To shut off the drive of the docking mechanism during coupling of the frames, sensors are used which are located on the joint. The sensors, which have a compressed forward motion plunger, have sliding contacts similar to those described above, or they have microswitches. Similar sensors are also used in the head of the docking mechanism rod, on the joint of the ring with the guides in peripheral type docking devices, etc. The union of terminal contacts in the block with closed casings and the implementation of sensors in the form of autonomous closed units helps protect them from contamination in work in open space. Experiments in vacuum chambers show that in closed hermetic units, due to the outgassing of materials, primarily plastic, a residual pressure of several pascal is maintained; in these conditions the coefficient of friction increases insignificantly. 3.5.3. Ball-Screw Converters These converters (Table 3.2) are in widespread use in docking mechanisms because of the following basic properties [19]: 1) the ability to convert forward motion into rotary motion and back; 2) high efficiency for both types of conversions; 3) high work reliability; 4) good configuration in mechanisms; 5) very effective (small mass for large transmitted loads and transmission ratio). These converters use nuts with end attachment by a baffle. The nuts are technologically efficient in manufacturing and monitoring (Figure 3.16). This technological efficiency, in the final analysis, insures the reliability of the ballscrew converter. The following requirements are made on ball-screw converters: 1) minimal moment of inertia of the nut; 2) maximum efficiency; 3) maintenance of working capacity for significant deformations of the screw (in “rod and cone” type docking devices). The thread of the nut with a toothed crown is installed on one four-track ball bearing with a slit ring. This support is compact, and has the minimum number of moving parts, which lowers the inertia of the unit. To reduce the inertia of the nuts the following basic measures are taken: 1) the nuts and other rotating parts
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