of the shoulder facing the interior of the tube body and covers said side, characterized in that the internal annular element ( 18 ) is made to engage pre-formed with the shoulder. The advantages of the annular element in accordance with the invention also comprise that fact that it can be used with all the methods for attaching the head and does not call for any constructional modification of the moulds used for attaching the head. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages, characteristics and details of the invention are brought out by the following detailed description of a preferred embodiment and the drawing, of which: 
       FIG. 1  shows an axial section through a first embodiment of the end of a tube with a dish-like disk (internal annular element) in the shoulder part of a tube head; 
       FIG. 2  shows a further embodiment in accordance with  FIG. 1  in which the internal annular element overlaps the forward end of the tube; 
       FIG. 3   a  shows a section through a mandrel with an applied and not pre-formed annular element; 
       FIG. 3   b  shows a section through a pre-formed annular element intended to cover only the shoulder part of the tube head; 
       FIG. 3   c  shows a section through a mandrel with an applied annular element in accordance with  FIG. 3   b;    
       FIG. 3   d  shows a section through a pre-formed annular element that covers the shoulder part of the tube head and the forward end of the tube; 
       FIG. 3   e  shows a section through a mandrel with an applied annular element in accordance with  FIG. 3   d;    
       FIG. 4  shows a schematic representation of a forming tool comprising mandrel and female mould 
   

   DETAILED DESCRIPTION 
   In  FIGS. 1 and 2  (identical parts are indicated by the same reference numbers in all figures) the reference number  10  designates tube bodies that, though only their head-sided terminal parts are actually shown, in each case, together with the heads generically indicated by  11 , constitute a packaging tube. 
   The tube body is made, for example, from a three-layered laminate. This laminate consists of a middle layer performing a blocking action, the blockage layer  12 , made of EVAL (ethylene-vinyl alcohol copolymer) or PETP (polyethylene terephthalate) covered on both sides by layers  13  and  14  made of PE (polyethylene), where the PE may be an LDPE (low density polyethylene), an HDPE (high density polyethylene) or a mixture of these. The layer  12  may be connected to the layers  13 ,  14  by means of intermediate layers (not shown) of copolymers. A blockage layer made of metal, preferably aluminium, may be used in place of the plastic blockage layer. For the production of tube bodies  10  it is advantageous to provide layers  13  and  14  made of polyethylene, because the good weldability of this material assures that the welded seems will be good and tight. 
   The head  11 , also known as headpiece, consists of a shoulder part  15  and a discharge (or neck)  16  with a discharge opening  17 , the outer surface of the discharge  17  being provided with engagement means for a tube closure, a thread for example. The head made of plastic material, preferably polyethylene, may be either pre-formed or formed in situ by means of injection moulding. Using the same material, the head  11  may also be formed by press-moulding a plasticized portion of material, i.e. a blank. Irrespective of whether injection or press moulding is used, the joining of the tube body  10  and the formation of the head  11  are mostly combined into a single working step by inserting the ends of the ends of the tube bodies  10  in the inject or press moulds and thus joining them to the head during its production process. When a prefabricated head is to be mounted on the end of a tube, this is obtained by melting the plastic material of the head and the tube and pressing them together. 
   Injection or press moulded polyethylene is more readily permeable for aromatics and fragrances, oxygen and carbon dioxide than a multi-layer plastic film. For this reason, the head  11  has to be sealed in order to give a diffusion resistance comparable to that of the tube body when better-quality materials have to be packed. According to  FIGS. 1 and 2 , diffusion-blocking devices  26  are therefore provided, in  FIG. 1 , for example, in the form of a dish-shaped disk  18  (also referred to as internal annular element) that bears against the internal surface of the shoulder part  15  facing the interior of the tube  10  and extends from the end  19  of the tube right up to the entry opening of the discharge  17  and preferably has its entire surface joined to the head  11 .  FIG. 2  shows an advantageous further development of the embodiment in accordance with  FIG. 1 . Accordingly, the internal annular element  18  is designed in such a manner that one of its ends covers and overlaps the tube end  19  engaged with the shoulder part  15  and then extends to the entry opening of the discharge  17 . This overlap assures better sealing between the internal annular element  18  and the tube end  19 . 
   Given prefabricated tube heads  11 , the internal annular element  18  in accordance with  FIGS. 1 and 2  can be glued into the tube heads or welded to them. 
   Preferably in keeping with the size of the tubes and the material with which they are to be filled, plastic monofilms, for example PET or PA (polyamide) or EVAL, will have a thickness between 15μ and 80μ, preferably between 20μ and 40μ. Plastic laminates (i.e. multi-layer films) will preferably have an overall thickness between 60μ and 200μ, preferably between 100μ and 140μ, inclusive of the thickness of a barrier layer, which may be made of PET, EVAL or PA, of between 5μ and 60μ preferably between 10μ and 30μ (μ=0.001 mm). 
   Multi-component dies consisting of a female mould  29  and a male mould (press mandrel)  28  are used when a head  11  is made by means of injection or press moulding. The head sealing means, i.e. the internal annular elements  18 , according to the invention with a PE layer  26   a , are prefabricated and placed on the mandrel, so that during the injection or pressing process for the formation of the head  11  the PE layer  26  becomes joined to the shoulder  15  and, in the case of the embodiment in accordance with  FIG. 2 , also with the tube body  10 . 
   When the internal annular element  18  in accordance with the invention overlaps the tube end  19 , the internal PE layer  14  of the tube body  10  will also become joined to the outer layer  26   a  of the internal annular element  18 , and thus assures even better sealing and also a strengthening of the joint between the tube body  10  and the head  11 . 
   The preferred embodiment of the internal annular element  18  described hereinabove is not limited to layer  26 ,  26   a  made of polyethylene and EVAL or PETP or PA. For these layers it is also possible to use polypropylene (Layer  26 ) with EVAL or PETP, PA or other materials suitable for barriers (Layer  26   a ). 
   According to the method in accordance with the invention, the internal annular elements  18  are to be pre-formed in order to avoid jointing defects, i.e. folding and/or waving of the internal annular element  18 , when it is pressed against or jointed to the internal surface of the shoulder  15 . In its simple form as illustrated by  FIG. 3   a , the internal annular element  18  is a round disk with a central round cut-out  27 , which is provided to permit the passage of the part  30  of the mandrel  28  that forms the discharge channel, and a circular fringe part  31  that surrounds the cut-out  27  and lies in a plane that is perpendicular to the centre line of the cut-out  27 , i.e. the angle “a” that the plane and the centre line constitute with respect to each other amounts to 90°, i.e. a right angle, when the annular element  18  is still in its non pre-formed condition. Bearing this in mind, . . . the term “pre-formed” has the meaning of any deviation of the angular position between said plane and centre line from the original right angle. Hereinbelow the pre-forming will be expressed in parts per hundred, i.e. as a pre-forming degree percentage (%). A pre-forming degree of zero % means that said plane and centre line form a right angle with respect to each other. Expressed in terms of the position of the annular element  18  on the mandrel  28 , this means that the circular fringe part ( 31 ) of the annular element  18  projects from the discharge-channel-forming part  30  of the mandrel  28 , i.e. from its axial centre line, at a right angle. Considering the mandrel  28 , an angle “b” is formed between the centre line of the discharge-channel-forming part  30  of the mandrel  28  and the surface of the mandrel that forms the inner surface of the shoulder  15  of the head  11 . A pre-forming degree of 100% will be constituted when the angle “a” between the plane  31  and the vertical centre line of the cut-out  27  of the annular element  18  corresponds to the angle “b” (angle of the tube shoulder) between the centre line of the discharge-channel-forming part  30  and the surface  32  of the mandrel  28 , i.e. when the pre-formed circular fringe part  31  lies on the surface  32  of the mandrel ( 28 ). Preferred in accordance with the invention are pre-forming degrees of between 20% (% of one hundred) and 95%, preferably between 40% and 60%. When the pre-forming degree is less than 20% or exceeds 95%, it is surprisingly no longer possible to be certain that no jointing defects will occur. 
   According to  FIG. 1 , the shoulder surface  15  is covered by an annular element  18 , whereas in  FIG. 2  the annular element covers the shoulder surface  15  and the jointed front end  15   a  of a tube body  10 .  FIG. 3   b  a shows a pre-formed annular element  18  whose fringe part  31  covers the shoulder surface  32  as a single-component fringe part  31   a .  FIG. 3   d  shows a pre-formed annular element  15  with a fringe  31  made up of two fringe parts  31   a  and  31   b , with the edge part  31   a  covering the shoulder surface  32 , while the fringe part  31   b  covers the jointing end  15   a.    
   According to  FIGS. 3   e  and  4 , the fringe part  31   a  corresponds to the mandrel surface  32  (also mandrel surface  32 ) and the fringe part  31   b  to the mandrel surface  33 , where the mandrel surface  33  makes a larger angle “c” with respect to the centre line of the part  30  than the angle “c”. The fringe part  31   b  may have the same pre-forming degree as the fringe part  31   a , in which case the lower limit of the pre-forming degree of 20% should once again not be understepped for the edge part  31   b , nor should the upper limit of 95% be exceeded. For the purpose of carrying out the invention, moreover, it has been found to be advantageous for the fringe parts  31   a  and  31   b  to have different pre-forming degrees, for example, when the fringe part  31   a  (which surrounds the part  30 ) has a pre-forming degree of 45%, the second fringe part  31   b  (which surrounds the first fringe part  31   a ) has a pre-forming degree of 80% of the pre-forming degree of the fringe part  31   a . Given a pre-forming degree of the fringe part  31   a  (or, expressed more generally, of a first partial surface) of between 40% and 85%, it is preferred to arrange for the fringe part  31   b  (or, expressed more generally, of a second partial surface) to lie in the range between 75% and 100% of this value. If, for instance, a pre-forming degree of 50% is chosen for the first partial surface, that of the second partial surface may amount to between 37.5% and 50%. It will also be advantageous if the annular elements  18  are warmed before they are placed on the mandrel  28  and then moved into the female mould  29  ( FIG. 4 ) in the warmed condition, subsequently adding the head by means of injection moulding or press forming. An advantageous temperature range is the one between 40° C. and 80° C., while the preferred temperatures of the annular elements  18  lie in the range between 45° C. and 60° C.