Safety syringe and needle and needle seat retracting device of safety syringe

A safety syringe comprising:

• a barrel being a hollow cylinder and having
• an inner wall;
• a large-diameter section having a front end and a rear end;
• a small-diameter section in a tapered-shape, formed on and protruding from the front end of the large-diameter section;
• a needle-group mounting end extending from the large-diameter section to the small-diameter section;
• an operating grip end defined at the rear end of the large-diameter section and opposite to the needle-group mounting end;
• and
• a barrel lumen in the large-diameter section of the barrel and having an engaging flange formed on and protruding from the inner wall of the barrel adjacent to the needle-group mounting end;
• a pushing element airtightly and slidably mounted in the barrel lumen of the barrel, and having
• a pushing rod having
• a pushrod chamber formed in the pushing rod;
• a front drug pushing end slidably mounted in the barrel lumen;
• and
• a rear operating end being opposite to the front drug pushing end and extending out of the barrel lumen;
• an inner airtight stopper airtightly and securely mounted in the front drug pushing end of the pushing rod, and extending into and airtightly mounted in the pushrod chamber;
• an outer airtight stopper securely connected to the front drug pushing end and the inner airtight stopper, and airtightly and slidably mounted in the barrel lumen;
• and
• an end cover securely mounted on the rear operating end of the pushing rod and having a holding tube formed on and through a center of the end cover;
• a retracting element airtightly and slidably mounted in the pushrod chamber of the pushing rod and having
• a pulling rod having
• a gripping end extending out of the pushrod chamber through the holding tube of the end cover;
• and
• an engaging end being opposite to the gripping end and extending in the pushrod chamber;
• and
• an airtight spigot securely connected to the engaging end of the pulling rod and adjacent to the inner airtight stopper;
• a needle group connected to the needle-group mounting end of the barrel, and having
• a needle having
• an outer end extending out of the needle-group mounting end;
• and
• an inner end mounted in the needle-group mounting end;
• a needle seat mounted around the needle at the inner end of the needle, mounted in the needle-group mounting end of the barrel, and having
• a front end being held in the small-diameter section;
• a rear end extending into the barrel lumen of the large-diameter section;
• and
• an engaging portion formed on the rear end of the needle seat and detachably engaging the inner airtight stopper of the pushing element;
• and
• a needle-seat fixing ring mounted around the needle seat and airtightly engaging the engaging flange in the large-diameter sect and
• wherein the pulling rod of the retracting element is moved backwardly relative to the pushing element by pulling the pulling rod, the airtight spigot is airtightly moved with the pulling rod apart from the inner airtight stopper along the pushrod chamber of the pushing rod to remove air in the pushrod chamber until the airtight spigot moves to a selected position of the pushing rod, a low pressure condition of selected intensity is formed in the pushrod chamber of the pushing rod, wherein after an injection process the pushing element is pushed forward to abut and move the needle-seat fixing ring, the needle-seat fixing ring is moved to disengage sequentially from the engaging flange of the barrel and the needle seat, the needle seat and the inner airtight stopper are moved into the pushing rod concomitantly, and a pressure difference between the low pressure condition of the pushrod chamber and the ambient atmospheric pressure attracts the inner airtight stopper and the needle seat that carries the needle simultaneously into the pushrod chamber to provide an automatically retracting effect to the needle and the needle seat.