Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2001-01-19
2003-06-03
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S620000, C073S643000, C073S655000, C073S634000
Reexamination Certificate
active
06571633
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a system and method for guiding a beam of light through the orthogonal axes of a mechanical positioning system for directing the beam at an object for ultrasonic testing, and more particularly, to a system and method for delivering a laser beam generated by a remote laser source through a gantry positioning system for use in detecting material defects of a test object using ultrasonic techniques.
BACKGROUND INFORMATION
It is desirable for a variety of applications to provide for mechanically directing a laser beam to any location within a predetermined volume. Many of these applications are tailored specifically for use within industrial manufacturing applications employing automated, robotics systems. Over the past several decades, the advent of robotics and laser light source technologies have led to many integrated systems for assembly line manufacturing . For example, robotics assembly systems incorporating laser technologies are very typical in automobile and even aircraft manufacturing plants for performing such tasks as welding.
For many systems, a robotic or gantry positioning system having a mechanical armature is often used to direct a laser beam to a variety of locations of a single workpiece. This armature itself provides for precision directing of the laser beam from the end of the mechanical armature. A laser beam delivery system is normally integrated into the gantry positioning system (GPS), particularly into the mechanical armature, for directing the laser beam from the end of the mechanical armature to any location within a predetermined volume. Specifically, the laser beam is then directed to portions of a workpiece and often from various fields of view for welding, cutting, ablating, or any variety of applications employing a laser beam. While the concept of incorporating a laser beam delivery system into a mechanical armature system for delivering to a workpiece is known to those skilled in the art, the methods and manners for accomplishing this goal may be very diverse.
Various technologies employ a method or system for directing a laser beam through a robotics system, e.g. U.S. Pat. No. 4,661,680 “End-of-arm tooling carousel apparatus for use with a robot” by R. L. Swensrud; U.S. Pat. No. 4,659,902 “Robot laser system” by R. L. Swensrud et al.; U.S. Pat. No. 4,539,462 “Robotic laser beam, delivery apparatus” by D. J. Plankenhorn. These technologies generally employ a plurality of tubular members, optically coupled to one another, through which a laser beam passes for directing the laser beam from the end of a GPS or “orthogonal axis manipulator system” (See Swensrud U.S. Pat. No. 4,659,902). These optical components for directing the laser beam through the laser beam delivery system may include spherical joint lenses or precision aligned mirrors at the pivotal connections of the armature of the GPS.
For GPSs that are relatively small in size and whose mechanical armature is light in weight, the directing of the laser beam through the armature may be provided by using a number of mirrors that are permanently located in fixed positions at the junctures of the mechanical armature. However, larger GPSs may include large carriage assemblies common to industrial workshops and other similar settings. The mechanical members of the GPS may bend and stress significantly depending on the position of the carriage assembly and the shape of the mechanical armature. These bends and stresses may result in laser beam steering within the segments of the GPS and ultimately may result in obstruction of the laser beam altogether. This stems from the fact that the mirrors are firmly attached to the mechanical armature of the GPS, and as the shape of the GPS bends, the mirrors: may come out of alignment. A common solution for this problem in those laser beam delivery systems that employ air cavity propagation of the laser beam in enclosed segments along the axes of the GPS is to require significantly large dimensioned enclosed segments to accommodate the substantial bending associated with a large GPS while maintaining a large working envelope. Additionally, larger mirrors may be required to accommodate and correct for this beam steering to ensure unobstructed transmission of the laser beam. This requirement may substantially increase the size of the laser beam delivery system within the GPS. This may also increase the cost for materials required for the laser beam delivery system as well as further complicate the integration of the laser beam delivery system into the GPS given its larger bulk.
Small GPSs may not suffer from such problems as severe bending and stresses given their relatively small size, yet the intrinsic different needs of various sized GPSs makes utilizing a single laser beam delivery system in variety of different sized GPSs extremely difficult. GPSs which are relatively small in size and light in weight do not require large members and mirrors through which a laser beam propagates; large GPSs require either a large working enveloped through which the laser beam travels or some additional modification to accommodate the bending of the mechanical armature of the GPS to maintain unobstructed laser beam propagation. However, some lasers suffer from beam pointing instabilities. This requires corrective alignment procedures to maintain long-term operation when employing long distance free space beam delivery methods. An approach for providing laser beam delivery through a gantry positioning system that is scaleable and adaptable to a variety of sizes and shapes of GPSs irrespective of the overall size and weight of the armatures of the GPS is desirable.
While a large GPS may comprise a laser beam delivery system with large members through which a laser beam propagates to overcome the problems of beam obstruction resulting from bending and stressing of the GPS as it changes shape, as described above, many problems remain in that the laser beam delivery system must be designed specifically for the GPS in question. The larger the size and heavier the weight of the GPS, the more beam steering may occur resulting in possible beam obstruction requiring larger members and mirrors to ensure unobstructed beam transmission. Such a solution to beam obstruction requires the size of the members through which a laser beam propagates be tailored specifically to the size, weight, and operating constraints of GPS in question.
Ultrasonic testing is a method which may be used to detect material defects in a objects comprised of various materials. A common application for ultrasonic testing is to detect inhomogeneities in composite materials. Ultrasonic testing may be used to serve a variety of industrial needs including identification of defects in manufactured goods for tuning of manufacturing processes. Manufacturers of products comprising composite material may wish to identify imperfections in their articles of manufacture to modify their manufacturing process to strive for greater repeatability and efficiency in their process or simply to identity problem areas within their process. Composite materials comprise many critical components within modern, high performance aircraft, and are becoming more common in terrestrial applications such as the automotive industry. Composite materials are desirable for many of their inherent attributes including light weight, high strength, and stiffness. Particularly for aircraft application, those composite material components, which may be large and complex in shape, are often flight critical necessitating strict assurance of material and structural integrity.
Unfortunately, these materials are sometimes fabricated with imperfections or develop them after several hours of use. These material defects may appear as a delamination of the surface of the material, porosity, an inclusion, debonds between bonded sub-components, or a void within the component itself. This inhomogeneity in the structure severely weakens it, providing a situation which might result in catast
Hughes & Luce LLP
Lockheed Martin Corporation
Miller Rose M.
Williams Hezron
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