Abstract

The invention relates to a smoke detector comprising: an ionisation chamber (20; 220), formed by a first electrode (11; 211) and a second electrode (12; 212), wherein electric charges can be generated by ionisation of the air; and a drift chamber (30; 230) different from the ionisation chamber (20; 220) and separated from the ionisation chamber (20; 220) by the second electrode (12; 212), the drift chamber (30; 230) being formed by the second electrode (12; 212) and a third electrode (13; 213) and allowing the penetration of the smoke particles from the environment of the detector inside the drift chamber (30; 230); the first electrode (11; 211) being able to be brought to an electrical potential in relation to the second electrode (12; 212), exceeding a critical electric potential value for generating, in the vicinity of the first electrode (11; 211), a corona discharge wherein the discharges ionising the air in the ionisation chamber (20; 220) are generated; the second electrode (12; 212) being provided with openings allowing the passage of the electric charges generated in the ionisation chamber from the ionisation chamber (20; 220) to the drift chamber (30; 230); the second electrode (12; 212) being able to be brought to an electric potential in relation to the third electrode (13; 213), allowing the electric charges that have entered the drift chamber (30; 230) to move from the second electrode (12; 212) to the third electrode (13; 213), the electric field created between the second electrode (12; 212) and the third electrode (13; 213) being at least 100 times weaker than the electric field created between the first electrode (11; 211) and the second electrode (12; 212); the detector also comprising a measuring device (55; 55R, 55M, 60) for measuring an electric variable representing the speed of movement of the electric charges between the second electrode (12; 212) and the third electrode (13; 213) in order to trigger an alarm when said electric variable is subjected to an abnormal variation.

IPC Classes  ?

• G08B 17/11 - Actuation by presence of smoke or gases using an ionisation chamber for detecting smoke or gas