US3780937A

US3780937A - Centrifugal gas separator with electric motor drive

Info

Publication number: US3780937A
Application number: US00118281A
Authority: US
Inventors: H Tahara; M Sakurai; H Yamada
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1970-02-27
Filing date: 1971-02-24
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25
Also published as: JPS514300B1

Abstract

A centrifugal gas separator is disclosed which employs a vertically oriented centrifuge drum mounted on suitable bearings within a stationary housing and driven by an electric motor. The electric motor is constructed in annular form with its stator portion fixed to the stationary housing and its rotor portion fixed to the centrifuge drum and positioned generally below its stator portion. When the electric motor is energized, the magnetic attraction between its stator and rotor portions tends to lift the centrifuge drum, thereby reducing the weight supported by the bearings and reducing bearing wear. In addition, elastic or magnetic devices are alternatively provided to dampen the vibration of the rotating centrifuge drum.

Description

United States Patent 1191 Tahara et al.

CENTRIFUGAL GAS SEPARATOR WITH ELECTRIC MOTOR DRIVE Assignee:

[22] Filed:

Inventors:

Appl. N0.:

Hisayoshi Tahara, Tokyo; Mituo Sakurai, Kawasaki; Hayatoshi Yamada, Tokyo, all of Japan Tokyo Shibaura Electric Company, Ltd., Kawasaki-shi, Kanagawa-ken, Japan Feb. 24, 1971 Foreign Application Priority Data Feb. 27, 1970 Japan 45/16483 U.S. C1. Int. Cl

233/24, 233/1 C v B04b 9/02 Field of Search 233/8, 1 C, 1 A,

233/1 R, 11, 13, 23 R, 23 A, 24; 74/573,

References Cited UNITED STATES PATENTS 11/1965 5/1945 12/1966 Zippe et a1 Wind et al. 233/D1G. 1 Peer Primary Examiner-George H. Krizmanich AttrneyOblon, Fisher & Spivak 7] ABSTRACT A centrifugal gas separator is disclosed which employs a vertically oriented centrifuge drum mounted on suitable bearings within a stationary housing and driven by an electric motor. The electric motor is constructed in annular form with its stator portion fixed to the stationary housing and its rotor portion fixed to the centrifuge drum and positioned generally below its stator portion. When the electric motor is energized, the magnetic attraction between its stator and rotor portions tends to lift the centrifuge drum, thereby reducing the weight supported by the bearings and reducing bearing wear. in addition, elastic or magnetic devices are alternatively provided to dampen the vibration of the rotating centrifuge drum.

8 Claims, 4 Drawing Figures PAIENTEUDEEZS ma 3.780.937 sum 1 or 2 FIG. 2

I Q Q 3 g INVENTORS IDISAYOSHI TAKARA MITUO SAKURAI HAYATOSHI YAMADA FIG.1

ATTORNEYS PATENTEUDEBZS 1915 3780.937

sum 2 or 2 FIGH CENTR-IFUGAL..GAS SEPARATOR WITH ELECTRIIG MOTOR DRIVE BACKGROUND OF THE INVENTION 1. Field Of The Invention The present invention=relates to gas separators, and more particularly to centrifugal gas separators which may be used, for example, for separating enriched uranium (U from gaseous uranium hexafluoride (UP 2. Description Of The Prior Art A Gas centrifuges customarily include an elongated cylindrical drum which is filled with the gas to be processed, then rotated at an extremely high angular speed. Because of the extremely high angular speeds and because of the weight of the centrifuge drum, it has been observed that gas centrifuges tend to wear out their drum supporting bearings in a relatively short time. Naturally, the useful life of a gas centrifuge is no longer than the life of the centrifuge bearings, since excellent bearings are crucial in order to maintain suitably high rotational speeds. Accordingly, in order to prolong the life of the centrifuge, it is necessary to minimize wear on the bearing surfaces. It has been found that one way of greatly reducing bearing wear is to minimize the weight load borne by the centrifuge bearings when the centrifuge drum is in operation.

SUMMARY OF THE INVENTION Accordingly, one object of the invention is to provide an electric motor driven centrifuge in which the rotor and stator portions of the driving electric motor are arranged so that the magnetic attraction between them lifts the centrifuge drum, and removes a portion of its weight from the drum bearings.

Another object of the invention is to provide a centrifuge having a rotating cylindrical drum of a relatively short axial length to reduce the vibration thereof.

Yet another object of the invention is to provide a gas centrifuge that includes either an elastic or a magnetic vibration damping device.

Briefly, these and other objects of the invention are achieved by constructing a vertically oriented centrifuge apparatus equipped with an annular electric motor. The rotor portion of the motor is mounted on the centrifuge drum, while the stator portion thereof is mounted to the centrifuge housing above the rotor portion. When the motor is energized, the magnetic attraction between the rotor and stator portions thereof tends to lift a portion of the weight of the centrifuge drum, thereby reducing bearing wear. Either a magnetic or an elastic device is secured to the drum bearing to dampen the vibration thereof.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying Drawings, wherein:

FIG. 1 is a partially cut-away illustration ofa first embodiment of the centrifuge apparatus of the instant invention;

FIG. 2 is a partially cut-away illustration of a second embodiment of the centrifuge apparatus of the instant invention;

FIG. 3 is a partially cut-away illustration of a third embodiment of the centrifuge apparatus of the instant invention; and,

FIG. 4 is a partially cut-away illustration of a fourth embodiment of the centrifuge apparatus of the instant invention.

DESCRIPTION OF THE PREFERRED.

' EMBODIMENT Referring now to the Drawings, wherein like reference numerals designate identical orcorresponding parts throughout the several views, and more particularly to FIG. 1 thereof. a cylindrical drum 10 is shown positioned in an evacuated cylindrical housing 11.

An annular shelf 12 is provided within housing 11 at an upper portion thereof. An annular disk-shaped damper 13 of elastic material is mounted on the shelf 12 and is held at the outer periphery thereof bya ring member 14.

The drum 10 includes an upper end plate 15, a hollow shaft 16 axially extended therefrom, a lower end plate 17 and a shaft 18 axially extended downward therefrom.

To rotatably suspend the drum 10 from damper 13, an annular tab 19 is provided around hollow shaft l6.v The annular tab 19 is mounted on an inner race of a bearing 20 which is also supported-in a central opening of the damper 13.

The damper 13 also supports a pair of conventional

gas sealing devices

21 and 22 at the innermost portion thereof to prevent gas from leaking along the surface of hollow shaft 16.

An annular shelf 23 is provided within housing 11 at the lower portion thereof for supporting an annularshaped damper 24 of elastic material which may be substantially the same as damper 13. Similarly, the outer periphery of the damper 24 is held by a ring 25. A bearing 26 is positioned in a central opening of the damper 24 for rotatably supporting shaft 18 of drum 10. A pair of conventional

gas sealing devices

73 and 74 are mounted on the innermost portion of damper 24 to prevent gas from leaking along the surface of the shaft 18.

In order to rotate the drum member 10, an electric motor 27 of the axial air gap type is mounted within housing 11. The electric motor 27 includes an annular or disk-shaped stator core 28 supported by the inner wall of housing 11 through stays 30 and an annular or disk-shaped rotor 31 mounted on end plate 15 of drum 10. The rotor 31 is preferably made of a plate of soft iron, permendur or the like, and has plated on the surface thereof a material having a relatively higher conductivity such, for example, as copper or aluminum, which is denoted by the numeral 32. An air gap 33 separates stator core 28 from rotor 31.

The motor 27 also includes a stator winding 29, which is energized from a high frequency A.C. voltage source (not shown) such, for example, as a motorgenerator set or a static inverter, which generates a revolving electromagnetic field in the air gap 33 to cause the rotor 31 to rotate.

In operation, as is well known in the art, a mixed gas to be isotopically separated is introduced into drum 10 through an inlet 34 in housing 11 and through a hollow shaft 16. The lower portion of the drum 10 is heated by a heater (not shown), and the upper portion of the drum 10 is cooled by a refrigerating apparatus (not shown), thereby producing a temperature gradient across the drum which causes the mixed input gas to positively circulate in the drum.

The centrifuging operation and the temperature gradient causes a gas separation, which results in a gas of a relatively light molecular. weight being exhausted through orifices 36 positioned in the peripheral area of end plate 17. The lighter gas is then expelled through an outlet 27. The separated gas of heavier molecular weight is exhausted through orifices 38 positioned peripherally in upper end plate 15. The heavier gas is then expelled through an outlet 39.

To prevent the separated gases from recombining within housing 11, a pair of ring members or gas seals 40 and 41 are mounted on the inner wall of housing 11. Narrow clearances 44 and 45 are defined between rings 40 and 41 and the side wall of drum 10 to impede the flow of gas therethrough into a common area 43. This separating effect may be enhanced by the provision of a nozzle 42 which extends through the side wall of housing 11 into space 43 between the inner wall of housing 11 and the side wall of drum 10. A carrier gas such, for example, as helium may be emitted from thenozzle 42 into the space 43, then directed partially to outlet 39 through the clearance 44 and partially to outlet 37 through the clearance 45.

Referring again to the electric motor 27, it will be readily understood that the rotor 31 of the motor 27 is lifted slightly upwards along with the drum 10 to which it is attached by the electromagnetic attractive force which occurs in the air gap 33 of the motor 27 during energization of the motor. Consequently, the thrust or lead on bearing due to the weight of drum 10 is effectively reduced, thereby prolonging the life of bearing 20. The same is, of course, true of bearing 26.

It can further be seen that with the use of the type of motor disclosed herein, the drum 10 does not require a conventional driving motor positioned on an extension of the axis of the drum. Accordingly, it is possible to shorten the entire axial length of the drum and motor combination. Thus, undesirable vibrations which result from a rotational body having a greater axial length can be effectively reduced.

It will also be apparent that the additional bearings necessary when conventional electric motors are used can be eliminated, whereby the total number of bearings can be reduced to prolong the life of the centrifuge apparatus.

. In another embodiment of the invention illustrated in FIG. 2, a mixed gas is introduced into drum 10 through an inlet 46, an enclosure 47 mounted on the housing 11, and a stationary pipe 48 extending through the hollow shaft 16 of the drum 10. In this embodiment of the invention, the separated light gas is exhausted from drum 10 into a lower chamber 50 through a hollow shaft 49 extending through a lower end plate 17 and is then expelled out of the chamber 50 through an outlet 51. The separated heavier gas is exhausted from the interior of drum 10 through hollow shaft 16 into an upper chamber 52, and is then expelled out of the chamber 52 through an outlet 53.

In a third embodiment of the invention, illustrated in FIG. 3, the interior of drum 10 is divided into three

chambers

54, 55 and 56 by means of a pair of

horizontal partition walls

57 and 58.

A mixed input gas is conducted into the intermediate chamber 55 of the drum 10 through inlet 46, housing which is connected to scoops 60 and extends through a hollow shaft 49 of the drum l0. Similarly,the separated heavier gas is conducted into the upper chamber 54 through orifices 62 provided in a peripheral portion of partition wall 57. Stationary scoops 63 are provided in chamber 54 for taking the gas out'of chamber 54, and are connected to a stationary hollow tube 64 which is located between pipe 48 and hollow shaft 16. Thus, the separated heavier gas is carried out of chamber 54 through scoops 63 and tube 64; the same then enters into chamber 52 and is exhausted through outlet 53.

In accordance with a still further embodiment of the invention illustrated in FIG. 4, an electric motor 65 is provided, which includes a stator core 66 of a cylindrical ring configuration mounted on an inner wall of housing 11 and having a stator winding 67 wound thereon. A cylindrical ring-like rotor 68, made ofa material such, for example, as a plate of soft iron or permendur, is mounted on the side wall of drum 10.

When the electric motor 65 is not energized, the magnetic center of stator core 66 is located at a slightly higher position than that of rotor 68. Accordingly, when the motor 65 is energized, the rotor 68 will be lifted upwards from its unenergized level by the electromagnetic pull occurring in the air gap between the rotor and stator elements. Thus, the thrust loaded on

bearings

20 and 26 due to the weight of drum 10 is reduced.

In the embodiment of FIG. 4, a plurality of electromagnets 69 are provided around shaft 18, each of which includes a core member 70. Core member 70 includes a pair of magnetic pole pieces facing the surface of shaft 18 through a small air gap. An exciting coil 71 is wound on each of the cores 70, and the cores 70 are mounted on an annular stay 72 around the periphery of shaft 18. The electromagnetic pull of magnets 69 is adjustable and functions to hold the axis of shaft 18 at a regular centered position without contacting with magnetic pole piece members. By properly adjusting the magnetic pull of the magnets 69, the vibration of the shaft 18 can be damped effectively.

Obviously, numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by letters patent of the United States is:

l. A centrifugal gas separator comprising: an enclosed housing, elongated cylindrical drum means vertically oriented within said housing, and adapted to receive a mixed gas to be separated,

bearing means mounted within said housing for rotatably supporting said drum means, electric motor means for driving said drum means mounted within said housing, said electric motor means comprising stator means and rotor means;

said rotor means rigidly mounted on said drum means,

and, said stator means rigidly mounted to said housing and positioned above at least a portion of said rotor means, such that upon energization of said electric motor means an electromagnetic attractive force is created between said stator means and said rotor means which tends to lift said drum means.

2. A centrifugal gas separator as in claim 1, wherein:

said rotor means and said stator means are both in the form of annular disks.

3. A centrifugal gas separator as in claim 2, wherein:

said rotor means is mounted to a top surface of said drum means.

4. A centrifugal gas separator as in claim 1, wherein:

said rotor means and said stator means are both cylindrical in form.

5. A centrifugal gas separator as in claim 4, wherein:

said rotor means is mounted on a peripheral surface of said drum means.

6. A centrifugal gas separator as in claim 1, further 5 comprising:

Claims

1. A centrifugal gas separator comprising: an enclosed housing, elongated cylindrical drum means vertically oriented within said housing, and adapted to receive a mixed gas to be separated, bearing means mounted within said housing for rotatably supporting said drum means, electric motor means for driving said drum means mounted within said housing, said electric motor means comprising stator means and rotor means; said rotor means rigidly mounted on said drum means, and, said stator means rigidly mounted to said housing and positioned above at least a portion of said rotor means, such that upon energization of said electric motor means an electromagnetic attractive force is created between said stator means and said rotor means which tends to lift said drum means.

2. A centrifugal gas separator as in claim 1, wherein: said rotor means and said stator means are both in the form of annular disks.

3. A centrifugal gas separator as in claim 2, wherein: said rotor means is mounted to a top surface of said drum means.

4. A centrifugal gas separator as in claim 1, wherein: said rotor means and said stator means are both cylindrical in form.

5. A centrifugal gas separator as in claim 4, wherein: said rotor means is mounted on a peripheral surface of said drum means.

6. A centrifugal gas separator as in claim 1, further comprising: vibration dampening means mounted within said housing.

7. A centrifugal gas separator as in claim 6, wherein: said vibration dampening means includes an element constructed of an elastic material.

8. A centrifugal gas separator as in claim 6, wherein: said vibration dampening means includes a magnetic element.