Patent Publication Number: US-2003234254-A1

Title: Vented fuel tank cap

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention.  
       [0002] The present invention relates to fuel tank caps for closing the filler neck of a fuel tank of a small internal combustion engine, particularly to a vented fuel tank cap.  
       [0003] 2. Description of the Related Art.  
       [0004] Small implements having gasoline powered engines, such as lawnmowers, garden tillers, snow blowers, sport vehicles, electrical generators and the like, have fuel tanks attached. For closing the fuel tank, a fuel tank cap is applied to the open end of a filler neck connected to and extending from the fuel tank. The fuel tank cap is commonly constructed to prevent escape of liquid fuel from the fuel tank while, at the same time, permitting venting of gases between the tank and the atmosphere.  
       [0005] One known fuel tank cap includes a generally dome-shaped flexible gasket extending below the interior of the fuel tank cap. The lower dome portion of the fuel tank cap includes holes therethrough for venting of vapors. Additionally, sufficient clearance is provided between internal threads on the fuel tank cap and external threads on the filler neck to define a path for venting of vapors. A narrow central post depends from the interior of the fuel tank cap and through the gasket. Below the gasket and vent holes, the central post also supports a baffle for deflecting liquid fuel away from the gasket vent holes. However, an extra manufacturing step is required to heat deform the end of the central post so that it will retain the baffle and gasket, adding expense and complexity to manufacturing.  
       [0006] Another known fuel tank cap includes a dome-shaped flexible gasket having a central vent hole and an integral downward depending tubular-shaped baffle around the vent hole which deflects liquid fuel away from the vent hole. The gasket has an annular rim that is retained by a matching annular notch in the fuel tank cap. However, separation of the gasket and baffle from the fuel tank cap is often a problem when the fuel tank cap is removed from the filler neck. Additionally, a separated or misaligned gasket may not properly seal between the fuel tank cap and the filler neck, resulting in liquid gas venting from the fuel tank.  
       [0007] Therefore, what is needed is a fuel tank cap assembly that better retains the flexible gasket component thereof while minimizing the number of components and assembly steps.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008] The present invention provides an improved vented fuel tank cap assembly. The vented fuel tank cap assembly includes a cap member having a disk-shaped cover portion and a cylindrical skirt portion extending therefrom. The cylindrical skirt portion includes internal threads for engagement to matching external threads located on the fuel tank neck portion. The internal and external threads cooperate to define a vent path therebetween. The cap member includes a tubular central post depending downward from the interior of the cover portion. Advantageously, the tubular central post is integral with the cap member. A filter element having a central hole for receiving the central post is located adjacent the interior of the cover portion. The filter element is held in position by a gasket having an annular rim surrounding a dome portion, the dome portion having a central hole disposed on the central post and compressing the filter against the interior cover portion. The annular rib around an outside diameter of the central post retains the gasket to the cap member slightly deforming the dome portion and sealing the annular rim against the interior surface of the cap member. Radial grooves are provided on the upper surface of the annular rim, i.e., the surface in contact with the interior surface of the cover portion.  
       [0009] The components of the vented fuel tank cap assembly are easily assembled. First, the filter element is slid onto the central post of the cap member, so that one side of the filter element is against the interior of the cover portion and the central post extends through the hole in the filter element. Second, the gasket is slid onto the central post, the dome portion extending away from the cap member. The dome portion is pressed toward the cap member cover portion, compressing and capturing the filter element, until the dome portion hole passes over the annular rib or other protuberance protruding from the central post. In this position, the annular rib retains the gasket and the filter element to the cover member and the annular rim is held in contact with the interior surface of the cover portion.  
       [0010] The assembled fuel tank cap provides a vent path for exchanging gases between the fuel tank and the surrounding atmosphere. The vent path is provided from the downward-depending end of the tubular central post, through the central post wall, through the porous filter element, through the grooves provided in the upper surface of the annular rim, and outwardly through the nonsealing threads of the cylindrical skirt member and neck filler portion to the surrounding atmosphere.  
       [0011] Advantageously, the vented fuel tank cap assembly firmly retains the gasket and filter element to the cap member. Also, the annular rim is held in position by the central post rib so that a seal is formed between the gasket and the filler neck end portion when the fuel tank cap is attached to the fuel tank. Additionally, the filter element and gasket are easily assembled with the cap member using a single step of positioning the filter element and gasket over the central post and rib. Thus, no additional manufacturing steps are required to complete the assembly or retain the components in position.  
       [0012] In one form thereof, the vented fuel tank cap assembly includes a cap member having a circular cap portion and a downwardly depending skirt portion, the skirt portion including an engagement portion for removably attaching the cap assembly to a filler neck portion of a fuel tank, the cap portion including a cylindrical post depending from an interior of the cap portion, the post having at least one rib extending exteriorly around at least a portion thereof. The cap assembly further includes a gasket having an annular rim surrounding a dome portion and an opening in the dome portion, wherein the opening fits around the post and the rib retains the gasket to the cap member.  
       [0013] In another form thereof, the vented cap assembly includes a cap member having a circular cap portion and a downwardly depending skirt portion—the skirt portion including an engagement portion for removably attaching the cap assembly to a filler neck portion of a fuel tank, the cap portion including a post depending from an interior of the cap portion; and a circular gasket having an opening defined therethrough, an upper surface engageable with the interior surface of the cap portion, and a lower surface opposite the upper surface, the opening disposed around the central post; the post defining a vent path for communication of gases adjacent the lower surface with gases adjacent the upper surface.  
       [0014] In yet another form thereof, the vented fuel tank cap assembly for a filler neck end portion of a fuel tank includes a cap member having a circular cap portion and a downwardly depending skirt portion, the skirt portion including nonsealing threads for removably attaching the cap assembly to the filler neck end portion, the cap portion including a tubular post depending from an interior surface of the cap portion, an interior surface of the tubular post defining a first deflection surface and a first vent path therethrough; and a gasket having an annular rim surrounding a dome portion and an opening defined in the dome portion, the opening engaged around the tubular post, the gasket and an exterior surface of the tubular post defining a second deflection surface; the annular rim contacting the interior of the cap portion and forming at least one second vent path therebetween.  
       [0015] In another form thereof, in combination, a fuel tank having a fuel tank neck portion, and a fuel tank cap having: a cap member including a circular cap portion and a downwardly depending skirt portion, the skirt portion including an engagement portion for removably attaching the cap to the filler neck portion, the cap portion including a tubular post depending from an interior of the cap portion, the tubular post having a rib extending exteriorly around at least a portion thereof; and a gasket having an annular rim surrounding a dome portion and an opening in the dome portion, wherein the opening fits around the tubular post and the rib retains the gasket to the cap member. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
     [0016] The above-mentioned and other features and advantages of the invention, and the manner of obtaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
     [0017]FIG. 1 is a side perspective view of a lawnmower having a small internal combustion engine, a fuel tank, and a fuel tank cap assembly in accordance with the present invention;  
     [0018]FIG. 2 is a side perspective view of a portion of the engine of the lawnmower of FIG. 1, showing the fuel tank cap assembly;  
     [0019]FIG. 3 is a sectional view taken along line  3 - 3  of FIG. 1;  
     [0020]FIG. 4 is an exploded perspective view from above of the fuel tank cap assembly of FIG. 1; and  
     [0021]FIG. 5 is an exploded perspective view from below of the fuel tank cap assembly of FIG. 1.  
     [0022] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an exemplary embodiment of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
    
    
     DETAILED DESCRIPTION  
     [0023] Referring to FIGS. 1 and 2, lawnmower  10  having a small internal combustion engine includes fuel tank  14 . Fuel tank  14  has an open filler neck end portion  16  (FIG. 2) providing an opening therein for filling fuel tank  14  with fuel. Vented fuel tank cap assembly  12  is attached to filler neck end portion  16  to prevent liquid fuel from escaping fuel tank  14 . Lawnmower  10  is an exemplary implement. Vented fuel tank cap assembly  12  may also be attached to a fuel tank filler neck end portion on other types of small implements having gasoline powered engines, for example garden tillers, snow blowers, sport vehicles, and electric generators. Alternatively, vented fuel tank cap assembly  12  may be attached to other tanks or reservoirs requiring venting of vapors.  
     [0024] Referring now to FIGS.  3 - 5 , vented fuel tank cap assembly  12  generally includes cap member  31 , filter element  18 , and gasket  20 . Gasket  20  is attached to cap member  31  and captures filter element  18  between cap member  31  and gasket  20 .  
     [0025] Referring to FIG. 3, cap member  31  includes disk-shaped cover portion  32  and downwardly depending cylindrical skirt portion  33 . The interior of skirt portion  33  defines threads  39  that engage filler neck threads  17  defined on the outside of filler neck end portion  16 . The fit and engagement of cap member threads  39  with filler neck threads  17  retains cap member  31  to filler neck  16  while defining a vent passage therebetween for escape of fuel vapors.  
     [0026] Depending downwardly from interior surface  34  of cover portion  32  is central post  35 . Central post  35  is shown as generally tubular, having a cylindrically-shaped exterior surface  36  and a cylindrically-shaped interior surface  37 . Central post  35  is integrally formed with cap member  31 , which may be molded of plastic or other similar material. Post  35  may be another shape, such as a square or triangular cross-section, for example. Additionally, post  35  may depend from the center of cover portion  32  or from another part of cover portion  32 .  
     [0027] Referring to FIGS. 4 and 5, gasket  20  includes an annular generally flattened sealing rim  21  surrounding a downwardly depending dome-shaped cavity  24 . The central bottom portion of dome  24  defines hole  25  therethrough. Gasket  20  has an upper surface  22  and an opposite lower surface  23 . The upper surface  22  of annular rim  21  defines four grooves  28  circumferentially spaced around annular rim  21 . Notches  29  are defined on the outside edge of annular rim  21  adjacent each groove  28 . Gasket  24  is advantageously made of rubber or other material that is impervious to and non-reactive with liquid fuel and which is flexible.  
     [0028] Filter element  18  is generally rectangular shaped and defines a hole centrally therethrough. Filter element  18  allows transmission of fuel vapor and atmospheric gases but is generally impervious to liquid fuel. Filter element  18  may be constructed of reticulated flexible polyurethane with open pores of approximately 50 per inch, for example, or other similar porous material which will trap liquid fuel, yet allows vapors to pass therethrough. Filter element  18  is positioned between cover portion  32  and gasket  20  in dome-shaped cavity  24 .  
     [0029] Fuel tank cap  10  operates to allow fuel vapor to vent from fuel tank  14  and/or to allow atmospheric gases to enter fuel tank  14 . As shown in FIGS. 3 and 5, vent path slot  41  is defined vertically along a portion of the length of central post  35 . Specifically, slot  41  extends through the tubular wall of central post  35  from the downwardly depending end, toward cover portion  32 , ending at slot end  42 . Advantageously, slot end  42  is located above the level of dome  24  and adjacent to filter element  18 . Additionally, grooves  28  between upper surface  22  of rim  21  and interior surface  34  of cap portion  31  and notches  29  define a vent path therethrough. Thus, fuel vapor escapes fuel tank  14  by passing from the interior of central post  35 , through vent path  41  at slot end  42 , through porous filter element  18 , and into the space defined between gasket dome  24  and cover portion  32 . The vent path for escaping fuel vapors continues through grooves  28  and notches  29  between annular rim  21  and cover portion interior surface  34 , and between nonsealing threads  39  and filler neck threads  17 .  
     [0030] Referring to FIG. 3, the vented fuel cap assembly  12  is assembled as follows. Hole  19  of filter element  18  slides onto central post  35  until a surface of the filter is compressed against interior surface  34  of cover portion  32 . Gasket  20  then slides onto central post  35  until hole  25  passes over and is engaged by annular rib  43  defined around an external portion of central post  35 , thereby retaining gasket  20  to cap member  31 . In this engaged position, gasket  20  is firmly retained to cap member  31 , and dome  24  is slightly deformed toward cap member  31  and annular rim  21  is sealingly compressed against interior surface  34  of cover portion  32 . Rib  43  may be a single annular protuberance defined around part of or the entire diameter of central post  35 , or may alternatively be a segmented series of protuberances, a single protuberance, or other arrangement of protuberances.  
     [0031] In this arrangement, vented cap assembly  12  may be threadably engaged to filter neck end portion  16  and operates to prevent liquid fuel from escaping fuel tank  14  while providing venting of fuel vapors to the atmosphere. As cap member  31  is screwed onto filler neck end portion  16 , annular rim  21  of gasket  20  is captured between a top end of filler neck end portion  16  and interior surface  34  of cover portion  32 , thus forming a seal between lower surface  23  of rim  21  and filler neck portion  16 .  
     [0032] In this installed position, vented cap assembly  12  forms two deflection surfaces that resist venting of liquid fuel from fuel tank  14 . The first is formed by exterior surface  36  of central post  35  and by gasket  24  which is sealably pressed against the upper end of filler neck end portion  16 . The second deflection surface is defined by the interior surface  37  of central post  36 . The deflection surfaces reduce splashing of liquid fuel toward the vent path, thus ensuring only fuel vapors are vented.  
     [0033] The escape of liquid fuel from fuel tank  14  is further prevented by the difficulty of liquid fuel reaching vent path  41  along slot end  42  and the resistance of filter element  18  to the flow of liquid fuel. Liquid fuel that reaches filter element  18  will be drained by gravity back through vent path  41  and back into fuel tank  14 .  
     [0034] While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It should be understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.