| 摘要 |
<p>In a sound generator of the type having a motor powered piston (7 - 9) limiting a chamber (18) connected to a resonance tube (16) and which is adapted to generate sound waves for cleaning heat exchange surfaces, the said piston (7 - 9) is according to the invention provided with two axially spaced piston membranes (8, 9) and a device (19) for erecting a vacuum between the two membranes (8, 9) and thus ensuring only tensile stresses in said membranes (8, 9) thereby increasing their life time. <IMAGE></p> |
