Prefilled syringe trainer and resetting mechansim

A resettable injection training device, comprising:

• a body comprising an inner body and an outer body, the body having a proximal end and a distal end, and a chamber defined within the body, the outer body having at least one first protrusion on an inner surface thereof;
• a plunger slidable within the body;
• a retractable shield comprising a proximal end and a distal end, and being retractable and extendable relative to the body, the shield comprising at least one second protrusion on an outer surface thereof, wherein when the shield is in a retracted position the at least one second protrusion abuts the at least one first protrusion, and wherein a first threshold force on the plunger causes the at least one second protrusion to traverse the at least one first protrusion to extend the shield, the shield comprising at least one third protrusion proximal to the at least one second protrusion, wherein the at least one third protrusion abuts the at least one first protrusion when the shield is extended;
• a biasing member comprising a first end and a second end, the first end abutting a proximal end of the body, and the second end abutting the proximal end of the shield, wherein extension of the biasing member extends the shield, and retraction of the shield biases the biasing member, wherein the biasing member is configured to apply a biasing force to the shield less than the first threshold force, and wherein when the shield is in an extended position, a second threshold force applied to the distal end of the shield retracts the shield, wherein the second threshold force comprises a force of (x) N that is greater than the biasing force;
• and
• one or more tab portions in the body, each tab portion comprising at least one fourth protrusion extending into the chamber, wherein the at least one fourth protrusion comprises a locking surface configured to abut the at least one third protrusion to lock the shield in an extended position;
• and
• an unlocking component in contact with the body, wherein compression of the unlocking component releases the at least one fourth protrusion from the at least one third protrusion, allowing movement of the at least one third protrusion relative to the at least one fourth protrusion to retract the shield.