THE METHOD AND APPARATUS FOR SLITTING BROKE ROLLS

This invention relates to a method by which a broke roll, composed of paper or board web, is stripped by slitting and to an apparatus which applies the method.

The broken rolls are stripped at paper and board mills and the material is returned to the process through the pulper. The released cores are either re-used or burned.

Many ways to strip material web rolls are known in the art.

The butt rolls for instance are stripped by unwinding, with an apparatus disclosed in the patent publication FI 71108. Even larger rolls are stripped by unwinding.

Unwinding is a relatively slow method.

To strip a roll by splitting with a guillotine is a much faster way. Such solutions have been disclosed for example in patent publications FI 61650, US 2804140, US

3675525 and GB 1131567. The disadvantage of stripping a roll by guillotines is the difficult controllability of the material flow. If the stripped material comes to the pulper in over-sized batches, the pulper is in danger of getting jammed. Frequently also the core is damaged so badly that it cannot be reused.

Therefore, the broke rolls are stripped nowadays usually by a shuttling knife.

The advantages are the sufficient stripping speed and good controllability of the material flow.

The embodiment of shuttling knife resembles the manual plough cutting where a wooden plough-shaped knife cuts the roll open only by couple of web layers at a time. A further developed embodiment of the wooden plough resembling a hand plane is disclosed in the US patent publication 5715605.

The patent publication US 4506575 discloses the stripping of broke rolls by planing with a double-bladed knife.

The technique disclosed in the patent publication US 3605542 explains the stripping of a broke roll by ploughs. The solution described as an invention in this publication resembles a gap-toothed chain saw.

The solution which is meant for stripping the metal web reel and which resembles a chain saw is disclosed in US patent publication 3204501. Several freely rotating, slitting blades are placed in the chain.

The patent publication US 4864906 discloses a stripping process by planing with a freely rotating blade.

For instance the patent publication US 5759350 discloses the stripping done by a fluid jet. The publication contains also an extensive review of prior art.

The above-mentioned solutions, closest to this invention, all have one major problem which is especially the uncertain loosening of web layers. Even though the cutting itself can be managed irrespective of the cutting methods, however, with certain paper and board qualities the cut web layers just will not open easily. In addition to difficult material more problems may occur, in case the broke rolls have been stored outside for a while and for instance the upper web layers are glued together due to moisture and changes in temperature. The stripping of the rolls must run smoothly and without problems so that the stripping apparatus can be operated unmanned. In an automatic system the cut webs are to be transferred right away, either through a slide plate or on a conveyor, as a constant flow into the pulper.

The patent publications EP 1178877 / SE 519378 disclose a solution which combines the cutting by freely rotating / non-rotating shuttling blade and partial opening of the groove by a plough. Air blowing is used in case of soft tissue instead of the mechanical plough.

The solution disclosed in said EP/SE- publications shows quite a number of drawbacks.

The description of the invention of the SE publication p.4, lines 27 - 28 / mentions only the usage of air jets as ploughs but not how the air jets are located and where they are directed to.

The mechanical opening device, the plough, only has a partial contribution in the process of loosening the web layers. First of all, the plough works only tangentially in relation to the roll to be stripped by only pushing the web layers sidewards.

The plough cannot intrude underneath the web layers. Furthermore, web layers cut with one cutting movement cannot be ploughed earlier than just in connection with the next cutting movement. It has to be made sure that the plough is placed sufficiently above the cutting edge of the blade. In an automatic system, this restricts the possible adaptation of the mass flow suitable for the pulper. The easiest way to

influence the mass flow is to make adjustments in the cutting depth. In case the cutting depth exceeds the height difference between the plough and the blade, the web layers are cut by the plough and not by the blade. The patent claim 4 of the EP publication states, however, that the blade cuts the material deeper than the plough. Therefore, the difference in heights must be at least as large as the maximum cutting depth. The cutting depth when approaching the core might be about 10 mm. This means that the last web layers which lay closest to the core are not ploughed at all. But, however, these light layers especially would require assistance in loosening. When the cores are conveyed further, web layers left on the core open uncontrolled and cause malfunctions.

Figure 1 in the reference publication EPl 178877 shows an embodiment which is not suitable as basis for an automatic system. Feeding webs of an entire roll from the pallet to the pulper requires work and has all the disadvantages typical to a guillotine. The development of an automatic stripping system could be based on the method illustrated in Fig. 2 of the publication EPl 178877. The description of the invention should, however, be complemented in this case by the feeding of broke rolls into the stripping system and by the removal of the core after the cutting. The functionality of this embodiment is restricted in practice by following disadvantages. The roll supporting arms move along the shafts 16,17, and when cutting proceeds further, they lift the roll towards the cutting blade operating at a fixed height. This means that the broke roll with a weight of several, sometimes even ten thousand kilograms, must be lifted up by some millimetres every few seconds. This causes a lot of strain on the drives of vertical movement.

Compressed air as the source of power for cutting, results in high operating expenses. The turning point of the shuttling movement of the cutting blade must be placed somewhat outside the broken roll. This means that, due to e.g. the swayings, clearances and released stresses at the roll, the return movement of the cutting blade does not always hit the same line as the previous movement. When the successive cuts are done with a small offset in relation to each other, narrow web strips are created from the web layers cut open but not yet ploughed aside. These strips are

very harmful. They get onto photocells and into conveyor structures causing operational malfunctions and increase the need for cleaning measures.

The object of present invention is to create a method and apparatus in order to eliminate the drawbacks of known solutions and especially to boost the loosening of the layers. The characteristics of the invention are presented more precisely in the characterising parts of the independent patent claims.

This invention provides considerable advantages.

The exact air jet flow, which is directed underneath the web layers, combined with the lifting ploughing loosens even the most difficult materials in a very effective way.

The point of the ploughing ripping element can be placed substantially at the same depth as the cutting blade, ie. to the bottom of the cut groove. In this way the web layers, that are cut but not yet ploughed aside, do not get on the way of the successive cutting. The exact cutting line will not change either, since one of the blades can stay in connection to the roll during the reversion stage. Consequently there will be no creation of narrow strips.

The broke roll can be stripped automatically down to the core and the core is not being damaged.

The following describes the invention with references to the attached illustrations.

Figure 1 presents the cutting and ripping apparatus according to the invention as seen from the side.

Figure 2 presents the cutting and ripping elements, seen from the top, cut at the axis of the rotating blades.

Figure 3 presents the automatic stripping system for broke rolls.

Figure 4 presents a ploughing blade, illustrated against the direction of movement, the left side cut in the middle.

Figure 1 presents a way of operation where the broken roll 1 is lifted to the cutting position supported by shafts 12 pushed into the core openings. The shafts are attached to arms 13 as illustrated in Fig. 3. The supporting structures with their power and transmission means are known from the prior art. The power transmission can be done for example by means of chains or screws.

The cutting shuttle 4 presented in Fig. 1 is positioned in the turning point of the substantially horizontal cutting movement of the shuttle. Bearing units 8 are fastened to the cutting shuttle module, and are steered by the guide beam 9 substantially parallel to the axis of roll 1. The power transmission for the cutting movement of the shuttle is known from the prior art, and may be executed for instance by a gear motor 14 and toothed belt. An electric motor is equipped preferably with a frequency converter. The shuttle module moves vertically towards the material web roll 1 along with independent bearing carriages, known from prior art, and is steered by substantially vertical guide bars 15. The power transmission is advantageously done by screws, toothed belts, chains or by similar means. Adapted solutions known from the prior art are not described in details. Two freely rotating blades 5,6 are attached to the cutting shuttle 4. The bearing arrangement of the blades is known from the prior art. A two-sided ploughing blade 7 is placed between the first 5 and the second 6 rotating cutting blade in the cutting direction, between them most advantageously in the middle. Between the cutting edges 7a, 7b of the ploughing blade there are ripping wings (7c,7d). On the one hand their opening effect is based on the lifting ploughing and on the other hand on the properly directed air jets.

The lifting ploughing means that the wings of the plough protrude underneath the web layers Ia and thus apply not only a tangential force to the cut material webs, but additionally apply even the force F, which tends to lift the cut material webs away from the material web roll.

The edges 7a and 7b ploughing in the cutting direction are placed together with the cutting edges of the rotating cutting blades 5 and 6 at the same cutting plane A. Air nozzles 10 and 11 in the ploughing blade 7 are placed in the ripping wings 7c and 7d, substantially transversal to the cutting direction, so that the air jets are focused

towards the sides of the cut groove, between the cut web layers and/or underneath them. In this way, the ripping of the web layers takes place by the combined efforts of lifting by ploughing and lifting by air jets.

The ploughing blade 7 is illustrated in Figure 4 in the cutting phase as seen against the cutting direction. The left side of the figure is cut at the middle of ripping wing 7c. The air flow from the nozzle 10 is directed between the stripped web layers Ia and the surface of the unopened broke roll 1 thus extending the lifting impact to the web layers further than the span of the ripping blade 7c reaches. The air jet also makes the loosened web layers flutter which intensifies the ripping effect. The cutting edge points 7aa and 8bb of the ploughing blade 7 are preferably placed at substantially the same tangent with the rotating cutting blades 5 and 6, which tangent lies at the bottom of the cut groove. This embodiment of the invention suits best for the cutting of strong paper and board.

The ploughing blade 7 is connected to the shuttle 4 by means of the height adjusting equipment 21. By means of arrangement known from the prior art the position of the ploughing blade can be adjusted automatically or manually in relation to the rotating blades. The manual adjustment can be realised advantageously either by screws, wedges or similar tools and the automatic adjustment by actuators replacing the aforementioned tools. Another alternative is to connect the adjustment equipment to the clamps of rotating blades.

In one embodiment of the invention the ploughing blade 7 is placed so much closer to the material web roll 1 than the rotating blades 5,6 that only the ploughing blade 7 cuts and air jets which intrude between and/or underneath the web layers loosen them. This embodiment of the invention is suitable especially for cutting soft materials. Figure 3 reviews the operation of an automatic handling and stripping system for broke rolls. On the entry side at least the arm 13 is lifted over the broke roll. The broke roll is transferred to a position between the arms by the conveyor 16. The arms 13 are lowered down to the height of the core 17 opening and shafts 12 pushed into the core openings. Then they lift the broke roll 1 up to the stripping position. The slope plate 18 is lifted up to the position 18b for transportation sloping to the pulper. After this the horizontal guide beam 9 accommodating the cutting shuttle 4 lowers the

knives down to the height for the initial cutting. The cutting process is started and proceeds in the way described afore. The stripped material webs slide along the slope plate into the pulper 20. After the stripping is concluded, the slope plate is lifted up to the position 18c. The arms release the core 17 and the core falls onto the slope plate and rolls into the container 19. The slope plate retracts aside to bypass position 18a. Other embodiments of the invention can also be applicable. Most essential is, however, that in the cutting movement the ploughing blade follows the freely rotating cutting blade and contributes already during the same cutting movement also in the loosening of the cut web layers. Further, it is also essential that the cut web layers are loosened by the means of precise air jets which direct the air flow to the sides of the cut groove between the cut web layers and/or underneath them substantially transversal with regards to the direction of the cutting movement. The most advantageous embodiment of the invention presents both the handling and the stripping of broke rolls automatically.