Injection pen solution transfer apparatus and method

An injection pen apparatus for medicament injection comprising:

• a medicament cartridge assembly formed to receive and contain a medicament therein, and having a movable plunger slidably mounted in said cartridge assembly;
• a holding sleeve dimensioned to receive said medicament cartridge assembly therein;
• a solution transfer device including an axially movable displacement rod;
• a coupling mechanism removably coupling said solution transfer device to both said plunger and to said holding sleeve and formed to slidably and rotatably support said displacement rod along an axial direction thereof, said coupling mechanism including a sleeve mounting assembly removably mounting said coupling mechanism to said holding sleeve, and a locking device formed and dimensioned to require joining of said displacement rod relative said sleeve mounting assembly after uncoupling of said displacement rod from said plunger and before uncoupling of a remainder of said solution transfer device from said holding sleeve.

A method for removing a solution transfer device, having a movable displacement rod, from an injection pen device formed for medicament injection, the pen injection device including a medicament cartridge assembly formed to receive and contain a medicament therein and having a movable plunger slidably mounted in said cartridge assembly, a holding sleeve dimensioned to receive said medicament cartridge assembly therein, and a coupling mechanism removably coupling said solution transfer device to said plunger and to said holding sleeve, the method comprising the steps of:

• preventing uncoupling of said solution transfer device from said holding sleeve until said displacement rod is uncoupled from said plunger to prevent premature removal of said plunger from said cartridge;
• uncoupling said displacement rod from said plunger;
• and
• after said uncoupling step, removing a remainder of said solution transfer device from said holding sleeve.