Patent Application
20150122444
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.
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
The following description may be further understood with reference to the accompanying drawings in which:
The drawings are shown for illustrative purposes only.
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
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
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. A series of mutually spaced pins 49 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
The spherical mounting arrangements 23 allow for flexure, or localized rotation, of the profiling plate around one or two axes shown diagrammatically in
In particular and again with reference to
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
The remaining components of the doctor blade holder system of
Referring to
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
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
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.
As also shown in
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
Again with reference to
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 61900727 | Nov 2013 | US |
