Single-use device for injection

Single-use device for injection comprising a syringe (1) which is provided with a front nose (1a) which supports an injection needle (2), and with a rear collar (1b), the said syringe delimiting a chamber which is filled with a dose of fluid to be injected, and is sealed by a piston (4) which is rendered integral with one of the ends of a piston rod (5), which is provided with a thruster (6) at its opposite end, the said device for injection being characterised in that it comprises a device for protection after the syringe (1) has been used, comprising:

• a protective sheath (7), consisting of two tubular bodies (8, 9), which are known as the front body and the rear body, and are provided with assembly means (12, 18) which make it possible to render the bodies integral one in the extension of the other, the front body (8) having a diameter which is conjugated relative to that of the syringe (1), and a length which is designed to accommodate the said syringe partially, and the rear body (9) having a diameter which is larger than that of the collar (1b) of the said syringe, and comprising finger-support units (23);
• a ring (24) which is disposed in the rear body (9), which comprises means (29, 31) for locking the collar (1b) of the syringe (1), and can make it possible to introduce the said syringe (2), by presenting the needle opposite the rear body (9) of the protective sheath (7);
• the ring (24) and the rear body (9) comprising:
• first means (20, 22, 27) for relative locking in translation, which can make it possible to introduce the said ring in the said rear body, by presenting the ring opposite the surface of assembly of the latter with the front body (8), and defining a first locking position, known as the position for injection, which allows the injection to take place when the device for injection has been assembled;
• second means (20, 22, 28) for relative locking in translation, which define a second locking position, known as the position for protection after use, which is obtained after rearward sliding of the ring (24) inside the rear body (9), in which the injection needle (2) is accommodated in the front body (8);
• the ring (24) and the front body (8) being provided with stop means (10a, 31), which can keep resilient means (42) compressed in the first locking position, for injection;
• and
• the ring (24) or the rear body (9) comprising a rear portion (26) which is deformable radially, and supporting the first locking means (27) in translation, which portion is designed to be deformed by the thruster (6) of the piston rod (5) at the end of the path of the latter, such as to release the said first locking units, and to permit displacement of the ring (24) towards its second locking position, for protection after use.