GB2258831A

GB2258831A - Apparatus for applying a surface coating to granular material e.g. seeds

Info

Publication number: GB2258831A
Application number: GB9117930A
Authority: GB
Inventors: Paul David Pratt
Original assignee: Turner Grain & Feed Milling Li
Current assignee: Turner Grain & Feed Milling Li
Priority date: 1991-08-20
Filing date: 1991-08-20
Publication date: 1993-02-24
Anticipated expiration: 2011-08-20
Also published as: GB2258831B; GB9117930D0

Abstract

Granular material (for example seeds) is provided with a surface coating by dropping the material downward through a falling curtain of coating material. The granular material is fed by a feed screw 12 to the top of a column 16 and fails through the bottom of the column as a cylindrical curtain. Coating material is dispersed in a circular spray pattern which intersects the cylindrical curtain of the falling granular material. The outlet end of the feed screw has an axially movable collar 50 which can be moved to vary the position of the feed screw outlet relative to the axis 36 of the column 16. <IMAGE>

Description

APPARATUS FOR APPLYING A SURFACE COATING TO GRANULAR MATERIAL This invention relates to apparatus for applying a surface coating to granular material. The invention is particularly applicable to the application of a surface coating to seeds.

Such surface coatings are applied primarily for the control of disease in plants which will grow from the seeds, but can be applied for other purposes as well. The surface treatment may be applied in liquid or powder form. In either case the surface treatment material forms a more or less continuous coating on the seed surface.

The invention is not however limited to the surface treatment of seeds. The invention may also be applied to other types of granular material to which a surface coating has to be applied.

Machines for the treatment of seeds are known. In some such machines, the seed is dropped onto a distribution cone which causes the seed to flow as an even cylindrical curtain which falls past a rotating disc. The disc produces a radial spray of atomised surface treatment material such that the cylindrical curtain of seed passes through the atomised treatment material.

It is desirable that the cylindrical curtain of falling seed is even around its whole circumference, and the present invention aims to facilitate the production of an even cylindrical curtain; particularly in respect of machines with a relatively low, but continuous throughput.

According to the invention, there is provided apparatus for applying a surface coating to granular material, the apparatus comprising a feed screw for delivering the granular material to the top of a column through which the granular material can fall as a cylindrical curtain, means for dispersing coating material in a circular spray pattern which intersects the cylindrical curtain of the falling granular material, wherein the outlet end of the feed screw is provided with a collar which can be moved axially relative to the feed screw to vary the position of the feed screw outlet relative to the axis of the column.

Preferably the column includes a stationary central shaft, a stationary distribution cone connected to the shaft and centred around the shaft, and an atomising disc mounted at the bottom of the tube, below the distribution cone, with the drive for the atomising disc, and the feed of treatment material to the atomising disc both passing through the shaft.

The feed screw is preferably generally horizontal.

Because of the presence of the shaft it is not possible to deposit the granular material directly on the apex of the distribution cone. However it is necessary to ensure that the granular material is evenly distributed around the cone so that an even cylindrical curtain is produced.

Different seeds have different flow characteristics arising from the different grain size, shape and surface characteristics. It is however desirable to be able to use the same machine to treat a variety of different types of seed at different throughput rates, and to ensure even distribution of the treatment material on the seed.

It has surprisingly been found that the distribution of the seed onto the inclined surface of a stationary distribution cone is significantly affected by the distance from the cone axis at which the seed is discharged from a horizontal feed screw. In order to obtain the best possible range of delivery possibilities from the feed screw, the discharge end of the feed screw is preferably cut off at an angle relative to the feed screw axis, and is surrounded by a cylindrical collar which can be moved axially relative to the angled end of the discharge screw. The collar can then be moved backwards or forwards along the length of the feed screw housing to vary the way in which the granular material is discharged from the feed screw.

The collar may be continuously moveable relative to the end of the feed screw housing, or may be moveable in discrete steps. In either case it is preferable that the collar is moveable at least between one extreme position where the whole of the angled cut-off end of the feed screw housing is exposed, and an opposite end position where none of the angled cut-off end of the feed screw housing is exposed.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of apparatus in accordance with the invention for applying a surface coating to seeds; Figure 2 is a schematic, partly cut away, view of part of the apparatus of Figure 1; Figure 3 is a perspective view, again with part cut away, of the end of a feed screw of the apparatus of Figure 1; Figures 3a and 3b are cross sections through the component shown in Figure 3, showing two alternative positions of the collar; and Figure 4 is a detail of another part of the apparatus shown in Figure 1.

Figure 1 shows an apparatus which has a feed hopper 10 into which seed to be treated is loaded. A horizontal feed screw 12 rotates in a housing 14 and carries seed from the hopper 10 to the top of a treatment column 16. The treatment column has a central, stationary shaft 18 with a distribution cone 20 at its lower end. These components are contained within an annular housing 22. Below the cone 20 is an atomisation disc 24 onto which treatment liquid is dropped, so that the liquid is sprayed outwards in a pattern which intersects with a falling curtain of seed. The seed which has thus been contacted by the treatment material drops to the bottom of an elevation screw 26 which lifts the treated seed, whilst at the same time tumbling the seed and continuing the mixing, to a discharge point 28.

The apparatus shown is designed to treat seed at a continuous flow rate of two, four or six tonnes per hour.

The hopper 10 has a capacity of sixty kilograms of seed.

Three motors (not shown in Figure 1) are provided. One drives the feed screw 12 as indicated by the double headed arrow 30. A second motor drives the atomising disc 24 as indicated by the double headed arrow 32, and a third motor drives the elevation screw 26 as indicated by the double headed arrow 34. The other arrows shown in Figure 1 indicate the direction of seed flow through the apparatus.

Figure 2 shows the mixing column in more detail. The central shaft 18, which is stationary, forms a passage through the column for a drive shaft 36 for the atomising disc 24, and for conduits 38 for treatment material which lead to the upper surface of the disc 24. Liquid can be fed through these conduits 38 using a peristaltic pump, and this material falls onto the upper surface of the spinning atomising disc and is then dispersed in a fine spray from the periphery of the disc. It is also possible to use a treatment material in the form of a powder instead of a liquid, but in this case the atomising disc 24 will have to be replaced by a suitable distribution device for powder.

The seed to be treated is delivered into an upper section 40 of the housing 22, passes through a neck 42 and then onto the inclined surface of the distribution cone 20. From the distribution cone, the seed passes down through an annular section 44 of the column where it forms an even cylindrical curtain which intersects with the spray of treatment material produced by the atomising disc 24.

In order to ensure an even cylindrical curtain of seed, it is very important to ensure that the seed is evenly distributed around the central shaft 18, in the upper housing section 40. Because the flow characteristics of granular seed vary from seed type to seed type, and because the throughput rate of the apparatus may vary, it is not satisfactory to simply deposit the seed into one part of the upper section 40. In order to ensure that the seed is correctly distributed around the shaft 18, an arrangement as shown in Figures 3 is provided at the output end of the feed screw 12. At the delivery end of the screw 12 there is a tubular end section 46 which has its open end cut off at an angle as shown at 48. This tubular section 46 is surrounded by a collar 50 which can be moved between the position shown in Figure 3a and the position shown in Figure 3b. The collar 50 will be moved to its retracted position (as shown in Figure 3a) when the rate of seed flow increases, and to its forward position (Figure 3b) when the rate of flow decreases. Pre-calibrated positions of the collar 50 may be provided for specific additions (eg wheat at two tonnes per hour or oats at four tonnes per hour).

Once a regular distribution of seed into the upper section 40 has been assured, then an even cylindrical curtain of grain will fall through the annular gap 44.

It will be noted that no rotation of the distribution cone 20 is required. It is desirable to avoid rotation of the distribution cone, since this avoids the necessity for a further motor and for any requirement to seal between rotating and non-rotating parts of the central shaft 18 and the conduits 38.

Below the mixing column, there is a receiving section illustrated in Figure 4. The receiving section consists of a funnel 52 above a tubular section 54. The inclined surface 56 of the funnel 52 will be set so that the falling curtain of seed lands on the inclined surface, and so that the atomised spray of treatment material impinges upon the cylindrical curtain at a position slightly above the point at which the curtain itself impinges on the inclined surface 56. This improves the coating of the seed with the treatment material because any treatment material which passes through the curtain and reaches the inclined surface 56 will then run down the surface 56 where it will make contact with the falling seed. Furthermore any treatment material which rebounds from the surface 56 will again make contact with the curtain of seed.

The seed with the treatment material then drops onto the bottom of the elevation screw 26, and in travelling up the elevation screw the seed is tumbled together to improve the distribution of the treatment material on the seed surface.

A probe 58 is provided in the hopper 10 to detect the presence of seed so that the machine will not be run without seed in it.

The mixing column is made of stainless steel, and the components of the column can be easily dismantled for cleaning, particularly the funnel 52 and the tubular section 54.

Access doors are provided both in the housing 14 of the feed screw 12 and in the housing of the elevation screw 26 so that the machine can be completely cleaned down after operation.

Dust extraction facilities can be included. One dust extraction point 60 is shown, by way of example, in Figure 1 but dust can also be extracted from other parts of the apparatus where necessary.

The apparatus described can be used to produce treated seed irrespective of the type of seed or of the throughput rate.

The machine is relatively compact and, because of the stationary distribution cone, is simple in construction.

Claims

1. Apparatus for applying a surface coating to granular material, the apparatus comprising a feed screw for delivering the granular material to the top of a column through which the granular material can fall as a cylindrical curtain, and means for dispersing coating material in a circular spray pattern which intersects the cylindrical curtain of the falling granular material, wherein the outlet end of the feed screw is provided with a collar which can be moved axially relative to the feed screw to vary the position of the feed screw outlet relative to the axis of the column.

2. Apparatus for applying a surface coating as claimed in Claim 1, wherein the column includes a stationary central shaft, a stationary distribution cone connected to the shaft and centred around the shaft, and an atomising disc mounted at the bottom of the tube, below the distribution cone, with the drive for the atomising disc, and the feed of treatment material to the atomising disc both passing through the shaft.

3. Apparatus for applying a surface coating as claimed in Claim 1 or Claim 2, wherein the feed screw is generally horizontal.

4. Apparatus for applying a surface coating as claimed in any preceding claim, wherein the discharge end of the feed screw is cut off at an angle relative to the feed screw axis, and is surrounded by a cylindrical collar which can be moved axially relative to the angled end of the discharge screw.

5. Apparatus for applying a surface coating as claimed in Claim 4, wherein the collar can be moved backwards or forwards along the length of the feed screw housing to vary the way in which the granular material is discharged from the feed screw.

6. Apparatus for applying a surface coating as claimed in Claim 5, wherein the collar is continuously moveable relative to the end of the feed screw housing.

7. Apparatus for applying a surface coating as claimed in Claim 5, wherein the collar is moveable in discrete steps.

8. Apparatus for applying a surface coating as claimed in Claim 6 or Claim 7, wherein the collar is moveable at least between one extreme position where the whole of the angled cut-off end of the feed screw housing is exposed, and an opposite end position where none of the angled cut-off end of the feed screw housing is exposed.

9. Apparatus for applying a surface coating to granular material, substantially as herein described with reference to the accompanying drawings.