Abstract:
The invention provides a doctor blade holder system that includes a doctor blade support structure, an adjustment profiling plate, and a series of adjustment mechanisms. The doctor blade support structure includes an elongated slot for receiving a doctor blade and a separate elongated slot to house mounting hardware. The adjustable profiling plate causes pressure to be applied to the working blade in a continuous manner along the length of the working blade, wherein the profiling plate is mounted to a holder mounting plate with a series of pairs of mounting structures allowing unconstrained flexure, or rotation, of the profiling plate with respect to holder mounting plate around two axes. The series of adjustment mechanisms attach to the holder mounting plate and acting on the profiling plate, wherein the adjustment mechanisms are capable of displacing the profiling plate in a bi-directional manner.

Description:
PRIORITY 
     This application claims priority from U.S. Provisional Application Ser. No. 61/900,727 filed Nov. 6, 2013, the entire content and substance of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present invention generally relates to doctor blade holders and relates in particular to doctor blade holders that may be used with roll surfaces wherein the roll surface is not uniform. 
     For example, certain types of rolls, such as Yankee rolls used for making tissue paper, may have very large diameters that are not uniform along the longitudinal direction of the roll. Certain such rolls, for example, may have a diameter at the center of the roll that is greater than the diameter(s) at the ends of the roll. This may be by design to facilitate the transfer of an intermediate tissue product onto the roll, but presents difficulties in trying to provide a doctor blade that matches the surface of the roll. 
     Conventionally, adjustments of the position of a doctor blade along the length of a roll have been achieved by providing adjustment screws at spaced apart locations (e.g., every few inches) along the length of the doctor blade holder that urge the doctor blade closer to the roll surface. Unfortunately, however, such adjustments may compromise other portions of the doctor blade holder, such as locations where the doctor blade holder is attached to a holder mounting plate or doctor back, and may further introduce inconsistencies in the pressure applied by the doctor blade onto the roll surface. 
     There remains a need therefore, for a doctor blade holder that efficiently and effectively permits small localized adjustments of the position of a doctor blade without the above attendant drawbacks. 
     SUMMARY 
     In accordance with an embodiment, the invention provides a doctor blade holder system that includes a doctor blade support structure, an adjustment profiling plate, and a series of adjustment mechanisms. The doctor blade support structure includes an elongated slot for receiving a doctor blade and a separate elongated slot to house mounting hardware. The adjustable profiling plate causes pressure to be applied to the working blade in a continuous manner along the length of the working blade, wherein the profiling plate is mounted to a holder mounting plate with a series of mounting structures allowing unconstrained flexure, or rotation, of the profiling plate with respect to holder mounting plate around one or two axes. The series of adjustment mechanisms attach to the holder mounting plate and acting on the profiling plate, wherein the adjustment mechanisms are capable of displacing the profiling plate in a bi-directional manner. 
     In accordance with another embodiment, the invention provides a doctor blade holder system that includes a doctor blade support structure, a plurality of adjustment mechanisms, and a plurality of movable attachment mechanisms. The doctor blade support structure includes an elongated slot for receiving a doctor blade and a separate elongated slot to house mounting hardware for attaching the doctor blade support structure to a holder mounting plate. The plurality of adjustment mechanisms attach to the holder mounting plate and acting on a profiling plate, wherein the adjustment mechanisms are capable of displacing the profiling plate relative to the holder mounting plate. The plurality of movable attachment mechanisms are for attaching the doctor blade support structure to the holder mounting plate yet permit the profiling plate to move with respect to the holder mounting plate 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following description may be further understood with reference to the accompanying drawings in which: 
         FIG. 1  shows an illustrative diagrammatic view of a doctor blade holder system in accordance with an embodiment of the present invention; 
         FIG. 2  shows an illustrative diagrammatic sectional view of the doctor blade holder system of  FIG. 1 ; 
         FIG. 3  shows an illustrative diagrammatic isometric view of the doctor blade support structure of the doctor blade holder system of  FIG. 1 ; 
         FIG. 4  shows an illustrative diagrammatic isometric view of the profiling plate of the doctor blade holder system of  FIG. 1 ; 
         FIG. 5  shows a partial illustrative diagrammatic sectional view of the doctor blade holder of  FIG. 1  wherein actuation of an adjustment mechanism has caused relative movement of a profiling plate mounting structure with respect to a holder mounting plate mounting structure; 
         FIG. 6  shows an illustrative diagrammatic view of a doctor blade holder system in accordance with another embodiment of the present invention that includes at least one load sensor in the doctor blade cartridge; 
         FIG. 7  shows an illustrative diagrammatic view of a doctor blade holder system in accordance with a further embodiment of the present invention involving different adjustment mechanisms and different spherical type mounting arrangements; 
         FIG. 8  shows an illustrative diagrammatic sectional view of a doctor blade holder system in accordance with a further embodiment of the present invention involving different adjustment mechanisms and different spherical type mounting arrangements; 
         FIG. 9  shows an illustrative diagrammatic isometric view of the profiling plate of the doctor blade holder system of  FIG. 7 ; 
         FIG. 10  shows a partial illustrative diagrammatic sectional view of the doctor blade holder of  FIG. 7  wherein actuation of an adjustment mechanism has caused relative movement of a profiling plate mounting structure with respect to a holder mounting plate mounting structure; and 
         FIG. 11  shows an illustrative diagrammatic view of the doctor blade holder system of  FIG. 7  wherein actuation of an adjustment mechanism has caused relative movement of a profiling plate mounting structure with respect to a holder mounting plate mounting structure. 
     
    
    
     The drawings are shown for illustrative purposes only. 
     DETAILED DESCRIPTION 
     The present invention provides an improved doctor blade holder that may be used for creping tissue off of a dryer roll in a tissue making machine (e.g., a Yankee dryer). Doctor blade holders of the invention provide precise adjustment features allowing the creping blade to be loaded more uniformly against the Yankee surface. Further, embodiments of the invention will help to preserve the Yankee surface by minimizing blade chatter and vibration. In addition to tissue manufacturing applications, doctor blade holders of the invention may be used in many other manufacturing processes where a product or contaminants need to be removed or scraped off of the surface of a rotating roll, belt or other moving surface. 
     Referring to  FIGS. 1-5 , in accordance with an embodiment, the present invention provides an improved doctor blade holder assembly that includes a doctor blade support structure  3 , a profiling plate  4  and a back-up blade  5 . The doctor blade support structure  3  retains a doctor blade  2 , in close proximity to the generally cylindrical surface of a Yankee dryer  1 . The doctor blade support structure  3 , includes a doctor blade receiving groove  6 , which is preferably fitted with a doctor blade cartridge  7 . The doctor blade cartridge  7 , includes multiple internal spacer elements  37  that are attached to both side walls of the cartridge and provide support to the bottom edge of the doctor blade. The top edge of the doctor blade, the working edge, is pressed against the Yankee surface  1 . The back-up blade may have a thickness of about 0.025 inch to about 0.250 inch. 
     The doctor blade support structure  3  includes two integrated wear bars. The first wear bar  8  is secured in the wall of the doctor blade support structure  3  closest to the Yankee surface, while the second wear bar  9  is secured in the wall of the blade support structure  3  furthest from the Yankee surface  1 . The wear bars  8  and  9  provide contact points for the blade while it is in operation, and also during insertion and removal of the blade  2  from the doctor blade support structure  3 . 
     The doctor blade support structure  3  also includes a T-shaped longitudinal slot  10  that spans the full length of the structure. This T-shaped slot  10  is used for mounting purposes. A series of milled out recesses  11  (shown in  FIG. 3 ) are spaced along the length of the member. The remaining lands  12  between the recesses, mate against the holder mounting plate  13  to provide a stable mounting for the blade support structure  3 . 
     Additionally, a clamping bar  14  is contained within the T-slot  10 . The clamping bar  14  may be formed of a continuous length, or may be configured as a series of segmented bars. The clamping bar  14  has a series of holes spaced in the longitudinal direction. The holder mounting plate  13  has a series of tapped holes  15  that are spaced in alignment with the tapped holes in the clamping bar  14 . The holder mounting plate  13  also has a series of tapped holes  40  for receiving shoulder screws  26  (as discussed in more detail below) as well as a series of clearance holes  42 ,  44  for receiving an adjustment mechanism  29  (as also discussed in more detail below). 
     The cap screws  16  pass through holes  47  in the profiling plate  4  are used to force the clamping bar  14  against an inner surface of the T-slot  17 , which in turn forces the blade support structure  3 , firmly against the holder mounting plate  13  of the doctor beam. Preferably, a shallow groove  18 , corresponding to the width and location of the lands  12  is machined in the holder mounting plate  13  to ensure that the blade support structure  3  will remain straight and fixed in the proper location. The doctor blade support structure  3  may also be formed of one continuous member or may be segmented in order to reduce manufacturing costs. If it is segmented, then an additional load-bridging member may be utilized. This load-bridging member would provide a connection between segments and would serve to align the facing ends of adjacent segments. 
     When the blade  2  is loaded against the Yankee surface  1  there are four contact forces or contact lines of force acting on it. The first, is the contact line  19 , between the working edge of the blade and the Yankee surface; the second, is the contact line  20  between the back-up blade  5  and the outer surface of the working blade; the third, is the contact line  21  between the wear bar  8  closest to the Yankee surface and the inner surface of the working blade; and the fourth is the contact force  22  between the base of the cartridge and the bottom edge of the blade. Preferably, the doctor blade support structure is an aluminum extrusion. However, it could also be a fiber reinforced plastic (composite material) pultruded or laid up to obtain the correct geometry, or may be an assembly of metallic components. 
     The profiling plate  4  extends in the longitudinal direction and is attached along the bottom edge thereof to the holder mounting plate  13  with spherical type mounting arrangements  23 . Adjustment mechanisms  29  are provided along the longitudinal direction of the profiling plate  4  and the holder mounting plate  13  that permit the profiling plate  4  to be moved a small amount away from the holder mounting plate  13  in order to accommodate small variations in the distance between the tip of the doctor blade  2  and the roll surface  1 . This is shown in more detail in  FIG. 5 , which shows the holder in cross-section with the profiling plate adjusted towards the Yankee. For example and as discussed above, certain Yankee doctor rolls may have diameters at the ends of the roll that are smaller than the diameter at the center of the roll (e.g., be barrel-shaped). In this case, the adjustment mechanisms  29  provide that the blade may be pushed toward the roll surface at the ends to match the shape of the roll surface. 
     The spherical mounting arrangements  23  allow for flexure, or localized rotation, of the profiling plate around one or two axes shown diagrammatically in  FIG. 2 . In accordance with an embodiment, the spherical mounting arrangement  23  may include a spherical thrust bearing having mounting structure elements  24  and  25 , that cooperate to with a shoulder screw  26  and a cupped washer  27  (e.g., a Bellville type spring washer) to provide a small range of movement of the profiling plate  4  with respect to the holder mounting plate  13  responsive to movement of the adjustment mechanism  29 . In particular, as the adjustment mechanism urges the profiling plate  4  toward the roll surface, the cupped washer and the profiling plate mounting structure  25  moves with the profiling plate, while the holder mounting plate mounting structure  24  remains with the holder mounting plate  13 . 
     In particular and again with reference to  FIG. 5 , during adjustment of the adjustment mechanism  29 , the shoulder screw  26  and the convex portion  24  of the assembly remain fixed, while the cupped washer  27  and the concave portion  25  of the assembly move with the profiling plate to accommodate the pivoting motion of the profiling plate  4  caused by the movement of the profiling plate  4  with respect to the holder mounting plate  13  (which, again was caused by adjustment of the adjustment mechanism  29 ). In accordance with further embodiments of the invention, many other spherical mounting designs may be used to provide the required freedom of movement of the profiling plate  4  with respect to the holder mounting plate  13 . 
     A series of spaced, rectangular-shaped, openings  28  are machined in the profiling plate allowing the lands of the doctor blade support structure  12  to pass through, and mate up to the holder mounting plate. The profiling plate  4  may be one continuous member or it may be segmented in order to increase flexibility or reduce manufacturing costs. If it is segmented, then an additional load-bridging member would be utilized. This load-bridging member would provide a connection between segments and would serve to align the facing ends of adjacent segments. A series of adjustment mechanisms  29  are threaded through the holder mounting plate  13  and act on the upper area of the profiling plate  4 . 
     One embodiment of these adjustment mechanisms  29  consists of a rotatable, externally threaded body and a flanged connection to the profiling plate. A preferred design has an inner removable flange  30  that is attached to the main body of the adjustment mechanism  29  with a left-hand threaded connection  31 . By machining this connection with left-hand threads, the forces applied to the flange will serve to tighten the flange rather than loosen it when adjustments are made. These adjustment mechanisms  29  may be set independently, within a range, to force the upper edge of the profiling plate  4 , into or away from the back-up blade  5 . The back-up blade  5 , in turn, transfers this movement, and associated force, directly into the working blade  2 . This feature allows precise control of the contact load  19  between the working blade and the Yankee surface, continuously across the full width of the Yankee. Again, this is important because the typical Yankee surface is not straight but is crowned in a barrel-shaped manner where the radius at the center of the Yankee is slightly larger than at its edges (typically 0.025 to 0.125 inch). 
     Once each adjustment mechanism, item  29 , is set, a special cap, item  32 , with female threads is screwed onto the adjustment mechanism  29  and tightened. This action serves to lock the adjustment mechanism  29  at the desired setting, while also preventing process contaminants from interfering with the threads or filling the wrench socket  33 . 
     The inner surface  34  of the profiling plate  4  in conjunction with an outer surface  35  of the blade support member  3  combine to create a cavity for the back-up blade  5  and the blade pressure equalizing tube  36 . This equalizing tube  36 , applies an even pressure along the bottom of the back-up blade. This effect is transferred to the contact interface  20  between the back-up blade and the working blade, helping to ensure that the working blade is loaded evenly against the Yankee surface. Preferably, the equalizing tube  36  is filled with a viscous liquid; however, it could be a solid material (for example an elastomer) for high-load or high-temperature applications. 
     If desired, the internal spacer elements  37 ′ may be equipped with load or vibration sensors, such as strain gages, to measure the force transmitted through the axis of the doctor blade  2  (as shown in  FIG. 6 ). The tissue manufacturing operation will find value in monitoring this force as it is closely related to the frictional force, or tangential force, between the working edge of the doctor blade  2  and the Yankee surface  1 . In other words, this force is what is required to remove the tissue sheet from the Yankee.  FIG. 8  for example, shows the use of load or vibration sensors  38  that are embedded in the base of the doctor blade support structure  3  (beneath the doctor blade cartridge  7 ′) in order to sense the tangential force transmitted through the doctor blade. 
     The remaining components of the doctor blade holder system of  FIG. 6  are the same as those of the embodiment of  FIGS. 1-5  and bear the same reference numerals. As with the system shown in  FIG. 5 , the profiling plate  4  of  FIG. 6  is shown displaced from the holder mounting plate  13  by actuation of an adjustment mechanism  29 , wherein both the cupped washer  27  and the profiling plate mounting structure  25  move with the profiling plate, and the holder mounting plate mounting structure  24  remains with the holder mounting plate  13 . 
     Referring to  FIGS. 7-11 , in accordance with a further embodiment, the present invention provides an improved doctor blade holder assembly that again includes a doctor blade support structure  50 , a profiling plate  52  and a back-up blade  106 . The doctor blade support structure  50  retains a doctor blade  56 , in close proximity to the generally cylindrical surface of a Yankee dryer. The doctor blade support structure  50 , includes a doctor blade receiving groove  58 , preferably fitted with a doctor blade cartridge  60 . The doctor blade cartridge  60 , includes multiple internal spacer elements  62  that are attached to both side walls of the cartridge and provide support to the bottom edge of the doctor blade. The top edge of the doctor blade, the working edge, is pressed against the Yankee surface  1 . The back-up blade may have a thickness as discussed above. The doctor blade support structure  50  includes two integrated wear bars similar to the wear bars  64 ,  66  discussed above with reference to the embodiment of  FIGS. 1-5 . 
     The doctor blade support structure  50  also includes a T-shaped longitudinal slot  68  that spans the full length of the structure. This T-shaped slot  10  is used for mounting purposes. A series of milled out recesses  70  (shown in  FIG. 9 ) are spaced along the length of the member. The remaining lands  72  between the recesses, mate against the holder mounting plate  74  to provide a stable mounting for the blade support structure  50 . 
     A clamping bar  75  is contained within the T-slot  68 . Again, the clamping bar  75  may be formed of a continuous length, or may be configured as a series of segmented bars. The clamping bar  75  has a series of holes spaced in the longitudinal direction. The holder mounting plate  74  has a series of tapped holes  76  that are spaced in alignment with the tapped holes in the clamping bar  75 . The holder mounting plate  74  also has a series of tapped holes  78  for receiving shoulder screws  80  as well as a series of clearance holes  82  for receiving an adjustment mechanism  84  as shown in  FIG. 10 . The cap screws  86  pass through holes  88  in the profiling plate  4  are used to force the clamping bar  75  against an inner surface of the T-slot  68  as discussed above. 
     The profiling plate  52  extends in the longitudinal direction and is attached along the bottom edge thereof to the holder mounting plate  74  with a different embodiment of an adjustment mechanism  84 . Again, adjustment mechanisms  84  are provided along the longitudinal direction of the profiling plate  52  and the holder mounting plate  74  that permit the profiling plate  52  to be moved a small amount away from the holder mounting plate  74  in order to accommodate small variations in the distance between the tip of the doctor blade  56  and the roll surface.  FIG. 11  shows the holder in cross-section with the profiling plate adjusted towards a Yankee (away from the holder mounting plate). 
     As also shown in  FIGS. 8 and 11 , the profiling plate  52  may include a series of mutually spaced pins  90  that are pressed into the holder mounting plate  74  to provide a primary support for the profiling plate  52  in the vertical direction. 
     The spherical mounting arrangements  92  of the present embodiment also allow for flexure, or localized rotation, of the profiling plate around one or two axes shown diagrammatically in  FIG. 2 . A longitudinal fulcrum or ridge  93  is machined into the profiling plate  52  to create a center of rotation. In accordance with an embodiment, the spherical mounting arrangement  92  may include a spherical thrust bearing having mounting structure elements  94  and  95 , that cooperate to with a shoulder screw  96  to provide a small range of movement of the profiling plate  52  with respect to the holder mounting plate  74  responsive to movement of the adjustment mechanism  84 . In particular, as the adjustment mechanism urges the profiling plate  52  toward the roll surface, the profiling plate mounting structure  94  moves with respect to the shoulder screw, while the holder mounting plate mounting structure  95  remains with the shoulder screw. 
     Again with reference to  FIG. 11 , during adjustment of the adjustment mechanism  84 , the shoulder screw  96  and the concave portion  95  of the assembly remain fixed, while the convex portion  94  of the assembly move with the profiling plate to accommodate the pivoting motion of the profiling plate  4  caused by the movement of the profiling plate  4  with respect to the holder mounting plate  13  (which, again was caused by adjustment of the adjustment mechanism  29 ). In accordance with further embodiments of the invention, many other spherical mounting designs may be used to provide the required freedom of movement of the profiling plate  4  with respect to the holder mounting plate  13 . 
     As discussed above, series of spaced, rectangular-shaped, openings  70  are machined in the profiling plate allowing the lands of the doctor blade support structure to pass through, and mate up to the holder mounting plate. The profiling plate  52  may be one continuous member or it may be segmented in order to increase flexibility or reduce manufacturing costs. If it is segmented, then an additional load-bridging member would be utilized. This load-bridging member would provide a connection between segments and would serve to align the facing ends of adjacent segments. Alternatively, a series of mutually spaced vertical cuts  98  may be provided in the profiling plate  52  to increase flexibility. The series of adjustment mechanisms  84  are threaded through the holder mounting plate  74  and act on the upper area of the profiling plate  52 . 
     One embodiment of these adjustment mechanisms  84  consists of a rotatable, externally threaded body and a flanged screw  100  connection to the profiling plate. This mechanism is capable of accommodating the angular movement of the profiling plate  52 . A preferred design has an inner removable flanged screws  100  that are attached to the main body of the adjustment mechanism  84  with a left-hand threaded connection. Again, by machining this connection with left-hand threads, the forces applied to the flange will serve to tighten the flange rather than loosen it when adjustments are made. Spherical washers  102 ,  104  mate with spherical surfaces machined on the flanged screw  100  and the adjustment mechanism  84  to allow for the angular movement of the profiling plate. 
     Again, these adjustment mechanisms may be set independently, within a range, to force the upper edge of the profiling plate, into or away from the back-up blade  106 . The back-up blade, in turn, transfers this movement, and associated force, directly into the working blade. As discussed above, this feature allows precise control of the contact load between the working blade and the Yankee surface, continuously across the full width of the Yankee. Once each adjustment mechanism is set, a special cap  108 , with female threads is screwed onto the adjustment mechanism  84  and tightened. Again, this action serves to lock the adjustment mechanism at the desired setting, while also preventing process contaminants from interfering with the threads or filling the wrench socket. An equalizer tube  110  may also be used as discussed above. 
     Those skilled in the art will appreciate that numerous modifications and variations may be made to the above disclosed embodiments without departing from the spirit and scope of the present invention.