Chain

Abstract

A chain (11) has a plurality of pairs of inner link plates (14) and a plurality of pairs of outer link plates (15), which are arranged so as to be alternately positioned in the series direction. Each pair of inner link plates (14) has a first connection pin (17a) and a second connection pin (17b). At least one of the two outer link plates (15) in each pair has a first engagement groove (21) and a second engagement groove (22). In a state in which the chain (11) extends linearly, the outer link plate (15) having the first engagement groove (21) and the second engagement groove (22) engages, within the second engagement groove (22), with the first connection pin (17a) of the adjacent inner link plate (14) on the rear side in the series direction, and engages, within the first engagement groove (21), with the second connection pin (17b) of the adjacent inner link plate (14) on the front side in the series direction.

Description

chain

[0001] The present disclosure relates to chains.

[0002] Patent document 1 describes a chain in which a plurality of links are connected in series so as to be rotatable, and which is bendable in one direction intersecting the direction of the series, but is not bendable in the opposite direction.

[0003] 35, the chain 60 includes a plurality of connected links 61. The plurality of links 61 are engaged with a sprocket 70. The chain 60 can move forward and backward as the sprocket 70 rotates.

[0004] As shown in Figures 36 and 37, the link 61 includes a block-shaped main body 62, a rotation restricting portion 63, a bearing portion 64, and a pin 65 shown in Figure 35. The rotation restricting portion 63 includes a protruding portion 63a that protrudes upward from the rear end of the main body 62, and a notched recess 63b that is formed by cutting the main body 62 in the vertical direction on the rear surface of the main body 62. The width of the protruding portion 63a in the left-right direction decreases as it extends upward. The width of the notched recess 63b also decreases as it extends upward. The notched recess 63b has a shape that corresponds to the shape of the protruding portion 63a, so that the protruding portion 63a of another link 61 can be accommodated within the notched recess 63b.

[0005] The bearing portion 64 has a pair of cylindrical first bearing portions 64a formed on the left and right above the front end portion of the main body portion 62, and a cylindrical second bearing portion 64b formed below the front end portion of the main body portion 62.

[0006] 35 to 37, the multiple links 61 are rotatably connected by inserting a pin 65 into the first bearing portion 64a and the second bearing portion 64b of adjacent links 61 while they are overlapping each other. When the multiple links 61 are moved in a straight line, the main bodies 62 of the multiple links 61 come into contact with each other. Furthermore, the multiple links 61 are fixed in a straight line by engaging the protruding portion 63a of one link 61 with the notched recess 63b of the link 61 two links ahead.

[0007] The protrusions 63a and the recesses 63b are disengaged from the state in which the links 61 are fixed in a straight line. Then, because the main bodies of the links 61 are in contact with each other and the bearings 64 are located at the front ends of the main bodies 62, the links 61 rotate only in the direction indicated by the arrows in Figure 35. In other words, the chain 60 bends only in one direction intersecting the serial direction in which the links 61 are connected.

[0008] Japanese Patent Application Laid-Open No. 2020-2988

[0009] Incidentally, in the chain 60 of Patent Document 1, when a load is applied to the linear chain 60 in the serial direction of the chain 60, the load is received by the pins 65 connecting adjacent links 61 and by the main bodies 62 of adjacent links 61. The chain 60 of Patent Document 1 has a complex structure because the main bodies 62 of the links 61 are block-shaped and the rotation restricting portions 63 have protrusions 63a and notched recesses 63b.

[0010] A chain according to one aspect of the present disclosure comprises: a plurality of pairs of inner link plates and a plurality of pairs of outer link plates arranged so as to be alternately positioned in a serial direction; a plurality of bushings, each bush connecting two of the inner link plates in a corresponding pair; and a plurality of body pins rotatably inserted into the plurality of bushings, wherein the two outer link plates in each pair are arranged to sandwich two pairs of inner link plates adjacent to each other in the serial direction from the outside, and the two outer link plates in the corresponding pair are arranged on both ends of each body pin, and the plurality of bushings and the plurality of body pins are arranged so that two bushings connect two of the inner link plates in each pair, respectively, and two body pins are positioned between the two outer link plates in each pair. In this chain, if one of the inner link plate and the outer link plate is designated as a first link plate and the other link plate is designated as a second link plate, the first link plate of each pair has a first connecting pin and a second connecting pin that connect the first link plates in that pair, and at least one of the two second link plates in each pair has a first engagement groove and a second engagement groove, and when the chain is extended linearly, the second link plate having the first engagement groove and the second engagement groove engages with the first connecting pin of the adjacent first link plate on the rear side in the serial direction, at the second engagement groove, and also engages with the second connecting pin of the adjacent first link plate on the front side in the serial direction, at the first engagement groove.

[0011] FIG. 1 is a partial perspective view of a chain and sprocket according to a first embodiment. FIG. 2 is a partial perspective view of the chain according to the first embodiment. FIG. 3 is an exploded perspective view schematically showing a portion of the chain according to the first embodiment. FIG. 4 is a partial cross-sectional view taken along line 4-4 in FIG. 2. FIG. 5 is a partial cross-sectional view taken along line 5-5 in FIG. 2. FIG. 6 is a partial left side view of the chain according to the first embodiment. FIG. 7 is a partial left side view of the chain according to the first embodiment with the rear side curved. FIG. 8 is a partial perspective view of the chain according to the second embodiment. FIG. 9 is a partial perspective view of the chain according to the second embodiment from a different angle. FIG. 10 is an exploded perspective view schematically showing a portion of the chain according to the second embodiment. FIG. 11 is a partial cross-sectional view taken along line 11-11 in FIG. 8. FIG. 12 is a partial cross-sectional view taken along line 12-12 in FIG. 8. FIG. 13 is a partial left side view of the chain according to the second embodiment. FIG. 14 is a partial left side view of the chain according to the second embodiment with one link located at the rear end thereof curved. FIG. 15 is a partial left side view of a chain according to a second embodiment, in which a link positioned one step further forward has been bent from the state shown in FIG. 14 . FIG. 16 is a partial right side view of a chain according to a second embodiment. FIG. 17 is a partial right side view of a chain according to a second embodiment, in which a link positioned one step further forward has been bent from the state shown in FIG. 17 . FIG. 18 is a partial right side view of a chain according to a third embodiment, in which a link positioned one step further forward has been bent from the state shown in FIG. 17 . FIG. 19 is a partial perspective view of a chain according to a third embodiment. FIG. 20 is a partial perspective view of a chain according to a third embodiment, from a different angle. FIG. 21 is an exploded perspective view schematically showing a portion of a chain according to the third embodiment. FIG. 22 is a partial cross-sectional view taken along line 22-22 of FIG. 19 . FIG. 23 is a partial cross-sectional view taken along line 23-23 of FIG. 19 . FIG. 24 is a partial left side view of a chain according to a third embodiment. FIG. 25 is a partial left side view of a chain according to a third embodiment, in which a link positioned one step further forward has been bent from the state shown in FIG. 25 . FIG. 26 is a partial left side view of a chain according to a third embodiment, in which a link positioned one step further forward has been bent from the state shown in FIG. 25 . Figure 27 is a partial perspective view of a chain according to a fourth embodiment. Figure 28 is a partial perspective view of the chain according to the fourth embodiment from a different angle. Figure 29 is an exploded perspective view schematically showing a part of the chain according to the fourth embodiment. Figure 30 is a partial cross-sectional view taken along line 30-30 in Figure 27. Figure 31 is a partial cross-sectional view taken along line 31-31 in Figure 27.Fig. 32 is a partial left side view of a chain according to a fourth embodiment. Fig. 33 is a partial left side view of a state in which one link located at the rear end of the chain according to the fourth embodiment is bent. Fig. 34 is a partial left side view of a state in which a link located one link further forward from the state shown in Fig. 33 is bent. Fig. 35 is a partial cross-sectional view of a chain and sprocket according to the prior art. Fig. 36 is a perspective view of a link according to the prior art. Fig. 37 is a perspective view of a link according to the prior art from a different angle.

[0012] <First embodiment> A chain 11 according to the first embodiment will be described. As shown in Figures 1 to 3, the chain 11 of the first embodiment includes a plurality of inner links 12 and a plurality of outer links 13 arranged in the serial direction of the chain 11. The plurality of inner links 12 and outer links 13 are arranged so as to be alternately positioned in the serial direction.

[0013] In the following description, the serial direction in which the multiple inner links 12 and the multiple outer links 13 are connected in series and extend, based on the point where the multiple inner links 12 and the multiple outer links 13 extend linearly, is referred to as the longitudinal direction X. The direction perpendicular to the longitudinal direction X and in which a pair of link plates face each other is referred to as the lateral direction Y. The direction perpendicular to both the longitudinal direction X and the lateral direction Y is referred to as the vertical direction Z.

[0014] The left side of the paper in Fig. 1 is the front in the front-to-back direction X, and the right side is the rear. The back side of the paper in Fig. 1 is the right side in the left-to-right direction Y, and the front side is the left side. The top side of the paper in Fig. 1 is the top in the up-down direction Z, and the bottom side is the bottom side.

[0015] 1, the plurality of inner links 12 and outer links 13 are meshed with a sprocket 50. The chain 11 can move forward and backward in the forward and backward direction X as the sprocket 50 rotates.

[0016] 3 to 5, the inner link 12 includes a pair of inner link plates 14 serving as first link plates that are arranged opposite each other with a distance D1 in the left-right direction Y. The inner link 12 also includes a pair of tubular bushings 16 that are located between the pair of inner link plates 14 and connect the pair of inner link plates 14 together.

[0017] As shown in Figures 3 to 5, the inner link 12 has a pair of pins 17 (hereinafter also referred to as "connecting pins 17") located above the pair of bushings 16. The pair of pins 17 connect the inner link plates 14 in the pair. Therefore, the pair of inner link plates 14 has a pair of pins 17 (connecting pins 17). The connecting pin 17 located at the front is referred to as the first connecting pin 17a, and the connecting pin 17 located at the rear is referred to as the second connecting pin 17b. The connecting pins 17 pass through the pair of inner link plates 14 and protrude outward on both sides in the left-right direction Y.

[0018] As shown in Figures 3 to 5, each outer link 13 includes a pair of outer link plates 15 serving as second link plates, which are arranged opposite each other with a distance D2 in the left-right direction Y of the chain 11. The outer link 13 also includes a rod-shaped pin 18 (hereinafter also referred to as the "main pin 18") rotatably inserted into a bushing 16. The two outer link plates 15 in each pair are arranged to sandwich two pairs of inner link plates 14 adjacent to each other in the fore-and-aft direction X from the outside, and are arranged at both ends of the main pin 18. Therefore, in the chain 11, the multiple pairs of inner link plates 14 and the multiple pairs of outer link plates 15 are arranged alternately in the fore-and-aft direction X. The multiple bushings 16 and the multiple main pins 18 are arranged such that the two bushings 16 connect the two inner link plates 14 in each pair, and the two main pins 18 are located between the two outer link plates 15 in each pair.

[0019] 2 and 3, a pair of outer link plates 15 have the same shape. Each outer link plate 15 has a pair of engagement grooves 20. The engagement groove 20 located at the front is referred to as a first engagement groove 21, and the engagement groove 20 located at the rear is referred to as a second engagement groove 22. Each of the two outer link plates 15 in each pair has a first engagement groove 21 and a second engagement groove 22.

[0020] When the chain 11 is extended linearly, the first connecting pin 17a of each pair of inner link plates 14 engages with the second engaging groove 22 of the adjacent pair of outer link plates 15 on the front side. Also, the second connecting pin 17b of each pair of inner link plates 14 engages with the first engaging groove 21 of the adjacent pair of outer link plates 15 on the rear side.

[0021] The chain 11 will be described in detail below. <Inner Link Plate> As shown in Figure 3, the inner link plate 14 is made of plate material. The inner link plate 14 has a main body 30 and an engaging portion 31 that is continuous with the main body 30. The engaging portion 31 extends upward from the front end of the main body 30 at the upper end of the main body 30 and protrudes further forward than the front end of the main body 30. When the inner link plate 14 is viewed from the left side in the left-right direction Y, the inner link plate 14 has a crank-shaped bent shape due to the engaging portion 31 protruding forward.

[0022] The body portion 30 of the inner link plate 14 has a pair of through holes 30a on both outer sides in the fore-and-aft direction X, sandwiching a center portion in the fore-and-aft direction X. The bushings 16 are press-fitted into the through holes 30a. As will be described later, by press-fitting both ends of the bushings 16 into the through holes 30a of the body portion 30, the inner link plates 14 of the pair are arranged opposite each other with a distance D1 between them.

[0023] As shown in Figure 4, the distance D1 between the pair of inner link plates 14 is not particularly limited, but is preferably 0.6 mm to 55 mm. The engaging portion 31 of the inner link plate 14 has a pair of through holes 31a on both outer sides in the fore-aft direction X, sandwiching the center portion in the fore-aft direction X. The connecting pins 17 are press-fitted into the through holes 31a.

[0024] A line passing through the center of the pair of through holes 30a in the main body portion 30 and a line passing through the center of the pair of through holes 31a in the engagement portion 31 extend parallel to each other. As shown in Figure 4, the thickness T1 of the inner link plate 14 is not particularly limited, but is preferably 0.1 mm or more and 80 mm or less.

[0025] <Outer Link Plate> As shown in Figure 3, the outer link plate 15 is made of plate material. The outer link plate 15 has a main body 40 and an engaging portion 41 that is continuous with the main body 40. The engaging portion 41 extends upward from the front end of the main body 40 at the upper end of the main body 40 and protrudes further forward than the front end of the main body 40. When the outer link plate 15 is viewed from the left side in the left-right direction Y, the outer link plate 15 has a crank-like bent shape due to the engaging portion 41 protruding forward.

[0026] The main body portion 40 of the outer link plate 15 has a pair of main body pin insertion holes 40a on both outer sides in the front-rear direction X, sandwiching the center portion in the front-rear direction X. The main body pins 18 are press-fitted into these main body pin insertion holes 40a.

[0027] As will be described later, both ends of the main pin 18 are press-fitted into the main pin insertion hole 40a of the main body 40, so that the outer link plates 15 of the pair are positioned opposite each other with a gap D2 between them.

[0028] As shown in FIG. 4, the distance D2 between the outer link plates 15 in a pair is not particularly limited, but is slightly larger than the distance D3 between the outer sides of the inner link plates 14 in a pair.

[0029] The distance D2 between the outer link plates 15 of a pair is preferably 0.45 mm or more and 85 mm or less. The thickness T2 of the outer link plates 15 is not particularly limited, but is preferably the same as the thickness T1 of the inner link plates 14.

[0030] As shown in Figure 3, the outer link plate 15 has a pair of engagement grooves 20. The first engagement groove 21 located at the front extends obliquely upward and rearward from below the front end of the engagement portion 41. In other words, the first engagement groove 21 extends at an angle with respect to the fore-and-aft direction X. The width of the first engagement groove 21 is configured to be slightly larger than the outer diameter of the second connecting pin 17b.

[0031] 3, of the pair of engagement grooves 20, the second engagement groove 22 located at the rear extends obliquely downward and forward from above the rear end of the engagement portion 41. In other words, the second engagement groove 22 extends at an angle with respect to the front-rear direction X. The width of the second engagement groove 22 is configured to be slightly larger than the outer diameter of the first connection pin 17a.

[0032] The following description will be based on the outer link plate 15 located on the front side in Figure 6. Figure 6 is a side view of the rear end of the chain 11 as seen from the left side in the left-right direction Y. For convenience, the reference outer link plate 15 is indicated by a thick line.

[0033] 6, the first engagement groove 21 of the outer link plate 15 extends in the direction of rotation (see arrow E) when the outer link plate 15 is rotated around a first main body pin 18a (described later) as the rotation center. When the chain 11 is extended linearly, the first engagement groove 21 engages with the second connecting pin 17b of the first inner link 12a located in front of the outer link plate 15.

[0034] 6, the second engagement groove 22 of the outer link plate 15 extends in the direction of rotation (see arrow F) when the outer link plate 15 is rotated around a second main body pin 18b (described later) as the rotation center. When the chain 11 is extended linearly, the second engagement groove 22 engages with the first connecting pin 17a of the second inner link 12b located behind the outer link plate 15.

[0035] When the chain 11 extends linearly, a line L1 passing through the center of the second connection pin 17b engaged in the first engagement groove 21 and the center of the first connection pin 17a engaged in the second engagement groove 22 extends linearly along the extension direction of the chain 11. Furthermore, when the chain 11 extends linearly, a line L2 passing through the centers of the pair of main body pin insertion holes 40a of the main body 40 extends linearly along the front-to-rear direction X in which the chain 11 extends. Furthermore, the lines L1 and L2 extend parallel to each other.

[0036] 3 and 5, the bushing 16 is configured to have a cylindrical shape. Specifically, the bushing 16 has a cylindrical peripheral wall in a cross section along the radial direction.

[0037] The bushing 16 is formed separately from the pair of inner link plates 14, and both axial ends thereof are press-fitted into through holes 30a in the main body portions 30 of the inner link plates 14. The thickness of the bushing 16, i.e., the thickness T3 of the peripheral wall of the bushing 16, is not particularly limited, but is preferably 0.05 mm or more and 5 mm or less.

[0038] The outer diameter of the bushing 16, i.e., the outer diameter of the peripheral wall of the bushing 16, is not particularly limited, but is preferably 0.4 mm or more and 45 mm or less. The inner diameter of the bushing 16, i.e., the inner diameter of the peripheral wall of the bushing 16, is not particularly limited, but is preferably 0.3 mm or more and 35 mm or less.

[0039] As shown in FIG. 4, the length of the bushing 16 is not particularly limited, but is preferably the same as or slightly smaller than the distance D3 between the outer sides of the inner link plates 14 in a pair.

[0040] 3 and 4, the connection pin 17 is configured in a rod shape. Specifically, the connection pin 17 has a cylindrical shape with a circular outer shape in a cross section along the radial direction.

[0041] The first connection pin 17a is press-fitted into the front through-hole 31a of the engagement portion 31 of the inner link plate 14, and the second connection pin 17b is press-fitted into the rear through-hole 31a. The first connection pin 17a and the second connection pin 17b have the same shape. Both tip ends of the first connection pin 17a and the second connection pin 17b pass through the through-hole 31a and protrude outward on both sides of the pair of inner link plates 14 in the left-right direction Y.

[0042] As shown in Fig. 4, the diameter T4 of the connection pin 17 is not particularly limited, but is preferably 0.3 mm or more and 35 mm or less. Note that Fig. 4 shows the connection pin 17 as viewed from the side.

[0043] 3 and 5, the main pin 18 is configured in a rod shape. Specifically, the main pin 18 has a cylindrical shape with a circular outer shape in a cross section along the radial direction.

[0044] The first main pin 18a is press-fitted into the front main pin insertion hole 40a in the main body portion 40 of the outer link plate 15, and the second main pin 18b is press-fitted into the rear main pin insertion hole 40a. The first main pin 18a and the second main pin 18b have the same shape. The connecting pin 17 and the main pin 18 also have the same shape.

[0045] As shown in Fig. 5, the diameter T5 of the main pin 18 is not particularly limited, but is preferably the same as the diameter T4 of the connection pin 17. Note that Fig. 5 shows the main pin 18 as seen from the side.

[0046] The following describes the material of each component of the chain 11. <Material of Each Component of the Chain> There are no particular restrictions on the material of the components of the chain 11, namely, the inner link plates 14, the outer link plates 15, the bushings 16, the connecting pins 17, and the main pins 18, and any material known for use in chains 11 can be used as appropriate.

[0047] Examples of known materials include metal, resin, etc. Among these, metal is preferable because it can improve mechanical strength. A method for manufacturing the chain 11 will be described below.

[0048] <Method of Manufacturing Chain> The method of manufacturing the chain 11 includes a forming step of forming a metal plate material or the like into a predetermined shape, and an assembly step of assembling the components obtained in the forming step. Each step will be described below.

[0049] (Forming Process) In the forming process, each component is formed using a metal or other plate material. When forming the inner link plate 14 and the outer link plate 15, for example, the plate material is punched into a predetermined shape. The through holes 30a, 31a in the inner link plate 14 and the main body pin insertion holes 40a in the outer link plate 15 can also be formed by punching. The engagement grooves 20 and insertion holes 24 in the outer link plate 15 can also be formed by punching.

[0050] Furthermore, when forming the bushing 16, for example, the plate material is punched into a predetermined shape and then curved into a cylindrical shape. In other words, it is curled into a cylindrical shape. After curling, the ends of the plate material are joined together. Here, joining the ends of the plate material means bringing the ends of the plate material into contact with each other.

[0051] When forming the connection pins 17 and the main body pins 18, for example, a metal rod is drawn and then cut to a predetermined length. After the forming process, a heat treatment process such as quenching may be performed.

[0052] (Assembly Process) In the assembly process, the components obtained in the molding process are assembled to produce the chain 11. As shown in Figure 3, first, a plurality of inner link plates 14 are prepared, and one end of the bushing 16 is press-fitted into two through holes 30a in the main body 30 of each inner link plate 14. Also, one end of the first connection pin 17a and the second connection pin 17b are press-fitted into two through holes 31a in the engaging portion 31 of each inner link plate 14. The tips, which are the one end of the first connection pin 17a and the second connection pin 17b, pass through the through holes 31a and protrude from the inner link plate 14.

[0053] Another inner link plate 14 is attached to the bushing 16, first connection pin 17a, and second connection pin 17b that have been press-fitted into the inner link plate 14. Specifically, the other end of the bushing 16 is press-fitted into the two through holes 30a of the main body 30 of the other inner link plate 14. Also, the other end portions of the first connection pin 17a and the second connection pin 17b are press-fitted into the two through holes 31a of the engagement portion 31 of the other inner link plate 14. The tips, which are the other end portions of the first connection pin 17a and the second connection pin 17b, pass through the through holes 31a and protrude from the inner link plate 14. By repeating the same procedure, multiple inner links 12 are produced.

[0054] Next, a plurality of outer link plates 15 are prepared, and one end of each of the first main pin 18a and the second main pin 18b is press-fitted into the two main pin insertion holes 40a of each outer link plate 15.

[0055] Next, prepare the two inner links 12 manufactured as described above. For the inner link 12 located at the front of the two inner links 12, insert the first main pin 18a, one of the two main pins 18 attached to the outer link plate 15, into the rear bushing 16 of the inner link 12.

[0056] Furthermore, for the inner link 12 that is located rearward of the two inner links 12, the second main pin 18b attached to the outer link plate 15 is inserted into the front bushing 16 of the inner link 12. Furthermore, another outer link plate 15 is attached to the other ends of the first main pin 18a and the second main pin 18b inserted into the bushings 16 of the two inner links 12. Specifically, the other ends of the first main pin 18a and the second main pin 18b inserted into the bushings 16 of the two inner links 12 are press-fitted into the two main pin insertion holes 40a of the other outer link plate 15.

[0057] By the above procedure, the first main pin 18a and the second main pin 18b are joined to the two main pin insertion holes 40a of each of the two outer link plates 15 in the pair. This completes the outer link 13. The two inner links 12 are also connected by one outer link 13.

[0058] The above procedure is repeated to connect the inner links 12 and the outer links 13 so that the inner links 12 and the outer links 13 are positioned alternately in the length direction. The chain 11 can be manufactured by the above procedure. The order in which the components of the chain 11 are assembled can be changed as needed.

[0059] <Operation Mechanism for Releasing Straightened Chain> As shown in Figure 6, to release the straightened state of the chain 11, the inner link 12 is rotated clockwise at any position on the chain 11 around the second main pin 18b as the center of rotation. This disengages the second engagement groove 22 of the outer link plate 15 from the first connecting pin 17a of the inner link 12. Alternatively, the outer link plate 15 is rotated clockwise at any position on the chain 11 around the first main pin 18a as the center of rotation. This disengages the second connecting pin 17b of the inner link 12 from the first engagement groove 21 of the outer link plate 15.

[0060] By repeating at least one of the above operations, the straight state of the chain 11 can be released. As shown in Figure 7, when the straight state of the chain 11 is released, the chain 11 bends only downward, which is a direction that intersects with the serial direction in which the multiple inner links 12 and outer links 13 are connected. The chain 11 can also be straightened by performing an operation opposite to the operation for releasing the straight state described above.

[0061] <Operations and Effects> The operation of the chain 11 of the first embodiment will be described. As shown in Figure 6, when the chain 11 is extended linearly, the tip of the second connecting pin 17b of the first inner link 12a engages with the first engagement groove 21 of the reference outer link plate 15. Furthermore, the tip of the first connecting pin 17a of the second inner link 12b engages with the second engagement groove 22 of the outer link plate 15. In other words, when the chain 11 is extended linearly, the outer link plate 15 having the first engagement groove 21 and the second engagement groove 22 engages with the second connecting pin 17b of the adjacent inner link plate 14 on the front side in the serial direction, in the first engagement groove 21, and also engages with the first connecting pin 17a of the adjacent inner link plate 14 on the rear side in the serial direction, in the second engagement groove 22.

[0062] Furthermore, a line L1 passing through the center of the second connection pin 17b engaged in the first engagement groove 21 and the center of the first connection pin 17a engaged in the second engagement groove 22 extends parallel to a line L2 passing through the centers of the pair of main body pin insertion holes 40a of the main body 40. Furthermore, the lines L1 and L2 extend linearly along the front-to-rear direction X in which the chain 11 extends.

[0063] As shown in FIG. 6 , when a load is applied to the rear end of the chain 11 in a direction pushing it forward along the fore-and-aft direction X (see arrow A), the chain 11 can receive the load at the engagement point between the first connecting pin 17a and the second engaging groove 22 and at the engagement point between the second connecting pin 17b and the first engaging groove 21. The chain 11 can also receive the load at the engagement point between the first main pin 18a and the bushing 16 (see FIG. 3 ) and at the engagement point between the second main pin 18b and the bushing 16 (see FIG. 3 ). That is, the load can be received at two points (arrows a and b) along lines L1 and L2, and the forward-facing load can be distributed and received at two points. Furthermore, because lines L1 and L2 are parallel and extend in the direction of extension of the chain 11, the load can be distributed in a balanced manner. This allows the chain 11 to move linearly in a more stable manner.

[0064] Furthermore, even if a load is applied to the rear end of the chain 11 in a direction pulling it backward (opposite to the direction of arrow A), the first engagement groove 21 and the second engagement groove 22 extend at an angle with respect to the front-to-rear direction X, so that the engagement between these engagement grooves 20 and the connecting pin 17 is unlikely to be released. Therefore, the rearward load is distributed and received at two locations, allowing the chain 11 to move linearly in a more stable state.

[0065] Furthermore, the chain 11 of the first embodiment receives a load through the first engagement groove 21 and the second engagement groove 22 of the outer link plate 15, and the first connecting pin 17a and the second connecting pin 17b of the inner link plate 14. Therefore, the structure of the inner link 12 and the outer link 13 for receiving the load is simplified.

[0066] In addition, by releasing the engagement between the first engagement groove 21 of the outer link plate 15 and the second connecting pin 17b of the inner link 12, or between the second engagement groove 22 of the outer link plate 15 and the first connecting pin 17a of the inner link 12, the chain 11 can be bent only downward.

[0067] The effects of the chain 11 of the first embodiment will be described. (1-1) When the chain 11 is extended linearly, the tip of the second connecting pin 17b of the first inner link 12a engages with the first engagement groove 21 of the outer link plate 15. Also, the tip of the first connecting pin 17a of the second inner link 12b engages with the second engagement groove 22 of the outer link plate 15. Also, the outer link 13 and the first inner link 12a are connected via the first main pin 18a, and the outer link 13 and the second inner link 12b are connected via the second main pin 18b.

[0068] Therefore, the structure of the chain 11 for bearing the load is simplified. The simplified structure of the chain 11 allows the weight of the chain 11 to be reduced. (1-2) When the chain 11 is extended linearly, a load along the front-to-rear direction X can be borne by the engagement points between the first connecting pin 17a and the second engaging groove 22 and the engagement points between the second connecting pin 17b and the first engaging groove 21. The load can also be borne by the engagement points between the first main pin 18a and the bushing 16 and the engagement points between the second main pin 18b and the bushing 16. In other words, the load can be distributed and borne at two points along the lines L1 and L2, allowing for a well-balanced load. This allows the chain 11 to move back and forth in a more stable state, and improves the buckling strength of the chain 11.

[0069] (1-3) By rotating the outer links 13 and the inner links 12 around the first main pin 18a and the second main pin 18b, the chain 11 can be more easily released from its straight state and bent in only one direction. This also makes it easier to straighten the chain 11.

[0070] Second Embodiment A chain 11 according to a second embodiment will now be described. As shown in Figures 8 and 9, the shape of the outer link plates 15 on the left and right sides of a pair of outer link plates 15 in the left-right direction Y is different.

[0071] As shown in Figure 8, the outer link plate 15 located on the left is the second A link plate (hereinafter also referred to as the "second A outer link plate 15a"). The second A outer link plate 15a has the same shape as the outer link plate 15 of the first embodiment and has a first engagement groove 21 and a second engagement groove 22.

[0072] As shown in Figure 9, the outer link plate 15 located on the right is the second B link plate (hereinafter also referred to as the "second B outer link plate 15b"). The second B outer link plate 15b has a main body 40 that is the same shape as the outer link plate 15 of the first embodiment. The second B outer link plate 15b has an engaging portion 41 that is continuous with the main body 40. The engaging portion 41 extends upward from the rear end side of the upper end of the main body 40 and protrudes further rearward than the rear end of the main body 40.

[0073] As shown in Figure 10, the second-B outer link plate 15b has an engaging portion 41 that protrudes rearward, resulting in a crank-shaped bent shape. The engaging portion 41 of the second-B outer link plate 15b has a third engaging groove 23 and an insertion hole 24. The third engaging groove 23 extends diagonally downward and forward from above the rear end of the engaging portion 41. In other words, the third engaging groove 23 extends at an angle relative to the fore-and-aft direction X. The width of the third engaging groove 23 is slightly larger than the outer diameter of the first connecting pin 17a. The insertion hole 24 of the engaging portion 41 of the second-B outer link plate 15b is larger than the outer diameter of the second connecting pin 17b, and the second connecting pin 17b is inserted into it.

[0074] As shown in Figure 10, the inner links 12 have the same shape as the inner links 12 of the first embodiment. As shown in Figures 11 and 12, the arrangement of the outer link plates 15, inner link plates 14, bushings 16, connecting pins 17, and main pins 18 is the same as that of the chain 11 of the first embodiment.

[0075] <Outer Link Plates> The second A outer link plate 15a and the second B outer link plate 15b will now be described with reference to FIGS.

[0076] Figures 13 to 15 are side views of the rear end of the chain 11 as viewed from the left side in the left-right direction Y. Figures 16 to 18 are side views of the rear end of the chain 11 as viewed from the right side in the left-right direction Y. Of the multiple outer link plates 15a shown in Figure 13, the reference second A outer link plate 15a (hereinafter also referred to as the "reference second A outer link plate 15a") is indicated by a thick line. The inner link 12 located forward of the reference second A outer link plate 15a is referred to as the first inner link 12a. The inner link 12 located rearward of the reference second A outer link plate 15a is referred to as the second inner link 12b. Another second A outer link plate 15a (hereinafter also referred to as the "another second A outer link plate 15a") is located behind the second inner link 12b. The inner link 12 located at the rear end of the chain 11, rearward of the other second A outer link plate 15a, is referred to as the third inner link 12c.

[0077] 13, the first engagement groove 21 of the reference second-A outer link plate 15a extends in the direction of rotation (see arrow E) when the outer link 13 is rotated around the first main pin 18a. When the chain 11 is extended linearly, the first engagement groove 21 engages with the second connecting pin 17b of the first inner link 12a.

[0078] 13, the second engagement groove 22 of the reference secondA outer link plate 15a extends in the direction of rotation (see arrow F) when the outer link 13 is rotated around the second main pin 18b. When the chain 11 is extended linearly, the second engagement groove 22 engages with the first connecting pin 17a of the second inner link 12b.

[0079] Of the multiple outer link plates 15b shown in Figure 16, the reference second B outer link plate 15b (hereinafter also referred to as the "reference second B outer link plate 15b") is indicated by a thick line. The first inner link 12a is located in front of the reference second B outer link plate 15b. The second inner link 12b is located behind the second B outer link plate 15b. Another second B outer link plate 15b (hereinafter also referred to as the "another second B outer link plate 15b") is located behind the second inner link 12b. Furthermore, the third inner link 12c is located behind the other second B outer link plate 15b, at the rear end of the chain 11.

[0080] As shown in Figure 16, the reference second-B outer link plate 15b has a third engagement groove 23 and an insertion hole 24 into which the second connecting pin 17b is inserted. The third engagement groove 23 extends in the direction of rotation of the first connecting pin (see arrow G) when the third inner link 12c is rotated around the second main body pin 18b. The insertion hole 24 of the reference second-B outer link plate 15b extends in the direction of rotation of the second connecting pin 17b (see arrow H) when the second inner link 12b is rotated around the second main body pin 18b.

[0081] Similarly, the insertion hole 24 of another secondB outer link plate 15b extends along the rotation direction (see arrow J) of the second connecting pin 17b when the third inner link 12c is rotated around the second main body pin 18b. Therefore, when the third inner link 12c is rotated around the second main body pin 18b, the third inner link 12c can be rotated along the direction in which the second connecting pin 17b moves within the insertion hole 24.

[0082] When the chain 11 is extended in a straight line, the third engagement groove 23 of the reference second B outer link plate 15b engages with the first connecting pin 17a of the third inner link 12c. In addition, within the insertion hole 24, the second connecting pin 17b abuts against the front edge of the insertion hole 24.

[0083] <Operation mechanism when releasing the straightened state of the chain> As shown in Figure 13, when the chain 11 is extended in a straight line, the tip of the second connecting pin 17b of the first inner link 12a engages with the first engagement groove 21 of the reference second-A outer link plate 15a. Also, the tip of the first connecting pin 17a of the second inner link 12b engages with the second engagement groove 22 of the reference second-A outer link plate 15a.

[0084] To release the chain 11 from its straight state, the following three-step procedure is performed: (First Step) In the first step, the third inner link 12c located at the rear end of the chain 11 is rotated clockwise around the second main body pin 18b.

[0085] 14, the second engagement groove 22 of the other second-A outer link plate 15a extends in the direction of rotation (see arrow F) when the second-A outer link plate 15a is rotated around the second main body pin 18b. Therefore, when the third inner link 12c is rotated around the second main body pin 18b, the engagement between the first connecting pin 17a of the third inner link 12c and the second engagement groove 22 is released.

[0086] The state shown in Figure 14 viewed from the right side appears as shown in Figure 17. As shown in Figure 17, by rotating the third inner link 12c, the third engagement groove 23 of the reference second-B outer link plate 15b is disengaged from the first connecting pin 17a of the third inner link 12c. Furthermore, the second connecting pin 17b of the third inner link 12c moves rearward within the insertion hole 24 of another second-B outer link plate 15b located in front of the third inner link 12c. The second connecting pin 17b comes into contact with the rear edge of the insertion hole 24.

[0087] (Second Stage) From the state of FIG. 17 (the state of FIG. 14), the third inner link 12c is further rotated counterclockwise (clockwise in FIG. 14).

[0088] Then, since the second connection pin 17b of the third inner link 12c abuts against the rear edge of the insertion hole 24 of another second B outer link plate 15b, the other second B outer link plate 15b also rotates counterclockwise with the first main body pin 18a as the center of rotation.

[0089] That is, another second B outer link plate 15b located rearward of the reference second B outer link plate 15b rotates counterclockwise together with the third inner link 12c around the first main body pin 18a as the rotation center, resulting in the state shown in Figure 18. When the state in Figure 18 is viewed from the left side, it becomes the state shown in Figure 15.

[0090] 15, the first engagement groove 21 of the other second-A outer link plate 15a and the second connecting pin 17b of the second inner link 12b are disengaged. Here, we will explain the state in which the first connecting pin 17a of the third inner link 12c is engaged with the third engagement groove 23 of the reference second-B outer link plate 15b, as shown in FIG. 16. In this state, rotation of the other second-B outer link plate 15b around the first main pin 18a is restricted.

[0091] This is because the extension direction of the third engagement groove 23 is along the rotation direction (see arrow G) around the second main pin 18b, but not along the rotation direction around the first main pin 18a. Even if an attempt is made to rotate the other second-B outer link plate 15b around the first main pin 18a, the first connecting pin 17a of the third inner link 12c will not be released from its engagement with the third engagement groove 23 of the reference second-B outer link plate 15b. Therefore, the other second-B outer link plate 15b is restricted from rotating counterclockwise around the first main pin 18a.

[0092] In other words, in order to rotate another second B outer link plate 15b around the first main body pin 18a as the center of rotation, it is necessary to rotate the third inner link 12c in advance to release the engagement between the first connection pin 17a and the third engagement groove 23.

[0093] (Third Stage) From the state of FIG. 18 (the state of FIG. 15), the second inner link 12b is further rotated counterclockwise (clockwise in FIG. 15) around the second main body pin 18b as the center of rotation.

[0094] As a result, from the state shown in Figure 18, the engagement between the first connection pin 17a of the second inner link 12b and the third engagement groove of the second B outer link plate (not shown) located forward of the reference second B outer link plate 15b is released.

[0095] By performing the above-described first, second, and third steps in order, the straight state of the chain 11 can be released. The chain 11 bends only downward, which is a direction that intersects with the serial direction in which the multiple inner links 12 and outer links 13 are connected. In addition, the chain 11 can be straightened by performing the opposite operation to the above-described operation that releases the straight state.

[0096] <Operation and Effects> The operation of the chain 11 of the second embodiment will be described. As shown in FIG. 13 , when a load is applied to the rear end of the chain 11 in a direction pushing it forward along the fore-and-aft direction X (see arrow A), the chain 11 can receive the load at the engagement point between the first connecting pin 17 a and the second engaging groove 22, the engagement point between the second connecting pin 17 b and the first engaging groove 21, the engagement point between the first connecting pin 17 a and the third engaging groove 23 (see FIG. 16 ), and the engagement point between the second connecting pin 17 b and the insertion hole 24 (see FIG. 16 ). The chain 11 can also receive the load at the engagement point between the first main pin 18 a and the bushing 16 (see FIG. 10 ) and the engagement point between the second main pin 18 b and the bushing 16 (see FIG. 10 ). That is, the load can be received at two locations (arrows a and b) along lines L1 and L2, and the load acting forward can be distributed and received at two locations. Furthermore, since the lines L1 and L2 extend along the longitudinal direction X in which the chain 11 extends and are parallel to each other, the load is distributed in a well-balanced manner, and the chain 11 can be moved linearly in a more stable state.

[0097] Furthermore, even if a load is applied to the rear end of the chain 11 in a direction pulling it rearward (opposite to the direction of arrow A), the first engagement groove 21, second engagement groove 22, third engagement groove 23, and insertion hole 24 extend at an angle with respect to the front-to-rear direction X, so that the engagement grooves 20 and insertion holes 24 are unlikely to be disengaged from the connecting pin 17. Therefore, the rearward load is distributed and received at two locations along the lines L1 and L2, allowing the chain 11 to move linearly in a more stable state.

[0098] In addition, the chain 11 of the second embodiment receives the load of the connecting pin 17 using the first engagement groove 21, the second engagement groove 22, the third engagement groove 23, and the insertion hole 24, and the structure of the inner link 12 and the outer link 13 for receiving the load is simplified.

[0099] To release the straightened state of the chain 11, the chain 11 can be bent by rotating it in order, starting from the third inner link 12c located at the rear end. The chain 11 is configured so that it cannot be bent from the inner link 12 or outer link 13 located midway along the chain 11. When the straightened state of the chain 11 is released, the chain 11 can only be bent downward.

[0100] The effects of the chain 11 of the second embodiment will be described. (2-1) The second-A outer link plate 15a has a first engagement groove 21 and a second engagement groove 22, and the second-B outer link plate 15b has an insertion hole 24 into which the second connecting pin 17b of the inner link 12 is inserted and a third engagement groove 23 with which the first connecting pin 17a of the inner link 12 engages. When the chain 11 is extended linearly, the second connecting pin 17b and the first connecting pin 17a of the inner link 12 engage with the first engagement groove 21 and the second engagement groove 22. Furthermore, the first connecting pin 17a of the inner link 12, which is located rearward of the third engagement groove 23, engages with the third engagement groove 23.

[0101] Therefore, the structure of the chain 11 for bearing the load is simplified. The simplified structure of the chain 11 allows the weight of the chain 11 to be reduced. (2-2) When the chain 11 is extended linearly, a load acting along the front-to-rear direction X can be received at the engagement points between the first connecting pin 17a and the second engaging groove 22, the engagement points between the second connecting pin 17b and the first engaging groove 21, the engagement points between the first connecting pin 17a and the third engaging groove 23, and the engagement points between the second connecting pin 17b and the insertion hole 24. The load can also be received at the engagement points between the first main pin 18a and the bushing 16 and the engagement points between the second main pin 18b and the bushing 16. In other words, the load can be received in a balanced manner because it can be distributed between two points along the lines L1 and L2. This allows the chain 11 to move back and forth in a more stable state, and improves the buckling strength of the chain 11.

[0102] (2-3) The chain 11 can be bent only downward by rotating the chain 11 in order, starting from the third inner link 12c located at the rear end of the chain 11. The chain 11 is configured so that it cannot be bent from the inner link 12 or the outer link 13 located midway along the chain 11, which allows the chain 11 to be used in a more stable state when it is straightened.

[0103] (2-4) The second-B outer link plate 15b has an insertion hole 24 into which the second connecting pin 17b of the inner link 12 is inserted. Therefore, when the inner link 12 rotates around the second main body pin 18b, the inner link 12 is prevented from rotating excessively relative to the second-B outer link plate 15b. Furthermore, the second-B outer link plate 15b can be rotated in conjunction with the rotation of the inner link 12.

[0104] Third Embodiment A chain 11 according to a third embodiment will now be described. As shown in Figures 19 to 21, each of the two outer link plates 15 in a pair has a two-layer structure in which two outer link plates 15 are stacked. The two outer link plates 15 in a pair have symmetrical shapes in the directions in which they face each other along the left-right direction Y.

[0105] In each outer link plate 15, the outer link plate 15 located on the outside of the two-layer structure is referred to as the 3A outer link plate 15c (first layer), and the outer link plate 15 located on the inside is referred to as the 3B outer link plate 15d (second layer).

[0106] As shown in Figure 21, the third-A outer link plate 15c has the same shape as the second-A outer link plate 15a of the second embodiment. The third-B outer link plate 15d has the same shape as the second-B outer link plate 15b of the second embodiment. Therefore, the third-A outer link plate 15c has a first engagement groove 21 and a second engagement groove 22 in the engagement portion 41. The third-B outer link plate 15d has a third engagement groove 23 and an insertion hole 24 in the engagement portion 41.

[0107] The third-A outer link plate 15c and the third-B outer link plate 15d have their main bodies 40 overlapping each other, with the first main pin 18a press-fitted into the front main pin insertion hole 40a and the second main pin 18b press-fitted into the rear main pin insertion hole 40a. By press-fitting the first main pin 18a and the second main pin 18b, the third-A outer link plate 15c and the third-B outer link plate 15d are integrated.

[0108] The outer link plates 15 have a two-layer structure consisting of a third-A outer link plate 15c and a third-B outer link plate 15d. Therefore, each of the two outer link plates 15 in a pair has a first engagement groove 21, a second engagement groove 22, a third engagement groove 23, and an insertion hole 24.

[0109] As shown in Figures 22 and 23, the arrangement of the outer link plates 15, inner link plates 14, bushings 16, connecting pins 17, and main pins 18 is the same as that of the chain 11 of the first and second embodiments.

[0110] <Outer Link Plates> The third-A outer link plate 15c and the third-B outer link plate 15d will now be described with reference to Figures 24 to 26.

[0111] Figures 24 to 26 are side views of the rear end of the chain 11 as viewed from the left side in the left-right direction Y. Of the multiple two-layer outer link plates 15 shown in Figure 24, the reference third-A outer link plate 15c and third-B outer link plate 15d are indicated by thick lines. The inner link 12 located in front of this third-A outer link plate 15c is referred to as the first inner link 12a. The inner link 12 located behind the third-A outer link plate 15c is referred to as the second inner link 12b. Another third-A outer link plate 15c is located behind the second inner link 12b. The inner link 12 located behind this third-A outer link plate 15c and at the rear end of the chain 11 is referred to as the third inner link 12c.

[0112] 24, the first engagement groove 21 of the reference third-A outer link plate 15c extends in the direction of rotation (see arrow E) when the third-A outer link plate 15c is rotated around the first main pin 18a. When the chain 11 is extended linearly, the first engagement groove 21 engages with the second connecting pin 17b of the first inner link 12a.

[0113] 24, the second engagement groove 22 of the reference third-A outer link plate 15c extends in the direction of rotation (see arrow F) when the third-A outer link plate 15c is rotated around the second main pin 18b. When the chain 11 is extended linearly, the second engagement groove 22 engages with the first connecting pin 17a of the second inner link 12b.

[0114] 24, when the chain 11 is extended in a straight line, the third engagement groove 23 of the third-B outer link plate 15d (shown by a thick line) engages with the first connecting pin 17a of the third inner link 12c. The second connecting pin 17b of the third inner link 12c abuts against the front edge of the insertion hole 24 of another third-B outer link plate 15d.

[0115] <Operation mechanism when releasing the straightened state of the chain> As shown in Figure 24, when the chain 11 is extended in a straight line, the tip of the second connecting pin 17b of the first inner link 12a engages with the first engagement groove 21 of the reference third-A outer link plate 15c. Also, the tip of the first connecting pin 17a of the second inner link 12b engages with the second engagement groove 22 of the reference third-A outer link plate 15c.

[0116] To release the chain 11 from its straight state, the following three-step procedure is performed: (First Step) In the first step, the third inner link 12c located at the rear end of the chain 11 is rotated clockwise around the second main body pin 18b.

[0117] As shown in Figure 25, the second connection pin 17b of the third inner link 12c abuts against the rear edge of the insertion hole 24 of the other third-B outer link plate 15d. As shown in Figure 25, the second engagement groove 22 of the other third-A outer link plate 15c extends in the rotation direction (see arrow F) when the third-A outer link plate 15c is rotated around the second main pin 18b. Therefore, when the third inner link 12c is rotated around the second main pin 18b, the first connection pin 17a of the third inner link 12c is disengaged from the second engagement groove 22 of the other third-A outer link plate 15c. At the same time, the first connection pin 17a of the third inner link 12c is disengaged from the third engagement groove 23 of the reference third-B outer link plate 15d.

[0118] (Second stage) The third inner link 12c is further rotated clockwise from the state shown in Figure 25. Then, because the second connecting pin 17b of the third inner link 12c abuts against the rear edge of the insertion hole 24 of the other third-B outer link plate 15d, the other third-B outer link plate 15d also rotates clockwise around the first main body pin 18a.

[0119] In other words, another 3A outer link plate 15c and a 3B outer link plate 15d located behind the reference 3A outer link plate 15c rotate clockwise together with the third inner link 12c around the first main body pin 18a as the center of rotation, resulting in the state shown in Figure 26.

[0120] 26, the first engagement groove 21 of the other third-A outer link plate 15c and the second connecting pin 17b of the second inner link 12b are disengaged. Here, we will explain the state in which the first connecting pin 17a of the third inner link 12c is engaged with the third engagement groove 23 of the reference third-B outer link plate 15d, as shown in FIG. 24. In this state, the other third-B outer link plate 15d located in front of the third inner link 12c is restricted from rotating counterclockwise around the first main pin 18a.

[0121] This is because the direction in which the third engagement groove 23 extends is along the rotation direction (see arrow G) around the second main body pin 18b, and not along the rotation direction around the first main body pin 18a.

[0122] Even if an attempt is made to rotate the other third-B outer link plate 15d around the first main body pin 18a, the first connecting pin 17a of the third inner link 12c will not be released from engagement with the third engaging groove 23 of the reference third-B outer link plate 15d. Therefore, the other third-B outer link plate 15d located in front of the third inner link 12c is restricted from rotating counterclockwise around the first main body pin 18a.

[0123] In other words, in order to rotate the other third-A outer link plate 15c and the third-B outer link plate 15d around the first main body pin 18a, it is necessary to rotate the third inner link 12c, which must first disengage the first connecting pin 17a from the third engagement groove 23.

[0124] 26, the second inner link 12b can be rotated clockwise around the second main body pin 18b. Rotating the second inner link 12b clockwise disengages the first connecting pin 17a of the second inner link 12b from the second engagement groove 22 of the reference third-A outer link plate 15c. At the same time, the first connecting pin 17a of the second inner link 12b disengages from the third engagement groove 23 of the third-B outer link plate (not shown) that is positioned in front of the reference third-B outer link plate 15d.

[0125] By performing the above-described first, second, and third steps in order, the straight state of the chain 11 can be released. The chain 11 bends only downward, which is a direction that intersects with the serial direction in which the multiple inner links 12 and outer links 13 are connected. In addition, the chain 11 can be straightened by performing the opposite operation to the above-described operation that releases the straight state.

[0126] <Operations and Effects> The operation of the chain 11 of the third embodiment will be described. As shown in FIG. 24 , when a load is applied to the rear end of the chain 11 in a direction pushing it forward along the fore-and-aft direction X (see arrow A), the chain 11 can receive the load at the engagement point between the first connecting pin 17a and the second engaging groove 22, the engagement point between the second connecting pin 17b and the first engaging groove 21, the engagement point between the first connecting pin 17a and the third engaging groove 23, and the engagement point between the second connecting pin 17b and the insertion hole 24. The chain 11 can also receive the load at the engagement point between the first main pin 18a and the bushing 16 (see FIG. 21 ) and the engagement point between the second main pin 18b and the bushing 16 (see FIG. 21 ). In other words, the load can be received at two locations (arrows a and b) along lines L1 and L2, and the load acting forward can be distributed and received at two locations. Furthermore, since the lines L1 and L2 extend along the longitudinal direction X in which the chain 11 extends and are parallel to each other, the load is distributed in a well-balanced manner, and the chain 11 can be moved linearly in a more stable state.

[0127] Furthermore, even if a load is applied to the rear end of the chain 11 in a direction pulling it rearward (opposite to the direction of arrow A), the first engagement groove 21, second engagement groove 22, third engagement groove 23, and insertion hole 24 extend at an angle with respect to the front-to-rear direction X, so that the engagement grooves 20 and insertion holes 24 are unlikely to disengage from the connecting pin 17. The rearward load is distributed and received at two locations along lines L1 and L2, allowing the chain 11 to move linearly in a more stable state.

[0128] 21, in the chain 11 of the third embodiment, both of the two outer link plates 15 in a pair have a double-layer structure, and each has a third-A outer link plate 15c and a third-B outer link plate 15d. This allows the load along the arrow A and the load in the opposite direction to be distributed in a more balanced manner.

[0129] Furthermore, the chain 11 of the third embodiment receives a load through the first engagement groove 21 and second engagement groove 22 of the third-A outer link plate 15c, the third engagement groove 23 and insertion hole 24 of the third-B outer link plate 15d, and the first connecting pin 17a and second connecting pin 17b of the inner link 12. This simplifies the structure of the links for receiving the load.

[0130] To release the straightened state of the chain 11, the chain 11 can be bent by rotating it in order, starting from the third inner link 12c located at the rear end. The chain 11 is configured so that it cannot be bent from the inner link 12 or outer link 13 located midway along the chain 11. When the straightened state of the chain 11 is released, the chain 11 can only be bent downward.

[0131] The effects of the chain 11 of the third embodiment will be described below. (3-1) The third-A outer link plate 15c has a first engagement groove 21 and a second engagement groove 22, and the third-B outer link plate 15d has an insertion hole 24 into which the second connecting pin 17b is inserted, and a third engagement groove 23. When the chain 11 is extended linearly, the first connecting pin 17a, which is located rearward of the third engagement groove 23, engages with the third engagement groove 23.

[0132] Therefore, the structure of the chain 11 for bearing the load is simplified. The simplified structure of the chain 11 allows the weight of the chain 11 to be reduced. (3-2) When the chain 11 is extended linearly, a load acting along the longitudinal direction X can be received at the engagement points between the first connection pin 17a and the second engagement groove 22, between the second connection pin 17b and the first engagement groove 21, between the first connection pin 17a and the third engagement groove 23, and between the second connection pin 17b and the insertion hole 24. The load can also be received at the engagement points between the first main pin 18a and the bushing 16 and between the second main pin 18b and the bushing 16. In other words, the load can be received in a balanced manner because it can be distributed and received at two points along the lines L1 and L2. Therefore, the load can be received in a balanced manner because it can be distributed and received at two points along the lines L1 and L2. This allows the chain 11 to move back and forth in a more stable state, and also improves the buckling strength of the chain 11.

[0133] (3-3) Both of the two outer link plates 15 in the pair have a double-layer structure, and each has a third-A outer link plate 15c and a third-B outer link plate 15d. Therefore, the rear end of the chain 11 can receive a load pushing forward along the fore-and-aft direction X and a load pulling backward in a more balanced and distributed manner.

[0134] (3-4) The chain 11 can be bent only downward by rotating the chain 11 in order, starting from the third inner link 12c located at the rear end of the chain 11. The chain 11 is configured so that it cannot be bent from the inner link 12 or the outer link 13 located midway along the chain 11, which allows the chain 11 to be used in a more stable state when it is straightened.

[0135] (3-5) The third-B outer link plate 15d has an insertion hole 24 into which the second connecting pin 17b of the inner link 12 is inserted. Therefore, when the inner link 12 rotates around the second main body pin 18b, the inner link 12 is prevented from rotating excessively relative to the third-B outer link plate 15d. Furthermore, the third-A outer link plate 15c and the third-B outer link plate 15d can be rotated in conjunction with the rotation of the inner link 12.

[0136] <Fourth Embodiment> A chain 11 according to a fourth embodiment will now be described. As shown in Figures 27 to 31, each of the two outer link plates 15 in a pair has a two-layer structure in which two outer link plates 15 are stacked. The two outer link plates 15 in a pair have symmetrical shapes in the direction in which they face each other along the left-right direction Y. As in the other embodiments, the inner link plate 14 corresponds to the first link plate, and the outer link plate 15 corresponds to the second link plate.

[0137] In each outer link plate 15, the outer link plate 15 located on the outside of the two-layer structure is referred to as the 4A outer link plate 15e (first layer), and the outer link plate 15 located on the inside is referred to as the 4B outer link plate 15f (second layer).

[0138] As shown in Figure 29, the fourth-A outer link plate 15e corresponds to the third-A outer link plate 15d of the third embodiment. That is, the fourth-A outer link plate 15e has a main body portion 40 including a pair of main body pin insertion holes 40a and an engagement portion 41 including the third engagement groove 23. The engagement portion 41 of the fourth-A outer link plate 15e has a recess 25 instead of the insertion hole 24 of the third-A outer link plate 15d. The recess 25 is located above the rear main body pin insertion hole 40a and in front of the third engagement groove 23. The recess 25 is shaped like a notch cut out from the corner of the engagement portion 41 of the fourth-A outer link plate 15e. The recess 25 may have another shape, such as a groove shape.

[0139] The fourth-B outer link plate 15f corresponds to the third-A outer link plate 15c of the third embodiment. That is, the fourth-B outer link plate 15f has a main body portion 40 including a pair of main body pin insertion holes 40a, and an engagement portion 41 including the first engagement groove 21 and the second engagement groove 22.

[0140] The fourth-A outer link plate 15e and the fourth-B outer link plate 15f have their main bodies 40 overlapping each other, with the first main pin 18a press-fitted into the front main pin insertion hole 40a and the second main pin 18b press-fitted into the rear main pin insertion hole 40a. By press-fitting the first main pin 18a and the second main pin 18b, the fourth-A outer link plate 15e and the fourth-B outer link plate 15f are integrated.

[0141] As described above, each of the two outer link plates 15 in a pair has a two-layer structure consisting of the fourth A outer link plate 15 e and the fourth B outer link plate 15 f. Therefore, in this embodiment, each of the two outer link plates 15 in a pair has the first engagement groove 21, the second engagement groove 22, the third engagement groove 23, and the recess 25. In other embodiments, it is sufficient that at least one of the two outer link plates 15 in a pair has the recess 25.

[0142] As shown in Figures 30 and 31 , the configurations of the inner link plates 14, bushings 16, connecting pins 17, and body pins 18 are the same as those of the chain 11 of the third embodiment. However, as shown in Figure 30 , the length of the first connecting pin 17a is longer than the length of the second connecting pin 17b. Specifically, the length of the first connecting pin 17a is longer than the distance D4 between the inner surfaces of the fourth-A outer link plates 15e of each pair of outer link plates 15, and the length of the second connecting pin 17b is shorter than the distance D4. Therefore, the first connecting pin 17a can engage with the fourth-A outer link plate 15e of each pair of outer link plates 15, while the second connecting pin 17b cannot engage with the fourth-A outer link plate 15e of each pair of outer link plates 15. The lengths of the first and second connecting pins 17a, 17b are longer than the distance D2 between the inner surfaces of the fourth-B outer link plates 15f of the paired two outer link plates 15. Therefore, the first and second connecting pins 17a, 17b can engage with the fourth-B outer link plates 15f of the paired two outer link plates 15.

[0143] <Outer Link Plates> The fourth A outer link plate 15e and the fourth B outer link plate 15f will now be described with reference to Figures 32 to 34.

[0144] Figures 32 to 34 are side views of the rear end of the chain 11 as viewed from the left side in the left-right direction Y. Of the multiple two-layer outer link plates 15 shown in Figure 32, the reference outer link plate 15 (15e, 15f) is indicated by a thick line. The inner link 12 connected to the reference outer link plate 15 via the first main pin 18a is referred to as the first inner link 12a. The inner link 12 connected to the reference outer link plate 15 via the second main pin 18b is referred to as the second inner link 12b. The second inner link 12b is connected to another outer link plate 15 via the first main pin 18a. The inner link 12 connected to another outer link plate 15 via the second main pin 18b is referred to as the third inner link 12c.

[0145] 32, the first engagement groove 21 of the reference fourth-B outer link plate 15f extends in the direction of rotation (see arrow E) when the fourth-B outer link plate 15f is rotated around the first main pin 18a. When the chain 11 is extended linearly, the first engagement groove 21 engages with the second connecting pin 17b of the first inner link 12a.

[0146] The second engagement groove 22 of the reference fourth-B outer link plate 15 f extends in the direction of rotation (see arrow F) when the fourth-B outer link plate 15 f is rotated around the second main pin 18 b. When the chain 11 is extended linearly, the second engagement groove 22 engages with the first connecting pin 17 a of the second inner link 12 b.

[0147] The third engagement groove 23 of the reference fourth-A outer link plate 15e extends in the direction of rotation (see arrow G) when another fourth-B outer link plate 15f is rotated around the second main pin 18b. When the chain 11 is extended linearly, the third engagement groove 23 of the reference fourth-A outer link plate 15e engages with the first connecting pin 17a of the third inner link 12c. Furthermore, when viewed from the thickness direction of the fourth-A outer link plate 15e, the recess 25 of the reference fourth-A outer link plate 15e is recessed in the direction of rotation of the first connecting pin 17a of the second inner link 12b around the second main pin 18b. In other words, the recess 25 is recessed so as not to interfere with the rotation range of the first connecting pin 17a around the axis of the second main pin 18b. The second main body pin 18b here refers to the main body pin 18 located at the rear of the pair of main body pins 18 aligned in the front-rear direction X of the second inner link 12b.

[0148] <Operation mechanism when releasing the straightened state of the chain> As shown in Figure 32, when the chain 11 is extended in a straight line, the tip of the second connecting pin 17b of the first inner link 12a engages with the first engagement groove 21 of the reference fourth-B outer link plate 15f. Furthermore, the tip of the first connecting pin 17a of the second inner link 12b engages with the second engagement groove 22 of the reference fourth-B outer link plate 15f. The tip of the first connecting pin 17a of the third inner link 12c engages with the third engagement groove 23 of the reference fourth-A outer link plate 15e. In other words, the reference outer link plate 15 engages with the first inner link 12a, the second inner link 12b, and the third inner link 12c.

[0149] To release the chain 11 from its straight state, the following three-step procedure is performed: (First Step) In the first step, the third inner link 12c located at the rear end of the chain 11 is rotated clockwise around the second main body pin 18b.

[0150] As shown in Figure 33, the first connecting pin 17a of the third inner link 12c approaches the other fourth-A outer link plate 15e. However, because the other fourth-A outer link plate 15e has a recess 25, the first connecting pin 17a of the third inner link 12c does not interfere with the other fourth-A outer link plate 15e in the state shown in Figure 33. In other words, in the state shown in Figure 33, a gap exists between the first connecting pin 17a of the third inner link 12c and the other fourth-A outer link plate 15e in the rotational direction of the third inner link 12c.

[0151] As shown in Figure 33, when the third inner link 12c is rotated around the second main body pin 18b, the first connecting pin 17a of the third inner link 12c is disengaged from the second engaging groove 22 of the other fourth A outer link plate 15e. At the same time, the first connecting pin 17a of the third inner link 12c is disengaged from the third engaging groove 23 of the reference fourth A outer link plate 15e.

[0152] (Second stage) The third inner link 12c is further rotated clockwise from the state shown in Figure 33. This causes the other fourth A outer link plate 15e and the other fourth B outer link plate 15f, which are connected to the third inner link 12c via the second main body pin 18b, to rotate clockwise around the first main body pin 18a.

[0153] That is, the other fourth-A outer link plate 15e and the other fourth-B outer link plate 15f located rearward of the reference fourth-B outer link plate 15f rotate clockwise together with the third inner link 12c around the first main body pin 18a as the rotation center, to the state shown in Figure 34. When the state shown in Figure 34 is reached, the first engagement groove 21 of the other fourth-B outer link plate 15f and the second connecting pin 17b of the second inner link 12b are disengaged from each other.

[0154] 32, the state in which the first connecting pin 17a of the third inner link 12c is engaged with the second engagement groove 22 of the reference fourth-B outer link plate 15f and the third engagement groove 23 of the reference fourth-A outer link plate 15e is described. In this state, the other fourth-A outer link plate 15e located in front of the third inner link 12c is restricted from rotating counterclockwise around the first main pin 18a. This is because the extension direction of the third engagement groove 23 is along the rotation direction (see arrow G) around the second main pin 18b, but not along the rotation direction around the first main pin 18a.

[0155] Even if an attempt is made to rotate the other fourth-A outer link plate 15e around the first main body pin 18a, the first connecting pin 17a of the third inner link 12c will not be released from its engagement with the third engagement groove 23 of the reference fourth-A outer link plate 15e. Therefore, the other fourth-A outer link plate 15e located in front of the third inner link 12c is restricted from rotating counterclockwise around the first main body pin 18a. In other words, in order to rotate the other fourth-A outer link plate 15e and the other fourth-B outer link plate 15f around the first main body pin 18a, the third inner link 12c must be rotated. In other words, the third inner link 12c must be rotated to release the engagement between the first connecting pin 17a and the third engagement groove 23 in advance.

[0156] (Third Stage) In the state shown in Figure 34, the second inner link 12b can be rotated clockwise around the second main body pin 18b. Rotating the second inner link 12b clockwise disengages the first connecting pin 17a of the second inner link 12b from the second engagement groove 22 of the reference fourth-B outer link plate 15f. At the same time, the first connecting pin 17a of the second inner link 12b disengages from the third engagement groove 23 of the third-B outer link plate (not shown), which is positioned in front of the reference fourth-A outer link plate 15e.

[0157] By performing the above-described first, second, and third steps in order, the straight state of the chain 11 can be released. The chain 11 bends only downward, which is a direction that intersects with the serial direction in which the multiple inner links 12 and outer links 13 are connected. In addition, the chain 11 can be straightened by performing the opposite operation to the above-described operation that releases the straight state.

[0158] <Operations and Effects> The operation of the chain 11 of the fourth embodiment will be described. As shown in Figure 32, when a load is applied to the rear end of the chain 11 in a direction pushing it forward along the fore-and-aft direction X (see arrow A), the chain 11 can receive the load at the engagement point between the first connecting pin 17a and the second engaging groove 22, the engagement point between the second connecting pin 17b and the first engaging groove 21, and the engagement point between the first connecting pin 17a and the third engaging groove 23. The chain 11 can also receive the load at the engagement point between the first main pin 18a and the bushing 16 (see Figure 29), and the engagement point between the second main pin 18b and the bushing 16 (see Figure 29). In other words, the load can be received at two locations (arrows a and b) along lines L1 and L2, and the load directed forward can be distributed and received at two locations. Furthermore, since the lines L1 and L2 extend along the longitudinal direction X in which the chain 11 extends and are parallel to each other, the load is distributed in a well-balanced manner, and the chain 11 can be moved linearly in a more stable state.

[0159] Furthermore, even if a load is applied to the rear end of the chain 11 in a direction pulling it backward (opposite to the direction of arrow A), the first engagement groove 21, second engagement groove 22, and third engagement groove 23 extend at an angle with respect to the front-to-rear direction X, so these engagement grooves 20 are unlikely to disengage from the connecting pin 17. The rearward load is distributed and received at two locations along lines L1 and L2, allowing the chain 11 to move linearly in a more stable state.

[0160] 29, in the chain 11 of the fourth embodiment, both of the two outer link plates 15 in a pair have a double-layer structure, and each has a fourth-A outer link plate 15e and a fourth-B outer link plate 15f. This allows the load along the arrow A and the load in the opposite direction to be received in a more balanced and distributed manner.

[0161] Furthermore, the chain 11 of the fourth embodiment receives a load through the first engagement groove 21 and second engagement groove 22 of the fourth-B outer link plate 15f, the third engagement groove 23 of the fourth-A outer link plate 15e, and the first connecting pin 17a and second connecting pin 17b of the inner link 12. This simplifies the structure of the links for receiving the load.

[0162] To release the straightened state of the chain 11, the chain 11 can be bent by rotating it in order, starting from the third inner link 12c located at the rear end. The chain 11 is configured so that it cannot be bent from the inner link 12 or outer link 13 located midway along the chain 11. When the straightened state of the chain 11 is released, the chain 11 can only be bent downward.

[0163] The effects of the chain 11 of the fourth embodiment will be described. (4-1) The fourth-A outer link plate 15e has a third engagement groove 23, and the fourth-B outer link plate 15f has a first engagement groove 21 and a second engagement groove 22. When the chain 11 is extended linearly, the first connecting pin 17a, which is located rearward of the third engagement groove 23, engages with the third engagement groove 23. Therefore, the structure of the chain 11 for receiving a load is simplified. By simplifying the structure of the chain 11, the weight of the chain 11 can be reduced.

[0164] (4-2) When the chain 11 is extended linearly, a load acting along the longitudinal direction X can be received at the engagement points between the first connecting pin 17a and the second engaging groove 22, between the second connecting pin 17b and the first engaging groove 21, and between the first connecting pin 17a and the third engaging groove 23. The load can also be received at the engagement points between the first main pin 18a and the bushing 16 and between the second main pin 18b and the bushing 16. In other words, the load can be received in a balanced manner because it can be distributed between two points along the lines L1 and L2. This allows the chain 11 to move back and forth in a more stable manner, and improves the buckling strength of the chain 11.

[0165] (4-3) Each of the two outer link plates 15 in a pair has a double-layer structure including a fourth-A outer link plate 15e and a fourth-B outer link plate 15f. This allows the chain 11 to receive the load acting on the chain 11 in the forward and backward directions X in a more balanced and distributed manner.

[0166] (4-4) The chain 11 can be bent only downward by rotating the chain 11 in order, starting from the third inner link 12c located at the rear end of the chain 11. The chain 11 is configured so that it cannot be bent from the inner link 12 or the outer link 13 located midway along the chain 11, which allows the chain 11 to be used in a more stable state when it is straightened.

[0167] (4-5) The fourth-A outer link plate 15e has a recess 25. Therefore, as shown in Figures 33 and 34, interference between the fourth-A outer link plate 15e and the first connecting pin 17a can be avoided when the chain 11 moves back and forth. Note that the smaller the turning radius of the chain 11, in other words, the smaller the radius of the sprocket 50, the closer the second connecting pin 17b will be to the fourth-A outer link plate 15e. For this reason, it is preferable that the recess 25 in the fourth-A outer link plate 15e be sized according to the radius of the sprocket 50 that drives the chain 11.

[0168] <Modifications> The first to fourth embodiments (hereinafter also referred to as the present embodiments) can be modified and implemented as follows: The present embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0169] In the present embodiment, the inner link plate 14 is the first link plate and the outer link plate 15 is the second link plate, but this is not limiting. The outer link plate 15 may be the first link plate and the inner link plate 14 may be the second link plate. In other words, the inner link plate 14 and the outer link plate 15 may be interchanged.

[0170] In the third embodiment, the outer link plate 15 has a two-layer structure, and the third-A outer link plate 15c and the third-B outer link plate 15d are integrated by press-fitting the first main pin 18a and the second main pin 18b. However, this is not limited to this embodiment. The means by which the third-A outer link plate 15c and the third-B outer link plate 15d are integrated is not particularly limited. For example, they may be integrated by welding or adhesive. Furthermore, the third-A outer link plate 15c and the third-B outer link plate 15d may be formed from a single plate material. In other words, the outer link plate 15 may have a single-layer structure. For example, the integrated third-A outer link plate 15c and the third-B outer link plate 15d may be produced by punching and press-forming a single plate material. This is the same in the fourth embodiment.

[0171] The outer link plates 15 may have a three-layer structure or more. Similarly, the inner link plates 14 may have a two-layer structure or more. In this embodiment, rollers may be fitted around the bushings 16.

[0172] In the present embodiment, the second-B outer link plate 15b and the third-B outer link plate 15d have the insertion holes 24 into which the second connecting pins 17b are inserted, but this is not limiting. The insertion holes 24 may be grooves. That is, the edges of the insertion holes 24 may reach the outer peripheries of the second-B outer link plate 15b and the third-B outer link plate 15d, and may be formed as engagement grooves cut out from the outer peripheries of the second-B outer link plate 15b and the third-B outer link plate 15d.

[0173] The shapes of the first engagement groove 21, the second engagement groove 22, and the third engagement groove 23 are not limited to those in the present embodiment. The shapes of these engagement grooves 20 can be selected as appropriate.

[0174] 11...chain, 12...inner link, 13...outer link, 14...inner link plate, 15...outer link plate, 17...connecting pin, 17a...first connecting pin, 17b...second connecting pin, 18...main body pin, 18a...first main body pin, 18b...second main body pin, 20...engaging groove, 21...first engaging groove, 22...second engaging groove.

Claims

1. A chain comprising: a plurality of pairs of inner link plates and a plurality of pairs of outer link plates arranged so as to be alternately positioned in the serial direction; a plurality of bushes, each bush connecting two of the inner link plates in a corresponding pair; and a plurality of body pins rotatably inserted into the plurality of bushes, wherein the two outer link plates in each pair are arranged so as to sandwich from the outside two pairs of inner link plates adjacent to each other in the serial direction, and the two outer link plates of the corresponding pair are arranged on both ends of each body pin, and wherein the plurality of bushes and the plurality of body pins are arranged so that the two bushes respectively connect the two inner link plates in each pair and the two body pins are positioned between the two outer link plates in each pair, and wherein if one of the inner link plates and the outer link plates is designated as a first link plate and the other link plate is designated as a second link plate, A chain characterized in that the first link plates of each pair have a first connecting pin and a second connecting pin that connect the first link plates in that pair, and at least one of the two second link plates in each pair has a first engagement groove and a second engagement groove, and when the chain is extended in a straight line, the second link plate having the first engagement groove and the second engagement groove engages with the first connection pin of the adjacent first link plate on the rear side in the serial direction in the second engagement groove, and engages with the second connection pin of the adjacent first link plate on the front side in the serial direction in the first engagement groove.

2. A chain according to claim 1, wherein each of the two second link plates in each pair has the first engagement groove and the second engagement groove.

3. A chain as described in claim 1, wherein, of the two second link plates in each pair, one is designated as the second A link plate and the other is designated as the second B link plate, the second A link plate has the first engagement groove and the second engagement groove, the second B link plate has an insertion hole into which the second connecting pin is inserted and a third engagement groove, and when the chain is extended in a straight line, the adjacent first connecting pin located rearward of the third engagement groove engages with the third engagement groove.

4. A chain as described in claim 1, wherein each of the two second link plates in each pair has the first engagement groove and the second engagement groove, as well as an insertion hole into which the second connecting pin is inserted, and a third engagement groove, and when the chain is extended in a straight line, the adjacent first connecting pin located rearward of the third engagement groove engages with the third engagement groove.

5. A chain as described in claim 1, wherein the two second link plates in each pair each have a two-layer structure, a first layer of the two-layer structure has the first engagement groove and the second engagement groove, and a second layer of the two-layer structure has an insertion hole into which the second connecting pin is inserted and a third engagement groove, and when the chain is extended in a straight line, the first connecting pin of the first link plate of each pair engages with the second engagement groove of the first layer of the corresponding pair of second link plates adjacent to the front side in the serial direction, and the second connecting pin of the first link plate of each pair engages with the first engagement groove of the first layer of the corresponding pair of second link plates adjacent to the rear side in the serial direction, and the adjacent first connecting pin engaged with the third engagement groove of the second layer of the second link plate of each pair is arranged to be adjacent to the rear of the third engagement groove.

6. A chain as described in claim 1, wherein at least one of the two second link plates in each pair has the first engagement groove, the second engagement groove, the third engagement groove, and a recess, and is configured to be rotatable relative to the first link plate via the main body pin located between the two second link plates in that pair that is located on the rear side in the serial direction, wherein when the chain is extended in a straight line, the third engagement groove is engaged with the adjacent first connection pin that is located rearward of the third engagement groove in the serial direction, and wherein the recess is recessed in the rotation direction of the first connection pin, with the main body pin located on the rear side as the rotation center when viewed from the thickness direction of the second link plate.