Patent Publication Number: US-7901200-B2

Title: Molding apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a molding apparatus for compacting powder into a predetermined shape. 
     2. Related Background Art 
     A known molding apparatus for compacting powder is a servo press machine, for example, as described in Japanese Patent Application Laid-Open No. 8-225804. This servo press machine has a die movable between a molding position and a molding removal position, a lower punch fixed at a predetermined position, and an upper punch vertically movable, and is arranged to fill a raw powder into a molding cavity constructed of the die and the lower punch and thereafter lower the upper punch to compact the raw powder by the upper punch and the lower punch, thereby obtaining a molded article. 
     SUMMARY OF THE INVENTION 
     However, the above-described conventional technology has the following problem. For continuously carrying out an overfill operation and an underfill operation, it is necessary to continuously move the die upward and downward. For this reason, if the die is attempted to move at high speed, the die will overshoot by virtue of inertia of the die and it will be hard to move the die as intended. Therefore, it was infeasible to perform the continuous overfill and underfill operations at high speed. 
     An object of the present invention is to provide a molding apparatus capable of performing the continuous overfill and underfill operations at high speed. 
     The present invention provides a molding apparatus for compacting a powder into a predetermined shape, comprising: a die having a cavity into which the powder is filled; a lower punch arranged to be inserted into the cavity from a lower side of the die; an upper punch arranged to be inserted into the cavity from an upper side of the die to compact the powder filled in the cavity, in cooperation with the lower punch; a feeder for feeding the powder into the cavity; a first cam driving system having a first cam for vertically moving the die relative to the lower punch; a second cam driving system having a second cam for vertically moving the upper punch; a third cam driving system having a third cam for moving the feeder forward or backward relative to the cavity; a contact member connected to the first cam driving system; a stopper located above or below the contact member and arranged to regulate relative vertical movement of the die with respect to the lower punch, in cooperation with the contact member; a fourth cam driving system having a fourth cam for vertically moving the stopper; and drive synchronizing means for rotating the first cam, the second cam, the third cam, and the fourth cam in synchronism. 
     As molding is performed by means of the molding apparatus as described above, a molded article is fabricated as follows during a rotation of the first cam, the second cam, the third cam, and the fourth cam in synchronism. Namely, the powder is first filled from the feeder into the cavity in a state in which the feeder is moved forward up to above the cavity by the third cam driving system. Then an overfill operation is carried out. Specifically, the die is raised relative to the lower punch by the first cam driving system and thereafter the die is lowered relative to the lower punch to stop temporarily. The relative lowering and stopping operation of the die with respect to the lower punch is forcibly carried out, for example, in such a manner that the contact member is brought into contact with the stopper during the downward motion of the stopper by the fourth cam driving system. Then the feeder is moved backward away from the cavity by the third cam driving system and thereafter an underfill operation is carried out. Specifically, the die is slightly raised relative to the lower punch. The relative raising operation of the die with respect to the lower punch is forcibly carried out, for example, in such a manner that the contact member is kept in contact with the stopper during the upward motion of the stopper by the fourth cam driving system. Then the upper punch is lowered by the second cam driving system to compact the raw powder by the upper punch and the lower punch, thereby obtaining the molded article. Thereafter, the die is lowered relative to the lower punch by the first cam driving system to push out the molded article. 
     Incidentally, as far as the rotating speed of the cam is not so high, it is possible to carry out the aforementioned overfill and underfill operations by means of the first cam driving system only. However, where the rotating speed of the cam is raised in order to increase efficiency of production of the molded article, the die will overshoot by virtue of the inertia if the relative motions of the die with respect to the lower punch vary continuously. For this reason, if the overfill and underfill operations are carried out by means of the first cam driving system only, the relative motions of the die with respect to the lower punch will fail to follow the motion of the first cam. 
     In contrast to it, the present invention adopts the following configuration: there are the contact member, stopper, and fourth cam driving system provided, and during the overfill and underfill operations, the contact member is in contact with the stopper whereby, for example, the die is forcibly lowered, stopped, and raised in accordance with the motion of the fourth cam of the fourth cam driving system. For this reason, the die will rarely overshoot even if the relative motions of the die with respect to the lower punch vary continuously at high speed. As a result, the overfill and underfill operations can be carried out in succession while the first cam, the second cam, the third cam, and the fourth cam are rotated at high speed. 
     Preferably, the molding apparatus further comprises means for adjusting a height position of the contact member or the stopper. When the height position of the contact member or the stopper is changed, the distance varies between the contact member and the stopper. This changes the timing to regulate the relative vertical movement of the die with respect to the lower punch, and a relative displacement amount of the die with respect to the lower punch, so as to change a filling amount of the powder into the cavity. Therefore, the filling amount of the powder into the cavity can be adjusted by adjusting the height position of the contact member or the stopper. 
     Preferably, the drive synchronizing means has a main shaft coupled to the first cam, the second cam, the third cam, and the fourth cam, and a drive motor for rotating the main shaft. In this case, the first cam, the second cam, the third cam, and the fourth cam are rotated in synchronism by simply rotating the main shaft by the drive motor. Therefore, the drive synchronizing means can be realized in the simple structure and at low cost. 
     Preferably, the first cam has such a shape as to sequentially raise, stop, lower, and stop the die relative to the lower punch, in a predetermined angular range; the fourth cam has such a shape as to sequentially lower, stop, and raise the stopper, in the predetermined angular range; the stopper is located above the contact member; the contact member and the stopper regulate relative upward movement of the die with respect to the lower punch in such a manner as to first raise and stop the die relative to the lower punch in accordance with movement of the first cam, subsequently lower, stop, and raise the die relative to the lower punch in accordance with movement of the fourth cam, and then stop the die relative to the lower punch in accordance with movement of the first cam. In this case, the overfill and underfill operations can be carried out securely in succession during one rotation of the first cam, the second cam, the third cam, and the fourth cam at high speed. 
     The present invention permits the molding apparatus to perform the continuous overfill and underfill operations even at high speed. This enables high-quality molded articles to be efficiently produced with little variation in dimensions and others. 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of an embodiment of the molding apparatus according to the present invention, as a front view thereof. 
         FIG. 2  is a sectional view of the molding apparatus shown in  FIG. 1 , as a side view. 
         FIG. 3  is a sectional view of the molding apparatus shown in  FIG. 1 , as a top plan view. 
         FIG. 4  is a front view of a die set shown in  FIG. 1  (including cross sections in part). 
         FIG. 5  is sectional views showing an adjustment handle and an adjusting mechanism shown in  FIGS. 1 to 3 . 
         FIG. 6  is a conceptual diagram of a die driving system including a die driving cam shown in  FIGS. 1 to 3 . 
         FIG. 7  is a conceptual diagram of an upper ram driving system including an upper ram driving cam shown in  FIGS. 1 to 3 . 
         FIG. 8  is a conceptual diagram collectively showing a feeder driving system and a pressurizing air cylinder driving system including the die driving cam and the upper ram driving cam shown in  FIGS. 1 to 3 . 
         FIG. 9  is a conceptual diagram of the feeder driving system including a feeder driving cam shown in  FIGS. 1 to 3 . 
         FIG. 10  is a conceptual diagram of a stopper driving system including a die regulating cam shown in  FIGS. 1 to 3 . 
         FIG. 11  is a cam curve diagram showing shapes of the die driving cam, die driving cam, feeder driving cam, and die regulating cam shown in  FIGS. 1 to 3 . 
         FIGS. 12 to 16  are step diagrams showing a procedure of performing molding by means of the molding apparatus shown in  FIGS. 1 to 3 . 
         FIG. 17  is a diagram showing an actual operation of the die in the cam diagram shown in  FIG. 11 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the molding apparatus according to the present invention will be described below in detail with reference to the drawings. 
       FIG. 1  is a sectional view of an embodiment of the molding apparatus according to the present invention, as viewed from the front.  FIG. 2  is a sectional view of the molding apparatus shown in  FIG. 1 , as viewed from the side.  FIG. 3  is a sectional view of a cam part of the molding apparatus shown in  FIG. 1 , as viewed from the top. In each of the drawings, the molding apparatus  1  of the present embodiment is a cam press machine for compacting a powder of a material, such as a powder of a magnetic material or a powder of a dielectric material, into a predetermined shape (e.g., a rectangular parallelepiped shape). The molding apparatus  1  has a frame  2 , a die set (lower ram)  3  installed in the upper portion of this frame  2 , and an upper ram  4  located above the die set  3 . 
     The die set  3 , as shown in  FIG. 4 , has a fixed plate  5  fixed to the frame  2 . Two rods  6  extending vertically penetrate the fixed plate  5  so as to be slidable. A base  7  is fixed to the upper end of each rod  6  and a connection plate  8  is fixed to the lower end of each rod  6 . A die  9  is mounted on the base  7 . There are a plurality of cavities  10  (five cavities herein) formed in the die  9 , and the cavities  10  penetrate the die  9  vertically and are to be filled with the material powder. A feeder  11  is provided on the die  9  so that it can freely move in cross directions (directions normal to the plane of  FIG. 4 ). The feeder  11  has a feeder cup  11   a  for supplying the material powder into each cavity  10 . A projection  12  is disposed on the fixed plate  5 . A plurality of lower punches  13  (five lower punches herein) to be inserted into the respective cavities  10  from the lower side of the die  9  are fixed to the upper portion of the projection  12 . 
     Two vertically extending rods  14  are arranged on both sides of the die  9  while standing upright on the base  7 . These rods  14  slidably penetrate an elevator  15  forming a part of the upper ram  4 . The elevator  15  is provided with a plurality of upper punches  16  (five upper punches herein) to be inserted into the respective cavities  10  from the upper side of the die  9 . Each upper punch  16  cooperates with the counter lower punch  13  to compact the material powder filled in the cavity  10 . 
     Returning to  FIGS. 1 to 3 , a ram body  4   a  is located above the elevator  15 . This ram body  4   a  is provided with a pressurizing air cylinder  17 . The ram body  4   a  is connected through two vertically extending rods  18  to a frame body  19  located in the lower portion of the frame  2 . 
     A frame body  21  is connected through a connecting member  20  to the connection plate  8  of the die set  3 . Each rod  18  slidably penetrates the frame body  21 . A nut portion  22  is fixed to the lower portion of the frame body  21 . An adjustment screw  23  is screwed into the nut portion  22 . A contact member  24  is fixed to the lower end of the adjustment screw  23 . A pad plate  25  is provided at the top portion of the contact member  24  (cf.  FIG. 5 ). Two stoppers  26  to engage the pad plate  25  are arranged with the adjustment screw  23  in between, above the contact member  24 . The contact member  24  and each of the stoppers  26  function to regulate upward movement of the die  9 . 
     The height position of the contact member  24  is adjustable by means of an adjustment handle  27  and an adjusting mechanism  28  disposed in the front end portion of the frame  2 . The adjusting mechanism  28 , as shown in  FIG. 5 , has an adjustment shaft  29  connected to the adjustment handle  27 . A worm gear  30  is attached to the tip of the adjustment shaft  29 . The worm gear  30  meshes with a spur gear  32  attached to the contact member  24 , through an intermediate gear  31 . 
     As the adjustment handle  27  is rotated, the contact member  24  rotates through the adjustment shaft  29 , worm gear  30 , intermediate gear  31 , and spur gear  32 . With the rotation of the contact member  24 , the adjustment screw  23  vertically moves while being screwed relative to the nut portion  22 . This varies the height position of the contact member  24 . As the height position of the contact member  24  varies in this manner, the distance changes between the contact member  24  and the stoppers  26  and it results in changing a moving distance before contact of the pad plate  25  with the stoppers  26 . A scale  33  for monitoring the moving distance of the contact member  24  to the stoppers  26  is provided below the contact member  24 . 
     The molding apparatus  1  further comprises a die driving system  34 , an upper ram driving system  35 , a feeder driving system  36 , and a stopper driving system  37 . The die driving system  34  vertically moves the die  9 . The upper ram driving system  35  vertically moves the upper ram  4 . The feeder driving system  36  anteroposteriorly (laterally) moves the feeder  11 . The stopper driving system  37  vertically moves each stopper  26 . 
     The die driving system  34 , as also shown in  FIG. 6 , has a die drive cam  38  and a lever  39 . The lever  39  is journaled on a shaft part  40  provided on the frame  2 . A cam follower  41  in direct contact with the die drive cam  38  is provided at the base end of the lever  39 . The tip portion of the lever  39  is connected so as to be rotatable relative to the frame body  21 . Two air cylinders  42  are provided between the frame body  21  and the frame  2 . These air cylinders  42  prevent the cam follower  41  from disengaging from the die drive cam  38  during rotation of the die drive cam  38 . 
     The upper ram driving system  35 , as also shown in  FIGS. 7 and 8 , has an upper ram drive cam  43  and a lever  44 . The lever  44  is journaled on a shaft part  45  provided on the frame  2 . A cam follower  46  in direct contact with the upper ram drive cam  43  is provided at the base end of the lever  44 . The tip portion of the lever  44  is connected so as to be rotatable relative to the frame body  19 . Four air cylinders  47  are provided between the frame body  19  and the frame  2 . These air cylinders  47  prevent the cam follower  46  from disengaging from the upper ram drive cam  43  during rotation of the upper ram drive cam  43 . 
     The pressurizing air cylinder  17  (described previously) is attached to the ram body  4   a  of the upper ram  4 . A piston rod  17   a  of the pressurizing air cylinder  17  is fixed through a connecting member  62  to the elevator  15  (cf.  FIG. 1 ). This results in connecting the piston rod  17   a  to each upper punch  16  through the connecting member  62  and the elevator  15 . The pressurizing air cylinder  17  is driven by a cylinder driver  63  having an air pressure source and an air valve. The cylinder driver  63  performs such control as to drive the pressurizing air cylinder  17 , after completion of compression and pressure holding operation (described later) by the upper punches  16  and lower punches  13 . The pressurizing air cylinder  17  may be an air cylinder with a locking function, and the locking function is released only during driving. 
     The feeder driving system  36 , as also shown in  FIG. 9 , has a feeder drive cam  48  and a lever  49 . The lever  49  is journaled on a shaft part  50  provided on the frame  2 . A cam follower  51  in direct contact with the feeder drive cam  48  is provided at the base end of the lever  49 . The tip portion of the lever  49  is connected to a link  52  connected to the feeder  11 . An air cylinder  53  is provided between the lever  49  and the frame  2 . The air cylinder  53  prevents the cam follower  51  from disengaging from the feeder drive cam  48  during rotation of the feeder drive cam  48 . 
     The stopper driving system  37 , as also shown in  FIG. 10 , has a die regulating cam  54  and a lever  55 . The lever  55  is journaled on a shaft part  56  provided on the frame  2 . A cam follower  57  in direct contact with the die regulating cam  54  is provided at the base end of the lever  55 . The tip portion of the lever  55  is connected to each stopper  26 . An air cylinder  58  is provided between the lever  55  and the frame  2 . The air cylinder  58  prevents the cam follower  57  from disengaging from the die regulating cam  54  during rotation of the die regulating cam  54 . 
     The die drive cam  38 , upper ram drive cam  43 , feeder drive cam  48 , and die regulating cam  54  are connected to a main shaft  59  located in the lower portion of the frame  2 . The main shaft  59  is rotated by a drive motor  60 . As the main shaft  59  is rotated by the drive motor  60 , those cams  38 ,  43 ,  48 , and  54  rotate in synchronization. The cams  38 ,  43 ,  48 , and  54  are constructed, for example, of plate cams or split cams. 
     As the die drive cam  38  rotates with rotation of the main shaft  59 , the lever  39  rocks, so that the frame body  21  vertically moves in a state in which each air cylinder  42  is reciprocating. The vertical motion of the frame body  21  results in vertically moving each rod  6  connected through the connecting member  20  to the frame body  21 , and then vertically moving the die  9  relative to the lower punches  13  in conjunction therewith. As the upper ram drive cam  43  rotates with rotation of the main shaft  59 , the lever  44  rocks, so that the frame body  19  vertically moves in a state in which each air cylinder  47  is reciprocating. The vertical motion of the frame body  19  results in vertically moving the upper ram  4  through each rod  18  connected to the frame body  19 , and then vertically moving the upper punches  16  in conjunction therewith. As the feeder drive cam  48  rotates with rotation of the main shaft  59 , the lever  49  rocks in a state in which the air cylinder  53  is reciprocating, and the feeder  11  anteroposteriorly moves on the die  9  through the link  52 . As the die regulating cam  54  rotates with rotation of the main shaft  59 , the lever  55  rocks in a state in which the air cylinder  58  is reciprocating, and each stopper  26  vertically moves. 
     Shapes of the die drive cam  38 , upper ram drive cam  43 , feeder drive cam  48 , and die regulating cam  54  are defined according to the cam curve diagram (diagram indicating motions of the cams) as shown in  FIG. 11 . The die drive cam  38  has a shape according to a cam curve R of a solid line shown in  FIG. 11 . The upper ram drive cam  43  has a shape according to a cam curve S of a chain line shown in  FIG. 11 . The feeder drive cam  48  has a shape according to a cam curve T of a coarsely dashed line shown in  FIG. 11 . The die regulating cam  54  has a shape according to a cam curve U of a densely dashed line shown in  FIG. 11 . The horizontal axis of  FIG. 11  represents angles of rotation from a reference position (0°), and the vertical axis of  FIG. 11  represents the height positions of the cams  38 ,  43 , and  54  and the anteroposterior position of the cam  48 . The scale of the cam curves of the cams  38 ,  43 , and  54  is different from that of the cam curve of the cam  48 . 
     Specifically, the die drive cam  38  has such a shape as to finely raise the die  9  from its initial height position in a region of about 10° to 20° with respect to the reference position, stop the die  9  in a region of about 20° to 55°, raise the die  9  in a region of about 55° to 90°, stop the die  9  in a region of about 90° to 110°, slightly lower the die  9  in a region of about 110° to 125°, stop the die  9  in a region of about 125° to 190°, slightly lower the die  9  in a region of about 190° to 220°, stop the die  9  in a region of about 220° to 295°, lower the die  9  to the initial height position in a region of about 295° to 330°, and stop the die  9  in a region from about 330° to the reference position. 
     The initial height position of the die  9  is such a height position that the upper ends of the lower punches  13  put into the cavities  10  slightly project out from the upper surface of the die  9 , as shown in  FIG. 12 . The die driving system  34  is configured, as shown in  FIG. 13 , so that when the die drive cam  38  finely raises the die  9  from the initial height position in the region of about 10° to 20° with respect to the reference position, the upper ends of the lower punches  13  move into the cavities  10 . 
     The upper ram drive cam  43  has such a shape as to fully raise the upper punches  16  from its initial height position in a region from the reference position to 45°, stop the upper punches  16  in a region of about 45° to 115°, fully lower the upper punches  16  in a region of about 115° to 190°, stop the upper punches  16  in a region of around 190°, further lower the upper punches  16  in a region of about 190° to 225°, stop the upper punches  16  in a region of about 225° to 275°, slightly raise the upper punches  16  in a region of about 275° to 295°, stop the upper punches  16  in a region of about 295° to 330°, and raise the upper punches  16  to the initial height position in a region from about 330° to the reference position. 
     The feeder drive cam  48  has such a shape as to move the feeder  11  forward from its initial position in a region from the reference position to about 15°, stop the feeder  11  in a region of about 15° to 25°, further move the feeder  11  forward in a region of about 25° to 60°, repeat fine forward and backward motions of the feeder  11  in a region of about 60° to 105°, fully move the feeder  11  backward in a region of about 105° to 165°, stop the feeder  11  in a region of about 165° to 345°, and move the feeder  11  forward to the initial position in a region from about 345° to the reference position. 
     The feeder driving system  36  is configured, as shown in  FIG. 12  (D), so that when the feeder drive cam  48  rotates about 15°-25° from the reference position, the feeder  11  stops just before the cavities  10 . 
     The die regulating cam  54  has such a shape as to stop the stoppers  26  at their initial height position in a region from the reference position to 90°, lower the stoppers  26  in a region of about 90° to 115°, stop the stoppers  26  in a region of about 115° to 155°, raise the stoppers  26  to the initial height position in a region of about 155° to 180°, and stop the stoppers  26  in a region from about 180° to the reference position. 
     Although the cams  38 ,  43 ,  48 , and  54  are depicted in a circular shape as simplified in  FIGS. 6 to 10 , it is needless to mention that the actual shapes of the cams  38 ,  43 ,  48 , and  54  are the special shapes including curve portions and straight portions. 
     Next, a procedure of performing molding by means of the molding apparatus  1  constructed as described above will be described based on  FIGS. 12 to 17 .  FIG. 17  is a diagram showing the actual operation of the die  9  by a chain double-dashed line W in the cam curve diagram shown in  FIG. 11 . 
     It is assumed herein that the height position of the contact member  24  is preliminarily adjusted by the adjustment handle  27  so that the pad plate  25  of the contact member  24  butts the stoppers  26  at a point of about 100° rotation of the main shaft  59  (cams  38 ,  43 ,  48 , and  54 ) from the reference position (cf.  FIGS. 11 and 17 ). Compacts are made every cycle of a rotation of cams  38 ,  43 ,  48 , and  54 . 
     In a state in which the cams  38 ,  43 ,  48 , and  54  are at the reference position, as shown in  FIG. 12  (A), the die  9 , upper punches  16 , feeder  11 , and stoppers  26  are located at the initial setting position where compacts  61  obtained in a previous cycle are pushed out of the die  9 . Namely, the die  9  is located at such a height position that the upper ends of the lower punches  13  put into the cavities  10  slightly project out from the upper surface of the die  9 . This makes it possible to readily and securely take out the compacts  61  obtained in the previous cycle, from the cavities  10 . The upper punches  16  are located at a height position a predetermined distance apart from the die  9 . The feeder  11  is located at a position a predetermined distance away backward from the cavities  10  on the die  9 . The compacts  61  made in the previous cycle are mounted on the lower punches  13 . 
     As the cams  38 ,  43 ,  48 , and  54  start rotating from the initial state in the predetermined direction, the upper punches  16  rise as shown in  FIG. 12(B)  and the feeder  11  moves forward toward the cavities  10  on the die  9  as shown in  FIG. 12(C) . As the cams  38 ,  43 ,  48 , and  54  are further rotated, the feeder  11  temporarily stops just before the cavities  10 , as shown in  FIG. 12(D) , and the die  9  is raised a little, as shown in  FIG. 13(A) , to pull the upper ends of the lower punches  13  slightly into the cavities  10  (cf. A in  FIG. 17 ). 
     This prevents the feeder  11  from touching the compacts  61  and the upper ends of the lower punches  13 , and thus can prevent damage to the compacts  61  and lower punches  13 . After the compacts  61  are pushed out of the cavities  10 , the compacts  61  swell by virtue of a spring back phenomenon. Therefore, even after the upper ends of the lower punches  13  are pulled into the cavities  10 , the compacts  61  are kept from returning into the cavities  10  in accordance with the operation of the lower punches  13 , and the compacts  61  are thus left as mounted over the cavities  10  on the die  9 . 
     With further rotation of the cams  38 ,  43 ,  48 , and  54 , as shown in  FIGS. 13(B)  and (C), the feeder  11  again moves forward on the die  9  to push the compacts  61  made in the previous cycle. Since at this time the lower punches  13  are kept below the upper surface of the die  9 , the feeder  11  will never collide with the lower punches  13 . Since the feeder  11  is arranged to temporarily stop immediately before contact with the compacts  61  as described above, the speed of the feeder  11  is fully kept down upon contact with the compacts  61  after resumption of forward movement of the feeder  11 . For this reason, the feeder  11  imposes no excess impact on the compacts  61  and the feeder  11  smoothly pushes the compacts  61 . This can prevent damage to the compacts  61  or the like. 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 13(D) , the feeder  11  further moves forward on the die  9  to move the compacts  61  away from the cavities  10 . Then the feeder  11  stops at the position where it covers the cavities  10  (cf. B in  FIG. 17 ). Since the cavities  10  are constantly covered by the compacts  61  and feeder  11  in this manner, little air enters the cavities  10 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 14(A) , the die  9  is raised to a predetermined height position and the material powder J is drawn and filled from the feeder  11  into the cavities  10  (cf. B in  FIG. 17 ). Since at this time the feeder  11  is kept at a standstill, the material powder J is supplied straight down into the cavities  10 . In addition thereto, the feeder  11  is continuously subjected to shaking operation, i.e., fine forward and backward motions of the feeder  11  (cf. C in  FIG. 17 ). Therefore, it is feasible to efficiently and uniformly fill the material powder J into the cavities  10 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, the stoppers  26  are lowered. Since at this time the die  9  is at a standstill, the stoppers  26  come to butt the contact member  24 . For this reason, the die  9  is switched from the operation according to the motion of the die drive cam  38 , into an operation according to the motion of the die regulating cam  54 . Therefore, as shown in  FIG. 14(B) , the die  9  is lowered according to the downward motion of the stoppers  26  in a state in which the contact member  24  butts the stoppers  26 . This carries out an overfill operation of the material powder J (cf. D in  FIG. 17 ). 
     The overfill operation is a filling operation to fill the material powder J in a state in which a powder fill depth of the cavities  10  is preliminarily kept large, thereafter lower the die  9  so as to slightly decrease the powder fill depth of the cavities  10 , and push an excess amount of the material powder J back to the feeder  11 . An overfill amount corresponds to a lowered distance X of the die  9  at that time (cf.  FIG. 17 ). By executing this overfill operation, it becomes feasible to reduce voids upon filing of the material powder J into the cavities  10  and to densely fill the material powder J into the cavities  10 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 14(C) , the feeder  11  moves backward away from the cavities  10 , thereby performing a striking operation of the material powder J. Furthermore, the upper punches  16  start to be lowered. 
     Then the stoppers  26  begin to be raised after a lapse of a predetermined time, whereupon the die  9  is raised while the contact member  24  is kept in contact with the stoppers  26 , as shown in  FIG. 14(D) . The die regulating cam  54  is formed so that the stoppers  26  move away from the contact member  24  after a rise of a predetermined distance. For this reason, the die  9  returns from the operation according to the motion of the die regulating cam  54 , again into the operation according to the motion of the die drive cam  38  to become at a standstill. This results in carrying out an underfill operation of the material powder J (cf. D in  FIG. 17 ). 
     The underfill operation is a filling operation to raise the die  9  after completion of the filling of the material powder J into the cavities  10 , and thereby to lower the material powder J below the upper surface of the die  9 . An underfill amount corresponds to a rise distance Y of the die  9  at that time (cf.  FIG. 17 ). By executing this underfill operation, the material powder J can be prevented from flowing over the cavities  10 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 15(A) , the upper punches  16  enter the cavities  10  and then the upper punches  16  temporarily stop in a state in which the upper struck level of the material powder J coincides with the lower end faces of the upper punches  16  (cf. E in  FIG. 17 ). At this time, since the aforementioned underfill operation creates a space in the upper portion of each cavity  10  (cf. FIG.  14 (D)), it becomes easier for the upper punches  16  to enter the cavities  10 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 15(B) , the die  9  is lowered while the upper punches  16  are also lowered, thereby effecting compacting of the material powder J by the upper punches  16  and the lower punches  13  (simultaneous pressing up and down) (cf. F in  FIG. 17 ). At this time, it is desirable to set the lowering speed of the upper punches  16  larger than the lowering speed of the die  9 . 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 15(C) , the die  9  and upper punches  16  both stop for a predetermined time to maintain the pressing state of the material powder J by the upper punches  16  and the lower punches  13  (pressing hold) (cf. G in  FIG. 17 ). At this time, since the supply pressure of the pressurizing air cylinder  17  by the cylinder driver  63  is smaller than the compacting pressure by the upper punches  16  and the lower punches  13 , the piston rod  17   a  of the pressurizing air cylinder  17  is in a most contracted state. The pressing hold time is desirably a time enough to stabilize the shape, size, etc. of the compacts obtained from the compacted material powder J. 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 15(D) , the pressing state switches from the pressing of the material powder (compacts) J by the upper punches  16  into pressing of the compacts J by the pressurizing air cylinder  17 . Specifically, the upper ram  4  is slightly raised by the upper ram drive cam  43  (cf. H in  FIG. 17 ). At this time, the pressurizing air cylinder  17  is driven by the cylinder driver  63  so as to urge the upper punches  16  under a predetermined pressure against the compacts J. Namely, the piston rod  17   a  of the pressurizing air cylinder  17  is expanded with the rise of the upper ram  4 , so that the upper punches  16  may be kept at the same height position. By pressing the compacts J by the pressurizing air cylinder  17  in this manner, it becomes feasible to prevent damage to the compacts J or the like due to strain caused by the compacting of the material powder J. 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 16(A) , the rise operation of the upper ram  4  is stopped while the compacts J are continuously pressed by the pressurizing air cylinder  17 . As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIGS. 16(B)  and (C), a hold down operation is carried out while the compacts J are further kept in the pressed state by the pressurizing air cylinder  17 . Namely, the die  9  is lowered to the aforementioned initial setting position, whereby the compacts J are pushed out of the die  9  (cf. H in  FIG. 17 ). At this time, the pressure exerted on the compacts J by the pressurizing air cylinder  17  (hold pressure) is a pressure smaller than the compacting pressure on the compacts J. 
     As the cams  38 ,  43 ,  48 , and  54  are further rotated in the same direction, as shown in  FIG. 16(D) , the upper punches  16  are raised with a rise of the upper ram  4  to move away from the compacts J. The above completes one cycle of molding operation. 
     By stopping the rise operation of the upper ram  4  and carrying out the hold down operation while the upper punches  16  are pressed against the compacts J by the pressurizing air cylinder  17  as described above, it is feasible to suppress pressure variation due to expansion (displacement) of the piston rod  17   a  of the pressurizing air cylinder  17 . For this reason, the hold pressure is stabilized, so that excellent moldability can be assured. As a result, without need for provision of a special complicated mechanism or for execution of cumbersome electric control, the compacts J can be securely pushed out from the cavities  10  of the die  9 , while preventing damage to the compacts J or the like and keeping the hold pressure constant. 
     In the molding operation by the molding apparatus  1 , where the height position of the contact member  24  is changed by the adjustment handle  27 , the cam curve U of the die regulating cam  54  is vertically shifted on the cam curve diagram (cf.  FIGS. 11 and 17 ), relative to the cam curve R indicating the motion of the die drive cam  38 . This changes a displacement amount before the contact member  24  comes into contact with the stoppers  26 , and, in other words, it changes the timing when the contact member  24  comes into contact with the stoppers  26 . Since the shape of the cam curve U itself is kept unchanged, the change of the timing alters the displacement amount after the contact of the contact member  24  with the stoppers  26 . Therefore, it changes the overfill amount (cf. X in  FIG. 17 ) and the underfill amount (cf. Y in  FIG. 17 ) at that time, so as to vary the filling amount of the material powder J into the cavities  10 . 
     Incidentally, the rotating speed of the main shaft  59  (cams  38 ,  43 ,  48 ,  54 ) needs to be raised in order to increase the efficiency of production of compacts. At this time, where a time for one rotation of the main shaft  59  is set sufficiently short, e.g., about 0.75 sec (80 rpm), it is difficult to achieve the aforementioned operation of the die  9  by the die drive cam  38  only. The reason is that the downward and upward motions of the die  9  are continuously carried out within an extremely short time during the execution of the overfill operation shown in  FIG. 14(B)  and the underfill operation shown in  FIG. 14(D)  and thus high-speed rotation of the die drive cam  38  will result in causing wavelike shakes (overshoot) in the motions of the die  9 . This overshoot results from the fact that the cam follower  41  leaves the die drive cam  38  at an unintended timing and the die  9  fails to follow the motion of the die drive cam  38 . 
     The present embodiment is provided with the contact member  24  and stoppers  26  for regulating the upward movement of the die  9 , and the stopper driving system  37  having the die regulating cam  54  for vertically moving the stoppers  26 . The contact member  24  is kept in contact with the stoppers  26  during execution of the overfill operation and underfill operation, whereby the die  9  is forcibly lowered, stopped, and raised in accordance with the motion of the die regulating cam  54 . Since the die  9  is moved up and down by the combination of the die drive cam  38  with the die regulating cam  54  as described above, the die  9  rarely overshoots even during rotation of the main shaft  59  at high speed, and the die  9  operates according to the preset motions. This allows the continuous overfill and underfill operations to be carried out at high speed in a cycle. 
     The present embodiment is provided with the adjustment handle  27  and the adjusting mechanism  28  for adjusting the height position of the contact member  24 . By manually operating the adjustment handle  27 , it is feasible to readily adjust the filling amount of the material powder J into the cavities  10 . 
     The present invention is by no means limited to the above embodiment. For example, the above embodiment showed the molding form by the so-called withdrawal method of fixing the lower punches  13  to the frame  2  and vertically moving the die  9  relative to the frame  2 , but the present invention is not limited to it. It is also possible to adopt a configuration wherein the die  9  is fixed to the frame  2  and wherein the lower punches  13  are vertically moved relative to the frame  2 . The point is that the die  9  is arranged to be vertically movable relative to the lower punches  13 . 
     The above embodiment is provided with the adjustment handle  27  and the adjusting mechanism  28  for adjusting the height position of the contact member  24 , but the present invention is not limited to this. It is also possible to adjust the filling amount of the material powder J into the cavities  10 , by adjusting the height position of the stoppers  26  instead of the contact member  24 . The stoppers  26  may be located below the contact member  24  as long as the die  9  is operated so as to carry out the aforementioned overfill and underfill operations. 
     The above embodiment was arranged to fix the die drive cam  38 , upper ram drive cam  43 , feeder drive cam  48 , and die regulating cam  54  to the main shaft  59  and to rotate the main shaft  59  by the drive motor  60 , but the present invention is not limited to this. It is also possible to rotate the die drive cam  38 , upper ram drive cam  43 , feeder drive cam  48 , and die regulating cam  54  by respective different drive motors. In this case, the drive motors need to be controlled so as to rotate these cams  38 ,  43 ,  48 , and  54  in synchronism. 
     The molding apparatus  1  of the above embodiment is provided with a plurality of cavities  10  formed in the die  9  and with a plurality of upper punches  16  and lower punches  13  corresponding thereto, but the present invention is not limited to this. It is needless to mention that the present invention is also applicable to a molding apparatus provided with an upper punch  16  and lower punch  13  one each. 
     From the invention thus described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.