Method and apparatus for closing containers

A method of sealing a lid to a flange surrounding the open mouth of a container, said method comprising

• supporting the flange of the container on a support having a cavity in which the body of the container is freely suspended, the support resting on a frame,
• positioning a lid 20 in facing relation with the flange,
• positioning a welding die around the lid in facing relation with a surface of the lid remote from the surface of the lid facing the flange of the container,
• providing said support with a part-spherical surface facing a corresponding part-spherical surface of a resting means,
• introducing a pressure medium between the part-spherical surfaces of the support and the resting means so that a gap is formed between the support and the resting means in which gap the pressure medium is present and provides relatively frictionless support of said support on said resting means,
• providing relative movement between the welding die and the resting means towards one another to lift the support and the container therewith off the frame so that the container and the support are now supported by the resting means via said gap so that said lid and said flange come into abutment with one another over the entire circumferential extent thereof with substantially the same pressure, due to relative rocking movement of said support with respect to said resting means, via the pressure medium in said gap, which enables the lid and flange to align themselves, and
• continuing said relative movement between the welding die and the resting means towards one another to cause the resting means and the support to take up said gap and come into locked contact with one another along said part-spherical surfaces thereof, and apply the now aligned lid and flange against one another with pressure to form a seal therebetween.