Patent Publication Number: US-7913530-B2

Title: Closing method and closing machine

Description:
FIELD OF THE INVENTION 
     This invention relates to an improvement in a closing method and a closing machine 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. 
     A closing machine used in the closing operation comprises an outer diameter chuck that grips an outer peripheral surface of the work piece, and a chuck spindle that drives the outer diameter chuck to rotate together with the work piece. The work piece is closed by pressing the rotating die against the work piece at an offset to the rotating work piece. 
     The closing method and closing machine described above are disclosed in JP2002- 153930A. 
     During a closing operation in a conventional closing machine, a die is pressed against a work piece so as to be brought into sliding contact therewith, and as a result, the die rotates in accordance with the work piece, which rotates at a higher speed than the die. 
     However, during a closing operation in this conventional closing machine, when the die accelerates to catch up with the work piece, the rotation of the die cannot catch up with the rotation of the work piece quickly due to the large inertial mass of a drive system that rotates together with the die, and as a result, a tact time increases. Herein, the tact time is defined as a time required for closing a single workpiece. 
     It is therefore an object of this invention to provide a closing method and a closing machine with which a rotating die can catch up with a rotating work piece quickly. 
     SUMMARY OF THE INVENTION 
     This invention provides a closing method for closing an open end of a work piece by pressing a rotating die against the work piece rotating about an axial center, characterized in that the die, which is disposed coaxially with the work piece, is supported rotatably by a die support shaft, a torque of a motor is transmitted to the die support shaft via a power transmission mechanism, a torque input into the power transmission mechanism from the die support shaft is blocked via a one-way clutch, and during closing operation, the die is pressed against the work piece so as to contact the work piece slidingly such that the die rotates in accordance with the work piece, which rotates at a higher speed than the die. 
     This invention also provides a closing machine for closing an open end of a work piece by pressing a rotating die against the work piece rotating about an axial center, characterized by a die support shaft that supports the die, which is disposed coaxially with the work piece, rotatably a power transmission mechanism which transmits a torque of a motor to the die support shaft and a one-way clutch which blocks a torque that is input into the power transmission mechanism from the die support shaft. During a closing operation, the die is pressed against the work piece so as to contact the work piece slidingly such that the die rotates in accordance with the work piece, which rotates at a higher speed than the die. 
     According to this invention, while the die accelerates to catch up with the work piece during a closing operation, the one-way clutch blocks torque transmission from the die support shaft to the power transmission mechanism, and therefore the die support shaft rotates freely relative to the power transmission mechanism, leading to a reduction in the inertial mass of a drive system that rotates together with the die. As a result, the rotation of the die catches up with the rotation of the work piece quickly, enabling a reduction in the tact time and an improvement in productivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a closing machine, illustrating an embodiment of this invention. 
         FIG. 2  is a plan view of the closing machine. 
         FIG. 3  is a front view of the closing machine. 
         FIGS. 4A-4H  are views showing closing processes. 
         FIG. 5  is a side view of a die driving device. 
         FIG. 6  is a plan view of the die driving device. 
         FIG. 7  is a front view of the die driving device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention will now be described in further detail with reference to the attached drawings. 
       FIGS. 1 to 3  show the overall constitution of a closing machine  1 . In  FIGS. 1 to 3 , 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 overall constitution of the closing machine  1  will now be described. 
     Two chuck spindles  20  which drive a work piece  9  to rotate about its axial center, and a single die driving device  40  which drives a die  4 , are provided in a central portion of the closing machine  1 . The chuck spindles  20  perform a reciprocating motion in the X axis direction relative to a pedestal  3  via a chuck spindle moving device  30 , to be described later, thereby moving alternately to the central portion of the closing machine  1  so as to bring the work piece  9  face to face with the die  4 . 
     The closing machine  1  performs a closing operation to close an open end of the work piece  9  by heating the work piece  9 , which is constituted by a metal pipe material, using a high-frequency heating device  2 , and pressing the die  4  against the rotating work piece  9  such that the work piece  9  undergoes plastic deformation. 
     A thrust stopper moving device  60 , which is positioned in front of the chuck spindle  20  for closing the work piece  9  so as to support an end portion of the work piece  9 , and a core moving device  50 , which moves a core  5  inside the work piece  9 , are provided in the central portion of the closing machine  1 . 
     A pair of conveyors  18  and a work piece introducing device  10  are provided respectively on the left and right rear portions of the working machine  1 . The work piece  9  is conveyed forward in the Y axis direction by each of the conveyors  18  and then conveyed forward in the Y axis direction by each of the work piece introducing devices  10 , which are capable of movement in the Y axis direction. Thus, the work piece  9  is introduced into and gripped by the respective left and right chuck spindles  20 . 
     While one of the chuck spindles  20  is positioned in the central portion of the working machine  1  during a closing operation, the other chuck spindle  20  is positioned on either the left or right end portion of the closing machine  1  so as to receive the work piece  9  conveyed by the respective work piece introducing devices  10 . 
     A discharge device  17  for discharging the work piece  9  following the closing operation is provided at the front portion of the closing machine  1 . The discharge device  17  causes a hand  13  gripping the work piece  9  to reciprocate in the X axis direction relative to the pedestal  3  such that the work piece  9 , which is pushed out from the left and right chuck spindles  20 , is conveyed to a conveyor  19  disposed on the right-hand front portion of the closing machine  1 . 
     Once the closing operation is complete, the work piece  9 , which is at a high temperature of 1000° C. or more, is conveyed to a cooling device  70  (see  FIG. 3 ) by the conveyor  19  and cooled by the cooling device  70 . The cooling device  70  is provided on the front right side of the closing machine  1 . 
       FIGS. 4A to 4G  show a series of processes performed by the closing machine  1  to close the work piece  9 . Each process of this closing method will now be described in sequence. 
     Referring to  FIG. 4A , an inner diameter chuck  8  of the work piece introducing device  10  is inserted into the work piece  9  such that the inner diameter chuck  8  grips the inner peripheral surface of the work piece  9 . 
     Referring to  FIG. 4B , the work piece introducing device  10  causes the inner diameter chuck  8  to advance in the Y axis direction such that the work piece  9  is inserted into an outer diameter chuck  7  of the chuck spindle  20 . Thus, the outer diameter chuck  7  grips the outer peripheral surface of the work piece  9 . 
     Referring to  FIG. 4C , the work piece introducing device  10  causes the inner diameter chuck  8  to retreat in the Y axis direction such that the inner diameter chuck  8  is extracted from the work piece  9 . Next, the chuck spindle moving device  30  moves the chuck spindle  20  in the X axis direction until the work piece  9  is stopped in an operation position facing the die  4 . 
     Referring to  FIG. 4D , the thrust stopper moving device  60  moves a thrust stopper  6  to a thrust operation reference position supporting a base end portion  9   b  of the work piece  9 . 
     Referring to  FIG. 4E , the core moving device  50  introduces the core  5  into the inside of the work piece  9 . 
     Referring to  FIG. 4F , the chuck spindle  20  drives the work piece  9  and the core  5  to rotate. Meanwhile, the die  4  is pressed against the heated work piece  9  by the die driving device  40 . Thus, a tip end portion  9   a  of the work piece  9  is steadily reduced in diameter between the die  4  and the core  5  such that finally, the tip end portion  9   a  of the work piece  9  closes to form a bottom portion  9   c.    
     Referring to  FIG. 4G , the die driving device  40  moves the die  4  rearward in the Y axis direction away from the work piece  9 . Meanwhile, the thrust stopper moving device  60  moves the thrust stopper  6  forward in the Y axis direction away from the thrust operation reference position, and the core moving device  50  removes the core  5  from the inside of the work piece  9 . 
     To close another work piece  9  thereafter, the chuck spindle moving device  30  moves the chuck spindle  20  in the X axis direction such that the work piece  9  faces the inner diameter chuck  8 , as shown in  FIG. 4A . Then, as shown in FIG,  4 B, the work piece introducing device  10  causes the inner diameter chuck  8  to advance in the Y axis direction such that the base end portion  9   b  of the unclosed work piece  9  abuts against the bottom portion  9   c  of the closed work piece  9 , and thus the closed work piece  9  is pushed out of the outer diameter chuck  7 . 
     To terminate the closing operation of the work piece  9 , the work piece introducing device  10  causes the inner diameter chuck  8  to advance in the Y axis direction, as shown in  FIG. 4H , such that the inner diameter chuck  8  abuts against the bottom portion  9   c  of the closed work piece  9 , and thus the closed work piece  9  is pushed out of the outer diameter chuck  7 . 
     The overall constitution of the closing machine  1  was described above. 
     Next, the constitution of the die driving device  40  shown in  FIGS. 5 to 7  will be described. 
     The die driving device  40  comprises a die support shaft  41 , the die  4  being attached to a front end portion thereof, a die support case  42  which supports the die support shaft  41  rotatably via a bearing not shown in the figure, two guide rails  44  which support a sliding table  43  carrying the die support case  42  movably in the Y axis direction, and a hydraulic cylinder  45  which drives the sliding table  43  in the Y axis direction. The hydraulic cylinder  45  moves the die support case  42  forward in the Y axis direction during a closing operation in accordance with the output of a controller, not shown in the figure, such that the die  4  is pressed against the work piece  9 . 
     The die driving device  40  comprises the die support shaft  41  which supports the die  4  rotatably, a power transmission mechanism  401  which transmits the rotation of a motor  46  to the die support shaft  41 , and a one-way clutch  410  which inputs torque from the power transmission mechanism  401  to the die support shaft  41  while blocking torque input from the die support shaft  41  to the power transmission mechanism  401 . 
     The one-way clutch  410  has a rotation transmission mechanism which transmits torque from the motor  46  to the die support shaft  41  but blocks torque transmission from the die support shaft  41  to the motor  46 . 
     The power transmission mechanism  401  comprises a pulley  403  connected to an output shaft  402  of the motor  46 , a pulley  404  connected to the die support shaft  41  side, and a belt  405  wrapped around the two pulleys  403 ,  404 . 
     The one-way clutch  410  is interposed between the die support shaft  41  and an output shaft  406  of the power transmission mechanism  401 , and serves to block torque transmission from the die support shaft  41  to the output shaft  406  of the power transmission mechanism  401 . 
     One end of the output shaft  406  of the power transmission mechanism  401  constitutes the one-way clutch  410 , and the pulley  404  is connected to the other end. 
     In a process performed prior to a closing operation, the motor  46  drives the die  4  to rotate via the one-way clutch  410  and drives the work piece  9  to rotate via the chuck spindle  20 . The rotation speed of the die  4  is set to be slightly lower than the rotation speed of the work piece  9 . 
     During the closing operation, the die  4  is pressed against the work piece  9  so as to contact the work piece  9  slidingly. As a result, the die  4  catches up with the work piece  9 , which rotates at a higher speed than the die  4 , such that the die  4  and work piece  9  rotate at a substantially identical speed. 
     While the die  4  accelerates to catch up with the work piece  9 , the one-way clutch  410  blocks torque transmission from the die support shaft  41  to the output shaft  406  of the power transmission mechanism  401 . Thus, the output shaft  406  of the power transmission mechanism  401  is cut off from the die support shaft  41  via the one-way clutch  410 , and therefore the die support shaft  41  rotates freely relative to the output shaft  406  of the power transmission mechanism  401 , leading to a reduction in the inertial mass of the drive system that rotates together with the die  4 . As a result, the rotation of the die  4  catches up with the rotation of the work piece  9  quickly, enabling a reduction in the tact time required to close a single work piece  9  and an improvement in productivity. 
     On the other hand, in a case where the one-way clutch  410  is interposed between the output shaft  402  of the motor  46  and the pulley  404  of the power transmission mechanism  401 , the die support shaft  41  rotates together with the pulley  403  of the power transmission mechanism  401 , causing the belt  405  to revolve, and therefore, even if the one-way clutch  410  blocks torque transmission from the die support shaft  41  to the motor  46  while the die  4  accelerates to catch up with the work piece  9 , the rotation of the die  4  catches up with the rotation of the work piece  9  slowly due to the large inertial mass of the drive system that rotates together with the die  4 , and as a result, the tact time increases. 
     It should be noted that the power transmission mechanism  401  for transmitting the rotation of the motor  46  to the die support shaft  41  is not limited to a constitution comprising the pulleys  403 ,  404  and the belt  405 , and may employ gears or another mechanism, for example. 
     INDUSTRIAL APPLICABILITY 
     The closing method and closing machine of this invention are not limited to a closing operation such as that described above, for closing an open end of a work piece, and may be used in a spinning operation to reduce the diameter of a work piece by pressing a die against the rotating work piece.