Abstract: A needle covering mechanism for a hypodermic syringe includes a protective cover sleeve which is movable between a retracted position in which a needle is exposed and an extended position in which the needle is covered. A retainer includes first detents which by means of a spacer is forced to engage indentations in the cover sleeve to prevent a movement of the cover sleeve towards the extended position. The spacer is made from a material which after some time in contact with an injectant loses its mechanical strength, and some time after filling the syringe with an injectant, the spacer deforms, the first detents slip out of the indentations in the cover sleeve, and a spring forces the cover sleeve to the extended position.

Abstract: A needle covering mechanism (1) for a hypodermic syringe (2) comprises a protective cover sleeve (4) which is movable between a retracted position in which a needle (27) is exposed and an extended position in which the needle (27) is covered. A retainer (9) comprises first detents (16) which by means of a spacer (11) is forced to engage indentations (25) in the cover sleeve (4), to prevent a movement of the cover sleeve (4) towards the extended position. The spacer (11) is made from a material which after some time in contact with an injectant loses its mechanical strength, and some time after filling the syringe (2) with an injectant, the spacer (11) deform, the first detents (16) slip out of the indentations (25) in the cover sleeve (4), and a spring (8) forces the cover sleeve (4) to the extended position.