EP2904270B1 - Housing for an axial ventilator - Google Patents

Description

The present invention relates to a housing for an axial fan, comprising a wall ring with an inlet nozzle portion and an outflow-connected annular diffuser with an inflow opening and an outflow opening and a holder for an electric motor of the fan, which is arranged in an interior of the housing.

In such known cases, see US 2,144,035 , the diffuser is produced as a sheet metal part, resulting in relatively high production costs, however, and also has the known solution, especially in the middle and lower pressure range relatively poor efficiencies and a high noise level.

The US 5,567,200 discloses an axial fan having a fan wheel, a motor, a housing for the fan wheel, and attachment means for securing the motor to the housing. The housing has an annular wall which is arranged at a certain distance from end regions of the blades of the fan wheel. In addition, the housing has an opening through which the housing can be flowed through with air. The attachment means extend substantially between the annular wall and the fan and are formed so as to support the annular wall on all sides to maintain the distance between the wall and fan.

From the DE 20 2010 016 820 U1 a diffuser for a fan is known, comprising an inlet opening and an outlet opening for a gaseous medium, which flows from the inlet opening in an axial main flow direction enclosed by an outer housing diffuser interior to the outlet opening. In this case, the cross section of the outlet opening is larger than the cross section of the inlet opening and the cross section of the diffuser interior is enlarged, starting from the cross section of the inlet opening to the cross section of the outlet opening, wherein the outer housing forms a diffuser interior on the outside bounding outer diffuser. The cross section of the outer diffuser transitions along the main flow direction from a circular cross section at the inlet opening to a non-circular cross section at the outlet opening. Furthermore is arranged concentrically to the outer diffuser, an inner diffuser, which limits the interior of the diffuser with an inner housing.

US 2012/039731 A1 discloses an axial fan according to the preamble of claim 1.

The present invention is based on the object, on the one hand to achieve a cost reduction and on the other hand to improve the efficiency and noise in the middle and lower pressure range. In addition, the installation should be simplified.

The invention consists of a housing according to claim 1.

This is achieved in that the outer diffuser is formed from at least two partial annular sections, which are connected by means of mechanical connection means on its outer peripheral surface, and the holder of a plurality on one inner peripheral surface of the diffuser with one end attachable, circumferentially spaced, fastened in the edge region of its inflow opening Struts which are mounted with their other end to a motor flange of a motor housing of the electric motor. Advantageously, the outer diffuser is formed from four partial ring sections and four equidistant struts are provided, which are formed in particular from two parallel spokes. In particular, the outer diffuser according to the invention consists of plastic, and the mechanical connection of the individual partial ring sections takes place by means of screws or rivets or by plug connections. Due to the multi-part nature of the outer diffuser, the tool costs are reduced. Furthermore, the outer diffuser expands from its inflow opening to its outflow opening conically with a cone angle α relative to its center axis XX, preferably from 10 ° to 18 °, in particular 12 ° to 15 °. The course of the peripheral wall of the diffuser can be made both straight and curved from the inflow opening to the outflow opening. It is advantageous if the diffuser has a height measured in the direction of the longitudinal axis XX above arranged in the wall ring blades of the axial fan which is greater than / equal to 200 mm to 800 mm, with a ratio of L: D1 of 0.25 to 1.0, preferably 0.25 to 0.8, where L is the height of the outer diffuser measured in the direction of the longitudinal axis XX above the blades arranged in the wall ring and D1 is the diameter of the inflow opening. This advantageous design of the efficiency of the housing according to the invention and the noise is achieved especially in the middle and lower pressure range.

According to the invention, an inner diffuser, which extends from the inflow opening to the outflow opening and has a closed circumferential wall, is arranged within the outer diffuser, preferably centric to its center axis, and which can be connected to the motor flange of the motor housing of the electric motor in the region of the inflow opening , wherein in the interior of the inner diffuser, the motor housing of the electric motor is accommodated. Advantageously, the inner diffuser here has in the connection region for the motor flange a peripheral wall with a circular flow cross-section and forms an annular section which merges into an air duct section having a polygonal, in particular quadrangular, cross section, in particular with rounded corners. This air guiding section has, in particular starting from the annular section, an end facing towards the opposite end, i. H. to the outflow opening, expanding interior space.

The inventive arrangement and design of the inner diffuser prevents a hub backflow and optimizes the efficiency. According to the invention, in an opening plane of the outer diffuser running perpendicular to the longitudinal axis X-X in the region of the outflow opening, a protective grid, in particular circular, is arranged, which is connected with its outer peripheral edge to the outer diffuser. Here, according to the invention, the inner diffuser is also connected to the protective grid, by resting on the protective grid on its side facing in the discharge direction end cover, which is so releasably connected to the Luftleitabschnitt of the inner diffuser fastening means that the protective grid between the end cover and the air guide is included. The protective grid preferably has square meshes. Here is a large mesh size, for example, from 30 mm to a maximum of 40 mm, in square mesh advantage. By supporting the protective grille on the inner diffuser a "walkability" of the housing according to the invention is ensured. Furthermore, a plug connection between the inner diffuser and the motor flange may be provided, whereby the assembly is substantially simplified.

Fig. 1

eine perspektivische Ansicht von oben auf ein erfindungsgemäßes Gehäuse mit darin befindlichem Elektromotor mit montiertem Lüfterrad,

Fig. 2

einen Schnitt entlang der Schnittlinie II-II in Fig. 1,

Fig. 3

eine perspektivische Ansicht von unten auf einen erfindungsgemäßen Außendiffusor mit montiertem Elektromotor und Axiallüfterrad,

Fig. 4

eine Einzelheit bei IV in Fig. 2,

Fig. 5

eine perspektivische Ansicht eines erfindungsgemäßen Innendiffusors ohne Abschlussdeckel,

Fig. 6

eine Teilansicht einer weiteren Ausführungsform eines erfindungsgemäßen Gehäuses,

Fig. 7

eine perspektivische Ansicht eines erfindungsgemäßen Gehäuses mit Tragstern mit Steckverbindung für einen erfindungsgemäßen Innendiffusor vor einer Montage des Außen- und Innendiffusors,

Fig. 8

eine Einzelheit gemäß Fig. 7 bei A,

Fig. 9

eine perspektivische Ansicht eines erfindungsgemäßen Steckverbinders und

Fig. 10

eine Teilansicht gemäß Fig. 8 mit aufgestecktem Innendiffusor.

Advantageous embodiments of the invention are contained in the subclaims and will be explained in more detail with reference to the embodiments illustrated in the accompanying drawings. Show it:

Fig. 1

a perspective view from above of an inventive housing with befindlichem electric motor with mounted fan,

Fig. 2

a section along the section line II-II in Fig. 1 .

Fig. 3

a perspective view from below of an outer diffuser according to the invention with mounted electric motor and axial fan,

Fig. 4

a detail at IV in Fig. 2 .

Fig. 5

a perspective view of an internal diffuser according to the invention without end cap,

Fig. 6

a partial view of another embodiment of a housing according to the invention,

Fig. 7

a perspective view of a housing according to the invention with a star carrier with plug connection for an internal diffuser according to the invention prior to assembly of the outer and inner diffuser,

Fig. 8

a detail according to Fig. 7 at a,

Fig. 9

a perspective view of a connector according to the invention and

Fig. 10

a partial view according to Fig. 8 with attached inner diffuser.

In the Fig. 1 to 10 the same parts or functionally identical parts are always identified by the same reference numerals. If certain described and / or removable from the drawings features of the housing according to the invention or its components are described only in connection with an embodiment, but these are also essential according to the invention regardless of this embodiment as a single feature or in combination with other features of the embodiment and are claimed as belonging to the invention.

As is clear from the Fig. 1, 2 and 3 In particular, there is an inventive housing for an axial fan 1 of a wall ring 2 with an inlet nozzle section 3, which is made in particular of metal. This inlet nozzle section 3 encloses a suction channel 4, which is circular in cross-section. An annular outer diffuser 6 is connected to the wall ring 2 at the free end of the inlet nozzle section 3 and has an in particular circular inflow opening 7 and an in particular circular outflow opening 8. The flow direction of a medium to be transported through the housing by means of the axial fan 1 is indicated by Z. The axial fan 1 consists of an electric motor 9 with which a paddle wheel 11 is drivingly connected. The outer diffuser 6 consists of at least two partial ring sections 12, wherein in the illustrated embodiment, four partial annular sections 12 are shown, which are connected to each other by means of mechanical connection means 13 on an outer peripheral surface of the outer diffuser 6. Each partial ring section 12 extends over a specific peripheral region, so that in the fully assembled state the partial annular sections 12 are connected to form a circumferentially closed annular section. The outer diffuser 6 is advantageously made of plastic and the connecting means 13 may be, for example, screws, rivets or a latching connection. Furthermore, the housing according to the invention has a holder of at least three struts 14, which circumferentially have mutually equal distances. These struts 14 are fastened in the edge region of the inflow opening 7 on the inner peripheral surface of the outer diffuser 6. At its other end, the struts 14 can be fastened to a motor flange 16 of the electric motor 9 or a housing 17 of the electric motor 9. For attachment to the motor flange 16, the struts 14 are suitably connected to each other at the end via an annular flange 14a, wherein the annular flange 14a by means of connecting means, for. B. screws is attached to the motor flange 16. The struts 14 form a supporting star with the annular flange 14a.

In particular Fig. 2 can be seen, the outer diffuser 6 has a height L measured in the direction of the longitudinal axis XX above arranged in the wall ring 2 and the inlet nozzle section 3 blades of the blade wheel 11, which is in particular greater than / equal to 200 mm to 800 mm inclusive. Here is a ratio of L / D1 of preferably 0.25 to 1.0, in particular 0.25 to 0.8, wherein D1 is the diameter of the inflow opening 7 of the outer diffuser 6. The outer diffuser 6 expands from its inflow opening 7 to its outflow opening 8 conically with a relative to its central axis XX cone angle α of in particular 10 ° to 18 °, preferably 12 ° to 15 °.

Furthermore, it is off Fig. 4 to recognize that the outer diffuser 6 has on its outer side in the region of the inflow opening 7 corresponding to the number of struts 14, ie in the present embodiment, four mounting portions 18. These attachment regions 18 are in particular outwardly flared at an angle γ between 90 ° and 90 ° + α and preferably have an angled portion 19 at their free end. This angled portion 19 extends at an angle β to the longitudinal axis XX. This bend 19 abuts against a tab 21, which is formed on the ends of the struts 14 and is also arranged at the angle β to the longitudinal axis XX. The angle β must be ≥ 90 ° + α (α = cone angle). For attachment of the outer diffuser 6 to the struts 14, the bend 19 is bolted to the respective associated tab 21, for example by means of a screw 22. At the same time the wall ring 2 is screwed with a radially projecting annular collar 23 via a screw to the tab 21. As a result of this design of the attachment regions 18, subsequent assembly or disassembly of the complete system without a wall ring is provided Fig. 3 possible without having to remove the items.

How to continue the Fig. 1 to 3 and 5 can be seen, according to the invention inside the outer diffuser 6, an inner diffuser 26 is arranged.

und die Formel $$\mathrm{\Delta }{A}_i=A_{2i}-A_{1i}=\pi \times \left(d_1+k\times L\right)\times \left(k\times L\right)$$

ermittelt wird und die so ermittelte Austrittsfläche A_2i des Luftleitabschnitts 29 sich max. um 20% vom ermittelten Optimalwert unterscheidet, wobei A_1i die Öffnungsfläche des Innendiffusors 26 zu Beginn seines ringförmigen Abschnitts 28 ist, und A_2i die Öffnungsfläche des Innendiffusors an seinem am Schutzgitter 36 angrenzenden Ende. Vorteilhafterweise besitzt der Luftleitabschnitt 29 abgerundete Ecken 32. In diesen Ecken 32 sind Anschlussdome 33 mit Einschraublöchern vorgesehen. Wie aus Fig. 2 ersichtlich ist, ist der Innendiffusor 26 derart bemessen, dass in seinem Innenraum das Motorgehäuse 17 des Elektromotors 9 aufgenommen werden kann. Zum Befestigen des Innendiffusors 26 an dem Motorflansch 16 weist der Innendiffusor 26 an dem dem Motorflansch 16 zugekehrten Ende des ringförmigen Abschnitts 28 vorzugsweise radial nach innen weisende Befestigungslaschen 34 auf. Mit diesen Befestigungslaschen 34 kann der Innendiffusor 26 an dem Motorflansch 16 mittels Befestigungsmitteln befestigt werden. Hierzu sind im Befestigungsflansch Löcher 60 vorgesehen, durch die die Befestigungsmittel hindurch verlaufen. Beidseitig der Löcher 60 sind Versteifungsabschnitte 35 im Winkelbereich zwischen den Befestigungslaschen 34 und dem Innendiffusor 26 angeformt.The arrangement of the inner diffuser 26 is preferably centric to the longitudinal axis XX. The inner diffuser 26 extends from the inflow opening 7 to the outflow opening 8 and has a closed circumferential wall 27. In the region of the inflow opening 7, the inner diffuser 26 can be connected to the motor flange 16 of the motor housing 17. For this purpose, the inner diffuser 26 in the connection region with the motor flange 16 has a circular cross-section, annular portion 28 with the inner diameter d ₁ , in an air duct 29 with a particular square, in particular square cross section with preferably rounded corners passes. As far as the design of the outer diffuser 6 and the inner diffuser 26 is concerned, moreover, it is fully applicable to the WO 2012/084725 A1 Referenced. Starting from the annular section 28, the air guide section 29 has an exit surface A _{2i which} changes in relation to the section 28, wherein the optimum surface change ΔA _{i corresponds} to its entry surface A _1i via an expansion _factor k $$k=\left(\frac{\sqrt{{\left({\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">D</figure-callout>}}_1+2\times L\times \tan \alpha \right)}^2-\left({\mathrm{<figure-callout\; id="1"\; label="D"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">D</figure-callout>}}_1{}^2-{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_1{}^2\right)\times \left(\frac{L}{D_1}-0.45\times {\left(\frac{\mathrm{<figure-callout\; id="1"\; label="L\; D"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">L\; </figure-callout>}}{D_{}}\right)}^2+1\right)}-{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_1}{2\times L}\right)$$

and the formula $$\mathrm{\Delta }{A}_i=A_{2i}-{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">A</figure-callout>}}_{1i}=\pi \times \left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_1+k\times L\right)\times \left(k\times L\right)$$

is determined and the thus determined exit area A _{2i of} the Luftleitabschnitts 29 max. A _{1i is} the opening area of the inner diffuser 26 at the beginning of its annular portion 28, and A _{2i is} the opening area of the inner diffuser at its end adjacent to the protective grille 36. Advantageously, the Luftleitabschnitt 29 has rounded corners 32. In these corners 32 Anschlußdome 33 are provided with screw holes. How out Fig. 2 it can be seen, the inner diffuser 26 is dimensioned such that in its interior, the motor housing 17 of the electric motor 9 can be accommodated. For fastening the inner diffuser 26 to the motor flange 16, the inner diffuser 26 has attachment tabs 34, preferably pointing radially inward, at the end of the annular section 28 facing the motor flange 16. With these fastening tabs 34, the inner diffuser 26 can be attached to the motor flange 16 by means of fastening means. For this purpose, holes 60 are provided in the mounting flange, through which the fastening means extend. On both sides of the holes 60 stiffening portions 35 are formed in the angular range between the mounting tabs 34 and the inner diffuser 26.

Furthermore, the Fig. 1 to 4 It can be seen that, according to the invention, in a plane perpendicular to the longitudinal axis XX opening plane of the discharge opening 8 a, preferably circular, protective grid 36 is arranged, which is connected with its outer peripheral edge 37 with the outer diffuser 6 in the edge region of its discharge opening 8. This can be a screw connection. The protective grid 36 is formed from individual grid wires 38 which are arranged in a crosswise manner so as to form quadrangular, preferably square meshes 39. The mesh size, ie the distance between the parallel running grid wires 38 is 30 mm to a maximum of 40 mm. The outer diffuser 6 has, in its peripheral region encompassing the discharge opening 8, recesses 41 which are adapted to the contour of the grid wires 38, so that the grid wires 38 are received in these recesses 41. The protective grid 36 has radially inwardly projecting fastening tabs which cooperate with fastening projections 42 formed on the inside of the outer diffuser 6 and are connected to the outer diffuser 6 by means of screws which are screwed into the fastening projections 42.

Furthermore, it can be seen that the inner diffuser 26 according to the invention has a cover cover 43 which rests on the protective grid 36 on its outflow-facing side and with the air duct 29 via fasteners, such as screws, so releasably connected, that the protective grid 36 between the end cap 43 and the air guide 29 is included. To fasten the end cover 43 by means of screws, the connection domes 33 serve in the corners 32 of the inner diffuser 26, in which the screws are screwed through the end cover 43 into the connection domes 33. For receiving the protective grid 36 with its grid wires 38 in the edge region of the air guide section 29, this invention also has recesses 44 which are adapted to the shape and size of the grid wires 38.

Furthermore, it can be seen that the inner diffuser 26 in the region of its annular portion 28, in particular in the diffuser interior protruding bulges 46 has. By the channels formed by the bulges 46 extend the spokes of the struts 14 in the assembled state, so that the outer wall portion of the Innenendiffusors 26 is not interrupted by the struts 14, but also forms a closed wall surface in this area.

A diffuser unit according to the invention consisting of the outer diffuser 6 and the inner diffuser 26 including the protective grid 36 and the end cover 13 may expediently in its preassembled state with the fan unit consisting of fan 1, the wall ring 2 and the supporting star formed from the struts 14 and the annular flange 14a be connected by plugging and screwing. The screwing is done appropriately as to Fig. 4 described, wherein the outer diffuser 6 z. B. is screwed with eight screws 22. The plug connection takes place between the inner diffuser 26 and the supporting star in the region of the annular flange 14a. For this it is advantageous, see Fig. 7 to 10 when the connector is formed of a plurality of latching connectors 50 which are fastened to the annular flange 14a, with which in particular a non-positive or kraftformschlüssige connection between the annular flange 14a and the inner diffuser 26 is made. These latching connectors 50 are preferably formed as snap hooks, see Fig. 9 , These snap hooks comprise a cylindrical attachment portion 51, which preferably has an external thread 52, with which it is screwed into a threaded bore in the annular flange 14a. The attachment portion 51 has a central longitudinal axis XX. In the axial direction of the longitudinal axis XX, a latching section 53 adjoins the attachment section 51. Between the fastening portion 51 and the latching portion 53, a plate-shaped stopper portion 54 is provided in particular, which delimits the screw-in path of the fastening portion 51. The latching portion 53 comprises a central shaft 55 which terminates in particular in a frusto-conical tip 56, wherein the tip 56 forms the smaller frusto-conical surface with its end face. In the transition region between the tip 56 and the shaft 55 z. B. two opposing spring-elastic locking arms 57 formed. These latching arms 57 extend in the axial direction of the longitudinal axis XX on the attachment portion 51 and extend obliquely to the longitudinal axis XX that they form an angle δ of 36 ° ± 3 ° together in a plane passing through the longitudinal axis XX, vertical plane. At their free ends, the latching arms 57 each have an angle section 58 on the end, which is angled relative to the latching arms 57 in such a way that it towards the longitudinal axis XX extends. Here, a radial distance A between the ends of the latching arms 57 is greater than a radial distance B between the ends of the angle sections 58. The latching connector 50 is preferably made as a plastic molding. The abutment portion 54 has circumferentially advantageously two opposing flats 59, which can serve as a key surfaces for a wrench. Preferably, four latching connectors 50 are respectively screwed offset at 90 ° to each other on the annular flange 14a. In Fig. 8 is the screwed state of a latch connector 50 to recognize. In Fig. 10 the mounting position of an inner diffuser 26 of the diffuser unit is shown in detail, wherein in particular the locking connection between the inner diffuser 26 and the latch connector 50 can be seen. The inner diffuser 26 has for this purpose in its fastening tabs 34, the holes 60, the diameter of which is matched with the radial distances A and B of the resilient latching arms 57 that the latching arms 50 are pressed radially through the respective hole 60 when pushing through the latching connector 50 and spring back after completion of the insertion and engage behind in this position, the edge region of the holes 60. With the existing at their ends angle portions 58 they lie with their outer surfaces on the inner edge of the holes 60 under pretension. The angle sections 58 have here such an inclination to the longitudinal axis XX that self-locking is given, so that the locking arms 57 can not be moved due to occurring force in the case of operation from the mounting detent position. A release is possible only by a manual compression of the latching arms 57. Tolerance deviations between the components can be compensated for by means of the angular sections 58, which bear against the inner edge of the respective hole 60 with prestress in the assembly position. In addition, a centering of the diffuser unit according to the invention during assembly via the existing on the shaft 55 locking arms 57. The axial height of the plate-shaped stop portion 54 is less than the depth of the respective hole 60 in the mounting tabs 34 of the inner diffuser 26th

In Fig. 6 a further embodiment of a housing according to the invention is shown in partial view. In this case, the wall ring 2 protrudes with its inlet nozzle section 3 into the outer diffuser 6 through its inflow opening 7, so that an overlapping area is present between the inlet nozzle section 3 and the outer diffuser 6 in the region of its adjacent to the inflow opening 7 section. As a result, an axial gap 47 is formed between these two parts, can enter through the air from the outside into the interior of the outer diffuser 6. As a result of the overlap or overlap, the air entering through the axial gap 47 flows parallel to the air conveyed in the diffuser interior, so that there is no flow running transversely to the conveyed air, which could result in disturbing turbulences.

As in particular from Fig. 3 can be seen, the inventive design of the housing allows that the outer diffuser 6, the inner diffuser 26, the protective grid 36 and the struts 14 can be prefabricated with the consisting of electric motor 9 and paddle wheel 11 axial fan 1 as a unit. This unit can then be fixed on site with an already preassembled wall ring 2.

The invention is not limited to the illustrated and described embodiments, but the scope of protection is determined by the following claims.

Claims (13)

1. A housing for an axial ventilator (1), consisting of a wall ring (2) with an inlet nozzle section (3) and an annular outside diffusor (6) connected to the wall ring (2) on the outlet side and having an inlet opening (7) and an outlet opening (8) as well as a holder for an electric motor (9) of the ventilator (1), which is situated in the interior of the housing, wherein the holder consists of a plurality of struts (14) that can be attached at the edge of the inlet opening (7) of said holder to an interior circumferential surface of the outside diffusor (6), said struts being fastened thereto at one end and spaced at distances from one another circumferentially, and the other end of said struts can be mounted onto a motor flange (16) of a motor housing (17) of the electric motor (9), and wherein the outside diffusor (6) widens conically from its inlet opening (7) to its outlet opening (8) with a cone angle (α) in relation to its central longitudinal axis (X-X),
   wherein
   situated in the outside diffusor (6) is an inner diffusor (26) that extends from the inlet opening (7) to the outlet opening (8) and which has a closed circumferential wall (27) and which can be connected to the motor flange (16) of the motor housing (17) in the surface of the inlet opening (7), wherein the motor housing (17) of the electric motor (9) can be placed in the interior of the inner diffusor (26), and wherein
   a protective grating (36) is affixed in an opening plane of the outlet opening (8) that extends perpendicular to the longitudinal axis (X-X), which protective grating is connected at its external circumferential edge (37) to the outside diffusor (6), wherein the outside diffusor (6) in its circumferential wall in the surface of the outlet opening (8) has recesses (41) for the insertion of grating wires (38) of the protective grating (36),
   characterized in that the outside diffusor (6) is formed by at least two partial ring segments (12) that are connected by mechanical connection means (13) at the external circumferential surface of the outside diffusor, wherein
   wall areas (31) of the inner diffusor (26) have at the edge of their free ends recesses (44) for the insertion of the grating wires (38), and the inner diffusor (26) has an end cover (43) which is supported on the protective grating (36) on its side facing in the outlet direction and which is fastened to an air guiding section (29) via fastening devices so that the protective grating (36) is enclosed between the end cover (43) and the air guiding section (29), wherein
   the inner diffusor (26) can be connected via a plug connection (50, 60) to the motor flange (16)
   wherein preferentially
   the plug connection is formed by a plurality of snap-in connectors (50) which are attached to a ring flange (14a) that connects the struts (14) at their ends,
   wherein
   the snap-in connectors (50) each consist of a snap-in hook.
2. The housing of claim 1,
   characterized in that the outside diffusor (6) is formed by four partial ring segments (12).
3. The housing of claim 1 or 2,
   characterized in that four struts (14) at a distance to another are present which in particular each consist of two parallel spokes.
4. The housing of any one of the claims 1 through 3,
   characterized in that the outside diffusor (6) opens conically from the in cross-section circular inlet opening (7) to the in cross-section circular outlet opening (8) at a cone angle (α) of between 10° to 18°, especially 12° to 15°, in relation to its central longitudinal axis (X-X).
5. The housing of any one of the claims 1 through 4,
   characterized in that the outside diffusor (6) is made from plastic.
6. The housing of any one of the claims 1 through 5,
   characterized in that the outside diffusor (6) has a height (L) measured in the direction of the longitudinal axis (X-X) above the paddles of the paddle wheel (11) of the axial ventilator (1) arranged in the wall ring (2), which is larger/equal to 200 mm up to 800 mm inclusively, with a ratio L/D1 of 0.25 to 1.0, preferentially 0.25 to 0.8, wherein D1 is the diameter of the inlet opening (7).
7. The housing of any one of the claims 1 through 6,
   characterized in that the circumferential wall (27) in the connection surface for the motor flange (16) has an, in cross-section, circular, ring-shaped section (28) that transitions into the air guiding section (29) with an in
   particular rectangular cross section, wherein its edges (32) are preferentially rounded, wherein preferentially
   the air guiding section (29), starting at the ring-shaped section (28), has an outlet surface (A_2i) that changes towards the opposite end, wherein the ideal surface change (ΔA_i) in relation to its inlet surface (A_1i) is determined using an expansion factor (k) with $$k=\left(\frac{\sqrt{{\left(D_1+2\times L\times \tan \alpha \right)}^2-\left(D_1{}^2-d_1{}^2\right)\times \left(\frac{L}{D_1}-\mathrm{0,45}\times {\left(\frac{L}{D_1}\right)}^2+1\right)}-d_1}{2\times L}\right)$$

   

   and the formula $${\mathrm{\Delta A}}_{\mathrm{i}}={\mathrm{A}}_{2\mathrm{i}}-{\mathrm{A}}_{1\mathrm{i}}=\mathrm{\pi }\times \left({\mathrm{d}}_1+\mathrm{k}\times \mathrm{L}\right)\times \left(\mathrm{k}\times \mathrm{L}\right)$$

   

   and wherein the outlet surface (A_2i) of the air guiding section (29) so determined differs by at most 20 % from the determine ideal value, wherein (A_1i) is the outlet surface of the inner diffusor (26) at the start of its section (28), and (A_2i) is the outlet surface of the inner diffusor (26) at its end adjacent to the protective grating (36).
8. The housing of any one of the claims 1 through 7,
   characterized in that the wall ring (2), the outside diffusor (6) and the struts (14) can be fastened using fastening devices (18, 19, 21, 22, 23), wherein preferentially
   the wall ring (2) and the outside diffusor (6) have respective radially orientated contact surfaces (19, 21) corresponding to the circumference which are touching each other in the fastened state and which are fastened to each other with fastening devices (22) running in the direction of the longitudinal axis (X-X) and which are fastened to the struts (14).
9. The housing of any one of the claims 1 through 8,
   characterized in that the wall ring (2) with its inlet nozzle section (3) projects in the outside diffusor (6) through its inlet opening (7) so that in an overlap surface an axial gap (47) in the direction of the central longitudinal axis (X-X) is created, wherein preferentially
   the struts (14) fasten the outside diffusor (6) and the wall ring (2) to the motor housing (17) with fastening devices running radially to the longitudinal axis (X-X), wherein preferentially
   the outside diffusor (6) has a plurality of fastening surfaces (18) that are widened towards the exterior and which have at their free ends an angular deflection (19), wherein the angle (β) of the angular deflection (19) is ≥ 90° + α, with α = cone angle of the outside diffusor (6).
10. The housing of claim 1,
    characterized in that the snap-in hook has a fastening surface (51) for fastening to the ring flange (14a) and a lock surface (53) in axial direction from said ring flange (14a), wherein preferentially the fastening surface (51) has the form of an external thread surface with circumferential external thread (52), and/or wherein preferentially a contact surface (54) is between the fastening surface (51) and the lock surface (53).
11. The housing of claim 10,
    characterized in that the lock surface (53) consists of a shaft (55) to which are attached at least two radially elastic connectors (57) with circumferential distance to another and running along the longitudinal axis (X-X) of the snap-fit connector (50) and said radially elastic connectors (57) run from a tip (56) of the shaft (55) in the direction of the fastening surface (51) and which together enclose an angle (δ) of 36° ± 3° and which preferentially have at their ends in the direction of the longitudinal axis (X-X) angled deflections (58), wherein preferentially
    the tip (56) has the shape of a truncated cone wherein the smaller truncated cone surface is located at the free end of the tip (56).
12. The housing of claim 11,
    characterized in that the interior diffusor (26) has holes (60) in fastening clips (34) the diameter of which is so adjusted to the radial spaces (A, B) of the spring arms that the connector arms (57) when inserting the snap-fit connector (50) are radially compressed and spring back again after termination of the insertion process and that in this position the fastening clips (34) engage at the edge of the holes (60) and with the pretension of the angled deflections (58) fit to the edge created by the holes (60), wherein preferentially
    the angled deflections (58) have such an angle towards the longitudinal axis (X-X) that a self-locking effect occurs in case of contact with the edge of the holes (60).
13. The housing of claim 12,
    characterized in that the snap-fit connector (50) is made as plastic-molded part.

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