GB2225307A - Sorting articles according to size - Google Patents

Abstract

Apparatus for sorting masses (e.g. crushed rock) according to size comprises a channel having an open bottom the width of which gradually increases along the length of the channel and means to move the masses along the channel. The means to move the masses may comprise two conveyor belts 21 and 22 forming the sides of the channel, with their lower edges forming the open bottom. In a further embodiment one side of the channel incorporates fixed elements, or consists wholly of a fixed element. In a modification, the channel may have stationary sides, with the masses being moved by a screw running along the channel, or by mounting the channel with a downwards slope and differentially oscillating the sides of the channel. The sorting apparatus may be incorporated in a rock crushing and sorting system. <IMAGE>

Description

Material esr~ Apparatus The present invention relates to material handling apparatus, and more specifically to apparatus for sorting masses according to size.

A well known type of rock crushing apparatus comprises a pair of rotating rollers between which rocks to be crushed are passed. It is often required that the pieces of crushed rock produced by the crushing apparatus shall be of a desired size range. This can be achieved to some extent by setting the gap between the rollers, this gap being controlled hydraulically. However, such control is fairly crude. A better degree of control can be achieved by an operator observing the crushed rock and adjusting the gap accordingly, but this technique also has obvious drawbacks.

It is often also desirable to grade the crushed rock, so as to separate the pieces of the desired size range from the detritus of small particles and oversized pieces. This generally involves some form of riddling or sieving, usually using grids consisting of a plurality of parallel bars. The crushed rock is passed over the grids, with small pieces falling through the grids and larger pieces passing across them. This technique has various disadvantages; for example, means are needed to ensure that the retained pieces of rock pass -across the grids, a different grid is required for each different grading size required, and pieces of rock are liable to become stuck between the bars of the grids.

The main object of the present invention is to provide an improved technique for sorting the pieces of crushed rock from a rock crusher according to size. This technique can be applied as part of a control system for a rock crusher for controlling the size of the crushed pieces more accurately. It can also be applied more generally to the sorting of masses of a wide variety of types according to size; such masses can, for example, be fruit or vegetables.

According to its main aspect the present invention provides apparatus for sorting masses according to size, comprising a channel with an open bottom the width of which increases gradually along the length of the channel, and having means for moving the masses along the channel in the direction of increasing width of the open bottom.

The means for moving the masses may comprise conveyor belting. The sides of the channel may be symmetrical and wholly formed by two conveyor belts forming the two sides and running .at the same speed. This arrangement minimizes the stress on the masses being sorted, and is suitable for sorting fragile masses such as delicate fruits. Alternatively, one side of the channel may incorporate fixed elements, or consist wholly of a fixed element, or the conveyor belting on one side of the channel may run at a different speed from that on the other side. These arrangements cause the masses being sorted to be Jostled as they are carried along.Such jostling is suitable for high flow rates of masses of widely differing sizes, since it reduces the chance of a mass being retained in the channel by other, larger masses past the point where it could fall through the open bottom of the channel, It is also suitable for masses of markedly non-spherical shapes, since it causes the masses to be presented to the open bottom of the channel in continuslly varying orientations.

Instead of conveyor belting, the means for moving the masses may comprise a screw running along the channel, or mounting means supporting the channel so as to slope downwards in the direction of decreasing width of the open bottom, preferably in combination with means for shaking the channel. The shaking means may comprise means for oscillating one or both sides of the channel.

A rock crushing system embodying various aspects of the invention and variant sorters thereof will now be described, by way of example, with reference to the drawings, in which: Fig. 1 is a general diagrammatic view of the system; Fig. 2 is a perspective view of the sorting channel of the system; Fig. 3 is a general diagrammatic view of a screw driven sorter; and Fig. 4 is a general diagrammatic view of a gravity and oscillation driven sorter.

The rock crushing system, Fig. 1, consists of a pair of rollers 10 and 11, a feed belt 16, and output sorting and transport apparatus. The axle of roller 10 is mounted directly on the housing 12 of the system; the axle of roller 11 is carried on a hydraulic adjustment ram 14 mounted on the housing 12 of the system. Rocks 15 to be crushed are fed into the gap between the rollers by a conveyor belt 16. The gap between the rollers 10 and 11 is adjusted so that the masses in the crushed rock produced are of the desired size range.

The crushed rock produced by the rollers is fed into a sorting channel 20, through which the pieces of crushed rock fall at distances from the rollers proportional to their sizes. A series of. hoppers 24 to 28 is arranged beneath the channel 20. The two end hoppers 24 and 28 receive small detritus and oversized pieces of rock respectively, feeding belts 30 and 31 as shown, hopper 28 extends beyond the end of the channel 20, to collect any pieces of rock which are too large to fall through the channel at all.

The sorting channel 20 consists of two conveyor belts 21 and 22 arranged to form a V section channel, as shown in Fig. 2, with their bottom edges 23 slightly separated to form a narrow gap or slot, and arranged slightly diverging from each other so that the slot widens gradually from the beginning of the channel to the end. The two belts are driven at the same speed and in the same direction, so that the crushed rock falling into the beginning of the channel ~ from the rollers 10 and 11 is carried along the channel by the belts. It is evident that each piece of rock will fall through the slot at the bottom of the channel when it has been carried along the channel to the point where the slot has become wide enough to match the diameter of the piece.

As shown, the pieces of rock are sorted into three groups; the small detritus, the pieces of the desired size range, and the oversized pieces. The pieces of the desired size range are, as shown, sorted further according to size by the three hoppers 25 to 27 before passing to a common output conveyor 33. The hoppers 25 to 27 feed the conveyor 32 via three respective sensors 32, which sense the flow of rock pieces through the three hoppers. The outputs of these sensors are -fed to a control unit 40, which controls the hydraulic adjustment device 14. The control unit 40 also performs other known control functions, such as opening the gap between the rollers fully if the crusher becomes jammed. - In the desired state, most of the pieces of rock pass through the middle hopper 26, and relatively small and roughly equal numbers of pieces pass through the two flanking hoppers 25 and 27. If the number of pieces passing through hopper 25 differs markedly from the number passing through hopper 27, the control unit 40 detects this and adjusts the gap between the rollers to restore the system to the desired state.

The control unit may be arranged to provide an alarm signal if, for example, the total movement of the upper roller 11 towards the lower roller 10 becomes excessive or if the adjustments of the position of the upper roller 11 become unduly frequent. Both these conditions are likely to arise if the rollers become excessively worn.

The control unit may be located in a remote location, or may feed an associated unit in a remote location, so that the system can be monitored and/or controlled from a remote location.

Of course, the system could work with only two hoppers receiving pieces of the desired size range. This would result in the flow of pieces through both hoppers being fairly large. The system could also work with only one hopper receiving pieces of the desired size range, with the flows through the detritus and oversized hoppers being used to control the operation. It may also be desirable to monitor the flows of detritus and oversized pieces in addition to, the flows through the hoppers 25 and 27, to permit correction if the system is badly out of adjustment (e.g. on starting up) and produces very few pieces of the desired size.

The sensors may be of any stlitable type, e.g. impact sensors counting the numbers of pieces falling into the hoppers, optical sensors detecting the passage of pieces of rock or the mean obscuration caused by the flow of pieces, weight sensors detecting the weight of rock pieces falling on the outlet passages of the hoppers, flaps deflected by the passage of rock pieces past them, or any other suitable type. The sensing may be fairly crude, since all that is required is a rough comparison between two fairly low flow rates.

If the flow rate of crushed rock from the rollers is reasonably high, then the pieces of rock will form, a continuous stream of a mixture of pieces rather than a series of isolated pieces. The flow of small detritus which starts at the beginning of the channel 20 will cause a certain amount of rearrangement and mixing or stirring of the pieces in the stream retained in the channel, and this, together with the natural tendency of larger pieces to rise in such a mixture, will minimize the chance of pieces being carried much beyond the point at which the slot at the bottom of the channel is wide enough for them to fall through.

If greater certainty of sorting is required, however, the channel may be modified by using narrower conveyor belts with fixed extensions provided at their lower edges. The conveyor belts ensure that the masses being sorted are carried along the channel, but the fixed strips along their lower edges provide retarding forces on the masses, which are therefore jostled and rotated. This has the effect of mixing or stirring the masses in a mixture of masses so that small masses are not trapped above larger ones, of rotating the masses so that they present continually varying aspects to the slot, and of counteracting any slight tendency of the masses towards agglomeration.

Similar effects can be achieved by running the conveyors at different speeds, running them at varying speeds, or replacing one of them by a fixed strip. It may also be advantageous in such cases for the two sides of the channel to be at different angles to the vertical.

The sorting size of the system can be changed by moving the hoppers along underneath the channel or changing the hopper selection. However, the sorting size can also conveniently be changed by adjusting the angle between the conveyors, i.e. by changing the distance between the bottom edges 23 of the conveyors at the wide end of the channel 20. Such adjustment can be made without ill effects while the system is running; even if the ends of the conveyors are moved closer together, provided that it is not made excessively rapidly. This is because although the gap between the bottom edges 23 of the conveyors 21 and 22 is reduced by such adjustment, the pieces of rock are being carried along by the conveyors, so they will always see a steadily widening gap.

The conveyors may consist of conventional flat band belts. However, such belts are liable to slippage, both longitudinal and sideways, and both types of slippage may have adverse effects. (Longitudinal slippage may cause damage to delicate masses, while sideways slippage may cause the gap to vary and so reduce the efficiency of sorting by size.) These effects can be reduced or eliminated by using more elaborate forms of belt, such as an escalator or "travolator" type, providing the belts with logngitudinal locating ribs on their rear faces which engagage in corresponding circular grooves on the driving and supporting rollers, or attaching chains to the rear- faces of the belts which engage with driving and locating sprocket wheels own the rollers.

Another known form of rock crusher comprises a vertical roller which rotates inside a concentric cylindrical casing which is internally tapered. The rocks to be crushed are fed into the top of the casing, and as they become trapped between the inner roller and the inwardly tapering walls of the casing, so they are crushed, the crushed pieces emerging from the open bottom end of the casing. The degree of crushing is controlled by raising or lowering the roller in the casing so as to vary the width of the gap between the bottom end of the roller and the casing. It will be realized that the present sorting apparatus is equally applicable to such crushed.

Fig. 3 shows an alternative form of sorter. A channel is formed by two sides 40 and 41 with a gap 42 between them which widens gradually from the front (input) end of the channel to the far end. These two sides 40 and 41 are curved as shown, so that the channel is approximately semicircular in section.

A screw 43 extends along the length of the channel as shown, fitting in the channel. A motor (not shown) drives the axle 44 of the screw 43. A mixture of masses to be sorted is fed into the front end of the channel. As the screw 43 rotates, so it carries the masses along the channel, and the masses are sorted by each mass falling through the slot or gap 42 between the two halves 40 and 41 of the channel when it has been carried along the channel to the point where the slot has become wide enough to match the diameter of the mass.

Fig. 4 shows a further alternative form of sorter. A channel is formed by two sides 50 and 51 with a gap 52 between them which widens gradually from the far (input) end of the channel to the near end. The channel also slopes downwards from the far end to the near end. In addition, the two sides 50 and 51 of the channel are supported by means. (not shown) which allow them to oscillate to and fro in the direction of the channel.

The sides 50 and 51 have, at their lower ends, extensions 53 and 54 rigidly attached to them as shown. The shaft of a motor 55 has a crank 56 attached to it, and the outer end of this crank is coupled to the end of the extension 53 by means of a link 57, pivoted to both extension 53 and crank 56 as shown. The ends of the extensions 53 and 54 are pivoted to the ends of a link 58 which is in turn pivoted on a fixed pivot 59. Hence the rotation of the motor 55 causes the side 50 to oscillate to and fro, and the side 51 to oscillate oppositely.

Masses fed onto the input (upper) end of the channel are therefore caused to travel down the channel, and so be sorted by size, by the influence of gravity, with the oscillation of the sides of the channel assisting in overcoming any tendency of the masses to become lodged in place.

Claims (18)

C leg i m s5

1 Apparatus for sorting masses according to size, comprising a channel with an open bottom the width of which increases gradually along the length of the channel, and having means for moving the masses along the channel in the direction of increasing width of the open bottom.

2 Apparatus according to claim 1 wherein the means for moving the masses comprise conveyor belting.

3 Apparatus according to claim 2 wherein the sides of the channel are symmetrical and wholly formed by two conveyor belts forming the two sides and running at the same speed.

4 Apparatus according to claim 2 wherein one side of the channel incorporates fixed elements, or consists whdlly of a fixed element.

5 Apparatus according to any one of claims 2 to 4 including means for driving the conveyor belt on one side of the channel at a different speed from that on the other side.

6 Apparatus according to claim 1 wherein the means for moving the masses comprise a screw running along the channel.

7 Apparatus according to claim 1 wherein the means for moving the masses along the channel comprise mounting means supporting the channel so as to slope downwards in the direction of decreasing width of the open bottom.

8 Apparatus according to claim 7 including means for shaking the channel.

9 Apparatus according to claim 8 wherein the shaking means comprise means for differentially. oscillating the sides of the channel.

10 Apparatus according to any previous claim including means for moving the two sides of the channel on opposite sides of the gap apart and together.

11 Apparatus for sorting masses according to size, substantially as herein described with reference to the drawings.

12 Apparatus according to any previous claim including means for monitoring the relative quantities of masses falling through different regions of the channel.

13 Apparatus for crushing and sorting material, comprising crushing means for crushing large masses into smaller masses, feeding apparatus according to claim 12 and having the degree of crushing controlled by the monitoring means.

14 Apparatus according to claim 13 wherein the crushing means comprise a pair of rollers between which the material to.be crushed is passed.

15 Apparatus according to claim 13 wherein the crushing means comprise a vertical roller inside a coaxial drum with the material to be crushed being fed into the space between the roller and the drum.

16 Apparatus according to any one of claims 13 to 15 wherein the monitoring means includes means located at a remote location.

17 Apparatus according to any one of claims 13 to 16 wherein the monitoring means detects excessive positioning and/or adjustment of the rollers and thereupon generates an alarm.

18 Apparatus for crushing and sorting material, comprising crushing means for crushing large masses into smaller masses, sorting meansfor sorting the resulting masses, and means for monitoring the average size of the crushed masses and adjusting the degree of crushing to maintain that average at a desired value.

19 : Apparatus for crushing and sorting rock, substantially as herein described with reference to the drawings.