Transcript No Slide Title

Welcome to a
School
Dale L. Kohlsmith
Director of Training
Numatics, Inc.
The Heart of Every Numatics Valve:
The matched Spool & Sleeve
What is Matched?
Both the spool and sleeve are:
- made of exactly the same material
- tooled to be a mated for life set, with an
extremely close fit
What is the Material?
440 C Stainless Steel:
- an alloy of primarily tooling steel and stainless steel
- stainless for corrosion resistance
- tool steel for machining and hardening
What is the Material?
Often the spool & sleeve come from the same
batch or pour.
Why?
So they “like” each other…
No danger of corrosion -- electrolysis.
How precise is the tolerance?
By today’s manufacturing standards,
the spool & sleeve can be with in 10 one millionths
of an inch of being true and perfectly round,
.000010 in. =.00025mm
Allows for the Air Bearing Principle
&
Makes it impossible to incorrectly assemble
the spool and sleeve
Because the spool and sleeve are matched
with the same material, tooled to precise tolerances and...
designed to have the same mass
The expansion and contraction coefficient
are the same, so variations in normal
ambient industrial temperatures
will not cause jamming.
How smooth a finish?
Better than 2 micro inch (2AA or 2RMS)
AA - Arithmetic Average
RMS - Root Means Squared
is simply the average of the peaks and valleys
in the finish of the metal
How smooth a finish?
Better than 2 micro inch (2AA or 2RMS)
This is glass smooth so there is no metal seal or wear
Any smoother could impede the Air Bearing Effect
What is the air bearing principle?
The minuscule clearance between the spool and sleeve
allowing an intentional leakage of air across the
spool lands coupled with the smooth
finish, centers the spool within
the sleeve preventing metal to metal contact...
Providing a friction less fit (i.e. an air bearing effect
with no wearing parts)
How close is the clearance
needed to allow
the air bearing?
“That which is sufficient to create
the air bearing effect”
Is there a required pressure needed to
maintain the air bearing effect?
Yes, about 1/100 psig or a vacuum to
force air across the lands.
Can a rubber packed spool & sleeve have
an air bearing?
No, this is why they generally must be lubricated
to be able to move with a “bubble tight” fit.
They don’t run dry and they rely on a friction fit,
therefore no air bearing
Will a rubber packed valve leak air?
Yes, because starting with the first shift,
the “O” rings begin chewing themselves up
-- committing suicide -As rings begin to wear, air will blow by -- leak
Also there will almost always be open crossover...
Construction
Poppet Type --- Mechanical/Solenoid/Pilot
Position 1
EXHAUST
CYLINDER
SUPPLY
Flow paths when “B” pilot is pressurized or in command
Crossover
EXHAUST
CYLINDER
SUPPLY
Position 2
EXHAUST
CYLINDER
SUPPLY
Flow paths when “A” pilot is pressurized or in command
Construction
Spoppet Type --- Solenoid Air Pilot
CYL
Position 1
CYL
EXH
IN
EXH
Flow paths when “B” pilot is pressurized or in command
Crossover
CYL
EXH
Position 2
CYL
CYL
CYL
EXH
EXH
IN
IN
EXH
Flow paths when “A” pilot is pressurized or in command
Does a Numatics Valve have open crossover?
No, all ports are blocked during valve shift…
Valve start in “B” position.
Closed crossover in mid-position, no port may
pass air to another.
Valve in “A” condition, complete shift.
Can an “O” ring make an effective
dynamic seal?
“...they (“o”rings) are not a ‘universal’ seal applicable
to all sealing problems. Certain limitations must
be imposed upon their use, among them, high
temperatures, high frictional rubbing speeds,
cylinder ports over which seals must pass, and…”
- Parker Seals, Catalog ORD 5703, 1981
How can Rubber Packed Valves Compete?
35-65% of their business is Replacement part
business:
Sell two valves -- one Repair Kit…
Sell three valves -- two Repair Kits…
Etc.
Numatics < 2%
due to non-wearing parts
Numatics Valves only use static “O” rings.
- to seal flow galleries in the valve body
- to float the sleeve assembly within the
valve body
Floating?
Floating spool & sleeve -- the spool & sleeve
“float” within the valve body…
This prevents twisting or torqueing of the sleeve
and allows for equal masses.
Spool in body valves can jam due to torqueing or
thermal expansion or contraction.
How hard?
Hardened through heat treating to
58 - 62 Rockwell “C”
- so that the spool and sleeve will be harder than any
potential contaminants (ex. - pipe scale)
Why round holes in the sleeve?
- to act as a rudimentary filter to predetermine
particulate size allowed to enter the
spool area (where it shall be chopped)
& to still provide optimal air flow through the
valve.
Because Numatics spool & sleeve do not have
dynamic “O” rings, have precise tolerances, an extremely
smooth finish and is very hard...
The spool lands are made razor sharp.
…this sharpness should not be mistaken
for burrs
The spool lands are
made razor sharp.
This along with the equally
sharp holes will guillotine
any stray particulate.
Therefore the valve is self-cleaning.
Can an “O” ring chop particulate?
Of course not,
but what about that windshield wiper action?
Can an “O” ring chop particulate?
Do your windshield wipers clean the greasy chunks off?
Balanced Design?
Balanced Design…
“There is no relationship to the pressure
passing through the valve and the force
required to shift the valve”
Therefore our spool & sleeve may be direct
solenoid operated - due to the constant shifting force.
We can be Multi-purpose...
… because of:
- balanced design
- in line tolerancing
- spool & sleeve style
We can be Multi-purpose...
… allowing us to pipe our 5 ported 4 way
valve more than 50 different ways,
-
vacuum and/or pressure
dual pressure
back flow
2 way, 3 way, 4 way and 4way dual exhaust
- etc.
We can also have a Detent...
- holds valve in place
- in vertical attitude
- in loss of power
- changes a momentary signal to a constant
condition
- allowing your PC (programmable controller)
to send an instant signal
(.000002 sec) to change a condition
Symbology:
P