Roll or roller – Concentric layered annulus – Specific composition
Reexamination Certificate
2000-10-20
2002-04-30
Cuda-Rosenbaum, I (Department: 3726)
Roll or roller
Concentric layered annulus
Specific composition
C492S050000, C492S053000, C029S895210
Reexamination Certificate
active
06379290
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 199 51 038.5, filed on Oct. 22, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a roll, e.g., for smoothing paper webs, that includes a hard roll core made of, e.g., metal and an elastic layer provided on an outside of the hard roll. The covering layer includes a radially outer functional layer and a radially inner connecting layer arranged to connect the functional layer to the roll core.
2. Discussion of Background Information
Elastic rolls of this kind are used, e.g., in the satining of paper webs. Here, one elastic roll forms, in each case together with a hard roll, a press gap through which the paper web to be treated is guided. While the hard roll has a very smooth surface made of, e.g., steel or chilled cast iron and is responsible for the smoothing of the side of paper web facing it, the elastic roll acts on the opposite side of the paper web to effect a homogenizing and compacting of the paper web in the nip. The order of magnitude of the rolls ranges from lengths of about 3-12 m and diameters from about 450-1500 mm. They can withstand line forces of up to about 600 N/mm and compressive stresses of up to about 130 N/mm
2
.
As the trend in paper manufacturing is toward performing satining in an online operation, i.e., toward guiding the paper web exiting the paper machine or coating machine directly through the paper smoothing apparatus (calender), higher demands than previously are made on the rolls of the smoothing apparatus, particularly with respect to temperature resistance. As a result of the high transportation speeds of the paper web required in online operation and the high rotation speeds of the calender rolls associated with this, the nip frequency, i.e., the frequency with which the covering is compressed and relieved of its load again, is increased, which in turn leads to increased roll temperatures. These high temperatures arising in online operation lead to problems which can even lead to the destruction of the plastic coatings in known elastic rolls. With known plastic coatings, maximum temperature differences of around 20° C. are permissible over the width of the roll and, the plastics conventionally used for the coating have a substantially higher coefficient of thermal expansion than the conventionally used steel rolls or chilled cast-iron rolls so that high axial stresses occur between the steel roll or the chilled cast-iron roll and the plastic coating associated with it due to an increase in temperature.
So-called hot spots, at which a peeling or even a breaking open of the plastic layer occurs, arise dine to these high stresses in conjunction with hot regions occurring particularly in spot form.
These hot spots can occur when, in addition to the mechanical stresses and the relatively high temperature, crystallization spots exist in the form of, e.g., defective adhesive bonds, deposits or above-average recesses in the elastic coating, e.g., due to creases or foreign bodies on the paper web. In these cases, the temperature to the crystallization spots can increase from the normal about 80° C.-90° C. to more than about 150° C., due to which the above-mentioned destruction of the plastic layer occurs.
To achieve a high service life of the elastic rolls, it must be ensured that the covering layer is not destroyed by either its internal heating, which occurs in operation, or by high local mechanical excessive stresses, which occur in operation.
SUMMARY OF THE INVENTION
The present invention provides a roll of the kind generally mentioned above, in which the risk of the occurrence of hot spots is reduced and high local excessive stresses will also not lead to the destruction of the elastic covering layer.
Accordingly, the present invention includes a roll, similar in general to that mentioned above, in which the inner connecting layer and the outer functional layer each include a soft matrix material with fibers embedded therein. The matrix material of the functional layer is a highly elastic material with a damping factor of tan &dgr; less than about 0.02 and the matrix material of the connecting layer is a highly damping material with a damping factor of tan &dgr; greater than about 0.05. The damping factor tan &dgr; is defined here by the equation tan &dgr;=E′/E″, where E represents the modulus of elasticity with its real part E′ and its imaginary part E″.
In accordance with the invention, the covering layer is split into two partial layers, each of which is optimized for its respective task. While the local excessive stresses are taken up and damped by the highly damping matrix material in the connecting layer, so that the elastic roll is relatively insensitive to high local excessive stresses, the flexibility of the roll surface required for a high quality staining result and the low internal warming of the outer regions of the covering layer are ensured by the highly elastic material of the functional layer.
The matrix material preferably includes a plastic material, e.g., a thermosetting plastic or a thermoplastic. It must be pointed out here that the term “soft” when used in connection with the matrix material, is only to be understood in relation to the outer side of the metal roll, in particular the steel roll, termed as “hard.”
The heat dissipation inside the connecting layer is increased and the desired stiffness of the connecting layer is achieved by the fibers embedded in the matrix material of the connecting layer. The same applies to the fibers embedded in the functional layer, such that the heat, which only occurs to a lower degree here due to the highly elastic matrix material, is dissipated essentially completely via the fibers.
In accordance with an advantageous embodiment of the invention, the fiber content of the connecting layer is approximately 40 to 70 vol. %, in particular approximately 50 to 60 vol. %. The fiber content of the functional layer, in contrast, is advantageously approximately 5 to 30 vol. %, in particular approximately 8 to 20 vol. %.
Since the connection layer should have a greater stiffness than the functional layer and, since a higher heat dissipation is required in the radially inner connecting layer, the connecting layer has a higher fiber content than the functional layer.
The connecting layer preferably has a greater radial thickness than the functional layer, with the radial thickness of the connecting layer advantageously being approximately 30 to 70%, in particular approximately 50%, greater than the radial thickness of the functional layer. Suitable values for the radial thickness of the connecting layer can be approximately 8 to 15 mm, preferably approximately 12 mm, and for the radial thickness of the functional layer approximately 5 to 12 mm, preferably approximately 8 mm.
The desired property of the connecting layer with respect to a high capability to take up large local excessive stresses is improved by its greater radial thickness since the large local excessive stresses are greatly damped by the relatively thick connecting layer.
In accordance with another preferred embodiment of the invention, the fibers of the functional layer and/or of the connecting layer have a higher thermal conductivity than the matrix material in which they are embedded. The fibers of the functional layer and/or the connective layer can be made of, e.g., carbon fibers and/or metal fibers.
In this way, it is achieved that the heat occurring inside the functional layer and/or the connecting layer is dissipated fast and safely before the heat occurring can lead to the destruction of the covering layer.
Further, fillers, whose thermal conductivity is, e.g., greater than the thermal conductivity of the matrix material in each case, can advantageously be present in the functional layer and/or connecting layer in addition to the fibers
Cuda-Rosenbaum I
Greenblum & Bernstein P.L.C.
Voith Sulzer Papiertechnik Patent GmbH
LandOfFree
Elastic roll and process of producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Elastic roll and process of producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Elastic roll and process of producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2878261