Method for shaping a glass tube preform

Claim 1

A METHOD OF PRODUCING A PIPETTE THE MAJOR LENGTH OF WHICH EMBRACES ASPIRATING AND CAPILLARY TUBES OF DIFFERENT BORE DIAMETERS SEPARATED BY AN INTERMEDIATE CHAMBER OF LARGER DIAMETER THAN SUCH BORES, SUCH METHOD INCLUDING ENSLEEVING A TUBE OF GLASS OVER A MANDREL HAVING TWO CYLINDRICAL SECTIONS OF DIFFERENT DIAMETERS DEFINED BY A ZONE OF JUNCTURE, DISPOSING A SHELL OF DESTRUCTIBLE MATERIAL ON SAID MANDREL ADJACENT SUCH JUNCTURE OF THE MANDREL SECTIONS WITH A PORTION OF THE SHELL BODY CONTACTING THE SURFACE DEFINING THE JUNCTURE THEREOF TO THEREBY RETAIN THE SHELL AGAINST MOVEMENT LONGITUDINALLY OF SAID MANDREL IN ONE DIRECTION AND WITH ITS OUTER SURFACE SPACED FROM THE MANDREL TO DEFINE A SPACE CORRESPONDING TO THE LARGER CHAMBER DIAMETER, SAID SHELL HAVING INCLUDED THEREIN A MIXING BEAD MADE OF A MATERIAL SUBSTANTIALLY UNAFFECTED BY THE ACTION OF ACID AND BEING OF A DIAMETER LARGER THAN THE ASPIRATING AND CAPILLARY TUBES OF THE PIPETTE, APPLYING HEAT TO SAID TUBE TO RENDER IT PLASTIC, SUBJECTING THE INTERIOR OF THE TUBE TO VACUUM TO CONSTRICT SAID TUBE TO CONFORM TO THE DIAMETERS OF SAID MANDREL AND SHELL AND ONLY THEN MOVING THE TUBE AND MANDREL AXIALLY OF EACH OTHER FOR A DISTANCE SUCH THAT THE MANDREL IS WITHDRAWN FROM THE TUBE BORE IN THE DIRECTION OF THE LARGER CYLINDRICAL SECTION AND WITH SAID SHELL RETAINED WITHIN THE TUBE CHAMBER AND DISSOLVING SAID DESTRUCTIBLE SHELL IN ACID.

Claim 2

THE METHOD OF MAKING A TUBULAR GLASS ARTICLE HAVING A RELATIVELY SMALLER BORE FROM A TUBULAR GLAS BLANK HAVING A RELATIVELY LARGER BORE BY SHRINKING THE GLASS BLANK AROUND A TUBULR MANDREL WHICH CONSISTS OF: FIRST ENSLEEVING THE TUBULAR GLASS BLANK OVER THE TUBULAR MANDREL; SUCKING AIR FOM A FIRST END ONLY OF SAID TUBULAR GLASS BLANK WITHOUT SUCKING AIR OUTWARDLY FROM THE OTHER END; APPLYING A HEAT SOURCE T THE TO THE TUBULAR GLASS BLANK TO SOFTEN THE GLASS AT A POINT ADJACENT THE FIRST END OF THE BLANK AND PROGRESSIVELY SHIFTING THE HEAT SOURCE IN A DIRECTION TOWARDS THE SECOND END OF THE BLANK TO PROGRESSIVELY SOFTEN THE GLASS WHILE CONTINUING TO SUCK AIR FROM THE SAID FIRST END ONLY OF THE TUBULAR GLASS BLANK TO REDUCE THE PRESSURE IN SAID BLANK TO CAUSE IT TO SHRINK AROUND SAID MANDREL; SIMULTANEOUSLY FLOWING COOLING FLUID THROUGH THE TUBULAR MANDREL THROUGHOUT THE HEATING OPERATION TO MAINTAIN THE MANDREL AT A TEMPERATURE LOWER THAN THE TEMPERATURE OF THE CORRESPONDING PORTIONS OF THE GLASS BLANK; AND FINALLY AFTER RELATIVE COOLING OF THE PARTS SHIFTING THE SHRUNKEN TUBULAR GLASS ARTICLE AND MANDREL RELATIVE TO EACH OTHER LONGITUDINALLY TO SEPARATE THE ARTICLE FROM THE MANDREL.