METHOD OF SEALING ABUTTING FUEL CELL PLATES BY MEANS OF A POLYTETRAFLUORETHYLENE SPIRAL

Abstract: Sealing of fluid passages defined by first and second surfaces of first and second fuel cell plates is realized by applying teflon material in spiral form to pre-selected re­ gions of at least one of the first and second surfaces.

Description: FUEL CELL METHOD USING PTFE SPIRAL Background of the Invention This invention relates to fuel cells and fuel cell components and, in particular, to a method of fabrication of same so as to retard gas and liquid leakage. In fuel cell constructions, it is sometimes the case that abutting surfaces of adjacent plates are utilized to define fluid (liquid or gas) passages for the cell. One such situation is described in copending application Serial No. 338,354 = Eurapean#app1n. xb. 83 100 127.8 wherein first and second plates of adjacent first and second fuel cell subvassemblies each define a section of a fuel cell cooler. In particular, the first plate has channels which open out of a first surface of the plate and a second surface of the second plate is abutted against this channeled first surface during stacking. This closes the channels and the two plates thereby together define closed passages for carrying a cooling fluid. In order for the first and second plates to properly define these closed passage, it is essential that pre-selected regions i.e., those bordering the outermost channels, of the first and second sufaces, be sealed against fluid leakage. This may be accomplished by applying a sealing material to the pre-selected regions of one or the other or both of the surfaces. Previously, such sealing material has been applied by placing a flat, thin piece of polytetrafluoroethylene (teflon) in these regions. H:wever, application of teflon in this manner has not been found to be entirely satisfactory, since the flat teflon has little resiliency and may not conform to the irregularities of the abutting surfaces leaving minute gaps for fluid leakage. It is therefore an object of the present invention to provide a method of applying teflon material to pre-selected regions of abutting first and second surfaces of adjacent fuel cell plates in a manner to create a better fluid sealing effect. Suflary of the Invention In accordance with the principles of the present invention, the above and other objectives are realized by applying the teflon material formed into a spiral to the pre-selected regions of the first surface of the first plate. When the second surface of the second plate is then abutted against the first surface of the first plate, a highly effective fluid seal brought about by the spiral form of the teflon is found to result in the pre-selected regions of the first surface and the corresponding abutting regions of the second surface. Brief Description of the Drawing The above and other features and aspects of the present invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings, in which: Fig. 1 shows a channeled fuel cell plate to which teflon material in the form of a spiral has been applied; Figs. 2 and 3 show the fuel cell plate I in abutting relationship to a similar channeled plate and to a flat plate, respectively; and Fig. 4 illustrates a method for creating the teflon spiral used on the plate of Fig. l. Detailed Description In Fig. 1, 11 is a fuel cell plate having channels 12 opening out of a first surface 13 of the plate. The plate 11 isto be used in conjunction with a second plate having a second surface which is to abut the surface 13 to thereby define closed passages for carrying a fluid. In Fig. 2, the second plate 21 is similar to the plate 11 in that it has channels 22 opening out of a second surface 23. These channels align with the channels 12 of the plate 11 to define the closed fluid channels 32 of the composite assembly 31. In one type of fuel cell construction, the plates 11 and 21 might be the two halves of a fuel cell cooler. Furthermore, these plates might be carried at the ends of fuel cell sub-assemblies which are stacked to thereby define the cooler as disclosed in the above-mentioned copending application. In any case, when the plates 11 and 21 are placed in abutting relationship, it is important that the fluid flowing in the closed passages pass through and not leak out of the sides 33 of the assembly. In accordance with the invention, such leakage is retarded by applying a teflon seal of paticular configuration to pre-selected regions of the abutting surface of at least one of the plates 11 and 21. More particularly, as shown in Fig. 1, teflon material 41 arranged in spiral configuration is applied to regions 14 and 15 of the surface 13, such regions bordering the outermost of the channels 12. With the teflon spirals 41 applied as aforesaid, a very effective seal is found to result when the regions 14 and 15 are abutted against the corresponding regions 24 and 25 of the surface 23 of the plate 21. It is believed that the spiral configuration of the teflon adds resiliency to the teflon so that when it is squeezed between corresponding abutting surface regions 14 and 24 and 15 and 25, it is able to adapt to the surface irregularities of each of these regions. As a result, the likelihood of through gaps for the escape of fluid is significantly reduced and an overall more effective seal is realized. The spiral form of teflon used in Figs. 1 and 2 can be realized as shown diagramatically in Fig. 4 by rotating a conventional thin flat piece or strip of teflon 51 at one end 52, while holding the other end 53 stationary. Typically, a piece of teflon of thickness .003 inches and width 0.5 inches may be rotated to provide a spiral form which will have a thickness of .06 inches and width of .06 inches. The initial strip of teflon may be teflon commercially sold by Dupont under the product name Teflon PTFE. The teflon spiral 41 when applied to the regions 14 and 15 may be tacked or adhered to the surfaces at points along the regions 14 and 15 if desired. This may be realized by placement of a glue such as, for example, pLV-2000 HS Viton Cement, at selected positions such as 14', 14" and 14" and 15', 151 and 15"', as shown in Fig. 1. Also, it should be noted that the plate 21 need not have channels 22 in its surface 23, but instead the surface 23 might be flat as shown in Fig. 3. In such case, the channels 12 may be deeper to provide the same passages as provided by the two channeled plates. In all cases, it is understood that the abovedescribed arrangements are merely illustrative of the many possible specific embodiments which represent applications of the present invention. Numerous and varied other arrangements can readily be devised without departing from the spirit and scope of the invention. Thus, for example, instead of applying the teflon in spiral form to the surfaces 14 and 15 it could have been applied to the surfaces 24 and 25. Also it could have been applied both to surfaces 14 and 15 and surfaces 24 and 25.

Claims: What is Claimed Is 1. A method for use with first and second fuel cell plates, said plates having first and second surfaces to be placed in abutting relationship to define a fuel cell assembly, said surfaces when in abutting relationship defining passages for carrying fluid and said surfaces having pre-selected regions which when said surfaces are in abutting relationship abut to provide a seal to retard leakage of fluid from said passages, the method comprising: prior to abutting said surfaces, applying polytetrafluzxe ettqleae material in the form of a spiral to the pre selected regions of at least one of said first and second surfaces. 2. A method in accordance with claim 1 further comprising: abutting said first and second surfaces 3. A method in accordance with claim 1 wherein: said step of applying includes applying said spiral polyb* > a- fl'#o#1ene material to said pre-selected regions of said first and second surfaces 4. A method in accordance with claim 1 wherein: said first plate has channels running therethrough and opening out of said first surface; and said pre-selected regions of said first surface border the outermost of said channels 5. A method in accordance with claim 4 wherein: the pre-selected regions of said second surface border said channels when said first and second surfaces are in abutting relationship. 6. A method in accordance with claim 5 wherein: said second surface is flat 7. A method in accordance with claim 5 wherein said second surface has channels running there through which align with the channels of the first surface when the first and second surfaces are in abutting relationship. 9. A method in accordance with claim 1 further comprising: applying adhesive to selected positions of said pre-selected regions of said one surface for securing said spiral polytetrafluoroethylene material to said surface. 9. A method in accordance with claim 1 further comprising: prior to applying said spiral polytetrafluoroethylene material, forming said spiral polytetrafluoroethylene material including: securing a flat strip of polytetra fluoroethylene material at one end and rotating the other end of said strip of polytetrafluoroethylene material with said end secured. 10. The fuel cell assembly made by the method of claim 2.

Inventors: CHI, CHANG VUM
Applicants: ENERGY RESEARCH CORPORATION
Application year: 1984
Main classification: H01M8
IPC codes: H01M8