ES2798433T3 - Radial blower for suction hoods - Google Patents

Abstract

Radial blower (1), in particular for suction hoods, which has an impeller rotation axis (R) and which comprises: - a housing (2) with a first axial suction opening (3) and a second opening (4 ) of axial suction opposite the first suction opening (3) and an outlet opening (5) in a tangential direction, the outlet opening (5) defining an opening plane (36), - a unit (6, 7) transport disposed in a transport space (27) within the housing (2) and having an electric motor (6) and an impeller (7) connected to a rotor of the electric motor (6), in which a portion (14 tangential outlet of the housing (2) forms an outlet channel delimited by an outer wall portion (30) and an inner wall portion (31) opposite the outer wall portion (30), wherein, in a cutting plane parallel to the opening plane (36), the outlet channel and outlet opening (5) define a flow section in which the stop portion (31) Internal d forms a flattened base (33) substantially parallel to the axis of rotation (R), and the outer wall portion (30) forms an arc-shaped boundary (34), the ends of which are connected to the ends of the flattened base (33), characterized in that the internal wall portion (31) is shaped like an arc of a circle in longitudinal cross section, in a cut plane orthogonal to the axis of rotation (R), which has a radius greater than the external radius of the impeller (7), or in the range of 4/3 to 6/3 of the outer radius of the impeller (7).

Description

DESCRIPTION

Radial blower for suction hoods

The present invention relates to a radial blower, in particular for suction hoods, of the type comprising a housing with two opposite axial air suction openings and a radial air outlet opening, as well as a transport unit with a electric motor and an impeller located inside the housing. Radial blowers of the type mentioned above are known, for example, from EP 2365224, EP 0985829, JPH 046600 and US 2010/183433.

The blowers of the prior art have some disadvantages. They present a high consumption of electrical energy and a limited maximum flow rate (the electrical energy consumed being the same) and, therefore, still unsatisfactory energy efficiency.

Known blowers exhibit a high back pressure gradient, unstable vortices, and unplanned flow gaps at the outlet opening.

At the suction openings, known blowers exhibit resistance and kinetic energy losses of the conveyed gas due to sudden change in air flow direction, with unwanted flow gaps and local vortices.

DE 102015213471 describes a fan module having a housing with a flow channel, in which a noise isolating element is arranged in the flow channel.

JPS 5372205 describes a muffler for reducing noise generated during the operation of a centrifugal blower.

Therefore, the object of the present invention is to provide a radial blower of the mentioned type having such characteristics as to solve at least some of the drawbacks mentioned with reference to the prior art.

It is a particular object of the invention to suggest a radial blower that is improved from the fluid dynamic point of view, to reduce energy consumption, the flow being the same and increasing the maximum flow, the size and the electrical power consumed being the same.

It is a further object of the invention to suggest a radial blower that exhibits low noise and vibration levels, by virtue of an improved fluid dynamic geometry.

These and other objects are achieved by a radial blower according to the attached claim 1.

Preferably, guide radii are formed in at least one of the suction openings, such guide radii extend from a radially outer zone of the suction opening towards a radially innermost zone and are shaped such as to deflect air flow that enters the suction opening towards the direction of rotation of the impeller.

The guide spokes form "static blades", capable of directing the flow, optimizing its trajectory and conferring movement in the same direction of movement as the impeller. This reduces the required torque and improves the energy efficiency of the blower.

According to the invention, a tangential outlet portion of the housing forms an outlet channel delimited by a (radially) outer wall portion and an inner (radially) wall portion opposite the outer wall portion.

Preferably, a guide core is formed by a peripheral wall of the housing and by the internal wall has a cross section in the shape of a cusp (in a cut plane orthogonal to the axis of rotation), which converges towards a free edge and where said free edge is substantially rectilinear and parallel to the axis of rotation.

According to the invention, the outlet channel and the outlet opening define a flow section delimited by: - a flat base parallel to the axis of rotation, and

- an arc-shaped boundary, the ends of which are connected to the ends of the flat base.

The tunnel-shaped configuration of the outlet channel with a flat base and the upper arc-shaped delimitation helps to reduce the back pressure gradient, which acts against the flow direction, reduces the separations of unplanned flow and increases both energy efficiency and mass flow, the outer dimensions and motor type being the same.

To better understand the invention and appreciate the advantages thereof, some non-limiting example embodiments will now be described with reference to the drawings, in which:

vista delantera del soplador radial de la figura 1;Figure 1 is an exploded perspective view of a radial blower in accordance with the invention; figure 2 is a

front view of the radial blower of figure 1;

Figures 3 and 4 are two opposite side views of the radial blower of Figure 1;

Figure 5 is a perspective view of a half cover of the housing of the radial blower of Figure 1; Figures 6 and 7 are views of the inlet opening of the blower housing of Figure 1;

Figures 8 and 9 are detailed views of the inlet openings shown in Figures 6 and 7 with indication of some characteristic geometric parameters;

Figure 10 is a cross-sectional view (taken along a cutting plane XX tangential to a circumference of the axis of rotation of the motor) of a guide radius of an air inlet opening, on the side opposite to the side of the engine, in a radially internal region;

Figure 11 is a cross-sectional view (taken along a section plane XI-XI tangential to a circumference of the axis of rotation of the motor) of a guide radius of the air inlet opening, on the opposite side next to the engine, in a radially outer region;

Figure 12 is a cross-sectional view (taken along a section plane XII-XII tangential to a circumference in the axis of rotation of the motor) of a guide radius of an air inlet opening on the side of the motor;

Figures 13 and 14 are sectional views, taken according to a plane perpendicular to the axis of rotation, of a sequence of blades of the blower impeller, with the indication of some characteristic geometric parameters, according to the embodiments;

Figure 15 is a radial sectional view of a half cover of the blower housing according to one embodiment;

Figure 16 is an enlarged view of a detail of Figure 15;

Figures 17 and 18 are side views of an internal side of a half cover of the blower housing, with the indication of some characteristic geometric parameters, according to one embodiment;

Figure 19 is a view of a blower outlet zone according to one embodiment,

Figure 20 shows an impeller for the blower according to one embodiment,

A radial blower, in particular for domestic suction hoods, is indicated as a whole by the reference number 1 in the figures. The blower 1 defines an axis of rotation R of the impeller and the definitions of position or orientation "axial", "radial", "circumferential" and "peripheral" refer to the axis of rotation R or to geometric shapes developed around the axis of rotation R Furthermore, in the present description, the term "radially inward" means "approaching the axis of rotation R" and the term "radially outward" means "moving away from the axis of rotation R".

The blower 1 comprises a housing 2 with a first axial suction opening 3 and a second axial suction opening 4, opposite the first suction opening 3, and a radial or tangential air outlet opening 5, as well as a unit of conveyor arranged inside the housing 2 and having an electric motor 6 and an impeller 7 connected to the rotor and / or to the drive shaft 8 of the electric motor 6.

The electric motor 6 is fixed to the housing 2 on two opposite sides or cantilevered only on one side and integral in rotation, for example, by means of a plurality of support portions or spokes protruding from an edge 10 of the first opening 3 suction and, in the case of the motor support on both sides, by means of a further plurality of support portions or radii projecting from an edge 10 'of the second suction opening 4.

Detailed description of the accommodation 2

The housing 2 has a substantially toroid shape with two side walls 11, 12 that delimit the suction openings 3, 4, and with a peripheral wall 13 and a substantially tangential portion 14, which forms the air outlet opening 5.

The housing 2 is formed by two half-covers 15, 16, which are connected to each other along a joint line 17 in the peripheral wall 13 by complementary joint edges 18, which may be in the shape of a step or slit to create a labyrinth connection interface, and possibly one or more alignment pins 19 protruding from the joining edge 18 of one of the half-covers 15, 16 respectively and housed in corresponding alignment holes 20 formed in the joining edge 18 of the other half deck. The attachment edges 18 may also comprise attachment ridges or ridges 22 projecting radially outward from the housing 2 and having a lower section to accommodate one or more attachment clips or profiles 21, in particular "O" or "O" shaped clips. "C", or alternatively holes to receive the connecting screws, which lock the two half covers 15, 16 against each other.

This results in a simple, robust and particularly accurate assembly of the housing.

The suction openings 3, 4 are preferably substantially circular and coaxial with the impeller 7, which is also circular.

The housing 2 internally delimits a circumferential transport space 27, which gradually widens in a radial direction from a zone with a minimum initial section 28 to a zone with a maximum final section 29 (Figure 18). The radial extension with respect to the axis of rotation R of the minimum initial section 28 is preferably in the range of 75 mm to 85 mm and the radial extension with respect to the axis of rotation R of the maximum end section 29 is preferably in the range of 115mm to 130mm.

Description of suction openings 3, 4

The suction openings 3, 4 comprise protection grids 24, 25, which can also form the structure to support the motor-drive unit 6 7.

The protection grid 24, 25 can also be formed in one piece with the respective side walls 11, 12 or with the respective half-covers 15, 16 or be manufactured separately and then applied over them.

According to one embodiment (figure 1), the first suction opening 3 (motor side), the first protection grid 24 for the first suction opening 3 and a structure for supporting the motor 6 are formed by a plate 23 of support that has been made separately and then connected to the first half-cover 15, for example, by means of screws or rivets, by pressure or by other means of fixing.

Advantageously, the support plate 23 and the motor 6 can be connected to each other to form a pre-assembled grill motor unit, which can be mounted on the first half-cover 15.

According to an alternative embodiment, the support plate 23 is formed in one piece with the first half-cover 15, thus being obtained in a direct support of the motor 6 on the half-cover.

The second suction opening 4 (opposite side to the motor side), the second protection grid 25 for the second suction opening 4 and, if provided, an additional portion to support the motor 6, can be formed in one piece with and on the second half-cover 16 (figure 3) or, alternatively, by a second plate, made separately and then connected to the second half-cover 16, for example, by means of screws or rivets, by pressing or by other fixing means (not shown).

One or both of the protective grids 24, 29 and / or the motor support structure form a plurality of guide spokes 9, 9 'which extend from a radially external zone of the suction opening 3, 4 towards a radially more zone. internal and shaped to deflect the air flow entering the suction opening 3, 4 towards the direction of rotation of the impeller 7. In this way, the guide spokes 9, 9 'form "static blades", capable of directing the flow, optimizing its path and conferring movement in the same direction of movement as the impeller 7. This reduces the necessary torque and improves the energy efficiency of the blower 1. According to one embodiment, the spokes 9, 9 The guide 's form a substantially rectilinear outer edge 64 (relative to housing 2) to improve the uniformity of the outer shape, which is important for the protection function, and to reduce resistance to flow. The guide spokes 9, 9 'are preferably inclined forward, that is, with the radially outer end disposed further forward than the radially inner end, viewed in the direction of rotation of the impeller (Figure 3, 4). Like rotating blades, this "static blade" configuration consisting of guide radii 9, 9 'reconciles the need to minimize energy losses and flow resistance with the need to divert flow in the direction impeller rotation 7.

The guide spokes 9, 9 'are plate-shaped with a cross section (taken along a cutting plane tangential to the axis of rotation R) inclined with respect to the axial direction and possibly curved in the shape of an arc (figure 10 , 11, 12).

According to an advantageous embodiment (figure 12), the guide spokes 9 of the first suction opening 3 have a concave front surface 62, oriented towards the direction of rotation of the impeller 7, a convex rear surface 63, opposite the surface front 62, the axially outer edge 64 (preferably flat) and an axially inner edge surface 65, preferably rounded. In a cut plane tangential with respect to the axis of rotation R,

the front surface 62 has a concave arc shape, for example the arc of a circle,

- the rear surface 63 has a convex arc shape, for example the arc of a circle,

- possibly, the thickness of the guide radius 9 gradually narrows from the axially outer edge 64 to the axially inner edge 65.

The exit angle a_ua of the front surface 62 of the guide radius 9 (motor side), seen in section taken along the plane tangential to the axis of rotation R (the angle of orientation of the front surface 62 at the end axially internal 65 in the direction of rotation with respect to the axial direction) is in the range between 7 ° and 11 °, preferably about 9 °.

The exit angle a_up of the rear surface 63 of the guide radius 9 (motor side), seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the rear surface 63 at the end axially internal 65 in the direction of rotation with respect to the axial direction) is in the range between 3 ° and 6 °, preferably about 4.8 °.

The entry angle a_ia of the front surface 62 of the guide radius 9 (motor side), seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the front surface 62 at the end axially external 64 in the direction of rotation with respect to the axial direction) is in the range between 60 ° and 74 °, preferably about 67.8 °.

The entry angle a_ip of the rear surface 63 of the guide radius 9 (motor side), seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the rear surface 63 at the end axially external 64 in the direction of rotation with respect to the axial direction) is in the range between 42 ° and 60 °, preferably about 51.4 ° (FIG. 12).

More generally, considering a median line of the cutting profile of the guide radius 9, the entry angle of the guide radius 9 is greater than the exit angle of the guide radius 9.

Advantageously, the guide spokes 9 of the first suction opening 3 (motor side) have a substantially constant cutting shape along their longitudinal extension, except for the radially outer and inner ends.

The axially inner end 65 of the guide spoke 9 is positioned forward in the direction of rotation with respect to the axially outer end 64 of the same guide spoke 9. The chord 66 of the spokes 9 (indicated in figure 12) has an angle 67 of orientation of the chord in the direction of rotation with respect to the axial direction comprised between 33 ° and 43 °, advantageously approximately 38 °.

According to an advantageous embodiment (figure 10, 11), the guide radii 9 'of the second suction opening 4 (side opposite the motor side) can have a deformation or twisting along a longitudinal axis thereof. Advantageously, the width of the profile of the guide spokes 9 'increases from a minimum width (Figure 10) near the radially inner end to a maximum width (Figure 11) near the radially outer end.

The guide spokes 9 'have a concave front surface 62', facing the direction of rotation of the impeller 7, a convex rear surface 63 ', opposite the front surface 62', the axially outer edge 64 '(preferably flat) and an axially inner edge surface 65 '(preferably rounded). In a cutting plane tangential to the axis of rotation R,

- the front surface 62 'is concave in the shape of an arc,

- the rear surface 63 'is convex in the shape of an arc,

- possibly, the thickness of the guide radius 9 gradually narrows from the axially outer edge 64 to the axially inner edge 65.

The exit angle a_ua 'of the front surface 62' of the guide radius 9 ', seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the front surface 62' at the axially inner end 65 'in the direction of rotation with respect to the axial direction) is between 11 ° and 15 °, preferably about 13.2 ° in the radially outer region and preferably about 13.3 ° in the radially inner region.

The exit angle a_up 'of the rear surface 63' of the guide radius 9 ', seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the rear surface 63' at the axially inner end 65 'in the direction of rotation with respect to the axial direction) is in the range between 7 ° and 13 °, preferably about 9.8 ° in the radially outer region and preferably about 9.9 ° in the radially inner region.

At the radially external end (Figure 11), the entry angle a_ia 'of the front surface 62' of the guide radius 9 ', seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the leading surface 62 'at the axially outer end 64' in the direction of rotation with respect to the axial direction) is in the range between 39 ° and 49 °, preferably about 44.4 °.

At the same radially external end (figure 11), the entry angle a_ip 'of the rear surface 63' of the guide radius 9 ', seen in section taken along the plane tangential to the axis of rotation R (the orientation angle of the rear surface 63 'at the axially outer end 64' in the direction of rotation with respect to the axial direction) is in the range between 38 ° and 48 °, preferably about 43.7 °.

More generally, considering a median line of the cutting profile of guide radius 9 ', the entry angle of guide radius 9' is greater than the exit angle of guide radius 9 '.

The axially inner end 65 'of the guide spoke 9' is positioned forward in the direction of rotation with respect to the axially outer end 64 'of the same guide spoke 9'. The chord 66 'of the spokes 9' (figures 10 and 11) has an orientation angle of the chord 67 'in the direction of rotation with respect to the axial direction: - greater at the radially outer end than at the radially inner end , more particularly

- between 24 ° and 34 °, advantageously approximately 29 ° at the radially external end (figure 11),

- between 15 ° and 25 °, advantageously approximately 20 ° at the radially inner end (figure 10).

The guide spokes 9, 9 'are arranged in a constant pitch, for example, 21 guide spokes 9 on the motor side and 19 guide spokes 9' on the side opposite the motor side.

Furthermore, the guide spokes 9, 9 ', of each suction opening 3, 4 may be connected to each other by means of one or a plurality of reinforcing rings 68, possibly concentric to the axis of rotation R. On the motor side A single reinforcing ring 68 may be provided, while on the opposite side three or two reinforcing rings 68 'may be provided which also act as a guard to prevent access to the impeller.

According to one embodiment (Fig. 8) in the first suction opening 3 (motor side), the relationship between the radial extension 69 of the guide radius 9 and the external radius 70 of the first suction opening 3 is in the range 0.28 to 0.4, preferably about 0.34.

The guide radii 9 may extend from an inner radius 71 of the first suction opening 3 of 39mm to 48mm, preferably about 43.3mm, to the outer radius 70 of 60mm to 72mm, preferably approximately 66 mm.

The guide spokes 9 are preferably inclined forward, that is, with the radially outer end disposed further forward than the radially inner end, viewed in the direction of rotation of the impeller, with an angle 72 of inclination with respect to the radial direction that passes through the radially inner end of guide radius 9, 5.8 ° to 7.3 °, preferably about 6.7 ° (Figure 8).

According to one embodiment (Figure 9) in the second suction opening 4 (side opposite the motor side), the relationship between the radial extension 69 'of the guide radius 9' and the external radius 70 'of the second opening 4 suction is in the range of 0.5 to 0.7, preferably about 0.58.

The guide radii 9 may extend from an inner radius 71 'of the second suction opening 4 of 22mm to 32mm, preferably about 27.4mm, to an outer radius of 70mm of 60mm to 72mm, preferably about 66mm.

The guide spokes 9 'are preferably inclined "forward", that is, with the radially outer end disposed further forward than the radially inner end, viewed in the direction of rotation of the impeller, at an angle 72' of inclination with respect to the radial direction passing through the radially inner end of guide radius 9 ', from 10 ° to 16 °, preferably about 13.6 ° (Figure 9).

According to one embodiment, the guide spokes 9, 9 'also protrude axially outward from the housing 2, which confers an outwardly bulging, eg frusto-conical shape to the protection grid 24, 25. In this way, a larger axial space can be exploited to divert the flow, the actual flow section of the suction opening 3, 4 being the same.

The guide spokes 9, 9 'contribute to a reduction in flow resistance, an increase in flow rate, the electrical energy consumed by the motor is the same, particularly at high speeds and flow rates. The guide radii 9, 9 'further contribute to a more gradual distribution of the deflection of the air flow, a reduction of the angle of attack between the flow entering the impeller 7 and the blades 26, 43 of the impeller 7.

Detailed Description of Tangential Outlet Portion 14

The tangential outlet portion 14 of the housing 2 forms an outlet channel delimited by an outer (radially) wall portion 30 which connects approximately tangentially to the peripheral wall 13 near the end section 29 of the transport space 27 and a inner (radially) wall portion 31, opposite to outer wall portion 30 and connected to peripheral wall 13 in initial section 28, protrudes approximately toward outer wall portion 30 and / or toward peripheral wall 13 in the area transition with the tangential portion 14 and determining the transition from the peripheral wall 13 to the inner wall portion 31.

The air outlet opening 5 is delimited by a tubular end 35 of the tangential portion 14, comprising an external connecting flange 38 and defining an opening plane 36 and an outlet direction 37 possibly perpendicular to the opening plane 36.

According to one embodiment, the guide core 32 has a cross-section (in a cutting plane taken along the axis of rotation R), possibly cusp-shaped, which converges towards a free edge 42 that is substantially rectilinear and parallel to the axis of rotation R and preferably extends from the first side wall 11 to the second side wall 12.

The portion of the inner wall 31 extends from the free edge 42 of the guide core 32 to the tubular end 35, to the free end of the tangential portion 14 (Figure 5,18), and has a cut-away shape (in the cutting plane parallel to the opening plane 36) substantially parallel to the axis of rotation R, so that the outlet channel and the outlet opening 5 define (starting from the free edge 42 of the core 32) a flow section delimited by: - a flattened base 33, possibly flat, parallel to the axis of rotation R, and

- an arc-shaped boundary 34, the ends of which are connected to the ends of the flattened base 33. The inner wall portion 31 that forms the flattened base 33 extends from the free edge 42 of the core 32 in a gradually converging manner toward a direction parallel to the direction of the apex of the opposite outer wall portion 30, viewed in a section plane perpendicular to the axis of rotation R (Figure 17,18). Preferably, the inner wall portion 31 and the apex direction of the opposite outer wall portion 30 include an opening angle 77 of less than 45 °, preferably in the range of 5 ° to 30 °, more preferably in the range of 5 ° to 15 °, viewed in a cut plane perpendicular to the axis of rotation R.

The inner wall portion 31 has a circular arc shape in longitudinal cross section, in a cutting plane orthogonal to the axis of rotation R, having a radius greater than the outer radius of the impeller 7, preferably 4/3 to 6 / 3, advantageously about 5/3, of the outer radius of the impeller 7.

The height 73 of the outlet channel flow section (measured perpendicular to the base 33) gradually increases from the free edge 42 of the core 32 to the tubular end 35, but said height 73 remains less than 70%, preferably less than 65%. % of external diameter 74 of tubular end 35 (Figure 17).

According to a preferred embodiment, the height 73 of the flow section is approximately 1/2 of the outer diameter 74 of the tubular end 35 at the free edge 42 of the core 32 is approximately 3/5 of the outer diameter 74 of the tubular end 35 at the latter, with a tolerance of / - 5%.

The configuration of the outlet channel as a "tunnel with flat base and upper arc delimitation" helps to reduce the back pressure gradient, which acts against the flow direction, reduces unplanned flow separations and increases both energy efficiency and mass flow, being the external dimensions and the type of motor the same.

In the preferred embodiment, the tubular end 35 has a cylindrical shape with a circular cross section and the boundary 34 forms a section of the circular cross section.

The same tubular end 35 and the internal wall portion 31, possibly together with other walls of the housing 2, delimit an external auxiliary compartment 75, which is separated with respect to both the outlet opening 5 and the transport space 27. With a particular advantage, this auxiliary compartment can accommodate an electrical control panel 76 for the motor 6. In this way, the space in the gap between the peripheral wall 13 and the tangential cut 14, as well as a part of it, is used. tangential portion 14 that is not used to transport air.

In one embodiment (Figure 19), the outlet opening 5 is provided with a non-return shutter flap 78, which is steerable and preferably elastically biased towards a closed position (in the opposite direction to the air outlet direction), and it can be moved (towards the outside of the housing) to an open position by pushing air flow out of the outlet opening 5. The shape and position of the shutter flap 78 may be such as to increase, in the open position, the extent of the surface of the flattened base 33, extending it out of the housing. This prevents the return of fumes to the fan and further reduces the formation of vortices and flow gaps.

The housing 2 is advantageously made of plastic material by injection molding, in particular of polypropylene, for example, filled with glass fibers, glass balls, talc, etc.

Detailed description of the impeller 7

The impeller 7 comprises a first plurality of blades 26 extending between a front ring 39 (engine side) and a central wall 41, as well as a second plurality of blades 43 extending between a rear ring 44 opposite the front ring 39 and the central wall 41, in which the second plurality of blades 43 is advantageously angularly offset with respect to the first plurality of blades 26.

The blades 26, 43 are arranged at a constant angular pitch, eg 56 blades at an angular pitch of p = 6.43 °. A single "irregular" blade can be provided arranged at different distances from adjacent blades, eg pi = 6.93 ° and p2 = 5.93 °.

This arrangement of blades 26, 43 prevents the impeller from reaching resonance oscillation and therefore reduces noise and vibrations from the radial blower.

The central wall 41 is a substantially closed wall (figure 1), or is provided with cooling openings 79 (for a more effective cooling of the engine 6) alternating with closed areas in the form of radial radii 80 (figure 20), with a portion central cup or dome 45 adapted to accommodate a front portion, more precisely the rotor, of the electric motor 6, and a connecting seat 46 for fixing the impeller 7 to the drive shaft 8 or to the rotor. The connecting seat 46 may comprise a metal hub molded in conjunction with the central portion 45 made of plastic material. The impeller 7 is advantageously injection molded and made of polypropylene or ABS.

According to an advantageous embodiment (Figures 13, 14), the blade 26, 43 has a concave front surface 47, facing the direction of rotation of the impeller 7, a convex rear surface 48 opposite the front surface 47 and a surface 49 of the radially inner edge of the blade 26, 43, in which, in a cut plane perpendicular to the axis of rotation R,

the front surface 47 has a concave arc shape with a first radius of curvature 50, which increases from a minimum value in a radially inner or intermediate zone to a maximum value in a radially outer zone;

the rear surface 48 has a convex arc shape with a second radius of curvature 51, which increases from a minimum value in a radially inner or intermediate zone to a maximum value in a radially outer zone;

the radially inner surface 49 may have a convex arc shape, for example an arc of a circle having a third radius of curvature 52 less than the first radius 50 and less than the second radius 51.

The exit angle a_u of the blade 26, 43 (the angle of orientation of the radially outer end of the blade 26, 43 in the direction of rotation with respect to a plane radial to the axis of rotation R and passing through said end radially external) is in the range between 49 ° and 60 °, and is advantageously approximately 54.3 °, while the entry angle a_i of the blade 26, 43 (the orientation angle of the radially inner end of the blade 26 , 43 against the direction of rotation with respect to a plane radial to the axis of rotation R and passing through said radially inner end) is in the range between 43 ° and 54 ° and is advantageously approximately 48.7 ° (figure 13).

Both the radially inner and the radially outer ends of the blades 26, 43 are oriented in the direction of rotation of the impeller 7 and the ratio a_i / a_u between the entry angle a_i and the exit angle a_u (as shown in the figure 13) is in the range of 0.8 to 1.0, preferably 0.9.

This particular shape of the blades contributes to reducing the flow resistance and to a separation of the flow of the blades 26, 43 in a single and highly concentrated zone at their radially outer end.

Advantageously, the ratio between the radial extension 54 of the blade 26, 43 and the external radius 55 of the impeller 7 is in the range of 0.185 to 0.245, preferably about 0.22.

The blades 26, 43 may extend from an inner radius 56 in the range of 55mm to 65mm, preferably about 59.2mm, to the aforementioned outer radius 55 in the range of 68mm to 80mm, preferably about 75mm. 2 mm.

Advantageously, the blades 26, 43 have a constant cross-sectional shape along their axial extent with the exception of rounded end portions and a slight taper from the central wall 41 axially outward to facilitate removal from the mold.

The radially outer end of the blade 26, 43 is positioned forward in the direction of rotation with respect to the radially inner end of the blade itself 26, 43. The chord 57 of the blades 26, 43 (indicated in Figure 14) has a internal chord orientation angle 58 in the direction of rotation with respect to a plane radial to the axis of rotation R and passing through the radially internal edge of the blade) comprised between 17 ° and 23 °, advantageously approximately 19.9 ° , as well as a chord angle 59 of external orientation in the direction of rotation with respect to a plane radial to the axis of rotation R and passing through the radially external end of the blade) comprised between 12.5 ° and 18.5 °, advantageously about 15.6 °.

The maximum thickness 50 of the blades 26, 43 is advantageously chosen in the range of 2 mm to 3.3 mm, preferably approximately 2.8 mm.

The maximum distance 51 between the chord 57 and the rear surface 48 of the blades 26, 43 is advantageously chosen in the range of 5.7 mm to 6.5 mm, preferably about 6.1 mm.

The maximum thickness 50 and also the maximum chord distance 51 of the blade are in a central span that has one third of the total radial extent of the blade.

The shape and arrangement of the components of the impeller 7, in particular of the blades 26, 43, also contribute to an improvement towards an optimization of the performance of the blower 1. The air flow follows the complete profile of the blades 26, 43 without recirculation and without the formation of unplanned flow separation zones, which would increase noise levels and imply a higher consumption of electrical energy.

As a whole, the invention makes it possible to create a very compact, silent and energy efficient blower, the transport performance (flow, speed, pressure) being the same.

Claims (14)

1. - Radial blower (1), in particular for suction hoods, which has an impeller axis of rotation (R) and which comprises: - a housing (2) with a first axial suction opening (3) and a second axial suction opening (4) opposite the first suction opening (3) and an outlet opening (5) in a tangential direction, defining the outlet opening (5) an opening plane (36), - a transport unit (6, 7) arranged in a transport space (27) inside the housing (2) and having an electric motor (6) and an impeller (7) connected to a rotor of the electric motor (6) , wherein a tangential outlet portion (14) of the housing (2) forms an outlet channel delimited by an outer wall portion (30) and an inner wall portion (31) opposite the outer wall portion (30) , in which, in a cut plane parallel to the opening plane (36), the outlet channel and the outlet opening (5) define a flow section in which the inner wall portion (31) forms a base flattened (33) substantially parallel to the axis of rotation (R), and the outer wall portion (30) forms an arc-shaped delimitation (34), the ends of which are connected to the ends of the flattened base (33), characterized in that the internal wall portion (31) has the shape of an arc of a circle in longitudinal cross section, in a cutting plane orthogonal to the axis of rotation (R), which has a radius greater than the external radius of the impeller (7), or in the range of 4/3 to 6/3 of the outer radius of the impeller (7). 2. - Blower (1) according to claim 1, wherein a guide core (32) formed between a peripheral wall (13) of the housing (2) and the inner wall portion (31) has a cross section cusp-shaped, converging on a free edge (42), seen in a cutting plane orthogonal to the axis of rotation (R), in which said free edge (42) is substantially rectilinear and parallel to the axis of rotation (R ). 3. - Blower (1) according to claim 2, wherein the flattened base (33) of the outlet channel extends from the free edge (42) of the core (32) in a gradually convergent manner towards a direction parallel to the direction of the apex of the outer wall portion (30), viewed in a cut plane perpendicular to the axis of rotation (R). 4. - Blower (1) according to one of the preceding claims, wherein the inner wall portion (31) and the direction of the apex of the outer wall portion (30) include an opening angle (77) of less than 45 °, or in the range of 5 ° to 30 °, viewed in a cut plane perpendicular to the axis of rotation (R). 5. - Blower (1) according to one of the preceding claims, in which the height (73) of the flow section of the outlet channel is less than 65% of the external diameter (74) of a tubular end (35 ). 6. - Blower (1) according to one of the preceding claims, in which a tubular end (35) and the internal wall portion (31) delimit at least a part of an auxiliary compartment (75) outside the channel of outlet and transport space (27), in which the auxiliary compartment receives an electrical control plate (76) for controlling the motor (6). 7. - Blower (1) according to one of the preceding claims, in which guide radii (9, 9 ') are formed in at least one of the suction openings (3, 4), said radii extending from a radially outer area of the suction opening (3, 4) towards a radially innermost zone and having a shape and inclination such as to divert the flow of air entering the suction opening (3, 4) towards the direction of rotation of the impeller (7). 8. - Blower (1) according to claim 7, wherein the guide radii (9, 9 ') form an axially external edge (64) substantially rectilinear and are inclined "forward", with the end radially external disposed further forward than the radially inner end, viewed in the direction of rotation of the impeller. 9. - Blower (1) according to claim 7 or 8, in which the spokes (9, 9 ') guide are plate-shaped with a cross section, according to a cutting plane tangent to the axis of rotation (R), having a curved shape of an arc and inclined with respect to the axial direction. 10. - Blower (1) according to claim 9, in which the guide spokes (9, 9 ') have a concave front surface (62, 62'), oriented in the direction of rotation of the impeller (7) , and a convex rear surface (63, 63 ') opposite the front surface (62, 62'), an axially outer edge (64) and a rounded axially inner edge (65), wherein in a plane cut tangent to the axis of rotation (R), - the front surface (62, 62 ') has the shape of a concave arc, - the rear surface (63, 63 ') is in the shape of a convex arc, - the thickness of the guide radius (9, 9 ') gradually tapers from the axial outer edge (64, 64') towards the axially inner edge (65, 65 '). 11. - Blower (1) according to claim 10, wherein in cross section according to a cutting plane tangent to the axis of rotation (R), the entry angle of the guide radius (9, 9 ') relative to the axial direction is greater than the exit angle of the guide radius (9, 9 ') relative to the axial direction. 12. - Blower (1) according to one of claims 7 to 11, in which an axially internal edge (65, 65 ') of the guide radius (9, 9') is positioned forward in the direction of rotation of the impeller (7) with respect to the axially outer edge (64) of the same guide radius (9). 13. - Blower (1) according to one of claims 7 to 11, wherein the guide radii (9 ') of the second suction opening (4) on a side opposite to the side of the motor (6) have a torsion along their longitudinal extension and the width of the profile of the guide spokes (9 ') increases from a minimum width near the radially inner end to a maximum width near the radially outer end, and / or in the place where which the guide radii (9, 9 ') project axially out of the housing (2), forming an outwardly projecting protective grid (24, 25). 14. - Blower (1) according to one of the preceding claims, in which a non-return closure flap (78) is connected to the outlet opening (5), said flap being rotatable and elastically pushed towards a closed position and movable towards an open position by the thrust of air flow exiting the outlet opening (5), in which the closing flap (78) has a flat shape and a position such that, in the open position, the superficial extension of the flattened base (33), elongating it towards the exterior of the housing.