APPARATUS IN A TUBE FILLING AND SEALING MACHINE FOR HEATING A PORTION OF THE INSIDE OF A PLASTICS PACKAGING TUBE

Abstract: The invention relates to an apparatus in a tube filling and sealing machine for heating a portion of the interior surface (2) of a plastics packaging tube (1) which is open at one end. Means are provided for directing a spot type light from at least one light source (S1, S3) to a predetermined level on the interior surface (2) around the internal perimeter of the tube while the tube is rotated, so as to generate heat build-up at said surface in order to soften the plastics material to activation temperature. Said at least one light source will typically be a laser source. A heat sink means (20) is arranged in a position for circumferentially enclosing the tube end at level where said spot type light is swept, said heat sink means being in rotational sliding contact with the tube for improving the transfer of any excess of heat energy.

Description: TITLE: Apparatus in a tube filling and sealing machine for heating a portion of the inside of a plastics packaging tube FIELD OF THE INVENTION: The invention relates to an apparatus in a tube filling and sealing machine for heat-activation of a portion of the interior surface of a plastics packaging tube which is open at one end, as defined in the preamble of claim 1. The sealing process in such machines comprises two steps, first heat- activation of the inner surface of an open end of a plastics tube which is to be sealed and then clamping the end together between sealing jaws. BACKGROUND TO THE INVENTION: In order to provide a transverse seal at the open end of a flexible plastics tube, it is known to insert a hot air heating device into said open end (see US-A-4 511 426). Hot air is then forced out through a plurality of small openings in the nozzle of said open end and around the inner periphery of the tube, so as to activate the inner surface of the plastics tube all the way around its inner periphery. The term "activation" means the softening of the material on the inner surface of the tube to an extent such that when a mechanical clamping force and cooling is applied to the outer surface of said hollow tube and the tube is flattened, the opposing internal surfaces are sealed together by fusion there between. The actual temperature required to activate the plastics material depends on the plastic material concerned. Whilst such a solution has proven to be a valuable improvement over other available arrangements, the device normally has a hot air nozzle made of metal which itself requires time to reach operating temperature. Thus, transient effects of starting-up the device have to be taken into account when operating the device so that the correct temperature is obtained. Additionally, the appearance and type of seal or weld-seam obtainable by the hot-air technique is inherently restricted to the design of the hot-air nozzle, specifically the hot-air outlets. If for instance a "fancy" design is desirable, say a sealed tube end reminding the curvature of a hand or foot, this requires a specific nozzle design for each "fancy" end seal. SUMMARY OF THE PRESENT INVENTION: The present invention seeks to obviate the aforesaid disadvantages by providing an apparatus in accordance with claim 1 , wherein the energy from a light source is used to accurately and selectively activate the desired area(s) of the plastics material. Preferred features of the invention are defined in the dependent claims. With the apparatus of the invention, excellent control of the heat dissipation in and around the sealing zone is obtained, by suitable control of the intensity of the light beam which emanates from the source, and by arranging a heat sink outside the tube at a level essentially corresponding to the one where, on the tube inside, the spot type light beam acts. By arranging the heat sink as a cylindrical sleeve or ring having an inner diameter essentially equal to the nominal diameter of the tube, said heat sink will be useful also for presenting a perfectly round, circular tube end for heat activation, and the tube end will be centred, having the same axial centre line as the tube support and the cylindrical heat sink. Also, the invention allows the light source and associated equipment to be located completely outside the tube end at a remote location. Such an arrangement can lead to an increase in the filling level (i.e. the proportion of the tube which is filled) and an increase in processing speed. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will now be described with reference to certain non-limiting embodiments thereof depicted in Figs. 1 to 8, in which Fig. 1 shows a first embodiment of the invention with a laser light source directed on to the upper open end of a plastics tube which is made to rotate, Fig. 2 shows a second embodiment of the invention similar to Fig. 1 but in which an angled reflecting or refracting surface is used, Fig. 3 shows schematically a section of an intermittently operating tube filling machine, where the heating station and clamping station are shown, and the heating station is operating, Fig. 4 shows the same section as in figure 3, but with the clamping station operating, Fig. 5 shows schematically the means for rotating the tube support and the tube, Fig. 6 shows the clamping jaws in an active position, Fig. 7 shows a schematic cross section of a multi light source arrangement for heat activation of a tube, and Fig. 8 is a view from above of the arrangement in fig. 7. In Fig. 1 , a source of light such as a laser source Si is arranged such that its light beam 3 is directed onto the inner surface 2 of a tube 14 at a particular level. The level chosen is the location which is later to be clamped together by sealing jaws (Fig. 6) so as to form the seal once the inner surface has been activated. The tubes are plastics tubes or plastics laminated tubes made for example by extrusion or co-extrusion. Typically PE or PP tubes are used, although other types are possible. The beam is of the spot light type such that it has a spread (i.e. an extent) in the vertical direction which is adequate to provide a suitable seal width. Typically such a spread would be 2 or more millimetres. At the open end thereof, the filled tube is inserted into a cylindrical sleeve or ring 20, having a through going central circular opening 27 therein. The diameter of the opening is essentially equal to the nominal tube diameter. As the tubes, coming from transport boxes and forwarded to the heating station in the tube filling and sealing machine, at their open ends, may have a cross section other than perfectly circular, this means that in the heating station in figure 1 , the tube end outside will be brought into close, but slideable, contact with the walls of the opening 27 and centred with respect to line A-A. The insertion into the opening is facilitated by the truncated conical entering surface 28. By being provided with a conduit 29 for a cooling medium, the sleeve 20 and the walls of the opening 27 are maintained at a temperature level for transferring, by conduction, any excess of heat energy at the tube outside to the sleeve and the cooling medium. This means that the sleeve acts as a heat sink preventing deformation of the tube end, particularly the outside thereof, in case the heat energy supply to the tube inside would be too high. Applied in a tube filling and sealing machine, the laser arrangement of figure 1 is incorporated in station 10 in figures 3 and 4. An endless conveyor composed of chain links 24 carries in each link a tube support 25, each carrying a tube 14. In the heating station 10, there is arranged means (not shown) for lifting the tube support 25 and the tube to an elevated position. In this position, the tube support 25 (as shown in figure 3) is at a level above the conveyor links 24 and the tube end is inserted into the heat sink sleeve 20 as shown in figure 1. In this elevated position, the tube support, joumalled for rotation, is engaged by a rotating disc 30 (fig. 5) driven by a rotating shaft 31 from a motor 32. The rotation speed of the tube may be several hundred rpm. without causing outflow of the contents 4 of the tube. The heat sink sleeve 20 will not disturb the rotation, instead the transfer of any excess of heat energy will be improved, just because of the rotation and the sliding contact. On said rotation of the tube support 25 and tube, there may be superimposed an oscillation in the longitudinal axis of the tube. Such superimposed oscillation can be used for widening the extension of the heat activated region in the direction of the longitudinal axis of the tube or, which is most interesting, to design said "fancy" types of seals mentioned in the introduction of the specification. Taking into consideration the impact of the heat balance from the temperature adjustable heat sink 20 (sleeve), the output power of the laser Si is adjusted such that the intensity of the beam 3 at the inner surface only causes the inner surface to be activated but does not cause the outer surface to become deformed. In this way, distortion of the tube which might affect any printing thereon can be kept to a minimum. For each type of plastics material and application, the required intensity can be determined by simple experimentation. After the heating of the inner surface of the tube in station 10 in figure 3, the tube is forwarded one step to the clamping station where clamping jaws 22 (see also Fig. 6) press the heat activated tube inner surface into a transverse or other type of end seal. Normally, the clamping jaws are cooled by means of an arrangement similar to the one for the heat sink sleeve. As can be seen, no equipment needs to be located inside the closed volume of the tube 14. Thus, when the tubes are indexed into the heat-activation station and lifted by tube supports 25, the heat-activation can commence immediately. Additionally, since no equipment is inside the tube, the level of the contents 4 may be higher. In particular, no heat shield will be required to protect the contents as is the case with hot air activation devices. In a further embodiment of the invention as depicted in Fig. 2, light from a light source S 3 is directed down a light tube 9 towards a reflecting surface angled appropriately such that light reaches the inner surface 2 at the desired location. In the embodiment depicted, the reflecting surface is arranged at approximately 45° to the incoming light beam, although the angle can be altered according to circumstances. For example, if it is desired to locate all the equipment outside of the open tube, the casing 9 and the reflecting surface can be arranged so that light can be re-directed on to the inner surface 2 by being reflected at a larger angle of incidence. In the embodiment of Fig. 2, the tube 1 is rotated and, optionally, oscillated to heat around the internal periphery. The operation of the clamping or sealing jaws in order to clamp the tube end together is shown schematically in Fig. 6 and does not need to be described in more detail here. In the arrangement shown in figs. 7 and 8, the tube 14 is supported for rotation in the same manner as in the previous embodiments. Instead of having one single light source Si, in the present case a laser source, there are in total five laser sources arranged at mutually equidistant angel positions around the perimeter of the tube 14 at a level somewhat above the open end of the tube. Whilst the invention has been described with respect to certain preferred embodiments thereof, the invention is not limited thereto and may be varied widely within the scope of the appended claims. For example, although the invention has been described with respect to a laser source(s), it is of course possible to use a different light source(s) and appropriate focusing means (e.g. optical focusing means) to obtain the required intensity at the appropriate location.

Claims: CLAIMS 1. Apparatus in a tube filling and sealing machine for heating a portion of the interior surface (2) of a hollow flexible plastics packaging tube (1) which is open at one end and where said portion to be heated is heat activateable for sealing, and said machine is provided with means for forwarding tubes to processing stations and means for supporting said tubes during transportation and processing, said apparatus having at least one light source (Si, S3) for providing heat-activation energy, means (Si, 7, 10) for directing spot type light (3) from said at least one light source to a predetermined limited spot type area of said interior surface (2), and means (30, 31, 32) for rotating the tube around the longitudinal axis thereof for sweeping said heat activating limited spot type light around the perimeter of said interior surface, for activation of said interior surface at a predetermined level thereon, characterized in that a heat sink means (20) is arranged in a position for circumferentially enclosing the tube end outside at a level where said spot type light is swept, said heat sink means having a heat sink sleeve in rotational sliding contact with the tube for improving the transfer of any excess of heat energy, because of the rotation and the sliding contact. 2. Apparatus as in claim 1, characterized in that said heat sink means has a through going circular opening (27) of a diameter essentially corresponding to the tube nominal diameter, and that, the end of the opening facing the open tube end before the tube is inserted in said opening, is formed as a widening truncated conical end portion (28) forming an entering portion. 3. Apparatus as in claim 2, characterized in that said heat sink means has a passage (29) for a cooling medium. 4. Apparatus as in anyone or any of the preceding claims, characterized in that means are provided for lifting said tube sup- port means (25) for inserting said open tube end in said heat sink means opening (27). 5. Apparatus as in anyone or any of the preceding claims, characterized in that oscillating means are arranged for said tube support means (25) in said heat activation position for defining a predetermined heat activated width or pattern by said at least one spot type light at said predetermined level. 6. Apparatus as in anyone or any of the preceding claims, characterized in that said at least one light source is a laser. 7. Apparatus as in anyone or any of the preceding claims, characterized in that said at least one light source comprises several light sources at mutual equidistant angel positions around the tube perimeter and at a level above the open tube end.

Inventors: LINNER HANS, LINNER, HANS
Applicants: LINNER HANS, NORDEN PAC DEV AB, LINNER, HANS, NORDEN PAC DEVELOPMENT AB
Application year: 2000
Main classification: B29C65
IPC codes: B29B13, B29C35, B29C57, B29C65, B65B7