GB2150048A - Pulsator device - Google Patents

Abstract

An electro-magnetic pulsator device (1), for use in material treatment apparatus such as a mineral jig, shaking table or vibratory screen, comprises an actuating spindle (2) which is slidingly received in a housing (6, 7, 8) and which is operatively coupled to an oscillatable member of the apparatus. The spindle (2) is given a pulsating action for vibration of the member by electromagnetic means (4, 5) which includes magnetic disc blocks (4, 5) spaced apart by a distance greater than the required pulsation amplitude. A radial metal reaction disc (3) attached to the spindle (2) is located in the space between the magnetic blocks (45) and serves to transmit the electromagnetic pulsation forces to the spindle (2). Electrical control means controlling the magnetic currents serves to control the spindle pulsation. The pulsator device provides a smooth and quiet operation, with readily controllable pulsation. <IMAGE>

Description

SPECIFICATION Pulsator device The present invention relates to a pulsator device for use in material treatment apparatus including a vibratory treatment table or container, and especially but not exclusively to mineral concentrators and separators (generally referred to as mineral jigs) and like apparatus.

Concentration and separation of heavy and other materials from a slurry is commonly achieved by a jigging effect on the slurry in mineral jigs and like apparatus. In particular, a pulsation action is applied to the slurry by suitable means, and concentration is usually achieved by a combination of elutriation and hindered settling and certain other process characteristics achieved by the pulsation action.

The most common mineral jig is probably that known as the Yuba jig (pulsator box type): this jig is described in U. K. Patent specification No. 61 2 874. Another form of jig is the Pan American type which employs vertical pulsations, and yet a further mineral jig which in this instance uses both vertical pulsation and centrifugal action is described in U. K. Patent specification No. 1 516 135.

The Yuba jig is a multi-cell jig comprised by box constructions and concentration is achieved by a multi-stage operation involving a cross-flow movement of the slurry relative to the pulsation direction: in particular the jig can include up to five box constructions or cells in one flow line to increase the treatment capacity of the jig. Each cell or unit and each unit houses an upper container in the form of a perforated basket, the basket containers of succeeding units being at reduced levels for the creation of a weir type flow pattern. The box constructions also contain outlets for discharge of concentrates.Two box constructions can be located in spaced parallel relationship with pulsator apparatus therebetween. and this pulsation apparatus creating horizontal pulsations of the contents of the cell normally comprises a plurality of eccentric drives each located between a pair of opposed cells and each having a double action characteristic (i.e.

of double ended form) for oscillation of the opposed cells. The eccentric drives are directly connected to the cells and can have a common input. These eccentric drive pulsators are of rugged design and are consequently reasonably reliable.

U. K. Patent No. 1 516 135 discloses a separator comprising a casing having a lower cone part connected to the upper casing part by a diaphragm to enabie the cone to be oscillable.

The upper casing part houses a rotary perforated basket receiving the slurry to be treated. The casing is filled with water and the slurry is subjected to both a centrifugal force caused by the rotation of the basket, and to a vertical pulsation effect by virtue of the oscillatory cone. In this jig, the pulsation drive comprises an eccentric mechanism coupled to the lower cone by a fulcrum lever. The stroke length of the pulsator may be 1 2mm to 1 9mm with a speed of for example 120-140 strokes/minute. The above prior art pulsator drives have the following disadvantages: 1) There is considerable difficulty in adjusting the stroke length. Adjustment can be achieved for example by altering the stroke or amplitude of the said eccentric mechanism or by repositioning the fulcrum point of the fulcrum lever but this is a fairly time consuming operation and requires the jig to be halted.

2) Changing of the stroke speed requires adjustment of the prime mover.

3) The mechanical eccentric drives are relatively noisy in operation and inefficient.

It is an object of the present invention to provide a pulsator drive obviating or mitigating the above disadvantages.

According to the present invention a pulsator drive for use in material treatment apparatus such as a mineral jig comprises an actuating element adapted to be linked to or operatively engage an oscillable member of said treatment apparatus: support means for said actuating element; and electrical oscillating means for effecting reciprocation of said element.

Preferably said oscillatory means comprises an electrical magnetic device.

The electrical oscillating means are preferably linked to control means serving to control operating parameters, such as for example stroke length, stroke speed and waveform of the oscillating action.

In a preferred embodiment. the actuating element comprises a rod member including a radial disc located between spaced opposed electric magnets which are variably energisable to cause oscillatory movement of the disc and consequently the rod, and electric circuit means are provided for selective energisation of the magnets. The electric circuit means can be arranged to provide the oscillating rod with different stroke lengths, stroke speeds and stroke waveforms, in response to an appropriate input command signal.

The pulsator device can be arranged to be double acting by having each end of the actuating element adapted to be linked to or operatively engage an oscillable member.

Further, it would be possible for the pulsator device to include two electrical oscillating means operating in tandem for increased power output.

Preferably sensing means are provided to sense movement of the actuating element, the sensing means being coupled to the control means whereby oscillating movements of the element can be controlled and regulated.

These sensing means can comprise a light responsive (intensity) sensing device dependent on movement of the actuating element, and the actuating element is preferably shaped to provide the desired operating characteristics of the sensing device, for example if the element comprises a rod then the rod could be formed with a cone shaped end.

However, other forms of sensing means are possible, such as capacitive or inductive sensing means.

The pulsator device of the present invention is very suitable for use in automatic treatment processes since it will possible to adjust characteristics of the pulsating movement instantaneously and automatically, to meet treatment requirements.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a sectional side elevation of a pulsator device for mineral jigs and like apparatus and according to the present invention; Figure 2 shows a block diagram of the control arrangement for the pulsator device of Fig. 1; Figure 3 shows an elevational view of one form of mineral jig including the pulsator device of Fig. 1; Figure 4 shows an elevational view of another form of mineral jig including a modified form of the pulsator device of Fig. 1; Figure 5 shows a tandem arrangement of pulsator device; and Figure 6 shows a control chart of a continuous automatic concentration process in a mineral jig apparatus.

Referring to the drawings and particularly Figs. 1 and 2, a pulsator 1 for use in mineral jigs and other mineral separation and concentration apparatus is of electro-magnetic form and comprises an oscillating metallic spindle 2 carrying a metal reaction disc 3, the spindle 2 having an upper part 2A screwed into a lower part 2B so that the disc 3 is clamped therebetween, and the spindle 2 passes through bores in a pair of magnetic disc blocks 4, 5 located on either side of the disc 3. The magnetic disc blocks 4, 5 are located in a cylindrical housing 6, and are retained by closure caps 7, 8 bolted to the housing 6.

The caps 7, 8 include cylindrical extensions 9, 10 containing bushings 11 to slidably support the spindle 2, and the extension 10 additionally carries a flange 1 2 to enable the pulsator 1 to be bolted to a suitable base support (not shown in Fig. 1). The spindle 2 includes a clevis or equivalent coupling 1 3 adapted to couple the pulsator 1 to a pulsatory portion of the jig or other concentrator.

Each of the magnetic blocks 4, 5 includes a bobbin 14 for the electromagnetic windings, and current feed conduits (not shown) to the windings pass in through the housing 6 via respective bores 15, 1 6. The blocks 4, 5, are spaced apart by a distance (for example 30 mm) greater than the maximum displacement amplitude desired from the oscillating spindle 2.

Oscillating movement of the disc 3 (and consequently of the spindle 2) is achieved by controlled opposite pulling effects of the electromagnets 4, 5, and to this end the electromagnetic pulsator 1 is coupled to an appropriate electric control circuit for the magnets. A suitable circuit is shown diagramatically in Fig. 2. Thus referring to Fig. 2, a position measuring device 1 7 senses the position of the spindle 2 and generates an output in the form of a voltage signal Vp representing the axial displacement of the spindle 2 from a neutral (datum) position.The difference between this voltage Vp and the output VG of a waveform generator 1 8 produces an error voltage V,, at the output of an error forming amplifier 1 9 A control system 20 acts upon this error voltage Ve to produce a drive voltage f(V,) to drive two ampifiers 20 and 21. These amplifiers 20. 21 supply control currents 1,. 12 to the two electromagnets 4, 5 so that they pull in opposite directions axially to maintain the spindle 2 such that the error voltage Ve is equal to zero.

Where larger electromagnetic designs are used, it will be desirable to apply feedback to the control system 20 of voltage proportional to current and magnetic flax in the electromagnets 4, 5: these feedbacks are the values cfb and Sbfb shown in Fig. 2. The control circuit can conveniently cater for oscillations of different desired amplitude and also for different frequencies of oscillation. Further, the waveform pattern of the spindle oscillation may be varied.

The position measuring device 1 7 can be of any suitable form. For example, the device 1 7 could operate on variable light intensity principles, and for this measuring arrangement the spindle 2 of Fig. 1 is provided with a conical nose 22 while the extension 10 has aligned bores 23, 24 at the level of the cone 22, for the light beam of the measuring apparatus. Such light intensity sensing devices are well established and it will not be necessary therefore to describe the device in any greater depth. As an alternative an induction or capacitance type transducer device could be used for measurement of the spindle position.

Fig. 3 shows the pulsator 1 used in a Pan American mineral jig 25. The jig 25 comprises a pair of open top containers 26 arranged side-by-side; and each container 26 has a fixed top part 27 of cylindrical form with a frusto conical bottom 28 while an oscillable pulsation cone 29 below bottom 28 slidably interifts with an annular mouth 30 of the bottom 28, an annular sealing diaphragm 31 being located betwen the cone 29 and the mouth 30.

A perforated jig grid and basket 32 is located in the cylindrical part 27, while the bottom 28 receives water inlet pipes 33. The cone 29 includes an outlet nozzle 37 for heavy minerals which pass through the perforated basket during the concentration process.

Vertical oscillation of the cones 29 is achieved by a pivotal beam 34 supported on a central trunnion 35, the beam 34 being coupled to the cones 29 of both containers by bearing blocks 36, and the spindle 2 of pulsator 1 is coupled to an end of the beam 34 to impart an appropriate swinging motion to the beam.

In operation each container 27 is filled with water to the level of the basket 32 while a slurry containing the materials to be concentrated is fed into the basket 32, and the slurry is subjected to vertical pulsations created in the water by the moving cone 29. Fig. 4 shows the invention applied in a Yuba type mineral jig 37. The Yuba jig 3 is a horizontal flow concentrator (the flow direction being out of the paper in Fig. 4) and the jig 37 shown comprises a tandem arrangement of concentrator cell arrays. Each cell array comprises two side-by-side sets 38A, 38B of three cell units (i.e. the jig has 1 2 cells in all) - Fig. 4 shows a discharge end view of the sets. The cells of each set constitute respectively input, intermediate and output cells 39, 40, 41 (only output cell 41 being fully shown in Fig.

4) with the slurry flow being from the input to the output cells, and each cell 39 - 41 houses a receptacle for slurry in the form of a mild steel retaining grid 42 with an M. S. lower grid and basket 43 therebelow, while a discharge 44 for heavy mineral concentrates is located at the bottom of a lower converging portion of the ceil. Feed conduits 45 for water are provided.

The receptacles of the cells 39-41 of a set are arranged with a descending order of location so that a weir type flow pattern is present between input and output.

Three electromagnetic pulsators 1A are used (only one being shown in Fig. 4) and these are generally similar to that pulsator of Fig. 1: however in this case the pulsator 1 A is of double-ended action form with a connector 1 3 at each end of the spindle 2 whereby the pulsators 1A can jig the tandem arrangement.

More specifically each pulsator 1A is directly coupled to equivalent cells of the opposed cell sets 38A, and pulsation effect is achieved via rubber diaphragms 46. Each diaphragm 46 is coupled to an outer rubber diaphragm 47 of the set 38B by tie rods 48 so that cells of the cell sets 38A, 38B can move in unison. As will be understood, in this jig the pulsation action is transverse to the direction of slurry flow. Both in this embodiment and in the embodiment of Fig. 3, the pulsation action can be readily adjusted to give different amplitudes and frequencies of oscillation, and the waveform of the oscillation may also be varied, for example from a smooth sinusoidal form to a more abrupt trapezoidal form. These oscillation adjustments lead to the possibility of greatly improved concentration.

It will be appreciated that when rig pulsation diaphragms (item 46 of Fig. 4) are coupled with tie rods or coupled back to back at either end of the pulsator 1 then the motions of these diaphragms are reciprocal and hence asymmetric wave forms are reversed: the above reference to variation of the waveform of the pulsator 1 should not be confused with this characteristic.

In some cases more power may be desired from the electromagnetic pulsator 1 but without too great a change in the diameter of the magnets (and casing 6), and in these circumstances the tandem arranged pulsator of Fig.

5 would be advantageous. In this example two casings 6A, 6B surround the spindle 2, each housing a magnetic pair 4, 5, and the spindle 2 includes a pair of reaction discs 3 each associated with a respective magnet pair.

The spindle position measuring device 1 7 is shown, and as can be seen the pulsator of Fig. 5 is a double acting form. The dashed lines in Fig. 1 indicate how this pulsator would be adapted into a tandem arrangement.

The electromagnetic pulsator 1 (1A) particularly lends itself to use in an automatically controlled mineral concentration process, and such a process is schematically shown in Fig.

6. This process involves the measurement of: a) Velocity of slurry (by device 52A) passing to a dewatering/desliming hydrocyclone 55, the underflow from which is fed to mineral jig 57.

b) Slurry density (by device 53A) c) Velocity of concentrate (by device 52B) discharged from jigs, and d) Density of concentrate (by device 53B) The signals from the devices 52A, 53A, 52B. 53B are fed to a controller 54 which calculates: a) The rate of feed to the jig: b) The rate of production of concentrate; and c) The ratio of (a) to (b) above and hence the reduction ratio induced by the pulsators (1) of the jig. The recovery efficiency of a jig relates inversely to the reduction ratio induced by the jig, i.e.

mass of concentrate.

mass of feed The controller 54 compares calculation (c) above with input instructions K and sends a command signal to the pulsation control device 56 of pulsators 1 to increase or decrease frequency and/or amplitude of pulsations and thereby increase or reduce the amount of concentrate produced by the jig. Overflow from the hydrocyclone 55 is either recirculated to plant or discharged to waste.

In addition to convenient adjustability, the electromagnetic pulsator of the present invention is considerably smoother and quieter in operation than previous mechanical pulsating drives. The pulsator 1 could be applied in other treatment processes, for example in shaking table separators and in vibrating screen separators.

It will be understood that modifications are possible in the above described pulsators of the present invention. For example, only a single controlled magnet may be used operating in conjunction with a return spring; a two magnet system with flux and current feedback to control the spindle position could also be used. It would be possible to provide magnet windings formed, insulated and fitted without the use of the bobbins 14. Instead of having the pulsations transverse to the slurry flow as in the jig of Fig. 4, it would be possible to have the pulse action in some other direction.

Claims (9)

1. A pulsator drive for use in material treatment apparatus such as a mineral jig comprising an actuating element adapted to be linked to or operatively engage an oscillable member of said treatment apparatus; support means for said actuating element; and electrical oscillating means for effecting reciprocation of said element.

2. A pulsator drive as claimed in claim 1, wherein said oscillatory means comprises an electrical magnetic device.

3. A pulsator drive as claimed in claim 1 or 2, wherein the electrical oscillating means are linked to control means serving to control operating parameters, such as for example stroke length, stroke speed and waveform of the oscillating action.

4. A pulsator drive as claimed in any one of the preceding claims, the actuating element comprises a rod member including a radial disc located between spaced opposed electric magnets which are variably energisable to cause oscillatory movement of the disc and consequently the rod, and electric circuit means are provided for selective energisation of the magnets.

5. A pulsator drive as claimed in claim 4, wherein electric circuit means are arranged to provide the oscillating rod with different stroke lengths, stroke speeds and stroke waveforms, in response to an appropriate input command signal.

6. A pulsator drive as claimed in any one of the preceding claims wherein the drive is arranged to be double acting by having each end of the actuating element adapted to be linked to or operatively engage an oscillable member.

7. A pulsator drive as claimed in any one of claims 1 to 5, wherein the drive includes two electrical oscillating means operating in tandem for increased power output.

8. A pulsator drive as claimed in any one of the preceding claims, wherein sensing means are provided to sense movement of the actuating element, the sensing means being coupled to the control means whereby oscillating movements of the element can be controlled and regulated.

9. A pulsator drive as claimed in claim 8.

wherein the sensing means comprise a light responsive (intensity) sensing device dependent on movement of the actuating element, and the actuating element is shaped to provide the desired operating characteristics of the sensing device.

1 0. A pulsator drive for use in material treatment apparatus substantially as hereinbefore described with reference to Figs. 1 to 3 or Fig. 4 or Fig. 5 of the accompanying drawings.