US2185955A - Screening plate with channels - Google Patents

Description

Jan. 2, 1940. B scHIBBYE I SCREENING PLATE WITH CHANNELS Filed Jan. 30, 1936 sk'ei/ UNITED [STATES zssssss PAT Eur cr tics SCREENING rLA' r'E Wrrn CHANNELS Lauritz Benedictus Schibbye, "Svartvik, Sweden,

assignor to Linkiipings Armatur-Och Metallfabriks Aktiebolag, ,Linkoping, Sweden Application January'so, 1936, Serial No."61,623

. In Sweden February 6, 1935 2 Claims,

The present invention relates to apparatus for screening cellulose fiber and more particularly pertains to means for controlling the movement of r the fibers which do not pass through openings of the first screen.

In flat screens and other screens where the material to be screened, such as cellulose fiber strongly diluted with water, is moved over the screening surface there will arise a concentration of unscreenable particles on the surface as a natural consequence of the screenable particles having gradually been screened away. This fact is a great drawback in screens of the above mentioned type since this concentration of unscreenable particles often contain heavy parts which gather directly on the screening surface thus preventing screenable objects to pass the screens. The concentration of the said unscreenable heavy parts also involves other drawbacks. They may be subdivided and thus follow the screened material and deteriorate the same or fill the holes in the screening surface and thus decrease the efii-' In rinsing the screens with ciency of the screens. water and steam the heavy particles may penetrate the screen and follow the screened material. They require much water to be moved over the screening surface. The screens may also be sucked dry.

It is obvious that the longer the screening surface is made in the direction of flow of the material the greater the concentration of the unscreenable particles will be in that part of the screening surface which the material finally passes. In order to reduce the drawbacks concentration screens have formerly been used which have been short in the direction of fiow of the material, but the advantage of making the screens short in that manner is counteracted by the fact that several parallel screening surfaces must be used in order to maintain the output. In view of the subdivision of the unscreenable particles, which may be the consequence of the concentration of the same at the remotest part of the screening surface this portion of the screening surface has been provided with smaller holes and slits in order to prevent as much as possible unsuitable particles from accom panying screened material.

Also other methods, for instance rapid feeding motion of the material and water jets directed along the screens have been used to neutralize the above-mentioned drawbacks.

The object of the present invention is to prevent a concentration of heavy and unsuitable particles by providing the screening surface with channels without holes or with fine holes in which channels the heavy particles of the material to be screened collect. The channels are disposed in the direction of flow orsubstantially insuch direction and may be of various shapes and cross section, just as the screen surface between the channels, are formed according to the nature of the material to be screened and to other circumstances. I

- The accompanying drawing illustrates two embodiments of the invention.

One embodiment is illustrated in Figures 1, 2' and 3, Figure 1 showing a top plan view of a screening plate, Figure 2 a section on line II--II of Figure l, and Figure 3 part of such a section in a larger scale. The other embodiment is illustrated in Figures 4 and 5, in which Figure 4 shows a top View of a screening plate and Figure 5 a section on line V-V of Figure 4.

As is shown, in both'embodiments the screening surfaces l are made oblique towards the channels 2. During the operation of the screen the heavy and thick particles which donot pass the screen I have a tendency for moving sideways at each pulsation so that they will soon fall into the channels. Each screening plate according to the drawing is relatively short in relation to the width of the screen, and therefore each screen is composed of several such plates arranged behind each other in the direction of fiow, each subsequent screening plate being situated at a lower level than the preceding one. As shown in the drawing each screening plate, at the edges lying perpendicularly to the direction of flow, has a plane surface orextension 3 at a level with the bottom of the grooves, the said bottom being located lower than the screen surfaces. The mass, having passed a screening plate, the heavier particles lying on the bottom of the channels will be mixed together and with the lighter mass flowing on the screening plate, whereby an equalization of the material takes place, but it is clear that passing from a preceding to a subsequent screening plate the heavier particles tend to continue in the channels of the latter screening plateand further from screening plate to screening plate in the same way. When several screens are coupled in series an equalization of the material will take place not only between the screen plates but also between the screens. The shape of the bottom on which the mass is moved between the screens may be provided with channels like the screening plate itself. The equalization of the material obtained between each screening plate may, thus, take place more or less between the screens as well as I also before the first screen if the material is conducted to the said screen on a bottom having grooves opening on a plane surface at the place of transition to the first screen.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

'1. In apparatus for screening cellulose fiber, a screening plate comprising a plurality of raised portions spaced from each other and extending substantially in the direction in which the cellulose fiber is to be moved over the screening plate, said raised portions having openings therein to cause fibers to pass therethrough, the portions of said screening plate between said raised portions providing channels having solid bottom surfaces extending substantially in the direction in which the fiber is to be moved over the screening plate whereby the fibers which will not pass through said openings fall into said channels for movement over the screening plate and an extension arranged at the ends of said raised portions substantially in alignment with the bottom of the channels so that the fibers in the channels may spread on the extension.

2. In apparatus for screening cellulose fiber, a screening plate comprising a plurality of raised portions spaced from eachother and extending substantially in the direction in which the cellulose fiber is to be moved over the screening plate, said raised portions having openings therein to cause fibers to pass therethrough, the portions of said screening plate between said raised portions providing channels integrally formed from the raised portions and having solid bottom surfaces extending substantially in the direction in which L. B. SCI-IIBBYE.

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