Apparatus for soldering the winding to the commutator of an electric machine

An apparatus for soldering the wires of the rotor winding of an electric machine to its commutator. The apparatus comprises a tank with molten solder and heaters, a magneto-hydrodynamic pump for the solder, a device for holding the rotor, and a device for the protection of the molten solder from oxidation. The device for holding the rotor comprises a base in the shape of a hollow cylinder with holes and having a chamfered bottom part of the internal surface thereof in which there is movable disposed a replacement nozzle, which is made up of a sleeve and a rotor holding case rigidly connecting together. The nozzle reciprocates in the base. The commutator of the rotor to be solder is inserted into the case. Between the sleeve and the case there is formed a ring-shaped duct, connected with a booster zone which directs the molten solder toward the commutator. To the upper part of the base there is attached a device for the protection of the molten solder from oxidation; such device comprises a hood with a central hole and a gas distributor, connected to a source of inert gas. When there is no rotor inside the case, the nozzle is lifted by the molten solder under the action of the Archimedes' forces, and the molten metal is returned into the bath thereof in the tank through the holes in the base, while the sleeve is sealed against the hood to avoid the flowing out of inert gas provided above the molten solder.

This invention is related to Minchev et al., U.S. Pat. Nos. 4,331,279 and 
4,375,270. 
This invention relates to an apparatus for soldering the winding of an 
electric machine to its commutator; the invention is useful in the 
production of commutator-type electric motors and generators. 
A known apparatus for soldering the winding of an electric machine to its 
collector is disposed in Bulgarian Pat. No. 31,621 which corresponds to 
U.S. Pat. No. 4,375,270. Such apparatus comprises a single-phase 
magneto-hydrodynamic pump with a booster zone and a bath with molten 
solder and heaters. The magnetic circuit of the single-phase 
magneto-hydrodynamic pump is enclosed at one end thereof by a winding, and 
at the other end by the booster zone. The inlet end of the booster zone is 
connected to the bottom of the solder bath, while its outlet end is 
connected to a base, which is rigidly fastened to the bottom of the tank 
containing the bath. This base is a hollow cylinder with a conical bottom 
and a central hole, in which a nozzle is located concentrically therewith. 
This nozzle is made up of a sleeve and a case. The upper end of the 
internal surface of the sleeve is chamfered at an angle smaller than 90 
degrees with respect to the axis of the base. The upper end of the 
external surface of the case is chamfered and parallel to the chamfered 
end of the internal surface of the sleeve. 
A drawback of this known apparatus lies in the necessity of switching-off 
the single-phase magneto-hydrodynamic pump when the soldered rotor is 
replaced, because of the danger of filling the case seat with solder. This 
inevitably results in a certain reduction in the productivity of the 
apparatus. Moreover, the electro-magnetic system of the single-phase 
magneto-hydrodynamic pump is of the open type, and this results in an 
impairment of the energy characteristics of the apparatus and an increase 
in the consumption of copper and electrotechnical steel. The protection of 
the molten solder in the bath is achieved by fluxing, but no measures are 
taken for the protection from oxidation of the flow of molten solder which 
washes the commutator segments. 
It is therefore a general object of the present invention to provide an 
apparatus for soldering the winding of an electric machine to its 
commutator, which, in addition to the advantages of the existing apparatus 
such as that disclosed in the above referred-to patents, provides a total 
protection of the molten solder from oxidation, and is particularly 
characterized by an increased productivity and a reduced consumption of 
copper and electrotechnical steel and electrical energy. 
These objects are achieved by an apparatus for soldering the winding of an 
electric machine to its commutator in accordance with the invention. Such 
apparatus comprises a single-phase magneto-hydrodynamic pump with a 
booster zone, a tank containing a bath of molten solder and heaters, and 
an arrangement into which the rotor to be soldered is positioned. The core 
of the single-phase magneto-hydrodynamic pump is enclosed at its one end 
by the winding of the pump, and at its other end by the booster zone. The 
inlet end of the booster zone is connected to the bottom of the tank 
containing the solder bath, while its outlet end is attached to a base 
which is rigidly fastened to the bottom of the tank. The base is a hollow 
cylinder, and the bottom end of its internal surface is chamfered with 
respect to its axis at an angle smaller than 90 degrees. Concentrically in 
the base there is located a nozzle, which is made up of a sleeve and a 
case, which are rigidly fastened one to another. The sleeve is a hollow 
cylinder and the upper end of its internal surface is chamfered at an 
angle smaller than 90 degrees with respect to the axis of the base. The 
case is a hollow cylinder with a conical bottom, and the upper end of its 
external surface is chamfered and is parallel to the chamfered upper end 
of the internal surface of the sleeve. 
Above the chamfered part of the base there are disposed uniformly and at 
equal height a number of holes. The bottom end of the sleeve is chamfered 
and is parallel to the bottom end part of the internal surface of the 
base. The sleeve and the base are connected by a loose fit. To the bottom 
end of the base there is connected the booster zone, which comprises a 
pipe and a cylindrical vessel. This cylindrical vessel comprises a top 
disc, a bottom disc, and a side surface. The bottom disc and the top disc 
are disposed close to one another and have central holes therein, said 
holes being connected to the core and the one end of the pipe, 
respectively. The other end of the pipe is connected to the bottom end of 
the base. The bottom of the bath is connected to the top disc by means of 
one or more metal conduits. The pipe and the top disc are made of 
ferro-magnetic material. Concentrically to the winding and the bottom disc 
there are provided two or more external magentic circuits, such circuits 
being connected at their one end to the core and at their other end to the 
top disc. The pipe encloses the core with which it is concentric. To the 
upper end of the base there is fastened a protective hood. The hood is 
made up of a cylindrical part and a cover, which is attached tightly to 
the cylindrical part. The cover has a central hole. The cylindrical part 
is partially immersed in the molten solder, encloses the base, and is 
rigidly fastened to the base by means of carriers. Underneath the cover 
around the central hole there is disposed a gas distributor which is a 
ring-shaped pipe with holes, such pipe being connected via a reducing 
valve to a source of inert gas. 
The apparatus of the invention has the following main advantages: An 
increase of labor productivity and the facilitation of the attendance of 
the apparatus as a result of the elimination of the forced pause in the 
process cycle during which the soldered rotor is removed from the 
apparatus and replaced by a rotor to be soldered. This makes the apparatus 
convenient for robotization; a considerable reduction of the consumption 
of copper and electrotechnical steel, and of electrical energy as a result 
of the reduction of the magnetic resistance along the path of the working 
magnetic flux. The molten solder is protected from oxidation, this 
resulting in the preservation of its physical and chemical 
characteristics, and produces a saving of solder and a lengthening of the 
time of operation of the apparatus without the need for cleaning it.

Turning first to FIG. 1, beneath a tank 1 containing molten solder 2 and 
electrical resistance heaters (not shown) there is disposed a single-phase 
magneto-hydrodynamic pump for molten metals. Such pump has a winding 3, a 
central core 4, and a booster zone. To the bottom of the tank 1 there is 
fastened an arrangement for holding a rotor 5 to be soldered. Such 
arrangement comprises a base 6 in the form of a central sleeve and an 
exchangeable nozzle mounted therein. The base 6 is a hollow cylinder, the 
bottom end of the internal surface of which is chamfered with respect to 
its axis at an angle smaller than 90 degrees. The nozzle is made up of a 
sleeve 7 and a case 8, the sleeve and case being rigidly fastened to each 
other by a number of carriers, of which one is shown at 23. The nozzle 
reciprocates from an upper position thereof, shown in FIG. 1, to a lower 
position thereof shown in FIG. 2. The sleeve 7 is a hollow cylinder, the 
upper end of the internal surface of which is chamfered at an angle 
smaller than 90 degrees with respect to the axis of the base 6. The case 8 
is a hollow cylinder with a conical bottom, the upper end of the external 
surface of which is chamfered and is parallel to the chamfered upper end 
of the internal surface of the sleeve 7. 
The core 4 is enclosed at its lower end by the winding 3, and at its upper 
end by the booster zone. Above the chamfered part of the base 6 there are 
disposed a number of holes 9 (one shown) disposed at the same height. The 
bottom end of the sleeve 7 is chamfered and is parallel to the bottom 
conical part of the internal surface of the base 6. The sleeve 7 fits 
loosely within the base 6. The booster zone is connected to the bottom end 
of the base 6. The booster zone comprises a pipe 10 and a cylindrical 
vessel. The cylindrical vessel comprises a top disc 11, a bottom disc 12, 
and a ring 13 which connects the outer edge portion of disc 12 to the top 
disc 11, as shown. The discs 11 and 12 are disposed close to one another 
and have central holes therein, the core 4 extending through the central 
hole in the bottom disc 12 and being connected to such disc at such 
location. The lower end of the pipe 10 is connected to the top disc 12 at 
the central hole therein, and at its top is connected to the bottom of the 
tank 1 by means of one or more (two shown) vertical metal conduits 14. The 
pipe 10 and the top disc 11 are made of ferro-magnetic material. 
Concentric with the winding 3 and the sleeve member 13 there are disposed 
two or more external magnetic circuits 15, connected at the bottom to the 
bottom end of the core 4 and at its upper end to the top disc 11. The pipe 
10 is disposed around and is concentric with the core 4. 
To the upper part of the base 6 there is fastened a protective hood, which 
comprises a cylindrical part 16 and a cover 17, the cover being tightly 
attached to the part 16. The cover 17 has a central hole 18 therein. The 
cylindrical part 16 is immersed partly in the solder bath 2, encloses the 
base 6, and is rigidly fastened to it by means of a number of carriers 19 
(one shown). Beneath the cover 17 around the central hole 18 there is 
disposed a gas distributor 20, which is a ring-shaped pipe with holes 
therein, distributor 20 being connected via a reducing valve (not shown) 
to a source of inert gas (not shown) by a pipe 24. Between the base 6 and 
the case 8 there is formed a guiding channel 21. The upper chamfered ends 
of the sleeve 7 and the case 8 form a ring-shaped duct 22. 
The above-described apparatus operates as follows: The initial melting of 
the solder in the bath 1 is effected by means of the above-described and 
not shown electric resistance heaters and by induction by the single-phase 
magneto-hydrodynamic pump. After the melting of the solder, the nozzle 
composed of the sleeve 7 and the case 8 is lifted into the position 
thereof shown in FIG. 2 (in accordance with the law of Archimedes) the the 
sleeve 7 touches the cover 17. Thus a close space is formed, which is 
limited by the base 6, the surface of the molten solder 2, the protective 
hood, and the sleeve 7. By means of the gas distributor 20, this space is 
filled with protective gas (nitrogen, for example) at a suitably low 
pressure. The molten solder 2, sucked from the bottom of the tank 1, 
passes through the metal conduits 14, the booster zone, the holes 9, and 
returns into the bath 1. Access of atmospheric air to the solder is then 
precluded. 
Turning now to FIG. 2, it will be seen that when a rotor 5 to be soldered 
is placed in the seat therefor in case 8, the nozzle, that is the sleeve 7 
and the case 8, moves downwardly under the action of the weight of the 
rotor , thereby to close the holes 9 in the base 6. The molten solder 2 
flows out from the ring-shaped duct 22, simultaneously washing all the 
segments of the commutator of the rotor, and returns to the tank 1. When 
the nozzle moves downwardly, the sleeve 7 is separated from the cover 17, 
and the protective gas begins to pass between the flow of molten solder 2 
and the cover 17, thus forming a protective gas pad or enclosure. After 
the soldering process is terminated, the rotor 5 is lifted out of the case 
8, thus restoring the nozzle to the position thereof shown in FIG. 1, and 
ending the working cycle of the apparatus. 
In cases when it is necessary to solder a rotor 5 with the diameter of the 
commutator thereof differing from that of the preceding rotor, the nozzle, 
that is the sleeve 7 and the case 8, is replaced by a new nozzle with a 
suitable diameter of seat in the case 8 thereof. Then the afore-described 
working cycle of the apparatus is repeated. 
Although the invention is described and illustrated with reference to a 
single preferred embodiment thereof, it is to be expressly understood that 
it is in no way limited to the disclosure of such preferred embodiment but 
is capable of numerous modifications within the scope of the appended 
claims.