US2467021A - Sewage screening apparatus - Google Patents

Description

April 12 1949- A. JFlscHEl-a 2,467,021

SEWAGE. SCREENING APPARATUS Filed Nov. 22, 1944 2 Sheets-Sheet 1 F G. 2. INVENTOR:

VANTHONY J. FISCHER, `zy

` ATTORNEY -Aprl12,1949 lA.J.|=|$ ;HER 2,467,021

SEWAG'E SCREENING APPARATUS Filed Nov. 22, 1944 2 Sheets-Sheet 2 INVENTOR.'

ANTHONY J. FISCHER,

ATTORNEY Patented Apr. 12, 1949 SEWAGE :SCREENING APPARATUS Anthony '-J. Fischer, Manhasset, IN.i-Y.;"ass'ignjorto (Ines) ,\NeW'GYOi-k,' N. EY., a

The Dorr Company corporation: ofDelaware ,Application November 22, 1944,5erilNOf564L690 Cl. 21B-44,4

15' Claims. l1

,This invention .relates to the Itreatment .of `raw sewage, and more `particularlyto the screening stage which may precede .the removal ofsolids from the. sewageby. settling.

The Yscreening l stage as 'herein .contemplated employs a bar screen .for Aintercepting sewage vsolids .of a size whichitisnot ldesirable to have ipass .on intoa subsequenttreatmentstage such as settling, and it.furthercontemplates the use Vof ,a screen, in conjunction with comminuting apparatus wherebythe screeningsor screen rejects are reduced .prior rto being r11e-.introduced 'into the stream of sewage for further treatment. The .screenings .collect .on-.oratthe screen and arecurrently or .periodically .removed y.therefrom for .comminution .It is among theobjects .ofthis invention to. pro- ,duce .an .improved Acombination screening `and ,.comminuting. apparatus. which is simple. relative- Lly -.inexpensive,. easy= to .operate .-an'd overhaul,..and .which is. compact, ArequiringaJ minimumof conrcrete work,..gates, .valves,.penstocks .mathe like.

fThe basic .formI of the.. apparatus.. according to this invention is simplied,for.instance, inrthat .it .avoids the .by-pass :channel .and .accessories ithereof as found in. somef.known...apparatusf com- .bination .of this class, also in that..it.dispenses with special mechanical automatic screenfclean- .ing .means :found in ranother fclass, whereby fsewage solids .retained onztopof aV bar screen. are

raked to the comminutingrapparatus.

Another object isto providev for 4a :combination screening and comminuting apparatus .which allows .to convertl fromi one modeay .of- .operation .to another, namely ifrom `the .mode v,of l*automatic self-cleaning 'operation of -the screen -while -the .comminuting apparatus is-avai1able for this oper- -atiomto a mode of.. cleaningfthezscreen by-.removingfsewage solids therefrom .to' av point outside the .sewage stream .-when.- the comminuting. means :are motI available for autom-atie;self-cleaning.

Isattainthese obj ectsloy.A providing .a construcftion-.inwhich .I intercept the sewagersolids-.at'the underside of Y al substantially1 horizontal scr.een,=in Iwhich I `draw the'solids together with-liquidf'from .underneath, that lis .from the. iniluent'; side of the .,screen, .deliver f them -to comminutinjg treatment and then :return themto,.the sewagestream. .My rconstruction .further rprov'des means toioptionally move the screerrromiits.normallymorizontal ,position f to a .substantially .inclined :solids intercepting, position;,permittingithe interceptedfsolids .to`be raked u p theinline to apointodischarge 'or disposal above the liquid level during such *periods as the .comminuting .apparatus fis not favailable :for 'normalself -cleaning operation.

YAccording to "one Tfeature 'the *bar "screen iis mounted Csorasto ibe ^positiona-ble `bya swinging movement Ifrom a normally Lhorizontal totally submerged'sol-ids intercepting dposition toan'abnormal inclined partially *emerged *solids intercepting position.

According to another/'feature'theibarscreen is 4swingable labout 'trunnions from the oneito tlre otherlposition.

'According I to a 1 still 'more specicV feature the -bar 'screen' that isfswingable"aboutthetrunriions rhas xaihandle"memberffor'manipulating thescreen from pan operating platform above the nsew'elge screen, andalso serving ias ailockingmeansor securing the bar screeniin "at least One of :its positions.

-Still -ifurther expressed-the invention is embodied in combined screening' -and kcomminuting apparatus 'having '-aflow-chann'el' structure vembodying a bottom and transversely-spaced iside `walls rising therefrom .and defining a downstream -owchannel portion wherein' there is; interposed -a transversely-'extending"bar screen of Whichthe bars .are `transversely-spaced. The screen 'is "-tiltable Vvabout `a h'orizorital varmi `transversely-.ex-

tending axial line into a selected normal operative b position thereforwhereat it ,'islocated so.a`s toleprovidea 'screeningroof affordingat the ,under` side `thereof *an upstream or.`flowreceiving vface Aimmediately overlying a solids settling-out region within which screen-outsolids .of certainselectetl -sizes: are .received and'ifrom which 4such solids. can be removed by :a disintegrating Vtype ,of ipumping l-means andifrom whichsolids pumped thereby are deliverabletherefrom and returnable Yasnpurnped Icomminuting 'solids .to 'the .sewage flow screen. The "screen yis valso tiltable .about .said ,axiallline into av selected extreme abnormal operative; position ,therefor .by,.a movement'in `which the forward end of thescreexrmoves v downwardly .into .engagement with .the .bottom .of the channel `structure while .the Avprevious :rear Eend :of Lthe screenY moves -npwardly 4into an :elevati-on :proxizmate :thatcof f, the .upperl edge. o'ftheside1-w'alls,\to

.Wi.t, into. an abnormalzoperative positionv iny which thelflow-receiving facefof the screen when-Yin :normal :operative position ltherefor'has become gthe 'vif-low discharge face and is located l"at the lunder side -'of 'theabnormally positioned screen. While-the: screen in" itsnormal operative .position therefor-` is relatively" horizontal, nevertheless the 'screen-"overlies a settling-out region i.but.is vnot limited to a position-..whereat it.is.substantially "horizontal, .the-.essential .functioning `.being that the screen .is positioned so .that normally .the

under upstream or flow-receiving face portion thereof overlies and defines a roof of a solidssettling-out region but which screen is positionable for abnormal operative position by tilting the forward end of the screen downwardly and in engagement with the bottom .of the flowchannel whereby the previous upper or ow discharge face of the screen of normal operative position still continues as an upper face but becomes a flow-receiving face of the screen of abnormal operative position.

The invention possesses other objects and features of advantage, some of which with the foregoing will be set forth in the following description. In the following description and in the claims, parts will be identied by specic names for convenience, but they are intended to be as generic in their application to similar parts as LA he art ,will permit. In the accompanying drawment of the invention known to me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto.

The novel features considered characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as .to its organization and its method of operation, together with additional objects and advantages thereof, vwill best be understood from the following description of a specific embodiment when read in Connection with the accompanying drawings in which Fig. 1 is a longitudinal section through the sewage flow channel comprising screening and comminuting apparatus in combination;

Fig. 2 is a plan view upon thesewage flow channel and apparatus shown in Fig. 1;

Fig. 3 is a cross-section along'the line 3-3 in Fig. l, or along the line 33 in Fig. 2;

Fig. 4 is a cross-section along the line 4-4 in Fig. l, or :along'zthe line 4-4 in Fig. 2;

` Fig.V 5 is a cross-section along the line 5-5 in Fig, 1, or :along the line 5-5' in Fig. 2.

In the drawings a raw sewage ilow channel structure III is shown to hav-e associated with it or interposed in it a sump or coarse solids trap I I, an upflow section or screening chamber I2, a coarse screen or vertical coarse grating I3 between the trap II and the screening chamber I2, with a partially submerged wall portion I 4 eX- tending transversely of the flow channel IG above the coarse grating I3, and an emergency overflow opening I 4a being provided in the wall I 4. The coarse grating I3 lodges vertically removable in vertical groove elements I3a and I 3b xed to the sides ofthe channel structure.

A bar screen I5 mounted in the chamber I2 Vis pivotally movable about a horizontal axis which substantially bisects the screen, ,as indicated by trunnions I6 or the like. At one end the screen has -pivotally connected therewith a handle or .swingable member I'I which can be manipulated from the operating iioor or platform P constituting the top of the channel structure I 0. Normally the screen I5 lis in the horizontal position (shown in full lines in Fig. 1) 'with the handle member I'I in vertical .position and just protruding above the operating platform P. In this position the screen divides the screen chamber I2 intoa lower or influent portion I8 and an upper or effluent portion I3. l

By pulling up on handle I1 the bar screen can be rotated into the inclined (doit and dash line) position shown in Fig. 1, and it can be locked ings'there has been illustrated the best embodi- 4 in this position by turning the handle I'I from vertical down to horizontal as indicated by arrows I la, and allowing it to lodge in a corresponding depression 20 provided in the operating floor P.

With respect .to the screening `chamber I2 the flow channel IE may be said to comprise an influent portion 2i leading thereto and lan eflluent portion 22 leading therefrom. The flow channel structure is further dened by parallel side walls 23 and 24 which also form the side walls for the sump I I and the screen chamber I2, .and by a bottom 25.V

The sump II is more specically defined by a rear wall 2B, a front `wall 21, and a bottom 28 upon which is shown to rest a basket 29 for receiving the coarse or heavy matter sinking into trap II, and whereby such matter may be raised from Ithe trap II and above the platform P after removing a platform grating 30 above the itrap. Y The screening chamber or upiiow section I2 is more specifically defined by the coarse grating I3, the partially submerged wall `portion I4, vby a horizontal bottom portion 3l, and' an inclined bottom portion 32 which meets the horizontal bottom 25 of the flow channel in a corner portion 33. When in horizontal posi-tion one end of the screen I5 closes upon the lower edge of the wall portion I4, while the other end of the screen closes upon the corner portion 33 of .the channel bottom. A removable floor grating 34 is shown to overlie the screen chamber I2.

Upon the operating `floor P is mounted a motor driven pump 35 of the solids cutting or comminuting type and herein briefly termed a cutter pump. A drive motor 36 land the pump have a common base3I which in turn is fastened to the operating floor P. An induction pipe 38 leads from the influentside of the screen I5 to the inlet end of the cutter pump 35, which pipe is herein s-hown to consist of a series of flanged sections which comprise (see Fig. l) a horizontal straight section 39, a reducing section 40, an e1- bo-w 4I, an elbow 42, and (see Fig. 5) ya horizontal straight section 43, an elbow 44, a Vertical straight section45,` and an elbow 46 connecting with the inlet end ofthe pump.

The pump 35 -has a dual outlet, that is a pair of outlets or flanges for connections 4l and 48 facing in opposite directions.

The outlet 4'! connects with ra discharge conduit 49 leading to a point of the sewage stream well past -or downstream of the screen chamber I2, and shown to comprise a short ilanged :pipe section, a shut-olf or control valve-50 of the elbow type and a vertical terminal pipe section 52 having a splash plate 52a. The opposite pump outlet 48 connects with .a discharge conduit 53 including a shut-01T or control valve 54, a horizontal section 55, a T-shaped pipe section or lateral 56 connecting downwardly with a shut-off or cont-rol Valve 57- and a vertical outlet branch 58 having a splash or diifusing plate 58e and leading to a point of the sewage flow directly above or at the effluent ordownstream side of the bar screen I5, the lateral 56 connecting horizontally with a horizontal pipe section -60 which in iturn connects with' a shut-off or control valve 59 flanged to `an elbow `6I connecting downwardly with a vertical discharge branch 62 having a splash plate 62a. If suiiicient solids have collected at the influent or upstream side, that is at theunderside of the lscreen I5, to partially clog the same, this will manifest itself byestablishing a diaerennai d between theiiquid levels at the nfluentjor' upstream and the efryuen''t or down# stream sides of the screen.

Operation Normally the bar screen I5 is in the horizontal position shown in Fig 1, and the cutter pump 35 is started periodically in order to transfer sus'- pended sewage solids from the influent side to the eliluent side of the screen comminuting step such as is being carried out by the solids reducing or cutting effect of `the pump 35. y

During the periods that the cutter pump 35 is not running the raw sewage passes through the ilow channel I in the manner indicated by the full line arrows A, namely from the iniiuent section ZI of the flow channel IIJ across the coarse solids sump I I, then somewhat downwardly through the coarse grating I3 and underneath the partially submerged wall portion M into the influent section I8 of the screen chamber I2, then upwardly through the bar screen I'5 into the eflluent section I9 of the chamber I2, whence the stream continues horizontally into and through the eilluent section 22 of the flow channel Il).

As the flow of sewage through the channel II) proceeds sewage solids accumulate at or adhere to the under side of the horizontally disposed bar screen I gradually clogging the same to the eX- tent that a super-elevation or differential d of liquid levels establishes itself, namely the superelevation of the liquid at the influent side over the level of the liquid at the effluent side of the screen I5.

Periodically, that is to say either in a predetermined time cycle or else in response to a predetermined degree of super-elevation d, the cutter pump 35 is started to draw liquid and oversized solids from the under side of screen I5 downwardly as indicated by the dot and dash line arrows B into and through the induction conduit 38, to comminute the over-sized sewage solids passing through the cutter pump, and to discharge the raw sewage containing the comminuted solids, that is, with the latter in suspension, at a suitable or desired point into the raw sewage stream in the flow channel I0. The capacity of the pump 35A is preferably greater than the flow of sewage through the channel I0, in order to enable the pump 35 to set up or induce in or to super-impose upon the normal stream of sewage the downward flow according to the dot and dash line arrows B as opposed to the general flow direction of the sewage during the periods when the pump is not operating.

Depending upon the settings of the shut-off or control valves 55, 54, 51 or 59, the sewage containing the comminuted solids may be returned to different points of the streamin the fiow channel I0. If returned by way of branch outlet 53 directly above screen I5 the comminuted matter may partly pass away with the general sewage stream into the eiliuent section 22 of channel I0, and partly it may follow the downward ow tendency induced in or superimposed upon the sewage stream by the action of the pump 35, and pass downwardly through the screen l5 to be once more recirculated through the pump whereby recomminution of sewage solids may be eiected. If sent through the branch outlet 52 the comminuted matter will largely pass away with the general sewage stream and without being recirculated or recomminuted. `If sent through branch outlet 62 all the comminuted matter is compelled to Apass through the influent section I8 of the by way of aisolidsscreen chamber l2 with a relatively greater chance for the sewage solids to be recirculated through the pump 35 and thus to be recomminuted, except for that portion of the raw sewage which in casesof excessl sewage flow may pass unscreened from the influent section ZI of channel I0 through the emergency opening |45 directly to the eilluent side of the screen I5.

The operation of the cutter pump 35 accomplishes two things, in that it reduces the solids in the raw sewage to a desirable size adapted for subsequent sewage treatmentl steps, and inthat it removes cloggings from the screen I5.

If and when the pump 35 is being overhauled or its dual function not available for any other reasons while the sewage stream may continue piling up over-sized solids, the screen I5 can be swung into the inclined (dot and dash line) position in which case what was previously the influent side of the screen I5 proper now becomes the effluent side, while the effluent side now becomes the influent side. This inclined position of the screen I5 allows the over-sized solids accumulating thereon to be raked up the incline of the screen to a point of disposal outside of the sewage stream. In this position the operation of the screen may be continued until automatic, that is self-cleaning operation of the screen can be restored along with the restoration of the comminuting step when the pump is again available for such operation.

I claim:

1. A combination sewage screening and comrninuting apparatus comprising a sewage flow-v channel structure embodying a bottom and transversely-spaced side walls rising from and dening a downstream channel portion; a positionable bar screen having transversely-spaced screening bars and so located with respect to the flow channel structure as lto provide normally an intercepted-solids-receiving region underneath the screen and being tiltable to an opposite extreme abnormal operative position to present that which was a previous upstream flow-receiving face as a downstream now-discharge face; trunnion-means determining the location of a horizontal transversely-extending axis which substantially bisects the screen and mounted in the side walls of said channel structure whereby said screenv is functionally disposed within said channel portion and is tiltable about said axis between said two extreme operating screening positions; means for withdrawing screen-out solids from said region;

` means for comminuting such withdrawn solids;

and means for returning such suspended comminuted solids to the sewage flow.

2. The apparatus according to claim l, in which there is provided an operating platform carried by the side walls; and in which there is included a positioning member swingably connected with an end portion of the bar screen and provided whereby to lift that end of the bar screen from normal position into an abnormal screening position; said positioning member being located with lrespect to the platform and swingable into horizontal position over and into engagement with said platform whereby it becomes effective to lock the bar screen in its said abnormal screening position.

3. The apparatus according to claim l, in which said withdrawal means including solids-comminuting pump having power drive means for the pump, intake pipe means leading from the upstream side of the Yscreen to the pump and discharge pipe :means leading from the pump to ad- 7 iacentthezdownstreamasido .o the-Sorten thel la-tteris in its normal operative position, said, pump and pipinegqhavine sufoiorltwolumotlfio capacity to force the liquid` discharge from the discharge pipe means through the rscreen against the now of sewage upwardly l through ,the screen when the latter is -inits normal operativevposition. 41 4.1 A combination of sewage screening and comminuting apparatus according to claim` 1, in which aA-transverse partial partition extends from side wallto'side wall. part way downwardly within the sewage ow channel structure but :terminating-above andin` spaced relationship with respect to the bottom of thenow-through channel portion in which the .positionable screen yis located which when the positionable screen is in its normal `operative position therefor it is disposed whereat one end thereof closes upon the lower portion of the partial partition while the other end thereof closes upon a portion of the bottom of the sewage flow channel structure' and in Awhich thepositionable screen when in abnormal position thereof is disposed whereat the end of the screen which was previously closed upon the transverse partial partition nowcloses upon another portion ofithebottom of the channel structure" i f- "l i' 1.5. Al combination. sewage screening and comminuting apparatus according to claim l, in which the sewage-flow channel structure embodies a transversely-extending wall portion constituting a partial partitioning means extending downwardly within the ow channel portion'but terminating in vertically-spaced relationship with respect to the bottom of the flow-channel structure and in which the positionable bar screen is tiltably carried on and by a transversely but horizontally-extending axial providing means which in turn is supported by and from the channel structure and in which said screen when in normal operative position therefor extends horizontally and bridges the space between the side walls and between the lower portion of the partial partitioning member and a portion of the bottom of the channel structure, which said screen when tilted into its abnormal operative position moves so that the forward upstream end swings downwardly and rearwardly towards and into closure position with respect to a portion of the bottom 1 of the channel structure while the other end of the screen swings upwardly and forwardly to an elevation proximate that of the top of the side walls of the structure,

6. A combination of sewage screening and comminuting apparatus according to claim 1, in which a transverse partial partition extends from side wall to side wall and part way downwardly within the flow channel structure whereat a lower portion of the partial partition terminates at elevation above and in spaced relationship with respect to said bottom and whereat the upper portion of the partial partition provides an overflow weir at elevation lower than that of the upper edge portions of the side walls and at elevation lower than that of the upper end of the positionable screen when in its abnormal operative position, in which the positionable screen when in its normal operative position is disposed whereat one end thereof closes upon the lower portion of the partial partition while the other end thereof closes upon a portion of the bottom of the channel structure, and in which the positionable screen when in its abnormal operative position is disposed Whereatthe end of the screen which was 1n which there is provided acrossthe downstream;v

- channel portion a preliminary coarse screen lo;v

cated upstream with; respectmto thejpositionableA screen in any operative position of the latter, and in which themeans for returning Suspendedpcomminuted solids includes a pump and discharge conduit section adapted fordelivering such re;- turned comminuted solids upstream relative to the preliminary coarse screen. .i e y y *A ,l A combination. sewage screening and comminuting apparatus comprising a flow-channel structure providing a screening chamber, an inrluent channel from'which influent liquid is passed into an upstream section of said screening cham: ber and an eiiuent channel into which screened liquid is passed from a downstream section of f said screening chamber, said channel structure embodying a bottom member providing in succession an upstream influent channel oor portion, a screening chamber Iloor portion and a downstream effluent channel floor portion vrof which said screening chamber lloor portion is of low elevation as compared with the iloor portions of the influent and eliiuent channels, said channel structure also embodying transversely-spaced side walls rising from said bottom and therewith forming a channel structure within and by which there is located and provided the aforementioned influent channel, as well as the screening chamber and the eluent channel, a tiltable bar screen located in said screening chamber of which the bars thereof are transversely spaced, transverselyand horizontally-extending axial line providing means carried by said channel structure and by which said screen is mounted so as to be tiltable about said axial line and at will placeable to either a normal operative or abnormal operative sewage screening position, and which screen when in either of said operative positions therefor functionally divides the screening chamber into an upstream influent receiving section and a downstream screened sewage section from which screened sewage passes into the eluent channel, which screen when tilted into its normal operative position divides the screening chamber whereby the influent receiving section inwardly extends below while the downstairs screened sewage section extends from above the screen, but which screen when tilted into its abnormal operative position divides the screening chamber whereby the influent receiving section inwardly extends above while the downstream screening section extends from below the screen; means for operatively positioning said tiltable screen about said axial line whereby at one time said screen is in its normal operative position with respect to said screening chamber whereat the under-face portion of the screen is the face initially engaged by the downstream owing stream passing through the screen and whereby at another time said stream is in abnormal operative position whereat the previous upper-face portion of the screen is the face initially engaged by downstream flowing stream of the sewage passing through the screen, said screen being mounted positionably with respect to the flow-channel structure so that when in its normal operative position it provides a screening roof over an underlying solids settlingout region within which the settled-out solids Atend to collect, a 4disintegrating type .ef jpumping means providing a suction conduit section with intake end leading from the aforementioned settlingout region, said pumping means 4.also having a discharge `conduit section available for returning pumped discharge to the sewage flow.

9. Apparatus according to claim 8, in which the pumping means has a discharge conduit section available for returning pumped discharge to the sewage flow at a locality upstream with respect to the tiltable screen.

l0. Apparatus according to claim 8, in which there is a coarse screen interposed across the flow-channel structure at a locality upstream with respect to the influent receiving section of the screen chamber and in which the pumping means has a discharge conduit available for returning pumped discharge into the sewage flow `at a locality upstream with respect to the coarse screen.

11. Apparatus according to claim 8, in which the pumping means has a discharge conduit section leading to and terminating directly over the screen when the latter is in normal operative position therefor and in which the pumping means has sufficient volumetric capacity to force liquid from said discharge conduit section downwardly through the screen against the ow of sewage normally upwardly through the screen.

12. A combination sewage screening and comminuting apparatus comprising a now-channel structure embodying a bottom and transversely- `spaced horizontally-extending walls rising therefrom and defining a downflow channel portion, a tiltable bar screen in said channel portion, a transverselyand horizontally-extending axial member mounted on said structure; means for operatively positioning said tiltable screen about the axis of said axial member for moving said screen with respect to said channel portion at one time into a normal operative stream-screening position at which the under face of the screen is initially engaged by the downflowing stream of sewage and at another time passing forwardly therethrough into an abnormal operative streamscreening position at which the previous upper face portion of the screen is the face initially engaged by the downflowing stream of sewage passing therethrough, said screen being mounted on said axial member and positioned with respect to the flow-channel structure so that when in normal operative position it provides a screening roof overlying a solids settling-out region within which the settled-out solids tend to collect within the forward section thereof and through which the thus screened sewage flows forwardly and upwardly through said spaces between the bars of the screen and thence downstream with respect to the screen, a disintegrating type of pumping means having g, suction conduit with intake end leading from a forward section of the aforementioned region overlain by the screen, which intake end is thusly located upstream with respect to the screen when in normal operative position therefor but is located downstream with respect to the screen when in its abnormal operative position, said pumping means having valve-controlled discharge conduit sections of which one when open is available for delivering pumped liquid downstream with respect to the screen when in normal operative position therefor and of which another when open is available for delivering pumped liquid against the downstream side of the screen when the ylatter is in normal operative position therefor.

13.v A combination sewage screening and comminuting apparatus according to claim 12, in which there is a screening grid upstream with respect to the tiltable screen and functioning as a screening means which is relatively coarse as compared with the tiltable screen and which said pumping means has a valve-controlled discharge conduit which when open delivers pumped liquid upstream with respect to the screening grid means.

14. A combination sewage screening and cornminuting .apparatus according lto claim 12, in which the pumping means has three valve-controlled discharge sections of which one when open passes pump discharge to a locality upstream with respect to the tiltable screen regardless as to the position of the latter, of which another valve controlled discharge section delivers pumped liquid into a region downstream with respect to the tiltable screen when in its normal operative position but upstream with respect to the tiltable screen when in its abnormal opererative position, and a valve-controlled third section of which when the valve thereof is open dclivers pumped liquid downstream with respect to said tiltable screen regardless of the operative position therefor 15. A combination sewage screening and comminuting apparatus comprising a flow-channel structure embodying a bottom and transverselyspaced horizontally-extending walls rising therefrom and defining a downfiow channel portion; a tiltable bar screen in said channel portion; a transverselyand horizontally-extending axial member mounted on said structure; means for operatively positioning said tiltable screen about the axis of said axial member for moving said screen with respect to said channel portion at one time into a normal operative stream-screening position at which the under face of the screen is initially engaged by the downflowing stream of sewage and at another time passing forwardly therethrough into an abnormal operative streamscreening position at which the previous upper face portion of the screen is the face initially engaged by the downflowing stream of sewage passing therethrough, said screen being mounted on said axial member and positioned with respect to the flow-channel structure so that when in normal operative position it provides a screening roof overlying a. solids settling-out region within which the settled-out solids tend to collect within the forward section thereof and through which the thus screened sewage iiows forwardly and upwardly through said spaces between the bars of the screen and thence downstream with respect to the screen; a disintegrating type of pumping means having a suction conduit with intake end leading from a forward section of the aforementioned region overlain by the screen, which intake end is thus located upstream with respect to the screen when in normal operative position therefor but is located downstream with respect to the screen when in its abnormal operative position, said pumping means having valvecontrolled discharge conduit section which when open delivers pumped liquid downstream with respect to the screen when in normal operative screening position but upstream with respect to the screen when in abnormal operative screening position.

ANTHONY J. FISCHER.

(References on following page) REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Whiting Oct. 21, 1884 Buckingham Nov. 26, 1907 Rowley Mar. 28, 1911 Cuttle June 4, 1918 Strange Dec. 9, 1919 Welser, Jr Nov. 14, 1922 Kivari Feb. 16, 1932 Number 10 Number

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