Separation disc for a centrifugal separator and a method for manufacturing the separation disc

Abstract

A separation disc for a centrifugal separator and a method for manufacturing the separation disc are disclosed. The separation disc is of metal material and adapted to be compressed in a stack of separation discs inside a centrifugal rotor for separating a liquid mixture. The separation disc has a truncated conical shape with an inner surface and an outer surface and a plurality of spacing members extending a certain height above at least one of the inner surface and the outer surface for providing interspaces between mutually adjacent separation discs in the stack. The spacing members are of such small size that each one of them has a width which is less than 2 mm along the surface of the separation disc. The surface of the separation disc is configured with a distribution pattern of the small-sized spacing members, in such a way as to provide equidistant interspaces in the compressed disc stack.

Claims

1. A separation disc for a centrifugal separator, comprising: an outer surface and an inner surface; a plurality of small-sized spacing members extending a predetermined height from at least one of the inner surface and the outer surface for providing an interspace between mutually adjacent separation discs in a stack of separation discs, the small-sized spacing members having a width less than 1.5 mm along one of the inner surface and the outer surface of the separation disc; and a distribution pattern of the small-sized spacing members to provide equidistant interspaces in the compressed disc stack, wherein the separation disc has a truncated conical shape, wherein a thickness of the separation disc is less than 0.4 mm, wherein an outer diameter of the separation disc is at least 400 mm, wherein the small-sized spacing members are distributed on one of the inner surface and the outer surface of the separation disc at a distance in the range of 10-60 mm from each other, wherein the small-sized spacing members are spot-formed, and wherein the width of the small-sized spacing members corresponds to a diameter of the small-sized spacing members.

2. The separation disc according to claim 1, wherein the distribution pattern is in the form of an evenly distributed pattern with a same distance between adjacent small-sized spacing members throughout the separation disc.

3. The separation disc according to claim 1, wherein the small-sized spacing members are integrally formed in one piece with the material of the separation disc.

4. The separation disc according to claim 1, further comprising large-sized spacing members having a greater width than a width of the small-sized spacing members.

5. The separation disc according to claim 4, wherein the large-sized spacing members are provided in the form of separate pieces of narrow strips or circular blanks of sheet metal, which are attached to one of the inner surface and the outer surface of the separation disc.

6. The separation disc according to claim 4, wherein the large-sized spacing members are attached to the outer surface of the separation disc, and wherein the small-sized spacing members are formed on the inner surface of the separation disc.

7. The separation disc according to claim 1, wherein the separation disc is provided with distribution holes for feeding and distributing the liquid mixture into the interspaces in a stack of separation discs.

8. A stack of separation discs for a centrifugal separator, the stack of separation discs comprising: a plurality of separation discs of metal material adapted to be compressed in the stack of separation discs inside a centrifugal rotor for separating a liquid mixture, wherein each separation disc of the plurality of separation discs comprises: a truncated conical shape having an inner surface and an outer surface; a plurality of small-sized spacing members extending a predetermined height from at least one of the inner surface and the outer surface for providing interspaces between mutually adjacent separation discs in the stack, a width of which is less than 1.5 mm along one of the inner surface and the outer surface of each separation disc, a distribution pattern of the small-sized spacing members providing equidistant interspaces in the compressed disc stack, wherein the thickness of each separation disc is less than 0.4 mm, wherein the outer diameter of each separation disc is at least 400 mm, wherein the small-sized spacing members are distributed on one of the inner surface and the outer surface of each separation disc at a distance in the range of 10-60 mm from each other, wherein the small-sized spacing members are spot-formed, and wherein the width of the small-sized spacing members corresponds to a diameter of the small-sized spacing members.

9. The stack of separation discs according to claim 8, further comprising large-sized spacing members having a greater width than a width of the small-sized spacing members.

10. The stack of separation discs according to claim 9, wherein the large-sized spacing members are provided in the form of separate pieces of narrow strips or circular blanks of sheet metal, which are attached to one of the inner surface and the outer surface of the separation disc.

11. The stack of separation discs according to claim 9, wherein the large-sized spacing members are attached to the outer surface of the separation disc, and wherein the small-sized spacing members are formed on the inner surface of the separation disc.

12. The stack of separation discs according to claim 9, wherein the separation disc is provided with distribution holes for feeding and distributing the liquid mixture into the interspaces in the stack of separation discs.

13. The stack of separation discs according to claim 8, wherein the small-sized spacing members are integrally formed in one piece with the material of the separation disc.

14. A separation disc for a centrifugal separator, the separation disc being made of a metal material, and having a truncated conical shape with an inner surface and an outer surface, said separation disc comprising: a plurality of small-sized spacing members extending a certain height above at least one of the inner surface and the outer surface for providing interspaces between mutually adjacent separation discs in a stack of separation discs, the spacing members having a width which is less than 1.5 mm along one of the inner surface and the outer surface of the separation disc; large-sized spacing members having a greater width than a width of the small-sized spacing members; and a distribution pattern of the small-sized spacing members of the separation disc to provide equidistant interspaces in the compressed disc stack, wherein the thickness of the separation disc is less than 0.4 mm, wherein the outer diameter of the separation disc is at least 400 mm, and wherein the small-sized spacing members are distributed on one of the inner surface and the outer surface of the separation disc at a distance in the range of 10-60 mm from each other.

15. The separation disc for a centrifugal separator according to claim 14, wherein the small-sized spacing members are spot-formed, and wherein a width of the small-sized spacing members corresponds to a diameter of the small sized spacing members.

16. The separation disc for a centrifugal separator according to claim 14, wherein the large-sized spacing members are provided in the form of separate pieces of narrow strips or circular blanks of sheet metal, which are attached to one of the inner surface and the outer surface of the separation disc.

17. The separation disc for a centrifugal separator according to claim 14, wherein the large-sized spacing members are attached to the outer surface of the separation disc, and wherein the small-sized spacing members are formed on the inner surface of the separation disc.

18. The separation disc for a centrifugal separator according to claim 14, wherein the separation disc is provided with distribution holes for feeding and distributing the liquid mixture into the interspaces in a stack of separation discs.

19. The separation disc for a centrifugal separator according to claim 14, wherein the small-sized spacing members are integrally formed in one piece with the material of the separation disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which

(2) FIG. 1 shows a view of a separation disc in general,

(3) FIG. 2 shows an inner-surface-view of a separation disc according to a first embodiment of the invention,

(4) FIG. 3 shows an enlarged part of the first embodiment in FIG. 2,

(5) FIG. 4 shows the small-sized and spot-formed spacing members in cross-section of the inner surface of the separation disc,

(6) FIG. 5 shows a cross-section of a second embodiment of the separation disc having the small-sized and spot formed spacing members in combination with a larger sized spacing member,

(7) FIG. 6 shows a device and a method for manufacturing the separation disc made of thin sheet metal,

(8) FIG. 7 shows a flow formed separation disc with a see through part showing the small-sized recesses the device.

DETAILED DESCRIPTION

(9) FIG. 1 shows a very schematic view of a separation disc 1 for a centrifugal separator. A plurality of such separation discs 1 are arranged and compressed on top of each other to form a stack of separation discs inside a centrifugal rotor for separating a liquid mixture. As can be seen, the separation disc 1 has a truncated conical shape with an inner surface 2 and an outer surface 3. The inner surface 2 and/or the outer surface 3 of the separation disc 1 is provided with spacing members (not shown in FIG. 1) to form interspaces between the separation discs 1 in the stack. The general design and function of the separation discs and the centrifugal separator are both well known to a person skilled in the art, and will therefore not be described any further hereinafter.

(10) FIG. 2 shows an inner-surface-view of a separation disc according to a first embodiment of the invention. Hence, an inner surface 2 of the separation disc 1 is shown which is provided with a plurality of spacing members 4, 5 which are also shown in FIG. 3. The spacing members 4 and 5 are formed in one piece with the (metal) material of the separation disc 1. A first ring of the small-sized spacing members extends around the outer perimeter of the separation disc. A second ring has the small-sized spacing member and large-sized spacing members which are larger than the small-sized spacing members. The second ring is spaced radially inwardly from the first ring. A plurality of the small-sized spacing members are between the second ring and the central opening. The small-sized spacing members and the large-sized spacing members alternate in the second ring. This is achieved in a flow forming process described below.

(11) Furthermore, as can be seen in FIG. 3, the spacing members 4 and 5 are of different shapes; a spot-formed spacing member 4 and an elongated spacing member 5. The diameter of the spot-formed spacing member 4 corresponds to its width. Hence, the diameter of the spot-formed spacing member is the same as its width. The elongated spacing member 5 however is several times longer than it is wide, and it is furthermore curved along its length. Both spacing members 4 and 5 in this embodiment each have approximately the same width of 1 mm. The length of the elongated spacing members 5 is however approximately 6 mm, i.e. six times its width. The elongated spacing member 5 may be provided, when there's no conventional large-sized spacing member, in order to secure that the elongated spacing members matches with adjacent separation discs due to manufacturing tolerances and inaccuracies (e.g. a play or clearance required for mounting the separation discs on a so called distributer). The large sized spacing members are an elongate shape having a length greater than a width with an elongate side extending in a direction of the length of the large-sized spacing members extends in a circumferential direction of the separation disc. The elongation will secure a support at least in part of the adjoining spacing members 5 of adjacent separation discs, even when these elongated spacing members 5 are slightly displaced relative to one another due to said inaccuracies.

(12) It should be noted that the size of the spacing members 4 and 5 are greatly exaggerated in the drawings for the sake of clarity. In practice they would be of much smaller appearance on the separation disc surface and distributed at a much greater number on the surface. A separation disc 1 of the type shown in this embodiment would typically have an outer diameter 6 of much larger size than 200 mm, e.g. in a larger sized centrifugal rotor the separation discs' outer diameter 6 would be even larger than 400 mm. Accordingly, the spacing members 4 and 5 have a very small size (meaning the width of 1 mm along the surface of the separation disc) in relation to the size of the separation disc. Hence, a great number of these small-sized spacing members 4 and 5 are distributed on the inner surface 2 of the separation disc 1 in such a way as to provide equidistant interspaces in the compressed disc stack.

(13) The shown separation disc 1 is further provided with distribution holes 7 for feeding and distributing the liquid mixture into the interspaces in the stack of separation discs. These distribution holes 7 are well known in the art of centrifugal separators and will not be further described here. The distribution holes 7 are between the second ring and the plurality of the small-sized spacing members forming the first ring.

(14) FIG. 4 shows a cross-section of said small-sized and spot-formed spacing members 4 on the inner surface 2 of the separation disc 1. As can be seen, the spacing members 4 are formed in one piece with the material of the separation disc 1. The presently utilized manufacturing techniques (or the flow forming technique) for producing separation discs 1 is the main reason why the integrally formed spacing members 4 are provided on the inner surface 2. However, they may as well be arranged on the outer surface 3 of the separation disc. The integrally formed spacing members 4 may for instance be provided on the outer surface 2 by a pressing technique. Furthermore, the inner surface 2 of the separation disc 1 is provided with the small-sized spacing members 4 only. Hence, no other spacing members (such as larger sized spacing members) are provided on the surface. However, the small-sized spacing members may also be combined with larger sized spacing member (i.e. having a larger width). Such a combination is described below in a second embodiment of the separation disc shown in FIG. 5.

(15) FIG. 5 shows a cross-section of the small-sized and spot formed spacing members 4 in combination with a larger sized spacing member 8. The spacing member 8 is provided on the outer surface 3 of the separation disc 1. Furthermore, it is of substantially greater width (several times greater than the diameter of the small-sized distance members 4). In this particular embodiment the shown spacing member 8 is also spot-formed (i.e. a circular blank of sheet metal) and has a width (or diameter) which is about six times greater than the diameter of the small-sized distance members 4. Consequently, the diameter of the spot-formed and large-sized spacing member 8 is about 6 mm. The large-sized spacing members 8 may however, as an alternative, have an elongated shape (not shown). The large-sized spacing members may be of any known form, e.g. in the form of separate pieces of narrow strips or circular blanks of sheet metal which are attached to the separation disc by a suitable fastening method, such as welding (spot-welding). The large-sized spacing members 8 and the small-sized spacing members 4 have the same height above their respective surfaces 2 and 3. FIG. 5 further shows that the inner surface 2, in an area opposite the large-sized spacing member 8, is not provided with any small-sized spacing members 4. Consequently, the large-sized spacing member 8 of the separation disc 1 will abut a flat inner surface area of an upper adjacent separation disc 1 in the stack. The conventional spacing members 8 have a much greater width, and may thereby support a greater portion of the forces in the compressed disc stack. Accordingly, a reduced portion of the compressive forces is supported by the small-sized spacing members 4, which are distributed in order to secure or maintain an equidistant height on the interspaces between the large-sized spacing members 8.

(16) FIG. 6 shows a device and a method for manufacturing the separation disc 1 made of thin sheet metal. The device comprises a mandrel 1 with a truncated conical support surface 2 which by means of a motor M is rotatable about its geometric axis X. In the example shown, the geometric axis X is oriented horizontally, which is of course not necessarily the case. The mandrel 1 has a plurality of recesses 4 and 5 distributed about the geometric axis X on the support surface 2. The recess 4 and 5 may, as shown, be spot-formed or elongated and straight (as shown) or curved (not shown). Both the spot-formed recesses 4 and the elongated recesses 5 have a depth corresponding to the intended distance (or interspaces) between two adjacent separation discs fitted in a centrifugal separator, e.g. 0.3-0.8 mm. An initially planar circular sheet metal disc 6 is fastened to the apex end of the mandrel 1, coaxially with the support surface 2, by a retainer means 7. Engagement means (not shown) of both the mandrel 1 and the sheet metal disc 6 ensure that the sheet metal disc 6 accompanies the rotation of the mandrel 1 during the operation.

(17) A roller 8 is disposed at an axial level close to the apex end of the support surface 2 and at a radial distance from the central axis X, the roller 8 being rotatable about a central axis Y. The roller 8 is supported by a shaft 10 which is itself supported for rotation by a retainer 11. The retainer 11 is movable vertically and horizontally by means of a motor (not shown), as indicated by two arrows pointing respectively upwards and downwards and two arrows pointing respectively left and right. The motor for moving the roller 8 vertically and horizontally and guiding the position of the roller 8 relative to the support surface 2 may take many different forms which are well known and are therefore not described in more detail. A further second retainer 12 is arranged on the retainer 11. The second retainer 12 supports a tool 13 comprising a cutter 14. The tool 13 is movable as indicated by two arrows pointing respectively left and right relative to the retainer 12 so that the position of the cutter 14 relative to the surface of the metal sheet 6 can be set in such a way as to achieve a desired cutting depth for the material-removing machining. Such material-removing may not be necessary however if for instance a desired separation disc thickness and smoothness on the outer surface 3 is achieved in the manufacturing process. Hence, the tool 13 and cutter 14 may not be necessary for achieving this.

(18) The separation disc is manufactured by flow forming the metal sheet 6 by means of the roller 8 and the mandrel F. The roller 8 forms the separation disc over the mandrel 1 with the truncated conical support surface 2 having the recesses 4 and 5 of relatively large size. The mandrel 1 is also provided with small-sized recesses 4 and 5 (not shown in FIG. 6) corresponding to the small-sized spacing members 4 and 5. Through the recesses 4, 5, 4 and 5 it is possible to make both large-sized spacing members and small-sized spacing members which are flow formed in one piece with the separation disc 1. The mandrel 1 will in any case be provided with a distribution pattern of the small-sized recesses 4 and 5 to form the small-sized spacing members 4 and 5 in one piece with the separation disc 1 in such a way as to provide equidistant interspaces in the compressed stack of separation discs.

(19) As an alternative, the mandrel may be provided with only small-sized recesses 4 and 5 (shown in FIG. 7). FIG. 7 shows a flow formed separation disc 1 with a see through part showing the small-sized recesses 4 and 5 on the support surface 2 of the mandrel F. Consequently, the shown mandrel 1 is only provided with small-sized recesses 4 and 5 corresponding to the small-sized (spot-formed and elongated) spacing members 4 and 5 of the separation disc 1 shown in FIG. 2.

(20) Furthermore, small-sized spacing members 4 and 5 may be flow formed on the inner surface 2 of the separation disc 1, wherein large-sized spacing members in the form of said separate pieces may be attached to the outer surface 3 of the separation disc 1 (as previously mentioned).