US3335946A

US3335946A - Separating disks for centrifuges

Info

Publication number: US3335946A
Application number: US447209A
Authority: US
Inventors: Putterlik Jan
Original assignee: Czech Academy of Sciences CAS
Current assignee: Czech Academy of Sciences CAS
Priority date: 1964-04-14
Filing date: 1965-04-12
Publication date: 1967-08-15
Anticipated expiration: 1984-08-15
Also published as: GB1098007A; SE316422B

Description

Aug. 15, 1967 .1. PUTTERLl K 3,335,946

SEPARATING DISKS FOR CENTRIFUGES Filed April 12, 1965 INVENTOR.

United States Patent VO 3,335,946 SEPARATING DISKS FOR CENTRIFUGES Jan Putterlik, Prague, Czechoslovakia, assignor to Ceskoslovenska akademie ved, Prague, Czechoslovakia Filed Apr. 12, 1965, Ser. No. 447,209 Claims priority, application Czechoslovakia,

Apr. 14, 1964, 2,155/64 2 Claims. (Cl. 233-41) This invention relates generally to the separating disks of centrifuges used in separating the liquid and solid constituents of a slurry or dispersion so as to obtain a concentrated slurry or dispersion, that is, the solids with a much reduced proportion of the liquid, or a clarified liquid.

Centrifuges of the type described above generally include a hollow bowl rotated about its axis and containing an axial series of spaced, frusto-conically shaped separating disks of somewhat smaller diameter than the bowl shell. The slurry, dispersion or other incoming material to be centrifuged, is admitted through feed channels which discharge near the outer edges of the separating disks, and the clarified liquid is removed from the bowl through an outlet positioned at or near the axis of rotation. Thus, the liquid constituent is made to flow centripetally, or radially inward, through the spaces between the separating disks in order to reach the outlet for the liquid and, during such flow, the solid particles are driven centrifugally so as to collect in the radially outward portion of the bowl shell beyond the perimeters of the separating disks. Discharge nozzles are further provided, in certain existing centrifuges, for discharging the concentrated solids which collect in the outer peripheral portion of the bowl shell.

In existing centrifuges of the described character, the separating disks are formed of thin sheet metal which is either stainless steel or treated so as to resist corrosion. Such existing sheet metal separating disks are further provided with spacing projections in the form of metal stampings which are welded to the conical surfaces of the disks at radially spaced intervals. It will be apparent that the manufacture of such sheet metal separating disks is difiicult and costly, as the disks must be accurately shaped and have smooth surfaces in order to ensure the high operating efliciency, and relatively low power consumption of the centrifuge.

The existing separating disks of sheet metal have two further substantial disadvantages. The sheet metal pre viously used for the separating disks has a high modulus of elasticity in tension, for example, up to 20,000 kg./mm. in the case of steel, and, by reason of such high modulus of elasticity, the separating disks formed of sheet metal respond readily to vibration of the bowl or rotor of the centrifuge, which vibration may result from the dynamic unbalance of the separating disks. The vibrations of the separating discs interfere with the centrifugal separation of the dispersion or slurry in the thin layers or flows passing between the separating disks. Further, the sheet metal for forming the separating disks usually has a specific gravity of approximately 8.0 which may be almost eight times larger than the specific gravity of the dispersion flowing between the separating disks so that any inaccuracy in the shape and balance of the separating disks with respect to the axis of rotation constitutes a source of dynamic unbalance giving rise to vibration of the rotated bowl or rotor. Such dynamic unbalance cannot be easily eliminated by balancing of the several separating disks, as it is difiicult to ensure the same relatively large number of disks will be assembled in the same order or sequence whenever the bowl or rotor is opened and has the disks removed therefrom.

Accordingly, it is an object of this invention to provide separating disks for centrifuges which avoid the above mentioned disadvantages of the separating disks that have been heretofore available.

In accordance with an important aspect of this invention, separating disks for centrifuges are formed of a material having a modulus of elasticity which is no greater than 1,000 kg./mm. and a specific gravity no greater than approximately 2.0, that is, not exceeding approximately two times that specific gravity of the dispersion which is to be centrifuged.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of an illustrative embodiment thereof which is to be read in connection with the accompanying drawing, wherein:

FIG: 1 is an elevational view of a separating disk for a centrifuge in accordance with this invention; and

FIG. 2 is a sectional view taken along the lines 22 on FIG. 1.

Referring to the drawing in detail, it will be seen that a separating disk 10 embodying this invention may be generally fr-usto-conical in shape and have radially directed rims 11 and 12 extending along its inner and outer peripheries. At least one of the conical surfaces of the disk 10 has suitably spaced projections 13 extending therefrom for the purpose of uniformly spacing apart adjacent separating disks when the latter are assembled in the bowl or rotor of a centrifuge.

In accordance with this invention, the separating disk 10 is formed of a material having a modulus of elasticity not greater than approximately 1,000 kg./mm. and a specific gravity not greater than approximately 2.0. Many different types of synthetic resin materials satisfy the foregoing requirements for forming separating disks in accordance with this invention, such as, for example, polyethylene, polyvinyl chloride, polypropylene, textile and glass laminates, resins and the like. Separating disks for centrifuges formed of such synthetic materials in accordance with this invention can be conveniently molded, for example, by injecting molding, so that the spacing projections 13 can be simultaneously formed with the remainder of each separating disk and form integral parts of the latter.

When separating disks are formed of a material with a relatively low modulus of elasticity, as in accordance with this invention, such disks serve to damp the vibrations of the rotated rotor or bowl and thus do not vibrate or respond to vibration of the rotor or bowl arising from any dynamic unbalance of the latter. By reason of their vibration damping properties, the separating disks embodying this invention secure the smooth and elfective centrifugal separation of the solids from the liquid constituents in the layers of flows passing between the adjacent separating disks. Due to the fact that the material forming the separating disks in accordance with this invention has a specific gravity which is much closer to the specific gravity of the dispersion or slurry being centrifuged than is the specific gravity of the previously known sheet metal separating disks, the disks embodying this invention do not cause any appreciable or significant dynamic unbalance of the rotor or bowl. Even if there are inaccuracies in the shapes of the separating disks embodying this invention or in their concentricity with respect to the axis of rotation, such inaccuracies are substantially compensated by the filling of the spaces between adjacent separating disks with the dispersion flowing therethrough and having a specific gravity which is, at the worst, only one-half of the specific gravity of the material forming the disks.

Since separating disks embodying this invention can 3 be conveniently molded by injection molding or other conventional molding procedures, the same can be very economically produced, particularly when one considers that the spacing projections are simultaneously formed thereon, rather than being separately attached, as in the case of the previously existing sheet metal separating disks, It will also be apparent that injection molded separating disks embodying this invention can be formed with a perfectly accurate shape and with smooth surfaces so as to promote the effective centrifugal separation of the liquid and solid constituents of a dispersion.

Although the materials proposed for forming of the separating disks in accordance with this invention have a strength which is relatively low when compared with that of the sheet metal previously used for separating disks, such relatively low strength is not disadvantageous by reason of low specific gravity of the proposed materials which makes it possible for the stress resulting from the centrifugal force to be compensated, at least to a considerable extent, by the centripetal, or radially inwardly directed force or hydrostatic lift acting on the separating disks as a result of the radially inwardly directed flow between adjacent disks. The separating disks formed from the proposed synthetic materials in accordance with this invention have a further advantage in the resistance to abrasion of such materials by the dispersion flowing between the separating disks.

Although an illustrative embodiment of this invention has been described in detail herein with reference to the accompanying drawing, it is to be understood that the invention is not limited to that precise embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention, except as defined in the appended claims.

What is claimed is:

1. A separating disk for a centrifuge, said disk being of a material having a specific gravity of less than approximately 2.() and a modulus of elasticity in tension of less than approximately 1000 kg./mm.

2. A molded separating disk for a centrifuge, said disk being of generally frusto-conical configuration and having integral spacing projections extending from at least one surface thereof, said disk being of a synthetic material having a specific gravity of less than approximately 2.0 and a modulus of elasticity in tension of less than approximately 1000 kg./mm.

References Cited UNITED STATES PATENTS 989,099 4/1911 Wright 233- 1,168,452 1/ 1916 Anderson 233-29 3,235,174- 2/1966 Downey 233-l9 M. CARY NELSON, Primary Examiner.

H. KLINKSIEK, Assistant Examiner.

Claims

1. A SEPARATING DISK FOR A CENTRIGUGE, SAID DISK BEING OF A MATERIAL HAVING A SPECIFIC GRAVITY OF LESS THAN APPROXIMATELY 2.0 AND A MODULUS OF ELASTICITY IN TENSION OF LESS THAN APPROXIMATELY 1000 KG./MM.2.