INJECTION DEVICE FOR MEDICAL INJECTIONS Russian patent published in 2013 - IPC A61M5/24 A61M5/315 

FIELD: medicine.

SUBSTANCE: invention refers to medical equipment, namely to a pre-filled injection device. The pre-filled injection device for medical injections comprises a cartridge mounted in a body and containing a liquid therapeutic preparation, and a piston rod assembly containing a piston rod and a base. The cartridge has a distal end overlapped with a membrane, and a proximal end overlapped by a movable plunger which is movable in the distal direction under the action of the piston rod assembly so that to squeeze out a liquid therapeutic preparation between the membrane and movable plunger. The mutual position of the piston rod and plunger in the axial direction is specified during the assembly of the injection device making the piston rod base mutually rested against the movable plunger. The piston rod assembly represents an individual part permanently attached to the piston rod mutually resting against the movable plunger. A method for assembly of the above device involves the following stages: (i) bringing the piston rod assembly comprising the piston rod and base thereof presenting an individual component in a resting contact with the plunger and (ii) attaching the piston rod base permanently to the piston rod herewith making the piston rod base mutually rest against the movable plunger. According to the second version of the pre-filled injection device for medical injections, the mutual axial position of the piston rod assembly and plunger is specified during the assembly of the injection device. The injection device comprises a mechanism for dose measuring and injection to measure and inject a dose of the liquid therapeutic preparation. The cartridge and the mechanism for dose measuring and injection are built in the body. The body has a first portion and a second portion rigidly fixed with respect to each other by a joint. The body position is longitudinally adjustable and comprises an instrument to fix the above body parts rigidly in the position that has been longitudinally adjusted. The mechanism for dose measuring and injection comprises the piston rod assembly, while the cartridge comprises a movable plunger. Once two body parts are found in the permanent connection, the piston rod assembly and plunger are in the resting contact. A method for assembly of the pre-filled injection device according to the second version involves (i) bringing the piston rod assembly into the resting contact with the plunger and the permanent attachment of the first part and the second part of the body in the above position.

EFFECT: invention enables minimising (preferentially eliminating) a gap between the distal end of the piston rod assembly and plunger.

6 cl