Transcript Pneumatic Components & Systems

Pneumatic Components &
Systems
Team 1640
Clem McKown – mentor
November 2008
Topics
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What are pneumatics?
What are pneumatics good for?
How pneumatics work
The pneumatic system
Variations on the theme
What are pneumatics
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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
Retracted
Cylinder
Extended
Cylinder
What are pneumatics good for?
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Mechanisms requiring (2) discrete states
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Gear shifters
Gripper articulation
Lifters
Brakes
…and a significant force or displacement
Strengths
Strengths
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Simple
Strengths
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Simple
Easy to control
Strengths
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Simple
Easy to control
Can apply a lot of force from a small, light
package
Strengths
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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
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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
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A significant weight “investment” (~10
lbm) in a pneumatic system is needed
for the first pneumatic device
Drawbacks
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A significant weight “investment” (~10
lbm) in a pneumatic system is needed
for the first pneumatic device
Cylinders can be subject to damage
Drawbacks
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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
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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
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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-position
pneumatic
actuator
driving a
4-way
ball valve
pneumatically
driven flow
control valves
(butterfly type)
How it works
⅛” NPTF Air Port (Retraction)
Typically,
pressure
is applied
to one port
while the
other is
vented to
atmosphere
- so DP is
regulated
gauge
pressure
(60 psi max)
Seals
Piston
Rod
Cylinder
Force = Area (in2) x D Pressure (lbf/in2)
Extension Area = Cylinder CS Area
Subtract Rod CS Area for Retraction
⅛” NPTF Air Port (Extension)
More works
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We may specify
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Cylinder Diameter – sets Force @ a pressure
Stroke Length
Mounting Options
Rod Material
Rod Extensions
Spring Return
….
Stroke
Length
Cylinder Specs
Air Pressure (gauge):
Dimension (in)
Nominal
3/4"
7/8"
1-1/16"
1-1/4"
1-1/2"
1-3/4"
2"
2-1/2"
3"
Cyl ID
0.750
0.875
1.063
1.250
1.500
1.750
2.000
2.500
3.000
Rod OD
0.250
0.250
0.313
0.438
0.438
0.500
0.500
0.500
0.625
Area (in2)
Extend
Retract
0.44
0.39
0.60
0.55
0.89
0.81
1.23
1.08
1.77
1.62
2.41
2.21
3.14
2.95
4.91
4.71
7.07
6.76
(Bimba DXP/DX/DP)
2
60 lbf/in
Force (lbf)
Extend
27
36
53
74
106
144
188
295
424
Retract
24
33
49
65
97
133
177
283
406
Mass (lbm)
Base
0.21
0.32
0.33
0.71
0.73
1.64
1.62
2.27
3.87
per inch
0.03
0.03
0.05
0.08
0.08
0.11
0.15
0.17
0.26
Length (in)
Base
3.75
3.56
3.84
4.72
4.38
5.75
5.62
5.62
6.50
The pneumatic system I
(the investment)
Users
Pressure
Regulator
Pressure
Gauge
High Pressure
High-Pressure
Air Storage
High-Pressure
Air Storage
Gauge
Low Pressure
Pressure
Pressure
Vent
Valve
Pressure
Safety
Valve
Pressure
Switch
Motor
Controller
Spike
Compressor
The pneumatic system II
(the solenoid valve)
All ports
⅛” NPTF
Port B
Vent A
State A
A
B
Air Supply
(Pressure)
Vent B
V
P
V
State B
A
B
Port A
V
P
V
The pneumatic system III
(device control)
State A – Extends rod
State B – Retracts rod
¼” flexible tubing
Air
Pressure
Controller
Spike
A restrictor valve in Vent B
slows extension speed
without affecting retraction
speed
The pneumatic system III
(device control)
If you are using pairs of
cylinders which are activated
together, they can be driven
by common solenoids
State A – Extends rod
State B – Retracts rod
¼” flexible tubing
Air
Pressure
Controller
Spike
A restrictor valve in Vent B
slows extension speed
without affecting retraction
speed
Plumbing – Tubing Fittings
Male Elbow - SMC KQL07-34S
Male Connector - SMC KQH07-34S
Tee - SMC KQT07-00
Restrictor Elbow - SMC NAS2201F-N01-07S
Something outside the box
In 2006
Team 386 created high vacuum
with cylinders
Team 386 (2006)
a better vacuum
Team 386 used suction to lift ringers,
but was underwhelmed by the vacuum
developed by venturi
Team 386 (2006)
a better vacuum
Team 386 used suction to lift ringers,
but was underwhelmed by the vacuum
developed by venturi
Retracting the smaller cylinder
Team 386 (2006)
a better vacuum
Generates a high
vacuum on the
larger cylinder
Retracting the smaller cylinder
Team 386 (2006)
a better vacuum
Separate cylinder sets were used for
each suction cup, providing redundancy
Generates a high
vacuum on the
larger cylinder
Retracting the smaller cylinder
Team 386 (2006)
a better vacuum
Separate cylinder sets were used for
each suction cup, providing redundancy
Extending the small cylinders released
the vacuum and dropped the ringer
Breaks the vacuum
Extending the smaller cylinder