Abstract: A heatable sealing head comprises a resiliently yielding pressure element and has at least one cup spring. The pressure element serves to transmit pressure and heat to a closure lid insertable between the sealing head and the rim of a container, this lid to be deformed about portions of the container rim. In the relaxed normal position, the sealing head includes a conical contact surface for the closure lid. The contact surface can be resiliently bent back against the pressure of the rim of the container mouth. The metallic closure lid is provided with thermoplastic material on the side facing the container rim. For the purpose of improving the fixing of the closure lid to the container rim, the contact surface of the pressure element projects increasingly radially inward starting from the sealing head.

Abstract: A heatable sealing head includes resilient, yielding cup springs which transmit pressure and heat to a thin cover insertable between the sealing head and the container rim. This cover, which may be metallic and is coated on the underside with a thermoplastic material, is thereby deformed about portions of the container rim. The cup springs are disposed conically in their relaxed state so that their radially outer portions are situated closer to the cover than their radially inner portions, by which they are fixed to the sealing head. For increasing the flexibility of the cup springs, a spacer piece is inserted between an outer cup spring facing the cover and at least one cup spring nearer the sealing head in order to keep the radially inner portions of these two cup springs spaced from one another while leaving a clearance space between the radially outer portions of the spaced cup springs.