WO1994024675A1

WO1994024675A1 - Visual inspection tool

Info

Publication number: WO1994024675A1
Application number: PCT/US1993/009566
Authority: WO
Inventors: Mark A. Overbay; Samuel B. Crabtree
Original assignee: Combustion Engineering, Inc.
Priority date: 1993-04-12
Filing date: 1993-10-07
Publication date: 1994-10-27
Also published as: TW240315B; AU5170993A

Abstract

A visual inspection tool (24), attached to a manipulator (20), is disclosed for inspecting a tube end (26) of a tube sheet of a steam generator (12). A fuse light (40) is mounted inside the housing adjacent to a light guide (46). An outer mirror (58) surrounds the light guide and has a cutaway portion (60) adjacent to the fuse light to allow light into the light guide. An inner mirror (64) is located at the top of the light guide and is supported on the housing axis. The outer and inner mirrors are designed such that light directed by the light guide to the top of the housing simultaneously reflects from the outer and inner mirrors onto the outer (120) and inner (118) portions of the tube end, respectively. A camera (78) receives the light reflected by the tube end and generates tube image data. At a remote location, a technician can see a panoramic view of the tube without repositioning the manipulator (20).

Description

VISUAL INSPECTION TOOL BACKGROUND OF THE INVENTION The present invention relates to an end effector for a remote manipulator, and more particularly, to an end effector which enhances visual inspection of the end of a tube in a tube sheet of a nuclear steam generator.

Typically, a nuclear steam generator has thousands of closely-spaced tubes affixed at an end of a tube sheet. As these tubes become worn, they may fail; consequently, they require routine servicing. This servicing usually involves repairing the tubes or simply plugging them.

These tubes are typically serviced from a remote location through the use of a robotic cantilever device, which is commonly referred to as a manipulator. Before any servicing takes place, the manipulator must be accurately placed under the tube. If a positioning error is made, there may be serious consequences. For example, a faulty tube could go unrepaired, while a neighboring satisfactory tube was plugged. This faulty tube could then leak radioactive material, which could force an unplanned shutdown of the nuclear steam generator.

Because of the need for an accurate positioning device, an improved positioning device was disclosed and patented in U.S. Pat. No. 4,891,767 to Rzasa et al. This positioning device ensures highly accurate placement of the manipulator. Because the manipulator can now be more accurately placed than before, fewer tubes are erroneously repaired. Unfortunately, Rzasa's invention focused primarily on positioning the manipulator. It was unconcerned with the tool attached to the manipulator, commonly known as an end effector.

Even though this new manipulator is more accurate and fewer tubes are erroneously repaired, there is still a need to verify that the proper tubes were actually serviced. Furthermore, there is also a need to verify that the servicing was done properly and according to industry specifications. For example, two particular points of interest on a serviced tube include the weld (which plugs a tube) and the area surrounding the weld, commonly known as the heat affected zone. After ensuring that each weld meets industry standards, the heat affected zone must also be checked.

In the past, the end effectors attached to the manipulator were limited. Typically, with these end effectors, a technician, at a remote location, could see only one view of the tube end at a given time. For example, the technician could only view the outer portion of the tube end; he could not simultaneously view both the outer and inner portions of the tube end. Because these views were not on his monitor simultaneously, it was difficult for him to verify the accuracy of servicing and the condition of the weld. Furthermore, it was difficult for the technician to check the work because he was forced to reposition the manipulator to obtain other views.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an end effector for a manipulator which can be used to verify that a pre-selected tube was serviced. It is another object of the invention to provide an end effector for a manipulator which can be used to verify that all servicing was done properly and according to specifications. It is still another general object to provide an end effector which can examine both a weld and a heat affected zone of a serviced tube.

It is a more particular object to provide an end effector which can provide a panoramic view of the tube end without repositioning the manipulator.

These and other objects are accomplished in accordance with the invention, in which an end effector illuminates the work surface of the tube end, and through a series of mirrors, provides a panoramic view of the tube end without repositioning the manipulator.

In the preferred embodiment, the invention comprises a housing having an inside, an outside, a top, an opposed bottom, and an axis extending through the top and bottom. An illuminating means, such as a fuse light, is mounted inside the housing. A light guide is secured inside the housing and adjacent to the illuminating means. An outer mirror is located at the top of the light guide and is adapted in size and shape to surround the tube end. An inner mirror is located at the top of the light guide and is supported on the housing axis. A camera is positioned within the housing and beneath the light guide. A transmitting means is electrically connected to the camera for sending tube image data to a monitor at a remote location.

In operation, light travels from the light source into the light guide. The light guide redirects the light upward to the top of the housing. The outer and inner mirrors are adapted in size and shape such that light directed by the light guide to the top of the housing simultaneously reflects from the outer and inner mirrors onto the outer and inner portions of the tube end, respectively.

The outer mirror has a frustroconical portion having a mirror surface turned inwardly toward the axis, for reflecting light from the outer portion of the tube end toward the camera. Conversely, the inner mirror includes a frustroconical portion having a mirror surface turned outwardly from the axis, for reflecting light from the inner portion of the tube end toward the camera. The camera receives the light reflected by the tube end and generates tube image data. The transmitting means forwards the tube image data from the camera to the monitor at the remote location. At this remote location, a technician can verify that the tube was properly serviced by examining its weld and its heat affected zone. The technician sees three "lines-of-sight" on his remote monitor. One line- of-sight extends from the camera to the outer mirror and radially inward onto the outer portion of the tube. The second line-of-sight stretches directly from the camera to the bottom of the tube. The third line-of-sight extends from the camera to the inner mirror and radially outward onto the inner portion of the tube. Because of the positioning of the mirrors, the technician can see all views of the tube end without repositioning the manipulator.

After the servicing of that tube has been approved, the technician at the remote location guides the manipulator to the next tube and repeats the above- mentioned process.

BRIEF DESCRIPTION OF THE DRAWINGS A detailed description of the preferred embodiment of the invention is set forth below, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a tube sheet region of a nuclear steam generator and a remote manipulator (which is known in the art) with an attached end effector, constructed in accordance with the present invention;

FIG. 2 is a side view of the end effector, also known as a visual inspection tool, affixed to the manipulator; FIG. 3 is a partial cross-sectional view of the inspection tool shown in Fig. 2, taken along line 3-3, showing the tool positioned inside a tube end;

FIG. 4 is a top plan view of the inspection tool affixed to the manipulator; FIG. 5 is a partial cross-sectional view of a portion of the inspection tool - namely, a tube probe, an outer mirror, and a camera - showing the tube probe inserted into a tube end and three "lines-of-sight" extending between the tube end and the camera; FIG. 6 is a view of the three "lines-of-sight"

- as seen by a technician at a remote location on his monitor;

FIG. 7 is a cross-sectional view of a plugged tube, taken along line 7-7 of FIG. 5, with the tool removed for clarity;

FIG. 8 is a cross-sectional view of an outer mirror;

FIG. 9 a top view of the outer mirror;

FIG. 10 is a side view of a light guide; and FIG. 11 is a top view of the light guide supported within ths outer mirror.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a lower plenum region of a nuclear steam generator 12, having a transverse tube sheet 14 in which are affixed a multiplicity of tubes 16, some of which have been serviced. Typically, a support structure, such as a stay column 18, provides a stable mounting structure for a temporary manipulator arm 20, which may be supported by a strut 22. The arm 20 carries an end effector 24, constructed in accordance with the present invention, for insertion into the open ends 26 of the tubes.

It should be appreciated that, although the preferred embodiment of the invention will be described with reference to a tube of a nuclear steam generator, the invention may be utilized in other environments. For example, the invention is particularly useful where a panoramic view of any tubular member is needed. The end effector 24 may be attached to any suitable manipulator arm 20. One suitable manipulator arm is disclosed in U.S. Pat. No. 4,891,767 to Rzasa et al. The disclosure of that patent is hereby incorporated by reference. FIG. 3 shows the invention in partial cross- section. In particular, the invention has a housing 28, which includes an inside portion 30, an outside portion 32, an open* top 34, an opposed bottom 36, and an axis 38 extending through the top and bottom. The housing 28 is preferably made of aluminum and is ideally black and anodized to reduce light reflections.

A means for illuminating 40 the housing 28 and the vicinity of the tube end 26 is affixed to the inside 30 of the housing and at substantially the top 34 of the housing. Any illuminating means will suffice, such as a conventional twelve-volt fuse light. The fuse light is affixed to the housing by a fuse holder, or any suitable connecting means, 42. Additionally, a light bracket 44 secures the fuse holder to the housing 28. A light guide 46, such as one manufactured of transparent optics quality plastic stock, preferably that marketed under the trademark Lexan, is secured within the housing 28 at substantially the top 34 of the housing, adjacent to the illuminating means. In the preferred embodiment, the light guide is made of a solid piece of Lexan. The light guide 46 has a top 48, a bottom 50, a side or surface 52, and a idplane 56. The top 48 of the light guide 46 is adjacent the top 34 of the housing 28. In its preferred embodiment, the light guide is angled inwardly toward the axis 38 at substantially its midplane, as shown in FIGS. 2, 3. The light guide directs light from the illuminating means 40 to the top of the housing. One can readily arrive at a suitable shape for the light guide, by routine iteration about the basic shape described herein.

An outer mirror 58 is secured to the top 48 of the light guide 46 and is adapted in size and shape to surround the tube end 26. The outer mirror has a cutaway portion 60 adjacent to the illuminating means 40, which allows light from the fuse light to pass to the light guide 46. The outer mirror further includes a frustroconical portion 62 having a mirror surface turned inwardly toward the axis 38 and extending slightly above the top 48 of the light guide. An inner mirror 64, located at the top of the light guide 46 and supported on the housing axis 38, is adapted in size and shape to enter and exit the tube end 26.

A tube probe 66 is centered above the light guide 46. The tube probe 66 is adapted in size and shape to enter and exit the tube ends 26 of the steam generator 12. The tube probe consists of essentially three components: a pilot portion 68, the inner mirror 64, and a shaft 70. The substantially tubular pilot portion 68, at the top of the tube probe 66, guides the probe into the center of the tube end 26. In its preferred embodiment, the probe 66 has a rounded tip 72 to facilitate, entry into the tube end. The inner mirror 64 is secured at the probe bottom 74. The tube probe 66 is connected to the housing 28 by the shaft 70. The shaft attaches to the inner mirror bottom 76 and extends downwardly into the light guide 46 and is secured under the illuminating means 40. Directly beneath the light guide 46 is a camera means 78, secured within the housing 28, for receiving light reflected by the tube end and generating tube image data. Any suitable camera means will suffice, such as the one manufactured and marketed by Toshiba, model number CCD Mod. #IK M30 A. The camera includes a lens 80 having a top 82 and bottom 84, wherein the top of the lens is spaced from the bottom 50 of the light guide 46. The camera also includes a focus ring 86 and a means 88 for focusing the camera. In the preferred embodiment, the camera is focused by a drive gear 90 in mesh with a driven gear 92, both of which are adjacent to the lens 80 of the camera, and both of which cooperate to move the lens in an axia,l direction toward and away from the stationary light guide. The drive gear and driven gear are remotely operated by a conventional twelve-volt D.C. motor 94. The drive gear 90 and driven gear 92 can be any suitable gears, such as those manufactured by W.M. Berg Inc. , Spur Gear model number PW48B40A, made of brass. The driving gear is connected to the motor by a shaft 96, as shown in FIG. 3. One thrust washer 98, such as the one manufactured by W.M. Berg Inc., model number CD8-2, of Teflon, separates the drive gear 90 from the shaft. A second thrust washer 100 overlies the drive gear 90. A hex nut 102 and a belville washer 104, respectively, overlie this second thrust washer 100.

A connector 106 for attaching the housing 28 to the manipulator is also shown in FIG. 3. Any suitable connecting means will suffice, such as the connector manufactured by Bendix, model number PT02A-8P. FIGS. 2, 4 show the effector 24 connected to the manipulator arm 20 in more detail. In particular, an elongated bracket 108, extending from the effector, is positioned above the arm of the manipulator. The bracket 108 and the arm 20 are interconnected by two cylindrical, rubber mountings 110, 112, such as those manufactured by Stock Drive Products, model number 10Z2-301A and secured in place by hex nuts 114, 116.

As shown in FIG. 5, each tube end, such as 26, has three portions that are inspected: an inner portion 118, an outer portion 120, and a bottom portion 122. In operation, the tube probe 66 is inserted into a tube end 26 which may contain a plug 124. When properly placed, the outer mirror 58 surrounds the tube end, while the camera means 78 is positioned directly below the tube. After the illuminating means 40 is turned on, light travels into the light guide 46. The light guide directs the light to the top 34 of the housing 28. The inner mirror 64 and the outer mirror 58 simultaneously reflect the light from the top of the housing onto the inner portion 118 and outer portion 120 of the tube end, respectively.

The camera means 78 receives the light reflected by the tube end 26 and generates tube image data. This data is electronically transmitted, via cable 126, to a remote location, such as a monitor 128. (See FIGS. 3, 6. )

This monitor 128 displays three lines-of-sight, as shown in FIGS. 5, 6. One line-of-sight 130 extends from the camera 78 to the outer mirror 58 and radially inward onto the outer portion 120 of the tube end. The second line-of-sight 132 stretches directly from the camera to the bottom 122 of the tube end. The third line-of-sight 134 extends from the camera to the inner mirror 64 and radially outward onto the inner portion 118 of the tube end.

FIG. 7 shows, in detail, a weld 136 of tube end 26. This weld includes two metal sections 138, 140 separated by a plug 142. A heat affected zone 144 is also shown. The technician, at his remote location, must inspect this heat affected zone 144 to ensure that it meets industry standards. With this end effector, the technician sees a panoramic view of this weld without repositioning the manipulator. FIGS. 8, 9, 10, 11 show one available set of outer mirror 58' and light guide 46' respectively. The frustroconical reflecting surface 62' of the mirror is supported above a pedestal portion 146 by three legs 148 spaced one hundred twenty degrees apart. The light guide 46' fits within the legs, so as to be supported by the pedestal portion 146 and span the space 60' between the reflecting surface 62' and the pedestal portions 146. The pedestal portion 146 is supported by, or forms part of, the housing 34 shown in FIG. 3.

It should thus be appreciated that the apparatus described herein is well adapted to accomplish the objective of providing a panoramic view of a tubular member. Variations of the particular components and equipment described herein may be substituted without departing from the scope of the invention as set forth in the claims. For example, many elements were described as being made of a particular metal, such as aluminum. While the use of the listed metal is ideal, any suitable material will suffice.

Claims

We claim:

CLAIMS 1. A visual inspection tool for inspecting the end of a tube in a tube sheet of a steam generator, the tube end having an outer and an inner portion, comprising: a. a housing having an inside, an outside, a bottom, an opposed top, and an axis extending through the top and bottom; b. an illuminating means for providing light inside the housing; c. a light guide within and at substantially the top of the housing, the light guide having a transparent bottom and an opposed top, wherein the light guide directs light from the illuminating means to the top of the housing; d. an outer mirror at the top of the light guide and adapted in size and shape to surround the tube end; e. an inner mirror located at the top of the light guide and supported on the housing axis, wherein the inner mirror is adapted in size and shape to enter and exit the tube end such that light directed by the light guide to the top of the housing simultaneously reflects from the outer and inner mirrors onto the outer and inner portion of tube end, respectively; f. a camera means, secured within the housing in optical alignment with the light guide, for receiving the light reflected by the tube end through the light guide and generating image data of the tube end; and g. a transmitting means, electrically connected to the camera means, for sending tube image data from the camera means to a remote location.

2. The visual inspection tool of Claim 1, wherein the outer mirror includes a frustroconical portion having a mirror surface turned inwardly toward the axis, for reflecting light from the outer portion of the tube end toward the camera means.

3. The visual inspection tool of Claim 1, wherein the inner mirror includes a frustroconical portion having a mirror surface turned outwardly from the axis, for reflecting light from the inner portion of the tube end toward the camera means.

4. The visual inspection tool of Claim 1, wherein the light guide has a midplane, the light guide being turned inwardly toward the axis at substantially the light guide midplane.

5. The visual inspection tool of Claim 1, wherein the outer mirror has a cutaway portion adjacent to the illuminating means, wherein the cutaway portion allows light from the illuminating means to pass to the light guide.

6. The visual inspection tool of Claim 1, wherein the inner mirror projects from a shaft centrally located in the light guide.

7. The visual inspection tool of Claim 1, wherein the inner mirror has a top and an opposed bottom, the top of the mirror being fixedly attached to a substantially cylindrical tube probe, the probe adapted in size and shape to enter and exit the tube end, wherein the tube probe guides the inner mirror to a proper position within the tube end.

8. The visual inspection tool of Claim 1, further comprising a means for focusing the camera means.

9. The visual inspection tool of Claim 8, wherein the means for focusing the camera means includes a drive gear in mesh with a driven gear, the drive gear and driven gear adjacent the lens of the camera means for moving the lens in an axial direction.

10. The visual inspection tool of Claim 1, wherein the illuminating means for providing light inside the housing includes a fuse light.

11. The illuminating means of Claim 10, wherein the fuse light is attached to the housing by a fuse holder.

12. The visual inspection tool of Claim 1, further comprising a manipulator and a connector means for attaching the housing to the manipulator.

13. The visual inspection tool of Claim 1, further comprising a monitor means for receiving the image data and generating video images from the camera means.

14. A visual inspection tool for inspecting the end of a tubular member, the tubular end having an outer and an inner portion, comprising: a. a housing having an inside, an outside, a bottom, an opposed top, and an axis extending through the top and bottom; b. an illuminating means for providing light inside the housing; c. a light guide inside the housing and at substantially the top of the housing, the light guide having a transparent bottom and an opposed top, wherein the light guide directs light from the illuminating means to the top of the housing; d. an outer mirror at the top of the light guide and adapted in size and shape to surround the tubular end, the outer mirror having a frustroconical portion having a mirror surface turned inwardly toward the axis; e. an inner mirror located at the top of the light guide and supported on the housing axis, the inner mirror having a frustroconical portion having a mirror surface turned outwardly from the axis, wherein the inner mirror is adapted in size and shape to enter and exit the tubular end such that light directed by the light guide to the top of the housing simultaneously reflects from the outer and inner mirrors onto the outer and inner portion of tubular end, respectively; f. a camera means, secured within the housing, for receiving the light reflected by the tubular end and generating tube image data, the camera means having a lens, the lens having a top and an opposed bottom, wherein the top of the lens optically mates with and receives reflected light through the bottom of the light guide; and g. a transmitting means, electrically connected to the camera means, for sending tube image data from the camera means to a remote location.

15. The visual inspection tool of Claim 14, wherein the inner mirror reflects light from the inner portion of the tube end toward the camera means.

16. The visual inspection tool of Claim 14, wherein the outer mirror reflects light from the outer portion of the tube end toward the camera means.

17. The visual inspection tool of Claim 14, wherein the light guide includes an outer surface and a midplane, the light guide outer surface being turned inwardly toward the axis at substantially the light guide midplane.

18. The visual inspection tool of Claim 14, wherein the outer mirror has a cutaway portion adjacent to the illuminating means, wherein the cutaway portion allows light from the illuminating means to pass to the light guide.

19. The visual inspection tool of Claim 14, wherein a shaft is attached to the bottom of the inner mirror, the shaft being centrally located in the light guide.

20. The visual inspection tool of Claim 14, wherein the inner mirror has a top and an opposed bottom, the top of the mirror being fixedly attached to a substantially cylindrical tube probe, the probe adapted in size and shape to enter and exit the tube end, wherein the tube probe guides the inner mirror to its proper position within the tube end.

21. The visual inspection tool of Claim 14, further comprising a means for focusing the camera means.

22. The visual inspection tool of Claim 21, wherein the means for focusing the camera means includes a drive gear in mesh with a driven gear, the drive gear and driven gear adjacent the lens of the camera means for moving the -lens in an axial direction.

23. The visual inspection tool of Claim 14, further comprising a manipulator and a connector means for attaching the housing to the manipulator.

24. The visual inspection tool of Claim 14, further comprising a monitor means for receiving the image data and generating video images from the camera means.

25. A visual inspection tool for inspecting the end of a tube in a tube sheet of a steam generator, the tube end having an outer and an inner portion, comprising: a. a housing having an inside, an outside, a bottom, an opposed top, and an axis extending through the top and bottom; b. an illuminating means for providing light inside the housing; c. a light guide inside the housing and at substantially the top of the housing, the light guide having a transparent bottom and an opposed top, wherein the light guide directs light from the illuminating means to the top of the housing, and wherein the light guide includes a midplane, the light guide being turned inwardly toward the axis at substantially the light guide midplane; d. an outer mirror at the top of the light guide and adapted in size and shape to surround the tube end, the outer mirror having a frustroconical portion having a mirror surface turned inwardly toward the axis, the outer mirror having a cutaway portion adjacent to the illuminating means, wherein the cutaway portion allows light from the illuminating means to pass to the light guide; e. an inner mirror located at the top of the light guide and supported on the housing axis, the inner mirror having a frustroconical portion having a mirror surface turned outwardly from the axis, wherein the inner mirror is adapted in size and shape to enter and exit the tube end such that light directed by the light guide to the top of the housing simultaneously reflects from the outer and inner mirrors onto the outer and inner portion of tube end, respectively; f. a camera means, secured within the housing, for receiving the light reflected by the tube end and generating tube image data, the camera means having a lens, the lens having a top and an opposed bottom, wherein the top of the lens optically mates with and receives reflected light through the bottom of the light guide; g. wherein the inner mirror and outer mirror reflect light from the inner and outer portion, respectively, of the tube end toward the camera means; h. a transmitting means, electrically connected to the camera means, for sending tube image data from the camera means to a remote location; and i. a monitor means for receiving the image data and generating video images from the camera means.

26. The visual inspection tool of Claim 25, wherein a shaft is attached to the bottom of the inner mirror, the shaft being centrally located in the light guide.

27. The visual inspection tool of Claim 25, wherein the inner mirror has a top and an opposed bottom, the top of the mirror being fixedly attached to a substantially cylindrical tube probe, the probe adapted in size and shape to enter and exit the tube end, wherein the tube probe guides the inner mirror to its proper position within the tube end.

28. The visual inspection tool of Claim 25, further comprising a means for focusing the camera means.

29. The visual inspection tool of Claim 28, wherein the means for focusing the camera means includes a drive gear in mesh with a driven gear, the drive gear and driven gear adjacent the lens of the camera means for moving the lens in an axial direction.

30. The visual inspection tool of Claim 25, further comprising a remote manipulator and a connector means for attaching the housing to the manipulator.