US3926661A

US3926661A - Centrifuge construction

Info

Publication number: US3926661A
Application number: US438606A
Authority: US
Inventors: Werner Steprath
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-02-01
Filing date: 1974-02-01
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16

Abstract

A rotor is mounted for rotation about a first axis, and a screen drum is mounted on the rotor for rotation about a second axis parallel to but laterally offset from the first axis. A conveying screw is mounted in the screen drum for rotation jointly with the rotor about the first axis and it has screw flights which extend close to an inner circumferential surface of the screen drum. A single drive rotates the screen drum at a first circumferential speed, and rotates the rotor and conveying screw at a different second circumferential speed, so that the screen drum on the one hand and the rotor and conveying screw on the other hand perform a relative rotation. An admitting arrangement admits a liquidcontaining mass into the screen drum. the liquid escapes from the screen drum during centrifuging and the centrifuged material forms on the inner circumferential surface of the screen drum a layer which, due to the difference between the first and second speeds, moves incrementally towards the conveying screw which engages it and removes it from the screen drum.

Description

nited States Patent 11 1 Steprath Dec. 16, 1975 [73] Assignee: Maschinenfabrik Buckau R. Wolf Aktiengesellschaft, Grevenbroich,

Germany [22] Filed: Feb. 1, 1974 [21] Appl. No: 438,606 [30] Foreign Application Priority Data Feb. 3, 1973 Germany ..2305326 [52] US. Cl. 127/19; 210/380; 233/7;

233/22; 233/25 [5i] Int. Cl. B04b 5/00; B04b 9/08; Cl3f H06 [58] Field of Search 127/19, 56; 233/3, 7, 22, 233/25; 210/380 Primary ExaminerMorris O. Wolk Assistant Examiner-Sidney Marantz Attorney, Agent, or Firm-Michael S. Striker 5 7] ABSTRACT A rotor is mounted for rotation about a first axis, and a screen drum is mounted on the rotor for rotation about a second axis parallel to but laterally offset from the first axis. A conveying screw is mounted in the screen drum for rotation jointly with the rotor about the first axis and it has screw flights which extend close to an inner circumferential surface of the screen drum. A single drive rotates the screen drum at a first circumferential speed, and rotates the rotor and conveying screw at a different second circumferential speed, so that the screen drum on the one hand and the rotor and conveying screw on the other hand per- [56] References cued form a relative rotation. An admitting arrangement UNITED STATES PATENTS admits a liquid-containing mass into the screen drum. 1,146,269 7/1915 Mauss 233/25 X the liquid escapes from the screen drum during centri- 1,339,272 5/1920 Mauss .1 233/25 fuging and the centrifuged material forms on the inner QUiI'OZ 1 v. circumferential urface of the creen drum a layer 2,883,054 4/1959 'f 127/19 X which, due to the difference between the first and secgggi E 6 0nd speeds, moves incrementally towards the convey- 10/1966 Rotel 210/380 X mg screw WhlCh engages 1t and removes it from the 3,402,821 9/1968 Peck 210/380 x Screen drum- 3,6'27,l38 12/1971 Peck 1 233/22 X 3,718,220 2/1973 Titus 233/22 X 10 Claims, 2 Drawing Figures U.S. Patent Dec. 16, 1975 Sheet 1 of2 3,926,661

FIG.

US. Patent Dec. 16, 1975 Sheet20f2 3,926,661

CENTRIFUGE CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates to a centrifuge construction and more particularly to a continuously operating centrifuge which is especially but not exclusively suitable for the production of sugar.

Continuous centrifuges are already well known, including in the field of sugar production. It is known to provide centrifuges of this general type for use where differential centrifugal forces are required. Generally speaking, however, centrifuges of the prior art which provide for differential centrifugal force acting upon the material being centrifuged, are not suitable for the centrifuging of finished sugar or the like, because in operation the sugar crystals impinge at high speed against a wall of the drum which causes them to crack and become blind. This latter term refers to a condition in which the sugar no longer has crystalline appearance, and thus lacks the optical appeal associated with sugar. This makes sugar produced in this manner very difficult to sell.

SUMMARY OF THE INVENTION It is, accordingly, a general object of the present invention to provide a novel centrifuge construction which avoids the disadvantages of the prior art.

More particularly, it is an object of the invention to provide a continuously operating centrifuge which can be used for centrifuging of finished sugar or analogous products, and which reliably precludes the possibility that the centrifuged crystals might be flung against a wall during operation of the centrifuge, or might even move only along this wall of the centrifuge drum during the centrifuging operation.

An additional object of the invention is to provide such an improved centrifuge construction in which the centrifuged crystals are discharged from the centrifuge drum in a region of relatively small acceleration and travel speed.

In keeping with the above objects, and with others which will become apparent hereafter, one feature of the invention resides, in a centrifuge, in a combination which comprises a rotor mounted for rotation about a first axis, and a screen drum mounted on the rotor for rotation about a second axis parallel to but laterally offset from the first axis. A conveying screw is mounted in the screen drum for rotation jointly with the rotor about the first axis, and the conveying screw has screw flights which extend close to an inner circumferential surface of the screen drum.

Drive means is provided for rotating the screen drum at a first circumferential speed, and for rotating the rotor and conveying screw at a different second circumferential speed. Admitting means admits a liquidcontaining mass into the screen drum so that during centrifuging the liquid can escape from the latter. The retained centrifuged material forms on the inner circumferential surface of the screen drum a layer which, due to the difference between the first and second speeds and the thus obtained relative angular movements of the screen drum and conveying screw, moves incrementally towards the conveying screw for engagement by the same and conveyance out of the screen drum.

The drive means may utilize a single drive motor which, since it imparts different angular velocities to the screen drum on the one hand, and the rotor and conveying screw on the other hand, causes not only rotation of the screen drum and rotor with the conveying screw in one and the same direction, but also causes a superimposed relative angular movement between the screen drum and the rotor with the conveying screw on the other hand. The layer which forms on the inside surface of the screen drum, and from which liquid has escaped due to the centrifugal force, travels incrementally together with the wall of the screen drum away from the axis of the main rotation, that is it moves into zones where it is subjected to higher centrifugal acceleration and where further liquid thus is removed from it. As this incremental travel continues, the now largely liquid-free material, for instance sugar crystals, approaches the main axis of rotation again, to finally reach the vicinity of the conveying screw which en gages increments of the layer and removes them from the conveying drum. During the entire operation the crystals or similar material remain in position on the inner circumferential wall of the screen drum and do not perform any movement relative to the latter. The discharge of the centrifuged material takes place in a region of low acceleration and therefore in a zone of low mass forces.

The centrifuge construction according to the present invention has the advantage, by comparison to the prior art, that no fracturing or breaking-down of the crystal or other centrifuged material takes place on the inner circumferential surface of the screen drum, due to impact or movement relative to this surface, and that at the time of discharge the centrifuged crystals are subjected to almost no impact forces, so that the disadvantages resulting in the prior art in the formation of, for instance, blind sugar, are avoided.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best undertood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is an axial section through a centrifuge according to the present invention; and

FIG. 2 is a section taken on line II-II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Referring now to FIGS. 1 and 2, wherein one exemplary embodiment of the invention is illustrated, the housing of the novel centrifuge will be seen to be designated with reference numeral 1. Mounted in the housing 1, by means of axially spaced antifriction bearings 2 and 3, is a rotor 4 which is composed of two axially spaced disk members 5 and 6. These have eccentrically arranged

circular recesses

7 and 8 provided in their inwardly facing surfaces, that is in those surfaces which face one another in axial direction. The members 5 and 6 are also provided with central bores through which a hollow shaft 9 extends on which the members 5 and 6 are fixed, for instance by means of non-illustrated flanges, by shrink fitting or the like.

As FIG. 2 shows most clearly, the hollow shaft 9 is provided with an axially extending slotted opening 10 through which the centrifuged crystals or similar material can enter into its interior. The length of the opening corresponds to the length of the screen drum 16. One edge 11 bounding the opening 10 engages or is located directly proximal to the inner circumferential surface of the screen drum 16 and is configurated as a scraper or doctor blade which engages beneath the layer 35 of centrifuged material (see FIG. 2) to lift it off the inner circumferential surface of the screen drum 16 and guide it into engagement with the conveying screw 23 which extends through the hollow shaft 9.

It is clear that the

recesses

7 and 8 are provided eccentrically on the members 5 and 6, as previously pointed out; diametrally opposite the location of the

recesses

7 and 8 the members 5 and 6 have

portions

12 and 13 which are configurated as counterweights, that is which are suitably massive and heavy to act as counterweights. These counterweights may, incidentally, be arranged to cooperate in known manner with an arrangement (known per se) for automatic compensating of imbalances. (See DT-PS 2 140 006 or US. Pat. Application Ser. No. 279,170).

The recess 7 accommodates an anti-friction bearing 14, and the recess 8 similarly accommodates an antifriction bearing 15. The screen drum 16 is mounted for rotation in these

bearings

14 and 15 and is composed of two flat annular members 17 and 18 which are connected by a circumferential screen wall 19 so that with the latter they form the screen drum 16.

Bearing rings

20 and 21 are provided by means of which the drum 16 is journaled in the

anti-friction bearings

14 and 15, respectively.

In the region of the bearing ring 20 the screen drum 16 is also provided with an internal ring gear 22 the teeth of which mesh with the teeth of a pinion which is fixedly mounted on the shaft 24 of the conveying screw 23. Also mounted on this shaft 24 is a belt pulley 26 by means of which the shaft 24 is driven in rotation so that the screw flights of the screw 23 which are mounted on the shaft 24 and fixed to the same, rotate with the shaft. In the region of the annulus 18 the flights of the screw 23 are interrupted at 23a.

The shaft 9 is formed at its left-hand end (with respect to FIG. 1) with a collecting chamber 36, and it is further formed with a passage 37 the opposite ends of which communicate with the chamber 36 and the interior of screen drum 16, respectively. A conduit 39 extends into an open end of the chamber 36 and the material to be centrifuged is admitted into this chamber via the conduit 39.

At the opposite axial end from the chamber 36, the shaft 9 is formed with a further chamber 38 through which the centrifuged material is to be expelled by the screw 23.

A second belt pulley 27 is fixedly mounted on the shaft 9 in the region of the chamber 36; the diameter of the belt pulley 27 is somewhat larger than that of the belt pulley 26. Both pulleys 26 and 27 are driven, via

belts

28 and 29, respectively, from an output pulley 30 of a common drive motor 31. It is evident that the diameter differential of the belt pulleys 26 and 27 will cause the shaft 24 to rotate somewhat faster than the shaft 9.

FIG. 2 shows that the axis of rotation of the shaft 24 of the conveying screw 23 coincides with the main axis of rotation 33 of the rotor 4. The conveying screw 23 is so mounted that its outer diameter intersects the inner diameter of the screen drum 16 and a tangent, that is the arrangement is such that the screw 23 can engage and remove the layer 35' of centrifuged material which has formed on the inner circumferential surface of the screen drum 16. The axis of rotation of the screen drum 16 is identified with reference numeral 34 in FIG. 2, and electro-motor 31 is mounted in suitable manner, for instance by means of a socket 32 or the like, on the centrifuge housing 1.

In operation, the material to be centrifuged is admitted via the conduit 39 into the chamber 36, and travels from there through the passage 37 into the interior of the screen drum 16. It is discharged into the screen drum 16 at the location A shown in FIG. 2, with the result that in this region a layer 35 of the material will form on the inner circumferential surface of the screen drum 16. Because of the high-speed rotation of the rotor 4 and the consequent centrifugal action, liquid is centrifugally removed from the layer 35, that is the liquid passes out through the screen openings of the screen drum 16.

During the rotation of the rotor 4 the screen drum 16 performs a relative angular movement, that is a movement with respect to the rotor 4 at the same time as the screen drum also rotates with the rotor 4 about the axis 33. The result of this relative angular movement is that the material which has been admitted at A in FIG. 2 will travel slowly and incrementally in clockwise direction towards the opening 10 of the shaft 9. Evidently, the dwell time of the material in the screen drum 16, that is the time required for any increment of the layer 35 to travel from the location A to the opening 10, can be varied by varying the speed at which the screen drum 16 rotates with reference to the rotor 4. Such a variation can be obtained by changing the diameter of the pulley 27 with respect to that of the pulley 26, and this in turn can be done by utilizing variable sheaves or the like.

In any case, as soon as the increments 35' of the layer 35 that is the now centrifuged crystals or the like, reach the vicinity of the opening 10, and come in contact with the edge 1 1 thereof, they are lifted off the inner circumferential surface of the screen drum 16 and directed towards the conveyor screw 35 which engages the material and ejects it axially from the screen clrum 16, or rather from the hollow shaft 9 which extends through the screen drum 16, through the chamber 38.

It is pointed out that although in the illustrated embodiment the axes of rotation of the rotor 4 and the screen drum 16 have been shown to be horizontal, it is well within the concept and intent of the present invention to have these axes be either vertical or substantially vertical, without in any sense departing from the concepts of the invention.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a centrifuge, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set 'forth in the appended claims.

1. In a centrifuge, a combination comprising a rotor mounted for rotation about a first axis; a screen drum mounted on said rotor for rotation about a second axis parallel to but laterally offset from said first axis; a conveying screw mounted in said screen drum for rotation jointly with said rotor about said first axis, said conveying screw having screw flights which extend close to an inner circumferential surface of said screen drum; drive means for rotating said screen drum at a first circumferential speed, and for rotating said rotor and convey ing screw at a different second circumferential speed; and admitting means for admitting a liquid-containing mass into said screen drum, so that during centrifuging the liquid can escape from the latter whereas the retained centrifuged material forms on said inner circumferential surface which, due to the difference between said first and second speeds, moves incrementally towards said conveying screw for engagement by the same and conveyance out of said screen drum.

2. A combination as defined in claim 1, wherein said rotor comprises a hollow shaft extending eccentrically through said screen drum and internally accommodating said conveyor screw, and a pair of disk members mounted on said shaft axially spaced from one another and fixed to said shaft for rotation therewith, said shaft having an axially extending slot in its circumferential wall through which said retained centrifuged material of said layer enters.

3. A combination as defined in claim 2, wherein said disk members each have one radial side where said screen drum is located, and a diametrically opposite radial side which is configurated as a counterweight.

4. A combination as defined in claim 3; and further comprising means cooperating with said counterweights and operative for effecting automatic correction of imbalances of said rotor.

5. A combination as defined in claim 2, wherein said slot is bounded by an edge portion configurated as a scraper for scraping increments of said layer from said inner circumferential surface of said screen drum.

6. A combination as defined in claim 2, wherein said screen drum is provided with an internal gear surrounding said second axis; and wherein said conveying screw comprises a shaft member extending through said screen drum and ring gear, and a pinion fixedly mounted on said shaft member and meshing with said ring gear.

7. A combination as defined in claim 2, wherein said hollow shaft comprises one end portion projecting axially outwardly past one of said. disk members and being formed with an inlet chamber, and another end portion projecting axially outwardly past the other of said disk members and being formed with an outlet chamber into which said conveying screw extends.

8. A combination as defined in claim 7, wherein said hollow shaft is further provided with a passage having one open end communicating with said inlet chamber, and another open end communicating with the interior of said screen drum.

9. A combination as defined in claim 8, wherein said admitting means communicates with said inlet chamber for admitting into the same said mass which travels via said passage into said screen drum.

10. A combination as defined in claim 1, wherein said drive means comprises a single drive motor.

Claims

1. IN A CENTRIFUGE, A COMBINATION COMPRISING A ROTOR MOUNTED FOR ROTATION ABOUT A FIRST AXIS; A SCREEN DRUM MOUNTED ON SAID ROTOR FOR ROTATION ABOUT A SECOND AXIS PARALLEL TO BUT LATERALLY OFFSET FROM SAID FIRST AXIS; A CONVEYING SCREW MOUNTED IN SAID SCREEN DRUM FOR ROTATION JOINTLY WITH SAID ROTOR ABOUT SAID FIRST AXIS, SAID CONVEYING SCREW HAVING SCREW FLIGHTS WHICH EXTEND CLOSE TO AN INNER CIRCUMFERENTIAL SURFACE OF SAID SCREEN DRUM; DRIVE MEANS FOR ROTATING SAID SCREEN DRUM AT A FIRST CIRCUMFERENTIAL SPEED, AND FOR ROTATING SAID ROTOR AND CONVEYING SCREW AT A DIFFERENT SECOND CIRCUMFERENTIAL SPEED; AND ADMITTING MEANS FOR ADMITTING A LIQUID-CONTAINING MASS INTO SAID SCREEN DRUM, SO THAT DURING CENTRIFUGING THE LIQUID CAN ESCAPE FROM THE LATTER WHEREAS THE RETAINED CENTRIFUGED MATERIAL FORMS ON SAID INNER CIRCUMFERENTIAL SURFACE WHICH, DUE TO THE DIFFERENCE BETWEEN SAID FIRST AND SECOND SPEEDS, MOVES INCREMENTALLY TOWARDS SAID CONVEYING SCREW FOR ENGAGEMENT BY THE SAME AND CONVEYANCE OUT OF SAID SCREEN DRUM.

7. A combination as defined in claim 2, wherein said hollow shaft comprises one end portion projecting axially outwardly past one of said disk members and being formed with an inlet chamber, and another end portion projecting axially outwardly past the other of said disk members and being formed with an outlet chamber into which said conveying screw extends.