Dust cap for eye joint

Abstract

The purpose of the present invention is to suppress detachment from an eye joint metal fitting and to reduce costs.　The present invention is provided with uneven parts 18 (a cylindrical part-side uneven part 20 and a shaft part-side uneven part 22), which allow detachable engagement with an inner peripheral part of a cylindrical part 1204 and an outer peripheral part of a shaft part 1404, and hold a state where the shaft part 1404 is inserted into the cylindrical part 1204. The cylindrical part-side uneven part 20 is configured such that a plurality of inner peripheral part-side protruding parts 2002 protruding from the inner peripheral part and extending in the circumferential direction of the inner peripheral part are arranged in the axial direction of the cylindrical part 1204. The shaft part-side uneven part 22 is configured such that a plurality of outer peripheral part-side protruding parts 2202 protruding from the outer peripheral part, extending in the circumferential direction of the outer peripheral part, and detachably engaging with the inner peripheral part-side protruding parts 2002 are arranged in the axial direction of the shaft part 1404.

Description

Dust cap for eye joint

[0001] The present invention relates to a dust cap for an eye joint.

[0002] Eye joint fittings are used together with eye bolts (union bolts) to connect hoses and other equipment. Eye joint fittings often include a metal eye joint body with an eye bolt insertion hole formed therethrough, and a tube that protrudes from the eye joint body and is connected to the hose.

[0003] The eye bolt has a flow path extending inside its shaft, a first opening formed at the part of the shaft that is positioned inside the eye bolt insertion hole when the eye bolt is inserted into the eye bolt insertion hole and that communicates with the flow path, and a second opening formed at the tip surface of the shaft or on the outer surface of the shaft that protrudes from the eye bolt insertion hole and that communicates with the flow path.

[0004] The eyebolt insertion hole has an inner diameter at both ends to allow the shank of the eyebolt to pass through, and openings are provided on both end faces of the eye joint body. The middle portion of the eyebolt insertion hole has a large diameter portion with an inner diameter larger than the opening to facilitate communication with the first opening of the eyebolt.

[0005] The eye joint fitting is attached to the equipment side by placing one of the end faces on both sides of the eye joint body on the surface of the equipment side via an annular sealing member, and with an annular sealing member placed on the other end face, inserting the eye bolt into the eye bolt insertion hole of the eye joint body, the underside of the eye bolt head elastically contacting the other end face via the sealing member, and screwing the male thread of the eye bolt shaft into the female thread on the equipment side.

[0006] Therefore, the end faces on both sides of the eye joint body where the eyebolt insertion hole opening is provided serve as sealing surfaces, and scratches can cause fluid leakage during use. To prevent scratches on the sealing surfaces on both end faces of the eye joint body, eye joint dust caps are used. Conventional eye joint dust caps include a pair of lids covering both end faces of the eye joint body. One of the pair of lids has a cover plate covering the end face and a tubular portion protruding from the cover plate and having an inner periphery with an outer diameter smaller than the inner diameter of the opening. The other of the pair of lids has a cover plate covering the end face and a shaft portion protruding from the cover plate and having an outer periphery that is removably inserted into the inner periphery of the tubular portion. The pair of lids is maintained in contact with the end faces on both sides of the eye joint body by friction between the inner periphery of the tubular portion and the outer periphery of the shaft portion.

[0007] Japanese Patent Application Laid-Open No. 2020-133731

[0008] On the other hand, eye joint dust caps are molded using flexible resin or hard rubber. Generally, the coefficient of friction of resin varies greatly depending on the material used, and the coefficient of friction of rubber varies depending on the type of rubber used, and also varies greatly depending on the type and blending ratio of additives mixed in. Therefore, even if the inner surface of the cylindrical portion and the outer surface of the shaft portion are formed with a predetermined dimensional accuracy, the desired coefficient of friction may not be obtained depending on the material used for the eye joint dust cap, which has the disadvantage of limiting the materials that can be used for eye joint dust caps.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a dust cap for an eye joint that is advantageous in preventing the eye joint fitting from coming off during storage or transportation, regardless of the material used.

[0010] In order to achieve the above-mentioned object, one embodiment of the present invention is a dust cap for an eye joint, comprising a pair of lids covering both end surfaces of an eye joint body having an opening for an eyebolt insertion hole, one of the pair of lids having a cover plate portion covering the end surface and a tubular portion protruding from the cover plate and having an inner periphery and an outer surface with an outer diameter smaller than the inner diameter of the opening, the other of the pair of lids having a cover plate portion covering the end surface and a shank portion protruding from the cover plate and having an outer periphery that is releasably inserted into the inner periphery of the tubular portion, and characterized in that the inner periphery of the tubular portion and the outer periphery of the shank are provided with uneven portions that are releasably connected to keep the shank inserted into the tubular portion. In addition, one embodiment of the present invention is characterized in that the uneven portion provided on the inner peripheral portion of the cylindrical portion, that is, the cylindrical portion-side uneven portion, is configured by a plurality of inner peripheral portion-side convex portions extending circumferentially of the inner peripheral portion, lined up in the axial direction of the cylindrical portion, and the uneven portion provided on the outer peripheral portion of the shaft portion, is configured by a plurality of outer peripheral portion-side convex portions extending circumferentially of the outer peripheral portion, which can be engaged with and disengaged from the inner peripheral portion-side convex portions, lined up in the axial direction of the shaft portion. In one embodiment of the present invention, an inner peripheral portion of the cylindrical portion is provided with an inner peripheral side recess, where the inner peripheral side convex portion is removed in the circumferential and axial directions of the cylindrical portion, and the inner peripheral side convex portion is configured to be shorter in length than the entire circumference of the inner peripheral portion of the cylindrical portion; an outer peripheral portion of the shaft portion is provided with an outer peripheral side recess, where the outer peripheral side convex portion is removed in the circumferential direction of the outer peripheral portion of the shaft portion and in the axial direction of the shaft portion, and the outer peripheral side convex portion is configured to be shorter in length than the entire circumference of the outer peripheral portion of the shaft portion; the inner peripheral side recess and the outer peripheral side convex portion face each other in the radial direction of the cylindrical portion, and when the outer peripheral side recess and the inner peripheral side convex portion are in a position where they face each other, the shaft portion is movable in the axial direction of the cylindrical portion. Furthermore, one embodiment of the present invention is characterized in that the shaft portion and the tubular portion have a base portion located on the cover plate portion side and a tip portion away from the cover plate portion, and the uneven portion is provided only on the inner periphery of the tubular portion near the tip portion and at least on the outer periphery of the shaft portion near the base portion.In one embodiment of the present invention, the shaft portion and the tubular portion have a base portion located toward the cover plate portion and a tip portion distant from the cover plate portion, and the uneven portion is provided only on an outer periphery of the shaft portion near the tip portion and at least on an inner periphery of the tubular portion near the base portion. In another embodiment of the present invention, the shaft portion is formed in a cylindrical shape and is provided with a shaft portion-side slit extending in the protruding direction of the shaft portion and opening at the tip in the protruding direction to allow radial inward deformation of the shaft portion, or a tube portion-side slit extending in the protruding direction of the tubular portion and opening at the tip in the protruding direction to allow radial outward deformation of the tubular portion. In another embodiment of the present invention, the shaft portion further includes a tube portion-side gripping portion provided on the surface of the cover plate opposite the surface from which the tubular portion protrudes and for operating one of the cover portions, and a shaft portion-side gripping portion provided on the surface of the cover plate opposite the surface from which the shaft portion protrudes and for operating the other cover portion. In one embodiment of the present invention, the cover plate is formed in a circular shape, and the barrel-side gripping portion and the shaft-side gripping portion are provided to extend along the diameter of the cover plate. In another embodiment of the present invention, the cover plate of the pair of cover parts is provided with an operating piece that is used to pull out the shaft part from a state in which the shaft part is inserted into the barrel. In another embodiment of the present invention, the outer periphery of the cover plate of the pair of cover parts is formed in an uneven shape.

[0011] According to one embodiment of the present invention, an eye-joint dust cap is provided that is advantageous in preventing detachment from the eye-joint fitting during storage or transportation, since the inner periphery of the cylindrical portion and the outer periphery of the shank are provided with concave and convex portions that can be engaged and disengaged with each other, and the concave and convex portions maintain the inserted state of the shank in the cylindrical portion while the concave and convex portions are engaged with each other, without any limitation on the material used. Furthermore, if the cylindrical portion-side concave and convex portions have a plurality of inner periphery-side convex portions that protrude from the inner periphery and extend circumferentially of the inner periphery, arranged in the axial direction of the cylindrical portion, and the shank-side concave and convex portions have a plurality of outer periphery-side convex portions that protrude from the outer periphery, extend circumferentially of the outer periphery, and are engaged and disengaged with the inner periphery-side convex portions, this is advantageous in preventing detachment from the eye-joint fitting. Furthermore, if an inner peripheral portion of the cylindrical portion is provided with an inner peripheral recessed portion formed by removing the inner peripheral convex portion in the circumferential and axial directions of the cylindrical portion, and an outer peripheral portion of the shank is provided with an outer peripheral recessed portion formed by removing the outer peripheral convex portion in the circumferential direction of the outer peripheral portion of the shank and along the axial direction of the shank, so that the inner peripheral recessed portion and the outer peripheral convex portion face each other in the radial direction of the cylindrical portion and the shank can move in the axial direction of the cylindrical portion when the outer peripheral recessed portion and the inner peripheral convex portion are in the opposing position, this is advantageous in making it easier to pull out the shank from the cylindrical portion. Furthermore, if the uneven portion is provided only in a portion of the inner peripheral portion of the cylindrical portion near the tip and in at least a portion of the outer peripheral portion of the shank near the base, the cylindrical portion has a simple configuration and is advantageous in terms of easy manufacturing. Furthermore, if the uneven portion is provided only on the outer periphery of the shank near the tip and at least on the inner periphery of the cylindrical portion near the base, the shank will have a simple configuration, which is advantageous for easy manufacturing. Furthermore, if the shank is formed into a cylindrical shape and is provided with a shank-side slit that extends in the protruding direction of the shank and is open at the tip in the protruding direction, allowing the shank to deform radially inward, or if the shank-side slit is provided in the protruding direction of the cylindrical portion and is open at the tip in the protruding direction, allowing the shank to deform radially outward, this will facilitate coupling and release of the uneven portion of the cylindrical portion and the uneven portion of the shank, which will be advantageous for facilitating insertion and removal of the shank from the cylindrical portion.Furthermore, if a cylindrical portion-side gripping portion is provided on the surface of the cover plate opposite the surface from which the cylindrical portion protrudes, and a shaft portion-side gripping portion is provided on the surface of the cover plate opposite the surface from which the shaft portion protrudes, the pair of covers can be easily operated, which is advantageous for facilitating the removal of the shaft portion from the cylindrical portion. Furthermore, if the cover plate is formed in a circular shape and the cylindrical portion-side gripping portion and the shaft portion-side gripping portion are provided extending along the diameter of the cover plate, the pair of covers can be easily rotated, which is advantageous for facilitating the removal of the shaft portion from the cylindrical portion. Furthermore, if the cover plates of the pair of covers are provided with operating pieces used to remove the shaft portion from a state in which the shaft portion is inserted into the cylindrical portion, the pair of covers can be easily operated, which is advantageous for facilitating the removal of the shaft portion from the cylindrical portion. Furthermore, if the outer peripheries of the cover plates of the pair of covers are formed in an uneven shape, the pair of covers can be easily gripped, which is advantageous for facilitating the removal of the shaft portion from the cylindrical portion.

[0012] 1 is a perspective view of a dust cap for an eye joint according to a first embodiment; FIG. 2 is a plan view of a dust cap for an eye joint according to a first embodiment; FIG. 3 is a sectional front view of a dust cap for an eye joint according to a first embodiment; FIG. 4 is a sectional view showing the state in which the shaft portion has begun to be inserted into the cylindrical portion, and FIG. 5 is a sectional view showing the state in which the shaft portion has been inserted into the cylindrical portion and the cover plate portion is abutting the end surface portion; FIG. 5 is a perspective view of a dust cap for an eye joint in which a cylindrical portion-side grip portion and a shaft portion-side grip portion are provided on the cover plate; FIG. 6 is a perspective view of a dust cap for an eye joint in which an operating piece is provided on the cover plate; FIG. 7 is a perspective view of a dust cap for an eye joint in which the outer periphery of the cover plate portion is formed in an uneven shape; FIG. 8 is a perspective view of a dust cap for an eye joint according to a second embodiment; FIG. 9 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 10 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 11 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 12 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 13 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 14 is a plan view of a dust cap for an eye joint according to a second embodiment; FIG. 15 is a plan view of a shaft portion, and FIG. 16 is a plan view of a cylindrical portion. FIG. 17 is a sectional front view of a dust cap for an eye joint according to a second embodiment; FIG. 10 is a perspective view of a dust cap for an eye joint in which a cylindrical portion-side gripping portion and a shaft portion-side gripping portion are provided on the cover plate portion. FIG. 11 is a perspective view of a dust cap for an eye joint in which an operating piece is provided on the cover plate portion. FIG. 12 is a perspective view of a dust cap for an eye joint of a third embodiment. FIG. 13 is a plan view of a dust cap for an eye joint of the third embodiment. FIG. 14 is a perspective view of a dust cap for an eye joint of a fourth embodiment. FIG. 15 is a perspective view of a part of the inner peripheral portion of the cylindrical portion. FIG. 16 is a perspective view of a dust cap for an eye joint of a fifth embodiment. FIG. 17 is a part of the outer peripheral portion of the shaft portion. FIG. 18 is a perspective view of a dust cap for an eye joint of a sixth embodiment.

[0013] (First Embodiment) An embodiment of the present invention will now be described with reference to the drawings. An eye-joint dust cap 10A according to this embodiment, as shown in Figures 1 to 3, is attached to an eye-joint fitting. First, the eye-joint fitting will be described with reference to Figure 4(A). The eye-joint fitting 50 includes a metal eye-joint body 52 and a tube 54 protruding from the eye-joint body 52.

[0014] The eye joint main body 52 is connected to, for example, a device, and the tube 54 is connected to a hose. An eyebolt insertion hole 56 is formed through the eye joint main body 52, and openings 5602 of the eyebolt insertion hole 56 are located on end surfaces 5202 on both sides of the eye joint main body 52. ​​Between the openings 5602 on both ends of the eyebolt insertion hole 56, i.e., the intermediate portion in the extending direction of the eyebolt insertion hole 56, is formed as a large-diameter portion 5604 whose inner diameter is larger than that of the openings 5602, and the large-diameter portion 5604 is in communication with a flow path 5402 of the tube 54.

[0015] The eye joint fitting 50 is arranged by connecting a hose to the tube 54, inserting an eyebolt through the eyebolt insertion hole 56, and attaching the eye joint body 52 to the mounting surface of the equipment. In this case, an annular seal member (not shown) is interposed around the shank of the eyebolt between one of the end faces 5202 on both sides and the mounting surface of the equipment, and another annular seal member (not shown) is interposed around the shank of the eyebolt between the other end face 5202 and the underside of the eyebolt head, so that the eye joint body 52 of the eye joint fitting 50 is liquid-tightly or airtightly joined to the mounting surface of the equipment. Because the end faces 5202 on both sides of the eye joint body 52 function as sealing surfaces, the end faces 5202 are protected from damage by the eye joint dust cap.

[0016] 1, eye joint dust cap 10A of this embodiment is configured to include a pair of lids 12, 14 that cover end surface 5202 on both sides of eye joint main body 52, and connecting piece 16. Eye joint dust cap 10A is made of flexible resin or hard rubber, and pair of lids 12, 14 and connecting piece 16 are molded integrally.

[0017] 1 to 3, one of the pair of lids 12, 14, 12, has a lid plate 1202 and a tubular portion 1204. The lid plate 1202 is formed in a circular shape with a uniform thickness and a size that covers one of the end faces 5202 on both sides of the eye joint body 52.

[0018] The tubular portion 1204 protrudes from the center of the cover plate portion 1202 and is cylindrically shaped with an outer circumferential surface and an inner periphery having a uniform outer diameter that is smaller than the inner diameter of the opening 5602 of the end face portion 5202 of the eye joint main body 52. ​​As shown in FIGS. 4(B) and (C), the height of the tubular portion 1204 from the cover plate portion 1202 is slightly smaller than the distance between the end faces 5202 on both sides of the eye joint main body 52. ​​The inner periphery of the tubular portion 1204 is provided with an uneven portion 18. The uneven portion 18 will be described later. The inner periphery of the tubular portion 1204 is formed with an uneven portion 18 consisting of a plurality of recesses recessed radially inward of the tubular portion 1204 and a plurality of protrusions protruding radially outward of the tubular portion 1204. The uneven portion 18 will be described later.

[0019] The other cover 14 of the pair of covers 12, 14 has a cover plate 1402 and a shaft 1404. The cover plate 1402 is formed in a circular shape with a uniform thickness and a size that covers the other of the end face 5202 on both sides of the eye joint main body 52, and is formed with the same thickness and outer diameter as the cover plate 1202 from which the cylindrical portion 1204 protrudes.

[0020] In this embodiment, the shaft portion 1404 is cylindrical and formed into a cylindrical shape with a uniform inner diameter. The cylindrical shaft portion 1404 protrudes from the center of the cover plate portion 1402 and has an outer periphery that is removably inserted into the inner periphery of the cylindrical portion 1204. As shown in FIGS. 4B and 4C , the height of the cylindrical shaft portion 1404 from the cover plate portion 1402 is formed to be slightly smaller than the dimension between the end surfaces 5202 on both sides of the eye joint main body 52. ​​In this embodiment, the height of the shaft portion 1404 is formed to be the same as the height of the cylindrical portion 1204 from the cover plate portion 1202, ensuring a large contact area between the inner periphery of the cylindrical portion 1204 and the outer periphery of the shaft portion 1404, which is advantageous in maintaining stable protection of the end surfaces 5202 on both sides by the cover plates 1202, 1402, as described below. The outer periphery of the shaft portion 1404 is formed with an uneven portion 18 consisting of a plurality of recesses recessed radially inward of the shaft portion 1404 and protrusions protruding radially outward of the shaft portion 1404. Although the shaft portion 1404 may be formed in a solid shape, forming it in a cylindrical shape as in this embodiment is advantageous in terms of reducing weight.

[0021] Here, the uneven portion 18 of this embodiment will be described. The cylindrical portion-side uneven portion 20, which is the uneven portion 18 that constitutes the inner peripheral portion of the cylindrical portion 1204, is configured by arranging a plurality of inner peripheral portion-side convex portions 2002, which protrude radially inward of the cylindrical portion 1204 and extend circumferentially of the inner peripheral portion, at equal intervals in the axial direction of the cylindrical portion 1204. In this embodiment, as shown in Fig. 3, the inner peripheral portion-side convex portions 2002, each having a sawtooth cross section, extend all around the inner peripheral portion of the cylindrical portion 1204 in the circumferential direction, and are arranged at equal intervals from a base portion 1204A located on the cover plate portion 1202 side to a tip portion 1204B remote from the cover plate portion 1202.

[0022] Furthermore, the shaft portion-side uneven portion 22, which is the uneven portion 18 that constitutes the outer periphery of the shaft portion 1404, is configured by arranging a plurality of outer periphery-side convex portions 2202 at equal intervals in the axial direction of the shaft portion 1404. The outer periphery-side convex portions 2202 protrude radially outward from the shaft portion 1404, extend circumferentially around the outer periphery, and are engageable with and disengageable from the inner periphery-side convex portions 2002. In this embodiment, as shown in Fig. 3, the outer periphery-side convex portions 2202, each having a sawtooth cross section, extend all around the periphery of the shaft portion 1404 in the circumferential direction, and are arranged at equal intervals from a base portion 1404A located on the cover plate portion 1402 side to a tip portion 1404B remote from the cover plate portion 1402.

[0023] The inner diameter of the valley of the inner circumferential side convex portion 2002 of the cylindrical portion 1204 and the outer diameter of the tip of the outer circumferential side convex portion 2202 of the shaft portion 1404 are formed to be equal in size, or alternatively, the outer diameter of the tip of the outer circumferential side convex portion 2202 is formed slightly larger than the inner diameter of the valley of the inner circumferential side convex portion 2002. The outer diameter of the tip of the outer circumferential side convex portion 2202 protruding from the outer circumferential portion of the shaft portion 1404 is formed slightly larger than the inner diameter of the tip of the inner circumferential side convex portion 2002 protruding from the inner circumferential portion of the cylindrical portion 1204. Therefore, as shown in Figures 4(B) and (C), when the shaft portion 1404 is inserted into the tubular portion 1204, the uneven portion 18 that constitutes the inner circumference of the tubular portion 1204 and the outer circumference of the shaft portion 1404 are detachably coupled, that is, the inner circumference side convex portion 2002 and the outer circumference side convex portion 2202 are fitted together and coupled, thereby maintaining the state in which the shaft portion 1404 is inserted into the tubular portion 1204.

[0024] The inner circumference side convex portion 2002 and the outer circumference side convex portion 2202 are not limited to having a sawtooth cross section as in this embodiment, and may, for example, have a V-shaped or hemispherical cross section extending around the entire circumference. However, if they are formed into a sawtooth shape that is inclined toward the cover plate portions 1202 and 1402 as in this embodiment, this is advantageous in that it makes it easier to insert the shaft portion 1404 into the tube portion 1204 and makes it less likely to come out.

[0025] Furthermore, the uneven portion 18 (the cylindrical portion side uneven portion 20 and the shaft portion side uneven portion 22) is not limited to extending circumferentially as in this embodiment, and various conventionally known engagement and disengagement structures can be adopted, such as a structure in which hemispherically protruding convex portions and hemispherically recessed concave portions are scattered.

[0026] The connecting piece 16 extends between the pair of lid portions 12, 14 and connects the pair of lid plate portions 1202, 1402. It has a slender, flexible shape. While the connecting piece 16 may be omitted, providing the connecting piece 16 prevents the loss of the lid portions 12, 14, which would otherwise be separated from each other, i.e., the loss of the eye-joint dust cap 10A, and is advantageous in improving handleability. The shape of the connecting piece 16 may be rod-like or the like, and is not limited to a thin plate shape as in the embodiment. In short, it need only be flexible, and the cross-sectional shape may be any shape.

[0027] Next, a method of using eye joint dust cap 10A of this embodiment will be described. When using eye joint dust cap 10A, as shown in Figures 4(A) and (B), connecting piece 16 is bent to align paired lids 12, 14 with each other over eyebolt insertion hole 56, and cylindrical shaft 1404 is inserted into tubular portion 1204, causing cover plates 1202, 1402 of paired lids 12, 14 to abut against end surfaces 5202 on both sides of eye joint body 52. ​​This abutting state of cover plates 1202, 1402 of paired lids 12, 14 against end surfaces 5202 on both sides of eye joint body 52 is maintained by the engagement of inner circumferential projection 2002 of tubular portion 1204 and outer circumferential projection 2202 of shaft 1404.

[0028] Furthermore, when removing the pair of cover portions 12, 14 from the eye joint body 52, the cover plate portion 1402 is grasped and the shaft portion 1404 is pulled out from the cylindrical portion 1204.

[0029] To facilitate the removal of the shaft portion 1404 from the tube portion 1204, as shown in FIG. 5 , a tube portion-side grip 24 may be provided on the surface of the cover plate 1202 opposite the surface from which the tube portion 1204 protrudes, and a shaft portion-side grip 26 may be provided on the surface of the cover plate 1402 opposite the surface from which the shaft portion 1404 protrudes. In this embodiment, the cover plates 1202, 1402 are formed in a circular shape as described above, and the tube portion-side grip 24 and the shaft portion-side grip 26 are provided extending along the diameter of the cover plates 1202, 1402, with concave side surfaces 2402, 2602 formed to allow the operator's fingers to hook thereon. Providing the tube portion-side grip 24 and the shaft portion-side grip 26 in this manner facilitates the operation of the pair of covers 12, 14, which is advantageous for facilitating the removal of the shaft portion 1404 from the tube portion 1204.

[0030] As shown in FIG. 6 , the cover plates 1202, 1402 of the pair of lids 12, 14 may be provided with an operating piece 28 used to remove the shaft portion 1404 from the tubular portion 1204 after it has been inserted therein. In this embodiment, the operating piece 28 extends linearly from the outer periphery of the cover plates 1202, 1402, with a gripping recess 2802 at its end for easy gripping. The operating piece 28 also extends in a direction parallel to the connecting piece 16, minimizing space required when the eye joint dust cap 10A is attached to the eye joint main body 52. ​​Providing the operating piece 28 in this manner facilitates operation of the pair of lids 12, 14, which is advantageous for easily removing the shaft portion 1404 from the tubular portion 1204. 6, the operation piece 28 is provided on both the cover plate portions 1202 and 1402, but it may be provided on either one of them. However, providing it on both is advantageous in terms of improving operability.

[0031] 7, the outer peripheries of the cover plate portions 1202, 1402 of the pair of cover portions 12, 14 may be configured to be formed in an uneven shape 30. By forming the outer peripheries of the cover plate portions 1202, 1402 in this manner in an uneven shape 30, the pair of cover portions 12, 14 can be easily grasped, which is advantageous in facilitating the removal of the shaft portion 1404 from the cylindrical portion 1204.

[0032] According to the eye joint dust cap 10A of this embodiment, the inner periphery of the tubular portion 1204 and the outer periphery of the shaft portion 1404 are provided with uneven portions 18 (tubular portion-side uneven portions 20 and shaft portion-side uneven portions 22) that are detachably coupled to keep the shaft portion 1404 inserted into the tubular portion 1204. This prevents the eye joint fitting 50 from coming off due to vibrations or loads being applied in the axial direction of the eye joint main body 52 when the eye joint fitting 50 is stored or transported, and it can be used with eye joint fittings 50 that have different thicknesses in the axial direction of the eye joint main body 52, which is advantageous for reducing costs. Furthermore, the uneven portions 18 (tube-side uneven portions 20 and shaft-side uneven portions 22) provided on the inner periphery of the cylindrical portion 1204 and the outer periphery of the shaft portion 1404 are configured to be detachably connected; in other words, the uneven portions 18 (tube-side uneven portions 20 and shaft-side uneven portions 22) are configured to be mechanically connected, so even if the coefficient of friction varies depending on the material used, as in the prior art documents, the effect is small. Therefore, the problem of limiting the materials that can be used for the eye joint dust cap, as in the prior art documents, is eliminated, and the eye joint dust cap can be manufactured using inexpensive materials, which is advantageous for reducing the cost of the eye joint dust cap. Furthermore, the cylinder-side uneven portion 20 is configured with a plurality of inner-periphery-side convex portions 2002 that protrude from the inner periphery and extend circumferentially of the inner periphery, lined up in the axial direction of the cylinder portion 1204, and the shaft-side uneven portion 22 is configured with a plurality of outer-periphery-side convex portions 2202 that protrude from the outer periphery, extend circumferentially of the outer periphery, and are engageable with and disengageable from the inner-periphery-side convex portions 2002, lined up in the axial direction of the shaft portion 1404, which is advantageous in preventing detachment from the eye-joint fitting 50. Furthermore, by providing the cylinder-side gripping portion 24 on the cover plate portion 1202 and the shaft-side gripping portion 26 on the cover plate portion 1402, the pair of covers 12, 14 can be easily operated, which is advantageous in facilitating the removal of the shaft portion 1404 from the cylinder portion 1204. Furthermore, by providing the operating pieces 28 on the cover plate portions 1202 and 1402, the pair of cover portions 12 and 14 can be easily operated, which is advantageous in that the shaft portion 1404 can be easily pulled out from the tube portion 1204.Furthermore, by forming the outer periphery of the cover plate portions 1202 and 1402 into the uneven shape 30, the pair of cover portions 12 and 14 can be easily grasped, which is advantageous in facilitating the removal of the shaft portion 1404 from the tube portion 1204.

[0033] Second Embodiment In the first embodiment, the inner circumferential side convex portion 2002 and the outer circumferential side convex portion 2202 extend around the entire circumferential direction, whereas in the second embodiment, the inner circumferential side convex portion and the outer circumferential side convex portion are shorter than the entire circumferential direction. An eye-joint dust cap 10B according to the second embodiment will be described with reference to Figures 8 to 13. In the following description of the embodiment, the same parts and members as those in the first embodiment will be denoted by the same reference numerals and their description will be omitted, and the following description will focus on the differences from the first embodiment.

[0034] The uneven portion 18 of this embodiment will be described. The uneven portion 18, which is the cylindrical portion-side uneven portion 32 provided on the inner periphery of the cylindrical portion 1204, is configured by arranging a plurality of inner periphery-side protrusions 3202, which protrude radially inward of the cylindrical portion 1204 and extend circumferentially around the inner periphery, in the axial direction of the cylindrical portion 1204. In this embodiment, as shown in FIGS. 8 to 11 , the inner periphery-side protrusions 3202, each having a sawtooth cross section, are configured to be shorter than the entire circumferential circumference of the inner periphery of the cylindrical portion 1204, and are arranged in plurality from the base 1204A to the tip 1204B. The inner periphery of the cylindrical portion 1204 is provided with an inner periphery-side retracted portion 3204, which is made up of the inner periphery of the cylindrical portion 1204 from which the inner periphery-side protrusions 3202 have been removed along the circumferential and axial directions of the inner periphery of the cylindrical portion 1204.

[0035] In this embodiment, the inner circumferential side convex portions 3202 and the inner circumferential side retracted portions 3204 are provided in two locations and each extend a length that is ¼ of the entire circumference of the inner circumferential portion of the cylindrical portion 1204. In other words, the inner circumferential portion of the cylindrical portion 1204 is configured such that two inner circumferential side convex portions 3202 and two inner circumferential side retracted portions 3204, each having a central angle of 90°, are alternately arranged.

[0036] The shank-side uneven portion 34, which is the uneven portion 18 provided on the outer periphery of the shank 1404, is configured by arranging a plurality of outer periphery-side convex portions 3402 in the axial direction of the shank 1404. The outer periphery-side convex portions 3402 protrude radially outward from the shank 1404, extend circumferentially around the outer periphery, and are engageable with and disengageable from the inner periphery-side convex portions 3202. In this embodiment, as shown in FIGS. 8 to 11 , the outer periphery-side convex portions 3402, each having a sawtooth cross section, are configured to be shorter than the entire circumferential circumference of the outer periphery of the shank 1404, and are arranged in plurality from the base 1404A to the tip 1404B. The outer periphery of the shank 1404 is provided with an outer periphery-side retracted portion 3404, which is made up of the outer periphery of the shank 1404 from which the outer periphery-side convex portions 3402 have been removed in the circumferential direction of the outer periphery of the shank 1404 and in the axial direction of the shank 1404.

[0037] In this embodiment, outer peripheral convex portions 3402 and outer peripheral side retracted portions 3404 are provided in two locations and each extend a length that is one-fourth of the entire circumference of the outer peripheral surface of shaft portion 1404. In other words, outer peripheral surface of shaft portion 1404 is configured with outer peripheral convex portions 3402 and outer peripheral side retracted portions 3404, each with a central angle of 90°, arranged alternately in pairs.

[0038] As in the first embodiment, the outer diameter of the tip of the outer circumferential convex portion 3402 protruding from the outer circumferential portion of the shaft portion 1404 is slightly larger than the inner diameter of the tip of the inner circumferential convex portion 3202 protruding from the inner circumferential portion of the cylindrical portion 1204. Therefore, when the shaft portion 1404 is inserted into the cylindrical portion 1204, as in the first embodiment, the uneven portions 18 provided on the inner circumferential portion of the cylindrical portion 1204 and the outer circumferential portion of the shaft portion 1404 are detachably coupled, i.e., the inner circumferential convex portion 3202 and the outer circumferential convex portion 3402 are fitted together and coupled, thereby maintaining the state in which the shaft portion 1404 is inserted into the cylindrical portion 1204.

[0039] Furthermore, in this embodiment, when the shaft portion 1404 is inserted into the tubular portion 1204, the inner circumferential side convex portion 3202 and the outer circumferential side convex portion 3402 face each other in the radial direction of the tubular portion 1204, and when the inner circumferential side retraction portion 3204 and the outer circumferential side retraction portion 3404 are in opposing positions, the inner circumferential side convex portion 3202 and the outer circumferential side convex portion 3402 are coupled together, thereby maintaining the state in which the shaft portion 1404 is inserted into the tubular portion 1204.

[0040] Furthermore, in this embodiment, unlike the first embodiment, when the shaft portion 1404 is inserted into the cylindrical portion 1204, the inner peripheral side retracted portion 3204 and the outer peripheral side convex portion 3402 face each other in the radial direction of the cylindrical portion 1204, and when the outer peripheral side retracted portion 3404 and the inner peripheral side convex portion 3202 are in a position where they face each other, the shaft portion 1404 is movable in the axial direction of the cylindrical portion 1204. In other words, the shaft portion 1404 can be easily inserted into the cylindrical portion 1204 and the cylindrical portion 1204 can be easily removed from the cylindrical portion 1204.

[0041] 4A and 4B, when using eye joint dust cap 10A, connecting piece 16 is bent to position paired lids 12, 14 opposite eyebolt insertion hole 56, and one or both of paired lids 12, 14 are then rotated so that inner periphery-side recess 3204 and outer periphery-side protrusion 3402 face each other and outer periphery-side recess 3404 and inner periphery-side protrusion 3202 face each other. Then, cylindrical shaft 1404 is inserted into cylindrical portion 1204, and cover plates 1202, 1402 of paired lids 12, 14 abut against end faces 5202 on both sides of eye joint body 52.

[0042] Next, when one of the pair of lids 12, 14 is rotated while the cover plates 1202, 14 of the pair of lids 12, 14 are in contact with the end surfaces 5202 on both sides of the eye joint body 52, the inner peripheral convex portion 3202 and the outer peripheral convex portion 3402 gradually join together. After being rotated 90 degrees, the entire inner peripheral convex portion 3202 and the entire outer peripheral convex portion 3402 join together, and the inner peripheral retracted portion 3204 and the outer peripheral retracted portion 3404 face each other. As the entire inner peripheral convex portion 3202 and the entire outer peripheral convex portion 3402 join together, the cover plates 1202, 1402 of the pair of lids 12, 14 are maintained in contact with the end surfaces 5202 on both sides of the eye joint body 52.

[0043] Furthermore, when removing the pair of cover portions 12, 14 from the eye joint main body 52, one of the pair of cover portions 12, 14 is rotated 90° so that the inner circumference side retraction portion 3204 and the outer circumference side convex portion 3402 face each other and the outer circumference side retraction portion 3404 and the inner circumference side convex portion 3202 face each other, and then the cover plate portion 1402 is grasped and the shaft portion 1404 is pulled out from the tube portion 1204.

[0044] 12 , in order to facilitate the removal of the shaft portion 1404 from the tube portion 1204, a tube portion-side grip 36 may be provided on the surface of the cover plate 1202 opposite the surface from which the tube portion 1204 protrudes, and a shaft portion-side grip 38 may be provided on the surface of the cover plate 1402 opposite the surface from which the shaft portion 1404 protrudes. In this embodiment, the cover plates 1204, 1204 are formed in a circular shape as described above, and the tube portion-side grip 36 and the shaft portion-side grip 38 are provided extending along the diameter of the cover plates 1202, 1402, and the side surfaces 3602, 3802 are formed in a concave shape so that the operator's fingers can hook thereon.

[0045] Furthermore, one of the barrel-side gripping portion 36 and the shank-side gripping portion 38 is provided to extend in the same direction as the connecting piece 16, and the other gripping portion is provided to be perpendicular to the connecting piece 16. In this embodiment, one gripping portion is the shank-side gripping portion 38, and the other gripping portion is the barrel-side gripping portion 36. Providing the barrel-side gripping portion 36 and the shank-side gripping portion 38 in this manner facilitates the rotational operation of the pair of lid portions 12, 14, which is advantageous for facilitating the removal of the shank 1404 from the barrel portion 1204. Furthermore, in this embodiment, because the barrel-side gripping portion 36 is provided perpendicular to the shank-side gripping portion 38 and the connecting piece 16, rotating the barrel-side gripping portion 36 until it is in the same direction as the extending direction of the shank-side gripping portion 38 corresponds to a 90° rotation, which is advantageous for grasping the rotation angle of the barrel-side gripping portion 36.

[0046] 13 , the cover plates 1202, 1402 of the pair of lids 12, 14 may be provided with operation pieces 40, 42 that are used to remove the shaft portion 1404 from a state in which the shaft portion 1404 is inserted into the cylindrical portion 1204. In this embodiment, the operation pieces 40, 42 extend linearly from the outer peripheries of the cover plates 1202, 1402, and have gripping projections 4002, 4202 at their ends for easy gripping. One of the operation pieces is provided to extend in line with the connecting piece 16, and the other operation piece is provided perpendicular to the connecting piece 16. In this embodiment, one operation piece is the operation piece 42 on the shaft portion 1404 side, and the other operation piece is the operation piece 40 on the cylindrical portion 1204 side.

[0047] Providing the operation pieces 40, 42 in this manner makes it easier to operate the pair of cover portions 12, 14, which is advantageous in facilitating the removal of the shaft portion 1404 from the tube portion 1204. Furthermore, in this embodiment, by providing the operation piece 40 perpendicular to the extending direction of the operation piece 42 and the connecting piece 16, rotating the operation piece 40 until it is in the same direction as the extending direction of the operation piece 42 will result in a 90° rotation, which is advantageous in understanding the rotation angle of the operation piece 40.

[0048] The eye joint dust cap 10B of this embodiment achieves the same effects as the first embodiment. Furthermore, the cylindrical portion-side concave-convex portion 32 is provided with an inner-periphery-side retracted portion 3204 formed by removing the inner-periphery-side convex portion 3202 along the circumferential direction of the inner periphery of the cylindrical portion 1204, and the shank-side concave-convex portion 34 is provided with an outer-periphery-side retracted portion 3404 formed by removing the outer-periphery-side convex portion 3402 along the circumferential direction of the outer surface of the shank 1404. The inner-periphery-side retracted portion 3204 and the outer-periphery-side convex portion 3402 face each other in the radial direction of the cylindrical portion 1204, and when the outer-periphery-side retracted portion 3404 and the inner-periphery-side convex portion 3202 are positioned opposite each other, the shank 1404 can move in the axial direction of the cylindrical portion 1204. This configuration is advantageous in that it makes it easier to pull out the shank 1404 from the cylindrical portion 1204. Furthermore, providing the cover plate 1202 with the barrel-side gripping portion 36 and the shank-side gripping portion 38 facilitates operation of the pair of covers 12, 14, which is advantageous for easily pulling out the shank 1404 from the barrel 1204. Furthermore, providing the barrel-side gripping portion 36 perpendicular to the shank-side gripping portion 38 and the connecting piece 16 means that rotating the barrel-side gripping portion 36 until it is in the same direction as the extending direction of the shank-side gripping portion 38 will result in a 90° rotation, which is advantageous for understanding the rotation angle of the barrel-side gripping portion 36. Furthermore, providing the cover plate 1202 with the operating pieces 40, 42 facilitates operation of the pair of covers 12, 14, which is advantageous for easily pulling out the shank 1404 from the barrel 1204. Furthermore, by arranging the operating piece 40 perpendicular to the operating piece 42 and the connecting piece 16, rotating the operating piece 40 until it is in the same direction as the extension direction of the operating piece 42 will result in a 90° rotation, which is advantageous in understanding the rotation angle of the operating piece 40.

[0049] In the second embodiment, the inner circumference of the cylindrical portion 1204 is divided into four, with the inner circumference convex portions 3202 and the inner circumference retracted portions 3204 arranged alternately, and the outer circumference of the shaft portion 1404 is similarly divided into four, with the outer circumference convex portions 3402 and the outer circumference retracted portions 3404 arranged alternately. However, in the present embodiment, the division ratio is different. An eye-joint dust cap 10C according to the third embodiment will be described with reference to FIGS. 14 and 15.

[0050] In this embodiment, the inner periphery-side convex portions 3206 and the inner periphery-side retracted portions 3208 are each provided at three locations, extending a length that is 1 / 6 of the entire circumference of the inner periphery of the cylindrical portion 1204. That is, the inner periphery of the cylindrical portion 1204 is configured with three inner periphery-side convex portions 3206 and three inner periphery-side retracted portions 3208, each with a central angle of 60°, arranged alternately. Furthermore, the outer periphery-side convex portions 3406 and three outer periphery-side retracted portions 3408 are each provided at three locations, extending a length that is 1 / 6 of the entire circumference of the outer periphery of the shaft portion 1404. That is, the outer periphery of the shaft portion 1404 is configured with three outer periphery-side convex portions 3406 and three outer periphery-side retracted portions 3408, each with a central angle of 60°, arranged alternately.

[0051] The method of using the eye joint dust cap 10C is the same as that of the second embodiment, but after inserting the shaft portion 1404 into the cylindrical portion 1204 and before removing the shaft portion 1404 from the cylindrical portion 1204, one of the pair of lid portions 12, 14 is rotated 60° about the axis of the cylindrical portion 1204. Also, the cover plate portion 1202 may be configured to have a cylindrical portion-side grip portion 36, a shaft portion-side grip portion 38, and operation pieces 40, 42. The eye joint dust cap 10C of this embodiment provides the same effects as the second embodiment.

[0052] In the first to third embodiments described above, the inner circumferential side protrusions 2002, 3202, 3206 are arranged continuously from the base 1204A to the tip 1204B, and the outer circumferential side protrusions 2202, 3402, 3406 are arranged continuously from the base 1404A to the tip 1404B, but they may be arranged discontinuously as long as the inner circumferential side protrusions and the outer circumferential side protrusions fit together. However, if they are arranged continuously, the insertion of the shaft 1404 into the tube 1204 can be adjusted to match the thickness of the eye joint main body 56.

[0053] In the second embodiment, the cylindrical portion 1204 and the shaft portion 1404 are divided into four sections, and in the third embodiment, the cylindrical portion 1204 and the shaft portion 1404 are divided into six sections, with convex portions (inner peripheral convex portions, outer peripheral convex portions) and retracted portions (inner peripheral retracted portions, outer peripheral retracted portions) arranged alternately. However, the number of divisions is arbitrary. Therefore, for example, the cylindrical portion 1204 and the shaft portion 1404 can be divided into two sections (180°), eight sections (45°), ten sections (36°), twelve sections (30°), or any other desired ratio, with convex portions and retracted portions arranged alternately. Note that the greater the number of divisions, the easier it is to insert the shaft portion 1404 into the cylindrical portion 1204 but the easier it is to remove it. Conversely, the fewer the number of divisions, the harder it is to insert the shaft portion 1404 into the cylindrical portion 1204 but the harder it is to remove it.

[0054] (Fourth embodiment) In the second embodiment, a plurality of inner circumferential projections 3202 are provided on the cylindrical portion 1204 from the base portion 1204A to the tip portion 1204B, but as shown in Figures 16 and 17, an inner circumferential projection 3210 may be provided only on the inner circumferential portion of the cylindrical portion 1204 near the tip portion 1204B. In this embodiment, as shown in Figure 17, one inner circumferential projection 3210 is provided on the inner circumferential portion of the cylindrical portion 1204 at the tip portion 1204B.

[0055] 16, in this embodiment, outer peripheral convex portions 3402 of shaft portion 1404 are provided in multiple positions from base 1404A to tip 1404B, but it is sufficient that they are provided at least in a portion of the outer peripheral portion of shaft portion 1404 closer to base 1404A. Therefore, for example, outer peripheral convex portions 3402 may be provided only in a portion of the outer peripheral portion of shaft portion 1404 closer to base 1404A, or from base 1404A to approximately the middle between base 1404A and tip 1404B. However, if outer peripheral convex portions 3402 are provided from base 1404A to tip 1404B, they can be applied to eye joint fittings 50 that have different thicknesses in the axial direction of eye joint main body 52, improving convenience.

[0056] According to the dust cap for eye joint 10D of this embodiment, the same effects as those of the second embodiment are achieved, and the cylindrical portion 1204 has a simple structure, which is advantageous in terms of easy manufacturing.

[0057] Fifth Embodiment In the second embodiment, a plurality of outer peripheral convex portions 3402 are provided on the shaft portion 1404 from the base portion 1404A to the tip portion 1404B, but as shown in Figures 18 and 19, an outer peripheral convex portion may be provided only on a portion of the outer periphery of the shaft portion 1404 near the tip portion 1404B. In this embodiment, as shown in Figure 19, one outer peripheral convex portion 3410 is provided on the tip portion 1404B of the outer periphery of the shaft portion 1404.

[0058] 18 , in this embodiment, multiple inner circumferential projections 3202 are provided on tubular portion 1204 from base 1204A to tip 1204B, but it is sufficient that they are provided at least in a portion of the inner circumferential portion of tubular portion 1204 closer to base 1204A. Therefore, for example, inner circumferential projections 3202 may be provided only in a portion of the inner circumferential portion of tubular portion 1204 closer to base 1204A, or from base 1204A to approximately the middle between base 1204A and tip 1204B. However, if inner circumferential projections 3202 are provided from base 1204A to tip 1204B, they can be applied to eye joint fittings 50 that have different thicknesses in the axial direction of eye joint body 52, improving convenience.

[0059] According to the dust cap for eye joint 10E of this embodiment, the same effects as those of the second embodiment are achieved, and the shaft portion 1404 has a simple configuration, which is advantageous in terms of easy manufacturing.

[0060] Sixth Embodiment In the second embodiment, the tube portion 1204 and the shaft portion 1404 are formed in a cylindrical shape, but as shown in Fig. 20, a configuration in which slits are further provided may be adopted. In this embodiment, as in the second embodiment, the shaft portion 1404 is configured such that outer periphery-side convex portions 3402 and outer periphery-side retracted portions 3404, each of which is one-quarter of the circumference obtained by dividing the entire circumference into four, are alternately arranged, and each of the two outer periphery-side retracted portions 3404 is provided with a shaft portion-side slit 44. The shaft side slit 44 is located in the circumferential center of the outer peripheral side retreat portion 3404, extending in the protruding direction of the shaft portion 1404 and opening at the tip in the protruding direction. When the shaft portion 1404 is inserted into or removed from the tubular portion 1204, this allows the shaft portion 1404 to deform radially inward, thereby facilitating the coupling and uncoupling of the inner peripheral side convex portion 3202 (uneven portion 18) of the tubular portion 1204 and the outer peripheral side convex portion 3402 (uneven portion 18) of the shaft portion 1404.

[0061] 20 shows that the shaft portion 1404 is provided with a slit, but the slit may also be provided in the cylindrical portion 1204 (not shown). That is, as in the second embodiment, the cylindrical portion 1204 is configured such that inner circumferential portion convex portions 3202 and inner circumferential portion retracted portions 3204, each of which is a quarter of the circumference of the cylindrical portion 1204, are alternately arranged, and each of the two inner circumferential portion retracted portions 3204 may be provided with a cylindrical portion slit. If the tubular portion side slit, like the shaft portion side slit 44, is located in the circumferential center of the inner peripheral portion side retreat portion 3204, extending in the protruding direction of the tubular portion 1204 and opening at the tip in the protruding direction, this allows the tubular portion 1204 to deform radially outward when the shaft portion 1404 is inserted into or removed from the tubular portion 1204, thereby making it easy to couple and unclip the inner peripheral portion side convex portion 3202 (uneven portion 18) of the tubular portion 1204 and the outer peripheral portion side convex portion 3402 (uneven portion 18) of the shaft portion 1404.

[0062] The dust cap 10F for eye joint of this embodiment achieves the same effects as the second embodiment, and also makes it easier to connect and disconnect the uneven portion 18 of the tubular portion 1204 and the uneven portion 18 of the shaft portion 1404, which is advantageous in facilitating insertion and removal of the shaft portion 1404 from the tubular portion 1204.

[0063] 10A, 10B, 10C, 10D, 10E, 10F Dust cap for eye joint 12, 14 Lid portion (pair of lid portions) 1202, 1402 Lid plate portion 1204 Cylinder portion 1404 Shaft portion 16 Connecting piece 18 Concave and recessed portion 20, 32 Cylinder portion-side concave and recessed portion 2002, 3202, 3206, 3210 Inner peripheral portion-side convex portion 3204, 3208 Inner peripheral portion-side retracted portion 22, 34 Shaft portion-side concave and recessed portion 2202, 3402, 3406, 3410 Outer peripheral portion-side convex portion 3404, 3408 Outer peripheral portion-side retracted portion 24, 36 Cylinder portion-side grip portion 26, 38 Shaft portion-side grip portion 28, 40, 42 Operation piece 30 Concave and recessed shape 44 Shaft side slit 50 Eye joint fitting 52 Eye joint body 5202 End surface portion 54 Tube body 56 Eye bolt insertion hole 5602 Opening 5604 Large diameter portion

Claims

1. A dust cap for an eye joint comprising a pair of lids covering both end faces of an eye joint body having an opening for an eyebolt insertion hole, one of the pair of lids having a cover plate covering the end face and a tubular portion protruding from the cover plate and having an inner periphery and an outer periphery with an outer diameter smaller than the inner diameter of the opening, the other of the pair of lids having a cover plate covering the end face and a shaft portion protruding from the cover plate and having an outer periphery which is releasably inserted into the inner periphery of the tubular portion, wherein the inner periphery of the tubular portion and the outer periphery of the shaft portion are provided with uneven portions which are releasably connected to maintain the shaft portion inserted into the tubular portion.

2. A dust cap for an eye joint as described in claim 1, characterized in that the uneven portion provided on the inner circumference of the cylindrical portion is configured by a plurality of inner circumference side convex portions extending circumferentially of the inner circumference, lined up in the axial direction of the cylindrical portion, and the uneven portion provided on the outer circumference of the shaft portion is configured by a plurality of outer circumference side convex portions extending circumferentially of the outer circumference and capable of engaging with and disengaging from the inner circumference side convex portions, lined up in the axial direction of the shaft portion.

3. A dust cap for an eye joint as described in claim 2, characterized in that: an inner circumference of the cylindrical portion is provided with an inner circumference side recess by removing the inner circumference side convex portion in the circumferential and axial directions of the cylindrical portion, the inner circumference side convex portion being configured to be shorter in length than the entire circumference of the inner circumference of the cylindrical portion; an outer circumference side recess by removing the outer circumference side convex portion in the circumferential direction of the outer circumference of the shaft portion and along the axial direction of the shaft portion, the outer circumference side convex portion being configured to be shorter in length than the entire circumference of the outer circumference of the shaft portion; and the inner circumference side recess and the outer circumference side convex portion face each other in the radial direction of the cylindrical portion, and when the outer circumference side recess and the inner circumference side convex portion are in a position where they face each other, the shaft portion is movable in the axial direction of the cylindrical portion.

4. A dust cap for an eye joint as described in claim 1, characterized in that the shaft portion and the tubular portion have a base portion located on the cover plate side and a tip portion remote from the cover plate portion, and the uneven portion is provided only on the inner periphery of the tubular portion near the tip portion and on at least the outer periphery of the shaft portion near the base portion.

5. A dust cap for an eye joint as described in claim 1, characterized in that the shaft portion and the tubular portion have a base portion located on the cover plate side and a tip portion remote from the cover plate portion, and the uneven portion is provided only on the outer periphery of the shaft portion near the tip portion and at least on the inner periphery of the tubular portion near the base portion.

6. A dust cap for an eye joint as described in claim 1, characterized in that the shaft portion is formed in a cylindrical shape, and a shaft portion-side slit is provided which extends in the protruding direction of the shaft portion and is open at its tip in the protruding direction to allow the shaft portion to deform radially inward, or a cylindrical portion-side slit is provided which extends in the protruding direction of the cylindrical portion and is open at its tip in the protruding direction to allow the cylindrical portion to deform radially outward.

7. A dust cap for an eye joint as described in claim 1, further comprising: a cylindrical portion-side gripping portion provided on the face of the cover plate opposite the face from which the cylindrical portion protrudes, for operating one of the cover portions; and a shaft portion-side gripping portion provided on the face of the cover plate opposite the face from which the shaft portion protrudes, for operating the other cover portion.

8. A dust cap for an eye joint as described in claim 7, characterized in that the cover plate portion is formed in a circular shape, and the tube side gripping portion and the shaft side gripping portion are provided extending along the diameter of the cover plate portion.

9. A dust cap for an eye joint as described in claim 1, characterized in that the cover plate portions of the pair of cover portions are provided with an operating piece that is used to pull out the shaft portion from a state in which the shaft portion is inserted into the cylindrical portion.

10. The dust cap for eye joint according to claim 1, characterized in that the outer periphery of the cover plate portion of the pair of cover portions is formed in an uneven shape.

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