| 摘要 |
<p>A support frame is provided for support in a body of water with the level of the water disposed, generally, at a predetermined level on the frame and a mount is provided and supports a generally horizontal sample support screen therefrom. The mount includes portions thereof horizontally spaced apart about the support screen and inward of corresponding peripherally spaced portions of the support frame. A plurality of elongated, coiled expansion springs extend and are connected between the mount portions and the aforementioned corresponding peripherally spaced portions of the support frame in at least a partially tensioned state and support the mount and screen from the frame. Lift structure is connected between the frame and the mount operative to intermittently direct and release upward thrusts on the mount and the expansion springs support the screen, when the latter is in a static condition, at a level at least slightly below the aforementioned predetermined level. A sample hopper is supported from the frame above the screen and includes a lower variably openable gravity outlet spaced above the aforementioned predetermined level in substantially vertical alignment with the center of the screen.</p> |
