June 26, 1951
2 5, 5 oo 5.. 3 4
A. P. B`ENTLEY
OVER-PRESSURE PROTECTIVE DEVICE
Filed June 19, 1950
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Arthu‘r“ E? Bentley’
His Attorney.
2,558,534
Patented June 26, 1951
UNiTEDsTATEs PATENT OFFICE
2,558,534
.
OVER-PRESSURE PRÓTECTIVE DEVICE
Arthur P. Bentley, Scotia, N. Y., assignor to Gen
eral Electric Company, a corporation of New
York
Application June 19, 1950, Serial- No. 169,020
3 Claims. (Cl. 'I3-389)
.
l
This invention relates to 'an over-pressure
protective device and, in particular, to a- protec
tive device for a diiîerential gauge of the type
used to measure the flow of an expansible fluid
through a conduit.
By conduit is meant any conductor which is
2
differential gauge from a pressure source to be
measured.
.
It is a stil further object of this invention to
provide a new and improved over-pressure pro
tective device that is simple in construction and
automatic in operation.
Further objects and advantages of this inven
tion will become apparent and the invention will
direct its flow. The flow may be caused by a
be more clearly understood from the following
pressure differential produced by the resistance
description referring to the accompanying draw
10
of a heat exchanger, an orifice in an obstruction
ing, and the features of noveltywhich charac
plate, or the like. The pressure differential pro
terize this invention will be pointed out with
duced by such a resistance can be correlated
particularity in the claims annexed to and
with the rate of flow through the conduit; con
forming a part of this specification.
sequently, it is important to be able to measure
Briefly, this invention comprises a device
the pressure differential.
responsive to a predetermined 'pressure dif
A differential pressure gauge is a convenient
fential between two points or on opposite sides
apparatus for making such measurement. By
of some obstruction or resistance within a conduit
differential gauge is meant an instrument re
to activate valves that cut on’ the supply of com
sponsive to diñerence in pressures on opposite
20 pressible fluid to a differential gauge whereby
adapted to constrain a compressible ñuid and
sides of a resistance. The pressure differential
is indicative of the flow across that resistance
and, in addition, the pressure differential indi
- cates the value ofthe resistance offered.
This
pressure differential can be transmitted to a '
meter for a direct reading of the differential
pressure.
In diiîerential gauges of the type described,
frequently one of the operative elements is a
delicate bellows4 that expands and contracts in
the gauge is temporarily isolated from the con
duit; the compressible fluid within the diñer
ential gauge is balanced to equalize the pressure
acting on the differential gauge; and finally
when the differential pressure in the conduit
again recedes below the predetermined limit, the
gauge is automatically reconnected to the con
duit.
,
In the drawing, »the single figure is a simple
schematic drawing of the operating elements of
30
response to the pressure diñerential on its op
this invention.
`
posite sides. Because of its delicate sensitivity,
Referring to the drawing, a conduit l is shown
however, a high unbalanced pressure will rup
having an obstruction 2 defining a central orifice
ture the material of the bellows. Such a high
or opening 3. The obstruction 2 separates the
unbalanced pressure can be a result of the ex
conduit into a compartment 5 which is the high
plosion that takes place within the expansible
pressure compartment and a compartment 5a
iluid or it can be caused by an obstruction that
which is the low pressure compartment. The
blocks the passage of fluid through the conduit.
difference in pressure between the two com
It should be pointed out at this time that while
partments is caused by the resistance> to the
a bellows operated differential meter has been
flow of compressible ñuid oñ`ered by oriñce 3.
40
and will be referred to, such a reference has been
An over-pressure protective device 6 comprises
selected merely to illustrate more clarly the
a pair of axially juxtapositioned cylinder blocks
operation of. this invention, and it is not intended
‘i and 1a which are spaced apart by a flexible
to .be a limitation of its scope, which-is broad
diaphragm 8 and removably interconnected by a
enough to operate on many types of differential
45 plurality of bolts 9.
meters.
I
.Cylinder blocks 'l and 'la each provide a
It is an object of this invention to provide a
cylinder l0 and il, respectively, which, in turn,
device which will protect a differential meter
are separated by the flexible diaphragm 8.
against an excessive differential pressure.
As will be hereinaftery described, cylinder I0
It is a further object of this- invention to pro
is
further subdivided into three cylindrical com
50
vide a new and improved over-pressure protective
partments Illa, Illb, and Illc, while cylinder Il
device for a differential gauge.
is subdivided into three cylindrical compart
ments Ila. IIb, and llc.
TheI cylindrical compartment ißb is provided
tective device that operates in response to com
with
a piston I3 which is axially slidable therein,
pressible ñuids to automatically disengage a 55
It is a still further object of this invention to
provide a new and improved over-pressure pro
2,558,584 ,
3
»
and cylindrical compartment I Ibis provided withv
a second piston I4 which is axially slidable there
in. The two pistons, in turn, are rigidly-inter
connected by an axial rod I5 which causes the
pistons to move one with the other.
_
Diaphragm 8, which divides cylinder blocks 1
and 1a, is generally circular and provided with
an axial opening through which rod I5 is passed.
Diaphragm 8, which in a preferred embodiment
is made of neoprene or other impregnated mate
rial, is secured to rod I5 substantially midwayalong its length, either by cement, or by a ring
(not shown).
Piston I3 is provided with a threaded bore I8
and a threaded ferrule I1 that is provided with
a central axial passageway I8, while piston I4 is
provided with a threaded bore I9 and a threaded
ferrule 20 that is provided with a central axial
In similar` fashion, a conduit 43 connects the
low pressure side 5a of conduit I to over-pressure
device 6. A bore 44 conducts the compressible
fluid through the cylinder block 1, while a bore
45 registers with bore 44 and conducts the fluid
through the skirt of piston I8 into compartment
Ilib. A bore 46 connects compartment I 0c with
a conduit 41 that connects over-pressure device 8
with the compartment 28 of meter 28. This con
' duit 41 allows the compressible fluid from com
partment IIIc to pass into the meter compartment
28 and act in opposition to the pressure within
compartment 28.
A cap 48 threadedly engages the internal
threaded end 48a of shell 1 and a plug 43 thread
edly engages a threaded recess 48a in the upper
end of cap 48. Plug 49 and cap 48 define a valve
chamber 50.
passageway 2l. In accordance with this struc
A valve 5I is positioned in valve chamber 50
ture, piston I3 divides cylinder I0 into compart 20 and has a valve stem 52 that passes through cap
ments IIlb and IIlc which are interconnected by
48 into compartment Illc. Valve stem 52 is posi
passageway I8, while piston I4 divides cylinder
II into compartments IIb and IIc which are
interconnected by passageway 2 I.
tioned to be actuated by piston I3 to be raised
to expose a bore 53 provided in cap 48 that inter
connects valve 5II with bore 46. Cap 48 is further
‘ In order to guide the axial movement of rod 25 provided with an opening 54 `that threadedly
I5, a web 22 is provided in cylinder block 1 and
a web 23 is provided in lower cylinder block 1a.
Web 22 separates compartment IIIb from com
partment Illa, while web 23 separates compart
engages a conduit 55 that interconnects conduit
42 and valve chamber 50.
With this structure, when valve 5I is raised by
piston I3, the compressible fluid in conduit 42
ment IIb from compartment IIa. Web ‘22 is pro 30 can pass through conduit 55 into valve chamber
vided with a passageway 24 that provides com
50, thence past valve 5I into bore 53 to bore 48
munication between compartment IIIa and com
and conduit 41 to balance the pressure in conduits
partment IUb, while web 23 is provided with a
42 and 41.
passageway 25 that provides communication
-' A spring 55 is interpositioned between plug 45
between compartment IIa and compartment IIb. 35 and valve 52 to maintain it closed over bore 53.
With this structure, the steady state pressure '
Spring 56 is a light spring that serves the sole
in compartment Illa is always equal to that of
purpose of keeping the valve closed. A second
compartment Illb, while the steady state pressure
spring 51 is calibrated and defines the operating
in compartment IIa is always equal to that of
differential at which the over-pressure device will \
compartment I Ib. Furthermore, in a steady state 40 function. Spring 51 is positioned between cap 48
condition, the pressure in compartment I0c is
equal to that of compartments I0b and Illa, and
the pressure in compartment IIa is equal to that
in compartments I Ic and 'I Ib, since the compart
and piston I3 to prevent piston I3 from opening
valve 52 until the force exerted by spring 51 is
5 of conduit I to over-pressure device 8. A bore
ment IIIb to act on the lower surface of a piston
offset by pressure on pistons I3 or I4 after an
explosion or by diaphragm 8 if a high differential
ments on each side of diaphragm 8 are all inter
is slowly built up. The »pistons I3 or I4 do not
connected.
actuate the valve when the high differential is
A meter 26 is shown as comprising a cylindrical
slowly built up because of the interconnecting
shell or housing 21 deñning a, compartment 28,
passageways heretofore described.
which is subdivided by an expansible bellows 30
Since cap 48 is threadedly engaged with shell
to provide a compartment 29. The diiîerence in 50 1, the spring 51 is readily removable to be inter
pressure between compartment 28 and compart
changed with one having a different spring con
ment 29 causes bellows 30 to expand or- contract,
stant. This structure permits the differential
depending upon the direction of the pressure
rating of the over-pressure protective device to
be changed.
y
differential. A rod 3I is connected to and sup
ported by the free end of bellows 30. Rod 3|
In operation, this new and improved over
extends through the upper portion 32 of Icylin
pressure device operates and functions as fol
drical housing 21 and is supported by a packing
lows. Expansible fluid, such as gas, air, or the
nut 33. Rod 3| is pivotally connected to a meter
like, from the high pressure side 5 of conduit I
needle 34 which pivots about a fulcrum 35,. A - passes through conduit 38 and bores 39. and 48 to
point 36 on needle 34 indicates on a scale 31 the 60 compartment IIc to act on the bottom surface
~pressure diiîerential 4between compartments 29
of piston I4. The expansible fluid from the low
and 28 in response to the movement of bellows 30.
pressure portion 5a of conduit I' passes through
A conduit 38 connects the high pressure side
conduit 43 and and bores 44 and 45 to compart
39 through cylinder block 1a registers with a bore 65 I3. The expansible fluid from-compartment IIc
40 through the skirt of piston I4 to allow the
passes through bore 2| in ferrule 25 to the upper
compressible iluîd to pass from the high pressure
surface of piston I4 into compartment IIb and
side 5 of conduit I to compartment I Ic on the
through bore 25 to compartment IIa to act
bottom of piston I4. A bore 4I in cylinder block
on one side of diaphragm I2. 'I'he expansible
1a connects compartment IIb above piston I4 70 ñuid from compartment IIIb passes through bore
with conduit 42 that connects the over-pressure
24 to compartment Ilia to act on the other side
device 8 with the housing 21 of meter 25. Con
of diaphragm I2. Under these conditions, the
duit 42 conducts the compressible fluid from com
pressure from the low side 5a of conduit I, plus
partment IIb to compartment 29 within the bel
the pressure of the interchangeable spring 51,
lows 30.
'
75 acts in one vdirection on rod I5 and diaphragm
2,558,584
8, while the expansible fluid from the high pres
sure compartment 5 in conduit I acts in the other
direction on rod I5 and diaphragm 8. Under nor
mal operating conditions for any selected spring
6
ing a cylinder block having two axially aligned
cylinders, a flexible diaphragm separating said
cylinders, a separate piston movably mounted in
each ot' said cylinders, a rod rigidly interconnect- ì
ing said pistons secured to said diaphragm, con
duit means- connecting corresponding sides of
ous supply of expansible fluid acts on either side
said pistons one to each side of said press-ure
of the bellows 30 in meter 26. The pressure bal
differential source, conduit means connecting
ance between compartments 28 and 29 on either
said cylinders to the pressure gauge, said pistons
side of the bellows influences the direction of
l0 moving in response to a predetermined pressure
needle 34 and its reading on scale 31.
differential to close said conduit means connect
If an explosion occurs, for example, in the high
ing said cylinders to the gauge.
pressure compartment 5 of conduit I, then high
2. An over-pressure protective device for auto
pressure fluid passes through conduit 38 to the
matically disconnecting a differential gauge from
lower surface of piston I4 to force piston I4 and
a differential pressure source at a predetermined
rod I5 up; thus, piston I4 closes over bore 4I
value of differential pressure and for automati
and piston I3 closes over bore 46. This shuts ofî
cally re-connecting the differential gauge to the
the supply of expansible fluid to meter 26 and,
source when the differential pressure decreases
thus, protects it from the high differential pres
to a value less than said predetermined value,
sure that might exist because of the explosion
in-the high pressure compartment. In addition, 20 comprising a circumferential wall defining an
axially extending cylinder to house a first piston
as rod I5 and pistons I4 and I3 are moved up,
and a second piston, each slidable in said cylin
valve stem 52 is actuated to raise valve 5I and
der, a rod rigidly interconnecting said pistons, a
interconnect conduits 41 and 55. With the pas
~flexible diaphragm secured to said rod transverse
sage of fluid from the high pressure conduits 42
and 55 into valve chamber 50 and through it into 25 to the axis of said continuous wall to divide said
cylinder into two axially juxtapositioned com
conduit 41, the pressure in compartments 28 and
partments, conduit means for conducting an
29 of meter 26 is equalized to relieve any strain
51, a steady state condition exists and a continu
elastic fluid from the high pressure side of said
differential source to one side of said ñrst piston,
passes through orifice 3 in conduit I to reduce the 30' conduit means for conducting an elastic fluid
high unbalanced pressure between compartments
from the low pressure side of said difîertial source
5 and 5a in conduit I, the pressure from com
to the corresponding side of said second piston,
partment 5a of conduit I acting on one side of
each of said pistons having a steady state position
diaphragm 8, plus the pressure caused by spring
and an actuated position, conduit means posi
51, will offset the .pressure from the high pres
tioned in said wall above the steady state position
sure compartment 5 acting on the opposite'side
of each of said pistons to connect said over-pres
of diaphragm 8, whereupon piston I3 and pis
sure device to said differential gauge, said pistons
ton I4 connected by rod I5 will move down to
being actuated in response to a sudden prede
expose bores 44 and 4I, respectively. This move
termined pressure differential to close said con
ment connects meter 26 to conduit I and the dif -III duit means positioned above said piston steady
on bellows 30.
As soon as enough of the compressible fluid
ferential pressure is again recorded. With this
structure, it is obvious that the over-pressure
protective device is an automatic instrument
state position to prevent rupturing of said dif
ferential gauge.
3. An over-pressure protective device for auto
matically disconnecting a differential gauge from
that responds to any differential pressure be
yond the preset differential determined by spring
51.
Speciñcally, if the differential pressure de
termined by spring 51 is exceeded, the over-pres- _
a differential pressuresource at a predetermined
'value of differential pressure and for auto
sure protective device automatically disconnects
meter 26 from conduit I; then, when the dif
matically re-connecting the differential gauge
to the source when the differential pressure de
creases to a value less than said predetermined
ferential again recedes below the predetermined 50 value, comprising a hollow cylinder block defin
limit, the over-pressure device automatically re
connects meter 26 to conduit I.
It is to be noted that whether the high pres
sure differential is caused by either an explosion
or whether the high differential is slowly built
up, the over-pressure protective device still func
tions to shut off the supply of the expansible
fluid to the meter. Obviously, the use of such an
over-pressure protective device saves much time
and effort and expense, since it protects sensitive 60
ing a central cylinder, a first piston and a second
piston each slidable in said cylinder and each
having an actuated and a steady state position, a
rod rigidly interconnecting said pistons, a flex
ible diaphragm secured to said rod transverse
to the axis of said cylinder to separate said cyl
inder into two axially juxtapositioned com
partments, a hollow cap positioned at the end of
one of said compartments, a valve including a
valve rod positioned in said cap with said valve
rod extending therethrough into one of said
pressures`
\
Modifications of this invention will occur to
axial compartments to be actuated by the move
those skilled in the art and it is desired to be
ment of the first of said pistons, a plug in said
understood, therefore, that this invention is not
cap at the end opposite said valve to define with
to be limited to the particular embodiment dis
said cap a valve chamber, a first spring posi
closed, but is intended to cover all modifications
tioned between said valve and said plug to main
which are within the spirit and scope of this in
tain said spring in a closed position, a calibrated
vention.
spring positioned between the end of said cap
What I claim as new and desire to secure by 70 and the first of said pistons to surround said
Letters Patent of the United States is:
valve rod, conduit means for conducting
1. An over-pressure protective device for auto
elastic fluid from the high pressure side of said
matically disconnecting a pressure gauge from
differential source to one side of the second of
a source of differential pressure at a predeter
said pistons, a bore extending through said sec
mined value of differential pressure compris
differential instruments from high unbalanced
7
ond piston to connect said iirst side of said sec
ond piston to said diaphragm, conduit means for
conducting an elastic iluid from the low pressure ‘
sideof said diiierential source to a correspond
ing side of said iirst piston'and to the other side
of said diaphragm, conduit means positioned'
above the steady state position of ‘each of said
pistons to connect said over-pressure devices to
said diiïerential gauge, conduit means connect
ing said conduit positioned above said steady
state position of said second piston to said valve
s
a
l
_.
v
built-up> predetermined pressnn differential te
vmovesaicipistonstcitlieiractuatedlpositiamtoA
close said conduits positioned above said piston
steady state position to isolate» _said diilerentisl. .
gauge from said'dißerentialpreesure source, said "
pistons automatically returning -rw their~ steady
state position when said dißerential pressure re
cedes below said predetermined level to auto
matically re-connect said diiiereniial gauze to
said diiierential pressure source.' '
ARTHUR P. my.'
housing, said pistons automatically responding
to a sudden predetermined pressure dinerential
summons crrsn
to close said conduits positioned above said pis
The renewing references are of
ton steady state positions to isolate said diiîer 15 ille
of this patent:
. record m the
ential gauge from said differential pressure
source and to actuate said valve rod to intercon
nect said conduits connecting said _differential
gauge to said over-pressure protective device to
balance the pressure in said conduits and to re
lieve any stress on said differential gauge, said
diaphragm automatically responding to a slowly
Number
UNITED STATE PATENTS
Name
Date
2,345,464
2,374,523
2,402,171
De Giers ........ -_ Mar. 28, 1944Beecher .......... -_ Apr. 24, 1945
Lutes et ai. ______ _- June 18. 1946
‘ 2,470,288
Childs ........... -_ May 17, 1949