Multiple drum centrifugal

May 7, 1940.

2,199,849

T. A. BRYSON

MULTIPLE DRUM CENTRIFUGAL Filefl Aug. 2, 1935

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Patented May 7, 1940

2,199,849

UNITED STATES PATENT OFFICE

2,199,849 MULTIPLE DRUM CENTRIFUGAL Tandy A. Bryson, Troy, N. Y. Application August 2, 1935, Serial No. 34,375 9 Claims. (Cl. 233—17)

My invention relates to improved feeding means for centrifugal machines of the sedimentation type for the treatment of liquid material, and particularly, but not exclusively, to those in which 5 two or more rotatable drums of different size and different separating capacity are coaxially arranged in nested relation, and to which the material to be treated is fed in parallel.

As pointed out in my copending application 10 Serial No. 653,271, filed January 24, 1933, it is quite essential that the material treated in each drum of a multiple drum centrifugal machine of this type be subjected to- substantially the same force-time effect. Where the drums are nested 15 one within the other, they are naturally of different diameter and the centrifugal force-effect decreases from a maximum in the outer drum to a minimum in the inner drum. This being so, the material must be subjected to treatment for 20 longer periods of time in the inner drums than in the outer drum. The relative separating capacities of a plurality of drums of different diameters and rotating at the same number of revolutions per minute are in accordance with the 25 squares of their respective radii. This being so, the material to be treated should be fed to the drums at different rates and in accordance with this rule.

One of the objects of my invention is to provide 30 a simple feeding means whereby material withdrawn from a common source of supply will be positively fractionated and delivered to the respective drums at rates proportional to their separating capacities. A further object is to pro35 vide a feeding means which will positively accelerate the material in the direction of drum rotation so that vzhen it reaches the drums it will already have a high circumferential velocity thus leaving much less of the work of acceleration for 40 the drums to do. This means that there will be less scour in the drums, the average rotative speed of stock within the drums will be increased, and hence more centrifugal force will be applied to the stock, and the separation will be conducted 45 more efficiently. In other words, by subjecting the stock in the drums to a greater centrifugal force than is now possible with present types of feed, the stock may be passed through the drums at higher velocity and yet be subjected to the same 50 force-time effect. Hence, a higher feed rate can be maintained and the separating capacity of the unit thereby increased.

With these objects in view my invention includes the novel elements and the combinations 55 and arrangements thereof described below and illustrated in the accompanying drawing, in which—

Fig. 1 is a fragmentary elevation, partially in section, of my machine;

Fig. 2 is a bottom plan view of the interior of a 5 frusto-conical element forming part of the feeding means;

Fig. 3 is a fragmentary development showing the inside surface of the frusto-conical element illustrated in Fig. 2; 10

Fig. 4 is a fragmentary section through the feed assembly in the plane 4—4 of Fig. 2;

Fig. 5 is a fragmentary section through the feed assembly in the plane 5—5 of Fig. 2; and,

Fig. 6 is a fragmentary section through the feed 15 assembly in the plane 6—6 of Fig. 2.

Referring to the drawing, centrifugal machines to which my feeding means is applicable generally comprise an outer stationary casing I and a circumferential gutter or trough 2 into which the 20 treated material is discharged. Rotatably mounted in suitable bearings 3 and 4 in the central portion of the casing 1 is a spindle 5 driven by means of a pulley S and the belt or rope 7. Secured to the upper portion of the spindle and 25 rotatable therewith is a frusto-conical hub 8, the bottom of which is carried out horizontally, as shown at 9, and serves to support the drum assembly. The outer drum is shown at 10, the intermediate drum at li, and the inner drum at 12. 30 The outer drum may be supported directly on the horizontal lip 9 as shown at 13; the intermediate drum may be supported on projections 14 so that its bottom is raised somewhat above the level of the bottom of drum ί 0; and the inner- 35 most drum 12 may be supported on a perforated baffle 15 secured within drum I i, and so¹ that its bottom is positioned at a somewhat higher elevation than the bottom of the intermediate drum i I. The drums may be held in spaced, concentric 40 relation, coaxial with the spindle 5, by any appropriate means, but are preferably maintained in this relative relation by the ribs 40 and the baffles 15, as shown. At the bottom, the innermost drum 12 is provided with an inwardly pro- ⁴⁵jecting lip 16, the intermediate drum is provided with a similar lip (7, and the bottom 9 of the hub 8 forms the equivalent of an inwardly projecting lip for the outer drum f 0. At the top, ₅₀each of the drums is provided with an inwardly projecting lip as shown at 18, 19 and 20, and it is to be noted that the elevation of the tops of the drums increases from the outer to the inner drum so that the material may be discharged 55

2,169,849 over the tops of the inner drums without interference.

Coaxial with the spindle 5 and the frustoconical hub 8, is an outer frusto-conical shell or 5 element 2i spaced from the hub 8 to provide therebetween a passage for the flow of material to be treated. The space between the frustoconical elements 8 and 21 is subdivided into a plurality of vertically extending ducts 22 by 10 means of a plurality of circumferentially spaced vanes 23. These vanes 23 extend from the top of the outer frusto-conical element to the bottom thereof and may be secured thereto by rivets or other means, as shown at 24. Preferably, these 15 vanes are not elements of the frusto-conical surface 21 but are made in spiral form as shown in Figs. 2 and 3; it being understood that the upper ends of the spirals are further advanced, in the direction of rotation, than the bottoms of 20 the spirals. In other words, the bottoms of the vanes trail the tops thereof as the device rotates. A common feeding cone or funnel 25 having a depending cylindrical portion 26 receives all of the material to be treated and discharges it into 25 the ducts between the frusto-conical members. As the liquid material passes outwardly in contact with the upper portions of the vanes 23, it is not only picked up thereby and rapidly accelerated in the direction of rotation of the drums 30 but is actually displaced downwardly and driven into the ducts between the frusto-conical elements.

Since the separating capacities of the drums are not equal, it follows that the flow capacity 35 of the ducts must be proportioned to conform to the separating capacities of the respective drums which they feed. In Fig. 2 I have shown twelve ducts, four of which 27 are arranged to discharge into the outermost drum through the 40 orifices 32 at the bottom. These are the largest ' ducts and the discharge orifices which will be later described are distributed symmetrically about the axis of rotation. Similarly, the ducts 28 have the lowest flow capacity and are ar43 ranged to discharge into the innermost drum through orifices 29 which are likewise symmetrically disposed 90° apart about the cone 2 ί. The flow capacity of the intermediate ducts 30 which feed the middle drum is, of course, intermediate 50 the flow capacities of the ducts feeding the inner and outer drum, and the discharge orifices 31 therefor are symmetrically disposed about the periphery of the cone 21.

It will be observed from a consideration of 55 Figs. 2, 3, 4, 5 and 6 that the discharge orifices 29, 31 and 32 are arranged at different levels. The outer conical shell 21 may terminate at the bottom at the proper elevation so that material discharged therefrom will be projected into the 60 outer drum, and ducts 28 and 39 are blocked at the proper elevation to discharge into the inner and intermediate drums, respectively, by the blocks 33 and 34.

The orifices 32 discharge partly upon the ring 65 35 secured to the hub 8 below the orifices 32 and at an elevation somewhat above the portion 9 which forms the inwardly projecting lip at the bottom of the outer drum. A spinner ring 36 is secured to the frusto-conical element 21 at the 70 bottom of the orifices 31 and the top of this spinner ring is at a somewhat higher elevation than the top of the inwardly projecting lip 17 of the intermediate drum 11. Likewise a spinner ring 37 is secured to the conical element 2! at 75 the bottom of the orifices 29 and the top of this spinner ring is at a somewhat higher elevation than the top of the inwardly projecting lip 16 of the innermost drum.

From the foregoing it will be apparent that as the material is discharged from the common 5 feeding means 25 into the space between the frusto-conical elements 8 and 21 the total supply will be positively divided or fractionated, by means of the vanes 23, into a plurality of separate streams which, in turn, are subdivided into 10 groups so that each group feeds one of the drums. By properly proportioning the flow capacities of the ducts between the frusto-conical elements, the material fed to the machine will be positively fractionated and delivered to the various drums 15 in accordance with their respective separating capacities. Due to the presence of the vanes 23 in the space between the frusto-conical elements the liquid material will be rapidly accelerated in the direction in which the drum assembly is 20 rotated so that as it is delivered from the orifices 29, 31 and 32 it will have a substantial cir- . cumferential velocity.

I find that by extending the vanes 23 entirely to the top of the conical element 21 and inclin- 25 ing the upper -portions thereof at an angle of about 45° to the cone elements they act . as efficient impellers, not only to give the stock a spinning motion, to develop a velocity head which will force it into the space between the cones, 30 but, because of their inclination to the vertical, they will actually displace the stock downwardly and drive it into the space between the cones.

I also find that if the vanes are . curved roughly in accordance with the path -which .the mate- 35 rial would take if the vanes were omitted, unnecessary turbulence is avoided and the possibility of the formation of eddies where fiber may be deposited and built up eventually :to clog the duct is minimized. I also prefer to leave the bottom portions of the vanes .at an angle of not ⁴⁰less than about 15° to the cone elements rather than attempt to push the stock around to a complete vertical flow.

From the foregoing, it will be apparent that ₄₅the advantages to be derived from using my. invention are not confined solely to its application to a multiple drum type of machine. Since the separating efficiency of each, drum in the assem bly is increased it follows that the separating ef- ₆₀ficiency of any single drum machine may be increased by using impeller vanes in a conical feeding duct, whereby the stock passing therethrough is positively accelerated in the direction of rotation of the drum and delivered to the 55 -drum with a high circumferential velocity, thus reducing scour and increasing the average centrifugal force -acting upon the stock during the time it is in the drum.

While I have described my invention in its pre- go ferred embodiments, it is to-be understood that the words which I have used are words of description rather than of limitation. Hence, Changes within the purview of the appended claims may be made without departing from the' 65 true scope and spirit of my invention in its broader aspects.