METHOD AND DEVICE FOR END CLOSURE OF PACKAGING TUBES

Abstract: The invention relates to a method and a device for end closure of packaging tubes. In one embodiment, the tube which is to be sealed presents an intermediate wall having a surplus length across the tube cross section, and the intermediate wall being fixed at the filling end of the tube to the tube wall and elsewhere along two joining locations extending along the length of the tube. Between these joining locations and the fixing sites at the tube end there are material portions of the intermediate wall. A hot air nozzle with two sub-members forming a gap therebetween is inserted into the opening in the filling end, possibly with re-forming of the filling end, and parts of the intermediate wall and the inside of the tube intended for sealing are heat activated in a non-contacting manner. In another embodiment, the tube which is to be sealed presents an intermediate wall formed in one piece with the tube and joined to this along two joining locations extending along the length of the tube. A device producing a clamping action is pressed against the heat activated tube end and the intermediate wall. Said arrangement has a pair of clamping jaws arranged for translatory motion perpendicular to the tube axis and initially in a direction at an angle to a line through said joining locations.

Description: TITLE: Method and device for end closure of packaging tubes FIELD OF THE INVENTION: The invention relates to packaging tubes of the so-called flexible type, i.e. tubes with a tube body manufactured from material which allows the body to be squeezed for emptying the packaging contents. More precisely, the invention relates to flexible packaging tubes with an intermediate wall which forms two product-receiving compartments in the tube, the compartments being separated from one another. Such packaging tubes are used for allowing the containment of different product types as well as delivering a mixture of the products which is obtained in-situ. The invention is intended to provide a method and device for end closure of such intermediate wall tubes. BACKGROUND TO THE INVENTION: Tubes with intermediate walls are manufactured inter alia by starting from web-like flexible material, e.g. polythene, polypropylene or other thermoplastic materials, in a longitudinal direction, by joining, along a pair of welded seams, a material layer serving as an outer tube wall to a material layer serving as an intermediate wall, which intermediate wall material layer is normally thinner than the outer material layer. The width of the outer material web is thereby larger than the width of the material web which is intended to form the intermediate wall, and the relationship between the widths is often chosen so that after longitudinal sealing of the outer layer and forming this into a circular tube, the intermediate wall presents a length over the cross-section of the tube which exceeds the diameter of the tube. The length of the intermediate wall is often chosen so that it corresponds to half the circumference of the tube, which means that with so-called planar sealing of the filling end of the tube, the intermediate wall presents the same length as the flattened tube end during sealing and afterwards. It has however shown itself to be the case that this surplus of length in the intermediate wall, which per se can be advantageous in the ready-sealed tube end, results in difficulties even at the filling stage. In order to overcome this, the applicant previously produced a method and device which allows the introduction of the filling nozzle on respective sides of the intermediate wall. Two relatively well-defined spaces in the closure end of the packaging tube are thereby created by the intermediate wall being stretched and spot welded to the inside of the tube at two substantially diametrically opposed positions. This spot welding is done in a filling machine and, for continued efficient handling in the machine after filling with product/products, the filling end of the tube with corresponding end of the intermediate wall has to be capable of being sealed in a rational manner to form an end closure. Tubes with intermediate walls are also manufactured by injection moulding, in one-piece, a tube body, breast and intermediate wall. Due to the manufacturing method, the intermediate wall in this case is of thicker material compared to the first-mentioned type of intermediate wall tube. The greater material thickness results in problems with sealing the tube end. In order to achieve such sealing, the intermediate wall has been allowed to finish at a distance from the tube end. With the aid of contacting heated jaws, heat energy from the outside of the tube is supplied to the inside of the tube in an encircling end area of the tube at a level above the intermediate wall. Thus, in the tube filling machine, directly after the heat-activation station following the embossing station, embossing jaws operating perpendicularly to the intermediate wall during the entire sealing process have been used to press the ends of the tube together in said encircling end area in order to thereby create a seal there. However, such a seal does not always ensure the production of a joint which is free of passages between the two product containing compartments, which the intermediate wall is intended to achieve. OBJECT OF THE INVENTION: The object of the invention is to solve the problem of end closure of packaging tubes of the types mentioned in the introduction, and to provide a solution which, while maintaining productivity in a tube filling machine, provides a complete handling of intermediate wall tubes, in principle in a manner which is equal to the highly effective handling of conventional tubes. The solution to the problem should furthermore be such that a minimum of disturbance is required in existing tube filling lines. SUMMARY OF THE INVENTION: The solution to the problem underlying the invention, when dealing with packaging tubes of the first mentioned type, is found by the realisation that it is possible, in the present connection of material wall thicknesses of a highly varying degree and material of different types as well as with addition of material layers in different areas of the produced sealing area, with special forming of a hot air nozzle to heat-activate the complicated material composite or geometry respectively, so that acceptable heat sealing is obtained in all areas of the produced end closure, also including any areas with double-layered intermediate walls and areas with up to and including triple intermediate walls. It has been found that if the heat activation of the material layer is done by non-contacting application of hot gas, commonly hot air, against the inside of the tube as well as on respective sides of the intermediate wall, in that the hot air nozzle is formed with a pair of sub-elements, the necessary conditions arise for achieving uniformity and for achieving the required conditions in the complicated material structure or nature respectively, which conditions are suitable for heat sealing the filling and closure end of the tube respectively. Claim 1 defines the basic condition for solving the problem, and the claims dependent on claim 1 define a further development of the basic idea. Claim 8 defines a device for carrying out the method, and claims 9 and 10 define further developments of the device. The solution to the problem underlying the invention, when dealing with the packaging tubes of the second type mentioned, is found by the realisation that it is possible, in the present connection of material wall thicknesses achievable by injection moulding and with the intermediate wall finishing at the level of the tube end or at a distance from it, by special forming of a hot air nozzle and special movement patterns of the embossing jaws to heat- activate and thereafter press together the complicated material geometry so that acceptable heat sealing is obtained in all areas of the end closure which is created, including also any areas where the intermediate wall is present. It has been found that if the heat activation of the material layer is produced by non-contacting application of hot gas, normally hot air, against the inside of the tube as well as on respective sides of the intermediate wall, by means of the hot air nozzle being formed with a pair of sub-members, the necessary conditions arise for achieving uniformity and for achieving the required conditions which are suitable for heat sealing in the filling and closure ends of the tube respectively. Claim 10 defines the basic condition for solving the problem. Claim 11 defines a device for carrying out the method. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 schematically shows a cross-section of an intermediate wall tube as it appears after manufacture. Fig. 2 shows the tube of Fig. 1 with the intermediate wall fixed to the tube at a pair of additional connection points. Fig. 3 schematically shows the cross-section of Fig. 2 re-formed with a forming tool and with the tube in a position for heat activation of those surfaces of the tube material which are to be sealed together in a later stage. Fig. 4a shows the tube taken out of the forming tool in Fig. 3 and, shown in arrows, a possible compressing direction in the station in the filling machine where the closure is formed, Fig. 4b shows a second preferred compressing direction for the heat- activatable filling end of the tube, Fig. 5a shows the tube cross-section and the intermediate wall during clamping according to Fig. 4a and clearly shows the material composition and geometry which is present, Fig. 5b shows the tube cross-section and the intermediate wall during compression according to Fig. 4b, Fig. 6 shows a view from below of a first embodiment of two sub-members forming a hot air nozzle, Fig. 7 shows a side view of the nozzle in Fig. 6, Fig. 8 is a perspective view of the nozzle in Fig. 6, Fig. 9 shows a view from below of a second embodiment of a divided nozzle with modified tube cross-section schematically added, Fig. 10 shows the nozzle of Fig. 9 in side view, and Fig. 11 shows the nozzle of Fig 9 in perspective view. Fig. 12 schematically shows a cross-section of an intermediate wall tube, injection moulded in one piece (the tube breast is not shown), Fig. 13 shows the tube cross-section and the intermediate wall while being clamped together according to Fig. 12. The tube 10 schematically shown in Fig. 1 from the filling end includes in a traditional manner an end (not shown) comprising a tube breast provided with an emptying orifice, and in the embodiment shown being manufactured from a flat blank and by means of longitudinal sealing 14 being given a substantially circular cross-section. Depending on the type of material of the tube body, where the material can be a monomer material of any suitable polyolefin, e.g. polythene, polypropylene etc., or a laminate of plastic material with barrier properties or metal foil or alternatively metallised film, the cross- section will have more or less a predefined shape. Additionally, the damage or effects that are caused by the conveyance of the tubes will effect the cross-section that finally ends up in the tube filling machine. In the tube body 10 there is an intermediate wall 11 which is joined to the planar tube body blank or tube body respectively by longitudinal seals 12, 13. The material of the intermediate wall 11 in the shown embodiment is of a material type which is heat sealable to the tube blank or the inside of the tube body, e.g. the material type may be an identical type as the material of the tube body 10, or respectively its inner layer if the tube body 10 is formed of a laminate. The intermediate wall 11 has a surplus of length which means that within the tube body 10 it describes approximately the curve which is shown in Fig. 1. The length often corresponds to half the circumference of the tube body 10, with the intention that when the tube filling end is in a flattened condition, opposing sections of the tube body and intermediate wall respectively will present the same diametrical length. As mentioned in the introduction, the surplus length of the intermediate wall however results in problems of introducing the filling nozzle into the filling end, such that in reality one has often resorted to stretching the intermediate wall 11 in the area of the filling opening in accordance with that shown in Fig. 2. The intermediate wall 11 has here been spot welded to the tube body wall adjacent the upper edge of the filling opening, or at a short distance from this, whilst of course the connections 12, 13 still join the intermediate wall along the whole length of the tube body up into its tube breast and into the emptying orifice. By stretching the intermediate wall 11 the cross-section in Fig. 1 will be changed. The shape change which occurs depends to a large extent on the elasticity of the tube body material. Due to the spot welding of the intermediate wall, the cross-sectional shape will normally assume an oval or elliptical form in accordance with Fig. 2. The intermediate wall 11 can be more or less stretched depending on the elasticity of the tube body material, and the dashed line 11' depicts a case with deformed cross-section but with a slack intermediate wall 11'. The connections 15, 16 of the intermediate wall give rise to material portions 11a, 11 b between respective spot welds 15, 16 and the adjacent connection locations 12, 13 at the tube wall. In practice it is difficult to lay these material portions 11a, 11 b closely against the inside of the tube wall especially since the material properties of the tube wall can present a return action tendency back to the original form of Fig. 1 , whilst the material in the thinner intermediate wall 11 does not have a corresponding tendency. The result is that between the intermediate wall portions 11a, 11 b and the inside of the tube wall there will be a space which makes a uniform heat-activation of the intermediate wall and the inside of the tube wall difficult. Moreover, as already mentioned, in certain applications the stretching of the intermediate wall 11 can be insufficient for creating a well-defined geometry for heat activation, which can additionally complicate the situation. In such application use is made of a re-forming step, where a forming tool 17 with a forming opening 18 with a substantially right-angled four-sided shape is applied to the outside of the tube body at the filling end. By dimensioning this opening 18 in such a way that the opening deforms, i.e. presses together, the cross-sectional dimension of the tube end in Fig. 2 in both the horizontal and vertical directions, the sections 11 a and 11 b will be brought closer to the inside of the tube body and the intermediate wall 11 will be tightened into a stretched condition. Fig. 3 shows such a condition. The dashed lines 19, 20 show a pair of non- contactingly operating sub members 19, 20 of a hot air nozzle for heat activation of those areas of the intermediate wall and the inside of the tube which will later be put together as a tube end seal. From the Figure it is clear that the cross-section of these sub-members together form a substantially right-angled four-sided shape and that this right- angled quadrilateral (in the plane of the forming tool) has about the same orientation as the quadrilateral which is formed by the tube body end in the forming tool 17. By means of this well-defined mutual orientation between the sub-members of the nozzle and the tube cross-section, it is possible to empirically determine a heat activation suitable for end closure of the mentioned different sections of the intermediate wall and the tube end which is to be sealed for forming the end closure. Moreover it is possible to vary the distance as well as the hot air release from activation location to activation location for the non-contacting heat activation, whereby the heat transfer in e.g. the positions 11a, 11b for double material layers (the intermediate wall and the tube wall in Fig. 3) can be intensified by reducing the distance and/or increasing the release of hot air. With a gap 21 between the sub-elements 19, 20, it is possible (also empirically) to control the heat transfer to both sides of the intermediate wall 11. The forming tool 17 also serves to externally control temperature conditions of the tube body at its sealing end, by the tool being connected to a cooling medium inlet 22 for circulation of cooling medium, e.g. water through an encircling channel 23. The forming tool 17 and the hot air nozzle 24 comprising the sub-members 19, 20 is arranged in a heat activation station (not shown) in the tube filling machine. Filled tubes are then fed intermittently to this station, and the filling end of a tube present in the station is contacted by the forming tool 17 and after re-forming the hot air nozzle's sub-members 19, 20 will be located in the position which is depicted in Fig. 3 and which is also shown in Fig. 9. After a heat activation is carried out according to Fig. 3, the tube is released from the heat activation station and is conveyed further to a clamping jaw station where its clamping jaws (embossing jaws) achieve a clamping of the tube end in accordance with the arrows 25, 26 (Fig. 4a, 4b). As is clear from Fig. 5a, the intermediate wall 11 in this embodiment is laid together to form a total of three layers, where also the outer layer is to be put together with the inside of the tube, where the outer layer is also to be put together with the inside of the tube wall. It is thus essential that the heat activation produced according to Fig. 3 achieves sufficient heat activation for acceptable heat sealing in all sections. In the embodiment according to Fig. 5b the build up of layers is easier to handle from a sealing point of view. The intermediate wall here lies as a single layer in the area of the tube end. With the described embodiment of the hot air nozzle and the forming tool, the conditions for sufficient heat activation are determined empirically. In certain applications where the conditions are favourable, especially concerning the material of the intermediate wall and the tube body, it is possible to omit the re-forming step and to use a hot air nozzle design of Figures 6-8. In this special case, there is still a gap 21a intended to receive the intermediate wall 11 , and the sub-members 19a, 20a are so designed that a non-contacting heat activation is possible. Even in this latter case, the design of gap 21a as well as the outer contour of the sub-members 19a, 20a is determined in an empirical manner. So far the invention has been described in connection with a specific embodiment of a packaging tube, however, as mentioned in the introduction, it is understood that the invention may also be applied in other areas, for example in applications where the tube and intermediate wall are manufactured in one piece by injection moulding or in a similar manner. The tube 10, schematically shown in Fig. 12 from the filling end, includes in a traditional manner an end (not shown) comprising a tube breast provided with an emptying orifice, and in the embodiment shown being manufactured by injection moulding and being given a substantially circular cross-section. In the tube body 10 there is an intermediate wall 11 which is formed as one piece with the tube body by injection moulding and is connected to this at connection locations 12, 13. The intermediate wall extends into the tube breast and there delimits two separate delivery passages all the way up to the emptying ends. At the other end of the tube body, the intermediate wall extends into the end edge of the tube body or finishes at a particular, predetermined distance from this end edge. Fig. 12 indicates in dashed lines 19, 20 a pair of non-contactingly operating sub-members 19, 20 of a hot air nozzle for heat activation of those areas of the intermediate wall and of the inside of the tube which are later to be put together to form a tube end seal. From the figure it is clear that the cross-section of these sub-members substantially corresponds to the cross-section of the sub-compartments of the tube formed by the intermediate wall. By means of this well-defined form of the sub-members and the respective orientation between the sub- members of the nozzle and the tube cross-section, an empirically determinable heat activation suitable for end sealing of the sections of the intermediate wall and the tube ends which are to be sealed for forming the end closure is made possible. By means of the form and the placement of openings for hot air release, it is possible to vary the distance as well as the hot air release from activation location to activation location for the contactless heat activation. With a gap 21 between the sub-members 19, 20, the heat transfer to both sides of the intermediate wall 11 can (also empirically) be controlled. The hot air nozzle 24 including the sub-members 19, 20 is arranged in a heat activation station (not shown) in a tube filling machine. Filled tubes are thereby fed intermittently to this station, and in this position a filling end of a tube present in the station is heat activated by the sub-members 19, 20 of the hot air nozzle, as shown in Fig. 12. After heat activation has been performed according to Fig. 12, the tube is removed from the heat activation station and transported further to a clamping jaw station where its clamping jaws (embossing jaws) achieve a squashing of the tube end in accordance with the arrows 25, 26. As shown by said arrows, the clamping jaws or embossing jaws act against the outside of the tube body and perform a movement by which the tube body is pressed by a pair of opposed jaws, which after pressing against the tube body perform opposed translatory movement in a plane perpendicular to the longitudinal axis of the tube, in the direction of arrows 25, 26, i.e. initially in a direction at an angle to the extension of the intermediate wall. By means of this initial "angled" pressing, the circular cross-section is progressively changed (step 2) to a planar seal with the intermediate wall included in the seal or (depending on the extent of the intermediate wall in the longitudinal direction of the tube) with its upper edge directly merging into this, in order to separate, without any passages, the two compartments which are formed by the intermediate wall. The initial pressing of the embossing or clamping jaws thus allows the intermediate form shown in Fig. 13 to be laid flat in the final stage, with the intermediate wall securely positioned within the end seal or in direct connection in a passage-free manner relative to this. Although the invention has been described in connection with specific embodiments of packaging tubes, it is understood that the invention may also be applied in other areas, for example where an intermediate wall does not extend in a straight line across the tube cross-section, but instead in an S- formed manner for example. For this, the sub-members of the nozzle are given a corresponding cross-section and the initial pressing direction for the clamping jaws is thereby defined in relation to an imaginary straight joining line between the connection locations with the tube body.

Claims: CLAIMS: 1. Method for end closure of packaging tubes (10) provided with an intermediate wall (11 ) intended to form two product-receiving compartments separated from one another, whereby the intermediate wall extends across the tube body and substantially along the whole length of the tube body along a first pair of joining locations (12, 13), and with a second pair of joining locations (15, 16) at the filling end, whereby each of these and one of said first joining locations between them hold a portion (11 a, 11 b) of the intermediate wall, characterized in that a hot air nozzle (24; 24a) is formed with a gap (21 ; 21 a), in that a pair of sub-members (19, 20; 19a, 20a)) defined by the gap of the hot air nozzle are introduced without contact for heat activation of the intermediate wall (11 ) and the inside of the tube in the area of the filling end, and in that after heat activation, the hot air nozzle is removed and the filling end is sealed by a device which produces a clamping action. 2. Method according to claim 1 , characterized in that a forming tool (17) is applied externally against the filling end so that the intermediate wall (11 ) is maintained stretched in the filling end and both of said portions (11 a, 11 b) of the intermediate wall are brought closer to the inside of the tube, in that the hot air nozzle (19, 20) is introduced into the tube through its filling end on respective sides of the intermediate wall, in that after heat activation of the inside of the filling end and the intermediate wall the hot air nozzle is removed, and in that the filling end is sealed by an arrangement providing a clamping action with the forming tool being out of an operable position. 3. Method according to claim 2, where the filling end of the tube and the intermediate wall arranged therein present a substantially elliptical shape with the intermediate wall (11 ) stretching across the minor axis of the end opening, characterized in that the forming tool (17) is designed and applied so that it re-forms the filling end into a substantially right-angled, four-sided shape. 4. Method according to claim 3, characterized in that the hot air nozzle (24) with two substantially identical sub-members (19, 20) defining a substantially right-angled cross-section with an inner gap (21 ) for receiving the intermediate wall, is brought to the heat activating position with the stretched intermediate wall free from contact in the gap and free from contact against the inside of the tube. 5. Method according to claim 4, characterized in that the sub- members (19, 20) are designed so that they together define a substantially four-sided cross-section. 6. Method according to claim 5, characterized in that the placement of the gap and the placement of hot air outlet openings of the sub-members are chosen so that the concentration of heat energy is obtained on wall sections comprising said portions of the intermediate wall between the first and second joining locations. 7. Device for end closure of packaging tubes (10) provided with an intermediate wall (11 ) intended to form two product-receiving compartments separated from one another, whereby the intermediate wall extends across the tube body and substantially along the whole length of the tube body along a first pair of joining locations (12, 13), and with a second pair of joining locations (15, 16) at the filling end, where each of these and one of said first joining locations (12, 13) between them hold a portion (11a, 11 b) of the intermediate wall, characterized by a hot air nozzle (24; 24a) comprising a pair of sub-members (19, 20; 19a, 20a) which between them form a gap (21 ) for accepting the intermediate wall (11 ), and in that the sub-members are formed with hot air delivery openings in the gap as well as elsewhere, and in that the hot air nozzle is dimensioned to be inserted in a non-contacting manner into the opening in the filling end on respective sides of the intermediate wall. 8. Device according to claim 7, characterized by a forming tool (17) arranged to be applied externally against the filling end, and dimensioned so that during heat activation it holds the intermediate wall (11 ) stretched in the filling end and forcefully closer to both portions (11 a, 11b) of the intermediate wall against the inside of the tube. 9. Device according to claim 8, characterized in that the forming tool (17) is cooled and presents a substantially four-sided forming opening (18). 10. Method for end closure of packaging tubes (10) provided with an intermediate wall (11 ) intended to form two product receiving compartments separated from one another, whereby the intermediate wall extends across the tube body and substantially along the whole length of the tube body along a first pair of joining locations (12, 13), characterized in that a hot air nozzle (24) is formed with a gap (21 ), in that a pair of sub-members (19, 20) defined by the gap of the hot air nozzle are introduced without contact for heat activation of the intermediate wall (11 ) and the inside of the tube in the area of the filling end, and in that after heat activation, the hot air nozzle is removed and the filling end is sealed by a device which produces a clamping action, and that the device producing the clamping action is pressed with a translatory motion at right angles to the longitudinal axis of the tube and initially in a direction at an angle to a line through said joining locations. 11. Device for end closure of packaging tubes (10) provided with an intermediate wall (11 ) intended to form two product receiving compartments separated from one another, whereby the intermediate wall extends across the tube body and substantially along the whole length of the tube body along a first pair of joining locations (12, 13), characterized by a hot air nozzle (24) comprising a pair of sub-members (19, 20) which between them form a gap (21 ) for accepting the intermediate wall, and in that the sub-members are formed with hot air delivery openings in the gap as well as elsewhere, and in that the hot air nozzle is dimensioned to be inserted in a non-contacting manner into the opening in the filling end on respective sides of the intermediate wall, and that an embossing-clamping arrangement is arranged to achieve clamping of the tube end, after hot air activation, by means of clamping jaws arranged for translatory motion perpendicular to the axis of the tube and initially in a direction at an angle to a line through said joining locations.

Inventors: LINNER HANS, LINNER, HANS
Applicants: LINNER HANS, NORDEN PAC DEV AB, LINNER, HANS, NORDEN PAC DEVELOPMENT AB
Application year: 1998
Main classification: B65B7
IPC codes: B29C65, B65B7, B65B51