WO2010039094A1

WO2010039094A1 - A separating disk and a disk package for a centrifuge rotor

Info

Publication number: WO2010039094A1
Application number: PCT/SE2009/051082
Authority: WO
Inventors: Kjell Klintenstedt; Sven Olov Olsson; Lars Johan Rudman
Original assignee: Alfa Laval Corporate Ab
Priority date: 2008-09-30
Filing date: 2009-09-30
Publication date: 2010-04-08
Also published as: EP2349576A4; EP2349576A1; EP2349576B1; SE0802057A1; SE532916C2

Abstract

The invention refers to a separating disk and a disk package for a centrifuge rotor of a centrifugal separator for separation of components in a supplied medium. The separating disk (20) extends around an axis (x) of rotation and has a tapering shape along the axis (x) of rotation with an inner surface and an outer surface (21 ). The separating disk is manufactured of a material. The separating disk comprises a number of distance members (25) extending at a certain height away from at least one of the inner surface and the outer surface. The tapering shape of the separating disk has been provided through pressing of a blank of the material against a tool having a shape corresponding to the tapering shape of the pressed separating disk. The separating disk has a thickness which varies with the distance from the axis of rotation. The height of the distance members (25) varies with the distance from the axis (x) of rotation in such a way that this varying height compensates for the varying thickness.

Description

A separating disk and a disk package for a centrifuge rotor

The present invention refers to a separating disk adapted to be included in a disk package of a centrifuge rotor of a centrifugal separator according to the preamble of claim 1. The invention also refers to a disk package for a centrifuge rotor of a centrifugal separator comprising a plurality of separating disks which are provided on each other in the disk package according to the preamble of claim 15.

Today separating disks for disk packages in centrifuge rotors are normally manufactured through pressure turning of plane disk to a desired tapering shape, for instance a conical shape. This method of manufacturing has the disadvantage that the manufacturing is expensive and time-consuming. Each separating disk has to be pressure turned individually in a pressure lathe. Another disadvantage of the pressure turning method is that it is difficult to produce irregular shapes such as protrusions in the pressure turned disk. A further disadvantage of the pressure turning method is the difficulty to achieve a sufficient surface smoothness without subsequent treatment of the surface. A poor surface smoothness can lead to deteriorated hygienic properties.

According to the present invention, it is instead proposed to manufacture the separating disks through draw and/or stretch pressing of a plane blank to the desired tapering shape. There are today several different press methods which can be of interest in this context, deep-drawing, pressing between fixed tool, hydroforming etc. It is however difficult to achieve finished separating disks with a uniform thickness in a radial direction through pressing. Different pressing methods have also given different results regarding the thickness variation obtained.

RECOKU COPY-TRANSLATION (Ru'e 12,4) SUMMARY OF THE INVENTION

The object of this invention is to provide a separating disk and a disk package having a high and uniform quality and being able to be manufactured to low costs.

This object is achieved by the separating disk initially defined, which is characterized in that the separating disk has a thickness which varies with the distance from the axis of rotation and that the height of the distance members varies with the distance from the axis of rotation in such a way that this varying height compensates for the varying thickness.

Thanks to such a varying height of the distance members, a uni- form and tight abutment between the separating disks in the plate package can be ensured. Advantageously, the sum of the height of the distance member and the thickness of the separating disk is constant or substantially constant along the whole distance member. Consequently, a constant or substantially constant angle of inclination of the whole disk package can be ensured. It is to be noted that although the thickness variation of each individual separating disk is small, this variation adds up in a disk package comprising a large number of separating disks, which can result in a large problem of accuracy with regard to the disk package. Advantageously, the height of the distance members varies with the distance from the axis of rotation in such a way that each distance member abuts uniformly an outer surface or an inner surface of an adjacent separating disk in the disk package. Thanks to the fact that the separating disk has been produced through pressing against a form, a very high surface smoothness can be achieved.

According to an embodiment of the invention, the thickness of the separating disk increases with an increasing distance from the axis of rotation, wherein the height of the distance members decreases with an increasing distance from the axis of rotation. Certain press methods will result in such an increase of the thickness, which can be compensated for in accordance with the invention.

According to an other embodiment of the invention, the thickness of the separating disk decreases with an increasing distance from the axis of rotation, wherein the height of the distance members increases with an increasing distance from the axis of rotation. Other press methods will instead result in such a decrease of the thickness, which also can be compensated for in accordance with the invention. It is to be noted that the person skilled in the art in light of this information can configure the distance members in such a way that they provide the desired compensation for the specific press method to be used in the individual case.

According to a further embodiment of the invention, the distance members have an extension from a radially inner position to a radially outer position, and wherein the height varies along the extension. Such distance members with an elongated extension offers an advantageous support for the separating disks in the disk package. Thanks to the varying height, a tight abutment along the whole extension can be ensured.

According to a further embodiment of the invention, each distance member has a width at the inner surface and/or outer surface seen in a normal direction to said surface, wherein the width of at least some of the distance members vary with the distance from the axis of rotation.

According to a further embodiment of the invention, at least some of the distance members have a spot-like extension and wherein the height varies with the distance of the spot-like distance members from the axis of rotation. In such a way, a proper and supporting abutment can be ensured for each distance member. According to a further embodiment of the invention, the distance members are formed by protrusions in said material. With such protrusions, no distance members attached afterwards are needed, but the distance members can be manufactured in a very effective and inexpensive manner. Such protrusions, which are an integrated part of the material of the separating disk, improve the hygienic properties of the separating disk, i.e. reduce the collection of dirt and particles at the distance members and simplify the cleaning of the separating disk. Advantageously, the tapering shape and the protrusions of the separating disk may have been produced through pressing of said blank against a tool having a shape corresponding to the tapering shape with the protrusions of the pressed separating disk. In such a way, the manufacturing of the separating disk is facilitated in a significant manner since the subsequent step for attachment of distance members is not needed. It is to be noted that such a pressing enables many further advantages. For instance, stiffening folds or embossings can be achieved in an easy manner, and the shape, position and extension of the distance members may be varied in an arbitrary manner, and thus be adapted to all imaginable separation cases.

According to a further embodiment of the invention, the protru- sions comprise a number of pairs of protrusions, which each comprises a first protrusion extending away from the outer surface and a second protrusion extending away from the inner surface, wherein the first and second protrusions are displaced in relation to each other in a peripheral direction of the separating disk. Advantageously, the first and second protrusions may be provided adjacent to each other in a peripheral direction of the separating disk.

According to a further embodiment of the invention, the first pro- trusion forms a channel-like depression of the inner surface, wherein this depression is configured to permit collection and transport of one of said components radially outwardly or inwardly on the inner surface. Furthermore, the second protrusion can form a channel-like depression of the outer surface, wherein this depression is configured to permit collection and transport of one of said components radially outwardly or inwardly on the outer surface.

According to a further embodiment of the invention, all protrusions extend in the same direction with respect to the outer sur- face and wherein each protrusion is delimited by two opposite side lines extending towards an outer edge of the separating disk. In this case, all separating disks in the disk package may be identical.

The object is also achieved by the disk package initially defined, which is characterized in that each separating disk has a thickness, which varies with the distance from the axis of rotation, and that the height of the distance members varies with the distance from the axis of rotation in such a way that this varying height compensates for the varying thickness of the separating disks. Such a disk package has a constant, or substantially constant, angle of inclination for the whole disk package.

Advantageous embodiments of the disk package are defined in the dependent claims 16-21 . Especially, it may here be mentioned that the separating disks may comprise a plurality of second separating disks, wherein the first and second separating disks are provided in an alternating order in the disk package and wherein the second separating disks lack distance mem- bers. In this case, it is particularly suitable to let the height of each distance member of a first separating disk vary in such a way that it compensates for the varying thickness of said one first separating disk and for the varying thickness of an adjacent second separating disk. In such a way a uniform angle of incli- nation and a tight abutment are ensured for the whole disk package. The separating disks included in the disk package may also comprise the features which are defined in the dependent claims 5-14.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now to be explained through a description of various embodiments and with reference to the drawings attached hereto. Fig. 1 discloses a partly sectional side view of a centrifugal separator with a centrifuge rotor.

Fig. 2 discloses a sectional side view through a disk package of the centrifugal separator in Fig. 1 .

Fig. 3 discloses a view from above of a separating disk of the disk package according to a first embodiment. Fig. 4 discloses a side view of the separating disk in Fig. 3. Fig. 5 discloses a section through the disk package in Fig. 2. Fig. 6 discloses a section similar to the one in Fig. 5 of a part of a disk package according to a second embodiment. Fig. 7 discloses a view similar to the one in Fig. 3 of a separat- ing disk according to a third embodiment.

Fig. 8 discloses a view similar to the one in Fig. 3 of a separating disk according to a forth embodiment.

Fig. 9 discloses a section similar to the one in Fig. 5 through a disk package with separating disks according to the forth em- bodiment.

Fig. 10 discloses a section similar to the one in Fig. 5 through a disk package with separating disks according to a fifth embodiment. Fig. 1 1 discloses a section similar to the one in Fig. 5 through a disk package with separating disks according to a sixth embodiment.

Fig. 12-14 discloses a sectional view of a first variant of a press tool for pressing a separating disk. Fig. 15 discloses a plan view of a tool part of the press tool on Figs. 12-14. Fig. 16-18 discloses a sectional view of a first variant of a press tool for pressing of a separating disk.

Fig. 19 discloses a plan view of a tool part of the press tool in Figs. 16-18.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Fig. 1 discloses a centrifugal separator which is adapted for separation of at least a first component and a second component of a supplied medium. It is to be noted that the disclosed centrifugal separator is disclosed as an example and that the configuration thereof may be varied. The centrifugal separator comprises a frame 1 , which may be non-rotatable or stationary, and a spindle 2 which is rotably journalled in an upper bearing 3 and a lower bearing 4. The spindle 2 carries a centrifuge rotor 5 and is arranged to rotate together with the centrifuge rotor 5 around an axis x of rotation in relation to the frame 1 . The spindle 2 is driven by means of a drive member 6 which is con- nected to the spindle 2 in a suitable manner in order to rotate the latter at a high velocity, for instance via a drive belt 7 or a gear transmission, or through direct drive, i.e. the rotor (not disclosed) of the drive member 6 is directly connected to the spindle 2 or the centrifuge rotor 5. It is to be noted here that ele- ments having the same function has been provided with identical reference signs in the various embodiments to be described.

The centrifugal separator may comprise a casing 8 which is connected to the frame 1 and which encloses the centrifuge ro- tor 5. Furthermore, the centrifugal separator comprises at least one inlet 9, which extends through the casing 8 and into a separation space 10 which is formed by the centrifuge rotor 5 for feeding of the medium to be centrifuged, and at least a first outlet for discharged from the separation space 10 of the first com- ponent which has been separated from the medium and a sec- ond outlet for discharge from the separation space 10 of the second component which has been separated from the medium.

In the separation space 10, there is a disk package 19 which ro- tates with the centrifuge rotor 5. The disk package 19 comprises or is assembled of a plurality of separating disks 20 which are piled onto each other in the disk package 19, see Fig. 2. A separating disk 20 according to a first embodiment is disclosed more closely in Figs. 3 and 4. Each separating disk 20 extends around the axis x of rotation and rotates around the axis x of rotation in a direction R of rotation. Each separating disk 20 extends along a rotary symmetric, or virtually rotary symmetric, surface which tapers along the axis x of rotation, and has a tapering shape along the axis x of rotation with an outer surface 21 , which is convex, and an inner surface 22, which is concave. The tapering shape of the separating disks 20 may also be conical or substantially conical, but it is also possible to let the tapering shape of the separating disks 20 have a generatrix which is curved inwardly or outwardly. The separating disks 20 thus have an angle α of inclination in relation to the axis x of rotation, see Fig. 2. The angle α of inclination may be 20-70°. Each separating disk 20 also has an outer edge 23 along the radially outer periphery of the separating disk 20 and an inner edge 24 which extends along the radially inner periphery of the separating disk 20 and defines a central opening of the separating disk.

Between the separating disks 20, there are distance members 25 which are provided on the outer surface 21 and/or the inner surface 22 and arranged to ensure the formation of an inter- space 26 between adjacent separating disks 20 in the disk package 19, see Fig. 5. Each separating disk 20 comprises at least one portion without distance members 25 on the outer surface 21 and/or the inner surface 22. The separating disks 20 may be provided around a so called distributor 27. The separat- ing disks 20 are compressed against each other in the disk package 19 with a pre-tensioning force in such a way that the distance members 25 of a separating disk abuts sealingly an adjacent separating disk 20, especially against the above mention portion of an adjacent separating disk 20. The separating disks 20 may also be fixedly connected to each other, for instance through brazing.

As can be seen in Figs. 1 and 2, the centrifuge rotor 5 also comprises a number of inlet disks 28 which are centrally provided in the distributor 27. These inlet disks 28 may be manu- factured in a similar manner as the separating disks 20. The inlet disks 28 may be plane, as disclosed in Fig. 1 and 2, or conical. The inlet disks 28 may have distance members with a similar configuration as the distance members 25 of the separating disks 20.

The tapering shape of the separating disks 20 has been provided through pressing of a blank of a material against a tool part. The material may be any pressable material, for instance metal material, such as steel, aluminium, titanium, various alloys etc., and also suitable plastic materials. The tool part to be described more closely below has a shape corresponding to the tapering shape of the pressed separating disk 20. It is to be noted, however, that the separating disks 20 as a consequence of such a pressing may obtain a thickness t that varies with the distance from the axis x of rotation.

In the first embodiment disclosed more closely in Figs. 3-5, the distance members 25 are formed as protrusions in the material, wherein the tapering shape and the protrusions of the separat- ing disk 20 have been produced through pressing of the blank against the tool part having a shape corresponding to the tapering shape with the protrusions of the press separating disk 20. In the first embodiment the distance members 25 comprise first distance members 25 in the form of first protrusions 31 and sec- ond distance members 25 in the form of second protrusions 32. The protrusions thus comprise a number of pairs of protrusions, wherein each of the pairs comprises a first protrusion 31 extending away from the outer surface 21 and a second protrusion 32 extending away from the inner surface 22. The first and second protrusions 31 , 32 are displaced in relation to each other seen in a normal direction with regard to the outer surface 21. In the embodiment disclosed, the first and second protrusions 31 , 32 are provided adjacent, or directly adjacent, to each other in a peripheral direction of the separating disk 20. It is possible to provide the distance members 25, i.e. in the embodiments dis- closed the first and second protrusions 31 , 32 in each pair at a significant distance from each other, for instance in such a way that a first protrusion 31 is located at the centre between two second protrusions 32. Possibly, the protrusions 31 , 32 may then be given a more wide shape and in an extreme case extend substantially straight from the peak of a first protrusion 31 to the peak of the adjacent second protrusions 32, which means that there is no marked beginning or marked end of the distance members 25.

As can be seen in Fig. 5, the first protrusion 31 abuts the inner surface 22 of the adjacent separating disk 20, whereas the second protrusion 32 abuts the outer surface 21 of an adjacent separating disk 20. The first protrusion 31 will thus form a channel-like depression of the inner surface 22 and this depression is configured to collect and transport one of said components radially outwardly or inwardly on the inner surface 22. The second protrusion 32 forms, in a corresponding manner, a channel- like depression of the outer surface 21 , wherein this depression is configured to collect and transport one of said components radially outwardly or inwardly on the outer surface 21. In the first embodiment, the second protrusion 32 is located after the first protrusion 31 with regard to the direction R of rotation. With regard to the outer surface 21 , the channel-like depression thus precedes the upwardly projecting first protrusion 31 . With regard to the inner surface 22, the channel-like depression instead fol- lows the downwardly projecting second protrusion 32. Inverted relations arise if the direction of rotation is the opposite.

The first and second protrusions 31 and 32 have a height h above the outer surface 21 and the inner surface 22, respectively, see Fig. 5. This height h determines also the height of the interspaces 26 between the separating disks 20 in the disk package 19. Since the thickness t of the separating disks 20 may vary with the distance from the axis x of rotation, the first and second protrusions 31 and 32 may advantageously be configured in such a way that the height h varies with the distance from the axis x of rotation. As can be seen in Fig. 3, the distance members 25, i.e. the first and second protrusions 31 and 32, have an extension from a radially inner position to a radially outer position, wherein the height h varies along this extension in such a way that this varying height compensates for the varying thickness. In such a way a tight and uniform abutment between the first and second protrusions 31 and 32 against the inner surface 22 and the outer surface 21 , respectively, can be ensured along the whole or substantially the whole extension of the protrusions 31 , 32.

Depending on the actual press method, the thickness t of the separating disk 20 may increase with an increasing distance from the axis of rotation, wherein the height h decreases with an increasing distance from the axis x of rotation. The thickness t of the separating disk 20 may also decrease with an increasing distance from the axis x of rotation, wherein the height of the distance members 25 increases with an increasing distance from the axis x of rotation. It is to be noted that the varying height h can be provided in an advantageous manner since the separating disks 20 are manufactured in a press method and pressed against a tool part with a corresponding shape. The tool part can thus have projections and depressions, respectively, which are configured for the formation of the protrusions, and which have been given a varying height h in accordance with the applied press method in connection with the tool manufacturing.

The press method also makes it possible in an easy manner to let the extension of the protrusions 31 , 32 be straight and radial or substantially radial, straight but inclined in relation to a radial direction, or curved at least if the protrusions 31 , 32 are seen in the direction of the axis x of rotation. In the first embodiment the extension of the protrusions 31 , 32 extends from in the proximity of the inner edge 24 to in the proximity of the outer edge 23.

The press method also makes it possible to configure the distance members 25, i.e. the first and second protrusions 31 , 32, with a width at the inner surface and/or the outer surface 21 seen in a normal direction to the inner surface or the outer surface 21 , wherein this width of at least some of the distance members 25 varies with the distance from the axis of rotation.

Furthermore, the press method also enables the formation of stiffening folds or embossings (not disclosed) of the separating disks 20. Such folds may be straight or curved or extend in suitable directions.

Each of the first and second protrusions 31 and 32 comprises at least one contact zone 33 intended to abut the inner surface 22 and the outer surface 21 , respectively, of an adjacent separating disk 20 in the disk package 19. As can be seen in Fig. 5, the contact zone 33 has a continuously convex shape seen in a cross section, in the first embodiment in a cross section trans- versally to a substantially radial direction. In the first embodiment, the contact zone 33 extends along the whole, or substantially the whole, extension of the first and second protrusions 31 and 32. With such a continuously convex shape of the contact zone 33 a small contact area between the contact zone 33 and the adjacent separating disk 20 is ensured, i.e. the contact area approaches zero. The contact zone 33 may in the first embodi- ment be defined to form a line abutment, or substantially a line abutment, against the inner surface 22 and the outer surface 21 respectively, of the adjacent separating disk 20 along the whole extension of the protrusions 31 and 32.

As can be seen in Figs. 2 and 5, the separating disks 20 comprise first separating disk 20' and second separating disks 20". The first separating disks 20' comprise the first and second protrusions 31 and 32 which have been described above. The sec- ond separating disks 20" lack such protrusions, i.e. they comprise, or consist of, only one of the above mentioned portion without distance members 25. The second separating disks 20" thus have an even, or substantially even, tapering shape. The first and second separating disks 20' and 20" are provided in an alternating order in the disk package 19, i.e. every second separating disk 20 is a first separating disk 20' and every second separating disk is a second separating disk 20".

As can be seen in Fig. 3, each separating disk 20 comprises one or several recesses 35 along the inner edge 24. Such recesses may have the purpose of enabling a polar positioning of the separating disks 20 in the disk package 19. Furthermore, each separating disk 20 comprises one or several recesses 36 along the outer edge 23. The recesses 36 may have the purpose of permitting transport of the medium through the disk package 19 and feeding of the medium into the different interspaces 26. It is to be noted that the recesses 35 and 36 may be advantageous for reducing the inherent stresses in the material in the pressed separating disk 20. The recesses 36 may be replaced by holes which in a manner known per se extend through the separating disk 20 and are provided at a distance from the inner and the outer edges 24, 23.

The separating disks are polar positioned in such a way that the first protrusions 31 of the first separating disks 20' are in line with each other in the disk package 19 seen in the direction of the axis x of rotation, see Fig. 5. Such a configuration of the disk package 19 is advantageous since it makes it possible to include a pre-tensioning in the disk package 19 when it is mounted. The second separating disks 20" will during the com- pressing of the disk package 19 be deformed elastically alternately upwardly and downwardly by the first and second protrusions 31 and 32 of the adjacent separating disks 20'. During operation of the centrifugal separator, forces arise in the second separating disks 20", which forces strive to straighten out the elastic deformation. Consequently, the abutment force between the separating disks 20 in the disk package 19 increases. In the embodiment disclosed, the first and second separating disks 20' and 20" have the same thickness t. However, it is to be noted that the first and second separating disks 20' and 20" may have different thicknesses t. Especially, the second separating disks 20", which lack protrusions, may have a thickness t which is significantly smaller than the thickness t of the first separating disks 20'. It is also to be noted that the height h of each distance member 25 of a first separating disk 20' varies in such a way that it compensates for the varying thickness t of the first separating disk 20' and for the varying thickness t of an adjacent second separating disk 20".

According to a second embodiment of the disk package 19, see Fig. 6, also each second separating disk 20" may comprise a number of distance members in the form of pressed first and second protrusions 31 and 32, i.e. all separating disks 20 are provided with first and second protrusions 31 and 32. In this case, the separating disks 20 mat be polarly positioned in such a way that a first protrusions 31 of the first separating disks 20' are displaced in relation to the first protrusions 31 of the second separating disks 20" in the disk package 19 seen in the direction of the axis x of rotation.

According to a variant of the invention, the second separating disks 20 or the portions without distance members of the sepa- rating disks 20 may be provided with plastically deformed portions where the contact zone 31 of a first and/or second protrusion 31 , 32 abuts or is intended to abut. The height of these plastically deformed portions is significantly lower than the height of the first and second protrusions 31 , 32. In such a way a secure positioning of the separating disks 20 in relation to each other is created.

It is to be noted here that for achieving the above mentioned pre-tensioning in the disk package 19, it is possible to provide the disk package 19 with distance members 25 which can not be deformed and for instance be formed by conventional distance members which are brazed or welded to the separating disks 20, but which are located in a corresponding manner as the first and second protrusions 31 and 32. Such conventional distance members may also have a continuously convex contact zone as has been described above.

Fig. 7 discloses a third embodiment where the distance mem- bers 25 have a spot-like extension. Also in this embodiment, the height of the distance members 25 may vary with the distance of the spot-like distance members 25 from the axis x of rotation. These distance members 25 may advantageously also be configured as first protrusions 31 extending away from the outer surface 21 and second protrusions 32 extending away from the inner surface 22. Each protrusion 31 , 32 may advantageously have a continuously convex shape seen in a section transver- sally to a peripheral direction and transversally to a radial direction. In this embodiment, the contact zone 33 may be defined to form a point abutment, or substantially a point abutment, against the inner surface 22 or the outer surface 21 of the adjacent separating disk 20. The protrusions 31 and 32 are displaced in relation to each other and may be provided at a distance from or adjacent to each other. Moreover, it is to mentioned here that the separating disks 20 according to a further alternative may comprise both spot-like distance members 25 and elongated distance members 25.

Figs. 8 and 9 disclose a forth embodiment of a pressed separat- ing disk 20, where the distance members 25 are formed by protrusions 50 which all extends in the same direction away from the outer surface 21. Each protrusion 50 is delimited by two opposite side lines 51 , which extend towards the outer edge 23 of the separating disk 20. In this embodiment, all separating disks 20, or substantially all separating disks 20, are identical. Fig. 9 discloses how the separating disks 20 are polarly positioned and abuts each other. In an area around each of the side lines 51 , the protrusions 50 comprise a contact zone 53 on the outer surface 21 and a contact zone 53 on the inner surface 22. In the disk package 19, the contact zone 53 of a separating disk 20 abuts the contact zone 53 of an adjacent separating disk 20. Also here, each contact zone 53 has continuously convex shape seen in a cross section transversally to a substantially radial direction. The contact zones 53 extend along the whole, or sub- stantially the whole, extension of the protrusions 50, and can be defined to form a line abutment, or substantially a line abutment, between the separating disks 20.

In the forth embodiment, the protrusions 50 have substantially the same width as the areas between the protrusions 50. It is to be noted, however, that the width of the protrusions 50 also could be larger or smaller than the width of these areas. As can be seen Fig. 8, the protrusions 50 extend radially, or substantially radially from in the proximity of the inner edge 24 to in proximity of the outer edge 23. It is possible to let the protrusions 50 slope in relation to a radial direction and/or extend all the way to the inner edge 24 and/or all the way to the outer edge 23. Also according to the forth embodiment, it is possible to let the height of the protrusions 50 vary in order to compen- sates for a varying thickness of the pressed separating disk 20. It is to be understood that the polar positioning of the separating disks 20 may be varied in many different ways in addition to the ways disclosed in Figs. 5 and 6. Fig. 10 discloses a fifth embodiment where two first separating disks 20' are provided be- side each other and each such pair of first separating disks 20' are separated by a second separating disk 20". The first protrusion 31 of a first separating disk 20' in such a pair lies opposite to the second protrusion 32 of the second first separating disk 20' in this pair, and opposite the first protrusions 31 of corre- sponding disks 20' in the remaining pairs.

Fig. 1 1 discloses a sixth embodiment which is similar to the fifth embodiment, but differs from the latter since one of the first separating disks 20' has been modified and is a third separating disk 20'" which comprises a first protrusion 31 but no second protrusion 32. The first protrusion 31 of the third separating disk in each pair lies opposite to the second protrusion 32 of the first separating disk 20' in each pair. In the fifth embodiment, a space which is closed in a cross-section is formed. Thanks to the absence of the second protrusion 32 of the third separating disk 20'", a lateral opening into this space is formed. It may also be mentioned that this closed space disclosed in Fig. 10 may be open at the ends through a variation of the length of the protrusions along their extension.

Figs. 12 to 15 disclose a first variant of a press tool for manufacturing a separating disk as defined above. The press tool is intended to be introduced into a press (not disclosed) of a suitable design. The press tool comprises a first tool part 61 and a second tool part 62. The first tool part 61 has a concave shape against which the outer surface 21 of the separating disk 20 abuts after finished pressing. The first tool part 61 has a substantially plane bottom surface and a surrounding tapering side surface, in the example disclosed a surrounding substantially conical side surface. The first tool part 61 thus have a shape corresponding to the tapering shape of the pressed separating disk 20. In the case that the separating disk 20 is provided with protrusions 31 , 32, 50, the first tool part 61 also comprises first from elements 63 which are located on the surrounding tapering side surface and which correspond to the shape of these protru- sions, in the disclosed press tool, the protrusions 31 and 32. The press tool comprises, or is associated with, a holding member 64, which is arranged to hold the blank 90 to be pressed against the first tool part 61 with a holding force. If the separating disk 20 lacks protrusions a first tool part 61 without first form elements 63 is used.

Furthermore, the press tool comprises a supply device arranged to permit supply of a liquid at a pressure between the blank 90 and the second tool part 62. The supply device comprises chan- nels 65 extending through the second tool part 62 through the surface of the second tool part 62 which faces the blank 90.

The first tool part 61 also comprises one or several second form elements 66, see Fig. 15, for forming a or several centering members of the pressed blank 90 in order to enable later centering of the blank 90 in connection with a successive processing of the blank 90. The form elements 66 are located on the bottom surface, which means that the centering members are provided in a central area of the blank 90. It is also imaginable to provide the centering members in an edge area of the blank 90, wherein corresponding second form elements will be located outside the tapering side surface.

Furthermore, the first tool part 61 comprises a plurality of evacuating passages 67 for evacuation of gas present between the blank 90 and the first tool part 61. The evacuating passages 67 have a very small flow area and are provided to extend through the bottom surface and the surrounding tapering side surface of the first tool part 61 . Especially, it is important that there are evacuating passages 67 extending through these surfaces at the first form elements 63 forming the first and second protrusions 31 and 32, and at the second form elements 66 forming the centering member.

The press tool is arranged to permit, in a charging position, in- troduction of the blank 90 to be pressed between the first tool part 61 and the second tool part 62. Thereafter, the blank 90 is clamped between the first tool part 61 and the holding member 64 see Fig. 12. The first tool part 61 and/or the second tool part 62 are then displaced in a first part step in the direction towards each other to a final position, see Fig. 13. The first part step can be regarded as a mechanical press step. Thereafter, a liquid with a pressure is supplied in a second part step into a space between the blank 90 and the second tool part 62 through the channels 65 in such a way that the blank 90 is pressed to abut- ment against the first tool part 61 and takes its final shape, see Fig. 14. During the second part step, the gas present between the blank 90 and the first tool part 61 will be evacuated via the evacuating passages 67. The second part step can be regarded as a hydroforming step.

Figs. 16 to 18 disclose a second variant of a press tool for manufacturing of a separating disk as defined above. The press tool is intended to be introduced in a press (not disclosed) of a suitable design. The press tool comprises a first tool part 61 and a second tool part 62. The first tool part 61 has a concave shape against which the outer surface 21 of the separating disk 20 abuts after finished pressing. The first tool part 61 has a surrounding tapering side surface, in the example disclosed a surrounding substantially conical side surface. The first tool part 61 thus has a shape corresponding to the tapering shape of the pressed separating disk 20. In the case that the separating disk 20 is provided with protrusions 31 , 32, 50, the first tool part 61 also comprises first form elements 63, which are located on the surrounding tapering side surface and which correspond to the shape of these protrusions, in the disclosed press tool, the protrusions 31 and 32. The press tool comprises or is associated with a holding member 64 which is arranged to hold the blank to be pressed against the first tool part 61 with a holding force. If the separating disk 20 lacks protrusions, a first part tool 61 without first form elements 63 is used.

The second tool part 62 has a projecting central portion 80 arranged to extend through and engage a central opening of the blank 90 to be pressed. By means of this central portion 80, the blank 90 may be positioned in the press tool before pressing. The first and second tool part 61 and 62 furthermore has a respective form element 81 and 82, respectively, which in cooperation with each other are arranged to form, when the first and second tool parts 61 , 62 are moved towards each other, an area around the central opening in such a way that the material in this area forms a centering member 91 extending cylindrically, or at least partly cylindrically, and concentrically with the axis x of rotation, see Fig. 18. The second tool part 62 also comprises a sealing element 83, which is provided radially outside the projecting central portion 80. The sealing element 83 extends around the central portion at a distance from the latter. The sealing element 83 is arranged to abut sealingly the blank 90 around the central opening. The total press force is reduced thanks to the fact that the centre of the blank 90 inside the sealing element 83 has been masked and thus is not subjected to any pressing. The central portion 80, which positions the blank 90, will also permit guiding of the flow of material in the blank 90 in an initial stage of the pressing with regard to how much material is transported from the centre of the blank 90 and from the peripheral parts of the blank 90. The guiding of the flow of mate- rial can be provided by varying the size of the central opening and/or by varying the holding force.

Furthermore, the press tool comprises a supply device arranged to permit supply of a liquid at a pressure between the blank 90 and the second tool part 62. The supply device comprises chan- nels 65 extending through the second tool part 62 through the surface of the second tool part 62 facing the blank 90.

Furthermore, the first tool part 61 comprises a plurality of evacuating passages 67 for evacuating gas present between the blank 90 and the first tool part 61 . The evacuating passages 67 have a very small flow area and are provided to extend through the bottom surface and the surrounding tapering side surface of the first tool part 61. Especially, it is important that there are evacuating passages 67 which extend through these surfaces at the first form elements 63 forming the first and second protrusions 31 , 32, and at the second form elements 66 forming the centering member.

The press tool is arranged to permit, in a charging position, introduction of the blank 90 to be pressed between the first tool part 61 and the second tool part 62 in such a way that the projecting central portion extends through the central opening. Thereafter, the blank 90 is clamped between the first tool part 61 and the holding member 64, see Fig. 16. The first tool part 61 and/or the second tool part 62 are then displaced in a first part step in a direction towards each other to a final position, see Fig. 17. The first part step can be regarded as a mechanical press step. Thereafter, a liquid at a pressure is supplied in a second part step into a space between the blank 90 and the second tool part 62 through the channels 65 in such a way that the blank 90 is pressed to abutment against the first tool part 61 and takes its final shape, see Fig. 18. The sealing element 83 then prevents the liquid from reaching the central opening. Dur- ing the second part step, the gas present between the blank 90 and the first tool part 61 will be evacuated via the evacuating passages 67. The second part step can be regarded as a hydro- forming step.

After the pressing, the blank 90 is removed from the press tool and transferred to any suitable processing machine (not dis- closed). The blank 90 is centered in the processing machine by means of the centering member or members. The processing machine is then arranged to form, in a subsequent processing step, the inner edge 24 and the outer edge 23 of the separating disk 20.

This subsequent processing step comprises forming of the above mentioned one or several recesses 35 along the inner edge 24 and the above mentioned one or several recesses 36 along the outer edge 23. The subsequent processing step may comprise any suitable cutting or shearing operation.

It is to be noted that the first tool part 61 instead of a concave shape may have a convex shape, wherein the inner surface 22 of the separating disk 20 will abut the first tool part 61 after finished pressing.

It is to be noted that the separating disks 20 may be provided with a certain surface roughness on the outer surface and/or the inner surface. Such a surface roughness can be provided through a treatment in advance of the whole, or a part or parts of the outer surface 21 and/or the inner surface 22, for instance in that the actual surface is etched before the separating disk is pressed. The surface roughness will remain after the pressing. It is also imaginable to configure one or both tool parts 61 , 62 with a surface roughness, wherein the pressing will provide the desired surface roughness of the actual surface of the outer surface and/or inner surface of the separating disk. Suitable examples of the surface roughness is disclosed in SE-B-457612. The roughness may thus comprise a plurality of flow influencing members having a certain height over the actual surface and a certain mutual distance. The relation between the certain height and the certain distance may lie in the interval 0,2-0,5. As indicated above, it is possible to provide selected parts with a roughness. Different parts of the actual surface may also have different roughness. Advantageously, only one of the outer sur- face 21 and the inner surface 22 is provided with a roughness. The protrusions 31 , 32 suitably have no roughness as well as the surface portions against which the protrusions 31 , 32 abut.

The invention is not limited to the embodiments disclosed but may be varied and modified with in the scope of the following claims. Especially, it is to be noted that the described separating disks may be used in substantially all kinds of centrifugal separators, for instance such where the centrifuge rotor has fixed openings for radial discharge of sludge, or intermittently openable such openings, see Fig. 1. The invention is applicable to centrifugal separators adapted for separation of all kinds of media, such as liquids and gases, for instance separating of solid or liquid particles from a gas.

Claims

1 . A separating disk adapted to be included in a disk package (19) of a centrifuge rotor (5) of a centrifugal separator adapted for separation of components in a supplied medium, wherein the separating disk (20) extends around an axis (x) of rotation and has a tapering shape along the axis (x) of rotation with an inner surface (22) and an outer surface (21 ), wherein the separating disk (20) is manufactured of at least one material, wherein the separating disk (20) comprises a number of distance members (25) extending at a certain height (h) away from at least one of the inner surface (22) and the outer surface (21 ), wherein the tapering shape of the separating disk (20) has been provided through pressing of a blank (90) of the material against a tool (61 ) having a shape corresponding to the tapering shape of the pressed separating disk (20), characterized in that the separating disk (20) has a thickness (t), which varies with the distance from the axis (x) of rotation, and that the height (h) of the distance members (25) varies with the distance from the axis (x) of rotation in such a way that this varying height (h) compensates for the varying thickness (t).

2. A separating disk according to claim 1 , wherein the height (h) of the distance members (25) varies with the distance from the axis (x) of rotation in such a way that each distance member (25) abuts uniformly an outer surface (21 ) or an inner surface (22) of an adjacent separating disk (20) in the disk package (19).

3. A separating disk according to anyone of claims 1 and 2, wherein the thickness (t) of the separating disk (20) increases with an increasing distance from the axis (x) of rotation and wherein the height (h) of the distance members (25) decreases with an increasing distance from the axis (x) of rotation.

4. A separating disk according to anyone of claims 1 and 2, wherein the thickness (t) of the separating disk (20) decreases with an increasing distance from the axis (x) of rotation and wherein the height (h) of the distance members (25) increases with an increasing distance from the axis (x) of rotation.

5. A separating dick according to anyone of the preceding claims, wherein the distance members (25) have an extension from a radially inner position to a radially outer position, and wherein the height (h) varies along the extension.

6. A separating disk according to anyone of the preceding claims, wherein each distance member (25) has a width at the inner surface (22) and/or the outer surface (21 ) seen in a normal direction to said surface, and wherein the width of at least some of the distance members (25) varies with the distance from the axis (x) of rotation.

7. A separating disk according to anyone of claims 1 to 4, wherein at least some of the distance members (25) have a spot-like extension, and wherein the height (h) varies with the distance of the spot-like distance members (25) from the axis (x) of rotation.

8. A separating disk according to anyone of the preceding claims, wherein the distance members (25) are formed by protrusions (31 , 32) in said material.

9. A separating disk according to claim 8, wherein the taper- ing shape and the protrusions (31 , 32, 50) of the separating disk (20) have been provided through pressing of said blank (9) against a tool (61 ) having a shape corresponding to the tapering shape with the protrusions (31 , 32, 50) of the pressed separating disk (20)

10. A separating disk according to anyone of claims 8 and 9, wherein the protrusions (31 , 32) comprise a number of pairs of protrusions which each comprises a first protrusion (31 ) extending away from the outer surface (21 ) and a second protrusion (32) extending away from the inner surface (21 ), wherein the first and second protrusions (31 , 32) are displaced in relation to each other in a peripheral direction of the separating disk (20).

11 . A separating disk according to claim 10, wherein the first and second protrusions (31 , 32) are provided adjacent to each other in a peripheral direction of the separating disk (20).

12. A separating disk according to claim 1 1 , wherein the first protrusion (31 ) forms a channel-like depression of the inner sur- face (22) and wherein this depression is configured to permit collection and transport of one of said components radially outwardly or inwardly on the inner surface (22).

13. A separating disk according to anyone of claims 1 1 and 12, wherein the second protrusion (32) forms a channel-like depression of the outer surface (21 ) and wherein this depression is configured to permit collection and transport of one of said components radially outwardly or inwardly on the outer surface (21 ).

14. A separating disk according to anyone of claims 8 and 9, wherein all protrusions (50) extend in the same direction with regard to the outer surface (21 ) and wherein each protrusion (50) is delimited by two opposite side lines (51 ) extending towards an outer edge (23) of the separating disk (20).

15. A disk package for a centrifuge rotor of a centrifugal separator adapted for separation of components in a supplied medium and comprising a plurality of separating disks (20), which are provided on each other in the disk package (19), wherein the separating disks (20) comprise a plurality of first separating disks (20'), wherein each separating disk (20) extends around an axis (x) of rotation and has a tapering shape along the axis (x) of rotation with an inner surface (22) and an outer surface (21 ), wherein each separating disk (20) is manufactured of at least one material, wherein at least each first separating disk (20') comprises a number of distance members (25) extending at a certain height (h) away from at least one of the inner surface (22) and the outer surface (21 ), wherein the tapering shape of the separating disk (20) has been provided through pressing of a blank (90) of the material against a tool (61 ) having a shape corresponding to the tapering shape of the pressed separating disk (20), characterized in. that each separating disk (20) has a thickness (t), which varies with the distance from the axis (x) of rotation, and that the height (h) of the distance members (25) varies with the distance from the axis (x) of rotation in such a way that this varying height (h) compensates for the varying thickness (t) of the sepa- rating disks (20).

16. A disk package according to claim 15, wherein the height (h) of the distance members (25) varies with the distance from the axis (x) of rotation in such a way that each distance member (25) abuts uniformly an outer surface (21 ) or an inner surface (22) of an adjacent separating disk (20) in the disk package (19).

17. A disk package according to anyone of claims 15 and 16, wherein the thickness (t) of the separating disk (20) increases with an increasing distance from the axis (x) of rotation and wherein the height (h) of the distance members (25) decreases with an increasing distance from the axis (x) of rotation.

18. A disk package according to anyone of claims 15 and 16, wherein the thickness (t) of the separating disk (20) decreases with an increasing distance from the axis (x) of rotation and wherein the height (h) of the distance members (25) increases with an increasing distance from the axis (x) of rotation.

19. A disk package according to anyone claims 15 to 18, wherein the separating disks (20) comprise a plurality of second separating disks (20") and wherein the first and second separating disks (20', 20") are provided in an alternating order in the disk package (19).

20. A disk package according to claim 19, wherein the second separating disks (20") lack distance members.

21. A disk package according to claim 20, wherein the height (h) of each distance member (25) of a first separating disk (20') varies in such a way that it compensates for the varying thickness (t) of said one first separating disk (20') and for the varying thickness (t) of an adjacent second separating disk (20").