Welcome to a

School

Dale L. KohlsmithDale L. Kohlsmith

Director of TrainingDirector of Training

Numatics, Inc.Numatics, Inc.

The Heart of Every Numatics Valve: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 assemblethe spool and sleeve

Because the spool and sleeve are matchedwith 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 smoothfinish, centers the spool within

the sleeve preventing metal to metal contact...

Providing a friction less fit (i.e. an air bearing effectwith no wearing parts)

How close is the clearanceneeded to allow

the air bearing?

“That which is sufficient to createthe air bearing effect”

Is there a required pressure needed to maintain the air bearing effect?

Yes, about 1/100 psig or a vacuum toforce air across the lands.

Can a rubber packed spool & sleeve havean air bearing?

No, this is why they generally must be lubricatedto 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...

ConstructionPoppet Type --- Mechanical/Solenoid/Pilot

Position 1

Flow paths when “B” pilot is pressurized or in command

EXHAUST

SUPPLY

CYLINDER

CrossoverEXHAUST

SUPPLY

CYLINDER

EXHAUST

SUPPLY

CYLINDER

Flow paths when “A” pilot is pressurized or in command

Position 2

ConstructionSpoppet Type --- Solenoid Air Pilot

Position 1

Flow paths when “B” pilot is pressurized or in command

Crossover

Flow paths when “A” pilot is pressurized or in command

Position 2

EXH IN EXH

CYL CYL

EXH IN EXH

CYL CYL

EXH IN EXH

CYL CYL

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 effectivedynamic seal?

“...they (“o”rings) are not a ‘universal’ seal applicable to all sealing problems. Certain limitations mustbe imposed upon their use, among them, high temperatures, high frictional rubbing speedsfrictional rubbing speeds,

cylinder ports over which seals must passcylinder 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 sleeveand allows for equal masses.

Spool in body valves can jam due to torqueing orthermal expansion or contraction.

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)

How hard?

Why round holes in the sleeve?

- to act as a rudimentary filter to predetermineparticulate size allowed to enter thespool area (where it shall be chopped)

& to still provide optimal air flow through the valve.

Because Numatics spool & sleeve do not havedynamic “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 mistakenfor burrs

The spool lands aremade razor sharp.

This along with the equallysharp holes will guillotine

any stray particulate.

Therefore the valve is self-cleaning.

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?

Can an “O” ring chop particulate?

Balanced Design?

Balanced Design…

“There is no relationship to the pressurepassing 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

… 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 be Multi-purpose...

We can also have a Detent...

- holds valve in place- in vertical attitude- in loss of power

- changes a momentary signal to a constantcondition

- allowing your PC (programmable controller)to send an instant signal (.000002 sec) to change a condition

Symbology:

P