Hydraulic actuators: cylinders

1
Hydraulic actuators cylinders

• Cylinder types

Double acting piston
Single acting work can be done only in one
direction
Work is done in both directions
Plunger
Piston rod on both sides
Piston
Tandem
Fast moving
Telescopic
Telescopic
Fast moving
2
Hydraulic cylinders

• Hydraulic cylinder

Hidraulikus munkahengerek Rögzítopálcás kivitel 1.
Rögzítopálcás hidraulika henger, a hengerfejen
található karimás rögzítéssel
3
Hydraulic cylinders

• Hydraulic cylinder

Hidraulikus munkahengerek Hengeres kivitel 1.
Hengeres építési móddal készült hidraulika henger
4
Hydraulic cylinders

• Properties

The cylinders have to be good quality steel with
close tolerances. There have to be good sealing
both at the piston rod and at the cylinder. With
time dirt may come in and damage the surfaces.
This has to be possibly reduced. In this case,
the leakage will increase all the time.
5
Hydraulic cylinders

• Calculation of cylinders

friction forces
inertial forces
maximum load
slow motion, can be often neglected
Outward
Backward
6
Hydraulic cylinders

• Calculation of cylinders

1. Stick-slip
2. Transition
3. Normal behaviour

Hydraulic cylinders should be possibly operated
in the 3rd region for smooth operation. If the
cylinder is new, the leakage losses are
negligibly small so that ?c ?mech
at higher pressures
7
Hydraulic cylinders

• Checking for buckling

Maximum permissible force
n safety factor 1-3,5 lk buckling length I1
moment of inertia of the piston rod E elasticity
modulus of the rod material
8
Hydraulic cylinders

• Cushioning of cylinders

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
Rotary hydraulic actuators

• Swivel vane rotary actuator

Parallel piston rotary actuator
Limited angle in both directions Maximum angle
always smaller than 360 The same torque in both
directions
Párhuzamdugattyús lengohajtás
Limited angle rotary actuator
Limited angle rotary actuator
Piston rotary actuator
With rack and gear coupling Here maximum angle
may be larger than 360
Mindkét irányban azonosan muködo hengerrel és
fogasléces meghajtással muködtetett tolódugattyús
lengohajtás
Forgódugattyús lengohajtás menettel muködtetett
meghajtócsappal
???
???
10
Big pictures

• End of normal presentation
• Beginning of big pictures

11
Hydraulic cylinders

• Cylinder types plunger

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
Hydraulic cylinders

• Cylinder types piston, single acting,
  pressing-cylinder

Spring
inside
outside
13
Hydraulic cylinders

• Cylinder types piston, single acting, puller

Spring
inside
outside
14
Hydraulic cylinders

• Cylinder types piston, double acting

Velocity is different
15
Hydraulic cylinders

• Cylinder types piston, double acting
• Piston rod on both side

Velocity is the same in both directions
16
Hydraulic cylinders

• Cylinder types piston, double acting
• Piston rod on both side

Velocity is different in the two directions
depending on cross section ratio of the rods
17
Hydraulic cylinders

• Cylinder types double acting piston, tandem

18
Hydraulic cylinders

• Cylinder types single acting, fast moving

19
Hydraulic cylinders

• Cylinder types double acting, fast moving

20
Hydraulic cylinders

• Cylinder types telescopic, single acting

Large working paths or limited space
21
Hydraulic cylinders

• Cylinder types telescopic, double acting

Large working paths or limited space
22
Hydraulic cylinders

• Checking for buckling

Eulers cases
1. Case One end free One end fixed Or trunnion
at end
2. Case Two ends pivoted and guided
3. Case One end guided and pivoted, other end
fixed
4. Case Two ends fixed and guided
Picture
Free buckling length
mounting style
mounting style
mounting style
mounting style
Manner of end fixing
Note
23
Hydraulic cylinders

• Cushioning of cylinders

1. Piston
2. Cushion nose
3. Cylinder cap
4. Stroke volume
5. Cushion orifice
6. Throttle
7. Cushion adjustment screw
8. Mother
9. Non-return valve
10. Gas valve

24
Rotary hydraulic actuators

• Parallel piston rotary actuator

25
Rotary hydraulic actuators

• ???

26
Rotary hydraulic actuators

• Rack-and-pinion piston-type rotary actuator

27
Rotary hydraulic actuators

• Limited angle rotary actuator

28
Rotary hydraulic actuators

• Limited angle rotary actuator

29
Rotary hydraulic actuators

• Helix actuator