US2856124A

US2856124A - Centrisweep

Info

Publication number: US2856124A
Application number: US608337A
Authority: US
Inventors: Horace F Cook; George L Nelson
Original assignee: Bird Machine Co Inc
Current assignee: Bird Machine Co Inc
Priority date: 1956-09-06
Filing date: 1956-09-06
Publication date: 1958-10-14
Anticipated expiration: 1975-10-14

Description

Oct. 14, 1958 F. COOK ETAL 2 CENTRISWEEP Filed Sept. 6, 1956 r 3 Sheets-Sheet 1 if f/ m 14/ 1 I Z4 1/ 1/ I Q55 .17 l:

Oct. 14, 1958 H. F. COOK ,ET AL 2,856,124

CENTRISWEEP Filed Sept. 6, 1956 V 3 Sheets-Sheet 2 Oct. 14, 1958 H. F. COOK ET AL 2,856,124

CENTRISWEEP Filed Sept. 6, 1956 I5 Sheets-Sheet 3 United CENTRISWEEP Application September 6, 1956, Serial No. 608,337 6 Claims. (Cl. 233-7) This invention relates to a centrifugal separator of the type having a sweeper blade for sweeping the interior of the centrifuge bowl to remove the solid particles of the centrifuged material from the bowl endwise thereof, the separation of the solid particles from the liquid being carried out by centrifugal sedimentation.

One object of the present invention is to provide a centrifugal separator of the foregoing type constructed and arranged to handle a slurry containing friable solid par ticles with a minimum of degradation and attrition of the particles.

Another object is to provide a separator of the type described capable of handling liquid suspensions of fibrous material without jamming and with a minimum of tearing or degradation of the fibers.

Another object is to provide a centrifugal separator of the type described having an improved construction in which the interior rotating assembly as a whole can be dynamically balanced.

Another object is to provide a centrifugal separator for which means for driving the sweeper blade are shielded from contact with the material to be centrifuged.

Still another object is to provide such a separator in which the relative movement of the centrifuge bowl and of the sweeper blade is such that each particle of centrifuged material swept out of the bowl follows a smoothly curved path of the same geometrical shape across the interior of the bowl, the periphery of the sweeper blade being maintained perpendicular to the path of sweeping at each point on the path to minimize the shearing, or fracturing forces on any solid particles being swept out.

A further object is to provide such a separator in which the rotational speed of the sweeper blade about its own axis is substantially constant, thereby maintaining a substantially uniform load on the sweeper blade rotating mechanism and avoiding problems of backlash.

Other and further objects will be apparent from the drawing and from the description which follows:

In the drawings:

Fig. l is a view in side elevation, partly broken away and in section, of one embodiment of the invention;

Fig. 2 is a view in end elevation of the embodiment shown in Fig. 1;

Fig. 3 is a view in section taken along the line 3-3 of Fig. 1;

Fig. 4 is a view in elevation of the sweeper blade;

Fig. 5 is a view in side elevation on an enlarged scale, partly broken away and in section, showing the manner in which the sweeper blade is mounted within the rotary bowl;

Fig. 6 is a view in cross-section showing another embodiment of the invention; and

Fig. 7 is a view in cross-section showing still a third embodiment of the invention.

Referring to Fig. 1, the device of the present invention comprises a housing 10 mounted on a support 12 having an outlet 14 for liquid efliuent material. A pair of pedestates atent

ice A tals

16, 18 support main bearings 20, 22 in which are journaled aligned hollow shafts 24, 24'. Sheave 26 is secured to the flanged end of shaft 24 by means of

bolts

28, 28 and is driven from motor 30 by means of belt 32.

Rotary bowl 35 is supported between and secured to opposing ends of

shafts

24, 24 by means of

spiders

36, 36, bowl 35 being located within stationary housing 10 and being ro'tatabiy driven together with shafts 24, 24' by means of motor 3% (Fig. 2).

At the opposite end of shaft 24 and driven therefrom is a differential drive mechanism 34 of the type described in Piper U. S. Patent 1,962,461 granted June 12, 1934. Within the interior of hollow shaft 24 is mounted a second shaft 33 supported by bushing 39 and driven from drive mechanism 34, which may be adjusted to provide any desired speed ratio between

shafts

24 and 38. It will be understood that any other suitable means may be provided for maintaining a predetermined differential between the speeds of the two shafts. in practice it has been found that a ratio of the order of 144:143 is satisfactory but it will be understood that the ratio may be varied over a wide range.

Shaft 38 serves to support and rotate a hub member 46 (Fig. 5) bolted to a flanged end 48 of shaft 38 within rotary bowl 35 so that bowl 35 and hub 46 have a common axis of rotation. Hub 46 is provided with diametrically opposing passages 50, 5t) connecting the :interior of hub 46 with the interior of rotary bowl 35, and is supported at its opposite end by bushing 39 on hollow shaft 38, being secured thereto by bolting to flanged end 48'. The free end of shaft 38 is positioned by thrust bearings 51 within sheave 26.

Extending through hollow shaft 38 is a stationary influent supply pipe 52 mounted on bracket 54 which is secured to pedestal 18. An aperture 56 adjacent the inner closed end 58 of supply pipe 552 at the center of hub 46 is provided to introduce the liquid influent or slurry into the interior of the device, the infiuent passing through apertures 56, St in hub 46 as the latter rotates.

A pair of oppositely disposed efiiuent discharge pipes 69, 60 extend inwardly from the periphery of rotary bowl 35, each pipe being adjustable in position and provided with a deflector 62 which serves to deflect influent slurry as it emerges through openings and prevent loss of feed solids into the filtrate.

Sweeper blade 64 (Fig. 4-) has a generally closed periphery matching that of theinterior of bowl 35, being preferably of generally circular configuration and is mounted on hub 2-6 (Fig. 5) for rotation about its own axis of symmetry, as represented by a line passing through the center of blade 64 perpendicular to the plane defined by its periphery. The axis of symmetry of blade 64 intersects the aXis of rotation of bowl 35 and of hub 46 at an acute angle, so that as bowl 35 rotates with respect to hub 46 about their common axis of the plane of rotation of the blade oscillates with respect to the bowl with the margin or periphery of the blade sweeping across substantially the entire inner face of the shell from end to end. At every position of blade 64, opposite portions of its periphery extend adjacent opposite ends of bowl 35. To permit simultaneous rotation of blade 66 about its own axis of symmetry, it is secured to bearing ring 70 and to ring gear 72 by means of bolts 74, 74. Ring gear 72 is provided with a radially outwardly extending flange 76 which is engaged by an overlying shoulder of locking ring 78 which in turn is secured to a flan R6 of hub 46 by means of bolts 80. 80. Two O-rings 32-, 82 are provided to seal ring gear 72 from contact with the slurry entering the hub a d rotarv she l thronsh inlet 56.

Meshing with ring gear 72 and serving to drive the same is a pinion gear 84 mounted for rotation about shaft-38.and keyed at 86 to shaft 24 for rotation therei ring 885 i's k secured in place-on shaft 38 .by-means* of-" a snapring. Seals9 0,,*9tl arejprovided' to prevent access. of the slurry or its components to" the shaft bearings-or to the' gears, while seal9li-serves tocontain the lubricantfor the gears. Boltedto'hub 46- and extending. axially outwardlylbeyond rotary bowl 35 are members92; 92'

which. serve to balance the unsymmetrical distribution of mass ofrhub 46, ring gear 72 and blade 64, and also serve as plows to remove from the. interior of spokes 96. of. spider 36'. any accumulated material which tends to. build; up. in. these locations.

Because of the 2:1 ratio between ring gear 72. and pinionv 84. andthe speed differential between bowl 35 and" hub46 .(on which sweeper plate 64 is mounted), bowl 35. advances 90 with-respect tosweeper blade 64 during each.one-halfrev-olution of thesweeper blade about the axis of bowl 35. Accordingly, it is necessary to provide four gaps or apertures 65, 65 (Fig. 4) which are 90. apart in the. periphery of sweeper blade 64 to permit itto. pass the two

discharge pipes

60, 60 during its. sweeps. Since the path across the face of bowl 35 traced by these apertures is dilferent during the return half of the sweep of blade 64, any particulate materiallleft during the first half of the sweep in the track of the gaps 65 is swept out during the return half. Blade 64lmay also be provided with

ribs

66, 66 which serve both as reinforcing or strengthening elements and as deflectors tending to prevent material fromsliding across the face of rotating blade 64 and through

gaps

65, 65

Bafiles 100,100, 102, 102 are provided within the interior of stationary housing 16 to compartmentalize this housing and separate the central zone between

baffle members

102, 102 into which discharge pipes 60 empty, from the side compartments adjacent spiders 36,316, Access openings provided with removable covers, 104, 104may be provided at any suitable locations about stationary housing It). A labyrinth type seal be tween shaft 24 and housing It) is provided by means of fiinger plates 106, 166 which are secured to shaft 24 adjacent the end walls of housing It). Semi-circular shields 108, 1% are provided extending inwardly from the walls of housing 10 and overlying the upper half of

fiinger plates

106, 106 as seen in Fig. 5 to deflect toward the interior of housing any material running down the walls of the housing.

In operation of the device, rotary bowl 35 is driven together with

shaft

24, 24 at any suitable speed, say from 1000 to 3000 R. P. M., in the case of a machine having a bowl 35 which is inches in diameter, by means of motor 30, belt 32 neously hub 46 is driven from shaft 38 through drive mechanism 34 at a slightly lower speed, hub 46 rotating in the same direction as rotary bowl 35. When bowl 35,, for example, is driven at 1800 R. P. M. and the speed ratio in drive mechanism 34 is 144:143, the speed of hub 46 is l787 /2 R; P.'M., so that bowl rotates at a speed of 12 /2 R. P. M. with respect to hub 46., This difference in speed may be varied without limit, but preferably is from 4 to 40 R. P. M. Because of this speed diiferential the plane defined by the outer periphery of sweeper blade 64 mounted on hub 46' oscillates with respect to bowl 35, sweeping from one end oftthe bowl adjacent shaft 2.4.',.the number of cycles per minute being equal to the speed differential, which in the specific example given above is. at the ratio of 12 /2 cycles per minute. Furthermore, sweeper blade 64 is simultaneously rotated about its own axisof symmetry bythe interaction of ring gear 72and pinion 84, so that the total speed'of rotation of the sweeper blade about the axis of the hub and sheave 26. Simultashaft 24 to the other end adjacent g which 'itis introduced thereafter.

is dififerent from the speed of the bowl and the speed of the hub andmidway between these two speeds--when the ratio of ring gear 72 to pinion 84 is 2:1. That is, the speed of blade 64 about its own axis of symmetry is 6% R. P. M. with respect to the hub 46. According ly, the apparent speed of blade 64 with respect to bowl 35 (measured about theaxisof rotation of bowl 35) is also 6% R. P. M., the speed of blade 64 about the axis of the hub being interm'ediatethe speed of the hub and of sweeper blade 64; simultathev bowl. This rotation neously about two "diver gent axes causes each portion of the periphery of blade64 to sweep across the inner face of bowl 35 with the blade being maintained substantially-perpendicular to the directionof sweep at each point along the path and with a minimum of shearing effect upon the material being swept out of bowl 35, as will be explained more fully hereinafter.

The slurry which is to be separated into its solid andliquid components is introduced through inlet pipe sea-11 emerges through aperture into the interior of rotary bowl by centrifugal force as bowl '35 rotates. Because the slurry is" equally divided between of which is always on the'opposite 35. ,-Inother words, theinfluent slurry is deposited uniformly andprogressively on 35, in synchronismwith thesweepingadvance of: sweeper pipes 60; 60 whence it baffiestfiz, 162; ber 112st the withdrawn through: effluent pipe passes into thezone between While. the sclidparticulate material-Ht) is accumulating in a layer adjacent the inner'face of rotary bowl35i sweeper blade 64Zis sweeping slowly back and forth and sweeps the solid material toward spiders'36, 36 until a bed of solid material has accumulated in the form shown in Fig-5.

from. the surface of the faces 114, ments of housing 10. Itfwill'be'noted that of

outlet pipes

60, 66 is adjusted liquid within rotary shell 35 reaches to a point-between pipes 68 and the outer margins of faces 114. That portion of the arcuate faces 114 together with any portion of the bed of solid particles beyond'the margin of theliqu'id may be termed a beach are swept orscraped by blade '64." This'mode of operation permits substantially complete separation of. I'the' solid and liquid phases as the -solid is swept across the beach. by sweeper blade 64; Any solid material'iinpinging upon the inner face of'spokes plows 92, 92 and'the solid material the position drops out the bottom of the side compartments of housing 10, into any suitable" 56 into the interior of hub 46 whence it passes through passages50, 50 35, on opposite sides" of sweeper blade 64, andimpinges upon the inner face of the generally cylindrical bowl35; being held

in'place passages

50, 50 each side of'sweeper'blade 64 fromthe other aperture, there-is a balancedload on' opposite faces of the sweeper blade as well as on bowl-- the inner face of have" as shown 'in' 110 'hav'e been" separated begins to-overflowthe innerl'nargin of outlet of'housing It) and accumulates in chambottom of housing 10 whence it maybe 14 at the same rate at Thereafter each sweep of sweeper blade'64 scrapes-all additional centrifugally settled solid material bed and sweeps it'across arcuate 11-4 of spiders '36, 36 into the side compartso that thelevel of across which the

sblidparticles

96, 96 is: removedbr the bed of solid material 110 and the beach. This con- -struction and mode of operation provides for a direct push upon each solid particle substantially in the direction of travel of the particle at all times and moves each particle out of rotary bowl 35 with a minimum shearing effect of sweeper blade 64 upon solid particles.

This minimal shear effect provides improved operation of the device when separating frangible or friable crystalline materials from liquid slurries. The solid material separated from the slurry by the action of the present device is remarkably free from broken or fractured particles, as well as free from scratches on the smooth faces of the particles, a feature which is particularly important in the case of certain crystalline materials such as sugar and a variety of other organic and inorganic crystalline solids. The minimal shear effect also makes the machine of the present invention particularly useful for separating fibrous material from liquid suspensions with strikingly improved results as compared with conventional centrifugal separators. When used with such fibrous suspensions the machine is remarkably free from jamming, does not appreciably tear or degrade the fibers, and provides highly effective separation of liquid from the fibers.

As pointed out above, the solid portion of the slurry may be allowed to accumulate within rotary bowl 35 to form a bed across the surface of which fresh solid material is swept out of bowl 35 by means of sweeper blade 64. However, in the embodiment shown in Fig. 6, the accumulation of the bulk of this solid material is rendered unnecessary by the provision of filler members 120, 125) made of any suitable material such as rubber, plastic, stainless steel, etc., and shaped to provide a generally spherical inner surface for bowl 35. This embodiment provides for use of the machine with slurries containing solids which might decompose if allowed to stand for appreciable periods of time.

There is shown in Fig. 7 still another embodiment of the invention in which sweeper blade 130 is rigidly secured directly to hub 132 as by bolting thereto. In this embodiment of the invention, in which sweeper blade 130 rotates about only a single axis of rotation, namely the axis of rotation of hub 132 and of rotary bowl 35, there is a small amount of shear between the face of the sweeper blade and the particles of solid material being swept out of bowl 35. However, only two

apertures

65, 65 in the periphery of sweeper blade 130 which are 180 apart are required in this embodiment, in order to clear any given number of outlet pipes provided they all lie in the same plane perpendicular to the axis of rotation. In addition, in this embodiment the bowl 35 may be polygonal instead of circular in cross-sectional configuration and blade 130 may have a mating or matching polygonal periphery. Indeed, in this embodiment blade 130 may be polygonal even when bowl 35 is cylindrical or spherical, the centrifugally settled solid particles building up on the inside of bowl 35 providing a configuration which matches that of blade 130. While this small amount of shear may be tolerated in the case of certain solid materials without producing excessive fracturing or tearing of the solid material, the embodiments of Figs. 5 and 6 in which the sweeper blade 64 rotates about its axis of symmetry are preferred.

Although specific embodiments of this invention have been described herein, it is not intended to limit the invention solely thereto but to include all of the obvious variations and modifications within the spirit and scope of the appended claims.

We claim:

1. A centrifugal separator comprising a rotary bowl, a hub mounted within said bowl for rotation about the axis of rotation of said bowl, a sweeping blade mounted on said hub within said bowl, said blade having a pcriphery lying generally in a plane, the axis of symmetry normal to said plane intersecting the axis of rotation of the bowl at an acute angle with opposite portions of the periphery extending adjacent opposite ends of the bowl, said blade being mounted for rotation with respect to the hub about said axis of symmetry, and means for rotating said bowl and said hub simultaneously at different speeds in the same direction about said axis of rotation and for simultaneously rotating said blade about said axis of symmetry at a speed different from both the speed of the bowl and the speed of the hub about said axis of rotation while maintaining a fixed ratio between the speed of the bowl and that of the blade to cause the blade to sweep the bowl from end to end and to remove material from the bowl endwise thereof.

2. A centrifugal separator as defined in claim 1 in which the hub and bowl both rotate in the same direction with the hub rotating at a speed less than that of the bowl, and the apparent rotation of the blade about the axis of rotation of the bowl is in the same direction as the hub and bowl and at a speed intermediate that of the hub and that of the bowl.

3. A centrifugal separator as defined in claim 1 in which the difference in speed between the hub and the bowl is from 4 to 40 revolutions per minute, and the speed of the blade is approximately onehalf of said difference.

4. A centrifugal separator comprising a rotary bowl, a hub mounted within said bowl for rotation about the axis of rotation of the bowl, a sweeping blade having a closed periphery lying generally in a plane mounted on said hub within said bowl with the axis of symmetry normal to the plane of the periphery of the blade intersecting the axis of rotation of said bowl at an acute angle whereby opposite portions of said periphery extend adjacent opposite ends of said bowl, means for rotating said bowl and said hub simultaneously in the same direction while maintaining a fixed ratio between the speed of the bowl and that of the hub, and drive means interconnecting said bowl and said blade for simultaneously rotating said blade about said axis of symmetry at a speed different from both the speed of the hub and the speed of the bowl while maintaining a fixed ratio between the speed of the bowl and that of the blade, whereby the periphery of the blade sweeps the interior of the bowl from end to end to remove therefrom endwise of the bowl a portion of the centrifuged material.

5. A centrifugal separator as defined in claim 4 in which the drive means includes a gear mounted for rotation with said bowl and a second gear intermeshing with the first mounted for rotation with said blade about said axis of symmetry and in which said hub includes means for shielding said gear from contact with the material being centrifuged within said bowl.

6. A centrifugal separator comprising a rotary bowl, a hub mounted within said bowl for rotation about the axis of rotation of the bowl, means for rotating said bowl and hub simultaneously while maintaining a fixed ratio between the speeds thereof with the speed of the bowl exceeding that of the hub by 4 to 40 revolutions per minute, a sweeping blade having a generally circular periphery mounted on said hub for rotation about the axis of symmetry of the periphery of the blade, said axis of symmetry intersecting the axis of rotation of the hub and bowl at an acute angle whereby opposite portions of the periphery extend adjacent opposite ends of the bowl, the blade sweeping the interior of the bowl from end to end upon rotation of said bowl and hub to remove endwise of the bowl a portion of the centrifuged material, and means interconnecting said bowl and blade for simultaneously rotating the blade about said axis of symmetry while maintaining the speed of the blade with respect to the hub about said axis of symmetry equal to a fixed fraction of the difference in speed between the hub and the bowl.

References Cited in the file of this patent UNITED STATES PATENTS 2,414,421 Small Ian. 14, 1947 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,856,,124 October 14, 1958 Horace F. Cook et alw It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected belowa Column 6, line 49, for "gear" read m gears 0 I (SEAL) Attest:

KARL HQ AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents