Presentation on theme: "HYDRAULICS & PNEUMATICS"— Presentation transcript:
1 HYDRAULICS & PNEUMATICS ActuatorsPresented by: Dr. Abootorabi
2 Hydraulic CylindersActuators 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 BarrelThe 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 barrelPiston rod and headBarrel and its end piecesWiper seal, or scraper, prevents dirt and water from entering the cylinder during rod retraction.
5 Hydraulic CylindersVarious seals are used in a cylinder
6 Hydraulic CylindersVarious seals are used in a cylinder
7 Hydraulic CylindersVarious seals are used in a cylinder
8 Hydraulic CylindersCylinders are typically classified by operating principle:Single-actingDouble-actingSingle-actingDouble-acting
9 Hydraulic CylindersSingle-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 pistonForce output varies between extension and retraction
10 Hydraulic Cylinders Single-acting cylinder hydraulic ram (or plunger cylinder): piston and rod form one unit
15 Hydraulic CylindersEffective piston area is reduced on retraction due to the rod cross section.
16 Hydraulic CylindersTelescoping cylinders are available for applications requiring long extension distances:Rod is made up of several tubes of varying size nested inside of the barrelEach tube extends, producing a rod longer than the cylinder barrelTypical example is the actuator that raises the box on a dump truck
17 Hydraulic Cylinders Telescoping cylinders: The maximum force is at the collapsed positionThe speed will increase at each stage, but will not allow much force
18 Hydraulic CylindersCylinders often use hydraulic cushions (to brake high stroke speeds):Provide a controlled approach to the end of the strokeReduces 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 CylindersA variety of mounting configurations are used to attach the cylinder body and rod end to machinery:Fixed centerlineFixed noncenterlinePivoting centerlineExpected cylinder loading is the major factor in the selection of the mounting style.
21 Hydraulic CylindersHead-end (Fixed centerline) flange mount
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 velocityEffective areaQ [m3/s] = A [m2] X [m/s]
34 Hydraulic CylindersSelecting a cylinder (Example)
35 Hydraulic CylindersSelecting a cylinder (Example)
36 Hydraulic CylindersSelecting a cylinder (Example)
37 Hydraulic CylindersHydraulic cylinder manufacturers provide detailed specifications and basic factors such as:BoreStrokePressure ratingOther 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-pinionVaneHelical piston and rod
41 Limited-Rotation Hydraulic Actuators Rack-and-pinion limited rotation actuatorHere maximum angle may be larger than 360°.
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 toolsClamping of workpiecesOperation of large valvesLimited-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 MotorsSystem 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:GearsVanesPistons
47 Hydraulic MotorsThe external gear hydraulic motor is the most common and simplest of the basic motor types:Unbalanced load on the bearings
48 Hydraulic MotorsThe most common internal gear motor has a gerotor design
56 Hydraulic MotorsHydraulic 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 unitParallel 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