Abstract:
A system for reducing escape to the atmosphere of hydrocarbon fuel vapors from a fuel tank for a combustion engine powered device including at least one functional member that directly communicates with the fuel tank and is constructed to receive and retain hydrocarbon vapors therein. The functional member may further include a bed of activated carbon-based material for adsorbing and purging of the hydrocarbon vapors. The functional member is otherwise useful to the device beyond the vapor handling function and may be incorporated into a handlebar assembly, frame component, housing, cover, and the like thereby reducing component parts and reducing cost and complexity of the device.

Description:
FIELD OF THE INVENTION 
     The present invention relates to controlling fuel evaporative emissions, and more particularly, to a system for reducing hydrocarbon fuel vapor emissions from a fuel system. 
     BACKGROUND OF THE INVENTION 
     Many devices, such as lawn mowers, weed trimmers, leaf blowers, and the like, are powered by hydrocarbon fuel burning engines. Due to their relatively high volatility, hydrocarbons quickly vaporize from the liquid fuel. Such hydrocarbon vapors can escape to the atmosphere from a fuel tank or other fuel system components. Increasingly, the evaporative emissions of such devices are being strictly regulated by various governments and agencies. Large, costly fuel vapor venting components and storage systems typically are not practical for small engine applications. 
     SUMMARY OF THE INVENTION 
     A vapor treatment system for treating hydrocarbon fuel vapors from a combustion engine powered device including at least one functional member that directly communicates with a fuel tank of the device, and is constructed to receive and retain or hold hydrocarbon fuel vapors therein. The functional member may further include a bed of activated carbon-based material for storing or releasably retaining the hydrocarbon vapors. The functional member is otherwise useful to the apparatus beyond the vapor handling function and may be incorporated into a handlebar assembly, frame component, housing, cover, and the like thereby reducing component parts and reducing cost and complexity. 
     The vapor treatment system may further include a vent line that communicates a tubular member having a carbon-based bed with a fuel tank of the device. The vapor vent permits fuel vapors to flow out of the fuel tank to the tubular member comprising the carbon-based material for environmental treatment thereof. 
     At least some objects, features and advantages of some embodiments of the invention include providing a fuel vapor treatment system for combustion engine powered devices, such as lawn mowers for example, that is cost efficient, does not require any additional structural parts, and effectively treats hydrocarbon fuel vapor emissions to thereby prevent vapors from being emitted into the atmosphere from the fuel tank, is durable, reliable, of relatively simple design and economical manufacture and assembly, and in service has a long useful life. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
         FIG. 1  is a perspective view of a walk-behind lawn mower including a handlebar assembly with a carbon canister; 
         FIG. 2  is an enlarged perspective view of the handlebar assembly of the lawn mower of  FIG. 1 ; 
         FIG. 3  is an enlarged fragmentary cross-sectional view of a first embodiment of a connector body and carbon canister of the handlebar taken along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a perspective view of the connector body of the carbon canister; 
         FIG. 5  is a cross-sectional view of the connector body taken along line  5 - 5  in  FIG. 1 ; 
         FIG. 6A  is a sectional view taken along line  6 A- 6 A of  FIG. 4 ; 
         FIG. 6B  is a sectional view of a modified connector body; 
         FIG. 7  is a schematic view of a passive purge arrangement of the hydrocarbon vapor emissions system; 
         FIG. 8  is a schematic view of an active purge arrangement of the hydrocarbon vapor emissions system; 
         FIG. 9  is a schematic view of a second embodiment of an evaporative emissions treatment system; 
         FIG. 10  is a perspective view of a handlebar assembly for the evaporative emissions treatment system of  FIG. 9 ; and 
         FIG. 11  is a schematic view of a modified evaporative emissions treatment system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring in more detail to the drawings,  FIG. 1  illustrates a first embodiment of a vapor emissions treatment system  10  for a fuel-powered walk-behind lawn mower  11  that has a fuel tank  12  communicating with a vapor canister  16  that preferably is incorporated into an existing and otherwise functional portion of the mower  11 , such as a handlebar assembly  18 . The vapor or carbon canister  16  as they are sometimes called, may be disposed within or form part of the handlebar assembly  18 . The carbon canister  16  can otherwise replace a tubular member on the lawn mower  11 , and preferably houses a carbon-based bed of material for effectively adsorbing or absorbing hydrocarbon-based fuel vapors. Once in the canister  16 , the hydrocarbon vapors may be desorbed or purged from the canister  16  and routed back into the fuel tank  12  or directed to a fuel burning engine  19 . 
     The fuel tank  12  may be of a conventional design such as blow molded or vacuum formed plastic with a suitable shape for the specific engine application for which the fuel tank  12  will be used, such as for a rotary lawn mower as described herein. As shown in  FIG. 1 , the fuel tank  12  comprises a generally rounded rectangular shape and has a fill spout  21  closed by a removable fuel cap  22 . When the fuel tank  12  is filled with a relatively volatile fuel, such as gasoline, and capped with the fuel cap  22 , some of the fuel relatively quickly begins to vaporize thereby increasing the pressure inside the fuel tank  12 . As the volume of the fuel vapor increases the pressure within the fuel tank  12  increases if the tank is not vented. Even without a vent, hydrocarbon vapors can escape from the fuel tank  12  through non-sealed areas and permeate through unsealed areas or gap such as between the fuel cap  22  and the spout  21  in the top  20  of the fuel tank  12 , and may more slowly permeate through the fuel tank walls and fuel lines. 
     To reduce the level of fuel vapors that permeate and escape from the fuel tank  12 , a flexible vapor line  14  connects to the fuel tank  12  to the canister  16  to route the hydrocarbon vapors to the canister  16  for storage therein. The vapor line preferably communicates with the tank through a valve  26  which is preferably located near the top of and in the fuel tank  12 . The valve  26  preferably prevents the flow of liquid fuel to the canister  16  even if the lawnmower is significantly tilted or inverted, and permits fuel vapors to pass through it at least when the lawnmower is in its normal operating orientation or attitude (e.g. not significantly tilted or inverted). The valve may be of the type disclosed in pending U.S. patent application Ser. No. 10/955,795 filed Sep. 30, 2004, which is incorporated herein by reference in its entirety. The valve  26  may open in response to increased pressure inside the fuel tank  12 , or may be normally open and closed only when acted on by liquid fuel. 
     In general, carbon canisters include a bed of porous carbon-based material received within a canister housing, where hydrocarbon vapors are removed from, adsorbed or absorbed by the carbon-based material and relatively hydrocarbon free air can be discharged from the canister. After removal or adsorption of the hydrocarbon vapors, the relatively hydrocarbon free air can then be vented to the atmosphere. When the engine is running with the throttle at least partially open, the pressure drop produced in the fuel tank tends to create an air or vapor flow from the carbon canister toward the fuel tank  12  which desorbs or removes the hydrocarbon fuel vapors from the carbon material. The vapors are then routed back into the fuel tank  12  or to the engine  19  for use in powering the engine. 
     As best shown in  FIGS. 1 and 2 , the handlebar assembly  18  is tubular and includes a U-shaped handle section  28  having a laterally extending handle  30  and a pair of transverse legs  32 ,  34  extending from each end of the handle  30 . One leg  32  is connected by a nut and bolt  36  to a straight extension tube  38  which is connected at its other end to a blade housing  40  ( FIG. 1 ) of the lawn mower  11 . The other leg  34  preferably includes a vent hole  42  open to the atmosphere and is received over a reduced diameter end  108  of a tubular casing  46  and connected thereto by a nut and bolt  48 . The vent  42  could be on either leg  34  or  32 , and a vent in leg  32  may produce better results and require a smaller canister. The vent also could be disposed in other locations as desired. A cross bar  50  preferably extends between and is connected to each of the legs  32 ,  34  preferably by the bolts  36 ,  48 . The casing  46  is connected at its other end to a connector body  52  which in turn is connected to the blade housing  40 . As shown in  FIG. 5 , a bolt  54  is disposed through an opening  56  in the casing  46  and an opening  58  in the connector body  52  to connect them together upstream adjacent one end of the casing  46 . 
     As best shown in  FIGS. 2-4  and  6 A, the connector body  52  comprises a tubular metal body  60  having a passage  61 , an open end  62 , and a generally closed end  64  with a through hole  66 . The open end  62  has a diameter sized so that it fits within the casing  46  of the canister  16  and preferably has a shoulder  68  engaged by an end of the casing  46 . The closed end  64  of the connector body  52  preferably is formed by compressing the tubular structure of the body  60 . The body  60  of the connector body  52  has a metal fitting  70  that preferably is welded to the outer surface  72  of the body  60 , and is designed to mate with one end of the vent line  14  to communicate the vent line with the passage  61 . Alternatively and as shown in  FIG. 6B , the connector body  52 ′ can be formed in one piece with a solid integral end  64 ′ by investment or die casting or by injection molding. The body  60 ′ and the open end  62 ′ preferably are substantially the same as the similar sections of the body  60  as shown in  FIG. 6A . A metal fitting  70 ′ may have a head  74  that is press fit through an opening  76  and a stop flange  78  that limits insertion of the fitting  70 ′ into the opening  76 . The fitting  70 ′ communicates the vent line  14  with the canister  16 . 
     Since hydrocarbon vapors will be present within the casing  46  and connector body  52 ,  52 ′ as best shown in  FIGS. 3 and 5 , a seal  80  or washer preferably is disposed between a head  82  of the bolt  54  and body  46 , and another seal  84  or washer preferably is disposed between a nut  86  received on the bolt  54  and the body  46 . The seals  80 ,  84  restrict or prevent the escape to the atmosphere of hydrocarbon vapors. The seals  80 ,  84  preferably are formed of an elastomer such as a high durometer elastomer such as EPDM, Viton, Buna N or the like and may be coated on, carried by or separate from the bolt  54  and nut  86 . 
     In reference now to  FIG. 2 , the carbon canister  16  is defined in part by or carried in or by the casing  46  which preferably is a hollow, elongated cylindrical metal tube with an interior that defines a chamber in which a bed of activated carbon-based material  90  is received. The casing  46  is preferably straight and elongated to create a longer flow path for distribution of hydrocarbon vapors through the canister  16  for better carbon bed utilization and less flow restriction. As defined herein, activated carbon refers to a highly porous carbon-based structure that exhibits relatively high adsorption and desorption efficiencies of organic compounds from gases and liquids. It is preferable that the casing  46  be relatively long with its cross-sectional diameter smaller than its length and preferably equal to or less than ¼ of its length. Preferably, the casing  46  or a chamber in the casing has a volume suitably sized based of fuel type, temperature change, absorption capacity of specific carbon and required amount of carbon, and by way of example and without limitation, may be from between 30 cc and 100 cc, and more preferably of about 40 to 60 cc for retaining the activated carbon. Desirably the chamber or casing  46  has a volume that is at least 1/50 of the volume of the fuel tank  12 . In one presently preferred embodiment, the activated carbon particles are pellets and may be any carbon-based material suitable for a carbon canister as is known to one skilled in the art. 
     As shown in  FIG. 3 , to retain the carbon material  90  while permitting gaseous flow into and out of the canister, retainer discs  92 ,  94  are disposed at the opposed ends of the carbon bed and preferably are formed of a mesh or an open cell foam or other material permitting hydrocarbon vapor and air to freely flow therethrough. The disc  92  retains and traps carbon granules or pellets to prevent contamination of the fuel tank  12 , and the disc  94  disposed on the other end of the canister  16  is used to prevent carbon granules or pellets from flowing into the atmosphere through an air vent hole  96 . 
     The air vent hole  96  is formed through a bottom surface  98  of a plastic plug or cup  100  which preferably has a chamfered edge  101  adapted to engage a shoulder  103  of the casing  46 . The cup  100  retains a biasing member such as spring  102  that is disposed within the canister  16 . The spring  102  provides a compression load on the carbon material to secure the carbon bed  90  inside the body  46  of the canister  16  and to reduce vibration and movement of the carbon material  90  which tends to break down the carbon pellets or granules structure. The spring  102  may act on the disc  94  through a more rigid back-up disc, or screen  104  that permits free or substantially unrestricted gaseous flow. The screen  104  may have an axially extending flange  106  to guide it within the body  46 . 
     At one end  108  the casing  46  preferably is slightly reduced in diameter to an outer diameter approximately equal to the inner diameter of the adjacent tubular leg  34  of the handlebar assembly  18 . Thus, the canister  16  is assembled to the handlebar assembly  18  by sliding the end  108  of the body  46  inside the leg  34  of the handlebar assembly  18  and connecting them together with the bolt  48  as previously described. 
     During assembly, the plastic cup  100  is inserted into the casing  46 , bottom  98  first, and the spring  102  is inserted thereafter. The back up disc  104  is then inserted into the casing, followed by the disc  94 . A predetermined volume of activated carbon material  90 , preferably in pellet form, is poured into the casing  46  and then the other disc  92  and a backup disc  110  are placed in the casing  46  and the connector body  52  is then inserted into the casing  46  of the canister  16  and bears on the disc  110  to compress the carbon bed  90  into a tight pack by compressing the spring  102 . 
     In use, fuel vapors flow from the fuel tank  12  and into the canister  16  by way of the vent line  14 , fitting  70 , connector body passage  61  and casing  46  in which the carbon material  90  is contained. Hydrocarbon vapors are adsorbed by the carbon material  90  and relatively hydrocarbon free air is permitted to vent from the carbon canister through the air vent hole  96  that communicates with the atmosphere through the vent hole  42  in the leg  34  of the handlebar assembly. In this manner the fuel tank  12  is vented to the atmosphere only through the canister  16 . 
     The canister  16 , may be purged of hydrocarbons either passively or actively. The term “passive purging” refers to the process of removing captured hydrocarbon fuel vapor from the canister  16  by natural means such as by gravitational forces or by a pressure drop between, for example, the fuel tank  12  and the canister  16 . A passively purged system for the present invention is shown in  FIG. 7 . As the pressure inside the fuel tank  12  increases, the valve  26  opens and allows fuel vapors to pass through the hose  14  and into the carbon canister  16  via the connector body  52 . When a subatmospheric pressure exists inside the tank, the valve  26  opens and air from the atmosphere flows through the air vents  42 ,  96  and desorbs the hydrocarbons from the carbon bed  90 . The hydrocarbons then flow back into the fuel tank  12  and may subsequently be used to power the engine of the lawn mower  11 . Typically, these pressure changes relative to the surrounding atmospheric pressure are produced by temperature changes such as diurnal temperature changes. 
     For an actively purged system, as shown in  FIG. 8 , a purge control valve  120  is disposed in the vent line  14  to selectively communicate the vent line  14  with a purge line  122  that preferably communicates with an intake manifold or other low pressure engine intake. The term “active purging” refers to the process where captured fuel vapor in the canister  16  is drawn out of the canister  16  by a pressure gradient generated between the purge line  122  and the canister  16 . Fuel vapor is purged from the canister  16  by opening the solenoid operated valve  120  (which could be pneumatically or otherwise actuated) to communicate the reduced pressure signal through the purge line  122  to the canister  16 . Air is drawn in through the canister vent  96 , down through the bed  90  and desorbs the fuel vapor therefrom. The fuel vapor can be delivered either to the engine  19  for combustion or back into the fuel tank  12 , for example. 
       FIG. 9  is a schematic representation of a second vapor emissions treatment system  124  for a walk-behind lawn mower (not shown) which includes a fuel tank  112  having a vent line  14  attached thereto that communicates with a support tube  116  of a handlebar assembly  118 . The support tube  116  defines a suitable volume (inner diameter (ID) and length) or container for capturing and retaining hydrocarbon vapors. The vapors may then be purged from the support tube  116  by a vacuum generated by or in a carburetor  120  and used for powering an internal combustion engine  119 . 
     As shown in  FIG. 10 , the support tube  116  of the handlebar assembly  118  houses or stores hydrocarbon vapors therein. The tube  116  is generally U-shaped and includes a first end  122  sealed from the atmosphere with a connector body  52 ,  52 ′ therein and a second end  124  including a vent hole  126 . The tube  116  is designed having a specific internal diameter (ID) and length (volume) suitable for capturing and retaining or holding all or substantially all of the hydrocarbon vapors emitted from the fuel tank  112 . The vent line  14  is attached to the fitting  70 ,  70 ′ of the connector body  50 ,  52 ′. 
     The ID and the length of the tube  116  preferably are determined according to certain assumptions or design conditions relating to anticipated volumes of fuel vapor that must be captured or accounted for. One representative tube  116  has an ID of 0.75 inches and length of 54 inches, thereby providing a total volume of 127.2 cubic inches. In a fuel tank with a capacity of 0.5 gallons, or 115.5 cubic inches, a change in volume of about 8.8 cubic inches will occur over a 24-hour temperature change of 40° F. from 65° F. to 105° F. Since the volume of the fuel tank itself does not change, the expanded volume of 8.8 cubic inches of vaporized fuel must exit the fuel tank. The expansion of the vapor thus produces a slow gas flow within the tube  116 . With this slow flow and since hydrocarbons are heavier than air, the hydrocarbon vapors generally will remain in the handlebar tube  116  until a first upwardly inclined leg  128  becomes filled. Theoretically, in a 24-hour period the temperature will increase for some time and then decrease. The cooling down period will cause some retraction of the volume of vapor from the tube  116  and some return flow to the fuel tank  112 . Because a portion of the vapor has actually changed state from liquid to vapor and not all of the vapor will condense back to liquid form, a true reversible process is not achieved and thus some of the hydrocarbon vapors will remain in the tube  116 . Once the first vertical leg  128  becomes saturated and likewise a second vertical leg  130  becomes saturated, hydrocarbon vapors may escape to the atmosphere through the vent hole  126 . To prevent hydrocarbon vapors from escaping to the atmosphere in the event that the handlebar tube  116  becomes completely saturated, activated carbon may be disposed within the vertical leg  130  of the tube  116  near the air vent hole  126  to adsorb hydrocarbons prior to gaseous discharge to the atmosphere. 
     With reference again to  FIG. 9 , the hydrocarbon vapors that are captured inside the handlebar tube  116  may be purged by a low or subatmospheric pressure generated in the area of or communicated with the tube  116 . The low pressure may be generated by the operating engine to pull air from the atmosphere through the vent hole  126  and into the tube  116 . The low pressure also draws the hydrocarbon vapors captured in the tube  116  out of the tube  116  and into the vent line  14 . The vapors pass through a vapor channel formed in a roll-over valve  126  and into a purge hose  128 . The hydrocarbon vapors are then drawn into an air cleaner housing  130  through a hydrocarbon vapor port  132 , while air from the atmosphere is also drawn into the housing  130  through an air port  134  via the subatmospheric pressure generated by the operating engine. An orifice  136  is provided in the air cleaner housing  130  to control the pressure drop therein. Since hydrocarbon vapors are heavier than air, the hydrocarbon vapors will tend to stay toward the bottom of the housing  130 , while the air will rise to the top. While separated, the hydrocarbon vapor and air pass through an air cleaner  138  and are then drawn into the carburetor  120 , where they are mixed with liquid fuel delivered from a carburetor bowl  140  supplied with liquid fuel from the fuel tank  112 . The air/fuel mixture is then fed into the engine  119  for combustion thereof. Alternatively, as shown in  FIG. 11 , the hydrocarbon vapors in the purge hose  128  may be fed into a the mixing passage  142  of the carburetor  120  instead of the air cleaner housing  130 . 
     Accordingly, fuel vapor from the fuel tank preferably is stored in an existing functional member of the combustion engine powered apparatus that preferably includes an existing chamber, such as the interior of the casing  46 , in which the vapor may be received. The existing functional member of the apparatus may include one or more, or a portion of the following, by way of examples without limitation: a frame component, a housing, a handlebar assembly, a handle, a cowling, a cover, a bracket, a tank, a support, a wheel, and the like. By providing the vapor storage, with or without a bed of carbon material, in an existing functional member of the apparatus, the size and shape of the apparatus is not changed, the function of its components is not changed, a separate housing for vapor storage is not needed, and a relatively closed loop and contained vapor control system can be provided. 
     While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit and scope of the invention as defined by the following claims.