EP0534062B1 - Method for making, filling and closing bags - Google Patents

Abstract

The invention relates to a method for making, filling and sealing bags from a tubular web of thermoplastic film which is preferably provided with gussets and is printed in a formatted manner, in which method the leading end of the tubular web of film in each case is provided with a transverse welding seam, a section forming an open bag is severed from the tubular web of film, the bag is then filled and the open side of the bag is closed via a transverse welding seam. To achieve the object to provide a method of this type which guarantees that the filled bags are always filled so that they are tight and taut, provision has been made for the length of the sections of web of tubular film to be varied in accordance with the filling level of the bag, for the tubular web of film to be intermittently advanced up to a printed mark once the transverse welding seam which seals the bag has been formed, for the section forming the bag to be severed by means of a separating cut without simultaneous formation of the transverse welding seam which seals the following tubular section, for the following web of tubular film to be advanced in turn through a comparatively short adjustable length, for the advanced section of the tubular web of film to be severed once again, on an optional basis, and for the transverse welding seam which seals the following tubular section to be formed.

Description

The invention relates to a method for producing, filling and closing sacks from a tubular film web made of thermoplastic material, preferably provided with side gussets and printed in format printing, in which the respective leading end of the tubular film web is provided with a transverse cut seam and a section forming an open sack of the tubular film web is separated and in which the sack is then filled and the open side of the sack is closed by a transverse weld seam, the length of the tubular film sections formed already being varied in accordance with the filling height of the sack.

Such methods are largely known in the prior art. For example, the sections that later form the sack are pulled off a hose chain according to a previously known method. This hose chain is perforated at predetermined intervals so that the sections corresponding to the later sack can be torn off at the perforation. After the bottom weld seam has been closed, the individual tube sections are fed to a filling funnel for filling, for example with a granulate. After a predetermined amount of the filling material has been filled, the open sacks are removed, tightened on their open side and sealed in a specially provided edging device.

From DE 30 07 246 a machine for producing packs is known with which the generic method can be carried out. A disadvantage of this device, however, is that the use of such a device for printed bags is very complex and leads in particular to high losses of packaging material.

EP 0 420 821 also discloses a method for producing a vacuum pack for free-flowing products. Here, package blanks are made from stiff, but relatively flexible, composite packaging materials, which, prior to opening the packaging sleeve, are shortened by a pack section by a punch to a corrected length of the pack blank according to a statistically controlled trend control, the trend control being regulated by the measured values of the filling punch heights that result from the packaging after the product has been filled and compacted.

Furthermore, a device according to DE-OS 37 15 685 has sliding and preferred rollers, through which the front end of the tubular film web, each provided with a transverse weld seam, freely hanging in the vertical direction intermittently by one bag or sack length between each opening in a horizontal plane. and welding jaws performing closing movements is pushed through a welding device. A cross cutting device is arranged below the welding jaws and below this cross cutting device are arranged in pairs grippers provided on a transport device which hang the bags or sacks separated from the tubular film web and provided with bottom weld seams with a horizontal conveying direction over a cooling section for cooling the cross weld seams to a filling station Feed transporting transfer device. Here the transport device consists of a secondary support piece with radial arms, which is rotatably mounted about a vertical axis and at the free ends of which the grippers provided in pairs are arranged. The cooling section consists, as it were, of a cooling carousel, which feeds the bag workpieces provided with the transverse weld seams and separated from the tubular path from the welding station on a circular path to a device for transferring the bag workpieces to the filling station. If this device has, for example, four radial arms, a welding device and a cutting device are located above the first station. According to this prior art, a sack already provided with a transverse weld seam is inserted into the first opened pair of grippers from above in each cycle for the production of a sack, and is preferably gripped and cut off over a sack length. A new cross weld seam is then formed at the end of the tubular path, while the cooling carousel rotates intermittently through an angle of 90 ° and remains in this position until another sack with a cross weld seam has been inserted into the subsequent station. This is repeated in a four-arm cooling carousel until the first station has rotated 270 ° in three cycles. At this point the cross weld seam has cooled and the sack is transferred to a transfer device which transports the sack to a filling station. After the sack has been filled, a further transverse weld seam is then applied to close the filled sack after the open side of the sack has been pulled tight.

In the filling station, the sack is filled with a predetermined amount of filling material, a predetermined weight of filling material usually being filled in. Now, however, the contents, for example a granulate to be filled, have the same Weight different bulk volumes. This is due, for example, to a different moisture content in the bulk material. Due to the different bed heights, it can now happen that the bag has an undesired free space between the filler and the filler after it has been closed by the transverse weld seam. This means that the bags are not filled to the brim, which has disadvantages in particular when handling the bags further.

When this method is carried out with a device according to DE-OS 37 15 685, there is also the problem that an adjustment of the trimming device arranged in the same device is not provided, so that, depending on the bulk density of the filling material, the bags - as desired - tight or filled with an undesirable air gap between the product and the sealing cross weld.

The object of the present invention is to further develop the generic method in such a way that even with printed tubular film webs it is ensured that all bags are tight and bulky, i.e. without unwanted dead volume, and the loss of packaging material should be minimized.

According to the invention, the object is achieved on the basis of a generic method by a method with the features of the characterizing part of patent claim 1.

This invention is based on the knowledge that the pouring properties of the filling material do not change abruptly. So it is determined by the operating personnel that due to a change in the bulk density, the bulk volume of the filling material is changed, the operator varies the length of the tubular film web sections formed and adjusts the respective fill level of the filling material in the sack by appropriate adjustment of the sliding and preferred rollers of the device which prefers the tubular film web. According to the method according to the invention, it is now advantageously prevented that the tubular film web is severed at a printed point by varying the length of the tubular film web section formed in each case. It is crucial that the tubular film web is always pulled up to a print mark on the opening edge of the sack to be cut off, that it is then cut off and that the bottom weld seam of the following section then varies according to the length of the section to be formed, depending on the setting due to the fill level by the operator becomes. Depending on the fill level of the filling material, a tubular film web section a few centimeters long is created, which can be collected separately and sent for recycling. Optionally, this tubular film section, in particular if it has only a very small width, can remain on the sack as a protrusion.

If corner welds are simultaneously applied when cutting and attaching the transverse weld seams, as is known, for example, from EP-A 00 21 463, it must be taken into account that the corners of the opening edge of the leading bag and the corners on the bottom weld seam of the subsequent bag section are not at the same time here can be attached with a tool, as would be easily possible, for example, with a tubular film web with scattering pressure. Therefore, according to a further advantageous embodiment of the present invention, the corner welding takes place at the opening edge of the bag section and at the bottom seam in each case using a separate corner welding tool. Depending on the length of the intermediate section, the section can then be readjusted manually or automatically between the separate corner welding tools. In an advantageous manner, all corner weld seams can be formed simultaneously with the transverse weld seam closing the subsequent hose section.

Alternatively, the corner weld on the opening edge of the bag section can be carried out simultaneously with the separating cut and the corner weld on the bottom seam can be carried out simultaneously with the formation of the transverse weld seam. With this process variant, however, it is accepted that the duration of the process sequence is comparatively longer, since with simultaneous corner welding at the opening edge of the bag section with the implementation of the separating cut, it is no longer the time for cutting the web but the welding time for the corner welding that determines the speed .

Fig. 1:

eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens zum Herstellen von Beuteln oder Säcken mit Kühlkarussell in schematischer Darstellung in Seitenansicht,

Fig. 2:

einen Schnitt durch die Vorrichtung gemäß Linie II-II in Fig. 1

Fig. 3:

den in Fig. 1 mit strichpunktierter Linie eingekreisten Teil in vergrößerter Darstellung,

Fig. 4:

den mittleren Teil der Vorrichtung gemäß Fig. 1 in vergrößerter Darstellung und

Fig. 5:

die aus Fig. 4 ersichtliche Verriegelungsplatte in Draufsicht.

An embodiment of the invention is explained below with reference to the drawing. In this shows:

Fig. 1:

1 shows a device for carrying out the method according to the invention for producing bags or sacks with a cooling carousel in a schematic representation in a side view,

Fig. 2:

a section through the device according to line II-II in Fig. 1st

Fig. 3:

the part circled in Fig. 1 with a dash-dotted line in an enlarged view,

Fig. 4:

the central part of the device of FIG. 1 in an enlarged view and

Fig. 5:

the locking plate shown in Fig. 4 in plan view.

A frame 1 has side walls 2 and 3, which are indicated in FIG. 2. Both side walls 2, 3 are connected to each other by a crossbar 4. This cross-member 4 carries approximately in the middle a downwardly projecting fixed axis 21, on which a swivel arm 5 is mounted near the cross member 4, which via a pressure-piston-cylinder unit 6, the cylinder of which is held by a support piece, in one of two possible end positions can be moved.

From Fig. 5 it can be seen that the pivot arm 5 designed as an angle lever carries a molded part 5 'at its free end and is provided with a locking roller 7 in its angular region. The function of these parts is discussed further below in the description.

Furthermore, a further vertical axis 8 is fastened to the cross member 4, which carries a four-armed turntable 9 below the swivel arm 5, which can be rotated by a motor 11 at intervals of 90 ° by a toothed belt 10. The direction of rotation of the turntable is indicated by an arrow A in FIG.

From Fig. 2 it can be seen that the freely cantilevered arms 9a of the turntable 9 forming a hub, as it were, carry fittings 12, each of which has two upwardly projecting pins 13. A lever 14 is mounted rotatably about each pin 13 and is designed as a gripper 15 at its free end. Each of these grippers 15 rests against the counter surface 17 under the force of the springs 16, each shaped piece being provided with two counter surfaces 17. The mutually facing levers 14 of two adjacent arms 9a are functionally connected to one another via a link 18 in such a way that the two associated grippers 15 open or close simultaneously, for example to be able to grip and hold a bag 19.

The grippers 15 are opened by the wedge-shaped or curved cam surfaces of the molded part 5 'of the support arm 5. If the support arm 5 is pivoted by extending the piston rod of the pressure medium-piston-cylinder unit, the molded part 5' presses the pressure rollers 20 connected to the levers 14 Form piece 12 apart so that the grippers 15 pivot about the pin 13 and detach from the associated counter surfaces 17. At the same time, the grippers 15 of adjacent shaped pieces are released via the handlebars 18. In the position shown in FIG. 2, the gripper units 15 facing the upper and the right-hand edge of the drawing would thus be released when the pressure medium-piston-cylinder unit 6 is actuated.

In order to ensure that damage occurs when the motor 11 is switched on unintentionally due to the pivoted-out shaped piece 5 ', the securing roller 7 mounted in the angular region of the pivot arm 5 runs into a guide groove 22 of a locking plate 23 when the pivot arm is pivoted to open the grippers. This locking plate 23 is firmly connected to the turntable 9 by means of screw bolts 24, so that it is prevented from rotating by the securing roller 7 of the swivel arm 5, for as long as the molded part 5 'is between the rollers 20 of a molded part 12.

From Fig. 1 it can be seen that a hose 26 runs from a roll 25 from above into an inlet station 27. This inlet station 27 is connected in a stationary manner to the frame-shaped frame 1 and can be seen in more detail in FIG. 3. 3 shows the central axis 8 of the cooling carousel and part of the turntable 9. A hose section 19 provided with a bottom seam is clamped by the grippers 15 and the counter surfaces 17 of the turntable 9, but is initially still connected to the hose track 26. Above the grippers 15 and 17 there is a coupling rod 28, which is guided in parallel on the handlebars and carries at its end facing the track 26 a clamping strip 29 which interacts with a counter strip 31 fastened in a support 30 fixed to the frame. In addition to the counter bar 31, the carrier 30 also has a knife groove 32 and a welding jaw 33. A knife 34 is immersed in the knife groove 32 to separate the bag 19 from the tubular web 26, while a second welding jaw 35 interacts with the welding jaw 33 in order to provide the leading end of the tubular web 26 with a transverse weld seam.

The tubular web 26 is printed in format printing. In this case it is important that the pressure is not cut when the tube sections are formed. Therefore, the preference of the tubular web is clocked by means of a print mark arranged at the opening edge of the respective sack. The corresponding operator now changes the length of the bag section by cutting away a more or less long strip between the opening edge of the bag section and the bottom weld seam of the following bag section. These cut away tubular sections can be collected and sent for recycling. When the separating cut is formed at the opening edge, the knife 34 placed on the tubular web 26 without the welding jaw 33. After corresponding preference around the intermediate section to be cut away, the knife 34 is placed again on the tubular web 26, but this time together with the welding jaw 33. The separating cut of the intermediate section and the transverse weld seam of the subsequent bag section are therefore carried out or formed at the same time.

A further clamping device is provided above the welding jaws 33 and 35, which clamps the tubular web 26. This consists of a pivoting lever 39 which is provided with a clamping strip 38 and which can be moved via a pressure medium-piston-cylinder unit 40. An arm carrying a roller 41 is fixedly connected to the pivot lever 39, the roller 41 being at a distance from a guide piece 43 in the clamping position of the pivot lever 39. This guide piece 43 is connected to a lever 44 which is held against a stop 46 via a spring 45. The pivot point of the lever 44 lies on the axis of the preferred roller 47. It has a downward-facing shoulder which is designed as a counter-holder 48 to the terminal strip 38. To release the clamping, the pressure-piston-cylinder units 37 and 40 are first actuated after the formation of a bottom seam and a separation cut, and as a result the coupling rods 28, 36 and the lever 39 are pivoted away. In the course of this movement, the roller 41 comes into contact with the cam surface of the guide piece 43. This causes the counter-holder 48 to pivot in the direction of the arrow C, which on the one hand releases the freely hanging end of the web 26 from the welding jaw 33 and on the other hand deflects it. This deflection ensures that the web does not collide with the carrier 30 when it is advanced by a sack length by the preferred rollers 47 and 51 at the next cycle.

In order further to prevent the web 26 from being able to wrap around the preferred rollers 47 and 51, the preferred rollers are provided with annular grooves 49, 50 into which stripping fingers 52 and 53 engage. Of these fingers, the fingers 52 are held in place on the frame and the fingers 53 are attached to the counter-holder 48 as wiping rakes.

Claims (5)

1. Method for making, filling and closing bags from a tubular film web (26) of thermoplastic material which is preferably provided with side folds and is printed on by format printing, in which method the respectively leading end of the tubular film web (26) is provided with a transverse weld seam and a section forming an open bag is cut off from the tubular film web (26), and in which method the bag is then filled and the open side of the bag is drawn taut and is closed by a transverse weld seam, the length of the tubular film web sections (19) formed already being varied according to the filling level of the bag, characterized in that the length of the tubular film sections (19) formed can be set by an operator by corresponding setting of the sliding and drawing-forward rollers (47, 51) of the apparatus drawing the tubular film web (26) forward, in that, after forming of the transverse weld seam closing the bag, the tubular film web (26) is drawn forward cyclically up to a printing mark; in that the section (19) forming the bag is cut off by means of a separating cut without simultaneous formation of the transverse weld seam closing the following tube section (19); in that the following tubular film web (26) is in turn drawn forward by a comparatively short adjustable length; in that optionally the drawn-forward section (19) of the tubular film web (26) is again cut off; and in that the transverse weld seam closing the following tube section (19) is formed.
2. Method according to Claim 1 with additional corner welding of the sections (19) forming the bags, characterized in that the corner welding takes place at the opening edge of the bag section (19) and at the bottom seam, in each case by means of a separate corner-welding tool.
3. Method according to Claim 2, characterized in that the distance between the separate corner-welding tools is automatically readjusted, if appropriate.
4. Method according to Claim 2 or 3, characterized in that all the corner weld seams are formed simultaneously with the transverse weld seam closing the following tube section (19).
5. Method according to Claim 2, characterized in that the corner welding is performed at the opening edge of the bag section (19) simultaneously with the separating cut and in that the corner welding takes place at the bottom seam simultaneously with the formation of the transverse weld seam.

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