| 摘要 |
The drill stand has a vertical column and a clamp moveably mounted on the column. A carriage adapted to support a drill is moveably mounted on the column for movement with and with respect to the clamp. A link is pivoted on the clamp and has two pivot locations. A lever arm is pivotally connected to the carriage and has two roller pivots selectively engageable with either of the pivot locations to change the force multiplication and travel distance as the arm is pivoted about the selected pivot location. Each pivot location is at the end of a track having one portion on a curve centered on the link connection to the clamp and another portion on an arc centered on the pivot location associated with the other of the tracks. Each roller engages one of the tracks. The pivot locations are closer together than are the rollers so only one roller can be in a pivot location at one time. The link can be moved about its pivot connection to the clamp to select which of the rollers will be in its associated pivot location. A detent arrangement, including a protrusion on the link and a leaf spring engageable with the protrusion when said arm is raised, acts to retain a selected roller in its pivot location.
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