GB1427007A - Gas detection - Google Patents

Abstract

1427007 Valves DEFENCE SECRETARY OF STATE FOR 8 May 1973 [12 April 1972] 16812/72 Heading F2V [Also in Division G1] A multi-position valve assembly for use in vapour detection apparatus comprises two discs 12, 14 of glass-filled polytetrafluoroethylene and of specified dimensions, disc 12 being rotatable through a limited angle by means of lever 20 and disc 14 being fixed relative to a framework or casing, the contacting faces of the discs having in them channels providing three different flow paths through the valve corresponding to three positions of disc 12 attained when lines 52, 54, 56 on disc 12 are aligned with line 58 on disc 14. In the embodiment of the drawings, with disc 12 of Fig. 2A superimposed on disc 14 of Fig. 2B, and line 52 aligned with line 58, a first flow path for atmosphere to be tested comprises tube 34, channels 64, 66 (channel 66 containing a heatable platinum coil), 68 and 70 while simultaneously there is formed a carrier gas flow path through tube 38, channels 72, 74, 76 and 78; when line 54 is aligned with line 58 and the assembly is in its second position there is a carrier gas flow path through tube 38, channels 74, 80, 82, 84, 86 and 64 and tube 34 and also through channels 72, 74, 76, 78; when line 56 is aligned with line 58 and the assembly is in its third position, there is a carrier gas flow path through tube 38, channels 72, 74, 80-86 and 64, 66, 76, 78. Lever 20 may be operated by means of a mechanized connection between the lever and a switch (26) used to close an electrical circuit for heating coil 22. The apparatus as a whole may be operated automatically using battery driven electric motor or spring-power.