| 摘要 |
To comply with U.S. Government requirements of a quiet machine tool with a dBA rating less than 90, the noise produced by a hexagonal piece of bar stock rotating inside a stock tube is reduced to well below this level by providing a composite stock tube. An outer cylindrical metal tube houses a plurality of axially aligned tubular elements, the lengths of which are sufficiently short and all physical dimensions and characteristics of which are such as will limit to a frequency range greater than 2,000 Hz. (preferably greater than 16,000 Hz.), the noise vibrations caused by the rotating bar and which vibrations, in the absence of this invention, could be transmitted to the space surrounding the stock tube at a level above 80 dBA. The tubular segments are supported within the outer tube by support means comprising elastic rings which radially separate the tubular segments from the outer tube and preferably axially separate adjacent tubular segments.
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