US1741498A

US1741498A - Continuous-settling apparatus

Info

Publication number: US1741498A
Application number: US265793A
Authority: US
Inventors: Samuel I Bousman
Original assignee: Dorr Co
Current assignee: Dorr Co
Priority date: 1928-03-29
Filing date: 1928-03-29
Publication date: 1929-12-31
Anticipated expiration: 1946-12-31
Also published as: NL36038C; BE357812A; GB308770A; DE569289C

Description

s. l. BOUSMAN CONTINUOUS SETTLING APPARATUSy Dec. 31,1929.

5 Sheets-Sheet l Filed March 29, 1928 Dec. 3l, 1929.

S. l. BOUSMAN CONTINUOUSl SETTLI NG APPARATUS 3 Shets-Sheet 2 Filed March 29, 1928 Dec. 3l, 1929. s. l. BOUSMAN CONTINOUS SETTLING APPARATUS Filed March 29, 1928 v 3 sheets-sheet Patented Dec. 3l, 1929 UNITED STATES PATENT oFFI'cE SAMUEL I. BOUSMAN, OF DENVER, COLORADO,- ASSIGNOR TO-THE`DORR COMPANY, OF

NEW YORK, N. Y., A CORPORATION OF DELAWARE coNTINUoUs-sE'r'rL'ING Arranriri'rs.4

Application led March 29, 1928. Serial No. 265,793.

This invention pertains to apparatus for 4sweeping non-circular areas with a continuous rotary movement, and 1s especially adaptedfory use in sedimentation apparatus such as clarifiers where settled solids are swept to a point of discharge. It is frequently desirable tolemploy clarifier tanks differing from the old round shape, rectangular tanks being usuallyv preferred; but the removal of solids from the corners of such tanks, especially where the solids are heavy' as in metallurgical operations, presents a dify ficult problem. Drag Scrapers are subject to excessive wear and the submerged bearings are a constant source of trouble; while rotary mechanisms heretofore successfully used in practice are of the articulated type which with some materials requires periodical replacement of the submerged wearing partst necessarily employed. y i

The general object of this invention is to provide sweeping mechanism for the purpose indicated which is entirelyfree from submerged wearing surfaces or bearings, and is adapted to move heavy solids continuously to a point of discharge. Furthermore, the preferred arrangement is suitable for practical construction in the larger sizes sometimes required in sedimentation operations, clarifiers of two hundred feet in' diameter being now in operation.

It is likewise, desirable, according tomodern practice, to eliminate the bridge-like superstructures generally used for supporting the mechanism; and the present inven,

tion is adapted for support and drive without the use of a superstructure. It is also advantageous to employ peripheral drive on larger units, since for efficient sedimentation the linear speed of the outer end of the sweeping arm .must not exceed a predetermined rate, as higher speeds will produce agitation which will disturb sedimentation. It is extremely/` diiiicultto provide the lproper peripheral speed with a central drive in clariiers of large size; while peripheral drive with a nonround clarifier tank has heretofore been considered impracticgl. This problem has been solved by the present invention, permitting the construction of rectangular clariiers in the large sizes employing'peripheral drive.

The arrangement however involves serious secondary problems, including the` provision ofa suitable central support,^proper electrical connections which should extend from a ery of the tank, additional raking capacity near the center of the clarifier,- and adjustability to the inevitable irregularities in the supporting and guiding means around the periphery of the clarifier.

In general the present invention contemplates the usel of a sweeping member supported and guided at oneI end by means extending around the periphery of the tank and which may follow a periphery of any desired contour: The other end of the sweeping member 1s supported inthe in rior ofthe tank, preferably at the center by cans permitting both reciprocation and rotation; and for larger units the support should be a" central pillar mounted Iin the clarifier. An independent central sweeping or raking device may also be rotatably mounted in the clarilier, and may be operated by the mainsweep.

This construction in turn involves many secondary problems of supportin and arranging the parts. The preferre embodiment of the invention is set forth in the following description taken in connection with the accompanying drawings, in which Fig. lis a plan view of a sedimentation apparatus or clarifier embodying the invention; Fig. 2 is a transverse vertical section on-line 2--2 of Fig. l, the sweeping or raking mechanism being shown in' side elevation;

' ners. The feed enters through feed launder 11y and passes through inlets .12 into the clari- .The sweeping device, which in practice is t usually referred to asa rake, includes a main reciprocating rake unit supported and guided at its outer end along the periphery of the clarifier, and'supportecl and guided adjacent its inner end at a point which preferably is at the center of the clarifier, by means which permits the unit to slide inwardly and outwardly in conformity with the movements of the outer end of the unit, while also permitting the necessary rotary movement. Though a considerable variety of supporting structures ,for this purpose may be employed, the preferred form includes theuse of a pillar 15 in approximately the center of the clarifier, with a suitable structure permitting bothreciprocation and rotation ofthe rake unit mounted on the upper end of the pillar. The latter also supports an auxiliary rake unit rotating with the main rake lunit and adapted to sweep the central portion of the clarifier. The solids are carried by these units to a suitable discharge which should be located adjacent the center of the clariiier, and may conveniently include a gutter 16 about the base of the pillar 15, and an underflow discharge pipe 17 communicating with the bottom of the gutter.

The main rake unit comprises in general a framework, raking means on the bottom thereof, supporting means on the inner end, and supporting and driving means on the outer end. The framework in the form illustrated comprises a truss 18 having spaced upper members 19 and spaced lower members 20, suitably interconnected and braced. Rakes. 2l are mounted on its lower members 20, preferably comprising vertical blades set at an angle to the direction of travel of thetruss 18 and positioned to sweep toward the center solids which have settled on the clarifier bottom. These rakes.may be constructed and arranged in accordance with standard practice, and ma be of any known type, the invention not eing ,restricted to the luse of a series of separate rakes'. The rakes should extend along the bottom of truss 18 from a position adjacent the tank margin for a distance suiiicicnt to provide suitable overlap with the auxiliary rakes during the entire cycle of rotation. l

The supporting and driving unit 1s shown best in Figs. -3 and l. The. arrangement illustrated includes a framework carrying the end of the truss 18 and supported by roller means on a suitable track 22 which passes around the periphery of the tank, and may be bridged over the feed inlets and the discharge for .supernatant liquid. A self-containedV electric motor drive unit is included, preferably engaging the supporting roller or wheel;

and means also is provided for engaging `the track 22 or other suitable structure for moving the truss 18 back and forth over the pillar 15. -f

The supporting frame includes a bed plate 23 on which the truss 18 is supported .as by mounting the upper member 19 on opposite ,j

ends of the bed plate 23. An electric motor 24 is also mounted on the bed plate and is connected by belting 25 to pulley 26 on Worm 27 which drives worm gear 28 whose vertical shaft 29 carries at its lower end a bevel gear 30 meshing with a bevel gear 31 suitablycon-4 nected to a supporting and driving roller or wheel. An upper housing-32 mounted on the bed plate 23encloses the worm 27 and worm gear 28 including suitable bearings for both, and preferably of the completely enclosed type adapted to cant. The bevel gear -30 projects from the lower part of the upper housing 32.

The supporting and guiding parts arev mounted on a carriage 33 which should have pivotal movement relative to the bed plate 23. For this purpose the upper part of the carriage 33 includes a roller race 34 formed between suitable annular surfaces on thelupper face of the carriage 33 and the lower face of the bed plate 23, in which a suitable series of rollers 35 mounted in rings 36 in the usual manner. is provided, the rotary myement be filled with a suitable lubri\ being restricted to a fixed axis by a/'suitable v means, such as the circular flange 37 on the bed plate 23 engaging a circular recess 38 in the carriage 33.

For obtaining adequate traction it is preferable to employ the supporting roller for. traction purposes; and in the form shown this is conveniently accomplished by employing a roller 39 integral with the hub-.of gear 31 and having a wearing shoe 40 resting on the track 22. The roller 39, and of course the gear 31, are mounted on a shaft 4l carried in 'suitable bearings 42 in the carriage 33.

Means is also provided on carriage 33 for resisting lateral movement as the carriage moves the adjacent end of the truss toward or from the pillar 15. This preferably comprises means such as rollers engaging opposite sides of the track 22, whichnay consist of standard railroad rails. tion shown guide rollers 43 are mounted in pairs on opposite sides of the track 22 at each end of the carriage 33, adapted to engage the sides of the track, the rollers of each pair being suiiiciently spaced from the track to permit the necessary curvature of same when rounding the corners of the clarifier.

The -construction for supporting and guiding the inner end of the main rake truss 18 and for supporting and rotating the auxiliary rakes, is shown in Figs. 5 and 6. ln general, this arrangement includes a sliding support permitting reciprocationof the truss 18, a rotating support for said truss, a rot-ating In the construci support for the auxiliary rakes, and an actuating connection between the auxiliary rake support and the parts rotatedr by the truss 18. In the construction shown a spider 44 is mounted on the upper end of pillar 15 and carries a circular track 45 on which is mounted the revolving head indicated generally at 46, which mayv include an outer frame ring 47 having an annular bearing flange 48 resting on thetrack 45, a suitable lubricant belng' provided between track 45 and the flange 48.

A supporting frame 75 for the truss 18 ispivotally mounted on opposite sides of the head 46, as by means of pivot shafts 49 extending through bearings in the frame ring .47 and mounted on-the side members 50 which with the end members 51 form a' rectangular supporting frame for the truss 18, the frame being of suliicient size to clear the head 46. The truss 18 is'supported by the frame in suitable-manner, as by means of rollers 52 carried by shafts 53 mounted in the frame.

A suitableV track is provided in connection with the upper members 19 of the rtruss 18.

for supporting the latter on the rollers 52.`

This track may consist of a channel 54 resting on each pair of aligned rollers and connected as by plates.55, angle 56 and plates 57 with the truss member 19. The rollers 52 have flanges 58 bearing against the inner faces of the channel tracks 54 to ensure rotation ofthe frame 'with the truss 18.

Itis desirable to provide electric drive connections'for the motor 24 from the pillar 15. While such connections may be accomplished in various ways, including the use of flexible wiring, a preferred arrangement is illustrated, which includes sliding contacts between fixed conductors on the pillar v15 and the rotating head 46, and sliding connections between conductors on the head 46 and coliductors on the truss 18v which reciprocates relatively thereto. While a considerable variety of constructions may be employed, the form illustratedl includes an inner frame ring 59 connected to the outerv frame ring 47 by an annular top plate.60, the ring 59 prefer.

ably including also inner bearings for the pivot shaft 49. A series of bus rings 61 mounted on insulation 62 on the inner face of the-frame ring 50 contact with a series of 'brushes 63 connected to wires passing downwardly through the cable 64 in the pillar 15, v

the brushes being mounted on an annular plate 65 resting on the spider 44 and .extend-A `being covered by a hood 70. The brushes 67 contact with. a vertical series of bus bars 71 mounted on a block of insulation 72 carried by a channel 54. A suitable cable .73 running along a top member 19 of the truss 18 connects the bus bars 71 with the motor 24.

Auxiliary raking means may be provided for raking the central portion of the clarifier both for the purpose of raking portions of theV bottom not conveniently covered by the main `rakes 21, and. because of the substantially greater proportion of solids near the center of the clarifier, normally requiring additional raking to preserve the propereven travel of the solids to the central discharge. The auxiliary rakes may conveniently be supported from and actuated by the frame 75 or equivalent connections to the rotatin head 46, whichV is automatically revolved y the truss 18. In'the form shown four auxiliary rake arms are provided, including a long arm 74 extending in a direction generally opposite to that of the truss 18g a short arm 76 extending under the truss 18 and side arms 77 spaced between the arms 74 and 76. These arms are mounted onvv any suitable framework such as a rectangular bottom frame 78 to which the arms are directly attached; hangers 79 connecting the bottom frame 78-with the frame 75, preferably connecting 7with the end lmembers 51 ofv the latter; and suitable brac- It is preferable in most cases'to provide the raking zone, of the auxiliary rakes with a slight slope toward the gutter 16, forming a central cone 81; and to employ a relatively flat surface 82 from the cone 81 tothe pel lla() riph'ery ofthe tank, over which the rakes 20 are operative. When. this construction is employed the auxiliary rake 76 and the adj acent portions of thev truss 18 are arranged so that the latter may slide in and out over said rake; but if desired all auxiliary rakes lying inthe path of reciprocation of the rakes 21 may be dispensed with, in which case the use of a slope in the cone area 6l is optional, de# pending upon the material treated. It should be noted that while the cone 81 is shown as extendingkover a relatively small part of a clarifier area, this is for purely illustrative-purposes, as it may be extended as far as desired toward the sides of the tank, the primary function of the truss 18 being to scrape the corners of the tank in a zone outside of a circle drawn from the axis of rotation'of the truss as a center with the distance to the nearest point on the sidewalls of the clarifier as a radius. v y

In operation the motor 24 is started by connecting the cable 64 with a suitable source ofeletricity (not shown) starting the motor 24 which through theintermediate gearing described rotates the roller 39, propelling the carriage 33 along the track 12. As the carriage 33 travels awav from the pillar 15 it is held on vthe ltrack 22 -by rollers 43, pulling the truss 18' outwardly, the channel tracks 54 traveling over rollers 52 and rotating frame 75 and head 46 through engagement with the flanges 58 of said rollers. The auxiliary rakes 74, 76 and 77 are rotated over the cone l88 with the frame 75, while` the rakes on .truss 18 ysweep the plane surface 82'cont1nul ously.' As the carriage 33 approaches a corner guide rollers 43 cause carriage 33 to follow the track, the relative rotation betweensaid carriage andthe bed plate 23 beingtaken up by' the bearing rollers 35; and rollers 43 vengage the inner sideof-the track as the carriage33- approaches the pillar 15, the truss 18 rolling inwardly on rollers 52. It is extremely diflicult to lay the track 22 either' in perfect ali nment or in a true horizontal posit-ion; but 1t will be appareht that any defeet in radial alignment is immaterial' since the carriage 3 3. will follow a track of any contour and the truss 18 isl free to move radially with the carria e; while minor variations in the level of t e track are -accommodated by the pivotal sup ort ofthe frame 75 carrying the truss 18. ince the rollers 52 need not be positioned so that the rakes 21 will have reciprocating movementin a horizontalkdirection, the surface 82 likewise is not restricted to the horizontal; and it is well recognized that in certain fields of use aslope toward the center may be of Value.

The clarifier o cratesl in the usual way,

l with a steadyy Vgra ual lo'w vfrom feed to overflow, which in the form illustrated involves a flow across the entire tank from one side to another, although other arrangements of eed'and overow are well known and may be employed; The solids settling'on the bottom are carried by the rakes 21 to the cone 81, and

are then carried by the rakes 21-a to the discharge gutter 16, `from which they flow through outlet pipe 17, being assisted if de-y sired by scrapers83 mounted on the auxiliary 'rake arms and extending into and across.

the gutter adjacent the walls thereof.v

While this invention has'been described as applied to a square' tank for .which itis pri! marily adapted, it will be apparent that it may also be fitted into tanksvvarying widely in contour, and .that thel mechanism may readily tbe 'installed in existing rectangular tanks whose dimensions do not vary too radi? cally from lthe square. Furthermore, while the invention is primarily designed forA sedimentation purposes, Vfor which purpose it is `a. continuous sweeping movement over a nonround surface or zone may be required; and the apparatus itself is capable of actuation at a speed which may be utilized for stirring or other operations under proper conditions. It should also-be recognized that while peripheral drive and a central support from the bottom of the tank are both considered pref erable, itis possible 'to' dispense with either of these features under suitable conditions which will be apparent to those skilled in the art.

I claim: f

l. Apparatus for sweeping a peripheral zone of a non-circular area including a sweeping member, means for guiding the outer end of the member along the periphery of the area, a support on which the inner end 'of the member is mounted by means permitting reciprocation of the member relative to the support,',`and means for driving the member.

2. Apparatus for raking a peripheral zone of the bottom of a non-circular sedimentation tank including a raking member, means for guiding the outer end of the member along the periphery of the tank, a support on which the inner end of the member is mounted by means permitting reciprocation of the member relative to the support, and means for driving the member.

3. Apparatus for raking a peripheral zone ported, and means for driving the member. .u

A 5. Apparatus for raking a peripheral zone of the bottom of a non-circular sedimentation tank including a raking member, means for of the bottom of a non-circular sedimentation A.

guiding the outer end of the member along the periphery of the tank, a support, a rotatableiele'ment on the support on which the inner end of the raking member is slidably mounted, and driving connections between said memberand element.

6. 'Apparatus for raking a peripheral zone of the bottom of a non-circular sedimentation tank including a raking member, means ,for guiding the outer end of the member along the periphery of the tank, a support, and a rotating element on the support including supporting means at opposite sides of the axis of rotation on which the inner end of said member is'slidably supported.

port, a frame rotatably mounted on the track, and sliding supporting bearings on oppositev sides of the axis of rotation of the frame engaging the inner end of the member.

9. Apparatus for raking the bottom of a non-circular`sedimentation tank including a raking member, means for guiding the outer end of the member along the periphery of the tank, a support, a rotatable element on the support and roller bearings supporting the inner end of the raking memberon said element, said roller bearings being rconstructed and arrapged to permit Vertical 4movements ofthe inner end ofthe member corresponding to vertical movements of the outer end of said member during travel around the periphery of the tank.-

l 10. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, means'y for guiding the outer end of the member along theperiphery of the tank, a support, a revolving head mounted on thesupport for rotation about a fixed axis, supporti/ng means movably mounted on the head,- and means forl slidably supporting the inner end of the member upon said`support- I raking member, means for guiding the outer ing means.

11. Apparatus for raking the.bottom of a non-circular sedimentation tank including a end ofthe member along the periphery of the tank, a support, arevolving head mounted on the support for rotation about a iixed axis, supporting means pivotally mounted on the head, and means for slidably supporting'the inner end of the member upon said supporting means. v

12. Apparatus for raking the bottom of Ura non-circular sedimentation tank including'a raking member, means for guiding the outer endof the member along the periphery of the tank, a support, a revolving head mounted on the support for rotation about a fixed axis,

and supporting means pivotall-y mounted on the head at opposite ysides thereof.

13. Apparatus for raking kthe bottom of noncircular tanks including a raking member, means for guiding the outer end of themember along the periphery of the tank, a central pedestal support in the tank extending above the li uid level, means for mounting the inner en of the member on said suptank, and means `for supporting theinner end of the member within the periphery of the tankl permitting reciprocation of said inner end, one of said supporting means including a single point of support transversely of said member, and the other supporting meansv comprising -at least two points of support transversely of said member, the construction being such that a three point support arrangement is provided permitting said member to adjust its transverse position to the relative positions of the supports at all points during rotation of said member.

1 5. Apparatus for sweeping the bottom of non-circular sedimentation tanks including a raking member, means for guiding the'outer end of the member along the peripheryl of the tank, a single roller supporting saidu outer end, a support for the inner end of the memi ber, and'means for supporting said inner end upon the support at two points spaced horizontally transversely of the member..

16. Apparatus for raking a peripheral zone of the bottom of a non-circular sedimentation tank including a raking member, means for guiding the outer end of the member along the periphery 'of the tank, a support on which the inner end of the member is mounted by means permitting reciprocation of the member relative to the support, and means at the outenend of'said member for propelling said outer end along the periphery of the tank.

17. Apparatus for raking a peripheral zone ofthe bottom of a non-circular sedimentation tank including la raking member, means for guiding the outer end of the member along the periphery of the tank, a support on which the inner end of the member is mounted by means permitting reciprocating of the member relative to the support and electrical means at the outer end of said member for propelling said outer end along the periphery the peripheryof the tank, a support on which the inner end of the member is mounted by" means permitting reciprocation of the member relative to thsupport, electricaldr'rving means at the outer end of said member for propelling said outer end along the periphery of the tank and electrical connections extending from said electrical driving means along said member and said support,

tions mounted on the member and said rotating element.

20. Apparatus` for raking the bottom of a non-circular sedimentation tank including a raking member, a support, a rotating element on the support on which the inner end of the member is slidably supported, electrical driving means at the outer end of the member for propelling said end along the periphery of the`tank, and electrical connections to saiddriving means extending along the member and including sliding connections mounted on saidrotating element and support.

2l. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, a support for the inner end of the member, a track extending around the periphery of the tank, means for supporting the outer end of the member, and means on said member engaging opposite faces of the track to guide the outer end of the member along vthe/periphery of the tank.

v 22. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, a support for the inner end of the member, a trackway extending around the periphery of the tank, a drive frame on.

the outer end of the member, drive means on the frame, a roller'supporting said frame and traveling along the track, and gearing connections between the drivel means and the roller. 1

23. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking membera support for the inner end outer end of the of the member a supporting roller for the member traveling around the periphery of the tank, a carriage on which the rolleris mounted, and al rotatable bearing supporting-the outer end of said'member on -the carriage. 'V y 24. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, a supportdor the inner end of the memberfa supporting roller lfor the' outer end of the member traveling around the periphery-of the tank, a carriage on which. the roller is mounted, a drive frame on the outer end of the member, drive means mounted thereon, av rtatable bearing supporting the drive frame on the carriage, and drivin connections between the driving means and the roller.

25. Apparatus for raking the bottom yof a non-circular sedimentation tank including a raking member, a support for the inner end of the member, and means for su porting and driving the outer end of the mem er` along the lperiphery ofthe tank including a s pporting roller adapted to travel along the periphery, a carriage on which the roller is mounted, an annular roller bearing track on saldcarriage on Which the outer end of the member is supported, and drive means on said outer end 4connected to the roller.`

26. Apparatus for raking the bottom of a lnon-circular sedimentation tank including a raking member, a support for the inner end of the member and means forsupporting and driving the outer end of the member includ-- ing a rollei` adapted to travel yalongthe p eriphery of the tank, a carriage on Which said roller is mounted, "a gear connected to said roller and carried by the carriage, a bearing on said carriage on which the outer end .of the member 1s freelysupported Aand drive gearing on said outer end engaging the 'gear on the carriage, the construction being such that said carriage and the outer end of the member are freely separable `by relative Vertical movement. y 27.. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, a support for the (inner end of the member, and means for supporting and guiding the outer end of the membei' along the periphery, a roller on the track, a carriage carrying said roller and mounted on the outer en d 0j the member and aplurality of pairs of guide rollers mounted on the carriage andv Aengaging opposite faces of the track, the adjacent faces of the/rollers of each pair being spaced apart a distance sufficiently in excess of the transverse dimensions of the track adjacent the corners of thetank to com-,1v

pensate for thecurvature ofthe `track at such 28. AApparatus. yfor raking'the bottom ofia^ non-circular sedimentation tank including a raking member, means for supporting and guiding said member over the peripheral .por-

tions ofthe tank bottom and means forl rak-l.

'central portion of the tank bottom and driv( 120 ing connections between said member and the means for raking the central portion.

30. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, means for guiding the outer end of the member along the periphery of the tank, a support, central raking means mounted on the support, and means for supporting the inner end of said member on the central raking means.

31. Apparatus for raking the bottom of a l non-circular sedimentation tank including a raking member, means for guiding the outer end oi' the member along the periphery of the tank, a pedestal support on the bottom of the tank, central raking means rotatably mounted on said support above the Water level, and

means for slidably supporting the inner end of the raking member on said central raking means.

32. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, means for guiding the outer end of the member along the periphery of the tank, a support, central raking means rotatably mounted on the support, means for slidably mounting the inner end of said member on the support, and driving connections between said inner end and said raking means.

33. Apparatus for raking the bottom of a non-circular sedimentation tank including a raking member, means for guiding the outer end of the member along theperiphery of the tank, a support, a frame rotatably mounted on the support, meansfor slidably supporting the inner end of the member on the frame and raking means depending from the frame.

34. Apparatus for raking lthe bott-om of a non-circular sedimentation tank including a l raking member extending radially in said tank to the periphery thereof means for impelling said member along the periphery of the tank in a non-circular path to rake a peripheral zone in said tank7 and central raking means raking the circular zone 1n said tank Which includes the entire inner margin o said peripheral zone, the construction being' such that the entire bottom of said tank is raked by saidv raking member and central rakf ing means.

35. Apparatus for raking the bottom of a non-circular sedimentation tank including a raklng member, means for impelhng said member along a non-clrcular peripheral zone on the bottom of the tank and central raking means in said tank extending beneath the path of said raking member.

36. Sedimentation apparatus including a non-circular sedimentatlon tank having' a bottom comprisinga conical circular central portio'nfand a flat peripheral portion extending fromthe central portion to the periphery of the tank; rotating raking means traveling over the central'portion and rotating raking means traveling overthe peripheral portion of the bottom.

In testimony whereof I aliX my signature.

SAMUEL I. BOUSM'AN.