Dental syringe having a medication filled carpule and a retractable needle cannula

A syringe including a hollow syringe body and a hollow syringe cylinder each of said body and said cylinder being axially aligned with one another and having open proximal and distal ends, said syringe comprising;

• a fluid filled carpule to be loaded into said cylinder, said carpule having a piston located at a proximal end thereof and movable through said carpule for expulsing the fluid contents thereof;
• a double ended needle cannula to be interconnected with said carpule so that one end of said cannula penetrates said carpule and the other end of said cannula projects outwardly through the distal end of said cylinder for injecting the fluid of said carpule;
• a piston stem movable axially through said syringe body to be connected to the piston of said carpule for controlling the movement of said piston through said carpule;
• a control rod advanceable distally through said syringe body and into said cylinder and having a retaining sleeve at one end thereof for surrounding and engaging the proximal end of said carpule to prevent the relocation of said carpule through said cylinder;
• catch means extending outwardly from and being movable with said control rod through said syringe body;
• and
• locking means associated with said syringe body for releasably engaging the catch means of said control rod a said control rod moves distally through said syringe body for locking said control rod at its distally advanced position and maintaining the retaining sleeve of said control rod in engagement with said carpule.

A syringe including a hollow syringe body and a hollow syringe cylinder, each of said body and said cylinder being axially aligned with one another and having open proximal and distal ends, said syringe comprising:

• a fluid filled carpule having a piston movable therethrough for expulsing the fluid contents thereof;
• a double ended needle cannula to be interconnected with said carpule so that one end of said cannula penetrates said carpule and the other end of said cannula projects outwardly through the open distal end of said cylinder for injecting the fluid of said carpule;
• a piston stem movable axially through said syringe body and into said cylinder to be connected to the piston of said carpule for controlling the movement of said piston through said carpule;
• a hollow control rod for receiving said piston stem therethrough, said control rod advanceable distally through said syringe body and into said cylinder and having a retaining sleeve at one end for surrounding and engaging the proximal end of said carpule to prevent the relocation of said carpule through said cylinder;
• a flexible spring arm attached at one end thereof to said control rod and having a release button extending from the opposite end, said spring arm being movable with said control rod through said syringe body;
• a hole formed through said syringe body to removably receive the release button of said spring arm as said control rod moves distally through said syringe body for locking said control rod at its distally advanced position and maintaining the retaining sleeve of said control rod in engagement with said carpule;
• and
• compression spring means surrounding said control rod at the interior of said hollow syringe body, said spring means compressed against the normal spring bias when said control rod is moved to and locked at its distally advanced position, said compression spring means expanding when the release button of said spring arm is removed from the hole in said syringe body to release said control rod from its distally advanced position and drive said control rod proximally through said syringe cylinder and thereby retract said needle cannula into said cylinder through the open distal end thereof.