Pneumatic Components & Systems

Team 1640Clem McKown – mentor

November 2008

Topics

What are pneumatics? What are pneumatics good for? How pneumatics work The pneumatic system Variations on the theme

What are pneumatics Mechanisms which

use air pressure to apply mechanical force and displacement (work)

The pneumatic devices we use are basically binary actuators – either retracted or extended

RetractedCylinder

ExtendedCylinder

What are pneumatics good for?

Mechanisms requiring (2) discrete states Gear shifters Gripper articulation Lifters Brakes

…and a significant force or displacement

Strengths

Strengths Simple

Strengths Simple Easy to control

Strengths Simple Easy to control Can apply a lot of force from a small,

light package

Strengths Simple Easy to control Can apply a lot of force from a small,

light package Force is limited by air pressure and

cylinder diameter

Strengths Simple Easy to control Can apply a lot of force from a small,

light package Force is limited by air pressure and

cylinder diameter No adverse consequence if cylinder is

stopped (no stalled motors) or reversed – compressed air is a spring

Drawbacks

Drawbacks

A significant weight “investment” (~10 lbm) in a pneumatic system is needed for the first pneumatic device

Drawbacks

A significant weight “investment” (~10 lbm) in a pneumatic system is needed for the first pneumatic device

Cylinders can be subject to damage

Drawbacks

A significant weight “investment” (~10 lbm) in a pneumatic system is needed for the first pneumatic device

Cylinders can be subject to damage

Repair impossible

Drawbacks

A significant weight “investment” (~10 lbm) in a pneumatic system is needed for the first pneumatic device

Cylinders can be subject to damage Repair impossible Not well suited for non-binary

actuation

In Industry Pneumatic actuators are extensively

used by the Chemical Process Industry due to their intrinsic safety and their ability to fail safe (w/ spring return)

2-positionpneumatic

actuatordriving a

4-wayball valve

pneumaticallydriven flowcontrol valves(butterfly type)

How it works

Piston

Cylinder

Seals

⅛” NPTF Air Port (Extension)

⅛” NPTF Air Port (Retraction)

Rod

Force = Area (in2) x Pressure (lbf/in2)Extension Area = Cylinder CS AreaSubtract Rod CS Area for Retraction

Typically,pressureis appliedto one portwhile theother isvented toatmosphere- so P isregulatedgauge pressure (60 psi max)

More works We may specify

Cylinder Diameter – sets Force @ a pressure Stroke Length Mounting Options Rod Material Rod Extensions Spring Return ….

Stroke

Length

Cylinder Specs (Bimba DXP/DX/DP)

Air Pressure (gauge): 60 lbf/in2

Length (in)Nominal Cyl ID Rod OD Extend Retract Extend Retract Base per inch Base

3/4" 0.750 0.250 0.44 0.39 27 24 0.21 0.03 3.757/8" 0.875 0.250 0.60 0.55 36 33 0.32 0.03 3.56

1-1/16" 1.063 0.313 0.89 0.81 53 49 0.33 0.05 3.841-1/4" 1.250 0.438 1.23 1.08 74 65 0.71 0.08 4.721-1/2" 1.500 0.438 1.77 1.62 106 97 0.73 0.08 4.381-3/4" 1.750 0.500 2.41 2.21 144 133 1.64 0.11 5.75

2" 2.000 0.500 3.14 2.95 188 177 1.62 0.15 5.622-1/2" 2.500 0.500 4.91 4.71 295 283 2.27 0.17 5.62

3" 3.000 0.625 7.07 6.76 424 406 3.87 0.26 6.50

Dimension (in) Area (in2) Force (lbf) Mass (lbm)

The pneumatic system I(the investment)

Motor

Compressor

Pressure

Switch

PressureSafetyValveH

igh

-Pre

ssu

reA

ir S

tora

ge

Hig

h-P

ress

ure

Air

Sto

rage

Pressure

Gauge

Pressure

Gauge

PressureVentValve

Pressure

Regulator

Hig

h P

ress

ure

Low

Pre

ssure

Users

Controller Spike

The pneumatic system II(the solenoid valve)

Air Supply(Pressure)

Vent B

Vent A

Port A

Port B

Supply/Vent Side

Output Side

A B

V P V

State AA B

V P V

State B

All ports⅛” NPTF

The pneumatic system III(device control)

SpikeController

AirPressure

A restrictor valve in Vent Bslows extension speedwithout affecting retractionspeed

¼” flexible tubing

State A – Extends rodState B – Retracts rod

The pneumatic system III(device control)

SpikeController

AirPressure

A restrictor valve in Vent Bslows extension speedwithout affecting retractionspeed

¼” flexible tubing

State A – Extends rodState B – Retracts rod

If you are using pairs ofcylinders which are activatedtogether, they can be drivenby common solenoids

Plumbing – Tubing Fittings

Tee - SMC KQT07-00

Male Elbow - SMC KQL07-34SMale Connector - SMC KQH07-34S

Restrictor Elbow - SMC NAS2201F-N01-07S

Something outside the box

In 2006Team 386 created high

vacuumwith cylinders

Team 386 (2006) a better vacuum

Team 386 used suction to lift ringers,but was underwhelmed by the vacuumdeveloped by venturi

Team 386 (2006) a better vacuum

Retracting the smaller cylinder

Team 386 used suction to lift ringers,but was underwhelmed by the vacuumdeveloped by venturi

Team 386 (2006) a better vacuum

Retracting the smaller cylinder

Generates a highvacuum on the larger cylinder

Team 386 (2006) a better vacuum

Retracting the smaller cylinder

Generates a highvacuum on the larger cylinder

Separate cylinder sets were used foreach suction cup, providing redundancy

Team 386 (2006) a better vacuum

Extending the smaller cylinder

Breaks the vacuum

Separate cylinder sets were used foreach suction cup, providing redundancy

Extending the small cylinders releasedthe vacuum and dropped the ringer