Patent Publication Number: US-2023150071-A1

Title: Wheel holding device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Japan application serial no. 2021-187541, filed on Nov. 18, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a wheel holding device for holding a wheel used in an omnidirectional moving device. 
     Related Art 
     Patent Document 1 (Japanese Patent No. 6746655) discloses a method of manufacturing a wheel used in an omnidirectional moving device. The wheel includes an annular-shaped core body and a plurality of free rollers rotatably supported by the core body. The method of manufacture the wheel includes: a first step of forming a plurality of notches in a straight line-shaped pipe member; a second step of attaching a plurality of free rollers to the straight line-shaped pipe member; a third step of bending the pipe member at a plurality of spots to fill the plurality of notches to form the pipe member into an annular shape; and a fourth step of welding end parts of the pipe member to each other and welding edge parts of each notch to each other. 
     To facilitate the welding work of the pipe member in the fourth step, a wheel holding device for holding the wheel is desired. The wheel including the annular-shaped core body and the plurality of free rollers rotatably supported by the core body does not have a central part, so there is no suitable device for holding the wheel. 
     SUMMARY 
     In an embodiment of the disclosure, a wheel holding device ( 1 ) holds a wheel ( 4 ) including an annular-shaped core body ( 2 ) and a plurality of free rollers ( 3 ) rotatably supported by the core body. The wheel holding device includes a central member ( 40 ) including an outer peripheral part capable of expanding and contracting in a radial direction. The central member holds the wheel with the outer peripheral part of the central member urging an inner peripheral part of the wheel radially outward. 
     According to this embodiment, it is possible to provide a wheel holding device for holding a wheel including an annular-shaped core body and a plurality of free rollers rotatably supported by the core body. A central member is arranged at a central part of the annular-shaped wheel and can hold the wheel at its outer peripheral part. The outer peripheral part of the central member can extend radially outward and come into contact with the inner peripheral part of the wheel. 
     In the above embodiment, the central member may include a chuck ( 42 ); a plurality of bases ( 43 ) which are radially movably supported by the chuck and form the outer peripheral part of the central member; and a plurality of urging members ( 44 ) which urge the respective bases radially outward with respect to the chuck. 
     According to this embodiment, the structure of the central member can be simplified. 
     In the above embodiment, the central member may include a stopper ( 54 ) detachably attached to the chuck. The stopper may restrict radially inward movement of the base by coming into contact with each of the bases. 
     According to this embodiment, radially inward contraction of the core body can be suppressed. For example, it is possible to suppress contraction of the core body during welding and maintain the core body in an appropriate shape. 
     In the above embodiment, the central member may include a plurality of lock members ( 61 ) detachably attached to the chuck. The plurality of lock members may restrict movement of the bases with respect to the chuck by coming into contact with each of the bases. 
     According to this embodiment, the lock member can maintain the base radially inward against the urging force of the urging member. This facilitates the work of arranging the wheel on the outer circumference of the central member. 
     In the above embodiment, the wheel holding device may include at least one band member ( 81 ) which extends along an outer peripheral surface of one of the free rollers and includes two end parts detachably attached to one of the bases. 
     According to this embodiment, when the position of the base is fixed by the lock members, the position of the wheel can be kept constant by bringing the wheel into close contact with the bases by the band members. 
     In the above embodiment, the wheel holding device may include a clamping device ( 70 ) including a bracket ( 71 ); and a pair of holding pieces ( 72 ) which are provided on the bracket and sandwich the free rollers in a circumferential direction of the wheel. 
     According to this embodiment, when a part of the core body in the circumferential direction is cleaved, the core body can be held in an annular shape by the clamping device. The clamping device is useful, for example, when a straight pipe is bent in an annular shape and welded. 
     In the above embodiment, the bracket may be detachably attached to one of the bases. 
     According to this embodiment, it is possible to prevent the bracket from falling off from the wheel. 
     In the above embodiment, the bracket may have at least one opening ( 79 ) for exposing, to outside, the core body arranged between the free rollers arranged between the pair of holding pieces. 
     According to this embodiment, it is possible to perform operations such as welding on the core body with the clamping device attached to the wheel. 
     In the above embodiment, the pair of holding pieces may be detachably attached to the bracket. 
     According to this embodiment, after the bracket is arranged with respect to the wheel, the pair of holding pieces can be attached to the bracket. This facilitates the work of attaching the clamping device to the wheel. 
     In the above embodiment, the plurality of bases may each have an engaging groove ( 49 ) which extends in a circumferential direction and receives a part of the free roller. 
     According to this embodiment, the wheel holding device can hold the wheel with good stability. 
     In the above embodiment, the wheel holding device may include a pedestal ( 41 ) which rotatably supports the chuck. 
     According to this embodiment, the wheel can be rotated by rotating the central member. Accordingly, a processing device can process each part in the circumferential direction of the core body without moving an operation part of the processing device. 
     According to the above configuration, it is possible to provide a wheel holding device for holding a wheel including an annular-shaped core body and a plurality of free rollers rotatably supported by the core body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a front view of a wheel holding device according to an embodiment. 
         FIG.  2    is a cross-sectional view of an omnidirectional moving device including a wheel. 
         FIG.  3    is a side view of the wheel. 
         FIG.  4    is a cross-sectional view of the wheel. 
         FIG.  5    is a side view showing a straight line-shaped core body. 
         FIG.  6    is a cross-sectional view showing the straight line-shaped core body. 
         FIG.  7    is a perspective view showing the straight line-shaped core body. 
         FIG.  8    is an exploded perspective view of the wheel holding device according to the embodiment. 
         FIG.  9    is a cross-sectional view of the wheel holding device holding the wheel. 
         FIG.  10    is a cross-sectional view of a clamping device clamping the wheel. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the disclosure provide a wheel holding device for holding a wheel including an annular-shaped core body and a plurality of free rollers rotatably supported by the core body. 
     Hereinafter, a wheel holding device  1  according to the disclosure will be described with reference to the drawings. As shown in  FIG.  1   , the wheel holding device  1  holds a wheel  4  including an annular-shaped core body  2  and a plurality of free rollers  3  rotatably supported by the core body  2 . In particular, the wheel holding device  1  is used during production of the wheel  4 . As shown in  FIG.  2   , the wheel  4  is used in an omnidirectional moving device  5 . The omnidirectional moving device  5  is used for electric wheelchairs, trolleys, or personal mobility devices. 
     (Structure of Wheel  4 ) 
     As shown in  FIG.  3   , the wheel  4  includes a core body  2  formed in an annular shape centered on an axis A. The core body  2  is formed by bending a pipe member  7  having a circular cross section into an annular shape and welding its two end parts to each other. The pipe member  7  is made of a metal such as stainless steel. A line passing through a center of the cross section of the core body  2  is defined as a core body center line B. The core body center line B extends in a circumferential direction centered on the axis A. 
     As shown in  FIG.  4   , each free roller  3  is supported by the core body  2  via a bearing  8  which is a radial bearing. The bearing  8  may be a ball bearing including an inner race  11 , an outer race  12 , a plurality of balls  13  interposed between the inner race  11  and the outer race  12 , and a retainer (not shown) holding the plurality of balls  13 . 
     Each free roller  3  includes a sleeve  15  and a rubber ring  16  provided on an outer peripheral surface of the sleeve  15 . The sleeve  15  may be made of metal. The rubber ring  16  may be bonded to the outer peripheral surface of the sleeve  15  by vulcanization bonding or the like. The bearing  8  is arranged inside the sleeve  15 . In this embodiment, two bearings  8  are press-fitted inside each sleeve  15 . At a central part of an inner peripheral surface of the sleeve  15 , a protrusion  17  which projects radially inward and extends in the circumferential direction is formed. The outer races  12  of the two bearings  8  come into contact with the protrusion  17  and a cylinder-shaped spacer  18 , so that the two bearings  8  are spaced apart from each other. 
     The inner race  11  of each bearing  8  is fixed to an outer peripheral surface of the core body  2 . The core body  2  is press-fitted into the inner race  11  of each bearing  8 . Further, a locking claw  19  projecting outward is formed on the outer peripheral surface of the core body  2 . 
     The locking claw  19  is formed by cutting a part of the core body  2  outward. The locking claw  19  locks an edge part of the inner race  11  and restricts movement of each inner race  11  and the spacer  18  with respect to the core body  2  in the circumferential direction centered on the axis A. 
     Each of the plurality of free rollers  3  rotates with respect to the core body  2  on the core body center line B. Further, each of the plurality of free rollers  3  rotates with respect to the core body  2  on an axis parallel to a tangent line centered on the axis A. 
     (Production Method of Wheel) 
     As shown in  FIG.  5    to  FIG.  7   , the core body  2  is formed by bending a pipe member  7  having a circular cross section and extending in a straight line shape. The pipe member  7  has a first end part  21  and a second end part  22  in a longitudinal direction. The core body  2  in an initial state extending in a straight line shape has a plurality of notches  23  arranged at equal intervals in the longitudinal direction. Each notch  23  is formed in a same shape. Further, each notch  23  is arranged at a same position in a circumferential direction centered on the core body center line B of the core body  2 . Each notch  23  penetrates from an outer peripheral surface to an inner peripheral surface of the core body  2 . Each notch  23  extends in a range of at least 270 degrees or more in the circumferential direction centered on the core body center line B of the core body  2  in the initial state. Each notch  23  extends in a range of 330 degrees in the circumferential direction centered on the core body center line B of the core body  2 , for example. Each notch  23  is formed by a first cut surface  24  having a planar shape and a second cut surface  25  having a planar shape. The first cut surface  24  and the second cut surface  25  intersect with each other by a ridge line  26  having a straight line shape. The notch  23  is formed in a triangular shape when viewed from a direction parallel to the ridge line  26 . An expansion part  30  is provided on a side of the notch  23  opposite to the ridge line  26  side. In the longitudinal direction of the pipe member  7 , the expansion part  30  is formed to be larger than the notch  23 . In this embodiment, the notch  23  is formed in an isosceles triangle when viewed from a direction parallel to the ridge line  26 . An angle formed by the first cut surface  24  and the second cut surface  25  may be set to a value obtained by dividing substantially 360 degrees by the number of the free rollers  3 . In the core body  2 , a portion of the core body  2  opposite to each notch  23  is referred to as a connecting part  27 . A first end surface  28  parallel to the first cut surface  24  is formed at the first end part  21 , and a second end surface  29  parallel to the second cut surface  25  is formed at the second end part  22 . In the longitudinal direction of the pipe member  7 , the second cut surface  25  is arranged next to the first end surface  28 , and the first cut surface  24  is arranged next to the second end surface  29 . 
     In the core body  2 , a cylinder-shaped roller support part  31  is formed respectively between the adjacent notches  23 . A plurality of slits  32  for forming the locking claws  19  are formed on a side opposite to the notch  23  in the circumferential direction of the core body  2 . A pair of slits  32  are provided for each roller support part  31 . The slit  32  penetrates the core body  2  from the outer peripheral surface to the inner peripheral surface. The slit  32  has a first portion  32 A extending in the circumferential direction of the core body  2  along two ends in a longitudinal direction of the roller support part  31 , and a pair of second portions  32 B extending from two ends of the first portion  32 A to a side opposite to the roller support part  31 . Each locking claw  19  is defined by the first portion  32 A and the pair of second portions  32 B. 
     First, as a first step, a plurality of notches  23 , a plurality of slits  32 , a first end surface  28 , and a second end surface  29  are formed on a straight line-shaped core body  2 . The plurality of notches  23 , the plurality of slits  32 , the first end surface  28 , and the second end surface  29  may be formed by laser processing. 
     Next, as a second step, a plurality of free rollers  3  each attached with a pair of bearings  8  and a spacer  18  are respectively arranged on roller support parts  31  of the straight line-shaped core body  2 . The pair of bearings  8  are press-fitted into a sleeve  15  of the free roller  3  and fixed. The straight line-shaped core body  2  is press-fitted into each bearing  8  from its end part. In this state, the pair of bearings  8  attached to one free roller  3  are arranged on the roller support part  31  and are arranged between a pair of slits  32 . 
     Next, as a third step, each locking claw  19  is pushed and bent outward of the core body  2 . Accordingly, the pair of bearings  8  and the sleeve  15  are sandwiched between a pair of locking claws  19 , and the position of the free roller  3  is fixed with respect to the longitudinal direction of the core body  2 . Each locking claw  19  is pushed and bent outward of the core body  2  by a pressing rod inserted inside the core body  2  through an expansion part  30 , and projects from the outer peripheral surface of the core body  2 . Accordingly, the end part of each locking claw  19  comes into contact with the edge part of the inner race  11  of the bearing  8 . 
     Next, as a fourth step, the core body  2  is bent at each connecting part  27  to form an annular shape. Each connecting part  27  is bent so that the corresponding notch  23  is filled, that is, the first cut surface  24  and the second cut surface  25  of the corresponding notch  23  come into contact with each other. Accordingly, the first end surface  28  and the second end surface  29  of the core body  2  can come into contact with each other. If the holding force for maintaining the core body  2  in the bent state disappears, the first end surface  28  and the second end surface  29  of the core body  2  would become separated from each other due to springback of the core body  2 . 
     Next, as a fifth step, the first end surface  28  and the second end surface  29  of the core body  2  are welded to each other, and the first cut surface  24  and the second cut surface  25  of each notch  23  are welded to each other. Accordingly, the core body  2  is maintained in an annular shape, and the main wheel is completed. The wheel holding device  1  according to this embodiment is suitable for holding the wheel  4  before welding in the fifth step. 
     (Wheel Holding Device) 
     As shown in  FIG.  1   ,  FIG.  8   , and  FIG.  9   , the wheel holding device  1  includes a central member  40  having an outer peripheral part that can be expanded and contracted in the radial direction. The wheel holding device  1  includes a pedestal  41  which supports the central member  40 . The central member  40  includes a chuck  42 , a plurality of bases  43  which are supported by the chuck  42  to be movable in the radial direction and form the outer peripheral part of the central member  40 , and a plurality of urging members  44  which urge the respective bases  43  radially outward with respect to the chuck  42 . 
     The chuck  42  is formed in a disk shape centered on a central axis C. The chuck  42  is supported by the pedestal  41  to be rotatable on the central axis C. Each of the bases  43  includes a peripheral wall part  46  which faces an outer peripheral surface of the chuck  42  and extends in an arc shape in the circumferential direction, an outer wall  47  which extends from the peripheral wall part  46  toward the central axis C side along an outer surface of the chuck  42 , and an inner wall  48  which extends from the peripheral wall part  46  toward the central axis C side along an inner surface of the chuck  42 . That is, a part of the chuck  42  is arranged between the outer wall  47  and the inner wall  48  of the base  43 . The outer wall  47  and the inner wall  48  may be formed in a fan shape. The plurality of bases  43  may each have an engaging groove  49  which extends in the circumferential direction and receives a part of the free roller  3 . The engaging groove  49  may be formed on the outer peripheral part of the peripheral wall part  46  and extend to two end parts of the peripheral wall part  46  in the circumferential direction. The engaging groove  49  may have a semi-circular cross section. Each of the bases  43  may be formed in a same shape as each other. 
     A guide groove  51  penetrating in a thickness direction is formed in the outer wall  47  of each base  43 . At least one guide pin  52  passing through the guide groove  51  is coupled to the chuck  42 . A movement direction of the base  43  with respect to the chuck  42  is restricted by the guide pin  52  coming into contact with the guide groove  51 . In this embodiment, two guide pins  52  are provided for one guide groove  51 . With the two guide pins  52  coming into contact with the guide groove  51 , an inclination angle of the base  43  with respect to the chuck  42  is kept constant. In this embodiment, two guide grooves  51  are provided in one outer wall  47 . The inner wall  48  may be provided with a guide groove  51  and a corresponding guide pin  52  may be provided. 
     The movement of each base  43  with respect to the chuck  42  is restricted between a contracted position and an expanded position by the contact between the guide groove  51  and the guide pins  52 . When the base  43  is at the contracted position, a distance between the base  43  and the central axis C is minimized. When the base  43  is at the expanded position, the distance between the base  43  and the central axis C is maximized. 
     The urging member  44  is, for example, a compression coil spring, and is provided between the outer peripheral wall of the chuck  42  and the inner peripheral wall of each base  43 . Each urging member  44  urges the corresponding base  43  toward the expanded position. In this embodiment, the urging member  44  is interposed between a cylinder-shaped first member screwed into the chuck  42  and a second member having one end movably supported inside the first member and another end screwed into the base  43 . 
     The central member  40  includes a stopper  54  which is detachably attached to the chuck  42  and restricts the radially inward movement of the base  43  by coming into contact with each of the bases  43 . A coupling hole  55  formed along the central axis C is formed at the center of the chuck  42 . The stopper  54  includes a shaft part  56  inserted into the coupling hole  55 , and a head part  57  which is provided at one end of the shaft part  56  and is wider in the radial direction than the shaft part  56 . A female screw may be formed on an inner peripheral surface of the coupling hole  55 , and a male screw screwed into the female screw may be formed on an outer peripheral surface of the shaft part  56 . With an outer peripheral part of the head part  57  coming into contact with an end part of the outer wall  47  of each base  43  on the central axis C side, the movement of each base  43  toward the contracted position side is restricted. When the outer peripheral part of the head part  57  comes into contact with the end part of the outer wall  47  of each base  43  on the central axis C side, each base  43  may be arranged at a predetermined position between the contracted position and the expanded position. 
     The central member  40  includes a plurality of lock members  61  which are detachably attached to the chuck  42  and restrict the movement of the base  43  with respect to the chuck  42  by coming into contact with the respective bases  43 . A lock hole  62 , which is a through hole, is formed in the outer wall  47  and the inner wall  48  of each base  43  and the chuck  42 . By inserting the lock member  61  into each lock hole  62 , the movement of the base  43  with respect to the chuck  42  is prohibited. The lock member  61  may be, for example, a pin. 
     The wheel holding device  1  includes a clamping device  70  in addition to the central member  40 . The clamping device  70  is attached to one of the plurality of bases  43 . The clamping device  70  includes a bracket  71  and a pair of holding pieces  72  which are provided on the bracket  71  and sandwich a plurality of free rollers  3  in the circumferential direction of the wheel  4 . 
     The bracket  71  includes a main body part  74 , and a first wall  75  and a second wall  76  which extend from the main body part  74  in a same direction at an interval from each other. The first wall  75  and the second wall  76  are formed in plate shapes facing each other. A distance between the first wall  75  and the second wall  76  is set to be larger than an outer diameter of the free roller  3 . The first wall  75  is detachably connected to a side surface of the outer wall  47  of one base  43  by a fastening member such as a bolt, and the second wall  76  is detachably connected to a side surface of the inner wall  48  of the same base  43  by a fastening member such as a bolt. Accordingly, the main body part  74  is arranged at an interval radially outward of the peripheral wall part  46  of the base  43 . A distance between the main body part  74  and the peripheral wall part  46  is set to be larger than the outer diameter of the free roller  3 . The main body part  74  is arranged on the outer side of the wheel  4  held by the outer peripheral part of the base  43 . 
     As shown in  FIG.  10   , each of the pair of holding pieces  72  is formed in a plate shape. One of the holding pieces  72  is connected to one end of the main body part  74  in the circumferential direction centered on the central axis C, and the other of the holding pieces  72  is connected to another end of the main body part  74  in the circumferential direction. The pair of holding pieces  72  extend from the main body part  74  toward the central axis C side and face each other in the circumferential direction centered on the central axis C. The pair of holding pieces  72  may be detachably attached to the main body part  74  by a fastening member  78  such as a bolt. 
     As shown in  FIG.  1    and  FIG.  8    to  FIG.  10   , the bracket  71  has at least one opening  79  for exposing, to the outside, the core body  2  arranged between the free rollers  3  arranged between the pair of holding pieces  72 . The opening  79  is formed respectively in the first wall  75  and the second wall  76 . 
     As shown in  FIG.  1    and  FIG.  8   , the wheel holding device  1  may include at least one band member  81 . The band member  81  extends along the outer peripheral surface of one of the free rollers  3  of the wheel  4  arranged on the outer peripheral part of the central member  40 , and has two end parts detachably attached to one of the bases  43 . In this embodiment, two band members  81  are attached to each base  43 . Two end parts of the band member  81  are locked to locking parts  82  provided on the outer surface of the outer wall  47  and the outer surface of the inner wall  48  of the base  43 . 
     A method of holding the wheel  4  before welding (the wheel  4  for which the processes up to the fourth step have been completed) by the wheel holding device  1  will be described. The wheel  4  before welding is arranged in a substantially annular shape, but the first end surface  28  and the second end surface  29  of the core body  2  are separated from each other due to springback. 
     First, the plurality of lock members  61  are inserted into the lock holes  62 , and each base  43  is maintained at a predetermined position with respect to the chuck  42 . This facilitates the work of arranging the wheel  4  on the outer circumference of the central member  40 . Further, the stopper  54  is coupled to the chuck  42 . With the lock members  61  inserted into the lock holes  62 , a gap is formed between the stopper  54  and each base  43 . Next, the wheel  4  before welding is arranged on the outer peripheral part of the central member  40 , that is, on the outer peripheral part of each base  43 . At this time, the inner peripheral part of the wheel  4  is received by the engaging groove of the peripheral wall part  46  of each base  43 . Further, two end parts of the core body  2  constituting the wheel  4  are arranged at a center in the circumferential direction of the base  43  attached with the clamping device  70 . 
     Next, the plurality of band members  81  are attached to the corresponding bases  43 . Accordingly, the wheel  4  is held between the plurality of bases  43  and the plurality of band members  81 . The plurality of band members  81  maintain the wheels  4  in a substantially perfect circle along the outer peripheral parts of the respective bases  43 , and the first end part  21  and the second end part  22  of the core body  2  are close to each other. 
     Next, in this state, as shown in  FIG.  1    and  FIG.  10   , the bracket  71  of the clamping device  70  is attached to the base  43 . At this time, the pair of holding pieces  72  may be removed from the bracket  71  or may be temporarily movably held to the bracket  71 . With the bracket  71  attached to the base  43 , the pair of holding pieces  72  are temporarily held to the bracket  71  by the fastening members  78 . At this time, the free roller  3  attached to the first end part  21  of the core body  2  and the free roller  3  attached to the second end part  22  of the core body  2  are arranged between the pair of holding pieces  72 . In this state, the fastening member  78  is tightened so that the pair of holding pieces  72  approach each other. The free roller  3  attached to the first end part  21  of the core body  2  and the free roller  3  attached to the second end part  22  of the core body  2  are sandwiched by the pair of holding pieces  72  to maintain the first end surface  28  and the second end surface  29  of the core body  2  in contact with each other. In this state, a contact part between the first end surface  28  and the second end surface  29  of the core body  2  is exposed to the outside through the opening  79  of the bracket  71 . Then, the contact part between the first end surface  28  and the second end surface  29  is welded through the opening  79  of the bracket  71 . The welding may be, for example, laser welding. Accordingly, the core body  2  is maintained in an annular shape. 
     Next, the pair of holding pieces  72  and the bracket  71  are removed from the base  43 . Further, the plurality of band members  81  are removed from the bases  43 . Then, the plurality of lock members  61  are removed from the corresponding bases  43 . Accordingly, due to the urging force of the urging member  44 , the base  43  moves toward the expanded position side, and the outer peripheral part of the base  43  comes into contact with the inner peripheral part of the wheel  4 . 
     Next, respective contact parts between the first cut surface  24  and the second cut surface  25  of the core body  2  are welded. The welding may be laser welding. At this time, an irradiation part of a welding device may be arranged at a predetermined position, and by rotating the chuck  42 , a welding position in the circumferential direction of the wheel  4  may be changed. 
     Due to contraction arising from the welding, a radius of the wheel  4  gradually decreases as the welding progresses. At this time, each base  43  moves toward the central axis C side against the urging force of the urging member  44 , and the contact state with the wheel  4  is maintained. Each base  43  can move toward the central axis C side until it comes into contact with the stopper  54 . After each base  43  comes into contact with the stopper  54 , each base  43  supports the wheel  4  from the inner side to suppress contraction of the wheel  4 . Accordingly, the core body  2  can be maintained in an appropriate shape. 
     After the welding is complete, the stopper  54  is removed from the chuck  42 . Accordingly, the base  43  becomes movable toward the central axis C side. Then, by moving the plurality of bases  43  toward the central axis C side against the urging force of the plurality of urging members  44 , the inner peripheral part of the wheel  4  and the outer peripheral parts of the plurality of bases  43  are separated from each other, and the wheel  4  is removed from the central member  40 . 
     The wheel holding device  1  according to the disclosure holds a wheel  4  including an annular-shaped core body  2  and a plurality of free rollers  3  rotatably supported by the core body  2 . A central member  40  is arranged at a central part of the annular-shaped wheel  4  and can hold the wheel  4  at its outer peripheral part. The outer peripheral part of the central member  40  can extend radially outward and come into contact with the inner peripheral part of the wheel  4 . 
     The clamping device  70  can hold the cleaved core body  2  in an annular shape, and the first end surface  28  and the second end surface  29  of the core body  2  can be easily welded. Since the bracket  71  is formed with an opening  79 , the welding work on the core body  2  becomes possible with the clamping device  70  attached to the wheel  4 . Since the pair of holding pieces  72  are detachably attached to the bracket  71 , after the bracket  71  is arranged with respect to the wheel  4 , the pair of holding pieces  72  can be attached to the bracket  71 . This facilitates the work of attaching the clamping device  70  to the wheel  4 . 
     When the position of the base  43  is fixed by the lock members  61 , the position of the wheel  4  can be kept constant by bringing the wheel  4  into close contact with the bases  43  by the plurality of band members  81 . 
     The wheel  4  is used in the omnidirectional moving device  5 . The omnidirectional moving device  5  includes, for example, as shown in  FIG.  2   , a frame  91 , a pair of drive disks  92  rotatably supported by the frame  91 , the annular-shaped wheel  4  arranged between the pair of drive disks  92 , and a pair of electric motors which rotate the respective drive disks  92 . The pair of drive disks  92  transmit the driving force of the electric motors to the wheel  4 . 
     The frame  91  has a pair of sidewall parts extending downward from a lower part of the vehicle body. As shown in  FIG.  2   , a support shaft  97  extending in the left-right direction is bridged to a pair of lower ends of the frame  91 . The pair of drive disks  92  are rotatably supported on the support shaft  97 . The pair of drive disks  92  rotate on the axis of the support shaft  97 . The position of each drive disk  92  in the left-right direction with respect to the support shaft  97  is restricted. The drive disks  92  face each other at a distance in the left-right direction. 
     The drive disks  92  are respectively arranged on two sides of the annular-shaped wheel  4 , and apply a frictional force to the wheel  4  to rotate the wheel  4  on the axis A and around the annular-shaped core center line B. The drive disk  92  includes a disk-shaped base  101  rotatably supported by the frame  91 , and a plurality of drive rollers  102  which are rotatably supported on an outer peripheral part of the base  101  to be inclined to each other and come into contact with the wheel  4 . The base  101  is arranged coaxially with the support shaft  97 . 
     Driven pulleys  104  are respectively provided on opposite surfaces of the drive disks  92 . The driven pulley  104  is provided coaxially with the drive disk  92 . The driven pulley  104  is connected by a belt  106  to a drive pulley provided on an output shaft of the electric motor. As the electric motors rotate independently of each other, the drive disks  92  rotate independently of each other. 
     In each omnidirectional moving device  5 , when the pair of drive disks  92  rotate in a same direction at a same rotational speed, the wheel  4  rotates together with the pair of drive disks  92 . That is, the wheel  4  rolls forward or backward on the axis A. At this time, the drive roller  102  of the drive disk  92  and the free roller  3  of the wheel  4  do not rotate with respect to the core body  2 . In each omnidirectional moving device  5 , when there is a difference in rotational speed between the pair of drive disks  92 , with respect to a force in the circumferential (tangential) direction arising from rotation of the pair of drive disks  92 , a component force in an orientation orthogonal to this force acts on the free rollers  3  of the wheel  4  from the left and right drive rollers  102 . Since the axis of the drive roller  102  is inclined with respect to the circumferential direction of the drive roller  102 , a component force is generated due to the difference in rotational speed between the drive disks  92 . Due to this component force, the drive roller  102  rotates with respect to the base  101 , and the free roller  3  rotates with respect to the core body  2 . Accordingly, the wheel  4  generates a driving force in the left-right direction. 
     The vehicle body moves forward as the left and right omnidirectional moving devices  5  rotate forward at a same speed. The vehicle body moves backward as the left and right omnidirectional moving devices  5  rotate backward at a same speed. The vehicle body turns to the right or left as a speed difference is generated in the rotation of the left and right omnidirectional moving devices  5  in the front-rear direction. The vehicle body translates in the right or left direction as the free rollers  3  of each wheel  4  of the left and right omnidirectional moving devices  5  rotate. 
     Although the specific embodiments have been described above, the disclosure may be widely modified without being limited to the above embodiments. The pedestal  41  may include a mechanism for changing a height and an orientation of the central member  40 . The shape and number of the bases  43  may be freely changed. The bracket  71  of the clamping device  70  may be attached to the pedestal  41 . One of the holding pieces  72  may be formed integrally with the bracket  71 . The main body part  74  of the bracket  71  may sandwich at least one free roller  3  with the base  43 .