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.

متقدم

Unknown

التعليمات

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."

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).

المواد لهذه الخطوة:

أنبوب زجاجي1 kind not given

زجاج مجهول1 قطعة

الأدوات المطلوبة:

شعلة نفخ زجاج طاولية

فرن التلدين

طريقة تشكيل مجهولة

أبعاد غير معروفة

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.

الأدوات المطلوبة:

مضخة تفريغ

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.

الأدوات المطلوبة: