Self-sliding solution for the barrel of a biological microscope
The first step: use both hands to hold two coarse adjustable handwheel, relative force tighten. To see if the problem can be solved, if the problem can not be solved, it is necessary to use a special double-column plate hand to a coarse adjustment of the handwheel screwed down, add a piece of friction, the handwheel tightened, if the rotation is very difficult, then add the friction film is too thick, can be replaced with a thin one. To the handwheel rotation is not difficult, easy to move up and down the lens barrel, and does not slide on its own shall prevail. Friction film can be used waste photographic film and less than 1 mm thick soft plastic sheet with a perforator punch.
The second step: check the rough adjustment of the handwheel shaft gears and mirror tube on the rack meshing status. The up and down movement of the mirror barrel is driven by the gear to complete the rack. Gear and rack of the best mesh state in theory is the rack of the index line and gear index circle tangent. In this state, the gear rotates easily, and the wear on the rack is minimised.
Nowadays, there is a wrong practice of adding shims behind the rack so that the rack presses tightly against the gear to stop the mirror tube from sliding down. At this point, the index line of the rack intersects the index circle of the gear, and the tooth tips of the gear and rack are pressed against each other's tooth roots. As the gears rotate, severe grinding occurs between them. The rack is made of copper and the gear is made of steel. Therefore, the grinding between each other will wear out the teeth on the rack, and many copper chips will be produced on the gear and rack. *After that, the rack will be severely worn and unusable. Therefore, you should never raise the rack to prevent the mirror tube from sliding down. The only way to solve the problem of the barrel slipping on its own is to increase the friction between the coarse adjustment handwheel and the eccentric sleeve. There is one exception to this rule, and that is when the indexing line of the rack is out of phase with the indexing circle of the gear. In this case, when the coarse adjustment handwheel is turned, the same phenomenon of idling and slipping will occur, affecting the up and down movement of the mirror tube. If this by adjusting the rough adjustment handwheel eccentric bushing, can not adjust the gear and rack meshing distance. Can only be in the rack and pinion after padding the appropriate sheet to solve the problem. Add shims to adjust the gear and rack meshing distance of the standard is: turn the coarse adjustment handwheel is not difficult, but also not idle.
After adjusting the distance, add some neutral grease between the gear and rack. Let the cylinder move up and down a few times that can be. Finally, we must also put the eccentric shaft sleeve on the two compression screws tighten. Otherwise, when you turn the coarse adjustment handwheel, the eccentric shaft sleeve may follow the rotation, and the rack is jammed, so that the mirror can not move up and down. If you turn the handwheel with too much force, the rack and the eccentric sleeve may be damaged. If the eccentric bushing still turns after tightening the compression screw, it is because the hole of the compression screw is not tightened. This is due to the fact that the threads of the screw holes of the compression screws have not been correctly changed. Because manufacturers change the threads by machine, there are often one or two threads are not changed in place. At this time, even if the compression screw is not screwed in place, the eccentric bushing will not be pressed. Found that this kind of failure, as long as the M3 tapping screw hole threads can be tapped through to solve the problem. I used this method to completely solve the problem of 30 sets of biomicroscope eccentric shaft sleeve with the rotation of my school.
