Self-injector

A self-injector with stored energy for application of a contained liquid active substance, the self-injector comprising:

• a housing;
• a holder for holding a syringe to be inserted with a cylinder;
• a piston;
• and
• a sealing pin and a needle for hydraulically ejecting the liquid active substance through the needle by the piston, the self-injector characterized in that:
• the piston is actuated by a piston slide guided along a rail in the housing by means of a first pivot lever articulated to the piston slide, the actuation of the piston being triggered by a piston sliding plate being pushed into the housing when the self-injector is pressed onto a body surface, an end of the first pivot lever is articulated to a first pivotable spring leg of a prestressed torsion spring having a plurality of coils that is in a pretensioned state, and a second spring leg of the torsion spring stationarily locked to the housing,
• wherein a first pivoting movement of the first pivotable spring leg is triggered by releasing the first pivotable spring leg from the pretensioned state, and
• wherein in a first pivoting phase with the first pivotable spring leg, the piston slide is articulated at the end of first pivotable spring leg, the piston is pushed into the syringe, a barb on the piston slide is latched onto the syringe, and in a subsequent pivoting movement of the first pivotable spring leg with the piston slide, the syringe is withdrawn in the housing.