| 摘要 |
A double-walled exhaust pipe is used with an internal combustion engine and includes a first elongate outer tube (17) and a second elongate inner tube (15) positioned concentrically within the outer tube (17) and affixed at the ends. A chamber (25) is created between the inner and outer tubes which extends substantially their entire length and is sealed against the atmosphe re by welding at the ends of the tubes. A one-way valve (20) and (22) is affixe d to the outer tube (17) and in fluid communication with the chamber (25) so that a vacuum having a negative pressure at least 20 inches of mercury can b e drawn. The outer tube (17) preferably has a greater wall thickness than the inner tube (15).
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