JP2007327217A - Manhole structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manhole structure with a locking mechanism which positively protects a manhole cover from being opened without permission, prevents the deposition of sediment in a space between a claw bar hole and a blocking piece, and the wobbling of a closing plug when a lock is released, and always allows smooth lock releasing operation. <P>SOLUTION: The locking mechanism is formed of a lock weight 11, the closing plug 12, a spring 13, an engaging claw 14 formed on the inner surface of the cover bearing frame 1, etc. The lock weight 11 is formed of a forked hanging arm 19 with a pair of rocking shafts 18, a lock base 20 and a lock claw 21, and a spring bearing arm 22 projecting diagonally downward. The closing plug 12 is formed of a blocking piece 31 for blocking the claw bar hole 5, a slide shaft 32 projecting from the lower surface of the blocking piece 31, a stopper piece 33, etc. Then a slide shaft 35 is vertically slidably guided and supported in a guide groove 26 formed in the vicinity of the rocking shafts 18, and held by a restriction rod 38 in a manner of being incapable of lifting upward. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a manhole structure having a lock mechanism that locks and holds the manhole cover so that it cannot be opened is provided between the manhole cover and the cover receiving frame. It relates to a certain manhole structure.

  A manhole structure provided with this type of locking mechanism is known from Patent Document 1. There, a lock mechanism is constituted by a lock weight instructed to be swingable by a manhole cover, a closing plug for closing the burl hole, a spring for pushing up and biasing the closing plug.

  The lock weight includes a weight body with a guide boss, a pair of suspension arms projecting on the left and right sides of the weight body, swinging shafts projecting on both sides of the upper end of the suspension arm, and a rear surface of the weight body. It consists of a cast product that is integrally provided with a protruding lock claw. The closing plug is formed by a rectangular base, a closing piece protruding from the upper surface of the base, a slide shaft protruding from the lower surface of the base, and a rubber packing attached to the upper surface of the base. The slide shaft is guided and supported by a guide boss so that it can slide back and forth.When the lock weight is locked, the entire closure plug is pushed up by a spring so that the closing piece can close the burl hole from the back side of the lid. It has become. Patent Document 2 also discloses a similar locking mechanism.

Japanese Patent Laying-Open No. 2005-36560 (paragraph number 0015, FIG. 3) Japanese Patent No. 3616920 (paragraph number 0018, FIG. 3)

  According to the lock mechanism provided with the closing plug as described above, it is possible to prevent rainwater or earth and sand from flowing into the manhole through the bar hole. In addition, even if the internal pressure of the manhole suddenly rises during heavy rain, the lock weight can be hooked and held by the lid receiving frame, and the lock mechanism can prevent the manhole lid from separating from the lid receiving frame. . However, since the rubber hole is closed to the inner edge of the opening of the burl hole to close the burr hole, earth and sand may accumulate and fill in the space between the burr hole and the closing piece. Therefore, when trying to unlock the lock mechanism to open the manhole cover, the accumulated earth and sand cannot get in the way of pushing down the closure plug, and it takes a lot of time to open the manhole cover. .

  A slide shaft protruding from the lower part of the stopper plug is supported by a guide boss provided at the lower part of the weight main body so as to be slidable up and down. In other words, since the weight main body is supported by the suspension arm having a large vertical dimension, the stopper plug must be slid and guided by the guide boss provided far away from the swing shaft. For this reason, when the stopper plug is pushed down with the bar key, the stopper plug may be rattled by the margin gap between the slide shaft and the guide boss, and the lock mechanism cannot be unlocked smoothly. In Patent Document 2, in order to prevent rattling of the stopper plug, a separate guide surface for slidingly guiding the stopper plug is provided on the weight body, and the structure of the weight body is complicated accordingly.

  The object of the present invention is that the lock mechanism cannot be unlocked unless a bar key for unlocking is used, and it is possible to reliably prevent the manhole cover from being opened without permission, such as tampering. A lock mechanism that eliminates sediment accumulation in the space between the closing pieces and prevents the stopper plugs from rattling when the stopper plug is pushed down with the bar key so that the lock can always be unlocked smoothly. It is in providing the manhole structure provided with. The object of the present invention is to provide a smooth closure of the unlocking operation by directly sliding and guiding the closure plug in the vicinity of the swing shaft of the main body, and can be applied without problems to a widely used manhole structure. The object is to provide a manhole structure having a lock mechanism.

  The manhole structure of the present invention includes a lid receiving frame 1 embedded in the ground, a manhole cover 2 connected to the lid receiving frame 1 through a hinge mechanism so as to be opened and closed, and a space between the manhole cover 2 and the lid receiving frame 1. And a locking mechanism that holds the manhole cover 2 so that it cannot be opened. The lock mechanism includes a lock weight 11 pivotally supported by the manhole cover 2, a closing plug 12 slidably guided and supported by the lock weight 11, a spring 13 that pushes up and biases the closing plug 12, A downward engaging claw 14 provided on the inner surface of the lid receiving frame 1 corresponding to the weight 11 is included. The lock weight 11 has a bifurcated suspension arm 19 having a pair of swing shafts 18 at the upper end, a lock base 20 extending downward continuously from the suspension arm 19, and a protrusion on the outer surface of the lock base 20. The lock claw 21 is integrally provided with a suspension arm 19 and a spring receiving arm 22 projecting obliquely downward from the lock base 20. The closing plug 12 includes a closing piece 31 that fits into the burl hole 5 from the back side of the lid, a slide shaft 32 that protrudes obliquely downward from the lower surface of the closing piece 31, a slide groove 35 provided in the slide shaft 32, a slide A stopper piece 33 is formed so as to protrude toward the upper end of the shaft 32. The closing plug 12 is guided and supported by a guide groove 26 whose slide shaft 35 is formed between the suspension arms 19 of the lock weight 11 so that it can only slide up and down, and is fixed to the lock weight 11 so as to intersect the slide groove 35. The control rod 38 is held so as not to float off. The spring 13 is arranged between the lower part of the closing plug 12 and the spring seat 24.

  As shown in FIG. 5, the slide center axis L of the closing plug 12 is inclined so as to pass through the vicinity of the rotation center R of the swing shaft 18, more preferably through the rotation center R of the swing shaft 18. The majority of the face wall of the closing piece 31 is positioned inside the intersection point P between the upper surface of the closing piece 31 and the slide center axis L.

  A restriction wall 28 that defines a swing limit of the lock weight 11 in the lock direction is formed on the lock base 20. In a normal state, the stopper piece 33 is in contact with the inner opening edge of the burl hole 5, and the restriction wall 28 is in contact with the inner surface of the lid receiving frame 1, thereby restricting the swing of the lock weight 11.

  A pair of retaining walls 29 and a spring seat 24 that cover the left and right sides of the spring 13 are formed on the spring receiving arm 22. A drainage notch 30 is formed in each of the upper portion of the retaining wall 29 and the lower portion facing the spring seat 24.

  In the present invention, a pair of swing shafts 18, a bifurcated suspension arm 19, a lock base 20, a lock claw 21, and a spring receiving arm 22 protruding obliquely downward from the suspension arm 19 and the lock base 20. The lock weight 11 was configured by such means. Further, a closing piece 31 that fits into the burl hole 5 from the back side of the lid, a slide shaft 32 that projects obliquely downward from the lower surface of the closing piece 31, a stopper piece 33 that is formed to project toward the upper end of the slide shaft 32, etc. The stopper plug 12 is constructed, and the slide shaft 35 is guided and supported by the guide groove 26 formed between the suspension arms 19 of the lock weight 11 so that only the vertical slide is possible.

  As described above, when the slide shaft 35 of the stopper plug 12 is slid and guided by the guide groove 26 provided between the suspension arms 19, the stopper plug is located at a position closer to the swing shaft 18 as compared with the conventional lock mechanism. 12 can be slid and guided. In addition, the slide shaft 35 is held by the restriction rod 38 so as not to float off. Therefore, when the closing plug 12 is pushed down with the bar key T, the locking plug 12 can be reliably prevented from rattling, and the unlocking operation of the locking mechanism can be performed smoothly.

  In the normal state, the burr hole 5 is always closed by the closing piece 31 of the closing plug 12, and in order to unlock the lock weight 11, the lock weight 11 must be unlocked according to a predetermined procedure. Therefore, it is difficult to open the lock mechanism due to mischief or the like, and it is possible to reliably prevent the manhole cover 2 from being opened without permission. Further, in the present invention, rainwater and earth and sand are caused to flow into the back side of the lid from the gap between the burl hole 5 and the closing piece 31, and sediment is prevented from accumulating in the space between the burr hole 5 and the closing piece 31. Therefore, the stopper plug 12 can be pushed down smoothly and smoothly without being disturbed by earth and sand.

  The slide center axis L of the closure plug 12 is inclined so as to pass in the vicinity of the rotation center R of the swinging shaft 18, whereby the majority of the face wall of the closing piece 31 is moved between the upper surface of the closing piece 31 and the slide center axis L. According to the lock mechanism positioned on the inner side of the intersection P with the lock lever 11, when the stopper plug 12 is pushed down with the bar key T, the direction of the tilting moment generated by the push-down force coincides with the direction in which the lock weight 11 is locked. be able to. Therefore, the operation of pushing down the stopper plug 12 can be reliably performed in a state where the lock weight 11 is prevented from swinging in the unlocking direction.

  A restriction wall 28 that defines the rocking limit of the lock weight 11 in the locking direction is formed on the upper portion of the lock base 20. In a normal state, the stopper piece 33 contacts the inner opening edge of the burl hole 5, and the restriction wall 28 is According to the lock mechanism that can regulate the swing of the lock weight 11 by coming into contact with the inner surface of the lid receiving frame 1, it is possible to eliminate the swing of the lock weight 11 due to the external vibration, and the manhole on the slope. Even when it is provided, the lock weight 11 can be prevented from swinging in the unlocking direction by the urging force of the spring 13 and the rotational moment due to its own weight, and the locked posture can be maintained. Furthermore, when the closing plug 12 is pushed down, the lock weight 11 can be reliably prevented from wobbling, so that the slide center axis L of the closing plug 12 is positioned in the vicinity of the rotation center R of the swing shaft 18. As a result, the unlocking operation of the locking mechanism can be performed more reliably.

  If the notch 30 for drainage is formed in each of the upper part of the retaining wall 29 provided on the spring receiving arm 22 and the lower part facing the spring receiving seat 24, the rainwater and earth and sand flowing from the burl hole 5 are closed off. 12 is allowed to flow down along the slide shaft 32 and the spring recess 27 and can be discharged from the upper and lower cutouts 30 during that time, so that sediment can be prevented from accumulating on the surface of the lock weight 11, the closing plug 12 or the spring 13. Unlocking operation can be performed smoothly.

(Example) FIGS. 1-9 shows the Example of the manhole structure based on this invention. In FIG. 2, the manhole structure includes a cover receiving frame 1 embedded in the ground, a manhole cover 2 connected to the cover receiving frame 1 through a hinge mechanism so as to be opened and closed, and a space between the manhole cover 2 and the cover receiving frame 1. And a locking mechanism that locks the manhole cover 2 so that it cannot be opened.

  The lid receiving frame 1 is attached to the inner corner portion of the ring-shaped cylindrical wall 1a whose upper and lower surfaces are open, the flange-shaped embedded seat 1b protruding around the lower end of the cylindrical wall 1a, and the cylindrical wall 1a and the embedded seat 1b. It consists of a cast product integrally provided with a group of reinforcing ribs and the like. On the upper part of the inner surface of the cylindrical wall 1a, a mounting surface 3 for fitting and mounting the manhole cover 2 is formed in a tapered shape. On the diameter line between the lid receiving frame 1 and the manhole cover 2, a hinge mechanism and a lock mechanism are arranged opposite to each other.

  The manhole cover 2 is made of a disk-shaped cast product, and a tapered surface 4 (see FIG. 1) that fits the previous mounting surface 3 is formed on the peripheral surface thereof. On the periphery of the manhole cover 2, a burl hole 5 for unlocking the lock mechanism is formed in an elongated shape, and a section for assembling the lock weight 11 so as to surround the inner surface opening of the burl hole 5. A wall 6 is formed, and bearing recesses 7 that pivotally support the lock weight 11 are formed on the inner left and right sides of the wall 6. As shown in FIG. 4, a recess 6a for avoiding a contact buffer with a slide shaft 32 described later is cut out at the center of the bridge wall of the partition wall 6 formed in a U-shape.

  The hinge mechanism is composed of a rectangular hinge metal fitting 8 pivotally supported on the inner surface of the manhole cover 2 and a metal fitting receiving frame 9 projecting from the inner surface of the cover receiving frame 1. The hinge fitting 8 and the fitting receiving frame 9 are configured so that the manhole cover 2 can be opened by reversing 180 degrees or the manhole cover 2 can be opened horizontally.

  In FIG. 1, the lock mechanism includes a lock weight 11 that is pivotally supported by a manhole cover 2, a closure plug 12 that is guided and supported by the lock weight 11 so as to be reciprocally slidable, and a compression that pushes and biases the closure plug 12. A coil-shaped spring 13 and a downward engaging claw 14 provided on the inner surface of the lid receiving frame 1 corresponding to the lock weight 11 are formed. A contact wall 15 is provided on the inner surface of the lower end of the engagement claw 14 so as to define a swing limit of the lock weight 11 in the lock direction.

  As shown in FIGS. 1 and 3, the lock weight 11 includes a bifurcated suspension arm 19 having a swing shaft 18 at its upper end, and a lock base 20 that extends downward continuously from the suspension arm 19. A rectangular lock claw 21 protruding from the outer surface of the lock base 20 and alternately facing the engagement claw 14; and a spring receiving arm 22 protruding diagonally downward from the suspension arm 19 and the lock base 20; It is made of a casting product integrally provided with wing pieces 23 and the like that are formed on both sides of the lock base 20. A spring receiving seat 24 is formed at the lower end of the spring receiving arm 22, and a protrusion 25 for restricting the movement of the spring 13 is integrally formed on the seat surface. The wing piece 23 is provided to adjust the position of the center of gravity of the lock weight 11.

  As described above, when the spring receiving arm 22 protrudes obliquely downward, the lock weight 11 is biased by the tilting moment due to its own weight in a state where the lock weight 11 is pivotally supported by the bearing recess 7 of the manhole cover 2. can do. By the way, in the lock weight 11 of the present invention, the tilting moment due to its own weight is gained by projecting the spring receiving arm 22 obliquely downward, that is, by increasing the moment arm, so compared with the conventional lock weight, The appearance can be simplified with a slender and clean appearance. Further, the vertical dimension of the suspension arm 19 is significantly shorter than the vertical dimension of the conventional suspension arm.

  As shown in FIGS. 3, 6, and 7, a guide groove 26 that guides and supports a slide shaft 32 of the stopper plug 12, which will be described later, is formed between the suspension arms 19 so as to be only slidable up and down. 22 is formed with a spring recess 27 for receiving the spring 13 continuously to the lower end of the guide groove 26. The lock base 20 above the lock claw 21 is formed with a regulation wall 28 that contacts the contact wall 15 of the engagement claw 14 described above. As shown in FIG. 7, a pair of retaining walls 29 protrude from the left and right sides of the spring recess 27, and drainage cutouts 30 are formed in the upper part and the lower part facing the spring seat 24, respectively.

  The stopper plug 12 includes a horizontal closing piece 31 having one rounded end, a slide shaft 32 having a quadrangular cross section projecting obliquely downward from the lower surface of the closing piece 31, and both sides near the upper end of the slide shaft 32. It is made of a stainless steel fitting integrally provided with a stopper piece 33 formed so as to project and a spring receiving shaft 34 protruding from the lower end of the slide shaft 32. The slide shaft 32 is formed with a slide groove 35 along the axis thereof penetrating left and right.

  The lower end of the spring 13 is externally fitted to the protrusion 25 of the spring seat 24, and the slide shaft 32 is fitted into the guide groove 26 with the spring receiving shaft 34 being fitted into the upper end of the spring 13, and further orthogonal to the slide groove 35. By tightening and fixing both ends of the regulating rod 38 assembled to the lock weight 11 with hexagon socket head bolts 39, the entire stopper plug 12 is guided and supported so as to be slidable obliquely up and down along the guide groove 26. 13 can be pushed up. The slide shaft 32 is held by the restriction rod 38 so as not to be lifted off from the guide groove 26.

  As shown in FIGS. 3 and 4, the rocking shaft 18 of the lock weight 11 to which the stopper plug 12 and the spring 13 are assembled is assembled to the bearing recess 7 on the back of the lid, and the retaining bracket is fastened and fixed to one side of the partition wall 6. By restricting the one swing shaft 18 from coming off at 40, the lock weight 11 can be pivotally supported integrally with the manhole cover 2. In a state where the manhole cover 2 is connected to the cover receiving frame 1 via a hinge mechanism and the opening surface of the cover receiving frame 1 is closed, the closing piece 31 of the closing plug 12 is inserted into the burr hole 5 from the back side of the cover as shown in FIG. The hole space is slowly closed.

  In the assembled state, the stopper piece 33 of the stopper plug 12 is in contact with the inner opening edge of the burl hole 5 under the pushing force of the spring 13. Further, since the lock weight 11 receives the urging force of the spring 13 and further receives the rotational moment due to its own weight, it always tries to swing in the lock direction (clockwise direction in FIG. 1). 15 is held in the received state.

  As described above, when the lock weight 11 is stretched and held between the manhole cover 2 and the cover receiving frame 1, the lock weight 11 is prevented from swinging due to external vibration, and the regulation wall 28 collides with the contact wall 15. Thus, it is possible to reliably prevent a collision sound from being generated. Further, even when the manhole is provided on the slope, the lock weight 11 can be prevented from swinging in the unlocking direction by the urging force of the spring 13 and the rotational moment due to its own weight, and the locked posture can be maintained. .

  During a storm, rainwater and earth and sand flow into the back of the lid through the gap between the burl hole 5 and the closing piece 31. However, the rainwater and earth and sand that have flowed in flow along the slide shaft 32 and the spring recess 27 of the stopper plug 12 and finally from the notches 30 provided on the upper and lower sides of the spring receiving arm 22. 11, the stopper plug 12 or the spring 13 does not accumulate on the surface, so that the lock weight 11 can always be unlocked smoothly.

  The bar key T is used when the lock weight 11 is unlocked. As shown in FIG. 1, the lower end of the bar key T is formed in an inverted T shape, and has a pair of latching claws 43 having an inverted V-shaped cross section. When the latching claw 43 is inserted from the burl hole 5 and the bar key T is pushed in with the flat claw lower surface 44 applied to the surface wall of the closing piece 31, the closure plug 12 is attached to the spring 13 as shown in FIG. Depressed against power.

  If the burl key T is rotated 90 degrees while maintaining this depressed state, the upper end of the latching claw 43 sinks into the lower surface of the inner peripheral wall of the burl hole 5, so that the repulsive force of the spring 13 is applied to the manhole cover 2. It can be received. In this state, when the burl key T is tilted toward the outer edge side of the manhole cover 2 as shown in FIG. 9, the lock weight 11 swings counterclockwise about the swing shaft 18 and switches to the unlocked posture. Therefore, it can be opened by lifting the manhole cover 2 in that state. At this time, a part of the slide shaft 32 intersects with the partition wall 6, but since the recess 6a is formed at the intersecting portion, the lock weight 11 can be unlocked without hindrance.

  Incidentally, since the partition wall 6 provided with the recess 6a is provided on the inner surface of the widely used manhole cover 2, the lock weight 11 of the present invention is used in the existing manhole cover not provided with the stopper plug. By replacing the lock weight, a tamper-proof function can be added as a lock mechanism including the closing plug 12. Compared with the case where the whole manhole cover is replaced, only the lock weight 11 needs to be replaced, so that the cost for replacement can be significantly reduced.

  In the lock mechanism described above, the slide shaft 35 of the stopper plug 12 is guided and supported by the guide groove 26 formed between the suspension arms 19 so as to be slidable up and down. In other words, since the stopper plug 12 is slid and guided by the guide groove 26 provided in the vicinity of the swing shaft 18, it is possible to well prevent the stopper plug 12 from rattling when the stopper plug 12 is pushed down by the bar key T. . Further, as described above, the lock weight 11 is stretched and held between the manhole cover 2 and the cover receiving frame 1 so that the stopper plug 12 can be pushed down with no room for wobbling. It can always be unlocked smoothly.

  As shown in FIG. 5, the slide center axis L of the closure plug 12 is normally inclined so as to pass through the rotation center R of the swing shaft 18, and the upper surface of the closing piece 31 and the slide center axis L are With respect to the intersection point P, the majority of the face wall of the closing piece 31 is located inside the intersection point P. Therefore, when the closing plug 12 is pushed down, most of the claw lower surface 44 of the latching claw 43 comes into contact with the inside of the intersection P, and as a result, a tilting moment in the locking direction acts on the lock weight 11. Then, the lock weight 11 can be fixed in a state where the regulating wall 28 is received by the contact wall 15. That is, when the closing plug 12 is pushed down, the lock weight 11 can be reliably prevented from swaying, and the lock unlocking operation of the lock mechanism can be performed reliably and smoothly.

  In the normal state, the burr hole 5 is always closed by the stopper plug 12, and in order to unlock the lock weight 11, the stopper weight 12 is pushed down to a predetermined position with the dedicated bar key T, and then the lock weight 11 is moved. It must be swung in the unlocking direction. Therefore, it is difficult to open the lock mechanism due to mischief or the like, and it is possible to reliably prevent the manhole cover 2 from being opened without permission. For example, even if an attempt is made to push down the stopper plug 12 with a pickaxe to pry open the manhole cover 2, only the tilting moment in the locking direction acts on the lock weight 11, so the lock weight 11 cannot be unlocked. The manhole cover 2 cannot be opened.

  In the above-described embodiment, the slide groove 35 is formed as a lateral through groove. However, the slide groove 35 is not necessary and can be formed in a notch shape. The slide shaft 32 can be formed of a round shaft or a shaft having a tunnel cross-section in which a flat surface is formed on a part of the peripheral surface.

It is a vertical side view which shows the locking mechanism of a manhole cover. It is a vertical side view of a manhole. It is the sectional view on the AA line in FIG. It is the BB sectional view taken on the line in FIG. It is CC sectional view taken on the line in FIG. It is the DD sectional view taken on the line in FIG. It is the EE sectional view taken on the line in FIG. It is a vertical side view which shows the unlocking middle state of a locking mechanism. It is a vertical side view which shows the unlocking completion state of a locking mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cover frame 2 Manhole cover 11 Locking weight 12 Closure plug 13 Spring 14 Engaging claw 18 Oscillating shaft 19 Suspension arm 20 Lock base 21 Locking claw 22 Spring receiving arm 31 Closure piece 32 Slide shaft 33 Stopper piece

Claims (4)

A cover receiving frame (1) embedded in the ground, a manhole cover (2) connected to the cover receiving frame (1) through a hinge mechanism so as to be opened and closed, a manhole cover (2), and a cover receiving frame (1) And a locking mechanism that holds the manhole cover (2) so that it cannot be opened,
The lock mechanism includes a lock weight (11) pivotally supported by a manhole cover (2), a closing plug (12) slidably guided and supported by the lock weight (11), and a closing plug (12). A spring (13) that pushes up and biases, and a downward engaging claw (14) provided on the inner surface of the lid receiving frame (1) corresponding to the lock weight (11),
The lock weight (11) includes a bifurcated suspension arm (19) having a pair of swing shafts (18) at its upper end, and a lock base (20) extending downward continuously from the suspension arm (19). , And a lock claw (21) protruding from the outer surface of the lock base (20) and a spring receiving arm (22) protruding obliquely downward from the suspension arm (19) and the lock base (20). In preparation for
The closing plug (12) includes a closing piece (31) fitted into the burl hole (5) from the back side of the lid, a slide shaft (32) projecting obliquely downward from the lower surface of the closing piece (31), and a slide shaft A slide groove (35) provided in (32) and a stopper piece (33) formed to protrude toward the upper end of the slide shaft (32),
The closing plug (12) is guided and supported by the slide groove (35) so that the slide shaft (35) can only slide up and down by a guide groove (26) formed between the suspension arms (19) of the lock weight (11). ) In a state intersecting with the lock weight (11) and is held so as not to be lifted off.
A manhole structure in which a spring (13) is arranged between the lower part of the closure plug (12) and the spring seat (24). The slide center axis (L) of the stopper plug (12) is inclined so as to pass near the rotation center (R) of the swing shaft (18),
The manhole structure according to claim 1, wherein a majority of the face wall of the closing piece (31) is located inside an intersection (P) between the upper surface of the closing piece (31) and the slide center axis (L). On the upper part of the lock base (20), a regulation wall (28) that defines a rocking limit in the lock direction of the lock weight (11) is formed.
In a normal state, the stopper piece (33) is in contact with the inner opening edge of the burl hole (5) and the regulating wall (28) is in contact with the inner surface of the lid receiving frame (1), so that the lock weight (11) is swung. The manhole structure according to claim 1 or 2, wherein A pair of retaining walls (29) and a spring seat (24) covering the left and right of the spring (13) are formed on the spring receiving arm (22),
The manhole structure according to any one of claims 1 to 3, wherein a drainage cutout (30) is formed in each of an upper portion of the retaining wall (29) and a lower portion facing the spring seat (24).

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