Patent Publication Number: US-2022219913-A1

Title: Conveying apparatus and method

Description:
TECHNICAL FIELD 
     The present invention relates to conveying apparatus and method that mainly convey a finished article, a half-finished article, a part, or the like of a wearable article while varying the speed thereof. 
     BACKGROUND ART 
     This kind of conveying apparatus includes a plurality of pads, and receives workpieces from an upstream side in a reception position by the pads and delivers the workpieces to a downstream side in a delivery position. Variations in pad conveyance speed between the reception and delivery cause variations in the space between the workpieces between the reception position and the delivery position. 
     This kind of conveying apparatus usually includes a large number of pads that are driven and rotated by a rotating shaft, a supporting ring that is rotatably supported around the rotating shaft and supports the pads in such a way that the pads move in a predetermined orbit, and a guide mechanism that is provided between the pads and the rotating shaft and guides the relative movement of the pads and the supporting ring. A large number of sliders, whose number is the same as that of pads, are mounted on a rail of the guide mechanism so as to be slidable in a circumferential direction. Each slider is guided by the rail and is accelerated and decelerated in the circumferential direction together with the pad by a variable speed mechanism (PTL 1). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: WO 2018/011905 (FIG. 4) 
       
    
     SUMMARY OF INVENTION 
     In order to increase the number of workpieces that are conveyed by this kind of conveying apparatus per unit time, it is necessary to increase the number of articles that can be obtained by the conveying apparatus, that is, the number of pads and the number of sliders. However, an increase in the number of articles that can be obtained by the conveying apparatus causes interference between adjacent sliders; thus, there is an upper limit to the number of pads. 
     Moreover, the sliders of the guide mechanism guiding the pads are placed in positions closer to an inner circumferential side than the pads. Consequently, the distance between adjacent sliders is smaller than the distance between adjacent pads, which makes the adjacent sliders tend to interfere with each other. 
     Furthermore, an attempt to narrow the space between the workpieces also causes interference between the sliders. 
     Therefore, an object of the present invention is to make it possible to increase the number of workpieces that can be conveyed by a conveying apparatus per unit time by narrowing the pitch between workpieces in the conveying apparatus provided with a variable speed mechanism and in a conveying method and thereby support high-speed processing. 
     In a first aspect, the apparatus of the present invention includes: a rotating shaft  10 ; 
     first pads  1  and second pads  2  arranged around the rotating shaft  10 , the first and second pads orbiting along an orbit with their speeds being varied, the first and second pads being alternately arranged so as to be adjacent to each other in a circumferential direction R and each holding a workpiece W; 
     a variable speed mechanism  20  provided for each of the first and second pads, the variable speed mechanism  20  for accelerating and decelerating each of the first and second pads during the orbiting; 
     a first slider  1 S provided for each of the first pads  1  in a different position in an axial direction S of the rotating shaft, the first slider  1 S orbiting with the corresponding first pad  1  with speed of the first slider  1 S being varied; 
     a second slider  2 S provided for each of the second pads  2  in a different position in the axial direction S of the rotating shaft, the second slider  2 S orbiting with the corresponding second pad  2  with speed of the second slider  2 S being varied; 
     a first rail  1 L supporting the first pads  1  via the first sliders  1 S, the first rail  1 L guiding the first sliders  1 S and not guiding the second sliders  2 S; and 
     a second rail  2 L arranged so as to be spaced apart from the first rail  1 L and supporting the second pads  2  via the second sliders  2 S, the second rail  2 L guiding the second sliders  2 S and not guiding the first sliders  1 S. 
     In the first aspect, the method of the present invention includes: a step of conveying in which the first and second pads  1  and  2  convey the workpieces W with speeds of the first and second pads  1  and  2  being varied; 
     a step of accelerating in which circumferential velocities of the first and second pads  1  and  2  are accelerated by the respective variable speed mechanisms  20 ; 
     a step of moving and separating in which the first and second pads  1  and  2  move in a state where a distance between the first pad  1  and the second pad  2  is increased and the first pad and the second pad are separated with each other after speeds of the first and second pads increased in the step of accelerating; 
     a step of decelerating in which the circumferential velocities of the first and second pads  1  and  2  are decelerated by the respective variable speed mechanisms  20 ; and 
     a step of moving and approaching in which the first slider  1 S and the second slider  2 S, which have been decelerated in the step of decelerating, overlap each other in a part in the circumferential direction R, which causes the first pad  1  and the second pad  2  to approach each other, and the first pad  1  and the second pad  2  move in this state where the first pad  1  and the second pad  2  have approached each other. 
     In the first aspects, the first and second pads  1  and  2  are adjacent to each other in the circumferential direction R, and the first sliders are individually provided for the first pads  1  and the second sliders are individually provided for the second pads  2 . That is, the first and second sliders are adjacent to each other in the circumferential direction R, are separated from each other in the axial direction S, and overlap each other in a part in the circumferential direction during deceleration. This makes it possible to reduce the pitch between the first and second pads  1  and  2  that are adjacent to each other in the circumferential direction R. 
     This reduces the pitch between the workpieces held by the pads, which makes it possible to increase the number of workpieces that can be conveyed by the conveying apparatus per unit time and support high-speed processing. 
     Moreover, it is possible to form each slider so as to be long in the circumferential direction, which stabilizes an orbiting operation of each pad. 
     In a second aspect, the apparatus of the present invention includes: first pads  1  and second pads  2  arranged around an axis  10 S, the first and second pads orbiting along an orbit with their speeds being varied, the first and second pads being alternately arranged so as to be adjacent to each other in a circumferential direction R and each holding a workpiece W; 
     a first slider  1 S and a second slider  2 S provided for each of the first and second pads  1  and  2  in different positions with each other in an axial direction S of the axis  10 S, the first and second sliders orbiting with the first and second pads  1  and  2  with speeds of the first and second sliders  1 S and  2 S being varied; 
     a first rail  1 L supporting the first pads  1  or the second pads  2  via the first sliders  1 S, the first rail  1 L guiding the first sliders  1 S and not guiding the second sliders  2 S; and 
     a second rail  2 L arranged so as to be spaced apart from the first rail  1 L, the second rail supporting the first pads  1  or the second pads  2  via the second sliders  2 S, the second rail guiding the second sliders  2 S and not guiding the first sliders  1 S, 
     wherein, for each of the first pads  1 , a first contact length L 11  by which the first slider  1 S is in contact with the first rail  1 L is longer than a second contact length L 12  by which the second slider  2 S is in contact with the second rail  2 L, and 
     wherein, for each of the second pads  2 , a third contact length L 21  by which the first slider  1 S is in contact with the first rail  1 L is shorter than a fourth contact length L 22  by which the second slider  2 S is in contact with the second rail  2 L. 
     In the second aspect, the method of the present invention includes: a step in which the first and second pads  1  and  2  convey the workpieces W with speeds of the first and second pads  1  and  2  being varied; 
     a step of accelerating in which circumferential velocities of the first and second pads  1  and  2  are accelerated; 
     a step in which the first and second pads  1  and  2  move in a state where a distance between the first pad  1  and the second pad  2  is increased and the first pad and the second pad are separated with each other after speeds of the first and second pads increased in the step of accelerating; 
     a step of decelerating in which the circumferential velocities of the first and second pads  1  and  2  are decelerated; and 
     a step in which the first slider  1 S and the second slider  2 S, which have been decelerated in the step of decelerating, overlap each other in a part in the circumferential direction R, which causes the first pad  1  and the second pad  2  to approach each other, and the first pad  1  and the second pad  2  move in this state where the first pad  1  and the second pad  2  have approached each other. 
     In the second aspect, the first and second sliders provided for each of the first and second pads  1  and  2  that are adjacent to each other in the circumferential direction R are separated from each other in the axial direction S; therefore, the first slider of the first pad and the second slider of the second pad, each having a long contact length by which each slider is in contact with the rail, can overlap each other in a part in the circumferential direction during deceleration. This makes it possible to reduce the pitch between the first and second pads that are adjacent to each other in the circumferential direction. 
     Thus, as in the case of the first aspect, it is possible to increase the number of workpieces that are conveyed per unit time and support high-speed processing. 
     Moreover, since the contact length of the first slider of the first pad and the contact length of the second slider of the second pad are long, an orbiting operation of each pad is stabilized. 
     It is to be noted that the contact length by which the first or second slider is in contact with the rail means the length, from one circumferential end to the other circumferential end, of the first (or second) slider supporting one pad. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic front view of a conveying apparatus showing one embodiment of the present invention. 
         FIG. 2  is a schematic longitudinal sectional view of the conveying apparatus taken along the line  4   b - 4   b  of  FIG. 4 . 
         FIGS. 3A and 3B  are schematic plan views showing a pad and a holding base. 
         FIGS. 4( a ), ( b ), and ( c )  are schematic front view, sectional view, and rear view, respectively, of a guide mechanism. 
         FIG. 5( a )  is a front view of a variable speed mechanism,  FIGS. 5( b ) and ( c )  are longitudinal sectional views showing second and first sliders, respectively, and  FIG. 5( d )  is a front view showing a part of the guide mechanism  30 . 
         FIG. 6  is a schematic perspective view of a conveying apparatus showing another embodiment of the present invention. 
         FIG. 7  is a schematic perspective view showing a rail and a slider. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the preferred conveying apparatus of the first aspect, the first and second rails  1 L and  2 L are attached to one supporting ring  3 . 
     In this case, there is no need to provide a supporting ring for each rail. 
     More preferably, the supporting ring  3  includes a first surface  1 F which is one-side surface in the axial direction S and a second surface  2 F which is the other-side surface in the axial direction S, and the first rail  1 L and the second rail  2 L are attached to the first surface  1 F and the second surface  2 F, respectively. 
     In this case, a guide mechanism including a supporting ring, a rail, and a slider is likely to be compact. 
     Preferably, the first rail  1 L and the second rail  2 L are each formed in a shape of an endless loop. 
     In this case, the prevision of each rail is high. 
     Preferably, a pair of the first rails  1 L is provided in such a way that the first rails  1 L are separated from each other in the axial direction S and a pair of the second rails  2 L is provided in such a way that the second rails  2 L are separated from each other in the axial direction S, the first sliders  1 S are provided for each rail of the first rails  1 L, and the second sliders  2 S are provided for each rail of the second rails  2 L. 
     In this case, it is possible to support the pad by a pair of rails separated from each other in the axial direction S and the pad is not supported in a cantilever manner, which results in high durability and stability. 
     Preferably, the conveying apparatus further includes a tubular portion  31  that rotatably supports the rotating shaft, and the supporting ring  3  is rotatably supported on the tubular portion  31 . 
     In this case, the supporting ring  3  rotates with the pads at high speeds and each slider reciprocates in response to variations in speed. This makes each slider and each rail less likely to be worn away and increases durability thereof. 
     In the preferred conveying method, a step in which the first pads  1  and the second pads  2  receive the workpieces W from an upstream apparatus and the first pads  1  and the second pads  2  deliver the workpieces W to a downstream apparatus in the moving and separating step. 
     In this case, it is possible to perform what is called a repitch operation that increases the distance between two workpieces which are close to each other. 
     In the preferred conveying apparatus of the second aspect, for each of the first pads  1 , the number of the first sliders  1 S is larger than the number of the second sliders  2 S, and, for each of the second pads  2 , the number of the first sliders  1 S is smaller than the number of the second sliders  2 S. 
     In this case, after making the shapes and sizes of the first and second sliders uniform, it is possible to set the first and second sliders so as to have the aforementioned contact length relationship only by a difference in the number of first or second sliders supporting each pad. 
     For example, each of the first pads  1  may be supported by two first sliders  1 S and one second slider  2 S and each of the second pads  2  may be supported by one first slider  1 S and two second sliders  2 S. 
     More preferably, a first length L 1  of each of the first pads  1  in the circumferential direction R is shorter than the first contact length L 11  and longer than the second contact length L 12 , and a second length L 2  of each of the second pads  2  in the circumferential direction R is longer than the third contact length L 21  and shorter than the fourth contact length L 22 . 
     In this case, a slider having a contact length longer than the length of each pad in the circumferential direction achieves stable orbiting of the pad. 
     Any feature illustrated and/or depicted in conjunction with one of the aforementioned aspects or the following embodiments may be used in the same or similar form in one or more of the other aspects or other embodiments, and/or may be used in combination with, or in place of, any feature of the other aspects or embodiments. 
     The present invention will be understood more clearly from the following description of preferred embodiments taken in conjunction with the accompanying drawings. Note however that the embodiments and the drawings are merely illustrative and should not be taken to define the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying drawings, like reference numerals denote like components throughout the plurality of figures. 
     EMBODIMENTS 
     Hereinafter, one embodiment of the present invention will be described in accordance with the drawings. 
     First, an outline of the present manufacturing apparatus will be described. 
     In  FIG. 1 , the present manufacturing apparatus includes an upstream roll (an upstream apparatus)  4 , a variable speed conveying apparatus  5 , and a downstream roll (a downstream apparatus)  6 . The variable speed conveying apparatus  5  includes a plurality of first and second pads  1  and  2  alternately in a circumferential direction R. The above-mentioned rolls  4  and  6  and the pads  1  and  2  for holding convey workpieces W. 
     The pads  1  and  2  for holding rotate along the orbit of the variable speed conveying apparatus  5  with the speeds of the pads  1  and  2  being varied, and receive the workpieces W from the upstream roll  4  in a reception position P 1  and deliver the workpieces W onto the downstream roll  6  in a delivery position P 2 . 
     Next, the details of a variable speed mechanism  20  of this embodiment will be described. The variable speed mechanism  20  is provided for each of the pads  1  and  2  and accelerates and decelerates each of the pads  1  and  2  while the pads  1  and  2  are orbiting. 
     As shown in  FIG. 1 , a plurality of crank arms  22  are arranged on one driving wheel  21  with an equiangular pitch. The space between the crank arms  22  is unchangeable, and arm centers  220 , which are the rotation centers of these crank arms  22 , rotate with the driving wheel  21  at the same angular speed. The driving wheel  21  rotates with a rotating shaft  10  in the circumferential direction R at a constant angular speed. 
     A cam roller  223  for varying speed is provided in a position separated from the arm center  220  of each crank arm  22 , and the cam roller  223  moves along a cam groove  44  for varying speed of  FIG. 2 . The cam groove  44  for varying speed is eccentric with respect to a center of drive  210 , which is the rotation center of the driving wheel  21 , and is immovable. Thus, the distance from the center of drive  210  to the cam roller  223  periodically increases and reduces depending on the positions of the cam roller  223  and the cam groove  44 . 
     Consequently, each crank arm  22  of  FIG. 1  periodically swings within a given angular range and the tip of the crank arm  22  periodically swings. That is, in the approximately left half of an area shown in  FIG. 1 , the tip of each crank arm  22  is displaced from the arm center  220  of the crank arm  22  in a conveyance direction along the circumferential direction R; in the approximately right half of the area shown in  FIG. 1 , the tip of each crank arm  22  is displaced in an opposite direction. 
     A link lever  23  pin linked to the tip of each crank arm  22  and each of the first and second pads  1  and  2  pin linked to the link levers  23  are also displaced in conjunction with a swing of the tip of the crank arm  22 . Due to the above-mentioned swing of each crank arm  22 , the distance between the arm center  220  of the crank arm  22  and each of the pads  1  and  2  varies; therefore, the space between the first pad  1  and the second pad  2  that are adjacent to each other also varies. Consequently, the angular speeds of the first and second pads  1  and  2  for holding and the space between the pads  1  and  2  in the circumferential direction R vary. 
     Next, a guide mechanism  30  guiding the above-mentioned orbiting of the pads  1  and  2  will be described. 
     As shown in  FIG. 2 , the first and second pads  1  and  2  are guided by the guide mechanism  30  along the above-mentioned orbit via first and second bases  1 B and  2 B, respectively, which are long in an axial direction S. The guide mechanism  30  includes first and second sliders  1 S and  2 S, first and second rails  1 L and  2 L, and a supporting ring  3  in the shape of a doughnut-shaped plate, which are shown in  FIGS. 2 and 4 . 
     In  FIG. 2 , the driving wheel  21  integrally rotates with the rotating shaft  10 . The rotating shaft  10  is rotatably supported on the inner circumferential side of a tubular portion  31 . On the other hand, the supporting ring  3  is rotatably supported on the outer periphery of the tubular portion  31 . A driving force of an unillustrated motor may be input to the supporting ring  3  to make the supporting ring  3  rotate at a constant angular speed. 
     In  FIGS. 5( b ) and ( c ) , the first rail  1 L and the second rail  2 L are attached to a first surface  1 F which is one surface of each supporting ring  3  in the axial direction S and a second surface  2 F which is the other surface in the axial direction S, respectively. Consequently, the first rail  1 L and the second rail  2 L are provided so as to be separated from each other in the axial direction S and parallel to each other. Moreover, a pair of first rails  1 L is arranged such that the first rails  1 L are parallel to each other, and a pair of second rails  2 L is also arranged such that the second rails  2 L are parallel to each other. 
     As shown in  FIGS. 4( a ) and ( c ) , each of the rails  1 L and  2 L is an endless annular ring (perfect circle). Only the first slider  1 S is slidably attached to the first rail  1 L of  FIG. 4( b ) . On the other hand, only the second slider  2 S is slidably attached to the second rail  2 L. 
     In  FIG. 2 , the sliders  1 S and  2 S and the rails  1 L and  2 L are placed in positions closer to the center of drive  210  than the pads  1  and  2 . That is, the orbital paths of the sliders  1 S and  2 S are located in positions closer to an inner circumferential side than the orbital paths of the pads  1  and  2 . 
     In  FIG. 5 , the first sliders  1 S are provided for the respective first pads  1  in different positions from the second sliders  2 S in the axial direction S of the rotating shaft  10  ( FIG. 2 ) and orbit with the first pads  1  with the speeds of the first sliders  1 S and the first pads being varied. The second sliders  2 S are provided for the respective second pads  2  in different positions from the first sliders  1 S in the axial direction S of the rotating shaft  10  ( FIG. 2 ) and orbit with the second pads  2  with the speeds of the second sliders  2 S and the second pads being varied. The above-mentioned first rail  1 L of  FIG. 2  supports the first pads  1  via the first sliders  1 S and the first bases  1 B, and guides the first sliders  1 S and does not guide the second sliders  2 S. On the other hand, the second rail  2 L supports the second pads  2  via the second sliders  2 S and the second bases  2 B, and guides the second sliders  2 S and does not guide the first sliders  1 S. 
     In the present embodiment, each rail is formed so as to be convex in cross section and each slider is formed so as to be concave in cross section. However, each rail may be formed as a concave groove and each slider may be formed so as to be convex. 
     In  FIG. 2 , a cam drum  32  may be fixed to the tubular portion  31 . First and second cam grooves  41  and  42  that displace the pads  1  and  2 , respectively, in the axial direction S are provided in the cam drum  32 . 
     In  FIG. 2 , the first and second pads  1  and  2  are attached to the first and second bases  1 B and  2 B, respectively, in such a way that the first and second pads  1  and  2  can reciprocate in the axial direction S. On the other hand, the first and second pads  1  and  2  include first and second cam followers  1 C and  2 C fitted into the first and second cam grooves  41  and  42 , respectively. 
     Consequently, the above-mentioned first and second pads  1  and  2  of  FIG. 3A  separate from each other in the circumferential direction R and also separate from each other in the axial direction S as shown in  FIG. 3B  while rotating in the circumferential direction R ( FIG. 1 ). 
     As shown in  FIG. 3A , the pads  1  and  2  have roughly triangular shapes facing in opposite directions and can approach each other in the circumferential direction R. Therefore, the first base  1 B and the second base  2 B of  FIG. 3A  approach each other in the reception position P 1  of  FIG. 1 , that is, at low speeds. 
     On the other hand, in the reception position P 1 , the first and second sliders  1 S and  2 S of  FIGS. 4( a ) and ( c )  are relatively displaced to the extent that a part of the first slider  1 S and a part of the second slider  2 S overlap each other in the circumferential direction R. This makes it possible to increase the length (size) of each of the sliders  1 S and  2 S in the circumferential direction R and thereby make stable guidance possible and, at the same time, to reduce the pitch between the above-mentioned pads  1  and  2  of  FIG. 1  and thereby increase the number of pads  1  and  2 . 
     This makes high-speed conveyance of small workpieces possible. 
     Next, a method of variable speed conveyance of the workpieces W of  FIG. 1  will be described. 
     Variable speed conveyance of the workpieces includes the following steps: a conveying step, an accelerating step, a moving and separating step, a decelerating step, and a moving and approaching step. 
     The first and second pads  1  and  2  of  FIG. 1  receive the workpieces W from the upstream roll  4  in the reception position P 1  by sucking the workpieces W and making them cling thereto by negative pressure. The first and second pads  1  and  2  that have received the workpieces W perform the step of conveying the workpieces W by orbiting with the speeds of the first and second pads  1  and  2  being varied. Then, after delivering the workpieces W to the downstream roll  6  in the delivery position P 2 , the first and second pads  1  and  2  of  FIG. 1  return to the reception position P 1  with the speeds thereof being varied. The following are detailed descriptions of these operations. 
     In the above-mentioned accelerating stroke (period), the circumferential velocities of the first and second pads  1  and  2  that have received the workpieces W in the reception position P 1  are accelerated by the variable speed mechanisms  20 . As a result, the speeds of the pads  1  and  2  are gradually increased and the pitch between the first and second pads  1  and  2  that are adjacent to each other is increased; in this way, the moving and separating step is performed. 
     It is to be noted that the operation and structure of the variable speed mechanism  20  are well known per se and disclosed in, for example, WO 2018/011905, the contents of which are incorporated herein in their entirety. 
     That is, in the moving and separating step, the first and second pads  1  and  2  holding the workpieces W move and orbit in a state in which the distance between the first pad  1  and the second pad  2 , whose speeds were increased by acceleration, is increased. 
     On the other hand, the first and second pads  1  and  2  separate in the circumferential direction R as shown in  FIGS. 3A and 3B  by being guided by the first and second cam grooves  41  and  42 , respectively, of the cam drum  32  as shown in  FIG. 2 , and then the distance between the first and second pads  1  and  2  is increased in the axial direction S. 
     Then, the first and second pads  1  and  2  of  FIG. 1  arrive at the delivery position P 2  abutting on the downstream roll  6  and deliver the workpieces W held thereby to the downstream roll  6 . At the time of this delivery, the circumferential velocities of the pads  1  and  2  may be in any one of the following states: the circumferential velocities of the pads  1  and  2  are being accelerated, the circumferential velocities of the pads  1  and  2  are being increased, and the circumferential velocities of the pads  1  and  2  are constant. 
     When the workpieces W are delivered in a state in which they are separated in both the circumferential direction R and the axial direction S of  FIG. 3  as described above, the workpiece W may be a panel placed in a main body portion of a disposable diaper. A method for placing such a panel is disclosed in WO 2017/056952 A1, for example. 
     After the above-mentioned delivery, the circumferential velocities of the first and second pads  1  and  2  of  FIG. 1  are decelerated by the variable speed mechanisms  20  from the delivery position P 2  until arrival at the reception position P 1 : in this way, the decelerating step is performed. During this deceleration, the first and second pads  1  and  2  approach each other in the axial direction S along the first and second cam grooves  41  and  42  of  FIG. 2  and approach each other in the circumferential direction R as shown in  FIG. 3A . 
     When arriving at the reception position P 1  in a state in which the first and second pads  1  and  2  of  FIG. 1  approach each other in the circumferential direction R, the first and second pads  1  and  2  receive the workpieces W from the upstream roll  4 . 
     In this case, when the workpiece W is small, the pads  1  and  2  of  FIG. 3A  are also small in the circumferential direction R and the pads  1  and  2  can approach each other. On the other hand, the orbiting of the pads  1  and  2  is guided by the guide mechanism  30  of  FIG. 4 . 
     The first and second sliders  1 S and  2 S of the guide mechanism  30  of  FIG. 4  need a certain length in the circumferential direction R in order to stabilize guidance of the pads in the circumferential direction R. Thus, in the reception position P 1 , the adjacent sliders  1 S and  2 S overlap each other in the circumferential direction R. 
     That is, a step is performed in which, in the reception position P 1  of  FIG. 4 , the first slider  1 S and the second slider  2 S after deceleration overlap each other in a part in the circumferential direction R, which causes the first pad  1  and the second pad  2  of  FIG. 5  to approach each other, and the first pad  1  and the second pad  2  move in this state in which they have approached each other. During this step, the first pad  1  and the second pad  2  receive the workpieces W from the upstream roll  4  in the reception position P 1 . 
     The reason why this overlapping is made possible is that, in  FIG. 5 , the first slider  1 S of  FIG. 5( c )  guiding the first pad  1  in the circumferential direction R slides on the first rail  1 L and the second slider  2 S of  FIG. 5( b )  guiding the second pad  2  of  FIG. 5( a )  in the circumferential direction R slides on the second rail  2 L. That is, the reason is that, since the first slider  1 S and the second slider  2 S, which are adjacent to each other, of  FIG. 5( d )  slide on the first and second rails  1 L and  2 L separated from each other in the axial direction S as shown in  FIGS. 5( b ) and ( c ) , they can approach each other in an overlapping state as shown in  FIG. 5( d ) . 
     Incidentally, in the present invention, there is no need for the pads  1  and  2  to move in the axial direction S as shown in  FIGS. 3A and 3B . Moreover, the pads  1  and  2  may include mechanisms that make them turn around the normal to a drum after separating in the circumferential direction R. This mechanism is described in, for example, WO 2005/075163, the contents of which are incorporated herein in their entirety. 
     Moreover, the rails  1 L and  2 L of  FIGS. 5( b ) and ( c )  may be arranged side by side on the outer circumferential surface of the supporting ring  3 , not on the first surface  1 F or the second surface  2 F of the supporting ring  3 . 
     Furthermore, the pads of the aforementioned embodiment are roughly triangular or pentagonal in shape; they may be square or rectangular in shape. 
     In addition, the first pad and the second pad may be completely identical in shape. 
     Moreover, each pad may include, for example, a machining apparatus such as an anvil. Furthermore, each pad may hold the workpiece by sucking the workpiece and making it cling thereto by negative pressure or may hold the workpiece by a needle, a hook, or the like. 
     Next, another embodiment of the variable speed conveying apparatus  5  will be described. 
       FIGS. 6 and 7  show the variable speed conveying apparatus and the guide mechanism  30 , respectively, of the other embodiment. 
     In  FIG. 6 , the variable speed conveying apparatus  5  includes a large number of first and second pads  1  and  2 , a large number of first and second sliders  1 S and  2 S, and first and second rails  1 L and  2 L. 
     The first and second pads  1  and  2  are arranged around an axis  10 S, orbit along an orbit with the speeds thereof being varied, are alternately arranged so as to be adjacent to each other in a circumferential direction R, and convey workpieces while holding them. Also in the present embodiment, as in the case of the aforementioned embodiment, the pads  1  and  2  rotate along the orbit of the variable speed conveying apparatus  5  with the speeds of the pads  1  and  2  being varied, and receive the workpieces (not shown in the drawing) from an unillustrated upstream roll in a reception position P 1  and deliver the workpieces (not shown in the drawing) onto a downstream roll in a delivery position P 2 . 
     It is to be noted that, also in the present embodiment, the workpiece may be held by being sucked and made to cling to the outer surface of the pad. 
     Next, the details of the guide mechanism  30  will be described. 
     The first and second sliders  1 S and  2 S are provided for each of the first and second pads  1  and  2  in different positions in an axial direction S of the axis  10 S and orbit with the first and second pads  1  and  2  with the speeds of the first and second sliders  1 S and  2 S being varied. 
     It is to be noted that, as in the case of the aforementioned embodiment, the axis  10 S is the axis of the rotating shaft  10  (see  FIG. 2 ). 
     The first rail  1 L supports the first pads  1  or the second pads  2  via the first sliders  1 S, and guides the first sliders  1 S and does not guide the second sliders  2 S. On the other hand, the second rail  2 L supports the first pads  1  or the second pads  2  via the second sliders  2 S, and guides the second sliders  2 S and does not guide the first sliders  1 S. 
     As is clearly shown in  FIG. 7 , the above-mentioned second rail  2 L is arranged so as to be separated from the above-mentioned first rail  1 L and parallel thereto. It is to be noted that, as in the case of the above-mentioned embodiment, the rails  1 L and  2 L are fixed to a supporting ring (not shown in the drawing) that is driven and rotated. 
     Also in the present embodiment of  FIG. 6 , as in the case of the aforementioned embodiment, the sliders  1 S and  2 S and the rails  1 L and  2 L are placed in positions closer to the axis  10 S than the pads  1  and  2 . That is, the orbital paths of the sliders  1 S and  2 S are located in positions closer to an inner circumferential side than the orbital paths of the pads  1  and  2 . 
     As shown in  FIG. 6 , each first pad  1  is supported by two first sliders  1 S and one second slider  2 S. On the other hand, each second pad  2  is supported by one first slider  1 S and two second sliders  2 S. 
     It is to be noted that the sliders  1 S and  2 S have the same or symmetrical shape and structure. 
     As described above, the number of sliders supporting each of the pads  1  and  2  is set; therefore, for each first pad  1 , a first contact length L 11  by which the first sliders  1 S are in contact with the first rail  1 L is longer than a second contact length L 12  by which the second slider  2 S is in contact with the second rail  2 L. Moreover, for each second pad  2 , a third contact length L 21  by which the first slider  1 S is in contact with the first rail  1 L is shorter than a fourth contact length L 22  by which the second sliders  2 S are in contact with the second rail  2 L. 
     In  FIG. 6 , a first length L 1  of each first pad  1  mentioned above in the above-mentioned circumferential direction R is shorter than the first contact length L 11  and longer than the second contact length L 12 . 
     On the other hand, a second length L 2  of each second pad  2  in the circumferential direction R is longer than the third contact length L 21  and shorter than the fourth contact length L 22 . 
     Since the contact lengths L 1  to L 4  of the sliders  1 S and  2 S are set for the lengths L 1  and L 2  of the pads  1  and  2  in this manner, it is possible to prevent adjacent sliders from interfering with each other even when adjacent first pad  1  and second pad  2  approach each other. 
     On the other hand, it is possible to support the first pad  1  with two first sliders  1 S and one second slider  2 S, which stabilizes support in the circumferential direction. Moreover, support of the second pad  2  in the circumferential direction is also stabilized in a similar manner. 
     It is to be noted that two first sliders  1 S supporting the first pad  1  may be provided as one first slider  1 S which is long in the circumferential direction R. Likewise, two second sliders  2 S supporting the second pad  2  may be provided as one second slider  2 S which is long in the circumferential direction R. 
     Next, a method of variable speed conveyance of the workpieces will be described. 
     Variable speed conveyance of the workpieces includes the following steps: a conveying step, an accelerating step, a moving and separating step, a decelerating step, and a moving and approaching step. 
     The first and second pads  1  and  2  of  FIG. 6  receive the workpieces from the upstream roll in the reception position P 1  by sucking the workpieces and making them cling thereto by negative pressure. The first and second pads  1  and  2  that have received the workpieces perform the step of conveying the workpieces by orbiting with the speeds of the first and second pads  1  and  2  being varied. Then, after delivering the workpieces to the downstream roll in the delivery position P 2 , the first and second pads  1  and  2  return to the reception position P 1  with the speeds thereof being varied. The following are detailed descriptions of these operations. 
     In the above-mentioned accelerating stroke (period), the circumferential velocities of the first and second pads  1  and  2  that have received the workpieces in the reception position P 1  are accelerated by variable speed mechanisms  20 . As a result, the speeds of the pads  1  and  2  are gradually increased and the pitch between the first and second pads  1  and  2  that are adjacent to each other is increased; in this way, the moving and separating step is performed. 
     It is to be noted that the operation and structure of the variable speed mechanism  20  are well known per se and disclosed in, for example, WO 2018/011905, the contents of which are incorporated herein in their entirety. 
     Then, the first and second pads  1  and  2  arrive at the delivery position P 2  abutting on the downstream roll and deliver the workpieces held thereby to the downstream roll. At the time of this delivery, the circumferential velocities of the pads  1  and  2  may be in any one of the following states: the circumferential velocities of the pads  1  and  2  are being accelerated, the circumferential velocities of the pads  1  and  2  are being increased, and the circumferential velocities of the pads  1  and  2  are constant. 
     After the above-mentioned delivery, the circumferential velocities of the first and second pads  1  and  2  are decelerated by variable speed mechanisms, which are similar to those described above, from the delivery position P 2  until arrival at the reception position P 1 ; in this way, the decelerating step is performed. During this deceleration, the first and second pads  1  and  2  approach each other in the circumferential direction R. 
     When arriving at the reception position P 1  in a state in which the first and second pads  1  and  2  approach each other in the circumferential direction R, the first and second pads  1  and  2  receive the workpieces from the upstream roll. 
     A step is performed in which, in the reception position P 1  of  FIG. 7 , the first slider  1 S and the second slider  2 S after deceleration overlap each other in a part A in the circumferential direction R, which causes the first pad  1  and the second pad  2  of  FIG. 6  to approach each other, and the first pad  1  and the second pad  2  move in this state in which they have approached each other. During this step, the first pad  1  and the second pad  2  receive the workpieces from the upstream roll in the reception position P 1 . 
     The reason why this overlapping is made possible is that, in  FIG. 6 , the first slider  1 S guiding the first pad  1  in the circumferential direction R slides on the first rail  1 L and the second slider  2 S guiding the second pad  2  in the circumferential direction R slides on the second rail  2 L. That is, the reason is that, since the first slider  1 S and the second slider  2 S of  FIG. 7  that move in parallel to each other slide on the first and second rails  1 L and  2 L separated from each other in the direction of the axis  10 S, the first slider  1 S and the second slider  2 S can approach each other in a state in which they overlap each other in the circumferential direction R. 
     While the preferred embodiments have been described above with reference to the drawings, a person skilled in the art would easily conceive of various changes and modifications based on the description within the scope obvious to the person skilled in the art. 
     For example, there is no need for the supporting ring to rotate in synchronization with the rotating shaft. Moreover, a supporting member which is not continuous in a circular fashion may be adopted in place of the supporting ring. 
     The speed of each pad may be constant in the reception position from the start to end of reception. 
     The upstream apparatus and the downstream apparatus may be conveyors and the like, not rolls. 
     Therefore, these changes and modifications are construed as being included in the scope of the present invention defined by the claims. 
     INDUSTRIAL APPLICABILITY 
     In addition to finished articles of various absorbent articles such as disposable pants and diapers, the present invention can be used in conveyance in the manufacture of parts and half-finished articles of these absorbent articles. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : first pad 
               2 : second pad 
               1 B: first base 
               2 B: second base 
               1 C: first cam follower 
               2 C: second cam follower 
               1 S: first slider 
               2 S: second slider 
               1 L: first rail 
               2 L: second rail 
               1 F: first surface 
               2 F: second surface 
               10 : rotating shaft 
               10 S: axis 
               20 : variable speed mechanism 
               21 : driving wheel 
               210 : center of drive 
               22 : crank arm 
               220 : arm center 
               223 : cam roller 
               23 : link lever 
               3 : supporting ring 
               30 : guide mechanism 
               31 : tubular portion 
               32 : cam drum 
               4 : upstream roll (apparatus) 
               5 : variable speed conveying apparatus 
               6 : downstream roll (apparatus) 
               41 : first cam groove 
               42 : second cam groove 
               44 : cam groove for varying speed 
             P 1 : reception position 
             P 2 : delivery position 
             R: circumferential direction 
             S: axial direction 
             W: workpiece 
             L 1 : first length 
             L 2 : second length 
             L 11 , L 12 , L 21 , L 22 : first to fourth contact lengths