Syringe assembly

A syringe assembly which comprises:

• a syringe body having an open distal end and an open proximal end, and defining therein a passage;
• a plunger comprising a main body having a distal end and a proximal end, and a gasket mounted on a distal end portion of said main body and adapted to be slidably and liquid-tightly housed in said syringe body, the distal end of said plunger defining a columnar body that is located distally of the gasket;
• a needle-mounting member for having threadably mounted therein a needle, said needle-mounting member being detachably screwed into a distal end portion of said syringe body;
• plunger-engaging means provided on said needle-mounting member;
• and
• needle-mounting member-engaging means formed adjacent a distal end portion of said gasket, and adapted to be engaged with said plunger-engaging means;
• said needle-mounting member and said plunger further comprising:
• (i) torque-transmitting means for transmitting torque from said plunger to said needle-mounting member in a direction to release an engagement between said syringe body and said needle-mounting member, said torque transmitting means including a plurality of first ribs formed on said columnar body and a plurality of second ribs formed on said needle-mounting member, each of said first ribs having a side surface which is substantially parallel to an axial direction of said main body, each of said second ribs having a side surface which impinges upon said side surface of one of the first ribs when the plunger is rotated in a direction to release engagement between said syringe body and said needle-mounting member to thereby transmit torque from the plunger to the needle-mounting member;
• and
• (ii) engagement-releasing means for releasing an engagement between said needle-mounting member-engaging means and said plunger-engaging means through rotation of said plunger in a direction which maintains engagement between said needle-mounting member and said syringe body, said engagement-releasing means including a plurality of first slant surfaces and a plurality of second slant surfaces, said first slant surfaces being disposed on said first ribs and being inclined with respect to said side surfaces on said first ribs, said second slant surfaces being disposed on said second ribs and being inclined with respect to said side surfaces on said second ribs, said first slant surfaces being movable over the second slant surfaces when said plunger is rotated in a direction for maintaining engagement between said needle-mounting member and said syringe body to release engagement between the needle-mounting member-engaging means and said plunger-engaging means.