Valves for use in laboratory glassware

Claim 1

IN LABORATORY GLASSWARE, A VALVE WHICH COMPRISES A GLASS BARREL HAVING AN INTERNAL SURFACE OF THE SHAPE OF A SURFACE OF REVOLUTION TAPERING FROM ONE END TO THE OTHER, PASSAGEWAYS THROUGH THE WALL OF THE BARREL TO THE INTERIOR THEREOF, THE PASSAGEWAYS HAVING OPENINGS IN THE INTERNAL SURFACE OF THE BARREL AND INTERSECTING A PLANE THROUGH THE AXIS OF SUCH SURFACE, A PLUG OF A TOUGH, NON-VOLATILE, NONSTICKING SYNTHETIC MATERIAL ROTATABLY MOUNTED IN THE BARREL AND HAVING A CIRCUMFERENTIAL SEALING STRIP BETWEEN ITS ENDS IN CONTACT WITH AN AREA OF THE INTERNAL SURFACE OF THE BARREL CONCENTRIC WITH THE AXIS OF SUCH SURFACE AND CONTAINING AT LEAST ONE OF THE PASSAGEWAY OPENINGS, THE SEALING STRIP BEING NOT SUBSTANTIALLY WIDER THAN THE DIAMETER OF THE OPENING CONTAINED IN SUCH AREA AND THE PLUG HAVING CIRCUMFERENTIAL SECTIONS ON OPPOSITE SIDES OF THE SEALING STRIP OUT OF CONTACT WITH THE INTERNAL SURFACE OF THE BARREL, A PASSAGEWAY THROUGH THE PLUG IN A PLANE THROUGH THE PLUG AXIS, THE PASSAGEWAY HAVING AT LEAST ONE END OPENING IN THE OUTER SURFACE OF THE SEALING STRIP BETWEEN THE LATERAL EDGES THEREOF, RELATIVELY NARROW BEARING STRIPS ENCIRCLING THE PLUG AND IN CONTACT WITH THE INTERNAL SURFACE OF THE BARREL NEAR ITS ENDS, AND MEANS FOR YIELDINGLY DRAWING THE PLUG INTO THE BARREL TO MAINTAIN CONTACT BETWEEN THE SEALING AND BEARING STRIPS AND THE INNER SURFACE OF THE BARREL.