Cassette, medicine injection device, and medicine injection system

A cassette to be loaded to a drug injection device, the cassette comprising:

• a cartridge holder including a first end at which an injection needle is attachable and detachable, a second end having a holder opening, and a holder columnar space being located between the first end and the second end and capable of accommodating a drug cartridge, wherein the drug cartridge includes:
• a cylinder including a first end at which the injection needle is insertable and extractable, a second end at which a cylinder opening is located, and a cylinder columnar space located between the first end and the second end;
• a drug placed in the cylinder columnar space;
• and a gasket being placed in the cylinder columnar space and capable of moving along a longitudinal direction of the cylinder columnar space;
• a cassette cap being supported in the neighborhood of the second end of the cartridge holder so as to be capable of opening and closing the holder opening, the cassette cap including a first end having a cap opening that is opposed to the holder opening, a second end having a piston insertion opening, and a cap columnar space located between the first end and the second end, wherein, in an open state, the cassette cap allows the drug cartridge to be movable into and out of the holder columnar space of the cartridge holder, and, in a closed state, the cassette cap closes the holder opening to disallow the drug cartridge to be removed while allowing the gasket of the drug cartridge inserted into the holder columnar space to be exposed in the piston insertion opening;
• and
• a locking mechanism being located in the cap columnar space of the cassette cap and at least including a rotation lock unit that is supported so as to be capable of pivoting around an axis of the cap columnar space, wherein,
• the rotation lock unit has a shape that engages with a piston of the drug injection device for moving the gasket of the drug cartridge,
• while the drug cartridge is inserted in the cartridge holder and the cassette cap is in a closed state, the rotation lock unit pivots between a lock position for disallowing the cassette cap to open and an unlock position for allowing the cassette cap to open,
• the rotation lock unit includes a unit throughhole having a cross-sectional shape that corresponds to a cross-sectional shape of a leading end portion of the piston perpendicular to an axis of the piston,
• as the leading end portion of the piston is inserted from outside into the unit throughhole of the rotation lock unit and the piston rotates around the axis of the piston, the rotation lock unit pivots within the cassette cap, the locking mechanism further includes:
• a cassette button provided on the cartridge holder so as to be capable of being pressed;
• and
• a pair of engaging portions respectively provided on the cassette button and on the cassette cap, the engaging portions being capable of engaging with each other, when the rotation lock unit is in the unlock position, the cassette button is pressable so that the pair of engaging portions are disengaged from each other while the cassette button is pressed, and when the rotation lock unit is in the lock position, the cassette button is unpressable and the pair of engaging portions are engaged with each other.