The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 06, 1985
Filed:
Mar. 30, 1981
Dilip K Das, Bedford, MA (US);
Kaplesh Kumar, Wellesley, MA (US);
Ernest C Wettstein, Acton, MA (US);
The Charles Stark Draper Laboratory, Inc., Cambridge, MA (US);
Abstract
Apparatus and method for forming radial orientation rare earth-transition metal magnets in continuous arc rings by hot isostatic pressing. A method includes the steps of compacting rare earth-transition metal powders having a particle size up to 40 microns into radially oriented rings in a mold provided with a radially aligning field, stacking a plurality of compacted radially oriented rings within an annular cavity within a sealed, evacuated cannister to form a cylinder of a predetermined height, subjecting the cannister to temperatures in the range of 900.degree. to 1150.degree. C. under a gas pressure of 15 kpsi to densify the compacts, and cooling the cannister and the compacts to room temperature. An apparatus for performing the above-described method, includes a mold for forming green compacts having a central iron core or mandrel, an outer housing forming an annular space between it and the iron mandrel, plungers for compacting into a ring rare earth-transition metal powder within the annular space, and means for forming a radially oriented magnetic field. The magnetic field forming means includes a pair of electromagnetic coils with bucking fields disposed on opposite axial ends of the annular space. Ferromagnetic paths guide the flux through the inner and outer walls of the mold and through the powder to form a radial field for powder alignment. A cannister is used for forming magnets from the green compacts and the cannister is typically composed of a soft iron that will collapse around the magnets and transmit compressive forces to the green compacts for densification thereof. The cannister includes an annular space for stacking green compacts bounded by inner and outer walls and an evacuation tube. A central mandrel may be provided if a ring magnet having a predetermined inner diameter is desired.