US2362706A - Concentrating apparatus - Google Patents

Description

1944. J. H. MACARTNEY 3 17 6 CONCENTRAT I NG APPARATUS Filed Jah. 24, 1942 4 Sheets-Sheet 1 m (Tl mac Q T I! 1; T In .LJ J. I I

u \li E? HZH V INVENTOR. 1mm H. Mauznvsr ATTORNEY.

Nov. 14, 1944. J MACARTNEY 2,362,706

CONCENTRATINVG APPARATUS Filed Jar '24, 1942 j 4 Sheets-Sheet 2 INVENTOR. Jul-m5 H Mncnsruzy ATTORNEY.

1944. J. H/MACARTNEYI Q 2,362,706

CONCENTRATING APPARATUS Filed Jan. 24, 1942 4 Sheets-Sheet 5.

INVENTOR. Jomv h. MA CARTNEY ATTORNEY.

Nov. 14, 1944.

J. H. MACARTNEY CONCENTRATING APPARATUS Filed Jan. 24, 1942 BY I Arm/aver 4 Sheets-Sheet 4 Patented Nov. '14, 1944.

UNITED STATES PATENT OFFICE 2,362,706 CONCENTRAlTING APPARATUS John H. Macartney, San Francisco, Calif. Application January 24, 1942, Serial No. 428,098

4 Claims.

This invention relates to an amalgamation and concentration method and apparatus.

The primary object of this invention is to pro-' vide an apparatus whereby metallic values from ores can be recovered in a greater percentage than by methods and apparatus heretofore in use,

and wherein the amalgamation andconcentration can be performed simultaneously.

Another object of the invention is to provide apparatus whereby most of the metallic values,

for instance, flour gold, rusty'gold, or microscopic,

or colloidal gold, or silver, or other amalgamable metals, whether tarnished or coated, are saved by amalgamation while all other non-amalgamable metals and compounds are saved as concentrates in the same operation,

Another object of this invention is to provide apparatus wherein metallic particles and concentrates are agitated while confined in channels in such a manner that all the amalgamable particles are brought in contact with'an amalgamating surface and, at the same time, all the non-amalgamable metallic particles or concentrates are advanced toward a discharge end of the respective channels and are automatically withdrawn from the channels at a predetermined rate of speed.

Another object of this invention is to provide apparatus in which electric current is utilized for activating the amalgamating materials, and wherein the electric current is interrupted in synchronism with the oscillation of the materials so as to facilitate the withdrawal of the concentrates by the exertion of the full force of inertia on the materials in one direction only.

Another object of this invention is to provide an apparatus wherein an amalgamating table is so arranged and so oscillated as to collect and discharge the concentrates in a predetermined.

manner; means being provided for so directing the flow of pulp as to facilitate the collection of metallic values at the riiiles of a table, at the bottoms of which riflles are provided amalgamating surfaces; furthermore, means being provided to produce an electric charge through the fiuid, the concentrates and the amalgamating plates between the respective riffles.

Other objects of the invention together with the foregoing will be set forth in the following de-' scription of the preferred method, and the preferred embodiment of means for practicing the same, which is illustrated in the drawings accompanying and forming part of the specification. It

is to be understood that I do not limit myself to the embodiment disclosed in said description and preferred forms within the scope of my inven- 7 tion.

With the foregoing and other objects in view, which will be made manifest in the following detailed description, reference is had to the accompanying drawings for the illustrative embodiment of the invention, wherein:

Fig. .1 is a plan view of the amalgamator and concentrator, constructed in accordance with my invention.

Fig. 2 is a partly sectional side view of my amalgamator and concentrator.

Fig. 3 is a sectional view of the amalgamator and concentrator, the section being taken on the lines 3-3 of Fig. 2. 4

Fig. 4 is a fractional partly sectional view of the apparatus, showing the relation of the riflles and the overhead electrodes.

Fig. 5 is a sectional detailed view of the adjustable eccentric mechanism for oscillating the table.

, Fig. '7 is a fractional sectional view showing the adjustable discharge mechanism for the ,corrthe drawings as I may adopt variations of my 55 centrates, and

Fig. 8 is a sectional view of the adjustable feed at the head of the table.

The method of my invention includes as steps the feeding of crushed ore in the form of socalled pulp so that the heavy metallic particles or ores from the pulp collect and are confined in substantially parallel channels .and are in such channels so agitated and oscillated that all the amalgamable metals are intimately contacted with an amalgamating surface in the channels, and the non-amalgamable particles, as concentrates, are progressively advanced toward a dis charge end of each of said channels, at which ,point the non-amalgamable particles and concentrates are discharged from the channels at a pre-determined rate. 'The method also includes as a step the passing of electric current through the pulp as it flows over said channels and also through the collected material in the channels and to the amalgamating plate in such a manner as to activate the amalgamating material and expedite the amalgamation of all amalgamable metals. method is intermittent, so that the electric circult is open during such oscillating stroke of these channels which exert forces to advance the nonamalgamable concentrates toward the discharge ends of the channels.

In detail in this method the pulp is introduced at a feed side or end of a table, on which table This electric current in the present are formed transverse rifiles, over which the pulp flows. from the pulp into the channels of the rifiies.

The heavier metallic particles descend The bottom of the table is formed by an amala. higher end of its channel. Electric current is passed through a circuit which includes the pulp fluid as an electrolyte, the current flowing from the pulp toward the amalgamating plate so as to precipitate finely divided minerals-from the pulp and settle the compounds of these metals in the respective channels. This electric circuit is broken when the channels and the table are os-'- cillated transversely in a direction away from the discharge ends of the channels, so as to allow the inertia of the settled metals and concentrates to advance them towards a discharge end. The electric current is again closed when the table is oscillated in the opposite direction. All the channels, in addition to the transverse oscillation, also moved with a rocking motion having a vertical component of force so as to agitate the material in the riilles and to preventpacking. The fluid in the channels is also directed into whirls and eddies to assure further intimate contact of all amalgamable metals with the amalgamating surface.

In detail, my apparatus includes a firm foundation or base l6, on the blocks H, of which is adjustably supported a table l8. On the bottom l9 of this table 18, is provided an amalgamator plate 2I.' This amalgamator plate in the present illustration is preferably made of copper which is provided with silver plating and covered with a layer of mercury. The longitudinal sides of the table l8 are formed by transversely inclined blocks 22 which extend upward along each longitudinal edge of the table I8. It is preferable that these side blocks 22 be made of insulating material of hard wearing surface. The table I8 is provided with a comparatively large number of transverse riflles 23 which extend across the table between the blocks 22 so as to provide closed channels 24 between said rifiies 23. At the feed end of the table I8 is provided a feed box 26 from which the pulp is fed over the table l8 and over the riflles 23. It is to be noted that the feed end of the table is higher than the tail end of the; table so as to provide a suitable slope for the flow of the pulp over theriffles.

The tailing end of the table I8 is provided with the usual apron, over which the gangue is discharged. The concentrate side 21 of the table l8 extends over a longitudinal chute 28. Each channel 24 has an outlet 29 through the bottom plate 2i above the chute 28 and a suitable valve mechanism 3| controls these outlets 29 of the channels 24. The table I8 is transversely reciprocated bysuitable eccentric mechanisms, as illustrated at 32.

The feed box 26 on the feed end of the table l8 has an open top into which the ore pulp is fed. A deflector plate 33 extends from the top edge 34 of the box nearest to the table l8, rearwardly and downwardly into the box 26 so that the pulp is spread over this deflector plate and discharges evenly across the entire width of the box 26. The bottom of the box 26 is provided with a silver plated copper plate 36,-over which is spread a pool of mercury. The first amalgamation of amalgamable values or metals occurs in the pool of mercury in the bottom of the feed box 5. A

The entire table and riflies are 7 flow over the discharge side of the table.

feed outlet 31 from the feed box is regulated by an adjustable plate 38 in the manner shown in Fig. 8, namely, a portion of the outlet 31 toward the discharge side of the table is partially covered by the plate 38 so as to provide restricted The plate has elongated slots 39 which slidably fit over bolts 4|, which latter in turn are threadedly secured to the wall of the box 26.

The riflles 23 are formed substantially in the manner shown .in Figs": 3 and 4. Each riiile 23 consists of a bar made of insulating material,

preferably of hard wood. The top of each riffie 23 is inclined downwardlytoward the feeding end of the table. A riflle plate 42, preferably made of hard-wearing metal, is secured over the inclined top of each riflie 23. Each rifile plate 42 extends beyond the edge of the riflles 23 toward the tailing end of the table. It is to be noted that the angle of the riifle plates 42 is such that the concentrates, or heavier particles from the pulp deposited on the riflle plates 42, work back by gravity into the channel 24' preceding the respective rilfie plate 42. The length of extension of each riffle plate 42 beyond the \rifile 23 is such that the pulp and water'flowing over the riffle plate 42 eddies over the highest edge of each plate 42 into the pocket formed under said plate extension, and the eddying currents thus partially prevent the packing of the concentrates and bring all the free amalgamable metals in contact with the amalgamating bottom of the channels 24. Mother words, the riflies and riflle plates are so arranged that the gangue washes over the riffle plates 42 but the metallic particles and concentrates wash back' on the inclined surface of the respective riflle plates 42, into the channels 24 and under the whirling pocket or trap beneath the overhanging portion of the respective preceding riflies 42.

The non-amalgamable metals and concentrates work toward the discharge ends of the -channels 24 so as to be discharged through the outlets 29. This is accomplished by transverse oscillation of the table. The working of the concentrates and the discharge through the channel outlet 29 is determined by the transverse incline of the table, the degree of oscillation of the table, and by the control of the openings of the channel outlets 29.

The control of the channel outlets 29 is accomplished by the valve mechanism 3|, shown in detail in Fig. 7. A valve plate 43 is slidably held against the under side of the bottom plate 2| adjacent to a group of outlets 29 by means of springs 44. The valve plate 43 is of such length that it extends over a number of outlets 29 for simultaneous control of a group of. outlets 29. Each spring 44 is supported in a suitable bushing 46 and on a fixed base 41 secured to the table I8. From each plate 43 extends an arm 48 to the outside of the table l8 and each arm 48 terminates in a vertical flange 49. A bracket 5| extends from the table to the outside of and opposite each flange 49. An adjusting screw 52 is rotatable in the bracket 5| and is threaded into the adjacent flange 49 so that by rotating the adjusting screw 52 in opposite directions the flan e 49, the arm 48 and the plate, 43 can be moved in respective directions and regulate the effective openings of agroup of the discharge outlets 29. A spring 53 between a bracket 5| and the fiange 49 bears against the latter and aids in the inward adjustment of the plate 43.

The table. is is mounted on a sub-frame 53 formed by longitudinal and transverse beams and bars. From this subframe extend vertical brackets, in the herein illustration a pair at each end of the table. The pair of brackets 66 near the tailing end of the table have preferably a fixed connection with the table 16 by means of suitable bolts 51. The pair of brackets 56 near the feeding end of the table are forked at the top and securing bolts 59 extend through the slots 6| of these forked bracket ends. Thus the longitudinal inclination of the table I6 can be reguwith a vertical component in addition to the.

horizontal component of oscillation and will keep the material in the channels agitated and more or less in a loose mass so as to assure contact of all the amalgamable substances with the amalgamating plates in the channels. Th discharge side of the table is preferably held higher than the eccentric side by raising the bearing lated by loosening the bolts 99 and raising or lowering the feeding end of the table l8 and then tightening the bolts 59 to hold the feeding and of the table in the adjusted position on the brackets 56. The sub-frame 54 has under each end thereof opposed pairs of leg brackets 62 which have thereon rollers 63 positioned so that end of the drive shaft 63 is' formed a driving flange 66 for each eccentric mechanism 32, which flange has an elongated recessin 66 its outer face arranged substantially upon the diameter of thepircular flange 64. This recess 66 is made shorter than the diameter of the flange 64 by suitable end blocks in the recess so as to provide a limited track. It is preferable that this recess 66 becut of dove-tail cross section. An eccentric block 61 is slidably held in the recess 66. The eccentric block 61 is shorter than the recess 66 and it may be adjusted in various relative positions by opposed set'screws 66 extending into the opposite ends of the recess 66 from the outer periphery of the driving flange 64. From this eccentric block 61 extends a stub shaft 69 and an eccentric pin II. An eccentric cam 12 is mounted on the stub shaft 69 and has a hole 13 in its face nearer the driving flange 66 for engagement with the eccentric pin II. An eccentric shoe 14 on the eccentric cam I2 is journaled on plate 62 on the discharge side. This adjustment of the bearingplates 62 is performed by adjusting screws 66 extending upwardly through the blocks I1 so as to engage the under side of the respective bearing plates 62 for raising or lowering the bearing plates 62 on the respective sides of the table to different angles. The stroke of oscillation is regulated by adjusting the position of the eccentric block 61 in the recess 66 of the driving flange 64 as heretofore described. In this manner, the speed of the lateral discharge of the concentrates from the channels-can be more accurately regulated. For instance, in the event there is a tendency for packing of concentrates, the bearing plates 62 on the discharge side of the table are raised so that the table holds the channels at steeper upward angles toward the discharge side; This increases the vertical component of rocking and oscillation, agitates the concentrates more vigorously and prevents packing. In the event of more fluidity of concentrates the discharge side of the table'may be lowered toward the hori zontal level of rocking so as to provide for a speed of discharge according to the density of thepulp and concentrates. The rapidity of oscillation is also adjusted by the eccentric adjustment so that r in case of heavier or denser concentrates the eccentricity and stroke of oscillation are shortened and in case of lighter concentrates the stroke is lengthened. Thus both vertical and horizontal components of oscillationcan be easily regulated.

the stub shaft 69 and is held in place by a suitable nut 16. A connecting rod 'l'l connects the eccentric shoe 14 to an extension I6 extended downwardly from the sub-frame 54. Thus, when 'the drive shaft 661s rotated the eccentrics reciprocate the sub-frame 56 and the frame l6. Dur ing this reciprocation, the entire table and subframe move onthe rollers 63. Springs 19 betweefi fixed brackets 6| on the block I! and the side of the sub-frame 66 adjacent the eccentric mechanisms 32 aid the movement of the table in one direction.

For each roller 63 there is provided an adjustable track in the form of a pivoted wedgeshaped plate 62. The rollers 63 are grooved on their peripheries and the plates 62 are .of such width as to fit into the roller grooves and prevent longitudinal displacement of the table l6. Each wedge-shaped plate 62 is pivoted on a bracket 66' on the base block II. The top bearing surfaces of the plates 62 are inclined so asto converge toward the free ends of the plates 62 downwardly and toward the discharge side of the apparatus. In this manner, during: the first stroke of the reciprocation the entire table travels upward on the inclined bearing plates 62 and on the return strok it'travels downward and toward the eccentricside. This introduce a'rocking motion It is to be noted that the chute 26 extends on a downward incline toward the tailing end of the apparatus. In this illustration a receiving apron or hopper 66 is provided on the under side of the table l8 below the outlets 29 in such a manner that the concentrates or material from said outlets 29 drop into this apron 66. This apron 66 slopes downwardly to above the chute 28 so as to discharge into the chute' 26. The

apron 66 oscillates with the table I6 and therefore the necessity for scraping is obviated. A pipe 61 extends through the entire length of the apron 66. A plurality of nozzle openings 66 are provided on the pipe 61. These nozzles 66 face inwardly toward the portion of the apron where the concentrates are received from the outlets 29. Clear water is pumped through the pipe 61 and is directed by the nozzles 66 over the concentrates on the apron so as to-wash the same downwardly into the chute 26. The concentrates are then collected from the chute and treated in the usual manner.

Electric current is applied for the precipita tion of the metals from the pulp by the use of electrodes. A suitable number of anodes are supported in contact with the pulp or fluid above the riflles of the table. the bottom of the table N forms the, cathode and is connected to the negative terminal or a source of electricity; In the herein illustration posts 9l' are supported on the base of the machine. On each of these posts is pivoted a substantially horizontal lever 92 which extends transversely table II, and has its other end pivoted at 96 on The amalgamating plate on the posts 9I spaced above the pivoting of the lever 92. By disconnecting the link from the post the levers 92 with the electrodes thereon can be lifted off the table I8 so as to allow access to the table for the clean-up operation or the like. Each lever 92 has a pair of spaced supporting brackets 91 extended downwardly therefrom. These brackets 91 are adjustable vertically on the lever 92 so as to allow for the adjustment of the spacing of the electrodes above the table I8. These brackets 91 are made of insulating matsrial. Through these brackets 91 extend conductor bars 98. These conductor bars 98 extend longitudinally of the table I8 and are securely supported in" the aligned brackets 9'! of the respective levers 92. On these conducto bars 98 are adjustably supported conductor clips 99 which in turn support electrode plates IOI. It is to be noted that each electrode plate IOI is supported on two conductor clips 99 which in turn can be slidably adjusted on the conductor bars 98. The electrode plates are disposed at an in- .cline toward the tailing end of the table and toward the direction of the flow of the pulp over the table I8. It is preferable that-the lower edges of the electrode plates IOI be substantially aligned with the respective upper edges of the rifile plates 42. By this arrangement theelectrode plates IOI are held out of contact with the concentrates collected on the rifiles or in the channels 24. These electrode plates IOI are near the top level of the flow over the rifiles and also functionas baffles to smooth the surface rifiles in the flowing pulp. By calming the flow of pulp on the topof the r'ifiles the settlement of the heavier particles and concentrates on the tops of the riille plates is facilitated. While in this illustration an electrode plate IOI is shown above each channel 24 and nearer to the heel of the riffle' plate 42 on the tailing side of the channel 24, nevertheless it is to be understood that the positions of these plates,'as well as the number of the plates over a table, is determined in accordance with the extent of current and the extent of baflling required in connection with particular types of pulp and ores.

The electric circuit is illustrated in a more or lessdiagrammatic way in Fig. 1 of the drawings. A conductor conduit I02 connects the conductor. bar 98 to a suitable brush terminal I03 of a circuit breaker I04. Another brush terminal 3 of the circuit breaker I04 is connected to the positive terminal of a source of electricity indicated at I00. A connecting conductor I06 connects the amalgamator plate 2I-to a movable contact I01 which is held by suitable springs I08 in sliding engagement between stationary contacts I09, which latter are supported on a fixed post III. A suitable conductor or wire 2 connects one of the stationary contacts I09 to the negative terminal of thesource of electricity I00. This rotary circuit breaker I04 is formed by a semicylindrical conductor half and a complemental insulator half cylinder I I4. Therefore, whenever the conductor half of the circuit breaker is in contact with the brushterminals I03 and H3 then the electric circuit through the table is closed, during the other half of the revolution of the circuit breaker I04 the circuit is open. This rotating circuit breaker I04 is mounted on the drive shaft 63 in such a manner that the conductor half of the circuit breake I04 is in contact with the terminals I03 and [I3 during the stroke of the eccentrics'and of the table I8 toward the discharge side of said table, and the inciprocation of the table toward the eccentric side, thereby the concentrates are allowed to .freely travel in the channels toward the discharge side under the force of inertia exerted during this return stroke.

The various moving parts of this apparatus are driven in the usual manner by the drive shaft 83.

Power is transmitted to a pulley H8, and 'a suitable fly wheel II1 balances the rotation for uniform speed.

The amalgamation in the feed box 26 is also activated electrically. A conductor bar I I8 is suitably supported in the ends of the feed box and from this bar depends an electrode plate H9 so that the lower edge of said plate is spaced above the pool of mercury in the bottom of the feed box 28. The conductor bar H8 is connected by a conduit to the conductor bars 98. The bottom plate 38 in the feed box 28 is connected to the amalgamating bed plate 2|. Thus, intermittent current is provided in the feed box at the same frequency as on the table I8.

It is to be noted that the intermittent current herein used causes pulsation of the mercury on the respective plates.. When the current is applied the mercury rises and it appears to swell and when the current is broken then the mercury flattens back onto the plate, This rhythmic pulsation of the mercury keeps the mercury clean and active, and renders it effective, irrespective of oil or impurities that might otherwise impair the amalgamating efiect of mercury. This action also accelerates the precipitation of metallic values from the pulp and their amalgamation with the mercury. The current also acts upon the concentrates in the manner heretofor described in connection with the oscillation and rocking forces on the table, namely, it hinders the movement of the concentrates toward the oscillating side of the table but releases the concentrates from an action of electricity when the concentrates work toward the discharge side of the table. It is preferable to use direct current of low voltage. For instance it was found practicable to use a I current of 6 to 10 volts at about amperes divided over the entire table surface.

In operation the crushed or pulverized ore is fed in fluid pulp form into the feed box 28 and it is distributed over the baflle plate 33 in such a manner that the pulp is discharged with even flow near the mercury pool on the bottom of the box 26. The pulp flows over the mercury pool on the bottom of the feed box and past the electrode H9 in said feed box. At this point the free amalgamable values or metals sink into the mercury pool in the bottom of the feed box 26 and amalgamate with the mercury. This amalgamation is intensified by the pulsation of the mercury under the action of the intermittent current as heretofore described. The sangue with the unessence.

the discharge side of the table is restricted by the adjustable gate 38. This flow on the discharge ,side is controlled according to the density or packing of the concentrates on the higher or discharge side of the table.

The pulp flows over the table l8 and under the anode plates Illl, by which plates the surface flow is smoothened before flowing over the followin riflle plates 42. The heavier concentrates and metals work back on the riflle plates, 42' into the respective channels 24 and the residue continues to flow with the gangue over the successive riflles. During this flow the electric current precipitates the metallic values from the pulp into the chantable. The gangue, free of most concentrates andrecoverable metals, is passed out through the tailing end of the table. The non-amalgamable compounds trapped in the channels 24 work upwardly toward the discharge side of the table, confined in the respective channels 24, by the force of the transverse oscillation as well as the transverse and vertical rocking of the table I8 by the eccentric mechanisms 32 and on the suitably adjusted bearing plates 82. The vertical and horizontal components of this rocking and re-, ciprocating motion of the table are adjusted and determined in accordance with the density 'of the concentrates in the channels and in accordance with the tendency of the concentrates to pack in the channels. The concentrates are continuously discharged through the channel outlets 29 onto the swinging of the anode plates and conductors ofl the table and into out of way position. To facilitate the clean upthe valve plates under the groups of channel outlets 29 are withdrawn so as to fully open the outlets of the channels from' which the amalgamates are withdrawn. Then the amalgamates are scraped off the bottom plate by a suitable rubber scraper 'or the like and are removed through the channel outlets 29 into the apron 86 and into the chute 28 where they :are

. collected. Thereafter fresh mercury is placed upon the amalgamating plate, the electrodes are replaced in position, and the operation of the apparatus is continued as heretofore-described.

During all of the above operations, the flow and removal of the concentrates and operation is under direct control;

Quick adjustments of the flow of pulp and the-flow of washing water can be made by the respective gates and valves; speedy adjustment of the eccentricity of the electric oscillating mechanism and of the bottom bearing plates suitably vary the horizontal and vertical components of rockingand oscillation,

the aprons 86 from where they-are washed down into the chute 28 by fresh water from the pipe 81. The concentrates are then collected from the chute 28 for the usual treatment.

As the table is oscillated the flow of current from the anode plates IM to the amalgamating bottom plate is interrupted, in synchronism with the reciprocation of the table, by the rotary circuit breaker operated by the same drive shaft '63 which also operates the eccentric mechanism 32 for the reciprocation of the table. The action of this intermittent electric current quickens the precipitation of free values, controls the flow of pulp without contacting the concentrates in the channels. The anode plates l0! are so adjusted with respect to the riflle channels that they smooth the surface riifles in the flow of the pulp at such points where the settlement of the heavier metals is aided by smoothness, without interfere ing with the whirling and eddylng action within the channels and under the overhanging higherv portions of the riflle plates 42.

This operation is continued without interruptlon until suchtime that a cleanup of the amalgamated values is desired. For the purpose of such clean up, the flow of the pulp is stopped,

the operation of. the apparatus otherwise is continued until all of the concentrates are washed and removed from the apparatus and from the chute 28. Thereafter the apparatus is stopped and the link 93 is disconnected so as to allow the number of anode plates can be controlled and be easily and quickly adjusted to suit the particular type of ore or concentrates to be'recovered. The operation of the machine, as well as the method, provide a continuous and efiicient recovery of a large'percentage of values from crushed ores.

I claim:

1. In a device of the character described, a rifile table having substantially transverse rifiles, means for oscillating the table in a direction sub 'stantially parallel to the riffies so as to precipi tate concentrates toward one end of the .riiiles, conductors immersed in the gangue passing over the riffles, a conductor element in the rifiles spacedfrom said first conductor so that a current passes through the pulp and concentrates between said rifiles, and means to interrupt said current during the portion of-oscillation which precipitates the concentrates toward said ends of the rifiles.

2. Means to pass an electric current through ..the gangue and precipitated metals at the rifiles of an oscillating concentrating table, comprising conductor bars extended longitudinally above table and connected to "a terminal of a source of electricity, a plurality of securing elements extended downwardly from the conductor bars and being adjustable longitudinally on the said bars, electrodes supported on said securing elements so as to be partly immersed inthe gangue flowing over the rillles of the table, means to connect the other terminal of the source of electricity to the space between riilles in which the metals and compounds are precipitated from the gangue, and means to repeatedly interrupt said electric current during the strokes of oscillation in one direction and close the electric current during the strokes of oscillation in the opposite direction.

3. In a concentrating table of the character described having discharge means along one longitudinal side-of the table, the combination with means to oscillate the table transversely and means to form an electric circuit through the gangue and said table; of an eccentric mechanism included in said oscillating means, and a circuit breaker'operated with the rotation of the eccentric mechanism to break said electric circuit during each stroke of oscillation away from the discharge side.

4. In a concentrating table of the character described, having an amalgamating deck, and means to pass'an electric current through the pulp and precipitates at, the riflies of the table;

'of afeed box formed on the intake end of "the 7 surface, an electrode in the box spaced from the 10 bottom and connected to act substantially in synchronism with the electric circuit of the table, an outlet from the box to feed the pulp out over the table, said table having discharge means for the concentratesat one side thereof, and means to restrict and regulate the feed flow at the portion of the box outlet nearer to'the concentrate side of the table.

JOHN H. MACARTNEY.

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