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(11) | EP 1 923 146 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Screening apparatus |
| (57) A screening apparatus comprises a casing (2) provided with a first part (5) comprising
a cylindrical portion (6) arranged for receiving a material to be screened, with a
second part (7) arranged for receiving a screened material, and with a screening net
(4) supported by a supporting ring (9) and interposed between said first part (5)
and said second part (7), said screening net (4) being mounted so as to abut on a
seat (8) of said first part (5), said seat being formed by a fold (8) obtained in
said cylindrical portion (6).
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[0001] The invention relates to a screening apparatus and a method for making a casing included in the apparatus.
[0002] In particular, the invention relates to a screening apparatus that is usually used in production systems of various types, for example systems for manufacturing ceramic products, for screening materials that were produced by apparatuses, or which have to supply apparatuses, installed inside the aforesaid systems.
[0003] Screening apparatuses are known comprising a cylindrical casing provided with a supply opening through which a material to be screened is fed to a screening net.
[0004] The casing comprises a first part arranged for receiving the material to be screened and a second part arranged for receiving a screened material.
[0005] The screening net is interposed between the first part and the second part and is supported by a supporting ring.
[0006] The supporting ring is fixed to a supporting element positioned between the first part and the second part and is arranged for supporting and maintaining tensioned the screening net.
[0007] The supporting ring further comprises a side surface facing a side wall of the first part and having a lesser diameter than the latter.
[0008] Such apparatuses further comprise an angular abutting ring, operationally positioned above the supporting ring.
[0009] The angular abutting ring comprises a first side weldable to the side wall of the first part and a second side protruding from the side wall and arranged for abutting on the screening net, or, if present, a circular sealing washer associated with the abutting ring, arranged for safeguarding the screening net and for preventing the material to be screened from passing through the latter and the abutting ring.
[0010] The abutting ring is arranged for preventing the material to be screened from being deposited in an annular gap defined between the side wall of the first part and the side surface of the supporting ring.
[0012] In this case, the abutting ring is made from a circular sheet rotatably supported by a spinning lathe.
[0013] Subsequently, by means of a suitable tool, edge zones of the plate are folded until an angular deformed zone is obtained. Subsequently, the plate is cut to measure by a cutting tool that removes an internal circular portion of the plate.
[0014] Alternatively, the abutting ring can be obtained from a welded tubular element, or screw base.
[0015] In this case, there is provided folding inward an edge portion of the tubular element until a further angular deformed zone is obtained.
[0016] Once the abutting ring has been obtained through one of the aforesaid methods, the latter is welded by an operator to the cylindrical wall of the first part of the casing.
[0018] This is due in particular to the costs that are necessary for making, in one of the ways disclosed above, the abutting ring.
[0019] A further drawback is that such apparatuses are excessively slow and laborious to assemble, which entails a further financial cost.
[0020] This is mainly due to the abutting ring, which has to be welded by an operator to the first part of the casing.
[0021] A still further drawback is that such apparatuses may lacerate the screening net, also in the presence of a sealing washer, in the event of deterioration of the latter. In fact, the second side of the abutting ring comprises an abutting surface facing the screening net provided with a sharp edge that, by coming into contact with the screening net, may damage the screening net, and in the most serious cases, cut the screening net.
[0024] A still further object is to provide screening apparatuses that do not damage the screening nets.
[0026] In a first aspect of the invention, there is provided a screening apparatus comprising a casing provided with a first part comprising a cylindrical portion arranged for receiving a material to be screened, with a second part arranged for receiving a screened material, and with a screening net supported by a supporting ring and interposed between said first part and said second part, said screening net being mounted so as to abut on a seat of said first part, characterised in that said seat is formed by a fold obtained in said cylindrical portion.
[0027] In a second aspect of the invention, there is provided a method for making a part of a casing of a screening apparatus arranged for receiving a material to be screened comprising rolling an edge portion of said part until a fold is obtained.
[0028] Owing to these aspects of the invention, it is possible to obtain screening apparatuses that are simple and cheap to make.
[0029] In fact, said fold is obtained by directly rolling in said cylindrical portion of said casing, which enables the costs to be eliminated that are necessary for making and for mounting an angular abutting ring.
[0030] Further, owing to these aspects of the invention it is possible to obtain screening apparatuses that do not damage the screening nets.
[0031] In fact, said fold comprises an abutting surface arranged for abutting on said screening net, or, where present, a sealing washer, devoid of sharp edges.
[0032] The invention can be better understood and implemented with reference to the attached drawings that illustrate an embodiment thereof by way of non-limiting example, in which:
Figure 1 is a fragmentary cross section of a screening apparatus;
Figure 2 is an enlarged detail of Figure 1;
Figures 3 to 5 are schematic frontal views of a first apparatus arranged for making a first part of a casing included in the screening apparatus in Figure 1;
Figures 6 and 7 are schematic frontal views of a second apparatus, that is alternative to the first apparatus shown in Figures 3 to 5, arranged for making a first edge and a second tilted edge of the aforesaid first part;
Figure 8 is a fragmentary cross section that shows a screening apparatus made according to a version;
Figure 9 is a fragmentary cross section that shows a screening apparatus made according to a further version;
Figure 10 is a fragmentary cross section that shows a screening apparatus made according to a still further version.
[0033] With reference to Figures 1 and 2, there is shown a screening apparatus 1 that is usually used in production systems of various types, for example systems for manufacturing ceramic products, for screening materials that were produced by apparatuses, or which have to supply apparatuses, installed inside the aforesaid systems.
[0034] The screening apparatus 1 comprises a substantially circular casing 2 provided with a supply opening 3 through which material to be screened is fed to a screening net 4.
[0035] The casing 2 comprises a first part 5 provided with a cylindrical portion 6 arranged for receiving the material to be screened and a second part 7 arranged for receiving the screened material.
[0036] The cylindrical portion 6 is provided with an angular fold 8 comprising a first side 16, extending substantially parallel to an axis z of the screening apparatus 1, and a second side 17, substantially perpendicular to the first side 16.
[0037] The second side 17 comprises an abutting surface 11 provided with a rounded edge 12 and facing the screening net 4.
[0039] The sealing washer 13 is arranged for protecting the screening net 4 and for preventing material to be screened from passing through the latter and the abutting surface 11. It should be noted how, in use, the rounded edge 12 does not damage the screening net 4 in the event of deterioration of the sealing washer 13.
[0040] In an embodiment of the invention, which is not shown, the abutting surface 11 abuts directly on the screening net 4. In this case the sealing washer 13 is not provided.
[0041] The first part 5 further comprises, at a first end 15 thereof, a first tilted edge 14, obtained, as will be better disclosed below, folding an end portion 18 of the first side 16.
[0042] The first tilted edge 14 faces, in use, a further first tilted edge 19, the further first tilted edge 19 being obtained in a further first end 20 of the second part 7.
[0043] The first part 5 further comprises, at a second end 21 thereof, opposite the first end 15, a second tilted edge 22, obtained, as will be better disclosed below, by folding a further end portion 23 of the cylindrical portion 6.
[0044] The second tilted edge 22 has a maximum diameter that is substantially the same as a maximum diameter of the first tilted edge 14 and defines, in use, the supply opening 3.
[0045] Alternatively, as shown with reference to Figure 8, the second tilted edge 22 has a maximum diameter that is less than a maximum diameter of the first tilted edge 14 and defines, in use, the supply opening 3.
[0046] With reference to Figure 9, there is shown a screening apparatus 1 provided with a first part 5 and with a further first part 105 that are mutually superimposed.
[0047] The first part 5 and the further first part 105 each comprise an end edge 22 provided with a first wall 101 arranged substantially perpendicularly with respect to axis Z, of a second wall 102 arranged substantially parallel to the axis Z and with a third wall 103 arranged obliquely with respect to the axis Z, the third wall 103 defining a conical tubular portion having a section that decreases approaching the second wall 102.
[0049] The third wall 103 has a maximum diameter that is substantially equal to a maximum diameter of the first tilted edge 14 and defines, in use, the supply opening 3.
[0050] The second tilted edge 22 can act as a support for the further first part 105 mounted above the aforesaid first part 5 to make a screening apparatus provided with several screening nets. Also in the embodiment of the screening apparatus 1 shown in Figures 1 and 2 and in the embodiment of the screening apparatus 1 shown in Figure 10, the second tilted edge 22 can act as a support for a further first part mounted above the first part 5.
[0051] With reference to Figure 10, there is shown a screening apparatus 1 provided with a first part 5 comprising an end edge 22 provided with first wall 106 arranged obliquely to the axis Z of a second wall 107 arranged substantially parallel to the axis Z and with a third wall 108 arranged obliquely to the axis Z, the first wall 106 and the third wall 108 each defining a conical tubular portion having a decreasing section nearer the second wall 102.
[0053] The third wall 108 has a maximum diameter that is substantially equal to a maximum diameter of the first tilted edge 14 and defines, in use, the supply opening 3.
[0054] The screening apparatus 1 further comprises a fixing element 25 arranged for fixing the first part 5 to the second part 7.
[0055] The fixing element 25 is arranged, in use, for contacting a first external surface 26 and a further external surface, which is not shown, respectively of the first tilted edge 14 and of the further first tilted edge 19.
[0056] The first tilted edge 14 and the further first tilted edge 19 further comprise respectively a first internal surface 28 and a further first internal surface that are mutually facing and define a circular housing 30 arranged for receiving supporting washer means 10.
[0057] The supporting washer means 10 acts as a support for a supporting ring 9 arranged for supporting and keeping in tension, by means of a pair of net-tensioning rings 31, the screening net 4.
[0058] The supporting ring 9 comprises a first surface 33 facing, in use, the abutting surface 11, and a second surface 34, suitably shaped for supporting the net-tensioning rings 31 and facing the first side 16 of the fold 8.
[0059] In this manner, in use, an annular gap 35 is defined between the first side 16 and the second surface 34 bound above by the first surface 33.
[0060] This prevents the material to be screened from becoming deposited in the gap 35 and damaging the supporting ring 9.
[0061] The screening apparatus 1 further comprises slide means 39 positioned in the second part 7 and arranged for conveying the screened material to a side opening 38 obtained in a side wall 37 of the second part 7.
[0062] From the side opening 38 there projects a discharge 36 arranged for discharging the screened material from the screening net 4 from the screening apparatus 1.
[0063] The screening apparatus 1 further comprises a base, which is not shown, connected to the second part 7 by springs, not shown, that enable the casing 2 to oscillate with respect to the base.
[0064] This oscillation is triggered by a vibrator, which is not shown, for example with eccentric masses, driven by an electric motor.
[0065] With reference to Figures 3 to 5 there is shown a first apparatus 40 arranged for making the fold 8, the first tilted edge 14 and the second tilted edge 22 of the first part 5 of the casing 2.
[0066] The first apparatus 40 comprises a base 41 from which a spindle 42 projects that is rotatable around a first axis X1 by a motor 43, for example electric.
[0067] The spindle 42 rotationally supports an expander 44 arranged for locking a tubular element 45, or screw base.
[0068] The first apparatus 40 further comprises first supports 46, for example three in number, mutually angularly equidistant, mounted on the base 41, and each arranged for rotationally supporting a first rest roller 47.
[0069] The first rest rollers 47 are free to rotate around a second axis X2 substantially perpendicular with respect to the first axis X1 and are arranged for supporting, in use, the tubular element 45.
[0070] The first apparatus 40 further comprises a second support 48 arranged for supporting at an end region 49 thereof a first abutment roller 50 that is free to rotate around a respective rotation axis that is substantially parallel to the second axis X2.
[0071] The first abutment roller 50 is movable between a first operating position W1 (Figures 3 and 4) and a second operating position W2 (Figure 5) in which an external surface 51 of the tubular element 45 respectively abuts and does not abut.
[0072] The second support 48, further slidingly supports a first slide 52 driven to slide by a first actuator 53 substantially parallel to the second axis X2.
[0073] The first slide 52 rotationally supports a first substantially cylindrical forming roller 54.
[0074] The first forming roller 54, which is operationally positioned below the first abutment roller 50 and is free to rotate around a respective rotation axis that is substantially parallel to the first rotation axis X1, is arranged for interacting with an internal surface 55 of an edge portion 56 of the tubular element 45.
[0075] In particular, the first slide 52 is movable between a first position L1 (Figure 4) and a second position L2 (Figures 3 and 5) in which respectively the first forming roller 54 folds or does not fold the edge portion 56 outwards.
[0076] In particular, in the first position L1, the first slide 52 abuts on a first mechanical stroke stop, which is not shown, which is suitably adjusted and locked.
[0077] The first apparatus 40 further comprises a third support 57 comprising a first support side 60 and a second support side 61 that are mutually opposite and extend parallel to the second axis X2 (Figure 4).
[0078] The first support side 60 and the second support side 61 are arranged for respectively slidingly supporting a second slide 58 and a third slide 59 driven to slide respectively by a second actuator 62 and by a third actuator 63 substantially parallel to the second axis X2.
[0079] The second slide 58 rotatingly supports a substantially conical second forming roller 64, that is free to rotate around a respective rotation axis that is substantially parallel to the first axis X1 and arranged for folding outwards the end portion 18 of the first side 16 to make the first tilted edge 14 and the further end portion 23 to make the second tilted edge 22.
[0080] In particular, the second slide 58 is movable between a further first position T1 (Figure 5) and a further second position T2 (Figure 4) in which respectively the second forming roller 64 folds or does not fold the end portion 18 or the further end portion 23 outwards.
[0081] In particular, in the further first position T1, the second slide 58 abuts on a second mechanical stroke stop, which is not shown, which is suitably adjusted and locked.
[0082] The third slide 59 rotatingly supports a second abutment roller 65, which is operationally positioned above the second forming roller 64, which is free to rotate around a respective rotation axis that is substantially parallel to the second rotation axis X2.
[0083] The second abutment roller 65 is movable between a further first operating position W3 (Figures 4 and 5) and a further second operating position, which is not shown, in which it respectively abuts and does not abut on a further external surface 66 of the first side 16.
[0085] With reference to Figure 3 there is shown the first apparatus 40 in a first operating configuration A.
[0086] In the first operating configuration A the tubular element 45 is positioned on the first apparatus 40.
[0087] This positioning comprises positioning the tubular element 45 on the first rest rollers 47, the expander 44 being inserted into a cavity 67 of the tubular element 45.
[0088] In the first operating configuration A, the first slide 52 is in the second position L2, the first abutment roller 50 is in the first work position W1, the second forming roller 64, which is not shown, is in the further second position T2 and the second abutment roller 65, which is not shown, is in the further second operating position.
[0091] With reference to Figure 4, there is shown the first apparatus 40 in a second operating configuration B.
[0092] In the second operating configuration B the first slide 52 is in the first position L1, the first abutment roller 50 is in the first work position W1, the second forming roller 64 is in the further second position T2 and the second abutment roller 65 is in the further first operating position.
[0093] In this manner, in the second operating configuration B the first apparatus 40 folds the edge portion 56 of the tubular element 45 outwards, rotated and locked by the expander 44, until the angular fold 8 is obtained.
[0094] In other words, in the second operating configuration B the first abutment roller 50 and the first forming roller 54 cooperate to increase a diameter of the tubular element 45 substantially at the edge portion 56.
[0095] With reference to Figure 5 there is shown the first apparatus 40 in a third operating configuration C.
[0096] In the third operating configuration c the first slide 52 is in the second position L2, the first abutment roller 50 is in the second work position W2, the second forming roller 64 is in the further first position T1 and the second abutment roller 65 is in the further first operating position W3.
[0097] In this manner, in the third operating configuration C the first apparatus 40 folds the end portion 18 of the first side 16 of the fold 18 outwards, the tubular element 45 being rotated and locked by the expander 44, until the first tilted edge 14 is obtained.
[0098] In other words, in the third operating configuration C the second abutment roller 65 and the second forming roller 64 cooperate to make the first tilted edge 14.
[0099] Below, the operations are disclosed but not illustrated that are necessary to make the second tilted edge 22 shown in the embodiments of screening apparatus 1 shown in Figures 1 and 2 and in Figure 8.
[0100] Initially, the tubular element 45 provided with the fold 8 and with the first tilted edge 14 is removed from the first apparatus 40.
[0101] Still subsequently, the tubular element 45 is repositioned in the manner disclosed above on the first apparatus 40, so that a further edge portion 78, opposite the edge portion 56 of the tubular element 45, rests on the first rest rollers 47.
[0103] In this manner, in the third operating configuration C the first apparatus 40 folds the further edge portion 78 of the cylindrical portion 6 outwards, the tubular element 45 being rotated and locked by the expander 44 until the second tilted edge 22 is obtained.
[0104] In other words, in the third operating configuration C the second abutment roller 65 and the second forming roller 64 cooperate to make the second tilted edge 22 having a maximum diameter substantially equal to a further maximum diameter of the first tilted edge 14.
[0105] With similar methods, the apparatus 1 can make the second tilted edge 22 specified in the embodiments of screening apparatus 1 shown in Figure 9 and in Figure 10.
[0106] With reference to Figures 6 and 7 there is shown a second apparatus 68 that is usable alternatively to the first apparatus 40 to make the first tilted edge 14 and the second tilted edge 22 - specified in the embodiments of screening apparatus 1 shown in Figures 1 and 2 and in Figure 8 - starting from a tubular element 45 provided with the fold 8. The second apparatus 68 comprises a resting surface 71 on which, in use, the end portion 18 of the first side 16 of the fold 8 and the further edge portion 78 rest.
[0107] The resting surface 71 is defined by a supporting table 69 and by second rest rollers 70, fixed to the supporting table 69 and free to rotate around a respective rotation axis.
[0108] The second rest rollers 70 are arranged for reducing the friction between the supporting table 69 and the tubular element 45.
[0109] In an embodiment of the invention, which is not shown, the resting surface 71 is defined by a further supporting table that is smooth and lubricated.
[0110] The supporting table 69 is hinged on a pivot 72 and is driven to rotate around the aforesaid pivot 72 by a fourth actuator 73, for example a hydraulic actuator.
[0111] The second apparatus 68 further comprises a third abutment roller 74 rotated by a second motor, which is not shown, around a respective rotation axis that is substantially parallel to a third axis X3 and arranged for acting as a support and for abutting on a further internal surface 75, opposite the further external surface 66, of the first side 16 of the fold 8.
[0112] The second apparatus 68 further comprises a roller 77, which is movable towards and away from the third abutment roller 74.
[0113] The roller 77 is rotated by the second motor, the second motor driving the third abutment roller 74 and the roller 77 by a pair of gears, or alternatively by a third motor, which is not shown, around a respective rotation axis that is substantially parallel to the third axis X3 and is arranged to abut on the further external surface 66, of the first side 16 of the fold 8.
[0115] In Figure 6 there is shown the second apparatus 68 in a first configuration D in which it is arranged for making the first tilted edge 14.
[0116] Initially, the tubular element 45 provided with the fold 8 is positioned on the second apparatus 68.
[0117] Such a positioning inserts the first side 16 of the fold 8 into a gap, which is not shown, defined between the third abutment roller 74 and the roller 77 until the tubular element 45 rests on the resting surface 71.
[0118] In this manner, the tubular element 45 is supported by the third abutment roller 74 that abuts on the further internal surface 75.
[0119] Subsequently, it brings the roller 77 near the third abutment roller 74, until it abuts on the further external surface 66.
[0120] In this manner, the end portion 18 is positioned between the roller 77 and the third abutment roller 74.
[0121] Still subsequently, the roller 77 and the third abutment roller 74 are driven that rotate the tubular element 45.
[0122] Subsequently, whilst the roller 77 and the third abutment roller 74 rotate the tubular element 45, the supporting table 69 is rotated by a desired angle around the pivot 72 by the fourth actuator 73.
[0123] In this manner, the supporting table 69, the roller 77 and the third abutment roller 74 fold the end portion 18 of the first side 16 outwards so as to obtain the first tilted edge 14.
[0124] With reference to Figure 7 there is shown the second apparatus 68 in a second configuration E in which it is arranged for making the second tilted edge 22.
[0125] In the second configuration E, the second apparatus 68 comprises a fourth abutment roller 174, having a greater height than the third abutment roller 74, arranged for acting as a support and for abutting on a still further internal surface 155 of the further edge portion 78.
[0126] Further, in the second configuration E, the second apparatus 68 comprises a further roller 177, having a greater height than the roller 77, which is movable towards and away from the fourth abutment roller 174.
[0127] The further roller 177 is arranged for abutting on a still further external surface 151 of the further edge portion 78. The operation of the second apparatus 68 with reference to Figure 7 is disclosed below.
[0129] This positioning provides inserting the further edge portion 78 in a further gap, which is not shown, defined between the fourth abutment roller 174 and the further roller 177 until the tubular element 45 rests on the resting surface 71.
[0130] In this manner, the tubular element 45 is supported by the fourth abutment roller 174 that abuts on the still further internal surface 155.
[0131] Subsequently, the further roller 177 approaches the abutment roller 174, until it abuts on the still further external surface 151.
[0132] In this manner, the further end portion 78 is positioned between the further roller 177 and the fourth abutment roller 174.
[0133] Still subsequently, the further roller 177 and the fourth abutment roller 174 are rotated that rotate the tubular element 45.
[0134] Subsequently, whilst the further roller 177 and the fourth abutment roller 174 rotate the tubular element 45 the supporting table 69 is rotated at a desired angle around the pivot 72 by the fourth actuator 73.
[0135] In this manner, the supporting table 69, the further roller 177 and the fourth abutment roller 174 fold the further edge portion 78 of the first part 5 outwards so as to obtain the second tilted edge 22.
[0137] In fact, the fold 8 is obtained by rolling directly in the cylindrical portion 6 of the casing 2, which enables the costs to be eliminated that are necessary for making and mounting an angular abutting ring.
1. Screening apparatus comprising a casing (2) provided with a first part (5) comprising
a cylindrical portion (6) arranged for receiving a material to be screened, with a
second part (7) arranged for receiving a screened material, and with a screening net
(4) supported by a supporting ring (9) and interposed between said first part (5)
and said second part (7), said screening net (4) being mounted so as to abut on a
seat (8) of said first part (5), characterised in that said seat is formed by a fold (8) obtained in said cylindrical portion (6).
2. Apparatus according to claim 1, wherein said fold (8) is obtained in an edge portion
(56) of said cylindrical portion (6).
3. Apparatus according to claim 1, or 2, wherein said fold comprises an angular fold
(8).
4. Apparatus according to any preceding claim, wherein said first part (5) substantially
comprises at a first end (15) thereof a first tilted edge (14).
5. Apparatus according to claim 4, wherein said first tilted edge (14) is an end portion
of said fold (8).
6. Apparatus according to claim 4, or 5, wherein said first part (5) comprises at a second
end (21) thereof, opposite said first end (15), a second tilted edge (22) arranged
for defining a supply opening (3) for said material to be screened.
7. Apparatus according to any one of claims 4 to 6, wherein said second part (7) comprises
at a further first end (20) thereof a further first tilted edge (19), facing said
first tilted edge (14).
8. Apparatus according to claim 7, and comprising a housing (30) defined between said
first tilted edge (14) and said further first tilted edge (19) and arranged for receiving
fixing means (10) arranged for fixing said supporting ring (9) to said casing (2).
9. Method for making a part (5) of a casing (2) of a screening apparatus (1) arranged
for receiving a material to be screened comprising rolling an edge portion (56) of
said part (5) until a fold (8) is obtained.
10. Method according to claim 9, wherein said rolling comprises folding outwards said
edge portion (56) until an angular fold (8) is obtained.
11. Method according to claim 10, wherein said folding outwards comprises increasing a
diameter of said part (5) at said edge portion (56).
12. Method according to claim 11, wherein said increasing comprises pressing an external
surface (51) of said part (5), positioned upstream of said edge portion (56), against
abutting means (50).
13. Method according to claim 12, wherein said pressing comprises pressing outwards an
internal surface (55) of said edge portion (56).
14. Method according to any one of claims 9 to 13, wherein after said rolling there is
provided still rolling an end portion (18) of said angular fold (8) until a first
tilted edge (14) is obtained.
15. Method according to claim 14, wherein said still rolling comprises still folding outwards
said end portion (18).
16. Method according to claim 15, wherein said still folding outwards comprises still
pressing a further external surface (66) of said end portion (18) against further
abutting means (50).
17. Method according to claim 16, wherein said still pressing comprises still pressing
outwards a further internal surface (75) of said end portion (18).
18. Method according to claim 15, wherein said still folding outwards comprises positioning
said end portion (18) between roller means.
19. Method according to claim 18, wherein after said positioning there is provided tilting
by a desired angle a portion of said part (5) with respect to said end portion (18).
20. Method according to any one of claims 14 to 19, wherein after said still rolling there
is provided further rolling a further edge portion (78) of said part (5), opposite
said edge portion (56), until a second tilted edge (22) is obtained.
21. Method according to claim 20, wherein said further rolling comprises further folding
outwards said further edge portion (78).
22. Method according to claim 21, wherein said further folding outwards comprises further
pressing a still further external surface (151) of said further edge portion (78)
against said further abutting means (50).
23. Method according to claim 22, wherein said further pressing comprises further pressing
outwards a still further internal surface (155) of said further edge portion (78).
24. Method according to claim 21, wherein said further folding outwards comprises still
positioning said further edge portion (78) between further roller means.
25. Method according to claim 24, wherein after said still positioning there is provided
still tilting by a desired angle a further portion of said part (5) with respect to
said further edge portion (78).
26. Method according to any one of claims 9 to 25, wherein said rolling comprises rotating
said part (5).