Insulator and Heat Exchanger for Ultra High Vacuum,
High Voltage Discharge Chamber,
W. J. Wheeler
Glass Technician
University of Wisconsin
Madison, Wisconsin
whee112923@aol

Fabrication of 18" Diameter Glass Tube

Half an inch either way was sufficient. The hand wheel rotated along with the central pipe, the chucks, the tubing, and the covers for the ends of the tubing, and was rotated faster by hand to impart motion to the glass in one direction, and held counter to the rotation to reverse direction of' chuck travel. It was found that this method gave us very sensitive control over movement of the glass prior to sealing, even though done remotely through commands and hand signals to an assistant.

A 3:1 ratio between the central shaft of the machine and a pulley held in the tailstock jaws of the Litton lathe gave us about the desired speed for sealing, 20 rpm. At this step up ratio, we found that the Litton lathe develops enough torque to overcome any imbalance in the 18 inch tube, and consequent erratic rotation. Only on the first sealing operation was it necessary to balance the machine to overcome weight differences due to different wall thickness per section. A steel bar was clamped to chuck jaws well back from the heated area. This balanced the entire rotating portion before seals were made.

Half an inch either way was sufficient. The hand wheel rotated along with the central pipe, the chucks, the tubing, and the covers for the ends of the tubing, and was rotated faster by hand to impart motion to the glass in one direction, and held counter to the rotation to reverse direction of' chuck travel. It was found that this method gave us very sensitive control over movement of the glass prior to sealing, even though done remotely through commands and hand signals to an assistant.

To mount the sections of glass tubing on the chucks we lifted and held the central 6-inch steel tube with the overhead crane, removed one "A" frame, slid the glass tubing over the open end, then replaced the "A" frame. The ends of the tubing were sealed to make the assembly airtight with galvanized metal covers held in place with heat resistant tape. Access to the interior for blowing was made through the shaft of the hand wheel and holes were drilled in the 6 inch steel pipe to admit pressure of blowing to inside of glass assembly.

Figure 4

After sufficient preheating, the oxygen/hydrogen burners were wheeled into place, lit, and adjusted for maximum heat, At the point that the heated ends began to bead up and get noticeably heavier, the movable chuck was engaged, closing the gap between the ends of the glass tubing. Heating was continued until a smooth seal was accomplished. Although provision was made to blow into the center area, it was not necessary, as the speed of rotation (20 rpm) kept the glass from either spinning out or shrinking in. Sealing time was about 15 minutes per seal, Only in the later stages of sealing was it found necessary to paddle the seal with a graphite tool to maintain roundness, this due largely to uneven wall thickness in the glass cylinder.

Glassblowers were protected from excessive heat during sealing operations with aluminum coated full length shop coats, and welders face masks. The use or these safety devices allowed us to move at will as close as we wished to the heated zone

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