JPS6478817A - High-frequency welder fusion bonding of composite sheet - Google Patents

Abstract

PURPOSE:To prevent the damage of a composite sheet due to generation of sparks and increase the degree of fusion bonding to a core material, by a method wherein a plurality of steps of the increasing of current and constant state holding operation for a while is repeated, thereafter, the current is reduced once and the constant state holding is effected for a while, then, the current is increased again and the constant state holding is effected for a while. CONSTITUTION:A composite sheet 2, consisting of an expandable PVC 2a and a fabric 2b, is laminated on a core material 1 and the laminate is inserted between electrodes 4, 5 of a high-frequency welder. The lower electrode 4 of the high-frequency welder is established on an aluminum substrate 6 in a form corresponding with the pattern of the weld line of a composite sheet 2 while the upper part thereof is projected and is coated with an insulating material 7. The upper electrode 5 is descended on the core material 1 and the composite material 2, set between the upper and lower electrodes, to pinch and press them between the lower electrode 4, then a high-frequency voltage, generated by a high-frequency generator 3, is impressed between both electrodes to conduct a high-frequency current. The increase of the current and constant state holding for a while are repeated three times, then, the current is increased to effect the primary fusion bonding of the composite sheet 2 and the current is reduced once to hold it in a constant state for a while. The current is increased again to a value near the crest of the current before reducing the current and the current is held in constant for a while whereby the composite sheet 2 may be welded and fixed to the core material 1 perfectly.