US2261487A - Sedimentation apparatus - Google Patents

Description

Nov. 4, 1941. c. H. scoTT ETAL SEDIMENTATION APPARATUS Filed Deo. 8, 1958 4 Sheets-Sheet 2 .MLU-n ATTORNEY.

Nov. .4, 1941. c.' H. SCOTT ETAL 2,261,487

SEDIMENTATION APPARATUS y, INVENTORS 1 CHA/afs H. 56077, Jo///v QA/0M?,

bloes- ATTORNEY.

Patented Nv.4, 1941 f sEmMENrArroN APPARATUS Charles Harold Scott, Westport, Conn., and John P. Kolb, Queens Village, N. Y., assignors to l'Ihe Dorr Company, Inc., New York, N. Y., a corporation of Delaware Application December 8, 1938, Serial No..2`44,506

4 Claims.

The invention is in fields relating to -thickeners, clariers or similar sedimentation apparatus embodying a cornered non-circular basin or tank and an associated sedimented impelling and transfer assemblage that is horizontallyturnable about a vertically-extending main axis and which comprehends (l) a main raking mechanism movable in closed circular paths over a circular section ofthe tank bottom and-adapted for transferring sedimented material from diverse portions of the circular bottom section of the tank to a sediment-discharge means leading from a lower interior portion of the tank, and (v2) a corner-exploring and Icleaning mechanism disposed for successively entering or exploring each corner of the tank, adapted for engaging sedimented material at diverse portions of the successive corner sections for transferring the sedimented materia/l engaged thereby to the central floor section from whence it is ultimately transferred to the sediment discharge by the functioning of the main raking mechanism.l The invention hereof is particularly concerned with a novel form of corner-cleaning mechanism and with a novel manner of embodying the same in the sediment-raking assemblage of which it constitutes a part.

The main raking mechanism embodies one or more rake arms generally formed of metal such as steel, in the form of structural shapes and fiat connecting plates, all of which are rigidly secured together as by riveting or welding. These arms carry or have embodied therein raking blade elements inclined with respect to tho forward path or travel of the arm whereby sedi-g mented material engaged thereby is impelled and progressively transferred to a sediment discharge generally located at or near the central portion of the circular iioor section of the tank bottom. Of these main raking arms at least one, possibly more, is preferably constructed with sufficient rigidity and strength for a'ording support from the outer end thereof for the cornercleaning mechanism referred to and such main arm may be termed a strong rigid main arm. This corner-cleaning mechanism is auxiliary to the main raking mechanism. The corner-cleaning mechanism is carried from a strong rigid arm or can'ier and adapted to explore the tank corners. It comprehends the auxiliary raking element or blade that is bodily swingable from said rigid arm or carrier through the medium of pivoted horizontally-spaced links theinner ends of which are mounted on hinge memberslcarried thereof, constantly engages this guiding strip asvv at an outer end of a vstrong rake arm of the main raking mechanism. Because of the horizontal spacing arrangement and disposition of the link constructions, one of the links may be referred to as an outer forward link while the other may be referred toas an inner rear link. The cornercleaning mechanism embodiesthe links just referred to and also the auxiliary sludge raking element, which is in effect a comer-cleaning or raking blade. The exploring mechanism also includes a yieldable forcing means adapted to press constantly, in a general more or less outward radial direction, the free ends of the swingable links and the associated corner-raking blade carlied therefrom. The auxiliary or corner raking blade which is carried from thefree ends of the swingable links is of substantial horizontal extent or length. It is held and" positioned so that one end thereof is constantly outwardly disposed from the main axis as compared to the other end which is disposed inwardly or nearer to the main axis about which the main raking mechanism turns. The length of this auxiliary raking blade or corner-exploring element is such that for all positions thereof the innermost 'end reaches to and preferably extends somewhat over the peripheral portion of the circular area that is served by the main raking mechanism. The corner-exploring element as a whole may be viewed as trailingly disposed with respect to that portion of the sediment-raking assemblage from which it is carried through the mediumof the swingable links. In fact, the swingable links and particularly the free ends thereof also have what may be viewed as trailing disposition with respect to the arm upcin which they are mounted and with respect to which they swing as the arm moves in closed horizontal paths about said main axis.

The tank has a guiding or resisting member` provided as by a stationary strip or track. This strip may be located so as to define the outer margin of a non-circular settling floor portion or other'cornered area' within the tank. This strip is embodied in the tank as a part stationary therewith and generally within the lower interior y portion thereof, but it is'not necessarily withinr the lower portion of the tank according to the broader aspect kfor phasesof the invention. A member of the comer-cleaning mechanism, generally the outer end. of the corner-raking blade the comer-cleaning mechanism moves forwardly in closed paths within the tank whereby the cor- 7 ner-raking blade is alternately moved.` to and I from the outermost extended and the innermost retracted positions therefor incident to its alternately being forced outwardly by the yielding pressing means referred to, as such outward movement is permitted by the outwardly progressing section of the guiding strip and inwardly against the constant pressure of the yielding pressing means because of the cam guiding action of the stationary inwardly progressing section of the guiding strip.

. swingable horizontally-spaced links, the free or swinging ends of which are connected to horizontally-spaced sections or portions of the corner-exploring element and more particularly to horizontally-spaced sections or portions of the corner-exploring element that are inwardly spaced from the outer end of the corner-exploring element whereby the latter during any inward or outward movement thereof is under the guiding influence of the links.

The invention according to one aspect thereof involves the employing of a comer-cleaning mechanism having a corner-raking element pivotally mounted at or near the free ends of horizontally-spaced swingable links that are in turn pivotally mounted on hinge members carried at the free outer end of a main raking arm which is in turn provided with sediment-raking elements functionally disposed for operation over a circular section 'of the tank bottom incident to the forward movement of the raking arm in closed circular paths abo ut a vertically-extending axis within the tank.

'I'his invention may be still further described as residing in a corner-raking blade of substantial horizontal extent that is pivotally supported from the free rear ends of a pair of links or link constructions that are horizontally-spaced with respect to each other so las to provide an outwardly-disposed link and an inwardly-disposed link, the forward ends of which links arepivotally mounted on a movable carrier that is turnable about a vertical main axis within the tank. The links which are thus pivotally mounted on the movable carrier or outwardly-extending arm, are disposed so that the free ends thereof are rearmost whereby the linksvare trailingly vdisposed with respect to the outer end of the carrier or arm from which they are supported.

In the practical embodiment of a construction .designed for realizing the aspects or features above referred to, there is vemployed a yieldable or constantly outwardly pressing means forA continually forcing the corner-raking blade to the outermost position therefor and also a stationary guiding strip or track section functioning to determine the successive outermost positions of the exploring sediment-raking element and to provide cam-like guiding surface as to those sec- Certain of said prior'structures have been inO successful operation for several years.' However,

the main raking arms thereof have been relatively light and comer-cleaning elements and vide a cornered non-circular clarifier or settler having main rake arms of suicient rigidity to afford the necessary or required support for extensible andretractable corner-exploring sludgeremoving means and to improve the manner of mounting as well as the mode of operation thereof; also to equip the main rake arms with an extension arm operating solely and continuously at the trailing edge of the main rake arm in spaced relation thereto whilehaving arcuate reciprocation substantially radially of the circular area served by the main rake arms, whereby the extensible and retractable rake arm is adapted to operate within the corners of the clarifier beyond said circular area for removing sediment or sludge from the corner areas into the circular area operated on by the main rake arms.

A further object of the invention is to allow the said corner-cleaning blade to have greater freedom of movement to enable it to operate more effectively within the corner areas of the clarifier in both its enteringI and departing movements. l

With the above indicated and other objects in view, the ,invention consists in the construction and novel combination and arrangement of parts illustrated in the accompanying drawings and set forth in the claims hereto appended, it being understood that various changes in the form, proportion and minor details of construction within the scope of the claims may be esorted to without departing from the spirit of the invention or sacrificing any of the advantages thereof.

Asillustrative of a manner in which the invention hereof may be structurally embodied in an apparatus or unit of the class referred to, reference is made to the accompanying drawings constituting a part of this specification.

In said drawings Fig. 1 is a plan view of one embodiment of this invention.

Fig. 2 is a partial sectional view taken as on the planes indicated by the broken lines 2-2 of Fig.' 1.

Fig. 3r is a vertical view showing the tank or basin construction partially in sections and in this figure/the horizontally-turnable raking assemblage occupies a position somewhatdiiferent from that shown in Fig. 1 wherein the rake arms of this Fig. 3 are in'position practically at right angles to aside wall of the tank.

Fig. 4 is a plan view illustrative of a main rake arm and the comer-exploring mechanism carried by and from. the outer end thereof. In this figure the raking blades have been omitted l from the underside of the main arm.`

Fig. 5 is a perspective view illustrating details4 of the corner-exploring mechanism and the mode by which 'the horizontally-swingable corner-exploring element is supported by and carried from the outer end of a main rake arm. In this ngure certain longitudinal ,or relatively horizontal members of the main arm' have been indicated by dash and dot lines and therein is illustrated by `full lines a certain transverse frame construction which is rigidly connected to or which I 3 ing assemblage I2 are mounted so as to derive suitable support for the assemblage from a stationary bearing means and so as to have moveengagement with the stationary guiding track or strip.

Figs. '1 and 8 are longitudinal and transverse views of a track-engaging block employed at the outer or track-engaging end of the corner-exploring element, Fig. 8 being a view taken as on line 8-8 of Fig. 'I looking in the direction of the arrows.

Fig. 9 is a detailed vertical fview partially in sections and illustrates .the manner in which the corner-exploring element is connected by a pivot-providing means to the outer ends of horizontally-swingable links and so as to lbe supported therefrom.

The sedimentation unit shown in plan in Fig. 1, and of which a vertical view partly in section appears in Fig. 3, includes a cornered non-circular settling tank I I and a horizontally-turnable sediment-raking assemblage I2. This assemblage embodies ajmain raking mechanism or rotary carrier I3 turnable in circular paths about a vertically-extending main axis and disposed for operating over an underlying circular floor section of the tank bottom; and an auxiliary or cornerexploring or cleaning mechanism I4 constructed and disposed for functioning within cornered sections and operating over underlying cornered floor sections outlying but contiguous the aforementioned circular oor section.

The settling tank II may be made of any suitable material; it is frequently made of concrete. It embodies a bottom I5 providing a cornered non-circular settling floor area, an upstanding hollow pier I6 centrally disposed with respect to the non-circular settling oor area and a cornered non-circular marginal wall Il. The tank also has sump I8 vprovided in the bottom thereof. The sump portion and the pipe I9 leading therefrom provide a sediment discharge leading from the lower interior portion of the tank. At the upper portion of the tank there is a marginal member providing an overflow Weir at 2| that determines the normal operative level of the liquid within the tank. supernatant liquid within the tank overflows this weir as and when the height of the normal level is exceeded. The overflow liquid passes into an eilluent launder 22 and therefrom through an opening or conduit 23 is leading from the tank. The member or members providing this weir and the overilow launder construction constitute eluent' lwithdrawal means that determine the normal level of the liquid within the tank and whereby supernatant liquid passes as clarified eflluent from the tank.

An inuent pipe or conduit 24 which is either horizontal or approximately so leads` inwardly below the oor ofthe tank to the hollow interior ment in closed horizontal paths about'a vertically-extending main axis.- In thesonst'ruction shown this sediment-raking assemblage I2 derives its support from a stationary bearing member 30 which is carried by and from the pier but this assemblage might be otherwise supported in order that it may have its horizontal turning movement in closed paths about a vertically-A extending main axis. In the construction shown a stationary superstructure 3| is indicated which derives some of its support from the marginal portion of the tank and some from the stationary pier. This stationary structure- 3l provides a walkway affording access to a stationary motor 32 and stationarily housed speed reducing and power transmission mechanism 33 that are provided for imparting horizontal turning movement to the members constituting the sediment-v raking assemblage.

The sediment-raking assemblage I2 embodies a turnable bearing member 34 which` derives its support from the stationary bearing member 30 on said pier or from any other suitable associated stationary bearing member. An arm-support- 'ing cage or carrier 35 is secured to, .depends from and .turns with the turnable bearing member 34. From the lower end of the cagey or carrier 35 there radially extend and are carried'structural arms 3B that move in circular horizontal paths about the xed axis about which the sedimentraking assemblage turns. These arms 35 embody vertically and horizontally-spaced longitudinal members such as 31, 38, 39 and 40 which are suitably connected Iby transverse ties or diagonal braces such as 4I to 48 inclusive and connecting plates such as 49, 50, 5I and 52 into a skeleton type of fabricated steel or other metallic construction whereby a relative y'light,

` rigid and strong arm results.

. ciently rigid to support thereby and from the outer ends thereof the auxiliary or corner-exploring mechanism I4 heretofore referred to. In the construction shown the radial arms 35 arein fact cantilever arms horizontally-,turnable by and extending from the carrying member 35 therefor. 'I'he cantilever arms 36 and the carryof the pier I6.v The pier has orifice sections 25 providing discharge ports 26 leading from the hollow interior, thereof by which ports incoming liquid is delivered into the upper central portion of the liquid-holding ysection within the tank. Such delivery of inilowing liquid is into a central stilling lwell or chamber 21 provided within the marginal limits of a baille or intermediate wall portion 423.

The members constituting thesediment-raking member 35 just referred to may be collectively but broadly referred to as providing a horizontally-turnable carrier, or carriers, by and from which the exploring and raking mechanism,

`or mechanisms, is or are' supported.

By reference to Figs. 1 and 2, it will be noted that the bottom of the tank has a corner noncircular settling oor area or section marginally dened by a cornered non-circular guiding sectionwhich in fact is provided by the guiding strip .l or marginal track 60, having four straight sections 6I and a corresponding number of interspersed cornerllet sections 52.

The corner-exploring or auxiliary raking-` mechanism has a corner-cleaning member, or

comer-exploring member constituting a mechanical element 63 having a depending sedi- -ment-engaging blade or sludge-raking member or portion 64. The mechanical element or mem-1 ber 63 may be broadly viewed as a movable rake Ill may collectively be viewed and described as an auxiliary raking or corner-cleaning element of substantial horizontal extent or length. In the construction shown the outer end portion of the corner-cleaning element or blade 63 is constantly yieldably pressed 'in an outward direction so that the outer end portion thereof constantly engages and presses against the marginal track or guiding strip 60. This outward forcing is by a yieldable pressing mechanism 65 (see Figs. 4, 5 and 6), that includes a forcing-weight 66, a chain 61 passing over a guide pulley 68 and connected to the free or movable end 69 of swingable arm on and rigidly connected to the pivoted end portion 1| of a horizontally-swingable link 12. lThere are two horizontally-swingable links,`

12 and 13 for each corner-exploring mechanism and the free rear ends 14 and 15 thereof have pivotal connections at 16 and 11 to horizontallyspaced sections of the corner-cleaning element 63. Each` of these pivotal connections .16 and 11 is inwardly spaced a substantial but different distance from the extreme outer end of the bladed member 63. As previously indicated the links 12 and 13, and more particularly the free rear ends thereof, have trailing disposition with respect to the structural arm or carrier member 36 from which they are pivotally mounted since the free or rear ends of the links constantly trail or are disposed in the wake of said carrier member or arm as it moves forwardly along the closed horizontal circular path of travel therefor.

Two comer-exploring mechanisms are shown in Fig. 1. It would be feasible to employ only one such mechanism. Each of these mechanisms embodies acorner-exploring element or blade 63 just referred to. In the construction shown each cornerg-exploring element 63 derives s wingable support from the horizontally-swingable hinged links 12 and 18 that are pivotally mounted on fixed hinge-providing members 86 and 8l that are secured to and carried at the rear or outer ends of the horizontally-turnable carriers or cantilever rake-carrying arms thereof. In Figs. 4 and 5 it will be seen that the hinge-providing members 86 and 8( are in fact upper and lower horizon'- tals connected by horizontally-spaced verticals 82 and 83 and provide at 86 and 86 and 81 and 88 horizontally-spaced upper and lower; hinge ele- -ments affording pintle axial. portions at 8| land 82 whereby and from which the pintle or piv-y oted ends of the horizontally-swingable 1inks12 and 13 are carried. In other words, the pintle axes 9( and 92 of these links 'may be broadlyviewed as horizontally-spaced one outwardly with respect to the otheror as more specifically viewed as horizontally-spaced one outwardlyand forwardly with respect to the other. These pintle axes are so arranged or disposed that the links have substantially horizontal swinging movement.

The links, 4or swingable link constructions just referred to', have sufficient rigidity of construction to ensure that the` outer ends thereof will not bend or substantially deflect during the operative movement thereof. Between the outer ends 'vertically-extending pivot pin 84 that is mounted in a bearing member at the outer swinging ends of the swinging link to which it corresponds. Each pivot pin also extends through receiving portions provided therefor at 96 by a part of the corner-cleaning element 63. i

From Figs. 5 and 9 it will be manifest that the pivotal construction just described provides a means whereby the rear outer end of each link is pivotally connected to the comer-cleaning element 63 and also whereby it can be supported as well as guided by the links as required during th in and out movement thereof.

One of the links 12 and 13 may herein be considered as a guide means horizontally spaced from the other link, and operatively connecting the rotary carrier I3 with the corner-exploring member or element 64. Both links, or otherwise expressed, one link and the guide means are coactive and eliective to guide said exploring-element in a fully pre-determined horizontal bodily movement relative to the rotary carrier (3 in in'- ward and outward directions with respect to the vertical main axis oi' rotation of the carrier I3. It will be understood that the term bodily movement signifies the movement of a body or element in which allv points of the body move in non-pivotal fashion with respect to the reference system. Such a bodily movement, for instance, in a horizontalplane may represent and in the case of the movement of the present corner-exploring member, does represent the resultant of a bodily linear movement plus a pivotal movement. Such composite bodily movement may kinematically also be termed as compound bodily movement.

' The outermost end of each corner-cleaning element 63 is provided with a lignum vitae slide block 91 which is secured to the outer end portion of the corner-cleaning element through the medium of bolts 96 and 99 as are shown in Figs. '7 and 8. A strip marked |00 shown in Figs. 5, 7 and 9 serves as a squeegee at the lower edge of the raking blade 64 and is of brass or any sult-v able material to serve this purpose.

In the construction shown a circular central portion of the floor of the tankbottom slants slightly downwardly and inwardly, all ofthe tank bottom or iloor lmight be horizontal, and the main raking mechanism primarily functions to serve the circular central portion of the floor, namely, the section immediately underlying the area over 'which the main raking mechanism travelsin closed circular paths about a main vertically-:extending axis. As to the outlying corner oor sections that are contiguous the circular central sections that are served by the auxiliary corner-exploring and raking mechanism these 4are horizontal and of approximately'triangular form a s will be seen from an inspection of Fig. 2 1n conlunction with Fig. y1. In Fig. l there are shown in plan four of these approximately tri` angular sections and they are within the confines noted by a portion of a straight linevsection 6|,

wall a small downwardly and inwardly sloping fillet-like section of which the slope is relatively steep, and which is provided for deflecting or directing sedimented material into the cornered triangular oor section to which the sloping fillet corresponds; 'I'hese sloping fillets are provided sc as .to avoid retention of any substantial residual deposits in the extreme corner areas left outside of the settling area as marginally defined by the guiding strip or marginal track 60.

The hinge-providing members 80 and 8| have been embodied in a relatively strong but light end frame provided for and at the outer end of a rake-carrying arm or main raking member |3. This end frame includes the upper and lower hinge-providing members 80, 8|, the horizontally-spaced vertical members 82 and 83 connecting the same, vertically-spaced horizontal members |02 and |03 to which the upper and lower ends of the vertical members 82 and 83 are connected 20' tire end frame is diagonally braced. The horizontals |02. and |03 are respectively connected to wardly into the liquid-holding section of the tank and includes the main and auxiliary raking mechanism which are conjointly employed for the longitudinals 31 and 38 and 38 and 40 of the 25 rake-arm or main raking member |3. The end frame structure just described may be viewed as embodied in and constituting an outer end frame j that imparts, rigidity and strength to the boxlikeV rake-arm structure that is formed of the 3u aforementioned longitudinal members which` are `not only connected by the end frame just described but also by other transversely and diagonally-extending members into a strong formation which is relatively rigid throughout its 35 length and which is well adapted to withstand any torsional strains about a substantially horizontally-extending line, to wit, torsional strains, that might tend to be set up or created by the trailing auxiliary comer-raking mechanism in- 4u cause of its being supported in offset relationship l from a pivotal-support, or supports, located at its outer end of the main raking arm I3, namely,

through the medium of a laterally-extending member or members, constituting or providing a horizontally-swingable carrying element therefor. c

The operation of the device to which this in 55 vention relates is as follows: Y

vIncoming liquid having matter `therein to be settled therefrom is supplied through the inuent pipe or horizontal feed conduit 24, passes upwardly through the rising leg or passageway pro- 6 vided by the hollow central pier I6 and ultimately passes as delivered influent through discharge openings 26 of the port-providing section 25 at* the top of the pier. The thus delivered incoming liquid is stilled and dispersed or spread out within the initial receiving chamber 21 which is marginally-deiined by the baiiled or intermediate wall portion 28. The liquid passes from within this initial receiving chamber toward the marginal etliuent launder 22 so that ultimately the claried 70 supernatant liquid overflows the Weir 2| and passes into the launder and therefrom on its way from the sedimentation tank.

Settleable solids precipitate and collect as sediment at or ove1- the entire area of the cornered g5 lrespectively raking the circular central section at the bottom of the tank and the outlying cornered sections that are c posed with respect to the central section just referred to. As already pointed out the raking assemblage ismounted and actuated so that it has forward ,turning :movement in horizontal closed paths about a vertically-extending axis which is concentric with the hollow pier. Themain raking mechanism has horizontal turning movement in circular paths so that the sedimentengaging elements or raking blades thereof travel over the underlying circular central oor section and the sediment-engaging elements or raking blades thereof function to impel and transfer sediment engaged thereby from diverse parts of the circular central oor section toward and into sediment discharge I6, from which it is ultimately passed from the bottom of the tank. During this horizontal turning movement of the main raking mechanism there is also a horizontal forward turning movement of the auxiliary or corner-raking mechanism in closed non-circular paths. The' horizontal movement of this auxiliary mechanism in closed non-circular paths is under the progressive guiding and the constantly outwardly pressing inuence of the stationary guiding track or strip on the one hand and the yieldable butconstantly outwardly pressing influence of the pressing weight 4mechanism 65 heretofore described. According to the combined operating influences just described the cornercleaning element 63 of the auxiliary raking mechanism is constantly urged toward the outermost position therefor by the pressing weight 66 and the flexible connecter which is connected to swingable-arm 10 that is integral with or connected to a part of the linkage mechanism or swingable element by which the corner-cleaning element or member 63 is swingably supported. In this way the forward or outer end of the bodily-movable corner-cleaning element 63 is constantly but yieldably outwardly pressed against the stationaryguiding track or strip 60 and follows along a path defined by the track or strip. This corner-exploring element as has already been pointed out is provided with a slide block 81 which is preferably of lignum vitae whereby there is realized a type of sliding member which is well .adapted to function in a liquid.y

medium and to withstand wear during the constant pressing engagement which it has with the guiding track or strip 60 and which in the form shown is stationarily located at the bottom of the tank and is embodied in the structure constituting the tank. As the result of this engagement with the track and of the constant outward-pressure embodied by the yieldable pressing means, it will be seen that the horizontally-swingable corner-cleaning element follows the track or guiding strip defining the outer margins of the non-circular cornered sections of the settling noor area and is well adapted to function within the outlying cornered section of the tank and over the cornered floor portions thereof. Thus,

as the sediment-raking mechanism 'turnsl it sediment passed to or Ion diverse parts of the inlying central circular floor section or area and to transfelthe sediment engaged thereby toward and ultimately to the sediment discharge sump I8.

In connection with each non-circularly raked cornered floorsection it is to be noted that the sediment supporting area or sediment-receiving and supporting surface is preferably flat and horizontal or substantially so. As to the circularly-raked central section, this may be either flat and horizontal or dished'according to the desires of an operator or designer. 4

That which is herein referred to as the forward end of a section of the track or guiding strip 60 is determined by that which is referred to as the forward raking movement of the sediment-raking assemblage. 60 it will be noted that while it functions as a relatively continuous member, it is preferably made up of the four straight sections 6| and the four arcuate or llet sections B2 assembled one after the other so as to provide a relatively continuous surface. As to vthese sections 6| and 62 the rear end of each is positioned in overlapping arrangement and radially outside of the forward end of the associated adjacent guiding section.

With respect to the track or strip This arrangement of the overlapping ends isv clearly indicated in Fig. 1. In order to realize a preferred forni the rear end of each track section is bent so as to extend outwardly and then rearwardly relative to the preceding main portion thereof, whereby a receiving-space is provided for the forward end of the contiguous or associated adjacent sections and whereby the guiding surfaces of the adjacent sections are ar ranged so as to provide a smooth continuity from one section to the other.

As to the end frame construction by 'which the horizontally- swingable links 12 and 13 are supported from the outer'ends of the structural form of rake-carrying arms 36 of the, main raking mechanism |3 it is feasible to mount that portion of the end frame which comprises the upper and lower horizontals 80 and 8|, the horizontallyspaced verticals 82 and 83 and the crossing diagonals |02 so as to be adjustable in practically any direction with respect to the upper and lower horizontals |02 and |03 which are connected to or embodied in the structures constituting th rake-carrying arms 36. i

This adjustment may be attained by the employment and provision of suitable adjusting and securing instrumentalities such as slotted portions provided in members, to wit, the vertical members 82 and 83 and the arm-carried horizontals |02 and |03, bolts employed for adjusting and securing purposes, to wit, such as pass through the slotted portions referred to whereby,

for example, the verticals 82 and 83 can be vertically positioned with respect to and secured to the horizontals |02 and |03. and shims which, for example, may be employed for effecting certain desired vertical alignments by being placed between certain of the members such as, for example, between either or both of Vthe vertical members 82 yand 83 on Vthe one hand and either or both of the horizontal members |02 and .|03 on l pintle axes about which the links have horizontal swinging movement and whereby said links will have properoperative movement therefor in substantially true horizontal paths. By such adjustment there is also realized the proper perative positioning and horizontal swinging movements of the comer-cleaning element or member 63 with respect to and over the relatively at and horizontal floor surfaces of the outlying corner flr portions of the settling area of the tank bottom and above which the corner-cleaning element successively has operative sediment-raking and transferringl movements as it travels in horizontal non-circular closed paths about the verti- `cally-extending axis that is concentric with the upstanding pier yI8.

In the construction shown there are two main rake-carryingarms that are substantially in diametrical alignment because of their extending in opposite radial directions from the horizontallyturnable cage or carrier 35 therefor. Also in the construction las shown there is a corner-exploring and raking mechanism M provided for and carried vfrom the outer end of each rake-carrying arm 36.

It is feasible toemploy a sediment-raking assemblage having,diametrically-aligned rake-carrying arms, as the arms 38, but with only one comer-exploring vand raking mechanism for the assemblage. In the instance just referred to the horizontally-swingable links `of thecorner-exploring andraking mechanism andthe parts carried thereby may be supported from the outer end `of only one of the rake-carrying arms. In such a construction it is advisable to provide counterweight meansA for the rake arm which does not carry or support the horizontallyswingable links. The counterweight required may be prvided entirely, or in part, by a dead weight so to speak,I secured, for example, to the outer'end of the rake-carrying arm which does not support or carry the horizontally-swingable links, or this counterweight may be provided in part or wholly by extending -the chain B1 past the center pier I8 whereby the sheave 33 and the forcing-weight ,68 may be disposed on and carriedby the rake-carrying arm which does not carry the horizontally-swingable links insteadof on the rake-carrying arm which has at the free outer end thereof the horizontally- swingable links 12 and 13 and the parts carried thereby. In this way the forcing-weight I8 becomes a counterweightto balance in whole or in part the unevenloading on the sediment-raking assemlblage and which would otherwise exist because of the horizontally-swingable links and the corner-cleaning element G3 supported therefrom being carried by onlyone of the arms.

In the event it becomes desirable to provide a construction or arrangement in which theI ing regard to the positioning of the arm i and its link l2 with respect to each other.

We claim: A 1

1. A sedimentation unit comprising a settling tank, means for feeding liquid thereto, an ef.

fluent means determining the normal level of the liquid within the tank, a sediment discharge leading from the tank, means providing a, cornered non-circular stationary guide track marginallydeining a cornered iioor area of the tank, a sediment-raking assemblage turnable in closed paths about a main vertically-extending axis and including a corner-exploring mechanism having a horizontally-movable corner-cleaning element of substantially horizontal extent 'for functioning over successive cornered oor sections, and yieldable pressing means for continuously forcing the corner-cleaning element toward the outermost permissible positions therefor as determined by said guide tracklwith which it constantly engages; said corner-exploring mechanism being characterized in that it comprises a horizontally-turnable carrier provided thereupon with hinges having vertically-extending pintle axial portions that are horizontallyspaced with one pintle axis further outwardly disposed from the mainaxis than is the other pintle axis, horizontally-spaced swngable links and forwardly disposed with respect to the other horizontally-swingable link.

3. A sedimentation unit as deiined in and by claim 1, according to which the corner-cleaning element is pivotally connected to the free trailing ends of the horizontally-swingable links so -as to be carried thereby and so as to depend therefrom.

4. In a sediment-conveying mechanism for collecting sediment over and from a settling of the settling area into the circular portion thereof, an exploring element, a link between said exploring element and said carrier, means to pivotally mount one end of said link on said trailingly disposed with respect to said carrier,

of which the forward end of an outer link is swingably mounted on and carried from the pintle portion of an outer hinge and of which the forward end of an inner link is mounted on and carried by the pintle portion of an inner hinge, and pivot members for connecting the free trailing ends of said swingable links to horizontally-spaced sections of the horizontallymovable corner-cleaning element with sections lhorizontally-spaced from the outer end of said element V'whereby thelatter is caused and permittedto have successive horizontal in and out swinging movement under the combined actuating and guiding inuences of said yieldable pressing means and the non-circular stationary guide track as the corner-exploring mechanism turns about the main vertically-extendingl axis.

2. A sedimentation unit as dened in and by claim 1, according to which one pintle axis is both forwardly and outwardly disposed with `respect to the other pintle axiswhereby one of said horizontally-swingable links -is outwardly carrier for horizontal angular movement about a vertical axis, means to pivotally connect th'e exploring member with the other end of said link, to move horizontally 'about a vertical axis,

means for movably connecting a portion of said' carrier, which portion is horizontally spaced from the point of pivotal mounting of said link on said carrier, with a portion of said exploring element, that is horizontally spaced from the point of pivotal connection of said link with the exploring element, said connecting means being effective to permit the exploring element to be moved bodily and pivotally in a horizontal plane, said link and said connecting means being coactive and effective to guide said exploring element in a. horizontal bodily movement relative to the carrier in inward and outward directions with -respect to the vertical main axis of the carrieryand control means cooperatively associated with saidv carrier and with said exploring element, said control means comprising a guide track extending along the outer marginsA of the settling area, and means mounted on the carrier and connected tofthe exploring element foryieldingly pressing the outer end of said exploring element against saidtrack as the carrier rotates.

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