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止め輪（サークリップまたはスナップリング）とは、穴または軸に加工した溝に嵌め込み、隣接する部品を固定するファスナーの一種。溝からはみ出している板幅部分が部品の固定を実現している。
特徴
[編集]止め輪は、その他ファスナーに比べて以下の利点がある。
- 部品1つあたりに必要な材料が少ない。
- 製品全体の軽量化を達成する。
- 止め輪を嵌め込む溝を穴または軸に加工するだけでよいため、廃棄物・生産コストを削減する。
種類
[編集]止め輪は大きく分けて3種類存在する。
- 偏心型止め輪
- スラスト方向取り付けタイプ
- ラジアル方向取り付けタイプ
- 溝加工不要タイプ
- ベベル型・湾曲型止め輪
- 同心型止め輪
- スパイラルリング（巻き止め輪）
- 単巻タイプ
- 二重巻タイプ
- 多重巻タイプ
偏心型止め輪
[編集]偏心型止め輪は、板幅が先端部にかけて細くなっているのが特徴であり、装着時には溝壁と先端のギャップ部を除いて、すべての面で接触している。また、先端にあるラグ部が留めとして機能しているため、より高い荷重に対応する止め輪である。[1]
スラスト方向取り付けタイプ
[編集]ラジアル方向取り付けタイプ
[編集]溝加工不要タイプ
[編集]ベベル型・湾曲型止め輪
[編集]同心型止め輪
[編集]材質
[編集]炭素鋼（カーボンスプリングスチール）製が一般的であるが、耐食性、硬度などの要件によってはステンレス鋼、ベリリウム銅、インコネル製なども使われる。[2]
表面処理
[編集]保存期間・耐食性を高めるため、大きく分けて4種類の表面処理がある。[3]
- リン酸塩皮膜処理
- リン酸塩のみ（保存期間の延長）
- リン酸塩とオイル（8時間に及ぶ耐塩水噴霧性を付加）
- コーティング付きリン酸塩
- 重リン酸塩とオイル（72時間に及ぶ耐塩水噴霧性を付加）
- 六価クロム皮膜処理
- 亜鉛めっき光沢付き（48時間に及ぶ耐塩水噴霧性を付加）
- 亜鉛めっき（96時間に及ぶ耐塩水噴霧性を付加）
- コーティング付き亜鉛めっき二クロム酸塩（240時間に及ぶ耐塩水噴霧性を付加）
- コーティング付き重亜鉛めっき二クロム酸塩（480時間に及ぶ耐塩水噴霧性を付加）
- 三価クロム皮膜処理
- 亜年めっき三価クロム（96時間（白さび）/240時間（赤さび）に及ぶ耐塩水噴霧性を付加）
- その他コーティング
- オイル皮膜（保存期間の延長）
Tapered section retaining rings
[編集]
Tapered section retaining rings decrease symmetrically from the center to the free ends, remaining circular when contracted or expanded within the limits of normal use. This assures contact with the groove along the entire periphery of the ring. These rings may be installed axially (horizontally along the center point of an axis) or radially (externally along the radius of a circle). Depending on the size of the ring in question, it may be manufactured in one of two ways:
- For smaller rings: using a die and stamping on a press from a coil of steel or copper
- For larger rings: wire forming, in which rectangular wire is coiled into the shape of the ring.
Axially assembled
[編集]
Axially assembled retaining rings are installed into machined grooves in housings/bores (internal) or on shafts (external). These rings are manufactured with lug holes—small holes in the lugs of both axial internal and external retaining rings—that are used to install/remove them, using pliers designed for this purpose.
Inverted retaining rings
[編集]Inverted retaining rings are a variation of axially assembled rings in which the lug holes are inverted to fit in the bottom of the groove. Inverting the lugs allows greater clearance on a shaft or in a housing and forms a higher uniform shoulder good for retaining bearings and other components with large corner radii or chamfers.
Beveled retaining rings
[編集]Beveled retaining rings feature a 15° beveled or angled edge. This angle allows the ring to wedge itself between the groove and the retained part until it can go no farther, effectively “locking” everything in place. Think of placing a cork in a bottle. The cork is forced into the opening until it is wedged as far into the opening as possible. The same thing happens when a beveled retaining ring is installed into an application. The ring is wedging itself into place between the groove wall and the retained part, resulting in what is referred to as rigid end-play take-up.
Bowed retaining rings
[編集]Bowed retaining rings are curved versions of standard flat internal and external retaining rings and exert a pre-load on an assembly when installed in the groove. This takes up the end-play and acts like a spring, which keeps the assembly in compression.
In manufacturing, parts can not be produced to an exact dimension; as a result, if they are made on the low side of the tolerance, they will be loose or have play on the shaft when a standard ring is installed. If they are made on the high side of the tolerance, they will extend further into the groove and prevent a standard ring from being fully installed. Compensating for accumulated tolerances is what bowed retaining rings are designed to do, by acting as a spring once installed into the groove.
Radially assembled
[編集]
Radially assembled retaining rings are installed externally into machined grooves on a shaft. These rings have no lug holes and must be installed using applicators.
Self-locking
[編集]Self-locking retaining rings can be installed in a housing/bore or on a shaft that has not had a groove machined into it. Self-locking rings with no lug holes are impossible to remove without either destroying the ring or warping it out of specified tolerances.
Constant section retaining rings
[編集]Constant section retaining rings (snap rings[4]) feature a uniform, constant section. In other words, the material used to make the ring is the same width at any point along the circumference of the ring. When they are contracted or expanded, they take on an elliptical deformation. As a result, they contact the groove at three or more isolated points but never continuously around the periphery. These rings are made from either flat or round wire.
Spiral retaining rings
[編集]
Spiral retaining rings are axially installed into housings/bores (internal) or onto shafts (external), making 360° contact with the groove. Spiral retaining rings have no ears or lugs to interfere with the assembly. These rings are manufactured by coiling flat wire into the shape of the finished retaining ring. Spiral rings are provided with a removal notch to simplify the removal process. No special tools are required for installation or removal. Spiral Retaining Rings can be economically produced in special alloys like stainless steel because the manufacturing process eliminates scrap.
Protective finishes
[編集]The following are various surface finished used on retaining rings:[5]
- Passivation
- Phosphate
- Zinc plating (Trivalent and Hexavalent)
- Oil
- Cadmium plating
See also
[編集]- Circlip
- Snap ring[6]
- E-ring[7]
- Spiral ring - provides 360° of coverage[8]
- E-ring[7]
- Bowed E-ring - bowed to take up end play[7]
- Klip (also known as a poodle ring) - similar to an E-ring but with larger ears that provide a large surface area against the retained part[9]
- Self-locking ring - does not require a groove[8]
- Split ring (also known as an X-washer) - fits into external grooves and is closed with a pair of pliers[9]
- Low clearance ring (also known as a crescent ring)[7]
- Spirolox Retaining Rings (also known as a Spiral Rings)[10]
References
[編集]Notes
[編集]- ^ http://www.rotorclip.com/about_retaining_rings.php
- ^ http://jp.rotorclip.com/products/material.html
- ^ http://jp.rotorclip.com/products/finishes.html
- ^ http://www.smalley.com/retaining_rings/snap_rings.asp
- ^ http://www.rotorclip.com/material-finishes-packaging/finishes.php
- ^ McMaster, p. 3192.
- ^ a b c d McMaster, p. 3194.
- ^ a b McMaster, p. 3196.
- ^ a b McMaster, p. 3193.
- ^ Spirolox Retaining Rings[1]
Bibliography
[編集]- Rotor Clip Co., Inc. catalog (12th ed.), Rotor Clip Co., Inc
- McMaster-Carr catalog (114th ed.), McMaster-Carr.
- Smalley Steel Ring Catalog (2012 ed.), Smalley Steel Ring.