| 摘要 |
<p>A device for ball games providing an adjustable rebound force, comprising a frame structure and a sheet. The sheet is directly attached to the frame structure at least partly along an outer rim of the sheet. The device further comprises a tensioning means for providing the sheet with a tension. The tensioning means can be an expandable element operated hydraulically or pneumatically. The rebound force can be adjusted in an easy and fast way by changing the pressure in the expandable element.</p> |
