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Патент USA US3060304

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Och 23. 1962
_
w. M. LEEDS
3,060,294
CIRCUIT INTERRUPTER
Filed Oct. 30, 1957
2 Sheets—Sheet 1
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WITNESSES
WK 4W
Dim WM
INVENTOR
Winthrop M. Leeds
BY
WKW
ATTORNFY
United States Patent
1C6
3,060,294
Patented Oct. 23, 1962,
2.
1
the pedestal reservoir so that contaminated, arced gas
3,060,294
CIRCUIT INTERRUPTER
Winthrop M. Leeds, Forest Hills, Pa., assignor to West
inghouse Electric Corporation, East Pittsburgh, Pa., a
corporation of Pennsylvania
will not be forced under pressure back into the gas reser
voir pedestal, and breakage of the pedestal reservoir will
not affect the maintenance of gas pressure over the liquid
level in the sump.
_
Further objects and advantages will readily become
apparent upon reading the following speci?cation, taken
in conjunction with the accompanying drawings, in which:
Filed Oct. 30, 1957, Ser. No. 693,306
8 Claims. (Cl. 200-148)
FIG. 1 is a side elevational view of a circuit interrupter
This invention relates to circuit interrupters in general
and, more particularly, to arc-extinguishing structures 10 embodying the principles of the present invention, with
the contact structure being indicated in the closed-circuit
and operating mechanisms therefor.
position;
In U.S. patent application ?led January 22, 1957, Serial
FIG. 2 is a fragmentary, enlarged, partly diagrammatic,
vertical sectional view through a portion of the upper end
to the assignee of the instant application, there is dis 15 of the circuit interrupter of FIG. 1, with the contactv
structure being likewise shown in the closed-circuit posi
closed and claimed a type of circuit interrupter utilizing
tion; and,
a serially related pair of arc-extinguishing units disposed
FIG. 3 is a fragmentary, top plan view of a portion
at the opposite ends of a single terminal bushing, each
of the circuit interrupter of FIG. 2, with a portion of the
of the units being disposed within a surrounding weather
proof porcelain casing. The units were of the puffer type, 20 intermediate housing broken away to illustrate the indi
cator mechanism, again the contact structure being indi
in which a piston and ori?ce, movable with the movable
cated in the closed-circuit position.
contact, reciprocally operate within an operating cylinder
Referring to the drawings, and more particularly to
to force compressed gas through the ori?ce to effect eX
FIG. 1 thereof, the reference numeral 1 generally desig
tinction of the are established therein.
It is a general object of the present invention to im 25 nates a circuit interrupter of the type including a pair of
laterally extending arc-extinguishing units 2 (FIG. 2),
prove upon the circuit interrupter described in the afore
enclosed within horizontally extending weatherproof cas
said application, and particularly to bring about more
ings 3, in this particular instance being made of porcelain.
effective and rapid operation by the utilization of a hy
The inner ends of the porcelain casings 3 are secured
draulic operating mechanism.
Another object of the invention is to provide an im 30 to ring-shaped mounting ?anges 4 by cement 5, and, as
shown in FIG. 2, the porcelain casings 3 are supported
proved hydraulic operating mechanism for a pair of
in a horizontal manner, extending laterally outwardly
serially related arc-extinguishing units, in which the
from an intermediate mechanism housing 7. The interior
operation of the two movable contact structures is syn
8 of the intermediate mechanism housing 7 is preferably
No. 635,400, now Patent No. 2,981,814, by Robert E.
Friedrich, entitled, “Circuit Interrupters,” and assigned
chronized mechanically so that assurance may be had
that both arc-extinguishing units are operating in a satis
35 ?lled with air at atmospheric pressure.
factory manner by opening and closing substantially
simultaneously.
Still a further object of the invention is to provide an
improved hydraulic operating mechanism for a circuit
interrupter utilizing arc-extinguishing units, each of which
effects the compression of gas, in which an improved
seal is provided to prevent the contamination of the
The intermediate mechanism housing 7 is supported at
the upper end of an upstanding insulating gas reservoir
pedestal 9, more clearly shown in FIG. 1. The pedestal
9 is formed from a suitable Weatherproof material, in
this particular instance porcelain. The pedestal 9, in
turn, is supported on top of .a lower mechanism compart-.
ment 10, which may have a door 11 opened by a manually
hydraulic operating ?uid with the arc-extinguishing gas.
operable handle 12.
The mechanism compartment 10
arc-extinguishing units in which an improved indicator
devce is employed to positively indicate the open and
closed-circuit positions of the movable contact.
A further object of the invention is to provide an im 50
sulating operating cylinder 14, supported at the end of
a hydraulic operating cylinder 15. Reciprocally movable
may rest upon any suitable base 13.
Another object of the invention is to provide an im 45
As more clearly shown in FIG. 2, each of the two
proved circuit interrupter utilizing a pair of serially related
serially related arc-extinguishing units 2 includes an in
proved circuit interrupter in which the one or more arc
extinguishing units are supported upon an upwardly ex
within the operating cylinder 14 is a piston 16 having a
laterally jutting ori?ce portion 17. The piston 16 is
carried by a movable contact 18, the latter being disposed
at the end of a contact rod 19. Located at the inner end
tending insulating pedestal serving as a gas reservoir
of the contact rod 19 is a differential piston, generally
chamber, in which the interior of the insulating reservoir
by the reference numeral 20.
pedestal is hollow and ?lled with a compressed gas of 55 designated
Cooperable with the movable contact 18 is. a relatively
relatively high dielectric strength.
stationary contact 21, the latter being supported by a
Yet a further object of the invention is to provide an
conducting
closure cap 22. The closure cap 22 may have
improved circuit interrupter of the type speci?ed in the
immediately preceding paragraph, in which the upstand
a terminal stud 23 a?ixed thereto, to which may be con
nected an external line conductor, not shown.
ing pedestal in addition serves as a conduit for the arc~ 60
As shown in FIG. 2, the closure cap 22 is secured, by
extinguishing gas to the one or more interrupting cham
any suitable clamping means, to a ring-shaped mounting
bers.
flange 24, the latter being affixed, as by cement 25, to the
Another object is to provide an improved hydraulic
operating mechanism in which gas pressure is employed
outer end of the porcelain casing 3. Preferably the inner
surface of the porcelain casing 3 has intersecting conical,
tapered surfaces 26, intersecting at the point 27, for a
upon the liquid level in the sump, so that a positive 65
pressure exists at all times in the control line leading
purpose to be explained hereinafter.
from the pilot valve to the main operating valve. This
Each of the two differential pistons 20 has a rack 28
prevents air leakage into the control line by such posi
secured thereto, as shown in FIG. 2, which racks 28
mesh with a pinion gear 29 ?xed on a shaft 30, the latter
tive pressure.
A further object is to provide an upstanding pedestal 70 extending outwardly from'the operating cylinder 15 in a
manner more clearly illustrated in FIG. 3 of the drawings.
gas reservoir for a circuit interrupter in which suitable
As illustrated in FIG. 3, the indicator shaft 30 has a
check valves are employed in the feed lines leading from
3
3,060,294
4
pinion gear 31 keyed thereto adjacent its outer end, which
pinion gear 31 meshes with a larger gear 32, the latter
effecting the rotation of a second indicator shaft 33.
Disposed externally of the intermediate mechanism hous
ing 7, at the outer end of the indicator shaft 33, is an
the conduit 65 upwardly through a control conduit or op
erating line 66. The upper end of the control conduit 66
terminates within a space 67 below the plunger piston 46.
A drain conduit 68 interconnects the space 69 above the
plunger piston 46 with the drain conduit 54.
The regions 70 within each porcelain casing 3 are con
indicator pointer 34, the latter indicating the “open” and
“closed” positions of the interrupter 1, as more clearly
nected by a conduit 71 through an upstanding feed con
shown in FIG. 1 of the drawings.
duit 72 and through a check valve 73 to the region 59
The outer sides of each differential piston 20 is con
within hollow gas reservoir pedestal 9.
stantly maintained under high pressure, as caused by the 10
In the closed~circuit position of the interrupter the
presence of a high-pressure operating ?uid, such as ‘oil
electrical circuit therethrough includes left-hand terminal
35, disposed within a pair of opening conduits 36, the
stud 23, closure cap '22, stationary contact 21, movable
latter being connected together and with an enlarged sup
contact 18, movable contact operating rod 19, conducting
ply conduit 37. The upper end of the hydraulic conduit
hydraulic operating cylinder 15 to the other conducting
37 is connected to a high pressure accumulator, generally 15 movable contact rod 19 and, in a similar manner, to the
designated by the reference numeral 38.
other line terminal stud 23, as shown in FIG. 1.
The high-pressure accumulator 38 includes a reservoir
When it is desired to effect the opening of the circuit
tank ‘39, within which is situated a movable piston or
interrupter 1, the pilot valve 64 is operated, either man
diaphragm 40 biased downwardly under pressure by a
ually or electromagnetically, to thereby permit high
suitable gas, such as nitrogen N2 disposed under pressure
pressure hydraulic ?uid, such as oil 35, to pass from the
in the region 41 at the upper end of the reservoir tank
high pressure conduit 63, through control conduit 66 to
39. The nitrogen is preferably under high pressure, say
space 67 below plunger piston 46. Since the space 69,
2,000 pounds per square inch gauge.
above plunger piston 46, is connected by the drain con
'It will be obvious, therefore, that the accumulator 38
duit 68 to a relatively low pressure, the plunger piston
maintains the hydraulic ?uid, such as oil 35, under pres— 25 46 rapidly moves upwardly against the opposition af
sure of 2,000 p.s.i. within the hydraulic conduits 36,
forded by biasing spring 49. This will cause the sleeve
thereby tending to force the differential piston 20 and
valve 47 to move upwardly, closing off the inlet region
hence the movable contact rods 19 toward each other in
53 of the main hydraulic Valve 44, and opening the out
the opening direction.
let space 74 of main hydraulic valve 44, through con~
To maintain the movable rods 19 in the closed-circuit 30 duit 42, with the space 75 on the back sides of the dif
position a hydraulic conduit 42 is connected to the hy
ferential pistons 20. Since the space 76 on the front
draulic operating cylinder 15 in back of the differential
sides
of the differential pistons 29 is constantly main
pistons 20, and since the contact rods 19 move out of
tained
at high pressure, the pistons 20' will be rapidly
the chamber 15, the effective closing area of the pistons. 20
is greater than the effective opening area. Equal pres 35 moved toward each other by the high-pressure hydraulic
fluid 35 to thereby effect the separation of the movable
sure conditions on both sides of the differential pistons 20
contacts 18 away from the stationary contacts 21.
will, therefore, cause the movable contact structures 18
An arc, not shown, will be established between each
to remain in the closed-circuit position, as shown in
pair of contacts 18, 21 within each ori?ce 17, and will
FIG. 2.
be extinguished by the flow of ?uid, such as SP6, com?
The lower end of the hydraulic conduit 42 is con
pressed within the space '77 back of each piston 16. This
nected to a main hydraulic valve, generally designated by
compressed SP6 will be forced out of the space 77, within
the reference numeral 44. The main hydraulic valve 44
the operating cylinder 14, through the insulating ori?ce
includes a casing 45, within which reciprocally moves a
17, to effect extinction of the are drawn between the
plunger piston 46, carrying a sleeve valve 47 through a
contacts 18, 21.
spider 48. The sleeve valve 47 is biased downwardly by
Since the motion of the two movable contact operat
a compression biasing spring 49. ‘In addition, the sleeve
ing
rods 19‘ is synchronized by the meshing of the two
valve 47 has a plurality of, in this particular instance,
movable racks 28 with pinion gear 29, the two contact
four openings 50, which connect at all times an annular
gaps will close simultaneously, dividing the voltage
space 51, within casing 45, with the region 52 within
stresses substantially equally. Also on opening there will
sleeve valve 47.
be established substantially equal arc-extinguishing con
The supply conduit 37, as shown in FIG. 2, connects
ditions within each arc-extinguishing unit 2, so that each
with the space 53 within the upper end of the valve casing
arc-extinguishing unit will contribute its full share to the
45. Connected to the lower end of the valve casing 45 is
interrupting
effort.
a drain conduit 54, composed of insulating material and
To
prevent
the contamination of the SP6 with the hy
extending downwardly interiorly within the insulating gas 55
draulic ?uid, such as oil 35, there is provided at each
reservoir pedestal 9. The lower end of the insulating
outer end of the hydraulic operating cylinder 15 a seal
drain conduit 54 communicates with a sump 55, located
ing region 78, which is connected, by a drain pipe 79,
at ground potential within the mechanism compartment
to the main drain conduit 54. Thus, any high-pressure
10 (FIG. 1).
oil 35, which may lea‘k along the contact rod 19 through
Disposed above the oil level 56 within the sump 55 is
a suitable arc-extinguishing gas, such as sulfur hexa
?uoride ‘SP6 maintained at a suitable lower pressure, such
as 60 p.s.i. The SP6 at 60 p.s.i. within the region 57 of
the sump 55 also communicates by way of conduit 58
and a check valve 58a to the region 59 interiorly of the
insulating gas reservoir pedestal 9.
The sump 55 is also connected by a conduit 60 through
a ?lter 61 to a compressor pump 62.
The oil 35 may
60
the opening 80‘ within the hydraulic operating cylinder
15, will merely drain downwardly through the drain pipe
79 through drain conduit 54 to the sump 55. It will be
noted that the pressure within the sealing region 78 is the
same as the pressure within the region 70 within porce
65 lain casing 3 so that, as a result, there will be no tend
ency for the SP6 to leak along the contact rod 19‘ through
opening 81 within insulating operating cylinder 14.
The rotation of pinion gear 29‘, by the racks 28, will
thus be pumped to a high pressure and fed through a
effect corresponding rotative movement of the indicator
conduit 63 upwardly interiorly through pedestal 9 back
up into the supply conduit 37, and hence into the high 70 shaft 30, and hence, through the gears 31, 32 (FIG. 3)
pressure accumulator 38. A pilot valve 64 is provided in
a conduit 65 interconnecting high-pressure conduit 63 and
the low pressure drain 54. This pilot valve 64 controls
effect an external indicating movement of the indicator
pointer 34, as more clearly illustrated in FIG. 3 of the
drawings.
All the time that the units 2 are in the open circuit
the admission of high-pressure hydraulic ?uid 35 from 75 position,
the pilot valve 64 remains in the position per
s,0eo,294.
6
5
mitting high pressure oil to communicate with the space
67 beneath the plunger piston 46, thereby maintaining
No. 693,309, ?led October 30, 19-57, by Albert P. Strom,
and assigned to the assignee of the instant application.
‘Certain features of the master control valve 44 are de
the slide valve 48 in its upper position, blocking off en
trance region 53. This upward position of sleeve valve
48 is in opposition to the force of gravity and to the force
scribed and claimed in United States patent application,
Serial No. 709,233, now Patent No. 3,008,017, ?led Jan~
uary 16, 1958, by Albert P. Strom and William H.
Fischer and assigned to the same assignee as the present
a?orded by the biasing spring 49.
When it is desired to effect the closing of the circuit
through the interrupter 1, the pilot valve 64 is manually
application.
Although there has been shown and described a specific
or electromagnetically operated to its other position, so
as to connect the space 67 below plunger piston 46 to the 10 structure, it is to be clearly understood that the same,
was merely for the purpose of illustration, and that‘
main drain conduit 54. The spring 49, and the force of
changes and modi?cations may readily be made therein
gravity, will move the plunger piston 46 downwardly, it
by those skilled in the art, without departing from, the
being apparent that now the pressure within the spaces 67,
spirit and scope of the invention.
69 are equal, as brought about the drain pipe 68. The
I claim as my invention:
downward movement of the ‘slide valve 47 will close off 15
1. A circuit interrupter including a sealed casing. con
the drain region 74 of main hydraulic valve 44 and will
taining an arc extinguishing gas, separable contacts dis
open up the inlet high-pressure region 53. Thus, high
posed within said sealed casing separable to establish an
pressure oil 35 will pass through the high-pressure inlet
are, a movable contact rod for effecting the movement
region 53 across the upper end of sleeve Valve 47, through
openings 50 and annular space 51, and through conduit 20 of one of said separable contacts, a hydraulic mecha
nism for actuating said movable contact rod including a
42 to the region 75 in back of the differential pistons 20.
hydraulic operating cylinder, a hydraulic piston secured
Since the rear faces of the di?erential pistons 20 have a
adjacent one end of said movable contact rod and mov
greater effective cross-sectional area than the front faces,
able within said hydraulic operating cylinder, means de
as caused by the cross-sectional area of the contact rods
19, the movable contacts 13 will be moved outwardly 25 ?ning a bore out of said hydraulic operating cylinder
from operating cylinder 15 and into contacting engage
along which said movable contact rod moves, a sealing
ment with the stationary contacts 21. This will complete
chamber disposed along said bore of the hydraulic operat~
ing cylinder and containing said arc-extinguishing gas, a
the electrical circuit through the interrupter 1.
It is to be understood that instead of employing oil 35,
drain for said sealing chamber, and the gas pressure of
any suitable hydraulic fluid may be employed. In addi 30 the arc-extinguishing gas within said sealing chamber be
tion, instead of using SP6 any suitable arc-extinguishing
ing substantially the same as the gas pressure adjacent
the separable contact within said sea'led casing in the
gas may be utilized.
From the foregoing description it will be apparent
closed circuit position of the circuit interrupter.
that there is provided a high-speed hydraulically actuated
2. A circuit interrupter including a sealed casing con
circuit interrupter, in which the contact motion is syn 35 taining an arc extinguishing gas, separable contacts dis
chronized. An equalizing seal is provided to prevent the
posed within said sealed casing separable to establish an
contamination of the liquid with the arc-extinguishing
?uid. Entrance of hydraulic oil into the heated arcing
arc, a movable contact rod for effecting the movement of
one of said separable contacts, a hydraulic mechanism
‘for actuating said movable contact rod including a hy—
chamber might cause a chemical reaction between the
oil vapors and the heated and arced SFS gas. Division 40 draulic operating cylinder, a hydraulic piston secured ad
of voltage between the units 2 could be achieved by suit
jacent one end of said movable contact rod and movable
able capacitor tubes extending within the porcelain casings
3 for such voltage dividing purpose. Also, when using
within said hydraulic operating cylinder, means de?ning
a bore out of said hydraulic operating cylinder along
SP6, should the ambient temperature reach a su?iciently
low value to cause the condensation of SP6, the tapered
which said movable contact rod moves, a sealing cham
ber disposed along said bore of the hydraulic operating
cylinder and containing said arc-extinguishing ‘gas, a drain
interior surfaces of the porcelain casings 3 will provide
ready drainage for the liquid SP6.
The use of SP6 at 60 p.s.i. within hollow gas reservoir
for said sealing chamber, and the gas pressure of the arc
insulating pedestal 9 will improve the voltage-withstand
ing ability of the porcelain pedestal 9, and, in addition,
extinguishing gas within said sealingchamber being sub
stantially less than the hydraulic driving pressure.
50
3. A circuit interrupter including separable contacts,
will permit the pedestal 9 to serve as a conduit from the
pipe 58 to the lower end of the feed conduit 72. More
over, should pressure be lost within pedestal 9, as a result
a movable contact rod for effecting the movement of
one of the separable contacts, a hydraulic mechanism for
of cracking thereof or leakage, the check valve 73 will
operating cylinder, a hydraulic piston movable within
said hydraulic operating cylinder and secured adjacent
actuating said movable contact rod including a hydraulic
prevent the pressure dropping within the casings 3, thereby
maintaining adequate dielectric strength between the con
tacts 18, 21 should they be separated at this time.
Also the check valve 73 will prevent the high arcing
pressure within the regions 70 of the extinguishing units
one end of said movable contact rod, said hydraulic op
erating cylinder having a bore through one wall thereof
through which the movable contact rod moves, a sealing
chamber disposed along said bore of the hydraulic op
2 from backing into the feed line 72 and forcing con 60 erating cylinder, a drain for said sealing chamber, and
taminated, arced gas back into the gas reservoir 9.
said sealing chamber containing gas at a relatively low
The check valve 58a will prevent a loss of pressure
pressure compared to the hydraulic driving pressure.
in the region 57 above the liquid level in the sump 55,
4. A circuit interrupter of the gas blast type including
should the porcelain casing 9 crack and lose its gas pres
an upstanding hollow insulating pedestal, one or more
65
sealed interrupting units supported from the upper end
An important feature of the invention is the main
of said hollow pedestal, arc-extinguishing means includ
tenance of this gas pressure in the region 57 of sump
ing piston putter means disposed in at least one sealed
55, for this will maintain a positive pressure within con
interrupting
unit, hydraulic operating means at high po
trol line 166, even though the latter is connected to the
sump by pilot valve 64. Otherwise a negative pressure 70 tential for actuating said piston puffer means, a gas under
pressure within said sealed interrupting units, and the
could exist in control line 66 by the height of the liq
same gas at substantially the same pressure completely
uid therein, and air leakage through the seals for the
?lling said hollow pedestal.
line 66 might result.
5. A circuit interrupter including a hollow supporting
Certain features of the circuit interrupter are set forth
and claimed in United States patent application, Serial 75 pedestal completely ?lled with an arc-extinguishing gas
sure.
3,060,294
under pressure, a sealed interrupter casing containing
the same gas supported at the upper end of said support
ing pedestal, arc-extinguishing means including piston
puffer means disposed interiorly Within said sealed in
terrupter casing, hydraulic operating means for actuating
said piston puffer means, and a gas feed conduit inter
connecting the interior of said hollow supporting pedestal
8. A circuit interrupter including a pair of diverging
sealed interrupter casings, a pair of relatively stationary
contacts disposed at the outer extremities of the sealed
interrupter casings, ‘a pair of cooperable movable con
tacts movable toward each other and carrying gas-blast
putter pistons, a pair of movable contact rods supporting
said pair of movable contacts and having a pair of ac
with the sealed interrupter casing so that the pressure
tuating pistons secured thereto at the inner ends thereof,
of the gas within the sealed casing is substantially at
a ?uid motor at high potential having a single operating
the pressure of the gas within said hollow supporting 10 cylinder within which is disposed said pair of actuating
pedestal.
6. A circuit interrupter including a pair of diverging
‘sealed interrupter casings, a pair of relatively stationary
pistons, rectilinear motion of said actuating pistons away
from each other within said single operating cylinder
re?ecting closing motion of said pair of movable contact
contacts disposed at the outer extremities of the sealed
‘rods and movable contacts, a movable rack associated
interrupter casings, a pair of cooperable movable con 15 with each actuating piston, a pinion gear disposed sub
tact rods carrying gas-blast puffer pistons, a hydraulic
operating mechanism for actuating said movable pair of
contact rod-s including a hydraulic operating cylinder
at high potential, a pair of hydraulic pistons secured to
adjacent inner ends of said movable contact rods and
reciprocally movable within said hydraulic operating
cylinder, means for constantly maintaining high hydraulic
stantially centrally Within said single operating cylinder
and meshing with the two movable racks to synchronize
their motion, said ?uid motor having a source of high
pressure ?uid, and valve means for admitting high
pressure ?uid from said source to ‘the region within said
single operating cylinder between the actuating pistons
to e?fect simultaneous outward closing motion of the pair
pressure upon the outer sides of the hydraulic pistons
of movable contact rods, and a rotatable indicator shaft
tending to effect opening operation thereof, means for
connected to said pinion gear and extending through a
reducing the hydraulic pressure between the hydraulic 25 wall of said operating cylinder to e?ect an external in
pistons relative to the pressure on the outer faces thereof,
dication of the position of the movable contacts.
a movable rack associated with each hydraulic piston,
:and a pinion gear disposed substantially centrally within
References Cited in the ?le of this patent
said hydraulic operating cylinder and meshing with the
two movable racks to synchronize the opening and clos 30
UNITED STATES PATENTS
ing motion of the pair of movable contact rods.
1,706,746
Rice ________________ __ Mar. 26, 1929
7. A circuit interrupter including a pair of diverging
sealed interrupter casings, a pair of relatively stationary
contacts disposed at the outer extremities of the sealed
interrupter casings, a pair of cooperable movable con 35
tact rods carrying gas-blast puffer pistons, a hydraulic
operating mechanism for actuating said movable pair
of contact rods including a hydraulic operating cylinder
at high potential, a pair of hydraulic pistons secured to
adjacent inner ends of said movable contact rods and
reciprocally movable within said hydraulic operating
cylinder, means for constantly maintaining high by
draulic pressure upon the outer sides of the hydraulic
pistons tending to effect opening operation thereof,
means for reducing ‘the hydraulic pressure between the 45
hydraulic pistons relative to the pressure on the outer
faces thereof, a movable rack associated with each hy
draulic piston, and a pinion gear disposed substantially
1,895,907
1,933,356
Baum ________________ __ Jan. 31, 1933
Warner ______________ __ Oct. 31, 1933
2,206,324
2,281,139
2,436,190
2,449,518
2,541,917
2,555,898
2,604,562
2,611,846‘
2,662,133
2,678,983
2,719,195
2,748,226
2,757,261
2,783,337
Lade ________________ __ July 2,
Clark ______________ __ Apr. 28,
Boisseau et al _________ __ Feb. 17,
Strorn ______________ __ Sept. 14,
De Mers ____________ __ Feb. 13,
Paterson et a1. ________ __ June 5,
Paul ________________ __ July 22,
Applegate __________ __ Sept. 23,
Burmeister ____________ __ Dec. 8,
Strorn ______________ __ May 18,
Thibaudat __________ __ Sept. 27,
MacNeill et a1 _________ __ May 29,
Lingal et al ____________ _. July 31,
Beatty ______________ __ Feb. 26,
centrally within said hydraulic operating cylinder and
meshing with the two movable racks to synchronize the 50
opening and closing motion of the pair of movable con
tact rods, and an indicator shaft connected to said pinion
gear and extending through the Wall of the hydraulic
operating cylinder to give an external indication of con
tact rod position.
1940
1942
1948
1948
1951
1951
1952
1952
1953
1954
1955
1956
1956
1957
FOREIGN PATENTS
599,970
755,016
760,355
765,524
Great
Great
Great
Great
Britain
Britain
Britain
Britain
________ __ Mar. 25,
________ __ Aug. 15,
________ __ Oct. 31,
__________ __ Jan. 9,
1948
1956
1956
1957
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