Patent Publication Number: US-7897016-B2

Title: Headbox apparatus for a papermaking machine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a Complete application pursuant to Provisional patent application U.S. Ser. No. 60/898,628 filed Jan. 31, 2007 and a continuation-in-part of U.S. Ser. No. 60/875,836 filed Dec. 19, 2006 which was filed as a Complete application on Dec. 18, 2007 Express Mail label EB 713308134 U.S. and a continuation-in-part of U.S. Ser. No. 11/642,054 filed Dec. 19, 2006 now U.S. Pat. No. 7,794,570 which was filed as a Complete application pursuant to Provisional application U.S. Ser. No. 60/763,439 filed Jan. 30, 2006. All of the disclosure and subject matter of the aforementioned applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a headbox apparatus for a papermaking machine. 
     More specifically, the present invention relates to a headbox apparatus for a papermaking machine in which the apparatus defines a flow path for stock flowing between an upstream header and a downstream slice lip. 
     BACKGROUND OF THE INVENTION 
     In a headbox of a papermaking machine, a vertical tube bank is located inside the headbox nozzle and distributes a uniform flow of fluid from the headbox delivery system to the headbox nozzle. The vertical tube bank is located between the pond sides and is trapped by the apron support structure and the top of the headbox nozzle. The fluid or stock is accelerated through the vertical slot openings into rectangular chambers located adjacent to one another. The discharge side of the vertical tube bank is nearly 100% open area into the headbox nozzle. The vertical openings provide a more uniform flow distribution requiring less mixing of individual flow streams and a uniform pressure drop across the tube bank which produces a better basis weight profile. 
     The vertical tube bank is constructed from metallic material. The flow passages in the tube bank are highly polished to prevent fiber from adhering to the surfaces. 
     In the headbox of the present invention, the tube bank is constructed from multiple segments or is constructed from a single block of material. When constructed from multiple pieces, the tube bank can be welded or glued together. Alternatively, clamping forces are utilized with through bolts to contain the internal forces of the stock pressure. The tube bank is constructed from multiple pieces stacked together to form the vertical tube bank. Multiple distinct sections that change the flow area within the flow chamber are assembled one after the other. The vertical tube bank front and drive side outside flow channels, or multiple front and drive side channels near the front and drive side walls, include a mechanism that alters the flow in these outer slots. This flow alteration provides a tool for controlling fiber orientation. 
     The tube bundle is fixed in location inside the headbox by locating devices. The vertical tube bank upstream surface has a series of vertical slots located on an equal pitch across the entire length of the tube bank. The width of the vertical slots are designed such that the width of the slot can be easily changed. Changing the slot width changes the velocity of the stock flow entering the tube bank resulting in improved fiber distribution. 
     The vertical tube bank is designed such that the range of fluid velocities in the initial section of the tube bank is between 3 and 50 feet per second. The exiting velocity range from the vertical tube bank is 1 to 20 feet per second. 
     The vertical tube bank can be fed from either a cross machine header or multiple flow injection hoses and can be used in combination with a dilution control of the flow leading to the tubebank. When used with a cross machine header, the vertical tube bank segments themselves may contain a series of holes that can deliver dilution control water into the cross machine header. The dilution control water is then transported through multiple holes located vertically between the vertical slots. The dilution water is carried into the next adjacent slot. 
     More specifically, the headbox apparatus according to the present invention includes the following features: 
     1. The vertical tube bank minimizes the mixing requirements of multiple individual tubes. 
     2. The mixing of flows is primarily in the cross machine direction, reducing rotational flows and maximizes cross machine mixing. 
     3. The vertical tube bank is constructed from one or multiple pieces. 
     4. The vertical tube bank is constructed with a series of slots on equal or near equal pitch across the entire width of the headbox. 
     5. The front side and drive side slots include a mechanism to alter the flow rate through these slots either by width or entrance configuration. 
     6. The vertical slot width can be easily modified to increase or decrease the pressure drop across the tube bank. 
     7. The vertical tube bank is located inside the headbox in the wet end side of the nozzle between the pond sides, apron support structure and nozzle roof. 
     8. The vertical tube bank is constructed of multiple MD and CD direction adjacent zones with varying open areas. 
     9. The vertical tube bank discharge side has greater than 85% open area into the nozzle area of the headbox. 
     10. The vertical tube bank can be utilized in headboxes where the delivery of fluid to the headbox is completed by means of a tapered header or a multiple tube/hose delivery system. 
     11. The vertical tube bank is operated in conjunction with a dilution control system or without a dilution control system. 
     12. The vertical tube bank may contain multiple holes to deliver dilution water through the block and into the tapered header. 
     More particularly, a conventional headbox distributor uses a tube array to spread the pulp slurry as uniformly as possible across the width of a paper machine headbox prior to the start of the drainage or other thickening process. The tube array is generally made up of individual round inlet tubes mounted is some manner to cause acceleration of the flow into each tube from a cross machine header or other form of supply of the slurry prior to the tube array. The pressure drop from the acceleration of the flow at the inlet of each tube within the array is critical to the uniformity of the flow within each tube and therefore to the uniformity of the cross machine uniformity of the headbox in general. This acceleration of the flow is also a factor in the operational cleanliness of the headbox operation. The exit end of a typical tube array may take on many shapes (round, hexagonal, rectangular or square or other shape) but eventually the flows exiting each individual tube must be re-joined prior to or within the nozzle of the headbox prior to discharge to the drainage area. The reorientation of the round tube entrance flow to the eventual rectangular shape of the nozzle will create disturbances in the flow in all directions. These disturbances must be damped or reduced in some way prior to discharge out the slice so as not to cause nonuniformities in the paper web. 
     The purpose of the present invention is to create the necessary pressure drop and subsequent uniform cross machine flow distribution using only vertical channels in the flow distributor. This will minimize non-cross machine flow disturbances improving cross machine uniformity of the flow. The use of only vertical channels also improves the cross machine characteristics of the fiber slurry by minimizing non cross machine forces on the fibers by the fluid flow. The design is equally applicable to headboxes using dilution to control the headbox profile or other mechanical profile controls techniques. 
     Further advantages of this invention are simplicity of manufacturing using easily manufactured turbulence generating devices and improved structural stiffness within the headbox to withstand internal pressures of the fluid flow. 
     Therefore, the primary feature of the present invention is the provision of a headbox apparatus that overcomes the problems associated with the prior art headboxes and which makes a significant contribution to the papermaking art. 
     Another feature of the present invention is the provision of a headbox apparatus for a papermaking machine that is easier and less costly to manufacture when compared with prior art headboxes. 
     A further feature of the present invention is the provision of a headbox apparatus for a papermaking machine that improves mixing of the pulp prior to discharge thereof to a downstream drainage arrangement. 
     Other features and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description of a preferred embodiment of the present invention contained herein. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a headbox apparatus for a papermaking machine. The headbox apparatus defines a flow path for stock flowing between an upstream location and a downstream slice lip. The apparatus includes a plurality of blocks which are anchored within the flow path between the upstream location and the slice lip. Each block and an adjacent block of the plurality of blocks define therebetween a flow tube for the flow therethrough of the stock. The flow tube has an upstream portion having an upstream and a downstream end. Additionally, the flow tube has a downstream portion which has an upstream and a downstream extremity. The upstream extremity of the downstream portion extends from the downstream end of the upstream portion. The downstream portion of the flow tube has a volume which is greater than a further volume of the upstream portion of the flow tube such that when the stock flows from the upstream portion to the downstream portion of the flow tube, the stock is mixed within the downstream portion. 
     The upstream location in one arrangement of the present invention is a cross machine header. However, in another embodiment, the upstream location includes multiple flow injection hoses. 
     In a more specific embodiment of the present invention, the plurality of blocks are fabricated from high density polypropylene. However, the blocks could be fabricated from stainless steel, ceramic material or synthetic material. 
     Also, each block of the plurality of blocks has a first and a second end and each block has a first portion which extends from the first end of the block. 
     Furthermore, each block has a second portion which extends from the first portion to the second end of the block. 
     The first portion of the block defines a first and a second side, the first side of the first portion being planar. The second side of the first portion is also planar, the second side being disposed spaced and parallel relative to the first side. 
     Moreover, the second portion of the block defines a first and a second face, the first face of the second portion defining a surface and a further surface. 
     Additionally, the second face of the second portion defines a facing and a further facing. 
     More specifically, the first face is disposed spaced and parallel relative to the second face, with the first face and the second face being spaced apart by a distance which is less than a further distance between the first and second sides of the first portion. 
     Also, the second portion of the block defines a first rib which is disposed between the surface and the further surface, the first rib extending between the first portion and the second end of the block. 
     Moreover, the second portion of the block defines a second rib which is disposed between the facing and the further facing, the second rib extending between the first portion and the second end of the block. 
     The first portion defines a first ramp which extends between the first side of the first portion and the surface. 
     Also, the first portion defines a second ramp which extends between the second side of the first portion and the further facing. The arrangement is such that the flow tube is defined between the adjacent blocks so that when stock flows through the upstream portion of the flow tube into the downstream portion of the flow tube, the stock is mixed and is guided between the second rib of the block and the first rib of the adjacent block. The apparatus is structured such that when the stock flows into the downstream portion of the flow tube, a first and second vortex is generated within the downstream portion. The first vortex is disposed adjacent to the facing of the block and between the facing of the block and the surface of the adjacent block. 
     Furthermore, the second vortex is disposed adjacent to the further facing of the block and between the further facing of the block and the further surface of the adjacent block so that mixing of the stock within the downstream portion of the flow tube is enhanced. 
     Additionally, the first vortex has a rotational direction which is opposite to a further rotational direction of the second vortex for further enhancing mixing of the stock within the downstream portion of the flow tube. 
     More particularly, the opposite rotational directions of the first and second vortices is predictably achieved by virtue of the ramp of the adjacent block and by the second ramp of the block. The ramp of the adjacent block guides the flow of stock flowing from the upstream portion of the flow tube to generate the first vortex so that the first vortex rotates within the downstream portion of the flow tube in the rotational direction. 
     Also, the second ramp of the block guides the flow of stock flowing from the upstream portion of the flow tube to generate the second vortex so that the second vortex rotates within the downstream portion of the flow tube in the further rotational direction opposite to the rotational direction so that impact of the first and second vortices on a flow consistency and a velocity uniformity of the stock is reduced. 
     Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings which show a preferred embodiment of the present invention. However, such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims. 
     Included in such modifications would be the provision of a dilution control system for introducing dilution fluid into the flow tube or upstream thereof for controlling the cross machine basis weight profile of the resultant web. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a preferred headbox apparatus according to the present invention for a papermaking machine; 
         FIG. 2  is an exploded view of the blocks shown in  FIG. 1 ; 
         FIG. 3  is a view taken on the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a view taken on the line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a view taken on the line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a sectional view taken on the line  6 - 6  of  FIG. 1 ; 
         FIG. 7  is a view taken on the line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a view taken on the line  8 - 8  of  FIG. 6 ; 
         FIG. 9  is a view taken on the line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is an enlarged sectional view taken on the line  10 - 10  of  FIG. 8 ; and 
         FIG. 11  is an enlarged sectional view taken on the line  11 - 11  of  FIG. 8 . 
     
    
    
     Similar reference characters refer to similar parts throughout the various FIGS. of the drawings. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a headbox apparatus generally designated  10  according to the preferred embodiment of present invention for a papermaking machine. As shown in  FIG. 1 , the headbox apparatus  10  defines a flow path  12  for stock  14  flowing as indicated by the arrow  16  between an upstream location such as a header  18  and a downstream slice lip  20 . The apparatus  10  includes a plurality of blocks  22 ,  23  and  24  which are anchored within the flow path  12  and  16  between the header  18  and the slice lip  20 . Each block such as block  22  and an adjacent block  23  of the plurality of blocks  22 - 24  define therebetween a flow tube generally designated  26  for the flow therethrough of the stock  14 . The flow tube  26  has an upstream portion  28  having an upstream and a downstream end  30  and  32  respectively. Additionally, the flow tube  26  has a downstream portion  34  having an upstream and a downstream extremity  36  and  38  respectively. The upstream extremity  36  of the downstream portion  34  extends from the downstream end  32  of the upstream portion  28 . The downstream portion  34  of the flow tube  26  has a volume V 1  which is greater than a further volume V 2  of the upstream portion  28  of the flow tube  26  such that when the stock  14  flows as indicated by the arrow  16  from the upstream portion  28  to the downstream portion  34  of the flow tube  26 , the stock  14  is mixed within the downstream portion  34 . 
     In a more specific embodiment of the present invention, the plurality of blocks  22 - 24  are fabricated from high density polypropylene. 
     Also, it will be understood by those skilled in the art that instead of a cross machine direction tapered header  18 , multiple flow injection hoses could be used at the upstream location. Also, the headbox could be provided with a stock dilution control for controlling the cross machine direction profile of the resultant web. 
       FIG. 2  is an exploded view of the blocks generally designated  22  and  23  shown in  FIG. 1 . As shown in  FIG. 2 , each block such as block  22  of the plurality of blocks  22 - 24  has a first and a second end  42  and  44  respectively, the block  22  having a first portion  46  which extends from the first end  42  of the block  22 . 
     Furthermore, the block  22  has a second portion  48  which extends from the first portion  46  to the second end  44  of the block  22 . 
     The first portion  46  of the block  22  defines a first and a second side  50  and  52  respectively, the first side  50  of the first portion  46  being planar. The second side  52  of the first portion  46  is also planar, the second side  52  being disposed spaced and parallel relative to the first side  50 . 
     Moreover, the second portion  48  of the block  22  defines a first and a second face  54  and  56  respectively, the first face  54  of the second portion  48  defining a surface  58  and a further surface  60 . 
       FIG. 3  is a view taken on the line  3 - 3  of  FIG. 2 . As shown in  FIG. 3 , the second face  56  of the second portion  48  defines a facing  62  and a further facing  64 . 
     More specifically, the first face  54  is disposed spaced and parallel relative to the second face  56 , with the first face  54  and the second face  56  being spaced apart by a distance D 1  which is less than a further distance D 2  between the first and second sides  50  and  52  respectively of the first portion  46 . 
     As shown in  FIG. 2 , the second portion  48  of the block  22  defines a first rib  66  which is disposed between the surface  58  and the further surface  60 , the first rib  66  extending between the first portion  46  and the second end  44  of the block  22 . 
     Moreover, as shown in  FIG. 3 , the second portion  48  of the block  22  defines a second rib  68  which is disposed between the facing  62  and the further facing  64 , the second rib  68  extending between the first portion  46  and the second end  44  of the block  22 . 
     As shown in  FIG. 2 , the first portion  46  defines a first ramp  70  which extends between the first side  50  of the first portion  46  and the surface  58 . 
     As shown in  FIG. 3 , the first portion  46  defines a second ramp  72  which extends between the second side  52  of the first portion  46  and the further facing  64 . The arrangement is such that the flow tube  26  as shown in  FIG. 1  is defined between the adjacent blocks  22  and  23  so that when stock  14  flows as indicated by the arrow  16  as shown in  FIG. 2  through the upstream portion  28  of the flow tube  26  into the downstream portion  34  of the flow tube  26 , the stock  14  is mixed within the downstream portion  34  the stock  14  being guided between the second rib  68  of the block  22  and the first rib  66  of the adjacent block  23 . 
       FIG. 4  is a view taken on the line  4 - 4  of  FIG. 2 . As shown in  FIG. 4 , the apparatus  10  is structured such that the stock  14  flowing into the downstream portion  34  of the flow tube  26  separates into a first vortex  74 . The first vortex  74  is disposed adjacent to the facing  62  of the block  22  and between the facing  62  of the block  22  and the surface  58  of the adjacent block  23 . 
       FIG. 5  is a view taken on the line  5 - 5  of  FIG. 2 . As shown in  FIG. 5 , the apparatus  10  is structured such that the stock  14  flowing into the downstream portion  34  of the flow tube  26  separates into a second vortex  76 . The second vortex  76  is disposed adjacent to the further facing  64  of the block  22  and between the further facing  64  of the block  22  and the further surface  60  of the adjacent block  23  so that mixing of the stock  14  within the downstream portion  34  of the flow tube  26  is enhanced. 
     Additionally, as shown in  FIG. 4 , the first vortex  74  has a counter clockwise rotational direction as indicated by the arrow  78  which is opposite to a clockwise further rotational direction as shown in  FIG. 5  such clockwise further rotational direction being indicated by the arrow  80 . Accordingly, the counter rotating vortices  74  and  76  as shown in  FIGS. 4 and 5  respectively further enhance mixing of the stock  14  within the downstream portion  34  of the flow tube  26 . 
     More particularly, as shown in  FIGS. 3-5 , the opposite rotational directions as indicated by arrows  78  and  80  respectively of the first and second vortices  74  and  76  is predictably achieved by virtue of the first ramp  70  of the adjacent block  23  and by the second ramp  72  of the block  22 . The first ramp  70  of the adjacent block  23  as shown in  FIG. 4  guides the flow of stock flowing from the upstream portion  28  of the flow tube  26  to generate the first vortex  74  so that the first vortex  74  rotates within the downstream portion  34  of the flow tube  26  in the rotational direction as indicated by the arrow  78 . 
     Also, as shown in  FIG. 5 , the second ramp  72  of the block  22  guides the flow of stock flowing from the upstream portion  28  of the flow tube  26  to generate the second vortex  76  so that the second vortex  76  rotates within the downstream portion  34  of the flow tube  26  in the further rotational direction  80  opposite to the rotational direction  78  so that impact of the first and second vortices  74  and  76  respectively on a flow consistency and a velocity uniformity of the stock  14  is reduced. 
       FIG. 6  is a sectional view taken on the line  6 - 6  of  FIG. 1 . As shown in  FIG. 6 , each of the blocks  22 - 24  has a first and a second rib  66  and  68  respectively. Also, each of the blocks  22 - 24  has a first and a second ramp  70  and  72  respectively. 
       FIG. 7  is a view taken on the line  7 - 7  of  FIG. 6 . As shown in  FIG. 7 , each of the blocks  22 - 24  has a second end  44 . Also, each of the blocks  22 - 24  has a first and a second ramp  70  and  72  respectively. Additionally, each of the blocks  22 - 24  has a first and a second rib  66  and  68  respectively. 
       FIG. 8  is a view taken on the line  8 - 8  of  FIG. 6 . As shown in  FIG. 8 , the block  22  has a first rib  66 . Also, the block  22  has a first ramp  70 . 
       FIG. 9  is a view taken on the line  9 - 9  of  FIG. 8 . As shown in  FIG. 9 , the block  22  has a second end  44 . Also, the block  22  has a first and a second ramp  70  and  72  respectively. Additionally, the block  22  has a first and a second rib  66  and  68  respectively. 
       FIG. 10  is an enlarged sectional view taken on the line  10 - 10  of  FIG. 8 . As shown in  FIG. 10 , the block  22  defines the second ramp  72  which guides the stock flow to generate a vortex  76  in a clockwise rotational direction  80  as shown in  FIG. 5 . 
       FIG. 11  is an enlarged sectional view taken on the line  11 - 11  of  FIG. 8 . As shown in  FIG. 11 , the block  23  defines the first ramp  70  which guides the stock flow to generate a vortex  74  in a counter clockwise rotational direction  78  as shown in  FIG. 4 . 
     In operation of the headbox apparatus  10  of the present invention, the stock  14  flows into the flow tube  26  as indicated by the arrow  16 . The velocity of the flow of the stock  14  increases during passage thereof through the upstream portion  28  of the flow tube  26 . Such increased velocity assists in maintaining the cleanliness of the flow tube. As the stock  14  exits from the upstream portion  28  of the flow tube  26  into the larger volume V 1  of the downstream portion  34  of the flow tube  26 , the velocity of the stock  14  is reduced and vortices  74  and  76  are generated within the downstream portion  34  of the flow tube  26 . The downstream portion  34  with volume V 1  is a single chamber but is to a degree divided into an upper chamber  100  and a lower chamber  102  by the rib  68  of the block  22  and the rib  66  of the adjacent block  23  as shown in  FIGS. 4 ,  5 ,  8 ,  10  and  11 . 
     The vortex  74  generated within the upper chamber  100  as shown in  FIGS. 4 and 11  is caused to flow in a generally counter clockwise direction  78  because as the stock  14  flows from the upstream portion  28  into the upper chamber of the downstream portion  34 , the first ramp  70  of the adjacent block  23  guides such stock flow in the counter clockwise direction  78 . 
     Conversely, the vortex  76  generated within the lower chamber  102  as shown in  FIGS. 5  and  10  is caused to flow in a generally clockwise direction  80  because as the stock  14  flows from the upstream portion  28  into the lower chamber of the downstream portion  34 , the second ramp  72  of the block  22  guides such stock flow in the clockwise direction  80 . Thus, the opposite rotational directions of the vortices  74  and  76  enhance mixing of the stock  14  within the upper and lower chambers which are interconnected with each other. Therefore, the stock  14  within the downstream portion  34  of the flow tube  26  is thoroughly mixed before discharge thereof through the slice lip  20 . 
     It will be understood by those skilled in the art that the blocks  22 - 24  could be fabricated from stainless steel, ceramic material or any suitable synthetic material. 
     Also, the present invention could include a dilution control mechanism for introducing diluting fluid into one or more flow tubes or upstream relative to the flow tubes for controlling the cross machine basis weight profile of the resultant sheet. 
     The headbox according to the present invention provides a unique arrangement for enhancing mixing of stock flowing through the flow tubes of a tube bank of a headbox.