IT1271833B - Monitor device for presence of mine gas - Google Patents

Abstract

A device for signalling acoustically and/or visually the presence of mine gas, especially in coal mines, comprising: a tubular cylindrical body 1, at least partly made of electrically conducting material, with both the terminal openings closed by corresponding screens 2, 3 of material with elevated thermal conductivity; a resistor 4 fed with electric energy such as to be maintained constantly at the temperature of ignition of the mine gas (around 650 degrees Centigrade), situated inside said tubular body 1 and connected to the latter between two diametrically opposite points of its inner wall; a bar 5 of electrically conducting and thermally expandable material, situated inside said tubular body 1 close to said resistor, with a first end connected at one point to said tubular body 1 and the second end, opposite the first, situated at short distance from the point diametrically opposite that of said point of connection to said tubular body 1; at least one acoustic and/or luminous monitor unit 6, 7 situated on said tubular body 1; the arrangement being such that, when mine gas is present, said gas moves axially through said tubular body 1 and when it makes contact with said resistor 4 it ignites with substantial increase in temperature, bringing about the superheating of said bar 5 and its consequent elongation until said second end comes into contact with the internal wall of said tubular body 1, thereby closing the circuit to actuate said monitor units. <IMAGE>