Method for dielectric sealing of polyester materials

Claim 1

IN A METHOD FOR DIELECTRICALLY BONDING SUPER-IMPOSED PORTIONS OF THERMOPLASTIC MATERIAL BY APPLYING A RADIO FREQUENCY VOLTAGE OF PREDETERMINED FREQUENCY THERETO BY MEANS OF A PAIR OF SPACED OPPOSING ELECTRODES LOCATED IN A CIRCUIT HAVING MEANS TO VARY THE REACTIVE IMPEDANCE THEREIN, SAID ELECTRODES BEING RESILIENTLY URGED INTO CONTACT WITH SAID PORTIONS TO COMPRESS THE MATERIAL DURING BONDING, THE IMPROVEMENT COMPRISING: (A) TUNING THE CIRCUIT TO AN IMPEDANCE VALUE WHICH IS SUFFICIENTLY FAR OFF RESONANCE AT SAID PREDETERMINED FREQUENCY TO PREVENT SUCH BONDING UPON APPLICATION OF SAID RADIO FREQUENCY VOLTAGE; (B) APPLYING RADIO FREQUENCY VOLTAGE OF SAID PREDETERMINED FREQUENCY TO SAID CIRCUIT; (C) VARYING THE REACTIVE IMPEDANCE IN THE CIRCUIT TO BRING THE CIRCUIT NEAR RESONANCE AT SAID FREQUENCY SO THAT VOLTAGE ACROSS THE ELECTRODES BECOMES SUFFICIENT TO CAUSE SOFTENING AND FUSING OF THE SUPERIMPOSED PORTIONS AND MOVEMENT OF SAID ELECTRODES TOWARD ONE ANOTHER AS SAID PORTIONS ARE COMPRESSED THEREBETWEEN DURING FUSING; AND (D) CONTINUING TO VARY SAID REACTIVE IMPEDANCE TO MAINTAIN SAID CIRCUIT NEAR RESONANCE AT SAID FREQUENCY TO COMPENSATE FOR A CHANGE IN CAPACITANCE CAUSED BY SUCH MOVEMENT OF SAID ELECTRODES DURING SUCH FUSING.