Patent ID: 7717876

Claim:
An improved retractable needle safety syringe comprising a hollow cylinder, a needle holder at an end of said hollow cylinder, a needle fixed to said needle holder, a piston with an operating stem sliding in said hollow cylinder, wherein said stem has an axial hole in which there is seated an extractor element having an end portion protruding from said axial hole and structure suitable for connecting to said needle holder, and wherein said extractor element is connected to a retraction pre/loaded spring, said extractor element and operating stem having connecting means suitable for determining an axial interference between stem and extractor element stronger than the force exerted by the spring on the extractor element and wherein, with the extractor element in stroke end position connected to the needle holder, the operating stem can be further pushed forward relative to the extractor element so that said connecting means release from each other, thus allowing the retraction of the extractor element with the connected needle holder into the axial hole of the operating stem wherein said connecting means comprises an internal annular tooth on the stem, an internal shoulder on the stem between the needle and the annular tooth, and an annular projection on the extractor element for interacting with said annular tooth and said annular tooth and said shoulder defining an annular internal recess on the stem, between the annular tooth and the shoulder, in which the annular projection of the extractor element is free to slide axially during forward movement of the piston and further comprising a sealing element mounted around said end portion of the extractor element protruding from said axial hole.