Note: Descriptions are shown in the official language in which they were submitted.
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The invention of which the present disclosure is offered
for public dissemination if adequate patent protection is available
relates to the field of providing safe hermetic seals for actuators
by which something inside of a highly isolative process apparatus
may be actuated from the outside. The term "highly isolative" is
used here with respect to apparatus from which nothing must be
permitted to escape, an example being a nuclear reactor.
The essential principles of safe sealing used in this
invention were taught by the applicant's prior United States Patent
No. 3,933,052. Hermetic sealing of the actuator was accomplished
by use of a diaphragm, actually a bellows, which permitted
necessary movemen-t oE a par-t oE -the actuator while providing a
hermetic seal be-tween :i-t and the highly isolative appara-tus. Such
hermetic sealing by a diaphragm was old, but according to the
underlying principle of that patent, it is given a previously
unattained safety by confining a sealing liquid on the outside of
the diaphragm and using it to apply to the outer face of the
diaphragm a compensating pressure exactly equal to the pressure
applied to the inner face by the highly isolative apparatus.
As is oEten the case, the structure worked out for
initially embodying this principle was relatively co~plex. For
example, it included three additional diaphragms or bellows besides
the one forming the main hermetic seal. According to the present
invention, a simplified diaphragm system is provided in which the
equalized compensating pressure results from the fact that the
diaphragm system can accommodate itself positionally to the volume
of the confined sealing liquid which is therefore placed under this
compensating pressure by the diaphragm system.
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Specifically, the present invention provides a valve
apparatus used in controlling fluid in a wo:rking environment and
seallng the working environment from an external environment, said
valve apparatus comprising: a valve housing having an external
opening exposed to the external environment and having a chamber
in communication with said external opening and said working
environment, an actuator means mounted for longitudinal movement
within said external opening and said chamber so as to control the
fluid in the working environment, a first flexible membrane means
disposed in said chamber and connected to said housing, a second
flexible membrane means disposed within said chamber and connected
to said actua-tor means, and a guiding means disposecl with.i.n sa:i.d
chamber and movable rela-tive to said actuator means, said guiding
means being connected to said Eirst and second flexible means so
as to guide said first and second flexible means as said first and
second flexible means move within said chamber.
The sealing liquid must ordinarily be confined behind the
hermetic diaphragm by a non-hermetic seal such as one using packing
rings or a rotary seal for the actuating shaft where it passes
through the seal housing to the external atmosphere. According to
the prior patent, the minute seepage of sealing liquid through such
an outer seal caused no great difficulty because this sealing liquid
could be replenished as needed through a separate valved replenish-
ment port. Of course, if the packing gland deteriorates to the
point of leaking badly, constant replenishment would become a
problem. According to the present invention, lt is possible to
replace the packing gland wlthout loss of the compensating pressure
on the sealing liquid. This is accomplished by letting the
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diaphragm system extend, as the sealing liquid is lost through the
outer seal, to a terminal position at which it creates a temporary
seal between the outer seal and the confined sealing liquid. This
temporary seal may serve both for maintaining the sealing liquid
confined so that it can exert the compensating pressure on the
diaphrgam and also to permit removal of the packing gland and its
replacement.
The present invention also incorporates a fail-safe
feature. There will be no disaster if there should be a failure to
replenish the sealing liquid when some or much of it has leaked out
through the packing. Ins-tead, the diaphragm sys-tem, as it expands
to occupy the space left by the leak:Lng sealing liquid, comes to a
safe terminal point. In one Eorm, at thls point -the dlaphragm is
s~ructurally restrained in a manner -that prevents rupture of the
diaphragm. In the other form a temporary seal is formed to prevent
Eurther loss of liquid. Under either condition it may not be
possible, or may be difficult, to operate the control actuator.
This seeming disadvantage is actually an advantage in that an
operator who attempts to operate the actuator will realize that
special servicing such as the supply of more sealing liquid is
required.
~ dvantages of the invention will be more apparent from
the following description, and from -the drawings.
FIGURE 1 is a sectional view, approximately along an
axial plane, of one preferred form of the invention.
FIGURE 2 is a fragmentary view similar to FIGURE 1 but
showing the diaphragm fully ex-tended.
FIGURE 3 is a sectional view of another preferred form
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of the invention, -taken approximately on an axial plane.
FIGURE 4 is a fragmentary view similar to a portion of
FIGURR 3 but showing the terminal or fully extended position of
the membrane system.
Although the following disclosure offered for public
dissemination is detailed to ensure adequacy and aid understanding,
this is not intended to prejudice that purpose of a patent which is
to cover each new invention concept therein no matter how others
may la-ter disguise it by variations in form or additions or further
improvements. The claims at the end hereof are intended as the
chief aid toward this purpose, as it is these that meet the require-
ment of pointing out the parts, improvements, or combinations in
which the inventive concepts are ~ound.
Both forms oE the present invention are concerned with
maintaining a reliable hermetic seal between a movable actuator
shaft 11 and an isolative apparatus 12 within which a valve or
other piece of equipment is to be actuated by the actuator 11. The
apparatus 12 is isolative in the sense that some process takes
place within it that must be kept isolated from the surrounding
atmosphere. One example is a nuclear reactor within which radio-
active particles are in the process atmosphere which must not be
allowed to escape even in minute quantities. The present invention
assumes that relatively limited movement of the actuator 11 is a~1
that is required. In FIGURE 1, both limited pivotal movement and
limlted longitudinal movement could be required, whereas in FIGURE
3 it is assumed that limited longitudinal movement is enough.
In FIGURE 1, the main element of the hermetic seal is a
diaphragm 13 made of an elastomeric material immune to or highly
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resistant to the process a-tmosphere. The material known as
neoprene rubber is an example of an elastomer which would be suit-
able for the diaphragm for a great many process atmospheres.
It may be assumed that the diaphragm 13 is molded to a
shape having approximately the cross section shown in FIGURE 1, the
shape being also described as generally tubular but doubled back.
One end of the tubular structure is sealed to shaft 11 by a
ferrule-like hose clamp 14 while the other outer end of the tubular
diaphragm structure is sealed between base plate 16 and flange 17
with sufficient clamping force developed by the screws 18 to ensure
a hermetic seal. Although the base plate may be secured to the
isolative apparatus 1.2 in a varlety of manners, perlpheral we]dlng
has been lllustrated because of lts dependable nature as a hermetic
seal.
It will be apparent that one face of the dlaphragm 13
which may be called its inner face is exposed to the process atmos-
phere or working atmosphere of -the isolative apparatus 12. Accord-
ing to the prior patent of the present inventor, the outer Eace of
the dlaphragm 13 ls exposed to a seallng llquld whlch ls confined
adjacent to the diaphragm so that lt can exert on the outer face of
the diaphragm a pressure exactly or approxlmately equal to the
pressure on the lnner face of the diaphragm 13 so as to protect the
diaphragm 13 from any rupturing differential force which would
otherwise result from a high pressure on the inner face of the
diaphragm. According to the present invention, the sealing liquid
is conflned with the space 21. Part of this space 21 is between
the diaphragm 13 and housing 22 which is secured in place by its
flange 17. The confined space 21 may also extend between the
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diaphragm 13 and actuator 11.
In order for the sealing liquid to be confined within the
space 21, there must be an outer seal between the housing 22 and
the shaf-t 11. It must be capable of withstanding pressure equal to
the process atmosphere pressure. Because the shaft 11 must move
with respect to the housing 22, practical considerations dictate
the use of a packing seal 23 or other rubbing type of seal. The
packing may be kept under necessary pressure by a packing gland or
nut 24.
Some means should be provided for forcing the sealing
liquid into the space 21. This has been illustrated as a conven-
tional nipple 26 for a grease gun. Such nipples conventionally
i.nclude a ball check valve so that grease can be forced into the
space 21 under pressure but cannot flow out from this space through
the fitting 26. A plug type of seal may be provided if greater
dependability is required. The light grease such as is commonly
used in grease guns is an ideal type of sealing liquid.
Some means should be provided for knowing when the supply
of liquid sealant in space 21 should be replenished through the
nipple 26 (unless replenishing is automatic). According to FIGURE
1, the seepage of sealing liquid past the packing 23 is caught in
a transparent jar 31 which may have thereon an indication of the
level which, when reached by the escaped liquid wlthin the jar 31,
indicates the need for supplying replacement liquid through nipple
26. Alternatively, the jar 31 could be graduated, with markings
indicating the number of strokes of the grease gun needed to replace
the escaped liquid. Of course, it is desirable that the quantity of
escaping liquid be as small as possible. Hence, two sealing rings
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23 have been shown between the drain por-t 33 and space 21. To be
sure that all escaping liquid is trapped in jar 31, a third sealing
ring 34 may be provided on the outside of a drain ring 36. The
gland 24 compresses all of the seal rings 23 and 34 so that they
spread to engage the actuator 11 with suita:ble pressure for forming
a seal without causing objectionable resistance to the movement of
actuator 11. In the event of continuing leakage of sealing liquid
from space 21 without replenishment through nipple 26, diaphrgam 13
would eventually stretch to the position shown in FIGURE 2. It will
be observed that there is still no danger of rupture of the
diaphragm 13 by pressure of the isolative or process a-tmosphere
against -the inner surEace of diaphragm 13, because subs-tan-tially
the en-tire sur:Eace o:E d.iaphragm 13 is supported by either the
inner surEace of housiny 22 or the sur:Eace oE sha.Et or ac-tua-to:r 11.
FIGURE 2 illustrates a visible clearance be-tween -the actua-tor 11 and
the housing 22, but this is exaggerated for the sake of illustra-
tion. There should be only enough clearance, if any, to ensure
easy movement of the actuator 11. With such a small clearance, it
is immaterial that the diaphragm will. be unsupported in the very
small area where -this clearance is found. In fact, process pres-
sure which might tend to burst the diaphragm 13 merely presses it
firmly against both actuator 11 and the adjacent portion o-f housing
22 so as to form a temporary additional seal between the housing
and the shaft. This permits replacing the packing rings 23, in the
event that they have deteriorated to the point of permitting exces-
sive leakage of the sealing liquid. Of course, to replace them the
packing gland 24 is removed.
The surfaces supporting the diaphragm are smoothly con-
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toured (free from corners) so that the diaphragm will not be sub-
jected to excessive local stressing.
In some instances the elastomeric diaphragm of FIGURES 1
and 2 may be undesirable and the use of metal bellows may be pre-
ferred. If rotation or substantial pivoting of the actuator is
required, a sealed drive such as that of the prior patent mentioned
may be needed. However, if only longitudinal movement of the
actuator is required a bellows system having considerable resem-
blance to the features of FIGURES 1 and 2 may be used, as shown in
FIGURE 3. Here, the shaft or actuator llA is shown extending into
an isolative apparatus 12. It might, however, extend merely to or
toward the isolative apparatus, termlnating at a point short oE the
appar~tus where it coulcl perEorm such a function as press:ing a con-
trol button.
The hermetic seal in this instance is illustrated as a
bellows system including an outer bellows 41, an inner bellows 42,
and a piston 43 to which both of the bellows are hermetically
attached as by brazing. The lower end of bellows 41 is hermetically
attached to housing base 46 and the lower end of bellows 42 is
hermetically attached to actuator llA. Thus, the bellows system
forms a hermetic seal between the housing base 46 and the actuator
llA. The housing base 46 is provided with a flange 47 which is
hermetically attached, as by peripheral welding, to the isolative
apparatus 12.
One of the reasons why an elastomeric diaphragm may be
unsuitable is if the temperature of the isolative atmosphere might
be too high for it. With such high temperatures in mind, the hous-
ing base 46 has been illustrated with cooling fins 48. If
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necessary, there could be further cooling as by circulating a
cooling medium which, after absorbing heat from the seal structure
would pass through a heat-dissipating radiator and return. The
cooling medium could be the sealing liquid, being drawn from and
returned to the confined sealant space 21 wi.thin the housing 49 and
outside of the bellows system 41, 42 and 43. Of course, the circu-
lating cooling system should, in this instance, be hermetically
sealed and of a nature to be a branch of the confined space 21.
The piston 43, in FIGURE 3, preferably has a free-sliding
fit with housing 49, and either a free-sliding fit or a slight
clearance around actuator 11~. It is thus able -to accommodate
itself to the quantity of seallng liquid confined withln space 21,
much of which wil:l usually be above piston ~3. The p.i.ston ~3 will
therefore transmit to the sealing liquid the pressure of the iso-
lative atmosphere, so that the sealing liquid located externally of
the bellows 41 and 42 will have the same pressure, or substantially
the same, as the isolative atmosphere. Thus, there will be the
compensation descri.bed in the prior patent so that the pressure of
the internal atmosphere will have no tendency to rupture the
bellows.
FIGURE 3 illustrates diagrammatically a system for main-
taining within the space 21 an ideal quantity of sealing liquid.
This is accomplished by automatically replenishing the liquid to
whatever extent leakage occurs past packing rings 23. This auto
matic replenishing system may be considered diagrammatic inasmuch
as its details will be largely a matter o~ choice by a particular
designer. It should have a constantly pressurized source 51 for
the sealing liquid. The pressure should be a little higher than
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any to be encountered in -the isolative atmosphere. If only moder-
ate pressures will be in the isolative atmosphere, the source
could be gravitational, such as a raised tank of the liquid. If
very high pressures are to be encountered in the isolative atmos-
phere, the source could be a closed tank of the sealing liquid with
gas applied above it in the tank from a gas cylinder to maintain
it under a predetermined pressure.
The pressurized source 51 should supply its sealing
liquid through a valve 52 biased to the closed position but pressed
open when piston 43 engages the tip of valve ball 53. This will
press the valve ball 53 out of engagement with its seat so that the
pressurized source can force sealing liquid into space 13, moving
piston 43 downwardly (retracting it) untll it allows valve ball 53
to s~at and shut ofE the Elow oE sealing liquid.
In FIGURE 3, the condult between the pressurized source
and valve 52 has been illustrated as including a check valve 56,
an on-off valve 57 and a reducing valve 58. The check valve 56 pre-
vents any loss of pressure on the sealing liquid in space 13 in the
event of failure of the supply system. The on-off valve 57 wil~ be
closed when it is desired to change the packing rings 23, as will
be described. The reducing valve 58 may not be needed unless the
pressure of the pressurized source would otherwise be much higher
than the maximum expected pressure of the isolative atmosphere. If
~ a cylinder of pressurized or liquified gas is the source of the
; pressure, this reducing valve would be in a different position,
where it controls the gas pressure.
With automatic replenishing system illustrated in FIGURE
3, the leakage-trapping jar 31 is less needed than in FIGURE 1, but
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lt may be provided anyway as a matter of cleanliness and so that
need for replacing packing rings 23 can be detected. In the event
of the excessive leakage of these packing rings, the valve 57 will
be closed so that the leakage will allow piston 43 to move upwardly
until it squeezes O-ring 61 to form a temporary seal between housing
49 and actuator llA as seen in FIGURE 4. With this temporary seal,
the nut or gland 24 may be removed to permit replacement of the
packing rings 23. The attendant's practice will probably be to
loosen gland 24 as soon as he has closed valve 57, so that the seal-
ing liquid will quickly leak through packing rings 23 until O-ring
61 has been sufficiently distorted to effectuate its temporary seal.
When -the leakage stops, the attendant will remove gland 24 and
replace the packing rings 23. Ile will then reopen valve 57 which
will supply enough replacement sealing liquid to thrust the piston
43 downwardly (retracting it) until it allows valve ball 53 to seat
and shut off the replacement flow of sealing liquid.
As the piston 43 is moved away from O-ring 61, the O-
ring would return to its normal position in which it is out of con-
tact with actuator llA so as not to be worn or flattened by the
movements of this actuator. It can hold itself in place by
resilient engagement of its outer peripheral surface with housing
49. Also, housing 49 could be provided with a lip extending
slightly under the greatest diameter of O-ring 61 to ensure its
retention.
Although anyone desiring to use this invention will prob-
ably do his own engineering, some effort has been made to illus-
trate the invention in practical form. It is assumed that much of
the assembly will be performed before the housing 22 or 49 is
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applied. Access to clamping ring 14 may then be achieved by raising
the outer portion of diaphragm 13. Likewise, access to brazing the
lower end of bellows 42 to actuate llA can be achieved by upwardly
compressing the bellows 41.
From the foregoing, it is seen that an improved and
simplified device using the principles of this applicant's prior
United States Patent No. 3,933,052 has been provided. In this
instance, the same membrane which forms the flexible hermetic seal
between the transmission means or actuator and the seal housing
transmits to the compensating sealing liquid on the extrior of the
membrane the pressure of the working a-tmosphere. This is accom-
plished by havlng a portion oE the membrane accommodate i-tself in
its position to the quantity oE conEined sealing liquid. This,
in turn, requires an excess of the diaphragm material so that a
portion of it can move independently of the actuator.
In addition the improved pressure-compensated sealed
transmission device of the present invention has "fail-safe" charac-
teristics. If the outer seal for the transmission means should
fail, or if the attendant fails to replenish sealing liquid which
has slowly seeped through this outer seal, the membrane still will
not be subjected to a rupturing danger resulting from a high
differential between the internal and external pressures, because
the membrane must stretch to a point at which it is Eully protected.
It may be that the transmission means may no longer work easily but
that fact will warn the attendant that the device needs replenish-
ment of the liquid. Indeed, the ideal would be to incorporate some
automatic locking device which prevents operation of the trans-
mission means while it is stretched to the limit.
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In 1-ts preferred forms, the present invention also forms
a temporary seal between the confined sealing liquid and the outer
seal, when the limit in stretching (or the terminal position) has
been reached, so that the outer seal may be serviced, as by replac-
ng it.
One preferred form of the invention includes automatic
means for replacing the sealing liquid as needed. Stretching of
the membrane to the terminal point, with the advantages previously
mentioned, would thus only occur in the event of failure of the
automatic replenishing device, or in the unli]cely event that the
outer seal failed so thoroughly as to let leakage exceed the supply
furnished by -the automatic replenishing device. A preferred Eorm
oE the automatic replenishing device can be shut oEE, when ServiCinCJ
of the outer seal is desired, to permit the membrane to stretch to
its terminal point and produce the temporary seal mentioned.
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