US2295943A

US2295943A - Thickener

Info

Publication number: US2295943A
Application number: US156840A
Authority: US
Inventors: John H V Finney
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-08-02
Filing date: 1937-08-02
Publication date: 1942-09-15
Anticipated expiration: 1959-09-15

Description

Sept. 1-5 1942. J. H. V. FI NNEY 2,295,943

' THICKENER Filed Aug. 2, 1937 4 Sheets-Sheet l ziwumm \JOHN H MHNNEY,

Wax/- M alto mm J. H; V. FINNEY THICKENER 4 Sheets- Sheet 4 Filed Aug. 2, 1937 IN mu I SPWW JOHN H. VF /vs),

Sept. 15, 1942.

Patented Sept. 15, 1942 THICKENER John H. V. Flnney, Denver, 0010., assignor Homer 6. Hirsch, El Paso, Tex.

Application August 2, 1937, Serial No. 156,840

v a 18 Claims. (01. 210-55) This invention relates generally to the art of removing solid matter which settles from suspended solid particles in various liquids, and more particularly to machines known as thickener-s and clarifiers in use in the fields of metallurgy, water clarification, sewage disposal, and in various chemical and industrial processes, for the removal of the solids from liquids in a continuous or intermittent operation.

a An object of the invention is to provide a.

thickener or clarifler which is structurally characterized by the provision of simple and highly eiilcient safety means operable to prevent damage to the sludge working or raking element and other mechanism of the machine should same become overloaded by excessive resistance oflered to the movement of the element from any cause such as an obstruction in the tank, or settled solids accumulating therein beyond a predetermined quantity as a result of feeding solids in suspension to the tank at a higher rate than the sludge is discharged from the'tank, all in such manner as to automatically elevate the raking element sufliciently toreduce the raking load to. a safe maximum;

Another object is to provide a machine of the above described character wherein an accumulation of settled solids in the bottom of the tank following discontinuance of the operation of the machine will cause the raking element to be elevated when the machine is again placed in operation, to a level at which the raking load will not be excessive, and will then permit the raking element to remove solids from the top of the mass at a maximum rateuntll the excess amount of solidshas been cleared from the tank and the raking elementoccupies its lowermost position.

Another object is to provide a safety device of the above described character which also functions to proportionately raise the raking element should the rate of feed of suspended solids temporarily become excessive and the solids accumulate in excess of the predetermined safe raking capacity, yet permitting the raking element to.

lower proportionately when a normal feeding rate'is resumed, so that at all times the raking element will operate at maximum raking capacity and without any possibility of becoming damaged by an excessive raking load.

A further object is to provide a warning signal -which is activated at a predetermined point in the raising movement of the raking element, and which also embodies means for discontinuing operation of the raking element should the waming signal be disregarded and raising movement of the raking element continue.

Another object is to provide lubricating means for the bearings which mount the raking element to rotate, and which means is so associated with the bearings submerged in the liquid under treatment, as to prevent the liquid and solids therein from reaching the bearing and damaging same.

A further object is to provide means for rigidly supporting the raking element for rotation about a vertical axis in the settling tank, and to arrange the bearings for the raking element so as to eliminate bending stresses upon the supporting shaft of the element, and yet support the entire weight of the raking mechanism therefrom in a. balanced condition so as to obviate the necessity for a superstructure across the tank to support the mechanism.

With these and other objects in view, the inventionconsists in the combinations .and arrangements of elements as set forth in the following specification and particularly pointed out in the appended claims. a

In the accompanying drawings.

Fig. 1 is a plan view of the thickener embodying this invention;

Fig. 2 is an enlarged partial vertical sectional view taken on line 22 of Fig. 1 with parts shown in elevation;

Fig. 3 is a fragmentary vertical sectional view taken on line 3-3 of Fig. 2, with certain associ- 'ated electrical circuit arrangements shown schematically;

Figs. 4 and 5 are enlarged detail sectional views of the upper and lower portions respectively of the rotary mounting, driving, and lifting assembly for the raking element;

Fig. 6 is a fragmentary sectional view similar to Fig.4 but showing certain parts in the position they occupy when the raking element has been automatically raised to its upper extreme posi-,

tion;

Fig. 7 is a diagrammatic view illustrating the forces present in the automatic raising and lowering means for the raking element when the latter is in operation;

Fig. 8 is a fragmentary side view illustrating a .modified form of safety means for raising the raking element;

Fig. 9 is-a vertical sectional view taken on line 9-4 of Fig. 8; and

Fig. 10 is a fragmentary sectional view of a modified form of bearing protector.

Referring specifically to Figs. 1 to 7 of the drawings, the invention is shown for the purpose certain of illustration, associated with a receptacle in the form of a circular, open-top tank I supported horizontally on a suitable foundation H, a depressed portion |2 of which has rigidly secured thereon by anchor bolts |3 a socket 4 disposed co-axially of the tank.

Fixed at its lower end in the socket l4 and projecting perpendicularly upward through the center of the tank to a point considerably above the latter is a hollow stationary shaft or axle l5 upon which is rotatably mounted a sludge working means in the form of a raking element R. to be later fully described in detail.

The floor I6 of the tank i0 is provided with a large central opening from which depends a sludge discharge cone l8 welded to the socket I4 and having an outlet i9 to which is connected a suitable pipe line with which a sludge pump (not shown) can be associated to draw oil sludge from the tank.

A suitable framework 2| is rigidly secured at 22 to the upper peripheral portion of the tank In, or to a suitable structure supported independently of the tank, and is rigidly connected by transverse channel members 23-23 to a collar 24 in which the upper portion of the shaft I5 is secured. The framework co-acts with suitable uy cables 2525 connected to the framework 25 and'to the periphery of the tank or to any suitable external anchoring means independent of the tank, to rigidly support the shaft in its vertical position.

The framework supports a walkway 26 and a feed launder 21 above the top of the tank, the latter being inclined towards the center of said tank to deliver' liquid and solids in suspension to an inlet in the form of a feed well 28 supported by the framework 2| around the shaft l5 and including a screen 29 for removing chips and large particles from the liquid. A float 39 in the feed well is provided to reduce the velocity of the liquid and cause the liquid to be gently distributed over the entire area of the feed well to thus not disturb the quiet surface of the liquid in the tank. An overflow launder 3| at the rim of the tank receives clarified liquid therefrom and includes a suitable discharge pipe 32 for conducting such liquid away from the tank for storage or further treatment.

The raking element R, which is mounted for rotation and vertical movement on the shaft i5, comprises a driving sleeve 33 to which are rigidly secured at their inner ends and by tie-rods 34, arms 35 having raking blades 36 arranged at such angles as to rake settled solids on the tank floor l6 towards the discharge cone l8 during 'rotation of the element. In the present instance,

four equally spaced arms are shown, although this number may vary in different size installations. Scraper blades 31 project from the arms 35 into the discharge cone l8 to maintain sludge therein in a fluid state so that it can be drawn out through the outlet l9.

The sleeve 33 is journaled on the shaft l5 by means of upper and

lower bearings

38 and 39 respectively, and the weight of the raking element is supported by a thrust bearing 40 (Fig. 4) The bearing 49 is interposed between a collar 4| and the upper one of two

end flanges

42 and 43 of the hub 44 of diametrically opposed torque arms 45-45. The lower flange 43 is welded or otherwise fixed to the upper end of the sleeve by bolts 48 threaded into a connector 49 freely slidable in the shaft l5.

A manual lift screw 59having a head 5| at its lower end, extends freely through the connector 49 and shaft l5, and is threaded through a worm wheel 52 constituting a nut and mounted on a thrust bearing 53 seating in the collar 24. The worm wheel constantly meshes with a worm 54 fixed to a shaft 55 journaled inbearings 56 and 51 (Fig. 1) on the framework 2| and having a handwheel 58 which, when rotated in one.

direction, causes the worm wheel to co-act with the screw 59 in lifting the raking element B, through the medium of the connector 49 and head 5| of the screw. Thus a manually operable means is provided for lifting the raking element whenever it is desired to do so.

In order to prevent rotation of the screw 50 during rotation of the wheel 52, said screw may be provided with a longitudinal keyway 59' adapted to be engaged by a suitable key (not shown) in the collar 24.

Fixed to the shaft l5 beyond the upper end of the slots 41 is a collar 59 supporting a thrust bearing 69 for a driving member in the form of a sprocket wheel 6| rotatably mounted on the shaft l5 by means of a bushing 62. A sprocket chain 63 connects the sprocket wheel 6! with a sprocket 65 adapted to be driven by an electric motor 66 through a suitable speed reducing mechanism 61 and a belt, and pulley connection 68 between the mechanism and motor, all of which is supported on the framework 2| as clearly shown in Fig. 2.

Chains 69--69 are connected to the torque arms -45 and to the sprocket wheel 6| at the same radial distance from the axis of the shaft i5, and broadly constitute an operative connection between the raking element R and the driving mechanism therefor, by which the raking element is caused to be rotated and to be raised or lowered bodily according as the resistance to 33, and the collar 4| is confined against rotation the-raking movement of the element increases or decreases, all of which will be fully described in the operation of the invention.

The

bearings

38 and 39 co-act with the shaft l5 and sleeve 33 to define therebetween an annular lubricant reservoir I0 communicating with the upper ends of the bearings and adapted to be supplied with grease through a suitable fitting H (Fig. 4). As the level of the grease is normally above the level of liquid in the tank III, the hydrostatic head of the grease will be in excess of that of the liquid so that the grease tends to flow downward past the bearing 39 which is submerged in the liquid and is thus protected against the upward flow of liquid and suspended solids, which, if abrasive or corrosive, would damage the bearing.

As shown in Fig.5, the lower end of the sleeve 33 projects below the bearing 39 as indicated at 12 for coaction with the shaft IS in providing an annular pocket 13 in which grease which has worked past the bearing 39 will float so as to form a mechanical seal to prevent liquid and suspended solids from rising to the bearing.- The lower end of the bearing 39 is in substantially unobstructed communication with the interior of the tank below the liquid level in view of the fact that the sleeve 33 is spaced from and free from engagement with the shaft l5 below the lower end of the bearing. Thus liquid will flow upwardly through the space between the shaft and the hydrostatic head of the lubricant. A skirt I4 fixed to the scraper blades 31 and to a flange IS on the sleeve 33, protects the exposed lower portion of the shaft l5 against abrasion by sludge in the discharge cone ll.

As shown in Fig. 3, an alarm means may be provided so that the operator will be advised of an overloaded condition of the apparatus, and provision mayalso be made for interrupting the driving power to the raking means in the event that the safe operating load is exceeded. Such alarm means may comprise a plurality of electact I6 being positioned to be engaged by the outer end of one of the arms 45 upon rotation thereof when the raking assembly is in its lowermost or normal operating position, the contact 16' being positioned to be engaged by such arm when the device has been overloaded to the extent that the raking assembly is raised any predetermined amount, and the contact 11 being positioned to be engaged by said arm when the upper limit of safe operating overload has been reached.

As the arms 4 and the associated raking as sembly are raised into position to engage the contact IS, an electrical circuit is completed through a relay I8, closing the contact I9 and energizing a signal lamp 80. A suitable latch member 19' is preferably employed in position to engage the armature of the relay 18, holding the same in contacting position, in view of the fact that the electrical contact I6 will bebut momentary. The. lamp 80 will remain lighted as long as the device is being subjected to an overload, but

Fig. 1, each of the chains exert a pull on the end of the respective torque arms li-JI, tending to rotate the raking element in the same direction and concurrently tending to lift the raking element bodily due to the resistance to rotation of the raking element which is offered by settled solids onv the floor of the tank. As

' shownvin Fig. 3, the chains act upon the torque trical contact members I6, I6, and II, the con- I should the device return to its lowered position (due to a change in the operating conditions within the thickener), so that the contact I6 is en.-

gaged, the latch-releasing relay 8| will be energized, retracting latch member I9 to release the armature of the relay I8, and extinguishing the lamp 8!. Should the raking assembly be considerably overloaded, so that the arms and the associated mechanism are raised to a point such that the contact 11 will be engaged, a circuitwill be completed through relay 82 and the circuit breaker 82' will be actuated, breaking the current supply circuit 83 associated with the actuating motor 66, and the operation of the thickener thus stopped. The alarmcontrolling contact I6 may be placed at any desired position between the lowermost position of the arms 45 and the position of said arms for maximum safe overload.

The operation of the invention is as follows:

Let it be assumed that a liquid with solid particles in suspension is being delivered by the feed launder 21 to the feed well 28; and that the raking element R is being driven in the direction of the arrow in Fig. 1. As the solid particles settle out of the liquid to the floor 16 of the tank III, the blades 36 slowly rake the solids towards the discharge cone l8, fromwhich the solids are drawn out through the outlet I! in the form of a thick pulp. It will be understood that in a thickener the object is to obtain pulp of a certain density. whereas in a clarifier the object is to obtain an I overflow liquid in the overflow launder 3| which is free of the suspended solid particles.

The device of the present invention is intended for operation as either a thickener or clarifier, but for purposes of simplicity the device will be termed a "thickener hereinafter and in the subjoined claims. It will be clear that as the sprocket wheel 6| is being driven in the direction of the arrow in reaction thereof upon the raking element, reference will be had particularly to Figs. 3 and 7, particularly the latter figure in which AB represents one of the chains 89 extending from its connection a on the sprocket wheel 6| to b, its connection to one of the torque arms 45, it being understood that a hnd b are situated at the same radial distance from the axis of the shaft l5.

At B there will be a horizontal i'orce L tangential to the circle of motion of the point B re- 4 sulting from the torque in the raking element created by the resistance oifered'to its rotation by the scraping load. The weight of the raking "assembly and solidswhich have settled thereon creates a downward force W so that the resultant of these forces is the tension T in the chain, the direction of which resultant is the inclination of the chain. In order to overcome these forces and rotate the raking assembly, the sprocket wheel Bl must exert identical but directly opposite forces L and W at the point A.

The weight W may be considered substantially constant, whereas the force L varies in accordance with the resistance of the scraping load in the tank. When L is zero the resultant Twill be equal in value and direction to W so that the chain will hang vertically, whereas when L equals W the resultant T will incline downwardly and a rearwardly relative to the direction of rotation. at an angle of 45. Thus from zero load to a load in which L equals W, the chain changes its direction from the vertical to an inclination of 45".

As the chain AB is of constant length it will be evident that point B must be elevated sufllciently to permit the chain to assume the angle of 45, thus raising the point B (and the associated raking structure) by an amount equal to 6-11 cos 45, where d designates the length AB of a chain.-

In one practical embodiment of the invention, the proportioning of the chain and associated parts is such that the chain will operate between the angles of 30 and as shown in vl ig. 3, wherefrom it will be seen that the operating "lift of the machine will be d cos 30-d cos 60. The minimum angle of 30 is fixed by the thrust bearing'lll which supports the raking element in a predetermined extreme lowered position.

L=.577 of W (th weight of the raking element and solids carried thereby), the raking element will not rise but will operate with its weight sun-- Thus as L=w tan 0, it" will be clear that if 0=30, then L will equal .577W. Therefore for all loads from zero until a load is reached in which Ported by the thrust bearing III.

When L exceeds 577W, the inclination of the chains will exceed 30 and the raking elementwill be lifted to cause the connector 49 to rise on of the head SI of the bolt 50, and the weight by the chains.

of the raking element is then caused to be borne Should the load increase sufficiently to force the chains to assume an angle I of 60, the force L will be 1.73W, the maximum load that the machine is intended to carry safely.

Prior to reaching this extreme raised position, the signal lamp 80 will be actuated, indicating a partial overloading of the device. Should its warning be disregarded, the circuit to the motor 66 will be disrupted to discontinue operation'of the machine when the extreme raised position of the raking element is reached, as above described, thus positively preventing damage to the mechanism.

It will be manifest from the foregoing description that the thickener is fully automatic in its operation to maintain a predetermined definite lowered position from zero load to a predetermined proportion of full load, and to then rise upon a further increase in load until the full load position is reached at which position the operation of the driving mechanism is discontinued before any damage can be done.

Should there be a power failure during operation of the machine, and an accumulation of settled solids during the period in which the power is off, the raking element will automatically rise to a level at which the raking load is not :xcessive, when power is restored, upon which the raking element will remove solids from the top of the bed at a maximum rate until the accumulation is removed and the raking element reaches its extreme lowered position. Thus it will be apparent that should the rate of feed of suspended solids to the tank become excessive, the raking element will rise automatically and then gradually lower as the accumulation of settled solids is discharged from the tank and a normal feed is resumed. Should a solid object fall into the tank and obstruct rotationof, the ranking element, the latter will rise so as to 'all of the blades 35 will be equally relieved of the raking load. Furthermore, due to the submerged position of the lower bearing 39 directly opposite the arms, the shaft I will be relieved of bending stresses resulting from variations in the raking load.

'When it is desired to lift the raking element manually, as, for example, when periodically op-- erating the machine, the handwheel 58 will be suitably rotated for this purpose.

Referring now to Figs. 8 and 9, there is herein shown a second form of automatic safety means for effecting the raising and lowering movements of the raking element in accordance with the resistance to raking movement offered thereto. This means comprises complementary helicoi-.

dal cams I00 and IN, the former of which is constructed on the upper end of the hub I02 of the driving sprocket wheel 6Ia supported. by a ball thrust bearing 60a seating in a collar 59a fixed to the transverse channel members 23a- 23a of the framework 2Ia.

The cam IOI is formed on the lower end of a collar I03 keyed at I03 to the driving sleeve 33a of the raking element and confined against upward axial displacement relative to the sleeve by a nut I04 threaded on the latter. The sleeve 33a may be journaled on the stationary shaft I5a-in the same manner as the sleeve 33 is joumaled on the shaft I5 of the first described form of the invention. The shaft I5a extends to a point above the nut I04, and its upper end is fixed in a collar I05 secured t other transverse members I06I06 of the framework 2la. To these members guy cables I0I may be secured, and connected to the tank to coact with the framework 2Ia in rigidly supporting the shaft I5a.

As the operation of this form of automatic safety means is similar to the form first described, it will suflice to state that normally the raking element will be suspended in its lowermost position shown in Figs. 8 and 9 by the collar I03 and will maintain this position until a predetermined safe maximum raking load is being carried.

Should the raking load increase above this maximum the cams I00 and IOI will coact in response to relative rotation between the driving sprocket wheel 6Ia and the collar I03 caused by the increased resistance ofiered to the raking movement of the raking element, to raise the latter until the excessive raking load is sufficiently reduced, following which the sprocket wheel and collar will reversely rotate relatively and the cams will reversely coact to lower the raking element.

It will thus be manifest that the cams I00 and IIII and the chains 69-69 constitute radically different means for accomplishing the same result, and clearly illustrate the broad scope of this feature of the invention.

Reference will now be had to Fig. 10 in which is illustrated a modified form of rotary mounting for the raking element which differs from the first described form of rotary mounting in the provision of inner and outer sleeves H0 and III between which is freely received a protector sleeve II2 fixed to the socket Mb. The inner sleeve III) is fixed at its upper end to the collar 43b of the torque arm 45b, and is journaled on the stationary shaft or axle I5b by the upper and lower bearings 38b and 39b. The outer sleeve II I is secured at its upper end by bolts II3 to the collar 43b and has the arms 35b of the raking element secured thereto.

As the upper end of the protector sleeve II2 is above the level of liquid in the tank, it will be clear that the bearings 38b and 39b, and the shaft I5b will be fully protected against corrosive and abrasive actions of various liquids and suspended or settled solids. The protector sleeve IIZ provides a mechanical barrier around the inner sleeve H0 from the base of the discharge cone I8!) and insures that none of the contents can reach the bearings and shaft. This feature, in addition to the functioning of the lubricant reservoir between the bearings, assures proper lubrication thereof under all working conditions.

It will be understood that the sprocket wheel structure shown at GI or Blb may be replaced by a worm wheel, gear or other suitable type of drive. Furthermore, it will be understood that the several novel features of the invention herein disclosed may be independently employed in connection with any suitable type of rotary thickening or clarifying apparatus. In particular, the lifting mechanismherein described may be employed independently of the preferred form of shaft and bearing structure which I have shown. For example, the center column such as I5 or I5b may be omitted and the driving sprocket 6| or 6Ib or other equivalent drive member may be 2,295,943 supported by thrust bearing means and journaled' in suitable radial bearing means, said bearing means being carried by a bridge truss over the tank structure as in the conventional Dorr thickener, and the raking assembly maybe carried by and operatively associated with the drive means through the agency of lifting mechanism of one of the types herein described.

I claim:

1. In a thickener, a receptacle having an inlet for liquid and an outlet for sludge; means" for moving settled solids in the liquid towards the outlet; means for driving the first means; means coacting with the driving means and first means to raise the latter bodily in the receptacle in response to resistance to the movement of the first means; and means by which operation of the sleeve and raking mechanism in response to the resistance offered to rotational raking movement; means transmitting to the shaft vertical loads imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to support the shaft and its loads indedriving means is caused to be discontinued when the first means has been raised to a predetermined extreme elevated position.

2. Ina thickener, a receptacle having an inlet' for liquid and an outlet for sludge; rotary and vertically adjustable means in the receptacle for moving settled solids towards the outlet; means for rotating, the first means; and engaging helic-oidal cams of constant slope coaxially arranged relative to the first and second means and operatively connecting them to raise the first means in response to resistance offered to rotation cally vary the vertical position of the sleeve and 4 raking mechanism in'response to the resistance pendently of the tank.

6. In a thickener, a tank having an inlet for liquid-solids mixture and an 'outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the shaft for rotational and vertical movement; a rotary raking mechanism attached to the sleeve and rotatable within the tank to move settled solids to said outlet; drive means for rotatingv the sleeve and raking mechanism; means supporting the sleeve and transmitting to the shaft throughout the range of' vertical movement of the sleeve with respect to the shaft vertical loads imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to support the shaft and its loads independently of the tank.

'7. In a thickener, a tank having an inlet for liquid-solids mixture and an outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the Shaft'for rotational and vertical movement; a rotary raking mechanism attached to the sleeve and rotatable within the tank to move settled solids to said outlet; drive means for rotating the sleeve and raking mechanism including a driving member, and a driven member rigidly secured to the sleeve and provided with an inclined surface drivingly engaged by the driving member, said drive means being adapted toautomatically vary the vertical position of the sleeve and raking mechanism in response to the resistance ofiered to rotational offered to rotational raking movement; 'means I transmitting to the shaft vertical loads'imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to' support the shaft and its loads independently of the tank.

4'. In a thickener, a tank having an inlet for liquid-solids mixture and an outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the shaft for rotational and vertical movement; a rotary raking mechanism attached to the sleeve and rotatable within the tank to move settled solids to said outlet; drive means for rotating the sleeve and raking mechanism including a pair of engaging cams to automatically vary the vertical position of the sleeve and raking mechanism in response to the resistance offered to rotational raking movement; means transmitting to the shaft vertical loads imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to support the shaft and its loads independently of the tank.

- 5. In a thickener, a tank having aninlet for liquid-solids mixture and an outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the shaft for rotational and vertical movement; a rotary raking mechanism attached to the sleeve and rotatable withinthe tank to move settled'solids to said outlet; drive means for rotating the sleeve and raking raking movement; means transmitting to the shaft vertical loads imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to support the shaft and its loads independently of the tank.

8. In a thickener, a tank having an inlet for liquid-solids mixture and an outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the shaft for rota.-

' tional and vertical movement; a rotary raking mechanism attached to the sleeve and rotatable within the tank to move settled solids to said outlet; drive means for rotating the sleeve and raking mechanism including a driving member, and a driven member rigidly secured to the sleeve, one

of said two members being provided with an inclined surface engaged by the other member, said drive means being adapted, to automatically vary the vertical position of the sleeve and raking mechanism in response to the resistance offered to rotational raking movement; means transmitting to the shaft vertical loads imposed by the sleeve and raking mechanism; and means at the lower end of the shaft adapted to support the shaft and its loads independently of the tank.

9. ln a thickener, a tank ,having an inlet for liquid-solids mixture and an outlet for settled solids; a centrally located vertical stationary shaft; a sleeve mounted on the shaft for rotational and vertical movement; a rotary raking mechanism including a driving member provided with an inclined surface engaging a driven member rigidly secured to the sleeve and adapted to mechanism attached to the sleeve and rotatable within the tank to move settled solids to said outlet; drive means for rotating the sleeve and raking mechanism including means to vary automatically the vertical position of the sleeve and raking mechanism in response to the resistance offered to rotational raking movement; and means supporting the sleeve and transmitting to the shaft throughout the range of vertical movement of the sleeve with respect to the shaft vertical loads imposed by the sleeve and raking mechanism.

10. In a thickener of the type in which a raking element is rotated in a liquid receptacle having inlet and outlet means for liquid and outlet means for sludge, the combination comprising: means rotatably mounting the raking element in the receptacle including a lower bearing adapted to be submerged in the liquid; and means defining a lubricant reservoir extending above the liquid level and in communication with the upper end of said bearing to feed lubricant thereto under the greater hydrostatic head of the lubricant, whereby to prevent upward fiow of liquid to the bearing, the lower end of said bearing being in substantially unobstructed communication with the interior of the receptacle below the liquid level, whereby liquid will fiow into said bearing in the absence of said greater hydrostatic head.

11. In a thickener of the type in which a raking element is rotated in a liquid receptacle having inlet and outlet means for liquid and outlet means for sludge, the combination comprising: means rotatably mounting the raking element in the receptacle including a lower bearing adapted to be submerged in the liquid; means defining a lubricant reservoir extending above the liquid level and in communication with the upper end of said bearing to feed lubricant thereto under the greater hydrostatic head of the lubricant, whereby to prevent upward flow of liquid to the bearing; and means defining a space below said bearing in which lubricant working past the bearing can collect to aid in preventing liquid and suspended solids from rising to the bearing, said space communicating with the lower end of saidbearing and being in communication below the lower end of said bearing with the interior of the receptacle below the liquid level, whereby liquid will flow into said bearing in the absence of said greater hydrostatic head.

12. In a thickener of the type in which a rakmg element is rotated in a liquid receptacle having inlet and outlet means for liquid and outletmeans for sludge, the combination comprising:

a vertical shaft in the receptacle; a raking element having inner and outer mounting sleeves; means mounting said inner sleeve for rotation on said shaft; and means interposed between said sleeves for isolating the inner sleeve, mounting means, andshaft from the contents of the receptacle.

13. In a thickener of the type in which a raking element is rotated in a liquid receptacle having inlet and outlet means for liquid and outlet means for sludge, the combination comprising: a vertical shaft in the receptacle; a raking element having inner and outer mounting sleeves; means mounting said inner sleeve for rotation on said shaft; a protector sleeve interposed freely between said inner and outer sleeves and extending from a point below the inner sleeve to a point above the level of liquid in the receptacle; and means for supporting the protector sleeve to seal off the interior thereof from the contents of the tank.

14. In a thickener of the type in which a raking element is rotated ina liquid receptacle having inlet and outlet means for liquid and outlet means for sludge, the combination comprising: a vertical shaft in the receptacle; a raking ele- 1 ment having inner and outer mounting sleeves;

ing element is rotated in a liquid receptacle having inlet and outlet means for liquid and outlet means for sludge, the combination comprising: a raking element having a driving sleeve; means coacting with said sleeve to mount the raking element for rotation in the receptacle; and means coacting with the receptacle and sleeve to isolate the latter from the contents of the receptacle.

16. Rake mounting mechanism for a thickener of the type comprising a tank containing a body of liquid and having inlet and outlet means for liquid and outlet means for sludge and in which a rake is submerged and rotated in said body of liquid, said mechanism comprising: a sleeve with an open lower end extending from above the liquid level to a point below the liquid level and attached to the rake; a stationary shaft extending upwardly from the bottom of the tank within the sleeve; a bearing within the sleeve at a point lower than the tank liquid level rotatably mounting the sleeve on the shaft, said bearing substantially filling the space between the shaft and sleeve so as to form a lubricant; reservoir above thebearing; and a body of fluid lubricant con tained within the reservoir and extending upwardly from the bearing to a point above the liquid level in the tank so as to cause lubricant to flow past the bearing and thereby prevent access of tank liquid to the bearing through the open end of the sleeve, the lower end of said bearing being in substantially unobstructed communication with the liquid through the open lower end of the sleeve, wh'ereby liquid will flow into said bearing in the absence of said body of lubricant.

17. Rake mounting mechanism for a thickener of the type comprising a tank containing a body of liquid and having inlet and outlet means for liquid and outlet means for sludge and in which a rake is submerged and rotated in said body of liquid, said mechanism comprising: a sleeve with an open lower end extending from above the liquid level to a point below the liquid level and attached to the rake; a stationary shaft extending upwardly from the bottom of the tank within the sleeve; and spaced upper and lower bearings within the sleeve rotatably mounting the sleeve on the shaft, the lower bearing being beneath the tank liquid level and substantially filling the space between the shaft and sleeve so as to form a lubricant reservoir above the bearing, and providing within the reservoir a lubricant containing space in which the hydrostatic head of the lubricant is greater than the hydrostatic head of the tank liquid, whereby to prevent upward flow of liquid to the bearing, said sleeve being spaced from and free from engagement with the shaft below the bearing and communicating freely through its open lower end with the liquid, whereby the liquid will flow upwardly between the shaft and sleeve to the bearing in the absence of the hydrostatic head of the lubricant.

18. Rake mounting mechanism for a thickener of the type comprising a tank containing a body of liquid and having inlet and outlet means for liquid and outlet means for sludge and in which a rake is submerged and rotated in said body of liquid; said mechanism comprising: a sleeve with an open lower end extending from above the liquid level to a point below the liquid level and attached to the rake; a stationary shaft extending upwardly from the bottom of the tank within the sleeve; a bearing within the sleeve at a point lower than the tank liquid level rotatably mounting the sleeve on the shaft, said bearing substantially filling: the space between the shaft and sleeve so as to form alubricant reservoir above the bearing; and a body of fluid lubricant contained within the reservoir above the bearing and extending upwardly from the bearing to a point above the liquid level in the tank so as to cause lubricant to flow past the bearing and thereby prevent access of tank liquid to the bearing through the open end of the sleeve, the sleeve projecting below the bearing to provide a pocket in which lubricant passing the bearing collects to aid in preventing access of tank liquid to the bearing, said sleeve being spaced from and free from engagement with the shaftbelow the bearing and communicating freely through its open lower end with the liquid,- whereby the liquid will flow upwardly between the shaft and sleeve to the bearing in the absence of the hydrostatic head of the lubricant.

JOHN H. V. FINNEY.