US3918016A - Electrically conductive plates providing eddy current damping for an electro-magnetic device - Google Patents

Electrically conductive plates providing eddy current damping for an electro-magnetic device Download PDF

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Publication number
US3918016A
US3918016A US526688A US52668874A US3918016A US 3918016 A US3918016 A US 3918016A US 526688 A US526688 A US 526688A US 52668874 A US52668874 A US 52668874A US 3918016 A US3918016 A US 3918016A
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United States
Prior art keywords
members
winding
electrically conductive
cavity
eddy current
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US526688A
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English (en)
Inventor
George Frankl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ZF International UK Ltd
Original Assignee
Lucas Industries Ltd
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Filing date
Publication date
Application filed by Lucas Industries Ltd filed Critical Lucas Industries Ltd
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Publication of US3918016A publication Critical patent/US3918016A/en
Anticipated expiration legal-status Critical
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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
    • H01F7/08—Electromagnets; Actuators including electromagnets with armatures
    • H01F7/14—Pivoting armatures

Definitions

  • a torque motor comprises a frame including a pair of opposed and spaced side members formed from a material having a high magnetic permeability.
  • a cavity is defined between the members in which is mounted a pivotal permanent magnet, the cavity also including a winding so that when the winding is energised, the magnet will tend to turn about the pivotal axis.
  • the side members are interconnected at their side edges by a pair of plate members formed from electrically conductive but non-magnetic material, the plate members acting to provide eddy current damping when the magnet is moved'relative to the frame.
  • This application relates to electromagnetic devices of the kind known as torque motors, and comprising in combination, a frame including a pair of opposed and spaced side members formed from a material having a high magnetic permeability and defining an internal cavity, a permanent magnet pivotally mounted within the cavity and a winding mounted within the cavity, the arrangement being such that when the winding is energised the magnet will tend to turn about its pivot axis so that its magnetic axis will be aligned with that of the winding.
  • the object of the present invention is to provide such a device in an improved form.
  • the side members are interconnected at their side edges by a pair of plate members formed from electrically conductive non-magnetic material, the presence of said plate members acting to provide eddy current damping when the magnet is moved relative to the frame.
  • FIG. 1 shows a cut away perspective view of part of one example of a device to which the invention may be applied
  • FIG. 2 is a section through the complete device of FIG. 1,
  • FIGS. 3 and 5 are views similar to FIG. 2, but in each case showing the addition of the nonmagnetic plates, and
  • FIG. 4 is a plot of torque against angle for different values of current.
  • the device comprises a frame which includes a pair of oppositely disposed and spaced side members 11 and a pair of end members 12 which interconnect the end edges of the members 11. At least the members 11 are formed from a magnetisable material having a high magnetic permeability and preferably formed from soft iron.
  • the frame defines a cavity in which is located a rotor 13 constructed as a permanent magnet and polarised so that the faces of the rotor which are presented to the members 11 are of opposite magnetic polarity. The effect of this is that the rotor will try to assume the position in which it is shown in FIGS. 1 and 2.
  • the rotor is pivotally mounted within bearings defined in the end members.
  • a winding 14 which for ease of assembly is formed in two parts.
  • the winding extends around the internal surfaces of the members 1 1 and 12 so that its magnetic axis is normal to the pivot axis of the rotor and parallel to the planes containing the surfaces of the members 11.
  • the rotor tends to pivot about its axis so that the magnetic axis of the rotor becomes aligned with that of the winding 14.
  • the winding 14 may be shaped to permit the rotor greater angular movement, and to concentrate the windings of the coil in the position where the magnetic field between the rotor and the frame is strongest.
  • FIG. 4 The type of characteristic obtained is shown in FIG. 4, in which the torque is plotted against the angle of the rotor for varying values of current flowing in the winding.
  • the slope of the zero current curve can be defined as the stiffness, and the value of the stiffness can be varied by varying the proportions of the devices.
  • the rotor and the inner face of the frame are cylindrical. In this manner, the speed of response is increased since the moment of inertia of the rotor is reduced.
  • FIGS. 3 and 5 also show the provision of plate members 15 formed from electrically conductive non-magnetic material. It will be appreciated that the plate members 15 may be applied to the example shown in FIGS. 1 and 2.
  • the plate members interconnect the side edges of the side members.
  • the presence of the plate members 15 provides eddy current damping when the rotor moves relative to the frame.
  • the presence of the plate members 15 has of course no influence upon the characteristics which are shown in FIG. 4.
  • the provision of the damping does however modify the speed of response and minimise over-shoot which may occur when a change in the current flowing through the windings takes place.
  • the plate members are formed from non-ferrous material such for instance as brass or copper.
  • An electromagnetic device comprising a frame including a pair of opposed and spaced side members formed from a material having a high magnetic permeability and defining an internal cavity, a permanent magnet pivotally mounted within the cavity and a winding mounted within the cavity whereby when the winding is energised the magnet will tend to turn about its pivot axis so that its magnetic axis will be aligned with that of the winding characterised in that the side members are interconnected at their side edges by a pair of plate members formed from electrically conductive non-magnetic material, said plate members acting to provide eddy current damping when the magnet is moved relative to the frame.
  • a device characterised in that the end edges of the side members are interconnected by end members, said end members defining bearings for the rotor.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dynamo-Electric Clutches, Dynamo-Electric Brakes (AREA)
  • Vibration Prevention Devices (AREA)
US526688A 1973-11-28 1974-11-25 Electrically conductive plates providing eddy current damping for an electro-magnetic device Expired - Lifetime US3918016A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB55118/73A GB1491209A (en) 1973-11-28 1973-11-28 Electromagnetic torque motor

Publications (1)

Publication Number Publication Date
US3918016A true US3918016A (en) 1975-11-04

Family

ID=10473013

Family Applications (1)

Application Number Title Priority Date Filing Date
US526688A Expired - Lifetime US3918016A (en) 1973-11-28 1974-11-25 Electrically conductive plates providing eddy current damping for an electro-magnetic device

Country Status (3)

Country Link
US (1) US3918016A (enrdf_load_stackoverflow)
FR (1) FR2252690B2 (enrdf_load_stackoverflow)
GB (1) GB1491209A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0375093A3 (en) * 1988-12-23 1991-12-18 Dresser Industries, Inc. Sensitive electrical to mechanical transducer
US5257639A (en) * 1988-12-23 1993-11-02 Dresser Industries, Inc. Electropneumatic positioner

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3843646C2 (de) * 1988-12-23 1994-05-26 Spinner Georg Elektromagnetischer Schalterantrieb

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1809634A (en) * 1929-10-12 1931-06-09 Union Switch & Signal Co Electrical relay
US2932752A (en) * 1956-08-20 1960-04-12 Nat Res Dev Torque motors
US3058038A (en) * 1959-11-20 1962-10-09 Weston Hydraulics Ltd Torque motor with null balance
US3794868A (en) * 1971-08-31 1974-02-26 R Haigh Electromagnetic device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1809634A (en) * 1929-10-12 1931-06-09 Union Switch & Signal Co Electrical relay
US2932752A (en) * 1956-08-20 1960-04-12 Nat Res Dev Torque motors
US3058038A (en) * 1959-11-20 1962-10-09 Weston Hydraulics Ltd Torque motor with null balance
US3794868A (en) * 1971-08-31 1974-02-26 R Haigh Electromagnetic device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0375093A3 (en) * 1988-12-23 1991-12-18 Dresser Industries, Inc. Sensitive electrical to mechanical transducer
US5257639A (en) * 1988-12-23 1993-11-02 Dresser Industries, Inc. Electropneumatic positioner

Also Published As

Publication number Publication date
FR2252690A2 (enrdf_load_stackoverflow) 1975-06-20
GB1491209A (en) 1977-11-09
FR2252690B2 (enrdf_load_stackoverflow) 1977-03-25

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