Disposable safety syringe

Claim 1

A disposable safety syringe, comprising: a) a syringe barrel ( 1 ); b) an injection needle ( 5 ), being integral with a needle-carrier ( 4 ), which is fitted on the tapered fore end ( 101 ) of the syringe barrel ( 1 ); c) a plunger ( 2 ) which is slidable in the syringe barrel ( 1 ) having an injection stroke which extends from a retracted syringe-filling position to an advanced syringe-emptying position, and is fitted at its back with a manually drivable stem ( 3 ), driven out of the syringe barrel ( 1 ) through the open rear end thereof; d) a needle-covering sleeve ( 14 ), which is axially fitted on the syringe barrel ( 1 ), so as to slide from a retracted rest position, in which it leaves the needle ( 5 ) exposed, into an advanced safety position, in which it entirely covers the needle ( 5 ); e) hook-like interacting means ( 12 , 13 ), which are provided at the rear side of the syringe barrel ( 1 ) and at the rear side of the needle-covering sleeve ( 14 ), and are initially engaged with each other so as to retain the needle-covering sleeve ( 14 ) in its retracted rest position, whereas they are automatically disengaged from each other by the stem ( 3 ) of the plunger ( 2 ), in the last portion of the injection stroke of the plunger ( 2 ), thereby releasing the needle-covering sleeve ( 14 ); f) a spring ( 16 ), interposed between a spring-bearing projection on the rear end of the syringe barrel ( 1 ) and a spring-bearing projection ( 17 ), inside the needle-covering sleeve ( 14 ), which stresses the needle-covering sleeve ( 14 ), once it is released from the hook-like means ( 12 , 13 ), towards its advanced safety position, first by making it elastically adhere to the patient body, and then by progressively advancing it, on extracting the needle ( 5 ) from the patient body, at the end of the injection, until it entirely covers the extracted needle ( 5 ); g) clamping means ( 19 , 21 ) which automatically lock the needle-covering sleeve ( 14 ) in its advanced safety position, preventing it from axially moving in either direction; h) the means ( 19 , 21 ) for locking the needle-covering sleeve ( 14 ) in its advanced safety position are held and/or formed at least partially by a mounted sleeve-clamping ring ( 18 ), which is provided and preferably mounted and fitted on the fore end of the syringe barrel ( 1 ); i) one or more retaining tongues ( 19 ), formed of one piece with the sleeve-clamping ring ( 18 ) and extending forwards in the axial direction by their free fore ends, which retaining tongues may be elastically moved radially inwards, that is towards the longitudinal axis of the syringe; k) one or more retaining teeth ( 20 ) provided on the inner part of the needle-covering sleeve ( 14 ), each associated to a tongue ( 19 ) for retaining the sleeve-clamping ring ( 18 ), each of these retaining teeth ( 20 ) being provided with a rear flank which is substantially transverse to the longitudinal axis of the syringe and interacts as a bearing surface with the free end of the retaining tongue ( 19 ) associated thereto, and with a fore flank, which is inclined forwardly radially outwards and interacts as a deflecting surface with the free end of the retaining tongue ( 19 ) associated thereto; l) a radial stop projection ( 21 ), which is provided at the rear end of the sleeve-clamping ring ( 18 ) and interacts as an abutment with an inner stop projection ( 17 ) of the needle-covering sleeve ( 14 ); m) all this in such a way that, in the last portion of the forward stroke of the needle-covering sleeve ( 14 ), the retaining tooth/teeth ( 20 ) thereof elastically and radially push, by their inclined fore flanks, the associated retaining tongue/s ( 19 ) inwards, passing beyond them, and enabling them to elastically snap radially outwards, so as to engage their free fore ends with the transverse rear flanks of the associated retaining tooth/teeth ( 20 ), while the inner stop projection ( 17 ) of the needle-covering sleeve ( 14 ) contacts the rear abutment projection ( 21 ) of the sleeve-clamping ring ( 18 ), characterized in that the retaining tongues ( 19 ) of the sleeve-clamping ring ( 18 ) are slidably engaged by their free fore ends in corresponding inner longitudinal grooves ( 414 ) of the needle-covering sleeve ( 14 ), in which grooves ( 414 ) their respective retaining teeth ( 20 ) are provided, and said inner longitudinal grooves ( 414 ) of the needle-covering sleeve ( 14 ) are formed in corresponding outer longitudinal ribs ( 314 ) of the needle-covering sleeve ( 14 ).