WO2016174689A1

WO2016174689A1 - Magnetic brake

Info

Publication number: WO2016174689A1
Application number: PCT/IT2015/000118
Authority: WO
Inventors: Giuseppe ARRAS
Original assignee: Lafer Spa
Priority date: 2015-04-29
Filing date: 2015-04-29
Publication date: 2016-11-03

Abstract

Magnetic brake comprising a first disc (12) and a second disc (14), wherein the first disc (12) and the second disc (14) are installed, during use, facing each other respectively with a first face (13) and a second face (15). On the first disc (12) and the second disc (14) are installed, respectively, first permanent magnets (18) and second permanent magnets (22), disposed in positions coordinated with respect to each other, angularly distanced along respective circumferences (C1, C2).

Description

"MAGNETIC BRAKE"

FIELD OF THE INVENTION

Forms of embodiment described here concern a magnetic brake applicable to a rotary motor, for example an electric motor, although applications to other types of motors are not excluded, for example hydraulic or pneumatic motors.

BACKGROUND OF TFIE INVENTION

Electromagnetic brakes are known, which comprise a brake disc, connected to the shaft of an electric motor, an electromagnet activated by an electric command circuit, and a mobile anchoring device subject to elastic members that tend to keep it pressed against the brake disc.

During the normal functioning of the motor, the electric command circuit excites the electromagnet which attracts the mobile anchoring device, enabling the brake disc connected to the drive shaft to rotate freely.

When the electric command circuit does not power it, the electromagnet loses its excitation and the mobile anchoring device is kept pressed against the brake disc, exerting the desired function of braking the drive shaft.

This technical solution is very complex and is relatively expensive.

Furthermore, electromagnetic brakes have considerable axial sizes, and this requires making a drive shaft and protective cover that are longer than those of a standard motor.

Another disadvantage is caused by the feed of the command circuit of the electromagnet, which leads to high energy consumption, as well as the need to provide complex cabling and the necessary precautions against risks of an electric nature.

Magnetic brakes are also known, which comprise a first metal disc, installed sliding on a drive shaft and made to rotate selectively by the drive shaft. On the first metal disc first permanent magnets are installed, distanced angularly with respect to each other according to a pattern on the perimeter of a circumference.

In particular, the first permanent magnets are installed on the first disc, disposing them all with a particular polarity facing toward one of the two faces of the first disc.

The known magnetic brake also comprises a second metal disc installed fixed with respect to the motor, and facing the first metal disc.

Second permanent magnets are installed on the second metal disc, also disposed distanced angularly with respect to each other according to a pattern on the perimeter of a circumference.

In particular, the second permanent magnets are disposed in a position and according to a configuration coordinated with that of the first permanent magnets.

The second permanent magnets are installed on the second metal disc disposing them all with a particular polarity facing toward one of the two faces of the second metal disc.

In particular, the first and second metal discs are installed so as to dispose the first permanent magnets and the second permanent magnets facing each other with the same polarity.

Braking is obtained by magnetic attraction between the first permanent magnets of the first disc and the metal portion of the second metal disc comprised between the second permanent magnets, and by magnetic attraction between the second permanent magnets of the second disc and the metal portion of the first metal disc comprised between the first permanent magnets.

If there is an attempt by the drive shaft to begin rotating again, the first permanent magnets and the second permanent magnets are disposed facing each other with the same polarities, reciprocally repelling each other and returning the first metal disc and the second metal disc to a condition of connection and reciprocal attraction.

One disadvantage of magnetic brakes of this type is that they do not guarantee a sufficient force of attraction/repulsion between the two metal discs, so that the braking action may not be optimal if they are not used in a low inertia system, for example on electric motors coupled with a reducer.

There is therefore a need to perfect a magnetic brake that can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to supply a magnetic brake that can be enabled and/or disenabled without needing an electric command circuit and the corresponding electric cabling.

Another purpose of the present invention is to obtain a magnetic brake with relatively limited sizes and costs compared with known solutions. Another purpose of the present invention is to obtain a magnetic brake that is more effective and efficient compared with known solutions in the state of the art.

Another purpose of the present invention is to obtain a magnetic brake that guarantees high standards of reliability in all functioning conditions.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, a magnetic brake comprises at least a first disc, or rotor disc, and a second disc, or stator disc, installed during use facing each other with respectively a first face of the first disc and a second face of the second disc.

The first disc can be associated with a rotor part of a rotary motor, while the second disc can be associated with a stator part of the rotary motor.

According to one aspect of the invention, first permanent magnets and second permanent magnets are installed respectively on the first disc and the second disc, disposed angularly distanced with respect to each other along the perimeter of respective circumferences CI and C2 and in positions coordinated with each other.

According to another aspect of the present invention, the first permanent magnets are installed, facing toward the first face of the first disc, with an alternate North-South polarity, that is, N-S-N-S, so that a magnet with North polarity is disposed between two magnets with South polarity and vice versa.

According to another aspect of the present invention, the second permanent magnets are also installed facing toward the second face of the second disc with alternate North-South polarity.

This solution of the magnetic brake, unlike known solutions, allows to obtain a magnetic brake that is more efficient and effective in the braking action.

The disposition of the permanent magnets with alternate polarity on both the first disc and the second disc allows that, in a braking condition, the first magnets with north polarity couple magnetically with the second magnets with south polarity of the second disc, and in the same way, the first magnets with south polarity couple magnetically with the second magnets with north polarity. In the active condition of the motor, that is, when the magnetic brake is de-activated, the drive torque imparted by the motor between the first disc and the second disc allows to overcome the magnetic action between the permanent magnets, so that no braking action is imparted. In a dynamic condition, that is, with the rotor part rotating, the attractive magnetic action between the discs is cancelled, whereas if the first disc slows down, the magnetic attractive action increases so as to completely brake the rotor part of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of some forms of embodiment, given as a non- restrictive example with reference to the attached drawings wherein:

- fig. 1 is an exploded view of a magnetic brake according to forms of embodiment described here;

- fig. 2 is a partly sectioned lateral view of a magnetic brake according to forms of embodiment described here in a first operating condition;

- fig. 3 is a partly sectioned lateral view of a magnetic brake according to forms of embodiment described here in a second operating condition;

- fig. 4 is a front view of a component of a magnetic brake according to forms of embodiment of the present invention;

- fig. 5 is a front rear view of another component of a magnetic brake according to forms of embodiment of the present invention;

- fig. 6 is a front view of another component of a magnetic brake according to possible forms of embodiment of the present invention;

- fig. 7 is a partly sectioned lateral view of a magnetic brake according to further forms of embodiment described here.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF SOME FORMS OF EMBODIMENT

We shall now refer in detail to the various forms of embodiment of the present invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof.

Forms of embodiment described using figs. 1-7 concern a magnetic brake 10 applicable to a motor 52.

In particular, the magnetic brake 10 can be installed partly on a rotor part of the motor 52, for example on a drive shaft 50 of the motor 52, and partly on a stator part of the motor 52, for example the fixed guard 54 of the motor 52.

According to forms of embodiment described using figs. 1-3 and 7, the magnetic brake 10 comprises at least a first disc 12, or rotor disc, and a second disc 14, or stator disc.

Both the first disc 12 and the second disc 14 are provided in their center with a through hole 17 through which the drive shaft 50 is positioned through.

The first disc 12 is installed on the drive shaft 50 and is made to rotate solidly therewith.

The second disc 14 is installed on the guard 54 and is stationary during use. The first disc 12 and second disc 14 are installed, during use, facing each other respectively with a first face 13 of the first disc 12 and a second face 15 of the second disc 14.

On the first disc 12 and second disc 14, first permanent magnets 18 and second permanent magnets 22 are respectively installed, disposed angularly distanced along respective circumferences CI, C2 according to a ring configuration.

According to possible forms of embodiment, shown for example in figs. 1 , 4 and 6, the number of the first permanent magnets 18 is equal to the number of second permanent magnets 22.

According to the present invention, the first permanent magnets 18 and the second permanent magnets 22 are disposed in coordinated positions so that a second permanent magnet 22 corresponds to each first permanent magnet 18.

According to possible solutions, the circumferences CI and C2 have substantially the same diameter sizes. According to one possible solution (fig. 4), the first permanent magnets 18 and respectively the second permanent magnets 22 are disposed angularly distanced by an angular pitch P substantially constant between adjacent pairs of first permanent magnets 18 and respectively second permanent magnets 22.

According to the present invention, the angular pitch P between the first permanent magnets 18 is equal to the angular pitch P between the second permanent magnets 22.

This condition, combined with the identical diameter of the circumferences C 1 and C2, allows to obtain a positioning of the first permanent magnets 18 coordinated with that of the second permanent magnets 22. This ensures that a second permanent magnet 22 corresponds with each first permanent magnet 18 and, during use, is located facing it.

According to a possible solution, the first permanent magnets 18 and respectively the second permanent magnets 22 are distanced from each other, with respective peripheral edges, by an angular distance D less than the angular pitch P. In this way it is possible to dispose the first permanent magnets 18 and respectively the second permanent magnets 22 substantially adjacent to each other, obtaining a much more concentrated distribution of the latter with respect to known solutions. Given the same sizes of the magnetic brake 10, this allows to increase the number of permanent magnets and therefore to increase the braking action of the magnetic brake 10.

According to one aspect of the present invention, the first permanent magnets 18 are installed, facing toward the first face 13 of the first disc 12, with an alternate North-South polarity, that is, N-S-N-S... so that a magnet with a north polarity is disposed between two magnets with a south polarity and vice versa.

According to another aspect of the present invention, the second permanent magnets 22 are also installed facing toward the second face 15 of the second disc 14, also with an alternate North-South polarity.

According to possible solutions, the first permanent magnets 18 are installed in an even number on the first disc 12, so that two first permanent magnets 18 with the same polarity are not installed adjacent to each other.

According to possible solutions, the second permanent magnets 22 are installed in an even number on the second disc 14, so that two second permanent magnets 22 with the same polarity are not installed adjacent to each other.

The number of permanent magnets, moreover, determines by how many degrees the first disc 13 has to rotate with respect to the second disc 14 to take the magnetic brake 10 to a released condition.

According to the forms of embodiment described using figs. 4 and 6, a small rotation of the first disc 12 with respect to the second disc 14 is sufficient, for example about 10°, to determine a first permanent magnet 18, having a certain polarity, being positioned above a second permanent magnet 22 having the same polarity, thus determining the repulsion of the first disc 12 and the second disc 14.

According to possible solutions, shown for example in figs. 1-3, the first disc 12 can be provided with a plurality of first seatings 16 in which the first permanent magnets 18 are disposed, according to a configuration substantially analogous to that described above. This solution allows to ensure a precise and stable positioning of the first permanent magnets 18.

According to a possible form of embodiment of the present invention, which can be combined with all the embodiments described here, the second disc 14 can be provided with a plurality of second seatings 20 in which the second permanent magnets 22 are disposed, according to a configuration substantially analogous to that described above

In the braking operating condition, shown for example in fig. 2, the first permanent magnets 18 and the second permanent magnets 22 are reciprocally coupled with each other by magnetic attraction. Each of the first permanent magnets 18 of the first disc 12 attracts one of the second permanent magnets 22 of the second disc 14 having a polarity opposite to its own, thus bringing the first disc 12 into contact with the second disc 14.

In this braking operating condition, the magnetic brake 10 is stably braked, since any modification of this state is prevented not only by the force of attraction between the first permanent magnets 18 and second permanent magnets 22 having opposite polarities, but also by the first permanent magnets 18 and the second permanent magnets 22 located adjacent to the one considered and having opposite polarities. For example, if a first permanent magnet 18 with north polarity, in the braking condition is attracted by a second permanent magnet 22 with south polarity, if there is an attempt to make the first disc 12 rotate in any direction of rotation, the first permanent magnet 18 with north polarity would be positioned partly above a second permanent magnet 22 with north polarity. Therefore, a repulsive force would be created between magnets such as to return the first permanent magnet 18 with north polarity to a condition of attraction with the second permanent magnet 22 with south polarity.

In the non-operating condition of the magnetic brake, the torque imparted by the motor 52 is such as to overcome the forces of magnetic attraction between the first permanent magnets 18 and the second permanent magnets 22, so as to allow a free rotation of the drive shaft 50 with respect to the guard 54.

Since in the dynamic condition the force of magnetic repulsion prevails over the force of attraction, the first disc 12 separates from the second disc 14, moving away from it and allowing the free rotation of the drive shaft 50. When the drive shaft 50 slows down again, the force of attraction between the first permanent magnets 18 and the second permanent magnets 22 with opposite polarity present on the first disc 12 and the second disc 14 prevails over the force of repulsion between the first permanent magnets 18 and the second permanent magnets 22 having the same polarity, and takes the magnetic brake 10 to a braking condition. According to some forms of embodiment, the first disc 12 can be made of a non-magnetic material, for example a metal material that is not affected by magnetic influence.

According to some forms of embodiment, the second disc 14 can be made of a non-magnetic material.

Merely by way of example, the first disc 12 and the second disc 14 can be made of a material chosen from aluminum, copper, titanium, stainless steel, tungsten. Materials of a non-magnetic type, having a relative magnetic permeability very near to one, are not subject to magnetic effect, or only to a very small extent, and therefore are advantageous to use because they allow to prevent possible distortions of the magnetic field generated by the first permanent magnets 18 and the second permanent magnets 22.

According to forms of embodiment described using figs. 1-6, the magnetic brake 10 comprises sliding members 55 configured to allow at least one of either the first disc 12 or the second disc 14 to slide reciprocally closer to/away from each other.

In particular, the sliding members 55 allow the first disc 12 and the second disc 14 to move reciprocally closer to/away from each other so as to take the first permanent magnets 18 into contact with the second permanent magnets 22, in the braking condition, or to reciprocally distance them if the motor 52 is active.

According to possible forms of embodiment shown in figs. 2 and 3, the sliding members 55 are associated with the first disc 12 while the second disc 14 is installed in a fixed position. In this solution, the sliding members 55 allow translation in a direction parallel to the axial extension of the drive shaft 50, moving closer to/away from the second disc 14.

According to the forms of embodiment shown in figs. 2 and 3, the sliding members 55 comprise a toothed hub 24, solidly installed on the drive shaft 50. The toothed hub 24 can be keyed to the drive shaft 50, for example by means of mechanical members such as a key, a tongue, grooved shafts or suchlike.

The toothed hub 24 is provided with at least one tooth, in this case a grooved profile 25, made on the external surface and during use in contact with the first disc 12.

The first disc 12 is provided, in turn, with a grooved profile 27, substantially mating in size and shape with the grooved profile 25 of the toothed hub 24.

The first disc 12 can slide axially along the grooved profile 25, but remaining solid in rotation with the drive shaft 50.

According to a variant shown in fig. 7, the sliding members 55 are associated with the second disc 14 and allow the second disc 14 to move closer to/away from the first disc 12.

According to this form of embodiment, the first disc 12 is keyed to the drive shaft 50 and is axially constrained with respect to it.

The guard 54 is provided with guide elements 36, in this case guide pins on which the second disc 14 is installed, able to slide in a direction parallel to the axial development of the drive shaft 50.

According to the form of embodiment shown in fig. 7, the guide elements 36 are installed parallel to the axial development of the drive shaft 50.

According to a possible solution, the second disc 14 is provided with guide holes 38 into which, during use, the guide elements 36 are inserted through. According to the form of embodiment shown in figs. 2 and 3, the first disc 12 is interposed between the guard 54 of the motor 52 and the second disc 14.

According to this form of embodiment, the second disc 14 has a hollow seating 30 in which, during use, the first disc 12 is positioned, with the possibility of moving axially along the drive shaft 50.

The second permanent magnets 22 are installed, according to the configurations described above, in the hollow seating 30.

This solution allows to contain the overall bulk of the magnetic brake 10, obtaining a rather compact combination.

According to possible forms of embodiment of the present invention, shown for example in figs. 1-3, 5 and 7, the magnetic brake 10 comprises a magnetic homogenization element 34 associated with at least one of either the first disc 12 or the second disc 14, on one face of the first disc 12 and/or of the second disc 14 opposite the first face 13 and/or respectively to the second face 15, and configured to homogenize the magnetic field generated by the first permanent magnets 18 and/or the second permanent magnets 22.

According to a possible solution of the present invention, the magnetic homogenization element 34 can comprise a foil made of metal material having magnetic properties.

According to forms of embodiment described using figs. 2 and 3, the magnetic homogenization element 34 is disposed in direct contact with the first permanent magnets 18.

According to possible solutions, for example shown in fig. 7, the magnetic homogenization element 34 can be disposed in direct contact with the first permanent magnets 18 and the second permanent magnets 22.

Applicant has carried out tests to measure the intensity of the forces of attraction and repulsion between the first permanent magnets 18 and the second permanent magnets 22 in the presence and absence of the magnetic homogenization element 34, and has found that the presence of the latter determines an increase in the intensity of such forces of more than 10%, up to 20%, with respect to the solutions w^?here it is not installed.

Applicant has carried out other tests to measure the variation in the intensity of the forces of attraction and repulsion between first permanent magnets 18 and second permanent magnets 22 when the magnetic homogenization element 34 is located near or in contact with the permanent magnets.

The results of the tests have shown that if the magnetic homogenization element 34 is in direct contact with the permanent magnets, the intensity of the forces of attraction/repulsion is higher by 5%, also up to 10% with respect to the intensity of the forces detected with the magnetic homogenization element 34 not in direct contact with the permanent magnets.

According to forms of embodiment shown for example in figs. 1, 2 and 3, the magnetic brake 10 can comprise a sealing ring 40 interposed between the second disc 14 and the guard 54 of the motor 52, to prevent impurities from entering into the hollow seating 30 of the second disc 14 and damaging, for example, the latter and the first disc 12.

According to some forms of embodiment, which can be combined with all the embodiments described here, the magnetic brake 10 can comprise another sealing ring 42, for example an O-ring, installed between the second disc 14 and the drive shaft 50, to prevent possible impurities from entering into the interspace between the latter two and damaging the first disc 12 and the second disc 14.

According to some forms of embodiment of the present invention, shown for example in figs. 1-3 and 7, the magnetic brake 10 can comprise a flange 28 attached to the guard 54 of the motor 52 and configured to connect the second disc 14 to the guard 54.

The connection of the second disc 14 to the flange 28 can be carried out with threaded connections, as shown for example in figs. 2 and 3, or by the guide elements 36 described above, as shown for example in fig. 7.

It is clear that modifications and/or additions of parts may be made to the magnetic brake as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of magnetic brake, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

1. Magnetic brake comprising a first disc (12) and a second disc (14), said first disc (12) and said second disc (14) being installed, during use, facing each other respectively with a first face (13) and a second face (15), on said first disc (12) and said second disc (14) being installed, respectively, first permanent magnets (18) and second permanent magnets (22), disposed in positions coordinated with respect to each other, angularly distanced along respective circumferences (CI, C2), characterized in that said first permanent magnets (18) are installed, facing toward said first face (13) of said first disc (12), with an alternate North-South polarity, and said second permanent magnets (22) are installed, facing toward said second face (15) of said second disc (14), with an alternate North-South polarity.

2. Magnetic brake as in claim 1, characterized in that said first permanent magnets (18) and respectively said second permanent magnets (22) are disposed angularly distanced by an angular pitch (P) substantially constant between adjacent pairs of first permanent magnets (18) and respectively second permanent magnets (22), and in that the angular pitch (P) between said first permanent magnets (18) is equal to the angular pitch (P) between said second permanent magnets (22).

3. Magnetic brake as in claim 2, characterized in that said first permanent magnets (18) and respectively said second permanent magnets (22) are distanced from each other, with respective peripheral edges, by an angular distance (D) less than said angular pitch (P).

4. Magnetic brake as in any claim hereinbefore, characterized in that said first permanent magnets (18) and said second permanent magnets (22) are installed in an even number respectively on said first disc (12) and said second disc (14).

5. Magnetic brake as in any claim hereinbefore, characterized in that said first disc (12) is provided with a plurality of first seatings (16) in which said first permanent magnets (18) are disposed.

6. Magnetic brake as in any claim hereinbefore, characterized in that said second disc (14) is provided with a plurality of second seatings (20) in which said second permanent magnets (22) are disposed.

7. Magnetic brake as in any claim hereinbefore, characterized in that said first disc (12) is made of a non-magnetic material.

8. Magnetic brake as in any claim hereinbefore, characterized in that said second disc (14) is made of a non-magnetic material.

9. Magnetic brake as in any claim hereinbefore, characterized in that it comprises sliding members (55) configured to allow the sliding of at least one of either said first disc (12) or said second disc (14) reciprocally closer to/away from each other.

10. Magnetic brake as in claim 9, characterized in that said sliding members (55) are associated with said first disc (12) and said second disc (14) is installed in a fixed position.

1 1. Magnetic brake as in claim 9, characterized in that said sliding members (55) are associated with said second disc (14) and allow said second disc (14) to move reciprocally closer to/away from said first disc (12).

12. Magnetic brake as in any claim hereinbefore, characterized in that it comprises a magnetic homogenization element (34) associated with at least one of either said first disc (12) or said second disc (14), on one face of the first disc (12) and/or of the second disc (14) opposite said first face (13) and/or respectively to said second face (15), and configured to homogenize the magnetic field generated by the first permanent magnets (18) and/or the second permanent magnets (22).

13. Combination of a rotary motor and a magnetic brake as in any claim hereinbefore, wherein said first disc (12) is installed on a rotor part of said motor (52), and said second disc (14) is installed on a stator part of the motor (52).