| 摘要 |
<p>A pneumatic extraction head for underwater debris, in particular sand and gravel, comprises a housing (16), a base plate (21) located at the bottom of the housing and forming an inlet opening for the debris, and a flange plate (22) located at the top of the housing for connection with an extraction pipe and a compressed air duct. A joint extending inside the housing between the base plate and the flange plate and surrounding the inlet opening for the debris serves to form an annular space for compressed air between the inner wall of the housing and the outer wall of the joint. Several mutually-spaced outlet openings for the compressed air in the compressed air space are provided in the base plate around the debris inlet opening. These outlet openings are provided with spring-loaded nonreturn valves.</p> |
