US2132380A - Jig - Google Patents

Description

Oct. 11, 1938. J. c. ATTWOOD 2,132,380

JIG

Filed March 4, 1935 5 SheetS-Sheet l D\SCHARGE.

f/vvE/v TOE: I John G. Affwooaf.

A TT X Oct.. 11, 1938. I J. G. ATTwooD Filed March 4, 1935 5 Sheets-Sheet 2 [An/EN TOR. Jo/7n G AffWOOO',

AT 'Y Oct. 11, 1938. J. G. ATTWOOD JIG Filed March 4, 1935 5 Sheets-Sheet 5 [/VVENTOE'. John G H/fwooafl ATT'Y J. G. ATTWOOD JIG Oct. 11, 1938.

Filed March 4, 1955 5 Sheets-Sheet 4 f/VVENTOR John G H77wooof ATT'X Patented 11, 1938 PATENT I OFFICE John G. Attwood, Columbus, Ohio, assignor to The Jeiirey Manufacturing Company, a corporation of Ohio Application March 4, 1935, Serial No. 9,147

4 Claims.

This invention relates to a jig and particularly to an automatic means for controlling the discharge of refuse from a jig.

An object of the invention is to provide a new 5 and improved automatic means for controlling the discharge of refuse from a jig whereby a refuse bed of substantially constant depth may be obtained.

Another object of the invention is to provide 10 an improved float for an automatic refuse discharge mechanism of a jig, which float is substantially fish-shaped.

A more specific objectof the invention is to provide a new and .nproved automatic means for is controllingthe depth of a refuse bed on a jig screen, which means is extremely sensitive in operation, yet is very rugged and which includes a flsh-shaped fioat mechanism which is entirely submerged in the jig bed during operation.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Referring to the accompanying drawings: Fig. 1 is a side elevational view of a jig com- 25 prising my invention, with parts shown in sec tion;

Fig. 2 is a front end elevational view of the device of Fig. 1, with parts removed to illustrate certain operating details more clearly;

30 Fig. 3 is an enlarged plan view of the float controlled mechanism of my invention, with parts shown in section;

Fig. 4 is an enlarged elevational view of the mechanism of Fig. 3;

35 Fig. 5 is an enlarged plan view of the fishshaped float comprising my invention;

Fig. 6 is an enlarged elevational view of the float of Fig. 5;

Fig. 7 is a sectional view on the line l-'| of 40 Fig. 6;

Fig. 8 is an enlarged sectional view on the line 8-4 of Fig. 1;

Fig. 9 is an enlarged elevational view of the operating means for the refuse discharging rotary .35 valve;

Fig. 10 is a sectional view on the line llL-lt of Fig. 9; and

Fig. 11 is a sectional view on the line il-ll of Fig. .1. v 50 Referring particularly to Figs. 1 and 2 of the drawings, there is illustrated a two-compartment jig comprising my invention. It is evident, however, that the number of compartments may be increased or decreased without departing from 55 the invention.

Said jig comprises a frame I built up of longitudinal and lateral I-beams and upstanding angle members and plates forming a rigid construction which supports a tank 2 formed into two compartments 3 and 4. Said compartments 3 5 and 4 are similar in most respects. At the left of compartment 3, as viewed in Fig. l, the tank 2 is provided with a material receiving chute 5 which is adapted to receive the raw material to be treated, such as raw coal as it is received from 10 a mine. This raw coal may or may not have been previously screened to regulate the size range of the material to be treated. Adjacent the right hand end of the tank 2, as viewed in Fig. 1, there is provided a discharge chute 6 for discharging the i5 clean coal from the jig.

Within each of the compartments 3 and 4, there is provided a perforate screen plate I which is pivoted at its forward end at 8 and supported by adjustable hangers 9 adjacent the rear end thereof. As is seen in Fig. 2 of the drawings, there are two hangers 9 in each compartment, which hangers are positioned adjacent the side walls of the tank 2. These adjustable hangers provide for an adjustable determination of the inclination of the screen plate which is an important factor in controlling the rate of travel of the bed of materials thereacross and maintaining said rate of travel uniform whereby there will be no piling up of material followed by a land-slide thereof. In addition, this adjustable screen provides for a uniform depth of refuse bed over the entire screen which provides uniform conditions of jigging throughout the bed and provides for adjustment of the bed whereby all particles of refuse, regardless of size, will flow toward the refuse discharge opening it at the same rate. This adjustable screen cooperates with the hereinafter described float mechanism to makepossible an automatic withdrawal of refuse while maintaining constant conditions of jigging.

Adjacent the pivotal position 8 of the screen plate I, there is provided an adjustable plate 9' forming a refuse discharge opening ill of adjustable size which leads to a refuse discharge chute ll within which is positioned a rotary refuse discharge valve IZ which, when rotated, is adapted to discharge accumulated refuse in the chute II into the boot i3 of an elevating mechanism, generally indicated at M, which is operative to remove the refuse from said boot l3 and discharge it outside the jig. The elevating mechanisms M for the two compartments 3 and 4 are driven from a common electric motor I5 through an appropriate drive gearing including the coupling shaft I6.

Within the bottom of each of the compartments 3 and 4, there is provided a diaphragm I'I, preferably circular in circumference, which is flexibly attached to a flange forming a stationary bottom of the compartment by means of a flexible ring I8, preferably made of rubber. Means are provided for imparting a reciprocatory motion to said diaphragm [1 along an axis which is slightly inclined to the vertical andwhich is approximately perpendicular to the plane of the screen plate I. This means comprises a bracket IT to the bottom of which is attached a piston l8 (Fig. 11) carried by a piston rod l9, which piston l8 fits into a cylinder 20 adapted to be supplied with substantially constant air pressure from an air line 2|. Pivoted to said bracket I1 is a pair of connecting rods 22 which are pivoted to a rocker beam 23, which rocker beam 23 is pivoted to bracket 24 rigidly attached to the inclined frame channels 25. The rocker beam 23 carries a roller 26 adapted to cooperate with a cam 21 mounted upon a shaft 28. The cam 21 has a groove forming both top and bottom tracks 2'la and 21b within which groove the roller 26 is adapted to move. The-connecting rods 22 are pivotally connected to a block 29, which block 29 may be slidably adjusted along track 30 on the rocker beam 23. This adjustment of the block 29 provides for adjustment of the stroke of the diaphragm l'l during each cycle of operation.

An electric motor 3| (Figs. 1 and 2) is provided for driving the shafts 28 of each of the compartments 3 and 4, said shafts 28 being connected by a chain-and-sprocket mechanism 32 including an adjustable chain ten'sionlng idler 33. It is evident that as the motor 3| is driven the diaphragms ll of the compartments 3 and 4 will be reciprocated causin'g pulsating movement of the fluid in the tank 2 with respect to the screens 1. In the preferred arrangement,' the cycle of operation of these two diaphragms is 180 degrees out of phase thereby'making the load more uniform on the motor 3|, though this arrangement is by no means necessary.

The function of the cylinder 20 is to balance the load on each side of thediaphragm I'I so that the motor 3| need supply only sufllcient energy to reciprocate said diaphragm. That is, the air pressure in the line 2| is supplied to the cylinder 20 and acts upon a piston within said cylinder 20 to balance the normal load on top of the diaphragm I'I.

An appropriate valve 34 is provided for each of the compartments 3 an 4 to control the admission of water to the tanks of said compartments.

It will be evident from the above description that when material to be treated-such as raw coal-is fed'to'the jig'over the chute 5, it will be subjected to a jigging operation on the screen plate I by the upward and downward movements of water through said screen plate 'I. This jigging operation will be so regulated as to effect a separation of the particles of material, whereby the refuse, such as shale, will form a bed directly on the screen plate I while the clean coal and possibly the lighter fractions of refuse, such as bone, will form in layers above the refuse. That is, stratification will take place within the compartment 3 with the refuse on the bottom and the coal on theitop. The coal will then be discharged over the adjustable height weir 35 of compartment'3 into compartment 4 where an additional'jigging operation will take place with further stratification of the materials with the lighter particles of refuse now forming the refuse bed and the clean coal forming the upper strata. The clean coal, after being subjected to a jigging operation in said compartment 4, will be discharged over the chute 6.

The refuse forming abed on the screen I will be discharged into the chute I I through the opening Ill and then discharged by the valve l2 into the boot l3 of the elevating mechanism l4, by which elevating mechanism l4 it is elevated to a discharge position and discharged from a nozzle 36. As the refuse from the compartments 3 and 4 are discharged from separate nozzles 36, they will be separately received and may be given individual treatment, if desired. In some instances, it has been found that the refuse from the second compartment 4 may have suflicient heat value to be sold as low grade fuel.

The principal feature of my invention lies in the mechanism for controlling the discharge of the refuse which accumulates on the screen 1. Extensive tests have demonstrated that to'obtain the most satisfactory stratification of the materials and consequently the most eflicient separation of coal and refuse, the bed of refuse which forms on the screen plate 'I' should be of reasonably constant depth. It is the primary function of the automatic refuse discharge means of my invention to keep this refuse bed at a reasonably constant depth and to make this operation entirely' automatic. While numerous attempts have been previously made to produce this desired result, none has been entirely satisfactory in actual operation, of which I am aware. The above mentioned tests have indicated certain difficulties in known devices which are overcome in the construction of my invention.

It has been discovered that the float of an automatic mechanism should be of the totally submerged type and in my invention a float 3'! of the totally submerged type is provided. The reason the float should be of the totally submerged type lies in the fact that due to the upward and downward movement of the water in the com- , partments 3 and 4 the float has a tendency to rise and fall ,in said compartments. Unless the float is of the totally submerged type, this rising and falling thereof causes a variation in the amount of water displaced by said float from one instant of time to the next during a complete cycle of operation. This means that in effect the weight of the float is constantly varying from instant to instant during a cycle of operation. Where the float is totaly submerged, this variation is avoided. It has also been discovered that for the totally submerged float to be entirely satisfactory, said float must be so designed that nothing will vary its effective weight. If the submerged float has a-flat top or even a gradually sloping top, it is found in actual operation that particles of material will rest on the top of the float and thus change its effective weight. This may be caused by the presence of a dead spot directly above the float due to lack of stream lining for the upwardly moving water and also due to the inherent tendency for a flat surface to support any material that may fall thereon.

One of the important features of my invention therefore lies in the construction of the totally submerged float whereby it has a very sharp back or top. In fact, as is well illustrated in the drawings, the float is substantially fishshaped. m

Referring particularly to Figs. 5, 6 and 7, it is seen that the float has a fairly bunt nose 38 and an extremely stream-lined tailportion 39. The

. rounded, as best illustrated in Fig. '1. The top or back 41 of the float forms a relatively sharp angle and presents smooth surfaces 42 and 43 which make a relatively sharp acute angle with the vertical. A rib 44 is provided at the center line of the back 41, as best seen in Fig. 5. This particular construction of the float has been found to be very satisfactory: for it effectively prevents any accumulation of material thereon which might tend to vary the effective weight thereof. Furthermore, as the float rises through the bed of material due to the action of the upwardly moving water on the bottom thereof, the top or back thereof will cut through the bed and water will flow past the sharply inclined surfaces 42and 43 and prevent any particles from resting thereon. As the water flows downwardly past the float, it will scour the surfaces 42 and 43 and prevent the accumulation of any particles of material thereon.

D As illustrated in Figs. 5, 6 and 7, the float 31 is preferably of hollow construction and in practice may be made of cast aluminum. Core holes 45 are provided for removing the core sand after the float is cast. These core holes 45 will, of course, be sealed, as .by an aluminum plug. The float 31 is also provided with an integral extension 46 provided with appropriate bolt holes and is adapted to receive a connecting post 41.

As is illustrated in Figs. 3 and 8 of the drawings, the post 41 is preferably of hollow construction and may Well be formed of aluminum to reduce its weight. vides for a. minimum of weight with a maximum of strength. As is seen from Figs. 3 and 8 of the drawings, the post 41 is also stream-lined to reduce its disturbing effect in the bed of materials.

As best seen in Figs. 3 and 4 of the drawings, the float 31 is connected to a parallel motion mechanism so that the position of the float 31 may control the operation of the valve 12. In

.order that the float 31 may be extremely sensitive, the parallel motion mechanism is made as light as possible and the moving parts are mount-- ed upon anti-friction bearings, such as needle bearings. Said linkage mechanism comprises a pair of upper spaced arms 48 between which extends a shaft 49 which. is mounted in sockets 59 of said arms 48 by anti-friction roller bearings 51. (Fig. 3.) The shaft 49 extends through a block 52 which is connected to a lower block 53 by a shaft 54. The blocks 52 and 53 and the shaft 54 ,are positioned within the post 41. Also loosely mounted on the shaft 49 is a pair of spacers 55 adapted to clamp the outside of said post 41} Clamping nuts 56 are provided which. may effect a clamping of the post 41 with respect to said shaft 49. This construction is also duplicated with respect to the lower arms 51 of the parallel motion mechanism.

The post 41 is provided with elongated apertures 58 whereby the position of the, float may be adjusted with respect to the parallel motion This hollow construction pro-' adjusted as thus the gravity of separation of coal and refuse may be adjustably determined. The arms 48 of the parallel motion mechanism are keyed to a shaft 63 and are mounted in a.

bracket 64 by anti-friction roller bearings 65. The bracket 64 is carried on a cross-beam 66 which extends between the side walls of the tank 2. Mounted on said beam 66 and adjacent one end thereof is another bracket 61 which supports one end of the shaft 63 by a non-friction roller bearing 68. The lower arms 51 of the parallel motion mechanism are keyed to a small stub shaft which a is mounted on the bracket 64 by roller bearings in a manner similar to that by which arms 48 are mounted on said bracket. It is thus evident that the friction of the parallel motion mechanism is reduced to a minimum. In addition, the

weight of the moving parts of said mechanism is reduced to a minimum by employing light weight materials, such as aluminum. This results in a very sensitive mechanism which has been found necessary to provide a satisfactory automatic refuse discharge control device.

Keyed to the shaft 63 is an operating lever 69 which is provided with a plurality of holes to receive selectively a couple link 19 which is attached to a downwardly extending rod 11, which rod 11 carries at its lower end an adjustable connecting link 12 provided with anelongated aperture 13, as best illustrated in Fig. 9 of the drawings. The position of the float 31 is effective to control the position of a shield 14 which, inturn, is effective to determine the rate of rotation of the refuse discharge valve 12.

Before describing in detail the construction of the valve operating mechanism, attention is directed to Fig. 1 of the drawings for consideration of the general mode of operation thereof.

Associated with the shaft 28 is a crank 15 which is effective to reciprocate the rod 16 continuously while the jig is operating. This rod 16 imparts a continuous reciprocatory movement to the bell crank 11. The bell crank 11 carries a pawl 18, or a plurality of said pawls with tips spaced 2. fraction of a tooth apart, adapted to cooperate with a ratchet wheel 19 to rotate said wheel periodically. The shield 14 is effective to determine the number of notches on the ratchet wheel 19 which will be engaged by the pawl or pawls 13 during each reciprocation thereof. As was above described, the position of the shield 14 will be determined by the average position. of the float 31. The elongated .slot 13 is provided so that the reciprocatory movement of the float 31 in response to pulsations of the water will not be transmitted to said shield 14 but said shield will assume a position determined by the average or mean position of said float 31.

It has been found from experience that the refuse discharge mechanism should be so adjusted that in normal operation the pawl 18, or one of said pawls if two are employed, will ratchet over at least one tooth of the ratchet wheel 19 during each reciprocation of the bell crank 11, whereby there will be a substantially continuous withdrawal of refuse from the bed formed on the screen 1. If the refuse tends to becomedeeper than the pre-determined amount.

the shield will be withdrawn to allow pawl 18 to ratchet over more teeth of the rachet wheel 19, for each oscillatory movement of the bell crank lever 11. By this mode of operation, variations in the depth of the refuse bed are small and thus constant conditions of jigging are presented. As was above set forth, the shield I4 is so adjusted and is so balanced that it will remain at any angular position to which it is moved. This is provided by balancing the mechanism which moves with said shield I4 so that in any angular position of adjustment it will be in static balance.

The details of the mechanism for rotating the valve I2 are best seen in Figs. 9 and 10 of the drawings. The discharge valve I2 is of the paddle wheel type and is mounted upon a shaft 88, which shaft 88 is carried at its outer end by a bifurcated bracket 8|. Said bracket 8I is provided with inner and outer bearing sleeves 82 and 83, respectively. The ratchet wheel 19 is keyed to the shaft 88. The shield I4 is carried on arms 84 which arms are journaled on the inner portions of the bearing sleeves 82 and 83. The arms 84 also carry a bifurcated bracket 85 which carries a pin 86 which projects into the elongated aperture I3 of the coupling link I2. Arms 84 also carry counter-weights 81 which are eifective to produce the above mentioned static balance of those parts which are rigid with the shield I4 for any angular position of adjustment of said shield I4. It is thus evident that shield 14 will remain in any position of adjustment to which it is moved by the float 31.

Bell crank lever 11 comprises two arms IIa and IIb, which arms are journaled to the outer portions of the bearing sleeves 82 and 83, respectively. It is evident that as said bell crank lever 11 is journaled to the stationary bearing sleeves 82 and 83, rotation of the shaft 88 and of the valve I2 will beaffected only to the extent that shield I4 provides for engagement of the pawl I8 with the ratchet wheel I8. Arms IIa and "D are sufficiently spaced from the arms 84 on the bearing sleeves 82 and 83 so as to transmit no reciprocatory motion to said shield I4. If desired, spacing washers may be placed between the arms IIa and 11b and the arms 84, which washers may be keyed to the bearing sleeves 82 and 83 to provide a positive isolation of said bell crank lever 11 and the arms 84. It has been found in practice, however, that these spacers are usually not necessary.

To provide for a ready removal of the valve I2 through the side of the tank 2 a removable plate 88 (fig. 10) is provided which cooperates with the ring 89 welded to the side of said tank 2. The internal diameter of the ring 89 is greater than the external diameter of the paddle wheel valve I2. An appropriate packing gland 98 is provided to perform a water-tight connec-' tion between the plate 88 and the shaft 88.

valve I2, yet in normal operation there will be asufiiciently close fit between the valve I2 and the chute II to prevent any material, even 'if very fine, from passing into the boot I3 less it is discharged by rotation of the valve I2.

A typical illustration of the mode of adjusting the device of my invention is as follows:

The capacity of the jig is, of course, known and raw coal is fed thereto at this capacity. The

percentage of refuse will be known within'reasonable limits, and as illustrative it may be known to be from 5 to 10 per cent. With material of the size range being treated, it is known that the approximate refuse bed depth which is desired. For example, with a size range of %"-6 mesh, an average refuse bed depth of 6 inches may be desired. The post 41 is therefore adjusted so that arms 48 and 5'! will be horizontal with the refuse bed 6 inches deep.

The coupling link I8 (Fig. 4) is so adjusted with respect to the lever 69 that the range of speeds at which shaft 88 may be rotated is sumcient to take care of the range of variations in refuse accumulation normally encountered, with a maximum movement of the lever arms 48 and 51 of 15 degrees both above and below the horizontal, making '30 degrees total variation. If the refuse variations are relatively low, then the effective length of arm 69 may be made relatively short whereby the maximum variation in the angular movement of shaft 88 for each reciprocation of bell crank 11 will be from zero, when the float is below normal and arms 48, 51 are 15 degrees below the horizontal, to the angle subtended by two teeth of ratchet wheel I8, when the float is above normal and arms 48, '51 are 15. degrees above normal. Under the latter condition, the rate of discharge of valve I2 will be approximately twice the normal rate of accumulation of the refuse. When the refuse bed is at a normal depth, the average position of the arms 48, 51 will be substantially horizontal under which conditions shaft 88 will rotate through the angle subtended by one tooth of ratchet wheel I9 during each oscillation of the bell crank 'IIand this rate of oscillation will be adjusted to remove the refuse at substantially the same rate it accumulates, in normal operation. If the refuse begins to accumulate at a rate faster than it is withdrawn, then float 31 will rise and shaft 88 will be rotated through the angle subtended by two ratchet teeth during each oscillation of the bell crank 11 whereby refuse is discharged at twice the normal rate until a normal bed depth is again established. Should the bed depth fall below normal, which is improbable under the above mentioned adjustment, the shaft 88 will not rotate at all until a normal bed depth is established.

It is evident, of course, that the float 31 continuously oscillates with the pulsations of the 5Q bed under the influence of diaphragm II, but as aforesaid, shield I4 assumes a position determined by the average position of said float 31 and controls the angular rotation of shaft 88 for each reciprocation of bell-crank 11.

Should it be found that there is a wide variation in the refu .e content of the material, then the link I8 may be connected to lever 69 to increase the effective length of said lever 68, whereby the angle through which shaft 88 is rotated for each reciprocation of bell crank 11 is that subtended by teeth of ratchet wheel I9 which may vary in number from 0 to 3, or 0 to 4, for a total average angular movement of the arms 48, 51 of 38 degrees. The ranges above mentioned may be increased, if desired. In addition, the rod II may be effectively shortened or lengthened whereby the minimum anguiar'rotation of shaft 88 will be that determined by the angles subtended by 1 or 2 teeth. For example, the range through an angle subtended by one or more teeth of the ratchet wheel 19 without removing refuse faster than it accumulates. When two pawls 18 are used half a tooth movement of the ratchet wheel 18 is possible and this may be employed to obtain a greater range of operation of the refuse ejector. For example, the range may then be from 0 to 2 or from to 3 teeth. These ranges are, of course, merely illustrative and obviously may be expanded or contracted, as desired.

In addition to the mentioned adjustment, which essentially affects the position and range of movement of shield 14 and the rate of oscillation of the bell crank 11, it is necessary to adjust the screen I, as previously mentioned, to obtain uniformity in the depth of the refuse bed over the entire area of the screen, as well as uniformity of the'constituents thereof and uniformity in the rate of movement of said bed over said screen I. Said screen 1 should be adjusted so that the refuse will not tend to pile up and then create a land-slide but will move continuously and uniformly. When proper adjustment of the mechanism is made, as aforesaid, the withdrawal of refuse is completely automatic.

The gravity of separation of the material may be adjusted by adding or subtracting washers 62. An increase in the number of said washers results in an increased gravity of separation.

It is evident that the mechanism of my invention for controlling the discharge of refuse is a very sensitive mechanism, yet it is relatively rugged and free from parts which may get out of adjustment. This extremely sensitive mechanism has been found to be very effective to maintain a relatively constant depth of refuse bed which is necessary for consistent jigging conditions and an ultimate clean separation of coal and refuse. Every effort is made to reduce the mass of the moving parts which move in unison with the float 3! and to reduce any frictional surfaces which might tend to reduce the sensitivity thereof. In addition, as has been above pointed out, the particular shape of the float 31 is a very important feature of my invention.

In the operation of the jig, raw coal will be fed to the chute 5 and fall through the jigging liquid to the screen I, forming a bed of material. The cyclic upward and downward movement of the jigging liquid through the screen 1 will stratify the bed of material with the high gravity refuse on the bottom and the coal on top. During this stratifying action the bed will be cyclically expanded and contracted to perfect the stratification. The float 31 will act much like a large particle of material and, particularly as it is totally submerged, will be Stratified in the bed according to its size and weight. These qualities are so determined that said float 31 will be Stratified on top of the refuse bed, and within and at the bottom of the bed of coal. The float 31 thus does not truly float on the liquid surface but is actually stratified on top of the refuse bed.

too shallow the float comes to rest at a lower position and decreases the rate of operation of said discharge valve 12.

After the highest gravity refuse is removed from the first compartment 3 the material passes over weir 35 into the second compartment 4' where the intermediate gravity refuse is removed in a manner similar to that above described. The float.mechanism is adjusted, by means of washers 62, to reduce the effective weight of the float 31 in said compartment 4 over what it' was in compartment 3 so the float 31 will properly stratify on top of the intermediate gravity refuse.

The clean coal passes from compartment 4 over the chute 6 to be treated as a final clean coal product.

While in the description given the apparatus was described as particularly useful for cleaning coal, for which it is primarily designed, it may also find other useful fields of application.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I wish therefore not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

1. In a separator, the combination with. a material support, of means for controlling the depth of refuse on said support comprising, a rotary refuse discharge valve, a ratchet wheel adapted to operate said valve, a pawl for operating said wheel, means for reciprocating said pawl, a shield for determining the extent of movement of said ratchet wheel during each reciprocation of said pawl, means for adjusting the position of said shield comprising a totally submerged elongated float having a pointed back whereby material will not tend to accumulate thereon and having a relatively flat rounded bottom to rest on said refuse bed, and mechanism for connecting said float and said shield including non-friction mountings, whereby said float will control said shield.

2. In a jig, the combination with a screen, of means for maintaining a uniform depth of refuse on said screen comprising, a rotary discharge valve, a ratchet wheel for rotating said valve, a lever, means for'reciprocating said lever, a pawl carried by said lever adapted to engage said ratchet wheel, a shield adapted to determine the extent of rotation of said ratchet wheel for each reciprocationof said lever, a totally submerged float having a sharp top and adapted to indicate the depth of refuse on said screen, linkage mechanism connecting said float and shield including a lost motion connection whereby said shield assumes a position determined by the average positionof said float, and means to balance said shield whereby it will remain in any adjusted position. 1

3. In a separator, the combination with a material support, of means for stratifying material on said support to form a bed of refuse, means for discharging refuse including a rotary valve, a ratchet wheel for rotating said valve, a lever, means for reciprocating said lever, a pawl carried by said lever adapted to engage said ratchet Wheel, a shield constructed and arranged to determine the extent of rotation of said ratchet wheel for each reciprocation of said lever, a totally submerged float having a sharp top and said pawl and ratchet means to determine the extent of movement of said valve, means for adjusting the position of said shield comprising an elongated totally submerged float having a pointed back whereby material will not tend toaccumulate thereon and having a relatively flat rounded bottom substantially devoid of comers adapted to rest on said refuse bed, and mechanism for connecting said float and shield whereby said float will control said shield.

JOHN G. A'I'I'WOOD.

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