Apparatus for injecting a pharmaceutical with automatic syringe retraction following injection

A pharmaceutical delivery apparatus comprising a housing extending between a distal end and a proximal end, a syringe carriage rotatably fixed and axially movable within said housing between a first position and second position, a medication-filled syringe held within said carriage and including a needle having a proximal tip, said needle tip being disposed within said housing when said carriage is in said first position, said needle tip projecting from said housing beyond said proximal end for insertion into an injection site when said carriage is in said second position, a plunger axially extending from said housing distal end and manually shiftable in the proximal direction, said plunger rotatably fixed and axially movable within said housing, means on said carriage and said housing and said plunger for causing said carriage to advance from said first position to said second position and for injecting medicine from said syringe when the plunger is manually plunged proximally toward said housing, and means on said carriage and said plunger for causing said carriage to retract from said second position to a position at which said needle tip is again disposed within said housing when the plunger shifts distally, wherein the improvement comprises:

• a collar within said housing, said collar including at least one cammable surface;
• means on said collar and said plunger for releaseably latching said collar to said plunger for travel therewith during the manual shifting of the plunger in the proximal direction that causes needle insertion and injection of medicine from said syringe, said latching means being released when said collar is rotated from a first angular orientation within the housing to a second angular orientation within the housing;
• a biasing means for forcing said collar and plunger apart in an axial direction when said latching means is released to force said plunger distally within said housing from said collar;
• means axially and rotatably fixed in said housing for engaging said at least one cammable surface as said collar travels proximally with the plunger during injection to shift said collar rotationally from said first angular orientation to said second angular orientation, thereby releasing said latching means to allow said biasing means at an end of injection to drive said plunger distally and retract the needle tip by action of said means on said carriage and said plunger for causing said carriage to retract.