Unwinding station The invention relates to a method for unwinding a material web, in particular a paper or board web, with optional positioning of the material web for a sub- sequent machine unit for processing the material web, having an unwinding station which comprises a primary unwinding device with a wound reel drive, at least one secondary unwinding device and a gluing and separating device, wherein the wound reel is first unwound in the primary unwinding device and after its transfer is further unwound in a secondary unwinding device and, during a roll change, a new wound reel is inserted into the primary unwinding device and the gluing and separating device connects the material web of the secondary unwinding device to the material web of the new wound reel and severs the material web running from the secondary unwinding device to the splicing point.
Unwinding stations of the type addressed here are known.
They are used for the continuous unwinding of a material web from a wound reel and are ar- ranged upstream of a machine for processing the material web, for example a coating machine or a calender.
WO-A1-2009/135805 describes a method for unwinding a material web.
A known unwinding station comprises a primary and a secondary unwinding device, which are used to guide a wound reel.
A full wound reel is initially guided by the primary unwinding device as the material web is unwound.
Be- ginning at a desired diameter of the wound reel, the latter is transferred from the primary to the secondary unwinding device.
For this purpose, for example, use is made of pivoting arms that can be pivoted about an axis, which act on the wound reel on both sides and transfer it to the secondary unwinding device by means of a pivoting movement.
Furthermore, an additional, pivotable auxiliary drive is provided, which drives the wound reel during this transfer.
A new, full wound reel is then fed to the primary unwinding device and the material web wound on the same is connected to the material web running off the wound reel carried by the secondary unwinding device, before the material web has been completely unwound.
Provided for this purpose is a gluing de- vice, which often has a gluing roll that can be pivoted about an axis and via which the material web running off the wound reel carried by the secondary unwinding device is guided to the following material web processing machine — as seen in the running direction of the material web.
To connect the two material webs to each other, the gluing roll is pivoted and pressed against the wound reel carried by the primary unwinding device.
At the same time, the material web running off the wound reel carried by the secondary unwinding device is severed by means of a cutting device.
Here, it is normally necessary to consider that the top side of the material web located on the wound reel can optionally point upwards or downwards as it is fed to the following machine unit.
Accordingly, there is a secondary unwinding device in each case on both sides of the primary unwinding device, which is relatively complicated.
Added to this is the fact that the new, full wound reel has to be transported over a sec- ondary unwinding device to the primary unwinding device.
This is problem- atic, simply as a result of the high weight of the full wound reel.
The object of the invention is, therefore, to reduce the outlay for the optional position of the material web during the unwinding.
According to the invention, the object has been achieved in that the single secondary unwinding device is arranged between the primary unwinding de- vice and the following machine unit, and, to change the position of the mate-
rial web (1) to be unwound, the primary unwinding device (3) is driven in a direction of rotation corresponding to the position, and, in the case of an in- tended unwinding of the new wound reel with the web top side pointing downwards, the splice between the material webs is carried out when the new wound reel of the primary unwinding device is at a standstill or when the new wound reel of the primary unwinding device has a rotational speed of between 0 and 4 m/s.
Here, to change the position of the material web to be unwound, the primary unwinding device is driven in a direction of rotation corresponding to the po- sition.
This means that the connection of the web end of the secondary un- winding device to the full wound reel of the primary unwinding device is car-
ried out independently of the current or intended direction of rotation of the primary unwinding device.
Irrespective of the web running direction of the material webs to be connected, it is advantageous for a safe roll change if the connection between the material webs is carried out when the new wound reel of the primary unwinding device is at a standstill or when the new wound reel of the primary unwinding device has a rotational speed of between 0 and 4 m/s, preferably between 0 and 1 m/s.
If, at the splicing point, the web running direction of the material web coming from the secondary unwinding device is opposite to the current web running direction of the full wound reel of the primary unwinding device, i.e. it is intended to unwind the new wound reel with the web top side pointing down- wards, then this leads to a drop in the web tension.
Therefore, if it is intended to unwind the new wound reel with the web top side pointing downwards, a web tensioning method should be initiated.
Since the secondary unwinding device is always located between the primary un- winding device and the following machine for processing the material web, the unwinding of the new wound reel in such a way that the top side in the wound reel subsequently points downwards leads to the aforementioned op- posite direction as it is connected to the web end of the secondary unwinding device.
The drop in the web tension is intended to be prevented or at least limited with regard to time period and/or intensity by the web tensioning method.
To increase the web tension, a web tensioning device in the form of a tension- ing roll can be pressed into the run of the material web after the primary un- winding device and/or a web tensioning device in the form of a blower ele- ment can direct blown air into the run of the material web.
Irrespective of or in addition to this, it is likewise advantageous if the wound reel of the primary unwinding device is briefly driven in the opposite direction to increase the web tension.
To complete the transfer, after the material web has been severed, a drive of
— the secondary unwinding device can drive the wound reel counter to the un- winding direction in order to wind up the web end remaining there.
With respect to the unwinding station, it is important that the single secondary unwinding device is arranged between the primary unwinding device and the machine unit following in the web running direction, and the primary unwind-
ing device for changing the position of the material web to be unwound can be driven in a direction of rotation corresponding to the position.
To assist the unwinding, the secondary unwinding station should also have a drive here.
The production of a connection between the material webs is additionally
— made easier if the primary unwinding device is fixed and the secondary un- winding device is mounted such that it can be displaced towards the primary unwinding device for the purpose of taking over a wound reel.
In cases with a loss of web tension, in particular when the top side of the material web is pointing downwards, it is advantageous if the material web is assigned at least one web tensioning device after the primary unwinding de- vice.
This web tensioning device should preferably be designed as a blowing ele- ment, in particular as a blower box or blower pipe and/or as a tensioning roll. 5 Particular advantages result if the following machine unit is a smoothing de- vice or a coating machine or in particular is a roll cutting machine.
The invention is to be explained in more detail below with reference to an exemplary embodiment.
In the appended drawing, Figures 1 to 6 show a sche-
matic side view of the unwinding station and the progress of the unwinding.
The unwinding station described below can be used in particular in conjunc- tion with a roll cutting machine or the like as a following machine unit 2.
In the unwinding station, material webs 1 wound onto drums to form wound reels 7 are connected to each other, that is to say made endless, so that con- tinuous processing operation is possible in a roll cutting machine arranged downstream of the unwinding station — viewed in the running direction 9 of the material web 1.
To this end, the unwinding station has a primary unwinding device 3 with a wound reel drive, only one secondary unwinding device 4 with a wound reel drive and a gluing and separating device 5. The working position of the sec- ondary unwinding device 4 is located between the primary unwinding device
3 and the machine unit 2 following in the web running direction 9, i.e. the roll cutting machine.
As can be seen in Figure 1, the unwinding begins in the primary unwinding device 3, to which the full wound reel 7 is fed.
Here, a wound reel 7, which can have a diameter of 3500 mm and more, for example, is wound on the drum.
The primary unwinding device 3 and the secondary unwinding device 5 are connected to each other via a guide device, which comprises two running rails 8 running parallel to each other and horizontally.
While the primary unwinding device 3 is advantageously fixed in the web running direction, the secondary unwinding device 4, together with its drive, is mounted such that it can be displaced along the guide device from its work- ing position to the primary unwinding device 3 and back again for the purpose of taking over the already predominantly unwound wound reel 7.
The drums, provided with bearing journals at their ends, are each mounted in a receiving fork of the secondary unwinding device 4. Figure 2 shows the unwinding station after the wound reel 7 has been taken
— over by the secondary unwinding station 4, and Figure 3 shows the unwinding station after a new, full wound reel 7 has been subsequently taken over by the primary unwinding station 3. The fully wound reel 7 can be transported to the primary unwinding device 3 without having to overcome an otherwise usual secondary unwinding device 4.
The direction of rotation of the wound reel 7 in the primary 3 and therefore also in the secondary unwinding device 4 can be chosen such that the top side of the material web 1 points downwards or upwards as it is fed to the following machine unit 2. Here, the top side of the material web 1 always relates to the wound reel 7. The position of the material web 1 in the following machine unit 2 is important in particular when the two web sides have different material properties and the position of the side during the further processing, in partic- ular in the following machine unit 2, is of importance.
As distinct from known solutions, this is made possible here with only one secondary unwinding device 4, which considerably reduces the outlay.
If the following machine unit 2, as illustrated in the figures, is located on the left of the secondary unwinding device 4, then unwinding in the clockwise direction (illustrated dashed) leads to the top side of the material web 1 point- ing downwards as it reaches the following machine unit 2. During unwinding in the anticlockwise direction, the top side of the material web 1 points up- wards.
The diameter of the wound reel 7 and therefore the extent of the unwinding is detected by a distance sensor.
When the unwinding and therefore the diameter of the wound reel 7 reaches a predefined value, according to Figure 3, then, as can be seen in Figure 4, the material web 1 coming from the secondary unwinding device 4 is connected with the material web 1 of the new, full wound reel 7 of the primary unwinding device 3 and glued via the gluing and separating device 5. Furthermore, the gluing and separating device 5 severs the material web 1 coming from the secondary unwinding device 4 before the splicing point.
To wind in the overhanging paper tail following the separation of the outgoing web end, the drive of the secondary unwinding device 4 then drives the wound reel 7 briefly counter to the unwinding direction.
The gluing and separating device 5, which is known and is responsible for connecting the web ends, is located underneath the primary unwinding device 3 and can be adjusted for the purpose of adaptation to changing diameters of full wound reels 8. The gluing and separating device 5 of the unwinding station comprises a glu- ing carriage, which holds the gluing roll.
A cutting device, which has a knock-off knife preferably provided with serra- tions, is also attached to the gluing carriage.
Figure 5 shows the case in which the current or intended unwinding direction of the new, full wound reel 7 at the splicing point coincides with the running direction of the material web 1 running off the secondary unwinding device
4. Since problems with regard to the web tension do not have to be expected here, the connection between the material webs can be carried out when the new wound reel 7 of the primary unwinding device 3 has a rotational speed of between 0 and 4 m/s. If it is intended to unwind the new wound reel 7 with the web top side pointing downwards, however, a drop in the web tension is to be expected. Therefore, a web tensioning method should be initiated, as indicated in Figure 6. Thus, to increase the web tension, it is possible to drive the wound reel 7 of the primary unwinding device 3 briefly in the opposite direction. However, alternatively or additionally, according to Figure 6, a web tension- ing device 6 can also be activated. The web tensioning device 6 is located between the new wound reel 7 of the primary unwinding device 3 and a de- flection roll 10 following in the web running direction 9. In particular, a tensioning roll can be pressed into the run of the material web 1 asa web tensioning device 6 and/or a blowing element can direct blown air into the run of the material web 1. In order to minimise the web tension problems, in particular when the web top side is pointing downwards, the connection between the material webs 1 should be carried out when the new wound reel 7 is at a standstill or when the new wound reel 7 of the primary unwinding device 3 has a rotational speed of between 0 and 1 m/s. To simplify the transfer of the already predominantly unwound wound reel 7 to the secondary unwinding device 4, the two wound reel drives are arranged on different sides of the machine. In practical terms, the larger drive of the primary unwinding device 3 for the full wound reel 7 is located on the machine side, and the smaller drive for the predominantly unwound wound reel 7 of the secondary unwinding device 4 is arranged on the side of the machine that is accessible to the operator.
It is important here that, following the transfer, the drive of the secondary unwinding device 4 remains coupled with the wound reel 7 until the end of the unwinding, i.e. the unwinding station manages with two drives.
In addi-
tion, the larger drive of the primary unwinding device 3 is fixed and only the smaller drive is displaceable, which simplifies the construction.
During the entire process, the web draw is controlled, which counteracts wind-
ing defects.