Axial fan

Abstract

An axial fan has a housing and a motor with motor shaft and blower wheel attached to the motor shaft. The blower wheel has fan blades attached to a hub and provided with a leading and a trailing edge, respectively. A suspension arrangement is provided with a brace part made from flat material. The brace part connects motor and housing and has a length measured in a direction from motor to housing. The brace part is arranged on edge in an airflow direction and has a width measured in the airflow direction. The brace part has two limbs extending lengthwise in length direction of the brace part. The limbs are spaced apart from each other and delimit opposite sides of an opening formed by a punch-out in the flat material and extending along some of the length. The limbs are arranged one behind the other in airflow direction.

Claims

1. A method for manufacturing an axial fan, the axial fan comprising: a cylindrical housing; a motor arranged in and surrounded by the cylindrical housing, wherein the motor comprises a motor shaft; a blower wheel attached to the motor shaft; the blower wheel comprising a hub and fan blades attached to the hub; the fan blades comprising a leading edge and a trailing edge, respectively; a suspension arrangement comprising at least one brace part that is a flat sheet metal part; the at least one brace part comprising a first end, positioned radially outwardly and directly connected to a cylindrical inner wall of the cylindrical housing, and further comprising a second end, opposite the first end and directly connected to an outside of a motor housing of the motor, so that the motor is connected to the cylindrical housing by the at least one brace part, wherein the at least one brace part has a length and said length is measured from the motor housing of the motor to the cylindrical housing; the at least one brace part arranged axially at a level of the motor housing and arranged in a direction of airflow through the cylindrical housing so as to be positioned edgeways and having a width measured in the direction of airflow; the at least one brace part comprising two limbs extending lengthwise in a direction of said length of the at least one brace part from the first end to the second end, wherein the two limbs are spaced apart from each other and delimit opposite sides of at least one opening formed by a punch-out in the flat sheet metal part and extending along most of said length, wherein the two limbs are arranged one behind the other in the direction of airflow, wherein the at least one opening extending along most of said length reduces noise emission and flow resistance of the axial fan; wherein the method comprises: producing by casting in a mould identical castings as blade blanks; cutting the blade blanks by a cylindrical cut to a desired external diameter of the blower wheel; imparting by cutting a final contour of a fan blade to the blade blanks, wherein the final contour is matched to the external diameter and a stepped angle of the fan blades.

2. A method for manufacturing an axial fan, the axial fan comprising: a cylindrical housing; a motor arranged in and surrounded by the cylindrical housing, wherein the motor comprises a motor shaft; a blower wheel attached to the motor shaft; the blower wheel comprising a hub and fan blades attached to the hub; the fan blades comprising a leading edge and a trailing edge, respectively; a suspension arrangement comprising at least one brace part that is a flat sheet metal part; the at least one brace part comprising a first end, positioned radially outwardly and directly connected to a cylindrical inner wall of the cylindrical housing, and further comprising a second end, opposite the first end and directly connected to an outside of a motor housing of the motor, so that the motor is connected to the cylindrical housing by the at least one brace part, wherein the at least one brace part has a length and said length is measured from the motor housing of the motor to the cylindrical housing; the at least one brace part arranged axially at a level of the motor housing and arranged in a direction of airflow through the cylindrical housing so as to be positioned edgeways and having a width measured in the direction of airflow; the at least one brace part comprising two limbs extending lengthwise in a direction of said length of the at least one brace part from the first end to the second end, wherein the two limbs are spaced apart from each other and delimit opposite sides of at least one opening formed by a punch-out in the flat sheet metal part and extending along most of said length, wherein the two limbs are arranged one behind the other in the direction of airflow, wherein the at least one opening extending along most of said length reduces noise emission and flow resistance of the axial fan; wherein the method comprises: producing by casting in a mould a blade blank that comprises a material accumulation as a winglet blank in an area of a wing tip of a fan blade to be produced from the blade blank, wherein the material accumulation is thicker than a remaining blade blank body of the blade blank; machining or processing the winglet from the winglet blank and matching the winglet to an external diameter and a stepped angle of the fan blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail with reference to two embodiments shown in the drawings. The following are shown:

(2) FIG. 1 a perspective view of a first embodiment of an axial fan according to the invention,

(3) FIG. 2 a lateral view of the axial fan according to FIG. 1,

(4) FIG. 3 and FIG. 4 in illustrations corresponding to those of FIGS. 1 and 2 a second embodiment of an axial fan according to the invention,

(5) FIG. 5 and FIG. 6 perspective views of further embodiments of brace parts of the axial fan according to the invention,

(6) FIG. 7 and FIG. 8 perspective views of different embodiments of mountings for the motor of the axial fan according to the invention,

(7) FIG. 9 cross sections of various designs of the openings in the brace parts delimiting limbs of the brace parts of the axial fan according to the invention,

(8) FIG. 10 various exemplary embodiments of blade blanks for manufacturing the fan blades of the axial fan according to the invention, and fan blades made thereof of the axial fan according to the invention with winglet contours.

DESCRIPTION OF PREFERRED EMBODIMENTS

(9) The axial fans according to FIGS. 1 to 4 are characterized by high efficiency and by a flow-optimised motor suspension arrangement that significantly contributes to the high efficiency. The axial fan comprises a fluidically optimised blower wheel featuring a special geometry, which is yet to be described, and high efficiency of the blower wheel. Drive motors with high motor efficiency are used in the axial fan, for example rotary-current internal rotor motors or electronically commutated external rotor motors. Furthermore, the axial fans according to FIGS. 1 to 4 are characterized by flow-optimised motor suspension arrangements.

(10) The axial fan according to FIGS. 1 and 2 comprises a motor 1 which in the exemplary embodiment shown is an internal rotor motor. The latter is held, by means of a suspension arrangement 2, on a cylindrical housing 3 that encloses the motor 1 at radial spacing. Said cylindrical housing 3 forms an outer tube of the fan and is arranged so as to be coaxial to the motor 1. As shown in FIG. 2, the motor 1 is arranged in such a manner that it does not axially protrude beyond the housing 3.

(11) The suspension arrangement 2, which advantageously comprises sheet metal parts, is attached to the inside of the housing 3 and to the outside of the motor 1. In the exemplary embodiment shown, the suspension arrangement 2 comprises three brace parts 4 to 6 and one attachment part 8. The brace parts 4 and 5 are designed so as to be mirror-symmetrical to each other, each comprising an opening 7 that extends over a large part of its length. The brace parts 4 and 5 merge in one piece into each other by way of the attachment part 8 on the motor side, by way of which attachment part the brace parts 4, 5 are attached to a mounting block 9. The mounting block 9 is provided on the outside of the motor 1; it has a planar contact surface for the planar attachment part 8. In the exemplary embodiment the mounting block 9 is spaced apart from an axial plane of the motor 1, which axial plane extends parallel to its support surface.

(12) The attachment part 8 extends, across the axis of the motor 1, slightly beyond the mounting block 9 (FIG. 1) from where at an obtuse angle it makes a transition to the brace parts 4, 5, which comprise the opening 7, wherein in each case the free end 11 of said brace parts 4, 5 is angled in such a manner that it can be attached so as to rest against the inner wall of the housing 3. Because of the opening 7 the brace parts 4, 5 comprise two limbs 12, 13 that are situated in one plane. The limbs 12, 13 extend in a converging manner in the direction of the free end 11. The openings 7 do not extend as far as the ends of the brace parts 4, 5, and consequently the ends of the brace parts 4, 5 are of a solid design, thus providing adequate strength in the region of the attachment on the motor 1 and on the housing 3.

(13) Advantageously, the limbs 12, 13 have a width that approximately corresponds to 3 times to 15 times the sheet metal thickness, preferably to 5 times the sheet metal thickness. This results in optimal strength of the suspension arrangement while providing minimal flow resistance.

(14) The support part 6 is designed so as to be approximately U-shaped; it comprises two limbs 14, 15 that converge in two directions on the housing 3, which limbs 14, 15 merge by way of a short cross piece 16. The cross piece 16 rests against the inner wall of the housing 3 and is attached in a suitable manner to said housing 3, for example by means of at least one screw 17. The cross piece 16 can also be welded to the inner wall of the housing 3.

(15) The free ends 18, 19 of the limbs 14, 15 are angled outwards in opposite directions. As shown in FIG. 1, the free ends 18, 19 rest against the attachment part 8 of the brace parts 4, 5. Thus the attachment part 8 and the support part 6 can be attached together on the mounting block 9 of the motor 1. Attachment can take place by means of screws 20, or also by welding.

(16) The brace parts 4 to 6 are made from flat material, preferably from sheet metal parts, wherein the sheet metal part for the brace parts 4 and 5 is bent, and for forming the openings 7 is punched. The support part 6 is bent to the described approximately U-shaped design. The sheet metal parts are arranged so as to be approximately on edge relative to the direction of airflow, and consequently they provide only little resistance to the flow. The limbs 14, 15 are arranged so as to be parallel to an axial plane of the motor 1.

(17) The support part 6 is situated in the middle between the two brace parts 4, 5. In this manner the motor 1 is securely suspended from the housing 3. The brace parts can be manufactured very easily and economically from the sheet metal parts. The flow resistance of the brace parts 4 to 6 can be optimally adapted to a particular application by selecting the size and/or design and/or position of the openings 7 of the brace parts 4, 5. Moreover, the angle at which the brace parts 4 to 6 are arranged relative to each other can be adapted to the flow characteristics. In the example shown the brace parts 4 and 6 or 5 and 6 are arranged at angles >90 relative to each other. Depending on the required flow resistance this angle between the brace parts can be varied, for example it can be 90, less than 90, or significantly more than 90. Since the limbs 12, 13 of the brace parts 4, 5 are arranged one behind the other in the direction of airflow through the housing 3, and since the limbs 14, 15 extend with their wide dimensions in the direction of the airflow, the flow resistance of the suspension arrangement 2 is minimal.

(18) As shown in FIGS. 1 and 2, the brace parts 4 to 6 extend from the mounting block 9 of the motor 1 obliquely in the direction of the inlet end 21 of the housing 3. The attachment points of the two brace parts 4, 5 on the housing 3 are at the same height, while the cross piece 16 of the brace part 6 is spaced apart further from the inlet end 21 than are the free ends 11 of brace parts 4, 5.

(19) A hub body 23, from which fan blades 24 protrude, is non-rotatably attached to the motor shaft 22 (FIG. 2). Said fan blades 24 are of a convoluted design and comprise a profiled cross section. Depending on the size of the axial fan a different number of fan blades 24 are provided on the hub body 23. For example, 3 to 15 fan blades 24 can be provided that are circumferentially arranged on the hub body 23, either evenly or unevenly distributed. As shown in FIG. 2, the fan blades 24 have a profile 25 that resembles that of the wing profile of an aircraft.

(20) The hub body 23 and the fan blades 24 attached to it advantageously comprise different materials. Thus it is advantageous when the hub body 23 is an aluminium casting that is of a lightweight construction and economical to manufacture. The fan blades 24 advantageously comprise a fibre-reinforced plastic material so that economical manufacture is also possible. In this arrangement the fan blades 24 are of a lightweight and high-strength construction. In order to be able to set the step angle of the fan blades 24 the fan blades 24 are provided, in the known manner, on the hub body 23 so as to be pivotable on axes situated across, preferably perpendicular to, the axis of rotation of the blower wheel 23, 24.

(21) The fan blades 24 have a concave curved leading edge 26 and a convex curved trailing edge 27. In order to minimise noise emission during operation of the axial fan, the trailing edge 27 is designed according to the law of bionics. Thus the trailing edge 27 can be undulating or, as shown in the exemplary embodiment, serrated. Such a profile shape of the trailing edge 27 is advantageously provided along the entire length.

(22) The profile 25 of the fan blade 24 is designed in such a manner that the fan blade in the region of the trailing edge 27 essentially ends in a point while the profile 25 in the region of the leading edge 26 is rounded. Such a profile design is advantageously provided along the entire length of the fan blade 24.

(23) At their radially outward edge 28 the fan blades 24 comprise a cylindrical section, irrespective of the step angle selected in the particular case. Consequently, when viewed in the direction of the axis of the fan, the edges 28 are situated on a common cylinder surface whose axis coincides with the axis of rotation of the hub body 23. In this manner the air gap 29 between the outer edge 28 of the fan blades 24 and the inner wall of the housing 3 can be set in such a manner that optimum flow capacity with minimum noise emission is achieved. The described cylindrical section can be carried out by subsequent machining on the already assembled blower wheel 23, 24, for example by milling or sawing of the fan blades 24. Consequently, the air gap geometry can be optimised easily and reliably. In this manner the air gap 29 can be set to be very small so that leakage flow is very small.

(24) In one embodiment (not shown) the fan blades 24 comprise a winglet on the outer edge 28. With the use of such fan blades the airflow through the air gap 29 can be further reduced, because together with a narrow air gap 29 they form considerable resistance to any leakage flow around the outer edge 28. The winglets can be produced by machining the fan blades 24 on the outer edge 28. To this effect the fan blades 24 are machined in such a manner that the respective winglet is created on the edge 28. Such machining is carried out in such a manner that a rounded transition is formed from the pressure side to the suction side of the fan blades 24. The winglets can be provided on the suction side and/or on the pressure side of the fan blades 24.

(25) The motor 1 and the blower wheel 23, 24 are situated within the cylindrical housing 3. By way of the suspension arrangement 2 the motor 1 with the blower wheel 23, 24 is reliably held on the housing 3. Because of the described design of the brace parts 4 to 6 the suspension arrangement 2 offers only minimal flow resistance. In conjunction with the described design of the fan blades 24, which design results in high efficiency of the blower wheel, an axial fan results that features great overall efficiency.

(26) The fact that the hub ratio D.sub.a/D.sub.n of the blower wheel 23, 24 ranges from approximately 0.2 to approximately 0.6, and preferably is approximately 0.45, contributes to the high overall efficiency. D.sub.a denotes the external diameter of the blower wheel, and D.sub.n denotes the hub diameter.

(27) On the hub 23 the fan blades 24 have a ratio of chord length S to blade height H in the range of approximately 0.5 to approximately 0.65, preferably of approximately 0.57, and on the free end a ratio of approximately 0.75 to approximately 0.90, preferably of approximately 0.84.

(28) In the embodiment according to FIGS. 3 and 4 the fan blades 24 are designed and arranged on the hub body 23 in the same manner as in the previous embodiment. Advantageously, for adjustment of the step angles, the fan blades 24 are adjustably connected to the hub body 23. The fan blades 24 comprise the profiled trailing edge 27 and the profile 25 that is designed in accordance with the previous embodiment.

(29) The suspension arrangement of the motor 1 is formed by discharge guide vanes 30 that are provided in the direction of flow of the conveyed air with axial spacing downstream of the blower wheel 23, 24. Advantageously, the discharge guide vanes 30 comprise sheet metal; however, they can also be manufactured from correspondingly rigid plastic. The discharge guide vanes 30 extend between the housing 3 and an interior tube 31 that is arranged so as to be coaxial to the housing 3. The guide vanes 30 are suitably attached, for example welded or screwed, to the inside of the housing 3 and to the outside of the tube 31. The number of discharge guide vanes 30 depends on the size of the axial fan. For example, 3 to 25 such discharge guide vanes can be provided. In the exemplary embodiment shown there are 7 discharge guide vanes 30 that form the motor suspension arrangement.

(30) Within the tube 31 an annular flange 32 is attached that is designed as a flat ring to which the motor 1 can be attached. At the motor end the tube 31 is open so that for attachment to the annular flange 32 the motor 1 can be inserted in the tube 31. The motor 1 advantageously comprises a counter flange that comes to rest against the annular flange 32 and is suitably connected to it, preferably with the use of screws. The motor 1 can, for example, be a flange motor or an EC-external rotor motor to whose motor shaft the blower wheel 23, 24 is non-rotatably attached.

(31) Advantageously, the discharge guide vanes 30 are gradually curved over their width. The curvature is selected in such a manner that high efficiency is achieved. In conjunction with the design of the blower wheel 23, 24, which design has been described in the context of FIGS. 1 and 2, high overall efficiency results, wherein noise emission during operation is minimal.

(32) When the discharge guide vanes 30 comprise sheet metal, they can be manufactured economically essentially by being cut out and rolled.

(33) In order to achieve good cooling of the motor 1 the tube 31 comprises circumferentially arranged openings 33 at the height of the annular flange 32.

(34) For the remainder, the blower wheel 23, 24 is designed in the same manner as the blower wheel of the previous embodiment, so that reference is made to the description of said embodiment.

(35) The described axial fans can be manufactured in a host of different design sizes. As an example, the internal diameter of the housing 3 can be in a range of approximately 200 mm to approximately 1,800 mm.

(36) When the fan blades 24 in the preferred manner comprise the described plastic material, it is possible, for manufacturing the fan blades 24, to use only one single injection mould for the various design sizes of the fan. The injection mould is tailored to the longest length of the fan blades 24. When shorter fan blades 24 are required, they are cut to the required length. The same also applies to fan blades 24 made from cast metal.

(37) FIG. 5 shows the two brace parts 4, 5 that are interconnected by way of the attachment part 8. Each of the brace parts 4, 5 has an opening 7. In contrast to the previous embodiments these openings do not have a circumferential edge. Instead, on the edge adjacent to the attachment part 8 a support part 34, 35 has been bent out transversely, with each support part 34, 35 comprising an opening 7. The support parts 34, 35 and the parts of the brace parts 4, 5 that comprise the openings 7 extend obliquely to each other so that in each case they encompass an angle with the planar attachment part 8. The free ends 36, 37 of the support parts 34, 35 are angled in the same direction as the free ends 11 of the brace parts 4, 5. The angular arrangement 11, 36, 37 is selected so that the brace parts 4, 5 and the support parts 34, 35 can be reliably attached, resting against the inner wall of the housing 3. In the exemplary embodiment the angular arrangements comprise two through-openings for attachment screws or the like.

(38) The angular arrangements 36, 37 can also point in a direction that differs from the direction of the angular arrangements 11 of the brace parts 4, 5.

(39) The openings 7 are likewise delimited by two limbs 38, 39; 40, 41 that extend so as to converge in the direction of the free end 36, 37. The openings 7 end at some distance from the attachment part 8 and also from the free ends 36, 37.

(40) Similar embodiments that do not comprise an additional opening 7 are also conceivable.

(41) The support parts 34, 35 are manufactured in that an approximately u-shaped punching is made in the brace parts 4, 5 in such a manner that the support parts 34, 35 can be bent out into the position shown in FIG. 5.

(42) The brace parts 4, 5, the attachment part 8 and the support parts 34, 35 are advantageously made in one piece; they comprise sheet metal material. This allows simple and economical manufacture. Because of the additional support elements 34, 35, when compared to the previous exemplary embodiments, the stability of the suspension arrangement is considerably improved. Furthermore, still more secure attachment of the motor 1 to the housing 3 is ensured. The brace parts 4, 5, the attachment part 8 and the support parts 34, 35 can easily be installed and deinstalled, for example by means of screws or rivets. These components do not have to be welded, and consequently there is no need for an expensive welding procedure.

(43) In terms of their size and/or shape and/or position the openings 7, 7 can be provided such that the flow resistance of the air becomes minimal. Since the suspension arrangement comprises flat material in the manner described and comprises the openings 7, 7, the suspension arrangement is of a lightweight design despite its good stability.

(44) FIG. 6 shows a further option of designing the suspension arrangement. The two brace parts 4, 5 are of the same design as in the previous exemplary embodiment. As an example, the attachment part 8 comprises a bent-out tab 42 at mid-length, with the free end of said tab 42, for example, comprising a through-opening for an attachment screw or the like. The free end is angled so that it can be installed at the required position within the axial fan.

(45) Because of the bent-out tab 42 the attachment part comprises an opening 7. As is the case in the previous exemplary embodiments, the two brace parts 4, 5 extend, diverging, from the attachment part 8 over the same side of the attachment part. The tab 42 extends obliquely over the other side of the attachment part 8.

(46) FIGS. 5 and 6 merely show exemplary embodiments in terms of the design of the brace parts with the openings. These exemplary embodiments are not to be interpreted to be limiting in any way.

(47) FIG. 7 diagrammatically shows that the housing 3 can be connected, by way of several brace parts 43, to a pot 44 in which the motor 1 is accommodated. The pot 44 is cylindrical in design and is situated so as to be coaxial to the housing 3. The braces 43 are of an identical design, each comprising the opening 7 that is delimited by the limbs 12, 13 which extend radially outwards in a converging manner. The radially outer and the radially inner ends 11, 16 are angled in such a manner that the brace parts 43 can be attached to the inner wall of the housing 3 and to the outer wall of the pot 44. The brace parts 43 are arranged on edge, as is the case in the previous exemplary embodiments.

(48) As is shown as an example in FIG. 8, the pot 44 can also comprise a u-shaped design. The brace parts 43 are attached to the limbs 45, 46 of the pot 44, which limbs 45, 46 are arranged so as to be parallel to each other. The brace parts 43 are of an identical design to that of the embodiment according to FIG. 7. Their radially outer end 11 is attached to the inside of the housing 3, and their radially inner end 16 is attached to the outsides of the limbs 45, 46 of the pot 44, which outsides face away from each other. The motor 1 (not shown) is supported by the u-shaped pot 44.

(49) Moreover, the pot 44 can also comprise an angular shape and can completely encase the motor, as is the case in the exemplary embodiment according to FIG. 7.

(50) FIGS. 7 and 8 show that the brace parts 43 are advantageously arranged so as to be rotationally symmetrical and/or mirror-symmetrical to each other.

(51) FIG. 9 shows various possible designs of the cross sections of the limbs 12, 13, 38 to 41 of the brace parts 4, 5, 34, 35, 43. By transversely cutting and rounding or chamfering the cutting edges, the opening 7 can be designed in such a manner that noise emission is minimal.

(52) FIG. 9a shows a rectangular cross section as is obtained initially during punching or laser cutting. The cutting edges are sharp, and the cutting surfaces are approximately perpendicular to the surfaces of the flat material.

(53) In the cross section of FIG. 9d all the edges are rounded. This can result in a significant reduction in noise emission because the sharp edge has been eliminated. It is also possible for only some of the edges of the cross sections to be rounded.

(54) In an embodiment with a cross section according to FIG. 9b a similar effect is achieved as in the embodiment according to FIG. 9d. In the exemplary embodiment according to FIG. 9b the edge is chamfered.

(55) In the embodiment according to FIG. 9e acoustic and aerodynamic advantages are achieved in that the cut is not made so as to be perpendicular to the surface of the flat material, but instead obliquely to it. The alignment of the cut surface can better be adapted to the direction of flow than is the case in a cut made perpendicularly to the surface of the flat material.

(56) In particularly advantageous embodiments according to FIGS. 9c and 9f the design options of oblique cutting according to FIG. 9e and of rounding or incorporating a chamfer are combined in order to obtain optimal acoustic characteristics.

(57) In conjunction with the particular design of the openings, it is also possible to optimise the cross sections of the limbs of the brace parts and of the support parts, which limbs delimit the openings, in such a manner that the flow resistance and noise emission are minimal. The openings and the limbs can be attuned to each other in such a manner that, depending on the particular application of the axial fan, optimally low flow resistance and noise values are achieved. In conjunction with the described ratio of width to thickness of the limbs of the brace parts and of the support parts, which limbs delimit the opening, in the range of approximately 3 to approximately 15, thus minimum flow resistance and minimum noise emission result at optimum strength of the suspension arrangement.

(58) As already described, advantageously it is possible to set the step angle of the fan blades 24 in that said fan blades 24 are provided to be correspondingly adjustable on the hub body 23.

(59) In addition to the aforesaid, or instead of these adjustable blades, in an advantageous design different external diameters can be achieved from essentially identical blanks in that the blanks are cut to various external diameters. These blanks can be castings that initially are manufactured identically and that are then adapted to the particular external diameter required.

(60) Additionally or alternatively it is possible to implement various external diameters of the fan blades 24 in that essentially identical individual blade blanks are installed on hub bodies of different diameters and, if necessary, are cut in terms of the external diameter or are subsequently machined.

(61) When the fan blades 24 comprise a winglet on the radially outer edge 28, the aforesaid can also be made from the blanks. It is not possible for the winglets themselves to be provided in the mould, because their geometry or their position depends on the external diameter of the blower wheel and on the stepped angle. It is thus advantageous when the blade blanks are not only cut in a cylindrical cut, as described above, but are given a special contour, in particular by way of machining, or in the case of plastics possibly by thermoforming, which special contour can be attuned to the particular external diameter and the particular stepped angle. This results in very good flexibility during construction or installation of the particular fan. Thus, optimum acoustic characteristics of the fan blades and thus of the fan are achievable for every external diameter and stepped angle.

(62) FIGS. 10a and 10d show exemplary options, in section view approximately perpendicularly to the surface of the blade suction side or blade pressure side, relating to the design of a single blank of a fan blade. In the exemplary embodiment according to FIG. 10a the blank 24 is rectangular in shape with parallel longitudinal sides and a narrow end 47 that extends at a right angle to the aforesaid. This shape results in particular when, in the design of the original blade casting tool or mould, the design of a winglet was not yet provided for.

(63) In the exemplary embodiment of a blade blank according to FIG. 10d, a winglet blank 48, which is a thickening or accumulation of material, is already provided in the wing tip region, from which winglet blank the final winglet, adjusted to the actual stepped angle and to the external diameter, is created. In this exemplary embodiment the winglet blank 48 comprises a rectangular cross section; however, in principle it may have any desired cross section.

(64) FIGS. 10b and 10c diagrammatically show two embodiments of winglets that have been created by subsequent machining of a blank according to FIG. 10a. The embodiment according to FIG. 10c has a cross-sectional contour of the winglet that is straight, in contrast to the embodiment according to FIG. 10b that has a rounded contour. However, both winglets can be produced from identical blade blanks. Furthermore, any other forms are conceivable, provided they can be manufactured from a blade blank like the blank according to FIG. 10a. The scope and nature of the invention consists in particular of manufacturing winglets, optimally adapted to any desired external diameters and at any desired stepped angles, in a subsequent process step from a blank. It is, furthermore, possible to manufacture, from a blank, winglets of different contours, which winglets are optimally adapted to the particular flow conditions.

(65) FIGS. 10e and 10f show cross sections of winglets, analogous to those of the previous description of FIGS. 10b and 10c, which winglets were created from a blank according to FIG. 10d. FIG. 10f shows a fan blade of shorter length (smaller external diameter) but of a similar winglet contour as the fan blades according to FIG. 10e. Both fan blades can be made from an identical blank.

(66) The winglet blank 48 in the blank according to FIG. 19d provides an advantage in that more design options relating to the winglet are available. However, in order to implement these additional design options, a winglet blank 48 in the mould of the blade is provided right from the start.

(67) The design of the gradient of the winglet contour in the longitudinal direction of the blade can be freely selected. The only decisive factor consists of all the winglets to be realised being geometrically within the contour of the associated blank, according to the external diameters and stepped angles. The winglets are added in an additional process step following casting or moulding of the blanks.

(68) The described design of the blanks for the fan blades and the winglets applies irrespective as to whether the fans comprise the suspension arrangement or the special conditions of the described fan blade geometries described with reference to FIGS. 1 to 9. With the use of the blanks, the fan blades (with or without winglets) can be optimally attuned to the respective fan, in particular also to the respective external diameter of the blower wheel and to the stepped angle, and consequently the optimum design of the respective fan can be achieved from the blanks.

(69) Furthermore, it is possible for the blade blanks to already comprise winglet blanks which subsequently can be optimally adjusted to the respective application by corresponding machining. In principle the winglet shape of a blank can be of any design.