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Hydraulic and Pneumatic Actuators and their Application Areas. Elena Ponomareva JASS 2006 – St. Petersburg. Introduction. Figure A. Automatic Pneumatic Drive :
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JASS 2006 – St. Petersburg
Figure A. Automatic Pneumatic Drive:
UGM -units of gas networks and mains; PA - pneumatic amplifiers; PE - pneumatic engines; MT - the mechanism of transfer; CSD -converting and summing device; ACE - amplifiers of capacity of electric signals; EMC - electromechanical converters; DF - devices of feedbacks; AC - adjusting circuits; IF - internal feedbacks; GG -a source of gas energy
The combined gas law
The ideal gas law
All pneumatic actuators can be subdivided into the following types:
diaphragm pneumatic actuators;
pneumatic power cylinders;
gas-engine pneumatic actuators;
turbine pneumatic actuators;
jet pneumatic actuators;
combined pneumatic actuators.
Figure 1.1. The membrane pneumatic actuator:
1 - the connecting pipe of the second cavity; 2 - the connecting pipe of the first cavity; 3 - the membrane; 4 - the case; 5 - the rod; G1 - the second charge of a gas stream in the first cavity; G2-the second charge of a gas stream in the second cavity; p1 - pressure of gas in the first cavity; р2 - pressure of gas in the second cavity; xr - moving of the rod
Figure 1.2. The sylphon pneumatic actuator:
1 - the connecting pipe of the second cavity; 2 - the connecting pipe of the first cavity; 3 - the case; 4 — the rod with the piston of the first cavity; 5 - a sylphon of the first cavity; 6 – the closing up of the sylphon of the first cavity
As compressed air moves into the cylinder, it pushes the piston along the length of the cylinder. Compressed air or the spring, located at the rod end of the cylinder, pushes the piston back.
A double acting pneumatic cylinder has two- directed powered motion, with pressure on both sides.
Double-acting double-rod cylinder – double-acting cylinder with a piston rod extending form each end.
The piston rods are connected with the same piston. Double-rod cylinders provide equal force and speed in both directions.
Festo Copac Linear Actuator
Ideal for vertical use
The ZSC series is available in five sizes with piston diameters of 6 to 25 mm and strokes from 10 to 100 mm (in 10 mm increments). The mini slides operate at a speed between 0.05 to 0.5 m/s (0.16 to 1.6 ft/s) at an operating pressure of 1.5 to 7 bar (22 to 102 psi).
The GPC series is ideal for all applications that demand absolute precision and side
load capacity. Compared to standard cylinders, cylinders from this series offer extremely
precise movement, high side load capacities, and also torsion protection.
This results in fewer outer guides to design and set up machines.
Tandem cylinders ADVUT
By connecting 2, 3 or 4 cylinders with the same piston diameter and stroke in series, the force in the advance stroke (thrust) can be doubled, tripled or quadrupled in comparison to a single cylinder.
Shock influence is required in a number of technological operations, such as punching, marking, punching of holes. In this case we useshot pneumocylinders.
Figure 1.3. The scheme of the shot pneumocylinder:
A, b, c – cavities; 1, 3, 4 – channels; 2 - aperture
In technological operations when the executive mechanism is, for example, the cutting tool or a gearshift, it is necessary to establish two and more fixed positions, multiposition pneumocylinders or pneumatic positioners are used.
Figure 1.4. Threeposition pneumocylinder:
A, B, C -control valves; 1, 2, 3 –channels; T1, T2 –pneumothrottles; a, b – cavities; Рip- pressureof compressed air in cavities a and b
Figure 1.5. The hose pneumocylinder:
1 – hose;
2 - rollers of the carriage;
3 - control valve;
Figure 1.6 Rotary pneumoactuator:
1, 2, 5 - channel; 3 - piston; 4 - chain transfer; A - cavity;Рip - pressure
Figure 1.7 Chamber rotary pneumoactuator:
1 – channel;
2 - chamber;
3, 4 – levers;
5 - detail
The pneumomotor with the limited angle of turn is applied to perform oscillating movements of the output shaft or its rotation on the definite angle.
Figure 1.8 The pneumomotor with the limited angle of turn:
1 - case; 2 - blade: 3 - target shaft; 4 - compaction; 5, 6 - fittings; 7 - stops
Figure 1.9 Lateral force Fq as a function of stroke length l.
Figure 1.10 Pneumomuscle:
1 - internal elastic tube;2 - braid; 3, 4 – covers;5 – feeding channel
Figure 1.12 Geometrical parametersof reduced pneumomuscles:
1 - braid; 2 - internal elastic tube;
3 – pantograph’s cell
Figure 1.11 Comparative characteristics of output efforts of the power cylinder and the pneumomuscle:
1 - power cylinder; 2 - pneumomuscle
Figure 1.13 The artificial muscle:
1 – casing; 2 - elastic tube; 3 – thermoelement; 4 – filler; 5 - electric leading-out wires
Figure 1.14 The electropneumatic actuator:
1 - amplifier of direct current; 2 - electromechanical converter; 3 - choker; 4 - nozzles, 5 - throttles, 6, 7 - executive pneumocylinders, 8, 9 - feedback sensors 10 - spring, 11 - flywheel
v = fluid velocity along the streamline
g = acceleration due to gravity on Earth
h = height from an arbitrary point in the direction of gravity
p = pressure along the streamline
ρ = fluid density
The second, more general form of Bernoulli's equation
φ is the gravitational potential energy per unit mass
ω is the fluid enthalpy per unit mass
εis the fluid thermodynamic energy per unit massBernoulli's Equation
Figure 2.1. The hydraulic cylinder:a - one- sided action with a returnable spring;b— double-sided action controlled by the differential scheme;1 — plunger;2 — spring;3 — basic sealant;4 — antisplash sealant; 5 — piston;6 — nternal sealant; 7 — rod;8 — a basic external sealant;9 — antisplash external sealant;10 — rod’s cavity;11 — supply circuit; I, II — positions of a control valve;F — external force;S— the full area of the piston;S' - the ring area of the piston;Q, q —submission and plums of a stream accordingly
Figure 2.2. The hydraulic cylinder with a double-sided rod: a - with the fixed rod; b — with the fixed hydraulic cylinder and a control valve; 1—internal consolidation; 2, 5 — antisplash external consolidations; 3, 4 — basic external consolidations; F - external force; h — course of the piston; p1, р1' — low pressure; p2, р2' — high pressure; Q — the charge; v — speed of the piston
Figure 2.3. The three-high-speed hydraulic cylinder: 1,3, 6 — hydrolines; 2 — the internal hydraulic cylinder; 4, 5 — cavities; F— external force; S1 - area of the hydraulic cylinder 2; S2, S3- area of cavities 5 and 4 accordingly
Figure 2.4. The telescopic hydraulic cylinder:
1,6-pistons; 2, 3 — cavities; 4 — sleeve; 5 — hydroline; 7 — supply; F- the external force; S1. S2 —the area of cylinders with pistons 1 and 6 accordingly; S3, S4- areas of cavities 2 and 3 accordingly
Figure 2.5. The hydraulic cylinder with trailer throttle brakes and the protected rod:
1 - throttle; 2,3 - sockets; 4 — rubber sylphon; 5 — return valves; 6,7- ledges of the piston; 8 — ring volume; other designations see on fig. 2.2
Figure 2.6. The piston of the hydraulic cylinder with fixing devices:
1 - sealant element;
2 — conic surface;
3 — ball;
4 — spring;
5, 7 — cavities of the hydraulic cylinder;
6 — piston
Figure 2.7. Consolidation of rods (a, b) and pistons (c, d) of hydrocylinders:
a – with a round rubber ring; b,c – with V-look cuffs; d — with a bilateral cuff; 1 — aprotective ring; 2 — plastic persistent ring; 3 — rubber ring; 4 — nut; 5— dividing plastic cuff; 6 — consolidating rubber cuff; 7 — directing belt of a cuff; 8— cuff; 9 — bilateral cuff
Figure 2.8. Hydraulic Jack
In this system , areservoir and a system of valves has been added to a simple hydraulic lever to stroke a small cylinder or pump continuously and raise a large piston or an actuator a notch with each stroke.
Figure 2.9. Basic schemes of a hydraulic actuator:
a - forward movement; b — rotary movement; c — hydromotor; 1 — hydraulic engine; 2 — hydraulic control valve; 3 — hydrotank; 4 — adjustable pump; 5 — safety valve; F — working force
Figure 2.10. The scheme of a hydraulic actuator with the closed circulation of a liquid:
1 - adjustable pump; 2— auxiliary pump; 3 — downflow flap; 4 — return flap; 5— safety flaps; 6 — hydraulic engine (adjustable hydromotor); a, b — hydrolines
Figure 2.11. The scheme of a hydraulic actuator with a regulator of a stream:
1— regulator; 2 — adjustable throttle; 3 — reducing valve; Рth - pressure in a throttle upon an input; Рp - pressure of the pump
Figure 2.12. The scheme of a hydraulic actuator with steady output rotation frequency:
1 - a pump; 2 — a hydromotor; 3 — the shaft of the hydromotor; 4 — a centrifugal regulator; 5 — the valve of the hydraulic control valve ; 6 — the hydrocylinder; 7 — a disk
Figure 2.13 The scheme of a stream divider:1 — throttles; 2, 3 — apertures; 4 — a piston; 5 — a sleeve; M — a point of division of stream Q on streams Q1, and Q2
Figure 2.14 The scheme of a follower hydraulic actuator of cross-section submission of a support of the copy machine tool:
1 - piston; 2 — cavity; 3 — hydraulic control valve; 4 — bringing hydroline; 5 —probe; 6 — master cam; 7 — the case of the hydraulic cylinder; 8 — the case of the support; 9 — support
Figure 2.15 The scheme of the hydraulic booster with a mechanical feedback::
1 - point (hinge); 2—draft; 3 — piston; 4 — power cylinder; 5 — hydraulic control valve; 6 — rod (an output link); 7 — a point of an output link; 8 — differential lever; n, m – links of a double-shouldered lever
Linear/swivel clamp CLR
Swivel/linear units DSL
Festo servopneumatic systems
Executive devices – hydro- and pneumocylinders, hydro- and pneumomotors and so on.
Sensors, controllers and operating control
Sensors – contacts,inductive, capacitive, optical, hydraulic, pneumatic, PLC.Control Systems
Let's consider a control system of a pneumatic or hydraulic drive with the use of PLC controller. The block diagram of system is specified in the following diagram.
The right product for the right demands …
Pneumatic processing centers
Figure 5.2. The scheme of the pneumatic processing center for material’s sawing:
1 -work material; 2 -a power cylinder for a longitudinal motion; 3 - a power cylinder for a vertical motion; 4 – saw; 5 – supports; 6 – rotary actuator
Figure. 5.1. The scheme of the pneumatic machining center
Table: Scopes of systems with pneumatic muscles
Figure 5.3. The scheme of batching:
1 – tank; 2 – fluid; 3 – a lever with a ladle; 4 - power cylinder; 5 – accepting chamber
Figure 5.5. The scheme of the mobile robot:
1,2 – longitudinal pneumatic cylinders; 3,4 – transversal pneumatic cylinders; 5 – lifting cylinder; 6 – pedipulator; 7 – metaldetector; 8 – infra-red sensor; 9 – the chemical sensor; 10 – sensor of longitudinal position movement; 11 - sensor of cross-section position movement; 12 - block of valves; 13 – block of rotation; 14 – electronic compass; 15 – onboard compass
Figure 5.7. The scheme of the mobile robot with vertical displacement:
1 - longitudinal movement module; 2 - rotating movement module; 3 – console; 4,5 - vacuum gripping devices; 6,7 - elevating cylinders; 8 –trajectory of turn