| 摘要 |
A hammer drill has a transmission housing 280 is formed from two clamshell halves of durable plastics or cast metal material. The transmission housing 280 is mounted on first and second damping springs 284 and 286 at its rearward end. The transmission housing 280 is also mounted on parallel rails (not shown) disposed within the tool housing 222 such that the transmission housing 280 can slide a small distance relative to the tool housing 222. The forward end of the transmission housing 280 has a generally part conical portion 290, which abuts a corresponding part conical portion 292 formed on the tool housing 222. The interface defined by conical portions 290 and 292 defines a stop against which the transmission housing 280 rests against the tool housing 222 in the inoperative condition of the hammer drill 220. When the hammer drill 220 is being used, a gap opens up between the conical surfaces 290 and 292 which helps to damp axial and lateral vibrations that would otherwise be transmitted from the tool bit (not shown) to the user. However, the gap is sufficiently small that the hammer drill 220 and the transmission housing 280 can still be adequately controlled by the user, and the part conical shape of the interface also assists in aligning the transmission housing 280 with the tool housing 222 in order to give a user greater control over the direction of the tool bit. |
