Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...
Reexamination Certificate
1999-04-15
2001-05-08
Silverman, Stanley S. (Department: 1731)
Paper making and fiber liberation
Apparatus
Running or indefinite length product forming and/or treating...
C162S360300, C162S198000, C162S360200, C162S358100, C162S358300, C162S253000, C162S262000, C162SDIG004, C162S205000, C100S073000, C100S074000, C100S161000
Reexamination Certificate
active
06228222
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 198 16 759.8, filed on Apr. 16, 1998, the disclosure of which is expressly incorporated by reference herein in its entirety.
The invention relates to a press arrangement for the treatment of a material web in a plurality of press gaps, comprising a roll which has a flexible press jacket supported from the inside and which forms a respective press gap with each of at least two further driven rolls.
An arrangement of this kind is, for example, known from DE-OS 43 21 404 and serves there for the dewatering of a fiber material web. However, a compact arrangement of this kind causes problems, in particular with respect to the drive of the rolls. In this respect changing and unfavorable mechanical loadings of the flexible press jacket can arise in particular.
The flexible press jacket permits the formation of press gaps extended in the web running direction, for example through the support on concavely shaped support elements. On the other hand, the flexible press jacket, however, also requires the most accurate synchronization possible of the speed of the driven rolls, because otherwise a jacket deformation arises. A mechanical or electrical coupling of the drives is very complicated and expensive.
The invention is thus based on the object of providing a press arrangement of the initially named kind in which a common speed of the driven rolls is achieved in a manner which is as simple and accurate as possible. Moreover, a situation should be achieved in which a mechanical loading of the flexible press jacket is ensured which is as constant as possible and as considerate as possible over the full range of speed and line forces of the press arrangement.
In accordance with the invention this object is satisfied in that rolls the drive power or the speed at one of the driven is regulated in accordance with a predetermined desired value.
In this connection a regulation of the drive power or of the speed of the other driven roll can be dispensed with as a further simplification. In the end result, the same speed arises at the non-regulated roll as at the regulated roll through the coupling via the flexible press jacket.
Since the drive power must largely be expended for friction and compression, it is of advantage to regulate the drive powers of the two driven rolls and to keep the ratio constant in accordance with the circumstances and/or to adapt it to the ratio of the line forces of the two corresponding press gaps.
In this way account is in particular taken, in advantageous manner, of the fact that the line forces have a decisive influence on the drive power that is required.
A cylindrical press jacket which is of a shape which is as stable as possible is of advantage for a simple drive of the rolls.
However, as a result of the use of the flexible press jacket for the coupling between the press gaps, a deformation of the press jacket can still arise, even though to a small extent. In order to counteract this, the press gaps should have the smallest possible spacing from one another, and the regulated roll should be arranged in the web running direction after the unregulated roll. In the end result, speed differences merely lead to restricted deformation of the short section between the press gaps.
It is, however, also possible, to at least partly support the run of the flexible press jacket between the press gaps.
As an additional element for the coupling between the press gaps, a belt, for example in the form of a felt, screen or press belt, can also be guided through the two press gaps and should itself preferably be driven. In order to make the coupling efficient, the belt should be guided in such a way that it leaves the first press gap approximately tangentially with respect to the driven roll and runs into the second press gap approximately tangentially with respect to the driven roll.
The press arrangement is particularly suited for the dewatering and/or smoothing of paper, card or tissue webs.
The object underlying the invention is further satisfied in accordance with the invention in that the maximum line force and/or the drive power of a front press gap considered in the web running direction is controllable and/or regulatable, at least within a certain range, in dependence on the maximum line force or the drive power of a rear press gap when considered in the web running direction.
As a result of this design, a mechanical loading of the flexible press jacket, which is as constant as possible and also as considerate as possible is ensured over the full range of speeds and line forces of the press arrangement.
A preferred practical embodiment of the press arrangement of the invention is characterized in that the rear driven roll associated with the rear press gap can be operated at a higher drive power than the front driven roll associated with the front press gap, and in that the ratio of the drive powers of the two driven rolls is controllable and/or regulatable in dependence on the ratio of the maximum line forces of these two driven rolls. Since the rear driven roll is operated at a higher drive power than the front driven roll, it is ensured that the flexible press jacket is always pretensioned during the normal operation in the direction of the rear press gap.
It is also of advantage if the ratio between the maximum line force of the front press gap and the maximum line force of the rear press gap is kept constant, and the ratio between the drive power or the desired current value of the front driven roll and the drive power or the desired current value of the rear driven roll is proportional to and preferably the same as the constant ratio of the maximum line forces of the two press gaps. In this case the ratio between the maximum line force of the front press gap and the maximum line force of the rear press gap can in particular be kept at a constant value smaller than 1, and the ratio of the drive powers or of the desired current values of the driven rolls can be the same as this ratio of the maximum line forces which is kept constant. Since the ratio of the maximum line forces of the two press gaps is kept smaller than 1, it is simultaneously also ensured that the drive power of the front driven roll remains smaller than that of the rear driven roll and the flexible press jacket accordingly remains prestressed in the direction of the rear press gap.
In an expedient practical embodiment the roll having the flexible press jacket can be supported from the inside in the region of the front and rear press gaps, in each case by at least one pressure loadable support element, and the maximum line force of a respective press gap can be correspondingly set via the relevant pressure. In this case it is of advantage if the pressure of the support element provided in the region of the rear press gap is controllable and/or regulatable in dependence on a predeterminable desired value, and the pressure of the support element provided in the region of the front press gap is adjustable in dependence on the pressure of the rear support element. In this connection the rear support element can be connected via a central valve, preferably a central proportional pressure reducing valve, to a hydraulic pressure source, and the front support element can be adjustable in dependence on the pressure of the rear support element in a specific range via an additional valve, preferably an additional proportional sequential valve with &Dgr;P function.
For the monitoring of the function of the additional valve, a further valve is expediently provided, preferably a proportional sequential valve with &Dgr;Pmax function, which opens on exceeding a difference pressure value, in particular a difference pressure value determined by area ratios, in order to take care, if necessary, of a pressure compensation between the rear and the front support element.
The driven rolls can basically also each be supported from the inside by at least one support element arranged in the
Meschenmoser Andreas
Steiner Karl
Zierhut Andreas
Greenblum & Bernstein P.L.C.
Halpern Mark
Silverman Stanley S.
Voith Sulzer Papiertechnik Patent GmbH
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