A safety vein syringe with retractable special needle, comprising:
- (A) a syringe barrel having a first end, a second end and a first axis extending from the first end to the second end, the syringe barrel being formed with an internal barrel chamber surrounding the first axis by an equal distance, the first end of the barrel being disposed with a needle socket extending away from the first and second ends, the needle socket defining a needle holder cavity surrounding a second axis by an equal distance, the second axis being spaced from the first axis by a first distance, an eccentric annular shoulder section being formed between the barrel chamber and the needle holder cavity, the second end of the syringe barrel being formed with an opening;
- (B) a plunger having a first and a second end, the first end being disposed with a piston and fitted into the barrel, the plunger having a centrally disposed third axis, after the plunger is installed into the barrel, the third axis coinciding with the first axis of the barrel, the first end of the plunger having a fourth axis spaced from the third axis by a second distance with is equal to the first distance;
- (C) a needle holder having a first end and a second end, the second end of the needle holder being formed with a fitting section fitted in the needle holder cavity of the needle socket, the needle holder having a fifth axis coinciding with the second axis after the fitting section of the second end of the needle holder is fitted into the needle holder cavity;
- (D) an injection needle inserted into the first end of the needle holder;
- (E) a guiding mechanism including:
- (a) a first guiding section disposed inside the second end of the barrel adjacent said opening, said first guiding section including at least a pair of projecting sections with at least a pair of guiding channels formed therebetween;
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- (b) a second guiding section defined by at least a pair of outwardly directed ribs extending between the piston and the second end of the plunger, the ribs being respectively slidably fitted in the guiding channels to prevent rotation of the plunger relative to the barrel, whereby the plunger and the barrel can only be axially slid relative to each other with the fourth axis being maintained in coincidence with the second axis;
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- (F) a needle pulling mechanism including:
- (a) a first needle pulling member having a first end and a second end, the first end of the first needle pulling member being integrally connected to the second end of the needle holder coincident with the fifth axis;
- and
- (b) a second needle pulling member having a first end and a second end, the first end being connected to a portion of the first end of the plunger coincident with the fourth axis, the first and second needle pulling members being moved toward each other and hooked together when the plunger is slid within the barrel toward the first end thereof, whereby subsequent pulling of the plunger from the first end of the barrel toward the second end thereof pulls the needle holder together with the injection needle into the barrel.