Patent Number: 052079767
Section: description

DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like are words of convenience and are not to be construed as limiting terms. Referring now to the drawings, and particularly to FIG. 1, there is shown a nuclear fuel pellet surface defect inspection apparatus, generally designated by the numeral 10, which employs a pellet slide and inspection assembly 12 for separating and inspecting pellets P in accordance with the principles of the present invention. In its basic arrangement, the inspection apparatus 10 includes the pellet slide and inspection assembly 12 and a pellet infeed conveyor 14 at the input side of the assembly 12 and a pellet discharge conveyor 16 at the output side of the assembly 12. More particularly, the pellet infeed conveyor 14 can be a vibratory conveyor and the pellet discharge conveyor 16 can be a belt conveyor. Referring to FIGS. 1-3, the pellet slide and inspection assembly 12 basically includes a pellet slide 18, an inspection station 20, and an ultrasonic inspection head 22. As also seen in FIGS. 4-10, the pellet slide 18 of the assembly 12 is an upstanding plate-like structure defining an inclined track 24. The track 24 is V-shaped in cross-section adapting it to support a cylindrical pellet P therealong. The track 24 has a lower exit end 26 adjacent to the discharge conveyor 16 and an upper entry end 28 adjacent to the infeed conveyor 14. The inclined orientation of the track 24 places its entry end 28 at a higher elevation than its exit end 26 such that a pellet P received at its entry end 28 will slide under the influence of gravity downwardly to its exit end 26 without any motive assistance. The inspection station 20 is located along the inclined track 24 between and spaced from both the entry and exit ends 26, 28 thereof. The inspection head 22 is mounted at the inspection station 20 and is operable to transmit and receive sound energy to and from a pellet P as it moves through the inspection station 20. One pellet at a time is inspected for surface defects at the inspection station 20. Each pellet P is pushed over an upper ledge or edge 18A of the pellet slide 18 by another pellet P located behind it on the vibratory infeed conveyor 14. As each pellet goes over the edge 18A, it accelerates down the slide track 24, thereby creating a space or separation between it and the next succeeding pellet when pushed over the edge 18A. In such manner, each pellet P will move through the inspection station 20 one at a time. The inclined track 24 of the pellet slide 18 also has an upper portion 24A which extends from the entry end 28 of the track 24 through the inspection chamber 20 and a lower portion 24B which extends from the inspection chamber 20 to the exit end 26 of the track 24. The upper portion 24A of the track 24 defines a substantially linear path of movement of the pellets from the entry end 28 of the track 24 through the inspection chamber 20. Likewise, the lower portion 24B of the track 24 defines a substantially linear path of movement of the pellets from the inspection chamber 20 to the exit end 26 of the track 24. However, as can be readily observed in FIGS. 2 and 4, the lower portion 24B has a shallower, or more gradual, slope than the upper portion 24A of the track 24 so that the pellet P decelerates as it moves from the upper portion 24A to the lower portion 24B of the track 24. The deceleration reduces the velocity of the inspected pellet as it approaches the exit end 26 of the track 24. Thus, after each pellet P moves through the inspection chamber 20, it is decelerated by the change (decrease) in the slope of the slide track 24, which greatly reduces the possibility of the pellet chipping due to contact with the discharge conveyor 16 at the exit end 26 of the pellet slide 18. Referring to FIGS. 11-16, inspection station 20 of the pellet slide and inspection assembly 12 includes lower and upper sound reflectors 30, 32 between which each pellet P travels through the inspection station 20. The upper sound reflector 32 has a recess 33 defined in a bottom thereof and a semicircular groove or cavity 36 defined in the recess 33 so as to provide recessed bottom surface portions 31 extending along opposite sides of the semicircular cavity 36. The lower sound reflector 30 has a semicircular groove or cavity 34 defined on a top thereof so as to provide top surface portions 35 extending along opposite sides of the semicircular cavity 34. The lower semicircular cavity 34 is complementary in size to the upper semicircular cavity 36. The lower sound reflector 30 inserts into the recess 33 of the upper sound reflector 32 so as to mate therewith at the respective top and bottom surface portions 31, 35 such that the respective have complementary semicircular grooves or cavities 34, 36 form an annular, or preferably cylindrical, inspection chamber 38 through which each pellet P moves as the pellet slides down the inclined track 24. The annular inspection chamber 38 completely encloses the circumferential surface of the pellet P as the pellet moves through the chamber 38 which provides improved accuracy in the sound signals reflected back to the inspection head 22. The upper sound reflector 32 having a central opening 32A through which extends a lower portion of a horn 40 of the inspection head 22 mounted at the inspection station 20. Sound transmitting and receiving transducers (not shown) are contained by the inspection head 22. The sound energy is transmitted and received through the central opening 32A of the upper reflector 32. The upper sound reflector 32 also mounts light transmitting and sensing devices 42, 44 in alignment with first and second series of spaced apart holes 46, 48 defined through the body of the reflector on opposite sides of the inspection chamber 38. The transmitting devices 42 transmit light across the inspection chamber 38 and thus across the path of movement of a pellet P through the chamber. The sensing devices 44 receive the light transmitted across the inspection chamber 38 and thereby sense the position of the pellet P as it moves through the inspection chamber 38. Also, retainer bolts 50 and blocks 52 are attached to the upper reflector 32 for retaining the devices 42, 44 in the desired positions thereon in alignment with the series of holes 46, 48. More particularly, the inclined track 24 of the pellet slide 18 has a cutout 54 located in its upper portion 24A, between and spaced from the entry and exit ends 28, 26 thereof. The lower sound reflector 30 has spaced legs 30A by which it is disposed over in straddling relation the slide 18 within the cutout 54 of the track 24. The lower reflector 30 also includes a pair of slots 56 seating a pair of rails 58. The rails 58 extend and bridge between opposite edges 54A of the track cutout 54 for supporting the pellet P as it moves through the inspection chamber 20, as can be seen in FIG. 3. A pellet ejector device (not shown) may be disposed adjacent the exit end 26 of the track 24. It can be operated to prevent an inspected pellet found to be defective from exiting from the track 24 onto the discharge conveyor 16. Instead, the defective pellet can be diverted by the ejector device into a container for collection of the defective pellets. Since the ejector device forms no part of the present invention, it need not be illustrated nor described in any further detail. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.