APPARATUS AND METHOD FOR INSPECTING GLASS SHEETS

Abstract: A pair of bent glass sheets (28, 29) are supported along a peripheral edge portion (26) in a nesting fixture (20) below a gap detector (21) for detecting ''good'' and ''bad'' nested pairs of glass sheets. The gap detector includes a laser beam source (34) for directing a light beam (35) at an outer surface of the nested sheets in a line generally perpendicular to a longitudinal axis of the sheets. A reflected beam (39) from the surface of the sheets is sensed by a row of cameras (43) which generate an image of the contours of the sheets. The image is compared with predetermined limits to detect unacceptable gaps between the sheets or unacceptable contour deviations.

Description: Description APPARATUS AND METHOD FOR INSPECTING GLASS SHEETS Technical Field The present invention relates generally to an inspection apparatus for a glass sheet production line and, more particularly, to a device for determining the nestability of pairs of bent glass vehicle windows. Background Art In the known methods of making and shaping glass, defects may inadvertently be produced in the glass which render the glass optically imperfect. Defects may also be produced in the glass during subsequent manufacturing operations such as during a bending operation, for example. Among the optical imperfections that may be produced is surface distortion. Surface distortion, as the term is used herein, generally refers to variations in the desired surface contour, i.e. concave and convex portions. Surface distortion in glass causes the glass surface to reflect a distorted image. For example, convex portions shrink the image and concave portions magnify the image. When excessive distortion is present, the distorted images detract from the usefulness of the glass as a vehicle window. In addition, when laminated windshields are being produced, the two pieces of curved glass must nest properly or gaps will be formed between the facing surfaces which render the final laminated assembly useless. In addition to other methods , one approach which has been proposed for detecting surface distortion of a piece of glass is disclosed in U.S. Patent No. 3,857,637. This patent shows an inspection apparatus which utilizes a light source and a position sensing photodetector for detecting concave and convex defects on the inspected surface. The light source, such as a continuous laser, directs a beam of light on the upper surface of a glass plate traveling at a constant speed along a predetermined path relative to the light source. The position sensing photodetector is mounted to detect the portion of the light beam reflected by the upper inspected surface of the glass plate. If the inspected surface is flat, the reflected portion of the beam will be received by the photo detector along a predetermined reference line. When the light beam is reflected from concave or convex portions in the surface, the reflected beam will be displaced from this reference line. The inspection apparatus includes means responsive to the detector output signals to produce a surface flatness profile showing the nature of the surface curvature and the altitude of the curvature. While such an apparatus is capable of determining the surface flatness of a sheet of glass, there is no means provided for analyzing the data for determining whether the distortion level of an inspected sheet of glass is unacceptable. Also, such an apparatus is subject to errors in changes in glass position during the measurement process. U.S. Patent No. 2,253,054 discloses a basic system for determining the flatness of glass including deviations from parallelism of two surfaces. A light source is directed at an angle toward a surface and the reflected beam is focused on a screen whereby a curved surface will create a double image. With this device, it is possible to measure and distinguish both deviations in flatness over one surface and deviations from parallelism of the two surfaces known as "wedging" . Collimated light is passed through the two marginal zones of a weak cylindrical lens whose longitudinally central portion has been masked off. The light strikes the surface to be tested and is reflected back through the lens to form an astigmatic image on a ground glass or similar viewing screen positioned at a distance from the lens equal to the focal length of the double lens system. In a case of "wedging", each marginal zone separately forms two distinct line images whereas a distorted but unwedged glass sample give two images only when both sides of the lens are used . U.S. Patent No. 3,799,679 discloses a glass distortion scanning system having a light source such as a laser for generating a beam of light having a finite width at an oblique angle with a glass ribbon. The reflected images from the two surfaces of the glass are detected by a scanning photomutiplier tube for measuring the rate of change of the center-to-center spacing of the two images. The center-to- center spacing of the reflected beams varies as the distortion of the glass varies, and the rate of change of the spacing is a measure of the refractive power of distortion in the glass . In U.S. Patent No. 4,306,808, there is shown an optical flaw detection system utilizing a laser beam which line scans the surface of a glass ribbon. The beam is incident at a high angle with respect to the normal. Deviation of the light transmitted through the glass ribbon is used as an indication of a defect. In U.S. Patent No. 4,310,242, there is shown an apparatus for measuring the optical characteristics of a contoured windshield. A beam of light is projected along an optical axis onto a beam splitter. The reflected segment passes through the transparent body and is reflected back along the same path toward the beam splitter by a retro-reflective screen lying at the image plane of the beam. The portion of the reflected beam passing directly through the beam splitter is detected by an optical sensor in substantial orientation with the axis of the beam reaching it. Distortions and multiple imaging are detected by shape changes and images, respectively, in a pattern of opaque areas superimposed on the originating beam. It is much more difficult to inspect a contoured sheet of glass for the proper shape than a flat sheet of glass. The inspection process is further complicated where two sheets of contoured glass must nest properly in order to form a laminated structure with an intervening sheet of plastic material. Currently, gaps due to mismatched contours of the facing surfaces can only be detected after the laminated windshield has been formed at a substantial cost in labor and materials. Thus, it is desirable to determine the nestability of two sheets of contoured glass prior to the lamination process. Disclosure of the Invention The present invention concerns a method and apparatus for inspecting pairs of bent or contoured glass sheets for nestability in a process for manufacturing laminated windshields for vehicles. Two stacked sheets are placed in a nesting fixture which engages a peripheral edge portion of the sheets. A laser beam is directed at an outer surface of the nested sheets and the reflected ' beam is detected. The shape of the reflected beam is sensed to detect defects. In a preferred embodiment, the nesting fixture supports the nested sheets in a generally horizontal plane. A camera array is positioned above and directed toward the upper surface of the sheets to receive the reflected light. The laser beam is scanned along a line generally perpendicular to the longitudinal axes of the sheets and parallel to the camera array. A gap between the sheets is sensed as two spaced apart lines and a surface distortion is sensed as a deviation from an envelope desired profile. Brief Description of the Drawings In the accompanying drawings: FIG. 1 is block diagram of a laminated windshield manufacturing line incorporating an inspection apparatus for nested pairs of glass sheets in accordance with the present invention; FIG. 2 is a combined perspective view and block diagram of the inspection apparatus shown in FIG. 1; FIG. 3 is a combined side elevation and block diagram of the inspection apparatus shown in FIG. 2; FIG. 4 shows various images generated by the inspection apparatus of FIG. 2; FIG. 5 is block diagram of a laminated windshield manufacturing control system incorporating the inspection apparatus according to the present invention; FIG. 6 and FIG. 7 are representations of images generated on the monitor of FIG. 5; and FIG. 8 is flow diagram of the method of inspecting glass sheets in accordance with the present invention. Statement of the Invention In accordance with the present invention there is provided a method of inspecting bent transparent sheets comprising the steps of: a) engaging a peripheral edge portion of at least two transparent sheets with a nesting fixture and supporting the sheets in a nested position; b) directing a light beam at an outer surface of the nested sheets; c) scanning the light beam in a predetermined path across the outer surface to generate a reflected beam; and d) sensing the reflected beam and identifying the nested transparent sheets as "good" or "bad". Also, in accordance with the invention, there is provided an apparatus for inspecting nested sheets of transparent material, comprising: a nesting fixture for engaging a peripheral edge portion of at least two nested sheets of transparent material; a light beam source for generating a light beam; means for directing said light beam in a predetermined scanning path across an outer surface of the nested sheets to generate a reflected beam; and means for sensing said reflected beam generated by the reflection of said light beam from the surfaces of the nested sheets and identifying "good" and "bad" nestability of the nested sheets . Description of the Preferred Embodiment There is shown in FIG. 1 a laminated windshield manufacturing line 11 which incorporates a nestability inspection station according to the present invention. Sheets of glass to be formed into windshields exit from a furnace 12 at one end of the line 11 and travel in a direction identified by an arrow 13 toward an opposite end of the manufacturing line. The furnace 12 heats a series of individual glass sheets (not shown) each of which enters a bending press 14 after exiting the furnace 12. The bending press forms the desired contours in the sheet of glass which then moves to a blasthead station 15. The blasthead station 15 generates a predetermined pattern of cooling air for tempering the glass sheets. In many instances, the sheets of glass utilized in a laminated windshield are not tempered and the blasthead station 15 is not utilized in the manuf cturing line 11. After the blasthead station 15, the sheets are subjected to cooling by a cooling fan in order to reduce the glass temperature and render them stable enough to be handled in subsequent operations. Next, the sheets of glass are transported by a conveyor 17 to a peripheral checking fixture 18. The fixture 18 engages the periphery of each sheet of glass to determine whether that sheet of glass will properly match the corresponding opening in a vehicle. The glass sheets are then transported by a flipper conveyor 19 which flips the sheets upside down and delivers them to a nesting fixture 20. The sheets are inspected as a stacked pair in the nesting fixture 20 by a gap detector 21 in accordance with the present invention. If the pairs of sheets pass inspection, they are transferred to a packing station 22 for further transport to an area where they will be laminated with sheets of plastic material to form laminated windshields. In a modern manufacturing process, it is important to gather information concerning process steps and characteristics of the product and issue commands to change the manufacturing processes. Thus, a host computer 23 can be provided as shown in FIG. 1. The host computer 23 is connected to a bus line 24 which also is connected to all of the stations and controls 12 and 14 through 22. Thus, the host computer 23 can receive information signals from and generate command signals to any of the stations and controls associated with the manufacturing line 11. There is shown in FIG. 2 the nesting fixture 20 and the gap detector 21 according to the present invention. The nesting fixture 20 includes a ground engaging base 25 attached to a generally upwardly extending perpherial support wall 26. The base 25 and the wall 26 are shown as being fixedly mounted on any suitable support surface such as a floor 27 of the manufacturing facility. Shown mounted on the nesting fixture 20, resting on the upper edge of the support wall 26, is a pair of contoured glass sheets 28 and 29 which are to be tested for nestability prior to lamination into a vehicle windshield. A track 30 extends in a generally horizontal direction parallel to the longitudinal axes of the glass sheets 28 and 29 represented by a line 28a extending from one side edge 28b to an opposite side edge 28c. The track 30 is spaced above the nesting fixture 20 and has opposite ends secured to any suitable supporting structure 31 which is fixed with respect to the floor 27. The gap detector 21 includes a carriage 32 which engages the track 30. The carriage 32 is movable from one end of the track to the other under the precise control of any suitable servo system. For example, a servo motor 33 can be controlled to move the carriage 32 along the track 30 to each of a plurality of positions with respect to the glass sheets 28 and 29. A light beam source 34 generates a light beam 35 to a scanning mirror 36. Typically, a laser beam source is utilized to generate a laser beam. The mirror 36 rotates in a plane which is perpendicular to the longitudinal axes 28a of the glass sheets 28 and 29. Thus, the laser beam 35 is reflected by the mirror 36 as an incident beam 37 and is projected onto the upper surface of the upper glass sheet 28. The speed of movement of the mirror 36 is such that the incident beam 37 forms a solid line 38 defining a scanning path typically between opposite edges, the top 28d and bottom 28e edges, of the glass sheet 28. The incident beam 37 is reflected from the upper surface of the glass sheet 28 as a reflected beam 39 which strikes a facing surface of a reflecting screen 40 in the gap detector 21. The reflected beam 39 is reflected by the reflecting screen 40 as an image beam 41. The reflecting screen 40 directs the image beam 41 through a lens 42 into a camera 43. As shown in FIG. 3, a side elevation view of the nesting fixture 20 and a bloc diagram of the gap detector 21, the scanning mirror 36 rotates about a pivot point 44 as symbolized by an arrow 45 to scan the beam 37 between opposite edges 28d and 28e of the stacked glass sheets 28 and 29. A plurality of the lenses 42 and cameras 43 are positioned in a row and are aimed to receive the image beam 41 at a plurality of predetermined positions as the image beam 41 is reflected by the reflecting screen 40. The row is generally perpendicular to the longitudinal axes 28a and generally parallel to the outer surface of the sheet 28. Thus, each of the cameras 43 senses a portion of the reflected beam 39 corresponding to a predetermined position along the line 38 shown in FIG. 2. Although not shown in the interest of clarity, the laser beam source 34, the scanning mirror 36, the reflecting screen 40, the lenses 42, and the cameras 43 are all mounted on the carriage 32 by suitable supports and travel with the carriage from one end to the other end of the track 30. Thus, the line 38 can be moved along the longitudinal axes 28a of the glass sheets from one side edge 28b to the opposite side edge 28c in order to scan all of the surfaces. Any conventional servo control mechanism can be utilized to rotate the gap detector 21 to maintain the required angle between the incident beam 37 and a plane including the line 38 and extending normal to the upper surface of the glass sheet 28 as the line 38 is moved along the axes 28a of the glass sheets 28 and 29. There is shown in FIG. 4 three images of the type formed on the reflecting screen 40 by the reflected beam 39. An image 46 represents a pair of the glass sheets 28 and 29 which not only nest together without any gaps, but are also contoured properly to form a "good" laminated windshield structure. An image 47 represents a "bad" nesting pair. An upper line 48 generated from the upper glass sheet 28 and a lower line 49 generated from the lower glass sheet 29 are separated by a distance defining a gap 50 which will produce an unacceptable laminated windshield. An image 51 represents a pair of glass sheets which nest properly, but which contain an unacceptable distortion in the form of a convex portion 52 in area where the glass sheets should be concave. The images 46, 47 and 51 shown in FIG. 4 represent reflections from the four surfaces of the glass sheets 28 and 29 along the line 38. Obviously, a human observer could monitor the reflecting screen 40 and decide whether the image on the screen represented a "good" or a "bad" nested pair of glass sheets. However, as shown in FIG. 5, the apparatus according to the present invention can be incorporated in a control system for the manufacturing line 11. A microprocessor 53 can be connected to the bus 24 for the exchange of information with the host computer 23. The microprocessor 53 is connected to a servo control 54 by lines 54a and 54b. The servo control 54 is connected to the servo motor 33 in the gap detector 21 by lines 54c. The microprocessor ' 53 sends command signals on the line 54a for positioning the gap detector 21. Position feedback signals are sent from the servo control 54 to the microprocessor 53 on the line 54b. The operation of the camera array 43 in the gap detector 21 is controlled by control signals generated by the microprocessor 53 on a line 55 to coordinate the gathering of the information contained in the image beam 41. Signals generated by the camera array 43 representing the image beam 41 are sent on a line 56 to a buffer 57. The microprocessor 53 can then read the information from the buffer 57 on a line 58. The microprocessor 53 can process the information from the camera array 43 and generate any type of desired display on a line 59 to a monitor 60. For example, the upper line 48, the lower line 49 and the gap 50 could be generated on the monitor 60 in enlarged form by the microprocessor 53. Another use for the monitor 60 is a comparison of the image with predetermined limits. For example, there is shown in FIG. 6 an image 61 generated from a pair of nested glass sheets. The microprocessor 53 can generate on the monitor 60 a pair of envelope lines 62 and 63 which define the permissible range in which the image 61 must fall in order to be a "good" pair of glass sheets. Since the image 61 crosses the upper envelope line 62 at a distorted area 64, a "bad" nested pair of glass sheets has been sensed. Another example is the measurement of gaps between the nested pairs of glass sheets. In FIG. 7, the upper line 48 and the lower line 49 from the image 47 of FIG. 4 can be compared with a pair of gap tolerance lines 65 and 66 generated on the monitor 60. The gap tolerance lines 65 and 66 extend generally parallel at a predetermined spacing which represents the maximum allowed gap between a pair of glass sheets. As can be seen in FIG. 7, the gap 50 exceeds the tolerance limit and a "bad" pair has been sensed. Also shown in FIG. 5 is an alarm signal line 67 connected between the microprocessor 53 and an alarm indicator 68. When the microprocessor 53 detects a "bad" pair of glass sheets having for example the distortion 64 shown in FIG. 6 or the gap 50 shown in FIG. 7, an alarm signal can be generated on the line 67 to the alarm indicator 68. The alarm indicator 68 can be any conventional device such as a visual or audio indicator to signal an operator that a "bad" pair of glass sheets has been detected. Of course, the alarm signal can also be utilized to control a device to automatically discard a "bad" pair of glass sheets from the nesting fixture 20. In its simplest form, the method according to the present invention involves scanning an outer surface of a pair of nested glass sheets utilizing a light source and a detector. For example, the laser beam source 34 of FIG. 2 can be turned around to direct the laser beam 35 at the upper surface of the upper glass sheet 28. If the laser beam source 34 is fixed with respect to the floor 27, the nesting fixture 20 could be moved to scan the laser beam 35 in a predetermined pattern across the upper surface of the upper glass sheet 28. The reflected beam 39 could be directed to the surface of the reflecting screen 40 or directly through the lens 42 into the camera 43. Alternatively, the nesting fixture 20 can be fixed with respect to the floor 27 and the laser beam source 34 can be moved to scan the laser beam 35 across the upper surface of the upper glass sheet 28. In a completely automated system, the reflecting screen 40 of FIG. 2 and FIG. 3 can be eliminated and the array of cameras 43 can be pointed toward the upper surface of the upper glass sheet 28 to receive the reflected beam 39 through the associated lenses 42. The resolution of the system according to the present invention is determined by the number and type of cameras 43 utilized. Typically, the camera 43 is linear array of light sensitive diodes. The diodes in the array can be, for example, one thirty- second of an inch apart thereby determining the number of cameras required to inspect any predetermined size sheet of glass. The servo motor 33 can represent a two axis servo system which controls the position of the carriage 32 along the track 30 and the angle of the incident beam 37 with respect to a normal extending from the upper surface of the upper sheet of glass 28. There is shown in FIG. 8 a flow diagram of the method of operating an automatic inspection system according to the present invention. The method starts at a circle 69 and enters an instruction set 70 where information pertaining to a "good" pair of nested glass sheets is loaded or stored. For example, as shown in FIG. 5, the host computer 23 can send information concerning "good" nested pairs to the microprocessor 53 for storage and later comparison with the data obtained from actual inspections. Also, known "good" nested pairs can be run through the gap detector 21 and the information obtained by the camera array 43 can be stored in the microprocessor 53 memory thereby "teaching" the system the profile of a "good" nested pair of glass sheets. After the "good" pair information has been loaded in the system, the first nested pair is placed in the nesting fixture 20 and an instruction set 71 is executed to obtain the identification of the pair from the host computer 23. The host computer 23 identifies each sheet of glass as it passes through the manufacturing line 11. An instruction set 72 is executed whereby the camera array 43 is controlled to scan the nested pair in the nesting fixture 20. As stated above, the information generated by the camera array 43 is typically stored in a buffer 56 until it is read by the microprocessor 53 such as during the execution of an instruction set 73. Next, an instruction set 74 is executed to perform comparisons of the data read from the pair being inspected with the stored data from a "good" pair of nested glass sheets. The microprocessor 53 can activate the monitor 60 utilizing an instruction set 75 for displaying the images of FIG. 4, FIG. 6 and FIG. 7. Next, a decision point 76 is entered to determine whether the nested pair under inspection is "good" or not. If the pair is "bad", the method branches at "NO" and executes an instruction set 77 whereby the alarm 68 is activated. If the nested pair is "good", a branch is made at "YES" from the decision point 76. The "YES" branch and the instruction set 77 both lead to an instruction set 78 whereby the microprocessor 53 sends data on the inspected pair of nested glass sheets to the host computer 23. The method then enters a decision point 79 where a check is made to see if the just inspected nested pair is the last pair to be inspected. If additional pairs are to be inspected, the method branches at "NO" back to the instruction set 71. If the last nested pair has been inspected, the method branches at "YES" to a stop circle 80. The inspection information, sent by the microprocessor 53 to the host computer 23 over the bus 24, can be used for inventory control purposes and general production statistics. Also, this information can be utilized to make adjustments in the manuf cturing line 11 shown in FIG. 1. For example, the information from the microprocessor 53 not only identifies the type and degree of distortion, but also identifies the location on the glass sheets. Thus, the host computer can recognize that the type of distortion is caused by one of the operations performed by the furnace 12, the bending press 14, the blast head 15 or the cooling fan 16. Accordingly, the host computer 23 can act to correct or adjust the associated operation to eliminate the distortion.

Claims: WHAT IS CLAIMED IS 1. A method of inspecting bent transparent sheets comprising the steps of: a. engaging a peripheral edge portion of at least two transparent sheets with a nesting fixture and supporting the sheets in a nested position; b. directing a light beam at an outer surface of the nested sheets; c. scanning the light beam in a predetermined path across the outer surface to generate a reflected beam; and d. sensing the reflected beam and identifying the nested transparent sheets as "good" or "bad". 2. The method according to claim 1, wherein said transparent sheets are glass sheets . 3. The method according to either of claims 1 or 2, wherein said step b. is performed by generating said light beam as a laser beam. 4. The method according to claim 3, wherein said step c. is performed by directing said laser beam at a scanning mirror to generate an incident beam as a line on the outer surface generally perpendicular to a longitudinal axis of the nested transparent sheets and moving said incident beam along the longitudinal axis of the nested sheets from one side edge to an opposite side edge of the transparent sheets. 5. The method according to claim 1, wherein said step d. is performed by comparing said reflected beam with predetermined limits. 6. An apparatus for inspecting nested sheets of transparent material, comprising: a nesting fixture for engaging a peripheral edge portion of at least two nested sheets of transparent material ; a light beam source for generating a light beam; means for directing said light beam in a predetermined scanning path across an outer surface of the nested sheets to generate a reflected beam; and means for sensing said reflected beam generated by the reflection of said light beam from the surfaces of the nested sheets and identifying "good" and "bad" nestability of the nested sheets. 7. Apparatus according to claim 6, wherein said nesting fixture includes a ground engaging base attached to a generally upstanding support wall, an edge of said support wall adapted to engage the peripheral edge portion of the nested sheets . 8. Apparatus according to claim 6, wherein said nesting fixture is movable relative to said light beam source . 9. Apparatus according to claim 6, wherein said light beam source generates a laser beam as said light beam. 10. Apparatus according to claim 6, wherein said means for directing includes a scanning mirror for reflecting said light beam as an incident beam onto the outer surface of the nested sheets . 11. Apparatus according to claim 6, wherein said means for sensing includes a lens and camera responsive to said reflected beam for generating information signals and including means responsive to said information signals for identifying "good" and "bad" nested sheets. 12. Apparatus according to claim 6, wherein said means for sensing includes a plurality of cameras positioned in a row extending generally perpendicular to a longitudinal axis of the nested sheets and generally parallel to the outer surface of the nested sheets, each of said cameras being responsive to at least a portion of said reflected beam for generating information signals identifying "good" and "bad" nested sheets . 13. Apparatus according to claim 6, wherein said means for sensing includes a reflecting screen for generating an image beam from said reflected beam and a camera responsive to said image beam for identifying "good" and "bad" nested sheets . 14. Apparatus according to claim 6, wherein said means for directing and said means for sensing are mounted on a carriage and including means for moving said carriage relative to said nesting fixture to direct said light beam along said predetermined scanning path. 15. Apparatus according to claim 14, including a servo motor coupled to said carriage for moving said carriage along a longitudinal axis of the nested sheets. 16. Apparatus according to claim 14, including a servo motor coupled to said light beam source for maintaining said light beam at a predetermined angle with respect to the outer surface of the nested sheets. 17. Apparatus according to claim 6, including a microprocessor connected to said means for directing for generating command signals to said means for directing to define said predetermined scanning path. 18. Apparatus according to claim 17, wherein said means for sensing includes a camera array connected to said microprocessor, said microprocessor generating control signals and said camera array being responsive to said control signals and said reflected beam for generating information signals representing the nested sheets. 19. Apparatus according to claim 18, including a monitor connected to said microprocessor, said microprocessor being responsive to said information signals for generating a visual image of the nested sheets on said monitor. 20. Apparatus according to claim 18, including an alarm connected to said microprocessor, said microprocessor being responsive to said information signals for generating an alarm signal to activate said alarm to identify "bad" nested sheets . 21. An apparatus for inspecting nested glass sheets, comprising : a nesting fixture having a base attached to generally upstanding peripheral support walls adapted to engage a peripheral edge portion of at least two nested glass sheets ; a laser beam source for generating a laser beam; means for directing said laser beam at an outer surface of the nested glass sheets in a predetermined scanning path to generate a reflected beam; and means for sensing said reflected beam and identifying "good" and "bad" nested glass sheets. 22. Apparatus according to claim 21, including a microprocessor, a servo control, and a servo motor connected to said servo control and coupled to said means for directing, said microprocessor being connected to said servo control for generating command signals to control said servo motor to define said predetermined scanning path. 23. Apparatus according to claim 22, including a camera array connected to said microprocessor, said microprocessor generating control signals to said camera array, said camera array being responsive to said control signals and said reflected beam for generating information signals representing "good" and "bad" nested glass sheets.

Inventors: ANGELL BARBARA L, MCCOMB WALTER D, RUDOLPH ANDREW W, ANGELL, BARBARA, L., MCCOMB, WALTER, D., RUDOLPH, ANDREW, W.
Applicants: LIBBEY OWENS FORD CO, LIBBEY-OWENS-FORD CO.
Application year: 1989
Main classification: G01B11
IPC codes: G01B11, G01N21