US Patent 9981086 Automatic injection device

An automatic injection device for delivering a dose from a medicine containing syringe includes a housing for containing the syringe, a force applicator for applying a force to eject medicine from the syringe, a trigger coupled to the force applicator for releasing the force applicator to cause an injection, a boot covering a needle attached to the syringe to protect and maintain sterility of the needle, and a mechanical interlock. The mechanical interlock prevents actuation of the trigger prior to removal of the boot. When the boot is removed, the mechanical interlock allows for actuation of the trigger.