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

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Presentation on theme: "HYDRAULICS & PNEUMATICS Presented by: Dr. Abootorabi Actuators 1."— Presentation transcript:

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

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. 2

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. 3

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. 4

5 Hydraulic Cylinders Various seals are used in a cylinder 5

6 Hydraulic Cylinders Various seals are used in a cylinder 6

7 Hydraulic Cylinders 7 Various seals are used in a cylinder

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

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 9

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

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

12 Hydraulic Cylinders Double-acting cylinder 12

13 Hydraulic Cylinders Double-acting cylinder types: 13

14 Hydraulic Cylinders Double-acting cylinder types: 14

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

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 16

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 17

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 18

19 Hydraulic Cylinders 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. Cylinders with end position cushioning: 19

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. 20

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

22 Hydraulic Cylinders Fixed-noncenterline mount 22

23 Hydraulic Cylinders Pivoting-centerline, clevis mount 23

24 Hydraulic Cylinders Pivoting-centerline, trunnion mount 24

25 Hydraulic Cylinders Types of mounting: 25

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

27 Hydraulic Cylinders Cylinder characteristics 27

28 Hydraulic Cylinders Cylinder characteristics 28 d p : cylinder dia. A p : cylinder area d ST : piston rod dia.

29 Hydraulic Cylinders Speed at which the cylinder extends or retracts is determined by: Flow Rate (Q) Effective Area (A) 29 Q [m 3 /s] = A [m 2 ] X  [m/s] Piston velocity Effective area

30 Hydraulic Cylinders Buckling resistance 30

31 Hydraulic Cylinders Selecting a cylinder (Example) 31

32 Hydraulic Cylinders Selecting a cylinder (Example) 32

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

34 Hydraulic Cylinders Selecting a cylinder (Example) 34

35 Hydraulic Cylinders Selecting a cylinder (Example) 35

36 Hydraulic Cylinders Selecting a cylinder (Example) 36

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 37

38 Hydraulic Cylinders Typical manufacturer’s catalog page 38 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. 39

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

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

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

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

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 44  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. 45

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. 46 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 47

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

49 Hydraulic Motors Basic vane motor (unbalanced) 49

50 Hydraulic Motors A basic, balanced vane motor 50

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

52 Hydraulic Motors Inline piston motor 52

53 Hydraulic Motors Inline piston motor 53

54 Hydraulic Motors Bent-axis piston motor 54

55 Hydraulic Motors Radial piston motor 55

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 56

57 Hydraulic Motors Motors in series 57

58 Hydraulic Motors Motors in parallel 58

59 Hydraulic Motors Motors in parallel with flow control 59

60 Hydraulic Motors Hydraulic motor formulas: 60 Power:

61 The end. 61


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