Abstract:
A fuel cap operable to close an opening of a fuel tank. The fuel cap includes an outer shell having a protrusion and a shell locking member. The fuel cap includes a detection mechanism for sensing a level of fuel within the tank. The fuel cap further includes an assembly component engageable with the outer shell to support the detection mechanism on the outer shell. The assembly component defines a groove operable to receive the protrusion. Additionally, the assembly component includes a component locking member. The outer shell and the assembly component are engageable with one another by a relative axial movement followed by a relative rotational movement about an axis. Once engaged, the outer shell and the assembly component are fixed against disengagement by engagement of the shell locking member and the component locking member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Priority is hereby claimed to U.S. Provisional Patent Application Ser. No. 60/727,088 filed on Oct. 14, 2005, the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to fuel gauge caps. More particularly, the invention relates to an improved structure and method for assembly of a fuel gauge cap. 
     SUMMARY 
     In one embodiment, the invention provides a fuel cap operable to close an opening of a fuel tank. The fuel cap includes an outer shell having a protrusion and a shell locking member. The fuel cap includes a detection mechanism for sensing a level of fuel within the tank. The fuel cap further includes an assembly component engageable with the outer shell to support the detection mechanism on the outer shell. The assembly component defines a groove operable to receive the protrusion. Additionally, the assembly component includes a component locking member. The outer shell and the assembly component are engageable with one another by a relative axial movement followed by a relative rotational movement about an axis. Once engaged, the outer shell and the assembly component are fixed against disengagement by engagement of the shell locking member and the component locking member. 
     In another embodiment, the invention provides a fuel cap for closing an opening of a fuel tank and for displaying a level of fuel in the tank. The cap includes an outer shell having an interior region. The outer shell includes a first protrusion and a second protrusion having different proportions and extending into the interior region. The fuel cap includes a detection mechanism for sensing and responding to the level of fuel in the tank. The fuel cap further includes an assembly component defining grooves for receiving a portion of the detection mechanism. The assembly component defines a first slot and a second slot for respectively engaging the first protrusion and the second protrusion. 
     In yet another embodiment the invention provides a method of assembling a fuel cap for closing an opening of a fuel tank. The cap includes an outer shell having a protrusion formed thereon and an assembly component formed with an L-shaped slot including an axial portion and a lateral portion. The method comprising the acts of axially joining the outer shell and the assembly component such that the protrusion is received in the axial portion of the L-shaped slot, rotating the outer shell and the assembly component relative to each other about an axis such that the protrusion moves from the axial portion to the lateral portion of the L-shaped slot, and automatically locking the outer shell and the assembly component against substantial relative rotation about the axis. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a fuel cap; 
         FIG. 2  is an exploded assembly view of the fuel cap of  FIG. 1 ; 
         FIG. 3  is an exploded assembly view of a portion of the fuel cap of  FIGS. 1 and 2 ; 
         FIG. 4  is a perspective view of the fuel cap of  FIGS. 1-3  in a first partially assembled state; 
         FIG. 5  is a perspective view of the fuel cap of  FIGS. 1-4  in a second partially assembled state; 
         FIG. 6  is a top view of the fuel cap of  FIGS. 1-5 ; 
         FIG. 7  is a cross-sectional view of the fuel cap taken along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a perspective view of an assembly component of the fuel cap of  FIGS. 1-7 ; 
         FIG. 9  is a first cross-sectional view of the assembly component taken along line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a first cross-sectional view of the assembly component taken along line  10 - 10  of  FIG. 8 ; 
         FIG. 11  is a first cross-sectional view of the assembly component taken along line  11 - 11  of  FIG. 8 ; 
         FIG. 12  is a bottom view of an outer shell of the fuel cap of  FIGS. 1-6 ; 
         FIG. 13  is a perspective view of an end cap for the fuel cap; and 
         FIG. 14  is a front detail view of the fuel cap, illustrating the attachment locations for the end cap of  FIG. 13 . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  illustrate a fuel cap  20  for use with a container (not shown) such as a fuel tank having a threaded opening. The fuel cap  20  includes a closure portion  24  and a level detection mechanism  28 . The closure portion  24  includes an outer shell  32  having threads for engaging the threaded opening. A sealing element  34  provides a seal between the closure portion  24  and the threaded opening. The level detection mechanism  28  includes a frame  36  having two legs  36   a  and  36   b , an output rod  40 , and a float member  44 . The float member  44  is buoyant in most liquids (e.g., gasoline, diesel fuel, etc.) such that it is responsive to the level of fuel within the tank as described in further detail below. As shown in  FIG. 3 , the float member  44  is formed with a recessed portion  46  and a slot  48 . The slot  48  is formed through the central portion of the float member  44  along a main axis A of the fuel cap  20  and is configured for engaging the output rod  40  in a close-fitting manner. The float member  44  is additionally formed with guide slots  52  parallel to the main axis A and configured to receive the frame legs  36   a  and  36   b.    
     An end cap  54  is coupled to the frame  36  to retain the output rod  40  in position, axially whether stationary or rotating about the main axis A. The end cap  54  snaps onto the frame  36  from the side at three locations with grooves  54   a  and  54   b  engaging the respective frame legs  36   a  and  36   b  and a third groove  54   c  engaging the horizontal portion of the frame  36  between the two legs  36   a  and  36   b  (see  FIGS. 13 and 14 ). The output rod  40  has a substantially flat cross-section and includes a first end  40   a  and a second end  40   b . The output rod  40  is non-planar between the first end  40   a  and the second end  40   b . In some embodiments, the output rod  40  has an overall twist angle between the first end  40   a  and the second end  40   b  of between about 180 degrees and about 360 degrees. In some embodiments, the overall twist angle is about 288 degrees. The second end  40   b  of the output rod  40  is coupled to an indicator needle  56  such that rotation of the output rod  40  coincides with similar rotation of the indicator needle  56 . The indicator needle  56  includes a base  57  formed with barbs  58  on an exterior surface thereof. The outer shell  32  is formed with an inner annular lip or projection  59  for engaging the barbs  58  when the indicator needle  56  is pressed into the outer shell  32 . The base  57  is split along its length to allow elastic compression of the base  57  as the indicator needle  56  is inserted into the outer shell  32 . When the barbs  58  snap over the projection  59 , the base  57  returns to its previous, non-compressed shape, and the indicator needle  56  is retained in axial position relative to the outer shell  32 . 
     An indicator dial  60  includes indicia  64  associated with the fuel level within the associated tank. In some embodiments, the indicator dial  60  is constructed of a metallic material, such as aluminum, and the indicia  64  are printed thereon. In some embodiments, the indicia  64  are inscribed in, integrally formed with, or adhesively coupled to the indicator dial  60 . The indicator dial  60  includes an aperture  66 , which is engageable with a post  67  formed as part of the outer shell  32  to register the indicator dial  60  and the outer shell  32  in a predetermined relative orientation. Other methods of registering the indicator dial  60  and the outer shell  32  are within the scope of the invention. A lens or “crystal”  68  covers the indicator needle  56  and the indicator dial  60 . The crystal  68  is constructed of a highly transparent material to allow a user to clearly see the position of the indicator needle  56  in relation to the indicia  64 . The crystal  68  is mounted to the outer shell  32  by a weld, such as an ultrasonic weld. In some embodiments, the crystal  68  is mounted to the outer shell  32  by a snap fit, adhesive or cohesive bonding material, or another appropriate means. 
     The fuel cap  20  includes an assembly component  72  coupled to the outer shell  32  and to the frame  36 . The assembly component  72  includes a flange  73  for engaging the sealing element  34  as discussed below. The frame legs  36   a  and  36   b  include respective ends  74  and  76 , which are bent about 90 degrees from the frame legs  36   a  and  36   b . The assembly component  72  is formed to include a pair of slots  80  for receiving the ends  74  and  76 . The slots  80  are open toward the “top” or “outer” side of the fuel cap  20 . When the ends  74  and  76  are received within the respective slots  80  as shown in  FIG. 4 , the frame  36 , the output rod  40 , and the float member  44  are coupled to the assembly component  72  to rotate therewith (e.g., during cap installation and removal). The assembly of the frame  36  and the assembly component  72  is not direction-specific (i.e., either of the frame ends  74  and  76  can be received in either of the slots  80 ). The assembly of the indicator needle  56  to the second end  40   b  of the output rod  40  is direction-specific to ensure that the indicator needle  56  indicates “empty” when the float member  44  is substantially all the way down and indicates “full” when the float member  44  is substantially all the way up. 
       FIGS. 2 and 3  illustrate the interconnecting features of the outer shell  32  and the assembly component  72 . The outer shell  32  is formed with a boss  84  in its interior region. The boss  84  is generally cylindrical and is open in its center to allow the output rod  40  to pass through to the top side of the outer shell  32 . The boss  84  is formed to include a first protrusion  88  and a second protrusion  90  as shown in  FIG. 12 . The first and second protrusions  88  and  90  are evenly spaced about the circumference of the boss  84  and have dissimilar size. Specifically, the first protrusion  88  is smaller than the second protrusion  90 . In some embodiments, the first and second protrusions  88  and  90  have dissimilar shape, regardless of their relative size. In some embodiments, the outer shell  32  includes a single protrusion rather than two dissimilar protrusions. 
     The assembly component  72  includes first and second slots  94  and  96  for engagement with the first and second protrusions  88  and  90 , respectively. The first slot  94  includes a first portion  94   a  oriented substantially parallel to the main axis A and a second portion  94   b  oriented substantially perpendicular to the main axis A. Likewise, the second slot  96  includes a first portion  96   a  oriented substantially parallel to the main axis A and a second portion  96   b  oriented substantially perpendicular to the main axis A. Thus, the first and second slots  94  and  96  are generally L-shaped. The respective first portions  94   a  and  96   a  are spaced circumferentially on the assembly component  72  to align with the first and second protrusions  88  and  90 , respectively. The first portion  94   a  of the first slot  94  has a width substantially equal to the width W 1  of the first protrusion  88 , and the first portion  96   a  of the second slot  96  has a width substantially equal to the width W 2  of the second protrusion  90 . The second portions  94   b  and  96   b  are open to the first portions  94   a  and  96   a , respectively allowing the protrusion  88  to be moved from the first portion  94   a  to the second portion  94   b  and the protrusion  90  to be moved from the first portion  96   a  to the second portion  96   b  when the outer shell  32  and the assembly component  72  are rotated relative to each other about the main axis A. 
     In addition to the mating protrusions  88  and  90  and slots  94  and  96 , the outer shell  32  and the assembly component  72  include respective locking members. The assembly component  72  includes a recess  100  for receiving a detent  104  of the outer shell  32 . The detent  104  is positioned on the distal end of a snap lever or finger  108 . Although formed as part of the outer shell  32  in the illustrated embodiment, the snap lever  108  is flexible and elastically deformable such that the detent  104  is movable relative to the remainder of the outer shell  32 . The detent  104  includes a ramped edge  112  on the side facing the snap lever  108 . The detent  104  engages a ridge  116  bordering the recess  100  during assembly as described in further detail below. 
     Assembly of the fuel cap  20  is designed to be relatively simple. The float member  44  is inserted into the frame  36  by gently pulling the frame legs  36   a  and  36   b  apart. The output rod  40  is threaded into the central slot  48  in the float member  44 . The end cap  54  is snapped onto the frame  36  to retain the first end  40   a  of the output rod  40  and provide a stop for the float member  44 , defining its “empty” position. The frame legs  36   a  and  36   b  are gently squeezed together and inserted into the slots  80  in the assembly component  72 . Because of the orientation of the two frame ends  74  and  76  in the slots  80 , torsional strength between the assembly component  72  and the frame is high without the need for adhesives or welding. Another benefit of this orientation is that it yields a large amount of space in the center of the fuel cap  20  without a large outside diameter of the fuel cap  20 . This allows the output rod  40  and the indicator needle  56  to be positioned along the main axis A in the fuel cap  20 , coplanar with the two frame legs  36   a  and  36   b , enabling a wide sweep range of the indicator needle  56  across the indicator dial  60 . For example, in the illustrated embodiment, approximately 80 percent of the indicator dial  60  is within the sweep range of the indicator needle  56 . This is useful to the user, who is able to read the fuel level quickly and more accurately. 
     The outer shell  32  is joined axially with the assembly component  72  such that the first protrusion  88  enters the first portion  94   a  of the first slot  94  and the second protrusion  90  enters the first portion  96   a  of the second slot  96 . The outer shell  32  and the assembly component  72  are pressed axially together to align the first and second protrusions  88  and  90  with the second portions  94   b  and  96   b  of the respective slots  94  and  96 . When the outer shell  32  and the assembly component  72  are pressed axially together, the snap lever  108  is deformed, flexing outwardly due to contact of the detent  104  with the ridge  116  of the assembly component  72 . The outer shell  32  and the assembly component  72  are rotated relative to one another about the main axis A such that the first and second protrusions  88  and  90  move toward the closed ends of the second slot portions  94   b  and  96   b  of the respective slots  94  and  96 . After sufficient relative rotation between the outer shell  32  and the assembly component  72  in this manner, the detent  104  becomes aligned with the recess  100 , allowing the snap lever  108  to snap back into its non-flexed state. 
     The detent  104  being located in the recess  100  prevents substantial relative rotation between the outer shell  32  and the assembly component  72  about the main axis A. The positioning of the first and second protrusions  88  and  90  in the second slot portions  94   b  and  96   b  prevents substantial axial movement between the outer shell  32  and the assembly component  72 . Thus, the outer shell  32  and the assembly component  72  are easily assembled, but not easily disassembled. The only way to pull the outer shell  32  and assembly component  72  axially apart is to align the first and second protrusions  88  and  90  with the first slot portions  94   a  and  96   a , which requires breakage of the detent  104  or prying up of the snap lever  108  to remove the detent  104  from the recess  100 . 
     Further assembly of the fuel cap  20  includes laying the indicator dial  60  onto the outer shell  32  such that the post  67  engages the aperture  66  in the indicator dial  60 . In this position, the indicator dial  60  lies directly on top of the snap lever  108 , substantially preventing the snap lever  108  from being upwardly flexed to remove the detent  104  from the recess  100 . Once the indicator dial  60  is in place, the indicator needle  56  is pressed onto the second end  40   b  of the output rod  40 , and the crystal  68  is fixedly coupled to the outer shell  32  by ultrasonic welding. Thus, the fuel cap  20  cannot be disassembled or tampered with once assembled, unless it is cracked, severed, or broken in some way. 
     When the fuel cap  20  is installed with a fuel tank, the fuel level within the tank determines the position of the indicator needle  56  relative to the outer shell  32  and indicator dial  60 . The float member  44  is buoyant in the fuel such that it maintains a position at the top of the fuel volume within the tank. Because of the twisted shape of the output rod  40 , the position of the float member  44  along the main axis A determines the rotational orientation of the output rod  40  and the indicator needle  56 . The fuel cap  20  is calibrated to indicate the correct amount of remaining fuel with the indicator needle  56  and the indicia  64  on the indicator dial  60 . The recessed portion  46  of the float member  44  fits down over the end cap  54  when the float member  44  is at the bottommost or “empty” position. By arranging the float member  44  lower along the main axis A, the “empty” indication is more accurate. By lowering the center of mass of the float member  44  toward the first end  40   a  of the output rod  40  and the end cap  54 , the float member  44  will attain a position that is closer to the bottom of the tank and the true “empty” condition before indicating that the tank is “empty”. 
     The indicia  64  may be provided in one of a multitude of known manners. In the illustrated embodiment (as shown in  FIGS. 2 and 6 ), the indicator dial  60  is provided with a single band of increasing width between the “empty” and “full” symbols. Alternately, individual fractional markers (either numeric or symbolic) can be provided as indicia on the indicator dial  60 .