Patent Application
20130020427
The present invention relates to a rewinding machine for producing logs of web material wound around tubular winding cores.
The invention also relates to a new winding method for producing logs of web material around tubular winding cores.
In the production of logs of wound web material, such as rolls of toilet paper, kitchen towel or the like, reels of large diameter, called parent reels, are initially formed, from which the web material is then unwound and rewound on logs of smaller diametric dimensions, corresponding to the dimensions of the end product destined for sale, and of axial length equal to a multiple of the axial dimension of the rolls destined for final use. These logs are subsequently cut to form the rolls destined for use, which are packaged.
Rewinding machines, in particular for the field of tissue paper converting, for manufacturing rolls of toilet paper, kitchen towels and similar products, are completely automatic high speed machines that can process one or more plies of cellulose fiber fed at high speeds, even equal to or greater than 1000 m/min. Modern rewinding machines therefore form logs of wound material with high rates, up to one log every 1-2 seconds or less.
After a log has been wound a series of operations must be carried out, which are defined as a whole as “exchange phase”. In the exchange phase operations are performed to sever the web material, unload the finished log, fasten the leading edge of the web material (obtained by severing the web material) to the new winding core that is inserted in the machine and start winding of the new log.
These operations must be carried out at very fast frequency to avoid slowing the production cycle, as the average speed of the web material is not modified during the exchange phase. Vice versa, there is only a possible local variation of the speed of the web material in the area in which this is to be severed.
U.S. Pat. No. 5,979,818 describes a new generation rewinding machine, wherein the web material is wound in a winding cradle preferably formed by a group of three winding rollers. The web material is guided around a first winding roller and passes through a winding nip defined between the first winding roller and a second winding roller. Positioned upstream of this nip is a support surface of the winding cores that are inserted in an inlet of a channel defined between said support surface and the first winding roller. In some embodiments described in this prior art document, positioned along the channel is a web material severing member, preferably designed and arranged in such a manner as to sever the web material by pinching it against the first winding roller and causing local slowing of the web material between the pinch point and the log being wound in the winding cradle. This slowing causes tension of the web material and finally severing thereof, preferably along a perforation line produced by a perforator positioned upstream of the winding cradle.
Machines based on this principle are extremely flexible, reliable and capable of producing logs with high axial lengths at very high speeds, equal to or even greater than 1000 m/min.
The product manufactured with these machines is susceptible to further improvements, as the web material wound on each winding core has, in the innermost turn, a fold-back that constitutes, due to its length, a slight defect at least for certain types of product. The length of this fold-back depends on the point in which the web material is severed. This point is positioned at a certain distance from the contact point of the web material with the new winding core. The portion of web material between the point of fastening to the new winding core and the point of severing is folded to form a fold-back of a length corresponding to the distance between these two points.
Moreover, the severing member is provided with pressure pads with which it presses the web material against the winding roller. The pressure exerted by the pads causes rapid wearing of the pads which consequently need to be adjusted, as otherwise at a certain point the pads would no longer press sufficiently against the winding roller and would no longer cause severing of the web material. Typically, this adjustment must be carried out about once every two weeks and, as this is a mechanical adjustment, requires a manual operation.
In some embodiments of current rewinding machines designed on the basis of the teaching of the aforesaid patent, the pressure exerted by the severing member on the winding roller is high and causes the whole of the rewinding machine to vibrate. Besides representing a structural problem, which causes wear of the mechanical parts and noise, this can have negative effects on the correct operation of the machine, as tearing of the web material may not take place in the desired point, which is identified by a precise perforation line of the web material.
US-A-2004/0061021, U.S. Pat. No. 6,877,689 and U.S. Pat. No. 7,175,127 disclose rewinding machines wherein the web material severing member is controlled in such a manner as to cause tearing of the web material between the two points of the web material defined by the area of contact with the severing member and the area of contact with the new core inserted in the winding channel. Operating in this manner a shorter fold-back is obtained. However, the machine looses a great part of its reliability, as a resuit of decreased control of the web material in the exchange phase and it is more difficult to achieve high production speeds.
According to one aspect, the object of the invention is to produce a rewinding machine that overcomes, completely or in part, at least one of the drawbacks of prior art rewinding machines. The object of some embodiments of the invention is to provide a more efficient rewinding machine, and in particular a rewinding machine with which a product of better quality is obtained even at high production rates and without loss of the advantages typical of the most modern and reliable rewinding machines known in the art.
The object of some embodiments of the invention is to provide a rewinding machine wherein the frequency of operations to adjust the severing member of the web material is reduced and/or wherein adjustment can take place more efficiently, without requiring long machine stops and mechanical operations on machine members.
The object of yet other embodiments of the invention is to provide a rewinding machine wherein the vibrations caused by operation of the web material severing member are reduced.
Substantially, in one embodiment the invention provides a rewinding machine for winding a web material around a tubular core, comprising: a first winding roller, around which said web material is guided, at least partly defining a winding cradle; preferably a second winding roller, defining with the first winding roller a nip through which the web material is fed; a winding cores support surface, arranged to receive a winding core and to convey it toward the winding cradle and defining with the first winding roller a feed channel for the winding cores, in which channel the cores are fed in contact with the support surface and with the web material guided around said first winding roller; a winding core inserter for inserting winding cores in the channel; a web material severing member, which can be inserted in the channel to sever the web material, said severing member interacting with the first winding roller and with the web material guided around said first winding roller to cause severing thereof; preferably a motor for controlling said severing member, which controls the severing member modifying the speed of the severing member when it is positioned inside said channel. Specifically, the severing member is accelerated after severing of the web material has taken place. Such acceleration avoids collision between the severing member and the new core advancing along said channel even though severing of the web material is performed by keeping the severing member quite near to the new core. This reduces the length of the leading portion of the web material which folds back upon start of winding around the new core.
Speed variation must be intended in general as an acceleration without reversal of movement or with reversal of movement. I.e. acceleration can be understood as an acceleration of the severing member without reversal of the advancement movement thereof, or else as a reversal of the direction of motion. In preferred embodiments the acceleration of the severing member is caused by a motor under the control of a suitably programmed electronic control unit.
By varying the speed of the severing member while it is positioned in the cores feed channel it is possible to make the severing member interact with the web material at an optimal speed to cause severing of the web material and subsequently modify the speed of the severing member (with or without reversal of speed and therefore of the direction of movement) to avoid collision with the core being fed along the channel. In this manner, it is possible to move the severing point of the web material closer to the winding core that is inserted in the channel, thus reducing the length of the tail edge of web material that is wound on the new winding core, producing a log of better quality, without having to reduce the production speed, determined by the feed speed of the web material.
In some preferred embodiments of the invention, the motor that operates the severing member can be designed and controlled in such a manner as to control the severing member such as to insert and advance the severing member in the channel with a direction of feed opposite with respect to the direction of feed of the cores along the channel. In this case, during the web material severing step the severing member is moved toward a core insertion end of said channel and therefore toward a core inserted therein. Subsequently, reversing the movement of the severing member, it is moved away from the insertion end of the channel. In substance, the severing member is inserted in the core feed channel in a position downstream of the winding core and close to the winding cradle. Subsequently, movement of the severing member continues toward the inlet of the channel, i.e. in the opposite direction with respect to the direction of feed of the cores and of the web material in the channel. This ensures that, by interacting with the web material, for example pinching it against the winding roller, the severing member causes severing of the web material between the position of contact with the web material and the log being wound in the winding cradle. Subsequently, by reversing the movement thereof, the severing member is withdrawn from the channel, exiting substantially in the same area in which it was inserted in the channel.
In the second step of its movement, the severing member therefore moves in a direction substantially concordant with the direction of feed of the winding core, avoiding collision therewith.
In other words, in this embodiment the severing member is controlled according to a reciprocating movement, preferably a rotary reciprocating movement, traveling along a same trajectory in one direction and then in the opposite direction, the severing member interacting with the web material and causing severing thereof in the point of reversal of its trajectory.
With a configuration of this type it is possible both to reduce the length of the tail of web material that is folded back after severing of the web material and to reduce the vibrations caused in the rewinding machine as a result of the action of the severing member against the winding roller. Moreover, it is also possible to adjust the severing member to compensate for wear without the need to stop the machine and to act manually on the mechanical members. In fact, in this case it is possible to carry out the adjustments from a control panel, modifying the movement of the motor that causes operation of the severing member. When the pads of the severing member become worn, it is sufficient to extend the trajectory of the severing member moving the point in which movement is reversed closer to the inlet of the channel, thus always obtaining adequate pressure of the severing member against the winding roller, sufficient to obtain tearing of the web material. For example, it could be sufficient to increase the angle of rotation of the web material severing member by a hundredth of a degree each week in the opposite direction with respect to the direction of feed of the winding cores.
Besides the possibility of performing this adjustment through an interface from the control panel without the need to act manually on mechanical members, in this embodiment of the invention there is substantially less wear with respect to conventional machines, provided with a severing member that rotates without reversing the rotational movement during the whole of the exchange cycle. This is due to the fact that it is possible to maintain the necessary pressure between pad and web material at a constant minimum value, still sufficient to cause tearing. According to a particularly advantageous embodiment of the invention, it is possible to adjust this pressure between pad and web material as a function of the resistance of the portions of web material between the perforations defining a perforation line. In this manner, tearing is caused as a function of the type of product. Alternatively, or additionally, it is possible to adjust the pressure between pad and web material as a function of the speed of the web material. In fact, when the speed increases a lower pressure of the pad against the web material is necessary to cause tearing thereof.
Due to the lower pressure between pad and paper (and therefore lesser thrust of the pad against the roller) a reduction of the vibrations is also obtained and consequently the mechanical stress caused by this effect is reduced or eliminated, as is the risk of severing of the web material imprecisely and not coincident with the perforation line along which the machine must tear the web material.
In other embodiments, the severing member is controlled to move inside the cores feed channel without reversing the advancement speed thereof, but in such a manner as to be accelerated after having interacted with the web material causing severing thereof. In substance, the severing member is made to advance along the channel at a lower speed with respect to the feed speed of the web material, to cause severing of the web material as a result of slowing thereof caused by interaction with the severing member. Subsequently, the speed of the severing member is increased so as to prevent collision with the core that is being fed in the channel. In practice, in some embodiments the severing member advances in the cores feed channel at variable speed: a first lower speed to interact with the web material and cause tearing thereof downstream of the point of interaction with the severing member; and a second higher speed to withdraw the severing member from the channel before collision with the winding core. The severing point of the web material is in this manner brought closer to the point of contact between the winding core and the web material guided around the winding roller, thus reducing the length of the tail of web material that is folded back when the first turn is formed around the winding core.
In some embodiments the severing member is provided with a rotational movement around an axis outside said channel. In other embodiments, the severing member can be provided with a linear movement.
In some embodiments the severing member is controlled to interact with said web material and cause severing thereof moving at a speed no greater than 70% and preferably no greater than 50% of the speed of the web material. When the severing member is provided with a rotational movement, speed of the severing member is intended as the peripheral speed that the member assumes in the point of contact with the web material, as it is this speed that determines the conditions of interaction with the web material and therefore the action to obtain tearing or severing of the web material.
In some embodiments the feed movement of the winding core in the channel is controlled, for example by providing a rotating member arranged in a position along said channel, opposite said first winding roller and at a distance therefrom such as to allow the passage of a winding core between the first winding roller and the rotating member. The rotating member is positioned, with respect to the direction of feed of the core in said channel, upstream of the area of interaction between the severing member and the web material; the rotating member being controlled by an actuator to control the feed movement of the core along said channel.
According to a different aspect, the invention provides a method for winding a web material around a winding core in a rewinding machine, comprising the steps of:
According to some preferred embodiments of the method according to the invention, the severing member is inserted in the channel with a movement in a direction opposite the direction of feed of the web material in said channel, is pressed against the web material, causing severing thereof in a position between the severing member and a log being formed in the winding cradle and subsequently the movement of the severing member is reversed to remove it from the channel.
Further advantageous features and embodiments of the invention are set forth in the appended claims, which form an integral part of the present description.
The invention will be better understood by following the description and accompanying drawing, which shows practical non-limiting embodiments of the invention. More in particular:
With initial reference to
Upstream of the nip 7 between the winding rollers 1 and 3 (with respect to the direction of feed of the web material N) a channel 9 extends, formed between the cylindrical surface of the first winding roller 1 and a support surface 11 of the winding cores A which are inserted in sequence in the machine. Insertion of the cores A inside the channel 9 is obtained with a core inserter 13, which picks up the cores from a feed conveyor, not shown, along which a glue applicator can also be provided to apply a glue according to annular or longitudinal lines on the winding cores A to allow adhesion of the web material N at the start of winding of each log L. The inserter 13 represented in the figures is indicated purely by way of example, it being understood that the cores can be fed to the machine with any inserter of suitable shape.
Positioned below the support surface 11 of the cores A is a support unit 15 for a severing member indicated as a whole with 17. The severing member 17 rotates around an axis B, placed below the support surface 11 of the winding cores A and therefore outside the feed channel 9 of the winding cores into the rewinding machine. In its general lines the severing member 17 is similar to the one described for exampie in U.S. Pat. No. 5,979,818, whose content is incorporated in the present description. However, as will be apparent hereunder, the method with which it is controlled is different with respect to that provided in prior art machines, in order to solve the aforesaid problems.
The severing member 17 is provided with an end 17A for example constituted by or bearing one or more pads made of material with high friction coefficient, such as rubber or the like, and preferably elastically yielding. These pads 17A interact with the web material N guided around the winding roller 1 to cause pinching thereof and severing as a result of slowing of the web material N with respect to the winding speed defined by the peripheral speed of the winding roller 1.
The rotational movement of the severing member 17 around the axis B is controlled by a motor, indicated schematically with 19. The motor 19 is only schematically represented in the figures. It can be replaced, for example, by a motor arranged coaxially with respect to the rotation axis B of the severing member 17, to which it transmits motion directly. In other embodiments, a gear, a transmission or a combination thereof can be arranged between the motor 19 and the rotation shaft of the severing member 17.
The motor 19 is controlled by an electronic programmable control unit 21 indicated schematically in
With reference to the sequence of
The severing member 17 is currently rotating in clockwise direction (in
In the step shown in
The severing member 17 in the meantime has fully entered the cores feed channel 9 and has advanced until it presses or pinches the web material N against the cylindrical surface of the winding roller 1.
For this purpose the radial dimension of the severing member 17 is such as to cause sufficient interference between the end pads 17A of the severing member 17 and the winding roller 1. The web material N is thus pinched by the severing member 17, and more precisely by the pads 17A thereof, against the opposite surface of the winding roller 1. In some embodiments, the severing member 17 has a plurality of pads 17A mutually spaced apart and aligned along the transverse direction, i.e. the direction orthogonal to the plane of the figures and therefore parallel to the axes 1A, 3A of the winding rollers 1, 3. According to some embodiments the winding roller 1 preferably has a surface structure characterized by substantially smooth annular bands, corresponding to the position of the pads 17A, and annular bands with high friction coefficient, for example coated with a grip, interposed between the annular bands with low friction coefficient. This causes slipping of the web material pinched by the pads 17A against the smooth annular bands of the cylindrical surface of the winding roller 1, as the speed of the severing member 17, i.e. the peripheral speed of the pads 17A in the contact point with the web material N, is lower than the peripheral speed of the winding roller 1, i.e. the winding speed of the web material N on the log L. In this manner excess tension of the web material N is generated between the log L completing its winding in the winding cradle 1, 3, 5 and the point in which the web material N is pinched against the winding roller 1 by the pads 17A of the severing member 17A. This tension exceeds the tearing point of the web material N causing severing of this material and therefore the formation of a trailing edge LC and of a leading edge LT (
This tearing is achieved by suitably controlling the peripheral speed of the pads 17A, i.e. the speed of the severing member 17. This speed can, for example, be equal to 30% of the feed speed of the web material N around the winding roller 1.
Once the web material N has been severed, the motor 19 causes an acceleration of the severing member 17, which is thus moved away from the core A which is advancing by rolling along the channel 9. The instant in which acceleration of the severing member 17 starts can be determined by detecting effective severing of the web material, for example with an optical system or a system detecting the tension of the web material. In other embodiments, after experimentally determining the time required to achieve tearing of the web material, also as a function of the difference between peripheral speed of the winding rollers and peripheral speed of the severing member 17, it is possible to set the instant of angular acceleration, for example as a function of the angular position assumed by the severing member in the exchange phase.
By controlling the severing member 17 at a variable speed along the channel 9 during the exchange cycle the important advantage is achieved of moving the severing point of the web material N (i.e. the point in which the leading edge LT and the trailing edge LC are formed) toward the point in which the core A inserted in the feed channel 9 of the cores is in contact with the web material N guided around the winding roller 1. As a consequence, the portion of web material N that will be folded back inside the first turn of web material formed around the winding core A will be much smaller than that of conventional machines, while maintaining the important advantage of performing severing of the web material downstream instead of upstream of the severing member 17, with reference to the direction of feed of the web material N around the winding roller 1.
In the description above, the severing member 17 is controlled by the motor 19 under the control of the programmable control unit 21 in such a manner as to advance with a rotating movement always in the same direction (arrow f17) but at variable speed during the exchange phase: in a first time interval the severing member 17 is rotated at low speed to obtain reliable tearing of the web material as a result of the tension caused inside said material; in a second time interval the severing member 17 is accelerated to avoid collision with the winding core A.
This allows the severing point of the web material N to be moved closer to the point in which the latter is pinched by the winding core A and therefore, ultimately, reduction of the length of web material folded back inside the first turn of the new log that will be formed around the winding core A. This is due to the fact that collision with the winding core A is avoided as a result of to acceleration of the severing member 17 after the web material has been severed. This acceleration prevents collision with the winding core A even if the severing member 17 acts in proximity of the winding core A, to reduce the length of the fold-back of web material in the first turn of the log L, and at low speed, to ensure rapid severing of the web material also in the case of particularly elastic material.
In short, in this embodiment the severing member 17 is controlled by the motor 19 under the control of the control unit 21 in such a manner as to reverse its rotational movement around the axis B. In a first time interval the severing member 17 rotates counter-clockwise (in the figure) moving toward the end of the feed channel 9 of the cores, to perform severing of the web material, while in a second time interval it rotates in the opposite direction, i.e. clockwise (in the figure) to be withdrawn from inside the feed channel 9 of the winding cores and therefore avoid collision with the new winding core fed into the channel 9.
More in particular,
In
Upstream of the severing member 17 the web material N is slackened and starts to adhere to the new winding core A.
At this point the severing member 17 can reverse its movement and be withdrawn from the feed channel 9, as can be seen in
The severing member 17 remains in this position until the subsequent exchange cycle.
As observed previously with reference to the sequence of
In practice, in this embodiment the severing member 17 is therefore provided with a reciprocating movement, preferably but not necessarily a rotating reciprocating movement with reversal of direction when the severing member 17 is inside the channel 9 in front of the winding core, i.e. downstream of the new winding core and between the latter and the log L that is about to be unloaded from the winding cradle 1, 3, 5.
In this embodiment once again the core is prevented from colliding with the severing member 17 and moreover the fold-back of web material that is folded inside the log is very short, due to the fact that the line along which severing of the web material takes place is close to the new core A being inserted. Furthermore, in this case the angular position in which reversal of the alternate movement (of rotation in the example illustrated) of the severing member 17 takes place can also be programmed and modified. This allows the machine to be adjusted to compensate the wear of the pads 17A of the severing member 17, gradually moving back the point in which movement is reversed.
In other embodiments, not shown, the alternate movement of the severing member 17 is a linear movement, for example controlled through a rotary motor and a drive with threaded rod and nut, or by a linear motor.
A further improved embodiment of the rewinding machine illustrated in
In the embodiment shown in
When the severing member 17 is in the position illustrated in
In the embodiment of
It is understood that the drawing shows just one example, provided merely as a practical demonstration of the invention, which can vary in its forms and arrangements, without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| FI2010A000025 | Feb 2010 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IT11/00037 | 2/14/2011 | WO | 00 | 10/3/2012 |
