Tube Seam Weld Inspection Device

This invention relates to imaging and inspection devices and particularly to tubing weld seam inspection devices used in combination with conventional tube forming machines.

A tube forming machine is a device which takes strip stock from a roll and, through a series of operations, converts it into a welded tube. The first step of the process is edge conditioning where rust and uneven edges are removed. The strip then passes between a series of rollers mounted on shafts where a curve is formed in the strip. At every pass after that, the radii gets smaller so that the strip takes the form of a cylinder in preparation for welding.

In a typical manufacturing operation, the tubing thus formed is moving along its longitudinal axis at a high rate of speed and, therefore, timely inspection is critical. Without such timely inspection, tremendous amounts of material would be wasted due to the improper seam alignment and the resulting low quality seam weld.

Ideally when tubing is formed from strip stock on conventional tube forming machines, both edges of the strip are joined in the weld box at the same height. Previous to the present invention, the most common method for inspection for edge alignment was for the operator to hold his gloved hand on the weld seam. This was not a desirable condition for safety and accuracy reasons. Off-line, the inspector could cut samples and inspect them under a microscope, but that required too much time to detect and take corrective action. What was needed was an on-line, non-contact, real-time monitoring system to measure edge alignment. However, as a result of the edge conditioning, tube forming, and welding processes, the environment becomes very dirty, and it is in this dirty environment that the inspection is expected to take place.

The present invention provides a low cost, simple and easy to implement vision system to detect edge misalignment, and is designed to operate in a dirty environment. In accordance with the present invention, a live image is displayed on a monitor.

Imaging and inspection systems are known in the prior art. See, for example, Shiozumi et al., U.S. Pat. No. 4,734,766; Tsikos, U.S. Pat. No. 4,979,815; Heesemann, U.S. Pat. No. 4,839,994; Rottenkolber et al., U.S. Pat. No. 4,111,557; White, U.S. Pat. No. 4,498,778; Wang et al., U.S. Pat. No. 4,812,614; Clocksin et al., U.S. Pat. No. 4,616,121; Masaki et al., U.S. Pat. No. 4,492,847; Nayar et al., U.S. Pat. No. 4,988,202; Kremers et al., U.S. Pat. No. 4,596,919; Case, Jr. et al., U.S. Pat. No. 4,542,279; Povlick et al., U.S. Pat. No. 4,590,356; Fryer New Product Bulletin, 1989, Subject: Light Sectioning; and Oldelft, The Robot's Eye, undated.

The present invention constitutes a significant improvement over the prior art because it is relatively low cost, easy to install, and effective for the purpose intended, i.e., readily to show that the seam weld produced by a conventional tube forming machine is out of specification. For instance, the prior art shows lasers used to monitor seams in manufacturing processes, but the prior art systems involve complicated laser scanning techniques and monitoring techniques for laser scanning, or complicated algorithms to analyze the data provided by the laser image.

According to the present invention an apparatus is provided for visualizing a longitudinal seam weld on a moving tube in a conventional tube forming environment, wherein the apparatus comprises means for projecting a steady plane of light on the tube seam weld as the tube moves longitudinally past the projecting means, means for imaging a reflection of the projected light from the tube seam weld, and means for displaying the reflection image. It also provides an apparatus for visualizing a seam weld on a moving tube, wherein the apparatus comprises a laser light source, lens means for forming the laser light into a steady plane of light, a plurality of mirrors to direct the plane of light to intersect the tube seam weld and to direct the reflection of the intersection to a camera, and a monitor to display the reflection imaged by the camera.

The present invention also provides an apparatus for visualizing a seam weld on a tube moving longitudinally in the direction of its axis, wherein the apparatus comprises a container formed to include an interior region and an aperture facing the moving tube and its seam weld, the container being positioned in spaced-apart relation to the tube seam weld. It further comprises light means for providing a planar light, the light means being mounted in the interior region, means for directing the planar light out of the interior region of the container through the aperture to intersect the tube seam weld, wherein the directing means are mounted in the interior region. It further comprises means for imaging the light pattern on the tube seam weld, the imaging means being mounted in the interior region, means for displaying the imaged points of intersection connected to the imaging means, the displaying means being positioned outside the container, source means for supplying electrical power to the light source and the imaging means, the power source means being mounted in the interior region, and transparent means for covering the aperture to keep workplace contaminants out of the interior region.

The present invention also provides an apparatus for optically determining departures in shape of a workpiece, where the apparatus comprises a container formed to include an interior region and an aperture, the container being positioned in spaced-apart relation to the workpiece, a planar light source mounted in the interior region, and a camera mounted in the interior region. It further comprises a plurality of mirrors arranged in the interior region to direct the planar light through the aperture to intersect the workpiece and to direct the reflection of the light pattern which passes through the aperture toward the camera, a power supply mounted in the interior region to provide electrical power to the apparatus, and a transparent aperture cover attached to the container in an aperture closing position to keep workplace contaminants out of the interior region.

The present invention further provides an edge alignment measuring system for inspecting alignment of a pair of edges of a strip that abut one another at a seam weld to form a tube, wherein the system comprises means for projecting a steady plane of coherent light across the seam of the tube to produce a first light pattern on one of the edges and a second light pattern on the other edge. It further provides means for displaying the first and second light patterns side-by-side to indicate a discontinuity between the first and second light patterns so that misalignment of the edges relative to one another is detected.

Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.

FIG. 1 shows an illustrative embodiment of the weld seam inspection device, partially broken away, in position on a tube forming and welding production line;

FIG. 2 is a representation of three rollers in a weld box used to control the match of a seam tube;

FIG. 3 is a sectional view of an alternative embodiment of the imaging system showing the layout of components;

FIG. 4 generally shows a spaced-apart relationship between the weld seam inspection device and the tube;

FIG. 5 is a view looking down on the tube from the inspection device along the line 5--5 of FIG. 4 showing the light pattern on the tube;

FIGS. 6, 7, and 8 show variations of the light pattern based on degree of match and amount of scarf;

FIG. 6a is a cross section of a tube having a good match with a deep scarf;

FIG. 6b shows the light pattern associated with the match and scarf conditions of FIG. 6a;

FIG. 7a is a cross section of a tube having a poor match with a shallow scarf;

FIG. 7b shows the light pattern associated with the match and scarf conditions of FIG. 7a;

FIG. 8a shows a good match with a good scarf; and

FIG. 8b shows a light pattern associated with the match and scarf conditions of FIG. 8a.

An illustrative embodiment (FIG. 1) of a weld seam inspection device 10 for tube welding comprises an imaging system 12 and a monitor 14 to display an image. The imaging system 12 comprises a container 16 formed to include an interior region 18 and an aperture 19. Holding means 17 is provided to hold the container 16 in a fixed position above a moving tube 24 as shown in FIG. 1. A transparent aperture cover 21 is attached to the container to keep contaminants out of the container. A planar light source 20, such as the LaserMax, Inc. Model MDL-200-670-5 or a Melles Griot Model S1167/P Line Projector, is attached to the interior region 18. The plane of light begins as a spot and cylindrical lens 25 spreads the light at a 30.degree. angle so that it is about 3 inches wide at 6 inches from the source. A mirror 22, also attached to the interior region 18, reflects the planar light from the source 20 through the aperture 19 to intersect a tube 24 forming a light pattern 26. A second mirror 28 attached to the interior region 18 directs an image of the light pattern 26 passing through the aperture 19 into a camera 32, such as the Video Runner Model 1020 manufactured by Marshall Electronics, Inc. of Culver City, Calif., which is attached to the interior region 18. A conventional video monitor 14 is electrically connected to the camera 32 and displays the image of the light pattern 26 received by the camera 32. Thus, the container 16 holds the light source 20, mirrors 22 and 28, and camera 32. Therefore, as shown in FIG. 3, container 16 acts as a means for holding the light projecting and reflection imaging means in a fixed position relative to the longitudinally moving tube 24. In an alternative embodiment, as shown in FIG. 3, a power supply 34 is also mounted in the interior region 18 and provides electrical power to components of the imaging system 12. It will be appreciated that the power supply need not be so mounted, but rather power could be supplied by means connected to an external source.

FIG. 1 illustrates the principles involved in the present invention, and it will be appreciated that the light source 20, mirror 22, aperture 19, mirror 28 and camera 32 may be located and positioned at various angles and distances in accordance with the present invention. It has been found that the 45.degree. projection and 45.degree. reflection is ideal and preferable for the tube forming machine environment in which the present invention works. In particular, the present invention is used in combination with conventional tube forming and welding machines and is preferably made such that it will fit in the very tight and irregularly shaped area just above the tube after it is welded and scarfed.

In operation, strip material 36 is fed into a tube shaping apparatus 38 and then into a welding apparatus 40. It will be appreciated that the shaping apparatus 38 and welder 40 ar.RTM.illustrated diagrammatically in FIG. 1, and that these apparatus are very well-known and need not be discussed in detail. There are several tube forming machine suppliers from which such machines can be acquired. Typical suppliers are Yoder Manufacturing Co., Bedford Heights, Ohio and T&H Machine Co., Addison, Ill. Upon exiting the welding apparatus 40 the tube 24 passes under a scarfing tool 42 which is moved up and down by an adjustment mechanism 44 to remove the desired amount of scarf 46 from the weld 43. After scarfing, the tube 24 passes under the imaging system 12 where a steady plane of light 23 is directed onto the tube 24 forming a light pattern 26. The light pattern 26 is imaged by the camera 32, and the image is displayed on a monitor 14.

In the alternative embodiment of FIG. 3, the planar light source 20 directs a plane of light 23 to the first mirror 22 which reflects the plane of light 23 through the aperture 19 and onto the tube 24 illustratively and preferably at an angle of incidence of 45.degree. to the vertical. The reflection of the light pattern 26 reflected from the tube 24 illustratively and preferably at an angle of 45.degree. to the vertical is received by the mirror 28 through the aperture 19 and directed to the lens 30 and camera 32. It will be appreciated that the light source 20 and camera 32 could be positioned to obviate the need for mirrors 22 and 28. However, the embodiment of FIG. 3 represents a compact arrangement suitable to the typical tube forming machine workplace environment. The monitor 14 displays the image viewed by the camera 32, where it is interpreted by an operator to determine the degree of match and the degree of scarf. When the degree of scarf is determined to be outside of acceptable limits, the operator can adjust the scarfing tool 42. When the edges of the seam 52 do not match properly, the operator can adjust the weld box 47 located within the welding apparatus 40 by adjusting the rollers 48, 49 and 50 inwardly or outwardly as necessary. It will be appreciated that such tube forming machine rollers 48, 49 and 50 are conventional.

FIG. 6b shows the light pattern 26 on the tube 24 when the tube seam edges 58 match properly, but where the scarfing tool 42 cut too deep, as indicated by the relatively long straight portion 56 of the light pattern 26. FIG. 6a shows the cross section of a tube with the match and scarf conditions that match the light pattern of FIG. 6b.

FIG. 7b shows the light pattern 26 on the tube 24 when the tube seam edges 58 do not match properly, producing a discontinuity 54 in the light pattern 26. The relative shortness of the straight portion of 56 the light pattern 26 indicates a shallow scarf. FIG. 7a shows the cross section of a tube with the match and scarf conditions that match the light pattern of FIG. 7b.

FIG. 8b shows the light pattern 26 on the tube 24 when the tube seam edges 58 match properly and the relative shortness of the straight portion 56 of the light pattern 26 indicates a good scarf. FIG. 8a shows the cross section of a tube with the match and scarf conditions that match the light pattern of FIG. 8b.

Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.