the following detailed description , which references and incorporates the above - identified figures , describes and illustrates one or more specific embodiments of the invention . these embodiments , offered not to limit but only to exemplify and teach , are shown and described in sufficient detail to enable those skilled in the art to implement or practice the invention . thus , where appropriate to avoid obscuring the invention , the description may omit certain information known to those of skill in the art . as used herein , the term “ profile ” refers to the general outline of a portion of an object taken in or projected onto a plane generally perpendicular to a major surface of the object . thus , for example , in some flat capacitors , profile means the outline of the capacitor case and / or the capacitor stack taken in a plane perpendicular to the major surfaces of the case or the capacitor stack . as used herein , the term “ staggered ” refers to the existence of an offset between respective adjacent surfaces of two or more juxtaposed or proximate objects . thus , for example , the offset can result from offsetting one of the objects relative the other object or controlling the relative size and placement of the objects . fig1 shows a portion of an exemplary capacitor 100 incorporating the present invention . capacitor 100 includes a stack 102 of two or more electrically coupled capacitor modules 102 a , 102 b , 102 c , 102 d , and 102 e within a capacitor case 104 . modules 102 a - 102 e are staggered so that their edges generally ( or at least a portion of side of the stack ) define a profile 106 that generally conforms or is substantially congruent to an adjacent curved interior portion 104 a of capacitor case 104 . fig2 a section view of capacitor 100 taken along line 2 — 2 , shows that modules 102 a - 102 e are staggered in two dimensions . in this view , capacitor modules 102 a - 102 e define a profile 108 , which is generally congruent to a curved portion 104 b of case 104 . although profiles 106 and 108 are quite distinct in this exemplary embodiment , other embodiments make profiles 106 and 108 substantially congruent . in the exemplary embodiment , each capacitor module includes a three - layer etched and / or perforated anode , a cathode , and at least one electrolyte - carrying separator between the anode and the cathode . the anode and cathode comprise foils of aluminum , tantalum , hafnium , niobium , titanium , zirconium , or combinations of these metals . additionally , each capacitor module is sandwiched between two pairs of electrolyte - carrying separators , with the separators extending beyond the anode and cathode to prevent undesirable shorting with the case . alternatively , separate insulative layer can be placed between the capacitor modules and the case interior walls to prevent shorting . exemplary separators comprise kraft paper , and exemplary electrolytes include ethylene - glycol base combined with butrylactone . in other embodiments , the capacitor modules take other forms having different numbers of anode layers and separators . for example , in some embodiments , the anodes , cathode , and separators in one or more of the capacitor modules are staggered to define curved module faces that confront the interior surfaces 104 a or 104 b of the case . also , in some embodiments , one or more of the anodes or cathodes are coupled to the case , making it either anodic or cathodic . to define the staggered edge faces and thus the curved profile , some embodiments which provide the curved profile in a single dimension , use a set of generally congruent modules of different sizes . for example , one embodiment includes four generally d - shaped modules , each with a common width and height , but with four successively smaller lengths . the modules are stacked , each module having at least one edge aligned vertically with the corresponding edges of adjacent modules . fig3 shows an exemplary implantable heart monitor 300 including a monitor housing 310 and two capacitors 320 and 330 . monitor housing 310 includes curved portions 312 and 314 and adjoining straight portions 316 and 318 . capacitor 320 includes case 322 and eleven capacitor modules 324 . case 322 includes a curved portion 322 a and a straight portion 322 b , respectively confronting curved portion 312 and straight portion 316 of housing 310 . capacitor modules 324 include a set of staggered modules 324 a and a set of unstaggered modules 324 b . the set of staggered modules 324 a confront curved portion 322 a of case 322 and have edges arranged to define a curved profile 326 generally congruent to the profile of curved portion 322 . modules 324 b , which are vertically aligned , confront straight portion 322 b of case 322 . similarly , capacitor 330 includes case 332 and eleven capacitor modules 334 . case 332 includes curved portion 332 a and a straight portion 332 b , which confront respective portion 314 and 318 of housing 310 . capacitor modules 334 include staggered modules 334 a , which confront curved portion 332 a of case 332 , have front edges arranged to define a curved profile 336 generally congruent to the profile of curved portion 332 a . modules 334 b confront straight portion 332 b of case 332 . notably , the exemplary embodiment provides each of modules 324 and 334 with three anodes placed between one or more separators and at least one cathode placed adjacent one of the separators . ( fig3 shows the separators cross - hatched .) however , the invention is not limited to any particular module arrangement . indeed , some embodiments of the invention use other ( greater or lesser ) numbers of anodes as well as modules . moreover , some embodiments mix modules of different arrangements within the same capacitor case . this allows greater flexibility in exploiting the space available in the case as well as the housing . for more details , see co - assigned and co - pending u . s . patent application which is entitled mixing of multiple anodes within a single aluminum electrolytic flat capacitor ( attorney docket 279 . 264us1 ) which is incorporated herein by reference . additionally , other embodiments of the invention construct capacitor cases 322 and 332 as a single case having two adjacent compartments with a common wall . modules 324 and 334 are each placed in a respective compartment . the cathodes in modules 324 and the anodes of modules 334 are electrically coupled to the case ; an external anode terminal is coupled to the anodes of module 324 ; and an external cathode terminal is coupled to the cathodes of module 334 , thereby effecting a series connection of the two capacitors using two external terminals instead of the four that are conventionally provided . this arrangement can be made by providing two ( first and second ) aluminum case bodies having the desired curved portions , placing capacitor modules in the first case body , and welding a cover to the first case body . other capacitor modules can then be stacked and placed in the second case body . the cover of the first case body is then put on the opening of the second case body and welded in place . for further details , see co - pending and co - assigned u . s . patent application which is entitled multi - compartment electrolytic capacitor ( attorney docket 279 . 264us1 ), and which is incorporated herein by reference . fig4 shows a perspective view of an exemplary capacitor - battery assembly 400 including two stacked u - shaped capacitors 410 and 420 and a battery 430 nested within the capacitors . for sake of brevity , capacitor 420 , which is of substantially identical size , shape , and structure as capacitor 410 in this exemplary assembly , is not described separately . however , the invention is not so limited . capacitor 410 includes legs 412 and 414 , respective middle ( or intermediate ) portions 416 , and terminals 418 . legs 412 and 414 , which are parallel in the exemplary embodiment , include respective curved surfaces 412 a and 414 a , and respective flat end surfaces 412 b and 414 b . fig5 a front view of assembly 400 without battery 430 , shows that curved surfaces 412 a and 414 b are generally congruent to each other and to respective curved profile 502 and 504 defined by capacitor modules 500 . further , it shows a housing 510 ( in phantom ) having a curved or concave portions 512 and 514 generally congruent with or conformant to curved ( or convex ) surfaces 412 a and 414 a . in the exemplary embodiment , curved profiles 502 and 504 are quarter segments of an ellipse or circle , and surfaces 412 a and 414 a are portions of an ellipsoid or sphere . the exemplary embodiment provides the modules with one or more of the single or multiple anode structures noted previously . thus , modules 500 may include modules with differing anode structures as desired to fit a given height . fig6 a side view of assembly 400 , shows that the curved surfaces 412 a and 414 a are generally perpendicular to end surfaces 412 a and 412 b . middle portion 416 is also shown as having a curved portion 416 a which is congruent to a curved profile 506 defined by capacitor modules 500 and a curved portion 516 of monitor housing 510 . fig7 is a top view of assembly 400 , showing the general u - shape of capacitor modules 500 . this figure also shows that battery 430 includes terminals 432 . fig8 , and 10 , all cross - sectional views , show respective four - capacitor assemblies , each illustrating a flexible capacitor - level approach to reducing the voids in implantable - device housings . in a mass - production context , the capacitor - level approach allows one to prefabricate a set of capacitors of different sizes , different curvatures , and even of different capacitor technologies , and then to assemble the capacitors to conform to the available space within a housing . in particular , fig8 a cross - sectional view , shows an exemplary capacitor assembly 800 . capacitor assembly 800 includes a monitor housing 810 and four separate capacitors 820 , 830 , 840 , and 850 . housing 810 includes curved portions 810 a , 810 b , 810 c , and 810 d . capacitors 820 , 830 , 840 , and 850 include respective capacitor cases 822 , 832 , 842 , and 852 , and respective terminals pairs 824 , 834 , 844 , and 854 . ( for clarity , the figure omits the internals of these capacitors .) cases 822 , 832 , 842 , and 852 have respective curved portions 822 a , 832 a , 842 a , and 852 a that are generally congruent to and confront respective curved portions 810 a , 810 b , 810 c , and 810 d of housing 810 . the cases also have respective widths ( or heights ) w 1 , w 2 , w 3 , and w 4 each of capacitors terminal pairs 824 , 834 , 844 , and 854 includes an anode terminal and a cathode terminal . though not shown , the exemplary embodiment interconnects the terminals to achieve a series connection of two capacitances . this exemplary embodiment provides the four capacitors with a common width . however , other embodiments provide one or more of the capacitors with a different width . for example , in some embodiments , widths w 1 and w 4 are equal , and widths w 2 and w 3 are equal , but different from widths w 1 and w 2 . additionally , two or more of the capacitors , for example , capacitors 820 and 830 or capacitors 820 and 830 , can be combined into a single capacitor . and , still other embodiments use different numbers of capacitors , such as three , five , or six . thus , the invention is not limited to an particular number of capacitors . fig9 a cross - sectional view , shows an exemplary capacitor assembly 900 . capacitor assembly 900 includes a monitor housing 910 and four separate capacitors 920 , 930 , 940 , and 950 . housing 910 includes curved portions 910 a and 910 b . capacitors 920 , 930 , 940 , and 950 include respective capacitor cases 922 , 932 , 942 , and 952 , which have respective widths ( or heights ) w 1 , w 2 , w 3 , and w 4 , and respective lengths l 1 , l 2 , l 3 , and l 4 . cases 922 and 932 have respective end walls 922 a and 932 a which confront curved portion 910 a ; and cases 942 and 952 have respective end walls that confront curved portion 910 b . in this exemplary embodiment , the capacitors lack individual curved profiles , but have different sizes to reduce voids between their respective cases and the monitor housing . more precisely , one or more of the capacitors has a different width and / or length . as shown , lengths l 1 and l 4 are equal to a length la , and lengths l 2 and l 3 are equal to a different length lb . also , widths w 2 and w 3 are equal to a width wa , and widths w 1 and w 4 are not equal to each other or to the width wa . however , in some embodiments , the capacitors have a common width . fig1 , a cross - sectional view , shows an exemplary capacitor assembly 1000 . capacitor assembly 1000 includes a monitor housing 1010 and four separate capacitors 1020 , 1030 , 1040 , and 1050 . housing 1010 includes curved portions 1010 a and 1010 b . capacitors 1020 , 1030 , 1040 , and 1050 include respective capacitor cases 1022 , 1032 , 1042 , and 1052 . cases 1022 , 1032 , 1042 , and 1052 have respective widths w 1 , w 2 , w 3 , and w 4 , and respective lengths l 1 , l 2 , l 3 , and l 4 . additionally , cases 1022 , 1032 , 1042 , and 1052 are offset from a common reference plane p by respective offsets o 1 , o 2 , o 3 , and o 4 . in this exemplary embodiment , widths w 1 , w 2 , w 3 , and w 4 are equal , and lengths l 1 , l 2 , l 3 , and l 4 are equal . further , offsets 01 and 04 are equal , and offsets o 2 and 03 are equal but larger than offsets o 1 and o 4 . in other embodiments , each of the offsets is larger than the previous offset , creating descending steps . in the exemplary embodiments of fig8 - 10 , the four capacitors are aluminum electrolytic capacitors , with each capacitor including one or more capacitor modules of similar or dissimilar structures ( as previously described for other exemplary capacitors .) however , other embodiments provide the four capacitors as wet - tantalum , ceramic , dry - film capacitors , or other types of capacitors . still other embodiments provide combinations of different numbers of capacitors and different types of capacitors . fig1 is a block diagram of implantable heart monitor 1100 which incorporates one or more teachings of the present invention . specifically , monitor 1100 includes a housing 1110 , lead system 1120 , which after implantation electrically contact strategic portions of a patient &# 39 ; s heart , a monitoring circuit 1130 for monitoring heart activity through one or more of the leads of lead system 1120 , and a therapy circuit 1140 . circuit 1140 includes a component 1142 which incorporates one or more capacitors , such as capacitors 100 and 300 , capacitor - battery assembly 400 , or one or more of capacitor assemblies 800 , 900 , or 1000 . monitor 1100 operates according to well known and understood principles to perform defibrillation , cardioversion , pacing , and / or other therapeutic functions . in addition to its application to implantable heart monitors , or cardiac rhythm management devices , the teachings of the present invention are applicable to photographic flash equipment . indeed , these teachings are pertinent to any application where small , high - energy capacitors are desirable . in furtherance of the art , the present inventors have devised several new capacitor structures having curved profiles and capacitor assemblies for reducing voids in implantable medical devices . the curved profiles generally facilitate efficient use of curved capacitor cases and curved housings for implantable medical devices . in some exemplary embodiments , the capacitors include staggered capacitor modules or elements to define the curved profiles , and in other embodiments , the capacitors themselves are staggered . the embodiments described above are intended only to illustrate and teach one or more ways of practicing or implementing the present invention , not to restrict its breadth or scope . the actual scope of the invention , which embraces all ways of practicing or implementing the teachings of the invention , is defined only by the following claims and their equivalents .
implantable heart - monitoring devices , such as defibrillators , pacemakers , and cardioverters , detect onset of abnormal heart rhythms and automatically apply corrective electrical therapy , specifically one or more bursts of electric charge , to abnormally beating hearts . critical parts in these devices include the capacitors that store and deliver the bursts of electric charge . some devices use flat aluminum electrolytic capacitors have cases with right - angle corners which leave gaps when placed against the rounded interior surfaces of typical device housings . these gaps and voids not only waste space , but ultimately force patients to endure implantable devices with larger housings than otherwise necessary . accordingly , the inventors devised several capacitor structures that have curved profiles conforming to the rounded interior surfaces of device housings . some exemplary capacitor embodiments include two or more staggered capacitor elements , and other embodiments stagger capacitors of different types and / or sizes .