| 摘要 |
A switching method includes starting up a percussion device in acting on a control device arranged to vary the striking stroke of the striking piston between a short striking stroke and a long striking stroke. The percussion device is forced to operate on a short striking stroke for a predetermined period of time from the starting up of the device, and in acting on the control device so as to allow the percussion device to operate on a long striking stroke, after the expiry of the predetermined period of time. |
