Abstract: A retractable needle safety syringe (11) with plunger locking mechanism is disclosed. Locking means (36) are provided in the body (12) of the syringe to engage the plunger (13) once it is retracted after use, so that the syringe is rendered incapable of being used further. The locking means is preferably provided by a twist lock feature. A region of weakness (24) is also provided in the plunger so that after the needle is retracted into the body of the syringe, and the plunger engaged with the locking means, the plunger is broken off so it cannot be depressed again.

Abstract: An auto retractable safety syringe (11) is disclosed. The syringe has barrel (12) which has a hollow plunger (13) located therein. The plunger has piston means (39) associated therewith so as to be sealingly slideable within the barrel. The syringe further has a needle cartridge assembly (14) located in the barrel, the needle cartridge assembly comprising a needle (20), needle hub (21), and a housing (15, 16) therefor. The needle cartridge assembly is initially releasably engaged on the end of the plunger in a retracted state within the barrel prior to use, and is movable to and engageable with the end (25) of the barrel where the needle extends therefrom in an in-use position for performing an injection. During this time the plunger is withdrawn from engagement with the cartridge, so as to function in known manner as a plunger for taking fluid into the barrel and causing it to be injected into a patient.

Abstract: A safety syringe comprising a syringe barrel (12), a plunger (13), a needle (14), a needle hub (15) integral with the needle, a needle gland (16) to accommodate the needle-and hub, and a needle cap (19) to protect the needle prior to use. The plunger has engagement means (25, 36) located on its end to engage with the needle hub in order to retract the needle from the gland and into the syringe barrel after the syringe has been used. The plunger is provided with a threaded split bush (28), which has a multi start thread. When the plunger is fully retracted with the needle attached, the plunger has one or more lugs (31) that come into contact with the threaded split bush so that the plunger is thereby locked. Hence the needle is locked in the barrel. The plunger may be snapped off retaining the needle safely within the syringe barrel.

Abstract: A retractable syringe (11) is disclosed wherein the needle (14) is located initially in a first storage position enclosed within the syringe body (12). In a second in-use position, the needle extends from the body of the syringe. To move needle from first to second position, the plunger (13) connects the needle boss (15) with the syringe body ens (16). The plunger is then disengaged from the needle boss enable the plunger to be withdrawn and thereby take in fluid into the syringe. Upon completion of injection the plunger engages with the needle boss enabling the plunger to be withdrawn, the needle remaining attached. Engaging the plunger to the needle boss requires the same amount of force as to perform the injection. Lateral forces act to engage the needle boss and the end of the plunger, for example by utilising a cam mechanism in the form of a finger lock device (26).