Electric heating – Metal heating – By arc
Reexamination Certificate
1999-07-23
2001-12-11
Elve, M. Alexander (Department: 1725)
Electric heating
Metal heating
By arc
C219S121610, C219S121620, C219S121680, C219S121710, C219S121800, C219S121810, C219S121730
Reexamination Certificate
active
06329632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and device for machining holes or shapes of varying profile in a mechanical workpiece using an excimer laser. It is applicable in particular in aeronautical engineering to the piercing of cooling holes in the vanes and combustion chamber of a turbine engine.
2. Summary of the Prior Art
It is known to machine holes of varying profile using an electro-discharge machining (or EDM) technique. This technique has the major disadvantage of requiring the use of an electrode having a shape which is identical to the shape required for the hole that is to be made, this electrode itself having to be machined. Furthermore, this machining process is too slow.
The piercing of holes of varying profile using a laser beam and means for rotating the beam about the generatrix of a cone is also known, such as from French patent No. 2637524. The hole produced is funnel-shaped, but the dimensions of the conical part and the length of the cylindrical part downstream of the conical part are difficult to control in an industrial process.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and a device for machining holes or shapes of varying profile that allows the drawbacks of the known methods and devices to be overcome.
For this purpose, the invention makes use of an excimer laser. Machining is performed without relative displacement of the laser beam with respect to the mechanical workpiece. Instead, the beam emitted by the excimer laser is shaped by inserting, in an unfocussed part of the beam path, a diaphragm or a screen which has an aperture of predetermined shape so that only a beam whose cross section is the desired size and shape is allowed to pass.
More particularly, according to one aspect of the invention, a device for machining a hole or a shape of any cross section in a mechanical workpiece comprises an excimer laser which emits a beam in the form of pulses, a device for focussing said beam, and a screen disposed between the excimer laser and the beam focussing device, said screen being provided with an aperture having a predetermined shape and said screen being movable in a plane perpendicular to the laser beam.
Alternatively, a diaphragm comprising variable-aperture shutters may be used in place of the screen.
According to a further aspect of the invention, a method of machining holes or shapes of varying profile in a mechanical workpiece using an excimer laser comprises the steps of emitting a laser beam in the form of pulses toward the mechanical workpiece that is to be machined, blocking off part of the laser beam to select a predetermined cross section of said beam, and automatically varying the cross section of the laser beam in real time during machining according to the profile of the hole that is to be made in the workpiece and in accordance with a predetermined variation law.
Preferred features and advantages of the invention will become apparent from the following description of the preferred embodiments, given by way of non limiting example, with reference to the appended drawings.
REFERENCES:
patent: 5016149 (1991-05-01), Tanaka et al.
patent: 5585019 (1996-12-01), Gu et al.
patent: 5656186 (1997-08-01), Mourou et al.
patent: 6034349 (2000-03-01), Ota
Fournier Gérard Albert Félix
Vigneau Joël Olivier Alfred Abel
Elve M. Alexander
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Societe Nationale d'Etude et de Construction de Moteurs d&a
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