NL8201640A - Unit for welding and weld cooling of continuous foil tube - moved step wise positions foil independently at welding and cooling stations - Google Patents

Abstract

The arrangement is intended for producing spaced welds in a continuous length of foil tube which is intermittently moved alongside one or more welding stations and subsequent weld cooling stations . The foil material is stopped at the stations for the welding and cooling operations respectively, positioning of the material at the cooling stations being controlled independently of its positioning at the welding stations. Positioning may be via respective detectors responding to the same or to different markings on the material which may be printed or burned-in. Positioning at the cooling stations may be with reference to a perforation applied in a preceding welding station . Welding and weld cooling on continuous foil tube e.g. in manufacture of coherent length of foil bags.

Description

V

825039 / Keijser

Short designation: Method and device for making welds in a web of intermittently transported tubular film material.

The Applicant mentions as inventor: A.W.J.Leloux in Dedemsvaart

The invention relates to a method for making welds in a web of intermittently transported tubular film material, wherein, after the welds have been applied in one or more stations, the welded places are cooled in one or more subsequent stations.

With a view to obtaining a good and constant quality of the welds, it is important that the web is kept as free as possible from stresses both during the welding and during the cooling of the welding locations. On the other hand, however, one has to deal with the phenomenon that shrinkage or stretching of the film web occurs during the making of the welds and during cooling to an extent which is not completely controllable and which therefore shows some variation. Partly because of this, therefore, when the web is moved intermittently along the welding stations and cooling stations in the usual manner, a position difference can arise. Thus, assuming that the position of the web is primarily set relative to welding stations, the result will be that the location of the welds made may differ slightly in relation to the cooling stations, causing uneven and in some cases insufficiently timely timely cooling can occur.

The object of the invention is to provide an improved method or device in this situation, with which ultimately a higher quality and a better consistency of the quality of the welds can be achieved.

To this end, it is characteristic of the method according to the invention that the position adjustment of the web with respect to the cooling stations is carried out independently of the position adjustment with respect to the welding stations.

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These independent settings can be achieved using the same mark on the web, e.g. a commonly used burned or printed mark. In many cases, however, a tear-off perforation is made simultaneously with the making of a weld in the web, and then preferably the position is adjusted with respect to the welding stations by observing the tear-off perforation, while the adjustment with respect to the welding stations take place in the usual manner by observing the classic burn-in marking.

The device is based on the known embodiment comprising means for continuously feeding and discharging the web, means for intermittently moving the web along welding and cooling stations, one or more welding stations, one or more stations behind cooling the welds made, and means for position adjustment of the web relative to. the welding stations.

According to the invention, this device is characterized in that between the continuously operating feed and discharge means for the web there are at least two sets of intermittently operating transport rollers, which can be braked and brought to a standstill independently, which, in addition to the means for the position adjustment of the track relative to the welding stations, separate means are provided for position adjustment of the track relative to the cooling stations, and in each cycle the position of the one track section relative to the welding stations is determined by one set of transport rollers, and that of the other web section relative to the cooling stations by the other set.

The two sets of intermittently operating transport rollers can be driven by the same motor but via two separately operable clutches and brakes.

The various measures according to the invention can be combined without any problem with the necessary adjustments to the machine in view of the fact that the same machine must often be suitable for processing 8201640 V * v -3 pipe material of different width, and also to applying welds at different longitudinal distances, more particularly to produce bags of different lengths.

The invention will be explained below with reference to the appended drawing of an exemplary embodiment of the device. The single figure schematically shows a view of the complete welding machine.

In a manner known per se, the middle portion 10 of the machine is adapted to move the film web intermittently and to carry out the required operations during standstill times. On the one hand there is an uninterruptedly operating supply device for the pipe material, indicated in its entirety by 2, and on the other, a discharge device in its entirety indicated by 3, and also uninterruptedly operating.

The feeder comprises a head 4 for an unwinding spool 5 on which the tubular film material, after extrusion, has been wound up to a large length. The trestle with the reel can be driven in front of the machine with the aid of a lifting truck 6. The web is unwound by a driven unwinding roller 7 which is carried by a pivoting arm 8. This arm 8 can be lifted by a lifting cylinder 9 during the changing of the roll, but normally rests on the roll under its own weight. When unwinding, the position of the web 10 / in width direction is determined by the foil control unit 11.

The web then passes through a known dancer 12 which allows the transition between the continuous motion of the web in the feed section 2 and the intermittent movement in the edit section 1. The unwinding roller 7 rotates continuously, but its speed is adjusted depending on of the dancer's behavior.

On the other side of the processing part 1 of the machine, which is yet to be described in more detail, a similar dancer 13 is again included as a transition to the uninterruptedly operating discharge device 3. On that side there is a take-up trestle 14 and a swing arm again. 15 with lift 8201640

• I

- 4-cylinder 16 carried winding roller 17, which takes care of winding the web. A foil control 18 adjusts the position of the web in width direction relative to the take-up roll.

5 In the machining part 1 of the machine, a drive motor 19 provides for the intermittent driving of a first set of transport rollers 20 and a second set of transport rollers 21 for the film web 10. A first welding station is located immediately behind the first transport rollers 20, 22, and that any suitable type can make welds. Shortly behind it, there is a clamping device 23 which, together with the continuously pressed transport rollers 20, can ensure that the web 10 is kept in station 22 during welding.

Then the web 10 passes through a second welding station 24, is then guided over a guide plate 25 to be passed through a first cooling station 26 and then through a second cooling station 27. A little further the path continues between the second set of transport rollers 21 and then leaves the machine via 20 the aforementioned dancer 13.

The welding station 24, the guide plate 25 and the cooling station 26 are each individually height adjustable relative to the frame of the machine, to adapt to different bag lengths, or more generally different unit distances between the welds to be applied. A detector 28 is connected to the carrier for the welding unit 24 to detect a mark on the web. This can be a photocell that detects a common mark in the form of a printed or burnt stripe. The signal derived therefrom can be used as a control signal for the position adjustment of the portion of the web 10 during the operation of the welding stations 22 and 24.

A detector 29 is connected to the carrier of the cooling station 27. This can also be a photocell device which, for controlling the position adjustment of the part of the track 10 in the cow stations 26 and 27, detects the same mark as the photocell 28. Because almost always, at the same time 8201640 -5- With the application of welds in a tubular foil web, a tear-off perforation is applied in the web, which is then generally done in the second welding station 24, that perforation can advantageously be used as the mark-5 on the web on which the detection device 29 responds. After all, this perforation lies right next to the weld arranged in the welding station 24, and its location relative to that weld is thus unambiguously determined. The point is that in the second part of the treatment the welds are properly adjusted with respect to the cooling devices, and the perforation immediately adjacent to such a weld is therefore an excellent indication. Detection devices for perforation lines are known.

For independently stopping the film web 10 in the part located in the welding stations 22, 24 - i.e. the left part of the loop in the drawn arrangement, of the different stations in the machine - and of the other part of the foil web, on the right-hand side of the loop, relative to the cooling stations 20 26 and 27, ensures that the sets of drive rollers 20 on the one hand and 21 on the other can be stopped independently, for which purpose they each have their own drive motor from the same drive motor 19. have link not shown. Furthermore, when setting up the machine, care must be taken to ensure that the guide plate 25 is not set so low that stresses occur in the foil web. After all, the intention is precisely to avoid those stresses. The plate 25 should therefore be set so high that the loop at the four processing stations is tension-free, while there should still be some play in case the transport rollers 21 have to give the right-hand part of the loop a slightly greater displacement path. then given by the rollers 20 to the left portion of the loop. Incidentally, the machine is operated in the manner described below. It is believed that this method of control is so simple that it is possible to dispense with drawing a control circuit separately.

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When a welding cycle has ended, the entire section of the foil web between the dancers 12 and 13 is transported at high speed. This occurs because both the first set of transport rollers 20 and the second set of transport rollers 21 are coupled to the motor 19. The two sets of transport rollers make at that high speed a set number of revolutions corresponding to a transport distance slightly smaller than the unit length (bag length). Thereafter, as is known per se, the speed of the motor is reduced, and thus also the transport speed of the foil web. In addition, however, the detection devices 28 and 29 are then activated. As the film web 10 moves at a reduced speed, the photocell 28 will signal the mark on the web. Thereby, a control signal is output whereby the coupling between the motor 19 and the first set of rollers 20 is disengaged and the rollers 20 are decelerated so that the film web 10 in the left-hand part of the loop is in the correct position with respect to the welding stations 22, 24 to comes to a standstill.

Irrespective of this, when the perforation detector 29 detects a perforation in the slow-running film web, a control signal is output, whereby the coupling between the motor 19 and the second set of rollers 21 is disengaged and braked, so that the right-hand part of the loop on the right place comes to a stop.

It will therefore be clear that, when correctly adjusted, the foil web remains free of stresses and the web is brought into the correct position with respect to the welding units on the one hand and with regard to the cooling units, independently of the shrinkage or the elongation of the foil strip as a result of welding.

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Claims (6)

1. Method for making welds in a web of intermittently transported tubular film material, wherein, after the welds have been applied in one or more stations, the welded places are cooled in one or more subsequent stations, characterized in that the position adjustment of the web with respect to the cooling stations is performed independently of the position setting with respect to the welding stations. Method according to claim 1, characterized in that different marks on the track are used for two position settings. 3. Method according to claim 2, wherein for the position adjustment of the web relative to the welding stations a printed or burnt-in mark is used, and wherein further a tear-off perforation is applied in the web simultaneously with the making of a weld, with the characterized in that the position of the web relative to the cooling stations is adjusted by observing the tear-off perforation. 4. Apparatus for making welds in a web of tubular film material, comprising means for continuously feeding and discharging the web, means for moving the web intermittently past welding and cooling stations, one or more welding stations, one or more stations located behind it for cooling the welds made, and means for position adjustment of the web relative to the welding stations, characterized in that at least two sets of intermittently operating transport between the continuous operating feed and discharge means for the web -30 rollers are provided, which can be independently braked and brought to a standstill, that in addition to the means for position adjustment of the web relative to the welding stations, separate means are provided for position adjustment of the web relative to of the cooling-35 stations, and in each cycle the position of the one track section relative to the welding stations is determined by 8201640 -8- + ► '* - * ί one set of transport rollers, and that of the other track section relative to the cooling stations by the other set. Device according to claim 4, characterized in that the two sets of intermittently operating transport rollers are driven by the same motor but via two separately operable clutches and brakes. 6. Device as claimed in claim 4 or 5, wherein in one of the welding stations there is also provided a perforation device for making a tear-off perforation in the web, characterized in that the means for the position adjustment of the web relative to the cooling stations are of a type that can detect the location of a perforation. 8201640