Patent Publication Number: US-2018043489-A1

Title: Work conveying pallet

Description:
TECHNICAL FIELD 
     The present invention relates to a work conveying pallet which is conveyed to a work station by a pallet conveying apparatus while carrying a work. 
     BACKGROUND ART 
     Conventionally, a pallet conveying apparatus is known which mounts works to be processed on pallets and conveys the pallets together with the works in a manufacturing line. In the pallet conveying apparatus, a machine tool in a processing station at a conveyance destination performs a predetermined processing on the works mounted on the pallets. The present applicant proposed a pallet conveying apparatus for conveying a plurality of pallets (work conveying pallets) carrying works with respect to a processing station along a rectangular track (see, for example, JP2011-93032A). 
     The work conveying pallet conveyed by this pallet conveying apparatus includes a base in the form of a flat plate carrying a work, a linear motion block provided on the base and configured to be movable on a guide rail provided along a conveyance path and a locking member provided on one arbitrary surface of the base and to be locked to the pallet conveying apparatus. The pallet conveying apparatus for conveying such a pallet includes a toothed belt in which recesses and projections are alternately connected one after another in a longitudinal direction along the rail on which the pallet is movably mounted. The locking member of the pallet is formed with projections and recesses engageable with the recesses and projections of the toothed belt. The pallet is conveyed by circulating the toothed belt with the projections and recesses of the locking member engaged with the projections and recesses. 
     The pallet conveying apparatus having such a structure is for conveying the pallet along the rectangular track. When the toothed belt is circulated, the projections and recesses formed on the locking member of the pallet are engaged with the recesses and projections at an arbitrary position of the toothed belt. Thus, it can be expected to increase a work conveying speed and positioning accuracy while preventing a deviation of the pallet with respect to the toothed belt and easily change a pallet conveying pitch. 
     SUMMARY OF INVENTION 
     However, in the case of providing a plurality of types of work stations for performing different processings along the pallet conveyance path, a processing time for the work mounted on the pallet may differ in each work station. In the presence of a work station with a relatively long processing time, it is supposed to convey the pallets carrying the works along a rectangular track. In such a case, in the work station having a relatively long processing time, there is a trouble that congestion of the pallets finished with the processing in a relatively short processing time in a previous different work station is caused and efficient processing becomes difficult. 
     Thus, it is convenient if a single conveyance path along which another work station where processing is finished in a relatively short time is present can be connected to a plurality of conveyance paths along which work stations having a relatively long processing time are present. However, it is difficult to change the conveyance path of the pallets and connect the single conveyance path to a new conveyance path so as to collect the pallets in the single conveyance path. Further, there have been conventionally no such pallet conveying apparatuses. 
     Here, if the pallet conveying apparatus can easily change the pallet conveyance path, it is also possible to connect a single conveyance path to the plurality of conveyance paths. For example, it becomes also possible to convey a plurality of types of works having different contents of processing along a single conveyance path and, thereafter, sort them to a plurality of conveyance paths separately provided for each content of processing. Thus, the pallet conveying apparatus capable of easily changing the pallet conveyance path is preferable. 
     The present invention was developed, focusing on such a problem and aims to provide a work conveying pallet enabling a conveyance path to be easily changed. 
     According to one aspect of the present invention, a work conveying pallet includes a base in the form of a flat plate having front and back principal surfaces and a plurality of side surfaces, the front and back principal surfaces being configured to carry a work, a linear motion block provided on the base, the linear motion block being configured to move on a guide rail provided along a conveyance path, and locking members configured to be locked to a circulation belt of a pallet conveying apparatus, wherein the locking members are provided on at least two surfaces out of the front and back principal surfaces and the plurality of side surfaces of the base. 
     According to another aspect of the present invention, a pallet conveying apparatus for conveying the work conveying pallet includes a plurality of guide rails configured such that the work conveying pallet is movably mounted thereon, a pallet feeding part configured to convey the work conveying pallet along the plurality of guide rails, and a pallet moving part configured to move the work conveying pallet from one guide rail out of the plurality of guide rails to another guide rail, wherein the work conveying pallet feeding part includes a circulation belt having recesses and projections engageable with at least one locking member provided on the front and back principal surfaces and the plurality of side surfaces of the base of the work conveying pallet. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a work conveying pallet in a first embodiment of the present invention, 
         FIG. 2  is an enlarged view of a section C of  FIG. 5 , 
         FIG. 3  is a top view showing a first pallet conveying apparatus for conveying pallets, 
         FIG. 4  is an arrow view along line A-A of  FIG. 3 , 
         FIG. 5  is a sectional view along line B-B of  FIG. 3 , 
         FIG. 6  is a sectional view along line E-E of  FIG. 3 , 
         FIG. 7  is a sectional view along line F-F of  FIG. 3 , 
         FIG. 8  is a sectional view along line G-G of  FIG. 3 , 
         FIG. 9  is a sectional view along line H-H of  FIG. 3 , 
         FIG. 10  is a sectional view along line J-J of  FIG. 5 , 
         FIG. 11  is a top view showing a pallet conveying apparatus in a second embodiment of the present invention, 
         FIG. 12  is a sectional view along line K-K of  FIG. 11 , 
         FIG. 13  is a sectional view along line L-L of  FIG. 11 , 
         FIG. 14  is a sectional view along line M-M of  FIG. 11 , 
         FIG. 15  is a sectional view along line N-N of  FIG. 11 , 
         FIG. 16  is a perspective view showing a moving part for moving a work conveying pallet of the present invention while turning the work conveying pallet by 180°, 
         FIG. 17  is a perspective view, corresponding to  FIG. 16 , showing another moving part for moving the work conveying pallet of the present invention while turning the work conveying pallet by 180°, 
         FIG. 18  is a perspective view showing a moving part for obliquely moving the work conveying pallet of the present invention, and 
         FIG. 19  is a perspective view, corresponding to  FIG. 18 , showing a moving part for obliquely moving the work conveying pallet of the present invention while erecting the work conveying pallet. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one embodiment of the present invention is described with reference to the accompanying drawings. 
     First Embodiment 
     A work conveying pallet and a pallet conveying apparatus in a first embodiment of the present invention are described with reference to  FIGS. 1 to 10 . 
     A work conveying pallet  11  of the present embodiment includes, as shown in  FIGS. 1 and 6 , a base  13  in the form of a flat plate composed of front and back principal surfaces for carrying an unillustrated work and a plurality of side surfaces, linear motion blocks  12  provided on the base  13  and configured to be movable on a plurality of guide rails  21 ,  22 ,  121  and  122  provided along a conveyance path of a pallet conveying apparatus  10  to be described later, and locking members  14  to which later-described circulation belts  32 ,  132  of the pallet conveying apparatus  10  are to be locked. 
     Specifically, as further shown in  FIGS. 3 to 5 , the work conveying pallet  11  includes the linear motion blocks  12  configured to be movable on corresponding first to fourth guide rails  21 ,  22 ,  121  and  122  across linear motion guide rails  21   c ,  22   c ,  121   c  and  122   c , the base  13  screwed to the linear motion blocks  12  and a plurality of locking members  14  provided on the base  13 . 
     The linear motion blocks  12  may be commercially available ones sold together with the linear motion guide rails  21   c ,  22   c ,  121   c  and  122   c  and preferably include unillustrated roller retainers. By using the linear motion blocks  12  with the roller retainers, frictional resistance when the work conveying pallet  11  moves on the first to fourth guide rails  21 ,  22 ,  121  and  122  can be drastically reduced while movements of the linear motion blocks  12  in a width direction (Y-axis direction) and the inclination thereof with respect to each linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c  are prohibited. 
     A mounting tool  16  for mounting an unillustrated work is assumed to be provided on one side part of the base  13 . This mounting tool  16  is provided on the base  13  and used to stably mount the unillustrated work on the base  13 . This mounting tool  16  is used with the structure thereof appropriately changed depending on the type of the work to be mounted on the work conveying pallet  11  and desired to be processed. In the work conveying pallet  11  of the present embodiment, the linear motion blocks  12  are fixed to the other side part on a surface of the base  13  as shown in  FIG. 1 . 
     A characteristic configuration of the work conveying pallet  11  of the present embodiment is that the locking members  14  are provided on at least two surfaces out of the front and back principal surfaces and the plurality of side surfaces of the base  13 . Particularly, the locking members  14  are preferably provided on at least one surface out of the front and back principal surfaces and at least one of the plurality of side surfaces of the base  13 . 
     In the present embodiment, the locking members  14  of the work conveying pallet  11  are respectively provided on the both principal surfaces of the base  13  between the linear motion blocks  12  and the mounting tool  16  and both side surfaces facing in the Y-axis direction of the base  13 . Here, in the present embodiment, the locking members  14  provided on the both principal surfaces of the base  13  may be referred to as first locking members  14  and the locking members  14  provided on the both side surfaces of the base  13  may be referred to as second locking members  14 . 
     In the work conveying pallet  11  thus configured, the locking members  14  to which the circulation belts  32 ,  132  of the pallet conveying apparatus  10  are to be locked are provided on at least two surfaces out of the front and back principal surfaces and the plurality of side surfaces of the base  13 . Thus, the pallet conveying apparatus  10  can convey the work conveying pallet  11  while locking the work conveying pallet  11  on at least one or both of those two surfaces. Specifically, the work conveying pallet  11  can be locked by one locking member  14  and conveyed in one direction. In this state, the work conveying pallet  11  can also be locked by another locking member  14  and conveyed in another direction. 
     Thus, according to the work conveying pallet  11  of the present embodiment, the conveyance path can be easily changed as compared to conventional pallets provided with a locking member only on one arbitrary surface of a base, and a degree of freedom in designing the pallet conveying apparatus  10  for conveying the work conveying pallet  11  can be increased. 
     An example of the pallet conveying apparatus  10  for conveying the work conveying pallet  11  of the present embodiment is specifically shown in  FIGS. 3 to 10 . In each figure, three axes of X, Y and Z orthogonal to each other are set, wherein it is assumed that an X axis extends substantially in a horizontal lateral direction, a Y axis extends substantially in a horizontal front-back direction and a Z axis extends in a vertical direction. The configuration of the pallet conveying apparatus  10  is described below using X, Y and Z directions. 
     The pallet conveying apparatus  10  of the present embodiment conveys the work conveying pallet  11  carrying a work, stops the work conveying pallet  11  before machine tools  1  to  6  (see  FIG. 3 ) installed along a conveyance path thereof, and holds the work carried on that pallet  11  at predetermined positions. The pallet conveying apparatus  10  is used such as in the case of processing the work carried on the work conveying pallet  11  by those machine tools  1  to  6 . 
     It should be noted that the number of machine tools  1  to  6  (see  FIG. 3 ) differs depending on the content of works required to be processed, and the number of the work conveying pallets  11  conveyed at one time may be appropriately increased or decreased according to the number of the machine tools  1  to  6 . 
     As shown in  FIGS. 4 and 5 , the pallet conveying apparatus  10  of the present embodiment includes a plurality of guide rails  21 ,  22 ,  121  and  122  for movably mounting the work conveying pallets  11 . The plurality of guide rails  21 ,  22 ,  121  and  122  include a first guide rail  21 , a second guide rail  22 , a third guide rail  121  and a fourth guide rail  122 . 
     As shown in  FIG. 6 , a case where the pallet conveying apparatus  10  includes the first and third guide rails  21 ,  121  separated in the Y-axis direction and extending in parallel to each other in the X-axis direction and the second and fourth guide rails  22 ,  122  at a predetermined interval in the Z-axis direction from the first and third guide rails  21 ,  121  and provided in parallel to each other is shown in the present embodiment. 
     It should be noted that, in the first to fourth guide rails  21 ,  22 ,  121  and  122 , a positional relationship of the first and second guide rails  21 ,  22  or a positional relationship of the third and fourth guide rails  121 ,  122  is an upper-and-lower positional relationship if the Z-axis direction of  FIG. 3  is a vertical direction. Further, if the Y-axis direction is a facing direction, the first or second guide rail  21 ,  22  and the third or fourth guide rail  121 ,  122  are positioned on one side and on the other side. As just described, the first and third guide rails  21 ,  121  are provided substantially on the same plane and the second and fourth guide rails  22 ,  122  are provided substantially on the same plane. 
     In the present embodiment, the first guide rail  21  may be referred to as an “upper position on the one side”, the second guide rail  22  as a “lower position on the one side”, the third guide rail  121  as an “upper position on the other side” and the fourth guide rail  122  as a “lower position on the other side”. Further, the first and second guide rails  21 ,  121  may be referred to as an “upper position” and the second and fourth guide rails  22 ,  122  as a “lower position”. 
     Each of the second and fourth guide rails  22 ,  122  located below is for mounting the work conveying pallets  11  in a horizontal state. The second and fourth guide rails  22 ,  122  respectively include second and fourth supporting plates  22   b ,  122   b  directly fixed on a mount  9  and commercially available second and fourth linear motion guide rails  22   c ,  122   c  fixed to the upper edges of the second and fourth supporting plates  22   b ,  122   b  by screwing. 
     The first and third guide rails  21 ,  121  located above are for mounting the work conveying pallets  11  in a horizontal state similarly to the second and fourth guide rails  22 ,  122 . The first and third guide rails  21 ,  121  respectively include first and third supporting plates  21   b ,  121   b  provided side by side above the second and fourth supporting plates  22   b ,  122   b  via brackets  21   a ,  121   a  fixed onto the mount  9  and commercially available first and third linear motion guide rails  21   c ,  121   c  fixed to the upper edges of the first and third supporting plates  21   b ,  121  by screwing. 
     The first and third guide rails  21 ,  121  and the second and fourth guide rails  22 ,  122  are separated in the Y-axis direction at an interval larger than a length of each work conveying pallet  11  in the Y-axis direction, and respectively provided to extend in the X-axis direction in parallel to each other. 
     Here, the first to fourth linear motion guide rails  21   c ,  22   c ,  121   c  and  122   c  of the first to fourth guide rails  21 ,  22 ,  121  and  122  have the same shape. Thus, even if the work conveying pallet  11  mounted on any one of the first to fourth guide rails  21 ,  22 ,  121  and  122  is moved to and mounted on the other guide rail  21 ,  22 ,  121  or  122 , that work conveying pallet  11  is movable on this other guide rail  21 ,  22 ,  121  or  122 . 
     In the work conveying pallet  11  of the present embodiment, the linear motion blocks  12  are fixed to the one side part on the surface (back side in  FIG. 1 ) of the base  13  as shown in  FIG. 1 . Thus, by movably supporting the linear motion blocks  12  across any one of the corresponding first to fourth linear motion guide rails  21   c ,  22   c ,  121   c  and  122   c  of the first to fourth guide rails  21 ,  22 ,  121  and  122 , the work conveying pallet  11  is movably mounted on each guide rail  21 ,  22 ,  121 ,  122  in a horizontal state. 
     Referring back to  FIGS. 3 to 5 , the pallet conveying apparatus  10  includes first and second pallet feeding parts  31 ,  131  for conveying (moving) the work conveying pallets  11  respectively mounted on the first to fourth guide rails  21 ,  22 ,  121  and  122  along the first to fourth guide rails  21 ,  22 ,  121  and  122 . 
     The first pallet feeding part  31  provided to correspond to the first and second guide rails  21 ,  22  has the same structure as the second pallet feeding part  131  provided to correspond to the third and fourth guide rails  121 ,  122 . 
     Specifically, the first pallet feeding part  31  includes an endless first circulation belt  32  provided along the first and second guide rails  21 ,  22  and configured to circulate in a predetermined direction, and a first circulating mechanism  33  for circulating the first circulation belt  32 . Further, the second pallet feeding part  131  includes an endless second circulation belt  132  provided along the third and fourth guide rails  121 ,  122  and configured to circulate in a predetermined direction, and a second circulating mechanism  133  for circulating the second circulation belt  132 . 
     As shown in  FIGS. 4 and 5 , at least two supporting columns (not shown) are provided on each of the second and fourth supporting plates  22   b ,  122   b  of the second and fourth guide rails  22 ,  122 , and four driven pulleys  34 ,  134  are rotatably supported via these supporting columns. Each of the first and second circulation belts  32 ,  132  is mounted to enclose these four driven pulleys  34 ,  134 . 
     Further, as shown in  FIG. 6 , servo motors  33 ,  133 , which are first and second circulating mechanisms for circulating the first or second circulation belt  32 ,  132 , are respectively provided on the first and third supporting plates  21   b ,  121   b . Drive pulleys  35 ,  135  are respectively provided on rotary shafts  33   a ,  133   a  of the servo motors  33 ,  133 . 
     The drive pulley  35 ,  135  is provided on the same plane as the corresponding four driven pulleys  34 ,  134 . The servo motors  33 ,  133  are mounted on the first and second supporting plates  21   b ,  121   b  to turn the first or second circulation belt  32 ,  132  between a pair of vertically adjacent driven pulleys  34 ,  134  on one side and mount the first or second circulation belt  32 ,  132  on the drive pulleys  35 ,  135 . 
     When the servo motors  33 ,  133  are driven by a command from an unillustrated controller, the rotary shafts  33   a ,  133   a  rotate together with the drive pulleys  35 ,  135 . The first or second circulation belt  32 ,  132  mounted on the drive pulleys  35 ,  135  circulates while enclosing the four driven pulleys  34 ,  134 . 
     The first and second circulation belts  32 ,  132  provided to correspond to the first and second pallet feeding parts  31 ,  131  are so-called toothed belts having the same structure. The first and second circulation belts  32 ,  132  are such belts that recesses and projections  32   a ,  32   b ,  132   a ,  132   b , which are trough and crest parts extending in the width direction, are alternately connected in a longitudinal direction as shown in each enlarged view of  FIGS. 4 and 5 . The work conveying pallet  11  is formed with projections and recesses  14   a ,  14   b  engageable with the recesses and projections  32   a ,  32   b ,  132   a ,  132   b . The projections and recesses  14   a ,  14   b  are formed on the first locking members  14  constituting the work conveying pallet  11 . 
     The first locking members  14  are respectively provided on the both principal surfaces of the pedestal  13 . If the work conveying pallet  11  is mounted on the second or fourth guide rail  22 ,  122  located on a vertically lower side, the first locking members  14  provided on an upper side of the pedestal  13  are engaged with the first or second circulation belt  32 ,  132 . On the other hand, if the work conveying pallet  11  is mounted on the first or third guide rail  21 ,  121  located on a vertically upper side, the first locking members  14  provided on a lower side of the pedestal  13  are engaged with the first or second circulation belt  32 ,  132  similarly to the linear motion block  12 . As just described, the driven pulleys  34 ,  134  are provided at four corners of the second supporting plates  22   b ,  122   b  to circulate the first and second circulation belts  32 ,  132 . 
     Thus, the first to fourth guide rails  21 ,  22 ,  121  and  122  of this pallet conveying apparatus  10  are configured to include the first and third guide rails  21 ,  121  provided along the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  facing in one direction of the first and second circulation belts  32 ,  132 , i.e. facing upward and located on the vertically upper side and the second and fourth guide rails  22 ,  122  provided along the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  facing in a direction opposite to the one direction, i.e. facing downward in the present embodiment and located on the vertically lower side. 
     When the first locking members  14  of the work conveying pallet  11  come into contact with the first or second circulation belt  32 ,  132 , the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  formed on the first or second circulation belt  32 ,  132  are engaged with the projections and recesses  14   a ,  14   b  formed on the first locking members  14 . Further, when the first or second circulation belt  32 ,  132  sinks to be separated from the first locking members  14  along the driven pulley  34 ,  134 , the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  of the first or second circulation belt  32 ,  132  and the projections and recesses  14   a ,  14   b  of the first locking members  14  are disengaged. The pallet conveying apparatus  10  of the present embodiment is configured as just described. 
     Here, as shown in  FIGS. 4 and 5 , first and second supporting members  37 ,  137  for preventing the slack of the first and second circulation belts  32 ,  132  and the separation of the first and second circulation belts  32 ,  132  from the first locking members  14  are provided between the upper two driven pulleys  34 ,  134  and between the lower two driven pulleys  34 ,  134 . The first and second supporting members  37 ,  137  are mounted on the second supporting plates  22   b ,  122   b  via attachments  38 ,  138 . 
     As shown in the enlarged views of  FIGS. 4 and 5 , when the projections and recesses  14   a ,  14   b  of the first locking members  14  are engaged with the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  of the first or second circulation belt  32 ,  132 , a movement of the work conveying pallet  11  in the X-axis direction independent of the rotation of the first or second circulation belt  32 ,  132  is prohibited. Thus, when the first or second circulation belt  32 ,  132  having the work conveying pallet  11  engaged therewith is circulated, the work conveying pallet  11  moves together with the first or second circulation belt  32 ,  132 . In this way, the work conveying pallet  11  is conveyed along the first to fourth guide rail  21 ,  22 ,  121 ,  122  adjacent to the first or second circulation belt  32 ,  132 . 
     In the present embodiment, when the first or second circulation belt  32 ,  132  is circulated, the work conveying pallet  11  mounted on the first or third guide rail  21 ,  121  located on the vertically upper side and the work conveying pallet  11  mounted on the second or fourth guide rail  22 ,  122  located on the vertically lower side simultaneously move at the same speed in directions opposite to each other as shown by solid-line arrows of  FIGS. 4 and 5 . 
     As shown in  FIGS. 3 to 5 , First and second pallet moving parts  41 ,  141  are respectively provided at one end parts of the first to fourth guide rails  21 ,  22 ,  121  and  122  provided in parallel to each other. Further, third and fourth pallet moving parts  51 ,  151  are respectively provided at the other end parts of the first to fourth guide rails  21 ,  22 ,  121   122 . Fifth and sixth pallet moving parts  61 ,  161  are respectively provided at end parts of the third and fourth pallet moving parts  51 ,  151  opposite to the first to fourth guide rails  21 ,  22 ,  121   122 . 
     The first and second pallet moving parts  41 ,  141  provided at the one end parts of the first to fourth guide rails  21 ,  22 ,  121   122  lower the work conveying pallet  11  mounted on the first or third guide rail  21 ,  121  located above to the second or fourth guide rail  22 ,  122  located on the vertically lower side. Further, conversely, the first and second pallet moving parts  41 ,  141  may lift the work conveying pallet  11  mounted on the second or fourth guide rail  22 ,  122  to the first or third guide rail  21 ,  121 . It should be noted that the first and second pallet moving parts  41 ,  141  have the same structure. 
     As shown in  FIG. 7 , the first and second pallet moving parts  41 ,  141  in the present embodiment respectively include first and second short rails  42 ,  142  configured such that the work conveying pallet  11  is mountable thereon and first and second rail moving mechanisms  43 ,  143  for moving the first and second short rails  42 ,  142  upward or downward between an upper first position and a lower second position. The first position is a position connected to (on the same plane as) the linear motion guide rail  21   c ,  121   c  of the first or third guide rail  21 ,  121 . Further, the second position is a position connected to (on the same plane as) the linear motion guide rail  22   c ,  122   c  of the second or fourth guide rail  22 ,  122 . 
     The same rails as the linear motion guide rails  21   c ,  22   c ,  121   c    122   c  of the first to fourth guide rails  21 ,  22 ,  121   122  are used as the first and second short rails  42 ,  142 . A length W (see  FIG. 3 ) of the first or second short rail  42 ,  142  in the X-axis direction is equal to or longer than a length L (see  FIG. 1 ) of the work conveying pallet  11  in the X-axis direction. 
     The first or second short rail  42 ,  142  is configured to make the work conveying pallet  11  movable between the first or second short rail  42 ,  142  and the linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c  when the first or second short rail  42 ,  142  is connected to the linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c  of the first to fourth guide rail  21 ,  22 ,  121 ,  122 . Specifically, the work conveying pallet  11  separated from the first or second circulation belt  32 ,  132  and moved from the linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c  is mounted on the first or second short rail  42 ,  142 . Further, the first or second short rail  42 ,  142  is configured to make the work conveying pallet  11  mounted thereon movable to the linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c.    
     As shown in  FIGS. 3 to 5 and 7 , the first and second rail moving mechanisms  43 ,  143  for vertically moving such first and second short rails  42 ,  142  include first and second supporting plates  44 ,  144  (see  FIG. 1 or 7 ) having the first and second short rails  42 ,  142  respectively mounted on upper edges, and first and second Z-axis direction telescopic actuators  45 ,  145  for moving the first and second supporting plates  44 ,  144  in the Z-axis direction with respect to the mount  9 . 
     Each of the first and second Z-axis direction telescopic actuators  45 ,  145  is composed of a long and narrow box-shaped housing  45   d ,  145   d , a ball screw  45   b ,  145   b  provided to extend in a longitudinal direction inside the housing  45   d ,  145   b  and to be rotationally driven by servo motors  45   a ,  145   a , a follower  45   c ,  145   c  threadably engaged with the ball screw  45   b ,  145   b  and configured to parallelly move, and the like. The first and second Z-axis direction telescopic actuators  45 ,  145  are configured such that the follower  45   c ,  145   c  threadably engaged with the ball screw  45   b ,  145   b  is movable along the longitudinal direction (vertical direction) of the housing  45   d ,  145   d  when the servo motor  45   a ,  145   a  is driven to rotate the ball screw  45   b ,  145   b.    
     In the present embodiment, the first and second supporting plates  44 ,  144  provided with the first or second short rail  42 ,  142  are mounted on the followers  45   c ,  145   c  of the first and second Z-axis direction telescopic actuators  45 ,  145  to be movable in the Z-axis direction. The drive of the servo motors  45   a ,  145   a  of the first and second telescopic actuators  45 ,  145  is controlled by the unillustrated controller. Specifically, the servo motors  45   a ,  145   a  are connected to the controller, and the first and second rail moving mechanisms  43 ,  143  are configured to be able to move the first and second short rails  42 ,  142  upward and downward in the Z-axis direction together with the first and second supporting plates  44 ,  144  by driving the servo motors  45   a ,  145   a  by a command from the controller. 
     When the first or second short rail  42 ,  142  is connected to the first to fourth guide rail  21 ,  22 ,  121 ,  122 , the work conveying pallet  11  moving on the first to fourth guide rail  21 ,  22 ,  121 ,  122  is movable from the first to fourth guide rail  21 ,  22 ,  121 ,  122  to the first or second short rail  42 ,  142 . Thus, the first and second pallet moving parts  41 ,  141  respectively include first and second pallet locking mechanisms  46 ,  146  for limiting movements of the work conveying pallets  11  mounted on the first and second short rails  42 ,  142 . 
     The first and second pallet locking mechanisms  46 ,  146  are configured to be engageable with the work conveying pallets  11  mounted on the first and second short rails  42 ,  142  and respectively include endless first and second auxiliary belts  47 ,  147  provided to circulate along the first and second short rails  42 ,  142  and first and second auxiliary circulating mechanisms for circulating the first and second auxiliary belts  47 ,  147 . 
     Auxiliary pulleys  48 ,  148  on which the first and second auxiliary belts  47 ,  147  extending along the first and second short rails  42 ,  142  are respectively mounted are rotatably supported on one end parts of the first and second supporting plates  44 ,  144  in the X-axis direction. Further, auxiliary drive pulleys  49 ,  149  on which the first and second auxiliary belts  47 ,  147  are respectively mounted are rotatably supported on the other end parts of the first and second supporting plates  44 ,  144  in the X-axis direction. The first and second auxiliary circulating mechanisms are composed of servo motors  50 ,  150  (see  FIG. 3 ) respectively mounted on the first and second supporting plates  44 ,  144 . The auxiliary drive pulleys  49 ,  149  are mounted on rotary shafts  50   a ,  150   a  of the servo motors  50 ,  150 . The auxiliary drive pulleys  49 ,  149  are provided on the same planes as the auxiliary pulleys  48 ,  148  and, as shown in  FIGS. 4 and 5 , the first and second auxiliary belts  47 ,  147  are mounted on the auxiliary drive pulleys  49 ,  149  and the auxiliary pulleys  48 ,  148 . 
     When the servo motors  50 ,  150  are driven by a command from the unillustrated controller, the first and second auxiliary belts  47 ,  147  are respectively circulated along the first and second short rails  42 ,  142  via the auxiliary drive pulleys  49 ,  149  and the auxiliary pulleys  48 ,  148 . 
       FIG. 2  is an enlarged view of a section C of  FIG. 5  and shows the configuration on the side of the first short rail  42  in detail as a representative. The auxiliary belt  47  is a belt in which recesses and projections  47   a ,  47   b  having the same shapes as the recesses and projections  32   a ,  32   b  of the first circulation belt  32  and extending in the width direction are alternately connected in the longitudinal direction. The first auxiliary belt  47  is configured such that the recesses and projections  47   a ,  47   b  thereof are engageable with the projections and recesses  14   a ,  14   b  formed on the first locking members  14  provided on the same lower side as the linear motion block  12  of the work conveying pallet  11  when the work conveying pallet  11  is mounted on the first short rail  42 . Although not shown, the second auxiliary belt  147  is configured similarly to the first auxiliary belt  47  also on the side of the second short rail  142 . 
     Accordingly, when the first and second circulation belts  32 ,  132  and the first and second auxiliary belts  47 ,  147  are circulated at the same speed, the work conveying pallets  11  moving on the first and third guide rails  21 ,  121  or the second and fourth guide rails  22 ,  122  are movable to the first or second short rail  42 ,  142  connected to the first to fourth guide rail  21 ,  22 ,  121 ,  122 . Further, the work conveying pallet  11  mounted on the first or second short rail  42 ,  142  is lifted or lowered between the first or third guide rail  21 ,  22  located on the vertically upper side and the second or fourth guide rail  22 ,  122  located on the vertically lower side. 
     Referring back to  FIGS. 3 to 5 , the third and fourth pallet moving parts  51 ,  151  are respectively provided at the other end parts of the first to fourth guide rails  21 ,  22 ,  121   122 . The third and fourth pallet moving parts  51 ,  151  lift or lower the work conveying pallet  11  between the first and third guide rails  21 ,  121  and the second and fourth guide rails  22 ,  122  similarly to the first and second pallet moving parts  41 ,  141 . However, the third and fourth pallet moving parts  51 ,  151  are structured differently from the first and second pallet moving parts  41 ,  141 . 
     Specifically, as shown in  FIGS. 8 and 10 , the third and fourth pallet moving parts  51 ,  151  in the present embodiment respectively include third and fourth short rails  52 ,  152  configured such that the work conveying pallet  11  is mountable thereon, and third and fourth rail moving mechanisms  53 ,  153  for lowering or lifting the third and fourth short rails  52 ,  152  between an upper third position and a lower fourth position. The third position is a position connected to (on the same plane as) the linear motion guide rail  21   c ,  121   c  of the third or third guide rail  21 ,  121 . Further, the fourth position is a position connected to (on the same plane as) the linear motion guide rail  22   c ,  122   c  of the second or fourth guide rail  22 ,  122 . 
     The third and fourth short rails  52 ,  152  have the same structure as the first or second short rail  42 ,  142  of the first and second pallet moving parts  41 ,  141 . When the third and fourth short rails  52 ,  152  are connected to the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c  of the first to fourth guide rails  21 ,  22 ,  121 ,  122 , the work conveying pallets  11  are movable between the third and fourth short rails  52 ,  152  and the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c . Specifically, the work conveying pallet  11  separated from the first or second circulation belt  32 ,  132  and moved from the linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c  is mounted on the third and fourth short rails  52 ,  152 . Further, the third and fourth short rails  52 ,  152  move the work conveying pallets  11  mounted thereon to the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c.    
     As shown in  FIGS. 3 to 5, 8 and 10 , the third and fourth rail moving mechanisms  53 ,  153  for vertically moving such third and fourth short rails  52 ,  152  respectively include horizontal third and fourth supporting plates  54 ,  154  having the third and fourth short rails  52 ,  152  mounted on end edges, and third and fourth Z-axis direction telescopic actuators  55 ,  155  for moving the third and fourth supporting plates  54 ,  154  in the Z-axis direction with respect to the mount  9 . 
     The third and fourth Z-axis direction telescopic actuators  55 ,  155  have the same configurations as the first and second Z-axis direction telescopic actuators  45 ,  145  of the first and second pallet moving parts  41 ,  141 . Thus, repeated description is omitted. 
     In the present embodiment, the third and fourth supporting plates  54 ,  154  on which the third and fourth short rails  52 ,  152  are provided are attached to followers  55   c ,  155   c  of the third and fourth Z-axis direction telescopic actuators  55 ,  15  to be movable in the Z-axis direction. The drive of servo motors  55   a ,  155   a  of the third and fourth Z-axis direction telescopic actuators  55 ,  155  is controlled by the unillustrated controller. Specifically, the servo motors  55   a ,  155   a  are connected to the controller, and the third and fourth rail moving mechanisms  53 ,  153  are configured to be able to lift and lower the third and fourth short rails  52 ,  152  in the Z-axis direction together with the third and fourth supporting plates  54 ,  154  by driving the servo motors  55   a ,  155   a  by a command from the controller. 
     When the third and fourth short rails  52 ,  152  are connected to the first to fourth guide rails  21 ,  22 ,  121 ,  122 , the work conveying pallets  11  moving on the first to fourth guide rails  21 ,  22 ,  121 ,  122  can move from the first to fourth guide rails  21 ,  22 ,  121 ,  122  to the third and fourth short rails  52 ,  152 . To this end, the third and fourth pallet moving parts  51 ,  151  respectively include third and fourth pallet locking mechanisms  56 ,  156  for limiting movements of the work conveying pallets  11  mounted on the third and fourth short rails  52 ,  152 . 
     The third and fourth pallet locking mechanisms  56 ,  156  are configured to be engageable with the work conveying pallets  11  mounted on the third and fourth short rails  52 ,  152  and respectively include endless third and fourth auxiliary belts  57 ,  157  configured to circulate along the third and fourth short rails  52 ,  152  and third and fourth auxiliary circulating mechanisms for circulating the third and fourth auxiliary belts  57 ,  157 . 
     Auxiliary pulleys  58 ,  158  on which the third and fourth auxiliary belts  57 ,  157  extending along the third and fourth short rails  52 ,  152  are respectively mounted are rotatably supported on one end parts of the third and fourth supporting plates  54 ,  154  in the X-axis direction. Further, auxiliary drive pulleys  59 ,  159  on which the third and fourth auxiliary belts  57 ,  157  are respectively mounted are rotatably supported on the other end parts of the third and fourth supporting plates  54 ,  154  in the X-axis direction. 
     The third and fourth auxiliary circulating mechanisms are composed of servo motors  60 ,  160  mounted on the third and fourth supporting plates  54 ,  154 . The auxiliary drive pulleys  59 ,  159  are mounted on rotary shafts  60   a ,  160   a  of the servo motors  60 ,  160 . The auxiliary drive pulleys  59 ,  159  are provided on the same plane as the auxiliary pulleys  58 ,  158  and the third and fourth auxiliary belts  57 ,  157  are respectively mounted on the auxiliary drive pulleys  59 ,  159  and the auxiliary pulleys  58 ,  158 . 
     When the servo motors  60 ,  160  are driven by a command from the unillustrated controller, the third and fourth auxiliary belts  57 ,  157  are respectively circulated along the third and fourth short rails  52 ,  152  via the auxiliary drive pulleys  59 ,  159  and the auxiliary pulleys  58 ,  158 . 
     As shown in  FIG. 10 , the third and fourth auxiliary belts  57 ,  157  are belts in which recesses and projections  57   a ,  57   b ,  157   a ,  157   b  having the same shapes as in the first and second circulation belts  32 ,  132  and extending in the width direction are alternately connected in a longitudinal direction. The third and fourth auxiliary belts  57 ,  157  are configured such that the recesses and projections  57   a ,  57   b ,  157   a ,  157   b  thereof are engageable with the projections and recesses  14   a ,  14   b  formed on the second locking members  14  provided on the side surfaces (side edges) of the pedestals  13  of the work conveying pallets  11  when the work conveying pallets  11  are mounted on the third and fourth short rails  52 ,  152 . 
     Specifically, one principal surfaces of the third and fourth auxiliary pulleys  57 ,  157  provided with the recesses and projections  57   a ,  57   b ,  157   a ,  157   b  and one principal surfaces of the first and second circulation belts  32 ,  132  provided with the recesses and projections  32   a ,  32   b ,  132   a ,  132   b  differ in orientation, and these principal surfaces are orientated perpendicular to each other to be at right angles to each other. 
     It should be noted that the one principal surfaces of the third and fourth auxiliary belts  57 ,  157  of the third and fourth pallet moving parts  51 ,  152  provided with the recesses and projections  57   a ,  57   b ,  157   a ,  157   b  are also oriented perpendicular to the one principal surfaces of the first and second auxiliary pulleys  47 ,  147  of the first and second pallet moving parts  41 ,  141  provided with the projections and recesses  14   a ,  14   b ,  147   a ,  147   b . Thus, although not shown, the first and second pallet moving parts  41 ,  141  and the third and fourth pallet moving parts  51 ,  151  can be arranged adjacent to each other. 
     Further, principal surfaces of fifth and sixth auxiliary belts  67 ,  167  of the later-described fifth pallet moving parts  61 ,  161  provided with recesses and projections  67   a ,  67   b ,  167   a ,  167   b  are substantially on the same planes as the one principal surfaces of the third and fourth auxiliary belts  57 ,  157  of the third and fourth pallet moving parts  51 ,  151  provided with the recesses and projections  57   a ,  57   b ,  157   a ,  157   b.    
     In this way, a plurality of sets of the first and second pallet moving parts  41 ,  141 , the third and fourth pallet moving parts  51 ,  151 , the fifth and sixth pallet moving parts  61 ,  161  and the first to fourth guide rails  21 ,  22 ,  121  and  122  can be arranged adjacent to each other if necessary. Thus, various pallet conveying apparatuses and conveyance modes can be constructed according to the number of machine tools, a work processing process, a processing sequence, a pallet return timing or the like. 
     Here, with the work conveying pallet  11  located on a boundary between the first to fourth guide rail  21 ,  22 ,  121 ,  122  and the third or fourth short rail  52 ,  152  as shown as an example in an upper part of  FIG. 10 , the first or second circulation belt  32 ,  132  is locked to the first locking members  14  provided on the lower side of the work conveying pallet  11  and the second locking members  14  provided on the side surface (side edge) of the pedestal  13  of the work conveying pallet  11  are locked to the third or fourth auxiliary belt  57 ,  157 . 
     Accordingly, if the first and second circulation belts  32 ,  132  and the third and fourth auxiliary belts  57 ,  157  are circulated at the same speed, the work conveying pallets  11  moving on the first to fourth guide rails  21 ,  22 ,  121 ,  122  move to the third and fourth short rails  52 ,  152  connected to the first to fourth guide rails  21 ,  22 ,  121 ,  122 . Further, if the first and second circulation belts  32 ,  132  and the third and fourth auxiliary belts  57 ,  157  are circulated at the same speed in opposite directions, the work conveying pallets  11  moving on the third and fourth short rails  52 ,  152  move from the third and fourth short rails  52 ,  152  to the first to fourth guide rails  21 ,  22 ,  121 ,  122 . 
     The fifth and sixth pallet moving parts  61 ,  161  provided via the third and fourth pallet moving parts  51 ,  151  at the other end parts of the first to fourth guide rail  21 ,  22 ,  121  and  122  horizontally move the work conveying pallet  11  between the first and third guide rails  21 ,  121  provided at a predetermined interval in the Y-axis direction. Further, the fifth and sixth pallet moving parts  61 ,  161  similarly horizontally move the work conveying pallet  11  between the second and fourth guide rails  22 ,  122  provided at a predetermined interval in the Y-axis direction. 
     As shown in  FIG. 9 , the fifth and sixth pallet moving parts  61 ,  161  in the present embodiment include fifth and sixth short rails  62 ,  162  configured such that the work conveying pallet  11  is mountable thereon, fifth and sixth rail moving mechanisms  63 ,  163  for parallelly moving the fifth and sixth short rails  62 ,  162  from a fifth position on one side to a six position on the other side, and fifth and sixth pallet locking mechanisms  66 ,  166  for limiting movements of the work conveying pallets  11  mounted on the fifth and sixth short rails  62 ,  162 . The fifth position is a position connected to the linear motion guide rail  21   c ,  22   c  of the first or second guide rail  21 ,  22 . Further, the sixth position is a position connected to the linear motion guide rail  121   c ,  122   c  of the third or fourth guide rail  121 ,  122 . The fifth and sixth short rails  62 ,  162  have the same structure as the first to fourth short rails  42 ,  52 ,  142  and  152  of the first to fourth pallet moving parts  41 ,  51 ,  141  and  151 . 
     The fifth and sixth pallet locking mechanisms  66 ,  166  have the same structure as the third and fourth pallet locking mechanisms  56 ,  156  and include endless fifth and sixth auxiliary belts  67 ,  167  provided on the fifth and sixth supporting plates  64 ,  164  and configured to circulate, and fifth and sixth auxiliary circulating mechanisms for circulating these fifth and sixth auxiliary belts  67 ,  167 . 
     In the present embodiment, four fifth and sixth supporting plates  64 ,  164  are mounted on the mount  9  via supporting columns  71 ,  171 . Out of those, two fifth supporting plates  64  are mounted via the supporting column  71  at positions where the sixth auxiliary belt  67  is locked to the second locking members  14  provided on the side edge of the work conveying pallet  11  when the work conveying pallet  11  moves to an extension of the first or second guide rail  21 ,  22  located on the one side. 
     Further, the other two sixth supporting plates  164  are mounted via the supporting column  171  at positions where the sixth auxiliary belt  167  is locked to the second locking members  14  provided on the other side edge of the work conveying pallet  11  when the work conveying pallet  11  moves to an extension of the third or fourth guide rail  121 ,  122 . 
     As shown in  FIGS. 9 and 10 , auxiliary pulleys  68 ,  168  on which the fifth and sixth auxiliary belts  67 ,  167  are respectively mounted are rotatably supported on one end part of each of the four fifth and sixth supporting plates  64 ,  164  in the X-axis direction, and auxiliary drive pulleys  69 ,  169  on which the fifth and sixth auxiliary belts  67 ,  167  are respectively mounted are rotatably supported on the other end parts of the fifth and sixth supporting plates  64 ,  164  in the X-axis direction. 
     The fifth and sixth auxiliary circulating mechanisms are servo motors  70 ,  170  respectively mounted on the fifth and sixth supporting plates  64 ,  164 . The auxiliary drive pulleys  69 ,  169  are respectively mounted on rotary shaft  70   a ,  170   a  of the servo motors  70 ,  170 . 
     The auxiliary drive pulleys  69 ,  169  are provided on the same planes as the auxiliary pulleys  68 ,  168  and the fifth and sixth auxiliary belts  67 ,  167  are respectively mounted on the auxiliary drive pulleys  69 ,  169  and the auxiliary pulleys  68 ,  168 . 
     When the servo motors  70 ,  170  are driven by a command from the unillustrated controller, the fifth and sixth auxiliary belts  67 ,  167  are circulated via the auxiliary drive pulleys  69 ,  169  and the auxiliary pulleys  68 ,  168 . 
     As shown in  FIG. 10 , the fifth and sixth supporting plates  64 ,  164  are mounted on the mount  9  via the supporting columns  71 ,  171  such that the fifth and sixth auxiliary belts  67 ,  167  are circulated along the fifth and sixth short rails  62 ,  162  when the fifth and sixth short rails  62 ,  162  are present on extensions of the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c  of the first to fourth guide rails  21 ,  22 ,  121 ,  122 . 
     When the fifth and sixth short rails  62 ,  162  are connected to the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c  of the first to fourth guide rails  21 ,  22 ,  121 ,  122  via the third and fourth short rails  52 ,  152 , the work conveying pallets  11  moving from the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c  via the third and fourth short rails  52 ,  152  are mounted on the fifth and sixth short rails  62 ,  162 . Further, the fifth and sixth short rails  62 ,  162  are configured such that the work conveying pallets  11  mounted on the fifth and sixth short rails  62 ,  162  are movable to the linear motion guide rails  21 ,  22   c ,  121   c ,  122   c  via the third and fourth short rails  52 ,  152 . 
     Further, the fifth and sixth auxiliary belt  67 ,  167  are belts in which recesses and projections  67   a ,  67   b ,  167   a ,  167   b  having the same shapes as in the first and second circulation belts  32 ,  132  and extending in the width direction are alternately connected in a longitudinal direction. The fifth and sixth auxiliary belts  67 ,  167  are configured such that the recesses and projections  67   a ,  67   b ,  167   a ,  167   b  are engageable with the projections and recesses  14   a ,  14   b  formed on the second locking members  14  provided on one or the other side edges of the work conveying pallets  11  when the work conveying pallets  11  are mounted on the fifth and sixth short rails  62 ,  162  connected to the linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c  via the third and fourth short rails  52 ,  152 . 
     Accordingly, when the first and second circulation belts  32 ,  132 , the third and fourth auxiliary belts  57 ,  157  and the fifth and sixth auxiliary belts  67 ,  167  shown in  FIG. 10  are circulated at the same speed, the work conveying pallets  11  moving on the first to fourth guide rails  21 ,  22 ,  121 ,  122  are movable up to the fifth and sixth short rails  62 ,  162  via the third and fourth short rails  52 ,  52  connected to the first to fourth guide rails  21 ,  22 ,  121 ,  122 . Further, the work conveying pallets  11  mounted on the fifth and sixth short rails  62 ,  162  are moved from the fifth and sixth short rails  62 ,  162  to the first to fourth guide rails  21 ,  22 ,  121 ,  122  via the third and fourth short rails  52 ,  152 . 
     As shown in  FIG. 9 , the fifth and sixth rail moving mechanisms  63 ,  163  for moving such fifth and sixth short rails  62 ,  162  in the horizontal direction are composed of fluid pressure cylinders  63 ,  163  disposed between the fifth and sixth supporting plates  64 ,  164  separated in the Y-axis direction. The fluid pressure cylinders  63 ,  163  respectively include body portions  63   a ,  163   a  actually disposed between the fifth and sixth supporting plates  64 ,  164  separated in the Y-axis direction and sliders  63   b ,  163   b  provided atop those body portions  63   a ,  163   a  and movable in the longitudinal direction by a fluid pressure. 
     In the present embodiment, the fifth and sixth short rails  62 ,  162  are provided on the sliders  63   b ,  163   b . The sliders  63   b ,  163   b  are configured to move in the Y-axis direction together with the fifth and sixth short rails  62 ,  162  by an inflow pressure of fluid in response to a command from the unillustrated controller. 
     When the fifth and sixth short rails  62 ,  162  are connected to the first or second guide rail  21 ,  22 , the projections and recesses  14   a ,  14   b  of the second locking members  14  provided on one side edges of the work conveying pallets  11  mounted on the fifth and sixth short rails  62 ,  162  are engaged with the recesses and projections  67   a ,  67   b  of the fifth auxiliary belts  67  of the fifth pallet moving part  61  on one side. In this way, the work conveying pallets  11  are locked to the fifth pallet moving part  61 . 
     When the fifth and sixth short rails  62 ,  162  move toward positions connected to the third or fourth guide rails  121 ,  122  on the other side, the engaged projections and recesses  14   a ,  14   b  of the second locking members  14  of the work conveying pallets  11  are separated from the recesses and projections  67   a ,  67   b  of the fifth auxiliary belts  67  of the fifth pallet moving part  61  on the one side, whereby the locking thereof is released. 
     Thereafter, when the fifth and sixth short rails  62 ,  162  reach positions to be connected to the third or fourth guide rail  121 ,  122 , the projections and recesses  14   a ,  14   b  of the second locking members  14  provided on the other side edges of the work conveying pallets  11  are engaged with the recesses and projections  167   a ,  167   b  of the sixth auxiliary belts  167  of the sixth pallet moving part  161  on the other side, whereby the work conveying pallets  11  are locked to the sixth pallet moving part  161 . 
     In the pallet conveying apparatus  10  of the present embodiment, when the work conveying pallet  11  of the present embodiment is mounted on the first or third guide rail  21 ,  121  as shown in  FIGS. 3 to 5 , the projections and recesses  14   a ,  14   b  of the first locking members  14  provided on the lower side of the base  13  are respectively engaged with the recesses and projections  32   a ,  32   b  or  132   a ,  132   b  of the first or second circulation belt  32 ,  132  provided along the first or third guide rail  21 ,  121 . Thus, by driving the servo motor  33 ,  133  serving as a drive mechanism to circulate the first or second circulation belt  32 ,  132 , the work conveying pallet  11  of the present embodiment can be conveyed along the first or third guide rail  21 ,  121 . 
     On the other hand, in the pallet conveying apparatus  10  of the present embodiment, when the work conveying pallet  11  of the present embodiment is mounted on the second or fourth guide rail  22 ,  122  as shown in enlarged views of  FIGS. 4 and 5 , the projections and recesses  14   a ,  14   b  of the first locking members  14  provided on the upper part of the work conveying pallet  11  are respectively engaged with the recesses and projections  32   a ,  32   b  or  132   a ,  132   b  of the first or second circulation belt  32 ,  132  provided along the second or fourth guide rail  22 ,  122 . Thus, by driving the servo motor  33 ,  133  serving as a drive mechanism to circulate the first or second circulation belt  32 ,  132 , the work conveying pallet  11  of the present embodiment can be conveyed in an opposite direction along the second or fourth guide rail  22 ,  122 . 
     Thus, in the present embodiment, the pallet conveying apparatus  10  can be provided which can convey the work conveying pallet  11  in the one direction by locking the upper first locking members  14  to the first or second circulation belt  32 ,  132  and can convey the work conveying pallet  11  in the other direction (opposite direction in the present embodiment) by locking the lower first locking members  14  to the first or second circulation belt  32 ,  132 . In this way, it is possible to increase a degree of freedom in designing the pallet conveying apparatus  10  for conveying the work conveying pallet  11  of the present embodiment. 
     Particularly, in the pallet conveying apparatus  10  described above, the work conveying pallets  11  of the present embodiment respectively mounted on the first or third guide rail  21 ,  121  or the second or fourth guide rail  22 ,  122  are locked to the single first or second circulation belt  32 ,  132 . By circulating the first or second circulation belt  32 ,  132 , the work conveying pallets  11  of the present embodiment respectively mounted on the first or third guide rail  21 ,  121  or the second or fourth guide rail  22 ,  122  can be simultaneously moved in different directions. Thus, a separate circulation belt for returning the work conveying pallets  11  toward a side where the work conveying pallets  11  were mounted is unnecessary and the number of components of the pallet conveying apparatus  10  can be reduced, whereby it can be prevented that the manufacturing cost (unit price) of the pallet conveying apparatus  10  is pushed up. 
     On the other hand, the work conveying pallet  11  of the present embodiment is moved between the first to fourth guide rails  21 ,  22 ,  121  and  122  by first to sixth pallet moving parts  41 ,  51 ,  61 ,  141 ,  151  and  161 . 
     Specifically, the work conveying pallet  11  of the present embodiment is moved together with first to sixth short rails  42 ,  52 ,  62 ,  142 ,  152 ,  162  by first to sixth rail moving mechanism  43 ,  53 ,  63 ,  143 ,  153 ,  163  in a state where the work conveying pallet  11  of the present embodiment is mounted on the first to sixth short rails  42 ,  52 ,  62 ,  142 ,  152 ,  162  provided in the first to sixth pallet moving part  41 ,  51 ,  61 ,  141 ,  151  and  161 . 
     First to sixth auxiliary belts  47 ,  57 ,  67 ,  147 ,  157  and  167  are utilized in mounting the work conveying pallet  11  of the present embodiment on the first to sixth short rails  42 ,  52 ,  62 ,  142 ,  152  and  162  and moving the work conveying pallet  11  from the first to sixth short rails  42 ,  52 ,  62 ,  142 ,  152 ,  162  to the first to fourth guide rails  21 ,  22 ,  121  and  122 . 
     Here, in the work conveying pallet  11  of the present embodiment, the second locking members  14  are provided also on at least one of the plurality of side surfaces of the base  13 . Since the first to sixth auxiliary belts  47 ,  57 ,  67 ,  147 ,  157  and  167  are also provided with recesses and projections to which the first or second locking members  14  of the work conveying pallet  11  are lockable, it is possible to increase a degree of freedom in disposing the first to sixth auxiliary belts  47 ,  57 ,  67 ,  147 ,  157  and  167 . 
     As just described, the degree of freedom in designing the pallet conveying apparatus  10  for conveying the work conveying pallet  11  of the present embodiment can be reliably increased as compared to conventional work conveying pallets and work conveying apparatuses provided with a locking member only on one arbitrary surface of a base. 
     Second Embodiment 
     A pallet conveying apparatus in a second embodiment of the present invention is described with reference to  FIGS. 11 to 15 .  FIGS. 11 to 15  show a pallet conveying apparatus  100  for conveying a work conveying pallet  11  in the second embodiment of the present invention. 
     In each figure, three axes of X, Y and Z orthogonal to each other are set, wherein it is assumed that an X axis extends substantially in a horizontal lateral direction, a Y axis extends substantially in a horizontal front-back direction and a Z axis extends in a vertical direction. The configuration of this pallet conveying apparatus  100  is described below using X, Y and Z directions. It should be noted that the configuration of the work conveying pallet  11  in the present embodiment is not described to avoid repeated description since being similar to that in the first embodiment. 
     The pallet conveying apparatus  100  in the second embodiment is provided with six guide rails on which the work conveying pallet  11  of the present invention is movably mounted. Out of these six guide rails, four guide rails  21 ,  22 ,  121  and  122  are similar to those of the pallet conveying apparatus  10  in the first embodiment except that the first and third guide rails  21 ,  121  and the second and fourth guide rails  22 ,  122  extend straight in an X-axis direction and are arranged to be continuous. Thus, the first to fourth guide rails  21 ,  22 ,  121  and  122  are not described to avoid repeated description. 
     Further, as shown in  FIG. 12 , the pallet conveying apparatus  100  of the present embodiment includes a first pallet feeding part  31  for conveying the work conveying pallets  11  mounted on the first and second guide rails  21 ,  22  along the first and second guide rails  21 ,  22  and a second pallet feeding part  131  for conveying the work conveying pallets  11  mounted on the third and fourth guide rails  121 ,  122  along the third and fourth guide rails  121 ,  122 . These first and second pallet feeding parts  31 ,  131  are also similar to those of the pallet conveying apparatus  10  in the first embodiment. Thus, the first and second pallet feeding parts  31 ,  131  are also not described to avoid repeated description. 
     As shown in  FIG. 11 , fifth and sixth guide rails  221 ,  321 , which are the remaining two out of the six guide rails, are provided to extend in the X-axis direction at a predetermined interval in a Y-axis direction from the third guide rail  121  such that the three guide rails  121 ,  221  and  321  are parallel to each other. 
     As shown in  FIG. 13 , the fifth guide rail  221  includes a fifth supporting plate  221   b  directly fixed onto a mount  9  and a commercially available fifth linear motion guide rail  221   c  fixed to the upper edge of the fifth supporting plate  221   b  by screwing. 
     Further, as shown in  FIG. 14 , the sixth guide rail  321  includes a sixth supporting plate  321   b  directly fixed onto the mount  9  and a commercially available sixth linear motion guide rail  321   c  fixed to the upper edge of the sixth supporting plate  321   b  by screwing. 
     Here, first to sixth linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c ,  221   c ,  321   c  of the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  are identical. It is assumed that, even if the work conveying pallet  11  mounted on any one of the guide rails is moved to and mounted on another guide rail, that work conveying pallet  11  is configured to be movable along this other guide rail  21 ,  22 ,  121 ,  122 ,  221 ,  321 . 
     As shown in  FIGS. 11 and 12 , seventh pallet moving parts  181  are respectively provided at one end parts (i.e. sides where the third and fourth guide rails  121 ,  122  are not facing the first and second guide rails  21 ,  22 ) of the third and fourth guide rails  121 ,  122  and between the third and fourth guide rails  121 ,  122  and the first and second guide rails  21 ,  22 . 
     The seventh pallet moving part  181  is for moving the work conveying pallet  11  mounted on any one of the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  to another guide rail  21 ,  22 ,  121 ,  122 ,  221 ,  321 . 
     It should be noted that since these seventh pallet moving parts  181  have the same structure, one of them is described as a representative below. 
     As shown in  FIGS. 11, 12 and 15 , the seventh pallet moving part  181  in the present embodiment includes a seventh short rail  182  configured such that the work conveying pallet  11  is mountable thereon, and a seventh rail moving mechanism  183  for moving the seventh short rail  182  to a position connected to the first to sixth linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c ,  221   c ,  321   c  of the first to sixth guide rail  21 ,  22 ,  121 ,  122 ,  221 ,  321 . 
     The same rails as the first to sixth linear motion guide rails  21   c ,  22   c ,  121   c ,  122   c ,  221   c  and  321   c  of the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  are used as the seventh short rails  182 . 
     The first and second guide rails  21 ,  22  and the third and fourth guide rails  121 ,  122  are provided to be continuous in a longitudinal direction extending in an X-axis direction while being spaced apart by a distance slightly longer than a length of the seventh short rails  182 . 
     When the seventh short rail  182  is connected to the first or second linear motion guide rail  21   c ,  22   c  of the first or second guide rail  21 ,  22  by the seventh pallet moving part  181 , that seventh short rail  182  is arranged to be continuous to the third or fourth linear motion guide rail  121   c ,  122   c  of the third or fourth guide rail  121 ,  122 . 
     The pallet conveying apparatus  100  of the present embodiment is configured such that, in a state where the seventh short rails  182  are continuous, the work conveying pallet  11  can be moved from the first to sixth linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c ,  221   c ,  321   c  and mounted on the seventh short rail  182  and the work conveying pallet  11  mounted on the seventh short rail  182  can be moved to the first to sixth linear motion guide rail  21   c ,  22   c ,  121   c ,  122   c ,  221   c ,  321   c.    
     As shown in  FIG. 15 , the seventh rail moving mechanism  183  for moving such a seventh short rail  182  includes a seventh supporting plate  184  having the seventh short rail  182  mounted on an upper edge, a seventh Z-axis direction telescopic actuator  185  for moving the seventh supporting plate  184  in the Y-axis direction with respect to the mount  9  and a Y-axis direction telescopic actuator  186  for moving the seventh Z-axis direction telescopic actuator  185  with respect to the mount  9 . 
     In the present embodiment, the seventh supporting plate  184  having the seventh short rail  182  provided thereon is mounted on a follower  185   c  of the seventh Z-axis direction telescopic actuator  185  movably in the Z-axis direction. Further, to make the seventh supporting plate  184  movable in the Y-axis direction together with the seventh Z-axis direction telescopic actuator  185 , a housing  186   d  of the Y-axis direction telescopic actuator  186  is mounted on a housing  185   d  of the seventh Z-axis direction telescopic actuator  185  via brackets  187 . A follower  186   c  of the Y-axis direction telescopic actuator  186  is fixed to the mount  9  via a support column  188 . 
     Each of servo motors  185   a ,  186   a  of the seventh Z-axis direction and Y-axis direction telescopic actuators  185 ,  186  is connected to an unillustrated controller, and the operation thereof is controlled by the controller. As just described, the seventh rail moving mechanism  183  is configured to make the seventh short rail  182  movable in a predetermined YZ plane. 
     Accordingly, when the seventh short rail  182  of the seventh pallet moving part  181  is connected to the first to sixth guide rail  21 ,  22 ,  121 ,  122 ,  221 ,  321 , the work conveying pallet  11  moving on any one of the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  is moved from that guide rail to the seventh short rail  182 . Further, the seventh pallet moving part  181  includes a pallet locking mechanism  191  for limiting a movement of the work conveying pallet  11  mounted on this seventh short rail  182 . 
     This pallet locking mechanism  191  is configured to be engageable with the work conveying pallet  11  mounted on the seventh short rail  182  and includes an endless seventh auxiliary belt  192  provided along the seventh short rail  182  to circulate and a seventh auxiliary circulation mechanism for circulating the seventh auxiliary belt  192 . 
     An auxiliary pulley  193  around which the seventh auxiliary belt  192  extending along the seventh short rail  182  is mounted is rotatably supported on one end part of the seventh supporting plate  184  in the X-axis direction. Further, an auxiliary drive pulley  194  around which the seventh auxiliary belt  192  extending along the seventh short rail  182  is mounted is rotatably supported on the other end part of the seventh supporting plate  184  in the X-axis direction. The seventh circulation mechanism is composed of a servo motor  195  mounted on the seventh supporting plate  184 . The auxiliary drive pulley  194  is mounted on a rotary shaft  195   a  of the servo motor  195 . The auxiliary drive pulley  194  is provided on the same plane (not shown) as the auxiliary pulley  193  and the seventh auxiliary belt  192  is mounted around the auxiliary drive pulley  194  and the auxiliary pulley  193 . 
     When the servo motor  195  is driven by a command from the unillustrated controller, the seventh auxiliary belt  192  is circulated along the seventh short rail  182  via the auxiliary drive pulley  194  and the auxiliary pulley  193 . 
     The seventh auxiliary belt  192  is a belt in which recesses and projections having the same shapes as those of first and second circulation belts  32 ,  132  and extending in a width direction are alternately connected one after another in a longitudinal direction. The recesses and projections of the seventh auxiliary belt  192  are configured to be engageable with projections and recesses  14   a ,  14   b  formed on the work conveying pallet  11 . Thus, when the first or second circulation belt  32 ,  132  and the seventh auxiliary belt  192  are circulated at the same speed, the work conveying pallet  11  moving on the first to fourth guide rail  21 ,  22 ,  121 ,  122  is moved to the seventh short rail  182  connected to the first to fourth guide rail  21 ,  22 ,  121 ,  122 . 
     As shown in  FIG. 11 , the pallet conveying apparatus  100  includes third and fourth pallet feeding parts  231 ,  331  for conveying the work conveying pallets  11  mounted on the fifth and sixth guide rails  221 ,  321  along the fifth and sixth guide rails  221 ,  321 . The third and fourth pallet feeding parts  231 ,  331  include endless third and fourth circulation belts  232 ,  332  configured to be engageable with the work conveying pallet  11  and provided along the fifth and sixth guide rails  221 ,  321 , and third and fourth circulation mechanisms  233 ,  333  for circulating the third and fourth circulation belts  232 ,  332 . 
     As shown in  FIGS. 13 and 14 , fifth and sixth supporting members  234 ,  334  respectively stand near the fifth and sixth guide rails  221 ,  321  on the mount  9 . Horizontal plates  235 ,  335  are respectively mounted on the upper ends of the fifth and sixth supporting members  234 ,  334 . The horizontal plates  235 ,  335  are provided substantially at the same height as the linear motion guide rails  221   c ,  321   c  of the fifth and sixth guide rails  221 ,  321 , whereby the second locking members  14  of the work conveying pallet  11  are engaged with the third and fourth circulation belts  232 ,  332  when the work conveying pallet  11  moves on the fifth and sixth guide rails  221 ,  321 . 
     As shown in  FIG. 11 , three driven pulleys  236 ,  336  are provided on the periphery of each of the horizontal plates  235 ,  335 , and the third and fourth circulation belts  232 ,  332  are wound to enclose these three driven pulleys  236 ,  336 . 
     Further, servo motors  233 ,  333  serving as circulation mechanisms for circulating the third and fourth circulation belts  232 ,  332  are provided on the horizontal plates  235 ,  335 , and drive pulleys  237 ,  337  are mounted on rotary shaft  233   a ,  333   a  of the servo motors  233 ,  333 . A drive pulley  237 ,  337  is provided on the same plane as the three driven pulleys  236 ,  336 . A pair of turning pulleys  238 ,  338  for turning the third and circulation belts  232 ,  332  are rotatably supported on the horizontal plate  235 ,  335  near the drive pulley  237 ,  337  such that the third and fourth circulation belts  232 ,  332  are mounted around the drive pulleys  237 ,  337 . 
     When the servo motors  233 ,  333  are driven by a command from an unillustrated controller, the rotary shafts  233   a ,  333   a  rotate together with the drive pulleys  235 ,  335 . The third or fourth circulation belt  232 ,  332  mounted on the drive pulleys  237 ,  337  circulates while enclosing the three driven pulleys  236 ,  336 . 
     As shown in an enlarged view of  FIG. 11 , the third and fourth circulation belts  232 ,  332  are belts in which recesses and projections  232   a ,  232   b ,  332   a ,  332   b  extending in the width direction as in the circulation belts  32 ,  132  are alternately connected one after another in a longitudinal direction. The projections and recesses  14   a ,  14   b  engageable with those recesses and projections  232   a ,  232   b ,  332   a ,  332   b  are formed on the second locking members  14  of the work conveying pallet  11 . The second locking members  14  are provided on both sides of the base  13 , and the second locking members  14  on the both sides provided to face the horizontal plates  235 ,  335  are respectively engaged with the third and fourth circulation belts  232 ,  332 . 
     When the third and fourth circulation belts  232 ,  332  come into contact with the second locking members  14 , the recesses and projections  232   a ,  232   b ,  332   a ,  332   b  formed on the third and fourth circulation belts  232 ,  332  are engaged with the projections and recesses  14   a ,  14   b  of the second locking members  14 . Further, when the third and fourth circulation belts  232 ,  332  are lifted and separated from the second locking members  14 , the recesses and projections  232   a ,  232   b ,  332   a ,  332   b  of the third and fourth circulation belts  232 ,  332  and the projections and recesses  14   a ,  14   b  of the second locking members  14  are disengaged. The pallet conveying apparatus  100  of the present embodiment is configured as just described. 
     Here, as shown in  FIGS. 13 and 14 , third and fourth supporting members  239 ,  339  for preventing the slack of the third and fourth circulation belts  232 ,  332  between the driven pulleys  236 ,  336  and preventing the third and fourth circulation belts  232 ,  332  from being separated from the second locking members  14  are mounted on the horizontal plates  235 ,  335 . 
     When the projections and recesses  14   a ,  14   b  of the second locking members  14  are engaged with the recesses and projections  232   a ,  232   b ,  332   a ,  332   b  of the third or fourth circulation belt  232 ,  332  as shown in an enlarged view of  FIG. 11 , a movement of the work conveying pallet  11  in the X-axis direction independent of the rotation of the third or fourth circulation belt  232 ,  332  is prohibited. Thus, when the third or fourth circulation belt  232 ,  332  having the work conveying pallet  11  engaged therewith is circulated, the work conveying pallet  11  moves together with the third or fourth circulation belt  232 ,  332 . In this way, the work conveying pallet  11  is conveyed along the fifth or sixth guide rail  221 ,  321  adjacent to the third or fourth circulation belt  232 ,  332 . 
     In the pallet conveying apparatus  100  of the present embodiment configured as described above, as in the first embodiment, when the work conveying pallet  11  of the present invention is mounted on the first or third guide rail  21 ,  121  as shown in  FIGS. 11 and 12 , the projections and recesses  14   a ,  14   b  of the first locking members  14  provided on the lower side of the base  13  are engaged with the recesses and projections  32   a ,  32   b  or  132   a ,  132   b  of the first or second circulation belt  32 ,  132  provided along the first or third guide rail  21 ,  121 . Thus, by driving the servo motor  33 ,  133  serving as a drive mechanism to circulate the first or second circulation belt  32 ,  132 , the work conveying pallet  11  of the present embodiment can be conveyed along the first or third guide rail  21 ,  121 . 
     On the other hand, when the work conveying pallet  11  of the present embodiment is mounted on the second or fourth guide rail  22 ,  122 , the locking members  14  provided on the upper part of the work conveying pallet  11  are engaged with the first or second circulation belt  32 ,  132  provided along the second or fourth guide rail  22 ,  122 . Thus, by driving the servo motor  33 ,  133  serving as the drive mechanism to circulate the first or second circulation belt  32 ,  132 , the work conveying pallet  11  of the present embodiment can be conveyed in an opposite direction along the second or fourth guide rail  22 ,  122 . 
     Further, when the work conveying pallet  11  of the present embodiment is mounted on the fifth or sixth guide rail  221 ,  321 , the locking members  14  provided on the side edge of the base  13  are engaged with the third or fourth circulation belt  232 ,  332  provided along the fifth or sixth guide rail  221 ,  321 . Thus, by driving the servo motor  233 ,  333  serving as a drive mechanism to circulate the third or fourth circulation belt  232 ,  332 , the work conveying pallet  11  of the present embodiment can be conveyed along the fifth or sixth guide rail  221 ,  321 . 
     Accordingly, with the work conveying pallet  11  of the present embodiment, it is possible to provide the pallet conveying apparatus  100  capable of conveying the work conveying pallet  11  in one direction or the opposite direction by locking the second locking members  14  to the third or fourth circulation belt  232 ,  332  of the pallet conveying apparatus  100  besides in the case of the pallet conveying apparatus  10  of the first embodiment. In this way, it is possible to increase a degree of freedom in designing the pallet conveying apparatus  100  for conveying the work conveying pallet  11  of the present embodiment. 
     Here, the work conveying pallet  11  of the present embodiment is moved between the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  by two seventh pallet moving parts  181 . The seventh rail moving mechanism  183  moves the work conveying pallet  11  by moving the seventh short rail  182  together with the work conveying pallet  11  of the present embodiment after the work conveying pallet  11  of the present embodiment is mounted on the seventh short rail  182  of the seventh pallet moving part  181 . 
     It should be noted that a case where the work conveying pallet  11  is configured such that the mounting tool  16  for mounting the work is provided on one side part of the base  13  and the linear motion blocks  12  are provided on the other side part of the base  13  has been described in the above first and second embodiments. However, this mounting tool  16  may be provided in a center on the upper side of the base  13  and the linear motion blocks  12  may be provided in a center on the lower side of the base  13 . 
     Further, a case where the mounting tool  16  is provided on the base  13  in the form of a flat plate has been described in the above first and second embodiments. However, the mounting tool  16  may be provided in a through hole formed in the base  13 . If such a mounting tool  16  is provided, the work can be mounted through the base  13  via the through hole and both upper and lower surfaces of the work can be processed. 
     Furthermore, a case where the work conveying pallet  11  of the present embodiment is moved between the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221 ,  321  by moving the first to seventh short rail in the Y-axis direction or Z-axis direction while a locked state of the first or second locking members  14  to the first to seventh auxiliary belt  47 ,  57 ,  147 ,  157 ,  67 ,  167 ,  192  is maintained after the work conveying pallet  11  of the present embodiment is mounted on the first to seventh short rail  42 ,  52 ,  62 ,  142 ,  152 ,  162 ,  182  by circulating the first to seventh auxiliary belt  47 ,  57 ,  147 ,  157 ,  67 ,  167 ,  192  has been described in the above first and second embodiments. 
     However, the locked state of the first or second locking members  14  to the first to seventh auxiliary belt  47 ,  57 ,  147 ,  157 ,  67 ,  167 ,  197  may not be maintained in moving the first to seventh short rails  42 ,  52 ,  62 ,  142 ,  152 ,  162 ,  182 . 
     (Modifications) 
     Hereinafter, modifications of the guide rails and pallet moving parts of the pallet conveying apparatus of the present invention are described with reference to  FIGS. 16 to 19 . 
     A case where the work conveying pallet  11  mounted on a guide rail  421  is conveyed with a circulation belt  432  of the pallet conveying apparatus locked to the first locking members  14  on the lower surface of the work conveying pallet  11 , for example, as shown in  FIG. 16  is described as one modification of the present invention. In this case, after the work conveying pallet  11  is moved from the guide rail  421  to a short rail  442 , the short rail  442  is elevated in a state carrying the work conveying pallet  11  and the work conveying pallet  11  and the circulation belt  432  are first disengaged. Then, the short rail  442  carrying the work conveying pallet  11  is rotated by 180° in a horizontal plane and lowered again. After being rotated by 180° again, that work conveying pallet  11  may be moved from the short rail  442  to another guide rail  521 . It should be noted that when that work conveying pallet  11  is moved to the other guide rail  521 , a new circulation belt  532  is engaged with the first locking members  14  of the work conveying pallet  11 , whereby the work conveying pallet  11  can be moved by the circulation of that circulation belt  532 . 
     Further, a case where the work conveying pallet  11  mounted on the guide rail  421  is conveyed with the circulation belt  432  of the pallet conveying apparatus locked to the second locking members  14  on the side surface of the work conveying pallet  11  as shown in  FIG. 17  is described. In this case, after the work conveying pallet  11  is moved from the guide rail  421  to the short rail  442 , the short rail  442  carrying the work conveying pallet  11  is elevated or lowered, whereby the work conveying pallet  11  and the circulation belt  432  are first disengaged. Then, after the short rail  442  carrying the work conveying pallet  11  is rotated by 180° in a horizontal plane and, thereafter, lowered or elevated again. After being rotated by 180° again, that work conveying pallet  11  may be moved from the short rail  442  to the other guide rail  521 . It should be noted that when that work conveying pallet  11  is moved to the other guide rail  521 , the new circulation belt  532  is locked to the first locking members  14  of the work conveying pallet  11 , whereby the work conveying pallet  11  can be moved by the circulation of that circulation belt  532 . 
     As just described, in the pallet moving part, the engagement (locking) of the first or second locking members  14  and the circulation belt  432  may be first released during the movement of the work conveying pallet  11 . By employing such a configuration, it is also possible to easily change the direction of the work conveying pallet  11  during the movement on the guide rail. 
     Further, a case where the work conveying pallet  11  is moved between the first to sixth guide rails  21 ,  22 ,  121 ,  122 ,  221  and  321  by moving the first to seventh short rails  42 ,  52 ,  62 ,  142 ,  152 ,  162 ,  182  carrying the work conveying pallet  11  in the Y-axis direction or Z-axis direction has been described in the above first and second embodiments. 
     However, the pallet conveying apparatus may be configured such that the short rail  442  is obliquely moved as shown in  FIG. 18 . Specifically, the pallet conveying apparatus may be configured such that the short rail  442  is connected to the other guide rail  521  by moving the short rail  442  moved from the guide rail  421  and carrying the work conveying pallet  11  in an oblique direction and, thereafter, the work conveying pallet  11  is moved from the short rail  442  to the other guide rail  521 . 
     Even if the short rail  442  is moved in the oblique direction in this way, the engagement (locking) of any one of the first and second locking members  14  by the pallet conveying apparatus can be released by starting the movement in the oblique direction since the work conveying pallet  11  is provided with the first and second locking members  14  on the front and back principal surfaces and the plurality of side surfaces of the base  13 . Then, in a state where the short rail  442  is connected to the other guide rail  521 , this locking member or any one of the other first and second locking members  14  can be locked to another circulation belt or the like of the pallet conveying apparatus. 
     Further, the pallet conveying apparatus may be configured such that the short rail  442  is rotated around an axial center when being obliquely moved as shown in  FIG. 19 . When the short rail  442  carrying the work conveying pallet  11  is rotated around the axial center thereof, the base  13  of the work conveying pallet  11  can be inclined from a horizontal state. For example, if the short rail  442  is rotated by 90° from a lowermost part to an uppermost part as shown in  FIG. 19 , the base  13 , which was vertical, can be horizontally located. Further, by inclining the base  13  in the horizontal state, the work conveying pallet  11  can be moved to the other guide rail  521  with the base  13  held in a vertical state. 
     Even in this case, since the work conveying pallet  11  is provided with the first and second locking members  14  on the front and back principal surfaces and the plurality of side surfaces of the base  13 , the engagement (locking) of any one of the first and second locking members  14  by the pallet conveying apparatus can be released by starting the movement in the oblique direction. Then, in a state where the short rail  442  is connected to the other guide rail  521 , this locking member or any one of the other first and second locking members  14  can be locked to another circulation belt or the like of the pallet conveying apparatus. As just described, also in the modifications of the present invention, a degree of freedom in designing the pallet conveying apparatus for conveying the work conveying pallet  11  can be increased by easily changing a conveyance path. 
     It should be noted that the movement of the work conveying pallet  11  between the guide rails can be also realized, using a robot arm or the like instead of the pallet moving parts shown in  FIGS. 16 to 19 . 
     As described above, the characteristic configuration of the present invention is that the first and second locking members  14  are provided on at least two surfaces out of the front and back principal surfaces and the plurality of side surfaces of the base  13 . Specific examples of this configuration include (a) case where the locking members are provided on the front and back surfaces of the base, (b) case where the locking members are provided on the back surface and the side surface, (c) case where the locking members are provided on the front surface and the side surface of the base and (d) case where the locking members are provided on two side surfaces of the base. 
     An embodiment of (a) case where the locking members are provided on the front and back surfaces of the base is as described above using  FIGS. 4 and 5 , and an embodiment of (b) case where the locking members are provided on the back surface and the side surface is as described above using  FIGS. 3 and 11 . 
     Further, (c) case where the locking members are provided on the front surface and the side surface of the base is as described above using the second and fourth guide rails  22 ,  122  located below in  FIGS. 4 and 5 . Besides, it is also possible to employ a configuration of moving the work conveying pallet  11  between the second and fourth guide rails  22 ,  122  located below by arranging the fifth and sixth pallet moving parts  61 ,  161  at both end sides of the second and fourth guide rails  22 ,  122  and the first and second pallet feeding parts  31 ,  131 . 
     Further, (d) case where the locking members are provided on two side surfaces of the base is as described above using  FIG. 17 . Besides, it is also possible to employ a configuration of moving the work conveying pallet  11  between the fifth and sixth guide rails  221 ,  321  by arranging the fifth and sixth pallet moving parts  61 ,  161  at both end sides of the fifth and sixth guide rails  221 ,  321  and the third and fourth pallet feeding parts  231 , 331 . 
     The pallet conveying apparatus and the pallet conveying method in which any one of the first to six pallet moving parts  41 ,  141 ,  51 ,  151 ,  61  and  161  or the seventh pallet moving part  181  is arranged at the end parts of the first and second guide rails  21   22 , the third and fourth guide rails  121 ,  122  and the fifth and sixth guide rail  221 ,  321  have been described in the above first and second embodiments. 
     Besides these embodiments, it is also possible to use a plurality of sets of guide rails with the first and second guide rails  21 ,  22 , the third and fourth guide rails  121 ,  122  or the fifth and sixth guide rails  221 ,  321  serving as one set. In this case, any one or a combination of the first to sixth pallet moving parts  41 ,  141 ,  51 ,  151 ,  61  and  161  and the seventh pallet moving part  181  can be used at end parts of or between a plurality of sets of guide rails. 
     Specifically, in the present invention, the pallet conveying apparatus and a conveyance mode can be constructed according to the number of machine tools, work processing steps, a sequence thereof, a pallet return timing or the like. 
     This application claims priority based on Japanese Patent Application No. 2015-27208 filed with the Japan Patent Office on Feb. 16, 2015, the entire contents of which are incorporated into this specification.