Patent Publication Number: US-9421676-B2

Title: Extraction tool for tangless spiral coil insert

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Section 371 of International Application No. PCT/JP2013/064552, filed May 20, 2013, which was published in the Japanese language on Dec. 5, 2013, under International Publication No. WO 2013/180039 A1, and the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to an extraction tool for a tangless spiral coil insert for extracting a tangless spiral coil insert which has been attached to a work from the work. 
     BACKGROUND ART 
     When a weak female screw makes it impossible to obtain a high tightening force while directly tapping into a work comprising a light metal such as aluminum, plastics, or cast iron, it is conventional practice to use a spiral coil insert for the purpose of guaranteeing a high reliable screw tightening. 
     There are a tanged spiral coil insert and a tangless spiral coil insert, but the tanged spiral coil insert requires an operation of removing a tang, after being attached to a work, and further an operation of collecting the tang removed. Therefore, the tangless spiral insert, which does not require such operations, is occasionally used. 
     A patent literature 1 discloses an attachment tool for such a tangless spiral coil insert. 
     This will be described below with reference to  FIGS. 7 to 9  appended to the present patent application. 
     An attachment tool  300  is provided with a tubular member  301 , and a mandrel assembly  302  supported by the tubular member  301 . A pivotal claw  303  is disposed in a hollow  304  formed in a longitudinal direction of the mandrel assembly  302 , and the pivotal claw  303  is provided with a hook section  305  engaging with a notch  101  ( FIG. 9 ) of an end coil section  100   a  of a tangless spiral coil insert  100  at one leading end thereof. 
     In this example, the pivotal claw  303  is biased about a pivotal shaft  307  by a spring  306 , and, the pivotal claw  303  is configured to pivot on the pivotal shaft  307  so that the hook section  305  sinks into the notch  101  of the end coil section  100   a  on a coil-insertion direction outlet side of the coil insert  100  when the mandrel assembly  302  moves in a direction of an arrow  308  and the other end  309  of the pivotal claw  303  has entered a hole formed in the mandrel assembly  302 . 
     The attachment tool  300  for a tangless spiral coil insert described in the patent literature 1 was excellent in operability, but in particular the mandrel assembly  302  provided with the pivotal claw  303  was complex in structure, and was difficult to manufacture or assemble, and accordingly resulted in a factor in high product cost. 
     Therefore, the present inventor proposed an insertion tool described in a patent literature 2. 
     That is, as shown in  FIGS. 6( a ) and 6( b )  appended to the present patent application, the insertion tool described in the patent literature 2 is provided, for inserting a tangless spiral coil insert  100  (see  FIGS. 7 and 9 ) to a work, with a mandrel  41  a leading end section of which is constituted as a screw shaft  45 , and a pivotal claw  80  which is a slender member and is provided with an actuation section  82  provided at one end thereof with a claw section  81  engaging with a notch  101  of an outlet-side end coil section  100   a  of the tangless spiral coil insert  100  screwed to the screw shaft  45  and a support section  83  formed integrally with the activation section  82 . The pivotal claw  80  is attached to a pivotal-claw attachment groove  71 , the support section  83  is pivotally attached to the mandrel  41  by a pivotal shaft  84 , and biasing means  88  ( 88   a ,  88   b ) acts on the support section  83  to bias the claw section  81  outward in a radial direction of the screw shaft  45  such that a hook section  90  formed in the claw section  81  elastically engages with the notch  101  of the tangless spiral coil insert  100 . 
     An insertion tool for a tangless spiral coil insert having thus configured is simple in structure and easy in manufacture and assemble as compared with a conventional tool, and, accordingly it can be reduced in manufacturing cost, and besides, is excellent in operability. 
     PRIOR ART DOCUMENT 
     Patent Literature 
     Patent Literature 1: Publication of Japanese Patent No. 3849720 
     Patent Literature 2: Japanese Patent Application No. 2010-269710 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The present inventor has focused on the characterized configuration of the insertion tool for a tangless spiral coil insert described in the patent literature 2 and, as a result of studying whether or not the configuration of such an insertion tool can be applied to an extraction tool for a tangless spiral coil insert, has found that realization can be achieved considerably favorably. 
     That is, an object of the present invention is to provide an extraction tool for a tangless spiral coil insert that is simple in structure and is also easy in manufacture and assemble as compared with a conventional tool, accordingly that can be reduced in manufacturing cost and besides, is excellent in operability. 
     Means for Solving the Problems 
     The above object is achieved by an extraction tool for a tangless spiral coil insert according to the present invention. In summary, the present invention is an extraction tool for a tangless spiral coil insert comprising, for extracting the tangless spiral coil insert which has been attached to a work from the work, 
     a mandrel a leading end section of which is constituted as a screw shaft, and 
     a pivotal claw provided with an actuation section which is a slender member and is provided at one end thereof with a claw section engaging with a notch of an end coil section of the tangless spiral coil insert positioned on a surface side of the work and a support section integrally formed with the actuation section, wherein 
     the mandrel has a small-diameter shaft section formed with the screw shaft and a slender-cylindrical tubular shaft section which is formed to continuously connect to the small-diameter shaft section and an outer diameter of which is larger than an outer diameter of the small-diameter shaft section; 
     a pivotal-claw attachment groove is formed in the small-diameter shaft section and the tubular shaft section from an end face of the small-diameter shaft section in an axial direction of the mandrel over a predetermined length in order to install the pivotal claw; 
     the pivotal claw is attached to the pivotal-claw attachment groove and the support section is pivotally attached to the mandrel by a pivotal shaft; 
     the tubular shaft section is provided with biasing means acting on the support section of the pivotal claw; and 
     the biasing means acts on the support section to bias the claw section outward in a radial direction of the screw shaft such that a hook section formed on the claw section elastically engages with the notch of the end coil section of the tangless spiral coil insert positioned on a surface side of the work. 
     According to an aspect of the present invention, the biasing means is provided with a compression coil spring housed inside the tubular shaft section and a spring reception member caused to abut on an end face of the support section of the pivotal claw by the compression coil spring. 
     According to another aspect of the present invention, the pivotal claw is constituted as a slender plate member, the claw section is formed in a plate-thickness end-face region of a predetermined distance from a leading end of the plate member, a rear end face of the support section abutting on the spring reception member of the biasing means is inclined in a widthwise direction, and the spring reception member engages with the inclined rear end face to bias the claw section outward in a radial direction of the screw shaft. 
     According to another aspect of the present invention, a guide section further projecting beyond the pivotal claw outward in the axial direction of the screw shaft to be capable of being screwed or inserted into the coil insert is integrally formed in a leading end section of the screw shaft. 
     Effects of the Invention 
     According to the present invention, the extraction tool for a tangless spiral coil insert is simple in structure and is also easy in manufacture and assemble as compared with a conventional tool. Accordingly, the extraction tool for a tangless spiral coil of the present invention can be reduced in manufacturing cost, and besides, is excellent in operability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1( a )  is a central longitudinal sectional view of a mandrel to which a pivotal claw is attached in an embodiment of an extraction tool for a tangless spiral coil insert according to the present invention,  FIG. 1( b )  is a plane view of the mandrel to which the pivotal claw is attached, and  FIG. 1( c )  is a front view of the pivotal claw; 
         FIG. 2  is a partial plane view showing another embodiment of the screw shaft; 
         FIG. 3( a )  is a perspective view of a claw section of the pivotal claw,  FIG. 3( b )  is a front view for explaining a state of engagement between a hook section of the claw section and a notch of an inlet-side end coil section of a spiral coil insert,  FIG. 3( c )  is a front view for explaining a state of engagement between an inclined section of the claw section and the notch of the inlet-side end coil section of the spiral coil insert, and  FIG. 3( d )  is a perspective view of the spiral coil insert; 
         FIG. 4-1  is a perspective view of an embodiment of the extraction tool for a tangless spiral coil insert according to the present invention; 
         FIGS. 4-2 ( a ) and  4 - 2 ( b ) are perspective views for explaining one example of use of the extraction tool for a tangless spiral coil insert according to the present invention; 
         FIGS. 5( a ), 5( b ), 5( c ) and 5( d )  are sectional views for explaining motion and operation of the extraction tool for a tangless spiral coil insert according to the present invention shown in  FIG. 4 ; 
         FIG. 6  shows an insertion tool for a tangless spiral coil insert developed by the present inventor and described in patent literature 2,  FIG. 6( a )  is a central longitudinal sectional view of a mandrel to which a pivotal claw has been attached in the insertion tool for a tangless spiral coil insert, and  FIG. 6( b )  is a front view of the mandrel to which the pivotal claw has been attached; 
         FIG. 7  is a perspective view showing one example of a conventional insertion tool for a tangless spiral coil insert; 
         FIG. 8  is a sectional view of the conventional insertion tool for a tangless spiral coil insert shown in  FIG. 7 ; and 
         FIG. 9  is a front view for explaining a state of engagement between a hook section of a claw section of an insertion tool for a tangless spiral coil insert and a notch of an end coil section of a spiral coil insert. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     An extraction tool for a tangless spiral coil insert according to the present invention will be described below in further detail with reference to the drawings. 
     Embodiment 1 
     (Overall Tool Configuration) 
       FIG. 4-1  illustrates an overall configuration of an embodiment of an extraction tool  1  for a tangless spiral coil insert in accordance with the present invention. According to the present embodiment, the extraction tool  1  for a tangless spiral coil insert is of a manual type, and has a mandrel assembly  40 . 
     The mandrel assembly  40  is provided with a mandrel  41 . A mandrel drive handle  50  is provided on the mandrel  41 , so that the mandrel  41  is configured to be rotationally driven manually. A screw shaft  45  configuring a leading end section of the mandrel  41  is rotated by rotating the mandrel  41  by the drive handle  50 . At this time, in order to facilitate rotational operation of the mandrel  41  with the mandrel drive handle  50 , as shown in  FIG. 4-2 ( b ), a grip pipe  51  which an operator can grasp can be rotatably attached to the mandrel  41 . The grip pipe  51  can be attached to the mandrel  41 , for example, by forming annular groove  52  in the mandrel  41  in advance and attaching a retaining ring  53  to the groove  41  as necessary. 
     The extraction tool  1  for a tangless spiral coil insert of the present invention is one for extracting a tangless spiral coil insert  100  which has been already attached to a work  200 , as shown in  FIGS. 5( a ) to 5( d ) , and accordingly, by causing the leading-end screw shaft  45  of the extraction tool  1  for a tangless spiral coil insert to adapt to an inlet-side coil section (namely, a coil section on a surface side of the work which the extraction tool  1  approaches)  100   b  of the coil insert  100  which has been attached to the work  200  and rotating the mandrel drive handle  50 , the screw shaft  45  of the mandrel  41  is screwed from the inlet-side coil section  100   b  of the coil insert  100  toward an other-side coil section  100   a  opposite to the inlet-side coil section  100   b , namely, into the coil insert ( FIGS. 5( a ) and 5( b ) ). Next, when the mandrel drive handle  50  is reversed, the screw shaft  45  rotates reversely to the last rotation to be returned from the inside of the coil insert in a direction of the inlet-side coil section  100   b  for disengagement from the coil insert  100 , so that the claw section  81  engages with the notch section  101  of the coil section  100   b  and the coil insert  100  is extracted from the work  200 . This will be described later in detail. 
     (Mandrel Assembly) 
     Next, the mandrel assembly  40  that configures a characterized section of this invention will be described with reference to  FIGS. 1( a ) to 1( c ) ,  FIG. 2 ,  FIGS. 3( a ) to 3( d ) , and  FIG. 4 . 
     As described above with reference to  FIG. 4 , the mandrel assembly  40  is provided with the mandrel  41 , and according to this embodiment, a leading end section of the mandrel  41  is constituted as the screw shaft  45 . 
     In further explanation, the mandrel  41  has a small-diameter shaft section  42  formed with the screw shaft  45  and a tubular shaft section  43  formed so as to continuously connect to the small-diameter shaft section  42  and larger in outer diameter than the small-diameter shaft section  42 , and having a predetermined inner diameter in  FIG. 4 . Further, the tubular shaft section  43  is integrally connected to a drive shaft section  44  attached with the mandrel drive handle  50 . For example, an inner-diameter joint section  44   a  of the drive shaft section  44  is inserted into an inner-diameter section of the tubular shaft section  43  to be fixed by a pin  44   b.    
       FIGS. 1( a ) and 1( b )  illustrate a state where the mandrel assembly  40  has been disposed horizontally,  FIG. 1( a )  is a central longitudinal sectional view and  FIG. 1( b )  is a plane view.  FIG. 1( c )  is a front view of a pivotal claw  80 . 
     The small-diameter shaft section  42  of the mandrel  41  is constituted as the screw shaft  45  where a male screw  70  which can be screwed to an inner-diameter screw section (female screw) of the tangless spiral coil insert  100  over a predetermined length L from a left end in  FIGS. 1( a ) and 1( b )  has been formed. 
     According to this embodiment, the pivotal claw  80  is attached to the small-diameter shaft section  42  and the tubular shaft section  43  of the mandrel  41  along an axial direction of the mandrel  41 . A leading end face  81   a  of the pivotal claw  80  is disposed so as to be retreated from a leading end face  42   a  of the screw shaft  45  inward by a predetermined distance L 45   a  (a length of about one to five thread ridges). A region  45   a  of the length L 45  a of the screw shaft  45  functions as a guide section when the screw shaft  45  is inserted into the coil insert  100 , as described later in detail. 
     In this embodiment, as shown in  FIGS. 1( a ) and 1( b ) , one pivotal-claw attachment groove  71  is formed from the left end face  42   a  of the mandrel  41  in the axial direction by a length L 71  over an entire region (namely, L 71   a  (=L 42 )) of the small-diameter shaft section  42  a length of which is set to the length L 42  and a region of the length L 71   b  of the tubular shaft section  43 . In the small-diameter shaft section  42 , the pivotal-claw attachment groove  71  is formed to have a depth H toward a center direction of the small-diameter shaft section  42  and a width W, and in the tubular shaft section  43 , the pivotal-claw attachment groove  71  is formed so as to extend through a thickness section of the tubular shaft section  43 . The left end section on the figure of the pivotal-claw attachment groove  71  of the small-diameter shaft section  42  is opened in the end face  42   a  of the screw shaft  45 . 
     As specific dimensions for reference, in this embodiment, setting has been made such that a length L 42  of the small-diameter shaft section  42 =20 mm, an outer diameter D of the screw shaft  45 =5 mm, and a length L of the screw shaft  45 =7 mm (L 45   a= 1 mm) in the mandrel  41 . Setting has been made such that the tubular shaft section  43  has a length L 43 =40 mm, an inner diameter d 43 =7 mm, and an outer diameter D 43 =8 mm, and setting has been made such that a length L 44  of the drive shaft section  44 =53 mm (L 44   a= 14 mm), and an outer diameter D 44 =8 mm (D 44   a= 7 mm). Setting has been made such that the pivotal-claw attachment groove  71  has a length L 71   a  (=L 42 )=20 mm, L 71   b= 24 mm, and a depth H=4.5 mm. 
     The pivotal claw  80  is a slender member, in particular in this embodiment, a plate member made of a metal having a thickness (t)=1.3 mm, for example, made of a steel, and it is movably attached in the pivotal-claw attachment groove  71  set to have a width (W) slightly larger than the plate thickness (t)=1.3 mm, for example, W=1.4 to 1.5 mm. Further, the pivotal claw  80  is swingably attached to the tubular shaft section  43  by a pivotal shaft  84  via a pivotal-shaft reception hole  84   a  at a central section in the longitudinal direction. 
     In further explanation, the pivotal claw  80  is composed of an activation section  82  positioned in the small-diameter shaft section  42  on a left side of the pivotal shaft  84  and a support section  83  positioned in the tubular shaft section  43  on a right side of the pivotal shaft  84 . 
     A width W 2  of the actuation section  82  is set narrower than a width W 3  of the support section  83 . The width W 3  of the support section  83  is set to a narrowest width W 3  min in a continuous connection section thereof with the actuation section  82  and it is set to a largest width W 3  max in a rear end region of the support section  83 . The width W 3  max of the support section  83  is made slightly smaller than the inner diameter d 43  of the tubular shaft section  43  such that the actuation section  82  can be pivoted about the pivotal shaft  84 . A gap g 1  is provided between an upper face  83   a  of the support section  83  and an inner wall of the tubular shaft section  43 . Further, an lower face  83   b  of the support section  83  is also set to have a shape inclined upward from a rear end position toward the pivotal shaft  84 , and a gap g 2  gradually increasing is formed between a lower face  83   b  of the support section  83  and the inner wall of the tubular shaft section  43 . 
     As specific dimensions for reference, in this embodiment, setting has been made such that an entire length L 80  of the pivotal claw  80 =46 mm, setting has been made such that a length L 82  of the actuation section  82  from a leading end (a left end in  FIG. 1 ) of the pivotal claw  80  to the pivotal-shaft reception hole  84   a= 23 mm, and a width W 2 =1.53 mm, and setting has been made such that a length L 83  of the support section  83  from the pivotal-claw reception hole  84   a  to a rear end (a left end in  FIG. 1 )=23 mm, and the maximum width W 3  max=4.5 mm, the minimum width W 3  min=3.5 mm. Further, the actuation section  82  is inclined at an angle θ1=4° to the support section  83  from a position of the distance L 80   a= 30 mm from the leading end  81   a.    
     Further, setting has been made such that a length L 82   a  of the actuation section  82 =18.5 mm and a length L 83   a  of the support section  83 =26 mm. In the above configuration, as shown in  FIG. 1( c ) , a level-difference section  85  is formed in a connection section between the actuation section  82  and the support section  83 , and in this embodiment, setting is made such that an angle θ2 forming this level-difference section  85 =120°. Accordingly, a length L 85  of the level-difference section  85  is set to about 1.5 mm. 
     In a region of the leading end  81   a  of the actuation section  82  of the pivotal claw  80 , on the left side in  FIG. 1 , as described above, a claw section  81  is informed. The claw section  81  engages with the notch  101  of the end coil section  100   a  on the inlet side of the tangless spiral coil insert when the screw shaft  45  is disengaged from the coil insert by reversing the mandrel  50  after the screw shaft  45  has been inserted into the coil insert attached to the work by temporarily rotating the mandrel drive handle  50 . That is, the claw section  81  is formed in a plate-thickness end face region of the predetermined length L 81  from the leading end  81   a  of the actuation section  82  constituted as a plate member. The details of the claw section  81  will be described later. 
     Incidentally, the leading end face  81   a  of the claw section  81  is located at a position retreated by a predetermined distance L 45  a from the leading end face (a left face in  FIG. 1 )  42   a  of the screw shaft  45 . The region  45   a  of the length L 45  a of the screw shaft  45  functions as a guide section for first screwing the leading end screw shaft  45  into about one to five thread ridges (ordinarily the number of thread ridges is about one to two) of the female screw in the inlet section region of the coil insert  100  when performing a work for extracting the coil insert  100  installed in the work by the coil insert extraction tool  1 . Therefore, in order to enhance the function as the guide section, in this embodiment, regarding the shape dimensions of the above mandrel  41 , the length L 42  of the small-diameter shaft section  42  can be increased from 20 mm to 26 mm and the length L can be increased from 7 mm to about 13 mm (L 45  a is increased from 1 mm to 6 mm). 
     Incidentally, alternatively, as shown in  FIG. 2 , a shaft-shaped guide section projecting outward in an axial direction of the screw shaft  45  to fit the inner-diameter section of the coil insert  100  installed in the work, which is obtained by removing the thread ridges in the leading end region L 70   a  of the screw shaft  45 , can be adopted. 
     Thus, by providing the region  45   a  functioning as the guide section having the predetermined length in the leading end section of the screw section  45 , a predetermined extraction workability can be improved. 
     On one hand, a rear end face (the right end face in  FIG. 1 ) of the support section  83  of the pivotal claw  80  is constituted as an inclined face  87  inclined by an angle α in a widthwise direction to a vertical line extending at a right angle of an inner wall face of the tubular shaft section  43  in  FIG. 1( a ) . In this embodiment, the angle α has been set to 5°. However, the angle α is not limited to only this value. 
     As shown in  FIG. 1( c ) , a pressing force (A) from the biasing means  88  is imparted to this inclined face  87  and the inclined end face  87  of the support section  83  is pressed downward (B), so that the claw section  81  of the pivotal claw  80  can be pivoted upward (C) to engage with the notch  101  of the tangless spiral coil insert  100 . Further, when the claw section  81  is pushed downward, the inclined face  87  is made movable upward. 
     In this embodiment, the biasing means  88  is provided with a compression coil spring  88   a  housed inside the tubular shaft section  43  and a spring reception member  88   b  caused to abut on the inclined end face  87  of the support section  83  of the pivotal claw  80  by the compression coil spring  88   a . The spring reception member  88   b  is constituted as a step-like short shaft member and is formed of a large-diameter section  88   b   1  abutting on the compression coil spring  88   a  and a small-diameter section  88   b   2  abutting on the inclined end face  87 . As described above, the spring reception member  88   b  is pressed (A) to the inclined end face  87  of the pivotal claw  80  by the compression coil spring  88   a , thereby pressing the inclined end face  87  of the pivotal claw  80  downward (B) in  FIG. 1( c ) . Accordingly, as described above, the claw section  81  of the pivotal claw  80  is biased outward in the radial direction (C) of the screw shaft  45 . Thereby, as described later in detail, the hook section  90  formed on the claw section  81  elastically engages with the notch  101  of the tangless spiral coil insert  100 . 
     Of course, the biasing means  88  is not limited to only the above configuration, but for example, a ball caused to abut on the inclined end face  87  of the support section  83  of the pivotal claw  80  by the compression coil spring  88   a  can be adopted instead of the spring reception member  88   b , as shown in  FIG. 6( a ) . 
     Next, the claw section  81  of the pivotal claw  80  will be described. 
     As described above, the extraction tool  1  for a tangless spiral coil insert of the present invention is one for extracting the tangless spiral coil insert  100  which has been already attached to the work  200 , and accordingly, as shown in  FIGS. 5( a ) to 5( d ) , the screw shaft  45  of the mandrel  41  is screwed from the inlet side of the coil insert  100  into the other end opposite thereto, namely, into the coil insert by causing the leading end screw shaft  45  of the extraction tool  1  for a tangless spiral coil insert to adapt to the inlet side of the coil insert  100  attached to the work  200  and performing rotation with the mandrel drive handle  50 . Next, when the mandrel  50  is reversed, the screw shaft  45  is rotated reversely to the last rotation to be returned from inside of the coil insert to the inlet side. 
     Accordingly, as described above, the claw section  81  is formed at the leading end section of the actuation section  82  of the pivotal claw  80  of the extraction tool  1  of the present invention on the left side in  FIG. 1 . The claw section  81  engages with the notch  101  of the end coil section  100   b  on the inlet side of the tangless spiral coil insert  100  when the screw shaft  45  is disengaged from the coil insert  100  by rotating the mandrel  50  reversely after the screw shaft  45  is screwed into inside of the coil insert which has been attached to the work  200  by rotating the mandrel drive handle  50 . That is, the claw section  81  is formed in a plate thickness end face region of the predetermined distance L 81  from the leading end  81   a  of the actuation section  82  constituted as a plate member. Next, details of the claw section  81  will be described. 
     A hook section  90  is formed in the claw section  81  of the pivotal claw  80 . This hook section  90  engages with the notch  101  of the end coil section  100   b  on the inlet side of the coil insert  100 , namely, on the side of insertion of the tool for the coil insert  100  which has been attached to the work  200  at an extraction time of the tangless spiral coil insert  100 , as is understood also with reference to  FIGS. 3( a ) to 3( d ) . 
     The claw section  81  is constituted as an approximately-rectangular plate member having predetermined shape dimensions, namely, the length L 81  and the thickness T 1 , the width W 1  (namely the plate thickness (t) of the pivotal claw  80 ), and movable smoothly in a radial direction of the screw shaft  45  within the pivotal-claw attachment groove section  71 . 
     An upper face of the claw section  81  is set so as to be approximately equal to an outer diameter of the screw shaft  45  or project slightly in the radial direction. The claw section  81  can be pushed into the attachment groove  71  against the biasing means  88  to the support section  83 , namely, a biasing force of the compression coil spring  88   a  by pushing the upper face thereof in a center direction of the screw shaft  45 . 
     Further, with reference to  FIG. 3( a ) , the claw section  81  will be described.  FIG. 3( a )  illustrates one example of the claw section  81  used in this embodiment. Further, one example of the tangless spiral coil insert  100  is illustrated in  FIG. 3( d ) . 
     In this embodiment, the hook section  90  is formed on one face of the claw section  81 , namely, on a face on a near side thereof in  FIG. 3( a ) . The hook section  90  elastically engages with the notch  101  of the end coil section  100   b  on the inlet side of the oil insert  100  at a reverse rotation time after the hook section  90  has rotated together with the screw shaft  45  to be screwed into the tangless spiral coil insert  100 , as shown in  FIG. 3( b ) . The hook section  90  can be formed in a shape engaging with the notch  101  of the end coil section  100   b  (see  FIG. 3( d ) ) of the coil insert  100 . A depth E of a recess of the hook section  90  is set such that the notch  101  of the coil insert  100  is maintained in the recess  90  to continue to contact with a concave face of the recess during extraction work, as shown in  FIGS. 3( a ) and 3( b ) . 
     Incidentally, in this embodiment, an inclined section  91  is formed on the opposite side (a rear face) to the hook section  90 . The inclined section  91  constitutes a guide function for the end coil section  100   b  ( FIG. 3( d ) ) of the coil insert  100  to push the claw section  81  slightly projecting for an outer periphery of the screw shaft inward against a biasing force imparted by the biasing means  88  to screw the claw section  81  into the screw shaft  45  smoothly when screwing the screw shaft  45  into the coil insert  100  which has been attached to the work, as shown in  FIG. 3( c ) . 
     As specific dimensions of the claw section  81  for reference, in this embodiment, setting has been made such that a length L 81 =1.6 mm, a height T=2.5 mm, and a width W 1  (=t)=1.3 mm in  FIG. 3( a ) . A recess amount E of the hook section  90  is set to about 0.1 to 0.3 mm. 
     The shape of the claw section  81  is not limited to one having the structure shown in the above embodiment explained with reference to  FIG. 3( a ) , but other various modifications may be anticipated by persons skilled in the art. 
     (Motion Aspect and Operation Method of the Tool) 
     Next, particularly, with reference to  FIGS. 5( a ), 5( b ), 5( c ) and 5( d ) , a motion aspect and an operational method of the extraction tool  1  for a spiral coil insert of the present invention thus configured will be described. 
     First, as shown in  FIG. 5( a ) , the leading end section of the screw shaft  45  of the extraction tool  1  for a spiral coil insert is caused to face the end coil section  100   b  on the inlet side (namely, a surface side of the work  200 ) of the coil insert  100  which has been attached to the work  200 . 
     Next, the leading end section of the screw shaft  45  is caused to adapt to the inlet-side end coil section  100   b  of the coil insert  100  and the mandrel drive handle  50  is rotated in a predetermined direction (here, in a clockwise direction as viewed from the tool side to the coil insert side) indicated by an arrow, as shown in  FIG. 5( b ) . Thereby, as shown in  FIG. 5( b ) , first, the leading end guide section  45   a  (for example, about one to two thread ridges) of the screw shaft  45  is screwed into the inner circumferential screw section of the coil insert  100 . By further rotating the mandrel drive handle  50 , the screw shaft  45  is screwed in the direction of an other-end coil section  100   a  of the coil insert  100 , namely, into the inside of the coil insert  100 , and the hook section  90  of the claw section  81  which has been installed in the screw shaft  45  reaches the notch  101  of the inlet-side end coil section  100   b  of the spiral coil insert  100 . 
     Of course, in the case that the thread ridges are not formed on the leading-end guide section  45   a  of the screw shaft, as shown in  FIG. 2 , the leading-end guide section  45   a  of the screw shaft  45  is caused to adapt to the inlet-side end coil section  100   b  of the coil insert  100  and it is inserted into the inside of the coil insert  100 , as shown in  FIG. 5( b ) . Next, the mandrel drive handle  50  is rotated in the predetermined direction (clockwise direction) indicated by the arrow. Thereby, the leading end thread ridges of the screw shaft  45  start to screw to the inner circumferential screw section of the coil insert  100 . By further rotating the mandrel drive handle  50 , the screw shaft  45  is screwed in the direction of the other-end coil section  100   a  of the coil insert  100 , namely, into inside of the coil insert  100 , and the hook section  90  of the claw section  81  which has been installed in the screw shaft  45  reaches the notch  101  of the leading-end coil section  100   b  of the spiral coil insert  100 . 
     Even in each case described above, by further rotating the mandrel drive handle  50  in the predetermined direction (clockwise direction), as shown in  FIG. 3( c ) , the inclined section  91  formed on the opposite side (rear face) of the hook section  90  abuts on the end coil section  100   b  of the coil insert  100 , thereby pushing the claw section  81  slightly projecting from the outer periphery of the screw shaft inward against a biasing force imparted by the biasing means  88 , which results in smooth screwing of the claw section  81  into the screw shaft  45 . 
     At a time point at which approximately an entirety of the hook-section screw shaft  45  has been screwed into the coil insert  100 , namely, the claw section  81  is introduced into the coil insert  100 , the screw shaft  45  is located at a position of at least two, three or more female screw thread ridges of the coil insert  100 . 
     In this state, as shown in  FIG. 5( c ) , when the mandrel drive handle  50  is rotated in the reverse direction (counterclockwise direction) indicated by an arrow, the screw shaft  45  is moved in a disengagement direction from the coil insert  100 , namely, in the direction of the inlet-side end coil section  100   b  of the coil insert  100 . Then, the hook section  90  of the claw section  81  which has been installed in the screw shaft  45  reaches the notch  101  of the leading-end coil section  100   b  of the spiral coil insert  100 . The claw section  81  engages with the notch  101  of the end coil section on the inlet side of the tangless spiral coil insert  100 , as shown in  FIG. 3( b ) . Accordingly, by performing rotation of the mandrel drive handle  50  continuously, the tangless spiral coil insert  100  is reversely rotated by the hook section  90  of the claw section  81 , so that the spiral coil insert  100  is removed from the work  200 , as shown in  FIG. 5( d ) . 
     According to this embodiment, the spiral coil insert  100  can be extracted from the work  200  with good workability. 
     In the above embodiment, the present invention has been described as the manual extraction tool for a tangless spiral coil insert, but the present invention can be applied similarly to an electric extraction tool for a tangless spiral coil insert to obtain similar operation and effect. An entire configuration of the electric extraction tool for a spiral coil insert, except for the characterized sections of this invention, is well-known to persons skilled in the art. Accordingly, further detailed description is omitted. 
     DESCRIPTION OF REFERENCE NUMERALS 
       1  Extraction tool for a spiral coil insert 
       40  Mandrel assembly 
       41  Mandrel 
       42  Small-diameter shaft section 
       43  Tubular shaft section 
       44  Drive shaft section 
       45  Mandrel screw shaft 
       45   a  Guide section 
       70  Male screw 
       71  Pivotal-claw attachment groove 
       80  Pivotal claw 
       81  Claw section 
       82  Actuation section 
       83  Support section 
       84  Pivotal shaft 
       85  level-difference section 
       86  Notched recess 
       87  Inclined end face 
       88  Biasing means 
       88   a  Compression coil spring 
       88   b  Spring reception member 
       90  Hook section