Flame monitor for burner with reversibly movable screen - closes safety valve when UV radiation ceases to excite photocell during variable periods of window opening

摘要

Ultraviolet radiation from the flame is monitored by a photocell (3) on to whose cathode (3a) the radiation is conc. by a lens (5) through an axial bore (4) and window (8a). The opaque screen (18) interposed between the window (8a) and the photocell (4) is moved into and out of the optical path at intervals of about 1 second by a reversible stepping motor (16). The periodicity can be varied to suit the qualities of flame in various burners. USE/ADVANTAGE - Esp. on gas-fired boilers. Failures arising from weakening of restoring spring conventionally fitted to sliding screen are avoided.