A fluid injecting system with needle retraction by vacuum

A fluid injecting system (100), comprising:

• an injector (A) having an injector body (10);
• a plunger shaft (30);
• a plunger assembly (20) having an inner plunger barrel (21) slidable within an outer plunger barrel (22), said inner plunger barrel (21) having a locking means (35) configured to restrict movement of said outer plunger barrel (22) in forward direction, said outer plunger barrel (22) and said inner plunger barrel (21) are configured to form a united plunger barrel (40) when said outer plunger barrel (22) is pulled out at its full length;
• a fluid-cartridge (B) having a fluid (53) and a hypodermic needle (72) for injecting said fluid (53) at an injectable site;
• wherein said fluid-cartridge (B) is configured to releasably engage with said injector (A) at a proximal end (P) of said injector (A);
• wherein a vacuum (V) is created between said outer plunger barrel (22) and said inner plunger barrel (21) upon formation of said united plunger barrel (40);
• wherein forward movement of said united plunger barrel (40) transfers said fluid (53) from said fluid-cartridge (B) into said injectable site;
• wherein said hypodermic needle (72) retracts within empty fluid-cartridge (B) due to release of said vacuum (V) and said injector (A) is disengaged from said fluid-cartridge (B) for reuse.