Electric connection of braids on a circuit breaker terminal

Several braids (26) to connect a moving contact (10) to a lug (14) for the current lead are attached to the lug by welding under pressure, the ends (32) of the braids (26) being placed in slots (34, 36, 38) made in the face of the lug (14). The welding occurs without any need of hard solder.

BACKGROUND OF THE INVENTION 
The invention relates to a fixed electric connection of flexible conductors 
such as braids, with a large section on the end of a flat section terminal 
or lug. 
Circuit breakers or interrupters for current of high intensity, for example 
of few thousands amperes, comprise flexible conductors, for example shunts 
or braids, to connect the moving part, especially the moving contact 
fingers and the lug for the current leading. The end of these flexible 
conductors is generally linked together onto the upper surface of the lug 
for the current leading by welding or tightening by bolts. These fixing 
modes give full satisfaction for conductors of limited section, but are 
not easily applied to shunts or braids of high section required for the 
current flow across the above-mentioned circuit breakers. 
The object of the present invention is to allow a fixed connection of 
flexible conductors, especially of high section braids, on a flat shaped 
lug. 
SUMMARY OF THE INVENTION 
According to the invention a plurality of slots are made in the face of the 
end of the lug. The cross-section of the slots corresponds to the one of 
the conductor or conductors introduced in each slot without any play, the 
end of the conductor being heated by resistance and compressed to secure 
the flexible conductors by welding to the lug. 
By making more or less deep slots, it is possible to increase the 
attachment surface of the flexible conductors and to accommodate housings 
admitting ends of these flexible conductors, in particular braids. As used 
herein, the flexible conductors will be called braids, but other types of 
conductors can be used of course. 
The electric and mechanical connection of the braids to the lug is made in 
a welding press of high capacity likely to distort the teeth defined by 
the slots to compress and to enclose the ends of the braids in the slots 
and to carry out a welding without any need of hard solder. The absence of 
tin or another hard solder precludes the diffusion of tin inside the braid 
and thus to become rigid. The face of the lug for the current lead can be 
cut into battlements all along its width to define a course of slots, each 
one of which receives the end or the ends of one or several juxtaposed or 
superimposed braids in the slot. The braids housed in the slots makes 
their positioning easier and permits the linking of all the braids to the 
lug for the current lead by a single operation which does not require any 
annealing. This cut in battlements reduces the section of projecting 
teeth, which allows their distortion under the compression force exerted 
by the press and a compression of the braids ends inserted between the 
teeth. 
The invention is also relative to an electric circuit breaker having 
several braids, especially for the link between movable contact fingers 
and the terminal or lug. In the equipments of high intensity, it is common 
to use several connection braids, the rigidity of which is below the one 
of a single braid of high section. All these braids which can be connected 
to one or several fingers of moving contact, is fastened to the lug for 
the current leading by putting the ends of these braids in slots 
accommodated in the end of the lug according to the present invention. As 
an indication it can be noted that according to the invention the link by 
slot allows one to attach onto a thin lug of 45 mm wide by 8 mm thick five 
braids each having a section of 40 square mm. Furthermore the section of 
braid connected to the lug can be increased by making the slots deeper. 
The braids stretch outside the slots in the extension of the lug, or 
perpendicular to the lug according to preferred embodiment. When a large 
number of braids are connected on the same lug, it is recommended to place 
several braids in a same slot instead of multiplying the number of slots 
by reducing the width of the teeth which would weaken the assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the figures, a moving contact 10 of an apparatus for switching off high 
intensity current, for example of an electric circuit breaker of the type 
described in the U.S. Pat. No. 7,770,922, cooperates with a fixed contact 
12. These contacts are connected to a lug 14 for the current lead and to 
an outgoing lug 16 respectively, the moving contact 10 which is being able 
to be moved into an opening position to interrupt the current. The moving 
contact 10 built for rated intensities of several thousands amperes is 
made by five fingers 18 mounted on the same axis 20 locked with a 
contact-carrier (not shown) driven by the mechanism of the circuit 
breaker. Each finger or contact 18 comprises laminations 22, 24, the 
number of these laminations being able to be different of course. The 
moving contact 10 is connected to the lug 14 by five braids 26, each one 
associated with one of the contact fingers 18. The end 28 of the braid 26 
is inserted in a slot 30 made at the bottom part of the contact finger 18, 
the attachment being achieved by a tin soldering. The opposite end 32 is 
bound to the lug 14 for the current lead by welding under pressure in 
slots 34, 36, 38. In the example illustrated by the Figures, the lug 14 of 
a 8.times.45 mm section shows on its face 40 three notch shaped slots 34, 
36, 38 crossing the height of the lug 14. The battlement shaped slots 34, 
36, 38 are delimited by teeth 42, each one of the terminal slots 34, 38 
receiving of two braids 26, whereas the middle slot 36 receives the end 32 
of a single braid. The width of the terminal slots 34, 38 is greater than 
the slot 36 of course. The braids are introduced in the slots 34, 36, 38, 
so as to extend perpendicular to the lug 14, although a different 
arrangement especially in the alignment of the braid 26 with the lug 14 
being can be used. 
FIGS. 3 and 4 illustrates the method used to solder braids 26 to the lug 
14. It can be seen that this lug 14 is inserted between the jaws 44 of a 
welding press, the slotted part facing the moving electrode 46 of the 
press. The braids 26 are mounted in slots 34, 36, 38, this installation 
being done by simple insertion of the ends 32 in the slots before the 
electrode 46 is applied on the face 40 of the lug 14. The electrode 46 
covers the whole face 40 and the high pressure (able to reach several 
thousands kilos) and the effect of electric heating (the current intensity 
being able to be of several tens of thousands amperes), the teeth 42 are 
crushed by compressing and welding the braids in the slots 34, 36, 38. The 
soldering is carried out by heating and compression without any need of 
hard solder and without any annealing. The crushed or wide-mouthed form of 
the teeth 42 under the pressure effect is illustrated by FIGS. 4 and 5. 
The attachment of all the braids 26 is accomplished by a single operation 
without requiring accessories to hold or position the braids 26. The ends 
32 placed in a same slot 34, 38 can be juxtaposed according to the way 
shown on the Figures, or superimposed, the depth of the slot 34, 38 then 
being appropriate to the number of superimposed ends 32. It is clear that 
the ends 32 located in a same slot 34, 38 can belong to braids 26 
connected to a same contact finger 18, which allows the reduction of the 
section of these braids 26, or that any other arrangement is possible. The 
section of the slots 34, 36, 38 is adapted to the one of the ends 32 so 
that the latter is put in the slots without any play before the welding 
operation. According to the invention, the connection by soldering does 
not increase the over-all dimensions of the connection lug 14 and it keeps 
the flexibility of the braids 26 which permits their length to be limited. 
According to the invention the method is especially appropriate to weld 
copper braids 26 on copper lugs 14, but it can be applied to different 
welding materials on aluminum lugs. This process is especially interesting 
to attach several braids 26 to the same lug 14, but it would not go beyond 
the limits of the invention by applying it to an attachment of a single 
braid. 
It is not necessary to describe in more details the welding press which is 
a classical type or the method which relates to the mounting of the lug 14 
between the jaws 44 of the press, the braids 26 being inserted in the 
slots 34, 36, 38, and to the application of the moving electrode 46 on the 
face 40 under high pressure for a soldering in resistance by the usual 
way. Those skilled in the art can supply these details.