Welding thermoplastic strapping, especially of polypropylene, for packaging by measuring thickness changes in the strapping

摘要

Optimum welding conditions are established by determining the total thickness of the two straps (11a,11b) being welded during the welding stage and comparing with a set value. When this value is reached a control signal is generated to interrupt the heat supply. An Independent claim is made for the welding equipment in which the heating arrangement has a switch operated by a pressure member (31) when the gap between the latter and a strap supporting surface (18) exceeds a set value.