Rewinding method and machine for making logs of paper web and the like

Abstract: A method and a machine for the rewinding a web (1) for making a log (2a), in particular for the production of rolls of toilet paper, rolls of all purpose wipers or household non woven fabric, industrial rolls and the like. The rewinding is carried out according to the steps of feeding a web (1) of paper into a winding cradle (4); arranging upstream of the cradle (4) a counter support roller (8) comprising at least a cutting slit (9) transversal to the web and a cutting roller (11) with a blade (10) so that it is possible the cut or tearing of the web (1) for contact of the blade (10) with the web (1); concluding the winding of the log (2a); winding the new log (2b) up to a predetermined length of the web (1); rotating with sliding the counter support roller (8) on the web (1) during the winding of the new log (2b) for causing the blade (10) to cut the web in a desired chosen location.

Description: Field of the invention The present invention relates to a rewinding method for making logs starting from a web, for example used for the production of rolls of toilet paper, rolls of all purpose wipers, household non woven fabric, industrial rolls and the like. Furthermore, the invention relates to a rewinding machine that carries out this method. Background of the invention Rewinding machines are known wherein a winding step is carried out on a log which is in contact surface with winding rollers. More precisely, the log is formed starting from a web of paper, continuous or with transversal perforations, which is carried by first dragging means, is wound partially on an upper winding roller, is in contact with a lower winding roller and is kept against the two upper and lower winding rollers by means of a pressure roller. The three rollers define a channel, or winding cradle, wherein the log is formed and the web of paper is supplied continuously and pulled by the surface frictional contact of the rollers on the log. Normally, in the winding cradle the log is formed on a tubular core. Once the log has reached a predetermined diameter, normally calculated by checking the length of the developed paper, the web is cut or torn and the log is pushed away from the winding cradle at the side of the lower winding roller and, at the same time, a new core is supplied into the cradle by a pusher. It is possible, however, to wind the log without core as well. As disclosed in EP-A-0 454 633, some types of rewinding machines, at the end of each roll winding step, provide a blade that cuts transversally the web by pressing against the upper winding roller. The upper winding roller has one or more cutting slits with which a retractable blade engages mounted on an adjacent cutting roller. This system has the drawback that it does not allow cuts having length not multiples of the circumference of the upper winding roller, or not multiples of the distance between two successive cutting slits when several cutting slits are provided for. In the case, instead, of rewinding machines in which the web is torn, there is the drawback that the tearing step is subject to being carried out incorrectly. Actually, the web is stopped upstream of, or onto, the upper winding roller and the tearing is caused by the pulling action, on the web kept still, of the lower winding roller, on which the log is pushed by the pressure roller. Normally, it is sufficient to create a speed difference between said two rollers at the moment of the exchange in order to effect the tearing. However, the tearing sometimes cannot be made correctly, since it depends on the correct growth of the log being wound as well as on the presence and quality of the transversal perforation. Furthermore, with the tearing method, rolls can be obtained whose development is multiple of the pitch between two transversal perforations only. Finally, in case of rolls without transversal perforations, for example industrial rolls, in order to effect the tearing it is necessary to make a special auxiliary perforation on the web at the end of the development of each roll. Summary of the invention It is an object of the present invention to provide a rewinding method of a web of paper for making logs, wherein the passage from a roll to the successive one is carried out by cutting the web and wherein the development of the web wound on the log after the cutting step has whichever desired length. It is another object of the present invention to provide a rewinding machine of a web of paper for making logs that is capable of cutting the web upstream the winding zone in a desired location. These and other objects are achieved by the web winding method for making a log according to claim 1. Preferably, the front end is pulled towards the winding cradle by a suction step carried out by the counter support roller. Preferably, the winding cradle comprises an upper winding roller, a lower winding roller and a pressure roller, the upper winding roller comprising suction means for capturing at least the front end of the web and starting the winding of the new log. In a preferred embodiment, the upper winding roller has a plurality of radial holes, the front end of the web being captured by a predetermined sector of said holes belonging to an outer drum by means of an inner drum rotatable coaxially but in a way independent from the outer drum and suitable for selectively connecting the predetermined sector of the holes with a suction chamber. The synchronisation between the inner drum, the cutting roller and the counter support roller is obtained by a control step of driven axes operated by a computer, whereby, for every chosen web development between two successive cuts the computer arranges a reset phase of the counter support roller with respect to the blade and a relative rotation between the outer drum and the inner drum. According to another aspect of the present invention, a rewinding apparatus is claimed comprising the features of independent claim 7. The cutting blade urges against the counter support roller for cutting the web creating a tail end of the previous log and a front end of a new log. Preferably, the counter support roller comprises suction means for dragging the front end towards the winding cradle. Preferably, the winding cradle comprises an upper winding roller, a lower winding roller and a pressure roller, the upper winding roller comprising means for capturing the front end of the web, said means for capturing may be suction means. The upper winding roller comprises preferably an outer drum having a plurality of holes and an inner drum rotatable independently from the outer drum and suitable for connecting a predetermined sector of the holes with a suction chamber, whereby it is possible in turn to capture the front end by means of a predetermined sector of the outer drum. In an advantageous embodiment of the invention the inner drum, the counter support roller and the cutting roller are brought into rotation by axes driven by at least a motor operated by a control unit that adjusts the cutting length of the web of said log, the motor decelerating or accelerating the rotation of said axes and causing said counter support roller to slide with respect to said web. In order to facilitate the sliding, the counter support roller has a surface with a plurality of small air blowing holes for reducing further the friction with respect to said web during the sliding step. Brief description of the drawings Further characteristics and/or advantages of the rewinding method and of the rewinding apparatus according to the present invention will be made clearer with the following description of an embodiment thereof, exemplifying but not limitative, with reference to attached drawings wherein: figure 1 shows a cross sectional view of a rewinding machine according to the present invention; figures from 2 to 5 show four different positions of the tail end of the web of the log being wound and of the front end of the web of the new log to be wound, as well as supplying steps of the core; figure 6 shows the position of the rewinding machine of the previous figures ready for a cut at the conclusion of a log winding phase and a diagrammatical view of the means for adjusting the cutting length. Description of a preferred embodiment With reference to figure 1, a rewinding apparatus of a web 1 for making a log 2a comprises a feeding roller 3 of web 1 and, downstream of it, a winding cradle 4 wherein log 2a is wound. Cradle 4, according to the prior art, comprises an upper winding roller 5, a lower winding roller 6 and a pressure roller 7. The latter follows the growth of log 2a with the tasks of assuring its continuous contact with winding rollers 5 and 6 and of controlling its diameter growth. According to the invention, between feeding roller 3 and upper winding roller 5 a counter support roller 8 is provided on which web 1 rests. Counter support roller 8 is driven independently and has at least a cutting slit 9 in which a retractable blade 10 of a cutting roller 11 can engage. Cutting roller 11 brings periodically blade 10 against counter support roller 8 at the slit 9 for cutting web 1. When the cut has not to be carried out blade 11 retracts for not causing an undesired cut of the paper. At the conclusion of each log, blade 10 urges against counter support roller 8 for cutting web 1 creating a tail end 1a of previous log 2a and a front end 1b of a new log. According to the invention, counter support roller 8 has suction holes 12a and 12b along the edges of slit 9, suitable for capturing and dragging respectively tail end 1a and front end 1b of web 1. Also upper winding roller 5 comprises suction means comprising an outer drum 14 having a plurality of holes 15 and an inner drum 16 rotatable coaxially and independently from outer drum 14 and suitable for connecting, by means of radial walls 17, a chosen sector S of holes 15 with a suction chamber 18. This way it is possible in turn to capture front end 1b by means of a different chosen sector S of holes 15 of outer drum 14. Log 2a already wound is dragged continuously rotating within cradle 4 by tangential friction against upper winding roller 5, lower winding roller 6 and pressure roller 7. The winding started about a core 20a, which had been supplied into cradle 4 by a loading unit 21 that draws cores 20 from a chute guide 22. In particular, a core 20b is ready for being wound around to form a log starting from front end 1b of web 1. Counter support roller 8 has a smooth surface, continuous or discontinued by circumferential grooves, for providing a support to web 1, for allowing the cutting or tearing and for permitting, at predetermined moments, the sliding of the web thereon. In order to make easier the sliding for certain types of web having a greater friction factor its surface can also have a plurality of small air blowing holes. The winding steps of web 1 for making a log 2a are the following. The web of paper 1 is supplied into winding cradle 4 about core 20a up to a chosen length development predetermined upstream of feeding roller 3. Then, as shown in figure 1, after that a desired amount of web 1 has been developed upstream of cradle 4, counter support roller 8, at cutting slit 9, and transversal blade 10 of cutting roller 11 cut or tear web 1 separating tail end 1a from front end 1b. Cutting or tearing are equivalent at this stage since, with the presence of transversal perforations on the web, the action of the blade makes easier the tearing, whereas without perforation the blade carries out an actual cutting. Then the various steps of bringing the front end towards the cradle are successively carried out, and precisely: suction holes 12a and 12b capture (fig. 1) respectively tail end 1a and front end 1b allowing to counter support roller 8 to pull them (fig. 2) up to bring them into contact with upper winding roller 5; then, holes 15 of outer drum 14 of upper winding roller 5, at the sector S for dragging front end 1b, become active owing to the position of walls 17 of the inner drum 16 (fig. 3) and take tail end 1a and front end 1b; the latter is either folded, (like in figure 4) by means of suction by a portion of sector S at a certain distance from the transversal edge, or dragged just starting from the edge, according to how the outset of winding on core 20b is made; the rotation between outer drum 14 and inner drum 16 is synchronous for bringing (fig. 4) front end 1b towards cradle 4; at the same time loading unit 21 pushes a core 20b of log 2b so that this encounters (fig. 5) front end 1b at the entrance of cradle 4, which is at the same time freed from log 2a already wound. Once started winding log 2b (fig. 6), inner drum 14, counter support roller 8 and cutting roller 11, with blade 10 retracted (fig. 5) continue to rotate, up to the conclusion of log 2b same. Always as shown in figure 6, during the winding of log 2b inner drum 14, counter support roller 8 and cutting roller 11, for going back to the starting position of figure 1, by means of a check on the rotation of their axes 23, 24 and 25, in a predetermined step of the winding phase do not rotate any more in synchronism with the speed of web 1, but do different rotations, variable in turn according to the position of the cut to make. More precisely, counter support roller 8 slides relatively to web 1, rotating of a relative angle 23a without braking or accelerating the web, since there is only a slight friction between web 1 and roller 8 surface. Also cutting roller 11 and inner drum 16, in a way independent from outer drum 14, make a relative rotation 24a and 25a of equal linear development with respect to the movement of web 1. The synchronisation between inner drum 14, cutting roller 11 and counter support roller 8 is obtained by means of a control of the axes 23, 24 and 25 operated by the CPU 26, not shown in more detail since easily obtainable by a man of the art. Therefore, for every length of web chosen between two following cuts, CPU 26 arranges the phase reset of counter support roller 8 with respect to web 1, calculating the speed of the same for example starting from the speed of axis 27 of feeding roller 3 in synchronism with a relative rotation of cutting roller 11 and of inner drum 16 with respect to outer drum 14. It is possible, as shown diagrammatically in figure 6, that axes 23, 24 and 25 of counter support roller 8, of cutting roller 11 and of inner drum 16 are driven by a single motor 28 and connected by means of transmissions of suitable ratio, CPU 26 operating the rotation of the motor responsive to the speed of web 1. Alternatively, the three axes are driven by distinct motors, for example DC motors, even of brushless type, and brought into rotation in synchronism by CPU 26, which always operates their rotation responsive to the speed of web 1. In both cases, the result is achieved that every log is wound with a web development having desired length. In fact, after rotation according to angles 23a, 24a, 25a at a speed, even slow, chosen by CPU 26, there is the possibility of cutting the web at a chosen location. All this is done independently from the circumference of roller 5 and without adversely affecting the winding phase of the log within cradle 4 by rollers 5, 6 and 7. It is possible that counter support roller 8 has more than one cutting slit 9 for reducing further the time during which the web slides on roller 8 The foregoing description of a specific embodiment will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims: Winding method of a web (1) for making a log (2a), in particular for the production of rolls of toilet paper, rolls of all purpose wipers or household non woven fabric, industrial rolls and the like, comprising the steps of: feeding a web (1) of paper to a winding cradle (4); characterised with the steps of : arranging upstream of said cradle (4) a counter support roller (8) comprising at least a cutting slit (9) transversal to the web, (1) wherein said counter support roller (8) is distinct from the elements making up said winding cradle (4); arranging a cutting roller (11) that faces said counter support roller (8) and comprises at least a blade (10) transversal to the web (1), said web running between said counter support roller (8) and said cutting roller (11); cutting or tearing said web (1) by contact of said blade (10) with said web (1) in a predetermined moment (8) at said slit (9), the cut or tearing creating in said web (1) a tail end (1a) and a front end (1b); conclusion of the winding of the log (2a) having said tail end (1a) and introducing said front end (1b) into said cradle (4) for starting the winding of a new log (2b); winding the new log (2b) up to a chosen length development of said web (1); rotation with sliding of said counter support roller (8) on said web (1) during the winding of said new log (2b) for allowing the blade (10) to cut the web in a desired chosen location. Winding method according to claim 1, wherein at least said front end (1b) is dragged towards said winding cradle (4) by a suction step (12a, 12b) carried out by said counter support roller (8). Winding method according to claim 1, wherein said winding cradle (4) comprises an upper winding roller (5), a lower winding roller (6) and a pressure roller (7), said upper winding roller (5) for starting the winding of said new log capturing by suction means at least said front end (1b) of said web (1). Winding method according to claim 3, wherein said upper winding roller (5) has a plurality of radial holes (15) made on an outer drum (14), said front end being captured by a chosen field (S) of holes (15) of said outer drum (14) by means of a co-axial inner drum (16) rotatable independently from the outer drum (14) and suitable for selectively connecting said chosen field (S) of said holes (15) with a suction chamber (18) present in said inner drum (16). Winding method according to claim 4, wherein a step of synchronisation between said inner drum (16), said cutting roller (11) and said counter support roller (8) is provided whereby, for every chosen web length development between two successive cuts an acceleration or deceleration of said counter support roller (8), of said cutting roller (11) and of said inner drum (16) with respect to said web (1) is done. Winding method according to claim 5, wherein said step of synchronisation is obtained by means of a control operated by a computer (26) of the driven axes of rotation (23,24,25) of said counter support roller (8), of said cutting roller (11) and of said inner drum (16). Rewinding apparatus of a web for making a log comprising: means for feeding (3) and dragging a web (1); a winding cradle (4) within which said log (2a, 2b) grows downstream said means for feeding (3); characterised in that it comprises a counter support roller (8) on which said web (1) rests in the space interval between said means for feeding (3) and said cradle (4), said counter support roller (8) having at least a cutting slit (9) and being distinct from the elements making up said winding cradle (4); a cutting roller (11) suitable for bringing periodically a transversely oriented cutting blade (10) against said counter support roller (8) at said slit (9) for cutting or tearing said web (1); means for decelerating or accelerating said cutting roller (11) and said counter support roller (8) between one cut or tear and the successive one, with the web (1) not in permanent frictional contact with the counter support roller (8). Rewinding apparatus according to claim 7, wherein said cutting blade (10) urges against said counter support roller (8) for cutting or tearing said web (1) creating a tail end (1a) of the previous log (2a) and a front end (1b) of a new log (2b). Rewinding apparatus according to claim 7, wherein said counter support roller (8) comprises means for dragging said tail end (1a) and said front end (1b) towards said winding cradle (4). Rewinding apparatus according to claim 9, wherein said means for dragging said tail end (1a) and said front end (1b) towards said cradle (4) comprises suction holes (12a, 12b). Rewinding apparatus according to claim 7, wherein said winding cradle (4) comprises an upper winding roller (5), a lower winding roller (6) and a pressure roller (7), said upper winding roller (5) comprising means for capturing at least said front end (1b) of said web (1). Rewinding apparatus according to claim 11, wherein said means for capturing at least said front end (1b) of said web (1) comprises suction means. Rewinding apparatus according to claim 11 or 12, wherein said upper winding roller comprises an outer drum (14) having a plurality of holes (15) and an inner co-axial drum (16) rotatable independently from the outer drum and comprising means (17) for connecting a predetermined sector (S) of said holes with a suction chamber (18), whereby it is possible in turn to capture at least said front end (1b) by means of a different chosen field (S) of said outer drum (14). Rewinding apparatus according to claim 12, wherein said inner drum (16), said counter support roller (8) and said cutting roller (11) are brought into rotation by driven axes (23,24,25) operated by at least a motor (28) operated by a control unit (26) that adjusts the cutting length of the web (1) of said log (2a, 2b), said motor (28) decelerating or accelerating the rotation of said axes (23,24,25) causing said counter support roller (8) to slide (23a) with respect to said web (1). Rewinding apparatus according to claim 11, wherein said counter support roller (8) has a low friction smooth surface, continuous or comprising a plurality of circumferential grooves. Rewinding apparatus according to claim 11, wherein said low friction smooth surface has a plurality of small air blowing holes.

Inventors: DE MATTEIS ALESSANDRO, LANDUCCI SERGIO, DE MATTEIS, ALESSANDRO, LANDUCCI, SERGIO
Applicants: M T C MACCHINE TRASFORMAZIONE, M T C - MACCHINE TRASFORMAZIONE CARTA S.R.L.
Application year: 1998
Main classification: B65H19
IPC codes: B65H19