Electric heating – Metal heating – By arc
Reexamination Certificate
1999-11-09
2001-09-18
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121670, C219S121780, C219S121840
Reexamination Certificate
active
06291795
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates generally to laser systems and, more particularly, to a system for transmitting a high-power laser beam onto a workpiece for welding, cutting or other processing of the workpiece with an unfocused laser beam.
High-power, such as 2000 Watt average power, lasers have a wide variety of applications, such as precision drilling, cutting and welding of metal workpieces. Neodymium:Yttrium-aluminum-garnet (Nd:YAG) lasers are particularly useful for such purposes. The beam generated by a laser, such as a Nd:YAG laser, must be transmitted to a work station where the beam is directed onto the material of the workpiece. In the prior art, system comprising an assembly of mirrors, lenses and prisms is used to transmit the laser beam to the work station. While this type of arrangement functioned satisfactorily in some applications, such a system is bulky and the flexibility with which the beam may be maneuvered about the workpiece is limited.
Conventional focused welding techniques are known, such as an electron beam welding system which utilizes a gun which focuses an electron stream by manipulating a magnetic focus coil, or in the case of a laser which utilizes a focusing head or output coupler that comprises a series of lenses and mirrors for receiving an emerging laser beam from an end of a fiber optic cable and delivering and focusing such laser beam to a desired spot on the workpiece. A typical laser welding system uses at least one mirror to reflect the laser beam into the lens and at least one lens to focus the laser beam onto the workpiece.
However, in many instances the workpiece is accessible only through narrow openings. The size of the focusing head may prevent it from accessing the workpiece through the opening. This requires disassembling the components of the workpiece in order to perform the operation or prevents access altogether (cannot be welded).
Moreover, when a weld is made through a narrow opening, the resulting large beam diameter impinges on the sides of the opening. Further, the reach of the beam is limited and may only be to one half of a joint's length and thus requires that the weld be made with two passages-one from each side of the joint. Welding half of the joint at a time results in overlapping of the weld at the center and launching the beam from outside the narrow opening may cause impingement melting on the top of the opening.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a laser system for operating on a workpiece which is accessible through a narrow opening without having to disassemble the workpiece. Further, the present invention provides for a continuous pass weld and thus eliminates the need for multiple passes and overlap regions as well as eliminating impingement of the beam on other areas of the workpiece.
In accordance with the present invention, a system is provided for delivering a laser beam through a fiber optic cable onto a workpiece. The laser beam enters through a first end of the cable, propagates through the cable and emerges from the second end thereof. The fiber optic laser beam delivery system further comprises a blade which has a top portion and a bottom portion parallel to one another. The top portion has a curved front end which extends towards the bottom portion. The fiber optic cable overlaps the top portion of the blade and the emerging second end of the cable extends past the curved front end of the blade. The fiber optic cable is exposed and does not have any protective armor covering and/or poly/Kevlar® covering on the emerging second end of the cable. The emerging second end of the cable is polished to minimize beam diffusion and back reflection.
The blade supports and guides the fiber optic cable into an opening to access the joint to be operated on. The blade also supports a fiber burn back circuitry, as well as two gas tubes which delivers shield gas to the emerging second end of the fiber optic cable and a cover gas to the workpiece.
The present invention does not utilize a focusing head or output coupler which is conventionally attached to the second end of the fiber optic cable.
By removing the focusing head or output coupler and using, instead, a fiber optic cable having an exposed and polished end, very close positioning of the laser beam on the workpiece can be achieved even in a confined space.
Standoff distance is critical for this type of welding and is controlled by a CNC-3-axis fiber manipulator. By controlling the fiber standoff and travel speeds, welds with penetrations of up to 0.100 inches have been made in Inconel® 690 material.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.
REFERENCES:
patent: 4273127 (1981-06-01), Auth et al.
patent: 5129897 (1992-07-01), Daikuzono
patent: 5318023 (1994-06-01), Vari et al.
patent: 6110167 (2000-08-01), Cozean et al.
Jogerst James D.
Jones Gary L.
Knapp Mark C.
Heinrich Samuel M.
Marich Eric
The United States of America as represented by the United States
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