LABYRINTH DISK STACK HAVING DISKS WITH INTEGRAL FILTER SCREENS

PILE DE DISQUES A LABYRINTHE AYANT DES DISQUES A FILTRES INCORPORES

English Abstract

Case 4239

LABYRINTH DISK STACK HAVING DISKS WITH
INTEGRAL FILTER SCREENS

ABSTRACT

A multi-turn labyrinth disk (10) is provided for a
pressure reduction disk stack (12) which has an integral
filter screen (34). The filter screen (34) comprises a
series of small area passages (A2) located on the peri-
phery of the disk (10) which lead to a common high
capacity radial passage (32) used to supply a series of
multi-turn labyrinth paths (18).

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for subjecting particulate fluid flow to
a labyrinth passage between the inlet and outlet of the
device comprising:
a multi-turn labyrinth disk stack with integral inlet
filter having a series of disks with inlet and
outlet circumferences forming the inlet and
outlet of said disk stack;
means for allowing fluid flow in the device to flow
from the inlet circumference of the disk stack
to the outlet circumference of the disk stack;
each disk of said series having a series of small
area openings located around the entire inlet
circumference of said disk forming an inlet
filter for the particulate fluid flow through
the device and leading to a large circumferent-
ial passageway;
each of said series of disks having a series of multi-
turn passages located proximately to said large
circumferential passageway, each multi-turn
passage having a substantially constant area
significantly larger than the area of each of
said series of circumferential passages to
prevent the blocking of the passageway by a
particle of the particulate fluid flow passing
through the inlet filter of said disk; and
outlet means located on each of said series of disks
proximate to said multi-turn passages to exhaust



the particulate fluid from the disk stack of the
device.

2. A disk stack as set forth in claim 1 wherein said
outlet means on each of said series of disks includes a
pressure equalization passageway radially extending proxi-
mate to the outlet of said series of multi-turn labyrinths.

3. A disk stack as set forth in claim 1 wherein the
area of said multi-turn labyrinth passages of each of said
series of disks is significantly less than the total area
of the series of small openings.
4. A disk stack as set forth in claim 3 wherein on each
of said series of disks the area of said large circumferent-
ial passage is significantly larger than the area of one of
said multi-turn passages.
5. A disk stack as set forth in claim 4 wherein on each
of said series of disks said multi-turn passages are formed
by lands extending from the surface of said disk to a common
height to allow a flat surface to seal the passageways there-
between.

Description

~lZtit~




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LABYRINTH DISK STACK HAVING DISKS ~IITH
INTEGRAL FILTER SCREENS

TECHNICAL FIELD

The present invention relates to labyrinth disk
stacks generally and particularly to disks comprising
such disk stacks wherein the disks have an integral
filter screen.

BACKGROU~'D ART
. .

In labyrinth disk stacks which are used for pres-
sure reduction the fluid flow-may be from the inside
diameter of the disk stack to the outside diameter of
the disk stack or from the outside to the inside. The
latter is usually selected if the fluid passing through
the disk is apt to be contaminated with solid particles.
In this manner the solid particles too large to pass
through the disk passages collect on the larger diame-
ter where they are more easily removed and are less apt
to interfere with other valve parts frequently located
in the inner diameter.
~ assa~es in the disk may be of uniform cross
section area for fluids which do not expand with reduc-
ing pressure or may be designed to expand at a precise
rate with each turn to control the velocity as a fluid

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expands with reduced pressure. In either instance design
performance of the device is highly dependent on the
relative cross section area of each passage and any major
disturbance thereto can seriously affect the efficiency
of that passage and even lead to destructive velocities,
due to the fact that a reduction in passage area means
higher pressure drop and higher velocity at that point.
Since the fluids that such a stack will handle
often have dirt particles therein, such dirt particles
tend to block or restrict the inlets to the fluid passages
thereby reducing flow through the disk stack passageways
-and increasing the pressure drop across the inlets to the
passageways. The increased pressure drop wedges the dirt
particles into the inlets of the passageways as well as
the passageways themselves making any cleaning operations,
such as back-flushing, or other cleaning difficult if not
impossible. The blocked inlets and passages are progres-
sively rendered ineffective and the partial openings of
the passageways tend to erode the passageways due to the
increased velocity of the fluid flowing through the par-
tially blocked passageways.
The placing of separate screens and filters along
the periphery of the disk stack is expensive and cumber-
some since it requires not only an extra part to be addedto the disk stack but also adds another assembly step
thereby escalating the cost of the disk stack. Also the
blockage of a part of the screen renders the covered
labyrinths of the stack inoperative.

SUMMARY QF THE INVENTION

The present invention solves the problems associated
with known prior art devices as well as others by provid-
ing disks for a disk stack which disks have an integral

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filter screen. This integral filter screen includes a
multitude of reduced area inlets which allow low velocity
fluid flow into a common high capacity circumferential
passage proximate to the integral screen which radial pass-

age is used to feed the various multi-turn labyrinth passage-
ways of the disk stack. The low velocity and small pressure
drop across this integral filter screen reduces any tend-
ency for dirt particles to stick in the filter inlets or
openings thereby preventing the lodging of the particles
and allowing easier cleaning and back-flushing. The high
capacity circumferential passage feeding the various multi-
turn labyrinth passageways allows up to 70 to 80 percent of
the filter inlets or openings to be blocked before disk
performance is impaired since the radial passage will feed
all of the labyrinth passageways.
The invention provides a device for subjecting part-
iculate fluid flow to a labyrinth passage between the inlet
and outlet of the device comprising a multi-turn labyrinth
disk stack with integral inlet filter having a series of
disks with inlet and outlet circumferences forming the
inlet and outlet of said disk stack; means for allowing
fluid flow in the device to flow from the inlet circumfer-
ence of the disk stack to the outlet circumference of the
disk stack; each disk of said series having a series of
small area openings located around the entire inlet circum-
ferenceof said disk forming an inlet filter for the part-
iculate fluid flow through the device and leading to a large


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circumferential passageway; each of said series of disks
having a series of multi-turn passages located proximately
to said large circumferential passageway, each multi-turn
passage having a substantially constant area significantly
larger than the area of each of said series of circumferential
passages to prevent the blocking of the passageway by a
particle of the particulate fluid flow passing through the
inlet filter of said disk; and outlet means located on each
of said series of disks proximate to said multi-turn passages
to exhaust the particulate fluid from the disk stack of the
device.
These and other aspects of the present invention will
be more clearly understood from a review of the following
description of the preferred embodiment when considered
with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
-
Fig. 1 is a perspective view of a multi-turn laby-
rinth disk stack utilizing the disks of the present invent-
ion.
Fig. 2 is a side view of one disk of the Fig. 1 disk
stack.
Figs. 3 and 3a are top views of the Fig. 2 disk.

DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now -to Figs.l through 3, it will be seen
that a series of disks 10 may be stacked together into

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a disk stack assembly 12 by having the bottom surface 14
of one disk 10 placed on top of the top surEace 16 of the
adjoining disk 10 thereby sealing the multi-turn laby-
rinths 18 of each disk 10 with the flat bottom surface 14
of the adjoining disk 10. The very last top disk of the
stack assembly ]2 may be sealed with a flat cover sheet
19. The disk stack assembly 12 is held together in a
well-known manner by means such as a series of nuts 20
extending through aligned alignment holes 22 of each
disk 10 to hold the disk stack assembly 12 in proper
orientation and rigidity. Bolts 24 are threaded onto the
nuts 20 to compress the disk stack 12 and prevent fluid
leakage therefrom although the stack assembly 12 could also
be preloaded and brazed into a single unit. The assembled
disk stack assembly 12 may then be inserted into various
devices such as control valves which are used to redllce
fluid pressure as well as the noise usually present in many
pressure reducing control techniques.
This particular disk stack assembly 12 is intended
to allow fluid flow from the external periphery of the
disk stack assembly 12 through each of the multi-turn
labyrinth paths 18 of each disk 10 of the disk stack assembly
12 and into a common central opening 26 of the disk stack
assembly 12 from where it is exhausted.
With particular reference to Figs 2 and 3~ it will
be understood that each disk 10 has 24 sectors 28 each
having a multi-turn labyrinth assembly 18 defining a fluid
flow path of approximately 24 turns and of substantially

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identical width. Since the height of the lands 30 defining
the multi-turn sector labyrinths 18 is substantially ident-
ical, the cross-sectional area of the albyrinth passage 18
is substantially identical and shall be referred to as area
Al.
A high capacity of circumferential passage 32 is
located along the outside periphery of each sector 28 and
supplies fluid to all of the 24 sector passageways 18.
An integral filter screen 34 is circumferentially located
proximate to the circumferential passage 32. The cross-
sectional area of the high capacity common circumferential
passage 32 shall be referred to as A3 and this area A3 is
made greater than the area Alof the labyrinth passageway
18 to insure that the passage 32 will be able to supply
fluid to all 24 sectors of the labyringh passageways 18.
The integral screen assembly 34 has multiple inlet
passages per sector, each passage having a cross-sectional
area A2. The total area of the inlet massages A2 is made
to be also greater than the area of the labyrinth passage
Al to insure sufficient fluid flow to the passage 32.
From the forementioned area ratios, it will be seen that
the relative velocity of the fluid flowing through the
screen areas A2 is relatively low in velocity as compared
to the fluid velocityin the passageways 18 which have an
area of Al. Should some of the integral filter screen 34
areas A2 be blocked, the fluid flow would increase through
the remaining areas A2 but they would still feed the common
high capacity circumferential passage 32 in sufficient




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quantity to allow fluid to be supplied to the entire laby-
rinth passageways 18 of the entire disk 10. In fact 70 to
80 percent of -the areas A2 would have -to be blocked before
flow would be impaired to the passageways 18.
The outlet of the multi-turn labyrinth 18 exhausts
into a common outlet ring 36 used to equalize pressure
at the outlet o the disk. This ring 36 equalizes the
pressure and flow through the passages 18 which may be
throttled by plug (not shown) movement in the central outlet
26. Such a pressure equalization ring 36 tends to elimin-
ate plug vibration and controls the tendency for the plug
to move tightly against one side of the bore with result-
ing increased friction and wear on that side of the bore.
An outlet 40 extends from the pressure equalization ring 36
into the central opening 26 to allow the fluid which has
been reduced in pressure to be exhausted evenly out of
the disk stack 10, 12.
Certain modifications and improvements will occur
to those skilled in the art upon reading this specificat-
ion. As an example the integral filter screen could be
located on the inner diameter of the stack as opposed to
the shown location on the outside diameter of the stack.
The invention is equally applicable to a steam or gas
pressure reductionvalve where the fluid is compressible
and expands proportional to the progressive pressure re-
duction steps, necessitating a progressively expanding
passage area Al rather than the constant area Al required



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for noncompressible liquid as described above and pictured
in Figs. 1, 3 and 3a. It will be understood that such
improvements and modifications have been deleted herein
for the sake of conciseness and readability but are proper-
ly intended to be within the scope of the following claims.