Patent Practice and Procedure
IPSE '97
Final Exam


INSTRUCTIONS: This is an open book examination. You mayuse the MPEP, your class materials, and other materialsyou think might be helpful except you may NOT use priorPTO Registration Exams andlor answers. Your exam numberand/orSection Teacher's name should be placed on your bluebook.

Draft FOUR (4) CLAIMS: a single independent claim and asingle dependent claim to the electrochemical cell, andsingle independent claim and a single dependent claim tothe method of making the electrochemical cell. Theindependent article claim must be the broadest claim foran electrochemical cell which includes all criticallimitations necessary for the cell to function and whichis not anticipated by the disclosed prior art. Thedependent article claim should cover an electrochemicalcell having the cathode collector with the preferredporosity. The independent method claim must be thebroadest claim which includes all necessary steps to forma closed electrochemical cell containing an electrolytesolution and which is not anticipated by the prior artmethod. The dependent method claim should cover the stepsfor forming the cathode collector having the preferredporosity. The independent claims are worth 25 points each,and each dependent claim is worth 12.5 points.

You may not be your own lexicographer to name theelements of the disclosed invention. You must use theterminology set forth in the Provisional PatentApplication. No credit will be given for a Jepson typeclaim. Points will. be deducted for: claiming subjectmatter not within the scope of the Provisional PatentApplication; using claim language which is vague andindefinite; using claim language which does not haveantecedent basis; failing to positively recite elements andinterrelate elements in the article claim; claimingunnecessary limitations; presenting 1'a claim that defines aninoperative invention or is anticipated by the prior art;misspelled words and poor grammar; and failing to followthese directions.

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You have successfully completed your first assignment atMarkman Hilton Davis. Now the senior partner has asked youto prepare another set of claims. This time, however, aprovisional patent application has been filed on July 17,1996 under 37 CFR 1.53(b)(2). Until this morning, theinventors have failed to answer your numerous letters andtelephone calls reminding them that the formal patentapplication must be filed today.

The senior partner has handed you the followingProvisional Patent Application including a description ofprior art, a description of the invention and drawings.The application discloses an electrochemical cell (i.e. abattery) and a method of making the electrochemical cell.

ELECTROCHEMICAL CELL AND METHOD OF MAKING SAME

Description of the Prior Art

A prior art electrochemical cell is manufactured byBattery Corporation according to a process that involvesusing a flat "U" shaped spring with two legs, as shown inFIGS. 1 and 2.

The electrochemical cell includes a cylindricalcontainer 2 that is electrically conductive. The container must be made of metal and is preferably stainless steel orany corrosion resistant nickel alloy. A porous cathodiccollector 4 is formed before tubular separator 6 isinserted into the cell. A fine powder of acetylene black(carbon) and TEFLON (trademark forpolytetrafluoroethylene) is molded into two halfcylindrical annular members. The annular members areinserted into the container and heated for 30 minutes at370OF to expand the members so that they become. lockedfirmly in the container. Separator 6 is made of non-woven glass fibers, which is inserted into container 2 and is insurface contact with the cathode collector material. Thebottom end 8 of the separator 6 is radially foldedinwardly, supporting a bottom separator 10.

The cell further includes two half -cylindrical anodemembers 14 and 20 made of lithium having flat end surfaces16, 18, 22, and 24. Both half -cylindrical anode memberscollectively form the anode of the cell. A flat "U" shapedspring member 28 with legs 32 and 34 was compressed andinserted into the axial opening 26 defined by the anodemembers. When the compressive force on the spring memberis released, the anode is mechanically biased radiallyoutward thereby imparting a good physical contact betweenthe anode, separator and cathode collector of the cell.Electrically conductive backing screens 15 and 17 arenecessary to provide a substantially uniform andcontinuous pressure contact over the inner wall of theanode members. An extended leg 30 of the spring member 28is projected through a central opening 38 in insulatingdisc 36 and then welded to a two part stainless steelcover consisting of elements 40 and 42 which are welded toeach other.

Before sealing the cover to the container, the voids inthe container must be filled with a conventionalelectrolyte solution consisting of LiALCL4 (lithiumaluminum tetrachloride) and S02C12 (thionyl chloride). Theelectrolyte solution must permeate through the anode,separator and cathode collector of the cell. The separatormaterial must have a porosity of at least 25%, preferablyabout 45%, so as to permit -the electrolyte to permeatethrough and contact the anode, thus establishing aniontransfer path between the anode member and the cathodecollector material. The insulating disc 36 has aperipheral depending skirt 44 disposed between cover 40and the upper inner wall of the container 2 for sealingthe cell through a conventional crimping technique.

The reason for mechanically biasing the anode is toprevent an increase in the internal resistance in thecell. If the cell is assembled without biasing the anode,initially there is good contact between the anode,separator and cathode collector. However, as the celldischarges, the contact between these components decreasesas the anode material is dissolved and electrochemicallyreacts with the cathode collector material. The reactionresults in a decrease in the volume of the anode and anincrease of the internal resistance in the cell. Bymembers are being consumedbiasing the anode, as the anode members during discharge,the spring exerts a force against the anode therebymaintaining good physical and ionic contact between theanode members, separator, and the cathode collector of thecell.

In the prior art cell, there have been difficultiesinserting the spring member into the axial cavity of thecell. The "U" shaped spring member was difficult tocompress and insert in the cell without damaging the anodemembers.


Brief Description of the Drawings

FIG. 1 is a cross-sectional view of an electrochemical cellaccording to the prior art;

FIG. 2 is a cross-sectional view of FIG. 1 along section 22;

FIGS. 4 and 5 are perspective views of the method of formingthe cylindrical spring according to the present invention;

FIG. 6 is a top view of the electrochemical cell accordingto the present invention; and

FIG. 7 is a perspective view of the electrochemical cellaccording to the present invention.


Description of the Invention

The present invention includes a method of making a cellsimilar to the prior art except that the present inventionuses a cylindrical spring on which a sheet of anodematerial (lithium) is wrapped before the spring isinserted into the axial cavity in the cell. The usefullife and the total energy output from the cell areincreased because the anode surface area in contact withthe separator is increased.

The cell, FIG. 6, includes metal container 21, porouscathode collector 4', and tubular separator 61. Thecontainer and the cathode collector form a first terminalfor the cell. The porous cathode collector 41 must have aporosity of at least 25% to permit permeation of theelectrolyte solution. According to a preferred method ofmaking the porous cathode collector, a fine powderconsisting of carbon (acetylene black) and TEFLON is used tomold two half cylindrical annular members. The annularmembers are inserted into the metal container 2' andheated for exactly 2 minutes at 360 deg. F and then at 390deg. F -for exactly 12 minutes. The heating expands theannular members so that a single porous cathode collector41' is formed which is firmly locked in contact with thecontainer2'. This preferred method of making the two halfcylindrical annular members increases the porosity of theporous cathode collector to more than 65%, resulting in alonger battery life.

A rectangular sheet of stainless steel is used for spring9. The thickness of the spring is not critical. The sheetis formed, for example, by cutting or stamping, to fitwhatever size cell is being assembled. The two opposingends of the sheet are bent to form flanges 11, 13 as shownin FIG. 4. A split mandrel 5, FIGS. 4 and 5, is used toinsert the spring into the axial cavity 33 of the cell.The length of the flanges from the bend to the end is thesame as the depth of the slot 17 of the mandrel. One ofthe flanges is inserted into slot 17 of the mandrel andthe mandrel is rolled along the sheet until the secondflange is reached and also inserted into slot 17. Thecompressed sheet of spring material forms a compressedlongitudinally split cylindrical shaped spring. The mutualpressure exerted by the opposing flanges facing each otherkeeps the spring from uncoiling.

After the spring material is wrapped about the mandrel, asheet of lithium metal 19 is wrapped about the compressedspring, in a way which is mechanically similar to wrappingaluminum foil wrap around an object, as shown in FIGS. 4and 5. The lithium metal forms the anode element of thecell. Opposing edges 21, 23 of the lithium sheet arealigned with the bend edges of flanges 11, 13 so that thelithium sheet will not. be stretched when the spring isreleased.

The mandrel is inserted into the axial cavity 33 of thecontainer 21. A plastic push rod, not illustrated in thedrawings, is used in the slot 17 to push flanges 11, 13while the mandrel is extracted from the axial cavity ofthe cell to release the spring and anode assembly. Thereleased spring presses the anode 19 radially outwardsagainst the separator 61. Because there is only one slotin the anode in this assembly, more anode material can beinserted into the cell and the surface area in contactwith the separator 61 is significantly larger than withthe prior art cell and method, thus providing a cell withlonger useful life. Forming the compressed spring,wrapping the anode material over the spring, and insertingand releasing the spring in the axial cavity of _thecontainerare essential steps in making a cell having the advantagesof the present invention.

A conductive lead 29, FIG. 7, of nickel can befastened to either one of flanges 11, 13. Lead 29 is thenwelded at 35 to a suitable metal cover 37. The metal coveris used to close the container 21 using an insulating discin the same manner as disc 36 in the prior art. The anode19, spring 9, conductive lead 29 and cover 37 form thesecond terminal of the cell. Prior to closing, anelectrolyte solution, such as that disclosed in the priorart, is added to the container.

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EXTRA CREDIT (1 point each - Answer in Blue Book):

1.	In addition to the claims, what item was not requiredto be filed with the provisional patent application under37 CFR 1.53(b) (2), but must now be filed with a formalapplication under 37 CFR 1.53(b)(1)?
2.	(True/False) Designing around claims in U.S. Patents toavoid infringement is contrary to the constitutionalpurpose of the U.S. patent system.
3.	(True/False) Functional language in a claim is per seindefinite under 35 U.S.C. 112, second paragraph.
4.	When responding to a restriction requirement, what onething MUST the applicant do?
5.	(True/False) In responding to a rejection under 35U.S.C. 103, the burden is initially on the applicant toshow that the invention accomplishes unexpected results?
6.	State briefly (1 sentence) what a patent examiner mustshow to reject a claim as anticipated under 35 U.S.C. 102.
7.	Name one of the Patents of the Week from PatentPractice and Procedure.