Plunger rod head for activating needle safety device

A passive needle safety device for protecting the needle of an injection syringe after medication has been delivered to a patient comprising

• a body that can hold a syringe,
• a telescoping guard fitting, over the body, and
• a spring deployed between the guard and body such that the guard is urged in an extended configuration distally relative to the body, the improvement comprising,
• trigger fingers for holding the guard and body together in an un-extended configuration against the force of the spring, and a plunger rod with a plunger head which pushes against the trigger fingers, the plunger head having an angled surface that provides a lateral component of force to the trigger fingers to displace them from the latched configuration to an unlatched configuration,
• wherein the angled surface of the plunger head extends from a lateral edge of the plunger head to the plunger rod at a constant angle of and is approximately 20° so as to provide consistent activation of the trigger fingers with a low and constant plunger rod force.