EP0494028B1 - Magnetic chuck with permanent magnets - Google Patents

Description

The present invention relates to a magnetic carrier with permanent magnets, provided with a switching device which, in one position, allows the attraction of objects made of ferromagnetic material by the carrier and which, in another position, makes this carrier inactive.

• des pièces polaires en nombre pair, réparties autour d'un axe sensiblement vertical, reliées entre elles par des parties en matériau amagnétiques, et entre lesquelles sont disposés des aimants permanents fixes, à sens d'aimantation horizontal tel que deux pièces polaires consécutives soient de polarités opposées ;
• au-dessus des pièces polaires, un disque ou plateau amagnétique, monté tournant autour dudit axe sensiblement vertical, et comprenant d'autres aimants permanents répartis circonférentiellement en un nombre pair de groupes, ces autres aimants permanents étant aimantés verticalement de telle sorte que deux groupes d'aimants consécutifs soient de polarités opposées ;
• des moyens de manoeuvre pour l'entraînement en rotation du disque ou plateau tournant autour dudit axe sensiblement vertical entre une première position angulaire, pour laquelle les champs magnétiques des aimants permanents fixes et desdits autres aimants permanents portés par ce disque ou plateau s'additionnent pour créer des pôles alternativement "Nord" et "Sud" sur les faces inférieures de toutes les pièces polaires, et une seconde position angulaire pour laquelle ces champs magnétiques se soustraient, rendant neutres les faces inférieures des pièces polaires ;
• des moyens de suspension ou d'attache de ce porteur magnétique, prévus dans sa partie supérieure.

More particularly, this invention relates to a magnetic carrier with permanent magnets comprising:

• pole pieces in even number, distributed around a substantially vertical axis, interconnected by parts made of non-magnetic material, and between which are fixed permanent magnets, in the direction of horizontal magnetization such that two consecutive pole pieces are of opposite polarities;
• above the pole pieces, a non-magnetic disk or plate, mounted rotating around said substantially vertical axis, and comprising other permanent magnets distributed circumferentially in an even number of groups, these other permanent magnets being magnetized vertically so that two groups consecutive magnets are of opposite polarities;
• operating means for the rotational drive of the disc or turntable around said substantially vertical axis between a first angular position, for which the magnetic fields of the fixed permanent magnets and of said other permanent magnets carried by this disc or tray add up for create alternately "North" and "South" poles on the lower faces of all the pole pieces, and a second angular position for which these magnetic fields are removed, making the lower faces of the pole pieces neutral;
• means of suspension or attachment of this magnetic carrier, provided in its upper part.

Such a permanent magnet magnetic carrier, combining sense permanent magnets horizontal magnetization and permanent magnets in the direction of vertical magnetization, is known from document US-A-4419644.

The embodiment described in this document comprises pole pieces forming two series of coaxial pole pieces, arranged in two concentric rings, the fixed permanent magnets being inserted radially between the two rings of pole pieces, and being magnetized in the radial direction. Thus, each fixed magnet corresponds to two pole pieces, and the concentric embodiment results in a significant bulk of the magnetic carrier in the radial direction, without its attraction surface being increased.

The present invention aims to eliminate these drawbacks by providing a magnetic carrier with permanent magnets of simplified structure and of reduced bulk, therefore particularly compact.

• les aimants permanents fixes à sens d'aimantation horizontal sont disposés entre deux pièces polaires se succédant en direction circonférentielle par rapport à l'axe sensiblement vertical précité,
• le disque ou plateau tournant prend la forme d'un disque ou plateau amagnétique dans lequel sont insérés les autres aimants permanents à sens d'aimantation vertical, répartis circonférentiellement en un nombre pair de groupes le nombre de groupes étant égal à celui des pièces polaires, et
• au-dessus du disque ou plateau tournant est disposée une plaque sensiblement horizontale de fermeture du champ magnétique.

To this end, in the magnetic carrier with permanent magnets object of the invention, belonging to the genus specified in the introduction, it is provided that:

• the permanent permanent magnets in the direction of horizontal magnetization are arranged between two pole pieces which succeed one another in a circumferential direction relative to the above-mentioned substantially vertical axis,
• the disk or turntable takes the form of a nonmagnetic disk or plate in which the other permanent magnets with vertical magnetization directions are inserted, distributed circumferentially in an even number of groups, the number of groups being equal to that of the pole pieces, and
• above the disc or turntable is arranged a substantially horizontal plate for closing the magnetic field.

Thus, the magnetic carrier with permanent magnets object of the invention is characterized by pole pieces arranged in a single ring, the fixed permanent magnets being inserted circumferentially (and either radially) between the pole pieces, and the number of these pole pieces being thus halved in comparison with the document US-A-4419644. Advantageously, the permanent permanent magnets with a direction of horizontal magnetization, arranged between the pole pieces, are magnets of the "ferrite" type, while the other permanent magnets with a direction of vertical magnetization, inserted in the disc or turntable, are magnets of the "rare earth"type; these latter magnets are preferably presented as pellets, each group of these magnets comprising several particles distributed over a sector of the disc or turntable, sector whose angle at the center corresponds to the angular extent of a pole piece.

In a particular embodiment of the invention, the magnetic carrier comprises four pole pieces arranged in a square, and the disc or turntable comprises four groups of permanent magnets each occupying a sector of 90 °, so that for a position angle of the disc or turntable the lower faces of the four pole pieces constitute two "North" poles and two "South" poles arranged diagonally, a 90 ° rotation of the disc or plate making the lower faces of these four pole pieces neutral.

• Figure 1 est une vue en perspective éclatée, montrant les principaux composants d'un porteur magnétique conforme à la présente invention, en position de travail ;
• Figure 2 est une vue en coupe verticale du porteur magnétique, toujours en position de travail, suivant II-II de figure 1 ;
• Figure 3 en est une vue en coupe horizontale suivant III-III de figure 2, mais en position de repos ;
• Figure 4 est une vue en coupe verticale similaire à figure 3, mais correspondant à la position de repos.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of nonlimiting example, an embodiment of this magnetic carrier with permanent magnets:

• Figure 1 is an exploded perspective view showing the main components of a magnetic carrier according to the present invention, in the working position;
• Figure 2 is a vertical sectional view of the magnetic carrier, still in the working position, along II-II of Figure 1;
• Figure 3 is a horizontal sectional view along III-III of Figure 2, but in the rest position;
• Figure 4 is a vertical sectional view similar to Figure 3, but corresponding to the rest position.

The magnetic carrier shown in the drawing comprises four pole pieces 1 of mild steel, of generally parallelepiped shape, arranged in a square and distributed around a substantially vertical axis 2. The pole pieces 1 are connected together by parts made of non-magnetic material 3, to form a massive block.

Between the pole pieces 1 are also arranged four groups of fixed permanent magnets 4, in the direction of horizontal magnetization. The groups of magnets 4 are oriented in such a way that under the effect of these magnets two consecutive pole pieces 1 are of opposite polarities, one forming a "North" pole and the other forming a "South" pole. Thus, overall, the four pole pieces 1 constitute two "North" poles arranged diagonally and two "South" poles also arranged diagonally. The fixed permanent magnets 4 are, for example, magnets of the "ferrite" type.

Above the block formed by the pole pieces 1, by the non-magnetic parts 3 and by the fixed permanent magnets 4, there is provided a non-magnetic disc 5 horizontal, mounted rotating around the vertical axis 2. In the non-magnetic disc 5 are inserted other permanent magnets 6, distributed circumferentially into four groups of magnets according to an arrangement clearly visible in FIGS. 1 and 3.

Each group of said other magnets 6 occupies, on the rotating disc 5, a circle sector of approximately 90 °. Said other magnets 6, in the sense of vertical magnetization, are presented as pellets, each group of said other magnets 6 comprising several pellets distributed over the extent of the corresponding sector. In each group, the orientation of said other magnets 6 is the same, but this orientation is alternated from one group of magnets to the next. Thus, the disc 5 comprises two groups of said other diametrically opposite magnets 6 whose lower faces form "North" poles, and two other groups of said other magnets 6, interposed between the previous ones, whose lower faces form "South" poles. Said other permanent magnets 6 are, for example, magnets of the "rare earth" type.

Above the rotating disc 5 is disposed a fixed horizontal plate 7 of generally square shape, made of mild steel, ensuring the closing of the magnetic field between the upper poles of said other permanent magnets 6 of the disc 5. Screws 8 made of non-magnetic material, arranged at the angles of the plate 7 beyond the perimeter of the disc 5, ensure the connection of the plate 7 with the block formed of the pole pieces 1, non-magnetic parts 3 and fixed magnets 4.

The horizontal plate 7 has a central opening, in which a bearing 9 is mounted. The disc 5 is linked in rotation to a shaft 10 which passes through the bearing 9 and which carries, above the plate 7, an operating member 11 such as a button, handle or lever, allowing manual control of the rotation of the disc 5 around the vertical axis 2.

Finally, as shown in particular in FIG. 1, a suspension or attachment member 12 in the form of a handle, turned upwards, is fixed to the horizontal plate 7 by means of the screws 8; the suspension member 12 surmounts the operating member 11 and it can extend diagonally thus connecting two non-consecutive angles of the plate 7.

In a particular angular position of the rotating disc 5, the “North” poles formed by the lower faces of two of the groups of said other magnets 6 carried by this disc 5 are in contact with the upper faces of the two pole pieces 1, the polarity of which (under the effect of groups of fixed magnets 4) is also "North". The “South” poles formed by the lower faces of the two other groups of said other magnets 6 carried by the disc 5 are then in contact with the upper faces of the two other pole pieces 1, the polarity of which (under the effect of the groups of magnets fixed 4) is also "South". Thus, the magnetic fields of the fixed permanent magnets 4 and of said other permanent magnets 6 carried by the disc 5 add up, to create four poles alternately "North" and "South" on the lower faces of the pole pieces 1 - see FIGS. 1 and 2. The magnetic carrier is then in the working position, that is to say that it is capable of attracting a load 14 of ferromagnetic material, applying against the lower faces 13 of the four pole pieces 1.

Advantageously, the lower faces 13 of the four pole pieces 1 are bordered by bevelled facets 15, in particular on their inner sides, to properly concentrate the magnetic field on the lower faces 13 and also to have facets 4 in the center of the wearer. adapted to attract an object, for example spherical or conical.

It is now assumed that the rotating disc 5 occupies an angular position offset by 90 ° with respect to that previously considered. The “North” poles formed by the lower faces of two of the groups of said other magnets 6 carried by this disc 5 are then brought into contact with the upper faces of the two pole pieces 1, the polarity of which (under the effect of the groups of magnets fixed 4) is "South". The “South” poles formed by the lower faces of the two other groups of said other magnets 6 carried by the disc 5 are, as for them, brought into contact with the upper faces of the two other pole pieces 1 whose polarity (under the effect of the groups of fixed magnets (4) is "North". In this position, and providing that the magnetic field total of the fixed magnets 4 is equal to the total magnetic field of said other magnets 6 carried by the disc 5, one obtains a subtraction of these fields such that the lower faces 13 of the four pole pieces 1 become neutral, the magnetic circuit being closed by the inside of the carrier - see figures 3 and above all 4. It is therefore, for the magnetic carrier, a rest position for which no load is attracted by the pole pieces 1.

Thanks to the operating member 11, the operator conveniently rotates the disc 5 a quarter of a turn to pass from the working position to the rest position, or vice versa.

• en modifiant la forme des aimants permanents et/ou en changeant le nombre d'aimants dans chaque groupe d'aimants ;
• en utilisant des aimants de types autres que ceux mentionnés ;
• en remplaçant le disque tournant par tout autre support analogue, tel qu'un plateau, en matériau amagnétique ;
• en montant tous moyens équivalents, en lieu et place des organes de manoeuvre et de préhension ou d'attache décrits plus haut ;
• en modifiant le nombre des pièces polaires et des groupes d'aimants tout en conservant un nombre total pair et une répartition selon le même principe, par exemple en prévoyant seulement deux pièces polaires auquel cas le passage de la position de travail à la position de repos nécessite une rotation d'un demi-tour du disque tournant, ou en prévoyant six pièces polaires auquel cas le passage de la position de travail à la position de repos nécessite une rotation de 60° du disque tournant ;
• en adaptant la forme des pièces polaires, notamment de leur partie inférieure, en fonction des objets à manipuler ;
• en utilisant le dispositif décrit ci-dessus à d'autres utilisations que le levage et notamment à la fixation de pièces et accessoires divers.

Of course, the invention is not limited to the only embodiment of this magnetic carrier with permanent magnets which has been described above, by way of example; on the contrary, it embraces all the variants of implementation and application respecting the same principle. Thus, in particular that one would not depart from the scope of the invention:

• by changing the shape of the permanent magnets and / or by changing the number of magnets in each group of magnets;
• using magnets of types other than those mentioned;
• by replacing the rotating disc with any other similar support, such as a plate, made of non-magnetic material;
• by mounting all equivalent means, in place of the operating and gripping or attachment members described above;
• by changing the number of pole pieces and groups of magnets while keeping an even total number and a distribution according to the same principle, for example by providing only two pole pieces in which case the transition from the working position to the rest position requires a half-turn rotation of the rotating disc, or by providing six pole pieces in which case the transition from the working position to the rest position requires a rotation of 60 ° of the rotating disc;
• by adapting the shape of the pole pieces, in particular of their lower part, according to the objects to be handled;
• using the device described above for other uses than lifting and in particular for fixing various parts and accessories.

Claims (5)

1. A magnetic chuck having permanent magnets, including:

   - an even number of pole pieces (1) distributed around a substantially vertical axis (2), connected together by portions (3) of non-magnetic material, and between which are disposed fixed permanent magnets (4) magnetized in a horizontal direction, such that two consecutive pole pieces (1) are of opposite polarity (N,S);

   - above the pole pieces (1), a disc or plate (5) rotatably mounted about said substantially vertical axis (2) and including other permanent magnets (6) circumferentially distributed in an even number of groups, these other permanent magnets (6) being vertically magnetized, such that two consecutive groups of magnets are of opposite polarity (N,S);

   - operating means (11) for driving the rotatable disc or plate (5) in rotation about said substantially vertical axis (2) between a first angular position for which the magnetic fields of the fixed permanent magnets (4) and of said other permanent magnets (6) carried by the disc or plate (5) are added together to create alternately "North" and "South" poles on the lower faces (13) of all the pole pieces (1), and a second angular position, for which these magnetic fields are subtracted from one another, rendering the lower faces (13) of the pole pieces (1) neutral;

   - suspension or attachment means (12) for this magnetic chuck, provided in its upper portion, characterised in that :

   - the fixed permanent magnets (4) magnetized in a horizontal direction are disposed between two pole pieces (1) succeeding one another in a circumferential direction with respect to the aforementioned substantially vertical axis (2),

   - the rotatable disc or plate (5) takes the form of a non-magnetic disc or plate into which are inserted said other permanent magnets (6) magnetized in a vertical direction, distributed circumferentially in an even number of groups, the number of groups being equal to that of the pole pieces (1), and

   - above the rotatable disc or plate (5) is disposed a substantially horizontal plate (7) for closing the magnetic field.
2. A magnetic chuck having permanent magnets according to Claim 1, characterised in that the fixed permanent magnets (4) magnetized in a horizontal direction, disposed between the pole pieces (1), are magnets of the "ferrite" type, whilst said other permanent magnets (6), magnetized in a vertical direction, inserted into the rotatable disc or plate (5), are magnets of the "rare earth" type.
3. A magnetic chuck having permanent magnets according to Claim 1 or 2, characterised in that said other permanent magnets (6), magnetized in a vertical direction, are in the form of pellets, each group of these magnets having several pellets distributed over a sector of the rotatable disc or plate (5), the angle at the centre of this sector corresponding to the angular extent of a pole piece (1).
4. A magnetic chuck having permanent magnets according to any one of Claims 1 to 3, characterised in that it includes four pole pieces (1) disposed in a square, and in that the rotatable disc or plate (5) has four groups of permanent magnets (6) each occupying a sector of 90°, in such a way that for an angular position of the rotatable disc or plate (5) the lower faces (13) of the four pole pieces (1) constitute two "North" poles and two "South" poles disposed diagonally, a rotation through 90° of the disc or plate (5) rendering neutral the lower faces (13) of these four pole pieces (1).
5. A magnetic chuck having permanent magnets according to any one of Claims 1 to 4, characterised in that the lower faces (13) of the pole pieces (1) are edged by chamfered facets (15), particularly on their internal sides.

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