Image Number 3 for United States Patent #7799002.
An improved safety hypodermic syringe includes a reciprocal tubular needle sheath disposed on the exterior of the syringe body, a latch mechanism engaging the syringe body and the sheath to latch the sheath in a needle-covering position after delivering contents from the syringe body, and a spring engaging the syringe body and the sheath and expandable to move the sheath to cover the needle point, where the spring is a non-uniform helical spring having multiple 360.degree. turns each turn uniformly spaced from adjacent turns, each 360.degree. turn comprising first and second alternating angled portions, the first of the alternating angled portions being at a first angle to a plane perpendicular to an axis through the center of the helical spring and the second angled portions being at a second lesser angle to the plane perpendicular to the axis.
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