| 摘要 |
PURPOSE:To raise the efficiency of operations by a method in which two non- return chains paid out of two take up drums are built in an expandible multistage type boom, one of them is connected with a rake, and the other is connected to the lowest stage boom. CONSTITUTION:A driver is actuated to turn sprockets 40 and 41 toward the directions of arrows (a) and (b). No-back chains 89 are sent out of winding drums 10 and 11 and lowered, and expandible booms 4 are extended in the order of 4d, 4c, 4b, and 4a to lower a rake 2. When only the chain 9 for opening and closing the rake 2 is pulled up, the rake 2 becomes of horizontal attitude and the rake claw 2a is fitted into a screen 1. The chain 8 and 9 are further pulled up and wound around the drums 10 and 11, and as the boom 4 is pulled up, dust, etc., adhered to the screen 1 are removed out by the rake 2.
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