Hydraulics

Hydraulic actuators: cylinders ,[object Object],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

Hydraulic cylinders ,[object Object],Hidraulikus munkahengerek Rögzítőpálcás kivitel 1. Rögzítőpálcás hidraulika henger, a hengerfejen található karimás rögzítéssel

Hydraulic cylinders ,[object Object],Hidraulikus munkahengerek Hengeres kivitel 1. Hengeres építési móddal készült hidraulika henger

Hydraulic cylinders ,[object Object],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.

Hydraulic cylinders ,[object Object],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

Hydraulic cylinders ,[object Object],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 ,[object Object],[object Object],[object Object],at higher pressures F f 1 v 2 3 η c Δ p outwards inwards

Hydraulic cylinders ,[object Object],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:

Hydraulic cylinders ,[object Object],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.

Rotary hydraulic actuators ,[object Object],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 ??? ???

Big pictures ,[object Object],[object Object]

Hydraulic cylinders ,[object Object],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)

Hydraulic cylinders ,[object Object],Spring inside outside

Hydraulic cylinders ,[object Object],Velocity is different

Hydraulic cylinders ,[object Object],[object Object],Velocity is the same in both directions

Hydraulic cylinders ,[object Object],[object Object],Velocity is different in the two directions depending on cross section ratio of the rods

Hydraulic cylinders ,[object Object]

Hydraulic cylinders ,[object Object],Large working paths or limited space

Hydraulic cylinders ,[object Object],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

Hydraulic cylinders ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Rotary hydraulic actuators ,[object Object]

Hydraulics

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