Abstract:
A fuel supply system for an outboard marine engine includes a vapor separator ( 28 ) having a uni-directional vapor vent device ( 36 ) for preventing fuel leakage when the engine ( 12 ) is tipped on its side. The vapor separator ( 28 ) includes an enclosed interior chamber ( 50 ) which is filled with liquid fuel by a suction pump. A separate, high pressure pump transfers the liquid fuel from the interior chamber ( 50 ) to a fuel injection system ( 32 ) of the engine ( 12 ). The vapor vent device ( 36 ) includes a generally tubular casing having an enclosed top end permeated by an escape passage ( 84 ), and a float ( 94 ) slidably disposed within the casing ( 82 ) for movement toward and away from sealing engagement with the escape passage ( 84 ). A spring ( 98 ) urges the float ( 94 ) toward a sealed condition against the escape passage ( 84 ), but is too weak to overcome the weight of the float ( 94 ) unless the engine ( 12 ) is tipped more than about 25 degrees from vertical, or unless the level of fuel in the interior chamber ( 50 ) lifts the float ( 94 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application entitled Marine Fuel Vapor Separator with Vent Control Device having Ser. No. 60/727,151 and filed Oct. 14, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel vapor separator used in a fuel delivery system of a marine engine for preventing fuel spills when the engine is tipped sideways. 
     2. Related Art 
     Small outboard marine engines are usually detachably mounted to the transom of a boat. These engines typically include an integrated fuel system which draws liquid fuel under suction from a can or tank in the boat. The fuel is routed through a vapor separator unit to condense or discharge vapors and then delivered at high pressure to a fuel injection system. 
     Fuel vapor is a long recognized issue in the marine fuel industry. The fact that fuel is withdrawn from the tank at negative pressure is a main factor. Boat safety regulations require that fuel routed between tank and engine be sucked under a vacuum. This prevents fuel spilling into the boat should the fuel line rupture. However, at such low pressures, the fuel readily vaporizes. This, combined with the high temperatures and jarring conditions, leads to a threat of vapor lock. 
     Vapor separators are designed to address this excessive vapor issue. In addition to the naturally arising vapors from the vacuum drawing step, heated fuel from the fuel rail is returned to the vapor separator where fuel vapors are condensed back to liquid before the fuel is re-introduced to the high pressure pump and fuel rail. As needed, fuel vapors can be vented to atmosphere or pulled into the engine intake system through a vacuum line connection. 
     The vapor vent system in most marine vapor separators includes a float activated valve for automatically closing the vent line whenever the fuel level in the separator rises above a predetermined level. This valve prevents liquid fuel from being sucked into the engine through the vacuum line. Additionally, the valve mechanism is designed to close the vent line when the engine is tipped so that liquid fuel does not, through gravity, drain out the vacuum vent line. 
     Vapor vent valve arrangements in the prior art are commonly constructed according to the float and needle valve principle, in which a buoyant float is supported just below the vapor vent line and connected to a needle valve which closes when the liquid fuel in the vapor separator lifts the float. A typical prior art vent valve system is depicted in  FIG. 4 . These floats are commonly carried on a pivot pin, with the rotational axis of the float pivot being oriented parallel relative to the pivotal axis of the engine mounting bracket so that the float will close the vent passage whenever the engine is rotated to a tilt (i.e., prop out-of-water) condition. This is important so that liquid fuel does not run out of the engine when it is shut off and tilted into the boat. 
     Smaller outboard marine engines are often light enough to be manually removed from the boat after use and stored on a trailer, in a vehicle trunk, or perhaps the bed of a pick-up truck. If the outboard marine engine is laid on its side, which would be the intuitive method so as to protect the prop and tiller arm, the pivotal axis of the vent valve mechanism is not likely to permit closure of the float valve. As a consequence, it is possible for liquid fuel to leak from the engine into the vehicle. Accordingly, it would be desirable to have an improved fuel vapor separator in which the vent control device can accommodate engine tippage in non-conventional directions. 
     Vapor separators are not used in automotive applications because the factors which produce excessive vapors in marine applications are not present. Some automotive emission systems incorporate a so-called “roll-over” vent valve into the fuel tank. However, these systems are passive features of the emission system that simply protect the open vent line to the vapor collection canister. The automotive engine will continue to operate unaffected and without interruption if this roll-over vent valve is disabled or removed. Not so in marine fuel systems, where the vapor vent valve is an active component which will disable the entire engine if not functioning properly. An additional distinction between marine and automotive applications of vapor vent valves is in what they are intended to protect. Automotive roll-over vapor vent valves protect tippage of the fuel tank, whereas marine vent valves protect tippage of the engine-mounted vapor separator. 
     SUMMARY OF THE INVENTION 
     The invention comprises a fuel supply system for an outboard marine engine. The fuel supply system includes a vapor separator having an enclosed interior chamber for collecting a volume of liquid fuel and fuel vapors. A suction pump transfers the liquid fuel under negative pressure from a remote fuel tank to the interior chamber of the vapor separator. A high pressure pump transfers liquid fuel under positive pressure from the interior chamber to a fuel injection system of the engine. The vapor separator includes a vent valve device communicating with the interior chamber for permitting the escape of fuel vapors trapped in the interior chamber. The vent valve device includes a generally tubular casing having an enclosed top end permeated by an escape passage. A float is slidably disposed within the casing for movement toward and away from pressing engagement with the escape passage. A sealing feature perfects a fluid and vapor tight seal between the float and the escape passage when the float is pressed thereagainst. The vent valve device further includes a biasing element operatively interposed between the casing and the float for urging the float toward the escape passage. 
     A fuel supply system according to the subject invention overcomes the shortcomings and disadvantages of the prior art by providing a uni-directional vent valve device for the vapor separator of an outboard marine engine. Thus, the uni-directional nature of the vent valve device prevents liquid fuel leakage from the engine when it is tipped in any direction. Therefore, if the outboard marine engine is laid on its side for transportation, fuel will not leak. 
     The invention also contemplates a vapor separator including a uni-directional vapor vent device for a fuel supply system for an outboard marine engine. The vapor separator includes an enclosed interior chamber for collecting a volume of liquid fuel and fuel vapors. A top wall encloses the interior chamber and includes a vapor outlet. The vent valve device is disposed in the top wall and communicates with the vapor outlet for permitting the escape of fuel vapors trapped in the interior chamber through the vapor outlet. The vent valve device includes a generally tubular casing having an enclosed top end permeated by an escape passage. A float is slidably disposed within the casing for movement toward and away from pressing engagement with the escape passage. A sealing feature perfects a fluid and vapor tight seal between the float and the escape passage when the float is pressing thereagainst. The vent valve device includes a biasing element operatively interposed between the casing and the float for urging the float toward the escape passage. 
     Furthermore, the invention contemplates a top wall for a vapor separator as used in a fuel system for an outboard marine engine. The top wall includes a vapor outlet, and a receiving pocket. A vapor passage connects the receiving pocket to the vapor outlet for directing the flow of fuel vapors therethrough. A vent valve device is disposed in the receiving pocket for selectively blocking the escape of fuel vapor and liquid through the vapor outlet. The vent valve device includes a generally tubular casing having an enclosed top end permeated by an escape passage. A float is slidably disposed within the casing for movement toward and away from pressing engagement with the escape passage. The vent valve device includes a biasing element operatively interposed between the casing and the float for urging the float toward the escape passage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein: 
         FIG. 1  is a side elevation view of a typical outboard marine engine; 
         FIG. 2  is a schematic diagram of a fuel delivery system for an outboard marine engine; 
         FIG. 3  is a cross-sectional view of a marine vapor separator according to the subject invention; 
         FIG. 4  is a cross-sectional view of a prior art top wall and vent control device; 
         FIG. 5  is a front elevation view of a vent control device; 
         FIG. 6  is a perspective sectional view of the subject vent control device with the float shown in the open condition; 
         FIG. 7  is a perspective sectional view as in  FIG. 6  but showing the float in a closed condition; 
         FIG. 8  is an exploded view depicting the component parts of the subject vent control device; 
         FIG. 9  is a simplified view depicting the venting of fuel vapors through the vent control device when the float is in an open condition; 
         FIG. 10  is a view as in  FIG. 9 , but showing the float in a closed condition as the result of rising fuel level in the vapor separator; and 
         FIG. 11  is a view as in  FIGS. 9 and 10 , but showing the vapor separator tipped at an approximate twenty-five degree angle and the float moved into the closed condition as the result of the biasing effect of the spring, thus preventing the escape of liquid fuel through the vent valve. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a general depiction of an outboard marine engine  12  affixed to the transom  14  of a boat is shown in  FIG. 1 . Small outboard marine engines  12  of this type are usually mounted on a bracket  16  so that the engine  12  can be quickly removed from the boat for transportation and/or maintenance. The bracket  16  includes a tilting feature which allows the motor head to be rotated into the boat, with the propeller  18  swinging up out of the water, to facilitate launching and maneuvering through shallow conditions. As an example, the motor  12  may be pivoted about axis A between these use and non-use positions, as well as for trim control. 
     An engine of the type shown in  FIG. 1  commonly runs on a liquid fuel like gasoline or ethanol. Liquid fuel is drawn from a fuel tank  20  by an engine-mounted marine fuel system, generally shown at  22  in  FIG. 2 . Except for the fuel tank  20  and a supply line  24 , the remainder of the fuel system  22  is fully integrated into the engine  12  so that these components are removed from the boat, together with the engine  12 . A low pressure fuel supply pump  26  sucks fuel from the tank  20  through the supply line  24 . The fuel is delivered to a vapor separator, generally indicated at  28 . The vapor separator  26  collects and discharges vapors given off from the incoming low pressure fuel and also from the hot, agitated fuel returning from the engine  12 . A high pressure pump  30  then pumps the fuel under pressure into the fuel injector system  32  to be consumed by the engine. Unused fuel is returned to the vapor separator  28  via return line  34 . A vent valve device, generally indicated at  36 , is provided with a vacuum fitting  38  for connection to the engine intake vacuum system. The vacuum creates a negative pressure in vent line  40  so that fuel vapors can be cycled through the engine  12 . 
     Referring now to  FIG. 3 , an exemplary vapor separator  28  is depicted for illustrative purposes. Those of skill will understand that the specific configuration of the vapor separator  28  can take many forms. In this example, the high pressure fuel pump  30  includes a fuel intake  42  at its bottom end and an outlet  44  at its top end leading directly to the fuel injector system  32 . Electrical power is supplied to the high pressure pump  30  through wires  46 . A schrader valve  76  is provided at the top of pump  30  to allow pressure testing of the outlet pressure. The separator assembly  28  includes a hollow, generally cylindrical housing  48  forming a hollow interior chamber  50 . On the top end of the housing  48  is mounted a top wall  52 . An O-ring  54  seals the perimeter of the top wall  52  against the top edge of the housing  48  to create a liquid and vapor-tight seal. A socket-like receiving pocket  55  is formed in the underside of the top wall  52  for receiving the vent valve device  36 . 
     Positioned over the bottom end of the housing  48  is a bottom wall  56 . An O-ring seal  58  seals the junction between housing  48  and bottom wall  56  to prevent liquid and vapor leakage. The separator assembly  28  also comprises a mounting flange  60  having an opening  62  formed there through for attachment inside the engine  12 . A rubber grommet  64  positioned within the opening  62  provides vibration isolation. 
     A vapor passage  66  terminates in a vapor outlet  68  formed through the top wall  52  and as part of the vacuum fitting  38 . The receiving pocket  55  communicates with the vapor passage  66 . The vapor outlet  68  is connected to the intake manifold of the engine by the vent line  40 . Positioned at the lower end of the vapor passage way  66  is the subject vent valve device  36 . The vent valve device  36  is distinguished from the prior art constructions such as illustrated in  FIG. 4 , for example, which characteristically include a needle valve having a needle valve plunger and a needle valve seat. A float assembly is mounted to the needle valve assembly and comprises a support arm and a float attached to one end of float arm. The other end of float arm is pivotally mounted to the support arm by a pivot pin so that the float can pivot up and down. Thus, the needle valve plunger is mounted on the float arm so that when the float is pivoted upwardly, the needle valve plunger closes against the needle valve seat sealing the needle valve. However, when the float pivots downwardly, the needle valve plunger disengages from the needle valve seat, thus opening the valve and allowing vapor and air from the chamber to pass through to the vapor passageway and out the vapor outlet. The pivot pin is oriented so that its axis is generally parallel to the motor tilt axis A, with the needle valve assembly lying generally between the pivot pin and the motor tilt axis A so that when the motor is rotated to a prop out-of-water condition, the needle valve assembly closes. 
     Referring again to the subject invention as depicted in  FIG. 3 , the top wall assembly  52  is shown including a pressure relief valve  70  which communicates with the vapor passageway  66  through a passageway  72 . The pressure relief valve  70  opens when the pressure within the chamber  50  exceeds a predetermined limit to allow internal air and vapor to escape through the passage  72  and the outlet  68 . 
     The bottom wall  56  has a fuel return inlet connected to a fuel return line  34  ( FIG. 2 ) from the fuel rail  32  of the engine  12  so that excess fuel from the fuel rail  32  is returned into the chamber  50  of the vapor separator assembly  28 . The bottom wall assembly  56  also comprises of hollow interior portion  74  which communicates with the internal chamber  50 . A schrader valve  76  is positioned at the end of the fuel inlet channel for drainage and pressure release. The fuel inlet  78  from the low pressure pump  26  extends through the bottom wall assembly  56  and communicates with the hollow interior portion  74  of the bottom wall assembly  56 . An optional cooling coil  80  is positioned in the chamber  50  and circulates cooling fluid to act as a heat exchanger cooling the fuel contained within the chamber  50  to minimize vaporization. 
     The problem inherent in prior art vent control configurations, such as the pivoted float assembly depicted in  FIG. 4 , arises when an engine  12  is laid on its side. When laid on its side, the float pin may not be oriented properly to allow the needle valve to close against the valve seat. As a result, liquid fuel may escape through the vapor passage causing a hazardous spill. 
     Referring to  FIGS. 5-7 , the subject vent valve device  36  is shown including a generally tubular, cup-like casing  82  having an open bottom end and a closed top end. Escape passage  84  forms a passageway for the escaping fuel vapors from the top of the casing  82  into the vapor outlet  68 . A self-locking cap  86  is affixed to the upper most end of the casing  82  and includes a flexible skirt  88  for developing a fluid and vapor tight seal within the receiving pocket  55 . As shown in  FIGS. 5 and 8 , an optional self-locking retainer ring  90  may be provided to resist disconnection of the vent control device  36  once inserted into the receiving pocket  55 . Protrusions  91  on the casing  82  limit the depth into which the cap  86  can be inserted into the receiving pocket  55 . 
     The open bottom end of casing  82  is closed with a perforated plug  92  through which both liquid fuel and fuel vapors are free to pass. A float  94  is free to slide axially within the casing  82  between the escape passage  84  and the plug  92 . The float  94  includes a sealing feature which, in the embodiment depicted, comprises a resilient sealing pad  96  adapted to press in sealing contact against the mouth of the escape passage  84 . In  FIG. 8 , the resilient sealing pad  96  and mouth of the escape passage  84  are shown to be formed on a slight angle, relative to the longitudinal sliding direction of the float  94 , and are so structured as to mate in full surface-to-surface contact with one another. The float  94  may be keyed to the interior of the casing  82  so that it can only fit within the casing  82  in a particular orientation and cannot rotate as it slides up and down. This keying of the float  94  within the casing  82  is particularly advantageous in situations where the resilient sealing pad  96  is required to seat upon the mouth of the escape passage  84  in a particular orientation like that of the angled configuration shown in  FIG. 8 . There is ample clearance space between the sides of the float  94  and inner wall of the casing  82  so that vapors flow freely through. 
     A light biasing element  98 , preferably but not necessarily of the coiled compression spring variety, is interposed between the plug  92  and the float  94  for urging the float  94  toward the mouth of the escape passage  84 . However, the spring  98  is too weak to overcome the normal gravitational weight of the float  94  in the absence of a buoyant liquid such as fuel. Thus, when the fuel level is below the level of the vent control device  36  within the vapor separator assembly  28 , the spring  98  is not strong enough to lift the float  94  away from its full open position as shown in  FIGS. 6 and 9 . 
     Referring now to  FIGS. 9-11 , the subject vent control device  36  is shown disposed in the upper fragment of the vapor separator assembly  28 .  FIG. 9  depicts the condition where the fuel level  100  is lower than the vent control device  36 . In this condition, vapor, as depicted by the line  102 , is drawn out of the vapor separator assembly  28  under the negative pressure created at the vapor outlet  68 . The vapor  102  passes through the porous plug  92 , around the ribbed sides of the float  94 , through the escape passage  84 , through the cap  86  and into the vapor passage  66 . 
       FIG. 10  depicts a condition where the fuel level  100  has risen within the vapor separator assembly  38 , thus lifting the float  94  within the casing  82 . When the fuel level  100  climbs high enough, the resilient sealing pad  96  atop the float  94  engages the mouth of the escape passage  84 , thus closing the vapor passage  66  to any further vapor venting. In this condition, if excess vapor pressure builds within the vapor separator assembly  28 , the pressure relief valve  70  will discharge the excessive pressure before a catastrophic failure occurs. 
       FIG. 11  depicts a condition where the vapor separator assembly  28  is tilted, such as occurs when the engine  12  is stored or otherwise tipped into a non-conventional orientation. Here, the fuel level  100  is shown below the vent valve device  36  such that the float  94  does not receive buoyancy. In this situation, the effect of the light spring  98  becomes critical. As depicted, the normal gravitational weight of the float  94  is separated into x and y vectors, with the y vector comprising the vertical (normal) dimension. The counteracting effect of the spring  98  becomes sufficient at a predetermined angle  104  to automatically move the float  94  toward its closed condition, with the resilient sealing pad  96  pressed against the mouth of the escape passage  84 . Thus, even though the fuel level  100  is relatively low within the vapor separator assembly  28 , the vent control device  36  is nevertheless closed, thereby shutting a leak path for liquid fuel through the vapor outlet  68 . While the angle  104  may be established at generally 25° from vertical, other angular measures may be desirable, and can be predetermined based upon the designed spring force constant of the spring  98 . 
     Accordingly, prior art designs use a float and hinge pin (as in  FIG. 4 ) which mean that the axis of motion for the float needs to be placed as close to parallel to the tilt/trim axis of the engine as possible so that the float will not allow fuel to vent during normal tilted storage of the engine. Sideways tilting of the engine however, such as when the engine is placed in the trunk of a car, cannot assure closure of the vent line and could lead to fuel leakage. Nevertheless, the subject vent valve device  36  functions at any tilted angle as a shut-off valve so that liquid fuel will be prevented from escaping the vapor separator assembly  78  even if the engine  12  is laid on its side. The subject vent control device  36  comprises a self-contained unit that does not depend on a fixed axis for float operation. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.