Carbon fiber doctor blade

Information

  • Patent Grant
  • 6491754
  • Patent Number
    6,491,754
  • Date Filed
    Tuesday, June 13, 2000
    24 years ago
  • Date Issued
    Tuesday, December 10, 2002
    22 years ago
Abstract
An apparatus for one of direct and indirect application of a coating medium onto a traveling fiber material web includes at least one doctor element for application and/or metering of the coating medium. At least one doctor element is formed of a carbon fiber material.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention.




The present invention relates to doctor blades, and, more particularly, to a doctor blade for leveling and/or metering a layer of liquid or viscous coating medium.




2. Description of the Related Art.




A doctor blade is used to level and/or meter coating medium onto a moving background. With direct application of the coating medium, a moving background is a material web, such as a paper or cardboard web. With indirect application, a moving background is the surface of a transfer element which transfers the coating medium onto the material web.




It is known for a doctor blade to be formed of materials such as high carbon spring steel, beryllium copper, stainless steel or fiberglass. A problem is that these materials have generally poor wear characteristics.




What is needed in the art is a doctor blade that has higher strength and better wear characteristics.




SUMMARY OF THE INVENTION




The present invention provides a doctor blade formed of a high strength composite material, such as carbon fiber. Also provided are various arrangements for positioning such a doctor blade relative to the moving background.




The invention comprises, in one form thereof, an apparatus for one of direct and indirect application of a coating medium onto a traveling fiber material web. At least one doctor element applies and/or meters the coating medium, and is formed of a carbon fiber material.




An advantage of the present invention is that, because of the higher strength and wear characteristics of the carbon fiber material, the doctor blade has a longer useful life.




Another advantage is that the doctor blade has better lubricity because of the carbon material.




Yet another advantage is that the position of the doctor blade relative to the moving background can be closely controlled.











BRIEF DESCRIPTION OF THE DRAWINGS




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:





FIG. 1

is a fragmentary, side view of one embodiment of the apparatus of the present invention;





FIG. 2

is a fragmentary, side view of another embodiment of the apparatus of the present invention;





FIG. 3

is a fragmentary, side view of yet another embodiment of the apparatus of the present invention; and





FIG. 4

is a fragmentary, side view of a further embodiment of the apparatus of the present invention.











Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.




DETAILED DESCRIPTION OF THE INVENTION




Referring now to the drawings, and more particularly to

FIG. 1

, there is shown one embodiment of a doctor blade apparatus


10


of the present invention, which generally includes a doctor blade


12


, a doctor holder


14


, a first air hose


16


and a second air hose


18


. Doctor blade apparatus


10


operates to level and/or meter coating medium on a surface


20


of roll


22


.




Doctor blade


12


is formed of a carbon fiber material, providing doctor blade


12


with high levels of strength and durability. Doctor blade


12


includes a body portion


24


and a T-shaped projection


26


extending therefrom. Body portion


24


includes a chamfered first end


28


for engaging the coating medium on surface


20


. An opposite end


30


of body portion


24


is clamped in a fixed position in doctor holder


14


. Projection


26


includes a base


32


and head portion


34


oriented perpendicular to base


32


.




Doctor holder


14


includes a base


36


and an extending arm


38


having respective clamping devices


40


and


42


for securely holding end


30


of doctor blade


12


. Base


36


includes a cavity


44


having a through slot


46


opening into a wider chamber


48


. Chamber


48


retains each of air hoses


16


,


18


and head


34


of projection


26


therein.




During operation, end


28


of doctor blade


12


can be moved away from or toward surface


20


by adjusting the relative air pressures in hoses


16


and


18


. For example, if the pressure within hose


16


is increased relative to the air pressure in hose


18


, hose


16


exerts a force on head


34


, thereby moving projection


26


away from wall


50


of chamber


48


. Movement of projection


26


away from wall


50


tends to cause a rotation of doctor blade


12


about its end


30


, clockwise in

FIG. 1

, such that end


28


is moved toward surface


20


of roll


22


. A gap


52


is shown between end


28


and surface


20


. Increasing the air pressure in air hose


16


reduces gap


52


and may cause end


28


to come into contact with surface


20


and/or the coating medium that is carried in direction


54


on surface


20


.




Conversely, increasing the air pressure in hose


18


relative to the air pressure in hose


16


exerts a force on projection


26


that moves projection


26


away from wall


56


of chamber


48


. Such movement of projection


26


causes end


28


to move away from surface


20


to thereby increase or create gap


52


. Thus, by adjusting the air pressure in hoses


16


and


18


, the size of gap


52


, or the force exerted by end


28


on surface


20


, can be tightly controlled.




In an alternative embodiment (not shown), air hose


16


or air hose


18


is replaced by a spring, such as a coil spring. Thus, the spring and the air hose exert opposite forces on projection


26


to establish an equilibrium position of end


28


. By adjusting the air pressure within the air hose, the position of end


28


can be closely controlled.




In another embodiment (FIG.


2


), a doctor holder


58


includes a slot


60


for retaining an air hose


62


which actuates an end


64


of carbon fiber doctor blade


66


. Doctor blade


66


includes a pivot point in the form of a recess


68


for receiving a projection


70


of doctor holder


58


. Projection


70


extends parallel to doctor blade


66


and includes, at its distal end, a ball


72


with a circular cross section. Ball


72


and recess


68


form a ball-and-socket type of joint which allows doctor blade


66


to rotate in the plane of the page, as indicated by double arrow


74


.




In operation, increasing the air pressure within air hose


62


causes hose


62


to inflate and thereby push end


64


away from doctor holder


58


. As doctor blade


66


rotates about recess


68


, end


76


of doctor blade


66


is moved toward surface


20


of roll


22


, as described above with respect to FIG.


1


. Conversely, deflation of air hose


62


allows end


76


to move further away from surface


20


.




In a third embodiment (FIG.


3


), a carbon fiber doctor blade


78


includes a projection


80


having a ball


82


at the distal end thereof. Doctor holder


84


includes a recess


86


for receiving ball


82


. Together, ball


82


and recess


86


form a ball-and-socket type joint for allowing pivoting of doctor blade


78


in the directions indicated by double arrow


88


.




Doctor blade


78


is symmetrical about a imaginary line


90


that bisects doctor blade


78


through projection


80


. End


92


of doctor blade


78


is also chamfered and is identical to end


94


. Thus, once end


94


has become worn down from use to the point where it no longer operates effectively, doctor blade


78


can be reversed such that the unworn end


92


is repositioned adjacent to surface


20


, and the worn end


94


is repositioned such that it can be actuated by hose


62


. More particularly, ball


82


can be removed from recess


86


such that doctor blade


78


is disengaged from doctor holder


84


. Doctor blade


78


can then be turned 180 degrees and reattached to doctor holder


84


by inserting projection


80


into recess


86


.




In use, similarly to the embodiment of

FIG. 2

, inflation of air hose


62


results in end


94


being moved toward or biased against surface


20


of roll


22


. Conversely, deflation of hose


62


results in a decrease in pressure on end


92


, thereby allowing end


94


to rotate away from surface


20


.




In a fourth embodiment (FIG.


4


), doctor holder


96


includes a projection in the form of a T-shaped post


98


with a base


100


and a dovetailed head


102


. Carbon fiber doctor blade


104


includes a pivot point in the form of a recess


106


having a throughslot


108


leading into a relatively wider chamber


110


.




In operation, the dovetailed configuration of head


102


allows doctor blade


104


to pivot about post


98


as air hose


62


actuates end


112


of doctor blade


104


. Similarly to the embodiments of

FIGS. 2 and 3

, inflation of air hose


62


results in end


114


of doctor blade


104


being moved toward or being biased against surface


20


of roll


22


. Deflation of air hose


62


allows end


114


to rotate away from surface


20


in the direction of arrow


116


.




In the embodiments shown herein, the doctor blades include a projection or a recess on the same side of the doctor blade that is actuated by an air hose. However, it is to be understood that the doctor blade can also have a projection or a recess on a side of the doctor blade that is opposite from the side of the doctor blade that is actuated by an air hose.




It is also possible for the doctor blades of

FIGS. 1 and 4

to have identically chamfered opposite ends that allow the doctor blade to be reversed, similarly to the doctor blade of FIG.


3


.




The actuators may be in a form other than an air hose. For example, the actuators may be in the form of an electromagnetically actuated ram.




Backing roll


22


has been shown as rotating clockwise in

FIGS. 1-4

. However, it is also possible for roll


22


to rotate counterclockwise in each of the embodiments. In this case, the doctor blade would function to clean roll


22


or to remove a sheet from surface


20


of roll


22


.




The doctor blade has been shown in

FIGS. 1-4

as being in a linear, unloaded state. However, it is to be understood that the doctor blade can be deflected if the doctor blade is loaded against roll


22


, for instance.




While this invention has been described as having a preferred design, 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.



Claims
  • 1. An apparatus for at least one of leveling and metering a layer of coating medium on a traveling substrate, said apparatus comprising:a fixed structure having a projection; a doctor element including: a first end associated with the traveling substrate; a second end disposed opposite said first end; and a fixed pivot point disposed between said first end and said second end, said fixed pivot point comprising a recess pivotably receiving said projection, said projection extending substantially parallel to said doctor element; and an actuator configured for rotating said second end of said doctor element about said pivot point to thereby rotate said first end of said doctor element one of toward and away from the traveling substrate.
  • 2. The apparatus of claim 1, wherein said doctor element is formed of a carbon fiber material.
  • 3. The apparatus of claim 1, wherein said actuator comprises an air hose.
  • 4. The apparatus of claim 1, wherein said doctor element is substantially symmetrical about an imaginary line bisecting said doctor element through said fixed pivot point.
  • 5. The apparatus of claim 1, wherein said fixed pivot point further comprises a projection having a substantially circular cross section, said fixed structure further comprising a recess for pivotably receiving said projection of said fixed pivot point.
  • 6. The apparatus of claim 1, wherein said projection has a substantially circular cross section.
  • 7. The apparatus of claim 1, wherein said projection comprises a T-shaped post with a base and a dovetailed head, said base having a first width, said dovetailed head having a second width greater than said first width.
  • 8. The apparatus of claim 1, wherein said recess includes a throughslot in communication with a chamber, said throughslot having a first width, said chamber having a second width larger than said first width.
US Referenced Citations (7)
Number Name Date Kind
4789432 Goodnow et al. Dec 1988 A
5356519 Grabscheid et al. Oct 1994 A
5824154 Freti Oct 1998 A
5870657 Nagame et al. Feb 1999 A
5980692 Goodnow et al. Nov 1999 A
6134405 Zona Oct 2000 A
6299732 Rekila Oct 2001 B1
Non-Patent Literature Citations (2)
Entry
J. A. Kent, Riegel's Handbook of Indrustrial Chemistry, Ninth Edition, pp. 789-791, 1992.*
Kirk-Othmer, Encyclopedia of Chemical Technology, Fourth Edition, pp. 1-5, 16, and 17, 1993.