Abstract:
A cap for a fluid container that includes an outer member and an inner member is provided. The outer member has an inner surface that has at least one finger projecting away therefrom. The inner member is located within the outer member and may rotate relative to the outer members. The inner member also has a recess that has a plurality of ratchet teeth to engage the at least one finger of the outer member. Each ratchet tooth has a torque limiting surface against which the at least one finger is capable of transmitting torque up to a threshold and against which the at least one finger is capable of slipping when the threshold is exceeded. The inner member rotates relative to the outer member when the at least one finger slips against the torque limiting surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/034,545 filed Mar. 7, 2008, the disclosure of which is hereby incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       FIELD OF THE INVENTION 
       [0003]    The invention relates to a cap for a fluid container that provides an indication when the cap is properly tightened. 
       BACKGROUND OF THE INVENTION 
       [0004]    A removable cap is a well known component for sealing an opening of a fluid container. Most caps are threaded components that use a compressible gasket for engaging another component to seal the fluid container. However, gaskets can be damaged due to repeated over-tightening. This may permit fluids to leak from the container. As such, many types of caps include torque limiting features to prevent the cap from being over-tightened. In the loosening direction, however, a larger torque can be applied to assure that the cap can be removed. In addition, groups such as the California Air Resources Board require some type of indication when the cap is properly tightened if the cap is used to seal a fuel tank. As such, some caps include components that provide an audible indication when the cap is sufficiently tightened. 
         [0005]    However, there are several limitations to torque limiting and sound producing caps. For example, some designs may include several individual components, resulting in relatively high manufacturing and assembly costs. In addition, some designs require a large envelope for the torque limiting components. Therefore, space may be limited for other components of the cap. 
         [0006]    Considering the limitations of previous cap designs, including those designed to meet the requirements of the California Air Resources Board, an improved cap for a fluid container is needed. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a cap for a fluid container that includes an outer member and an inner member. The outer member has a longitudinal axis and an axially facing inner surface. The inner surface has at least one finger projecting from the inner surface in the direction of the longitudinal axis. The inner member is located within the outer member and may rotate relative to the outer member about the longitudinal axis. The inner member also has a recess that has a plurality of ratchet teeth to engage the at least one finger of the outer member. Each ratchet tooth has a locking surface against which the at least one finger is capable of transmitting torque in the loosening direction. Each ratchet tooth also has a torque limiting surface against which the at least one finger is capable of transmitting torque up to a threshold in the tightening direction and against which the at least one finger is capable of slipping when the threshold is exceeded in the tightening direction. The inner member rotates relative to the outer member when the at least one finger slips against the torque limiting surface. 
         [0008]    In a preferred form, the ratchet teeth engage the at least one finger along the axial direction spaced from the inner surface of the outer member. In the loosening direction, the ratchet teeth engage a longitudinal end surface and in the tightening direction the ratchet teeth engage a longitudinal side surface of the at least one finger. 
         [0009]    In other aspects of the invention, the teeth of the outer member may have an arcuate shape or a constant cross section in the direction of the longitudinal axis. Preferably, multiple fingers engage multiple ratchet teeth. In addition, the cap may include a tether assembly and the cap preferably meets the requirements of the California Air Resources Board when used as a cap for a fuel tank. 
         [0010]    The foregoing and other objects and advantages of the invention will appear in the detailed description that follows. In the description, reference is made to the accompanying drawings that illustrate a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
           [0012]      FIG. 1  is a side view of a cap of the present invention; 
           [0013]      FIG. 2  is an exploded perspective view of the cap of  FIG. 1 ; 
           [0014]      FIG. 3  is a sectional view along the line  3 - 3  of  FIG. 1 ; 
           [0015]      FIG. 4  is a sectional view along the line  4 - 4  of  FIG. 1 ; 
           [0016]      FIG. 5  is a perspective view of an outer member of the cap of  FIG. 1 ; 
           [0017]      FIG. 6  is a perspective view of an inner member of the cap of  FIG. 1 ; and 
           [0018]      FIG. 7  is a detail view of the area  7 - 7  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Referring to  FIGS. 1-6 , a cap  10  according to the present invention includes an outer member  12  (shown separately in  FIG. 5 ) and an inner member  14  (shown separately in  FIG. 6 ) housed therein. Referring to  FIGS. 4 and 5 , the outer member  12  is generally circular in shape and defines a longitudinal axis  16 . The outer member  12  also includes a plurality of fingers  17  that project away from an inner surface  18  in the direction of the longitudinal axis  16 . Although seven fingers  17  are shown in the figures, it is possible to design an outer member  12  with a different number of fingers  17 . Referring to  FIG. 5 , the fingers  17  may be fixed to the inner surface  18  around the entire perimeter of the interface between the fingers  17  and the inner surface  18 , and referring to  FIG. 3 , the inner surface  18  of the outer member  12  may have an arcuate shape near the interface between the fingers  17  and the inner surface  18 . Referring now to  FIGS. 5 and 7 , each finger  17  includes a bottom surface  15 , an inner longitudinally extending side surface  21 , an outer longitudinally extending side surface  23 , and longitudinally extending end surfaces  25  and  27 . Referring to  FIG. 7 , the longitudinally extending end surfaces  25  and  27  define a major axis  33  of the lateral cross section of each finger  17 . The longitudinally extending side surfaces  21  and  23  define a minor axis  35  of the lateral cross section of each finger  17 . 
         [0020]    The longitudinally extending end surface  25  is preferably flat as viewed in  FIG. 7 . The surfaces  21 ,  23 , and  27  are preferably arcuate as viewed in  FIG. 7 , forming blade-shaped fingers  17 . However, other shapes are possible, such as those that would provide generally straight fingers  17 . In any case, the fingers  17  preferably have a constant cross section in the direction of the longitudinal axis  16 . However, each finger  17  preferably tapers inwardly, as shown in  FIG. 7 , from the longitudinally extending end surface  27  near the longitudinal axis  16  to the opposite longitudinally extending end surface  25 . In addition, the fingers  17  are preferably spaced about the longitudinal axis  16  at equal angles from one another, although other configurations are possible. For example, the fingers  17  may be spaced apart to form a patterned arrangement or groups of fingers  17 . The function of the fingers  17  will be described in further detail below. 
         [0021]    The outer member  12  also includes a plurality of reinforcing sections  20 . The reinforcing sections  20  are preferably spaced about the longitudinal axis  16  at equal angles from one another. Each reinforcing section  20  has two side surfaces  22 , a top surface  29 , and an intermediate surface  24 . As such, the reinforcing sections  20  preferably secure the inner member  14  within the outer member  12  as described below. In addition, the reinforcing sections  20  may provide rigidity for the outer member  12 . The outer member  12  has an outer surface  31  that may be indented to match the shape of the reinforcing sections  20 . Such an outer surface  31  may provide a component that is easier to manufacture and easier for a user to grip. 
         [0022]    The outer member  12  further includes a plurality of retainer ridges  26  that project radially inwardly toward the longitudinal axis  16 . Like other components, the retainer ridges  26  may be spaced about the longitudinal axis  16  at equal angles from one another. The retainer ridges  26  also preferably secure the inner member  14  within the outer member  12  as described below. 
         [0023]    Referring to  FIGS. 2 and 6 , the inner member  14  is generally circular in shape and defines a longitudinal axis  28 . The inner member  14  includes an upper surface  30 , an outer surface  32 , a retainer ring  36 , an open bottom (not shown), and a recess  38 . The interior of the inner member  14  includes internal threads  40 , as shown in  FIG. 3 . The internal threads  40  connect to an externally threaded component of the fluid tank. Still referring to  FIG. 3 , the retainer ring  36  is engaged by the retainer ridges  26  of the outer member  12 . The outer surface  32  of the inner member  14  is engaged by the intermediate surfaces  24  of the reinforcing sections  20  of the outer member  12 . In addition, the upper surface  30  is engaged by the inner surface  18  of the outer member  12 . The engagement of these components prevents relative translation of the inner member  14  relative to the outer member  12 . However, the inner member  14  and the outer member  12  are permitted to rotate relative to one another about the longitudinal axis  16 . This aspect will be described in further detail below. 
         [0024]    Referring to  FIG. 6 , the recess  38  of the inner member  14  includes an outer surface  44  that faces radially inward and has a plurality of ratchet teeth  46 . The ratchet teeth  46  preferably have a constant cross section in the direction of the longitudinal axis  28 . Like other components, the ratchet teeth  46  may be spaced about the longitudinal axis  28  at equal angles from one another. The ratchet teeth  46  project away from the outer surface  44 , and referring to  FIG. 7 , each ratchet tooth  46  also has a locking surface  48  and a torque limiting surface  50 . The locking surfaces  48  and the torque limiting surfaces  50  engage the fingers  17  of the outer member  12  in operation of the cap  10 . Specifically, the locking surfaces  48  and the torque limiting surfaces  50  preferably engage the longitudinally extending end surfaces  25  and the outer longitudinally extending side surfaces  23 , respectively, of the fingers  17  during operation of the cap  10 . This engagement is at an axial position along the fingers  17  that is spaced from the inner surface  18  of the outer member  12  as shown in  FIG. 3 . 
         [0025]    The inner member  14  may support a tether assembly  42  and a gasket  43  as shown in  FIGS. 1-3 . The tether assembly  42  and the gasket  43 , if provided, may be of any appropriate type commonly used with caps. For example, the tether assembly  42  may include a tether connector  52  that secures a cord  54  and an anchor  56  to the inner member  14 . The tether connector  52  is preferably connected to the inner member  14  by friction welding. This process is well known in the art. In addition, the tether connector  52  also secures the gasket  43  within the inner member  14 . The tether assembly  42  could also permit the cap  10  to meet specific requirements, such as those of the California Air Resources Board. 
         [0026]    Referring to  FIGS. 3 and 4 , the cap  10  is tightened and connected to a threaded component (not shown) by rotating the cap  10  in a clockwise direction (as viewed from  FIG. 4 ). The outer longitudinally extending surfaces  23  of the fingers  17  engage the torque limiting surfaces  50  ( FIG. 7 ) as the internal threads  40  engage the threaded component. This prevents the outer member  12  and the inner member  14  from rotating relative to one another. However, the gasket  43  in the inner member  14  engages the threaded component when the cap  10  has sufficiently connected to the threaded component and sealed the fluid tank. Compression of the gasket increases the amount of torque required to continue threading the cap  10  onto the threaded component. The interface between the fingers  17  and the torque limiting surfaces  50  cannot transmit this increased torque, and the fingers  17  slip over the ratchet teeth  46  with continued clockwise rotation of the cap  10 . Those skilled in the art will recognize that the fingers  17  slip over the torque limiting surfaces  50  since each of these surfaces applies a force in a direction in which each finger  17  deflects relatively easily. That is, each torque limiting surface  50  applies a force generally in the direction of the minor axis  35  of the lateral cross section of the finger  17 . This causes the portion of each finger  17  that contacts the ratchet tooth  46  to bend in multiple directions. Specifically, the portion of each finger  17  that contacts the ratchet teeth  46  bends inward away from the ratchet teeth  46  and upward toward the inner surface  18  of the outer member  12 . Therefore, the outer member  12  and the inner member  14  rotate relative to one another with continued clockwise rotation of the cap  10 . This preferably causes a clicking sound to indicate that the cap  10  is sealed tightly against the threaded component. 
         [0027]    The cap  10  is loosened and disconnected from the threaded component by rotating the cap in a counter-clockwise direction (as viewed from  FIG. 4 ). The longitudinally extending end surfaces  25  of the fingers  17  engage the locking surfaces  48  ( FIG. 7 ) as the internal threads  40  disengage the threaded component. This prevents the outer member  12  and the inner member  14  from rotating relative to one another. Unlike the process for connecting the cap  10  to the fluid tank, the fingers  17  will not slip over the ratchet teeth  46  when the cap  10  is disconnected. This is due to the angle of the locking surfaces  48 . Additionally, those skilled in the art will recognize that each locking surface  48  applies a force to the finger  17  in a direction in which the finger  17  does not easily deflect. That is, each locking surface  48  applies a force in the direction of the major axis  33  of the lateral cross section of the finger  17 . This causes the portion of each finger  17  that contacts the ratchet tooth  46  to compress slightly in the direction of the major axis  33 . However, this compression does not cause the fingers  17  to slip over the locking surfaces  48 . 
         [0028]    The outer member  12  and the inner member  14  are preferably made of nylon and formed in an injection molding process. The injection molding process, in addition to forming internal threads in a component during such a process, is well known in the art. Other types of materials may be used to form these components provided that the coefficient of friction between the fingers  17  and the ratchet teeth  46  and the modulus of elasticity are considered. Changes in the coefficient of friction and the modulus of elasticity will change the amount of torque that may be transmitted from the outer member  12  to the inner member  14 . In addition, the outer member  12  and the inner member  14  may be assembled by simply pushing the inner member  14  into the outer member  12  in the orientation shown in  FIG. 3 . However, the retainer ring  36  will cause the outer surface  31  of the outer member  12  to deflect slightly due to contact with the retainer ridges  26 . The inner member  14  will snap in place when the retainer ring  36  moves past the retainer ridges  26 . 
         [0029]    It should be noted that the torque limiting components of the cap  10  of the present invention occupy relatively little space. This is due to the fact that the fingers  17  and the ratchet teeth  46  are contained within the recess  41  of the inner member  14  when the cap  10  is assembled. 
         [0030]    As discussed above, the cap of the present invention can be used as a cap for a fuel tank to meet the requirements of the California Air Resources Board. This is achieved by providing a cap that includes a tether assembly and components that provide an indication when the cap is properly tightened. These components help ensure that a proper seal is formed by providing an audible indication and discouraging use of caps that are not provided with the fuel tank. It should also be noted that the cap of the present invention has been identified as a fuel cap by way of example. The cap may be used to seal other types of fluid containers, such as oil containers, chemical containers, or other containers that use similarly designed caps. As such, the cap of the present invention may have a nominal diameter in the range of approximately 1.5″ to 3.5″. However, those skilled in the art will recognize that the aspects of the present invention can be applied to a cap of any size. 
         [0031]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.