Jet injector having a mechanism for creating air-in-tip

摘要

An injector for injecting a fluid medicament includes an injector body, a medicament chamber and a plunger that can be advanced into the chamber to expel medicament from the distal end of the chamber. An air-in-tip mechanism is provided within the injector body for partially withdrawing the plunger from the chamber to create an air pocket in the chamber adjacent the distal end. The air-in-tip mechanism includes a gripper ring that is positioned within the injector body and initially oriented to allow the plunger to move freely through the gripper ring. A user operable button is attached to the gripper ring to first tilt the gripper ring until it engages the plunger and then move the plunger proximally to create the air pocket. Alternatively, a face cam and push rod assembly can be activated when the injector's locking nut is turned to automatically tilt and move the gripper ring.