Magnetic seal for magnetic particle clutches and brakes

Claim 2

A magnetic particle device having (a) at least two coaxial members arranged for rotation relative to one another, (b) a gap formed between mutually-confronting surfaces of at least two of said members, and (c) a supply of magnetic particles in contact with at least one of said members, one of said coaxial members being a shaft made of a non-magnetic material, improved sealing means for preventing magnetic particles which intrude into said gap from migrating in said gap along said mutually-confronting surfaces, said improved sealing means comprising at least one annular permanent magnet fixed to one of said mutually-confronting surfaces and disposed concentrically with and close to the other of said mutually-confronting surfaces, said at least one magnet having a magnetic field with a strength sufficient to cause intruding magnetic particles to agglomerate at said at least one magnet so as to block said gap and thereby prevent further migration of intruding particles.

Claim 3

In a magnetic particle device having a shaft made of a non-magnetic material, a radially-extending disk affixed to the shaft, an armature assembly comprising an annular magnetic armature member surrounding said shaft and confronting said disk, said armature member being spaced axially from said disk and radially from said shaft, magnetic particles positioned in the space between the disk and said armature member, means for rotatably supporting the shaft for rotation on its axis relative to said armature member, and electrically energizable means for establishing a magnetic field through the disk and said armature member so as to cause said particles to produce a torque-transmitting coupling between the disk and the armature assembly, the improvement comprising an improved sealing means for preventing the escape of magnetic particles from the space between the disk and said armature member, said sealing means comprising at least one annular magnet disposed in the space between said shaft and said armature member, said at least one magnet being secured to one of said shaft or said armature member and being spaced from the other of said shaft or said armature member, the field strength of said at least one magnet being sufficiently strong to attract and agglomerate magnetic particles which intrude into the space between said armature member and the shaft so as to form a clot of particles which effectively prevent the migration and escape of other particles lengthwise of said shaft.

Claim 4

In a magnetic particle device having a shaft made of a non-magnetic material, a radially-extending disk affixed to the shaft, an armature assembly comprising an annular magnetic armature member surrounding said shaft and confronting said disk, said armature member being spaced axially from said disk and radially from said shaft, magnetic particles positioned in the space between the disk and said armature member, means for rotatably supporting the shaft for rotation on its axis relative to said armature member, and electrically energizable means for establishing a magnetic field through the disk and said armature member so as to cause said particles to produce a torque-transmitting coupling between the disk and the armature assembly, the improvement comprising an improved sealing means for preventing the escape of magnetic particles from the space between the disk and said armature member, said sealing means comprising at least one annular magnet disposed in the space between said shaft and said armature member, said at least one magnet being secured to one of said shaft or said armature member and being spaced from the other of said shaft or said armature member, the field strength of said at least one magnet being sufficiently strong to attract and agglomerate magnetic particles which intrude into the space between said armature member and the shaft so as to form a clot of particles which effectively prevent the migration and escape of other particles lengthwise of said shaft.

Claim 5

A magnetic particle device comprising: a shaft; a radially-extending disk affixed to said shaft; an armature assembly comprising first and second annular magnetic pole pieces surrounding said shaft on opposite sides of said disk, said pole pieces each having an annular end surface confronting and axially spaced from said disc and a cylindrical inner surface radially spaced from and close to said shaft; a non-magnetic member extending between said first and second pole pieces and closing off the space between said pole pieces and said disc beyond the peripheral edge of said disk; magnetic particles positioned in the space between said disk and said pole pieces; means for rotatably supporting said shaft for rotation on its axis relative to said armature assembly; electrically energizable means for establishing a magnetic field through said disk and said armature assembly so as to cause said particles to produce a torque-transmitting coupling between said disk and said pole pieces; sealing means for preventing the escape of magnetic particles from the space between said disk and said pole pieces by migration between said shaft and said first pole piece, said sealing means comprising at least one annular magnet surrounding and spaced from said shaft, and a non-magnetic retaining means securing said at least one magnet to said cylindrical inner surface of said first pole piece adjacent said disc and close to said shaft, said retaining means comprising first and second axially spaced members between which said at least one magnet is sandwiched; the field strength of said at least one magnet being sufficiently strong to attract and agglomerate magnetic particles which intrude into the space between said first pole piece and said shaft so as to form a clot of particles which effectively prevent the migration and escape of other particles lengthwise of said shaft.

Claim 6

A magnetic particle device comprising: a shaft; a radially-extending disk affixed to said shaft; an armature assembly comprising first and second annular magnetic pole pieces surrounding said shaft on opposite sides of said disk, said pole pieces each having an annular end surface confronting and axially spaced from said disc and a cylindrical inner surface radially spaced from and close to said shaft; a non-magnetic member extending between said first and second pole pieces and closing off the space between said pole pieces and said disc beyond the peripheral edge of said disk; magnetic particles positioned in the space between said disk and said pole pieces; means for rotatably supporting said shaft for rotation on its axis relative to said armature assembly; electrically energizable means for establishing a magnetic field through said disk and said armature assembly so as to cause said particles to produce a torque-transmitting coupling between said disk and said pole pieces; sealing means for preventing the escape of magnetic particles from the space between said disk and said pole pieces by migration between said shaft and said first pole piece, said sealing means comprising at least one annular magnet surrounding and spaced from said shaft, and a non-magnetic retaining means securing said at least one magnet to said cylindrical inner surface of said first pole piece adjacent said disc and close to said shaft, said retaining means comprising first and second axially spaced members between which said at least one magnet is sandwiched; the field strength of said at least one magnet being sufficiently strong to attract and agglomerate magnetic particles which intrude into the space between said first pole piece and said shaft so as to form a clot of particles which effectively prevent the migration and escape of other particles lengthwise of said shaft.

Claim 7

Apparatus according to claim 3 comprising additional sealing means having at least one annular magnet surrounding and spaced from said shaft and non-magnetic retaining means securing said at least one magnet to said cylindrical inner surface of said second pole piece adjacent said disk and close to said shaft, said retaining means comprising first and second axially spaced members between which said at least one magnet is sandwiched, said additional sealing means serving to prevent escape of magnetic particles from the space between said disk and said pole pieces by migration between said shaft and said second pole piece.

Claim 8

Apparatus according to claim 4 wherein an annular groove is formed in said cylindrical inner surfaces of said first and second pole pieces adjacent said annular end surface and said sealing means are located in said grooves.

Claim 9

Apparatus according to claim 3 wherein said sealing means comprises a pair of annular rings of soft magnetic material flanking said at least one first annular magnet, and first and second axially spaced members of said non-magnetic retaining means hold said rings of soft magnetic material in contact with said at least one annular magnet.

Claim 10

Apparatus according to claim 3 wherein said shaft is made of non-magnetic material.

Claim 11

Apparatus according to claim 3 wherein said non-magnetic retaining means is flush with said annular end surface of said first pole piece.

Claim 12

Appartus according to claim 3 wherein said sealing means is spaced axially from said annular end surface of said first pole piece.

Claim 13

Apparatus according to claim 3 wherein said sealing means is secured in an annular groove formed in said cylindrical inner surface, said groove intersecting said annular end face of said first pole piece.

Claim 14

Apparatus according to claim 3 wherein said sealing means is located in an annular groove formed in said cylindrical inner surface of said first pole piece, said groove being spaced axially from said annular end face of said first pole piece.

Claim 15

Apparatus according to claim 3 wherein said non-magnetic retaining means comprises a non-magnetic cup ring of L-shaped cross section surrounding the outer circumferential edge and flanking a first side of said at least one annular magnet, and a non-magnetic spacer ring flanking a second side of said at least one annular magnet.