EP2441574A1 - Method and device for constructing open bases at end sections of tubular bag bodies - Google Patents

Abstract

The method involves opening an end region of a tubular bag body (10) during transportation of the body in a flat manner, where the body is formed from fabric of stretched plastic tapes or plastic sheet. A widening tool is introduced into the end region and moved in transport direction (T) of the body at speed that is increased relative to transport speed (V) of the body until the tool runs against an inner side of the body. The tool is moved out of a front corner flap (10j) by relatively slowing down the movement of the tool with respect to the transport speed, where the flap is pressed. An independent claim is also included for a device for forming an open base at an open end of a tubular bag body.

Description

The invention relates to a method and a device for forming open trays at open end regions of tubular bag bodies, which bag bodies are preferably made from a fabric of stretched plastic tapes, wherein the bag body transported flat in a transport direction transversely to its longitudinal extent at a transport speed and during the Transports are opened to be folded end portions of the tubular bag body.

Chest bags, also called cross-bottom bags, are sacks of parallelepiped shape, which are manufactured in bag making machines by providing tubular bag bodies whose open end portions are folded into cross bottoms. The bag bodies are guided lying flat through the clothing plant, so that two layers of the tubular bag body abut each other. For bottom formation, the two layers are separated at the end regions of the tubular bag body and one of the two layers is folded over as a side flap by 180 ° to itself, creating an open bottom, in which the other layer forms a second side flap. By folding a layer at the end of the tubular bag body is formed at the front and rear of this end portion each have a triangular envelope. This process is called in the jargon also "Aufziehen". In a further processing sequence valve leaflets can be inserted (for the production of "box valve sacks" which can be filled with filler through the valve) and the final bottom configuration is produced by overlapping the bottom side flaps. The overlapping bottom side flaps are glued together or thermally welded depending on the material of the bag body. Alternatively or additionally, bottom cover sheets can be placed on the overlapped bottom side flaps and glued or welded to them.

Such a Sackkonfektionsanlage is in the patent AT 408 427 B described.

A disadvantage of this known bag making plant, however, the required cyclic operation has been found that makes high demands on the drives and limits the throughput of processed to bag bodies. The time required for cyclic mounting of the floors, including the required fixation of the raised floors, may even be an upper limit to the performance of the entire sack making apparatus.

Therefore, attempts have already been made to form open bottoms during the continuous transport of tubular bag bodies through a bag-making unit. Such a Sackkonfektionsanlage is in the DE 10 2008 017 442 A1 described.

The quality of a box bag depends essentially on the geometrically exact design of the floors. This means that the triangular corner envelopes must approximate as closely as possible the shape of an isosceles triangle, because only then is it possible to form bottom side flaps whose side edges are in the state of the open bottom parallel to a ground center line and thus parallel to each other. Only when the bottom side flaps have these parallel to the ground center line extending side edges, it is again possible to strike them overlapping each other parallel to the ground center line. And only if the turning of the Bodenseitenklappen is geometrically accurate, the finished sack bottom has a rectangular shape, which makes the bag well processed and stackable. Warped floors often have poor tightness and strength.

The basic problem with the formation of soils in end regions of tubular bag bodies is that in most bag making plants, the layers of the bag body end regions after opening have a geometrically undefined shape and it is very difficult to produce geometrically precisely defined bottoms starting from this geometrically undefined shape. One solution to this problem is in the patents AT 407 236 B and AT 406 755 B described. In this solution, the superposed layers of the tubular bag body are separated by suction devices. Subsequently, a slide between the bag body layers is introduced, which folds down a bottom side flap on itself in cooperation with a ruler and fixes the other bottom side flap at the same time against displacement. By using the slider geometrically accurate bottom side flaps are formed. In this known device, the corner envelopes are formed by the folding of a bottom side flap, however, do not always have the desired exact shape due to the geometrically indeterminate starting position, so that the further processing of the bag floor by inserting Ventilzetteln, wrapping the Bodenseitenklappen and connecting to a ground cover sheet is difficult.

There is therefore still a need for a method and an apparatus for forming geometrically exact open bottoms at open end regions of tubular bag bodies in order to further process these bag bodies in subsequent processing stations to box bags or box valve bags of high quality. Soil formation should take place while the bag bodies are transported continuously, because with a continuous transport of the bag body, a higher performance compared to the cycle operation can be achieved in bag production. Therefore, it is also an object of the invention is to get in continuously operated Sackkonfektionsanlagen because of the simultaneous running in several directions operations much higher risk of forming warped floors under control.

The present invention achieves this object by providing a method for forming open trays at open end portions of tubular bag bodies, wherein the bag bodies are transported flat in a transport direction transversely to their longitudinal extent at a transport speed and during opening the end portions of the tubular bag bodies to be folded are opened , according to the features of claim 1.

The present invention also achieves this object by providing a device for forming open trays at open end regions of tubular bag bodies, wherein the bag body flat transported in a transport direction transversely to its longitudinal extent at a transport speed and opened during transport to the folding end portions of the tubular bag body are, according to the features of claim 10.

The method according to the invention and the device according to the invention are particularly suitable for processing bag bodies made of stretched plastic tapes. The plastic tapes may be made of polyethylene or polypropylene and optionally provided with a plastic coating. Likewise, the stretched fabric web may be provided with a plastic coating to achieve the tightness of the fabric, to improve printability, and to adjust other desirable properties. Bags of stretched plastic tape have superior strength over paper or plastic film bags, but tend to slip in the manufacturing process and are also harder to fold than, for example, paper. Therefore, it is of particular advantage that these bag bodies can be handled by the present invention. According to the invention, but also bag body made of plastic film or other materials or composite materials are processed.

As a rule, bottoms are formed at both end regions of the tubular bag body.

Further embodiments, advantages and features of the invention will become apparent from the dependent claims and the following description of exemplary embodiments.

In the inventive method for forming an open bottom at an open end portion of a tubular bag body, which bag body is preferably made of a fabric of stretched plastic tape or a plastic film, the bag body is transported lying flat in a transport direction transversely to its longitudinal extent at a transport speed and during transport opened to be folded end portion of the tubular bag body. A spreading tool is inserted into the open end region of the tubular bag body. The spreading tool is moved in the transport direction at a speed which is increased relative to the transport speed until the spreading tool runs against the inside of the tubular bag body at the front part of the opened end region with at least two front contour points defined on the spreading tool and thereby said front part a front corner envelope in the form of a substantially isosceles triangle spreads, each leg of the front triangular Eckumschlags rests against at least one front contour point of the expansion tool. Then, the spreading tool is moved out of the front corner envelope by relatively delaying its movement relative to the transport speed, and the generated front corner envelope is pressed.

A device according to the invention for forming an open bottom at an open end region of a tubular bag body comprises a transport device for transporting the bag body in a flat state in a transport direction transversely to its longitudinal extent at a transport speed, and an opening device for opening the foldable end portions of the tubular bag body during their Transport on the transport device. The apparatus further comprises a spreading tool, which is insertable into the open end region of each tubular bag body during its transport on the transport device, wherein the spreading tool is movable in the transport direction at a speed increased relative to the transport speed until it - seen in the transport direction - the front part reached the open end region and with at least two am Spreading tool defined front contour points runs against the inside of the tubular bag body and spreads said front part to a front corner envelope in the shape of a substantially isosceles triangle, each leg of the front triangular Eckumschlags rests against at least one front contour point of the spreading tool, and wherein the spreading tool the front corner envelope is moved out by relative delaying its movement relative to the transport speed. The device further comprises a pressing device for pressing the generated front corner envelope.

With this invention, it is possible to form an open bottom in an end region of a tubular bag body having a well-defined geometric shape from the tip of the front triangular corner turn, this well-defined geometric shape being manifested overall in a precise, open bottom in turn allows the production of bags of the highest quality and dimensional stability.

A further improvement of the exact definition of the desired geometric shape of the open bottom can be achieved according to the invention, when the spreading tool is moved in the open end region of the tubular bag body in the transport direction with a reduced or negative speed relative to the transport speed, until it is the rear one, viewed in the direction of transport Achieved part of the open end portion and runs with at least two defined on Spreizwerkzeug rear contour points against the inside of the tubular bag body and spreads said rear part to a rear corner envelope in the form of a substantially isosceles triangle, each leg of the rear triangular Endumschlags at least one rear Contour point of the spreading tool rests. After the formation of the rear corner turn, the spreading tool is moved out of the rear corner turn by relatively accelerating its movement against the conveying speed, and the generated rear corner turn is pressed by a pressing means.

Advantageously, bottom side flaps are formed from the tube layers at the open end region, which extend on opposite sides of a bottom center line, whereby the formation of the opened bottom is completed geometrically determined and the bag body can be transferred in this configuration to further processing stations.

If, prior to the opening of the end region of the tubular bag body, this end region is brought along a transport line from the first plane of the flat bag body into a substantially orthogonal second plane, the subsequent opening of the end region can be particularly simple. In particular, in this embodiment, a bottom side flap of the open end portion may be formed by folding a first tube layer onto itself along a fold line extending in the direction of transport, and forming the other bottom side flap from a second tube layer by folding this second tube layer into the plane of the flat bag body becomes. Thus, the open bottom is again in the plane of the bag body, which greatly facilitates the pressing and transport to other processing stations.

It is also advantageous if the spreading tool is guided away from the end region of the bag body after the formation of the front triangular corner envelope and optionally also of the rear triangular corner envelope, so that the bag body can be transported further unhindered. It is particularly preferred if the spreading tool is moved away only after the fixation of the tip of the front Eckumschlags by a pressing device from the front corner envelope of the bag body. In this way it is reliably prevented that the front corner envelope begins to unfold after or even while the spreading tool moves out of the front corner envelope. This feature is particularly useful for bag bodies of slipping and unfolding material, such as e.g. Plastic film or woven plastic tape, especially useful.

In principle, it is possible with the present invention to form exact front and rear corner envelopes, even if the expansion tool rests with only one contour point on each leg of the corner envelopes. However, the method according to the invention will be more stable in hard production operation if the spreading tool is equipped with front contour lines and, optionally, rear contour lines for the formation of the rear corner turn. These contour lines define portions of the legs of the front triangular corner envelope and optionally also portions of the legs of the rear triangular corner envelope, wherein the contour lines may extend over the entire length of the legs.

As particularly well suited for a continuous transport of the bag body during its processing has been found when opening the end portion of the tubular bag body by pulling apart the abutting tubular layers of the bag body.

In a preferred embodiment of the invention, the opening device comprises suction devices which can be switched on and off in each case to a tube layer at the end region of the tubular bag body, and can be moved away from one another at the same time as transport speed in the transverse direction of the transport direction, after contact with the respective tube layer and activation of the suction effect Transport direction are movable. Such opening device works very reliable and low maintenance. It has proved to be favorable for highly reliable opening operations when the center axes of the suction devices in the transport direction T congruent or successively offset, preferably offset.

In an advantageous embodiment of the invention, the spreading tool has an arm and plates and / or rods mounted on this arm, on which the front contour points or contour lines and optionally also the rear contour points or contour lines are defined. The plates and / or bars may each be specially adapted to particular bag proportions or materials. It is further preferred if the plates and / or bars are arranged symmetrically to the transport direction, because this automatically enforced that the formed corner envelopes are aligned symmetrically to the transport direction.

By the spreading tool is mounted on a rotating drive, for example, oriented in the transport direction toothed belt or chain drive, the rotating drive is accelerated and delayed relative to the transport speed, realizes a very reliable and low-maintenance drive, with the main drive, the for the Transport the bag body is responsible, can be synchronized.

If the spreading tool is designed as a split tool, so that the pressing device protrudes into the spreading tool or can be passed without colliding with it, the pressing of the corner envelope can already begin while the spreading tool is still in the corner envelope. As a result, the pressing device fixes the corner envelope against unfolding and warping. The pressing device expediently comprises compression belts, pressure rollers and / or contact sliding elements.

• Fig. 1 bis Fig. 6 schematische perspektivische Ansichten von Teilen einer erfindungsgemäßen Vorrichtung zur Erläuterung des erfindungsgemäßen Verfahrens;
• Fig. 7A und Fig. 7B eine erste Ausführungsform eines Spreizwerkzeugs in der Perspektive und in Draufsicht;
• Fig. 8A und Fig. 8B eine zweite Ausführungsform eines Spreizwerkzeugs in der Perspektive und in Draufsicht;
• Fig. 9A und Fig. 9B eine dritte Ausführungsform eines Spreizwerkzeugs in der Perspektive und in Draufsicht;
• Fig. 10 eine perspektivische Teilansicht einer ersten Ausführungsform einer Anpresseinrichtung;
• Fig. 11 eine perspektivische Ansicht einer zweiten Ausführungsform einer Anpresseinrichtung; und
• Fig. 12 eine perspektivische Ansicht einer dritten Ausführungsform einer Anpresseinrichtung.

The invention with its features and advantages will now be explained in detail with reference to exemplary embodiments with reference to the drawings. In the drawings show:

• Fig. 1 to Fig. 6 schematic perspective views of parts of a device according to the invention for explaining the method according to the invention;
• FIGS. 7A and 7B a first embodiment of a spreading tool in perspective and in plan view;
• 8A and 8B a second embodiment of a spreading tool in perspective and in plan view;
• Figs. 9A and 9B a third embodiment of a spreading tool in perspective and in plan view;
• Fig. 10 a partial perspective view of a first embodiment of a pressing device;
• Fig. 11 a perspective view of a second embodiment of a pressing device; and
• Fig. 12 a perspective view of a third embodiment of a pressing device.

The method according to the invention for forming an open bottom at an open end region of a tubular bag body will now be described with reference to FIGS Fig. 1 to Fig. 6 explained process steps explained. The method proceeds in a device 1 according to the invention for forming an open bottom at an open end region of a tubular bag body, which is referred to below as a bottom opening device 1. From this bottom opening device 1 are in Fig. 1 to Fig. 6 for clarity, only the features essential to the invention shown. Parts of the bottom opening device 1, which have nothing to do with the invention or are familiar to those skilled in the art, have been omitted from the drawings.

The bottom opening device 1 has a transport device 2 in the form of a conveyor belt and moves continuously with a transport speed V in a transport direction T. On the transport device 2 are tubular bag bodies 10 in flat lying state with their longitudinal extent L transversely to the transport direction T. The bag body 10 are on secured to the conveyor belt by means not shown holding means against slipping. Such holding means include, for example, strips of ferromagnetic material, which are placed on the bag bodies 10 and of the Bottom of the conveyor belt with magnets that move together with the conveyor belt, are attracted to the conveyor belt and thereby press the intermediate bag body 10 to the conveyor belt. Alternatively, the conveyor belt is formed as a perforated conveyor belt, wherein from the underside of the conveyor belt, a vacuum is applied, which sucks the bag body 10 to the conveyor belt.

The tubular bag body 10 are made for example of fabric of stretched plastic tape. The plastic tapes may comprise a polyethylene or polypropylene material. Optionally, the fabric has a plastic coating. The tubular bag body 10 may alternatively be made of plastic film.

The tubular bag body 10 has two opposing open end portions 10e, 10f. The end portion 10e is to be formed into a cross bottom, as explained below. In further processing, the end portion 10f may also be formed into a cross bottom in the same manner as the end portion 10e, thereby producing a box bag or box valve bag.

In Fig. 1 It can be seen that the tubular bag body 10 initially rests flat on the transport device 2 in a first plane ε1. In this flat lying state, a first and a second tube layer 10a, 10b abut each other. Then, the end portion 10e of the tubular bag body 10 is brought by means of a folding bar 12, which is referred to in the jargon as "Vorbruchleiste", and baffles 11a, 11b from the first level ε1 of the flat bag body in a substantially orthogonal thereto extending second level ε2.

Fig. 2 shows the bag body 10 with fully orthogonal upward (in the second level ε2) folded end portion 10e. The folding bar 12 continues in the transporting direction T and, in cooperation with the deflecting plate 11a, now has the task of holding the end region 10e of the bag body 10 folded in the second plane ε2 in this angular position relative to the first plane ε1 in which the bag body 10 lies , A generally designated by the reference numeral 20 opening means comprises two suction devices 13, 14 which are reciprocally transversely to the transport direction T on symbolically shown cross members 15, 16. The cross members 15, 16 may be formed, for example, as rails or pivot arms. Alternatively, the cross members 15, 16 piston-cylinder assemblies, wherein the suction means 13, 14 sit at the free ends of the piston and in such a way transversely to the transport direction T back and forth. The cross members 15, 16 are movable by means of longitudinal members 17, 18 in the transport direction T with the transport speed V. The longitudinal members 17, 18 may be formed, for example, as rails, pivot arms or piston-cylinder arrangements. The exact design of cross members and side members does not matter; It is only essential that the suction devices 13, 14 are movable both transversely to the transport direction T and in the transport direction T.

In Fig. 2 a method step is shown, in which the two suction devices 13, 14 have been brought into contact with the first tube layer 10a or the second tube layer 10b from opposite sides in the end region 10e. A vacuum is switched on so that the first suction device 13 sucks in the first tube layer 10a and the second suction device 14 sucks in the first tube layer 10b. It should be noted that the suction devices 13, 14 move synchronously with the transport device 2 at the transport speed V in the transport direction T, so that no distortion of the tube layers 10a, 10b can occur. Then, the two suction devices 13, 14 start to move away from one another transversely to the transport direction V (arrows P1 or P2), thereby pulling a tube layer 10a, 10b with them and thereby open the end region 10e of the tubular bag body 10.

Fig. 3 shows the end portion 10e of the tubular bag body 10 in the open state, in which between the tube layers 10a, 10b, a free space 10g is formed. It can also be seen in this illustration that meanwhile the vacuum has been switched off by the suction devices 13, 14 and the two suction devices 13, 14 have disengaged from the tube layers 10a, 10b and can therefore be moved upstream against the transport direction T to open the end of the next bag body. It can be seen further in this illustration that the open end region 10e has a geometrically largely undefined shape. Now, a spreading tool 21 is inserted into the clearance 10g of the opened end portion 10e, whereby the spreading tool 21 moves in a circular arc (arrow P3) into the opened end portion 10e. In this case, the sheet movement of the spreading tool 21 has a directed in the transport direction T movement component with respect to the transport speed V higher relative speed V1R. The spreading tool 21 is driven by one or more parallel rotating toothed belt or one or more parallel rotating roller chains, the toothed belt 25 or the chain is respectively aligned by at least 2 pulleys or sprockets 26, 27 in the transport direction T. The bottom opening device is thus formed from one or more, preferably two spreading tools, wherein the distance between the spreading tools can be variable by separate drive units. In each case one of the pulleys 26, 27 is connected to a controllable drive, so that synchronized with the clock in which the bag body 10 run through the bottom opening device 1, the spreading tool with respect to the transport speed V can be accelerated and delayed.

Out Fig. 4 It can be seen that the circular arc movement of the Spreizwerkzeugs 21 after it has passed around the pulley 26, has passed into a translational movement in the transport direction T by pulling it from the lower run of the toothed belt 25. Due to the still existing higher relative speed V1R relative to the transport speed T, the spreading tool 21 moves faster than the bag body 10 and therefore runs against the inside of the tubular bag body at a front part 10v of the open end area 10e, with front contour points 23p, 24p of the spreading tool 21 first come into contact with the bag body. These front contour points 23p, 24p represent end points of front contour lines 23v, 24v of the spreading tool 21 (see also FIG FIGS. 7A and 7B ), which also come into contact with the front part 10v of the end portion 10e of the bag body 10. Thereby, the spreading tool 21 spreads the front part 10v to a front corner turn 10j having the shape of a substantially isosceles triangle. The legs 10k, 10m of the front triangular corner turn 10j are defined by at least one front contour point of the expansion tool abutting against it. In the case of the spreading tool 21 chosen in this exemplary embodiment, both the front contour points 23p, 24p and the front contour lines 23v, 24v of the spreading tool 21 rest on the legs 10k, 10m. Incidentally, the isosceles triangle is a right-angled isosceles triangle.

Fig. 4 shows the state in which the front corner envelope 10j has been completely formed by the spreading tool 21. *** " It can also be seen in this illustration that the isosceles triangular shape of the front corner impact 10j is positioned symmetrically to a center line M of the opened end portion 10e. By the spreading tool 21 forms the front triangular Eckumschlag 10j, it folds at the same time a front portion of the first tube layer 10a around the folding bar 12 around back on itself, so that this area of the tube layer 10a is again in the first level ε1. Likewise, the spreading tool 21 folds a front region of the second tube layer 10b into its original position into the first plane ε1. In this way, the formation of the bottom side flaps 10u, 10t from the two tube layers 10a, 10b is started.

After the front triangular corner envelope 10j has been formed, the spreading tool 21 is moved rearwardly out of the front corner envelope 10j by relative delaying its movement relative to the transport speed T, continuing the folding of the tube layers 10a, 10b and thus forming the bottom side flaps 10u, 10t from the two tube layers 10a, 10b progresses. Even before the spreader tool 21 retreats from the front corner envelope 10j, the tip 10s of the front corner envelope 10j has come to a pressing device 28, which initially holds the tip 10s and successively the entire front corner envelope 10j in the defined shape and prevents the Corner envelope 10j unfolded again. In this embodiment, the pressing device 28 is formed as a pressure belt 28 a, which is aligned in the transport direction T and rotates about two pulleys 28 b, 28 c, of which Fig. 3 to Fig. 6 only the rear pulley 28b is shown. Fig. 10 but shows the complete pressing device 28. By transporting the bag body 10, the entire end portion 10e is pulled along the bottom center line M under the pressing device 28, whereby the folded bottom side flaps 10u, 10t are kept in a defined form and unfolding is prevented.

Fig. 5 shows a process state in which the spreading tool 21 has been moved in the open end 10e of the tubular bag body 10 in the transport direction T with a relative to the transport speed V reduced or negative speed V2R until it - seen in the direction of transport T - the rear part 10h of has reached open end portion 10e and has accumulated with at least two defined on Spreizwerkzeug rear contour points 23q, 24q against the inside of the tubular bag body and thereby said rear portion 10h has spread to a rear corner envelope 10p in the form of a substantially isosceles triangle. These rear contour points 23q, 24q represent end points of rear contour lines 23h, 24h of the spreading tool 21 (see FIG FIGS. 7A and 7B ) which also come in contact with the rear part 10h of the end portion 10e of the bag body 10 and define the legs 10q, 10r of the rear triangular corner turn 10p. Incidentally, the isosceles triangle is a right-angled isosceles triangle. How to get out Fig. 5 can recognize, at this time, the formation of the two bottom side flaps 10u, 10t completed.

The term "relative to the transport speed V reduced or negative speed V2R", as used above, means that the spreading tool 21, although in the transport direction, but at a lower speed than the transport speed V is moved, or that the spreading tool is temporarily stopped, or that the spreading tool is moved counter to the transport direction T.

As in Fig. 6 9, after the rear triangular corner turn 10p has been formed, the spreading tool 21 is moved out of the rear corner turn 10p by relatively accelerating its movement V3R from the conveying speed T, to the pulley 27 where it moves in a circular arc movement to one of the end portion 10e is then brought back along the upper run of the toothed belt 25 to the open bottom of the subsequent bag body (or the next but two, if two spreading tools are provided, etc.) to form.

As in Fig. 3 to Fig. 6 such as FIGS. 7A and 7B shown, the spreading tool 21 is formed as a split tool, wherein on an arm 22, two plates 23, 24 are mounted, which leave a distance between each other 21 a. At edges of the plates 23, 24, the front and rear contour points 23p, 24p, 23q, 24q are defined, as well as the front and rear contour lines 23v, 24v, 23h, 24h. The split shape of the spreading tool 21 allows the pressing device 28 to extend through the clearance 21a and thereby hold down and press the folded front and rear corner envelopes 10j, 10p and bottom side flaps 10u, 10t earlier than when collision to prevent with the spreading tool 21 - would have to be arranged further downstream of the spreading tool 21.

8A and 8B show a first alternative embodiment of a spreading tool 30. The first alternative spreading tool 30 differs from the spreading tool 21 in that only one plate 31 is formed on the arm 22 having edges defining front contour lines 31vl, 31vr and rear contour lines 31h1, 31hr. The first alternative spreading tool 30 is thus not a split tool.

Figs. 9A and 9B show a second alternative embodiment of a spreading tool 32. The second alternative spreading tool 32 differs from the spreading tool 21 in that two obliquely directed rods 33, 34 are formed on the arm 22, the tips of which define contour points 33p, 34p. The rods 33, 34 are arranged at a distance 32a from each other. It is thus a split tool, wherein by the distance 32a a pressing device is guided. Since each bar 33, 34 defines only one contour point 33p, 34p, the second alternative spreading tool 32 is suitable depending on the installation position only for producing a front or rear corner turn. To both the front To produce corner cover as well as the rear corner envelope, two second alternative spreading tools 32 must be combined, for example, by being mounted one behind the other and in the reverse installed position on the toothed belt 25.

Fig. 11 shows an alternative pressing device 35 in the form of a press shoe made of a material with good sliding properties with respect to the bag body.

Fig. 12 shows a further alternative pressing device 36 in the form of a rotatable pressure roller.

Claims (21)

A method for forming an open bottom at an open end portion of a tubular bag body (10), which bag body is preferably made of a fabric of stretched plastic tape or a plastic film, wherein the bag body lying flat in a transport direction (T) transversely to its longitudinal extent (L) with transported a transport speed (V) and during the transport of the folding end portion (10e) of the tubular bag body is opened, characterized by
inserting a spreading tool (21, 30, 32) into the open end region of the tubular bag body,
moving the spreading tool in the transporting direction (T) at a speed (V1R) which is increased relative to the transporting speed (T), until the spreading tool (21) has the front part (10v) of the opened end region defined with at least two on the spreading tool, as seen in the direction of transport front contour points (23p, 24p, 33p, 34p) runs against the inside of the tubular bag body and thereby spreads said front part (10v) to a front corner envelope (10j) in the shape of a substantially isosceles triangle, each leg (10k, 10m) the front triangular corner turn (10j) abuts on at least one front contour point (23p, 24p; 33p, 34p) of the spreading tool (21),
moving the spreading tool (21) out of the front corner envelope (10j) by relatively delaying its movement relative to the transport speed (V), and
pressing the generated front corner envelope (10j). A method according to claim 1, characterized in that the spreading tool (21, 30, 32) in the open end region (10e) of the tubular bag body (10) in the transport direction (T) with a relative to the transport speed (V) reduced or negative speed (V2R) is moved until it reaches the - viewed in the direction of transport - the rear part (10h) of the open end portion and runs with at least two defined on Spreizwerkzeug rear contour points (23q, 24q, 33p, 34p) against the inside of the tubular bag body and thereby said rear part (10h) spreads to a trailing corner envelope (10p) in the shape of a substantially isosceles triangle, each leg (10q, 10r) of the trailing triangular end envelope (10p) at at least one trailing contour point (23q, 24q; 33p, 34p) of the spreading tool is applied,
moving the spreading tool (21, 30, 32) out of the rear corner envelope (10p) by relatively accelerating its movement relative to the transport speed (V), and
the pressing of the generated rear corner envelope (10p). A method according to claim 1 or 2, characterized in that from the tube layers (10a, 10b) at the open end region bottom side flaps (10u, 10t) are formed, which extend on opposite sides of a bottom center line (M). Method according to one of the preceding claims, characterized in that prior to the opening of the end region of the tubular bag body, this end region (10e) extends along a fold line extending in the transport direction from the first plane (ε1) of the flat bag body into a second plane extending substantially orthogonally thereto (FIG. ε2) is brought. A method according to claim 4, characterized in that a bottom side flap (10u) of the open end portion is formed by folding a first tube layer (10a) on itself along a fold line extending in the direction of transport, and another bottom side flap (10t) of a second tube layer (10b ) is formed by this second tube layer (10b) in the plane (ε1) of the flat-lying bag body (10) is folded. Method according to one of the preceding claims, characterized in that the spreading tool (21, 30, 32) after the formation of the front triangular Eckumschlags (10j) and optionally also the rear triangular Eckumschlags (10p) from the end portion (10e) of the bag body is led away. Method according to one of claims 1 to 6, characterized in that the spreading tool (21,30,32) only after the fixation of the tip (10s) of the front corner envelope (10j) by a pressing device (28, 35, 36) from the front Corner envelope (10j) of the bag body is led away. Method according to one of the preceding claims, characterized in that the spreading tool (21, 30) with front contour lines (23v, 24v, 31vl, 31vr) and optionally also rear contour lines (23h, 24h, 31hl, 31hr) is equipped, the sections of Define legs (10k, 10m) of the front triangular corner envelope (10j) and optionally also portions of the legs (10q, 10r) of the rear triangular corner envelope (10p). Method according to one of the preceding claims, characterized in that the opening of the end portion of the tubular bag body by pulling apart of the abutting tubular layers (10a, 10b) of the bag body takes place. Device (1) for forming an open bottom at an open end region (10e) of a tubular bag body (10), which bag body is preferably made of a fabric of stretched plastic tape or plastic film, with a transport device (2) for transporting the bag bodies (10). in a flat state in a transport direction (T) transversely to its longitudinal extent (L) at a transport speed (V), and with opening means (20) for opening the end regions of the tubular bag bodies to be folded during their transport on the transport device,
marked by
a spreading tool (21, 30, 32) insertable into the open end portion (10e) of each tubular bag body during its transport on the transport means,
wherein the spreading tool (21, 30, 32) in the transport direction (T) with a relative to the transport speed (V) increased speed (V1R) is movable until it reaches - seen in the direction of transport - the front part (10v) of the open end portion and with at least two defined on the expansion tool front contour points (23p, 24p, 33p, 34p) runs against the inside of the tubular bag body and thereby said front part (10v) spreads to a front corner envelope (10j) in the form of a substantially isosceles triangle, each leg (10k, 10m) of the front triangular corner turn (10j) abuts on at least one front contour point (23p, 24p; 33p, 34p) of the expansion tool, and wherein the expansion tool (21, 30, 32) from the front corner turn (10j) by relative Delaying its movement relative to the transport speed (V) is moved out,
and a pressing device (28, 35, 36) for pressing the generated front corner envelope. Apparatus according to claim 10, characterized in that the spreading tool (21, 30, 32) in an open end region (10e) of the tubular bag body in the transport direction (T) with a relative to the transport speed (V) reduced or negative speed (V2R) is movable until it reaches the rear part (10h) of the open end region viewed in the direction of transport and with at least two rear contour points (23q, 24q; 33p, 34p) defined on the spreading tool Inside of the tubular bag body and thereby spreads said rear part (10h) to a rear corner envelope (10p) in the form of a substantially isosceles triangle, each leg (10q, 10r) of the rear triangular end envelope (10p) at at least one rear contour point (10p). 23q, 24q, 33p, 34p) of the spreading tool, and wherein the spreading tool (21, 30, 32) is movable out of the rear corner turn (10p) by relatively accelerating (V3R) its movement relative to the transporting speed (V), and wherein a Pressing device (28, 35, 36) is provided for pressing the generated rear corner envelope. Apparatus according to claim 10 or 11, characterized by an end region folding device, by means of which the end regions (10e) of the tubular bag body (10) along a in the transport direction (T) extending fold line from a first plane (ε1) in a substantially orthogonal thereto second level (ε2) can be brought, wherein the end region folding device preferably comprises a folding strip (12) with a folding edge extending in the transport direction (T) and at least one deflecting plate (11a, 11b). Device according to one of claims 10 to 12, characterized in that the spreading tool (21, 30, 32) after the formation of the front triangular Eckumschlags (10j) and possibly also the rear triangular Eckumschlags (10p) in a remote from the end region of the bag body position can be brought. Device according to one of claims 10 to 13, characterized in that the spreading tool (21, 30) front contour lines (23v, 24v, 31vl, 31vr) and optionally also rear contour lines (23h, 24h, 31hl, 31hr), the sections of Define legs (10k, 10m) of the front triangular corner envelope (10j) and optionally also portions of the legs (10q, 10r) of the rear triangular corner envelope (10p). Device according to one of claims 10 to 14, characterized in that the spreading tool has an arm (22) and plates (23, 24, 31) and / or rods (33, 34) mounted on this arm, on which the front contour points or Contour lines and optionally also the rear contour points or contour lines are defined. Apparatus according to claim 15, characterized in that the plates (23, 24, 31) and / or rods (33, 34) are arranged symmetrically to the transport direction. Device according to one of Claims 10 to 16, characterized in that the spreading tool (21, 30, 32) is mounted on a revolving drive, for example a toothed belt (25) or chain drive oriented in the transport direction, the revolving drive being mounted relative to the transport speed ( T) can be accelerated and delayed. Device according to one of claims 10 to 17, characterized in that the spreading tool (21, 32) is designed as a split tool, so that the pressing device (28, 35, 36) protrudes into the spreading tool or can be passed without colliding with it. Device according to one of claims 10 to 18, characterized in that the pressing device (28, 35, 36) compression belt, pressure rollers and / or Anpressgleitelemente. Device according to one of claims 10 to 19, characterized in that the opening device (20) on and off switchable suction means (13, 14), which in each case a tube layer (10a, 10b) at the end portion (10e) of the tubular bag body (10 ) can be fed, and after the concern of the respective tube layer and switching on the suction transverse to the transport direction (T) away from each other wegbewegbar and simultaneously with transport speed (V) in the transport direction (T) are movable. Device according to one of claims 10 to 20, characterized in that the center axes of the suction devices (13,14) in the transport direction T congruent or successively offset, preferably arranged offset.

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