Abstract:
A fuel cap has a torque member attached to an upper portion of a casing body. The torque member is a disk-shaped plate to transmit a rotational torque applied to a handle to the casing body. An interlocking recess and interlocking claws, which constitute a plate attachment mechanism, are arranged on the upper portion of the casing member. Fitting of the interlocking claws in the interlocking recess causes the torque member to be attached to the casing body in a freely rotatable manner. This simple structure of the invention effectively prevents the fuel cap from being easily damaged by an inadvertent operation, such as a careless drop of the fuel cap, and ensures the sufficient sealing properties of the fuel cap even under application of an external load.

Description:
This application claims the benefit of and priority from Japanese Applications No. 2002-212785 filed Jul. 22, 2002 and No. 2002-281576 filed Sep. 26, 2002, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a cap device that is detachably attached to a tank opening member. 
   2. Description of the Related Art 
   One known example of the cap device is disclosed in JP No. 10-329861A.  FIG. 38  is a partly broken view illustrating a prior art fuel cap  200  for a vehicle. The fuel cap  200  includes a casing body  202 , and a cover  210  attached to an upper flange  204  of the casing body  202 . The flange  204  has an outer ring element  206  for fixation of the cover  210  and a linkage element  208  for linkage with the casing body  202 . The linkage element  208  has a fragile portion including a notch  209 . The fragile portion makes a starting point of breaking the linkage element  208  when a large external force in any of diverse directions is applied to the flange  204  via the cover  210 . In the case of application of a large external force onto the periphery of the fuel cap  200 , for example, due to a collision of the vehicle, this structure breaks the linkage element  208  at the fragile portion and thereby keeps the sealing properties of a fuel tank from the outside. 
   The fuel cap  200  of the prior art structure may, however, be broken at the fragile portion to be unusable even by a simple inadvertent use other than a collision of the vehicle, for example, a careless drop of the fuel cap  200  during fuel supply or application of a twisting static load to the lower end of the cover  210 . 
   Setting the breaking load at the fragile portion to a specific range of loading, which excludes the possible load level in the case of the inadvertent use, however, has lots of difficulties, since the setting is adjustable only by the direction and the depth of the notch  209  in the narrow flange  204 . 
   SUMMARY OF THE INVENTION 
   The object of the present invention is thus to solve the drawback of the prior art technique and to provide a cap device of a simple structure that is not easily damaged by an inadvertent operation, such as a careless drop of a cap, and ensures the sufficient sealing properties even under application of an external load. 
   To solve the above problem, the present invention provides a cap device that opens and closes a tank opening. The cap device comprises a closer that closes the tank opening, a handle mechanism operable to open and close the tank opening, a disk-shaped torque member that is rotatably mounted on the closer, the torque member being configured to transmit rotational torque applied to the handle mechanism to open and close the tank opening to the closer and a plate attachment mechanism that rotatably attaches the torque member to the closer. The plate attachment mechanism is configured such that part of the torque member is elastically deforms by an external force applied to the handle mechanism, thereby detaching the torque member from the closer. 
   In the cap device of the present invention, when a rotational torque either in the closing direction or in the opening direction is applied to the manipulation mechanism in the state of the closer set on the tank opening, the rotational torque is transmitted via the torque member to the closer and makes the closer close the tank opening. 
   The torque member is attached to the closer in a rotatable manner by the plate attachment mechanism. The plate attachment mechanism is configured to elastically deform part of the torque member or part of the closer, so as to be coupled with and released from the closer. The torque member is thus readily attached to and detached from the closer by elastic deformation of the constituent of the plate attachment mechanism, which corresponds to part of the torque member or part of the closer. 
   The load of making the torque member detached from the closer is readily set by changing the shape and the number of the elastically deformed constituents of the plate attachment mechanism or their mechanical strength. This arrangement thus facilitates optimized setting of the breaking load against external forces in a diversity of directions with no restriction by the shape of the sealing portion of the closer. 
   The plate attachment mechanism supports the torque member on the closer in a rotatable manner. This structure desirably reduces a variation in rotational torque due to a displacement of the torque member in the diametral direction or in the vertical direction, thus ensuring a stable clamping force to attain the sufficient sealing properties. 
   In one preferable application of the present invention, the cap device further includes a handle attachment mechanism that supports the manipulation mechanism on a circumference of the torque member in a freely rotatable manner. Elastic deformation of the handle attachment mechanism, which corresponds to part of the torque member, attains attachment and detachment of a cover member and a handle included in the manipulation mechanism. This arrangement facilitates attachment and detachment of the cover member and the handle from the torque member and ensures easy disengagement of the cover member or the handle under application of an external force. 
   A careless drop of the cap during fuel supply may apply a large external force to the cap and cause the cover member or the handle to be detached from the torque member. The detached cover member or handle can be attached again to the torque member by elastic deformation of he handle attachment mechanism. This arrangement desirably prevents the cap device from being unusable only by a careless drop of the cap, unlike the prior art cap that is easily broken at the fragile portion. 
   In one preferable embodiment of the above application, the manipulation mechanism includes a handle, and a cover member that is joined with the handle and encircles an upper portion and the circumference of the torque member. The handle attachment mechanism includes an elastically deformable interlocking claw formed on one of the cover member and the torque member, and a matched interlocking element formed on the other of the cover member and the torque member to engage with the interlocking claw. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an illustrative diagram showing in partial cutaway a cap device comprising a fuel cap pertaining to a first embodiment of the invention; 
       FIG. 2  is an illustrative diagram showing in partial cutaway a cap device rotatable by grasping the handle with the fingers and raising it up; 
       FIG. 3  is an illustrative diagram showing the relationship of the casing interlocking portion of the casing body to the filler neck; 
       FIG. 4  is a plan view showing the cover; 
       FIG. 5  is a perspective view showing parts on top of the fuel cap disassembled; 
       FIG. 6  is a front view showing the handle detached from the cover; 
       FIG. 7  is a front view showing an enlargement of the area around the axially supported portion of  FIG. 6 ; 
       FIG. 8  is a diagram viewed in the direction of arrow  8  in  FIG. 7 ; 
       FIG. 9  is an illustrative diagram illustrating the procedure for assembling the handle to the cover; 
       FIG. 10  is a sectional view taken along line  10 — 10  in  FIG. 7 ; 
       FIG. 11  is a sectional view showing the handle prior to being assembled with the axial support portion; 
       FIGS. 12A ,  12 B and  12 C are illustrative diagrams illustrating the procedure for rotating the handle; 
       FIG. 13  is a perspective view showing the fuel cap disassembled; 
       FIG. 14  is an illustrative diagram illustrating the clutch mechanism in non-interconnected mode; 
       FIG. 15  is an illustrative diagram illustrating the clutch mechanism in interconnected mode; 
       FIG. 16  is an illustrative diagram illustrating the relationship of the handle to the button of the clutch member; 
       FIG. 17  is a sectional view taken in the vicinity line  17 — 17  in  FIG. 15 ; 
       FIGS. 18A ,  18 B and  18 C are illustrative diagrams illustrating operation of the first clutch unit; 
       FIG. 19  is an illustrative diagram illustrating the second clutch unit; 
       FIGS. 20A and 20B  are illustrative diagrams illustrating operation of the second clutch unit; 
       FIG. 21  is a perspective view showing the torque member; 
       FIG. 22  is a perspective view showing principal elements of the torque member enlarged; 
       FIG. 23  is a sectional view of the area around the top of the casing body; 
       FIG. 24  is a perspective view showing the torque transmission mechanism; 
       FIG. 25  is a plan view showing the torque transmission mechanism; 
       FIG. 26  is an illustrative diagram illustrating operation carrying over from  FIG. 25 ; 
       FIG. 27  is an illustrative diagram illustrating operation carrying over from  FIG. 26 ; 
       FIGS. 28A and 28B  are illustrative diagrams illustrating frangible portion of the torque portion; 
       FIG. 29  is a sectional view of the area around the tether mechanism; 
       FIG. 30  is a plan view of the tether mechanism; 
       FIG. 31  is a perspective view illustrating the tether mechanism; 
       FIG. 32  is a perspective view illustrating operation of the tether mechanism; 
       FIG. 33  is an illustrative diagram illustrating operation carrying over from  FIG. 32 ; 
       FIG. 34  is a perspective view showing the rear end of a vehicle being fueled with the fuel cap detached from the filler neck; 
       FIGS. 35A ,  35 B and  35 C are illustrative diagrams illustrating operation of the handle; 
       FIGS. 36A ,  36 B and  36 C are illustrative diagrams illustrating operation of the handle; 
       FIG. 37  is a graph illustrating the relationship of angle of rotation to rotational torque applied to handle; 
       FIG. 38  is a sectional view showing a cap device 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   (1) General Structure of Fuel Cap  10   
     FIG. 1  is an illustrative diagram showing in partial cutaway a cap device comprising a fuel cap  10  (cap) pertaining to a first embodiment of the invention. In  FIG. 1 , the fuel cap  10  is attached to a filler neck FN having a filler opening FNb (tank opening) for supplying fuel to a fuel tank, not shown. The cap  10  comprises a casing body  20  (closer) made of polyacetal or other synthetic resin material, an inner cover  30  closing the upper opening of the casing body  20 , forming a valve chamber  24 ; a regulator valve  35  housed within the valve chamber  24 ; a cover  40  made of nylon or other synthetic resin and mounted on the upper portion of the casing body  20 ; a handle  45  mounted on the upper face of the cover  40 ; a clutch mechanism  60  and the torque transmission mechanism  80  (interconnecting mechanism); a tether mechanism  100 ; and a gasket GS installed on the outside rim of the upper portion of the casing body  20  to provide a seal between the casing body  20  and the filler neck FN. 
   In the fuel cap  10  shown in  FIG. 2 , grasping the handle  45  and raising it upward while rotating allows the fuel cap  10  to be attached to or detached from the filler neck FN to close or open the filler opening FNb. External pressure in the opening direction applied to the cover  40  and the handle  45  in the upper portion of the fuel cap  10  will simply cause it to turn freely, so that the fuel cap  10  does not come away from the filler neck FN. 
   (2) Arrangement of Parts 
   The various parts of the fuel cap  10  pertaining to the present embodiment are described in detail hereinbelow. 
   (2)-1 The Casing Body  20   
   In  FIG. 1 , the casing body  20  comprises a substantially round outer tube  21  and a valve chamber molding  22  integrally provided to the interior of the outer tube  21 . The valve chamber molding  22  houses a positive pressure valve and negative pressure valve that function as a regulator valve  35 . The inner cover  30  is welded by an ultrasonic welding technique onto the upper portion of the valve chamber molding  22  to form the valve chamber  24 . 
   The gasket GS is installed to the outside of the bottom edge of a flange  21   b  in the upper portion of the casing body  20 . The gasket GS is interposed between a seal retaining portion  21   a  of the flange  21   b  and the filler opening FNb of the filler neck FN so as to be forced against the seating face of the filler neck FN when the fuel cap  10  is tightened in the filler opening FNb, providing a sealing action. 
     FIG. 3  is an illustrative diagram showing the relationship of the casing interlocking portion  20   a  of the casing body  20  to the filler neck FN. The casing interlocking portion  20   a  is formed on the bottom outside wall of the outer tube  21 . A opening interlocking portion FNc is formed on the inside wall of the filler neck FN. In a portion of the inside wall of the opening interlocking portion FNc is formed a neck insertion notch FNd into which the casing interlocking portion  20   a  is insertable in the axial direction. With the casing interlocking portion  20   a  aligned with the neck insertion notch FNd and the fuel cap  10  inserted into filler opening FNb of the filler neck FN, turning the fuel cap  10  by a predetermined angle (about 90°) causes the casing interlocking portion  20   a  to be engaged by the opening insertion notch FNc to attach the fuel cap  10  to the filler neck FN. 
   (2)-2 Inner Cover  20   
   As shown in  FIG. 1 , the inner cover  30  has a flange  32  formed on the outside wall of the inner cover  30 , the bottom edge of the flange  32  being ultrasonically welded to the top of the valve chamber molding  22 . 
   (2)-3 Structure of the Cover  40   
   The cover  40  comprises an upper wall  41  and a side wall  43  formed at the outside rim of the upper wall  41 , integrally molded in a cup configuration. Support projections  43   a  extend from the lower interior of the side wall  43 . The support projections  43   a  are arranged at six equidistant locations along the inside rim of the side wall  43 . The support projections  43   a  mate with the outside rim of the torque member  90  of the torque transmission mechanism  80  to rotatably attach the cover  40  to the casing body  20  via the torque member  90 . The cover  40  attachment structure is described in detail later. 
     FIG. 4  is a plan view showing the cover  40 . The cover  40  is made of polyamide (PA), polyethylene (PP), acrylonitrile-butadiene-styrene (ABS) or polycarbonate (PC). The cover  40  is made of conductive resin material so as to constitute part of a ground path, indicated by the double-dotted lines in  FIG. 2 . The conductive resin material may be imparted with electrical conductivity by adding a metal filler (e.g. stainless steel, nickel, chromium, zinc, copper, aluminum, gold, silver, magnesium or titanium filler or some combination thereof) etc. Metal filler content is from 1 to 30 wt %. The reason is that amounts of less than 1 wt % do not give electrical conductivity, whereas in excess of 30 wt % the resin becomes highly viscous in injection molding process of the cover  40 , possibly resulting in injection molding defects due to metal filler clogging or pooling. 
   An indicia portion DP is formed on the surface of the upper wall  43  of the cover  40 . The indicia portion DP comprises of indicia such as text describing function, warning, description line, record or bar code, marked by laser irradiation. 0.01 to 3 wt % of carbon is added for the purpose of laser irradiation. Marking by laser irradiation is not possible with carbon content below 0.01 wt %, whereas in excess of 3 wt % the energy of the laser is absorbed by the cover  40  as a whole, so that localized coloration in the indicia portion DP is not possible. 
   (2)-4 Structure of Handle  45   
     FIG. 5  is a perspective view showing parts on top of the fuel cap disassembled. The handle  45  comprises a rectangular handle body  46  with chamfered corners. The handle body  46  is of semicircular configuration having an actuating recess  46   a  produced by recessing its outside edge at the center. The actuating recess  46   a  serves as a recessed location for inserting a finger to provide ease of operation when the handle  45  has been lowered into the retracted position (see  FIG. 1 ). 
   (2)-5 Axial Support Mechanism  50   
   The handle  45  is rotatably mounted on the upper wall  41  of the cover  40  by means of an axial support mechanism  50 . The axial support mechanism  50  comprises axial support portions  51 ,  51  projecting from the upper wall  41  of the cover  40 , and axially supported portions  55 ,  56  formed on the handle  45  and rotatably supported by the axial support portions  51 ,  52 . 
   (2)-5-1 Axial Support Portions  51 ,  52   
     FIG. 6  is a front view showing the handle  45  detached from the cover  40 . The axial support portions  51 ,  52  are members for rotatably supporting the handle  45  and are provided in a pair in the center of the cover  40 . The axial support portion  51  comprises a leg portion  51   a  and an axle portion  51   b  projecting from the side of the leg portion  51   a , and the handle  45  is rotatable about the axle portion  51   b  while supported thereby. The axial support portion  52  comprises a leg portion  52   a  and an axle portion  52   b  projecting from the top of the leg portion  52   a . An axle hole  52   f  is formed in the side of the axle portion  52   b.    
   (2)-5-2 Axially Supported Portions  55 ,  56   
   The axially supported portions  55 ,  56  are formed extending from the bottom to the center of the handle  45  and are provided so that the handle  45  may be supported via the axial support portions  51 ,  52  provided on the cover  40 . The axially supported portion  55  comprises an opening  55   a  open at the bottom and at one side of the handle  45 , and an axle hole  55   b  of round cross section communicating with the opening  55   a  in the axial direction. The opening  55   a  and the axle hole  55   b  are configured to axially support the axle portion  51   b  of the axial support portion  51 . 
   The axially supported portion  56  comprises an opening  56   a , and has a pin mounting hole  56   g  connecting with the opening  56   a .  FIG. 7  is a front view showing an enlargement of the area around the axially supported portion  56  of  FIG. 6 , and  FIG. 8  is a diagram viewed in the direction of arrow  8  in  FIG. 7 . The pin mounting hole  56   g  communicating with the opening  56   a  is formed on the side of the opening  56   a . Pin mounting hole  56   g  passes through the side of the handle  45 . A pin  56   h  fits into the pin mounting hole  56   g . The distal end of the pin  56   h  has a support insert  56   i  for insertion into an axle hole  52   f.    
   (2)-5-3 Assembly of the Handle  45   
     FIG. 9  is an illustrative diagram illustrating the procedure for assembling the handle  45  to the cover  40 . To assemble the handle  45  to the cover  40  by means of the axial support mechanism  50 , the axial support portion  51  is mated with the axially supported portion  55 , and then the axial support portion  51  is inserted into the opening  56   a  of the axially supported portion  56 , the inserting the pin  56   h  into the pin mounting hole  56   g ; finally, the support insert  56   i  is mated with the axle hole  52 . In this way the handle  45  may be rotatably mounted on the cover  40  via the axial support mechanism  50 . 
   (2)-5-4 Urging Mechanism  57   
     FIG. 10  is a sectional view taken along line  10 — 10  in  FIG. 7 , and  FIG. 11  is a sectional view showing the handle  45  prior to being assembled. The handle  45  is urged towards the retracted position by means of the urging mechanism  57 . The urging mechanism  57  comprises a cam  58  projecting from the side of the axial support portion  52 , and a cam support portion  59  provided to the handle  45 . In  FIG. 11 , a cam face  58   a  of the cam  58  is defined by center axis O 1 , an arcuate face  58   b  of substantially semicircular configuration of radius r 1 , a center O 2  offset from center axis O 1 , and a curving convex face  58   c  of radius r 2 . The cam support portion  59  is bifurcated so that the cam face  58   a  is held between a resilient cam support piece  59   a  and a cam support rib  59   b . The resilient cam support piece  59   a  is configured as a cantilever piece that resiliently flexes while following the cam face  58   a  as the handle  45  rotates. On the inside of the resilient cam support piece  59   a  is formed a cam guide face  59   c  conforming in shape to the arcuate face  58   b . The cam support rib  59   b  is integrally formed with the handle body  46  and is arranged substantially parallel to the resilient cam support piece  59   a.    
     FIG. 12  illustrates the procedure for rotating the handle  45 . The handle  45  is supported such that it can rotate within a 90° range by means of the axial support mechanism  50 , that is, upraised from the retracted position pressed against the upper wall  41  of the cover  40  as shown in  FIG. 12(A)  to the position shown in  FIG. 12(B) , and finally to the upraised handling position shown in  FIG. 12(C) . When the handle  45  is not in the retracted position it is urged towards the retracted position (in the direction indicated by the arrow in  FIG. 12(B) ) by means of the urging mechanism  57 . That is, when the handle  45  is positioned at an angle between the retracted position and the handling position, the resilient cam support piece  59   a  pushes under spring force against the arcuate face  58   b  of the cam  58 , whereby the resilient cam support piece  59   a  exerts pushing force towards center O 2 . Since this pushing force is eccentric with respect to center axis O 1  (which is the center of rotation of the handle  45 ), counterclockwise moment M 1  is created. This moment M 1  translates to force rotating the handle  45  about center axis O 1 . The handle  45  is thereby urged in the counterclockwise direction towards the retracted position from any position between the handling position and retracted position. 
   (2)-6 Clutch Mechanism  60   
     FIG. 13  is a perspective view showing the fuel cap  10  disassembled,  FIG. 14  is an illustrative diagram illustrating the clutch mechanism  60  in non-interconnected mode, and  FIG. 15  is an illustrative diagram illustrating the clutch mechanism  60  in interconnected mode. The clutch mechanism  60  is a mechanism for transmission/non-transmission to the torque transmission mechanism  80  of rotational torque applied to the handle  45 , and comprises a clutch member  70 , a clutch spring  92  and the clutch arm  93  formed on the torque portion  90 , and a cam face  62  formed on the lower face at both sides of the handle  45 . 
   (2)-6-1 Clutch Member  70   
   In  FIG. 13 , the clutch member  70  is integrally molded by injection molding and comprises a clutch body  71 . The clutch body  71  comprises an upper wall  72  of circular disk shape and a side wall extending downwardly from the outside edge of  72  so that the space surrounded by the upper wall  72  and the side wall  73  forms a storage recess  71   a  (see  FIG. 14 ). 
   The upper wall  72  has an annular projection  72   a  projecting therefrom. As shown in  FIG. 14  this annular projection  72   a  prevents the two from becoming wedged together so as to facilitate vertical motion of the clutch member  70 . The upper wall  72  shown in  FIG. 13  has buttons  74 ,  74  projecting therefrom at locations 180° apart with respect to the center of the clutch member  70 . The buttons  74 ,  74  are retractably positioned in through-holes  41   a  formed in the cover  40 . 
   (2)-6-2 Clutch Urging Mechanism  61   
   Three the clutch springs  92  are positioned at 120° intervals about the circumference on the upper face of the torque member  90 . The clutch springs  92  impart spring force in the vertical direction relative to the clutch member  70 . Each the clutch springs  92  comprises an arm  92   a  coplanar with the upper face of the torque member  90  and extending in the circumferential direction, and a pushing projection  92   b  projecting up from the upper face of the torque member  90  at the distal end of the arm  92   a . The clutch springs  92  are of cantilever design, with one end thereof inclinable within a notch  92   c  in the upper face of the torque member  90 , thereby urging the clutch member  70  upwardly. 
     FIG. 16  is an illustrative diagram illustrating the relationship of the handle  45  to the button  74  of the clutch member  70 . The upper face of the button  74  is a sloped the pushing face  74   a . A cam face  62  for pushing against the pushing face  74   a  is formed on the lower face of the handle  45  at both sides. The cam face  62  is designed so that with the handle  45  in the handling position, the button  74  of the clutch member  70  is pushed downwardly, and so that in the retracted position the button  74  s not pushed downwardly. 
   With this arrangement for the clutch urging mechanism  61 , rotating the handle  45  from the retracted position shown in  FIG. 14  to the handling position shown in  FIG. 15  causes the cam face to push against the pushing faces  74   a  of buttons  74 ,  74 , so that the clutch member  70  is pushed downwardly in opposition to the urging force of the clutch springs  92  and moves to the lower position, whereas in the retracted position, force ceases to be applied to buttons  74 ,  74  so that the clutch member  70  is returned to its original position by the clutch springs  92 . 
   (2)-6-3 First Clutch Unit  63   
     FIG. 17  is a sectional view taken in the vicinity line  17 — 17  in  FIG. 15 , and  FIG. 18  illustrates operation of the first clutch unit  63 . The first clutch unit  63  is a mechanism for transmitting rotational torque applied to the handle  45  in the closing direction, regardless of whether the handle is in the handling position or retracted position. 
   The first clutch teeth  75  are formed all the way around the inside rim of the side wall  73  of the clutch member  70 . The first clutch teeth  75  comprise a right-angled the interlocking face  75   a  extending in the radial direction and a sloping face  75   b  inclined a predetermined angle with respect to the interlocking face  75   a ; the teeth are substantially right triangular in shape when viewed in cross section. 
   On the outside rim of the torque member  90  there are provided clutch arms  93  for interlocking with interlocking faces  75   a . The clutch arms  93  are positioned at 120° intervals about the circumference on the upper outside rim of the torque member  90 . Each the clutch arm  93  comprises an arm  93   a  extending along the circumferential direction, and a interlocking end  93   b  provided at the distal end of the arm  93   a . The interlocking end  93   b  is formed by a surface in the radial direction so as to interlock with a interlocking face  75   a . The interlocking face  75   a  is thicker than the interlocking end  93   b  so as to normally maintain the interlocked state regardless of whether positioned above ( FIG. 18(A) ) or below ( FIG. 18(B) ) the torque member  90  of the clutch member  70 . 
   As shown in  FIGS. 81(A)  and (B), when the clutch member  70  is rotated in the clockwise direction, the interlocking end  93   b  interlocks with the interlocking face  75   a , creating a torque transmission state in which the torque member  90  rotates in unison therewith in the clockwise direction. This torque transmission state is maintained regardless of whether the handle  45  is in the handling position of  FIG. 18(A)  or the handling position of  FIG. 18(B) , since in either state the interlocking face  75   a  of the clutch member  70  is in abutment with the interlocking end  93   b.    
   On the other hand when the clutch member  70  is rotated in the counterclockwise direction as illustrated in  FIG. 18(C) , there results a non-interconnected mode in which the sloping face  75   b  of the first clutch teeth  75  follows along the outside face of the arm  93   a  so that the torque member  90  does not rotate. In this way the first clutch teeth  75  and clutch arms  93  constitute a one-way clutch mechanism which normally interlocks in the clockwise direction (closing direction) to transmit rotational torque, and which does not transmit rotational torque in the counterclockwise direction (opening direction). 
   (2)-6-4 Second Clutch Unit  65   
     FIG. 19  is an illustrative diagram illustrating the second clutch unit  65 . The second clutch unit  65  is a mechanism for transmitting rotational torque applied in the opening direction to the handle  45 , only when the handle is in the handling position. 
   The second clutch teeth  76  are formed all the way around the bottom outside rim of the upper wall  72  of the clutch member  70 . Each the second clutch teeth  76  comprises a substantially vertical the interlocking face  76   a  and a sloping face  76   b  inclined by a predetermined angle with respect to the interlocking face  76   a , to produce a substantially right triangular cross section. 
   On the upper face of the torque member  90  are formed second clutch interlocking portions  94  for interlocking with the second clutch teeth  76 . The second clutch interlocking portions  94  are positioned at 120° intervals about the circumference in the upper portion of the torque member  90 . Each the second clutch interlocking portion  94  comprises a vertical interlocking face  94   a  interlocking with a interlocking face  76   a , and a sloping face  94   b  abutting a sloping face  76   b.    
     FIG. 20  illustrates operation of the second clutch unit  65 . As shown in  FIG. 20(A) , when the clutch member  70  is positioned upwardly by the spring force of the clutch spring  92  of the clutch mechanism  60 , the interlocking faces  76   a  of the clutch member  70  are not interlocked with the interlocking faces  94   a  of clutch interlocking portions  94 . Therefore the torque member  90  does not rotate even if the clutch member  70  is rotated. 
   As shown in  FIG. 20(B) , when the clutch member  70  is positioned downwardly in opposition to the spring force of the clutch spring  92  of the clutch mechanism  60 , the interlocking faces  76   a  of the clutch member  70  interlock with the interlocking faces  94   a  of clutch interlocking portions  94 . Turning the clutch member  70  is the counterclockwise direction (opening direction) causes the torque member  90  to rotate in unison therewith in the same direction. In this way, the second clutch teeth  76  and second clutch interlocking portions  94  constitute a one-way clutch mechanism that transmits rotational torque only when the torque member  90  is in the down position, while not transmitting rotational torque in the clockwise direction. 
   (2)-7 Structure of the Torque Member  90   
     FIG. 21  is a perspective view showing the torque member  90 . The torque member  90  comprises a two-stage disk of resin having a projecting portion and interlocking portion in its center. That is, the torque member  90  comprises a torque plate body  91 . The torque plate body  91  comprises an upper disk  91   a , an annular portion  91   b  situated at the outside bottom of the upper disk  91   a , and connector portions  91   c  connected at three locations to the annular portion  91   b . The upper disk  91   a  comprises a clutch spring  92  which carries the clutch mechanism  60  described earlier, and is provided on its outside edge with clutch arms  93 . 
   (2)-7-1 Torque Member  90  Mounting Structure 
   As shown in  FIG. 22 , the interlocking claws  97  are formed on the inside rim of the annular portion  91   b  of the torque member  90 . The interlocking claws  97  are configured as tongue pieces extending towards the center of the torque member  90  and are resiliently deformable in the axial direction.  FIG. 23  is a sectional view of the area around the top of the casing body  20 . An interlocking recess  21   c  is formed around the upper outside rim of the outer tube  21  of the casing body  20 . The interlocking claws  97  are forced into the interlocking recess  21   c  to rotatably mount the torque member  90  on the upper outside rim of the casing body  20 . 
   An interlocking recess  91   d  is formed around the outside rim of the annular portion  91   b , allowing the cover  40  of the torque member  90  to be rotatably supported within the interlocking recess  91   d  by detaining therein the support projection  43   a  on the inside wall of the side wall  43  of the cover  40  (see  FIG. 1 ). 
   (2)-7-2 Structure of the Torque Transmission Mechanism  80   
   The torque transmission mechanism  80  shown in  FIG. 1  is a mechanism that enables confirmation that the fuel cap  10  has been attached to the filler neck FN at a predetermined level of rotational torque, by providing the user with a tactile warning if excessive rotational torque above a predetermined level is applied to the handle  45  during the operation of closing the filler opening FNb with the fuel cap  10 . 
     FIG. 24  is a perspective view showing the torque transmission mechanism  80 , and  FIG. 25  is a plan view showing the torque transmission mechanism  80 . The upper inside rim of the outer tube  21  has formed thereon a body interlocking portion  25  constituting part of the torque transmission mechanism  80 , described later. The body interlocking portion  25  extends around the entire inside circumference of the outer tube  21  and has a peak configuration composed of a first interlocking face  25   a  slanted substantially in the circumferential direction and a second interlocking face extending substantially in the radial direction. 
   An inner annular portion  91   e  of hollow cylindrical configuration is formed in the bottom of the upper disk  91   a  of the torque member  90 , and three the resilient torque pieces  95  are formed at 120° intervals about the circumference on the outside edge of the inner annular portion  91   e . As shown in  FIG. 25 , the resilient torque pieces  95  take the form of arched cantilever pieces having their support points at the supporting terminal portions  95   a , and having the torque piece interlocking portions  96  projecting from their outside edges, with the spaces  95   c  to the inside of the torque piece interlocking portions  96 . Each the torque piece interlocking portion  96  has a first interlocking face  96   a  formed on a first face thereof and a second interlocking face  96   b  formed on a second face. First interlocking face  96   a  is configured so as to come into abutment at a vertical face thereof with a first interlocking face  25   a  of the body interlocking portion  25  with clockwise rotation of the torque member  90 ; when pushed in the radial direction from the center by a body interlocking portion  25  the torque piece interlocking portions  96  undergoes resilient deformation so as to the constrict space  95   c , as shown in  FIG. 26 . 
   (2)-7-3 Torque Member  90  Breaking Mechanism 
   As shown in  FIG. 28(A) , the frangible grooves  98   a  constituting part of the frangible portions  98  are formed along the outside edge of the upper disk  91   a  of the torque member  90 , between it and the connector portion  91   c . The frangible grooves  98   a  are located at three areas in the circumferential direction, these the frangible grooves  98   a  being provided along the circumference of a circle connecting the cutout portions between connector portions  91   c  in the circumferential direction. 
   Referring now to  FIG. 28(B) , if the cover  40  or the handle  45  should be subjected to a strong external force such as that produced in an automobile collision, the frangible portions  98  supporting the cover  40  will separate at the outside edges thereof or the interlocking claws  97  will detach from the interlocking recess  21   c  beginning at the frangible portions  98 . At this time the seal retaining portion  21   a  of the casing body  20  supporting the gasket GS is not damaged so that the seal is not lost. An additional reason for providing the torque member  90  with the frangible portions  98  is that by forming the frangible portions  98  in the upper portion of the casing body  20  there are no limitations as to the shape of the seal retaining portion  21   a , making it a simple matter to optimize breaking load for external forces in various directions. 
   (2)-8 Tether Mechanism  100   
     FIG. 29  is a sectional view of the area around the tether mechanism  100 ,  FIG. 30  is a plan view of the tether mechanism  100 , and  FIG. 31  is a perspective view illustrating the tether mechanism  100 . The tether mechanism  100  is designed to prevent the fuel cap  10  from falling off or becoming lost during fueling, and comprises a tether rotation support  101 , a connector member  110 , and a support end  120 . As shown in  FIG. 29 , the tether rotation support  101  is rotatably supported on one end of a support wall  99  of the torque member  90 . Specifically, the tether rotation support  101  has an annular configuration extending all the way around the support wall  99  and has an open square cross section defined by an outer the annular outer wall  102 , the floor  103  and annular the inner wall  104 , with an annular recess  101   a  therebetween. The outer the annular outer wall  102  is taller than annular the inner wall  104 . The interlocking projections  102   a  project from the inside face of the annular outer wall  102 . As shown in  FIG. 30 , the interlocking projections  102   a  are situated at six locations equal distances apart along the circumference, and when the interlocking claws  99   a  of the support wall  99  are snapped into the annular recess  101   a  these interlock with the interlocking projections  102   a  as shown in  FIG. 29  so that the tether rotation support  101  is rotatably supported on the torque member  90 . 
   The tether mechanism  100  is integrally molded by injection molding of thermoplastic elastomer (TPEE) or thermoplastic resin (e.g. PP). As shown in  FIG. 30  a first end of the connector member  110  is connected to the tether rotation support  101 , inclined with respect thereto by a predetermined angle α (5°–180°). The connector member  110  comprises a connector member body  112  and a flex portion  114 . The flex portion  114  is located in proximity to a first connecting end  110   a  at one end of the connector member  110 . Flex portion  114  is composed of inverted “U” shapes connected together in a substantially “S” configuration and is coplanar with the tether rotation support  101  so that when subjected to force in the direction indicated by arrow d 1  in  FIG. 32  the connector member body  112  will bend along the outside perimeter of the cover  40 . 
   In  FIG. 31  a support end  120  is formed at a second connecting end  110   b  at the other end of the connector member  110 . The support end  120  is of tabular configuration fanning out towards the distal end and is formed by twisting at a right angle, i.e. 90°, with respect to the connector member  110 . A detent projection  122  projects from the support end  120 . As shown in  FIG. 34 , the detent projection  122  is rotatably supported on a support portion formed on the back face of the fuel cover FL. When fuel cover FL is opened away from the filler neck FN the fuel cap  10  is suspended via the connector member  110  fixed to the support end  120 . When at this point the fuel cap  10  is released the cover  40  of the fuel cap  10  drops toward the exterior panel of the vehicle, suspended away from the vehicle panel due to the 90° bend with respect to the connector member  110 , enabling the fueling operation. That is, the fuel cap is located away from the vehicle panel during fueling and therefore does not interfere with the fuel nozzle and preventing fuel on the casing body  20  from dripping onto the vehicle panel. 
   With the fuel cap  10  removed, the fuel cap  10  is then replaced in the filler opening FNb of the filler neck FN and the handle  45  turned in the closing direction shown in  FIG. 32 ; as the tether rotation support  101  is rotatable with respect to the torque member  90  ( FIG. 29 ), and as the connector member  110  is not subjected to any appreciable force from the fuel cover FL or the fuel cap  10  so as to remain slack on a substantially straight line, the opening/closing operation of the fuel cap  10  is not impaired. At this time the connector member  110  flexes at the flex portion  114  so that the connector member body  112  flexes along the outside perimeter of the cover  40 . 
   When fuel cover FL ( FIG. 34 ) is subsequently shut the connector member body  112  is pushed longitudinally from the position illustrated in  FIG. 32  in association with the motion of fuel cover FL. Longitudinal force on the connector member body  112  is converted to force tending to rotate the tether rotation support  101  in the counterclockwise direction so that the tether rotation support  101  rotates smoothly causing the connector member body  112  to coil around the cover  40  as illustrated in  FIG. 33 . Since the connector member body  112  coils around the cover  40  in this way it can be accommodated within the space behind the fuel cover FL and does not hinder opening and closing of the fuel cover FL. 
   As shown in  FIG. 29 , the tether rotation support  101  of the tether mechanism  100  is supported by a torque member  90  of polyacetal having a smooth surface, enabling it to rotate smoothly about the outside rim of the torque member  90  so that the opening/closing operation of the fuel cap  10  is not impaired. The torque member  90  is moreover fabricated of highly swelling-resistant polyacetal and therefore experiences negligible change in shape that would increase outside diameter, so that the ability of the tether rotation support  101  to rotate is not diminished. Further, as the tether rotation support  101  is formed of pliable thermoplastic elastomer (TPEE) or thermoplastic resin (PP) bending thereof at the flex portion  114  can be assured. 
   (3) Fuel Cap  10  Assembly Procedure 
   To assemble the fuel cap  10 , first, the handle  45  is attached to the cover  40  as shown in  FIG. 9 . The regulator valve  35  is also installed in the valve chamber  24  of the casing body  20  as shown in  FIG. 1 , and the flange  32  of the inner cover  30  is ultrasonically welded onto the upper portion of the valve chamber molding  22 . Next, as shown in  FIG. 23 , the interlocking claws  97  of the torque member  90  are forced into the interlocking recess  21   c  of the casing body  20  to attach the torque member  90  to the casing body  20 . The button  74  of the clutch member  70  is aligned with the through-hole  41   a  in the cover  40 , attaching the clutch member  70  to the cover  40  and then interlocking the support projection  43   a  of the cover  40  with the interlocking recess  91   d  to attach the cover  40  onto the torque member  90 . Then as shown in  FIG. 29  the tether rotation support  101  of the tether mechanism  100  is forced over the interlocking claws  99   a  of the support wall  99  to attach the tether mechanism  100  to the torque member  90 . This completes assembly of the fuel cap  10 . 
   (4) Fuel Cap  10  Operation 
   Following is a description of the opening and closing operation when attaching or replacing the fuel cap  10  in the filler opening FNb of the filler neck FN. 
   (4)-1 Fuel Cap  10  Closing Operation 
   With the fuel cap  10  detached from filler opening FNb, the handle  45  is pulled upright with the fingers as shown in  FIG. 14 , whereupon the handle  45  rotates about axial support portions  51 ,  52  shown in  FIG. 14 , in opposition to the spring force of the urging mechanism  57  (see  FIG. 10 ) and the clutch spring  92  (see  FIG. 20 ). Rotation of the handle  45  causes the cam face  62  to push against the pushing face  74   a  of the button  74  of the clutch member  70 . The clutch member  70  then moves downwardly in opposition to the urging force of the clutch spring  92  of the torque member  90  as shown in  FIG. 15 . 
   Next, as shown in  FIG. 3  the casing interlocking portion  20   a  of the casing body  20  is aligned with the neck insertion notch FNd of the filler neck FN and inserted therein in the axial direction. Clockwise force is then applied to the handle  45  and is transmitted to the clutch member  70  via the cover  40 , the cover  40  the through-hole  41   a  and the button  74  of the clutch member  70 , causing the clutch member  70  to rotate. Since the interlocking faces  75   a  of the first clutch teeth  75  normally interlock with the interlocking ends  93   b  of clutch arms  93  of the torque member  90  as shown in  FIG. 18(A) , the torque member  90  rotates in tandem with rotation of the clutch member  70 . It should be noted that even if the user does not move the handle  45  to the handling position, i.e., even with the handle in the retracted position, the interlocking ends  93   b  are interlocked with the interlocking faces  75   a  as shown in  FIG. 18(B)  so that rotational torque is transmitted from the clutch member  70  to the torque member  90 . 
   As the torque member  90  rotates, the first interlocking faces  96   a  of the torque piece interlocking portions  96  of the torque member  90  press against first interlocking faces  25   a  of body interlocking portions  25  at the interlock locations illustrated in  FIG. 25 . This causes the handle  45 , the cover  40 , the clutch member  70 , the torque member  90  and the casing body  20  to rotate in unison in the direction of closing the filler opening FNb, with the casing interlocking portions  20   a  (see  FIG. 3 ) interlocking with opening interlocking portion FNc with increasing force. When reaction force created by this interlocking force exceeds a predetermined level of rotational torque, the torque piece interlocking portions  96  in the state shown in  FIG. 26  now ride over the body interlocking portions  25 . 
   At this point the first interlocking faces  96   a  of the torque piece interlocking portions  96  are forced in the radial direction by the reaction force from the first interlocking faces  25   a , causing the resilient torque pieces  95  to resiliently deform so as to constrict the width of the spaces  95   c , so that the torque piece interlocking portions  96  ride up over body interlocking portions  25 . This provides to the user with a tactile warning of over-tightening. In this state the fuel cap  10  is attached to the filler opening FNb at a predetermined level of tightening torque. 
   When the handle  45  is subsequently released it is subjected to spring force created by the resilient cam support piece  59   a  pinching the cam face  58  (see  FIG. 36 ) and to the spring force of the clutch spring  92  transmitted to handle via the button  74 , and rotates about axial support portions  51 ,  52  to return to the retracted position. 
   (4)-2 Fuel Cap  10  Closed State 
   In the state shown in  FIG. 1 , the handle  45 , the cover  40 , and the clutch member  70  are not constrained in the opening direction (counterclockwise direction) by the torque member  90  and the casing body  20 , and thus rotate freely. Thus, if the cover  40  and/or the handle  45  should be subjected to external force as in a collision, they will simply turn freely without rotational torque being transmitted to casing member  20  through the torque transmission mechanism  80 , so that there is no loss of seal. 
   (4)-3 Procedure for Opening the Fuel Cap  10   
   The procedure for opening the fuel cap  10  is initiated by pulling up the handle  45  as shown in  FIG. 15 . This causes the cam face  62  in the lower center of the handle  45  to push against the pushing face  74   a  of the button  74  of the clutch member  70 , so that the clutch member  70  moves downwardly. In this state, turning the handle  45  counterclockwise causes the interlocking faces  76   a  of the second clutch teeth  76  to interlock with the interlocking faces  94   a  of second clutch interlocking portions  94  as shown in  FIG. 20(B) , so that the torque member  90  rotates in the counterclockwise direction in tandem with rotation of the clutch member  70  in the same direction. 
   In this state, the second interlocking faces  96   b  of the torque piece interlocking portions  96  interlock with the second interlocking faces  25   b  of body interlocking portions  25  as shown in  FIG. 27 . The second interlocking faces  96   b  and the second interlocking faces  25   b  come into abutment substantially in the radial direction and do not produce center-directed force tending to cause the resilient torque pieces  95  to constrict the spaces  95   c , so that the torque piece interlocking portions  96  do not ride over body interlocking portions  25 , but instead transmit rotational torque applied to the handle  45  to the casing body  20 . As a result the handle  45 , the cover  40 , the clutch member  70 , the torque member  90  and the casing body  20  rotate in unison in the clockwise direction. 
   The casing interlocking portion  20   a  then comes away from the opening interlocking portion FNc of the filler neck FN so that the casing body  20  is released from the constraining force of the filler neck FN. The fuel cap  10  can now be removed from the filler neck FN by pulling out in the axial direction. 
   (4)-4 Operation of the Handle  45  the Urging Mechanism  57   
     FIG. 35  illustrates the return operation of the handle  45  by the clutch spring  92 , and  FIG. 36  illustrates the return operation of operation of the handle  45  by the urging mechanism  57 . When opening or closing the handle  45 , the handle  45  is rotated from the retracted position to the handling position; this is done in opposition to rotational torque returning the handle  45  to the retracted position, due to spring force of the clutch spring  92  and the urging mechanism  57 . Rotational torque is normally energized in the return direction is for the following reasons.
     (1) As the vehicle is driven the handle  45  is kept flat on the cover so as to not project significantly thereabove, making it more difficult for the handle  45  to be subjected to external force.   (2) Chattering of the handle  45  is reduced so that strange noises are not produced during driving.   
   The reason for using two resin springs as the urging mechanism  57  and the clutch spring  92  to produce rotational torque in the return direction is as follows. 
     FIG. 37  is a graph illustrating the relationship of angle of rotation to rotational torque applied to the handle. In  FIG. 37 , rotational torque produced by the urging mechanism  57  is graphed by a broken line, rotational torque produced by the clutch spring  92  by a dotted and dashed line, and total rotational torque applied to the handle  45  by a solid line. As will be apparent from  FIG. 37 , the urging mechanism  57  is set to high rotational torque at small angles of less than 45°, while the clutch spring  92  is set to high rotational torque at large angles of from 45° to 90°. 
   Rotational torque levels are set in this way for the following reason. The spring force produced by the urging mechanism  57  depends on the shape of the cam face  58   a  of the cam  58 , making it difficult to produce a shape for a cam that can generate a high level of rotational torque over a wide control range. For the clutch spring  92  to generate rotational torque over a wide control range it would be necessary for the torque member  90  to move with a large stroke. Further, where only a single resin spring is used to generate rotational torque over a wide control range it will be necessary for the resin spring to flex appreciably, which over a period of several years may lead to failure. By using instead two resin springs, it is possible to achieve rotational torque for stable return over a wide range of 0–90°. 
   (5) Working Effects of the Fuel Cap  10   
   In addition to the working effects described above, the fuel cap  10  affords the following working effects. 
   (5)-1 In the process of closing the fuel cap  10 , tactile warning is provided when the torque piece interlocking portions  96  of the torque member  90  ride up over body interlocking portions  25  of the casing body  20  as shown in  FIGS. 25 and 26 , so that the user may determine that the fuel cap  10  has been tightened to a predetermined level of torque, thereby allowing the cap to be attached to a predetermined level of torque regardless of any resilience on the part of the gasket GS etc. 
   (5)-2 With the fuel cap  10  closing the filler opening FNb as shown in  FIG. 1 , the clutch member  70  does not move in tandem with the casing body  20  in the opening direction, due to the clutch mechanism  60 , and thus even if the handle  45  should be subjected to force in the opening direction due to some unforeseen external force, it will simply turn freely with respect to the casing body  20 . Therefore the casing body  20  will not be subjected to external force applied to the handle  45  and will remain seated in the filler opening FNb. The fuel cap  10  can therefore maintain a seal without becoming loosened by unforeseen external force. 
   (5)-3 With the fuel cap  10  attached to filler opening FNb as shown in  FIG. 1 , the handle  45  is placed in the retracted position by spring force and returns to this position from the upraised handling position during the opening/closing operation, and is therefore not susceptible to external force such as that occurring in a vehicle collision or the like, so that it is not subjected to force tending to loosen the fuel cap  10 . Additionally, even where the handle  45  is of appreciable size, since it is positioned laying flat on the upper wall  41  of the cover  40  in the closed position, a minimal amount of space around the filler opening is required to accommodate it. 
   (5)-4 As shown in  FIG. 24 , the body interlocking portions  25  of the torque transmission mechanism  80  are formed at equal distances all the way around the inner cover  30 , whereby rotational torque may be transmitted immediately to the casing body  20  without changing the position of the handle  45 , and whereby uniform rotational torque may be transmitted regardless of the position of the torque piece interlocking portions  96 . 
   (5)-5 With the fuel cap  10  in the closed state, the handle  45  turns freely in the opening direction whereby the user may turn the handle  45  to the desired position, improving ease of opening/closing. 
   (5)-6 As shown in  FIG. 1 , with the fuel cap  10  in the closed state the handle  45  can be visually confirmed to be lowered into the retracted position, and it will be readily understood that opening/closing can be accomplished by upraising it, thereby providing superior operation to the button operation arrangement described in the prior art. 
   (5)-7 As shown in  FIG. 18 , the first clutch unit  63  transmits rotational torque even when the handle  45  is not in the handling position, so that even if the user neglects to move the handle  45  to the handling position it is still possible to close the tank opening with the casing body  20 . The first clutch unit  63  ( FIG. 18 ) and the second clutch unit  65  ( FIG. 20 ) turn freely in the opening direction when the handle  45  is in the retracted position, so that the casing body  20  will not be rotated by external force and will not lose seal. 
   The foregoing detailed description of the invention has been provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. The foregoing detailed description is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Modifications and equivalents will be apparent to practitioners skilled in this art and are encompassed within the spirit and scope of the appended claims.