GB1311450A - Control of the temperature of glass melts in a crucible - Google Patents

Abstract

1311450 Crucibles; heat pipes HERMANN HEYE 20 March 1970 [22 July 1969] 55143/72 Divided out of 1310603 Headings F4B and F4U [Also in Division C1] The temperature of the glass melt in a crucible is controlled by fitting the crucible side or base with a heat pipe, i.e. a closed heat transfer system which comprises a hollow chamber conta ining a capillary structure holding a heat trans - fer medium and which incorporates a closed space within which the heat transfer medium can flow when vaporized, as when the crucible is heated to melt the glass and one part is hotter than the rest, the vaporized medium flowing away from the hotter region to condense in another region and the capillary structure returns the condensed medium to the region of vaporization, the heat pipe thereby maintaining homogeneity of the internal surface of the crucible. As shown, a melting crucible 310 is fitted with one or more heat pipes in a number of different ways. On the left, side walls 317 enclose heat pipes 320, 351, 352 and 353 and base 318 with one or more radial heat pipes 321, the wall 317 being heated as by electrical conductors 325 in a protective housing 327 and the base 318 being heated as by gas burners 330 regulated by valve 333. On the right, side wall 317 and 318 are themselves formed as heatpipes 335 which may be joined as shown, the base part being heated as by electrical conductors 339. In each case, the heat pipe 320, 321 335 has its inner surface provided with a capillary structure 323, 324, 337 holding the heat transfer medium. The crucible 310 is closed by a cover-plate 340 which may be pierced by a heat pipe 342 extending down almost to the base 318 and then angled along the base, to ensure a vertical homogenization of the melt 3 14 for a large crucible. Externally of the coverplate, a temperature control sleeve 345 may be traversed by a fluid control medium. Above the surface of the melt, the heat pipe may have a protective sheath which may be filled with molten glass to prevent corrosion. For working temperatures of between 1300‹ and 1600‹ C. and up to 1 metre depth of melt in the crucible, the outer casing and capillary structure may be of W with the heat transfer medium Pb for use outside the melt i.e. in the crucible walls or, for any position, of Ti+Zr+Mo with Li as medium. The capillary structure may be wire mesh, with or without an annular gap between the mesh and outer casing.