Note: Descriptions are shown in the official language in which they were submitted.
~04S'796
The present invention relates to electric coils and
more particularly to the production of compact coils in
which the space occupied b~ the windings is filled out as
far as possible with the winding material itself, e~gO coils
in which the so-called space factor is highO Especially in
voice coils ~or loud speakers it is important that the coil
is as compact as possible9 since the air gap in which the
coil works should be as narrow as possible, but also in
other coil devices such as transformers it may be generally
desirable to use compact coils also because a good heat con-
ductivity of the coil is desirableO An associated problem
is that the windings should be bonded together by a suit-
able binding material such as a thermoplastics, and for
making a compact coil, o course, it should be ensured that
the desired high space factor is not counteracted by an
unnecessary surplus of binding material between the windingsO
Usually the wire is coated with a thin layer of the binding
material, and the ready wound coil is subjected to a heat
treatment whereby the coatings o~ the juxtapposed wire port-
ions ~loat together so as to thereafter provide a firm bond-
ing of the windings~ An easy manner o providing the nece5-
sary heat is to connect the terminals o the coll with a
current source so as to use the coil l~sel~ as a heater
elementO
~ relatively good space factor is obtainable with the
use o~ a thln bonding material coating and by winding the
coil in such a manner that each wire portion is rested against
two underlying wire portions and not on the top of one under-
lying wire portion~ A still better space factor would be
obtainable with the use of wire of rectangular or hexagonal
cross section, but such a wire is more expensive than a
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round wire, and in automatic coil winding problems will occur
due to twist tendencies of the wire, whereby the space factor
would not at all be goodO
The invention relates to a method of producing compact
electric coils wound of insulated wire of round cross section~
al shape~ and i-t is the purpose of the invention to provide
a method whereby an improved space factsr is obtainableO
According to the invention the coil, upon being wound,
is maintained or mounted on a mandrel filling out the coil,
whereafter the coil is subjected to a treatment involving
radial compression o the winding layers until the wire in
each winding becomes deformed by its surface portions at
each place being pressed substantially flat against the sur-
faces of the ad~oining wire portions o~ the ad~acent windings.
Hereby the windings will be deformed so as to engage each
other .in a v~ry compact mannerO The compression of the wlnd-
ing layers may be efected by a pùrely mechanical pressure,
preferably applied with the coil in a heated condition, but
according to the invention it is highly advantageous to e-
fect the compression by means of a thermal treatment as
described below.
The lnvention also comprlses an apparatus or carry-
:lng ou~ the method according to the invention, as defined in
th~ app~nd~d claim~0
In the following the invention is described in more
detail with reference to the accompanying drawing, in which
~ ig~ l ls a sectional view of a voice coil wound on a
mandrel,
Fig~ 2 is a corresponding view of the coil at a later
stage o the production thereof,
FigO 3 is a detailed sectional view of the winding
layers o another coil upon deormation thereof,
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FigO 4 is a schematic view of a combined coil winding
and forming apparatus~
Fig. 5 is a plane view partly in section illustrating
alternative mechanical defor~ation of the wires,
FigO 6 is a graphic illustration of the thermal treat-
ment o the mandrel and the coil, and
Fig~ 7 is a similar illustration of the diameter variat-
ions of the mandrel and the coil, respectively, during the
thermal treatment thereofO
For producing a compact coil according to the invention
the coil i5 wound from ordinary round coil wire 2 coated by
a }ayer 4 of a suitable insulating and binding material such
as polyamid or polyamid-phenol~ The coil is wound on a tubu-
lar body 6 of a thin sheet or ~oil material which is placed
on a mandrel 8, and as well known the winding may be ef~ected
with the mandrel being stationary or rotary. The coil is
wound w~th the wlre somewhat prestretched and so as to have
each wire portion in one wire layer rested against two wire
portions of the adjoining layer.
As mentioned, in order to heat the coil ~or makin~ the
binding material 4 run together it is cu~tomary to slmply
connect the coil terminals to an electric current source
whereb~ h~at :L~ rapidly gen~rated ln the coil windings~ By
this heating the windings will expand somewhat, but during
not
the followi.ng cooling thereo they will~retract themselves
against the ~andrel because the binding or bonding material
~olidi:fies to boncl the ~indi~gs before the coil. gets cold~.
According to the invention, however, a di~ferent heat-
ing method is used, vizo consisting in supplying heat locally
to the mandrel, from which the heat will be trans~erred to
the coil windingsO The heat may be supplied to the mandrel
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in any of a variety of manners~ and it is shown by way.of
example only that the mandrel may be provided with internal
channels 10 for r~ceiving a heating medium from an external
sourceO
When the mandrel is heated locally the first result will
be a radial expansion of the mandrel itself, whereby the coil
wire is generally stretchedO Thereafter the heat is trans- .
ferred to the windings so as to gradually soften the binding
material 4 and cause the windings to expand thermally, thus
also causing the stretch of the wire to be reducedO When the
windings have been heated to the necessary degree for soften-
ing the binding material the supply of heat to the mandrel is
stopped, whereafter the mandrel will still far some time re-
main hot and expandedO
The next and perhaps most lmportant step oE the method
according to the invention .is to cool the coil winding from
the outside thereo while the mandrel is still expanded, pre-
ferably by a positive coo~ing7 eOg~ with a blast of cold air,
gas or atomized liquid or by means of cooling claws brought
into contact with the exterior coil sur~aceO This cooling
causes th~ coil winding to crimp, and since the mandrel ls
still expan~ed the crlmping o the wire results in the build-
ing up o~ a consiclerable stretch 1~ the wir~ ancl correspond-
ingly a cons:Lderable ~nwardly directed pressing force of an
outer winding layer against an inner winding layer and fur-
ther against the surface o~ the mandrel through the sheet 60
The forces pro~uced hereby are strong enough to cause the
single wire portions to be pressure deformed by their engage-
ment with the adjoining portions, and as illustrated in figO
2 the result is that the juxtapposed wire portions will get
deformed into a honey comb cross sectional shape so as to be
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rested against each other in a practically plane surface-to-
surface-relationship rather than a tangential engagement
between round wires. This involves that an optimal space fac-
tor is obtained and that also the bonding between the juxt-
apposed wlre surface portions becomes optimalO It should be
mentioned that the wire is able to withstand a considerable
stretching force due to the overall frictional engagement be-
tween the juxtapposed wire portionsO
When thereafter also the mandrel is cooled the associated
contraction thereof will make the coLl structure easily re-
leasable from the mandrel, since at that time the coil has
already been stabilized in its deformed shape~ If desired,
for further reducing the maximum thickness of the coil wind-
ing the outer surface of the coil may be ground for removing
any surplus oE bonding materialO
The honey comb structure will be still more expressed
in a coil having three or more winding layers, as illustrated
in fig. 3 whlch shows a raction of a four layer coil made
`according to the inventionO Besides, this coil has been wound
direct on the mandrel without the use o a tubular body 6.
: The mandrel may be cooled naturally or by means of a
cooling medium applied to the exterior or interior of the
mandrel, and upon the removal of the coil therefrom the man-
drel ma~ rec~i~e a new coil member to be treated, with the
mandrel us~d ~ith~r a~ a winding mandrel or as a mandrQ1
for receiving an already wound coil memberO
Generall~ the important eature o the invention is the
crimping of the coil windings a~ainst a mandrel or core mem-
ber which in the heated condition of the coil fills out the
space inside the coil and maintains its diameter while the
crimping o the windings is going on. Thus, it is not essen-
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S796
tial, though highly advantageous that the mandrel should besubjected to a positive heating9 since it could alternatively
be mechanically expanded and contractedO The deformation
caused by the cooling crimping of the coil is not primarily
dependent of the coil previously having been heated to any
particular temperature9 hut by the said preheating up to e~gO
300C it is obtained that the bonding material ~ flows to-
gether and th t the subsequent crimping deformation of the
wire is facilitatedO Due to the high crimping force, however,
the wire would get deformed even without being particularly
hotO
Principally the coil may be removed rom the mandrel
without the latter -Eirst being contracted, since the crimped
coil could be reheated for expansion without the deormed
wire cross section being redeEormed into the orlginal round
shap~J Moreover~ the wire deEormation principally could be
efEected mechanically by forcing clamp jaws against the coil
or by expanding the mandrel with the coil supported inside a
surrounding cylindric element, preferably while the coil is
heated, or by treating the coil with a pressing roller moved
along the int~rior or exterior side o:F the coil~
As mentlorlc~cl the invent:Lon also comprises an apparatus
~or eE~ect~rlcJ ~h~ coll cle~ormation accord:lng to th~ prlnciples
described hereinbeforeO The apparatus may be combined with a
winding mach.ine so as to automatically receive on its mandrel
or mandr~ls the coil members wound by the windlng machine, or
the apparatus may be integral with the winding machine, the
expansion mandrels thereoE being used additionally as winding
mandr~ls~ whether being of the stationary or the rotary typeO
The mandrels may be arranged in a row on a movable support
such as a turn table7 which is designated 12 in fig~ l, and
104S796
which moves the mandrels successively past a receiving stat-
ion in which they receive the coil members eith~r as wound
onto the mandrels or supplied thereto from an independent
winding machine, and further to a heating station in which -~
the mandrels are heated eOg. by means of hot oil or air sup-
plied to the interior channel system 10 through holes or
slots 14 in a glider body 16 engaging the support 12. ~or
the invention, however, it is entirely unimportant how the
heating is effected, because also the coil is allowed to be
heated, i.e. the heating could well be effected from the
outside of the mandrel, e.g. by means of a high frequency
heating technique.
Thereafter the support 12 is moved further to or past
a coil cooling station in which suitable means are provided
for cooling the coils from the outside thereof, e.g. simply
by a blast of cold air or gas or atomized water whereby the
said defoxmation of the coil wire will take place. The next
station is a reject station in which the coils are removed
from the mandrels upon these in the meantime having been
~ cooled either by natural cooling or by means of a cooling
medium supplied to the internal channel system L or in any
other manner. From this latter station the mandrels are moved
back to the initial receiving station. Alternatively the appa-
ratus may be provided with means for a mechanically controlled
expansion and contraction of the mandrels or with the above
mentioned means for mechanically pressing the coil members.
It should be mentioned that coils wound of aluminium
or soft coppar wire are particularly well suited to be treated
in the described manner and that the invention eliminates or
reduces the normal problem of the coil thickness being locally
increased at the crossing areas where the wire ~rom one wind-
~045796
ing crosses the top of an underlying wire for passing to thenext winding9 this problem being due to the fact that the
winding layers are wound with alternating pitch; at the said
crossing areas the wire will be deformed into a flat shape
by the crimping of the coil whereby the said local increase
of the thickness will disappearn In figO 3 such.a wire cros-
sing is illustrated with the wire W as the central wire in
the crossing area shownO
The invention is usable also for the production of coils
of non-circular shape, but normally it should be preferred to
first wind and treat a round coil which is pressed into its
desired shape a~ter having been crimped and removed from the
mandrelO
The invention also comprises a coil produced by the de-
scribed method so as to have an improved space factorO For
some coils the space factor itself is not important, but it
is very important that an associated advantage is a very firm
bonding of the coil windings to each other and to the bobbin~
if any, whereby a very rigid coil is obtained, and that the
heat conductivety of the coil will be very goodO
By way of example an apparatus according to the invention
is schematically illustrated in figO 40 It comprises a turn
table 20 having a number of radially protruding mandrels 22
and gear means (not shown~ for turning the table stepwise,
whereby the mandrels are successively brought to rest in the
various stations of the apparatusO A first station is a wind-
ing station in which a well known winding device 24 operates
to wind a coil 25 on the mandrel, the mandrel thereafter being
moved stepwise through three positions constituting a heating
stationO In each of these positions is placed a heater unit
26,28 and 30, respectively7 each having a heated rod member
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~L~9L5'7~
32 which is reciprocally arran~ed so as to be shiftable be-
tween an active position in which it projects into an outer
cylindric cavity 34 of the mandrel 22 so as to heat the man~
drel from the inside thereof, and a retracted, inoperative
position in which it allows the turn table to be rotatedO
The elements 32 miyht as well represent the exhaust spouts
o~ air heater units.
The coil winding device 24 leaves the wire uncut between
the coils wound on the consecutive mandrels, so the wire, as
shown at 369 will extend stretched between the consecutive
coils in the said heating station9 whereby there are no pro-
blems as to anchoring of loose wire ends of the coilsD B~
the heating the mandrels 22 expand and trans~er heat to the
coils 25 whereb~ the coating on the coil wire is soEtenedO
In the next station, designated 38, the coil is sub~ected to
a blast of cold alr produced b~ a blower ~0 and directed
towards the outside o~ the coil by sultably arranged outlet
openings 42 o~ an air duct system ~4~ ~ereby the coil 25 or
at least the outer surface thereof is almost immediately
cooled down to below the softening or melting point of the
bonding coating on the wire and the coil starts crimping
while the mandr~l is still hot~ Also in the next position,
designated 4G the coil .i.5 subjected to the cooling air where-
b~ its cr:Lmpin~ :Ls compl~ted acJalnst the mandrel which is
still e~panfled though its temperature has decreased somewhat
from its maximumO Between the positions 38 and 46 is provided
a cutting clevice ~8 whi.ch is actuable to cut the exposed
wlre portion 36 which is now bonded t~ the respective coils
at the places where it leaves the coilO
Also in the ~ollowing position, designated 50, the cool-
ing blast is directed against the mandrel and the coil, and
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1045796
rejector means ~not shown, but well known in the art) are pro-
vided for removing the coil from the mandrel~ In the meantime
the mandrel has cooled down sufficiently to contract itself
to such a degree that the coil is readily releasable there-
fromO
In the following position, designated 52, the mandrel is
further cooled, if necessary, before it is moved~further to
the winding station. If applicable the tubular core 6 or a
similar bobbin may be placed on the mandrel in the position
; 10 52 if not in the winding station itselfO
As mentioned? the winding station may be substituted by
a station in which ready wound coil members are mounted on
the mandrels 22. Further, as mentioned, the means for effect-
ing the pressing of the coils may be substituted partly or
entirely by mechanical pressing means, an example of such an
arrangement being shown in fig. 5. An expansible mandrel 60
is made of two or more segments 62 having cylindric exterior
.
~ ~ ~ surface portions and conical interior surface portions cooper-
:
~ ating with a conical end portion 64 of a rod 66 which is oper-
: :
20~ ~ able, by control means not shown, to be forced into the inte-
rior;space of the split mandrel 60 so as to cause the segments
thereof to expand. The mandrel is rested on a base plate 68
and is Lntroduceable into a cylindric member 70 together with
., .
a coil member 72 mounted on the mandrelO When the mandrel is
expanded by means of the rod 66 the coil will be pressed be-
tween the mandrel and the inner side of the cylindric member
70, and thereafter, upon contraction of the mandrel, the coil
is rejectable from the cylindric member by means of the base
plate 68 being pushed through the cylindric member.
The cylindric member 70 may be segmented and have each
of its segments operatively connected with means such as hy-
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,.. ,. , . , ,. , , . , :
~4~i796
draulic cylinders 74 for moving the se~ments radially whereby
a positive pressin~ ~orce may be applied additionally or alter--
nativel~ against the exterior side of the coilO
The mandrel 60 may be representative of the mechanically
expansible mandrel which is mentioned hereinbefore in connect-
ion with the described cooling crimping of the coil member)
and both the mandrel 60 and the se~mented cylindric ~ember 70
may be representative of the above mentioned mechanical cool-
ing claw means for effecting the crimping cooling o~ the heated
coil memberO
Though the desired deformation of the coil wire is thus
effectable by mechanical means the described thermally effected
deformation will normally be highly preferableO The interre-
lated ~igsO 6 and 7 show the variation of the mandrel dlameter
~igO 6, solid li.ne) an~ the coil diameter ~figO 6, dotted
line) a9 a ~unction o~ the tlme during which th~ described
heating and cooling i9 going on~ until the coil is removed
from the mandrel at the moment tR~ and figO 7 correspondingly
shows the temperature variation of the mandrel (solid line)
and the coil ~dotted line)O In figO 7 the temperature TM re-
presents the melting point of the bonding material on -the
coil w:i.reO rl!his material starts to solldify when the coil tem-
peratur~ at the moment tl, drops below ~M~ ~nd a short t.ime
therca:~k~r~ at tlte ~noment t~, the mate.rial has s~t su~ici~nt~
ly to therea~ter maintain the coil diameter substantially
constant wh:ile thc mandrel is still shrinking by the ~urther
coollncJ thereo~a In view o~ the ~oregoing detailed descr~ption
of the heating/cooling cycle~ however, it is not deemed neces
sary to explain the curves of ~igsO 6 and 7 in more detailO
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