US2707561A - Stabilizer for centrifugals operated with a liquid charge - Google Patents

Description

2 Sheets-Shee 1 May 3, 1955 J. igERTRICH STABILIZER F R CENTRIFUGALS OPERATED WITH A LIQUID CHARGE Flled April 30, 1949 IN VEN TOR. (1451521 /7KIfiI6/l J. HERTRICH May 3, 1955 m w E P 0 ma A G m m RC D m1 cm I R L A R E w I B A T s 2 Sheets-Sheet 2 Flled April 50, 1949 Hill I N V EN TOR. lager/1 fiEKTK/fi mf 4270405 .r

United States Patent 0 STABILIZER FOR CENTRIFUGALS OPERATED WITH A LIQUID CHARGE Joseph Hertrich, Hamilton, Ohio, assignor to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Application April 30, 1949, Serial No. 90,622

9 Claims. (Cl. 210-63) machine can be safely operated with a body of liquid in 1.

its spinning basket.

The invention is applicable to centrifugals having baskets of either the solid bowl or the perforated wall type, in which the charge processed comprises at least an inner layer of liquid. The charge material treated in such centrifugals is usually a liquid or sludge from which either liquid and suspended solid components or different liquid components are separated by centrifugal force.

It is well known that the effectiveness of centrifugal separation varies with the speed and the radius of rotation of the charge in the centrifugal basket, which determine the centrifugal force applied. It is also well known that the speed attainable safely in practical operations using a large basket is far more limited in processing a liquid or sludge that forms a body of liquid in the basket than it is in processing charge material that forms a solid or non-flowing body in the rotating basket. In the former case the annular layer or wall of liquid in the basket becomes uneven under certain critical speed conditions, and when the basket is operated on a solidly mounted shaft the resulting unevenness of weight distribution produces intensive vibrations that become intolerable beyond certain limiting speeds of rotation. When the basket is mounted on a gyratory shaft the resulting eccentricity of weight causes the basket to gyrate dangerously and even to strike against its surrounding casing or curb under certain conditions.

Accordingly, centrifugal separations requiring the presence of a rotating annular body of liquid in a large spinning basket have been limited in effectiveness heretofore by the instability of the centrifugal operation with a liquid charge. This instability has imposed severe limitations upon the speeds of rotation safely to be reached,

and by thus limiting the available centrifugal force it has kept centrifugal separation inapplicable, as a commercially practical matter, to various liquid charge materials that otherwise might be processed to advantage in centrifugal machines.

The principal object of the present invention is to pro- Patented May 3, 1955 that excessive vibrations or gyrations produced in operating a centrifugal basket at a high speed with an annular body of liquid in the basket can be prevented, or can be overcome after having commenced, by imposing a drag or obstruction upon fluid rotating with the spinning basket adjacent the inner face of the charge therein so as to retard the rotation of the fluid in a portion of its orbit. For this purpose a drag member may be held in the path of the rotating fluid, for example, a member presenting stationary surfaces in said path which lie in planes transverse to the axis of the charge rotation and are spaced apart in the direction of that axis over a large part of the height of the charge.

The drag member preferably is made with a plurality of vertically spaced baflles or blades having edges disposed horizontally or at a small angle to horizontal and movable to insert these edges into the surface of the liquid of the spinning charge without objectionable disturbance of the liquid.

While the greatest stabilizing effect may be obtained by thus engaging the drag member with the liquid of the charge, it has been found that a degree of stabilization effective to prevent undue swaying of the basket under many circumstances can be obtained by merely holding the drag member close to the charge liquid across the path of the strong air currents which circulate there as the basket spins at high speed. In either case, the edge of each blade imposes a drag upon the surface of the spinning liquid along an are lying transverse to the axis of the charge rotation.

A stabilizer quite effective for the purposes of this invention may be provided as a group of vertically spaced blades held inside the spinning basket, lying transverse to its axis of rotation, and movable horizontally to from the surface of a liquid charge in the basket. Whenever excessive vibrations or gyrations occur in the centrifugal operation at high speeds, or during stages of such operation when they would otherwise occur, the group of blades may be moved bodily toward the surface of the liquid, either to approach it closely or actually to immerse the blade edges in the liquid surface, thereby imposing a drag on a spinning fluid component of the system which retards its rotation in the zone of the stabilizer with consequent avoidance or prevention of basket instability.

A further feature of this invention arises from the discovery that the efficiency of the centrifugal separation as well as the stability of the centrifugal operation may be influenced favorably by imparting a certain directional flow to the inner surface of the rotating body of liquid in the centrifugal basket, particularly in counteraction to a flow generally induced on the same surface from the introduction of liquid charge material at one end portion of the spinning basket. This directional force may be applied to the surface of the rotating liquid by a slight inclination of stabilizing projections or blades across paths of rotation of the liquid. For example, in operating with a vertical centrifugal basket to which liquid charge material is introduced at the bottom, the liquid added to the spinning charge generally runs up the liquid inner surface of the charge, but by inserting. stabilizing blades into the liquid surface at a slight downward inclination this action may be avoided so as to bring about a more eflicient centrifugal separation or settling of solids, apparently through more even distribution of the added material into the charge.

Other objects, features and advantages of this invention will become apparent from the following detailed description of an illustrative embodiment and from the accompanying drawings in exemplification thereof, wherein:

Fig. 1 is a plan view of portions of a centrifugal ma- 3 chine embodying a liquid stabilizer in assembly with other elements according to this invention;

Fig. 2 is a perspective view of the liquid stabilizer;

Fig. 3 is a vertical section taken approximately along line 33 of Fig. 1; and

Fig. 4 is a fragmentary vertical section taken approximately along line 44 of Fig. 1.

According to the illustrated embodiment, the invention is applied to a centrifugal machine employing a large open-top vertical basket 1 which is carried by a vertical shaft 2 suspended from an overhead gyratory centrifugal head or mounting (not shown) of any suitable or known construction. The basket is enclosed within a surrounding stationary casing or curb 3 in well known manner, so that liquid filtered through or overflowing the basket is collected by the casing. The basket may be one of the solid wall or bowl type, in which case the cylindrical side wall 4 is imperforate; or wall 4 may be a perforated wall when separating fine particles of solids from a sludge or slurry, if it is pre-lined by solids to form a filtering medium suitable for retaining the fine particles.

The side wall 4 is held between the basket bottom 5 and the open basket top 6 so as to define an inwardly opening annular space 7 in which a charge is held and subjected to centrifugal separation at high speeds of rotation in the operation of the machine. As is well understood in the art, this space may be either uninterrupted as here shown or divided into separate annular channels by vertically spaced horizontal partition rings, the latter arrangement being commonly used in known practices where a liquid or sludge constitutes the charge material in process.

As seen in Figs. 1 and 3, the casing 3 has a top 3a which extends inwardly to overlie the inner edge of the basket top 6. A portion 31) of this casing top may be utilized for mounting the liquid stabilizer and other parts, although various other supporting structures may serve as well. A feed tube 10 extends vertically through por tion 312 to a location inside the basket where the tube end 11 delivers liquid charge material introduced through the tube to the bottom of the basket. The feed tube is mounted on the casing top by means of a hub 12, with respect to which the tube is turnable about its axis for the purpose hereinafter described.

It will be evident that when a liquid charge material is supplied through tube 10 and the basket 1 is in rotation, the material is walled up by centrifugal force as an annular charge 14 (Fig. 4) in the space 7 (Fig. 3). This charge comprises at least an inner layer of liquid having a liquid inner surface 15, while suspended solids or other components of greater specific gravity in the charge material may build up as a layer at the inside of the basket wall 4. The liquid at 15 forms a free surface of revolution which has a paraboloidal form.

The removal of liquid from the basket 1 may be accomplishcd by overflowing liquid from the basket, for example, over the rim 6a of the basket top 6 into the surrounding casing 3, or by gradual filtration of the liquid layer through accumulated solids and a filtering medium next to wall 4 when this wall is perforated, or to any desired extent by the action of a scoop element 16. This scoop element comprises a curved tube 17 held inside the basket by a bracket 18a on a vertical stub shaft 18, and having a mouth 1 disposed away from the charge surface 15 in one position of shaft 13 but movable into that surface in another position so as to scoop liquid from the surface. The curve of the scoop tube leads it to a discharge end 20 which lies above rim 6a in space between the basket top 6 and the casing top 30, so that liquid scooped into the tube at 19 from the rotating liquid surface is discharged over the top of the basket into the casing. The scoop shaft 18 is supported turnably in a hub 21 above casing top portion 312, hub 21 in turn being held, for example, by a strap 22 fixed to the feed tube hub 12.

Referring now more particularly to the manner of stabilizing the centrifugal operation, a stabilizer is pro vided which comprises a plurality of blades 31 lying transverse to and spaced apart along the axis of rotation of the basket, and movable horizontally as a unitary group toward and away from the liquid surface 15, with their free edges 32 nearly parallel to lines of rotation of air currents and liquid at the surface of the charge. The blades 31 may be held as a unitary group by welding or otherwise mounting them upon a base 33 which extends vertically in spaced relation to the basket shaft 2 and which may be secured to a vertical support in the form of a sleeve 34 extending downward into the basket on the turnable feed tube 10. The sleeve 34 is fitted to turn with the feed tube 10. Hence it is evident that upon counterclockwise movement of tube 10 about its axis from the position shown in Figs. 1 and 4, the stabilizer 30 is moved closer to the charge or even to a position Where the blade edges 32 will enter the spinning liquid surface 15.

According to a further feature of this invention, as seen in Figs. 3 and 4, the blades 31 preferably slope laterally from the tube support 10' at a slight pitch or downward inclination from horizontal, so that in entering the spinning liquid in the basket they will impart a general downward flow to the surface of the liquid charge. A downward pitch of only about inch in 6 inches of blade length is satisfactory, and the pitch should be slight in order to avoid too much disturbance of the liquid surface. The downward fiow thus imparted to this surface counteracts the tendency of liquid introduced from end 11 of the feed tube to run up the same surface, and thus a better distribution of added charge material and a better centrifugal separation are obtained.

As illustrated in Figs. 1 and 3, further provisions are made for convenient movements of the stabilizer 30 and the scoop element 16 to and from their respective active and inactive positions under manual control by an attendant of the centrifugal machine. For this purpose an operating mechanism indicated generally at is connected with the turnable stabilizer support or feed tube 10 and extends to an operating position outside and at the front of the casing 3, where this mechanism may be moved by an attendant watching the stabilizer and the surface of the rotating liquid in the basket 1; and a similar operating mechanism indicated generally at is connected with the scoop element support or stub shaft 18 and extends similarly to the same operating position, where an attendant manipulating the scoop element can watch its action upon the liquid content of the spinning basket.

The stabilizer operating mechanism 40, in the form shown, includes an arm 41 secured to and extending radially from the turnable feed tube 10 atop its hub 12, a connecting rod 42 articulated at one end to the end of arm 41, and a long lever 43 mounted to turn on a fixed fulcrum 44. Lever 43 has a backward extension 45 articulated to the other end of connecting rod 42 and a forward extension terminating in a handle 46 at the front of the machine. The scoop operating mechanism comprises, similarly, an arm 51 fixed to and extending radially from the top of the stub shaft 18, a connecting rod 52 articulated to the end of this arm, and a long lever 53 mounted on fulcrum 44 below lever 43 with a backward extension 55 articulated to rod 52 and a forward extension terminating in handle 56 at the attendant's station.

In the full line positions of the operating mechanisms as seen in Fig. 1, where lever 53 lies directly below lever 43, the stabilizer 40 and the scoop element 16 are both disposed away from the rotating liquid surface in the basket 1 substantially as they appear in Fig. 4. The stabilizer element is inserted into the liquid surface when handle 46 of lever 43 is moved to its broken line position in Fig. 1, and the scoop element is activated when the attendant moves handle 56 of lever 53 to its broken line position in the same figure.

The operation of the present invention will be apparent from the foregoing description, but a further understanding of its importance and its effects may be gained from examples of practical application of the invention.

One of these involves its use substantially as here described for the separation and drying of precipitated calcium carbonate of extremely fine particle sizes from a liquid slurry in which the particles are formed. In this practice the basket wall 4 may be a perforated wall lined with a very fine filtering medium, such as paper pulp, and the basket may be one of large diameter, say 40 inches, suspended from a gyratory mounting or head in known manner and adapted for operation to high speeds in the range of about 1700 to 2200 R. P. M. The basket may be rotated at less than its full speed while the slurry is introduced so as to form an annular precoating or layer of calcium carbonate inside the basket wall by filtration of the slurry liquid, and then it may be brought to a higher speed, say 1800 R. P. M., with continued introduction of the slurry to the spinning charge.

With a suitably slow rate of feeding the slurry, its liquid content can be filtered off through the solids and filtering medium in the basket, but this requires objectionable expenses of time and power in processing each complete charge, and care must be exercised to avoid the accumulation of a body of liquid in the charge, unless this invention is used to avoid the instability likely to result.

With a much faster rate of feeding, which hitherto has not been commercially practicable under the stated conditions, the charge liquid accumulates as an annular inner layer of the rotating charge while the solids build up at a fast rate, and surplus liquid overflows the rim 6a of the basket top, being thus discharged in a manner similar to that commonly employed in operations using a basket of the bowl or solid wall type. This manner of operation heretofore has been dangerous and hence impracticable in that the basket is likely to start gyrating and strike the surrounding casing, with danger of complete disruption of the fast spinning machine, under unequal weight distribution in the liquid content of the charge.

With the use of this invention, however, the instability of the centrifugal operation performed in this manner is overcome simply by inserting the stabilizing blades to a small depth in the surface of the rotating liquid. Their insertion to a depth of about inch is generally satisfactory. Whenever a tendency toward'excessive gyration or vibration is observed, therefore, the operator merely engages the stabilizing blades with the liquid surface of the charge, and smooth, stable machine operation is immediately restored. Each operating cycle thus can be continued with very fast feeding of the liquid charge material into the basket spinning at a very high speed, until the basket is substantially full of the separated solids. The charging then may be discontinued, and the scoop element may be activated to remove any surplus liquid from the inner surface of the charge. Then the basket may be accelerated, if desired, to an even higher speed, say 2200 R. P. M., at which residual liquid adhering to the solid particles is filtered off electively by extreme centrifugal force so as to yield the calcium carbonate in a relatively dry form.

According to another example, this invention may be applied for the separation of suspended solid particles from liquid, such as in the clarification of sugar juice, by use of a large centrifugal basket of the bowl type with or without horizontal partition rings in the basket. In case of a basket with rings, the stabilizing projections or blades are preferably spaced so that at least one of them will enter the body of liquid in each annular channel of the spinning basket. Through such an application of the invention it is possible to achieve the centrifugal separation of very fine suspended solids from liquids on a large scale in a safe and economical manner, and at an efficiency far in excess of that heretofore attained, by reason of the much greater speeds of rotation and centrifugal forces that can be safely applied to the liquid basket charge.

The present invention serves not only to enable the safe and stable operation of heavy-duty centrifugals with liquid charges at speeds and centrifugal forces far higher than were safely attainable heretofore, but it also alleviates the need, heretofore envisioned, for exceedingly rigid and expensive constructions or mountings of centrifugal machines intended for operation with liquid charges at high speeds.

It will be understood that the new principles, methods or structures herein disclosed or utilized in the illustrative embodiment may be employed in various ways or forms without departing from the invention defined in the appended claims.

I claim:

1. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, a stabilizer comprising a drag member held inside the basket having a group of relatively fixed, substantially fiat bafiie elements lying in planes transverse to and spaced apart in the direction of the axis of the basket and presenting free edges movable to and from the surface of said liquid while the basket is spinning at high speed.

2. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, a stabilizer comprising a drag member held inside the basket having a group of blades lying in planes transverse to and presenting free edges spaced in the direction of the axis of the basket and movable to dispose said free edges in and away from the surface of said liquid while the basket is spinning at high speed.

3. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, a stabilizer comprising a drag member held inside the basket and movable to and from the surface of said liquid while the basket is spinning, said member having a base extending in the direction of the axis of the basket and a plurality of spaced blades on said base lying in planes transverse to said axis with edges facing said liquid surface so as to be insertable into said surface by movement of said member in a direction away from said axis.

4. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, a stabilizer comprising a drag member held inside the basket and movable toward and from the surface of said liquid while the basket is spinning, said member having a base extending in the direction of the axis of the basket and a plurality of spaced blades on the base lying in planes transverse to said axis with substantially parallel edges facing said liquid surface, and manually operable mechanism connected with said base and extending to an operating position outside the machine for moving the stabilizer so as to insert said edges into the spinning liquid surface.

5. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, and comprising a feed tube arranged to introduce liquid charge material into one end portion of the basket, a stabilizer comprising a drag member held inside the basket having a plurality of relatively fixed blades lying in planes transverse to and spaced apart in the direction of the axis of the basket with free edges to face the inner surface of the spinning liquid, said member being movable in a path transverse to said axis so as to move said free edges to and from the inner surface of the spinning liquid, said blades having a slight inclination across the direction of rotation of said surface toward said one end portion.

6. In combination with a centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, a stabilizer comprising a drag member held inside the basket adjacent the surface of the charge while the basket is spinning, said member having a base extending in the direction of the axis of the basket and a plurality of blades on said base lying transverse to said axis with substantially parallel edges to face said surface, a feed tube extending into said basket for introducing liquid charge material, said base mounted on said feed tube, and means mounting said feed tube for movement to activate and inactivate the drag member.

7. In combination with a vertical centrifugal machine whereof the basket in rotation holds a spinning annular charge having at least an inner layer of liquid, and comprising a stationary casing surrounding the basket, a feed tube extending vertically into the basket to introduce liquid charge material near the basket bottom, said tube mounted in fixed position for turning movement on a vertical axis, a stabilizer mounted on said feed tube inside the basket comprising a plurality of vertically spaced blades extending transversely to said axis, said blades having free edges to face the spinning liquid, mechanism connected with said tube and extending to an operating position outside said easing for turning said tube to activate and inactivate the stabilizer, a scoop element inside the basket near the top thereof movable to and from a position to remove I 8 the rotating basket adjacent to the inner surface of the charge and having a plurality of substantially parallel relatively fixed blades spaced apart in the direction of and lying in planes transverse to the axis of the basket.

9. A stabilizer for a centrifugal machine whereof the basket in rotation has at least an inner layer of liquid in its charge, comprising a drag member having a base to be held inside and extend in the direction of the axis of the basket over a major portion of the internal height of the basket, a plurality of spaced substantially parallel blades extending transversely from said base in substantially horizontal planes, said blades having edges disposed to enter fluid spinning with a charge in the basket and being inclined so as to lie at a slight angle to said axis.

References Cited in the file of this patent UNlTED STATES PATENTS 662,214 Wood Nov. 20, 1900 994,631 Berrigan June 6, 1911 1,002,471 Thelitz Sept. 5, 1911 1,202,936 White Oct. 31, 1916' 1,212,638 Herr Jan. 16, 191/ 1,267,419 Kaita May 28, 1918 1,286,626 Herr Dec. 3, 1918 2,013,109 Reynolds Sept. 3, 1935' 2,056,890 Pecker Oct. 6, 1936 2,313,644 Hvid Mar. 9, 1943 2,370,999 Schutte Mar. 6, 1945 FOREIGN PATENTS 442,943 France Apr. 25, 1912

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