GB2072605A - Elevator buckets - Google Patents

Abstract

A bucket (3) for an elevator (1) is provided with louvres (9) to restrict the direction of flow of material (10) into and out of the bucket (3). Thus, the bucket (3) can be filled substantially to capacity when used in a centrifugal discharge elevator (1), the louvres (9) preventing premature discharge of the material (10) whilst allowing full discharge down a delivery chute (6) at the required time. The invention is particularly suitable for use in grain elevators. <IMAGE>

Description

SPECIFICATION Buckets This invention relates to buckets for use in elevators, and is particularly although not exclusively concerned with buckets for use in centrifugal discharge grain elevators.

Conventionally, a centrifugal discharge elevator comprises a continuous belt or chain which is driven around a lower pulley and an upper pulley, usually arranged vertically above the lower pulley. Buckets are boited at intervals to the belt or chain. Material to be'delivered by the elevator is usually fed into the buckets at the foot thereof. The material may simply flow into a boot, from where it is dredged by the digging action of the buckets, or more elaborate feeding mechanisms may be employed. As the buckets round the upper pulley, centrifugal force acts on the material therein, which is then ejected into a chute.

Various designs of buckets have been proposed, for dealing with different materials and different output requirements. Usually, of course, it is desired to optimise the rate at which the elevator can deliver a given material. If known buckets are filled more than, say, 60 % to 75 % full, then material tends to be spilled from the buckets prematurely, due to centrifugal force as the buckets round the upper pulley. If the buckets are made too deep, then the material tends to remain in the buckets under the influence of centrifugal force whilst rounding the upper pulley.

Similarly, if the front face of the buckets is too steeply inclined, then the material again tends to stay in the buckets as they round the upper pulley.

Increasing the speed of the belt or chain causes a corresponding increase in the centrifugal force acting on the material, thus increasing any tendency for premature discharge of the material. Also, increased belt or chain speed beyond a certain value leads to undue wear on the drive system. If buckets are made too shallow and spaced too closely together, then they tend to fan out to an insufficient degree as they round the lower pulley, leading to difficulties in charging the buckets sufficiently with the material. Alternatively, if the buckets are made too deep, difficulties are again encountered in charging them with material, as the material feed point requires to be positioned at a higher level, thus leading to an undesirable and inefficient increase in the height of the overall elevator system.

In view of the above difficulties, the rate at which a given size of known centrifugal discharge elevator can discharge material has been limited. In this context, the size of an elevator is generally determined by the width of the buckets (i.e. across the width of the belt) and the height of the elevator between its feed and discharge points.

The present invention aims to provide a generally improved bucket for use with an elevator. In preferred embodiments of the invention, there are provided buckets which can be bolted directly onto existing grain elevators of the centrifugal discharge type, to replace and markedly increase the delivery rate afforded by existing buckets.

According to the present invention, there is provided a bucket for an elevator, the bucket having a plurality of louvres to restrict the direction of flow of material into and out of the buckets.

To assist in understanding the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, in which: Figure 1 shows a section part of a grain elevator employing buckets in accordance with the invention; and Figure 2 is a cross-sectional view of one of the buckets of Figure 1.

Figure 1 shows part of a grain elevator 1 having a belt 2 on which there is mounted a plurality of buckets 3. The belt 2 is disposed in a vertical leg 4 of the elevator, and is mounted for rotation about a lower pulley (not shown) and an upper pulley 5. As shown in Figure 1 by arrows, the upper pulley 5 rotates in a clockwise direction. Grain is discharged by the elevator into a discharge chute 6.

In use, grain to be delivered is fed into a boot at the lower pulley region, where the buckets 3 in turn are filled with grain, by a scooping action. The buckets 3 are then raised to the upper pulley 5. As the buckets 3 rotate around the pulley 5, the grain contained therein is subjected to centrifugal force. The elevator is so arranged that, as each bucket 3 moves over a top dead centre position, the centrifugal force begins to cause the grain to be ejected from the buckets, and substantially all of the grain in the buckets is ejected into the discharge chute 6 by the time the buckets leave the upper pulley 5 to travel down again towards the lower pulley.

A bucket 3 is shown to a larger scale in Figure 2.

The bucket 3 has a solid base 7, a solid rear wall 8, and two solid side walls (not shown). The bucket is open at the top. The front of the bucket is provided with three louvres 9. The bottom louvre 9 is formed as an extension to the base 7. Each of the louvres 9 is inclined at an angle a to the horizontal. Thus, the louvres 9 serve as baffles to restrict the direction to flow of grain into and out of the bucket 3 via the front face thereof. The bucket 3 is provided with holes (not shown) by which it may be secured to the belt 2 by bolts, in a conventional manner. In use, the bucket 3 can be filled substantially fully with grain 10, as illustrated.

The buckets 3 are advantageously so dimensioned that they can fit directly onto the belt 2 of a conventional elevator. For example, if the elevator 1 is adapted to operate with conventional "six-inch" buckets, the illustrated buckets 3 may have a width of 150 mm, a height of 110 mm and a depth (perpendicular to the belt 2) of 115 mm. The spacing between successive buckets 3 along the belt 2 is preferably equal to or less than the spacing between corresponding points on successive louvres 9 of one bucket. The angle a is advantageously 35 .

We have found that, in use of an elevator as illustrated, the buckets 3 can be filled to capacity and arranged to discharge the grain centrifugally with negligible spillage. Thus, for example, the rate of delivery of grain using an elevator as illustrated can, we have found, be more than twice the rate of delivery of the same elevator using hitherto existing buckets. To achieve this improved rate, it is not nec.essarytoalterthespeed of the belt 2.

In the art of centrifugal discharge elevators, there is a so-called "ideal speed" at which, when a bucket is at top dead centre, the centrifugal force acting verticaly upwards exactly counteracts the gravitational force acting downwards on the material in the bucket. In practice, however, present day manufacturers inevitably design their elevators to run at speeds in excess of the "ideal speed". A customary running speed is one which gives a centrifugal force twice that of the gravitational force at top dead centre. We have found that an elevator as illustrated may be run at such a speed with negligible spillage in the vertical leg 4 of the elevator.

It will be appreciated that the design of the buckets 3 is very important. Firstly, they must permit substantial filling at a lower end of the elevator and secondly, they must prevent the grain from being discharged prematurely at the upper end of the elevator, whilst ensuring complete discharge down the discharge chute 6.

Considering the first requirement, it is of importance that the buckets 3 fan out as they pass around the lower pulley 2. Due to this, grain can be forced in to a bucket 3 through the top thereof and also between the louvres 9. Thus, as the buckets 3 proceed vertically upwards, they may be almost completely filled. In fact, we have found in use that grain may even be satisfactorily piled on top of the buckets 3, and in the spaces between the louvres 9, without undue losses.

Considering now the second requirement, it will be appreciated that, as a bucket 3 travels over the upper pulley 5, the vector resultant of the centrifugal and gravitational forces progressively changes direction with respect to that bucket. Therefore, during the first 90" (approximately) of travel of the bucket, the vector resultant crosses the louvres 9 at such an angle as to inhibit ejection of grain from the bucket 3. For the next 90" of travel, the vector resultant acts to discharge the grain between the louvres 9 and out of the top of the bucket. As mentioned above, we found somewhat to our surprise that an elevator as illustrated would work satisfactorily even when the buckets 3 were somewhat piled, such that a virtual column of grain was being transported upwards.This may be due to the fact that a few degrees latitude is allowable for premature discharge of grain during which the grain moves a negligible distance radially outwards. In any event, the elevator was found to work entirely satisfactorily.

By way of example, in a elevator of conventional construction but with buckets as described above, of "six-inch" size, the belt speed was about 300 ft/min and the upper pulley speed about 90 r.p.m. With 100 % bucket capacity, the theoretical delivery rate was about 45 ton/hour. In fact, due to piling of the buckets 3, we recorded a delivery rate of about 50 ton/hour. This compares with a nominal delivery rate of 20 ton/hour with a conventional bucket. If it is desired to operate at higher belt speeds (as some known machines do), higher delivery rates are achievable.

Thus, it may be appreciated that an existing elevator may readily be converted by replacing known buckets with those as illustrated, to achieve substantial increases in delivery rate. Other than up-rating the drive motor as may be necessary, no further modifications to existing plant, and in particular no alteration in the overall height thereof, may be necessary, provided that grain may be fed into the buckets 3 sufficiently quickly.

Although the illustrated elevator and buckets are particularly advantageous, modifications may be made thereto. For example, the width of the buckets 3 (and the elevator in general) may be adapted to any other width elevator, standard or otherwise. The angle a may be varied somewhat, for example, within the range 30 to 40". The louvres 9 maybe made longer or shorter, and may or may not overlap.

In the illustrated arrangement, account is taken of the natural angle of repose of a pile of grain, which angle is about 300. Allowing for settling of the grain during use of the elevator 1, an angle of perhaps 20 to 25 to the horizontal may be struck from the front of a louvre 9 to intercept the rear edge of an upper louvre. The number of louvres 9 may be varied.

Although the illustrated elevator is for use with grain, it will be appreciated that buckets in accordance with the invention may be used for elevating granular material of many other suitable types, the dimensions and configurations of the buckets being varied as required. The illustrated leg 4 of the elevator 1 is vertical. However, buckets in accordance with the invention may be adapted for use with elevators which are inclined to the vertical.

The illustrated buckets are of substantially uniform cross-section (as shown in Figure 2) over their entire width, so that they have a generally rectangular appearance, apart from the inclined louvres. However, they could be of other shapes if desired. They are advantageously formed in one-piece from metal, or any other suitable material. For example, they may be formed from a one-piece stamping which optionally includes all of the louvres, and is then bent to shape and finally welded, preferably seamlessly.

Claims (20)

1. A bucket for an elevator, the bucket having louvres to restrict the direction of flow of material into and out of the bucket.

2. A bucket according to claim 1, having a solid base, a solid rear wall, two solid side walls, an open top and a front face on which said louvres open.

3. A bucket according to claim 1 or 2, wherein a lower one of said louvres is formed as part of a base of the bucket.

4. A bucket according to claim 1, 2 or 3, wherein said louvres are inclined to the horizontal at an angle in the range 30 to 40 , when the bucket is upright.

5. A bucket according to claim 4, wherein said angle is substantially 35 .

6. A bucket according to any preceding claim, wherein said louvres overlap.

7. A bucket according to any of claims 1 to 5, wherein said louvres do not overlap.

8. A bucket according to any preceding claim, wherein the cross-section of the bucket, transversely of the direction of extent of the louvres, is substantially constant in said direction.

9. A bucket according to claim 8, wherein said cross-section is generally rectangular, apart from said louvres.

10. A bucket according to any preceding claim, being of a size and configuration adapted to carry grain or like granular material.

11. A bucket according to any preceding claim, having three louvres.

12. A bucket substantially as hereinbefore de scabed with reference to the accompanying drawing.

13. An elevator having a bucket according to any preceding claim.

14. An elevator according to claim 13, being a centrifugal discharge elevator.

15. An elevator according to claim 13 or 14, arranged to elevate said bucket substantially vertically.

16. An elevator according to claim 13, 14 or 15, wherein a plurality of identical buckets are secured to a belt or chain, the spacing between successive buckets being equal to or less than the spacing between corresponding points on successive louvres of one bucket, said louvres being uniformly spaced.

17. An elevator substantially as hereinbefore described with reference to the accompanying drawing.

18. A method of converting an elevator, comprising removing buckets from a belt or chain thereof, and mounting in their place buckets in accordance with any of claims 1 to 12.

19. An elevatorwhich has been converted buy a method in accordance with claim 18.

20. A method of elevating grain or like granular material, comprising filling buckets with the grain or material, elevating the buckets, and discharging the grain or material therefrom under centrifugal force, the buckets being in accordance with any of claims 1 to 12.