Patent Description:
An electric motor is an electrical machine able to convert electrical energy into mechanical energy. More precisely an electric motor produces a linear or a rotary force (torque) which is transferred to an external device, system or mechanism by a mechanical connection. The electric motors are classified in two main groups: linear motors and rotary motors. As known, a rotary electric motor typically comprises a hollow frame that develops along a longitudinal axis so as to define a longitudinal cavity inside which an annular stator assembly is arranged. A first endshield and a second endshield are rigidly fixed to the frame at opposite end thereof. A rotor is supported by the two endshields at its opposite ends so as to rotate coaxially and internally to the stator.

According to a first known solution, an electric motor is provided with air cooling means comprising an axial fan arranged inside a cavity defined in one of the two endshields. The axial fan is mounted on the rotor shaft at one end opposite to the one used to transfer the mechanical torque to an external device or system. The frame is provided with axial fins protruding outwards in order to increase the exchange surface useful to dissipate heat generated during the operation of the electric motor. The air motion is induced by the rotation of the rotor. Indeed, following such a rotation, the axial fan blows up air on the outer surface of the frame so as to reduce its temperature by convention.

This solution is typically provided on constant speed electric motor. According to a different solution, usually installed on variable speed electric motors, an axial fan is arranged in a cavity of an endshield and operated independently from the rotor, by means of another motor. In this case, the air is usually blown up across the stator and/or frame axial channels. In some cases, the air may be blown also up on the rotor and the overhangs. In some known embodiments, the frame has a rectangular section, considered in a plane orthogonal to the rotor axis, and it is provided with axial channels each of which provided at a corresponding corner of the section.

As a fact, the most of the electric motors on the market are air cooled. However, in some applications, for example in the field extrusion plastic processes wherein the use of air is a critical factor in terms of environmental cleanliness or whenever the noisiness has to be minimized, liquid cooled electric motors are preferred. Typically, water, glycol or oil are used as cooling fluids. According to a first known embodiment, the cooling is obtained by means of a liquid jacket or a coil pipe that surrounds the frame of the motor in which the stator and the rotor are arranged. Examples of known liquid cooled electric motors are disclosed in <CIT> and <CIT>.

According to a further known embodiment, the liquid cooling system comprises a plurality of pipes each of which inserted in a corresponding channel longitudinally defined through the frame of the electric motor. Overall, these pipes define a cooling circuit by means of which the cooling fluid subtracts heat from the frame. Indeed, the heat is transmitted from the frame to the pipes by conduction and then from the pipes to the cooling fluid by convection.

In order to allow the circulation along the pipes, the latter are mutually connected each other at their ends. On this regard, according to a known solution, the body of the endshields is machined so as to define a plurality of connecting channels each of which hydraulically connects two ends of different pipes. These channels are obtained close to the surface of the endshield addressed to be connected to the frame and their axis of development lay on a plane orthogonal to the longitudinal axis. These channels are connected to the pipes of the frame by means of axial holes defined longitudinally through the endshield body. The ends of two different pipes are inserted in two corresponding axial holes while appropriate hydraulic plugs are used to close the connecting channel at their end. Therefore, the cooling liquid exiting from a pipe can enter into the connecting channel that diverts it to another pipe. The hydraulic plugs avoid the liquid to exit from the connecting channel, i.e., from the endshield.

Usually, since the diameter of the connecting channels as well as the diameter of the pipes through the frame cannot be much increased, in order to guarantee a sufficient cooling effect, the motor is designed so as to have the highest number of them. This solution allows to increase the length of the hydraulic circuit so as to compensate the relatively low flow rate circulating along the pipes and connecting channels and imposed by their diameter. However, overall, this technical solution is particularly complex and is a critical aspect in terms of manufacturing times and of costs. Further, several sealing interfaces (e.g., O-Rings or other similar devices) have to be provided to guarantee the correct sealing between the different components in mutual contact. The higher the number of sealing interfaces, the higher is the complexity, the time needed to assemble and the risk of failure (e.g., an O-ring wrongly mounted or missing). This in turn requires an accurate sealing test after the whole assembling and a complex recovery procedure if the test goes wrong. Moreover, the pipes must be inserted by pressing them to achieve a good contact with the stator laminations. Alternatively, they can be easily inserted with small interference but this leads to a very poor heat conduction characteristic.

The main aim of the present invention is providing a liquid cooled electric motor which makes it possible to overcome or mitigate the aforementioned problems of the known art.

In the context of this aim, an object of the present invention is providing a liquid cooled electric motor that allows to simplify the manufacturing of the endshields at least for what concerns the liquid fluid circulation therein.

Another object of the present invention is providing a liquid cooled electric motor that can be easily configurated, in terms of hydraulic cooling circuit, depending on the use and/or of the space available for its installation.

A further object is providing a liquid cooled electric motor easy to manufacture at industrial level, at competitive costs with similar electric motors of the state of the art.

This aim and these objects, together with other objects that will become evident from the following description and accompanying drawings, are achieved, according to the present invention, by a cooled electric motor, according to claim <NUM> and the related dependent claims set out below.

In a general definition, a liquid cooled electric motor, according to the invention, comprises:.

The electric motor according to the invention is characterized in that said hydraulically connecting channel comprises at least a first section configured by the coupling of a collector element with a seat defined by one of said endshields. The seat has a coupling surface that develops around said longitudinal axis, said collector being a ring-shaped body with an outer surface and an inner surface, wherein said outer surface couples with the coupling surface of the seat, wherein said outer surface and said coupling surface are shaped so as to configure the first section of said connecting channel following their coupling.

According to an embodiment, said hydraulic connecting channel comprises a second section and a third section wherein said first section is comprised between said second section and said third section, wherein said second section and said third section make said first section communicating with a corresponding of said circulation channels.

According to a preferred embodiment, said ring-shaped body comprises a slot which develops from the outer surfaces along an angular sector around said longitudinal axis, wherein said first section of said hydraulic connecting channel is configured by the coupling surface of the seat and by the surfaces defining such at least one slot.

According an embodiment, said second section and said third section are defined by two cavities each of which communicates with at least one of said circulation channels, and wherein at least two of said cavities comprises a corresponding opening that makes the corresponding cavities communicating with the first section of said hydraulic connecting channel.

Preferably, said one of said endshields comprises four cavities each of which communicates with at least one of said circulation channels, and wherein each of the cavities comprises a corresponding opening at the coupling surface; the ring-shaped body is coupled with said seat so that the slot communicates with two of said cavities by the corresponding openings. According to a possible embodiment, the ring-shaped body comprises two slots symmetrically defined with respect to a diametral plane containing said longitudinal axis; when the ring-shaped body is coupled with the seat, a first slot hydraulically connects a first cavity with a second cavity while a second slot hydraulically connects a third cavity and the fourth cavity. According to a possible embodiment of the ring-shaped body, the outer surface of said ring-shaped body comprises a first portion and a second portion which are separated by said at least one slot, at least along the angular sector along which it develops; each of the portions comprises at least a circumferential groove that develops for an angle of <NUM>° around the longitudinal axis, wherein such groove accommodates a sealing element.

Preferably, the first portion is closer to the frame than said second portion and wherein said first portion comprises two or more circumferential grooves each of which to accommodate a sealing element.

According to a possible embodiment, the frame has a rectangular shaped cross section, wherein said cross section is considered on a plane orthogonal to said longitudinal axis. According to another embodiment, at least one of said endshields has a prismatic shape defined by four side external surfaces that develop on planes two by two parallel.

Preferably, at least one of the endshields comprises four external open cavities each of which defined at one of its corners, wherein each corner is identified by two external surfaces of the endshield, wherein the open cavities accommodate connecting means to connect said frame to the endshield and/or to connect a hydraulic connector to feed or to discharge the cooling fluid flowing in said circulation channels.

According to a possible embodiment, the frame is obtained by extrusion process and the circulation channels are defined during such extrusion process or alternatively the frame is obtained from a single casting piece as well as the circulation channels are obtained in the casting itself. The frame <NUM> could be also obtained by means of a 3D printing process.

According to a further embodiment, said plurality of circulation channels comprises a first couple, a second couple, a third couple and a fourth couple of circulation channels wherein each of these couples is defined at a corresponding corner of said frame. Preferably, for at least one of the couples of the circulation channels, the channels are symmetrically arranged with respect to a radial plane containing the longitudinal axis, wherein the radial plane is a symmetric plane also for the corresponding corner.

Further characteristics and advantages of the invention will emerge from the description of preferred, but not exclusive embodiments of an electric motor according to the present disclosure, non-limiting examples of which are provided in the attached drawings, wherein:.

Referring to the above-mentioned figures, the present invention relates to a liquid cooled electric motor <NUM>, preferably having a variable rotational speed. The electric motor <NUM> comprises a frame <NUM> that develops along a longitudinal axis <NUM> and two endshields <NUM>, <NUM> that are connected at opposite ends of the frame <NUM>. Preferably, the frame <NUM> is defined by an extruded body made of metallic material, preferably made of aluminum.

The frame <NUM> has a first end surface 5A and a second end surface 5B that develop orthogonally to the longitudinal axis <NUM> and whose mutual distance defines the longitudinal length of the frame <NUM>. On this regard, such a length may vary depending on the size of the electric motor <NUM>. Also, the shape of the transversal section (namely the section considered on a plane orthogonal to the longitudinal axis <NUM>) of the frame <NUM> may vary as a function, for example, of the installation for which the electric motor is designed. Preferably, the transversal section has a rectangular shape, more preferably a square shape, with four blunt corners C1, C2, C3, C4 (see for example <FIG>, <FIG>, <FIG> and <FIG>). This means the frame <NUM> comprises four main external surfaces <NUM>, <NUM>, <NUM>, <NUM> that lay on planes two by two parallel.

The electric motor <NUM> also comprises a stator assembly <NUM> and a rotor assembly <NUM>. According to a solution known per se, the stator assembly <NUM> is arranged, at least partially, in a longitudinal cavity <NUM>' (indicated in <FIG> and <FIG>) defined by the extruded body of the frame <NUM>. The rotor assembly <NUM> is arranged in a cylindrical longitudinal space defined by the stator assembly <NUM>. The configuration of the stator assembly <NUM> and/or the rotor assembly <NUM> are not relevant for the present invention. A skilled person is aware of possible configurations that such assemblies may assume in this kind of electric motors.

In any case, the rotor assembly <NUM> comprises a rotor <NUM> which is supported, at opposite terminal parts 31A-31B, by the endshields <NUM>,<NUM> so as to rotate about the longitudinal axis <NUM>. More precisely, the rotation is allowed by bearing means 35A-35B (see <FIG>) interposed between a corresponding terminal part 31A, 31B of the rotor <NUM> and a corresponding of said endhields <NUM>,<NUM>. A drive end 3A of the rotor <NUM> protrudes outside one of the two endshields to be connected to transfer the rotary force (torque) to an external device, system or mechanism, according to a solution known per se. In the figures, the endshield from which the drive end 3A protrudes is indicated with the reference <NUM> and with the acronym DE <NUM> in the present description. Instead, the other endshield, opposed to the DE, is indicated with the reference number <NUM> in the figures and with the acronym NE <NUM> in the present description.

The electric motor <NUM> comprises first connecting means 15A and second connecting means 15B for connecting the DE <NUM> and the NE <NUM>, respectively, to a corresponding end surface 5A-5B of the frame <NUM>. In the embodiment shown in the Figures, the DE <NUM> is connected to the first surface 5A by first connecting means 15A and the NE <NUM> is connected to the second surface 5B by second connecting means 15B (see for example <FIG>, <FIG>, <FIG>). More in detail, both the connecting means 15A-15B (first and second) comprise a plurality of axial bolts longitudinally screwed in the frame <NUM>, namely according to a direction parallel to the longitudinal axis <NUM>.

Each of the two endshields (DE <NUM>, NE <NUM>) comprises a body with an internal cavity <NUM>, <NUM> (see <FIG> and <FIG>) in which corresponding bearing means 35A, 35B are arranged to support the rotor <NUM>, as above indicated (see <FIG>). More precisely, at least the internal cavity <NUM> of the DE <NUM> develops through the entire axial length thereof to allow the drive end 3A of the rotor <NUM> to protrude outside (see <FIG>, <FIG> and <FIG> in combination).

Each of the endshields DE <NUM>, NE <NUM> further comprises a transversal coupling surface <NUM>, <NUM> which is stably in contact with a corresponding end surface 5A, 5B of the frame <NUM> due to the fixing action of the corresponding connection means 15A, 15B. For this purpose, each of the transversal coupling surfaces <NUM>,<NUM> develops on a plane orthogonal to the longitudinal axis <NUM>. Preferably, a sealing element (not shown in the figures) is placed between the transversal coupling surface <NUM>, <NUM> of each endshields <NUM>,<NUM> and the corresponding end surface 5A, 5B of the frame <NUM>. The sealing element (for example made of paper for seals) has the purpose to seal off, at the endshields <NUM>,<NUM>, the liquid cooling means provided for cooling the electric motor <NUM>.

According to a possible embodiment, the two endshields <NUM>, <NUM> have a prismatic shape defined by four side external surfaces 12A, 12B, 12C, 12D-22A, 22B, 22C, 22D that develop on planes two by two parallel. Preferably, for each of the two endshields <NUM>, <NUM>, each external surface 12A, 12B, 12C, 12D-22A, 22B, 22C, 22D develops on a plane that is parallel to one on which an external surface <NUM>, <NUM>, <NUM>, <NUM> of said frame <NUM> develops.

In the embodiment shown in the figures, the first connecting means 15A comprise four axial bolts each of which arranged at a corner of the first end surface 5A of the frame <NUM> and of the corresponding transversal surface <NUM> of the DE <NUM>. A similar solution is provided, mutatis mutandis, also for the second connecting means 15B that connects the second end surface 5B to the transversal surface <NUM> of the NE <NUM>. However, a different number of bolts could be provided for the first connecting means 15A and for the second connection means 15B.

As shown in <FIG>, the DE <NUM> comprises four external open cavities 11A, 11B, 11C, 11D each of which defined at one of its corners, wherein each corner is identified by two external surfaces 12A, 12B, 12C, 12D of the DE <NUM> lying on orthogonal planes. These cavities 11A, 11B, 11C, 11D are provided for positioning the connecting means 15A (axial bolts) and, in the case, for positioning hydraulic connectors used to feed or to discharge the circulation channels <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' of liquid cooling means as below described. Further, the cavities 11A, 11B, 11C, 11D may be advantageously used for arranging fixing means (for example fixing bolts 17A) useful for connecting the DE <NUM> to a surface and/or to another device.

As shown in <FIG> a similar solution is provided for NE <NUM> that comprises four external open cavities 21A, 21B, 21C, 21D with a similar configuration of those provided for DE <NUM> and with the same purposes. On this regard, each of the external open cavities 21A, 21B, 21C, 21D is defined at one of the corners of the DE <NUM>, wherein each corner is identified by two external surfaces 22A, 22B, 22C, 22D lying on orthogonal planes; further, each of the external open cavities 21A, 21B, 21C, 21D is opened on a corresponding side external surface 22A, 22C and on a surface opposite to the transversal coupling surface <NUM> of the NE <NUM>. The external open cavities 21A, 21B, 21C, 21D are provided for positioning connecting means 15B, hydraulic connectors <NUM>, <NUM>, <NUM>', <NUM>" and/or fixing means 17B.

The electric motor <NUM> according to the invention comprises liquid cooling means to dissipate heat generated during its operation. Such a cooling means comprise a plurality of circulation channels <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' for the circulation of a cooling fluid, preferably, but non exclusively, water. These circulation channels <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' are preferably defined directly by the frame <NUM> so that the cooling liquid, flowing along the channels, exchanges heat directly with the frame <NUM>.

Preferably, these circulation channels <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' are axially oriented, i.e., they develop mainly along a direction parallel to the longitudinal axis <NUM>. On this regard, the circulation channels <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' are preferably defined during the extrusion process by means of which the frame <NUM> is obtained. Alternatively, they can be obtained by machining the frame <NUM>, that is by drilling it longitudinally. As above, the frame <NUM> could be obtained by an extrusion process, a casting process or a 3D printing process or any other process suitable for the purpose.

According to an alternative embodiment (not shown in the figures), the circulation channels can be defined by pipes inserted in corresponding longitudinal holes defined through the frame <NUM>. In this case, the heat exchange between the cooling fluid and the frame is "indirect" due to the interface of the pipes along which the fluid flows.

In view of what above, for the purposes of the present invention the expression "circulation channel" wants generally to indicate a channel which crosses longitudinally (i.e., parallelly to the longitudinal axis <NUM>) the frame <NUM> and along which the cooling fluid flows to exchange heat "directly" or "indirectly" with the frame in order avoid the overheating thereof.

In the embodiment shown in the figures, the frame comprises a first couple <NUM>-<NUM>', a second couple <NUM>-<NUM>', a third couple <NUM>- <NUM>' and a fourth couple <NUM>-<NUM>' of circulation channels wherein each of these couples is defined at a corresponding corner of the frame <NUM> as it can be seen in <FIG> showing the end surface 5A of the frame <NUM> addressed to be connected to the contacting surface <NUM> of the DE <NUM>.

For each of said couples of circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', the two channels are symmetrically arranged with respect to a radial plane <NUM> containing the longitudinal axis <NUM>, wherein said radial plane <NUM> is a symmetric plane also for the corresponding corner C1, C2, C3, C4.

Always with reference to <FIG> and <FIG>, the transversal section (perpendicular to axis <NUM>) of the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' has a polygonal shape so as to occupy as mush as possible the area of the corresponding corner, i.e. area of the transversal section comprised between the two external surfaces of the <NUM>, <NUM>, <NUM>, <NUM> of the frame <NUM> identifying the corner C1, C2, C3, C4 and the internal cavity <NUM>' of the frame itself. This solution allows to increase the flow rate of the cooling liquid usable.

Further, as shown in <FIG>, the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' are preferably finned inwardly. This solution allows to increase the heat exchange surface with the cooling fluid. The fins can be easily obtainable by means of the extrusion process used to manufacture the frame <NUM>.

According to the invention, the cooling means comprise at least a hydraulic connecting channel <NUM>, <NUM>A,<NUM>B (see <FIG> and <FIG>) defined in one of the endshields <NUM>, <NUM> for connecting hydraulically two of the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>'. The expression "defined in" wants to indicate that the connecting channel is comprised in the space occupied by a corresponding endshields <NUM>, <NUM>, i.e. the space delimited by its external surfaces 12A-12B-12C-12D, 22A-22B-22C-22D. Further, for the purposes of the present invention, the expression "connecting channel" wants to indicate generally a "space" or a "conduit" in which the cooling fluid exiting from a circulation channel can flow up to the entry of another circulation channel, independently from the shape and of such a space/conduit.

According to the present invention, the hydraulic connecting channel <NUM>, <NUM>A,<NUM>B comprises at least a first section <NUM>,<NUM>A,<NUM>B defined by the coupling of a collector element <NUM>', <NUM>" with a seat <NUM>', <NUM>" defined by the body of said one of the endshields <NUM>, <NUM>. In other words, the collector element <NUM>', <NUM>" and the seat <NUM>', <NUM>" are shaped so that the first section <NUM>,<NUM>A,<NUM>B of the channel <NUM>, <NUM>A,<NUM>B is defined only following their coupling.

Therefore, according to the invention, the hydraulic communication between two of said circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' is obtained by the coupling of at least two components (one of the endshields <NUM>,<NUM> and a collector element <NUM>', <NUM>") which are manufactured separately. This technical solution allows to simplify the machining of the endshields and consequently the costs and times for this operation. Further, this solution allows to increase the size of the hydraulic connecting channel and consequently to increase the cooling liquid flow rate.

According to an embodiment, shown also in the figures, the hydraulic connecting channel <NUM>, <NUM>A,<NUM>B comprises also a second section and a third section that make the first section <NUM>,<NUM>A,<NUM>B communicating with a corresponding of said circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>'. In particular, the second section and the third section are preferably defined only by the structure of the corresponding endshields <NUM>, <NUM>.

According to a preferred embodiment shown in the figures, the seat <NUM>', <NUM>" has an annular configuration and develops around the longitudinal axis <NUM>. Preferably, the seat <NUM>', <NUM>" comprises a coupling surface 71A', 71A" whose shape is, at least partially, cylindrical developing around the longitudinal axis <NUM>. The collector element <NUM>', <NUM>" is a ring-shaped body with an outer surface 61A', 61A" and an inner surface 61B', 61B'' wherein the outer surface 61A', 61A" couples with the coupling surface 71A', 71A" of the seat <NUM>', <NUM>". When coupled with the seat <NUM>', <NUM>", the ring-shaped body <NUM>', <NUM>" (i.e., the collector element <NUM>', <NUM>") is coaxial with the longitudinal axis <NUM>.

More precisely, the coupling surface 71A', 71A" of the seat <NUM>', <NUM>" and the outer surface 61A', 61A" of the ring-shaped body <NUM>', <NUM>" are shaped so as to define said first section <NUM>,<NUM>A,<NUM>B of the connecting channel <NUM>, <NUM>A,<NUM>B. Preferably, the ring-shaped body <NUM>', <NUM>" comprises at least one slot <NUM>', <NUM>'A, <NUM>'B that develops inwardly (i.e. toward the longitudinal axis <NUM>) from the outer surface 61A', 61A". Preferably, such a slot has a U-shape, considered on a radial plane containing the longitudinal axis <NUM>.

The slot <NUM>', <NUM>'A, <NUM>'B develops for a pre-stablished angular sector (angle α) around the longitudinal axis <NUM>. Preferably, this angular sector is less than <NUM>°, as an example the angle can be <NUM>°. Therefore, in such an embodiment, the first section <NUM>,<NUM>A,<NUM>B of the hydraulic connecting channel <NUM>, <NUM>A,<NUM>B is delimited by the surfaces of said slot <NUM>', <NUM>'A, <NUM>'B and by the cylindrical coupling surface 71A', 71A" of the seat <NUM>', <NUM>" to which the outer surface 61A', 61A" of the ring-shaped body <NUM>', <NUM>" is coupled.

According to an alternative solution, not shown in the figures, the outer surface of the ring-shaped body could be cylindrical while the coupling surface of the seat could be configured so as to define a slot which develops in the endshield body; such alternative solution is conceptually equivalent to the one shown in the figures. In this alternative solution, the first section of the channel would be defined by the surface of the endshield slot and by the outer surface of the cylindrical ring-shaped body.

The <FIG> are views showing the NE <NUM> and the ring-shaped body <NUM>" couplable with the seat <NUM>" of the same NE <NUM>. As shown, the seat <NUM>" develops axially from the transversal coupling surface <NUM> of NE <NUM>. This means, when the electric motor <NUM> is assembled, the ring-shaped body <NUM>" is adjacent to the end surface 5B of the frame <NUM>. On this regard, <FIG> clearly shows the arrangement of the ring-shaped body <NUM>" with respect to the frame <NUM> and the seat <NUM>" of the NE <NUM>.

According to a preferred embodiment, considering the NE <NUM>, the second section and the third section of the connecting channel are configured by two cavities 92A',92B', 92C', 92D' defined of the NE <NUM>, each of which being hydraulically connected to at least one of the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>'. Each of the cavities 92A',92B', 92C', 92D' comprises a corresponding opening 9A-9B-9C-9D that makes it communicating with the first section of the connecting channel.

More precisely, in the <FIG>, the NE <NUM> comprises four cavities 92A',92B', 92C', 92D' each of which develops axially from the transversal coupling surface <NUM> of NE <NUM> (see <FIG>). Each of these cavities 92A',92B', 92C', 92D' is located a corner of the NE <NUM> so as to face a corresponding couple of circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' (see <FIG> and <FIG>). This allows the cooling fluid to flow from a cavity 92A',92B', 92C', 92D' to the corresponding couple of circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' or vice versa.

Further, each of these cavities 92A',92B', 92C', 92D' comprises a corresponding opening 9A'-9B'-9C'-9D' at the coupling surface 71A" of said seat <NUM>". The ring-shaped body 61A" is coupled with said seat <NUM>" so that the first section <NUM>A,<NUM>B of the hydraulic channel <NUM>, <NUM>A,<NUM>B communicates with two of the four cavities 92A',92B', 92C', 92D' by means of the corresponding openings 9A'-9B'-9C'-9D'. In other words, according to the invention, at least two of the above cavities 92A', 92B', 92C', 92D' of the NE <NUM> are made hydraulically connected by means of the first section <NUM>A,<NUM>B of the hydraulic channel <NUM>A,<NUM>B resulting from the coupling of the slot <NUM>" of the ring-shaped body <NUM>" with the coupling surface 71A" of the seat <NUM>".

On this regard, in the embodiment shown in <FIG>, at the NE <NUM>, the ring-shaped body 61A" is arranged in the seat <NUM>" so as to define two hydraulic connecting channels <NUM>A,<NUM>B. The two cavities 92A' and 92B' correspond to the second section and the third section of a first hydraulic channel <NUM>A being hydraulically connected by a first slot <NUM>'A of the ring-shaped body <NUM>". Analogously the two cavities 92C' and 92D' are hydraulically connected by a second slot <NUM>'B of the ring-shaped body <NUM>" defining the second section and the third section of a second hydraulic channel <NUM>B.

However, as below better clarified, the angular position of the ring-shaped body <NUM>", chosen for the arrangement in the seat <NUM>", determines which couple of cavities 92A',92B', 92C', 92D' of the NE <NUM> become hydraulically connected via the first section <NUM>A, <NUM>B of a hydraulic channel <NUM>A, <NUM>B, wherein in any case such a first section is defined by the coupling of the ring-shaped body <NUM>" with the seat <NUM>" of the NE <NUM>.

On this regard, looking in combination <FIG> and <FIG>, at the transversal coupling surface <NUM> of the NE <NUM>, each cavity 92A',92B', 92C', 92D' has a section geometrically corresponding to that of the cross section of the two circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' to which it faces. This solution optimizes the cooling liquid flow in both the directions.

Further, each cavity 92A',92B', 92C', 92D' preferably comprises a service opening 97A', 97B', 97C', 97D' for the possible connection of a hydraulic connector <NUM>, <NUM>, <NUM>', <NUM>" useful to supply or to discharge the cooling liquid from the hydraulic circuit defined by the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>' and the hydraulic connecting channels <NUM>A, <NUM>B (see <FIG>). When any hydraulic connector is not necessary, then such services openings 97A', 97B', 97C', 97D can be closed by a plug element.

As shown in <FIG> and <FIG>, for the DE <NUM> the same technical solutions, just above disclosed, are provided. In particular, the DE <NUM> comprises four cavities 92A,92B, 92C, 92D, that develop from the transversal coupling surface <NUM> of DE <NUM>, wherein each cavity faces a corresponding couple of circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>'. Further, for each cavities 92A, 92B, 92C, 92D of the DE <NUM>, an opening 9A-9B-9C-9D is provided in order to allow the hydraulic communication with the space defined by the coupling of the slot <NUM>' of the ring-shaped body <NUM>' with the seat <NUM>', namely with the first section <NUM> of a corresponding hydraulic connecting channel <NUM>. Therefore, also for the DE <NUM>, the second section and the third section of the hydraulic connecting channel <NUM> are defined by the corresponding cavities 92A,92B, 92C, 92D.

As for the NE <NUM>, also the cavities 92A,92B, 92C, 92D of the DE <NUM> may comprise a service opening 97A, 97B, 97C, 97D for the same purposes above indicated (see <FIG>).

<FIG> refer to possible embodiments of a ring-shaped body <NUM>',<NUM>" couplable with a corresponding seat <NUM>', <NUM>" of a corresponding end-shields <NUM>, <NUM>. In particular, in <FIG> the ring-shaped body is indicated with the reference number <NUM>', while the one in <FIG> is indicated with the reference number <NUM>". However, this indication does not want to limit in any way the use of the one of the illustrated ring-shaped body <NUM>', <NUM>" to a specific endshield (the NE <NUM> or the DE <NUM>). In other words, each one of the two illustrated bodies <NUM>', <NUM>" could be installed in NE <NUM> or alternative in DE <NUM>. Therefore, the ring-shaped body <NUM>', provided in the DE <NUM> in <FIG>, could be installed in the NE <NUM>, while the ring-shaped body <NUM>", provided in the NE <NUM> in Figure 4A, could be installed in the DE <NUM>. Further, for both of the endshields (<NUM>, <NUM>), the same ring-shaped body (<NUM>', <NUM>") could be provided.

In detail, in the embodiment shown in <FIG>, the ring-shaped body <NUM>' has a sole slot <NUM>' which develops from the outer surface 61A' toward the inner surface 61B'.

In particular, the section view of <FIG> shows the U shape of the slot <NUM>'. As shown, the outer surface 61A' comprises a first portion 611A and a second portion 621A which are separated by the slot <NUM>', at least along the angular sector along which it develops according to what above indicated. With reference in particular to <FIG>, following the assembly of the electric motor <NUM>, the portions 611A and 621A' are located respectively close and distal with respect to the frame <NUM>. Each of these portions 611A', 621A' comprises at least a circumferential groove <NUM> which develops for an angle of <NUM> around the longitudinal axis <NUM>. Such a groove <NUM> has the purpose to accommodate a sealing element (for example an O-ring) to seal the slot <NUM> and to avoid the exit of liquid from it).

As clearly illustrated in <FIG>, the first portion 611A comprises two (but they could be more) circumferential grooves <NUM> each of which to accommodate a sealing element. This increase the sealing effect on the part of the outer surfaces 61A' that faces the surface of the longitudinal cavity <NUM>' of the frame <NUM> at the end of the circulation channels <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', that is the part most subjected to the action of the cooling liquid (see <FIG>).

According to the possible embodiment shown in <FIG>, the ring-shaped body <NUM>" comprises two slots <NUM>'A, <NUM>'B symmetrically defined with respect to a diametral plane containing the axis of the body (longitudinal axis <NUM> when the electric motor <NUM> is assembled). These slots <NUM>'A, <NUM>'B have the same configuration of that shown in <FIG> and above described. With reference to <FIG>, when the ring-shaped body <NUM>" is coupled with the seat <NUM>', a first slot <NUM>'A, hydraulically connects a first cavity 92A' with a second cavity 92B', while a second slot <NUM>'A, <NUM>'B hydraulically connects the remaining cavities, namely the third cavity 92C' and the fourth cavity 92D'.

Overall, in the NE <NUM> shown in <FIG> it is possible to identify a first connecting channel <NUM>A in which the first section <NUM><NUM> is configured by the coupling of the ring-shaped body <NUM>" with the coupling surface 71A" of the seat <NUM>", while the second section and the third section are respectively configured by the first cavity 92A' and the second cavity 92B'. At the same time a second connecting channel <NUM>B is created, wherein the first section <NUM>B thereof is defined by the second slot <NUM>'B of the ring-shaped body <NUM>" coupled with said coupling surface 71A". The third cavity 92C' and the fourth cavity 92D' define respectively the second section and the third section of this second connecting channel <NUM>B. According to the purposes of the present invention, each of these two connecting channels <NUM>A, <NUM>B hydraulically connects two couples <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>'.

However, as above already, for both the endshields <NUM>, <NUM> the hydraulic connections between the cavities 92A, 92B, 92C, 92D-92A', 92B', 92C', 92D' can vary depending on the angular orientation chosen for the ring-shaped body <NUM>',<NUM>" when coupled with the corresponding seat <NUM>', <NUM>". For example, with respect to the condition shown in <FIG> or <FIG>, if the ring-shaped body <NUM>' of NE <NUM> was rotated of an angle of <NUM>° in the clock-wise direction (see arrow W in <FIG>), then the first slot <NUM>'A would make the first cavity 92A' and third cavity 92C' hydraulically connected, while the second slot <NUM>'B would connect the second cavity 92B' and the fourth cavity 92D'.

The use of an angularly adjustable ring-shaped body <NUM>',<NUM>" having one slot or two slots, allows to configure one or more hydraulic circuit by means of which the electric motor <NUM> is cooled. As a fact, the angular positioning of the ring-shaped body <NUM>', <NUM>" determines the mode by means of which the frame <NUM> is cooled. On this regard, <FIG> refer a first cooling mode of the electric motor <NUM> shown in <FIG> and <FIG>.

In <FIG>, an installation plane X is indicated. With respect to such a plane X, the circulation channels <NUM>-<NUM>', <NUM>-<NUM>' are hereinbelow named "couples of bottom channels" since defined respectively along a corresponding bottom corner C1, C2. The other circulation channels <NUM>-<NUM>', <NUM>-<NUM>' are named "couples of upper channels" since defined along corresponding upper corners C3, C4 of the frame <NUM>.

The NE <NUM> of the embodiment of <FIG> contains a ring-shaped body angularly adjusted so as to connect hydraulically the two couples of bottom channels <NUM>-<NUM>', <NUM>-<NUM>'. For this purpose, the ring-shaped body <NUM>" of the NE <NUM> may have a sole slot. Indeed, the DE <NUM> contains a ring-shaped body <NUM>' having two slots according to what above disclosed and shown in <FIG>. In particular, the ring-shaped body <NUM>' of DE <NUM> is adjusted so that each of said two slots <NUM>'A, <NUM>'B hydraulically connects one channel of the couple of upper channels <NUM>-<NUM>', <NUM>-<NUM>', with a corresponding one of the bottom channels <NUM>-<NUM>', <NUM>-<NUM>' defined on the same side with respect to reference plane Y, containing the longitudinal axis <NUM> and orthogonal to the installation plane X.

With reference to <FIG>, by means of a hydraulic inlet connector <NUM>, at the NE <NUM> the cooling fluid is inserted in a first couple of upper channels (<NUM>-<NUM>'). Such a connector <NUM> is arranged in a corresponding of the external open cavity 21A provided by the structure of the NE <NUM>. As shown by the arrows of <FIG>, the cooling fluid crosses longitudinally the frame <NUM> (arrow T1) so as to reach the DE <NUM> wherein it is diverted (arrow T2) by the ring-shaped body <NUM>' (in particular by a first slot <NUM>'A) to the entry of the of first couple of bottom channels (<NUM>, <NUM>'). Then, the cooling fluid comes back to the NE <NUM> (arrow T3) to be diverted, by the corresponding ring-shaped body <NUM>', to the second couple of circulating bottom channels (<NUM>-<NUM>') provided on the other side of the frame <NUM> (arrow T4 in <FIG>). With reference to <FIG>, the cooling fluid flows newly towards the DE <NUM> (arrow T5) wherein it is diverted to the second couple of upper channels (<NUM>, <NUM>') by a second slot <NUM>'B of the ring-shaped body <NUM>' provided in the DE <NUM> (see arrow T6). Finally, the cooling fluid comes back to the NE <NUM> (arrow T7) to exit by means of an outer hydraulic connector <NUM> arranged in a corresponding second external open cavity 21B of the NE <NUM>.

Therefore, in the embodiment shown in <FIG>, in view of the configuration of the hydraulic circuit, the same flow rate of cooling fluid flows four times longitudinally along the frame <NUM>.

<FIG> refer to a second cooling mode of the electric motor <NUM> of <FIG>. Also in this case, the DE <NUM> contains a ring-shaped body <NUM>' having two slots <NUM>'A, <NUM>'B and adjusted with the same purposes above indicated for the solution of <FIG>. Instead, the NE <NUM> contains a ring-shaped element without any slot so as to avoid any hydraulic communication between the couples of circulation channels (both upper and bottom). This solution results in two hydraulic circulation circuits each of which defined on a side of the frame <NUM>. These circuits are symmetric with respect to the plane Y above defined. The arrows (V<NUM>-V<NUM>-V<NUM> and V<NUM>', V<NUM>', V<NUM>') in <FIG> clearly show the fluid circulation direction in the two circuits. As shown, for each of the two sides (indicated with S1 and S2) of the frame <NUM>, a hydraulic inlet connector <NUM>'-<NUM>" is arranged at an upper external open cavity 21A, 21C of the NE <NUM>, while a hydraulic outlet connector <NUM>', <NUM>" is arranged at a bottom external open 21B, 21D of the NE <NUM>. In this case, for each of the circuits, the cooling fluid flows twice longitudinally along the frame <NUM>.

In view of what above, the use of the ring-shaped body above (with none, one or two slots) allows to configure different cooling modes depending on the installation, the space available for hydraulic connections and the operative conditions required to the electric motor, and in particular, depending on the cooling circuit.

Claim 1:
Liquid cooled electric motor (<NUM>) comprising:
- a frame (<NUM>) that develops along a longitudinal axis (<NUM>);
- a first endshield (<NUM>) and a second endshield (<NUM>) connected at opposite ends (<NUM>,<NUM>) of said frame (<NUM>);
- a stator assembly (<NUM>) and a rotor assembly (<NUM>), wherein said stator assembly (<NUM>) is arranged, at least partially, in a longitudinal cavity (5A) of said frame (<NUM>) and wherein said rotor assembly (<NUM>) is arranged, at least partially, in a longitudinal space defined by said stator assembly (<NUM>) and supported, at opposite ends, by said endshields (<NUM>, <NUM>) so as to rotate about said longitudinal axis (<NUM>);
liquid cooling means to dissipate the heat generated during the operation of said electric motor (<NUM>), wherein said cooling means comprise a plurality of circulation channels (<NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>') defined through said frame (<NUM>) for the circulation of a cooling fluid, and at least one hydraulic connecting channel (<NUM>,<NUM>A,<NUM>B) for connecting hydraulically two of said circulation channels (<NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>', <NUM>-<NUM>') at one of said endshields (<NUM>,<NUM>),
characterized in that said at least one hydraulic connecting channel (<NUM>,<NUM>A,<NUM>B) comprises at least a first section (<NUM>,<NUM>A,<NUM>B) configured by the coupling of a collector element (<NUM>',<NUM>") with a seat (<NUM>', <NUM>") defined by said one of said endshields (<NUM>, <NUM>), wherein said seat (<NUM>', <NUM>") has a coupling surface (71A', 71A") that develops around said longitudinal axis (<NUM>), said collector element (<NUM>', <NUM>") being a ring-shaped body with an outer surface (61A', 61A") and an inner surface (61B', 61B'') wherein said outer surface (61A', 61A") couples with said coupling surface (71A', 71A") of said seat (<NUM>', <NUM>"), wherein said outer surface (61A', 61A") and said coupling surface (71A', 71A") are shaped so as to configure said first section (<NUM>,<NUM>A,<NUM>B) of said hydraulic connecting channel (<NUM>,<NUM>A,<NUM>B) following their coupling.