US4641787A
Expired / Lapsed
US
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Method of comminuting rare earth powder for producing rare earth magnet
Assignee: Polaroid Corp
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Filing: 1983-09-26
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Granted: 1987-02-10
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Expires: 2003-09-26
Abstract
Abstract A method of comminuting a rare earth metallic alloy powder by impact milling for facilitating formation of an improved rare earth magnet.
Inventors
- 👤 Christian C. Petersen
- 👤 Ernst C. Wettstein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:38
CPC Classifications
B; B02; B02C; B02C23/00; B02C23/18; B02C23/24; B02C19/00; B02C19/0012; B02C19/0018; B02C19/0025; B02C19/0056; B22; B22F; B22F9/00; B22F9/02; B22F9/04; Y; Y10; Y10S; Y10S241/00; Y10S241/14
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
112 words
A method of comminuting rare earth metallic particulate comprising the steps of: impacting the particulate against at least one impacting surface in a treatment zone by projecting the particulate under centrifugal force against said surface at a velocity sufficient to cause comminution of at least a portion of the particulate; maintaining at least the treatment zone and the impact surface in a temperature range which inhibits oxidation of the particulate while promoting fracture of the particulate; and, employing an inert gaseous medium in the treatment zone to prohibit combustion of the impacted particulate and having significantly low concentrations of oxygen and water vapor so as to substantially eliminate oxidation of the particulate.
Claim 2
Independent Claim
112 words
A method of comminuting rare earth metallic particulate comprising the steps of: impacting the particulate against at least one impacting surface in a treatment zone by projecting the particulate under centrifugal force against said surface at a velocity sufficient to cause comminution of at least a portion of the particulate; maintaining at least the treatment zone and the impact surface in a temperature range which inhibits oxidation of the particulate while promoting fracture of the particulate; and, employing an inert gaseous medium in the treatment zone to prohibit combustion of the impacted particulate and having significantly low concentrations of oxygen and water vapor so as to substantially eliminate oxidation of the particulate.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein the particles are samarium cobalt particles and are projected at a speed of about 900 feet per second.
Claim 4
Dependent Claim
37 words
The method of claim 2 further including the step of reducing the sticking of the projected particulate against a wall, in part defining the treatment zone, by having the wall provided with a highly polished, non-sticking surface.
Claim 5
Dependent Claim
41 words
The method of claim 1 wherein said impacting step comprises comminuting the particulate so that it falls within a size range wherein the average diameter of the resulting comminuted particulate generally corresponds to a grain structure having a single magnetic domain.
Claim 6
Dependent Claim
23 words
The method of claim 4 including the preliminary step of selecting particulate in a size range between about 60 mesh to 100 mesh.
Claim 7
Dependent Claim
13 words
The method of claim 4 wherein the particulate is a samarium cobalt alloy.
Claim 8
Dependent Claim
17 words
The method of claim 2 wherein said inert gas maintains said temperature range in the treatment zone.
Claim 9
Dependent Claim
39 words
The method of claim 7 wherein said temperature range maintained in the treatment zone during impacting is up to about 100° F. so as to substantially reduce oxidation of the particulate which would otherwise increase with increases in temperature.
Claim 10
Dependent Claim
18 words
The method of claim 8 wherein the treatment chamber temperature is not allowed to rise above room temperature.
Claim 11
Dependent Claim
25 words
The method of claim 9 wherein the gas in the treatment chamber temperature does not inhibit operation of temperature sensitive components associated with the process.
Claim 12
Dependent Claim
28 words
The method of claim 7 wherein the inert gaseous medium is nitrogen introduced to said chamber at a temperature that maintains the treatment chamber within said temperature range.
Claim 13
Dependent Claim
18 words
The method of claim 11 wherein the concentration of both oxygen and water vapor is about 10 ppm.
Claim 14
Dependent Claim
26 words
The method of claim 1 wherein the concentration of oxygen is less than 100 ppm and the concentration of water vapor is less than 100 ppm.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-02-09 | 1990-08-11 | 1991-02-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-09 | 1994-08-11 | 1995-02-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-09 | 1998-08-11 | 1999-02-10 | $7700.00 | Window Closed / Lapsed |