Winding – tensioning – or guiding – Unwinding – With attachment to preceding material
Reexamination Certificate
2000-09-22
2002-10-15
Jillions, John M. (Department: 3654)
Winding, tensioning, or guiding
Unwinding
With attachment to preceding material
Reexamination Certificate
active
06464163
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a method in a paper machine, coating machine, intermediate winder, unwind stand of a slitter-winder, or in any other device for treatment of a web.
A particular subject of the invention is a method in splicing in a continuous unwind stand, in which method the web on a new machine reel to be introduced in the unwind stand is joined at fall speed with the web of the machine reel that is being emptied by cutting off the web and by pressing the web of the machine reel that is being emptied into contact with the splice provided on the new machine reel.
A second particular subject of the invention is a method in equipments for coating of a paper web, in which method the paper web is coated with a layer of paste from at least one side by making the paper web pass through at least one coating station and through at least one dryer section, and in which method the running of the paper web to be coated is monitored by means of at least one monitoring device, the cutting off of the paper web to be coated being carried out based on a signal transmitted by said monitoring device.
The invention also concerns a device in a paper machine, coating machine, intermediate winder, unwind stand of a slitter-winder, or in any other device for treatment of a web.
A particular subject of the invention is also a device in splicing in a continuous unwind stand, in which the web on a new machine reel to be introduced in the unwind stand is joined at full speed with the web of the machine reel that is being emptied by cutting off the web and by pressing the web of the machine reel that is being emptied into contact with the splice provided on the new machine reel.
A second particular subject of the invention is also a device in equipments for coating of a paper web, by means of which coating machine the paper web is coated with a layer of paste from at least one side by making the paper web pass through at least one coating station and through at least one dryer section, and in which coating machine the running of the paper web to be coated is monitored by means of at least one monitoring device.
BACKGROUND OF THE INVENTION
In off-machine coating machines, a continuous unwind stand is used in which the new machine reel to be introduced in the unwind stand is joined at full speed with the tail of the machine reel that is being emptied. In modern high-speed coating machines, the splicing method is, in principle, the same irrespective of the manufacturer of the machine. At the end of the web on the new machine reel, in advance, a splice is prepared by means of double-sided adhesive tape, which splice is attached to the reel face by means of pieces of adhesive tape. The circumferential speed of the new machine reel is raised to a level 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, for example, by means of a roll or brush. The old web is cut off by means of a blade from above the splice.
The splicing in an unwind stand has become problematic at the current running speeds (1200 . . . 1600 meters per minute). Out of this reason, the running speed of the splicing machine is often lowered for the time of splicing. At a high speed, a vacuum is formed in the what is called splicing gap placed between the machine reel and the splicing roll brought to the vicinity of said reel, which vacuum can be pulsating if the new machine reel is non-circular. The vacuum tends to attract the old web partly into contact with the splice even before splicing, and the vacuum also causes fluttering of the old web. Further, the vacuum tends to separate the tape splice from the face of the new machine reel, in which case the new machine reel is opened before splicing. In order that the running of the web should be controlled, at the splicing roll a bend is required, which again requires stretching of the web when the splicing roll is hit quickly onto the face of the new machine reel. Attempts are made to keep the tension peak caused by the hitting of the roll in splicing low by using a little splicing gap (8 . . . 12 mm), which produces an intensive vacuum effect Even the bending angle that is used currently causes a problematic tension peak in the web. At higher running speeds an even larger bending angle would be required.
In the FI Patent Application No. 942869, a splicing device for a continuous unwind stand is described, by whose means 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. The 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, and at least one second roll. 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.
At high running speeds and in particular with heavy paper grades, in flying splicing, a problem has been the control of the cut-off tail of the old machine reel. After the splicing, attempts are made to stop the reel spool that is being emptied quickly. Paper must not be unwound to such an extent that it cannot be controlled by means of blowing of air. The tail of the cut-off web and any paper chips must be kept away from the splicing nip. If the cut-off tail ends up onto the web, it causes a web break. Also smaller paper chips can cause a web break if chips are carried along with the web, for example, to a coating station. Even if a paper chip separated from the tail did not cause a web break, it, however, causes cleaning work after splicing.
In order to solve this problem, some manufacturers have constructed inverted unwind stands in which the geometry has been turned upside down. It is the purpose of the inverted geometry that, after the splicing, the cut-off tail and any paper chips that are separated fall away from the web by the effect of gravity. At higher speeds (higher than 1400 meters per minute), even this is not of any use, because the air flows present on the faces of the departing web and of the large machine reel that is being unwound are so intensive that the direction of the gravity remains insignificant.
Traditionally, for the control of the cut-off web, blowings have been employed, by whose means attempts are made to guide the tail around the reel spool to be slowed down and to prevent access of the tail and of separated chips to the departing web. Attempts are made to stop the reel spool that is being emptied by means of mechanical brakes quickly. This requires high capacity from the brakes and, thereby, causes rapid wear of the brakes. The brake pads of the brakes must be renewed frequently. At present, a typical stopping time of about 4 seconds is in use. With the present-day technology, a target time for stopping the reel would be about 1.5 seconds, irrespective of the speed or of the size of the reel spool. In large machines, such a time would involve a braking capacity of up to 10 MW. At present, there are production machines in which the brake devices must be replaced even at intervals of 2 months, which means, among other things, a considerable expense in terms of money.
In very narrow unwind stands (width about 1 meter) of the revolver type, which are used at printing machines, occasionally, a double-sided tape is used on an intermediate roll placed before the cut-off roll, which tape captures the cut-off tail around it. After splicing, the intermediate roll is unwound and cleaned manually. The tape is difficult to remove from the intermediate roll, but this is necessary after each splicing cycle. In large high-speed unwind stands (roll diameter &phgr;=1000 mm, length 8000 mm) such fitting of tapes and manual cleaning a
Kinnunen Jorma
Linnonmaa Jukka
Mikkonen Silvo
Jillions John M.
Metso Paper Inc.
Steinberg & Raskin, P.C.
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