| 摘要 |
<p>Apparatus is provided for protecting crops from frost damage in the form of a vertical tower fixed to the earth against gyration, a rotor on top with two airfoil blades extending upward at a conical angle and drive means drivingly connected to the rotor through a vertical shaft, said tower projecting substantially above the level of the trees to be protected and sufficient to pick up air in the inversion layer and deliver it to the ground in a generally cylindrical mass to spread out radially without substantial disturbance of the soil.</p> |
