Patent Publication Number: US-7720565-B2

Title: Ring management system

Description:
This application is a Divisional of application Ser. No. 10/475,143, filed on Nov. 26, 2003 now U.S. Pat. No. 7,251,545, and for which priority is claimed under 35 U.S.C. §120. Application Ser. No. 10/475,143 is the national phase of PCT International Application No. PCT/JP02/02247 filed on Mar. 11, 2002 under 35 U.S.C. §371, which also claims priority to Application No. 2001-122208 filed in Japan on Apr. 20, 2001, Application No. 2001-167296 filed in Japan on Jun. 1, 2001, Application No. 2001-167297 filed in Japan on Jun. 1, 2001, and Application No. 2001-194668 filed in Japan on Jun. 27, 2001 under 35 U.S.C. §119. The entire contents of each of the above-identified applications are hereby incorporated by reference. 

   TECHNICAL FIELD 
   The present invention relates to a ring management system for a plurality of rings having elasticity in the radius direction for layered ring configuration. 
   BACKGROUND ART 
   A non-stage speed change gear (CVT) belt used for a speed change gear in an automobile and the like includes a plurality of endless metal rings (hereinafter, referred to simply as “rings”) layered in the thickness direction. Each ring is manufactured to have a different circumferential length and thickness preset according to its layer. These rings are selected, combined, and produced into a layered ring. 
   Each of the rings is produced so as to satisfy the size of each layer but actual size may be slightly different from the set values. Combination of such rings may not produce a layered ring of high quality. 
   Rings are firstly measured in size and then placed on a storage shelf or the like. According to the measurement values, rings to be combined are selected. The selected rings are taken out of the storage shelf and layered, thereby obtaining a layered ring of high quality. 
   Conventionally, measurement of the plurality of rings, storage of the rings after the size measurements, selection of rings, and ring layering have been separately performed and each step or transition therebetween has been performed by a corresponding staff. Difference in quality of the staff work fluctuates production efficiency and quality of the layered rings. 
   DISCLOSURE OF THE INVENTION 
   It is therefore an object of the present invention to provide a ring management system capable of improving production efficiency and quality of layered rings. 
   A ring management system according to a first embodiment of the present invention comprises size measurement means for measuring size of the ring, first convey means for moving the ring whose size has been measured by the size measurement means, first storage means having a plurality of storage positions for storing rings conveyed in by the first convey means, second convey means for conveying out the rings from the first storage means, and control means including memory means for storing for each of the rings, size measured by the size measurement means in association with the storage position in the first storage means, first selection means for selecting a ring for constituting a stacked ring according to the ring size stored in the memory means, and first instruction means to instruct the second convey means so as to convey out the ring selected by the first selection means from the storage position in the first storage means corresponding to the size of the ring stored by the memory means. According to this invention, the size measurement means, the first convey means, the first storage means, and the second convey means perform ring size measurement, convey for storage, storage, and convey for stacking. This eliminates difference in work quality of each working staff and can improve stacked ring production efficiency and quality. 
   Moreover, rings to constitute a stacked ring are selected by the first selection means according to the size measured by the size measurement means. Then, a ring stored at a storage position in association with the ring size stored by the memory means is conveyed out by the second convey means and stacked for a stacked ring. Thus, a plurality of rings constituting a most appropriate combination are selected and accurately taken out of the first storage means, thereby producing a high-quality stacked ring. 
   Moreover, the ring management system according to the first embodiment further comprises third convey means for conveying rings out of the first storage means, and second storage means having a plurality of storage positions for storing rings conveyed in by the third convey means, wherein the control means further includes second selection means for selecting a ring whose storage time in the first storage means reaches a predetermined time or more or having identical sizes at a predetermined number or more of places from rings being stored in the first storage means, and second instruction means for instructing the third convey means to convey out the ring selected by the second selection means from the storage position in the first storage means stored in association with the ring storage time or size and convey it into the second storage means. 
   According to this invention, it is possible to eliminate a situation that the same ring is stored in the first storage means for a time exceeding a predetermined time or too many rings having identical size are stored in the first storage means. Thus, it is possible to suppress reduction of the selection range of the convey-in position of the ring in the first storage means and eliminate stagnation of convey of the ring into the first storage means. 
   Furthermore, the ring management system according to the first embodiment of the present invention further comprises: fourth convey means for conveying rings from the second storage means, wherein the memory means stores for each of the rings, the size measured by the size measurement means in association with the storage position in the second storage means, in case rings stored in the first storage means cannot be selected, the first selection means selects a ring from the rings stored in the second storage means so as to constitute a stacked ring, and the first instruction means instructs the fourth convey means to convey out the ring selected by the first selection means from the storage position in the second storage means stored in association with the size of the ring by the memory means. 
   According to the present invention, when it is impossible to select an appropriate ring to constitute a stacked ring from the first storage means, the ring is selected and conveyed out from the rings stored in the second storage means. 
   Moreover, in the ring management system according to the first embodiment of the present invention, the size measurement means., the convey means, and the storage means include holding means for holding a circular ring in substantially elliptic shape. 
   According to the present invention, ring size is measured while a ring is maintained in the substantially elliptic shape and deformation in the radius direction of the ring by the restoration elasticity is suppressed. This increases the size measurement accuracy. Moreover, after the size measurement, the ring is conveyed and stored while maintaining the substantially elliptic shape. This eliminates the situation that the ring in the substantially elliptic shape is deformed by its restoration elasticity in an unpredicted direction to contact with and damage something or to be damaged itself. Furthermore, the ring is handled as “a substantially elliptic work having a constant width in the short-axis direction” regardless of the difference in ring size. Accordingly, holding means handling this work have common specifications in constituting the convey means and storage means, thereby enabling substitution and flexibility. 
   In order to produce a high-quality stacked ring, it is necessary to select appropriate rings to constitute the stacked ring and it is necessary to accurately measure the circumferential length and thickness of the rings as the selection condition. 
   To cope with this, the size measurement means includes a pair of rollers arranged with rotation shafts parallel to each other and the shaft-to-shaft distance can be changed, circumferential length measuring means for measuring the circumferential length of a ring through the shaft-to-shaft distance of the pair of rollers while driving to rotate the ring hung over the pair of rollers and given a predetermined tension by the increase of the shaft-to-shaft distance of the rollers, thickness measurement means for measuring thickness of the ring hung over the pair of rollers and given a predetermined tension at an intermediate position between the rollers. 
   In the size measurement means constituting the ring management system of the present invention, firstly, a ring is hung over a pair or rollers and the shaft-to-shaft distance of the rollers is increased to apply a predetermined tension to the ring. The ring is driven to rotate by the pair of rollers and the ring circumferential length is measured according to the shaft-to-shaft distance of the pair of rollers. 
   Next, rotation of the pair of rollers is stopped and the ring thickness is measured by the thickness measurement means while applying a predetermined tension to the ring. Thus, by measuring the thickness while applying a predetermined tension to the ring, bending of the ring is prevented and it is possible to appropriately measure the thickness. Moreover, since it is possible to measure thickness of a plurality of rings under the common condition, it is possible to obtain ring measurement data appropriately used when deciding stacking order of the rings. Furthermore, it is possible to measure the ring circumferential length and ring thickness continuously with a high efficiency. 
   Moreover, the thickness measurement means includes a pair of contacts arranged at the inner circumferential side and the outer circumferential side of a ring hung over the pair of rollers in such a manner that they can advance/retrieve so as to be in abutment with each other, and contact advance/retrieve means for bringing the contacts into abutment with the inner circumferential surface and the outer circumferential surface of the ring, and means for measuring the thickness of the ring hung over the pair of rollers by a displacement of a contact with respect to the other contact. 
   According to the present invention, it is possible to measure a ring thickness only by measuring displacement of one of the contacts with respect to the other contact. Thus, with a simple configuration, it is possible to perform a highly accurate measurement. 
   Upon size measurement, thermal expansion or shrinkage may be caused in one or two of the rollers due to heat generated by driving of the rollers or the ambient temperature. When the ring outer circumferential length is measured based on the shaft-to-shaft distance between the rollers, there may be involved a large measurement error affected by the temperature. 
   To cope with this, the ring management system further comprises temperature measurement means for measuring temperature of at least one of the rollers, and data correction means for correcting measurement data obtained by the circumferential length measurement means and the thickness measurement means, according to the temperature measured by the temperature measurement means. 
   According to the present invention, the measurement data obtained by the circumferential measurement means and the thickness measurement means which have been affected by thermal expansion or shrinkage caused in one or two of the rollers due to heat generated by driving of the rollers or the ambient temperature can be corrected according to the temperature of at least one of the rollers. Accordingly, even when the temperature of one of the rollers fluctuates and measurement values fluctuate because of the thermal expansion and shrinkage, it is always possible to obtain accurate measurement data. 
   In order to reduce the convey space of a plurality of rings, a plurality of rings aligned in the lateral direction (ring radius direction) are preferably aligned in the vertical direction (ring axis direction). In this case, for example, after each ring is sandwiched by robot arms, robot arms can move vertically and horizontally. However, the robot arms require a comparatively large space for movement. Moreover, the ring convey requires a comparatively long time, lowering the work efficiency. For this, aligning means requiring a small drive space and capable of rapidly converting aligning direction of a plurality of rings is desired. 
   To cope with this, the ring management system according to the first embodiment of the present invention, further comprises aligning means for aligning in the perpendicular direction, a plurality of rings which have been measured in size and aligned in the horizontal direction before being conveyed into the first storage means by the first convey means, the aligning means including horizontal aligning means having a plurality of holding means for holding a plurality of rings arranged in the horizontal direction, perpendicular aligning means having a plurality of holding means for holding a plurality of rings arranged in the perpendicular direction, convey means for moving the perpendicular aligning means in the aligning direction of a plurality of rings by the horizontal aligning means and lifting up so that the holding means of the perpendicular aligning means successively oppose to the holding means of the horizontal aligning means, moving means for successively moving a plurality of rings held by the holding means of the horizontal aligning means onto the holding means of the perpendicular aligning means in synchronization with the movement of the perpendicular aligning means by the convey means, and convey-out means for conveying out the plurality of rings held by the holding means of the perpendicular aligning means while maintaining the arrangement in the perpendicular direction. 
   According to this invention, firstly, rings aligned in the horizontal direction by the horizontal aligning means are successively moved onto the holding means of the perpendicular aligning means which gradually rises up while moved in the lateral direction by the moving means. Thus, the plurality of rings which have been aligned in the horizontal direction are aligned in the perpendicular direction by the perpendicular aligning means. Thus, aligning of a plurality of rings can easily be converted from the horizontal direction to the perpendicular direction. 
   Moreover, the ring management system according to the first embodiment of the present invention further comprises perpendicular aligning means for aligning in the perpendicular direction a plurality of rings aligned in the horizontal direction before being conveyed into the first storage means by the first convey means after the size measurement by the size measurement means, the aligning means including a plurality of holding means arranged in the horizontal direction for holding a plurality of rings, moving means for successively moving one holding means immediately below another holding means, so that the plurality of holding means arranged in the horizontal direction are aligned in the perpendicular direction, and convey-out means for conveying out the rings held by the plurality of holding means arranged in the perpendicular direction while maintaining the state aligned in the perpendicular direction. 
   According to the present invention, a plurality of rings are firstly aligned in the horizontal direction by being held by a plurality of holding means arranged in the horizontal direction. Then, the moving means moves one of the holding means immediately below another holding means and thus successively moves the holding means, thereby arranging the plurality of holding means in the perpendicular direction. Thus, the plurality of rings aligned in the perpendicular direction. That is, moving of the holding means can rapidly converts the ring alignment direction, thereby improving work efficiency. 
   Moreover, the aligning means includes a slider for moving one holding means toward another holding means, a support member which can be lifted up and down along a guide rod extending from the slider and having holding means at the upper portion thereof, urging means for urging the support member upward, an inclined portion provided on the support member and is gradually inclined downward toward the other holding means, and a cam roller for pressing the support member against the urging force by the urging means via the inclined portions as the slider moves, so as to guide one holding means immediately below the other holding means. 
   According to the present invention, only by moving a holding means at the upstream side by the slider toward the holding means at the downstream side, the inclined portion and the cam roller are brought into sliding abutment, so as to lower the holding means of the upstream side via the support member. Thus, it is possible to smoothly move the other holding means from the upstream side to immediately below the other holding means at the downstream side. This simplifies the system configuration and rapidly converts the ring alignment direction. 
   In order to solve the aforementioned problems, a ring management system according to a second embodiment of the present invention comprises size measurement means for measuring size of a ring by hanging the circular ring over a pair of rollers whose shaft-to-shaft distance can be changed so that the ring is in the substantially elliptic shape, first convey means for moving the ring removed from the pair of rollers, while sandwiching the ring by sandwiching means so as to maintain the substantially elliptic shape of the ring which tends to return to circular shape, first storage means having a plurality of storage positions for storing rings conveyed in by the first convey means and released from the sandwiching means of the first convey means while regulating the ring tending to return to a circular shape from the substantially elliptic shape in the short-axis direction with regulating means, and second convey means for conveying out the rings from the first storage means by releasing the ring from the regulating means of the first storage means by sandwiching the ring and reducing the sandwiching interval while maintaining the substantially elliptic shape with sandwiching means. 
   According to the present invention, ring size is measured while the ring is maintained in the substantially elliptic shape and deformation in the radius direction of the ring by the restoration elasticity is suppressed. Accordingly, it is possible to increase the size measurement accuracy. 
   Moreover, after the size measurement, the ring is conveyed and stored while maintaining the substantially elliptic shape. Accordingly, it is possible to prevent a situation that the ring in the substantially elliptic shape is deformed in an unexpected direction by its restoration elasticity to contact with and damage something or to be damaged itself. 
   Furthermore, the ring is handled as “an substantially elliptic work having a constant width in the short-axis direction” regardless of the difference in ring size. Accordingly, holding means handling this work have common specifications in constituting the convey means and storage means, thereby enabling substitution and flexibility. 
   Moreover, the size measurement means, the first convey means, the first storage means, and the second convey means perform a series of procedures including the ring size measurement, convey for storage, storage, and convey for stacking. This eliminates the difference of work caused by different working staffs and can improve the stacked ring production efficiency and quality. 
   Moreover, the ring management system according to the second embodiment of the present invention further comprises third convey means for releasing a ring stored in the substantially elliptic shape in the first storage means, from the regulating means of the first storage means by sandwiching the ring and reducing the sandwiching interval with sandwiching means and conveying the ring while maintaining the substantially elliptic shape, and second storage means having a plurality of storage positions for storing rings and released from the sandwiching means of the third convey means while regulating the ring tending to return to a circular shape from the substantially elliptic shape in the short-axis direction with regulating means. 
   Furthermore, the ring management system according to the second embodiment of the present invention further comprises fourth convey means for conveying out the rings from the second storage means by releasing the ring from the regulating means of the second storage means by sandwiching the ring and reducing the sandwiching interval while maintaining the substantially elliptic shape with sandwiching means. 
   Moreover, the ring management system according to the second embodiment of the present invention further comprises hanging means, wherein the circular ring is sandwiched by sandwiching means so as to be in the substantially elliptic shape whose long-axis direction is matched with the roller-from-roller departing direction of the size measurement means and the ring is conveyed outside of this pair of rollers, and the size measurement means releases the ring conveyed outside the rollers by the hanging means, from the sandwiching means of the hanging means by increasing the shaft-to-shaft distance of the rollers, so that the ring is hung over the rollers. 
   Furthermore, the ring management system according to the second embodiment of the present invention further comprises removal means for removing the ring from the pair of rollers, which ring tends to return to the circular shape from the substantially elliptic shape with reduction of the shaft-to-shaft distance of the pair of rollers of the size measurement means, by sandwiching the ring in the short-axis direction, so as to maintain the substantially elliptic shape. 
   Moreover, in the ring management system according to the second embodiment of the present invention further comprises aligning means for aligning the rings in the horizontal direction while regulating the ring, which tends to return to the circular shape from the substantially elliptic shape after being removed form the pair of rollers of the size measurement means, in its short-axis direction and keeping its substantially elliptic shape with first regulating means, and conveying the ring after releasing the rings from the first regulating means by sandwiching the ring aligned in the horizontal direction in the substantially elliptic shape and reducing the sandwiching interval with sandwiching means, and aligning the rings in the horizontal direction while keeping their substantially elliptic shapes after releasing the rings from the sandwiching means by regulating the ring, which tends to return to the circular shape from the substantially elliptic shape when the sandwiching interval of the sandwiching means is increased, in its short-axis direction with second regulating means, wherein the first convey means convey the ring while keeping its substantially elliptic shape, after releasing the rings, which have been aligned in the horizontal direction by the aligning means, from the second regulating means of the aligning means by sandwiching the rings and reducing the sandwiching interval with sandwiching means. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  explains a configuration of the ring management system according to an embodiment of the present invention. 
       FIG. 2  explains an essential portion of an induction unit. 
       FIG. 3  is a front view of a size measurement unit. 
       FIG. 4  is a side view of the size measurement unit. 
       FIG. 5  explains ring thickness measurement method in the size measurement unit. 
       FIG. 6  and  FIG. 7  explains configuration of an aligning unit. 
       FIG. 8  explains operation of the aligning unit. 
       FIG. 9  explains an essential portion of a first and a second convey unit. 
       FIG. 10  explains configuration of the first and second convey units and a first stocker. 
       FIG. 11  and  FIG. 12  explain function of the ring management system. 
       FIG. 13  and  FIG. 14  explain an aligning unit according to a second embodiment. 
       FIG. 15  and  FIG. 16  explain operation of the aligning unit according to the second embodiment. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   Description will now be directed to a ring management system according to an embodiment of present invention with reference to the attached drawings. The ring management system shown in  FIG. 1  includes: a conveyer belt  50 ; an induction unit  100 ; a size measurement unit  200 ; an aligning unit  300 ; a first convey unit  400 , a first stocker (first storage means)  500 ; a second convey unit  600 ; a second stocker (second storage means)  700 ; a stacking unit  800 ; a conveyer belt  850 ; and a control unit  900 . 
   The conveyer belt  50  conveys a plurality of rings w in the original substantially elliptic shape in lateral direction (radius direction) (indicated by arrow  1  in  FIG. 1 ). 
   As shown in  FIG. 2 , the induction unit  100  includes: a rail  102  extending in the convey direction of the ring w; a frame  104  movable along the rail  102 ; a pair of right and left sandwiching means  110  movable together with the frame  104 . The sandwiching means  110  includes: two pairs of claws  112  opposing to each other; a cylinder  116  for horizontally moving the claws  112  via a rod  114  in a vertical direction against the opposing direction; and a rotary actuator  118  for rotating the cylinder  116  in a direction vertical to the axial direction. By the induction unit  100 , the ring w which tends to return to a substantially circular shape is regulated by the opposing two pairs of claws  112  and sandwiched in the substantially elliptic shape. 
   The induction unit  100  places the ring w conveyed by the conveyer belt  50  on a pair of rollers  210  and  220  of the size measurement unit  200  as substantially elliptic “hanger means” (arrow  2  in  FIG. 1 ). Moreover, the induction unit  100  removes the ring w from the pair of rollers  210  and  220  as “removal means” while maintaining the substantially elliptic shape and transports it to the aligning unit  300  (arrow  3  in  FIG. 1 ). 
   Now explanation will be given on the configuration of the size measurement unit  200  with reference to  FIG. 3  and  FIG. 4 . 
   The size measurement unit  200  as the “circumferential length measurement means” of the ring w includes: a drive roller  210 ; a follower roller  220  placed below and in parallel to the drive roller  210 ; a first displacement sensor  230  for outputting a signal according to a displacement amount of the follower roller  220  in the perpendicular direction; and calculation means  231  consisting of a CPU and the like measuring the circumferential length (inner circumferential length)  1  of the ring w according to the output signal from the first displacement sensor  230 . 
   The drive roller  210  has its shaft supported via a bracket  212  by a column  204  extending from a basement  202 . The drive roller  210  is driven to rotate by a drive motor  214  (drive means) provided at the back of the column  204 . The bracket  212  has an upper limit switch (not depicted). Above a bearing block  216  of the drive roller  210 , there is provided a temperature sensor  218  for outputting a signal according to the temperature of the drive roller  210  measured via the bearing block  216 . 
   The follower roller  220  is shaft-supported by the bracket  222 . The bracket  222  is engaged with two rail members  206  vertically extending on the column  204  via an engagement member  224  so as to be slidable along the rail members  206 . Moreover, the bracket  222  is lifted up by a cylinder  228  via a rod.  226  connected to the lower portion thereof. Furthermore, the bracket  222  applies by its weight, tension to the ring w hung over pair of the rollers  210  and  220 . The rail member  206  has a lower limit switch  208  at a lower portion thereof. 
   The first displacement sensor  230  has expandable contact  232 . The contact  232  is in abutment with the lower portion of the bracket  222  on a perpendicular line including the axial center of the drive roller  210  and the axial center of the follower roller  220 . The contact  232  is urged in the direction of the bracket by urging means (not depicted) such as a spring member and the tip end of the contact  232  is displaced together with the bracket  222 . 
   Moreover, the size measurement unit  200  includes as the “thickness measurement means” of the ring w: an inner contact  240  to oppose to inner circumferential surface of the ring w hung over both the rollers  210  and  220  and an outer contact  250  to oppose to the outer circumferential surface of the ring w hung over both the rollers  210  and  220 ; a second displacement sensor  260  for outputting a signal according to a displacement amount of the outer contact  250 ; and calculation means  261  composed of a CPU or the like for measuring the thickness t of the ring w according to the output signal from the second displacement sensor  260 . 
   Inner contact  240  is horizontally driven by the cylinder  242 . The outer contact  250  is horizontally driven by the second displacement sensor  260 . 
   The size measurement unit  200  measures the circumferential length of the ring w hung over the pair of rollers  210  and  220  in the substantially elliptic shape according to displacement during rotation of the rollers  210  and  220 . Moreover, the size measurement unit  200  measures the thickness of the ring w hung over the pair of rollers  210  and  220  in the substantially elliptic shape. It should be noted that here the “circumferential length” of the ring w is a length along the inner circumferential length of the ring w, i.e., “inner circumferential length”. 
   Explanation will be given on configuration of the aligning unit  300  with reference to  FIG. 6  and  FIG. 7 . 
   The aligning unit  300  includes first holding means  310  and second holding means  320  as configuration of “horizontal aligning means”. Moreover, the aligning unit  300  includes perpendicular aligning means  330 . The perpendicular aligning means  330  has upper holding means  331  and lower holding means  332  for aligning rings w in a perpendicular direction. 
   Furthermore, the aligning unit  300  includes first moving means  340  and second moving means  350  for moving the ring w held by the first holding means  310  and the second holding means  320  onto the upper holding means  331  and the lower holding means  332  of the perpendicular aligning means  330 ; and convey-out means  360  for conveying out a pair of rings w aligned in a perpendicular direction by the perpendicular aligning means  330 . 
   The first holding means  310  and the second holding means  320  respectively have plates  314  and  324  where the ring w is placed and regulating means  312  and  322  for regulating the ring w placed on the plates  314  and  324  from both sides into an substantially elliptic shape. 
   The first moving means  340  has a pair of arms  344  for sandwiching the ring w in the substantially elliptic shape via a plurality of claws  342  positioned between regulating means  312  of the first holding means  310 . Moreover, the first moving means  340  includes a cylinder  346 . By this cylinder  346 , advance/retrieval is performed with respect to the perpendicular aligning means  330  guided by the rail provided on a table  301 . 
   The second moving means  350 , almost identically to the first moving means  340 , includes a pair of arms  354  at a changeable distance for sandwiching the ring w as in the substantially elliptic shape via a plurality of claws  352  positioned between the regulating means  322  of the second holding means  320 . Moreover, the second moving means  350  includes a cylinder  356 . By this cylinder  356 , advance/retrieval is performed with respect to the perpendicular aligning means  330  guided by the rail  358  provided on the table  301 . 
   The upper holding means  331  and the lower holding means  332  of the perpendicular aligning means  330  respectively include regulating means  333  and  334  for regulating the ring w into the substantially elliptic shape from both sides. 
   In the aligning unit  300  for moving the perpendicular aligning means  330 , there are provided a first inclined guide portion  335  inclined left-upward and a second inclined guide portion  336  in parallel to the first inclined guide portion  335  on an intermediate table  302 . The first inclined guide portion  335  has a first slider  337  moving along the inclination and the first slider  337  is connected to the perpendicular aligning means  330 . The second inclined guide portion  336  has a second slider  338  moving along the inclination and the second slider  338  is connected to the first inclined guide portion  335 . 
   The convey-out means  360  is composed of upper convey means  361  and lower convey means  362 . The upper convey means  361  and lower convey means  362  have a pair of arms  364  at a changeable distance for sandwiching the ring w in the substantially elliptic shape via a plurality of claws  363 . Moreover, the convey-out means  360  has a cylinder  366 . By this cylinder  366 , advance/retrieval is performed with respect to the perpendicular aligning means  330  guided by the rail  368  provided on the table  301 . 
   After the size measurement by the size measurement unit  200 , the aligning unit  300  aligns the ring w (arrow  3  in  FIG. 1 ) transported by the induction unit  100 , in the substantially elliptic shape in the lateral direction. Moreover, the aligning unit  300  vertically aligns the rings w aligned in the lateral direction in the substantially elliptic shape. 
   As shown in  FIG. 9A  and  FIG. 9B , the first convey unit  400  includes first sandwiching means  410  for sandwiching the ring w at a changeable distance via the pair or arms  412  having a claw portions  414 . Moreover, as shown in  FIG. 10 , the first convey unit  400  includes: first horizontal drive means  420  for horizontally driving the first sandwiching means  410 ; first perpendicular drive means  430  for perpendicularly driving the first sandwiching means  410  and the first horizontal drive means  420  along a first columnar member  402  extending outside the outer circumference of the first stocker  500 ; and first rotation means  440  for rotating the first columnar member  402  around its axis. 
   The first convey unit  400  transports the ring w from the aligning unit  300  by sandwiching the ring w by the first sandwiching means  410  in the substantially elliptic shape (arrow  4  in  FIG. 1 ). The first sandwiching means  410  is driven in the perpendicular direction and the horizontal direction while sandwiching the ring w in its substantially elliptic shape and conveying into the first stocker  500  (arrow  5  in  FIG. 1 ). 
   As shown in  FIG. 10 , the first stocker  500  is substantially cylindrical and has a plurality of storage chambers  502  partitioned in a circumferential direction and axial direction and having an open outer circumference. The first stocker  500  can be rotated around its axis by the first rotation means  510 . Each of the storage chambers  502  has regulating means  504  (see  FIG. 1 ) for regulating the ring w from both sides so as to prevent returning to circular shape. The first stocker  500  stores a plurality of rings w conveyed by the first convey unit  400  while regulating the rings w by the regulating means  504  so as to be in the substantially elliptic shape. 
   The second convey unit  600  has configuration identical to the first convey unit  400 . The second convey unit  600  sandwiches the ring w by the second sandwiching means  610  and conveys the ring in the substantially elliptic shape from the first stocker (arrow  6  in  FIG. 1 ). Moreover, the second convey unit  600 , as the “third convey means” of the present invention sandwiches the ring w by the second sandwiching means  610  and conveys the rings in its substantially elliptic shape out of the first stocker  500  and conveys the rings into the second stocker  700  (arrow  6 ′ in  FIG. 1 ). Furthermore, the second convey unit  600  as the “fourth convey means” of the present invention sandwiches the ring w by the second sandwiching means  610  and conveys the ring w in its substantially elliptic shape out of the second stocker  700  (arrow  6 ″ in  FIG. 1 ). The second convey means  600  temporarily stores the plurality of rings w conveyed out of the first stocker  500  or the second stocker  700  according to the stacking order and transports them to the stacking unit  800  (arrow  7  in  FIG. 1 ). 
   The second stocker  700  has configuration almost identical to that of the first stocker  500 . The second stocker  700  is rotated around its axis by the second rotation means  710 . Moreover, the second stocker  700  stores a plurality of rings w conveyed in by the second convey unit  600  while regulating the rings w from both sides so as to maintain the substantially elliptic shape. 
   In the stacking unit  800 , a plurality of rings w returned to the substantially circular shape are stacked to form a stacked rings R which are transported to the conveyer belt  850  (arrow  8  in  FIG. 1 ). 
   The conveyer belt  850  conveys the stacked rings R formed by the stacking unit  800  outside (arrow  9  in  FIG. 1 ). 
   The control unit  900  is composed of a personal computer and a computer program for exhibiting various functions including the ring w management is installed. The control unit  900  includes: a timer  906 ; memory means  908 ; first selection means  910 ; first instruction means  912 ; second selection means  920 ; and second instruction means  922 . 
   The timer  906  measures storage time τ of each of the rings w in the first stocker  500 . 
   The memory means  908  stores for each of the rings w: a circumferential length  1  and thickness t, storage time τ measured by the timer  906 , and storage position in the first stocker  500  and the second stocker  700 . 
   The first selection means  910  selects a ring w according to the circumferential length  1  and the thickness t stored in memory means  908  so as to obtain a most appropriate combination. The first instruction means  912  instructs the second convey unit  600  to transport the ring w selected by the first selection means  910  to the stacking unit  800  and gives various instructions to the respective units which will be detailed later. 
   The second selection means  920  selects a ring w to be transported from the first stocker  500  to the second stocker  700  according to the storage time τ and the size (1, t) of the ring w stored in the memory means  908 . The second instruction means  922  instructs to transport the ring w selected by the second selection means  920  from the first stocker  500  to the second stocker  700 . 
   Explanation will be given on the function of this system having the aforementioned configuration with reference to  FIG. 1  to  FIG. 12 . Only main signals and data transmitted and received between the units will be explained below. However, other data and signals according to the communication protocol and the program language used in this system may also be transmitted and received. 
   Firstly, induction unit  100  sandwiches a substantially circular ring w conveyed by the conveyer belt  50 , so as to be in the substantially elliptic shape. More specifically, the sandwiching means  110  is moved above the conveyer belt  50  together with the frame  104  along the rail  102  shown in  FIG. 2 . Moreover, the cylinder  116  is rotated by the rotary actuator  118  so that the claw portion  112  is directed downward. Here, the ring w is pushed in the horizontal direction by the sandwiching means (not depicted) at the end portion of the conveyer belt  50 , so as to have the substantially elliptic shape. The cylinder  116  lowers the claw portion  112  to the position of the ring w via the rod  114 . Here, the pushing by the sandwiching means at the end portion of the conveyer belt  50  is released and the ring w tends to return to the circular shape but is regulated by the claw portion  112  in the short-axis direction and sandwiched while maintaining the substantially elliptic shape. Moreover, since the claw portion  112  is lifted up by the cylinder  116 , the ring w is lifted up from the conveyer belt  50  (dotted line in  FIG. 2 ). 
   Next, the induction unit  100  sandwiching the ring w in the substantially elliptic shape by the sandwiching means is transported to the size measurement unit  200  (arrow  1  in  FIG. 1 ). More specifically, the sandwiching means  110  is moved together with the frame  104  along the rail  102  shown in  FIG. 2  up to a position opposing to the pair of rollers  210  and  220  of the size measurement unit  200 . Moreover, the rotary actuator  118  rotates the cylinder  116  so that the cylinder  116  is substantially horizontal and the claw portion  112  opposes to the pair of rollers  210  and  220 . 
   Next, the size measuring unit  200  measures the circumferential length  1  and thickness t of the ring w. The measurement procedure will be explained with reference to  FIG. 3  to  FIG. 5 . 
   Firstly, the cylinder  228  drives upward the bracket  222  and the follower roller  220 . When an upper portion of the bracket  222  is brought into abutment with the lower limit switch  208 , the cylinder  228  stops. Here, the claw portion  112  is driven forward via the rod  114  by the cylinder  116  of the induction unit  100  so that the ring w is positioned outside of the pair of rollers  210  and  220  while maintaining the substantially elliptic shape. 
   Next, upward urging by the cylinder  206  is released and the bracket  222  lowers by its weight together with the follower roller  220  along the rail member  224 . Here, the ring w becomes prolonged substantially elliptic shape and released from the claw portion  112  of the sandwiching means  110  of the induction unit  100  and becomes tense. The sandwiching means  110  of the induction unit  100  is driven rearward by the cylinder  116 . 
   Subsequently, the drive roller  210  is rotated by the drive roller  214  and the ring w is rotated. Here, the first displacement sensor  230  transmits an output signal according to a displacement amount of the follower roller  220  (i.e., displacement amount of the contact  232  with respect to the highest position of the bracket  222 ) to the calculation means  231 . Moreover, the temperature sensor  218  transmits an output signal according to the temperature of the drive roller  210  to the calculation means  231 . The calculation means  231  calculates the circumferential length (inner circumferential length)  1  of the ring w from the diameters of the rollers  210  and  220  and the shaft-to-shaft distance between the rollers  210  and  220  according to the output signal from the first displacement sensor  930 . Moreover, the calculation means  231  corrects the circumferential length  1  of the ring w according to the output signal from the temperature sensor  218 . 
   This reduces the measurement error due to thermal expansion of the drive roller  210 , thereby accurately measuring the circumferential length  1  of the ring w. Moreover, since the contact  232  is provided on a line connecting the axis of the drive roller  210  and the follower roller  220 , the displacement of the follower roller  220  can be accurately detected. It should be noted that displacement of the follower roller  220  may be continuously measured during rotation of the ring w, so as to use the amplitude average during the constant rotation of the ring w as a displacement amount. In this case, the circumferential length  1  of the ring w can be measured more accurately. 
   Next, the drive motor  214  is stopped, rotation of the drive roller  210  is stopped, and the thickness of the ring w tense with the weight of the bracket  222  is measured. That is, firstly, as shown in  FIG. 5A , the cylinder  242  is driven to bring the inner contact  240  into abutment with the inner circumferential surface the ring w. Here, the abutment weight is preferably about 100 g which does not deform the ring w. 
   Next, as shown in  FIG. 5B , the second displacement sensor  260  drives the outer contact  250  into abutment with the outer circumference of the ring w. Here, the second displacement sensor  260  transmits an output signal according to a displacement amount of the outer contact  250  to the calculation means  261 . Moreover, the temperature sensor  218  transmits an output signal according to the temperature of the drive roller  210  to the calculation means  261 . According to the output signal from the second displacement sensor  260 , the calculation means  261  measures the thickness t of the ring w. Moreover, according to the output signal from the temperature sensor  218 , the calculation means  261  corrects the thickness t of the ring w. It should be noted that it is also possible that the ring w is successively rotated by a predetermined angle by the drive roller  210  and thickness values at a plurality of positions are used to obtain an average thickness t. 
   Moreover, the measurement data concerning the circumferential length li and the thickness ti measured and corrected by the calculation means  231 ,  261  are transmitted from the size measurement unit  200  to the control unit  900  (arrow d 1  in  FIG. 11 ). 
   After measurement of the circumferential length  1  and the thickness t, the ring w is transported by the sandwiching means  110  of the induction unit  100  while maintaining the substantially elliptic shape into the aligning unit  300  (arrow  3  in  FIG. 1 ). More specifically, the claw portion  112  is driven forward by the cylinder  116  shown in  FIG. 2  up to the position outside the ring w hung over the pair of rollers  210  and  220 . After this, the shaft-to-shaft distance between the pair of rollers  210  and  220  is reduced, thereby releasing tension and the ring w tends to return to substantially circular shape but is regulated by the claw portion  112  in the short axis direction. Thus, the claw portion  112  sandwiching the ring w in the substantially elliptic shape is driven backward by the cylinder  116  and the cylinder  116  is rotated downward by the rotary actuator  118 . The claw portion  112  is moved together with the frame  104  along the rail  102  upward of the plates  314  and  324  of the aligning unit  300  (virtual line in  FIG. 7 ). 
   Next, rings w aligned in the horizontal direction by the aligning unit  300  are aligned in a perpendicular direction. This aligning procedure will be explained with reference to  FIG. 6  to  FIG. 8 . 
   Firstly, ring w which has been transported by the sandwiching means  110  of the induction unit  100  is placed on the plates  314  and  324 . Then, the holding distance of the sandwiching means  110  is enlarged and the ring w tending to return to the substantially circular shape is regulated by the regulating means  312  and  322  provided on the plates  314  and  324 . Thus, as shown in  FIG. 6 , a pair of rings w are aligned in the horizontal direction by the first holding means  310  and the second holding means  320  while maintaining the substantially elliptic shape. 
   Next, the first convey means  340  sandwiches the ring w held by the first holding means  310 , by the arm  344 . The arm  344  reduces the interval and the ring w becomes prolonged substantially elliptic shape and released from the regulating means  312 . The first moving means  340  is made to advance by the cylinder  346  and moves the ring w onto the upper holding means  331  of the perpendicular aligning means  330  (virtual line in  FIG. 6 ) while maintaining the substantially elliptic shape. Furthermore, the arm  344  increases the sandwiching interval, which regulates the ring w tending to return to the substantially circular shape in the short-axis direction with the regulating means  333  and held as the substantially elliptic shape by the upper holding means  331  as shown in  FIG. 8A . 
   Next, as shown in  FIG. 8B , the first slider  337  moves along the first inclined guide portion  335  and the perpendicular aligning means  330  is moved to the opposing position of the second moving means  350 . Thus, the perpendicular aligning means  330  is lifted up into the first inclined guide portion  335  and the lower holding means  332  opposes to the arm  354  of the second moving means  350 . 
   The second moving means  350  sandwiches by the arm  354 , the ring w held by the second holding means  320 . The arm  354  reduces its interval to prolong the substantially elliptic shape of ring w and the ring w is released from the regulating means  322 . The second moving means  350  is made to advance by the cylinder  356  and moves the ring w onto the lower holding means  332  of the perpendicular aligning means  330  while maintaining its substantially elliptic shape. Furthermore, the arm  354  enlarges the sandwiching interval, which regulates the ring w tending to return to the substantially circular shape, in the short-axis direction with the regulating means  334 . As shown in  FIG. 8B , the ring w is held in its substantially elliptic shape by the lower holding means  332  of the perpendicular aligning means  330 . Thus, a pair of rings w arranged in the horizontal direction on the first and the second holding means  310  and  320  are aligned in the perpendicular direction while maintaining the substantially elliptic shape. 
   Next, as shown in  FIG. 8C , the second slider  338  moves along the second inclined guide portion  336  and the perpendicular aligning means  330  is moved to the opposing position of the convey means  360 . The upper convey mean  361  and the lower convey means  362  of the convey means  360  sandwich a pair of rings w aligned in the perpendicular direction by the perpendicular aligning means  330 . The arm  364  reduces its interval to prolong the substantially elliptic shape of the ring w and the ring is released from the regulating means  333 ,  334 . The convey means  360  is made to advance by the cylinder  366  and conveys the rings w aligned in the perpendicular direction to the convey out section  370  while maintaining the substantially elliptic shape. 
   Thus, according to the aligning unit  300 , only by successively moving the rings w by the first moving means  340  and the second moving means  350  onto the perpendicular aligning means  330  gradually lifted up by the first inclined guide portion  335 , a pair of rings aligned in the horizontal direction is aligned in the perpendicular direction. 
   It should be noted that it is possible to additionally provide holding means other than the first and the second holding means  310  and  320 , moving means according to this holding means, holding means and convey means in the perpendicular aligning means  330 , so that three or more rings w aligned in the horizontal direction are aligned in the perpendicular direction. Moreover, as the mechanism to move the perpendicular aligning means  330 , the second inclined guide portion  336  and the second slider  338  may be omitted, and the first inclined guide portion  335  may be extended to extend the moving distance of the first slider  337 . 
   Next, the first instruction means  912  of the control unit  900  decides a storage position pi of the ring w in the first stocker  500  (s 1  in  FIG. 11 ). 
   Moreover, the first instruction means  912  transmits “first rotation data” according to the storage position pi to the rotation means  510  of the first stocker  500  (arrow d 2  in  FIG. 11 ). The rotation means  510  receives this data and rotates the first stocker  500  so that a storage chamber  502  located at the storage position pi opposes to the first convey unit  400 . 
   Furthermore, the first instruction means  912  transmits “first convey data” to the first convey unit  400  (arrow d 3  in  FIG. 11 ). The first convey unit  400  receives this data and sandwiches by the sandwiching means  410 , the rings w aligned in a vertical direction in the convey out section  370  of the aligning unit  300 . The sandwiching means  410  reduces its sandwiching interval (see  FIG. 9A  and  FIG. 9B ) and the ring w is released from the arm  364  of the convey-out means  360 . The ring is conveyed into the storage chamber  502  at the storage position pi of the first stocker  500  while maintaining the substantially elliptic shape (arrow  5  in  FIG. 1 ). With increase of the sandwiching interval of the sandwiching means  410 , the ring w tends to return to the substantially circular shape but is regulated in the short-axis direction by the regulating means  504  and stored in the storage chamber  502  at the storage position pi while maintaining the substantially elliptic shape. 
   Here, the timer  906  starts counting the storage time τi of the ring wi in the first stocker  500  (s 2  in  FIG. 11 ). Moreover, the memory means  908  stores for each of the rings wi: the circumferential length li, the thickness ti, the storage position pi in the first stocker  500 , and the storage time τi (s 3  in  FIG. 11 ). 
   Furthermore, the second selection means  920  selects a ring wk whose storage time τk exceeds a predetermined time τ (s 4  in  FIG. 11 ). Moreover, the second selection means  920  selects some of the number of rings wk stored in the first stocker  500  and having identical size (1, t) stored in the memory means  908  and exceeding a predetermined number n (s 5  in  FIG. 11 ). 
   Then, the second instruction means  922  decides the convey-in position qk of the ring wk selected by the second selection means  920 , in the second stocker  700  (s 6  in  FIG. 11 ). 
   Moreover, the second instruction means  922  transmits “third rotation data (part 1)” to the rotation means  510  of the first stocker  500 , according to the storage position pk of the ring wk in the first stocker  500  and the convey-in position qk into the second stocker  700  (arrow d 4  in  FIG. 3 ); transmits “third rotation data (part 2)” to the rotation means  710  of the second stocker  700  (arrow d 5  in  FIG. 3 ); and transmits “third convey data” to the second convey unit  600  (arrow d 6  in  FIG. 2 ). 
   The rotation means  510  receives the data and rotates the first stocker  500  so that the storage chamber  502  at the storage position pk opposes to the second convey unit  600 . Moreover, the rotation means  710  rotates the second stocker  700  so that the storage chamber  702  at the convey-in position qk opposes to the second convey unit  600 . The second convey unit  600  sandwiches the ring wk by the sandwiching means  610  and conveys it out of the storage position pk of the first stocker  500  while maintaining the substantially elliptic shape (arrow  6  in  FIG. 1 ). Moreover, the second convey unit  600  sandwiches the ring wk by the sandwiching means  610  and conveys it into the storage chamber  702  at the convey-in position qk of the second stocker  700  while maintaining the substantially elliptic shape (arrow  6 ′ in  FIG. 1 ). With increase of the sandwiching interval of the sandwiching means  610 , the ring wk tending to return to its substantially circular shape is regulated by the regulation means  704  in the short-axis direction and is released from the sandwiching means  610  so as to be stored in the second stocker  700  while maintaining the substantially elliptic shape. 
   Here, the memory means  908  stores the circumferential length li, thickness ti, the storage position pi of the ring wi in the second stocker  700  (s 7  in  FIG. 11 ). 
   Subsequently, the first selection means  910  selects a plurality of rings wj to constitute a most appropriate combination according to the circumferential length li and the thickness ti of the ring wi stored in the memory means  908  from the first stocker  500  (s 8  in  FIG. 12 ). 
   Then, the first instruction means  912  transmits “second rotation data” to the rotation means  510  of the first stocker  500  according to the storage position pj of the ring wj selected by the first selection means  910  (arrow d 7  in  FIG. 12 ). The rotation means  510  receives the data and rotates the first stocker  500  so that a storage chamber  502  containing the ring wj opposes to the second convey unit  600 . 
   Moreover, the first instruction means  912  transmits “second convey data” to the convey unit  600  according to the storage position pj of the ring wj (arrow d 8  in  FIG. 12 ). The convey means  600  receives the data and sandwiches the ring wj by the sandwiching means  610  and the sandwiching interval is reduced to prolong the substantially elliptic shape of the ring wj so as to be released from the regulating means+ 504  (see  FIG. 9A  and  FIG. 9B ). After this, the second convey unit  600  conveys out the ring wj from the storage position pj in the first stocker  500  while maintaining the substantially elliptic shape (arrow  6  in  FIG. 1 ) and conveys it to the stacking unit  800  (arrow  7  in  FIG. 1 ). 
   Moreover, when it is impossible to select all the rings w constituting a stacked ring in the first stocker  500 , the first selection means  910  selects a ring w appropriate to constitute the stacked ring R from the second stocker  700  according to the circumferential length lk and the thickness tk of the ring wk stored in the memory means  908  (s 9  in  FIG. 12 ). 
   The first instruction means  912  transmits “fourth rotation data” to the rotation means  710  according to the storage position qk of the ring wk selected by the first selection means, in the second stocker  700  arrow d 9  in  FIG. 12 . The rotation means  710  receives this data and rotates the second stocker  700  so that the storage chamber  702  containing the ring wk opposes to the second convey means  600 . 
   Moreover, the first instruction means  912  transmits “fourth convey data” to the second convey unit  600  according to the storage position qk of the ring wk (arrow d 10  in  FIG. 12 ). The second convey unit  600  receives this data, sandwiches the ring wk by the sandwiching means  610 , and reduces the sandwiching interval to prolong the substantially elliptic shape of the ring wj and release the ring wj from the regulating means  704 . Then, the second convey unit  600  conveys out the ring wk while maintaining the substantially elliptic shape from the storage position qj of the second stocker  700  (arrow  6 ″ in  FIG. 1 ) and conveys the ring to the stacking unit  800  (arrow  7  in  FIG. 1 ). 
   The stacking unit  800  stacks a plurality of rings w transported by the second convey unit  600  in the radius direction, so as to constitute a stacked ring R and conveys the stacked ring R to the conveyer belt  850  (arrow  8  in  FIG. 1 ). Thus, the stacked ring R is conveyed out by the conveyer belt (arrow  9  in  FIG. 1 ). 
   According to the ring management system of the present embodiment, with the help of the size measurement unit  200 , the first and second convey units  400  and  600 , the first or second stocker  500  or  700 , and the stacking unit  800 , a series of steps including the size measurement of the ring w, convey, storage, and stacking can be performed without trouble (arrows  1  to  9  in  FIG. 1 ). Accordingly, there is no trouble of difference in work quality depending on the working staffs and it is possible to improve the production efficiency and quality of the stacked ring R. 
   Moreover, ring wj constituting the stacked ring R is selected by the first selection means  910  according to the circumferential length lj and the thickness tj (size) measured by the size measurement unit  200 . Then, a ring in the storage position pj stored in the memory means  908  in association with the size of the ring wj is conveyed out by the second convey unit  600  and stacked. Accordingly, a plurality of rings wj constituting a most appropriate combination are selected and accurately taken out of the first stocker  500  or the second stocker  700 , thereby producing a high-quality stacked ring R. 
   Furthermore, the size measurement unit  200  measures the circumferential length  1  and the thickness t of the ring w which is kept in the substantially elliptic shape with suppressed deformation in the radius direction by the restoration elasticity. This can increase the size measurement accuracy. 
   Moreover, during a series of steps (arrows  2  to  7  in  FIG. 1 ), the ring w is continuously kept in the substantially elliptic shape. Therefore, the ring w which has been made substantially elliptic during the above serial steps is deformed in an unexpected direction by its restoration elasticity or scratched by contact with something. Furthermore, the ring w can be handled as “an substantially elliptic work having a constant width in the short-axis direction” regardless of the difference in the size (1, t) Accordingly, holding means handling this work have common specifications, under which the convey means and storage means are constituted, thereby enabling substitution and flexibility. 
   Moreover, it is possible to prevent that the same ring wk is stored in the first stocker  500  for a time exceeding a predetermined time τ or the first stocker contains more rings wk having the same size than a predetermined number n. This suppresses reduction of the selection width (s 1  in  FIG. 11 ) of the convey-in position pi of the ring wi in the first stocker  500  and prevents stagnation of the convey/convey-in of the ring wi (arrow  5  in  FIG. 1 ). 
   Moreover, when a ring wj appropriate for constituting the stacked ring R is not selected from the first stocker  500 , a ring w is selected from the second stocker  700 . 
   It should be noted that the first selection means  910  may select a ring wj conveyed out of the first stocker  500  so that the convey-in position pi of the ring wi in the first stocker  500  opposes to the convey-out position pj of the ring wj. 
   In this case, it is possible to simultaneously perform the convey-in of the ring wi into the convey-in position pi by the first convey unit  400  and the convey-out of the ring wj from the convey-out position pj by the second convey unit  600 , thereby increasing the production efficiency. 
   Moreover, the ring wj conveyed out from the first stocker  500  may be selected so that the opposing position of the convey-in position pi of the ring wi in the first stocker  500  is in the nearest position from the convey-out position pj of the ring wj in the circumferential direction. 
   There is also a case that the ring wi conveyed into the first stocker  500  and the ring wj conveyed out cannot be selected so that the convey-in position pi of the ring wi in the first stocker  500  opposes to the convey-out position pj of the ring wj. In this case after the ring wi is conveyed into the first stocker  500 , the first stocker  500  should be rotated when the ring wj is conveyed out. As the ring w conveyed out from the first stocker  500 , the ring wj at the nearest position to the opposing position of the convey-in position pi of the ring wi is selected as described above. For this, it is possible to minimize the rotation amount of the first stocker  500  during convey-out, thereby increasing the production efficiency of the stacked ring R. 
   It should be noted that in the aforementioned aligning unit  300 , the rings w are aligned in the perpendicular direction when the rings w are moved from the first holding means  310  and the second holding means  320  onto the upper holding means  331  and lower holding means  332  of the perpendicular aligning means  330 . As another configuration, rings w may be aligned in the perpendicular direction by arranging first holding means  310  and second holding means  320  from the horizontal direction to the perpendicular direction. Explanation will be given on aligning unit  300  having the other configuration with reference to  FIG. 13  to  FIG. 16 . Like components are denoted by like reference symbols and their explanations are omitted. 
   In the aligning unit  300  of the other configuration, the perpendicular aligning means  330 , the first moving means  340 , and the second moving means  350  are omitted. Moreover, a first guide portion  311  extends in a horizontal direction along the arrangement direction of the first holding means  310  and the second holding means  320  and a second guide portion  321  extends below the first guide portion  311  in parallel. The first guide portion  311  has a first slider  313  moving along the first guide portion  311 . The first slider  313  is connected to the first holding means  310 . The second guide portion  321  has a second slider  323  moving along the second guide portion  321 . The second slider  323  is connected to the first guide portion  311  and the second holding means  320 . 
   As shown in  FIG. 13  and  FIG. 14 , the first holding means  310  has a guide rod  317  extending downward via a support frame (support member)  315 . The guide rod  317  can come out of the first slider  313  and by this the support frame  315  can be lifted up and down. Moreover, the support frame  315  is urged upward by a spring member (urging means)  319 . Furthermore, on the support frame  315 , there is provided a cam member  318  having an inclined surface  316  gradually lowering toward the second holding means  320 . 
   As shown in  FIG. 14 , the second holding means  320  is connected to the second slider  323  via a support frame  325  through which the first holding means  310  can move. On the support frame  325 , there is provided a cam roller  326  sliding along an inclined surface  316  formed on the cam member  318 . 
   Explanation will be given on operation of the aligning unit  300  with reference to  FIG. 15  and  FIG. 16 . Firstly, a pair of rings w are arranged in the horizontal direction and regulated by the regulating means  312  and  322  and held by the first holding means  310  and the second holding means  320  while maintaining the substantially elliptic shape. 
   Next, as shown in  FIG. 15A , the first slider  313  moves along the first guide portion  311  and the first holding means  310  moves toward the second holding means  320 . Here, the cam roller  326  of the second holding means  320  slides along the inclined surface  316  formed on the cam member  318  of the first holding means  310 , and the support frame  315  of the first holding means  310  is relatively pushed downward. When the first slider  313  moves along the first guide portion  311 , as shown in  FIG. 15B , it goes below the first holding means  310  and the first holding means  310  is moved immediately below the second holding means  320 . Thus, the pair of rings w arranged in the horizontal direction are aligned in the perpendicular direction. 
   Subsequently, as shown in  FIG. 15C , the second slider  323  moves along the second guide portion  321 , and the holding means  310  and  320  are moved to the position opposing to the convey-out means  360  ( FIG. 13 ). An upper holding portion  361  and a lower holding portion  362  of the convey-out means  360  sandwich the pair of rings w held by the holding means  310  and  320  while maintaining the vertical arrangement and moves the rings w to the convey-out section  370  by the cylinder  366 . 
   Thus, by placing rings w in the holding means  310  and  320  moved in the horizontal direction by the first guide portion  311  and the second guide portion  321 , it is possible to align the pair of rings w arranged in the horizontal direction, in the perpendicular direction. It should be noted that in addition to the first holding means  310  and the second holding means  320 , it is possible to add another holding means according to the number of rings w, so that three or more rings arranged in the horizontal direction are aligned in the perpendicular direction.