TWI745044B

TWI745044B - Seamless link connection structure

Info

Publication number: TWI745044B
Application number: TW109128804A
Authority: TW
Inventors: 王文濱
Original assignee: 雅邦企業股份有限公司
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2021-11-01
Also published as: TW202208761A

Abstract

The present invention relates to a seamless link connection structure, which includes two outer links and two inner links. An inner side of each outer link plate is formed with a concave portion between two first coupling portions at two ends thereof. A connecting surface is connected between each first coupling portion and the concave portion. The connecting surface is gradually tapered inward from each first coupling portion toward the concave portion. An outer side of each inner link plate is provided with a pair of bent portions each extending from an outermost edge of each second coupling portion toward the connecting surface. A gap is defined between each bent portion and the connecting surface. A width of the gap is smaller than the minimum thickness of a narrow tooth of a chainring, thereby preventing the tooth from being jammed in the gap.

Description

內外鏈片無縫式接合構造 Seamless joint structure of inner and outer links

本發明係有關於一種鏈條變速時，薄鏈齒不會卡入間隙內，而發出噪音或造成危險之內外鏈片構造。 The invention relates to an inner and outer chain piece structure in which thin sprocket will not get caught in the gap, and generate noise or cause danger when the chain is shifted.

一般自行車之變速機構，通常是位於自行車前方的厚薄齒盤上，係交錯間隔環設有複數個厚度不同的厚、薄鏈齒，而位於自行車後方則設有複數個大、小不同直徑並排的變速齒盤，然後經由撥鏈器撥動鏈條於該等變速齒盤之間互相轉換。變速用的該變速齒盤則環設有複數個厚度較薄的薄鏈齒。而鏈條則於二內鏈片之間形成有空隙較小的容納容間，以對應卡入厚薄齒盤上的厚度較薄的鏈齒，以及變速齒盤上的薄鏈齒。而二外鏈片之間則形成有空隙較大的容納空間，以供可以對應卡入厚薄齒盤上的厚度較厚的鏈齒，以及變速齒盤上的薄鏈齒。不論鏈條是要從大、小變速齒盤之間脫離或卡入時，均會使得鏈條之外鏈片、內鏈片與厚薄齒盤之厚、薄鏈齒造成阻礙，以致於影響到變速時的平順操作，以及發出噪音或造成機件的損壞。 The speed change mechanism of a general bicycle is usually located on the thick and thin gear plate at the front of the bicycle. The staggered spacer ring is provided with a plurality of thick and thin sprockets with different thicknesses, and at the rear of the bicycle, there are multiple large and small sprockets with different diameters side by side. The gears are shifted, and the chain is shifted by the derailleur to switch between the gears. The gear wheel used for gear shifting is provided with a plurality of thin sprocket teeth of relatively thin thickness. In the chain, an accommodation space with a small gap is formed between the two inner chain pieces to correspond to the thin sprocket on the thick and thin gear plate and the thin sprocket on the speed change gear plate. An accommodation space with a larger gap is formed between the two outer chain pieces, so that the thicker sprocket on the thick and thin gear plate and the thin sprocket on the variable gear plate can be correspondingly clamped. Regardless of whether the chain is to be detached from or stuck between the large and small gears, it will cause obstacles to the thick and thin sprocket of the outer chain, inner chain, and thick and thin chain gears, which will affect the shifting time. The smooth operation, as well as noise or damage to the mechanical parts.

因此有中華民國108年3月16日所公開之發明第201910663號之「自行車鏈條」，主要係揭露：包括一第一內鏈板及一第一內鏈板。該第一內鏈板包括一第一內鏈端部部分、一第二內鏈端部部分及一第一內鏈中間部分。該第二內鏈板包括一第三內鏈端部部分、一第四內鏈端部部分及一第二內鏈中間部分。一第一內鏈端部邊緣具有圍繞第一內鏈中心軸線延伸之一第一倒角，使得該第一倒角之一部分安置於一第一圓周區域中，當沿該第一內鏈中心軸線之一軸向方向觀看時，該第一圓周區域界定為自一第一內鏈縱向中心線至一第一參考線。該第一圓周區域小於14度。 Therefore, there is Invention No. 201910663 "Bicycle Chain" published by the Republic of China on March 16, 108, which mainly discloses: including a first inner chain plate and a first inner chain plate. The first inner chain plate includes a first inner chain end portion, a second inner chain end portion and a first inner chain middle portion. The second inner chain plate includes a third inner chain end portion, a fourth inner chain end portion and a second inner chain middle portion. The end edge of a first inner chain has a first chamfer extending around the central axis of the first inner chain, so that a part of the first chamfer is disposed in a first circumferential area when along the central axis of the first inner chain One axis When viewed downward, the first circumferential area is defined from a longitudinal centerline of a first inner chain to a first reference line. The first circumferential area is less than 14 degrees.

惟上述專利前案或現今的鏈條構造，主要如第九圖所示，係於二外鏈片A的相對內側分別設有一凹部A1，而二內鏈片B的端緣形成有一凸部B1。該凹部A1雖然可以增加厚薄齒盤之厚鏈齒卡入時的容納空間，使得卡入時較為平順，卻也使得該凸部B1與該凹部A1的相對面之間會形成一間隙C，於變速時，造成變速齒盤上厚度較薄之薄鏈齒D旋轉傾斜進入時，會容易卡入於該間隙C內，使得該薄鏈齒D會被卡住而無法變速，而卡住的該薄鏈齒D，將會使得該外鏈片A及該內鏈片B被撬開而分離，以致於造成斷鏈，因此在使用上有其缺點及危險性存在。 However, in the previous patent or the current chain structure, as shown in the ninth figure, a concave portion A1 is respectively provided on the opposite inner sides of the two outer link pieces A, and a convex portion B1 is formed on the end edge of the two inner link pieces B. Although the concave portion A1 can increase the accommodating space when the thick sprocket of the thick and thin chainring is inserted, making the insertion smoother, it also makes a gap C formed between the convex portion B1 and the opposite surface of the concave portion A1. When shifting, when the thin sprocket D on the shifting chainring is rotated and inclined, it will easily get stuck in the gap C, so that the thin sprocket D will be stuck and cannot be shifted, and the stuck The thin chain teeth D will cause the outer chain piece A and the inner chain piece B to be pried and separated, which will cause the chain to be broken. Therefore, there are disadvantages and dangers in use.

爰此，有鑑於目前習知的內外鏈片接合構造具有上述的缺點。故本發明提供一種內外鏈片無縫式接合構造，包含有至少二外鏈片，係相對設置，該外鏈片的二端分別設有一第一結合部，該第一結合部上設有一第一軸孔，該二外鏈片的相對內側面於該二第一結合部之間形成有一凹部，該二第一結合部與該凹部相接處則設有一連接面，該連接面係由該第一結合部朝向該凹部逐漸內縮；至少二內鏈片，係結合於該二外鏈片的該相對內側面之間，該外鏈片的二端分別設有一第二結合部，該第二結合部上設有一第二軸孔，以供一銷軸穿入於該第二軸孔及該第一軸孔內，以結合該二內鏈片及該二外鏈片，該二內鏈片的相對外側面於該二第二結合部的最外緣，朝向該連接面設有一彎折部，該彎折部與該連接面之間具有一間隙，該間隙係小於一變速齒盤之薄鏈齒的最小厚度。 In view of this, in view of the above-mentioned shortcomings of the conventional inner and outer link joint structure. Therefore, the present invention provides a seamless joint structure of inner and outer links, which includes at least two outer links, which are arranged oppositely. The two ends of the outer links are respectively provided with a first joint part, and the first joint part is provided with a first joint part. A shaft hole, the opposite inner sides of the two outer chain pieces are formed with a recess between the two first joining parts, and a connecting surface is provided at the junction of the two first joining parts and the recess, and the connecting surface is formed by the The first joining portion gradually shrinks inward toward the recess; at least two inner link pieces are connected between the opposite inner sides of the two outer link pieces, and two ends of the outer link pieces are respectively provided with a second joining portion, the first A second shaft hole is provided on the two connecting parts for a pin to penetrate into the second shaft hole and the first shaft hole to combine the two inner chain pieces and the two outer chain pieces. The two inner chains The opposite outer sides of the sheet are provided at the outermost edge of the two second joining parts, facing the connecting surface with a bent part, and there is a gap between the bent part and the connecting surface, and the gap is smaller than that of a gear wheel. The minimum thickness of the thin sprocket.

上述連接面係呈一弧面。 The above-mentioned connecting surface is an arc surface.

上述彎折部的表面對應於該連接面設呈為相同形狀的另一弧面。 The surface of the above-mentioned bending portion is provided with another arc surface having the same shape corresponding to the connecting surface.

上述連接面係呈一斜面。 The above-mentioned connecting surface is an inclined surface.

上述彎折部的表面對應於該連接面設呈為相同形狀的另一斜面。 The surface of the above-mentioned bending portion is provided with another inclined surface having the same shape corresponding to the connecting surface.

上述技術特徵具有下列之優點： The above technical features have the following advantages:

1.外鏈片之連接面由第一結合部朝向凹部逐漸內縮，內鏈片的相對外側面設有一彎折部，該彎折部與該連接面之間具有一間隙，利用該間隙小於一變速齒盤之薄鏈齒的最小厚度，故可避免造成薄鏈齒卡住。 1. The connecting surface of the outer chain piece gradually shrinks inward from the first joining portion toward the concave portion, and the opposite outer side of the inner chain piece is provided with a bent portion. There is a gap between the bent portion and the connecting surface, and the gap is smaller than The minimum thickness of the thin sprocket of a variable speed chainring, so it can avoid the thin sprocket from getting stuck.

2.利用連接面係呈弧面，該彎折部的表面對應於該連接面設呈為相同形狀的弧面，除了使得該薄鏈齒不會被卡住外，可避免外鏈片及內鏈片被薄鏈齒撬開而分離或斷鏈，使用上可確保其安全性，而且變速時能迅速定位且不會發出任何的噪音。 2. The connecting surface is curved, and the surface of the bent portion corresponds to the curved surface with the same shape as the connecting surface. In addition to preventing the thin sprocket from being jammed, it can avoid the outer chain and the inner chain. The chain pieces are separated or broken by the thin sprocket. The safety can be ensured in use, and it can be positioned quickly during shifting without making any noise.

3.利用連接面係呈斜面，該彎折部的表面對應於該連接面設呈為相同形狀的斜面，除了使得該薄鏈齒不會被卡住外，可避免外鏈片及內鏈片被薄鏈齒撬開而分離或斷鏈，使用上可確保其安全性，而且變速時能迅速定位且不會發出任何的噪音。 3. The connecting surface is inclined, and the surface of the bent portion is corresponding to the connecting surface with the same inclined surface. In addition to preventing the thin chain teeth from being jammed, it can avoid the outer chain piece and the inner chain piece. The chain can be separated or broken by the thin chain teeth. It can be used to ensure its safety, and it can be positioned quickly during shifting without making any noise.

1:外鏈片 1: Outer chain piece

11:第一結合部 11: The first joint

12:第一軸孔 12: The first shaft hole

13:凹部 13: recess

14:連接面 14: Connection surface

2:內鏈片 2: inner chain piece

21:第二結合部 21: The second joint

22:第二軸孔 22: second shaft hole

23:銷軸 23: pin shaft

24:彎折部 24: Bending part

241:表面 241: Surface

3:外鏈片 3: Outer chain piece

31:第一結合部 31: The first joint

32:第一軸孔 32: The first shaft hole

33:凹部 33: recess

34:連接面 34: connecting surface

4:內鏈片 4: inner chain piece

41:第二結合部 41: The second joint

42:第二軸孔 42: second shaft hole

43:銷軸 43: pin shaft

44:彎折部 44: Bending part

441:表面 441: Surface

A:外鏈片 A: Outer chain piece

A1:凹部 A1: recess

B:內鏈片 B: inner chain piece

B1:凸部 B1: convex part

C:間隙 C: gap

D:薄鏈齒 D: Thin sprocket

E1:薄鏈齒 E1: Thin sprocket

E2:薄鏈齒 E2: Thin sprocket

F:間隙 F: gap

[第一圖]係為本發明第一實施例之組合剖視圖。 [The first figure] is a combined cross-sectional view of the first embodiment of the present invention.

[第二圖]係為本發明第一圖中II部分放大示意圖。 [The second figure] is an enlarged schematic diagram of part II in the first figure of the present invention.

[第三圖]係為本發明第一實施例外鏈片之立體外觀圖。 [Third Figure] is a three-dimensional external view of the chain piece with the exception of the first embodiment of the present invention.

[第四圖]係為本發明第一實施例內鏈片之立體外觀圖。 [Fourth Figure] is a three-dimensional external view of the inner link of the first embodiment of the present invention.

[第五圖]係為本發明第一實施例薄鏈齒卡入外鏈片及內鏈片之間的示意圖。 [Fifth Figure] is a schematic diagram of the thin sprocket in the first embodiment of the present invention stuck between the outer chain piece and the inner chain piece.

[第六圖]係為本發明第二實施例之組合剖視圖。 [Figure 6] is a combined cross-sectional view of the second embodiment of the present invention.

[第七圖]係為本發明第六圖中VII部分放大示意圖。 [Figure 7] is an enlarged schematic diagram of part VII in Figure 6 of the present invention.

[第八圖]係為本發明第二實施例內鏈片之立體外觀圖。 [Eighth Figure] is a perspective view of the inner chain piece of the second embodiment of the present invention.

[第九圖]係為習知外鏈片及內鏈片之組合剖視圖。 [Figure 9] is a sectional view of the combination of the conventional outer chain piece and the inner chain piece.

請參閱第一圖及第二圖所示，本發明第一實施例係包含有：二外鏈片1及二內鏈片2，其中： Please refer to the first and second figures. The first embodiment of the present invention includes two outer links 1 and two inner links 2, in which:

至少二外鏈片1，係相對設置。如第三圖所示，該外鏈片1的二端分別設有一第一結合部11，該第一結合部11上設有一第一軸孔12。又該二外鏈片1的該相對內側面於該二第一結合部11之間形成有一凹部13，該二第一結合部11與該凹部13相接處則設有一連接面14，該連接面14係呈一弧面，該連接面14係由該第一結合部11朝向該凹部13逐漸內縮。 At least two outer chain pieces 1 are arranged oppositely. As shown in the third figure, two ends of the outer link piece 1 are respectively provided with a first coupling portion 11, and the first coupling portion 11 is provided with a first shaft hole 12. In addition, the opposite inner side surfaces of the two outer link pieces 1 are formed with a concave portion 13 between the two first joining portions 11, and a connecting surface 14 is formed where the two first joining portions 11 and the concave portion 13 meet. The surface 14 is an arc surface, and the connecting surface 14 gradually shrinks inward from the first joining portion 11 toward the concave portion 13.

至少二內鏈片2，係結合於該二外鏈片1的該相對內側面之間。如第四圖所示，該內鏈片2的二端分別設有一第二結合部21，該第二結合部21上設有一第二軸孔22，以供一銷軸23穿入於該第二軸孔22及該第一軸孔12內，以結合該二內鏈片2及該二外鏈片1。又該二內鏈片2的相對外側面於該二第二結合部21的最外緣，朝向該連接面14設有一彎折部24，該彎折部24的表面241對應於該連接面14設呈為相同形狀的另一弧面，使該彎折部24與該連接面14之間具有一間隙F，該間隙F係小於一變速齒盤之薄鏈齒E1的最小厚度〔如第五圖所示〕。 At least two inner links 2 are connected between the opposite inner sides of the two outer links 1. As shown in the fourth figure, two ends of the inner chain piece 2 are respectively provided with a second coupling portion 21, and a second shaft hole 22 is provided on the second coupling portion 21 for a pin shaft 23 to penetrate through the second coupling portion 21. The two shaft holes 22 and the first shaft hole 12 are used to combine the two inner link pieces 2 and the two outer link pieces 1. In addition, opposite outer sides of the two inner link pieces 2 are provided on the outermost edges of the two second joining portions 21, facing the connecting surface 14 with a bending portion 24, and the surface 241 of the bending portion 24 corresponds to the connecting surface 14. Set another arc surface of the same shape so that there is a gap F between the bent portion 24 and the connecting surface 14, and the gap F is smaller than the minimum thickness of the thin sprocket E1 of a variable speed chain (such as the fifth Shown in the picture].

使用時，如第一圖及第五圖所示，利用複數該外鏈片1及該內鏈片2即可組合成為一鏈條。當該鏈條變速時，該變速齒盤之該薄鏈齒E1則會嚙合卡入於該二外鏈片1的該相對內側面之間，利用該外鏈片1於該二第一結合部11之間所形成的該凹部13，可以增加該薄鏈齒E1卡入時的容納空間，使得卡入時可更為平順而沒有阻力。又在卡入的過程中，由於該連接面14係呈弧面，該彎折部24的表面241對應於該連接面14設呈為相同形狀的另一弧面，該彎折部24與該連接面14之間的該間隙F，係小於該薄鏈齒E1的最小厚度，因此該薄鏈齒E1則不會卡入於該間隙F內，使得該薄鏈齒E1不會被卡住而無法變速，進而造成該等外鏈片1及該等內鏈片2被撬開而分離或斷鏈，因此在使用上可確保其安全性。而且使得該鏈條變速時能迅速定位且不會發出任何的噪音。 When in use, as shown in the first and fifth figures, a plurality of the outer chain pieces 1 and the inner chain pieces 2 can be combined to form a chain. When the chain is shifted, the thin sprocket E1 of the shifting chainring engages and engages between the opposite inner sides of the two outer chain pieces 1, and the outer chain piece 1 is used in the two first joining parts 11 The recessed portion 13 formed therebetween can increase the accommodating space of the thin sprocket E1 when the thin sprocket E1 is inserted, so that it can be inserted more smoothly without resistance. In the process of clamping, since the connecting surface 14 is arcuate, the surface 241 of the bending portion 24 corresponds to another arc surface with the same shape as the connecting surface 14, and the bending portion 24 is The gap F between the connecting surfaces 14 is smaller than the minimum thickness of the thin sprocket E1, so the thin sprocket E1 will not be caught in the gap F, so that the thin sprocket E1 will not be jammed. Unable to change speed, which in turn causes these external links The piece 1 and the inner chain pieces 2 are pried apart to separate or break the chain, so their safety can be ensured in use. Moreover, the chain can be quickly positioned without making any noise when changing speed.

請參閱第六圖及第七圖所示，本發明第二實施例係包含有：二外鏈片3及二內鏈片4，其中： Please refer to the sixth and seventh figures, the second embodiment of the present invention includes two outer links 3 and two inner links 4, of which:

至少二外鏈片3，係相對設置。該外鏈片3的二端分別設有一第一結合部31，該第一結合部31上設有一第一軸孔32。又該二外鏈片3的相對內側面於該二第一結合部31之間形成有一凹部33，該二第一結合部31與該凹部33相接處則設有一連接面34，該連接面34係呈一斜面，該連接面34係由該第一結合部31朝向該凹部33逐漸內縮。 At least two outer chain pieces 3 are arranged oppositely. Two ends of the outer link piece 3 are respectively provided with a first coupling portion 31, and the first coupling portion 31 is provided with a first shaft hole 32. In addition, the opposite inner sides of the two outer link pieces 3 are formed with a concave portion 33 between the two first joining portions 31, and a connecting surface 34 is formed where the two first joining portions 31 and the concave portion 33 meet. 34 is an inclined surface, and the connecting surface 34 gradually shrinks inward from the first joining portion 31 toward the concave portion 33.

至少二內鏈片4〔如第八圖所示〕，係結合於該二外鏈片3的該相對內側面之間。該內鏈片4的二端分別設有一第二結合部41，該第二結合部41上設有一第二軸孔42，以供一銷軸43穿入於該第二軸孔42及該第一軸孔32內，以結合該二內鏈片4及該二外鏈片3。又該二內鏈片4的相對外側面於該二第二結合部41的最外緣，朝向該連接面34設有一彎折部44，該彎折部44的表面441對應於該連接面34設呈為相同形狀的另一斜面，使該彎折部44與該連接面34之間具有一間隙F，該間隙F係小於一變速齒盤之薄鏈齒E2的最小厚度。 At least two inner link pieces 4 (as shown in the eighth figure) are connected between the opposite inner sides of the two outer link pieces 3. Two ends of the inner chain piece 4 are respectively provided with a second coupling portion 41, the second coupling portion 41 is provided with a second shaft hole 42 for a pin 43 to penetrate into the second shaft hole 42 and the first shaft hole 42 A shaft hole 32 is used to combine the two inner chain pieces 4 and the two outer chain pieces 3. In addition, opposite outer sides of the two inner link pieces 4 are provided on the outermost edges of the two second joining portions 41, facing the connecting surface 34, with a bending portion 44, and a surface 441 of the bending portion 44 corresponds to the connecting surface 34 Another inclined surface with the same shape is provided so that there is a gap F between the bent portion 44 and the connecting surface 34, and the gap F is smaller than the minimum thickness of the thin sprocket E2 of a variable speed chainring.

第二實施例與上述第一實施例之差異僅在於：該連接面34係呈斜面，該彎折部44的該表面441對應於該連接面34設呈為相同形狀的另一斜面，使該彎折部44與該連接面34之間的該間隙F小於該薄鏈齒E2的最小厚度。如此，於該鏈條進行變速時，該薄鏈齒E2則不會卡入於該間隙F內，使得該薄鏈齒E2不會被卡住而無法變速，進而造成該等外鏈片3及該等內鏈片4被撬開而分離或斷鏈，因此在使用上可確保其安全性。而且使得該鏈條變速時能迅速定位且不會發出任何的噪音。 The only difference between the second embodiment and the above-mentioned first embodiment is that the connecting surface 34 is an inclined surface, and the surface 441 of the bent portion 44 is provided with another inclined surface having the same shape corresponding to the connecting surface 34, so that the The gap F between the bent portion 44 and the connecting surface 34 is smaller than the minimum thickness of the thin sprocket E2. In this way, when the chain is shifting, the thin sprocket E2 will not be caught in the gap F, so that the thin sprocket E2 will not be stuck and cannot be shifted, thereby causing the outer chain pieces 3 and the Wait for the inner chain piece 4 to be pried apart to separate or break the chain, so its safety can be ensured in use. Moreover, the chain can be positioned quickly and does not emit any noise when changing speed.

綜合上述實施例之說明，當可充分瞭解本發明之操作、使用及本發明產生之功效，惟以上所述實施例僅係為本發明之較佳實施例，當不能以此限定本發明實施之範圍，即依本發明申請專利範圍及發明說明內容所作簡單的等效變化與修飾，皆屬本發明涵蓋之範圍內。 Based on the description of the above-mentioned embodiments, when one can fully understand the operation and use of the present invention and the effects of the present invention, the above-mentioned embodiments are only the preferred embodiments of the present invention, and the implementation of the present invention cannot be limited by this. The scope, that is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the description of the invention, are all within the scope of the present invention.

1:外鏈片 1: Outer chain piece

11:第一結合部 11: The first joint

12:第一軸孔 12: The first shaft hole

13:凹部 13: recess

14:連接面 14: Connection surface

2:內鏈片 2: inner chain piece

21:第二結合部 21: The second joint

22:第二軸孔 22: second shaft hole

23:銷軸 23: pin shaft

24:彎折部 24: Bending part

241:表面 241: Surface

F:間隙 F: gap

Claims

一種內外鏈片無縫式接合構造，包含有：至少二外鏈片，係相對設置，該外鏈片的二端分別設有一第一結合部，該第一結合部上設有一第一軸孔，該二外鏈片的相對內側面於該二第一結合部之間形成有一凹部，該二第一結合部與該凹部相接處則設有一連接面，該連接面係呈一弧面，該連接面係由該第一結合部朝向該凹部逐漸內縮；至少二內鏈片，係結合於該二外鏈片的該相對內側面之間，該內鏈片的二端分別設有一第二結合部，該第二結合部上設有一第二軸孔，以供一銷軸穿入於該第二軸孔及該第一軸孔內，以結合該二內鏈片及該二外鏈片，該二內鏈片的相對外側面於該二第二結合部的最外緣，朝向該連接面凸出設有一彎折部，該彎折部的表面對應於該連接面設呈為相同形狀的另一弧面，該彎折部與該連接面之間具有一間隙，該間隙係小於一變速齒盤之薄鏈齒的最小厚度。 A seamless joint structure for inner and outer chain pieces, comprising: at least two outer chain pieces, which are arranged opposite each other, and two ends of the outer chain pieces are respectively provided with a first coupling portion, and a first shaft hole is provided on the first coupling portion , The opposite inner side surfaces of the two outer link pieces form a concave portion between the two first joining portions, and a connecting surface is formed at the junction of the two first joining portions and the concave portion, and the connecting surface is an arc surface, The connecting surface gradually shrinks inward from the first joining portion toward the recess; at least two inner links are connected between the opposite inner sides of the two outer links, and two ends of the inner links are respectively provided with a first Two coupling parts, the second coupling part is provided with a second shaft hole for a pin to penetrate into the second shaft hole and the first shaft hole to join the two inner links and the two outer links Piece, the opposite outer sides of the two inner chain pieces are protruding from the outermost edge of the two second joining portions toward the connecting surface with a bending portion, and the surface of the bending portion is set to be the same as that of the connecting surface On the other arc surface of the shape, there is a gap between the bent portion and the connecting surface, and the gap is smaller than the minimum thickness of the thin sprocket of a gear plate.