US3648084A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Linear induction motors
Assignee: NAT RES DEV
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Filing: 1970-06-16
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Granted: 1972-03-07
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Expires: 1990-06-16
Abstract
Abstract The magnetic field of a linear motor is evenly distributed over the airgap between the primary and secondary members by providing a ladderlike grid structure of conductors at each side, by interleaving the laminations with conductive stampings near the sides, by strips of conductive material on or near the surface of the stator, or by chamfering the edges.
Inventors
- 👤 Eric Roberts Laithwaite
- 👤 Hugh Robert Bolton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 08:31
CPC Classifications
H; H02; H02K; H02K41/00; H02K41/02; H02K41/025
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
169 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap, an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member, and flux reducing means for effectively reducing the density of said magnetic field at the said side edges to produce a substantially uniform field over the entire surface of said primary member which is adjacent to said airgap including an electrically conducting member extending outside the side edges of said block and positioned with respect to said block so that the magnetic field generated by said winding generates circulating currents in said member to reduce the density of said field at said side edges.
Claim 2
Dependent Claim
169 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap, an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member, and flux reducing means for effectively reducing the density of said magnetic field at the said side edges to produce a substantially uniform field over the entire surface of said primary member which is adjacent to said airgap including an electrically conducting member extending outside the side edges of said block and positioned with respect to said block so that the magnetic field generated by said winding generates circulating currents in said member to reduce the density of said field at said side edges.
Claim 3
Dependent Claim
30 words
The primary member as claimed in claim 1 in which the conducting material is in the form of a series of closed loops parallel to the surface of the block.
Claim 4
Dependent Claim
26 words
The primary member as claimed in claim 2 in which the loops are contiguous and form a ladderlike grid structure at each side of the block.
Claim 5
Dependent Claim
49 words
The primary member as claimed in claim 3 in which each grid structure includes at least one member lying in a longitudinal slot in the surface of the block and one other member lying outside the side edge of the block to provide a return path for circulating current.
Claim 6
Dependent Claim
28 words
The primary member as claimed in claim 1 in which the conducting material is in the form of thin strips lying parallel to the surface of the block.
Claim 7
Dependent Claim
52 words
The primary member as claimed in claim 1 wherein said block is constructed of laminations of magnetically permeable material lying in planes generally perpendicular to said airgap, and said flux reducing means comprises strips of electrically conductive material interleaved between said laminations and located near the side edges of said primary member.
Claim 8
Dependent Claim
127 words
A linear motor primary member including electrically conducting material positioned in the neighborhood of the side edges thereof and extending beyond the side edges thereof so that the magnetic field of the primary member generates circulatory currents therein to reduce the magnetic field at the side edges, said conducting material being in the form of closed loops parallel to the surface of said primary member, said loops being contiguous in the form of a ladderlike grid structure at each side of said primary member, and wherein, each said grid structure includes; at least one member lying in a longitudinal slot in the surface of said primary member, and one other member lying outside the edge of said primary member to provide a return path for circulating current.
Claim 9
Dependent Claim
127 words
A linear motor primary member including electrically conducting material positioned in the neighborhood of the side edges thereof and extending beyond the side edges thereof so that the magnetic field of the primary member generates circulatory currents therein to reduce the magnetic field at the side edges, said conducting material being in the form of closed loops parallel to the surface of said primary member, said loops being contiguous in the form of a ladderlike grid structure at each side of said primary member, and wherein, each said grid structure includes; at least one member lying in a longitudinal slot in the surface of said primary member, and one other member lying outside the edge of said primary member to provide a return path for circulating current.
Claim 10
Dependent Claim
157 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap, an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member, and flux reducing means for effectively reducing the density of said magnetic field at the said side edges to produce a substantially uniform field over the entire surface of said id primary member which is adjacent to said airgap, the said flux reducing means comprising the surface of said block adjacent to said airgap being shaped to provide an airgap which has a maximum width at the side edges of the block.
Claim 11
Dependent Claim
157 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap, an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member, and flux reducing means for effectively reducing the density of said magnetic field at the said side edges to produce a substantially uniform field over the entire surface of said id primary member which is adjacent to said airgap, the said flux reducing means comprising the surface of said block adjacent to said airgap being shaped to provide an airgap which has a maximum width at the side edges of the block.
Claim 12
Dependent Claim
104 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap and shaped to provide an airgap which has a maximum width at the side edges of the block, and an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member.
Claim 13
Dependent Claim
104 words
A moveable primary member for a linear electromagnetic motor producing substantially no self-centering forces and having a fixed secondary member made of electrically conductive material and an airgap between said primary member and said secondary member, said primary member comprising: a block of magnetically permeable material having side edges and slots in the surface thereof adjacent to said airgap and shaped to provide an airgap which has a maximum width at the side edges of the block, and an electrical winding positioned in said slots for generating a travelling magnetic field in a magnetic circuit including said block, said airgap and said secondary member.
References Cited (Backward Citations)
US3426887A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-03-07 | 1975-09-06 | 1976-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-03-07 | 1979-09-06 | 1980-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-03-07 | 1983-09-06 | 1984-03-07 | $7700.00 | Window Closed / Lapsed |