GB664225A - Method of filling thermostat tubes - Google Patents

Abstract

664,225. Filling thermostat tubes. VAPOR HEATING CORPORATION. Nov. 8, 1949 [Nov. 19, 1948], No. 28624/49. Class 125(ii). [Also in Group XIII] A method of filling a thermostat tube 41 with a highly oxidizable temperature sensing material, e.g. a thallium amalgam, while the tube is out of contact with the atmosphere comprises placing the tube, open at one end, into a vessel which is being flushed with a non-oxidizing fluid to remove air from within it, and which contains the amalgam out of contact with the open end of the tube, closing the vessel and providing a vacuum within it, immersing the open end of the tube in the amalgam, releasing the vacuum from the vessel and refilling it with the non- oxidizing fluid so that the pressure of the latter, which is equal to the external atmospheric pressure, urges the amalgam into the evacuated interior of the tube. A vessel 10, containing thermostat tubes 41 and having its cork 15, provided with a valve 16, removed, is flushed with nitrogen fed to it from a container 13 by way of a tube 35 and an auxiliary chamber 29. A pipe 17 connects the chamber 29 to the vessel 10 and provides with a diametrically opposite pipe (not shown), connected through a valve to a vacuum pump, a pivotal mounting for the vessel 10 on brackets 21 fixed to the upright 22 of a stand 11 which carries also an abutment 23 for the vessel 10. The cork 15, with its valve 16 open, is plugged into the vessel 10 and a quantity of amalgam stored under H 2 SO 4 in a vessel 37 is supplied through a tap 38 and a pipe 34 into the chamber 29 where it remains surrounded by nitrogen and out of contact with the tubes 41. The valve 16 is closed, the supply of nitrogen cut off and the vessel 10 and the chamber 29 are connected to the vacuum pump. While the vessel 10 is being exhausted it is heated to about 250‹F. e.g. by a lamp 40, to remove any traces of moisture within the vessel 10. The vessel is placed upright and clasped in a bracket 24 fixed to the upright 22. This movement pours the amalgam from the chamber 29 into the vessel 10 where it covers the ends of the tubes 41. The vacuum pump is disconnected from the vessel 10 and nitrogen is again flushed through the apparatus so that its pressure, equal to the external atmospheric pressure, forces the amalgam into the evacuated interiors of the tubes 41 to fill them. They are then withdrawn from the vessel 10 and sealed at their open ends. In order to leave the correct amount of amalgam in each tube, so that metal electrodes 45, 46, Fig 6, are contacted at the required predetermined temperature, the end of each tube is heated to produce vapour which expands the end of the tube into a bulb. The surplus amalgam is withdrawn into this bulb and the upper part of the tube is sealed and broken off to leave a shorter finished tube, Fig. 6. The amalgam contains 8À73 per cent of thallium.