IT202000013102A1 - BALANCING DEVICE FOR ROTATING PIECES - Google Patents

Description

DESCRIPTION

BALANCING DEVICE FOR ROTATING PIECES

The present invention relates to a balancing device for rotating pieces of the type specified in the preamble to the first claim.

Various types of balancing devices for rotating pieces are currently known.

In particular, on board rotating devices, such as machine tools or other machinery, there are balancing devices capable of constantly maintaining the center of mass of the rotating portion in the selected position. Generally, the said center of mass of the rotating portion ? maintained in correspondence with the axis of rotation, so that unwanted centrifugal forces are not created.

Said balancing devices are generally inserted in balancing apparatuses which also comprise means for measuring the unbalances, suitable for verifying and measuring the presence of an unbalance.

The imbalance? consequently regulated and cancelled, or reduced to the maximum, by said balancing device, constrained to the rotating portion.

The latter comprises two unbalanced masses with respect to the axis of rotation of the rotating piece, and therefore each comprising a suitably identical unbalance, ie of the same mass. The balancing device also comprises two motors, one for each mass, suitable for rotating said masses around the axis of rotation itself.

The position of the unbalanced masses affects the center of mass of the rotating portion.

Indeed, if the same masses are opposite, offset at 180? with respect to the axis of rotation, their unbalances cancel each other out and the balancing device does not change the position of the center of mass of the assembly made up of the rotating portion and the balancing device.

Conversely, if the masses are not opposite, their unbalances do not cancel each other out and the balancing device generates an unbalance. The said imbalance in turn ? suitably made equal and opposite to the imbalance of the rotating portion, so? that the position of the center of mass of the assembly made up of the rotating portion and the balancing device is changed and is positioned along the axis of rotation or the pi? close to it as possible.

Said masses are generally moved, with respect to the rotating piece and to modify the portion of the center of mass, by means of electric motors and mechanical connections. As described for example in the patent application EP-A-2717032 by the same Applicant.

Patent application US-A-17886005 instead shows masses moved directly from the fixed portion.

The patent application EP-A-19158944, by the same Applicant, shows balancing masses moved by motors inside the masses themselves.

The patent application EP-A-13156332, by the same Applicant, shows some moved balancing masses constituted by wires or tapes wound around reels placed in eccentric positions with respect to the axis of rotation, so that the winding and unwinding around different spools involves a mass transfer and a change in the center of mass of the balancing device.

The prior art described includes some drawbacks.

In particular, said devices are very complex and therefore could be subject to problems if not constantly reviewed.

They are also very subject to wear.

An additional drawback? given by the fact that not ? is it possible to miniaturize a lot of systems cos? complex.

The complexity? and the problems are further accentuated by the considerable forces at play. In fact, the said pieces in rotation can reach speed? of the order of magnitude of tens of thousands of revolutions per minute.

In this situation, the technical task underlying the present invention? devising a balancing device capable of substantially obviating at least part of the aforementioned drawbacks.

In the context of this technical task ? an important object of the invention is to obtain a balancing device which is simple and robust.

Another important purpose of the invention ? make a balancing device that is accurate.

Not the last purpose of the invention ? make a balancing device that is economical.

The technical task and the specified aims are achieved by a balancing device as claimed in the attached claim 1.

Preferred technical solutions are highlighted in the dependent claims.

The characteristics and advantages of the invention are clarified below by the detailed description of preferred embodiments of the invention, with reference to the attached drawings, in which:

Fig. 1 shows a diagram of the balancing device according to the invention. In this document, measurements, values, shapes and geometric references (such as perpendicularity and parallelism), when associated with words such as "about" or other similar terms such as "almost?" or "substantially", are to be understood as less than measurement errors or inaccuracies due to production and/or manufacturing errors and, above all, less than a slight deviation from the value, measure, shape or geometric reference to which ? associated. For example, these terms, if associated with a value, preferably indicate a deviation of no more than 10% of the value itself.

Also, when used, terms such as ?first?, ?second?, ?superior?, ?inferior?, ?main? and ?secondary? do not necessarily identify an order, a priority? of relationship or relative position, but can simply be used for pi? clearly distinguish between different components.

Unless otherwise specified, as apparent from the following discussions, terms such as "processing", "computing", "determination", "computing", or the like are understood to refer to the action and/or processes of a computer or similar electronic calculation that manipulates and / or transforms data represented as physical, such as electronic quantities of registers of a computer system and / or memories in, other data similarly represented as quantities? in computer systems, logs or other devices for storing, transmitting or displaying information.

The measurements and data reported in this text are to be considered, unless otherwise indicated, as performed in an ICAO International Standard Atmosphere (ISO 2533:1975).

With reference to the Figures, the balancing device according to the invention ? globally indicated with the number 1.

It ? suitably part of a balancing apparatus, hereinafter described, comprising a rotating piece 10. Said rotating piece 10 ? preferably constituted by the rotor of a machine tool, for example a grinding wheel or the like, or by other devices and defines a rotation axis 10a.

The balancing device 1 comprises a fixed portion 2, preferably fixed for example with respect to the ground, and a mobile portion 3, preferably rotatable and defining a central axis 3a.

The mobile portion 3 ? preferably integrally constrainable to the rotating piece 10 so that the central axis 3a substantially coincides with said axis of rotation 10a.

The balancing device 1 has the purpose of eliminating the unbalances of the system comprising the movable portion 3 of the balancing device 1 and the rotating piece 10. These unbalances are eliminated when the center of mass of the system movable portion 3 and rotating piece 10 lies along the axis of rotation 10a. The movable portion 3 preferably comprises at least one eccentric mass 30 rotatable about the central axis 3a, and more? preferably two eccentric masses 30, and not balanced with respect to the central axis 3a. Each eccentric mass 30 ? preferably rotatable, independently of the other mass and of the rest of the movable portion 3 around the central axis 3a.

The eccentric masses 3 are for example constituted by two annular elements, with their axis along the central axis 3a, having asymmetrically relieved portions or the like. The balancing device 1 also preferably comprises means 4 for moving the individual eccentric masses 30, able to rotate around the central axis 3a and the individual eccentric masses 30, with respect to the other eccentric masses 30 and the remaining part of the movable portion 3, integral with the rotating piece 10. The movement means 4 preferably comprise a magnetic brake 40. As known, the magnetic brakes used for high-speed trains? and the like, therefore in technical fields completely different from the present, use the phenomenon of eddy currents.

Eddy currents are induced currents in a conductor that is immersed in a changing magnetic field. This variation can be caused by the mutual movement between the magnetic field and said conductor. The changing magnetic field generates the circulation of electrons in the conductor, in accordance with Faraday's law. These electrons, therefore this moving electric current, in turn generate a magnetic field in the opposite direction to the variation of the applied magnetic field which opposes said reciprocal movement between the magnetic field and the conductor. Such opposition? the force behind the operation of magnetic brakes.

The magnetic brake 40 preferably comprises at least one conductive portion 41, made of conductive material, and at least one magnetic portion 42 capable of creating a magnetic field acting on the conductive portion 41.

One of the two portions 41 and 42, and preferably the conductive portion 41? preferably integral with the eccentric mass 30 and, more? still preferably the conductive portion 41 coincides with the eccentric mass 30, for example the eccentric mass ? metal with high conductivity? such as in metallic material including predominantly aluminum or copper. Preferably, the other of the portions 41 and 42, and more? preferably the magnetic portion 42, ? fixed with respect to the rotation of the piece 50. Pi? preferably, there are two magnetic portions 42, one for each mass, or only one movable in the direction of the central axis 3a.

The magnetic portion 42 comprises, in a first preferred example, a permanent magnet 43, for example neodymium, and means 44 for adjusting the distance between the permanent magnet 43 and the conductive portion 41.

The adjustment means 44 can define a trajectory lying, at least partly in the radial direction with respect to the central axis 3a. The regulating means 44 can furthermore comprise an electric motor or the like.

In a second preferred example, not shown in the figures, the magnetic portion 42 comprises an electromagnet, preferably of annular shape or annular sector and arranged around said eccentric masses.

In a third example, the magnetic portion 42 comprises an electromagnet made from at least one coil having a radial axis with respect to the central axis 3a. In this case the adjustment means 44 may or may not be present. Pi? preferably, said coils are more? of one, preferably between two and eight, plus? preferably four. They are preferably arranged at constant circumferential intervals about the axis 3a.

To allow movement by means of the magnetic brake 40, the eccentric masses 30 are preferably constrained to the remaining part of the mobile portion 3, or directly to the rotating piece 10, by means of a rotational bearing with non-zero friction 31, such as a polymeric bearing or the like. This bearing 31 binds the masses 30 with sufficient resistance to the remaining part of the mobile portion 3 to support the rotational accelerations of the rotating piece 10, and, at the same time, allows the magnetic brake 40 to move, braking it, the eccentric mass 30 with respect to to the remaining part of the mobile portion 3.

Inside the device 1 there are preferably sensors for detecting the angular position of each eccentric mass 30, in order to facilitate the balancing procedure.

The balancing apparatus comprising said balancing device 1 and, preferably means for detecting the unbalance, such as known accelerometers which can be inserted into the device 1 or not, a synchronism sensor for detecting rotation of the axis 10a, electric power supply means, connected to the aforementioned electric motors or electromagnets, control means, suitable for receiving the information, transmitting it and for controlling the movement means 4 and the other elements. The balancing apparatus can? furthermore comprising sensor means able to perceive the contact between the rotating piece 10 and the piece being worked, in particular when the first one? consisting of a grinding wheel or similar tool.

The operation of the balancing device 1, and of the balancing apparatus, previously described in structural terms,? the following.

It defines a new procedure for moving an eccentric mass 30 around a central axis 3a, to modify the center of mass of a rotating piece 10. In this procedure, the eccentric mass 30 ? preferably moved by magnetic braking, preferably operated by moving means 4 preferably comprising a magnetic brake 40 of the type preferably previously described.

The method takes place preferably through the previously described balancing device 1 and, preferably through the previously described balancing apparatus.

In detail, the movable portion 3 of the balancing device 1 is integrally constrained to a shaft of the rotating piece 10, so that the central axis 3a substantially coincides with the axis of rotation 10a.

Initially, if the rotating piece ? balanced, the two eccentric masses 30 are offset by 180?, so that the balancing device 1 is also balanced and also the whole of the two objects.

If an unbalance occurs in the rotating piece 10, the unbalance detection means perceive it, measure it and send it to the control means.

These control the movement means 4 which increase the magnetic field in correspondence with the eccentric masses 30.

In particular, a permanent magnet 43 ? approached, through the adjustment means 44, to the conductive portion 41 constituted by the eccentric mass 30. Alternatively, or in addition, the electromagnet creates a magnetic field more? or less strong in the vicinity? of the eccentric mass 30.

The eddy currents created by the magnetic field formed by the permanent magnet 43 create a movement of current along the eccentric mass 30 which opposes the reciprocal movement between the permanent magnet 43 and the eccentric mass 30. The latter being in rotational movement around the axis 10a , the same is braked and varies angular position with respect to the rest of the mobile portion 3, thanks to its rotational drive around the bearing 31.

The eccentric masses 30 are therefore rotated until? the unbalance of the balancing device 1 is not ? equal and opposite to the unbalance of piece 10, in such a way as to balance it.

If the magnetic field is reduced, for example by moving the permanent magnet 43 away from the eccentric mass 30 or by decreasing the magnetic field of the electromagnet, the parasitic currents decrease their intensity. and the magnetic field decreases its strength. The eccentric mass 30 then returns to being integral with the remaining part of the movable portion 3 and with the rotating piece 10. The balancing device 1 according to the invention achieves important advantages. In fact, the balancing device ? simple and robust, not including complex rotational motors and the like. It can therefore also be placed on board rotating elements exceeding tens of thousands of revolutions per minute.

For the same reasons it? buy for a song.

The invention? susceptible of variations falling within the scope of the inventive concept defined by the claims. In this context, all the details can be replaced by equivalent elements and the materials, shapes and dimensions can be any.

Claims (10)

1. Balancing device (1) for rotating workpiece (10), - said piece in rotation (10) defining an axis of rotation (10a), - said balancing device (1) comprising: - a fixed portion (2), - a movable portion (3) defining a central axis (3a), called movable portion (3) - being constrainable to said rotating piece (10) so that said central axis (3a) substantially coincides with said axis of rotation (10a), and - comprising at least one eccentric mass (30) rotatable around said central axis (3a) and not balanced with respect to said central axis (3a), - movement means (4) of said at least one eccentric mass (30), able to rotate said eccentric mass (30), with respect to said rotating piece (10) around said central axis (3a), and characterized in that said movement means (4) comprise a magnetic brake (40). 2. Balancing device (1) according to claim 1, wherein said magnetic brake (40) comprises at least one conductive portion (41), made of conductive material, and at least one magnetic portion (42) able to create a magnetic field acting on said eccentric mass (30). The balancing device (1) according to claim 2, wherein said conductive portion (41) is integral with said eccentric mass (30) and said magnetic portion (42) ? fixed with respect to rotation around said axis of rotation (10a). 4. Balancing device (1) according to claim 3, wherein said conductive portion (41) coincides with said eccentric mass (30). 5. Balancing device (1) according to any one of claims 2-5, wherein said magnetic portion (42) comprises at least one electromagnet. 6. Balancing device (1) according to claim 5, with axis in the radial direction with respect to said central axis (3a). 7. Balancing device (1) according to any one of claims 2-6, wherein said magnetic portion (42) comprises a permanent magnet (43) and means (44) for regulating the distance between said permanent magnet (43) and said portion conductive (41). 8. Balancing device (1) according to the preceding claim, wherein said regulating means (44) comprise an electric motor. 9. Machine tool comprising a balancing device (1) according to any one of the preceding claims. 10. Process for moving an eccentric mass (30), around a central axis (3a), to modify the center of mass of a rotating piece (10), said eccentric mass (30) being moved by means of magnetic braking.