KR101711010B1 - Self-rising Type Multi Manhole System - Google Patents

Abstract

The present invention relates to a multifunctional self-floating manhole system, efficiently securing safety of a passenger and a vehicle. The multifunctional self-floating manhole system comprises a manhole frame, a manhole cover, a lifting rotary shaft unit, and a locking unit.

Description

{Self-rising Type Multi Manhole System}

The present invention relates to a self-lifting multifunctional manhole system, and more particularly, to a self-lifting multifunctional manhole system in which a manhole cover is connected to a manhole frame when internal pressure of a certain pressure range is applied to a manhole for collecting communication, And a self-lifting multi-function manhole system capable of effectively preventing theft of a manhole cover and effectively securing the safety of a pedestrian and a vehicle.

Generally, a manhole buried in the ground is divided into a use for installing or repairing electricity, water and gas facilities, and a collection for collecting sewage and stormwater on the road. The manhole is divided into a lower frame and a manhole cover When the top of the frame is covered with the manhole cover, the manhole cover is received and held inside the frame entrance, and is embedded in the ground, concrete, and asphalt at a predetermined depth.

However, the structure of the existing manhole is merely mounted on the upper part of the manhole cover to form a detachable coupling structure. Since the cast iron is used as the material, there is a theft accident due to the rise of the scrap price, There is a problem that the manhole cover is opened and the security hole is opened so that it is very difficult to install in a place where security is required.

[0004] As a prior art disclosed to solve the above-described problems, Korean Patent Registration No. 1092838 (December 14, 2011) discloses a manhole cover having a seating surface around an inner circumferential surface thereof, A manhole cover and a support block detachably installed in the inside of the manhole cover and supporting a locking / unlocking function of the manhole cover, wherein a female screw is formed at a central portion of the support block, A locking shaft provided at the upper end of the shaft with a key fixing groove formed at the lower end thereof and penetrating the shaft hole, a shaft through hole into which a lower end of the locking shaft is inserted and a male threaded portion formed around the shaft hole, A drive shaft which forms a keyhole and in which an upper portion of a key guide slot is formed at an upper side or a lower side on one or both sides of the shaft hole inner surface, And the locking key is inserted into the key locking groove at the lower end of the locking shaft so that one end or both ends of the locking key are guided by the inner circumferential surface key guide slot of the shaft hole to move up and down. Apparatus is known.

However, in the case of the above-described conventional manhole, it is troublesome that the locking device should be replaced and repaired after a certain period of time. Further, when the locking device is released, the frame and the manhole cover are completely separated, There is a problem that a safety accident such as a fall of a pedestrian or the inflow of a vehicle is continuously generated because the work is performed with the manhole cover being opened by the weight of the manhole cover in the course of the construction work.

Also, when the influent flow exceeding the design standard is inputted in the event of summer heavy rain, the manhole lid is released due to the rainwater inflow amount and the back flow in the rain water pipe. In the case where the lock device is designed in the manhole cover as described above, The load is accumulated in a state of increased pressure, thereby causing an explosive manhole release phenomenon along with a pipe breakage phenomenon. In such a case, when there is a person or a vehicle on the manhole cover, there is a problem that it is exposed to a very dangerous safety accident.

Conventionally, snowy roads due to winter snowfall are often formed, and there is a problem that slip accidents occur continuously when a pedestrian or a vehicle passes through because the road surface of the manhole is smooth.

Patent Registration No. 10-1092838 (December 14, 2011)

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a manhole cover which is constructed by interconnecting manhole lids to integrate the manhole lids when the inner pressure is generated in the manhole, thereby preventing the manhole cover from being stolen, And it is an object of the present invention to provide a self-lifting multifunctional manhole system capable of enhancing the security of a vehicle and security in a manhole, and minimizing a safety accident caused by separation and separation of a manhole cover.

In addition, the present invention is to provide a self-lifting multi-function manhole system capable of preventing a slip phenomenon of a pedestrian or a vehicle on the snowy road because it constitutes a surface of a non-slip on the top surface of a manhole cover.

The self-lifting multifunctional manhole system proposed by the present invention is characterized in that the self-lifting multifunctional manhole system is provided with an inlet formed to be fixed to the upper end of a through-hole for entry into a duct and vertically penetrated to the inside thereof and having a protruding step formed on the inner surface of the inlet, A manhole frame extending inwardly and forming a shaft receiving hole and a receiving end portion provided at positions opposed to each other; And a shaft engagement groove formed at a lower portion corresponding to the shaft engagement hole, the shaft engagement groove being received in the upper surface of the inlet hole of the manhole frame so as to be closeable and being seated on the step portion, A manhole cover provided with a manhole cover; A lifting / lowering shaft unit coupled to an upper portion of the shaft coupling groove so as to support a rotation action of the manhole cover when the manhole cover is opened and closed and to be vertically movable on an axis of the manhole frame; A locking unit installed on the through hole of the manhole cover to be rotatable and capable of flowing upward and downward on a locking end of the manhole frame and capable of setting a locked state or an unlocked state of the manhole cover; And when the manhole cover is locked from the lock unit and the inflow rate of the inflow rate of the manhole cover is in the range of 0.40 to 1.68 m3 / s, the manhole cover is automatically lifted by the inner pressure of the manhole, The manhole cover is floatable at 15 to 20 mm so as to ensure the safety of the pedestrian and the vehicle while discharging the air pressure.

The manhole cover is formed with a protrusion pattern portion protruding from the upper surface and arranged in a predetermined pattern, and the protrusion pattern portion has a coefficient of friction of 0.68 to 0.75 for preventing slipping.

The elevating and lowering rotary shaft unit includes a connection head portion corresponding to the shaft engagement groove and rotatably supporting the manhole cover, and a connecting head portion extending downward from the connection head portion and received in the shaft receiving hole of the manhole frame, And a separation protrusion formed laterally at a lower portion of the flow neck and contacting the shaft stop of the manhole frame.

Wherein the lock unit includes a hinge shaft rotatably coupled to the through hole of the manhole cover, a push operation portion formed to extend upward with respect to the hinge axis and exposed through the through hole and pressably operable, A guide neck portion that extends downwardly and flows into the engaging end portion of the manhole frame and flows in the up and down direction, and a guide protrusion formed laterally at the lower portion of the guide neck portion and contacting with the engaging end portion.

The lock unit is constructed to have a strength capable of being broken by a load when the flow rate of the inflow into the pipeline is applied to the manhole cover in a pressure range corresponding to not less than 1.68 m 3 / s.

Further, the present invention further includes a fall prevention unit, which is installed in the inlet port of the manhole frame so as to be openable and closable, and has a structure in which a plurality of grill bars are arranged at intervals from each other.

Wherein the fall preventing unit includes a grating body connected to a plurality of steel bars in an inlet space of the manhole frame, a support shaft frame supporting the grating body so as to open and close the grating body, As shown in Fig.

The load strength of the fall preventing unit is 4.5 to 5.0 (kN).

According to the self-lifting multi-function manhole system of the present invention, since the manhole cover can be locked while connecting the manhole cover integrally and rotatably on the manhole frame, the manhole cover can be prevented from being stolen, It is possible to prevent a fall accident caused by the absence of the manhole cover and to protect the safety of the pedestrian and the vehicle. Furthermore, when the manhole cover is locked, the manhole cover can be self-lifted by 15 to 20 mm due to the pressure in the manhole, so that the pressure generated by the concentrated rain or the backwashing is discharged. As the manhole cover is opened to one side, it is possible to minimize the loss due to natural disasters and safety accidents.

In addition, the self-lifting multi-function manhole system according to the present invention has a non-slip type protrusion pattern portion on the surface of a manhole cover, thereby preventing sliding accident on a pedestrian or a vehicle, thereby further enhancing safety .

Further, the self-lifting multi-function manhole system according to the present invention includes the fall prevention unit mounted in the manhole frame so as to be openable and closable, thereby preventing the fall of a pedestrian or a vehicle even after the manhole cover is opened.

1 is a plan view showing an embodiment according to the present invention;
2 is an exploded perspective view showing an embodiment according to the present invention;
3 is a sectional view showing an embodiment according to the present invention.
4 (a) and 4 (b) are plan views showing first and second embodiments of the protruding pattern portion in the manhole cover according to an embodiment of the present invention, respectively.
5 is a perspective view showing an elevating and lowering rotary shaft unit according to an embodiment of the present invention.
6 is a perspective view illustrating a lock unit in an embodiment according to the present invention;
7 is a cross-sectional view illustrating a floating state of a manhole cover in an embodiment according to the present invention.
8 is a front view showing an open state of a manhole cover in an embodiment according to the present invention.
9 is a plan view showing another embodiment according to the present invention.

The present invention relates to an apparatus and a method for controlling an air conditioner, which comprises an inlet formed to be fixed to an upper end of a through hole for entering an inside of a duct and vertically penetrated to the inside thereof and having a protruding step formed on an inner surface of the inlet, A manhole frame for forming a shaft receiving hole and an engaging end portion; And a shaft engagement groove formed at a lower portion corresponding to the shaft engagement hole, the shaft engagement groove being received in the upper surface of the inlet hole of the manhole frame so as to be closeable and being seated on the step portion, A manhole cover provided with a manhole cover; A lifting / lowering shaft unit coupled to an upper portion of the shaft coupling groove so as to support a rotation action of the manhole cover when the manhole cover is opened and closed and to be vertically movable on an axis of the manhole frame; A locking unit installed on the through hole of the manhole cover to be rotatable and capable of flowing upward and downward on a locking end of the manhole frame and capable of setting a locked state or an unlocked state of the manhole cover; And when the manhole cover is locked from the lock unit and the inflow rate of the inflow rate of the manhole cover is in the range of 0.40 to 1.68 m3 / s, the manhole cover is automatically lifted by the inner pressure of the manhole, The multi-function manhole system according to the present invention is characterized by a self-lifting multi-function manhole system in which the manhole cover is lifted up to 15 to 20 mm so as to secure the safety of a pedestrian and a vehicle while discharging air pressure.

Next, a preferred embodiment of a self-lifting multi-function manhole system according to the present invention will be described in detail with reference to the drawings.

1 and 2, a self-lifting multi-function manhole system according to the present invention includes a manhole frame 10, a manhole cover 20, a lifting and rotating shaft unit 30, and a lock unit 40).

As shown in Figs. 1 and 2, the manhole frame 10 is formed in a round-shaped, donut-shaped cross-section, and a flange end portion 19 extending outward at the lower end of the outer circumferential surface is formed and installed on a structure such as concrete or asphalt As a possible structure, it is fixed by using a plurality of bolts at the upper end of the through hole for entry into the pipeline.

As shown in FIGS. 2 and 3, the manhole frame 10 has an inlet 11 vertically penetrating the inside thereof to allow the operator to enter and exit the manhole cover 20, The manhole cover 20 introduced into the manhole frame 10 can be seated against the stepped portion 13 because the stepped portion 13 protruding inward is formed on the inner surface of the manhole frame 11 .

Since the step portion 13 is formed so as to correspond to the thickness of the manhole cover 20, the position of the step portion 13 in the manhole frame 10 corresponds to the thickness of the manhole cover 20, It is preferable that the upper surface of the manhole cover 20 and the upper end of the manhole frame 10 are formed so as to be located on the same line.

The manhole frame 10 is formed with a shaft stop 15 and an engaging end 17 extending inward on the step portion 13.

The shaft stop 15 and the stop end 17 are positioned on the manhole frame 10 such that the shaft stop 15 and the stop end 17 are opposed to each other .

The shaft latch 15 forms a shaft hole 16 corresponding to the elevating rotary shaft unit 30 and vertically penetrating the elevating rotary shaft unit 30 so as to partially receive the elevating rotary shaft unit 30. [

The locking end portion 17 is positioned so as to correspond to the locking unit 40 and is protruded so as to engage with the lower end of the locking unit 40. [ In other words, the locking end portion 17 has a block-like shape, and a pair of blocks are disposed to be spaced apart from each other, so that one side thereof is opened, and the locking unit 40 is opened So that it can be released by the rotation action of the lock unit 40. [

The manhole cover 20 has a circular cross-sectional shape and is received on the upper jaw portion 13 so as to be capable of closing the upper surface of the inlet 11 of the manhole frame 10.

The manhole cover 20 is formed with protrusion pattern portions 21 protruding from the upper surface thereof and arranged in a predetermined pattern.

The protrusion pattern portion 21 is protruded to have a height of 5 to 20 mm with respect to the upper surface of the manhole cover 20, so that slippage in the eye is effectively prevented.

The projection pattern portion 21 has a coefficient of friction of 0.68 to 0.75 for preventing slipping.

As shown in Fig. 4, the protrusion pattern portion 21 is configured such that the individual protrusions have pin or triangular cross-sectional shapes.

When the protrusion of the protrusion pattern portion 21 is formed in the shape of a pin as shown in FIG. 4A, the height of the protrusion is 5 to 10 mm, and the gap between the protrusions is narrowed to prevent damage to another contact surface, It is preferable that the protrusion of the protrusion pattern portion 21 be formed so as to have a triangular sectional shape as shown in FIG. 4 (b), and that the individual protrusions are arranged in different directions, It is preferable that the height is formed to be 10 to 20 mm so that the interval between the projections is relatively secured to satisfy the coefficient of friction for preventing slippage.

As described above, if the protrusion pattern portion 21 of the non-slip shape is formed on the surface of the manhole cover 20, it is possible to prevent slip accident in the eyes of the pedestrian or the vehicle, thereby further improving the safety.

The manhole cover 20 is provided with a shaft coupling groove 25 formed at a lower portion corresponding to the shaft receiving hole 15 and forming a space in which the elevating and rotating shaft unit 30 can be mounted, And a through hole 27 penetrating in a vertical direction corresponding to the lock unit 15 and forming a space into which the lock unit 40 can be mounted.

The manhole cover 20 is made of cast iron of a natural material added with 2.0 to 3.6% carbon in iron having a melting point of 1150 캜 as a material, and has a melting recovery rate of 95% or more.

When the cast iron of the above-described condition is used in the manhole cover 20 as described above, the manhole cover 20 (having a low recycling ratio (80% or less) as the existing low carbon content is mixed with the metal (lead, mercury, ), It is possible to suppress environmental destruction caused by scrap metal recycling and to establish a resource circulation function.

The lifting and lowering shaft unit 30 has a function of integrally connecting the manhole cover 10 and the manhole cover 20 and also supports a rotating action of the manhole cover 20 when the manhole cover 20 is opened and closed.

As shown in FIG. 3, the lifting and lowering shaft unit 30 is axially connected to the shaft engagement groove 25 of the manhole cover 20 to rotatably support the manhole cover 20.

The lifting and lowering shaft unit 30 supports the manhole cover 20 vertically movably in a state of being accommodated on the manhole frame 10. That is, on the shaft stop 15 of the manhole frame 10, and is movably coupled up and down.

3 and 5, the lifting and rotating shaft unit 30 includes a coupling head 31 coupled to the shaft coupling groove 25 and rotatably supporting the manhole cover 20, A flow neck portion 33 extending downward from the connection head portion 31 and a release preventing jaw 35 protruding laterally from the lower portion of the flow neck portion 33.

The manhole cover 20 is extended from the manhole frame 10 so as to be vertically movable and accommodated in the shaft hole 16 of the shaft hole 15 of the manhole frame 10 And is formed to be vertically movable in the longitudinal direction.

The departure prevention pin 35 is formed on both sides of the lower portion of the flow neck 33 so as to contact the shaft stop 15 of the manhole frame 10 when the manhole cover 20 is moved upward.

The lock unit 40 is provided to set the manhole cover 20 from the manhole frame 10 to a locked state or an unlocked state.

3, the lock unit 40 is rotatably installed on the through hole 27 of the manhole cover 20 and is rotatably mounted on the engaging end 17 of the manhole frame 10 And flows upward and downward.

3 and 6, the lock unit 40 includes a hinge shaft 41 rotatably coupled to the through hole 27 of the manhole cover 20, A guide neck portion 45 extending downward with respect to the hinge shaft 41 and a hooking protrusion 47 protruding from the lower portion of the guide neck portion 45.

The pushing operation part 43 is formed extending upwardly with respect to the hinge shaft 41 to be exposed through the through hole 27. That is, when the upper surface is exposed on the through hole 27 of the manhole cover 20 and the worker presses downward, the lock unit 40 rotates to move from the engaging end 17 of the manhole frame 10 The locking protrusion 47 is released so that the unlocking state is established in which the manhole cover 20 can be opened by the locking unit 40. [

The guide neck portion 45 extends downwardly from the hinge shaft 41 and flows into the engagement end portion 17 of the manhole frame 10 so that the guide neck portion 45 can move in the vertical direction in contact with the engagement end portion 17 .

The hooking protrusion 47 protrudes laterally from the left and right sides of the guide neck 45 and contacts the hook end 17 to lock the manhole cover 20 in a locked state.

As shown in FIG. 7, the manhole cover 20 is self-floatable from 15 to 20 mm from the manhole frame 10 according to the pressure in the manhole. That is, when the manhole cover 20 is locked from the lock unit 40 and the inflow rate of the inflow rate of the manhole cover 20 is 0.40 to 1.68 m3 / s, the manhole cover 20 is automatically lifted by the inner pressure of the manhole Since the water pressure or the air pressure inside the manhole cover 20 is discharged, the manhole cover 20 is raised to 15 to 20 mm so as to ensure the safety of the pedestrian and the vehicle.

For example, when the amount of precipitation is about 20 mm per hour and the inflow rate of the channel is 0.40 m 3 / s, the manhole cover 20 floats, and the separation preventing jaw 35 of the lifting / The engaging protrusions 47 of the lock unit 40 are engaged with the engaging end portions 17 of the manhole frame 10 at the same time that the manhole cover 10 is engaged with the shaft latching openings 15, 15 to 20 mm. At this time, the lifted state of the manhole cover 20 is maintained in a floating state until a pressure of 1.68 m 3 / s is applied to the channel so that water pressure or air pressure is discharged.

The lock unit (40) has a strength at which the lock unit can be broken by a load when a flow rate in the channel is applied to the manhole cover in a pressure range corresponding to 1.68 m 3 / s or more. 8, when the pressure range corresponding to the inflow rate of 1.68 m3 / s or more is continuously applied to the manhole cover 20, the lock unit 40 is broken and the manhole cover 20 is moved up and down by the lifting / The manhole cover 20 is rotated with respect to the elevating and rotating shaft unit 30 to open the manhole while maintaining the state of being integrated with the manhole frame 10 by the lifting and rotating shaft unit 30.

That is, according to the self-lifting multi-function manhole system of the present invention constructed as described above, the manhole cover 20 is integrally connected to the manhole frame 10 in a rotatable manner so that the manhole cover 20 can be locked It is possible to prevent the manhole cover 20 from being stolen to thereby prevent local economic loss and to protect the safety of the pedestrian and the vehicle by preventing the fall accident caused by the member of the manhole cover 20 in advance.

Further, according to the present invention, since the manhole cover 20 can be self-lifted by 15 to 20 mm due to the pressure of the manhole in the locked state of the manhole cover 20, it is possible to discharge the pressure generated by the concentrated backwash or the water / When the pressure is generated, the lock unit 40 is broken and the manhole cover 20 is opened to one side, it is possible to minimize a loss or a safety accident due to a natural disaster.

As shown in FIG. 9, another embodiment of the self-lifting multi-function manhole system according to the present invention is characterized in that the manhole frame 10 is installed in the inlet 11 of the manhole frame 10 so as to be openable and closable, And a fall prevention unit (50) formed of a bottomed structure.

The fall preventing unit 50 includes a grating main body 51 provided in the manhole frame 10, a support shaft frame 53 for rotating the grating main body 51, And fixing means 55 for fixing.

The grating main body 51 is structured to be seated in the space of the inlet 11 of the manhole frame 10. The manhole frame 10 is provided with a support chin 14 capable of supporting the grating main body 51 in a horizontal state ). That is, the lower end of the grating body 51 can be brought into contact with the base 14 so as to stably support the closed state of the grating body 51.

The grating main body 51 is integrally connected by arranging a plurality of grating bars spaced from each other.

The grating body 51 is formed using a metal material so as to sustain a contact load on the upper side.

And the load strength of the fall preventing unit 50 is set to 4.5 to 5.0 (kN).

The support shaft frame 53 is pivotally connected to the manhole frame 10 to support the grating body 51 so as to open and close the grating body 51.

Although not shown in the drawing, the engaging means 55 is a structure that can be fixed on the manhole frame 10 in a closed state of the grating body 51, and has a coupling end protruding upward from one end of the manhole frame 10, And the grating main body 51 is formed with a coupling hole corresponding to the coupling end, so that the coupling hole can be contacted with the coupling end so that mutual coupling can be maintained.

That is, according to the present invention as in the above-described other embodiments, since the fall preventive unit 50 is installed in the manhole frame 10 so as to be openable and closable, even after the manhole cover 20 is opened, . ≪ / RTI >

In the other embodiments described above, the same configuration as that of the above-described embodiment can be employed, so that detailed description is omitted.

Hereinafter, the present invention will be described in more detail by way of examples. However, these experimental examples are only for illustrating the present invention, and the scope of the present invention is not construed as being limited by these experimental examples.

Experimental Example  One

After placing the specimen of the present invention on a testing machine, a high-quality rubber plate having a thickness of 6 mm was laid on the center of the specimen, and an iron load plate having a length of 400 mm, a width of 250 mm and a thickness of 50 mm was placed on the entire fall prevention unit Next, in the state where the test load applied in the vertical direction and the load plate were adjusted so as to be perpendicular, the test load was applied at a constant speed toward the vertical direction to measure the fall preventing load resistance (Experimental Example 1) The anti-falling resistance load was measured under the same experimental conditions (Comparative Example 1), and the average value of the results was shown in Table 1 below.

division Anti-fall load capacity (kN) Experimental Example 1 4.8 Comparative Example 1 2.8

As can be seen from the above Table 1, the load strength measurements of Comparative Example 1 showed significantly lower values than the open world highest load strength measurements (4.5 kN), whereas the load strength measurements of Experimental Example 1 It is confirmed that the load strength is higher than the highest load strength measurement value.

Experimental Example  2

The friction coefficient of the surface of the manhole cover was measured at three points using the DF tester for measuring the dynamic friction coefficient of the packing in the evaluation of the slip resistance of the manhole cover, and the average value was shown (Experimental Example 2) The friction coefficient of the surface was measured under the same experimental conditions, and the average value was shown (Comparative Example 2). The average value of the results was shown in Table 2 below.

division Sliding resistance (coefficient of friction) Experimental Example 2 0.72 Comparative Example 2 0.41

As can be seen from the above Table 2, the coefficient of friction of Comparative Example 2 was lower than that of the world's highest coefficient of friction (0.67), while the coefficient of friction of Experiment 2 was the highest in the world Which is higher than the measured value of the coefficient of friction.

Although the preferred embodiments of the self-lifting multifunctional manhole system according to the present invention have been described above, the present invention is not limited thereto, but may be modified in various ways within the scope of the claims, And is also within the scope of the present invention.

10: manhole frame 11: inlet 13:
15: shaft stop 16: shaft hole 17: engaging end
20: manhole cover 21: projection pattern part 25:
27: through hole 30: lifting / lowering shaft unit 31: connecting head
33: floating neck portion 35: release preventing jaw 40: locking unit
41: hinge shaft 43: push operating part 45: guide neck
47: engaging jaw 50: fall preventing unit 51: grating body
53: support shaft frame 55: engaging means

Claims (8)

And an inlet formed at an upper end of the through hole for entry into the duct and having an inlet vertically penetrated to the inside thereof and having a protruding step formed on an inner surface of the inlet, A manhole frame forming a shaft stop and a locking end; And a shaft engagement groove formed at a lower portion corresponding to the shaft engagement hole, the shaft engagement groove being received in the upper surface of the inlet hole of the manhole frame so as to be closeable and being seated on the step portion, A manhole cover provided with a manhole cover; A lifting / lowering shaft unit coupled to an upper portion of the shaft coupling groove so as to support a rotation action of the manhole cover when the manhole cover is opened and closed and to be vertically movable on an axis of the manhole frame; A locking unit installed on the through hole of the manhole cover to be rotatable and capable of flowing upward and downward on a locking end of the manhole frame and capable of setting a locked state or an unlocked state of the manhole cover; And when the manhole cover is locked from the lock unit and the inflow rate of the inflow rate of the manhole cover is in the range of 0.40 to 1.68 m3 / s, the manhole cover is automatically lifted by the inner pressure of the manhole, Wherein the manhole cover is raised to 15 to 20 mm so as to secure the safety of the pedestrian and the vehicle while discharging air pressure,
Wherein the protruding pattern portion has a triangular cross-sectional shape in which the individual protrusions are arranged in different directions, and the height of the protrusions is 10 To 20 mm, and has a coefficient of friction of 0.68 to 0.75 for anti-slip,
The elevating and lowering rotary shaft unit includes a connection head portion corresponding to the shaft engagement groove and rotatably supporting the manhole cover, and a connecting head portion extending downward from the connection head portion and received in the shaft receiving hole of the manhole frame, And a separation preventing protrusion protruding laterally from a lower portion of the flow neck portion and contacting the shaft retaining opening of the manhole frame so as to be engaged with the shaft retaining opening,
Wherein the lock unit includes a hinge shaft rotatably coupled to the through hole of the manhole cover, a push operation portion formed to extend upward with respect to the hinge axis and exposed through the through hole and pressably operable, And a guide protrusion formed laterally at a lower portion of the guide neck and contacting with the engaging end so as to be engaged with the engaging end, Wherein the lock unit is constructed to have a strength that can be broken by a load when the flow rate of the inflow into the pipeline is applied to the manhole cover in a pressure range corresponding to not less than 1.68 m 3 / s,
The fall preventing unit includes a fall preventing unit which is installed in an inlet of the manhole frame so as to be openable and closable and is formed by arranging a plurality of grating bars spaced apart from each other, And a coupling means for fixing the grating body on the manhole frame in a closed state, wherein a load intensity of the fall prevention unit is set to 4.5 to 5.0 < RTI ID = 0.0 > (kN). ≪ / RTI >
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