US3310232A - Centrifuge discharge means - Google Patents

Description

March 21, 1967 L. SHAPIRO 3,310,232

CENTRIFUGE DISCHARGE MEANS Filed Dec. 17. 1964 INVENTOR LEONARD SHAPIRO BY W ATTORNEY United States Patent ()fiice 3,31%,232 Patented Mar. 21, 1967 3,310,232 CENTRIFUGE DISCHARGE MEANS Leonard Shapiro, Upper Darby, Pa., assignor to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 17, 1964, Ser. No. 419,086 4 Claims. (Cl. 233-22) This invention relates to centrifuges. More specifically this invention relates to centrifuges provided with means 'for discharging separated liquids under positive pressure and in a manner that minimizes foaming of the liquids.

The prior art relating to centrifuging is replete with innumerable discharge devices for removing separated liquid from solid bowl machines. A common expedient is simply the provision of a ring dam or tube dam over which the separated liquid may spill to the outside of the bowl for collection by a suitable cover device. Alternatively, a skimmer tube dips into an inwardly facing trough or pocket mounted on the centrifuge bowl and scoops the liquid as it races by. In a different form the skimmer tube takes the shape of a paring disc which is disposed on the centrifuge axis and extends outwardly on all sides into the trough or pocket. The paring disc is equipped with angled passages into which the liquid rushes as the centrifuge rotates. A suitable inward discharge channel for the disc is provided.

In the separation of many liquids an essential consideration is the minimizing of turbulence once the liquid is separated. Some separated liquids are sensitive to such turbulence and may bruise or become aerated, undesirably producing a foam. A common example is the separating of orange juice from seeds, pulp, etc. wherein if the juice is aerated and foamed it rapidly deteriorates in taste and acquires a sharp and disagreeable flavor.

There have been many attempts in the past to minimize foam in the liquid discharge from a solid bowl centrifuge. One such attempt is documented in the US. Patent 2,302,168 which issued Nov. 17, 1942. In this patent lips on the inlet openings of the paring device extend outward from the passages so that the openings are sealed to the entry of foam into the discharge. While this patent represented a marked advance over the prior devices, the present invention relates to a refinement of the same general type of devicea paring device-and has for an object the reduction of foaming of liquid prior to and during its removal from the centrifuge.

There is exhibited when any stationary object is submerged in a body of liquid in a centrifugal field a phenomenon that is known as secondary flow." Secondary flow is the movement of the liquid out of the liquid body and up the outside of the stationary object. It arises because a thin film of liquid immediately adjacent to the immersed object is stationary with the object, and liquid outward from the film is moving at a velocity of the centrifuge bowl and is therefore under centrifugal pressure. There is hence a tendency for the liquid outward of the film to displace the film and force it up along the stationary object to and above the surface of the liquid body. As the liquid leaves the air-liquid surface it also exhibits a tangential velocity component which throws it outwardly away from the stationary object, causing great turbulence and splashing which entraps air and causes foaming.

Studies of the operation of paring devices for centrifuge liquid discharge have indicated that the considerable foaming in the liquid about a paring device is due to secondary flow. The present invention relates to means for avoiding turbulence normally developed by secondary flow of liquid in the indicated situation and for consequently promoting a smooth liquid-gas interface about the paring device. 1

There are, of course, incidental advantages attendant with the smoothing down of the liquid-vapor interface. For instance, there is the advantage that the position of the liquid-liquid interface within the bowl may be more accurately controlled by back pressure on the liquid discharge lines from the paring devices. Further, because the liquid-vapor interface about the paring device is smooth and no back pressure is needed simply for the purpose of keeping foam out of the discharge, the range of control attainable by this means is greater than were there a disturbed interface. There is the additional advantage to a smooth interface: less power is required to drive the centrifuge bowl. As explained, there is no need for back pressure on the paring device merely to avoid entry of foam into the centrifuge discharge line. Hence there is less power-consuming pumping necessary by the paring device. Further, with the liquid-vapor interface in smooth condition there is less power-consuming friction between the paring device and the liquid about it. All of these benefits flow from the present invention.

Other features of the invention will be apparent from a review of the following specification describing a preferred form of apparatus and reference to the drawings in which:

FIGURE 1 is a fragmentary sectional view of a centrifuge embodying the invention;

FIGURE 2 is an enlarged sectional view taken on line 22 of FIGURE 1; and

FIGURE 3 is a slightly enlarged sectional view of structure within section line 33 of FIGURE 1 and indicating a fiow of liquid about parts of the apparatus.

Briefly, in a centrifuge having a discharge paring device comprising a circular structure with passages from its periphery to an inward discharge channel, the invention is the provision of at least one annular rib disposed on -a side of the paring device and adapted to reduce disturbance of the liquid-air interface of the liquid in which the device is immersed.

Referring more specifically to the drawings, FIGURE 1 is a fragmentary sectional view of a centrifuge embodying the invention and generally designated 10. It comprises a bowl 12 mounted for rotation by a suspending and driving shaft 14. The bowl structure may include a set .16 of frusto-conical discs which are disposed about -a vaned center tube 16a and operate in the conventional manner to increase efficiency of the separation. The feed liquid is delivered to the lower end of the centrifuge by feed means (not shown).

Mounted on the top of the bowl 12 is the heavy discharge housing 18 and the light discharge housing 20. The housing 20 is supported on the dividing cone 22 secured between the upper end of the center tube 16a and the bowl top. Inbetween the dividing cone 22 and housing 18 are aplurality of spaced ribs 24 which space the elements properly and permit passage of the heavy liquid from the centrifuge bowl into a pocket 26 facing inwardly and formed between the housings 1-8 and 20. The ribs widen in the pocket 26 and comprise part of radial vanes 28 which assure rotation of the liquid within the pocket 26 with the bowl.

The housing 20 which together with the inward annular wall 30 also supported on the dividing cone 22 forms a pocket 32 which is provided with vanes 34. In operation separated light liquid from the centrifuge bowl spills over the annular wall 30 into the pocket 32.

Surrounding the drive and supporting shaft 14 is a stationary discharge assembly comprising the paring discs 36 and 38. The structure of the paring discs are comparable. As shown in FIGURE 2 the disc.36 is annular and provided with passages 37 which may be curved and extend from the periphery of the device to an inward discharge channel 40. The channel is formed between 3 the tubular exterior wall 42 of the paring device 36 and the tubular wall 44 of the lower paring device 38. Spacing ribs 46 are provided to hold the two tubular portions in proper relation.

The-lower paring device 38 similarly has extending inward from its periphery discharge passages 48 which extend to the inward discharge channel 56 between the tubular element 44 and the inner tubular element 52. Ribs 54 hold these two parts in proper relative position.

The paring device assemblies are supported as shown on the centrifuge cover which is stationary. The upper ends of the passages 40 and 50 communicate respectively with discharge conduits 56 and 58 as shown.

Focusing now on the particular area of the invention, it will be noted from FIGURE 2 that the opposite faces of the paring device 36 are provided with spaced annular ribs 60 and 62. These ribs which are disposed concentrically about the axis of the centrifuge serve (FIGURE 3) to deflect outward and into the liquid of the pocket 26, liquid moved inward by the secondary flow phe nomenon. It will be understood that the liquid level is such that some ribs are normally immersed in the liquid in the pocket 26.

Similarly ribs 60' and 62 are provided for the same purpose on the paring device 38.

A splash shield 64 is provided on the underface of the paring device 36 and also serves to control turbulence or splashing. Passages 66 through the paring disc 36 pro vide means for venting gas pressures which may develop on either side of the disc.

FIGURE 3 shows the paring disc 36 as submerged in operation to alternate liquid levels a and b. From the above description of the secondary flow phenomena it will be understood that liquid film adjacent the stationary paring device is forced by surrounding liquid pressure inward along the sides of the paring device and would tend to create a splash at the liquid level line L. However, due to the presence of the annular ribs 60 and 62, the inward flow is deflected laterally into the body of liquid (see arrows) and thus the air-liquid interface remains smooth and undisturbed.

The number of ribs used may, of course, be different from the number shown on the drawings. The number should not be increased so high that there is not sufiicient space to permit free circulation of liquid between adjacent ribs. Obviously if the ribs are not sufficiently spaced at primary objective of the invention will be defeated.

It should be understood that variations within the scope of the invention are possible. For instance the invention may be applied to a centrifuge having a hori zontal axis and to the paring device of a centrifuge of an altogether different type, for instance a worm centrifuge.

Therefore, it is to be understood that the, above par ticular description is. by way of illustration and not of limitation, and that changes, omissions, additions, substitutions, ,and/ or other modifications may be made without departing from the spirit of the invention. Accordingly, it is intended that the patent shall cover, by suitable expression in the claims, the various features of patentable novelty that reside in the invention.

I claim:

1. A centrifuge having a discharge paring device normally immersed in liquid to be discharged and comprising a circular structure with passages from its periphery to an inward discharge channel, a plurality of spaced annular ribs disposed on a side of the paring device inward from the periphery thereof and concentrically about the centrifuge axis, whereby the ribs serve to reduce disturbance of the liquid-air interface of the liquid in which the device is immersed.

*2. A centrifuge as described in claim 1 including additionally an outwardly and laterally extending annular splash shield disposed on said side inward from the ribs.

3. A centrifuge bowl having an axis of rotation, an

annular inwardly facing pocket mounted on the bowl concentric with the axis of rotation and receiving a discharge liquid from the bowl, the pocket having side walls extending inward to a radial level establishing a maxi mum depth of liquid for the pocket, a stationary takeoff device having a circular outer periphery disposed concentrically about the axis of rotation and extending outward into the pocket, the takeoff device having opposite substantially radial sides and passages from its periphery into an inward takeoff conduit, the improvement of at least one annular rib extending perpendicularly outward from one of said sides at a position inward from the periphery thereof and disposed concentric with the axis and at a radius greater than the level.

4. A centrifuge as described in.claim 3 including additionally an outwardly and laterally extending annular splash shield disposed on said side inward from the ribs.

References Cited by the Examiner UNITED STATES PATENTS 2,125,453 8/1938 Lindgren 233-22 2,197,911 4/ 1940 Andersson 23322 FOREIGN PATENTS 63,738 7/ 1945 Denmark. 91,209 6/1961 Denmark.

M. CARY NELSON, Primary Examiner.

HENRY T. KLINKSIEK, Examiner.

Claims (1)

1. A CENTRIFUGE HAVING A DISCHARGE PARING DEVICE NORMALLY IMMERSED IN LIQUID TO BE DISCHARGED AND COMPRISING A CIRCULAR STRUCTURE WITH PASSAGES FROM ITS PERIPHERY TO AN INWARD DISCHARGE CHANNEL, A PLURALITY OF SPACED ANNULAR RIBS DISPOSED ON A SIDE OF THE PARING DEVICE INWARD FROM THE PERIPHERY THEREOF AND CONCENTRICALLY ABOUT THE CENTRIFUGE AXIS, WHEREBY THE RIBS SERVE TO REDUCE DISTRIBANCE OF THE LIQUID-AIR INTERFACE OF THE LIQUID IN WHICH THE DEVICE IS IMMERSED.

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