Roll or roller – Spaced plural annulars along common shaft
Reexamination Certificate
2000-03-27
2001-10-23
Hughes, S. Thomas (Department: 3726)
Roll or roller
Spaced plural annulars along common shaft
Reexamination Certificate
active
06306069
ABSTRACT:
This invention concerns a spreader roll including a curved central shaft and in a rotary arrangement with this a roll segment including a cylindrical shell and at least one radial supporting device oriented against the curved shaft. Such devices are used e.g. to maintain the paper web width in paper manufacture.
BACKGROUND
It is a known practice to use so-called spreader rolls, which include a curved shaft, to which are arranged several cylindrical surface elements, so-called roll segments, which together form a longitudinal curved roll e.g. for guiding the paper web during the papermaking process. These roll segments in the spreader roll are usually joined to one another by various connecting means made of elastomer materials. These connecting means may hereby be glued to the inside of the cylindrical roll segments or they may form a sealing ring, against which the roll segments are compressed from both ends of the spreader roll. The purpose of the connecting means is both to ensure a uniform and similar rotation in all segments of the roll and at the same time to prevent impurities, mainly liquid of different kinds, from leaking in between the curved shaft and the surfaces of roll segments. The roll may also be provided with a rubber sock covering the segments.
However, the known art suffers from many drawbacks and defects. Firstly, it is difficult to arrange the connecting means to the cylindrical roll segments. The purpose of connecting means is to join adjacently located roll segments tightly to one another, so that no process liquid can penetrate into the spreader roll while it is rotating in the papermaking machine. Thus, the connecting means of the spreader roll may hereby be glued to the roll segments. However, such a glued joint is apt to break up little by little, whereby it will lead process water into the roll in this way. Such a construction is also difficult to repair, because each glued joint must first be undone for maintenance of the roll, whereupon the connecting means must once more be glued to the roll segments. The work thus demands very much time while the service life of the construction is not the best possible. Other traditional solutions are to arrange various types of sealing rings between the roll segments, whereby the roll segments will be compressed against each other, and the sealing ring will in this way seal the joints between the segments of the roll. However, such connecting devices are heavy and will be subject to much wear during the rotary motion of the roll, which in time will result in an occurrence of leakage and play.
If there is leakage between connecting means and roll segments, then as time passes process liquid, usually water, will leak into the spreader roll. Since the spreader roll includes a longitudinal curved homogenous shaft and also roll segments mounted on ball bearings, the leaking water will in time corrode the bearing surfaces in the roll segments. Bearings thus subject to corrosion will stop rotating before long, which will cause trouble in the spreader roll and will finally cause wear and tear in the paper web.
On the other hand, play in the connecting means results in an uneven and abrupt rotation of the roll segment. Such a motion will cause wear and tear in the paper web and will thus destroy the paper surface.
SUMMARY
With the present Invention the problems of the known solutions are avoided. The purpose of this invention is thus to provide a spreader roll, wherein the roll segments are arranged in such a way that any water leaking into the spreader roll can not affect the roll function negatively.
The said problems are solved through the characteristic features of the present invention which are described in the claims. A device according to the present Invention is characterised in that the radial supporting device and the curved shaft are assembled together with a slide bearing in a rotary fashion.
The invention is based on the idea that instead of shutting out water leaking from the papermaking machine to the spreader roll, the spreader roll is constructed in such a way that any leaking water will not cause any kind of problem for the mounting in bearings of roll segments to the spreader roll shaft.
Several considerable benefits are achieved with the present invention in comparison with state-of-the-art solutions. A spreader roll is thus obtained, the construction of which is much more durable than earlier solutions. The new bearing construction ensures that the roll segments will always rotate around the shaft at the same speed. In this way all imaginable wear and tear are avoided in the paper web.
It is an essential advantage that a long shaft diameter may be used without any big ball bearings. A big ball bearing tends to act as a slide bearing, because the load in a spreader roll is always very small compared with the load for which such a ball bearing is dimensioned.
Since the mounting of the roll segments In bearings to the shaft has a very low inertia according to the present invention, the roll segments will achieve their full rotary speed much faster than with earlier solutions. The work speed of the roll can hereby be achieved in a shorter time than with traditional solutions. This results in a more uniform transport speed in the paper web already in the early production phase, whereby cockling in the paper web is avoided and the paper obtains a higher quality.
Since water leaking in does not cause any kind of problem to the mounting in bearings according to the present invention, the service interval is considerable longer for a spreader roll provided with the present invention. In this way an improved reliability of service is obtained along with lower operating costs. Service costs are also reduced, because a construction according to the present invention is considerably easier to service.
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G. Kröger and M. Meyer, “Construction of an Air Bearing Assembly For Web-Spreading Rollers”, Jan. 1990, pp. 25, 29 and 30.
Butler Marc W.
Hughes S. Thomas
Suomen Intech Oy
Volpe and Koenig P.C.
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