CH628586A5 - Process for welding a plastic base part to a plastic container and device for carrying out the process - Google Patents

Description

The invention relates to a method for welding a plastic foot part to a plastic container and to an apparatus for performing the method. The plastic container can be a bottle, for example.

There is a great need for plastic containers that are suitable for storing beverages, for example. The advantages of a plastic container are its light weight and impact resistance. However, the types of plastic used for such purposes are relatively expensive, so that from an economic point of view it is necessary to keep the wall thickness of such containers as small as possible. On the other hand, however, it is necessary to make those areas of the container that are subject to particular stresses sufficiently stable. Such a requirement applies, for example, to the bottom of a bottle, in particular when the bottle is used to store pressurized goods, such as carbonated drinks. In order to be able to simultaneously meet the opposing requirements - thin-walled containers on the one hand and sufficient stability on the other - there is a need to make the container bottom spherical.

However, since a container with a spherical bottom cannot be placed on a surface, it is necessary to equip such a container with support elements or with feet. The feet can be formed, for example, by areas that protrude from the bottle base, such as bulges or by parts attached to the container. Such parts are attached to the container, for example, by snapping, riveting, welding or comparable fastening methods.

The invention is based on the object of specifying a method for welding a plastic foot part to a plastic container, which is particularly suitable for thin-walled containers and which also ensures reliable stability of the container when the container is deformed as a result of internal pressure. Furthermore, the thin-walled container base must not be weakened by welding the plastic foot part.

Furthermore, a device for performing the method is to be specified.

The object is achieved according to the invention by the features specified in the characterizing parts of claims 1 and 4.

Suitable plastics for carrying out the invention are polyethylene, polyethylene terephthalate, acrylonitrile and polyvinyl chloride. Advantageous embodiments of the invention are specified in the dependent claims.

An embodiment of the subject matter of the invention is explained in more detail with reference to the drawings. Show it:

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Fig. 1 is a perspective view of a device for welding plastic foot parts to plastic containers and

Fig. 2 is a sectional view through the bottom area of a plastic container and a plastic foot part before welding.

1 shows a turntable 100 which is arranged on a shaft driven by a drive element 101. The turntable 100 is driven step by step in accordance with the work cycles. On the turntable 100, specific holders 20 are arranged on a circular path around the axis of rotation for receiving plastic foot parts 30. The holders 20 are adapted to the dimensions of the plastic foot parts to be welded to the plastic container 10. Guide elements 21 which are adapted to the containers 10 are located above the holders 20.

An energy source 50, which has a welding mandrel 51, for example for an ultrasonic welding, is arranged below the turntable 100 and assigned to one of the cycle stages. The welding mandrel 51 can be displaced upwards from a position below the turntable 100 in such a way that it can be brought into contact concentrically through the respective holder 20 with the plastic foot part 30. In the position following the welding mandrel 51 in the direction of rotation of the rotary table 100, a cooling element 52, which can also be moved upward in the same sense as the welding mandrel 51, is arranged below the rotary table 100 and also has a mandrel 53 intended for contact with the plastic foot part 30.

Each of the holders 20 arranged on the turntable is assigned a hold-down device 40, which is used to hold down the respective plastic container 10 against the associated plastic foot part 30 over several cycle stages. The hold-down devices 40 can be connected to a pressure source 81 via valves, not shown, which, for example, supplies compressed air from a compressed air container. The lowered hold-down devices 40 seal against the respective neck of the plastic container 10 and, by opening the valves, enable

that an excess pressure is generated inside the plastic container 10.

Each hold-down device 40 has a rolling roller 41 which, in the lowered state of the hold-down device 40, rolls on the stationary pressure plate 80 over the circumferential area provided.

The plastic foot parts 30 stacked in a magazine 60 are fed individually by a feed element 61, for example a screw, in the direction of the respective holder 20. A suction nozzle 62, which can be adjusted from below through the rotary table 100, serves to hold the plastic foot part 30 supplied by the feed element 61 and to pull it into the holder 20. The suction nozzle 62 is permanently assigned to one of the cycle stages. The containers welded to the plastic foot part are removed from the rotary table 100 by means of a suction pipe 70 arranged above one of the cycle stages.

2 shows the arrangement of a holder 20 on the rotary table 100 in detail. The holder 20 consists of a cup-shaped ring 22 and a pressure body 23 arranged concentrically thereto. The pressure body 23 has a bore through which either the welding mandrel 51 or the mandrel 53 of the cooling element 52 (FIG. 1) can be set. Like the parts mentioned above, the plastic foot part 30 and the bottom area of the plastic container 10 are also shown in longitudinal section in FIG. 2.

The cup-shaped ring 22 of the holder 20 is preferably made of metal and is flexibly attached to the turntable 100 by means of a number of springs 24. It can therefore be moved from a position distant from the turntable 100 to a position just above the turntable 100. The inside diameter of the cup-shaped ring 22 is adapted to the outside diameter of the plastic foot part 30 in such a way that the cup-shaped ring 22 rests on the plastic foot part 30.

The pressure body 23 is screwed into the turntable 100 by means of a thread, whereby it can be adjusted with respect to the turntable 100. The bore extending through the pressure body 23 is dimensioned such that not only the welding mandrel 51 and the cooling mandrel 53 can be fed through the bore, but also that the suction nozzle 62 can be passed through. The upward pressure surface of the pressure body 23 runs approximately 15 flush with the inner bottom region of the cup-shaped ring 22 when a foot part 30 is inserted into the holder 20 and held down.

It can be seen from FIG. 2 that the middle bottom area of the container 10 is at a distance from the inside of the middle 20 bottom area of the foot part 30. This distance results in the initial position of the container 10 before it is held down. In the next operation, the container 10 is pressed against the foot part, whereby it is moved together with the edge of the foot part 25 30 in the direction of the turntable 100. In the position reached thereby, the container 10 presses with the central region of its base against the central region of the foot part 30. The cup-shaped ring 22 can follow the downward movement of the edge of the foot part 30 30, since it rests resiliently on the compression springs 24. In this position, which is pressed down against the turntable 100, the foot part 30 is welded to the bottom of the container 10 and the welding point is then cooled.

The mode of operation of the device described will be explained in more detail below. In the position labeled 1 on the rotary table 100, a foot part 30 is fed from the magazine 60 to the holder 20 by means of the feed member 61. The foot part is drawn into the holder 20 by means of the suction nozzle 62 which can be set in the direction of the foot part 30, whereby it is centered by the funnel-shaped guide element 21 in order to assume a correct position in the holder 20.

The turntable 100 is then rotated a 45 step in the direction of the arrow. In this position, designated by 2, a container 10 'is fed through a device (not shown), centered by the guide member 21' and placed on the foot part 30 'arranged in the holder 20'. The hold-down device 40 'is pivoted down so that it thus encloses the neck of the container 10' which is designed as a bottle.

After the turntable 100 has been rotated one step further, the interior of the container 10 "in the position indicated by 3 is acted upon by a pressure medium, provided that the resulting increase in rigidity during welding is necessary. The downholder 40 'which is pivoted down becomes held in the swiveled down position by its rolling roller 41 "rolling on the pressure plate 80 in order to keep the container 10" depressed over a rotation range of the turntable 100 comprising several working steps. In the depressed position, the container 10 "and the foot part take on the Weld the required position to each other.

65 After the turntable 100 has been rotated a further step in the direction of the arrow, the welding mandrel 51 connected to the energy source 50 is advanced to the central base region of the foot part 30 ″. The energy

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Source 50 can, for example, be set up to emit ultrasound, so that the plastic foot part 30 "'is heated in its central area with the central bottom area of the plastic container 10"' and these two parts are thereby welded to one another. The welding mandrel 51 is then pulled back into its position below the turntable 100.

In the position labeled 5 on the rotary table, the cooling mandrel 53 of the cooling element 52 is advanced to the central bottom region of the foot part 30IV in order to cool the material of the foot part 30IV and the container 10IV at the welding point. The cooling process lasts until the required strength of the connection between the foot part and the container is reached.

When the rotary table 100 is rotated by a further stage, the rolling roller 41IV is released from the stationary pressure plate 80. If the container 10IV was pressurized with a pressure medium, the container is relieved of this pressure medium. The hold-down device 40 returns to its starting position. The container connected to the foot part is now ready for removal from the device described. It can now be removed from the turntable 100 by means of an ejection device or by means of a suction pipe 70.

In the exemplary embodiment shown, between the cooling stage designated 5 on the rotary table 100 and the stage in which the container is removed by the suction pipe 70, further stages are provided, to which a test device and an ejection device can be assigned, by which the tests found to be faulty To remove containers from the turntable 100 before they have reached the position to which the suction pipe 70 is assigned.

There is also the possibility of centrally controlling the described device for executing the production process 5, for example by means of a microprocessor. A microprocessor supplies all signals in the form of pulses to carry out the control functions that are required to carry out the movements necessary for the production process.

In certain applications, the cup-shaped ring 22 can also be rigidly connected to the turntable 100. This embodiment is suitable in cases in which it is not necessary for the foot part 30 to resiliently rest on the container bottom, as is the case with the cup-shaped ring 22 supported elastically from 15.

Instead of the turntable 100 shown in the exemplary embodiment, it is also possible to arrange the individual production stations one behind the other in an at least approximately straight row. It is also possible to arrange the individual manufacturing stations in a stationary manner, to insert the containers and foot parts by hand and to transfer them to the subsequent processing station. In certain cases it can also be economical to combine the above-mentioned embodiments with one another. 25 The attachment of the foot part to the container base according to the invention enables an exact orientation of the foot part to the axis of the container. This ensures perfect stability of the container, so that the container can be filled without any problems. Older versions of the 30-ranger with the foot snapped onto the container could not guarantee an exact orientation of the foot to the axis of the container.

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Claims (14)

628586 1. A method for welding a plastic foot part (30) to a plastic container (10), characterized in that the foot part (30) in its central region by a pressure element (23) against the central bottom region of the container (10 ) and that energy is delivered to the areas held together by an energy source (50) in order to weld the foot part (30) with its central area to the central bottom area of the container (10). 2. The method according to claim 1, characterized in that the foot part (30) in its central region during the welding against its other, on the container (10) areas biased by the pressure body (23) against the central bottom region of the container (10) becomes. 2nd PATENT CLAIMS 3. The method according to claim 1 or 2, characterized in that a pressure is exerted on the middle bottom region of the container (10) during welding from the inside, either by putting the interior of the container under pressure or by means of a counter-holder. 4. The device for carrying out the method according to claim 1, characterized in that a holder (20) is provided for receiving the foot part (30), that a hold-down device (40) is provided to counter the container (10) with its bottom to hold the foot part (30), and that a welding element (51) intended to deliver welding energy is slidably arranged in order to be brought into contact with the foot part (30). 5. The device according to claim 4, characterized in that a deliverable on the welding point cooling element (53) is provided. 6. Device according to one of claims 4 or 5, characterized in that a pressure source (81) can be connected to the interior of the container to pressurize the container (10) during the welding and cooling process to increase its strength. 7. Device according to one of claims 4 or 5, characterized in that a with the inside of the container bottom during the welding and cooling process can be brought into contact with the counter-holder. 8. Device according to one of claims 4 to 7, characterized in that the holder (20) a cup-shaped ring (22) intended for centering the foot part (30) and a cup-shaped ring (22) arranged within the cup-shaped ring for contacting the middle one Has area of the foot part (30) certain pressure body (23) which is penetrated by the displaceable welding element (51). 9. The device according to claim 8, characterized in that the cup-shaped ring (22) is connected by means of compression springs (24) to a rotary table (100) carrying the holder (20), and that the pressure body (23) in the rotary table (100) is adjustable is fastened, so that when forces act on the edge of the foot part (3ü) in the direction of the turntable (100), the outer regions of the foot part can be displaced relative to its central bottom region resting on the pressure element (23). 10. Device according to one of claims 4 to 9, characterized in that a magazine (60) for receiving the foot parts (30) and a feed member (61) are provided in order to individually stack the foot parts (30) stacked in the magazine (60) Feed holder (20). 11. The device according to claim 10, characterized in that a guide member (21 ') is provided to feed a container (10') in the direction of the holder (20 '), wobèi the container (10') to the in the holder ( 20) lying foot part (30 ') is to be aligned. 12. Device according to one of claims 4 to 11, characterized in that a suction pipe (70) is provided in order to remove the container (10) welded to the foot part (30) by means of negative pressure from the holder (20). 13. The apparatus according to claim 9, characterized in that the turntable (100) can be driven step by step in order to move the container (10) in one step into one of the preceding and subsequent positions (2 to 7). 14. The apparatus according to claim 9, characterized in that the turntable (100) is essentially continuously driven to assemble the container (10) with the foot part (30).