WO1998038382A1

WO1998038382A1 - Method and device in calender in threading of paper

Info

Publication number: WO1998038382A1
Application number: PCT/FI1998/000163
Authority: WO
Inventors: Hannu Hanhikoski
Original assignee: Valmet Corporation; Vuorimies, Timo
Priority date: 1997-02-28
Filing date: 1998-02-25
Publication date: 1998-09-03
Also published as: FI101634B; DE19882133T1; FI101634B1; AU6101598A; FI970854A0

Abstract

In the method for threading of paper in a calender a narrower tail (T) separated from a wide paper web is passed between superimposed calender rolls (1) of the calender. During threading, the nips (N) between the calender rolls (1) are kept open, and the tail (T) is guided through the nips (N) between the opposite mantle surfaces of the calender rolls (1) by blowing air in a direction parallel to the air guide surfaces (3) following the path of travel of the paper web. The tail (T) is sucked against the mantle of the take-out leader roll (2) located between the nips (N) by means of a suction zone (2b) inside the roll.

Description

Method and device in calender in threading of paper

The invention relates to a method in a calender in threading of paper which is presented in the preamble of the appended claim 1. The in- vention also relates to a device for implementing the threading, which is of the type according to the preamble of the appended claim 6.

The invention relates particularly to threading in connection with a calender having the supercalender type geometry, wherein the tail is passed between the calender rolls superimposed in a stack and through take-out leader rolls outside the stack.

In threading of paper web through calenders of this type, rope transfer systems are generally used, in which the tail is guided between threading ropes arranged at the ends of the rolls. At the same time, the tail has to be pulled aside from the primary path of the paper web.

The rope systems have known drawbacks, such as the space they require in the cross machine direction and the aforementioned pulling aside, which may be a problem with weak grades of paper. Until now, there has been no system, with which threading could be implemented through the stack of calender rolls without utilizing rope systems.

The object of the invention is to present a method and a device, whereby it is possible for the tail to be passed between mantle surfaces of the rolls in the stack of calender rolls without rope systems. To achieve this aim, the method according to the invention is primarily characterized in what is presented in the characterizing part of the appended claim 1. When a narrower tail cut from the paper web is threaded, the nips located on the path of travel of the paper web and between the opposite calender rolls are kept open so that the tail can be passed between their mantle surfaces, simultaneously utilizing air guide surfaces following the path of the paper web and air blow in connection with them, in addition to which the tail is guided in between the nips by means of suction effected through take-out leader rolls.

As for the preferred embodiments of the method, reference is made to the appended dependent claims 2-5 and to the description hereinbelow. The device for implementing the invention is, for its part, characterized in what will be presented in the characterizing part of the appended claim 6. The device comprises air guide surfaces, blow nozzles ar- ranged in connection with them, a suction area arranged inside the take-out leader roll, and means for moving the calender rolls apart from each other during their drive. The air guide surfaces of the device are structures separate from calender rolls and take-out leader rolls, and they can easily be e.g. pulled out from the calender after threading has been completed and a full-width paper web is run through the calender.

As for the preferred embodiments of the device reference is made to the appended dependent claims 7-10 and to the description hereinbelow.

In the following, the invention will be described in more detail with reference to the appended drawing, which presents in a side view a calender during threading.

The calender presented in the drawing is an on-machine calender, in which, according to principles known as such, a paper web running from a drying section in the direction of arrow A is calendered by leading it through nips N between the superimposed calender rolls 1 along a winding path. The paper web is first guided to the upper end of the stack of calender rolls into the nip N between the two uppermost rolls 1. Between two successive nips N, which are on the opposite sides of the same calender roll 1 , the paper web is passed through a take-out leader roll 2 adjacent to the said roll 1. The drawing presents a calender structure comprising four calender rolls 1 , three nips N, and correspondingly two take-out leader rolls 2, but it is obvious that the invention is applicable for use in all calenders of similar type, regardless of the number of calender rolls/nips/take-out leader rolls. As for the invention, the surface structure of the calender rolls 1 is also unimportant, and it can consist of materials generally known in the art.

After the last nip N at the lower end of the stack of calender rolls, the paper web runs onwards toward the reel-up (arrow B). The path of the tail T separated from the edge of the paper web before calendering and having typically a width of 15-50 cm is illustrated with a broken line in the drawing. This approximates the future path of the paper web -after the web has been cut into full width with a diagonal cutter.

To move the tail T between the mantle surfaces of the calender rolls 1 , the calender rolls are separated from each other, i.e. they are vertically moved in the calender frame with respect to each other. Thus the nips N are opened to form a few millimeters wide slots between the mantle surfaces of the calender rolls 1. When the rolls 1 are apart from each other, they can all be driven, as well as the take-out leader rolls 2 can be driven, i.e. rotated as shown by arrows. The speed of the rolls is thus preferably in accordance with the threading speed.

To guide the tail T from the drying section into the nip N between the two uppermost calender rolls 1 , an air guide surface 3 is arranged before the nip and directed approximately in parallel direction with the path of travel of the paper web toward the nip N, and as close to it as possible . In connection with the air guide surface a blow nozzle 3a is arranged, an extension to which is at least part of the air guide surface 3 as far as to the nip N. The blow nozzle can be a wide nozzle slot or it can be composed of a series of adjacent narrower nozzles, and common to all of these alternatives is, that the nozzle brings about a Coanda effect, wherein the thin, wide air jet discharged from the nozzle starts to follow the subsequent guide surface 3, and produces a reduced pressure air cushion, which, between the guide surface 3 and the tail T, directs the latter toward the nip N.

After the nip N, there is a second air guide surface 3 directed from the nip N approximately to the area on the mantle of the take-out leader roll 2 which is intended to receive the paper web running from the first calender nip. Functionally, this air guide surface 3 can be seen as an extension to the air guide surface before the nip N, and to stabilize the travel of the tail T after the nip, a separate blow nozzle 3a is also arranged in connection with this surface in order to bring about a corresponding effect. Inside the take-out leader roll 2 which guides the paper web between the two successive nips N, a suction zone 2a is arranged in a sector of suitable size. The sector is located on the side of the take-out leader roll ^'2 away from the adjacent calender roll 1 , in other words in the area, where the paper web is intented to wind around the mantle of the take-out leader roll 2 by changing its direction. The tail T travels by means of the suction against the mantle of the roll 2, past this area in which a turn of almost 180°, typically 160-170°, occurs in its travel. The suction is effective in the sector of the suction zone 2a on the mantle of the take-out leader roll at a suitable width through orifices made in the vicinity of its end in order to pull the tail T against the mantle.

The suction zone 2a ends at the point where the tail T is desired to dis- engage from the take-out leader roll 2. This point is located before the area of the roll in which the joint tangent of the take-out leader roll 2 and the adjacent calender roll 1 touches the take-out leader roll. In order to secure detachment and to guide the tail T further towards the next nip N, the suction zone is immediately followed by a pressure zone 2b which has the size of a certain sector, is arranged inside the roll and produces a blow through the aforementioned orifices extending through the mantle of the roll. The blow detaches the tail from the mantle of the roll. Primarily the tail T is directed toward the next nip N by means of the air guide surface 3 located after the suction zone 2b. The air guide surface is directed from the vicinity of the mantle of the take-out leader roll toward the nip N and starts from a similar air nozzle 3a, the function of which is already described above.

After the nip N following the take-out leader roll 2, the principles for guiding the tail T via the take-out leader roll 2 located on the other side of the stack of calender rolls are the same, in other words the location of the parts is symmetrical with respect to the vertical center line of the stack of calender rolls.

The last nip is followed by yet one air guide surface 3, to which, at a distance, opens up a blow nozzle 3a of the aforementioned type in order to direct the tail T further toward the reel-up. In some cases possibly only one blow point, i.e. blow nozzle 3a is required for leading through one open nip N, in this case advantageously one located before the nip N, especially if the air guide surface 3 after the nip N and the air guide surface 3 before the nip N are arrange^'d as so direct extensions to each other as possible, and they are brought as close to the nip as possible. To stabilize the travel, a blow nozzle 3 after the nip N is, however, advantageous. Similarly, it is feasible that inside the take-out leader roll 2, a pressure zone 2b is not necessary, if the air guide surface 3 after the suction zone 2a has enough capacity to carry along the tail T. Replacing the nozzles with mere air guide surfaces depends on the stiffness of the paper web and corresponding properties of the tail.

Further, it is apparent from the drawing how the travel of the tail T can be primarily mechanically secured by means of the guide surface 4 which is located opposite to the primary air guide surface 3, and which, together with the air guide surface 3, forms a narrow passage, along which the tail T travels. Thus, a possible displacement of the tail T can be prevented and the tail is guided to travel the desired path better. Similarly, external factors and air currents possibly interfering with the travel can be minimized. The first guide surface 4 is arranged before the first nip N, and, at the same time, the guide surface 4 following the nip constitutes a curved protective surface at the take-out leader roll 2 at the location of the suction zone 2a. This surface ends in the blow nozzle 3a, from which the primary air guide surface 3 begins, opposite of which is the guide surface 4 forming the passage between the takeout leader roll 2 and the calender roll 1. The corresponding structures are at the location of the next take-out leader roll 2 which is situated on the opposite side. After the last nip N, there is also a guide surface 4 opposite to the air guide surface 3 equipped with the blow nozzle 3a.

Structurally, the aforementioned guide surfaces can be implemented with laminar guide plates, located on one edge in cross machine direction and having a particular width, for example the width of the tail T or somewhat wider than that, i.e. in practice on the other side of the longitudinal center line of the machine, in that area in the transverse direction in which the threading takes place. The suction zones and pressure zones inside the take-out leader rolls 2 can, in the direction of the axis of the roll, correspondingly extend over a section of the machine width in the edge on the tail side. It is, however, possible to use the aforementioned structures and the nozzles connected with them, as well as the zones of the take-out leader roll in a wider area, wherein they would also function during diagonal cutting. Similarly, the operation can be applied to a full-width web, wherein all the threading means have the width of the whole web.

Guide plates or corresponding air guide surfaces and the nozzles con- nected with them can be placed in a stationary manner in connection with the calender, or they can be arranged movable with respect to it either to a longer distance from the web or, in the cross machine direction, completely outside the web. The plates and nozzles can thus be assembled also in the same structure which can be moved as a unit, wherein for example at the location of the take-out leader roll 2, at least the guide surface 4 located after the nip N and curvedly covering in its end the mantle of the take-out leader roll 2, the blow nozzle 3a and the following air guide surface 3 directed from the roll to the nip N can form such a structure, which in the drawing is marked with the ref- erence number 5.

The structures required by the guide surfaces 3,4 and the blow nozzles 3a can be arranged, for example, in the calender frame which supports the calender rolls 1 , in a suitable way to be movable between the threading position and the position located further from the rolls by means of normal actuator solutions, which bring about the transfer of the aforementioned structures to desired directions.

Even though in the drawing the blow nozzles 3a and the guide surfaces 3 are situated below the path of the tail T, they can also be located above the same, and thus the locations of the guide surfaces 3 and 4 can be reversed.

Inside the take-out leader rolls 2, a suction zone 2a and a pressure zone 2b can be arranged by means known as such, for example with the help of arrangements used in drying sections in connection with the wire guide rolls. Thus, through the end of each roll, two conduits are brought from the air blower, one of which, leading to the suction zone 2a, is connected to the suction side of the blower, and the other, leading to the pressure zone 2b, is connected to its pressure side. As stated above, the width of the suction and pressure zone can vary at the end of the roll, and, in a specific case, it can also extend over the full width f-the roll.

When the threading of the paper web is started, the mantles of the calender rolls 1 are separated from each other and the rolls are driven, the guiding means of the threading are transferred into working positions, and the guiding blows from the nozzles as well as the pressures in the suction and blow zones of the rolls are set on. After this, the tail is directed to the calender and threading is implemented as described above.

After the tail T has been passed through the entire calender and its travel is normal, the paper web is widened into a full web width by means of the diagonal cutter located before the calender, suctions and blows are set off, the guide surfaces 3 and 4 are transferred, if necessary, further away from nips N and the nips N are closed. The nips can be closed in an optimal order with respect to the travel of the paper web. The means for separating calender rolls 1 from each other and transferring them into connection with each other can be actuators typically used in calenders.

Claims

Claims:

1. Method in a calender in threading of paper, in which a narrower tail (T) separated from a wide paper web is passed between superimposed calender rolls (1) of the calender, characterized in that

the nips (N) between the calender rolls (1) are kept open, the tail (T) is guided through the nips (N) between the opposite mantle surfaces of the calender rolls (1) by blowing air in a direction parallel to the air guide surfaces (3) following the path of travel of the paper web, and the tail (T) is sucked against the mantle of the take-out leader roll (2) located between the nips (N), by means of a suction zone (2b) located inside the roll.

2. Method according to claim 1 , characterized in that the detachment of the tail (T) from the take-out leader roll (2) before the next nip (N) is ensured by means of an air blow out through the mantle of the roll at the point of detachment.

3. Method according to claim 1 or 2, characterized in that the tail (T) is guided with the help of an air guide surface (3) both before and after the nip (N).

4. Method according to claim 3, characterized in that air is blown in a direction parallel to the air guide surface (3) before the nip (N) and again after the nip.

5. Method according to any of the aforementioned claims, characterized in that before and/or after the nip (N) the tail (T) is guided along a passage between the air guide surface (3) and the opposite guide surface (4).

6. Device in a calender in threading of paper, in which the calender contains superimposed calender rolls (1), which compose nips (N) in between them, through which the paper web is intended to travel, characterized in that the device comprises means for separating the rolls (1) from each other so that the nips (N) between them are opened, air guide surfaces (3) following the path of travel of the paper web through the nips, the air guide surfaces being provided with blow nozzles (3a) to produce an air stream for guiding the tail (T), a suction zone (2a) arranged inside a take-out leader roll (2), which guides the travel of the paper web between the nips (N), and the orifices opening from the suction zone to the outer surface of the mantle of the take-out leader roll (2) for guiding the tail (T) at the location of the take-out leader roll (2).

7. Device according to claim 6, characterized in that the suction zone (2a) inside the take-out leader roll (2) is followed in the direction of travel of the paper web by a pressure zone (2b) in order to facilitate the detachment of the tail (T) with the help of a blow directed through the said orifices.

8. Device according to claim 6 or 7, characterized in that the blow nozzle (3a) is arranged in connection with the air guide surface (3) both before and after the nip (N) located between the calender rolls (1).

9. Device according to any of the claims 6 to 8, characterized in that it contains, opposite to the air guide surface (3), a guide surface (4) which forms a passage for carrying the tail (T).

10. Device according to claim 9, characterized in that after the nip (N) opposite to the air guide surface (3), a guide surface (4) is located, which continues at the location of the suction zone (2a) of the take-out leader roll (2) as a guide surface covering its mantle, after which follows a blow nozzle (3a) and an air guide surface (3) directed as its extension toward the next nip (N).