Automatic injection device

A method of forming an automatic injection device having a distal end configured to deliver a medicament held in a container therein and a proximal end configured to be controllable by a user, the method comprising:

• providing a housing defining a confined inner space of the automatic injection device, the housing having a length extending from the proximal end to the distal end along a longitudinal axis;
• providing a helical biasing member disposed in the confined inner space of the housing along the longitudinal axis having an inner bore and a length extending from a first terminal end of the helical biasing member to a second terminal end of the helical biasing member opposite the first terminal end, an inner diameter of the helical biasing member at a middle portion between the first terminal end and the second terminal end having a first inner diameter greater than a second inner diameter at the first terminal end or at the second terminal end;
• and
• providing a syringe plunger having a first end extending into the container and a second bifurcated end extending into the inner bore of the helical biasing member along the longitudinal axis, the bifurcated end having a first flexible arm and a second flexible arm, the first arm having a first projection at a first end thereof and the second arm having a second projection at a first end thereof, the first and the second flexible arms able to flex inwardly and outwardly relative to the longitudinal axis within the inner bore of the helical biasing member while maintaining an annular gap between the syringe plunger and the helical biasing member.

A method of forming an automatic injection device to reduce the occurrence of a wet injection, the method comprising:

• providing an automatic injection device having a distal end configured to deliver a medicament held in a container therein and a proximal end configured to be controllable by a user;
• providing a housing having an inner surface defining a confined inner space of the automatic injection device, the housing having a length extending from the proximal end to the distal end along a longitudinal axis and a radial stop extending radially inward from a distal end of the inner surface;
• providing a helical biasing member disposed in the confined inner space of the housing along the longitudinal axis having an inner bore and a length extending from a first terminal end of the helical biasing member to a second terminal end of the helical biasing member opposite the first terminal end, an inner diameter of the helical biasing member at a middle portion between the first terminal end and the second terminal end having a first inner diameter greater than a second inner diameter at the first terminal end or at the second terminal end;
• providing a syringe plunger having a first end extending into the container and a second bifurcated end extending into the inner bore of the helical biasing member along the longitudinal axis, the bifurcated end having a first flexible arm and a second flexible arm, the first arm having a first projection at a first end thereof and the second arm having a second projection at a first end thereof, the first and the second flexible arms able to flex inwardly and outwardly relative to the longitudinal axis within the inner bore of the helical biasing member while maintaining an annular gap between the syringe plunger and the helical biasing member;
• engaging the first projection and the second projection with the radial stop to maintain the syringe plunger in a latched position;
• and
• providing a firing button including an inner ring configured to disengage the first projection and the second projection from the radial stop when the firing button is activated by the user.