Pneumatic Actuators
For power, motion and control
Introduction
Pneumatic actuators include linear cylinders and rotary actuators.
They are devices providing power and motion to automated systems, machines and processes.
A pneumatic cylinder is a simple, low cost, easy to install device that is ideal for producing powerful linear movement.
Speed can be adjusted over a wide range.
A cylinder can be stalled without damage.
Introduction
Adverse conditions can be easily tolerated such as high humidity, dry and dusty environments and cleaning down with a hose.
The bore of a cylinder determines the maximum force that it can exert.
The stroke of a cylinder determines the maximum linear movement that it can produce.
The maximum working pressure depends on the cylinder design. VDMA cylinders work up to 16 bar.
Thrust is controllable through a pressure regulator.
Basic Construction
1 cushion seal
2 magnet
3 cushion sleeve
4 barrel
5 guide bush
6 rod and wiper seal
7 front end cover
8 front port
9 reed switch
10 piston rod
11 wear ring
12 piston seal
13 rear end cover
14 cushion screw
Fundamental designs
Fundamental designs
Pneumatic actuators are made in a wide variety of sizes, styles and types including the following
Single acting with and without spring return
Double acting
Non cushioned and fixed cushioned
Adjustable cushioned
Magnetic
Rodless
Rotary
Single acting spring return
Single acting cylinders have a power stroke in one direction only
Normally in
Normally out
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Single acting no spring
Gravity or other external force to return the rod
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Double acting
Double acting cylinders use compressed air to power both the outstroke and instroke.
Superior speed control is possible
There are
Non-cushioned types
Fixed cushioned types
Adjustable cushioned types
Double acting non-cushioned
Non cushioned cylinders are suitable for full stroke working at slow speed.
Higher speeds with external cushions
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Double acting fixed cushions
Small bore light duty cylinders have fixed cushions
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D/A adjustable cushions
progressively slows the piston rod down over the last part of stroke
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Double acting magnetic
A magnetic band around the circumference of the piston operates reed switches to indicate positions of stroke.
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Rodless cylinders
Contain the movement produced within the same overall length taken up by the cylinder body.
For example, action across a conveyor belt, or for vertical lifting in spaces with confined headroom.
Movement is from a carriage running on the side of the cylinder barrel.
A slot, the full length of the barrel allows the carriage to be connected to the piston.
Long sealing strips on the inside and outside of the cylinder tube prevent loss of air and ingress of dust.
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Rodless cylinder
Double acting with adjustable cushions
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Rotary Actuators
Used for turning components, operating process control valves, performing a wrist action in robotic applications.
Provide angular reciprocating rotation up to 360o
Rotary vane types
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Rotary vane
Double acting with 270o angle of rotation
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Cushion design
Cushion design
Cushioning protects a cylinder and load by absorbing the energy at the end of stroke. This results in progressive deceleration and gentle contact between the piston and end cover.
Fixed cushioning with shock absorbing pads is applied to small light duty cylinders which have low mass in the piston, rod and load.
Larger cylinders have adjustable pneumatic cushions which function over the final 2 cm of stroke.
Fixed cushion design
Shock absorbent discs set into the end covers cushion the impact of the piston
Adjustable cushion design
Adjustable cushion design
The piston is moving to the left at speed.
Air is venting through the centre of the seal.
Adjustable cushion design
The cushion seal is pushed to the left and seals against it’s left hand edge and inside diameter.
Air can only escape past the cushion screw. The pressure builds up and cushions the piston.
Adjustable cushion design
The screw is set to bring the piston, rod and load to a gentle halt against the end cover.
Adjustable cushion design
A valve has been operated to power the piston out.
The cushion seal is pushed to the right. Grooves in the right hand edge and outside diameter bypass the screw.
Adjustable cushion design
The piston is started in the other direction un-restricted by the cushion screw setting.
Types of construction
Types of construction
The factors controlling the type of construction of a cylinder are
Size, duty, cost, style, standards and compatibility of materials
Sealed for life types
Low cost, light duty, small to medium bore cylinders. The piston is pre-greased for life on assembly and can be operated with non lubricated or lubricated air.
Types: micro cylinders, round line, small bore compact
Serviceable types
It is economical for the user to extend their life by replacement of worn seals and re-greasing. Also the replacement of accidentally damaged parts may be possible.
Types: small bore ISO, large bore compact, ISO/VDMA range, heavy duty.
Round line cylinders
Low cost, light duty, small to medium bore cylinders in the range 8mm to 63mm diameter.
The cylinders are sealed for life by rolling the barrel ends and end covers down to make a pressure tight seal.
For operation in the pressure range 1 to 10 bar.
Compact cylinders
Short overall dimension that is approximately one third of the zero stroke length of a comparable ISO design.
A magnetic piston is standard on the single and double acting versions
pressure range from 1 bar to 10 bar. Sealed for life.
Small bore ISO
ISO dimensioned cylinders in the range 10 mm to 25 mm bore both single and double acting screwed barrel construction.
A threaded rear end cover provides a choice of mounting by clamp nut or built in rear eye.
For operation with non-lubricated or lubricated air in the pressure range from 1 bar to 10 bar.
ISO / VDMA cylinders
Conforming to ISO and VDMA dimensions and with a wide range of mounting options.
Lightweight profile, double acting cylinders with integral tie rod construction in magnetic and non-magnetic versions.
Bore sizes range from 32mm to 125 mm diameter.
ISO / VDMA
Large bore double acting range external tie rod design
125 mm to 320 mm diameter
Magnetic version up to 200 mm non magnetic in all sizes.
Wide range of mountings.
1 to 16 bar (up to 200 mm) 1 to 10 bar (250 to 320 mm bore).
Mountings
Cylinder rigidly fixed to the machine or allowed to swivel as part of a linkage in one or more planes.
Fixing points will be the cylinder body and piston rod end.
Mountings for small bore
AK
B
C
F
G
L
UF
NUT
Mountings
Mountings for tie rod cylinders
A
AK
B
C
D
D2
F
G
L
M
R
S
SS
SW
UF
UH
UL
UR
NUT
Rigid mountings
B Rear Flange
G Front Flange
C Foot
A Tie rod extension
Articulated mountings
D Rear Clevis
H Centre
Trunnion
R Rear Eye
F Rod Clevis
L Rear Hinge
UF Universal rod Eye
M Front Hinge
UR Universal
rear Eye
Installation
Installation
A cylinder should be installed so that side loads on the piston rod bearing are reduced to a minimum or eliminated.
A side load is a force component acting laterally across the axis of the bearing.
Five typical installations that produce a side load follow with their possible solutions.
Side loads can rarely be eliminated completely, but by employing good engineering practice they can be reduced to an acceptable level.
Side load one
Avoid attaching an unsupported load to the piston rod.
Wherever possible support the load on slide or roller guides
Side load two
The weight of a long outstroked piston rod alone can produce a high bending moment.
It may be possible to hang the rod end from a roller track.
Side load three
Misalignment of the cylinder and a guided load can easily jamb the cylinder completely.
Installation of a front fork and slot will eliminate this type of side load.
The most common cause of cylinder failure !
Side load four
An offset load is a common source of bending moment acting on the end of a piston rod.
Install external heavy duty bearings to relieve the side load on the cylinder bearing.
Side load five
A horizontally mounted rear hinged cylinder will have the weight of the cylinder body creating a bending moment.
Fit a central trunnion at the point of balance
Non rotational guiding
Non rotational guiding
Add on guide block units
with slide or roller guides.
provide non rotational guiding and greater support against higher loads.
For low friction and best support use the version with twin roller guides
These units can be fitted with twin passive or active locking cartridges.
Locking and braking
Locking and braking
For safety in the event of air failure or as part of a machine sequence.
Stop and hold a load at any position in the stroke.
Passive or active piston rod locking unit
A range of these add on units is designed to suit ISO cylinders from 32 mm to 125 mm bore.
LINTRA® Rodless Cylinders
LINTRA® Cylinders
Rodless cylinders for:
Limited spaces
Simple installation
Long strokes
Neat attractive styling
High speed
Precision control
Large range:
Variants in structural strength
Twin stroke
Active braking
Passive braking
Curved design
Electric drive
Corrosion resistant
Operating principle
A full length slot in the barrel joins the piston and external carriage
The slot is sealed against pressure and dust with self holding inner seal and outer cover strips
Strips are continuously parted and re-sealed by the piston
The slot is only unsealed in the un-pressurised space between the piston seals
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Operating principle
The sealing strips are parted and closed as the piston moves through the stroke
Adjustable cushions
Dual connection ports at the left hand end
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LINTRA® applied
For action across a strip process
No overhang or mechanism required compared to a conventional piston
rod cylinder
The application shows a flying knife typical of use in the paper production industry
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LINTRA® applied
Lifting in places with limited headroom
Actuation contained within the length of the cylinder body
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LINTRA® Overview
Extruded aluminium alloy cylinder barrel with integral bearing guides
Internally or externally guided carriage
Roller guided carriage
Double carriages
Integral valve option
Bore sizes 16 to 80mm
Strokes up to 8.5 m
Adjustable cushion
Single end connections
Magnetic piston option
Dual integral grooves for sensor mounting
Guiding variants
The internally guided carriage is suitable for light duty applications
Externally guided carriage uses bearing grooves on two extrusion edges
For precision conditions, roller guides can be used
Secondary free carriage connected to powered carriage for guiding on all four extrusion edges
Braking cylinders
Holds the carriage firmly in any position against a fixed or variable load
The passive brake is held OFF by applied air pressure and clamped ON by a spring
The active brake is clamped ON by the application of air pressure
Mountings
A variety of mounting styles for fixing the cylinder body and load
Foot mountings style ‘C`
Carriage mounting plate style ‘UV`
Centre support style ‘V` for fixing the cylinder body at mid span
Swinging bridge style ‘S` up to 8O either side and up to 4mm vertical in the axis of the cylinder
Mountings
Provide movement in two planes
A right angle mounting system style ‘X’ allows the carriages of two rodless cylinders of the same bore to be joined
Styles ‘X1’ and ‘X2’ allow the combination of cylinders with different bore sizes
LINTRA® - LITE
Compact design giving smallest installation envelope
High quality proven seal design as used in LINTRA® cylinders
Magnetic and non magnetic option
Fixed buffer cushion and adjustable cushion options
Neat integrated rails for sensor mounting
Integrated foot mounting