| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas draft hood which is of minimum cost of manufacturing and assembling, and is equipped with a balancing instrument having a simple structure and realizing reliable and effective closure of a sash-window. SOLUTION: A gas draft hood 10 is provided with a working space 14, an access opening 15 to the working space, and a housing 11 containing a sash- window 16 movable between an upper position and a lower position for facilitating open and shut movements of the access opening 15. The hood 10 is further provided with a counter weight 27 to keep holding the sash-window 16 at any point between the two limiting positions. The weight of the counter weight can be reduced by changing a regulating weight 25. The regulating weight also can increase the weight of the sash-window for the sash-window to come down to a specified position after the sash-window is moved to a specified position. |
