| 摘要 |
<p>668,680. Seaming non-metallic sheet material. SINGER MANUFACTURING CO. Feb. 17, 1950 [April 6, 1949], No. 4122/50. Class 42 (i). [Also in Group XI] A machine for seaming dielectric sheet material by the application of a radio-frequency field comprises means for feeding the material progressively through the field, a reciprocatory electrode for periodically engaging the material, a stop to limit the material-engaging movement of the electrode, an oscillator, switch contacts for turning the oscillator on and off, a pivoted element carrying one of the contacts, means for actuating the element directly to close and open the contacts periodically, and a lostmotion connection between the electrode and the contact-carrying element whereby the electrode is actuated after the lost-motion has been taken up. As shown, a. roller 31 on the electrode bar 23 presses downwardly, on to the lower arm of a fork 17 which is pivoted at 19 and is spring-pressed on to the lift eccentric 16. Fork 17 carries the adjustable upper contact 51 of an oscillator switch, the lower contact 35 being carried by an extension bar 40 fixed to presser bar 36. Downward movement of electrode bar 23 is limited by engagement of a stop pin 33 with the upper surface 71 of bar 40. Switch contact 51 is biased downwardly by a spring 57. Owing to the lostmotion connection between fork 17 and roller 31, fork 17 continues to move downwardly after electrode bar 23 has been arrested by stop pin 33, and the switch contact 51 is set so that the switch closes immediately after the electrode comes to rest. Similarly the switch opens immediately before the electrode commences to rise again. Thus a maximum bonding time is provided consistent with avoidance of arcing.</p> |
