Apparatus for forming and inserting an internal lid in a container

Apparatus whereby an internal closure having a flat lid portion surrounded by an upwardly projecting rim portion is inserted into an upper end portion of a tubular container sleeve and whereby said rim portion is sealed to the sleeve by welding, said apparatus being of the type comprising a carrier in which a container sleeve is receivable for immobilized support, a welding ring in said carrier for surrounding said upper end portion of a sleeve therein and heating the same, and a piston means movable up and down relative to the carrier between a raised position above a sleeve in the carrier and a defined lowered position wherein the piston means is received in the carrier and at which a closure carried by the piston means has its rim portion radially opposite said welding ring, said piston means comprising coaxial upper and lower piston parts which are axially movable relative to one another and a resilient ring confined between said piston parts to be radially outwardly expanded by relative motion of said piston parts towards one another, for cooperation with the carrier in clamping the rim portion and the sleeve in tight engagement with one another, said apparatus being characterized by:

• A. said resilient ring being toroidal;
• B. said lower piston part having
• (1) a flat bottom surface for closely overlying the lid portion of a closure,
• (2) a circumferential groove which is spaced above said bottom surface and in which said resilient ring is closely received when unexpanded, and
• (3) an annular upper surface which is inclined downwardly and radially outwardly, into which said groove merges downwardly and which cooperates with said bottom surface to define a thin edge around the bottom of the lower piston part;
• C. said upper piston part having an annular lower portion with cylindrical and concentric radially inner and outer surfaces that concentrically surrounds said lower piston part above said annular upper surface thereon, said upper piston part further having an annular bottom surface with a radially inner edge and a radially outer edge at its respective junctions with said radially inner and outer surfaces
• (1) which annular bottom surface opposes said upper surface on the lower piston part,
• (2) which annular bottom surface has an arcuate cross-section profile between said inner and outer edges that substantially mates with the upper portion of the resilient ring when the same is unexpanded, and
• (3) which annular bottom surface has said radially outer edge at a level substantially below the level of said radially inner edge so that upon downward motion of the upper piston part relative to the lower piston part said annular bottom surface cooperates with said annular upper surface to so expand the resilient ring radially outwardly that the maximum girth thereof is in a plane which is parallel and near to said flat bottom surface and which passes through said welding ring all around the same.