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

A pre-filled syringe comprising:

• a. a medical barrel having an inner wall and an injectable drug product disposed in a product containing area of the medical barrel, the medical barrel having a distal dispensing end for dispensing the injectable drug product and an open proximal end configured for receipt of a convertible plunger;
• and
• b. a convertible plunger disposed within the medical barrel, the convertible plunger comprising:
• (I) a first subassembly comprising a connector body having a distal end and a proximal end, the first subassembly further comprising a plunger head, which is a separate component that is assembled to the distal end of the connector body, the plunger head having a liquid sealing section configured to contact and provide a seal against an interior wall of a medical barrel when disposed therein;
• (II) a second subassembly comprising an elongate ring carrier having a distal end and a proximal end, the distal end of the ring carrier being secured to the proximal end of first subassembly, the proximal end of the ring carrier being configured to be secured to a plunger rod, the ring carrier comprising an annular dispensing platform and an annular storage platform distal to the dispensing platform, the annular storage platform having a larger maximum diameter or cross-sectional width than the dispensing platform, the second subassembly further comprising a compressible and resilient storage ring disposed about the ring carrier and configured to displace axially thereon;
• (III) wherein the storage platform is more rigid than the storage ring;
• wherein the storage sealing section, when the storage ring is disposed about the storage platform, is maintained in an expanded state by outward radial pressure provided by the storage platform to create compression between the storage sealing section and the inner wall of the barrel, thereby rendering the convertible plunger in storage mode, the expanded state being reducible to a constricted state upon transitioning the storage ring to being disposed about the dispensing platform whereupon the compression between the storage sealing section and the inner wall of the barrel is reduced or eliminated, thereby rendering the convertible plunger in dispensing mode.

A convertible plunger comprising:

• a. a first subassembly comprising a connector body having a distal end and a proximal end, the first subassembly further comprising a plunger head, which is a separate component that is assembled to the distal end of the connector body, the plunger head having a liquid sealing section configured to contact and provide a seal against an interior wall of a medical barrel when disposed therein;
• b. a second subassembly comprising an elongate ring carrier having a distal end and a proximal end, the distal end of the ring carrier being secured to the proximal end of first subassembly, the proximal end of the ring carrier being configured to be secured to a plunger rod, the ring carrier comprising an annular dispensing platform and an annular storage platform distal to the dispensing platform, the annular storage platform having a larger maximum diameter or cross-sectional width than the dispensing platform, the second subassembly further comprising a compressible and resilient storage ring disposed about the ring carrier and configured to displace axially thereon, the storage ring comprising an outer surface facing generally radially outward away from the ring carrier, wherein when the storage ring is in an uncompressed state, the outer surface comprises a proximal end, a distal end and a radial plane of symmetry between the proximal and distal ends that is equidistant from the proximal and distal ends, wherein the outer surface is symmetrical on either side of the radial plane of symmetry;
• c. wherein the storage platform is more rigid than the storage ring.