Apparatus for compression molding of coil end turns

In order for a coil winding head, preferably to be reinforced by the baked-lacquer process, to be compression-molded with no need for preliminary pre-positioning by tape-wrapping and with no damage to the winding wires, a form shell apparatus is provided with a form core, which radially confines the coil end forms shape on the inside, with a radially advanced confining form shell divided into at least two parts in the circumferential direction. This multi-part shell radially confines the coil end turns on the outside. A compression form shell axially advanceable against the coil end turns confines the coil end turns in an axial direction. It has, on its inner and outer circumferential surfaces, integrally molded guide fingers, which extend axially in the direction of the coil end turns to be shaped. Corresponding guide grooves are molded into the form core and the confining form shell, into which guide grooves the guide fingers extend. Furthermore, the compression form shell has axial inner and outer compression fingers, which extend into the gaps of the coil winding head and press the winding of the said coil winding head in the radial or tangential direction. After assembly, the apparatus safely secures and protects the coil end turns in the desired position and shape.

FIELD OF THE INVENTION 
This invention relates to the field of electrical devices having electrical 
windings and more particularly to an apparatus for compression molding 
coil windings in a protective shell. 
DESCRIPTION OF THE PRIOR ART 
It is known from German Gebrauchsmuster No. 7,640,891 to provide a one-part 
mold shell, corresponding to the overall mold contour intended for the end 
turns of a coil. This known one part mold shell is pressed axially onto 
the end turns which extend beyond the end surface of the stator core until 
the front edge of the mold shell lies in contact with the end surface of 
the stator core. The coil end turns in this known apparatus must always be 
secured with tape, otherwise all the winding wires cannot be enclosed and 
pressed together, under adequate pressure from all sides, into the desired 
rounded shape for the end turns of the coil without damaging some of the 
windings. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide an apparatus in 
which the coil end turns are molded in such a manner as to ensure the 
total subsequent operating safety of the electric motor, even when the 
coil end turns protrude out of the ends of the slots of the end surface of 
a stator core in the case of an electric motor having windings 
mechanically wound in such slots. It is a further object of this invention 
to provide such an apparatus for use with pre-wound coils which are 
mounted on a stator core to shape and protect the end turns of the 
pre-wound coil without pre-forming or pre-strengthening by any process 
subsequent to coil mounting, especially by tape wrapping. 
Briefly stated in accordance with one aspect of this invention the 
aforementioned objects are achieved by providing an apparatus for 
compression molding of coil end turns, in particular of coil end turns 
which are not tape-wrapped, are generally cylindrical with an inside and 
outside, and are to be reinforced by the baked-lacquer process, with a 
form shell apparatus that can be pressed against the coil end turns. The 
apparatus includes: an inner form core as a part of said form shell 
apparatus, which radially confines the coil end turns form on the inside; 
a radially advanced outer confining form shell divided into at least two 
parts in the circumferential direction, which radially confine the coil 
end turns form on the outside; a compression form shell with an end 
surface contour for the coil end turns, which compression form shell can 
be advanced axially against the coil end turns. The outside and inside 
circumferential surfaces of the compression form shell outside of the end 
face contour of the coil end turns have outer and inner guide recesses 
cooperating with the inner and outer guide projections, respectively, into 
which said guide projections extend. 
With the apparatus in accordance with the invention, it is possible, first, 
by inserting the form core axially and advancing the outer confining form 
shell radially, to determine the shape of the coil winding mold up to the 
axial opening of the compression form shell; the axial compression form 
shell can then be pushed axially forward against the coil end turns, 
largely independently of the filling factor of the form shell apparatus 
thus provided by the form core, the confining form shell and the 
compression form shell, until the winding wires of the coil end turns are 
placed under an adequate pressure from all sides, preferably with the 
attainment of plastic deformation. The guide fingers, which do not take up 
any of the space usable for the winding and nonetheless can be designed 
with adequate strength, can enclose all the winding wires without any 
danger of kinking when the compression form shell is advanced. 
In order to guarantee adequate strengthening pressure on all winding wires 
from all sides, even in cases where, for example, the voids appearing in a 
winding which is wound in two stages cannot be completely filled by the 
axial pressure exerted by the compression form shell, one embodiment of 
the invention provides for molding additional inner or outer axial 
compression fingers integrally with the compression form shell. These 
inner and outer axial compression fingers extend into the gaps in the coil 
end turns and press the windings of said end turns in the radial or 
tangential direction when the compression form shell is advanced axially. 
Furthermore, in order to secure adequate spacing between the end surface 
of the stator core on the side toward the coil end turns and the windings 
of the coil end turns themselves, spacing projections on the confining 
form shell are provided. Preferably, these spacing projections extend 
radially into the gap between the end turns of the form core and the end 
surface of the stator core. In order for the form shells to be fabricated 
in accordance with the invention in an especially simple manner, provision 
is made that the guide projections, made as guide fingers, and the guide 
recesses, made as grooves, as well as the compression fingers and spacing 
projections, in each case in one piece, are molded onto the compression 
form shell or the reinforcing form shell or the inner form core 
respectively.

DESCRIPTION OF A PREFERRED EMBODIMENT 
FIG. 1 shows the form shell apparatus, placed on a receiving apparatus 8, 
with stator core 1 and its compression-molded coil end turns 11,12 in 
place. The essential components of the form shell apparatus are first 
described on the basis of the perspective exploded views of FIGS. 2 to 6. 
The form shell apparatus contains a bottom form shell 7, which shapes the 
bottom end turns of the coil 12, and a top compression form shell 2, which 
shapes the top end turns 11 of the coil. The compression form shell 2 
consists essentially of a compression part, which has an arched contour 25 
for the end face of the coil end turns, and the inner and outer 
circumferential surfaces of the compression part have outer guide fingers 
21 and inner guide fingers 22 as well as outer compression fingers 23 and 
inner compression fingers 24, the fingers being integrally molded and 
axially extending over the end surface contour 25 of the coil end turns. 
An inner form core 3 has, on its top end, guide grooves 31 which cooperate 
with the inner guide fingers 22 and the inner compression fingers 24, 
respectively, of the compression form shell 2. On the bottom end, of the 
inner form core there are guide grooves which cooperate with inner guide 
fingers 71 of the bottom form shell 7. 
Between the top part of the form core 3, with the guide grooves 31, and the 
bottom part of the form core, with the guide grooves 32, there is a middle 
part whose outer circumference is fitted to the rotor hole inside the 
stator core 1. 
A confining form shell 4,5 is divided into at least two parts 4 and 5 
respectively, which can be advanced radially and united. The confining 
form shell 4,5 has, on its inner circumferential surfaces, guide grooves 
41 and 51 corresponding to the outer guide fingers 21 and compression 
fingers 23, respectively, of the compression form shell 2. The bottom edge 
of the confining form shell 4,5 has spacing projections 42,52, which are 
radially and integrally molded. When both parts of the confining form 
shell 4,5 are laid against the coil end turns 11 which are to be molded, 
the spacing projections ensure an adequate spacing between the end surface 
of the stator core 1 and the winding wires of the coil end turns 11 that 
extend beyond the stator core end surface. In one half of the confining 
form shell 4,5, an opening 43 is provided for mounting a universal 
terminal on the stator core, by which the ends of the coil winding can, 
preferably, be pre-positioned or contacted, for example with automatic 
temperature controllers preconnected to the universal terminal and with 
connections for external power supply lines. 
FIG. 5 shows a pressure ring 6 that can be slipped over the outside of the 
two-part confining form shell 4,5 to hold it together. Pressure ring 6 
also has an opening 61, corresponding to the opening 43 in the confining 
form shell 4,5, for the universal terminal which is subsequently mounted 
on the stator core 1. Pressure rings that can be axially slipped over the 
outside may be replaced by, for instance, radially advanceable pressure 
jaws. 
Finally, FIG. 6 shows the bottom form shell 7, which also has guide fingers 
71 on its inside, by means of which the winding wires of the coil end 
turns 12 are enclosed in a funnel-like fashion and the contour of the 
bottom form shell surface is applied to the end face of the coil end 
turns. This contour is impressed into the bottom form shell 7 as a form 
surface that is not rotationally symmetric but is otherwise closed. 
For the compression molding of the coil end turns, the stator core 1, with 
the premolded or only loosely wound coil end turns 11,12, as shown in FIG. 
1, is placed in the bottom form shell 7 with the form core 3 inserted. At 
this time, by means of the guide fingers 71, the wires of the bottom coil 
end turns 12 are applied, in their entirety, to the coil end turns shape 
predetermined by the bottom form shell 7 as a closed contour. By this 
embodiment there is no danger of damage or kinking during this process. 
Next, for the molding or shaping of the top coil end turns 11, to whose 
formation the features of this invention essentially pertains, the two 
parts of the outer confining form shell 4,5 are advanced radially toward 
one another around coil end turns 11. The radial spacing projections 42,52 
extend under the bottom surface of the coil end turns 11 and ensure an 
adequate spacing between the end surface of the stator core 1 and the 
portions of the coil end turns 11 that extend beyond the stator core end 
surface. After the previous molding by the outer confining form shell 4,5, 
on the one hand, and the inner form core 3 on the other, the desired 
contour of the coil end turns 11 is completed by inserting the top 
compression form shell 2 axially into the open space between form core 3 
and confining form shells 4,5. 
When the compression form shell 2 is inserted axially, the guide fingers 
21,22 slide into the corresponding guide grooves 31 of the inner form core 
3. It is preferable for the guide fingers 21,22 to be arranged outside the 
contour 25 of the end surface of the coil end turns, and also to extend 
radially into the corresponding guide grooves 31 of the form core 3; as a 
result, on the one hand no space usable for the winding is wasted, and on 
the other hand the guide fingers 21,22 can be designed in an adequately 
safe manner for the procedure and can be provided with chamfered edges at 
their free ends, so as to form a funnel-shaped enclosure for the mating 
parts of the coil end turns. 
When the compression form shell 2 is inserted axially, the winding wires 
are preferably pushed into gaps already present and pressed against the 
boundary of the inner form core or of the outer confining form shell, a 
plastic deformation being achieved. So that pressure can be exerted from 
all sides on all the winding wires, even for example to the end turns of 
multiple-layer coils provided with offset coil groups in the gaps of 
adjacent coil groups one atop another. One embodiment of the invention 
provides for the compression form shell 2 further to have integrally 
molded inner and outer compression fingers 23 and 24 respectively, which 
(as shown, in particular, in FIGS. 7 and 8) also extend partway into the 
region of the end surface contour 25 of the coil end turns 25 of the 
compression form shell 2, in contrast to the guide fingers 21,22. 
As the guide fingers 21,22, the compression fingers 23,24 are also 
preferrably provided with chamfered edges at their free ends, so as to 
form a gradual funnel-shaped enclosure of the adjacent winding wires. In 
order for these essential features to be illustrated more clearly, FIG. 7 
is simplified to show only the guide fingers which appear in the section 
view VII--VII of FIG. 8. The spacing of the outer compression fingers 23 
and of the inner compression fingers 24 in FIG. 8 corresponds to the 
molding of a two-pole, single-phase winding arranged in two winding layers 
each with a principal phase and a secondary phase, and thus to a total of 
four coil groups, the gaps between two adjacent coil groups alternating 
from the top to the bottom winding layer and being spaced 90 degrees apart 
at the circumference. 
The apparatus for compression molding of pre-positioned or only loosely 
wound, coil end turns in accordance with the invention, which apparatus is 
especially simple to fabricate and easy to service, ensures damage-free 
enclosure of all winding wires and a deforming pressure such that all the 
winding wires, after compression molding and baked-lacquer reinforcement, 
which may be provided as a subsequent step. The winding wires are thus 
secured with the desired end face contour of the coil end turns provided 
without any danger of these wires springing back or coming loose from 
their fastening apparatus. 
It will now be understood that there has been disclosed an improved 
apparatus for compression molding and securing the end turns of coil 
windings. As will be evident from the foregoing description, certain 
aspects of the invention are not limited to the particular details of the 
examples illustrated, and it is therefore contemplated that other 
modifications or applications will occur to those skilled in the art. It 
is accordingly intended that the claims shall cover all such modifications 
and applications as do not depart from the true spirit and script of the 
invention.