Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Magnet structure or material
Reexamination Certificate
2000-07-31
2001-11-20
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Magnet structure or material
Reexamination Certificate
active
06320488
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of permanent magnet structures and, more particularly, to permanent magnet structures that produce an adjustable working magnetic field.
BACKGROUND OF THE INVENTION
Permanent magnet structures that produce a working magnetic field are well known in the art. The term “working magnetic field” as used herein refers to a magnetic field that is used to do a useful task. A magnetic field used to guide or focus an electron beam is an example of such a working magnetic field.
Some permanent magnet structures are composed of pieces of permanent magnet material arranged to form a shell having an interior cavity. Each piece of permanent magnet material has a magnetization that adds to the overall magnetization of the shell. Depending on the magnetization of the shell, a permanent magnet structure can be designed to produce a working magnetic field having a given magnitude parallel to a given axis in the cavity of the shell.
Some permanent magnet structures are designed to provide a working magnetic field having a magnitude or strength that can be mechanically adjusted. Such structures are typically composed of two permanent magnet shells, each producing a working magnetic field in their respective cavities. The shells are arranged such that their internal cavities share a common space, thereby forming a common internal cavity. Such an arrangement enables the working magnetic fields to interact in the common internal cavity to produce, e.g. by vector addition, a composite working magnetic field having a composite magnitude. In addition, the shells are arranged such that they can rotate independent of each other around the common internal cavity. The “rotatability” enables one to change the vector relationship between the working magnetic fields produced by each shell. As a result, the magnitude of the composite working field in the common internal cavity can be adjusted or changed by rotating one shell with respect to the other.
One such adjustable permanent magnet structure is described in U.S. Pat. No. 4,862,128, entitled “Field Adjustable Transverse Flux Source,” issued to the present inventor herein on Aug. 29, 1989, and incorporated herein by reference. As described therein, an adjustable working magnetic field can be obtained by assembling two cylindrical shells or “magic rings” such that one is embedded within the other so that they are axially aligned and the outer radius of the inner shell equals the inner radius of the outer shell. By rotating the shell of the outer magic ring around the inner magic ring, the magnitude of the working magnetic field in the cavity can be adjusted or changed without having to change the magnetization of either shell. Thus one has a structure that can be adjusted to produce a uniform magnetic field with any value in between, and including 2H
1
, where H
1
is the field produced by each cylindrical shell acting alone.
SUMMARY OF THE INVENTION
The present invention is directed to a permanent magnet structure that produces a tapered working magnetic field having a magnitude and pitch that can be mechanically adjusted.
To attain this, a permanent magnet structure in accordance with the principles of the present invention is composed of four or more permanent magnet shells. A first set of shells are oriented and magnetized such that they interact to produce a first working magnetic field. A second set of shells are oriented and magnetized such that they interact to produce a second magnetic field having a given magnitude. Both sets of permanent magnet shells are assembled such that they share a common internal cavity wherein the first and second working fields interact with each other to form a tapered working magnetic field. In addition, the first and second sets of permanent magnet shells are arranged such that they can be mechanically rotated around the common internal cavity. As described above, a mechanical movement or rotation of any one of the sets of shells directly affects the interaction (geometric addition) of the magnetic fields produced by the sets of shells, and thus directly affects both the magnitude and/or pitch of the tapered working magnetic field produced in the common internal cavity. As a result, one can adjust or change the pitch of the magnetic field in the common internal cavity by changing or rotating the relative position of one set of shells with respect to the other set of shells. Thus, in accordance with the principles of the present invention, the permanent magnet structure advantageously provides a working field having an adjustable magnitude.
In particular embodiments, the permanent magnet structure is composed of two sets of permanent magnet shells, each set being composed of two hollow substantially cylindrical shells that form a common internal cavity. Each set having one shell embedded within the other such that they are axially aligned and such that the outer radius of one is equal to the inner radius of the other. The sets of shells are arranged such that one set of shells is embedded within the other such that they are axially aligned and such that the outer radius of one set is equal to the inner radius of the other. The shells of one set are magnetized such that they produce a first working magnetic field having a given magnitude in the common internal cavity. The other set of rings are magnetized such that they produce a second working field having a given taper in the common internal cavity. The first and second working fields interact in the common internal cavity to form a composite working magnetic field having a given magnitude. The magnitude and pitch of the composite working magnetic field can thereby be adjusted by rotating the shells within each set of shells and/or by rotating one set of shells with respect to the other.
Although there may be a residual transverse field emanating inward or outward from the diametric axis along which the composite internal field is generated, the transverse field will be negligible on the axis where the work is actually done. These and other features of the invention will become more apparent from the Detailed Description when taken with the drawing. The scope of the invention, however, is limited only by the claims.
REFERENCES:
patent: 5034715 (1991-07-01), Leupold et al.
patent: 5068860 (1991-11-01), Hartemann et al.
patent: 5332971 (1994-07-01), Aubert
Barrera Ramon M.
Tereschuk George B.
The United States of America as represented by the Secretary of
Zelenka Michael
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