US2964188A - Separation of solids having different specific gravities - Google Patents

Description

Dec. 13, 1960 w. c. EVANS ET AL 2,964,138

SEPARATION OF souns HAVING DIFFERENT SPECIFIC GRAVITIES Fild May 13, 1957 Figl INVENTORS W/'///am C. Evans Eagmond 5-. Me uberg A tho/nay SEPARATION OF SOLIDS HAVING DIFFERENT SPECIFIC GRAVITIES William C. Evans, 112 /2 NW. 18th, Oklahoma City, Okla., and Raymond E. Neuberg, 2601 Robin Road, Midwest City, Okla.

Filed May 13, 1957, Ser. No. 658,595

2 Claims. (Cl. 209-453) This invention relates generally to improvements in methods and apparatus for separating solids, and more particularly, but not by way of limitation, to an improved method and apparatus for separating gold from sand.

The time-honored method of separating gold from sand by prospectors is by panning, wherein sand and water containing a minor proportion of gold dust is moved through and around a suitable pan until all of the sand is washed from the pan and only the gold remains. The pan is manipulated by hand and is variously tilted in all directions in an efiort to wash the sand away from the gold. This method is economical from an apparatus point of view, but a substantial amount of water is used and the method is extremely time consuming and tedious, with the results always being questionable.

Several devices have also been designed to wash the sand away from the gold by a centrifugal action. In these devices, water and the sand containing the gold are poured into a vessel which ordinarily has sloping sides, with circumferential ridges in the sloping side walls. The vessel is rotated about its center, usually at a substantial speed, whereby the water and solids are thrown to the outer wall of the vessel and the water tends to wash the sand up over the edges of the vessel. In these devices the gold is supposed to stay either in the bottom or in the ridges of the vessel side walls, with all of the sand being washed over the sides of the vessel. However, a portion of the gold is frequently carried with the sand and is lost in the separation process. Many of these devices also utilize means for retaining a body of mercury in the sides of the vessel to trap the gold as the vessel is being rotated or spun. In these devices, the gold is amalgamated and is subsequently distilled from the mercury. Extremely intricate retaining devices have been designed to retain the mercury in the desired location in the vessel, but, to the best of our knowledge, none of these devices have been widely accepted.

The present invention contemplates a novel method of separating the heavier of at least two solids from a mixture of the solids by using a liquid carrier, and is particularly adapted to the separation of gold from sand with the use of Water. The method utilizes centripetal force to provide a separation of the desired solid and facilitate draining ofi the liquid and the lighter of the solids. In a simple embodiment of this invention, I contemplate the use of an open-topped vessel which may be rotated about its center, and which has a drain or outlet in the central portion of the vessel. Sand, water and gold deposited in the vessel are first subjected to centrifugal force to move all of the materials toward the outer periphery of the vessel. The water is then subjected to centripetal force, whereby a portion of the water rushes to the center of the vessel and is drained through the outlet. The water carries the lighter solids along with it to the center of the vessel for discharge through the outlet. The materials are laternately sub- States Patent 2,964,188 Patented Dec. 13, 1960 jected to centrifugal and centripetal force to provide a gradual step-by-step draining of the water and lighter solids, with the heavier solids remaining in the outer portion of the vessel. When used by prospectors, the vessel can be rotated and stopped by hand to provide the alternating centrifugal and centripetal forces, thereby requiring very simple apparatus and enabling the prospector to constantly View the separation process.

An important object of this invention is to provide a simple method of separating solids of different specific gravities requiring the use of simply constructed and economical apparatus.

Another object of this invention is to provide a method of separating gold from sand which may be practiced with a minimum amount of training.

A further object of this invention is to provide a method of separating gold from sand which may be carried out manually by a prospector in a remote location.

Another object of this invention is to provide an increase in speed over present methods of separating gold from sand.

A still further object of this invention is to provide a precise method of separating gold from sand, wherein none of the gold will be lost in the separation process and the water used in the process can be saved and used over and over if desired.

Other objects and advantages of the invention will be evident from the following detailed description, when read in conjunction with the accompanying drawings which illustrate our invention.

In the drawings:

Figure 1 is a plan view of one type of apparatus which may be used in practicing the method of this invention.

Figure 2 is a vertical sectional view taken along lines 2-2 of Fig. 1.

Figure 3 is a plan view of a vessel illustrating a typical distribution of various solids in the vessel during a separation of the solids in accordance with this invention.

Figure 4 is a schematic plan view of a modified apparatus which may be used in practicing this invention.

Referring to the drawings in detail, and particularly Figs. 1 and 2, reference character 6 generally designates an open-topped vessel having a circular cross-section, with slightly tapered side walls 7. A suitable handle 8 is secured in the top portion of the vessel 6 to faciliate spinning or turning the vessel, as will be more fully hereinafter set forth. The side Walls 7 of the vessel 6 may be either sloping outwardly, as shown, or of any other desired configuration, such as being truly vertical. It is preferred that the bottom it) of the Vessel 6 have a plurality of concentric circumferential ridges 12 formed in the upper face thereof. The ridges l2 facilitate separation of solids deposited in the vessel 6, and may take any desired configuration, such, for example, as circles, or radially extending ridges (not shown). However, the present method may be practiced with a vessel having a substantially flat bottom, as will be more fully hereinafter set forth.

A drain pipe 14 is provided in the center of the bottom 10 of the vessel and preferably extends no higher than the top face of the bottom 10. Thus, solids moved to the center of the vessel 6 will easily enter the upper end of the outlet 14. A suitable stop-per or plug 16 is inserted in the upper end of the outlet 14 to prevent loss of liquid and solids from the vessel 6 prior to rotation of the vessel.

The vessel 6 is preferably supported on a table 18 through the use of suitable annular-shaped bearings 20 in such a manner that the vessel 6 may be rotated about its center. The bearings 20 may be of any suitable type which will permit relatively free rotation of the vessel 6. The table 18 is supported by legs 22 and has a bore 24 in the central portion thereof located directly below the outlet pipe 14. When it is desired to conserve water in practicing this invention, a second vessel 26 may be placed below the table 18 directly underneath the bore 24, The vessel 26 will, of course, be open-topped to receive liquid and solids falling through the outlet pipe 14 and bore 24.

In operation, the stopper 16 is inserted in the upper end of the outlet pipe 14 in the manner shown, and a liquid containing the solids to be separated are poured into the vessel 6. It will be assumed that the vessel 6 is being used to separate gold from sand and that the solids are carried by water. The proportion of sand to water poured into the vessel 6 can be varied through wide limits, depending principally on the skill of the operator. We have found that when using a vessel about ten inches deep, with a diameter of about ten inches at the bottom and twelve inches at the top, the invention can be practiced efl'iciently by pouring about a one inch layer of sand in the bottom of the vessel and a layer of about five inches of water above the sand. It will be assumed that the sand contains a minor proportion of finely divided gold.

The vessel 6 is then rotated about its center at a speed suflicient to move the water to the outer portion of the vessel as illustrated by the dashed lines in Fig. 2. The sand and gold will, of course, be moved to the outer portion of the vessel 6 by centrifugal force along with the water. When the water has moved outwardly away from outlet pipe 14, the stopper 16 is removed. The speed of the vessel 6 is then decreased; and the water, which will then move in a substantially circular orbit in the vessel, wiEl. provide a washing action toward the outlet pipe 14 by the action of centripetal force. A portion of the sand will be carried by the water toward the center of the vessel 6 and will flow down the drain pipe 14, along with a portion of the water. The gold, being heavier than the sand, will tend to remain on the bottom 10 in the outer portion of the vessel. However, if the sand starts moving toward the center of the vessel at a substantial speed, the sand will tend to carry the gold along with it out through the pipe 14. Therefore, when the sand starts moving toward the outlet pIpe 14 at a depth which would obscure the presence of gold in the sand, the speed of the vessel 6 is again increased to move the sand and water back toward the outer periphery of the vessel by centrifugal force. Also, the water must be kept in circular motion to provide the desired centripetal force. Thus, the vessel should again be rotated before the water stops turning.

When the speed of the vessel 6 is again such that the water is outwardly of the pipe 14, the speed of the vessel can be decreased to provide a further drainage of water and sand through the outlet pipe 14. These alternating steps are repeated until all, or substantially all of the sand is removed through the outlet pipe 14. When all of the water has been removed from the vessel without removing all of the sand, the solids will be in the positions illustrated in Fig. 3. The small circles indicate sand grains which will be arranged around the outlet pipe 14 in the central portion of the vessel 6; whereas the gold, indicated by small triangles, will be located near the outer periphery of the vessel 6. The Xs indicate a third solid, as described below.

As it is well known, some grains of sand are frequently about the same color as gold, making it difiicult to see particles of gold in sand, even though the sand may contain a substantial proportion of gold. It will thus be apparent that when the speed of the vessel 6 is being controlled manually through viewing the movement of sand in the bottom of the vessel, there is the constant possibility that the water will be subjected to a centripetal force too long in a single step and that some of the gold will be carried out through the outlet pipe 14 with the sand. Tofacilitate the visual control of the movement of the solids, another solid having a specific gravity between sand and gold and a color strikingly different from. both sand and gold may be mixed with the solids at the beginning of a separation operation. We have found that finely divided lead is particularly useful. The lead has a specific gravity between sand and gold and is sufficiently dark that it can be easily identified in sand in relatively minor proportions. When using lead or the like, the lead will tend to move toward the outlet pipe 14 ahead of the gold and behind the sand. Therefore, when slowing down the vessel 6 to provide a drainage of water and sand through the outlet pipe 14, the operator can easily determine the approach of the lead to the center of the vessel 6. When the operator sees lead progressing toward the center of the vessel, he can again increase the speed of the vessel to move the water and solids back toward the outer perIphery of the vessel. At the end of a separation operation using an indicator such as lead, the lead (indicated by small xs in Fig. 3) will assume a position between the sand and gold because of its relative specific gravity.

In practicing the present method in the manner described above, the vessel 6 can easily be rotated manually by use of the handle 8. When the speed of the vessel 6 should be increased, the operator merely places one finger against the handle 8 and spins the vessel. When the speed of the vessel 6 should be decreased, the operator can use one or both hands against the side walls of the vessel in the manner of a brake until the speed of the vessel should again be increased. The periods of subjecting the water and solids to centrifugal force and, alternately, centripetal force are controlled by the operator who will be watching the movements of solids over the bottom lti ot' the vessel. With a little practice, any prospector can efiiciently separate the gold by the present method. It will be readily understood, however, that the periods of centrifugal and centripetal force may be controlled automatically when the approximate proportions of gold, sand and water are known, and particularly the proportion of sand to water. With experience in practicing the method using uniform starting proportions of water and sand, the lengths of the periods may be precisely determined, and then the rotation and deceleration of the vessel 6 can be easily controlled, as by a mechanical drive system.

A further feature of note in practicing the method as above described, is that the water used in the method may be easily conserved and re-used as many times as desired. The water draining through the outlet pipe 14 will accumulate in the lower vessel 26 and can be poured back into the vessel 6 when a new operation is started. This feature is particularly important to prospectors operating in extremely dry areas. With this method, substantially the only water which will be lost is through evaporation.

As a modification of the method described above, we may use the apparatus illustrated in Fig. 4. In this embodiment of the invention, the water is supplied to the vessel 6 by means of a hose 28 and nozzle 3%. The nozzle 30 is arranged horizontally and substantially on a tangent with the inner periphery of the side walls 7 of the vessel, whereby water is introduced into the vessel on atangent as illustrated in Fig. 4. It will be apparent that water injected into the vessel in this manner will tend to flow circumferentially around the vessel 6. With the vessel 6 supported on bearings, such as the bearings 20 in Fig. 2, the water injected through the nozzle 30 will, by friction, drive the vessel in a rotating movement. The solids will normally be deposited in the vessel prior to water injection.

When the speed of the vessel equals the speed of the water, the solids will be subjected to a predominantly centrifugal force and will tend to move to the outerperiph-- cry of the vessel. However, when the angular speed of the water in the vessel exceeds the speed of the vessel, centripetal force created by the water tends to wash the solids toward the center of the vessel in the same manner as previously described. The sand, being lighter than the gold, will be washed ahead of the gold. When so much sand is being moved to the outlet 14 to obscure the presence of gold, the speeds of the water and vessel are again equalized to move the solids back out toward the outer periphery of the vessel. Water will, of course, be drained through the outlet 14 when subjected to centripetal force.

The relative speeds of the water injected through the nozzle 30 and vessel 6 may be controlled in either of two ways. Firstly, the rate of water injection may be retained constant and a brake applied to or released from the vessel 6 to decrease or increase the speed of the vessel. Secondly, the vessel 6 may be left free to rotate at all. times and the rate of water injection varied. In either event, the solids are subjected to alternating centrifugal and centripetal forces to effectively wash the sand from the gold. It will also be noted that the relative speeds may be automatically controlled, particularly when the speed of the vessel is controlled by an external braking action.

Still another embodiment of the method of this invention is by turning only the water, with the retaining vessel being held in a stationary position. In practicing the method in this manner, the vessel 6 is supported directly on a stationary table, such as the table 18, with the outlet pipe 14 extending downwardly through the bore 24. The vessel 6 will then be retained in a stationary position on the table. In this embodiment, we prefer to rotate water in the vessel 6 by use of the nozzle 30 arranged as described above. As water is continuously injected, the solids are poured into the vessel 6 near the outer periphery. The speed at which the solids are poured into the vessel will depend upon the speed of the water and the particle size of the solids; care being taken that too much of the lighter solid are not being added to obscure a view of the movement of solids in the vessel when the operation is manually controlled. The water, in being rotated in the stationary vessel 6, provides a centripetal washing action on the solids to move the lighter solids toward the outlet 14 ahead of the heavier solids in the same manner as described above.

Although we prefer to rotate the water by injecting the water tangentially into the stationary vessel, it will be understood that the water may be turned or rotated by various means. For example, in a small installation, the water may be rotated by the operator inserting his hand in the water and moving the hand around the inner periphery of the side wall 7. Also, the water may be turned by a suitable paddle mechanism (not shown). It is also to be noted that when only the water is rotated, 'the solids will be subjected only to a centripetal washing action.

In all of the various modifications of the present invention, the use of ridges in the bottom of the vessel 6, such as the concentric circumferential ridges 12, facilitates separation of the sand and gold. The sand and gold will, of course, constantly tend to settle to the bottom of the vessel when the water is being rotated, as well as when the water is quiescent. When the vessel 6 is being rotated at a substantial speed, the gold, being heavier than the sand, will tend to move to the outer periphery of the vessel ahead of the sand. However, when the water is subjected to centripetal force, the sand will tend to move before the gold. Thus, the sand will be carried toward the center portion of the vessel 6 ahead of the gold, with the sand being rolled along the bottom 10 of the vessel. The ridges 12 tend to reduce the inward movement of all of the solid materials, and particularly the inward movement of the gold, since the gold will be in substantially constant contact with the bottom 10 and will have the least tendency to be carried with the water. In other words, the ridges 12 retard the inward movement of the gold more than the inward movement of the sand. However, the centrifugal force of the gold will be substantial enough to move the gold outwardly over the ridges 12 to the outer periphery of the vessel when the vessel is rotated at a sufficient speed to move the water outwardly away from the outlet pipe 14.

From the foregoing it will be apparent that the present invention provides a simple method of separating the heavier of two solids from a liquid carrier by use of simply constructed and economical apparatus. The method is subject to extensive automatic control when the proportions of starting materials are retained constant. Also, the method is particularly adapted for use by prospectors in remote locations, and the water employed in the method may be re-used several times without any substantial waste. It will also be apparent that the present invention provides a precise method of separating a minor proportion of gold from sand the gold may be separated in a minimum of time. Also, a minimum of training is required to practice the method.

Changes may be made in the combination and arrangement of steps and procedures heretofore set forth, it being understood that changes may be made in the precise embodiments described without departing from the spirit and scope of the invention as defined in the following claims.

We claim:

1. A method of separating gold from sand and the like in a vessel containing such solids and water, comprising the steps of:

(a) mixing a third solid with the gold and sand having a density between gold and sand and a color different from gold and sand,

(b) spinning the vessel about its center to move the water and solids toward the outer portion of the vessel, and, alternately,

(c) reducing the angular velocity of the vessel until at least a portion of the water and sand move to the central portion of the vessel, and

(d) draining a portion of the water and sand from the central portion of the vessel each time the velocity of the vessel is reduced.

2. A method as defined in claim 1 characterized further in that said third solid is finely divided lead.

References Cited in the file of this patent UNITED STATES PATENTS 184,622 Hooper Nov. 21, 1876 560,435 Seymour May 19, 1896 872,555 Capps Dec. 3, 1907 1,795,017 Fischer Mar. 3, 1931 2,178,390 Bockel Oct. 31, 1939 2,743,815 Goodwin May 1, 1956 OTHER REFERENCES Ganot: Ganots Physics, Sixth Edition, William Wood and Company, N.Y., 1890, pages 38-39.

Taggert, A. F.: Handbook of Mineral Dressing, 1945, chapter 19, page 169.

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