Patent Publication Number: US-9422665-B2

Title: Headbox apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. 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 which defines a flow path for stock flowing between an upstream header and a downstream slice lip. 
     2. Background Information 
     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 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 such as round, hexagonal, rectangular, 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 of the slice so as to avoid 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 while minimizing the wall effects of the individual flow elements prior to the rejoining of the flows in the nozzle. Additionally, an added feature of accelerating the flow into the headbox nozzle is incorporated into the flow element design to further stabilize the flow exiting the headbox. 
     The entrance of each flow element is a slot shape and the discharge end of each tube is an open channel of square, rectangular, round or some other geometric shape. These flow elements can also have one or multiple changes in area between the initial flow element slot size and the discharge area of the flow element. Additionally, an added feature of accelerating the flow into the headbox nozzle is incorporated into the flow element design to further stabilize the flow exiting the headbox. The flow elements may or may not be used in conjunction with trailing members. Furthermore, the flow elements may or may not be designed to incorporate or work in conjunction with the use of a consistency profiling system. 
     The flow elements according to the present invention are nested together to form a close packed array on the discharge end, with little or no vertical wall continuous in any area across the width of the headbox. 
     To make the edge effect minimal to the pondsides, a special flow element can be supplied on each end which reduces flow instability due to side wall friction. This flow element may be larger in the entrance area than the rest of the flow elements. 
     Such larger inlet may additionally have an adjustable insert for flow and fiber orientation control. 
     The present invention uses a distributor consisting of simple slotted flow elements, expanding to another slotted expansion area (one or multiple), then to a larger discharge area. The arrangement according to the present invention will reduce cross machine non uniformity of both consistency and velocity of the stock flow. Additionally, an added feature of accelerating the flow into the headbox nozzle is incorporated into the flow element design to further stabilize the flow exiting the headbox. 
     The apparatus according to the present invention uses slots to minimize the vertical non uniformity of the open area at the discharge of the flow element and increases mixing of the flows in the cross machine direction at the discharge of the flow elements. 
     The present invention is applicable to the production of all grades of paper, and is usable with or without the inclusion of flow turbulence control sheets. 
     The elements according to the present invention can be fabricated out of many different types of materials including synthetic, ceramic, stainless steel, cast material, etc. 
     Such elements can also be used with or without a dilution control system or with or without the use of trailing members. 
     Therefore, it is a primary feature of the present invention to provide a headbox apparatus that overcomes the problems associated with the prior art arrangements. 
     Another feature of the present invention is the provision of a headbox apparatus that greatly reduces the impact of said upstream and downstream vortices on a flow consistency and a velocity uniformity of the stock. 
     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 header and a downstream slice lip. The apparatus includes a plurality of blocks which are anchored within the flow path between the header and the slice lip. Each block and an adjacent block of the plurality of blocks defines therebetween a flow tube for the flow therethrough of the stock. The flow tube has an upstream portion and a downstream portion that gradually widens in at least one step in a direction from the header to the slice lip. Each block has an upstream and a downstream end with each block defining an elongate divider extending between the upstream and the downstream ends. The arrangement is such that the divider defines a first and a second side. The block defines a first surface which is disposed adjacent to the first side of the divider and a second surface which is disposed adjacent to the second side of the divider. An upstream ramp is defined by the first surface for generating an upstream vortex adjacent to the first surface. A downstream ramp is defined by the second surface for generating a downstream vortex adjacent to the second surface. Each block defines a further elongate divider extending between the upstream and the downstream ends such that the further divider defines a further first and a further second side. The block defines a further first surface which is disposed adjacent to the further first side of the further divider. A further second surface is disposed adjacent to the further second side of the further divider. A further upstream ramp is defined by the further second surface for generating a further upstream vortex adjacent to the further second surface. Also, a further downstream ramp is defined by the further first surface for generating a further downstream vortex adjacent to the further first surface such that each of the blocks and the adjacent block of the plurality of blocks generate the upstream vortices which rotate in opposite directions relative to each other within the flow tube. Adjacent blocks also generate the downstream vortices which rotate in opposite directions relative to each other within the flow tube so that impact of the upstream and downstream 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic top plan view of a headbox apparatus according to the present invention; 
         FIG. 2  is a perspective view of the block 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. 2 ; end  34  and the downstream end  36 . 
         FIG. 5  is a view taken on the line  5 - 5  of  FIG. 2 ; and 
         FIG. 6  is a view taken on the line  6 - 6  of  FIG. 2 . 
     
    
    
     Similar reference characters refer to similar parts throughout the various views of the drawings. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic top plan view of a headbox apparatus generally designated  10  according to the present invention. As shown in  FIG. 1 , the headbox apparatus  10  defines a flow path  12  for stock generally designated  14  flowing between an upstream header  16  and a downstream slice lip  18 . The apparatus  10  includes a plurality of blocks  20 ,  21  and  22  which are anchored within the flow path  12  between the header  16  and the slice lip  18 . Each block such as block  21  and an adjacent block  22  of the plurality of blocks  20 - 22  define therebetween a flow tube  24  for the flow therethrough of the stock  14 . The flow tube  24  has an upstream portion  26  and a downstream portion  28  that gradually widens in at least one step  30  in a direction as indicated by the arrow  32  from the header  16  to the slice lip  18 . 
       FIG. 2  is a perspective view of the block  21 . As shown in  FIG. 2 , the block  21  has an upstream end  34  and a downstream end  36  with each block  21  defining an elongate divider  38  extending between the upstream end  34  and the downstream end  36 . The arrangement is such that the divider  38  defines a first side  40  and a second side  42 . The block  21  defines a first surface  44  which is disposed adjacent to the first side  40  of the divider  38  and a second surface  46  which is disposed adjacent to the second side  42  of the divider  38 . An upstream ramp  48  is defined by the first surface  44 . 
       FIG. 3  is a view taken on the line  3 - 3  of  FIG. 2 . As shown in  FIG. 3 , the ramp  48  is for generating an upstream vortex  50  adjacent to the first surface  44 . 
       FIG. 4  is a view taken on the line  4 - 4  of  FIG. 2 . As shown in  FIG. 4 , a downstream ramp  52  is defined by the second surface  46  for generating a downstream vortex  54  adjacent to the second surface  46 . Each block  21  defines a further elongate divider  56  extending between the upstream end  34  and the downstream end  36 . 
       FIG. 5  is a view taken on the line  5 - 5  of  FIG. 2 . As shown in  FIG. 5 , the further divider  56  defines a further first side  58  and a further second side  60 . The block  21  defines a further first surface  62  which is disposed adjacent to the further first side  58  of the further divider  56 . A further second surface  64  is disposed adjacent to the further second side  60  of the further divider  56 . A further upstream ramp  66  is defined by the further second surface  64  for generating a further upstream vortex  68  adjacent to the further second surface  64  as shown in  FIG. 3 . Also, a further downstream ramp  70  is defined by the further first surface  62  for generating a further downstream vortex  72  adjacent to the further first surface  62  as shown in  FIG. 3 . 
     As shown in  FIG. 3 , the arrangement is such that each block such as block  21  and the adjacent block  20  of the plurality of blocks  20 - 22  generate the upstream vortices  50  and  68  which rotate in opposite directions relative to each other within the flow tube  24 . Adjacent blocks  21  and  20  also generate the downstream vortices  54  and  72  which rotate in opposite directions relative to each other within the flow tube  24 , so that impact of the upstream and downstream vortices  50 ,  68  and  54 ,  72  on a flow consistency and a velocity uniformity of the stock is reduced. 
       FIG. 6  is a view taken on the line  6 - 6  of  FIG. 2 . As shown in  FIG. 6 , the divider  38  includes a first side  40  and a second side  42 . 
     In operation of the headbox apparatus  10 , pressurized stock  14  flows through the header  16  into each of the flow tubes  24  defined between adjacent blocks. As the stock  14  flows past the upstream ramp  48 , the vortex  50  is generated. Such stock then flows out towards the slice lip  18 . Also, stock flows towards the downstream ramp  52  for generating a vortex  54 . On the opposite side of the flow tube  24 , the block  20  has an upstream ramp  66  which generates a vortex  68  while a downstream ramp  70  generates a vortex  72 . These vortices  50 ,  54 ,  68  and  72  thoroughly and evenly distribute fibers within the stock so that the stock ejected from the slice lip has a uniform consistency and velocity.