Needleless injection device equipped with an improved injection nozzle

A needleless injection device comprising:

• a body forming a housing extending axially in a direction of injection from an upper radial seat of the housing along an injection axis;
• a gas generator;
• a tubular reservoir containing an active ingredient and a lower piston disposed below the active ingredient, the tubular reservoir extending axially in said housing from an upper end of the tubular reservoir to a lower end of the tubular reservoir;
• an upper piston having an upper axial surface;
• and
• a nozzle for injecting the active ingredient which is arranged at the lower end of the tubular reservoir and which extends axially in the direction of injection from the lower end of the tubular reservoir, the nozzle including an external thread adapted to be screwed onto a complementary tapping formed by the body such that the nozzle is configured to axially compress the reservoir on the upper radial seat of the housing and a central housing adapted to receive the lower piston, the external thread extending axially in the direction of injection from the lower end of the tubular reservoir to a position beyond the lower end the tubular reservoir and extending around the central housing,
• wherein the external thread of the nozzle includes a triangular section, said external thread being delimited by an upper face having a first angle relative to a radial axis perpendicular to the injection axis and a lower face having a second angle relative to said radial axis, wherein the first angle is greater than the second angle, and
• wherein an elastically deformable membrane extends axially in the reservoir and is configured to expel the active ingredient from the reservoir, the elastically deformable membrane has an accordion shape and a lower surface that abuts against the upper axial surface of the upper piston, the elastically deformable membrane further comprises an annular disc interposed axially between the upper end of the reservoir and the upper radial seat of the housing.