Plunger rod

A dimensionally stable plunger rod for use with a plunger in a cartridge or syringe barrel for manual or power-assisted withdrawal of fluid from a site or expelling fluid from the cartridge or syringe barrel, the plunger rod having first, second, third and fourth sides, a distal end and a proximal end comprising:

• an end disc at the distal end;
• a threaded member integral with said end disc to engage a plunger;
• a thumb rest at the proximal end for facilitating exertion of external pressure on the plunger rod;
• a central disc at about the mid-point between the end disc and thumb rest of the plunger rod to provide additional reinforcement between the end disc and the thumb rest;
• four longitudinal radially extending rectangular vanes spaced about 90° from each other and connected to said end disc and said thumb rest;
• on the first side of said plunger rod;
• a first pair of longitudinal radially extending reinforcing vanes;
• a second pair of longitudinal radially extending reinforcing vanes, both the first pair and the second pair of longitudinal radially extending reinforcing vanes being connected to the end disc and to the thumb rest;
• on the third side opposite to said first side of said plunger rod;
• a first pair of longitudinal radially extending reinforcing vanes;
• a second pair of longitudinal radially extending reinforcing vanes, both of the first pair and the second pair of longitudinal radially extending reinforcing vanes being connected to said end disc, to the central disc and to the thumb rest, wherein:
• each of said first pair and each of said second pair of longitudinal radially extending reinforcing vanes on the first side of said plunge rod and each of said first pair and each of said second pair of the longitudinal radially extending reinforcing vanes on the third side of said plunger rod forms an obtuse triangle with one of the longitudinal radially extending rectangular vanes, wherein the obtuse angle of said triangle is at the mid-point between said end disc and said thumb rest;
• on the second side of said plunger rod;
• a first pair of longitudinal radially extending supporting vanes forming a two-dimensional hourglass-shape surface extending from said end disc to the central disc and from the central disc to the thumb rest;
• and
• on the fourth side of said plunger rod;
• a second pair of longitudinal radially extending supporting vanes forming a two-dimensional hourglass-shape surface extending from said end disc to the central disc and from the central disc to the thumb rest.