Interconnect apparatus for fuel cells

A fuel delivery system for a fuel cell (400) includes a substrate (404) having a cavity (402) formed therein, an o-ring (408) embedded within the cavity, and a detachable tube (410) inserted though and retained within the o-ring. The tube (408), when inserted through the o-ring (408), forces the o-ring to expand and fill the cavity (402) thereby forming a liquid tight seal for the transfer of liquid (414) to a fuel cell chamber (416).

FIELD OF THE INVENTION

This invention relates generally to interconnect devices and more specifically to interconnect devices used for the transfer of liquids in fuel cell assemblies.

BACKGROUND OF THE INVENTION

Current technology for supplying liquid to a ceramic or laminate fuel cell device includes using epoxy to permanently glue tubes onto the ceramic substrate. Flexible tubing is then slid over the epoxied tubes to connect the liquid source to the ceramic. The traditional epoxy approach does not allow for changing tubes and can present alignment difficulties when changing out fuel cartridges. There also exists the potential for the tubes to get filled with epoxy, thereby preventing liquid from flowing through the tubes.

Prior art microfluidic interconnect approaches have included the use of thermoplastic tubing to make a flanged self-aligned interconnect. However, the use of thermoplastics requires several processing steps including heating and melting to create a seal. Other prior art approaches include the use of a patterned ferrule having a molded ring used in conjunction with a matching patterned tube to create a seal. However, the ferrule approach requires the use of several pieces including an additional substrate.

The interconnect approaches described above, as well as other traditional approaches, have issues with chemical compatibility, sealing, assembly difficulties, permanency, and lack of interchangeable parts.

Accordingly, a need exists for a simplified apparatus that provides the ability to connect and disconnect a fuel storage cartridge to a fuel cell. A system that could overcome the disadvantages associated with traditional interconnect approaches would be a great benefit to miniature fuel cell systems.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now toFIG. 1there is shown, in cross section, a microfluidic interconnect apparatus for a fuel cell in accordance with a first embodiment of the present invention. Interconnect apparatus100is formed as part of the fuel cell and includes a substrate102having a cavity104formed therein. In accordance with the present invention, embedded and retained within the cavity104is an o-ring106. A detachable tube108is slideably inserted through the o-ring106. Upon insertion of the tube108through the o-ring106, the o-ring expands filling the cavity104and forming a liquid tight seal for the transfer of liquid116to a fuel cell chamber118.

Tube108is preferably a substantially rigid tube formed of metal, plastic, or other suitably rigid material. Tube108provides for the transfer of liquid116to the fuel cell chamber118. Substrate102is preferably a ceramic substrate or laminate substrate, and in accordance with the first embodiment, includes first and second openings110,112respectively, for accessing the cavity104. A third opening114is aligned below the first opening110to provide access to the fuel cell chamber118. First and third openings110,114are preferably formed by multi-layer low temperature co-fired ceramic technology (ML LTCC). The second opening112, formed within substrate102, is preferably formed using the same technique. Alternatively, the openings104can also be formed by drilling or etching through portions of the substrate102. The cavity104is also preferably formed by multi-layer low temperature co-fired ceramic technology (ML LTCC). Alternatively, the cavity104can be formed by drilling or etching away an inner portion of the substrate102suitable in size for retaining the o-ring. The second opening112and cavity104are configured and dimensioned such that the o-ring106is capable of being pushed through the second opening and retained within the cavity. Once inserted into the cavity104, the o-ring106is properly aligned with the first and third openings110,114. The first opening110allows insertion of the substantially rigid tube108through the cavity104and the o-ring106and into the third opening114. The third opening114aligns with and accesses a channel122of the fuel cell chamber118. The tube108and first and third openings110,114are dimensioned to be wider than channel122to create a stop point for stopping tube108at the opening of the channel122. The tube108hits the substrate102at the stop point at the opening of the channel122. Thus, tube108accesses fuel chamber118.

In accordance with this first embodiment, a sealant material118, such as epoxy or other glue or adhesive, can be used to close off the second opening112. However, experiments have shown that it is not necessary to close off the second opening112if the cavity104and o-ring sizes are selected and formed so as to create a suitable retention and fit.

Once assembled, the interconnect apparatus100provides a fuel delivery system for a fuel cell. The fuel delivery system can include a fuel cartridge120for delivering fuel116to the fuel cell chamber118The fuel cell chamber118receives the fuel116through the interconnect apparatus100. The interconnect apparatus100is formed as part of the fuel cell. Again, fuel delivery system includes substrate102having the cavity104formed therein and the o-ring106located within the cavity. The detachable tube108is inserted though the o-ring106and cavity104, allowing for the transfer of fluid116from the fuel cell cartridge120to the fuel cell chamber118.

FIG. 2shows a top plan with partial cutaway view of the o-ring inserted into the cavity described inFIG. 1in accordance with the first embodiment of the invention. Like reference numerals are carried forward. Top view200shows the top of substrate102with the first and second openings110,112respectively on the right hand side and a cutaway view exposing the o-ring106on the left hand side. The o-ring106is slid into second opening112and once fully inserted, the o-ring center aligns with the first opening110(and third opening114not seen in this view).

FIG. 3shows a top plan view300of the tube108inserted into the assembly ofFIG. 1in accordance with the first embodiment of the invention. Tube108is inserted into first opening110, through the o-ring106, and third opening114. In accordance with the first embodiment, the sealant118is applied to close the second opening112. As seen in this view the sealant118is only used to fill the second opening112and not to retain the tube108. The o-ring106retained within cavity104holds tube108in place. The tube108, o-ring106, and cavity104provide a liquid tight seal for the fuel cell.

InFIG. 4, there is shown, in cross section, a “glueless” microfluidic interconnect apparatus400for a fuel cell in accordance with a second embodiment of the invention. In this embodiment, a cavity402is formed within substrate404having a first opening406through which to embed an o-ring408and through which to insert a detachable tube410. The o-ring408is embedded into the cavity402by inserting the o-ring through the first opening406. The tube is thus inserted through the first opening406, through the o-ring408, and into a second opening412. The first and second openings406,412and cavity402are preferably formed by multi-layer low temperature co-fired ceramic technology (ML LTCC). Other techniques, such as drilling or etching, can also be used to form the openings406,412and cavity402. The first opening406is formed large enough to accommodate the insertion of the o-ring408while the second opening412is formed more narrowly to accommodate the tube410. The cavity402is formed so as to create upper, lower, and side walls that retain the o-ring in place while allowing only for enough expansion to fill the cavity402once the tube410is inserted through the o-ring408. The tube410, when inserted through the o-ring408, forces the o-ring to expand and fill the cavity402thereby forming a liquid tight seal for the transfer of liquid414to a fuel cell chamber416. The second opening412aligns with and accesses a channel422of the fuel cell chamber416. The tube410and the second opening412are preferably dimensioned to be wider than channel422so as to create a stop point for stopping tube410at the opening of the channel422. Again, a liquid tight seal is formed when the tube410is inserted through the o-ring408. The advantage of this second embodiment is that it is glueless and requires less cavities.

Whether the cavity is formed with one access point (as described in the second embodiment) or two access points (as described in the first embodiment) is a matter of design preference. The overall concept of embedding an o-ring into a cavity within the substrate to retain a tube provides a quick connect and disconnect mechanism in accordance with the present invention. This connect/disconnect mechanism provides a liquid tight seal that allows for improved transfer of fluids into a fuel cell. The interconnect apparatus of the present invention also provides a gas tight seal for applications involving gas, as opposed to liquid.

FIG. 5shows a process of forming a liquid tight seal for a fuel cell in accordance with the overall concept of the present invention. The process500begins at step502by providing a substrate, forming a cavity within the substrate at step504, and embedding an o-ring within the cavity at step506. Next, by inserting a substantially rigid tube within the o-ring and thereby expanding the o-ring to fill the cavity at step508, a liquid tight seal in the fuel cell is formed.

Accordingly, there has been provided a fuel cell assembly that provides a liquid tight seal. The embedding of an o-ring within a cavity formed within the substrate provides a quick connect and disconnect mechanism for an insertable tube to access a fuel cell. Various sizes of tubes, o-rings, and cavity formation can be used to form the desired liquid tight seal. A significant advantage of the interconnect structure of the present invention is the ability to connect and disconnect the tubing, each time making a liquid tight seal. The interconnect apparatus of the present invention also provides a more efficient fuel cell assembly in that faulty assembly is minimized, fewer parts are used, possible contamination issues are minimized and the tube is far less apt to inadvertently get filled with epoxy. These advantages are of great benefit to miniature fuel cell systems.