Thomas Boch insulator design details

GLAZE-FILLED INSULATORS.

It is known that in the matter of glass and porcelain insulators for high-tension transmission lines, the latter have the advantage as regards mechanical strength; but the difficulty has been to produce high-voltage insulators of porcelain uniformly free from flaws. R. Thomas & Sons' Company, of East Liverpool, Ohio, claims to have accomplished the task of producing flawless insulators of porcelain which have also great mechanical strength. The insulator is "glaze-filled" and is patented by J. W. Boch, whose invention is based on the seemingly obvious fact that a thin piece of clay will mould and vitrify better than a thick piece. For this reason the insulator is made of two or more shells nested together. In Fig. 10 the figures 2 and 3 indicate the three shells which make up a triple petticoat insulator. The inner piece, 3, is moulded with a suitably-threaded socket, as shown by 4, for the usual pin, and the outer shell, 1, is provided with the usual notched head for the conductor; and, like the intermediate part, 2, made bowl-shaped, so that the three are relatively thin shells nested into each other. The individual parts are first dried separately in an oven, or kiln, by a process known as "biscuit firing;" the separate parts are next coated with glaze by being dipped in the glazing material, and are then fitted into each other and placed upside down in the position shown at 5. The parts thus put together and supplied with extra glaze at the joints, are put in the sagger with the petticoats uppermost and placed in the kiln. The glazing material melting, the shells are welded together by seams of glass-like glaze, which, it is claimed, are stronger than any of the other parts of the insulator.

Fig. 10 - Glazed Filled Insulators.