Container closed by a membrane type seal

The combination comprising:

• a container having an upwardly presented opening and a rim surrounding the opening and being formed entirely from a nonmetallic material capable of becoming plastic when heated above a prescribed temperature, the rim having a convex upwardly presented surface;
• a flexible seal membrane extended over the open top of container as well as over the convex upwardly presented surface of the rim, the membrane including a metal foil which is at least located in the area of the membrane overlying the rim of the container so that the membrane may be induction heated to the prescribed temperature by subjecting it to a magnetic field which undergoes rapid reversals in polarity, the membrane being heat sealed to the rim as a result of being induction heated above the prescribed temperature and simultaneously forced against a ridge formed integral with and projected upwardly from the convex rim such that the ridge deforms into a generally obliterated condition along the convex rim and in so doing accommodates any irregularities between the contacting surfaces of the membrane and the rim;
• and a lid including a cross portion which overlies the membrane and the container rim and a downwardly projecting skirt at the periphery of the cross portion, the skirt being sized to fit snugly around the rim, the cross portion having a preformed groove which aligns with and is directly above the rim, with the groove being defined in part by continuous beveled side surfaces which downwardly diverge and are spaced sufficiently apart to enable the rim to be partially received in the groove when the lid is forced downwardly, the side surfaces of the groove being arranged to confine the membrane such that it generally follows the contour of the convex upper surface of the rim so as to be in contact with that surface for a substantial distance in the lateral direction.