EP0105191B1 - Cutter for flexible webs - Google Patents

Abstract

In apparatus for cutting a web of flexible material, upper and lower cutters are mounted on a swivel arm movable by a control means which determines the position of the cut. The control means includes a pneumatic cylinder and piston pivoted to a control arm linked to or integral with the swivel arm and of a much shorter effective length than the swivel arm. The cutting action is initiated by inter-engagement between the swivel arm and a stop edge of the web.

Description

The invention relates to a device for the precise introduction of a cut into a web of flexible material to be cut at a standstill with a lower knife and an upper knife, at least one of which is driven, and with a feed device for the material web, with successive ones on the web Are attached stops, which serve to define a cutting line.

The creation of individual articles, pieces of tape or packs from a wide variety of materials, all of which show the physical properties of a flexible material and a certain degree of rigidity, generally plays a major role in technology. Often, cuts have to be made at certain points on an intermittently conveyed web made of flexible material. Such sheets of flexible material with a certain inherent rigidity can, for. B. made of plastic, rubber, thin wood, paper or cardboard. Bulk goods can also be inexpensively produced from such webs in large quantities per unit of time if one only thinks of the packaging, for example.

A particular problem arises in the field of liquid packs, in the production of which it is known to form a tube or a tube from the flat web pulled off a storage roll, which tube is filled and cut or first cut and then filled. If the material web does not yet have an incision at any point along the conveying direction, so that only a smooth average has to be introduced in order to separate one piece of web from the other, the problem of accurate cutting does not necessarily arise in such a critical manner as comparable when this is the case machining track already has creases, folds, cuts or perforations, which must always be kept at a precise distance from the cut to be made. Sheets of flexible material have tolerances due to fluctuations, e.g. B. thickness, temperature, composition fluctuations, etc. It is extremely expensive to detect the specified cuts, creases, folds of the web or the like by electrical or optical measures, in order to then cause a highly complicated control, the knife or knives exactly to have the incision made at the desired location.

From US-A-2 725 101 a device with the features described in the introduction is known. Due to the physical properties of the flexible web, there are fluctuations in lengths, thicknesses, folds, etc., so that the accuracy is inevitably burdened with a tolerance because the fine fine feed is arranged and works in several one-piece intervals of the web from the actual cut to be made. In addition, the actual feed takes place via a complicated movement mechanism with several angle levers, stops, shafts and swivel knives on one side of the path, and a reciprocating support plate on the other side of the path.

The web to be processed according to this prior art consists of only one position at least at the points where it carries a central slot, the ends of which are arranged at a distance from the web edges, which is why the web can be pressed in before the cut by the fine feed device . If you wanted to press in a two-ply web in a similar way, then this cut, which should form the stop after the press-in, would have to go through both layers. This additional condition is not fulfilled for all material webs. The known device therefore has a limited use, is of complex construction and does not achieve the desired accuracy.

From US-A-4 214 492 a device with an upper knife and lower knife is also known. In this way, a type of pliers is formed, at a distance from which a second pair of pliers can be pivoted over an arm and can be moved by a control device. With these cutting pliers, metal clips on sausage skin ends are to be gripped and removed. If the two pairs of pliers have been inserted between two sausage units, then one pair of pliers is moved relative to the other until there is contact with the ends of the sausages, as a result of which a signal provides pneumatic pressure build-up for cutting off. It is understood that when metal clips are removed from the sausage ends, the precision of the cut need not be overly precise. The structure and arrangement of the pliers-like cutting devices are quite complex, and the possibility of combining them with a cutting device according to the first-mentioned patent specification is not suggested to the person skilled in the art.

The object of the present invention is therefore to create a device for making a cut with the features of the type described in the introduction, with which the accuracy of the interface can be achieved and maintained with simple means.

This object is achieved in that the upper knife is rotatably articulated on the lower knife and that both knives are arranged on a swivel arm which can be moved by a drive device, and in that a control device is provided which, after a cut has been made, first opposes the swivel arm Direction of transport of the web moves and after passing through the next stop through the knife reverses its direction of movement and with Compared to the path of increased speed, the stop arranged in the direction of movement can be followed until one of the knives touches this stop, the path being stopped and a signal for the execution of the cut being generated when the path and swivel arm are at a standstill. The material web itself has the properties by means of which the knife and the control device immediately recognize the location for making the desired cut. If the material web is stopped and the lower or upper knife has placed itself against the stop of the material web, then the web and swivel arm are stationary. Only when this condition is reached (possibly also shortly afterwards) is there a signal for the cutting. This cut is achieved by the installation of the upper or lower knife directly at the stop, which means a partial cut, in exactly the desired line with an accuracy that cannot be achieved by other devices, without tolerances playing a role.

It is particularly advantageous if the control device has a pneumatic cylinder with a movable piston which is articulated at one end of a control arm, that at the other end the articulated arm is articulated at its end, while at least one knife is attached to the other end of the articulated arm , and if the lever of the control arm is significantly smaller than that of the swivel arm. Instead of a pneumatic cylinder, a solenoid, an electrical control device or a hydraulic cylinder can of course also be used, but in practice the use of a pneumatic cylinder has proven to be robust, simple and reliable. The swivel arm is therefore connected to this pneumatic cylinder via a control arm, with a lever ratio such that the swivel arm with the knives attached to it is considerably longer than the control arm. In this way, the force of the pneumatic cylinder, which ultimately acts on the knives, can be kept low without impairing the speed of movement of the swivel arm and its precise control. This low force ultimately acting in the cutting knives has the advantage that when the material web to be cut interacts on the one hand and the control device via the swivel arm on the other hand, the swivel arm to be controlled itself can be used as a sensing device, because a material web to be cut, even made of thin material, has no adverse effects , Deformations, indentations or compressions. The pneumatic cylinder therefore only needs to receive a simple pilot control, which it puts on the swivel arm and at the same time receives control signals from it.

Particularly expediently, the invention is further characterized in that for the interaction of the material web and the control device on the material web, a stop is provided for a system of the swivel arm, which can be moved away from the control device and can be swiveled towards the stop before the stop is cut. The stop on the material web can be created in a variety of ways. A wide variety of influences or treatments or changes in the material web take place in a continuous or intermittent machine. For example, in the case of an intermittently operating machine, an incision in the material web and an at least partial elevation of the material can take place before or after the incision in the conveying direction of the material web, so that this already gives a stop. The control device can then take signals from the marking by means of the measures according to the invention via the swivel arm of a material web marked in this way and then set up the measures to be carried out. Preferably, according to the invention, the swivel arm is here before the activity provided according to the invention, i.e. before the exact introduction of the cut, both first moved away from the stop and then - preferably after reversing the direction of movement - pivoted onto the stop. If, for example, the upper knife, the lower knife or both knives engage the stop on the material web, then the swivel arm is stopped, be it by the stop on the material web or by a control command in the control device, then the knife can immediately take action and Make the desired cut exactly where you want it.

It is expedient according to the invention if the stop on the material web is formed by at least one incision in the material web and folding it along at least one crease line running in the conveying direction of the material web. Especially when a tube is to be formed for the production of liquid packs, this overall tube, which corresponds to the length of the material web, must ultimately be divided or separated to form individual packs. It may be useful to partially cut the tube when the superplasticizer is in the up position and then to form the stop in the region of this incision by folding the material web in front of or behind the incision in the conveying direction of the material web. If exact folds or folds at precisely predetermined locations in the material web are desired, then crease lines are previously introduced in the material web in a manner known per se. Since a stop for the swivel arm according to the invention must have an edge transverse to the conveying direction of the material web, the fold should also take place transversely to the conveying direction of the material web, ie around a crease line in the conveying direction of the material web.

For the reasons mentioned above, the device according to the invention can be used particularly advantageously for separating partially cut, connected tube pieces which are formed from a coated paper web. A tube, tube or tube has the shape of a circle in cross section in the finished state. The stop in the material web can now be obtained particularly easily and advantageously when making partial incisions in such a tube in that the creasing lines which run along the tube surface lines are not arranged exactly on diametrically opposite sides. If you put a plane through the crease lines of such a tube or tube in your thoughts, then, according to the teaching of the invention, this plane should not run exactly through the center line (or the center point of the circle), but should be somewhat eccentric to it. In this way, one has the possibility that when the tube is partially compressed in the direction transverse to its longitudinal axis, one path comes closer to the shape of a plane than the other, because viewed in cross section, it is not halves of equal length, but sections of unequal length . Preferably, this is a section, e.g. B. the longer section seen in cross section, cut, and the short, already lying in one plane section uncut. Then these tube pieces hang together along the flat part and are cut along the partially curved, longer section. To separate the last cut must then be made exactly under the existing cuts. In order to achieve this, the device of the type described above offers, so to speak, a "searching knife" because the knife parts attached to the swivel arm search for the stop itself and thus for the point at which the finite average for separating or separating the tube pieces is to take place.

It can be seen from the above considerations by what simple means a device is created for very precisely and precisely making a cut at a desired location on a material web.

• Figur 1 schematisch im Schnitt eine Materialbahn und die Schneidvorrichtung mit ihrer abgebrochen gezeigten Halterung,
• Figur 2 perspektivisch einen abgebrochenen Teil der Materialbahn, wenn man von unten auf diese blickt,
• Figur 3 eine Seitenansicht dieser Materialbahn, wenn man z. B. von rechts vorn nach links oben in Figur 2 blickt,
• Figur 4 eine Draufsicht auf den Zuschnitt der Materialbahn vor der Faltung zum Tubus nach Figur 2,
• Figuren 5a und 5b schematische Querschnittsansichten einer schlauchförmigen Bahn im zusammengedrückten bzw. ungefalteten Zustand,
• Figuren 6a und 6b gleiche Darstellungen wie Fig. 5a und 5b, wobei jedoch die Rillinien an anderer Stelle in der Bahn angeordnet sind.
• Figur 7 eine Seitenansicht der Schneidvorrichtung nach einer bevorzugten Ausführungsform mit Pneumatikzylinder und
• Figur 8 eine Draufsicht auf die Messer mit Halterung und Materialbahn.

Further advantages, features and possible uses of the present invention result from the following description in connection with preferred exemplary embodiments. Show it:

• FIG. 1 shows schematically in section a material web and the cutting device with its holder shown broken off,
• FIG. 2 shows in perspective a broken-off part of the material web when looking at it from below,
• Figure 3 is a side view of this web of material when z. B. from the front right to the top left in FIG. 2,
• FIG. 4 shows a plan view of the cut of the material web before folding into the tube according to FIG. 2,
• FIGS. 5a and 5b show schematic cross-sectional views of a tubular web in the compressed or unfolded state,
• FIGS. 6a and 6b are the same representations as FIGS. 5a and 5b, but with the creasing lines being arranged elsewhere in the path.
• Figure 7 is a side view of the cutting device according to a preferred embodiment with pneumatic cylinder and
• Figure 8 is a plan view of the knife with holder and web.

FIG. 1 shows schematically the lower knife 1 and the upper knife 3 which is pivotably articulated on the axis of rotation 2 and which is fastened to a swivel arm 4. In between you can see with thick lines the schematic cross-section of a path formed into a tube or tube.

This path is shown even more clearly in perspective in FIG. 2 and in a side view in FIG. 3. To simplify the explanation of the invention, the web in the illustration in FIGS. 2 and 3 is turned upside down, ie the flat side lying in cross section at the bottom in FIG. 1 is at the top in FIGS. 2 and 3. The material web is generally designated 5 and should move in the direction of arrow 6. It consists of flexible material, in the embodiment shown in the drawings a relatively thick paper coated on both sides with plastic, as z. B. is used for the creation of liquid packs. A cut 7 is to be made in this coated paper, which extends from one longitudinal edge of the flat, web side to the other. On the opposite side shown in the cross-sectional view of FIG. 2, the overlap point 8 can be seen, at which the material web was shaped and welded to form the tube before being laid flat to form the flat part. From the side edges just described, which lie along creasing lines 25 (FIG. 4), in FIG. 2 reaching down to the overlap point 8, one can see the cut edges or incisions 9, 9 '. At the right end of the first left tube piece of FIG. 2, these incisions 9 and 9 'can again be seen as dashed lines, because these cuts lie below the flat surface of the web facing the viewer. Two dash-dotted lines 10, 10 'run transversely to the conveying direction 6 of the material web 5 in FIGS. 2 and 3. The distance between these two lines represents the tolerance range for making the cut in the web 5. Normal milk or fruit juice packs have a length of, for example, 3 mm. In the area between the two lines 10 and 10 ', the incision 7 must ultimately be made. He should connect exactly to the two incisions 9, 9 'so that the individual tube pieces of the total track 5 are separated at one and the same interface.

Figure 4 shows the top view of a flat sheet of plastic coated paper, i.e. flexible material, the conveying direction is shown again with the arrow 6. The web shown in FIG. 4 is divided into three parts, from which three tube pieces and ultimately three packages are later formed according to the last average. From the right-hand first third of the web one can see the embossing which runs across the entire width and is generally designated 11, with the aid of which a bottom or lid of the pack can later be formed. Across the embossing strip 11, i.e. in the conveying direction 6 of the path 5, two parallel creasing lines 25 can be seen.

On the left at a distance a from the embossing field 11 there are two incisions 9, 9 ′ which run transversely to the conveying direction 6 and extend from the outer edge to the respective crease line 25. Parallel to the embossing field 11, the area to the right of the incisions 12 with the width a later results in a transverse sealing seam for closing the package.

If the middle third of the web shown in FIG. 4 is moved to the left by a further feed in direction 6, the material web 5 is folded up along the creasing lines 25 upwards towards the viewer, the lower field shown in FIG. 4 first and then the upper one Field can be folded in or folded up. The left third is then shown in FIG. 4, again showing the overlap point 8. As a result of the incisions 9 and 9 ', the width of the material web 5 around these side panels has decreased.

If the material web 5 then advances further to the left in the conveying direction 6, then the above-mentioned average 7 should take place on the line shown by the arrow 7 in FIG. 4, which is exactly in line with the incisions 9 and 9 '.

So that the control device can cooperate with its swivel arm 4 with the material web 5, so that the cut 7 is exactly in line with the incisions 9, 9 ', a stop 12 is formed by the material web 5 itself, the water stop 12 most clearly emerges from Figure 7. It is created by holding down the left tube part shown in FIG. 7 and keeping the tube part lying to the right of the upper knife 3 free or popping open.

The inventive idea of how the cross-section of the tube shown in FIGS. 1 and 2 can be achieved is to be explained beforehand with reference to FIGS. 5 and 6. The cross section of the tube is shown as a circle in FIGS. 5b and 6b. At the points shown by the arrows 13, the creasing lines 25 are to be located, which run transversely to the plane of the paper and are therefore practically not visible in FIGS. 5 and 6. If an imaginary plane is laid through the creasing lines, the plane 14 shown in FIGS. 5b and 6b and shown by a dashed line is obtained would arrange that the imaginary plane 14 runs through the central longitudinal axis 15. However, this would have the disadvantage that when the hose or hose piece was laid flat in the state of FIG. 5a, two sides of the same length would result, which after laying flat have no different paper tension or spring force.

However, if the creasing lines 25 are arranged according to the arrows 13 at the point shown in FIG. 6b so eccentrically to the center of the tube so that the imaginary plane 14 does not run through the central longitudinal axis 15 of the tube, then the state of FIG. 6a results when laying flat with a lower shorter and an upper longer one, ie arched part. If one squeezes such a hose, which is shown schematically in cross section in FIG. 6a, the upper larger surface always strives to bulge into the position shown in FIG. 6a.

6a, the incisions 9 and 9 '(see FIG. 2) have been provided in the upper curved region of the tube in the state of FIG. 6a and the viewer facing the observer above the paper plane and thus above the paper plane Incisions 9 and 9 'imagined tube piece flat together, while the other tube piece running backwards from the paper plane is left in its unloaded state, then the viewer must find the state of FIG. 6a, ie the incisions 9, 9 'lie in the upper, longer, curved part, which thus represents the stop 12 shown in FIG.

According to FIG. 7, the material web 5, driven by drive rollers 16, runs from left to right in the conveying direction of arrow 6 into the cutting device. The left tube part, which is already provided with the cuts 9 and 9 ', is held down by the feed rollers 16, ie in the flattened state. as can be seen at the point of engagement of the two feed rollers 16. Not only the holder 18 for the feed rollers 16 but also the holder 19 for a pneumatic cylinder 20 with a piston 21 are attached to the carrier 17. At the articulation point 22, the piston 21 is articulated on the left end 23 of a control arm 24, while the latter can be pivoted about an axis of rotation 26 provided on its right end 25. The pivot arm 4 is also pivotably articulated about this axis of rotation 26, which in the illustration in FIG. 7 is suspended downward and is connected at its lower end 27 to the upper knife 3 and via the articulation point 2 (FIG. 1) to the lower knife 1. Swivel arm 4 and control arm 24 consist of a rigid piece. From Figure 7 it can be seen how the right edge of the upper knife 3 is brought into abutment against the stop 12 of the right part of the material web 5. In this state, the cut 7 can be made in the flat surface of the material web 5, the cut 7 then certainly being precisely aligned with the cuts 9, 9 '.

FIG. 8 shows the top view of the part of the cutting device shown in FIG. 7, the upper feed roller 16 and the material web 5 with the overlap point 8 and the incisions 9, 9 'being visible here. To simplify the illustration, the upper knife 3 and swivel arm 4 are omitted, so that only the lower knife 1 and its articulation point 2 for the upper knife can be recognized. To the right of the stop labeled 12, the tube piece is curved. so that it has the cross-sectional state according to FIG. 2 on the left or 6a, while on the left next to it the tube piece under the feed rollers 16 is still relatively compressed.

In operation, the cutting device works in such a way that when viewing FIG. 7 from the position shown there, the swivel arm 4 is pivoted to the left about the axis of rotation 26 in the direction of conveyance 6 in the conveying direction 6, so that, after a reversal of direction, controlled by the pneumatic cylinder 20, immediately to turn right again, ie in Figure 7 counterclockwise, at a speed that is greater than the conveying speed of the material web 5. In this way, the swivel arm 4 can then move with its upper knife 3 against the material web having incisions 9, 9 ', which is stopped in the state of FIG. 7 by control means (not shown). The force of the pneumatic cylinder is so weak about the ratio of the short lever of the control arm 24 at the top and the long lever of the swivel arm 4 at the bottom that the upper knife 3 does not get any damage against the stop 12. Due to the small force acting in the upper knife 3, the swivel arm 4 is stopped in the position shown in FIG. 7, and then the control signal for making the incision 7 takes place.

Claims (6)

1. Apparatus for precisely producing a cut (7) in a web (5) of flexible material which is to be cut into individual portions in the stationary condition, comprising a bottom blade (1) and a top blade (3), at least one of which is driven, and a feed means (16) for the web of material (5), wherein successive stops (12) which serve to establish a cut line are already provided on the web (5), characterised in that the top blade (3) is rotatably connected to the bottom blade (1) (at 2) and that both blades (1, 3) are arranged on a pivotal arm (4) which is movable by a drive means (20), and that there is provided a control means which after a cut has been made initially moves the pivotal arm (4) in the opposite direction to the direction of transportation (6) of the web (5) and reverses it in its direction of movement (6) after the next stop (12) has passed through the blades (1, 3) and causes it to follow the stop (12) preceding it in the direction of movement (6), at a higher speed than the web (5), until one (3) of the blades contacts said stop, the web being stopped and a signal for producing the cut being generated when the web (5) and the pivotal arm (4) are stationary.

2. Apparatus according to claim 1 characterised in that the control means (3, 4, 20) rises a pneumtic cylinder (20) with a movable piston (21) which is pivotally connected to the one end (23) of a control arm (24), that the pivotal arm (4) is connected with its one end to the other end (25) of the control arm (24) while at least one blade (3) is mounted to the other end of the pivotal arm (4), and that the lever (22-26) of the control arm (24) is substantially smaller than that (26-3) of the pivotal arm (4).

3. Apparatus according to claim 1 or claim 2 characterised in that for the cooperation of the web of material (5) and the control means (3,4, 20) provided on the web of material (5) is a stop (12) for contact of the pivotal arm (4) which can be moved away from the stop (12) by the control means (3, 4, 20) prior to the cutting operation and can be pivoted towards the stop.

4. Apparatus according to one of claim 1 to 3 characterised in that the stop (12) on the web of material (5) is formed by at least one cut (9, 9') in the web of material (5) and folding in same along at least one groove line (25) extending in the direction of conveying movement (6) of the web of material (5).

5. Use of the apparatus according to one of claim 1 to 4 for separating tube portions which have been partially cut into and which are joined together and which are formed from a coated paper web (5).

6. Apparatus according to claim 1 to 4 characterised in that the control arm (24) is made in one piece with the pivotal arm (4).

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