Patent Application
20060225647
1. Field of the Invention
This invention relates generally to web processing machines, such as paper machines and the like, and is concerned in particular with an improved apparatus for doctoring the rolls of such machines.
2. Description of the Prior Art
In known doctoring arrangements of the type disclosed for example in U.S. Pat. No. 5,279,710 (Aikawa), U.S. Pat. No. 4,906,335 (Goodnow et al.), and U.S. Pat. No. 4,665,859 (Dunlap et al.), the doctor blades are carried by holders that are rotatable about pivot rods. Under certain operating conditions, these holders have a tendency to vibrate or chatter due to the clearances that must necessarily be introduced between the relatively rotatable components.
In other known doctoring arrangements of the type disclosed for example in U.S. Pat. No. 6,328,853 (Goodnow et al.), the doctor blades are carried on flexible top plates that are fixed to and extend in cantilever fashion from base components of the holders. Such arrangements beneficially minimize the clearances that are the source of vibration and chattering problems. However, this advantage is partially offset by attendant compromises in blade conformability and uniformity of blade loading across the width of the surface being doctored, and a diminished ability to accommodate cross machine thermal expansion and contraction of the top plate.
In still other known doctoring arrangements of the type disclosed in U.S. Pat. No. 6,786,999 (Goodnow et al.), the doctor blade and top plate assembly is held in a clamp-type pivot or hinge along the back edge of the top plate. Loading and unloading tubes are disposed in compartments beneath the top plate. The loading tube is inflated and the unloading tube is deflated to pivot the assembly toward and thereby urge the doctor blade against the work surface. The inflation and deflation is reversed to pivot the assembly away from the work surface. Clamp-type hinges are composed of multiple separate components and achieve angular displacement by a frictional sliding between its relative parts.
An objective of the present invention includes the provision of an improved doctoring apparatus that provides an angular motion capability using a one-piece flexible hinge, that eliminates sliding friction losses within the hinge, that provides impact resistance, shock absorption, and vibration dampening, and that maintains a liquid-tight seal along the length of and between the top plate and a doctor back.
An additional objective of the present invention is to provide an alternative to reverse assembled stainless steel leaf and pin style hinges. The hinge should have a rotational capacity of ±6.5° of rotational motion, be able to operate at temperatures of up to about 200° F., more preferably be able to operate at temperatures of up to about 450° F., and be subject to typical paper machine conditions, including exposure to water and dilute chemicals.
In accordance an aspect of the present invention, a doctor blade holder has a top plate having a rear portion overlying a base structure and a front portion projecting forward from the base structure. Blade support members are carried by and cooperate with the front portion of the top plate to define forwardly open slots for receiving the doctor blade. A hinge is interposed between the rear portion of the top plate and the base structure. The hinge has a body portion defining a fulcrum about which the top plate pivots relative to the base structure, and has forwardly and rearwardly projecting integral flanges arranged respectively to underlie the top plate and overlie the base structure. The doctor blade holder has means for securing the forwardly projecting flange to the top plate and for securing the rearwardly projecting flange to the base structure.
The hinge may advantageously be molded or extruded from an elastomer, preferably from a high temperature elastomer, such as Viton, available from DuPont Dow Elastomers LLC of Wilmington, Del. The hinge may be reinforced, either internally or externally, by a fabric, a preferred example being Kevlar available from E. I. du Pont de Nemours and Company of Wilmington, Del. A core selected from the group consisting of extruded elastomer, fiberglass rod, stainless steel mesh, and stainless steel cable may be integrally incorporated into the molded or extruded hinge body. The hinge body may also be internally configured to define a chamber containing a pressurized fluid.
These and other features and objectives of the present invention will now be described in greater detail with reference to the accompanying drawings.
Referring to
Hinge 12 has a continuous cylindrical body 30, an upper flange 32 integrally projecting forwardly from the upper half of body 30, and a lower flange 34 integrally projecting rearwardly from the lower half of body 30. Upper flange 32 is removably attached to top plate 14 with screws 36 and a fastening strip 38. Lower flange 34 is removably attached to holder 16 with screws 40 and a fastening strip 42. Alternatively, rivets could be used in place of screws 36 and 40 and either with or without fastening strips 38 and 42. Hinge 12 may be formed from many different materials to meet different applications. For example, hinge 12 may be molded or extruded from a high temperature elastomer, such as Viton, available from DuPont-Dow Chemicals.
Using a flexible material for hinge 12 has several advantages. First, it permits top plate 14 and, ultimately, doctor blade 18 to rotate about body 30 of hinge 12 while allowing hinge 12 to be a single, unitary element. Second, hinge 12 provides impact resistance and shock absorbance capacity to apparatus 10. Third, hinge 12 forms a seal between top plate 14 and holder 16 along the entire continuous length of hinge 12 that greatly reduces or eliminates the infiltration of contaminants.
Blade support member 20 is attached by screws 44 to the underside of the forwardly projecting portion of the top plate 14. The forward portions of the blade support members cooperate with the underside of the top plate to define forwardly open slots 46 configured and dimensioned to receive and retain the rear edge of doctor blade 18. A plurality of blade support members are used to retain doctor blade 18 and are spaced one from another along the cross-machine direction.
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In light of the foregoing, it will now be appreciated by those skilled in the art that various changes may be made to the embodiment herein chosen for purposes of this disclosure without departing from the inventive concept defined by the following claims.
