Lesson 18

1. Lesson18 • Steeringgear • (舵机、操舵装置)

2. The steering gear is one of the most important services in the ship and its main function is to control the ship’s course.

3. There are four main types of steering gears employed for power operation of the rudder(舵叶),

4. (i) the steam steering gear, • (ii) the hydraulic steering gear, • (iii) the electric steering gear and • (iv) the electro-hydraulic steering gear.

5. The total system may be considered made up of three parts: control equipment, a power unit and a transmission to the rudder stock(舵杆).

6. Rudder stock Power unit Tiller Control equipment Transmission unit Rudder

7. The first part conveys(传递) a signal or desired rudder angle from the bridge (wheel house).

8. The second one provides the force, when required, to move the rudder to that angle.

9. The third is the means by which the movement of the rudder is accomplished.

10. According to the way the steering gear is operated, the steering gear may be divided into three kinds: hand-steering, followup (随动) steering and automatic steering.

11. The electro-hydraulic gear is now the most widely applied.

12. A two ram(撞杆) hydraulic gear consists of a hydraulic ram situated on the portside of the tiller(舵柄) and another ram on the starboard side,

13. linked at their outer ends to the tiller arm by a crosshead and swivel block(转动滑块),

14. Crosshead & swivel block Control rod Tiller arm Ram Rudder stock Hunting gear

15. Crosshead & swivel block

16. the other ends of the rams working inside their own hydraulic cylinders and pipes connect these cylinders to a hydraulic pump.

17. The tiller is firmly keyed to the rudder stock.

18. The pump is of special construction and may be axial or radial design.

19. The pump runs continuously in the same direction driven by an electric motor,

20. and the position of a movable plate or a floating ring inside the pump controls the suction and discharge of the oil.

21. When the plate or ring is in mid position, no oil is drawn;

22. when the plate or ring is moved in one direction from mid position, oil is drawn from one cylinder and discharged into the other;

23. when the plate or ring is moved in the opposite direction, the suction and discharge of the oil is reversed in direction.

24. The plate or ring is actuated by a control rod which is attached at its outer end to the hunting gear(随动机构).

25. A four-ram hydraulic steering gear may be fitted in large ships for greater steering power, instead of the two-ram type.

27. It is simply a double two-ram unit, so that the force of two diagonally opposite rams can act on the tiller to produce double the turning effect.

28. The pump control is moved by the telemotor(液压传动操舵装置)through a floating lever.

29. The other end of this lever is connected through a safety spring link to the rudder stock or tiller.

30. The telemotor is the receiver of the hydraulic remote control system from wheel on the bridge.

31. The linkage through the floating lever of telemoter, pump and rudder stock forms the hunting gear.

32. The pump is only required to deliver oil when the steering wheel is moved.

33. The hunting gear returns the pump operating rod to mid position as soon as the helmsman(舵手)stops turning the wheel.

34. When the rudder has moved through the angle corresponding to the wheel position, it will remain there until the wheel and telemotor are moved.

35. If a heavy sea strikes the rudder, the shock is transmitted through the tiller to the rams, this cause a sudden increase in oil pressure in one of the cylinders and the system.

36. If the pressure in the system rises to about 10 per cent above normal, double spring-loaded relief valves allow the tiller to give way slightly by by-passing a little of the oil into the other cylinder.

37. The resultant displacement of the rudder, tiller and ram crosshead moves the pump control rod through the hunting gear and the tiller is automatically brought back to its proper position.

38. The control equipment of steering gears • Telemotor controlThe telemotor has become, on many vessels, the standby steering mechanism, used only when the automatic steering fail.

39. It comprises atransmitter(发送器), a receiver, pipes and a charging unit(充电装置).

40. The transmitter, which is built into the steering wheel console (舵轮控制台), is located on the bridge and the receiver is mounted on the steering gear.

41. Two ramsin the transmitter move in opposite directions as the steering wheel is turned.

42. The fluid in the cylinders of the transmitter is therefore pumped down one pipe line and drawn in from the other.

43. The pumped fluid passes through piping to the receiver and forces the telemotor cylinder unit to move.

44. Thecylinderunit has a control spindle(轴)connected to it by a pin.

45. This control spindle operates the slipper ring or swash plate(倾斜盘) of the variable delivery pump, which controls the suction and discharge of the oil.

46. Electrical control The electrical remote control system is commonly used in modern installations since

47. since it uses a small control unit as transmitter on the bridge and is simple and reliable in operation.

48. The control box assembly is mounted on the steering gear.

49. Movement of the bridge transmitter results in electrical imbalance and current flow to the motor in the control box.

50. The motor drives,through a flexible coupling(柔性联轴节), a screw shaft, causing it to turn.