nota pneumatic and hydraulic system

ELECTRO-HYDRAULICS OVERVIEW AND APPLICATION

12.3 COMPARISON OF DIFFERENT TYPES OF CIRCUIT
DIAGRAM

In comparison with purely hydraulic control systems, electro-hydraulic control
systems exhibit the following advantages:
 Greater reliability

- Fewer moving components subject to wear required.
 Reduced planning and commisioning complexity, in particular in the case of

complex control systems
- The control program is electronically formulated and therefore can be

easily corrected and adapted.
 Reduced installation complexity

- Electrical signals can be easily transmitted over large distances via
cables.

- Mechanical signal transmission by means of rod linkage and cable pulls
or hydraulic signal transmission is far more complex.

 The control system can be easily modified and adapted
- The program can be easily and flexibly adapted to varying process
sequences if the control program is electronically formulated.

 Simpler exchange of information between several controllers
- Several PLCs can be networked via special communication interfaces if
the control programs are stored in a PLC. Exchange of information is
often effected via standardised, easy to use bus systems.

 Easy to deploy in automatic production plants
- In automation technology, the entire signal processing function is usually
effected electrically or electronically. Therefore, electro-hydraulic systems
can be more easily deployed in automatic production plants.

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12.4 DC POWER SUPPLY

12.4.1 Definitions of Direct current (DC).
Direct current (DC or continuous current) is the unidirectional flow of
electric charge. Direct current is produced by such sources as batteries,
thermocouples, solar cells and commutator-type electric machines of the
dynamo type. Direct current may flow in a conductor such as a wire, but
can also be through semiconductors, insulators or even through a
vacuum as in electron or ion beams. In direct current, the electric charges
flow in the same direction, distinguishing it from alternating current (AC).
A term formerly used for direct current was Galvanic current.

Direct current may obtained from an alternating current supply by use of a
current-switching arrangement called a rectifier, which contains electronic
elements (usually) or electromechanical elements (historically) that allow
current to flow only in one direction. Direct current may be into alternating
current with an inverter or motor generator set. (see figure 12.5)

BPLK Figure 12.5 Types of Direct current

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ELECTRO-HYDRAULICS OVERVIEW AND APPLICATION

Figure 12.6 shows a simple DC circuit consisting of a voltage source,
electrical lines, a control switch and a load (lamp).

I

V=12V + S
- H

Figure 12.6 DC circuit

When the control switch is closed, current I flows via the load. The
electrons move from the negative pole to the positive pole of the voltage
source. The direction of flow from quotes “positive” to “negative” was laid
down before electrons were discovered. This definition is still used in
practice today. It is called technical direction.

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SUMMARY

In this chapter we have studied to :

REFERENCES

1. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic, 1989
2. Electro-Pneumatics Basic Level TP 201 Text Book, Festo, 1998
3. FluidSim Pneumatic Software Version 4.0
4. Automation Studio Software Version 5.3

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COMPONENTS SYMBOLS AND DESCRIPTION OF ELECTRO-HYDRAULICS

CHAPTER 13 : COMPONENTS SYMBOLS AND
DESCRIPTION OF ELECTRO-
HYDRAULICS

INTRODUCTION

LEARNING OBJECTIVES

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13.1 INTRODUCTION COMPONENTS SYMBOLS
DESCRIPTIONS

13.1.1 Symbols for directional control valve

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13.1.2 Symbols for actuation directional control valve

13.2.3 Symbols forpressure valves

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13.1.4 Symbols for flow valves

13.1.5 Symbols for check valve

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13.1.6 Symbols for hydraulic cylinders and hydraulic motors

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13.1.7 Symbols for energy transmission and preparation

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13.1.8 Symbols for measuring devices

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13.2 ELECTRICAL SYMBOLS

13.2.1 Basic function

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13.2.2 Relay and coil

SUMMARY

In this chapter we have studied to :
1.

REFERENCES

1. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic
2. Electro-Pneumatics Basic Level TP 201 Text Book, Festo

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13.2.3 Electromechanical/Electromagnetic

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13.2.4 Switching devices

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13.2.5 Contacts

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13.2.6 Sensors

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SUMMARY

In this chapter we have studied to :

REFERENCES

3. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic, 1989
4. Electro-Pneumatics Basic Level TP 201 Text Book, Festo, 1998
5. FluidSim Pneumatic Software Version 4.0

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DEVELOPING ELECTRO-HYDRAULICS CIRCUIT

CHAPTER 14 : DEVELOPING ELECTRO-HYDRAULICS
CIRCUIT

INTRODUCTION

LEARNING OBJECTIVES

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14.1 RAPID TRAVERSE FEED CIRCUIT

14.1 Description of the circuit

In this circuit, the rapid advance circuit is only active in the direction of
extending. The physical basis of this circuit is that in relation to a certain
cylinder position, different resistances are effective. First, the cylinder
extends at rapid speed due to the fact that the flow on the annulus side is
directly fed to the tank through an interconnected directional control valve
(low resistance). When a specific position is reached, a sensor in
conjunction with a relay actuated the interconnected directional control
valve. The directional valve closes the connection and the flow is directed
exclusively through a 2 way flow control valve which reduces the flow,
and thus the extending velocity, to the set value. The retracting
movement of the cylinder should not be affected by this.

BPLK Figure 14.1 Rapid advance circuit (hydraulic circuit)

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Figure 14.2 Rapid advance circuit (electrical circuit)

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14.2 ACCUMULATOR CIRCUIT, PRESSURE LESS BYPASS

14.2.1 Description of the circuit

Accumulators are used for storing energy, damping pulsations, holding a
pressure constant, compensating for leakage as well as for the
suspension on vehicles. The circuit refers to the function of the storing
energy. For this purpose, a diaphragm type accumulator can be a
diaphragm, a bladder or a piston. When smaller accumulators are
required, diaphragm type accumulators are preferred. The physical basic
principle of energy storage is the compressibility of a gas volume.

BPLK Figure 14.3 Accumulator circuit (hydraulic)

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Figure 14.4 Accumulator circuit (electric)

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14.3 DISPLACEMENT/STEP CONTROL, EXISTING SEQUENCER
WITH BRANCH

14.4 FLOW DIVIDING VALVE, PILOT CONTROL

14.4.1 Description of the circuit

Throttle check valves belong to the group of flow control valves. The task
of these is to limit or throttle the flow in one direction and allow almost
unrestricted flow in the reverse direction. The circuit is to shows that an
adjustable throttle check valve can be used to vary the running velocity of
a cylinder in one direction of movement. In other direction, the flow is only
slightly throttled. In this case, the hydraulic fluid flows through the open
passage of the check valve element of the throttle check valve. In
addition, the effects of a meter in and meter out throttle on the pressure
conditions on the cylinder are to be shown.
Throttle check valves are throttles which in contrast to a fine throttle
(orifice), are temperature and viscosity dependent.
Throttles are control elements, which allow a certain amount of fluid to
pass through the element in dependence upon the differential pressure.
Such valves are used especially in applications, where the influence on
the cylinder in only requested in one direction. A typical field of application
would be, for example a lifting platform.

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DEVELOPING ELECTRO-HYDRAULICS CIRCUIT

a) Extending throttling (meter in) b) Extending throttling (meter out)

c) Retracting throttling (meter in) d) Retracting throttling (meter out)

BPLK Figure 14.5 Flow dividing circuit (hydraulic)

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DEVELOPING ELECTRO-HYDRAULICS CIRCUIT

Figure 14.6 Flow dividing circuit (electric)

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14.5 DIFFERENTIAL CYLINDER, SEQUENCE CONTROL WITH
EMERGENCY STOP AND INCHING MODE

14.5.1 Example of “Sawing machine”

Figure 14.7 Positional sketch of sawing machine

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DEVELOPING ELECTRO-HYDRAULICS CIRCUIT

Figure 14.8 Displacement step diagram of sawing machine

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Figure 14.9 Hydraulic circuit of sawing machine

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Figure 14.10 Electrical circuit diagram (control elements)

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Figure 14.11 Electrical circuit diagram (Sensor evaluation)

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Figure 14.12 Electrical circuit diagram (Sequential step circuit)

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Figure 14.13 Electrical circuit diagram (Circuitry of solenoid coils)

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DEVELOPING ELECTRO-HYDRAULICS CIRCUIT CIRCUIT, PRESELECT

14.6 HYDRAULIC DIFFERENTIAL
COUNTER

SUMMARY

In this chapter we have studied to :

REFERENCES

1. Fundamentals Of Pneumatic Control Engineering Text Book, Festo Didactic, 1989
2. Electro-Pneumatics Basic Level TP 201 Text Book, Festo, 1998
3. FluidSim Pneumatic Software Version 4.0

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