Abstract:
A headbox for a machine for producing a fibrous material web, in particular a paper or cardboard web, includes: a central assembly preferably forming the carrier elements of a turbulence generator, said assembly having a table leaf on the bottom side; and a headbox nozzle adjoining directly downstream in the machine running direction and extending in the machine transverse direction, said nozzle comprising at least one lower and one upper continuous nozzle wall extending over the machine width. The lower nozzle wall of the headbox nozzle of the headbox includes a lower lip plate, in particular a lower lip carrier plate, which is connected, in particular welded, to the table leaf of the central assembly by means of ribs extending in the machine running direction and spaced apart in the machine transverse direction. The ribs are designed in an elastic or pliable manner in the machine transverse direction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of PCT application No. PCT/EP2010/056519, entitled “HEADBOX FOR A MACHINE FOR PRODUCING A FIBROUS MATERIAL WEB, IN PARTICULAR A PAPER OR CARDBOARD WEB”, filed May 12, 2010, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a headbox for a machine for producing a fibrous web, in particular a paper or cardboard web, comprising a central assembly preferably forming the carrier elements of a turbulence generator; said assembly having a table leaf on the bottom side and further comprising a headbox nozzle adjoining directly downstream in machine direction and extending in transverse machine direction; said nozzle comprising at least one lower and one upper continuous nozzle wall extending across the machine width. 
         [0004]    2. Description of the Related Art 
         [0005]    A headbox of this type is known for example from publications DE 198 45 722 A1 and EP 0 997 578 A1 and EP 1 342 835 A2. 
         [0006]    The headbox discussed in the first publication has a lower nozzle wall mounted to slide on a support component of a base plate or table leaf and movable relative thereto in longitudinal flow direction. The lower nozzle wall is hereby movable in the desired direction through at least one for example mechanical, hydraulic and/or pneumatic adjustment device. This adjustment device engages on the support component and on the lower nozzle wall, and the support component extends over a substantial length of the lower nozzle wall. 
         [0007]    The headbox of the second referred to publication comprises a headbox nozzle having a lower nozzle wall and an upper nozzle wall. The upper nozzle wall is pivoted by means of a hinge around an axis extending in cross machine direction. In contrast, the lower nozzle wall is movable in machine direction on a stationary base plate or table leaf. 
         [0008]    These two illustrated headboxes represent a first headbox type with an open turbulence generator which in each instance is mounted stationary, in particular bolted onto the table top and which represents one central assembly. 
         [0009]    On a second headbox type the turbulence generator forming the central assembly is a closed design, in other words, it is an enclosed box-type turbulence generator. With a headbox of this type which is known for example from publication EP 1 653 000 A1 at least one heating chamber through which at least one fluid flows is provided. The sealed turbulence generator hereby assumes the function of a heat exchanger which takes the heat from the fibrous stock suspension fed to it and transfers it to the at least one fluid. Through this at least one heating chamber differential heating, or heating at different speeds of functionally important components of the headbox are equalized. 
         [0010]    Since on a headbox of the first type this heat exchanger system is not provided, or respectively cannot be realized, a differential thermal expansion of the functionally important components cannot be avoided, in particular during the start-up process of the headbox with a fibrous stock suspension at a temperature of up to 70° C. The components which are in contact with the stock, for example the two machine-wide nozzle walls and the turbulence pipes, expand faster than components which are not in contact with the stock, for example the cover plate of the turbulence generator and the table leaf. Due to the rigid connections of the components in contact with the stock and those not in contact with the stock, generally high tensions, in particular bending stresses and extensive deformations occur on the headbox, and in turn also on the headbox nozzle. These extensive deformations lead to disadvantageous operating conditions of the headbox which are well known to the expert, for example a different gap width of the headbox nozzle in cross machine direction and therefore also to distinctly negative quality characteristics in the fibrous web which is to be produced. Moreover, the increased tensions, in particular the bending stresses, can also lead to a structural failure of individual components, for example of the welding joints. 
         [0011]    In order to reduce or avoid the cited disadvantages, arrangements have already been made to provide the box-type components of the headbox on their inside circumference and preferably opposite the box walls which are contacted by the fibrous stock suspension with heating pockets which are flushed with a temperature moderating liquid. Heating pockets of this type are known for example from the German disclosure document DE 41 06 763 A1. In order to achieve an isothermal headbox up to six heating pockets were placed for example at different locations. 
         [0012]    The use of heating pockets however always represents a compromise since there are always warm and cold locations and they conditionally require many additional parts which—in regard to the use of a tempering fluid—enhance the risk of leakage. Moreover, the internal rib structure is expensive and the heating and distribution system for the tempering fluid is cost intensive, both in regard to purchase as well as operation. Also, the determination of the location and the size of the heating pocket is dependent upon the components used so that a greater range of variants occurs. The expensive foundation can also not be neglected since even with a non-operational heating system the occurring and not insignificant deformation forces must be absorbed. 
         [0013]    It is therefore the objective of the current invention, and what is needed in the art is, to improve a headbox of the type described at the beginning so that the known disadvantages of the current state of the art are most extensively, preferably completely, avoided. The headbox should in particular always ensure an as parallel and straight outlet gap on the headbox nozzle as possible with an as cost-effective as possible construction, simple handling and minimum maintenance expenditure. 
         [0014]    An as uniform as possible impingement line of the fibrous stock suspension jet coming from the headbox nozzle onto the at least one wire in the wire section should thereby also be achievable without problems. 
       SUMMARY OF THE INVENTION 
       [0015]    This objective is met in, and the present invention provides, a headbox of the type described at the beginning in that the lower nozzle wall of the headbox nozzle comprises a lower lip plate, in particular a lower lip support plate which is connected, in particular welded, to the table leaf of the central assembly by means of a plurality of ribs extending in machine direction and spaced apart in cross machine direction, and that the ribs are designed to be pliable or flexible in cross machine direction. 
         [0016]    The objective of the invention is hereby completely met. 
         [0017]    Through the new design of the connecting region between lower lip plate, lower lip support plate of the lower nozzle wall of the headbox nozzle, and the table leaf of the central assembly, sufficient sliding resilience is ensured in order to compensate for occurring tensions, in particular bending stresses and deformations. The redesign of this compensating connecting region has no structural-mechanical disadvantages compared to the current state of the art. The flexural strength in regard to a possible expansion of the headbox nozzle is the same, since the geometric moment of inertia of the ribs which are designed to be pliable and flexible only in cross machine direction is not being reduced. 
         [0018]    The required sliding resilience of the entire table construction of the central assembly is comprehensively provided in order to compensate for influences such as, for example, different thermal expansions in cross machine direction. 
         [0019]    Moreover, this new design does not need to provide explicit and possibly cost-intensive reinforcement in cross machine direction. 
         [0020]    Also, the material of the ribs which are designed to be pliable and flexible in cross machine direction only can be varied. One the one hand it can be a simple structural steel, on the other hand also a stainless steel. 
         [0021]    The individual ribs preferably extend at least partially generally vertically, that is perpendicular to the lower nozzle wall of the headbox nozzle and the table leaf of the central assembly. This arrangement provides an optimum opportunity to absorb and transmit the forces prevailing during operation of the headbox. 
         [0022]    The individual ribs moreover have preferably a rib thickness in the range of 10 to 75 mm, preferably 15 to 60 mm, in particular 20 to 50 mm. Due to these relatively small rib thicknesses the tensions, in particular the bending stresses in the joints, in particular in the weld seams, are also minimized. In principle, the smallest possible rib thicknesses are to be strived for, whereby they are however essentially dependent upon the machine speed of the machine for the production of the fibrous web and are therefore directly dependent upon the nozzle pressure prevailing in the headbox nozzle. 
         [0023]    The individual ribs moreover preferably have a rib separation in the range of 100 to 500 mm, preferably of 125 mm to 400 mm, in particular 150 to 250 mm. This arrangement provides again an optimum opportunity to absorb and transmit the forces prevailing during operation of the headbox. 
         [0024]    In principle, a reduction in the rib separation is preferable to an increase in the rib thicknesses. Therefore, a combination of 20 mm rib thickness and 200 mm rib separation is preferable for example to the combination of 40 mm rib thickness and 400 mm rib separation. 
         [0025]    Moreover, the table leaf of the central assembly—in the region facing the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle—is preferably provided with a chamfer forming a first bevel, whereby the chamfer can have a length of at least 25 mm, preferably at least 40 mm, in particular at least 50 mm. The table leaf of the central assembly can therefore receive a generously dimensioned slant at its rear and upper end, viewed in machine direction. 
         [0026]    Also the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle—in the region facing the table leaf of the central assembly—is preferably provided with a chamfer forming a second bevel, whereby the chamfer has preferably a length of at least 25 mm, preferably at least 40 mm, in particular at least 50 mm. The lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle can therefore receive a generously dimensioned slant at its frond and lower end, viewed in machine direction. 
         [0027]    These two bevels in the form of chamfers increase the minimum rib height in the addressed connecting region by a multiple. The connection between lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox and the table leaf of the central assembly can thereby be designed flexible and direct. 
         [0028]    Moreover, bevels formed by the two chamfers preferably encompass together an angle of 0 to 45°, preferably 5 to 30°, in particular 10 to 20°. The two chamfers may progress parallel to each other, or divergent. This allows for simpler insertion of ribs during the production process. 
         [0029]    The individual ribs which connect the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle with the table leaf of the central assembly are preferably structured to fill in, in the regions of the two chamfers in order to thereby maintain the necessary flexural strength of the table leaf of the central assembly. 
         [0030]    Moreover, the table leaf of the central assembly and the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle preferably have a perpendicular distance in the range of 10 to 100 mm, preferably 20 to 80 mm, in particular 25 to 65 mm, whereby the perpendicular distance between the theoretic inside extension of the table leaf of the central assembly and the theoretic corner edge of the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle is measured. This causes a largely inflexible, rigid and indirect connection between the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle and the table leaf of the central assembly. A certain varying deformation, in particular through thermal heating, can be compensated by this design. Greater deformations (in particular with large outlet widths) can however be absorbed only within limits, since the deformations may get relatively large in the outer regions (edges). 
         [0031]    The individual ribs are furthermore provided with a compensating gap in the region facing the front side of the table leaf, whereby the respective compensating gap has a height in the range of 2 to 15 mm, preferably 3 to 12 mm, in particular 5 to 10 mm. This ensures a defined contact with the adjacent components. 
         [0032]    Moreover, the joints between the table leaf of the central assembly and the individual ribs and/or between the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle and the individual ribs which are in the form of welding seams have preferably a welding seam thickness in the range of 3 to 15 mm, preferably 4 to 12 mm, in particular 5 to 10 mm. Ideally, the welding seams are to be in the form of fillet welds. 
         [0033]    Even with larger outlet widths, the tensions, in particular the bending stresses and consequently the deformations in the ribs and welded seams are kept in an acceptable range by this means. 
         [0034]    The minimum height of the individual ribs between the table leaf of the central assembly and the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle preferably assumes a value in the range of 1.5 to 4, preferably 2 to 3 times the perpendicular distance between the table leaf of the central assembly and the lower lip plate, in particular the lower lip support plate of the lower nozzle wall of the headbox nozzle. This again provides a substantial contribution toward maintaining the essential flexural strength of the table leaf of the central assembly. 
         [0035]    The individual ribs respectively are preferably connected directly or indirectly, in particular by at least one hinged joint and a base plate and/or a pedestal with the bed plate. This type of connection allows for a simple and rapid adjustment, in particular pivoting of the entire headbox. 
         [0036]    Moreover, the lower lip support plate of the lower nozzle wall of the headbox nozzle is equipped preferably on the upper and outlet side with a preferably positionable lower lip. This creates a practicable replacement possibility and noticeably improves production of the lower nozzle wall. 
         [0037]    The inventive headbox can also be used very advantageously in a machine for the production of a fibrous web from at least one fibrous stock suspension. Thereby, the preferably dilution water controlled headbox can be designed as a single layer or multi-layer headbox and the fibrous web may be a paper, cardboard or tissue web. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    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: 
           [0039]      FIG. 1  a schematic and partially cut side view of a headbox according to the current state of the art; 
           [0040]      FIG. 2  a schematic partial sectional side view of a preferred design form of a headbox according to the invention; 
           [0041]      FIG. 3  a schematic front view of the inventive headbox according to  FIG. 2 ; 
           [0042]      FIG. 4  a schematic perspective partial depiction of the headbox according to  FIG. 2 ; 
           [0043]      FIGS. 5 and 6  two schematic perspective partial views of a rib of the inventive headbox in  FIG. 2 ; and 
           [0044]      FIG. 7  a schematic sectional side view of the inventive headbox which is partially sectionally depicted in  FIG. 2 . 
       
    
    
       [0045]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0046]      FIG. 1  is a purely schematic illustration of a headbox  1  which is known from the current state of the art for a Fourdrinier-former in a machine to produce a fibrous web. The fibrous web may in particular be in the embodiment of a paper, cardboard or tissue web. 
         [0047]    In the current example, a central assembly  2  of known headbox  1  comprises a lower arm formed by a table leaf  3 , an upper arm progressing preferably at least partially essentially parallel thereto and formed by a cover plate  4 , an upstream first central component  5 , and a second central component positioned further back or downstream, viewed in machine direction L (arrow). Cover plate  4  and the two central components  5 ,  6  which are located between said cover plate  4  and table leaf  3  hereby form preferably support elements of a turbulence generator  7 . 
         [0048]    Central assembly  2  which, in the current design example is in the embodiment of a turbulence generator  7 , is equipped with several step diffusors or with continuous turbulence pipes. 
         [0049]    At least one fibrous stock suspension  9  is fed directly to central assembly  2 , for example through a lateral distribution manifold  8 . Feeding the at least one fibrous stock suspension  9  may also occur indirectly, for example through a preferably machine-wide intermediate chamber. 
         [0050]    Known headbox  1  further includes headbox nozzle  10  extending in cross machine direction Q (arrow) across machine width B (arrow), having a lower and an upper nozzle wall  11  or respectively  12 , extending respectively across machine width B (arrow). In the current design example, upper nozzle wall  12  can be pivoted by means of a hinge  13  around an axis A (swivel axis) (double arrow S) extending in cross machine direction Q (arrow). Moreover, in the current example the lower nozzle wall  11  which is in the embodiment of simple lower lip plate  14  is movable (double arrow V) in machine direction L (arrow) on stationary table leaf  3 . Lower lip plate  14  and lower nozzle wall  11  of headbox nozzle  10  represent one assembly. 
         [0051]    Headbox nozzle  10  is located immediately following central assembly  2  in machine direction L (arrow). 
         [0052]    The flow is directed to an outlet gap  16  via lower nozzle wall  11  and upper nozzle wall  12 , as well as lateral limits  15 , for example side plates or similar devices. The machine-wide stock jet emerging from outlet gap  16  is admitted onto a continuous revolving wire  18  in the region of a breast roll  17 . 
         [0053]    The stationary table leaf  3  for lower nozzle wall  11  or a stationary nozzle wall is supported on a bed plate  20  by several support elements  19  which are distributed across the machine width B (arrow). Support elements  19  are designed to be pliable or flexible in cross machine direction Q (arrow). 
         [0054]    Individual support elements  19  extend vertically, that is perpendicular to lower nozzle wall  12  or respectively to table leaf  3 . In the current example these support elements  19  are in the embodiment of plates, located parallel to machine direction L (arrow). They can however also be in the form of stud bolts or similar devices. 
         [0055]    In the current design example the support elements  19  are connected with bed plate  20  through a pedestal  21 , consisting for example of concrete. In principle, these support elements  19  can however also be connected directly with base plate  20 . At the other end, support elements  19  are respectively connected with table leaf  3 . In the case of a non-movable lower nozzle wall which, in other words is a single component together with the table leaf, the support elements would be connected with the non-movable lower nozzle wall. 
         [0056]    Upper nozzle wall  12  which is pivoted by means of hinge  13  around axis A is connected with a cross bar  23  which is located above axis A by means of several separate support elements  22  which are distributed across machine width B (arrow). Support elements  22  are again designed to be pliable and flexible in cross machine direction Q (arrow). 
         [0057]    One or several lifting elements  24  are hinged on the one hand on central assembly  2  and on the other hand on cross bar  23  by means of articulated axis  25  or respectively  26 . Through these lifting elements  24  upper nozzle wall  12  can thereby be pivoted around axis A in direction of double arrow S. The lifting elements may for example be threaded spindles, hydraulic cylinders and/or similar devices. 
         [0058]    Cross bar  23  may for example be in the embodiment of an upright sheet metal or a hollow beam. 
         [0059]    On the back end of cover plate  4  of central assembly  2 , viewed in machine direction L (arrow), a continuous hinged support  27  of hinge  13  extending in cross machine direction Q (arrow) is provided into which a counter element  28  which is provided on upper nozzle wall  12  engages. 
         [0060]    Known headbox  1  illustrated in  FIG. 1  is oriented substantially horizontally. It can however also be oriented with its outlet gap  16  slanting upwards into an inlet gap formed between two wires. 
         [0061]      FIG. 2  shows a schematic cut partial side view of a preferred design form of a headbox according to the invention. In regard to the general structural design of the illustrated inventive headbox  1  we refer you to the design and description of known headbox  1  illustrated in  FIG. 1 . 
         [0062]    Central assembly  2  of inventive headbox  1  again includes a table leaf  3 , a cover plate  4  preferably at least substantially parallel thereto, an upstream first central component  5  and a second central component  6 , located further back or downstream, viewed in machine direction L (arrow). Cover plate  4  and the two central components  5 ,  6  which are located between said cover plate  4  and table leaf  3  hereby form preferably support elements of a turbulence generator  7 . 
         [0063]    Lower nozzle wall  11  of headbox nozzle  10  however, comprises a lower lip plate  14 , in particular a lower lip support plate  14 . 1 , which is connected, in particular welded to, table leaf  3  of central assembly  2  by means of a plurality of ribs  29  extending in machine direction L (arrow) and spaced apart in cross machine direction Q (arrow). Ribs  29  are designed to be pliable or flexible in cross machine direction Q (arrow). 
         [0064]    The individual ribs  29  extend at least partially generally vertically, that is perpendicular to lower nozzle wall  11  of headbox nozzle  10  and table leaf  3  of central assembly  2  (see  FIG. 3 ). 
         [0065]    Moreover, table leaf  3  of central assembly  2 —in region  30  facing lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall H of headbox nozzle  10 —is provided with a chamfer  31  forming a first bevel  32 , whereby chamfer  31  preferably has a length L. 31  of at least 25 mm, preferably at least 40 mm, in particular at least 50 mm. 
         [0066]    Also lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10 —in region  33  facing table leaf  3  of central assembly  2 —is provided with a chamfer  34  forming a second bevel  35 , whereby chamfer  34  has preferably a length L. 34  of at least 25 mm, preferably at least 40 mm, in particular at least 50 mm. 
         [0067]    Bevels  32  or  35  respectively formed by the two chamfers  31  or  34  respectively preferably encompass an angle of 0 to 45°, preferably 5 to 30°, in particular 10 to 20°. At an angle W of 0° they progress parallel to each other, at an angle W of 45° they progress below a half right angle to each other. 
         [0068]    Furthermore, individual ribs  29  which connect lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  with table leaf  3  of central assembly  2  are preferably structured to fill in, in the regions of the two chamfers  31  or  34  respectively. 
         [0069]    Table leaf  3  of central assembly  2  and lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  have a perpendicular distance C in the range of 10 to 100 mm, preferably 20 to 80 mm, in particular 25 to 65 mm. The perpendicular distance C is hereby measured per definition between the theoretic inside extension  36  of table leaf  3  of central assembly  2  and theoretic corner edge  37  of lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10 . 
         [0070]    Moreover, the individual ribs  29  are provided with a compensating gap  40  in region  39  facing front side  38  of table leaf  3 , whereby the respective compensating gap  40  has a compensating gap height H.40 in the range of 2 to 15 mm, preferably 3 to 12 mm, in particular 5 to 10 mm. 
         [0071]    Minimum height H.29 of individual ribs  29  between table leaf  3  of central assembly  2  and lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  assumes a value in the range of 1.5 to 4, preferably 2 to 3 times the perpendicular distance C between table leaf  3  of central assembly  2  and lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10 . 
         [0072]    Lower lip support plate  14  of lower nozzle wall  11  of headbox nozzle  10  is equipped on the upper and outlet side with a preferably positionable lower lip  43 . 
         [0073]      FIG. 3  shows a schematic front view of headbox  1  according to the invention shown in  FIG. 2 . 
         [0074]    Individual ribs  29  have a rib thickness D. 29  in the range of 10 to 75 mm, preferably 15 to 60 mm, in particular 20 to 50 mm, and a rib separation T. 29  in the range of 100 to 500 mm, preferably of 125 mm to 400 mm, in particular 150 to 250 mm. 
         [0075]    Joints  41  which are in the form of welding seams  42  between table leaf  3  of central assembly  2  and individual ribs  29  and/or between lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  and individual ribs  29  have a welding seam thickness D. 42  in the range of 3 to 15 mm, preferably 4 to 12 mm, in particular 5 to 10 mm. For reasons of comprehension, welding seams  42  are shown over-dimensioned only on center rib  29 . 
         [0076]      FIG. 4  shows a schematic perspective partial illustration of inventive headbox  1  shown in  FIG. 2 . 
         [0077]    Central assembly  2  of inventive headbox  1  comprises a table leaf  3 , a cover plate  4  preferably at least substantially parallel thereto, an upstream—however not illustrated—first central component and a second central component  6 , located further back or downstream, viewed in machine direction L (arrow). Cover plate  4  and the two central components which are located between said cover plate  4  and table leaf  3  hereby form preferably again support elements of a turbulence generator  7 . 
         [0078]    Turbulence generator  7  is equipped with several step diffusors or with continuous turbulence pipes. 
         [0079]    Lower nozzle wall H of headbox nozzle  10  comprises a lower lip plate  14 , in particular a lower lip support plate  14 . 1  which is connected, in particular welded to table leaf  3  of central assembly  2  by means of a plurality of ribs  29  extending in machine direction L (arrow) and spaced apart in cross machine direction Q (arrow). Ribs  29  are designed to be pliable or flexible in cross machine direction Q (arrow). 
         [0080]    The individual ribs  29  extend at least partially generally vertically, that is perpendicular to lower nozzle wall  11  of headbox nozzle  10  and table leaf  3  of central assembly  2  (see  FIG. 3 ). 
         [0081]    Table leaf  3  of central assembly  2 —in region  30  facing lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10 —is provided with a chamfer  31  forming a first bevel  32 . Moreover, lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  is provided with a chamfer  34  forming a second bevel  35  in region  33  facing table leaf  3  of central assembly  2 . 
         [0082]      FIGS. 5 and 6  show two schematic partial depictions of a rib  29  of inventive headbox  1  shown in  FIG. 2 . 
         [0083]    Respective lower nozzle wall  11  of headbox nozzle  10  comprises a separate lower lip plate  14 , in particular a separate lower lip support plate  14 . 1  which is connected, in particular welded, to table leaf  3  of central assembly  2  by means of a plurality of ribs  29  extending in machine direction L (arrow) and spaced apart in cross machine direction Q (arrow). Ribs  29  are designed to be pliable or flexible in cross machine direction Q (arrow). 
         [0084]    The individual ribs  29  extend at least partially generally vertically, that is perpendicular to lower nozzle wall  11  of headbox nozzle  10  and table leaf  3  central assembly  2  (see  FIG. 3 ). 
         [0085]    The individual ribs  29  have a rib thickness D. 29  in the range of 10 to 75 mm, preferably 15 to 60 mm, in particular 20 to 50 mm (see  FIG. 5 ). 
         [0086]    Individual ribs  29  are furthermore provided with a compensating gap  40  in region  39  facing front side  38  of respective table leaf  3 . 
         [0087]    Table leaf  3  of the respective central assembly  2 —in region  30  facing lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10 —is provided with a chamfer  31  forming a first bevel  32 . Moreover, lower lip plate  14 , in particular lower lip support plate  14 . 1  of lower nozzle wall  11  of headbox nozzle  10  is provided with a chamfer  34  forming a second bevel  35  in region  33  facing table leaf  3  of central assembly  2 . 
         [0088]    The respective lower lip support plate  14  of lower nozzle wall  11  of individual headbox nozzle  10  is equipped on the upper and outlet side with a preferably positionable lower lip  43 . 
         [0089]      FIG. 7  is a schematic sectional side view of inventive headbox  1  which is depicted in partial sectional view in  FIG. 2 . 
         [0090]    In regard to the general structural design of the illustrated inventive headbox  1  we refer you to the design and description of known headbox  1  illustrated in  FIG. 1 . In regard to the inventive design of headbox  1  we refer you to the design and description of the inventive headbox  1  illustrated in  FIG. 2 . 
         [0091]    It can be clearly seen that individual ribs  29  of inventive headbox  1  are connected indirectly with bed plate  20 . The indirect connection occurs on the inlet side by means of at least one machine-wide hinge  44  and one pedestal  21  and on the outlet side by means of several lifting elements  45  arranged at a distance from each other and which are only indicated here. Lifting elements  45  may for example be threaded spindles, hydraulic cylinders and/or similar devices. Inventive headbox  1  is therefore adjustable in its position. 
         [0092]    Obviously, the connection may also be implemented directly by means of at least a hinged joint and a base plate and/or a pedestal. A direct connection of the inventive headbox  1  with bed plate  20  is also possible. 
         [0093]    Inventive headbox  1  illustrated and accordingly described in  FIGS. 2 through 7  can also be used very advantageously in a machine for the production of a fibrous web, in particular a paper, cardboard or tissue web. 
         [0094]    In summary it must be stated that the invention creates a headbox of the type described at the beginning, whereby the known disadvantages of the current state of the art are most extensively, preferably completely avoided. The headbox should in particular always ensure an as parallel and straight outlet gap on the headbox nozzle as possible with an as cost-effective as possible construction, simple handling and minimum maintenance expenditure. An as uniform as possible impingement line of the fibrous stock suspension jet coming from the headbox nozzle onto the at least one wire in the wire section should thereby also be achievable without problems. 
         [0095]    While this invention has been described with respect to at least one embodiment, 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. 
       COMPONENT IDENTIFICATION LIST 
       [0000]    
       
         
           
               1  Headbox 
               2  Central assembly 
               3  Table leaf (lower arm) 
               4  Cover plate (upper arm) 
               5  First central component (support element) 
               6  Second central component (support element) 
               7  Turbulence generator 
               8  Lateral manifold 
               9  Fibrous stock suspension 
               10  Headbox nozzle 
               11  Lower nozzle wall 
               12  Upper nozzle wall 
               13  Hinge 
               14  Lower lip plate 
               14 . 1  Lower lip support plate 
               15  Lateral limits 
               16  Outlet gap 
               17  Breast roll 
               18  Wire 
               19  Support element 
               20  Bed plate 
               21  Pedestal 
               22  Support element 
               23  Cross bar 
               24  Lifting element 
               25  Articulated axis 
               26  Articulated axis 
               27  Support hinge 
               28  Counter element 
               29  Rib 
               30  Region 
               31  Chamfer 
               32  First bevel 
               33  Region 
               34  Chamfer 
               35  Second bevel 
               36  Extension 
               37  Corner edge 
               38  Front side 
               39  Region 
               40  Compensating gap 
               41  Joint 
               42  Welded seam 
               43  Lower lip 
               44  Hinge, hinged connection 
               45  Lifting element 
             A Axis (Swivel axis) 
             B Machine width (arrow) 
             C Perpendicular distance 
             D. 29  Rib thickness 
             D. 42  Welded seam thickness 
             H.29 Minimum height 
             H.40 Gap height 
             L Machine direction (arrow, double arrow) 
             L. 31  Chamfer length 
             L. 34  Chamfer length 
             Q Cross machine direction (arrow) 
             S Double arrow (pivotability) 
             T. 29  Rib separation 
             Double arrow (movability) 
             W Angle