Discontinuously operating centrifuge and process for producing a centrifuge drum therefor

Abstract

The invention relates to a discontinuously operating centrifuge having a centrifuge drum which is rotatable about a drum axis and which comprises a cylindrical centrifuge shell, the centrifuge drum having openings for the discharge of a liquid phase which is obtained during centrifuging. A cover plate is fixedly connected to the top of the centrifuge shell, and a bottom plate is fixedly connected to the bottom of the centrifuge shell. The through-openings are of different size. According to the invention, the opening cross-sections are designed according to load and appropriate to load such that the openings have smaller opening cross-sections in the region of the cover plate plane and in the region of the bottom plate plane than in the region lying therebetween. The invention also relates to a process for producing a centrifuge drum for a discontinuously operating centrifuge of the type described above. The contour of the opening cross-sections of the openings in the centrifuge shell is produced by means of a cutting process in which a programmed, preferably continuous trajectory is traveled. Preferred cutting processes of this type are water jet cutting, laser beam cutting or contour milling.

Description

[0001] Discontinuously operating centrifuge and method for producing a centrifuge drum therefor

[0002] Description

[0003] The invention relates to a discontinuously operating centrifuge with a centrifuge drum rotatable about a drum axis, with a cylindrical centrifuge shell with openings for the discharge of a liquid phase arising during centrifugation, and a cover plate and base plate firmly connected to the centrifuge shell, the openings being of different sizes.

[0004] A discontinuously operating centrifuge of the aforementioned type, which is used in particular, for example, in the sugar industry, is known from DE 10 2018 007 790 A1 and WO2019 / 07647 A1. The centrifuge shell, which forms a sieve element, has different opening widths in the axial direction of the material flow. These opening widths become larger in the direction of the material flow. Furthermore, the openings in the centrifuge drum shell are formed at different distances (axial distances) in the axial direction of the shell and are of different sizes. Furthermore, the circumferential distances of the openings can vary if necessary. Reinforcement rings are also shown, which are dimensioned to different sizes depending on the load and load-appropriate.

[0005] EP 2 782 679 B1 discloses a discontinuous centrifuge, wherein the openings for the discharge of a liquid phase arising during centrifugation are designed such that the diameter of the opening cross-sections in the circumferential direction on the inside of the shell is smaller than the diameter of the opening cross-sections in the circumferential direction on the outside of the shell. Thus, the passage cross-sections of the openings widen outwards. The smallest width of the elliptical opening is identical on both the outside and inside of the cylindrical centrifuge shell. The largest width of the elliptical opening is larger on both the outside and inside of the cylindrical centrifuge shell. DE 1 916 280 discloses a periodically operating centrifuge with elliptical openings or perforations, wherein the main axis of the ellipse is oriented at right angles (transversely) to the drum axis.The ratio of major axis to minor axis is 1:5, preferably 1:10.

[0006] EP 1 693 112 B1 discloses a centrifuge drum with a drum shell in which the openings in the centrifuge shell are offset from one another both in the axial direction and in the circumferential direction of the drum shell, and the contours of the openings overlap in the axial direction, so that the drum circumference is covered with openings. The contours of the openings cover 5% - 30% of its area.

[0007] The invention aims to provide a discontinuously operating centrifuge with a centrifuge drum and a cylindrical centrifuge shell, in which the free, open passage areas of the openings are larger in the passage cross-section without adversely affecting the service life of the centrifuge. The aim is therefore to improve the service life or service life of such a discontinuously operating centrifuge. An increase in throughput is also to be achieved by reducing the weight of the centrifuge drum.

[0008] Furthermore, a method for producing a centrifuge drum for a discontinuously operating centrifuge is to be provided, in which the contour of the opening cross sections is cut in a cost-effective manner.

[0009] According to the invention, a discontinuously operating centrifuge is provided for this purpose, comprising a centrifuge drum rotatable about a drum axis, a cylindrical centrifuge shell with openings for the discharge of a liquid phase arising during centrifugation, a cover plate and base plate firmly connected to the centrifuge shell, the openings being of different sizes, which is characterized in that the opening cross sections are designed load-dependently and load-appropriately in such a way that the openings in the area of ​​the cover plate plane and the base plate plane have smaller opening diameters than in the area in between.

[0010] This inventive design of the discontinuous centrifuge allows for the dimensions of the opening cross-sections to be adjusted to achieve the largest possible opening cross-section with minimal stress conditions during operation, thus optimizing the service life of the centrifuge. This improves the service life and durability of such a discontinuous centrifuge. The larger opening cross-sections improve the outflow of the liquid phase generated during centrifugation, thus resulting in more favorable cycle times for the discontinuous centrifuge according to the invention. By reducing the weight or the mass inertia of the centrifuge cylinder, the throughput can be increased, and the cycle time per cycle of the discontinuous centrifuge can be reduced, while the overall capacity can be increased by increasing the number of cycles per unit time.The weight savings also allow the filling capacity per cycle of the discontinuous centrifuge to be increased.

[0011] Further advantageous embodiments of the discontinuously operating centrifuge are specified in the dependent subclaims 2 - 18.

[0012] In the preferred embodiment according to claim 2, the size of the opening cross sections of the openings of the centrifuge shell depends on the axial position relative to the drum axis.

[0013] According to a preferred development, the opening cross-sections of these openings are smallest in the range of 0.1 to 0.2 of the centrifuge bowl height relative to the base plate plane or cover plate plane arranged orthogonally to the drum axis. In particular, the openings have a substantially slot-shaped cross-section orthogonal to the drum axis and in the circumferential direction.

[0014] Claims 5 to 9 specify preferred size ratios of the slot-shaped cross-sections in the region of the cover plate plane and the base plate plane as well as the openings with slot-shaped cross-sections in the intermediate region of the centrifuge shell.

[0015] Preferably, the slot-shaped cross-section has substantially straight longitudinal flank sections orthogonal to the drum axis. Preferred size ratios for the straight longitudinal extension are specified in claims 11-13.

[0016] In the preferred embodiment according to claim 12, the opening cross-section is bone-shaped and the longitudinal extension of the slot-shaped cross-section has an opposite bend circle radius orthogonal to the drum axis.

[0017] Further preferred embodiments of the invention are set out in claims 14 and 15.

[0018] According to a preferred embodiment of the invention, the openings are divided by rings at an axial height relative to the drum axis. The pitch can vary from opening to opening in the row of openings in the axial direction. Preferably, the inside of the opening is the same size as the outside of the centrifuge shell.

[0019] Furthermore, according to the invention, a method for producing a centrifuge drum for a discontinuously operating centrifuge is provided, in which the contour accuracy of the openings is optimized, namely by pairwise water jet cutting, laser beam cutting or contour milling by means of a cutting process following a programmed, preferably continuous trajectory curve.

[0020] With this cutting process, one pair of openings is created for each setting and then the setting is advanced.

[0021] Preferably, the second contour of the openings of the paired opening pair in the direction of rotation of the centrifuge shell has an acute angle on the downstream opening flank to the adjacent tangent.

[0022] Preferably, the contour of the opening cross-sections is cut into the already rounded cylindrical centrifuge shell.

[0023] The invention will be explained in more detail below using preferred embodiments with reference to the accompanying drawings, which are not limitative in any way.

[0024] Figure 1 in the upper part an example of an opening or passage opening formed according to the invention;

[0025] Figure 2 shows a schematic example of the arrangement of the cover plate and base plate in conjunction with the centrifuge bowl in the resting position, with the cover plate and base plate firmly connected to the centrifuge bowl. The lower section of Figure 2 illustrates the load condition of such an arrangement in operation. The direction of rotation of the centrifuge drum is indicated by a circular arrow;

[0026] Figure 3 schematically shows a centrifuge bowl of the type according to the invention, wherein the openings in the region of the cover plate plane and the base plate plane have smaller cross-sectional openings than in the intermediate region, wherein reinforcement rings dimensioned in accordance with and depending on the load are provided on the outer circumference of the centrifuge drum; Figure 4 illustrates, in a sectional view, schematically dimensioned reinforcement rings and openings in the region near the cover plate and near the base plate and the intermediate region; the opening cross-sections are optimally adapted in length and width to the stress ratios between the centrifuge bowl and the reinforcement rings.

[0027] Figure 5 illustrates, on the one hand, the load conditions in an elliptical opening cross-section designed according to the prior art and, in the lower area, the position of the stress maxima in the operating state of the discontinuously operating centrifuge in a design of the opening cross-section of an opening according to the invention;

[0028] Figure 6 is a schematic embodiment of the opening with a counter-rotating radius of curvature orthogonal to the drum axis;

[0029] Figures 7 and 8 serve to schematically illustrate the method according to the invention for producing a centrifuge drum for a discontinuously operating centrifuge. Figure 7 illustrates the configuration of the paired openings per machine tool cycle, with the contour of the opening cross-sections of the openings in the centrifuge shell being generated by means of a programmed cutting process, preferably following a continuous trajectory. Figure 8 illustrates a procedure in which the second contour of the openings of the paired cut opening pair, in the direction of rotation of the centrifuge shell, has an acute angle to an adjacent tangent on the downstream opening flank.

[0030] Figure 1 shows a preferred embodiment of an opening according to the invention, designated overall by 1, in a sectional view at the top and a plan view below. 2 denotes a curved, cylindrical centrifuge shell. 3, for example, schematically denotes a reinforcement ring attached to the outer circumference of the cylindrical centrifuge shell 2. As can be seen from the sectional view schematically shown at the top of Figure 1, the opening 1 has an inner contour IK and an outer contour AK.

[0031] With reference to the top view in Figure 1 below, further details of the opening 1 according to the invention are explained. This opening 1 is designed in the shape of an elongated hole with a major axis a and a minor axis b. At the vertices of the elongated hole-shaped opening 1, the radius of the circle of curvature is small, rkk, and the radius of the circle of curvature is large, rk. gThe contour according to the invention or the passage opening is shown overall in bold broken lines, while one embodiment of the passage opening is shown in solid lines, such as that corresponding, for example, to an elliptical contour of a passage opening known from the aforementioned EP 2 782 679 B1. Between the two vertices, the slot-shaped passage opening 4 according to the invention has an approximately rectilinear longitudinal extension c.

[0032] As can be seen from this Figure 1, in particular the plan view shown at the bottom of Figure 1, the passage opening 4 according to the invention has a larger free open area compared to the passage opening known per se with an elliptical average cross-section, so that the liquid phase arising during centrifugation can flow off in an improved manner.

[0033] Figure 2 schematically illustrates the structure of a centrifuge drum in its resting state. A cover plate 6 at the top and a base plate 7 at the bottom are firmly connected to the centrifuge shell 2.

[0034] As can be seen from the lower illustration in Figure 2, in which the direction of rotation of the centrifuge drum or centrifuge shell is indicated by a circular arrow, the centrifuge or the centrifuge drum with the cylindrical centrifuge shell 2 is deformed by the centrifugal force during the operating state of the centrifuge. This results in corresponding tensile and bending loads between the cover plate 6 and the base plate 7 at the transition areas to the now curved cylindrical centrifuge shell 2. These additional loads are compensated for in the invention by correspondingly larger and smaller passage openings, as explained in more detail in connection with Figures 3 and 4.

[0035] Figure 3 shows a schematic, partially sectioned illustration of a centrifuge drum, designated overall by Z. The upper cover plate 6 and the lower base plate 7, as can also be seen in the upper illustration of Figure 2, are firmly connected to the centrifuge drum. 3 denotes reinforcing rings which are provided on the outer circumference of the centrifuge bowl 2 with different dimensions depending on the load and load-appropriate, as is known, for example, from the aforementioned DE 102018 007 790 A1 or WO2019 / 07647 A1. In the upper region A and in the lower region C, near the upper cover plate 6 and the lower base plate 7, the reinforcing rings 3 have a larger cross-section. The respective through-openings are schematically indicated by 1.

[0036] As can be seen from Figure 4 in conjunction with the above explanation of Figure 3, the passage openings 1 provided according to the invention have a smaller passage cross-section in the area near the upper cover plate 6 and also a smaller passage cross-section in the area of ​​the lower cover plate 6, as is schematically indicated in Figure 4. Thus, the radius of curvature in the upper area near the cover plate 6 is designated rkkA, whereby this designation also applies to the lower area near the base plate 7, as can be seen from Figure 4. In the intermediate or middle area of ​​the centrifuge shell 2, the passage opening has larger dimensions, whereby the radius of curvature there is designated rkkB.

[0037] As can be seen overall from Figure 4, the passage openings 4 have different radii of curvature both near the cover plate 6 and near the base plate 7 of the centrifuge shell 2 and they are dimensioned with a smaller passage cross-section in the upper and lower areas than in the middle area.

[0038] Figure 5 illustrates a significant difference between the invention and the prior art according to EP 2 782 679 B1 with regard to the location of the stress maxima. With the elliptical through-openings shown above in Figure 5, a stress concentration is obtained precisely at the transition areas between the cover plate 6 and the centrifuge shell 2, or at the transition area between the base plate 7 and the centrifuge shell 2 (shown in angled areas), with stress maxima in the elliptical through-opening located along the contour of the semi-major axis.

[0039] As can be seen from the schematic representation in Figure 5 below, in the invention, the design of the passage openings results in a position of the stress maxima not in the center, but the distance is eccentric, in particular in combination with the correspondingly designed reinforcement rings 3, which are not shown in detail in Figure 5.

[0040] Figure 6 illustrates an alternative embodiment of a passage opening 4. A significant difference from the passage opening in Figure 4 is that in the embodiment according to Figure 1, a straight line of the longitudinal extension c is provided, whereas in Figure 6, the longitudinal extension c preferably has an oppositely directed radius of curvature RK. Otherwise, the designations of the radii of curvature are analogous to Figure 1.

[0041] As can be seen from the above, according to the invention, the contours or opening cross-sections of the openings are designed to be variable, depending on the load and load-appropriate. This improves the outflow of the liquid phase generated during centrifugation in the centrifuge, thus shortening the centrifuge cycle times. Since the centrifuge drum, and in particular the centrifuge cylinder, is reduced in weight due to the openings, the mass inertia of the centrifuge drum is reduced, thereby reducing the cycle time per cycle. This results in an increase in overall capacity due to more cycles per unit time. Thanks to the weight savings, the fill volume per centrifuge cycle can also be increased.

[0042] Figures 7 and 8 serve to explain the method according to the invention for producing a centrifuge drum for a discontinuously operating centrifuge. As can be seen from Figure 7, the contour of the opening cross-sections of the openings in the centrifuge shell is created using a cutting process that follows a programmed, preferably continuous trajectory. For such a cutting process, waterjet cutting, laser cutting, and contour milling are preferred options.

[0043] Ha denotes the main axis of the opening cross-section in the outer area, Hi denotes the main axis of the passage cross-section of the openings in the inner area of ​​the centrifuge bowl.

[0044] With this cutting process, a pair of openings is cut for each setting, and then the setting is advanced. As an example, a 12° cycle is shown in Figure 7.

[0045] Figure 8 shows that, in the direction of rotation of the centrifuge bowl, the second contour of the openings of the paired openings on the downstream opening flank forms and encloses an acute angle a with the adjacent tangent t. This geometric contour generates a negative pressure-generating turbulence during rotation, which accelerates the centrifugal separation of the liquid phase.

[0046] 1 opening in total

[0047] 2 cylindrical centrifuge bowl

[0048] 3 reinforcement ring

[0049] 4 slot-shaped passage opening

[0050] 6 Cover plate

[0051] 7 Base plate

[0052] A area on the base plate

[0053] B area on cover plate

[0054] C Intermediate area

[0055] H axial height of the centrifuge bowl (in Fig. 3)

[0056] Z Centrifuge drum total

[0057] IK inner contour

[0058] AK Outer contour a Main axis b Minor axis rkk Small radius of curvature rk g Curvature circle radius large c Longitudinal extension or length extension rkkA Curvature circle radius rkkB Curvature circle radius

[0059] RK opposite curvature circle radius

[0060] Ha Main axis of the opening cross-section in the outdoor area

[0061] Hi Main axis of the opening cross-section in the interior in Figures 7 and 8 t Tangent in Figure 8 a Acute angle to t

[0062] VLrkkA length-radius ratio

Claims

Discontinuously operating centrifuge and method for producing a centrifuge drum therefor Patent claims 1. Discontinuously operating centrifuge with a centrifuge drum rotatable about a drum axis with a cylindrical centrifuge shell with openings for the discharge of a liquid phase arising during centrifugation, a cover plate and base plate firmly connected to the centrifuge shell, the openings being of different sizes, characterized in that the opening cross sections are designed load-dependent and load-appropriate in such a way that the openings in the area of ​​the cover plate plane (A) and base plate plane (C) have smaller opening cross sections than in the intermediate area (B).

2. Discontinuously operating centrifuge according to claim 1, characterized in that the size of the opening cross sections of the openings of the centrifuge shell is dependent on the axial position relative to the drum axis.

3. Discontinuously operating centrifuge according to claim 1 or 2, characterized in that in the range 0.1 to 0.2 of the centrifuge shell height (H) relative to the base plate plane (C) or cover plate plane (A) arranged orthogonally to the drum axis, the opening cross sections of the openings are smallest.

4. Discontinuously operating centrifuge according to one of claims 1 to 3, characterized in that the openings have a substantially elongated cross-section orthogonal to the drum axis and in the circumferential direction.

5. Discontinuously operating centrifuge according to claim 4, characterized in that the slot-shaped cross-section in the region of the cover plate plane (A) and in the region of the base plate plane (C) of the centrifuge shell has a length / width ratio of 3.0 to 4.0, preferably of 3.2 to 3.

7.

6. Discontinuously operating centrifuge according to claim 4 or 5, characterized in that the slot-shaped cross-section in the region of the cover plate plane (A) and the base plate plane (C) of the centrifuge shell has the smallest opening cross-section in the second row of rings.

7. Discontinuously operating centrifuge according to one of claims 4 to 6, characterized in that the slot-shaped cross-section in the intermediate region (B) of the centrifuge shell has a length / width ratio of 2.0 to 3.0, preferably of 2.5 to 2.

7.

8. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the slot-shaped cross-section in the region (A) and (C) of the centrifuge shell has a length / radius ratio (VLrkkA) of 10 to 15, preferably 12 to 13.

9. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the slot-shaped cross-section in the region (B) of the centrifuge shell has a length / radius ratio (VLrkkB) of 8 to 12, preferably of 9 to 11.

10. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the slot-shaped cross-section comprises substantially straight longitudinal flank sections orthogonal to the drum axis.

11. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the rectilinear length (c) of the slot-shaped opening cross-section essentially accounts for 30% to 60% of the total length (a) of the opening cross-section.

12. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the opening cross-section is bone-shaped.

13. Discontinuously operating centrifuge according to claim 12, characterized in that the longitudinal extension (c) of the slot-shaped cross-section has an opposite bend circle radius (RK) orthogonal to the drum axis.

14. Discontinuously operating centrifuge according to claim 13, characterized in that the center of the circle of curvature of the radius of curvature (RK) lies on the axis of symmetry (b) and the radius of curvature (RK) is 5 to 20 times greater than the total length (a) of the opening cross-section.

15. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the pitch of the rows of openings changes in the axial direction.

16. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the openings are divided by rings at an axial height relative to the drum axis.

17. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the pitch changes from opening to opening in the row of openings in the axial direction.

18. Discontinuously operating centrifuge according to one of the preceding claims, characterized in that the inside of the opening is the same size as the outside of the centrifuge shell.

19. A method for producing a centrifuge drum for a discontinuously operating centrifuge according to one of the preceding claims, characterized in that the contour of the opening cross sections of the openings in the centrifuge shell is produced by means of a cutting process following a programmed, preferably continuous trajectory.

20. Method according to claim 19, characterized in that water jet cutting, laser beam cutting or contour milling is used as the cutting method.

21. Method according to one of claims 19 or 20, characterized in that the cutting method creates one pair of openings per setting and then switches to the next setting.

22. Method according to one of claims 19 to 21, characterized in that the second contour of the openings of the paired openings, in the direction of rotation of the centrifuge shell, has an acute angle (α) on the downstream opening flank to the adjacent tangent (t). (Fig. 8) 23. Method according to one of claims 19 to 22, characterized in that the contour of the opening cross-sections is cut into the already rounded cylindrical centrifuge shell

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