| 摘要 |
781,444. Dielectric heating. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Sept. 22, 1953 [Oct. 13, 1952], No. 25601/52. Class 39(3) [Also in Group XL(c)] A high frequency generator is coupled to dielectric heater electrodes through an inductive coupling which is overcoupled such that at the frequency employed the voltage output over the working band of frequencies will be a maximum at each end of the band, and will have a reduced value intermediate the extreme frequencies, and the apparatus is so adjusted that with the dielectric load material cold the frequency is on the outer slope of the frequency characteristic,. whilst when the material heats up the frequency drifts through the adjacent maximum towards the further maximum. With such an arrangement a process of heating a dielectric material whose dielectric constant varies with its temperature consists in causing such variation to vary the resonant frequency of the load circuit such as initially to build up the voltage across the electrodes between which the material is placed over a prescribed time interval, and with further rise in temperature of the material to maintain a working voltage across the electrodes for a further period. During the voltage build-up the electrodes may be pressed together to remove air gaps in the material which may cause sparking. Specification 781,443 [Group VIII ]is referred to. |
