Note: Descriptions are shown in the official language in which they were submitted.
11 TR 04249-A
7~
This application is a division of Canadian Applica-
tion Serial No. 292,242 filed December 2, 1977.
This invention relates to means for substantially
reducing the tendency of the contacts of a vacuum-type
circuit interrupter to bounce apart in response to the
impact between the contacts occurring at the end of a
closing stroke of the movable contact. The invention also
relates to means for precisely controlling the forces
imposed on the movable contact by acceleration at the
start and the termination of a contact-opening stroke.
A vacuum-type circuit interrupter typically comprises
an evacuated housing, a stationary and a movable contact
within the housing, and stationary and movable contact rods
respectively supporting the contacts and extending between
te interior and exterior of the housing in sealed relation-
ship to the housing. It is advantageous to support such an
interrupter in a vacuum circuit breaker by providing a
substantially rigid support for the stationary contact rod.
When the interrupter is so supported, impact forces developed
~ 20 when the movable contact strikes the stationary contact
: at the end of a closing stroke are transmitted directly to
said support, effectively bypassing the housing. This
bypassing is desirable in that it greatly reduces the
mechanical loads that are imposed by such i.mpact forces on
the brittle glass or ceramic of the housing and on any glass-
to-metal seals and welded or brazed joints in the housing.
I have found that when the interrupter is supported
as in the lmmediately-preceding paragraph (instead of being
supported from its opposite, or movable-contact, end) there
is a much greater tendency for the contacts to bounce apart
in response to the closing impact. Such bouncing is undesir-
-- 1 --
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9 8 ~ 0 llTRO4249-A
able because it results in inter-contact arcing during the
bounce period, which leads to undue contact-erosion and
contact-welding. In studying this problem in a high-current
circuit breaker having a conventional actuating mechanism
(which comprises a contact-driving linkage coupled to the
movable contact through a conventional wipe mechanism), I
¦have found that $he rigid mounting of the stationary contact
results in opposing force on the ac~uating mechanism build-
ing up at an extremely rapid rate when the contacts impact.
10 I have further found that the inherent flexibility of ~he
linkage allows this abruptly-developed opposing force,
surprisingly, to temporarily reverse the motion of the out-
, put end of the actuating mechanism, thereby temporarily
pulling open the movable contact. Shortly thereafter, when
c 15 the linkage has deformed sufficiently to allow for a build-
. up of the required closing force to overcome this opposition,
: such closing force acts to drive the movable contact back
. into engagement with the stationary contact to complete the
~closing operation. The above-described stalling of the
20 lactuating mechanism accompanied by subsequent contact
separation can occurr I have found, despite the fact that
the operating device for the actuating mechanism is making
¦available more than enough closing energy at the input end
of the actuating mechanism to overcome the op~osing force.
- . 25 1I Summary
il An object of my invention is to greatLy reduce the
~above-described tendency for the movable contact to bounce
awaY from the stationary contact at the end of a closing
operation in .I vacuum interrupter that is mounted in generall~ ¦
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:LI)~8570 11TRO~I249-A ~ I
¦¦ the above-described manner (i~e., with its stationary
¦ contact rigidly supported).
¦ For the high current vacuum circuit breaker I am con-
¦ cerned with, high ope~.ting forces are required to close
I and hold closed t~e contacts when they are subjected to
¦i high fault currents, and also to open the c,ontacts at the
¦¦ required high speed. With respect to opening, a certain
- ¦ minimum impact force must be applied to the movable contact
. I at the time of contact-parting to assuxe that any welds
-- 10 ¦ between the contacts are immediately broken and further ~o
- ¦ maintain rapid contact-parting to minimize contact erosion.
~ A problem presented by these high opening impact forces is
r
that they have a tendency to produce such high accelerations
that the contacts of the interrupter can be deformed there-
by.
¦ Accordingly, another object of my invention is to
¦ provide, in a high-current vacuum circuit breaker, means
¦ for limiting the impact Eorces deveioped at the start of
¦ an opening operation to a prec:Lsely controlled level suffi-
. 20 ciently high to assure contact~parting at the required
-` ~peed yet sufficiently low to prevent deformation of the
. . . contacts .
Another object is to arre~t contact-opening motion
.-. . ! at the end of the opening stroke in such a way as to prevent
deformation o th~ contacts.
¦ Still another object is to provide in the wipe
: ¦I mechanism spring means capable of functioning both at the
`' il .
!I start and the termination of the opening stroke to achie~e
1I the two immediately-preceding objects.
; 30 , Still another object is to provide a wipe mechanism
for a vacuum circuit breaker which includes means for
¦¦ accomplishing all four of the objects set forth hereinabove~
.-.. , Ii' .
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5~ llTRO~249 -~
In carrying out the invention in one form, I provide
¦the vacuum-type circuit breaker with means for substantially
¦reducing the tendency of its contacts to bounce apart in
response to the impact produced Detween the contacts when
5 thev first engage at the end of a closing stroke. This
: Icircuit breaker includes a contact-wipe mechanism com-
¦prising a driving par~ and a wipe spring located between
¦the driving part and the movable contact which spring is
. ¦loaded to produce added closing force on the movable
10 ¦contact by continuing closing motion of the driving part
after the contacts initially engage at the end of the -
closing stroke. The wipe mechanism fur~her includes a
bounce-suppressing spring acting in opposition to the wipe
spring and discharging to aid said continui.ng closing
15 motion of said driving paxt d~ring the initial stages of
, ¦said continuing motion following initial contac~-engagement.
This discharge of the bounce-suppressing spring at this time
, appreciably reduces the rate alt which force builds up on
'' ihe contacts immediately following their initial engagement,
20 and this reduction in the rate of force build-up reduces
~ the tendency to produce contact-bounce. The bounce-suppress-
- ing spring has a stiffness sufficiently low to effectively
¦prevent separation o~ the contacts immediately following
r linitial contact-engagement at the end of the closing stroke.
~ 25 I In accordance with ~nother feature of my invention,
- ¦the contact-wipe mechanism further comprises force-trans-
~ llmitting means impacted by said driving part after a pre
-~- determined initial motion of said driving part in a contact-
jl
I! openin~ direction for transmitting contact opening force
- 30 I~lfrom said driving part to said movable contact. This
force-transmitting means comprises preloaded auxiliary
spring means that yields in response to said impact to
,......................................................... .
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/ ~ 0 q ~ ~ O llTRO4249-A ~ j
~I reduce the initial accelerating force applied to said
L ll movable contact. Opening-motion terminating means acts
near the end of an opening stroke to apply through said
auxiliary spring means a decelerating force to said mova~le
5 ll contact.
iI BRIEF DESCRIPTION OF THE DRAWINGS
For a better understandin~ o the invention, reference
. ¦I may be had to the accompanying drawings, wherei~:
¦¦ Fi.g. 1 is a sectional view, partly schematic, showing
a vacuum circuit breaker e~bodying one form of my invention~
The circuit breaker is shown in its fully-open position~
Fig. 2 is a side elevational view of a portion of the
~ structure of Fig. 1.
t, ¦ Fig. 3 illustrates the circult breaker of Fig. 1 -
r.'' 15 ¦ immediately after its contacts have engaged near the end
E' o a closing operation.
Fig~ 4 illustrates the circuit breaker of Fig. 1
after the closing operation has been completed.
Fig. 5 is a graphic showing of force on the output -
: 20 ¦ end of the circuit-breaker actuating mechanism during a
closing stroke. The solid line curve A represents this
~ force with a conventional actuating mechanism, and the
-` ! dotted line rurve B represents this force with the actu-
ating mechanism illustrated in Figs. 1-4.
: 25 jl Fig. 6 is a sectional view of a vacuum circuit breaker
;, '
~ embodying a modified form of my invention. In Fig. 6 the
~¦ circuit hreaker is shown in its fully-closed position.
~': I . ..
Fig. 7 shows the circuit breaker of Fig. 6 at the end
;j of a circuit-breaker opening stroke but while the contact
.' ' ~I .
.. i1
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... .11 ,
~ ~8~0 11TR04249-A l l
I ¦ rod 50 is undergoing limited overtravelO
, ¦ Fig. 8 shows a vacuum circuit breaker embodying anothe~
; modified form of my invention. In this figure, the circuit
: breaker is shown in its fully closed position.
. 5 Fig. 9 æhows the circuit breaker of Fig. 8 in a
; position through which it passes shortly after an opening
: operation has begun ~ut before the contacts have parted.
~ Fig. 10 shows the circuit breake~ of Fig. 8 in a
.- position through which it passes after a major portion of
an opening operation has taken place.
t: Fig. 11 shows the circuit breaker of Fis. 8 in a
. position through which it passes after the opening oper-
ation has advanced further and is near its completion.
, Conkact rod 50 in Fig. 11 is undexgoing limited overtravel
` 15 immediately following impact between parts 60 and 92.
.,., . , .
;DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
s.'`. . . ~
E~ODIMENT OF FIGS. 1-5
r... , Referring now to Fig. 1, there is shown ~ vacuum-type
circuit interrupter 10 comprising a highly evacuated
~- 20 housing 12. This housing 12 comprises a tu~ular casing
- ¦ 14 of insulating material such as glass and k~o end caps
; ~ ¦ 15 and 16 at opposite ends of the casing joined to the
¦¦ casing by suitable vacuum-tight glass-to metal seals 17.
!I Located within the evacuated housing 12 are two engageable
- ` 25 ¦I relatively-movable contacts 20 and 21. Contact 20 is a
¦~ stationary contact fixed to the inner end o~ a conductive
¦I stationary contact rod 20a, and contact 21 is a movable
!! contact fixed to the inner end of a movable conductive
¦! contact rod 21a-
,.,,,.. I .
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~ S70 11TRO4249-A
l:............. ji The two contact rods 20a and 21a extend between the
¦l interior and exterior of the evacuated housing 12 through
A ll openings in the end caps 15 and 16, respectively. A
~ vacuum-tight welded joint 22 secures stationary contact rod
`. 5 ¦1 20a to end cap 15. A flexible metal bellows 24 of con-
~ ventional form surrounds movable contact rod 21a and pro-
.. ¦ vides a flexi~le vacuum-tight joint therearound that allows
¦ contact rod 21a to be moved vertically without impairing .
. . the vacuum inside envelope 12. A tubular guide 25 suitably
'i 10 ¦ fixed to the lower end cap guides the movable contact rod
. 21a along a substantially straight-line.vertical path. -
~:~ For supporting the.interrupter, I provide a sub-
.. stantially rigid stationary support 30. In the illustrated
embodiment, this support 30 has a split end 32 forming two
: 15 arms which are tightly clamped about the stationary contact
. rod 20a by means of a clamping bolt 34. In one form of
.... ! the invention, these parts 30, 32 are o~ conductive
material and serve as part of the power circuit that ex-
¦I tends through the interrupter. .
1 For actuating movable contact.21, I provide an oper-
- I ating linkage 40 that comprises atrunnion41 Ihat is up-
wardly movable in a vertical direction from its position
of Fig. 1 to close the interrupter. As ~hown in Pigs. 1 .
and 2, trunnion41 is coupled to a horizontally-movable link .
!l 43 through two identical, interconnected bell-cranks 44
that are pivoted on a stationary pivot 45. One arm of each
bell-crank i5 pivotally connected to horizontally-movahle
¦¦ link 43 by a pivot 46, and the other arm is plvotally con-
nected to thetrunnion 41 by a pivot 48. The link 43 is
.,,~ il . .
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.. 1. _7_ .
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I I llTRo424g-A
¦ I adapted to be drivern in a horizontal closing direction by
a suitable operating device, such as shown and claimed,
- 1 for example, in my Can. Application Ser. 283,214, filed Jul
, 121,1977 and assigned to the assignee of the present invention.
5 l, That closing device, which is designated 10 in the afore-
said application, comprises a ~lywheel 30 driven by a
~i spring 40 closely coupled to the flywheel. The flywheel
, 1l 30 is mechanically connected through suitable force-trans-
~ mitting means (not shown in the present application) to the
,~ 10 I link 43 of the present application. Those parts of the
,- , drive train that are connected between flywheel 30 and the
t I trunnion ~l of the present application may be thought of as
the operating llnkage 40. The operating linkage also in~
, I cludes an opening spring biasing the linkage in a direction
r 15 !3 to open the contactS.
I' Trunnion 41 has a central hole 4~ that slidably
i xeceives an operating rod 50 that is positively coupled
~ , '.,
~, i to movable contact rod 21a. For transmitting closing force
~ from trunnion41 to operating rod 50, a compression-type
r- ` 20 il wipe spring 52 is provided. This wipe spring bears at its
,¦ lower end against trunnion41 and at its upper end against
! a shoulder 54 effectively fixed to operating rod 50 Com-
~, pression spring 52 is preloaded so that it exerts a pre-
determined upward force on operating rod 50 when the parts
~5 are in the position of Fig. l.
, Opposing the upwardly-acting force of wipe spring
," , , j .
- 52 on operating rod 50 is a disc spring 58 which exerts a
downward force on the operating rod 50. This disc spring
comprises one or more annular washers normally of a
.
generally conical shape located between the lower face of
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I, ~ ( llTRO4249-A
~g~
trunnion 41 and a stop 60 on the lo~er end of operating rod
¦50. Stop 60 is free to slide on the operating rod but is.
¦normally held by spring force against a nut 62 fixed to the
¦llower end of the operating rod, as shown ïn Fig. 1. The
5 1¦ wipe spring 52 is substantially stronger than .the disc
:llspring 58 and thus deflects the normally-conical disc spring
. ¦into the almost flat configuration of Fig 1 when the parts
: jare in their position of Fig. 1. The following parts may
..........'be thought of as constituting a wipe mechanism 65 for
..10 ¦coupling the aforesaid operating linkage 40 to the upper
end of operating rod 50: trunnion41, wipe spring 52, disc
~... ; ¦spring 58, parts 54, 60, and 62, and the lower end of oper-
E... ¦ating rod 50. The series combination of the wipe mechanism
. 165 and the aforesaid operating linka~e 40 connected thereto
:15 ¦may be thought of as an "actuati~g mechanism" ~or the ~ .
! movable contact. ` . .
Whentrunnion 41 is driven upwardly during a closing .
~ operation, it. transmits closing force through the wipe -
E~~¦mechanism 65 to operating rod 50 without substantially de-
20 ,Iflecting the springs 52 and 58 until movable contact 21
~engages stationary contact 2~. Thetrunnion 41 continues .
-¦¦t~ move upwardly following initial contact engagemen~, and
¦Ithis compresses t.~e wipe spring 5~ while allowing the disc .
~spring 58 to unload and return toward its normal generally
-~ 25 ¦I conical shape. Thls continued upward movement ofthe trunnio~
- il41 is referred to as wipe travel. Fig~ 3 depicts the parts
- : ¦, at an intermediate point in the course of such wipe travel.-
. Il Fig. 4 depicts the parts after such wipe travel has
been completed. It will be apparent ~rom Fig. 4 that the
30 i, additional wipe travel of the trunnion41 past the position
.. : - ,!
~ lof Fig. 3 further compresses wipe spring 52 and completely
-
. I . , _
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. .. : .,. ; . .... . . . .. ;, . ... ; ,; . ...
. ~ . . . ~ ~ . - .. . .. . . ' . . . .
- - - -,-., ; .. , .- ; ....
~ ~8~70 llTR04249-A
- lunloads disc spring 58, opening a gap between the lower side
¦of the trUnnionand the unloaded disc spring.
In working with a circuit breaker essentially the same
Ijas shown in Figs. 1-4 except without the disc spring 58, I
found that the contacts bounce apart imme~iately following
- Ijinitial contact engagement. This ~ehavior was initially
quite puzzling, particularly since the problem became worse
- Iwhen contact-wipe spring force was increased, which is
generally not the case with other contact-bounce phenomena.
¦In the course of my studies of this contact-bounce problem
. in such a circuit breaker, I found that the substantially
rigid mounting of the stationary contact ~Oa of the inter-
rupter combined wi~h the high wipe-spring force was causing
a high opposing force on the upper end of the oeprating rod
to be built up at an extremely :rapid rate upon contact
;limpact. I found further that the inherent flexibility of
the operating linkage 40 was allowing this abruptly de~elop~
¦led opposing ~orce, surprisinyly, to temporarily reverse the
¦motion of the operating rod 50, thereb~ temporarily pulling
~O llopen the movable contact 21. A short time thereafter when
` llthe operating-linkage had de~ormed sufficiently t~ build up
the required closing force on the operating rod to overcome
~- this opposition, the movable contact moved back into engage-
ment with the stationary contact~
~ 25 1 The manner in which this force was building up (in the
.... ,
~ I breaker withou~ disc spring 58) is depicted by curve A in
- i !, Fig. 5, where the orce is plotted against the stroke of the
.. , 1l
operating linkage 40. No force is present until the contacts
!l
~ Ilengage. But when the contacts do engage at point X in the
~llinkage stroke, the force builds up almost as a step functisn
~ito the value of the precompression load in the ~lipe spring,
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` ~Q~857~ llTR04249-A
thereafter increasing at a much lower rate as the linkage
continues moving through its wipe travel.
My solution to this contact-bounce problem is based
upon recognition of the need to apply the contact force
relatively gradually when the contacts initially engage on
closing. I have achieved this effect by providing the
above-described disc spring 58 related to the trunnion 41 in
the manner shown in Figs. 1-4. This disc spring 58 unloads
during wipe travel following initial contact-engagement in
the manner already described. Note that the disc spring 58,
being located between the trunnion and the stop 60, 62 on
the operating rod 50 tends to push the operating rod 50
downward, which is in the opposite direction to the force
exerted by the wipe spring 52. Thus, when the contacts
engage as in Fig. 3, the force acting on the contacts and
hence on the actuating mechanism 40, 65 is the difference
between the force exerted by the wipe spring 52 and that
exerted by the disc spring 58. The gradient of the disc
spring determines the distance travelled by the operating
linkage 40 (and hence the time elapsed) between initial
, _
contact-engagement and complete development of contact-
spring wipe force.
With the disc spring 58 present, the closing force at
the output~end of the actuating mechanism 40, 65 builds up
following initial contact-engagement in accordance with the
dotted line curve B of Fig. 5. It will be apparent that
this is a much more gradual force build-up than that
represented by curve A, illustrating performance without
the disc spring 58.
The precise value of the gradient of the disc spring
which is adequate to prevent contact-reversal can be deter-
~ 57~ llTRO~2~9-A
.,mined fro~ an analysis of a s:implified model ~f the
l~circuit-~reaker actuating mecllanism 40, 55, assuming tha~
such mechanism comprises N movable contac~-operating rods
11
; ' connected to the operating linkage 40, each through i~s
.. S l own wipe mechanism 65 substantially iden~ical to the wipe
~echanis~ 65 shown. The analysis discloses that there ~hould
~be a definite relationship between the ~tlffness gradient ~ .
; I,f the operating linkage 40 and the gtiffness gradient k
,of each of the disc springs 58 in the wipe mechanismj ox .
,Imechanisms, operated by the linkage. To prevent reversal
of the output end of the actuating mechanism, it is
. necessary that ~he followi~g inequality be maintained:
-............. . . .
l Nk >~ ~ [ - ~ } Max.
: 11, where ~ is the fundamental natural frequency of the
,Icircuit breaker operating linka~e 4~, expressed in radians
iper second, and t is time, measured from the time of initial
.contact engagement on closing. It is readily found th~
. .,the ~aximum positive value of. the right-hand side of ~hi~
.Irelationship is 0.22~ ~hus~ this relationship re~uires tha
.., . ji
l, ~ .22, or k ~ .22N
, ,1 .
¦i In the usual 3-phase circuit breaker, there are.three
,'interrupters a~d hence three wipe mechanisms, usually sub-
: . IiStantially the same, all operated by a common operating
. ........... ii
. .llinkage (such as 40). Hencej according to the i~bove relation- .
.. . ,;
,ship, in such a circuit breaker, k ~hould ~e ~ess ~han abou~
: !1. 5 K in order to prevent reversal of the out~ut end of the
,. ..
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.' 1'. .
.. . ., :: ~ . -
.. ... . . . . . . .
llTR04249-A
actuating mechanism. To provide adequate margin in such a
circuit breaker to insure against such reversal, it is pre-
ferred that the stiffness gradient k of the disc springs
be about e~ual to the stiffness gradient K of the operating
linkage.
Tests made with this actuating mechanism 40, 65
have confirmed that where the gradients k and K are sub-
stantially equal, such reversal of the operating rod 50
will be prevented, and performance free of bounce from this
source will be obtained.
Stated in general terms, the bounce-suppressing
spring 58 should have a stiffness gradient sufficiently
low to essentially prevent separation of the contacts
immediately following initial contact-engagement at the
end of the closing stroke.
Although the actuating mechanism 40, 65 of Figs. 1-4
is especially well suited for utilization in a circuit
breaker in which the generally stationary contact 20 is sub-
standially rigidly mounted on a stationary support, the
mechanism can also be used advantageously to prevent the
contacts from bouncing apart following initial engagement
where there is some slight yieldability or resilience in
the mounting for contact 20. In this respect, generally
speaking, introduction of the bounce-suppressing spring (58)
produces effective contact-bounce suppression (by preventing
the above-described contact separation) in those circuit
breakers where the opposing forces exerted on the operating
linkage upon contact-engagement increase rapidly (i.e., from
zero to the wipe-spring preload force g as seen in Fig. 5)
in a time tl which is substantially shorter than one~fourth
~ ~ .
.
~ 570 ~ llTRo4249-A
of the natural period T2 of vibration of the operating
I ¦! linkage.
' Opening of the circui~ breaker of Figs. 1-4 is
-~, lef~ected ~y driving thetrunnion41 downwardly from its
Iposition of Fig. 4. This downward motion substantially
Iflattens the disc spring 58 and thereafter applies downward
- ¦¦opening force to the operating rod 50.
-,, 11 . :
EMBODIMENT OF FIGS. 6 and ?
. ¦Starting an Openin~ Operation
- 10 Another object of my invention set forth hereinabove
-; lis to limit the impact forces developed at the start of an ,~
- ~opening operation to a precisely-controlled level suffi-
- Iciently high to ensure contact-parting at the required
¦speed, yet sufficiently low to prevent deformation of the
!contacts.
¦ Fig. 6 and 7 illustrate an arrangement for achieving
jthis objective. The parts thereof that correspon~ to
similar parts in Figs. 1 4 have been assigned the same
I!reference numerals as in Figs. 1-4. In Fig. 6 the circuit
.~ . 20 ¦¦ breaker is shown in its fully-closed position~
- : ~ The circuit ~reaker of ~igs. 6 and 7 does not have
the disc spri~g 5~ of Fig. l, but it does have an auxiliary
lspring 72 dispose~ ~etween a sleeve 74 and the stop 60.
Sleeve 74 is slidably mounted on operating rod 50. Auxiliary
2s ¦¦ spring 72 comprises a stack of annular conical disc springs.
¦IAu~iliary spring 72 is pr~loaded to a substantially ~reater
- ¦~force than the wipe spring 52. The preload in the auxiliarv
! spring is adjusted by suitably adjusting the nut 62 on the
lower end of operating rod 50 to the appropriate position.
-14-
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~ 7~ llTRo4249-A
¦IThe auxiliary spri~y 72 biases sleeve 74 upwardly into
l,e~gagement with a shoulder 76 on opera~ing rod 50. When.
¦the circuit ~reaker is in its closed position of Fig. 6,
!I the lower face 80 of trunnion 41 is spaced npwardly from
! sleeve 74 by a gap 82, which represents wipe traval.
. , .
, It should be noted that the auxiliary soring 72 in
: liFig. 6 is com.pressed between the shoulder 76 and the nut 62,
j~both on the operating xod 50O There is in this state no
I;net force developed by the auxilia~y spring 72 on the oper-
lo l! ating rod.
. ~¦ Circuit-breaker opening is effected by drivingtrunnion
... 141 rapidly downwardly. Initial dswnward movement takes
~-. ¦pla~e with little oppo~ition, allowin~ the trunnion41 to .
.. . accelexate to a relatively high speed under the actio~ .
~ 15 jlprincipally of forces exe.rted by wipe spring S2, wherPupon .
.: ,its lower face 80 strikes the.sleeve 74.a~d drives the
sleeve downwardly. This dnwnw2ird motion o~ sleeve 74 is
! transmitted through spring 72 to stop 60 and nut 62 on the
,o?erating rod, thus driving the operating rod downwardly
.: 20 ,Ithrough an opening stroke.
In the usual wipe spring arrangement, a ~houlder o~ .
other part corresponding to ~leeve 74 is rigidly fixea to
the operating roa 50. As a result, when a dxiving part
¦corresponding to thetrUnnion 41 strikes the sh~ulder~ it
25 lim~oses a very high impact force on the shoulder ~n~ the .
jioperating rod. This high force rapidly accelerates the
jmovable contact in a downward opening direction; and in a
rigidly coupled high-curre~ circuit breaker ~he resul~.ing
aceeleration can he so sev rP that it someti~ s deforms the.
3~ ~jmovable contact.
.,,, 11 . . .
,..'' '
. .,
! ' ; : . - , .
: , ' ' ' -:
~ ~8570 llTRO4249
. I can precisely control this force by making the
.. sleeve 74 slidable on rod 50, bv appropriately choosing
: the auxiliary spring 72, and by preloadi~g he spring by
adjusting nut 62 so that ~he spring devalops a force on
. I sleeve ~4 that is low enough ~o assure against damage t~
¦the movable contact as a result of opening im~act. When
: I the initially-motionle~s contact ~tructure is suhjected to
ian impact from trunnion 41, the impact i5 ~ransmitted only
. . Ithrough the auxiliary ~pring 72. Regardless o~ thP speed .
:. 10 ¦of the impact or the rigidity and mass of the impacting .
member, the maximum force which is transmitted to the contact
: structur~ is stri~tly limited o the magnitude of the com-
:. pression force provided by the auxiliary spring 72. .
. It is to be understood that the compression force is
. 15 made hi~h enough to assure ~hat a minimum accelerating or
.~ . ¦impact force is always transmitted in order to assure weld-
.: ~breaking between the contacts and to maintain rapid contact-
,- ¦parting to minimize con~act erosion.
i !! I am aware that prior to my present invention,
:. 20 ijattempts have been made to limi~ the impact force trans- .
.. . 3mitt~d to the movable contact at the st~rt of thP opening
. . ¦operation by providing a rubber washer on a part such as the
- I!stop 60 of ~ig. 4 that is i~pacted by the driving part (su~h
¦as the trunr.ion 41 of Fig. 4). (In this prior circuit
25 l¦breaker there ~as no disc spring such as 58 of Fig~ 4~O ~:
Such a rubber washer can in fact limit these opening i~pact
¦jforces to levels su~ficient to prevent damage t~ the m~vable
~- I,contact, but it cannot aid in arresting ~ontact-opening .
: ~motion at the end of the opening stroke in the ma~ner which
'jmy auxiliary spring 72 does, as will be explained in the
16- !
....
.. .
...... ;...... . ;. . . ,. .. ., .. ..... ... .... ,;.,.; .. i . .
.... .. .. . . .. .. .... , . . .. .. . .. . .; . , ...; .. ... .. . . . .
357al
llTRO4~49-A
next section of this specification. Moreover, it is to be
.: li
noted that this rubber washer could not function in my
I circuit breaker in the same manner as the disc.spring 58 o
!l
: IlFigs. 1-4 to prevent contact-separation immediately follow-
: 5 1! ing contact-engagement at the end of a closing stroke hecause
lit is much too stiff to do so. A ru~ber washer (or any
¦lother type of spring) which has the properties needed for
¦¦the transmitting the opening impact forces in the desired
¦imanner described above will be too stiff to eIfectively pre-
¦¦vent contact-separation immediately following contact-engage-
- ' ment on closing in a circuit breaker having an actuating
mechanism comparable to ~y mechanism. This is a basic
: reason why I provide an auxil~ary spring 72 for opening
,~ i impact purposes that is separate from and much more heavily
~! loaded than the bounce-suppress:ing spring.58. This is
. ¦¦especially apparent in the embodiment of Figs. 8-11, where
both springs are present, as wi:Ll soon be explained. `
Terminatin~ Openin~ Motion
il As shown in Fig. 7, near the end of the do~Ynward
¦opening stroke, the trunnion 41 strikes stationary opening
stop 90, and its downward motion is thereby a~ruptly
i! arrested. The operating rod 50, however, continues moving
downwardly through inertia against the opposition of wipe
i~spring 52. This continued downward motion carries the
stop 60 into engagement with another generally stationary
stop 92, thereby terminating downward motion of stop 60.
But the operating rQd 50 continues mo~ing downwardly through
linertia7 further compressing wipe spring 52. This latter
. motion is quickly arrested, however, because it also com-
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1 ~8s70 llTRO4249 -A
I
presses the relatively strong auxiliary spring 72 ~between
. I the downwardly-moving slee~e 74 and then-statlonary -~top .
:: 1 60). The combination of the wipe spring forc~ and the
I auxiliary spring force exerts an effective decelerating
5 I force on sleeve 74 and hence on operating rod 50~ At the
end of downward motion of operating rod 50, a short gap
has developed at 94 between nut 62 and stop 60, represent- -
ing the overtravel of the operating rod with respect to .
. ¦ stop 6~. ~o assure an absolute limit to the overtravel the .
- 10 I gap (100) between parts 74 and 60 is deliberately set to a
¦ prescribed limit. Part 74 will strike part 60 if operating
rod 50 continues overtraveling from its position of Pig. 7
. ~ to reduce the gap 100 to zeroO . - .
.. I Briefly summarizing this termination of opening motion .
i 15 ¦ the decelerating force applied to the operating rod 50 .
immediately following the trunnion's 41 engaging the stop
¦ 90, as above described, is limited to that provided by wipe
. . , spring 52. This low force is i.nadequate to arrest contact-
- li opening motion of the operating rod. To limit the contaot- .
: 20 '. opening motion to a prescribed overtra~el, the above-
described second overtravel stop 92 is provided to impact
the stop 60. The auxiliary spring 72 assures that tolerable
deceleration forces result ~rom impact of the stop 60 with
¦~stop 92. It should be noted that the total decelerating
25 .I force following engagement of stops 60 and ~2 is the sum of
the force from the auxiliary spring 72 and that from the
¦. wipe spring 52. With the above-described arrangement,
,~ overtravPl at the end of the opening s~ro~e i5 held to a : -
.` Ij tolerable level compatible with bellows restrictions, and
.` 30 . decelerating forces are still limited to levels compa~ible
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( llTRO4249-A
I with contact-stress restrictions.
¦¦ It should be further noted that the auxiliary spring
¦! 72 serves a multiple function. It limits the magnitude
¦ of the accelerating forces transmitted to the movable
¦ contact at the start of the opening operation and it also
,! limits the decelerating force applied to the movable
~ contact when this openin~ motion is terminated at the end
I of the opening stroke.
In a preferred form of the invention, stop 92 is
carried by link 43 as shown in Fig. 1. But since this
5top 92 is 5tationary when considered in the direction of
motion of cooperating stop element 60 (i~e. 7 vertically~
- stop 92 is referred to as being "generally stationary".
Closing of the circuit breaker of FigL ~ and 7 is
effected by driving trunnion 41 upwardly from its position
of Fig. 7 to its position of Fig. 6. After the c4ntacts
. . have engaged near the end of the closing stroke, trunnion
41 continues moving-through wipe travel into its position
¦ of Fig. 6, compressing wipe spring 52 in the usual manner.
'~ 20 1 It should be noted that during such closing motion, the
auxiliary spring 72 remains ~aptured between shoul~er 76
. . and stop 60 and therefore does not effectively enter into
the closing operation. -
It is to be understood that the impact-limiting
25 i arrangement of Fig. 6 and 7 is applicable not only to an ¦
¦l interrupter that has its stationary contact rod rigidly ¦
mounted on a stationary support (as in Figs. 1-4) but also
to an interrupter in which the interrupter is mounted, or
~¦ supported, at its opposite end (i.e~, its movable-contact
30 -~l end).
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: ~ 57~ llTRO4249-A
In one embodiment of my invention, a hook (not shown)
. ~ ¦ i5 pro~ided to block the trunnion 41 from reboundin~ in a
: closing direction after it strikes stop 90 near the end of
~ ~n opening operation. After downward overtravel of operat-
.. ing rod 50 pas~ the position of FigO 7 i~ terminated, oper-
.. I ating rod 50 re~ounds upwardly to carry sleeve 74 in~o en- .
. gagement with the lower face ~0 of the trunnion 41. The .
:: auxiliaxy spring yield~ in response to such engayement to
.. reduce the impact load produced by such engagement, ~hus .
. 10 serving another desirable function. -
''' . ' , :
. ~ EMBODIMENT OF FIGS. 8--11
- In Figs. 8-11, there is illustrate~ a modified.
circuit breaker haviny a compact wipe mechanism 65 that .
. incorporates both the bounce-suppressing means of Figs. 1-4
.. 15 and the impact force-controlling means of Figs.. 6 and i.
. In the arrangement of Figs. 8-11, the same reEerence
... . numerals have been used as in the other embodiments to
.~'!' ~ des.ignate corresponding parts. The auxiliary spring 72 in
. Figs. 8-11 is position~d between a sleeve 74 and a stop 60
.20 on the operatin~ rod 50 and ser~es essentially the same
.... function as it serves in Figs~ 6 ana 7. ~he disc spring
. I 58 of Fi~s. 8-11 is positioned between sleeve 74 and
trunnion 41 instead of between stop 60 and trunnion ~1, as
. in Figs. 1-4, but-it serves ess~ntially the same function
25 ¦ as the disc spring 58 in Figs.-1-4~ .
j In the em~odiment of Figs. 8-11, when the breaker .
:: I is in its at-rest open position, of the three springs 72,
. . Il 52, and 58 that are present, the auxiliary spring 72 is
.. ji loaded to the greate~t force, wipe spr~ng 52 is the next
.. ; ..: . .
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I llTRO424s -A
heaviest loaded, and disc spring 58 is the least loaded.
¦ Otherwise stated, auxiliary spring 72 is the strongest;
wipe spring 52 is the next strongest; and disc spring 58
is the weakest.
In Fig. 8 the circuit hreaker is shown in its fully-
closed position. Opening i5 effected by driving trunnion
41 downwardly through its successive positions o Figs. 9
and 10 into its final position of Fig. ll. Downward motion
of trunnion 41 is terminated when the trunnion encounters
stop 90, as shown in Fig. ll, but the operating rod 50
continues moving downwardly as a res~lt of inertia until
its downward movement is finally terminated shortly after
genarally stationary stop 92 engage~ stop 60 on the oper-
ating rod, as will soon be explained mor~ fully. Fig. ll
depicts tha parts immediately after stop 92 has engaged
stop 60, but opexating rod 50 is still undergoing downward
overtravel.
Downward motion of the trunnion 41 from its position
of Fig. 8 occurs with little opposition until the lower
face 80 of the trunnion strikes the upper face of sleeve
74, as shown in ~ig. 9. T~is partially compresses auxili~ry
s~ring 72 and temporarily separates sleeve 74 in a downward
direction from shoulder 76 (which actio~ is not specifically
¦ illustrated in the drawin~s). After this has occurred,
25 li continued downward opening motion of the trunnion is trans-
mitted to the o~erating rod 50 throu~h auxiliary spring 72,
thus carrying the operating rod through an opening stroke
¦! in essentially the sa~e manner as described with respect
jl to Figs. 6 and 7. Just prior to the downwardlv-moving
.... .
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llTRO4249-A
trunnion`s reaching its above-xeferred-to position of
Fig. 9, it encounters the disc spring 58 and thereaf~er
essenatially flattens the disc spring before reaching its
position o~ Fig. 9. The force transmit~ed through the disc
¦ spring 58 by this flattening action is relatively low in
` 1l view of the relative weakness of the ~isc spring, and as
a result downward motion of the oparating rod does not
¦ substantially commence until the shoulder 8~ on the trunnion
encounters the sleeve 74.
Downward motion of trunnion 41 from its position of
Fig. 9 into its position of Fig. 10 carries operating rod
50 through ~ost of its opening stroke, thereby carrying
movable contact 21 through most of its opening stroke.
When the downwardly-moving trunnion 41 flnally engages
stationary stop 90, its downward motion is terminated, but
downward motion o~ operating rod 50 (against the opposition
of wipe spring 52) continues through inertia until it is
terminated by generally stationary overtravel stop 92. As
shown in Fig. 11, this stop 92 I_ngages the downwardly-
moving stop 60 on the operating rod, causing the auxiliaryspring 72 to be compressed b~tween shoulder 76 and s~op 60,
thereby applying an additional effective decelerating
-force to the operating roa~ as described in connection with
¦ Fig. 6 and 7.
¦¦ It is advantageous to dissipate the opening energy
with multiple sequentially-acting stops, as has been-
¦ described hereinabove. These stops arrest the opening
~¦ motion in parts, causing relative motions which dissipateenergy and also reduce shock loads on any part of the
.30 1, system.
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llTRO424~-A
¦ Closing of the circuit breaker is effected by ~riving
I the trunnion 41 from its a~-rest, fully-open position
; ! (which is approximately that sho~n in Fig. 10) upwardly
back into its position of Fig. 8. The auxiliary spring 72
does not ef~ectively enter into this closing ~peration
¦ since it is trapped bet~een stop 60, 62 and shoulder 76 on
the operating rod. When the upwardly-moving trunnion 41
enters its position of Fig. 9, during the closing operation
the movable contact 21 engages stationary contact 20, and
further upward motion of operating rod 50 and sleeve 74 is
terminated. As a result, the disc spring ~8 begins un-
loading, returning to its more conical shape, as the
trunnion 41 continues moving upwardly toward ItS position
of Fig. 8. This unloading of the disc spring reduces the
rate of force build-up on the contacts during the brief
period i~nediatelv following contact engagement, thus re-
ducing the tendency of the contacts to bounce apart, all
as explained in connection with Figs. 1-5. The disc spring
58 of Figs. 8-11 is selected to have a stiffness grad~ent k
that bears essentially the same relationship to the stiff-
ness gradient K of the operating linkage 40 as is present
in the e~bodi~ent of ~igs. 1-5.
It will be apparent that the preload force on auxil-
iary spring 72 can be adjusted in the same manner as in
~5 Figs. 6 and 7, i.e., by adjusting of the positisn of nu~
¦ 62 on operating rod 50 when the circuit breaker is fully
¦ opened. This shifts the position o stop 60 on the oper-
~ ating rod to change the compression of auxiliary ~pring 72
¦ but does not affect the disc spring 58 since sleeve 74 bears
l,` aqainst the shoulder 76 on the operating rod.
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~ 57~ ~ llTRo4249 -A
It will be apparent Erom from the above description
of Figs. 8-11 that this wipe mechanism of Figs. 8-11 pre-
, I vents the contacts from bouncing apart immediately follow-
¦l ing closing engagement in essentially the same manner as
S I the embodiment of Figs. 1-5 and precisely sontrols the *orce
: ¦ on the movable contact at the start and termination o an
:: ¦ opening operation in essentially the same manner as the . . embodiment of Figs. 6 and 7. .
. While I have shown and described particular;embodi- .
ments of my invention, it will be obvious to those skilled .
. in the art that various changes and modi~ications-may be
.. made without departing from my invention in its broader
: . aspects; and I, therefore, intend herein to cover all such
;~. changes and modifications as fall within the true spirit
15 1l and scope of my invention. .
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