Patent GB-649356-A (GB)
Title: Radio frequency bar sealer for seaming dielectric sheet material
IPC: B29C65/04
Filed: 1948-06-04
Abstract: 649,356. Seaming non-metallic sheet material. SINGER MANUFACTURING CO. June 4, 1948, No. 15107. Convention date, Nov. 21, 1947. [Class 42 (i)] [Also in Group XI] In a machine for seaming dielectric sheet material using radio frequency electric heating comprising bar electrodes, a radio frequency oscillator, and a motor for relatively moving the electrodes into and out of bonding position, the oscillator is turned on when the electrodes reach a predetermined relative position and turned off after a predetermined elapsed bonding time, and selective switch means are provided for presetting control means for the motor to cause the motor to repeat continuously each operating cycle or to stop at the conclusion of each cycle. As shown, an upper bar electrode 12 is mounted to reciprocate in the head 13 of an arm 9, and a lower fixed electrode 11 is mounted in a bed 10. The lower, live electrode 11 is mounted in an insulating block 92, Fig. 2. The upper, earthed electrode 12 is mounted on a bar 62 carrying an adjustable block 64 and is biassed downwards by a spring 70 bearing on block 64, downward movement being limited by a stop pin 65. Electrode 12 is raised by engagement beneath block 64 of one end of a lever 72 which is biassed downwards by a spring 88 and is pivoted at 73. The other end of lever 72 is attached to a flexible steel band 76 which wraps partly around, and is secured to, a pulley 77 reversibly driven by a motor 80. Cams 81, 82 secured to pulley 77 operate limit switches 44, 47 respectively to reverse or stop motor 80 at the end of the desired movement of pulley 77 in either direction. Switchcontrolled electric circuits are provided to permit alternatively (a) manual, (b) continuous automatic, or (c) single-cycle automatic operation. Under continuous operation the following operative cycle occurs : with electrode 12 raised, and the work in position for sealing, switch 47 is in position to energize motor 80 so that it rotates in a direction to lower electrode 12. In the extreme " down position of electrode 12, switch 47 operates to stop the motor, to energize the electrodes, and to start a timer motor which after a predetermined interval shuts off the oscillator. Motor 80 is now oppositely energized to drive electrode 12 upwardly, so that the work can be removed, until switch 44 is actuated to reverse the motor, wherein the cycle is repeated. Provision is made under control of a manually-operated switch, for electrode 12 to dwell in the lowered position after the oscillator is cut off, the duration of the dwell being determined by another timing motor which is started when the oscillator is cut off. A " reject button is provided which when pressed causes reversal of motor 80. Single cycle operation is initiated by pressing a button, after which a single operative cycle takes place and electrode 12 comes to rest in its top position. For manual operation, lever 72 is raised and lowered by means of a cam 90 operated by a handle at the side of the machine. A limit switch 34 operated by lever 72 in its lowered position establishes radio-frequency voltage at the electrodes.