Patent Number: 053944461
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with a preferred embodiment of the invention (see FIGS. 3 and 4), the uncoupling rod centering gauge 100 comprises a platelike cross handle 102 having a generally square-shaped central portion and four arms 102a-102d extending therefrom. The arms are disposed at right angles relative to each other. The arms are sized such that the gauge cannot be inadvertently left in when reinstailing the CRD after maintenance. The central portion of cross handle 102 further has a pair of concentric rings 104, 106 welded to bottom surface and extending downward. Cross handle 102 sits atop spud 46 with guide ring 104 surrounding the fingers of spud 46 and with centering ring 106 projecting inside the spud. Centering ring 106 has an outer circumferential surface which provides support for the fingers on the inside of the spud by blocking radially inwardly directed flexure of the spud fingers. The annulus between rings 104 and 106 is dimensioned such that the spud fingers reside therein in a flexed state, the return spring force of the spud fingers acting to grip the centering ring 106, whereby the gauge 100 is held securely in place atop the spud. This process ensures that the spud fingers have not been damaged and are concentric. Centering ring 106 further has a circular cylindrical centering bore 108, which continues through cross handle 102. The diameter of centering bore 108 is slightly greater than the diameter of rod 48 of the uncoupling rod. When the uncoupling rod centering gauge is correctly seated atop the spud, free axial movement of rod 48 inside centering bore 108 indicates that the uncoupling rod is correctly installed in the spud. As shown in FIG. 5, the spud 46 has a clover-leaf shaped through-hole consisting of a central hole for receiving the uncoupling rod 48 (which is welded inside tube 43) and three lobes 114, commonly referred to as the "spud flow holes". The spud flow holes are arranged to intersect the central hole at equal angular intervals along the periphery thereof. The radius of each spud flow hole 114 is slightly greater than the radius of center hole. Since the diameter of tube 43 of the uncoupling rod is such that it fits snugly inside the center hole, it is true, albeit undesirable, that the uncoupling rod also fits inside any one of the spud flow holes. Thus, incorrect installation of the uncoupling rod is possible. The gauge of the present invention is designed to ensure correct installation of the uncoupling rod. The gauge is mounted on the spud after the uncoupling rod has been inserted. FIG. 3 shows an uncoupling rod (consisting of rod 48 and tube 43 welded together) which has been correctly inserted in the center hole 112 of spud 46. In this case, the uncoupling rod is free to slide up and down in the centering bore 108 of gauge 100 without binding. In the event that the uncoupling rod had been mistakenly inserted in one of the spud flow holes, binding of rod 48 inside centering bore 108 would occur, indicating incorrect installation. The gauge would then be removed and the uncoupling rod would be withdrawn from the spud flow hole and then re-inserted into the center hole of the spud. After assembly is complete, the CRD must be transported to the under vessel area. In the assembled state, spud 46 protrudes from the outer filter 45, exposing it to possible damage during CRD transport. Therefore, it is desirable to leave the uncoupling rod centering gauge 100 in place to protect the spud during transfer. The uncoupling rod centering gauge in accordance with the preferred embodiment of the invention has a cross handle for ease in handling. The outer perimeter of the gauge as defined by the ends of radially outwardly projecting arms 102a-102d has a radius such that the CRD cannot be installed inside the reactor if the gauge has not been removed from the spud. The preferred embodiment of the uncoupling rod centering gauge has been disclosed for the purpose of illustration. Variations and modifications of the disclosed structure which do not depart from the concept of this invention will be readily apparent to mechanical engineers skilled in the art of tooling. All such variations and modifications are intended to be encompassed by the claims set forth hereinafter.