US1535630A - Dry concentrator - Google Patents

Description

April 28, 1925.

w. H. POWELL DRY CONCENTRATOR Filed y 17, 1924 4 Sheets-Sheet "1 .lllllllll ...l|||l|ll|||l|| llllll lllll l I l l l l I I l l| llllllll w. H. POWELL DRY CONCENTRATCR Filed May 17, 1924 4 Sheets-Sheet 2 April 28, 1925.

1,535,630v w. H. POWELL 152w cbncnnwnuon Filed May 17, 1924 as j 5 /7 April 28, 192s.

w. H. POWELL DRY CONCENTRATOR Filed May 17, 1924 4 sheets-fine 4 -Patented Apr. 28, 1925.

PATENT OFFICE.

WILLIAM H; POWELL, or. ALBUQUERQUE. NEW MEXICO.

nnY ooncnurnaroni Application filed May 17,

To all whom it may (rouccrn Be it known that I, TILL'IAMIII. Pownrm, a citizen of the United States, residing at Albuquerque, in the county of Bernalillo and Stateoi. New Mexico,- have invented certain new and useful Improvements in Dry Concentrators; and I do hereby declare the following tobe a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to a dryconcent 'ator for the treatment or concentration of pulverized ore by the utilization of air currents, The apparatus is more especially designed for the concentration of ore where water is not available.

The difierence in specific gravity between the precious metals and accompanymg gangue has been generally avalled of in all efforts to concentrate ores, One of the prerequisites of successful concentration is that the ores must first be crushed or pnlverlzed to a point where the particles of precious metal are freed from the associated gangue. This pulverization sometimes results in the presence of a substantial quantity of gold in the very finely divided form commonly known as flour gold.

The common-1v practiced wet processes oii concentration, that isto say, those in which the separation is accomplished inthepresence of water, have universally failed to effeet a saving of the liner or flour gold because of the fact that the particles thereof are so small that their capillary attraction or the presence of grease causes them to float upon the ater and be carried away with the tailings. In a less'degree' this is also true of leaf or sheet gold. g

Definite areas in this country areknown to contain gold in paying quantitiesybut the absence oi suflicient water available for concentration of the ore has resulted in these properties remaining undevelopech The present apparatus is designedto accomplish the concentration of ores by the use of air instead ofwater, thus ei'labling properties in arid regions, to be brought into production.

hentwo particles of equal volume but of different specific gravitiesare subjectedtothe samecurrent of air, the heavier will settle more quickly and closer to the source of the air current than will the lighter particle. This fact has been availed of as one their greater niomentun 1924-. Serial No. 713,975.

of the principles of operation of my apparatus. It alsois well known that if two particles of different specific gravities have the same velocity imparted to them, the heavier will have the greater momentum, since momentum is theproduct of mass times the square of the velocity. This latter fact has beent-aken advantage of in my apparatus by disposing riflled vanes at a slight angle to the direction of the air blast so that the blast will" force the material which it carries against the vanes, the precious metals having the same velocity but agreater weight thus being driven into the rifl'les because of A primary feature of the invention, generally stated, consists in providing the apparatus with a series of vanes arranged in opposed sets so as to form a passage between them for the blast of air, the vanes being inclined to the vertical so as to counteract the tendency of the air blast to be deflected downward as a result of the ore particles falling through it, and also to assist the blast to carry the load of the gangue bydefleoting the blast upward. v

A further principal. feature of the invention consists, generally stated, in providing the vanes with riflies which incline slightly backward into the blast so that their upper ends are somewhat nearer the source of the blast than are their lower ends, thereby allowing the particles caughtin the riflles to be thrown back as the carriages upon which the vanes are mounted are jigged, and enabling the material to fall freely. l p A still further feature of the invention involves the en' ploymentof a casing provided with an openinglfor introducing pulverized ore and having anoutlet for the es vcape of gangue and air, in combination with a plurality of reciprocating carriages arranged one above another within the easing andin open communication vertically, each of the ca'rriages being provided on opposite sides with a plurali y 01 vanes set obliquely to the direction of reciprocationqof the; carriages and arranged in spaced and staggered relation so vas to form tortuous passages through which the air must pass, means for reciprocating the carriages with respect to each other, and means for causing a blast of air to flow through the passages between the vanes. i a a a Another feature of the invention consists in employing a casing provided with an opening for introducing pulverized ore and having'an outlet for the escape of gangue and air, in combination with a reciprocating carriage provided on opposite sides with a plurality of vanes disposed obliquely with respect; to the reciprocation of the carriage, the vanes on one side of the carriage being in staggered relation to those on the other side and being spaced to form a passage between them, means being provided for causing a blast of air to flow through the passage between the mics, and a series of screens for separating or dispersii'ig the ore being interposed between the airriage and the opening in the casing for the admission of pulverized ore. I

Other features of the invention, residing in particular combinations of parts and advantageous structural forms, will hereinafter appear and be particularly pointed out in the claims.

In the drawings illustrating a preferred form of the apparatus,

Figure 1 is a side elevation of a dry concentrator embodying the invention.

Figure 2 is a plan view of the construction shown in Fig. 1.

Figure I) a vertical central section of the apparatus shown in Fig. 1, the reciprocating carriages and associated vanes being in eleation;

Figure t is a detail transverse section on the line 4:4-. Fig. 3, looking in the direction of the arrows.

Figure 5 is a detail vertical section on the line .3-5, Fig. 2.

Figure 6 is a detail view, partly in plan and partly in section, illustrating a preferred form of mechanism for reciprocating or jigging the carriages.

Figure 7 is a plan view on a somewhat .eularged scale of one of the reciprocating carriages with the vanes removed.

Figure 8 is a plan view of one of the carriages and its associated vanes.

*Figu-re 9 is a detail elevational view of a portion of one of the carriages and the vanes mounted upon one side thereof.

Figure it) is a detail sectional view on the line 10-40, Fig. 9.

In the drawings, 1 indicates the casing of the concentrator apparatus which may adtrates containing the values fall and from which they may be removed through a cleanout opening The end of the casing which is adjacent the ore admission opening 2 is in open eomn'iunication with one or more conduits or windways (i which preferably correspond in number to the number of reciprocating carriages with which the apparatus is equipped and which also preferably con'n'nunicate with the casing at points sul.)stantially opposite the adjacent ends of the carriages. The air blast or air current may be produced in any desired manner, preferably by means of a fan T located within a suitable housing 8 which communicates at one end with the several wind-ways (5 and is open to the atmosphere at its other end. Means are preferably provided for regulating the amount of air passing from the fan housing 8 to the respective pipes or wind ways (3, said means being conveniently forn'ied as hinged plates 9 whose pivoted ends are disposed adjacent to the neighboring walls of the wind-ways 6. as more particularly shown in Fig. 1. plates may be swung up or down and may be fixed in their adjusted positions by bolts 10 carried thereby and projecting outwardly through arcuate slots ll in the sides of the fan housing. Plates or caps 12. which are secured to the hinged deflectors 9 through the bolts 10, serve to cover the slots 1]. in the fan casing S and also act as clamps which press tightly against the adjacent walls of the fan casing and etii'ectively hold the hinged members 9 in position when the bolts 10 are tightened.

For the purpose of feeding pulverized ore the casing 1 may have mounted upon it a hopper 13 comn'uinicating with the ore admission opening 2 of the casing. The flow of ore from the hopper may be conveniently regulated or checked by means of a pair of contacting relatively movable slotted plates or grids l4 and 15, respectively, the former being movable and the latter stationary. By sliding the plate H with respect to the fixed plate '15 the openings in the two plates may be brought to such a relation as to feed pulverized ore to the casing at any desired rate or to check its [low entirely, as will be readily understood. This is not only a simple and convenientmeans for controlling the feed of the pulverized ore. but it also has the advantage of distributing the ore with substantial uniformity to the set of screens 16 by which the material to be concentrated further dispersed or disseminated. These screens are arranged below the opening 2 of the casing so as to diffuse the falling ore as it enters the apparatus and meets the first blast of air, thus enabling the air to operate effectively upon the pulverized material.

The casing 1 is preferably provided upon its opposite sides with longitudinally e.\'-

These pivoted tending horizontally disposed bars or plates 17 which project beyond the end of the casing a sutiicient distance to afiord mountings .tor the rotatable cam carrying shafts 18 by which the several reciprocating 'arriages are jigged. The side plates 17, together with the walls of the casing 1, allord extended support for "the horizontally disposed journals 19 upon which the carriage supporting rollers 20 are revolublymounted. These rollers are arranged horizontally opposite each other in pairs and their journals are preferably screwed into the sides of the alsing 1 so that they may be hm'izontally adjustable in or out for the purpose of keep ing the reciprocating carriages in proper alinement and elin'iinating any undue side play thereof. Above each pair ot rollers the casing is provided on the inside with oppositely disposed longitudi1mll ext-ending platesor filler members 21 whose inner faces are arranged closely adjacent the forward ends of the vanes so as to prevent any ot' the pulverized material carried in the blast from passingbehindthe vanes. The side rails 23 ot the reciprocating carriages Ql ex tend under the lower ends of the fillers :21 and the upper endsof said fillers associated with the two lower carriagesare preferably beveled as at 25. By this means little or no obstruction is offered to the values as they drop. i a it The reciprocating carriages which are arranged one above another within the casing and provided withoppositely disposed sets of vanes 22, are open top and bottom so as to be in vertical communication with each other. i The frame ofeach carriage may advantageously be of skeleton construction formed of parallel horizontal angle irons 23 connected by suitable transverse ln'acing strapsQti. Oblique bracing straps 2i and 28, respectively, which are connected to the side rails 23 and transverse braces 26 of the carriages, may be en'n'iloyed to form means for securely supporting th'e=" \-"anes in their assembled positions. Round headed stove bolts may convenientlybe employed for attaching the vanes to the oblique braces 27 and 28. The forward ends of the car riages may also advantageously be constructed w1th kneelbraces 29 for stitiening the ends ot'the carriageswhere pggin'g force is applied.

Irfiorder that the mechanism by which the carriages are pgged shall not interfere with arranging the air tubes or wind-ways (3 in horizontal alinement with the upper portions of thevanes 22; the side rails 23 of the carriages are spaced upwardly a short distancetron'i the lower edges of the vanes associated therewith. This desired result' may be simply eliecte'd by tornnng herfs or slots 30 in the lower edges or the several vant ,slor the purpose of receiving the transversely extending bracing. straps 26. The

upper ends of the vanes 22 may be maintained in proper relation by means of straps 31 extending between said vanes and secured thereto. a

The vanes 22, although adapted to be made of metal, are preferably of woodand may advantageously be seven sixtecnthsol an inch thick. Parallel rillles 32 are formed on the opposed or inner faces of the se'\'* eral vanes, the said riiiles preferably being small, set closely together and having their bottoms somewhat rounded so as to prevent the particles otthe values from catching in sharp angles.

The vanes 22 on each side oi. each carriage are spaced with respect to each other longitudinally of the apparatus, those on one side of the carriage being in staggered or overlapping relation to those on the opposite side. The vanes extend obliquely iir ward from the opposite sides of the carriage so as to form a tortuous passage between them through which the air passes. In addition to being angularly disposed horizontally with respect to each other the vanes on the opposite sides of each carriage are preferably inclined to the vertical so as to diverge up *ardly, the anes at one side ol the carriage being inclined to one side of the vertical and those at the other side of the carriage being inclined to the opposite side of the vertical. This setting of the vanes 22 at a slight angle to the vertical is advantageous in that it counteracts the tend en'cy of the material tailing through the air blast. to deflect the blast downwardly; it also assists the current of air to carry the load of the gangue by deflecting the blast u 'iwardly.

The jriflies 32 are inclined back "ardly into the current of air so that their upper ends are nearer the source of the blast; or, in other words. the ritiles are cut in the vanes at an angle which slightly forward of the normal to a horizontal line lying in the plane of the vane. This enables the materials caught in the l'lljllES to be thrown back as the vanes are jigged by the reciprr. eating carriages, and allows the material to fall freely. i

The reciprocating carriages provided with the vanes 22 are jigged so as to move with respect to each other by means of cams 33 carried by the respective cam shafts 18 and set one hundred and twenty degrees apart. These shafts, which are driven in unison. may advantageously be revolved by the following mechanism: [Each of the cam shafts may have secured to it one or more sprocket wheels 34- as may be required to coo ierate with suitable chain belts 35 enabling one shaft" to be driven from the other. one of'the shafts 18 being extended sutliciently to receive a belt pulley 36 For driving one of said shafts 18. The respective cams 33 preferably cooperate with cam rollers 37 journaled on the ends of thrust rods 38 which are secured at their opposite ends to the corresponding carriages 2-1. Surrounding each of the carriage actuating rods 38 and secured thereto by means of a set screw, is a collar 39 which impinges against a metallic wear plate l0 forming a facing for the checking block 4:1 secured to and extending between the adjacent side bars of plates 17 of the casing. Encircling each thrust rod and interposed between the C011'6S1')O11(ll11g collar 39 and carriage 24 is a pipe or tube forming a buffer serving to hold the collar 39 in place under the shock of the recoil of the spring a3 interposed between said collar and the bearing block 44- upon which one end of said spring rests, thus relieving the roller 37 from undue shock when the spring expands.

[n the operation of the apparatus it will be perceived that a downward flow of pulverized ore is subjected to successive blasts or currents of air which blow out the gangue or lighter matter. The larger particles of the precious metal, which because of their malleability have not been pulverized to as great fineness as the gangue, readily separate themselves from the latter and fall through the air blasts into the bin at the bottom of the casing. Such *alues as may be carried by the blasts along with the gangue will be forced against the successive vanes and thus be separated out of the blast and work downward so as to be deposited in the bin.

In the particular form of apparatus illustrated in the drawings the pulverized ore is operated upon by three similar sets of :arriages 24.- with their associated rifiied vanes 22. the lower carriages being slightly advanced successively in the direction of the blast. The values held in the rifiles of the vanes of the uppermost carriage are worked downward as the carriages are jigged. As the values pass to the set of vanes on the carriage next below, the process is repeated, the values are further cleaned of gangue and more of the latter is carried off by the air. These operations are repeated through the vanes on the lowermost carriage, so that the concentrates containing the values finally fall into the bin a at the bottom of the apparatus while the gangue is carried away by the air and passes out of the apparatus through the opening 3 in the casing.

The presence of fine or flour gold in the pulverized ore may be met in operation either by classification or by the reduction of the entire aggregate to the point where the particles of the gangue are the same or approximately the same value as the gold. Greasy or rusty gold may be effectively treated by the apparatus, since water is not used in the process and particles of that character, or course, maintain their relative specific gravity with respect to the gangue particles.

In operating the apparatus the strength of the air blast should be suited to the rate of flow of the pulverized ore, the fineness to which it has been ground, and the presence therein of values in a very line state. (lenerally speaking, the finer the ore can he successfully pulverized the better the concentration that can be accomplished; but it is to be observed that there is a point of din'iinishing return beyond which it is unprofitable to go because the cost of more finely pulverizing ore will not be warranted by the additional return. The drier the ore the more etliciently the concentrator will perform its functions, and it is highly desirable that the presence of any considerable amount of moisture in the ]')ulverized ore be avoided. In order to obtain the best results it is preferable to treat each individual ore by itself and to the carriages at the rate found most suitable for the air blast applied to a given How of the pulverized material. It has been found that jigging the carriages 2st at rates 'arying from ten to sixty strokes per minute, depending upon the rate of flow of the ore and its character, iroduces satisfactory results.

lVhile I have shown and described a particular embodiment of the invention, it is to be understood that I do not intend to limit myself to precise details of construction, but regard the scope of my invention as being broadly defined by the following claims.

I claim 1- 1. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a reciprocating carriage within said casing provided on opposite sides with a plurality of vanes disposed obliquely to the direction of recipro cation of said carriage, the vanes on one side of the carriage being in staggered relation to those on the other side, and means for causing a current of air to pass through said casing between said vanes.

2. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a series of vanes within said casing spaced from each other and disposed in over-lapping relation so as to form a passage between them, some of said vanes being inclined to one side of the vertical and some being inclined to the other side of the vertical. and means for causing a current of air to pass through the passage between said vanes.

S A dry concentrator involving a casing provided with an opening touintroducing pulverized ore and having-an outlet for the escape or gangue and air, a series of vanes within said casing, said vanes being arranged in oppositely disposed sets forming a passage between them, the vanes of one set being angularly disposed both vertically and horizontallywithrespect to the van-es of the other set, and means for causing a current oi? air to pass through the passage between said vanes. a a

-.l:. A dry concentrator involving a, casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a series of vanes in said casing arranged in opposed sets spaced to provide a passage between them, the vanes of each set being substantially parallel and disposed in spaced relation and the vanes of one set being staggered with respectto the vanes of the other set, the vanes 01: each set forming an oblique angle with the *anes of the other set and. the said sets of vanes being inclined to the vertical so as, to diverge upwardly, and means for causing a current of air to pass along the passage between said set of vanes.

5. A dry concentrator involvinga casing provided with an opening for introducing pulverized ore and having an outlet for the escape oii gangue and air, of a series of vanes arranged in opposed sets spaced to afford a passage between them, and means for causing a current of: air to pass through said passage, the vanes oi cachset being obliquely disposed with respect to the vanes of the other set and the vanes of the respective sets beinginclined to the vertical so as to diverge upwardly, each of said vanes being provided with a plurality of riflies which are inclined backwardly into said current of air.

6. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gaugue and air, of a series of vanes arranged in opposed sets ail'ording a passage between them, and means for causing a current of air to pass through said passage,

each of the 'vanes being provide-d with a plurality of parallel rifiles, the vanes oi? one set being obliquely disposed with respect to the vanes oi the other set and the vanes of both sets being inclined to the vertical so as to diverge upwardly, and the said riflies being inclined backwardly into said current ot' a ir so that their lower ends arein advance of their upper ends.

7. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet forthe escape of gangue and air, .a reciprocating carriage provided on opposite sides with a plurality of vanes disposed obliquely to the direction of reciprocation of said carriage,

thevanes on one side oi said carriage ex tending at an angle to those on the other side, means interposed between said carriage and said ore admission opening in the casing torspreading said pulverized ore, and means for causing a current of air to pass through said casing between said vanes. i

81A .dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages each provided on opposite sides with a plurality of vanes dis-v posed obliquely to the direction of recipro cation of the said carriages, the vanes on one side of each cz'irriage being in staggered relation to the vanes on the other side o'fithe same carriage, and means for causing air to pass through said casing between the vanes of the several carriages.

9. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages each provided on opposite sides with a plurality of vanes disposed obliquely to the direction of reciprocation ot said carriages, said vanes also be iug inclined to the vertical, means for reciprocating said carriages to cause them to move with respect to each other, and means tor causing air to pass through said casing between the vanes and said carriages.

10. A dry concentrator involving a casing provided "with an opening for introducing pulverizedore and having an outlet for the escape .otair and gangue, a reciprocating carriage within said casingprovided on opposite sides with a plurality of vanes disposed obliquely to the direction of reciprocation oi. said carriage, the vanes on one side of the carriage being in staggered relation. to those on the other side so as to form a tortuous passage between them, and means for causing a current of air to pass along said passage.

11. A dry concentrator involving a casing provided with anopening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages arranged one above the other within said casing, said carriages being open vertically so as to communicate wvith each other and each being provided, with a series of vanes spaced from each other and disposedfin overlapping relation so as to form a passage between them, some of the vanes on each of said carriages being inclined to one side of the vertical and some being inclined to the opposite side of the vertical, means for reciprocating said carriages so as to cause them to move with relation to each other, and means for causing air to pass through said casing between said vanes.

.12. A dry concentrator involving a casing provided with an'opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality oi reciprocating carriages having closed sides and open at top and bottom, each of said carriages being provided on opposite sides with a plurality of vanes disposed obliquely to the direction or reciprocation ot the said carriages, the vanes on one side of each carriage being inclined to one side of the vertical and those on the other side ot the same carriage being inclined to the other side of the vertical, and means for causing a current of air to pass through the casing between said vanes.

13. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages arranged one above another within said casing and in open communication vertically, each of said carriages being provided on opposite sides with a plurality of vanes disposed obliquely to the direction of reciprocation of said carriages, the vanes on the opposite sides of each carriage t'orniing a tortuous passage between them, means for reciprocating said carriages so as to cause them to move with respect to each other, and means for causing air to pass through said passages between said vanes.

l-t. A dry concentratm' involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a reciprocating carriage provided on opposite sides with a plurality of vanes disposed obliquely with respect to the direction of reciprocation of said carriage, the vanes on one side ot the carriage being in staggered relation to those on the other side and being spaced therefrom so as to form a tortuous passage therebetween, a series of screens interposed between said carriage and the openin in said casing tor the admission of pulverized ore. valve means for controlling the delivery ot pulverized ore to said screens, and means for causing a current of air to pass through the passage between said vanes.

15. A dry concentrator involving :1 casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages arranged one above another within said casing and in open communication vertically with each other. a. series of anes mounted upon each of said carriages, said vanes being provided with riflles and being arranged in oppositely disposed sets forming a passage between them. the vanes of one set being angularly disposed both vertically and horizontally with respect to the "anes ot the other set. means for reciprccating said carriages so as to move them with respect to each other, and means for causing air to pass through the passages between said vanes.

16. A dry concentrator involving a casing I provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of relatively movable reciprocating carriages arranged one above another within said casing, each of said carriages being provided with a plurality of oppositely disposed 'anes having rifl'les, said vanes on each carriage being arranged in oppositely disposed sets forming a nissage between them, the vanes on one side of each carriage being disposed at an angle to those on the other side of the same carriage, means tor reciprocating said carriages so as to cause them to move with relation to each other, and means for introducing air currents into said casing substantially opposite the corresponding ends of each of said carriages.

17. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air. a plurality of reciprocating carriages open at top and bottom and arranged one above another within said casing, each of said carriages being provided with opposed sets of ri'llled vanes spaced to provide a passage between them, the *anes of each set being in spaced relation and the allies of one set being staggered with respect to the vanes of the other set on the same carriage, the sets of vanes on each carriage being inclined to the vertical. so as to diverge up *ardly. n'ieans for reciprocating said carriages. and means for causingair to pass through the passages between said vanes.

18 A dry concentrator involving a 'asing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality o't' re ci1r rocating carriages arranged one above another within said casing. said carriages being open at the top and bottom and each being provided with a plurality ot 'anes arranged in opposed sets affording a passage between them, means for reciprocating said carriages so as to cause them to move with respect to each other. and means for causing air to pass through said passages between said vanes, the vanes of each set on each carriage being obliquely disposed with respect to the other set on the same carriage and the allies of both sets on each carriage being'inclined to the vertical so as to diverge upwardly, and each of the vanes being provided with a plurality of ritlles which incline backwardly into said current of air so that their lower ends are in advance of their upper ends. I

19. A dry concentrator involving a casing provided with an opening for introducing pulverized ore and having an outlet for the escape of gangue and air, a plurality of reciprocating carriages open at top and bottom and ar 'anged one above the other Within said casing, means interposed between the uppermost carriage and the ore admission opening in the casing for spreading the pulvized ore, each of said carriages being provided with a series of vanes arranged in opposed sets forming a passage between them, means for synchronously reciprocating said carriages so as to cause them to move with respect to each other, and means for intr0- ducing'currents of air into said casing substantially opposite the corresponding ends of said carriages, the vanes of each set upon each carriage being obliquely disposed with respect to the vanes of the other set on the same carriage, the vanes of the respective sets on each carriage being inclined to the vertical so as to diverge upwardly, and each of said vanes being provided with a plu' rality of riflies which incline backwardly toward the air currents so that their lower ends are in advance of their upper ends.

In testimony whereof I atliX my signa ture, in the presence of two subscribing \vitnesses.

fitnesses E. L. FLANERY, M. Vixen.

WILLIAM H. POWELL.

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