a syringe 1 comprises in the first place a body 2 comprising a generally cylindrical side wall 3 of axis 4 . the side wall 3 has an upstream end which is open and a downstream end which is closed by a transverse wall 5 containing an orifice 6 and extended by a conical nozzle 7 of the “ luer ” or “ luer - lock ” type . at its upstream end , the body has both a collar 8 for a nurse to press against with the fingers , and an inward annular bead 9 . the syringe 1 also comprises a rod 10 forming a plunger , at the downstream end of which is a piston 11 . the piston 11 possesses three annular sealing lips , namely an upstream lip 12 , an intermediate lip 13 and a downstream lip 14 , designed to be in contact with the inside face 15 of the side wall 3 of the body 2 . an annular chamber is defined between each two successive lips . in the embodiment illustrated , the piston 11 therefore has two annular chambers 16 , 17 . the syringe 1 ( body and rod ) is here made of plastic , but it could be of glass . the rod 10 is designed to be inserted into the body 2 and slide along inside it leak - tightly when pushed by a user . the piston 11 and the inside of the body 2 are generally coated with silicone so that the piston slides easily . in this way an inner chamber is defined inside the body 2 , between the transverse wall 5 and the piston 11 . the inner chamber is filled with contents 18 which may be a medicinal solution , a solvent , etc . there is also usually a gas bubble 19 ( air or nitrogen , for example , depending on the case ) left inside this inner chamber . lastly , the syringe 1 comprises a removable cap 20 for closing the orifice 6 formed in the transverse wall 5 of the body 2 . the syringe 1 , prefilled and equipped with the rod 10 and cap 20 is put in a package of the type described earlier . the whole is then placed in an autoclave for steam sterilization of the syringe 1 . according to the invention , means of communication are formed in the body 2 of the syringe 1 to allow the steam to sterilize the annular chambers 16 , 17 of the piston 11 . in a first embodiment , shown in fig2 and 3 , the means of communication consist of at least one groove 21 formed essentially axially in the side wall 3 of the body 2 , from the inside face 15 . the groove 21 preferably leads out of the body 2 at the upstream end of the body , interrupting the bead 9 , locally . in a variant , the groove or grooves 21 need not lead out of the body but could have an upstream end situated close to the downstream face 22 of the bead 9 . the groove 21 , or each groove 21 has the following features : the axial distance d between the downstream face 22 of the bead 9 and the downstream end of the groove 21 is such that : h is the total axial length of piston 11 , h 12 , h 13 and h 14 are the axial lengths of the upstream 12 , intermediate 13 and downstream 14 sealing lips , respectively , of the piston 11 , h 16 is the axial length of the upstream annular chamber 16 of the piston 11 ; the radial depth p of the groove 21 is great enough to locally break the seal between the outer face of the upstream 12 and intermediate 13 sealing lips and the inside face 15 of the side wall 3 of the body 2 . fig2 shows the syringe 1 in the storage position ( syringe 1 at room temperature , for example in its package ). the capacity of the body 2 is adapted to suit the desired volume of the contents 18 so that , in this position , the piston 11 is situated downstream of the groove 21 . in this way the contents 18 ( in the liquid phase ) of the syringe 1 are isolated by the three lips 12 , 13 , 14 of the piston 11 . the chambers 16 and 17 are sealed off and the groove 21 has no function . at the start of the sterilization cycle , the syringe 1 in its package is placed in the autoclave chamber , at room temperature , and autoclave pressure is established . the contents 18 of the syringe are in the liquid phase , so there is no pressure on the piston 11 to push it out of body 2 of the syringe 1 . in any case , the pressure in the autoclave chamber acts on the rod 10 and tends to push the piston 11 into the body 2 of the syringe 1 . the piston 11 is therefore always in a position such as to isolate the contents 18 . the temperature in the autoclave chamber rises gradually to 121 ° c ., with an absolute pressure of around 2 bar . the contents 18 of the syringe 1 now vaporize , thus generating pressure inside the body 2 . this pressure is proportional to the temperature of the steam , and also varies as a function of the amount of gas ( the bubble 19 ) in the body 2 of the syringe 1 . when the pressure in the body 2 of the syringe 1 is generating a force greater than that exerted by the autoclave pressure on the rod 10 , added to the force required to make the piston 11 slide , the piston retreats until it contacts the bead 9 ( fig3 ). the steam 23 present in the autoclave chamber will now enter the groove 21 . given the dimensional relationships mentioned above , the steam 23 also passes into the annular chambers 16 , 17 , thereby sterilizing these chambers with so - called wet heat . in this position , the contents 18 of the syringe 1 are sealed off by the upstream lip 14 of the piston 11 , because the groove 21 has sufficient length to enable the two chambers 16 , 17 to communicate with the outside of the body 2 , and is sufficiently short for there to be no risk of contamination of the inner chamber . clearly , the dimensions of the body 2 of the syringe 1 and the volume of the contents 18 are chosen so that , during sterilization , the piston 11 makes firm contact with the bead 9 , and is therefore positioned correctly relative to the groove 21 . furthermore , the near incompressibility of the piston 11 ensures that the contents 18 remain sealed off because the upstream lip 14 stays at a distance from the groove 21 . at the end of the sterilization cycle ( in the cooling phase ), the pressure in the body 2 of the syringe 1 will gradually drop and the contents 18 of the syringe 1 will return to the liquid state . when the pressure in the autoclave chamber generates a force greater than that generated by the contents of the syringe 1 added to that necessary to make the piston 11 slide , the latter will move back along the body 2 of the syringe 1 to its initial position ( fig2 ). in a second embodiment , shown in fig4 and 5 , the means of communication consist of at least one orifice 24 formed in the side wall 3 of the body 2 . the orifice 24 , which is preferably circular and radial , has an upstream edge 25 and a downstream edge 26 : these are situated at distances d 25 and d 26 , respectively , from the downstream face 22 of the bead 9 , such that : d 26 & gt ; h 12 + h 16 + h 13 and d 26 & lt ; h − h 14 . once again the dimensions of the body 2 are adapted to the volume of the contents 18 so that , in the storage position ( fig4 ), the piston 11 is at a distance from the orifice 24 , so that the seal of the inner chamber is not affected by the orifice 24 . however , the orifice 24 is designed to place the two annular chambers 16 , 17 in communication with the outside of the body 2 , in order to allow steam 23 to enter during sterilization ( fig5 ), when the piston 11 is in contact with the bead 9 . finally , in a third embodiment , the means of communication are an annular slot 27 formed in the side wall 3 of the body 2 from the inside face 15 . this slot 27 has an upstream end 28 and a downstream end 29 , and has the following features : the axial distance d 28 between the downstream face 22 of the bead 9 and the upstream end 28 of the slot 27 is such that : d 28 & gt ; h 12 and d 28 & lt ; h 12 + h 16 ; the axial distance d 29 between the downstream face 22 of the bead 9 and the downstream end 29 of the slot 27 is such that : d 29 & gt ; h ; the radial depth p ′ of the slot 27 is great enough to locally break the seal between the outer face of the intermediate 13 and downstream 14 sealing lips and the inside face 15 of the side wall 3 of the body 2 ; and the axial length of the slot ( d 29 − d 28 ) is less than the total axial length h of the piston 11 . this last feature ensures that the inner chamber is sealed off from the outside of the body 2 of the syringe 1 whatever the position of the piston 11 in the body 2 , between the storage position and the position of contact with the bead 9 . in a variant the slot 27 may occupy only a fraction of the perimeter of the body 2 . as in the embodiments described above , the body 2 is designed on the basis of the volume of the contents 18 so that the piston 11 is situated at a distance from the slot 27 when in the storage position ( fig6 ): the integrity of the inner chamber is therefore not affected by the slot 27 . during sterilization ( fig7 ), the piston 11 is pushed against the bead 9 , and the slot 27 therefore places the inside of the body 2 in communication with the annular chambers 16 , 17 . in this embodiment , the steam with which the annular chambers 16 , 17 of the piston 11 are sterilized is formed by the contents 18 , in the gas phase , of the body 2 of the syringe 1 , rather than by steam from the autoclave chamber . one of the advantages of this embodiment is that it enables the downstream lip 14 of the piston 11 to be sterilized . thus , by adding means of steam communication situated upstream of the piston when the syringe is in the storage position and surrounding the annular chambers of the piston during sterilization , the invention enables steam to enter between the lips of the piston while maintaining the isolation of the syringe contents from the steam present in the autoclave chamber . it goes without saying that the invention is not limited to the embodiments described above by way of examples but that on the contrary it encompasses all variants . in particular , the means of communication could take the form of a suitable combination of the three individual embodiments that have been described .
the invention concerns a syringe comprising : a body including a cylindrical side wall having an open upstream end with an inner annular rim and a downstream end closed by a transverse wall provided with an orifice ; a shaft equipped with a plunger having at least two annular sealing lips between which is defined at least one annular chamber . the shaft , which can slide inside the body , defines inside the body an inner chamber designed to be at least partly filled with a content . delivery passages provided inside the body are configured to communication said annular chamber of the plunger with the outside of the body or with the inner chamber of the body , when the plunger is abutting against the annular rim .