Abstract:
A self-sealing flow frame is provided having a first frame component and a second frame component. Each frame component is provided with a tongue-and-groove configuration that when assembled forms a tessellation engagement, which creates the seal. When each frame component is assembled into a flow frame, with the inner surfaces facing towards each other, the tongue-and-groove arrangements create a seal profile that circumscribe constituent parts of a device within which the self-sealing flow frame is being employed. As the frame components are compressively secured and fastened together, a tessellation engagement of the seal profile forms the fluid seal. Fluids of the device are prevented from exfiltrating the device, and are contained within the self-sealing flow frame by the fluid seal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. Provisional Patent Application No. 62/030,712, filed on Jul. 30, 2014, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed generally towards a self-sealing framework for a fluid-containing apparatus and, more particularly, directed towards a self-sealing flow frame for a flow battery stack containing electrolyte fluids. 
     BACKGROUND OF THE INVENTION 
     A flow battery system is a rechargeable fuel cell exploiting the fluid dynamics, kinetics, and chemical potential properties of fluids containing electroactive elements (i.e., electrolytes) to convert chemical energy to electrical energy. The electrolytes typically comprise a catholyte fluid and an anolyte fluid, where each are stored in separate electrolyte tanks. At least one pump for each tank, directs the electrolytes from the electrolyte tanks and into a cell stack (comprising of one or more cells). The electrolytes come into contact with electrodes to generate electrical energy, which is typically stored in current collectors of the cell stack. A power source or load is placed into electrical communication with the cell(s) to selectively draw electrical power from the flow battery system. 
     Each cell typically comprises a positive electrode disposed on a first side of a membrane and a negative electrode disposed on a second side of a membrane. The membrane facilitates movement of the electroactive elements and the exchange of electric charges. A flow frame substantially encases the electrodes and membrane, and contains the electrolytes as they are directed into, and out from, the cell stack by the pump(s). The flow frame typically comprises two or more members that are configured to compress the cell components together, and are secured together via a fastener, fused together, or otherwise sealed. The flow frame creates a flow compartment within which the cell components are contained, and it is generally provided with inlets and outlets to facilitate fluid communication with a manifold that is in further fluid communication with the tanks. 
     In systems with multiple cells, a plurality of cells are arranged in electrical series, with each cell being separated by bipolar plates to facilitate passage of electricity while keeping the electrolytes inside. The bipolar plates create flow sub-compartments, such that each flow sub-compartment has opposite polarities and contains an electrode of a respective polarity. Monopolar plates are typically disposed at terminal ends of the stack, and the electrodes, monopolar plates, and bipolar plates are in electrical communication with the current collectors. 
     Performance of these flow battery systems is directly related to internal resistance, current transfer efficiency, the feed pressure of the pumps, and material degradation of the component parts. The electrolytes should generally exhibit high ionization and chemical kinetics and have a low viscosity. The electrodes generally should exhibit resistance to acid, have a high specific surface area, and be good electrical conductors. The membrane generally should enable ion transfer, but prevent, or at least inhibit, mixing of the electrolytes, and also exhibit consistent diffusion and electrical resistivity properties. The flow frame members generally should exhibit resistance to acid, maintain a steady compressive force upon the electrodes and membrane, and adequately contain the electrolytes as well as the component parts. 
     Prior art in this field consists of flow battery systems employing sealants and gaskets, such as rubber O-rings, disposed between the flow frame members to prevent leakage of the electrolyte from the cell. Use of separate seals in the flow battery system poses several problems. These seals tend to degrade, leading to a failure to contain electrolytes. The use of separate seals increases the number of parts comprising the flow battery system, which increases the probability of system failures and adds to manufacturing and maintenance costs. 
     The present invention is directed toward overcoming one or more of the above-identified problems. 
     SUMMARY OF THE INVENTION 
     The self-sealing flow frame for flow battery stack in accordance with the present invention includes a flow frame having a tongue-and-groove configuration that when assembled forms a tessellation engagement, which creates the seal. The flow frame comprises a first frame component and a second frame component. Each frame component is disposed on either ends of the constituent parts of the flow battery stack cell so as to sandwich the constituent parts. Each frame component comprises an end plate and two half-cell plates. The tongue-and-groove configuration is located on inner surfaces of each of the two half-cell plates. Each inner surface of each frame component faces the constituent parts of the flow battery stack cell, where the two half-cell plates of each frame component sandwich the electrodes. Each tongue-and-groove configuration comprises at least one channel and at least one tongue-protrusion that are molded into the inner surfaces of the half-cell plates. In assembly, the first frame component construction would be: a first half-cell plate lying adjacent the membrane; a second half-cell plate abutting the first half-cell plate while sandwiching the electrode; and, a first end plate lying adjacent the second half-cell plate. The same, yet mirrored, serial construction occurs on the other side of the membrane for the second frame component. As the first and second frame components are advanced towards each other and compress the constituent parts of the cell, the tongue-and-groove configurations of the half-cell plates engage, which creates an obstruction to fluid flow due to the tessellation of the engagement. 
     In a preferred embodiment, the self-sealing frame includes a first frame component having a first end plate with a plurality of first end plate fastening apertures, at least one first end plate inlet port, and at least one first end outlet port. The self-sealing frame further includes a first half-cell having a first half-cell inner surface, a first half-cell outer surface, at least one first half-cell inlet port, and at least one first half-cell outlet port. At least one first connector tab is disposed on an edge of the first half-cell. The self-sealing frame further includes a second half-cell having a second half-cell inner surface, a second half-cell outer surface, at least one second half-cell inlet port, and at least one second half-cell outlet port. 
     The first half-cell inner surface is provided with at least one channel or at least one tongue-protrusion, and the second half-cell inner surface is provided with at least one tongue-protrusion or at least one channel. Each channel and each tongue-protrusion is a contiguous concentric formation, such that profiles of each individual channel complement profiles of each individual tongue-protrusion so as to substantially align when the first half-cell inner surface is mated with the second half-cell inner surface to generate a first seal profile. 
     The first and second half-cells are further provided with half-cell fastening apertures disposed about a perimeter of each first and second half-cell, where each individual half-cell fastening aperture substantially aligns with an individual end plate fastening aperture when the first end plate is mated with said first and second half-cells. The first half-cell is provided with a first current collector aperture disposed in a central portion thereof and configured to contain, yet expose, an ancillary current collector on the first half-cell outer surface. 
     The self-sealing frame further includes a second frame component having a second end plate with a plurality of second end plate fastening apertures, at least one second end plate inlet port, and at least one second end outlet port. The self-sealing frame further includes a third half-cell having a third half-cell inner surface, a third half-cell outer surface, at least one third half-cell inlet port, and at least one third half-cell outlet port. At least one second connector tab is disposed on an edge of said third half-cell. The self-sealing frame further includes a fourth half-cell having a fourth half-cell inner surface, a fourth half-cell outer surface, at least one fourth half-cell inlet port, and at least one fourth half-cell outlet port. 
     The third half-cell inner surface is provided with at least one channel or at least one tongue-protrusion. The fourth half-cell inner surface is provided with at least one tongue-protrusion or at least one channel. Each channel and each tongue-protrusion is a contiguous concentric formation such that profiles of each individual channel complement profiles of each individual tongue-protrusion so as to substantially align when the third half-cell inner surface is mated with the fourth half-cell inner surface to generate a second seal profile. 
     The third and fourth half-cells are provided with half-cell fastening apertures disposed about a perimeter of each third and fourth half-cell, where each individual half-cell fastening aperture substantially aligns with an individual end plate fastening aperture when the second end plate is mated with the third and fourth half-cells. The third half-cell is provided with a second current collector aperture disposed in a central portion thereof and configured to contain, yet expose, an ancillary current collector on the third half-cell outer surface. 
     The first frame component and second frame component are configured to be placed in serial construction within a device having constituent parts and a fluid such that the first and second frame components sandwich the constituent parts and contain the fluid. The first and second seal profiles form a tessellation engagement with the constituent parts when the first and second frame components are compressively secured to each other. This tessellation engagement forms a fluid seal to prevent exfiltration or leakage of the fluid while the device is subject to positive pressure. Each of the inlet and outlet ports facilitate fluid communication with an ancillary manifold of the device. The first and second connector tabs facilitate electrical communication between the device and an ancillary load. 
     Other preferred embodiments include at least one of the first end plate and second end plate being planar. Some preferred embodiments provide for at least one of the half-cells to comprise polyphenylene sulfide or polyvinylidene fluoride. Of course, as will be appreciated by one skilled in the art, other materials having similar properties may be utilized. Another preferred embodiment has the seal profiles of each frame component configured to circumscribe the constituent parts of the device. 
     It is an object of the present invention to provide a flow frame for a flow battery stack having a first frame component and a second frame component, each having half-cells with a tongue-and-groove engagement arrangement. 
     It is a further object of the present invention to configure the tongue-and-groove arrangements to form a tessellation engagement when a first frame component and a second frame component are placed in serial construction with a device having constituent parts and a fluid. 
     It is a further object of the present invention to configure the tongue-and-groove arrangement to enable the tessellation engagement to create a fluid seal when the first frame component and second frame component are used to compress the constituent parts, such that the first and second frame components sandwich the constituent parts and contain the fluid of the device even when that device is subject to a positive pressure, thereby eliminating the need for O-rings, gaskets, or other sealing devices and sealants. 
     It is a further object of the present invention to provide a current collector aperture within at least one frame component to contain, yet expose, a current collector. 
     It is a further object of the present invention to provide at least one inlet port and at least one outlet port within at least one of the first frame component and second frame component to facilitate fluid communication with a manifold of the device. 
     It is a further object of the present invention to provide a least one of the first frame component and second frame component with at least one connector tab to facilitate electrical communication between the device and an ancillary load. 
     It is a further object of the present invention to provide fastening apertures such that torqueing fasteners applied through the fastening apertures enables the tessellation engagement to form an adequate and continuous seal about the perimeter of the seal profile. 
     Further features, aspects, objects, advantages, and possible applications of the present invention will become apparent from a study of the exemplary embodiments and examples described below, in combination with the Figures, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, aspects, features, advantages and possible applications of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings, in which: 
         FIG. 1  is a perspective view of the self-sealing flow frame of the present invention separated into its component parts; 
         FIG. 2  is a perspective side view of the self-sealing flow frame of the present invention showing the parts in assemblage; 
         FIG. 3  is a perspective front view of the self-sealing flow frame of the present invention showing the parts in assemblage; 
         FIG. 4A  illustrates a cross-sectional side view of the self-sealing flow frame of the present invention showing the parts in assemblage within a flow battery stack system; 
         FIG. 4B  illustrates an exploded partial cross-sectional side view of the self-sealing flow frame of the present invention showing the parts in assemblage within a flow battery stack system; 
         FIG. 4C  illustrates perspective views of a first half-cell and a first end plate of the present invention; 
         FIG. 5  is another exploded partial cross-sectional side view of the self-sealing flow frame of the present invention showing the parts in assemblage within a flow battery stack system; and, 
         FIG. 6  is a schematic the self-sealing flow frame of the present invention being used with a typical flow battery stack system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of an embodiment presently contemplated for carrying out the present invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles and features of the present invention. The scope of the present invention should be determined with reference to the claims. 
     Referring now to  FIGS. 1-6 , views of the self-sealing flow frame  10  separated into its component parts and in assemblage, in accordance with a preferred embodiment, are disclosed. The self-sealing flow frame  10  is a framework that is intended to be used within a flow battery stack  11  (see  FIG. 5 ); however, the self-sealing flow frame  10  is certainly not limited to such application. The self-sealing flow frame  10  exploits a tongue-and-groove configuration when sandwiching and compressing component parts of a device to contain fluids within that device without the need for separate and additional seals or gaskets; therefore, it can be appreciated that the self-sealing flow frame  10  can be used for analogous applications. The description of the self-sealing flow frame  10  will be as it is applied to a flow battery stack  11 , but this description is for exemplary purposes and is not intended to limit the use thereto. 
     The self-sealing flow frame  10  includes a first frame component  20   a  and a second frame component  20   b . The second frame component  20   b  is identical, or in some cases mirrored, to the first frame component  20   a , so for the sake of brevity and ease of illustration only one frame component  20   a ,  20   b  may be described in detail with the understanding that the other is identical or mirrored. The first frame component  20   a  comprises a first end plate  30   a , a first half-cell  40   a , and a second half-cell  50   a . Similarly, the second frame component  20   b  comprises a second end plate  30   b , and two half-cells  40   b ,  50   b . Each end plate  30   a ,  30   b  is a planar, rectangular member that is, in one exemplary embodiment, approximately twenty-four inches in width, eighteen inches in height, and one-fourth inches in depth; however, other shapes and dimensions may be utilized without deviating from the teachings of the self-sealing flow frame  10 . Each end plate  30   a ,  30   b  is configured to contain the half-cells  40   a ,  40   b ,  50   a ,  50   b  and constituent parts of the battery cell  11  in assemblage, and to facilitate flow of electrolyte into, and out from, the battery cell  11 . In this regard, each end plate  30   a ,  30   b  is provided with a plurality of end plate fastening apertures  60 , which are configured to receive fasteners, such as bolts, so that torqueing the fasteners advances each end plate  30   a ,  30   b  towards each other when the end plates  30   a ,  30   b  are disposed on either ends of the constituent parts of the flow battery stack cell  11 , thereby sandwiching the constituent parts. Each end plate  30   a ,  30   b  is further provided with end plate inlet ports  70  and end plate outlet ports  80  to facilitate fluid communication to a manifold of the flow battery system  11 . 
     Each half-cell  40   a ,  40   b ,  50   a ,  50   b  has an inner surface  41   a ,  51   a  and an outer surface  41   b ,  51   b . A plurality of half-cell fastening apertures  90  are disposed about the perimeter of the each half-cell  40   a ,  40   b ,  50   a ,  50   b , which are in alignment with the end plate fastening apertures  60  to facilitate securement of the first and second frame components  20   a ,  20   b  to each other via fasteners, such as bolts. Each half-cell  40   a ,  40   b ,  50   a ,  50   b  comprises a material that is non-reactive, acid resistant, and resilient, such as, for example, polyphenylene sulfide or polyvinylidene fluoride. The non-reactiveness is necessitated by the requirement to obviate repugnancy in chemical ionization reactions. The acid resistance is necessitated by the requirement to prevent material degradation due to contact with electrolytes. The resilient property is necessitated by the requirement to generate a seal between the first half-cells  40   a ,  40   b  and second half-cells  50   a ,  50   b  when under compressive forces; therefore, the frame components  20   a ,  20   b  must be able to be subjected to compressive forces without plastic deformation. 
     Referring now to  FIGS. 4A, 4B, 4C, 5, and 6 , views of the self-sealing flow frame  10  showing the parts in assemblage within a flow battery stack system  11 , in accordance with a preferred embodiment, are disclosed. Each first half-cell  40   a ,  40   b  is provided with at least one channel  100 , and each second half-cell  50   a ,  50   b  is provided with at least one tongue-protrusion  110 . It is understood that the channel  100  can be provided on each second half-cell  50   a ,  50   b  and tongue-protrusion  110  on each first half-cell  40   a ,  40   b  without deviating from the teachings of the self-sealing flow frame  10 . Each channel  100  is a contiguous concentric formation on the inner surface  41   a ,  51   a , and each tongue-protrusion  110  is similarly a contiguous concentric formation on the inner surface  41   a ,  51   a . The profiles of the channel(s)  100  and tongue-protrusion(s)  110  complement each other so that they align when a first half-cell  40   a ,  40   b  is mated with a second half-cell  50   a ,  50   b.    
     When mated, each individual channel  100  engages with each individual tongue-protrusion  110  to produce a contiguous seal profile  120  that circumscribes constituent parts (at least one electrode and a membrane) of a flow battery stack system  11 . In use, the first half-cell  40   a ,  40   b  and second half-cell  50   a ,  50   b  sandwich the electrode  15   a ,  15   b  within the contiguous seal profile. When the first frame component  20   a  is advanced towards the second frame component  20   b  to compress the constituent parts of the flow battery system  11 , the channels  100  engage the tongue-protrusions  110  while sandwiching the electrodes within the seal profiles  120 . Each channel  100  and tongue-protrusion  110  engagement creates a tessellation engagement that seals the electrolyte fluid  17   a ,  17   b  within the flow compartment  16  (see  FIG. 6 ). The compression of the frame components  20   a ,  20   b , along with the tessellation engagement, create a fluid barrier that prevents electrolyte fluid  17   a ,  17   b  from escaping the cell stack  11  even during operation when the cell stack  11  is under positive pressure from the pumps  19   a ,  19   b . The flow frame  10  seals by merely being assembled, and obviates the need for separate seals and gaskets. 
     The spacing of fastening apertures  60 ,  90  relative to the seal profile  120  and the number of fastening apertures  60 ,  90  must be such that torqueing the fasteners will enable the tessellation engagement to form an adequate and continuous seal about the perimeter of the seal profile  120 . 
     Referring now to  FIG. 6 , a schematic the self-sealing flow frame  10  being used with a typical flow battery stack system  11 , in accordance with the preferred embodiment, is disclosed.  FIG. 6  illustrates a typical flow battery cell stack architecture  11  arranged with the self-sealing flow frame  10 . This battery cell stack architecture  11  is common and well known in the art, and is used as an example to illustrate the utilization of the self-sealing flow frame  10 . It is understood that one skilled in the art would easily and without undue experimentation apply the self-sealing flow frame  10  to any variety of battery cell stack architectures  11 . 
     A simple battery cell stack architecture  11  comprises a membrane  14  with a positive electrode  15   a  disposed on one side of the membrane  14  and a negative electrode  15   b  disposed on the opposite side of the membrane  14 . The first frame component  20   a  is shown here being placed adjacent to the negative electrode  15   b  while the second frame component  20   b  is placed adjacent to the positive electrode  15   a ; however, other configurations may be utilized. When assembled, the flow frame  10  creates a flow compartment  16 . A catholyte fluid  17   a  is contained within the catholyte tank  18   a , which is in fluid communication with each negative electrode  15   b  via a catholyte pump  19   a . An anolyte fluid  17   b  is contained within the anolyte tank  18   b , which is in fluid communication with each positive electrode  15   a  via an anolyte pump  19   b.    
     Referring now back to  FIGS. 1, 4C, and 5  in an alternative embodiment, a current collector aperture  130  is disposed in a central portion of at least one of the first half-cells  40   a ,  40   b  to facilitate containing, yet exposing, a current collector  12  of the flow battery stack  11 . In this embodiment, the least one channel  100  and/or tongue-protrusion  110  is formed into the inner surface  41   a ,  51   a  concentrically with the current collector aperture  130  so that the at least one channel  100  and/or tongue-protrusion  110  circumscribes the current collector  12  when the self-sealing flow frame  10  is assembled. The current collector aperture  130  is preferably configured to retain the current collector  12  on the outer surface  41   b ,  51   b  of the first half-cell  40   a ,  40   b.    
     In an alternative embodiment, at least one half-cell inlet port  140   a  and at least one half-cell outlet port  140   b  are disposed in at least one of the first half-cells  40   a ,  40   b  and second half-cells  5   a ,  50   b  to facilitate fluid communication with a manifold of the flow battery stack system  11 . Each individual half-cell inlet port  140   a  is configured to fluidly communicate with an individual end plate inlet port  70 , and each individual half-cell outlet port  140   b  is configured to fluidly communicate with an individual end plate outlet port  80 . 
     In an alternative embodiment, at least one connector tab  150   a ,  150   b  is disposed on a first half-cell  40   a ,  40   b  (see  FIG. 3 ). Each connector tab  150   a ,  150   b  is configured to extend from an edge of the first half-cell  40   a ,  40   b  so as to protrude from edges of the first and second frame components  20   a ,  20   b  when the self-sealing flow frame  10  is assembled. Each connector tab  150   a ,  150   b  is further configured to enable transmission of electrical energy between the load and battery cell  11 . As the first frame component  20   a  is shown encasing the negative electrode  15   b  and the second frame component  20   b  is encasing the positive electrode  15   a , the tab connector  150   a ,  150   b  of the first half-cell  40   a  of the first frame component  20   a  would be the negative connector tab  150   a  and the that of the second frame component  20   b  would be the positive connector tab  150   b.    
     Additional serial construction configurations may be employed without deviating from the teachings of the self-sealing flow frame  10 , such as but not limited to, providing bipolar plates (not shown) between each end plate  30   a ,  30   b  and each first half-cell  40   a ,  40   b . Additional membranes (not shown) may be included between the first and second half-cells  40   a ,  40   b ,  50   a ,  50   b.    
     It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range.