NO143929B - APPARATUS FOR SORTING MATERIALS. - Google Patents

Description

The present invention relates to an apparatus for sorting pieces of material, comprising means for advancing the pieces of material through a sorting zone in a random stream in a wide path, and a scanning device which makes repeated scans across the stream of material in the sorting zone to detect light reflected from separate surfaces on each piece of material, when the scanner beam crosses the piece of material,

and to produce a scanning signal representative of the reflected light, and a deflector device disposed downstream of the scanner device and comprising a series of deflector means acting across the flow of material, each means in a first functional state permitting the passage of pieces of material along a preselected, undeflected path and in another functional state they deflect passing pieces of material from the preselected path as well as electronic devices that generate. control signals depending on the position of the scanner when it passes the material flow.

When sorting material pieces, e.g. pieces or particles of ore, it is advantageous to be able to analyze and evaluate each piece of material as it is passed through the sorting zone, so that the individual pieces of material can be rejected or accepted on the basis of the evaluation. This provides a very efficient sorting. It has proven difficult to separate the pieces from each other, so that they can be placed with the desired accuracy at suitable intervals, e.g. in rows of mutually separated pieces, and this can result in a material throughput that is less than if the pieces of material are advanced in an irregular stream. When the materials are carried in an irregular flow through a sorting zone, however, it is necessary that each piece of material is evaluated or analyzed based on the position that the piece of material occupies in the flow, so that a single piece can be accepted or rejected when it passes the rejection device. Although sorting an irregular stream usually results in greater material throughput and greater efficiency, such sorting will usually require a more complicated sorting system.

In a sorting device, e.g. of the photometric type, pieces of material pass through a sorting zone in a random stream, while a scanning device makes repeated scans across the stream, to produce a signal according to certain characteristics of the scanned pieces of material. The signal is accumulated for each scan to provide data representing the characteristics of the pieces of material. This data must be brought into relation to each piece of material and the position

of this, so that the individual piece of material can be accepted or rejected in accordance with the data analysis. This production of data in connection with a special piece of material and its position is called "tracking" in the sorting technique.

(tracking).

Different types of tracking systems are known from the past. An apparatus of a known type comprises e.g. a sorting zone with a number of imaginary channels extending longitudinally through the sorting zone. The channels are formed by a reject device which extends across the sorting zone, close to the end of the zone. The deflector device comprises a number of deflectors which are mounted side by side and which usually consist of air blowing nozzles which can direct an air jet, of the width of an "imaginary" channel, into a disordered material flow, thereby deflecting pieces of material which are advanced along the particular channel. The deflector can deflect a piece of material that is entirely in the associated channel, but it is uncertain whether a piece of material that is partly in the deflector's associated channel and partly in one or more adjacent channels will be deflected. In this device type, each channel is treated as a unit. A device may consist of a memory for storing data for characteristics, an analysis device for data analysis,

a decision device for issuing an acceptance or rejection signal on the basis of the analyzed data, as well as a control circuit for activating the respective rejection body in accordance with the decision signal. It thus appears that a piece of material which is situated partly in one channel and

partially in the adjacent channel, will be treated as two separate entities, and the control circuitry for each channel will process data for that channel, to convey a decision based on

the data relating to the channel. If the piece of material extends into a third channel, this third channel will treat this part as a unit. As the valuable part and the waste part can be located in different channels, it is impossible to carry out a correct sorting of a piece of material that is located in more than one channel.

A known apparatus of a different type was arranged with a view to analyzing each piece of material separately, without regard to the position of the piece of material or the number of channels occupied by it. This type of device was provided with a number of modules (less than the number of channels), where each module was "locked to" a piece of material. That is, when the scan encountered a new piece of material, the first free module was locked to this piece, and accumulated data exclusively for this piece for all intersecting scans. This data was then analyzed to produce a decision signal. This decision signal then had to be communicated to the relevant, special channels (i.e. awiseror<g>ans), and the longitudinal extent or dimension also had to be communicated to the repellers, for reasons of regulation of the repeller force. Although it was thereby normally possible to reduce the number of analysis and decision circuits, a significant number of complicated circuits would be required to bring a module

.in relation to the relevant channel or channels.

The present invention requires a relatively simple control circuit system, but will still provide good sorting of pieces of material which in previously known devices would be considered to be located in two or more channels.

The apparatus according to the invention is characterized by the fact that the control signals represent a number of mutually overlapping analysis channels, each of which runs parallel to the direction of movement of the pieces of material through the sorting zone,

that a circuit for each analyzing channel is arranged to receive the scanning signal and associated control signal for accumulating information from the scanning signal regarding pieces of material in the respective analyzing channel and for generating a decision signal on the basis of the accumulated information

regarding a piece of material, and that control means for each analyzing channel are arranged to activate one or more deflecting means which at least extend over the width of the analyzing channel in response to the determination signal.

Special advantages have been achieved according to the invention by using mutually overlapping analysis channels, instead of the previously used analysis channels which were placed side by side without overlapping. With the help of a circuit for each analysis channel, a clear decision signal can be produced regarding the piece of material in question and with the help of associated control devices for each analysis channel, one or more deflection devices can be correspondingly activated precisely.

Further features of the invention will be apparent from the following description with reference to the accompanying drawings.

. nings, in which:

Fig. 1 shows a schematic side view of a sorting facility which includes a transport system according to the invention. Fig. 2(A), 2(B) and 2(D) show a schematic partial view of the reject system in different versions of the sorting apparatus, indicating the different channels. Fig. 3 shows a schematic block diagram illustrating a

version of the invention.

Fig. 4 shows a waveform diagram that comes into use

in the description of the diagram according to fig. 3.

Fig. 5(A) and 5(B) show schematic drawings, comprising characteristic pieces of material in a sorting zone, which are used when describing the operation of the apparatus. Fig. 6(A) and 6(B) show schematic drawings of pieces of material touching each other. Fig. 7 shows a schematic block diagram illustrating

another version of the invention.

Fig. 8 (on the same drawing sheet as Fig. 1) shows a waveform diagram which is used in the description of the system according to Fig. 7.

The invention is described in connection with the sorting of ore, but it is obvious that the invention can be used as a means of transport in connection with the examination or sorting of other pieces of material.

When sorting ore, the dimensions or fractional size of the pieces or particles are of some importance. The indication of particle sizes is usually expressed by the dimensions of the square meshes through which the particles will or will not pass. A particle group such as is designated "-25 mm to +10 mm" (or simply "-25 mm + 10 mm") thus consists of particles that will pass through a sieve with 2 5 mm, square meshes, but which will not pass through a sieve with 10 mm, square stitches. The size of the stone pieces or particles that are generally considered suitable for sorting by automatic machinery lies, very roughly calculated, within the fraction "-150 mm + 10 mm", but it is not possible to sort the entire fraction, in the form of a random material flow, using a single machine. This is because the larger particles will tend to hide the smaller ones. The typical particle size for the material fed to a single sorting machine can be within any of the following fractions: -150 mm + 75 mm -125 mm + 50 mm -100 mm + 50 mm

-75mm + 35mm

-60 mm + 30 mm

-4 0 mm + 15 mm

-2 5 mm + 10 mm

It appears that the coarser sieve has a mesh size of approximately two to two and a half times the mesh size of the finer sieve. It has been shown in practice that this size ratio between the mesh widths provides efficient sorting, while maintaining a satisfactory sorting speed, without unwanted overshadowing of smaller particles.

The described transport system can be adapted to any of the above-mentioned size fractions. When designing the system, certain parameters must be selected for each grain fraction. The number of deflectors (normally in the form of air blower nozzles) must e.g. is selected, whereby the width or transverse extent of each organ is fixed. If a sorting device receives material of the fraction -40 mm + 15 mm and the sorting zone has a width of 800 mm, an appropriate arrangement can e.g. include 40 air blower nozzles, each of which has a width of 20 mm. The presence of a smaller particle within this fraction will, with the above-mentioned nozzle arrangement, induce a deflecting airflow from one nozzle or from two nozzles depending on the particle's position and shape, while a larger particle may require a blowout from two or possibly three nozzles. It is obvious that the choice of a particular air nozzle dimension will be linked to a particular grain fraction, possibly two or three fractions, and that a different choice must be made for other grain fractions.

Reference is made to fig. 1 which shows a sorting apparatus for sorting pieces of material which, for the sake of simplicity, is described as advancing through the apparatus in the form of a random stream in a wide path. The term "random stream in a wide path" is intended to denote a stream of particles which are carried forward in a given direction, and which are randomly spaced apart over a width sufficient for several particles to be carried side by side. A collection box 10 contains, as shown, a quantity of stone pieces or particles 11 which, from the collection box, are emptied onto a vibration table 12 which is suspended by springs 14. The vibration table 12 is driven in a known manner by a vibrator motor 15. From the table 12 the particles are transferred 11 to a sliding surface 19, where the particles 11 are accelerated and distributed, in the form of a random stream in a wide path, over the upper side of a conveyor belt 16. The endless belt 16 is supported by running rollers 17

between a main roller 18 and a drive roller 20. The drive roller 20 is driven by a motor 21.

The stone particles 11 on the belt 16 are advanced past a scanner device 22, and exit in a free-fall path at the main roller 18. The particles pass an avisor device 23 which can consist of

of a number of rejection bodies, e.g. air blower nozzles 24, which are placed side by side. A screen plate 25 is arranged, immediately above the nozzles 24, which protects the nozzles against accidental damage that may occur due to stones in an abnormal position. The screen plate 25 will not normally be touched by the passing particles.

A split plate 26 is placed under the air blowing nozzles 24 in a

such position, that. undeflected particles fall onto a belt 27, on one side of the plate, while deflected particles are carried to the other side of the plate, and fall onto a belt 28.

Regulation and control signals are exchanged through a line 30 between the scanner device 22 and the transport system device 31, and the reject device 23 receives control signals from the device 31 through a line 32. Through a line 33, the scanner device 22 supplies information regarding the scanned surface

to the transport system facility 31.

The transport system is based on the use of various analyzing and gate channels which can be described in general with reference to fig. 2. Fig. 2(A) shows a portion of the deflector device 23 with air blowing nozzles 24. Each of the nozzles 24 defines an imaginary channel, and there is shown a series of channels designated by B1, B2, B3, B4, etc. This is "exhaust ducts". A first analyzing channel, denoted A1, is centered on the dividing line between the exhaust channels B1 and B2. A second analysis channel, designated A3, is centered on the dividing line between the exhaust channels B3 and B4. These analyzing channels have an adjustable width that is greater than the width of one exhaust channel and less than the width of two exhaust channels, and which is preferably chosen such that it is just below the width of two exhaust channels. Another series of overlapping analyzing channels is provided, and one of these, indicated at A2, is shown centered on the dividing line between the exhaust channels B2 and B3. The analyzing channels A1, A3, A5, etc. as well as A2, A4, A6, etc. continue to overlap in the same way across the width of the deflector. A number of selector channels which are denoted by D1, D2, D3 etc. likewise extend over the full width of the deflector device. Each selector channel having a width somewhat less than the width of an exhaust channel is, as shown, centered on the dividing line between each exhaust channel. The width of the voter channel can also be adjusted to suit different sorting situations.

A part of an analyzing channel and a part of a selector channel, at each end of the deflector device, will, as appears, in reality be inactive, as no particles will appear outside the limits of the particle stream which only extends over the width of the deflector device.

It should be remembered that the channels are imaginary. This means that none of the channels are bounded by a physical wall. The channels can be said to be formed in the electronics of the transport system, as described below.

The selector channels D1, D2, etc. briefly define the width within which a particle must be tracked, in order for the respective analysis channels A1, A2, etc. to be activated. The analysis channels will not accumulate data until they are activated by the selector channel. If the selector channel is made narrower than the analysis channel, this will result in a tendency to prevent analysis of particles that barely extend into an analysis channel. If the data received by an analysis channel results in a decision to deflect a particle, this will result in the activation of two air blowing means 24. The two means that are activated are connected to the mutually adjacent exhaust channels, and the line that separates them is in the middle - line for the analysis channel that produced the signal for deflection.

It is obvious that if a voter channel had the same width as an analysis channel, the voter channel would be pointless. If a selector channel is considered unnecessary in a special apparatus for sorting special ore, the apparatus will consequently function without this channel, as appears from the description.

Fig. 2(B) shows a device which is provided with two adjacent rows of nozzles 24'. These nozzles 24' overlap each other in the same way as the analysis channels A1', A2', A3<1>, etc. Blowout channels Bl', B2<1>, B3', etc. are arranged, each of which is connected to a corresponding analysis channel. The shown exhaust channel has a somewhat larger width than an analysis channel, but the exhaust channel's width can be reduced to half the width of an analysis channel, or optionally increased to one and a half times the width of an analysis channel. In the same way as shown in fig. 2(A), the selector channels D1, D2, etc. are centered with respect to the respective analyzing channels A1', A2', etc.

As can be seen, the device according to fig. 2(B) practically the same mode of operation as the device according to fig. 2(A). A particle that is entirely located in e.g. the analysis channel A2' and which, due to its nature, triggers a deflection signal,

will induce an air jet from the nozzle corresponding to the exhaust duct B2'. While two nozzles will be activated in the device according to fig. 2(A), in the device according to fig. 2(B) only one nozzle is activated, but the width of the deflecting air jet may be practically the same, as the individual nozzles may be twice as large.

Figures 2(C) and 2(D) show devices with triple overlapping analysis channels. Fig. 2(C) shows nozzles 24 which form exhaust channels B1", B2", etc. and which are activated in groups of three. This involves e.g. that the analysis channel A2" will activate nozzles corresponding to the exhaust channels B2",

B3" and B4". In fig. 2(D), the analysis channel A2" will activate the nozzle corresponding to the exhaust channel B2" (which has roughly the same width as B2", B3" and B4" combined). It appears that the overlapping analysis channels consist of a first, second and third group. The first group includes the analysis channels A1", A4", etc., the second group includes the analysis channels A2", A5", etc., and the third group includes the analysis channels A3", A6", etc. Each channel in the second group A2", A5", etc. overlap adjacent channels in the first group. That is, channel A2" overlaps channel A1" to an extent that preferably does not exceed two-thirds of the width of an analyzing channel, and A2" overlaps channel A4" :L an extent which preferably does not exceed one third of the width of an analysis channel. Eu analysis channel in the third group (e.g. A3") similarly overlaps a pair of adjacent channels (e.g. Al" and A4") in the first group, one to an extent such as preferably not exceeding one third of the width of the channel, and the other to an extent preferably not exceeding two thirds of the width.

It will be realized that arrangements for overlapping in other multiples or other degrees can be used, depending on the construction requirements.

The power circuit system is subsequently described briefly in connection with fig. 3 and 4 which particularly relate to the channel arrangement according to fig. 2(A). A belt sensor 36 emits a signal, in accordance with the speed of the belt 16

(fig. 1) to a comparator 38. An oscillator 37 produces,

on a wire 40, a basic setting signal for the apparatus, which may be as indicated in fig. 4(a) and which is likewise transmitted to the comparator 38. The comparator 38 emits a control signal to the oscillator 37, for controlling the output signal from the oscillator 37, so that it corresponds at all times to the belt speed. Such control systems are known within this field. It will be seen that such a control arrangement is not essential for the inventor.

A scanner device 22, which can advantageously be of the type described in Canadian patent application 192,153, is arranged to carry out repeated scans across the sorting zone, for tracking light reflected from atsk.ilto surfaces on each particle, as it is crossed by the scanning beam . Mechanical and electrical scanning devices are known per se. The particles are advanced on the belt through the scanning zone, as previously described. The scanner device 22 receives a regulation and control signal from a scanning regulator 41 which in turn is regulated by control pulses on the line 40.

The scanner device 22 outputs an output signal to a signal discriminator 42, and this signal is representative of the reflected light received by the scanner device 22. The signal discriminator 42 may include AGC circuits and other stabilization circuits. The discriminator 42 also receives a regulation and control signal from a discriminator-regulator 43 which in turn receives control pulses from the line 40. The signal discriminator emits two output signals. One output signal represents the extent or dimension, and the other represents data relating to the characteristics of the reflected light. This data can e.g. include a rendering of a surface, of a white denomination that exceeds a preselected level of reflected light, of a black

value below a preselected level, of a squared white signal, of a squared black signal, and of counts representing

a swing from black to white, or vice versa, during a preselected period of time, or other values. These signals are transmitted through wires 44 and 45 respectively.

A shifter 46 which is set by control pulses on the line 40 delivers, on a cable 47, a series of selection signals for the exhaust channels, so that these channels can be activated in sequence over the sorting zone, synchronously with the scan. Three waveforms for the exhaust ducts are shown in fig. 4(b),

(c) and (d). The block 46 is marked in the drawing as a 40-stage shift mechanism, which assumes that 40 exhaust channels are arranged, but the shift mechanism will of course be selected in accordance with any number of channels required by the construction. A decade counter 50 counts the pulses on the wire 4 0 in groups of ten. In the described version, each exhaust duct can therefore be considered as consisting of ten parts. A decoder selector 51 is connected to the counter 50, whereby two output signals are produced on lines 52 and 53. The output power on line 52 consists of a series of start/stop pulses for the different analysis channels, while the output power on line 53 consists of a series of start/stops -pulses for the gate channels. The decoder selector 51 makes it possible to adjust the width of the analysis channels and the port channels by tenths of an exhaust channel, and the former two can be adjusted separately. The waveform in fig. 4 (e) shows e.g. a typical series of start pulses for the analysis channels, while the waveform in fig. 4(f) shows a typical sequence of stop pulses for the analysis channels. Similar pulses (not shown) for the gate channels are produced, as described, on wire 53.

A regulator 54, which normally includes a flip-flop, produces a waveform as shown in FIG. 4(g), which is used to obtain a decision, as described below. A regulator 55 receives a signal from the line 40 and from the shifter 46, and thereby produces a signal for regulating a deflector air jet, which is described in the following and which represents one pulse per scanning.

The power circuit system described so far is common. That is that there is one system for the appliance. The circuit system which

is described in what follows, mainly relates to an analysis channel. A corresponding circuit system is arranged for each channel. The dashed line 56 in fig. 3 generally indicates one analysis channel. All of the input powers to the circuit module indicated by the dashed line 56 are multiple input powers that are transferred to the other channels, except for the input power on wire 57 (from cable 47) which consists of the signal for that particular channel from the shifter 46.

The analysis channel circuit 60 receives a data signal on line 45, a start/stop signal for the analysis channel on line 52 and a channel selection signal on line 57. The start/stop signal and the selection signal are used to produce an analysis channel signal which is shown by the waveform (h)

in fig. 4. Two overlapping analysis channel waveforms are shown as an example in fig. 4(h) and 4(i). The circuit 60 will thus analyze the data received on the line 45 during a period of time such as corresponds to the waveform (h) in fig. 4. An output signal is thereby given to a calculator 61 which, in accordance with a preselected program, equalizes the accumulated data and produces an output signal, in accordance with the comparison result, which represents a decision to deflect, or not to deflect, concerning material particle. The decision

is represented by an input signal to an AND gate 62. Reference is made, solely as an example of a suitable decision flow circuit, to Canadian Patent Specification 923,601, issued March 27, 1973.

A gate circuit 63 receives an input signal from the regulator 54 and an input signal from the line 57, which represents the

particular channel, and emits a decision control signal (e.g. at waveform (g) in Fig. 4) only for this channel. This signal is another input signal to the AND gate 62.

The selector channel circuit 64 receives a start/stop signal from line 53 and a special channel signal from line 57. An output signal is produced as shown by waveform (j) in fig. 4. The signal represents the selector channel waveform in conjunction with the analysis channel waveform (h). Furthermore, fig. 4 another selector channel waveform (k) associated with the analysis channel waveform (i). It appears that the selector channel waveforms are centrally located within the respective analyzing channel waveforms and centrally located in relation to the boundary between the exhaust channel waveforms.

The selector channel circuit 64 produces an input signal to a control circuit 65 which receives another input signal in the form of

the surface signal on the wire 44. The control circuit 65 emits an output signal for each particle that is advanced in the time slot of this selector channel waveform, and the output signal is transmitted as a third input signal to the AND gate 62. An output signal is also transmitted to a shifter 66.

The output signal from the control circuit 65 to the shift mechanism 66 consists of a series of clock pulses at a rate of one pulse per scan, for each scan accompanied by a flat signal on wire 44 for the respective selector channel. The shifting mechanism 66 will thereby be charged in accordance with the length of a particle (measured in scans).

The second output signal from the control circuit 65 to the AND gate will block the AND gate 62 whenever a particle is present. Consequently, no output signal will be emitted from the AND gate 62, as long as the scanning beam crosses a particle in this channel. On the first scan that goes off, or no longer crosses, a particle in the special selector channel, an activation signal will be transmitted from the control circuit 65 to the AND gate 62. If the calculator 61 likewise produces an activation signal indicating that the particle is to be deflected, the AND -the port 62 transmits the decision control signal from the port 63 to the switching device 67, whereby the stored information is transferred from the device 66 to the device 67.

The signal from the regulator 55 controls the transmission of information from the shifter 67, through the line 68, to OR gates 70 and 71 which, by means of suitable delay devices, control air valve regulators 74 and 75 respectively, to produce a deflecting air jet in the respective exhaust ducts.

For the sake of simplification of drawings and description, the reset circuit is not shown. It is believed that one skilled in the art will realize that such a circuit system, which is known per se, will be necessary. The calculator 61 and the shifter 66 are thus reset, as soon as the transfer of information from the processor 66 takes place.

Although it is assumed that the operation of the transport system is understood, a brief description is given below that includes some examples of typical particles that are conveyed through the sorting zone.

Two pieces of material, e.g. pieces or particles of stone, are in fig. 5 denoted by 80 and 81 in the upper part (A) of the drawing and in the lower part (B). The two parts of the drawing are used to show how the overlapping channels process these special particles. The particles 80 and 81 shown have the same size and shape, but their position in the transverse direction in relation to the outer limits of the exhaust duct is different.

As shown in fig. 5(A), the particle 80 comprises a portion which is located in the analysis channel A7 and which will be analyzed in this channel, as described in the following. The scans indicated at 2, 3 and 4 will cross the particle 80, but as no part of the particle appears in the selector channel D7, no data will be produced for the analysis. In scan 5, part of the particle will appear in the selector channel D7, and data will be provided regarding the analysis in channel A7, as shown by the thick part of scan line 5. Scans 6-11 will likewise provide analysis data. The circuit system for channel A7 will therefore, on the basis of data from scans 5-11, decide whether the particle is to be accepted or rejected. If the particle is to be deflected (as described in connection with the device according to Fig. 2(A)), the deflector means for the exhaust channels B7 and B8 will be activated.

The particle 80 will likewise be analyzed in the analysis channel A8 which overlaps, and this is shown in part (B) of fig. 5.

Data from scans 2-12, as shown by thick lines, will be analyzed. As can be seen, the analysis channel A8 will analyze data for practically the entire particle, which will provide an accurate analysis.

As further appears from fig. 5, the particle occupies 81

a deviant position in the lateral direction, and, as shown in (A), the analysis channel A10 will analyze data from scans 2-12.

This channel A10 will analyze practically the entire particle and

make the best decision. If the particle is to be deflected,

become the deflectors for the exhaust ducts B10 and Bli activi-

cert. The particle 81, however, as can be seen from fig.

5(b), also analyzed by the analysis channel All. The scan 2

does not provide any analysis data, as nothing appears in the selector channel Dll during this scan. In scan 3, part of the particle 81 is scanned in the selector channel D11, as shown by the thick line'.

This initiates the analysis, and data from scans 4-12

will be analyzed by the analysis channel All. The data analyzed

seen by the analysis channel All, are indicated by thick lines.

It appears that only part of the particle is analysed

this channel.

It appears from the previous description in connection

with fig. 5 that, with an appropriate form of construction, a particle will in most cases be analyzed by more than one overlapping channel, but that one of the channels will analyze the entire particle, or a significant part of it, whereby it

an efficient sorting is achieved.

The situation is not quite so simple, if two particles

touch each other, but the system's accuracy will nevertheless be relatively high. Fig. 6(A) shows how two mutually touching particles 83 and 84 would be analyzed by the analysis channels A8 and A10, while fig. 6(B) shows how the same two particles would be analyzed by the analysis channel A9. The thick lines indicate the scans that produce data for the ana-

the light as previously mentioned. It appears from fig. 6(A) that the analysis channel A8 analyzes data from a very large part of the particle 83, while the analysis channel A10 analyzes data from a very large part of the particle 84. Each particle will therefore be analyzed, largely in its entirety, by separate channels, and the

an accurate sorting can be expected. If the particle 83 is to be deflected, the deflector means for the exhaust ducts B10 and B1 are activated. Each of the particles can thus be accepted or rejected without disturbing influence from the other analysis channel.

The analysis channel A9 will, however, also analyze data relating to the composite particle (particle 83 and 84), as shown by the thick lines in fig. 6(B). It appears that channel A9 covers approx. 50% of each particle's surface. If both particles are to be accepted or both rejected, the decision from channel A9 will be in accordance with the results from channels A8 and A10, and consequently without significance. In this situation, an accurate sorting will be achieved. The particles may in reality consist of ore and waste to varying degrees, and if one particle were to be accepted and the other rejected, the decision from channel A9 would not be predictable. The circuit system (in this case as described in connection with Fig. 2(A)) is arranged so that either channel A8 or channel A9 can cause a deflection in the exhaust channel B9, while channel A9 or channel AlO can similarly cause a deflection in channel B10. If the channel A9 does not cause a deflection in connection with the exhaust channels B9 and B10, the result will depend on the decisions from the channels A8 and A10. This does not affect the accuracy. If, on the other hand, the decision from channel A9 results in the release of a deflecting air jet for the composite particle, both particles 83 and 84 will probably be deflected, and in this situation sorting errors could occur. It is thus clear that if two particles touch each other and one consists of ore and the other of waste, and if the overlapping analysis channel which covers a relatively large part < of each particle, decides to deflect the particles, this could lead to sorting errors. The degree of error will depend on the position of the particles, their composition and size, as well as on other factors.

It is assumed that the operation of the transport system and the device has so far been made clear from the description. It is obvious that an alternative circuit system can be arranged to carry out the function of the particularly shown device. The preceding description generally relates to the overlapping channels which extend in the longitudinal direction (i.e. in the particle's

direction of movement through the sorting zone). Furthermore, it can

if desired, an arrangement of overlapping transverse channels is used to improve the delineation with respect to the material flow direction. Such an arrangement is described in connection with fig. 7.

The power circuit system according to fig. 7 is largely the same as shown in fig. 3, but an additional group of analysis modules is arranged which form overlapping channels which run parallel to the scanning direction. Each of the previously described modules (e.g. as shown at 56 in Fig. 3) is in this case replaced by a pair of modules. In addition, a scan counter 85 is arranged which receives one pulse per scanning from the shifter 46, as well as a decoder 86. The decoder produces overlapping pulse chains, as shown in fig. 8, which may include a high, for the duration of a scan, and a low, for example for 7 scans. The pulse chains are transferred to OR ports 90 and 91. The output signals from the control circuit 65 are also transferred to the respective OR port in the respective module. The effect of this is a cancellation of the output signals from the control circuits 65, which causes the circuits to issue the decision and reset to

the selected scan, whether the end of the particle is reached or not. The decision circuit system operates as before under the control of control circuit 65 during an interval of seven scans. The additional shifters 92 and 93 work like shifters 66 and 67

in the second module. The shifter 93 is, as shown, connected to the OR gates 70 and 71.

It is assumed that the operation according to fig. 7 is hereby clarified. The cost of an additional module group results in improved accuracy in the Y direction. The circuit system obtains decisions after a preselected number of scans and as the end of a piece of material leaves the scanning zone.

Claims (17)

1. Apparatus for sorting pieces of material, comprising means for advancing the pieces of material through a sorting zone in a random stream in a wide path, and a scanning device (22) which makes repeated scans across the stream of material in the sorting zone to detect light reflected from separate .surfaces on each piece of material, as the scanner beam crosses the piece of material, and to produce a scanning signal representative of the reflected light, and a deflector device (24) which is located downstream of the scanner device and which comprises a series of deflector means acting transversely across the material flow, where each member in a first functional state allows the passage of pieces of material along a preselected, undeflected path and in another functional state they deflect passing pieces of material from the preselected path as well as electronic devices (37,41,43) which generate control signals depending on the position of the scanner when this passes material litter mme, characterized by that the control signals represent a number of mutually overlapping analysis channels (A^,A2,...), each of which runs parallel to the direction of movement of the pieces of material through the sorting zone, that a circuit for each analyzing channel (56) is arranged to receive the scanning signal and associated control signal for accumulating information from the scanning signal regarding pieces of material in the respective analyzing channel and for generating a decision signal on the basis of the accumulated information regarding a piece of material, and that control devices (70) for each analysis channel are in-, directed in response to the determination signal to activate one or more deflector means extending at least across the width of the analysis channel. 2. Apparatus in accordance with claim 1, characterized in that the control signals representing a number of analysis channels (A^,Ag#••••) are arranged to represent at least two groups (A^,A^,A^ and Ag,A^) of analysis channels, where each group is shifted positionally in relation to each of the other groups, so that a preselected, overlapping arrangement is formed. 3. Apparatus in accordance with claim 1, characterized by that the overlapping analyzing channels comprise a first set (A-j^A-jjAcj) which is placed above the random stream in a wide path and has a predetermined distance to adjacent analyzing channels (A2,A4) and at least one other set (A2,A4) where each channel extends over a respective predetermined distance to adjacent channels in the first set and where each channel overlaps parts of channels in the first set close to the predetermined distance., between these (A2,A4), that a selector channel (D^,D.>) is arranged for each analysis channel, where the selector channel is centered in relation to a respective analysis channel and has a width smaller than the width of the analysis channel, that a first circuit system (64,65) is arranged for each selector channel, each of which receives the scan signal and a respective selector channel signal and produces an activation signal when a piece of material is detected in the respective selector channel, and that" another current circuit system (60,61) is arranged for each analysis channel, each of which receives an activation signal from a respective first current circuit system, the scanning signal and a regulation signal for the respective analysis channel and in the activated state accumulates information regarding pieces of material in the respective analysis channel and emits a decision signal on the basis of the accumulated information. 4. Apparatus in accordance with claim 3, characterized in that all analysis channels (A^, A2,...) have the same width. 5. Apparatus in accordance with claim 4, characterized in that the overlapping analysis channels consist of a first group (A^,.A3,A5) and a second group (A2,A4)., where each channel in the second group is centered in relative to a preselected one. spaces between mutually adjacent channels in the first group. 6. Apparatus in accordance with claim 5, characterized in that each channel in the second group (A2,A^) of analysis channels overlaps channel sections in the first group (A^A^A^j adjacent to the respective space to an extent that for each overlap is less than half the width of a channel. 7. Apparatus in accordance with claim 6, characterized in that the width of a deflection member (B-^,B2,....) is greater than half and less than the full width of an analysis channel (A^,A2,..), and that each control circuit activates two deflectors. 8. Apparatus in accordance with claim 7, characterized in that the deflectors (B-^,B2,...) are arranged side by side, in contact with each other, across the sorting zone. 9. Apparatus in accordance with claim 6, characterized in that the width of a deflector means (B^ ,B2 , ....) slightly exceeds the width of an analysis channel (A^,A2,...), and that the deflector device comprises a first row of deflector means which; in contact with each other, are placed side by side across the sorting zone, and a second row of deflectors which in the longitudinal direction are located adjacent to the first row, and where each member overlaps adjacent deflector members in the first row. 10. Apparatus in accordance with claim 9, characterized in that each control circuit operates one deflector member (B^,B2,...) . 11. Apparatus in accordance with claim 4, characterized in that the overlapping analysis channels form a first, a second and a third group (A^",A2",A^"), where each channel in the second group overlaps one channel in an adjacent channel pair in the first group to an extent that does not exceed two-thirds of that of one channel width, and overlaps the other channel in the adjacent channel pair to an extent that does not exceed one third of the other channel's width, and where each channel in the third group overlaps one channel in an adjacent channel pair in the first group to an extent not exceeding one third of the width of one channel, and overlaps the other channel in the adjacent channel pair to an extent not exceeding two thirds of the other channel's width. 12. Apparatus in accordance with claim 11, characterized in that the width of a deflecting member (B^",Bg) barely exceeds a third of the width of an analysis channel (A-^,Ag . ) 13. Apparatus in accordance with claim 11 or 12, characterized in that the deflectors (B^",Bg ",B^",...) are arranged, in mutual contact, side by side across the sorting zone, and that each control circuit operates three deflector means. 14. Apparatus in accordance with claim 11, characterized in that the width of a deflecting member (24 ' ' ' ,B^ ''.',Bg ' ' ') slightly exceeds the width of an analyzing channel (A^",Ag",. ..), and that the deflector device comprises a first row (B^''1,B^''') of deflector members which are placed in mutual contact, side by side across the sorting zone, a second row (Bg'<1>' ,B^''') of deflector members which are placed side by side in contact with each other and where each deflector member overlaps adjacent members in the first row by roughly two thirds and one third respectively of the width of a deflector member, as well as a third row of deflector members (B^''',Bg ' '*) which are placed side by side in mutual contact, and where each deflector member overlaps adjacent members in the first row by roughly one third and two thirds respectively of the width of one deflector member. 15. Apparatus in accordance with one of claims 1-3, characterized in that the deflector means consist of air blower nozzles (24) which direct a deflecting air flow towards the passing pieces of material. 16. Apparatus in accordance with one of claims 1-3, characterized in that additional electronic means (85,86) are arranged for generating additional control signals in connection with a preselected number of scans, where the signals represent a number of mutually overlapping analysis channels which each extending across the sorting zone and largely at right angles to the direction of the material pieces' advance through the sorting zone, and where the additional control signals are transmitted to the control circuit (56, 60, 61), to initiate the indication of the decision signal in intervals delimited by the preselected number of scans. 17. Apparatus in accordance with claim 3, characterized in that further electronic means (85, 86) are arranged for generating control signals which represent a pair of overlapping analysis channels (56, 56) which run in a transverse direction over the sorting zone and over the forward direction of the pieces of material and which is formed by a preselected number of scans, as well as means which, upon receiving the signals representing a transverse pair of overlapping analysis channels (70,71), initiates the emission of the decision signal, when a piece of material is scanned at intervals in accordance with the formation of mentioned channels at the preselected number of scans.