Abstract:
A stud locking device, which in an assembled condition can hold a target member to a support member, the target member defining a through hole, and the support member including an axially projecting stud; the stud locking device comprising: a first clip including an inner cylindrical portion with a first flange at a target end and defining a central bore for receiving the stud, and insertable at a base end through the mounting hole; and a second clip including: a outer cylindrical portion capable of receiving coaxially the first cylindrical portion; and a second flange provided at a target end of the outer cylindrical portion; and wherein a tapered bore is defined by and coaxial with the first flange and first cylindrical portion, the tapered bore open in the upper surface of the flange, narrowing with increasing axial distance from the open end, and connected to the central bore.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT/JP2013/71691, filed on Aug. 9, 2013, which claims priority from Japanese Patent Application No. 2012-180019, filed on Aug. 15, 2012, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a locking device usable for mounting a sheet-shaped target member (e.g., an undercover) to a support member (e.g., a panel of an automotive vehicle) having a stud (e.g., a threaded stud) fixed thereto. More specifically, it relates to a stud locking device usable for mounting the target member to the support member, in such a manner that it is lockedly engaged with the stud while retaining the target member. 
     Generally, a locking device is employed as a means to mount a sheet-shaped target member such as an undercover to a support member such as a panel of an automotive vehicle. In advance of an operation of mounting a wide sheet-shaped target member such as an undercover to a panel, a plurality of threaded studs are fixedly attached onto the panel at respective given positions thereof by welding or the like, and a plurality of mounting holes for receiving therein the respective studs are formed in the undercover at respective given positions thereof. Then, the target member is put to the panel and positioned to allow the studs to be inserted into corresponding ones of the mounting holes of the target member, and a plurality of nuts are engaged, respectively, with portions of the studs protruding from the target member by using a tool. In this manner, the target member is mounted to a support member such as a panel of an automotive vehicle. 
     There has been known a stud locking device designed to facilitate such a target member mounting operation and configured to clamp a target member from both sides thereof by a first clip and a second clip, and, in this state, receive a stud into a stud-receiving hole of the locking device to thereby mount the target member to the stud. 
     Published Japanese application JP2007/292146 A and its US counterpart application US2007/0248436 A discloses this type of locking device (stud locking device) comprising a first clip and a second clip. The first clip comprises an inner cylindrical portion, a flange configured to come into contact with one of opposite surfaces of the target member, and locking pawls formed inside the inner cylindrical portion, and the second clip comprises an outer cylindrical portion; and a flange configured to come into contact with the other surface of the target member. The locking device disclosed in US2007/0248436 A is configured to be lockedly engaged with each of a plurality of studs fixedly attached to a support member such as a panel of an automotive vehicle, while clamping a sheet-shaped target member by the first clip and the second clip, thereby mounting the target member to the support member. 
       FIG. 1  illustrates the locking device  1 ′ disclosed in US2007/0248436 A. The locking device  1 ′ comprises a first clip  2  made of a hard synthetic resin (and molded as a single piece), and a second clip  3  made of a hard synthetic resin and molded as a single piece. The first clip  2  has an inner cylindrical portion  2   b , and a flange  2   a  formed at one end of the inner cylindrical portion  2   b . The second clip  3  has an outer cylindrical portion  3   b , and a flange  3   a  formed at one end of the outer cylindrical portion  3   b . The inner cylindrical portion  2   b  of the first clip  2  is inserted into a mounting hole  9  of a sheet-shaped target member  5  to be mounted, and further inserted into the outer cylindrical portion  3   b  of the second clip  3 . Thus, the first clip  2  and the second clip  3  are couple together while clamping the target member  5  therebetween. When a stud  7  fixedly attached onto a support member  6  such as a panel of an automotive vehicle is inserted into a stud-receiving hole of the locking device  1 ′, a locking pawl  4  of the first clip  2  is lockedly engaged with a thread ridge of the stud  7 , so that the target member  5  is mounted to the support member  6 . A hexagonal hole  8  is formed in a central region of the flange of the first clip  2 . Thus, a hexagonal wrench can be engaged with the hexagonal hole  8  and rotated to further tighten up or detach the locking device  1 ′ with respect to the stud  7 . 
     In the locking device disclosed in US2007/0248436 A, the hexagonal hole is formed in a central portion of the first clip  2  to allow the hexagonal wrench to be rotated while being inserted therein. The hexagonal hole has a relatively small diameter and a relatively long length so as to ensure engagement with the hexagonal wrench, and thus it is difficult to visually ascertain how much the first clip is inserted with respect to the stud, even when viewed from above the hexagonal hole. If the first clip is not fully inserted, a pull-out load is likely to decrease. Moreover, in the locking device disclosed in US2007/0248436 A, a bottom of the first clip does not have a taper wall for allowing the stud to be received in the stud-receiving hole. Thus, when the stud is inserted into the stud-receiving hole, it is likely that there is difficulty in guiding and inserting the stud with respect to the stud-receiving hole. 
     Published Japanese application JP2009/162358 A discloses a stud bolt clip lockable to a stud bolt provided to stand on a vehicle panel of an automotive vehicle, or the like. The stud bolt clip is a single component. The stud bolt clip comprises: a pair of first locking members each formed to extend from a corner of a bolt insertion hole-side end of an inner surface of a respective one of two opposed sidewall portions, in such a manner that they are disposed in opposed relation to each other; and a pair of second locking members each formed to extend from an axially approximately central region of the inner surface of the respective one of the opposed sidewall portions, in such a manner that they are disposed in opposed relation to each other. Each of the first locking members has an inner surface formed with three first locking ribs engageable with thread grooves of a first stud bolt having a relatively small thread pitch, and each of the second locking members has an inner surface formed with three second locking ribs engageable with thread grooves of a second stud bolt having a relatively large thread pitch. 
     In an operation for locking to the first stud bolt having a relatively small thread pitch, the three first locking ribs are engaged with thread grooves of the first stud bolt, and either one of the three second locking ribs is engaged with a thread groove of the first stud bolt. In an operation for locking to the second stud bolt having a relatively large thread pitch, either one of the three first locking ribs is engaged with a thread groove of the second stud bolt, and the three second locking ribs are engaged with thread grooves of the second stud bolt. 
     The stud bolt clip disclosed in JP2009/162358 A can be locked to each of two types of stud bolts having different pitches. However, when the stud bolt clip is locked to the first stud bolt, only a part of the three second locking ribs is engaged with a thread groove of the second stud bolt. On the other hand, when the stud bolt clip is locked to the second stud bolt, only a part of the three first locking ribs is engaged with a thread groove of the first stud bolt. Thus, the stud bolt clip is likely to fail to be reliable mounted. Further, in an operation of attaching the stud bolt clip to a target member to be mounted, a pair of clamping ribs are inserted, respectively, into a pair of member through-grooves, and turned 90° to clamp the target member between the clamping ribs and a flange of the stud bolt clip. Thus, it is necessary to form, in the target member, a mounting hole together with the pair of quadrangular-shaped member through-grooves, i.e., take a lot of time and effort for processing of the target member. 
     Therefore, there is a need for a stud locking device capable of mounting a target member such as an undercover to a support member such as a panel of an automotive vehicle, readily and reliably. There is also a need for a stud locking device capable of readily ascertaining whether a clip is perfectly mounted to a stud. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a stud locking device capable of mounting a target member such as an undercover to a support member such as a panel of an automotive vehicle, readily and reliably. It is another object of the present invention to provide a stud locking device capable of readily ascertaining whether a clip is perfectly mounted to a stud. 
     In order to achieve the above objects, according to one aspect of the present invention, there is provided a stud locking device comprising a first clip and a second clip connected to each other while holding a target member from both sides thereof, wherein the stud locking device receives a stud fixed on a support member in a stud receiving space and is latched by the stud, by which the stud locking device is fixed onto the support member and the target member is mounted onto the support member. 
     wherein the first clip has: a hollow inner cylindrical portion insertable into a mounting hole of the target member; a flange provided at one end of the inner cylindrical portion; locking pawls formed inside the inner cylindrical portion and engageable with thread ridges of the stud; and a coupling means for coupling to the second clip, and 
     the second clip has: a hollow outer cylindrical portion capable of receiving therein the inner cylindrical portion of the first clip; a flange provided at one end of the outer cylindrical portion; and a coupling means for coupling to the first clip, and 
     wherein the first clip has a taper portion tapered from an upper surface of the flange thereof toward the inner cylindrical portion along a central axis thereof, whereby a tip of the stud can be viewed from the upper surface of the flange through the taper portion. 
     In the stud locking device of the present invention, the target member can be mounted to the support member readily and reliably through an operation of clamping the target member from both sides thereof by the first clip and the second clip, and engaging the locking pawl of the first clip with a thread ridge of the stud fixed to the support member. 
     In addition, the tip of the stud can be seen from the upper surface of the flange through the taper portion, so that it becomes possible to readily ascertain whether the clips are perfectly mounted to the stud. 
     Preferably, when the inner cylindrical portion of the first clip is inserted into the mounting hole of the target member, the flange of the first clip come into contact with one surface of the target member, and, when the inner cylindrical portion of the first clip is received in the outer cylindrical portion of the second clip, the flange of the second clip come into contact with the other surface of the target member. This makes it possible to reliably clamp the target member. 
     Preferably, the bottom portion of the inner cylindrical portion has a guide wall which has a taper tapered toward the flange of the inner cylindrical portion to guide the tip of the stud to the stud-receiving space. More preferably, the taper angle of the guide wall is in the range of 115 to 135°. This makes it possible to easily guide the tip of the stud to the stud-receiving space. 
     Preferably, the flange of the second clip has an elastic edge portion capable of elastically pressing the target member toward the flange of the first clip. This makes it possible to clamp the target member so as to avoid wobbling. 
     More preferably, the flange of the second clip is formed with two flange holes opposite from each other, each of which holes is narrow and long in a circumferential direction, which makes the elastic edge portion in the area adjacent to the flange holes more flexible. This makes it possible to elastically press the target member. 
     Preferably, the inner cylindrical portion has two pairs of the locking pawls along an axial direction thereof, and a plurality of ribs opposite from one another, each extending along the axial direction, and wherein the stud-receiving space is formed by the locking pawls and the ribs. This makes it possible to position the stud within the stud-receiving space. 
     Preferably, each of the locking pawls is engageable with two studs having different thread pitches, and has a plurality of first pawl tips insertable into thread grooves of the two studs having different thread pitches and a second pawl tip insertable into a thread groove of one of the two studs. This makes it possible to be reliably engaged with two studs having different thread pitches. 
     The present invention can provide a stud locking device capable of mounting a target member such as an undercover to a support member such as a panel of an automotive vehicle, readily and reliably. The present invention can also provide a stud locking device capable of readily ascertaining whether a clip is perfectly mounted to a stud. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a state in which a target member is mounted to a support member with a stud by using a conventional stud locking device. 
         FIG. 2  is a top plan view of a first clip of a stud locking device according to a first embodiment of the present invention. 
         FIG. 3  is a front view of the first clip in  FIG. 2 . 
         FIG. 4  is a right side view of the first clip in  FIG. 2 . 
         FIG. 5  is a sectional view of the first clip in  FIG. 2 , taken along the line V-V in  FIG. 2 . 
         FIG. 6  is a sectional view of the first clip in  FIG. 2 , taken along the line VI-VI in  FIG. 3 . 
         FIG. 7  is a sectional view of the first clip in  FIG. 2 , taken along the line VII-VII in  FIG. 2 . 
         FIG. 8  is a sectional view of the first clip in  FIG. 2 , taken along the line VIII-VIII in  FIG. 3 . 
         FIG. 9  is a sectional view of the first clip in  FIG. 2 , taken along the line IX-IX in  FIG. 4 . 
         FIG. 10  is a sectional view of the first clip in  FIG. 2 , taken along the line X-X in  FIG. 3 . 
         FIG. 11  is an enlarged view of the area XI in  FIG. 3 . 
         FIG. 12  is a perspective view of a second clip of the stud locking device according to the first embodiment of the present invention. 
         FIG. 13  is a top plan view of the second clip in  FIG. 12 . 
         FIG. 14  is a front view of the second clip in  FIG. 12 . 
         FIG. 15  is a bottom view of the second clip in  FIG. 12 . 
         FIG. 16  is a right side view of the second clip in  FIG. 12 . 
         FIG. 17  is a sectional view of the second clip in  FIG. 12 , taken along the line XVII-XVII in  FIG. 13 . 
         FIG. 18  is a sectional view of the second clip in  FIG. 12 , taken along the line XVIII-XVIII in  FIG. 13 . 
         FIG. 19  is a sectional view of the second clip in  FIG. 12 , taken along the line XIX-XIX in  FIG. 13 . 
         FIG. 20  is an enlarged view of the area XX of the second clip in  FIG. 17 . 
         FIG. 21  is a sectional view illustrating a state in which a target member is mounted to a support member with a stud by using the stud locking device according to the first embodiment of the present invention. 
         FIG. 22  is an enlarged view of the area XXII in  FIG. 21 . 
         FIG. 23  is a sectional view illustrating a state in which the stud locking device in  FIG. 21  is mounted to a stud having an incompletely threaded portion. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, the present invention will now be described based on an embodiment thereof. A stud locking device  1  according to a first embodiment of the present invention comprises a first clip  10  illustrated in  FIGS. 2 to 11 , which is made of a hard synthetic resin and molded as a single piece, and a second clip  30  illustrated in  FIGS. 12 to 20 , which is made of a hard synthetic resin and molded as a single piece. 
     Before describing each configuration of the first clip  10  and the second clip  30 , an outline of a configuration of the stud locking device  1  will be described.  FIG. 21  is a sectional view illustrating a state in which a target member  51  is mounted to a support member  52  with a stud  70  by using the stud locking device  1  according to the first embodiment of the present invention. The first clip  10  and the second clip  30  of the stud locking device  1  are coupled together while clamping a sheet-shaped target member  51  such as an undercover therebetween. When a stud  70  fixed onto a support member  52  such as a panel of an automobile vehicle is inserted into a stud-receiving space  24  of the stud locking device  1 , locking pawls  13  are lockedly engaged with a thread ridge of the stud  70 , and thus the target member  51  is mounted to the support member  52 . 
     The first clip  10  of the stud locking device  1  has a hollow inner cylindrical portion  12 , a flange  11  provided at a first or top end of the inner cylindrical portion  12 , and locking pawls  13  formed inside the inner cylindrical portion  12  and engageable with the stud  70 . The hollow inner cylindrical portion  12  is insertable into a mounting hole  53  of the target member  51 . The flange  11  is configured to, when the inner cylindrical portion  12  is inserted into the mounting hole  53 , come into contact with an upper surface  51   a  of the target member  51 . 
     The second clip  30  of the stud locking device  1  has a hollow outer cylindrical portion  32  capable of receiving therein the inner cylindrical portion  12  of the first clip  10 , and a second flange  31  provided at a first or top end of the outer cylindrical portion  32 . The second flange  31  is configured to, when the inner cylindrical portion  12  is received in the outer cylindrical portion  32 , come into contact with the lower surface  51   b  of the target member  51 . The first clip  10  also has a neck portion  17  provided on the inner cylindrical portion  12  and formed with a locking shoulder  18 . The second clip  30  also has a locking section  39  formed inside the outer cylindrical portion  32 . The locking shoulder  18  and the locking section  39  serve as a coupling means to mutually couple the first clip  10  and the second clip  30 . 
     A plurality of the studs  70  are fixedly attached onto the support member  52  by welding or the like, at given intervals and in a given layout, to retain a wide sheet-shaped target member such as an undercover at a plurality of positions. In the first embodiment, as the stud  70 , a threaded stud having a thread formed on a peripheral surface thereof is employed. Although the stud  70  may be a grooved stud having a peripheral groove formed on a peripheral surface thereof, the threaded stud is preferred from the viewpoint of convenience to detach the target member from the support member. 
     The sheet-shaped target member  51  such as an undercover is formed with a plurality of the mounting holes  53  at respective positions corresponding to those of the plurality of studs  70  to allow the studs  70  to penetrate therethrough. 
     With reference to  FIGS. 2 to 11 , the first clip  10  will be described.  FIG. 2  is a top plan view of the first clip of the stud locking device according to the first embodiment of the present invention.  FIG. 3 ,  FIG. 4  and  FIG. 5  are, respectively, a front view of the first clip, a right side view of the first clip, and a sectional view taken along the line V-V in  FIG. 2 . 
     As illustrated in  FIG. 3 , the first clip  10  has the hollow inner cylindrical portion  12 , and the flange  11  formed at one end of the inner cylindrical portion  12 . The inner cylindrical portion  12  is configured to be inserted into the outer cylindrical portion  32  of the second clip  30 . The inner cylindrical portion  12  is formed as a hollow cylindrical body capable of receiving therein the stud  70 , wherein a plurality of (in the illustrated embodiment, two) pairs of elastic locking pawls  13   a  and  13   b  engageable with the stud  70  are provided inside the inner cylindrical portion  12 . The inner cylindrical portion  12  has an inner diameter capable of allowing the stud  70  to be received therein, and an outer diameter capable of allowing the inner cylindrical portion  12  to be inserted into the outer cylindrical portion  32  of the second clip  30 . The flange  11  is configured to, when the inner cylindrical portion  12  is inserted into the mounting hole of the target member  51 , come into surface contact with the first (upper) surface  51   a  of the target member  51 . 
     As illustrated in  FIGS. 3 and 4 , the inner cylindrical portion  12  comprises a ring-shaped base section  12   a  as a lower section, a ring-shaped top section  12   b  as an upper section, and a sidewall section  12   c  extending between the base section  12   a  and the top section  12   b  in an axial direction thereof. 
     Further, a plurality of (in the illustrated embodiment, two) ribs  21  are formed to extend between the base section  12   a  and the top section  12   b  in the axial direction. As illustrated in  FIG. 8  which is a sectional view taken along the line VIII-VIII in  FIG. 3 , a distance between the opposed ribs  21  is slightly greater than an outer diameter of the stud  70 . The aforementioned stud-receiving space  24  for receiving therein the stud  70  is formed by the ribs  21  and the locking pawls  13 , and the received stud  70  is positioned to become coaxial with the first clip  10 . 
     As illustrated in  FIG. 6  which is a sectional view taken along the line VI-VI in  FIG. 3 , an outer surface of each of the rib  21  is formed such that an intermediate region thereof in an up-down direction comes close to the central axis, i.e., in a concave shape  21   a.    
     As illustrated in  FIG. 10  which is a sectional view taken along the line X-X in  FIG. 3 , the base section  12   a  of the inner cylindrical portion  12  is formed with a recess  19  beneath each of the ribs  21 . 
     A pair of opposed arms  16   b  are disposed to extend from a base end of the sidewall section  12   c  obliquely upwardly and inwardly within the stud-receiving space  24 . Each of the pair of lower locking pawls  13   b  is supported by a respective one of the pair of arms  16   b . Another pair of opposed arms  16   a  are disposed to extend from an intermediate region of the sidewall section  12   c  obliquely upwardly and inwardly within the stud-receiving space  24 . Each of the pair of upper locking pawls  13   a  is supported by a respective one of the pair of arms  16   a.    
     When the stud  70  is inserted into the stud-receiving space  24 , the arms  16   a ,  16   b  are bent to allow the stud  70  to be received in the stud-receiving space  24 . Pawl tips of the locking pawls  13   a ,  13   b  enter and come into engagement with respective thread grooves each formed between adjacent thread ridges of the stud  70 , to thereby lock the first clip  10  to the stud  70 . The arms  16   a ,  16   b  are elastically deformable, so that the first clip  10  can be pressed into the stud  70  by a moderate force. Once the locking pawls  13   a ,  13   b  come into engagement, they can be strongly locked with less risk of pull-out. The opposed locking pawls  13   a  ( 13   b ) are mutually offset in terms of a height position, in conformity to a thread pitch of the stud  70 . 
     In the present invention, each of the locking pawls  13   a ,  13   b  is configured to be engageable with two studs having different thread pitches. Specifically, in this embodiment, it is engageable with a stud bolt M 6  having a thread pitch of 1.0 mm and a stud bolt T 6  having a thread pitch of 1.6 mm. 
       FIG. 11  which is an enlarged view of the area XI in  FIG. 3  illustrates one of the lower locking pawls  13   b . Each of the upper locking pawls  13   a  has the same shape. Each of the lower locking pawls  13   b  has an upper-end pawl tip  61   b , an intermediate pawl tip  62   b , and a lower-end pawl tip  63   b . A section between the upper-end pawl tip  61   b  and the intermediate pawl tip  62   b  is formed as an upper valley  64   b . A section between the intermediate pawl tip  62   b  and the lower-end pawl tip  63   b  is formed as a lower valley  65   b  having a flat area longer than the upper valley  64   b . Each of the upper locking pawls  13   a  has three pawl tips and two valleys in the same manner. 
     Each of the upper-end pawl tip  61   b  and the lower-end pawl tip  63   b  can enter a thread groove of each of the stud bolt M 6  and the stud bolt T 6 . The intermediate pawl tip  62   b  can enter a thread groove of the stud bolt M 6 , and it can enter a space between adjacent thread ridges of the stud bolt T 6 . As above, each of the locking pawls  13   a ,  13   b  in this embodiment is engageable with the stud bolt M 6  and the stud bolt T 6 . 
     Returning to  FIG. 3 , the neck portion  17  is provided between the inner cylindrical portion  12  and the flange  11  and formed to have a diameter smaller than that of the inner cylindrical portion  12 . As illustrated in  FIG. 9  which is a sectional view taken along the line IX-IX in  FIG. 4 , the neck portion  17  has an inner surface formed with two pairs of second protrusions  17   b  at radially opposed positions located axially just above the ribs  21 , and a pair of first protrusions  17   a  at radially opposed positions located axially just above the locking pawls  13 . The opposed first protrusions  17   a  and the opposed second protrusions  17   b  function to position the stud  70  within the stud-receiving space  24 . 
     An edge of the top section  12   b  of the inner cylindrical portion  12  adjacent to the neck portion  17  forms the locking shoulder  18  serving as a first clip-side coupling means to couple the first clip  10  to the second clip  30 . As illustrated in  FIGS. 3 and 4 , the locking shoulder  18  is formed over approximately the entire circumference of an outer periphery of the top section. When the inner cylindrical portion  12  is inserted into the outer cylindrical portion  32  of the second clip  30 , the locking section  39  of the outer cylindrical portion  32  is engaged with the locking shoulder  18 , so that the second clip  30  and the first clip  10  are coupled to each other. 
     As illustrated in  FIG. 5  which is a sectional view taken along the line V-V in  FIG. 2 , a taper portion  14  tapered downwardly from an upper surface  11   b  of the flange  11  to the neck portion  17  is formed along the central axis. The taper portion  14  is continuous with the top section  12   b  of the inner cylindrical portion  12  in a region defining a stud through-hole  15 . The stud through-hole  15  has an inner diameter slightly greater than the outer diameter of the stud  70 . That is, it regulates the stud  70  to be positioned coaxial with the first clip  10 , but it does not come into engagement with the stud thread. No hexagonal wrench hole  8  is formed in the upper surface  11   b  of the flange  11 . 
     The taper portion  14  is formed, so that a tip of the stud  70  can be viewed with the naked eye by looking down into the taper portion  14  from the upper surface  11   b  of the flange  11 . In a situation where the first clip  10  is not sufficiently engaged with the stud  70 , it is impossible to sufficiently view the tip of the stud  70 , so that it becomes possible to immediately ascertain the insufficient engagement. 
     As illustrated in  FIGS. 5, 6 and 7 , each of the protrusions  17   a ,  17   b  is formed to extend from the upper surface  11   b  of the flange  11  to the stud through-hole  15 . A tool such as a flat-blade screwdriver can be inserted into the taper portion  14  in such a manner that a distal end of the tool is engaged with the protrusions  17   b  or the protrusions  17   a , and rotationally driven to rotate the entire first clip  10  including the inner cylindrical portion  12  around the central axis of the stud  70 . The tool can be used to rotate the entire first clip  10  including the inner cylindrical portion  12  around the central axis of the stud  70  to allow the locking pawls  13  to be further strongly engaged with the stud  70 . The tool can also be used to reversely rotate the first clip  10  to release the tightened state. Further, the tool can be used to rotate the first clip  10  to allow a raised portion on the target member to be received in a groove in a lower surface of the flange  11 , as mentioned below. 
       FIG. 21  is a sectional view illustrating a state in which the target member  51  is mounted to the support member  52  with the stud  7  by using the stud locking device  1 .  FIG. 22  is an enlarged view of the area XXII in  FIG. 21 . 
     The lower surface of the flange  11  has a plurality of linear grooves  27  arranged in parallel side-by-side relation. Each of the grooves  27  is configured to receive therein a respective one of a plurality of raised portions  56  formed on an upper surface of the target member  51 . Two protrusions  29  are formed on both sides of each of the grooves  27 . The raised portions  56  of the target member are engageable, respectively, with the grooves  27  to thereby prevent the first clip  10  from rotating about the central axis of the inner cylindrical portion  12 . When the first clip  10  is pushed into and coupled to the second clip  30  and then the first clip  10  is rotated by a small angle, each of the raised portions  56  is received in any one of the grooves  27 , so that it becomes possible to keep the stud locking device  1  from being loosened during use. Although the raised portions  56  of the target member  56  are engaged with the respective grooves  27 , the first clip  10  can be rotated when an operator detaches the target member, and the first clip  10  can be detached from the stud  70  by rotating the first clip  10  about the central axis of the stud  70  to disengage the locking pawls  13  from the thread ridges of the stud  70 . 
     As illustrated in  FIG. 5 , the base section  12   a  of the inner cylindrical portion  12  is formed with a guide wall tapered upwardly. The guide wall  23  is continuous with the stud-receiving space  24 . 
     The guide wall  23  of the first clip  10  can guide the tip of the stud  70  to the stud-receiving space  24  to allow the locking pawls  13  of the first clip  10  to be engaged with the thread ridges of the stud  70 . If a taper angle Δ of the guide wall  23  is excessively large, it is necessary to largely set a distance between the base section  12   a  and the arm  16  of the first clip  10 , resulting in increase in size of the first clip  10 . If the taper angle Δ of the guide wall  23  is excessively small, the tip of the stud is less likely to enter into an inlet of the guide wall  23 . As used in this specification, the term “taper angle of the guide wall ( 23 )” means an angle Δ defined between opposed surfaces of the guide wall ( 23 ) symmetrically with respect to the central axis in  FIG. 5 . Preferably, the taper angle Δ of the guide wall  23  is set in the range of 115 to 135°. In the first embodiment, the taper angle Δ of the guide wall  23  is set to 124°. 
     With reference to  FIGS. 12 to 20 , the second clip  30  will be described.  FIG. 12 ,  FIG. 13 ,  FIG. 14 ,  FIG. 15  and  FIG. 16  are, respectively, a perspective view, a top plan view, a front view, a bottom view and a right side view of the second clip  30 . 
     The second clip  30  has the hollow outer cylindrical portion  32 , and the flange  31  formed at one end of the outer cylindrical portion  32 . The outer cylindrical portion  32  is configured to receive therein the inner cylindrical portion  12  of the first clip  10 . The flange  31  has an upper surface configured to come into contact with the other surface (lower surface) of the target member  51 . The flange  31  has an outer edge portion formed as an elastic edge portion  38  extending obliquely upwardly and outwardly. The elastic edge portion  38  is capable of elastically pressing the lower surface of the target member  51  toward the flange  11  of the first clip  10 . Preferably, the elastic edge portion  38  of the flange  31  is protrudingly formed in the edge portion of the flange  31  in such a manner as to come into press contact with the target member  51 . 
     As illustrated in  FIG. 13  and  FIG. 18  which is a sectional view taken along the line XVIII-XVIII in  FIG. 13 , the flange  31  is formed with two flange holes  41  opposed to each other symmetrically with respect to the central axis of the second clip  30  and each elongated in a circumferential direction thereof. The flange holes  41  help elastic bending of the elastic edge portion  38 . 
     The outer cylindrical portion  32  is formed as a hollow circular tube having an inner diameter greater than the outer diameter of the inner cylindrical portion  12  of the first clip  10  so as to receive therein the inner cylindrical portion  12 . 
     The outer cylindrical portion  32  has the locking section  39 . The locking section  39  functions as a second clip-side coupling means to couple the second clip  30  to the first clip  10 . The locking section  39  is separated from the outer cylindrical portion  32  by a pair of lateral slits  34  extending in an axial direction of the outer cylindrical portion  32 , as illustrated in  FIG. 16 . The locking section  39  is further separated from a main body of the outer cylindrical portion  32  by an upper slit  35 , as illustrated in  FIG. 17  which is a sectional view taken along the line XVII-XVII in  FIG. 13 , and  FIG. 20  which is an enlarged view of the area XX in  FIG. 17 . 
     This facilitates elastic bending of the locking section  39 . As illustrated in  FIG. 20 , an engagement surface of the locking section  39  with the locking shoulder is formed at a certain angle (in this embodiment, 14°) with respect to the locking shoulder so as to prevent the first clip from being easily uncoupled therefrom. 
     When the inner cylindrical portion  12  of the first clip  10  is inserted into the outer cylindrical portion  32 , and the locking section  39  reaches an outer periphery of the neck portion  17 , the locking section  39  easily comes into elastic engagement with the locking shoulder  18  which is the coupling means of the first clip  10 . In order to reliably maintain the coupling to the first clip  10 , the locking section  39  is provided in a plural number (in the illustrated embodiment, two). 
     As illustrated in  FIG. 19  which is a sectional view taken along the line XIX-XIX in  FIG. 13 , the flange  31  and the outer cylindrical portion  32  are continuous with each other in the axial direction of the second clip  30 , in a region where there is not the flange holes  41  and the upper slit  35 . 
     As illustrated in  FIGS. 14 and 15 , a plurality of (in the illustrated embodiment, four) ribs  37  are formed on an outer surface of the outer cylindrical portion  32  to extend in the axial direction so as to increase strength of the outer cylindrical portion  32 .  FIG. 19  illustrates a cross-section along the rib  37 . 
     Refer to  FIG. 21  illustrating the state in which the target member  52  is mounted to the support member  52  with the stud  70  by using the stud locking device  1 , again. The stud locking device  1  comprises the second clip  30  and the first clip  10 . In the stud locking device  1 , the second clip  30  and the first clip  10  are coupled to each other while interposing the target member  51  therebetween, i.e., clamping the target member  51  by a certain clamping force. Based on the clamping force, the flange  31  of the second clip  30  and the flange  11  of the first clip  10  can clamp the target member without wobbling in the axial direction of the stud  70 . Based on the clamping force, the raised portions  56  of the target member  51  are pressed in such a manner as to be kept from being disengaged from the respective grooves  27  in the lower surface of the flange  11  of the first clip  10 . The elastic edge portion  38  of the flange  31  prevents wobbling of the target member  51  and prevents a relative movement between the first clip  10  and the second clip  30  about the central axis. This prevents the target member  51  from being demounted from the support member  52 . In the case where the target member  51  expands or contracts according to changes in temperature, the target member  51  can move in an in-plain direction. 
     With reference to  FIG. 21 , an operation of attaching the stud locking device  1  comprising the first and second clips  10 ,  30  configured as above, to the target member  51  in a clamping manner, and then mounting the target member attached to the stud locking device  1 , to the support member  52  having the stud  70  fixed thereto will be described. 
     In the step of attaching the stud locking device  1  to the target member  51 , the inner cylindrical portion  12  of the first clip  10  is positioned so as to be insertable into the mounting hole  53  of the target member  51 , and the outer cylindrical portion  32  of the second clip  30  is positioned so as to receive therein the inner cylindrical portion  12  being inserted into the mounting hole  53 . The first clip  10  is pushed to allow the inner cylindrical portion  12  to be inserted into the mounting hole  53 . Then, the second clip  30  is pushed to allow the outer cylindrical portion  32  to receive therein the inner cylindrical portion  12  of the first clip  10 . 
     As a result of the above operations, the target member  51  is sandwiched between the flange  11  of the first clip  10  and the flange  31  of the second clip  30 . Further, when the first clip  10  and the second clip  30  are pushed to each other, the locking section  39  of the second clip  30  is locked to the locking shoulder  18  of the neck portion  17  on the inner cylindrical portion  12  of the first clip  10 . When the locking shoulder  18  of the first clip  10  and the locking section  39  of the second clip  30  are locked together, the first clip  10  and the second clip  30  are coupled to each other, and the target member  51  is clamped between the flange  11  of the first clip  10  and the flange  31  of the second clip  30 . In this state, the elastic edge portion  38  as the outer edge portion of the flange  31  of the second clip  30  comes into press contact with the target member  51  to allow the target member  51  to be clamped by a given clamping force. 
       FIG. 22  is an enlarged view of the area XXII in  FIG. 21 . When the target member  51  is clamped between the flange  11  of the first clip  10  and the flange  31  of the second clip  30 , the raised portions  56  formed on the target member  51  are received in the respective grooves  27  in the lower surface of the flange  11  of the first clip  10 . Preferably, a cross-sectional shape of each of the grooves  27  is formed in conformity to a shape of a respective one of the raised portions  56 . 
     As above, the raised portions  56  are received in the respective grooves  27 . This prevents a relative movement between the first clip  10  and the second clip  30  about the central axis to thereby keep the stud locking device  1  from being un-tightened during use. 
     The protrusions  29  are formed at opposite edges of each of the grooves  27 . When an operator detaches the target member  51 , a tool such as a flat-blade screwdriver can be inserted into the taper portion  14  of the first clip  10 , and rotationally driven to rotate the first clip  10  around the central axis of the stud  70  to thereby disengage the locking pawls  13  from the stud  70 . In the case where a plurality of the mounting holes  53  are formed in the target member  51  at respective positions, a plurality of the stud locking devices  1  each comprising the first clip  10  and the second clip  30  are attached to a respective one of the mounting holes  53 . 
     For example, in the case where the support member  52  is a panel of an automotive vehicle, the target member  51  with the stud locking devices  1  attached thereto in the above manner is carried in an automotive vehicle assembling line or the like. 
     An assembling operator locates the target member  51  with the stud locking devices  1  attached thereto, at a given position with respect to the support member  52  such as a panel of an automotive vehicle. Specifically, the target member  51  is positioned in such a manner that the plurality of studs  70  fixedly attached onto the support member  52  are received, respectively, into hollow spaces of the inner cylindrical portions  12  of the first clips  10  of the plurality of stud locking devices  1 . The stud locking devices  1  are preliminarily attached to the target member  51 , so that the operator can give his/her full attention to the operation of positioning the stud locking devices  1  attached to the target member  51 , with respect to the studs  70 , because the operator is free of an operation of carrying the stud locking devices  1 . During the positioning, the tip of each of the studs  70  can be readily guided to the stud-receiving space  24  of a respective one of the first clips  10  by using the guide wall  23  of the first clip  10 . 
     After completion of the positioning operation, the target member  51  is pressed against the support member  52  in such a manner as to allow the stud  70  to be received in the stud-receiving space  24  inside the inner cylindrical portion  12  of the first clip  10 . As a result of this operation, the stud  70  is inserted into the stud-receiving space  24 , and the locking pawls  13  formed inside the inner cylindrical portion  12  are bent outwardly to allow the stud  70  to be sufficiently received in the stud-receiving space  24 . When further pressed, the locking pawls  13  slides on the thread formed on the peripheral surface of the stud  70 . When a lower surface of the outer cylindrical portion  32  of the second clip  30  comes into contact with the support member  52 , the locking pawls  13  stops sliding and comes into engagement with thread ridges of the stud  70 , so that the target member  51  is locked to the support member  52 . 
     After the target member  51  is mounted to the support member  52 , the flat-blade screwdriver may further be inserted into the taper portion  14  of the flange  11  of the first clip  10 , and rotationally driven to rotate the first clip  10  around the central axis of the stud  70  to allow the locking pawls  13  of the first clip  10  to be further tightly engaged with the stud  70 . Alternatively, the flat-blade screwdriver may be inserted into the taper portion  14  of the first clip  10 , and rotationally driven to reversely rotate the first clip  10  to release the tightened state and demount the target member from the support member  52 . 
       FIG. 23  is a sectional view illustrating a state in which the stud locking device in  FIG. 21  is mounted to a stud having an incompletely threaded portion. A stud  70  is formed with an incompletely threaded portion  71  in a region adjacent to a base end thereof. The incompletely threaded portion  71  has a shape after slightly crushing a thread ridge. In an operation of mounting the target member  51  to the stud  70 , there is a case where the target member  51  is mounted to the stud  70  by using a nut, instead of the stud locking device. In this case, the incompletely threaded portion  71  is provided so as to prevent loosening of a nut. 
     Further, there is another incompletely threaded portion  72  in a region adjacent to a tip of the stud  70 . The incompletely threaded portion  72  occurs during formation of thread ridges of the stud  70 . 
     In use of the stud locking device  1  according to this embodiment, if each of the locking pawls  13   a ,  13   b  is engaged with the incompletely threaded portion  71  ( 72 ), a contact between the incompletely threaded portion  71  ( 72 ) and each of the locking pawls  13   a ,  13   b  becomes unstable. 
     In this embodiment, the locking pawl  13  engageable with the stud  70  is provided in two-stage manner in an up-down direction. The incompletely threaded portion  71  is located in a region adjacent to the base end of the stud  70 , and the incompletely threaded portion  72  is located in a region adjacent to the tip of the stud  70 . Heretofore, a pair of upper and lower locking pawls  13   a ,  13   b  have been largely offset in the up-down direction. Thus, a part of a plurality of pawl tips of the upper locking pawl  13   a  comes into contact with a thread ridge of the incompletely threaded portion  72 , and a part of a plurality of pawl tips of the lower locking pawl  13   b  comes into contact with a thread ridge of the incompletely threaded portion  71 . 
     If the up-down directional offset between the pair of upper and lower locking pawls  13   a ,  13   b  is reduced, the pawl tips of the upper locking pawl  13   a  become less likely to come into contact with the thread ridge of the incompletely threaded portion  72 , and the pawl tips of the lower locking pawl  13   b  become less likely to come into contact with the thread ridge of the incompletely threaded portion  71 . 
     In one example of the first clip  10  in this embodiment, a height lb from an upper surface of the support member to the upper-end pawl tip  61   b  of a lower one (right one) of the pair of lower locking pawls  13   b  is 9.6 mm (conventionally, 8.6 mm). Thus, each of the lower locking pawls  13   b  becomes less likely to come into contact with the thread ridge of the incompletely threaded portion  71  on the side of the base end. 
     On the other hand, a height la from the upper surface of the support member  52  to the upper-end pawl tip  61   a  of a higher one (left one) of the pair of upper locking pawls  13   a  is 15.1 mm (conventionally, 16.1 mm). Thus, each of the upper locking pawls  13   a  becomes less likely to come into contact with the thread ridge of the incompletely threaded portion  72  on the side of the tip. 
     A distance from the upper-end pawl tip  61   b  of the lower one of the pair of lower locking pawls  13   b  to the upper-end pawl tip  61   a  of the higher one of the pair of upper locking pawls  13   a  is 5.5 mm (conventionally, 7.5 mm), so that each of the pawl tips  61 ,  62 ,  63  becomes less likely to come into contact with the incompletely threaded portion  71  ( 72 ). 
     In the above embodiment, the target member  51  can be mounted to the support member  52  readily and reliably by clamping the target member  51  between the flange  11  of the first clip  10  and the flange  31  of the second clip  30 , and inserting the stud  70  into the stud-receiving space  24  inside the inner cylindrical portion  12  of the first clip  10  to allow the locking pawls  13  to be engaged with the thread ridges of the stud  70 . 
     In addition, a head of the stud  70  can be viewed through the taper portion  14 , so that it becomes possible to readily ascertain whether the first clip  10  is perfectly mounted to the stud  10 . 
     It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.