| 摘要 |
A half-nut block containing a threaded bore and a larger, overlapping, unthreaded bore is engaged with a lead screw. The larger bore overlaps the threaded bore so that effectively a half-nut results. The half-nut comprises a face having an acute angle in relation to the lead screw and this angled face contacts the inside of a bearing block within which the half-nut is mounted. The bearing block is slidably mounted on a C-tube which is mounted around and extends along a predetermined length of the lead screw. Also mounted on the C-tube is an arm for transmitting the linear motion of the bearing block to a remote point such as the plunger of a syringe. The arm is coupled to the bearing block at points selected so that transmission to the arm of any wobbling of the bearing block is reduced. The arm includes a lever which engages a cam formed on the half-nut to force the half nut to disengage from the lead screw when the arm is to be moved to a new location on the lead screw. A spring bias is coupled to the half-nut block opposite the cam for urging the half-nut block back into contact with the lead screw after disengagement. A stop mechanism prevents undesired disengagement of the half-nut block from the lead screw when force is applied other than by the cam block.
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