Abstract:
A steel ball 11 is housed in a hole 10 which extends from an inner wall toward an outer wall of a nose piece 3 and obliquely rearward with respect to a rivet inserting port 6 as shown by an arrow A. An elastic ring 12 elastically pushes the ball 11 from the outer wall toward the inner wall so that a part of the ball 11 may project into the port 6 whereby the mandrel 5 is grasped. As the hole 10 extends obliquely rearward with respect to the port 6, the ball 11 can move easily when the mandrel 5 travels in the inserting direction but the ball 11 is difficult to move when the mandrel 5 travels in the direction opposite to the inserting direction. As a result, the ball 11 blocks the mandrel 5 from travelling.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority, under 35 U.S.C. §119(a)-(d), to JP Patent Application No. 2011-63624 filed Mar. 23, 2011, the contents of which are incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a blind rivet fastening device and, more specifically, to a nose piece at the front end of a blind rivet fastening device. 
       BACKGROUND OF THE INVENTION 
       [0003]    A blind rivet fastening device includes a hollow nose housing for accepting a blind rivet, a nose piece provided on the front end of the nose housing and having a rivet insertion port for inserting the mandrel of a blind rivet, a jaw case provided adjacent to the rear of the nose piece so as to be able to move forward and rearward inside the nose housing and having an inner circumferential surface formed so the inner diameter becomes smaller towards the front end, a jaw provided inside the jaw case so as to hold the mandrel of a blind rivet inserted into the port and having an outer circumferential surface slidably contacting the inner circumferential surface of the jaw case, and a jaw pusher provided adjacent to the rear of the jaw and inside the nose housing for applying pressure to the jaw in the forward direction. In this blind rivet fastening device, the rearward movement of the jaw case with respect to the port and the narrowing of inner diameter of the jaw grasping the mandrel of the blind rivet in the jaw, and the rearward movement of the jaw case and the jaw grasping the mandrel ruptures the mandrel of the blind rivet and fastens a component-to-be-fastened with the rivet body of the blind rivet. 
         [0004]    When a component-to-be-fastened is fastened with a blind rivet using a blind rivet fastening device, the mandrel of the blind rivet is inserted into an insertion port in the nose piece of the fastening device so that the rivet body pushes out from the nose piece. The fastening device is positioned so as to insert the rivet body into a mounting hole in the component-to-be-fastened, and the fastening device is operated to forcibly pull out the mandrel until it ruptures. The expanded and deformed sleeve of the rivet body fastens the blind rivet to the component-to-be-fastened. The ruptured mandrel is discharged to the rear of the blind rivet fastening device and is collected in a collector. The jaw case then returns to its starting position to load the next blind rivet. At this time, the ruptured mandrel is held by the jaw and a portion of the mandrel sometimes sticks out from the nose piece. In a pneumatic/hydraulic fastening device, the ruptured mandrel is suctioned and discharged to the rear using pneumatic pressure. Also, a holding means is proved to keep an inserted rivet from falling out. In a pneumatic-hydraulic fastening device, the rivet holding means ordinarily uses suction from pneumatic pressure. However, this is not economical because pneumatic pressure is needed between holding operations. In an electric fastening device, it is difficult to generation suction force, so another method has to be used to perform the holding operation. 
         [0005]    One prior art means of holding a rivet is to attach an elastic ring able to elastically hold a blind rivet slidably along its center line in the blind rivet insertion port of the nose piece (Published Unexamined Patent Application No. 6-262290). 
         [0006]    Another means of holding a rivet is to provide an engaging means for coming into contact with the mandrel of the inserted rivet and engaging the mandrel of the rivet. This engaging means is composed of an insertion hole provided to as to reach the insertion port from the outer circumferential surface of the nose piece, a bolt inserted into the insertion hole, and an elastic ring for pressing against the head of the bolt (Published Unexamined Patent Application No. 2008-168324). 
         [0007]    Another means of holding a rivet is to suction and hold a rivet using pneumatic pressure (Published Examined Utility Model Application No. 55-38603). 
         [0008]    In the rivet holding means of Patent Document 1 and Patent Document 2, the elastic ring applies elastic force perpendicularly to the center line of the blind rivet from the outer circumferential surface of the nose piece to the insertion port. Here, the elastic force applied to the blind rivet to move it in the insertion direction is the same as the elastic force applied to the blind rivet to move it in the direction opposite that of the insertion direction. Therefore, it can hold the rivet during insertion but cannot keep the mandrel from sticking out after fastening. When the elastic force is increased to keep the mandrel from sticking out, it becomes difficult to insert a rivet. Also, the rivet holding means in Patent Document 3 is uneconomical because it uses pneumatic pressure to suction and hold a rivet. 
         [0009]    The object of the prior art documents is simply to hold a rivet. It is not to keep it from sticking out. When a simple rivet holding function is provided, complications occur because the mandrel sticks out after fastening. When held with the mandrel sticking out, it is difficult to load the next rivet. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    Therefore, an object of the present invention is to provide a blind rivet fastening device which makes it easy to insert a blind rivet in a nose piece, keep the inserted blind rivet from falling out before fastening, and prevent the ruptured mandrel from sticking out of the nose piece after fastening. 
         [0011]    In order to achieve this object, the present invention is a blind rivet fastening device comprising a hollow nose housing for accepting a blind rivet, a nose piece provided on the front end of the nose housing and having a rivet insertion port for inserting the mandrel of a blind rivet, a jaw case provided adjacent to the rear of the nose piece so as to be able to move forward and rearward inside the nose housing and having an inner circumferential surface formed so the inner diameter becomes smaller towards the front end, a jaw provided inside the jaw case so as to hold the mandrel of a blind rivet inserted into the port and having an outer circumferential surface slidably contacting the inner circumferential surface of the jaw case, and a jaw pusher provided adjacent to the rear of the jaw and inside the nose housing for applying pressure to the jaw in the forward direction, the rearward movement of the jaw case with respect to the port and the narrowing of inner diameter of the jaw grasping the mandrel of the blind rivet in the jaw, and the rearward movement of the jaw case and jaw grasping the mandrel rupturing the mandrel of the blind rivet and fastening a component-to-be-fastened with the rivet body of the blind rivet, the blind rivet fastening device characterized in comprising a hole provided in the inner wall forming the port of the nose piece, an engaging means housed inside the hole, and a pressure-applying means for elastically pushing the engaging means towards the inner wall of the nose piece from the outer wall and causing a portion of the engaging means to protrude from the inner wall into the port, the hole extending from the inner wall towards the outer wall and rearward obliquely with respect to the rivet insertion port, and the front end of the hole opening into the port formed narrowly so the engaging means protruding into the port does not fall out. 
         [0012]    In an embodiment of the present invention, the engaging means can be a spherical component, a cylindrical component, or a bolt-shaped component. Also, the pressure-applying means can be an elastic ring or a spring. The elastic ring can be an O-ring. 
         [0013]    In the present invention, the hold accommodating the engaging means extends from the inner wall of the nose piece towards the outer wall and rearward obliquely with respect to the rivet insertion port. As a result, the engaging means can be easily moved rearward obliquely by the tip of the mandrel in the blind rivet moving in the insertion direction. However, because it is difficult for the engaging means to move rearward obliquely with respect to the mandrel moving in the direction opposite that of the insertion direction, movement of the mandrel is substantially prevented by the engaging means. In other words, the force needed by the mandrel to push up the engaging means after fastening is greater than the force needed by the inserted mandrel to push up the engaging means. Therefore, the present invention allows for the easy insertion of the blind rivet into the nose piece, and can hold the inserted blind rivet so that it does not fall out of the fastening device. Because the force needed by the mandrel to push up the engaging means after fastening is greater than the force needed by the mandrel held in the jaw to open the jaw, the mandrel is kept from sticking out of the nose piece after fastening. When the jaw has bitten into the mandrel and the force needed to open the jaw has become excessive, a large force applied from the mandrel to the engaging means can move the engaging means inside the hole rearward obliquely. The mandrel can then push up the engaging means after fastening. As a result, the fastening device does not break because the mandrel is sticking out from the nose piece after fastening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  A cross-sectional diagram showing the entire blind rivet fastening device in an embodiment of the present invention. 
           [0015]      FIG. 2  An enlarged cross-sectional view showing a blind rivet before insertion into the front end portion of the blind rivet fastening device in  FIG. 1 . 
           [0016]      FIG. 3  An enlarged cross-sectional view showing the blind rivet inserted into the front end portion of the blind rivet fastening device in  FIG. 2 . 
           [0017]      FIG. 4  A partial cross-sectional view similar to  FIG. 1  showing the operation of the blind rivet fastening device in the embodiment of the present invention. 
           [0018]      FIG. 5  A partial cross-sectional view similar to  FIG. 4  showing the operation of a pneumatic-hydraulic blind rivet fastening device of the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The following is an explanation of an embodiment of the present invention with reference to the figures.  FIG. 1  is a cross-sectional diagram showing the entire blind rivet fastening device in an embodiment of the present invention.  FIG. 2  and  FIG. 3  are enlarged cross-sectional views showing the front end portion of the blind rivet fastening device in  FIG. 1 . 
         [0020]    As shown in these figures, a nose housing  2  is provided at the front end of the blind rivet fastening device  1  to accept a blind rivet, and a nose piece  3  is provided at the front end of the nose housing  2 . The nose piece  3  has an insertion port  6  for inserting the mandrel  5  of the blind rivet  4 . As shown in  FIG. 2 , the blind rivet  4  is composed of a rivet body  4   a  and a mandrel  5 . However, as shown in  FIG. 3 , in order to receive and stop the rivet body  4   a  in the front end of the nose piece  3 , the nose piece  3  is configured so that only the mandrel  5  is received in the insertion port  6 . A jaw case  7  provided adjacent to the rear of the nose piece  3  inside the jaw housing  2 . The jaw case  7  is able to slide forward and rearward and has an inner circumferential surface formed so the inner diameter becomes smaller towards the front end. A jaw  8  is provided inside the jaw case  7  to grasp the mandrel  5  of the blind rivet  4  inserted into the insertion port  6  of the nose piece  3 . The jaw  8  has an outer peripheral surface slidably contacting the inner circumferential surface of the jaw case  7 . A jaw pusher  9  is provided adjacent to the rear of the jaw  8  inside the jaw housing  2 . The jaw pusher  9  pushes the jaw  8  in the forward direction, which comes into contact with the inner peripheral surface of the jaw case  7 . 
         [0021]    As shown in the partially enlarged cross-sectional views in  FIG. 2  and  FIG. 3 , a hole  10  is provided in the inner wall forming the insertion port  6  in the nose piece  3 , and a steel ball  11  is accommodated in this hole. A ring-shaped groove  13  is provided in the outer wall of the nose piece, and a portion faces the hole  10 . An O-ring  12  is provided in the groove  13 , and the O-ring  12  elastically pushes the steel ball  11  from the outer wall towards the inner wall. Some of the steel ball  11  protrudes from the inner wall into the insertion hole. As indicated by arrow A, the hole  10  extends from the inner wall towards the outer wall and rearward obliquely with respect to the insertion port. In this configuration, when the steel ball  11  is pushed up by the mandrel  5  of the blind rivet  4 , it can move rearward obliquely inside the hole as indicated by arrow B. 
         [0022]    The following is an explanation of the operation of the blind rivet fastening device in an embodiment of the present invention, which will also be compared with a pneumatic-hydraulic blind rivet fastening device of the prior art. 
         [0023]      FIG. 4  and  FIG. 5  are partial cross-sectional views similar to  FIG. 2  used to explain, respectively, a blind rivet fastening device in an embodiment of the present invention and a pneumatic-hydraulic blind rivet fastening device of the prior art. In  FIG. 4  and  FIG. 5 , (A), (B), (C), (D) and (E) show the blind rivet fastening device, respectively, in its starting position before a blind rivet has been inserted, after the blind rivet has been inserted, while the blind rivet is being fastened, after the device has returned to its starting position for the next fastening operation, and after the mandrel has been discharged. 
         [0024]    First, the operation of the blind rivet fastening device in an embodiment of the present invention will be explained. In  FIG. 4  (A), the blind rivet fastening device is in its starting position. In the starting position, the jaw case  7  is forward in the jaw housing  2  in order to allow for easy insertion of a blind rivet. The jaw  8  is to the rear of the nose piece  3  and cannot move forward, and the inner diameter of the jaw  8  becomes larger. At this time, the steel ball  11  is elastically pressed by the O-ring  12 , and a portion of the steel ball protrudes into the insertion port  6  in the nose piece  3 . 
         [0025]    In  FIG. 4  (B), the mandrel  5  of the blind rivet  4  is inserted into the insertion port  6 , and the mandrel  5  is received by the jaw  8  where the inner diameter has been widened. At this time, the steel ball  11  is pushed up by the inserted mandrel  5 , and the steel ball  11  moves inside the wall, as indicated by arrow C, obliquely rearward from the inner wall of the nose piece  3  towards the outer wall. In this configuration, when viewed from the traveling direction of the mandrel  5 , the steel ball  11  can move forward obliquely. As a result, the mandrel  5  can be inserted using light force. Because elastic force is applied by the O-ring to the steel ball  11 , the inserted mandrel  5  is held by the steel ball  11 . 
         [0026]    In  FIG. 4  (C), the jaw case  7  is driven rearward. Because the inner diameter of the jaw  8  becomes smaller, the jaw  8  holds the mandrel  5 . When the jaw case  7  is driven further to the rear, the mandrel  5  is pulled in the direction of arrow D, the sleeve of the rivet body is expanded and deformed, and the mandrel  5  is ruptured after the blind rivet  4  has been fastened in the component-to-be-fastened. When the mandrel  5  has been ruptured, the steel ball  11  returns to the position shown in  FIG. 4  (A), and a portion of the steel ball  11  protrudes into the insertion port  6 . 
         [0027]    In  FIG. 4  (D), the jaw case  7  moves forward as indicated by arrow E in order to perform the next fastening operation. At this time, the ruptured mandrel  5  held by the jaw  8  moves forward, and comes into contact with the steel ball  11  protruding into the insertion port  6 . Because the force needed for the mandrel to push up the steel ball  11  is greater than the force needed for the mandrel  5  grasped in the jaw  8  to open the jaw  8 , forward movement by the mandrel  5  is prevented by the steel ball  11  and it is pushed back as indicated by arrow F. 
         [0028]    In  FIG. 4  (E), the insertion of the next blind rivet  4  pushes the ruptured mandrel  5  to the rear, and the steps in  FIG. 4  (B) through  FIG. 4  (E) are repeated. 
         [0029]    The following is an explanation of the operation of a pneumatic-hydraulic blind rivet fastening device of the prior art. In  FIG. 5  (A), the blind rivet fastening device is in its starting position. In the starting position, the jaw case  7  is forward, the jaw  8  presses against the rear end of the nose piece, and the inner diameter of the jaw  8  is larger. 
         [0030]    In  FIG. 5  (B), the mandrel  5  of the blind rivet  4  is inserted into the insertion port  6 , and the mandrel  5  is received by the jaw  8  where the inner diameter has been widened. The blind rivet  4  is inserted in this state, and the inserted rivet  5 , unlike  FIG. 4  (B), is held inside the insertion port  6  by suction generated using pneumatic pressure. 
         [0031]    In  FIG. 5  (C), the jaw case  7  is driven rearward. Because the inner diameter of the jaw  8  becomes smaller, the jaw  8  holds the mandrel  5 . When the jaw case  7  is driven further to the rear, the mandrel  5  is pulled in the direction of arrow D, the sleeve of the rivet body is expanded and deformed, and the mandrel  5  is ruptured after the blind rivet  4  has been fastened in the component-to-be-fastened. 
         [0032]    In FIG (D), the jaw case  7  moves forward as indicated by arrow E. At this time, because the ruptured mandrel  5  held in the jaw  8  moves forward, unlike in  FIG. 4  (D), the mandrel  5  protrudes from the front of the device. 
         [0033]    Afterwards, in  FIG. 5  (E), the jaw case  7  moves forward to the starting position shown in  FIG. 5  (A). The jaw  8  is in the rear portion of the nose piece, the inner diameter increases, and the mandrel  5  departs from the jaw  8 . The sticking out mandrel  5 , unlike  FIG. 4  (E), is moved to the rear and discharged by suction using the pneumatic pressure.