Closure system for containers used in water cascade sterilization

A closure system for a screw top container intended to contain a pharmaceutical or surgical medium, the closure system comprising:

• a screw cap including a main body comprised of an annular wall with an internal thread for cooperating with an external thread adjacent an open end of the container, the body having a first open end for receiving the open end of the container and a second end closed by an end disc;
• a tamper-evident band connected to the screw cap at the open end of the main body by at least one severable linkage;
• and
• a sealing formation within the main body for forming a plurality of seals with the open end of the container, the sealing formation comprising:
• annular inner and outer seals, the inner seal configured to apply outward pressure to an internal surface of the open end of the container so as to form a first hermetic seal, the outer seal configured to apply inward pressure to an external surface of the open end of the container so as to form a second hermetic seal, wherein a cross-section of the outer seal comprises a flat perpendicular edge with respect to a horizontal axis when disengaged from the container, and
• a block between the inner and outer seals, the block defining a flat surface extending between and connecting the annular inner and outer seals such that the annular inner and outer seals extend from the flat surface, the flat surface providing a uniform area of contact to form in use a third hermetic seal with an upper surface of the open end of the container, wherein:
• the screw cap, sealing formation and tamper-evident band are integrally formed as a single unit for maintaining a hermetic seal;
• a total thickness of the screw cap in the region of the block is at least two times greater than a thickness of the end disc in regions of the end disc adjacent to the block on both a radially internal and radially external side of the block, thereby forming a hollow channel between the outer seal and the annular wall such that the outer seal does not contact an internal surface of the annular wall when the screw cap is fully secured to the container, whereby the block provides rigidity to the end disc so that first, second, and third hermetic seals are formed between the container and the inner seal, the outer seal, and the block when the container fitted with the screw cap is subjected to a water cascade sterilization process;
• and
• the tamper evident band comprises a main ring and a circumferential flange flexibly connected to and extending inward from an internal surface of the main ring at a flange base to a flange tip, and a plurality of partial slits are formed within the circumferential flange at the flange base and spaced from the flange tip.