Patent Number: 
Section: description

As used herein, the term xe2x80x9cfloatablyxe2x80x9d or xe2x80x9cfloatablexe2x80x9d indicates a freedom to move, a small amount, in several directions while still being retained. That is, when directed to an ultrasonic probe floatably mounted in a housing, floatable indicates that the probe, while still being retained by the housing, has the freedom to roll, pitch, and yaw, as well as freedom to move laterally. As shown in FIG. 1, an ultrasonic testing end effector 10 in accordance with the present invention is shown. The end effector is composed of two main components the wrist assembly 12 and a probe assembly 14. The wrist assembly 12, as shown in FIG. 2, includes the wrist motor assembly 20 and its housing 30, and the wrist shaft 40 and its housing 50. The probe assembly 14, as shown in FIG. 3, includes the clutch assembly 60 and its housing 70, a probe motor assembly 100 and its housing 110, a probe carriage assembly 130 and its housing 150, the probe 160, and camera assembly 180. Each of these assemblies will be described fully below. However, generally speaking, the probe assembly 14 rotates in a horizontal plane below the wrist assembly 12. As shown in FIG. 2, the end effector 10 is coupled to a robotic arm by mounting bracket 16. Mounting bracket 16 supports the wrist motor assembly 20. The wrist motor assembly includes a wrist motor 22 which has a resolver 26 and a wrist axle 24 ending in a motor gear 28. The wrist motor 22, the upper portion of the wrist axle 24, and resolver 26 are enclosed within a wrist motor assembly housing 30. The wrist motor 22 can be any type of common motor that drives a rotating axle. The resolver 26 is a device which tracks the rotational motion of the wrist axle so that the angular orientation of the wrist axle 22 can be determined electronically by such means as a computer. The wrist motor assembly housing 30 has an upper surface 34 and a lower surface 36. The upper surface 34 has a medial hole therethrough (not shown). A wrist motor assembly coupling 32 is sealably connected to the upper surface 34 about the medial hole and provides a port which is coupleable to a power source and pressurized air hose. The coupling 32 also provides access for data wires connecting the resolver 26 to a computer or digital converter. The wrist motor assembly housing lower surface 36 has a medial hole therethrough which allows the lower portion of the wrist axle 24 to pass through. The wrist axle 24 could be coupled with the clutch assembly 60 (described below) directly. In the preferred embodiment, however, the wrist axle motor gear 28 is rotatably coupled with a wrist shaft 40. The wrist shaft 40 is cylindrical and includes a wrist shaft body 41, a wrist gear 42 and a wrist shaft lower end 44. The wrist shaft lower end 44 may have a greater circumference than the wrist shaft body 41. The teeth of the wrist gear 42 are rotatably coupled with the teeth of the motor gear 28. The wrist shaft lower end 44 is generally circular except for a wrist shaft detent 46. The motor gear 28, wrist shaft body 41 and wrist gear 42 are enclosed within the wrist shaft housing 50. The wrist shaft housing 50 has an upper end 52 and a lower end 54. Both the wrist shaft housing upper end 52 and the wrist shaft housing lower end 54 have openings therethrough. A wrist motor housing seal 38 is disposed between the wrist motor assembly housing 30 and the wrist shaft housing upper surface 52. The wrist motor housing seal provides a water tight seal between the wrist motor assembly housing 30 and the wrist shaft housing 50. The wrist motor assembly 20 is attached to the wrist shaft housing upper end 52 with the wrist axle 24 passing through the wrist shaft housing upper end 52 opening. A wrist axle seal 25 is disposed between the wrist shaft housing 50 and the wrist axle 24. The motor gear 28 is disposed at the lower end of the wrist axle 24 within the wrist shaft housing 50. The wrist shaft 40 is aligned in parallel with the wrist axle 24. The wrist shaft body 41 extends through the wrist shaft housing 50 and passes through the opening in the wrist shaft housing lower surface 54. As shown in FIG. 3, a clutch pin assembly 60, which includes a clutch pin 62, a clutch pin housing 64, and a clutch pin spring 66, is enclosed within the clutch assembly housing 70. The clutch assembly housing includes a clutch assembly housing upper surface 74 with an opening therethrough, a clutch assembly housing lower surface 76 and a clutch assembly housing back plate 72. The clutch assembly housing upper surface 74 is rotatably connected to the wrist shaft housing lower surface 54. The wrist shaft housing lower surface 54 forms a bearing surface 56 at the point of contact between the wrist shaft housing lower surface 54 and the clutch assembly housing upper surface 74. The opening in the wrist shaft housing lower surface 54 and the opening in the clutch assembly housing upper surface 74 are aligned to allow the wrist shaft body 41 to pass from the wrist shaft housing 50 into the clutch assembly housing 70. The wrist shaft lower end 44 and wrist shaft detent 46 are disposed within the clutch assembly housing 70. The clutch pin housing 64 extends from the clutch assembly housing back plate 72 towards the wrist shaft lower end 44. The clutch pin housing 64 contains the clutch pin spring 66 and the clutch pin 62. The clutch pin spring 66 biases the clutch pin 62 against the wrist shaft lower end 44. As shown in FIG. 1, when properly aligned, the clutch pin end 68 is disposed within the wrist shaft detent 46. The clutch assembly housing 70 is attached to a frame 90. The frame 90 has a frame upper surface 92, a frame lower surface 94, a frame back end 96, and a frame front end 98. A carriage assembly motor assembly 100 is disposed below the frame back end 96. The carriage assembly motor assembly 100 includes a carriage assembly rotation motor 102, a carriage assembly axle 104 extending from the carriage assembly motor 102, a carriage assembly axle coupling 106 and a carriage assembly motor assembly housing 110. The carriage assembly rotation motor 102 is any common motor which can provide a rotational force to the carriage assembly axle 104. The carriage assembly motor assembly housing 110 is watertight and has a carriage assembly motor assembly housing back end 112, a carriage assembly motor assembly housing front end 114, a carriage assembly motor assembly housing coupling 116 and a carriage assembly motor assembly housing seal 118. The carriage assembly motor assembly housing back end 112 has an opening therethrough (not shown). The carriage assembly motor assembly housing coupling 116 is sealably connected to the carriage assembly motor assembly housing back end 112 about the medial hole. The carriage assembly motor assembly housing coupling 116 is coupleable to a power source and a positive pressure air tube. The carriage assembly axle 104 passes through an opening in the carriage assembly motor assembly housing front end 114. The carriage assembly motor assembly housing 110 is sealed from the external environment by the carriage assembly motor assembly housing seal 118, which is disposed annularly around the carriage assembly axle 104. The carriage assembly axle 104 terminates in a carriage assembly axle coupling 106. Attached to, or integral to, the frame front end 98 is a probe carriage housing 150 which is a hollow cylindrical structure forming a probe carriage housing cavity 157. The internal surface of the probe carriage housing cavity 157 provides a bearing surface 152. The probe carriage housing further includes a back end 154 and a front end 155, both having openings therethrough connected to the probe carriage housing cavity. A probe carriage housing stop pin 156 is located adjacent to the probe carriage back end 154, and a probe carriage housing retainer 158 is located adjacent to the probe carriage front end 155. The probe carriage assembly 130 is disposed within the probe carriage housing cavity 157 contacting the probe carriage housing bearing surface 152. The probe carriage assembly 130 is a hollow cylindrical body forming a probe carriage cavity 138 and having a coupling arm 131 extending therefrom. The probe carriage assembly coupling arm 131 terminates in a probe carriage coupling end 132 which is attached to the carriage assembly axle coupling 106 by a probe carriage coupling pin 134. The probe carriage assembly coupling arm 131 is offset from the center of the probe carriage assembly, so as to provide a probe carriage cord access notch 136. Along the inner surface 133 of probe carriage assembly 130 is a longitudinal probe carriage slot 142 having a length and a width. The probe carriage spring 140 and the probe 160 are disposed within the probe carriage cavity 138. The probe carriage spring 140 biases the probe 160 (described below) towards the front end of the probe carriage housing 155. The probe carriage assembly 130 is retained within the probe carriage housing 150 by the probe carriage housing retainer 158. The probe carriage assembly has at least one stop pin 144 extending from the probe carriage assembly back end 148. The probe 160 includes a cylindrical probe body 161 having a front portion 162 and a back portion 163. The front portion 162 terminates in a circular mating surface 164. The mating surface 164 has a groove 166 thereon, which bisects the circular mating surface 164. The probe body back portion 163 is enclosed within an annular ring 168. The annular ring 168 has at least one external projection 170. When the probe 160 is disposed within the probe carriage assembly 130, the annular ring projection 170 is loosely fitted within the probe carriage slot 142. The probe carriage slot 142 and projection 170 limit the horizontal movement of the probe 160 within the probe carriage assembly 130, including limiting range of motion provided by the probe carriage spring 140. The projection 170, which is preferably circular, has a diameter that is smaller than the length and the width of the slot 142. Thus, the probe 160 has a limited range, preferably about 2 degrees, of yaw, pitch, and roll within the probe carriage assembly 130. The probe carriage back end 172 has a cylindrical disk 174 attached thereto. The cylindrical disk 174 provides a mating surface for the probe carriage spring 140. When the probe 160 is disposed within the probe carriage assembly 130, the probe carriage spring 140 biases the probe 160 towards the front end of the probe carriage housing. As shown in FIGS. 1 and 4, in the preferred embodiment, a camera assembly 180 is attached to the frame upper surface 92 proximal to the frame front end 98. The camera assembly 180 includes a camera mounting bracket 184, a camera 182, a camera light mounting bracket 188, and a camera light 186. The camera mounting bracket 184 is attached to the frame 90 and provides support for the camera 182. The camera light mounting bracket 188, is attached to the camera 182 and provides support for the camera light 186. The camera 182 and the camera light 186 are oriented to point towards the probe 160. The camera 182 is connected by a cable (not shown) to a video display. The camera light 186 is connected by a power cord (not shown) to a power source. As shown in FIG. 5, a remotely operated service arm 200 (xe2x80x9cROSAxe2x80x9d or xe2x80x9crobot armxe2x80x9d) is disposed above a cylindrical pressure vessel 190 for a nuclear reactor 190. As shown on FIGS. 5 and 6, within the cylindrical pressure vessel 190 is disposed a baffle 192 constructed of a plurality of flat plates forming a grid-like pattern. The baffle plates are secured to each other by baffle bolts along the outer periphery of the grid. As shown in FIG. 7, the baffle bolts 300 installed in recesses 304 on the baffle plates and locked into place by a lock bar 302 which is welded to the fastener head and the baffle 192. The robot arm 200 is designed to position a variety of end effectors within the pressure vessel 190. As indicated by arrow X on FIG. 5, the robot arm moves toward or away from the pressure vessel wall 199 and, as indicated by arrow Y, the arm can rotate 360xc2x0 about its axis, thus providing access to any point along the circumference of the pressure vessel. The robot arm is further designed to allow its end to travel vertically as indicated by arrow Z, substantially the entire length of the pressure vessel cylinder 190. Because the baffle bolts may be oriented perpendicular to the pressure vessel cylinder wall, the robot arm 200 must provide an additional degree of freedom in order to access the baffle bolt head. The ultrasonic testing end effector 10, and more specifically the wrist assembly 20, provides the additional degree of freedom required to inspect the baffle bolt heads. The ultrasonic testing end effector 10 is mounted on the robot arm 200, so that the wrist axle 24 rotates in a plane perpendicular to the robot arm""s vertical plane of travel. In operation, resolvers 194, 195, 196 on the robot arm 200 track the position of the end of the robot arm 200 and provide feedback to a digital converter 212. Using data from the resolvers and a computer controlled positioning system 214, the operator positions the end effector adjacent to the baffle bolt to be tested. Once in position, the camera 182 will display the baffle bolt on the operator""s monitor 216. The operator then uses controls 218, 220, such as a joy-stick, to manually adjust the position of the mating surface of the probe 164 to be grossly aligned, within xc2x12 degrees of being perpendicular, with the baffle bolt. The operator then adjusts the orientation of the mounting surface groove 166 to be grossly aligned, within xc2x12 degrees, with the baffle bolt lock bar. The mating surface 164 is then moved into contact with the baffle bolt. The mating surface 169 is biased against the baffle bolt by the force of the probe carriage spring 140. In the event of a slight misalignment between the baffle bolt and the mating surface 164, the probe 160 will correct its alignment to be flush due to the play provided by the loose fit between the probe carriage slot 142 and the projection 170. Once the mating surface 164 is flush with the baffle bolt, an ultrasonic test may be performed. Once the test is complete, the end effector 10 can be moved to another baffle bolt. It is preferred to move the end effector either vertically or horizontally rather than diagonally. Because the baffle plates 192 run vertically, it is less likely that the end effector will catch on an edge while moving vertically. Conversely, given the proximity of the vessel wall to the sawtooth edge formed by the baffle plates, it is possible that the end effector will contact the baffle 192 during horizontal movement. Damage to the end effector 10 and the baffle 192 is prevented by the clutch assembly 60. In operation, the rotation of the wrist shaft 40 is translated to the clutch assembly 60 which is fixed to the frame member 90. The contact point between the wrist shaft 40 and the clutch assembly 60 is the clutch pin end 68 which is disposed within the wrist shaft detent 46. When the probe 160, carriage assembly 130 or the frame front end 98, contacts an immovable surface, such as a baffle plate 192, while the end effector 10 is being moved horizontally between baffle bolts, the clutch pin assembly 60, and all assemblies attached thereto will stop moving while the robot arm 200 and wrist motor assembly 20 continue to move. This action forces the clutch pin 62 to slide out of the wrist shaft detent 46 and contact the wrist shaft lower end 44. Because the wrist shaft lower end is cylindrical, there is little friction and the clutch pin assembly 60, and all assemblies attached thereto, will rotate freely about the wrist shaft lower end 44. Both the wrist motor assembly housing 30 and the carriage assembly motor assembly housing 110 have couplings 32, 116 that provide access for pressurized air tubes. In operation the pressurized air tube create a positive pressure within the wrist motor assembly housing 30 and probe motor assembly housing 110 so that any seal leakage results in air escaping from the wrist motor assembly housing 30 or carriage assembly motor assembly housing 110 rather than water infiltration into the housing 30, 110. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.