The invention concerns a splicing device for a continuous unwind stand, by means of which device the new machine reel brought to the unwind stand is connected at full speed with the web of the machine reel that is being emptied, which splicing device comprises a splicing roll, by whose means the web of the machine reel that is being emptied is pressed into contact with the splice placed on the new machine reel.

In off-machine coating machines, a continuous unwind stand is used, in which the new machine reel brought to the unwind stand is connected at full speed with the tail of the machine reel that is being emptied. With modern high-speed coating machines, the splicing method is, in principle, the same irrespective of the manufac¬ turer of the machine. To the end of the web of the new machine reel, a splice is prepared by means of a two-sided adhesive tape, which splice is attached to the face of the reel by means of pieces of fastening tape. The surface speed of the new machine reel is accelerated to a speed equal to the running speed of the machine, after which the web of the machine reel that is being emptied is pressed into contact with said splice by means of a roll or brush. The old web is cut off by means of a blade from above the splice.

At the current running speeds (1200 to 1600 metres per minute) the splicing at the unwind stand has become problematic. This is why the running speed of the coating machine is often lowered for the time of splicing. At high running speeds, the most important causes of the problem of splicing are air currents and the required high speed of movement of the splicing roll. At a high speed, a negative pressure is formed in the so-called splicing gap between the splicing roll that has been brought to the vicinity and the machine reel, which negative pressure may be pulsating if the new machine reel is non-circular or eccentric. The negative pressure attempts to pull the old web partly into contact with the splice even before splicing, and it also

causes fluttering of the old web. Moreover, the negative pressure attempts to detach the tape splice from the face of the new machine reel, in which case the new machine reel "explodes" before splicing. In order that the run of the web could be controlled, a bend is needed at the splicing roll, which again requires stretching of the web when the splicing roll is hit quickly against the face of the new machine reel. Attempts are made to keep the tension peak produced by the hitting of the roll in connection with the splicing low by using a small splicing gap (8...12 mm), which produces an intensive phenomenon of negative pressure. Even the bend angle that is used currently produces a problematic tension peak in the web. At high running speeds, an even larger bend angle would be required.

Thus, in the splicing devices of a continuous unwind stand, the principal problems are the high speed of the stroke of the splicing roll, the large bending angle of the web, and the negative pressure formed in the splicing gap. The negative pressure produces detrimental fluttering, and the possibility of detaching of the tape used for splicing is very high. When a large splicing gap is used, the risk of web break is increased. Likewise, when a large bending angle is used, the risk of web break is increased. When the splicing gap is made smaller, the consequence is an increased negative pressure and the resulting detrimental effects. When the splicing gap is made larger, the tension peak applied to the web, i.e. the risk of web break, becomes higher.

At present, as the splicing device of a continuous unwind stand, a splicing roll is commonly used, which usually has a 35 mm thick soft rubber face. The core material of the splicing roll is, as a rule, steel, but it may also be of some other material, such as, for example, carbon fibre.

The object of the present invention is to provide an improvement of the prior-art splicing devices of continuous unwind stands. A more specific object of the invention is to provide a splicing device for a continuous unwind stand, in which device the numerous detrimental factors present in the prior-art solutions are avoided.

The splicing device in accordance with the invention for a continuous unwind stand is characterized in that the splicing device comprises at least one second roll, and that the splicing roll and said second roll are attached to a lever device, which is mounted by means of an articulation point placed between the shafts of said rolls so that the run of the web before splicing and the run of the web during splicing are such that the length of the web during splicing and when said rolls are in their basic positions is substantially equal.

In the splicing device in accordance with the invention, the stretching of the web during striking of the splicing roll is eliminated by using two mobile rolls. Since the stretch of the web during movements of the rolls has been compensated for, it is possible to use a large splicing gap, such as, for example, 100 mm, in which case no disturbing negative pressure is formed in the splicing gap. This is why fluttering of the web is reduced and the risk of disintegration of the new machine reel becomes lower. In the solution in accordance with the present invention, the bending angle on the splicing roll can be increased, in which case the run of the web becomes more controlled. Nor is there a risk of premature adhesion of the web to the splicing tape in the solution in accordance with the invention.

In a preferred embodiment of the invention, the two rolls of the splicing device are attached to a lever, which is linked from an articulation point placed between the shafts of the rolls. The location of the articulation point is chosen depending on the bending angles at the splicing roll and the web guide roll, i.e. auxiliary roll, so that the length of the web during splicing and when the rolls are in their basic positions is substantially equal. In large machines, in which the roll diameters are large, it is possible to use low-weight composite rolls, in which case the weight of the splicing- roll mechanism does not become disturbingly large.

In a second preferred embodiment of the invention, a support wire is fitted to pass over the splicing roll and the auxiliary roll, in which case, besides a roll nip, also a wire nip is formed. In such a case, the time of adhesion in the splicing is multiplied in comparison with a situation in which the splicing roll and the new machine reel

form a roll nip alone. Moreover, in the solution in accordance with the invention, the adhesion of the splicing tape takes place even at a low gluing pressure, because the time of adhesion is sufficiently long. Thus, in the invention, it has been realized to increase the time of adhesion by increasing the distance over which the splicing tape is under pressure.

The invention will be described in detail with reference to a preferred embodiment of the invention illustrated in the figures in the accompanying drawings, the inven¬ tion being, however, not supposed to be confined to said embodiment alone.

Figures 1A, IB and 1C are side views of a prior-art splicing mechanism.

Figure 2 is a side view of a preferred embodiment of a splicing device in accordance with the invention.

Figure 3 is a side view of a second preferred embodiment of a splicing device in accordance with the invention.

In Figs. 1A, IB and 1C, the machine reel that is being emptied is denoted with the reference numeral 11 and the splicing roll with the reference numeral 12. The new machine reel is denoted with the reference numeral 13 and its sense of rotation with the arrow A. The tape splice is denoted with the reference numeral 14.

In the prior-art solution the new machine reel 13 is accelerated to the running speed, and the old web P is brought close to the face of the new machine reel 13. After this, the web P is pressed onto the face of the machine reel 13 by means of the splicing roll 12. The old web P is cut off by means of a cutting blade 15 above the splice 14. The prior-art splicing mechanism as shown in Figs. 1A...1C involves the drawbacks that have been described above.

Besides the splicing roll 12a, the splicing device in accordance with the invention comprises at least one second roll 12b, which is an auxiliary roll and, at the same

time, a web guide roll. The rolls 12a and 12b are mounted on a lever 16, which is linked from an articulation point 17 placed between the shafts of the rolls 12a and 12b. The distance of the articulation point 17 from the shaft of the roll 12a is denoted with the reference Si , and the distance from the shaft of the roll 12b with the reference S ₂ . The run of the web P before splicing is denoted with the reference W _j , and the run of the web P during splicing with the reference W ₂ . After the splicing device the web P runs further over the guide roll 18. The actuator of the splicing device is denoted with the reference numeral 19. The actuator 19 gives the splicing roll 12a a sufficiently quick stroke. The speed can be limited to the desired value by means of a viscous attenuator 20.

The location of the articulation point 17, i.e. the distances Si and S , are chosen, depending on the bending angles at the splicing roll 12a and the auxiliary roll 12b, so that the length of the web during splicing and when the rolls 12a and 12b are in the basic positions is substantially equal. In Fig. 2, the run of the web before the splicing Wi , i.e. the distance from the point Pi to the point P , is substantially equally long as the run of the web P during splicing W ₂ . P _j refers to the point of separation of the web P from the reel 11 to be unwound, and P ₂ refers to the point of arrival of the web P on the guide roll 18.

In the embodiment as shown in Fig. 2, as the actuator 19, a pneumatic bellows has been used, which is provided with a, for example, hydraulic attenuator 20. In particular in large machines, for example large coating machines, in which the roll diameters are large, it is possible to use low- weight composite rolls as the rolls 12a and 12b, in which case the weight of the splicing-roll mechanism does not become disturbingly large. The web-guide roll, i.e. the auxiliary roll 12b, does not necessar¬ ily have to be a composite roll, but it may be, for example, a steel roll.

Thus, in the solution in accordance with the invention, it has been realized to increase the splicing gap from the present-day gap size of about 8...12 mm, for example, up to 100 mm or even beyond. Further, in the solution of the invention, it has been possible to increase the bending angle without any detrimental effect.

In the solution shown in Fig. 3, the support wire 21 is fitted to pass over the splicing roll 12a and over the auxiliary roll 12b, in which case, besides the roll nip L _{l 5} also a wire nip L is formed. Of course, in the embodiment shown in Fig. 3, the support wire 21 also runs further over the guide roll 18.

In the embodiment shown in Fig. 3, the time of adhesion in the splicing is increased to a multiple as compared with the situation as per Fig. 2. Moreover, the adhesion of the splicing tape takes place even with a low gluing pressure, because the time of adhesion is sufficiently long. Thus, in the embodiment shown in Fig. 3, it has been realized to increase the gluing time by increasing the distance over which the splicing tape is under pressure.

The embodiment shown in Fig. 3 can be illustrated by means of the following practical example.

The length of the roll nip Li is, as a rule, of an order of 20...30 mm. In a corre¬ sponding way, the length of the wire nip 1^ is, as a rule, of an order of 200...1000 mm. For example, if the length of the roll nip L, is 25 mm and the nip pressure is 100 kP, the time of dwell is 1 ms. If the length of the wire nip I_2 is 600 mm and the pressure is 5 kP, the time of dwell is 24 ms. This has been calculated with a wire tension of 6000 N/m, with a machine-reel diameter of 2.5 m, and with a running speed of 1500 m per minute. From the example it is seen directly that, owing to the solution as shown in Fig. 3, the time of adhesion of the splicing tape can be made multiple, i.e., in this example, 24-fold.

Above, just one preferred embodiment of the invention has been described, and it is obvious to a person skilled in the art that numerous modifications can be made to said embodiment within the scope of the inventive idea defined in the accompanying patent claims.