Protective cover for motor-electric board for a radial fan

Abstract

A protective cover (2) for a radial fan (1) comprises a bowl-shaped body (20) forming a bottom wall (21) on an outer side (22) of the protective cover (2) intended to face away from the impeller housing (3), and a peripheral wall (23) extending from the bottom wall (21) towards an inner side (24) of the protective cover (2) and delimiting together with the bottom wall (21) a motor space (47) for accommodating an electric motor (11) and an electric control board (19) of the fan, a first connection edge (25) formed by the peripheral wall (23) and intended to face and / or rest from the outside against an impeller housing of the fan. The body (20) is made in several parts and comprises a first closed-loop half-body (30) forming at least a part of the peripheral wall (23) with the first connection edge (25) and with a second connection edge (31) opposite the first connection edge (25) and facing the outer side (22), and a second half-body (32) forming the bottom wall (21) with a third connection edge (33) facing the inner side (24) and complementary to the second connection edge (31).

Description

[0001] The subject of the present invention is a protective cover for wrapping and protecting an electric motor and an electric control board of a radial fan, for example a fan for conveying and / or pre-mixing a gas-air mixture in a gas boiler or water heater.

[0002] Known radial fans comprise an impeller arranged rotatably inside a volute, that is to say a housing of substantially toroidal shape having a first side wall, a second side wall opposite the first side wall, and a peripheral wall. In the first side wall an inlet opening is formed in a radially inner position (with respect to a rotation axis of the fan), but not necessarily central, of the housing. In the peripheral wall a tangential portion is formed with an outlet opening.

[0003] The impeller can be driven in rotation by an electric motor arranged outside the housing and connected to the second side wall opposite the inlet opening. A motor shaft extends from the rotor of the motor through a passage opening of the second side wall into the inside of the housing where it is connected, in rotationally fixed manner, to the impeller.

[0004] The electric motor comprises its own motor support with a stator seat that accommodates the stator of the motor, and with one or more bearings for supporting the motor shaft and the rotor of the motor. The motor support is screwed from the outside to the second side wall of the housing. To reduce the noise of the fan, dampers are provided between the motor support and the impeller housing, for example elastomeric bushings.

[0005] An electric control board of the electric motor is fixed, for example via screws, to the motor support, again externally to the fan housing.

[0006] The electric motor and the electric control board are in turn covered by a so-called protective cover, often called motor-board protection, cup-shaped with a peripheral wall and a bottom wall, made in one piece, positioned above and around the electric motor and the electric control board and screwed to the motor support. In this way the electric motor and the electric control board are protected from impacts and the external environment is protected from moving parts of the motor and from electrical components of the electric control board. The protective cover is known to be a single body of injection-moulded plastic material and comprises holes to receive connection screws and ventilation grilles to allow an airflow for cooling the motor and the electric control board.

[0007] Fans of the known art have vibration and noise problems, in particular of the protective cover, whose lower portion (peripheral wall) adjacent to the impeller housing exhibits oscillations of high amplitude that not only cause noise but may strike the electric control board and damage it.

[0008] Figures 22 and 23 show a protective cover of the known art deformed (with deformation amplitude enlarged to make it more visible) according to two different vibration modes. Figure 21 shows an example of position and shape of an electric control board, from which the skilled person may appreciate the risk of impact between a protective cover of the known art and the electric control board.

[0009] The object of the present invention is therefore to improve the protective cover and the radial fan so as to overcome the drawbacks of the known art, and more precisely to reduce the oscillation amplitudes of the protective cover and the risk of impacts between the protective cover and the electric control board, preferably without increasing the overall dimensions of the fan.

[0010] This object is achieved by means of a protective cover for a radial fan according to claim 1 and by means of a radial fan according to claim 13. The dependent claims relate to preferred and advantageous embodiments.

[0011] Thanks to a configuration of the protective cover in several parts connected to each other by tightening in discrete zones and by abutment with (friction) contact along continuous segments, it is possible to modify the vibration modes of the protective cover, with respect to the known art (see for example Figures 24 and 25 illustrating vibration deformation states according to two modes of the protective cover at two different frequencies), and consequently reduce the oscillation amplitude of the peripheral wall of the protective cover. This reduces the noise of the fan and the risk of damage to the electric control board due to vibrational impacts between the protective cover and the electric control board.Brief description of the figures

[0012] To better understand the invention and appreciate its advantages, some embodiments will be described below, with reference to the figures, in which: Figures 1 and 2 are perspective views of a radial fan according to an embodiment of the invention; Figure 3 is a rear view of the fan of Figure 1; Figure 4 is a sectional view according to the section plane IV-IV in Figure 3; Figure 5 is a sectional view according to a plane V-V in Figure 3; Figure 6 is an enlarged view of detail VI in Figure 4; Figure 7 is an enlarged view of detail VII in Figure 4; Figures 8 and 9 are sectional views of further details of the fan in Figure 1; Figure 10 is an enlarged view of detail X in Figure 5; Figure 11 is an exploded view of a radial fan with a protective cover according to an embodiment of the invention; Figure 12 shows a detail of a radial fan and of a protective cover, partially in section, according to an embodiment; Figures 13 and 14 are sectional views of details of the protective cover according to embodiments; Figure 15 is a perspective view of a first half-body of the protective cover according to an embodiment; Figures 16 and 17 are perspective views of a second half-body of the protective cover according to an embodiment; Figures 18, 19, 20 are side views, partially in section, of the second half-body of the protective cover according to embodiments; Figure 21 shows a radial fan with the electric motor, the electric control board and the development of a contour wall of the protective cover around the electric motor and the electric control board; Figures 22 and 23 show deformation states (with deformation amplitude enlarged) of a protective cover according to the known art in two different vibration modes Figures 24 and 25 show deformation states (with deformation amplitude enlarged) of a protective cover according to an embodiment in two different vibration modes. Description of embodiments

[0013] A radial fan 1 comprises: - - an impeller housing 3 with a first side wall 4, a second side wall 5 opposite the first side wall 4 and a peripheral wall 6 which together delimit a conveying space 7, in which the first side wall 4 forms an inlet opening 8 and the peripheral wall 6 forms an outlet opening 9; an impeller 10 arranged inside the conveying space 7; an electric motor 11 arranged outside the conveying space 7 and fixed from the outside to the second side wall 5 of the impeller housing 3; an electric control board 19 of the electric motor 11, arranged outside the conveying space 7 and fixed from the outside to the second side wall 5 of the impeller housing 3 or to the electric motor 11. -- A protective cover 2 positioned around the electric motor 11 and the electric control board 19 and fixed from the outside to the second side wall 5 of the impeller housing 3.

[0014] The electric motor 11 may comprise a motor support 12 forming a stator seat 13 in which a stator 14 of the motor 11 is arranged and locked, and a rotor seat 15 for the rotatable support of a rotor 16 of the motor 11 and of a motor shaft 17. The motor support 12 may be screwed from the outside to the second side wall 5 of the impeller housing 3. To reduce the noise of the fan 1, dampers 18 may be provided between the motor support 12 and the impeller housing 3, for example elastomeric bushings.

[0015] The impeller 3 can be driven in rotation by the electric motor 11. The motor shaft 17 extends from the rotor 16 through a passage opening of the second side wall 5 into the inside of the impeller housing 3 where it is connected, in rotationally fixed manner, to the impeller 10.

[0016] According to one aspect, the invention relates to a protective cover 2 per se suitable for the construction of a radial fan 1 of the type described above or similar.

[0017] The protective cover 2 comprises a bowl-shaped or cup-shaped body 20 made of polymer material forming: a bottom wall 21 on an outer side 22 of the protective cover 2 (intended to be) facing away from the impeller housing 3, and a peripheral wall 23 extending from the bottom wall 21 towards an inner side 24 of the protective cover 2 (intended to be) facing the impeller housing 3, and delimiting together with the bottom wall 21 a motor space 47 for accommodating the electric motor 11 and the electric control board 19, a first connection edge 25 formed by the peripheral wall 23 and (intended to be) facing and / or resting from the outside against the second side wall 5 of the impeller housing 3, optionally, at least a first ventilation grille 26 facing a first ventilation direction and at least a second ventilation grille 27 spaced from the first ventilation grille 26 and facing a second ventilation direction different from the first ventilation direction, a plurality of first screw seats 28 formed at least in the peripheral wall 23 and open towards the inner side 24 at the first connection edge 25.

[0018] The protective cover 2 further comprises a plurality of connection screws 29 accommodated in the first screw seats 28 for a screw connection of the protective cover 2 with the second side wall 5 of the impeller housing 3.

[0019] The body 20 is made in several parts and comprises: a first closed-loop (non-circular) half-body 30 forming at least a part of (or all of) the peripheral wall 23 with the first connection edge 25 and with a second connection edge 31 opposite the first connection edge 25 and facing the outer side 22, and a second half-body 32 forming the bottom wall 21 with a third connection edge 33 facing the inner side 24 and complementary to the second connection edge 31, second connection portions 34 formed in the first half-body 30 at the second connection edge 31 and corresponding third connection portions 35 formed in the second half-body 32 at the third connection edge 33 for a connection (by direct engagement and / or by additional members, for example the connection screws 29) of the first half-body 30 with the second half-body 32 along the second and third connection edges 31, 33.

[0020] Advantageously, the connection along the second and third connection edges 31, 33 forms discrete and concentrated tightening zones at the third connection portions 35 and abutment segments with continuous (friction) contact extending along the second and third connection edges 31, 33.

[0021] This configuration according to the invention modifies the vibration modes of the protective cover 2 (see for example Figures 24 and 25 illustrating vibration deformation states according to two modes of the protective cover at two different frequencies) and consequently reduces the oscillation amplitude of the peripheral wall 23 with the effect of reducing the noise of the fan 1 on which the protective cover 2 is mounted, and the risk of damage to the electric control board 19 due to vibrational impacts between the protective cover 2 and the electric control board 19.

[0022] According to a further aspect, the invention also relates to a complete radial fan 1 equipped with the protective cover 2.

[0023] The first half-body 30 and / or the second half-body 32 may be made by injection moulding, for example in polyamide, e.g. PA6 or PA66, fibre-reinforced, for example glass fibres.

[0024] The first screw seats 28 may be formed only in the first half-body 30 at the peripheral wall 23 only, such that the connection screws 29 accommodated in the first screw seats can tighten or lock only the first half-body 30 to the impeller housing 3, at first discrete connection positions 36, but not also the second half-body 32.

[0025] The first screw seats 28 may comprise one or more, preferably two, screw seats formed in portions of the peripheral wall 23 projecting towards the exterior of the body 20, as well as one or more, preferably two, screw seats formed in portions of the peripheral wall 23 projecting towards the interior of the motor space 47, as clearly shown in Figure 11. Arranging the first screw seats 28 partly externally and partly internally to the peripheral wall 23 influences the fastening constraints and therefore the natural frequencies and the vibration modes of the body 20, but also makes it possible to make versatile use of the available assembly space and not to interfere with the space for fastening and damping the motor 11 with respect to the impeller housing 3.

[0026] The first connection edge 25 may form a flange 37 or a wall portion oriented at an angle, towards the inside or towards the outside of the motor space 47, advantageously orthogonal to a rotation axis of the fan 1 or parallel to the second side wall 5, with the effect of stiffening the first connection edge 25 against lateral deformations and oscillations and increasing a contact or sealing interface with the impeller housing 3.

[0027] The second connection portions 34 comprise a plurality of, preferably two, second screw seats 38 and the third connection portions 35 comprise a plurality of, preferably two, third screw seats 39 aligned with the second screw seats 38 at second discrete connection positions 40, in which long connection screws 29 are inserted respectively into a pair of second screw seat 38 and third screw seat 39 and screwable into the second side wall 5 to pass through and tighten or lock both the first half-body 30 and the second half-body 32 to the impeller housing 3. This creates, at the second discrete connection positions 40, regions of greater stiffness also due to the extension of the long connection screws 29 passing through all three components 30, 32, 3.

[0028] Advantageously, the second discrete connection positions 40 are formed at diametrically opposite portions of the peripheral wall 23.

[0029] The second connection edge 31 and the third connection edge 33 form complementary steps 41, parallel to the extension direction of the second connection edge 31 and the third connection edge 33, and mutually engaged to create a constraint against lateral misalignment between the two half-bodies 30, 32 and to prevent vibrations in this interface region.

[0030] The third connection portions 35 comprise a plurality of, for example five, coupling brackets 42 protruding beyond the third connection edge 33 towards the inner side 24 such as to be positioned outside the motor space 47 next to the peripheral wall 23 and the second connection edge 31 formed by the first half-body 30. This embrace from outside of the second connection edge 31 prevents an undesired outward widening of the peripheral wall 23.

[0031] The second connection portions 34 comprise a plurality of, for example five, counter-coupling teeth 43 shaped for engagement, for example snap-fit or stop engagement, with the coupling brackets 42 at third discrete connection positions 44, without screws, where the first half-body 30 and the second half-body 32 are locally locked together. This creates, at the third discrete connection positions 44, regions of increased connection constraint locally limited to the second connection edge 31 and the third connection edge 33.

[0032] An inversion of the position of the coupling brackets 42 and the counter-coupling teeth 43 is not desirable, as it would not function to prevent an outward widening of the peripheral wall 23.

[0033] In order to prevent a vibration or local deformation of the second connection edge 31 towards the inside of the motor space 47 and to obtain a further localized stiffening, for example (but not only) at the third discrete connection positions 44, an inner surface of the second half-body 32 forms ribs 45 protruding beyond the third connection edge 33 so as to support the second connection edge 31 from inside the motor space 47.

[0034] Advantageously, at least some of the ribs 45 are formed at the third discrete connection positions 44 ( Figures 13, 15) in opposition to the coupling brackets 42, such that the coupling brackets 42 and the ribs 45 locally embrace the second connection edge 31 from two opposite sides.

[0035] The body 20 delimits at least one, preferably three, cable-pass windows 46 for the passage of cables and / or access from the outside to contacts of the electric control board 19 inside the motor space 47, for example a cable-pass window for cables or contacts of electronic control signals and a cable-pass window for cables or contacts of the power supply of the electric motor 11. The cable-pass windows 46 are preferably formed as interruption cavities of one or two of the first, second and third connection edges 25, 31 and 33. This facilitates manufacturing by injection moulding.

[0036] The impeller housing 3 may be formed in a known manner in aluminium or aluminium alloy.

[0037] The use in the present description, and in the claims, of numerical adjectives such as "first", "second", "third" in combination with nouns, such as "portion", "seat", "direction", etc., has the main purpose of giving different names to mutually distinct features, in order not to create confusion between features, and is not necessarily an indication of quantity or order. For example, the citation in the description or in the claims of a "second portion" does not imply the necessary presence of a "first portion" if not expressly indicated.

[0038] Furthermore, in order to describe the embodiments complete with all their features, with the aim of enabling the skilled person to readily implement the teaching, essential features of the invention have sometimes been described or listed (for example in the same sentence) together with other features not necessarily essential to achieve the technical effect of the invention and / or to define its protective scope, which is instead defined by the claims.Legend of reference signs in the figures

[0039] radial fan 1 protective cover 2 impeller housing 3 first side wall 4 second side wall 5 peripheral wall 6 conveying space 7 inlet opening 8 outlet opening 9 impeller 10 electric motor 11 motor support 12 stator seat 13 stator 14 rotor seat 15 rotor 16 motor shaft 17 dampers 18 electric control board 19 body 20 bottom wall 21 outer side 22 peripheral wall 23 inner side 24 first connection edge 25 first ventilation grille 26 second ventilation grille 27 first screw seats 28 connection screws 29 first half-body 30 second connection edge 31 second half-body 32 third connection edge 33 second connection portions 34 third connection portions 35 first discrete connection positions 36 flange 37 second screw seats 38 third screw seats 39 second discrete connection positions 40 complementary steps 41 coupling brackets 42 counter-coupling teeth 43 third discrete connection positions 44 ribs 45 cable-pass window 46 motor space 47

Claims

1. A protective cover (2) for a radial fan (1), wherein the radial fan (1) is of the type comprising: - an impeller housing (3) having a first side wall (4), a second side wall (5) opposite to the first side wall (4), and a peripheral wall (6) delimiting together a conveying space (7), wherein the first side wall (4) forms an inlet opening (8) and the peripheral wall (6) forms an outlet opening (9); - an impeller (10) accommodated in the conveying space (7); - an electric motor (11) arranged outside the conveying space (7) and fixed from the outside to the second side wall (5); - an electric control board (19) of the electric motor (11), arranged outside the conveying space (7) and fixed to the second side wall (5) or to the electric motor (11), - a protective cover (2) positioned around the electric motor (11) and the electric control board (19) and fixed from the outside to the second side wall (5), wherein the protective cover (2) comprises a bowl-shaped body (20) forming: - a bottom wall (21) on an outer side (22) of the protective cover (2) intended to face away from the impeller housing (3), and - a peripheral wall (23) extending from the bottom wall (21) towards an inner side (24) of the protective cover (2) intended to face the impeller housing (3) and delimiting, together with the bottom wall (21), a motor space (47) for accommodating the electric motor (11) and the electric control board (19), - a first connection edge (25) formed by the peripheral wall (23) and intended to face and / or be supported, from the outside, against the second side wall (5), - a first ventilation grille (26) facing a first ventilation direction and a second ventilation grille (27) spaced apart from the first ventilation grille (26) and facing a second ventilation direction different from the first ventilation direction, characterized in that the body (20) consists of several parts and comprises: - a first closed-loop half-body (30) forming at least a part of the peripheral wall (23) with the first connection edge (25) and a second connection edge (31) opposite to the first connection edge (25) and facing the outer side (22), and - a second half-body (32) forming the bottom wall (21) with a third connection edge (33) facing the inner side (24) and complementary to the second connection edge (31).

2. A protective cover (2) according to claim 1, comprising: - a plurality of first screw seats (28), formed in the peripheral wall (23) and open towards the inner side (24) at the first connection edge (25), and a plurality of connection screws (29) accommodated in the first screw seats (28) for a screw connection of the protective cover (2) to the second side wall (5), - second connection portions (34) formed in the first half-body (30) at the second connection edge (31) and corresponding third connection portions (35) formed in the second half-body (32) at the third connection edge (33) for connecting the first half-body (30) to the second half-body (32) along the second and third connection edges (31, 33), wherein the connection along the second and third connection edges (31, 33) forms discrete and concentrated tightening zones at the third connection portions (35) and continuous contact abutment segments extending along the second and third connection edges (31, 33).

3. A protective cover (2) according to claim 2, wherein the first screw seats (28) are only formed in the first half-body (30) at the peripheral wall (23) only, so that the connection screws (29) arranged in the first connection seats can lock only the first half-body (30) to the impeller housing (3), at first discrete connection positions (36), but not also the second half-body (32).

4. A protective cover (2) according to claim 3, wherein the first screw seats (28) comprise screw seats formed in portions of the peripheral wall (23) projecting towards the exterior of the motor space (47) and screw seats formed in portions of the peripheral wall (23) projecting towards the interior of the motor space (47),5. A protective cover (2) according to any one of the preceding claims, wherein the first connection edge (25) forms a flange (37) or is bent at an angle.

6. A protective cover (2) according to any one of claims 2 to 4, wherein the second connection portions (34) comprise second screw seats (38) and the third connection portions (35) comprise third screw seats (39) aligned with the second screw seats (38) at second discrete connection positions (40), wherein long connection screws (29) are inserted into a pair of second screw seat (38) and third screw seat (39), respectively, and are screwable into the second side wall (5) to lock both the first (30) and second (32) half-bodies to the impeller housing (3).

7. A protective cover (2) according to claim 6, wherein the second discrete connection positions (40) are formed at diametrically opposite portions of the peripheral wall (23).

8. A protective cover (2) according to any one of the preceding claims, wherein the second connection edge (31) and the third connection edge (33) form complementary steps (41) mutually engaged and parallel to the extension direction of the second connection edge (31) and the third connection edge (33).

9. A protective cover (2) according to any one of claims 2, 3, 4, 6, 7, wherein the third connection portions (35) comprise coupling brackets (42) protruding beyond the third connection edge (33) towards the inner side (24) and positioned outside the motor space (47) next to the peripheral wall (23) and the second connection edge (31) formed by the first half-body (30), wherein the second connection portions (34) comprise counter-coupling teeth (43) shaped for the engagement with the coupling brackets (42) at third discrete connection positions (44) wherein the first half-body (30) and the second half-body (32) are locally locked together.

10. A protective cover (2) according to any one of the preceding claims, wherein an inner surface of the second half-body (32) forms ribs (45) protruding beyond the third connection edge (33) so as to support the second connection edge (31) from inside the motor space (47).

11. A protective cover (2) according to claims 9 and 10, wherein at least some of the ribs (45) are formed at the third discrete connection positions (44) in opposition to the coupling brackets (42), so that the coupling brackets (42) and the ribs (45) locally embrace the second connection edge (31) from two opposite sides.

12. A radial fan (1) comprising a protective cover (2) according to any one of the preceding claims.

13. A radial fan (1) comprising: - an impeller housing (3) having a first side wall (4), a second side wall (5) opposite to the first side wall (4), and a peripheral wall (6) delimiting together a conveying space (7), wherein the first side wall (4) forms an inlet opening (8) and the peripheral wall (6) forms an outlet opening (9); - an impeller (10) accommodated in the conveying space (7); - an electric motor (11) arranged outside the conveying space (7) and fixed from the outside to the second side wall (5); - an electric control board (19) of the electric motor (11), arranged outside the conveying space (7) and fixed to the second side wall (5) or to the electric motor (11), - a protective cover (2) positioned around the electric motor (11) and the electric control board (19) and fixed from the outside to the second side wall (5), wherein the protective cover (2) comprises a bowl-shaped body (20) forming: - a bottom wall (21) on an outer side (22) of the protective cover (2) facing away from the impeller housing (3), and - a peripheral wall (23) extending from the bottom wall (21) towards an inner side (24) of the protective cover (2) facing the impeller housing (3) and delimiting, together with the bottom wall (21), a motor space (47) for accommodating the electric motor (11) and the electric control board (19), - a first connection edge (25) formed by the peripheral wall (23) and supported from the outside on the second side wall (5), characterized in that the body (20) is formed of several parts and comprises: - a first closed-loop half-body (30) forming at least a part of the peripheral wall (23) with the first connection edge (25) and a second connection edge (31) opposite to the first connection edge (25) and facing the outer side (22), and - a second half-body (32) forming the bottom wall (21) with a third connection edge (33) facing the inner side (24) and complementary to the second connection edge (31).

14. A radial fan (1) according to claim 13, comprising: - a plurality of first screw seats (28), formed in the peripheral wall (23) and open towards the inner side (24) at the first connection edge (25), and a plurality of connection screws (29) accommodated in the first screw seats (28) for a screw connection of the protective cover (2) with the second side wall (5), - second connection portions (34) formed in the first half-body (30) at the second connection edge (31) and corresponding third connection portions (35) formed in the second half-body (32) at the third connection edge (33) for connecting the first half-body (30) to the second half-body (32) along the second and third connection edges (31, 33), wherein the connection along the second and third connection edges (31, 33) forms discrete and concentrated tightening zones at the third connection portions (35) and support sections of continuous contact extending along the second and third connection edges (31, 33).

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