CA1175025A - Centrifugal screen separators - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A centrifugal screen separator in which the rotor is in the form of a spiral of constant diameter and pitch preferably with gaps at spaced intervals in the outer edge of the spiral shape.

Description

5;

2.

This invention relates to centrifugal screen separators.

With centrifugal screen separators a cylindrical screen is rotated at sufficient speed to effect a holding of the seed by centrifugal force against the inside face of the screen and there ar~ provided vanes within the screen to effect movement of the seed over the screen surface whereby to keep spreading this and to transfer the seed from one end of the separator to the other that is that seed or other material which is not able to pass through the screen apertures.

A particular problem with this type of arrangement is to achieve a most effective shuffling of the grain across the surface of the screen so as to provide a maximum changing of the position of the seed while using as small as possible energy in achieving~such an end.

According to this invention, it has been discovered that rather than providi~lg for independent vanes there has been found to be very significant advantage in providing -that the "shuffling" means be in the form of a spiraI.

It has been found advantageous that the spiral have gaps within the external portion so as to allow for periodic relaxation or return of shuffled grain back to the screen but that overall by providing the continuous spiral shape rather than the separate blades, firstly the cost of manufacture of suc~
a device is significantly lessened and in relation to the powPr required to drive a device handling a similar capacity a highly significant reduction in such power requirement has been observed.
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3.

The invention in one form then can be said to reside in a centrifugal screen separator for cleaning of grain and other seeds, of a type including a cylindrical screen and drive means arranged to provide for rotation of the cylindrical screen about its axis at a rotational speed sufficient to have the grain or other seed to be separated held against an inner screening surface of the screen, and seed displacement means within the cylinder being held so as to be rotatable at a speed different from the screen and arranged to have a scraper edge adjacent the inner screening surface of the screen whereby to effect a shifting of seed being cleaned from time to time over the screening face, the separator being characterised according to this invention in that the seed displacement means is comprised of a member or members having an outermost scraper edge of substantially constant spiral shape coaxial with the cylindrical shape of the screen and with a constant diameter and pitch along the cylindrical screen.

As previously stated in preference there are gaps at spaced intervals along the spiral path of the scraper edge and in preference these are located at approximately 120 intervals and further in preference have a tapered trailing edge.

Further in preference, the spiral member is provided by a sheet of metal which is formed into a spiral shape with the outer edge comprising one edge of the metal sheet and the inner edge of the spiral co~prising the other edge of the metal sheet which is in the form of a strip of constant width and thickness throughout its length and the strip is then in the form of an auger.

With such features, it has been discovered that there is significant power reduction necessary to drive the relatively rotating members, that is the cylindrical screen and the seed displacement means, and at least in some situations such as when there is some green fibre to be separated, it has been found to also provide a beneficial cleaning effect.

For a better understanding of this invention it will now be described with the assistance of drawings in which:-Figure 1 is a perspective view of the seeddisplacement means according to this preferred embodiment and Figure 2 is a view from one end of the article as shown in Figure 1.

Reférring in detail to the drawings, the seed displacement means 1 are comprised of a shaft 2 and a scraper member 3.

This scraper member 3 has an outermost scraper edge 4 which is of spiral shape and which has a plurality of spaced apart gaps 5 each of which have a leading edge 6 and a trailing edge 7.

The trailing edge 7 is shaped so as to be at an angle of 45 to the radius of the outer with respect to the axial centre.

5.

The spiral shape of the outer edge 4 is such as to be coaxiaL with the shaft 2 and as well a cylind-rical screen in which it is to be located and relat;,vely movable which is not shown.

Furthermore, the spiral shape of'the outer edge

4 as shown is of constant diameter apart of course from the incidental gaps 5 and of constant pitch 8 along the length of any cylindrical screen within which it is to be used.

With the seed displacement means as shown and located within a cylindrical cleaning screen with which it is coaxially positionecl and relatively rotated at appropriately relative speeds for instance where the screen has a diameter approximately 37 centlmetres, a screen revolution rate of 205 revolutions per minute and a rotation of the seed displacement means of 90 revolutions per minute would be typi,cal.

It is self-eviclent that the diameter of the seed displacement means as shown is such as not to have the`edge 4 scraping agaillst ~he inner face of the screen but to have this -.uffic;erltLy displaced therefrom to allow free relatlve movemellt without however being so far away with respect to any seed that seeds will not be effectively shifted across the screen face.

In practice, with the arrangement as shown, it has been Eo~lnd that very significant power reductions have taken place with respect to any cleaning capacity and while, because of the widely different types of seed and cleaning conditions that are encountered a fi~ed figure of power reduction cannot be given~
nonetheless this power reduction is very significant and provides a very significant development in,.the art.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A centrifugal screen separator for separating grain and other seeds, of a type including a cylindrical screen and drive means arranged to provide for rotation of the cylindrical screen about its axis as a sufficient rotational speed to have the grain or other seed intended to be cleaned, held against the inner screening surface of the screen, and seed displacement means within the cylinder adapted to be rotated relatively to the screen and thereby with scraper edges adjacent the inside screening surface of the screen effect the shifting of the seed from time to time over the screening face, the separator being characterised according to this invention in that the seed displacement means is comprised of a member or members having an outermost scraper working edge of substantially spiral shape of constant diameter coaxial with the cylindrical shape of the screen and constant pitch along any working length of the cylindrical screen.

2. A centrifugal screen separator as in Claim 1 further characterised in that there are gaps at spaced intervals along the spiral path of the outermost edge of the member or members.

3. A centrifugal screen separator as in either of the two preceding claims wherein the member or members providing the outermost scraper edge is comprised in each case of a sheet of metal strip in which the sheet has an outer spiral edge constituting the scraper edge and an inner spiral edge of smaller diameter than the outer spiral edge, the planar direction of the strip being aligned in a radial direction of the supporting shaft.

4. A centrifugal screen separator as in Claim 2 in which the gaps in the outer edge include a tapered trailing edge.

5. For use in a centrifugal screen separator, a seed displacement means characterised as in claim 1 or 2.