| 摘要 |
Each holder (25) accepts one pipette needle (26) and is located at the lower end of a vertical tube (15), which is driven up or down by a drive mechanism. The drive mechanisms are independent of each other. Preferred Features: Locking is provided for all drive tubes (15), to hold them in a predetermined lower end position and prevent upward movement. The locking mechanism has a locking slide, moving between locking and release positions. The drive tubes are either all held down, or free to rise or descend. The locking slide has an opening through which the drive tubes extend, spaced regularly. A stop on the tubes, is slightly wider than an enlarged part of the opening but smaller than the remaining part of the opening. Each drive mechanism has a motor coupled to a drive wheel. Drive wheels each rest against a drive tube, and can move them vertically. A freely-rotating guide wheel lies opposite the drive wheels. A switch or optical beam detects the lower- and/or upper end position of each drive tube. A supporting body carries the drive tube and mechanism. It is fastened with resilient play to a further support, for fastening to the holder of an automatic mechanism.
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