| 摘要 |
A choke system includes a hydraulic circuit which provides choke valve positioning that can be varied by the use of incremental steps. The incremental movement action in either the opening or closing direction is accomplished through the use of one of two hydraulic slave cylinders 31,42 which can either add or subtract a fixed volume of hydraulic fluid from the choke actuator 20. A series of check valves 58,60,62,66 provides direction for flow in the hydraulic lines, locking of the choke actuator, and re-filling of the slave cylinders during operation. The system eliminates excessive lines or solenoid valves and avoids the need for mechanical locking mechanisms. A "fast close" system may be provided which, instead of running through a series of steps to close the valve, provides valve control in a fast close line to move the choke actuator to the full closed position from anywhere in the travel over a shorter period of time than through normal stepping operation. |
