| 摘要 |
The invention relates to a high volume air sampler for sampling particulate matter in an area during a predetermined time period. It provides a structure having a vertically movable roof which may be raised to expose a filter paper during a sampling period and thereafter be lowered to seal the filter paper enclosure at the end of the sampling period. The roof is mounted on drive screws which serve to raise the roof at the start of the sampling period and to lower the roof at the end of the sampling period. A gear reducer and reversible motor serve to turn the drive screws through a chain and sprockets connected to such drive screws. A timer initiates the start of the sampling period and starts the reducer and motor which in turn through the drive screws, chain and sprocket assembly raises the roof of the high volume sampler. When the roof reaches its uppermost position a limit switch turns on a vacuum fan motor which thereby causes particulate to collect on the filter paper. At the end of the pre-set period the gear reducer and motor lower the roof, a second limit switch shuts off the vacuum fan motor, and the roof isolates the filter paper from further particulate fallout.
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