Note: Descriptions are shown in the official language in which they were submitted.
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ELECTP~ICAL CONTACTOR WITH IMPROVED
CROSSBAR STRUCTURE
This invention relates generally to electrical
; contactors and, more particularly, to a cross~bar and
bearing arrangement therefor.
As well known in the art, contactors, said to be
of the air-break type or the vacuum type according as their
contacts operate in air or in an evacuated envelope or
so-called vacuum bottle, are widely employed for the
purpose of performing switching operations, such as the
starting and stopping of motors, for example. Vacuum type
contactors, such as the one illustrated in Applicant's
Descriptive Bulletin IL16-200-32 "Westinghouse Type SJA
Vacuum Contactor" published in 1982, offer certain advan-
tages over air-break type contactors of comparable voltage
ratings, one of which is considerably less bulk due to the
fact that the contacts of a vacuum type contactor operate
, in a vacuum, thus re~uiring smaller clearances and less
contact separation so that the mechanisms for operating the
contacts likewise can be smaller and more compact. This
: compactness of vacuum-type contactors, regarded by manufac-
: 20 turers as well as users as a distinct advantage, also poses
a challenge to designers insofar as the crowding together
of component parts within the small space available can
create dielectric interference and breakdown. problems,
especially when the component parts include metallic
elements extending proximate to and between points of
different potentials. One such element to be found in
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conventional vacuum type contactors such as, for example,
the one shown in the above-mentioned Descriptive 3ulletin,
is a metallic shaft used to support what is yenerally
referred to in the art as the cross-bar assembly, i.e. the
movable structure which translates the action of the
contact operating means, such as an electromagnet and
kickout springs, into movements of the contacts and is
- common to, thus extending across, all phases of the
contactor.
10The invention has for its principal object to
; alleviate these problems, and it resides accordingly in an
electric contactor including a frame, contact means movable
to contact-open and contact-closed positions, operating
means including a movable structure which is operatively
connected to the contact means and pivotally movable so as
: to open and close same, and a pair of bearing assemblies
pivotally supporting the movable structure from said frame;
said movable structure comprising a unitary member formed
of an electrical insulating material and including two
substantially cruciform trunnion portions disposed on
opposite ends thereof, each of said bearing assemblies
including an annular bearing member which is rotatably
; supported in said frame and has one of said substantially
cruciform trunnion portions of the unitary member firmly
inserted therein.
This arrangement employing a unitary member
formed of insulating material and including cruciform
trunnion portions with annular bearing members thereon
provides strong pivotal support for the movable structure
without the use of a metallic shaft or the like. The
unitary member together with its cruciform trunnion por-
tions lends itself well to molding, and the trunnion
portions, being cruciform, can be readily held within close
tolerances enabling them to be accurately fit into the
annular bearing members with relative ease. Preferably,
the spaces defined between adjacent cross-arm portions by
the cross-arms of each cruciform trunnion portion and the
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annual bearing member thereon are filled with a cast resin,
such as epoxy, so as to round out each trunnion portionfand
thus increase its strength.
In a preferred embodiment of the invention to be
described in detail hereinafter, the annular bearing
; members on the trunnion portions of the unitary member are
the inner races of ball or roller bearings which, latter
are disposed in generally U-shaped recesses formed in
insulating portions of the contactor frame, and which are
retained in said recesses by means of resilient members
each secured to the frame in bridging relationship with
respect to the open end of the associated U-shaped recess
and engaging the outer periphery of the bearing seated
therein. This arrangement both facilitates the installa-
tion of the movable structure in the contactor frame, andpermits the two bearing assemblies of the movable structure
'~ to self-align with one another.
' The preferred embodiment of the invention will
now be described, by way of example only, with reference to
the accompanying drawings, in which:
Figure 1 is a front elevational view of a
, three-phase, alternating current vacuum-type contactor
; embodying the invention;
Figure 2 is a side elevational, partly sectional
view of the contactor, with some parts broken away for
clarity;
Figure 3 is a rear elevational view of the
contactor;
Figure 4 is a front elevational view of the
movable structure of the contactor; and
Figure 5 is a side elevational and partly sec-
tional view of the movable structure.
Referring now to the drawings, and to Figs. 1 to
3 in particular, the three-phase alternating-current vacuum
contactor 10 shown therein includes a preferably metallic
mounting plate or frame 12 to which is secured, e.g. bolted
as at 16, a frame 14 formed of a suitable insulation, such
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as plastics material. Relative sliding motion between the
frame 12 and frame 14 is further prevented by means of a
dowel or index ring member 18 on the frame 14 disposed in a
complementary hole or opening 20 in frame 12. Three vacuum
switches 22 are provided, one for each of the three phases
of the electrical system which the contactor 10 controls.
Each switch 22 has associated therewith a pair of terminals
26 and 28, the latter of which is electrically connected to
a movable contact stem 30 through a flexible conductor 32.
The movable contact stem 30 has disposed thereon a
spring-loaded flange member 34 and a threadedly engaged
flange member or cognut 36, between which extends a portion
40 of an electrically insulating cross-bar member 38, the
portion 40 having fastened thereto, as at 43 (Fig. 5), a
pivot plate 42 pivotally engaging the aforementioned flange
member 36. The cross-bar member 38 has an arm portion 44
and it includes a pair of coupling posts 46 extending
~' therefrom, and two bearing assemblies 48 disposed on the
; opposite ends of the cross-bar member 38 and seated in
U-shaped recesses 49 formed in the insulating frame 14.
; Mounted on the arm portion 44 is a magnetic armature 52
; having associated therewith an electromagnet 54 which is
;~ disposed on the frame 12. Connected to the frame 12 is one
end of a spring 56 having its other end connected to a link
bar 58 which is loosely, i.e. releasably, coupled with the
posts 46. When the electromagnet 54 is in a deenergized
; state, the spring 56 holds the link bar 58 in a position
adjacent the upper ends 60 of openings 84 formed in the
frame 12, thus holding the cross-bar member 38 in the
clockwise position shown in Fig. 2 and in which position
the movable contact means 30 of the vacuum switches 22 are
in their lowered, e.g. contact-open, positions. Upon
energization of the electromagnet 54, the armature 52 is
attracted, thus causing the cross~bar member 38 to be
rotated, in its bearing assemblies 48, counter-clockwise
against the action of the spring 56 so that the cross-bar
portions 40, in cooperation with the spring-loaded flanges
52~
38 on the associated contact stems 30, will lift the latter
to their actuated, e.g. contact-closed, positions.~ As
mentioned hereinbefore, the cross-bar member 38 is pivotal-
ly supported in the insulating frame 14 by means of the
bearing assemblies 48 seated in the respective U-shaped
recesses 49. Each bearing assembly 48 is held in the
associated recess 49 by means of a flexible member 53
secured, adjacent opposite ends thereof, to portions of the
frame 14 by means of screws or bolts 55, and bridging the
opening of the recess 49 so as to retain the bearing
assembly 48 in place, the arrangement being such as to
provide for self-alignment of the bearing assemblies 38
within the frame 14.
Referring once more to Figs. 2 and 3, the spring
56 is connected to the frame 12 through spring adjusting
means. More specifically, the frame 12 comprises two
lateral flange portions 62 and a backplate 61 therebetween,
the latter having secured, e.g. bolted, thereto, as at 68
. (Fig. 2) the electromagnet 54 and having thereon a spring
anchor 64 comprising a bracket secured to the back plate 61
`. by means of bolts, such as bolt 70. Supported from bracket
64 are two slightly inwardly angled adjusting screws 72
; which carry a retainer 73 threadedly engaged with the
screws 72 and having a hook portion 7~ of the spring 56
attached thereto. At its opposite end, the spring 56 has a
hook portion 76 which is inserted in an opening 78 formed
in the link-bar 58. The link-bar 58 has formed therein
symmetrically disposed rectangular cutouts 80 in which
inde~ed end portions of the coupling posts 46 of the
cross-bar member 38 are engaged, and in which said end
portions are held engaged through the action of the spring
56 pulling the link 58 against the posts 46, the latter
extending through elongage openings 82 provided in the back
plate 61. Movement of the link-bar 58 under the influence
of the spring 56 is limited by the opposite end walls of
the elongate openings 84 in the lateral flange portions 62A
of the backplate 61.
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Whilst the electromagnet 54 is deenergized, the
spring 56, acting through the link 58 and the coupling
posts 46, maintains the cross-bar assembly 38 and the
movable contact stems 30 of the vacuum switches 22 in the
position shown in Fig. 2, which is assumed herein to be the
contact-open position of the switches 22. When electrical
power is supplied to the electromagnet 54 through terminals
86, the armature 52 is magnetically attracted and thereby
causes the cross-bar assembly 38 to be rotated
counter-clockwise against the action of the spring 56, thus
lifting the movable contact stems 30 of the vacuum switches
- 22 so as to close the contacts of the latter.
Whenever it is desired to service or replace
internal parts of the contactor, e.g. the operating coil of
the electromagnet 54, and therefore it becomes necessary to
: remove the frame 14 from the frame 12, this can be done
without disturbing the adjustment of the spring 56. It is
achieved simply by releasing the screws 16 (Fig. 2) and
pulling the frame 14 from the frame 1~ far enough to
withdraw the dowels 18 from the holes 20, thereby enabling
the spring-loaded link 58 to become seated against the
`; stops formed by the end walls 60 of the elongate openings
, 84. This removes the spring tension from the coupling
posts 46 and thus enables them to be readily withdrawn from
the link 58 upon complete removal of the frame 14 away from
the frame 12. However, the spring assembly comprising the
link 58 and the kickout spring 58 is left undisturbed and
in a condition ready for subsequent reconnection with the
contactor mechanism without a need for readjustment of the
spring 56.
As seen from Fig. 5, the movable structure
~ comprising the cross-bar member 38 has the armature 52
- (which is formed of magnetic plates 98) secured, e.g.
riveted as at 100, to the arm portion 44 of the cross-bar
member, and has the pivot plates 42 (which pivotally engage
the cognuts 36 on the contact stems 30 of the various
vacuum switches 22) secured, e.g. bolted as at 43, to the
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respective cross-bar portions 40. The cross-bar member 38
itself is a unitary member formed of a suitable insulasting
material, such as plastics, and including two substantiail~
cruciform trunnion portions 90 formed at opposite ends
thereof.
With particular reference to Fig. 2 illustrating
one of the two bearing arrangements of the cross-bar member
as representative of both, it is seen therefrom that the
cruciform trunnion portion 90 shown therein is disposed
within the rotatable, annular inner bearing member, or
race, of a ball or roller bearing, being firmly inserted
thexein such that the distal ends of the cross-arms 93 ~nd
94 (see also Fig. 5) of the cruciform trunnion portion,
along their outer edges, such as edges 91 and 92, are in
firm frictional engagement with inner peripheral surface
portions of the inner race so that the cross-bar member and
the inner bearing members on its cruciform trunnion por-
tions will rotate as one.
~; Preferably, the spaces, such as sp~.~e 104,
defined by the inner bearing member and the cross~arms 93,
94 between adjacent cross-arm portions are filled with a
, hardened cast resin, such as epoxy, thereby in effect to
"round out" the cruciform trunnion portion 90 and thus add
strength to the bearing.
It will be appreciated that the above arrangement
embodying the invention provides strong and durable bearing
support for the movable structure without the use of a
metallic shaft or other metallic parts capable of creating
dielectric breakdown problems. Moreover, the cross-bar
member 38 together with the cruciform trunnion portions 90
thereon lends itself well to molding, e.g. injection
molding, as readily seen from Fig. 5 wherein the dash-dot
~- line 102 with the step 104 therein indicates where the two
sections of a suitable mold could meet, and wherein the
arrows A and B indicate the directions in which the two
sections would be moved in order to join and, after the
molding operation, to separate them. It will be noted that
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the cross-arms 93 and 94 of each cruciform trunnion portion
90 extend in and perpendicular to, respectively, a plane
containing the line 102 and the axis of rotation of the
movable structure; thus, the cruciform trunnion portions 90
molded integral with the cross-bar member 38 will not
interfere when the two mold sections are separated upon
completion of a molding operation.
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