Method for the manufacture of a layer winding

A method for the manufacture of a layer winding for transformers, measuring transformers, choke coils or the like is to be so improved that the insulation of such a layer winding exhibits practically no free spaces in the insulating tape edge areas. This is assured in that when reaching the outer end face (12) of a layer winding edge (4), the insulating tape (2) is continued to be wound and the band portion (13) of the insulating tape (2) which projects beyond the edge face (12) is continuously cut off. The remaining residual portion of the insulating tape (15) is then continued to be wound with zero pitch for such length of time until the free spaces which otherwise occur at the layer winding edge (4') are filled out.

The present invention relates to a method for the manufacture of a layer 
winding with a plurality of mutually changing layers of insulating tapes 
and conductors and to a layer winding made according to this method. 
A method for the manufacture of such a layer winding is disclosed in the 
DE-AS 21 57 452. In this method, all insulating layers and also the edge 
areas for the lateral determination of the winding conductor are wound 
from a single continuous insulating tape. This offers the advantage that 
the winding arrangement does not have to be stopped for the manufacture of 
the insulating tape layers and of the insulating tape edge areas. However, 
it entails the disadvantage that the insulating tape edge areas have free 
spaces which considerably reduce the mechanical strength of the insulating 
tape edge areas. 
The problem is to be solved with the present invention is to so improve 
this prior art method and the layer winding to be made therewith, that the 
insulation exhibits few possible free spaces or no free spaces. This is 
also true in the insulating tape edge areas. 
The underlying problems are solved, according to the present invention, in 
that upon reaching the outer end face of a layer winding edge, the 
insulating tape is continued to be wound and the tape portion of the 
insulating tape which projects beyond the end face, is continuously cut 
off. The remaining residual tape is then continued to be wound for such 
length of time without feed until the free spaces which otherwise would 
occur at the layer winding edge are filled out. In the layer winding 
according to the present invention, the free spaces at the edge of the 
free ends of the winding layers, which occur during the winding of the 
insulating layers with predetermined pitch, are compensated for by coaxial 
windings of the residual tape remaining within the outer edge zones of the 
edges. 
The free spaces in the edge areas of the winding layers which heretofore 
were troublesome for mechanical and also electrical reasons are 
practically completely eliminated by the present invention. One obtains 
therewith mechanically very stable edge areas and therewith also a high 
mechanical strength of the entire layer winding. Since the edge areas no 
longer have any free spaces, the electrical strength is better than with 
layer windings made according to the prior art method. Furthermore, in 
contrast to the prior art method, edge strips of different width can be 
used and therewith differently wide edge areas of the windings can be 
manufactured. By the use of a harder insulating material for the edge 
strip, an additional reinforcement or strengthening of the layer winding 
can be achieved.

Referring now to the drawing wherein like reference numerals are used 
throughout the various views to designate like parts, reference numeral 1 
designates a coil body, for example, of plastic material, Pertinax, 
Pressspan or the like. In FIG. 1, an insulating tape 2, for example, of 
paper, or of a plastic foil, is applied approximately in the middle third 
of an edge area 3 of the right first edge 4 and is wound with a 
predetermined starting pitch. For example, the pitch is selected in the 
FIG. 1 example so that with an overlap width of 1/3, a triple layer is 
obtained, as the first insulating layer generally designated by reference 
numeral 5. After the winding start of the insulating tape 2, an insulating 
edge strip 6 is inserted, or applied, and/or glued-on, in the edge area 3 
and is wound into an edge generally designated by reference numeral 4. The 
height H 1 of this edge strip 6 is at least approximately equal to the 
combined height of the insulating layer 5 and 7 the height of the winding 
layer 9 of a winding wire 8. While edge strip is being applied, the 
insulating tape 2 is continued to be wound in the same winding direction 
as the winding wire 8. 
The width of the strip edge 6 is smaller than the width of the insulating 
tape 2. The cross section of the winding wire 8 may be round, square or 
rectangular. However, foil conductors may also be used. The winding wire 8 
itself is insulated in a known manner, for example, surrounded with 
lacquer and/or provided with a covering or the like. 
After the formation of the first edge 4 in the indicated height H1, the 
winding wire 8 is placed against the inside 10 of the first edge 4. 
Subsequently, the insulating tape 2 and the winding wire 8 are wound in 
the direction of the arrow 11 with the insulating tape 2 leading the 
winding of the wire. 
When the insulating tape 2 reaches the left coil body edge, respectively, 
edge area 3' (see FIG. 2), the insulating tape 2 is continued to be wound 
with the same or possibly also with a changed, preferably reduced pitch, 
and the tape portion 13 projecting beyond the left end surface 12 of the 
coil body 1 is continuously cut off by a schematically indicated cutting 
mechanism 14 (see tape portion 13 in dash line in FIG. 3), until the width 
of the insulating tape 2 within this edge area 3' amounts to approximately 
one-third to one-fourth of the original tape width. Upon reaching this 
tape width, or shortly prior or shortly afterwards, especially with a 
width of the tape portion 13 of 15% to 30% of the original tape width, an 
edge strip 6' is inserted, or applied and/or glued on and subsequently the 
edge 4' is wound. The residual tape 15 (see FIG. 3) of the insulating tape 
2 is continued to be wound with the constant width of about 33% to about 
25% of the original tape width, especially together with the edge strip 
6'. The rim wedge which is formed at the edge during the customary winding 
with a pitch during the to-and-fro winding operation and which has the 
free spaces, is avoided, and all otherwise occurring free spaces 16 are 
filled out. For example, the last left tape third is no longer wound in 
FIG. 2 in the first insulating layer 5 so that this insulating layer 5 is 
only two-layered thereat. The filling out of the free space 16 which 
thereby occurs thereat, is achieved in that the next layer of the edge 
strip 6' is wound together with the residual tape 15 of constant width. 
The free space 16 which is disposed therebelow is completely filled out 
thereby. The length, respectively, number of the windings with the 
residual tape 15 which is then continued to be wound without pitch, is so 
selected and dimensioned that the surface of the second edge 4' extends 
again at least nearly parallel to the winding axis. The residual tape 15 
is then cut off and then is glued-on or otherwise attached with the end 17 
at its last layer or possibly on the edge strip 6'. For example, the 
gluing-on of the insulating tapes 2 or of the edge strips 6, 6' may take 
place in each case by means of an adhesive tape, adhesive on one side 
especially of a self-gluing insulating adhesive tape. 
The edge 4' is wound together with the edge strip 6' up to the height H 2 
of two winding layers which, in this case, corresponds approximately to 
the height of the first insulating layer 5 and twice the diameter of the 
winding wire 8. Subsequently, the edge strip 6' is cut off and its end 18 
is glued-on (see FIG. 3). 
Still further edge strips of a material with different hardness, density, 
electrical or mechanical strength, or with good suction capability in case 
of layer windings to be subsequently impregnated, or the like, can be 
wound into the edges 4, respectively, 4'. The edge strips 6, 6' may 
eventually become thicker than the thickness of the insulating tape 2. 
After completion of the second edge 4', the first winding layer 7 is then 
wound full with the winding wire 8 until the winding wire 8 abuts at the 
edge 4' on the inside thereof. Thereupon, the insulating tape 2 is 
immediately with predetermined pitch applied in the middle third of the 
edge 4' and both the insulating tape 2 as also the winding wire 8 are now 
continued to be wound with reversed pitch and reversed feed direction in 
the direction of the arrow 19. The insulating tape 2 thereby overtakes the 
winding wire 8 by reason of the larger pitch thereof. The insulating tape 
2 then arrives again first at the right side and the edge structure then 
takes place at the edge 4 with double winding height H 2 as described by 
reference to the edge 4'. A similar edge structure will result thereby, as 
is shown in FIG. 2 between the second and third winding layer. The winding 
operation is continued corresponding to the direction of arrow 20, 21, 
etc. until the calculated coil size of the layer winding is reached. 
If a layer winding is to be manufactured with taps or lead-outs, then the 
insulating layer 5, 5', 5", etc. is made as uniform as possible at a tap 
22, for example, by connection of the winding wire 8, or by the 
application and connection of an electrical connector or the like, 
corresponding to the permissive layer voltage. The pitch of the insulating 
tape 2 is increased within the area of the tap 22, especially on both 
sides thereof to maintain a proper thickness. However, it may also be of 
advantage to improve the insulation thereat. In that case, the pitch of 
the insulating tape 2 is decreased within this area. Advantageously, with 
increasing layer voltage, the pitch of the insulating tape 2 is reduced in 
a known manner stepwise or continuously. Especially also the pitch of the 
insulating tape 2 can be made smaller in middle winding layers than in 
further outwardly located winding layers because by reason of the greater 
heating-up or the like, higher electric loads may occur thereat. 
It may be advantageous for electrical or mechanical reasons to provide the 
cutting edge 23 of the residual tape 15, or of the entire inclined end 
section further inwardly than corresponds to the outer edge 24 of the edge 
strip 6, respectively, 6'. In that case, the free ends 24 of the edge 
strips 6, 6' project over the cutting edges 23 of the residual tape 15 by 
about 1 mm or slightly more as is shown in plan view on the developed 
insulation layer in FIG. 3. 
For better understanding of the method, the direction of rotation of the 
coil body 1 is indicated in FIG. 3 by arrow P. 
In order to fill the free spaces in the edge areas of the winding layers 
particularly effectively with insulating material, it is favorable if the 
insulating tape 2, after reaching the maximum edge projection, is returned 
in the opposite direction and if the insulating tape 2, respectively, the 
remaining residual tape 15 is then continued to be wound without feed for 
such length of time until the edge 4' is formed to the double height H 2 
of a winding layer. 
A particularly good mechanical connection between the insulating tapes 2 
and the edge strips 6, 6' results if at the instant or after the beginning 
of the insulating tape cut, an edge strip 6' is applied or inserted and is 
secured on the insulating tape 2. It is also favorable if the edge strip 
6' is wound at least partially together with the insulating tape 2, 
respectively, with the residual tape 15 up to the double height H 2 of a 
winding layer. 
While I have shown and described only one embodiment in accordance with the 
present invention, it is understood that the same is not limited thereto 
but is susceptible of numerous changes and modifications as known to those 
skilled in the art, and I therefore do not wish to be limited to the 
details shown and described herein but intend to cover all such changes 
and modifications as are encompassed by the scope of the appended claims.