Abstract:
Apparatus for electrically isolating interconnecting station nozzle and vehicle receptacle components during the refueling of high pressure gas into a vehicle tank comprising an electrically isolated vehicle tank inlet receptacle engageable with a refueling nozzle wherein the receptacle includes an assembly of mutually engageable electrically insulating media in conjunction with the vehicle receptacle mount to prevent electrical contact from the refueling nozzle to the vehicle chassis and gas tank in the refueling gas flow conduit system.

Description:
RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional application Ser. No. 60/713,023 filed on Aug. 31, 2005 which is incorporated herein by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to a system for eliminating the possibility of a static discharge during the refill of high pressure fuel storage tanks in hydrogen fuel cell powered vehicles. 
   BACKGROUND OF THE INVENTION 
   When hydrogen is used as a fuel in motor vehicles, a hydrogen fuel depot infrastructure for refueling must also be developed. Typically, present practice is that fuel is stored in on board tanks maintained at a maximum pressure in the range of about 5000 psi for hydrogen, and higher pressures in the range of about 10,000 psi or more are likely to be utilized in the future as the use of hydrogen becomes more widespread. During driving, a static charge may build up on the vehicle chassis. When the vehicle stops, the charge is usually dissipated to ground through the vehicle&#39;s tires; however, the rate of dissipation of the charge through the vehicle tires varies depending on the resistance of the tires and the resistance of the surface on which the vehicle is parked or stopped. If, at a refueling station or depot, the vehicle static charge energy is above a minimum threshold energy level that can cause the spark ignition of hydrogen gas, then it is unsafe to refuel the vehicle through the refill conduit connecting the fuel depot gas outlet and the vehicle tank inlet. If hydrogen were to leak at the depot refill nozzle or at the vehicle receptacle, a spark may occur when the refill nozzle is connected to the vehicle receptacle, which could potentially ignite the hydrogen. A conventional solution mitigates the static discharge problem, by manually connecting a grounding cable to the vehicle before refueling to avoid the potential for a spark to occur. 
   OBJECTS OF THE INVENTION 
   It is an object of the present invention to isolate any charge potential that could be present on the vehicle chassis from the refueling receptacle, and thus reduce the possibility of a static discharge during the refill of high pressure storage tanks in hydrogen fuel cell powered vehicles at a retail outlet fueling depot. 
   SUMMARY OF THE INVENTION 
   The invention is described more fully in the following description of the preferred embodiment considered in view of the drawings in which: 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1A  is a diagram showing typical static potential between the vehicle, the fuel depot and ground at a refueling station.  FIG. 1B  is a schematic diagram showing the electrical resistance and capacitance of the vehicle, earth and refueling pump circuit equivalent to the representation of  FIG. 1A .  FIG. 1C  is an electrical schematic diagram representing the circuit of  FIG. 1B . 
       FIG. 2  shows a cross section side view demonstrating the principles of the insulating properties of the invention showing a vehicle fuel refilling receptacle with reference to the vehicle tank inlet on a hydrogen powered vehicle. 
       FIG. 2A ,  FIG. 2B ,  FIG. 2C ,  FIG. 2D  and  FIG. 2E  depict cross section side views of embodiments of the invention. 
       FIG. 3  is a cross section side view of an alternative configuration of a vehicle fuel receptacle applying the insulating principles of the invention. 
       FIG. 3A  and  FIG. 3B  are cross section side views of further embodiments of the alternate configuration of the invention shown in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention electrically isolates the refueling receptacle from the vehicle chassis. The electrically isolated receptacle is engageable with a refueling nozzle from the station depot side. The vehicle receptacle includes electrically insulating media to prevent electrical contact from the refueling nozzle to the vehicle chassis and gas tank. With reference to the description herein, the nozzle is an external fuel dispensing device that is connected to the receptacle; in describing the invention, “nozzle” refers to the station nozzle and the application should be so read contextually in the event of any ambiguity. 
     FIG. 1A  depicts a typical static potential between the vehicle, the fuel depot and ground at a refueling station. In  FIG. 1A , the rear of the vehicle is shown as  1  having right rear tire  2  and left rear tire  3 . Hydrogen gas fuel tank  4  is interconnected through fuel conduit  6  to gas tank inlet  5 . Ground [earth] is shown at  20 . Refuel depot pump  10  is installed on base  11  and includes conduit  12  and nozzle  15  for interconnection with the fuel tank inlet  5 . Electrical charges in the ambient vehicle/fuel depot environment are respectively shown as positive, +, and negative, −.  FIG. 1B  shows the electrical circuit equivalent wherein C A  indicates capacitance between fuel cell vehicle  1  and earth  20  and C Z  indicates capacitance between fuel cell vehicle  1  and refueling pump  10  and earth  20 . R 1  indicates resistance between refueling pump  10  and ground or earth. As shown in  FIG. 1A  and  FIG. 1B , a static charge builds up on the vehicle chassis during driving. When the vehicle stops, the rate of dissipation of the charge through the vehicle tires varies depending on the resistance of the tires and the resistance of the surface on which the vehicle is parked or stopped. If, at a refueling station or depot, the vehicle static charge potential stored in the capacitor elements, C A  and C Z  of the circuit is above a minimum threshold energy level exceeding the limit of R 1 , a spark may occur that can cause the ignition of hydrogen gas. See  FIG. 1C . 
   Example A 
     FIG. 2  is a longitudinal side cross section view of an embodiment of the invention showing the exterior side of the vehicle receptacle (that joins with the station nozzle)  100  and the vehicle receptacle assembly  200  through which the fuel conduit is joined to the vehicle&#39;s hydrogen storage tanks in accordance with the invention. In the drawings of the  FIG. 2  and  FIG. 3  series shown, a frontal lateral cross section of the cylindrical elements involved is evident from the side views depicted and their respective explanations. Fuel depot receptacle connector  100  is conventional and includes interlocking means (not shown) to securely engage the pump nozzle with the fuel inlet of the vehicle tank. The interior side of the vehicle receptacle  200  leads from the receptacle through a conduit  250  to the vehicle fuel storage tank (not shown). The vehicle receptacle  200  is electrically isolated from both the vehicle body  400  and the fuel tank system  250 . The receptacle comprises vehicle body interior section  201  and mating vehicle body exterior section having integral interior extending element  202   i  sandwiching the section of the vehicle body  400  upon which the receptacle is mounted. Receptacle mating elements, element  201 , and element  202 , are affixed to the vehicle body by a plurality of fasteners insulated from contact with the vehicle body. As shown in the cross section, fastener  203  is insulated by grommets  204  and  205 ; fastener  206  is insulated by grommets  207  and  208 . A gasket or laminate layer of insulating material  220  at least coextensive with the facing receptacle elements is also secured by the fasteners and insulates the receptacle surface from the vehicle body. Insulating o-ring or gasket  210  prevents contact of any extending stem portion, alternatively of either of the station nozzle or the vehicle receptacle exterior section, and/or both, with the interior portion of the vehicle tank receptacle  201 . In this manner, the flow path of fuel in the station conduit from the nozzle  100  to the conduit for the vehicle tank system  250  is electrically insulated from the vehicle body and vehicle tank system. 
   In Example A, a vehicle fuel receptacle is isolated from a vehicle body and tank system while allowing a secure conduit for high pressure fuel gas flow from the nozzle to the tank. An exterior vehicle tank inlet receptacle is engageable with the refueling nozzle; the receptacle has a vehicle body interior flange and a mating vehicle body exterior flange with a cylindrical extending section concentric with the interior flange leading to the fuel tank. The receptacle flanges are disposed to and fasten the section of the vehicle body upon which the receptacle is mounted; an insulating gasket is essentially coextensive with the exterior flange and the vehicle body. Concentrically extending sections of the flanges and gasket are secured with respect to the vehicle body by electrically non-conducting fasteners, or equivalently, by electrically conductive fasteners insulated from the flanges and vehicle body by insulating grommets. An o-ring may be disposed within the interior extending section of the interior flange adjacent the end of the concentric section of the exterior flange that extends within the interior flange. In an example, an insulating sleeve is disposed around the outer surface of the extending interior section of the exterior flange; the sleeve may extend beyond the end of the extending interior section of the exterior flange and fold inwardly at the end thereof to enhance insulating qualities. 
   In embodiments, a recessed o-ring is disposed within the interior extending section of the interior flange between the sleeve and the extending section of the interior flange or a pair of recessed o-rings, a first o-ring disposed within the interior extending section of the interior flange, and a second o-ring disposed within the interior extending section of the exterior flange, may be disposed within the flange sections such that the o-rings sandwich the sleeve. Based on design factors, one o-ring may be formed from a metal and the second o-ring may be formed from an electrically insulating material. The sleeve for the extending section of the exterior flange may be a cylindrical metallic collar having interior and outer surfaces covered with an electrical insulator and the insulator may comprises a surface coating of a polymeric material. O-rings may be longitudinally offset from, or aligned with, one another. The gaskets and insulator materials are preferably a nylon as described below. 
   The object of the invention is to isolate and minimize any electrical charge that could be present on the vehicle chassis and prevent the creation of a spark when the station nozzle is connected to the vehicle receptacle. Because the station nozzle is electrically grounded, if the receptacle on the vehicle is directly connected to the vehicle chassis, and the chassis still holds a static electrical charge, a spark can occur across the air gap as the nozzle approaches the receptacle while connecting the two during the refueling process. This spark could potentially ignite a hydrogen/air mixture that could be present due to a leak or other factors in the nozzle or receptacle areas. Normally the vehicle is grounded via a grounding cable or thru the vehicle tires before the nozzle is connected to the receptacle. However, the user may forget to or purposely avoid connecting the grounding cable prior to connecting the nozzle, or the fueling pad surface may have too high a resistance to adequately ground through the tires. When the receptacle is electrically isolated from the vehicle chassis, then there is little or no possibility for the electrical charge on the vehicle chassis to gap across to the nozzle and create a spark that may potentially ignite the hydrogen. The invention thus creates a safer refueling environment for the user and can be utilized as a secondary layer of protection in case the primary protection, dissipation of static electrical charge via grounding to earth, fails. In the discussion of the embodiments, reference numerals for elements of the vehicle receptacle and the fuel station connector to the receptacle that are initially identified in prior drawings may be omitted, both to avoid redundancy and for purposes of clarity in explaining the invention; however, their presence is evident in context. 
     FIG. 2A  shows an embodiment in which a high strength engineering plastic material with good durability and electrical isolation properties, such as a nylon electrical insulating material, is molded into a shape  222  that fits around and/or is bonded to the outer surface of the conductive inner sleeve section  202  of the outer part of the receptacle. Insulating o-ring  221  is shown. As used herein, “nylon” refers to the synthetic polymer engineering material, nylon, and other suitable, or equivalent, high strength engineering plastic materials with electrical isolation properties, such high performance polyamides and other polymeric electrical insulating materials having properties of toughness, durability and wear resistance, with mechanical performance characteristics over a wide temperature range suitable for use in high pressure fuel delivery systems for automotive applications. 
   An embodiment is shown in  FIG. 2B , wherein a nylon engineering plastic material, is molded into a shape  223  that fits around and/or is bonded to the outer surface of the inner sleeve section  202  of the outer part of the vehicle receptacle. Shape  223  provides an insulating mechanism sealed on the inner surface and which is secondarily sealed in the assembly by an o-ring  224  interposed between the extending segment of the receptacle section  202  and the nylon insulating shape  223 . Assembly o-ring  210  is also shown. 
     FIG. 2C  shows an embodiment wherein the nylon electrically insulating engineering plastic material  225  is molded around a tubular metal collar  226  to form an insulating sleeve, which is then bonded to the inner male receptacle section  202   i  of the outer part  202  of the vehicle receptacle. The collar includes a folded over extending end section proximate the terminal end of receptacle section  202   i . Primary sealing occurs on the inner surface by bonding of the inner surface of the collar  226  to section  202   i ; secondary sealing results from pressures exerted by insulating o-ring  210  in part  201  and metallic o-ring  227  recessed in section  202   i . The polymeric insulating o-rings and gaskets shown include elements formed from nylon and other high strength engineering plastic materials having properties of toughness, durability, wear resistance, and mechanical performance over a wide temperature range, suitable for use in high pressure fuel delivery systems in automotive applications. 
     FIG. 2D  shows an embodiment wherein the electrically insulating nylon material  225  is molded around a metal collar  226  to form an insulating sleeve, which slides over and correspondingly engages the inner male receptacle sleeve section  202   i  of the outer part of the vehicle receptacle, extending beyond the terminal end thereof. Gas sealing occurs on the sandwich disposition of the insulator, namely collar  226  surrounded by plastic  225  between insulating o-ring  210  recessed in section  201  supplemental o-ring  228  recessed in section  202   i.    
     FIG. 2E  shows an embodiment wherein the electrically insulating engineering plastic material  225  is molded around a metal collar  226  to form an insulating sleeve, which slides over and engages with the inner male receptacle sleeve section  202  of the outer part of the vehicle receptacle. Gas sealing occurs as a result of circular forces generated by the sandwich disposition of the insulator, namely collar  226  surrounded by insulating plastic coating  225 , between o-ring  231  recessed in section  202   i  and o-ring  232  recessed in section  201 . 
   Example B 
     FIG. 3  is a side cross section view of another embodiment of the invention using a series of collinearly aligned gaskets and receptacle elements insulating the vehicle fuel receptacle from the vehicle body. In  FIG. 3  the exterior side of the receptacle that joins with the station nozzle  100  and the interior side of the receptacle  300  which is joined to the vehicle&#39;s hydrogen storage tank system in accordance with the invention are shown. Fuel nozzle receptacle  100  is conventional and includes interlocking means (not shown) to securely engage the pump nozzle with the fuel inlet of the vehicle tank. The interior side of the vehicle receptacle  300  leads from the nozzle through a conduit  350  to the vehicle fuel storage tank (not shown). The vehicle nozzle  100  is electrically isolated from both the vehicle body  400  and the fuel tank conduit system  350 . The receptacle comprises collinearly aligned elements  301   a , which includes a flange section  302  for securing the receptacle to the vehicle exterior body panel  400 . Separating flange  302  from the vehicle body  400  is an insulating gasket  310 . The flange  302  and gasket insulator  310  are fastened to the vehicle body by one or more fasteners such as  303 , insulated from the vehicle body and receptacle by grommets  304  and  305 , and  306 , insulated from the vehicle body and receptacle by grommets  307  and  308 . Exterior receptacle component  302  includes elements  301   a  and  301   b  separated from each other and insulated from each other by electrically insulating gasket  320  maintained in a fixed alignment by fasteners such as fastener  311 , insulated from section  301   a  and section  301   b , and fastener  314 , insulated from section  301   a  and section  301   b  by grommets  315  and  316 . In this manner, insulator  310  (held in place by the insulated fasteners) electrically isolates the vehicle body  400  from section  301   a  of the receptacle and insulator  320  (held in place by the insulated fasteners) electrically isolates the vehicle receptacle nozzle  100  from the vehicle tank system  250 . Fuel thus flows from the nozzle into the vehicle tank through an electrically isolated pathway  350  from the fuel pump to the vehicle tank. 
   In this example, the receptacle comprises a vehicle body flange having an exterior flange section disposed with respect to the vehicle body and an interior section extending from the exterior section toward the vehicle body interior. An insulating gasket is disposed between the exterior flange and the vehicle body in a sandwich relationship and a terminal is plate affixed to the interior extending end section of the vehicle body flange insulated by a gasket disposed between the end section of the vehicle body flange and the terminal plate. As in the above example, the flange, gaskets and plate are collinearly concentrically aligned such that an unobstructed fuel conduit is provided for high pressure hydrogen gas (or compressed natural gas). The exterior flange is insulated from the vehicle body by a flange in the gasket providing a central collar section extending over the inward extending section of the exterior flange from the vehicle body exterior. Fasteners securing the assembly, electrically insulate the receptacle from the vehicle body. In the embodiment shown, the plate gasket comprises a metal washer coated with an electrically insulating material and the plate gasket may be disposed between the aligned or offset o-rings. A reverse flange may be intrinsically formed at the interior facing end of the extending section of the exterior flange to receive a fastener for securing the plate with the insulator therebetween. 
   In  FIG. 3A , a nylon wrapping collar or sleeve  331  is molded around a disk  332 , which may be formed as a steel washer, that serves as structural support for high stresses in the filling system, and the gas sealing occurs by o-ring  333  recessed in the inner section  301   b  of the receptacle and o-ring  334  recessed in the outer section  301   a  of the receptacle. 
   In  FIG. 3B , an assembly is shown in which bolt  351  insulated by nylon grommet  353  and bolt  352  insulated by nylon grommet  351  and  354  secures cap  301   b  securely in position with the extending part  301   a  of the interior flange. Between cap  301  and flange element  301   b , an insulating washer  356  is provided. The washer comprises a high strength engineering nylon molded around a central steel disk that serves as structural support for high stresses. Central metal element  356  is coated or molded with insulating material  356   c . O-rings  356  and  357  recessed respectively in the facing ends of sections  301   a  and  301   b  provide the gas sealing. 
   The mechanism of the invention thus isolates electrical charge that is possibly present on the vehicle chassis that could create a spark when the station nozzle is connected to the vehicle receptacle. The possibility is reduced that a spark could potentially ignite a hydrogen/air mixture that might occur due to a leak in the nozzle or receptacle areas. When the receptacle is electrically isolated from the vehicle chassis, the possibility for the electrical charge on the vehicle chassis to gap across to the nozzle and create a spark resulting in the potential ignition of hydrogen is reduced. The invention thus creates a safer refueling environment for the user and can be utilized as a secondary layer of protection in the event that the primary protection—dissipation of static electrical charge via grounding to earth—fails. 
   Having described the invention in detail, those skilled in the art will appreciate that, given the present description, modifications may be made to the invention without departing from the spirit of the inventive concept herein described. Therefore, it is not intended that the scope of the invention be limited to the specific and preferred embodiments illustrated and described. Rather, it is intended that the scope of the invention be determined by the appended claims.