GB2039351A - Cascade grain drier - Google Patents

Abstract

A cascade grain drier comprises an inclined louvred bed 4 through which, in use, air is passed and a plurality of rotors 1 arranged with their axes extending transversely above the bed 4 and spaced apart lengthwise of the bed 4 and having vanes 2,3 extending outwardly from each rotor 1 to control the flow of grain down the bed 4, and means for varying the rate of flow of air through the bed 4. Extension paddles 18 are mounted on at least some of the vanes 2, each paddle 18 projecting from the radially outer transverse edge of the vane 2 on which it is mounted and having a width less than that of the vane 2 in the transverse direction of the bed and a length such that the combined length of the vane 2 and the paddle 18 from the axis of rotation of the rotor 1 is less than the distance between the axis of rotation and the nearest part of the upper surface of the bed 4. <IMAGE>

Description

SPECIFICATION Cascade grain dryer The invention relates to a grain drier of the cascade type (hereinafter called "a cascade grain drier") in which grain, seed or other like commodity to be dried (hereinafter called "grain") flows down an inclined louvred bed through which hot or cold air is passed.

An example of cascade grain dryer is described in British Patent Specification No. 1021133. In that cascade grain drier, the flow of grain down in a louvred bed is controlled by a plurality of transverse rollers spaced apart in the length of the bed and each having outwardly-extending vanes which serve to effect the movement of grain down the bed, the rollers either being rotated solely by the pressure of grain acting on the vanes or by powered driving means, alternate vanes in a direction circumferentially around each roller being radially-longer than the intermediate vanes and serving to act, when in their downwardly-extending positions as dams which restrain grain from flowing freely down the bed and so determine and maintain the depth of grain in the bed upstream of that roller.

One advantage of the cascade grain drier described in the aforesaid Specification is that the depth of grain on the bed can be increased compared with that possible in cascade grain driers known hitherto.

When commodities requiring comparatively low temperature drying are to be dried by passing comparatively cool, unheated or cooled airthrough the louvres of the bed, the depth of grain (as hereinbefore defined) on the bed should be as great as possible, thereby to perform the drying economically. Such commodities are rice and soya beans.

When there is a large depth of grain on the bed, the Applicant has found that the performance of the drier is improved by increasing the rate of flow of air through the bed either by increasing the volume of air or its inlet pressure to the louvres or both. The invention therefore provides in a cascade grain drier of the type comprising an inclined louvred bed through which, in use, air is passed and a plurality of rotors arranged with their axes extending transversely above the bed and spaced apart lengthwise of the bed and having vanes extending outwardly from each rotor to control the flow of grain (as hereinbefore defined) down the bed means for varying the rate of flow of air through the bed. This may be performed either by providing a fan which can be driven at variable speeds or by providing different speed fans.When a drier is to be used for hot air drying with a shallower depth of grain a lower speed fan or a lower speed of a variable speed fan would be selected and where a drier is to be used for cold air drying with a greater depth of grain, for example, for rice or soya bean drying, a higher speed fan our a higher speed of operation of the variable speed fan would be selected. The change of speed of the variable speed fan would be selected.

The change of speed of the variable speed fan may be provided by changing a pulley or gear wheel in a drive to the fan or by providing a movable belt on different diameter pulleys or by using a changespeed gear box.

Due to the increased depth of grain on the bed, the rotation of rollers like those described and illustrated in British Patent Specification No. 1021133 having alternate radially long and short vanes would tend to be stopped or slowed down by the pressure and volume of the grain acting on the vanes.

According to a further feature of the present invention, a cascade grain drier of the type comprising an inclined louvred bed through which, in use, air is passed and a plurality of rotors arranged with their axes extending transversely above the bed and spaced apart lengthwise of the bed and having vanes extending outwardly from each rotor to control the flow of grain (as herenbefore defined) down the bed and having means for varying the rate of flow of air through the bed is also provided with extension paddles mounted on at least some of the vanes, each extension paddle projecting from the radially outer transverse edge of the vane on which it is mounted and having a width less than that of the vane in the transverse direction of the bed and length such that the combined length of the vane and the paddle from the axis of rotation of the rotor is less than the distance between the axis of rotation and the nearest part of the upper surface of the bed.

Conveniently the paddles of each rotor are staggered relatively to each other in the widthwise direction of the vanes thereof so that the paddles during rotation of the rotor will together pass through the grain on the bed throughout substantially the whole width of the bed. For example, the paddles may be so arranged around a rotorthatthe radially outer ends of the paddles together define a helix co-axial with the axis of the rotor. Where the rotors are of a kind similarto the so-called rollers in the aforesaid specification in which alternate vanes of a rotor are radially longer than the intermediate vanes of the rotor, the paddles would be mounted on the radially-longer vanes only.

The provision of the paddles enables the depth of grain on the bed to be increased as the paddles will aid the rotation of the rotors through or by the increased depth of grain.

The invention also includes a rotor having the aforesaid extension paddles on vanes thereof and extension paddles, as aforesaid, for attachment to vanes of a rotor.

By way of example, a cascade grain drier in accordance with the invention is now described with reference to the accompanying drawings, in which: Figure lisa diagrammatic perspective view of a part of the bed of the grain drier; Figure 2 is a diagram showing an end view of one of the rotors in position over a portion of the bed of the grain drier; Figure 3 is a perspective view of the rotor shown in Figure 2, and Figure 4 is a detail view of one of the aforesaid paddles shown on the rotor of Figures 2 and 3.

Referring to Figure 1, the cascade drier has an inclined bed 4 bounded by side members 8. The bed 4 is formed from overlapping slats 5 forming louvres 6 through which compressed air is passed into grain flowing down the bed. The slats 5 and louvres 6 are shown in Figure 2. A plurality of rotors 1 of which one is shown in Figures 2 and 3 extend across the bed 4 between the side members 8 at equally-spaced intervals along the length of the bed. The rotors 1 are freely rotatable about shafts 12 by the grain as it flows down the bed, as will hereinafter be explained, although the rotors 1 could be power-driven. Beneath the bed a casing 9 encioses ducting and heating apparatus (not shown) whereby hot or cold air can be blown through the bed by a fan 14 shown mounted outside the casing 9. Alternatively, the fan 14 may also be positioned beneath the bed within the casing 9.In accordance with the invention a variable flow of air is required and so the fan 14 is shown driven by a variable speed gear box 15 and electric motor 16. At the bottom of the bed there is an elevator 10, of which only part of the housing thereof is shown, whereby the dried grain is removed from the grain drier.

As described in British Specification No. 1021133 and as shown in Figures 2 and 3 hereof, each rotor is a regular decahedron, although it may be of other cross-sectional shape, and has vanes 2 and 3 extending outwardly from the longitudinal edges at the corners of the decahedron. Alternate vanes 2 are substantially longer than the other vanes 3 in radial length. Also, as in the aforesaid British Specification, each of the said longer vanes 2 has holes 17 therein spaced apart along its width axially of the rotor 1.

The same reference numbers have been used for the same parts in this Specification as in the aforesaid British Specification.

The rotors 1 control the flow of grain 7 down the bed in the direction of arrow x in Figures 2 and maintain the depth of grain substantially uniform by virtue of the radially longer vanes 2 acting as dams by which the flow of grain will be retarded but which will permit the controlled downward flow by virtue of the continuous rotation of the rotors 1. provided the depth of grain does not exceed a predetermined value, at which the grain will build-up against the rotors 1 and prevent them turning and eventually flow over the top of the rotors, thereby nullifying their effect, the rotors 1 will be turned by the force of the grain bearing against successive radially longer vanes 2.The operation of the rotors 1 is described in the aforesaid British Specification and it is explained therein how the rotors having alternate radially longer and shorter vanes 2 and 3 can control a greater depth of grain than can rotors in which all the vanes are of the same radial length.

It has now been found that even greater depths of grain can be controlled by fitting extension paddles 18 on to at least some of the radially longer vanes 2 of the rotors 1, the paddles 18 having a width, in the axial direction of the rotors 1, considerably shorter than the axial length of a rotor 1. Such paddles 18 are shown in Figures 3 and 4. To control the depth of grain uniformly across the bed of the grain drier, the paddles 18 are staggered in their positions in the axial width of a rotor 1 on each of the radially longer vanes 2 of the rotor so that corresponding points along the outer edges of the paddles 18 define a helical locus around the rotor, as indicated in Figure 3 by chain line 19. Each paddle 18 is attached to a vane 2 by readily removable bolts and nuts 20 passing through a paddle 18 and the vane 2, as shown in Figure 4, so that where the grain is of a type requiring cold air drying and a greater depth of grain is required, the paddles 18 can befitted and where a smaller depth of grain is required, the paddles 18 can be removed. A greater depth of grain is required for drying rice or soya bean. Additionally the rate of flow of air can be varied according to the type of grain being dried by varying the speed of the fan 14 or by replacing the fan 14 by a fan having another operating speed.

Claims (8)

1. A cascade grain drier of the type comprising an inclined louvred bed through which, in use, air is passed and a plurality of rotors arranged with their axes extending transversely above the bed and spaced apart lengthwise of the bed and having vanes extending outwardly from each rotor to control the flow of grain (as hereinbefore defined) down the bed, the drier also including means for varying the rate of flow of air through the bed.

2. A cascade grain drier as claimed in Claim 1 further characterised by extension paddles mounted on at least some of the vanes of at least one of the rotors, each extension paddle projecting from the radially-outer transverse edge of the vane on which it is mounted and having a width less than that of the vane in the transverse direction of the bed and a length such that the combined length of the vane and the paddle from the axis of rotation of the or the respective rotor is less than the distance between the axis of rotation and the nearest part of the upper surface of the bed.

3. A cascade grain drier as claimed in Claim 2 in which the extension paddles are mounted on at least some of the radially-longer vanes of said rotor.

4. A cascade grain drier as claimed in Claim 3 in which at last one extension paddle is mounted on each of the radially-longer vanes of said rotor.

5. A cascade grain drier as claimed in Claim 4 in which the or an extension paddle on each radiallylonger vane is staggered in the axial direction of said rotor with respect to the or a paddle on each of the circumferentially-adjacent radially-longer vanes, whereby corresponding points along the radiallyouter edges of the paddles define a helical locus or loci around said rotor.

6. A cascade grain drier as claimed in any one of Claims 2 to 5 in which the paddles are detachably mounted on the respective vanes.

7. A rotor having extension paddles projecting from the radially-outer transverse edge of at least some of the vanes thereof for use in a cascade grain drier as claimed in any one of Claims 2 to 6.

8. A cascade grain drier constructed and arranged substantially as described herein and shown in the accompanying drawings.