| 摘要 |
<p>An automatic shift drill (10) for rotationally driving a bit into a laminated workpiece at one of two speeds according to the depth of the bit in the workpiece. A cam block element (182) has flag sections and gap sections corresponding to the various layers of the workpiece. The cam block element (182) is mounted on a spindle (80) of the drill (10) to move in translation with the bit. A stationary sensor head (160) has a vent (170) which is closed when it is adjacent to one of the flag sections and open when it is adjacent to one of the gap sections. A piston (72) within the drill (10) which is responsive to pneumatic pressurization shifts the rotational speed of the bit from one speed to the other speed. The vent (170) vents the piston when it is adjacent to a gap section to drive the bit at the appropriate speed through the corresponding layer and seals the piston when it is adjacent to a flag section to drive the bit at the other speed appropriate for the layer corresponding to the flag section.</p> |
