| 摘要 |
A coupling unit mountable in the exhaust train of an engine immediately downstream of the exhaust manifold provides a significant reduction in engine noise levels. The coupling unit does not include a rigid liner but comprises a flexible tubular coupling consisting essentially of inlet and outlet collar portions and an intermediate dual wrapped flexible central conduit portion. The flexible dual wrapped central portion consists of a longitudinally undulating, pressure-carrying conduit member and a concentric, vibration-dampening helicoidal covering. The flexible coupling has a length to inside diameter ratio in the range of 1:1 to 8:1, and permits limited multi-axis movement of one of the collar portions relative to the other. The flexible metal coupling is effective in reducing noise levels at engine speeds in the range of from idle speed up to about 5,000 rpm.
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