TWI634965B

TWI634965B - Combined chain mechanism

Info

Publication number: TWI634965B
Application number: TW106128080A
Authority: TW
Inventors: 張慶三
Original assignee: 聖杰國際股份有限公司
Priority date: 2017-08-18
Filing date: 2017-08-18
Publication date: 2018-09-11
Also published as: TW201912290A

Abstract

一種組合式鏈條機構，用以搭載多數個加工用刀具。其包括一基架與多數個鏈帶單元彼此樞接形成條帶狀結構，其中鏈帶單元受到水平方向及垂直方向的限制，使得其結構能適用於搭載水平向或是垂直向擺設的刀具。另外，鏈帶單元與基架的軌道以滾動方式配合，降低摩擦阻力，使得鏈條機構運轉更為順暢。 A combined chain mechanism for carrying a large number of machining tools. The utility model comprises a base frame and a plurality of chain belt units pivotally connected to each other to form a strip-shaped structure, wherein the chain belt unit is restricted by horizontal direction and vertical direction, so that the structure can be applied to a tool which is horizontally or vertically arranged. In addition, the chain unit and the track of the base frame are matched in a rolling manner to reduce the frictional resistance, so that the chain mechanism operates more smoothly.

Description

組合式鏈條機構 Combined chain mechanism

本發明係與鏈條式傳動機構有關；特別是指一種適用於搭載不同加工刀具使用的組合式鏈條機構。 The invention relates to a chain transmission mechanism; in particular to a combined chain mechanism suitable for use with different machining tools.

按，刀庫系統是提供自動化加工過程中所需之儲刀及換刀需求的一種裝置。已知刀庫的容量、佈局，針對不同的工具機而有不同形式，例如斗笠式刀庫、圓盤式刀庫或鏈條式刀庫。其中又以鏈條式刀庫可容納較多的刀具，其藉由鏈條將要替換的刀具傳遞到指定位置，再由換刀臂將刀具換裝到加工主軸上。 Press, the tool magazine system is a device that provides the storage and tool change requirements required for automated machining. The capacity and layout of the magazine are known to be different for different machine tools, such as bucket magazines, disc magazines or chain magazines. In addition, the chain type magazine can accommodate more tools, and the tool to be replaced is transferred to the designated position by the chain, and the tool is replaced by the tool change arm to the machining spindle.

請參圖1及圖2所示，為一種已知自動化機具中使用的鏈條式傳動機構，其包括一基架1與一鏈帶結構2，其中基架1包括平行設置的上軌條1a與下軌條1b，鏈帶結構2係可移動地設置於上軌條1a與下軌條1b之間，且鏈帶結構2包括多數片結合板2a與多數個刀套2b。請配合圖3所示，該些結合板2a以兩片一對的方式設置，每一對結合板2a之間套接兩個刀套2b，而其中一個刀套2b更同時為另一對結合板2a所套接，至此組成條帶狀的結構；而各個刀套2b係可供刀具(圖未示)安插其中。 1 and 2, which is a chain type transmission mechanism used in a known automatic machine, comprising a base frame 1 and a chain belt structure 2, wherein the base frame 1 includes upper rails 1a and parallel arranged The lower rail 1b, the chain structure 2 is movably disposed between the upper rail 1a and the lower rail 1b, and the chain structure 2 includes a plurality of sheet bonding plates 2a and a plurality of knife sleeves 2b. As shown in FIG. 3, the binding plates 2a are arranged in a pair of two pieces, and each of the pair of bonding plates 2a is sleeved with two knife sleeves 2b, and one of the sleeves 2b is simultaneously joined by another pair. The plate 2a is sleeved so as to form a strip-like structure; and each of the sleeves 2b is provided with a cutter (not shown).

上述鏈帶結構2係通過其各個刀套2b的外周面分別與上軌條1a及下軌條1b接觸，而可於上軌條1a與下軌條1b之間被控制移動。然而，刀套2b外周面與上軌條1a及下軌條1b之間為面接觸，使得鏈帶結構2在運轉時因摩擦力大而造成轉速慢，相對地影響換刀速率。其次，當刀套2b的外周面、上軌條1a或是下軌條1b有因摩擦而生磨損時，將有餘隙產生，不僅造成鏈帶結構2運轉的不順暢，更常伴隨著噪音的產生。 The chain belt structure 2 is controlled to move between the upper rail 1a and the lower rail 1b by the outer peripheral surfaces of the respective pockets 2b being in contact with the upper rail 1a and the lower rail 1b, respectively. Of course On the other hand, the outer circumferential surface of the knife sleeve 2b is in surface contact with the upper rail 1a and the lower rail 1b, so that the chain structure 2 has a high rotational speed due to a large frictional force during operation, and relatively affects the tool change rate. Secondly, when the outer circumferential surface of the knife sleeve 2b, the upper rail 1a or the lower rail 1b is worn by friction, a clearance is generated, which not only causes the chain structure 2 to operate unsmoothly, but is also accompanied by noise. produce.

另外，上述鏈帶結構2與上軌條1a及下軌條1b的配置關係，僅能適用於刀具呈水平向擺設使用，屬於專用設計，故無法在垂直或是水平擺設的刀具之搭載上產生互通性，因此，該已知的鏈條式傳動機構的通用性受到侷限。 In addition, the arrangement relationship between the above-mentioned chain structure 2 and the upper rail 1a and the lower rail 1b can only be applied to the horizontal arrangement of the cutter, and is a special design, so it cannot be produced on the vertical or horizontally mounted cutter. Interoperability, therefore, the versatility of the known chain drive mechanism is limited.

有鑑於此，本發明之目的在於提供一種組合式鏈條機構，係使鏈帶結構運轉順暢，且適用於搭載水平向或是垂直向擺設的刀具。 In view of the above, it is an object of the present invention to provide a combined chain mechanism that facilitates the operation of the chain structure and is suitable for use with horizontal or vertical knives.

緣以達成上述目的，本發明提供一種組合式鏈條機構，包含一基架與多數個鏈帶單元彼此樞接形成條帶狀結構。其中基架設有一上軌道與一下軌道，該上軌道具有一上引導槽與一上抵面，該下軌道具有一下引導槽與一下抵面；每一鏈帶單元進一步包括有一襯套與一刀套，其中襯套之頂部及底部分別設置有一上引導件與一下引導件，該上引導件與該下引導件分別落入該上引導槽與該下引導槽中，另有多數個側向滾動件結合於該襯套且分別與該上抵面及該下抵面接觸；刀套則組裝於該襯套之一軸孔中。 In order to achieve the above object, the present invention provides a combined chain mechanism comprising a base frame and a plurality of chain belt units pivotally connected to each other to form a strip-like structure. Wherein the base frame is provided with an upper rail and a lower rail, the upper rail has an upper guiding groove and an upper abutting surface, the lower rail has a lower guiding groove and a lower abutting surface; each chain belt unit further comprises a bushing and a knife sleeve, wherein the lining The top and the bottom of the sleeve are respectively provided with an upper guiding member and a lower guiding member, wherein the upper guiding member and the lower guiding member respectively fall into the upper guiding groove and the lower guiding groove, and a plurality of lateral rolling members are coupled to the The bushings are respectively in contact with the upper abutting surface and the lower abutting surface; the tool sleeve is assembled in one of the shaft holes of the bushing.

本發明之效果在於通過上引導件、下引導件及側向滾動件來限制襯套的移動方向，且側向滾動件與上軌道及下軌道以滾動方式配合可降低摩擦阻力。 The effect of the present invention is to limit the moving direction of the bushing by the upper guiding member, the lower guiding member and the lateral rolling member, and the lateral rolling members are frictionally matched with the upper rail and the lower rail in a rolling manner to reduce the frictional resistance.

〔本發明〕〔this invention〕

100‧‧‧組合式鏈條機構 100‧‧‧Combined chain mechanism

10‧‧‧基架 10‧‧‧ pedestal

12‧‧‧上軌道 12‧‧‧Upper track

121‧‧‧上抵面 121‧‧‧Meeting

122‧‧‧上引導槽 122‧‧‧Upper guide slot

14‧‧‧下軌道 14‧‧‧Lower orbit

141‧‧‧下抵面 141‧‧‧Affiliated

142‧‧‧下引導槽 142‧‧‧Lower guide slot

20‧‧‧鏈帶單元 20‧‧‧Chain unit

21‧‧‧襯套 21‧‧‧ bushing

211‧‧‧軸孔 211‧‧‧ shaft hole

212‧‧‧接耳 212‧‧‧ Ears

213‧‧‧樞耳 213‧‧‧ 枢 ear

214‧‧‧安座 214‧‧‧Seat

22‧‧‧軸桿 22‧‧‧ shaft

23‧‧‧第一對側向滾動件 23‧‧‧First pair of lateral rolling elements

24‧‧‧第二對側向滾動件 24‧‧‧Second pair of lateral rolling elements

25‧‧‧上引導件 25‧‧‧Upper guide

26‧‧‧下引導件 26‧‧‧Lower guides

27‧‧‧刀套 27‧‧‧Knife sets

28‧‧‧第一轉動軸 28‧‧‧First axis of rotation

29‧‧‧第二轉動軸 29‧‧‧second axis of rotation

30‧‧‧中心軸 30‧‧‧ center axis

圖1為已知鏈條式傳動機構的立體圖；圖2為圖1的局部剖視圖；圖3為圖1的部分結構俯視圖；圖4為本發明較佳實施例之組合式鏈條機構的立體圖；圖5為圖4的左側視圖；圖6為圖4的部分結構前視圖；圖7為圖4的部分結構立體圖；以及圖8為圖7的部分結構立體圖。 1 is a perspective view of a known chain drive mechanism; FIG. 2 is a partial cross-sectional view of FIG. 1; FIG. 3 is a partial plan view of FIG. 1; FIG. 4 is a perspective view of a combined chain mechanism according to a preferred embodiment of the present invention; 4 is a front view of the structure of FIG. 4; FIG. 7 is a partial perspective view of FIG. 4; and FIG. 8 is a partial perspective view of FIG.

為能更清楚地說明本發明，茲舉一較佳實施例並配合圖式詳細說明如後。請參圖4至圖8所示，本發明較佳實施例之組合式鏈條機構100係可做為自動化加工設備的刀庫系統，其包括一基架10以及由多數個鏈帶單元20彼此樞接所形成的條帶狀結構，其中基架10構成刀庫系統的主要穩定支撐結構，每一鏈帶單元20係可供結合加工使用的刀具(圖未示)。 In order to explain the present invention more clearly, a preferred embodiment will be described in detail with reference to the drawings. Referring to FIG. 4 to FIG. 8 , the combined chain mechanism 100 of the preferred embodiment of the present invention can be used as a tool magazine system for an automated processing device, which includes a base frame 10 and a plurality of chain belt units 20 pivoted to each other. The strip-like structure formed by the joining, wherein the base frame 10 constitutes a main stable supporting structure of the tool magazine system, each of the chain belt units 20 is a tool (not shown) that can be used in combination with the processing.

本實施例的基架10包括有上下平行設置的一上軌道12與一下軌道14，其中上軌道12與下軌道14是以耐磨材質製成，例如塑鋼材。上軌道12與下軌道14為對稱結構，在本實施例中，上軌道12與下軌道14分別由二長條狀的導軌構成，且各導軌的一面構成抵接面，其中上軌道12之導軌的抵接面定義為上抵面121，下軌道14之導軌的抵接面定義為下抵面141，又上抵面121係面對下抵面141；另，上軌道12之相鄰導軌之間形成上引導槽122，下軌道14之相鄰導軌之間形成下引導槽142。在其他實施例中，引導槽可以是自單一導軌結構的一側面凹陷所形成。 The base frame 10 of the present embodiment includes an upper rail 12 and a lower rail 14 which are arranged in parallel in the upper and lower directions. The upper rail 12 and the lower rail 14 are made of a wear-resistant material, such as a plastic steel material. The upper rail 12 and the lower rail 14 have a symmetrical structure. In the embodiment, the upper rail 12 and the lower rail 14 are respectively formed by two long rails, and one side of each rail forms an abutting surface, and the rail of the upper rail 12 abuts. The face is defined as an upper abutment surface 121, the abutment surface of the guide rail of the lower rail 14 is defined as a lower abutment surface 141, and the upper abutment surface 121 is a lower abutment surface 141; and the adjacent rail of the upper rail 12 Upper guide grooves 122 are formed therebetween, and lower guide grooves 142 are formed between adjacent guide rails of the lower rail 14. In other embodiments, the guide slots may be formed by recessing from one side of a single rail structure.

本實施例的每一鏈帶單元20包括有一襯套21、一軸桿22、多數個側向滾動件、一上引導件25、一下引導件26及一刀套27。其中襯套21為具有一軸孔211的中空實體結構，且襯套21的左右兩側分別沿著徑向凸伸出一接耳212與二樞耳213，其中一個襯套21的接耳212位於另一個襯套21的該二樞耳213之間，通過該軸桿22穿過該二樞耳213與該接耳212，使得相鄰襯套21彼此樞接(圖6參照)。 Each of the chain belt units 20 of the present embodiment includes a bushing 21, a shaft 22, a plurality of lateral rolling members, an upper guiding member 25, a lower guiding member 26 and a knife sleeve 27. The bushing 21 is a hollow solid structure having a shaft hole 211, and the left and right sides of the bushing 21 respectively protrude from the lug 212 and the two pivot ears 213 in a radial direction, wherein the lug 212 of one bushing 21 is located Between the two pivots 213 of the other bushing 21, the two shafts 213 and the lugs 212 are passed through the shaft 22 so that the adjacent bushings 21 are pivotally connected to each other (refer to FIG. 6).

襯套21上結合有該些側向滾動件，更具體地說，襯套21頂部及底部分別具有突起的安座214，該些側向滾動件包括有一第一對側向滾動件23與一第二對側向滾動件24。其中第一對側向滾動件23係通過第一轉動軸28而可轉動地位於襯套21頂部的安座214上，第二對側向滾動件24通過第二轉動軸29而可轉動地位於襯套21底部的安座214上，且第一轉動軸28與第二轉動軸29係平行通過該襯套21之軸孔211的軸線。在本實施例中，前述側向滾動件係選自軸承，且各對的側向滾動件可以是通過一支轉動軸而與襯套21結合，或是分別通過一支轉動軸而與襯套21結合。 The bushings 21 are combined with the lateral rolling members. More specifically, the top and bottom portions of the bushings 21 respectively have raised seats 214. The lateral rolling members include a first pair of lateral rolling members 23 and a first Two pairs of lateral rolling members 24. Wherein the first pair of lateral rolling members 23 are rotatably mounted on the seat 214 at the top of the bushing 21 by the first rotating shaft 28, and the second pair of lateral rolling members 24 are rotatably positioned in the lining by the second rotating shaft 29. The sleeve 214 is mounted on the bottom of the sleeve 21, and the first rotating shaft 28 and the second rotating shaft 29 pass parallel to the axis of the shaft hole 211 of the bushing 21. In this embodiment, the lateral rolling member is selected from a bearing, and each pair of lateral rolling members may be coupled to the bushing 21 through a rotating shaft or through a rotating shaft and a bushing respectively. 21 combined.

襯套21頂部及底部的安座214的中間部位分別再結合有上引導件25與下引導件26，其中上引導件25與下引導件26呈圓盤體，且分別通過一中心軸30而結合於對應的安座214上。在本實施例中，中心軸30係與對應的第一轉動軸28或第二轉動軸29呈正交設置，所述正交設置係指自襯套21的左右側面觀之的狀態而言，即容許中心軸30的軸線與轉動軸的軸線是呈前後錯位的。另外，該上引導件25位於第一對側向滾動件23的各個側向滾動件之間，該下引導件26位於第二對側向滾動件24 的各個側向滾動件之間，且上引導件25與下引導件26的外徑相當於引導槽的槽寬，故而能分別落入上軌道12的上引導槽122及下軌道14的下引導槽142中。較佳者，上引導件25及下引導件26亦可製作成具有轉動效果者。 The middle portion of the seat 214 of the top and bottom of the bushing 21 is respectively coupled with an upper guide 25 and a lower guide 26, wherein the upper guide 25 and the lower guide 26 are disk bodies and are respectively coupled by a central shaft 30. On the corresponding seat 214. In the present embodiment, the central shaft 30 is disposed orthogonally to the corresponding first rotating shaft 28 or second rotating shaft 29, and the orthogonal setting refers to a state viewed from the left and right sides of the bushing 21, That is, the axis of the central axis 30 and the axis of the rotating shaft are allowed to be displaced back and forth. In addition, the upper guide 25 is located between the respective lateral rolling members of the first pair of lateral rolling members 23, and the lower guiding member 26 is located at the second pair of lateral rolling members 24. Between each of the lateral rolling members, and the outer diameters of the upper guiding member 25 and the lower guiding member 26 are equivalent to the groove width of the guiding groove, so that they can fall into the upper guiding groove 122 of the upper rail 12 and the lower guiding groove of the lower rail 14, respectively. 142. Preferably, the upper guide 25 and the lower guide 26 can also be made to have a turning effect.

刀套27係以可拆離的方式組裝於襯套21之軸孔211中，刀套27可供刀具(圖未示)安插其中。 The knife sleeve 27 is detachably assembled in the shaft hole 211 of the bushing 21, and the knife sleeve 27 is inserted into a cutter (not shown).

本實施例之多數個鏈帶單元20彼此樞接組成條帶狀結構，其上可供容納較多刀具。每一鏈帶單元20的上引導件25與下引導件26落入對應的上引導槽122與下引導槽142中，且上引導件25與下引導件26的圓周面貼近對應導槽的槽壁，藉此限制了襯套21於水平之X方向移動；每一鏈帶單元20更通過第一對側向滾動件23及第二對側向滾動件24分別與上抵面121及下抵面141接觸，藉此限制了襯套21於垂直的Y方向移動，其中X方向與Y方向係呈正交。前述配置關係使得本創作的組合式鏈條機構100適用於搭載水平向或是垂直向擺設的刀具，改善習知鏈條皆為專用結構而不具通用性的缺失。 The plurality of chain belt units 20 of this embodiment are pivotally connected to each other to form a strip-like structure on which a plurality of cutters can be accommodated. The upper guide 25 and the lower guide 26 of each chain unit 20 fall into the corresponding upper guiding groove 122 and lower guiding groove 142, and the circumferential surfaces of the upper guiding member 25 and the lower guiding member 26 are close to the groove corresponding to the guiding groove. a wall, thereby restricting the movement of the bushing 21 in the horizontal X direction; each of the chain belt units 20 is further passed through the first pair of lateral rolling members 23 and the second pair of lateral rolling members 24 and the upper abutting surface 121 and the lower portion The face 141 is in contact, thereby restricting the movement of the bushing 21 in the vertical Y direction, wherein the X direction is orthogonal to the Y direction. The foregoing configuration relationship makes the combined chain mechanism 100 of the present invention suitable for the horizontal or vertical arranging of the knives, and the conventional chain is improved as a dedicated structure without the versatility.

另外，上引導件25、下引導件26及多數個側向滾動件不僅限制了襯套21的移動方向，且第一對側向滾動件23與第二對側向滾動件24的各個側向滾動件係與上軌道12及下軌道14以滾動方式配合，當本創作的組合式鏈條機構100受控制運轉時，大幅降低摩擦阻力，使得該組合式鏈條機構100運轉更為順暢。 In addition, the upper guide 25, the lower guide 26 and the plurality of lateral rolling members not only limit the moving direction of the bushing 21, but also the lateral directions of the first pair of lateral rolling members 23 and the second pair of lateral rolling members 24. The rolling member is engaged with the upper rail 12 and the lower rail 14 in a rolling manner. When the combined chain mechanism 100 of the present invention is controlled to operate, the frictional resistance is greatly reduced, so that the combined chain mechanism 100 operates more smoothly.

以上所述僅為本發明較佳可行實施例而已，舉凡應用本發明說明書及申請專利範圍所為之等效變化，理應包含在本發明之專利範圍內。 The above is only a preferred embodiment of the present invention, and equivalent changes to the scope of the present invention and the scope of the patent application are intended to be included in the scope of the present invention.

Claims

一種組合式鏈條機構，包含：一基架，係設有一上軌道與一下軌道，其中該上軌道具有一上引導槽與一上抵面，該下軌道具有一下引導槽與一下抵面；多數個鏈帶單元彼此樞接形成條帶狀結構，其中每一鏈帶單元包括：一襯套，於頂部及底部分別設置有一上引導件與一下引導件，該上引導件與該下引導件分別落入該上引導槽與該下引導槽中；多數個側向滾動件結合於該襯套且分別與該上抵面及該下抵面接觸，其中該些側向滾動件包括一第一對側向滾動件與一第二對側向滾動件，該第一對側向滾動件通過一第一轉動軸而可轉動地位於該襯套頂部，該第二對側向滾動件通過一第二轉動軸而可轉動地位於該襯套底部，且該第一轉動軸與該第二轉動軸平行通過該襯套之軸孔的軸線；以及一刀套，係組裝於該襯套之一軸孔中；藉此，該上引導件與該下引導件限制該襯套於X方向的移動，該些側向滾動件限制該襯套於Y方向的移動，其中X方向與Y方向係呈正交。 A combined chain mechanism comprises: a base frame, an upper track and a lower track, wherein the upper track has an upper guiding groove and an upper abutting surface, the lower track has a lower guiding groove and a lower abutting surface; and the plurality of chain belts The units are pivotally connected to each other to form a strip-like structure, wherein each of the chain belt units comprises: a bushing, and an upper guiding member and a lower guiding member are respectively disposed at the top and the bottom, and the upper guiding member and the lower guiding member respectively fall into the a plurality of lateral rolling members are coupled to the bushing and respectively in contact with the upper abutting surface and the lower abutting surface, wherein the lateral rolling members comprise a first pair of lateral rolling And a second pair of lateral rolling members rotatably located at the top of the bushing through a first rotating shaft, the second pair of lateral rolling members passing through a second rotating shaft Rotatablely located at the bottom of the bushing, and the first rotating shaft passes through the axis of the shaft hole of the bushing in parallel with the second rotating shaft; and a sleeve is assembled in one of the shaft holes of the bush; thereby, The upper guide and the lower guide The liner system moves in the X direction, the plurality of rolling member to limit lateral movement of the bush in the direction Y, wherein X and Y directions were orthogonal lines.

如請求項1所述之組合式鏈條機構，其中該上軌道及該下軌道分別包括二長條狀的導軌，該上軌道之導軌一面形成該上抵面，該下軌道之導軌一面形成該下抵面，且該上抵面面對該下抵面；該上軌道之相鄰導軌之間形成該上引導槽，該下軌道之相鄰導軌之間形成該下引導槽。 The combined chain mechanism of claim 1, wherein the upper rail and the lower rail respectively comprise two long rails, and one side of the rail of the upper rail forms the upper abutting surface, and one side of the rail of the lower rail forms the lower abutting surface And the upper abutting surface faces the lower abutting surface; the upper guiding groove is formed between adjacent rails of the upper rail, and the lower guiding groove is formed between adjacent rails of the lower rail.

如請求項1所述之組合式鏈條機構，其中該上引導槽係自該上抵面的中間部位凹陷形成，該下引導槽係自該下抵面的中間部位凹陷形成，且該上抵面面對該下抵面。 The combination chain mechanism according to claim 1, wherein the upper guiding groove is formed by being recessed from an intermediate portion of the upper abutting surface, and the lower guiding groove is recessed from an intermediate portion of the lower abutting surface, and the upper abutting surface Face the face of the next.

如請求項2或3所述之組合式鏈條機構，其中該上引導件與該下引導件分別通過一中心軸而設置於各對側向滾動件之間，且該中心軸與對應的轉動軸呈正交設置。 The combined chain mechanism of claim 2 or 3, wherein the upper guide and the lower guide are respectively disposed between each pair of lateral rolling members through a central axis, and the central axis and the corresponding rotating shaft Orthogonal settings.

如請求項4所述之組合式鏈條機構，其中該上引導件與該下引導件分別具有一圓盤體與對應的中心軸連接，該上引導件與該下引導件之圓盤體分別落入該上引導槽與該下引導槽中，且圓盤體的外徑相當於引導槽的槽寬。 The combination chain mechanism of claim 4, wherein the upper guide member and the lower guide member respectively have a disc body connected to a corresponding central shaft, and the upper guide member and the disc body of the lower guide member respectively fall The upper guide groove and the lower guide groove are inserted into each other, and the outer diameter of the disk body corresponds to the groove width of the guide groove.

如請求項1所述之組合式鏈條機構，其中每一鏈帶單元包括一軸桿；該襯套的左右兩側分別沿著徑向凸伸出一接耳與二樞耳，其中一該襯套的接耳係位於另一該襯套之該二樞耳之間，該軸桿穿過該二樞耳與該接耳，使得相鄰襯套彼此樞接。 The combined chain mechanism of claim 1, wherein each of the chain belt units comprises a shaft; the left and right sides of the bushing respectively project a lug and a second pivot along a radial direction, wherein the bushing The ear strap is located between the two pivots of the other bushing, and the shaft passes through the two pivot ears and the lug such that adjacent bushings are pivotally connected to each other.