Auto-injector

A cassette unit for use with an auto-injector having an electrically powered drive unit, said cassette unit comprising:

• a cassette unit housing defining a cassette unit housing cavity and a needle projection aperture, said cassette unit housing cavity arranged for receipt of a syringe comprising:
• a barrel for containing a volume of a liquid drug formulation;
• a hollow needle at a front end of said barrel, said hollow needle defining a needle tip for dispensing of said liquid drug formulation;
• and
• a plunger that is axially movable within the barrel;
• a removable cap that fits over and thereby, acts such as to close off, the needle projection aperture;
• and
• connecting to said removable cap, a needle cover defining a needle sheath for sheathing of said needle tip,
• wherein the removable cap is provided with a finger-grip feature that is sized and shaped for gripping by the finger of a user to allow for removal of the removable cap and needle cover from the cassette unit housing,
• wherein said cassette unit is arranged to releasably interfit with said electrically powered drive unit,
• wherein the removable cap is provided with one or more first engagement features arranged for selectively engaging one or more second engagement features of the cassette unit housing when the cap is in the capping position,
• wherein the first engagement features of the removable cap comprise through-holes for receiving the second engagement features of the cassette unit housing, and
• wherein an edge of the through-holes is configured to translate a force applied to the finger-grip feature in an axial direction to the second engagement features in a direction perpendicular to the axial direction,
• wherein each of said one or more second engagement features is in the form of a protruding arm having a forward end,
• wherein a ramp projects radially outwards from said forward end of said axially protruding arm, and
• wherein said ramp comprises a first ramp surface extending radially and rearwardly from the forward end of the arm and a second ramp surface extending radially and forwardly from a position part way along said arm, said first ramp surface and said second ramp surface meeting at a ramp summit.