Note: Descriptions are shown in the official language in which they were submitted.
~1~5578
METALLIZED FII.M CAPACITORS
Background of the Invention
This application is a division of Canadian Seria1
No. 305,939, filed June 21, 1978.
Electrical capacitors made of thin film dielectric material
which ~s metallized on both sides are used in large quantities in
electrical devices because of their reliability, their desirable elect-
rical characteristics and their relatively low cost. ~nited States
Patent No. 2, 470, 826 issued on May 24, 1949 to W. McMahon illus-
trates a capacitor in which a double sided metallized dielectric layer
is folded an odd number of times in a longitudinal direction. ~he
folded dielectric material may then be wound along its lon~iludinal
dimension and end terminations may then be applied to it by spraying
of metal against the edges of the wound capacitor segment. rrhe type
of capacitor described by McMahon patent i~ extremely desirable be-
cause substantially all of the dielectric layer of the capacitor is in the
electric field and the capacitor may be made without the insertion of
an additional dielectric layer in the main body of the capacitor, although
a short initial unmetallized dielectric strip and a protective terminating
dielectric strip may be employed with the capacitor, if defiired.
~he type of capacitor construction that s envisioned by McMahon
patent has a number of decided manufacturing and electrical advantages.
For example, the problem of masking the dielectric layer during elect-
rode evaporation when the electrode areas are applied to the film is su~-
stantially redused. In addition, no slitting is required as it is during the
.~" .
11(~5578
manufacture of conventionat wound ~ilm capacitors. Furthermore.
the capacitance per unit dielectric area is maximized bccause of the
substantially full use of the dielectric layer in the electric field. Shorter
winding lengths per unit capacitance are thereby required, reducing the
winding labor. ~he dielectric lengths can also be calibrated and pre-cut
to produce a capacitor of more accurate values. Another advantage of
thi~ bpe of capacitor i8 that there are no air layers between the metallized
electrodes and the pleated film surfaces and this substantially increases
the voltage, for example, one hundred volts or more, at which corona
discharge starts, making this capacitor commercially attractive for new
applications such as fluorescent lighting circuits. Previously, fifty gauge
film thickness or more was required of wound film capacitors to withstand
the corona. With the capacitor of the present invention, thirty-two gauge
or less dielectric film thickness may be utilized, making ~und film capa-
citors economically feasible for such applications.
~ he McMahon patent guggested that leads could be attached to his
capacitor by the well-known Schoop process. ~he application of high velocity
metallic spray coatings tothe edges of the capacitor described by Mc~qahon
is not commercially practical, however, because thc spray wi~ penetr~te
through the dielectric area at a pleat and thereby short one electrod~ to the
other. If the temperature and pressure of the spray are lowered, penet-
ration of the dielectric layers may be reduced but the adhesion of the metallic
spray will generally be very poor. Ihe multiple leads suggested in the
McMahon patent also are not satisfactory since they tend to tear the dielectric
,
ll(~S578
material and to make the capacitor bulky ancl inductivc.
In order to solve the above mentioned spray shorting problem at a
pleated edge, it has been suggested in Australian Patent No. 159, 958,
patented on November 24, 1954 to provide unmetallized dielectric strips
behind all of the pleats of a pleated metallized capacitor. While this solution
may provide a technically feasible method of attaching leads to apleated
metallized dielectric layer capacitor, the number of unmetallized strips
that are required on the dielectric layer greatly complicates the manu-
facturing proce~ for both the dielectric layer itself and the pleated
capacitor product. For example, in a capacitor having five pleats,
there must be, in addition to the two unmetallized n~argin areas, five
unmetallized strips that run along the entire length of the diclectric malerial,with three of these strips being on one side of the dielectric layer and two
of these strips being on the opposite side of the dielectric layer, It iB
apparent that the masking problems and the cost of manufacturing such a
specialized item make the solution of the Australian patent commercially
unattractive. lhis is especially true since the type of metallized dielectric
layer that is u$ed in the capacitor of the present invention, (in which only
the margin areas and one unmetallized central strp is required), is readily
commercially available. ~urthermore, the employment of an unmetallized
strip behind the single pleated capacitor of the McMahon patent, however, -
still would not proYide an end termination along the opposite edge of the
wound capacitor segment that would allow a metallized spray to be applied
to this edge because the ends of the dielectric layer of the McMahon patent
at this edge extended beyond both of the melallized electrodes and contact
between the metallic spray and the inner e]ectrode area would thereby be
prevented .
il~S578
~}~e leads of the capacitor of the Vnited States Patent No. 3, 854, 075,
i ssued l)eceml~cl~ 10, 1974 to John Philip Uhl, were used as mandrels
to wind the pleated capacitor segment about the center, in a manner
similar to that suggested in United States Patent No. 2, 887, 64g issued
May 19, 1959 to Daniel B. Peck. In the Uhl patent, conductive foil tabs
were inserted between the leads and the metallized electrode areas to
make positive contact with the electrode and to protect the electrode
from damage by the leads during winding. However, it has been
determined that this construction leads to a higher failure rate than
desirable due to opening of the electrode area around the periphery of the
metal foil, for reasons which are not completely understood.
~he configuration of the capacitor of the present invention provides
a product which has all of the advantages of single pleated, or single
pleated and wound, capacitors and also has the added advantage that it
may be manufactured with commercially available metallized dielectric
material. A further advantage of the present invention is that the same
basic starting material may be used to manufacture capacitors having a
number of different pleating combinations, which, of course, is not true
for the capacitor of the Australian patent, in which each pleat combin-
ation requires a specially manufactured die~ectric layer. In addition
to the use of the present invention to manufacture wound film capacitors,
it is also possible to utilize the invention to produce ceramic capacitors
in which the capacitor dielectric material is folded while the ceramic
material is still in a "green" state, in a manner similar to that dis-
closed in United States Patent No. 3, 223, 494 issued December 14;
1965 to J. W. Crownover.
il~557~
Thus broadly, the invention contemplates an electrical capa-
citor segment which comprises a dielectric layer having a center
line, a first metallized electrode layer applied to one side of
the dielectric layer so that an unmetallized margin extends along
each edge of a pair of parallel edges of the dielectric layer, and
a second metallized electrode layer applied to the other side of
the dielectric layer so that an unmetallized area is located ad-
jacent the second metallized electrode layer. The dielectric layer
is pleated once along the unmetallized areas off of the center line
10 so that one edge of the margin containing edges extends beyond the
other of the edges along the same end of the capacitor segment and
metallized spray material is in contact with the second electrode
layer.
In a further embodiment the invention contemplates an electri-
cal capacitor segment which comprises at least one group of pleated
layers comprising a dielectric layer, a first metallized electrode
layer applied to one side of the dielectric layer so that an un-
metallized margin extends along each edge of a pair of parallel
edges of the dielectric layer, a pair of metallized electrode
20 layers on the other side of the dielectric layer, and at least
one unmetallized strip that runs between the metallized layers on
the other side of the dielectric layer. The dielectric layer is
pleated M number of times where M = a ~ (N)b where a is an odd
number 3 or greater, and b is an even number 2 or greater, and
where N may be zero or any positive integer so that at least one
pleat of the pleated dielectric strip extends along one end of
the pleated dielectric layer beyond at least one other pleat that
extends along the same end as the extending pleat, or pleats, with
all of the extending pleats having unmetallized strips behind them
30 along their length. The edges of the metallized dielectric strip
which contain the margins extend along the opposite end of the
pleated dielectric layer beyond the other ple~ts that extend along
the same end as the margin containing edges, wherein the extending
pleat or pleats along the one end of the dielectric layer and the
margin containing edges along the other end of the dielectric layer
are sufficient in length to allow metallized spray material to be
sprayed against both of the ends without penetration of the spray
far enough to contact any of the pleats except the extending
pleat or pleats.
'~7'
~l~SS78
In another broad aspect, the invention comprehends
an electrical capacitor segment which comprises at least
one group of pleated layers including a dielectric layer,
a first metallized electrode layer applied to one side of
the dielectric layer so that an unmetallized margin extends
along one edgs of a pair of parallel edges of the di-
electric layer, and a second metallized electrode layer
applied to the other side of the dielectric layer so that
an unmetallized margin area extends along the opposite
parallel edge of the dielectric layer. The dielectric
layer is pleated an even number of times so that the margin
areas of the pleated dielectric strip extend along their
respective ends of the pleated dielectric layer beyond the
other pleats that extend along the same end as the respect`ive
margin areas, with the margin areas facing outwardly from
adjacent pleats and metallized spray material sprayed against
regions of the metallized electrode layers in the vicinity
of the margin areas which face inwardly toward adjacent
, pleats on both of the ends, but without penetration of
the spray far enough to contact any of the pleats.
ll~SS78
Description of the Drawings
:
~he present invention is illustrated by reference to the drawings
in which:
Fig. 1 is a perspective view of a portion of a metallized dielectric
layer which may be used in the construction of a capacitor in accordance
with the present invention;
F'ig. 2 is a perspective view of a partially pleated metallized di-
s~.' electr~c layer in accordance with Fig. 1 having five pleat lines;
. ~,, - ~
Fig. 3 i8 a perspective view of a fully pleated dielectric layer in
accordance with Fig. 1;
Fig. 4 is a perspective view of the fully pleated dielectric layer
of Fig. 3 which, in addition, shows a winding mandrel and an unmètallized
dielectric insert;
Fig. 5 is a diagrammatic showing of the winding of a
... .
capacitor segment in accordance with the construction of Fig. 4;
Fig. 6 is an end view of a capacitor segmcllt, bcfore le~d
attachment, that is wourd in accordance with the showing of Figs.
4 and 5;
Fig. 7 is an end view of the wound capacitor segment of Fig. 6
after it has been pressed into an oval shape;
Fig. 8 is a side view of ~ comptetcd c;~ citor follo~ hc
attachment of axial leads;
-- 7 --
g
.
ll~S578
Fig. 9 is a side view of a completed capacitor following attach-
ment of radial leads;
Fig. 10 is a perspective view of an alternate version of a capacitor
constructed in accordance with the present invenLion;
Fig. 11 is a perspective view of an additionat alternate embodi-
ment:
Fig. 12 is a perspective view of a further alternate embodiment;
Fig. 13 is a perspective view of a portion of a metalliz~d dielectric
layer which may be used in the construction of a capacitor in accordance
. 10 with the present invention;
~?ig. 14 is a perspective view of a ~ingle pleated dielectric layer
in accordance with ~ig. 13;
Fig. 15 is a perspective view of the fully pleated dielectric layer
of Fig. 14 which, in addition, shows a winding mandrel and an unn~etallized
dielectric insert;
Fig. 16 is a diagrammatic showing of the winding of a capacitor
segment in accordance with the construction o Fig. 15;
Fig. 17 is a perspective view of a portion of a metallized dielectric
layer which may be used in the construction of a capacitor in accor-
dance with the present invention;
Fig. 18 is a perspective view of a plcated metalli%eLl diclc~ctric
layer in accordance with Fig. 17 having two pleat lines;
,~
ll(~5S78
~ ig. 19 is a diagrammatic showing of the winding of a capacitor
segment in accordance with the construction of F`ig. 18; and
Fig. 20 is a perspective view of an alternate version of a
capacitor constructed in accordance with the present inventioll.
~echnical Description of the Invention
A portion of a commercially available metallized dielectric strip
which may be unwound from a reel, that is suitable for the- mal;ing of a
capacitor in accordance with the present invention is shown in Fig 1.
The metallized dielectric strip is formcd with a dielcctric l~ycr 12 oî
a thin film dielectric material, such as polyester, polypropylene, poly-
styrene, polycarbonate or other ~suitable material. ~ thin metallized
electrode layer 14 i6 applied to the upper surface of the dielectric layer
12 in such a fashion that unmetallized margin areas 16, 18 e~;tend along
the longitudinal edges of the strip 10. 'ru~O thin mctallizcd elcctrode
areas 20, 22 are applied to the lower surface of the dielectr;c layer
12 so that the metallized layer 20 extends to the left hand margin of
the layer as shown in Fig, 1, while the metallized layer 22 extends to
the right hand margin of the layer. A central unmetallized stri~ 24
lies between the metallized electrode areas 20, Z2.
In the embodimellt shown in Fig. 1, the longituàill~l dinlellsion of
the metallized strip 10 is shown along the arrows ~6 while the narro~
11(~5578
transverse dimension is shown along the arrows 28. ~he capacitor is
pleated along the imaginary line 30 which extends through the length of
the unmetallized central strip 24. 'rhis version of the prescllt invention,
however, is not limited to one in which folding is along longitudinal lines
S since a capacitor could be mad~ in accordance with the present invention
by pleating along transverse lines if the appropriate corresponding
metallized and unmetallized areas were provided.
A partially pleated capacitor is shown in Fig, 2 wherein one
pleat occurs along the longitudinal center line 30 and othcr pleats occur
along the longitudinal pleat lines 32, 34, 36 and 38. It is to be noted
that lines 32, 34, 36 and 3~ are spaced so that the center pleat 40 ex-
tends beyond the other pleats 42, 44 that run along the right hand long-
itudinal edge of the metallized strip 10 of Fig. 1 so that the inside of
the pleat 40 in the area 4G is unmetallized. ~he e~;tension of tlle
center pleat 40 beyond the pleats 42, 44 is preferably at lcast 0. 020
inches. In addition, it is noted that the pleats are positioned so that
the lOngitudinal ends 48, 50 of the metallized strip 10 are aligned with
each other but so that they extend beyond the pleats 52, 54 that run along
the left hand longitudinal edge of the metallized strip. Again, the ex-
tension of the ends 48, 50 beyond the ple~ts 52, 54 is pleferably at lcasL
0. 020 inches. ~he unmel;allized margin 16, therefore, faccs upwardly
while the unmetallized margin 1~ faces downwar-31y whcn thc capacitor
-- 10 --
ll~SS'7~
segment has been fully pleated as shown in ~ig. 3.
After the capacitor has been proccssed to form the capacitor seg-
ment shown in Fig. 3, a number of different additional processing steps
may be undertaken. ~or example, the pleated capacitor segment of
~ig. 3 could be used to form a capacitor merely by spraying the right
and left hand longitudinal edges of the segment with a metallized spray,
such as babbitt or other suitable metal, in accordance with convcntional
practice, and then electrical leads could be secured to them, ior e~;ample,
by soldering. Alternately, the capacitor segment of ~ig. 3 could be cut
along a transverse line, such as the line 43, and a number of such seg-
ments could be stacked upon each other, with the terminal end 50 of one
capacitor segment being adjacent to and aligned with the terminal cnd 48'
of the capacitor segment tl~at is positioned immecliatel~ belo~ it, as ShOWIl
diagrammatically by the dotted line representative of ~ig. 3, and tllen
their ends could be sprayed with a metallized spray and leads could then
be secured to the stacked array OI such segments. In conjuncticn with the
p resently pxeferred embodiment of the present invention, however, I;`ig. 3
represents two layers of a capacitor segment formed by ~vindinK of the di-
electric strip along the longiLudinal dimellsion of the stril~ 10, ~s sl~o~vn inFigs. 9 and 5, to form a wound capacitor. Another version of this capacitor
could be acllieved, however, by pleating the capacitor segment of Fig. 3 a
number of times transversely along transverse fold lines such as the linc
43, or alternately pleating several times, and then completing the segment
by winding the remainder of the length of the dielectric strip.
S78
~he winding of the ca~)~citor scgmellt Or I;`ig. 3 into a ~ound
capacitor may be achieved with various winding techniques, includin~ the
use of a removable split mandrel such as the mandrel 5G of Figs. 4 and 5.
An unmetallized dielectric strip 58 is desirably initially wound around the
mandrel to protect the metallized electrode areas of the metallized strip
10. Near the completion of winding, an additional unmetallized dielectric
strip 60 is desirably wound into the structure to form all outer protective
coating. ~he dielectric strip 60 may also be heat-sealed to itself to form
the pleated capacitor segment 61 which is shown in Fig. 6. ~he removal
of the mandrel 56 from the capacitor segment 61 leaves an opening 62 in
the unit. ~he opening 62 may be closed by applying pressure, or pressure
and heat, in accordance with the type of dielectric lsccl and convention.~l
manufacturing techniques, to the cap~citor segn~cnt ~1 so that it assul~-cs
an oval shape as shown in Fig. 7.
Once the capacitor segment of the embodiment of Figs. 4
through 7 has been wound, a metallized spray may then be directed
against the longitudinal edges of the unit in accordance witll corlventional
processing techniques to intercollncct thc elcc~rode 1a3 cr s alo1l~ tllese
edges and to provide for the connection of electrical leads to thc unit.
~Ihe metalllzed spray wilt penetrate into the open area betwecll the ends
48 and 50 on the left hand longitudinal edge of the capacitor segment,
as shown diagrammatically in Fig. 3 to a depth such as that indicated
-r
i~
ll(~S578
by the plane G5. 'rhe plane 65 indicates the maximum depth that any
high velocity spray particles will pcnetratc and it l-la~ t]l~lS l~c~ locatcd
any place between the ends 48 and 50 of the metallized strip 10 and the
edges of the pleats 52, 54. Accordingly, the metallized spray material
;~ will extend into the left hand opening of the capacitor between the ends
48, 50 far enough to make contact to the t~vo facing metallized electrode
areas 20, 22, but not so far that it will penetrate through the dielectric
material at the pleats 52, 54. ~he configuratioll of tlle present ir~vention
thus provides for reliable lead termination at the left hand longitudinal
edge of the capacitor segment of Fig. 3 witl~out the necessity of providing
unmetallized longitudinal strips along the inside of the pleats 52, 54,
thereby saving considerable processing expenses in the manufacture of
completed capacitors of this type.
'lermination to the right hand longitudinal edge of the capacitor
1~ segment of Fig. 3 is similarly provided by a metallized spray uh ich ex-
tends over the protruding center pleat 40 to a depth~ such as that
indicated by the plane 67, which is sufficient to allow the metallized
spray to make good contact to the electrode area 14, but which will
prevent the penetration of the spray metallic par~iclcs through the diclect-
ric at the pleats 42, 44. ~he locationof the plane ~7 may l~e anywhere
between the edges of the pleats 42, 44 and the cdge of the yleat 40 as
long as there is sufficient depth of spray to provide adcquate contact -
termination to the electrode area 14. Again, a considerable cost savin~s
-- 13 --
ll~SS78
is achieved by thc prescnt invention since thc ~leats 42, 44, lilce lhc
pleats 52, 54, did not have to be provided with tl~eir own unmetallized
strips. It will be noted in the present invention that only one unmetallized
strip 24 is required in the center of the metallized strip 10, and, thus,
the same general pattern may be used for various pleat configurations
and a ~eparate individually configurat~d mctallizcd st3i1) is nol rcquircd
for each pleat pattern.
.
Once the metallic spray has been applied to the edgés of the
capacitor segment of Fig. 7, either radial or axial leads may be applied
to it. For example, axial leads 70, 72 witll conventiollal spiral "pig-tail"
ends (not shown) may be soldered, arc-weldecl or conllected b~ ot11er lnealls
to the sprayed edge termination layers ~G, 68 al the ends of the wound
film capacitor segment ~1, as shown in Fig. 8. Altcrnate]y, radial leads
74, 76 may be soldered, arc-welded or connected by other methods to
1~ the sprayed metallized layers 66, 68 if a radial lead~d capacitor is desired, as shown in Fig. 9.
It will be noted from the foregoing dcscriytion that the number
of pleats that may be used to form a capacitor in accor~lance with the
previously described embodiment of the present invention is M where
M = 5 + (N)4 and N may be 0 or any positive integer. ~he number of
pleats M in a capacitor made in accordance with this cmbodiment,
therefore, will always be an odd numl)cr.
Other alternate versions of the present invention are shown in
llC~S578
,.. , ~
Figs. 10-12. In Fig. 10 the pleated capacitor segment is formed so that
the end pleats 42, 44 have unmetallized strips 46' behind tbese pleats
while the center pleat 40 does not. ~he two end pleats 42, 44 extend be-
yond the recessed center pleat 40. ~his version is less desiral~le, how-
S ever, than the version of :Fig. 3 because it requircs an ;Idclitio~ l stri,~.
Another alternate embodiment is shown in Fig. 11 wherein only
one of the end pleats 42 extends beyond the center pleat 40 and the other
of the end pleats 44. In this version only one unmetallized strip 46" is
required behind the extending end pleat 42, but the charging path is longer
-i 10 for this configuration than that of Fig. 3.
~,.' .
Still another alternate embodiment is ~hown in Fig. 12 which differs
from the version shown in }~ig. 3 in that intermediate dielectric layers
69, 69' are inserted between alternating groups 71, 73 of pleated layers
with the center pleat extended, as in Fig. 3, but with the alternating
groups 71, 73 Sacing in opposite directions. If the capacitor of
Fig. 12 iæ to be a wound embodiment, the alternating groups 71, 73
of pleated layers which face in opposite directions may be supplied
from a different pleated segment supply. Also, it is apparent that the
groups of pleated layers shown in Figs. 10 and 11 could be employed
u
to form a capacitor in accordance with the teaching of Fig. 12 by facing
alternating groups of these layers in opposite dircctions ancl b~ scpar-
ating these alternating groups with dielectric material.
.
-- 15 --
llC}SS78
A portion of another commercially available metallized dielectric strip
which may be unwound from a reel, that is suitable for a making of a
capacitor in accordance with the present invention is shown in Fig. 13.
~his metallized dielectric strip may also be formed with ~ dielcctric layer
112 of a thin film dielectric material, such ~s polye~tcI, pc)l~r~lopylenc,
polystyrene, polycarbonate or other suitable material. A thin metallized
electrode layer 114 is applied to the upper surface of the dielectric layer
112 in such a fashion that unmetallized margin areas 116, 118 extend along
the longitudinal edges of the strip 110. Iwo thin metallized electrode
areas 120, 122 are applied to the lower surface of the dielectric layer
112 so that thc metallized layer 120 extends to the left l~and margin of
the layer as shown in Fig. 13, while the metallized layer 122 extends to
the right hand margin of the layer. A central unmetallized strip 124
lies between the metallized electrode areas 120, 122.
In the embodiment shown in Fig. 13, the longitudinal dimension of
the metallized strip 110 is shown along the arrows 126 wllile the narro~
transverse dimension is shown along the arrows 128. 'This is to allow
the capacitor to be pleated along the imaginary line 130 which extends
through the length of the unmetallized central strip 124. ~his version
of the present invention, however, is also not limited to one in which folding
is along longitudinal lines since a capacitor could be made in accordance
with this version of the present inventioll by plcating ~long tralls~crse lillcsif the appropriate corrcsponding ~llctallizcd and unmctallizcd areas wcre
provided.
- 16 -
SS78
A capacitor with a single pleat 140 along linc 130 is sllown in ~ig. 14
which is sliglltly off of tllc center linc 131 of tlle mctallizcd strip 110
with the inside of the pleat 140 in the area being unmetallized. ~he longitudinal
ends 148, 150 of the met~sllized strip 110 are arranged in a staggered
pattern so that one end 48 extends beyond the other end 150 along the
left hand longitudinal edge of the metallized strip because of the off-center
pleat of the dielectric layer. ~he extension of tllc cn~ S l~eyon(l tl~c end
150 is preferably at least 0. 020 inches, and tllis extension allows the
metallic spray to make contact with at least the upwardly facing
electrode area 122 s~own in Fig. 14. The unmetallized margin 116
faces upwardiy while the ~snmetallized margin ll~ faces downwardly
when the capacitor segmen'c has been pleated as shown in Fig. 14.
After the capacitor has been processcd to form thc c~paciLor seg-
ment shown in ~ig. 14, a number of di~ferent addilional ~rocessing stcps
may be undertaken. For example, the pleated capacitor segment of
~ igo 14 could be used to form a capacitor merely by spraying the
right and left hand longitudinal edges of the segment wish a metallized
spray, such as babbitt or otl~er suital~lc melal, in accol dancc witll con-
ventional practice, and then electrical leads cou~ e securcd to them,
for e~;ample, by soldering. Alternately, the capacitor segment of :I?ig.
14 could be cut along a transverse line, such as the line 143, and a number
of such segments could be stacked u.~on cach otller, with tlle tcrminal
end 150 of one capacitor segment being adjacent to l~slt not c~tcnclin~ as
far as thc terminal end 14~3' of the capacitor scL~nlcllt ll~at is posi~io1lcd
immediately below it, as sho~vn diagrammatic~lly by tl-e (~otted line re-
~ -- 17 --
ll~S578
presentative of l~ig. 14, and then their ends could l)e sprayed with a met-
allized spray and leads could then be secured to thc stacked array of such
segments. In conjunction with the presently preferred ernbodiment of the
present invention, howevcr, Fig. 14 r~l~rcscnts two laycrs c-f a CapaCi~Ol`
segment formed by winding of the dielectric strip about the lon~itudinal
dimension of the strip 110, as shown in ~igs. 15 and 16, to form a wound
capacitor. Another version of this capacitor could be achieved, however, by
pleating the capacitor segment of Fig. 14 a number of times transversely
along transverse fold lines, such as the line 143, or alternately, pleating
several times and then completing the segment by Willding thc remaindcr of
the length of the dielectric strip.
l he winding of the capacitor segment of Fig. 14 into a wound
capacitor may be achieved with various winding techniques, including the
use of a split mandrel such as the mandrel 156 of Figs, 15 and 16, which
may be removed from the capacitor segmenl after it has becn wo~lnd.
An unmetallized dielectric strip 58 is desirably initiatly wound around
the mandrel to protect the metallized electrode areas of the metallized
strip 110. ~he winding of the capacitor segment then continues until it is
almost completed, at which time an additional unmetallized dielectric
~ strip 150 is then desirably wound into the structure to form an outer pro-
tective coating. ~he dielectric strip 160 may also bc heat-scalcd to itself
to form a pleated capacitor segment in the manner shown in Fig. 5. ~he
-- 18 --
.. ,.~,,,, i .
ll~S~i78
removal of the mandrcl 156 from the wound capacitor segment leaves an open-
ing in thc unit. ~his opening may be closed by applying pressure, or
pressure and heat in accordance with the type of dielectric layer used and
conventional manufacturing techniques to the capacitor segnlcnt so that
it assumes an oval shape as shown in Fig. 6.
Once the capacitor segment has been wound, a metallized spray
may then be directed against the longitudinal edges of the unit in accordance
with conventional processing techniques to interconnect the electrode
layers along these edges and to provide for the connectioll of clcctrical
leads to the unit. The metallized spray will penetrate into the opcn
area resulting from the staggering of the ends 148 and 150 on thc left
hand longitudinal edge of the capacitor segment, so that the inner
electrode provided by the metallized areas 120, 122, is contacted by
the sprayed metal particles, but so that the electrode layer 114 is not
contacted by such particles, as indicated by the imaginary ylalle lG5
which represents the maximum depth of penetration of the spray
particles. The configuration of the present invention thus provides
for reliable lead termination at the left hand longitudinal edge of the
capacitor segment of Fig. 14 in a manner such tllat metallizecl en~
~ terminations may be employed witl~ a single pleat metalli~e~l CapO-citor. ~ermination to tlle right hand longitudinal cdgc of thc callacitor
seg.nent of Fig. 15 is similarly provided by a metallized spray
which e~tends over the protruding center pleat 140 to a depth ~VIliCh_
-- 19 --
,~ ~
ilC~S578
is sufficieslt to allow the melallized spray to make good contact to the
electrode area 114.
Once the metallic spray has l~een applied to thc ~dgcs of thc
capacitor segment either radial or axial leads may be applied to it
as previously shown in Figs. 7 and 8.
A portion of another commercially available metallized dielectric
strip which may be unwound from a reel, that is suitable for a malcing
of a capacitor in accordance with the present invention is shown in
Fig. 17. ~his metallized dielectric strip may also be forrned with a
dielectric layer 212 of a thin film dielectric material, such as polycster,
polypropylene, polystyrene, polycarbonate or other suitable material. A
thin metallized electrode layer 214 is applied to the upper surface of
the dielectric layer 212 and a thin metallized electrode layer 220 is
applied to the lower surface of the dielectric laycr in sucll a fashioll
that unmetallized margin areas 216, 218 extend along the opposite long-
itudinal edges of the strip 210 on opposite sides of the strip.
in the embodiment shown in Fig. 17, the longitudinal dimension
of the metallized strip 210 is shown along the arrows 226 while the
narrow transverse dimension is shown along ti-e arro~vs 2~S. ~he
~ capacitor is pleated along two imaginary lines 230, 232 whicll cxten(l
through the length of the strip 210. ~his ~ersion of tl-e present invention,
however, is also not limited to one in which folding is along two longitudinal
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lines since a capacitor could be made in accordance ~itll tllis v er;sion of
the present invention by pleating along any even number of transverse lines.
A pleated capacitor is shown in Fig. 18 wherein one pleat occurs
along the longitudinal line 230 and another pleat occurs along the long-
S itudinal lines 232. It is to be noted that pleat lines 230, 232 are spaccd so
that the rnargin area 218 e~tends beyond the pleat 242 that I`UIlS ~11Oll~ thc
right hand longitudinal edge of the metallized sl:rip 210 of l~ig. 17 with tllc
margin area 218 facing downwardly~ 'rhe extension of the margin area
218 beyond the pleats 242 is preferably at least 0.020 inches. In addition,
it is noted that the margin area 216 is positioned so that it extencls beyond
the pleat 252 that runs along the left hand longiLudinal edge of the met-
allized strip and faces upwardly. ~gain, tllc c~:lcnsic)ll of tilC l~al~gi
area 215 beyond the pleat 252 is preferably at least 0. 020 inches.
After the capacitor has been processed to form the capacitor seg-
ment shown in Fig. 18, a number of different additional processing steps
may be undertaken. For example, thc pleated capacitor seglnent of
Fig. 18 could be used to form a c~pacitor merely by sp~ g thc rigl~t
and left hand longitudinal edges of the segmcnt witl~ a n~ctalli%cd s~t)ra
such as babbitt or other suitable metal, in accordance wilh COnVelltiOll
practice, and then electrical leads could be secured to them, for ex-
ample, by soldering. Alternately, the ca~acilor segment of Fig. 18
could be cut along a transverse line, such as the line 243, and a numl)er
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~ "-
1 l(~S578
of such segmcnts could l~c staclied upon cach otller, with tht! down-
~ardly iacing margin 218 of one capacitor segment being adjacent to
and aligned with a corresponding upwardly facing margin 218' of the
capacitor segment that is positioned immediately below it, as shown
diagrammatically by the dotted line representative of Fig. 18, and then
their ends could be sprayed with a metallized spray and leads could
then be secured to the stacl;ed array of such segments. In conjullction
with the presently preferred embodiment of the present invention, how-
ever, Fig. 19 represents two layers of a capacitor segment formed by
winding of the dielectric strip about the center of the longitudinal dimen-
sion of the strip 210, as shown in Fig. 19, to form a wound capacitor seg-
ment. Another version of this ca~citor could l~c achieved, ho~vcver, by
pleating, instead of winding, the capacitor segment o~ Fig. 18 a number
of times along transverse fold lines such as the line 243. Alternately,
the capacitor segment could be ple~ted transversely two or more times
about transverse lines, such as the line 243, and then the segment could
be completed by winding the remainder of the length of the
dielectric strip.
'Ihe winding of the capacitor segment of ~ ig. 18 into a u~und
capacitor may be achieved with various winding techniques, including
the use of a split mandrel such as the mandrel 25G of Fig. 19, which is
removed from the capacitor segment a~ter it has becn wound. An unmet-
allized dielectric strip (not shown) may l~e wound arouncl tl~e strllcturc~o
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l.l~S'j~8
form an outer protective coating. Ihis dielectric strip may be heat-
sealed to itself to form the pleated capacitor segn~ent, as shown
in Fig. 6. ~he removal of the mandrel 56 frorn the capacitor segment
leaves an opening in the unit. Ihe opening may again be closed by
applying pressure, or pressure and heat, in accorclance ~vitll thc t~pc
of dielectric layer used and conventional manufacturing techniques to
the capacitor segment so that it assumes an oval s)-ape, as shown in
Fig. 7.
Once the capacitor segment has been wound, a metal]ized spr~3y
may then be directed against the longit-lc3inal cclges of tl-~ unit in
accordance with conventional processing techni4ues to intcrconncct
the electrode layers along these edges and to provide for the connection
of electrical lcads to the unit. Ihe metallized spray will penetrate
into the open area between the margin 216 arcas Oll the left hand
longitudinal edge of the capacitor segment, as sl-~own dia~rammatically
in Fig. 18 to a clepth such as that indicated by lhe plane 2G~), so as
to make contact Wit'll the elcctrode area 220. ~he ~lane 2()G indicates
the maximum depth that any high velocity spray partic}es will pe~etrate
and it may thus be located any place between the end of the margin 216
areas of the metallized strip 210 and tlle edge of the pleat 252.
Accordingly, the metalli%ed spray rnaterial ;'Jill c~-len(l in~o tllc Icf~ _
hanà opening of the capacitor ~etween lhe mar~ 21G ~l~cas far c~-~ough to
make contact to the facing metalli~ed clectrodc on the other side c~f ,he
dielectric strip, but not so far that it will penetrate through til(
25 t;~ lielectric matcrial at tile picat 252.
11~5578 s
~ern~ination to the right halld longitudinal edge of the capacitor
segment of Fig. 18 is similarly provided l)y a metallized spra~ which
extends over the margin 218 area to a depth, such as that indicated
by the plane 268, which is sufficient to allow the metallized spray to ;~
make good contact to the electrode 214 on tlle inside of the m~rgin 218
area but ~vhich will prevent the penetration of the spray mct;lllic par-
ticles through the dielectric at the pleat 242. Ihe location o~ tllc pl~nc
268 may be anywhere between the edges of the pleat 242 and the end of
the margin area 218 as long as there is sufficient depth of ~p ray to pro-
- 10 vide adequate contact termination to the electrode area 214.. ~he con-
~;~ figuration of the present invention thus provides for reliable Icad ter-
~;~ mination at the longitudillal edges of tlle ca~acitor SCglllCnt of Fi~. lR
without the necessity of providing unmetallizcd lon~itudinal strips along
the inside of the pleats 242, 252, thereby saving considcrable processing
expenses in the manufacture of completed capacitors of this type.
Ç
Once the metallic spray has been applied to the edges of the
capacitor segment, either radial or axial leads Illay bc ap pliccl to it,
again as previously shown ln Figs. 7 and 8.
Another alternate versio,n of the present invention is shown in
Fig. 20, wherein two layers of either a wound or a stacked capacitor
,- segment is shown. 'rhis version differs from that sho~n in Fig. 18 ln
that intermediate dicleclric ]ayers 2G9, 2G9' are inserlcd bct~ccll ~Itcrltati
s ~ ,
groups 271, 273 of pleated layers of the capacitor segllIcnt ~h ich f~cc in
~: opposite directions. If the capacitor of Fig. 20 is to be a ~voulId embodi-
' ~25 ment, the alternating groups 271, 273 of pleated layers \~hicll face in
opposite directions may each be supplied from a diffcrent pleated seg-
:,~ ~ment supply.
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li(~5578
~he previously described embodiments of the prescnt invention
are illustrativc, but not exhaustive, of the various types of configurations
that may come within the scope of the present invention. For instance,
while winding about the exact center of the dielectric strip is preferred,
it is apparent that winding about any number of transversc lines offset
from the center, but intermediate the ends of the dielectric strip, arc
intended to be included within the scope of the present invention. It is
also further apparent that more than two longitudinal pleat lines may be
employed in the version shown in Fig. 18 wi~hin the scope of the present
invention.
.. . .
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