CONTROLLABLE   PITCH   PROPELLER   (WITH   CONSTANT   SPEED UNIDIRECTIONAL ENGINE) :

For unidirectional gas turbine and multidiesel drive of propulsion, this remote control propeller pitch adjustment can alter the ship speed both in ahead & astern direction without changing the prime mover speed or direction of movement.

A signal from bridge or engine control Room, activates the linkage so that the control valve moves to the desired position for supply and drainage of oil as required. As the signal from bridge displaces the linkage a distance A to suit the pitch requirement of the propeller blade, a double piston in the control valve is displaced. Supply line fluid flows through the open port into the shaft bore through a groove around the inside of the fixed oil transfer block. Oil is thus pumped to the desired side of the push-pull rod piston via a check valve and pushes the rod aft. Oil from the other side of the piston drains through another check valve. During drainage through the check valve, a non-return valve is held open by pressure from the supply side of the system to a piston attached to the non - return valve. Since the pressure is the same throughout the systems, and the piston area is greater than the attached non - return valve area, the force on the piston is greater and the valve is held open.

When the desired pitch setting of the blade is attained, the non-return valve in the check vlave closes due to the presure on the supply side dropping. As the push - pull rod moves, so does the feed back ring on the rod, until the feedback linkage lever is displaced a distance 'B'. When the distance 'B' has been achieved by the hunting feed back lever, the linkage control to the double piston in the control valve returns to its original position 'C and any further movement stops.

Longitudinal movement of the push - pull rod is converted into rotary pitch control motion of the blade by the Yoke, whose pins locate into a guide block fitted into a slot in the blade carrier. The blade carriers are mounted inside the hub and the foot of each blade is located on the blade carrier by 2 dowels and fixed by 6 to 8 bolts (sealed and locked). Each blade foot is sealed by rubber '0' ring.

In the event of failure of the control system, there is a local hand pump in the system to change pitch manually. Another failure mode is the "fail to full ahead". The push - pull rod moves against a large spring in the hub. Failure of control fluid pressure allows the return of the push - pull rod to "full ahead" position by the spring pressure.

C.P. PROPELLER BLADE CONNECTION

1  Propeller hub .

2  Hub cap
2a Hub cover

3  Blade connecting bolt

4  Blade foot

  5  Blade sealing ring

  6  Blade carrier

  7  Guide block

  8  Pin (cast on)

9  Yoke

10 Push rod

11 Tailshaft       

12    Protecting cap

13 Tap bolt

ATTAINING THE DESIRED PITCH ANGLE

C.P. PROPELLER BLADE CONNECTION   

Controllable Pitch Propellers

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