| 摘要 |
A motor driven valve comprises a clutch arrangement which prevents reverse rotation of the motor and so prevents damage to the motor during valve bounce. Preferably, a motor driven shaft 3 has mounted on it a toothed driven sleeve 5 and driving sleeve 7. Sleeves 5 and 7 have adjacent portions of the same external diameters which are surrounded by a close fitting coil spring 17. In use rotation of shaft 3 is transmitted to sleeve 7 by a connection, preferably comprising a slotted collar 9 of sleeve 7 and drive pin, which causes the spring 17 to wrap tightly onto the adjacent portions of sleeves 5, 7. Reverse motion of sleeve 5 (e.g. due to valve bounce) causes unwinding of spring 17 and decoupling of sleeves 5, 7. Alternatively a ratchet may be provided between the drive shaft and driven sleeve.
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