SYRINGE CAP ASSEMBLY

A syringe cap assembly includes a lock collar to be attached to an ejection port at a proximal end of the syringe, and a plastic cap screwed and thereby tightened into the lock collar. An external surface of the lock collar has projecting ribs that are each extended in an axial direction and are arranged in a circumferential direction to define recessed grooves, each recessed groove is extended in the axial direction and located between adjacent projecting ribs of the projecting ribs, and the adjacent projecting ribs are adjacent to each other in the circumferential direction. A bottom of an external surface of the plastic cap includes a protrusion extending in a direction toward the lock collar. At a stage where a tightening rotation of the plastic cap implemented by screwing the plastic cap into the lock collar is completed, the protrusion is located in the recessed groove between the adjacent projecting ribs.