Abstract:
An interlock monitoring system includes a magnetic proximity sensor within a poppet valve type coupler to detect whether the poppet valve is opened or closed. An open poppet valve indicates a proper connection. The sensor consists of dedicated electronics that prevent cheating, or bypassing, by either shorting out or opening the contacts to the sensor. In addition, a ferrous metal proximity switch is used to provide a redundant confirmation of proper connection of the coupler. The ferrous magnetic proximity switch will indicate whether or not the coupler is actually in contact with an appropriate connection. Each of the magnetic proximity sensor and the ferrous magnetic proximity switch must indicate a respective proper condition in order to determine a valid interlock condition.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a non-provisional application claiming priority from U.S. Provisional Patent Application No. 61/319,120 filed Mar. 30, 2010 entitled “Dynamic Self-Checking Interlock Monitoring System.” 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    In the fuel loading industry where a fuel truck is being loaded with a liquid or fuel that is often flammable, in order to meet mandated safety requirements, several parameters of the fuel transfer process are routinely monitored for compliance with loading operations standards. These parameters include, commonly, assuring that a static ground is present in order to prevent sparking and monitoring tank capacity in order to avoid an overfill condition and possible fuel spill. 
         [0003]    In addition, vapor recovery during the filling process, in order to meet environmental and safety guidelines, is becoming increasingly important. Many of the current fuel loading monitoring systems are inadequately equipped for detecting that vapor recovery is being properly implemented. 
         [0004]    In order to minimize the release of vapor into the atmosphere, as fuel is loaded into a modern tanker, the vapor in the vehicle is exhausted through a pressure valve at the top of the tank and run through piping that terminates in a coupling typically mounted on the rear of the vehicle. Many loading racks have a vapor recovery system to capture these vapors and either burn them off or otherwise process them. 
         [0005]    Operators of fuel loading stations need to make sure that the vapor hose is connected to prevent vapor being exhausted into the atmosphere. Thus, these operators need an automatic system to prevent the loading operation from commencing without the vapor capture and monitoring systems being in place. 
         [0006]    Currently, there are two approaches: 1) vapor monitoring in which a thermistor sensor is inserted into a vapor recovery hose. The thermistor sensor consists of two thermistors with one thermistor being a reference and isolated from the vapor flow and a second sensing thermistor positioned in the vapor flow. In operation, when the vapor is flowing, the thermistor in the flow is cooled by the vapor and the control electronics senses a difference in the respective thermistor resistances and indicates a vapor flow is established. This method is effective, however, it is known to take a not insignificant amount of time after the product or liquid is loaded before vapor starts to flow in order to make a reading. To deal with this delay, the operator must set a grace period (usually 1 to 5 minutes) before which the vapor monitoring system cannot be relied on to have sensed a vapor flow. If no vapor flow is detected after the grace period the controller stops the loading of fuel. The issue is that significant vapor can be sent into the atmosphere if the hose is not connected during this grace period while fuel is being added. 
         [0007]    A second method of vapor recovery uses a switch mounted on the vehicle that is activated by the coupling of the vapor recovery hose. This switch is connected in such a way that it enables on-board vehicle electronics (if so equipped) to prevent fuel loading without an indication that the vapor hose is connected. There are several weaknesses to this method including: 1) the switch is external to the truck and easily bypassed with locking pliers and the like; 2) not all vehicles have on-board electronics that would be compatible with the switch; and 3) the load rack operator is ultimately responsible for making sure the vapor recovery takes place. The loading rack operator, therefore, needs to confirm for themselves to prove to the appropriate regulatory authorities that they, and not the fuel truck drivers (many of whom are known to bypass the system in order to load up faster), are assuring that the vapor hose is connected. 
         [0008]    Traditionally, known vapor recovery systems use only the pressure from the tank to exhaust the vapor from the tank with a poppet valve located on the truck outlet to prevent vapors from leaking unless a vapor hose is connected. The rack side hose generally only has a pin that opens the poppet valve on the tanker connection. Recently, however, many rack operators have started using vacuum assist vapor recovery systems that contain a vacuum to draw residual vapor from the hose after the tanker has disconnected. 
         [0009]    In addition to the vacuum assist couplings on the rack side of the hose there are now hoses with integral poppet valves to further reduce vapor from escaping during fuel transfer. 
         [0010]    What is needed, however, is a system for automatically disabling fuel transfer if it is determined that the vapor recovery system is not properly connected. Such a system must be one that can be retrofitted onto existing trucks and racks and one that cannot be easily bypassed. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    Generally, an interlock monitoring system in accordance with an embodiment of the present invention includes a proximity sensor within a poppet valve hose type coupler to detect whether the poppet valve is opened or closed. The sensor consists of a proximity switch with dedicated electronics that prevents cheating by either shorting out or opening the contacts to the sensor. An insulated wire, for example Teflon®, travels through the vapor hose and out an exit port to allow the insulated wire to exit the vapor system without creating leaks. A dedicated controller provides intrinsically safe wiring to the sensor assembly and continuously monitors the connections as well as the sensor. Should either the sensor or any of its associated wiring not respond to a self-checking signal within an appropriate time, the controller considers that a fault condition and opens the control contacts stopping product flow until the fault condition is cleared. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    Various aspects of at least one embodiment of the present invention are discussed below with reference to the accompanying figures. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, not every component may be labeled in every drawing. The figures are provided for the purposes of illustration and explanation and are not intended as a definition of the limits of the invention. In the figures: 
           [0013]      FIGS. 1A and 1B  are cross-sectional drawings of a known vapor coupling poppet valve assembly; 
           [0014]      FIGS. 2A and 2B  are cross-sectional drawings of a vapor coupling poppet valve interlock assembly in accordance with a first embodiment of the present invention; 
           [0015]      FIGS. 3A and 3B  are schematics of alternate sensing circuits in accordance with multiple variations of the first embodiment of the present invention; 
           [0016]      FIGS. 4A and 4B  are cross-sectional drawings of a vapor coupling poppet valve interlock assembly in accordance with a second embodiment of the present invention; 
           [0017]      FIGS. 5A and 5B  are schematics of alternate sensing circuits in accordance with multiple variations of the second embodiment of the present invention; 
           [0018]      FIG. 6  is an alternate embodiment of a sensing circuit; 
           [0019]      FIG. 7  is another alternate embodiment of a sensing circuit; and 
           [0020]      FIG. 8  is another embodiment of the present invention where a vapor flow sensor is incorporated into the vapor coupler. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    This application claims priority to U.S. Provisional Application Ser. No. 61/319,120, filed on Mar. 30, 2010, titled “Dynamic Self-Checking Vapor Interlock Monitoring System” the entire contents of which is hereby incorporated by reference for all purposes. 
         [0022]    Referring now to  FIG. 1A , a known vapor coupler  100  usually provided as part of a filling rack includes a machined body  102  coupled to a flexible hose  104 . A pin assembly  106  is provided to open a poppet valve on a fuel truck. A poppet  108  is normally biased closed, as shown in  FIG. 1A , by a biasing spring  110 . 
         [0023]    In operation, when the fuel truck couples to the vapor coupler  100 , the poppet  108  is urged against the force of the biasing spring  110  by the coupling assembly of the truck as shown in  FIG. 1B . The force of the coupling compresses the spring  110  and allows the poppet  108  to open and vapor to flow. 
         [0024]    A vapor coupling poppet valve interlock  200  in accordance with a first embodiment of the present invention is presented in  FIGS. 2A and 2B . A magnet  202  is provided on the poppet  108  and its function will be described below. A mounting block  204  is provided inside the machined body  102  to hold a sensor  206  near the poppet  108 . The sensor  206  is positioned to detect the magnet  202  when the poppet  108  is opened by operation of a fuel truck connecting to a fueling rack. An output of the sensor  206  is provided by an output wire  208 , here shown with two conductors, running through the flexible hose and out through a vapor-tight exit port or gland, not shown. The wire  208  may be made from Teflon® or similar material so as to not be affected by the vapor and/or not cause a spark or otherwise create a possibly dangerous condition. 
         [0025]    Alternatively, the sensor  206  may be provided with wireless capabilities in order to communicate with the controller. Of course, the signal strength and characteristics would need to comply with any safety standards or regulations. Advantageously, a vapor coupler  100  with a wireless sensor would facilitate retrofitting of a system as only the coupling need be replaced and a wire would not need to be inserted through the hose. Further, a wireless system would not have a wire that might be susceptible to breakage due to it coiling or uncoiling as the hose is moved. 
         [0026]    Thus, as shown in  FIG. 2A  when the poppet  108  is in its “rest” position, the magnet  202  is far enough away from the sensor  206  that the system will indicate that the vapor recovery hose is not connected. As shown, in  FIG. 2B , however, when the poppet  108  is urged against the spring  110 , the sensor  206  will detect the magnet  202  and indicate that the vapor hose has been connected. 
         [0027]    The mounting block  204  and the sensor  206  are configured and placed to repeatably, and accurately, indicate whether the vapor recovery hose is connected. A monitoring system, not shown, will receive the output from the sensor  206 , along the wire  208 , and only allow the flow of fuel if the sensor indicates that the vapor recovery hose is properly connected. 
         [0028]    Referring now to  FIG. 3A , in one embodiment of the sensor circuit  206 - 1 , two normally-open magnetic reed switches  304  are provided in series with a diode  304 . A monitoring system, which will be generally described below, will detect the output of the sensor circuit  206 - 1  to determine the status of the vapor coupling. Thus, when not connected, the switches  304  will remain open. When, however, the poppet  108  is urged against the spring  110 , the magnet  202  will be closer to the switches  304  and they will close. Thus, when closed, the diode  302  will appear to the monitoring system and be detected as below. 
         [0029]    It should be noted that two switches  304  are placed in series with one another to provide a level of redundancy. One of ordinary skill in the art will understand that only one switch need be provided or more than two switches could be used. Similarly, multiple diodes could be provided for redundancy. 
         [0030]    An alternate embodiment sensor  206 - 2 , as shown in  FIG. 3B , incorporates two normally closed magnetic reed switches  306  in parallel with a diode  302 . When the poppet  108  is urged inward, the magnet  202  will cause the switches  306  to open thus placing the diode  302  across the output wires  208  for detection by the monitoring system. 
         [0031]    The foregoing embodiment of the present invention is an improvement over known systems as it is not at all visible to the user because all components are hidden from view, i.e., from the nozzle end of the hose. A user might be able to figure out that if you jammed the poppet valve in you might fool it so a second interlock is available to further frustrate cheats as will be described below. 
         [0032]    A vapor coupling poppet valve interlock assembly  400  in accordance with a second embodiment of the present invention is presented in  FIGS. 4A and 4B . Many components of this assembly  400  are the same as that shown in the embodiment presented in  FIGS. 2A and 2B . A ferrous metal proximity sensor  402 , such as the N-Series switch from Magnasphere Corp. of Waukesha, Wisc., is provided in the pin  106 . The ferrous sensor  402  comes in either a normally-open or normally-closed configuration and will switch states when in proximity with a ferrous metal such as the pin on the coupling mechanism of the truck. The sensor  402  is coupled, via a wire  404 , to a sensor  406  that will be described in more detail below. 
         [0033]    In operation, similar to the embodiment described above, when the vapor coupling assembly  400  is attached to the truck&#39;s connector, the poppet  108  and magnet  202  will be urged toward the sensor  406 . The ferrous metal proximity sensor  402  will change state and that change in state is coupled to the sensor  406 . 
         [0034]    One embodiment of the sensor  406  combined with the ferrous sensor  402  is shown in  FIG. 5A . As shown, a ferrous proximity sensor  402 - 1  is normally open and is provided in series with two normally open switches  304  and a diode  302 . In operation, when the vapor coupling is attached, these switches will all close and the diode  302  will be presented across the output wire  208 . 
         [0035]    Alternately, as shown in  FIG. 5B , normally closed switches  306  and a normally closed ferrous proximity sensor  402 - 2  are provided in parallel with a diode  302 . When the poppet  108  is urged open, the diode is presented across the output wire  208 . 
         [0036]    Advantageously, by inserting the ferrous sensor  402  into the pin  106  of the coupling, fuel operation requires both the poppet valve to be opened and a piece of metal to be in contact with the pin  106 . This additional sensor provides another level of confirmation of proper configuration prior to fueling. 
         [0037]    An existing controller such as is available from Scully Signal Company, Wilmington, Mass. may be coupled to the output of the sensor to determine proper vapor capture. The controller may consist of a power supply, intrinsically safe outputs to the sensor assembly and control relays. The controller has a comparator that compares a reference voltage to a preset voltage and when the preset voltage is less than the reference voltage a fueling relay remains open and no fuel flows. 
         [0038]    In operation, one wire of the output wire  208  is tied to ground and a small AC voltage or signal is applied to the other wire. The controller has within it a pair of capacitors and a pair of associated diodes that are connected to this AC signal. The circuit is designed as a pair of symmetrical charge pumps with respective voltages that are summed and added to the preset voltage. 
         [0039]    In the case of normally closed proximity and reed switches, both the positive and negative portions of the sine wave, i.e., the AC signal, charge their associated capacitors and the net voltage change is zero and no fuel flows. Conversely, when the wires are open, in the case of normally open switches, no current flows leaving both capacitors discharged and again resulting in a net voltage of zero that prevents the flow of fuel. 
         [0040]    When the poppet valve opens, in the case of normally closed parallel connected switches, the diode will allow only the negative portion of the sine wave to pass and as a result one capacitor will charge and the other will not. This will result in a net increase in the voltage across the capacitors and when added to the preset voltage will exceed the reference voltage. The comparator detecting this difference will close a relay indicating a valid vapor connection and fuel will flow. Similarly, when the series connected switches move into the closed position from their normally open position, the diode will be presented and operation will occur as described in the foregoing. 
         [0041]    The capacitors are chosen to have small discharge times and any interruption in the signal through the diode will allow the capacitors to discharge thus lowering the net voltage that will be detected by the comparator which will open the relay contacts and prevent fueling. 
         [0042]    In one embodiment, the sensors  206 ,  406  are housed in a threaded aluminum shaft to maintain their relative positioning and then potted to resist the vapor and to provide an intrinsically safe device in the explosive vapor. Of course other materials may be chosen. 
         [0043]    The sensor may be mounted into the mounting block  204  by operation of a threaded portion that allows the sensor to be adjusted relative to the back of the poppet and the magnet. 
         [0044]    Advantageously, the magnet  202  is mounted on the back of the poppet  108  which conceals it from view from the front of the coupling. This lowers the chances of tampering. 
         [0045]    In operation, the sensor  206 ,  406  is adjusted at an initial installation such that the switches just open when a mating coupling is completely inserted into the rack coupling. 
         [0046]    Where the poppet valve  108  travels up to 1 inch when a mating coupling is connected, the sensor may be adjusted such that the sensor only detects when the paddle arms are in the down position indicating a complete seal. 
         [0047]    As shown in  FIG. 6 , a Zener diode  502  may be used in place of the diode  302  and the controller modified accordingly to look for a particular voltage as would be understood by one of ordinary skill in the art. While the circuit shown in  FIG. 6  is represented as being implemented with normally open switches, one of ordinary skill in the art will understand how to implement with normally closed switches. 
         [0048]    As shown in  FIG. 7 , a resistor  602  may be used in place of the diode  302  and the controller modified accordingly to look for either a particular voltage, if part of a divider circuit, or a particular resistance value or change, as would be understood by one of ordinary skill in the art. While the circuit shown in  FIG. 7  is represented as implemented with normally closed switches, one of ordinary skill in the art will understand how to implement with normally open switches. 
         [0049]    In some applications it may be necessary to confirm that vapor is indeed flowing in addition to confirming that the hose has been mechanically coupled to the source. Accordingly, referring now to  FIG. 8 , a vapor sensor coupling  800  comprises the embodiment of the present invention shown in  FIGS. 2A and 2B , i.e., a magnetic sensor to determine whether the valve is open or closed, and a vapor flow sensor  802 . The vapor flow sensor  802  is provided in the expected vapor flow path and may be mounted on the same mounting block  204  as the sensor  206  or it may be mounted on its own separately from the sensor  206 . As one of ordinary skill in the art will understand, the vapor flow sensor  802  would be mounted in such a location that it would be exposed to the expected vapor flow path. 
         [0050]    In one embodiment, the vapor flow sensor  802  is of the known dual thermistor type. Alternatively, any known type of vapor flow sensor may be implemented as long as it meets the requirements of the system. A separate output wire  804  from the vapor flow sensor  802  is provided to provide an output signal back to a controller, similar to the wire  208  from the sensor  206 . As a result, the fueling controller is provided with a separate output as to the condition of vapor flow. 
         [0051]    Advantageously, the coupling  800  provides for both mechanical confirmation of the connection by operation of the magnetic proximity switch along with a mechanism for measuring the vapor flow right at the source. Measuring flow right at the source, or very close thereto, reduces the chances of the fuel controlling system receiving a false positive confirmation of vapor flow. In some instances it is known that turbulence present farther down the hose, for example, where multiple hoses may be each providing their respective flows to a system of baffles, can sometimes lead to an indication of flow where there is none, if the flow sensor is located there. Depending on the turbulence, an otherwise not flowing hose may be incorrectly identified as flowing properly. 
         [0052]    Another embodiment of the system  800  would include the ferrous material sensor and its corresponding circuitry in the system  800  as described above. 
         [0053]    While an embodiment of the present invention has been described with respect to a vapor recovery system, it should be noted that the features of the present invention may be used in other applications. Thus, the state of the valve may be detected in systems where a fluid other than vapor, for example, a liquid, is expected to flow. Accordingly, the sensor would be designed to function under those conditions. Similarly, if the fluid were corrosive, then the sensor, or any other exposed components, would be properly protected. 
         [0054]    While a poppet valve was described, it is expected that the teachings of the present invention may be applied to other types of valves including, but not limited to, a butterfly valve, a screw valve, a ball valve, a stem valve and a gate valve. One of ordinary skill in the art will understand how to apply these teachings to the various types of valves. 
         [0055]    The magnet, in one embodiment, is externally placed on the valve, an alternate embodiment of the present invention includes the magnet being provided within the valve. In one non-limiting example, a cavity or reservoir, may be provided within the valve material and a magnet placed within and covered over. Alternately, the valve itself, or a portion, may be magnetized if made from material that can be given a magnetic field. 
         [0056]    In addition, while an embodiment has been described with a magnetic proximity sensor on one side and a ferrous material sensor on the other, a ferrous material sensor may be used in place of the magnetic sensor. In this embodiment, instead of the magnet, a piece of ferrous material would be provided and, instead of the magnetic proximity switch, the ferrous material sensor, will detect the movement. This embodiment, of course, assumes that the valve assembly itself is not of a ferrous material. 
         [0057]    Having thus described several features of at least one embodiment of the present invention, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention should be determined from proper construction of the appended claims, and their equivalents.