Swivel casters

Abstract

Regarding swivel casters, the goal is to ensure smooth movement while reducing noise and vibration without increasing manufacturing costs. [Solution] A swivel caster 1A is provided, comprising a synthetic resin fork 2A having arms 21, 22 extending diagonally downward in a pair from the lower end of a cylindrical portion 20 through which a mounting hole 25 penetrates vertically along the center line, a metal mounting plate 4 having a mounting shaft 5 extending downward from the central part and attached to the bottom surface of the movable body, and a wheel 3 pivotally supported by an axle 6 supported by shaft holes 212, 211 at the tips of the left and right arms 21, 22, wherein the fork 2A is mounted so as to be able to pivot around the axis of the mounting shaft 5 with the mounting shaft 5 inserted into the mounting hole 25, the arms 21, 22 are shaped such that the width in the front-rear direction at the position through which the center line of the axle 6 passes is at least 3 / 5 of the vertical length from the lower end of the cylindrical portion 20 to the height of the center line of the axle 6.

Description

[Technical Field]

[0001] The present invention relates to a caster provided on the bottom surface of furniture, carts, or the like to facilitate movement thereof, and particularly relates to a swivel caster provided with a wheel turning mechanism that enables easy change of movement direction. [Background Art]

[0002] Swivel casters, which are provided in plural on the bottom surface of a moving body such as a cart to facilitate movement to a desired position, are known to have various characteristics and functions. In recent years, those suitable for use in corridors and indoor spaces of apartment buildings, such as for transporting parcel deliveries at destinations and moving indoor furniture, have been widely popularized.

[0003] In such corridors and indoor spaces of apartment buildings, noise and vibration accompanying the rotation of caster wheels tend to be a problem when conveying articles with a cart or the like. Therefore, in order to reduce the generation of such noise and vibration, as disclosed in Japanese Utility Model Publication No. 3-24902 (Document 1) and Japanese Patent Laid-Open Publication No. 10-291401 (Document 2), a swivel caster has been proposed in which a fork (yoke), which is a component having two arms holding both ends of an axle and being pivotably provided on a vertical mounting shaft, is formed by integral molding of synthetic resin.

[0004] The use of a synthetic resin fork as described above enables significant reduction in noise and vibration compared with conventional metal forks. However, in the swivel casters of Documents 1 and 2 mentioned above, since both arms of the fork are elongated diagonally downward with respect to the axis of the vertical mounting shaft to enable turning of the wheel, the arms are prone to bending under a large load. This deformation causes the mounting shaft to tilt, which reduces the turning performance of the wheel, and also has the disadvantage that noise is generated by the turning operation.

[0005] To address the reduced maneuverability and noise issues caused by such heavy loads, the fork described in reference 1 reduces resistance during turning by providing two radial ball bearings on both the upper and lower ends of the mounting shaft. However, even with reduced resistance during turning, maintaining driving stability is difficult due to the curvature of the arm, and radial ball bearings tend to lack durability against heavy thrust loads. Furthermore, housing the bearing components in a double configuration within the resin fork tends to increase costs.

[0006] On the other hand, in the fork described in reference 2, a single thrust ball bearing is provided in the center of the mounting shaft to ensure load-bearing capacity. However, if the arm deforms under a large load and the mounting shaft tilts, it must be said that a single thrust ball bearing alone is insufficient to adequately reduce noise and vibration while ensuring smooth operation. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Publication No. 3-24902 [Patent Document 2] Japanese Patent Application Publication No. 10-291401 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems, and its objective is to ensure smooth movement of a swivel caster while reducing noise and vibration without increasing manufacturing costs. [Means for solving the problem]

[0009] Therefore, the present invention provides a swivel caster comprising: a synthetic resin fork having a pair of left and right arms extending diagonally downward from the lower end of a cylindrical portion through which a mounting hole passes vertically in the center line; a metal mounting plate having a mounting shaft extending downward from the central part and attached to the bottom surface of a movable body; and a wheel supported on the tips of the left and right arms so as to be rotatable between the arms, wherein the fork is mounted below the mounting plate so as to be rotatable around the axis of the mounting shaft with the mounting shaft inserted into its mounting hole, wherein the arms are shaped such that the width in the front-rear direction at the position through which the center line of the axle passes is at least 3 / 5 of the vertical length from the lower end of the cylindrical portion to the height of the center line of the axle.

[0010] Thus, in a swivel caster in which left and right arms extend diagonally downward from the lower end of a cylindrical section and resin forks are rotatably mounted below the mounting plate, the width of the arms in the front-to-back direction at the position where the center line of the axle passes through is set to 3 / 5 or more of the vertical length from the lower end of the cylindrical section to the height of the center line. By providing wide arms in this manner, even if the arms supporting the axle are made of synthetic resin, deformation due to load is kept to a minimum, making it easier to achieve smooth movement while reducing the generation of noise and vibration during transportation.

[0011] Furthermore, if the aforementioned swivel caster is characterized in that, on the outer circumference of the openings on both the upper and lower sides through which the mounting holes of the cylindrical part pass, recesses for holding multiple balls are formed to surround the openings, and the balls placed in the recesses are held in place by sandwiching them from above and below with a pair of upper and lower donut-shaped ball-holding plates through which the mounting shaft is inserted, a pair of upper and lower thrust ball bearings are formed, then the upper and lower sides of the cylindrical part of the resin fork also serve as part of the ball bearing, which eliminates the need for dedicated bearing parts and reduces costs. In addition, by supporting both the upper and lower ends of the mounting shaft with thrust ball bearings, it is possible to significantly reduce noise and vibration while ensuring high load capacity and smooth running performance.

[0012] In this case, if the upper ball retaining plate is fixed to the upper outer edge of the opening of the mounting hole that penetrates the center of the mounting plate, with its outer circumference in close contact with the upper edge of the mounting plate, and thus integrated with the mounting plate, then the fork can be rotated with the upper end of the fork close to the lower side of the mounting plate, thus achieving both excellent load-bearing capacity and a compact design as a caster.

[0013] Furthermore, in a swivel caster equipped with the aforementioned thrust ball bearing, if the recesses for holding the balls on both the upper and lower surfaces of the cylindrical part are characterized by being multiple circular holes with a diameter and depth that allow a portion of the balls to be inserted and held, and are arranged in an annular shape at regular intervals surrounding the opening of the mounting hole, then it is possible to provide two thrust ball bearings, upper and lower, with a small number of balls. [Effects of the Invention]

[0014] According to the present invention, by setting the width in the front-to-back direction of the position through which the axle centerline passes in the resin arm to 3 / 5 or more of the vertical length from the lower end of the cylindrical part to the height of the axle centerline, it is possible to achieve smooth running while reducing the generation of noise and vibration without causing a surge in manufacturing costs. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of a swivel caster, which is an embodiment of the present invention. [Figure 2] (A) is a side view showing the configuration of the fork of the swivel caster in Figure 1, and (B) is a rear view of the fork in (A). [Figure 3] (A) is a plan view of the fork in Figure 2(A), and (B) is a bottom view of the fork in (A). [Figure 4] This is a vertical cross-sectional view of the swivel caster shown in Figure 1 with the wheels omitted. [Figure 5](A) is a plan view showing a modification of the fork of FIG. 2(A), (B) is a bottom view of the fork of (A), and (C) is a front view showing a state where a ball is held in the ball holding hole of the fork of (A). DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, modes for carrying out the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a perspective view showing a swivel caster 1A according to the present embodiment, FIGS. 2 and 3 show a fork 2A which is a component used in the swivel caster 1A, and FIG. 4 is a longitudinal sectional view showing the swivel caster 1A with a wheel omitted. This swivel caster 1A includes a mounting plate 4, a fork 2A, and a wheel 3, is disposed on the bottom surface of a moving body such as furniture or a trolley, and is intended to facilitate movement thereof, and is configured to be able to easily change the moving direction by the turning mechanism of the wheel 3.

[0018] That is, the swivel caster 1A according to the present embodiment includes: a synthetic resin fork 2A having a pair of left and right arms 21 and 22 (see FIG. 2) extending obliquely downward from the lower end side of a cylindrical portion 20 (see FIG. 3) in which a mounting hole 25 penetrates the center line in the vertical direction; a metal mounting plate 4 having a mounting shaft 5 (see FIG. 4) vertically provided downward from a central portion and having screw holes 41, 41, 41, 41 at four corners; and the wheel 3 having an axle 6 supported at the distal end sides of the left and right arms 21 and 22 and pivotally supported rotatably between the arms 21 and 22. As shown in FIG. 4, in a state where the mounting shaft 5 is inserted into the mounting hole 25 of the fork 2A, the fork is pivotally supported so as to be turnable around the axis of the mounting shaft 5 below the mounting plate 4, thereby constituting the aforementioned turning mechanism.

[0019] Then, as shown in Fig. 2(A), arms 21 and 22 of a fork 2A, which axially support an axle 6 of a wheel 3 by inserting the axle 6 through shaft holes 211 and 212, have a wide shape in which the front-rear width X at a position through which the center line of the axle 6 passes is not less than three-fifths of the vertical length Y from the lower end side of a cylindrical portion 20 to the height position of the center line of the axle 6. This point is the most prominent feature of the present invention. By forming the distal end sides of the synthetic resin arms 21 and 22 into the above-described wide shape with a small degree of tapering to increase the load-bearing strength thereof, the above-mentioned problems can be solved.

[0020] This is because, in conventional swivel casters, synthetic resin forks used for the purpose of ensuring quietness and the like have an arm that pivotally supports the wheel on the distal end side that is tapered, as seen in Documents 1 and 2, so the fork is easily bent under a large load, which makes it difficult to ensure smooth traveling and easily causes noise and vibration. Therefore, as a result of testing multiple types of patterns for the ratio of X to Y in the above-described arm shape, it was discovered that when the ratio is set to be not less than three-fifths as described above, the strength increases and the amount of deformation is significantly reduced.

[0021] Further, in the present embodiment, as shown in Fig. 3, annularly protruding peripheral walls 23 and 24 are respectively formed on the outer peripheral side of the openings on both upper and lower surfaces through which a mounting hole 25 of the cylindrical portion 20 penetrates. On the upper surfaces of the peripheral walls 23 and 24, recesses 230 and 240 are respectively formed, which are annular in top view and bottom view and have an arc-shaped vertical cross-section, for holding a plurality of balls to constitute a ball bearing.

[0022] Then, as shown in Fig. 4, balls 70 and 80 disposed in the recesses 230 and 240 are sandwiched from above and below by a pair of upper and lower donut-shaped ball retaining plates 7 and 8 made of metal, through which a mounting shaft 5 is inserted. While being fixed by caulking or the like on the distal end side of the mounting shaft 5, the balls 70 and 80 are retained by the concave portions of the ball retaining plates, thereby forming a pair of upper and lower thrust ball bearings.

[0023] In this way, by adopting a system in which both the upper and lower sides of the cylindrical portion 20 of the synthetic resin fork 2A constitute part of the thrust ball bearing, it is possible to keep manufacturing costs low without using relatively expensive dedicated bearing parts. Furthermore, by supporting both the upper and lower sides of the mounting shaft 5 with thrust ball bearings, it is possible to ensure high load-bearing capacity and smooth running performance while significantly reducing noise and vibration.

[0024] Furthermore, in this embodiment, the upper ball retaining plate 7 is fixed to the upper outer edge of the mounting hole 40 opening that penetrates the central part of the mounting plate 4, with its outer circumference in close contact with it, and is integrated with the mounting plate 4. With the upper end of the cylindrical portion 20 of the fork 2A close to the lower surface of the mounting plate 4, the fork 2A is able to rotate. As a result, the thickness of the combined portion of the mounting plate 4 and the cylindrical portion 20 of the fork 2A is kept small, resulting in excellent load-bearing capacity and a compact caster design.

[0025] Figure 5 shows a modified fork 2B, which is a synthetic resin component of the swivel caster 1A described above. Figure (A) is a top view, Figure (B) is a bottom view, and Figure (C) is a front view with the balls 70 installed. In this example, the recesses for holding the balls 70 and 80 on both the upper and lower sides of the upper and lower peripheral walls 27 and 28 of the cylindrical portion 26 have been changed to multiple circular recesses, which are holding holes 270 and 280, each having a diameter and depth capable of holding the balls 70 and 80. These are characterized by being arranged in annular shape at regular intervals surrounding the openings on both the upper and lower sides of the mounting hole 29, making it possible to construct a pair of upper and lower thrust ball bearings even with a small number of balls.

[0026] As described above, the present invention makes it possible to achieve smooth movement of a swivel caster equipped with a synthetic resin fork while reducing noise and vibration without increasing manufacturing costs. [Explanation of Symbols]

[0027] 1A Swivel caster, 2A, 2B Fork, 3 Wheel, 4 Mounting plate, 5 Mounting shaft, 6 Axle, 7, 8 Ball retaining plate, 20, 26 Cylindrical section, 21, 22 Arm, 23, 24, 27, 28 Peripheral wall, 25, 29 Mounting hole, 40 Mounting hole, 41 Screw hole, 70, 80 Ball, 230, 240 Recess, 270, 280 Retaining hole

Claims

1. A swivel caster comprising a synthetic resin fork having a pair of arms extending diagonally downward from the lower end of a cylindrical part through which a mounting hole passes vertically in the center line, a metal mounting plate having a mounting shaft extending downward from the center and attached to the bottom surface of a movable body, and a wheel supported on the tips of the left and right arms so as to be rotatable between the arms, wherein the fork is mounted below the mounting plate so as to be rotatable around the axis of the mounting shaft with the mounting shaft inserted into the mounting hole, wherein the arms are shaped such that the width in the front-rear direction at the position through which the center line of the axle passes is at least 3 / 5 of the vertical length from the lower end of the cylindrical part to the height of the center line.

2. The swivel caster according to claim 1, characterized in that a plurality of recesses for holding multiple balls are formed on the outer circumference of the openings on both the upper and lower surfaces of the cylindrical portion through which the mounting hole passes, so as to surround the opening, and a pair of upper and lower donut-shaped ball holding plates through which the mounting shaft is inserted hold the balls placed in the recesses from above and below, thereby forming a pair of upper and lower thrust ball bearings.

3. The swivel caster according to claim 2, characterized in that the upper ball retaining plate is fixed to the upper outer edge of the opening of the mounting hole that penetrates the central part of the mounting plate, with its outer circumference in close contact with the mounting plate.

4. The swivel caster according to claim 2 or 3, characterized in that the recesses for holding the ball on both the upper and lower surfaces of the cylindrical portion are a plurality of circular holes having a diameter and depth that allow a portion of the ball to be inserted and held, and are arranged in an annular shape at regular intervals so as to surround the opening of the mounting hole.

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