Convertible plungers and methods for assembling the same in a medical barrel

A convertible plunger comprising:

• a. an internal portion and a generally cylindrical exterior surface that surrounds at least part of the internal portion;
• b. the generally cylindrical exterior surface comprising a compressible and resilient storage sealing section that is maintained in an expanded state by outward radial pressure provided by the internal portion;
• c. the internal portion being comparatively more rigid than the storage sealing section;
• d. the expanded state being reducible to a constricted state by an operation that is applied to the internal portion of the plunger to reduce or eliminate the outward radial pressure;
• e. the storage sealing section in the constricted state:
• i. having a reduced maximum diameter or cross-sectional width than the storage sealing section in the expanded state;
• and/or
• ii. being less resistant to inward radial compression compared to the storage sealing section in the expanded state;
• f. wherein the storage sealing section is configured to be initially disposed in its entirety within a medical barrel while in a load position in which the storage sealing section is configured not to contact the medical barrel or to have reduced compression against the medical barrel compared to when the storage sealing section is in the expanded state, wherein the storage sealing section is configured to be set in the expanded state from the load position through application of a setting force onto the internal portion in a distal direction when the convertible plunger is disposed in the medical barrel;
• g. the operation being application of an actuation force onto the convertible plunger in the distal direction when the convertible plunger is disposed in the medical barrel;
• h. the convertible plunger further including a liquid sealing section on a distal end of the convertible plunger, the liquid sealing section having a generally cylindrical exterior surface configured to provide a seal against an inner wall of the medical barrel when the convertible plunger is disposed therein, the liquid sealing section having a film or a cap covering a product-facing surface and a sidewall of the liquid sealing section.