Patent Publication Number: US-8117881-B2

Title: Press-molding method and press-molding device

Description:
FIELD OF THE INVENTION 
     This invention relates to an improvement in a press-molding method and a press-molding device for press-molding the bottom portion of a work piece formed into a closed-end shape through implementation of a closing operation for closing an open end of a metal pipe material. 
     BACKGROUND OF THE INVENTION 
     In a closing method, a work piece constituted by a metal pipe material is rotated and a die is pressed against the work piece while the work piece is heated. Thus, the work piece undergoes plastic deformation as it gradually approaches the die, and as a result, an end portion of the work piece is formed into a closed bottom portion. 
     This closing method is disclosed in JP2002-153930. 
     The work piece formed into a closed-end shape through implementation of the closing operation is press-molded by a press-molding device. A conventional press-molding device comprises an inner die which is inserted into the inside end of the closed-end work piece, and an outer die disposed on the outside of the work piece. The inner die is driven by a hydraulic cylinder such that the bottom portion of the work piece is compressed between the inner die and the outer die. 
     In a conventional press-molding device, however, if the work piece moves when the inner die is inserted into the inside end of the work piece, the inner die may impinge on and damage the inner peripheral surface of the work piece. 
     To prevent this, the outer peripheral surface of the work piece may be gripped when the inner die is inserted into the inside end of the work piece so that the work piece does not move. However, when the outer peripheral surface of the work piece is gripped so that the work piece does not move, the work piece is unable to move in the axial direction thereof when the work piece is compressed between the inner die and outer die, and as a result, press-molding of the work piece cannot be performed smoothly. 
     Furthermore, a conventional press-molding device is structured such that the inner die is driven by a hydraulic cylinder and thereby inserted into the inside end of the work piece. As a result, the inner die cannot be moved quickly, leading to an increase in the tact time for press-molding a single work piece. 
     It is therefore an object of this invention to provide a press-molding method and a press-molding device for press-molding a work piece formed into a closed-end shape smoothly without damaging an inner peripheral surface of the work piece. 
     SUMMARY OF THE INVENTION 
     This invention provides a press-molding method for press-molding a bottom portion of a work piece having a closed-end shape between an inner die inserted into an inside end of the work piece and an outer die disposed on an outside of the work piece, comprising gripping the work piece via a core adjusting chuck mechanism so that the work piece can move in an axial direction thereof, moving the inner die in the axial direction via an inner die moving mechanism so that the inner die is inserted into the inside end of the work piece, restricting movement of the inner die via a stopper mechanism so that the inner die is supported in a processing position, and moving the outer die in the axial direction of the work piece via an outer die moving mechanism so that the bottom portion of the work piece is press-molded between the outer die and the inner die. 
     Further, this invention provides a press-molding device for press-molding a bottom portion of a work piece having a closed-end shape between an inner die inserted into an inside end of the work piece and an outer die disposed on an outside of the work piece, comprising a core adjusting chuck mechanism which grips the work piece so that the work piece can move in an axial direction thereof, an inner die moving mechanism which inserts the inner die into the inside end of the work piece by moving the inner die in the axial direction, a stopper mechanism which supports the inner die in a processing position by restricting movement of the inner die, and an outer die moving mechanism which press-molds the bottom portion of the work piece between the outer die and the inner die by moving the outer die in the axial direction. 
     According to this invention, during press-molding in which the work piece is compressed between the outer die and the inner die, the core adjusting chuck mechanism permits movement of the work piece in the axial direction thereof via rollers, and therefore, when the inner die moving mechanism moves the inner die to insert the inner die into the inside end of the work piece, the core adjusting chuck mechanism can grip the work piece, and the inner die can be prevented from impinging on the inner peripheral surface of the work piece and causing damage thereto. 
     When the outer die moving mechanism moves the outer die to push the work piece, the work piece moves in the axial direction relative to the core adjusting chuck mechanism, and the stopper mechanism restricts movement of the inner die such that the inner die is supported in the processing position. When the outer die pushes the work piece further, the work piece is compressed smoothly between the outer die and the inner die, and as a result the work piece is press-molded into a predetermined shape. 
     The inner die moving mechanism does not receive a load during press-molding, and therefore the inner die can be inserted into the inside end of the work piece via an air cylinder, for example. Hence, the inner die can be moved quickly, enabling a reduction in the tact time for press-molding a single work piece and an improvement in production efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a press-molding device, illustrating an embodiment of this invention. 
         FIG. 2  is a sectional view of the press-molding device. 
         FIG. 3  is a plan view of the press-molding device. 
         FIG. 4  is a front view of the press-molding device. 
         FIG. 5  is a sectional view of a core adjusting chuck mechanism and so on. 
         FIGS. 6A to 6F  are views showing processes for press-molding a work piece. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention will now be described in detail, in accordance with the attached drawings. 
     A press-molding device  80  shown in  FIGS. 1 to 4  press-molds a bottom portion  9   c  of a work piece  9  that has undergone a closing operation. 
     A closing machine rotates the work piece  9 , which is constituted by a metal pipe material, and presses a die against the work piece  9  while heating the work piece  9 . As a tip end portion of the work piece  9  gradually approaches the die, the work piece  9  is subjected to plastic deformation, and as a result, the bottom portion is formed into a completely closed shape. 
     The work piece  9 , which reaches a high temperature of 1000° C. or more following the closing operation performed by the closing machine, is cooled to approximately 100° C. by a cooling device not shown in the figure, and then conveyed to the press-molding device  80  and press-molded by the press-molding device  80 . 
     In  FIGS. 1 to 4 , three axes, namely X, Y, and Z, are set orthogonal to each other. It is assumed that the X axis extends in a substantially horizontal lateral direction, the Y axis extends in a substantially horizontal front-rear direction, and the Z axis extends in a substantially vertical direction. The constitution of the press-molding device  80  will now be described. 
     In  FIG. 3 , the press-molding device  80  is provided with an introduction table  81 , a press-molding machine  82 , and a discharge table  83 , which are arranged in series in the X axis direction. A chute  84  for discharging defective work pieces  9  is provided in series with the discharge table  83 . 
     As shown in  FIG. 1 , a conveyance device  84  is provided on an upper portion of the press-molding device  80 . The conveyance device  84  conveys the work piece  9  to the introduction table  81 , press-molding machine  82  and discharge table  83  in sequence. 
     The press-molding machine  82  press-molds the bottom portion of the work piece  9  between an inner die  521  inserted into an inside end of the work piece  9 , and an outer die  551  disposed on the outside of the work piece  9 . 
     The press-molding device  80  comprises a core adjusting chuck mechanism  501  which grips the work piece  9  so that the work piece  9  can move in the Y axis direction, an inner die moving mechanism  522  which moves the inner die  521  in the Y axis direction via an air cylinder  524  so that the inner die  521  is inserted into the inside end of the work piece  9 , a stopper mechanism  531  which supports the inner die  521  in a processing position by restricting movement of the inner die  521 , and an outer die moving mechanism  552  which moves the outer die  551  in the Y axis direction via a hydraulic cylinder  554  such that the bottom portion of the work piece  9  is press-molded between the inner die  521  and the outer die  551 . The inner die  521  and outer die  551  are disposed coaxially with the work piece  9 . 
     The inner die moving mechanism  522  comprises two guide rails  572  provided on a pedestal  571  so as to extend in the Y axis direction, a sliding table  523  which is supported movably via the guide rails  572 , and an air cylinder  524  which moves the sliding table  523 . The inner die  521  is connected to the sliding table  523 . 
     The inner die  521 , which takes the form of a rod, is connected to a front portion of the sliding table  523  at a base end portion thereof, penetrates a guide table  525  from a midway point thereof, and moves coaxially with the work piece  9 . 
     The guide table  525  is supported so as to be capable of moving in the Y axis direction via the guide rails  572 . The position of the guide table  525  relative to the pedestal  571  can be varied in accordance with variation in the length of the work piece  9  and so on via an adjustment mechanism  526 . 
     As shown in  FIG. 2 , when the air cylinder  524  contracts, the sliding table  523  retreats in the Y axis direction together with the inner die  521  such that the inner die  521  does not interfere with the work piece  9  introduced into and discharged from the core adjusting chuck mechanism  501 . 
     When the air cylinder  524  expands, the sliding table  523  advances in the Y axis direction together with the inner die  521  such that the inner die  521  is inserted into the inside end of the work piece  9  gripped by the core adjusting chuck mechanism  501 . 
     A positioning shaft  527  is connected to a rear portion of the sliding table  523 . In other words, the inner die  521  and the positioning shaft  527  project respectively from the front and rear end portions of the pedestal  571 . The positioning shaft  527  extends coaxially with the inner die  521 , and a tip end portion  527   a  thereof is supported by the stopper mechanism  531 . 
     As shown in  FIG. 4 , a support table  574  stands upright on the rear end portion of the pedestal  571 . The stopper mechanism  531  is provided on the support table  574 . The air cylinder  524  and the positioning shaft  527  are provided so as to penetrate the support table  574 . 
     The stopper mechanism  531  comprises a stopper plate  532  inserted into the path that is penetrated by the positioning shaft  527 , and an air cylinder  533  for driving the stopper plate  532 . The stopper plate  532  is supported elevatably relative to the support table  574 . 
     When the air cylinder  533  contracts, the stopper plate  532  is held in an elevated position relative to the support table  574 , and the positioning shaft  527  moves freely below the stopper plate  532 . 
     When the air cylinder  533  expands, the stopper plate  532  descends relative to the support table  574 , and the rear tip end portion  527   a  of the positioning shaft  527  contacts the stopper plate  532 . As a result, the stopper mechanism  531  restricts movement of the inner die  521  such that the inner die  521  is supported in a processing position. 
     The outer die moving mechanism  552  comprises a guide mechanism  553  which supports the outer die  551  movably in the Y axis direction, and a hydraulic cylinder  554  which drives the outer die  551 . 
     A support table  575  stands upright on a front end portion of the pedestal  571 . The hydraulic cylinder  554  and the guide mechanism  553  are connected respectively to the front and rear portions of the support table  575 . 
     The front and rear support tables  574 ,  575  are connected to each other via two beams  576 , thereby securing enough rigidity to prevent the support tables  574 ,  575  from collapsing in the front-rear direction. 
     As shown in  FIG. 5 , the core adjusting chuck mechanism  501  comprises left and right chucks  502 ,  503  provided as a front and rear pair, and by opening and closing the chucks  502 ,  503 , the outer peripheral surface of the work piece  9  is gripped. 
     The right chuck  502  is fixed to a chuck table  504 . The left chuck  503  is supported so as to be capable of moving in the X axis direction relative to the chuck table  504 . The left chuck  503  is driven by an air cylinder, not shown in the figure, and thus the left and right chucks  502 ,  503  are opened and closed. 
     The left and right chucks  502 ,  503  are each provided with a pair of rollers  505 . Each roller  505  is supported so as to be capable of rotating about an orthogonal axis to the Y axis relative to the left and right chucks  502 ,  503 . The work piece  9  that is gripped by the left and right chucks  502 ,  503  via the four rollers  505  can move in the Y axis direction in rotational contact with each roller  505 . 
     A chuck position switching mechanism  512  is provided for switching the position of the core adjusting chuck mechanism  501  in the Y axis direction. The chuck position switching mechanism  512  comprises front and rear sliding tables  507 ,  508  that are supported movably in the Y axis direction via left and right guide rails  572 , and an air cylinder  510  that drives the front and rear sliding tables  507 ,  508  to two positions. The chuck tables  504  provided as a front and rear pair are fixed to the front and rear sliding tables  507 ,  508 , respectively. 
     The front and rear sliding tables  507 ,  508  are connected such that the Y axis direction gap therebetween can be adjusted via an adjustment mechanism  509 . Thus, the gap between the front and rear chucks  502 ,  503  can be adjusted easily in accordance with variation in the length of the work piece  9  and so on. 
     A controller not shown in the figure operates the conveyance device  84 , the core adjusting chuck mechanism  501 , the inner die moving mechanism  522 , the stopper mechanism  531 , and the outer die moving mechanism  552  in a predetermined sequence in accordance with signals from position sensors  91  to  97  and so on, and as a result, the work piece  9  is press-molded automatically. 
     The press-molding device  80  operates automatically, and therefore there is no need for an operator  79  to operate the press-molding device  80  during a normal operation. 
     The work piece  9  is press-molded by performing each of the processes to be described below in sequence using the press-molding device  80  constituted as described above. 
     As shown in  FIG. 6A , the work piece  9  conveyed by the conveyance device  84  is gripped by the core adjusting chuck mechanism  501 . 
     As shown in  FIG. 6B , the inner die moving mechanism  522  moves the inner die  521  forward to insert the inner die  521  into the inside end of the work piece  9 . 
     As shown in  FIG. 6C , the stopper mechanism  531  lowers the stopper plate  532 . 
     As shown in  FIG. 6D , the hydraulic cylinder  554  of the outer die moving mechanism  552  moves the outer die  551  rearward such that the bottom portion of the work piece  9  is press-molded between the outer die  551  and the inner die  521 . 
     As shown in  FIG. 6E , the hydraulic cylinder  554  of the outer die moving mechanism  552  moves the outer die  551  forward. At the same time, the stopper mechanism  531  raises the stopper plate  532 , whereupon the inner die moving mechanism  522  moves the inner die  521  rearward to remove the inner die  521  from the work piece  9 . 
     As shown in  FIG. 6F , the core adjusting chuck mechanism  501  is opened, whereupon the press-molded work piece  9  is removed by the conveyance device  84 . 
     Returning to  FIG. 6A , the next work piece  9  conveyed by the conveyance device  84  is gripped by the core adjusting chuck mechanism  501 . Then, by repeating each of the processes described above, work pieces  9  are press-molded one by one. 
     The actions of the constitution described above will now be described. 
     During press-molding, in which the work piece  9  is compressed between the outer die  551  and the inner die  521 , the core adjusting chuck mechanism  501  permits movement of the work piece  9  in the Y axis direction via the rollers  505 , and therefore, when the inner die moving mechanism  522  moves the inner die  521  forward such that the inner die  521  is inserted into the inside end of the work piece  9 , the core adjusting chuck mechanism  501  can grip the outer peripheral surface of the work piece  9 , and the inner die  521  can be prevented from impinging on the inner peripheral surface of the work piece  9  and causing damage thereto. 
     When the hydraulic cylinder  554  of the outer die moving mechanism  552  moves the outer die  551  in the Y axis direction to press the work piece  9 , the work piece  9  retreats slightly while the outer peripheral surface thereof contacts the rollers  505  rotationally. Thus, the rear tip end portion  527   a  of the positioning shaft  527  contacts the stopper plate  532 , and as a result, the stopper mechanism  531  restricts movement of the inner die  521  such that the inner die  521  is held in the processing position. Hence, when the outer die  551  pushes the work piece  9  further, the work piece  9  is compressed smoothly between the outer die  551  and the inner die  521 , and as a result, the work piece  9  is press-molded into a predetermined shape. 
     The core adjusting chuck mechanism  501  grips the work piece  9  via the plurality of rollers  505  that contact the outer peripheral surface of the work piece  9  rotationally, and therefore core adjusting precision can be secured in relation to the work piece  9 , and the work piece  9  can be moved smoothly in the Y axis direction. 
     A stroke in which the hydraulic cylinder  554  of the outer die moving mechanism  552  moves the outer die  551  is much smaller than a stroke in which the air cylinder  524  of the inner die moving mechanism  522  moves the inner die  521 , and therefore the hydraulic cylinder  554  can be reduced in size and power. 
     The inner die moving mechanism  522  inserts the inner die  521  into the inside end of the work piece  9  by means of the expansion and contraction operations of the air cylinder  524 , and therefore the inner die  521  can be moved quickly, enabling a reduction in the tact time for press-molding a single work piece  9  and an improvement in production efficiency. 
     The inner die moving mechanism  522  comprises the sliding table  523  that moves in the Y axis direction, the inner die  521  projecting from the front portion of the sliding table  523  and the positioning shaft  527  projecting from the rear portion of the sliding table  523 , and the stopper mechanism  531  inserts the stopper plate  532  into the path penetrated by the positioning shaft  527 . Thus, the inner die  521  can be supported securely in the processing position. 
     The chuck position switching mechanism  512  is capable of switching the position of the core adjusting chuck mechanism  501  in the Y axis direction in accordance with variation in the length of the work piece  9  and so on. 
     INDUSTRIAL APPLICABILITY 
     As described above, the press-molding method and press-molding device according to this invention may be used to press-mold a bottom portion of a work piece having a closed-end shape between an inner die and an outer die.