Paper making and fiber liberation – Processes and products – Conditioning – preparing or repairing of apparatus
Reexamination Certificate
2001-01-12
2004-04-06
Fortuna, José A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Conditioning, preparing or repairing of apparatus
C162S190000, C162S264000, C162SDIG007, C141S364000, C141S106000
Reexamination Certificate
active
06716315
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Applications No. 200 005 99.5 and No. 100 148 73.5, filed on Jan. 14, 2000, and Mar. 24, 2000, respectively, the disclosures of which are expressly incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a water draining device for a paper machine or the like, in particular for a felted press of paper machines having a receiving tank extending at least essentially over the machine width. Moreover it relates to a press arrangement for dewatering a pulp web.
2. Discussion of Background Information
In previous conventional water draining devices, the press water is ordinarily drained by gravity. However, when used for a top felt, the amount of water thrown off into the tank cannot, in each situation, flow laterally to the edge of the tank by gravity. In particular, when the discharge cross-section of the tank is too small and/or the tank is not inclined sufficiently, water can flow back onto the felt.
From DE 25 09 057 C3, a suction box has already become known for sucking off water that passes through a wire, with the box being divided into a water suction chamber and an air suction chamber by means of a partition provided with apertures.
SUMMARY OF THE INVENTION
The present invention relates to creation of an improved water draining device in which it is possible to reduce a discharge cross-section of the tank accompanied by a corresponding saving of space without any problems. In addition, the present invention renders it impossible for water to flow back onto a felt in a paper machine. Furthermore, the present invention enables drainage, with only a very slight incline in the transverse direction, of water amounts that collect, without any problems.
The present invention further relates to a receiving tank including a first chamber that receives arriving water and is under ambient pressure, and a second chamber that is connected to the first chamber and is under vacuum, into which water collecting in the first chamber is sucked and from which the water is eventually drained.
The water draining device of the invention can be used with particular advantage in a press arrangement serving to dewater a pulp web, in particular, a paper or cardboard web, and having at least one elongated press nip in the web travel direction, since an increased volume of water must be taken into account with an elongated press nip.
It is advantageous for at least one of the first chamber and the second chamber to extend at least essentially over the entire machine width.
The first chamber and the second chamber are preferably connected to one another via several apertures distributed over the machine width.
It is also advantageous if the water is drained from the second chamber on at least one of the two machine sides.
In a preferred practical form of embodiment of the water draining device according to the present invention, the two chambers are connected to one another by throttling apertures.
The average direction of flow, i.e., the effective main flow direction of the water flow prevailing in the first chamber, can be at least substantially free of cross-flow.
On the other hand, the average direction of flow, i.e., the effective main flow direction of the water flow prevailing in the second chamber, can have a cross component running in the direction of the machine width.
In a preferred aspect of the invention, the first chamber and the second chamber are connected to one another by at least one pipe, whose one end opens in a respective connecting aperture in a partition provided between the first chamber and the second chamber and whose other end opens into the second chamber. Preferably, several pipes are distributed over the machine width. For example, 0.5 to 5 pipes can be provided per meter.
Preferably, the pipes have a diameter of about 10 to about 100 mm.
The vacuum of the second chamber is preferably smaller than about 0.2 bar, more preferably the vacuum of the second chamber is smaller than or equal to about 0.05 bar.
In one practical aspect of the water draining device of the present invention, the second chamber is limited by a pipe under vacuum that extends in the transverse direction and whose jacket is provided with apertures, via which the first chamber is connected to the second chamber formed by the interior of the pipe.
The receiving tank can be divided into segments over the machine width, or it can be constructed so as to be continuous over the machine width.
The vacuum prevailing in the second chamber is preferably produced by a volumetric pump.
The water can be sucked off from the tank or channel, for example, as in dry cylinders, or like the oil in NFP presses.
A small amount of air, e.g., a few liters per second (l/s), can also be sucked off through the suction apertures. Thus, for example, at a suction aperture diameter of D=5 mm and a pressure difference Dp=5,000 N/m
2
, a volume flow V-air of substantially less than 0.5 m
3
/min can result.
The water draining device of the invention can advantageously be used with a felted press, in particular, a single- or double-felted press, and, in particular, for a press arrangement having at least one longitudinal nip.
The present invention also relates to a press arrangement for dewatering a pulp web, in particular a paper, cardboard, or tissue web, in a machine for its production and/or finishing, composed of at least one press nip formed by two press rolls arranged approximately above one another and pressed against one another, through which, in addition to the pulp web, at least one dewatering belt running above the pulp web to receive the expressed water is conducted, whereby a water receiving device is arranged between the upper press roll and the dewatering belt.
The water thrown off thereby from the usually grooved and/or blind-bored press rolls, must be collected after the press nip and be drained. Otherwise, most of the thrown-off water is absorbed by the continuously revolving dewatering belts, which in particular with the upper dewatering belt, leads to a re-wetting of the pulp web. Water channels that receive and drain the thrown-off water generally serve this purpose.
In particular in cases in which the upper dewatering belt leaves the press nip approximately horizontally or even on an upward incline, however, the water channel can not be positioned sufficiently close to the press nip. As a result, only a relative small portion of the water thrown off from the upper press roll can be collected. The remainder predominantly reaches the upper dewatering belt, which then leads to considerable re-wetting of the pulp web, as already mentioned.
The present invention therefore also relates to improving the efficiency of the water receiving device of press arrangements. In this regard, the water receiving device can be formed by at least one suction channel projecting into the wedge-shaped area between the upper press roll and the dewatering belt and running transverse to the pulp web, which channel is connected to a source of reduced pressure. By using a suction channel, considerably more water can be drained than with a water channel. This is particularly true for press arrangements with an upper dewatering belt that runs approximately horizontally or even on an upward incline after the press nip. The reason for this is, in particular, that the suction channel can be led very far into the wedge-shaped area and the reduced pressure draws a great deal of water into the suction channel.
To encompass the main direction of the thrown-off water, it is sufficient for the suction channel to have a gap width of 1 to 50 mm, preferably 2 to 7 mm, at least in its initial zone. A certain minimum reduced pressure is required in the suction channel for the collected water to overcome the difference in height, particularly with a suction channel inclined upwards. The reduced pressure in the suction channel should therefore be betwee
Prinzing Hans
Steiner Karl
Wolf Robert
Fortuna Jos'e A.
Greenblum & Bernstein P.L.C.
Voith Paper Patent GmbH
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