Abstract: An evaporation closure is disclosed. One embodiment of the closure includes a cap, made of pliable material, which in turn includes a top wall having an opening, a skirt downwardly depending from the top wall and having a threadless internal wall adapted to slip on and sealingly engage a container, and biasing means integral with the skirt; and an elongated arm, which in turn includes a means for sealing the opening, pivotally attached to the cap for movement between a first position wherein the sealing means seals the opening and a second position wherein the sealing means does not seal the opening, the arm being biased toward the first position by the biasing means. Such a closure is useful for minimizing evaporation from containers, particularly automated clinical analyzer reagent bottles.A kit including in packaged combination component parts of the evaporation closure is also disclosed. Such a kit is useful for conveniently assembling the evaporation closures of the present invention.

Abstract: A centrifuge system includes a drive shaft bearing mounted to a drive shaft for engaging a solenoid actuated plunger in low friction contact over a predetermined angular velocity range of the drive shaft. The drive shaft bearing includes a frustoconical bearing surface that contacts a plunger bearing mounted in an end of the plunger when the solenoid actuates the plunger. The frustoconical bearing surface transforms vibrations of the drive shaft transverse to its axis of rotation into linear motion of the plunger relative to the drive shaft. The plunger is mounted inside the solenoid such that the solenoid, the plunger and the drive shaft are substantially concentric. The plunger is movable in the solenoid in response to application of an appropriate electrical current to the solenoid. However, the plunger fits sufficiently close within the solenoid that the force movement of the plunger arising from contact with the vibrating drive shaft bearing is damped by friction between the solenoid and the plunger.