Seal for a joint or juncture – Process of dynamic sealing
Reexamination Certificate
1999-03-04
2001-10-16
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Process of dynamic sealing
C277S580000, C277S583000, C162S371000
Reexamination Certificate
active
06302399
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 198 11 335.2, filed on Mar. 16, 1998, 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 sealing device for laterally sealing at least one overpressure and vacuum zone adjacent to a moving surface in a paper machine and a process for sealing the moving surface with the sealing device. The sealing device includes at least one sealing element positioned adjacent to the moving surface, a holder in which the sealing element is mounted movably toward and away from the moving surface, and at least one loading element adapted to load the sealing element in the direction toward the moving surface.
2. Discussion of Background Information
Sealing devices such as those generally discussed above have been utilized in forming sections, press sections, and/or dry ends of a paper machine, e.g., in suction rolls or blow rolls. Suction rolls generally include stationary internal suction boxes, which form zones with at least two pressure levels. In this manner, the sealing of the pressure zones occurs through sealing ledges, which generally extend at least substantially over the entire roller length.
To obtain the desired sealing action, it has generally been customary to press the sealing elements or sealing ledges against the relevant moving surface, e.g., the inner jacket surface of a perforated suction roll, via pressure elements. However, the friction appearing between the sealing element and relevant moving surface results in significant wear of the sealing element. To limit this wear, lubricants are generally applied to the sealing element via spray tubes, which increases costs. Moreover, during operation, those ledge-type sealing elements are also pressed by the respective vacuum against the inner jacket surface. Because of the sudden ventilation of the jacket perforations following the sealing ledge adjoining a respective vacuum zone, loud noise is also generated.
U.S. Pat. No. 5,580,424 discloses a sealing ledge type sealing device of the type discussed above in which the sealing ledge is radially pressed against a suction roll jacket by at least one air tube. After the sealing ledge has been applied against the suction roll jacket, the resultant ledge position is fixed by laterally pressing the sealing ledge against a bearing block, whereupon the radial contact force is reduced to zero. However, the design of this device also includes the disadvantage that, due to the frictional fixing, a respectively desired positioning of the sealing ledge cannot be maintained with the necessary accuracy. Instead, there is a danger that the positioning of the sealing ledge may change due to vibrations resulting in a gap of undefined width consequently developing between the sealing ledge and the vacuum roll jacket. This gap formation could lead to relatively high air leakage between the pressure chambers.
SUMMARY OF THE INVENTION
The present invention provides a sealing device of the type generally discussed above in which wear of the sealing element is reduced to a minimum and an accurately defined sealing gap may be set between the sealing element and the moving surface. Moreover, the relatively high noise level of the prior art device is substantially reduced.
The present invention includes at least one reset element adapted to move the sealing element in a direction away from the moving surface, thereby acting against the loading of the sealing element by the loading element. In this manner, a sealing gap is formed between the sealing element and the moving surface may be preset by actuation of at least one of the reset element and the loading element.
Based on the arrangement of the present invention, a defined sealing gap can be set and maintained during operation such that the desired sealing action may be achieved without pressing the sealing element against the relevant moving surface, thus, reducing wear of the sealing element to a minimum. Upon start-up of the paper machine, the sealing element may be pressed against the moving surface. During subsequent normal operation, the pressing of the sealing element against the moving surface may then be relieved by the reset element so that the sealing element is substantially no longer subject to any wear. Thus, lubricants are no longer necessary and the spray tubes required in the prior art may be eliminated. Further, the noise level is clearly reduced.
In an exemplary embodiment of the present invention, the loading element and the reset element may be formed by pressure tubes. For example, the loading element may be formed by a water tube and the reset element may be formed by an air tube.
At least one of the loading and reset elements may be acted on by an adjustable pressure. Further, it may be advantageous for the loading element and a reset element to be acted upon by the adjustable pressure independently of each other.
It may be preferable, e.g., at the time of start-up of the paper machine, to apply pressure to the loading element and to remove pressure, at least substantially, from the reset element so that the sealing element may be pressed by the loading element against the moving surface. In contrast, during the subsequent normal operation, pressure is applied to both the loading element and the reset element.
In accordance with the present invention, the sealing gap produced between the sealing element and the moving surface during operation may be set by an appropriate action on the loading element and/or the reset element.
A water volume of the loading element, which may be formed, e.g., by a water tube, may be held during operation to a preferably adjustable value.
According to the exemplary embodiment, the loading element and the reset element may be arranged one above the other in the movement direction of the sealing element. The loading element may be positioned between an end of the sealing element facing away from the moving surface and a stop affixed to the holder and the reset element may be positioned between the stop affixed to the holder and a stop connected to the sealing element. Thus, the loading element and the reset element may thus be supported on one common stop affixed to the holder.
In another exemplary embodiment of the present invention, at least two loading elements may be positioned adjacent each other in a travel direction of the moving surface. In addition, or alternatively, at least two reset elements may be positioned adjacent each other in the travel direction of the moving surface. Further, it may be preferable to provide the loading and reset elements in pairs, such that each loading element is respectively associated with a reset element.
The adjacently positioned loading elements and/or the adjacently positioned reset elements may be acted upon differently such that the sealing element may assume a skewed position relative to the moving surface during operation. In this manner, a gap may be formed between the sealing element and the moving surface that widens in the travel direction, which ventilates openings provided in the moving surface in a ventilation zone that follows a sealed zone. Thus, noise occurring, e.g., in the region of a transition between a vacuum zone and overpressure zone can be further reduced.
If the adjacently positioned loading elements are formed by water tubes, it may be preferable to provide water volumes to the loading elements that are differently adjustable. Further, the sealing element may be mounted in the holder so that, at least to a limited extent, the sealing element is pivotable.
In an alternative embodiment, the sealing element may be displaceable at least substantially linearly toward and away from the moving surface, i.e., the sealing element may be substantially non-pivotable mounted, and a surface of the sealing element arranged to face the moving surface may have a course or profile that differs from
Greenblum & Bernstein P.L.C.
Knight Anthony
Pickard Alison K.
Voith Sulzer Papiertechnik Patent GmbH
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