Patent Application
20080053874
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 an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates 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.
Referring now to the drawings, and more particularly to
Vessel 12 can be of any suitable configuration, such as a closed top or open top vessel. For ease of illustration, only one wall of vessel 12 is shown in
Rotor 14 is disposed within vessel 12, and has a generally circular cross-section when viewed from the top of
Screen plate 16 is disposed within vessel 12, in stationary opposition to rotor 14. Screen plate 16 includes a base plate 22 defining a working surface 24 on a side facing rotor 14. Working surface 24 includes a plurality of substantially parallel first grooves 26 extending in a first direction 28 and a plurality of substantially parallel second grooves 30 extending in a second direction 32. First grooves 26 intersect with second grooves 30, defining a cross-hatched pattern of grooves. First grooves 26 and second grooves 30 conjunctively define a plurality of lands 34 and depressions 36. In the embodiment shown, first grooves 26 and second grooves 30 intersect generally orthogonal to each other, but may also intersect at a different angle, thus changing the frontal shape of lands 34 and depressions 36. More particularly, depending upon the intersection angle between first grooves 26 and second grooves 30, as well as the spacing between first grooves 26 and second grooves 30, lands 34 may have a shape which is square shaped, rectangular shaped or diamond shaped.
Lands 34 and depressions 36 are each formed with a through-hole 38 extending through base plate 22 of screen plate 16. In the embodiment shown, each land 34 is formed with a centrally located through-hole 38 and each depression 36 is formed with a centrally located through-hole 38. However, it is possible that not all lands 34 and/or depressions 36 include a through-hole 38. Moreover, the through-holes 38 need not be centrally located within respective lands 34 or depressions 36.
Each land 34 includes a plurality of defibering edges 40, each of which is a linear edge in the embodiment shown. The particular edge which is used as a leading edge, defibering edge depends upon the direction of rotation of rotor 14. Defibering edges 40 are substantially sharp defibering edges to induce a maximum fluid shear effect in the fiber suspension. To that end, a plurality of adjoining side walls 42 extend between lands 34 and depressions 36, generally orthogonal to a respective land 34. Side walls 42 could possibly be positioned at a slight acute angle relative to a respective land 34 to provide a slight undercut and even sharper defibering edge.
In the embodiment shown, each land 34 lies in a common plane and each depression 36 lies in another common plane. Lands 34 extend between approximately 0.1 and 0.2 inch above depressions 36, and preferably extend approximately 0.13 inch above depressions 36. Base plate 22 has a total thickness of approximately 0.87 inch (from the back side to lands 34), and a thickness from the back side to depressions 36 of approximately 0.75 inch. Each land 34 and each depressions 36 has a generally square shape of approximately 0.75 inch by 0.75 inch. Of course, these dimensions may vary depending upon the application.
During manufacture, the plurality of substantially parallel first grooves 26 extending in first direction 28 are formed in base plate 22. The plurality of substantially parallel second grooves 30 extending in second direction 32 are then formed in base plate 22, whereby first grooves 26 intersect generally orthogonal with second grooves 30. The plurality of through-holes 38 are then formed in screen plate 22, with each through-hole 38 centrally positioned in a respective land or depression.
Screen plate 16 is particularly suited for pulping applications requiring high levels of attrition. This would typically be in a batch or continuous pulping application where the constant stock recirculation/multiple edge impacting would have a rapid defibering effect. This effectively reduces defibering/pulping times and thereby creates significant specific energy savings.
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.
