Presses – Methods
Reexamination Certificate
2001-11-21
2004-03-02
Ostrager, Allen (Department: 3725)
Presses
Methods
C100S16300R, C100S169000
Reexamination Certificate
active
06698340
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German patent application No. 100 57 991.4, filed on Nov. 23, 2000, 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 calender with a roll stack, which has two end rolls and several intermediate rolls in between, whereby two rolls that are adjacent to one another, each having a deflection, form a nip in operation. Moreover, the present invention relates to a process to treat a material web, which is guided through several nips and pressurized there, whereby each nip is formed by a first roll and a second roll adjacent to it.
2. Discussion of Background Information
This type of calender is used to glaze a paper web, for example. In this connection, it is desired to achieve the most uniform possible progression of pressure over the entire width of the paper web in order to avoid differences in thickness and quality transverse to the machine direction of the paper web. The paper webs to be glazed currently have widths in an order of magnitude of up to about 10 m. As a result, the correspondingly long rolls tend to “sag” due to their dead weight in the axial center, i.e., they have a deflection. Even if this deflection isn't all that large, it becomes noticeable as an interfering factor in the pressure treatment of the paper web or another material web.
Attempts have been made to act against this phenomenon. Thus, it is known, for example, from EP 0 679 204 B 1 to select the intermediate rolls in such a way that they all have the same intrinsic deflection, and to relieve the weight of the rolls and the so-called overhanging loads, i.e., the parts connected to the rolls, such as guide rolls or bearing housing, completely in terms of weight.
Another approach, which is described in DE 198 20 089 A1, assumes that one modifies the segment load profiles by initiating deformation forces at the roll pin of the intermediate roll. In doing so, one selects the deformation forces in such a way that, in order to exercise loading or relieving pressures, the intermediate rolls receive an essentially equal deflection, whereby a degree of the deflection is set in accordance with a specific modification of a roll-induced segment load difference between the upper and lower nips. The deflection-controllable rolls at the end of the roll stack are then adapted to this curvature. It is now observed that the glazing results are unsatisfactory in some cases despite this equal deflection.
SUMMARY OF THE INVENTION
The present invention provides for designing the load in the nip to be uniform.
According to the invention, the instant invention is directed to a calender of the type described above, in which the deflections of the adjacent rolls differ from one another, such that a second roll adjacent the convex side of a first roll has a weaker deflection than the first roll.
Thus, the instant invention indeed abandons the previously pursued approach of giving all rolls the same deflection or selecting the rolls in such a way that they naturally have the same deflection. However, this opens the possibility that the deflection in the nips can be brought closer to one another than was previously the case. Playing a role in this connection is the consideration that so far one did not take the different effects that are produced on the concave and convex sides into account in the case of the deflection of a roll. If the deflections are selected so that they are different, these effects can be taken into consideration.
In this connection, it is especially preferred that the adjacent rolls each have a deflection with which an amplitude of the deflection of the surface line at the convex side of the first roll essentially coincides with an amplitude of the deflection of the surface line of the adjacent second roll at its concave side. Thus, the deflections of the two rolls, which form the nip under consideration, can be adapted to each other in the nip so that the progression of pressure in the nip is essentially more uniform over the width of the material web. The adaptation will take place there where it is required. In this connection, it can be accepted without hesitation that the deflections of the two rolls as such, i.e., the deflection at the axes, deviate from one another. This type of deviation is even a prerequisite that brings the deflections at the two surface lines into conformity with one another.
It is preferred that at least one of the rolls that are adjacent to one another have a force initiation device. One is then no longer dependent upon selecting rolls that naturally have the required deflections. One can also bring about this type of deflection by initiating external forces.
The amplitude ƒ
EM
(i+1)
of the deflection of the second roll is preferably a function of the amplitude ƒ
EM
(i)
of the deflection of the first roll in accordance with the following relationship:
f
EM
(
i
+
1
)
=
(
2
D
(
i
+
1
)
K
2
)
2
+
4
D
(
i
+
1
)
K
2
·
f
EU
(
i
)
-
2
D
(
i
+
1
)
K
2
whereby
f
EU
(
i
)
=
f
EM
(
i
)
-
1
4
K
2
·
f
EM
(
i
)
2
·
D
(
i
)
;
and
K
=
16
AB
·
1
+
3
MbML
-
AB
AB
5
+
12
MbML
-
AB
AB
AB=Machine width
MbML=Bearing distance
D
(i)
=Diameter of the first roll
D
(i+1)
=Diameter of the second roll
i=Index of the first roll
i+1=Index of the second roll
The adjacent rolls preferably have different bearing distances if they deviate from one another in terms of at least one parameter. With this embodiment not just conformity of the deflections, or, more precisely, of the amplitudes of the deflections at the two adjacent surface lines of the two rolls forming the nip, are achieved, but there is also the opportunity to set equal elastic lines. As is generally known, the elastic lines are not just dependent upon the amplitude of the deflection, but, for example, also upon the curve shape of the elastic line, which, via thrust deformation, for example, depends upon the slenderness degree of the rolls. If one now has an opportunity to vary the bearing distances of the intermediate rolls, one then obtains the opportunity to actually also adapt the curve shape of the elastic lines of the surface lines to one another better, i.e., of the two lines limiting the nip.
The difference of the bearing distances preferably lies in a range of about 0.1% to about 2% as related to the greater bearing distance. This type of deviation is entirely tolerable. Greater deviations in the bearing arrangement are not required, because the forces that act on the bearing arrangement do not receive any essentially different points of application of force. Despite this, considerable advantages can be achieved with these small changes.
In this connection, it is preferred that the bearing distance of at least one intermediate roll can be changed. After replacing the affected roll, it is then possible to bring the elastic line into the desired shape, if necessary.
In this case, it is preferred that the seating of all rolls be accomplished symmetrically to the axial center. This also applies to the intermediate rolls, whose bearing distance is adjusted. This means though that one must undertake the adjustment of the bearing at both axial ends. The bend of the surface line of this roll is then adjusted to the bend of the corresponding second roll over the entire machine width.
Moreover, the instant invention is directed to a process of the type generally discussed above, in which deflections of the two rolls are selected so that they are different.
As explained above in connection with the calender, with different deflections of the rolls, i.e., their surface lines, it is possible to adjust the deflections to one another at the decisive locations, namely at the surface lines forming the nip. In this way, the glazing result is improved drastically over the machine
Junk Dieter
Linder Heiko
Greenblum & Bernstein P.L.C.
Nguyen Jimmy
Ostrager Allen
Voith Paper Patent GmbH
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