1. HYDRAULICS & PNEUMATICS
Actuators
Presented by: Dr. Abootorabi

2. Hydraulic Cylinders
Actuators are the components used in a hydraulic system to provide power to a required work location.
Cylinders are the hydraulic system components that convert fluid pressure and flow into linear mechanical force and movement.

3. Hydraulic Cylinders A basic cylinder consists of: Piston Piston rod
Barrel
The piston forms sealed, variable-volume chambers in the cylinder.
System fluid forced into the chambers, drives the piston and rod assembly.

4. Hydraulic Cylinders Seals prevent leakage between:
Piston and cylinder barrel
Piston rod and head
Barrel and its end pieces
Wiper seal, or scraper, prevents dirt and water from entering the cylinder during rod retraction.

5. Hydraulic Cylinders
Various seals are used in a cylinder

6. Hydraulic Cylinders
Various seals are used in a cylinder

7. Hydraulic Cylinders
Various seals are used in a cylinder

8. Hydraulic Cylinders
Cylinders are typically classified by operating principle:
Single-acting
Double-acting
Single-acting
Double-acting

9. Hydraulic Cylinders
Single-acting cylinder exert force either on extension or retraction:
They require an outside force to complete the second motion (either by a spring or by the weight load).
Double-acting cylinder generate force during both extension and retraction:
Directional control valve alternately directs fluid to opposite sides of the piston
Force output varies between extension and retraction

10. Hydraulic Cylinders Single-acting cylinder
hydraulic ram (or plunger cylinder): piston and rod form one unit

11. Hydraulic Cylinders
Single-acting cylinder
Scissor lifting table:

12. Hydraulic Cylinders
Double-acting cylinder

13. Hydraulic Cylinders
Double-acting cylinder types:

14. Hydraulic Cylinders
Double-acting cylinder types:

15. Hydraulic Cylinders
Effective piston area is reduced on retraction due to the rod cross section.

16. Hydraulic Cylinders
Telescoping cylinders are available for applications requiring long extension distances:
Rod is made up of several tubes of varying size nested inside of the barrel
Each tube extends, producing a rod longer than the cylinder barrel
Typical example is the actuator that raises the box on a dump truck

17. Hydraulic Cylinders Telescoping cylinders:
The maximum force is at the collapsed position
The speed will increase at each stage, but will not allow much force

18. Hydraulic Cylinders
Cylinders often use hydraulic cushions (to brake high stroke speeds):
Provide a controlled approach to the end of the stroke
Reduces the shock of the impact as the piston contacts the cylinder head

19. Hydraulic Cylinders Cylinders with end position cushioning:
Cushioning is not required for speeds of v<6 m/min.
This type of end position cushioning is used for stroke speed between 6 m/min and 20 m/min. At higher speed, additional cushioning or braking devices must be used.

20. Hydraulic Cylinders
A variety of mounting configurations are used to attach the cylinder body and rod end to machinery:
Fixed centerline
Fixed noncenterline
Pivoting centerline
Expected cylinder loading is the major factor in the selection of the mounting style.

21. Hydraulic Cylinders
Head-end (Fixed centerline) flange mount

22. Hydraulic Cylinders
Fixed-noncenterline mount

23. Hydraulic Cylinders
Pivoting-centerline, clevis mount

24. Hydraulic Cylinders
Pivoting-centerline, trunnion mount

25. Hydraulic Cylinders
Types of mounting:

26. Hydraulic Cylinders
The force generated by a cylinder is calculated by multiplying the effective area of the piston by the system pressure.
F=p.A
By consideration of mechanical efficiency:

27. Hydraulic Cylinders
Cylinder characteristics

28. Hydraulic Cylinders Cylinder characteristics dp: cylinder dia.
Ap: cylinder area
dST: piston rod dia.

29. Hydraulic Cylinders Q [m3/s] = A [m2] X  [m/s]
Speed at which the cylinder extends or retracts is determined by:
Flow Rate (Q)
Effective Area (A)
Piston velocity
Effective area
Q [m3/s] = A [m2] X  [m/s]

30. Hydraulic Cylinders
Buckling resistance

31. Hydraulic Cylinders
Selecting a cylinder (Example)

32. Hydraulic Cylinders
Selecting a cylinder (Example)

33. Hydraulic Cylinders Selecting a cylinder (Example)
Buckling resistance diagram:
Reference: Festo Didactic Hydraulic

34. Hydraulic Cylinders
Selecting a cylinder (Example)

35. Hydraulic Cylinders
Selecting a cylinder (Example)

36. Hydraulic Cylinders
Selecting a cylinder (Example)

37. Hydraulic Cylinders
Hydraulic cylinder manufacturers provide detailed specifications and basic factors such as:
Bore
Stroke
Pressure rating
Other details, such as service rating, rod end configurations, and dimensions

38. Hydraulic Cylinders Typical manufacturer’s catalog page
Bailey International Corporation

39. Limited-Rotation Hydraulic Actuators
Limited-rotation devices (swivel drive) are actuators with an output shaft that typically applies torque through approximately 360° of rotation.
Models are available that are limited to less than one revolution, while others may produce several revolutions.

40. Limited-Rotation Hydraulic Actuators
Most common designs of limited-rotation actuators are:
Rack-and-pinion
Vane
Helical piston and rod

41. Limited-Rotation Hydraulic Actuators
Rack-and-pinion limited rotation actuator
Here maximum angle may be larger than 360°.

42. Limited-Rotation Hydraulic Actuators
Vane limited-rotation actuator

43. Limited-Rotation Hydraulic Actuators
Helical piston and rod limited-rotation actuator

44. Limited-Rotation Hydraulic Actuators
Limited-rotation actuators are used to perform a number of functions in a variety of industrial situations:
Indexing devices on machine tools
Clamping of workpieces
Operation of large valves
Limited-rotation actuators are used in this robotic arm:

45. Hydraulic Motors Hydraulic motors are called rotary actuators.
They convert fluid pressure and flow into torque and rotational movement.

46. Hydraulic Motors
System fluid enters the housing and applies pressure to the rotating internal parts.
This, in turn, moves the power output shaft and applies torque to rotate a load.
Primary parts that produce the rotating motion in most hydraulic motors are either:
Gears
Vanes
Pistons

47. Hydraulic Motors
The external gear hydraulic motor is the most common and simplest of the basic motor types:
Unbalanced load on the bearings

48. Hydraulic Motors
The most common internal gear motor has a gerotor design

49. Hydraulic Motors
Basic vane motor (unbalanced)

50. Hydraulic Motors
A basic, balanced vane motor

51. Hydraulic Motors
Axial piston motors are available in two configurations:
Inline
Bent axis

52. Hydraulic Motors
Inline piston motor

53. Hydraulic Motors
Inline piston motor

54. Hydraulic Motors
Bent-axis piston motor

55. Hydraulic Motors
Radial piston motor

56. Hydraulic Motors
Hydraulic motors may be incorporated into circuits using series or parallel connections:
Series circuits: total system pressure is determined by adding the loads placed on each unit
Parallel circuits: each motor receives full system pressure; loads must be matched or equal flow supplied to each motor if constant speed is desired from each unit

57. Hydraulic Motors
Motors in series

58. Hydraulic Motors
Motors in parallel

59. Hydraulic Motors
Motors in parallel with flow control

60. Hydraulic Motors
Hydraulic motor formulas:
Power:

61. The end.