JP2013064439A - Chain structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chain structure with simple configuration which can prevent a chain from separating radially outward and disengaging from a sprocket wheel.SOLUTION: The chain structure 40 includes: a sprocket wheel 42 whose outer peripheral part is formed with a plurality of teeth; and a chain 12 which is wound at the outer peripheral part of the sprocket wheel 42 and has an engaging part 16e engaging with the teeth, wherein a side plate part 46 is disposed at either one end or both ends of the sprocket wheel 42 in an axial direction.

Description

  The present invention relates to, for example, a chain structure used in a chain transmission device that transmits a driving force to a sludge scraping plate of a sludge scraping machine.

  The sludge scraping machine is installed in the sewage treatment tank of the sewage treatment facility, etc., and sludge consisting of various components accumulated at the bottom of the sewage treatment tank is removed from one end of the bottom of the sewage treatment tank by the sludge scraping plate. The collected sludge was sucked out by a pump and transported to the next treatment facility outside the sewage treatment tank.

  FIGS. 7 to 12 are views referred to for explaining the conventional chain structure 2 used in the chain transmission device of the sludge scraper installed in the sewage treatment tank.

  As shown in FIG. 7, this conventional chain structure 2 is wound around a driving sprocket wheel 4, driven sprocket wheels 6, 8, 10 and these sprocket wheels 4, 6, 8, 10. The endless chain 12 and a plurality of flight plates 14 (sludge scraping plates) provided at predetermined intervals in the length direction of the chain 12 are configured (see Patent Document 1). .

  In FIG. 7, only one of the sprocket wheels 4, 6, 8, 10 and the chain 12 is shown, but each of these components is provided in pairs so as to face each other in the direction perpendicular to the paper surface in FIG.

  Further, since both ends of the flight plate 14 are fixed to the pair of chains 12, the chain 12 circulates in the length direction (clockwise direction in FIG. 7) by the rotational operation of the driving sprocket wheel 4. It was supposed to move as it moved.

  Then, the flight plate 14 moves in the leftward arrow direction in FIG. 7 along the bottom surface 3a of the sewage treatment tank 3 in the lower part of FIG. It was supposed to be collected in the sludge storage part 3b on the side.

  As shown in FIG. 8B, the sprocket wheel 4 of the conventional chain structure 2 includes a cylindrical boss portion 4b having a shaft hole 4a penetrating the length direction (left and right direction in the figure). The boss portion 4b is constituted by a disk-shaped tooth forming portion 4c protruding outward in the radial direction (radial direction of the sprocket wheel 4 in FIG. 8A) from the central portion in the length direction.

  And as shown to Fig.8 (a), in the outer peripheral part of the tooth | gear formation part 4c of the sprocket wheel 4, the tooth top part 4d (convex part) and the tooth bottom part 4e (recessed part) are alternated in the circumferential direction. It was supposed to be formed repeatedly.

  Such a sprocket wheel 4 is driven by a driving device such as a motor (not shown) via a rotating shaft 20 (see FIG. 10) attached to the shaft hole 4a so as not to rotate relative to the shaft hole 4a. It was supposed to rotate.

  As shown in FIGS. 9A and 9B, the chain 12 of the chain structure 2 includes a plurality of link plates 16 each having a pair of side plate portions 16c and 16d facing each other. They were connected in series in the length direction (left-right direction in the figure).

  That is, as shown in FIG. 9A, the left end portion of the link plate 16 in the figure is formed with a small interval between the pair of side plate portions 16c and 16d, and the right end portion in the figure is the pair of side plates. The interval between the portions 16c and 16d is formed large.

  Then, the outer side of the pair of side plate portions 16c and 16d having a smaller interval between the left end portions in FIG. 9A of the link plate 16 is a pair of the other link plate 16 having a larger interval between the right end portions in the drawing. The side plate portions 16c and 16d are connected to each other so that the end portions of the side plate portions 16c and 16d are overlapped with each other.

  These link plates 16 are connected to each other in such a manner that their respective ends can be rotated relative to each other by connecting pins 17 that are inserted through through holes 16a, 16b, 16a formed at the ends of the respective side plate portions 16c, 16d. It was like that.

  Further, the link plate 16 of the chain 12 connects the left end portions in FIG. 9A of the pair of side plate portions 16c and 16d arranged to face each other, and has a circular connection portion 16e (engagement). The chain 12 is formed by a pair of side plate portions 16c, 16d and adjacent connecting portions 16e, 16e between the connecting portions 16e, 16e of the two link plates 16, 16 connected to each other. It has a configured void S.

  As shown in FIG. 10, a part of the chain 12 is wound around the outer peripheral portion of the tooth forming portion 4 c of the sprocket wheel 4. That is, the chain 12 has a toothed portion 4d of the sprocket wheel 4 inserted into the gap S in the wound portion, and a connecting portion 16e is connected to the tooth bottom portion 4e of the sprocket wheel 4 and the toothed portion. The engaging portion 4f as a step portion between 4d and the tooth bottom portion 4e is engaged.

  Such a chain 12 is also wound around the outer peripheral portions of other driven sprocket wheels 6, 8, and 10 as shown in FIG. .

  For this reason, when the sprocket wheel 4 rotates, the chain 12 circulates in the length direction (clockwise direction in the figure).

  Then, as shown in FIG. 10, the lower end portion of the attachment 18 is fixed to the outer surface of each link plate 16 of the chain 12 by screw fastening means using bolts and nuts (not shown). It was like that.

  A flight plate 14 having a substantially U-shaped outer shape viewed from its side is fixed to the attachment 18 via a spacer 19 by screw fastening means using bolts and nuts (not shown). It was like that.

  In the conventional chain structure 2, as shown in FIG. 11, the pair of sprocket wheels 4 as described above are arranged facing each other at positions separated from each other in the left-right direction in the drawing. A pair of chains 12 provided with the attachment 18 as described above are wound around these sprocket wheels 4.

  The other sprocket wheels 6, 8, 10 were also arranged opposite to each other at positions separated from each other in the left-right direction in the figure, similarly to the sprocket wheel 4 shown in FIG. 11. A pair of chains 12 provided with attachments 18 are also wound around these sprocket wheels 6 and the like.

  Since the pair of sprocket wheels 4 arranged opposite to each other are attached to the same rotating shaft 20, they rotate in synchronization with each other via the rotating shaft 20. The pair of chains 12 wound around the wheel 4 also moved in synchronization with each other.

  The pair of attachments 18 are spanned between the respective upper end portions in FIG. 11 and are configured to integrally fix the long flight plate 14 having a length in the left-right direction. Is moved in a direction perpendicular to the length direction of the pair of chains 12 in the length direction (the direction perpendicular to the paper surface in the figure).

  Therefore, as shown in FIG. 7, the conventional chain structure 2 can scrape the sludge accumulated on the bottom surface 3a by the movement of the flight plate 14 fixed to the chain 12 in the sludge reservoir 3b on the left side in the figure. It was supposed to be.

JP 2002-273105 A

  However, the chain 12 in the conventional chain structure 2 has the following problems because the connecting part 16e of the link plate 16 is only engaged with the tooth bottom part 4e and the engaging part 4f of the sprocket wheel 4. .

  That is, when the water in the sewage treatment layer 3 is shaken due to an earthquake or the like and a large wave is generated and the force of the wave is applied to the chain 12 or the flight board 14, as shown in FIG. There was a possibility that the sprocket wheel 4 was disengaged and the chain 12 was removed.

  Since the chain 12 in the conventional chain structure 2 is formed of plastic having the advantage of not corroding, it is lighter than, for example, a chain formed of steel, and is easily affected by buoyancy. There is a problem that the chain 12 is likely to be detached from the sprocket wheel 4 due to the force.

  In view of the above problems, an object of the present invention is to provide a chain structure that has a simple structure and that can prevent the chain from being separated from the sprocket wheel by separating outward from its radius. Is.

In order to solve the above problems, the chain structure according to the present invention is:
A sprocket wheel having a plurality of teeth formed on its outer periphery,
In the chain structure provided with a chain having an engaging portion that is wound around the outer peripheral portion of the sprocket wheel and engages with the teeth,
A side plate is provided at one end or both ends in the axial direction of the sprocket wheel.

Moreover, the chain structure according to the present invention includes:
The side plates are respectively provided on end surfaces opposite to the opposing end surfaces of the pair of sprocket wheels arranged so that the end surfaces face each other.

Moreover, the chain structure according to the present invention includes:
The side plates are respectively provided on opposite end face sides of a pair of sprocket wheels arranged so that the end faces thereof face each other.

Moreover, the chain structure according to the present invention includes:
The side plates are provided at both ends in the axial direction of the sprocket wheel.

Moreover, the chain structure according to the present invention includes:
The outer shape of the side plate is a circular shape.

Moreover, the chain structure according to the present invention includes:
The outer shape of the side plate is formed in a polygonal shape.

Moreover, the chain structure according to the present invention includes:
The side plate is formed in a tapered shape so that the peripheral end portion of the surface on the sprocket wheel side is separated from the sprocket wheel as it goes radially outward.

Moreover, the chain structure according to the present invention includes:
The side plate is bent so that the peripheral end portion of the surface on the sprocket wheel side is separated from the sprocket wheel as it goes radially outward.

According to such a chain structure of the present invention,
A sprocket wheel having a plurality of teeth formed on its outer periphery,
In the chain structure provided with a chain having an engaging portion that is wound around the outer peripheral portion of the sprocket wheel and engages with the teeth,
By providing a side plate at one end or both ends in the axial direction of the sprocket wheel,
The structure is simple, and the chain can be prevented from being separated from the sprocket wheel by separating outward from its radius.

It is the elements on larger scale which expand and show the sprocket wheel 42 and its vicinity in the chain structure 40 which concerns on the 1st Embodiment of this invention, and a part is fractured | ruptured. It is CC sectional view enlarged sectional drawing in the chain structure 40 shown in FIG. FIG. 3A is a front view of the sprocket wheel 42 shown in FIG. 1, and FIG. 3B is an enlarged sectional view taken along the line DD in FIG. 3A. It is a figure for demonstrating the side-plate part 46 in the chain structure 40, Comprising: It is the partial expanded side sectional view which expands and shows one of the sprocket wheels 42 shown in FIG. It is a partial expanded side sectional view which expands and shows the sprocket wheel 62 and its vicinity in the chain structure 60 which concerns on the 2nd Embodiment of this invention. FIG. 6A is a front view of the sprocket wheel 62 shown in FIG. 5, and FIG. 6B is a cross-sectional view taken along line EE in FIG. 6A. It is a schematic sectional drawing which shows the whole structure of the chain structures 2 and 40 provided in the sludge scraper. FIG. 8A is a front view of the sprocket wheel 4 shown in FIG. 7, and FIG. 8B is a cross-sectional view taken along line AA in FIG. 8A. 9A and 9B are views showing the chain 12 shown in FIG. 7, in which FIG. 9A is a partially broken top view, and FIG. 9B is a rear view thereof. FIG. 8 is a partially enlarged front view showing the sprocket wheel 4 shown in FIG. FIG. 11 is an enlarged sectional view taken along line BB in the conventional chain structure 2 shown in FIG. 10. It is a figure for demonstrating the phenomenon in which the chain 12 in the conventional chain structure 2 remove | deviates from the sprocket wheel 4, Comprising: It is the partial expanded side view which expands and shows one of the sprocket wheels 4 shown in FIG.

  Hereinafter, the form for implementing the chain structure concerning the present invention is concretely explained based on a drawing.

  FIGS. 1 to 4 are views referred to for explaining a chain structure 40 according to the first embodiment of the present invention. In the chain structure 40 shown in these drawings, the same parts as those of the conventional chain structure 2 are denoted by the same reference numerals, and redundant description of the same structure as the conventional one is omitted except for a part thereof. Shall.

  As shown in FIGS. 1 and 2, the chain structure 40 according to the present embodiment has a sprocket wheel 42 instead of the sprocket wheel 2 in the conventional chain structure 2, and an outer peripheral portion of the sprocket wheel 42. This is different from the conventional chain structure 2 in that the chain 12 is wound around the chain 12.

  That is, as shown in FIG. 7, the chain structure 40 according to the present embodiment includes a driving sprocket wheel 42, driven sprocket wheels 56, 57, 58, and these sprocket wheels 42, 56, 57, An endless chain 12 wound around 58 and a plurality of flight plates 14 provided at predetermined intervals in the length direction of the chain 12 are configured.

  3B, the sprocket wheel 42 of the chain structure 40 includes a main body 44 and a pair of side plates 46 (side plates) provided at both ends of the main body 44 in the axial direction. Has been.

  A main body 44 of the sprocket wheel 42 has a cylindrical boss portion 44b having an axial hole 44a penetrating in the axial direction (left-right direction in the figure), and a radial direction (figure of the axial direction central portion of the boss portion 44b). It is comprised by the disk-shaped tooth | gear formation part 44c formed in the outer side (middle up-down direction).

  As shown in FIG. 3A, a tooth tip portion 44d (protrusion portion) and a tooth bottom portion 44e (concave portion) are alternately formed on the outer periphery of the tooth forming portion 44c of the main body portion 44 of the sprocket wheel 42. It is formed repeatedly in the circumferential direction.

  As shown in FIG. 3 (b), the sprocket wheel 42 has a side plate portion 46 on its inner side surface 46b on both ends of the boss portion 44b at both ends in the axial direction of the boss portion 44b of the main body portion 44, respectively. It is integrally fixed in contact with the end face 44g.

  The side plate portion 46 of the sprocket wheel 42 has a shaft hole 46a that is coaxial with the shaft hole 44a of the boss portion 44b of the main body portion 44 and has substantially the same diameter, and the outer shape thereof is formed in a circular plate shape. .

  An inner side surface 46b is formed on the main body 44 side of the side plate portion 46, and the peripheral end portion of the inner side surface 46b is separated from the sprocket wheel 42 toward the outer peripheral surface 46d. A tapered surface 46c is formed so as to reduce the thickness dimension.

  The chain 12 of the chain structure 40 is made of plastic, and as shown in FIG. 1, a part of the length of the chain 12 is wound around the outer peripheral portion of the tooth formation portion 44 c of the sprocket wheel 42. ing.

  That is, in the chain 12, the tooth tip portion 44 d of the sprocket wheel 42 is inserted into the gap S (see FIG. 9) between the adjacent connecting portions 16 e and 16 e in the wound portion, and the connecting portion 16e is engaged with a tooth bottom portion 44e of the sprocket wheel 42 and an engaging portion 44f as a step portion between the tooth tip portion 44d and the tooth bottom portion 44e.

  As shown in FIG. 7, the chain 12 is also wound around the outer peripheral portions of the driven sprocket wheels 56, 57, and 58 other than the driving sprocket wheel 42. The sprocket wheel 42 and the like rotate and circulate in the length direction (clockwise direction in the figure).

  As shown in FIG. 2, the chain structure 40 includes the sprocket wheel 42 (56, 57, 58), the chain 12, the attachment 18, and the like arranged at positions separated from each other in the left-right direction in the drawing. Similar to these, another set of sprocket wheels 42 (56, 57, 58), the chain 12, the attachment 18, and the like are arranged so as to face each other.

  Since the pair of sprocket wheels 42 arranged to face each other are attached to the same rotating shaft 20, they rotate in synchronization with each other via the rotating shaft 20. The pair of chains 12 wound around the sprocket wheels 42 are also moved in synchronization with each other.

  And a pair of attachment 18 is spanned between the upper end parts in each figure, and the elongate flight board 14 which has length in the left-right direction in the figure is fixed integrally. For this reason, the flight plate 14 moves in a direction perpendicular to its own length direction (perpendicular to the paper surface in FIG. 2) along with the movement of the pair of chains 12 synchronized in the length direction.

  As shown in FIG. 2, the outer peripheral surface 46 d of the side plate portion 46 of the sprocket wheel 42 is radially outward from the outline of the chain 12 engaged with the tooth forming portion 44 c of the main body portion 44 (upper side in the drawing). The diameter is set to be formed as follows.

  Further, the outer peripheral surface 46d of the side plate portion 46 does not contact the inner surface 14a on the inner side (sprocket wheel 42 side) of the flight plate 14 (sprocket wheel 42 side) fixed to the attachment 18 of the chain 12 in the length direction thereof. The radial dimension is set so as to be located on the radially inner side of the sprocket wheel 42 with respect to the trajectory of the inner surface 14a of the flight plate 14 at the time of movement.

  The pair of side plate portions 46 of the sprocket wheel 42 is set to have such a distance that the chain 12 is sandwiched between the inner side surfaces 46b and 46b in a non-contact state.

  As shown in FIG. 4, such a chain structure 40 is perpendicular to the length direction of the chain 12 even when the link plate 16 of the chain 12 is lifted off the tooth forming portion 44 c of the sprocket wheel 42. One end portion in the width direction (left and right direction in the drawing) (one end portion of the connecting pin 17) comes into contact with the tapered surface 46c radially outward from the inner side surface 46b of the pair of side plate portions 46, and the chain 12 has its travel locus. Can be prevented from coming off in the width direction.

  Since the sprocket wheel 42 is formed with a pair of side plate portions 46, the chain 12 comes into contact with the tapered surface 46 c radially outside the inner side surfaces 46 b of the pair of side plate portions 46, and in the length direction thereof. Guided while adjusting the vertical position in the width direction.

  For this reason, the portion of the chain 12 where the link plate 16 is about to come off from the tooth forming portion 44c of the sprocket wheel 42 is restored to the position of the tooth forming portion 44c of the sprocket wheel 42 again, It can be engaged.

  Further, the water in the sewage treatment layer 3 is shaken due to an earthquake or the like, and a large wave is generated. For example, the chain 12 wound between the sprocket wheels 56 and 42 shown in FIG. Even when the chain 12 is greatly deviated in the direction and deviated from the traveling locus, the chain 12 comes into contact with the tapered surfaces 46c and the inner side surfaces 46b of the pair of side plate portions 46 when the chain 12 is wound around the sprocket wheel 42. Therefore, it is possible to return to the normal traveling locus from the state deviated from the traveling locus of the chain 12.

  According to such a chain structure 40 according to the present embodiment, the water in the sewage treatment layer 3 is shaken by an earthquake or the like to generate a large wave, and the force of the wave is applied to the chain 12 or the flight board 14. Even in this case, the chain 12 can be prevented from coming off the sprocket wheel 42.

  Further, in the chain structure 40 according to the present embodiment, it is possible to prevent the chain 12 from coming off the sprocket wheel 42 even if the chain 12 is made of plastic.

  In addition, since the chain structure 40 according to the present embodiment is simple in structure, it can be easily manufactured and attached.

  Therefore, as described above, according to the chain structure 40 according to the present embodiment, the structure is simple, and the chain 12 is separated from the sprocket wheel 42 at a distance outward from the radius. Can be prevented.

  5 and 6 are views referred to for explaining a chain structure 60 according to the second embodiment of the present invention.

  The chain structure 60 according to the present embodiment has a sprocket wheel 62 instead of the sprocket wheel 42 in the chain structure 40 according to the first embodiment, and the chain 12 is disposed on the outer periphery of the sprocket wheel 62. The chain structure 40 is different from the chain structure 40 according to the first embodiment in that it is wound around.

  That is, as shown in FIG. 6B, the sprocket wheel 62 of the chain structure 60 is integrally provided at the right end portion in the drawing in the axial direction of the main body portion 44 and the boss portion 44b of the main body portion 44. It is comprised by the side plate part 66 (side plate).

  As shown in FIGS. 6A and 6B, the side plate portion 66 of the sprocket wheel 62 has a shaft hole 66a that is coaxial with the shaft hole 44a of the boss portion 44b of the main body portion 44 and has substantially the same diameter. The outer shape is formed in a polygonal plate shape.

  And the bending part 66c bent to the axial direction outer side of the main-body part 44 follows the outer peripheral surface 66d so that the peripheral edge part of the outer peripheral surface 66d vicinity may leave | separate from the main-body part 44 as it goes to the radial direction outer side. It is formed as follows.

  The bent portion 66c of the side plate portion 66 adjusts the position in the width direction perpendicular to the length direction of the chain 12 in the same manner as the tapered surface 46c of the side plate portion 46 according to the first embodiment. Thus, it is possible to prevent the movement track 12 from deviating in the width direction.

  In the pair of sprocket wheels 62 of the chain structure 60, as shown in FIG. 5, the side plate portions 66 are disposed on the pair of end surfaces opposite to the end surfaces on the opposite sides of the pair of main body portions 44, respectively. It has become.

  Also with the chain structure 60 according to the second embodiment of the present invention, the same effect as that of the chain structure 40 according to the first embodiment can be obtained. That is, the structure is simple, and it is possible to prevent the chain 12 from being separated from the sprocket wheel 62 away from the radius outward.

  In the chain structure 60 according to the second embodiment, the pair of sprocket wheels 62 has the side plate portions 66 arranged on the end surfaces opposite to the end surfaces of the pair of main body portions 44 facing each other. However, the side plate portions 66 may be arranged on the end surfaces of the pair of main body portions 44 facing each other.

  Further, in the sprocket wheel 42 and the like in the first embodiment, nothing is provided between the tooth forming portion 44 c of the main body portion 44 and the inner side surface 46 b of the side plate portion 46, and the side plate portion 46 is provided on the main body portion 44. However, for example, the side plate portion 46 and the like may be provided on the main body portion 44 with a spacer interposed between the tooth forming portion 44c and the inner side surface 46b of the side plate portion 46.

  In order to interpose a spacer between the tooth forming portion 44c and the inner side surface 46b of the side plate portion 46, the main body portion and the side plate portion are fastened by screwing a nut to a male screw portion of a bolt that is inserted through the through holes formed in the spacer. May be fixed integrally. By comprising in this way, a tooth | gear formation part and a side-plate part can be connected by a spacer, and it can reinforce so that it may not mutually approach and space apart.

  Further, in the sprocket wheel 42 and the like in the first embodiment, the main body portion 44 and the side plate portion 46 and the like are separate members, and they are integrally fixed. And the side plate portion may be integrally formed from the same member. Similarly, the boss portion and the tooth forming portion of the main body portion may be integrally formed from the same member.

  Further, the outer shape of the side plate portion 46 and the like in the first embodiment is formed in a circular shape or a polygonal shape, but is not limited to this, and is formed in another shape. You may come to be.

  In addition, a chain structure different from these embodiments may be configured by appropriately combining the structures of the chain structure 40 and the like according to the first embodiment.

  In the chain structure 40 and the like according to the first embodiment, the present invention is applied to the driving sprocket wheel and the driven sprocket wheel. The present invention may be applied only to any one of the driven sprocket wheels or all of the plurality of driven sprocket wheels.

2 Chain structure 3 Sewage treatment tank 3a Bottom surface 3b Sludge storage part 4 Sprocket wheel 4a Shaft hole 4b Boss part 4c Tooth formation part 4d Tooth part 4e Tooth bottom part 4f Engagement part 6, 8, 10 Sprocket wheel 12 Chain 14 Flight board 14a Inner side surface 16 Link plate 16a, 16b Through hole 16c, 16d Side plate portion 16e Connecting portion 17 Connecting pin 18 Attachment 19 Spacer 20 Rotating shaft 40 Chain structure 42 Sprocket wheel 44 Main body portion 44a Shaft hole 44b Boss portion 44c Tooth forming portion 44d Tooth tip Part 44e tooth bottom part 44f engaging part 44g end face 46 side plate part 46a shaft hole 46b inner side surface 46c taper surface 46d outer peripheral surface 56, 57, 58 sprocket wheel 60 chain structure 62 sprocket wheel 66 side plate part 66a shaft hole 66b inside Surface 66c bent portion 66d outer peripheral surface S void portion

Claims (8)

A sprocket wheel having a plurality of teeth formed on its outer periphery,
In the chain structure provided with a chain having an engaging portion that is wound around the outer peripheral portion of the sprocket wheel and engages with the teeth,
A chain structure comprising a side plate at one end or both ends in the axial direction of the sprocket wheel.   2. The chain structure according to claim 1, wherein the side plates are respectively provided on end surfaces opposite to end surfaces of the pair of sprocket wheels arranged so that the end surfaces thereof face each other.   The chain structure according to claim 1, wherein the side plates are respectively provided on opposite end face sides of a pair of sprocket wheels arranged so that the end faces thereof face each other.   The chain structure according to claim 1, wherein the side plates are provided at both ends of the sprocket wheel in the axial direction.   The chain structure according to any one of claims 1 to 4, wherein an outer shape of the side plate is formed in a circular shape.   The chain structure according to any one of claims 1 to 4, wherein an outer shape of the side plate is formed in a polygonal shape.   The said side plate is formed in the taper shape so that the peripheral edge part of the surface at the side of the said sprocket wheel may go away from the said sprocket wheel as it goes to a radial direction outer side. Chain structure.   The chain according to any one of claims 1 to 6, wherein the side plate is bent so as to be separated from the sprocket wheel as a peripheral end portion of a surface on the sprocket wheel side goes radially outward. Construction.

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