Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a contact device for low
voltage switch devices. More particularly, it relates to
contactors with at least two stationary contact bars having
contact pieces, as well as at least one electrically-
conductive contact bridge which is disposed in a c~ntact
bridge support and is movable by means of a spring force.
Contact devices of the aforementioned type are
known, for example, from DE-AS 25 25 467, CH-PS 247 323 and
CH-PS 451 288. In these contact devices, the contact
bridges consist of massive bars at the center of which a
single contact spring engages. It has been tried by means
of numerous structural measures to overcome the problem of
burn-off of the contact pieces, for example, by pivot
movements of the massive contact bridge with the movable
contact pieces or by roll motions of the movable contact
pieces on the stationary contact pieces. However, a common
disadvantage of all of these known contact devices is the
combined effect of the relatively large movable mass of the
contact bridge with the movable contact pieces. This
mass i8 required for this type of structure, because the
contact bridge in the form of a massive bar must be so
designed that the required contact pressure forces are
sufficiently transferred from the contact pressure spring.
This results, on the one hand, in a large mass of material
and, on the other hand, in a switch-on impact which, in
actual practice, cannot be prevented. In order to keep
these disadvantages to a minimum, it has been tried to keep
the contact bridges as short as possible. However, this
results in other problems, for example, construction
difficulties, insufficient switch safety, poor
accessibility to all individual parts, and the like.
lBt3~
It is therefore an obJect of the invention to
provide an improved contact ~evice, wherein a weight and
material saving is obtained, wherein simultaneously a
switch-on impact of the contacts is prevented and wherein
an improved adaptability of the movable contact pieces to
the position of the stationary contact pieces is obtained.
This object is obtained in accordance with the
invention in that the contact bridge consists of a flexible
material and that, for each of the contact pieces of the
contact bridge, a contact pressure spring is provided.
In this manner, a weight reduction of about half
or more, compared to the commonly known massive movable
contact bridges, can be obtained. Due to the lower weight,
there exists the possibility of making the flexible
connection between the two contact pieces relatively long,
so that unusually wider distances may be bridged. If need
be, one could switch the stationary contacts crosswise if a
plurality of stationary contact pieces are disposed in
pairs adjacent to each other, so that a plurality of
contact bridges are provided in one device. A further
advantage is the adaptability of the movable contact pieces
to the position of the stationary contact pieces. In
addition, a considerable stabilization of each movable
contact piece during the switch-on process is obtained due
to the considerable weight reduction of the contact bridge
and by the arrangement of a separate contact spring with
each contact piece. Due to known physical laws, a light
body impacts upon an obstacle at a lighter impact energy
than a heavy body, because of the equation:
.'71E~9~;
m-V2
E =
Therein, E = impact energy, m = mass of the moved body and
v = speed of the moved body.
The invention has a further advantage - namely,
the movement of the flexible contact bridge between the two
movable contact pieces has a dampening effect on the
switch-on impact of the conta~.ts which is prevented in
accordance with the invention. Since one can talk about an
impact-free contact device, the switch-on burn-off is
negligibly small which, in turn, permits a reduction in
size of the contact pieces or, at the same large size of
the contact pieces, a substantially higher life span.
Other objects and features of the present
invention will become apparent from the following detailed
description when taken in connection with the accompanying
drawings which disclose several embodiments of the
invention. It i~ to be understood that the drawings are
de~igned for the purpose of illustration onl~ and are not
intended as a definition of the limits of the invention.
In the drawings, wherein simllar reference charac-
ters denote similar elements throughout the several views:
Fig. 1 is a vertical sectional view through a
contact device shown in its switched-off position;
Fig. 2 is a vertica] sectional view, comparable
to that of Fig. 1, but showing the contact device in an
intermediate switch position wherein the contact pleces
~ust touch each other;
Fig. 3 is a vertical sectional view, comparable
to that of Fig. 1, but showing the contact device in a
switched-on position;
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Fi.~. 4 is a vertical sectional view through
another embodiment of the contact device shown in a
switched-off position;
Fig. 5 is a vertical sectional view, comparable
to that of Fig. 4, but showing the contact device in a
switched-on position;
Fig. 6 is a vertical sectional view through a
further embodiment of the contact device;
Fig. 7 is a vertical sectional view through a
contact device in still another embodiment of the invention;
Fi.g. 8 is a vertical sectional view of another
embodiment of the contact device with a connected magnet
system; and
Fig. 9 is a simpified horizontal sectional view
of the device shown in Fig. 8.
Referring now in detail to the drawings, Figs.
1-3 show one embodlment of the inventive contact device in
a low voltage switching device in three different switch
positions. Fig. 1 shows the switch-off pos~tion. The
switch device is provided with a lower housing portion 1
with a bottom la and two lateral cylindrical recesses lb.
The lower housing portion 1 supports an upper lid-like
housing portion 2. Two contact bars 3 and 4 are mounted
opposite each other at a distance from one another on
raised parts of bottom la; these bars are advantageously
retained by lateral guides lc or groove-like recesses.
These contact bars 3, 4 are provided with an outer,
essentially horizontal bar portion 3a or 4a, respectively,
an oblique downwardly-directed offet bar portion 3b, 4b, a
subsequent horizontal bar portion 3c, 4c and finally an
upwardly and outwardly bent bar portion 3d, 4d. On these
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latter bar portions 3d, 4d, stationary contact pieces 5, 6
are mounted. The fixed mounting of these stationary
contact pieces and of the described contact bars is
performed, on the one hand, by contact connecting screws 22
which, in their screwed-in position, engage with their
lower screw bolt ends 22a into the cylindrical recesses
]b. By a simple mounting of the upper housing portion 2,
the stationary contact bars 3,4 with the contact pieces 5,
6 are retained in their desired position. At the same
time, the contact connecting screws 22 serve to mount
outwardl~-leading electrical connecting lines 23.
In accordance with Fig. 1, a contact briage
support 7 in correspondingly-designed lateral guides is
vertica]ly-movable in the lid-like upper housing portion
2. This contact bridge support 7 is provided at its upper
end with an actuating button 7a which can be manually
pres6ed downwardly for switching on the contact device, or
it can be actuated by a magnet system coupled thereto (not
shown) or in an~ other suitable mechanlcal manner. Lateral
arms 7b are provided on contact bridge support 7 with outer
end pieces 10 which are each engaged by the upper ends of
pressure ~prings 9. The lower end of each pressure spring
9 is inserted into a cylindrical recess 11 of an
intermediary wall 12 of upper housing portion 2. When not
actuating the contact device, these pressure springs 9 act
in such a manner that the contact bridge support 7 remains
in the uppermost position as shown in Fig. 1. Furthermore,
a double-sided horizontal arm 8 is mounted on contact
bridge ~upport 7, the underside of which supports two
lateral contact pressure springs 13, 14.
A contact bridge 18 is guided through a recess 17
in contact bridge support 7, in a direction parallel with
respect to the drawing plane of Fig. 1. This contact
bridge 18 is also provided with contact pieces 20 at its
ends. Advantageously, the two contact pieces 20 are each
mounted on a contact piece support l9 which, in turn, is
connected with the corresponding end of the co~tact hridge
18. Advantageously, the fixed connection is established,
on the one hand, between contact piece æupports 19 and
contact pieces 20 and, on the other hand, between flexible
contact bridge 18 and contact piece supports 19 by means of
riveting, soldering, braze soldering, welding, Aot welding,
ultrasonic welding or squeezing, etc.
In accordance with the invention, contact bridge
18 is made from a flexible material and preferably from a
flexible wire. As a flexible wire, a stranded flat or
annular flexible wire is preferably used, depending on the
application and the spatial conditions which prevail.
Instead, the flexible contact bridge may al~o be
constructed from a different material which is flexible in
itself, for example, parallel running current leads, bands
or tapes which are coupled with each other at suitable
locations, for examp]e, in the area of the contact pieces.
The lower ends of the two contact pressure springs 13, 14
engage both ends of the flexible contact bridge in the area
where the contact pieces or the intermediate switch contact
piece supports are located. A rib 16 is provided inside
recess 17 of contact bridge support 7 which runs normally
with respect to the drawing plane of F;g. 1, but
which affords a clearance with respect to flexible
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contact bridge 18. In addition, a cam rib lS is provided
in the contact bridge suppoet 7 at both sides in close
proximity to contact pressure springs 13, 14. These cam
ribs are positioned in the switch-off position, in
accordance with Fig. 1, at a certain d;stance above the
flexible contact bridge 18 and, simultaneously, above
movable contact pieces 20. For sake of simplicity, only
one cam rib 15 is drawn on the left side of Fig. 1.
However, on the other side there is also a corresponding
cam rib. Finally, arc quench chambers are advantageously
mounted on the outside of the described contacts which are
shown in the form of arc quench chamber metal plates 21.
As shown in the embodiment of Figs. 1 and 2,
flexible contact bridge 18 is retained substantially in a
straight line in contact bridge support 7. Furthermore, in
this embodiment, stationary contact pieces 5, 6 are
advantageously disposed in planes which run obliquely to
the moving direction of movable contact pieces 20.
Advantageously, the oblique position is so chosen that the
contact pieces are directed in a rearwardly-ascending
oblique direction. This results in the following
advantages. Due to the oblique position of the stationary
contact pieces and the straight or horizontal disposition
of the movable contact pieces thereto when they are engaging
with each other, the movable contact pieces first abut a
predetermined outer edge during the switching-on process.
Due to the flexible design of the contact bridge, each
movable contact piece can forcibly adjust to the oblique
position of the corresponding stationary contact piece.
During the switching-off process, this operation takes
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place in a reversed sequence, i.e., at first the contact
faces of the superimposed contact pieces open to the
outermost edge without being lifted and without generating
an arc. During the further lifting of the movable contact
pieces, the contact then opens on the outer edge and an arc
is generated.
Preferably, the contact piece supports of the
stationary and movable contact pieces are provided with
massive arcing horns or arc discharge horns in the
discharge area of the arc. Since the arc is only generated
on the outermost predetermined edge of the contact pieces,
it is driven by the magnetic power lines of the stationary
contact bars and the arc quench sheet metal plates directly
from the predetermined burn-off range of the contact pieces
onto the arc discharge horns from where the arc again tears
off at the outer edge and only causes a burn-off at this
point. In thls context, it is advantageous that the arc
discharge horns are provided on the same plane as the
contact pieces and are tightly connected thereto. In this
manner, a sùfficient transfer of the arc from the burn-off
area of the contact pieces to the arc discharge horns is
obtained, because the arc does not have to overcome any
steps and therefore does not leave any burn-off tracks at
the burn-off range of the contact pleces; in other words,
it is directly deflected onto the arc discharge harns.
Due to the adaptability of the movable contact
pieces to the disposition of the stationary contact faces,
which i~ made possible with the flexible connection between
the two movable contact pieces with the assistance of the
flexible contact bridge, the distance of the arc discharge
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horns changes in a favorable manner, i.e., a very small
distance is created during opening and therefore a
favorable take over of the arc. Therefore, in addition to
the aforementioned low switch-on burn-off, there is also
the aforementioned low switch-off burn-off which causes a
reduction of the burn-off volume and, simultaneously, an
increase in the electrical life span of the contact device.
Therefore, in addition to the aforementioned
explained favorable switch-on impact conduct, there is also
a low burn-off volume and, simultaneously, an increase of
the electrical life span of the contact device.
The thermal stresses on the contact pieces is
also low, due to the invention. The predetermined outline
edge of the arc in the burn-off area of the contact pieces
assures that the remainder of the contact face remains free
from contamination, burn-off scratches and soot, which
means that the contact faces of the contact pieces always
remain clean in the switched-on position, so that the
contact occurs on a clean contact face between the contact
pieces. This results in a considerable advantage with
respect to the contact transfer resistance and the
resulting thermal stress with a permanent or continuous
electric current. Furthermore, during each switching
operation, a relative movement of the contact pieces toward
each other occurs, so that a certain self-cleaning of the
corresponding contact faces is additionally assured.
The invention provides considerable advantages
with respect to electrical switch-on weld safety. The
greatly increased electrical weld safety during switch-on,
in comparison to the state of the art, is the result of the
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impact-free behavior of the movable contact pieces and from
the oblique position of the stationary contact pieces, as
well as the adaptability of the movable contact pieces
relative to the stationary contact pieces. If, for
example, a contact is loaded beyond the limit of its
switch-on weld resistance, it is more or less rigidly
welded. This fusing occurs only at the first contact point
at the outer edge, due to the oblique position of the
stationary pieces. When, at this point, the corresponding
contact piece is moved further in the switch-on direction,
it turns or it pivots around the fused edge up to the
advanced oblique position of the stationary contact piece
which is made possible due to the flexible design of the
contact bridge. Due to this turn or pivot movement, the
fusing is again broken. The force required therefor, is
supplied by the corresponding contact pressure spring.
In this context, a further advantageous embodiment
of the invention is made possible - namely, in that contact
pressure springs 13, 14 are preferably disposed at an
acute angle with respect to the moving direction of the
movable contact pieces in contact bridge support 18. By a
corresponding oblique positioning of the contact pressure
Rpringsj the force for breaking the fusing may be increased.
In a further advantageous embodiment of the
invention, cam ribs 15 are disposed in contact bridge
support 7 in such a manner that the movable contact pieces
20 are forcibly pivoted into the oblique position corres-
ponding to the position of the stationary contact pleces.
In this manner, the breaking-off of the fusing is also
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enhanced in in that the cam rib during the switch-on
process pushes the fused movable contact piece, together
with an arc discharge horn, forcibly into the oblique
position corresponding to the stationary contact piece, so
that even a stronger fusing can be released even during the
switch-on process. This is particularly advantageous when
using condenser contactors.
Finally, in a further advantageous embodiment of
the invention, the contact pieces and/or the arc discharge
horns consist of diffferent burn-off materials on their
surfaces in such a manner that a material with a high
thermal load or carrying capacity is chosen in the area of
the arc outline edge and, in the remainder, a material with
a good electrical conductivity and lower current passage
resistance. In this manner, the themal capacity of the
contact device can be further increased
Figs. 2 and 3 which substantially conform to Fig.
1, show a different switch position with respect to Fig. 1.
In Fig. 2, the contact bridge support 7 is displaced against
the force of the springs 9 downwardly in such a manner that
the still horizontally-held movable contact pieces impact
with their outer edges against the stationary oblique
contact pieces. Flexible contact bridge 18 is bent
downwardly by rib 16 during a further pushing of the
contact bridge support 7, so that the cam rib 15 engages in
such a manner (as shown) that the movable contact pieces
are forcibly pivoted into the oblique position, as
described above. It is to be understood that, in this
switch-on position, contact pressure springs 13, 14 are
correspondingly compressed.
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In accordance with a further embodiment of the
invention illus~rated in Figs. 4 and 5, the stationary
contact pieces 5 and 6 are disposed in planes normal with
respect to the moving direction of movable contact pieces
20. Accordingly, contact bar portions 3d, 4d of contact
bars 3, 4 are deflected into this horizontal plane. As can
be clealy seen from Fig. 5, in this case, flexible contact
bridge 18 is further bent downwardly by rib 16, as soon as
the contact pieces meet each other. This also results in
advantageous moving conditions.
The embodiment of Fig. 6 substantially corresponds
to the embodiments of Figs. 1-3, however, contact bridge
support 7 is designed differently, and a different support
is providefl. This design has the purpose of allowing the
switch-off arc to discharge to all sides, since the contact
pieces are freely supported. Furthermore, in this design,
a positlve support of the contact piece support with their
associated contact pieces on the ends of the flexlble
contact bridge is made possible.
Furthermore, in particular embodiments and
applications, it is advantageous to provide the contact
piece support with the associated contact pieces in a
suspended or loose manner between corresponding abutments
of the contact bridge support and the contact pressure
springs. For this purpose, the embodiment in accordance
with Fig. 6 is suitable since the contact bridge support 7
is provided with further vertical guifles 7c on the inner
side of the contact pressure springs 13, 14. These guides
serve as an additional guide for guiding the flexible
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contact bridge between rib 16 and the lower part 7c of the
contact briage support for the inserted flexible contact
bridge.
Fig. 7 shows a contact device which, in the
principal construction, corresponds to the one of Figs. 4
and 5. However, in this particular embodiment, the contact
bridge consists of a flexible material in the form of one
or a plurality of leaf springs. In the embodiment according
to Fig. 7, two leaf springs 24 and 25 are serially-arranged
in the direction of movement of contact bridge 7 and they
are guided with free motion clearance or free play within
contact bridge support 7. Each leaf spring may be very
thin and preferably consists of copper-bronze or bras~-
bronze. When using such leaf springs, the contact pressure
springs which were used as helical springs in the previous
embodiments may be eliminated since the leaf springs
simultaneously serve as contact pressure springs for the
two movable contact pieces 20. Advantageously, the
connection between the two movable contact piece supports
and the ends of the two leaf spring 24, 25 is made, due to
the inherent spring pressure of the leaf springs. Thereby,
it is advantageous that the movable contact piece supports
19 are guided obliquely relative to the moving direction of
contact bridge support 7, preferably by means of
correspondingly obllquely-designed lateral shoulders or
abutments 7e. The contact faces 24a, 24b and 25a, 25b on
the ends of leaf springs 24 and 25 are advantageously
covered with a good conductive, thin contact material
layer. Thereby, the leaf springs are so designed that
their ends provide a dot support on contact piece
supports 19. Due to the dot engagement of the leaf spring
end, the two contact piece supports which are very small in
their mass can be very well ad~usted to the stationary
contact pieces during the switch-on process.
When using two leaf springs 24 and 25, they
advantageously have a different length. In such a case,
the two leaf springs are so designed and disposed that the
spring effect during the switch-on process occurs in a
timed sequence. In this manner, the switch-on forces for
the contact transmission during the switch-on process are
kept low. In practice, the outer longer leaf spring 24
exerts the first contact pressure until, after a defined
path, the second leaf spring 25 substantially reinforces
the contact pressure. The effect of the second leaf spring
15 occurs shortly before the final switch-on position,
i.e., the contact receives a relatively high contact
pre~sure for the current feeding which has a favourable
efect on the contact heating. Mostly, the inventive
contact devices are actuated by a magnetic drive (not
shown~. When using a magnetic drive, the further advantage
is obtained that, due to the aforementioned position of the
two leaf springs, this magnetic drive is loaded at the very
last moment of the switch-on process with the forae of the
second Jeaf spring, i.e., at the moment when it has its
largest pulling forces. Due to the stepwise arrangement of
the contact forces, a normal magnet is required and this
arrangement has a favourable effect on the wear of the
magnet. The two leaf springs of the movable f]exible
contact bridge may be directly or tightly superimposed with
respect to each other. In particular, when large switch
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capacities are require~, it is advantageous to maintain the
two leaf springs 24, 25 at a distance by means of individual
extensions or corrugations or any other suitable distance
spacers. Thereby, a very favourable large heat emission
face is obtained, especially for a maximum, permanent or
continuous current.
A further improvement of the embodiment of the
contact device in accordance with Fig. 7 can be obtained in
that a good current conducting flexible wire is associated
with at least one leaf spring. The flexible wire may
preferably be imbedded between the two leaf springs 24,
25. However, one can encompass one or both leaf springs
with the flexible wire.
The contact device in accordance with Fig. 7 has
a further advantage, especially for direct cuxrent
switching, in that a particularly large opening path of the
contact can be realized without enlaring the outer measure-
ments of the contact device. This is mainly possible
hecause the helical contact pressure springs of the afore-
mentioned embodiment can be eliminated. The advantage ofthe large opening path of the contact can also be obtained
in the subject device structure when the subject contact
bridge support is replaced with a contact bridge support
with the explained leaf springs, in accordance with Fig. 7.
The large opening path is of substantial importance for
controlling the arc, especially when using direct current.
In the aforementioned embodiments, only two
stationary contact bars and one flexible contact bridge are
provided. The inventive contact devices may be provided
with a plurality of pairs of contact bars and flexible
contact bridges mounted normally with respect to the
drawing plane, for example. The same is true for arranging
them in a superimposed relationship in one or more levels.
Figs. 8 and 9 show a further embodiment of the
invention. Here, it is shown that it is possible, due to
the low weight of the flexible contact bridges 18, to make
them relatively long and therefore to be able to mount the
stationary contact bars 3, 4 with the associatea stationary
contact pieces 5, 6 at such a large distance from each other
that one can remove the coil 28 of the lower housing 32,
which usually is mounted on a magnet core 27, upwardly from
the housing without requiring one to detach the total wiring
of the contact device. Only the lid 29 of the upper housing
31 has to be removed for removing or exchanging the coil 28.
Thereafter, one can remove the contact bridge support 7,
together with the contact bridges 18 or the contact bridges
alone, as well as the movable contact pieces which, in
turn, are mounted in a frame-like unit 30, together with
the connected armature 26. It is to be understood that the
bottom 31a of the upper housing portion 31 has such a large
opening that the coil 28 can be removed therethrough.
Therefore, the flexible contact bridges in this total
structure result in a considerable assembly simplification
and a substantial simplification during repairs when the
coil has to be replaced. In comparable structures, the
total device had to be disassembled and, above all, the
wiring leading to the outside had to be detached from the
stationary contact bars.
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Thus, while only several embodiments of the
present invention have been shown and described, it will be
obvious that many changes and modifications may be made
thereunto, without departing from the spirit and scope of
the invention.
