Method and apparatus for selbsttaetigen adaptation of the heating power of thermoelements controlled perspiration - or hot seal elements to different u.s. machines comprising them for the production of bags or sacks

摘要

Controlling the temperature of a heat sealing bar comprises monitoring the temperature of the bar and the temperature of the insulation pad behind the bar to provide a proportional control. The power is limited if the machine is stopped by switching in a constant back voltage. Pref. control is also effected by a circuit which increases heat input proportionally to the machine operation speed. (Alternatively the speed dependent circuit may oppose a normal working power load if the equipment is slowed down). Esp. for forming tubing from thermoplastic sheet during manufacture of plastic bags or sacks. With automatic response to weld throughput speed changes, machine stoppages, weld thickness variations, to achieve a continuous weld without overheating or non fused zones (esp. on restart after a stoppage).