IMPROVED TUBE DRIVE APPARATUS EMPLOYING FLEXIBLE DRIVE BELTS

Abstract: The invention relates to apparatus for driving a generally cylindrical, elongate member, such as a tube or rod, along and about the longitudinal axis thereof. The apparatus (14) has several drive units (24) arrayed about an axis corresponding to the longitudinal centerline (34) of the elongate member (12) to be driven. Each drive unit (24) comprises a pair of rotatable members (pulleys 50, 52), and an endless flexible drive belt (48) trained around the rotatable members in a manner enabling the drive belt itself to be drivingly engaged with the elongate member to be driven. At least the rotatable member (50) near said axis is adapted to be selectively angulated relative to said axis so as to render the motion imparted to the elongate member selectively variable between pure rotation about, and pure translation along, the longitudinal centerline of the elongate member (12).

Description: The present invention relates to apparatus for driving a substantially cylindrical elongate member, such as a rod or tube, along and about a longitudinal centerline thereof. Because of their critical roles as fuel, control and instrumentation rods in nuclear reactors, tubes composed of zirconium and other materials must meet very stringent quality control standards. Ultrasonic testing is one common method used to identify material flaws or unacceptable dimension deviations in the tubes. One conventional tube inspection technique involves moving a tube past ultrasonic testing device. The testing device includes an ultrasonic source with transducers located adjacent the moving tube which are capable of transmitting an ultrasonic signal toward the moving tube and receiving an echo from the tube, and then analyzing it to determine the acceptability of the tube. The ultrasonic source is capable of transmitting pulses in the megahertz range and so in order to effectively take advantage of this, the tube is moved longitudinally past the ultrasonic source and sometimes is simultaneously rotated axially, thus causing the pulses to strike along a helical pattern or path around the tube which results in a maximum number of meaningful data points. One conventional drive apparatus used for moving tubes past an ultrasonic testing apparatus in this manner employs an arrangement of three rotating rollers positioned radially with respect to the axis or centerline of the tube at approximately 120 degree intervals from one another around the circumference of the tube. The rollers are angularly oriented with respect to the tube centerline so as to produce simultaneously longitudinal movement and axial rotation of the tube. Each of the rollers has a polyurethane rim which engages the tube. The rim is mounted on a steel wheel driven by means of a steel-core belt trained over a drive wheel, and the shaft of the roller can be inclined with respect to that of the drive wheel so as to adjust the longitudinal movement and axial rotation of the tube. With such an arrangement, if the rim of a roller develops a flat spot from friction caused by improper alignment or a temporary binding condition, the flat on the rim will impact the tube once every revolution and, upon each impact, can possibly dent the tube; it also will cause the smooth motion of the tube to be interrupted and thereby make it difficult to synchronize the ultrasonic source with the passing tube. Furthermore, the steel-core belt driving each roller, although very durable, is relatively rigid and, as a result, restricts the angle through which the roller shaft can be adjusted relative to the tube centerline to approximately ten degrees. The invention has for its principal object to provide an improved tube drive apparatus which avoids these problems and limitations of the conventional drive arrangement used heretofore. Accordingly, the invention resides in a tube drive apparatus employing radially oriented flexible drive belts capable of drivingly engaging a tube at any angle within a ninety-degree range relative to the centerline of the tube. It is the flexibility of the belt which allows the shafts of the belted wheel and of the drive wheel to be inclined relative to each other anywhere from zero to ninety degrees, causing the tube correspondingly to merely rotate with no longitudinal movement or to longitudinally move with no rotation. Thus, the drive apparatus embodying the invention can be adjusted to axially rotate and longitudinally move the tube at a large number of combinations of rotational and longitudinal speeds along a helical or straight path past the ultrasonic inspection source, which is something that was impossible to achieve heretofore because of the relative rigidity of the previously used steel-core belts. In addition, by using belts rather than rollers to contact the tube, the greater length of the belt compared with the circumference of the roller provides a contact length equivalent to that of a roller having a much larger diameter, which yields a belt life much greater than that of the smaller-diameter polyurethane rollers. In summary, the versatility and performance of the drive apparatus embodying the invention are greatly enhanced over the conventional drive apparatus. More specifically, the improved tube drive apparatus has a plurality of drive units, mounting means disposing the drive units in respective orientations angularly displaced about and radially extending from a longitudinal centerline of a tube to be driven by the drive units, and power means drivingly coupled to the drive units for transmitting driving motion thereto. Each of the drive units comprises an endless flexible drive member and a pair of spaced rotatable members entraining the flexible drive member such that the flexible member can drivingly engage a tube for transmitting driving motion thereto. In addition, support means are provided for mounting the rotatable members in their spaced relationship and in a manner such that at least one of the rotatable members is angularly displaceable with respect to the other and relative to the centerline of the tube such that the driving motion transmitted to the tube by the flexible member can be apportioned between rotational and longitudinal motion. Furthermore, adjustment means are connected to the support means for changing the angular relationship of the one rotatable member relative to the centerline of the tube so as to correspondingly change the direction of the motion applied to the tube. A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevational view of a tube inspection station employing tube drive apparatus according to invention at both the entry and the exit ends of the station; Fig. 2 is an enlarged side elevational view of the tube inspection station of Fig. 1, showing the components of the improved tube drive apparatus in greater detail; Fig. 3 is an enlarged end elevational view of the improved tube drive apparatus located at the (entry)exit end of the inspection station, as taken along line 3--3 of Fig. 2; Fig. 4 is an enlarged top plan view of the improved tube drive apparatus located at the (entry)exit end of the inspection station, as taken along line 4--4 of Fig. 2; Fig. 5 is an enlarged longitudinal sectional view of one of the radially oriented drive units of the improved apparatus, as taken along line 5--5 of Fig. 3; Fig. 6 is a side elevational view, partly in section, of the one drive unit of the improved apparatus, as taken along line 6--6 of Fig. 5; Fig. 7 is a fragmentary sectional view of an end of another drive unit of the improved apparatus, similar to the corresponding end of the one drive unit of Fig. 5 but without a handle for manually rotating the improved apparatus; Fig. 8 is an enlarged cross-sectional view of the one drive unit as taken along line 8--8 of Fig. 6; Fig. 9 is another enlarged cross-sectional view of the one drive unit as taken along line 9--9 of Fig. 6; Fig. 10 is yet another enlarged cross-sectional view of the one drive unit as taken along line 10--10 of Fig. 6; Fig. 11 is an enlarged cross-sectional view of the one drive unit similar to that of Fig. 10, but showing the opposite extreme stop position of the rotatable inner cylinder; Fig. 12 is an end view of the one drive unit as seen along line 12--12 of Fig. 6; Fig. 13 is a schematic representation of the tube drive apparatus embodying the invention; Fig. 14 is a schematic representation of a fragmentary portion of the improved apparatus as seen along line 14--14 of Fig. 13, showing the belted wheel of one drive unit disposed generally perpendicular to the centerline of the tube for only axially rotating the tube. Fig. 15 is another schematic representation similar to that of Fig. 14 but showing the belted wheel disposed at an angle to the centerline of the tube for both axially rotating and longitudinally moving the tube; and Fig. 16 is still another schematic representation similar to that of Fig. 14 but showing the belted wheel disposed generally parallel to the centerline of the tube for only longitudinally moving the tube. In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings, and terms such as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are employed as words of convenience not to be construed as limiting terms. Referring now to the drawings, and particularly to Fig. 1, reference numeral 10 generally designates the station for ultrasonically inspecting tubes 12 to be used in fuel, control and instrumentation rods of a nuclear fuel assembly. The tube inspection station 10 employs tube drive apparatus 14 embodying the invention at both its entry end 16 and its exit end 18 for driving the tubes 12 (each about fifteen feet in length but connected together in a continuous string by couplers) in the direction of the arrow through a conventional inspection tank 19 in the station 10 and past conventional ultrasonic testing apparatus (not shown) associated therewith. The drive apparatus 14 at the entry end 16 feeds the tubes 12 from a tube delivery apparatus 20 upstream of the entry end 16 into the tank 19, and the drive apparatus 14 at the exit end 18 moves the tubes 12 from the tank to a tube removal apparatus 22 disposed downstream of the exit end 18 of the station. Since the inspection operation itself forms no part of the invention, it will not be described any further herein; indeed, it should be noted that the tube drive apparatus 14 of the invention could be used to drive tubes for purposes other than quality inspection. Referring now also to Figs. 2 to 4, each of the tube drive apparatus 14 at the entry and exit ends 16, 18 of the inspection station 10 includes a plurality of drive units 24, means in the form of a three-jaw self-centering scroll chuck 26 for mounting the drive units 24, and power means in the form of a motor 28 and drive train 30 for transmitting driving motion to the drive units 24. The chuck 26 is mounted on the inspection station frame 32 and supports the drive units 24 in respective orientations angularly displaced about and radially extending with respect to the longitudinal centerline 34 of the tube 12 received through the chuck 26. The adjustable scroll chuck 26 is a device of well-known construction and operation. As seen in Fig. 3, a wrench 36 is used to radially adjust the positions of the jaws of the chuck 26 to accommodate tubes of different diameters. Concurrently as the radial configuration of the chuck 26 is adjusted to fit the particular diametric size of the tube 12, the radial positions of the drive units 24 are also adjusted to fit the tube so as to ensure driving engagement therewith. The drive motor and trains 28, 30 are mounted on the inspection station frame 32 in such manner as to transmit drive motion to each of drive apparatus 14. One drive train 30, comprising a motion transmitting belt 38 and a series of pulleys 40, is associated with each drive apparatus 14, whereas the drive motor 28 is common to both drive trains, being connected thereto through a cross shaft 42 rotatably mounted on the frame 32 and having drive pulleys 44 secured thereto adjacent its opposite ends. A pivotal take-up and expansion mechanism 46 (Fig. 3) is operatively associated with one of the pulleys 40 of each drive train 30 for maintaining the motion transmitting belt 38 of the respective drive train 30 in a taut driving condition regardless of radial positions of the drive units 24. As seen from Figs. 2 to 4, and especially from Figs. 5 to 7 and 13, each drive unit 24 includes an endless flexible member in the form of a drive belt 48, such as one composed of polyurethane, and a pair of spaced inner and outer rotatable members in the form of circumferentially grooved wheels or pulleys 50, 52 which entrain the flexible drive belt 48 in a taut driving condition. The inner rotatable pulley 50 has a belt-carrying groove 54 which is shallower than the groove 56 in the outer pulley such that the part 58 of the endless drive belt 48 traveling around the inner pulley 50 extends outwardly beyond the periphery of the pulley 50 and drivingly engages the tube to transmit driving motion thereto. Furthermore, each drive unit 24 includes support means in the form of a mounting plate 60, an outer housing 62 attached in fixed relation to the plate 60, and an inner hollow cylinder 64 rotatably disposed in a cylindrical bore 66 formed through the outer housing 62. The drive unit 24 is mounted on the scroll chuck 26 by means of bolts 68 securing the plate 60 at its inner end to one of the jaws 69 of the chuck 26. A bearing 70 supported in the outer end of the plate 60 rotatably mounts a stub shaft 72 which has one of the pulleys 40 of the drive train 30 attached on its one end and has the outer rotatable pulley 52 of the drive unit 24 attached on its opposite end. Parenthetically, it should be mentioned here that one of the drive units 24 has attached on its outer stub shaft 72 a wheel handle 74 for manually operating the drive train 30, and thus the drive belts 48 of the drive units 24, so as to move the tube 12 by hand. As seen from Fig. 7, the stub shafts 72 of the other drive units 24 only have the outer pulley 52 on the end thereof since a handle, such as handle 74, is not necessary on each drive unit. As mentioned above, the outer housing 62 is attached in fixed relation to the mounting plate 60. The inner hollow cylinder 64 is supported for rotation relative to the housing 62 and plate 60 by a bearing 76 mounted in the cylindrical bore 66 defined through the housing 62. Another shorter stub shaft 78 is rotatably supported on an inner end of the hollow cylinder 64 and has the inner pulley 50 of the drive unit 24 attached thereto. As seen from Fig. 5 and 12, the inner and outer pulleys 50, 52 thus are aligned with and spaced from one another at opposite ends of the hollow interior of the cylinder 64 such that the drive belt 48 entrained about the pulleys can pass unobstructedly through the cylinder. Due to the fact that the cylinder 64 which supports the inner pulley 50 is rotatable relative to the outer housing 62 and the mounting plate 60 which supports the outer pulley 52, the inner pulley 50 and inner end 58 of the drive belt 48 entrained about the pulley 50 are angularly displaceable with respect to the outer pulley 52 and thus also relative to the centerline 34 of the tube. Thus, due to the flexibility of the drive belt 48, and by rotating the inner cylinder 64 relative to the outer housing 62, runs 80 of the drive belt 48 can be changed anywhere between generally parallel (Figs. 6 and 8 to 10) and criss-cross (Fig. 11) orientations; correspondingly, the driving motion transmitted to the tube 14 by the flexible drive belt end 58 can be apportioned anywhere between pure rotational and pure longitudinal motion. Finally, as seen from Figs. 5, 6 and 8 to 10, each drive unit 24 includes adjustment means in the form of circumferentially extending calibration and adjustment slots or recesses 82, 84 and a calibration gage 86 and adjustment worm gear or ratchet screw 88 threadably connected to the outer housing 62 and extending into the respective recesses in the inner rotatable cylinder 64. The calibration recess 82 includes a pair of stops 90, defined at opposite ends thereof, which represent ninety-degree angularly displaced extreme positions of the cylinder 64 and, thus, of the inner pulley 50 and the belt end 58. The calibration gage 86 is rotated to accurately preset where the positions of these stops 90 will actually be located. The outer end of the ratchet screw 88 has a knob 92 for manually rotating the screw, and a threaded inner end 94 adapted to mesh with teeth 96 defined in the adjustment recess 84. It is readily apparent that, by rotating the ratchet screw 88, the inner cylinder 64 can be rotated ninety-degrees between the two extreme limits shown in Figs. 10 and 11. Such rotation of the cylinder 64, as explained above, changes the angular relationship of the inner pulley 50 with respect to the outer pulley 52 and relative to the centerline 34 of the tube, thereby changing the runs 80 of the drive belt 48 between parallel (Figs. 8 to 10) and criss-cross (Fig. 11) orientations. The end 58 of the drive belt 48 can thereby be angularly changed relative to the centerline of the tube so as to vary the motion of the tube produced by engagement of the belt end 58 from solely axial rotation, as schematically depicted in Fig. 14, to solely longitudinal movement, as schematically shown in Fig. 16, and any combination of the two motions therebetween, as schematically indicated in Fig. 15.

Claims: Apparatus (14) for driving a substantially cylindrical, elongate member (12) about and along an axis corresponding to a longitudinal centerline (34) of the elongate member to be driven, said apparatus including several drive units (24) arrayed about said axis and supported in angularly spaced relationship with respect to each other, characterized in that each of said drive units (24) comprises - (a) an endless flexible drive member (48); (b) a pair of rotatable members (50,52) entraining said flexible drive member (48) in a manner enabling the latter itself to drivingly engage the elongate member (12) to be driven; (c) support means (60,62,64) supporting said rotatable members (50,52) in spaced relationship with respect to each other and such that at least one (50) of the rotatable members which is proximate to said axis is angularly displaceable relative to the latter so as to permit the driving motion transmitted to the elongate member (12) by the flexible drive member (48) to be selectively apportioned between a purely rotational motion and purely longitudinal motion; and (d) adjustment means (82,84,86,88) connected to said support means (60,62,64) for selectively changing the angular relationship of the angularly displaceable rotatable member (50) relative to said axis and, thus, to the longitudinal centerline (34) of the elongate member (12). Apparatus according to claim 1, characterized in that said flexible drive member (48) is a belt, and said one rotatable member (50) is angularly displaceable with respect to the other rotatable member (52) to an extent permitting a pair of runs (80) of said belt (48) to be changed between generally parallel and criss-cross orientations with respect to one another. Apparatus according to claim 1 or 2, characterized by power means (28,30) drivingly coupled to all of said drive units (24) for transmitting driving motion thereto. Apparatus according to claim 3, characterized in that said power means (28,30) is drivingly coupled to the other (52) of said rotatable members (50,52). Apparatus according to claim 1, 2, 3 or 4, characterized in that said support means (60,62,64) comprises a stationary outer member (60,62) which rotatably supports the other (52) of said rotatable members (50,52); and an inner cylinder (64) which is rotatably supported by said outer member (60,62) and rotatably supports said one rotatable member (50) such that rotation of said inner cylinder (64) relative to said outer member (60,62) causes said one rotatable member (50) to be angularly displaced relative to the other rotatable member (52). Apparatus according to claim 5, characterized in that said inner cylinder (64) is hollow, and said rotatable members (50,52) are disposed at opposite ends of the cylinder (64) and aligned with each other, said flexible drive member (48) extending through said cylinder (64). Apparatus according to claim 5 or 6, characterized in that said adjustment means (82,84,86,88) includes a calibration recess (82) formed in said inner cylinder (64) and having oppositely facing stops (90) defining rotational limits of said cylinder (64) and, thus, angular displacement limits of said one rotatable member (50) relative to the outer rotatable member (52); and a calibration gage (86) threadably connected to said outer member (60,62) and adjustably disposable in said recess (82) for determining the positions of said rotational limits of the cylinder (64). Apparatus according to claim 5, 6 or 7, characterized in that said adjustment means (82,84,86,88) includes an adjustment recess (84) formed in said inner cylinder (64) and having engageable elements (96) defined therein; and a ratchet screw (88) threadably connected to said outer member (60,62) and engaged with said engageable elements (96) in said recess (84) for rotating said inner cylinder (64) relative to said outer member (60,62) upon rotation of said ratchet screw (88).

Inventors: CLARENCE, DANIEL JOHN JR.
Applicants: WESTINGHOUSE ELECTRIC CORPORATION
Application year: 1987
Main classification: G21C17
IPC codes: G21C17, G01N29, G01B5, G01B7, B23Q5, B23Q1