TECHNICAL FIELD OF APPLICATION OF THE INVENTION

The present invention concerns the field of cooling systems for rotary machines. In particular, the present invention refers to a cooling fan that can be applied to a rotary machine consisting of an electric motor.

DESCRIPTION OF THE STATE OF THE ART

The use of rotary machines equipped with a rotary output shaft to which proper users are connected is widespread in various sectors, from the industrial to the domestic one.

Rotary machines of known type are the rotary electric machines, that is, machines powered via connection to an electric network, which transform electric power into mechanical power in a rotary output element constituted, more precisely, by the output shaft.

Rotary electric machines, which hereinafter are called electric motors for the sake of explanation simplicity, comprise an external stator part that encloses a rotary element, or rotor, bearing the output shaft.

The desired user is connected, according to the specific field of application, to one encK)f the output shaft.

The stator part is normally contained in an aluminium supporting element, or casing, substantially cylindrical in shape.

The electric motor comprises a series of electrical windings crossed by the current coming from the power supply network and associated with the stator or the rotor, according to the type of motor, for example depending on whether it is a direct current motor or rather a brushless motor.

It is known that during operation said motors are subjected to heating, mainly because of the leaks due to the Joule effect that occur along said electric windings when current passes through them. For this purpose, the external casing that supports the motor is provided with fins that favour the dispersion of heat for the purpose of avoiding the overheating of the motor and maintaining its efficiency at acceptable values.

In order to further favour the dispersion of heat, ventilation systems have been developed that direct an air flow onto the external fins, so as to dissipate the heat. In a ventilation system of known type a fan is installed directly on the output shaft, at one of its end projecting from the motor casing and opposite the end connected to the user. A- first type of fan of known type is constituted by a fan, called straight vane fan, with so-called mixed radial-axial operation, with which a covering element is externally associated. The fan-covering element unit causes the sucked air to be conveyed towards the fins of the electric motor.

This type of ventilation system, however, poses some drawbacks.

In particular, the flow rate of the air flowing out of the fan, understood as flow rate of the air conveyed towards the fins by the unit described above, isn't optimal and is directed incorrectly, causing insufficient dispersion of the heat and excessive heating of the electric motor. This is mainly due to the fact that owing to the rotation of the straight vanes most of the air is centrifuged and therefore directed radially towards the outside and against the covering element that in turn re-directs it towards the fins in axial direction. This causes a decrease in the flow rate of the outflowing air, also due to the turbulence created between the vane and the covering element, which results in reduced efficiency of the fan.

For this purpose fans are known which partly resolve this drawback.

A fan of this type comprises a hub to be connected to the output shaft and provided with an annular portion that extends radially towards the outside for a short section and with a plurality of radial vanes that extend from said hub.

The radial vanes develop in the axial rotation direction of the fan starting from the same plane of origin and are joined at their ends by a peripheral edge that surrounds them and comes into contact with the end of each vane for its entire axial extension.

The radial vanes together with the peripheral edge define a plurality of passage ducts for the air sucked by the fan and conveyed towards the fins of the electric motor.

In this fan, the air portion that is centrifuged by the rotating vanes is re-directed axially towards the fins by the peripheral edge, which for this purpose is also slightly curved towards the hub in order to favour the conveyance action in the desired direction with respect to the fan rotation axis, that is, towards the fins. A covering element is externally associated with said fan, in such a case mainly serving as a protection element rather than as a device for re-directing the air. Even this type of fans, however, poses the drawback that the flow rate of the air flowing out of the fan, understood as flow rate of the air conveyed towards the fins, isn't optimal and is directed incorrectly, causing insufficient dispersion of the heat and excessive heating of the electric motor. The main object of the present invention is therefore to overcome said drawback. In particular, it is .one object of the present invention to provide a fan for rotary machines that generates air flows that are better directed compared to those generated by the fans of known type, in order to obtain higher efficiency in the ventilation of the fins of the rotary machine to which it is applied. In this way the operating temperature of the rotary machine is reduced and the efficiency of the same increases.

SUMMARY OF THE PRESENT INVENTION

The present invention is based on the general consideration that iit is possible to improve the efficiency in the ventilation of the fins of a rotary machine by intervening in the shape of the radial vanes in their area facing towards the fins themselves when the fan is connected to the rotary machine.

According to a first embodiment of the invention, the subject of the invention is a fan carried out according to claim 1 , that is, a fan for a rotary machine suited to convey a cooling fluid and comprising:

- a hub portion comprising means for connection to a rotary element of said rotary machine for rotation in an axial direction;

- a peripheral portion that surrounds said hub portion and develops from an external peripheral edge towards the inside in order to define an inlet for said fluid;

- a plurality of radial elements that develop at least partially in said axial direction substantially starting from the same plane of origin and extend from said hub portion to said peripheral portion in order to define a plurality of passage ducts of said fluid coming from said inlet, at least one of said radial elements comprising an area that projects from said plane of origin in the direction opposite the direction of development of said radial elements.

Advantageously, the projecting area defines an extension of the fluid passage duct beyond the plane of origin of the radial elements so that the air is conveyed and directed towards the rotary machine in a more efficient manner compared to the fans belonging to the known art.

The projecting area preferably extends radially towards the outside.

Advantageously, the projecting area is defined within a portion that faces towards the fins of the rotary machine to which the fan is applied.

Preferably, the hub portion comprises a base portion that extends radially towards the outside. Advantageously, the fluid coming from the inlet that flows in the passage ducts is conveyed radially. from the base portion towards the outside, that is, towards the peripheral area of the fan, that is, the area that normally faces towards the fins of the rotary machine to which the fan is connected.

According to another embodiment of the invention, the subject of the invention is a rotary machine according to claim 19, that is, a rotary machine comprising a fan carried out according to the invention.

Advantageously, a rotary machine provided with a fan carried out according to the invention has an operating temperature that is lower than the operating temperature of the rotary machines of known type.

Preferably, the rotary machine comprises also a fan covering element.

Further embodiments of the present invention are described in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, objects and characteristics, as well as further embodiments of the present invention are defined in the claims and will be illustrated in the following description, with reference to the enclosed drawings; in the drawings, corresponding or equivalent characteristics and/or components are identified by the same reference numbers. In particular:

- Figure 1 shows a general view of a rotary machine equipped with a fan constructed according to a first embodiment of the invention;

- Figure 2 shows an exploded view of Figure 1;

- Figure 3 a shows the fan of the invention shown in Figure 2;

- Figure 3b shows a rear plan view of the fan shown in Figure 3a;

- Figure 3c shows a front plan view of the fan shown in Figure 3a;

- Figure 3d shows a section view according to plane I-I of the fan shown in

Figure 3c;

- Figure 3e shows a section view according to plane II-II of the fan shown in

Figure 3c;

- Figure 4a shows a second embodiment of the fan shown in Figure 3a;

- Figure 4b shows a rear plan view of the fan shown in Figure 4a;

- Figure 4c shows a front plan view of the fan shown in Figure 4a;

- Figure 4d shows a section view according to plane I-I of the fan shown in

Figure 4c;

- Figure 4e shows a section view according to plane II-II of the fan shown in Figure 4c;

- Figure 5 a shows .a third embodiment of the fan shown in Figure 3 a;

- Figure 5b shows a rear plan view of the fan shown in Figure 5 a;

- Figure 5 c shows a front plan view of the fan shown in Figure 5 a;

- Figure 5d shows a section view according to plane I-I of the fan shown in Figure 5c;

- Figure 5e shows a section view according to plane II-II of the fan shown in

Figure 5c;

- Figure 6a shows a fourth embodiment of the fan shown in Figure 3 a;

- Figure 6b shows a rear plan view of the fan shown in Figure 6a;

- Figure 6c shows a front plan view of the fan shown in Figure 6a;

- Figure 6d shows a section view according to plane I-I of the fan shown in

Figure 6c;

- Figure 6e shows a section view according to plane II-II of the fan shown in Figure 6c;

- Figure 7a shows a fifth embodiment of the fan shown in Figure 3 a;

- Figure 7b shows a rear plan view of the fan shown in Figure 7a;

- Figure 7c shows a front plan view of the fan shown in Figure 7a;

- Figure 7d shows a section view according to plane I-I of the fan shown in Figure 7c;

- Figure 7e shows a section view according to plane II-II of the fan shown in

Figure 7c;

- Figure 8a shows a sixth embodiment of the fan shown in Figure 3a;

- Figure 8b shows a rear plan view of the fan shown in Figure 8a;

- Figure 8c shows a front plan view of the fan shown in Figure 8a;

- Figure 8d shows a section view according to plane I-I of the fan shown in

Figure 8c;

- Figure 8e shows a section view according to plane II-II of the fan shown in

Figure 8c;

- Figure 9a shows a seventh embodiment of the fan shown in Figure 3a;

- Figure 9b shows a rear plan view of the fan shown in Figure 9a;

- Figure 9c shows a front plan view of the fan shown in Figure 9a;

- Figure 9d shows a section view according to plane I-I of the fan shown in

Figure 9c;

- Figure 9e shows a section view according to plane II-II of the fan shown in Figure 9c;

- Figure 10a shows an eighth embodiment of the fan shown in Figure 3 a;

- Figure 1 Ob shows a rear plan view of the fan shown in Figure 10a;

- Figure 10c shows a front plan view of the fan shown in Figure 10a;

- Figure lOd shows a section view according to plane I-I of the fan shown in Figure 10c;

- Figure lOe shows a section view according to plane II-II of the fan shown in

Figure 10c;

- Figure 11a shows a ninth embodiment of the fan shown in Figure 3a;

- Figure l ib shows a rear plan view of the fan shown in Figure 11a;

- Figure 11c shows a front plan view of the fan shown in Figure 11a;

- Figure l id shows a section view according to plane I-I of the fan shown in

Figure 1 1c;

- Figure 1 le shows a section view according to plane II-II of the fan shown in Figure 1 1c.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Although the present invention is described below with reference to its embodiments illustrated in the drawings, the present invention is not limited to the embodiments described below and illustrated in the drawings. On the contrary, the embodiments described and illustrated herein clarify some aspects of the present invention, the scope of which is defined in the claims.

It has been shown that the present invention is particularly advantageous when applied to rotary machines constituted by electric motors. It should in any case be underlined that the present invention is not limited to electric motors. On the contrary, the present invention can be conveniently applied to all the rotary machines that during operation are subjected to overheating and that are provided with a rotary shaft to which a fan can be applied, like for example in alternators. Figure 1 shows a general view of a rotary machine consisting of an electric motor M associated with a fan 1 constructed according to the invention, not visible since it is covered by a covering element C.

The rotary machine M, hereinafter referred to as the electric motor M, is provided at its periphery with fins Ml suited to disperse the heat produced by the electric motor M during operation.

In Figure 2 the electric motor M, the covering element C and the fan 1 are shown as they appear before being put together. In particular, it is possible to see one end E of the output shaft S of the electric motor M to which the fan 1 of the invention is connected.

The other end of the output shaft S, opposite the end E with respect to the motor M, and not visible in the figure, can be connected to a user.

The fan 1 is installed so that during rotation it is integral with the output shaft S and during the operation of the motor M it conveys the cooling fluid, consisting of air, towards the fins Ml, as schematically indicated by the arrows shown in Figure 1. It is thus possible to identify a flow rate Pi of the air entering the fan 1 and a flow rate Pu of the air leaving the fan 1 that, in fact, hits the fins Ml .

With reference to the figures from 3a to 3e, the fan 1 of Figure 2 is described according to the first embodiment of the invention.

The fan 1 comprises a hub portion 2 in the shape of a flange, comprising a cylindrical portion 3 provided with a through hole 4 in the axial direction X for connection and locking to the output shaft S. The cylindrical portion 3 is provided with two cuts 15, 16 that develop along the axial direction X and make the cylindrical portion 3 elastically yielding in order to facilitate the connection of the fan to the output shaft S. In construction variants of the invention, the number of cuts may be different from two, as shown for example in the embodiment described below with reference to the Figures from 1 la to l ie. A peripheral portion 5, circular in shape, surrounds the hub portion 2. The peripheral portion 5 is rounded in the shape of a dome and develops in the axial direction X starting from a circular external peripheral edge 6 with diameter D 1 towards the inside until defining a circular opening 7 with peripheral edge with diameter D2. Said circular opening 7 defines the inlet, or intake mouth, of the cooling fluid, constituted by air, when the fan 1 is set rotating in the axial direction X.

Eight equally distributed radial elements 8, each one of which is in the shape of a vane, develop in the axial direction X substantially starting from the same plane of origin Z, as shown in Figure 3d, and extend between the hub area 2 and the peripheral portion 5 defining eight inter- vane ducts 9 for the passage of the air coming from the inlet 7 and directed towards the back of the fan 1. The word "back" means the area of the fan 1 that is positioned along the axial direction X opposite the inlet 7 and that, in the configuration with the fan 1 installed on the electric motor M, faces towards the motor M itself and in particular towards the fins Ml. In construction variants of the invention, the number of radial elements and inter-vane ducts may be different from eight, as shown for example in the construction variant described below with reference to the Figures from 11a to l ie.

The radial elements 8 comprise, radially towards the outside, an area 30 that projects from the plane of origin Z and in the direction opposite the direction of development of the radial elements 8, as shown in particular in the cross section of Figure 3d.

The projecting area 30 is substantially rectangular in shape. However, in construction variants of the invention said shape may be different and the projecting area may be properly shaped depending also on the shape of the front of the motor M to which the fan 1 is connected.

The projecting area 30 is provided radially with an extension D4 equal to approximately 10% of the diameter Dl of the external peripheral edge 6 and an axial extension D5 equal to approximately 20% of the axial extension D6 of the radial element 8.

The radial extension D4 of the projecting area 30 preferably assumes values included between 10% and 30% compared to the radial extension Dl of the external peripheral edge 6 and the axial extension D5 of the projecting area 30 assumes values included between 10% and 30% compared to the axial extension D6 of the radial elements 8.

The projecting area 30, as shown in detail in Figure 3a, protrudes from the back of the circular external peripheral edge 6 of the peripheral portion 5.

The diameter D2 of the peripheral edge of the inlet 7 is equal to 0.8 times the value of the diameter Dl of the external peripheral edge 6.

When the fan 1 is connected to the motor M, the projecting area 30 described above is in a position facing the motor M, more particularly facing the fins Ml that are peripherally distributed on the motor M.

For this purpose, the projecting area 30 is preferably arranged on the corresponding radial element 8 in a position facing the fins Ml, and therefore, normally, radially towards the outside. Preferably, again, the radial extension D4 of the projecting area corresponds to the radial extension of the fins Ml of the motor M.

In construction variants of the invention, however, the projecting area 30 may be arranged radially in a position that is not external, and its radial extension D4 may be different from the radial extension of the fins Ml of the motor M. Independently of its position and its extension, the projecting area 30 contributes to improving the .conveyance of the air coming from the inlet 7 of the fan 1 directed towards the back of the fan 1, that is, towards the motor M, and flowing in the inter- vane ducts 9.

The projecting area 30, in fact, substantially defines an extension of the inter- vane duct 9 beyond the plane of origin Z. In this way the air is conveyed and directed towards the motor M, and in particular towards the fins Ml, in a more efficient manner compared to the fans of the known art.

When the fan 1 is rotating, in fact, the air coming from the inlet 7 and passing through each inter- vane duct 9 beyond the plane of origin Z is efficiently conveyed towards the motor M from the extension of the inter-vane duct 9 defined, in fact, by the projecting area 30.

A second embodiment of the fan 1 that is the subject of the invention is illustrated with reference to the Figures from 4a to 4e.

The fan 1 shown in said figures differs from the fan 1 of the first embodiment described with reference to the Figures from 3 a to 3 e only due to the fact that the projecting area 30 does not protrude from the back of the circular external peripheral edge 6 of the peripheral portion 5, but rather the peripheral edge 6 further extends along the axial direction X. As shown in particular in Figure 4a, at the back of the peripheral edge 6 a cylindrical section 40 is defined, whose axial extension D5 corresponds to the axial extension D5 of the projecting area 30.

The cylindrical section 40 contributes to further improving the conveyance effect caused by the projecting area 30 towards the motor M, as the extension of the inter-vane duct 9 beyond the plane of origin Z defined by the projecting area 30 prevents any leak between the inter- vane ducts and forces the air to be processed in a more efficient manner by the fan 1.

A third embodiment of the fan that is the subject of the invention is illustrated with reference to the Figures from 5a to 5e.

The fan 1 comprises a hub portion 2 in the shape of a flange, comprising a cylindrical portion 3 provided with a through hole 4 in the axial direction X for connection and locking to the output shaft S. The cylindrical portion 3 is provided with two cuts 15, 16 that develop along the axial direction X and make the cylindrical portion 3 elastically yielding in order to facilitate the connection of the fan 1 to the output shaft S. The hub portion 2 comprises a base portion 20 that extends radially towards the outside until reaching a circular edge 21 with diameter D3, better visible in Figure 5e.

A peripheral portion 5, circular in shape, surrounds the hub portion 2. The peripheral portion 5 is rounded in the shape of a dome and develops in the axial direction X starting from a circular external peripheral edge 6 with diameter Dl towards the inside until defining a circular opening 7 with peripheral edge with diameter D2. Said circular opening 7 defines the inlet, or intake mouth, of the cooling fluid, constituted by air, when the fan 1 is set rotating in the axial direction X.

Eight equally distributed radial elements 8, each one of which is in the shape of a vane, develop in the axial direction X substantially starting from the same plane of origin Z, as shown in Figure 5d, and extend between the hub area 2 and the peripheral portion 5 defining eight inter-vane ducts 9 for the passage of the air coming from the inlet 7 and directed towards the back of the fan 1.

The air coming from the inlet 7 that flows in the inter-vane ducts 9 is advantageously conveyed radially from the base portion 20 towards the outside, that is, towards the peripheral area that faces towards the fins Ml of the motor M when the fan 1 is connected to the motor M.

The radial elements 8 comprise, radially towards the outside, an area 30 that projects from the plane of origin Z and in the direction opposite the direction of development of the radial elements 8, as shown in particular in the cross section of Figure 5d.

The projecting area 30 is provided radially with an extension D4 equal to approximately 10% of the diameter Dl of the external peripheral edge 6 and an axial extension D5 equal to approximately 20% of the axial extension D6 of the radial element 8.

The radial extension D4 of the projecting area 30 preferably assumes values included between 10% and 30% compared to the radial extension Dl of the external peripheral edge 6 and the axial extension D5 of the projecting area 30 assumes values included between 10% and 30% compared to the axial extension D6 of the radial elements 8.

The projecting area 30, as shown in detail in Figure 5a, protrudes from the back of the circular external peripheral edge 6 of the peripheral portion 5.

The diameter D2 of the peripheral edge of the inlet 7 is slightly longer than the diameter D3 of the circular edge 21 of the base portion 20.

Between the peripheral edge of the inlet 7 and the circular edge 21 of the base portion 20 there is, therefore, a reduced empty space constituted by a ring whose radial extension is equal to D2-D3, as can be better seen in the plan views of Figures 5b and 5c.

In particular, said dimensional difference D2-D3 is equal to 2% of the dimension of the fan 1, meaning 2% of the diameter Dl of the circular external peripheral edge 6.

More generally, the difference D2-D3 can be expected to assume values around 3mm in a fan with external diameter Dl included between 80mm and 500mm. Said value of the empty space of 3mm is substantially related to the production . process of the fan 1 itself, in particular it is related to the moulding in a single piece.

In fact, if necessary, the base portion 20 can preferably extend further in radial direction towards the outside compared to the solution shown, so that the diameter D3 can be equal to or longer than the diameter D2 and therefore the value of the difference D2-D3 may be negative.

Analogously, the inlet 7 with its peripheral edge can extend further in radial direction towards the inside compared to the solution shown, so that the diameter D3 can be equal to or longer than the diameter D2 arid therefore the value of the difference D2-D3 may be negative.

In any case, it is possible to state that the internal peripheral edge of the inlet 7 substantially overlaps in radial direction the base portion 20, more particularly the circular edge 21 of the base portion 20.

An inlet 7 that substantially overlaps in radial direction the base portion 20 will probably cause the air coming from the inlet 7 and flowing through the inter-vane ducts 9 to be completely conveyed radially towards the outside against the inner wall of the external peripheral portion 5 and from here directed axially towards the back of the fan 1.

In this way all the air coming from the inlet 7 is conveyed towards the fins Ml of the motor M when the fan 1 is connected to the motor M, rather than towards other parts of the motor M.

However, the inlet 7 must not necessarily overlap in radial direction the base portion 20. It is possible to expect, in fact, that the diameter D2 of the peripheral edge of the inlet 7 will be longer than the diameter D3 of the circular edge 21 of the base portion 20 and that in any case it will be possible to obtain that most of the air coming from the inlet 7 is conveyed radially towards the outside against the inner wall of the external peripheral portion 5 and from here directed axially towards the back of the fan 1

It has been verified that said advantageous effect is worthy of note for values of the diameters D2 and D3 such that the difference D2-D3 is less than 30% of the diameter Dl of the external peripheral edge 6.

Said advantageous effect is even more considerable for values of the diameters D2 and D3 such that the difference D2-D3 is less than 5% of the diameter Dl of the external peripheral edge 6.

In all the cases described above, that is, both when the internal peripheral edge of the inlet 7 overlaps in radial direction the circular edge 21 of the base portion 20 and when the diameter D2 of the peripheral edge of the inlet 7 is longer than the diameter D3 of the circular edge 21 of the base portion 20, there is the advantage that the air coming from the inlet 7 is conveyed almost exclusively towards the inner wall of the external peripheral portion 5 and then directed towards the fins Ml of the motor M when the fan 1 is connected to the motor M, rather than towards other parts of the motor M itself.

The diameter D2 of the peripheral edge of the inlet 7 is equal to 0.8 times the value of the diameter Dl of the external peripheral edge 6.

A fourth embodiment of the fan 1 that is the subject of the invention is illustrated with reference to the Figures from 6a to 6e.

The fan 1 shown in said figures differs from the fan 1 of the second embodiment described with reference to the Figures from 5 a to 5 e only due to the fact that the projecting area 30 does not protrude from the back of the circular external peripheral edge 6 of the peripheral portion 5, but rather the peripheral edge 6 further extends along the axial direction X. As shown in particular in Figure 6a, at the back of the peripheral edge 6 a cylindrical section 40 is defined, whose axial extension D5 corresponds to the axial extension D5 of the projecting area 30.

A fifth embodiment of the fan 1 that is the subject of the invention is illustrated with reference to the Figures from 7a to 7e.

The fan 1 comprises a hub portion 2 in the shape of a flange, comprising a cylindrical portion 3 provided with a through hole 4 in the axial direction X for connection and locking to the output shaft S. The cylindrical portion 3 is provided with two cuts 15, 16 that develop along the axial direction X and make the cylindrical portion 3 elastically yielding in order to facilitate the connection of the fan 1 to the output shaft S.

A peripheral portion 5, circular in shape, surrounds the hub portion 2. The peripheral portion 5 is rounded in the shape of a dome and develops in the axial direction X starting from a circular external peripheral edge 6 with diameter Dl towards the inside until defining a circular opening 7 with peripheral edge with diameter D2. Said circular opening 7 defines the inlet, or intake mouth, of the cooling fluid, constituted by air, when the fan 1 is set rotating in the axial direction X.

Eight equally distributed radial elements 8, each one of which is in the shape of a vane, develop in the axial direction X substantially starting from the same plane of origin Z, as shown in Figure 7d, and extend between the hub portion 2 and the peripheral portion 5 defining eight inter-vane ducts 9 for the passage of the air coming from the inlet 7 and directed towards the back of the fan 1.

The radial elements 8 comprise, radially towards the outside, an area 30 that projects from the plane of origin Z and in the direction opposite the direction of development of the radial elements 8, as shown in particular in the cross section of Figure 7d.

The projecting area 30 is provided radially with an extension D4 equal to approximately 10% of the diameter Dl of the external peripheral edge 6 and an axial extension D5 equal to approximately 20% of the axial extension D6 of the radial element 8.

The radial extension D4 of the projecting area 30 preferably assumes values included between 10% and 30% compared to the radial extension Dl of the external peripheral edge 6 and the axial extension D5 of the projecting area 30 assumes values included between 10% and 30% compared to the axial extension D6 of the radial elements 8.

The projecting area 30, as shown in detail in Figure 7a, protrudes from the back of the circular external peripheral edge 6 of the peripheral portion 5.

The diameter D2 of the peripheral edge of the inlet 7 is equal to 0.7 times the value of the diameter Dl of the external peripheral edge 6.

In other words, the surface delimited by the inlet 7, that is, the area of the circle with diameter D2, is equal to approximately 50% of the surface delimited by the external peripheral edge 6, that is, the area of the circle with diameter D 1. It has surprisingly occurred that even if the surface area of the inlet 7 of the peripheral portioa 5 is reduced compared to the inlet of the fans belonging to the known art, with the same external diameter of the fan, the efficiency of the fan in terms of flow rate Pu of air leaving the fan increases considerably. In particular, the increase in the flow rate of the outflowing air that hits the fins Ml of the motor M causes a decrease in the operating temperature of the motor M.

It has been observed that said increase in efficiency is worthy of note for reductions of the surface area of the inlet 7 to values not below approximately 15% compared to the area delimited by the circular external peripheral edge 6 or, in other words, to values of the diameter D2 of the peripheral edge of the inlet 7 not below 0.4 times the value of the diameter Dl of the external peripheral edge 6.

Preferably, the surface area of the inlet 7 is maintained at values not below approximately 25% and not exceeding 42% compared to the area delimited by the circular external peripheral edge 6 or, in other words, to values of the diameter D2 of the peripheral edge of the inlet 7 not below 0.5 times the value of the diameter Dl of the external peripheral edge 6 and not exceeding 0.65 times the value of the diameter Dl of the external peripheral edge 6.

Even more preferably, the surface area of the inlet 7 is chosen so that it is equal to 36% of the area delimited by the circular external peripheral edge 6 or, in other words, the value of the diameter D2 of the peripheral edge of the inlet is chosen so that it is equal to 0.6 times the value of the diameter Dl of the external peripheral edge 6.

A sixth embodiment of the fan 1 that is the subject of the invention is illustrated with reference to the Figures from 8a to 8e.

The fan 1 shown in said figures differs from the fan 1 of the fifth embodiment described with reference to the Figures from 7a to 7e only due to the fact that the projecting area 30 does not protrude from the back of the circular external peripheral edge 6 of the peripheral portion 5, but rather the peripheral edge 6 further extends along the axial direction X. As shown in particular in Figure 4a, at the back of the peripheral edge 6 a cylindrical section 40 is defined, whose axial extension D5 corresponds to the axial extension D5 of the projecting area 30.

A seventh embodiment of the fan that is the subject of the invention is illustrated with reference to the Figures from 9a to 9e. The fan 1 comprises a hub portion 2 in the shape of a flange, comprising a cylindrical portion 3 provided with a through hole 4 in the axial direction X for connection and locking to the output shaft S. The cylindrical portion 3 is provided with two cuts 15, 16 that develop along the axial direction X and make the cylindrical portion 3 elastically yielding in order to facilitate the connection of the fan 1 to the output shaft S.

The hub portion 2 also comprises a base portion 20 that extends radially towards the outside until reaching a circular edge 21 with diameter D3, better visible in Figure 9e.

A peripheral portion 5, circular in shape, surrounds the hub portion 2. The peripheral portion 5 is rounded in the shape of a dome and develops in the axial direction X starting from a circular external peripheral edge 6 with diameter Dl towards the inside until defining a circular opening 7 with peripheral edge with diameter D2. Said circular opening 7 defines the inlet, or intake mouth, of the cooling fluid, constituted by air, when the fan 1 is set rotating in the axial direction X.

Eight equally distributed radial elements 8, each one of which is in the shape of a vane, develop in the axial direction X substantially starting from the same plane of origin Z, as shown in Figure 9d, and extend between the hub portion 2 and the peripheral portion 5 defining eight inter-vane ducts 9 for the passage of the air coming from the inlet 7 and directed towards the back of the fan 1.

The air coming from the inlet 7 that flows in . the inter-vane ducts 9 is advantageously conveyed radially from the base portion 20 towards the outside, that is, towards the peripheral area that faces towards the fins Ml of the motor M when the fan 1 is connected to the motor M.

The radial elements 8 comprise, radially towards the outside, an area 30 that projects from the plane of origin Z and in the direction opposite the direction of development of the radial elements 8, as shown in particular in the cross section of Figure 9d.

The projecting area 30 is provided radially with an extension D4 equal to approximately 10% of the diameter Dl of the external peripheral edge 6 and an axial extension D5 equal to approximately 25% of the axial extension D6 of the radial element 8.

The radial extension D4 of the projecting area 30 preferably assumes values included between 10% and 30% compared to the radial extension Dl of the external peripheral edge 6 and the axial extension D5 of the projecting area 30 assumes values included between 10% and 30% compared to the axial extension D6 of the radial elements 8.

The projecting area 30, as shown in detail in Figure 9a, protrudes from the back of the circular external peripheral edge 6 of the peripheral portion 5.

The diameter D2 of the peripheral edge of the inlet 7 is equal to 0.7 times the value of the diameter Dl of the external peripheral edge 6.

The diameter D2 of the peripheral edge of the inlet 7 is slightly longer than the diameter D3 of the circular edge 21 of the base portion 20, as can be seen in detail in the section shown in Figure 9e.

An eighth embodiment of the fan 1 that is the subject of the invention is illustrated with reference to the Figures from 10a to lOe.

The fan 1 shown in said figures differs from the fan 1 of the seventh embodiment described with reference to the Figures from 9a to 9e only due to the fact that the projecting area 30 does not protrude from the back of the circular external peripheral edge 6 of the peripheral portion 5, but rather the peripheral edge 6 further extends along the axial direction X. As shown in particular in Figure 10a, at the back of the peripheral edge 6 a cylindrical section 40 is defined, whose axial extension D5 corresponds to the axial extension D5 of the projecting area 30.

A ninth embodiment of the fan that is the subject of the invention is illustrated with reference to the Figures from 1 la to l ie.

The fan 1 comprises a hub portion 2 in the shape of a flange, comprising a cylindrical portion 3 provided with a through hole 4 in axial direction X for connection and locking to the output shaft S. The cylindrical portion 3 is provided with three cuts 15, 16 and 55 that develop along the axial direction X and make the cylindrical portion 3 elastically yielding in order to facilitate the connection of the fan 1 to the output shaft S.

The hub portion 2 also comprises a base portion 20 that extends radially towards the outside until reaching a circular edge 21 with diameter D3, better visible in Figure 1 le.

A peripheral portion 5, circular in shape, surrounds the hub portion 2. The peripheral portion 5 is rounded in the shape of a dome and develops in the axial direction X starting from a circular external peripheral edge 6 with diameter Dl towards the inside until defining a circular opening 7 with peripheral edge with diameter D2. Said circular opening 7 defines the inlet, or intake mouth, of the cooling fluid, constituted by air, when the fan 1 is set rotating in the axial direction X.

Ten equally distributed radial elements 8, each one of which is in the shape of a vane, develop in the axial direction X substantially starting from the same plane of origin Z, as shown in Figure 1 Id, and extend between the hub portion 2 and the peripheral portion 5 defining ten inter- vane ducts 9 for the passage of the air coming from the inlet 7 and directed towards the back of the fan 1.

The air coming from the inlet 7 that flows in the inter-vane ducts 9 is advantageously conveyed radially from the base portion 20 towards the outside, that is, towards the peripheral area that faces towards the fins Ml of the motor M when the fan 1 is connected to the motor M.

The radial elements 8 comprise, radially towards the outside, an area 30 that projects from the plane of origin Z and in the direction opposite the direction of development of the radial elements 8, as shown in particular in the cross section of Figure l id.

The projecting area 30 is provided radially with an extension D4 equal to approximately 10% of the diameter Dl of the external peripheral edge 6 and an axial extension D5 equal to approximately 25% of the axial extension D6 of the radial element 8.

The circular external peripheral edge 6 of the peripheral portion 5 extends along the axial direction X, as shown in particular in Figure 1 1a, in order to define at the back of the peripheral edge 6 a substantially cylindrical section 40 whose axial extension D5 corresponds to the axial extension D5 of the projecting area 30.

On the external surface of the peripheral portion 5 there are ten recessed ribs 80, better visible in Figure 1 la, at the level of the radial elements 8.

The diameter D2 of the peripheral edge of the inlet 7 is equal to 0.6 times the value of the diameter Dl of the external peripheral edge 6.

The diameter D2 of the peripheral edge of the inlet 7 is slightly longer than the diameter D3 of the circular edge 21 of the base portion 20, as can be seen in detail in the section shown in Figure l ie.

In all the embodiments described above the external peripheral edge, the inlet and the base portion are circular in shape. Said circular shape should be preferred, in terms of fan efficiency and simplicity of construction. However, in different embodiments of the invention not described herein, said shape may be different, for example a polygonal shape, preferably regular.

Again, the means for connecting the fan to the shaft of the electric motor may be different, like for example a connection with snap ring, or a connection with metal clamp and screws, or again a connection with plastic clamp.

It has thus been shown that the present invention allows all the set objects to be achieved. In particular, it makes it possible to provide a fan for electric motors that generates flow rates of outflowing air that ensure higher efficiency in the ventilation of the fins of the motor to which the fan is applied.

While the present invention has been described with reference to the particular embodiments shown in the figures, it should be noted that the present invention is not limited to the specific embodiments illustrated and described herein; on the contrary, further variants of the embodiments described herein fall within the scope of the present invention, which is defined in the claims.