Rewinder for the production of logs of paper material.

DESCRIPTION

The present invention relates to a rewinding machine for the production of logs of paper material with a tubular core.

More specifically, the invention relates to guiding the tubular cores on which the paper material for the production of logs is wrapped.

It is known that the production of items such as toilet paper rolls, kitchen paper and the like, involves, preliminarily, the production of longer rolls, commonly called "logs", by winding one or more webs or "plies" of paper around a tubular core, typically made of cardboard, in a machine called a "rewinder". The logs are subsequently subjected to transversal cutting to obtain shorter rolls for sale.

EP1725485B1 discloses a rewinder comprising a plurality of winding rollers configured to sequentially wind a web material around the tubular cores gradually introduced into the machine, and a pair of motorized mandrels. The latter engage each core on opposite sides during the winding, transmitting a rotational motion to the same core during at least part of the winding cycle.

The main purpose of the present invention is to ensure a correct control of the movement of the tubular cores inside the rewinder without however slowing down the production of the latter.

This result has been achieved, in accordance with the present invention, by adopting the idea of making a machine having the characteristics indicated in claim 1. Other features of the present invention are the subject of the dependent claims.

Thanks to the present invention, it is possible to stabilize the rotation of the cores inside the rewinder, reducing their vibrations, ensuring a correct radial distribution of the winding during the production of the logs, and at the same time ensuring a production that takes into account the increasing market demand. Currently, in fact, the rewinders can also produce 60 logs per minute, so that the stabilization of the cores during the production of the logs is a need particularly felt by the producers of paper rolls who, on the one hand, must satisfy increasingly more stringent demands in terms of quantities produced to reduce the unit cost of the finished product and, on the other hand, they must provide a finished product of good quality.

These and further advantages and characteristics of the present invention will be better understood by every person skilled in the art thanks to the following description and the attached drawings, provided by way of example but not to be considered in a limiting sense, in which:

- Fig.l represents a schematic side view of a rewinder for the production of logs of paper material which can be equipped with a cores stabilization system in accordance with the present invention;

- Fig. 2 schematically represents a path followed by a core while a log is being formed and until a formed log is released;

- Fig.3 represents a schematic side view of two core stabilization operating units acting simultaneously;

- Figs.4A-4D schematically represent the operating groups of Fig.3 in different operating phases;

- Figs 5A-5D show four perspective views of a core stabilization unit which illustrate, in particular, a pin (4) and a possible embodiment of a mechanism for moving the pin;

- Fig.6 represents a schematic front view of the operating groups (Gl, G2), in which while a group (Gl) is in the waiting configuration before inserting the relative pins (4) in a core (A) on which a log must be formed, a second group (G2) is in the stabilization configuration of the core of a log (FL) being formed;

- Fig.7 represents a side view of two core stabilization operating groups according to a possible implementation of the invention;

- Fig.8 is similar to Fig.3 but refers to the use of three operative cores stabilization groups;

- Figs. 9 and 10 concern a possible implementation modality of the configuration represented in Fig. 8.

In Fig.1 a rewinder (1) according to the present invention is schematically represented. According to a per se known construction scheme, the rewinder (1) is fed with a web of paper material (W), consisting of a single ply or of more superimposed paper plies, guided by suitable rollers (2) along a predefined path along which a perforation unit (3) is also arranged which generates perforation lines on the web (W) for dividing the web into single separable sheets along the perforation lines. Downstream of the perforation unit (3) there is a winding station (10) in which more winding rollers (Rl, R2, R3) with horizontal axis are placed. The first roller (Rl) and the second roller (R2) define a nip crossed by the web (W) and the cores (A) on which the web (W) is intended to be wound. The third roller (R3) is mounted on a movable arm (B3) connected to a respective actuator (A3) which allows it to be moved to and from the first roller (Rl). The cores (A) typically are tubular cores with a circular cross section and are fed through a corresponding feed channel (CA). The channel (CA) partially develops below the first roller (Rl). The web (W) is guided on the first winding roll (Rl). The cores (A) are oriented parallel to the rollers of (Rl, R2, R3). In practice, according to a per se known functional scheme, the rotation of the rollers (Rl, R2, R3) determines the rotation of the cores (A) in the winding station (10) and, on each core (A) that reaches this station, is wound a predetermined quantity, or a predetermined number of sheets, of the web (W) forming a corresponding log (L). The logs (L) thus produced are then ejected along an output surface (11) and are intended to be cut transversely to be divided into shorter rolls of commercial format by means of further cutting-off machines (not illustrated in the attached drawings) arranged downstream of the rewinder.

A rewinder according to the present invention comprises stabilizing means for the cores (A) suitable for stabilizing the cores during the production of the logs, with a plurality of pins (4) which can be axially inserted into the cores located in the winding station (10).

The pins (4) remain inserted in the cores (A) until the ejection of the logs from the rewinder.

The pins (4) are arranged on both the right and left sides of the rewinder, so that each of them is inserted in a corresponding side (AL, AR) of the cores (A) to be stabilized. Preferably, each pin is inserted into the cores (A) for a length (L4) of at least 60 mm. More preferably, each pin is inserted into the cores (A) for a length comprised between 60 mm and 500 mm.

The pins (4) consist of rods or tubes with a circular cross section whose external diameter is less than the internal diameter of the cores (A). Preferably, the external diameter of the pins (4) is lower by a value between 0.5 mm and 3 mm than the nominal internal diameter of the cores (A).

Each pin (4) is mounted on a respective stabilization unit comprising a carriage (40), on which the pin is mounted, connected to an actuator (41) which moves the carriage itself bi-directionally along the longitudinal axis of the pin as schematically indicated by the arrows “F4” in the attached drawings.

When the pins (4) are inserted into the cores (A) on which the web (W) is wound while the cores rotate in the winding station (10) of the rewinder, the cores are stabilized, since the oscillations or vibrations to the cores are normally subjected in the course of winding cause are drastically reduced.

For example, each pin (4) is in two parts (4 A, 4B), with a rear part (4A) fixed to the carriage (40) and a front part (4B) constrained to rear part (4 A) by means of an axial pin (not visible in the drawings). Therefore, the front part (4B), which is inserted into the core (A), is free to rotate on itself, avoiding slowing down the rotation of the core in which it is inserted. The pin (4) can also be rotated at a predetermined speed, around its longitudinal axis, by means of a corresponding rotary actuator (for example a rotary actuator mounted on the carriage 40) acting on the pin which, in this case, can be realized as a single element rather than in two parts.

With reference to the scheme of Fig. 2, starting from the instant in which a core reaches the point (Pl) of the start of the formation of a log between the winding rollers at the instant in which the formed log is ejected, each core, while it rotates around its own longitudinal axis, follows the path (T) that starts from said point (Pl), continues linearly along a first direction (dl) up to a point (P2) in which the formation of the log is completed, after which it continues again along a second direction (d2) parallel to the output surface (11) up to a point (P3) of releasing of the formed log.

In accordance with the present invention, each pin (4) remains inserted in the respective core (A) along the entire path (T), from the point (Pl) where the winding begins to the point (P3) where the log is released.

Each carriage (40) is mounted on a box-like support (42) inside which the respective actuator (41) is housed. On the sliding side of the carriage (40), the support (42) has a guide (43) engaged by the carriage (40).

The support (42) is engaged by a respective robotic manipulator (5) with two arms (50, 51) articulated on joints (500, 510) with axes parallel to the pins (4). Each manipulator (5) has a base (53) on which a first arm (50) is articulated by means of a first joint (500), and a second arm (51) articulated on the first arm by a second joint (510). The arrows "P5" and "S5" represent the rotation of the first arm (50) on the axis of the first joint (500) and respectively the rotation of the second arm (51) on the axis of the second joint (510). The support (42) is integral with the second arm (51). The second joint (510) constitutes the rear side of the second arm (51) and is inserted in a tubular body (501) which forms the front end of the first arm (50). An opening (502) is formed on the lateral surface of the tubular body (501) which allows the passage and movement of the second arm (51). The first joint (500) is inserted in the base (53) which is tubular in shape and has an opening (504) similar to the opening (502) of the tubular body (501) to allow the passage and movement of the first arm (50). The reference (511) denotes an axial end of the second joint (510) on which a gearmotor (not visible in the drawings) that controls rotation “S5” is connected. Similarly, the reference (503) indicates an axial end of the first joint (500) on which another gearmotor is applied (not visible in the drawings) which controls the rotation “P5”.

Therefore, each robotic manipulator (5) can be controlled in order to move a respective pin (4), through the respective support (42), along the trajectory (T) followed by the core (A) in which the pin is inserted.

In accordance with the present invention, said core stabilization means comprise two independent operating groups (Gl, G2), each of which comprises, on each of the right and left sides of the rewinder, a stabilization unit with a robotic manipulator (5) which moves a respective support (42), and therefore a respective pin (4), along a trajectory coinciding with the path (T) followed by each core (A) between the starting point (Pl) of the winding and the point (P3 ) where the log formed on the same core is released. It goes without saying that said operational groups (Gl, G2), although independent, act in a coordinated manner. It goes without saying, moreover, that the individual stabilization units of the individual groups (Gl, G2) are synchronized with each other. Since the operating groups (Gl, G2) are independent from each other, each of them can be in a position of waiting for a core (A) for the formation of a new log while the other engages a core on which another log is being formed. Therefore, it is not necessary to wait for the release of a log to stabilize a core on which another log will be formed. Consequently, a high production of logs can be ensured while maintaining a stabilization condition until each log is released.

With reference to the example of construction shown in the attached drawings, said stabilization units are four in number, with two stabilization units for each of said operating groups (Gl, G2). In practice, each core stabilization operating group comprises two stabilization units, one on the right side and one on the left side of the rewinder.

Figures 4A-4D schematically represent a possible operating cycle according to a side view of the right side of the winding station (10) of the rewinder. On the left side of the winding station (10) the stabilizing operating groups (Gl, G2) act in the same way. In Fig.4A the group (Gl) is with the respective pins inserted in a core on which a log (FL) is being formed between the winding rollers (Rl, R2, R3) while the group (G2) is with the respective pins inserted in a core on which a log (L) has already been formed. In this phase, the group (G2) accompanies the log (L) already formed along the exit surface (11) to the point of release of the log, where the pins of the group (G2) will be extracted from the respective core. In Fig.4B the group (G2) has released the log (L) already formed and has been placed in the position of engagement of a new core, that is, it is ready to engage a core on which another log will subsequently be formed. In the meantime, the group (Gl) is accompanying the log (FL) in formation along its growth trajectory (path comprised between the points Pl and P2 previously mentioned). In Fig.4C, while the group (G2) is waiting as in Fig.4B, the group (Gl) is engaging the core of the respective log which is now finished having reached its maximum diameter. In Fig.4D the group (G2) engages a core which subsequently has reached the winding rollers (Rl, R2, R3) while the group (Gl) accompanies the respective finished log (L) up to the release point, in which the pins of the group (Gl) will be extracted from the respective core.

Figs. 4A-4D show the relative positions of the arms (50, 51) of each group (Gl, G2) in various configurations assumed by the same groups during the formation and subsequent release of the logs.

In the diagram of Fig.3 it can be appreciated that, to avoid interference, the core stabilization operating units (Gl, G2) can be arranged at different heights with respect to the base (B) of the rewinder and can be arranged substantially counter-facing.

The use of several core stabilization operating groups acting in a coordinated but independent manner for the stabilization of the cores (A) allows to increase the winding speed of the paper on the cores in the winding station (10), and therefore to increase the production of the logs, without compromising the quality of the finished product.

At the release point (P3) a stop of the log (L) can be foreseen before the disengagement of the pins from the respective core. In this case, the operating groups (Gl, G2) stop at the release point (P3) for a predetermined time, after which the pins are brought out of the log that has reached this position. The stop made before the release determines a lower speed of the log in the post-release and exit phase from the rewinder. Alternatively, again in order to ensure a lower log output speed after release, the operating groups (Gl, G2) can be controlled in such a way that, after the completion of the logs (L), the arms (51) first move faster to free the winding rollers and then more slowly to the release point (P3). After the release of the log, logs braking means, known per se, able to reduce the rotation speed of the log, can intervene.

The core stabilization operating groups can more than two in number. For example, as schematically shown in Fig.9 and Fig.10, three independent core stabilization operating groups (Gl, G2, G3) can be arranged. In the representation of Fig. 9, while the operating group (Gl) stabilizes a core at the point (P2), the group (G3) is engaging another core at the point (P3) and the group (G2) is waiting for engaging a new core at point (Pl). Fig. 10 also shows the rollers (Rl, R2, R3) of the winding station, a log being formed between the rollers (R2, R3) and a log in the exit phase. For example, both on the right side and on the left side of the rewinder, the base (53) of each manipulator (5) can be mounted on the side of a vertical disk (D) rotating, as schematically indicated by the arrow “FD” in Fig. 9, around the respective central axis (AD) which is horizontal, i.e. parallel to the axis of the winding rollers (Rl, R2, R3). The bases (53) of the manipulators (5) are angularly equidistant from each other and, since they are fixed to the disc (D), their distance does not vary during the rotation of the latter. The rotation (FD) of the disc (D) is continuous and is controlled by a corresponding actuator (MD). For example, the latter is an electric motor or a gearmotor on whose output shaft a toothed wheel (RD) is mounted which engages a corresponding toothing formed on the outer edge (ED) of the disc (D). Each manipulator (D) is structured as previously described. In this case, however, the base (53) of each of them follows a circular trajectory (TD) during the production of the logs. In practice, in this example, during the production of the logs the manipulators (5), that is the core stabilization units, exchange their positions moving continuously on a circular trajectory.

From the description provided above, it results that a rewinder according to the present invention is a rewinder comprising:

- a winding station (10) in which winding rollers (Rl, R2, R3) are arranged between which tubular cores (A) are sequentially fed to form logs by winding a ribbon of paper material (W) around each one of said cores (A) while the cores (A) rotate with predetermined angular speed and follow a first path (dl) comprised between a first point (Pl) where the winding begins and a second point (P2) in which the winding ends;

- a second path (d2) of the logs (L) comprised between said second point (P2) and a third point (P3) in which the logs (L) are released; - means for stabilizing the cores (A) comprising members which can be inserted into the cores during their rotation in the winding station (10);

- a right side and a left side between which the said winding station (10) is arranged; wherein

- said cores (A) stabilization means comprise a plurality of independent stabilization units (Gl, G2, G3) adapted for simultaneously stabilizing a plurality of cores (A);

- each stabilization unit (Gl, G2, G3) comprises, on both the right and left sides of the rewinder, a pin (4) which can be axially inserted into the cores (A), and is configured and controlled to insert the pin (4) in a core (A) in said first point (Pl) and extract it from the core in said third point (P3).

From the description provided above, it also results that a rewinder according to the present invention may comprise one or more of the following features possibly combined with each other:

- each pin (4) is mounted on a respective stabilization unit comprising a carriage (40), on which the pin is mounted, enslaved to an actuator (41) which moves the carriage itself bi-directionally parallel to the longitudinal axis of the pin (4) or along this axis, and the carriage (40) and the actuator (41) are integral with a support (42) connected to respective handling means (5) controlled and configured for moving the support (42) with movements which bring the pin (4) along said first and second paths (dl, d2).

- said handling means (5) consist of robotic manipulators.

- in said third point (P3) the operating units (Gl, G2, G3) cause the pins (4) to stop before they are extracted from the cores (A).

- operating groups (Gl, G2, G3) control the translation speed of the pins (4) along the second path (d2) before extracting the pins (4) from the cores (A).

- the pins (4) consist of rods free to rotate around their respective longitudinal axes.

- the core stabilization operating units (Gl, G2, G3) (A) are controlled such that each of them can be put in a waiting position for a core (A) for the formation of a new log while another operating unit engages a core on which another log is being formed.

- the pins (4) are inserted in the cores (A) for a length (L4) comprised between 60 mm and 500 mm.

- said core stabilization units are two or three in number.

- said core stabilization units are connected to handling means which move them along a circular path (TD). In practice, the details of execution may in any case vary as regards the individual elements described and illustrated, without thereby departing from the scope of the idea of the solution adopted and therefore remaining within the limits of the protection granted by this patent in accordance with the following claims.