METHOD AND DEVICE IN THREADING OF A PAPER WEB

Abstract: The invention concerns a method in threading of a paper web from the dryer section to a following finishing device by means of a rope threading arrangement. In the method, in the dryer section (11), a leader strip is separated from the edge of the paper web (W), said leader strip is guided to between the ropes (K1, K2) included in the rope threading arrangement, and the leader strip is carried to the finishing device (10) on support of the ropes (K1, K2). At the inlet side of the last drying cylinder (2a) in the dryer section (11), a rope gap (KK) is formed out of the ropes (K1, K2), and the leader strip, which is supported by the drying wire (5), is transferred by means of air blowing into said rope gap (KK). The leader strip is passed by means of said ropes (K1, K2) over the last drying cylinder (2a) to the finishing device (10). The invention also concerns a device intended for carrying out the method.

Description: Method and device in threading of a paper web The invention concerns a method in threading of a paper web from the dryer section to a following finishing device by means of a rope threading arrangement, in which method, in the dryer section, a leader strip is separated from the edge of the paper web, said leader strip is guided to between the ropes included in the rope threading arrangement, and the leader strip is carried to the finishing device on support of the ropes. Further, the invention concerns a device for carrying out the method in threading of a paper web from the dryer section to a following finishing device, which device comprises a rope threading arrangement extending from the dryer section through the finishing device, in which arrangement the ropes run as a common loop. In the threading of a paper web, for example, from a forward dryer section through a film size press to an after-dryer section, in the present solutions and concepts applied by the applicant, a so-called Tail Shooter device is used, by whose means the leader strip of the paper web is shot into a rope gap. Thus, the strip runs as accompanied and supported by ropes through the film size press into the after-dryer section. Said solution is, however, not fully free from problems in all of its applica¬ tions. The most essential problems are encountered mainly in passing the leader strip to the ropes. The threading by means of ropes is in itself quite free from problems and easy to carry out. Problems arise, for example, from the rather short gap between the drying cylinder and the rope gap, in which gap the leader strip must be shifted to a relatively large extent in the lateral direction. Nor does the above Tail Shooter device, which is based on the air blow technique, shoot the leader strip in an invariable direction, but the path of the strip is often varied quite substantially when the properties of the strip vary. These properties that affect the path of the strip include weight, width, moisture, etc. Thus, the Tail Shooter device cannot be adjusted to operate optimally in all operating conditions, which vary from machine to machine. The leader strip also often remains a slack "strip bag" between the forward dryer section and the film size press, in which case, during the time of tightening of the strip, manual control from outside is needed. The object of the present invention is to provide a novel and improved method and device in threading of a paper web, by means of which threading arrangement in accordance with the invention, among other things, the above drawbacks related to the prior art are avoided. In view of achieving these objectives of the invention, which will be described in more detail in the following, the method in accordance with the invention is mainly characterized in that, at the inlet side of the last drying cylinder in the dryer section, a rope gap is formed out of the ropes, the leader strip, which is supported by the drying wire, is transferred by means of air blowing into said rope gap, and the leader strip is passed by means of said ropes over the last drying cylinder to the finishing device. On the other hand, the device in accordance with the invention is mainly character¬ ized in that, out of the ropes, at the inlet side of the last drying cylinder in the dryer section, a rope gap has been formed, into which the leader strip supported by the drying wire is fitted to be transferred by means of air blowing, the leader strip passing on support of the ropes over the last drying cylinder to the finishing device. By means of the invention, a number of significant advantages are obtained over the prior art, and of these advantages, for example, the following can be stated. In the threading arrangement in accordance with the invention, no slack strip bag is formed between the last drying cylinder in the forward dryer section and the film size press. The difference in draw between the forward dryer section and the after-dryer section can be regulated readily. In the threading arrangement in accordance with the invention, a fully supported draw of the leader strip is obtained between the forward dryer section and the after-dryer section. The operation of the transfer blowing is not sensitive to variations in the properties of the leader strip, nor is the run of the wide web placed at the side of the strip disturbed by the effect of the transfer blowing. Besides in a size press, the threading in accordance with the invention can also be applied in connection with other finishing devices. The invention is particularly usable in threading through a calender, in particular through a soft calender or an equivalent device, which is not followed by an after-dryer section. The result of all of these advantages is threading that operates considerably more reliably than in the prior art. The further advantages and characteristic features of the invention will come out in the following detailed description of the invention. In the following, the invention will be described by way of example with reference to the figures in the accompanying drawing. Figure 1 is a schematic overall illustration of the threading arrangement in accord¬ ance with the invention through a film size press from a forward dryer section to an after-dryer section. Figures 2A, 2B and 2C are more detailed illustrations of the threading arrangement, so that Fig. 2 A is a more detailed illustration corresponding to Fig. 1 of the thread¬ ing area itself, Fig. 2B shows the threading area viewed in the direction of the arrow B in Fig. 2 A, and Fig. 2C is a partial sectional view taken along the line C-C in Fig. 2A. Figure 2D shows a solution alternative to the embodiment shown in Fig. 2C. In Fig. 1 the film size press is denoted generally with the reference numeral 10. In Fig. 1 , the film size press 10 is illustrated fully schematically, but, in the normal way, it comprises size press rolls 10 j and 10 2 , which form a size press nip N between them. In Fig. 1, the forward dryer section is denoted generally with the reference numeral 11 , and similarly the after-dryer section is denoted generally with the reference numeral 12. The dryer sections 11,12 consist of drying cylinders and suction rolls, which have been arranged alternatingiy in accordance with a certain pattern, for example the arrangement shown in Fig. 1 , and over which the paper web W runs meandering. In the after-dryer section 12, said drying cylinders and suction rolls have not been illustrated in more detail, but in the forward dryer section 11 the drying cylinders are denoted with the reference numeral 2 and the suction rolls with the reference numerals 3 and 4. In Fig. 1 , the forward dryer section is a dryer section provided with single- wire draw, wherein the drying wire is denoted with the reference numeral 5. Thus, during operation of the machine, the paper web W runs in the forward dryer section 11 on support of the drying wire 5, and from the forward dryer section 11 the web W is passed through the nip N of the film size press 10 and further into the after-dryer section 12. During threading of the web, a cutter 1 placed in the forward dryer section 11 cuts an edge strip from the web W, which strip runs over the drying cylinders 2 and the suction rolls 3,4 on support of the drying wire 5. The transfer of the edge strip, i.e. of the leader strip, from the forward dryer section 11 into the nip N of the film size press 10 and from it further into the after-dryer section 12 is carried out by means of a rope threading. The rope threading arrangement consists of two ropes K j and K 2 , which run as a common loop from the forward dryer section 11 through the nip N in the film size press 10 into the after-dryer section 12. Even if it is not shown in detail in Fig. 1, the after-dryer section 12 can be provided with ropes of its own. In such a case, the transfer of the leader strip from the ropes K j ,K 2 passing through the nip N in the film size press 10 to the ropes of the after-dryer section 12 might be carried out, for example, in Fig. 1, in the area of the first lower cylinder of the after-dryer section. The leader strip 7 (FIG. 2B) is already transferred to the ropes K j ,K 2 by means of air blowing before the last drying cylinder in the forward dryer section 11, which cylinder is denoted with the reference numeral 2a in Fig. 1. The transfer to the ropes has been arranged so that, as is shown in Figs. 1 and 2A, at the inlet side of the last drying cylinder 2a of the forward dryer section 11 , a rope gap KK has been formed, into which the leader strip 7 is transferred by means of air blowing. As was described above, the ropes K j ,K 2 run from the forward dryer section 11 to the after-dryer section 12 as a common loop, in which case the rope gap KK is formed before the last dryer cylinder 2a by means of a rope pulley 6, which separates the ropes K j ,K 2 from one another. Since the leader strip 7 is still supported by the drying wire 5 at said point, it can be transferred sideways into the rope gap KK easily and in a controlled way by means of air blowing. In the area of the rope gap KK, a blow nozzle 8 has been arranged, out of which an air blowing is directed at the rope gap KK as inclined outwards from the web W in the way shown in Figs. 2 A and 2B, so that the air blowing grasps the leader strip 7 before the rope gap and shifts the strip under control into the rope gap KK. As is shown in Figs. 2 A and 2C, the last drying cylinder 2a in the forward dryer section 11 is provided with a separately journalled rope-groove ring 9 or equivalent, over which the ropes K j ,K 2 pass. Such a rope-groove ring 9, which is journalled on the drying cylinder 2a separately by means of a bearing 9a, is necessary because it is possible to produce a difference in speed between the forward dryer section 11 and the film size press 10 so as to tighten the leader strip 7. This possibility of tightening is essential in order that no slack strip bag should be formed between the last drying cylinder 2a in the forward dryer section 11 and the film size press 10. Owing to the separate joumalling, the ropes K l 5 K 2 can be set at a crawling speed when they are not needed for tail threading. Similar separately journalled rope- groove rings may also be fitted in connection with the rolls 10ι ,10 2 of the film size press 10 in order to produce a crawling speed. However, fitting of separately journalled rope-groove rings 9 in connection with the paper guide rolls P: is even more important than fitting of said rings in connection with the rolls 10 j ,10- > of the film size press. In Fig. 2D it is shown schematically that the separately journalled rope-groove ring 9 can be substituted for by a separate rope pulley 19. Such a separate rope pulley is preferable, because it can be journalled by means of a separate bearing 19a directly on the shaft 2a' of the cylinder 2a, or on the shaft of a roll, respectively. In such a case, the size of the bearing 19a is also substantially smaller and, therefore, the bearing is also substantially less expensive. As a summary of the above, it can be considered to be an essential feature of the invention that the transfer of the leader strip to the ropes is already carried out before the last drying cylinder 2a. Hereby the significant advantage is obtained that, at the point of transfer to the ropes, the leader strip is supported by the drying wire, for which reason it can be shifted sideways into the rope gap easily and in a controlled way. Above, the invention has been described by way of example with reference to the figures in the accompanying drawing. The invention is, however, not confined to the exemplifying embodiments illustrated in the figures in the drawing alone, which embodiments concern threading through a size press, but different embodiments of the invention may show variation within the scope of the inventive idea defined in the accompanying patent claims. It can be considered to be an advantageous embodi¬ ment of the invention that the threading in accordance with the invention by means of ropes is highly usable also when a leader strip is threaded through a soft calender or through an equivalent device which is not followed by an after-dryer section.

Claims: Claims 1. A method in threading of a paper web from the dryer section to a following finishing device by means of a rope threading arrangement, in which method, in the dryer section (11), a leader strip (7) is separated from the edge of the paper web (W), said leader strip (7) is guided to between the ropes (K-,,K 2 ) included in the rope threading arrangement, and the leader strip (7) is carried to the finishing device (10) on support of the ropes (Kι ,K 2 ), characterized in that, at the inlet side of the last drying cylinder (2a) in the dryer section (11), a rope gap (KK) is formed out of the ropes (K j ,K 2 ), the leader strip (7), which is supported by the drying wire (5), is transferred by means of air blowing (8) into said rope gap (KK), and the leader strip (7) is passed by means of said ropes (K, ,K 2 ) over the last drying cylinder (2a) to the finishing device (10). 2. A method as claimed in claim 1, characterized in that the blowing of air (8) is directed towards the rope gap (KK) as inclined outwards from the web so that the blowing grasps the leader strip (7) substantially before the rope gap (KK) and transfers it under control sideways into the rope gap (KK). 3. A method as claimed in claim 1 or 2, characterized in that, in threading, the leader strip (7) is tightened by means of the ropes (K j ,K 2 ) by subjecting the leader strip (7) to a difference in speed between the last drying cylinder (2a) in the dryer section (11) and the finishing device (10). 4. A method as claimed in any of the preceding claims, characterized in that after the tail threading the rope threading arrangement is set to a crawling speed. 5. A method as claimed in any of the preceding claims, characterized in that, in the method, the finishing device is a film size press (10) or equivalent, in which case the leader strip (7) of the paper web (W) is carried on support of the ropes (K j ,K 2 ) from the forward dryer section (11) of the film size press (10) through the film size press (10) into the after-dryer section (12). 6. A method as claimed in any of the claims 1 to 4, characterized in that, in the method, the finishing device is a calender or equivalent, in which case the leader strip (7) is carried from the dryer section (11) by means of the ropes (K j ,K 2 ) through said calender or equivalent. 7. A device for carrying out the method as claimed in any of the preceding claims in threading of a paper web from the dryer section (11) to a following finishing device, which device comprises a rope threading arrangement extending from the dryer section (11) through the finishing device (10), in which arrangement the ropes (K j ,K 2 ) run as a common loop, characterized in that, out of the ropes (K j ,K 2 ), at the inlet side of the last drying cylinder (2a) in the dryer section (11), a rope gap (KK) has been formed, into which the leader strip (7) supported by the drying wire (5) is fitted to be transferred by means of air blowing (8), the leader strip (7) passing on support of the ropes (K- = ,K 2 ) over the last drying cylinder (2a) to the finishing device (10). 8. A device as claimed in claim 7, characterized in that the blow nozzle (8) that produces the air blowing is directed as inclined outwards from the web so that the blowing of air shifts the leader strip sideways into the rope gap (KK). 9. A device as claimed in claim 7 or 8, characterized in that, in order to tighten the leader strip (7) and to produce a difference in speed in the leader strip (7) between the last drying cylinder (2a) in the dryer section (11) and the finishing device (10), the last drying cylinder is provided with a separately journalled rope- groove ring (9), with a separate rope pulley (19), or equivalent. 10. A device as claimed in any of the claims 7 to 9, characterized in that after the threading the rope threading arrangement is set to a crawling speed. 11. A device as claimed in any of the claims 7 to 10, characterized in that the finishing device is a film size press (10) or equivalent, in which case the ropes (K j ,K 2 ) of the rope threading arrangement pass from the forward dryer section (11) of said film size press (10) to the after-dryer section (12) through the film size press (10) while supporting the leader strip (7) between the dryer sections (11 ,12). 12. A device as claimed in any of the claims 7 to 10, characterized in that the finishing device is a calender or equivalent, in which case the rope threading arrangement extends from the dryer section (11) through said calender or equivalent.

Inventors: ILVESPAEAE HEIKKI, KUHASALO ANTTI, ILVESPAEAE, HEIKKI, KUHASALO, ANTTI
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1996
Main classification: D21F7
IPC codes: D21G9