This relates to an injection device (1) for a Spring driven Automatic Injection of Drug Liquid, through which the user can establish dose with a single size, the injection device (1) includes: a housing (3) which defines a Space. Previous window and has a longitudinal (7),A Dose adjustment of rotation (2) retained axially in the housing (3), a Rotary Drum Scale (4) leading indications (6) to indicate the size of the Dose Level, where the Drum (4) is functionally coupled to the dose adjustment for Q (2) EU rotates when the dose adjustment (2) is rotated to set a doseA Sliding element (11) provided with a sliding window (12), Said Sliding element (11) is adapted to slide axially in the housing (3) during the establishment of doseAnd Through The sliding window (12) are visible Directions (6) carried by the Drum of scale (4) such that the window (7) and the longitudinal sliding window (12) in combination with directions (6) form a screen size of doseAnd where the Drum Level (4) rotates with the Interior Space defined by the housing (3) during the establishment of dose and where the Inner surface of the Sliding element (11) is provided with an internal characteristic (29) which is coupled to an external thread (5) provided and The Outer surface of the Drum (4) scale and The sliding element (11) is guided.More axially in the housing (3) so that the Sliding element (11) is moved axially when the drum is rotated (Level 4), where a Spring impeller (14) is connected to the Drum Level (4) with a housing (3) end and the other end with such so the R Otaci\u00f3n relative Scale between the Drum (4) and accommodation (3) The Spring load Force.
