US Patent 9849242 Autoinjector

Described is an autoinjector comprising a front case having a first rib and a second rib, and a rear case telescopically coupled to the front case and having latch arms adapted to engage the first rib and the second rib. When the front case is in a first position relative to rear case, the latch arms are engaged to the first rib. When the latch arms disengage the first rib, the front case translates to a second position relative to the rear case, an axial distance between the front case and the rear case increases relative to the first position, the latch arms engage the second rib.