Patent ID: 8597233

Claim:
A pressure-stable cylinder/piston unit ( 1 ) which blocks water vapor and oxygen and formed for a needle-free injector, the pressure-stable cylinder/piston unit ( 1 ) characterized by: a chamber ( 3 ) arranged in a cylinder ( 2 ), the chamber ( 3 ) for long-term and sterile storage of an injection solution ( 4 ), a pressure-stable outer cylinder ( 13 ) having a jacket surface ( 11 ), the pressure-stable outer cylinder ( 13 ) including an end wall ( 5 ) with at least one nozzle bore or one outlet element ( 6 ) passing therethrough, a pressure-stable piston ( 7 ) arranged movably in the chamber ( 3 ) and blocking water vapor and oxygen, the chamber ( 3 ) formed with a first chamber ( 8 ) and a second, concentric chamber ( 9 ), wherein the cross section of the first chamber ( 8 ) is greater than the cross section of the second chamber ( 9 ), the pressure-stable outer cylinder ( 13 ) substantially surrounds the cylinder ( 2 ) in contacting relationship proximate the second chamber ( 9 ), a transition area between the first chamber ( 8 ) and the second chamber ( 9 ) is formed as an interior annular surface ( 16 ) of cylinder ( 2 ) and each nozzle bore or each outlet element ( 6 ) is closed in a sterile manner by a membrane ( 26 , 27 ) for blocking water vapor and oxygen and the membrane ( 26 , 27 ) opens at an overpressure, and the piston ( 7 ) comprising an inner piston body ( 18 ) and a flange ( 22 ), and an outer compressible piston ring ( 17 ) having an inner through hole approximating the outer diameter of the flange ( 22 ) and the inner piston body ( 18 ) and second concentric chamber ( 9 ), the inner piston body ( 18 ) and flange ( 22 ) in slideable pass-through relationship with respect to the outer compressible piston ring ( 17 ), the inner piston body ( 18 ) and the flange ( 22 ) when positioned in the first chamber ( 8 ) are axially surrounded in gas sealing relationship by the outer compressible piston ring ( 17 ) for blocking water vapors and oxygen in a pressure stable and sterile closing manner during long term storage of the injection solution ( 4 ) within the second concentric chamber ( 9 ), the inner piston body ( 18 ) and the flange ( 22 ) in slideable contacting relationship with cylinder ( 2 ) proximate the second concentric chamber ( 9 ) in preparation for and during injection, the outer compressible ring ( 17 ) together with the inner piston body ( 18 ) and the flange ( 22 ) during long term storage of the injection solution ( 4 ) substantially occupying the entire first chamber ( 8 ) in gas sealing relationship therewith, the outer compressible piston ring ( 17 ) at the distal end thereof in direct contacting and gas sealing relationship with the interior annular surface ( 16 ) of the cylinder ( 2 ) during long term storage of the injection solution ( 4 ).