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Патент USA US3092689

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June 4,_ 1963
b. J. LEONE
3,092,680
BLAST FURNACE CONTROL SYSTEM
Filed Nov. 25, 1957
3 sheets-sheet 1
INVENTOR
0770 J, LEONE
@W
June 4, 1963
o. J. LEONE
3,092,680
BLAST FURNACE CONTROL SYSTEM
Filed NOV. 25, 1957
3 Sheets-Sheet 2
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INVENTOR
0770 d. LEONE
June 4; 1963
o. J. LEONE
3,092,680
BLAST FURNACE CONTROL SYSTEM
Filed Nov. 25, 1957
3 Sheets-Sheet 5
_* I1”. 4.
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INVENTOR
orro u. LEONE
limited btates
ice
1
3,092,680
Patented June 4, 1963
2
desired, be connected directly to and across the stack of
furnace 10 as illustrated, for example, in the applicant’s
3,092,686
BLAST FURNACE CONTRGL SYETEM
Otto J. Leone, P50. Box 24, West Newton, Pa.
Filed Nov. 25, 1957, Ser. No. 698,811
controller 25 may be in the form of a pneumatic, hydrau
3 Claims. (Cl. 266-339)
lic or an electrical impulse transmitted through a con
Patent No. 2,625,386. Any corrective signal issued by
This invention relates to a system for blast furnace con
trol or the like and magnetomotive instrument construc
tions for use therewith. More particularly, my inven
tion pertains to an alternative system for achieving bene 10
?ts discussed in my copending application Serial No.
330,753, ?led January 12, 1953, now Patent No.
2,814,479.
current
In myconstruction
new system isdisclosed
providedherein,
through
an magnetic
induced means
to sense an undue rate of change in a pressure variable to
yield a corresponding induced current for the issuance of
ductor 28 to operator 24, or through a conductor 29 to
operator 21, or both, as determined by the overlap or
interlock relay provision within controller 25, as desired,
to maintain the differential pressure across stack 10 within
that selected differential pressure range which will main
tain furnace 10 relatively free from hanging, slipping,
packing and other troubles. And, additionally, controller
25 may be operatively connected to the blower volume
regulator to regulate its speed and delivery volume if
15 that means is selected in maintaining an appropriate ‘dif
ferential pressure ‘through the blast furnace.
In addition, a top ‘gas controller 30' is provided to act
a corrective signal for blast furnace control or like pur
at least upon an abnormal rate of increase in the top gas
pressure within gas line 14, such being an indication that
inertia and trouble-free construction is available to con 20 the furnace 10 is heading for trouble, or ‘at least is in
trol a blast furnace or the like and keep it signi?cantly
the initial stages of a di?iculty such as a slipping condi
free of hanging, scaffolding, packing and slipping troubles
tion. The top gas pressure is impressed upon controller
either when differential pressure control is being exer
30 through a pipe tap 31 and whenever any corrective
cised as taught by my Patent No. 2,625,386, or otherwise.
signal is issued by controller 30 in the form of an elec
Further advantages, features and objects of my inven
trical impulse, such will pass through a conductor 32
tion will be apparent from the following description and
to operator 20 to open main relief valve 17 quickly and
poses.
By such means, a further relatively fast, low
the accompanying drawings, which are illustrative only,
in which:
drop the pressure in the blast furnace system. Generally,
such opening of the main relief valve to spill out blast
air or “wind” will relatively quickly drop the top gas
FIGURE 1 is a schematic view of a blast furnace con
trol system utilizing a new instrument construction dis 30 pressure to a desired level. If wished, controller 30 may
closed herein;
also be hooked up to ‘a relief valve in the gas line such
FIGURE 2 is a schematic view of a further blast fur
as relief valve 15 or one farther from the furnace 10.
nace control system utilizing such an instrument con
The action of top gas controller 30 overrides the control
struction;
action of differential pressure controller 25 until the ex
FIGURE 3 is a diagrammatic view of a new indicating
cessive pressure rate condition or excessive pressure con
instrument construction suitable for use in the system
dition causing the issuance by controller 30 of a correc
shown in FIGURES l and 2;
FIGURE 4 is a diagrammatic view of a modi?ed indi
tive signal impulse is remedied whereupon the system
‘the opposite direction.
Referring to FIGURE 1 of the drawings, there is
automatically returns to the control action of controller
25. Controller 30 is also provided with a high limit
switch ‘for the top gas pressure which when actuated will
transmit a separate signal through an electrical conduc
tor 32a directly to operator 20 to open valve 17.
As pointed out in the applicant’s aforesaid prior in
ventions, the controllers may be interlocked, for example,
with the opening of the furnace bell so that the tendency
of such opening to upset pressure conditions will not
shown therein a blast furnace 10 to which a stock burden
.invoke control action during such opening. Further,
cator instrument construction;
FIGURE 5 is a partial view of a further modi?cation
of an instrument construction of this invention; and
FIGURE 6 is a view of an indicator instrument con
struction similar to that shown in FIGURE 3, but adapted
to be responsive to a selected rate of pressure change in
is supplied through a hopper 11 when a bell at the top
controls, such as controllers 25, 3t} and 34, may, if de~
is opened by a rod 12. Blast air is supplied to the bot
sired, have incorporated therein indicating, recording,
50
tom of the stack through a blast main or pipe 13 and
metering or other auxiliary functions as will be readily
gaseous products are taken off from the upper part of
recognized by those skilled in the art to whom this in
the stack through a top gas line or pipe 14 in which a
vention is disclosed.
normally closed relief valve 15 is usually provided. Blast
In the further system illustrated in FIGURE 2, parts
main 13 is provided with a main relief branch 16 which
thereof generally corresponding in structure and function
is normally closed by a main relief valve 17 and is also 55 ing to those shown in FIGURE 1 are provided with the
provided with an auxiliary relief branch 18 having a
same reference numerals with the addition of a prime
valve 19 therein. Valve 17 is provided with an “on-off”
accent thereto, respectively. Therein, the differential
pressure controller 25' also incorporates a differential
operator 20, which may be in the ‘form of a solenoid
pressure transmitter portion which pneumatically trans
operator, while valve 13 preferably is provided with a
proportioning operator 21 which enables valve 19 to be 60 mits through a pipe 33, a pneumatic impulse at the time
of and corresponding to changes in the differential
modulated from its fully closed to its fully open posi
pressure existing across the pressure taps 26’ and 27’.
tion. Gas line 14 normally communicates with a dust
The differential pressure impulse transmitted through
catcher and washer system 22 through which the gaseous
products from furnace 10 are led. A top gas pressure 65 pipe 33 is fed into a vdifferential rate controller 34 which
may be in the form of the instrument shown in FIG
control valve 23 is provided in line 14 and has a propor
URE 6 hereof. As and when the rate of change of
tioning operator 24 for the modulation of valve 23.
the differential pressure becomes abnormal in a decreas
As shown, the differential pressure within blast fur
ing direction, a corrective impulse is sent out by con
nace 10 is controlled by a differential pressure controller
troller 34 as an electrical impulse through a conductor
25 upon which is impressed normally the blast main 70 35 to a relay 36. Relay 36 is responsive so that it will
pressure ‘through a pipe tap 26 and the top gas pressure
transmit through conductor 38 a corrective signal to op
through a pipe tap 27. Such pipe taps may instead, if
erator 20’ when both controller 34 and controller 30’
3,092,680
are issuing a corrective output impulse to relay 36,
such impulse in the case of controller 3%’ being trans
mitted through conductor 32’. Preferably, the character
istics of controllers 30' and 34 will be selected such that
controller 36' will transmit its corrective impulse to
relay 36 slightly ahead of the corrective impulse trans
mitted by controller 34 to relay 36.’
‘In the case of the top gas pressure controller 36',
the high limit pressure switch is separately connected
to an electrical conductor 37 ’ so that any actuation there
of will send an independent signal .to operator 2%)’ for
the‘separate ‘opening of valve 17’ whenever the preset
high limit on the top gas pressure is reached. On the
other'hand, the rate of change parts of controller 3%’
58 is provided with a magnet ?eld 63a and core 63!?
with a circular gap 64 between in which a meter coil
65 can turn in accordance‘ with any current ?owing in
the leads 57. A concentrically pivoted index arm 66
is adjustably movable along scale 62 to the selected
setting. Arm 66 carries opposed spaced coils 76, leads
77 from which extend to a galvanometer terminal block
68 and from thence to an ampli?er 69 which in turn is
connected to a relay 70 operated by the ampli?er out
put to control a switch for the sending of a corrective
10 signal in the form of an electrical impulse from the
terminals of output terminal block 71 through the wires
in conductor 32 in the control system described above.
Swingable pressure arm 51 is also provided with a nor
are left connected to conductor 32’ leading to relay 36, 15 mally open high limit switch having a movable contact
72 which coacts with a ?xed contact 73 adjustably mount
which may have an electrical network therein such as
ed on panel 39 to be preset to the selected extent. As
that illustrated in FIGURE 7 of my aforesaid copend
long as the electrical switch represented by the contacts
ing application Serial No. 330,753, now Patent No.
72 and 73 is open no current will flow in the leads 74,
2,814,479, in which ‘the rate of change parts of controllers
30' and 34 are in ‘series and actuated in sequential rela 20 and vice versa. As and when contacts 72 and 73 do
engage one another, current will flow in the conductor
tion before an electrical signal can be sent over con
32a to operator 2t} and open main relief valve 17 to
ductor'38 to operator 2'0’ calling for the opening of main
prevent the top gas pressure, as distinguished from any
relief valve '17’ in the blast main .13’. As soon as the
rate of change thereof, from exceeding a predetermined
conditions causing the opening of valve 17' cease, the
valve 17' will be closedby operator 20’ and control of 25 high limit. Power lines L1 and L2 are connected to
terminal 67 to enable the wires in conductor 32a to be
the operation of blast furnace 10' will be automatically
energized whenever contacts 72 and 73 close, whether
returned to controller 25’ acting in a modulating fashion
or not such closure is accompanied by a su?lciently rapid
upon the operator 24’ or 21’, or both, or on the volume
axial movement of magnet 49 to produce a corrective
regulator of the blower, in selected, sequential or over
signal output from galvanometer 58 such as occurs when
lapping fashion as desired.
30
ever ‘?ag 75 moves into the ‘space between the opposed
One embodiment 39a of a top gas pressure instrument
coils 76. It will be readily recognized that in place of
suitable for use as controller 36 or 39’ is illustrated
such oscillatory coils 76, other commercial forms of
in FIGURE 3 and may be mounted on a panel 39 which
is suitably encased. The top gas pressure pipe 31 may
meters may be used which utilize a light and photoelectric
be suitably connected to an impulse pipe 46 which ex 35 cell in opposed relation for‘ interruption by an opaque
?ag, or which use contacts with a galvanometer for the
tends to the interior of instrument 30a, a valve 41 such
production of a corrective signal output.
as a needle valve being provided in line/4i) for pur
The magnetic pressure rate portion of instrument 30a
is shown in the form of an indicator having the scale S
the systemrwith which ‘it is to be used. The lower end
of pipe 40 communicates with the interior of a housing 40 along which the arm 51 is movable in accordance with
the normally changing’ top gas pressure values. As shown,
42 having apressure sensitive resilient bellows 43 in
arm 51 will move clockwise about its pivot ‘53 upon the
sealed relation to an annular ?ange wall 44 at one end
occurrence of ‘an increase in the top gas pressure and
of housing 42, the remm'nder of the wall being formed
counterclockwise upon a decrease therein from the shown
by the bellows 43 which has its interior open to the
atmosphere within instrument 30a. Bellows '43 is pro 45 position of head 45. Thus, even though the relative
poses of instrument adjustment and coordination with
vided with a head 45 and as pressure variations occur in
movement of magnetic member 49 into opening 55 may
the input impulse pipe 40, head 45 correspondingly
not be rapid enough to move pointer 61 to index posi
tion 66 at which the ?ag is between the coils 76, the
moves in one direction or the other with variations in
the pressure transmitted through pipe 4tlto the interior
of housing ‘42.
-
pointer 51 will still indicate changes in the'pressure with
50 in tap extension 46 just as pointer 61 will indicate all
induced currents ?owing in the leads 57 and their di
A rod 46 is provided with one end 47 ?xed to head
rection ‘due to the direction of movementof member 49
45 and its other ‘end 48 ?xed to a magnetic member such
relative to opening 55. In general, the limit of move
as permanent magnet 49 extending in a coaxial direc
ment of member 49 into opening 55 is preferably about
tion relative to rod 46. Rod 46 is provided with an
integral link ‘50 which may be used to pivotally connect 55 one-half of the length from the leading end thereof. Al
though the magnetic member 49 is shown with the north
rod 46 to a pressure responsive indicator arm'5l by
means of a‘pivot pin 52. Arm 51 is pivotally mounted
at'53 on panel 39. As the diaphragm of bellows 43
pole end leading, the polarity thereof could be reversed
in which event the settings on the respective scales would
have to be correspondingly displaced to the other side
by rod 46, there being su?‘icientflexibility in bellows 60 of the zero mark as would the high limit contacts 72 and
moves axially, arm 51 will be correspondingly moved
43 'to accommodate the arcuate action of pin 52 during
such motion. A solenoid coil 54 is provided with an
axial opening 55 in axial registry with the axis of mag
73 and the index arm 66.
In operation, so long as the rate of change of the top
gas pressure does not rise in a pressure increasing direc
tion to a value indicating that slipping may be incipient
net 49 and of a diameter such that magnet 49 can be
thrust into coil opening 55 by movements of bellows 43 65 or under way, any movement of magnet 49 within coil
opening 55 will not induce a su?icient current in the coil
to the left irom any pressure position such as that illus
trated in FIGURE 3. The'ends of coil 54 are respec
leads and galvanometer leads 57 to drive pointer arm
61 to the index position preselected by the setting of arm .
tively connected to terminals on a block 56 mounted on
panel'39 and those respective terminals are connected to
'66, and, no corrective signal will be issued by controller
the leads 57 of a galvanometer 58 of any commercial 70 361a. On the other hand, whenever the top gas pressure
in gas line 14 increases at a rate which is abnormal
type which is relatively fast and sensitive.
indicating the incipient or early stages of slipping, for ex
As shown, galvanometer '58 is provided with feeder
ample, the thrust of bellows head 45 to the left as viewed
springs 59 to bring shaft 66 and a pointer 61 carried
in FIGURE 3 will be more rapid and the consequent
thereby to a ‘zero position on a scale ‘62 whenever there
is no current ?owing in the leads 57. Galvanometer 75 current induced in coil 54 will be greater and sut?cient
3,092,680
5
6
to move pointer 61 into substantial registry with index
will flow through the conductor 32a (or 37’) for the
arm 66.
purpose described above.
A further modi?cation in such a controller is illus
When that occurs, a ?ag 75 passes between
two opposed oscillation coils 76 carried by arm 66 in
‘galvanometer 58. In so doing, the oscillatory energy
in the system of the coils 76 changes. Such coils 76 are
connected by leads 77 to terminal block 68 which in turn
is connected as described above to ampli?er 69 and relay
70.
Such change produced by the passage of ?ag 75
between coils 76 causes a corrective signal in the form of
trated in FIGURE 5 which shows that only certain parts
thereof have been changed. Parts shown in FIGURE 5
corresponding generally in construction and functioning
to parts shown in FIGURES 3 and 4 are marked with
the same reference numeral with the addition of a double
prime accent thereto. In such further modi?cation, core
an electrical impulse magni?ed in strength by the am 10 piece 49" is made into an electromagnet by an exciting
pli?er to pass through the conductor 32 to operator 20
coil 83 connected thereto. Exciting coil 83 is energized
to open main relief valve 17, thereby quickly dropping
by ?exible leads 84 which are connected to a direct cur
the blast main pressure, the differential pressure across
the blast furnace stack and arresting the abnormal rate
rent source 80' through a rheostat 81' (or suitably recti
?ed and ?ltered alternating cur-rent). The action and
of increase in the top gas pressure. When that abnor 15 operation of such further modi?cation shown in ‘FIGURE
mal rate of increase is so arrested, the pointer arm 61
5 are like those of the controllers illustrated in FIGURES
moves back toward its Zero position on the scale 62
3 and 4.
and in so doing removes the ?ag from between the coils
The new instrument construction illustrated in part in
76 with the result that there is a cessation of a signal
FIGURE 6 is like the controller 30a shown in FIGURE
sent out over conductor 32 from controller 300 which in 20 3 except that the FIGURE 6 construction is adapted to
turn causes operator 20 to return valve 17 to its nor
mally closed position.
operate upon the occurrence of an excessive rate of pres
sure change in a decreasing direction and, as such, is
‘If, under some circumstances, the top gas pressure
utilizable as the differential rate controller 34 in the
should increase toward a limiting pressure such as might
FIGURE 2 system. Further, the FIGURE 6 instru
be imposed by the strength of the seals on the dust 25 ment has no limit switch (contacts 72—73). The parts
catcher and washer system or the pressure limit strength
of the construction shown in FIGURE 6 which corre
of the top of the blast furnace, but at a rate insu?icient
spond generally in structure and function to parts shown
to produce an induced current in leads 57 which will
in FIGURE 3 are provided with the same reference nu
cause ?ag 75 to pass between oscillatory coils 76, the
merals with the addition of the letter “b” thereto. Thus,
system is nevertheless safeguarded because if, as and
in controller 34, whenever the differential pressure
when contatcs 72 and 73 close, a current will pass
through the stack 10' decreases at such a rapid rate as
through conductor 32a to operator 20 and open valve
to indicate, for example, incipient slipping, head 45b of
17 for a period of time to reduce the pressure in gas
bellows ‘43b will move rapidly to the right as viewed in
line 14 to a safe value for the equipment used. As
FIGURE 6 and operate a suitable meter to cause it to
such pressure goes down, bellows 43 will automatically 35 issue a corrective signal. In so moving, bellows 4312
move to the right, as viewed in FIGURE 3, and dis
will also swing arm 51b to the right-hand side of indica
engage contacts 72 and 73, whereupon valve 17 will
tor scale Sb. A galvanometer may be in controller 34
automatically close and the action of differential pres
like galvanometer 58 in which event, the pointer would
sure controller 25 will remain as the controller for the
move to the right of the zero position along scale 62 un
40
furnace operation within the prescribed differential pres
til, in the case of an abnormal rate of differential pres
sure limits subject thereafter as and when required to
sure change in a decreasing differential pressure direction,
the overriding and overtaking nature of the safeguards
provided by controller 30a.
the ?ag of the galvanometer will move between the oscil
lation coils and send out a corrective signal through con
In lieu of the top gas pressure controller 30a, a modi
ductor 35 to the relay 36 for the purpose described above
?ed controller illustrated in FIGURE 4 may be used 45 of operating operator 20', in series with a control action
and parts therein generally corresponding in structure and
by top gas pressure controller 30" due to an abnormal
functioning are provided with the same reference nu
rate of change in the increasing direction in the top gas
merals as those shown for controller 30a with the addi
pressure. As soon as a more normal pressure rate condi
tion of a prime accent thereto. In controller 30a’, end
tion is restored, valve 17' will reclose and control of the
48' of rod 46' is provided with a movable corepiece 49’ 50 differential pressure in the selected range will return to
which, however, is not magnetized but is made of a mag
controller 25'.
netic metal like soft iron. A ?eld is created for core 49’
Various changes in the arrangement and details of the
by a ?eld solenoid coil ‘78 which is energized through
illustrated embodiments may be made and further em
leads 79 by a source 80 of direct current which may be
bodiments may be provided without departing from the
adjusted in quantity by a rheostat 81, or any source of 55 spirit of my invention or the scope of the appended
recti?ed alternating current which has been suitably ?l
tered to reduce pulsating effects. Such excitation of coil
claims.
galvanometer 5S, ampli?er 69 and relay 70 shown in
troller, means for impressing the respective pressures
I claim:
78 and ?ux passing through core 49' will cause it to in
1. In a control for a blast furnace or the like, in com
duce an
in coil 54’ whenever rod 46' is moved
bination, a blast furnace, a gas line leading from the
by bellows 43’. The more rapid such movement the 60 upper portion of said blast furnace, a blast air main
leading to the lower portion of said furnace, a relief valve
greater the induced
and when the rate of increase
operatively connected to said gas line, a valve in said
in the top gas pressure in gas line 14 or 14', as the case
gas line to vary the opening therethrough, a normally
may be, becomes excessive, the rapidity of such axial
closed main relief valve operatively connected to said
movement of core 49' will be such that the coil leads
to a conventional meter control and relay system 82, 65 blast main, an auxiliary relief valve operatively con
nected to said blast main, a differential pressure con
which may have signal elements therein in the form of
controller 30a, or some other automatic control such as
a contact meter with a built-in relay, or any suitable com
mercial fast-acting potentiometric controller.
Thus, a
corrective signal is issued to the terminals on the block
71' and conductor 32 (or '32’), as the case may be,
whenever such top gas pressure rate is abnormal. Fur
ther, as and when contacts 72’ and 73' engage, current
substantially in said blast main and gas line upon said
di?erential pressure controller, a signal connection be
70 tween said differential pressure controller and a propor
tioning operator for said valve in said gas line, a signal
connection between said differential pressure controller
and a proportioning operator for said auxiliary relief
valve, means for operating at least one of said two last
75 mentioned valves in response to its said signal connection
3,092,680
7
respectively, a top gas pressure ‘controller, means for
impressing the pressure in said gas line upon said top
gas pressure controller, an on-oif operator for said main
relief valve, rate of change means operatively connecting
said top’ gas pressure controller to said main relief valve
operator, said rate of change means including means for
will cause said top gas pressure controller ‘to open said
normally closed blast main-relief valve.
3. In acontrol for av blast furnace or the, like, in com
bination, a differential pressure controller and trans
mitter for said blast furnace, means for impressing the
differential pressure through the stock burden in said
blast furnace upon said controller and transmitter for
routine control of said blast furnace, a differential pres
sure rate controller operatively connected to said dif
said pressure in said gas line, magnetic response means to 10 ferential pressure controller and transmitter responsive
to the rate of change in differential pressure, said rate
operate said on-o?f operator when said signal force has
controller
providing magnetically induced currents pro-v
a predetermined magnitude corresponding to a rate
portional to the rate of differential pressure change re
above said predetermined rate, said magnetic response
spectively at least in a decreasing direction to generate a
means being ineffective to operate said on-oif operator
corrective
impulse, a top gas pressure rate controller re
when the rate of change in said pressure in said gas line
sponsive to the rate of change in the gas pressure adja
is below said predetermined rate, and a high limit switch
generating ‘a magnetic signal force for said signal con
nections by‘ physical movement thereof relative to a
solenoid coil above a predetermined rate of change in
in said top gas pressure controller operatively connecting
‘the same to said operator for said main relief valve,
whereby an ‘abnormal rate of change in the pressure in
, cent the top of said stock burden, said last-named rate
from the upper portion of said blast furnace, a blast air
sued by said top gas pressure rate controller when cou
controller having a physically movable member providing
magnetically induced currents proportional to the rates
said gas line above said predetermined rate or the achieve 20 of pressure change respectively in an increasing direction
,to generate a corrective impulse when said member
ment of the high limit gas pressure value in said gas line
moves at a rate in excess of a predetermined rate, means
will cause said top gas pressure controller to override said
for rendering said physically movable member ine?ec
‘differential pressure controller by the opening of said nor
tive to generate said corrective impulse at a rate of change
mally closed main relief valve.
below said predetermined rate, a sequential relay opera
25
2. In a control for a blast furnace or the like, in com
tively connected to both said differential pressure rate
bination, a blast furnace, a differential pressure con
controller and said top gas pressure rate controller, said
troller connected to taps transmitting respective pressures
relay
being responsive to a leading corrective impulse is
at di?erent levels of said blast furnace, a gas line leading
main leading to the lower portion of said furnace, a valve 30 pled with a following corrective impulse issued by said
di?erential pressure rate controller, a relief valve con
in ‘said gas line to vary the opening therethrough, an oper
nected to the bottom of said blast furnace, and an opera
ator for said valve in said gas line, a normally closed
tor for said relief valve operatively connected to said re
‘blast ma'in relief valve, an operator for said blast main
lay to receive a corrective signal issued by said relay and
relief valve, means for operating said ?rst-named valve
7
'to regulate the pressure in said gas line, a top gas pres 35 open said valve.
sure controller connected-to said gas line, rate of change
References Cited in the ?le of this patent
means operatively connecting said top gas pressure con
UNITED STATES PATENTS
troller to said blast main relief valve operator, said rate
of change means including means for generating a mag
2,178,563
Cressy _______________ __ Nov. 7, 1939
40
netic signal ‘force by a movement thereof above a prede
2,430,757
Conrad et a1. ________ __ Nov. 11, 1947
2,436,639
Fans _______________ __ Feb. 24, 1948
termined rate relative to an energized coil and non-con
2,471,776
tact response means for said ‘force, said non-contact re
2,609,831
sponse means being ineffective to operatively connect
‘said top gas pressure controller to said blast main relief 45 2,625,386
2,751,576
valve operator at a rate of change below said predeter
2,814,479
mined rate, whereby an abnormal rate of change in the
pressure in said gas line above said predetermined rate
2,816,570
Reece _____________ __ May 31, 1949
MacGeorge __________ __ Sept. 9, 1952
Leone _______ _'_ _____ __ Jan. '13, 1953
Soergel et'al. _________ __ June 19, 1956
Leone ______________ __ Nov. 26, 1957
Coulbourn et a1 ________ __ Dec. 17, 1957
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