Turning – Process of turning
Patent
1983-12-22
1986-01-14
Vlachos, Leonidas
Turning
Process of turning
82 34R, 29DIG63, 29DIG87, 29DIG93, 239291, 239296, 239558, 407 11, 408 56, 408 61, B23B 100, B23Q 1100
Patent
active
045639248
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the technology of using ceramic cutting tools and control of conditions surrounding the use. This application is related to copending U.S. application Ser. No. 522,571, filed May 20, 1983, and assigned to the assignee of this invention.
BACKGROUND OF THE INVENTION AND PRIOR ART STATEMENT
As demonstrated in U.S. patent application Ser. No. 522,571, assigned to the assignee of this invention, the wear life of a substantially dense nonoxide ceramic, which is movingly interfaced at high temperatures or speed with a metal (of the type that forms a compound containing a metal oxide under the temperature conditions prevailing at the interface with the ceramic member), can be substantially improved by removing oxygen from between the ceramic member and the metal during such interfacing. In the referenced patent application, it was stated that a stream of inert gas, preferably nitrogen, should be directed at the cutting interface to reduce the presence of oxygen there, by at least 60% and optimally 100%. However, the ability to exclude oxygen at the higher percentages in this range is not easily obtained. If the flow of inert gas is from a source such as a nozzle, and is relatively slow so as not to consume a high quantity of the inert gas during the period of cutting, the rotation of the workpiece being cut sets up a boundary layer wind which blows the inert gas away from the workpiece surface, allowing oxygen or air to reach the workpiece in undesirable amounts. If the flow of inert gas is increased in intensity, such as by use of a needle-like jet, the suction created behind the high speed gas jet brings in oxygen or air, again exposing the workpiece to undesirable quantities of oxygen or air.
What is needed is an apparatus and method by which an inert atmosphere may be flowed into place at the interface of a cutting tool and rotating workpiece without eventual substantial displacement by air or an oxygen bearing gas.
SUMMARY OF THE INVENTION
The invention is an apparatus and method for reducing oxygen concentration at the interface between a cutting tool and a relatively rotating metal workpiece. The invention comprises a supporting means for holding the cutting tool in a predetermined position relative to the workpiece, and means positioned adjacent the interface for displacing the ambient atmosphere in the zone. The flow means is advantageously made effective to direct a plurality of discrete flows of inert gas between the cutting tool and workpiece in a manner to substantially reduce the oxygen concentration in the zone to a predetermined level, preferably by displacing the ambient atmosphere in the zone by at least 90%. The oxygen concentration the zone can be 5% or less when employing a plurality of streams or flows of inert gas, a first of which streams is directed closely adjacent the interface and at least a second of the streams is directed to partially surround the first stream.
In one embodiment, the streams of inert gas are directed by nozzles, at least certain ones of the nozzles having an axis substantially tangent to the contact of the tool with the workpiece, the other nozzles having axes parallel to said certain nozzles, and said nozzles each having an axis normal to a radius of the workpiece passing through said contact.
In another embodiment, the oxygen concentration in the zone may be reduced to a further level, at or below 1%, by employing flows of inert gas which are arranged in two concentric rings, the axes of said rings being coincident with a radius of said workpiece passing through said cutting tool contact. Preferably, the inert gas flow through the outer of said two rings has a lower flow rate than the inert gas passing through the innermost of said concentric rings. Advantageously, a low flow rate is characterized as being about one liter per minute and a fast flow rate is characterized as at least 10 liters per minute.
SUMMARY OF THE DRAWINGS
FIG. 1 is an elevational view of a mounting assembly for a cutting tool used to machine
REFERENCES:
patent: 2716914 (1955-09-01), Pigott
patent: 3526362 (1970-09-01), Jackson
patent: 3773262 (1973-11-01), Sparling
patent: 3990332 (1976-11-01), Flom et al.
patent: 4179486 (1979-12-01), Lange
American Machinist, May 24, 1954, pp. 155-159, "Machining Titanium with Coolants".
Runkle Franklin D.
Tennenhouse Gerald J.
Ford Motor Company
Kearns Jerry
Malleck Joseph W.
May Roger L.
Vlachos Leonidas
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