US2502840A - Jig - Google Patents

Description

APII 1950 v V w. HAYESl 2,502,840

.11G I Filed March e, 1945 7 sheets-sheet 2 INVENTOR #VILL/E HAYES,

a @ZM April 4, 1950 w. HAYES 2,502,840

JIG

Filed March 6, 1945 '7 Sheets-Sheet 5 INVENTOR Wm L /E HA VES,

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April 4, 1950 w. HAYES 2,502,840

JIG

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Patented Apr. 4, 1950 UNITED JIG Willie Hayes, Pratt City, Ala., assignor to Tennessee Coal, Iron and Railroad Company, a corporation of Alabama Application March 6, 1945, Serial No. 581,269

2 Claims.

heavier concentrate is maintained substantially constant in the cell of the jig, whereby overloading of the jig is prevented.

A still further object of the invention is the provision of a jig which insures the delivery of separated material of constant quality.

The above and further objects of the invention will become more apparent in the following description.

The jig of the present invention is useful in the separation of minerals of different specic gravities as, for instance, metal-bearing ores and coal from rock. For the sake of simplicity, the invention will be described in connection with its use in the washing of coal, that is, the separation of coal from various impurities such as rock, slate, and the like, but it is to be understood that the invention nds advantages in the separation of other materials, as above indicated.

The invention relates to jigs of the type wherein the material to be separated is fed onto a screen in a bath of liquid, and is subjected to rapidly recurring impulses of the liquid through the screen which tend to lift the material and to stratify it in accordance with its specic gravity. The finer, heavier, material passes through the screen and is drawn off from the bottom of the jig as a sludge. The heavier material retained on the screen which, in the case of the washing of coal, is composed of slate and other rocks, is removed from the screen through a rock valve, whereas the lighter material passes ovel` a barrier at the end of the cell. Such type of jig, which is well known, is disclosed in the Elmore patents, Nos. 1,077,876 and 1,327,537.

It has been recognized that for the vmost enicient operation of jigs of this type it is desirable to retain on the screenof the cell as uniform a depth of concentrates as possible, so that the action of the pulsating liquid upward through the screen and through such bed of concentrates will be uniform. In prior art designs it has been attempted to maintain such uniform depth of concentrates on the cell screen either by manually controlling the rate of feed of material into the cell and the rate of feed of heavy concentrates, which is rock in a coal washing jig, from the cell, o1' by manually controlling the lrate at which material is fed into the cell and automatically controlling the rate of discharge of rock from the cell in accordance with the depth of the rock bed on the screen. Such latter arrangement is shown in Elmore Patent No. 997,609.

Such methods of controlling the cell have worked fairly satisfactorily Where the composition of the material fed into the cell has stayed within fairly close limits. Such a condition is met, for instance, when coal mined from a vein of substantial thickness is hand-loaded at the mine face, since such hand loading excludes, to a large extent, pieces of rock and slate. Where, however, the composition of the material varies considerably and changes in the composition of the material being fed occur very rapidly, such methods of control are not satisfactory due to the operators inability to appreciate the need for a change in rate of in-feed before the harm has been done. It has been found that where coal is mined from a relatively thin vein and the coal is mechanically loaded at the mine face, such coal is apt to contain large amounts of rock and the rock content is apt to vary considerably from time to time. If, because of such rapid change in composition, the depth of rock in the cell becomes so high that the capacity of the rock valve is exceeded, the cell no longer separates completely the lighter from the heavier materials and certain amounts of such heavier materials are washed over with the lighter separated portions;

The present invention provides a jig which overcomes these `difficulties and produces a product of uniform quality'regardless of the rock content of the in-fed material or of the rapidity of change of such content. Such objects are accomplished by the provision ofmeans automatically controlling the height'of the rock bed in the jig cell by varying the rate of in-feed of the coal, thereby avoiding the possibility of overloading the jig. At the Sametime, however, the jig is kept working at full capacity and therefore at its maximum eiciency.

The invention will be more readily understood by reference to the accompanying drawings, in which:

Figure 1 is a view in side elevation of a coal Washing jig made in accordance with the present invention;

Figure 2 is a View in plan of the jig shown in Figure 1;

Figure 3 is a View in transverse cross-section 3 through the first cell of the coal washing jig, such section being taken along the line II-ll of Figure 2;

Figure 4 is a view in longitudinal cross-section of the in-feeding end of the jig;

Figure 5 is a detail view of the float-operated rock level indicating switch;

Figure 6 is a detail View of the door-positioning limit switch;

Figure 6A is a View in end elevation of a portion 0f the door-operating mechanism;

Figure 6B is a view in section through such portion of the door-operating mechanism, the section being taken along the line VIB in Figure 6A;

Figure '7 is an enlarged view of one portion of the door-positioning limit switch;

Figure 8 is an enlarged View of another portion of the door-positioning limit switch;

Figure 9 is a schematic view of a portion of the rock discharge valve operation mechanism: and

Figure 10 is a schematic wiring diagram of the electrical control for jig of the present invention.

The jig illustrated in the drawings consists of three cells serially arranged. The first cell. designated by the reference character 2, is fed with the raw coal to be washed, and discharges the lighter of the separated materials into the second cell 4 which in turn discharges the lighter of the materials separated in it into the third and final cell 6. Each of the cells is provided at the sides thereof, as shown in Figure 3, with four eccentrically actuated plungers 8 which reciprocate in vertical plunger chambers lil. plungers impart a series of surges or vibrations to the water with which the cell and the plunger chambers are iilled, whereby the water intermittently rises and falls through the screen oor of each cell and through the bed of material supported by such screen. The screen in the first cell is designated by the character I2. Such vertical motion of the water in the cell accomplishes the washing out of the line heavy particles from the material, which particles fall through the screen into the bottom or hutch Il! of the cell, from which they are discharged through hutch valve l5.

`Plungers 8 are driven by means of a horizontal drive shaft i3 which in turn is driven by a motor through the medium of a motor pinion rrleshinfr4 with the large gear on the end of shaft la, as shown in Figure 2. Bevel pinions 2i! and ZI are affixed to shaft I8 in position to mesh with pinions 22 and 23, respectively, on the longitidinal eccentric shafts 24 and 26, respectively, above plunger' chambers IE?. Eccentrics on shafts 'M and 2G are connected to plungers 8 and provide for the vertical reciprocation thereof.

The rapidly repeated surges of the water upwardly through the bed of the material on the screen straties the material into the lower, heavier, layer of rock R, and the upper lighter, more buoyant, layer of coal C, as shown in Figure Il. The feed of material into the cell at the left-hand end thereof tends to make such bed of greater depth at such point, the bed levelling out as it travels gradually to the right. rl"he rock layer R remains in contact with the screen and gradually travels into the rock valve pocket 32. whence it is fed into the generally star-shaped rotary rock valve 34 which discharges it into chute 35 leading to a refuse flume, when each pocket in the valve reaches its lower position. The lighter layer of coal C, on the other hand, is

` 4 progressively washed up and over end barrier 28 at the right-hand end of the cell and down inclined chute 3D into the succeeding cell il. It is to be understood that separation 0f the coal from the rock is not complete in the nrst cell, which explains the use of the two subsequent cells. but that usually some rock is washed over the barrier into the second cell, as shown in Figure 4 of the drawings. With the 3-cell jig as shown, the material discharged from the rock valves of the rst two cells is refuse, whereas that discharged from the rock valve 0f the third cell 5 is lowquality coal employed as boiler coal; the lighter material finally discharged from the third cell is i. high-quality washed coal which may be employed, for instance, in the making of coke.

t will be apparent from the above that if the rock layer R in the first cell has a thickness in excess of that desired and consequently a discharge rate materially in excess of theI capacity of the rotary rock valve of the rst cell, large quantities of rock will be washed over barrier 28 of the first cell, into the second cell. and that as a consequence, the second cell will be overburdened, and the discharge from the rockvalve of the` third cell may have an unduly high rock content. There will also be the further possibility oi the presence of some rock in the lighter diccharged material from the third cell.

The rock valves 34 of the iirst cell, as well those of the succeeding two cells, are driven by ratchet drive devices indicated generally at 138 in Figure Such ratchet drives are driven bv means of a vertical shaft Ml shown in Figure 2. which is driven olf shaft I8, shaft 4I] in turn driving a lower transverse shaft 42 to one end of which is aflixed a crank 44. Pitman l5 connected to crank 44 effects the oscillation of ratchet drive 38 of the rst cell, and pitmans M, which extend between the ratchet drive meer: of the rst, second, and third cells` drive the rock valves of the two latter cells. Adjustment of the, rate at which the rock valves are driven` is .accomplished by means of adjusting wheels 53 bv which the length of the ratchet arm of the particular ratchet drive of which it is a part mai1 be varied.

In accordance with the present invention. the first cell 2 of the jig is provided at the left, as

shown in Figures 1 and 2, with a coal bin 5l) into which the coal to be washed is fed. The lower portion of the coal bin is provided with a powerdriven revolvingr feeder 52 equipped with radial projections which pick the coal up and discharge it into the first cell. Coal thus discharged impinges upon angular deecting plate 54 positioned in the first cell, as shown. Control of the rate at which coal is fed from the bin to the rotary feeder is eifected by means of a vertically slidable bin closing gate 56, which may be adjusted by means of racks 58 affixed thereto, such racks meshing with pinions 60 on transverse shaft 62. Rotation of the shaft and consequent adjustment of the bin gate is accomplished by means of handwheel G4. The control of the rate of feed accomplished by gate 56 is in the nature of a rough adjustment, and once made, gate 56 may be left in the desired position.

Control of the rate of feed to the first cell within the limits necessary to effect automatic feedingv of the jig is accomplished by means of door 5S cooperating with the revolving feeder 52. said door being mounted, as shown, on a swinging frame pivoted about a shaft 52, whereby the free space between the revolving feeder and the lower end of the door may be varied. Such swinging of frame 68 is effected, in the modification `of the apparatus shown, by means of a gear motor lIt mounted on a platform supported on beams above the first cell 2. Driven shaft 'I2 lof the gear motor is connected to a vertical screw "I3 journaled in lower bearing 'I4 and in an upper bearing 'I6 on top of the door-positioning limit switch box TI. Screw 'I3 is composed of a lower portion 'I8 of substantial diameter, which effects the adjustment of frame 60, and an upper portion 80, shown in Figure 6, of somewhat smaller diameter. Nut 82 on lower screw portion 'I8 is provided with transverse arms 84 which slide in vertical guideways 86. The swinging frame 68 is provided with a door-operating arm 88 having an outer forked end, the arms of such fork having slots 90 therein for the reception of arms 84 of nut 82. Such structure makes possible the lowering or raising of the door 56, as required, by gear motor l0, such motor, in turn, turning screw 18, thereby raising or lowering arm 88 depending upon the direction of rotation of the motor.

The door operating mechanism is automatically operated in accordance with the height of the -v rock bed R in the first cell of the jig by the following mechanism acting in conjunction with the door-positioning limit switch device in switch box TI. A iioat III, which rests upon thetop of the rock bed R and is preferably of streamlined shape to facilitate the iiow of material past it, is mounted on the bottom end of float rod I I2. `Such float rod is positioned and guided for vertical movement by means of guide rollers H3, which are supported over the cell by means not shown. The float is held in contact with the top ,of the rock bed at a location where the bed tends to be level, with the desired amount of pressure by means of counterweights H5 held in counterweight holder IM at the upper end of the float rod. The rock level indicating switch, which is actuated by iioat rod H2, is shown in detail in Figure 5. Switch box H0, through the bottom and top of which float rod H2 extends, has mounted thereon on one side of the float rod an elongated bus bar H8 and on the other side of the float rod an insulating plate I I9 which mounts the contacts labeled FL3, FL2, FLI, FRI, FR2, and FVC. The first iive of these contacts are, as shown, of short extent, whereas the lowest, FVC, is of considerable length. The upper surfaces of such contacts are substantially flush with the top surface of the insulator I I9, to enable the contact arm I I1 which is mounted upon iioat rod H2 by an insulating bushing H'I, to ride freely thereover while still making contact therewith as the iioat rod rises and falls. Vertical adjust ment of arm I I 'I with respect to the float rod may be made by means of the set screw H8 in the insulating bushing I'I' upon which arm II'I is mounted. It will be apparent that such switch structure provides a means whereby the circuit is closed btween bus bar H8 and any one of the various contacts FL3, etc., only when contact arm I I1 touches one of the contacts.

The structure of the door-positioning limit switch mechanism in switch box 'I'I is shown more fully in Figure 6. As there shown, the switch is in the neutral position, corresponding to the normal or neutral position of the rock level contact arm I I'I shown in Figure 5. The switchoperating arm 94 is threadedly engaged with the screw 80 so as to be raised and lowered in accordance with the motion of door-operating nut 82. Rotation of arm is prevented by the provision of a rearwardly directed arm 96 attached thereto, said latter arm having a sliding engagement with the vertically fixed guide rod 98 positicned in the switch box.` Arm 04 is provided with a series of vertically-extending switch-operating fingers |00, IOI, |02, |03 and |04, said fingers being adjustable vertically of arm 94 and retained therein by means of set screws, as shown. Each of the switch-operating fingers is provided with an inclined forward end, as more clearly shown in Figures '7 and 8, for the operation of the microswitches.

The switch 2D, shown in Figure 7, is typical of switches ID, 2D, and 3D, whereas switch IU, shown in Figure 8, is typical of switches IU and 2U. Switch 2D has a switch element |05 which is held in raised circuit-breaking condition by a spring member |05 when switch-operating finger |0| is in the lower position shown by the dotted line. When such switch member is advanced vertically, however, as shown in full lines, it oontacts roller I 01 and depresses the switch member in order to complete the electric circuit through the switch.

The switch IU, however, which is provided with switch element |08, is of such construction that it is closedwhen the switch-operating finger |03 is positioned in the lower full line position shown. When member |03 is advanced upwardly to the dotted line position, it engages roller IIO on the end of spring |09, thereby depressing the switching element and breaking the electric circuit through the switch.

The door positioning limit switch functions, as will be more clearly apparent in considering the wiring diagram in Figure l0, to stop operation of the door adjusting motor 'I0 when the door has reached a predetermined position depending on the position of the float III. The door-positioning limit switch accomplishes this by breaking its particular contact through which the control circuit energized by closing of the float contact is completed, when the door reaches the required position. It will be obvious from a consideration of Figure 6 that limit switch ID opens at the first door position below normal, and that limit switches 2D and 3D operate similarly at the second and third positions, respectively, below normal. Limit switches IU and 2U open at the first and second positions, respectively, above normal. Each limit switch opens and remains open as long as the door is at or past that particular position away from the normal position of the door.

The operation of the automatically controlled feeding device for the jig thus far described will be more fully understood by reference to the schematic wiring diagram shown in Figure 10, in which the door-positioning limit switches are all shown closed, and the rock level contacts are all shown open, as they are when the rock level is of normal height and the door is in its normal position. The door-positioning motor 'I0 is caused to raise or lower the door whereby the mechanism tends to hold the rock level in the first cell such that thev contact arm IIi normally lies between contacts FLI and FRI. Such position, which is called the normal or neutral position, is attained when the height of the rock bed in the cell is at its optimum value. When arm I I1 is within such range and touching neither contact FLI nor FRI,

motor I0 is at rest and the door is held in xed position. If, however, the height of the rock bed should rise sufficiently to bring contact arm H1 into position to touch contact FLI, motor 'I0 is actuated to lower'the door to correct such condi- 7 tion' and to bring the' height of the rock bed back to its normal value. VIf the rock bed level rises still further, however, switch FL2 operates to cause motor 10 to lower the door still further. Switch FL3 is effective, when the rock level rises suflciently to cause it t complete the circuit, to operate motor to close the door still further to correct the condition. If the level of the rock bed falls, on the other hand, so as to cause contact arm |11 to touch contact FRI, motor 10 is caused to rotate in such direction as to raise the door to admit more coal, and thus to correct the condition and bring the rock level back to normal. Upon further fall of the rock bed level, however, should such occur, switch FR2 is operated to raise the door still further. If the rock level should, in spite of this, fall to such point that arm ||1 touches contact FVC, the ratchet feed mechanism 38 for the rst cell is caused to be ineffective, by a means subsequently to be described, whereby rotation of the rock valve 34 is stopped. It will be 'apparent that each of the various switches FLL PL2, FL3, FRA, FB2, and FVC closes the circuit, thereby operating motor 10, only when contact arm I |1 touches that particular contact.

The motor 10 is supplied from an appropriate three-phase alternating current source to which are connected the three lead wires LI, L2, and L3. Such source of current, besides supplying motor 10, is employed to energize the six relays, IL, 2L, 3L, R, 2R, and VC, corresponding to the six contacts, FLL etc., and also to energize the two operating coils of the reversing contactor RC. The reversing contactor RC is a conventional device having two operating coils and |91 which, when operated selectively, establish contacts for operating the motor in opposite directions. The contactor is of such construction that neither of such operating coils is energized when the contactor is in neutral position, and the circuit to the motor is broken and the motor is stopped.

The wiring diagram will be more readily understood by tracing the circuits therethrough which are utilized when the rock bed in the rst cell of the jig rises progressively from the normal level so as to close switches FLI, FLZ, and FL3 successively, and also the circuits which are energized when the rock bed level falls from the normal level so as to close switches FRI, FRZ, and FVC, successively.

First, assuming that the rock bed level has risen from normal to a point sufficiently to allow contact arm l i1 to touch Contact FLI motor 10 is actuated in a direction to lower the door, thereby decreasing the rate of feed of coal into the jig.

Such actuation is accomplished by the connection oi one side of the actuating coil |26 of relay IL to line L| through wire |20, wire |22, closed switch FLI, and wire |23, and by the connection of the other side of coil |26 to line L3 through wires I3| and |30, closed limit switch ID, and wire |28.

Energization oi' relay coil |26 closes its contacts |32 and |34, thereby energizing coil |36 of the reversing contactor RC in the following manner:

Current travels from lead L3 through wires |38, |39, 40, |42, and |44 to one side of coil |36, and from lead Ll through wires |20, |22, and |49, contact |34, wire |5I, contact 204, and wire |52, to the other side of coil |36. Thereupon the reversing contactor RC is thrown to close its contacts |54, |50, and |58 and to open normally closed Contact |00. The wires 'I'|, T2, and T3 of motor 10 are then connected to lines L3, L2, and LI, respectively, as follows:

From lead LI current flows to wire |62, wire |64, through contact |58, to wires |66 and |61, and thence to wire T3 of the motor. Current flows from lead L2 to wires |68, wire |69, through contact |56, to wire |10 and thence to wire T2 of the motor. Current flows from lead L3 to wire |38, wire |39, through contact |54 and wires |12 and |14 to line Tl of the motor. The motor operates to lower the door until operating finger |02 of the door-positioning limit switch is lowered suiciently to allow the opening of switch |D. This breaks the circuit to relay IL, the coil |36 of the reversing contactor is deenergized, the reversing contactor goes back to its neutral position, and the motor 10 stops.

If the rock bed level in the first cell of the jig continues to rise, contact arm ||1 passes contact FLI, and if the rise continues, the arm touches contact FL2. When such contact is made, relay 2L is energized as follows:

Current ows from lead LI through wires |20 and |22, contact FLZ and wire |16, to one side of the operating coil |11 of relay 2L. Current flows from lead L3 through wire |3|, wire |30, closed limit switch 2D, and wire |18, to the other side of coil |11.

Energization oi relay-operating coil |11 closes its contacts and |82, thereby energizing coil |30 of the reversing contactor in the following manner:

Current flows from lead L| through wires |20, |22, |83, |8I, contact |82, and wires |50, |5|, switch 204, and wire |52 to one side of coil |36. The other side of such coil is supplied from lead L3 through wires |38, |39, |40, |42, and |44. Operating coil |36 then throws the reversing contactor and operates motor 10 in the same direction as before, to lower the gate. Such operation of the motor continues until limit switch 2D is opened by the fall of operating nger I 0|, at which time the relay 2L is deenergized, the reversing contactor returns to neutral, and the motor stops.

The same sequence of operations follows, should the rock bed level in cell 2 rise sufficiently for contact arrn ||1 to touch contact FL3. In such case, operating coil 2|2 of relay 3L is energized with current from lead Ll through wires |20, |22, closed switch FL3, and wire 2|0 and from lead L3 through wires |3|, |30, closed limit switch 3D, and wire 2|4.

Upon energization of coil 2 |2 of relay 3L, contacts 216 and 2|8 of the latter are closed, and operating coil |33 of the reversing contactor is energized as follows:

Current flows from lead L| through wires |20, |22, |83, IBI, |84, |85, contact 2|8, wires 220, |50, |5|, switch 204, and wire |52 to one side of coil |36. The other side oi such coil is supplied with current from lead L3 through wires |38, |39, |40, |42, and |44. Coil |36 again operates the reversing contactor to establish connections so that motor 10 rotates in such direction as to lower the door, and the motor is stopped upon the opening of limit switch 3D and the consequent deenergization of relay 3L.

Assuming now that the rock bed level has been normal but has fallen to a level such that contact arm ||1 touches contact FRI, motor 10 is operated in the opposite direction, to raise the door, thereby to admit coal at a faster rate and correct such condition. In such case operating coil 222 of relay IR is energized as follows:

Current ows from lead LI through wires |20 and |22 through closed switch FR|, and through Wire |88 to one side of coil 222. The other side of such coil receives current from lead L3 through wires |3|, |30, closed limit switch |U, and wire |89.

Energization of coil 222 closes contacts |90 and |92 of relay IR, thereby energizing operating coil |91 of the reversing contactor RC. Coil |91 is energized as follows;

Current flows from lead L| through wires |20 and |22, closed contacts FRI, wire |88, contact |90, and wires 224, contact |92, wire |94, switch |60 and wire |96, to one side of coil |91. The other side of such coil receives current from lead L3 through wires |38, |39, |40 and |42. Energization of operating coil |91 causes the reversing contactor RC to be thrown in such direction as to close switches |98, 200, and 202 and to open normally closed switch 204. Leads LI, L2, and L3 will now-be connected to motor Wires Tl, T2, and T3, respectively, thereby operating the motor in the reverse direction and causing the door to rise. Connection of the motor to the current source leads is effected as follows:

Current flows from lead L| through wire |62, switch 202, and wire |14 to wire Tl. Current flows from lead L2 through wire |68, switch 200, and wires |2| and |10, to wire T2, and current ows from lead L3 through wire |38, switch |98, and wires |25, |66, and |61 to wire T3. Rotation of the motor 10 to effect opening of the door continues as long as switch FRl and limit switch IU are closed, and stops when either opens. Normally actuation of the motor is stopped by the opening of limit switch IU by the rise of operating finger |03.

If the rock level in the first cell 2 continues to fall, however, contact |1 will touch contact FB2 to energize relay 2R and again operate motor 10 in such direction as to raise the door. When this occurs, operating coil 228 of relay 2R is energized by means of current flowing from lead Ll, through wires |20, |22, closed switch FRZ, and wire 226 to one side of coil 228. The other side of such coil receives current from lead L3 through wires |3|, |30, closed limit switch 2U, and wire 229.

Energization of coil 228 of relay 2R causes closing of its contacts 230 and 234, thereby energizing operating coil |91 of the reversing contactor as follows:

Current flows from line LI through wires |20 and |22, closed contacts FR2, wires 226, 230, and 232, contact 234, wires 236 and |94, contact |60 and wire |96, to one side of coil |91. The other side of such coil receives current from lead L3 through wires |38, |39, |40, and |42. Motor 10 is thus operated again in such direction as to raise the door, and operates until either switch FRZ or limit switch 2U is broken.

If the rock level in the cell should continue to fall, contact arm ||1 will touch contact FVC. The closing of switch FVC operates relay VC in the following manner:

Current flows from lead LI through wires |20, |22, closed switch FVC, and wire 206 to one side of the operating coil 238 of the relay VC. The other side of such coil is supplied with current from lead L3 through wires |3|, 240, and 208. Energization of coil 238 of the relay closes its contact 242, thereby energizing the pawllifting solenoid 248 of the ratchet feeding device subsequently to be described, which is supplied with current from a separate current source,

l0 L4 and L5. Current then flows in the pawllifting solenoid circuit from line L4 through wire 244, contact 242, Wire 246, through solenoid coil 248, and back to lead L5.

Energization of solenoid coil 248 lifts the driving pawl of the ratchet mechanism shown in Figure 9 through which the rock valve 34 of the rst cell is driven. Thereupon discharge of rock from the first cell ceases, and remains stopped so long as switch FVG is closed, thereby allowing the level of the rock in the cell to build up. As shown in Figure 9, the ratchet drive mechanism for the rock valve consists of an arm 250 pivoted about the rock valve shaft 252 and operated by pitman 46, above described. Drive pawl 256, pivoted as shown on arm 250, coacts with ratchet wheel 254 aflixed to the valve shaft in such a manner as to cause intermittent rotation of the valve upon oscillation of arm 250. To prevent turning of the ratchet wheel 254 in a reverse direction, there is provided a springpressed holding pawl 258 attached as shown to a projection 260 on the side of the first cell near the location of the rock valve.

Energization of solenoid 248, which is attached to the upper end of arm 250 by a clamping meansn shown generally at 262, attracts the armature 284 attached to the upper surface of pawl 256 thereby pulling the pawl free of the ratchet teeth on ratchet wheel 254 and stopping rotation of the rock yalve.

The apparatus of the present invention above described therefore automatically insures the maintenance of the rock bed level of the first cell within such limits as to insure the optimumA operation of the first cell of the jig, and pre# vents the undue contamination of the lighter material carried over from the iirst cell with rock or other heavier material which Would occur if such rock bed should rise to an undesirably high level. Thus the two latter cells may continue the separation of the material in the most efficient manner. The apparatus is automatic in its operation, and functions to its fullest capacity while producing coal of uniformquality, regardless of the amount or rapidity of change of the rock content in the raw infed material.

It is to be understood that the apparatus of the present invention is capable of numerous variations obvious to one skilled in the art, and that its scope is to be defined by theappended claims.

Iclaim:

1. A jig for separating materials of differing specific gravity comprising a cell adapted to contain liquid, mechanism for feeding solid materials to said cell and including a gate which has a plurality of positions of adjustment, pulsing mechanism 'for stratifying solid materials in said cell according to their specific gravities, upper and lower discharges for removing materials from the upper and lower strata respectively, and control means for adjusting said gate by predetermined increments to its different positions of adjustment in accordance With incremental changes in the stratication level, said control means including a oat adapted to remain at the stratication level, a reversible elec- 'said circuits having normally closed limit switches corresponding with the different positions of adjustment of said gate, said mechanical linkage opening the limit switch in the energizing circuit when said gate reaches a predetermined position of adjustment corresponding with the stratiiication level of the particular set of contacts which are closed by said oat, said gate thus remaining stationary until a change in the quality of the feed changes the stratification level by an incremental distance of a magnitude suicient to close a different set of said contacts.

2. A jig for separating materials of differing specic gravity comprising a cell adapted to contain liquid, mechanism for feeding solid materials to said cell and including a gate which has a normal opening but is adjustable by xed increments for varying the feed rate, pulsing mech anism for stratifying solid materials in said cell according to their specific gravities, upper and lower discharges for removing materials from the upper and lower strata respectively, and control means for regulating the opening of said gate and thereby varying the feed rate by fixed increments in accordance with incremental changes in the stratication level, said control means including a reversible electric motor, a linkage operatively connecting said motor and said gate, a float within said cell adapted to remain at the stratication level and having a neutral position, an electric circuit for operating said motor to decrease the gate opening tok less than its normal opening and having a set of contacts which close as said oat rises a xed distance above its neutral position, an electric circuit for operating said motor in the opposite direction to increase the gate opening to more than its normal opening and having a set of contacts which close as said oat sinks a fixed distance below its neutral position, a limit switch in the rst circuit which is closed when said gate is at its normal opening and opened by said linkage when said gate has closed an incremental distance therefrom, and a limit switch in the second circuit which is closed when said gate is at its normal opening and opened by said linkage when said gate has opened an incremental distance therefrom, said limit switches automatically closing as said gate approaches its normal opening, the motor circuits remaining open and the gate stationary after each gate movement until the quality of the feed changes sufdciently to change the stratication level by a full increment.

WILLIE HAYES.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,294,757 Bloomeld Feb. 18, 1919 1,294,864 Bloomeld Feb. 18, 1919 1,345,060 Benson Jan. 29, 1920 1,619,807 Bloomfield Mar, 8, 1927 2,001,331 Peale May 14, 1935 2,132,755 Nichols Oct. 11, 1938 2,270,696 Brentz Jan. 20, 1942 2,272,188 Danielson Feb. l0, 1942 2,299,959 Brentz Oct. 27, 1942

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