| 摘要 |
A boring apparatus has a rotary member rotated by a motor, a transmission shaft transmitting its rotation to an electric drill by means of a rotation transmission mechanism for reciprocally moving the electric drill on the frame of the apparatus. The transmission shaft is selectively connected directly to the rotary member and connected operatively thereto through a coupling which is rotated reversely to the rotary member through a reduction mechanism and is designed to be disengaged from the transmission shaft when the shaft is directly connected to the rotary member and to be engaged with the shaft when the shaft is not directly connected to the roatary member. The apparatus has a selecting member which directly connects the shaft to the rotary member and disengages the coupling from the sahft. The apparatus is also provided with a switching mechanism automatically operating the selecting member to directly connect the shaft to the rotary member when the electric drill is lowered in a predetermined position. |
