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Heart Surgery

Magnetic-bearing-structure

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Magnetic bearing structure

Details

Inventors: Meeks, Crawford R.;
Assignee:
Primary Examiner: Skudy; R.
Assistant Examiner:
Attorney, Agent or Firm: Kelly, Bauersfeld & Lowry

A magnetic bearing structure is provided for supporting a rotatable member in a suspended position relative to a stationary member utilizing a constant flux axially polarized magnetic field and a variable flux radially polarized electromagnetic field. In one preferred form of the invention the bearing structure includes axially spaced apart rings associated with the stationary member, which hold a plurality of electromagnetic coils circumferentially about and radially spaced from a rotatable shaft. Electrical current is supplied to the coils generate a radially polarized electromagnetic field surrounding the shaft. At least one cylindrically shaped permanent magnet surrounds a portion of the shaft and is positioned generally between the pair of arcuate rings. The permanent magnet is axially polarized and is linked magnetically to the arcuate rings. Substantially all of the magnetic flux generated by the electromagnetic coils and the permanent magnet is direct radially through only a pair of air gaps between the shaft and the rings. Position sensors, along with a servo control circuit, detect and compensate for any radial displacement of the shaft to maintain it in a metastable position relative to the stationary member. In alternative embodiments the rotatable member may encircle the stationary member, and the permanent magnet may be replaced by a constant flux electromagnet.

DETAILED DESCRIPTION The present invention resides in an improved electromagnetic bearing structure for supporting a rotatable member in a suspended or levitated position with respect to a stationary member.
The bearing structure comprises, generally, first and second means associated with the stationary member and axially spaced from one another, for generating a radially polarized controllable electromagnetic field surrounding respective portions of the rotatable member.
Further, means associated with the stationary member and situated between the first and second electromagnetic field generating means, are provided for generating an axially polarized magnetic field.
Substantially all of the magnetic flux from the first and second electromagnetic field generating means and the axially polarized magnetic field generating means, is directed radially through only a pair of air gaps between the rotatable member and the stationary member, to provide magnetic flux coupling of the rotatable member to the stationary member.
The arrangement of the electromagnetic bearing structure of the present invention uniquely combines radially polarized, controllable electromagnetic fields with a relatively constant axially polarized magnetic field to produce a compact and spacially efficient system which is lightweight and which has a high degree of power efficiency.
Furthermore, the use of the primary axially polarized field significantly reduces eddy current and hysteresis losses in the rotatable member.
In its most basic form, the electromagnetic bearing structure of the present invention utilizes the relatively constant axially polarized magnetic field to generate a high density magnetic flux which is radially directed through the pair of air gaps between the rotatable member and the stationary member.
This provides a generally uniform magnetic field surrounding the rotatable member which, under perfect conditions, could theoretically suspend or levitate the rotatable member with respect to the stationary member

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