Patent ID: 8394069

Claim:
In combination with a disposable injector ( 4 ) having at least one cylinder-piston unit ( 100 ), the cylinder piston-unit ( 100 ) including a piston ( 111 ) and a cylinder ( 101 ) in operative arrangement, the piston ( 111 ) of which can move between two stroke end positions in relation to the cylinder ( 101 ), the cylinder-piston unit ( 100 ) comprising at least one sealing system ( 121 ) that seals a compensating space ( 135 ) from the surroundings ( 9 ), the improvement which comprises: the piston ( 111 ) is provided at its front surface with an axial annular groove ( 112 ) for accommodating a seal ring ( 114 ) or a permanently elastic seal material, the cylinder ( 101 ) carries a first seal element ( 127 ) and the piston ( 111 ) carries a second seal element ( 128 , 131 , 132 ) which is displaced with respect to the first by the piston stroke, the first seal element ( 127 ) includes a first fixing area ( 122 ) and the second seal element ( 128 , 131 , 132 ) includes a second fixing area ( 123 ), the two fixing areas ( 122 , 123 ) connected by means of a bellows ( 126 ) or by means of a bellows- or finger-stall-like sealing element ( 129 ).