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Патент USA US2547205

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April 3, 1951
R. E. FRIEDRICH
2,547,202
OIL CIRCUIT INTERRUPTER
Filed Sept. 27, 1947
2 Sheets-Sheet 1
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April 3, 1951
R. E. FRIEDRICH
2,547,202‘
OIL CIRCUIT INTERRUPTER
Filed Sept. 27, 1947
WITNESSES:
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2 Sheets-Sheet 2
6.6
INVENTOR
@W
Patented Apr. 3, 1951
2,547,262
UNITED STATES PATENT OFFICE
2,541,202
7
on. orncorr INTERRUPTER
Robert E. Friedrich, Pittsburgh, Pa, assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application September 2?’, 1947, Serial No. 776,569
6 Claims.
(C1. 200--150)
1
2.
This invention relates to circuit interruptcrs
in general, and more particularly, to arc-extin
guishing structures and operating mechanisms
therefor.
Fig. 2 is an enlarged vertical sectional view
through the left—hand arc-extinguishing unit of
Fig. 1, the contact structure, being shown in the
.
. closed circuit position;
A-‘ general object of my invention is to provide
Fig.3 is ‘a view taken at right angles to that
of Fig. 2 with the contact structure shown in the
partially open circuit position, and
Fig. 4 is an enlarged fragmentary view taken’
an improved circuit interrupter in which an im—
proved hydraulic operating mechanism is pro
vided to effect operation of the contact struc
ture.
Another object is to provide an improved arc
extinguishing unit in which the contact struc
ture is hydraulically operated and which is pro
vided with venting means to vent the unit fol—
substantially along the line IV—IV of Fig. 3. '
Referring to the drawings, and more particu
larly, to Fig. 1 thereof, the reference numeral I
designates a tank ?lled to the level 2 with a
suitable arc-extinguishing fluid 3, in this in
stance circuit breaker oil. Depending from the
lowing circuit interruption, which venting means
is actuated by-the improved hydraulic operating
mechanism.
Still another object is to provide an improved
circuit interrupter of the type establishing both
cover 4 of the tank I are a pair of terminal bush
ings 5 which support at their lower ends arc
extinguishing units, generally designated by the
reference character 6.
a pressure-generating :arc and an interrupting
The arc-extinguishing units 6 are electrically
arc with ?uid passage means interconnecting the
interconnected in the closed circuit position, as
two arcs. In my invention, I provide a separate
shown in Fig. l, by a bridging member ‘I recipro
?uid moving means to .assist in low current i..cally operated in a vertical direction by an in~
terruption and I provide a separate passage inter~
sulating lift rod 8. The lift rod 8 may be actuated
connecting the ?uid moving means with the in
in a vertical direction by suitable mechanism,
terrupting arc to prevent contamination of the 25 not shown, which is responsive to either manual
?uid sent by the ?uid moving means toward the
operation or to the existence of excessive cur
interrupting are.
rent conditions in the protected circuit.
A further object is to provide an improved arc
Referring to Fig. 2, which more clearly shows
extinguishing unit with venting means at op—
the internal construction of the arc-extinguish
posite ends thereof to provide a chimney vent
ing units it will be noted that a conducting con—
ing effect, and to provide hydraulic means which
not only e?ects separation of the contact struc
ture associated with the unit but also effects
opening of the venting means following inter
ruption of the circuit.
Another object is to provide an improved hy
draulic operating mechanism for the contact
tact foot 9 is threadedly secured and clamped to
the lower end of the terminal stud, not shown,
which extends interiorly through the terminal
bushing 5. integrally formed with the contact
foot 9 is the top metallic plate H] of the unit 5.
The plate Ill in conjunction with insulating tie
rods, not shown, ?xedly supports in place a plu
rality of insulating plates, more fully described
hereinafter and de?ning a relatively vented in
means of a circuit interrupter in which the con
struction is such as to minimize hydraulic fric
tion losses.
Still a further object is to provide
improved
circuit interrupter of the type speci?ed in the
immediately preceding paragraph in which a
terrupting chamber, generally designated by the
reference numeral H. A stationary contact !3
cooperates with a movable contact M to estab
lish an interrupting are 55 within the inter?
rupting chamber II, as more clearly shown in
Fig. 3. Rigidly secured to the'lower end of the
movable contact M is an insulating rod 16, the
lower end of which is ?xedly secured to another
movable contact member I‘! which makes engage
ment in the closed circuit position, as shown in
separate delayed acting low current piston is in~
corporated which is actuated following a prede~
termined opening movement of the hydraulic
operating mechanism.
Further objects and advantages will readily be—
come apparent upon reading the following speci
ings,
?cation
in which:
taken in conjunction with the
Figure l is a side elevational view, partly in
section, of an improved circuit interrupter ene
bodying my invention and shown in the closed
circuit position;
in)
with relatively stationary pressure—gen—
crating contacts 18.
_
The stationary contacts [3 are electrically con—
nected by a vertical spider construction IS with
relatively stationary contacts 29', the latter bear
-, ing against the external surface of the movable
2,547,202
contact [4 during the downward opening move—
ment thereof.
‘
end 4? of the movable contact member I‘! has an
The electrical connection between the stationary contacts i3, 28 may be effected by strap con
enlarged metallic cyindrical member Illa rigidly
secured thereto having diagonal cuts 43 formed
therein. The cuts 43 cooperate with an inwardly
extending ?ange portion 49 of the operating pis
nectors 2f, the latter being brazed to the outer
surfaces of the contacts I8, 20. Preferably, the
contacts i8, 25 are pivotally mounted by pins 22
and biased inwardly toward the movable con
tact structure by torsion springs 23.
The
movable
pressure-generating
contact
4
has a lost-motion connection with the lower end
4'! of the movable contact member H. The lower
ton 135 to provide a valve means, generally desig
nated by the reference numeral 58 which is closed
10 during the downward opening motion of the
operating piston :35 and movable contact member
member ll separates from the stationary pres"
sure~generating contacts l8 to establish a pres
H.
The valve means 50 closes during the open
ing operation by virtue of the fact that the flange
sure-generating are 26 within a relatively con
portion 49 covers the tops of the cuts or recesses
fined pressure-generating chamber, generally
48. During closing the valve means 58 is open
as later described.
designated by the reference numeral 2?. It will
be noted that there is provided a pair of verti~
A compression spring 52 is provided within the
lower end of the operating cylinder 39, having its
cally extending passages 28 interconnecting the
pressure-generating chamber 2‘! with the inter
rupting chamber ll. Thus, liquid under presw
lower end seated upon the closure cap 42 and
having its upper end bearing against an inwardly
sure from the pressure-generating chamber 2? 20 extending ?ange portion 53 of the operating pis~
may flow upwardly within the passages 23, as
indicated by the arrows 29, ‘into the interrupting
chamber i i to effect extinction of the interrupt~
ing arc l5 draw therein.
ton '65. Thus, during the closing upward motion
of the movable contact member H, the spring 52'
?rst raises the operating piston :35 to open the
valve means 58 and subsequently after the lost-'
Suitable insulating plate structure is provided 25 'motion
is taken up, strikes the cylindrical mem
de?ning the interrupting chamber i i which very
effectively directs liquid into intimate engage
ment with the interrupting are !5. This insulat
ing plate structure follows the teachings set forth
in United States patent application ?led Decem 30
ber 22, 1945, Serial No. 636,940, now Patent No.
On the other side of the ori?ce insulating plate
erally designated by the reference numeral 35.
Preferably, the vent plate 35 is composite and
consists of two identical halves 36 spaced later~
ally apart to provide a pair of opposed outwardly
extending vent passages 31, more clearly shown
in Fig. 3.
From the foregoing description, it will be ap
parent that the oil passes inwardly toward the
interrupting arc I5 through the opposed inlet
passages 32, thence through the orifices 34 pro
vided by the ori?ce plates 33 to exhaust out
wardly away from the interrupting arc l5 out
of the unit 6 through the opposed vent passages
31.
Extinction of the interrupting are it soon
follows and the circuit is interrupted.
It will be noted that the lower end of the mov
able contact member lll makes electrical engage
ment with contact clips 38 and passes down
wardly into an operating cylinder 3%. The op
erating cylinder 39 is threadedly connected at 49
to a cup-shaped metallic casting iii. The lower
end of the operating cylinder 39 is closed by an
apertured closure cap 122 threadedly secured, as
at 153, to the lower end of the operating cylinder
39. ' Apertures 44 are provided adjacent the lower
end of the operating cylinder 39 so that the region
below the operating piston ‘35 freely communi
cates with the region 55 which is substantially at
atmospheric pressure. The operating piston d5
since liquid can by pass the member 41a through
the recesses 48.
nism 54 also includes a pumping piston 55 havingv
an inwardly extending portion 56 which bears‘
against the outer surface of the operating cylin
der 39 being guided thereby. A battery of com
pression springs 5? is provided to bias the pump
ing piston 55 downwardly in the circuit opening
direction to thereby compress liquid within the
de?ne inlet passages 32, more clearly shown in
33 from the inlet plate 3l'is a vent plate, gen
being open during the entire closing operation
My improved hydraulically operated mecha
2,467,760, April 19, 19%, by Leon R. Ludwig, Ben
jamin P. Baker, and Winthrop M. Leeds, and
assigned'to the assignee of the instant applica
tion. Preferably, this plate structure consists of
?bre insulating piates of three different types.
The first type, designated by the reference char
acter 3!, has portions ‘removed therefrom to
Fig. 2. Adjacent each inlet insulating plate 3i
is, aninsulating ori?ce plate 33 having an ori?ce
34 provided therein through which passes the
movable contact member 14 during its opening
motion.
ber 41a to cause thereby upward closing motion
of the contact member ll, the valve means 50
I
.
region 58.
This liquid under pressure within the '~
region 58 may ‘pass through apertures 59 pros"
vided in the operating cylinder 39 to act down
wardly upon the operating piston 45 in the man
ner previously described.
The pumping piston 55 has a depending cylin
.
drical portion 60 which makes threaded engage
ment, as at Bl, with an insulating tube 62, the
lower end of which makes threaded engagement
with a metallic bumper 63. The bumper 63 is
in O preferably threaded, as at 64, adjacent the lower
end of the insulating tube 52.
The bridging member ‘I is composite, having an
upper conducting portion 65 and a lower insulat
ing portion 65. The portion 65 has an upwardly
extending piece iii which passes between a pair of
jaw-type stationary disconnect ?ngers 63, biased
toward each other by any suitable means, not
shown. The disconnect ?ngers 6B are electrically
connected by a connector 59 to the lower metallic
plate 19 of the unit 6.
I have provided a cylindrically-shaped follower
member ‘H which has an inwardly extending
?ange portion i2 at its upper end. The upper
edge 7.73 of the pumping piston 55 picks up the
follower member 'H during the closing stroke
against the downward biasing action exerted by
a compression spring ill.
The upper end of the
compression spring ‘it bears against the metallic
casting M, and the lower end of the compression
spring 14 bears against a radially outwardly ex
tending flange portion 75 of the follower member
‘I I.
To facilitate low current interruption when the _
pressure generated within the pressure-generat- '
ing chamber 21 by the pressure-generating arc _
5
2,547,202
6
2511s relatively low, I have provided a separate
independently movable pumping piston 7.6 which
is picked up during the closing stroke by a shoul
der portion 11 of the pumping piston 55. Arela
tively light compression spring 18 retracts the
pumping piston "56 in the closed position, as
shown in Fig. 2, forcing the upper end 19 thereof
against steps 89 ‘integrally formed with the
of the interrupter, as shown in Fig. .2, the elec
trical circuit therethrough includes conducting
contact foot 9, conducting plate it, .shunt =95.
stationary contact is, movable contact 14,
stationary contacts 20, strap connectors 2i, sta
tionary contacts l8, movable contact member :17,
contact .clips 33, casting 4], lower plate ‘it, con
nectors 59, stationary disconnect ?ngers 68, up
standing conducting piece 6'! of the bridging
casting 4i .
Consequently, during the opening stroke there 10 member ‘I and through the right-hand arc
is a time-delay before the follower member ‘H
picks up the pumping piston 75 to force it down
wardly by the action of the compression spring
14. The reason for the delayed action of the
extinguishing unit 6 in like manner to the other
terminal of the interrupter.
When it is desired to open the electrical circuit
passing through the interrupter, suitable mecha
nism, not shown, which is responsive to either
pumping piston 75 during low current interrup- ‘
tion is set forth and claimed in United ‘States
patent application ?led December 15, 1943, Serial
No. 5141366, now abandoned, and continued in
patent application Serial No. 6,436, ?led February
5, 1948, by Winthrop M. Leeds, Robert .E. Fried 20
rich, .and Francis J. Fry and assigned to ‘the
assignee of the instant application.
The downward opening movement of the
manual operation or to the existence of excessive
current conditions in the circuit, causes down
ward opening motion of the lift rod 8. The down
ward movement of the insulating liftrod 8 causes
corresponding downward opening movement of
the composite bridging member 1.
The downward movement of the bridging mem
ber ‘I permits the battery or" compression springs
pumping piston '15 ‘is effective to force oil out
51, to force the pumping piston 55 downwardly
wardly through apertures 8| provided in the cast .25 to compress oil within the region 53. This ,oil
ing 4| and upwardly as indicated by the arrows
under pressure within the region 58 passes
82 through a separate passage means, in this
through the apertures ~52 provided in the operat
instance consisting 'of two vertically extending
ing
cylinder 3?). This oil then acts upon the top
passages 83.
surface of the operating piston 55 to cause it to
By the provision of the passages 83,, separate 30 move downwardly against the biasing action 62>
from the passages 28, there is no possibility of
erted by the compression spring 52. After the
?uid within the passages 28 coming from the
lost-motion between the operating piston 45 and
pressure-generating are 26 contaminating the
the movabfe contact member I? is taken up, the
?uid within the vertical passages 83 moving up
valve means 59 is closed and the downward move
wardly from the auxiliary pumping piston ‘16. “ ment of the operating piston 45 carries the .mov
Thus, clean oil is provided by action of the pump
able contact H downwardly with it. Since the
ing piston 15.
insulating portion l6 interconnects the contacts
I have provided venting means 84, 85 at oppo
14, H, the pressure~generating are 26 and :the
site ends of the unit 5 to provide a chimney-like
interrupting are [5 will be substantially simul
venting arrangement, which venting means is
taneously established respectively within the
hydraulically actuated at the extreme end of the
pressure-generating chamber 21 and the inter
opening operation. This results since I have
rupting chamber H.
‘
provided a cylinder 86 secured, as by welding at
Oil under pressure from the pressure-generat
81, to the lower plate 19 of the unit 6. The
ing are 26 ?ows upwardly during high current
cylinder 96 has apertures 88 provided therein so
interruption through the passages '28 to effect
that during the initial downward opening motion
extinction of the interrupting are 15 within the
of the pumping piston 55 liquid will not be com
interrupting chamber i! in a manner as pre
pressed within the region 89. _ It is only near the
viously described. During this high current in
‘end of the opening operation, after interruption
terruption the auxiliary piston 76 is not effective
of the arcs has been completed, that the down
50 and is merely stalled by the high pressure exist
ward opening movement of the pumping piston
ing within the unit. One or more tubes 24 pro
55 is effective to compress oil within the region
vide substantially atmospheric pressure in the
89 and place the oil within the insulating tubes
region 25 in back of the pistons 55,, "it so that
95 under pressure. At this time the oil under
the biasing action exerted by spring 74 is over
pressure within the tubes 95} forces the pistons 9|
‘ come by the high pressure existing within the
associated with the venting means 84, 85 to open
unit. It is only during low current interruption
the valves 92 associated with the venting means
when the pressure within "the pressure-generat
84, 85. Thus, at the extreme end of the opening
ing chamber 2? is low that the auxiliary pumping
operation contaminated fluid
permitted to
piston it is effective to force oil upwardly through
freely flow out .of the unit by the simultaneous
the passages 83 and into the interrupting cham
opening of the venting means 84, 85 at opposite (if) ber I i to effect the extinction of theinterrupting
ends of the .unit 5.
In similar manner venting means 93 .is pro“
vided at the lower end of the pressure~generating
chamber 2?, as shown in Fig. 3. This permits the
pressure-generating chamber 2'! to be freely
vented
the extreme end or". the opening opera
tion. The pistons 9! associated with the vent
ing means 93 are actuated by oil under pressure
within tubes 24 which communicate with the a
region 89; Thus, all six of the pistons 9| are
simultaneously actuated by the ?nal downward
opening travel or" the pumping piston 55.
The-operation of my improved interrupter will
now be explained. In the closed circuit position
arc Hi established therein.
It will be noted that the areas of the pump
ing piston ‘55 and the operating piston is are
such as to cause considerable travel ofthe con
tact structure for a much shorter travel of the
the pumping piston 55. This gives high speed
opening essential for three cycle performance.
It will also be noted that the path between the
two pistons 55, 135 is short to reduce vto a mini“
mum hydraulic friction losses.
The pumping piston 55 continues to move
downwardly under the action of the compression
springs 5'! as permitted by downward motion of
the insulating portion IE6 of the bridging member
2,547,202
7
1. Finally, following interruption of the arcs,
the conducting piece 51, or the movable discon
nect contact, separates from the stationary dis
connect ?ngers 68 to insert two isolating. gaps
in the circuit, as more clearly shown by the dotted
lines 95 of Fig. 1.
.
.
It will therefore be apparent that the circuit
is broken within the unit 6 and not at the dis
connect contacts 61, 68, the latter separating only
following circuit interruption. It will be ob—
served that following interrupting of the arcs i5,
29 the pumping piston 55 establishes oil pres
sure within the regions 89 to effect opening of
the venting means 84, 85 at opposite ends of the
unit 5 to thereby permit contaminated fluid to
freely flow out of the unit 6 by the chimney
like vent passages formed. Also as shown in Fig.
3. the venting means 93 will be opened to permit
venting of the pressure-generating chamber 27.
Finally, the downward movement of the pump 20
ing piston 55 is halted by its striking the portion
91, and the compression spring 52 at this time
effects reclosure of the contact structure.
In
8
mal manner should reversal of the mechanism
take place at an intermediate point in-the clos
ing operation.'
v
'
From the foregoing, it will be apparent that
during the closing operation the actuating mem
ber 66 causes upward charging movement of the
pumping piston 55 to thereby cause opening of
the ?ap. valve 98 to draw oil through the aper
tures 99 into the region 58. Also the shoulder
portion 11 of pumping piston 55 picks up the
auxiliary piston 75. Further, the upper edge
13 of pumping piston 55 picks up the follower
member ‘H and effects the charging motion
thereof.
‘
During the initial downward movement of the
pumping piston 55, the compression spring 18
maintains the auxiliary pumping piston 16
against the stops 80 so that there is a prede
termined time interval before the piston 76 is
effective to pump oil.
-
From the foregoing, it will be apparent that m
improved interrupter is particularly applicable
for high speed reclosing operations due to the pro
vision of the venting means 84, 85 and 93. Thus,
other words, the compression spring 52 ?rst forces
the operating piston 45 upwardly to ?rst open 25 the gases which tend to contaminate the oil with
in the unit 6 are rapidly expelled therefrom fol
the valve means 59 permitting leakage of oil
around the lower end 4'! of the movable contact
member 11.
After the lost-motion is taken up and the valve
means 59 is open, the operating piston 45 picks
up the movable contact member 11, forcing the
lowing extinction of the arcs. To check the con
tact structure during installation of the inter
rupter, it is necessary only to thread a long stud,
not shown, into the tapped hole H39 and move the
two contacts 14, H and the insulating portion l6
vertically. The interrupter is easily installed re
latter upwardly to thereby effect re-engagement
quiring only that the bridging member ‘I be suf
of the contacts ll, l8, l4, 13. Hence the elec
?‘ciently aligned to cause the conducting portion
trical circuit is completed through the inter
rupter in the fully open circuit position thereof, 35 67 thereof to pass between the disconnect ?ngers
88, and that the piston 55 is su?iciently charged
the isolating gaps withstanding the impressed
before engagement of the disconnect contacts.
voltage.
.
Neither of these dimensions is very critical.
During the interruption of low currents, as
_Certain features of the contact structure in;
previously mentioned, the downward movement
of the follower member 1 I, as caused by the bias" 40 volving the contacts l4, ll tied together by the in
sulating rod l6,,together with the inverted order
ing action of the compression spring 14, picks up
ofithe pressure-generating chamber and the in
the auxiliary piston 16 to force fluid up through
the passages 83 and toward the interrupting are
[5.
'
A ?ap valve 98 is provided which closes the
region 58 during the opening operation and per
mits oil to enter the region 58 through holes 99
during the closing stroke.
During the closing operation of the interrupter,
suitable means causes upward closing motion of ;
the lift rod 8. This raises the bridging mem~
ber ‘l and ?rst causes engagement between the
bumper 53 and the insulation portion 68 of bridge
ing member 1. Thus, even before the discon
nect contacts 81, 68 are engaged, the bumper
63 has been moved upwardly a considerable dis
tance to thereby effect charging of the pumping
piston 55. The reason for this is that if exces
sive current conditions still exist in the circuit
during the closing operation and prestriking oc
curs between contacts 91, 58 to thereby reverse
the motion of. the operating mechanism, the
pumping piston 55- will have been suf?ciently
charged at this time of reversal to effect open
terrupter chamber, are set forth and claimed in
United States patent application ?led February
21, 1947, Serial No. 729,934 by Robert E. Friedrich
and Winthrop M. Leeds. Features involving the
hydraulic operating mechanism 54 are, in part,
covered by United States patent application ?led
October 30, 1946, Serial No. 706,735, now Patent
No. 2,463,029, March 1, 1949, by Francis J. Fry. A
further feature involving the part charging of the
pumping piston 55 during the closing stroke be
fore engagement of the disconnect ?ngers 6'1, 68
is described and claimed in United States patent
application ?led April 4, 1947, Serial No. 739,273
by Winthrop M. Leeds. The feature of broadly
providing a chimney effect is described and
claimed in United States patent application ?led
November 21, 1946, Serial No. 711,422, now Patent
No.'2,465,218, March 22, 1949, by Robert E. Fried
rich.
All of the foregoing applications are as
signed to the assignee of the instant application.
Although I have shown and described a speci?c
structure, it is to be clearly understood that the
ing of the contact structure in the manner pre 65 same was merely for the purpose of illustration
and that changes and modi?cations may readily
viously described. In other words, if the pump
be made therein by those skilled in the art with
ing piston 55 were not partly charged by the time
out departing from the spirit and scope of the
the contacts 67, 68 were sufficiently close to
appended claims.
gether to be conductively bridged by prestrik
I claim as my invention:
ing, the pumping piston 55 would be ineffective 70
'1. A circuit interrupter having contact means
to open the contact structure and the interrupter
operable to establish an are including a movable
would fail. By partly charging the pumping pis
contact, an operating piston for actuating the
ton- 55 before there is a possibility of flashover
movable contact, an operating cylinder within
between the disconnect contacts 51, 63, assurance
is had that'the breaker will operate in the nor— 75 which the operating piston moves, a movable
2,547,202
pump piston surrounding the operating cylinder
and having the region of compression immediately
adjacent the external surface of the operating
cylinder, and apertures through the operating
cylinder so that the travel of ?uid between the
two pistons will be short to minimize hydraulic
friction losses.
2. A circuit interrupter having contact means
operable to establish an are including a movable
10
5. A liquid break arc-extinguishing unit having
contact means including a movable contact mem
ber separable to establish an arc, a hydraulic op
erating mechanism for the movable contact mem
ber including an operating piston operatively con
nected with the movable contact member, an op
erating cylinder within which the operating pis
ton moves, a movable pumping piston for forc
ing liquid into the operating cylinder to effect
thereby opening motion of the operating piston
contact, an operating piston for actuating the 10
movable contact, an operating cylinder Within
and movable contact member, means biasing the
which the operating piston moves, a movable
pumping piston in a direction to separate the
pump piston surrounding the operating cylinder
contact means, an actuating member to charge
and having the region of compression immediate
the pumping piston during the closing opera
ly adjacent the external surface of the operating 15 tion of the unit against said biasing means, a
cylinder, apertures through the operating cylinder
follower member, means biasing the follower
so that the travel of ?uid between the two pistons
member in said direction, and a delayed acting
will be short to minimize hydraulic friction losses,
piston picked up after a predetermined travel of
means biasing the movable contact toward its
closed position, and valve means associated with
the operating piston to permit ?uid leakage
around the operating piston during the closing
movement of the movable contact.
3. A circuit interrupter including a pair of arc
extinguishing units, each unit having contact
means operable to establish an are including a
movable contact, an operating piston for actuat
ing the movable contact, an operating cylinder
within which the operating piston moves, a mov
able pump piston surrounding the operating cyl- '
inder and having the region of compression im—
mediately adjacent the external surface of the
operating cylinder, apertures through the op
erating cylinder so that the travel of ?uid between the two pistons will be short to minimize
hydraulic friction losses, and a movable bridging
member electrically connecting the two units in
series in the closed circuit position and charging
the two movable pump pistons associated with
the two units.
4. A liquid break arc-extinguishing unit having
contact means including a movable contact mem
ber separable to establish an arc, a hydraulic op
erating mechanism for the movable contact mem
ber including an operating piston operatively con
nected with the movable contact member, an op
erating cylinder within which the operating pis
ton moves, a movable pumping piston for forc
ing liquid into the operating cylinder to effect
thereby opening motion of the operating piston .
and movable contact member, means biasing the
pumping piston in a direction to separate the
contact means, an actuating member to charge
the pumping piston during the closing operation
of the unit against said biasing means, and an
other pumping piston operatively related to the
pumping piston to assist in low current inter
ruption.
the follower member to assist in low current in
terruption.
6. Aliquid break arc-extinguishing unit hav
ing contact means including a movable contact
member separable to establish an arc, a hydraulic
operating mechanism for the movable contact
member including an operating piston opera
tively connected with the movable contact mem
her, an operating cylinder within which the op
erating piston moves, a movable pumping piston
for forcing liquid into the operating cylinder to
effect thereby opening motion of the operating
piston and movable contact member, means bias
ing the pumping piston in a direction to sep
arate the contact means, an actuating member
to charge the pumping piston during the clos
ing operation of the unit against said biasing
means, venting means for the arc-extinguishing
unit, and means whereby the pumping piston
opens the venting means near the end of its open
ing motion in said direction to vent the unit.
ROBERT E. FRIEDRICH.
REFERENCES CITED
The following references are of record in the
?le of this patent:
UNITED STATES PATENTS
Number
Name
Date
2,102,768
Trencham et al. ____ Dec. 21, 1937
2,147,497
2,239,554
2,258,226
2,386,611
2,420,889
2,422,569
2,465,218
2,477,788
Prince et al. _____ __ Feb. 14,
Duf?ng __________ __ Apr. 22,
Skeats ___________ __ Oct. 7,
Ileman __________ __ Oct. 9,
Leeds ___________ __ May 20,
Leeds ___________ __ June 17,
Friedrich ________ __ Mar. 22,
Cumming _________ __ Aug. 2,
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