EP2823184B1 - Axial fan - Google Patents

Description

The invention relates to an axial fan according to the preamble of claim 1.

Axial fans are used for a wide variety of applications. Although axial fans have sufficient overall efficiency and low flow resistance, there are more and more applications where even higher requirements are placed on overall efficiency and/or flow resistance.

Axial fans are known ( DE 25 29 541 B2 ), in which the motor is attached to the housing via a suspension. The suspension is provided by radially extending struts extending between a stator hub and the housing. The struts are arranged approximately on edge in the flow direction of the air and are curved over their height. Since the struts are continuous over their length and height, the flow resistance is still too high. The struts also lead to an increase in the weight of the axial fan and contribute to the generation of noise during the operation of the axial fan.

In another known axial fan ( DE 10 2004 017 727 A1 ) the motor is attached to the housing by means of webs. The webs are also continuous and extend transversely to the flow direction of the air, resulting in a high flow resistance and a corresponding weight of the axial fan, as well as a loud operating noise.

Axial fans are also known ( DE 10 2011 015 784 A1 ), in which the motor is connected to the housing via approximately radial struts. The struts are designed as guide vanes and are arranged approximately on edge. They are also solid throughout.

In another known axial fan ( GB 429 958 ) the motor is connected to the housing via radial struts. In the connection area to the housing, the struts are widened. The struts also lead to a high flow resistance, to a high weight of the axial fan and to a noise development when the axial fan is in operation.

Finally, axial fans are known ( EP 0 259 061 A2 ), in which the motor is connected to the housing via L-shaped struts.

A fan is also known ( GB 2 281 102 A ), whose motor is connected to a housing via a suspension. The suspension includes diametrically opposed struts extending radially from an engine mount, the outer ends of which have fasteners bent at right angles for attachment to the inside of the housing. The struts are each formed by two adjacent strut elements, of which one strut element has an opening and the other strut element has a projection filling the opening.

It is further known ( U.S. 6,074,182 A ), in the case of a fan, to connect the housing of the motor to two upright U-rails via struts protruding transversely, which are provided with recesses along their length, which enable the motor to be attached to the U-rails at different heights.

With another known fan ( DE 27 27 119 A1 ) the motor is housed in a cylindrical housing supported by three flexible support arms attached to a bulkhead or other suitable support structure. The support arms are each provided with a recess in order to adjust the spring properties of the support arms.

Other fans are known ( CA 2 078 761 A1 , CN 201 687 772 U ), in which the motors are attached to the outside of housings by strut parts.

The invention is based on the object of designing the axial fan of the generic type in such a way that the axial fan has a high overall efficiency and only a low flow resistance. The axial fan should only have a low weight, be able to be produced inexpensively and, in particular, generate little noise during operation.

This object is achieved according to the invention with the generic axial fan with the characterizing features of claim 1.

The axial fan according to the invention is characterized in that at least part of the strut part is provided over a part of its length with at least one recess formed by a punching in the flat material. The flow resistance through the strut part is minimized by the recess. The shape and/or size and/or position of the recess can be adapted to the operating conditions of the axial fan, so that the optimal flow resistance can be set depending on the application. The recess in the strut part means that the weight of the axial fan is kept low. The more strut parts that are used as a suspension, the greater the weight reduction of the axial fan compared to axial fans with struts formed continuously over the length and height. The generation of noise from the axial fan according to the invention is greatly reduced because the size of turbulent separation areas is greatly reduced as a result of the recess. Since the strut part is also arranged approximately upright in the flowing air is, the flow resistance can be kept to a minimum in conjunction with the size and/or shape and/or position of the recess.

The strut part is formed by a sheet metal part. The use of sheet metal results in low manufacturing costs for the axial fan. The sheet metal part can be easily deformed if required for installation. It is easy to assemble and disassemble. In particular, it is not necessary to weld this sheet metal part at its ends, but its ends can be screwed, riveted or the like to the corresponding components of the axial fan. In the case of the strut part made of sheet metal, the recess can be produced very simply by stamping.

In order to achieve optimum strength of the suspension with minimum flow resistance, the legs of the strut part delimiting the recess are advantageously designed with a width which corresponds to approximately 3 to 15 times the flat material thickness, preferably 5 times the flat material thickness.

The recess is formed by punching out the flat material.

In a particularly advantageous embodiment, the recess in the strut part is designed in such a way that at least one support part protrudes from at least one edge of the recess. It is thus possible, for example, to introduce a U-shaped punching in a metal sheet and to bend the sheet metal part located between the edges of the punching out of the plane of the sheet metal. In this way the support part is formed, which protrudes from the strut part and is advantageously formed in one piece with it. In this way, the strut part can be provided with one or more support parts, which also significantly increase the stability of the strut part and thus also of the entire axial fan.

Both recesses with such a transversely projecting support part and recesses with a peripheral edge can be provided on a strut part.

A non-claimed axial fan can have several strut parts, which can be provided in a rotationally symmetrical arrangement. In this way, the motor can be optimally supported on the housing.

In a non-claimed embodiment, a pot can be provided to accommodate the motor, to which the inner end of the strut part is attached.

Depending on the design of the axial fan and/or the motor, this pot can be cylindrical or tubular or even angular. It is also possible to make the pot U-shaped so that it has no surrounding wall. The motor can then be suitably mounted in the U-shaped pot. The strut parts can also be easily mounted on a pot designed in this way.

In an embodiment not according to the invention, the axial fan can be designed in such a way that the motor is suspended by guide vanes, which are located behind the impeller in the direction of flow of the air. The engine mounting thus has the function of a guide wheel, with which an additional increase in efficiency is achieved. This axial fan is characterized by a very high overall efficiency because the fan blades at the hub of the impeller have a chord length to blade height ratio in the range from about 0.5 to about 0.65, preferably about 0.57.

The guide vanes are advantageously curved over their height in such a way that the flow resistance is minimal. In connection with the ratio of Due to the chord length to the blade height, the axial fan can be designed with a very high degree of efficiency with minimal flow resistance.

Advantageously, the vanes extend from an inner tube of the axial fan. This inner tube is coaxial with the housing and is connected to it by the guide vanes.

In a preferred embodiment, a mounting flange for the motor is provided in the inner tube. It can be partially inserted into the inner tube and attached to the mounting flange.

In order to achieve a high level of efficiency, it is advantageous if the fan blades are designed to be twisted.

It is advantageous if the fan blades can be adjusted about an axis lying transversely to the axis of rotation of the impeller. This allows the step angle of the fan blades to be adjusted to improve efficiency.

A further improvement in the overall efficiency is obtained in an advantageous manner if the fan blades have a ratio of chord length to blade height at their free end in the range from about 0.75 to about 0.90, preferably about 0.84.

Advantageously, the impeller has a hub ratio of about 0.2 to about 0.6, preferably about 0.45. This hub ratio, especially in connection with the ratios of chord length to blade height of the fan blades, contributes to the high overall efficiency of the axial fan.

An advantageous embodiment results when the trailing edge of the fan blades is formed bionic. Such a design contributes to an excellent overall efficiency of the axial fan. In this way, compared to known axial fans, an overall efficiency can be achieved be achieved, which is about 20% higher than the overall efficiency of known axial fans. The bionic shaping of the trailing edge of the fan blades also leads to only low noise emissions, so that the axial fan according to the invention, in addition to its high overall efficiency, also produces only low noise.

An advantageous embodiment results when the trailing edge of the fan blades has a wavy or jagged shape over at least part of its length. A suitable design of the profiling of the trailing edge can thus influence noise emissions.

Advantageously, the rear edge of the fan blades is convexly curved and the front edge is sickle-shaped.

Further features of the invention emerge from the further claims, the description and the drawings.

Fig. 1

in perspektivischer Darstellung einen erfindungsgemäßen Axialventilator,

Fig. 2

eine Seitenansicht des Axialventilators gemäß Fig. 1,

Fig. 3 und Fig. 4

in Darstellungen entsprechend den Fig. 1 und 2 eine zweite Ausführungsform eines nicht erfindungsgemäßen Axialventilators,

Fig. 5 und Fig. 6

jeweils in perspektivischen Darstellungen weitere Ausführungsformen von Strebenteilen des erfindungsgemäßen Axialventilators,

Fig. 7 und Fig. 8

in perspektivischer Darstellung unterschiedliche Ausbildungen von Aufnahmen für den Motor eines nicht erfindungsgemäßen Axialventilators,

Fig. 9

im Querschnitt verschiedene Ausgestaltungen von Aussparungen in den Strebenteilen des erfindungsgemäßen Axialventilators begrenzenden Schenkeln,

Fig. 10

verschiedene Ausführungsbeispiele von Flügelrohlingen zur Herstellung der Ventilatorflügel eines Axialventilators und daraus gefertigten Ventilatorflügeln eines Axialventilators mit Wingletkonturen.

The invention is explained in more detail using two embodiments shown in the drawings. Show it

1

a perspective view of an axial fan according to the invention,

2

a side view of the axial fan according to FIG 1 ,

3 and 4

in representations according to the 1 and 2 a second embodiment of an axial fan not according to the invention,

5 and 6

each in perspective representations of further embodiments of strut parts of the axial fan according to the invention,

7 and 8

in a perspective view, different designs of mounts for the motor of an axial fan not according to the invention,

9

in cross section, different designs of recesses in the strut parts of the axial fan according to the invention delimiting legs,

10

Various exemplary embodiments of blade blanks for producing the fan blades of an axial fan and fan blades of an axial fan made therefrom with winglet contours.

The axial fans according to the Figures 1 to 4 are characterized by a high level of efficiency and a flow-optimized engine mount, which contributes significantly to the high level of efficiency. The axial fan has an aerodynamically optimized impeller with a special geometry that is still to be described and a high impeller efficiency. Drive motors with high motor efficiency are used for the axial fan, for example three-phase internal rotor motors or electronically commutated external rotor motors. In addition, the axial fans are characterized according to the Figures 1 to 4 through flow-optimized engine mounts.

The axial fan according to the 1 and 2 has a motor 1, which is an internal rotor motor in the embodiment. It is attached via a suspension 2 to a cylindrical housing surrounding the motor 1 at a radial distance 3 held. It forms an outer tube of the fan and is arranged coaxially to the motor 1. How 2 1, the motor 1 is arranged so that it does not protrude axially beyond the housing 3.

The suspension 2, which is formed from sheet metal parts, is attached to the inside of the housing 3 and to the outside of the motor 1.

According to the invention, the suspension 2 consists of three strut parts 4 to 6 and a fastening part 8. The strut parts 4 and 5 are mirror-symmetrical to one another and are each provided with a recess 7 extending over a large part of their length. The strut parts 4 and 5 merge into one another in one piece via the engine-side fastening part 8 , via which the strut parts 4 , 5 are fastened to a fastening block 9 . The mounting block 9 is provided on the outside of the engine 1 and has a flat bearing surface for the flat mounting part 8. In the exemplary embodiment, the mounting block 9 is spaced from an axial plane of the engine 1 running parallel to its bearing surface.

The mounting part 8 extends transversely to the axis of the engine 1 slightly over the mounting block 9 ( 1 ) and then transitions at an obtuse angle into the strut parts 4 , 5 having the recess 7 , the free end 11 of which is angled in such a way that it can be attached to the inner wall of the housing 3 . As a result of the recess 7, the strut parts 4, 5 have two legs 12, 13 which lie in one plane. The legs 12, 13 run towards the free end 11 converging. The recesses 7 do not extend to the ends of the strut parts 4, 5, so that the strut parts 4, 5 are solid at their ends and thus have sufficient strength in the area of attachment to the motor 1 and to the housing 3.

The legs 12, 13 advantageously have a width which corresponds to approximately 3 to 15 times the sheet thickness, preferably 5 times the sheet thickness. This results in optimal strength of the suspension with minimal flow resistance.

The support part 6 is approximately U-shaped and has two legs 14, 15 which converge in the direction of the housing 3 and which merge into one another by means of a short crosspiece 16. The cross piece 16 rests against the inner wall of the housing 3 and is fastened to it in a suitable manner, for example with at least one screw 17. The cross piece 16 can also be welded to the inner wall of the housing 3.

The free ends 18, 19 of the legs 14, 15 are angled outwards in opposite directions to one another. How out 1 shows that the free ends 18, 19 rest on the fastening part 8 of the strut parts 4, 5. Thus, the attachment part 8 and the support part 6 can be attached to the attachment block 9 of the engine 1 together. The attachment can be done by screws 20, but also by welding.

The strut parts 4 to 6 are each made of flat material, namely sheet metal parts, the sheet metal part for the strut parts 4 and 5 being bent and punched to form the recesses 7 . The support part 6 is bent into the approximately U-shaped configuration described. In relation to the flow direction of the air, the sheet metal parts are arranged on edge so that they offer only little resistance to the flow. The legs 14, 15 are each parallel to an axial plane of the motor 1. The support part 6 is located centrally between the two strut parts 4, 5. In this way, the motor 1 is securely suspended on the housing 3. The strut parts can be manufactured very easily and inexpensively from the sheet metal parts. The flow resistance of the strut parts 4 to 6 can be optimally adapted to the application by selecting the size and/or design and/or position of the recesses 7 in the strut parts 4, 5. The angle at which the strut parts 4 to 6 are positioned relative to one another can also be adapted to the flow conditions. In the example shown are the strut parts 4 and 6 or 5 and 6 at angles >90° to each other. Depending on the required flow resistance, this angle between the strut parts can be changed, for example 90°, less than 90° or even significantly more than 90°. Since the legs 12, 13 of the strut parts 4, 5 are arranged one behind the other in the flow direction of the air through the housing 3 and the legs 14, 15 extend with their wide dimension in the flow direction of the air, the flow resistance of the suspension 2 is minimal.

As can be seen from the 1 and 2 results, the strut parts 4 to 6 extend from the mounting block 9 of the engine 1 obliquely in the direction of the inlet end 21 of the housing 3. The attachment points of the two strut parts 4, 5 on the housing 3 are at the same height, while the crosspiece 16 of the strut part 6 greater distance from the inlet end 21 than the free ends 11 of the strut parts 4, 5.

On the motor shaft 22 ( 2 ) sits non-rotatably a hub body 23, protruding from the fan blades 24. They are twisted and have a profiled cross-section. A different number of fan blades 24 is provided on the hub body 23 depending on the size of the axial fan. For example, 3 to 15 fan blades 24 can be provided, which are distributed uniformly or unevenly over the circumference of the hub body 23 . How out 2 As can be seen, the fan blades 24 have a profile 25 which is designed similar to the airfoil profile of an airplane.

The hub body 23 and the fan blades 24 attached to it are advantageously made of different materials. It is advantageous if the hub body 23 is an aluminum casting that can be produced inexpensively and is only light in weight. The fan blades 24 are advantageously made of fiber-reinforced plastic, which also makes cost-effective production possible. The fan blades 24 have a low weight and high strength. To the step angle of the fan blades 24 to be able to adjust, the fan blades 24 are pivotable on the hub body 23 in a known manner about axes lying transversely, preferably perpendicularly, to the axis of rotation of the impeller 23, 24.

The fan blades 24 have a concavely curved leading edge 26 and a convexly curved trailing edge 27. In order to minimize noise emissions during operation of the axial fan, the trailing edge 27 is designed according to the laws of bionics. The trailing edge 27 can be wavy or, as in the exemplary embodiment, jagged. This profiling of the trailing edge 27 is advantageously provided over the entire length.

The profile 25 of the fan blade 24 is designed in such a way that the fan blade in the area of the rear edge 27 tapers out essentially to a point, while the profile 25 is rounded in the area of the front edge 26 . This profile design is advantageously provided over the entire length of the fan blade 24 .

The fan blades 24 are provided with a cylindrical cut on their radially outer edge 28, independently of the step angle selected in each case. As a result, the edges 28 lie on a common cylinder jacket, seen in the axial direction of the fan, the axis of which is the axis of rotation of the hub body 23 . In this way, the air gap 29 between the outer edge 28 of the fan blades 24 and the inner wall of the housing 3 can be adjusted in such a way that an optimal delivery rate is achieved with minimal noise development. The cylinder trimming described can be carried out by machining the impeller 23, 24 that has already been assembled, for example by milling or sawing off the fan blades 24. The air gap geometry can thereby be easily and reliably optimized. In this way, the air gap 29 can be set very small, so that the flow loss is low.

In one embodiment (not shown), the fan blades 24 are provided with a winglet at the outer edge 28 . They can further reduce the air flow through the air gap 29 since, together with a narrow air gap 29, they form a high resistance to the leakage flow around the outer edge 28. The winglets can be created by post-processing the fan blades 24 at the outer edge 28 . For this purpose, the fan blades 24 are machined in such a way that the respective winglet is formed at the edge 28 . This machining is carried out in such a way 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 and/or on the pressure side of the fan blades 24 .

The motor 1 and the impeller 23, 24 are located within the cylindrical housing 3. The motor 1 with the impeller 23, 24 is reliably held on the housing 3 via the suspension 2. As a result of the design of the strut parts 4 to 6 described, the suspension 2 offers only minimal flow resistance. In connection with the design of the fan blades 24 described, which leads to a high impeller efficiency, an axial fan results which is characterized by a high overall efficiency.

The fact that the hub ratio D _a /D _n of the impeller 23, 24 is in a range from about 0.2 to about 0.6, preferably about 0.45, contributes to the high overall efficiency. D _a is the outside diameter of the impeller and D _n is the hub diameter.

The fan blades 24 have a chord length S to blade height H ratio at the hub 23 in the range of about 0.5 to about 0.65, preferably about 0.57, and a ratio in the range of about 0.75 to about 0.75 at the free end about 0.90, preferably about 0.84.

In the embodiment according to 3 and 4 the fan blades 24 are formed and arranged on the hub body 23 in the same way as in the previous embodiment. The fan blades 24 are advantageously connected to the hub body 23 so that they can be adjusted in order to set the step angle. The fan blades 24 have the profiled trailing edge 27 and the profile 25, which is designed according to the previous embodiment.

The suspension of the motor 1 is formed by guide vanes 30 which are provided at an axial distance behind the impeller 23, 24 in the direction of flow of the conveyed air. The guide vanes 30 are advantageously made of sheet metal, but can also be made of a correspondingly strong plastic. The guide vanes 30 extend between the housing 3 and an inner tube 31 which is arranged coaxially with the housing 3 . The guide vanes 30 are attached to the inside of the housing 3 and to the outside of the tube 31 in a suitable manner, for example welded or screwed. The number of vanes 30 depends on the size of the axial fan. For example, 3 to 25 such guide vanes can be provided. In the illustrated embodiment, there are 7 trailing vanes 30 which form the engine mount.

An annular flange 32 is fastened inside the tube 31, which is designed as a flat ring disk and to which the motor 1 can be fastened. The tube 31 is open at the motor-side end, so that the motor 1 can be inserted into the tube 31 for attachment to the annular flange 32 . The motor 31 is advantageously provided with a counterflange which rests on the annular flange 32 and is suitably connected to it, preferably by screws. The motor 1 can be, for example, a flange motor or an EC external rotor motor, on the motor shaft of which the impeller 23, 24 is fixed in a rotationally fixed manner.

The guide vanes 30 are advantageously continuously curved over their width. The curvature is selected in such a way that good efficiency is achieved. In connection with the based on the 1 and 2 described design of the impeller 23, 24 results in a high overall efficiency, with the noise during operation is minimal.

If the vanes 30 are made of sheet metal, they can be manufactured in a cost-effective manner essentially by cutting and rolling.

In order to achieve good cooling of the motor 1, the tube 31 is provided with recesses 33 distributed over its circumference at the level of the annular flange 32.

The impeller 23, 24 is otherwise of the same design as the impeller of the previous embodiment, so that reference can be made to the description relating to this embodiment.

The axial fans described can be manufactured in a wide variety of sizes. For example, the inner diameter of the housing 3 can be in a range from about 200 mm to about 1,800 mm.

If the fan blades 24 preferably consist of the plastic described, there is the possibility of using only a single injection mold for the production of the fan blades 24 for the different sizes of the fan. It is matched to the greatest length of the fan blades 24. If shorter fan blades 24 are required, they are cut to the required length. The same also applies to fan blades 24 which are made of cast metal.

figure 5 shows the two strut parts 4, 5, which are connected to each other via the fastening part 8. The strut parts 4, 5 each have a recess 7. In contrast to the previous embodiments, these recesses have no peripheral edge. Rather, a supporting part 34, 35 is bent out transversely on the edge adjacent to the fastening part 8 are each provided with a recess 7'. The support parts 34 , 35 and the parts of the strut parts 4 , 5 containing the recesses 7 extend at an angle to one another, so that they each enclose an angle with the planar fastening part 8 . The free ends 36, 37 of the support parts 34, 35 are bent in the same direction as the free ends 11 of the strut parts 4, 5. The bend 11, 36, 37 is chosen so that the strut parts 4, 5 and the support parts 34, 35 can be reliably attached to the inner wall of the housing 3 adjacent. In the exemplary embodiment, the bends have two passage openings for fastening screws or the like.

The bends 36, 37 can also point in a different direction than the bends 11 of the strut parts 4, 5.

The recesses 7 'are also by two legs 38, 39; 40,41 converging towards the free end 36,37. The recesses 7' end at a distance both from the fastening part 8 and from the free ends 36, 37.

Similar embodiments that do not have an additional recess 7' are also conceivable.

The support parts 34, 35 are produced in that an approximately U-shaped stamping is made in the strut parts 4, 5 in such a way that the support parts 34, 35 fit into the in figure 5 position shown can be bent out.

According to the invention, the strut parts 4, 5, the fastening part 8 and the support parts 34, 35 are formed in one piece with one another and consist of sheet metal material. As a result, simple and cost-effective production is possible. Due to the additional support elements 34, 35 compared to the previous exemplary embodiments, the stability of the suspension is increased considerably. In addition, an even more secure attachment of the motor 1 to the housing 3 is guaranteed. The strut parts 4, 5, the attachment part 8 and the support parts 34, 35 can be easily assembled and disassembled, for example by means of screws or rivets. These parts do not have to be welded, so that a costly welding process can be saved.

Regarding their size and/or shape and/or position, the recesses 7, 7' can be provided in such a way that the flow resistance for the air is minimal. Since the suspension consists of flat material in the manner described and has the recesses 7, 7', the suspension has only a low weight in spite of the high stability.

6 shows another possibility of designing the suspension. The two strut parts 4, 5 are of the same design as in the previous embodiment. The fastening part 8 has, for example, a bent-out tongue 42 halfway along its length, the free end of which is provided, for example, with a passage opening for a fastening screw or the like. The free end is angled so that it can be mounted at the required location inside the axial fan.

Due to the bent-out tongue 42, the fastening part has a recess 7". As in the previous exemplary embodiments, the two strut parts 4, 5 extend diverging from the fastening part 8 over the same side of the fastening part. The tongue 42 extends obliquely over the other side of the fastener 8.

The Figures 5 and 6 only show exemplary embodiments for the design of the strut parts with the recesses. These exemplary embodiments are not to be understood as limiting.

7 shows schematically that the housing 3 can be connected via a plurality of strut parts 43 to a pot 44 in which the motor 1 is accommodated. The pot 44 is cylindrical and is coaxial with the housing 3. The struts 43 are of identical design and have respectively the recess 7 which is delimited by the legs 12, 13 and which converge radially outwards. The radially outer and the radially inner end 11, 16 are angled in such a way that the strut parts 43 can be attached to the inner wall of the housing 3 and the outer wall of the pot 44. As in the previous exemplary embodiments, the strut parts 43 are arranged on edge.

How 8 shows by way of example, the pot 44 can also be U-shaped. The strut parts 43 are attached to the mutually parallel legs 45, 46 of the pot 44. The strut parts 43 are of the same design as in the embodiment according to FIG 7 . Its radially outer end 11 is fastened to the inside of the housing 3 and its radially inner end 16 is fastened to the outer sides of the legs 45, 46 of the pot 44 facing away from one another. The motor 1 (not shown) is carried by the U-shaped pot 44 .

In addition, the pot 44 can also have an angular outline and—as in the embodiment according to FIG 7 - completely surround the engine.

As can be seen from the Figures 7 and 8 results, the strut parts 43 are advantageously arranged rotationally symmetrically and/or mirror-symmetrically to one another.

9 shows various possible configurations of the cross sections of the legs 12, 13, 38 to 41 of the strut parts 4, 5, 34, 35, 43. The recess 7 can be designed such that the noise development is minimal by bevel cutting and rounding or chamfering the cut edges.

In Figure 9a a rectangular cross-section is shown, as initially results from punching or laser cutting. The cut edges are sharp and the cut faces are approximately perpendicular to the surfaces of the sheet material.

When cross sectioning the Figure 9d all edges are rounded. This can lead to a significant reduction in noise as the sharp edge is broken. It is also possible for only part of the edges of the cross section to be rounded.

In one embodiment with a cross section accordingly Figure 9b an effect similar to that in the embodiment shown in FIG Figure 9d . In the embodiment after Figure 9b the edge is provided with a chamfer.

In the embodiment according to Fig. 9e acoustic and aerodynamic advantages are achieved in that the cut is not made perpendicular to the surface of the flat material, but at an angle to it. The orientation of the cut surface can be better adapted to the direction of flow than with a cut made perpendicular to the surface of the flat material.

In particularly advantageous embodiments according to Figures 9c and 9f the design possibilities of bevel cutting are corresponding Fig. 9e and rounding or adding a chamfer in order to obtain optimal acoustic properties.

In connection with the respective design of the recesses, the cross sections of the legs of the strut and support parts delimiting the recesses can also be optimized in such a way that the flow resistance and the development of noise are minimal. The recesses and the legs can be matched to one another in such a way that, depending on the application of the axial fan, optimally low flow resistance and noise levels can be achieved. In conjunction with the described ratio of width to thickness of the legs of the strut part delimiting the recess and of the respective support part in the range of about 3 to about 15, this results in minimal flow resistance and minimal noise development with optimum strength of the suspension.

As already described, it is advantageously possible to adjust the step angle of the fan blades 24 by providing them on the hub body 23 in a correspondingly adjustable manner.

In addition to this or instead of these adjustable wings, in an advantageous embodiment, different outer diameters can be realized from essentially identical blanks by cutting the blanks to different outer diameters. These blanks can be cast parts that are initially manufactured essentially identically and are adapted to the desired outside diameter in each case.

It is additionally or alternatively possible to realize different outside diameters of the fan blades 24 in that essentially identical individual blade blanks are mounted on hub bodies with different diameters and, if necessary, the outside diameter is trimmed or reworked.

If the fan blades 24 are to be provided with a winglet on the radially outer edge 28, then these can also be manufactured from the blanks. The winglets themselves cannot yet be provided in the tool, since their geometry and their position depend on the outer diameter of the impeller and the stagger angle. It is therefore advantageous not only to cut the wing blanks with a cylinder cut, as described above, but also to give them a special contour, in particular by machining or, in the case of plastics, possibly by thermoforming can be matched to the respective stagger angle. This creates a very high level of flexibility in the design and assembly of the respective fan. Optimum acoustic properties of the blades and thus of the fan can thus be achieved for every outside diameter and stagger angle.

The Figures 10a and 10d show examples of how an individual blank for the fan blade can be designed, viewed in a section approximately perpendicular to the surface of the blade suction or pressure side. In the embodiment after Figure 10a the blank 24 has a rectangular shape with longitudinal sides lying parallel to one another and a narrow side 47 running at right angles thereto. This shape results in particular when the design of the original wing casting tool did not include the design of a winglet.

In the embodiment of a wing blank according to Figure 10d a thickening or an accumulation of material 48 (winglet blank) is already provided in the wing tip area, from which the final winglet, adapted to the actual stagger angle and outer diameter, is later formed. In this exemplary embodiment, the winglet blank 48 has a rectangular cross section, but in principle it can have any desired cross section.

In the Figures 10b and 10c two embodiments of winglets are shown schematically, which are produced by post-processing a blank accordingly Figure 10a have arisen. The embodiment after Figure 10c has a straight contour of the winglet in cross section, in contrast to the embodiment Figure 10b , which has a rounded contour. However, both winglets can be manufactured from the same wing blank. Any other shapes are also conceivable, as long as they are made from a wing blank, such as the blank here Figure 10a , are manufacturable. In particular, the idea is to manufacture winglets optimally adapted to any outside diameter and with any stagger angle in a subsequent work step from a blank. It is also possible to manufacture winglets of different contours from a blank, which are optimally adapted to the respective flow conditions.

In the Figures 10e and 10f are, analogous to the previous description of Figures 10b and 10c , winglets shown in cross-section, made from a blank after Figure 10d were designed. In Fig. 10f is a fan blade with a smaller length (smaller outer diameter) but similar winglet contour as the fan blade Figure 10e implied. Both fan blades can be manufactured from the same blank.

The thickening 48 in the blank after Figure 10d has the advantage that there are more design options for the winglet. In order to achieve these additional design options, however, a thickening 48 is provided from the beginning in the casting tool of the wing.

The shape of the course of the winglet contour in the longitudinal direction of the wing can be arbitrary. It is only decisive that all winglets to be realized are geometrically within the contour of the associated blank according to the outer diameter and stagger angle to be realized. The winglets are attached in an additional work step after casting the blanks.

The described design of the blanks for the fan blade and the winglets is independent of whether the fans are based on the Figures 1 to 9 described suspension or have the special conditions of the fan blade geometries described. By using the blanks, the fan blades (with and without winglet) can be optimally matched to the respective fan, in particular to the respective outer diameter of the impeller and to the stagger angle, so that the optimal design of the respective fan can be easily achieved from the blanks can be.

In addition, it is possible that the wing blanks are already provided with a winglet blank, which can then be optimally adapted to the respective application by appropriate processing. In principle, the winglet shape of the blank can be arbitrary.

Claims (3)

1. An axial fan having a motor (1), to which an impeller (23, 24) is fastened on the rotor side, from the hub (23) of which fan blades (24) protrude, which have a front and a rear edge (26, 27), and having a mounting bracket (2), with which the motor (1) is fastened on a housing (3) and which has strut parts (4 to 6) consisting of flat material and formed by a sheet-metal part, which strut parts connect the motor (1) to the housing (3) and are arranged approximately upright in the flow direction of the air,
   characterized in that the strut parts (4 to 6) are provided over part of their length with at least one recess (7) formed by a punched hole in the flat material, in that the motor (1) and the strut parts (4 to 6) are arranged inside the housing (3), in that the mounting bracket (2) consists of three strut parts (4 to 6) and a fastening part (8), of which two strut parts (4, 5) are constructed mirror-symmetrically to one another and respectively provided with the recess (7) and also merge in one piece via the motor-side fastening part (8), by means of which the two strut parts (4, 5) are fastened on a fastening block (9), which is provided on the outside of the motor (1) and has a flat bearing surface for the fastening part (8), and in that the third strut part (6) is constructed in an approximately U-shaped manner as a support part and has two legs (14, 15) running in a convergent manner in the direction of the housing (3), which legs merge via a short transverse piece (16) into each other which bears against the inner wall of the housing (3) and is fastened to the same, and in that the free ends (18, 19) of the legs (14, 15) are angled outwards oppositely to one another and rest on the fastening part (8).
2. The axial fan according to Claim 1,
   characterized in that at least one support part (34, 35) protrudes from at least one edge of the recess (7), which support part is advantageously constructed in one piece with the strut part (4, 5).
3. The axial fan according to Claim 1 or 2,
   characterized in that the ratio of the width to the thickness of legs (12, 13; 38 to 41) of the strut parts (4, 5) delimiting the recess (7, 7') lies in the range of approximately 3 to 5, preferably 5.

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