US3860165A

US3860165A - Centrifuge and method of operating the same

Info

Publication number: US3860165A
Application number: US397098A
Authority: US
Inventors: Bernhard Fiedler
Original assignee: Maschinenfabrik Buckau R Wolf AG
Current assignee: BWS Technologie GmbH
Priority date: 1972-09-14
Filing date: 1973-09-13
Publication date: 1975-01-14
Anticipated expiration: 1992-01-14
Also published as: BE804871A; GB1446923A; DE2245019C3; CS188901B2; FR2200061B1; DE2245019B2; DE2245019A1; IT998585B; NL7311857A; NL154435B; FR2200061A1

Abstract

An upright centrifuge basket has a lower end and an upper end and its interior diverges upwardly in cross-section. An accelerator cone is mounted in the basket in the region of its lower end to accelerate material being centrifuged. An electromotor is above the basket, extending in part into the same and having an output shaft which is connected with the accelerator member for rotating the basket which is thus suspended from the electromotor. The electromotor has cooling fins and is surrounded by an air-guide sleeve which is closed at its upper end and the lower end of which is open in the region of the accelerator member, so that cooling air which has been heated by contact with the electromotor is directed by the sleeve onto the material being centrifuged in the basket.

Description

[4 1 Jan. 14, 1975 Great Britain..................... 1/1957 Switzerland.......

[ CENTRIFUGE AND METHOD OF OPERATING THE SAME [75] Inventor:

Bernhard Fiedler G b h, Germany raven role Primary Examiner-George H. Krizmamch Attorney, Agent, or Firm-Michael S. Striker [73] Assignee: Maschinenfabrik Buckau R. Wolf Aktiengesellschaft, Grevenbroich, Germany [57] ABSTRACT An upright centrifuge basket has a lower end and an 22 Filed: Sept. 13, 1973 21 Appl. No.: 397,098

upper end and its interior diverges upwardly in crosssection. An accelerator cone is mounted in the basket in the region of its lower end to accelerate material being centrifuged. An electromotor is above the has- [30] Foreign Application Priority Data Sept. 14, 1972 Germany............................

233/24 B04b 15/02 23 R pended from the electromotor. The electromotor has [51] Int.

cooling tins and is surrounded by an air-guide sleeve which is closed at its upper end and the lower end of [58] Field of Search........... 233/3, 11

[56] References Cited which is open in the region of the accelerator member, so that cooling air which has been heated by UNITED STATES PATENTS contact with the electromotor is directed by the sleeve onto the material being centrifuged in the basket.

399,113 3/1889 Adams et 233/11 1 029F23EIGN PATENTS OR APPLICATIONS 10 Claims, 1 Drawing Figure 4/1958 Germany 233/11 BACKGROUND OF THE INVENTION The present invention relates generally to centrifuging, and more particularly to a novel centrifuge and to a method of operating the same.

Still more particularly, the present invention relates. to a continuously operating sugar centrifuge, and a method of operating the same.

In various types of centrifuges, including sugar centrifuges which operate continuously, it is known that the material being centrifuged must not cool, or not cool beyond a certain extent, because this causes a substantial increase in its viscostiy. It is known that for every temperature differential of 9, the viscosity will double during cooling. Insofar as sugar is concerned, or rather a sugar solution which is to be centrifuged, it is known that the possibility of centrifuging such a solution decreases, the greater the viscosity of the solution is. In fact, it may happen that the viscosity is so high that centrifuging of the solution, also known as syrup, is no longer possible.

It is, therefore, quite evidently undersirable to permit the material being centrifuged e.g., the syrup to cool, or at least to cool beyond a certain extent. On the other hand, it is virtually impossible to prevent cooling of the very thin layer of syrup which forms on the interior of the centrifuge basket, because the airmovements resulting from the rapid spinning of the basket will inevitably cause such cooling.

The prior art has proposed to overcome the problem by heating the syrup to a temperature higher than that required to obtain its desired viscosity while it is in the centrifuge basket, in the hope that the cooling which takes place during centrifuging will reduce the temperatue of the molasses only to the normal desired temperature, so that the viscosity of the syrup will not increase beyond that desired for centrifuging purposes. However, in this first place this requires very large containers with heated rotating stirring mechanisms. A relatively long period of time is required for the contents of such a container to be heated to the desired temperature. This, however, brings with it the danger that a large portion of the crystallized sugar returns into solution, and this re-dissolved sugar is lost from recovery because it'becomes part of the molasses and is thus withdrawn from sugar recovery operation. Moreover, the material of course loses heat during its transfer from the heating container to the centrifuge basket, so

that the remedy is not nearly as reliable as desirable. One proposal made in the prior art, and in particular in sugar centrifuges having a basket the interior of which diverges conically and which rotates about a vertical axis and has at its lower end an accelerator member, suggests that the interior of the basket be heated. This is accomplished by blowing steam into the basket. However, the steam not only heats the basket wall but also the housing of the centrifuge and therefore the sugar chamber which catches the sugar that is produced in the interior of the basket. This is disadvantageous because if the basket wall is heated, and the material to be centrifuged is admitted in cold state into the basket, the material will reach its most advantageous temperature and viscosity only after it has already travelled to a very substantial extent towards the outlet end of the basket. This means that that portion of the screen of the basket which is traversed by the material before it reaches the desired temperature and viscosity, is not at all, or improperly utilized for the centrifugal separation.

, Moreover, if steam is admitted into the interior of the centrifuge basket, the steam contacting the cooler material to be centrifuged will condense and form on the material a liquid film which dissolves the sugar. On the other hand, if hot air is used for this purpose, a special air heater is required which disadvantageously influences the complexity and expense of the arrangement.

SUMMARY OF THE INVENTION It is, accordingly, an object of the invention to overcome the disadvantages of the prior art.

More particularly it is an object of the present invention to provide an improved centrifuge, particularly a sugar centrifuge, which overcomes the aforementioned disadvantages and is capable of maintaining the material to be centrifuge at a desired temperature.

Another object of the invention is to provide such an improved centrifuge which is relatively simple in its construction.

An additional object of the invention is to provide a method of operating the novel centrifuge.

In keeping with the above objects, and others which will become apparent hereafter, one feature of the invention resides in a centrifuge, particularly a sugar centrifuge, which comprises an upright centrifuge basket having a lower end and an upwardly divering interior cross-section. An accelerator member is connected to the basket in the region of the lower end for accelerating material being centrifuged. An electromotor is at least in part above the basket and has an output shaft extending into the same and being connected with the accelerator member for rotating the basket. The electromotor has cooling fins and is surrounded by an airguide sleeve which has a lower open end in region of the accelerator member, so that air which is heated by contact with the electromotor for the purpose of cooling the same is directed by the sleeve onto the material being centrifuged in the basket.

In such a centrifuge, particularly in a continuously operating sugar centrifuge, the material to be centrifuged moves continuously at high speed and in form of a very thin film or layer over the inner surface bounding the interior of the drum or basket, towards the upper open outlet end of the basket. The air'guided by the sleeve is directed against this thin layer and is fully sufficient to prevent cooling of the material and to maintain it at sufficiently low viscosity so that it can be properly centrifuged.

Without exception, the electromotors used for driving the baskets of sugar centrifuges are air-cooled. They utilize their own impeller which draws -in cold air and makes it circulate past the cooling fins of the motor, whereby the air is heated through heat exchange with the cooling fins. This air is then vented and the heat energy which it has picked up from the cooling fins, is lost. The present invention recovers this heat energy, utilizing it to maintain the material to be centrifuged at the desired temperature at which it can be properly centrifuged. Moreover, the present invention, in using the heretofore lost heat energy, eliminates the necessity for an additional heater which would otherwise be required to preheat air to be directed against the material to be centrifuged. Thus, the construction of the centrifuge is less complicated and, moreover, it is less expensive. In addition, the operating costs of the centrifuge are reduced because the desired warming of the material being centrifuged is achieved without requiring the expenditure of additional energy, utilizing the heretofore lost thermal energy dissipated from the electromotor.

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 understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a somewhat diagrammatic vertical section through one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing now in detail it will be seen that reference numeral 1 identifies a closed housing having an upper open end which is closed by the cover 18. A centrifuge basket 2, the interior cross-section of which diverges from its lower end towards its upper end, has at the lower end a hub 3 on which a conical accelerator member is mounted by means of accelerating spokes 6. The basket 2 is suspended from a downwardly extending output shaft 4 of an electromotor 7, whighputputshaftiis connected with the accelerator member 5 and the hub 3.

The electromotor 7, which is of the air-cooled type, is mounted via a motor mount 11 and elastomeric vibration-suppressing buffer members 12, on the housing cover 18. It extends in part into the housing 1 and into the basket 2.

The outer circumference of the motor 7 is provided with cooling ribs 14 which are surrounded by a cylindrical air-guide sleeve 13 defining with the ribs 14 air guide channels 15. The opposite ends of the sleeve 13 are open so that air which is drawn in through the inlet opening 9 by the blades 8 of the impeller associated with the motor for cooling the same, can pass through the channels 15 in heat exchanging contact with the ribs or fins 14, in downward direction. This of course cools the motor 7 in the usual manner. At the same time, the cooling air becomes heated as it exchanges heat with the cooling fins 14. The thus heated air issues from the lower open air of the sleeve, which is located in the region of the accelerator member 5. For better guidance of the air, the lower end portion of the sleeve 13 conically converges, advantageously to an outer diameter which is no greater than the minimum inner diameter of the accelerator member 5.

The amount of cooling air which can be drawn into contact with the fins 14 by the blades 8, can be controlled by a control member, for instance a slide which can close the opening 9 to a greater or leser extent. This of course controls the amount of cooling air, and thereby the temperature of the air issuing into the interior of the basket 2 can be varied.

The material to be centrifuged, that is for instance syrup, is admitted via inlet 17 into the region of the accelerator member 5. Rotation of the basket 2 causes the material to flow towards the upper open end of the basket over the inner circumferential surface thereof, in a thin layer. It must be understood in this connection that although the basket 2 has not been shown as having openings, and although no inner screen has been illustrated in contact with the inner circumferential surface of the basket, this has been done only for ease of illustration. It should be understood that these will selfevidently be present. In fact, the construction of the basket 2 is completely conventional in the sugar centrifuging art.

The motor 7 is provided with a lower journal 19 and an upper journal 20, and extends so into the interior of the basket 2 that the lower journal 19 is located approximately at the level of the center of gravity of the basket 2.

The cooling air which is admitted through the opening 9 is heated by contact with the cooling fins 14 to such an extent that, when it is blown against the layer of material to be centrifuged, it will maintain the temperature of the material at such a level that the material retains the degree of viscosity necessary for proper centrifuging.

A further advantage of this construction is that the overall centrifuge height can be substantially lower than would otherwise be possible, which is an advantage in terms of saving valuable space. Moreover, the centrifuge will operate more quietly, especially due to the fact that the motor 7 is mounted on the cover 18 of the housing 1 and extends into the interior of the basket 2 to such an extent its lower journal 19 is located at or near the center of gravity of the basket 2. The arrangement of the member 5, and the provision of the elements 6 thereof, assures that the accelerator member 5 will not only draw the newly admitted material to be centrifuged, but also the warm air which issues from the sleeve 13, and will guide them jointly at the lowermost point of the basket interior onto the wall of the basket. This is of course enhanced by the fact that the portion 16 of the sleeve 13 is made downwardly convergent.

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 de scribed 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 withinthe 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:

1. A centrifuge, particularly a sugar centrifuge, comprising an upright centrifuge basket having a lower end and an upwardly diverging interior cross-section; an accelerator member connected to said basket in the region of said lower end for accelerating material being centrifuged; an electromotor at least in part above said basket and having an output shaft which extends into the same and is connected with said accelerator member for rotating said basket, said electromotor having cooling fins; and an air-guide sleeve surrounding said electromotor and shaft and having a lower open end in the region of said accelerator member, so as to direct air heated in said electromotor onto the material being centrifuged in said basket.

2. A centrifuge as defined in claim 1; further comprising a housing surrounding said basket and having an upper open end provided with a cover; and upper and lower journals mounting said electromotor on said cover, said electromotor extending into said basket to such an extent that said lower journal is located in the region of the center of gravity of said basket.

3. A centrifuge as defined in claim 2, said accelerator member having impeller spokes which are fixedly connected to said shaft.

4. A centrifuge as defined in claim 1, said sleeve having a cylindrical upper main portion, and a lower end portion which extends from said main portion to said lower open end and conically tapers in direction towards the latter.

5. A centrifuge as defined in claim 4, wherein said accelerator member has an inner diameter which is substantially equal to the smallest outer diameter of said lower end portion.

6. A centrifuge as defined in claim 1; further comprising a housing surrounding said basket and having an upper open end provided with a cover; and elastomeric mounting members mounting said electromotor on said cover.

7. A centrifuge as defined in claim 1; and further comprising means for regulating the flow of cooling air to said electromotor.

8. A centrifuge, particularly a sugar centrifuge, comprising an upright centrifuge basket having a lower end and an upwardly diverging interior cross-section; an accelerator member connected to said basket in the region of said lower end for accelerating material being centrifuged; an air-cooled electromotor at least in part above said basket and having an output shaft which extends into the same and is connected with said accelerator member for rotating said basket; and an air-guide sleeve connected to said electromotor and defining a passage for air heated by heat exchange with the electromotor, said passage communicating with the region of said accelerator member and directing the heating air onto the material being centrifuged in said basket.

9. In a method of operating a continuous centrifuge having an upright basket of upwardly divergent inner cross-section bounded by an internal surface of the basket, and an air-colled electromotor above the basket and suspending the same for rotation, the steps of rotating the basket by operating the electromotor with attendent development of heat in the latter; introducing viscous material to be centrifuged into the basket with attendant centrifuging of such material and distribution thereof on the internal surface of the basket when the latter is rotated; and advancing air in a path in which it exchanges heat with the electromotor and thereupon toward and along the internal surface of the basket in heat-exchange relation with the material distributed thereon, whereby the viscosity of such material is maintained at a predetermined value.

10. In a method as defined in claim 9, wherein the step of advancing comprises discharging the heated cooling air into the smaller-diameter lower end region of said basket.