WO2000030805A1 - Dispositif de retenue magnetique - Google Patents

Dispositif de retenue magnetique Download PDF

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Publication number
WO2000030805A1
WO2000030805A1 PCT/IB1999/001750 IB9901750W WO0030805A1 WO 2000030805 A1 WO2000030805 A1 WO 2000030805A1 IB 9901750 W IB9901750 W IB 9901750W WO 0030805 A1 WO0030805 A1 WO 0030805A1
Authority
WO
WIPO (PCT)
Prior art keywords
holding device
magnetic
magnetic holding
permanent magnets
plate
Prior art date
Application number
PCT/IB1999/001750
Other languages
English (en)
Inventor
Ian Asquith
Original Assignee
Eclipse Magnetics Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eclipse Magnetics Limited filed Critical Eclipse Magnetics Limited
Priority to AU62249/99A priority Critical patent/AU6224999A/en
Publication of WO2000030805A1 publication Critical patent/WO2000030805A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q3/00—Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine
    • B23Q3/15—Devices for holding work using magnetic or electric force acting directly on the work
    • B23Q3/154—Stationary devices
    • B23Q3/1546—Stationary devices using permanent magnets

Definitions

  • the present invention relates to magnetic holding devices, that is, devices for releasably securing workpieces by magnetism.
  • Magnetic holding devices or magnetic chucks as they are also known, are often used in preference to mechanical clamping means because of the ease and speed with which the workpiece may be secured to the chuck, and the improved access afforded to the workpiece by not having clamping means extending over the sides and upper surfaces of the workpiece.
  • the magnetic chuck's magnetism may be derived from permanent magnets, electromagnets, or from electropermanent magnets; electropermanent magnets are preferred.
  • Permanent magnets require mechanical positioning in order to grip and release the workpiece, and to release the workpiece requires the magnets to be pulled away in opposition to the attractive force.
  • Electromagnets are capable of being switched on and off at will, but in the event of a power failure, the workpiece will be released, as electricity must be constantly supplied to the magnets.
  • Known electropermanent magnets include arrangements of electromagnets and permanent magnets.
  • the magnetic switching unit consists of a head element made from steel known as a pole piece, and an electromagnetic coil surrounding a magnetic core placed beneath this.
  • the magnetic core may have its polarity reversed by the action of the electromagnet, but when the electromagnet is off the magnetic core is permanent. That is, the magnet core retains the magnetization induced by the current pulse, the applied field from the permanent magnets around the pole piece being insufficient to change the magnetization of the core.
  • An arrangement of such magnetic switching units is repeated across the chuck, and all the magnets and pole pieces are secured in a tray, comprising sides and a steel base, held together and securing the components by bolts.
  • the polarisation of the pole piece is set by the action of the electromagnet, so that when the magnetic chuck is in the 'on' setting to hold the workpiece, flux flows in a circuit from each permanent magnet, through the associated pole piece, out of the working surface, back into an adjacent pole piece and back to the opposite pole of the same or another magnet.
  • this magnetic flux will flow through the workpiece during its circuit, causing the workpiece to be securely held to the working surface.
  • a short pulse of current through the coil of the electromagnet is sufficient to reverse the polarisation of the magnetic switching unit's pole piece and solenoid core, after which the current may be discontinued.
  • a short pulse is sent through the electromagnet's coil in the reverse direction, causing a field of a sufficient strength to reverse the polarity of the core.
  • the whole of the flux from the permanent magnets is then directed downwards through the pole piece away from the working surface, so releasing the workpiece.
  • the electromagnet, the pole piece and the electromagnet's core together form a means of switching the direction of the magnetic field of the permanent magnets between flowing up through a magnetic switching unit, out of the working surface and back down through a neighbouring magnetic switching unit, and flowing down through a magnetic switching unit, through the base plate and thence upwards into a neighbouring magnetic switching unit.
  • the magnetic material of the magnetic switching unit must therefore be chosen so that the coercive force necessary to change the magnetization is more than that supplied from permanent magnets, but less than that from the electromagnet, and have a sufficiently high remanance when the electromagnet is switched of.
  • the details of this type of electropermanent magnetism are well known in the art.
  • the pole pieces, and sometimes the permanent magnets are arranged flush with the working surface of the magnetic chucks. Where the magnets do not extend to the working surface, the pole pieces are separated by a filler such as epoxy resin. In time this epoxy resin becomes brittle and cracks form. Such a surface is vulnerable to incursion by cooling and lubricating fluid between the gaps between the pole pieces and the magnets, or epoxy resin, as the case may be.
  • the permanent magnets For flux to be entirely directed downwards, the permanent magnets must be balanced with the solenoids' magnetic cores and each other, otherwise some stray flux will leak upwards through the pole piece and thence through the workpiece when the chuck is in the 'off setting, causing the working surface to grip the workpiece to some degree when release is required.
  • Permanent magnets however are rarely manufactured within the magnetic tolerances required for balancing, so the magnets must be altered during the construction of the chuck, usually by locating unbalanced magnets, chipping pieces off and retesting the working surface. Since altering one magnet will change the flux of surrounding magnets, such balancing of the magnets is a difficult procedure and stickiness is seldom eliminated.
  • the object of the present invention is to alleviate either or both of these problems.
  • a magnetic holding device including an engagement surface to engage a workpiece, a plurality of permanent magnets having their magnetic axes substantially aligned with the plane of the engaging surface, and at least one magnetic switching unit to alter the direction of the magnetic field from the permanent magnets, characterised in that the engagement surface is formed by a continuous homogeneous plate.
  • the continuous plate is composed of a ferromagnetic material.
  • pole pieces are included to separate the permanent magnets.
  • ferromagnetic plate there is preferably provided on the ferromagnetic plate a lower surface adapted so as to locate the permanent magnets.
  • Figure 1 shows an exploded perspective view of a magnetic holder device
  • Figure 2 shows an exploded perspective view of another embodiment of a magnetic holder device, with a cut-away showing internal structure.
  • the magnetic holding device comprises an array of magnetic switching units, separating an arrangement of permanent magnets 12, a steel base 16, four sides 18 (only the two appearing nearest the viewer are shown) and a working surface 20.
  • Each magnetic switching unit includes an electromagnet 14 (for clarity only one is shown) and a pole piece 10.
  • the pole pieces 10 are cuboid, having a square plan and a height less than that of the square side, the permanent magnets 12 being arranged on the four rectangular sides, the dimensions of the permanent magnets being approximately that of the rectangular side of the pole piece and of relatively thin thickness. Therefore each permanent magnet is disposed so that it is directly between two pole pieces, the permanent magnets thus forming a grid.
  • the poles of the permanent magnets 12 are upon the rectangular sides, the magnets being disposed so that any group of four permanent magnets making up a square or cell show the same polarity to the encompassed pole piece. Alternating pole pieces are thus surrounded in opposite senses by alternating cells of permanent magnets, so that the two types of pole pieces, those emanating flux when the chuck is in the On' state, and those receiving flux, are arranged in a chess board fashion.
  • An electromagnet consisting of a coil 14 around a permanent magnet core (not visible) is then placed beneath each pole piece 10.
  • the components so far described are placed in this arrangement upon the base 16, and the sides 18 and working surface 20 are added.
  • the components may be attached to the base 16 and sides 18 by bolts.
  • the working surface 20 may be similarly secured in place by bolts extending from the base up to the working surface, though these bolts should not of course extend through the whole thickness of the working surface.
  • the volume enclosed by the working surface, base and sides may be flooded with epoxy resin to ensure that the components are secured firmly and cannot vibrate during use.
  • the join between the top and the sides could be sealed by epoxy resin in the conventional fashion, the sides having a slight groove present upon one side to receive the working surface.
  • the circuitry and other aspects of the chuck are similar to those of a conventional chuck.
  • a workpiece is placed upon the working surface of the chuck.
  • a current is passed through the electromagnets' coils until the chuck has been magnetised. No further current is needed until it is necessary to remove the workpiece.
  • Magnets such as those of neodymium alloys (such as Neodymium Iron Boron) are suitable.
  • the thickness of the ferrous workpiece should be such then that it absorbs all the flux which remains extending above the magnets when the chuck is in the 'off setting, whilst not being so thick that too much flux is absorbed when the chuck is 'on' and it is wished to secure a workpiece to the working surface.
  • the working surface is formed as an integral piece with the sides, and then lowered onto the base in order to secure the components.
  • the working surface 20 is formed from a slab of ferromagnetic material, its thickness being that of the height of the sides in the previously described embodiments.
  • a series of channels 13 is formed in the slab such that a grid is formed, that is, two orthogonal sets of equidistant parallel lines, the channels extending through the material leaving a thickness corresponding to the thickness of the working surface described in the first embodiment.
  • Such channels can be formed by a line of equidistantly spaced milling wheels making two orthogonal passes through the working surface. Cuboid portions of ferromagnetic material 11 are left extending downwards from the working surface.
  • each magnet being the same length as the distance between two neighbouring parallel lines.
  • the magnets in the same way as in the previous embodiment, have their poles disposed upon their flat sides, and are arranged so that each square cell formed by a group of four magnets has either all north faces facing inwards, or all south faces, and these two types of cell are arranged in an alternating, chessboard type fashion.
  • the orientation of the magnets' poles is indicated here by the marks 'N' and 'S' corresponding to the magnets' north and south poles.
  • each cell of magnets is placed an electromagnet in a similar way to that previous described (in this figure none of the electromagnets have been shown).
  • a base 16 and sides 18 are then affixed to the working surface 20, for example by bolts.
  • the magnetic switching unit is made up of an electromagnet, and the portion of the working surface which extends downwards between a cell of permanent magnets.
  • the construction of the chuck, no longer having pole pieces, is made very much simpler.
  • the working surface 20 could alternatively be formed so that the grid of channels stops short of the side portions of the working surface, so that additional side portions are no longer necessary. Further refinements, such as altering the depth of the channels along their lengths to strengthen the working surface and help locate the magnets, could of course be introduced.
  • the portions of the working surface extending downwards could also extend through the electromagnets.
  • a continuous non-ferromagnetic working surface without alleviating the tendency of the workpiece to stick to the working surface, would however dissuade water and other contaminants from entering the chuck.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Jigs For Machine Tools (AREA)

Abstract

L'invention concerne un dispositif de retenue magnétique comprenant une surface de contact conçue pour venir en contact avec une pièce, une pluralité d'aimants permanents dont les axes magnétiques sont sensiblement alignés sur le plan de la surface de contact, et au moins une unité de commutation magnétique servant à modifier le sens du champ magnétique émis par les aimants permanents, la surface de contact étant constituée par une plaque homogène continue. Cette plaque continue est composée d'un matériau ferromagnétique comportant, de préférence, des pièces polaires afin de séparer les aimants permanents. La surface inférieure de la plaque est conçue de manière à positionner les aimants permanents et peut être pourvue de fentes fraisées avec précision dans lesquels les aimants permanents sont solidement fixés.
PCT/IB1999/001750 1998-11-24 1999-11-01 Dispositif de retenue magnetique WO2000030805A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU62249/99A AU6224999A (en) 1998-11-24 1999-11-01 Magnetic holding device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9825675.3 1998-11-24
GB9825675A GB2344220A (en) 1998-11-24 1998-11-24 Magnetic holding device

Publications (1)

Publication Number Publication Date
WO2000030805A1 true WO2000030805A1 (fr) 2000-06-02

Family

ID=10842922

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB1999/001750 WO2000030805A1 (fr) 1998-11-24 1999-11-01 Dispositif de retenue magnetique

Country Status (3)

Country Link
AU (1) AU6224999A (fr)
GB (1) GB2344220A (fr)
WO (1) WO2000030805A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102112271A (zh) * 2008-04-22 2011-06-29 意大利泰磁公司 单件磁性设备和所述单件磁性设备的制造方法
CN102922422A (zh) * 2012-10-18 2013-02-13 江苏无锡建华机床附件集团有限公司 快速定位电永磁吸盘系统
WO2021148581A1 (fr) 2020-01-22 2021-07-29 Onxeo Nouvelle molécule dbait et son utilisation

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE553879T1 (de) * 2008-04-22 2012-05-15 Tecnomagnete Spa Selbstverankernde magnetvorrichtung und steuereinheit zur steuerung der magnetvorrichtung
CZ303805B6 (cs) * 2009-12-09 2013-05-09 SVÚOM s.r.o. Rychloupínací magnetický mnohocetný drzák zkusebních vzorku zejména pro urychlené korozní zkousky
CN102371496B (zh) * 2010-08-26 2014-06-18 中国北车集团大同电力机车有限责任公司 导磁块、包括该导磁块的电磁吸力平台和铣床
GB2527106A (en) * 2014-06-12 2015-12-16 Steven Towle Magnetic chequerboard and playing pieces

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0109011A2 (fr) * 1982-11-16 1984-05-23 TECNOMAGNETICA di Cardone, Grandini, Zaramella & C. S.a.s. Appareil magnétique d'ancrage à agencement polaire quadrangulaire
WO1997000153A1 (fr) * 1995-06-15 1997-01-03 Philips Electronics N.V. Dispositif de blocage magnetique

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1022923B (it) * 1974-10-16 1978-04-20 Cardone Magneto Tecnica Apparecchiatura magnetica di ancoraggio
FR2333612A1 (fr) * 1975-12-04 1977-07-01 Braillon P Plateau magnetique a aimants permanents et electro-permanents
IT1099799B (it) * 1978-10-06 1985-09-28 Magnetotecnica Di Cardone Mich Apparecchiatura magnetica di ancoraggio
IT1212127B (it) * 1986-07-28 1989-11-08 Cardone Tecnomagnetica Apparecchiatura magnetopermanente di ancoraggio.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0109011A2 (fr) * 1982-11-16 1984-05-23 TECNOMAGNETICA di Cardone, Grandini, Zaramella & C. S.a.s. Appareil magnétique d'ancrage à agencement polaire quadrangulaire
WO1997000153A1 (fr) * 1995-06-15 1997-01-03 Philips Electronics N.V. Dispositif de blocage magnetique

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102112271A (zh) * 2008-04-22 2011-06-29 意大利泰磁公司 单件磁性设备和所述单件磁性设备的制造方法
CN102922422A (zh) * 2012-10-18 2013-02-13 江苏无锡建华机床附件集团有限公司 快速定位电永磁吸盘系统
WO2021148581A1 (fr) 2020-01-22 2021-07-29 Onxeo Nouvelle molécule dbait et son utilisation

Also Published As

Publication number Publication date
GB9825675D0 (en) 1999-01-20
AU6224999A (en) 2000-06-13
GB2344220A (en) 2000-05-31

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