Patent Publication Number: US-7213583-B2

Title: Small engine fuel tank with integrated evaporative controls

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to fuel tanks for small engines such as those employed in portable power equipment as, for example, lawn mowers and portable generator sets. Recent regulations for controlling the emission of fuel vapors have required installation of vapor storage devices to prevent escape of fuel vapors through the engine air inlet during periods when the engine is not operating and provide for purging when the engine is running. This recently imposed requirement on small engine manufacturers has created problems in installing the engines in the equipment in which they are to be used inasmuch as the equipment manufacturer commonly purchases the engine and fuel tank for installation as a subassembly during final assembly of the engine operated equipment. Thus, for the aforesaid equipment applications the burden of providing for fuel vapor emission control has been imposed upon the small engine manufacturer and has created problems in the design and installation of the tank and fuel system for the small engines. 
   In particular, the requirement for a vapor storage device has been found to create problems in mounting the tank and fuel system on a small engine as a prepackaged subassembly; and, has added additional costs in providing for the storage device and the mounting and vapor conduit interconnections between the storage device and the tank. Thus, it has been desired to provide a way or means of controlling fuel vapor emissions from a small engine tank installation in a manner which is self-contained and low in cost. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a small engine fuel tank with integral fuel evaporative controls including a storage canister and rollover valve disposed within the tank in a manner which provides adequate control of fuel vapor emissions during periods of engine inoperation, permits purging during engine operation and thus simplifies the mounting of the fuel vapor emission devices on the engine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a small engine fuel tank of the type intended for gravity fuel feed to the engine; 
       FIG. 2  is a section view taken along section indicating lines  2 — 2  of  FIG. 1 ; and, 
       FIG. 3  is a section view taken along section indicating lines  3 — 3  of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, the fuel tank assembly of the present invention is indicated generally at  10  and includes a tank  12  having wall structure  14  which may be formed conveniently by weldment about a mid-seam  16  in any manner well known in the art as, for example, by metallic or non-metallic welding as the case may be for the particular material employed for the tank. 
   The upper wall  18  of the tank has provided therein a filler tube  20  which may be integrally formed with the upper wall  18  and which is adapted for receiving thereover a closure cap  22  indicated in dashed outline in  FIG. 1 . The tube  20  extends downwardly into the interior of the tank to a desired depth for creating a vapor dome in the region beneath the upper wall  18  when the liquid level in the tank has risen to cover the lower end of tube  20 . 
   Tank  12  has a fuel feed outlet fitting  24  provided through the lower wall on the lower wall thereof with a fuel feed passage  26  formed therein for gravity feed of fuel. It will be understood that fitting  24  is adapted for connection to a fuel line (not shown) for connection to the engine fuel inlet. It will be understood that the feed passage may be disposed at other locations of the tank wall structure, for example, the upper wall  18  in small engines employing a fuel pump. 
   Tank  12  has a fitting  28  extending from the upper portion of the sidewall  30  and which has a vapor purge passage  32  formed therein. With reference to  FIG. 1 , the passage  32  is an atmospheric air inlet. 
   Inlet  32  communicates through the tank wall and to the interior of a vapor storage canister  34  which is disposed within the tank and preferably attached to the inside of the top wall  18  of the tank as shown in  FIGS. 2 and 3 . It will be understood that the canister  34  may contain any suitable adsorbent such as, for example, granulated charcoal material. 
   The canister  34  also has connected thereto a fitting  36  which has vapor outlet passage  38  formed therein and which extends outwardly through the side  30  of the tank to the exterior of the tank. With reference to  FIG. 1 , passage  38  communicates through a conduit  33  shown in dashed outline to the air inlet  40  of the vehicle engine. 
   Referring to  FIGS. 2 and 3 , a float operated vent valve indicated generally at  42  is disposed within the tank and preferably adjacent the inside surface of the upper wall  18  of the tank. Valve  42  has the vapor outlet passage  44  thereof communicating with the interior of the canister  34  as shown in  FIG. 2 . It will be understood that the valve  42  may either be attached to the side of the canister or the undersurface of the upper wall  18  of the tank. In the present practice of the invention, the vapor vent valve  42  is float operated as is known in the art. 
   Referring to  FIGS. 2 and 3 , the filler tube  20  is disposed through the tank wall with the lower end of tube  20  located or positioned at a desired level of liquid fuel fill such that, upon the liquid level reaching the lower end of the tube, the vapor dome above the liquid fuel is isolated from the filler tube and vapor can no longer escape through the filler tube. Accordingly, if the rate of fill is sufficient such that the vapor cannot escape rapidly enough through the vent valve  42 , the liquid fuel rises quickly in the filler tube alerting the operator that the tank is at the desired level of fill. This arrangement thus maintains a vapor dome in the fuel level above the tank and prevents slugging of liquid fuel into the vent valve  42  and the canister. 
   The surface of the liquid fuel at the level of the lower end of the filler tube  20  is denoted by the reference character L in  FIG. 3 . It will be understood that the region of the tank bordered by the wall structure thereof above the level L comprises a vapor dome as denoted by reference numeral  46 . 
   In the present practice of the invention, the filler tube  20  is shown as disposed through the upper wall  18  of the tank; however, it will be understood that the filler tube may be also located through the sidewall  30  if desired. 
   The present invention thus provides an integrated fuel vapor storage and vapor flow control system for a fuel tank of the type employed for small engines whereupon the tank may be located in close proximity to the engine or in certain applications mounted directly to the engine for modular assembly to the equipment in which the engine is employed. The present invention thus enables implementation of fuel evaporative control on a small engine with only a change in the fuel tank and does not require the addition of other related components to the engine assembly. 
   Although the invention has hereinabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.