Patent ID: 7815863

Claim:
An improved stopper having a probe on a projecting stem of said stopper, said probe forming a first seal adapted to sealingly seat in an inlet and close the same, said first seal precluding air entrapment within a test chamber upon being seated in said inlet, said probe having a distal end adapted to enter said inlet of said test chamber below an established fill level before said first seal closes said inlet, said distal end having a thickness sufficient to displace liquid upwardly through said inlet and position the surface of said fluid sample in a vestibule prior to said first seal closing said inlet and a plug on said projecting stem of said stopper proximal to said probe, said plug having a position along said projecting stem such that said vestibule remains open to an environment until after closing of said inlet by said probe then said plug engages with an enlarged mouth on said vestibule effecting a second seal to close the upper end of vestibule, wherein the improvement comprises: a. a single elastomer where the probe, the plug, and a stopper handhold are composed of said single elastomer; and b. a locking mechanism to engage with keeper elements on a cartridge, said mechanism having flexible walls on each side of said stopper handhold such that when said second seal closes the vestibule said flexible walls are compressed until they snap outwardly and allow said stopper to lock into place, said locking mechanism resists disengagement by twisting.