| 摘要 |
The invention relates to a pressure-driven apparatus for the sequential control of a multiphase operation, e.g. of a cementing head. A transmission arm (3) comprising a pawl (4) is supported on a cam shaft (9) connected to a pawl cylinder (1) having a built-in return force, directional control valves (8, 8′, 8″, and 8n) with a spring return member and roller (7), operated by the cam plates (6, 6′, 6″, and 6&pgr;) of the cam shaft (9), that are staggered relative to each other in a predetermined angle to a pawl disk (5) supported in bearings (10) and (10′). The pawl cylinder (1) will rotate cam shaft (9) to a predetermined angular position in the same rotational direction each time the system is supplied with pressure, and operate the directional valves (8, 8′, 8″, and 8&pgr;) with rollers (7), whereby the directional valves will apply pressure to actuators present so that cementing valves or other types of valves will open for a predetermined period of time until a timer control shuts off the pressure supply, the pressure is discharged, and the pawl cylinder returns to the starting position thereof. When pressure is supplied to pawl cylinder (1) after all operating phases have been completed, cam shaft (9) will rotate further on to return to the starting position thereof, and all directional control valves (8, 8′, 8″, and 8n) is closed.
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