Blood gas syringe

Claim 1

A blood gas syringe, which comprises; a barrel having a first open end for receiving a slidable plunger, a second open end adapted to mount a needle on the opening thereof and a bore communicating between said ends; and a plunger slidably mounted in the bore of said barrel, said plunger being at least partially withdrawable from said barrel through said first open end, said plunger comprising; (a) an elastomeric piston having an upper end and a lower end, a body joining said upper and lower ends, said body having a diameter less than the diameter of said bore, and a sealing flange radially disposed about the outer periphery of said body between the upper and lower ends, said flange forming a light sliding seal with the inner walls of said barrel; (b) a plunger rod having a first end extending out of the first open end of said barrel and a second end within the bore of said barrel; and (c) means for coupling without a rigid connection, said second end of said rod to the lower end of said piston, said means permitting the displacement of the first end of said rod out of axial alignment with said piston, without moving said piston out of said alignment, said means also permitting free rotation and axial movement of the rod without moving the piston, and wherein said means comprises a stud mounted in said piston and an opening in the second end of said rod, said stud including a spacing bar component extending distally from the connection with the piston and a stud cap at the terminal end of the spacing bar, said stud spacing bar being inserted in and retained in said opening by engagement of the stud cap with the portions of said rod defining said opening, said spacing bar being of a dimension permitting the rod to float thereon without a rigid connection between rod and piston, said rod being rotatable and axially displaceable upon the spacing bar.