Headbox

Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...

Reexamination Certificate

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Details

C162S347000, C162S344000

Reexamination Certificate

active

06248214

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority of German Patent Application 198 45 722.7, filed on Oct. 5, 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 headbox for a paper machine having a feed part, a central part extending across the machine width, and a nozzle extending across the machine width. The headbox also has at least one continuous wall that runs across the machine width transverse to the lengthwise flow direction. The central part may be formed of substantially vertical structural members that penetrate the entire pulp flow and can thereby be subject to compressive or tensile forces in a vertical direction across its entire width and across the machine width.
2. Description of Related Art Conventional headboxes are disclosed, for example, in EP 0 323 468 B 1 and EP 0 631 011 A1. These known headboxes are transversely divided overall into sections, i.e., transverse with respect to the lengthwise flow direction. The advantage of such a construction is that it is independent of width and that the easily manipulated reproducible parts reduce costs. However, the practical realization of such embodiments is difficult. For example, in the areas subject to the flow, a relatively large expenditure is required to prevent agglomeration of fibers and similar substances at the edges of the sections. The cost advantage previously achieved is thus lost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved, low cost headbox of the type specified above, in which the problems cited above are eliminated.
According to the invention, a headbox for a paper machine is provided which includes a feed part, a central part extending across a machine width, a nozzle extending across the machine width, having at least one continuous wall running transverse to a lengthwise flow direction; and a plurality of separate support devices distributed across the machine width are attached to the at least one continuous wall, the support devices absorbing and discharging nozzle expansion forces and influencing the nozzle aperture. The resulting lines of force of each support device lies at least substantially in a plane perpendicular to the direction of the machine width and in the flow direction, and the corresponding supporting forces individually, at least substantially, are directed to and absorbed in the central part in the plane of the flow direction.
The support device may be attached to two opposite walls. The central part may be divided into sections across the machine width. The central part may further include a turbulence generator and a plurality of step diffusers. The feed part may be divided into sections across the machine width.
According to another embodiment, the at least one nozzle wall may be mounted so that it can pivot around an axis extending transversely to the flow direction or can move in the flow direction. The at least one continuous nozzle wall has a flexural strength in the transverse direction, ranging from approximately 5×10
10
Nmm
2
to approximately 7.5×10
10
Nmm
2
per 100 mm of wall length measured in the flow direction. The at least one continuous nozzle wall may be positioned on the individual support devices in a sectional manner.
Each different support device may be individually connected to the central part and at least one continuous nozzle wall. Each support device may be independent so that, at least substantially, any tensile, compression, and/or bending forces are not transmitted therebetween. The at least one support device allocated to a pivoting nozzle wall may further include a static model with at least three bars, which are connected directly from the central part and the pivoting nozzle wall at least substantially at a joint connection location, The at least one bar near the feed part and at least one additional bar near the pivoting axis act on the central part, and at least a third bar acts on the pivoting nozzle wall. The at least three bars may be allocated to a respective support device in or symmetrical with respect to a plane that runs perpendicular to the direction of the machine width and in the lengthwise flow direction. The bar provided near the pivoting axis may directly or indirectly engage the pivotally mounted nozzle wall. In one embodiment, the length of at least one bar is adjustable. Further, the position of at least one point of contact of the bars with the central part or the pivoting nozzle wall is adjustable. Furthermore, a change in all support devices is made in a similar manner by a lifting device, a pneumatic or hydraulic cylinder, or a pneumatic spring bellow, by way of toggle joints allocated to the bars or by a temperature change. The bar lengths or a position of points of impact in all support devices may be changed simultaneously, in the same manner, and evenly, in order to evenly move a pivoting nozzle wall across the entire width in the direction of machine width.
The support devices may have at least one bar to which a device is allocated for individual additional fine adjustment of the nozzle wall. The fine adjustment device is actuated individually or together with other adjustment devices.
According to another embodiment, a one piece slide rest is formed from the bars and is supported on the central part. The one piece slide rest may be formed from the bars supported on the nozzle wall and has a joint connection location in which the bars engage.
According to another embodiment, the nozzle walls are structured without reinforcing ribs and reinforcing sections extending in the transverse direction. Further, the outside of the nozzle walls facing away from the flow may include grooves extending in the flow direction for averaging tension.
According to another embodiment, the headbox also includes a non-pivoting nozzle wall connected by means of ribs or sections to a headbox foundation. Further, the support devices may be equally spaced. Alternatively, the support devices are proportionally spaced. For example, the distances separating the support devices fall may within a range from approximately 50 to approximately 1,000 mm, and preferably in a range from approximately 200 to approximately 500 mm.
According to a further embodiment, the pivoting axis of the pivoting nozzle wall is located near the central part. In addition, the headbox may pivot around a transverse axis located near the nozzle end. In this case, two pivoted bearings may be provided between a headbox side wall and a lateral slide rest. The slide rest may be placed on a seat or a headbox foundation.
According to another embodiment, the headbox is pivoted by at least one adjustable support device that directly or indirectly engages the central part. The support device is provided at a distance from the nozzle end near the central part. The headbox may be pivoted by several support devices distributed across the machine width so that deflection of the headbox structure is at least substantially even in the transverse direction outside of support points. The pivoting axis near the nozzle end may be defined by guidance devices in which it is mounted.
According to another embodiment, the headbox is mounted on at least one support device comprising at least two support units that define two support points having different distances from the nozzle end, and carry out different lifting motions, so that the headbox can be pivoted approximately around the nozzle end.
According to a further embodiment, on the upstream side, a feeding plate is allocated to the central part and reinforces the central part or acts as an attachment element for additional functional elements, the feeding plate extending transversely to the flow direction substantially across the entire width of the central part. The feeding plate may form part of the feed part. In addition, the feeding plate may extend above the level of the feed part.
According to another embodiment, at le

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