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Cold Trap: Liquid-Air Well round the Line, in an Evacuated Jacket (Smith, US 2,513,114)
A cold trap freezes water and other vapours out of a vacuum line before they reach a gauge or a pump. D. W. Smith (US 2,513,114, filed 1944) blows it as one glass piece: the inlet tube runs down through an annular well of liquid air, and an outer jacket round the well opens into the outlet tube, so the pump keeps the jacket evacuated and it insulates the liquid air.
Only a small ring of liquid air is open to the room, so little boils away and the trap stays cold for long periods.
Source: D. W. Smith, "Liquid Air Trap", US Patent 2,513,114 (1950). Picture: its Figs. 1-2.
Advanced
Unknown
Instructions
1
1
Read Smith
Read Smith
"My invention consists in providing a cold trap integral with a tubular conduit and designed to surround the conduit with a cylindrical pool of liquid air; a double-walled, evacuated chamber being provided to insulate the liquid air from the atmosphere."
2
2
Blow the trap
Blow the trap
Make one glass piece (Fig. 1): an inlet tube running down through the middle; round it an annular well, open at the top, whose inner side is the inlet tube and outer side an inner wall; round the well a closed outer jacket coaxial with it, joined to the well at the top. Below, the inlet tube ends open inside the jacket, and the jacket narrows into the outlet tube (the jacket and the line share one vacuum). Smith says glass may be used and the material is not critical; no sizes, glass or blowing method are given (ours: a glassblowing torch and an annealing oven).
Materials for this step:
Glass Tube1 kind not given
Unknown Glass1 pieceTools needed:
Bench Glassblowing Torch
Annealing Oven
Unknown Forming Method
Unknown Dimensions3
3
Put it in the line
Put it in the line
Join the inlet tube to the side to be protected (Smith: the ion gauge) and the outlet tube to the vacuum pump. Pumping the line also evacuates the jacket, which then insulates the well.
Tools needed:
Vacuum Pump4
4
Fill and use
Fill and use
Fill the well with liquid air. Water, mercury and other vapours freeze onto the walls of the inlet tube inside the well and stay there. Only the small ring at the top of the well is open to the room, so the liquid air lasts a long time without topping up.
Tools needed:
Liquid AirMaterials
2- 1 kind not givenPlaceholder
- 1 piecePlaceholder
Tools Required
6- Placeholder
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- Vacuum Pump10% commissionMagento Legacy StoreLOCALPlaceholder
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