Simran instruction manual Description of RPU80/RPU160/RPU300

Description of RPU80/RPU160/RPU300

3.2Principle of operation (ref. figure 3-1 and figure 9-1)

RPU80/160/300 is reversible: that is the motor changes direction of rotation and the gear pump delivers oil to that side of the rudder cylinder dictated by the signal from the autopilot. The pump runs until the signal from the autopilot ceases. The pump unit has non-return valves on the outlets A and B. When running, the pressurized (or delivery) side will hold both non- return valves open, using direct oil pressure upon the valve on the delivery side. This oil pressure is also used to push a slide to open the valve on the suction side.

When the motor stops, the spring (8) in the non-return valve on the suction side returns the slide to the neutral position. Both non-return valves are now closed and the rudder cylinder locked. Both sides of the gear pump have suction valves to outlet C.

If the rudder cylinder is loaded in the same direction as the rudder command, the slide (10) precisely positions the non- return valve (suction side) such that the creation of a vacuum in the rudder cylinder is prevented. (A vacuum in the rudder cylinder would result in air being drawn past the seals round the cylinder piston rod, since these stops the oil pressure only). At that side of the valve block where the motor is connected, there is mounted sealing ring (15) and support ring (16) in the valve block. The support ring causes that the tank connection C can hold a maximum pressure of 7 bar (Ref. Hynautic steering systems).

Note !

1.A previous model of RPU80 Reversible Pump was simplified according to the principle diagram. (Ref. figure 3-1 and figure 9-2). The principle of operation was similar to that of RPU160. The (suction) valves, however, operated as combined suction and non-return (check) valves controlled by internal pressure and direction of oil flow. The resulting effect was a smoother non-return (check valve) function as compared to the one with separate non-return valves.

2.It should be observed however, that the previous model of RPU80 does not have the extra protection against internal leakage (bypass) as the other models with separate check valves.

20220422N 15

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