| 摘要 |
A rotary cutting device, primarily for grass mowers, includes a number of blade elements for cutting or air propelling purposes. To reduce noise, the rotating blades are provided with substantially flat leading and trailing edge portions formed along a major part of the leading edge and trailing edge, respectively, of the blade, cross sections of the leading edge flat portion being parallel to corresponding cross sections of the trailing edge flat portion and being connected thereto by an intermediate portion merging by smooth roundings into the respective flat portions, the cross sections being in respective cutting planes parallel to the axis of rotation and perpendicular to the longitudinal direction of the blade, such that the airflow past the blade follows the blade smoothly and shedded vortices are limited substantially to a relatively small cross-sectional area immediately following the trailing edge of the blade.
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