JP2024075505A - Suspended installation structure for work ladders - Google Patents

Abstract

To easily assemble a work ladder on the ground near the top surface of a manhole, and to suspend and install the work ladder in a state where the work ladder can be easily accessed from the top surface of the manhole.
[Solution] The suspended installation structure 100 for the work ladder comprises a frame body 110 erected near the periphery of the upper surface of the manhole, a connecting part 120 connecting the frame bodies 110 together in the horizontal direction, and a rod body 130 and a second rod body 140 hung across the upper part of the hole of the manhole 200, and the work ladder 160 is suspended downward from the rod body 130 toward the hole of the manhole 200 via a hanging member 164. A safety device 150 is attached to the worker's wearing equipment from the second rod body 140. A configuration in which the rod body 130 comprises a rod-shaped part 131 and a fall prevention body 132 having a length to be hung across the upper part of the manhole 200 and to be hung, and the second rod body 140 also comprises a second rod-shaped part 141 and a second fall prevention body 142 is preferable.
[Selected Figure] Figure 1

Description

The present invention relates to a structure for hanging and installing a work ladder used for work on manholes and the like installed in roads and buildings. More specifically, the present invention relates to a structure for installing a work ladder that can be brought to a site around the top of a manhole, installed, a work ladder for ascending and descending into the manhole, work performed inside the manhole, and removed from the site around the top of the manhole after work is complete.

Manholes in roads and buildings are installed for various purposes, such as power lines, communication cables, gas, water supply, and sewage systems, and workers climb into the manholes as needed to carry out work. Manholes vary in depth, but generally a work ladder is required.

The first type of work ladder, which is an older type, is a fixed metal ladder that is directly driven into the wall of the manhole. There are still many manholes of this old type remaining throughout Japan, and they make up a large proportion of the total, so in some ways this type is still the mainstream.
Fig. 12 shows a conventional work ladder with rungs (steps) fixedly installed in the wall of a manhole in concrete. Conventionally, a fixed ladder installed in the wall of a manhole as shown in Fig. 12 was used to ascend and descend. In this example, the posts of the fixed ladder are in the form of so-called H-beams, and a device was known in which a safety device was attached to the posts to ensure safety during ascending and descending (Patent Document 1: JP 2009-209672 A).

The second type of work ladder has a suspension frame formed in a part of the metal hole structure that forms the entrance portion of the manhole, and a suspension type work ladder is suspended from the suspension frame.
FIG. 13 is a diagram showing a second type of work ladder, in which a suspension frame is provided in a metal hole forming the upper surface of a manhole, and a suspension type work ladder is suspended from the suspension frame (Patent Document 2: JP 2020-012293 A).
Patent Document 2 proposes that even when pipes or the like pass through a manhole, limiting the space for suspending a suspension ladder and the metal hole suspension frame cannot provide a sufficient width for suspension, as shown in Figure 12(a), a suspension-enabled component can be supplied to suspend a work ladder while avoiding the pipes in the manhole, as shown in Figure 12(b).

The third type of work ladder is a work ladder in which a movable ladder can be pulled upward from a fixed ladder.
Figure 14 shows a third type of work ladder, which is a work ladder that has a structure that allows a movable ladder to be pulled upward from a fixed ladder fixed to the wall inside a manhole (Patent Document 3: JP 2011-256532 A).
As shown in Fig. 14, the movable ladder is connected to the fixed ladder, and the technology of Patent Document 3 can be said to be an improvement over the fixed work ladder shown in Patent Document 1. When using the first type of fixed work ladder, there is a small distance from the ground around the top surface of the manhole to the top rung (step), which is dangerous. Therefore, the third type of work ladder shown in Patent Document 3 has a structure in which a movable ladder that can be pulled out upward from the fixed ladder is connected, so that the ladder can be protruded further upward from the top surface of the manhole by pulling the movable ladder upward, and the worker can move from the movable ladder to the fixed ladder while firmly holding the movable ladder on the ground before descending into the manhole, and can then descend into the manhole.
Patent Document 3 also discloses a safety device for a movable ladder. A hanging frame for attaching a safety device is provided at the top end of the movable ladder, and safety can be ensured by attaching the safety device to the hanging frame and attaching it to the worker's belt, etc.

The fourth type of work ladder is a further improvement of the third type of work ladder, and is a work ladder in which the movable ladder connected to the fixed ladder has a bendable structure (Patent Document 4: JP 2013-249626 A).
Figure 15 shows a fourth type of work ladder, in which the upper part of the movable ladder connected to the fixed ladder has a bendable structure, and the movable ladder is long enough to fit inside a manhole when bent.
As shown in Fig. 15(a), when the manhole cover is opened, the bent part of the movable ladder is located on the top surface of the manhole. Since the bent part of the movable ladder is located on the top surface of the manhole and can be easily accessed from the ground near the top surface of the manhole, the operation of erecting the bent part can be performed safely as shown in Fig. 15(b).

JP 2009-209672 A JP 2020-012293 A JP 2011-256532 A JP 2013-249626 A

The above-mentioned conventional work ladders had problems.
As already mentioned, the first type of fixed metal ladder, which is directly installed in the wall of the manhole, has a small distance between the ground around the top of the manhole and the top rung (step), and it is dangerous to reach beyond this distance. The condition of the top rung (step) cannot be confirmed well, so it is dangerous to put your foot down and step on it in one go. You may miss your step, or the top rung (step) may be dirty and you may slip.

The second type of work ladder is suspended from a suspension frame that is part of the metal hole structure at the manhole entrance, and is easier for workers to access from the ground near the top of the manhole than the first type of work ladder, but it has the following problems.
The first problem is that the suspension frame cannot be attached to the metal hole structure at the manhole entrance. The suspension frame can be attached to the metal hole structure at the manhole entrance when the manhole is constructed, and the metal hole structure with the suspension frame needs to be poured with concrete at the same time as pouring concrete on the wall of the manhole. As already mentioned above, most manholes currently existing throughout Japan have a simple circular frame at the manhole entrance. In other words, the second type of work ladder can be used in the construction of new manholes or the reconstruction of existing manholes, but it is a technology that cannot be applied to existing manholes currently existing throughout Japan.
The second problem is that if a suspension frame is provided in the metal hole structure at the manhole entrance, the effective area of the hole at the manhole entrance cannot be made large; conversely, if the effective area of the hole at the manhole entrance is increased, the suspension frame will have to be provided along the wall surface of the metal hole, resulting in a curved shape, and the distance and length from the wall surface for the suspension frame cannot be sufficiently secured, meaning that only small suspension type work ladders can be used.

The third type of work ladder is constructed so that a movable ladder can be pulled out upward from a fixed ladder secured to the wall inside the manhole. Like the first type of work ladder, it is easy for workers to access it from the ground near the top of the manhole, but it has the following problems.
The first problem is that it is difficult to retrofit a movable ladder to a fixed ladder already installed in a manhole. In other words, the fixed ladder needs to have a structure that allows a movable ladder to be protruded from it, but as already mentioned above, many manholes currently existing throughout Japan have fixed ladders fixed to the manhole wall, and while this third type of work ladder can be used in the construction of new manholes or the reconstruction of existing manholes, it is a technology that cannot be applied to existing manholes currently existing throughout Japan.
The second problem is that in order to pull up the movable ladder from the fixed ladder already installed in the manhole, it is necessary to access at least the depth of the top rung of the fixed ladder. It is thought that a worker would reach his arm into the manhole from the ground near the top of the manhole, grab the movable ladder, and pull it up. This type of work is also dangerous. There is a part of the movable ladder that can be hooked with a tool, and a worker could use the tool to hook it from the ground near the top of the manhole and pull up the movable ladder, but this work is thought to be difficult.

The fourth type of work ladder is a work ladder in which a movable ladder connected to a fixed ladder of the third type is further bendable. This makes it easier for workers to access the manhole from the ground near the top surface than the third type of work ladder, but it has the following problems.
The problem is the same as the first problem described for the third type of work ladder, and it is difficult to retrofit the above-mentioned movable ladder to a fixed ladder already installed in a manhole. In other words, the fixed ladder needs to be equipped with a structure that allows the movable ladder to be protruded from it, but as already mentioned above, many manholes currently existing throughout Japan have fixed ladders fixed to the manhole wall, and this fourth type of work ladder can be used in the construction of new manholes or the reconstruction of existing manholes, but it is a technology that cannot be applied to existing manholes currently existing throughout Japan.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a suspended installation structure for a work ladder that can be used to suspend and install a work ladder in existing manholes throughout Japan without the need for construction work.
In particular, the objective of the present invention is to provide a suspended installation structure for a work ladder that can be easily assembled by workers on the ground near the top surface of a manhole at the site, and that can be installed in a state in which the work ladder can be easily accessed from the top surface of the manhole.

In order to achieve the above-mentioned objective, the work ladder hanging installation structure of the present invention is a work ladder installation structure that can be installed and removed on-site to enable work inside a manhole to be ascended and descended by workers, and is characterized in that it comprises a work ladder, a frame body having at least legs and erected near the upper periphery of the manhole, connecting parts that connect the frame bodies horizontally, and a rod body that is attached to the frame body and hung across the upper vicinity of the manhole hole, the work ladder has a hanging member that hangs from the rod body, and the work ladder is hung downward from the rod body via the hanging member toward the manhole hole.
The rod here means a so-called pole-shaped structure, which is attached to a frame body erected at a position facing the manhole. The rod is a structure that can be hung across the top of the manhole. There are no restrictions on the location of attachment to the frame body, but a stable location is preferable. For example, the frame frame of the frame body is preferable.

With the above-mentioned configuration, the suspended installation structure for a work ladder of the present invention can be easily constructed by bringing it into a manhole in the floor of a road or building that will be the work site, and while installing the work ladder, workers can always remain on the ground near the top of the manhole, ensuring safety during work.
Manholes to which the suspended installation structure for work ladders of the present invention can be applied can be directly applied to existing manholes currently existing throughout Japan, and no prior construction or modification of the manhole is required.

Further measures have been taken to prevent the rod from falling.
The rod is a structure made by combining at least two members.
The first member is a rod-like structure that is long enough to span across and latch onto the top of the manhole.
The second member is a fall prevention body, which may be a structure including a disk-shaped member with a diameter larger than the diameter of the manhole, or a cross-shaped structure with all sides longer than the diameter of the manhole.
By providing the rod with the fall prevention device in this way, even if an unexpected event occurs and the frame body of the installation structure for the work ladder or the support members attached to the frame body collapses, causing a so-called collapse of the scaffolding and causing a situation in which the worker may fall together with the work ladder, the fall prevention device can reliably catch on the entrance of the manhole and prevent further falls. In other words, a structure including a disk-shaped member with a diameter larger than the diameter of the manhole or a cross-shaped structure with both sides longer than the diameter of the manhole cannot pass through the entrance of the manhole, so the technical effect is that the fall prevention device always catches on the entrance of the manhole and prevents further falls.

Next, for the safety of the worker, a second rod is provided to support a safety device attached to the worker's equipment.
The second rod is a structure that is attached directly to the frame body or via a support member attached to the frame body and hung across the top of the manhole opening.
A safety device is attached to connect the second rod to the worker's harness.
By installing the safety device, the worker can work with his/her body supported by the second rod via the attachment and the safety device, thereby ensuring safety.

This second rod also has additional measures in place to prevent it from falling off.
The second rod has a structure including a second rod-shaped part having a length to span across the top of the manhole and hang on it, and a second fall prevention body, where the second fall prevention body includes a structure including a second disk-shaped member having a diameter larger than the diameter of the manhole, or a second auxiliary rod member which, when combined with the second rod-shaped part, forms a cross-shaped structure with all sides longer than the diameter of the manhole.
In this way, by providing the second rod with the second fall prevention body, even if an unexpected event occurs and the frame body of the installation structure for the work ladder or the support member attached to the frame body falls, causing a so-called collapse of the scaffolding and causing a situation in which the worker may fall together with the work ladder, the fall prevention body can be sure to catch on the entrance of the manhole and prevent further fall. In other words, a structure including a disk-shaped member with a diameter larger than the diameter of the manhole or a cross-shaped structure with both sides longer than the diameter of the manhole cannot pass through the entrance of the manhole, so the technical effect is that the fall prevention body always catches on the entrance of the manhole and prevents further fall.
In this way, if the rod is equipped with a fall prevention device and the second rod is also equipped with a second fall prevention device, even if an emergency occurs, the impact can be kept small and all parts and workers will not fall a large distance into the manhole.

The frame that is dynamically erected at the work site is also assembled in a unique way.
When the frame bodies are connected to each other at an angle via the connecting parts, the frame bodies can be assembled to surround or partition the upper surface of the manhole, allowing it to be installed as a protective fence during manhole work.
In addition, in order for the suspended installation structure of the work ladder of the present invention to function as a protective fence while working with a small number of people, it is preferable that the installation state is stable even when there are no workers near the manhole. A structure that ensures that it does not move or shift unexpectedly from the vicinity of the manhole hole is required. Therefore, as a jig that is hooked to the edge of the manhole hole from multiple directions and installed, a configuration is provided with multiple locking bodies of a predetermined length that can be extended from a frame body or connected to the frame body. One end of this locking body is provided with a hook shape that can be hooked to the edge of the manhole hole, and when installed around the manhole hole, the locking body is hooked to the edge of the manhole hole from multiple directions and installed. The configuration of the locking body may be such that the base end is attached to a part of the frame body and the tip has a key shape that can be hooked to the edge of the manhole. Any structure is acceptable as long as the tip can be hooked to the edge of the manhole.
By providing the locking body, the effect is obtained that the entire suspended installation structure will not move or shift in the outer circumferential direction.

Furthermore, it is necessary to prevent the entire suspended installation structure from moving or shifting in the inward direction, that is, to prevent the frame body from moving due to a contraction in diameter. Therefore, it is also preferable to provide a configuration with a diameter contraction prevention body that is installed between the frame bodies that are separated and not directly connected, or between the frame bodies at both ends that are separated as entrances for workers to enter and exit, and that maintains a predetermined distance between the separated frames to prevent the diameter from contracting.
The diameter reduction prevention body may be configured so that one end can be attached to a part of the frame body and the other end can be attached to a part of the opposing frame body. A member with a simple structure may be a rod-shaped body with a gripping mechanism at both ends that clamps and grips a part of the frame body. Any structure is acceptable as long as it can prevent diameter reduction.
It is effective to attach the diameter reduction prevention body between the frame bodies that are separated from each other. For example, if the guard fence is circular, it is attached between the frame bodies that face each other. Also, for example, if the guard fence has an entrance, it can be attached between the frame bodies that form the entrance after the worker enters the guard fence. There is no particular limit to the height at which the diameter reduction prevention body is attached, but since it acts like a tension rod, it is effective to lay it horizontally parallel to the ground.

Furthermore, for example, if a tiger-patterned fence board is attached to the frame body as a sign to inform passersby that construction is underway or to prevent approach, it can become a so-called protective fence (guard fence).
Furthermore, if a slope body is provided on the outer periphery of the legs of the frame body so that it is in contact with the ground, it will act as a protective fence to prevent foreign objects from falling from around the top surface of the manhole.

Here, the suspended work ladder is preferably a so-called telescopic ladder, taking into consideration ease of carrying it to the work site and deploying it inside a manhole.
An extendable ladder is a ladder whose basic unit is a ladder basic member having a pair of cylindrical support bodies arranged parallel to each other at a predetermined distance and a cross bar provided between the cylindrical support bodies, and the ladder basic members are sequentially connected to each other in a nested state so that they can slide in the cylindrical axial direction of the cylindrical support bodies.The ladder has a retracted storage state in which the ladder basic member is slidably stored, and an extended use state in which the ladder basic member is slidably extended.
By using an extendable ladder in this manner, the ladder's length is short, making it easy to transport, and when the ladder is deployed into a manhole, the length of the ladder can be easily extended at the work site and used to descend into the manhole.
It is preferable that a wire-shaped telescopic operating body is provided on the lowest rung of the work ladder, and by pulling up the wire-shaped telescopic operating body, a worker can contract the telescopic work ladder, which is in an extended use state, into a shortened stored state from around the top surface of the manhole.
After work inside the manhole is completed, the tent can be easily shortened, making removal easy and increasing work efficiency.

The suspended installation structure for a work ladder of the present invention can be easily constructed by carrying it into a manhole in the floor of a road or building where the work is to be carried out, and while installing the work ladder, workers can always remain on the ground near the top of the manhole, ensuring safety during work.
Furthermore, according to the suspended installation structure for a work ladder of the present invention, the applicable manholes can be directly applied to existing manholes currently existing throughout Japan, and no prior construction or modification of the manholes is required.
Furthermore, in the suspended installation structure for the work ladder of the present invention, the rod is equipped with a fall prevention device, so that even if an unexpected incident occurs and the frame body of the installation structure for the work ladder or the support members attached to the frame body collapses, causing the scaffolding to collapse and causing the worker to fall along with the work ladder, the fall prevention device can reliably catch on the entrance to the manhole and prevent further fall.

FIG. 1 is a diagram showing a schematic configuration example of a suspended installation structure 100 for a work ladder according to a first embodiment. 13 is a diagram showing an example of a configuration in which the connection angle of the left and right frame bodies 110 is adjusted via a connecting portion 120. FIG. 13 is a diagram showing a state in which a locking body 170 and a diameter reduction prevention body 180 are attached to a frame body 110. FIG. FIG. 1 is a diagram showing the rod 130 taken out. FIG. 1 is a diagram showing the second rod 140 taken out. 1A to 1C are diagrams showing an example of the structure of a work ladder 160 which is an extendable ladder. 13 is a diagram showing the telescopic work ladder 160 being extended. FIG. 13A and 13B are diagrams showing how the telescopic work ladder 160 is contracted. FIG. 1 is a diagram (part 1) showing the procedure for using the suspended installation structure 100 for a work ladder of the present invention. FIG. 2 is a diagram (part 2) showing the procedure for using the suspended installation structure 100 for a work ladder of the present invention. FIG. 3 is a diagram (part 3) showing the procedure for using the suspended installation structure 100 for a work ladder of the present invention. FIG. 1 shows a prior art work ladder with rungs (steps) fixed to the wall of a manhole through concrete. FIG. 1 is a diagram showing a second type of work ladder in the prior art disclosed in JP 2020-012293 A (Patent Document 2). FIG. 2 is a diagram showing a third type of work ladder in the prior art disclosed in JP 2011-256532 A (Patent Document 3). FIG. 1 is a diagram showing a fourth type of work ladder in the prior art disclosed in JP 2013-249626 A (Patent Document 4).

Hereinafter, an embodiment of the suspended installation structure for a work ladder of the present invention will be described with reference to the drawings.
It goes without saying that the scope of the present invention is not limited to the specific shapes, designs, numbers, angles, etc. shown in the following examples.

FIG. 1 is a diagram showing a schematic configuration example of a suspended installation structure 100 for a work ladder according to a first embodiment.
FIG. 1(a) shows a perspective view of a suspended installation structure 100 for a work ladder, and FIG. 1(b) shows a front view (the surface from which a worker ascends and descends).
FIG. 1( a ) is a perspective view showing the state before the work ladder 160 is suspended from the rod 130 .
Moreover, Figure 1 (b) is a cross-sectional view showing the state after the work ladder 160 has been suspended from the rod 130, and is a cross-sectional view taken at a height slightly above the height of the rod 130 so that the state in which the work ladder 160 is suspended from the rod 130 can be clearly seen.
1(a) and 1(b), a fall prevention body 132 and a second fall prevention body 142, which will be described later, are not shown in order to avoid making it difficult to understand the relationship between the members. The fall prevention body 132 will be described later with reference to FIG. 4. The second fall prevention body 142 will be described later with reference to FIG. 5.

The suspended installation structure 100 for a work ladder of the present invention comprises a frame body 110, a connecting portion 120, a rod body 130, a second rod body 140, a safety device 150, and a work ladder 160. A manhole 200 is also shown in FIG.
Each component will be described below.

The frame body 110 is a structure erected near the periphery of the upper surface of the manhole 200. In this example, it is equipped with a plurality of legs 111 and a frame portion 112, and is structured to be self-supporting by erecting it on the ground. In this example, it is an example of a configuration equipped with two legs 111 and capable of self-supporting. Note that the frame body 110 constituting the suspended installation structure 100 for a work ladder is basically equipped with legs 111 and capable of self-supporting, but among the plurality of frame bodies 110, some frame bodies 110 may not have legs 111 and may be supported from the left and right and lifted up in the air.
The frame portion 112 includes an upper frame and a lower frame, but is not limited thereto. The frame portion 112 may be in the form of a frame or a plate.

The connecting portions 120 are members that laterally connect the frame bodies 110 to each other. In the configuration example of Fig. 1, connecting members 121 that laterally connect the upper end frames of the frame portion 112 to each other are provided.
The connecting member 121 has a structure that allows connection to the frame portion 112 at both ends, and the connecting angle is freely adjustable. Therefore, the connecting angle of the left and right frame bodies 110 can be freely adjusted via the connecting portion 120.

The number of frame bodies 110 and the number of connecting parts 120 are not limited. In the configuration example of Fig. 1, there are six frame bodies 110 and five connecting parts 120 between them, and the frame bodies 110 and the connecting parts 120 are assembled to form a 16-sided polygon with five missing sides in the front direction when viewed from above. The missing corners become entrances for workers to enter and exit. A chain may be provided at the entrances. By assembling six frame bodies 110 and five connecting bodies 120 to surround a manhole 200, it can also function as a protective fence for the manhole 200.
In each drawing, the frame body 110 is hatched with the same large mesh pattern, and the frame body 120 is hatched with the same finer mesh pattern for ease of understanding.

2 shows an example of a configuration in which the connection angle between the left and right frame bodies 110 is adjusted via the connection portion 120. Various configurations are possible, and the one shown in FIG. 2 is merely one example.
FIG. 2(a) shows an example in which two more frame bodies 110 are added to the configuration formed by the six frame bodies 110 shown in FIG. 1(a) to make eight frame bodies 110, and seven connecting parts 120 are provided between them, and the frame bodies 110 and the connecting parts 120 are assembled to form an icosagon with five missing sides in the front direction when viewed from above. As in FIG. 1, the missing sides are entrances and exits for workers to enter and exit. A chain may be provided at the entrances and exits. By assembling the eight frame bodies 110 and seven connecting parts 120 to surround the manhole 200, it can also function as a protective fence for the manhole 200.
In addition, in Fig. 2(a), a fall prevention body 132 and a second fall prevention body 142 described later are not shown because it makes it difficult to understand the relationship between the members. The fall prevention body 132 will be described later with reference to Fig. 4. The second fall prevention body 142 will be described later with reference to Fig. 5.

FIG. 2B shows an example of an assembly of 14 frame bodies 110 and 14 connecting bodies 120. It is formed like a rectangle, with the front and back sides of the rectangle missing. In other words, there are two entrances for workers to enter and exit. Chains may be attached to the entrances. By assembling the rectangle formed by the 14 frame bodies 110 and the 14 connecting bodies 120 to surround the manhole 200, it can also function as a protective fence for the manhole 200.
In addition, in Fig. 2B, a fall prevention body 132 and a second fall prevention body 142 described later are not shown because it makes it difficult to understand the relationship between the members. The fall prevention body 132 will be described later with reference to Fig. 4. The second fall prevention body 142 will be described later with reference to Fig. 5.

The frame that is dynamically erected at the work site is also assembled in a unique way.
When the frame bodies are connected to each other at an angle via the connecting parts, the frame bodies can be assembled to surround or partition the upper surface of the manhole, allowing it to be installed as a protective fence during manhole work.

In order for the suspended installation structure for the work ladder of the present invention to function as a protective fence when a small number of people are working, it is preferable that the installation state is stable even when there is no worker watching near the manhole. However, it is better to have a structure that ensures that the ladder does not move or shift unexpectedly from the vicinity of the manhole even if a worker watching is present.
To prevent this, a locking member 170 is provided as a measure to prevent lateral displacement, and a diameter reduction prevention member 180 can be provided to prevent diameter reduction.
The locking body 170 is a member that can be extended from the frame body 110 or connected to the frame body. One end of the locking body 170 is provided with a hook shape that can be hooked onto the edge of the hole of the manhole 200. By providing this locking body 170, it is possible to restrict the entire protective fence, which is a suspended installation structure, from shifting laterally, that is, to restrict movement in the outer circumferential direction. By installing multiple locking bodies 170 in a balanced manner around the edge of the circular hole of the manhole 200, it is possible to easily fix the protective fence, which is a suspended installation structure, so that it does not shift in any direction.

FIG. 3 is a diagram showing a state in which the locking body 170 and the diameter reduction prevention body 180 are attached to the frame body 110. As shown in FIG.
As shown in Fig. 3, a plurality of locking bodies 170 may be provided around the periphery of the manhole 200, and each may be hooked onto the edge of the hole of the manhole 200 from a plurality of directions. In the example of Fig. 3, four locking bodies are provided. As shown in Fig. 3(b) viewed from above, it is not necessary to arrange them precisely so as to divide the circumference into four, but it is assumed that a good balance between the left and right sides will make the whole stable.
As shown in Fig. 3(c), the locking body 170 is attached to one end of the frame body 110 at a leg, and the tip of the locking body 170 is hooked onto the edge of the hole of the manhole 200, restricting the frame body 110 from moving in the outer circumferential direction (leftward in Fig. 3(c)). By arranging multiple locking bodies 170 in a balanced manner around the circumference of the manhole, the guardrail restricts movement so that the fence does not shift in any direction.
The shape of the locking body 170 may be any structure as long as the tip can be hooked onto the edge of the manhole.

Next, the movement of the protective fence toward the inner periphery where the diameter of the protective fence is reduced cannot be restricted by the locking member 170 alone. Therefore, a reduction prevention member 180 is provided to prevent the diameter from being reduced.
The diameter reduction prevention body 180 is a member that maintains a predetermined distance between separate frame bodies (i.e., between frame bodies that are not directly connected by connecting parts 120) or between entrances and exits through which workers enter and exit (between the frame bodies at both ends that are opened without the frame body 110) to prevent the diameter from reducing.
It is like a tension rod, and is a component that maintains a constant distance. It does not necessarily have to be rod-shaped, but the simplest shape is a rod-shaped component.
By providing the locking body, the effect is obtained that the entire suspended installation structure will not move or shift in the outer circumferential direction.

The diameter reduction prevention body 180 may be configured such that one end can be attached to a part of the target frame body, and the other end can also be attached to a part of the target frame body. A simple structure may be a rod-shaped body with gripping mechanisms 181 at both ends that clamp and grip parts of the frame body. Any structure is acceptable as long as it can prevent diameter reduction.

The configuration example of the diameter reduction prevention body 180 shown in Fig. 3 is an example of a rod-shaped body with gripping mechanisms 181 attached to both ends that clamp and grip a part of the frame body. In the example shown in Fig. 3(B), the space between the frame bodies 110 is an opening, and by attaching the gripping mechanisms 181 so as to clamp the support posts of the frame bodies 110 on both sides of the opening, the distance between the openings does not decrease, and as a result, the diameter of the entire protective fence does not decrease.
In this way, by the locking body 170 and the diameter reduction prevention body 180 working together, the protective fence, which is a suspended installation structure, does not shift laterally in either direction or reduce in diameter, and the installation state as a protective fence is stable.

The configuration example of the diameter reduction prevention body 180 shown in Fig. 3 is an example of a rod-shaped body with gripping mechanisms 181 attached to both ends that clamp and grip a part of the frame body. In the example shown in Fig. 3(B), the space between the frame bodies 110 is an opening, and by attaching the gripping mechanisms 181 so as to clamp the support posts of the frame bodies 110 on both sides of the opening, the distance between the openings does not decrease, and as a result, the diameter of the entire protective fence does not decrease.
The example shown in FIG. 3 is an example in which the device is attached to the entrance of a protective fence, but it may be attached between the frame bodies forming the entrance after the worker enters the protective fence.
3, it is effective to attach the diameter reduction prevention body 180 between the separated frame bodies 110. For example, if the protective fence is circular, it is effective to attach the diameter reduction prevention body 180 between the opposing frame bodies 110.
There is no particular limit to the height at which the diameter reduction prevention body is attached, but since it acts like a tension rod, it is effective to place it horizontally parallel to the ground.
In this way, by the locking body 170 and the diameter reduction prevention body 180 working together, the protective fence, which is a suspended installation structure, does not shift laterally in either direction or reduce in diameter, and the installation state as a protective fence is stable.

Returning to FIG.
The rod body 130 is a rod-shaped member that is attached to the frame body 110, and is a structure that is hung across the top of the hole of the manhole 200.
In the example of FIG. 1, the rod 130 is configured to include a rod-shaped portion 131 and a fall prevention body 132 .
The rod-shaped portion 131 has a length that allows it to be hung across the top of the manhole 200. In other words, the rod-shaped portion 131 is long enough to be hung across the frame bodies 110 that face each other across the entrance of the manhole 200 as shown in Figures 1 and 2. By providing this rod-shaped portion 131, it is possible to provide a structure that allows the work ladder 160 to be suspended and supported above the manhole 200.
The fall prevention structure 132 is a member that reliably prevents falls even if an unexpected event occurs and the frame body 110 of the work ladder installation structure 100 or the support members 113 attached to the frame body collapses, causing the scaffolding to collapse and causing a worker to fall along with the work ladder.
Here, the fall prevention body 132 is a structure including a disk-shaped member having a diameter larger than the diameter of the entrance of the manhole 200, or a cross-shaped structure with all sides longer than the diameter of the manhole.

FIG. 4 is a diagram showing the rod 130 taken out.
4A shows a case where the fall prevention body 132 is a structure including a disk-shaped member 132-1. The disk-shaped member 132-1 is attached to the surface of the rod-shaped part 131 of the rod body 130 that is farther from the manhole 200 so as not to obstruct the upper surface of the manhole 200, and is further mounted at an angle close to perpendicular to the ground.
The diameter r of the disk-shaped member 132-1 is larger than the diameter R of the manhole. As shown in Fig. 4(a), if the diameter r of the disk-shaped member 132-1 is larger than the diameter R of the manhole, the diameter r of the disk-shaped member 132-1 cannot pass through the diameter R of the manhole entrance no matter what posture or angle the member falls at, and the fall prevention body 132 can reliably catch on the entrance of the manhole 200 and prevent the member from falling further. The right side of Fig. 4(a) shows a case where the rod-shaped member 131, which was horizontal, falls at an angle close to vertical, but even if the rod-shaped member 131 falls in a posture that allows it to pass through, the fall prevention body 132-1 always collides with the edge of the manhole 200 and gets caught, so it does not pass through.

4B shows a case where the fall prevention body 132 is a structure including an auxiliary rod 132-2 forming a cross-shaped structure. The auxiliary rod 132-2 is attached to the surface of the rod-shaped part 131 of the rod body 130 that is farther from the manhole 200 so as not to obstruct the upper surface of the manhole 200, and is further mounted at an angle close to perpendicular to the ground.
The auxiliary rod 132-2 is attached perpendicular to the length of the rod portion 131, that is, the rod portion 131 and the auxiliary rod 132-2 form a cross-shaped structure, and each side is longer than the diameter of the manhole. If the cross-shaped structure has such a length, the cross-shaped structure formed by the rod portion 131 and the auxiliary rod 132-2 cannot pass through the entrance of the manhole 200 no matter what position or angle it falls at, and the fall prevention body 132 can reliably catch on the entrance of the manhole 200 to prevent it from falling any further.

Next, the second rod 140 will be described.
The second rod 140 is a rod-shaped member that is attached directly to the frame body 110 or via a support member 113 attached to the frame body 110, and is a structure that is hung across the top of the hole of the manhole 200.
In the example shown in FIG. 1, the mounting is performed via a support member 113 attached to the frame body 110.

The second rod body 140 is configured to include a second rod-shaped portion 141 and a second fall prevention body 142 .
The second rod-shaped portion 141 has a length sufficient to span and be hung across the upper part of the manhole 200. In other words, the second rod-shaped portion 141 has a length sufficient to span and be hung between the frame bodies 110 facing each other across the entrance of the manhole 200 as shown in Figures 1 and 2. By providing this second rod-shaped portion 141, it is possible to provide a structure that can support the safety device 150 in a suspended manner above the manhole 200.

The second fall prevention body 142 is a member that reliably prevents the worker from falling via the safety device 150 even if an unexpected event occurs and the frame body 110 of the work ladder installation structure 100 or the support member 113 attached to the frame body falls, causing a so-called collapse of the scaffolding and putting the worker in danger of falling along with the work ladder.
The second fall prevention body 142 is a structure including a disk-shaped member of diameter r2 larger than the diameter R of the entrance of the manhole 200, or a cross-shaped structure with all sides longer than the diameter of the manhole.

FIG. 5 is a diagram showing the second rod 140 taken out.
5A shows a case where the second fall prevention body 142 is a structure including a second disk-shaped member 142-1. The second disk-shaped member 142-1 is attached to the surface of the second rod-shaped portion 141 of the second rod 140 that is farther from the manhole 200 so as not to obstruct the upper surface of the manhole 200, and is further mounted at an angle close to perpendicular to the ground.
The diameter r of the second disk-shaped member 142-1 is larger than the diameter R of the manhole. As shown in Fig. 5(a), if the diameter r of the second disk-shaped member 142-1 is larger than the diameter R of the manhole, the diameter r of the second disk-shaped member 142-1 cannot pass through the diameter R of the manhole entrance no matter what posture or angle the worker falls at, and the second fall prevention body 142 can be reliably caught on the entrance of the manhole 200 to prevent the worker from falling further.

5B shows the case where the second fall prevention body 142 is a structure including a second auxiliary bar 142-2 forming a cross-shaped structure. The second auxiliary bar 142-2 is attached to the surface of the second rod-shaped part 141 of the second rod 140 that is farther from the manhole 200 so as not to obstruct the upper surface of the manhole 200, and is further mounted at an angle close to perpendicular to the ground.
The second auxiliary bar 142-2 is attached perpendicular to the length of the second bar 141, that is, the second bar 141 and the second auxiliary bar 142-2 form a cross-shaped structure, and each side is longer than the diameter of the manhole. With a cross-shaped structure of this length, the cross-shaped structure formed by the second bar 141 and the second auxiliary bar 142-2 cannot pass through the entrance of the manhole 200 no matter what position or angle it falls at, and the second fall prevention body 142 can reliably catch on the entrance of the manhole 200 to prevent it from falling any further.

Next, the safety device 150 is a device that connects between the second rod 140 and the wearing equipment worn by the operator.
By using the safety device 150, the worker wearing the harness can work with his/her body supported by the second rod 140 via the safety device 150.
The safety device 150 is not particularly limited and may have any structure as long as it has a wire that can be reeled in and reeled in and can reliably support the body of the worker, and may be one available on the general market. In general, for example, the wire of the safety device 150 has a structure in which a stopper works to stop the wire from being reeled out if the wire is suddenly reeled out. The safety device 150 is maintained at a position higher than the entrance of the manhole 200, and when the wire is stopped from being reeled out, the worker is left hanging in mid-air, but he or she will not fall, and a fall accident can be prevented.

Next, the work ladder 160 will be described.
The work ladder 160 is not particularly limited as long as it has sufficient structural strength for workers to ascend and descend and can be deployed inside the manhole. It may be a telescopic ladder or a non-telescopic ladder. Note that a non-telescopic ladder is difficult to handle when inserting the work ladder into the manhole at the start of work, and is also difficult to handle when removing the work ladder from inside the manhole at the end of work. In this configuration example, the work ladder 160 is a telescopic ladder.

An example of the structure of a telescopic work ladder 160 is shown in FIG.
As shown in FIG. 6, the work ladder 160 has a ladder base member 161 as a basic unit, and is structured such that a plurality of ladder base members 161 are connected in sequence in a telescopic, nested manner so as to be slidable.
The ladder basic member 161 comprises a pair of cylindrical support bodies 162 arranged parallel to each other with a predetermined gap therebetween, and a crosspiece 163 provided between the cylindrical support bodies 162. This ladder basic member 161 is the basic unit, and the ladder basic members 161 are sequentially connected to each other in a nested state in the cylindrical axial direction of the cylindrical support bodies 162 so as to be slidable therein.

6, the cylindrical support bodies 162 are a pair of support bodies arranged parallel to each other with a predetermined gap therebetween. The material for forming the cylindrical support bodies 162 is preferably a light metal such as aluminum that has high structural strength.
Each ladder base member 161 needs to have a certain degree of rigidity and strength. This is because the ladder base member 161 needs to have the mechanical strength to support the worker's ascent and descent as a suspended ladder at the work site. In addition, since a worker may ascend and descend while carrying some weight, the ladder base member 161 needs to be able to withstand that load.
The length of the cylindrical support body 162 for each ladder basic member 161 is not particularly limited, but may be any length appropriate for the stride length of a person ascending or descending one step at a time.
In this configuration example, a hanging member 164, which is a hook, is provided on the cylindrical support body 162 of the top ladder basic member 161. Also, in this configuration example, the height of the cylindrical support body 162 of the top ladder basic member 161 is such that a gripping portion 165 extends upward from the position of the hanging member 164.

The horizontal beam 163 is a horizontal member provided between the cylindrical support bodies 162, and is a portion on which a worker places his/her feet when ascending or descending. The horizontal beam 163 corresponds to one rung of the work ladder 160. In this example, the horizontal beam 163 is provided to connect the upper ends of the cylindrical support bodies 162 of the ladder basic members 161 to each other.
The horizontal rail 163 is preferably made of a light metal such as aluminum that has high structural strength. The horizontal rail 163 needs to have a certain degree of rigidity and strength. This is because it needs the mechanical strength to support the worker ascending and descending. In addition, since the worker may ascend and descend while carrying some weight of luggage, the horizontal rail 163 needs to be able to withstand that load.
The horizontal length of the crosspiece 163 is not particularly limited, but if it is assumed that workers will ascend and descend one at a time, it is preferable that the length be at least as long as the waist width of a person.

FIG. 7 is a diagram showing the telescopic work ladder 160 being extended.
7, the ladder base members 161 are arranged such that the diameters of the cylindrical portions of the cylindrical support bodies 162 from the top ladder base member 161 to the bottom ladder base member 161 successively increase from one ladder base member 161 to the other ladder base member 161, and they are nested and successively connected to each other so as to be slidable in the cylindrical axial direction of the cylindrical support bodies 162. In other words, the cylindrical support body 162 of the lower ladder base member 161 located immediately below the current ladder base member 161 has a cylindrical portion one size larger than that of the current ladder base member 161, and they are nested.
The tubular portion of the tubular support body 162 of the ladder base member 161 of this step can slide in and out relative to the tubular portion of the tubular support body 162 of the ladder base member 161 of the lower step, and is extended when pulled downward and contracted when pushed upward. When all of the ladder base members 161 of each step are in the contracted state, the entire work ladder 160 is in the contracted and stored state, and when all of the ladder base members 161 of each step are in the extended state, the entire work ladder 160 is also in the extended state.
In this example, the lowest horizontal beam 163 is a fixed horizontal beam, and is fixed to the cylindrical support body 162.
6, the gripping part 165 is configured to be extended upward to a position higher than the height of the hanging member 164, so that a worker can grasp it at the extended position. If the gripping part 165 is extended, the worker can start descending while grasping the gripping part 165, which has the advantage of improving safety and work efficiency.

The ladder base member 161 has a retracted storage state in which it is slidably stored, and an extended use state in which it is slidably extended.
7A is a diagram showing the state before deployment of the work ladder 160 at the work site. The work ladder 160 is brought to the work site, and a worker assembles the frame body 110 and the connecting part 120, and suspends the rod body 130. The figure shows the state in which the suspension member 164 is hung on the rod body 130, and the entire work ladder 160 is suspended in the contracted storage state before deployment. Each ladder basic member 161 is slidably stored relative to each other.

7B is a diagram showing the state in the middle of unfolding the work ladder 160 at the work site. Each ladder base member 161 is slidably extended, and the diagram shows the intermediate stage in which the work ladder 160 is extended to the extended use state.
At the start of work, the work ladder 160 is brought to the work site in the shortened and stored state shown in Fig. 7(a) and the hanging member 164, which is the hook of the work ladder 160, is hooked to the rod 130 of the suspended installation structure 100 for the work ladder installed on the top surface of the manhole, and the ladder base members 161 are made slidable relative to each other, releasing the shortened and stored state. As a result, each ladder base member 161 slides downward and is locked one after another, starting from the top ladder base member 161.

It is also preferable that each ladder base member 161 is provided with a locking mechanism (details not shown) and an unlocking mechanism (details not shown) that control whether the ladder base members 161 can slide relative to each other or not.

Here, the locking mechanism is a mechanism that temporarily locks the sliding of the ladder base members 161 at the connection points between the ladder base members 161 of each rung when the ladder base members 161 are in the extended use state. For example, a pin with a spring that is pressed and biased by the side of the cylindrical support body 162 is installed inside the crosspiece 163, and a hole is drilled in the cylindrical support body 162. When the sliding of the ladder base member 161 causes the cylindrical support body 162 to move downward and the pin of the crosspiece 163 comes to a position facing the hole in the cylindrical support body 162, the biased spring is released and the pin protrudes and fits into the hole, locking the mechanism.

In the configuration example of FIG. 7, the release of the biased spring at that time triggers a lever to protrude from the underside of the crosspiece 162. As described below, when the ladder base member 161 slides and rises from the bottom up during retrieval, the crosspiece 163 of the lower ladder base member 161 pushes up this lever protruding from the underside of the upper crosspiece 163, causing the pin to overcome the bias of the spring, shrink inward, and come out of the hole, thereby releasing the lock. Although not shown in detail, a similar structural example is described in detail in JP 2019-035289, a previous application by the applicant of this application.

In this configuration example, the work ladder 160 is equipped with a telescopic operating body 166 to simplify removal work.
A string or wire-like telescopic operating body 166 is attached to the lowest crosspiece 163 of the work ladder 160, and by pulling up the wire-like telescopic operating body 166, the telescopic work ladder 160, which is in an extended use state, can be contracted into a shortened storage state.
The telescopic operation body 166 may be a string or wire, and is preferably a strong steel wire, for example. As long as it has sufficient strength to pull up, a string may be used.
The work ladder 160 may be manually pulled up via the telescopic operating body 166 by an operator, but may also be raised and lowered by a mechanical drive device such as a winch (not shown).
In this way, the lowest ladder basic member can be raised and lowered via the telescopic operating body 166, thereby allowing the extension and shortening of the work ladder 160.
7(c) is a diagram showing a state in which the deployment of the work ladder 160 is completed. Each ladder base member 161 has been slidably extended, and the work ladder 160 is in an extended use state.

FIG. 8 is a diagram showing how the telescopic work ladder 160 is retracted.
8(a) shows the state before contraction begins. The lowest ladder base member is raised and lowered via the telescopic operation body 166.
8B is a diagram showing the state in the middle of recovering the work ladder 160 at the work site. Each ladder base member 161 is slid, and the diagram shows the intermediate stage in which the work ladder 160 is in a contracted state.
FIG. 8(c), following FIG. 8(b), shows an intermediate stage in which each ladder base member 161 is slid and the work ladder 160 is brought into a contracted state.
8(d) is a diagram showing a state in which the collapse of the work ladder 160 is completed. Each ladder base member 161 has been slid, and the work ladder 160 is in a collapsed state.

Next, the procedure for using the work ladder suspension installation structure 100 of the present invention will be described with reference to FIGS.
(Step 1)
As shown in the upper left and right figures of Figure 9, workers transport the suspended installation structure 100 of the work ladder 160 of the present invention and bring it to the work site, connect the frame body 110 with the connecting parts 120, assemble it, and surround the entrance of the manhole 200.
In this example, the frame bodies 110 are connected by connecting parts 120 and assembled into the shape shown in FIG. 1 and FIG. 2(a).

(Step 2)
Next, as shown in the lower diagram of FIG. 9 , the worker attaches the rod 130 to the frame body 110 and hangs it across the vicinity of the upper part of the entrance to the manhole 200.

(Step 3)
Next, as shown in the left diagram of Fig. 10, the worker attaches the second rod 140 to the frame body 110 and hangs it across the vicinity of the upper part of the hole of the manhole 200. In this example, the second rod 140 is attached to the support member 113 attached to the frame body 110, and is attached via the support member 113.

(Step 4)
Next, as shown in the right diagram of FIG. 10, the safety device 150 is attached to the second rod 140, and the safety device 150 is attached to the worker's wearing gear.
It should be noted that this step 4 may be replaced by step 5. Since it is considered safer for the worker to have the safety device 150 attached when deploying the work ladder 160 in step 5, the order of steps 4 and 5 is used here.

(Step 5)
Next, as shown in Figures 11 (a) and 11 (b), the hanging member 164 of the work ladder 160 is attached to the rod 130.
11(a) is a cross-sectional view taken at a height slightly above the height of the rod 130. FIG. 11(b) is a view showing the interior of the manhole 200, showing the work ladder 160 suspended vertically in the manhole 200 in a shortened state that has not yet been slid and extended. The frame body 110 and the connecting portion 120 are omitted from the illustration, and only a portion of the rod 130 is shown. The wall surface of the manhole is hatched with fine pitch, and the rod 130 is hatched with large pitch.
Fig. 11(c) is a diagram showing the state of deployment from the state of Fig. 11(b). As shown in Fig. 11(c), the worker carefully deploys the work ladder 160 and sets it to the extended use state. The worker loosens the wire that is the extension operation body 166 of the work ladder 160 suspended via the suspension member 164. The work ladder 160 is deployed into the manhole.
Note that step 5 may be replaced with step 4.

By carrying out the above steps 1 to 5, the work ladder 160 can be deployed inside the manhole, and the worker is ready to descend into the manhole.
The worker grasps the gripping part 165 and begins to descend, carefully descending the cross rail 163 one step at a time.

When workers have finished using the work ladder 160 at a work site such as a manhole, all of the workers climb the work ladder 160 and move to the suspension point, and then begin the retrieval work to retrieve the work ladder 160 of the present invention.
The procedure for changing the work ladder 160 from the extended use state to the shortened storage state can be carried out by following the steps from FIG. 11 to FIG. 9 in reverse.

Although the preferred embodiment of the present invention has been illustrated and described above, it will be understood that various modifications can be made without departing from the technical scope of the present invention. Therefore, the technical scope of the present invention is limited only by the description of the appended claims.

The work ladder suspension installation structure of the present invention can be widely used as a structure for suspending work ladders at work locations such as manholes.

REFERENCE SIGNS LIST 100 Suspension ladder 110 Frame body 120 Connection section 130 Rod body 140 Second rod body 150 Safety device 160 Work ladder

Claims (9)

A structure for installing a work ladder that can be installed and removed on-site so that a worker working inside a manhole can ascend and descend the work ladder,
The work ladder;
A frame body having at least a leg portion and erected near the upper surface periphery of the manhole;
A connecting portion that connects the frame bodies to each other in a lateral direction;
A rod is attached to the frame body and hung across the upper portion of the manhole,
The work ladder includes a suspension member suspended from the rod,
A suspension installation structure for a work ladder, characterized in that the work ladder is suspended downward from the rod via the suspension member toward the opening of the manhole. The rod-shaped portion has a length that allows it to cross the top of the manhole and be hooked, and a fall prevention body;
The suspended installation structure for a work ladder as described in claim 1, characterized in that the fall prevention body includes a structure including a disk-shaped member having a diameter larger than the diameter of the manhole, or an auxiliary rod member which, when combined with the rod-shaped portion, forms a cross-shaped structure, each side of which is longer than the diameter of the manhole. A second rod is attached directly to the frame body or via a support member attached to the frame body and hung across the top of the manhole;
a safety device that connects the second rod and the worker's equipment;
A suspended installation structure for a work ladder as described in claim 1, characterized in that the worker can work while his/her body is supported by the second rod via the attachment and the safety device. The second rod body includes a second rod-shaped portion having a length for hanging across the upper part of the manhole and a second fall prevention body,
A suspended installation structure for a work ladder as described in claim 3, characterized in that the second fall prevention body includes a structure including a second disk-shaped member having a diameter larger than the diameter of the manhole, or a second auxiliary rod member which, when combined with the second rod-shaped portion, forms a cross-shaped structure, each side of which is longer than the diameter of the manhole. The suspended installation structure for a work ladder according to any one of claims 1 to 4, in which the frame bodies are connected to each other at an angle via the connecting parts, and the frame bodies are installed as a protective fence that surrounds and separates the upper surface of the manhole. A plurality of locking bodies of a predetermined length are provided, the locking bodies being extendable from the frame body or connectable to the frame body,
A hook shape is provided at one end of the locking body so that it can be hooked onto the edge of the manhole,
A suspended installation structure for a work ladder as described in claim 5, characterized in that when installed around the manhole hole, the engaging body is hooked onto the edges of the manhole hole from multiple directions. The suspended installation structure for a work ladder according to claim 6, characterized in that it is provided with a diameter reduction prevention device that is installed between the frame bodies that are separated and not directly connected, or between the frame bodies at both ends that are separated as entrances for the workers to enter and exit, and that maintains the separation distance at a predetermined length to prevent the diameter from being reduced. The work ladder is characterized in that the basic unit of the work ladder is a ladder basic member having a pair of cylindrical support bodies arranged parallel to each other with a predetermined distance between them and a crosspiece provided between the cylindrical support bodies, and the ladder basic members are sequentially connected to each other in a nested state so that they can slide in the axial direction of the cylindrical support bodies, and the ladder basic members are a telescopic work ladder having a contracted storage state in which the ladder basic members are slidably stored and an extended use state in which the ladder basic members are slidably extended. The suspended installation structure for the work ladder described in claim 1 or 2. The structure for hanging a work ladder according to claim 8, characterized in that a wire-shaped telescopic operating body is provided on the lowest rung of the work ladder, and by pulling up the telescopic operating body, the telescopic work ladder in the extended use state can be contracted to the shortened storage state and removed from around the upper surface of the manhole.

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