The present invention relates in general to an impregnation plant for electric motor components and, in particular, to an equipment for supporting and handling the individual components being processed in the plant. Each component has an axial symmetrical structure (i.e., it features a radial symmetry) and specifically consists of a stator for electric motors.

As known, an electric motor is formed of a stator and a rotor. These two components are generally axial symmetric ones, more specifically cylindrical, and, when properly combined together, generate a magnetic field as necessary for operating the electric motor. The stator and/or the rotor of an electric motor can be respectively provided with electric windings, which traditionally comprises a coil of copper wires and, in the specific case of a stator, are usually housed in respective internal cavities (called “slots”) of the stator itself. Alternatively, the stator of an electric motor can be provided with a plurality of metal bars, typically made of copper, instead of a coil of copper wires (the so-called “hair pin” stators). Conversely, the rotor of an electric motor can be manufactured by using permanent magnets instead of a coil of copper wires. Both coils of copper wires and metal bars (but not permanent magnets) need to be impregnated with specific impregnating substances, typically formed of resins, as necessary to increment their mechanical strength and electrical insulation, as well as to improve heat dispersion.

The impregnation process for a stator and/or a rotor for electric motors can be obtained by using at least three different application technologies. In a first technology, the so-called “trickling” (or “drop by drop”) one, one continuous trickle of resin is dripped onto the wires of the stator or the rotor, driven into rotation around a horizontal axis, or onto the copper bars of the stator. The resin penetrates the interstices between the wires or the bars by capillarity, up to filling the empty spaces between these wires or these bars.

In a second technology, the so-called “roll dip” one, the stator or the rotor is driven into rotation around a generally horizontal axis. While in rotation, each component is at least partially dipped into a resin bath. A third technology, the so- called “dipping” one, the stator or the rotor is dipped into a resin bath, in this case with its axis generally vertical and no longer in rotation.

Irrespective of the technology adopted, the following steps shall be sequentially performed in an impregnation process for impregnating a stator and/or a rotor for electric motors. In a first pre-heating step, each stator and/or rotor is heated up to reaching a temperature that is ideal for applying the resin. This temperature is typically in a range from 80°C to 120°C. In this pre-heating step, there is no need for keeping the component into rotation and heating can be performed in a variety of ways, such as, for example, by using hot air, induction, a combination of hot air and induction, or by Joule effect, that is by making an electric current flow through the copper bars or wires. The pre-heating step can be performed either in specific ovens or by using other appropriate equipment.

The pre-heating step is followed by an impregnation step, during which each component gets in contact with the liquid resin. This liquid resin fills the cavities between the individual wires or between the copper bars and covers the exposed part of copper. In this impregnation step, in the case of the “trickling” technologies adopted for impregnating stators, the component shall be kept into rotation, its axis being generally horizontal or possibly with an angle of tilt of the axis typically ranging from +15° to -15° with respect to a horizontal plane. Optimum impregnation results can be achieved by acting on the speed and/or direction of rotation. The impregnation step is usually performed by using specific impregnation equipment, which are separate from ovens.

After being impregnated, each component undergoes a gelling step. In this gelling step, the temperature of the component is raised, so as to trigger a resin cross-linking process, wherefrom its hardening. Also during this gelling step, in the case of the “trickling” and “roll dip” technologies, the component shall be kept into rotation in order to prevent the resin, still in a liquid status, from dripping away. The gelling step might require a time duration variable from eight to fifteen-twenty minutes in order for it to be completed, depending on the resin type. Conversely, in the case of the dipping technology, gelling can be achieved while the component is vertically dipped, by making a current flow through the copper bars or wires (Joule effect). Once the component is taken out of the bath, the resin around the wires is consequently already thickened and does not drip away.

In the next baking step, the resin, now gelled and consequently thick, completes its cross-linking process. During the baking step, each component shall be kept at a temperature, but it is not needed for it to be kept into rotation any longer. The baking step can be performed either inside the same oven where the previous steps have been performed or by using another suitable equipment. Once the baking step is over, the component undergoes a final cooling step, during which the component itself is cooled down either by way of a forced ventilation (using ambient or cooled air) or by resting in the environment for a predetermined period of time.

In traditional impregnation plants used for electric motor components, the equipment used to support these components usually comprises one or more spring collets. Each spring collet is equipped with gripping means consisting, for example, of clamps, which act on the inner side surface of the hollow axial symmetrical body that the component (typically, but not exclusively, the stator) of the electric motor is made up. Therefore, the clamps, which are usually operated for opening and closing via appropriate actuator mechanisms, are configured for holding each axial symmetrical component from the inside during all of its processing steps in the impregnation plant.

Document US 2021/162450 A1 , filed in the name of the same applicant, discloses an impregnation plant for electric motor components according to the preamble of claim 1 . Further plants according to the prior art for impregnating electric motor components are disclosed, for example, in documents US 2016/126816 A1 , US 2022/094245 A1 and US 5685910 A.

A drawback that might frequently occur in traditional impregnation plants for electric motor components is due to the resin leaking from the copper bars or wires of the component. As a matter of fact, in the specific case of a stator, wires or bars are housed in respective cavities or slots present on the inner axial symmetrical surface of the stator itself, i.e., close to the points of contact of the clamps of the spring collets with such inner surface.

Consequently, resin, being not solidified yet and running the slots of the stator along the copper bars or wires that fill such slots by capillarity, might be attracted by the hot mass of the clamps of the spring collets. Therefore, resin might leak from these slots, notwithstanding the usual presence of a layer of insulating paper that at least partially coats the inner axial symmetrical surface of the stator. Not always is this layer of insulating paper capable of holding the resin, which is extremely fluid and consequently, because of the well-known capillarity phenomenon, easily spreads into the narrowest interstices.

Resin leakage might imply at least two main problems. A first problem, which is particularly severe, concerns contamination of the inner axial symmetrical surface of the stator, which the rotor will subsequently be put in. A second problem, less severe, but in any case an annoying one, concerns contamination of the gripping clamps of the collets, with a subsequent need for maintenance (collect cleaning).

An object of the present invention is therefore to provide an impregnation plant for electric motor components, in particular an equipment for supporting and handling the individual components being processed in the plant, that is capable of solving the above-mentioned drawbacks of the prior art in an extremely simple, cost- effective, and particularly functional manner.

In details, an object of the present invention is to provide an impregnation plant for axial symmetrical components of electric motors whose equipment used to support and handle the individual components are capable of reducing any leakages of resin from the body of the component itself as much as possible, so as to preserve it construction quality.

Another object of the present invention is to provide an impregnation plant for axial symmetrical components of electric motors whose equipment used to support and handle the individual components does not require corrective maintenance and/or cleaning operations insofar as possible.

A further object of the present invention is to provide an impregnation plant for axial symmetrical components of electric motors whose equipment for supporting and handling the individual components is provided with simple and reliable gripping means.

These objects according to the present invention are achieved by embodying an impregnation plant for axial symmetrical components of electric motors as disclosed in claim 1 .

Further features of the invention are highlighted by the dependent claims, which are integral parts of the present disclosure.

The features and advantages of an impregnation plant for axial symmetrical components of electric motors according to the present invention will be more apparent from the following explanatory, non-limitative, description, which makes reference to the attached schematic drawings, wherein: figure 1 is a perspective view of the main components of a preferred embodiment of the impregnation plant for axial symmetrical components of electric motors according to the present invention; figure 2 is a perspective view of one single heating station of the plant of figure 1 , shown in its heating or baking configuration; figure 3 is a perspective view of the heating station of figure 2, shown in a first impregnation configuration; figure 4 is a perspective view of the heating station of figure 2, shown in a second impregnation configuration; figure 5 is a perspective view of the heating station of figure 2, shown in a third impregnation configuration; figure 6 is a perspective view of a preferred embodiment of the components supporting and handling equipment belonging to the plant of figure 1 ; figure 7 is an enlarged view of the detail identified by VII in figure 6; figure 8 in an enlarged view of de detail identified by VIII in figure 6; figure 9 is a cross sectional view of the equipment of figure 6, wherein the impregnation nozzles are shown in a first operating position; figure 10 in another cross-sectional view of the equipment of figure 6, wherein the impregnation nozzles are shown in a second operating position; figure 1 1 is a perspective view of a single support device that holds an axial symmetrical (in particular, cylindrical) component of electric motors, wherein a part of the means used to handle such support device is shown; figure 12 is another perspective view of a single support device that holds an axial symmetrical (in particular, cylindrical) component of electric motors; figure 13 is a longitudinal cross-sectional view, i.e., one obtained along the axis of symmetry, of the support device and of the axial symmetrical component of figure 12; figure 14 is a cross sectional view, i.e., one obtained orthogonally with respect to the axis of symmetry, of the support device and of the axial symmetrical component shown of figure 12; and figure 15 is another cross-sectional view of the support device and of the axial symmetrical component of figure 12. With reference to the figures, a preferred embodiment of an impregnation plant for axial symmetrical components of electric motors according to the present invention is shown. The impregnation plant is referred to with the reference numeral 10 as a whole. The impregnation plant 10 comprises a plurality of working stations and equipment, monitored and controlled by a central processing unit. The impregnation plant 10 comprises at least one support frame 12 and one or more heating stations 14, which are configured for heating each component 100 to a predetermined temperature.

The impregnation plant 10 also comprises one or more motor-driven equipment 16 used to support and handle the components 100. Each of these equipment 16 comprises at least one gripping device 22 for a respective component 100, as well as first motor-driven rotation means 24, which are configured for imparting a rotatory motion to each gripping device 22, in both directions of rotation, around a predetermined rotation axis, which coincides with the axis of symmetry of the component 100 when held by a respective gripping device 22. Each of these equipment 16 also comprises second motor-driven translation means 26, which are configured for imparting a translatory movement from inside to outside to a respective heating station 14, and vice versa, to each motor-driven equipment 16 used to support and handle the components 100 along with their respective gripping devices 22.

The impregnation plant 10 also comprises one or more impregnation equipment 18, which are configured for at least partially coating each component 100 with an impregnating substance whenever such component 100 is held by a respective gripping device 22, and one or more transport and loading/unloading equipment 20, which are configured for transferring the components 100 from and to the heating stations 14. The impregnating substance might consist of resins or other similar impregnating fluids in a manner known per se.

The support frame 12 is preferably provided with one or more handling and guiding means 82, 84. Consequently, the impregnation equipment 18 and the transport and loading/unloading equipment 20 can be mounted on these handling and guiding means 82, 84 in a movable manner. For example, the handling and guiding means 82, 84 might consist of one or more upper sliding guides 82, positioned on the support frame 12 at one upper end thereof, and one or more lower sliding guides 84, positioned on the support frame 12 at a bearing surface. As shown in figure 1 , each impregnation equipment 18 can move along the upper sliding guides 82 and is electrically controlled, by the central processing unit, to move and selectively position above each of the heating stations 14 in the moment when the individual components 100 undergo the impregnation step.

According to a preferred embodiment of the impregnation plant 10, shown in the attached figures, each heating station 14 comprises an oven, equipped with at least an internal chamber 88 and at least one front closing door 90, i.e., a door arranged on one side of said oven 14. Each motor-driven equipment 16 used to support and handle the components 100, along with its respective gripping devices 22, is thus configured for moving between a retracted position, within the internal chamber 88 of the oven 14 (see figure 2, where the motor-driven equipment 16 used to support and handle the components 100 is not visible just because it is located inside the internal chamber 88 of the oven 14) and an advanced position, outside said internal chamber 88 of the oven 14 (figures 3, 4 and 5, wherein the motor-driven equipment 16 used to support and handle the components 100 is visible outside the oven 14).

Each impregnation equipment 18 is provided with a plurality of dispensing nozzles 86 configured for making a continuous trickle of impregnating substance (resin) drip down onto each component 100. The impregnating substance is dispensed by the dispensing nozzles 86 whenever each component 100 is in rotation on a respective gripping device 22 and when such gripping device 22 is in turn outside the internal chamber 88 of one of the ovens 14, as shown for example in figures 3, 4, and 5.

According to the invention, as shown in particular in figures 6 to 15, each gripping device 22 comprises at least one annular body 28 which is provided with at least one internal axial symmetrical cavity 30. This internal cavity 30 has a maximum dimension D1 , as measured in a radial direction, that is greater than the maximum dimension D2 as measured in a radial direction of each component 100, consequently this internal cavity 30 can house a respective component 100 internally thereto. The annular body 28 of each gripping device 22 also comprises at least one gripping means 32, which faces its respective internal cavity 30 to grip the outer side surface of the hollow axial symmetrical body that constitutes each component 100 and to hold such component 100 inside the internal cavity 30 of its respective gripping device 22.

So, each gripping device 22 operates as an “external gripper”, i.e., one capable of gripping a respective component 100, typically consisting of a hollow cylindrical stator, on its outer side surface. In other words, each gripping device 22 does not seize the inner side surface of each component 100 in any way, so as to allow the dispensing nozzles 86 to position at the usual points normally used to obtain an effective coating of the electric windings while the impregnating substance is dispensed by the impregnation equipment 18. As shown, for instance, in figures 9 and 10, these positioning points are typically located at the outer diameter of the front ring, the inner diameter of the front ring, the outer diameter of the rear ring, and the inner diameter of the rear ring of each component 100.

Each gripping device 22 shall keep its respective component 100 into rotation and shall be capable of allowing for an inversion of the rotation motion, as well as of varying its speed of rotation. Each motor-driven equipment 16 used to support and handle the components 100, along with its respective gripping devices 22, is consequently conveniently engineered to house in the internal chamber 88 of each oven 14 and shall be capable of tilting contextually with the oven 14 itself. As a matter of fact, at least one of the ovens 14 of the impregnation plant 10 is provided with tilting means 80, configured for imparting a tilting movement to the oven 14, hence to each component 100 with respect to a bearing plane of the support frame 12, , whenever such component 100 is mounted on a respective gripping device 22 and the motor-driven equipment 16 used to support and handle the components 100 is placed outside the oven 14.

Since each component 100 is typically formed of a hollow cylindrical stator, each annular body 28 of a respective gripping device 22 is also a cylindrical body, consequently each internal cavity 30 features a circular shape. Consequently, the maximum dimension D1 of the internal cavity 30 corresponds to the diameter of such internal cavity 30, as shown in figure 15.

As shown in figures 13 to 15, each gripping means 32 comprises at least one rod-shaped pusher element 34, which is movable, according to a reciprocating motion, within a respective guide hole 48 obtained in a radial direction on the annular body 28 of a respective gripping device 22. Each pusher element 34 also comprises, at an end thereof that faces the internal cavity 30, at least one clamping element 36 configured for bearing, by friction, on the side outer surface of the hollow axial symmetrical body that constitutes each component 100 placed inside such internal cavity 30. Each annular body 28 preferably comprises at least two or more gripping means 32, which are circumferentially equally spaced from each other, in order to exert an effective holding action on the component 100.

According to a preferred aspect of the present invention, and as shown in particular in figures 13 and 14, all gripping means 32 are operated simultaneously by way of a mechanism that sequentially comprises:

- at least one clamping key 38, which is placed on the outer circumferential surface of each annular body 28 and is operatable for rotation;

- at least one toothed wheel 40, on which the clamping key 38 meshes and is operatable for rotation by a corresponding rotation of such clamping key 38;

- at least one slewing ring 42, on which a respective toothed wheel 40 meshes and is movable with a circumferential motion within the annular body 28;

- at least one pin 44, which is integral with the slewing ring 42 on one side and with a respective pusher element 34 on the other side and is arranged perpendicularly to the direction of development of the pusher element 34; and

- at least one slot 46, which extends inside said annular body 28 between a first end 46A, having a greater distance from the geometric centre of the annular body 28, and a second end 46B, having a lower distance from the geometric centre of the annular body 28, so that a sliding movement of the pin 44 inside a respective slot 46 between its first end 46A and its second end 46B causes a corresponding sliding movement of its respective pusher element 34 within the guide hole 48 in such a direction as to get closer to the outer side surface of the hollow axial symmetrical body that constitutes each component 100 placed in the internal cavity 30, whereas a sliding movement of the pin 44 within a respective slot 46 between its second end 46B and its first end 46A causes a corresponding sliding movement of its respective pusher element 34 within the guide hole 48 in a direction away from the outer side surface of the hollow axial symmetrical body that constitutes each component 100 placed in the internal cavity 30 of the annular body 28.

In other words, the assembly formed of the clamping key 38, the toothed wheel 40, the slewing ring 42, the pin 44 and the “eccentric” slot 46 forms an eccentric mechanism, which is configured for imparting a reciprocating movement to each rod-shaped pusher element 34 within its respective guide hole 48 present on the annular body 28. Each rod-shaped pusher element 34 can additionally be conveniently provided with at least one compression spring 50, which is configured for compensating for any thermal expansions of the component 100 placed inside the internal cavity 30 of the annular body 28. As a matter of fact, such thermal expansion might raise on the side surface of each component 100 during its respective processing steps, in particular the heating step, in the impregnation plant 10.

As shown in the embodiment illustrated in figure 6 and in the enlarged views in figures 7 and 8, the first motor-driven rotation means 24 of each motor-driven equipment 16 used for supporting and handling the components 100 might sequentially comprise at least one first electric motor 52, a gear unit 54, at least one ring gear 58 integral with the annular body 28 of a single gripping device 22, and at least one second transmission shaft 60. The first transmission shaft 56 is operatively connected to the first electric motor 52 at a first end thereof, whereas a gear 64 is keyed on a second end of such first transmission shaft 56, configured for transmitting a rotatory motion from the first electric motor 52 to the gear unit 54. The second transmission shaft 60 is operatively connected to the gear unit 54 at a first end thereof, whereas a driving pinion 66 is keyed on a second end of such second transmission shaft 60, configured for transmitting motion from the gear unit 54 to the ring gear 58. Irrespective of the embodiment of the first motor-driven rotation means 24 of each motor-driven equipment 16 for supporting and handling the components 100, it is here emphasised that the rotation motion can be imparted to the gripping devices 22 either when these gripping devices 22 are in a retracted position, i.e., in the internal chamber 88 of each oven 14, or when these gripping devices 22 are in an advanced position, i.e., under the dispensing nozzles 86 of each impregnation equipment 18.

Preferably, each motor-driven equipment 16 for supporting and handling the components 100 can comprise one or more idle pinions 62 (visible, for example, in figures 6 and 1 1 ), which are configured for transmitting motion from the ring gear 58 operated by the driving pinion 66 to one or more gripping devices 22, whose ring gears 58 mesh the corresponding idle pinions 62. It is thus possible to drive a plurality of gripping devices 22 into rotation by using one motor-driven rotation means 24 of the motor-driven equipment 16 used for supporting and handling the components 100. As a matter of fact, it is convenient to have motor-driven equipment 16 at his/her disposal for supporting and handling the components 100 that comprise a plurality (for instance three, as shown in the figures) of gripping devices 22 arranged in parallel. An advantage is in that, by imparting a rotation motion and an inclination to one single gripping device 22, these movements are automatically transmitted to all the remaining gripping devices 22 arranged in parallel, while maintaining the phase relationships of the individual gripping devices 22. Also preferably, each gripping device 22 is mounted on one support frame 70 and is rotatable with respect to such support frame 70 through the interposition of a plurality of rolling bearings 68, as shown, for example, in figure 11 .

As shown in particular in figure 6, an embodiment of the second motor-driven translation means 26 of each motor-driven equipment 16 for supporting and handling the components 100 can sequentially comprise:

- at least one slide 72, which supports the gripping devices 22 and is movable according to a reciprocating motion along guides 74 integral with a respective heating station 14;

- at least one second electric motor 76; and

- at least one splined shaft 78, which is operatively connected to the second electric motor 76 at a first end thereof and to the slide 72 at a second end thereof.

The splined shaft 78 is configured for transforming a rotatory motion, as imparted by the second electric motor 76, into a reciprocating motion of the slide 72. In this way, a translation is obtained of the gripping devices 22 from the outside to the inside of each internal chamber 88 of a respective oven 14, and vice versa. As an alternative to the embodiment of the second motor-driven translation means 26 of each motor-driven equipment 16 for supporting and handling the components 100 as described above, these motor-driven translation means might also be formed of an anthropomorphic robot mounted on an axle.

It has been thus shown that the impregnation plant for axial symmetrical components of electric motors according to the present invention achieves the above highlighted objects. The impregnation plant for axial symmetrical components of electric motors according to the present invention, whose gripping devices do not interact with the inner side surface of any component, enable the nozzles used to dispense the impregnating substance to easily reach the critical dispensing points (outer diameter of the front ring, inner diameter of the front ring, outer diameter of the rear ring, and inner diameter of the rear ring of each component).

The impregnation plant for axial symmetrical components of electric motors according to the present invention, as conceived, is in any case susceptible of numerous modifications and variants, all falling within the scope of the same inventive concept; also, all details are replaceable by technically equivalent elements. In practice, the materials used, as well as their shapes and dimensions, might be whatsoever depending on the technical requirement. The scope of protection of this invention is therefore that defined by the attached claims.