An
injection device comprising a housing (1) and a
cartridge holder (2, 20), wherein the housing (1) has a rotatable
dose knob (4, 40) and an axially translatable button (5, 50) on its proximal side. The housing (1) includes: a
dose setting sleeve (6, 60), a non-rotatable tubular drive element (7, 70), a non-rotatable axially sliding
piston rod (15, 150), a gear (8, 80), and a drive spring (13, 130). The drive element (7, 70) is slidably mounted in the housing (1) and engages with the
dose setting sleeve (6, 60) by a threaded connection. The gear (8, 80) includes teeth (8.1, 80.1). The dosage setting sleeve (6, 60) is equipped with at least one
ratchet arm (6.4, 60.4) which engages with a gear (8, 80); the
piston rod (15, 150) has at least one row of
ratchet teeth (15.1, 150.1) on its outer surface; the drive element (7, 70) is fixedly connected to at least one drive arm (14, 140) at its distal end, which engages with the
ratchet teeth (15.1, 150.1) of the
piston rod (15, 150). The
injection device further includes: a non-rotatable but axially slidable button sleeve (9, 90) and a non-movable auxiliary sleeve (10, 100), the button sleeve (9, 90) engaging with the button (5, 50) at its proximal end, the auxiliary sleeve (10, 100) being located within the drive element (7, 70), wherein the button sleeve (9, 90) is separably and slidably engaged with the gear (8, 80), and the button sleeve (9, 90) is slidably engaged with the auxiliary sleeve (10, 100) by means of a connecting spring (12, 120).