JP2017047394A - Treatment apparatus for fermentation of organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely feed air while reducing cost in a treatment apparatus for fermentation of organic wastes.SOLUTION: This treatment apparatus comprises a treatment tank 20 where organic wastes 11 are treated by fermentation, a movable body 31 capable of reciprocating the treatment tank 20, an agitation rotor 41 provided in the movable body 31 to agitate the organic wastes 11 with the movement of the movable body 31, a plurality of grooves 55 provided in the bottom 21 of the treatment tank 20, and an air supply pipe 60 stored in the groove 55 and having air jet holes 65 that supply air supplied from an air supply source 51 into the organic wastes 11, the air supply pipe 60 keeping a plurality of annular protrusions 61, projecting on the outer periphery side, formed with predetermined intervals along the axial direction of the air supply pipe 60, and the air jet holes 65 intermittently formed along the circumference of the air supply pipe 60 in a plurality of annular grooves 63 formed between the plurality of annular protrusions 61.SELECTED DRAWING: Figure 5

Description

  The technology disclosed in this specification relates to a fermentation treatment apparatus for organic waste.

  Conventionally, the fermenting process that ferments organic waste such as animal manure and food residue to make compost is performed in a processing tank that is several tens of meters in length, and the agitator that runs on top of this processing tank. Is stirring the treated product. At this time, air is forcibly supplied into the treatment tank for the purpose of promoting the fermentation treatment. For example, as a method for forcibly supplying air, a method is known in which air is fed under the floor of the processing tank and air is supplied into the processing tank through a vent hole provided under the floor.

  However, in such a method, the air hole may be clogged with the processed material, and air may not be sufficiently supplied. Therefore, in Japanese Patent Laid-Open No. 8-309324 (Patent Document 1 below), a clogging removal tool for air holes is provided. Specifically, it has an air chamber in which air from the outside is blown under the floor of the treatment tank, and a number of vent holes are provided in this floor plate. In the air chamber, a clog remover having protrusions corresponding to the air holes is arranged, and the protrusions of the remover are inserted into the air holes from below to remove clogs.

JP-A-8-309324

  However, in the configuration of Japanese Patent Laid-Open No. 8-309324 (Patent Document 1), it is necessary to prepare clogging removal tools as many as the required number of ventilation holes. In addition, since an apparatus for driving each clog remover is required, the structure becomes complicated and the cost increases.

  An organic waste fermentation treatment apparatus disclosed in the present specification is provided in a treatment tank in which organic waste is subjected to fermentation treatment, a movable body capable of reciprocating the treatment tank, and the movable body, An agitation rotor for agitating the organic waste in accordance with the movement of the moving body, a plurality of grooves provided at the bottom of the treatment tank, and the air contained in the grooves and supplied from an air supply source to the organic And an air supply pipe having an air ejection hole for supplying the waste into the waste, and the air supply pipe has a plurality of annular protrusions projecting on an outer peripheral side thereof along an axial direction of the air supply pipe. The air ejection holes are intermittently formed in a plurality of annular grooves formed between the plurality of annular protrusions along the circumferential direction of the air supply pipe.

  According to such a configuration, even when organic waste enters the groove due to dropping or the like during stirring, the organic waste is restrained from being held by the annular protrusion and entering the annular groove. The And since an air ejection hole is provided in the annular groove part of an air supply pipe, it is suppressed that an organic waste clogs an air ejection hole. Therefore, it is not necessary to provide an apparatus for removing clogging, and air necessary for fermentation of organic waste can be supplied while reducing costs.

The following configuration may be adopted as an embodiment of the organic waste fermentation treatment apparatus disclosed in this specification.
The groove portion is a U-shaped groove whose inner surface has a width dimension substantially the same as the outer diameter of the air supply pipe, and the air injection hole is also formed on the bottom surface side of the U-shaped groove. It is good also as a structure provided.
According to such a structure, since the groove part is formed of the U-shaped groove, the construction becomes easy. In addition, since there is almost no gap between the inner surface of the U-shaped groove (groove portion) and the air supply pipe, organic waste hardly falls on the bottom surface side of the U-shaped groove, and the bottom surface side of the U-shaped groove. The air blowout holes in the air will not be clogged or blocked. Therefore, since air can be supplied also from the air ejection hole on the bottom side via the annular groove portion, the air necessary for fermentation of organic waste can be more reliably supplied.

Moreover, it is good also as a structure by which the said air ejection hole is provided in the position which differs in the circumferential direction between the said adjacent annular groove parts.
According to such a configuration, even when organic waste enters the groove due to a drop or the like during stirring, the positions where the air ejection holes are provided between the adjacent annular grooves are different from each other. It is suppressed that both of the air ejection holes of the annular groove are blocked by the organic waste. Therefore, the air necessary for fermentation of organic waste can be supplied more reliably.

  According to the organic waste fermentation treatment apparatus disclosed in this specification, it is possible to reliably supply air while reducing costs.

The top view which shows schematic structure of the fermentation processing apparatus in embodiment. Side view showing stirrer and air supply pipe Sectional view showing the stirring device and the air supply pipe FIG. 3 is an enlarged cross-sectional view of the air supply pipe portion of FIG. Sectional drawing which shows the use condition during the fermentation process of FIG. Partial cutaway view of air supply pipe

<Embodiment>
Embodiments will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the fermentation treatment apparatus 10 of the present embodiment is for performing a fermentation treatment of the organic waste 11, and a treatment tank 20 in which the organic waste 11 to be subjected to the fermentation treatment is accommodated. , A stirring device 30 capable of reciprocating with respect to the processing tank 20 and an air supply device 50 embedded in the bottom 21 of the processing tank 20 and supplying air to the organic waste 11 are provided.

  As shown in FIG. 1, the processing tank 20 has a substantially rectangular box shape with an open top, and its bottom 21 and side walls 23 are formed of, for example, concrete. Each dimension of the processing tank 20 is set to have a width of about 6 m, a depth of about 0.5 m, and a length of about several tens of meters, for example. In the following description, the input portion 25 of the organic waste 11 is the upstream side (right end side in FIG. 1), and the recovery portion 27 of the organic waste 11 after fermentation is the downstream side (left end side in FIG. 1). To do.

  Organic waste 11 such as chicken manure (organic waste to be fermented) is input into the input portion 25 of the processing tank 20 in a mountain shape by a dump truck or the like. In the processing tank 20, it ferments while the input organic waste 11 moves downstream, and it becomes the structure by which the organic waste 11 (compost) after fermentation is collect | recovered in the downstream collection | recovery part 27. ing.

  As shown in FIGS. 2 and 3, the stirring device 30 is a self-propelled moving body that reciprocates along a pair of rails 23 </ b> A laid on both side walls 23 of the treatment tank 20 from the upstream side toward the downstream side. 31 (an example of “moving body”) and a stirring rotor 41 provided in the self-running moving body 31. The organic waste 11 charged into the charging unit 25 is scooped up while being stirred by the stirring rotor 41, and moves from the upstream side to the downstream side.

  The self-propelled moving body 31 includes, for example, a solid, substantially rectangular frame 33 made of steel, and four traveling wheels 37 that are rotatably supported at the lower four corners of the frame 33 and are driven by a motor 35. . The power of the motor 35 is transmitted to the traveling wheel 37 by the chain 35A. The self-running moving body 31 can be reciprocated in the upstream direction and the downstream direction by driving and controlling the motor 35 by a control device (not shown). That is, the self-propelled moving body 31 is configured to be able to reciprocate between the input unit 25 side and the recovery unit 27 side (opposite side of the input unit 25) along the longitudinal direction of the processing tank 20.

  As shown in FIG. 2, the frame 33 is provided with a base portion 33A. An arm member 43 is attached to the base portion 33A so as to rotate up and down about the base end portion as an axis. Specifically, the arm member 43 extends from the base portion 33 </ b> A so as to be parallel in the downstream direction, and is attached via a hinge 45. Thus, the arm member 43 is displaced up and down by rotating around the hinge 45.

  As shown in FIGS. 2 and 3, the rotating shaft 41 </ b> A of the stirring rotor 41 is pivotally supported by a bearing 43 </ b> A extending downward from the arm member 43 so as to be rotatable in a direction orthogonal to the moving direction of the self-running moving body 31. Yes. A mounting base 43B is fixed to the upper surface of the arm member 43, and a motor 47 is installed on the mounting base 43B. The motor 47 is connected to the rotating shaft 41A via a chain 47A, and the rotating shaft 41A can be rotated by driving the motor 47 to rotate by a control device (not shown).

  As shown in FIGS. 2 and 3, a plurality of tilling claws 41 </ b> B are arranged on the rotation shaft 41 </ b> A of the stirring rotor 41 so as to be substantially perpendicular to the rotation shaft 41 </ b> A. The tip of the tilling claw 41B is bent toward the center in the length direction of the axis of the rotating shaft 41A. Such a tilling claw 41B is generally called a nail claw.

  As shown in FIG. 2, the stirring rotor 41 can be moved up and down by a hydraulic cylinder 49 attached to the arm member 43. That is, the hydraulic cylinder 49 is attached so as to connect the arm member 43 and the frame 33 while both ends thereof are rotatably supported. When the hydraulic cylinder 49 is extended, the tilling claw 41B of the stirring rotor 41 is separated from the vicinity of the bottom 21 of the processing tank 20. Further, when the hydraulic cylinder 49 is contracted, the tip of the tilling claw 41B of the stirring rotor 41 is lowered to the vicinity of the bottom 21 of the processing tank 20.

  The stirring rotor 41 is controlled so as to be driven to rotate in a state where the hydraulic cylinder 49 is contracted, that is, in a state where the stirring rotor 41 is lowered. Further, the base portion 33A is provided with a hydraulic pump unit (not shown) for driving the hydraulic cylinder 49 on the upper surface thereof. A wiring cord (not shown) connected to each driving device is attached to the frame 33, and this wiring cord is connected to a wiring rail (not shown) provided above the processing tank 20. It is suspended so as to be movable and connected to an external control device.

  When the stirring rotor 41 rotates in the direction of the arrow (arrow line A) in FIG. 2, the tip of the tilling claw 41B scoops up the organic waste while stirring it and drops it to the inside of the treatment tank 20 obliquely downstream. As a result, a trapezoidal trough having a cross section extending in the longitudinal direction of the processing tank 20 and having a height suitable for fermentation treatment is formed, and the stirrer 41 moves downstream by a predetermined distance each time the stirring rotor 41 stirs the straw. It is supposed to be. Thereby, the organic waste 11 thrown into the input part 25 (upstream end) of the processing tank 20 is fermented while moving in the processing tank 20 to the downstream side over several days to several tens of days. It is recovered from the recovery unit 27 (downstream end) of the tank 20.

  Then, the air supply apparatus 50 which supplies air to the organic waste 11 is demonstrated in detail. As shown in FIG. 1, the air supply device 50 includes an air supply source 51 that takes in air from the outside, a main pipe 53 that feeds air from the air supply source 51 into the processing tank 20, and a branch from the main pipe 53. And a plurality of (four in this embodiment) air supply pipes 60 extending in the longitudinal direction of the processing tank 20. A U-shaped groove 55 (an example of a “groove”) is embedded in the bottom 21 of the processing tank 20 at a place where each air supply pipe 60 is disposed.

  As shown in FIG. 1, the air supply source 51 is an electric blower (blower) or the like, and is provided outside, and takes in external air and sends it to a main pipe 53 connected to a predetermined pressure. . The main pipe 53 is made of a synthetic resin such as vinyl chloride, and is embedded in the bottom portion 21 in the vicinity of the recovery portion 27 of the processing tank 20. The main pipe 53 has a smooth cylindrical shape on both the inner and outer surfaces, and has an inner diameter of about 200 mm. A branch pipe is connected in the middle of the main pipe 53, and air can be blown to each air supply pipe 60 connected via the branch pipe. An end cap 53A is fitted to the end of the main pipe 53 (the end opposite to the air supply source 51).

  As shown in FIGS. 1 and 4, four U-shaped grooves 55 are embedded in the bottom portion 21 of the processing tank 20 in parallel so that the upper surface is opened. The U-shaped groove 55 is provided between the input unit 25 and the recovery unit 27 in parallel with the side wall 23 along the longitudinal direction of the processing tank 20, and extends to the upstream side of the air supply pipe 60. The U-shaped groove 55 is arranged at a position where the space between the side walls 23 is equally divided. Further, the U-shaped groove 55 is embedded in the bottom 21 so that the upper surface of the U-shaped groove 55 is flush with the surface of the bottom 21 of the processing tank 20. The U-shaped groove 55 has an inner dimension D of about 120 mm in width and depth, and can completely accommodate the air supply pipe 60. Thus, by forming the groove part which accommodates the air supply pipe 60 by the U-shaped groove | channel 55, a dimensional error with the air supply pipe 60 can be made small, aiming at cost reduction.

  The air supply pipe 60 is made of synthetic resin such as polyethylene, and as shown in FIG. 6, a plurality of annular protrusions 61 projecting to the outer peripheral side and a plurality of annular groove parts 63 formed between the annular protrusions 61. These are so-called corrugated pipes. The annular protrusions 61 of the air supply pipe 60 each have an independent trapezoidal mountain shape. The pitch between the annular protrusions 61 is about 10 mm to 15 mm. On the other hand, the valley width of the annular groove 63 is about 3 mm to 5 mm. Further, the inner surface of the air supply pipe 60 is a smooth surface, and its inner diameter φ1 is about 100 mm as shown in FIG. The outer diameter φ2 of the annular protrusion 61 of the air supply pipe 60 is about 118 mm. When the air supply pipe 60 is accommodated in the U-shaped groove 55, the inner surface of the U-shaped groove 55 and the annular protrusion There is almost no gap between 61 and 61. An end cap 67 is fitted to the upstream end of each air supply pipe 60 (the end opposite to the side connected to the main pipe 53) (see FIG. 1).

  As shown in FIGS. 4 and 6, the air discharge hole 65 is intermittently formed in the annular groove 63 along the circumferential direction of the air supply pipe 60. The air ejection holes 65 have a long hole shape extending in the circumferential direction, and are provided at four equal intervals in each annular groove portion 63. The length of the air ejection hole 65 in the circumferential direction is about 10 mm, and its width is about 2 to 3 mm. In addition, the air ejection holes 65 are provided at different positions between the adjacent annular groove portions 63. More specifically, the adjacent annular groove portions 63 are arranged in a so-called staggered pattern in which the air ejection holes 65 are alternately arranged at a position half the distance between the air ejection holes 65.

  With the above configuration, the U-shaped groove 55 is embedded in the bottom 21 of the processing tank 20, and the air supply pipe 60 is accommodated in the U-shaped groove 55, whereby the air supply pipe 60 is arranged on the bottom 21 of the processing tank 20. ing. In the state where the air supply pipe 60 is accommodated in the U-shaped groove 55, there is almost no gap between the side inner surface of the U-shaped groove 55 and the annular protrusion 61 of the air supply pipe 60. The organic waste 11 is suppressed from entering the bottom surface side of the groove 55. On the other hand, since a gap is provided between the inner surface of the U-shaped groove 55 and the annular groove portion 63 of the air supply pipe 60, the air ejection hole 65 on the side (bottom surface side, side surface side) in contact with the U-shaped groove 55. The supplied air is also supplied into the processing tank 20 through a gap between the annular groove 63 and the inner surface of the U-shaped groove 55.

  Next, the effect | action and effect of the fermentation processing apparatus 10 in this embodiment are demonstrated. In the initial state, as shown in FIG. 1, for example, the stirring device 30 stands by at the downstream end of the processing tank 20. In this state, a certain amount of the organic waste 11 is introduced into the input portion 25 (upstream end) of the treatment tank 20 by a dump truck or the like. Subsequently, the stirring device 30 moves to the upstream end of the processing tank 20 while rotating the stirring rotor 41 with the hydraulic cylinder 49 contracted and the stirring rotor 41 lowered.

  Then, the organic waste 11 stacked in a mountain shape is stirred by the stirring rotor 41 and moved to a downstream side by a predetermined distance (for example, about 50 cm), and becomes a bowl having a predetermined height (for example, about 50 cm). The stirring device 30 that has moved to the upstream end of the processing tank 20 stops the rotation of the stirring rotor 41 and extends the hydraulic cylinder 49 to raise the stirring rotor 41. It moves to the downstream end of the processing tank 20 in this state. Next, a certain amount of the organic waste 11 is again thrown into the empty space (input unit 25) where the organic waste 11 has moved by the dump truck. Then, the organic waste 11 is agitated by the agitator 30 again. By repeating the above operation, the organic waste 11 introduced into the upstream end of the treatment tank 20 is fermented over several days to several tens of days while moving in the treatment tank 20 to the downstream side. 20 is collected from the downstream end (collection unit 27).

In the process of stirring work by the stirring device 30 described above, air supply to the organic waste 11 by the air supply device 50 is also performed in order to promote fermentation of the organic waste 11. Next, the operation and effect of the air supply device 50 will be described.
When carrying out the above-described stirring operation, the organic waste 11 between the tilling claw 41B of the stirring rotor 41 and the bottom 21 of the treatment tank 20 is pushed toward the bottom 21 by the tilling claw 41B. Moreover, after the organic waste 11 stirred by the tilling claw 41B is lifted up above the stirring rotor 41, it moves to the downstream side by rotation and spontaneously falls. Thus, when the organic waste 11 is agitated, it is pushed by the tilling claw 41 </ b> B or falls from above the agitation roller 41, and tries to enter the U-shaped groove 55.

  Here, in this embodiment, as shown in FIG. 5, most of the organic waste 11 trying to enter the U-shaped groove 55 generally has a pitch between the annular protrusions 61 (annular groove 63. Therefore, it is prevented from entering into the annular groove 63 by being obstructed by the annular protrusion 61. Therefore, a relatively large lump of organic waste 11 does not reach the air ejection hole 65 provided in the annular groove portion 63, and clogging of the air ejection hole 65 is suppressed.

  Moreover, even if what is located in the upper part of the supply pipe 60 among many air ejection holes 65 is obstruct | occluded with the lump of the organic waste 11, the annular groove part 63 in which the air ejection hole 65 is formed is provided. In the annular groove 63 adjacent to each other, since the air ejection holes 65 are provided at different positions in the circumferential direction, even the air ejection holes 65 of the adjacent annular groove 63 may be covered with the organic waste 11. Disappear.

  Of course, a small lump of the organic waste 11 may enter the annular groove 63 and slide down to the bottom of the U-shaped groove 55, but they are minute and gradually from the bottom. Therefore, there is almost no possibility that the air discharge holes 65 formed downward in the lower half of the air supply pipe 60 are covered with the organic waste 11. The air freely ejected from the air ejection holes 65 provided on the bottom surface side (the lower half side of the air supply pipe 60) passes through a gap formed between the inner surface of the U-shaped groove 55 and the annular groove portion 63. It flows upward and is supplied to the organic waste 11 in the treatment tank 20.

  As described above, in the fermentation treatment apparatus 10 of the present embodiment, since the relatively large lump of the organic waste 11 cannot enter the U-shaped groove 55, the organic waste 11 passes through the air ejection holes 65 of the air supply pipe 60. It can suppress clogging. Therefore, it is not necessary to provide a device for removing clogging, and air necessary for fermentation of the organic waste 11 can be supplied while reducing costs.

  In addition, since the U-shaped groove 55 is used as the groove portion that accommodates the air supply pipe 60, the construction of the bottom portion 21 of the processing tank 20 is facilitated. Further, the U-shaped groove 55 has an inner surface whose width dimension is substantially the same as the outer diameter φ2 of the air supply pipe 60 (annular protrusion 61). Also, an air ejection hole 65 is provided. According to such a configuration, since there is almost no gap between the inner surface of the U-shaped groove 55 and the air supply pipe 60 (annular protrusion 61), the organic waste 11 falls on the bottom surface side of the U-shaped groove 55. The air ejection hole 65 on the bottom surface side of the U-shaped groove 55 is not clogged or blocked. Therefore, air can be supplied also from the air ejection hole 65 on the bottom surface side through the annular groove 63, so that the air necessary for fermentation of the organic waste 11 can be supplied more reliably.

  Moreover, the air ejection holes 65 are provided at different positions in the circumferential direction between the adjacent annular groove portions 63. According to such a configuration, even when the organic waste 11 has entered the U-shaped groove 55 due to dropping or the like during stirring, the position where the air ejection holes 65 are provided between the adjacent annular groove parts 63 is the same. Since it differs, it is suppressed that both the air ejection holes 65 of the adjacent annular groove part 63 are block | closed with organic waste. Therefore, the air necessary for fermentation of the organic waste 11 can be supplied more reliably.

<Other embodiments>
The technology disclosed in this specification is not limited to the embodiment described with reference to the above description and drawings, and for example, the following embodiments are also included in the technical scope.

  (1) The number and size of the air supply pipes 60 and the installation locations are not limited to the configuration of the above embodiment, and can be changed as appropriate. In the above embodiment, air is supplied from the air supply device 50 via the main pipe 53, but air may be supplied directly from the air supply device 50 to each air supply pipe 60.

  (2) In the above embodiment, the groove portion is formed by a U-shaped groove. However, when the concrete is placed on the bottom portion 21 of the treatment tank 20, the groove portion may be constructed by concrete.

  (3) In the above embodiment, the inner dimension D (the inner surface width dimension) of the U-shaped groove 55 is substantially the same as the outer diameter φ2 of the annular protrusion 61 of the air supply pipe 60. The dimension may be larger than the outer diameter φ2 of the annular protrusion 61 of the air supply pipe 60.

  (4) In the above embodiment, the air ejection holes 65 are provided at different positions in the circumferential direction between the adjacent annular groove portions 63, but may be provided at the same position. Moreover, although the number of the air ejection holes 65 between each annular groove part 63 was made the same, you may differ.

  (5) In the above embodiment, the air ejection holes 65 are provided at equal intervals on the entire surface, but the intervals may be uneven. Further, the air ejection holes 65 may be provided not in the entire surface but in the upper half, the lower half, and the upper two-thirds of the air supply pipe.

  (6) In the above-described embodiment, the annular protrusions 61 of the air supply pipe 60 each have an independent mountain shape, but may have a spiral continuous shape.

  (7) In the above embodiment, the air supply source 51 may be configured to include, for example, a boiler, an electric heater, or the like, so that warm air may be supplied to the air supply device 50. With such a configuration, warm air can be supplied to the organic waste 11, and fermentation of the organic waste 11 can be promoted even in a place where the outside air temperature is low, such as in winter.

  (8) In the above embodiment, the tilling claw 41B of the stirring rotor 41 is shaped like a spear, but the shape of the tilling claw 41B is not limited to this. Moreover, it is not necessary to make all the tilling claws 41B attached to the stirring rotor 41 have the same shape, and plural kinds of tilling claws 41B having different shapes may be attached.

  (9) In the above embodiment, the case where the organic waste 11 is fermented has been described. However, the organic waste 11 mixed with a mixture such as straw can be similarly treated. Note that the organic waste 11 is not limited to feces and may be garbage.

DESCRIPTION OF SYMBOLS 10 ... Fermentation processing apparatus 11 ... Organic waste 20 ... Treatment tank 21 ... Bottom part 30 ... Stirrer 31 ... Self-propelled moving body (moving body)
41 ... Stirring rotor 41A ... Rotating shaft 41B ... Tillage claw 50 ... Air supply device 51 ... Air supply source 53 ... Main pipe 53A ... End cap 55 ... U-shaped groove (groove)
60 ... Air supply pipe 61 ... annular protrusion 63 ... annular groove portion 65 ... air ejection hole 67 ... end cap φ1 ... air supply pipe inner diameter φ2 ... air supply pipe outer diameter D ... U-shaped groove inner dimension

Claims (3)

A treatment tank in which organic waste is fermented;
A movable body capable of reciprocating the treatment tank;
A stirring rotor that is provided in the moving body and stirs the organic waste in accordance with the movement of the moving body;
A plurality of grooves provided at the bottom of the treatment tank;
An air supply pipe having an air ejection hole that is housed in the groove and supplies air supplied from an air supply source into the organic waste;
The air supply pipe is formed with a plurality of annular protrusions projecting on the outer peripheral side thereof at predetermined intervals along the axial direction of the air supply pipe, and the air ejection holes are formed between the plurality of annular protrusions. An organic waste fermentation treatment apparatus formed intermittently in the plurality of annular grooves formed along the circumferential direction of the air supply pipe. The groove portion has a U-shaped groove whose inner surface has substantially the same width as the outer diameter of the air supply pipe,
The organic waste fermentation treatment apparatus according to claim 1, wherein the air supply pipe is provided with the air ejection holes on the bottom surface side of the U-shaped groove.   The organic waste fermentation treatment apparatus according to claim 1 or 2, wherein the air ejection holes are provided at different positions in the circumferential direction between the adjacent annular groove portions.

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