Novel injector

The utility model discloses a novel injector. The injector comprises a needle cylinder, a piston and a push-pull rod, the piston is positioned in the needle cylinder; the lower end of the push-pull rod is connected with the piston, the outer side of the needle cylinder is sleeved with an annular outer sleeve, an annular cavity is formed between the needle cylinder and the outer sleeve, the outer side of the push-pull rod is sleeved with an annular protection pipe, and the protection pipe is arranged in the cavity and moves in the axial direction of the cavity. According to the injector provided by the utility model, the annular protection tube is arranged on the outer side of the push-pull rod, so that when a medical worker sucks liquid medicine, fingers of the medical worker can only touch the protection tube and cannot touch the push-pull rod positioned in the needle cylinder, and the liquid medicine in the needle cylinder cannot be polluted; meanwhile, due to the fact that the protection tube moves in the