1. Field of the Invention
The present invention relates to a machine a machine for the production of a fibrous web, and, more particularly, to a former and former headbox.
2. Description of the Related Art
With suction formers, a longitudinal orientation of the fibers occurs at an appropriate increase in the operating speed of the paper machine in question. This may limit the scope of application of such suction formers to low operational speeds.
A relatively strong transverse orientation of the fibers, as well as a low longitudinal/transverse ratio can be achieved (see for example U.S. Pat. No. 5,876,364) through transverse movements that are indicated through various swirl-producing bodies in the turbulence block. However, a consequence of these transverse motions is the inherent danger of the suspension stream that is delivered by the headbox of the respective former bursting open when encountering an open surface, for example on the Fourdrinier wire.
The present invention provides an improved former and former headbox whereby the cited problems are eliminated.
The present invention provides a former, particularly a suction former of a machine for the production of a fibrous web, particularly a paper or cardboard web comprising a headbox equipped with at least one stock suspension feed, one turbulence block equipped with several channels and/or a tube generator equipped with several channels, and a headbox nozzle whose suspension jet strikes an exposed or open surface of a dewatering belt, specifically a wire. Turbulence generating elements are allocated to at least a section of the channels and/or the headbox nozzle, in order to create turbulent flows in the suspension substreams in the channels, or in the headbox nozzle. The side of the suspension stream facing away from the dewatering belt is covered at least partially by a wall. Based on this configuration, the danger of the suspension stream bursting open is reduced to a minimum. In addition, swirling motions of considerably higher intensity than occur on conventional Fourdrinier wire formers are now permissible.
The wall can be stationary or in motion. A stationary wall can, for example, be allocated to the headbox on which it can be installed adjustably. The wall can in addition, be permeable to water or impermeable to water. A movable wall or a wall in motion can be in the embodiment of an additional dewatering belt, that can specifically be in the form of a revolving wire.
In the coverage area the wall can possess an at least partially curved progression and/or an at least partially straight progression. Moreover, in a practical embodiment the lower wall has a maximum length of 90%, preferably of 60%, especially of 30% of the length of the upper wall. In a preferred practical embodiment of the former in accordance with the present invention, at least some of the channels are equipped with the turbulence generating inserts. Such turbulence generating inserts can basically be provided in the channels of a respective turbulence block and/or in the channels of a respective tube generator.
In hitherto conventional suction formers or in twin wire formers eddies occur in pairs in opposite rotational directions, that can lead to stripes. These are known as the so-called “Taylor-Görtler-Eddies” in Central Europe. The stripes occur especially in curved dewatering surfaces.
The present invention provides an improved former, particularly a suction former or twin wire former for a machine for the production of a fibrous web, specifically a paper or cardboard web, in which the previously cited problems are eliminated.
In accordance with an additional aspect of the present invention a former, specifically a suction former or twin wire former of a machine for the production of a fibrous web, specifically a paper or cardboard web is provided or this purpose; comprising a headbox that is equipped with at least one stock suspension feed, one turbulence block equipped with several channels and/or a tube generator equipped with several channels and a headbox nozzle. Turbulence generating elements are allocated to at least a section of the channels in order to create turbulent flows that rotate in the same direction in the suspension substreams in the channels. Same directional turbulence movement suppresses the undesirable stripes.
In a functional practical embodiment of the present invention helix type spirals are installed in at least a section of the channels in order to create turbulent flows that rotate in the same direction. Such helix type spirals can, for example, be installed in the channels of a turbulence block and/or in the channels of tube generator. The creation of turbulences through the means of helix type spirals can for example occur as described in U.S. Pat. No. 5,876,464.
Alternatively, or in addition, turbulent flows that are rotating in the same direction can be created particularly by the fact that, in a headbox comprising a tube generator, the supply of stock suspension through nozzles into a respective tube channel occurs asymmetrically and preferably at least essentially tangentially to the tube wall, relative to a center plane progressing in longitudinal direction through the tube channel. Advantageously, the stock suspension is fed through nozzles only on one side of the center plane respectively. Preferably, suspension supplied to the relevant pipe channels is fed into the various pipe channels through nozzles always on the same side of the respective center planes.
In contrast to Fourdrinier wires, the previously discussed, deliberately produced turbulences are kept very small in the sheet formation zone in other types of formers, particularly in suction and twin wire formers, since the surface of the suspension is “covered”, resulting in improved sheet formation, even at an increased stock consistency. In addition the headbox can be equipped with at least one feed for dilution water, air, chemicals and/or similar substances. The supply of dilution water, air, chemicals and/or similar substances may essentially occur in axial direction of a respective channel.
In accordance with an advantageous embodiment of the present invention, the wall can be located in an area opposite the forming roll and can be at least partially curved according to a radius of curvature that is preferably larger than or equal to the radius of the forming roll. Basically however, a smaller radius is also feasible, at least in sections. The wall can for example be stationary. Thereby it would preferably cover the circumferential surface of the forming roll, that is in a range of approximately 100 to approximately 400 mm. The stationary wall can particularly be rigid, deflection resistant or not deflection resistant.
In accordance with an additional advantageous design of the present invention whereby the wall is again provided in an area opposite the forming roll and is curved, at least partially, according to a curvature radius that is preferably larger than or equal to the radius of the forming roll, the wall can be movable or in motion and can be formed by an additional dewatering belt, particularly a revolving wire. In this instance, the wall preferably covers a circumferential area of this forming roll that is in the range of approximately 100 mm to approximately 1500 mm and/or corresponds with a circumferential angle of the forming roll of approximately 25° to approximately 120°.
The additional dewatering belt that forms the wall can be routed around a breast roll, prior to the area covering the forming roll, when viewed in the direction of belt travel. The curvature radius of the wall in the area covering the forming roll is preferably larger than the radius of the breast roll, or respectively the corresponding curvature radius of the wall in the area of this breast roll.
The headbox nozzle can be sectioned by at least one lamellar plate. A configuration without lamellar plates is also feasible. In a functional advantageous design at least one lamellar plate and/or at least one nozzle wall exhibit contours, especially swirl-producing washboard contours.
Alternatively, or in addition, at least one lamellar plate and/or at least one nozzle wall can have contours that serve to generate turbulent motion. At least one lamellar plate and/or at least one nozzle wall can for example be equipped with at least one interference body. Preferably the at least one interference body of the at least one nozzle wall is in the form of preferably a discontinuous tapering of the cross section. This formation provides a fluidic ideal turbulence chamber. In addition, at least one lamellar plate has a length not exceeding 70% of the length of the headbox nozzle.
In order to attain a sufficient effect, the headbox nozzle should be as short as possible. The headbox nozzle should preferably be shorter than approximately 400 mm. It is also advantageous if the outlet cross section of the channels or pipes is at least essentially round, since a square outlet cross section would dampen the effect.
In accordance with the present invention a headox is furthermore disclosed especially for a former of the relevant type previously described. Such a headbox includes at least one stock suspension feed, one turbulence block equipped with several channels and/or a tube generator equipped with several channels and a headbox nozzle. Turbulence generating elements are allocated to at least a section of the channels in order to create turbulent flows that rotate in the same direction in the suspension sub-streams in the channels.
In accordance with an additional aspect of the present invention a headbox, particularly for a former of the type previously described is provided, including at least one stock suspension feed, one turbulence block equipped with several channels and/or a tube generator equipped with several channels and a headbox nozzle. Turbulence generating elements are allocated to at least a section of the channels in order to create turbulent flows, rotating in the same direction, in the suspension sub-streams in the channels.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
d are cross-sectional views of various designs of the turbulence generating inserts of the present invention, viewed in the direction of arrow V in
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
A headbox 12 that is allocated to this former 10 includes a stock suspension feed 14, at least one turbulence block 18 that is equipped with several channels 16 and a headbox nozzle 20 whose suspension stream 22 strikes an exposed, that is an open surface 24′ of dewatering belt 24, which in this example is a wire.
Turbulence generating elements 26, in this example turbulence generating inserts, are allocated to at least one section of channels 16, in order to create turbulent flows 28 in the suspension substreams that are guided through the channels (also see
The side of suspension stream 22 facing away from the dewatering belt 24 is covered at least partially by wall 30. In the present example wall 30 is stationary, installed preferably adjustably on headbox 12. As can be seen in
As can be seen in
Wall 30 can include an upper wall shown at 30 and lower wall 30′. Lower wall 30′ has a lower wall length not greater than 90%, preferably 60%, especially 30% of an upper wall length.
Stationary wall 30 can for example cover a circumferential length L of forming roll 38, that is in a range of approximately 100 to approximately 400 mm. In
In the example illustrated in
In the present example wall 30 is impermeable to water. As can be seen especially from the following design examples, this type of wall may basically also be water permeable, especially if a movable wall or a wall in motion is provided in the embodiment of a dewatering belt, such as especially a wire.
As can be seen in
As illustrated in particular in
In an area opposite forming roll 38 movable wall 30 that is formed by dewatering belt 54 is curved, at least partially according to a curvature radius R1 that is preferably larger than or equal to radius R2 of forming roll 38. Movable wall 30 can, for example, cover a circumferential length L of the forming roll 38 that is in a range of approximately 100 to approximately 1500 mm and/or corresponds with a circumferential angle a of forming roll 38 of approximately 25° to approximately 120°. As can be seen in
In order to achieve an appropriate effect a respective headbox nozzle 20 should be as short as possible, whereby headbox nozzle 20 is preferably shorter than approximately 400 mm. The outlet cross section of channels 16 or pipes is preferably at least essentially round, since a square cross section would dampen the effect.
Other desired combinations of the various former variations, as well as of the various headbox variations are feasible.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
10102198.4 | Jan 2001 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP02/00415 | 1/17/2002 | WO |