GB2268867A - A star wheel for a separator. - Google Patents

Abstract

A rotatable star wheel has a plurality of radially outwardly extending resiliently deformable projections (2). At least one of the projections (2') is longer than the other projections (2) to facilitate, in use, transport of material over the star wheel. <IMAGE>

Description

A star wheel and a separator incorporating a star wheel The present invention relates to a star wheel and a separator incorporating a star wheel, particularly, but not exclusively, an agricultural separator, e. g. a stone and clod separator.

Traditionally, separation in agricultural machines has been carried out by transporting material, e. g. stone and clod, over a series of moving webs through which loose soil is encouraged, by mechanical agitation of the webs, to filter and fall back to the ground.

GB Patent 2 145 612 discloses a device for separating clod and/or stones from root vegetables or bulbs comprising two spaced parallel rotatable members each carrying a plurality of "star" wheels. These star wheels, which may be of rubber or plastics material, have a plurality of radially outwardly extending, resiliently deformable projections, or fingers.

Preferably, the leading edges of the projections are convex and the trailing edges are concave.

Further uses of rotatable members having star wheels are disclosed in our European patent application Nos.

90308299. 8 and 90308300. 4. In the latter application, rotatable shafts fitted with star wheels forming a star wheel bed replace the traditional webs. Not only do the star wheels provide more efficient separation, but the required "run" of the star wheel bed is considerably shorter than the traditional web.

Despite the considerable success of star wheels, some problems have arisen in practice. For example, when an agricultural machine is working down a steep hill material is hesitant to climb to the back of the star wheel bed. This problem can be overcome by using a stationary or moving mechanism above the star wheel bed. However, this involves more constructional parts making the separator more complicated and more costly.

An object of the present invention is to provide a star wheel which overcomes the above-mentioned disadvantages. In accordance with the invention at least one of the projections of the star wheel is longer than the other projections so as to facilitate, in use, transport of material over the star wheel. The incorporation of star wheels in accordance with the invention into the star wheel bed of a separator involves no additional components, reduces wear and keeps costs to a minimum. Furthermore, the efficient transport of material over the stars reduces the power requirement for driving the stars.

The star wheels in accordance with the invention may be used in any agricultural separating machine, e. g. a stone and clod separator, a grader, or even a harvester, particularly a potato or bulb harvester.

The use of star wheels in accordance with the invention need not be confined to agricultural separators, but could be in any situation in which star wheels could be used, e. g. for separating aggregate.

An embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a side view of a star wheel in accordance with the invention, Figure 2 is a plan view of part of a star wheel bed of a stone and clod separator, and Figure 3 is an end view of one of the rotatable members, of Figure 2.

In Figure 1, a star wheel has a hub 1 and ten resiliently-deformable fingers 2 radiating outwardly from the hub 1. The hub 1 has a central aperture 3 for accommodating a rotatable shaft of the same cross-section as fully described in our GB patent and European patent applications already referred to.

The star wheel shown in Figure 1 differs from known star wheels in one respect only, i. e. a finger 2' is substantially longer than the remaining fingers 2 and this feature facilitates transport of material over the star wheel during rotation thereof.

If required, further of the fingers 2 could have a greater length so that two or more fingers 2' are longer than the remaining fingers 2.

The increased length of the finger may be determined experimentally depending on the particular use to which the star wheel is put. For example the finger 2' could be twice, or even more than twice, the length of the remaining fingers 2. A preferred range is an increase in length of 10% to 150%.

The material of the star wheel shown in Figure 1 may be rubber of a particular Shore hardness, or any suitable plastics material, e. g. polyurethane.

In Figure 2 a star wheel bed comprises a plurality of parallel, rotatable members 6 each comprising a rotatable shaft 7 carrying normal star wheels 4 having fingers 2 of equal length, every fifth star wheel being replaced by a star wheel 5 according to the invention having a finger 2' (2", 2"' and 2"") longer than the remaining fingers 2. The star wheels 5 are preferably 90 out of phase with each other, as can be seen more clearly from Figure 3, so that the fingers 2', 2", 2'", 2"", respectively, of every fourth star wheel 5 are aligned. The most suitable spacing and phasing of the star wheels 5 will depend on the particular application, and may be determined by simple experimentation.

Preferably, the star wheels 4, 5 of each rotatable member 6 are rotationally offset relative to each other, so that the fingers 2, 2', 2", 2'" or 2"" of each star wheel are axially aligned with the gap between the fingers 2, 2', 2", 2'" or 2"" of an axially-adjacent star wheel as shown in Figure 3.

Furthermore, the star wheels 4, 5 of adjacent rotatable members 6 are staggered relative to each other so that the long fingers 2', 2", 2t" or 2"" of the star wheels 5 of one rotatable member 6 pass between the fingers 2 (or 2 and 2', 2", 2"' or 2"") of the star wheels of the adjacent rotatable member or members 6.

The star wheel bed may be used as the lifting conveyor disclosed in our European patent application No.

90308300. 4 or in the agricultural separator disclosed therein, or in the agricultural separator disclosed in our European patent application No. 90308299. 8.

Instead of a star wheel bed, only two rows of star wheels could be used as described in our GB 2 145 612.

However, the spacing of the two shafts carrying the two rows of star wheels must be sufficient to prevent the longer fingers 2' catching on the adjacent shaft.

The star wheel shown in Figure 1 and the star wheel bed shown in Figures 2 and 3 may be used in any other application where separation is advantageously performed by star wheels, e.g. in an aggregate grader.

Although the star wheel in Figure 1 is shown with ten fingers 2, the number of fingers may be varied to suit the particular application. A minimum of six fingers would normally be required, and this can be increased to eighteen or even more.

Claims (9)

Claims:

1. A rotatable star wheel for use in a separator and having a plurality of radially outwardly extending resiliently deformable projections, wherein at least one of the projections is longer than the other projections to facilitate, in use, transport of material over the star wheel.

2. A star wheel as claimed in claim 1, wherein the at least one projection is from 10% to 150% longer than the other projections.

3. A star wheel as claimed in claim 1 or 2, wherein there are from six to eighteen projections.

4. A star wheel as claimed in claim 1 or 2, wherein there are ten projections.

5. A star wheel for use in an agricultural separator substantially as herein described with reference to Figure 1 of the accompanying drawing.

6. A separator having a plurality of spaced rotatable members each comprising a row of star wheels, each star wheel having a plurality of radially outwardly extending resiliently deformable projections, wherein at least some of the star wheels are as claimed in any one of the preceding claims.

7. A separator as claimed in claim 6, wherein longer-projection star wheels are spaced by equal-length star wheels.

8. A separator as claimed in claim 6 or 7, wherein the star wheels of adjacent rotatable members are staggered relative to each other.

9. A separator having a plurality of spaced rotatable members substantially as herein described with reference to the accompanying drawings.