GB2046629A - Sorting apparatus and method - Google Patents

Abstract

Particles (24) of ore, e.g. having a radio-active component, are sorted by feeding the particles in a stream on a conveyor (12) past one or more detectors (14) to detect a specific ore characteristic in the particles and deflecting either the particles detected to include the characteristic above a predetermined level or the particles which do not include the characteristic or the particles which include the characteristic below the predetermined level from the stream by means of a fluid jet from a fluidically operated valve (18). <IMAGE>

Description

SPECIFICATION Sorting apparatus and method This invention relates to a method of and apparatus for sorting particulate material such as mineral ores and the like.

In a known method of sorting mineral ore particles a desired inherent characteristic of the ore such as colour, mass, reflectivity, conductivity and the like is detected in specific particles in a stream which is moved past means for detecting the characteristic.

The particles which include the desired characteristic are then deflected from the stream by means of an air jet blast from a valve controlled nozzle which is adapted for operation on a timed signal from means responsive to the detecting means. A problem with these sorting systems is that the timing of the air blast from the deflector valve nozzles is extremely critical and is complicated, particularly where the stream of particles is moving fast such as when projected into or free falling in space, by the inertia and frictional resistance to movement of the mechanical switch components of the valves. Additionally, as the moving part nozzle valves are generally required to operate in a hostile dust filled environment they are subject to mechanical failure and improper operation.

It is the object of this invention to provide a method of and apparatus for sorting particles which will minimise the above problems.

A method of sorting particles, of ore or the like according to the invention, includes the steps of passing a stream of the particles past means to detect a predetermined characteristic of the particles in the stream and deflecting particles which include the characteristic above a predetermined value from the stream by means of a fluid jet from a fluidically operated valve which is controlled by means responsive to the detecting means. Conveniently, the method includes the step of causing the fluid jet from the valve to pass through a nozzle which has a divergent throat to increase the velocity of the fluid jet.

According to the invention apparatus for sorting particles of ore or the like includes means for feeding a stream of the particles to be sorted past a detector adapted to measure a predetermined characteristic of each particle in the stream and a fluidically operated valve which is adapted on a signal from means responsive to the detecting means to blast particles having the predetermined characteristic above a predetermined level from the stream.

In one form of the invention the valve is a fluidically operated vortex valve. Preferably, the valve includes an outlet nozzle which has a divergent throat.

Further according to the invention the valve includes a valve body having a cavity including inlet and outlet ports for air at a first supply pressure, means for introducing air at a second supply pressure through ports arranged on the line of a circle into the body cavity, means in the cavity connected to the second air supply introducing means for generating an air vortex in the body cavity to inhibit the flow of air at the first supply pressure through the body cavity in use, valve means comprising an annular valve member which is located in the body and adapted for movement between a first position in which it obturates the ports to prevent the air at the second supply pressure from reaching the vortex generating means and a second position in which it is clear of the ports, and an electromagnetic coil for causing the valve memberto move between its two positions of operation.

In this specification a fluidic valve is taken to mean any valve through which a fluid is adapted to pass with the flow of the fluid being controlled by the flow of a second fluid.

The invention is now described by way of example with reference to the drawings in which: Figure 1 is a diagrammatic side view of one embodiment of a basic form of sorter of the invention.

Figure 2 is a sectional side elevation of a valve for use with the sorter of the invention.

Figure 3 is a half end elevation of the valve of Figure 2 shown in section on the line A-A in Figure 2, and Figure 4 is an enlarged fragmentary sectioned side elevation of the pilot air switch of the valve of Figure 2.

A simple embodiment of the sorter of the invention is shown in Figure 1 of the drawings to include a hopper 10, an endless belt conveyor 12, a detector arrangement 14, a computer 16, a particle deflector arrangement 18, and particle receiving stations 20 and 22.

In use, particles of ore 24 are discharged discretely from the hopper 10 onto the upper bight of the conveyor 12 and transported past the detector arrangement 14. The detector is adapted to measure a particular characteristic of the particles. For example, if the particles 24 are particles of ore which include a radio-active component, the detector could consist of a plurality of scintillation counters adapted to measure the radio-active radiation of the particles.

The detector arrangement could be adapted to measure the required characteristic of the particles 24 sequentially and in bands across the conveyor.

The characteristic measurement of each particle or closely spaced group of particles on the conveyor is then fed to the computer 16 and stored against the parameters of the system such as conveyor speed and the time which it will take that particle or group of particles to come into register with the direction of the output of the particle deflector 18. When the characteristic of the particle has been measured it is conveyed to and discharged from the discharge end of the conveyor into space. If the particles are uninterrupted in free fall they fall into the receiving station 22 from where they are conveyed to a reject station.

If the detector arrangement 14 is adapted to measure longitudinal bands of particles on the conveyor the sorter will include at least one deflector 18 which is suitably positioned to separate particles from each band in the falling stream of particles.

As a particle in the falling stream which has been measured by the detector to have a characteristic value above the predetermined level comes into register with the nozzle direction of the deflector 18 a signal from the computer 16 activates the deflector 18 to cause a blast of air from its nozzle to deflect the particle from its free fall path towards the receiving station 20 from whence it and other deflected particles are conveyed to an ore accept station.

From what has been said above it is obvious that the timing of the air blasts from the deflectors 18 must be exactly timed for accurate separation of the accept particles of ore from the falling stream.

The deflector valve 18 of the sorter of the invention is shown in Figures 2 to 4 of the drawings to include a valve body 28-having a front cover portion 30 and a back cover 32, a pilot valve body 34 and a swirl plate 36.

The cover 30 of the valve body includes an axially positioned venturi nozzle 38. The back cover 32 includes an air inlet adaptor 40 and on its outside face carries an annular groove 42. Four equally spaced ports 44 pass from the base of the groove 42 into the cavity of the housing.

Four sleeves 46 are located in complementally shaped recesses in the inner face of the cover 32 with their bores in register with the ports 44. The outer ends of the sleeves are similarly located in recesses in the swirl plate 36. The swirl plate is held in position in the body cavity by being sandwiched between the sleeves 46 and nozzle members 48 which are attached to the front cover 30 of the valve body. Both the swirl plate and nozzle members 48 carry bores which are in axial register with the ports 44 and bores in the sleeves 46.

The nozzle members 48 are more clearly seen in end elevation in Figure 3 to consist of square plates which each include a bore 50 which when the members are located in position in the valve body are in register with the bores in the sleeves 46 and a nozzle slot 52 which is directed into the space between the outer face of the swirl plate 36 and the inner face of the cover 30 as shown in the drawing.

The pilot valve body 34 includes a pilot air manifold 54, a coil housing 56 which carries an annular coil 58 and a valve member plate 60 which is sandwiched between the valve cover 32 and the coil housing.

The manifold 54 includes an annular cavity 62 and an adaptor 64 for connecting a supply air hose to the manifold.

The coil housing 56, as is more clearly seen in Figure 4, includes an annular chamber 66 in which the solenoid coil 58 is located. The chamber 66 is larger in dimension than the coil so that an air path is provided in the chamber over the coil. The air inlet to the chamber from the cavity 62 in the manifold is provided through ports 68. The downstream end of the chamber 66 is defined by a ring plate 70 which is located between the coil housing 56 and the plate 60.

The inner edge of the plate 70 is chamfered as shown in the drawing towards an outlet port 72 which is concentric with the axis of the valve body.

Both the coil housing and the plate 70 are flanged on the upstream side of the port 72 to provide a valve seat.

The valve member plate 60 includes an annular groove 74 and four sets of ports 76. The ports 76 in each set lead from the groove 74 into the groove 42 in the back cover 32 and are positioned concentrically about the axis of the ports 44 in the cover 32.

The base of the groove 74 in the plate 60 is recessed at 78 to provide a location for an annular valve member 80 which is made from a soft magnetic metal. Suitable spacer members, not shown, are located in the groove 74 to guide the movement of the valve member 80 in the axial direction of the valve body.

In use, air under supply and pilot pressure is connected to the adaptors 40 and 64 respectively with the pressure of the pilot air being about 1,5 times greater than the pressure of supply air connected to the adaptor 40. The pilot air flows through the cavity 62, the port 68, through the chamber 66, over the coil 58 and out of the port 72 to force the valve member 80 into the recess 78. The pilot air then flows through the groove 74, ports 76, groove 42, ports 44, sleeves 46 and from the nozzle slots 52 into the space between the swirl plate 36 and the inner face of the cover 30. The pilot air flowing from the nozzles 52 generates a vortex in the space between the plate 36 and the cover.The vortex so produced creates a back pressure which reduces the flow of supply pressure air which otherwise would flow around the swirl plate to the nozzle 38 to a small proportion of its unimpeded flow rate. This is the normal or switched off condition of the valve until an accept ore particle 24 is in register with the outlet of the nozzle 38. A suitably timed signal from the computer 16 then momentarily energises the coil 58 to cause the valve member 80 to be magnetically pulled rearwardly onto its seat over the port 72 to shut the pilot air from the nozzles 52 and so destroy the pilot air vortex.

Supply air now flows from the nozzle to deflect the particles from its natural fall path into the acceptsta- tion 20.

The dimensions of the bore of the nozzle 38 and its venturi throat as well as the supply air pressure rela tive to these parameters are so designed that the air blast from the nozzle 38 is supersonic. For super- sonic operation of the valve ofthe invention a typical supply air pressure is about 5,442 bars.

With the sorting apparatus of the inventionthe deflector valves are, with the exception of the valve member 80, free of moving parts and as a result can tolerate high dust densities or other hostile operating conditions which could arrest or hinder the operation of known moving part deflector valves used in ore sorting apparatus. The fluidic valve of the invention can be normally associated with valves in sorting applications. More importantly, however, the fluidic operation of the valve, being substantially devoid of inertia effects, provides the system with a faster response and sharper cut-off time than is possible with the valves presently being used for sorting purposes.

The invention is not limited to the precise method or constructional details as herein described and the sorting apparatus of Figure 1 could be replaced by any suitable apparatus which provides the same function. Additionally, the deflector valve 18 could consist of any suitable fluidically operated valve and not necessarily the embodiment of the valve illustrated in Figures 2 to 4 of the drawings.

In this description of the preferred form of the sorter of the invention and in the claims it is mentioned that particles of ore which include the desired characteristic are deflected by the system and valve from the falling stream of particles. This is, however, intended to include the situation where instead of the particles which include the desired characteristic the system and valve is adapted to deflect the particles which do not include the characteristic or only include the characteristic below a predetermined level from the stream, without departing from the scope of the invention.

Claims (10)

1. A method of sorting particles of ore or the like including the steps of passing a stream of the particles past means to detect a predetermined characteristic of the particles in the stream and deflecting particles which include the characteristic above a predetermined value from the stream by means of a fluid jet from a fluidically operated valve which is controlled by means responsive to the detecting means.

2. A method as claimed in Claim 1 including the step of causing the fluid jet from the valve to pass through a nozzle which has a divergent throat to increase the velocity of the fluid jet.

3. Apparatus for sorting particles of ore and the like including means for feeding a stream of the particles to be sorted past a detector adapted to measure a predetermined characteristic of each particle in the stream and a fluidically operated valve which is adapted on a signal from means responsive to the detecting means to blast particles having the predetermined characteristic above a predetermined level from the stream.

4. Sorting apparatus as claimed in Claim 3 in which the valve is a fluidic vortex control valve.

5. Sorting apparatus as claimed in either one of Claims 3 or 4 in which the valve includes an outlet nozzle which has a divergent throat.

i6. Apparatus as claimed in any one of Claims 3 to 5 in which the valve includes a valve body having a cavity including inlet and outlet ports for air at a first supply pressure, means for introducing air at a second supply pressure through ports arranged on the line of a circle into the body cavity, means in the cavity connected to the second air supply introducing means for generating an air vortex in the body cavity to inhibit the flow of air at the first supply pressure through the body cavity in use, valve means comprising an annular valve member which is located in the body and adapted for movement between a first position in which it obturates the ports to prevent the air at the second supply pressure from reaching the vortex generating means and a second position in which it is clear of the ports, and an electromagnetic coil for causing the valve memberto move between its two positions of operation.

7. Apparatus as claimed in Claim 6 in which the electromagnetic coil of the valve is annular in shape and concentric with the valve member.

8. Apparatus as claimed in any one of Claims 3 to 5 in which the valve includes a valve body having a cavity including inlet and outlet ports for air at a first supply pressure, means for introducing air at a second supply pressure through an annular port into the body cavity, means in the cavity connected to the second air supply introducing means for generating an air vortex in the body cavity to inhibit the flow of air at the first supply pressure through the body cavity in use, valve means comprising an annular valve member which is located in the body and adapted for movement between a first position in which it obturates the annular port to prevent the air at the second supply pressure from reaching the vortex generating means and a second position in which it is clear of the port, and an annular electromagnetic coil which is concentric with the valve member for causing the valve member to move between its two positions of operation.

9. Apparatus for sorting particles of ore and the like substantially as herein described with reference to and as illustrated in the drawings.

10. A particle deflector valve for use in apparatus for sorting particles of ore and the like substantially as herein described with reference to and as illustrated in Figures 2 and 3 of the drawings.