| 摘要 |
A method of heating glass tubes, particularly quartz tubes for the manufacture of optical fibres, where the tube is pre-heated, preferably by means of a gas flame, whereafter the tube is heated by means of microwave energy generated by a microwave generator (1), by introducing the tube axially into a microwave cavity (3) comprising in its end walls (6,7) or end surfaces openings for the tube. According to the invention, at least one electrical field is given a field image according to a TM-0n0-mode, preferably according to the TM-020-mode, which mode has a maxima (10) along the central axis (9;c-c) of the cavity (3) and a minima (11,12) on each side of and radially spaced from the central axis (9;c-c), where the electrical field portion located between the minima (11,12) is used for heating the wall of the glass tube (8). According to a preferred embodiment, an additional electrical field is caused to be formed by means of a second microwave generator (15), which field is given a field image according to a TE-01n-mode, preferably according to the mode TE-011, which field therewith is superposed upon the field according to the TM-0n0-mode. |
