US2086060A - Apparatus for the electrical separation of coal - Google Patents

Description

July 6, 1937. K. c. APPLEYARD ET AL 2,086,060

APPARATUS FOR THE ELECTRICAL SEPARATION OF COAL Fild Aug. 10, 1936 Patented July 6, 1937 UNITED v attests orrlcs APPARATUS FOR THE ELECTRICAL SEPARATION OF COAL Kenelm Charles Appleyard, Birtley, and Stanley Dallas Pollitt, Newcastle-on-Tyne, England, as-

signors to The Birtle ley, England y Company Limited, Birt- 2 Claims.

This invention relates to the separation of coal by electrical discrimination, and especially to apparatus for separation according to our British Patent No. 421,401, but it is not limited to such apparatus, especially, for instance, as regards voltages and amplification.

The object of the invention is to provide an improved or modified apparatus, especialy from the aspect of reducing the valve requirements in a number of machines working together, or in a machine of what might be called a multi-pass type, that is, where a number of sets of discriminating brushes or the like come into question.

The invention in brief consists in apparatus 5 for the sorting of coal by electrical discrimination, in which the different conductivity or like efiects produced in an electric circuit by the passage of the coal being sorted, which coal forms part of that circuit, are used to control a single electric discharge tube, which is rendered available to a, plurality of machines or coal separating paths, for instance, constituted by means of a conveyor band passing the coal through gaps between resilient electrical contacts, which electrical discharge tube acts to determine the disposition of the sorted materials.

The invention also consists in apparatus according to the preceding paragraph in which the electric discharge tube is rendered available to a plurality of discriminating devices by means of two or more commutators or rotary switches rotated at a suificiently high speed, one of these commutators being in connection with the anode of the discharge tube, and a series of relay circults, dealing with the control of the discharge arrangements, or with the maintenance of a suitable time interval by holding-on circuits, or by other desired devices, and another commutator being associated with the grid of the valve, and

the discriminating devices. 7

The invention also consists in apparatus according to either of the preceding two paragraphs, in which direct current is employed in connection with the devices associated with the anode commutator, and alternating current is employed in connection with the cathode side of the electric discharge device.

The invention also consists in apparatus for the sorting of coal, substantially as herein described.

One way of calrying the invention into effect by way of example will now be described with reference to the accompanying drawing, which represents diagrammatically a scheme for the electrical separation of coal from associated impurities. V V 7 Referring to the drawing, a grid controlled mercury vapour filled discharge tube I having an anode 2, a grid 3 and a cathode l is used to 5 deal with a conveyor band l5 constituting five coal separating channels it to M in each of which a piece of. coal is shown, each of which has what may be termed discriminating fingers in sets at right angles suitably electrically connected, as 0 shown conveniently in Figure 1 of the drawing accompanying the complete specification of British Patent No. 421,491, especially taken in conjunction with Figures 7 and 8 of that pat ent.

The discriminating devices numbered 5 to 9 1 5 and the valve I, with its associated circuits, are co-related by means of two five-part commutators, IE3 and H respectively, each commutator consisting of five elements l2 to It and H to ill corresponding in number to the five cleaning 20 channels, and each element being divided into four sections mutually opposed at right angles, the four sections of each element being electri cally connected.

The commutators ill and II have co-operating brushes 22 to 26 and 21 to 3! respectively which are electrically connected in each commutator, In the case of the commutator H, a connection is made from the brushes to the anode 2 of the valve I, and in the case of the other commutator I ll, a connection is made from the brushes to the grid 3 of the valve 9. For convenience, the commutators will therefore be referred to respectively as the anode and grid commutators.

Each of the above mentioned conductive sec- 35 tions of the commutator elements is of such a peripheral length that when the five elements of the commutators are fixed on the shaft 32, they may be so adjusted relative to one another that their corresponding brushes will make contact 40 with only one section at a time, and in a complete revolution of the shaft 32 each brush will have made four contacts on the corresponding element of the commutator orin all twenty separate contacts will have been made by the set 45 of brushes. The peripheral length of the contact also bears such a relation to the diameter of the commutator that the brushes in passing from one segment to another pass over a space of insulation. 50

The commutators are mounted on the hollow shaft 32 which is capable of being rotated at high speed, and on this shaft two sets of slip rings 33 and 34 are mounted, each set comprising five rings of conductive material, with co-operat- 55 ing brushes, the rings being insulated from the shaft and connected by leads passing through the inside of the shaft to their respective commutators IE and ii. The rings which are thus joined to the grid commutator have their respective brushes connected to one side of the discriminating fingers 5 to 9, the other side of these fingers being connected to earth.

The brushes of the set of slip rings 34 which are associated with the anode commutator H are electrically connected with a series of relay switches 35, 35, 31, 38 and 39. These relays when actuated energize solenoids M3, ll, 42, 43 and 4 3 which in turn open and close doors 45, 46, 41, 48 and 59 for the passage of one of the separated constituents, for example, stone (compare the hinged flaps shown in positions 54 and 44a in British specification No. 421,401) They may also control known hold-on circuits by way of auxiliary switches 6%, til, '62, E3 and 64 mechanically connected to the aforesaid relay switches, the function of the auxiliary switches being to see chat the circuit is closed for a'suitable time, and remains closed for a longer period than would be permitted solely by the valve action, having regard to the high speed of rotation of the commutator shaft 32, which speed may be for example between 700 and 2,000 revolutions per minute.

The power for the door operating solenoids 40 to M is conveniently derived from a source of alternating current 59 of substantial amount, for instance, at a high voltage, say 440 volts, and 50 cycles periodicity. The power for the relays is provided by a source of direct current, such as the battery Si or a motor generator, of voltage suitable for the work, say between 100 and 800 volts. When a battery is used, a number of cells are tapped elf and connected to earth, which really means that the earth connection is at some potential above earth, and this may be varied.

The relay coils 53 to El, which may have resistance-capacity circuits 52 connected in parallel as shown in the drawing, are connected to the positive end of the battery 5i through door limit switches 65, 56, 51%, 69 at the end of the relay coils remote from the slip rings, and are thereby always at a positive potential. From the other end of the relay coils 53, 5d, 55, 56 and 5'! connections are taken to the slip rings 34 and thence via the commutator l l to the anode 2 of the valve I. From this same end of each relay coil a connection is taken to one side of the corresponding auxiliary switch, of the group 653 to fi l, and from the other side of this auxiliary switch a connection is taken to the negative end of the battery 5! through a rheostat 58. Should one of the "elay switches, say 35, momentarily close due to the passage of current in the valve I, the corresponding auxiliary switch (it will retain a circuit through the solenoid lfi until the door &5 opens fully, so opening the limit switch 65 associated with it. In place of limit switches which open and break the circuit when. the doors reach the fully open position switches may be mounted inside the doors in such a position that the pieces of material passing through the doors will open the said switches and break the circuit. The ca hode l of the valve l is heated by a step-down transformer winding 59 from the source of alternating current 59.

In operation, the coal to be classified passing along any of the distributing channels is tested by a rapid series of impulses, due to the combined action of the high speed commutators l0 and II and the valve l, and in accordance with the result the filament.

of the test, it is caused to pass to the appropriate destination, that is, either through the trap doors or not through the trap doors 55 etc. The duration of contact of the brushes on any one segment of the commutator is of such small magnitude that should the valve pass current during the contacting period of this segment and the condition of the grid circuit have changed before another contact is made on this commutator so that current does not now pass, then such a single impulse is insuflicient to energize the relay to such an extent as to make its associated auxiliary switch make the hold-on circuit, and the door will therefore remain closed. The distance through which the relay parts must pass as a result of the passage of current in the valve itself before making contact on its auxiliary switch may be adjusted. Because of the very small inertia of the valve and the comparatively immense inertia of the relay parts, we are enabled to integrate the resistance of any piece of material as it passes through the brushes. Thus, if during the passage of a piece of material through the brushes the valve is connected thereto twenty times by the revolving commutators and passes current on fifteen occasions, the relay auxiliary switch can be so adjusted as to make contact and operate the trap door. By means of this integrator we are therefore enabled to separate hard coal from soft because of the greater conductivity of the hard. This has been extremely difilcult up till now, because of the fact that all soft coal contains streaks and laminations of hard which on making contact with the brushes operated the relay and opened the trap door.

General The grid circuit of the valve I may be connected through a resistance 10 to the negative side of the battery. It is therefore always at negative potential, but at a potential lower than that of The anode is always at a constant potential but due to the revolving commutators this potential is obtained via the different relay coils in turn, while the grid has applied to it the potentials of the various discriminating fingers in turn, which potential is dependent upon the nature of the piece of material at that instant between the said contacting fingers. The commutators being mechanically mounted on one shaft ensure that the anode current will always flow through the relay coil corresponding to the contacting finger which is at that instant supplying the grid potential. Because direct current is used there can never be any phase lag between the anode and grid, due, for example, to varying capacities of the material. The holding-on circuits give time for the doors to be opened, notwithstanding the fact that perhaps many impulses will have followed in the valve before in fact opening takes place.

We have found that by using a single selector valve circuit for a plurality of discriminating paths, in addition to the economy in valves, wiring and other matters, obtained in this way, in comparison with a single valve operating a single unit, there appear to be other advantageous efiects, especially, for instance, when the coal is even quite wet, because matters can be so adjusted that the valve will distinguish between the constituents of Wet coal, and permit the wet coal to pass, While rejecting the wet stone.

We claim:

1. Apparatus for sorting coal comprising a single grid controlled electric discharge tube, a set of flexible contacts for testing the coal, a multiple rotary switch adapted to complete a circuit successively with the flexible contacts arranged to contact pieces of coal fed along a plurality of separate parallel paths and a source of direct current in an electrical circuit which is arranged to influence the potential of the grid of the discharge tube, a set of relays, a second and corre- 10 sponding multiple rotary switch and a source of direct current in the anode circuit of the discharge tube and path selecting devices operated by a, source of alternating current and influenced by the current in the anode circuit of the'discharge tube to determine the path of each piece of coal. V

2. Apparatus for sorting coal electrically as claimed in claim 1 including a conveyor band along which the coal is passed through gaps between resilient electrical contacts.

KENELM CHARLES APPLEYARD. STANLEY DALLAS POLLITT.

7 CERTIFICATE OF CORRECTIONL'I. Patent No. 2,086,060. y 6; 957

1mm CHARLES APPLEYAR ET AL.

It is hereby 'certified that the above numbered patent was erroneously issued to "The Birtlej Compeny Limitedtas assignee of the entire interest in said invention whereas said patent shonl-d have been issued to the inventors, Kenelm Charles Appleyard and StanleyDallas Pollitt, and the Birtley Company Limited, 'said company being assignee of one-third interest only in said invention, as shown by the records of assigniuents in-this office; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of, the casein the Patent Office.

Signed and sealed this 12th day of QetoberfA. D. 1957.

Henry' Van Arsdale. (Seal) Acting Commissioner of Patents.

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