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Патент USA US2545888

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March 20, 1951
L. KOOISTRA
2,545,886
OPENABLE CLOSURE FOR CHAMBERS UNDER SUPERATMOSPHERIC INTERNAL
PRESSURE AND ASSOCIATED FLUID PRESSURE MEANS FOR
PREVENTING THE ESCAPE 0F FLUIDS THEREFROM
Filed Sept. 21, 1945
2 Sheets-Sheet 1
I
INVENTOR
lamberzf ffooz'sz?ra
Pig. 2
BY
M,
ATTORNEY
March 20, 1951
L. KOOISTRA
2,545,886
OPENABLE CLOSURE FOR CHAMBERS UNDER SUPERATMOSPHERIC INTERNAL
PRESSURE AND ASSOCIATED FLUID PRESSURE MEANS FOR
PREVENTING THE ESCAPE OF FLUIDS THEREFROM
Filed Sept. 21, 1945
,
2 Sheets-Sheet 2
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lNVENTOR
l amberé X00156”;
M
ATT'ORNEY
Patented Mar. 20; 1951
‘were
UNITED STATES PATENT 0mm}!
2,545,886
OPENABLE CLOSURE FOR CHAMBERS
UNDER SUPERATMOSPHERIC INTERNAL
PRESSURE AND ASSOCIATED FLUID
PRESSURE MEANS FOR PREVENTING
THE ESCAPE OF FLUIDS THEREFROM
Lambert Kooistra, Akron, Ohio, assignor to The
Babcock & Wilcox Company, Rockleigh, N. J.,
a corporation of New Jersey
Application September 21, 1945, Serial No. 617,719
9 Claims.
1
(Cl. 110-479)
2
The present invention relates in general to the
construction and operation of closure members
.
in the gases are maintained at superatmospheric
. pressures and an opening is provided affording
access to the interior of the chamber.
; ;
especially adapted for use with furnaces or other
similar closed chambered structures operating
A related object of my invention is the pro
vision of apparatus adapted to open and close
a furnace wall port while preventing the ejection
of high pressure gas through the port through‘.
out the opening and closing periods.
.“
under high internal gaseous pressures consider
ably above atmospheric and requiring access at
intervals without necessitating a shut-down or
causing interference with their prescribed func
tions. Structures suitable for the practice of my
' Another object is the provision of a closure
invention include boilers for example having a 10 member movable relative to a furnace wall open-1
combustion chamber together with a communi
ing wherebythe escape of high pressure gas ‘is
eating gas ?ow space wherein the gases of com- - ;
bustion are utilized mainly for the generation
prevented throughout substantially the entire
range of closure member movement.
.
and heating of vapor. In other suitable struc
An additional object is to prevent the ejection
tures the high pressure gases may be produced 15 of high pressure gas from a furnace wall open
for various other purposes such as for utilization
ing by directing ?uid toward the opening in a
in processes or as ahot motivegaseous ?uid for
series of high velocity jets converging within a
gas turbines.
tapering passage of minimum flow area adjacent
In such installations the enclosing walls are
the opening.
‘
‘ ‘
often ?uid cooled, to provide protection from 20 An object is also to provide, in conjunction _
high furnace temperatures and further are pref
with a furnace operating under superatmospheric
erably made gas-tight throughout to avoid the
internal pressures and having an access opening
troublesome andv dangerous’ condition resulting
in a ?uid cooled wall thereof, means for pre
from the ejection of high temperature'gases and
venting the ejection of hot products of combusé
25
other products of combustion. When a wall.
tion through the opening comprising a series of
opening is provided through which access may be
high velocity ?uid jets converging inwardly
had to the interior. for cleaning or other purposes
toward the opening within a tubular member
it is essential that the opening be ?tted with
secured to tubes lining the wall, the tubular mem
closure means suitably constructed and arranged
ber constituting a frame for a door adapted to
so as to maintain the continuity of the gas-tight
close the opening.
~
_
'
I
wall construction. Further, since it is essential
A further object is the provision "of apparatus
in many instances to gain access to the interior
associated with a furnace wall opening whereby
during normal furnace operation, it is highly de
at one period a ?uid under pressure is utilized
sirable to arrange in some manner to adequately 35 to prevent the ejection of furnace gases through
control or to actually prevent the discharge of
the opening and at another period is utilized to
hot products of combustion when the closure
means is removed or shifted to expose the
look a cover in place ‘over the opening.
opening.
There is an “indication in the prior art that
attempts have been made to restrict the escape’
of combustion gases through a- furnace wall
opening, in some instances through the use of air
or steam jets directed'either across the opening
in the form of a'screen, or' into the opening 45
toward the-interior of the furnace. ‘However,
the prior-art structures are inadequate for op
posing the discharge of high pressure gases andv
moreover do not provide among other features
the required interrelation between operation of
the closure means and the initiation of jet action.
to assure complete control of gas discharge under
all conditions.
>
>
I
Other objects include the provision of a closure
member adapted to be moved into open and;
closed positions relative to a furnace wall open-'1
ing and while the member is in the open pos‘i-4
tion to prevent the ejection of high pressure gas‘
from the‘ furnace by a'series'ofh‘igh velocity‘
?uid jets controllable only" when ‘the member is
inthe closed position.
'
’
3
_' ‘
‘.
The various features of novelty which char-ac
terize my invention are pointed out with ‘partic
ularity in the claims'annexed' to" and forming'ga'
part of this speci?cation. For 'a'better under
standing of the invention, its operating advan-v
tages and'speci?c ‘objects attained‘by' its use,
reference shouldibe’had to the’ accompanying '
' drawings and'descriptive matter in' which I have
An object of my invention therefore is to prel' ' illustrated and described a preferred embodiment
vent the ejection of gases from a chamber where— 55 of my invention.
/
2,545,886
'
-4
3
enters at substantially the same velocity and di
rection and gradually merges with the burning
Of the drawings:~,
Fig. 1 is a side elevation, mainly in section, of
stream of primary air and fuel, without disrupt
the lower portion of a steam generating unit
ing the helical flow path of the latter or separat
embodying my invention;
5
Figs. 2 and 3 are enlarged front and side ele
ing the primary air-fuel stream from the cir
cumferential chamber Wall by a layer or" second
vations, respectively, of portions of the structure
~-ary ~air. Combustion is: substantially, completed
sin-the primaryf'urnace‘chamber and the resulting
Fig. flwisla plan ‘section taken-along line “4-4
hot gases are discharged through the coaxially
of Fig. 3.
The steam generating unit illustrated in Figs. 10 larranged rearwardly ?aring outlet throat 25
which is formed with an angle of ?are of ap
1 and 2 is substantially the same as that‘dis
proximately'lti‘i‘to its axis to provide minimnm
closed in my copending joint application with
pressure drop'the'rethrough.
H. J. Kerr et al., Serial No.l552,1l20,' ?led August
.-~---According to one method of operation all of
31, 1944, except for certain»_featuresqpeculiar-to
the present invention as will 'appearrhereinafter, 15 the cembu'stion‘air may be supplied at a high
positive pressure, e. g. 40 in. 1-120, to the primary
the unit including a cyclone type of primary fur
‘furnace chamber and a decreasing positive pres
‘sure maintained throughout the remainder of the
nace 10 from which the products'iof'combustion --\'
?ow into a secondary furnace l2."- ‘The’walls'of
both furnaces are lined with wall cooling tubes
suitably arranged and connected so‘ as ‘to? form 20 ~1iOpen-i-i-‘1gs are provided in the Walls of the unit,
unit’
.
U,‘
.
,.
circuits paralleling the circulatory system of the
at various positions, through which operation of
boiler, the walls being of improved construction "
enabling the unit to beimaintained under rela
lance or other implement _inserteclwton dislodge
i'sl-agi‘onq'o'thfer‘iaccum ‘ ‘tio'rwisjjorflan oilburner or
tively, highaipositivei internal» pi‘ess'ure‘s'i through
_outy‘aslriully disclosed in the‘afo‘resaid prior ap
plication.
fI-‘?‘ri'
J; .t'.
:1.
the'furnace may be observed and, if desired, a
25
other device v"iitis’ert'ed to "initiate the combustion
‘or fuel introduce
~
\- The cyclone-- type-i primary?‘ .furnac‘e ? ID" "list . of
“
horizontally elongated substantially circular cross
section ‘and preferably ?red-*byiaipri'm'aryi burner
lkarrangednoaxially 'iithereoff in :‘the ‘outer "end
wall M, the burnerlbeingio?a suitable ‘type ‘for the
kindzof iuellto'ibe‘?red‘ which .for. present vpurposes
may be assumed .to beia crushed or granular ~fue1,
‘ oughpipe l5.
"
‘if n 7'
"
_erme'ansforone‘b'f su'ch’o'pen
.. $553‘. and 1%.‘ Where for. sim‘
ati'o anvbseltve?pn‘andilancine
“'
whee to as .opemneizij be‘.
.
I. bes".?g..‘assdcieted
with 'Yaff‘s‘ide'lwall» 29‘ of
jse‘condaryifurnace 1,2,
The" wan 2 sli‘ricmdéfsifa ‘ \ etal _, ka‘s'mg‘" 2 gaff welded
such
1111A‘ stream
1:287 bituminous
"of primary
"or semi-bituminous
'air'and granular
‘coal;
coal‘is
"1
35
tb'l‘t-héi outer side :ofwwall-tubes" 2})’ to j’pi , vide vwith
other walls of -‘similar5'constructio_ns'a? ‘completely
delivered at aiarelatively'zel'iigh “positive pressure
through the involute curved primary air-coal'pipe
sealed furnace‘ chamber ‘permitting operatic‘ , __
'li'ighpo‘sitiveiifu'i'f
' " "_
*jljooifs of“ the
~l5>which‘ opens tangentially into a'lower sideTpcr=
tion OfEbur-ner-T £13, 'thef‘e?eetive ?ow area of the
same 'ge'r'ieraf'type and f ‘
4' ‘ "
.
u'qr'rmy be‘ installed
slich. aw ihqvircled
pipe“ and : ‘thereby ithe' velocity of "the ' fuel-‘air 40
stream being“: controlled ‘by-a ' manually‘ operated
locations ‘3'66, 3w; etc, in walls of"the_1s_e_oondary
control damper IS. The burner is constructed to
impart a-iradia1.and'.forward motion‘to the en
a-wall‘ofthe'primaryjfurnace' I'D.’
tering'coaleair'streamf'and'the whirling stream
movestaxially'of the;prima'ry furnace in-a'helical
tubular‘ ir'a'r'ne'r'3'4 terminating‘ in "a conicaluinner
end portion-"ssfadiacént -‘th§“_op"ening 121 where it
is‘ secured 7as by ~w'eld'i'iig3to adjacentjwall tubes
~~
w
_.,.,
.
,A
-
~\
v‘
tion" throughout providing "a central passage '36
having‘ its wall portionm-g'l‘ adjacent vthev opening
at: the outer end of the burner 13 and a regulable
supplyzti‘ofrpreheatedwairr is.‘ delivered thereto ;
21 ~ or gradually reducing taper *tow'ardthe '_o1oen~w
ing";‘a1id ‘its wall portion 38 remote _from-the'open—
throughta'ducirv I 9 having‘an .involutefcur'ved'cons
nection tow the chamber '18, producinga whirling
stream of tertiary air which is directed axially
7"“:
'
~
"
ing of cylindrical‘formation; the tapering portion
31 _extendmg‘m substantially tangential‘ relation
to-"ltu'bes adjoining the opening Z'Iyfand being
''
joined'to the'cylindricalportion'38 by an inter
mediate‘ conical shoulder portion 39 facing the
‘'"ZAIII- axially‘? elongated “port 2 l- is ._ provided "for
admitting secondary air to the primary furnace
l0
a‘ pointangularly spaced approximately
li8ofltir'o'm- the point-ofientry of the primary air-“
fuel stream, the secondary air being'deliveredito"
thevportathrough'l a'imain ‘air duct'23f having "its
end;secti~on.?ttin’g=into and opening to the‘port'
2.l~,-:~the zvelocityrof. air‘ admission being controlled‘
byiwa ,rseries. of'dampers 24 arranged ito" maintain‘
the entering secondaryr‘airlstreamrlat all times?‘
along .ith'e-primaryriurnace chamber wall.'-* *1
Y1
' ,_
28;“ The-‘frame is-of‘bircular‘internal cross'sec
w
:circulan tertiaryair ich'amber I 8 'is arranged
of-"therburn‘ero
"
"The ' complete door7'assembly' ‘25 1 comprises a
path along‘ and iniconta'ct'ivith the‘cir'cular wall‘
.~..;.
furnace l2 and as indicated at 321g, tpzb‘an'dn 2p in
'The door frame fill'is' surrounded by a manifold
“extending axially from the outer end ofwthev
frainato'aloéation inwardly of 'tl'i'e‘shoulder 3'9."
Holes ‘42 are drilled through the inner wall “of
the'i'nainfold'a't the‘ sl’i'ou'lde'i‘?fl ‘for directing high
velocity *5 et'si’of 'air'ior other gaseous ?uid "into'Qthe
central passage ‘36 fthe ' air for -' ' ample being de-'
' liverediunder pressuie'oreo' ‘ sfi'; to the'manii
=5 "In accordance .with th'e'previous disclosure, the
fold'id‘l' through-‘1a pipeline: 53f having‘fa plug‘
primary air-fuel stream entersrthe?urnace cham " ‘ valve=45 therein? ZI‘l'ie'_'jet ‘holes or ports 42 "are:
arranged' _in" afcircul'ar'g rowfpi‘e'ferably ij at’ sub-1
beriinla;highivelocityzstreamwhirling"in a. clock
stantially equar circumferential‘. spacings," the
WiSEQdiI‘GClZiOIliWKh'! anvinner corfe' rof.v tertiary'v'air'
whirling
the.» same ‘direction? 1 .-The s r fuel-ail“ 70
mixture rapidly-‘ignites and‘thewburni'ng stream
?ows longitudinally of the ‘furnace chamber? "at "a
holes;42-'beingdrilledfi‘om‘ the front _face of the‘
manifold toiprovid'e' arr-outer row of: holes 45in
alignment ‘ther'eWith’i through "which the inner
holes‘v?z'may becle'a'ned uponre'moving the plug
high angular velocity in as?lm or layer following‘
screws '41‘; 'In"certaim'constructions where‘ it
a-helicali path along and vinrclose contact with the
furnace circumferential wall; r‘ The secondary air‘ 75 might not be possible to provide a corresponding
1 2,545,856
5
.
outer hole 46 for each inner hole 42, one or more
of the holes 42 could if necessary be cleaned from
inside the passage 36.
The frame 34 is symmetrically extended along
its horizontal diameter to provide two substan
tially semi-circular extension portions 48 and 49,
as shown in Fig. 3, each portion being formed
with a cavity 5| as shown in Fig. 4 providing a
continuation of the manifold space 4 I. The open
side of each cavity 5| ‘is closed by a. plug 52
screwed into the front wall of the frame and its
extension 48 or 49, the slot 52a facilitating assem
bly and removal. The plug 52- in extension 48
the inner face of the door plate 26a and possibly
interfering with opening movement.
In closing the door the operations are reversed,
?rst, the door plate 250. being swung into closed
position over the door frame passage 36 bringing
hole 51 again into alignment with the plug of
air valve 45. The valve is then turned off shut
ting off the supply of compressed air to manifold
44, except for a small amount of cooling air that
10 may be admitted, if desired, through a hole 13
in the plug of the valve. As a result of the ac—
companying drop in air pressure within the mani
fold, the springs 6| again force the hinge pin and
supports an axially movable hinge pin 53 about
latch pin inwardly to lock the door plate 26a in
which the door plate 26a is pivoted, while the 15 its closed seated position.
corresponding plug in extension 49 supports an
When a hole 13 is provided, the air admitted
axially movable catch pin 54. ,
therethrough serves to prevent hot gases from
Since the hinge pin 53 and catch pin 54 have
entering the passage 35 behind the door plate
similar mountings and are similarly actuated, a
26a, thereby helping to keep the door cool, and
description limited substantially to the illus 20 supplementing the cooling effect on the entire
trated catch pin assembly will cover the essential
door assembly resulting from the heat conducting
features of both. Accordingly, and referring par
engagement of the frame with the wall cooling
ticularly to Fig. 4, the catch pin 54 extends out
conduits 28. Additionally, if any slight outward
wardly from a manifold space 5| through a cen
leakage should occur, the leakage will be of air
tral hole 56 in plug 52, the pin having a slot 51 25 rather than of hot furnace gases.
formed in one side thereof adjacent its outer end,
During the period that the door is open, the
the axial width of the slot being greater than
air blown from holes 42 is directed toward the
the thickness of the door plate 26a at its circum
furnace chamber in high velocity jets converging
ferential edge 58. A disc 59 on the inner end of
at a point 14 for example along the central axis
the catch pin 54 serves as a seat for a spring 6| 30 of passage 36 in a zone of reduced flow area such
having one end bearing against the disc and its
as at or adjacent the restricted throat passage
opposite end against the inner face of the plug 52.
21 formed between wall tubes 28, the optimum
The spring 5| being under compression forces
the catch pin 54 inwardly so as to cause the outer
point of convergence being determined, by test
if necessary, with a view to rendering the jets
edge 62 of slot 51 to push against the outer face 35 fully eifectivein overcoming, the high static pres
of the door adjacent one end of its diameter,
while a similar spring 6| in extension 48 forces
the hinge pin 53 inwardly so as to cause the cotter
pin 63 through washer 64 to exert a correspond
sure of a given furnace under predetermined op
erating conditions.
‘
The improved form of closure means herein
disclosed is thus not limited in application to a
ing force against the door adjacent the opposite 40 boiler furnace operating at a positive pressure of
end of its diameter. Thus with the door 26 in
the order of 40 in. H2O, as indicated for the em
its closed position, as shown, and with a relatively
bodiment herein described, but may also be use
low or zero ?uid pressure within the manifold
fully applied to furnaces of various types oper
spaces 5|, the springs 6| serve to lock the 'door
ating at positive furnace pressures ranging up
?rmly against its seat at the outer end of 45 wardly to 90 or 100 p. s. i., wherein the problem
frame 34.
,
When the odor is in its closed position, the win-_
dow 55 is centered over the outer end of passage
of preventing the discharge. of high temperature
furnace gases becomes increasingly dif?cult.
Furthermore, apparatus in accordance with this
invention provides certain safety features which
36 enabling operation of the furnace to be ob
served through the opening21. In this position 50 are of particular importance with furnace pres
also, the hole 61 in the door is centered over the
sures of the magnitude mentioned, for example,
plug of valve 45 enabling a valve key or other
the door cannot be opened until after the air jets
tool to be inserted through the hole into engage
are in action and the required air pressure es
ment with the squared end 68 for manual control
tablished within the manifold to release the door,
of valve operation.
‘
and secondly, the air cannot be turned off until
When the door 26 is to be opened, the valve
the door is fully closed, thereby assuring com
key is inserted through hole 61 and the valve
plete and effective jet action throughout the en
turned on to admit high pressure air into the
tire period that the wall opening is uncovered.
manifold 4|, the air blowing through the jet holes
I claim:
42 at high velocity toward the furnace wall open 60
1. Closure means for a furnace wall access
ing 21 to prevent the ejection or blow-back of
furnace gases. At the same time, the air pressure
within the manifold forces both the hinge pin 53
and catch pin 54 outward, in opposition to the
action of springsfl, whereby the door cover 26a
is released from its seat.
The valve key is‘ then '
removed allowing the door to drop open and at
the same time block access ‘to air valve 45. The
opening comprising a frame having an interior
passage adapted to register with said opening,
a cover movable into open and closed positions
relative to said passage, means for directing gase
ous ?uid into said passage toward said opening
in a series of high velocity jets converging along
the central axis of said passage, and means re
sponsive to a decrease and an increase respeca
hinge pin 53 and catch pin 54 may each be formed
tively in the pressure of fluid forming said jets
with an enlarged intermediate ?ange portion 69 70 for locking and releasing said cover relative 'to
acting as a stop against the inner face of plug 52
said frame in the closed position relative to said
passage.
to limit outward pin movement, in which case
the extent of movement represented by space 1|
2. Ciosure means for a furnace wall access
is preferably less than thewidth of slot 51 to
opening comprising a frame having an interior
prevent the inner edge 12 from binding against 75 passage adapted to register with said opening;
8
7
v,outervwallportion.ofsaid frameurneans fort sup
a cover movable ‘into __9pen and I closed ’ positigns
, plying fluidfundén'pre sine‘; to Ysa'idmanifold, said
‘common 'vvall 'portio'rimb‘éing'
gaseous ?uidiinto- s d passage toward said‘ open
Fin‘g'i'
a‘iser'ies fsof
l velocity ‘ jets _'c_onverging
velocity streams, .a hinge lsupport .- for said . door
1along the central axisof said passage, and means .
responsive to "a decrease in the pressure of ?uid "
at 'one side of said passagaf'a "catch 'f,or..said»;'door
at the oppositeside‘of’said passage, said catch
forming ' T'said jets for ‘locking ‘_ said" cover ‘relative
to i said _ frame
being movable from a door-engaging position
\ithe {closed position‘ relative to
lsieidiliassage
"
‘
‘
‘In ‘combination with a wall structure hav
ports
for directing said ?uid intosaidpasuage. in'high
when the door is ‘closed to a positionreleasing
.10 said doorfor movement into openipos'ition, means
for biasing said ‘catch towardsaid door-engaging
position for normally retaining said door in
closed position, means responsivelto an increase
ing an opening ‘thereinto a chamber operable
under superatmospheric internal ‘pressure, ,clo
sure means for said opening comprising a door
in the pressure of ?uidsupplied to said manifold
for moving said catch into said door-releasing
position, and control means for varying said
vmovable Iinto open‘fand‘closed positions relative
to said opening; meansffor establishing a'?uid
pressure zone adjacent the’ outer ‘side of ' said ‘
‘opening’ for preventing ‘the ‘ej ection of gases from
said chamber when said door is in the open posi
manifold ?uid supply pressure.
’
tion, and means for controlling the supply ' of
.7. In combination with a furnace .wall having
an opening therein, closure means for saidopen
?uid under pressure to said zone, said control
ing comprising a door at ‘the outer end of said
means occupying a position at one side of the
opening movable ,into open and closed positions,
path of movement of said door and being“ oper
able from a ‘position at the opopsite side of said
path,v said door having an opening therein
through which said "control means is rendered
into said opening toward the inner end thereof,
means for controllingthepressure at which said
means for directing gaseous ?uid under pressure
?uid is directed into said opening, means opera
ble in response to a decrease in said fluid pres
sure for locking said door in the closed position
accessible for operation only when said door is
in" the: closed position.
'
'
4. In combination with a Wall structure hav
and in response to an increase in said ?uid pres
ing an opening therein to' a chamber operable
under superatmospheric internal pressure, clo
sure for releasing said door for movement into
sure means for said opening comprising a door
an open position.
8. In combination with a wall structure hav
movable into open and‘closed positions relative
to said'opening, means for maintaining a high
ing an opening therein to a chamber in which
a superatmospheric pressure is maintained, clo
velocity'gaseous ?uid ?ow through a zone adja
sure means for said opening comprising a door
at the outer end of said opening, means for di
recting gaseous ?uid under pressure into said
opening and effecting therein a gaseous ?uid ?ow
creating an inward suction at‘ said outer end,
means for controlling the pressure under which
cent s'a'iidppening for preventing the ejection of
gases from said chamber when‘ said door is in
the open position, means for controlling said
gaseous ?uid flow accessible for operation from
a predetermined location when the door is closed,
and means operable in response to‘ movement of
said door ‘for rendering'said control means in
40
accessible for operation from said location when
the door is open.
Said gaseous ?uid is directed into said opening,
means operable in response to variations in said
?uid pressure for locking said door in closed
position upon a decrease in said ?uid pressure
and for releasing said door for movement into an
open position upon an increase in said ?uid
pressure.
9. In combination with a wall structure hav
ing an opening therein to a chamber operable
'
5.‘Closure means for a furnace Wall opening
comprising a frame having an interior passage
adapted to register with said opening, a door for
said opening at the outer end of said passage, a
manifold arranged annul‘arly of said frame and
under, superatmospheric internal pressure, closure
having its inne‘r‘wall portion in common with an
outer wall portion of said frame, means for sup
means for said opening comprising a door mova
ble into open and closed positions relative to said
plying fluid under pressure to said manifold, said
common Wall-portion being provided with ports
opening, ?uid pressure means for preventing the
ejection of gases from said chamber, means in
for directing said ?uid into said passage in high
cluding a valve for controlling the operation of
velocity streams, a pin at one side of said pas
sage forming a pivot support for said door, a 55 said fluid pressure means, and means responsive
to movement of said- door for preventing opera
pin at the opposite side of said passage forming
tion of said valve except when said door is in the
a catch for said door, each of said pins extend
closed position.
ing into said manifold and functioning as a
‘
plunger movable in response to variations in ?uid
pressure within said manifold, means applying 60
an inwardly directed force to eachpin in opposi
tion'to' the outwardly directed force resulting
from exposure‘ to‘ said manifold ?uid pressure,
means ‘associated with an, outer end portion of
each pin for clamping said door in closed posi
tion against said frame upon inward movement
of ‘said pins in response to a decrease in said
manifold ?uid pressure, and control meansfor
varying said manifold fluid pressure.
nsE-sRENoEs CITED
The following references are of record in the
65
manifold arranged annularly o‘fsaid frame and
having'its innerwwall portion in common withan
?le'of'this'patent:
‘
'
UNITED ' s'rATEs PATENTS.
Number
144,002
6. Closure means for a furnace wall opening 70
comprising a frame having an interior passage
adapted to register with said opening, a door_for
said opening at the outer endiof said passage, a
LAMBERT KOOISTRA.
Name
Date
Stewart‘ __________ __ Oct. 22,, 1873
241,433
Simmons ________ __ May 10, 1881
‘740,757
l-lofmann ________ __>_ Oct. 6, 1903
805,295,
Hofmann ________ __ Nov. 21, 1905
1,861,334_._
Abel __________ __'___ Mayv 31, 1932
1,973,171
Jacobi __________ __ Sept.,11, 1934v
2,112,603
75. 2,360,855 .
Blizard ]_ _________ .._ Mar. 22,, 1938,
Dow _____________ _'__ Oct. 24, 191147
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