An improved safety hypodermic syringe includes a reciprocaltubular needle sheath disposed on the exterior of the syringe body, alatch mechanism engaging the syringe body and the sheath to latch thesheath in a needle-covering position after delivering contents from thesyringebody, and a spring engaging the syringe body and the sheath and expandableto move the sheath to cover the needle point, where the spring isa non- uniform helical spring having multiple 360° turns each turnuniformlyspaced from adjacent turns, each 360° turn comprising first andsecond alternating angled portions, the first of the alternating angledportionsbeing at a first angle to a plane perpendicular to an axis through thecenter of the helical spring and the second angled portions being at a secondlesser angle to the plane perpendicular to the axis.
