US3818399A - Permanent magnet devices - Google Patents

Permanent magnet devices Download PDF

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Publication number
US3818399A
US3818399A US00326532A US32653273A US3818399A US 3818399 A US3818399 A US 3818399A US 00326532 A US00326532 A US 00326532A US 32653273 A US32653273 A US 32653273A US 3818399 A US3818399 A US 3818399A
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United States
Prior art keywords
magnets
polepieces
permanent magnet
magnet device
support bars
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Expired - Lifetime
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US00326532A
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English (en)
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A Edwards
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James Neill Holdings Ltd
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James Neill Holdings Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23QDETAILS, 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
    • B23Q3/00Devices holding, supporting, or positioning work or tools, of a kind normally removable from the machine
    • B23Q3/15Devices for holding work using magnetic or electric force acting directly on the work
    • B23Q3/154Stationary devices
    • B23Q3/1546Stationary devices using permanent magnets

Definitions

  • ABSTRACT 21 Appl 32 ,532 A permanent magnet device comprising at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanent [30] Fmelgn Apphcauon Pnomy Data magnets in upper and lower rows magnetised in oppo- Feb. 2, 1972 Great Britain 4784/72 site directions through their thickness, associated with and lying between the pairs of polepieces, at least one [52] US. Cl. 335/295, 335/306 of the magnets being capable of movement relative to [51] Int. Cl.
  • H0lf 7/04 at least one other and relative to the pairs of pole-
  • References Cited magnetic field strength (the ON position) to a position UNITED STATES PATENTS where the extemal' magnetic field is reduced to sub- 2,972,4s5 2/1961 Ferchlandhl 335/295 stamlally Zero (the OFF 9 3,135.899 6/1964 Sears 335/295 1 25 Cl 14m F FOREIGN PATENTS OR APPLICATIONS 939.584 [0/1963 Great Britain. 335/295 8 l i I l l M!
  • PATENTED JUN 1 8 m4 SHEET 5 0F 5 This invention relates to permanent magnet devices and in particular relates to such devices when provided with a means to modify the external magnetic field of the permanent magnets by reduction, reversal, or complete elimination.
  • Such devices are alreadyknown, and in particular there are known work holding devices, e. g., permanent magnet chucks but such devices as are in present commercial use are known to have certain serious disadvantages.
  • one well-known design of magnetic chuck has been constituted by two packs of pennanent magnets and ferro-magnetic pole pieces, the relative position of the two packs determining whether or not there is an external magnetic field.
  • the upper pack of such a chuck is held stationary and its upper surface is the work holding surface; the lower pack is movable in relation to the upper pack.
  • Such a construction has two inherent and serious drawbacks. Firstly the attractive force between the packs is so great as to make the lower pack difficult to move unless mechanical means are provided to separate the packs slightly and make relative movement practicable.
  • the upper pack is unsupported except at its edges and therefore when pressure is applied to work pieces during milling, grinding etc., the work-holding surface is deflected, thereby limiting the flatness and accuracy of machining and in extreme cases causing chatter marks on the finished surface.
  • the object of the present invention is to provide a permanent magnet device which is easily switched from the on to the off position and is free from the disadvantages described above when used as a workholding device.
  • a permanent magnet device comprises at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanent magnets magnet'ised in opposite directions through their thickness, associated with and lying between the pairs of polepieces, at least one of the magnets being capable of movement relative to at least one other and relative to the pairs of polepieces from first position where the magnets and the polepieces co-operate to provide maximum external magnetic field strength (the ON position) to a position where the external magnetic field is reduced to substantially zero (the OFF position).
  • the relative movement may be such. that the magnets can be returned to their original position or moved to a third position where an external magnetic field is produced, opposite in direction to that provided by the first position.
  • the magnets and the polepieces provide external fields of maximum strength.
  • the two magnets may be moved, simultaneously or separately, relatively to each other by sliding between the polepieces until each bridges the gap between the pairs of polepieces, the OFF position.
  • the external field is reduced in strength until a critical position is reached at which the external fields become substantially zero, by virtue of the short circuit paths provided by the polepieces.
  • the magnets may be returned to their original position when the external field returns to its maximum value, or the movement may be continued so that each magnet becomes associated with the other pair of polepieces when the external fields are increased to a maximum but of reversed directions.
  • one magnet may be permanently held between one pair of polepieces and the second magnetised through its thickness in the reverse direction, moved from its posi tion between theother pair of polepieces to a position where both magnets are associated with one pair of polepieces.
  • the external magnetic field is gradually reduced until such time as both magnets lie between the same pair of polepieces, when-again complete short circuiting is provided to eliminate the external fields.
  • the magnet that has been moved may be returned to its original position to increase the magnetic fields back to a maximum or alternatively the second magnet may be held and the first magnet moved into association with the other pair of polepieces, when the external fields are increased to maximum but of reversed directions.
  • each polar surface of each magnet attracts, and is attracted by, the neighbouring ferromagnetic polepieces, and is, therefore, acted on by forces at its two polar surfaces which aresubstantially equal to one another but are in opposite directions. This substantial balancing of magnetic forces makes it particularly easy to slide the magnet between the polepieces in a direction transverse to its direction of magnetisation.
  • any number of aligned pairs of polepieces may be provided and there .may be a magnet associated with each pair of polepieces in the ON position, i.e., the position where an external magnetic force of maximum strength is provided.
  • two magnets may be provided in association with each pair of polepieces in the ON position, the two magnets being magnetised through their thickness in the same direction so that the corresponding face of each magnet associated with one of the pair of polepices is of the same polarity, the corresponding face of the magnets associated with the ad jacent pair of polepieces being of opposite polarity in that position.
  • Such an arrangement can be designed to provide a heavy concentration of flux at the exposed edges of the polepieces thus making the device eminently suitable as a work-holding device.
  • the magnets and the polepieces are readily so proportioned that the polar surface area of permanent magnet in contact with a polepiece is greater than the area of the same polepiece in contact with any ferromagnetic article held by the device.
  • the polepiece collects magnetic flux at low density from a large area of permanent magnet surface, and concentrates it into the limited area of polepiece surface in contact with the ferromagnetic article being held. Under such circumstances as is well established both practically and theoretically, the total attraction between a polar surface of a magnet and its adjoining polepiece is much less than the total attraction between the same polepiece and the ferromagnetic article held, although substantially the same total amount of magnetic flux passes across both boundaries as parts of the same magnetic circuit.
  • the magnets be positioned in appropriately shaped holes in a support -bar of non-magnetic material (e.g., brass of synthetic plastics material), there being separate support bars for the upper and lower rows of magnets.
  • the bar as a whole may be moved longitudinally between the polepieces by known and appropriate arrangements of levers, eccentrics, racks, pinions etc., and as it moves it carries the magnets with it.
  • the magnets may be either a tight or a loose fit in the support bar as may be appropriate for the method of manufacture, the magnetisation may take place either before or after the magnets have been fitted into the bar or the bar has been moulded around them. A very small mechanical clearance is allowed to permit the bars and magnets to slide freely between the rows of polepieces. Alternatively, when only one row of magnets are to be moved, the other row may be secured directly between the polepieces.
  • the magnetic device may be switched ON and OFF in sections if desired.
  • the magnets should be produced from so-called ferrite material, when thin magnets may be employed with a consequent narrow spacing of the polepieces, a distinct advantage particularly when the device is used as a magnetic chuck. In normal constructions the thickness of the polepieces is somewhat greater than the thickness of the magnets between them.
  • each polepiece- is normally in contact with four magnet polar surfaces corresponding to the upper and lower bars on each side, and each of these surfaces is of the same poCDCity. Exceptions are the four corner polepiecesof the construction which are in contact with one magnet polar surface only, and the other polepieces in the outermost rows and at one or both ends of each row, which are each in' contact with two magnet polar surfaces.
  • the flux diversion is particularly complete and the external magnetic field of the device can be controlled such as to substantially eliminate it or provide slight reversal, giving complete release of workpieces when the device is used as a workholder.
  • FIG. 1 is a diagrammatic representation of a flux switching device according to the invention in which both magnets associated with the pairs of polepieces move, the magnets being shown in the ON position;
  • FIG. 2 corresponds to FIG. 1, but shows the magnets in the OFF position
  • FIG. 3, 4 and 5 are sections on the lines IIIIII, IV-IV and V-V respectively of FIG. 2 showing the internal flux diversion paths;
  • FIG. 6 corresponds to FIG. 1, but shows an arrangement where only the upper magnets move, the magnets being shown in the ON position;
  • FIG. 7 corresponds to FIG. 6, but shows the magnets in the OFF position
  • FIG. 8 is a section on the line VIII VIII of FIG. 7 showing the internal flux diversion path
  • FIG. 9 is a plan view of a magnetic chuck in which the magnets are moved in accordance with FIG. 1;
  • FIG. 10 is a side elevation of FIG. 9;
  • FIG. 11 is a section on the line XIXI of FIG. 9;
  • FIG. 12 corresponds to FIG. 9, but shows a magnetic chuck in which the magnets are moved in accordance with FIG. 6;
  • FIG. 13 is a side elevation of FIG. 12;
  • FIG. 14 is a section on the line XIV-XIV of FIG. 12.
  • a flux switching device is shown as having a number of pairs of ferromagnetic polepieces I, be-
  • each magnet is magnetised through its thickness so that opposite polar faces of the magnets are of opposite polarity, and are positioned between the polepieces such that the corresponding polar faces of adjacent magnets in each row are of opposite polarity.
  • FIGS. 3, 4 and 5 illustrate the flux diversion paths between the magnets through the polepieces, which effectively reduce the external field to substantially zero.
  • the upper and lower-rows of magnets can be returned to the position shown in FIG. 1, when the external magnetic field is returned to maximum strength, but the magnets could be moved by half I a pole pitch in the opposite direction, when an external magnetic field of maximum strength would be created but of reverse direction to that of FIG. 1. That is, while viewing FIG.
  • FIGS. 6 and 7 a number of pairs of polepieces l are provided between which lie upper and'lower rows of magnets, each magnet again being magnetised through its thickness.
  • the lower row of magnets are secured between the I polepieces with corresponding polar faces on adjacent magnets of opposite polarity.
  • the magnets of the upper row positioned as shown by FIG. 6, the magnets of both rows combine with the polepieces to provide an external magnetic field of maximum strength.
  • the magnets 2 of the upper row are moved by a full pole pitch to the position shown in FIG. 7, when the corresponding polar faces of the magnets of the upper and lower rows associated with each pair of polepieces are of opposite polarity. The effect of this is to provide a flux diversion path through the polepieces as is shown by FIG.
  • the magnets 2 of the upper row may be returned to the position shown in FIG. 6, or they may be moved by a full pole pitch in the opposite direction (when a further pair of polepieces 1A would be provided) again to provide an external magnetic field of maximum strength
  • the magnet 2 that appears at the particular polepiece l first from the left of added polepiece 1A in FIG. 7 it can be seen that the resultant external magnetic fieldmay be considered to remain in the same direction between the shifted positions described, i.e. the magnetic field is toward the reference magnet after the top row is shifted in either direction as assumed above. Only when both the upper and lower rows are shifted by half a pole pitch apiece as in FIG. 1, would the field be of reversed direction to that of FIG. 6.
  • similar analysis of field directions with respect to other reference magnets 2 and other reference points in either FIG. 1 or FIG. 6 may be made as de sired.
  • the concept as defined above may be used in an instance where an external magnetic field is required, which field is required to be reduced, substantially eliminated, partially reversed or completely reversed. Because heavy concentration of flux can be arranged at the exposed edges of the polepieces and because the polepieces are held stationary as the magnets are moved (with relative ease by virtue of the selfbalancing of .magnetic attraction forces between the magnets and the polepieces) the flux switching device is eminently suitable as a work holding device (a magnetic chuck).
  • a magnetic chuck comprises a base plate 3 of non-magnetic material to which are secured end plates 4 and side plates 5 preferably of ferromagnetic material.
  • the base plate 3 has a series of rectangular recesses 6 (F IG.. 1 1) running longitudinally of the base plate into each of which is secured a number of polepieces 1 (FIG. 10), the polepieces being secured in place by bolts 7. It will be appreciated that any number of polepieces can be provided in both the longitudinal and transverse directions of the base plate 3) to suit a particular application.
  • the longitudinal gaps between adjacent rows of polepieces are maintained by transverse rods 5A bridging the side plates 5, with distance pieces 53 located between the polepieces.
  • the gaps are loaded with upper and lower rows of magnets 2 of high coercivity ferrite material in slab form, each row of magnets being located in a support bar 8 provided with recesses 9 in which the magnets are a close fit.
  • the lower support bar rests directly on the base plate 3 between the polepieces and the upper support bar rests on the top face of the lower support bar.
  • the gaps between the polepieces above the top face of the upper support bars are filled with non-magnetic material (preferably a suitable form of resin filler) prior to the application of the support bars to the gaps, the top face being machined after being filled to ensure that the upper surface of the polepieces are left exposed.
  • a further end plate 10 is secured to the side plates.
  • the mechanism to provide simultaneous movement of all the upper and all the lower support bars and thus magnets in opposite directions is provided.
  • the corresponding end of the upper and lower support bars are each provided with vertical slots 11 through which pass pins 12, the pins being located in and secured to rotatable locking plates 13, to one of which is secured an operating handle 14.
  • the length of the slots 11 is dictated by the degree of movement required of each support bar.
  • the upper and lower support bars are each intended to move by approximately half a pole pitch.
  • the handle 14 is operated to cause the pins 12 to move the upper and lower support bars to the position shown in FIG. 10, the ON position, when all the magnets and all the polepieces co-operate to provide an external magnetic field of maximum strength in the manner described with respect to FIG. 1.
  • the handle 14 is rotated in the opposite direction within the limits imposed by the lengths of the slots 11 in the support bars, to bring the upper and lower rows of magnets to the position corresponding to FIG. 2, when the magnets and the polepieces co-operate to provide internal flux diversion paths after the manner described with reference to FIGS. 3 to 5.
  • any ferromagnetic workpieces resting on the upper surface of the chuck can then be removed.
  • the application of the external field can cause'permanent magnetisation of the workpiece and it is therefore advisable that the lengths of the slots 11 are such as to allow a movement of the magnets to a point slightly beyond the position where the external field has been substantially eliminated, to provide a low strength external field of reverse direction thereby demagnetising the workpiece.
  • FIG. 12, 13 and 14 show a flux switching device again in the form of a magnetic chuck, but in this case embodying the principle depicted in FIGS. 6, 7 and 8, where only the row of magnets is moved by a full pole width.
  • a magnetic chuck has a non-magnetic base plate 15 provided with side plates 16 and end plates 17, 18, preferably of ferromagnetic material. On the inside faces of each side plate 16 are provided spaced locating pegs 19. To provide the longitudinal rows of polepieces l and lower fixed magnets 2 (again of ferrite material in slab form), transverse rows of polepieces and magnets are separately formed as packs. Polepieces in alternation with magnets are placed in a jig, there being adhesive applied to both polar faces of the magnets. Distance pieces are placed between the polepieces at their upper ends, and the whole assembly compressed to provide the required transverse spacing between adjacent polepieces and the pack held to allow the adhesive to eat.
  • the pack is then located between the side plates 16 on the pegs 19 by virtue of vertical slots 20 in the outside face of each outermost polepiece 1 and the pack secured from below, e.g., by bolts.
  • a series of spacers are placed in the longitudinal gaps between adjacent pairs of polepieces, the spacers being lubricated with, e.g., a silicone base lubricant, to effect sealing of the gaps between the spacers and the polepieces.
  • Resin is then run in to fill the gaps between the polepieces and the top surface finally ground to leave the polepieces with an exposed upper face.
  • the spacers are then removed and replaced by support bars having recesses into which magnets are fitted, the magnets again being thin ferrite magnets magnetised through their thickness to provide polar faces of opposite polarity.
  • the support bars are moved to a position such that the magnets assume a position equivalent to that shown in FIG. 6 whereby an external magnetic field is provided of maximum strength, and to reduce the magnetic field to substantially zero the rows of support bars moved until the magnets assume a position equivalent to that shown in FIG. 7 when internal flux diversion paths, as depicted in FIG. 8, are created with the resultant elimination of the external magnetic field.
  • each support bar 21 at its end adjacent the end plate 18 is provided with a rack 22 all the racks being engaged by a pinion 23 extending across the full width of the chuck through notches provided in the endmost polepieces.
  • the pinion is secured to a gear wheel 24 lying externally of one side plate 16, the gear wheel 24 engaging an internally toothed gear wheel 25 having a drive shaft 26 on which is mounted a handle 27.
  • a cover plate 28 encloses the epicyclic gearing 24, 25, the cover plate being provided with stops 29 (which may be adjustable) to limit movement of the handle 27.
  • the operating pinion is situated inwardly of the end plate and as a consequent, the endmost magnets must be shorter than the rest. This slightly reduces the maximum external field available at that point but this does not affect the overall performance of the chuck.
  • the position of the stops 29 is such that the movable magnets can be brought to a position where the external magnetic field has been reduced to substantially zero, or to a position where a low strength external magnetic field is created of reverse direction, to effect demagnetisation of a workpiece applied to the working surface.
  • FIGS. 9 and 11 can be applied to the work-holding device of FIGS. 12 and 14 and vice versa.
  • a permanent magnet device comprising at least two pairs of aligned plate-like polepieces of ferromagnetic material such as mild steel, and at least two permanet magnets in upper and lower rows magnetised in opposite directions through their thickness, associated with and lying between the pairs of polepieces, at least one of the magnets being capable of movement relative to the other and relative to the pairs of polepieces from a first position where the magnets and the polepieces co-coperate to provide a maximum external magnetic field strength an on position, to a position where the external magnetic field is reduced to substantially zero an off position.
  • a permanent magnet device as in claim 1 wherein the movable magnets are mechanically supported to hold the magnets in their positions between the polepieces and to move them as required.
  • magnets are produced from high coercivity ferrite material, when thin magnets may be employed with a consequent narrow spacing of the polepieces.
  • a permanent magnet device as in claim 8 comprising a base plate of non-magnetic material, side plates and end plates of ferromagnetic material, the base plate having a series of rectangular recesses run ning longitudinally of the base plate into each of which is secured a number of spaced polepieces, the longitudinal gaps between adjacent rows of polepieces being loaded with upper and lower rows of magnets, the gaps between the upper faces of the polepieces being filled with non-magneticmaterial.
  • a permanent magnet device as in claim 8 comprising a base plate of non-magnetic material, side plates and end plates of ferromagnetic material, the inside faces of the side plates being provided with spaced location pegs to locate transversely disposed packs of polepieces in alternation with magnets whereby adjacent packs provide the longitudinal rows of polepieces and lower fixed magnets, the gaps between the polepieces above the fixed magnets being loaded with the upper rows of magnets, and the gaps between the polepieces above the upper rows of magnets being filled with non-magnetic material.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Load-Engaging Elements For Cranes (AREA)
  • Footwear And Its Accessory, Manufacturing Method And Apparatuses (AREA)
  • Jigs For Machine Tools (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)
US00326532A 1972-02-02 1973-01-24 Permanent magnet devices Expired - Lifetime US3818399A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB478472A GB1401802A (en) 1972-02-02 1972-02-02 Permanent magnet devices

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US3818399A true US3818399A (en) 1974-06-18

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US00326532A Expired - Lifetime US3818399A (en) 1972-02-02 1973-01-24 Permanent magnet devices

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US (1) US3818399A (nl)
JP (1) JPS4891679A (nl)
AU (1) AU471516B2 (nl)
BE (1) BE794846A (nl)
CA (1) CA999336A (nl)
CH (1) CH584961A5 (nl)
DK (1) DK140878B (nl)
FR (1) FR2216658B1 (nl)
GB (1) GB1401802A (nl)
IT (1) IT978717B (nl)
NL (1) NL159607B (nl)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114532A (en) * 1976-10-12 1978-09-19 Dataproducts Corporation Impact printer magnet assembly
US4323150A (en) * 1980-05-02 1982-04-06 Fleetwood Systems, Inc. Magnetic rail construction
US4379277A (en) * 1979-08-27 1983-04-05 Braillon Philibert Maurice Magnetic chuck
US4468648A (en) * 1982-10-15 1984-08-28 Mamoru Uchikune Switchable permanent magnetic chuck
US4542890A (en) * 1982-12-28 1985-09-24 Braillon & Cie Magnetic chuck
US4687385A (en) * 1985-04-08 1987-08-18 Milwaukee Electric Tool Corporation Portable hole cutting power tool
US20060250714A1 (en) * 2005-05-06 2006-11-09 Von Limburg Felix Switchable magnetic device
CN103221179A (zh) * 2010-09-20 2013-07-24 蔡达光 结合永久磁铁和电磁铁的磁体保持装置
US9649770B1 (en) * 2016-03-28 2017-05-16 Hiwin Technologies Corp. Magnetic holding device with movable magnetic shielding device
US20180172637A1 (en) * 2016-12-15 2018-06-21 Caterpillar Inc. Magnetic particle inspection tool with 3d printed magnets

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2646784C3 (de) * 1976-10-16 1980-02-28 Heinrich Dr.-Ing. 4714 Selm Spodig Dauermagnetische Haftplatte
JPH0698545B2 (ja) * 1986-10-24 1994-12-07 フジ磁工株式会社 両面永久磁石チヤツク

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972485A (en) * 1958-12-03 1961-02-21 Gen Motors Corp Magnetic chuck
GB939584A (en) * 1961-01-21 1963-10-16 Neill James & Co Sheffield Ltd Improvements in or relating to permanent magnet chucks and holding devices
US3135899A (en) * 1960-12-19 1964-06-02 Hartley Co Magnetic work-holding table

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB874600A (en) * 1958-03-28 1961-08-10 Darwins Ltd Improvements in or relating to magnetic chucks and similar holding devices
FR1220631A (fr) * 1958-04-19 1960-05-25 Hagou Metaalfab N V Mandrin à aimants permanents

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972485A (en) * 1958-12-03 1961-02-21 Gen Motors Corp Magnetic chuck
US3135899A (en) * 1960-12-19 1964-06-02 Hartley Co Magnetic work-holding table
GB939584A (en) * 1961-01-21 1963-10-16 Neill James & Co Sheffield Ltd Improvements in or relating to permanent magnet chucks and holding devices

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114532A (en) * 1976-10-12 1978-09-19 Dataproducts Corporation Impact printer magnet assembly
US4379277A (en) * 1979-08-27 1983-04-05 Braillon Philibert Maurice Magnetic chuck
US4323150A (en) * 1980-05-02 1982-04-06 Fleetwood Systems, Inc. Magnetic rail construction
US4468648A (en) * 1982-10-15 1984-08-28 Mamoru Uchikune Switchable permanent magnetic chuck
US4542890A (en) * 1982-12-28 1985-09-24 Braillon & Cie Magnetic chuck
US4687385A (en) * 1985-04-08 1987-08-18 Milwaukee Electric Tool Corporation Portable hole cutting power tool
US20060250714A1 (en) * 2005-05-06 2006-11-09 Von Limburg Felix Switchable magnetic device
CN103221179A (zh) * 2010-09-20 2013-07-24 蔡达光 结合永久磁铁和电磁铁的磁体保持装置
US9649770B1 (en) * 2016-03-28 2017-05-16 Hiwin Technologies Corp. Magnetic holding device with movable magnetic shielding device
US20180172637A1 (en) * 2016-12-15 2018-06-21 Caterpillar Inc. Magnetic particle inspection tool with 3d printed magnets
US10234424B2 (en) * 2016-12-15 2019-03-19 Caterpillar Inc. Magnetic particle inspection tool with 3D printed magnets

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Publication number Publication date
DK140878C (nl) 1980-05-12
AU471516B2 (en) 1976-04-29
CH584961A5 (nl) 1977-02-15
DE2304818A1 (de) 1973-08-16
CA999336A (en) 1976-11-02
JPS4891679A (nl) 1973-11-28
BE794846A (fr) 1973-05-29
GB1401802A (en) 1975-07-30
DK140878B (da) 1979-12-03
AU5158573A (en) 1974-08-01
FR2216658A1 (nl) 1974-08-30
NL7301484A (nl) 1973-08-06
DE2304818B2 (de) 1975-08-28
FR2216658B1 (nl) 1978-03-03
IT978717B (it) 1974-09-20
NL159607B (nl) 1979-03-15

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