In various different fields there is often a need in some way to treat material in the form of large quantities of small particles. One such particulate material is plant seeds-grains such as wheat or barley, or the seeds of linseed (flax) or oil-seed rape, for example-and for these the treatment might be the application of a fungicide or the provision or a coating of some sort. Indeed, coatings of a water-impermeable but cold-breakable polymer are of value in allowing seed to be sown early in the warm Autumn of one year yet not germinate until the warmth of the Spring of the next (by when the ground is still not dry enough to drill seed).

This is especially useful in northern Countries, with very cold winters, such as Canada, where it is desirable to sow early in Autumn, while the ground is still soft enough to drill, and yet not have the seed germinate until the Spring of the next year, when it is warm enough for the young plant to survive.

One advantageous way to effect this type of treatment is to use a rotary coating machine of the kind available under the Mark ROTOGARD (RTM) from J E Elsworth Ltd, of King's Lynn, England. In this class of machine the seed-or whatever the particulate matter is-is contained within a cylindrical, drum-like, stator the bottom of which is a co-axial, cup-like rotor, having a flat base and outwardly-sloping sides, so that seed therein is thrown outwardly and upwardly as the rotor rotates (at about 300rpm), climbing up the inside of the rotor wall and eventually reaching the wall of the stator where, after travelling further up and round across that wall, it slows down to the point at which it falls back down into/onto the rotor, so forming a roughly tubular body of seed co-axial with the stator, and as it falls so the treatment fluid is sprayed laterally onto the inner surface of the tubular moving mass from a spray head located generally centrally and axially thereof.

When using such a rotary coating machine to spray-coat seed with some substance that will form on the seed a water-impermeable polymer coating (so as to allow the seed safely to overwinter in the ground without it germinating and then dying), the substance- the polymer precursor-is commonly sprayed on as a solution or slurry, typically an aqueous one containing around 50wt% polymer solids, and all the solvent/water has to be evaporated off to get the treated seed"dry" enough for storage and then subsequent use. Of course, this drying of the seed can be done in any conventional drying machine, but it would be convenient if each batch of treated seed could be dried in situ within the rotary treatment machine rather than having to be extracted therefrom and then subjected to a further processing/drying stage in a different machine in a different place.

It is this drying of a particulate material-in this case, seed-that the present invention is concerned with. In particular, the invention relates to a modified version of the rotary coating machine that allows the treated particulate material (such as seed) to be dried in situ during or after the treatment. This can be advantageous not only to allow the preparation of dried particles after a single treatment but also to facilitate the preparation in a single machine of multi-layer-coated particles by a series of sequential coating treatment/drying stages.

More specifically, then, the invention is a modified rotary treatment machine having means on or in the stator wall-and most conveniently the means is a simple aperture, most preferably formed as a vertical slot, in the stator wall-just above the upper edge of the rotor and through which in operation hot, and preferably dry, air can be blown into the already- treated/coated seed as it travels past, so speeding up the evaporation of the treatment solvent/water and thus improving the drying of the seed.

In one aspect, therefore, the invention provides a dryer based on a particulate-matter rotary treatment machine of the type having a cylindrical, drum-like, stator within which in operation the batch of matter particles is contained, within the bottom of which stator is a cup-like rotor, having a flat base and outwardly-sloping sides, so that in operation particles therein are thrown outwardly and upwardly as the rotor rotates, eventually reaching the wall of the stator where, after travelling up and round across the wall, they fall back down into/onto the rotor, the machine including treatment-fluid spray means having a stator- axially-located spray head central thereof from which treatment fluid can be sprayed laterally onto the moving mass of particles, and wherein there is means, on or in the stator wall adjacent the edge of the rotor, through which in operation drying air can be blown into the mass of particles as they travel past.

The dryer of the invention can be utilised to dry any sort of particulate matter that has just been spray treated therein, and while its primary use is envisaged as drying seeds (such as grains like wheat or barley, or oil-producing seeds such as rape and flax, or even larger ones such as palm nuts) nevertheless it can also be employed for treating and then drying a myriad of other particulate materials. Examples of such treatment include: pelleting seed (either to provide a biologically active or useful coating or simply to make them"bigger"so as to increase their ease of handling), as is done, say, to sugar beet seed; treating pelleted animal feed products to provide them with a vitamin coating; treating particles, or small items, of food for humans with spices, colouring, flavouring and the like (coating peanuts with salt and sugar, and breadcrumbs with colour); giving granules of plastics a layer of pigment or dye; and coating ceramic powders with slippery,"parting"agents to assist removal from the mould of some object moulded therefrom without it being damage.

While the rotary treatment machine is most conveniently one of the aforementioned ROTOGARD (RTM) machines, nevertheless it can be any machine having a drum-like stator at the bottom of which is a cup-like rotor. Typical rotor speeds are around 300rpm, although the smaller machines run a little faster than that.

In the rotary treatment machine some treatment fluid is sprayed onto the moving mass of particles from a spray head located within the stator and generally centrally of the tube-like body of particles (the spray is preferably disk-like, the treatment liquid being projected radially outwards in all 360° at once into the surrounding body of particles). The treatment, and thus the nature of the fluid, can be of any appropriate sort.

The invention is a modification of the rotary treatment machine by adding the improvement of means on or in the stator wall adjacent the rotor edge-just above the upper edge of the rotor-through which in operation drying air can be blown into the mass of particles as they travel past. There may, of course, be more than one such means, but usually a single means is sufficient.

While the drying air input means might be a pipe leading down the stator wall to the appropriate point adjacent the upper edge of the rotor, the preferred form the means takes is as an aperture-and especially a vertical elongate but narrow (ie, slot-like) aperture- created in the stator wall and through which the hot air can be blown from outside. For strengthening purposes the slot can if thought desirable have a central strut across it.

Typical dimensions for the stator used in the ROTOGARD rotary treatment machines are 15-lOOcm (6-40in) internal diameter, and with an internal height of about 50-70t of that diameter. For such machines typical dimensions for the air input means aperture slot are 20-40mm (and especially 30mm) wide and 200-400mm (especially 300mm) long.

On the outside of the stator wall the aperture most advantageously has connector means to which may be attached a pipe (or similar) to a source of hot air. In the case of a slotted aperture, this connector means is preferably a fish-tail connector, which may be angled up or down, or left or right, as required to fit most appropriately with the other elements of the machine and its environment. Preferably the angle is such as to return to the inside of the stator any particles that come out through the slot-ie, the bottom of the fishtail is steeply down in the airflow direction.

In a particularly-preferred form of rotary treatment machine the stator wall has a spoiler, or baffle, to introduce a mild turbulence into the particle flow around the wall, and so promote better mixing, and an advantageous form of such a baffle is an axially- parallel elongate"bump"along the wall inside surface and disposed normal to the particle movement direction.

Such a bump can be formed by a flat blade conveniently about 5in (12. 5cm) wide and set at an acute angle to the stator wall to give a gap about 2in (5cm) across, but is preferably a section of"angle iron" (but at a flatter angle, such as around 120°, rather than 90°). The baffle bump may be made of any suitable material (such as stainless steel), and may be secured to the wall in any appropriate manner. Where it is such a blade or angle piece then it is very much preferred that the slot be located behind this, the baffle's"trailing"edge then standing free (about 10mm or so) from the wall, to form a gap, so that the input hot air can emanate therefrom into and with the flowing seed. In one preferred form of treatment machine the baffle is "hingedly"mounted on the stator wall by a flexible hinge running its entire length, and by pushing the baffle back and forth so the trailing edge baffle gap is adjustable, right down to it being closed completely.

The gap's length is also most conveniently adjustable so that even with the stator only partially full of particulate material the drying air can be injected in only where it actually passes into that material, and thus not wastefully above the filling line. This is conveniently achieved by providing the gap with an integral sliding cover that moves down to reduce the height of the gap. Alternatively, the baffle may be formed in sections, which can be opened and closed independently so as to adjust the gap to correspond to the height of the load of the particulate matter.

In use, air-preferably both dry and hot-is blown into the particles as they travel past (dry air absorbs more moisture than damp, and hot air more than cold). Obviously the temperature of the air, and the rate at which it is blown in, depends on many circumstances, including the nature of the particulate material being dried, and in general the air should be as hot as possible, and blown in at as high a rate as possible, without causing any damage to the particulate material. For seed, a suitable air temperature is around 40°-50°C (any hotter might sterilise the seed), and an appropriate rate is around 300 to 500, especially 400, cubic feet per minute (this is around 8, 000-13, 000, especially 11, 000, litres a minute).

An embodiment of the invention is now described, though by way of illustration only, with reference to the accompanying diagrammatic Drawings in which: Figure 1 shows a cut-away perspective view of the stator and rotor assembly of a rotary treatment machine of the sort to which the invention relates; Figure 2 shows a sectional view of a rotary treatment machine much like that of Figure 1; Figure 3 shows a perspective view of an improved rotary treatment machine of the invention, with drying capability ; Figure 4 shows a perspective view of the fishtail connector used on the improved rotary treatment machine of Figure 3; and Figure 5 shows a partial view from above of the fishtail connector in position on the improved rotary treatment machine of Figure 3.

Figures 1 and 2 show part of a conventional rotary treatment machine of the sort to which the invention relates. The machine has a drum-like stator (11) at the bottom of which is a co-axial cup-like rotor (12) driven from below. The rotor 12 has a floor-like base portion (13) and an angled side wall (14) just reaching the lower part of the inside surface of the stator wall (15). As can be seen, in operation treating a mass of seed (16) the rotor 12 spins so as to fling the seed 16 out and then up the sloping part 14 into contact with the stator wall 15, up which the seed 16 flows before falling back down nearer the middle of the rotor's base 13.

Centrally of the stator 11, and extending thereinto generally co-axially from the top, is one or more pipe (as 17: there may be several such pipes, for different materials) carrying treatment fluid. The pipe 17 leads to a spinning-disc spray head (18); in operation its spinning causes treatment fluid (19) falling thereon to be flung out laterally towards the inner surface of the body of seeds as they fall back down onto the rotor base 13, so coating the seeds.

Figure 3 shows an improved rotary treatment machine of the invention, with drying capability, and Figures 4 and 5 show details of the fishtail connector used thereon, and how it is connected.

The general overall view of Figure 3 shows the stator drum (31) suitably mounted and associated with various control mechanisms (101), treatment fluid supply containers (102), and a particulate matter feed hopper (103); none of these are shown in detail. As best seen in Figure 5, the stator wall 15 has attached to it a baffle, or spoiler (104), in the form of a length of angle iron strip disposed parallel to the stator's axis (and thus across the line of motion of the seed). The strip is mounted to the wall by its leading edge (105), with its trailing edge (106) spaced slightly away from the inside wall surface to form a small gap.

Aligned with (but shorter than) the baffle 104, a slot (107) is cut right through the stator wall, giving access from outside the stator to the inside thereof via the baffle and the gap along its spaced trailing edge 106.

On the outside of the stator wall 15, and aligned with, and covering, the slot 107, is a fishtail connector (generally 108: see also Figure 3). At the slot end this connector 108 is flanged (109) to allow it to be fixed to the outside surface of the stator wall 15, and at the other end it is formed with a circular, tubular stub (110) onto which is in operation attached the pipe (not shown) bringing hot air from a source thereof (not shown). In this particular example the fishtail 108 is angled downwards and to the left (as viewed), to facilitate its connection to the hot air source.

The operation of the treatment and drying machine of Figure 3 will be self-evident. Seed 16 charged into the stator 11 is whirled around by the rotor 12, constantly moving both around and up and down as the machine operates. And as it does so, treatment fluid 19 is sprayed onto the inside surface of the mass of seeds (as they roll back down to the rotor). And either while this is actually happening or later, once the fluid treatment is finished, hot air is blown in through the slot 107 and out through the baffle gap into the seeds as they move past the trailing edge 106 of the baffle, warming them up, and speeding up the evaporation of the fluid treatment solvent/carrier, and thus drying the seeds.