Patent Publication Number: US-6658761-B2

Title: Method and apparatus for centrifugally dehydrating workpiece

Description:
The present application is based on Japanese Patent Applications Nos. 2001-135638, 2001-226858, 2002-33713, 2002-33714 and 2002-33715, which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a centrifugal dehydrating technology for removing a liquid such as a cleaning liquid adhered to a workpiece with a substantially rectangular plane (hereafter referred to also as a pallet or the like) such as a pallet or a tray or container similar thereto by the action of a centrifugal force. 
     2. Description of the Related Art 
     Conventionally, in a case where a pallet or the like formed of a resin is centrifugally dehydrated, it has been the general practice to effect centrifugal dehydration in a horizontal state in a state in which the pallet or the like is being conveyed on a conveyor. However, there are many cases where the pallet or the like is provided with a multiplicity of ribs to increase the strength, and a multiplicity of recessed portions are formed by those ribs, so that the actual situation has been such that the cleaning liquid gathered in the recessed portions cannot be easily removed even if centrifugal dehydration is performed. Accordingly, concerning the centrifugal dehydration of the pallet, a technique has been disclosed in which the pallet is rotated in an upright state (Japanese Utility Model Publication No. Hei. 6-52973). In this case, the cleaning liquid remaining in the recessed portions can be removed efficiently. However, in the case of this conventional technique, the center is liable to be offset at the time of holding the pallet, so that there has been a problem in that if the pallet is rotated as it is, the pallet becomes unstable due to an imbalance; and there is a large danger. Due to these circumstances, the holder has tended to be complex and large in size so as to hold the pallet securely. In addition, the types of pallets are very numerous, and it has been difficult to jointly use the same apparatus for the pallets of different sizes. 
     SUMMARY OF THE INVENTION 
     The present invention has been devised in view of the above-described conventional technical situation, and its object is to provide a centrifugal dehydration apparatus for a pallet or the like which, at the time of holding the pallet or the like, makes it possible to easily locate the center of gravity of the pallet or the like on the axis of rotation and is capable of easily suppressing the runout due to the centrifugal force. 
     In the invention, to overcome the above-described problems, a workpiece with a substantially rectangular plane is held an a diagonal line of its substantially rectangular plane by a pair of holders which are rotated by a rotator, and the diagonal line of the workpiece is aligned with an axis of rotation. Since the center of gravity of the workpiece is generally located on its diagonal line, the center of gravity of the workpiece is located on the axis of rotation according to the above-described structure. Accordingly, in accordance with the invention, it is possible to easily suppress the runout due to the centrifugal force. It should be noted that the alignment of the diagonal line of the workpiece with the axis of rotation, which is referred to herein, is not to be construed in a strict sense, and it suffices if it is possible to suppress the runout due to the centrifugal force to such an extent as to cause no hindrance by obviating an imbalance in rotation by substantially aligning the diagonal line of the workpiece with the axis of rotation. If the pair of corner portions of the workpiece are held on its diagonal line by the pair of holders, the diagonal line of the workpiece can be easily aligned with the axis of rotation. It should be noted that the direction of rotation of the workpiece may be changed over between forward rotation and reverse rotation, or the frequency of changeover may be set to two times or more. In addition, after the workpiece is subjected to cleaning in an upright state such that one edge thereof is set as a bottom, the workpiece may be tilted such that a corner portion thereof is set as a bottom, and centrifugal dehydration may be effected in the tilted state. Furthermore, the pair of holders may be each arranged to be capable of tilting in correspondence with abutment against two adjacent edge portions with each of the corner portions located therebetween when the pair of corner portions of the workpiece are respectively held by the pair of holders, and there may be further provided a supporting mechanism for supporting the two edge portions with the corner portion of a bottom of the workpiece located therebetween and a transfer mechanism for transferring the supporting mechanism. 
     Incidentally, the present invention may be employed to centrifugally dehydrate a planar workpiece such as a planar pallet, however, the shape of the workpiece is not limited to this. For example, the shape of the workpiece may be rectangular solid, cube, or the like. “A workpiece with a substantially rectangular plane” may be a workpiece having a contour with a substantially rectangular plane viewed from at least one direction. This type of workpiece has at least a pair of corner portions to be held when dehydrated. 
     Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a schematic diagram illustrating a layout concerning essential portions of an embodiment in accordance with the invention; 
     FIG. 2 is a front elevational view illustrating the portion of setting-up means for setting up a pallet; 
     FIG. 3 is a plan view illustrating the portion of the setting-up means; 
     FIG. 4 is a left side elevational view illustrating the portion of the setting-up means; 
     FIG. 5 is a partial enlarged view illustrating the setting-up means; 
     FIG. 6 is a front elevational view illustrating the portion of a tilting means for tilting the pallet; 
     FIG. 7 is a partial enlarged side elevational view illustrating the tilting means; 
     FIG. 8 is a front elevational view illustrating an internal structure of a dehydration chamber; 
     FIG. 9 is a side elevational view illustrating the internal structure as viewed from the center of the dehydration chamber; 
     FIG. 10 is an enlarged front elevational view of one transfer mechanism for making up a first transfer mechanism; 
     FIG. 11 is a plan view thereof; 
     FIG. 12 is a side elevational view thereof; 
     FIG. 13 is a front elevational view illustrating another operating state of the transfer mechanism; 
     FIG. 14 is a front elevational view illustrating still another operating state of the transfer mechanism; 
     FIG. 15 is an enlarged front elevational view of the other transfer mechanism for making up the first transfer mechanism; 
     FIG. 16 is a plan view thereof; 
     FIG. 17 is an enlarged plan view of one transfer mechanism for making up a second transfer mechanism; 
     FIG. 18 is an enlarged plan view of the other transfer mechanism for making up a second transfer mechanism; 
     FIG. 19 is a front elevational view illustrating the portion of a centrifugal dehydration means; 
     FIG. 20 is an enlarged vertical cross-sectional view of a lower holding means for holding a lower corner portion of the pallet; 
     FIG. 21 is a cross-sectional view taken along line A—A of FIG. 20; and 
     FIG. 22 is an enlarged vertical cross-sectional view illustrating an upper holding means for holding an upper corner portion of the pallet. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, a description will be given of an embodiment of the invention. FIG. 1 is a schematic layout drawing illustrating a layout concerning essential portions of an embodiment in accordance with the invention. Pallets  1  as workpieces are accommodated in a magazine  2  in a horizontally stacked state, and are conveyed to setting-up means  4  one by one through a discharge conveyor  3 . The pallet  1  conveyed to the setting-up means  4  is made set up such that a mounted surface becomes vertical with its one edge as a bottom, and is mounted on a carrying-in conveyor  5  in an upright state. The pallet  1  mounted on the carrying-in conveyor  5  is conveyed to a cleaning chamber  6  in the upright state, and the cleaning of the pallet  1  is effected as a cleaning fluid is sprayed to its both obverse and reverse surfaces through cleaning nozzles  7  and  8  serving as cleaning means disposed movably on both sides of the cleaning chamber  6 . Further, the respective side surfaces of the pallet  1  are also cleaned by using the cleaning nozzles  7  and  8  and unillustrated other cleaning nozzles. It should be noted that, in the conveyance of the pallet  1  to the cleaning chamber  6 ; irrespective of its size and shape, the pallet  1  is stopped such that a foremost portion of the pallet  1  is aligned with a reference position, and cleaning processing is carried out as the cleaning nozzles  7  and  8  are lowered from an upper edge portion while being reciprocally moved back and forth, for instance, by using the reference position as a reference. Further, it is possible to adopt a form in which cleaning is effected by vertically moving the cleaning nozzles  7  and  8  while the pallet  1  is being conveyed by the carrying-in conveyor  5  without being stopped. As the cleaning liquid, it is possible to use tap water, tap water with a detergent added thereto, a gas-liquid mixed solution in which a gas is mixed in a liquid, or in a case where the contamination is heavy, a liquid in which a cleaning liquid is heated or a liquid in which a particulate substance is mixed. In addition, it is possible to adopt a form in which rinsing cleaning is added after cleaning by a detergent. After cleaning, the cleaned pallet  1  as it is in the upright state is conveyed to a dehydration chamber  9 . The pallet  1  conveyed to the dehydration chamber  9  is tilted with its one corner as a bottom by a tilting means (which will be described later) when the pallet  1  is lifted up from the carrying-in conveyor  5 . The pallet  1  as it is in the tilted state is transferred to a centrifugal dehydration means  10 , and liquid drops adhered to the pallet  1  are subjected to centrifugal dehydration. Upon completion of the centrifugal dehydration, the pallet  1  as it is in the tilted state is conveyed to a carrying-out conveyor  11 , and after its tilted state is restored to the upright state with its one edge as a bottom, the pallet  1  mounted on the carrying-out conveyor  11 . The pallet  1  after being subjected to centrifugal dehydration and mounted on the carrying-out conveyor  11  is conveyed as it is in the upright state to an inverting means  12 . After being inverted to a horizontal state by the inverting means  12 , the pallets  1  are carried out in a stacked state or one by one by means of a pallet stocker  13  or the like. It should be noted that, in terms of the form of their use, the setting-up means  4  and the inverting means  12  differ from each other in that the pallet  1  in the horizontal state is made set up or the pallet  1  in the upright state is inverted to the horizontal state, but similar mechanisms are used as inverting mechanisms. 
     Incidentally, the planar pallet  1  is dehydrated according to the embodiment, however, a workpiece to be dehydrated is not limited to this. For example, the shape of the workpiece may be rectangular solid, cube, or the like. In the workpiece, a multiplicity of ribs and a multiplicity of recessed portions are provided. 
     Next, a description will be given of the respective above-described component parts. First, a description will be given of the aforementioned setting-up means  4 . FIG. 2 is a front elevational view illustrating the portion of the setting-up means  4 , FIG. 3 is a plan view, FIG. 4 is a left side elevational view, and FIG. 5 is a partial enlarged view thereof. The setting-up means  4  comprises as its principal elements lower-portion supporting members  14  and  15  spaced apart in parallel for supporting the underside of the pallet  1  as well as upper-portion supporting members  16  and  17  spaced apart in parallel in a direction perpendicular to the lower-portion holding members  14  and  15 . The arrangement provided is such that each of the pallets  1  conveyed one by one from the magazine  2  is inserted between the lower-portion holding members  14  and  15 , on the one hand, and the upper-portion supporting members  16  and  17 , on the other hand, and is set up. The upper-portion supporting members  16  and  17  are connected and fixed to the lower-portion holding members  14  and  15  by means of connecting members  18  and  19  in a state in which an interval allowing the pallet  1  to be inserted is provided therebetween. The upper-portion supporting members  16  and  17  are connected to each other by connecting members  20  and  21 . In addition, a retaining plate  22  is attached to the upper-portion supporting member  17 , and a lower end of the retaining plate  22  is set so as to jut out into, an insertion space for the pallet  1 , as shown in FIG. 4, in order to retain an end face of the pallet  1 . As shown in FIG. 3, the lower-portion holding members  14  and  15  are pivotally secured to a supporting shaft  25  by means of supporting plates  23  and  24 , respectively. In addition, the lower-portion holding members  14  and  15  are connected and fixed to each other by a connecting member  26 , and cylinders  27  and  28  for driving are installed at appropriate positions on the lower-portion holding members  14  and  15  or the connecting member  26 . It should be noted that reference numeral  29  in FIG. 4 denotes a reinforcing plate disposed between the connecting members  18  and  19 , on the one hand, and the upper-portion supporting members  16  and  17 , on the other hand. 
     As shown in FIG. 3, the discharge conveyor  3  extends to a position below the setting-up means  4  and is disposed so as to be located between the lower-portion holding members  14  and  15 . As such, when the pallets  1  accommodated in the magazine  2  are conveyed one by one to the setting-up means  4  by means of the discharge conveyor  3 , the pallet  1  is inserted between the lower-portion holding members  14  and  15 , on the one hand, and the upper-portion supporting members  16  and  17 , on the other hand, and a leading end portion in the advancing direction is retained by the retaining plate  22  and stops at its home position. Subsequently, as shown in the partial enlarged view in FIG. 5, if the cylinders  27  and  28  are driven to cause their output shafts  30  to project, the lower-portion holding members  14  and  15  are rotated upward about the supporting shaft  25  through connecting pins.  31 . Consequently, the pallet  1  inserted between the lower-portion holding members  14  and  15  and the upper-portion supporting members  16  and  17  is set up on the carrying-in conveyor  5  in a state in which one edge on the side retained by the retaining plate  22  is set as its bottom. Then, the pallet  1  mounted on the carrying-in conveyor  5  in the upright state is moved out from a gap portion  32  formed on the side of distal end portions of the upper-portion supporting members  16  and  17 , as shown in FIG. 4, and is conveyed as it is in the upright state to the cleaning chamber  6 . In the cleaning chamber  6 , a cleaning liquid is sprayed onto both obverse and reverse surfaces from the cleaning nozzles  7  and  8  disposed movably on both sides of the cleaning chamber  6 , thereby effecting cleaning. Subsequently, the pallet  1  is conveyed as it is in the upright state from the cleaning chamber  6  to the dehydration chamber  9 . At the time of this conveyance, the lower-portion holding members  14  and  15  and the upper-portion supporting members  16  and  17  function as guides and prevents the tilting down of the pallet  1 . In addition, the pallet insertion interval formed between the upper-portion supporting members  16  and  17  and the lower-portion holding members  14  and  15  is made to be used jointly for varying sizes of the pallets  1 , and permits to set up all the subject pallets. It should be noted that sealing means is provided at an inlet and an outlet of the cleaning chamber  6 , as required, so as to prevent the scattering of the cleaning liquid to the outside. 
     Next, a description will be given of a tilting means for tilting the pallet  1  by using one corner as a bottom when the pallet  1  conveyed to the dehydration chamber  9  is lifted up from the carrying-in conveyor  5 , as well as a first transfer mechanism for transferring the pallet  1  as it is in the tilted state to the centrifugal dehydration means  10  and a second transfer mechanism for transferring the dehydrated pallet  1  as it is in the tilted state from the centrifugal dehydration means  10  to the carrying-out conveyor  11  for carrying out. FIG. 6 is a front elevational view illustrating the tilting means for tilting the pallet  1 , FIG. 7 is a partial enlarged side elevational view thereof. As shown in FIG. 6, disposed at a predetermined position on the conveying surface of a chain conveyor  36  having, for example, two endless chains juxtaposed and trained between a pair of sprockets  34  and  35  for making up the carrying-in conveyor  5  is a tilting means  39  having a retaining portion  37  by which a front end portion of the pallet  1  conveyed by the chain conveyor  36  and a lower-edge supporting portion  38  formed integrally with and perpendicularly to the retaining portion  37  to support the lower edge of the pallet  1 . This tilting means  39  rotatably supports the pallet  1  by a supporting shaft  40  so as not to interfere with the motion of the chain conveyor  36 , and a distal end of its drive arm  41  is rotatably connected to an output shaft  43  of a cylinder  42  for driving. As such, when the pallet  1  being conveyed on the conveying surface of the chain conveyor  36  reaches the portion of the tilting means  39 , its leading end portion is first retained by the retaining portion  37  indicated by the two-dot chain line and the pallet  1  stops. Subsequently, as the cylinder  42  is driven at an appropriate timing to forwardly advance the output shaft  43 , and the tilting means  39  is thereby rotated about the supporting shaft  40 , it is possible to tilt the pallet  1  as indicated by the solid lines. At the time of this tilting, the cleaning liquid adhered to the pallet  1  drops down. In addition, since one corner of the pallet  1  is supported by this tilting means  39 , a model change due to a change of shape such as the size of the pallet  1  is not required, so that the joint use of the tilting means  39  can be made. It should be noted that, in the above process, when the pallet  1  has approached the retaining portion  37 , the arrival may be detected by a sensor, as required, and the chain conveyor  36  may be decelerated. In addition, the chain conveyor  36  may be stopped by adjusting its timing to the timing when the pallet  1  is retained by the retaining portion  37  and stops. Alternatively, the chain conveyor  36  may be stopped after the rotation of the tilting mechanism  39 , or may be kept in a constantly driven state for conveying an ensuing pallet  1 . In the drawings, reference numeral  44  denotes a drive motor for driving the chain conveyor  36 , and  45  denotes a supporting portion for rotatably supporting the cylinder  42 . 
     FIG. 8 is a front elevational view illustrating an internal structure of the dehydration chamber  9 , and FIG.  9  is a side elevational view illustrating the internal structure as viewed from the center of the dehydration chamber  9 . In this embodiment, as shown in FIG. 8, a pair of transfer mechanisms  46  and  47  making up the first transfer mechanism for lifting up the pallet  1  mounted on the tilting means  39  and set in the tilted state and for transporting the pallet  1  as it is in the tilted state to the centrifugal dehydration means  10  are disposed in both side portions on this side of the dehydration chamber  9 . In addition, as shown in FIG. 9, disposed on both side portions in the rear of the dehydration chamber  9  are a pair of transfer mechanisms  48  and  49  making up the second transfer mechanism for lifting up the pallet  1  for which dehydration processing by the centrifugal dehydration means  10  has been completed and which is in the tilted state, and for transferring the pallet  1  as it is in the tilted state to a tilt restoring means for restoring the pallet  1  disposed on the carrying-out conveyor  11  side from the tilted state to the horizontal state. It should be noted that the transfer mechanisms  46  and  47  making up the first transfer mechanism and the transfer mechanisms  48  and  49  making up the second transfer mechanism are arranged to move while being by supported and guided by upper and lower rails  50  to  53  laid horizontally on both side portions, respectively. In addition, as shown in FIG. 8, the installation height of the one transfer mechanisms  46  and  48  is set to be higher than the other transfer mechanisms  47  and  49 . 
     FIGS. 10 to  12  are enlarged views of the one transfer mechanism  46  for making up the first transfer mechanism. FIG. 10 is a front elevational view, FIG. 11 is a plan view, and FIG. 12 is a side elevational view. In addition, FIGS. 13 and 14 are front elevational views illustrating other operating states of the transfer mechanism  46 . As shown in FIG. 10, the transfer mechanism  46  has a square pipe-shaped attaching member  56  arranged to be horizontally movable along the rails  50  and  51  by means of fitting members  54  and  55  fitting slidably to the rails  50  and  51 . A rail  57  is vertically installed on this attaching member  56 , and a lifting plate  60  is liftably installed on the attaching plate by means of fitting members  58  and  59  fitting slidably to the rail  57 . This lifting plate  60  is connected by means of a connecting portion  63  to an output shaft  62  of a cylinder  61  installed on the attaching member  56 , and is arranged to be liftable as the cylinder  61  is driven. A supporting arm  65  for supporting the pallet  1  by means of a bearing  64 , as shown in FIG. 11, is rotatably attached to an outer surface of the lifting plate  60 . This supporting arm  65  is arranged such that after a jutting-out portion  66  jutting out horizontally along the bearing  64  is interposed, the supporting arm  65  is bent orthogonally to form a rotating arm portion  67  extending horizontally, and is then bent upward, as shown in FIG. 10. A supporting portion  68  for supporting an edge portion of the pallet  1  in the tilted state is provided at its distal end. It should be noted that the jutting-out portion  66  is for allowing the supporting portion  68  to jut out to a position below the pallet  1  mounted on the tilting means  39  disposed on the carrying-in conveyor  5  when the pallet  1  is lifted up. The supporting portion  68  is formed in a U-shape, and has an inclined surface  69  for abutting against the edge portion of the tilted pallet  1  and a pair of supporting pieces  70  and  71  on both sides of the inclined surface  69 , as shown in FIG.  12 . The internal width between the supporting pieces  70  and  71  is set to be wider than the thickness of the pallet  1 , so that the pallet  1  can be supported by being merely inserted between the supporting pieces  70  and  71 , and can be also used jointly for other pallets. It should be noted that, as for the supporting of the edge portions of the pallet  1  by the transfer mechanisms, stable transfer becomes possible by supporting the pallet  1  at positions as remote from the center as possible. In addition, if the inclined surface  69  is coated with a resin or the like which is capable of reducing the frictional resistance or adhesion, when the pallet  1  is supported while staggering the timing of lifting by the two moving mechanisms  46  and  47 , it is possible to smoothly proceed to a supporting state. At the same time, when the magazine  46  moves away from the pallet  1  after mounting the pallet  1  in a predetermined position, the separation of the inclined surface  69  and the edge portion of the pallet  1  can take place smoothly. 
     Further, a chevron-shaped drive arm  73  is rotatably attached to an outer surface of the aforementioned lifting plate  60  by means of a supporting shaft  72 , and a distal end portion of the drive arm  73  is rotatably connected via a connecting pin  78  to an output shaft  77  of a cylinder  76  which is rotatably mounted via a mounting member  75  on a mounting plate  74  secured to the outer surface of the lifting plate  60 . Furthermore, another end portion of a connecting member  80 , which is rotatably attached via a connecting pin  79  to an intermediate portion of the rotating arm portion  67  constituting a part of the supporting arm  65 , is rotatably connected via a connecting pin  81  to a bent portion at the central portion of the drive arm  73 . It should be noted that an internally threaded member  84  meshing with a feed screw shaft  83 , which is rotatably driven by a servo motor  82 , is installed on the rear surface of the attaching member  56 , and the arrangement provided is such that the horizontal movement of the transfer mechanism  46  is effected by the servo motor  82  by means of the attaching member  56 . 
     As for the transfer mechanism  46  arranged as described above, as shown in FIG. 13, when the cylinder  61  is driven to cause the output shaft  62  to project downward from the state shown in FIG. 10, the lifting plate  60  connected to the output shaft  62  via the connecting portion  63  is lowered while being guided by the fitting of the fitting members  58  and  59  with the rail  57  laid on the attaching member  56 , thereby downwardly moving the supporting portion  68  for the pallet  1 . In this state, as shown in FIG. 14, if the cylinder  76  is driven this time to retract the output shaft  77 , the chevron-shaped drive arm  73  connected to that output shaft  77  via the connecting pin  78  rotates downward about the supporting shaft  72 . Concurrently, the rotating arm portion  67  constituting a part of the supporting arm  65  is rotated downward about the bearing  64  by means of the connecting member  80  connected via the connecting pin  81  to the bent portion at the central portion of the drive arm  73 , thereby rotating the supporting portion  68  to a lower position, as shown in the drawing. As described above, the supporting portion  68  can be moved vertically by means of the lifting plate  60  by driving the cylinder  61 . In addition, the supporting portion  68  can be rotated about the bearing  64  between the horizontal position and the lower position by means of the supporting arm  65  by driving the cylinder  76 . 
     FIG. 15 is an enlarged front elevational view of the other transfer mechanism  47  for making up the first transfer mechanism, and FIG. 16 is a plan view thereof. As shown, most portions of this other transfer mechanism  47  are arranged symmetrically with those of the above-described transfer mechanism  46 . Namely, this transfer mechanism  47  is merely different in that the installation position of the rails  52  and  53  is low in view of the relationship for supporting the edge portion of the pallet  1  at a lower position than that of the above-described transfer mechanism  46  as shown in FIG. 8, and in that the shapes of a supporting arm  85  for supporting the pallet  1  and a supporting portion  86  provided at its distal end portion are different. Concerning the other portions, since arrangements symmetrical with those of the transfer mechanism  46  are adopted, and there are no basic differences in their functions, those portions are denoted by the same reference numerals, and a description thereof will be omitted. It should be noted that, as for the supporting arm  85 , as shown in FIG. 16, after a jutting-out portion  87  jutting out horizontally along the bearing  64  is interposed, the supporting arm  85  is bent orthogonally to form a rotating arm portion  88  extending horizontally, and the aforementioned supporting portion  86  for supporting the edge portion of the pallet  1  in the tilted state is directly provided at a distal end of the rotating arm portion  88 . The supporting portion  86  has an inclined surface  89  which abuts against the other edge portion of the tilted pallet  1  and is oriented in the opposite direction, as well as a pair of supporting pieces  90  and  91  on both sides of the inclined surface  89 . As shown in FIG. 15, an internally threaded member  94  meshing with a feed screw shaft  93 , which is rotatively driven by a servo motor  92 , is installed on the rear surface of the attaching member  56 , and the arrangement provided is such that the horizontal movement of the transfer mechanism  47  is effected by the servo motor  92 . 
     The horizontal movement and positioning of the transfer mechanisms  46  and  47  making up the first transfer mechanism are effected by controlling the driving of the servo motors  82  and  92 . Incidentally, when a cleaned pallet  1  is carried onto the tilting means  39  installed on the carrying-in conveyor  5 , the transfer mechanisms  46  and  47  are retreated in advance to positions where they do not interfere with the carrying-in operation of the pallet  1 . After the pallet  1  is mounted on the tilting means  39 , and by timing that the pallet  1  is tilted by the cylinder  42  at a predetermined angle, the transfer mechanisms  46  and  47  are horizontally moved by the servo motors  82  and  92 , and the supporting portions  68  and  86  are jutted out to positions below the pallet  1 . In this case, the output shafts  62  of both cylinders  61  of the transfer mechanisms  46  and  47  are caused to project to set the-lifting plates  60  at their lowered positions, and the output shafts  77  of both or one of the cylinders  76  of the transfer mechanisms  46  and  47  are retracted, as required, which, in turn, cause the chevron-shaped drive arms  73  downward about the supporting shafts  72  and cause the supporting arms  65  and  85  to rotate downward about the bearings  64  by means of the connecting members  80 . In the above-described manner, the supporting portions  68  and  86  supporting the pallet  1  jut out below the pallet  1  mounted on the tilting means  39  in a state in which the supporting portions  68  and  86  are respectively set in the lower positions. 
     Next, in the state in which the supporting portions  68  and  86  jut out below the pallet  1  mounted on the tilting means  39 , the output shafts  77  of the cylinders  76  are caused to project to rotate both supporting arms  65  and  85  to rotate upward about the bearings  64  so as to be restored to the horizontal state. At the same time, the output shafts  62  of both cylinders  61  of the transfer mechanisms  46  and  47  are retracted to raise the lifting plates  60 . It should be noted that the driving timings of the cylinders  76  and  61  may be concurrent or may be provided with a time lag. When the supporting portions  68  and  86  are raised in the above-described manner, the lower two edge portions of the pallet  1  are respectively inserted between the supporting pieces  70  and  71  and between the supporting pieces  90  and  91  and abut against the inclined surfaces  69  and  89 ; whereupon the pallet  1  is lifted upward from the tilting means  39  while the tilted state is being maintained. Subsequently, both servo motors  82  and  92  are driven to horizontally move both transfer mechanisms  46  and  47  making up the first transfer mechanism, and the pallet  1  as it is in the tilted state is transferred to a position above a lower holding means of the centrifugal dehydration means  10 . Then, the output shafts  62  of both cylinders  61  of the transfer mechanisms  46  and  47  are caused to project to lower the lifting plates  60 , and the pallet  1  as it is in the tilted state is mounted on the lower holding means of the centrifugal dehydration means  10 . The output shafts  77  of both or either one of the cylinders  76  of the transfer mechanisms  46  and  47  are retracted, as required, to rotate the drive arms  73  downward about the supporting shafts  72  and cause the supporting arms  65  and  85  to rotate downward about the bearings  64  by means of the connecting members  80 , thereby retreating the supporting shafts  68  and  86  so as not to cause a hindrance. At the same time, the upper portion of the pallet  1  is supported by an upper holding means. Subsequently, both servo motors  82  and  92  are driven to horizontally move both transfer mechanisms  46  and  47 , so that the transfer mechanisms  46  and  47  are retreated to positions where they do not interfere with the dehydration operation by the centrifugal dehydration means  10 , and remain on standby until the ensuing operation. 
     Next, a description will be given of the second transfer mechanism for transferring the pallet  1  after dehydration as it is in the tilted state from the centrifugal dehydration means  10  to the carrying-out conveyor  11 . FIGS. 17 and 18 illustrate the second transfer mechanism, in which FIG. 17 is an enlarged plan view of one transfer mechanism  48  for making up the second transfer mechanism, and FIG. 18 is an enlarged plan view of the other transfer mechanism  40 . As shown in FIG. 9, these transfer mechanisms  48  and  49  making up the second transfer mechanism are horizontally moved in directions opposite to the directions of the transfer mechanisms  46  and  47  making up the first transfer mechanism, and the pallet  1  subjected to dehydration processing is delivered to a tilt restoring means  95  consisting of a mechanism similar to that of the above-described tilting means  39  and adapted to receive the pallet  1  in the tilted state, restore it to the upright state, and mount it on the carrying-out conveyor  11 . Accordingly, when delivering the pallet  1  subjected to dehydration processing to the tilt restoring means  95 , the supporting portions for supporting the pallet  1  in the transfer mechanisms  48  and  49  need to jut out in directions opposite to the directions of the transfer mechanisms  46  and  47  making up the first transfer mechanism. For this reason, as shown in FIGS. 17 and 18, supporting arms  96  and  97  of the transfer mechanisms  48  and  49  are arranged such that after jutting-out portions  100  and  101  jutting out horizontally in directions opposite to the cases of the transfer mechanisms  46  and  47  along bearings  98  and  99  are interposed, the supporting arms  96  and  97  are bent orthogonally to form rotating arm portions  102  and  103  extending horizontally. Further, supporting portions  104  and  105  for supporting the edge portions of the pallet  1  in the tilted state are provided at their distal ends. The transfer mechanisms  48  and  49  making up the second transfer mechanism differ from the transfer mechanisms  46  and  47  making up the first transfer mechanism in the following aspects: First, the directions in which the aforementioned supporting portions  104  and  105  jut out are different. Secondly, although, in the case of the transfer mechanisms  46  and  47  making up the first transfer mechanism, since the pallet  1  is in a state of being wet with the cleaning liquid, even if portions of contact with the edge portions of the pallet  1  are merely the inclined surfaces  69  and  89 , the supporting portions  68  and  86  can be easily separated from the pallet  1 , in the case of the second transfer mechanism, the liquid has been removed from the surfaces of the pallet  1 ; and separation is difficult, it is necessary to devise a measure so that a frictional force is not applied to the portions of contact with the edge portions of the pallet  1  in the supporting portions  104  and  105  by providing rollers or the like as in shown in the drawings. In the other basic arrangements, however, there are no differences with the transfer mechanisms  46  and  47  making up the first transfer mechanism, and the transfer mechanisms  48  and  49  making up the second transfer mechanism are provided with similar functions. Incidentally, reference numeral  106  shown in FIG. 10 denotes a servo motor for driving one transfer mechanism  48  for making up the above-described second transfer mechanism, and the arrangement provided is such that the transfer mechanism  48  is moved horizontally by means of a feed screw shaft  107  and an internally threaded member  108  which are rotatively driven by that servo motor  106 . In addition, reference numeral  109  shown in FIG. 15 denotes a servo motor for driving the other transfer mechanism  49  for making up the above-described second transfer mechanism, and the arrangement provided is such that the transfer mechanism  49  is moved horizontally by means of a feed screw shaft  110  and an internally threaded member  111  which are rotatively driven by that servo motor  109 . 
     Next, a description will be given of the above-described centrifugal dehydration means  10 . As shown in FIG. 9, the centrifugal dehydration means  10  is disposed substantially in a central portion of the dehydration chamber  9 . FIG. 19 is a front elevational view illustrating the portion of this centrifugal dehydration means  10 . As shown in the drawing, the centrifugal dehydration means  10  has a lower holding means  112  and an upper holding means  113  for supporting diagonal corner portions of the pallet  1 , and effects centrifugal dehydration processing while by rotating while supporting the pallet  1  in the tilted state by these holding means  112  and  113 . FIG. 20 is an enlarged vertical cross-sectional view of the lower holding means  112 , and FIG. 21 is a cross-sectional view taken along line A—A thereof. As shown in the drawings, the lower holding means  112  consists of a rotating shaft  116  which is rotatably supported by an apparatus frame  115  by means of a bearing  114 , as well as a corner holding portion  120  which is formed by two side plates  117  and  118  disposed on an upper portion of the rotating shaft  116  and in which an accommodating space  119  is formed into which the corner portion of the pallet  1  can be inserted between the side plates  117  and  118 . A drive wheel  121  such as a gear is secured to a lower portion of the rotating shaft  116 , which is arranged to be rotatively driven by a motor  123  with a brake by means of a toothed belt  122  or the like, as shown in FIG.  19 . Incidentally, if an arrangement is provided such that, at the time of centrifugal dehydration, the rotating direction of the rotating shaft  116  is changed over between the forward and reverse directions so as to change over the rotating direction of the pallet  1 , the arrangement is very effective in terms of the dehydration effect. 
     As shown in FIGS. 20 and 21, a substantially U-shaped connecting member  125  is secured to the upper portion of the rotating shaft  116  by means of an end plate  124  formed integrally with the rotating shaft  116 , and the corner holding portion  120  is rotatably connected to that connecting member  125  by means of connecting pins  126  and  127  on both sides. Further, resilient members  133  and  134  such as springs are disposed between the corner holding portion  120  and a supporting plate  132  attached to the connecting member  125  side, such that the resilient members  133  and  134  are respectively fitted over rods  130  and  131  pivotally secured to supporting shafts  128  and  129  passed through the corner holding portion  120 , thereby constantly urging the corner holding portion  120  so as to return to the horizontal state shown in FIG.  21 . It should be noted that, in this embodiment, as described above, the corner holding portion  120  is rotatably connected to the aforementioned substantially U-shaped connecting member  125  by using the connecting pins  126  and  127  on both sides, and the space is thereby formed into which the corner portion of the pallet  1  can be inserted between these connecting pins  126  and  127 . Thus the arrangement is provided such that the apex portion of the corner portion can be aligned with the rotational center of the corner holding portion  120 . However, it is also possible to provide an arrangement in which, as indicated by the two-dot chain lines in FIG. 20, by using one supporting shaft, an intermediate portion of the supporting shaft is notched into a semicircular shape, thereby allowing the apex portion of the corner portion to be aligned with the rotational center of the corner holding portion  120 . Further, supporting shafts  139  to  142 , over which cylindrical rollers  135  to  138  are respectively fitted rotatably, are installed by being passed through the corner holding portion  120  and are respectively fixed by nuts. Incidentally, the supporting shafts  139  to  142  are positioned such that an intersection between a plane connecting abutting portions of the cylindrical rollers  135  to  136 , against which the pallet  1  abut, and a plane connecting abutting portions of the cylindrical rollers  137  and  138  is aligned with the centers of the connecting pins  126  and  127 . Namely, the supporting shafts  139  to  142  are positioned such that the apex portion of the corner portion of the pallet  1  is aligned with the centers of the connecting pins  126  and  127  when the pallet  1  is supported by the cylindrical rollers  135  to  138 . It should be noted that a pressing and supporting member  143  serving as a resilient clamping means is provided on the inner side of the corner holding portion  120  to cope with a change in the thickness of the pallet  1 , as shown in FIG. 20, so that the pallet  1  will not become shaky in its thickness wise direction. 
     FIG. 22 is an enlarged vertical cross-sectional view illustrating the upper holding means  113  for holding an upper corner portion of the pallet  1 . As shown, as for the upper holding means  113 , since arrangements similar to those of the above-described lower holding means  112  are adopted except that guide plates  144  and  145  for guiding the pallet  1  are provided and that a rotating shaft  146  is supported by a bearing  147  so as to be capable of rotating in conjunction with the rotation of the pallet  1 , the component parts will be denoted by the same reference numerals and a description thereof will be omitted. Incidentally, the guide plates  144  and  145  are useful such as when the upper corner portion of the pallet  1  mounted on the lower holding means  112  and having a different size or aspect ratio, in particular, is guided into and held onto the upper holding means  113 . 
     The pallet  1  transferred in the tilted state to a position above the lower holding means  112  by the transfer mechanisms  46  and  47  making up the first transfer mechanism is mounted with its lower corner portion inserted in the corner holding portion  120 , and is mounted as it is in the tilted state. At this point of time, the corner holding portion  120  maintains a substantially horizontal state by virtue of the resilient action of the aforementioned resilient members  133  and  134 . In due course of time, if a supporting frame  148  or the portion of the rotating shaft  116  is lowered by an appropriate method, and the upper holding means  113  is lowered, the corner portion of the upper portion of the pallet  1  is guided into the corner holding portion  120  by the guide plates  144  and  145 . In this case, in a case where the pallet  1  is square, the upper corner portion is guided into the corner holding portion  120  in a state in which the pallet  1  remains substantially in the tilted state. However, in a case where the pallet  1  is rectangular, the upper corner portion is guided into the corner holding portion  120  while gradually changing the tilted state such that the vertical diagonal line approaches the center of rotation which connects the lower holding means  112  and the upper holding means  113 . If the upper holding means  113  is further lowered, as the edge portion of the pallet  1  and the cylindrical rollers  135  and  136  or  137  and  138  abut against each other, both corner holding portions  120  of the lower holding means  112  and the upper holding means  113  are tilted by overcoming the resiliency of the resilient members  133  and  134  to allow the edge portions of the pallet  1  and the cylindrical rollers  135  and  136  and  137  and  138  to be brought into close contact with each other. Consequently, the diagonal line of the pallet  1  is set on the rotating shaft  116 , and stable centrifugal dehydration in which the amount of runout is small becomes possible. As described above, in various component parts of this pallet cleaning apparatus, joint use of the apparatus becomes possible. 
     Next, a description will be given of the results of an experiment on the dehydration effect which was conducted by using the above-described centrifugal dehydration means  10 . In experiment 1, with respect to a resin-made pallet after effecting ordinary water cleaning using the above-described centrifugal dehydration means  10 , changes in the dehydration effect were examined according to the presence or absence of the changeover between forward and reverse rotation and the frequency of changeover in the case where the change over was effected alternately at 5-second intervals. Incidentally, the rotational speed of the pallet was set to. 450 rpm. However, as for the rise concerning the rotational speed of the pallet at the time of the changeover between forward and reverse rotation, it took an acceleration time of 3 seconds or thereabouts until the target of 450 rpm was reached. Table 1 shows the results of the above-described experiment 1. It should be noted that the number of drops of water in the table shows the number of drops of water counted in a case where the pallet subjected to dehydration processing was placed on corrugated cardboard, and the number of drops of water adhered to the surface of the corrugated cardboard was counted at that time. In this case, the number of drops of water in which drops of water remaining inside the pallet moved round to the pallet surface through openings or the like formed in the mounting surface was also counted. From the results of this experiment 1, it became clear that the dehydration effect can be improved substantially if the changeover between forward and reverse rotation is effected even once as compared with the case where the changeover is not effected at all. In addition, it became clear that if the frequency of changeover between forward and reverse rotation is set to two or more, it is possible to obtain substantially satisfactory dehydration results which are free of problems in the actual use in the state persisting after centrifugal dehydration. In particular, it became clear that in the case where the frequency of changeover between forward and reverse rotation is set to three or more so that the pallet is rotated at least twice each in the forward and reverse directions, even more favorable dehydration results can be obtained stably. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Number of Water 
                   
                   
               
               
                   
                   
                 Drops Attached to 
                   
                   
               
               
                   
                 Method of Rotation of Pallet 
                 Corrugated Cardboard 
                 State of Draining off Surface 
                 State of Draining of Interior 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 No changeover 
                   
                 15 
                 slightly wet state 
                 a state in which 4 or 5 water 
               
               
                   
                 between Forward 
                   
                   
                   
                 drops are present in one 
               
               
                   
                 (F) and Reverse (R) 
                   
                   
                   
                 recessed portion on the rear 
               
               
                   
                   
                   
                   
                   
                 side in the forwardly 
               
               
                   
                   
                   
                   
                   
                 rotating direction 
               
               
                   
                 Changeover 
                 F → R 
                 8 
                 considerably dry state 
                 a state in which 1 or 2 water 
               
               
                   
                 between F and R: 1 
                   
                   
                   
                 drops are present in one 
               
               
                   
                   
                   
                   
                   
                 recessed portion on the front 
               
               
                   
                   
                   
                   
                   
                 side in the reversely 
               
               
                   
                   
                   
                   
                   
                 rotating direction 
               
               
                   
                 Changeover 
                 F → R → F 
                 5 
                 substantially Dry state 
                 a state in which water drops 
               
               
                   
                 between F and R: 2 
                   
                   
                   
                 are practically nil 
               
               
                   
                 Changeover 
                 F → R → F → R 
                 4 
                 substantially Dry state 
                 a state in which water drops 
               
               
                   
                 between F and R: 3 
                   
                   
                   
                 are practically nil and the 
               
               
                   
                   
                   
                   
                   
                 condition is more satisfactory 
               
               
                   
                 Changeover 
                 F → R → F → R → 
                 3 
                 substantially Dry state 
                 a state in which water drops 
               
               
                   
                 between F and R: 5 
                 F → R 
                   
                   
                 are practically nil and the 
               
               
                   
                   
                   
                   
                   
                 condition is more satisfactory 
               
               
                   
                 Changeover 
                 F → R → F → R → 
                 3 
                 well dry state 
                 a state in which water drops 
               
               
                   
                 between F and R: 9 
                 F → R → F → R → 
                   
                   
                 are practically nil and the 
               
               
                   
                   
                 F → R 
                   
                   
                 condition is more satisfactory 
               
               
                   
                   
               
               
                   
                 Forward: forwardly rotated for 5 seconds  
               
               
                   
                 Reverse: reversely rotated for 5 seconds  
               
            
           
         
       
     
     In experiment 2, by using the same apparatus as that of the above-described experiment 1, changes in the dehydration effect were examined in a case where the interval of changeover between forward and reverse rotation was varied in a state in which the frequency of changeover between forward and reverse rotation was set to 3 so that the pallet is rotated twice each in the forward and reverse directions. It should be noted that the rotational speed of the pallet was set to 450 rpm in the same way as in experiment 1. Table 2 shows the results of the above-described experiment 2. The number of drops of water in the table shows the number of drops of water counted in the case where the number of drops of water adhered to the surface of the corrugated cardboard was counted when the pallet subjected to dehydration processing was placed on the corrugated cardboard, in the same way as experiment 1. From the results of this experiment 2, it became clear that even if the interval of changeover between forward and reverse rotation is varied, there is not much difference in the dehydration effect in practical use. Namely, it became clear that if the frequency of changeover between forward and reverse rotation is set to an appropriate number, a more efficient dehydration effect can be obtained by setting the interval of changeover between forward and reverse rotation to a short duration. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Number of Water 
               
               
                   
                 Drops Adhered to 
               
               
                 Method of Rotation of Pallet 
                 Corrugated Cardboard 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Changeover between 
                 F → R → F → R 
                 4 
               
               
                 forward and reverse: 3 
                 operated for 5 seconds 
               
               
                   
                 each 
               
               
                 Changeover between 
                 F → R → F → R 
                 4 
               
               
                 forward and reverse: 3 
                 operated for 10 seconds 
               
               
                   
                 each 
               
               
                 Changeover between 
                 F → R → F → R 
                 3 
               
               
                 forward and reverse: 3 
                 operated for 15 seconds 
               
               
                   
                 each 
               
               
                 Changeover between 
                 F → R → F → R 
                 3 
               
               
                 forward and reverse: 3 
                 operated for 30 seconds 
               
               
                   
                 each 
               
               
                   
               
            
           
         
       
     
     In experiment 3, by using the same apparatus as that of the above-described experiment, changes in the dehydration effect were examined in the case where the rotational speed of the pallet was varied in the state in which the frequency of changeover between forward and reverse rotation was set to 3 so that the pallet is rotated twice each in the forward and reverse directions. Table 3 shows the results of the above-described experiment 3. The number of drops of water in the table shows the number of drops of water counted in the case where the number of drops of water adhered to the surface of the corrugated cardboard was counted when the pallet subjected to dehydration processing was placed on the corrugated cardboard, in the same way as experiment 1. The mark “◯” shows a state in which most of the drops of water were removed, while the mark “Δ” shows a state in which the drops of water were noticeable. From the results of this experiment 3, it became clear that if the rotational speed of the pallet is set to 350 rpm or more, a satisfactory dehydration effect can be obtained in view of both the number of drops of water remaining on the obverse surfaces and the state of draining on the side surfaces or the inner surfaces. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
                 Number of Water 
                   
               
               
                 Rotational 
                 Drops Adhered 
                 State of Draining 
               
            
           
           
               
               
               
               
               
            
               
                 Speed of 
                 to Corrugated 
                 Obverse 
                 Side 
                 Inner 
               
               
                 Pallet (rpm) 
                 Cardboard 
                 surface 
                 surface 
                 Surface 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 450 
                 3 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                 400 
                 3 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                 350 
                 4 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                 300 
                 8 
                 Δ 
                 ◯ 
                 Δ 
               
               
                 250 
                 20 
                 Δ 
                 ◯ 
                 Δ 
               
               
                   
               
            
           
         
       
     
     As described above, it became clear from experiments 1 to 3 that if the changeover between forward and reverse rotation is effected even once, the dehydration effect can be improved substantially as compared with the case of no changeover. In addition, concerning the frequency of changeover between forward and reverse rotation, it became clear that if it is set to two or more, it is possible to obtain substantially satisfactory dehydration results which are free of problems in the actual use in the state persisting after centrifugal dehydration. In addition, as for the interval of changeover between forward and reverse rotation, it became clear that even if it is set to a long duration, the dehydration effect is not improved much. Accordingly, if the interval of changeover between forward and reverse rotation is set to as short a duration as possible within a range that does not impose strains on the apparatus and the like, a more efficient dehydration operation is possible. Furthermore, concerning the rotational speed of the pallet, it became clear that if it is set to 350 rpm or more, a satisfactory dehydration effect can be obtained. 
     In the invention, since the arrangement provided is such that the pallet or the like is rotated while being held on its diagonal line, the center of gravity of the pallet or the like is situated on the axis of rotation. Hence, the runout due to the centrifugal force can be suppressed easily and accurately. Accordingly, even if the apparatus is rotated at high speed, safety can be ensured, and the efficiency of operation can be improved. In addition, since the pair of corner portions on the diagonal line are held, the center of gravity of the pallet or the like can be easily aligned with the axis of rotation, it is possible to accurately overcome the positional offset during the rotation of the pallet or the like. 
     The invention is not limited at all to the description of the mode for carrying out the invention and the description of the embodiments. The invention includes various modifications that can be conceived easily by those skilled in the art, without departing from the description of the scope of claim.