Injection Apparatus and Method

An on-body medical fluid injection device comprising:

• a housing;
• an injection needle movable between a retracted position within the housing and an injection position extending from the housing;
• an actuator associated with the needle for moving the needle between the retracted position and the injection position;
• a resilient bladder within the housing for containing medical fluid for injection through the needle when it is the injection position;
• an end of delivery member within the housing and biased for movement from a first position towards a second position, the end of delivery member being configured so as to:
• (i) engage the bladder when the bladder is substantially filled with medical fluid, such that the bladder prevents movement of the end of delivery member from the first position to the second position, and
• (ii) disengage from the bladder when it is substantially empty of medical fluid so as to allow movement of the end of delivery member from the first position to the second position;
• the end of delivery member, when in the first position, being cooperatively associated with the actuator to retain the injection needle in the injection position and, when in the second position, allowing the actuator to move the injection needle to the retracted position and provide an end of delivery indication;
• a premature lockout prevention system including an actuator engagement surface and an end of delivery member engagement surface, said actuator and end of delivery member engagement surfaces:
• (i) being aligned when the end of delivery member is in the first position to limit travel of the actuator engagement surface with respect to the end of delivery member engagement surface by engagement of the actuator and end of delivery member engagement surfaces;
• and
• (ii) being misaligned when the end of delivery member is in the second position so that the end of delivery member engagement surface does not interfere with travel of the actuator engagement surface.