Patent Number: 051125668
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to measurement devices in general and more particularly to a device which utilizes articulated sensors for dimensionally characterizing elongate components. There are numerous components in industrial and utility installations that require on-site inspection to verify continued serviceability. Such inspections may be required before the component is placed in service or it may be part of a maintenance program to ascertain whether the component can continue to be used. Component inspections frequently include dimensional measurements. A notable example, for present purposes, is the on-site inspection of components of a nuclear reactor, especially replaceable components such as control rods, fuel elements, and fuel channels. For example, a typical fuel assembly having a removable and reusable flow channel is shown in U.S. Pat. No. 3,689,358. Such channel is an elongate square, tubular member often formed of a Zircaloy alloy. It is necessary to assure that the four major exterior surfaces of such channels are sufficiently flat so as to not interfere with the insertion of control rods between fuel assemblies during operation in the nuclear reactor core. Dimensions of interest include face bulge, channel width, non-squareness, longitudinal bow, and twist. Dimensional tolerances over the length of such channel may be on the order of about 0.127 mm. Since channels and other reactor components which have been in service are radioactive, it is necessary that the measuring device be remotely operable under water to protect the equipment operator from exposure to radiation. Also, it is desirable that the measuring device be sufficiently portable for its repositioning within a water pool, for movement from one pool to another, and for removal to dry storage when not in use. Examples of prior art measuring devices can be found in U.S. Pat. Nos. 4,197,652 and 4,274,205. BROAD STATEMENT OF THE INVENTION One aspect of the present invention is a device for measuring dimensional characteristics of an elongate component which preferably is a nuclear reactor fuel channel. The device comprises an elongate rigid support that bears (i) an upper platform upon which is mounted a drive; (ii) a clamp mechanism for securing said component about its proximal at a reference position; and (iii) a lower platform which supports a pedestal for securing said component about its distal end in a reference position. Said device also has a sensor carriage movably mounted to said rigid support and operatively connected to said drive for movement along the elongate extent of said support and which has an opening penetrating therethrough for receiving said elongate component when it is secured by and substantially parallel to the rigid support. The sensor carriage comprises another aspect of the present invention. The sensor carrier bears a plurality of pivotally-mounted bell cranks spaced about said opening. Each bell crank has a wheel for riding on said component during movement of the carrier and being in contact with a sensor capable of providing a signal correlative to displacement of the bell crank during movement of the carrier along the elongate component. Preferred sensors comprise linear variable differential transformers that are mounted substantially parallel with the component and rigid support. As another aspect of the present invention there is a grapple assembly provided for securing the component for its placement in the device and removal from the device. The grapple assembly includes a grapple body and an actuator shaft secured thereto. Preferably, the actuator shaft is secured both at the upper platform and just above the grapple body. The grapple body and pedestal both desirably contain spring-biased bearing block assemblies that press on the inner walls of the elongate component for placing it in a reference position. Advantages of the present invention include a device that is portable and easily set-up at remote locations for providing dimensional characterization of elongate components, especially nuclear reactor fuel channels. Another advantage is a device that readily is mounted under water and easily operable by an operator remotely distanced therefrom. Other advantages include a unique grapple assembly for moving the elongate component and for securing it to the device. Further advantages include a unique carrier assembly which permits all exterior sides of the elongate component to be dimensionally characterized simultaneously. Yet another advantage are unique centering mechanisms that precisely and reproducably locate the elongate component in a position within the device. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.