Presses – Methods
Reexamination Certificate
2000-08-23
2003-02-25
Ostrager, Allen (Department: 3725)
Presses
Methods
C100S16200R, C100S047000
Reexamination Certificate
active
06523465
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 199 40 664.2, filed on Aug. 27, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for presetting a calender for a material web such as paper, cardboard, and the like. The calender has a roll stack comprising a lower roll designed as a sag compensation roll. This lower roll is rotationally secured via a carrier which can be lifted in the direction of the stack by utilizing external support devices which grip its ends. The lower roll also has a jacket which is supported on the carrier by internal support devices and the roll can be adjusted along its entire length in the direction of the stack. The calender also includes at least one middle roll which can be adjusted in the direction of the stack. Moreover, an upper roll, designed as a sag compensation roll is also utilized. The upper roll has a carrier which is held stationary at its ends and utilizes a jacket supported on the carrier by internal support devices. This upper roll is also seated on the carrier at its ends. The invention also relates to a calender for implementing this process.
2. Discussion of Background Information
Conventional calenders must be calibrated or preset before they can be loaded for a specific purpose. The aim of calibration is to produce a “straight” nip between the rolls in each case, i.e., for the rolls to lie against each other so as to have the same pressure across the entire calender width, i.e., in order to create a uniform line load in the nip.
One conventional procedure requires calculating a load from the following determinations; internal pressure in the upper roll, the upper roll jacket weight, the middle roll weight, the lower roll jacket weight, and any friction values in the calender, and that the pressures to be applied to the external and internal support devices. The accuracy of the settings were then checked by testing a nip impression using NCR paper. Such a procedure is laborious and time-consuming because even slight deviations between the actual quantities and the calculated quantities lead to deviations in the line load. Moreover, when corrections are made on the basis of nip impression tests, one is never quite certain whether the pressures should be changed overall or whether a mere zone correction should be undertaken. Further, the procedure also has an element of danger because the NCR paper must typically be pushed into the nip by hand.
SUMMARY OF THE INVENTION
The present invention provides for the presetting or calibration of the calender. Accordingly, the present invention provides a process for presetting a calender including a stack comprising a lower roll designed as a sag compensation roll. The lower roll is rotationally secured via a carrier which can be lifted in the direction of the stack by external support devices gripping its ends. A roll jacket is supported on the carrier by internal support devices wherein the roll can be adjusted along its entire length in the direction of the stack. The calender also has at least one middle roll which can be adjusted in the direction of the stack and an upper roll designed as a sag compensation roll. The upper roll has a carrier which is held stationary at its ends and whose jacket is supported on the carrier by internal support devices. The upper roll is also seated on the carrier at its ends. Moreover, pressure can be applied to the internal support devices of the lower roll such that the jacket of the lower roll forms approximately a cylinder with a horizontal axis. Accordingly, in closing the nips, the external support devices of the lower roll or its internal support devices are loaded with an increasing pressure. The process also provides that pressures acting in the external and internal support devices at the instant of the complete closing of the uppermost nip are recorded.
Accordingly, if a calender is utilized whose upper roll is a sag compensation roll without a jacket lift and whose lower roll is a sag compensation roll with a jacket lift, wherein the carriers of the upper roll are held stationary and the height of the carriers of the lower roll are made adjustable by external support devices, the presetting can be performed in a very simple manner. When the jacket of the lower roll corresponds to a cylinder having a horizontal axis, as a result of its loading, and maintains this shape while the nip is being closed due to pressure tracking, corresponding cylindrical shape is formed by a jacket of the upper roll at the instant of the complete closing of the uppermost nip. As a result, straight nips can be obtained in the entire roll stack. Moreover, the pressures acting at this instant can correspond to the basic setting and, building on this, the operating pressure values can be set.
In addition, the uppermost nip can be first closed in the center and thereafter closed progressively towards its sides. According to this design, it is only necessary to observe the closing conditions of the nip at one or both ends and this enables a very precise setting.
According to this process, it is possible that when the calender is put into operation or when the loads are changed (e.g., when a roll is changed), the upper and lower roll pressures of the calender can be calibrated by a single closing.
By tracking the pressure, e.g., the pressure applied to the one support devices of the lower roll is followed to the pressure applied to the other support devices, the provides that the carriers and jacket of the lower roll maintain their correlation to one another.
Moreover, the closing of the uppermost nip can be effected not only by loading the external or internal support devices of the lower roll with an increasing pressure, but also by decreasing the equal pressures applied to the internal support devices of the upper roll, e.g., the pressure applied to the internal support devices of the upper roll is decreased to close the uppermost nip.
However, the application of equal pressure can yield the best results, e.g., wherein approximately equal pressure is applied respectively to the correlated internal and external support devices.
The calibrating procedure can also be carried out automatically, e.g., wherein the pressures are automatically changed until a measuring signal detecting the instant of the complete closing of the uppermost nip occurs.
Optical detection of the nip closing may also be particularly favorable, e.g., such that the instant of the complete closing of the uppermost nip is detected optically.
Additional measures may be advisable for tracking the lower roll, e.g., such as those relating to the pressures applied to the internal support devices of the lower roll can be changed so that the distance between the jacket ends and the carrier remains constant. Moreover, the projecting weights of the middle rolls can also be compensated for in the usual manner.
The calender for implementing the process of the invention may include a roll stack including a lower roll designed as a sag compensation roll, whose rotationally secured carrier can be lifted by external support devices gripping its ends. The lower roll may have a jacket which is supported on the carrier in the direction of the stack by internal support devices such that the lower roll can be adjusted along its entire length in the direction of the stack. The calender can include at least one middle roll which can be adjusted in the direction of the stack and an upper roll designed as a sag compensation roll. The upper roll can have a carrier and be held stationary at its ends and may include a jacket supported on the carrier by internal support devices. The jacket can be seated on the carrier at its ends. Such a calender is particularly suited for carrying out the process described above. Moreover, the calender can include, in the area of at least the one end of the uppermost nip, a measurin
Greenblum & Bernstein P.L.C.
Nguyen Jimmy T
Ostrager Allen
Voith Sulzer Papiertechnik Patent GmbH
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