Hydraulics

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It is useful to know about the hydraulics cylinders and actuators

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Hydraulics

  1. 1. Hydraulic actuators: cylinders <ul><li>Cylinder types: </li></ul>Single acting: work can be done only in one direction Piston Double acting piston: Piston rod on both side s Plunger Work is done in both directions Telescopic Telescopic Fast moving Tandem Fast movi n g
  2. 2. Hydraulic cylinders <ul><li>Hydraulic cylinder </li></ul>Hidraulikus munkahengerek Rögzítőpálcás kivitel 1. Rögzítőpálcás hidraulika henger, a hengerfejen található karimás rögzítéssel
  3. 3. Hydraulic cylinders <ul><li>Hydraulic cylinder </li></ul>Hidraulikus munkahengerek Hengeres kivitel 1. Hengeres építési móddal készült hidraulika henger
  4. 4. Hydraulic cylinders <ul><li>Properties: </li></ul>The cylinders have to be good quality steel with close tolerances. The re have to be good sealing both at the piston rod and at the cylinder. With time dirt may come in and damage the surfaces . T his has to be possibly reduced. In this case, the leakage will increase all the time.
  5. 5. Hydraulic cylinders <ul><li>Calculation of cylinders </li></ul>friction forces inertial forces maximum load slow motion, can be oft en neglected Backward: Outward: Q A 2 A 1 p 1 p 2 v B v 0
  6. 6. Hydraulic cylinders <ul><li>Calculation of cylinders </li></ul>Hydraulic cylinders should be possibly operated in the 3 rd region for smooth operation. If the cylinder is new, the leakage losses are negligibly small so that : η c = η mech <ul><li>Stick-slip </li></ul><ul><li>Transition </li></ul><ul><li>Normal behaviour </li></ul>at higher pressures F f 1 v 2 3 η c Δ p outwards inwards
  7. 7. Hydraulic cylinders <ul><li>Checking for buckling </li></ul>n : safety factor: 1-3,5 l k : buckling length I 1 : moment of inertia of the piston rod E : elasticity modulus of the rod material Maximum permissible force:
  8. 8. Hydraulic cylinders <ul><li>Cushioning of cylinders: </li></ul>A hard impact of the piston at the end surfaces has to be inhibited – kinetic energy has to be absorbed. This is done by increasing the hydraulic resistance at the end of the stroke.
  9. 9. Rotary hydraulic actuators <ul><li>Swivel vane rotary actuator: </li></ul>Limited angle in both directions Maximum angle always smaller than 360° The same torque in both directions Piston rotary actuator: With rack and gear coupling Here maximum angle may be larger than 360° Mindkét irányban azonosan működő hengerrel és fogasléces meghajtással működtetett tolódugattyús lengőhajtás Párhuzamdugattyús lengőhajtás Forgódugattyús lengőhajtás menettel működtetett meghajtócsappal Limited angle rotary actuator Limited angle rotary actuator Parallel piston rotary actuator ??? ???
  10. 10. Big pictures <ul><li>End of normal presentation </li></ul><ul><li>Beginning of big pictures </li></ul>
  11. 11. Hydraulic cylinders <ul><li>Cylinder types: plunger </li></ul>smaller force, better efficiency, axial support is necessary but cylinder does not have to be so good quality Without inner buffer With inner buffer (pilot piston)
  12. 12. Hydraulic cylinders <ul><li>Cylinder types: piston, single acting, pressing-cylinder </li></ul>Spring inside outside
  13. 13. Hydraulic cylinders <ul><li>Cylinder types: piston, single acting, puller </li></ul>Spring inside outside
  14. 14. Hydraulic cylinders <ul><li>Cylinder types: piston, double acting </li></ul>Velocity is different
  15. 15. Hydraulic cylinders <ul><li>Cylinder types: piston, double acting </li></ul><ul><li>Piston rod on both side </li></ul>Velocity is the same in both directions
  16. 16. Hydraulic cylinders <ul><li>Cylinder types: piston, double acting </li></ul><ul><li>Piston rod on both side </li></ul>Velocity is different in the two directions depending on cross section ratio of the rods
  17. 17. Hydraulic cylinders <ul><li>Cylinder types: double acting piston, tandem </li></ul>
  18. 18. Hydraulic cylinders <ul><li>Cylinder types: single acting, fast moving </li></ul>
  19. 19. Hydraulic cylinders <ul><li>Cylinder types: double acting, fast moving </li></ul>
  20. 20. Hydraulic cylinders <ul><li>Cylinder types: telescopic, single acting </li></ul>Large working paths or limited space
  21. 21. Hydraulic cylinders <ul><li>Cylinder types: telescopic, double acting </li></ul>Large working paths or limited space
  22. 22. Hydraulic cylinders <ul><li>Checking for buckling: </li></ul>Euler’s cases Picture Free buckling length Manner of end fixing Note 1. Case One end free One end fixed Or trunnion at end mounting style mounting style mounting style 2. Case Two ends pivoted and guided 3. Case One end guided and pivoted, other end fixed 4. Case Two ends fixed and guided mounting style
  23. 23. Hydraulic cylinders <ul><li>Cushioning of cylinders: </li></ul><ul><li>Piston </li></ul><ul><li>Cushion nose </li></ul><ul><li>Cylinder cap </li></ul><ul><li>Stroke volume </li></ul><ul><li>Cushion orifice </li></ul><ul><li>Throttle </li></ul><ul><li>Cushion adjustment screw </li></ul><ul><li>Mother </li></ul><ul><li>Non-return valve </li></ul><ul><li>Gas valve </li></ul>
  24. 24. Rotary hydraulic actuators <ul><li>Parallel piston rotary actuator </li></ul>
  25. 25. Rotary hydraulic actuators <ul><li>??? </li></ul>
  26. 26. Rotary hydraulic actuators <ul><li>Rack-and-pinion piston-type rotary actuator: </li></ul>
  27. 27. Rotary hydraulic actuators <ul><li>Limited angle rotary actuator: </li></ul>
  28. 28. Rotary hydraulic actuators <ul><li>Limited angle rotary actuator: </li></ul>
  29. 29. Rotary hydraulic actuators <ul><li>Helix actuator: </li></ul>

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