The invention relates to a method and assembly in connection with a rotating roll for reducing the oscillations and/or increasing the rotational speed and/or dropping the noise level of a roll.

It is prior known that the oscillation frequency of load-bearing structures and/or supporting structures, such as the bearing blocks of a rotating roll, can be influenced by the size of steel beams and the type of steel material. Major benefits can be obtained by raising the natural oscillation frequency of the load-bearing structures and/or supporting structures of high-speed rolls. If the natural frequency of load-bearing structures can be increased, it will also be possible to increase the rotational speed of rolls and to upgrade thereby the process in terms of its profitability and process performance, e.g. by virtue of a more consistent quality standard. For example, paper machine rolls can be mentioned as one application. Another relevant application concerns conveyor rollers, the reduction of whose oscillations increases carrying capacity and/or service life and/or lowers noise level.

It is an object of the invention to provide a method and assembly capable of accomplishing these objectives.

In a method of the invention, this objective is achieved by having the load-bearing structures and/or supporting structures of a roll pasted with carbon-fiber reinforced mats and/or profiles, the dimensions, quantity and location thereof being selected such that the natural oscillation frequency of a load-bearing structure and/or supporting structure increases substantially with respect to the oscillation frequency of metal components included in the load-bearing structure and/or supporting structure.

With an assembly of the invention, this objective is achieved respectively by having the load-bearing structures and/or supporting structures of a roll pasted with carbon-fiber reinforced mats and/or profiles, having the dimensions, quantity and location thereof selected such that the natural oscillation frequency of a load- bearing structure and/or supporting structure has increased substantially with respect to the oscillation frequency of metal components included in the load- bearing structure and/or supporting structure.

The use of carbon-fiber reinforced mats and/or profiles is prior known e.g. in reinforcing steel bridges. However, the objective here has been a reduction of weight with respect to strength with no regard to the natural oscillation frequency of the structure. The same applies generally to the reinforcement of steel structures with carbon fiber composites, reference being made to JP 2000064505 as an example of the prior art.

According to the Applicant's research efforts, the natural frequency of steel structures can be significantly regulated or modified by pasting carbon-fiber reinforced mats and/or profiles to the steel structures. This knowledge is utilized in the invention in specific circumstances with an objective of substantially increasing the natural frequency of the load-bearing structures and/or supporting structures of rotating rolls, especially high-speed rotating rolls. Relevant examples of load- bearing structures and/or supporting structures include a stationary shaft within a rotating roll shell, upon which the shell is rotatably mounted with bearings. This type of load-bearing structures are employed in association with both conveyors and paper machine rolls. Another relevant example concerns bearing blocks for rolls.

A carbon-fiber reinforced mat and/or profile is pasted to a steel structure with constructional adhesives, typically by using an epoxy glue. The oscillation characteristics of a load-bearing structure and/or supporting structure can be influenced by selecting carbon fibers of various moduli of elasticity. The natural frequency can be further influenced by the selection of dimensions and thickness, i.e. quantity, for a presently used carbon fiber mat or profile. The location of a presently used mat or profile in a load-bearing structure and/or supporting structure has also an impact on natural frequency. There are prior known types of carbon fiber capable of raising the natural frequency of supporting structures typically by 10-50%, in some cases by even more than 50%. An extra benefit gained by the invention is due to the fact that the high internal friction of carbon fibers in a presently used mat or profile substantially dampens oscillations, which contributes to the same beneficial effect as raising the natural frequency, i.e. enables increasing the rotating speed or rolls, thus enhancing process performance and improving consistent quality standard. The invention is particularly suitable for use in the load-bearing structures and/or supporting structures of high-speed rotating rolls in paper making machines. Another specific application concerns conveyor rollers, particularly in high-performance pulp conveyors.

The material thickness of an employed carbon fiber mat and/or profile can be within the range of 1-20 mm, being typically in the order of 10 mm. The modulus of elasticity of carbon fibers is typically within the range of 150-400 GPa. Carbon fiber mats and/or profiles can be applied to load-bearing and supporting structures, such as stationary shafts and/or bearing blocks, along all surfaces whose shapes are suitable for such application. On the other hand, when applying the invention, the load-bearing and supporting structures can be designed for shapes which provide adequate surfaces and profiled cutouts suitable for the application of mats and/or profiles. It is also feasible to use e.g. separate beams which are completely covered with a carbon fiber mat and/or profile. Of course, mats can be also be applied to more extensive surfaces which are sufficiently flat in the longitudinal direction of fibers.