Apparatus for assembling a permanent-magnet electric motor to be used particularly in pumping devices, electric motor produced with such apparatus, and electric pump comprising such electric motor

An apparatus for assembling a permanent-magnet electric motor to be used particularly in pumping devices, which comprises a tubular element made of non-magnetic material, to be inserted and coupled in the axial cavity of a stator of an electric motor, and adapted to accommodate inside it a rotor of an electric motor.

The present invention relates to an apparatus for assembling a permanent-magnet electric motor to be used particularly in pumping devices.

The invention also relates to an electric motor produced with such apparatus, as well as an electric pump that comprises such electric motor.

As is known, pumping devices are typically constituted by a pump body to which an electric motor is coupled.

The pump body has a hollow body provided with ducts for suction and delivery, and within this body one or more impellers are keyed on the shaft for transmitting rotation by the electric motor.

In particular for circulators and electronic pumps, the use is increasingly widespread of permanent-magnet motors, in order to meet the requirement for high performance with medium-to-low power levels.

Assembly of this type of motor has a particular drawback during the positioning of the magnetic rotor inside the stator.

The rotor, in fact, is made of a material with highly magnetic characteristics, which exerts a force of attraction toward any ferromagnetic material.

On an assembly line, this element is difficult to manipulate owing to the presence of numerous tools and components made of ferromagnetic material, and there are also difficulties with its insertion into the stator, where the permanent magnets of the rotor tend to move towards the laminations of the stator and adhere to them, therefore making this assembly step difficult and hazardous for the operator.

The rotor should be inserted in its seat, which centers it on the rotation axis, but if the two elements come into contact before the coupling is achieved, it is substantially impossible to separate them and proceed with the assembly.

Nowadays the problem does not arise in the assembly of permanent-magnet electric motors coupled to pumps that have a supporting structure made of plastic material.

In these cases, the hydraulic part of the pump comprises a space made of plastic material from which a shank extends which contains the rotor and separates it from the stator.

This is the case shown, for example, in EP1801954.

However, there are motors for which the production and performance requirements do not allow the use of a structure made of plastic material.

The aim of the present invention is to provide an apparatus that is capable of making the manipulation of the rotor of a permanent-magnet electric motor easier, by guiding the assembly step.

Within this aim, an object of the invention is to make the steps of mounting the rotor inside the stator safe and easy.

Another object of the invention is to provide an apparatus that is structurally simple and easy to use, which can be produced easily and at low cost.

Another object of the invention is to provide an electric motor which is made with such apparatus.

Another object of the invention is to provide an electric pump that comprises an electric motor which is made with an apparatus according to the invention.

This aim and these and other objects which will become better apparent hereinafter are achieved by an apparatus for assembling a permanent-magnet electric motor to be used particularly in pumping devices, characterized in that it comprises a tubular element made of non-magnetic material, to be inserted and coupled in the axial cavity of a stator of a said electric motor, and adapted to accommodate inside it a rotor of an electric motor.

With reference to the figures, an apparatus according to the invention is generally designated with the reference numeral10.

The apparatus is designed for the assembly of an electric motor11of the type with permanent magnets to be used in pumping devices and to be accommodated inside a motor casing12as shown in Figures from4to6, and also7,8and9.

The apparatus10comprises a tubular element13and a grip element14for the operator, both shown inFIG. 4and both made of non-magnetic material, preferably made of plastic material.

In particular, the tubular element13is made of plastic material or of another material that is not influenced by magnetic influx, and which therefore is not subject to phenomena of magnetic attraction or repulsion between rotor and stator.

The tubular element13is adapted to be inserted and coupled in the axial cavity of a stator15of the electric motor11and is adapted to accommodate inside it a rotor16of the electric motor11.

The tubular element13is conveniently hollow and open at its ends.

In a first variation of embodiment of an electric motor11, which is also understood to be according to the invention, the tubular element13is locked inside the stator15by interference fit with the stator15, as shown inFIG. 7.

In such first variation of embodiment the tubular element13has a first end17thereof resting against a first bearing-supporting collar18, inside the space21for accommodating the stator15in the motor casing12, while the second, opposite end20is fitted over a second bearing-supporting collar22, which is part of a cover19for closing the motor casing12.

In a second variation of embodiment of an electric motor111, which is also understood to be according to the invention, the tubular element113is locked inside the stator115by interlocking between a first bearing-supporting collar118, inside the space121for accommodating the stator115in the motor casing112, and a second bearing-supporting collar122, which is part of a cover119for closing the motor casing112, as shown inFIG. 8.

In particular, a first end117of the tubular element113is inserted so as to rest in an annular groove123defined on the first collar118, while the opposite, second end120of the tubular element113is fitted over the second bearing-supporting collar122.

The rotor16has a rotating shaft24a first end25of which is designed to be introduced first to pass through the motor housing in order to be inserted into the pump body to interact with the impeller elements of the pump, while the second, opposite end26is designed to couple with the grip element14.

The grip element14comprises an actuation knob27and a supporting and centering portion28, for example disk-like, shaped complementarily to the corresponding outer contact surface29of the cover19, in order to facilitate the concentricity of positioning between the cover19, the rotor16and the grip element14.

The grip element14can be associated with the shaft24of the rotor16by way of a threaded coupling, between an axial threaded shank30protruding axially from the grip element14and a complementarily threaded axial hole31defined on the second end of the shaft24of the rotor16.

InFIG. 1the reference letter A designates the rotation to be imparted to the grip element14in its association with the rotor16, in order to screw it onto the latter, while inFIG. 6the reference letter B designates the rotation in the opposite direction to be imparted in order to separate the two elements at the end of the assembly of the electric motor11.

The figures also show the cover19of the motor casing12, which in the assembly is interposed between the rotor16and the grip element14, and the closure thereof onto the rest of the motor casing12occurs by way of the three screws32.

Use of the apparatus, according to the invention, is the following.

The tubular element13is accommodated inside the stator15, by inserting it with interference as shown inFIG. 7or by resting and interlocking as shown inFIG. 8.

In this manner it maintains its position inside the cavity of the stator15.

The grip element14is screwed onto the rotor16, interposing the cover19of the motor casing12between them, which substantially during assembly separates the magnetic area from the working area.

The operator grips the knob27of the grip element14in order to insert the rotor16inside the tubular element13which was previously positioned in the stator15.

In this manner the tubular element13is interposed between the stator15and the rotor16, preventing them from coining into contact.

During insertion the rotor16slides inside the tubular element13in the stator15, until it engages in an adapted seat that centers on its rotation axis.

The cover19is fixed to the rest of the motor casing12by way of the screws32, and the grip element14is unscrewed, as illustrated inFIG. 6.

If maintenance operations on the electric motor are necessary, the motor can be easily dismantled by recoupling the grip element14to the rotor16, in order to extract the latter from the stator15after having unscrewed the screws20of the cover19.

During these operations, the presence of the cylindrical element, which is already inside the stator, prevents the rotor from coining into contact with the stator.

The invention also relates to an electric motor11, which is made with an apparatus10as described above, which comprises, inserted and locked inside the stator15, a tubular element13adapted to accommodate inside it the rotor16of the electric motor11.

The invention also relates to a centrifugal electric pump40which comprises an electric motor11or111as described above.

In practice it has been found that the invention fully achieves the intended aim and objects, by providing an apparatus that is structurally simple and easy to use and to provide, by virtue of which the assembly of a permanent-magnet motor is easy and safe.

Furthermore it should be noted that in the assembling of the electric motor for pumping devices, the possibility of interposing the closing cover of the motor casing between the grip element and the rotor increases the degree of safety for the operator because it separates the magnetic area from the working area.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. 102015000062796 (UB2015A005296) from which this application claims priority are incorporated herein by reference.