WO2007055630A1

WO2007055630A1 - A method and a device for producing a separating disc for a centrifugal separator

Info

Publication number: WO2007055630A1
Application number: PCT/SE2006/000903
Authority: WO
Inventors: Sven-Åke NILSSON
Original assignee: Alfa Laval Corporate Ab
Priority date: 2005-09-01
Filing date: 2006-07-21
Publication date: 2007-05-18
Also published as: SE0501941L; DE112006002309T5; DE112006002309B4; SE528844C2

Abstract

A method and a device for producing a substantially conical separating disc (6c; 6d) made of sheetmetal (6) which on the one side has elevations (15a; 15b; 15c) formed integrally with the separating disc (6c; 6d) and on other side substantially no concavities or convexities, whereby the separating disc (6c; 6d) is pressed to a desired conical shape with the thus integrally formed elevations (15a; 15b; 15c), and an operation is performed whereby the opposite side of the separating disc (6c; 6d) from the side which has elevations (15a; 15b; 15c) is made even and the separating disc (6c; 6d) is made thinner by material being removed from that opposite side by material-removing machining.

Description

A METHOD AND A DEVICE FOR PRODUCING A SEPARATING DISC FOR A CENTRIFUGAL SEPARATOR

FIELD OF THE INVENTION

The present invention relates to a method and a device for producing a separating disc for a centrifugal separator, which separating disc has on the one side elevations formed integrally with the separating disc and on the opposite other side substantially no concavities or convexities. The elevations are needed as spacing means for holding thin separating discs in a stack of such discs at a certain distance from one another. The separating disc is pressed to a desired conical shape with the thus integrally formed elevations on one side of it.

BACKGROUND OF THE INVENTION AND PRIOR ART

Conical separating discs have been known for more than 100 years (see for example DE 48615) and have been extensively used in many types of centrifugal separator. Despite it also being about 100 years since it was proposed to provide a separating disc with elevations formed integrally with it (see for example SE 21700 and US 1 ,006,622), this technique is nevertheless not applied in practice when thin sheetmetal is used as material for separating discs. In contrast, it has been extensively possible to produce separating discs made of plastic which are provided with inte- grally formed spacing means. This is easy to do, since separating discs made of plastic can be manufactured by injection moulding technology. Separating discs made of thin sheetmetal are usually produced by pressure turning and are provided with spacing means in the form of narrow strips or small circles of sheetmetal which are fastened to the separating discs in various ways, usually by spot welding. An operation for attaching separate spacing means to separating discs, e.g. by welding, is both expensive and time-consuming.

A method for pressing separating discs with integrally formed elevations is referred to in DE 197 05 704, which involves pressure rolling of a sheetmetal blank over a pressure roll cone to produce a separating disc with integrally formed elevations. The sheetmetal blank is pressed over the pressure roll cone by means of a pressure roll. The pressure roll cone is provided with depressions which during the pressure rolling of the sheetmetal blank become filled with material from the blank.

In making separating discs with elevations according to the method referred to in DE 197 05 704, it may be difficult to achieve a separating disc on which the side opposite to that comprising said elevations is smooth. This is because, at the same time as material is pushed into the depressions in the pressure roll cone when the pressure roll passes over them during the forming of the separating disc to create said elevations, the position of the pressure roll is also affected by changes in the contact pressure between the pressure roll and the pressure roll cone and by the springing which take place during the pressure roll pass, thereby causing unevennesses on the opposite side. The subsequent mutual stacking of the separating discs in the centrifugal separator results in the creation of pockets between the elevations and the unevennesses on adjacent separating discs. These pockets lend themselves to accumulations of substan- ces processed in the centrifugal separator, which cannot subsequently be removed by normal washing of the centrifugal separator without taking the disc stack apart. Particularly for applications in the food and drug industry, which involve high hygiene requirements, it is very important to be able to clean all the surfaces in the centrifugal separator and guarantee a hygienic product unaffected by any accumulations of substances. Another problem in producing separating discs with elevations of this kind is being able to make separating discs at least as thin as hitherto which nevertheless have elevations of the same height, making it possible for at least as many separating discs as hitherto to be stacked at desired spacing in an available space in the centrifugal separator, thereby maintaining at least the same separation capacity of the centrifugal separator.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for producing a separating disc of the kind indicated in the introduction which ensures good hygiene in the centrifugal separator and is sufficiently inexpensive to be usable in practice while maintaining at least the same separation capacity of the centrifugal separator.

This object is achieved according to the invention by the side of the metal sheet opposite to the side which is provided with elevations being made even and by the metal sheet being made thinner by material being re- moved from this opposite side by material-removing machining.

According to the invention, the relating elevations may be formed by pressure rolling and/or pressing but also by embossing or bending.

According to an embodiment of the invention, the separating disc is produced by a method whereby the pressing is effected by a support body with a substantially conical support surface being arranged for rotation about the geometric axis of the conical support surface in order to form said separating disc, by said metal sheet being caused to abut firmly against the support body transversely to the geometric axis at one axial end of the conical support surface, by the support body and the metal sheet being caused to rotate at the same speed about the geometric axis, and by abutment being effected between a press element, which is rotatable about a central axis, and the side of the metal sheet which faces away from the support surface, with the result that during the rotation of the support body and the metal sheet the press element is pressed against the metal sheet and is caused by friction to roll against the metal sheet, without accompanying the metal sheet and of the support body in their rotation, and is guided axially and in the circumferential direction along a helicoidal path along, but at a chosen distance from, the support surface, so that the metal sheet is gradually caused to move along this helicoidal path to abutment against the support surface.

The elevations can thus be formed at substantially the same time as the metal sheet is pressed to abut against the support surface.

To this end, the support body may be provided with recesses so that material from the metal sheet will move into said recesses when the press element presses the metal sheet against the support body. The embodiment here concerned effects such a continuing relative movement between the press element and the support body that the press element is caused to press the metal sheet against the support body with such force, while the support body and the metal sheet rotate, that material from the metal sheet will move into said recesses in the support body. The pressing described above may be called pressure rolling, since the sheet acquires its shape by the press element under pressure with a rotary motion forcing the sheet to abut against the support body and thereby rolling out the separating disc. According to a further embodiment of the invention, the separating disc is produced by a method whereby the pressing is effected by a support body with a substantially conical support surface being arranged for the forming of said separating disc, by said metal sheet being caused to abut firmly against the support body transversely to the geometric axis at one axial end of the conical support surface, and by abutment being effected between a press element and the side of the metal sheet which faces away from the support surface, with the result that the press element is pressed against the metal sheet, which is thus caused to move gradually in its circumferential direction to abutment against the support surface. In the same way as in the previously mentioned embodiment, the elevations may be formed at substantially the same time as the metal sheet is pressed to abut against the support surface, and the support body may be provided accordingly with recesses for the forming of the elevations so that material from the metal sheet will move into said recesses when the press element presses the metal sheet against the support body. Alternatively, the press element may be provided on its outside with said recesses for the forming of the elevations, depending on which side of the metal sheet the elevations are to be situated. Although in this example the elevations are formed at the same time as the metal sheet is pressed to abut against the support surface, it is nevertheless perfectly possible within the scope of the present invention for the elevations to be formed at a stage which precedes or follows this pressing.

The support surface of said support body may have the shape of a truncated cone with an apex end and a base end, to which a sheetmetal disc may be fastened, or be firmly attached by means of a contact element, either at the apex end of support surface or at its base end. The support body, or portions of it, need not necessarily be exactly conical in shape, i.e. generatrices for the shape of the support body need not necessarily be entirely straight as viewed in respective axial sections through the support body. A support body with a shape such as just described has in this context to be regarded as still falling within the previously used expression "substantially conical support surface". Accordingly, the ex- pression "conical separating disc" also denotes a separating disc which correspondingly deviates from a strictly conical shape. Moreover, the substantially conical support surface may be situated on the outside of the support body and be provided with said recesses, the pressing being effected by the press element moving in a direction from said apex end towards said base end of the support surface and by the metal sheet being caused to abut against said outside of the support surface. Alternatively, the support body may be configured in some other conceivable way within the scope of the present invention. The press element may for example be adapted to pressing the metal sheet to abut against a support surface on the inside of the support body and to moving in a suitable direction in order to cause said abutment, depending on the configuration and orientation of the support body. Moreover, the support body with the metal sheet may for example instead be non-rotatable, in which case the press element will be rotatable about its own axis of rotation but also be disposed in a retainer which is rotatable about the geometric axis of the support surface.

According to the invention, material may be removed from the opposite other side of the metal sheet by various forms of material-removing machining.

According to an embodiment of the invention, the removal of material is effected by cutting machining which may, for example, take the form of turning, but any other suitable cutting machining method may also be used. The abovementioned sheetmetal disc which is to be converted to a conical separating disc may be entirely planar from the outset, with the result that both the conical shape of the separating disc and said elevations can be formed in a single operation without the metal sheet being moved away from the apex end of the support body, but this is not absolutely necessary. Alternatively, the metal sheet may already be of a conical or some other rotationally symmetrical shape. Moreover, the metal sheet may have a substantially smooth surface or the elevations may as men- tioned above be formed before the pressing of the separating disc.

During the forming of the elevations as above, material is moved from the metal sheet into the recesses. During the movement of that material it may be difficult to cause it to fill the whole recess. This may be due to the material being for example too hard, the recesses being too deep relative to their width or the pressure of the press element on the support body being too weak. The result may be a need for further machining such as embossing, bending, further pressing or some other suitable method for providing elevations formed according to the recesses.

Another object of the present invention is to provide a device for easy production of a separating disc of the kind indicated in the introduction. Such a device is defined in the claims set out below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described below with reference to the attached drawings, in which Fig. 1 depicts the main parts of a device for producing a conical separating disc made of thin sheetmetal by the method according to an embodiment of the invention,

Fig. 2 depicts a side view of another device for producing a conical separating disc made of thin sheetmetal by the method according to another embodiment of the invention,

Fig. 3 depicts a side view of the device according to Figure 2 at a later stage of the method according to the embodiment of the invention depicted in Figure 2,

Fig. 4 depicts a cross-section through parts of a device comprising a support body with recesses, a press element for forming a metal sheet with elevations, and a tool for material-removing machining, for producing a separating disc in accordance with a further embodiment of the invention,

Fig. 5 depicts a cross-section through the support body at a recess along the line l-l in Figure 4 according to another embodiment of the invention,

Fig. 6 depicts a cross-section according to Figure 5 and a press element for a further operation for concluding the method according to the embodiment of the invention depicted in Figure 5,

Fig. 7 depicts a further device for producing a conical separating disc made of thin sheetmetal by the method according to a further embodiment of the invention,

Fig. 8 depicts a side view of a support body according to the embodiment of the invention depicted in Figure 7 with an abutting disc-shaped metal sheet with the surface which the press element according to Figure 7 presses over the sheetmetal disc marked,

Fig. 9 shows two views of a finished separating disc produced by means of a device of the kind depicted in Figure 1 or Figure 2, and

Fig. 10 shows two views of an alternative separating disc produced by means of a device of the kind depicted in Figure 2.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Figure 1 depicts a device for producing a conical separating disc made of thin sheetmetal. The device comprises a truncated conical support body 1 with a conical support surface 2 which by means of a motor 3 is rotatable about its geometric axis X. In the example depicted, the geometric axis X is oriented horizontally, which is of course not necessarily the case. The support body 1 is provided on its support surface 2 with a plurality of elongate depressions or recesses 4 evenly distributed about the geometric axis X. Each recess 4 may, as depicted in Figure 1 , be straight and form an acute angle with such generatrices of the conical support body 1 as intersect it. If so desired, each of the grooves may be somewhat arcuate or straight and extend along a purely radial generatrix of the support body's conical support surface 2. Two circular depressions 5 are formed between two adjacent recesses 4. Both the recesses 4 and the circular depressions 5 have to be of a depth corresponding to the intended distance between two adjacent separating discs fitted in a centrifugal separator, e.g. 0.3 - 0.8 mm. An initially planar circular sheetmetal disc 6 is fastened to the apex end of the body 1 , coaxially with the support surface, by a retainer means 7. Engagement means (not depicted) of both the support body 1 and the sheetmetal disc 6 ensure that the sheetmetal disc 6 accompanies the rotation of the support body 1 during the operation which will be described later on.

A press element 8a disposed at an axial level close to the apex end of the support surface at a radial distance from the central axis X takes the form of a rotation body and is rotatable about a central axis Y. In the example depicted in Figure 1 , the central axis Y, which extends at an angle relative to the geometric axis X of the support surface 2, is situated vertically below the geometric axis X. The invention is of course not limited to this orientation and positioning.

The press element 8a 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 depicted), as indicated by two arrows pointing respectively upwards and downwards and two arrows pointing respectively left and right. The means for moving the rotatable press element 8a vertically and horizontally and guiding the position of the press element relative to the support surface may take many different forms which are well known in the field of sheetmetal pressure turning 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 can be set in such a way as to achieve a desired cutting depth for the material-removing machining.

In the embodiment depicted in Figures 2 and 3, the device comprises a support body 1 as in the embodiment depicted in Figure 1 , but Figures 2 and 3 depict a modified press element 8b which is shell-shaped so that it constitutes an inverted surface of the support body 1 relative to the latter. The press element 8b is movable axially relative to the geometric axis X.

The device according to Figure 1 works as follows:

The motor 3 causes the support body 1 and the sheetmetal disc 6 applied firmly to the latter to rotate about the axis X. Thereafter the rotatable press element 8a is moved by the retainer 11 and the associated motor to contact with the sheetmetal disc 6 from the right with respect to Figure 1. This contact has to occur at the radial distance from the geometric axis X at which the sheetmetal disc 6 is in contact with the radially innermost part of the conical support surface 2 of the support body 1. Thereafter the press element 8a is pressed axially against the sheetmetal disc 6 at a desired radial distance from the conical support surface 2 along a generatrix of the support surface 2, so that its shape is adapted to the shape of the support body. At this stage, the press element 8a will be caused by friction to roll against the sheetmetal disc 6 and hence to rotate about its central axis Y without accompanying the support body 1 and the sheet- metal disc 6 in their rotation. The rotation movements of the support body 1 and the press element 8a are represented by two arrows in Figure 1.

The retainer 11 and said motor proceed to press the press element 8a with great force axially and radially against the sheetmetal disc 6, thereby pressure-rolling the latter to the same conical shape as the support body 1.

When the pressure rolling has proceeded so far axially that the sheet- metal disc has reached the recesses 4 in the support body 1 , the press element 8a will, during the pressing, push material from the sheetmetal disc 6 down into these grooves 4.

The retainer 12 will also gradually bring the cutter 14 on the tool 13 to engage with the sheetmetal disc 6. During the continuing rotation of the metal sheet 6, the cutter will remove material from the conical surface of the metal sheet 6, resulting in a smooth surface without unevennesses.

The movement of the press element 8a and the tool 13 relative to the support body 1 and the engagement depth of the cutter 14 in the metal sheet 6 may be controlled by computer technology or in some other suitable way which is well known in relation to pressure turning and material-removing machining.

Figure 2 depicts a device with the support body 1 in side view and the press element 8b in cross-section for an alternative pressing method. The press element 8b is movable axially relative to the support body 1. The press element 8b is pressed axially against the sheetmetal disc 6 so that the latter's shape becomes adapted to the shape of the support body, as depicted in Figure 3.

Figure 4 depicts an axial section of parts of the support body 1 and the press element 8a along the central axis X and Y in Figure 1 and illustrates how the shape of the sheetmetal disc 6 changes during the pres- sure rolling operation described above. Instead of oblique recesses 4 as in Figure 1 , the support body 1 in Figure 2 has recesses 4a which extend along respective generatrices of the conical surface of the support means.

As may be seen, a central planar portion 6a of the sheetmetal disc 6 retains its initial thickness at the apex end of the support means 1 , whereas the thickness of the conical portion of the sheetmetal disc 6 has decreased. In the region of each recess 4a, the press element 8a has pushed material from the disc 6 into the recess 4a, resulting in the formation of an elevation 15a on the inside of the conical portion of the disc. Like the central portion 6a, a circumferential portion 6b of the sheetmetal disc which has not been subjected to pressure rolling retains its initial thickness.

As may be seen in Figure 4, the press element 8a has a circumferential portion with a special shape. The press element 8a thus exhibits an annular portion 16 situated at a distance from the conical surface of the support means 1. The press element's axial movement (to the left in Figure 4) during the pressure rolling will result in the annular portion 16 gradually encountering new portions of the sheetmetal disc 6. These portions of the sheetmetal disc 6 will be gradually converted to a certain reduced thickness by the annular portion 16. The subsequent achievement of the desired evenness of the surface against which the press element comes into contact with the sheetmetal disc 6 is by material- removing machining by means of the cutter 14 on the tool 13.

The operation described above comprising the pressure rolling of the sheet 6 and the removal of material may be effected in a single step. It may also be divided into a number of steps whereby the pressure rolling constitutes a first step and the removal of material from the metal sheet 6 a later step. This alternative may be applied if material from the metal sheet 6 does not fill said recesses 4a properly, as in the embodiment depicted in Figure 5. There may then be an intermediate step of pressing, embossing, bending or any other suitable method.

Figures 5 and 6 depict a cross-section through the support body at a recess 4a along the cross-section line l-l in Figure 4, and Figure 6 illustrates how a further press element 17, acting in the direction of the arrow, pushes material into the recess 4a in the support body 1 and completely fills the recess 4a with material from the sheet in a single step between the pressure rolling and the removal of material from the metal sheet 6.

In a further embodiment, may be seen in Figure 7, the press element 8c may exhibit a more cylindrical portion 18 and be at an angle with the generatrix of the support means 1. The result, see Fig. 8, is a larger abutment surface 19 with the sheetmetal disc 6, thereby ensuring that the press element 8c presses the sheetmetal disc 6 over the whole width of the recess 4. This results in a more even surface on the sheetmetal disc 6 because the pressure difference will be smaller when the press element 8c passes over the recess 4 during the pressure rolling. The press element 8a according to the device in Figure 1 may of course also exhibit a more cylindrical portion 18 so that the sheetmetal disc 6 will have a more even surface.

The result of the operation described will be a conical separating disc 6c of the kind illustrated in Figure 9, which has integrally formed elongate elevations 15b on its inside. As may be seen, the elevations 15b in Figure 9 are arcuate, whereas the elevations of a separating disc formed by means of the device in Figure 1 will be straight and concentrated like the recesses 4 and the circular depressions 5 in the support body 1.

Alternatively, the result of the operation described will be a conical sepa- rating disc 6d of the kind illustrated in Figure 10, which has integrally formed elongate elevations 15c on its outside. This depends on whether it is decided that said support body 1 or said press element 8b should comprise recesses or whether the support body is so designed that the metal sheet 6 is converted to a separating disc in, for example, a substantially shell-shaped support body comprising said recesses distributed over the shell-shaped surface round its circumference, in which case the elevations 15c would be formed on the outside of the separating disc as in Figure 10.

Claims

1. A method for producing a substantially conical separating disc (6c; 6d) made of sheetmetal (6), which on the one side has elevations (15a; 15b; 15c) formed integrally with the separating disc (6c; 6d) and on the opposite other side substantially no concavities or convexities, said separating disc (6c; 6d) being formed from a metal sheet (6) which is pressed to a desired conical shape and is provided with thus integrally formed elevations (15a; 15b; 15c) on one side of it,

c h a r a c t e r i s e d i n

- that the other side of the metal sheet (6) which is opposite to the side provided with elevations (15a; 15b; 15c) is made even and the metal sheet (6) is made thinner by material being removed from that opposite side by material-removing machining.

2. A method according to claim 1 , characterised in that said elevations (15a; 15b; 15c) are formed by embossing.

3. A method according to claim 1 , characterised in that said elevations (15a; 15b; 15c) are formed by bending.

4. A method according to claim 1 , characterised in that the pressing is effected

- by a support body (1 ) with a substantially conical support surface (2) being arranged for rotation about the geometric axis (X) of the conical support surface (2) in order to form said separating disc (6c; 6d), - by said metal sheet (6) being caused to abut firmly against the support body (1) transversely to the geometric axis (X) at one axial end of the conical support surface (2),

- by the support body (1 ) and the metal sheet (6) being caused to rotate at the same speed about the geometric axis (X), and

- by abutment being effected between a press element (8a; 8c), which is rotatable about a central axis (Y), and the side of the metal sheet (6) which faces away from the support surface (2), during the rotation of the support body (1) and the metal sheet (6), whereby the press element (8a; 8c) is pressed against the metal sheet (6) and is caused by friction to roll against the metal sheet (6), without accompanying the latter and the support body (1 ) in their rotation, and is guided axially and in the circumferential direction along a helicoidal path along, but at a chosen distance from, the support surface, so that the metal sheet is gradually moved along this helicoidal path to abut against the support surface.

5. A method according to either of claims 1 and 4, characterised in that said elevations (15a; 15b; 15c) are formed substantially at the same time as the metal sheet (6) is pressed to abut against the support surface (2).

6. A method according to claim 5, characterised in that the pressing is effected

- by the supporting body being provided with recesses (4; 4a) along the support surface (2) and - by a continuing relative movement being effected between the press element (8a; 8c) and the support body (1 ) and the metal sheet (6), and by the press element (8a; 8c) being caused to press the metal sheet (6) against the support surface (2), during rotation of the support body (1 ) and the metal sheet (6), with such force that material from the metal sheet moves into said recesses (4; 4a) in the support body (1 ).

7. A method according to claim 1 , characterised in that the pressing is effected

- by a support body (1 ) with a substantially conical support surface (2) being arranged for the forming of said separating disc (6c; 6d),

- by said metal sheet (6) being caused to abut firmly against the support body (1 ) transversely to the geometric axis (X) of the conical support surface (2), and

- by abutment being effected between a press element (8b) and the side of the metal sheet (6) which faces away from the support surface (2), whereby the press element is pressed against the metal sheet (6) so that the metal sheet (6) is caused to abut against the support surface (2).

8. A method according to claim 7, characterised in that said elevations (15a; 15b; 15c) are formed substantially at the same time as the metal sheet (6) is pressed to abut against the support surface (2).

9. A method according to claim 7 or 8, characterised in that the pressing is effected - by the support body (1) being provided along the conical support surface (2) with recesses (4; 4a), and

- by the press element (8b) being caused to press the metal sheet (6) against the support surface (2) with such force that material from the metal sheet (6) moves into said recesses (4; 4a) in the support body (1).

10. A method according to any one of claims 4-9, characterised in that a truncated substantially conical support surface with an apex end and a base end is adopted as the support surface (2).

11. A method according to any one of claims 4-10, characterised in that the pressing is effected by the metal sheet (6) being caused to abut against a support surface (2) situated on the outside of the support body

(1 ).

12. A method according to either of claims 10 and 11 , characterised in that the pressing is effected by the press element (8b) moving in a direction from said apex end towards said base end of the support body

(1 ).

13. A method according to any one of claims 1-12, characterised in that material is removed from the opposite other side of the metal sheet (6) by cutting machining.

14. A method according to claim 13, characterised in that material is removed from the opposite other side of the metal sheet (6) by turning.

15. A method according to any one of claims 1-14, characterised in that the metal sheet (6) is pressed against the support body (1 ) and material is removed from the metal sheet (6) without the metal sheet (6) being moved away from the support body (1 ).

16. A method according to any one of claims 1-15, characterised in that that an initially substantially planar metal sheet is adopted as the metal sheet (6).

17. A method according to any one of claims 1-15, characterised in that that an initially substantially conical metal sheet is adopted as the metal sheet (6).

18. A method according to any one of claims 1-17, characterised in that a metal sheet which before the pressing has a substantially smooth surface is adopted as the metal sheet (6).

19. A method according to claim 1 or any one of claims 4-18, characterised in that said elevations (15a; 15b; 15c) are formed by further pressing after the pressing of the metal sheet (6).

20. A device for producing a substantially conical separating disc made of sheetmetal (6) which on the one side has elevations (15a; 15b; 15c) formed integrally with the separating disc (6c; 6d) and on its opposite other side substantially no concavities or convexities, comprising

- a conical support body (1) with a substantially conical support surface (2), which has a geometric axis (X) and an axial first end and an axial second end,

- means (7) for firmly applying a metal sheet (6) to the axial first end of the conical support surface (2) transversely to said geometric axis (X),

- a press element (8a; 8b; 8c) adapted to being caused to abut against the side of the sheetmetal disc (6) which faces away from the conical support surface (2) and to being pressed against the metal sheet (6) so that the metal sheet (6) is caused to abut against the outside of the support body (1 ), and

- a device for moving the press element (8a; 8b; 8c) in a direction axially from said axial first end of the support surface (2) towards the axial second end of the support surface (2) and for pressing the press element (8a; 8b; 8c) during that movement with such force against the metal sheet (6) that the latter is pressed against the support surface (2), in order to move material from the metal sheet (6),

c h a r a c t e r i s e d i n - that either said conical support surface (2) on the support body (1 ) or a pressure side on said press element (8a; 8b; 8c) which faces towards the metal sheet (6) is provided with recesses (4; 4a) for receiving from the metal sheet (6) material which moves into said recesses (4; 4a) and forms elevations (15; 15a; 15b) when the press element (8a; 8b; 8c) is pressed against the outside of the supporting body (1 ), and

- that said device comprises means for removal by material-removing machining of material from said other side of the metal sheet (6) which during the process faces away from the recesses (4; 4a).

21. A device according to claim 20, characterised in that said support surface (2) takes the form of an outside surface on the support body (1 ).

22. A device according to claim 20 or 21 , characterised in that said means for material-removing machining comprises a tool (13) for cutting machining in order to remove material from the metal sheet.

23. A device according to claim 22, characterised in that said means for material-removing machining comprises a tool (13) for turning.

24. A device according to claim 21 , characterised in that said tool (13) for turning comprises a cutting means (14) for removing material from the metal sheet (6), and a support means resting against the metal sheet (6) for desired positioning of the cutting means (14) relative to the metal sheet (6) during said turning.

25. A device according to claim 24, characterised in that said support means comprises a backing roller rotatable about a central axis of its own.

26. A device according to claim 25, characterised in that said backing roller is at an angle to the generatrix of the support surface (2) and has an axial length which makes it possible for the portion of the backing roller which abuts against the metal sheet (6) during rotation in the circumferential direction of the support body to completely cover said recesses (4; 4a) in a direction substantially transverse to said recesses (4; 4a).

27. A device according to any one of claims 24-26, characterised in that said support means comprises said press element (8a; 8c) for supporting the tool during turning.

28. A device according to any one of claims 20-27, characterised in that said recesses (4; 4a) are arranged on an external conical support surface (2) on the support body.

29. A device according to any one of claims 20-27, characterised in that said recesses (4; 4a) are arranged on the outside of said press element (8b).