| 摘要 |
The beaver control screen has a cone-shaped screen having a base, an apex and a horizontal axis. A first set of spaced-apart rods extends from the base to the apex and are disposed in a first conical layer. A second set of rods is disposed in a second conical layer inside the first conical layer and extends toward the apex over a distance of about one-half the length of the first conical layer. The first and second conical layers are set at different angles with the horizontal axis such that a distance between a rod in the first layer and an adjacent rod in the second layer is a same distance along the adjacent rod. At the apex of the screen, the rods in the first conical layer are alternately affixed to the outside edge and to the inside edge of an annular plate.
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