Abstract:
A fuel cell unit incorporates a pair of plates; one plate an anode, the other a cathode. Respective anode and cathode plates are physically bonded together to form such pairs; wherein pluralities of the pairs are secured together to form commercially available fuel cells utilized to generate electric power. Material employed between respective pairs of plates are in the nature of resilient media arranged about selected areas of the plates to confine paths for fluids adapted to flow within said selected areas. A method of manufacturing such fuel cell units involves the injection of a rapidly curable liquid silicone material into aligned apertures of the respective plates, whereby liquid silicone material flows through and between the plates to a) seal between respective anode and cathode plates and to b) form an insulation layer on the backside of the anode.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 10/456,228, filed Jun. 6, 2003 which is a continuation of application Ser. No. 09/858,165, filed May 15, 2001, now U.S. Pat. No. 6,599,653, the entire contents of which are herein incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     The present invention relates to improved fuel cell assemblies for generating electric power, and more particularly to a method for providing resilient media between individual fuel cell plates and an insulation layer between fuel cell units. 
     BACKGROUND OF THE INVENTION 
     It is known to apply resilient sealing beads to and between the faces of fuel cell plates for controlling fluid flows between pluralities of such plates, stacked in pairs and bolted together for generating electric power. In a typical fuel cell stack arrangement, the pluralities of such plates are sandwiched together in a parallel, face-to-face pattern. The plates are held spaced apart by resilient sealing beads typically adhesively bonded to the face of at least one of any two adjoining plates. The sealing beads fit within grooves on the faces of the plates, and define paths or channels for fluids to flow between the plates. Normally, the fluids include not only fluid electrolytes used for generation of energy, but also coolants as will be appreciated by those skilled in the art. 
     The fuel cell plates employed in the usual fuel cell stack are normally formed of plastic composites that include graphite. The sealing beads are formed of an elastomeric material. The beads are normally adhesively applied to the plates by a bonding agent, although in some cases the beads are simply held in place by pressure of compression created by bolted connections between plates. Each fuel cell unit is comprised of a cathode and an anode plate. Between each cathode and anode plate of each cell flows a coolant material of either glycol-based anti-freeze or deionized water. Between each fuel cell unit flows two chemically reactive elements, hydrogen and oxygen, separated by a catalytic membrane. The hydrogen and oxygen elements react at the membrane to form water vapor in a type of reverse electrolysis. 
     The nature of the chemical reaction, along with a need for separation of the coolant from the reacting elements, occasionally requires that extreme or costly measures be taken to avoid leakage through or between the plates. Thus, an improved mechanism is needed to assure against leakage between adjacent fuel cell plates, one that is highly reliable, particularly in mass production manufacturing environments. 
     SUMMARY OF THE INVENTION 
     A fuel cell apparatus includes a plurality of individual fuel cell units, each including at least two facing, parallel plates, mated together. A resilient sealing media, preferably formed of an elastomeric material, is employed to seal the plates together. The sealing media may be applied in the form of a curable fluid sealing material, which after being cured in place, is adapted to facilitate control of fluid flows, such as coolants between the plates, and of electrolyte flows between fuel cells. Upon completion of manufacture, a plurality of such parallel, stacked plates that incorporate the present invention are separated by a plurality of discrete resilient sealing beads disposed over selective portions of the surfaces of the two facing plates. 
     The invention involves the manufacture of fuel cell units, each unit defined by a pair of plates comprising an anode and a cathode plate, in which the cathode plate and the anode plate are sealingly bonded together. Pluralities of such fuel cell units are stacked and secured together to form commercially available composite fuel cell structures utilized to generate electric power, either domestically (i.e. for home use) or for use in vehicles. 
     Specifically, an electrolytic fuel cell unit comprises at least a first plate and a second plate having opposing surfaces generally facing each other. The first and second plates each have at least one aperture substantially in registration with the other. The fuel cell unit further includes a first resilient media having a portion thereof disposed between the first and second plates. Further, a second resilient media is disposed on either the first or second plate. A portion of the second resilient media extends through the apertures to bond the plates together and compresses the portion of the first resilient media between the first and second plates. 
     The invention offers two alternative methods for manufacturing sealed pairs of fuel cell plates in a simple and efficient manner. The first method employed involves the injection of a curable liquid silicone into an aligned mold aperture of one of the mated plates, whereby liquid silicone flows via the apertures through the other plate, as well as between the plates in order to establish a seal between the plates. Moreover, the liquid silicone is injected into aligned apertures of cathode and anode plates, flows entirely through both plates, as well as between the plates, and forms an insulation layer on the backside of the bottom plate. In the preferred embodiment described herein, the bottom plate is the anode. Further, grooves on mating surfaces of the plates include at least one projection, whereby the projection is destroyed when the cured fuel cell plates are compressed in a mold. Accordingly, the cured liquid silicone between the plates is compressed to form a more effective seal. 
     The second alternative method of manufacturing sealed fuel cell plates includes first aligning a first plate, an anode, into a mold. Liquid silicone is injected through the aperture of the anode to dispose media on both surfaces of the anode. Media on one surface of the anode being an insulation layer. The liquid silicone disposed on the anode cures, then a second plate, or cathode is aligned in a mold such that second apertures of each plate are generally aligned. The plates are compressed and liquid silicone is injected through the second aperture. Media is disposed on outer surfaces of the first and second plates and within the aligned second apertures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a fuel cell unit according to a first embodiment of the type described in the present invention, including anode and cathode plates along with seals adapted for interposition between plates within grooves on the plate faces, and including an insulation layer on the backside of the anode. 
         FIG. 2  is a fragmentary cross-sectional view of an assembled molded and sealed fuel cell unit of  FIG. 1 , taken through an aperture at a corner of an assembled rectangular unit constructed in accordance with the present invention. 
         FIG. 3  is a perspective view of an anode plate including the presence of projections at the groove boundaries. 
         FIG. 4  is a cross-sectional view of the assembled molded and sealed fuel cell unit utilizing the anode plate shown in  FIG. 3  prior to applying additional pressure to remove the projections at the boundaries of the grooves. 
         FIG. 5  is a cross-sectional view of the assembled molded and sealed fuel cell unit under compression after applying additional pressure to remove the projections at the boundaries of the grooves as seen in  FIG. 4 . 
         FIG. 6  is a cross-sectional view of an assembled molded and sealed fuel cell unit of a second embodiment of the present invention. 
         FIG. 7  is a perspective view of the assembled molded and sealed fuel cell unit of the second embodiment of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 2 , an electrolytic fuel cell unit  10  is shown, which includes an anode plate  12  and a cathode plate  14 . Stacks of such fuel cell units  10  are assembled together to provide composite fuel cell structures (not shown) to generate electric power. In such a stack, an insulation layer  16  is interposed between each fuel cell unit  10 . 
     First and second resilient media  18 ,  20 , or gaskets, are interposed between each fuel cell unit  10 , as well as between each plate  12 ,  14 . Although the media  18 ,  20  are shown separately in  FIG. 1 , one embodiment of this invention provides a means by which the media  18 ,  20  are integrally connected in one single, contiguous mass of material as described below. In another embodiment of the invention, the insulation layer  16  is integrally formed with the first resilient media  18 . The insulation layer  16  is preferably and generally thicker than the media  18 ,  20  in both embodiments. 
     Each of the media  18 ,  20  is accommodated by a respective groove  22  in the cathode plate  14 , and a groove  23  in the anode plate  12 . The media  18 ,  20  are received in the grooves  22 ,  23  and are contiguous so as to define interior perimeters  32  and  34 , respectively, adapted to accommodate either a coolant or a fuel component. 
     In one embodiment of the invention, the grooves  23  of the anode  12  include projections  52  extending from the surface of the anode  12  as shown in  FIGS. 3 and 4 . The projections  52  are preferably formed of the same material as the anode  12 . The projections  52  increase the depth of grooves  23  to receive more resilient media  20 , thus forming a more efficient seal between the anode  12  and cathode  14  once the plates  12 ,  14  are compressed and the projections  52  are removed. Placing the projections  52  on one or both grooves  22 ,  23  of mating, parallel faces  13 ,  15  of the anode  12  and cathode  14  are contemplated by the present invention. The projections  52  are preferably positioned along the outer boundaries of the grooves  23 , as best seen in  FIG. 3 . 
     Referring now to  FIGS. 1 and 2 , fuel apertures  24  accommodate the admission and flow of hydrogen into the anode  12 . The anode  12  includes a series of grooves  46  for this purpose. Conversely, the cathode  14  includes a series of grooves  44 , which accommodate the admission and flow of oxygen. 
     Within the respective plates  12  and  14 , the fuel apertures  24 ,  25  are shown as  25   a  and  25   b , and  24   a  and  24   b , respectively. In the insulation layer  16  the fuel apertures  24 ,  25  are shown as  24   c  and  25   c . In the structures of the first and second resilient media  18  and  20 , fuel apertures for hydrogen are shown as fully circumferential apertures  26 A and  26 B, while fuel apertures for oxygen are depicted as fully circumferential apertures  28 A and  28 B. It will be noted that the respective oxygen and hydrogen apertures accommodate a cross flow over the plate reaction area  38 , to the extent that the apertures are diametrically opposed from each other within the rectangular plates  14  and  12 . 
     It will be appreciated by those skilled in the art that chemical reactions in the nature of a reverse electrolysis takes place within a fuel cell unit  10 . The reactions are created by the contact between the fuel components of oxygen and hydrogen, and enhanced by a catalytic membrane (not shown) positioned between adjacent stacked fuel cell units  10 . Thus, such reactions take place only between the fuel cell units  10 . Referring now particularly to  FIG. 2 , spaced areas between each of the mating, parallel faces  13  and  15  of each of the pairs of anodes  12  and cathodes  14 , respectively, are defined by inter-plate coolant grooves  42 . Primary fuel cell cooling thus takes place between each of the mated plates  12  and  14  of each fuel cell unit  10 . 
     Referring now particularly to  FIG. 1 , coolant ports  36  admit coolant into the coolant grooves  42  between the plates  12  and  14 . The ports  36  are shown respectively as  36   a  and  36   b  in the plates  14  and  12 , and as  36   c  in the insulation layer  16 . It is preferred that the coolant ports  36  are arranged to be medially located within the plates  12 ,  14  and substantially aligned with each other for optimal benefit, as those skilled in the art will fully appreciate. For this purpose, it will be noted that the resilient media  18  and  20  contain portions  30   a  and  30   b  designed as c-shaped portions to promote flows of coolant within their contiguous interior perimeter boundaries  32  and  34 , respectively. 
     One method of manufacturing the fuel cell unit  10  of the present invention will now be described. Referring specifically to  FIG. 2 , it will be noted that the respective resilient media  18 ,  20 , as well as the insulation layer  16  of  FIG. 1 , are all formed as a unitary, contiguous mass of material. This approach avoids the need to form separate insulation layer  16  and resilient media  18 ,  20  of  FIG. 1 , and thus reduces costs of manufacture. As earlier noted, the media  18 ,  20  and insulation layer  16  are preferably formed of an elastomeric material. For this purpose, a liquid silicone material may be injected under pressure through aligned apertures  48 ,  50 , which pass respectively through the anode  12  and the cathode  14 , as shown in  FIG. 2 . The apertures  48 ,  50  are preferably positioned within the grooves  22 ,  23  of the anode  12  and the cathode  14 , respectively, such that the silicon material can travel along and completely fill the grooves  22 ,  23 . 
     The respective anode and cathode plates  12 ,  14  are placed within a mold (not shown) with the anode  12  spaced from a floor of the mold. The mating parallel faces  13 ,  15  of the plates  12 ,  14  are maintained in a spaced relationship because of the projections  52 . Liquid silicone material is then forced through the apertures  48 ,  50  initially through the cathode  14  at a pressure of between about 300-700 lbs/in 2  which is sufficient to force the liquid silicone material through and between the plates  12 ,  14 , including the space between the bottom plate (anode  12 ) and the bottom or floor of the mold. Then the liquid silicone material is allowed to cure, typically within approximately two minutes at a temperature of between about 75-400 degrees Fahrenheit. 
     The cured fuel cell unit  10  is then transferred to a second mold (not shown). The second mold compresses the unit  10  at a pressure greater than the first mold. The greater pressure removes the projections  52  and presses the cathode  14  closer to the anode  12  as shown in  FIG. 5 . The resilient media  18  positioned between the plates  12 ,  14  is compressed to form a more effective seal as compared to conventional fuel cell units. 
     Referring to  FIGS. 6-7 , as an alternative to using projections  52  in the first method of the invention, a more effective seal may be generated by utilizing a two-step molding process. First, the anode  12  is placed in a mold (not shown) and liquid silicone material is injected through the aperture  48  and into the groove  23 . The liquid silicone material is disposed on both surfaces of the anode  12  to form the first resilient media  18  and the insulation layer  16 . Once the first resilient media  18  has cured, an aperture  54  formed in the cathode  14  is aligned in the mold (not shown) with an aperture  56  formed in the anode  12 . The apertures  54 ,  56  are preferably located outside the grooves  22 ,  23  and are generally larger in diameter than the apertures  48 ,  50 . Then, the cathode  14 , the anode  12  and the first resilient media  18  are compressed while liquid silicone material is again injected into the mold. The liquid silicone material is positioned on outer surfaces  58 ,  60  of the plates  12 ,  14  and within the second apertures  54 ,  56 . The liquid silicone material is allowed to cure to form the second resilient media  20  while the plates  12 ,  14  remain compressed to form a more effective seal with resilient media  18 . The temperatures and pressures of the two-step embodiment may be substantially identical as the temperatures and pressures of the first process described above. 
     Accordingly, each alternative method of manufacture produces a fuel cell unit  10  having a more effective seal than conventional fuel cell units because of the compression of the first resilient media  18  between the anode  12  and the cathode. 
     It is to be understood that the above description is intended to be illustrative and not limiting. Many embodiments will be apparent to those of skill in the art upon reading the above description. Therefore, the scope of the invention should be determined, not with reference to the above description, but instead with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.