Wound multi-anode electrolytic capacitor with offset anodes

A wound multi-anodic electrolytic capacitor has a multi-anode stack of strips of high foil gain tunnel-etched aluminum. Inner end edges the anodes in a multi-anode stack are offset from each other by a predetermined distance. Offsetting the end edges of the anodes advantageously reduces mechanical stresses in the capacitor windings. This increases the reliability of the capacitor and advantageously allows a smaller diameter mandrel opening, increasing the energy density per unit volume of the capacitor and allowing its volume to be reduced. When used in an implantable defibrillator or other cardiac rhythm management device, the smaller capacitor advantageously reduces its volume or, alternatively, allows the use of a larger battery, thereby prolonging its useable life.

TECHNICAL FIELD OF THE INVENTION 
This invention relates generally to capacitors and particularly, but not by 
way of limitation, to a wound multi-anodic electrolytic capacitor with 
offset anodes. 
BACKGROUND OF THE INVENTION 
Capacitors are electrical components that store electrical energy in an 
electromagnetic field between electrodes that are separated by a 
dielectric insulator. Each electrode carries a charge that is opposite in 
polarity to the charge on the other electrode. Capacitors find many 
applications in a wide variety of electric circuits. Some applications 
require the capacitor to withstand a high voltage between its electrodes. 
For example, some camera flash devices produce light by an electric 
discharge in a gas. A high voltage is required to create the discharge. A 
power converter transforms a low voltage obtained from a battery into a 
high voltage, which is stored on the capacitor and used to trigger the 
flash. In another example, external and implantable defibrillators deliver 
a high voltage electrical countershock to the heart. The countershock 
restores the heart's rhythm during cardiac arrhythmias such as 
life-threatening ventricular fibrillation. In an implantable 
defibrillator, a power converter transforms a low voltage (e.g., 
approximately 3.25 Volts), obtained from a battery, into a high voltage 
(e.g., approximately 750 Volts), which is stored on capacitors and used to 
defibrillate the heart. 
Electrolytic capacitors are used in cameras, defibrillators, and for other 
electric circuit applications. An electrolytic capacitor includes two 
electrodes: an anode and a cathode. The dielectric insulator between the 
anode and cathode is formed by anodizing the anode electrode (i.e., 
growing an oxide on the anode). The anode and cathode electrodes are 
physically separated from each other by a porous separator that is soaked 
with a conductive electrolyte solution. The electrolyte acts as a part of 
the cathode electrode. A parallel plate capacitor is formed by a 
substantially parallel planar arrangement of superjacent anode and cathode 
plates. A separator is interposed in between the anode and cathode 
electrode plates. A cylindrical capacitor is formed by winding anode, 
cathode, and separator strips into a spiraled cylindrical roll. For 
electrically connecting the capacitor in an electric circuit, tabs are 
joined to the anode and cathode. The tabs protrude outwardly from an end 
of the cylinder so that the capacitor can be connected in the electric 
circuit. 
By maximizing the energy density of a capacitor, its volume can be reduced. 
This is particularly important for implantable medical devices, such as 
implantable defibrillators, since the defibrillation energy storage 
capacitor occupies a significant portion of the implantable defibrillator 
device. Smaller implantable defibrillator devices are desired. Smaller 
defibrillators are easier to implant in a patient. Also, for a particular 
defibrillator size, a smaller capacitor allows the use of a larger 
battery, which increases the effective usable life of the implanted device 
before surgical replacement is required. Thus, one goal of implantable 
defibrillator design is to maximize capacitor energy density and minimize 
capacitor volume. 
The energy density of a capacitor increases in proportion to a 
corresponding increase in the surface area of the anode. For example, an 
anode having a particular macroscopic surface area can be roughened to 
increase its microscopic surface area. The capacitance per unit of 
macroscopic surface area, which is sometime referred to as the foil gain 
of the capacitor, increases as a result of roughening techniques. One such 
roughening technique includes tunnel-etching tiny openings partially or 
completely through the anode electrode strip. However, tunnel-etched 
electrodes are extremely brittle, making the anodes extremely susceptible 
to mechanical stresses, such as those stresses resulting from winding 
electrodes and separators into a cylindrical capacitor. Anode surface area 
is further increased by stacking multiple tunnel-etched anodes, thereby 
obtaining even more surface area and, in turn, an even capacitance per 
unit area of the anode stack. However, in such multi-anodic capacitors, 
stacking the anodes further increases the stresses resulting from winding 
the electrodes and separators into a cylindrical capacitor. 
Thus, there is a need for further reducing capacitor volume, increasing 
capacitor reliability, and reducing cost and complexity of the capacitor 
manufacturing process, for wound multi-anodic electrolytic capacitors used 
in implantable defibrillators, camera photoflashes, and other electric 
circuit applications. 
SUMMARY OF THE INVENTION 
The above-mentioned shortcomings, disadvantages and problems are addressed 
by the present invention, which will be understood by reading and studying 
the following specification. The present invention provides, among other 
things, a wound capacitor. The capacitor includes a first anode, including 
an end edge, a cathode, and a first separator between the first anode and 
the cathode. The first separator carries an electrolyte. A second 
electrode, which also includes an end edge, is substantially adjacent to 
the first anode. The first anode is in between the second anode and the 
first separator. A second separator is substantially adjacent to the 
cathode. The cathode is in between the first and second separators. The 
second separator is approximately adjacent to the second anode when wound. 
The first and second anodes, the first and second separators, and the 
cathode are spirally wound together into a cylindrical capacitor defining 
a concentric cylindrical axis. The end edges of the first and second 
anodes are approximately proximal to the cylindrical axis. The first and 
second anodes extend spirally outward from the end edges of the respective 
first and second anodes. The end edge of the first anode is offset from 
the end edge of the second anode by a first predetermined distance. 
In one embodiment, the invention provides a cardiac rhythm management 
system including the above-described capacitor. The cardiac rhythm 
management system includes an implantable defibrillator, which includes 
the capacitor, and a leadwire that is adapted to be coupled to a heart for 
delivering an electrical countershock energy that is stored on the 
capacitor. 
In various embodiments, the first predetermined distance is approximately 
between 1 millimeter and 10 millimeters. In one embodiment, the capacitor 
also includes a third anode. The third anode is substantially adjacent to 
the second anode. The second and third anodes are in between the second 
separator and the first anode when wound. The third anode is in between 
the second anode and the second separator when wound. The third anode is 
spirally wound together with the first and second anodes. The third anode 
includes an end edge that is approximately proximal to the cylindrical 
axis such that the third anode extends spirally outward from the end edge 
of the third anode. The end edge of the third anode is offset from the end 
edge of the second anode by a second predetermined distance. In one 
embodiment, the second predetermined distance is approximately between 1 
millimeter and 10 millimeters. A mandrel opening extends through the 
capacitor along the concentric cylindrical axis. The mandrel opening 
includes a diameter that is approximately between 1 millimeter and 5 
millimeters. 
In another embodiment, the present invention provides, among other things, 
a spirally wound cylindrical aluminum electrolytic capacitor. The 
capacitor includes a tunnel-etched aluminum first anode ribbon having an 
end edge. Also included is an aluminum cathode ribbon. Also included is a 
first separator ribbon including at least two paper ribbons impregnated 
with a liquid electrolyte. Also included is a tunnel-etched aluminum 
second anode ribbon including an end edge. Also included is a second 
separator ribbon including at least two paper ribbons impregnated with a 
liquid electrolyte. The first and second anode ribbons, the first and 
second separator ribbons, and the cathode ribbon are spirally wound 
together into a cylindrical capacitor defining a concentric cylindrical 
axis. Each winding of the cylindrical capacitor includes a stacked 
sequence of the second separator ribbon, the cathode ribbon, the first 
separator ribbon, the first anode ribbon, and the second anode ribbon. The 
end edges of the first and second anode ribbons are approximately parallel 
to each other and are also approximately parallel and approximately 
proximal to the cylindrical axis. The end edge of the first anode ribbon 
is offset from the end edge of the second anode ribbon by a first 
predetermined distance. 
Another aspect of the invention provides, among other things, a method of 
fabricating a capacitor. A stacked sequence of elements is formed. The 
stacked sequence of elements sequentially includes a second separator, a 
cathode, a first separator, a first anode, and a second anode, each having 
an end being approximately aligned with the other elements in the stacked 
sequence. The end of the first anode is displaced from the end of the 
second anode by a first predetermined distance. The stacked sequence is 
wound spirally outward from the ends of the stacked sequence of elements 
to form a resulting cylindrical capacitor. The ends of the stacked 
sequence of elements are approximately proximal to a concentric 
cylindrical axis of the capacitor. 
In various further embodiments, the method includes displacing the end of 
the first anode from the end of the second anode includes offsetting the 
first and second anodes by approximately between 1 millimeter and 10 
millimeters. A mandrel opening is formed to extend through the capacitor 
along the concentric cylindrical axis, the mandrel opening including a 
diameter that is approximately between 1 millimeter and 5 millimeters. 
In another embodiment, the present invention provides, among other things, 
a method of fabricating a capacitor. The method includes forming a stacked 
sequence of elements that sequentially includes a second separator, a 
cathode, a first separator, a first anode, a second anode, and a third 
anode, each having an end being approximately aligned with the other 
elements in the stacked sequence. The first anode is displaced from the 
end of the second anode by a first predetermined distance. The second 
anode is displaced from the end of the third anode by a second 
predetermined distance. The stacked sequence is wound spirally outward 
from the ends of the stacked sequence of elements to form a resulting 
cylindrical capacitor, such that the ends of the stacked sequence of 
elements are approximately proximal to a concentric cylindrical axis of 
the capacitor. 
In various further embodiments, the method includes displacing the end of 
the first anode from the end of the second anode includes offsetting the 
first and second anodes by approximately between 1 millimeter and 10 
millimeters. The end of the second anode is displaced from the end of the 
third anode by an offset that is approximately between 1 millimeter and 10 
millimeters. Winding the stacked sequence includes forming a mandrel 
opening extending through the capacitor along the concentric cylindrical 
axis, the mandrel opening including a diameter that is approximately 
between 1 millimeter and 5 millimeters. 
Thus, the present invention provides, among other things, a wound 
multi-anodic electrolytic capacitor. Inner end edges of anodes in a 
multi-anode stack are offset from each other by a predetermined distance. 
Offsetting the end edges of the anodes advantageously reduces mechanical 
stresses in the capacitor windings. This increases the reliability of the 
capacitor and allows a smaller diameter mandrel opening, increasing the 
energy density per unit volume of the capacitor and allowing its volume to 
be reduced. When used in an implantable cardiac rhythm management device, 
the smaller capacitor advantageously reduces the volume of the implantable 
device or, alternatively, allows the use of a larger battery, thereby 
prolonging its useable life. Other advantages will become apparent upon 
reading the following detailed description of the invention and viewing 
the accompanying drawings that form a part thereof.

DETAILED DESCRIPTION OF THE INVENTION 
In the following detailed description, reference is made to the 
accompanying drawings which form a part hereof, and in which is shown by 
way of illustration specific embodiments in which the invention may be 
practiced. These embodiments are described in sufficient detail to enable 
those skilled in the art to practice the invention, and it is to be 
understood that the embodiments may be combined, or that other embodiments 
may be utilized and that structural, logical and electrical changes may be 
made without departing from the scope of the present invention. The 
following detailed description is, therefore, not to be taken in a 
limiting sense, and the scope of the present invention is defined by the 
appended claims and their equivalents. 
The present invention provides, among other things, a wound multi-anodic 
electrolytic capacitor. Inner end edges of anodes in a multi-anode stack 
are offset from each other by a predetermined distance. Offsetting the end 
edges of the anodes reduces mechanical stresses in the capacitor windings. 
This increases the reliability of the capacitor and allows a smaller 
diameter mandrel opening, increasing the energy density per unit volume of 
the capacitor and allowing its volume to be reduced. When used in an 
implantable cardiac rhythm management device, the smaller capacitor 
reduces the volume of the implantable device or, alternatively, allows the 
use of a larger battery, thereby prolonging its useable life. Other 
advantages will also become apparent upon reading the following detailed 
description of the invention and viewing the accompanying drawings that 
form a part thereof. 
FIG. 1 is a schematic/block diagram illustrating generally, by way of 
example, but not by way of limitation, one embodiment of a cardiac rhythm 
management system 100 according to one aspect of the present invention. 
System 100 includes, among other things, cardiac rhythm management device 
105 and leadwire ("lead") 110 for communicating signals between device 105 
and a portion of a living organism, such as heart 115. In the illustrated 
example, device 105 includes an automatic implantable 
cardioverter/defibrillator (AICD), but any other apparatus for cardiac 
rhythm management is also included within the present invention. 
In the illustrated embodiment, portions of system 100 is implantable in the 
living organism, such as in a pectoral or abdominal region of a human 
patient, or elsewhere. In another embodiment, portions of system 100 
(e.g., device 105) are alternatively disposed externally to the human 
patient. In the illustrated embodiment, portions of lead 110 are disposed 
in the right ventricle, however, any other positioning of lead 110 is 
included within the present invention. In one embodiment, lead 110 is a 
commercially available endocardial defibrillation lead. System 100 can 
also include other leads in addition to lead 110, appropriately disposed, 
such as in or around heart 115, or elsewhere. 
In one example, a first conductor of multiconductor lead 110 electrically 
couples a first electrode 120 to device 105. A second conductor of 
multiconductor lead 110 independently electrically couples a second 
electrode 125 to device 105. Device 105 includes an energy source, such as 
battery 130, a power converter 135, such as a flyback converter, at least 
one defibrillation output capacitor 140, and a controller 145 for 
controlling the operation of device 105. In one embodiment, power 
converter 135 transforms the terminal voltage of battery 130, which is 
approximately between 2 Volts and 3.25 Volts, into an approximately 
700-800 Volt (maximum) defibrillation output energy pulse stored on the 
defibrillation output capacitor 140. In another embodiment, power 
converter 135 transforms the terminal voltage of two series-coupled 
batteries, which is approximately between 4 Volts and 6.25 Volts, into the 
approximately 700-800 Volt (maximum) defibrillation output energy pulse 
stored on the defibrillation output capacitor 140. It is understood that 
the present invention is also capable of operating using lower 
defibrillation energies (e.g., approximately between 0.1-40 Joules) and 
voltages (e.g., approximately between 10-800 Volts). 
FIG. 2A illustrates generally, by way of example, but not by way of 
limitation, one embodiment of a cylindrical capacitor 140. In one 
embodiment, capacitor 140 includes a case 200 for carrying, enclosing, or 
sealing a spirally wound aluminum electrolytic capacitor, as described 
below. Anode connection tab 205 and cathode connection tab 210 provide 
electrical access to respective anode and cathode terminals of capacitor 
140, as described below. In one embodiment, attachment of tabs 205 and 210 
is as described in O'Phelan et al., U.S. patent application Ser. No. 
09/063,692, entitled "ELECTROLYTIC CAITOR AND MULTI-ANODIC ATTACHMENT," 
which was filed on Apr. 21, 1998, and assigned to the assignee of the 
present invention, the entirety of which is incorporated herein by 
reference. Other techniques of attaching tabs 205 and 210 are also 
included in the present invention. 
FIG. 2B illustrates generally, by way of example, but not by way of 
limitation, one embodiment of a partially unrolled portions of a 
cylindrical aluminum electrolytic capacitor 140. Anode connection tab 205 
physically and electrically contacts portions of at least one anode of 
multiple anode stack 215, which is a ribbon or strip that forms a first 
electrode of capacitor 140. Cathode connection tab 210 physically and 
electrically contacts portions of cathode 220, which is a ribbon or strip 
that forms a second electrode of capacitor 140. One or more separators 225 
on each side of cathode 220 provides physical separation between cathode 
220 and anode stack 215 when spirally rolled up together into a 
cylindrically shaped capacitor 140. In one embodiment, each of separators 
225 includes one or more paper strips. For example, using two paper strips 
obtains redundancy that better protects against anode-to-cathode 
short-circuits in the event of pinholes in the paper strips. In one 
embodiment, permeable separators 225 carry a conductive electrolyte that, 
together with cathode strip 220 and cathode connection tab 210, forms the 
second electrode (i.e., a cathode electrode) of capacitor 140. However, 
the present invention is not limited to use only in capacitors using a 
liquid conductive electrolyte (e.g., a solid electrolyte could also be 
used). 
In FIG. 2B, the multiple anodes 215, separators 225, and cathode 220 are 
spirally wound around a mandrel into a cylindrical capacitor 140 defining 
a concentric cylindrical axis 230. The mandrel is removed, resulting in a 
mandrel opening 235 extending through capacitor 140 along cylindrical axis 
230. According to one aspect of the invention, the mandrel opening 235 has 
a diameter 240 that is approximately between 1 millimeter and 5 
millimeters (e.g., approximately 2.5 millimeters). As discussed below, the 
present invention allows, among other things, a smaller diameter 240 of 
mandrel opening 235 in comparison to conventional cylindrically wound 
capacitors. The smaller mandrel opening 235 increases the energy density 
per unit volume of capacitor 140. The higher energy density allows the 
volume of capacitor 140 to be reduced. This, in turn, allows reduction of 
the volume of implantable device 105 or, alternatively, allows the use of 
a larger battery 130, thereby increasing the implanted longevity of 
implantable device 105. 
FIG. 3 is a schematic diagram illustrating generally, by way of example, 
but not by way of limitation, a cross-sectional view of one embodiment of 
a portion of capacitor 140. Cathode 220 is separated from anode stack 215 
by separators 225A-B. Anode stack 215 includes a stacked configuration of 
multiple anodes, such as first anode 215A and second anode 215B (or 
optionally including even more anodes). In one embodiment, each of anodes 
215A-B is a high foil-gain tunnel-etched aluminum foil strip that has been 
anodized (i.e., a thin insulating aluminum oxide layer has been grown on 
each surface of each of the aluminum foil anodes 215A-B). The 
tunnel-etched anodes 215A-B are extremely brittle, making them extremely 
susceptible to mechanical stresses, such as those stresses resulting from 
winding the cylindrical capacitor 140. The aluminum oxide layer formed on 
first anode 215A provides a capacitor dielectric between first anode 215A 
and the conductive electrolyte carried by first separator 225A. The 
aluminum oxide layer formed on second anode 215B provides a capacitor 
dielectric between second anode 215B and the conductive electrolyte 
carried by second separator 225B when spirally wound as illustrated in 
FIG. 3. 
FIG. 3 illustrates one embodiment of how first anode 215A, second anode 
215B, first separator 225A, second separator 225B, and cathode 220 are 
spirally wound together into a cylindrical capacitor 140, defining a 
concentric cylindrical axis 230. Each winding of the cylindrical capacitor 
140 includes a stacked sequence (in a direction outward from cylindrical 
axis 230) of second separator 225B, cathode 220, first separator 225A, 
first anode 215A, and second anode 215B. Because of the spiral winding 
arrangement, the sequence is repeated for windings that are more distal 
from the cylindrical axis 230. That is, in the above sequence, second 
anode 215B is again followed by second separator 225B, cathode 220, etc. 
Because the sequence is repeated, the relationship between the elements is 
significant, not the choice of starting and ending elements in describing 
the sequence. 
According to one aspect of the invention, each of first anode 215A and 
second anode 215B include an end edge that is proximal to cylindrical axis 
235 and mandrel opening 235, such that first anode 215A and second anode 
215B extend spirally outward from their respective end edges. In one 
embodiment, the end edges of first anode 215A and second anode 215B are 
approximately parallel to each other. The end edge of first anode 215A is 
offset from the end edge of second anode 215B by a first predetermined 
distance d.sub.1, as illustrated in FIG. 3. The distance d.sub.1, is 
selected to be approximately between 1 millimeter and 10 millimeters 
(e.g., approximately between 5 millimeters and 7 millimeters). Offsetting 
the end edges of first anode 215A and second anode 215B obtains reduced 
winding stresses in the windings that are further away from the 
cylindrical axis 230. Thus, this aspect of the invention advantageously 
increases the reliability of capacitor 140. As discussed above, the 
reduced winding stresses also allows mandrel opening 235 to have a smaller 
diameter 240. This increases the energy density per unit volume of 
capacitor 140. For example, reducing the diameter 240 of mandrel opening 
235 from 4 millimeters to approximately 2.5 millimeters advantageously 
increases the energy density of capacitor 140 by approximately 5%. The 
higher energy density allows the volume of capacitor 140 to be reduced. 
This, in turn, allows reduction of the volume of implantable device 105 
or, alternatively, allows a larger battery 130, thereby increasing the 
implanted longevity of implantable device 105. 
FIG. 4 is a schematic diagram illustrating generally, by way of example, 
but not by way of limitation, a cross-sectional view of one embodiment of 
a portion of capacitor 140. FIG. 4 is similar to FIG. 3, but further 
including a third anode 215C, which is wound in between second anode 215B 
and second separator 225B, as illustrated in FIG. 4. According to one 
aspect of the invention, each of first anode 215A, second anode 215B, and 
third anode 215C include an end edge that is proximal to cylindrical axis 
235 and mandrel opening 235. First anode 215A, second anode 215B, and 
third anode 215C each extend spirally outward from their respective end 
edges. In one embodiment, the end edges of first anode 215A, second anode 
215B, and third anode 215C are approximately parallel to each other. The 
end edge of first anode 215A is offset from the end edge of second anode 
215B by a first predetermined distance d.sub.1, as described above. The 
end edge of the second anode 215B is offset from the end edge of third 
anode 215C by a second predetermined distance d.sub.2', as illustrated in 
FIG. 4. The distance d.sub.2 is selected to be approximately between 1 
millimeter and 10 millimeters (e.g., approximately between 5 millimeters 
and 7 millimeters). Offsetting the end edges of second anode 215B and 
third anode 215C obtains reduced winding stresses in the capacitor 
windings that are further away from the cylindrical axis 230, as discussed 
above with respect to FIG. 3. Although FIGS. 3 and 4 illustrate 
embodiments of the invention having 2 anodes and 3 anodes, respectively, 
the present invention includes the use of additional anodes, being offset 
from each other in a similar fashion. 
Example Method of Forming Cylindrical Capacitor 
FIGS. 2 through 4 illustrate various embodiments of portions of the present 
invention providing a cylindrical capacitor 140, as discussed above. In 
one example, the cylindrical capacitor 140 is formed by spiral winding 
using a capacitor winder apparatus. FIG. 5 is a schematic diagram that 
illustrates generally one example embodiment of such a capacitor winder 
500. In FIG. 5, capacitor winder 500 is a Model 820 dual anode lug 
capacitor winder available from Micro Tech Manufacturing, Inc. of 
Worcester, Mass. As illustrated, the capacitor winder 500 is capable of 
forming a cylindrical capacitor 140 having only 2 anodes in anode stack 
215. In one embodiment of the present invention, an anode stack 215 having 
2 anodes is provided and, in one embodiment, the end edges of the anodes 
are manually offset from each other. However, as discussed above, certain 
embodiments of the present invention utilize more than 2 anodes in anode 
stack 215. According to one technique of making one embodiment of the 
present invention, additional anode strips are trimmed to size, and the 
trimmed anode strips are manually inserted between the dual anode ribbons 
that are fed by reels on capacitor winder 500. In one embodiment, the end 
edges of the anodes are manually offset from each other. This provides an 
anode stack 215, which includes more than two anodes, in the resulting 
cylindrically wound capacitor 140. Alternatively, capacitor winder 500 can 
be modified. Additional reels and feeders can be added to supply the 
additional anode ribbons for forming a capacitor 140 having an anode stack 
215 that includes more than 2 anodes. 
In one embodiment, by way of example, but not by way of limitation, the 
anode stack 215 includes 3 anode layers 215A-C (as illustrated in FIG. 4). 
Each one of anode layers 215A-C formed of a tunnel-etched oxidized 
aluminum foil ribbon having a width of approximately 24 millimeters and a 
thickness of approximately 0.0041 inches. The cathode 220 is formed from 
an aluminum foil ribbon having a width of approximately 24 millimeters and 
a thickness of approximately 0.0012 inches. Each separator 225A and 225B 
includes two layers of a paper ribbon, each having a width of 27 
millimeters and a thickness of approximately between 12.7 and 20 microns. 
Anode stack 215, cathode 220, and paper separators 225A-B are cut to a 
desired length to obtain a particular capacitance value of capacitor 140. 
In one embodiment, the wound capacitor 140 has a cylindrical diameter of 
approximately 14.5 millimeters, and is held together (i.e., prevented from 
unwinding) by wrapping in an adhesive tape having a width of approximately 
26.6 microns and a thickness of approximately 53 microns. 
In one embodiment, anode tab 205 is only joined to a single anode in anode 
stack 215 for obtaining an electrical connection to other anodes in anode 
stack 215, as described in O'Phelan et al., U.S. patent application Ser. 
No. 09/063,692 entitled "ELECTROLYTIC CAITOR AND MULTI-ANODIC 
ATTACHMENT," (Attorney Docket. No. 00279.094US1), which was filed on Apr. 
21, 1998, and assigned to the assignee of the present invention, the 
entirety of which is incorporated herein by reference. 
CONCLUSION 
Thus, the present invention provides, among other things, a wound 
multi-anodic electrolytic capacitor. Inner end edges of anodes in a 
multi-anode stack are offset from each other by a predetermined distance. 
Offsetting the end edges of the anodes advantageously reduces mechanical 
stresses in the capacitor windings. This increases the reliability of the 
capacitor and advantageously allows a smaller diameter mandrel opening, 
increasing the energy density per unit volume of the capacitor and 
allowing its volume to be reduced. When used in an implantable cardiac 
rhythm management device, the smaller capacitor advantageously reduces the 
volume of the implantable device or, alternatively, allows the use of a 
larger battery, thereby prolonging its useable life. 
It is to be understood that the above description is intended to be 
illustrative, and not restrictive. Many other embodiments will be apparent 
to those of skill in the art upon reviewing the above description. The 
scope of the invention should, therefore, be determined with reference to 
the appended claims, along with the full scope of equivalents to which 
such claims are entitled.