JP7400618B2 - caster - Google Patents

Description

The present invention relates to casters.

A general caster is disclosed in FIG. 7 of Patent Document 1. This caster includes a bracket and wheels. The bracket has a first side wall extending vertically, and a second side wall facing the first side wall and extending vertically. The bracket is rotatable around a pivot axis that extends up and down with respect to a base on which a load is placed. The wheel is capable of rolling around a wheel axis that extends horizontally between the first side wall and the second side wall. The wheel axis is spaced apart from the pivot axis by an eccentric length.

A typical truck includes a base, four casters as described above that are fixed to the lower surface of the base and horizontally support the base, and a handle that extends upward from the base. When this trolley is towed by, for example, an automatic guided vehicle and after being towed, an operator pushes the trolley back in the direction in which it was being towed, the wheels of the casters are rotated 180 degrees around the pivot axis. Furthermore, the same applies when the front-rear automatic guided vehicle moves backward after moving its cart forward. In this way, when the cart must be moved in the opposite direction while a large load is placed on the base, the wheels rotate 180 degrees around the rotation axis while sliding on the floor. As a result, the initial load is large.

For this reason, Patent Document 1 proposes providing an elongated hole extending in a direction perpendicular to the rotation axis and the wheel axis in the first side wall and the second side wall. When the cart has to be moved in the opposite direction as described above, the wheel axis moves along both elongated holes, so the wheel slides on the floor and rotates 180 degrees around the rotation axis. There is no need to turn, and the initial load can be reduced. In addition, in the caster disclosed in Patent Document 1, racks extending in the same way as the elongated holes are provided on the first side wall and the second side wall, and a pinion that meshes with each rack is provided on the wheel, so that the wheel axis is aligned with both elongated holes. This prevents the wheel axis from twisting when moving.

Japanese Patent Application Publication No. 2003-237304

However, in the conventional caster described above, when the wheel axis moves through both elongated holes, it tends to roll on the floor surface. For this reason, it is difficult for the wheel axis to move within both elongated holes from the rear end to the front end, and the effect of reducing the initial load is diminished.

The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to provide casters that can increase the effect of reducing the initial load when a cart has to be moved in the opposite direction. This is an issue that must be resolved.

The caster of the present invention has a first side wall that extends vertically, a second side wall that faces the first side wall and extends vertically, and has a pivot axis that extends vertically with respect to a base on which a load is placed. A bracket that can pivot around the
a wheel that extends horizontally between the first side wall and the second side wall and is rotatable around a wheel axis;
In a caster, the wheel axis is spaced apart from the rotation axis by an eccentric length,
A guide is provided between the wheel and the first side wall and between the wheel and the second side wall, the guide being perpendicular to the pivot axis and extending in the front-rear direction from a front end located at the front to a rear end located at the rear. and an eccentric length changing mechanism that guides the wheel axis along the guide to change the eccentric length across the turning axis,
A one-way clutch mechanism is provided between the wheel and the bracket that allows the wheel to roll in a first direction and prohibits the wheel to roll in a second direction opposite to the first direction. established ,
The one-way clutch mechanism is provided between the wheel and the first side wall, and when the wheel axis is located at the rear end, the one-way clutch mechanism allows the wheel to roll forward, and the one-way clutch mechanism allows the wheel to roll forward. a first one-way clutch that prohibits rearward rolling and becomes unrelated to rolling of the wheel if the wheel axis is located at the front end;
Provided between the wheel and the second side wall, and when the wheel axis is located at the front end, it allows the wheel to roll in the rear direction and prohibits the wheel to roll in the forward direction. The vehicle is characterized in that it includes a second one-way clutch that is independent of rolling of the wheel when the wheel axis is located at the rear end .

For example, when a truck equipped with casters of the present invention is moved forward, the eccentric length changing mechanism positions the wheel axis at the rear end of the guide. In this state, the one-way clutch mechanism allows the wheels to roll in the first direction in which the truck moves forward. When the truck is stopped and moved backward, the eccentric length changing mechanism guides the wheel axis along the guide and changes the eccentric length across the turning axis. Therefore, the wheel axis moves toward the front end. During this time, the one-way clutch mechanism prohibits the wheels from rolling in the second direction in which the truck moves backward. Therefore, with this caster, when the wheel axis moves along the guide, there is no need for the wheel to rotate 180 degrees around the rotation axis P while sliding on the floor, and the wheel does not roll on the floor. . Therefore, the wheel axis can easily move from the rear end to the front end along the guide, and the effect of reducing the initial load is exhibited. If the wheel axis is located at the front end, the one-way clutch mechanism allows the wheels to roll in the second direction in which the truck moves backward.

Therefore, with this caster, it is possible to increase the effect of reducing the initial motion load when the cart must be moved in the opposite direction.

The one-way clutch mechanism includes a first one-way clutch provided between the wheel and the first side wall, and a second one-way clutch provided between the wheel and the second side wall. When the wheel axis is located at the rear end, the first one-way clutch allows the wheel to roll forward and prohibits the wheel from rolling backward, that is, reverse rotation. Furthermore, if the wheel axis is located at the front end, the first one-way clutch is independent of wheel rolling. When the wheel axis is located at the front end, the second one-way clutch allows the wheel to roll backward and prohibits the wheel from rolling forward, that is, reverse rotation. Furthermore, if the wheel axis is located at the rear end, the second one-way clutch becomes independent of wheel rolling. Therefore , the effects of the present invention can be achieved with a relatively simple structure.

The first one-way clutch includes a first gear fixed to the wheel, a first dog provided on the first side wall so as to be swingable in a plane parallel to the rotational direction of the wheel, and a first dog connected to the first gear. and a first biasing means for biasing toward the first biasing member. The first dog has a wheel axis located at the rear end, allows the wheel to roll forward, is disengaged from the first gear, and prohibits the wheel from rolling backward; It can have a state in which it is engaged with the first gear, and a state in which the wheel axis is located at the front end and is unrelated to the first gear. The second one-way clutch includes a second gear fixed to the wheel, a second dog provided on the second side wall so as to be swingable in a plane parallel to the rotational direction of the wheel, and a second dog connected to the second gear. and a second biasing means for biasing toward the base. The second dog has a wheel axis located at the front end, allowing the wheel to roll backwards and disengaging from the second gear, and a state in which the wheel axis is located at the front end and disengages from the second gear. It can have a state in which it is engaged with the second gear, and a state in which the wheel axis is located at the rear end and is unrelated to the second gear. In this case, the effects of the present invention can be achieved with a relatively simple structure.

The first dog may have a first end surface extending radially from the first swing center and a first orthogonal surface orthogonal to the first end surface. The first gear includes a first rocking tooth surface that contacts the first end surface against the first urging means to rock the first dog when the wheel rotates forward; and a first rocking tooth surface that makes the first dog swing. and a first engaging tooth surface which is continuous with the first engaging tooth surface and which yields to the first biasing means and engages the first orthogonal surface when the wheel rotates rearward. The second dog may have a second end surface extending in the radial direction from the second swing center, and a second orthogonal surface orthogonal to the second end surface. The second gear includes a second rocking tooth surface that contacts the second end surface against the second urging means to rock the second dog when the wheel rotates backward; and a second rocking tooth surface that swings the second dog. and a second engaging tooth surface which is continuous with the second engaging tooth surface and which yields to the second biasing means and engages the second orthogonal surface when the wheel rotates forward. In this case, the first dog and the second dog can be manufactured oppositely, and the first gear and the second gear can be manufactured as the same product with the front and back sides reversed, so that manufacturing costs can be reduced.

The first biasing means may be the dead weight of the first dog, and the second biasing means may be the dead weight of the second dog. Further, the first biasing means and the second biasing means may be tension springs.

A wheel is rotatable around the wheel axis by a wheel concentric with the wheel axis, a tire held on the wheel, a bearing device held on the wheel, and a bearing device, and rotation extending in the wheel axis direction. It can consist of an axis. In this case, since the wheels are suitably rotated around the rotating shaft by the bearing device, they can suitably roll on the floor surface.

With the casters of the present invention, it is possible to increase the effect of reducing the initial motion load when the cart must be moved in the opposite direction.

FIG. 1 is an exploded perspective view of a caster according to a first embodiment. FIG. 2 is a perspective view of the caster of Example 1. FIG. 3 is a longitudinal sectional view of the caster of Example 1. FIG. 4 is a cross-sectional view of the caster according to the first embodiment when it is moving forward. FIG. 5 is a cross-sectional view of the caster according to the first embodiment when the vehicle moves backward. FIG. 6 is a right side view of the caster according to the first embodiment when it is moving forward. FIG. 7 is a left side view of the caster according to the first embodiment when it is moving forward. FIG. 8 is a right side view of the caster according to the first embodiment at the time of switching. FIG. 9 is a left side view of the caster according to the first embodiment at the time of switching. FIG. 10 is a right side view of the caster according to the first embodiment when moving backward. FIG. 11 is a left side view of the caster according to the first embodiment when moving backward. FIG. 12 is a perspective view of a caster according to the second embodiment.

Embodiments 1 and 2 embodying the present invention will be described below with reference to the drawings.

(Example 1)
The caster of Example 1 includes a bracket 1, wheels 3, and a one-way clutch mechanism 5, as shown in FIGS. 1 and 2.

The bracket 1 has a top plate 7, a first side wall 9, and a second side wall 11. The top plate 7 is a rectangular flat plate in which the left and right lengths are longer than the front and back lengths. The four corners of the top plate 7 are provided with screw holes 7a to 7d.

The first side wall 9 is a flat plate in which an upper portion 9U and a lower portion 9D are integrated and extend vertically. The upper portion 9U has a square shape, and the lower portion 9D protrudes from the front and back than the upper portion 9U. Screw holes 9a and 9b are provided in the front and back of the upper surface of the upper portion 9U. A long hole 9c extending back and forth is provided through the lower portion 9D. The elongated hole 9c corresponds to a guide. Further, a screw hole 9d is provided in the lower portion 9D at the rear upper part of the elongated hole 9c.

The second side wall 11 is also a flat plate in which an upper portion 11U and a lower portion 11D are integrated and extend vertically. The upper portion 11U has a square shape, and the lower portion 11D protrudes from the front and back than the upper portion 11U. Screw holes 11a and 11b are provided in the front and back of the upper surface of the upper portion 11U. A long hole 11c extending back and forth is provided through the lower portion 11D. The elongated hole 11c also corresponds to a guide. Further, a screw hole 11d is provided in the lower portion 11D at the upper front side of the elongated hole 11c. The first side wall 9 and the second side wall 11 are symmetrical in plane except for the screw holes 9d and 11d.

In the bracket 1, the upper surface of the upper portion 9U of the first side wall 9 is in contact with the right end of the lower surface of the top plate 7, and the screw holes 7a and 7b are aligned with the screw holes 9a and 9b, and the screw holes 7a and 9b are aligned. A screw 13a is screwed into the hole 9a, and a screw 13b is screwed into the screw through hole 7b and the screw hole 9b. Further, in the bracket 1, the upper surface of the upper portion 11U of the second side wall 11 is brought into contact with the left end of the lower surface of the top plate 7, the screw holes 7c and 7d are aligned with the screw holes 11a and 11b, and the screw holes 7c and 11b are aligned. A screw 13c is screwed into the screw hole 11a, and a screw 13d is screwed into the screw through hole 7d and the screw hole 11b.

As shown in FIG. 3, the wheel 3 includes a wheel 15, a tire 17, a bearing device 19, and a rotating shaft 21. The wheel 15 includes a cylindrical portion 15a that is coaxial with the wheel axis O and extends horizontally on the left and right sides, a first flange 15b that extends in a direction away from the wheel axis O at the right end of the cylindrical portion 15a, and a first flange 15b that extends away from the wheel axis O at the right end of the cylindrical portion 15a. It consists of a second flange 15c that widens in the direction away from the wheel axis O at the left end.

The tire 17 is fixed within the cylindrical portion 15a, the first flange 15b, and the second flange 15c of the wheel 15. A bearing device 19 is provided within the cylindrical portion 15a, and a cylindrical rotating shaft 21 is press-fitted into the bearing device 19. The bracket 1 and the wheel 3 constitute an eccentric length changing mechanism 4 in which the elongated holes 9c, 11c and the rotating shaft 21 guide the wheel axis O along the elongated holes 9c, 11c.

The one-way clutch mechanism 5 includes a first one-way clutch 23 and a second one-way clutch 25, as shown in FIGS. 1 and 2. The first one-way clutch 23 includes a first gear 27, a first dog 29, and a weight 31. The second one-way clutch 25 includes a second gear 33, a second dog 35, and a weight 37.

The first gear 27 is fixed to the first flange 15b of the wheel 15, as shown in FIGS. 3 to 5. The first side wall 9 of the bracket 1 is located on the right side of the first gear 27. As shown in FIGS. 6, 8, and 10, the first gear 27 has first tooth surfaces 27a and second tooth surfaces 27b alternately and continuously formed on the outer peripheral surface. Each first tooth surface 27a is located on a plane containing the wheel axis O. Each second tooth surface 27b is located on a plane containing the wheel axis O. The first tooth surface 27a corresponds to a first swing tooth surface, and the second tooth surface 27b corresponds to a first engagement tooth surface.

As shown in FIGS. 1 to 5, the first dog 29 includes a rod 29R that extends vertically in a bar shape, and a plate-shaped stopper 29S fixed to the left side of the lower end of the rod 29R. A pin hole 29a is provided through the upper end of the rod 29R. A notch is formed at the rear end of the stopper 29S, and a weight 31 made of a bolt and a nut is fixed to the notch. The first dog 29 is configured to swing back and forth by aligning the pin hole 29a of the rod 29R with the screw hole 9d of the first side wall 9 of the bracket 1 and screwing the screw 39 into the screw hole 9d. . The center of the screw 39 corresponds to the first swing center S1. As shown in FIGS. 4 and 5, the front surface 291 of the stopper 29S extends in the radial direction from the first swing center S1. The front surface 291 corresponds to the first end surface. An upper surface 292 of the stopper 29S is perpendicular to the front surface 291. The upper surface 292 corresponds to the first orthogonal surface. The weight 31 corresponds to first biasing means.

The rotating shaft 21 of the wheel 3 is inserted through the elongated hole 9c of the first side wall 9, and a ring 41 is press-fitted into the right end of the rotating shaft 21. The first dog 29 swings around the first swing center S1, but its forward swing is restricted by the rod 29R coming into contact with the ring 41. When the rod 29R is in contact with the ring 41, the rod 29R is in a vertically extending state.

The second gear 33 is fixed to the second flange 15c of the wheel 15, as shown in FIGS. 3 to 5. The second side wall 11 of the bracket 1 is located on the left side of the second gear 33. As shown in FIG. 7, FIG. 9, and FIG. 11, the second gear 33 has first tooth surfaces 33a and second tooth surfaces 33b alternately and continuously formed on the outer peripheral surface. Each first tooth surface 33a is located on a plane containing the wheel axis O. Each second tooth surface 33b is located on a plane containing the wheel axis O. The first tooth surface 33a corresponds to a second swing tooth surface, and the second tooth surface 33b corresponds to a second engagement tooth surface.

As shown in FIGS. 1 and 3 to 5, the second dog 35 includes a rod 35R that extends vertically in a bar shape, and a plate-shaped stopper 35S fixed to the right side of the lower end of the rod 35R. A pin hole 35a is provided through the upper end of the rod 35R. A notch is formed in the front end of the stopper 35S, and a weight 37 made of a bolt and a nut is fixed to the notch. The second dog 35 is configured to swing back and forth by aligning the pin hole 35a of the rod 35R with the screw hole 11d of the second side wall 11 of the bracket 1 and screwing the screw 43 into the screw hole 11d. . The center of the screw 43 corresponds to the second swing center S2. As shown in FIGS. 4 and 5, the rear surface 351 of the stopper 35S extends in the radial direction from the second swing center S2. The rear surface 351 corresponds to the second end surface. The upper surface 352 of the stopper 35S is perpendicular to the rear surface 351. The upper surface 352 corresponds to the second orthogonal surface. The weight 37 corresponds to second biasing means.

The rotating shaft 21 of the wheel 3 is inserted through the elongated hole 11c of the second side wall 11, and a ring 45 is press-fitted into the left end of the rotating shaft 21. The second dog 35 swings around the second swing center S2, but its backward swing is restricted by the rod 35R coming into contact with the ring 45. When the rod 35R is in contact with the ring 45, the rod 35R is in a vertically extending state.

As shown in FIGS. 1 to 3, a bearing device 47 is fixed to the upper surface of the top plate 7 of the bracket 1 by a fixing means (not shown). The center of the bearing device 47 is a pivot axis P that extends vertically with respect to a base (not shown). Legs 49 projecting downward from the base are fixed to the inner ring of the bearing device 47. Therefore, the bracket 1 can be turned around the turning axis P. The elongated holes 9c and 11c of the first and second side walls 9 and 11 extend before and after the pivot axis P. Therefore, the wheel axis O is separated from the turning axis P by an eccentric length, and the eccentric length is changed across the turning axis P by the eccentric length changing mechanism 4.

The trolley includes a base, the four casters described above, and a handle extending upward from the base. A load is placed on the base. Consider a case in which the cart is towed by, for example, an automatic guided vehicle, and after being towed, an operator pushes the cart back in the direction in which it was being towed.

First, when moving this truck forward, as shown in FIGS. 4, 6, and 7, the wheel axis O is located at the rear end of the elongated hole 9c due to inertia force. In this state, the first one-way clutch 23 allows the wheels 3 of the truck to rotate clockwise as shown in FIG. 6 . That is, since the wheel axis O of the first dog 29 is located at the rear end of the elongated hole 9c, the front surface 291 of the stopper 29S comes into contact with the first tooth surface 27a of the first gear 27, and the first dog 29 swings backward. move. The first dog 29 that has swung backwards is swung forward due to its own weight due to the weight 31, and when the rod 29R contacts the ring 41, the first dog 29 comes into contact and swings again. In this way, the first dog 29 sequentially swings rearward as the front surface 291 of the stopper 29S sequentially contacts the first tooth surface 27a of the first gear 27. On the other hand, in the second one-way clutch 25, since the wheel axis O is located at the rear end of the elongated hole 9c, the second dog 35 is independent of the wheel 3, as shown in FIG. Therefore, the wheels 3 are allowed to roll in order to move forward.

When the truck is stopped and the wheel axis O is positioned at the rear end of the elongated hole 9c and the truck is moved rearward, the first one-way clutch 23 is connected to the rear of the wheel 3, as shown in FIG. Prohibits rolling. That is, when the wheel 3 attempts to reverse rotation, the second tooth surface 27b of the first gear 27 comes into contact with the upper surface 292 of the stopper 29S of the first dog 29, and the reverse rotation of the wheel 3 is prohibited. On the other hand, in the second one-way clutch 25, the second dog 35 is independent of the wheel 3, as shown in FIG. Therefore, the wheels 3 are only allowed to roll in order to move forward.

Therefore, in this caster, when the wheel axis O moves along the elongated holes 9c and 11c, the wheel 3 does not need to rotate 180 degrees around the rotation axis P while sliding on the floor surface, and the wheel 3 does not roll on the floor. Therefore, the wheel axis O can easily move from the rear end to the front end along the elongated holes 9c and 11c, and the effect of reducing the initial load is exhibited.

Note that when the truck is stopped and the wheel axis O is located approximately at the center of the elongated holes 9c and 11c due to inertia force as shown in FIGS. 8 and 9, the wheels 3 are stopped, so the first Both the first dog 29 of the one-way clutch 23 and the second dog 35 of the second one-way clutch 25 stop swinging.

In order to move the truck backwards, as shown in FIGS. 5, 10 and 11, if the wheel axis O is located at the front end of the elongated hole 9c, the first one-way clutch 23 will move as shown in FIG. Counterclockwise rolling of the wheels 3 of the truck as it moves backward is allowed. That is, in the first one-way clutch 23, since the wheel axis O is located at the front end of the elongated hole 9c, the first dog 29 is independent of the wheel 3. On the other hand, as shown in FIG. 11, in the second one-way clutch 25, since the wheel axis O is located at the front end of the elongated hole 9c, the rear surface 351 of the stopper 35S It touches and swings forward. The second dog 35 that has swung forward is swung backward due to its own weight due to the weight 37, and when the rod 35R comes into contact with the ring 45, the second dog 35 comes into contact and swings again. In this way, the second dog 35 sequentially swings forward as the rear surface 351 of the stopper 35S sequentially contacts the first tooth surface 33a of the second gear 33. Therefore, the wheels 3 are allowed to roll for backward movement.

When the truck is stopped again and the wheel axis O is positioned at the front end of the elongated hole 9c and the truck is moved forward, the second one-way clutch 25 is moved forward of the wheel 3 as shown in FIG. Prohibits rolling. That is, when the wheel 3 attempts to reverse rotation, the second tooth surface 33b of the second gear 33 comes into contact with the upper surface 352 of the stopper 35S of the second dog 35, thereby prohibiting the wheel 3 from reversing. On the other hand, in the first one-way clutch 23, the first dog 29 is independent of the wheel 3, as shown in FIG. Therefore, the wheels 3 are only allowed to roll for backward movement.

Therefore, with this caster, it is possible to increase the effect of reducing the initial load when the trolley is towed by an automatic guided vehicle and after being towed, the operator pushes the trolley back in the direction in which it has been towed. The same applies when a front-rear automatic guided vehicle moves backward after moving forward on its trolley. Note that this caster can also rotate on the floor using the bearing device 47.

In addition, in this caster, the first dog 29 and the second dog 35 can be manufactured oppositely, and the first gear 27 and the second gear 33 can be manufactured as the same product with the front and back sides reversed, so that manufacturing costs can be reduced. realizable. Furthermore, since the wheels 3 are suitably rotated around the rotating shaft 21 by the bearing device 19, this caster can suitably roll on the floor surface.

(Example 2)
In the caster of the second embodiment, as shown in FIG. 12, the first biasing means is a tension spring 51. Therefore, the stopper 29S of the first dog 29 is downsized. Although not shown, the second biasing means is also a tension spring. Therefore, the stopper 35S of the second dog 35 is also downsized. Also in this caster, the same effects as in the first embodiment can be achieved.

In the above, the present invention has been explained based on Examples 1 and 2, but the present invention is not limited to the above-mentioned Examples 1 and 2, and can be applied with appropriate changes without departing from the spirit thereof. Needless to say.

For example, the eccentric length changing mechanism 4 may be configured to prevent the wheel axis O from twisting when the wheel axis O moves through the elongated hole 9c. Furthermore, instead of the elongated holes 9c and 11c passing through the first side wall 9 and the second side wall 11, guides recessed in the first side wall 9 and the second side wall 11 may be used.

INDUSTRIAL APPLICATION This invention can be utilized for a trolley etc.

9...First side wall 11...Second side wall P...Turning axis center 1...Bracket O...Wheel axis center 3...Wheel 9c, 11c...Guide (elongated hole)
4...Eccentric length changing mechanism 5, 23, 25...One-way clutch mechanism (23...first one-way clutch, 25...second one-way clutch)
27...First gear 29...First dog 31, 51...First biasing means (51...Tension spring)
33...Second gear 35...Second dog 31...Second biasing means S1...First swing center 291...First end surface (front surface)
292...First orthogonal surface (top surface)
27a...First rocking tooth surface (first tooth surface)
27b...First engagement tooth surface (second tooth surface)
S2...Second swing center 351...Second end surface (rear surface)
352...Second orthogonal surface (top surface)
33a...Second rocking tooth surface (first tooth surface)
33b...Second engagement tooth surface (second tooth surface)
15...Wheel 17...Tire 19...Bearing device 21...Rotating shaft

Claims (6)

A bracket having a first side wall extending vertically, and a second side wall facing the first side wall and extending vertically, and pivotable around a pivot axis extending vertically with respect to a base on which a load is placed. and,
a wheel that extends horizontally between the first side wall and the second side wall and is rotatable around a wheel axis;
In a caster, the wheel axis is spaced apart from the rotation axis by an eccentric length,
A guide is provided between the wheel and the first side wall and between the wheel and the second side wall, the guide being perpendicular to the pivot axis and extending in the front-rear direction from a front end located at the front to a rear end located at the rear. and an eccentric length changing mechanism that guides the wheel axis along the guide to change the eccentric length across the turning axis,
A one-way clutch mechanism is provided between the wheel and the bracket that allows the wheel to roll in a first direction and prohibits the wheel to roll in a second direction opposite to the first direction. established ,
The one-way clutch mechanism is provided between the wheel and the first side wall, and when the wheel axis is located at the rear end, the one-way clutch mechanism allows the wheel to roll forward, and the one-way clutch mechanism allows the wheel to roll forward. a first one-way clutch that prohibits rearward rolling and becomes unrelated to rolling of the wheel if the wheel axis is located at the front end;
Provided between the wheel and the second side wall, and when the wheel axis is located at the front end, it allows the wheel to roll in the rear direction and prohibits the wheel to roll in the forward direction. The caster further comprises a second one-way clutch that is independent of rolling of the wheel when the wheel axis is located at the rear end . The first one-way clutch includes a first gear fixed to the wheel, a first dog provided on the first side wall so as to be swingable in a plane parallel to the rotational direction of the wheel, and the first dog. a first biasing means for biasing the first gear toward the first gear;
The first dog has a state in which the wheel axis is located at the rear end, allows the wheel to roll forward, and is not engaged with the first gear, and a state in which the wheel axis is located at the rear end, allowing the wheel to roll forward, and disengaging from the first gear. a state in which rolling is prohibited and engaged with the first gear; and a state in which the wheel axis is located at the front end and is unrelated to the first gear;
The second one-way clutch includes a second gear fixed to the wheel, a second dog provided on the second side wall so as to be swingable in a plane parallel to the rotational direction of the wheel, and the second dog. a second urging means for urging the second gear toward the second gear;
The second dog has a state in which the wheel axis is located at the front end, allowing the wheel to roll rearward and is not engaged with the second gear, and a state in which the wheel axis is located at the front end. 2. The caster according to claim 1, wherein the caster has a state in which rolling is prohibited and engaged with the second gear, and a state in which the wheel axis center is located at the rear end and is unrelated to the second gear. The first dog has a first end surface extending in a radial direction from a first swing center, and a first orthogonal surface orthogonal to the first end surface,
The first gear includes a first rocking tooth surface that comes into contact with the first end surface against the first urging means to rock the first dog when the wheel rotates forward; a first engaging tooth surface that is continuous with the first rocking tooth surface and which bends to the first biasing means and engages the first orthogonal surface when the wheel rotates backward;
The second dog has a second end surface extending in a radial direction from a second swing center, and a second orthogonal surface orthogonal to the second end surface,
The second gear includes a second swinging tooth surface that contacts the second end surface against the second urging means to swing the second dog when the wheel rotates backward; a second engaging tooth surface that is continuous with the second rocking tooth surface and that bends to the second biasing means and engages the second orthogonal surface when the wheel rotates forward; The caster according to claim 2 . The first biasing means is the own weight of the first dog,
The caster according to claim 2 or 3 , wherein the second biasing means is the own weight of the second dog. The caster according to claim 2 or 3 , wherein the first biasing means and the second biasing means are tension springs. The wheel is rotatable around the wheel axis by a wheel concentric with the wheel axis, a tire held on the wheel, a bearing device held on the wheel, and the bearing device, and The caster according to claim 5 , comprising a rotating shaft extending in the direction of the wheel axis.

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