Fast Movement in Hydraulic Systems

1. FFaasstt MMoovveemmeenntt HHyyddrraauulliicc SSyysstteemmss

2. Introduction
In hydraulic systems with single-sided pistons
we can distinguish different types of movements
(flow of the fluid) depending on the assembled
systems. These are slow (working) or fast,
forward or backward.

3. Differential system- working principle
[ ]
Q F v
tl
active surface of the piston 2
F m
velocity of the piston m
tl
v
- é
volumetric efficiency
s
-
ù
úû
êë
-
h
vh
vh
h
h
=

4. Adjustment of velocity,
differential system
1,2- dividers a1,b1,b2-
electromagnets
Fast (forward)
movement will be
activated when both
electromagnets a1
and b2 are switched
on
- attained velocity
- attained load

5. Adjustment of velocity,
differential system
Slow (forward)
movement will be
activated when a1
electromagnet is
switched on
In this case velocity will be
smaller than vr1 and the load will
be higher than Sr1

6. Adjustment of velocity,
differential system
Backward
movement will be
activated when only
b1 electromagnet is
switched on

7. I system
2 1
3
4
5
1- pump, 2- pressure relief
valve, 3- 4 way 3 positions
directional valve, 4-
hydraulic cylinder, 5- tank
Divider positions:
1 position- slow (working)
forward movement
2 position- fast forward
movement
3 position- backward
movement

8. II system

9. II system
Divider positions:
1 position- fast forward
movement
2 position- neutral
3 position- slow backward
movement

10. Wiring diagram of the I & II systems

11. III system
Divider positions:
Y1, Y2 switched on-slow
forward
movement
Only Y1 switched on-fast
forward
movement
Y1,Y3 switched on-slow
backward
movement

12. Wiring diagram of the III system

13. Application of fast movement
hydraulic systems
• Excavator arm control
• Airplane flap control
• Breaks control (in cars)
• Transmitters in agricultural machines
• Entrance gates mechanisms
• Cranes

14. Advantages and disadvantages
• Longevity
• Fluent change of velocities in the system; no vibrations
• Relatively cheap in exploitation
• Very accurate position of the piston cannot be
controlled
• Energy losses
• Leakages