Disposable needleless injector with a housing (200), in which at least one mechanical energy accumulator (50) of a spring, at least one cylinder unit (100) are arranged in each case -piston that at least occasionally can be filled with an active substance, at least one thrust plate for the actuation of the piston (60) and at least one trip unit (80), - where the plate for the actuation of the piston (60) is positioned between the spring energy accumulator (50) and the piston (111) of the piston-cylinder unit (100), - wherein the spring energy accumulator comprises at least one element prestressed spring (50) and - where the plate for actuating the piston (60), loaded by spring, is supported by means of support bars (240) or by means of pull hooks (250) to the housing ( 200), where the contact area between an individual support bar l (240) or individual traction hook (250) and the plate for actuating the plunger (60) represents a pair of wedge gears that presses out one of the corresponding support bars (240) or traction hooks (250 ), characterized in that - the housing (200) consists of a thin-walled sheet metal part (201, 202)； - the sheet part (201, 202) has a central front plate (210) and at least two legs (220, 250) protruding therefrom in an approximately vertical direction； - the legs (220) have at their free ends (as a housing for the cylinder (101) of the piston-cylinder unit (100) - two angled fixing elements (221), which engage in a notch) (104) of the outer contour of the cylinder (101)； - the sheet part (201, 202) has at least two support bars (240) or at least two pull bars (250), the free ends of which are curved at an angle, each one of them for configuring a support section (241, 251) for the plate for actuating the piston (60)； - the firing unit (80) comprises at least one firing element (82) slidably arranged on the housing (200)； - where the firing element (82) is a square tube that surrounds the sheet part (201, 202)； - where the firing element (
