GB2234149A

GB2234149A - Soil sieve and grading device

Info

Publication number: GB2234149A
Application number: GB8917291A
Authority: GB
Inventors: Timothy Needham; David Weston
Original assignee: Richard Pearson Ltd
Current assignee: Richard Pearson Ltd
Priority date: 1989-07-28
Filing date: 1989-07-28
Publication date: 1991-01-30
Anticipated expiration: 2009-07-28
Also published as: GB8917291D0; GB2234149B

Abstract

A soil sieve and grading device comprises an upstream and a downstream rotatable member (1, 2). The downstream rotatable member (2) comprises a plurality of axially-spaced starwheels (3) having angularly-spaced resilient fingers (9, 9'). The relative spacing of the rotatable members is adjustable between a first end position in which the ends of the fingers (9, 9') of the starwheels of the downstream rotatable member lie adjacent the upstream rotatable member (1) for fine sieving and a second end position in which the ends of the fingers of the starwheels of the downstream rotatable member are spaced from the upstream rotatable member for maximum grading. <IMAGE>

Description

Soil Sieve and Grading Device The present invention relates to a soil sieve and grading device.

Agricultural grading devices are known in which root crops, such as potatoes, can be graded, but these tend to be unsuitable for grading objects of irregular size. Irregular objects, e.g. wedge-shaped stones can become wedged between the spaced rollers used for grading.

An object of the present invention is to provide a soil sieve and grading device in which the above-described disadvantage is alleviated.

The invention provides a soil sieve and grading device as claimed in claim 1.

By suitable relative positioning of the rotatable members, soil sieving, fine grading or any degree of course grading can be obtained. Wedge-shaped articles, instead of jamming between the rotatable members, are carried upwardly by the flexible fingers and appear to "climb out" of the gap between the rotatable members.

In one preferred embodiment of the invention, the upstream rotatable member is a roller. Such an arrangement is very suitable for grading potatoes.

In another preferred embodiment of the invention, the upstream rotatable member is a further row of starwheels. This provides a very vigorous action suitable for soil sieving or grading say, animal feed root crops.

An embodiment of the invention will now be described with reference to the accompanying drawing, wherein: Figure 1 is a side view of two rotatable members. and Figure 2 is a plan view of the rotatable members of Figure 1.

In the drawing. upstream and downstream rotatable members 1. 2 each comprise a plurality of starwheels 3 mounted on parallel shafts 4, 5 drivingly rotatable in the same direction as shown by arrows 6. Each starwheel 3 has a central spacer bush 7 with a shaped axial bore 8 and a plurality of resilient angularly-spaced fingers 9 extending from the bush 7. The fingers are curved slightly in a rearward direction, i.e. their leading edges are convex and their trailing edges are concave.

The fingers 9 are known as "parrot-beak" shaped.

From Figure 1 it will be seen that the pitch of adjacent starwheels 3 on each shaft 4, 5 is slightly staggered, so that a finger 9' of a starwheel is aligned in an axial direction with the gap between the adjacent fingers 9 of the adjacent starwheel. Thus, the horizontal angularly-spaced gaps normally extending between the fingers of aligned starwheels are blocked by the fingers 9' of alternate starwheels. As a result of this arrangement, the fingers 9, 9' form helically-shaped rows around the axis. This ensures that, in use, slightly larger objects, which might fall into the gaps formed by aligned starwheels, are carried over.

The staggering of the pitch of the starwheels 3 is simply achieved by altering the pitch of the central bore 8. Thus, the sets of starwheels are formed in which the pitch of the bore 8 for each set differs by half the angular distance between adjacent fingers 9.

The bore 8 is preferably square shaped as shown, but could have any other suitable shape.

Each starwheel 3 has at least eight, and preferably 12, fingers 9. For small objects, e.g. gooseberries, starwheels with 16 fingers would be preferable. The diameter of the starwheels is about 15cm. The starwheels may be formed from rubber or polyurethane.

As can be seen from Figure 2, the rotatable members 1, 2 are axially staggered so that the fingers 9, 9' of rotatable member 1 are aligned with the gaps 10 between the starwheels of the other rotatable member 2.

In use, material flowing over the rotatable members is rotated both against the flow of material and also from side to side by the action of the fingers of the starwheels. This facilitates the grading of irregularly-shaped objects. For example, wedge-shaped potatoes or stones, instead of being jammed between the rotatable members 1, 2, tend to "climb" upwardly and are passed on with the objects being graded until the gap 11 corresponds to the size of the wedge-shaped article which then falls through, Larger objects are of course carried on further to fall through the appropriate larger gap 11.

Thus, in a first end position the fingers of the starwheels of the two rotatable members 1, 2 completely intermesh, the ends of the fingers almost, but not quite, touching the bushes 7, e.g. with a clearance of about 2cm. In this position, only fine particles can fall between the fingers, and the device acts solely as a soil sieve.

As the shafts are moved apart the gaps between the ends of the fingers and the bushes of the other rotatable member increase in size, so that larger objects, e.g.

stones and very small potatoes, fall through. As the rotatable members are moved further apart, the axial width of the gap 12 between adjacent fingers remains the same, although its length increases, and this allows elongate objects to fall through, e.g. kidney-shaped potatoes.

As the rotatable members 1, 2 are moved still further apart the fingers of the starwheels of the two rotatable members become disengaged so that the gap 11 is formed.

This, in combination with the gap 12. allows even larger objects to fall through. The gap 11 may be increased to. say, about locum.

By replacing every alternate one, two or more starwheels with a spacer bush, the gap 12 can be increased so that still larger objects can be graded, e.g. larger swedes or turnips.

Apparatus can be set up incorporating any desired number, e.g. ten, of the above devices with the spacing between rotatable members adjusted to provide the required grading. The gap 11 between the adjacent rows increases in the direction of rotation of the starwheels, and hence in the direction of travel of the objects being graded. The gap increase need not occur between each row of starwheels but may be in stages.

Thus, the gap 11 may be constant over two or three gaps and then be increased for the next two or three gaps.

This ensures that the maximum extraction of objects of the correct size is achieved at each stage.

The above-described embodiment with two rows of starwheels provides a vigorous action which makes it suitable for, e.g. old potatoes and animal-feed root crops, but unsuitable for grading, say, new potatoes, since the skins may be damaged. For such objects, the upstream rotatable member 1 should be in the form of a roller, e.g. a smooth roller of steel, plastics or other suitable material.

The grader can be used for other root crops, such as carrots, onions, turnips etc, for bulbs. and also for certain fruits, such as gooseberries.

Claims

Claims:

1. A soil sieve and grading device comprising an upstream and a downstream rotatable member, the downstream rotatable member comprising a plurality of axially-spaced starwheels having angularly-spaced resilient fingers1 and the relative spacing of the rotatable members is adjustable between a first end position in which the ends of the fingers of the starwheels of the downstream rotatable member lie adjacent the upstream rotatable member for fine sieving and a second end position in which the ends of the fingers of the starwheels of the downstream rotatable member are spaced from the upstream rotatable member for maximum grading.

2. A soil sieve and grading device as claimed in claim 1, wherein the upstream rotatable member is a roller.

3. A soil sieve and grading device as claimed in claim 1, wherein the upstream rotatable member also comprises a plurality of axially-spaced starwheels having angularly-spaced resilient fingers.

4. A soil sieve and grading device as claimed in claim 3, wherein the starwheel of the upstream rotatable member are axially-staggered relative to the starwheels of the downstream rotatable member, and the ends of the fingers of the starwheels of the upstream and downstream rotatable members intermesh for fine sieving.

5. A soil sieve and grading device as claimed in claim 3 or 4, wherein preselected starwheels are replaceable by spacers to enlarge the gaps between adjacent starwheels of the downstream and/or upstream rotatable member to increase the size of maximum grading.

6. A soil sieve and grading device as claimed in claim 3, 4 or 5, wherein adjacent starwheels the upstream and/or downstream rotatable member are angularly staggered so that when viewed in an axial direction each finger of each starwheel is aligned with the gap between adjacent fingers of the adjacent starwheel.

7. A soil sieve and grading device as claimed in claim 6, wherein the starwheels have a shaped central bore and the angular staggering of adjacent starwheels is achieved by angular staggering of the bores.

8. A soil sieve and grading device as claimed in claim 7, wherein the central bore is square-shaped.

9. A soil sieve and grading device as claimed in any one of the preceding claims, wherein each starwheel has eight or more resilient fingers.

10. A soil sieve and grading device as claimed in claim 9, wherein each starwheel has 12 resilient fingers.

11. A soil sieve and grading device substantially as herein described with reference to the accompanying drawing.

12. Agricultural apparatus comprising a plurality of soil sieve and grading devices as claimed in any one of the preceding claims, wherein the spacing between adjacent rotatable members is adjusted to provide successive grading as objects to be graded pass over the said devices.

13. Agricultural apparatus as claimed in claim 12 wherein the said spacing increases in stages, there being two or more spacings in each stage of substantially the same size.