Patent Document

BACKGROUND 
     The invention generally relates to a sensor mount assembly. 
     Many devices, such as fuel cells, use fluids to conduct heat or perform other functions in the device. Monitoring temperature, pressure and other properties of these fluids may require the use of a sensor. It is desirable that the sensor be mounted in a manner that is inexpensive and easy to manufacture, as well as easy to use. 
     A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. For example, one type of fuel cell includes a proton exchange membrane (PEM), often called a polymer electrolyte membrane, that permits only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is reacted to produce hydrogen protons that pass through the PEM. The electrons produced by this reaction travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions may be described by the following equations: 
     H 2 →2H + +2e −  at the anode of the cell, and 
     O 2 +4H + +4e − →2H 2  O at the cathode of the cell. 
     Because a single fuel cell typically produces a relatively small voltage (around 1 volt, for example), several serially connected fuel cells may be formed out of an arrangement called a fuel cell stack to produce a higher voltage. The fuel cell stack may include different flow plates that are stacked one on top of the other in the appropriate order, and each plate may be associated with more than one fuel cell of the stack. The plates may be made from a graphite composite or metal material and may include various flow channels and orifices to route the above-described reactants and products through the fuel cell stack. Several PEMs (each one being associated with a particular fuel cell) may be dispersed throughout the stack between the anodes and cathodes of the different fuel cells. The anode and the cathode may each be made out of an electrically conductive gas diffusion material, such as a carbon cloth or paper material, for example. Besides communicating products and reactants throughout the stack, the flow channels may also communicate a coolant to remove heat from the stack. 
     The reformate (containing the hydrogen), air and coolant that circulate through a fuel cell stack are examples of working fluids. The temperature and other properties of the working fluids, such as the reformate, may be monitored to maintain desired operating conditions. Ideally, the sensors that are employed for this purpose should be mounted in fixtures that are easy to manufacture, inexpensive, and that allow the sensor to be quickly installed and removed. 
     SUMMARY 
     In an embodiment of the invention, an assembly includes a receptacle and a sensor body. The receptacle includes an orifice and includes at least one tab for engaging a feature (e.g., a notch) of the sensor body. In another embodiment, the tab may be located on the sensor body and may be adapted to engage a feature of the receptacle. The sensor body is adapted to be inserted into the orifice. The sensor body includes a notch to receive the tab(s) to secure the sensor body in the receptacle and at least one prominence to lift the tab(s) out of the notch to release the sensor body from the receptacle when the sensor body is rotated. 
    
    
     Advantages and other features of the invention will become apparent from the following description, from the drawing and from the claims. 
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram illustrating a fuel cell stack with coolant system and sensor. 
     FIG. 2 is a perspective view of a receptacle of a sensor mount according to the present invention. 
     FIG. 3 is a top plan view of the receptacle of FIG.  2 . 
     FIG. 4 is a through section of the receptacle, taken along line  4 — 4  of FIG.  3 . 
     FIG. 5 is an enlarged through section of a tab, taken along line  5 — 5  of FIG.  3 . 
     FIG. 6 is a plan view of a sensor body of the sensor mount according to the present invention. 
     FIG. 7 is a through section of the sensor body, taken along line  7 — 7  of FIG.  6 . 
     FIG. 8 is an enlarged through section of the sensor body, taken along line  8 — 8  of FIG.  6 . 
     FIG. 9 is a perspective view of an alternative embodiment of the sensor body. 
     FIG. 10 is a through section of the alternative sensor body, taken along line  10 — 10  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an embodiment of a fuel cell system  10  includes a working fluid subsystem connected to a fuel cell stack  12 . The working fluid subsystem may include stack components (described below) that are designed to pass fluids, such as (reformate containing hydrogen), air or a coolant, as examples. 
     The working fluid subsystem is formed in part by plates (of the stack  12 ) that include flow channels for circulating the working fluids and manifold passageways (of the stack  12 ) that communicate the working fluid through the fuel cell system  10 . The fuel cell stack  12  may be formed from repeating units called plate modules  16 . An exemplary plate module  16   a  (having a design similar to the other plate modules  16 ) includes flow plates (graphite composite or metal plates, for example) that include flow channels to form several fuel cells. The flow plates also include aligned openings to form passageways of a manifold that communicates reactants such as hydrogen and air and the coolant with the stack  12 . As an example, the plate module  16   a  may include the following flow plates: bipolar plates  20  and  26 ; cathode cooler plates  18 ,  24  and  30 ; and anode cooler plates  22  and  28 . 
     An exemplary working fluid subsystem for hydrogen is illustrated in FIG. 1. A reformer  14  converts a hydrocarbon (natural gas or propane, as examples) into a hydrogen flow that is communicated to the fuel cell stack  12  for reaction with oxygen (provided by an air flow) to produce electrical power. To control the hydrogen production by the reformer  14 , a sensor  34  may be mounted in a female receptacle  38  to sense an anodic exhaust flow that exits the stack  12  through the receptacle  38 . This exhaust flow may include, for example, unconsumed hydrogen. The output signal of the sensor  34  may be communicated to a controller  36  that may control the reformer  14  in response to the temperature that is indicated by the sensor  34 . The sensor  34  may be any suitable sensor, typically a temperature sensor, such as a resistance temperature device (RTD) or a thermistor, but other sensors may also be used, such as pressure sense sensors or flow meters, to sense properties of the working fluid. 
     The sensor  34  is mounted in a quick release sensor mount assembly, illustrated in FIGS. 2 through 8. The sensor mount assembly includes the female receptacle  38 , illustrated in FIG. 2, and a male sensor body  40  illustrated in FIG.  6 . The sensor  34  is housed within the sensor body  40  and may include electrical circuitry  35  that is disposed within the sensor body  40  as well as a probe  80  (a metal probe, for example) that extends outside of and is secured to the sensor body  40 . The female receptacle  38  is illustrated as mounted on a segment of tubing  42  having a first flange  44  and a second flange  46  at opposite ends of tubing  42 . The flanges  44  and  46  may be used to mount the receptacle  38  to, for example, a manifold passageway of the stack  12  or other conduits to communicate a fluid. Thus, the receptacle  38 , however, could also be used on any segment or configuration of conduit or structure containing fluid. 
     Referring to FIGS. 3 and 4, the receptacle  38  includes a housing  48  that is mounted on the tube  42  and includes an orifice  50  that extends through the housing  48  and opens into the interior of the tube  42 . In some embodiments, the housing  48  is generally cylindrical. A proximal section  52  immediately adjacent the tube  42  has a cylindrical bore  54  extending or opening into the tube  42 . Filets  56  may be provided adjacent the union of the female receptacle  38  and the tube  42  to provide additional mechanical strength and support. 
     A distal segment  58  of the housing  48  may be frusta-conical. An interior bore  50  of the distal segment  58  becomes slightly smaller farther away from the tube  42 . The distal segment  58  is crenellated by four longitudinal slots  60 ,  62 ,  64  and  66  (see FIG. 3) that define two opposed tabs  68 ,  70 . One of the tabs  68  can be seen in an enlarged cross-section in FIG.  5 . Each of the tabs  68 ,  70  has an inwardly directed lip  72 ,  74 . Each lip  72  and  74  has an upwardly or distally facing inclined face  76  and a downwardly or proximally facing abutment surface  78 . As will be explained below, the tabs  68  and  70  with the associated lips  72  and  74  act to retain the sensor body  40  in the receptacle  38 . The invention is not limited by the particular placement of tabs. For example, tabs might extend from the orifice of the receptacle as shown in FIG. 4, or they might extend from the sensor body  40  (not shown). Other tab configurations are possible. It will be appreciated that suitable tabs may be include snap hooks, snap beams, or other arrangements, and that the tabs can be flat or annular. 
     In some embodiments, the housing  48  may be a plastic that is formed by injection molding. Each tab  68 ,  70  has a sufficient resiliency to grasp and release the sensor body  40 , as described herein. Of course, the tabs  68  and  70  may be constructed from materials other than plastic as long as long as the tabs  68  and  70  remain sufficiently resilient to grasp and release the sensor body  40 . It can be appreciated by those skilled in the art that because the receptacle  38  does not include threads for establishing a threaded connection with the sensor body  40 , the receptacle  38  may be easier to manufacture via injection molding than conventional sensor mount assemblies that use threaded connections, and may be easier to install (e.g., may not require rotation for installation). 
     Turning now to the sensor body  40 , a temperature sensor is illustrated in FIG.  6 . As explained above, any suitable sensor may be used with this invention, including, without limitation, flow sensors, pressure sensors and so on. The illustrated sensor body  40  may be made from an injection molded plastic (as an example) and may secure the probe  80  that extends proximally from a shaft  82  of the sensor body  40 . A main body  84  of the sensor body  40  is connected distally from the shaft and is generally configured to fit snugly in the orifice  50 . The main body  84  has a circumferential o-ring groove  86  for receiving an elastomeric o-ring, for sealably seating the sensor body  40  in the receptacle  38 . A chamfer  88  may be provided on the main body  84  proximally, adjacent the shaft  82 . A frusta-conical section  90  is provided distally from the main body  84 . This frusta-conical section  90  corresponds generally to the interior shape of the frusta-conical segment  58  of the receptacle  38 . A circumferential notch  92  distal from the frusta-conical segment  90  receives the lips  72 ,  74  on the tabs  68 ,  70 . This action snaps the sensor body  40  into the receptacle  38 . 
     A handle such as hexagonal head  94  above the notch  92  is provided so that the body  40  may be rotated to release it from the receptacle, as will be explained below. A connector  96  provides an electrical connection for a conductor (not shown) between the sensor and the controller  36 , for example. Of course, other forms of connectors would be used for different types of sensors such as, hydrogen, pressure or carbon monoxide sensors, as examples. 
     In the notch  92 , two longitudinal ridges  98 ,  100  are provided. These ridges  98 ,  100  can best be seen in FIG. 8 in through section. Preferably, the ridges are generally semicircular in cross-section, as can be seen in FIG.  8 . At least one ridge  98 ,  100  is provided for each tab  68 ,  70 . The ridges  98 ,  100 , are placed in the notch such that each ridge  98 ,  100  will engage in associated lip  72 ,  74  simultaneously when the sensor body  40  is rotated. The ridges  98 ,  100  act to spread the tabs, disengaging the lips from the notch and allowing the sensor  40  to be withdrawn from the receptacle. Although two opposing tabs and corresponding opposing ridges have been illustrated, it is clear that a single tab and ridge could be employed or that more than two tabs and ridges could also be used without departing from the teachings of the invention. 
     An alternative embodiment of the invention is shown in perspective view in FIG.  9 . Instead of ridges  98 , bores  102 ,  104  are provided which extend through the hexagonal head  94  and into the groove  92 . A key  106  is provided for releasing the sensor. The key  106  has a support ring  108  that will fit over any connector  96  on the sensor and that supports prongs  110 ,  112 . The prongs  110 ,  112  are inserted into the bores  102 ,  104  in place of the ridges  98 ,  100  and removably form the same configuration as the ridges  98 ,  100 . As can be seen in FIG. 10, with the key  106  in place, ridges  114 ,  116  are formed in the notch  92 . The lips are thereby disengaged to allowing the sensor to be withdrawn from the receptacle. It will be appreciated that the key arrangement described above provides the advantage of tamper resistance in that the key  106  is needed to remove the sensor from the receptacle. 
     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.

Technology Category: 3