Metal working – Method of mechanical manufacture – Multiperforated metal article making
Patent
1996-06-12
1998-03-17
Moon, Daniel
Metal working
Method of mechanical manufacture
Multiperforated metal article making
209397, 210498, B01D 3910
Patent
active
057273162
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of screen cylinders. Screen cylinders of the type to which the present invention pertains are typically used in removal of debris such as sand, rocks, metal pieces, resin etc. from a liquid suspension, for instance a fibrous stock used in pulp or paper making. The cylinders form a part of s screening device in which the slurry to be screened flows inside the cylinder and is forced to flow through the slotted screen. The inside of the cylinder is usually subjected to the action of hydraulic foils or the like agitating device which are used to further advance the screening efficiency by preventing the clogging of the screening slots.
The following United States patents also describe the field to which the present invention pertains: U.S. Pat. Nos. 3,941,703 (Binard), 3,631,981 (Young), 4,259,136 (Spiewok), 4,264,438 (Frejborg) and 5,064,537 (Chupka et al.) and 5,128,028 (Lamort), 5,200,072 (Frejborg). The disclosure of all of the above patents is incorporated herein by reference.
It is known, from the '072 Frejborg patent, to provide a screen drum by machining in one face of a stainless steel rectangular plate a plurality of grooves extending from one end of the plate to the other, to then machine, in the other face, narrow slots extending each full width, from one side of the plate to the other. The slots provide screening passages through the plate. The narrow slots extend generally at right angles to the grooves. The plate is then rolled into a cylinder, with the face in which the slots were machined inside. The ends of the plate are then welded to each other to enclose the screen cylinder. The machining of the grooves results in a number of peripheral ribs on the cylinder, each disposed between adjacent grooves.
German Offenlegungsschrift 41 07 905 (Sulzer-Escher Wyss) refers to the common general knowledge, namely that slots cut in a screen body are reduced in width when the body is rolled into a cylindric shape. The displacement of the neutral bend line due to the presence of ribs on the screen is also mentioned. Yet, viewed from the standpoint of the present invention, there is no recognition that the final width of the screening slots in the finished, cylindric screen can be controlled simply by selecting appropriate height of the prior to the rolling.
The width of the screen slots at the inlet end of each slot determines the degree of removal of contaminants from the screened stock. The smaller the width, the higher the degree of removal of rejects. Viewed from the standpoint of manufacture of the screens, the width of the slots depends mainly on the thickness of the circular cutter used in the milling of the slots. At the inlet end of each slot, a specifically shaped groove may be machined but the ultimate determining size of the slot passage is still the width of the inlet portion of the slot at the bottom of the profiled groove.
The minimum thickness of commercially available circular cutters used in machining the slots in screen plates is 0.15 mm (0.006 in.). The manufacturers of the screens prefer a somewhat thicker cutter as it is less prone to breaking during the machining process. The desired width of the slot in the rolled cylinder, however, prevented the use of thicker cutters to maintain the prescribed, relatively narrow width of the slots in order to secure the desired screening capability.
It is an object of the present invention to further advance the art of cylindric screen manufacture by providing a method of manufacture; and a product made by such method, where the ultimate width of the inlet end of the slots can be reduced, within practical limits, without having to use special thin cutters in machining the slots.
It is another object of the invention to provide a method of making a cylindric screen or to provide a cylindric screen produced by the method, where the ultimate width of the inlet part of the screen slots can be selectively controlled such that the same width of the slots in the planar plate p
REFERENCES:
patent: 3520418 (1970-07-01), Guinard
patent: 3631981 (1972-01-01), Young
patent: 3664502 (1972-05-01), Nichols
patent: 3941703 (1976-03-01), Binard
patent: 3957652 (1976-05-01), McGonigal
patent: 4259136 (1981-03-01), Spiewok
patent: 4264438 (1981-04-01), Frejborg
patent: 4406326 (1983-09-01), Wagner
patent: 4529520 (1985-07-01), Lampenius
patent: 4901417 (1990-02-01), Chupka et al.
patent: 4918807 (1990-04-01), Frejborg
patent: 4932112 (1990-06-01), Tikkanen
patent: 5023986 (1991-06-01), Gero et al.
patent: 5059324 (1991-10-01), Chen
patent: 5064537 (1991-11-01), Chupka et al.
patent: 5073254 (1991-12-01), Peisenherz et al.
patent: 5128028 (1992-07-01), Lamort
patent: 5200072 (1993-04-01), Frejborg et al.
patent: 5513757 (1996-05-01), Papetti
patent: 5524770 (1996-06-01), LeBlane et al.
patent: 5587077 (1996-12-01), Aaltonen et al.
CAE ScreenPlates Inc.
Moon Daniel
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