US 2631726 A
Abstract available in
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Description (OCR text may contain errors)
March 17, 1953 G. A. AUER HYDRAULIC CLASSIFIER I5 Sheets-Sheet 1 Filed Feb. 7,. 1949 lZZ IN VEN TOR.
March 17, 1953 G. A. AUER HYDRAULIC CLASSIFIER 3 Sheets-Sheet 2 Filed Feb. 7, 1949 I I I I III,IIIIIIIIIIlIIIIIIIIIIIIIIIIIIIIIIIIIIIII I I I I I I I I I I I I I I I I I I I I I I IIIIIIIIIIII/ INVENTOR.
March 17, 1953 G. A. AUER 2,631,726
HYDRAULIC CLASSIFIER Filed Feb. '7, 1949 s Sheets-Sheet 5 mun minus FZ::;9 6-
wire?" IN V EN TOR.
tributing wall. Numerals lfil3--ii4-l45-M6 indicate discharge ports for the controlled outflow of liquid and separated products from the chamber I26 at vertically superposed levels thereof. The ports discharge into associated collecting or discharge chambers indicated at Ml- I48l4l-l5l, respectively. Each discharge chamber is provided with a valved outlet, as di agrammatically shown in Fig. 2. It will be understood, or course, that simple valved outlets are shown in this figure only for convenience of representation. In a working structure, each outlet port, or each outlet from each discharge chamber may terminate in a downwardly directed discharge boot, such as diagrammatically shown at 2iili-2l)i2l22ll3 in Figures 4-7. boot may be connected with a housing such as shown in Fig. 4; at 2ii l2ii5-2il520l, and each such housing may be provided with suitable discharge means, for example, with a bucket elevator. A valved suction conduit may be provided in connection with each discharge boot and associated elevator housing for the purpose of withdrawing liquid coincident with the withdrawal of the separated product therefrom. These valved suction conduits are indicated in Fig. 4 at 2(l 3 21l92 lii2 l I, respectively. A pump 252 may be provided for drawing liquid from the conduits 208-2. It will be understood, of course, that these conduits may be connected with the elevator housings at higher levels thereof. Numeral i5i indicates an overflow.
A suitable gate of valve, e. g., a slide gate (not shown), may be provided directly at each of the outlet ports Hit-Hi5. It should be noted that the bottom of each of the discharge chambers l4ll50 is dished so as to provide for complete drainage.
Angularly adjustable flow control or flow-distributing baiiie members i52-l53-l54 are provided. Each of these members may be made in the form of a bar or strip, streamlined if desired, rotatably supported on a suitable shaft and extending transversely across the chamber l26 above the floor thereof. The shafts project to the outside and are angularly adjustable by suitable means, for example, hand wheels, as shown in:
Fig. 1. Hand wheel I55 is provided for angular adjustment of the flow control member I52; hand wheel ifit for angular adjustment of the flow control member 53; and hand wheel lEl for angular adjustment of the-flow control member I54. Additional such flow control members may be provided, if desired or necessary.
A relatively stationary flow control partition I58, indicated in Fig. 2 in dotted lines, may be provided in place of the flow control members l52|54, or in addition thereto, and disposed thereabove. This partition, if used, forms a roof over the flow-distributing bottom Wall and the upwardly inclined bottom space defined thereby constitutes the separating chamber of the machine. The partition also forms in such case the floor of an auxiliary top chamber which extends thereabove an may be used, as indicated in Figs. 6 and 7, as a turbulence mixing chamber adapted to discharge material into the separating chamber [26. The auxiliary chamber, as shown in Fig. '7, may serve as a mixing and feed chamber for the raw material or, as shown in Fig. 6, as a mixing chamber for a liquid heavy density separating medium.
The port or opening I25 which connects the mixing chamber with the separating chamber I26 maybe controlled-by a gate or valve-160. This Each valve is operable by a shaft |6l which is adjustable by means of a hand wheel such, for example, as indicated in Fig. l at I62.
Gates or valves |22a shown in Fi 2 in dotted lines may be provided in the end wall 122 of the mixing chamber for discharge of material from selected levels of this chamber into the separating chamber. These valves may be mounted just like the valve and operated by suitable levers or hand wheels (not shown), or they may be sliding valves and may be operated either from the side or from the top or" the structure, as desired.
There are several principal operating possibilities which will now be discussed.
Referring first to Figs. 2 and 4, the raw feed may be coal of a certain specific gravity, which is to be separated from heavier impurities, and for the sake of convenience it may be assumed that the largest particles are less than that is that the particle size of the raw feed is, for example, /4" or even smaller, down to 0".
The tank is first filled with liquid separating medium, water or a suitable heavy density liquid (sand, magnetite or powdered ore suspended in water), by injecting such medium through the inlets 535-436. The pump H2 is then started, after proper adjustment of the valves associated with the suction conduits 2il82i l, to withdraw adjusted amounts of liquid from vertically successive levels of the liquid body in the separating chamber, thus creating controlled hydraulic displacement of the liquid body, upwardly and laterally outwardly with upwardly decreasing intensity. Liquid medium being continuously injected through the inlets ltd-436 for upflow in the conduits i33-l3 (Fig. 3), flows out in jets, streams or sprays into the feed and mixing chamber, creating irrational agitation and turbulence therein. Mechanical agitation may be provided in the chamber, as previously mentioned and as indicated diagrammatically in Fig. 4.. Depending on the nature of the raw feed, both types of agitation, or either one, maybe used as desired. The raw feed is introduced into the hopper l3! and drops intothe irrationally agitated liquid in the feed and mixing chamber for passage therethrough, and is thus subjected to turbulent mixing agitation of a desired intensity to break up agglomerates, to prevent agglomeration and to produce wetting and thorough intermixing and dispersing of the solid particles in the liquid.
Previously known separators, generally and broadly speaking, and neglecting certain features which will presently appear, do the same thing. The raw feed is dropped into a tank containing a liquid medium, and liquid currents or air currents (which may be employed in the present structure) are injected into the body of the liquid medium, producing irrational turbulence and hydraulic displacement. Agitation is in addition produced by mechanical means, for example, rotating paddles, propellers or the like. In prior separators, separation as such is attempted in the presence of the irrational turbulence, while such turbulence is used in the present case only for the purpose of accomplishing dispersal and uniform distribution of the particles. The advantages will appear from the following considerations:
The turbulent agitation produces drawbacks which impede proper uniform distribution and dispersion of the solids in the liquid, which in prior separators is used as a mixing medium and also as a separating medium -It is believedthat one of the requirements for proper separation is uniform distribution or dispersion of the particles in the separating liquid, and this basic requirement is thus violated in prior separator structures and systems. The parent application and references mentioned therein may be consulted for details and theoretical considerations regarding this phase of the subject.
Irrational turbulence and agitation as applied in prior separators to the liquid separating medium interferes with the proper separation of the particles therefrom, because it impedes the organized Stratification of the particles. The industry is in this respect in av dilemma. Agitation must be applied to disperse and to distribute the particles in the liquid, and a degree of agitation that would be desirable to obtain substantially uniform distribution causes such turbulence that Stratification and clean-cut separation are made practically impossible. It is, of course, relatively easy to separate materials within relatively wide specific gravity and/or size ranges. The detriment becomes particularly manifest when it is attempted to separate solids of relatively small particle size and of a certain specific gravity which is relatively close to the specific gravities of the next heavier impurities. It may be mentioned here that there is no hydraulic separator known at the present time which is adapted to produce entirely satisfactory separation, e. g., of coal, of a specific gravity of, say, 1.35, and of a particle size ranging from less than to 0", and especially small size material ranging from /4 to 0", or smaller, which is to be separated from impurities having specific gravities, ranging from about 1.40- 1.45. Conditions like this and similar conditions are, nevertheless, very frequently encountered. The invention is intended to contribute toward remedying this shortcoming.
One of the characteristic features which distinguishes the present invention from the prior art resides in dispersing and substantially unifolimly distributing the solid particles in a. fluid medium, by the application and use of, irrational agitation, in a first passageway or feed or mixingchamber, where irrational turbulence. cannot conflict with the separation, and carrying out the separation of the. particles in accordance with the specific gravities thereof, by the use of controlled hydraulic displacement of the fluid body containing the solids thus dispersed, therein, in a second passageway or separating chamber, to accomplish organized substantially rational stratification and separation substantially in the absence of irrational turbulence. The prior art, in contradistinction, attempts to accomplish dispersion of the particles and separation thereof at, the same time; that is, it attempts to accom-. plish separation in the presence. of irrational and unpredictable turbulence.
The thoroughly intermixed and. hydraulicallymobile material leaves the mixing chamber through the port I25, and enters the fluid body in the separating chamber I26" which is continucusly rationally displaced substantially symmetrically upwardly and laterally outwardly, with upwardly diminishing intensity- It will be clear that in the presence relatively rational hydraulic displacement, the solids will stratify in accordance with their specific. gravities and/or sizes, the heaviest or largest components gravitating for discharge. toward the bottom and the lightest. or smallest floating for discharge toward the. top. g p
inspection of Figs. 2 and 4 will explain the of such .ucts. the discharge ports vary in order to produce the behavior of the material. The intermixed mass consisting of the liquid separating medium and the solids dispersed therein leaves the feed and mixing chamber in downward direction with a force which depends on the amount of liquid injected thereinto to supply the quantities of liquid withdrawn from the separating chamber. The particles entering the separating chamber are now subjected to the rational hydraulic displacement therein.
Stratification is initiated within the feed and mixing chamber by the hydraulic displacement caused by the action of the liquid currents issuing from the ports in the side walls. The mass of material is deflected at the bottom of the feed and mixing chamber in the direction of the prominent arrows shown in Figs. 2 and, 4. There is an upward component tending to lift the material generally in the. direction of the fiow control member I52. The heaviest particles tend to remain near and at the bottom, moving for discharge toward the outflow port I43, and the lighter particles are lifted up. From then on the displacement of the mass continues substantially without irrational turbulence, upwardly and laterally outwardly, with upwardly diminishing intensity, along the flow-distributing wall. or fioor, sweeping toward the overflow I52. The organized Stratification and discharge of separated products continues, the heavier particles moving along at and near the bottom of the stream in the separating chamber, for discharge at progressively higher levels, and the progressively lighter particles move along for discharge near its top layer. The outlets from the various chambers ll-I50, as previously remarked, may be connected with discharge boots 280-2213, respectively, and each boot in turn is connected with a housing such as shown at 28 3-2511, respectively, each of which contains suitable removal means, for example, a bucket elevator. Each housing is connected by means of; a valved conduit such as. 2Il8-'2II, respectively, with a pump 2I2 which withdraws adjustable amounts of liquid from the respective discharge ports I43i45 and associated dis,- charge, chambers Iii-45B. Liquid is thus removed from the discharge ports I43-I45 together with the corresponding separated prod- The amounts-of liquid withdrawn from hydraulic displacement within the separating chamber I26, as described. The lightest particles are discharged at the overflow I5I.
The organized stratification, and therefore separation, within the upwardly and laterally outwardly moving stream in the separating chamber may be assisted, if desired, by the injection of fluid or air currents, sectionally, through the floor plates ltd-4.42 (Fig. 2) which form the discharge .ports Its-M5, respectively. These plates may be perforated for this purpose and each may carry a hood at the bottom side, as indicated in Fig. 2 at me, which is connected with a suitable fluid or air supply. The supply of fluid to' the hoods may be uniform, or may be in upwardly lessenin amounts and/or pressure.
Irrational turbulence, which may occur in the separating chamber I26 in the form of eddies, is broken up by the flow control members I'52I54. Eddies that may be formed above these control members have no detrimental effect on the controlled material flow within the separating cham- It is understood of'coursethat sufiicient liquid must be added in the feed device to maintain any desired flow of liquid through the separating chamber toward the overflow. Makeup liquid, e. g., water, may also be added to the top level of the liquid within the separating chamber, as indicated by the broken arrow in Fig. 4. Makeup water added in thismanner will facilitate the floating of the coal to the top and its removal over the overflow, particularly in the case of heavy density operation.
The flow of the material within the separating chamber is thus regulated and controlled by the shape of the chamber having the upwardly sloping floor, by controlled injection of liquid, and by controlled withdrawal of material, that is, liquid and solids contained therein, from the various levels of the liquid body in the chamber. The side walls of the separating chamber may flare outwardly, as indicated in Fig. 1. The essential and determining factor in the creation of the relatively rational hydraulic displacement in the separating chamber is, however, seen in the injection of adjusted amounts of liquid and in the controlled withdrawal of liquid from vertically successive levels of the liquid body.
ihe gates I22a may be used for selectively admitting intermixed material into the separating chamber i26, in conjunction with the bottom port I25 or with this port closed by valve I60. This mode of operation may be explained with reference to Fig. 5.
It may be assumed in this case that the operation proceeds in accordance with the principles of heavy density separation; that is, a suitable heavy density material such as sand, magnetite or pulverized ore in suspension in water is used to form the liquid separating medium. Water may again be injected into the chambers I33-I34 (Fig. 3) through the inlets I35I36 for outflow into the feed and mixing chamber, as described before. Heavy density concentrate may be added to the liquid body in the feed chamber at the top, as indicated by the letters H. D. Raw feed is supplied, as before, to the hopper I31. Mechanical agitating means, as in the previously described case, may be provided, comprising a shaft I66 extending downwardly into the feed chamber, carrying suitable paddles or stirrer arms. The shaft may be driven by suitable drive means, including, e. g., bevel gears and a drive shaft iiil, as indicated in Fig. 4. The gate I60 is assumed to be Open and the gates I22a are assumed to be partially open, as desired or necessary. The materials, i. e., water, heavy density medium and the raw coal, are agitated and intermixed in the feed and mixing chamber, and stratification is thus initiated therein. The mas of heavy density liquid carrying preliminarily separated particles leaves the feed chamber at several places, namely, through the ports formed by the gates I22a and at the bottom through the port I25. As in the former case, adjusted amounts of liquid are withdrawn by the pump 2I2 (see Fig. l) from the various levels of the liquid body in the tank through the discharge ports I43-I46. Generally laterally directed current are thus produced, as before, which extend from the various inlet ports I22a and I25 laterally to the discharge ports 243446, and since these currents exercise a classifying r separating function, they will carry along the pre-selected materials issuing from the inlet ports and cause final separation thereof. The lightest component of the material, which may be coal, will flow for discharge to the overflow I5I. Makeup water may be added as in the case before, and for the same purpose, as indicated in Fig. 5 by the correspondingly marked dotted line. Progressively heavier components of the raw feed, e, g., bony coal, slate, rock, etc., will seek successively lower discharge levels and will be correspondingly discharged through the discharge ports I4 6-I45-- I44I43, into the chambers I5II-I49I48--I4I, and then through the boots 2EIfl--2lll2fl2203 for removal by the elevators 204265208207, respectively. The lateral flow, upwardly, laterally outwardly and downwardly, as indicated by the flow lines, is regulated in this embodiment by the angularly adjustable baffle members I52 I53I54. Additional such baflie members may be provided, if desired. The operation may be carried out by discharging over the overflow impurities lighter than coal, the coal through the port I46, and heavier components as before, through the ports I45I44I43, respectively. It will be observed that the angular adjustment of the bafiies I52I54 permits skimming of the stratified flow at the proper points of stratification of the various separated products.
The use of a flow control partition, such as indicated in Fig. 2 at I58, presents additional operating and control possibilities which may be discussed with reference to Figs. 6 and 7.
Referring first to Fig. 6, the partition I58 forms the roof of the separating chamber I26 disposed underneath, and thus forms the floor of an auxiliary mixing chamber 2I5 disposed thereabove. In the auxiliary chamber 2I5 may be provided agitating means comprising a shaft I92, carrying paddles or stirrer arms as shown, which is driven by a drive I93, this drive also actuating the connecting shaft I9I for rotating the shaft I which extends into the feed chamber I23 carrying paddles for agitating the raw feed therein. Water may again be supplied through the inlets I35-I36 for turbulent outflow into the feed and mixing chamber. Heavy density material may be supplied either to the feed chamber, together with the raw feed, as before (see Fig. 5), or into the auxiliary chamber 2I5, as indicated by the arrow H. D. The lower forward end of the flow control partition I58 may be provided with a valve flap 2I6 for controlling the outflow from the bottom of chamber 2 I5 into the separating chamber I26. The valve fiap 2 I6 is assumed to be adjusted for maximum opening. The valves I22a and the valve I60 may be open as before (Fig. 5). The mass of liquid carrying particles thoroughly intermixed therewith issues'through the ports controlled by the valves I22a and through the bottom port I25 controlled by the valve I60, In this case, heavy density medium being supplied to the auxiliary chamber 2I5, and the stirrer arms carried by the shaft I92 being in operation, the liquid within the chamber 2I5 will be agitated to cause dispersion of the solids therein, including heavy density solids as well as material particles. The lightest components of the material, which is assumed to be coal, will flow to the top in the auxiliary chamber 2 I5 for discharge at the overflow I5I. Heavier components drop downwardly and move through the gate-controlled space between the lower left end of the partition I58 and the inner wall of the feed chamber into the separating chamber I25 at the bottom of the structure. The heaviest component of the raw feed issues from the feed chamber through the port I25 into the separating chamber I26 at the bottom thereof for outflow through the discharge opening I43 into the discharge chamber I 41 from which the heavies material is removed, as in the previous cases, through the discharge boot 203 and discharge elevator Bill (Fig. 4), liquid being at the same time removed through the conduit 2 H (see Fig. 4) by operation of the pump 2l2. Successively lighter components move to the vertically successive discharge ports issues-me for discharge through the corresponding discharge chambers, associated discharge boots, and elevators ace-scenes, respectively.
The material is thus agitated and roughly separated in stages, first within the feed chamber which receives the raw feed from the chute I31, and second within the auxiliary chamber 2l5. The material which is fed to the auxiliary chamher through the ports controlled by the gates IZZa is in a sense pro-selected by the rough separation or Stratification which occurs in the feed chamber 123. It will contain a preponderant amount of smaller and lighter particles, depending on the level at which it is drawn from the feed chamber. Accordingly, the material discharged through the port i25 will be mainly of heavy specific gravity seeking the low discharge level from the separating chamber I26, and the,
material coming from the auxiliary chamber 2H5 will be mainly lighter material which is added to the flow in the separating chamber at a higher level and continues toward its upwardly disposed discharge ports. Light material components that may be trapped in the material flowing down in the feed chamber or with the material issuing from the. ports controlled by the gates I220: will seek the highest level within the separating chamber lZB and willv ultimately be discharged over the overflow I5 I The operation illustrated in Fig. 7 assumes injection of water through the inlets i35l36, as before, and injection of heavy density medium into the hopper l5? for tubulent intermixture with the water therein. The heavy density liquid then issues through the port I25 for controlled upward fiow within the separation chamber I26 and adjusted outflow therefrom through the discharge ports Mfi-JM-JQE-ME. The raw material is injected, if desired, together with a quantity of makeup water, into the auxiliary chamber 215 for tubulent intermixture with the liquid therein, and outflow at the bottom through the port controlled by gate 2 i6, downwardly, into the rationally upwardly and laterally outwardly displaced heavy density flow. The raw material particles, in a state of high agitation or hydraulic mobility, are thus eased down from the turbulent liquid in the auxiliary chamber 2 I5 into the rational heavy density liquid flow in the separation chamber for separation therein. The discharge removal of the separated products proceeds generally as described before.
Flow control baffles may be provided in the separating chambers of the structures shown in Figs. 6 and, 7, as shown in Fig. '7 in dotted lines marked I52l53-I54.
Auxiliary fluid inlets shown at H0 in Fig. 2 may, of course, be provided in each of the structures illustrated in Figs. 4-7, in each case for purposes already discussed.
R's-circulation of a product withdrawn from one or more of the various levels of the separating chamber I26 may be practiced, in each instance of operation, in accordance with explanations furnished in the previously mentioned parent application.
The particular mode of operation will depend in each case on the properties of the raw mate- I0 rial to be treated; on the speciflc gravities and the sizes of the particles thereof; on the amounts to be handled within certain periods of time; on the efficienc that may be desired in any one case of operation; and on other factors that may arise in actual practice. The examples given of the various modes of operation do not exhaust the possibilities of the invention, but show its versatility and adaptability to various operating requirements and conditions.
The separation of coal'has been described to give an example. The invention may be found useful the separation or classification as to particle size of other materials, including ores.
Reference has been made to raw feed of .certain particle size and certain specific gravities to give an example. There is no inherent limitation either as to particle size or to specific gravities of the solids of the raw feed.
A multi-level or multi-product separator such as disclosed herein will be particularly useful in treating raw feed resulting in seam-mining, that is, modern machine mining as distinguished from selective manual mining, which may produce appreciable and greatly fluctuating amounts of impurities, as pointed out more in detail in Patent No. 2,513,836, issued July 4, 1950, and in co-pending application Ser. No. 697,982. The co-pending application also discloses means for controlling the relative density of the separating liquid and means for controlling the operation of the discharge elevators, which may be incorporated in the system and apparatus disclosed herein.
Changes may be made within the scope and spirit of the appended claims.
I claim! 1. A separator of the class described comprising a tank for holding a liquid body, a substantially vertically extending partition in said tank defining therein a first chamber which extends substantially vertically and a second chamber which extends laterally of said first chamber, means for injecting into said first chamber a liquid and comminuted solids for intermixture therewith, a plurality of valves carried by said vertically extending partition at Vertically disposed fixed sections thereof, means for individually adjusting said valves to effect transfer of adjusted amounts of liquid carrying said comminuted solids selectively from corresponding vertical levels of said first chamber into said second chamber, a laterally extending partition in said second chamber spaced from the bottom thereof which separates said second chamber into a lower and an upper compartment, said lastnamed laterally extending partition directing in said second chamber the lateral flow of the intermixed liquid and cornminuted solids transferred thereinto from said first chamber, valve means for adjustably interconnecting said compartments to effect transfer of liquid medium therebetween, and means for adjustably withdrawing from a plurality of vertically successive levels of said second chamber liquid and comminuted solids carried by said liquid.
2. The separator structure as set forth in claim 1, together with means for feeding comminuted solids into said upper compartment.
3. The separator structure as set forth in claim 1, together with baflle means in said lower compartment for directing therein the flow of liquid carrying solids.
4. A separator of the class described comprising a tank forming a plurality of distinct hydraulically intercommunicating chambers including (a) a liquid inlet chamber and (b) a raw material feed chamber, both of which feed into a separating chamber, means for continuously supplying liquid to said liquid inlet chamber for controlled outflow into said separating chamber, discharge means for said separating chamber including means forming a plurality of discharge ports for continuously withdrawing adjusted amounts of liquid from a plurality of levels of the liquid body therein to create a substantially rational hydraulic classifying flow which proceeds with an upward component generally laterally across the space of said separating chamber and with upwardly decreasing intensity and substantially without producing irrational turbulence and then generally downwardly for discharge from said chamber, angularly adjustable fiow deflecting means in said separating chamber for controlling and directing the rational hydraulic classifying flow therein, means for irrationally agitating the liquid body in said raw material feed chamber, and means for feeding raw material particles into said feed chamber for injection into said rational hydraulic fiow in said separating chamber and for separation therein, separated particles moving with said flow for discharge with the amounts of liquid withdrawn from corresponding levels of the liquid body in said separating chamber.
5. The separator defined in claim 4, together with valve means for hydraulically adjustably interconnecting said liquid inlet chamber with said raw material feed chamber and both said chambers with said separating chamber.
6. The separator defined in claim 4, together with overflow means formed on said tank for receiving separated particles from upper strata of said raw material feed chamber and from said separating chamber.
7. Apparatus for separating raw materials composed of heterogeneously intermixed particles in accordance with the specific gravities and/or sizes thereof comprising means forming a downwardly converging liquid inlet chamber, means forming adjacent said inlet chamber an upwardly and outwardly flaring separation chamber, valve means for establishing hydraulic communication between said inlet and said separating chambers substantially at the apices thereof, agitating means for said inlet chamber. means for supplying liquid and heavy density material to said inlet chamber and means for operating said agitating means to intermix said heavy density material with the liquid therein so as to form a substantially uniformly intermixed heavy density separating medium for out flow therefrom into and upfiow within said separating chamber, means forming a material supply chamber which is in hydraulic communication with said separating chamber, means for irrationally agitating the liquid body in said material supply chamber, and means for gravitationally feeding raw material particles into the irrationally agitated liquid in said material supply chamber for passage into the upwardly displaced heavy density liquid in said separating chamber for separation therein.
8. The apparatus defined in claim 7, together with valve means for hydraulically interconnecting said inlet chamber with said material supply chamber at a plurality of levels thereof.
9. The apparatus defined in claim 7, wherein the agitating means for said inlet chamber is a solely hydraulically operating means.
10. The apparatus defined in claim 7, together with bafile means disposed in said separating chamber for controlling the hydraulic displacement therein.
GEORGE A. AUER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 118,379 Merrill Aug. 22, 1871 934,441 Hitchcock Sept. 21, 1909 934,611 Hitchcock Sept. 21, 1909 1,449,603 Hokanson Mar. 27, 1923 1,449,604 Hokanson Mar. 27, 1923 1,459,922 Nagel June 26, 1923 1,966,609 Chance July 17, 1934 2,139,047 Tromp Dec. 6, 1938 FOREIGN PATENTS Number Country Date 47,024 Germany May 4, 1889