Electric heating – Metal heating – By arc
Patent
1982-09-07
1985-02-26
Shaw, Clifford C.
Electric heating
Metal heating
By arc
250202, 318577, B23K 912
Patent
active
045019509
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to automated welding apparatus and more particularly to an improved optical seam sensor for use in a system adapted both for tracking a seam to be welded and for deriving information regarding the configuration of the seam.
2. Background Art
The desirability of removing the human operator from the immediate vicinity of a welding operation is widely recognized throughout industry. Accordingly, extensive and well publicized efforts have been made over the past decade to develop suitable machines capable of automatically manipulating a weld torch relative to a seam or groove to be welded. Presently available automated welding systems are insufficiently precise in their positioning of the weld torch and in their ability to deposit an optimum amount of weld material. This has limited the use of most currently available automated welding systems to spot welding and to distributed weld applications wherein the workpieces can be precisely fixtured to ensure accurate positioning and uniformity of the weld bead.
Additional efforts have been made to apply automatic guidance and control techniques to distributed weld situations; see for example, U.S. Pat. No. 3,924,094 for "Welding Control Arrangement with Orbital Torch-Mounted Transducing Assembly" which issued to Howard A. Hansen et al. on Dec. 2, 1975. While the mechanical weld-seam sensor developed by Hansen et al. has proved satisfactory for many applications, there exists a continuing need both for improved seam tracking capability, such as the ability to perceive and follow right angle turns, and for improved capability to analyze varying seam configurations, such as vertical and non-vertical seam walls and small variations in seam width and depth.
Substitutes for mechanical sensors typically incorporate optical recognition systems, scanning electron beams, eddy current establishing and monitoring systems, and the like. Many optical sensors proposed heretofore have encountered difficulty in welding applications owing to the intense glare from the welding operation tending to swamp the optical signal that is used for tracking purposes. In addition, existing optical tracking systems are typically dependent upon variations in the intensity of the received signal. Scale and surface irregularities can greatly affect the intensity of the reflection and hence create a noise factor and numerous difficulties. One such optical intensity-type system is shown in U.S. Pat. No. 3,757,125 for "Optical Tracking Apparatus" which issued to Okada et al. on Sept. 4, 1973.
An electron beam scanner utilizing a rotating scan path is disclosed in U.S. Pat. No. 3,775,581 for "Seam Tracking Method" which issued to Albert M. Sciaky on Nov. 27, 1973. In this system, a scanning electron beam is caused to rotate in a circular pattern about the seam to be tracked. Reflected and secondary emission electrons are collected by a nearby sensor. A sharp change in the number of observed reflected and secondary emission electrons occurs when the electron beam contacts the boundary of the seam. The points at which these sharp drops in the received signal are detected indicate the position of the seam relative to the center of the scan circle. A situation in which the center of the scan circle is offset relative to the center of the seam results in an unbalanced radian interval between the several sharp changes in signal intensity. The Sciaky system is effectively an intensity-dependent system, and, in common with the optical intensity dependent systems, lacks the ability to derive accurate information regarding physical characteristics of the seam, such as depth and wall configuration. Further, the sensing apparatus and weld torch utilized by Sciaky appear to be of fixed orientation relative to one another. This creates difficulties in following complex seam configurations.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention
REFERENCES:
patent: 2454959 (1948-11-01), Barnes
patent: 3135857 (1964-06-01), Von Voros
patent: 3757125 (1973-09-01), Okada et al.
patent: 3775581 (1973-11-01), Sciaky
patent: 3924094 (1975-12-01), Hansen et al.
patent: 3924095 (1975-12-01), Hansen et al.
patent: 3977793 (1976-08-01), Trotta
patent: 3993889 (1976-11-01), Sciaky
patent: 4021840 (1977-05-01), Ellsworth et al.
patent: 4225771 (1980-09-01), Justice et al.
patent: 4396832 (1983-08-01), Henderson
patent: 4417127 (1983-11-01), Nachev et al.
National Aeronautics & Space Administration-NASA Tech Brief, vol. 2, No. 4, Item 24, from JPL Invention Report 30-3809/NPO-14066, NASA Patent Specification-Multi-Channel Rotating Optical Interface for Data Transmission-77/101.
Publication from the Oct. 29, 1981 Edition of the Engineer Magazine.
Publication from the Sep., 1981 Edition of Product Engineering Magazine.
Publication from the Sep., 1981 Edition of Welding Design & Fabrication Magazine.
Caterpillar Tractor Co.
Noe Steven L.
Shaw Clifford C.
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