A disposable injector has a housing (10) in which are arranged at least one mechanicalspring energy accumulator (50), at least one cylinder-piston unit (100) thatcan be filled at least in part with an active substance, at least one piston actuationplunger (60) and at least one triggering unit (80). The spring energy accumulatorcomprises at least one pre-loaded spring element. The spring-loaded pistonactuation plunger has at least one traction rod (61) with at least one supportsurface (63) at the rear end thereof. Locking elements (16) supported on the housinglie on the support surface(s) and are secured in the locking position by a triggeringelement (82) placed in a locking position (8). The triggering element has a releaseposition (9) that causes the locking element (16) to be unlocked.
