GB2219726A - Decorticating machine - Google Patents

Abstract

In a mill specifically for grinding off the inedible hard cortex of the Winged Bean (PSOPHOCARPUS TETRAGONOLOBOUS) with minimum damage to the nutritious endosperm, grinding is performed by gravitating the beans repeatedly through an adjustable gap between a pair of abrasive coated horizontal axis drums A/1, A/2, which rotate at different speeds in opposite directions, downwards at the grinding gap. The drums are mounted in a container fed at one end (R, Fig 2 not shown) with raw beans. Partly cylindrical guide-sheets H/1, H/2 around the bottoms of the drums repeatedly force the beans being processed up to the tops of the drums to fall into the gap again, as they flow in spirals round the drums towards the overflow (S, Fig. 2). The cortex particles are separated from the endosperms by screening and aspiration. <IMAGE>

Description

DOUBLE-DRUM GRINDER OF THE CORTICES FROM HARD FOOD GRAINS.

THE TECHNICAL FIELD: AGRO-INDUSTRY This invention relates to a machine for removing the cortices of the types of grains (certain legumes, cereals and nuts) which cannot at present be decorticated either by longestablished conventional milling machines or by our patent G.B. 2195 227 A; published date 7/4/88, or by our E.C. Patent No. 86 309 215 of 27/1/87.

The first of the two patents is primarily for splitting off the brittle hulls (husks) of paddy rice to obtain brown rice grains, while the second Patent is for polishing the brown rice to white rice grains by the removal of some or all of their thin layers of soft bran coating, without breaking the whitened grains.

This new invention is primarily for removing the hard cortices which firmly encapsulate the edible endosperms of the seeds of a legume; the Winged Bean, (PSOPHOCARPUS TETRAGONOLOBOUS).

These beans originate in New Guinea, Asia, but small-scale cultivation has spread to some S. and S.E. Asian countries.

The beans grow in pods, each pod containing several beans which are similar in size and shape to green peas; nearly spherical. The cortices range in colour according to the species from pale beige, through brown, to nearly black.

The cortices are thin, hard, smooth and slippery. Their near-white endosperms are somewhat brittle.

Winged beans contain about the same high percentages of oils and proteins as soya beans.

Winged bean plants are wholly edible by man; leaves, shoots, immature seed pods and the bean seeds, above ground; and the tubers below ground. The merits of the Winged Bean are well known among food scientists as a potentially valuable supplementary crop for peoples too dependent for food on the high carbo-hydrates in polished rice, cereal flours, or roots of the cassava type.

These bean plants, if well exploited post-harvest, could provide beans rich in the oils and proteins needed for better balanced diets in developing countries, particularly.

It appears that lack of simple and effective machinery to remove the hard bean cortices, without undue damage to the edible endosperms, is discouraging expansion of Winged Bean cultivation. It is a fairly simple crop to grow in the humid tropics and sub-tropics.

The position is much worse for this bean than it would be for the paddy/rice post-harvest industry, had no machinery been developed in this century for hulling paddy and then polishing (bran removing) the brown rice.

Paddy processing into edible rice has depended for milleniums on pounding paddy in large mortars, using heavy pestles, followed by winnowing away all the splintered hulls, much crushed rice and most of the bran. This destructive process is still in domestic use; effective; labour but not capital intensive in Asia.

There is no apparatus for Winged Beans which is equivalent to the pestle and mortar for extracting edible rice from paddy.

DISCLOSURE OF THE INVENTION AND ITS ADVANTAGES The invention is comprised of two horizontal axis drums placed side by side with an adjustable gap between them. The cylindrical surfaces of the drums are covered with sharp abrasive.

The drums are rotated on axles at different speeds, the peripheral motions being downwards at the gap.

The drums operate in a container kept filled with beans.

The bottom of the container is lined with two partly cylindrical sheets, each surrounding the lower one-third area of one of the abrasive surface of a drum, with a larger gap than the one between the drums.

The raw beans are fed into the two corners of the container at one end and the outlets, for grain and debris of cortex, are at the corresponding corners at the other end of the container.

The rotation of the drums draws the beans down between them into the gap where they are groundby both of the drums. The speed at which the beans pass down through the gap is about the mean of the peripheral speeds of the drums.

The partly cylindrical sheets around the bottoms of the grinding drums divide the downy low of beans from the grinding gap and guide these separated flows around the bottoms of the drums, the impulse to flow coming partly from the rotating grinding drums. The beans then flow up and over the tops of the two drums and again down into the grinding gap.

The beans, fed into one end of the container, follow repeated spiral paths round the drums till they reach the far ends where they discharge, carrying with them the loosened particles of cortex. These are separated out by screening from the edible endosperms, assisted by aspiration.

The degree of cortex removal depends on the peripheral speeds of the drums and the number of times that each bean passes through the grinding gap. The gap size is related to the shape of the beans, to their maximum dimension, and it is large enough to prevent any bean being broken due to being pinched between these hard drums.

The cortices are so thin relative to the diameters of their beans that their abraded debris is insufficient to obstruct the process, even as it accumulates among the beans spiralling round the drums.

The main advantage of the machine described is its ability to make cheaply available, as marketable food, these high fat and protein beans to supplement the excessively starchy normal diets of many peoples in developing regions in the humid tropics and sub-tropics.

Another advantage is that the Winged Bean plants, including their tubers, are edible as vegetables and, being legumes, they provide their own nitrogen fertiliser and leave the soil enriched for the next crop.

There is a possibility that this basic machine could be adapted for grinding or polishing other grains including sorghums, millets, other cereals and dried coffee cherry.

These would need adjustments to the gap between the drums; the use of suitable abrasives on the drums; adjustments to drum speeds; the addition of particle aspiration during grinding,particularly for sorghums which have thick cortices which come off as a yellow cloud when abraded suitably.

THE DRAWINGS The attached sketches are two elevations and a plan of the double drum grinder, all shown wholly or partly in section.

A/1 and A/2 are the pair of grinding drums.

B/1 and B/2 are the heavy abrasive coatings on A/1 and A/2 drums.

C/i and C/2 are the axles on which the drums A/1 and A/2 are mounted.

D/1 and D/2 are roller bearings for the axles C/i and C/2.

E/1 and E/2 are roller-cum-thrust bearings for the axles C/i and C/2.

F/1 and F/2 are the fast and slow reduction gearboxes for the axles C/i and C/2 respectively.

G/1 and G/2 are the electric motors to drive the gearboxes F/1 and F/2.

H/1 and H/2 are the curved guide sheets for returning part ground grain to the tops of the drums for further grinding passes in the gap.

J is the adjustable grinding gap between drums A/1 and A/2.

K/1-2 represent the vertical side sheets of the container.

L/1-2 represent the vertical end sheets of the container.

M represents the removable top covering sheet of the container.

N represents the bottom (ground) sheet of the container.

P/1-4 show the vertical slots in 12/1-2 side sheets which enable the drums on their axles, to be lifted out for maintenance.

9 represents the screw adjustment, on axle C/2 to alterthe grinding gaps.

R represents the inlet for grains into the container.

S represents the overflow chute for well-decorticated endo-sperms and cortex particles from the container, which leads to equipment to sift out the particles from the endo-sperms.

Claims (9)

1. A machine specifically for grinding off the hard cortices of Winged Beans, comprising two abrasive coated drums on horizontal axes, side by side, with a gap between them, the drums rotating at different speeds, downwards at the gap; and inside a container into which the beans are fed at one end; they overflow at the other end after being forced repeatedly through the grinding gap and then spirally around the drum perimeters to the discharge ducts.

2. As in Claim 1, the gap between the abrasive coated drums is much greater, say 2 to 3 times, than the largest dimension of the beans so that no bean can be broken by being pinched between these hard drums.

3. As in Claims 1 and 2, the container has a pair of semi cylindrical sheets, one around the bottom of each drum but with a larger gap than the one between the drums.

4. As in Claims 1-3, the sheets meet nearly vertically under and along the grinding gap, so dividing the flow of beans into two and guiding each flow under and up the perimeters ofthe drums, the pressure on the beans to flow being supplied by the downwards forced flow in the grinding gap and then the rotation of the abrasive drums.

5. As in Claims 1 to 4, the double flow of beans reaches over the tops of the drums and then drops again into the grinding gap. The circulation of the beans in this manner is continued until enough of the cortices have been ground off.

6. As in Claims 1 to 5, the degree of cortex grinding is controlled directly by the rate of feed of raw beans into the container, the slower the feed the more numerous the spiral turns the beans make round the grinding drums to reach the discharge ducts.

7. As in Claims 1 to 6, the cortex of the Winged Bean is very thin and particles of abraded cortex occupy very little of the air space between the spherical beans so these particles travel with the beans out of the discharge ducts but do not interfere with the grinding process.

8. As in Claim 7, the particles of cortex are separated from the beans by sieving and aspiration after discharge from the container.

9. Apparatus using a pair of oppositely'rotating drums with abrasive coated sides, primarily for grinding off the hard cortices of Winged Beans to render their endosperms available as marketable food, high in proteins and oils, with reference to Figures 1 to 3 of the accompanying drawings.