1361130 Portable pressurised fire extinguishers WALTER KIDDE & CO inc 10 Nov 1972 [10 Nov 1971] 52163/72 Heading A5A A fire extinguisher having a safety valve to facilitate charging comprises container 11 closed by control head 13 which is formed with axial bore 15 housing main valve 29 and leading to main outlet 24 and with a further discharge passageway branching from bore 15 through which stem 32 of valve 29 projects and which houses movable O-ring 34 and safety valve member 37, stem 32 and member 37 being operatively connected by compression spring 41 so that the safety valve is urged closed when the main valve is open, the safety valve being acted on by the container pressure when the main valve is open and opened when this pressure exceeds the opposing spring force. Container 11, e.g. of stainless steel, has neck opening 12a in which is inserted control head 13, e.g. of polymerised formaldehyde, O-ring 14 forming a fluid-tight seal therebtween. Siphon tube 18 is mounted in lower part 21 of bore 15 and extends downwardly into 11. The upper part of 21 tapers at 22 to form a seat for head 31 of valve member 29, and narrower bore portion 23 leads from above seat 22 to main outlet 24 in protruding nose 46 of the head. Also communicating with bore 23 is bore 26 formed with stepped portions 27, 28 and housing stem 32 of 29. Stem 32 is depressed by lever 43 the latter is squeezed when with handle 45. Annular recess 36 in bore portion 28 supports O-ring 34 which can slide upwards toward portion 27 in which is housed valve member 37. Compression spring 41 is mounted between collar 39 on stem 32 and the bottom of recess 42 in 37, thus serving simultaneously to urge valve 29 upwards and valve 37 down. Container 11 is charged with, e.g. water or a dry powder and then pressurised with gas through passageway 24. With valve 29 open, spring 41 is compressed and exerts a forced downwardly on valve 37. If the container pressure exceeds this force, O-ring 34 is lifted off shoulder 36a and fluid is vented through the annular passageway surrounding valve 37.
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