DISPOSITIVO PARA LA FABRICACION DE BOLSAS DE UNA LAMINA CON-TINUA,DE DOS CAPAS,DE MATERIAL TERMOPLASTICO

摘要

Parallel, spaced apart backing rods are carried by a rotating cylinder and serve the continuously supplied web. Back-pressure bars are extensible to engage and cooperate with welding bars. The backing rods and back-pressure bars are movable from and toward each other and provided with means for guiding a web with low friction. Those welding bars which are disposed near that sector of the cylinder in which the backing rods are disposed when they are retracted are moved concentrically to and at the same angular velocity as the back-pressure bars outside that surface of the cylinder over which the back-pressure bars are disposed. The back-pressure bars consist of rotatably mounted rolls, which are provided with a covering of elastic material which resists the welding heat. The welding bars have knife edge-like welding edges facing the rolls.