tailieunhanh - Mechanical Devices Sourcebook 3rd ed mcgraw hil 2001 Episode 2 Part 3

Tham khảo tài liệu 'mechanical devices sourcebook 3rd ed mcgraw hil 2001 episode 2 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | __CHAPTER 12 FASTENING LATCHING CLAMPING AND CHUCKING DEVICES REMOTELY CONTROLLED LATCH This simple mechanism engages and disengages parallel plates carrying couplings and connectors. Fig. 1 The latch operation sequence is shown for locking in steps a through c and for unlocking in steps d through f . A new latch mates two parallel plates in one continuous motion see Fig. 1 . On the Space Shuttle the latch connects and disconnects plates carrying 20 fluid couplings and electrical connectors. The coupling connector receptacles are one plate and mating plugs are on the other plate . Designed to lock items in place for handling storage or processing under remote control the mechanism also has a fail-safe feature It does not allow the plates to separate completely unless both are supported. Thus plates cannot fall apart and injure people or damage equipment. The mechanism employs four cam gear assemblies one at each corner of the lower plate. The gears on each side of the plate face inward to balance the loading and help align the plates. Worm gears on the cam-gear assemblies are connected to a common drive motor. Figure 1 illustrates the sequence of movements as a pair of plates is latched and unlatched. Initially the hook is extended and tilted out. The two plates are brought together and when they are in. cm apart the drive motor is started a . The worm gear rotates the hook until it closes on a pin on the oppo 406 site plate b . Further rotation of the worm gear shortens the hook extension and raises the lower plate c . At that point the couplings and connectors on the two plates are fully engaged and locked. To disconnect the plates the worm gear is turned in the opposite direction. This motion lowers the bottom plate and pulls the couplings apart d . However if the bottom plate is unsupported the latch safety feature operates. The hook cannot clear the pin if the lower plate hangs freely e . If the bottom plate is sup ported the hook .