US3798581A - Electro-mechanically switched permanent magnet holding device - Google Patents

Electro-mechanically switched permanent magnet holding device Download PDF

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Publication number
US3798581A
US3798581A US00302132A US3798581DA US3798581A US 3798581 A US3798581 A US 3798581A US 00302132 A US00302132 A US 00302132A US 3798581D A US3798581D A US 3798581DA US 3798581 A US3798581 A US 3798581A
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United States
Prior art keywords
load
keeper
permanent magnet
keeper plate
magnetic
Prior art date
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Expired - Lifetime
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US00302132A
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English (en)
Inventor
N Anderson
C Southworth
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US Philips Corp
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US Philips Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/20—Electromagnets; Actuators including electromagnets without armatures
    • H01F7/206—Electromagnets for lifting, handling or transporting of magnetic pieces or material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C1/00—Load-engaging elements or devices attached to lifting or lowering gear of cranes or adapted for connection therewith for transmitting lifting forces to articles or groups of articles
    • B66C1/04—Load-engaging elements or devices attached to lifting or lowering gear of cranes or adapted for connection therewith for transmitting lifting forces to articles or groups of articles by magnetic means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0231—Magnetic circuits with PM for power or force generation
    • H01F7/0252—PM holding devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/064—Circuit arrangements for actuating electromagnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/06—Electromagnets; Actuators including electromagnets
    • H01F7/20—Electromagnets; Actuators including electromagnets without armatures
    • H01F7/206—Electromagnets for lifting, handling or transporting of magnetic pieces or material
    • H01F2007/208—Electromagnets for lifting, handling or transporting of magnetic pieces or material combined with permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F29/00—Variable transformers or inductances not covered by group H01F21/00
    • H01F29/14—Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias
    • H01F2029/143—Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias with control winding for generating magnetic bias

Definitions

  • This invention relates to an electro-mechanically switched permanent magnet holding device which is suitable for lifting or holding magnetic loads, and in which the magnetic attraction to the load may be simply switched on or off.
  • a permanent-magnet load lifting device has been proposed in which the attractive magnetic force of a permanent magnet is bistably switched between different magnetic circuits of the device. These circuits are typically a circuit path operating at the load end and a similar path at the opposite or keeper end.
  • a lift mode exists when a majority of flux is transferred to the load end by decreasing its reluctance and correspondingly increasing the reluctance at the keeper end.
  • a release mode exists when a majority of the flux is transferred to the keeper end with consequent reluctance changes in the respective circuits.
  • Switching the permanent magnet flux between the magnetic circuit including the keeper end plate and the magnetic circuit including the load is accomplished by applying a low energy control signal to an electomagnetic coil integrated with one or more of the magnetic circuits.
  • the control winding is energized so as to transfer a majority of the flux to the load end by decreasing its reluctance.
  • the keeper end plate is raised to create an air gap to further increase the reluctance of the keeper end circuit and drive even more of the flux through the load.
  • the present invention provides a magnetic device comprising a permanent magnet disposed between a pair of pole members which provide a first and a second magnetic circuit respectively through a load and a keeper end of the device.
  • a control winding is disposed about one of the pole members and a keeper plate is disposed on the pole faces and is movable a distance therefrom limited by a stop portion of a non-magnetic safety member. Spacing means are provided which extend from the keeper plate to the load end of the device for a distance which is equal to the length of the pole members plus the maximum air gap as hereinafter defined.
  • the device also includes means for passing a current pulse through the control winding in either direction.
  • maximum air gap is used throughout this specification to mean an air gap which is just greater than the largest non-magnetic gap at the load end which the magnetic device will encounter in use.
  • the spacing means in particular simplify separation of loads which are light in comparison to the mass of a lifting magnet.
  • the spacing means consist of spacer rods which slidably extend through bores in the pole members.
  • the keeper plate may be provided with a cover which surrounds the upper periphery of the magnet and pole members, and wherein sealing means may be located between the cover and the said upper periphery.
  • Current pulse switching through the control winding may be conducted manually but is preferably performed automatically.
  • FIG. 1 is a sectional front elevation of a lifting magnet
  • FIG. 2 is a simplified circuit diagram of an automatic magnet control circuit used to operate the lifting magnet
  • FIGS. 3 to 7 show front elevation views of the lifting magnet in a sequence of operations of lifting and unloading a load
  • FIG. 8 is a graph on which the attractive force be tween a magnet together with its pole members and a keeper plate are plotted against the length of the air gap.
  • a lifting magnet 1 comprises strontium ferrite permanent magnets 2 which are sandwiched between pole members 3, 4, 5 and 6 which consist of mild steel plates.
  • a control winding 7 surrounds an upper portion of the pole members 4 and 5.
  • L-shaped safety members 8 which are made of stainless steel and have stop portions 9 are secured to the pole members 3 and 6, the stop portions 9 limiting movement of a mild steel keeper plate 10 away from the pole faces.
  • a lifting eye 11 extends from one main face of the keeper plate 10 and non-magnetic spacing rods 12 extend from the opposite main face of the keeper plate 10, for a distance which is equal to the length of the pole members 3, 4, 5 and 6 plus a maximum air gap length of 0.9 mms. These spacing rods 12 are a sliding fit in bores 13 in the pole members 3 and 6.
  • a non-magnetic control rod 14 having a stop 15 slides in a bore 16 in the pole member 4.
  • the upper end of the control rod 14 operates a single pole monostable microswitch S1 and a bistable changeover switch S2.
  • the switches S1 and S2 are mounted on top of the keeper plate 10 and are arranged so that S2 operates before S1. These switches are operated by the control rod 14 whenever a load 17 and the keeper plate 10 are at a certain separation which is just greater than the length of the spacing rods 12.
  • the magnet control circuit comprises two 13 volt rechargeable nickel-cadmium batteries l8 and 19.
  • the microswitch S1 switches a capacitor C from a charging position to the base of a transistor 20.
  • the switch S2 reverses the connections to the control winding 7.
  • the capacitor C discharges into the base of transistor 20.
  • the transistor 20 conducts during this discharge which lasts for about 100 milliseconds, the control winding 7 is energised, and the magnet switches from a first condition to a second condition.
  • switch 51 connects C to the battery 19 so that it is charged for the next operation, while S2 remains closed in the same position.
  • S2 first operates reversing the connections to the control winding 7, then S1 discharges the capacitor C and the magnet switches from the second condition to the first condition.
  • FIG. 3 shows the magnetic device 1 being lowered in order to pick up the load 17 immediately before the capacitor discharges so as to permit a current pulse to pass through the control winding in a direction which will provide magnetic attraction between the pole members and the load 17, and a decreased magnetic attraction between the pole members and the keeper plate, during the application of the current pulse.
  • the discharge of the current pulse through the control winding results in the force of attraction between the pole faces and the load exceeding that between the pole faces and the keeper plate 10, so that the keeper plate 10 is lifted from the upper pole faces of the device as the ends of the spacing rods 12 abut against the load 17 and hence mechanically push the keeper plate 10 away from the upper pole faces.
  • the current pulse has ended, the majority of the flux from the magnet passes through the load 17 due to the non-magnetic gap which has been created between the upper pole faces and the keeper plate 10.
  • FIG. 4 shows the magnetic device 1 and load 17 immediately after a hoist (not shown) has begun to lift the keeper plate 10, at the instant when the switch S1 connects the capacitor C to the battery 19 so that it is charged for the next operation.
  • FIG. 5 shows the system after the load has been lifted clear of the ground, the keeper plate 10 then bears against the under side of the stop portions 9.
  • FIG. 6 shows the system after the load has been lowered to the ground, as the keeper plate 10 is being lowered towards the upper pole faces and immediately before the switch S1 is closed to discharge the condenser C through the transistor 20.
  • FIG. 7 shows the system immediately after the capacitor C has been discharged through the transistor 20.
  • the force of attraction between the upper pole faces and the keeper plate 10 is now greater than the attraction between the lower pole faces and the load 17 as a result of the electromagnetic force produced in the control winding 7 and the load 17 is pushed away from the lower pole faces by the spacer rods 12.
  • the magnetic device 1 can now be lifted away from the load 17.
  • FIG. 8 shows a graph on which the maximum load L which could be lifted varies with the length G of the non-magnetic gap between the pole faces and the load.
  • the remanence of the magnets 2 was 3,600 gauss and the coercivity was 3,000 Oe.
  • the control winding consisted of 350 turns of 24 gauge copper wire and had a resistance of 7.5 ohms.
  • the batteries 18 and 19 were each 3.5 inches long and 1 inch in diameter with a capacity of 200 mA. hours.
  • the voltage was 26.5 volts, falling on load to 23 volts. This arrangement gave approximately 1,100 ampere-turns from the control winding.
  • a pulse duration of milliseconds was used. This is longer than the minimum duration required, but results in a sufficiently low current consumption for there to be no problem with regard to battery life.
  • a test was conducted in order to determine the number oflifting operations which could be performed between battery charges, in which 1,400 switching operations were conducted at 4 second intervals, representing the carriage of 700 loads, and the batteries had not been discharged at the end of the test.
  • An electro-mechanically switched permanent magnet holding device comprising a permanent magnet disposed between a pair of pole members which provide a first and a second magnetic circuit respectively through a load and a keeper end of the device, a control winding disposed about one of the pole members for switching the permanent magnet flux between said first and second magnetic circuits, a keeper plate disposed on the pole faces at the keeper end of the device and movable a distance therefrom limited by a stop portion of a nonmagnetic safety member, spacing means which extend from the keeper piate to the load end of the device for a distance which is equal to the length of the pole members plus the maximum air gap to be encountered in normal use at the load end of the device, and means for passing a current pulse through the control winding in either direction.
  • spacing means comprises spacer rods which slidably extend through bores in the pole members.
  • An electro-mechanically switched permanent magnet holding device as claimed in claim 1, wherein the keeper plate is provided with a cover which surrounds the upper periphery of the magnet and pole members, and wherein sealing means are located between the cover and the said upper periphery so as to prevent dirt from entering the space between the keeper plate and the upper faces of the pole members.
  • An electro-mechanically switched permanent magnet holding device as claimed in claim 1, comprising one or more pairs of permanent magnets, each permanent magnet being disposed between a pair of pole members, said control winding being disposed about central pole-members which are disposed between the two magnets of a pair of magnets.
  • the means for passing a current pulse through the control winding include a non-magnetic control rod which retractably extends from the load end of the device so as to abut against the load, the control rod being adapted to operate a switch which controls a current pulse to the control winding when the space between the keeper plate and the load is just greater than said distance by which the spacing means extend from the keeper plate.
  • a magnetic lift device for transporting a magnetic load comprising, a permanent magnet, a pair of pole members with the permanent magnet disposed between said pole members so as to provide a first and a second magnetic circuit through a load end and a keeper end,
  • a lift device as claimed in claim 7 wherein the spacer means comprises a rod slidably extending through a bore in a pole number with one end secured to the keeper plate and the other end freely movable to contact a load member at the load end and retractable therefrom when the keeper plate is moved in a direction away from the load end of the device.
  • a lift device as claimed in claim 8 wherein said current pulse applying means comprises a switch secured to the keeper plate and a non-magnetic control rod retractably extending from the load end of the device so as to contact a load when in place, said control rod extending to the keeper plate so as to operate said switch at a predetermined separation between the keeper plate and the load.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Load-Engaging Elements For Cranes (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
US00302132A 1971-11-02 1972-10-30 Electro-mechanically switched permanent magnet holding device Expired - Lifetime US3798581A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB5079771A GB1372244A (en) 1971-11-02 1971-11-02 Electromechanically switched permanent magnet holding device
FR7243979A FR2209707B1 (enrdf_load_stackoverflow) 1971-11-02 1972-12-11
DE2261282A DE2261282A1 (de) 1971-11-02 1972-12-15 Elektromechanisch geschaltete haltevorrichtung mit einem dauermagneten

Publications (1)

Publication Number Publication Date
US3798581A true US3798581A (en) 1974-03-19

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Family Applications (1)

Application Number Title Priority Date Filing Date
US00302132A Expired - Lifetime US3798581A (en) 1971-11-02 1972-10-30 Electro-mechanically switched permanent magnet holding device

Country Status (4)

Country Link
US (1) US3798581A (enrdf_load_stackoverflow)
DE (1) DE2261282A1 (enrdf_load_stackoverflow)
FR (1) FR2209707B1 (enrdf_load_stackoverflow)
GB (2) GB1372244A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122423A (en) * 1976-05-14 1978-10-24 Le Material Magnetique Permanent magnet magnetic control device having two control air gaps
US4399482A (en) * 1979-02-08 1983-08-16 Inoue-Japax Research Incorporated Magnetic holder
US4461207A (en) * 1980-11-17 1984-07-24 International Business Machines Corporation Actuator mechanism for a printer or the like using dual magnets
US4893858A (en) * 1987-06-26 1990-01-16 Toyota Jidosha Kabushiki Kaisha Movable yoke-type lifting magnet device
US4965695A (en) * 1987-05-22 1990-10-23 Baumann Joseph D Permanent magnetic retaining device to move, affix or carry ferromagnetic parts or loads with electronic switching of the magnetic flux to release the carried load
US5630634A (en) * 1994-12-27 1997-05-20 Michael W. Stowe Device for magnetically engaging objects having variable surface contours
US9067290B2 (en) 2010-05-25 2015-06-30 Ixtur Oy Attaching device, attaching arrangement and method for attaching an object to be worked to a working base

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257141A (en) * 1963-06-17 1966-06-21 Indiana General Corp Magnetic transfer device
US3316514A (en) * 1965-03-29 1967-04-25 Westinghouse Electric Corp Fail safe electro-magnetic lifting device with safety-stop means
US3683239A (en) * 1971-06-17 1972-08-08 Oded E Sturman Self-latching solenoid actuator

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3389356A (en) * 1965-08-23 1968-06-18 American Chain & Cable Co Fail-safe permanent magnet lifting device with a movable bias keeper
FR1531933A (fr) * 1967-07-19 1968-07-05 Westinghouse Electric Corp Aimant de levage à transfert de flux
DE1756503C3 (de) * 1968-05-30 1973-07-19 Koppers Gmbh Heinrich Vorrichtung zur Anzeige von an Lasthebemagneten haengenden Lasten

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257141A (en) * 1963-06-17 1966-06-21 Indiana General Corp Magnetic transfer device
US3316514A (en) * 1965-03-29 1967-04-25 Westinghouse Electric Corp Fail safe electro-magnetic lifting device with safety-stop means
US3683239A (en) * 1971-06-17 1972-08-08 Oded E Sturman Self-latching solenoid actuator

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4122423A (en) * 1976-05-14 1978-10-24 Le Material Magnetique Permanent magnet magnetic control device having two control air gaps
US4399482A (en) * 1979-02-08 1983-08-16 Inoue-Japax Research Incorporated Magnetic holder
US4461207A (en) * 1980-11-17 1984-07-24 International Business Machines Corporation Actuator mechanism for a printer or the like using dual magnets
US4965695A (en) * 1987-05-22 1990-10-23 Baumann Joseph D Permanent magnetic retaining device to move, affix or carry ferromagnetic parts or loads with electronic switching of the magnetic flux to release the carried load
US4893858A (en) * 1987-06-26 1990-01-16 Toyota Jidosha Kabushiki Kaisha Movable yoke-type lifting magnet device
US5630634A (en) * 1994-12-27 1997-05-20 Michael W. Stowe Device for magnetically engaging objects having variable surface contours
US9067290B2 (en) 2010-05-25 2015-06-30 Ixtur Oy Attaching device, attaching arrangement and method for attaching an object to be worked to a working base

Also Published As

Publication number Publication date
DE2261282A1 (de) 1974-06-20
FR2209707A1 (enrdf_load_stackoverflow) 1974-07-05
GB1372244A (en) 1974-10-30
FR2209707B1 (enrdf_load_stackoverflow) 1977-07-22
GB50797A (enrdf_load_stackoverflow)

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