Improvements in machines for joining sheet materials by the heating effect of electric stress alternating at high frequency

摘要

599,894. Seaming non-metallic sheet materials. BRITISH INSULATED CALLENDER'S CABLES, Ltd., QUAYLE, J. C., and JONES, P. Oct. 25, 1945, No. 28194. [Class 42 (i)] In a machine for joining superimposed layers of thermoplastic material by passing the latter between two pressure rollers, at least one of which is driven to forward the material, while the contacting surfaces are heated by a highfrequency electric field, a single member is provided to vary the intensity of the electric field and the speed of the material, simultaneously and in the same sense. An overriding control may be provided to pre-set the ratio between the speed of movement and the degree of heating. The machine comprises a work-table 1, standard 10 and overhanging arm 9. A lower roller 3 on a shaft 5 is driven through reduction gearing 6 from a direct current electric motor 4, and an upper roller 2 on a shaft 20 is driven from the shaft 5 through bevel gears 7, 12, 14, 15, 16, 17, 23,. 24 and shafts 11, 13, 19, the shaft 19 consisting of two telescopic parts in splined engagement, a spring 25 keeping the gear 24 in engagement with the gear 23. The bearings 21 of the shaft 20 are loaded by springs 22 and may be pressed down or lifted by a lever 26. The roller 3 comprises electrodes 27, 28 separated by insulating material and connected by spring contacts 29, 30 to the output of a high-frequency oscillator 31. The latter is supplied with alternating current through a variable transformer 40, the adjustable members of which are connected through a variable gear 44 and common shaft 43 with the rheostat 37 controlling the voltage supplied to the armature of the motor. -The field of the motor is independently excited, or may be a permanent magnet, but a field winding in series with the armature winding is preferably provided, to prevent decrease, or produce an increase, of speed with increasing mechanical load. The voltages applied to the motor armature and the oscillator input are simultaneously controlled by rotating the shaft 43 by means of rack mechanism 47 linked to a pedal 45, the ratio between them being pre-set by the manual control 49 of the variable gear 44. The oscillator may be as described in Specification 599,893, [Group XL], incorporating a mechanically movable device for varying the output voltage, which is in that case adjusted simultaneously with the speed control for the rollers. Specification 599,898 also is referred to.