Patent Publication Number: US-2003233821-A1

Title: Link plate for restricting back bending of a silent chain

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001] This application claims an invention, which was disclosed in Japanese Patent Application Number 2002-182412, filed Jun. 24, 2002, entitled “Link Plate for Preventing Cordal Action of a Silent Chain.” The benefit under 35 USC §119 (a)-(d) or 35 USC §365(b) of the Japanese application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates to a silent chain, and more particularly, to an oscillation-restrictive structure for restricting chordal oscillation of a chain span of a silent chain.  
       [0004] 2. Description of Related Art  
       [0005] A silent chain is generally comprised of a plurality of link plates each having a pair of pin apertures and teeth, arranged in lateral and longitudinal directions, and pivotably connected by connecting pins inserted in the pin apertures.  
       [0006] In a silent chain, when engagement frequency, determined by the number of teeth and rotational speed of a sprocket around which a silent chain is wrapped coincides with resonance frequency of the chain, determined by the length of a chain span and tension of the chain, resonance occurs and the chain begins to oscillate violently in the lateral direction, which generates noise.  
       [0007] In order to restrict oscillation of a chain span or chordal oscillation that causes noise, a silent chain with spring links has been conventionally used.  
       [0008] A spring link, as shown in Japanese patent application laying-open publication No. 10-54445, has a wavy corrugation. When a spring link is incorporated into a silent chain, it is compressed in the thickness direction between the adjacent link plates. Thereby, resilient force of a spring link due to compressive deformation imparts frictional force to the adjacent link plates. Bending resistance of the chain is thus increased and chordal oscillation of the chain is restricted.  
       [0009] However, in such a method using the spring link, the silent chain receives friction loss even at the time of power transmission, thus resulting in decrease in the power transmission ratio. Also, although a spring link itself does not contribute to power transmission capability of a chain, it makes the width of the entire chain larger. Furthermore, during prolonged use, contact surfaces of link plates adjacent to a spring link wear, thereby decreasing oscillation-restrictive force on chordal oscillation.  
       SUMMARY OF THE INVENTION  
       [0010] A first aspect of the present invention is directed to a link plate in use for a silent chain in which a plurality of link plates are interleaved in lateral and longitudinal directions and pivotably connected by connecting pins. The link plate includes a link plate body with a pair of teeth and a pair of pin apertures formed in the link plate body to receive the connecting pins. The link plate body includes a protrusion that protrudes in the thickness direction and is adapted to interfere with a shoulder portion of the adjacent link plate or a guide link so as to restrict back bending of the silent chain.  
       [0011] According to the first aspect of the present invention, when a silent chain is going to bend toward the backside thereof due to oscillation such as resonance, protrusions of the link plates come into contact with the shoulder portions of the adjacent link plates or the guide links. Thereby, back bending of the link plates or the guide links is restricted, thus causing the lateral oscillation of a chain span to be disposed on the normal bending side of a chain. As a result, chordal oscillation of a silent chain can be restricted.  
       [0012] In this case, protrusions of the link plates will not hinder normal bending movement of a silent chain or normal articulation of link plates at the time of engagement of a silent chain. These protrusions will not generate friction loss, either. Thereby, chordal oscillation of a silent chain can be restricted without decreasing power transmission efficiency of a silent chain.  
       [0013] In a second aspect of the present invention, a protrusion of a link plate is disposed on a link plate&#39;s centerline above a pin aperture&#39;s centerline. In this case, each back bending of a pair of adjacent link plates or guide links can be equally restricted.  
       [0014] In a third aspect of the present invention, a shoulder portion of a link plate has a flat portion that extends upwardly perpendicular to the pin aperture&#39;s centerline of the link plate. In this case, at the time of back bending of a silent chain, protrusions of the link plates come into contact with the flat portions of the adjacent link plates, thereby restricting back bending of a silent chain.  
       [0015] In a fourth aspect of the present invention, a protrusion of a link plate is formed integrally with a link plate body by applying a compressive process of press working to the link plate body. In this case, an additional member other than a link plate body is not needed, thereby decreasing the number of components.  
       [0016] The protrusion of a link plate may be a pin inserting through a link plate body as described in a fifth aspect of the present invention. In this case, although an additional member other than a link plate body is needed, single pin can substitute for each of the protrusions of a plurality of link plates by providing a pin to insert a plurality of link plates.  
       [0017] In a sixth aspect of the present invention, a silent chain is comprised of a plurality of link plates each having a protrusion.  
       [0018] In a seventh aspect of the present invention, the link plates each have a protrusion and are disposed at a random pattern along the length of a chain. At portions of a chain where protrusions are provided, back bending of link plates or guide links are restricted, whereas at portions of a chain where protrusions are not provided, back bending of link plates or guide links are allowed to occur. Also, portions having protrusions act as nodes of chordal oscillation of a chain. In this case, nodes of chordal oscillation are disposed at a random pattern along the length of a chain.  
       [0019] Therefore, according to the seventh aspect of the present invention, during operation, chordal lengths or span lengths defined by the nodes vary aperiodically along the length of a chain between the sprockets. Thereby, resonance will not occur in a silent chain in the case of any rotational speed and tension.  
       [0020] An eighth aspect of the present invention is directed to a guide link in use for a silent chain in which a plurality of link plates are interleaved in lateral and longitudinal directions and pivotably connected by connecting pins. The guide link is provided for maintaining a silent chain in place on the sprocket and includes a guide link body and a pair of apertures formed in the guide link body to receive connecting pins. In the eighth aspect of the present invention, a guide link includes a protrusion that protrudes in the thickness direction and is adapted to interfere with shoulder portions of the adjacent link plates so as to restrict back bending of the silent chain.  
       [0021] According to the eighth aspect of the present invention, when a silent chain is going to bend toward the backside thereof due to oscillation such as resonance, protrusions of the guide links come into contact with the shoulder portions of the adjacent links. Thereby, back bending of the link plates is restricted, thus causing the lateral oscillation of a chain span to be placed on the normal bending side of a chain. As a result, chordal oscillation of a silent chain can be restricted.  
       [0022] In this case, protrusions of the guide links will not hinder normal bending movement of a silent chain or normal articulation of link plates at the time of engagement of a silent chain. These protrusions will not generate friction loss, either. Thereby, chordal oscillation of a silent chain can be restricted without decreasing power transmission efficiency of a silent chain.  
       [0023] In a ninth aspect of the present invention, a protrusion of a guide link is disposed on a guide link&#39;s centerline above a pin aperture&#39;s centerline. In this case, each back bending of a pair of link plates adjacent to the guide links can be equally restricted.  
       [0024] In a tenth aspect of the present invention, a protrusion is formed integrally with a guide link body by applying compressive process of press working to the guide link body. In this case, an additional member other than a guide link is not needed, thereby decreasing the number of components.  
       [0025] A protrusion of a guide link may be a pin inserting through a guide link body as described in an eleventh aspect of the present invention. In this case, although an additional member other than a guide link body is needed, single pin can substitute for each of the protrusions of a plurality of guide links by providing a pin to insert a plurality of guide links.  
       [0026] In a twelfth aspect of the present invention, a silent chain is formed of a plurality of guide links each having a protrusion.  
       [0027] In a thirteenth aspect of the present invention, guide links each having a protrusion are disposed at a random pattern along the length of a chain. At portions of a chain where protrusions are provided, back bending of link plates is restricted, whereas at portions of a chain where protrusions are not provided, back bending of link plates is allowed to occur. Also, portions having protrusions act as nodes of chordal oscillation of a chain. In this case, nodes of chordal oscillation are disposed at a random pattern along the length of a chain.  
       [0028] Therefore, according to the thirteenth aspect of the present invention, during operation, chordal lengths or span lengths defined by the nodes vary aperiodically along the length of a chain between the sprockets. Thereby, resonance will not occur in a silent chain in the case of any rotational speed and tension.  
       [0029] A fourteenth aspect of the present invention is directed to a bending-restrictive link for restricting back bending of a silent chain, which includes a link body without teeth and a pair of apertures formed in the link body to receive connecting pins. The link body has a protrusion formed integral therewith that protrudes in the thickness direction and is adapted to interfere with a shoulder portion of an adjacent link plate or an adjacent guide link to restrict back bending of a silent chain.  
       [0030] According to the fourteenth aspect of the present invention, when a silent chain is going to bend toward the backside thereof due to oscillation such as resonance, protrusions of the bending-restrictive links come into contact with the shoulder portions of the adjacent link plates or the guide links. Thereby, back bending of the link plates or the guide links is restricted, thus causing the lateral oscillation of a chain span to be placed on the normal bending side of a chain. As a result, chordal oscillation of a silent chain can be restricted.  
       [0031] In this case, protrusions of the bending-restrictive links will not hinder normal bending movement of a silent chain or normal articulation of link plates at the time of engagement of a silent chain. These protrusions will not generate friction loss, either. Thereby, chordal oscillation of a silent chain can be restricted without decreasing power transmission efficiency of a silent chain.  
       [0032] In a fifteenth aspect of the present invention, a protrusion of the bending-restrictive link is formed integrally with the link body by applying compressive process of press working to the link body.  
       [0033] In a sixteenth aspect of the present invention, a silent chain is comprised of bending-restrictive links with protrusions.  
       [0034] In a seventeenth aspect of the present invention, bending-restrictive links each having a protrusion are disposed at a random pattern along the length of a chain. At portions of a chain where protrusions are provided, back bending of the link plates or the guide links are restricted, whereas at portions of a chain where protrusions are not provided, back bending of the link plates or the guide links are allowed to occur. Also, portions having protrusions act as nodes of chordal oscillation of a chain. In this case, nodes of chordal oscillation are disposed at a random pattern along the length of a chain.  
       [0035] Therefore, according to the seventeenth aspect of the present invention, during operation, chordal lengths or span lengths defined by the nodes vary aperiodically along the length of a chain between the sprockets. Thereby, resonance will not occur in a silent chain in the case of any rotational speed and tension. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
     [0036]FIG. 1 is a top plan view of a portion of a silent chain according to a first embodiment of the present invention.  
     [0037]FIG. 2 is a front elevational view of a portion of a silent chain of FIG. 1.  
     [0038]FIG. 3 is an enlarged view of a portion of FIG. 1.  
     [0039]FIG. 4 is a front elevational view of a link plate with a protrusion.  
     [0040]FIG. 5 is a schematic illustrating operation of a silent chain of FIG. 1.  
     [0041]FIG. 6 is a schematic illustrating operation of a silent chain of FIG. 1.  
     [0042]FIG. 7 is a variant of a protrusion, which corresponds to FIG. 3.  
     [0043]FIG. 8 is a variant of a protrusion, which corresponds to FIG. 3.  
     [0044]FIG. 9 is a top plan view of a portion of a silent chain according to a second embodiment of the present invention.  
     [0045]FIG. 10 is a front elevational view of a portion of a silent chain of FIG. 9.  
     [0046]FIG. 11 is an enlarged view of a portion of FIG. 9.  
     [0047]FIG. 12 is a front elevational view of a guide link with a protrusion.  
     [0048]FIG. 13 is a schematic illustrating operation of a silent chain of FIG. 9.  
     [0049]FIG. 14 is a schematic illustrating operation of a silent chain of FIG. 9.  
     [0050]FIG. 15 is a variant of a protrusion, which corresponds to FIG. 11.  
     [0051]FIG. 16 is a variant of a protrusion, which corresponds to FIG. 11.  
     [0052]FIG. 17 is a top plan view of a portion of a silent chain according to a third embodiment of the present invention.  
     [0053]FIG. 18 is a front elevational view of a portion of a silent chain of FIG. 17.  
     [0054]FIG. 19 is a perspective view of a bending-restrictive link.  
     [0055]FIG. 20 is a first variant of a bending-restrictive link.  
     [0056]FIG. 21 illustrates a second variant of a bending-restrictive link. (a) is a front elevational view thereof, and (b) is a bottom view thereof.  
     [0057]FIG. 22 illustrates a third variant of a bending-restrictive link. (a) is a front elevational view thereof, and (b) is a bottom view thereof.  
     [0058]FIG. 23 illustrates a fourth variant of a bending-restrictive link. (a) is a front elevational view thereof, and (b) is a bottom view thereof. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0059] First Embodiment  
     [0060] As shown in FIGS. 1 and 2, a silent chain  1  is comprised of a plurality of link plates  2 ,  2 ′ each having a pair of teeth  21  and pin apertures  22 , which are interlaced in lateral and longitudinal directions and pivotably connected by connecting pins  3  inserted in the pin apertures  22 . Guide links  4  are provided on the sides of the outermost link plates  2  to maintain a silent chain  1  in place on a sprocket. A guide link  4  has a pair of pin apertures  42  for receiving ends of the connecting pins  3 .  
     [0061] As shown in FIG. 3, a link plate  2 ′ forms a guide row  2 A disposed at the same position as the guide link  4  along the chain length direction, whereas a link plate  2  forms a link row (or non-guide row)  2 B disposed between the guide rows  2 A adjacent to each other in the chain length direction.  
     [0062] A link plate  2  has a protrusion  20  formed thereon that protrudes in the thickness direction. A protrusion  20 , shown in FIG. 4, is disposed on the link centerline C L  above the pin aperture centerline C P . Also, a link plate  2  has a pair of shoulder portions  23  on opposite sides thereof. A shoulder portion  23  is formed with a flat surface that extends generally perpendicular to the pin aperture centerline C P . A link plate  2 ′ has the same shape as the link plate  2  except that protrusion  20  is not present. In addition, a shoulder portion  23  is not necessarily provided for link plate  2 , as long as it is provided for link plate  2 ′.  
     [0063] Next, a bending direction of a silent chain that is composed in the above-mentioned way will be explained using FIGS. 5 and 6. FIG. 5 indicates the state where each link plate  2 ,  2 ′ has been bent in the engagement direction from the straight pulled state of link plates  2 ,  2 ′. FIG. 6 shows the state where each link plate  2 ,  2 ′ has been bent in the backward or rearward direction.  
     [0064] As shown in FIG. 5, when each link plate  2 ,  2 ′ bends toward the engagement side, or inwardly, each link late  2 ,  2 ′ rotates around each pin aperture  22 . At this time, each shoulder portion  23  of the link plates  2 ′ does not interfere with the protrusion  20  of the link plate  2 , and thus, bending movement of each link plate  2 ,  2 ′ on the engagement side is smoothly conducted. In this case, protrusion  20  of a link plate  2  does not hinder bending movement of each link plate  2 ,  2 ′ at the time of engagement of a silent chain, and does not generate friction loss, either. Chordal oscillation of a silent chain can be restricted without decreasing power transmission efficiency.  
     [0065] In contrast, as shown in FIG. 6, when each link plate  2 ,  2 ′ bends toward the rearward side, or outwardly, due to oscillation such as resonance, each link late  2 ,  2 ′ rotates around each pin aperture  22  in a direction different from the above-mentioned engagement direction. At this time, each shoulder portion  23  of the link plates  2 ′ interferes with the protrusion  20  of the link plate  2 , and thus, bending movement of each link plate  2 ,  2 ′ on the rearward side is restricted. In such a manner, back bending of a silent chain is restricted, thereby causing lateral oscillation of a chain span to be placed mainly on the engagement side. As a result, chordal oscillation of a silent chain may be restricted.  
     [0066] Also, in this case, since a protrusion  20  is provided on the link centerline of a link plate  2 , back bending of two link plates  2 ′ adjacent to the link plate  2  in the thickness direction can be equally restricted. Protrusion  20  is provided only on a link plate  2  in a link row  2 B, but the present invention is not limited to such an embodiment. A similar protrusion may be provided on a link plate  2 ′ in a guide row  2 A. Protrusion  20  is integral with a link plate  2 , but the present invention is not limited to this embodiment.  
     [0067] Furthermore, since a protrusion  20  is formed integrally with a link plate  2  by applying compressive process of press working, such as pressing a distal end of a punch against a surface of a link plate  2 , additional member other than a link plate  2  is not needed, thereby decreasing the number of components.  
     [0068] In addition, in the above-mentioned embodiment, each protrusion  20  of the outermost link plate  2  is disposed between the link plates  2 ′, shown in FIG. 3, but the present invention is not limited to this embodiment. A protrusion  20  of the outermost link plate  2  may be disposed between the adjacent guide links  4 . In this case, at the time of back bending of a silent chain, a shoulder portion of each guide link  4  interferes with a protrusion  20  of a link plate  2 , thereby restricting back bending of a link plate  2  and guide link  4 .  
     [0069]FIGS. 7 and 8 illustrate examples where pins inserting through the link plates form protrusions. In FIG. 7, a pin  25  is provided that penetrates a link plate  2  in a center position among three link plates  2  forming a link row  2 B. The position where pin  25  penetrates a link plate  2  is the same position where a protrusion  20  is formed. Each end portion of a pin  25  extends to the vicinity of each outermost link plate  2 . Pin  25  of FIG. 7 functions in substantially the same way as each protrusion  20  shown in FIG. 3.  
     [0070] In FIG. 8, a pin  25  penetrates two link plates  2 ′ forming a guide row  2 A. Each end portion of a pin  25  extends to the vicinity of each guide link  4 . In this case, at the time of back bending of a silent chain, each shoulder portion of link plates  2  interferes with a pin  25 , thereby restricting back bending of each link plate  2 ,  2 ′.  
     [0071] In both cases shown in FIGS. 7 and 8, a link plate  2  or a guide link  4  that is disposed beside the end of a pin  25  prevents the pin  25  from falling out of a chain. Therefore, pin  25  does not need to be fixed to the link plates  2 ,  2 ′ in which it penetrates.  
     [0072] Although an additional pin needs to be provided discretely from a link plate, a single pin can constitute each protrusion of a plurality of link plates by providing a pin adapted to penetrate a plurality of link plates.  
     [0073] Additionally, in the above-mentioned embodiment, the entire link rows  2 B are composed of link plates with protrusions  20 , but the present invention is not limited to this embodiment. A link row  2 B with protrusions  20  and a link row  2 B without protrusions  20  may be irregularly disposed along the length of a silent chain.  
     [0074] In this case, in a linear chain span between a drive sprocket and a driven sprocket around which a chain is wrapped, a link row  2 B with protrusions  20  and each guide row  2 A on opposite sides thereto are restrained from back-bending, whereas a link row  2 B without protrusions  20  and each guide row  2 A on opposite sides thereto are not restrained from back-bending.  
     [0075] Thereby, in operation, guide rows  2 A that are restrained from back-bending function as nodes of chordal oscillation or chordal action, and each length of chords or spans that are defined by these nodes varies aperiodically in a linear chain span between the sprockets. Resonance can thus be prevented from occurring at any rotational speed and tension.  
     [0076] Second Embodiment  
     [0077] In the second embodiment, a guide link  4  has a protrusion  40 . Protrusion  40  is, as shown in FIG. 12, disposed on a link centerline C L  above pin aperture centerline C P . Each link plate  2 ,  2 ′ forming guide row  2 A and link row  2 B, respectively, doe not have any protrusions. Each link plate  2  forming a link row  2 B has a shoulder portion  23  similar to that of the first embodiment.  
     [0078] Next, a bending direction of a silent chain composed in the above-mentioned way will be explained using FIGS. 13 and 14.  
     [0079]FIG. 13 indicates the state where each link plate  2 ′ has been bent in the engagement direction from the straight pulled state of the link plate  2 ′ and a guide link  4 . When each link plate  2 ′ bends toward the engagement side, or inwardly, each link plate  2 ′ rotates around each pin aperture  22 . Each shoulder portion  23  of the link plates  2 ′ does not interfere with the protrusion  40  of the guide link  4 , and thus, bending movement of each link plate  2 ′ on the engagement side is smoothly conducted. In this case, protrusion  40  of a guide link  4  does not hinder bending movement of each link plate  2 ′ at the time of engagement of a silent chain, and does not generate friction loss, either. Chordal oscillation of a silent chain can be restricted without decreasing power transmission efficiency.  
     [0080]FIG. 14 shows the state where each link plate  2 ′ has been bent in the backward or rearward direction. In contrast to FIG. 13, when each link plate  2 ′ bends toward the rearward side, or outwardly, due to oscillation such as resonance, each link late  2 ′ rotates around each pin aperture  22  in a direction different from the above-mentioned engagement direction. At this time, each shoulder portion  23  of the link plates  2 ′ interferes with the protrusion  40  of the guide link  4 , and thus, bending movement of each link plate  2 ′ on the rearward side is restricted. In such a manner, back bending of a silent chain is restricted, thereby causing lateral oscillation of a chain span to be placed mainly on the engagement side. As a result, chordal oscillation of a silent chain can be restricted.  
     [0081] Since a protrusion  40  is provided on the link centerline of a guide link  4 , back bending of two link plates  2 ′ adjacent to the guide link  4  in the thickness direction can be equally restricted.  
     [0082] Furthermore, since a protrusion  40  is formed integrally with a guide link  4  by applying compressive process of press working, such as pressing a distal end of a punch against a surface of a guide link  4 , additional member other than a guide link  4  is not needed, thereby decreasing the number of components.  
     [0083] In addition, a protrusion  40  may be provided discretely from a guide link  4 . FIGS. 15 and 16 illustrate examples where a pin penetrating a guide link forms a protrusion.  
     [0084] In FIG. 15, a pin  45  is provided on each guide link  4  that penetrates each guide link  4 . The position where pin  45  penetrates guide link  4  is the same position where a protrusion  40  is formed. Each end portion of a pin  45  extends to the vicinity of a link plate  2 ′. A pin  45  of FIG. 15 functions in substantially the same manner as that of each protrusion  40  shown in FIG. 9.  
     [0085] In FIG. 16, a pin  45  penetrates not only a guide link  4  but also the entire link plates  2 ′ composing a guide row  2 A. That is, pin  45  extends over the entire chain in the chain width direction. In this case, at the time of back bending of a silent chain, each shoulder portion of the entire link plates  2  composing a link row  2 B interferes with a pin  45 , thereby restricting beck bending of each link plate  2 ,  2 ′ more securely.  
     [0086] Although an additional pin needs to be provided discretely from a guide link, a single pin can constitute each protrusion of a guide link and a plurality of link plates by providing a pin adapted to penetrate a plurality of link plates in a guide row.  
     [0087] In the above-mentioned embodiment, the entire guide links are provided with protrusions  40 , but the present invention is not limited to this embodiment. A guide link  4  with protrusions  40  and a link  4  without protrusions  40  may be irregularly disposed along the length of a silent chain. Additionally, in both cases of FIGS. 15 and 16, opposite ends of a pin  45  are fixed to each guide link  4 .  
     [0088] In this case, in a linear chain span between a drive sprocket and a driven sprocket around which a chain is wrapped, a guide row  2 A with protrusions  40  and each link row  2 B on opposite sides thereto are restrained from back-bending, whereas a guide row  2 A without protrusions  40  and each link row  2 B on opposite sides thereto are not restrained from back-bending. Thereby, in operation, guide rows  2 A that are restrained from back-bending function as nodes of chordal oscillation or chordal action, and each length of chords or spans that are defined by these nodes varies aperiodically in a linear chain span between the sprockets. Resonance can thus be prevented from occurring at any rotational speed and tension.  
     [0089] Third Embodiment  
     [0090] In the third embodiment, a bending-restrictive link  5  is provided in a link row  2 B. A bending-restrictive link  5 , shown in FIG. 19, is  8 -shaped and has a pair of pin apertures  52 . The bending-restrictive link  5  also has a protrusion  50  that protrudes in the thickness direction. The protrusion  50  is disposed on a link centerline at the upper end of the link  5 . The protrusion  50  is formed by applying a bending process of press working to the link body after blanking the link body. Link plate  2 ′ composing a guide row  2 A has a shoulder portion  23  formed therewith similar to that of the first embodiment.  
     [0091] When each link plate  2 ′ bends toward the engagement side, or inwardly, each shoulder portion  23  of the link plates  2 ′ does not interfere with the protrusion  50  of the bending-restrictive link  5 , and thus, bending movement of each link plate  2 ′ on the engagement side is smoothly conducted. The bending-restrictive link  5  does not hinder bending movement of each link plate  2 ′ at the time of engagement of a silent chain, and does not generate friction loss, either. Chordal oscillation of a silent chain can thus be restricted without decreasing power transmission efficiency.  
     [0092] In contrast, when each link plate  2 ′ bends toward the rearward side, or outwardly, due to oscillation such as resonance, each link late  2 ′ rotates around each pin aperture  22  in a direction different from the above-mentioned engagement direction. At this time, each shoulder portion  23  of the link plates  2 ′ interferes with the protrusion  50  of the bending-restrictive link  5 , and thus, bending movement of each link plate  2 ′ on the rearward side is restricted. In such a manner, back bending of a silent chain is restricted, thereby causing lateral oscillation of a chain span to be placed mainly on the engagement side. As a result, chordal oscillation of a silent chain can be restricted. Also, in this case, since a protrusion  50  is provided on the link centerline of a bending-restrictive link  5 , back bending of two link plates  2 ′ adjacent to the bending-restrictive link  5  in the thickness direction can be equally restricted.  
     [0093] Bending-restrictive link  5  is not limited to an example shown in FIG. 19, but examples shown in FIG. 20 to  23  may be used.  
     [0094] A bending-restrictive link  5  shown in FIG. 20 has a pair of protrusions  53  that protrude in the thickness direction. Each protrusion  53  is disposed symmetrically relative to the link centerline. The protrusions  53  are formed by applying bending process of press working after blanking the link body. A bending-restrictive link  5  shown in FIG. 21 has a protrusion  54 , or upraised portion, protruding in the thickness direction and having a V-shaped cross section by applying compressive process of press working to the center of the link.  
     [0095] Bending-restrictive links  5  shown in FIGS. 22 and 23 have protrusions  55 ,  56  on either side thereof. The protrusion  55  is formed by bending a band-shaped portion, which has been formed in a blanking process, at an acute angle in the link thickness direction. The protrusion  56  is formed by bending a similar band-shaped portion in a V-shape or U-shape in cross section.  
     [0096] At the time of back bending of a silent chain comprised of bending-restrictive links  5  of FIGS. 22 and 23 and protrusions  55 ,  56  interfere with a shoulder portion of a link plate that is adjacent to the bending-restrictive link  5  in the chain length direction on the side of protrusions, thereby restricting bending movement of link plates, and bending of a silent chain can thus be restrained.  
     [0097] Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.