Abstract: A machine for heat sealing articles between two continuous webs of plastic material comprises two parallel synchronously driven shafts, each of which has a pair of wheels on it which are brought into pressure relationship for heat sealing. One shaft is mounted for yielding perpendicularly to its rotational axis and carries a cam follower disc. The follower disc is raised intermittently and the seal wheels are thereby separated, to relieve pressure and omit sealing, with a cam that is on the other shaft and is engaged periodically for rotation by means of a clutch.