Caster

Abstract

To provide a caster capable of suppressing frictional force occurring between a free roller rotatably attached to a base wheel and a contact object when the swivelable base wheel is used in a state of being laid against the contact object. [Solution] A swivel mechanism 19 having three or more free rollers 11-18 is freely rotatable around a swivel axis C, and each free roller 11-18 is 1) arranged to surround the swivel axis C, 2) rotated in the same direction by less than 90 degrees based on a virtual axis parallel to the swivel axis passing through the center of the free roller, relative to the conventional arrangement in which a virtual line perpendicular to the swivel axis C passing through both the center of the free roller and the swivel axis C is perpendicular to the rotation axis of the free roller, and 3) when viewed along the swivel axis C, the angle formed by each virtual line passing through the center of adjacent free rollers around the swivel axis C is α degrees, and the actual angle difference between each adjacent free roller and the conventional arrangement is β1 degrees and β2 degrees, where β1>α / 2 and β2>α / 2.

Description

[Technical Field]

[0001] The present invention relates to a caster having a base wheel to which a plurality of free rollers are attached. [Background technology]

[0002] An omnidirectional mobile mechanism that can move in all directions is configured such that a sphere that rolls on a running surface is supported by casters so that it can rotate in all directions, as disclosed in Patent Documents 1 and 2. Examples of casters that can be used for this purpose include ball casters and omniwheels. While ball casters have the advantage of being able to support a sphere with little force, dust that adheres to the sphere can easily get in between the ball of the ball caster and the part that supports the ball so that it can rotate freely, and if dust gets in this area, it can cause noise and malfunction. For this reason, ball casters require regular maintenance such as cleaning.

[0003] As shown in Figure 6(A), the Omni-Wheel 100 can rotatably support the sphere 101 by providing a plurality of free rollers 103 rotatably attached to a rotatable base wheel 102 so that they come into contact with the sphere 101. This has the advantage that even if dust adhering to the sphere 101 moves from the sphere 101 to the free rollers 103, it is difficult for it to get into the area around the rotation axis (sliding part) of the free rollers 103.

[0004] However, the free rollers 103 of the omni-wheel 100 generally have a small diameter and a low load-bearing capacity. To increase the load-bearing capacity, free rollers 103 with a large diameter can be used, but this would increase the size of the omni-wheel 100 as a whole. When the omni-wheel 100 supports the sphere 101 so that it can rotate freely, it is usually used with the base wheels 102 in an upright position, as shown in Figure 6(A). Therefore, if a large omni-wheel 100 is used, the omni-directional movement mechanism becomes longer in the height direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7487969 [Patent Document 2] Japanese Patent Application Publication No. 2023-7732 Summary of the Invention [Problem to be solved by the invention]

[0006] In this regard, as shown in Figure 6(B), if the base wheels 102 are laid down relative to the sphere 101, the omnidirectional movement mechanism can be prevented from becoming longer in the height direction. Note that even when the base wheels 102 are laid down, as in the case where the base wheels 102 are placed upright, only some of the free rollers 103, not all of them, come into contact with the sphere 101.

[0007] However, when the base wheel 102 is laid down, a problem occurs in that the frictional force between the free roller 103 and the ball 101 remains large depending on the direction of rotation of the ball 101. For example, as shown in Figure 7, suppose that the sphere 110 rotates in the direction of the arrow while two adjacent free rollers 112 and 113 of the omni-wheel 111 are in contact with the sphere 110. If the free rollers 112 and 113 are arranged symmetrically with respect to the direction of rotation of the sphere 110, the forces that the free rollers 112 and 113 receive from the sphere 110 will be balanced, and the base wheel 114 of the omni-wheel 111 will be stationary.

[0008] At this time, since the rotation axes of the free rollers 112 and 113 are not parallel to the rotation axis of the sphere 110, the frictional force between each of the free rollers 112 and 113 and the sphere 110 increases. Also, even if the stationary base wheel 114 rotates clockwise or counterclockwise for some reason, the omniwheel 111 tries to return to its original orientation in which the forces that the free rollers 112 and 113 receive from the sphere 110 were balanced.

[0009] The problem of a persistently large friction force between a free roller and a contact object with which the free roller makes contact is not limited to cases where the contact object is a sphere rotatably supported by an omni-wheel. For example, the same problem occurs when a vehicle with an omni-wheel runs on a running surface with the free rollers in contact with the running surface with the base wheels laid down (i.e., when the running surface of the vehicle is the contact object).

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a caster that can suppress the frictional force that occurs between a free roller rotatably attached to a base wheel and a contact object when the swivelable base wheel is used by laying it down against the contact object. [Means for solving the problem]

[0011] The caster according to the present invention, which is in accordance with the above-mentioned object, is a caster in which a swivel mechanism having three or more free rollers is swivelable around a swivel axis, and each of the free rollers is: 1) arranged around the pivot shaft to surround the pivot shaft, 2) In comparison with a conventional arrangement in which an imaginary line passing through both the center of the free roller and the turning axis and perpendicular to the turning axis is orthogonal to the rotation axis of the free roller, the orientation is rotated by less than 90 degrees in the same direction with respect to an imaginary axis passing through the center of the free roller and parallel to the turning axis, 3) When viewed along the pivot axis, the angle formed by the imaginary line passing through the center of one of the free rollers adjacent around the pivot axis and the imaginary line passing through the center of the other adjacent free roller is defined as α degrees, the angular difference between the actual arrangement of one of the adjacent free rollers and the conventional arrangement is defined as β1 degrees, and the angular difference between the actual arrangement of the other adjacent free roller and the conventional arrangement is defined as β2 degrees, where β1>α / 2 and β2>α / 2. [Effects of the Invention]

[0012] According to the caster of the present invention, when the base wheel is used by laying it down against the contact object, a state in which large frictional forces are generated between the two free rollers adjacent around the pivot axis and the contact object, and the forces that the two free rollers receive from the contact object are balanced can be avoided, and the frictional forces generated between the free rollers and the contact object can be suppressed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a caster according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 10 is an explanatory diagram of a conventional arrangement of free rollers. [Figure 5] FIG. 10 is an explanatory diagram showing the angle difference between the actual arrangement of free rollers and the conventional arrangement. [Figure 6] (A) and (B) are explanatory diagrams showing how a sphere is rotatably supported by an omnifoil. [Figure 7] 10 is an explanatory diagram showing the movement of an omni-wheel that rotatably supports a sphere. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, with reference to the accompanying drawings, embodiments embodying the present invention will be described to aid in understanding the present invention. 1 to 3, in a caster 10 according to one embodiment of the present invention, a swivel mechanism 19 having three or more free rollers 11 to 18 is swivelable around a swivel axis C, and the free rollers 11 to 18 are arranged so as to surround the swivel axis C. This will be described in detail below.

[0015] 1 to 3, the turning mechanism 19 includes three or more (eight in this embodiment) free rollers 11 to 18, a roller support 20 to which the eight free rollers 11 to 18 are rotatably attached, and a cover body 21 fixed to the roller support 20. As shown in FIG. 2, the roller support 20 has a structure in which eight openings 22 corresponding to the eight free rollers 11 to 18 are formed in a disk-shaped member.

[0016] As shown in Figures 2 and 3, the free rollers 11 to 18 are rotatably attached to axles 11a to 18a, respectively. Therefore, the free rollers 11 to 18 are rotatable about the axles 11a to 18a, respectively, and the rotation axes R1 to R8 of the free rollers 11 to 18 are aligned along the axes of the axles 11a to 18a, respectively. The rotation axes R1 to R8 here are not actual shaft members but conceptual axes for expressing the rotational motion of the free rollers 11 to 18, and the same applies to the rotation axis C of the rotation mechanism 19, which will be described later. Note that the rotation axes R3 to R8 are omitted from Figure 3.

[0017] The cover body 21 is fixed to the roller support body 20 and positions the axles 11a to 18a on the roller support body 20. The cover body 21 and the roller support body 20 form an internal space that accommodates most of each of the free rollers 11 to 18. A portion of each of the free rollers 11 to 18 protrudes outward from the internal space formed by the cover body 21 and the roller support body 20 through each opening 22. In the following description, it is assumed that each of the free rollers 11 to 18 protrudes downward from each of the openings 22.

[0018] 1 and 2, a vertically disposed shaft member 23 penetrates the centers of the circular cover body 21 and the roller support body 20 in a plan view. The upper part of the shaft member 23 protrudes from the cover body 21, and the protruding upper part of the shaft member 23 penetrates a circular movable plate 24 and a circular fixed plate 25 that are in contact with the cover body 21. The fixed plate 25 is provided above the movable plate 24 at a distance from the movable plate 24. A thrust bearing 26 is provided between the fixed plate 25 and the cover body 21, and has an opening in the center where the movable plate 24 is disposed. The fixed plate 25 is fixed to the shaft member 23 by a nut 27 fixed to the shaft member 23.

[0019] The movable plate 24, cover body 21, and roller support body 20 are able to swivel (rotate) freely relative to the shaft member 23 and fixed plate 25 by means of a thrust bearing 26 and a flanged bearing 28 attached to the shaft member 23. Therefore, the swivel mechanism 19 is able to swivel freely around the shaft member 23. Note that a bush or the like may be used instead of the flanged bearing 28. In this embodiment, the swivel axis C of the swivel mechanism 19 is aligned with the axis of the shaft member 23.

[0020] As shown in Fig. 3, the free rollers 11-18 are arranged at equal intervals around the pivot axis C (shaft 23) (in this embodiment, clockwise when viewing the caster 10 from the bottom). In this embodiment, the free rollers 11-18 have the same diameter and widthwise length, and their centers are arranged at the same height, but this is not limited to this. For example, of the eight (i.e., three or more) free rollers 11-18, at least one may have a different diameter from the others, or all may have different diameters (in this case, the widthwise length is also the same).

[0021] Furthermore, the free rollers 11 to 18 do not need to be arranged at equal intervals around the rotation axis C; for example, the interval between the free rollers 11 and 12 around the rotation axis C may be different from the interval between the free rollers 12 and 13 around the rotation axis C. It should be noted that, as used herein, words such as equal, identical, equally spaced, perpendicular, etc., mean substantially equal, etc., or substantially in that order.

[0022] In addition, as shown in Figure 3, the free roller 11 is rotated by less than 90 degrees in a specified direction (counterclockwise or clockwise) around a virtual axis Q1 that is parallel to the pivot axis C and passes through the center of the free roller 11, as compared to the conventional arrangement (see Figure 4) in which a virtual straight line L1 that is perpendicular to the pivot axis C and passes through both the center of the free roller 11 and the pivot axis C is perpendicular to the rotation axis R1 of the free roller 11.

[0023] This is also true for each of the free rollers 12 to 18. Therefore, for example, in the conventional arrangement shown in Fig. 4, in which an imaginary straight line L2 that passes through both the center of the free roller 12 and the rotation axis C and is perpendicular to the rotation axis C and the rotation axis R2 of the free roller 12 are orthogonal, the free roller 12 is also rotated by less than 90 degrees in the same direction as the rotation direction of the free roller 11 from the conventional arrangement, which is less than 90 degrees, with respect to an imaginary axis Q2 that passes through the center of the free roller 12 and is parallel to the rotation axis C, as shown in Fig. 3.

[0024] In addition to these, as shown in Figure 5, for free rollers 11 and 12 adjacent to each other around the rotation axis C, the angle formed by an imaginary line L1 passing through the center of one free roller 11 and an imaginary line L2 passing through the center of the other free roller 12 is α degrees, the angular difference between the actual arrangement of one free roller 11 and the conventional arrangement is β1 degrees, and the angular difference between the actual arrangement of the other free roller 12 and the conventional arrangement is β2 degrees, where β1 > α / 2 and β2 > α / 2. Note that 90 > β1 and 90 > β2.

[0025] This is also true for free rollers 12 and 13 adjacent to each other around the pivot axis C, free rollers 13 and 14 adjacent to each other around the pivot axis C, free rollers 14 and 15 adjacent to each other around the pivot axis C, free rollers 15 and 16 adjacent to each other around the pivot axis C, free rollers 16 and 17 adjacent to each other around the pivot axis C, free rollers 17 and 18 adjacent to each other around the pivot axis C, and free rollers 18 and 11 adjacent to each other around the pivot axis C.

[0026] As explained so far, by (1) arranging the free rollers 11 to 18 around the rotation axis C, (2) arranging the free rollers 11 to 18 in a direction rotated by less than 90 degrees in the same direction from the conventional arrangement based on a virtual axis passing through their centers, and (3) arranging the free rollers 11 to 18 so that β1 > α / 2 and β2 > α / 2 between any two adjacent free rollers 11 to 18, it is possible to prevent excessive frictional forces from occurring between the free rollers 11 to 18 and the objects they come into contact with.

[0027] Here, the contact object that the free rollers 11-18 come into contact with is, for example, a sphere rotatably supported by the caster 10, or a running surface on which a vehicle equipped with the caster 10 runs. The caster 10 according to this embodiment is assumed to be used such that the rotation axis C is arranged perpendicular or nearly perpendicular to the contact object, and such that one or two free rollers 11-18 are always in contact with the contact object at the same time. Note that three free rollers 11-18 may be in contact with the contact object at the same time.

[0028] In this embodiment, the angle difference between the actual arrangement and the conventional arrangement is equal for each of the free rollers 11 to 18. That is, β1 and β2 are equal for each combination of free rollers 11, 12, free rollers 12, 13, free rollers 13, 14, free rollers 14, 15, free rollers 15, 16, free rollers 16, 17, free rollers 17, 18, and free rollers 18, 11 that are adjacent around the rotation axis C.

[0029] However, this is not limited to this. β1 and β2 may be different in one or more of the eight pairs of free rollers 11, 12, free rollers 12, 13, free rollers 13, 14, free rollers 14, 15, free rollers 15, 16, free rollers 16, 17, free rollers 17, 18, and free rollers 18, 11 that are adjacent to each other around the rotation axis C.

[0030] In particular, by making β1 and β2 different in all of the eight pairs, it is possible to suppress noise that occurs when the free rollers 11 to 18 rotate in contact with the contact object. This is because it is possible to prevent the same sound (for example, sound with the same frequency) from being generated between adjacent free rollers 11 to 18 that have the opportunity to come into contact with the contact object at the same time.

[0031] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions that do not depart from the gist of the present invention are within the scope of application of the present invention. For example, in the above embodiment, in each pair of adjacent free rollers around the rotation axis of the rotation mechanism, the angle (α) formed by the imaginary line passing through the center of one free roller and the imaginary line passing through the center of the other free roller is all less than 90 degrees, but this is not limited to this. [Explanation of symbols]

[0032] 10: caster, 11 to 18: free roller, 11a to 18a: axle, 19: swivel mechanism, 20: roller support, 21: cover body, 22: opening, 23: shaft material, 24: movable plate, 25: fixed plate, 26: thrust bearing, 27: nut, 28: flanged bearing, C: swivel axis, L1, L2: virtual straight line, Q1, Q2: virtual axis, R1 to R8: rotation axis

Claims

1. A caster in which a swivel mechanism having three or more free rollers is swivelable around a swivel axis, Each of the free rollers is 1) The rotating shaft is disposed around the rotating shaft, 2) In comparison with a conventional arrangement in which an imaginary line passing through both the center of the free roller and the pivot axis and perpendicular to the pivot axis is orthogonal to the rotation axis of the free roller, the orientation is rotated by less than 90 degrees in the same direction with respect to an imaginary axis passing through the center of the free roller and parallel to the pivot axis, 3) A caster characterized in that, when viewed along the swivel axis, the angle formed by the imaginary line passing through the center of one of the free rollers adjacent around the swivel axis and the imaginary line passing through the center of the other of the adjacent free rollers is α degrees, the angular difference between the actual arrangement of one of the adjacent free rollers and the conventional arrangement is β1 degrees, and the angular difference between the actual arrangement of the other of the adjacent free rollers and the conventional arrangement is β2 degrees, where β1 > α / 2 and β2 > α / 2.

2. The caster according to claim 1, characterized in that, in each of the free rollers, β1 and β2 are different in all pairs of the free rollers adjacent to each other around the rotation axis.

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