the syringe depicted in fig1 to 5 comprises a glass syringe body 2 , one end of which is equipped with a separate injection needle 3 protected , prior to use , by a protector 4 depicted in chain line in fig1 . this syringe body 2 , which is intended to contain a liquid 5 that is to be injected , is closed at its other end by a plunger seal 6 , actuated by a stem 7 . mounted on the syringe body 2 , in the rear part thereof , is a sleeve 8 coaxial with the syringe body and secured to the latter by a bush 9 which bears against the syringe body 2 via longitudinal ribs 10 . the sleeve 8 is connected to the bush 9 by two radial tabs 12 . the sleeve 8 is equipped , at its rear end , with a partial collar 13 projecting outwards . this syringe comprises a tubular piece 14 , the length of which is approximately equal to the length of the syringe body increased by the length of the needle 3 and which , starting from its rear end , has two longitudinal slots 15 , each serving for the passage of one tab 12 which connects the sleeve 8 and the bush 9 . the tubular piece 14 is intended to be engaged over the syringe body 2 and to slide relative to the latter inside the sleeve 8 . in the embodiment depicted in fig1 to 5 , the stem 7 of the plunger 6 comprises , at its rear end , flexible tabs 16 extending the stem and facing from the inside outwards , and of which the free ends form a collar 17 facing outwards . this collar 17 is intended to be engaged in an annular groove 18 formed on the inside of the tubular piece 14 , at a distance from the rear end thereof that is at least equal to the length of the needle . the rear end of the tubular piece 14 may be closed off by a cap 19 which has a rim 20 which caps the tubular piece so as to prevent the possible opening thereof which may result from the presence of the slots 15 . in the embodiment depicted in fig2 the front part of the tubular piece 14 is equipped with an extension 22 which is frangible at a thinned zone 23 . this extension is intended to sheathe the needle before the syringe is used . starting out with a syringe , as depicted in fig2 the use of the syringe is as follows . the operator removes the extension 23 of the tubular piece and the needle protector 4 . he may introduce the needle into the patient in an entirely normal way by holding the syringe by the sleeve 8 , between the index and middle fingers , and pressing the cap 20 of the tubular piece 14 with his thumb . the axial movement of the tubular piece 14 results in a corresponding driving of the stem 7 and of the plunger 6 , causing the liquid 5 contained in the syringe to be injected into the body of the patient . when , at the end of injection , the tabs 16 forming an elastic cone come into contact with the body of the syringe , the latter pushes the tabs 16 closer together and their collar 17 escapes from the groove 18 in the tubular piece 14 , as shown in fig4 . throughout the injection phase , the front part of the tubular piece has gradually sheathed the syringe body 2 until , at the end of injection , it has come into contact with the skin of the patient . continuing to push on the tubular piece 14 allows the needle to be completely sheathed by the front of the piece 14 , as shown in fig5 as the needle is gradually pulled out of the skin . the complete syringe is retracted into the tubular piece 14 and can be disposed of without the risk of stick injury to the operator or to cleaning staff . fig6 depicts an alternative form of the attachment of the rear end of the stem 7 to the inside of the tubular piece 14 . in this case , the flexible tabs 16 at their free ends form a collar 17 , in the exterior face of which is formed a groove 25 in which an annular rib 26 formed on the inside of the tubular piece 14 is intended to engage . the stem 7 is detached from the tubular piece 14 under the same conditions as hereinabove . fig7 and 8 illustrate another embodiment of the invention , in which the same elements are denoted by the same references as previously . in this instance , the stem 7 is of constant cross section and has axial slots 27 opening into its rear edge . the stem 7 also has a peripheral collar 28 , interrupted by the slots 27 . this collar has a chamfered outer edge 29 . the collar 28 is intended to engage in an annular groove 30 in the tubular piece 14 so as to put together the stem and the tubular piece . when , at the end of injection , the stem 7 is axially immobilized , the rear part of the stem 7 can close up , by virtue of the presence of the slots 27 , the chamfered surfaces 29 allowing this closing - up movement and , consequently , the stem 7 can detach axially from the tubular piece 14 , the translational movement of which can be continued so as to sheathe the needle , as shown in fig8 . fig9 depicts an alternative form of this syringe , in which the syringe body 2 is made of synthetic material and forms a single piece with the sleeve 8 to which it is connected by tabs 12 . in this instance , there is no intermediate bush 9 as there was before . as is clear from the foregoing , the invention affords a great improvement to the existing art by providing a safety syringe equipped with an automatic device for protecting the needle at the end of injection , this protection being achieved without the operator having to perform a deliberate movement . furthermore , the selling price of this syringe is not appreciably higher than that of a conventional syringe , insofar as the protective device consists merely of one additional component — the tubular piece — or two additional components , insofar as the sleeve does not form an integral part of the syringe body . as goes without saying , the invention is not restricted simply to the embodiments of this syringe which have been described hereinabove by way of example ; on the contrary , it encompasses all alternative forms thereof .
this syringe comprises a tubular piece surrounding the body of the syringe and driving the stem of the plunger of the syringe . during injection , the tubular piece slides forward on the body . at the end of injection the tubular piece detaches from the stem and , its front part can continue to slide in order to sheathe the needle .