Linear electromagnetic machine
First Claim
1. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, wherein said magnet is annular in form and there is included a ferromagnetic sleeve on that side of said magnet which is remote from the conductor, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine.
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Accused Products
Abstract
A linear electromagnetic machine for generating a force acting between two members relatively movable along an axis, one of which is capable of producing a magnetic field the direction of at least part of which extends substantially radially of the said axis and the other of which comprises or includes a conductor, conveniently in the form of a coil, in which an electric current can flow substantially perpendicularly of the magnetic field so as to generate a force between the two members substantially parallel to the axis. The radial magnetic field is generated by permanent magnets orientated with their direction of magnetisation axially, the pole pieces acting to concentrate the magnetic flux to follow a radial path through the coils.
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Citations
20 Claims
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1. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, wherein said magnet is annular in form and there is included a ferromagnetic sleeve on that side of said magnet which is remote from the conductor, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine.
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11. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, said one of said two members has a plurality of magnets, and pole pieces, and said other of said members has a plurality of conductors, the axial length of each magnet and the axial length of each pole piece are the same and equal to twice the radial thickness of the conductor, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine.
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12. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, said second member comprises an axially extending body of ferromagnetic material in which there are a plurality of coils spaced apart axially by separators of ferromagnetic material, and the separators are so shaped as to have a constant radial reluctance with the respect to the pole pieces of the first member and the separators are parallel and skewed with respect to the axis of the machine by an angle such that two diametrically opposed regions of the separators are displaced axially by a distance equal to the axial width of a conductor, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine.
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13. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, said second member comprises an axially extending body of ferromagnetic material in which there are a plurality of coils spaced apart axially by separators of ferromagnetic material, and the separators are so shaped as to have a constant radial reluctance with the respect to the pole pieces of the first member and the separators are positioned perpendicular to the axis of the machine and so shaped as to provide a series of slots having a regular cyclic form the axial amplitude of which is equal to the axial width of each of the coils, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine.
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14. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, said second member comprises an axially extending body of ferromagnetic material in which there are a plurality of coils spaced apart axially by separators of ferromagnetic material, and the separators are so shaped as to have a constant radial reluctance with the respect to the pole pieces of the first member and the ferromagnetic body is of modular construction and the separators are separated by circumferential spacers the axial length which is equal to the axial width of the coils; - the assembly being clamped together by tie rods,
the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine. - View Dependent Claims (15, 16, 17, 18, 19)
a control unit adapted to respond to the signals from said transducer, said the control unit is adapted to produce three quasi DC drive currents arranged to have a zero sum at all times. -
16. The linear electromagnetic machine of claim 15, wherein, the drive currents are defined by the relations;
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I1=a*sin(x+offset) I2=a*sin(x+offset+2/3π
)I3=a*sin(x+offset+4/3π
)where a is the current drive signal, x is an absolute (cyclic) phase command corresponding to the displacement of the armature of the machine from a datum position, and offset is a preset phasing parameter which relates to the datum position of the armature of the machine.
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17. The linear electromagnetic machine of claim 15, wherein said armature has associated therewith said transducer for determining at least one of its position, velocity and acceleration, and the magnitude and direction of the current applied to any one coil by said control means is determined by the output from the said transducer.
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18. The linear electromagnetic machine of claim 17, wherein the axial dimension of each coil is one sixth of the armature magnetic period and said control means are adapted to supply each set of six coils with three phase current, each pair of coils separated by two other coils receiving the same phase in opposite directions.
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19. The linear electromagnetic machine of claim 17, wherein the coils supplied with a given phase are connected in series with alternating polarity.
- the assembly being clamped together by tie rods,
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20. A linear electromagnetic machine for generating a force acting between first and second members relatively movable along an axis,
said first member constituting a stator of said machine, said second member constituting an armature of said machine, one of the said two members including at least one magnet orientated with its direction of magnetisation substantially parallel to said axis of relative movement and having associated pole pieces, the other of said two members having a conductor in which an electric current can be caused to flow, said pole pieces having a circumferential surface from which a radial magnetic field extends, said radial magnetic field intersecting said conductor of said other member perpendicularly of the direction in which said electric current flows, whereby to generate a force between said two members acting substantially parallel to said axis, the length of said armature along said axis is less than the length of said stator, and an outer casing is provided for resisting the escape of magnetic fields generated within the machine, wherein the coils follow curvilinear or rectilinear axially sinuous path circumferentially around the said axis.
Specification