Abstract: A disposable syringe cartridge including a molded plastic cylinder having an open end and a closed end with inlet and outlet nipples integrally formed in the closed end, and a plastic piston head slidably received in the open end of the cylinder and pivotably connected to a plastic piston rod. The piston head utilizes a quad-type sealing ring providing a pair of adjacent sealing surfaces with the cylinder, and includes a square expansion flange rounded at each of its corners to conform in shape to the cylinder, with a rubber annular sealing boot extending between the open end of the syringe cylinder and the piston rod. A flange formed on the outer circumferential edge of the sealing boot is received over the open end of the cylinder and is captured by an annular cap that is ultrasonically welded to the cylinder, while a bead formed on the inner circumferential edge of the sealing boot is received in a groove defined by a pair of adjacent annular flanges formed on the piston rod.

Abstract: A syringe having a barrel and a plunger moveable axially in the barrel is provided with locking means for locking the plunger to the barrel. The locking means includes cam means carried between the barrel and the plunger, and means for moving the cam into a position forcing the plunger into binding contact with the barrel.