Refractory shields for curved and straight superheater tubes

Claim 1

A refractory shield for protecting correspondingly shaped sections of straight and curved superheater tubes against attack by the products of combustion comprising: a pair of elongated refractory half shields of identical interchangeable, interfitting, interlocking size and shape adapted when one half shield is turned longitudinally end for end relative to the other half shield to fit laterally together, be shifted longitudinally a short distance relative to one another, cammed and interlocked together to close diametrically opposite joints between the half shields and thereby cover and protect a section of a superheater tube of corresponding shape, each half shield having an elongated sidewall portion of predetermined thickness and longitudinal length between opposite ends thereof, extending circumferentially between and to diametrically opposite inner sides lying in a central plane; a plurality of identical mating camming portions spaced longitudinally between the opposite ends of and along the sidewall adjacent each of the diametrically opposite inner sides of the sidewall and each camming portion having a central junction lying in a radial plane at its center and located substantially the same predetermined distance from an adjacent one of the opposite ends as is the central junction of another camming portion situated adjacent the same one of the diametrical opposite inner sides is from the other adjacent one of the opposite ends, a raised inclined cam of predetermined identical size, shape, and inclination extending from a portion of the sidewall and the diametrically opposite inner side on one and the same side of the central junction and the central plane of the half shield, and each raised cam having and inclined from a small end portion at one side of the camming portion to a larger end portion at the central junction, and, an overhanging recessed inclined cam receiving portion of predetermined identical mating size, shape and inclination projecting from a portion of the sidewall portion and the diametrically opposite inner side and situated on the opposite and same side of the central junction and the central plane, and each recessed inclined cam receiving portion having and inclined opposite to the raised cam from a small end portion at an opposite side of the camming portion to a larger end portion at the central junction, adapted to laterally enter a space of greater width adjacent each of the camming portions of the other half shield and moved longitudinally a relatively small distance to matingly engage the raised inclined cams of the other identical half shield turned end for end relative to the other of the pair of identical half shields whereby the overhanging recessed inclined cam receiving portions and the raised inclined cams of each of the pair of identical half shields slidably engage one another and simultaneously pull and lock the pair of half shields together and close the joints therebetween.