Metered drop dispenser

Claim 1

AN ACCURATELY METERED DROP DISPENSER SUITABLE FOR USE IN PERFORMING MICROTITRATIONS AND WHICH MAY BE READILY STERILIZED FOR REUSE, SAID DISPENSER COMPRISING: AN ELONGATED BARREL DEFINING A RESERVOIR AND FORMED OF A FIRST MATERIAL WHICH IS RESISTANT TO PERMANENT DEFORMATION AT STERILIZING TEMPERATURE AND HAS A FIRST COEFFICIENT OF THERMAL EXPANSION, SAID BARREL HAVING OPENINGS AT EACH END; A TUBULAR DROPER ELEMENT ATTACHED TO SAID BARREL AT ONE END TO FORM AN EXTENSION THEREOF AND FORMED OF A SECOND MATERIAL HAVING A SECOND COEFFICIENT OF THERMAL EXPANSION GREATER THAN THAT OF SAID FIRST MATERIAL AND WHICH IS ALSO RESISTANT TO PERMANENT DEFORMATION AT STERILIZING TEMPERATURES; SAID DROPPER ELEMENT HAVING A THROUGH BORE WHICH IS ENLARGED AT ONE END TO EMBRACE THE EXTERIOR OF SAID BARREL ONE END, SAID DROPPER ELEMENT THROUGH BORE HAVING AN OUTWARDLY FLARED CONOIDAL CONCAVE SURFACE AT ITS OPPOSITE END PROVIDING THE SOLE SURFACE OF SAID DISPENSER TO WHICH LIQUID WITHIN A DROP BEING FORMED CAN ADHERE BY SURFACE TENSION DURING FORMATION OF SUCH A DROP BY PASSAGE OF LIQUID FROM SAID RESERVOIR THROUGH SAID THROUGH BORE TO SAID ELEMENT OPPOSITE END; SAID DROPPER ELEMENT THROUGH BORE HAVING ALSO AN ELONGATED CYLINDRICAL INTERMEDIATE PORTION OF NO GREATER DIAMETER THAN THE DIAMETER OF THE OPENING OF SAID BARREL ONE END WHEREBY, UPON ASSEMBLY OF SAID DROPPER ELEMENT ON SAID BARREL ONE END, SAID DROPPER ELEMENT BORE INTERMEDIATE PORTION FORMS A FLUID PASSAGE EXTENSION OF THE OPENING THROUGH SAID BARREL ONE END; THE EXTERIOR SURFACE OF SAID DROPPER ELEMENT AT SAID OPPOSITE END INTERSECTING SAID CONCAVE SURFACE IN A CIRCULAR LINE AND INTERSECTING THE PLANE DEFINED BY SAID CIRCULAR LINE SUBSTANTIALLY PERPENDICULARLY THEREBY PRECLUDING VARIATION IN THE VOLUME OF A DROP BEING FORMED ON SAID CONOIDAL CONCAVE SURFACE INCIDENT TO ADHESION OF LIQUID TO AN EXTERIOR SURFACE OF SAID DROPPER ELEMENT, AND MEANS ON THE ENGAGED SURFACES OF SAID BORE ONE END AND SAID BARREL ONE END FORMING A FLUID TIGHT SEAL BETWEEN SAID BARREL AND SAID DROPPER ELEMENT AND MAINTAINING SAID BARREL AND ELEMENT IN ASSEMBLY AT NORMAL AMBIENT TEMPERATURES WHILE PERMITTING RELATIVE DIFFERENTIAL RADIAL EXPANSION THEREOF AS THEY ARE SIMULTANEOUSLY HEATED TO STERILIZING TEMPERATURES.