PURPOSE: To conduct experiments safely and smoothly by installing a drive means for driving the rotation of a detection means for detecting the presence of a person, a switch means with a timer, and a sprocket and a lower limit switch means for stopping the drive means.
CONSTITUTION: The elevating and lowering mechanism for an observation door 17 of a fume hood is equipped with a detection means 22 for detecting the presence of a person, a switch means with a timer which is turned on after a specified time when the detection means 22 detects the absence of a person and turned off immediately when the presence of a person is detected, and a drive means 25 for driving a sprocket 26 through a clutch means 27 which is directly connected with the sprocket 26 when the switch means is turned or and released from the sprocket 26 when the switch means is turned off. A chain is set at the positions of wires 18, 19 which correspond at least to the length of the vertical stroke of the observation door 17, and the drive of the drive means 25 is stopped by a lower limit switch means 30 in relation to the position of the chain 28 when the observation door 17 is brought down automatically to a specified position.
UEJIMA TADASHI
SATO MINORU
