Safety protection device for tunnel water pressure smooth blasting construction

Abstract

The invention relates to the field of construction safety protection, and discloses a tunnel water pressure smooth blasting construction safety protection device which comprises a supporting platform and further comprises a first protection plate, and a connecting rod mechanism and a driving mechanism for driving the connecting rod mechanism to deform are arranged between the supporting platform and the first protection plate. The first protection plate is provided with a folding position and an unfolding position, when the first protection plate is located at the folding position, the first protection plate is close to the supporting platform and is parallel to the supporting platform, and when the first protection plate is located at the unfolding position, the first protection plate is vertically arranged on one side of the supporting platform. At least one side of the supporting platform is provided with an auxiliary supporting structure used for fixing the supporting platform on the ground, and the problems that when the supporting platform is not used, a large amount of space is occupied, and a measuring path is shielded are solved.

Description

Technical Field

[0001] The invention relates to the technical field of construction safety protection, and in particular to a tunnel water pressure smooth blasting construction safety protection device. Background Art

[0002] Tunnel hydraulic smooth blasting construction is a new blasting construction method that uses technologies such as water injection in the blasthole and precise control of blasting parameters to reduce dust, reduce surrounding rock disturbance, and improve tunnel forming quality, in the context of traditional blasting that easily causes surrounding rock damage and prominent over-excavation and under-excavation problems. During blasting, some stones may escape from the control range and become flying stones. Flying stones have great kinetic energy and can cause serious trauma once they hit the human body. The impact of flying stones may damage the outer casing of instruments and meters, causing displacement and deformation of precision components, affecting the normal use of equipment.

[0003] These not only pose a serious threat to the life safety of construction workers, which may cause physical injury or even death, but also damage the construction equipment and instruments in the tunnel, affecting their normal operation and service life, and have an adverse impact on the surrounding environment. Therefore, there is an urgent need for safety protection devices specifically for tunnel hydraulic smooth blasting construction to reduce various risks, ensure smooth construction and meet safety and environmental protection requirements.

[0004] However, the traditional device simply places the support platform on the ground, or uses a small number of fixing points, such as simple anchor bolts, to fix it, which takes up a lot of space when not in use and blocks the measurement path. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a tunnel water pressure smooth blasting construction safety protection device, which solves the problems of occupying a large amount of space when not in use and blocking the measurement path.

[0006] In order to achieve the above-mentioned objectives, in a first aspect, the present invention provides a tunnel water pressure smooth blasting construction safety protection device, comprising a support platform and a first protective plate, a connecting rod mechanism and a driving mechanism for driving the connecting rod mechanism to deform are arranged between the support platform and the first protective plate, the first protective plate has a folded position and an unfolded position, when it is in the folded position, the first protective plate is close to the support platform and the two are parallel to each other, when it is in the unfolded position, the first protective plate is erected on one side of the support platform, and at least one side of the support platform is provided with an auxiliary support structure for fixing it to the ground.

[0007] Optionally, the connecting rod mechanism includes a first connecting rod having one end rotatably connected relative to the support platform, and a second connecting rod having one end rotatably connected to the other end of the first connecting rod, the other end of the second connecting rod is rotatably connected to one side of the first protective plate, and the other side of the first protective plate is rotatably connected to the support platform.

[0008] Optionally, a first limit block is fixedly provided on the upper surface of the support platform, one end of the first connecting rod is rotatably connected to the first limit block via a rotating shaft, the other end of the first connecting rod is rotatably connected to a first rotating column, one end of the second connecting rod is fixedly connected to the first rotating column, the other end of the second connecting rod is rotatably connected to a second rotating column, the second rotating column is fixedly connected to a first connecting block, the first connecting block is fixedly connected to the first protective plate, and a second limit block is also fixedly provided on the upper surface of the support platform, a third rotating column is rotatably provided on the second limit block, the third rotating column is fixedly connected to a second connecting block, and the second connecting block is fixedly connected to the first protective plate.

[0009] Optionally, a synchronous driving structure is provided between the auxiliary supporting structure and the connecting rod mechanism.

[0010] Optionally, the synchronous drive structure includes a first rotating rod fixedly connected to the rotating shaft, a second rotating rod rotatably connected to the first rotating rod, a slider is fixedly connected to the second rotating rod, the auxiliary support structure is fixedly connected to the slider, and a sliding guide structure is provided between the slider and the support platform to limit its sliding in a vertical direction.

[0011] Optionally, the sliding guide structure includes two first fixed blocks fixedly arranged on the side surfaces of the supporting platform, and a sliding groove cooperating with the sliding block is formed between the two first fixed blocks.

[0012] Optionally, the auxiliary support structure includes an auxiliary plate and ground nails fixed on the auxiliary plate.

[0013] Optionally, the first protective plate has a cavity opened along the horizontal direction, and a second protective plate is slidably arranged on at least one side of the cavity.

[0014] Optionally, a protection plate driving mechanism is provided between the second protection plate and the first protection plate for driving the second protection plate to fold or unfold.

[0015] Optionally, the protection plate driving mechanism includes a double-threaded screw rotatably disposed in the cavity and two screw sleeves matched with the double-threaded screw, and the second protection plate is rotationally connected to the corresponding screw sleeves through a third connecting rod.

[0016] Working principle: When the device is needed, first place the supporting platform on the ground, and then the worker rotates the turntable to drive the lead screw to rotate. When the lead screw rotates, it drives the traveling block to move. Since the traveling block is provided with two sections of opposite threads, and the outer wall of the traveling block slides in contact with the inner wall of the inner cavity opened inside the first protective plate, it is ensured that the traveling block will only move up and down and will not rotate on its own. Therefore, the traveling blocks on the upper and lower sides move toward the middle. When the traveling block starts to move, it will drive the limit column to move, and then drive the third connecting rod to rotate with the H-shaped column as the axis. Since the length of the third connecting rod is fixed, it will push the H-shaped column to move, thereby driving the upper and lower bases to move. When the bases on both sides move, they will simultaneously push the second fixed blocks on both sides to move outward, and then drive the second protective plate to move outward, so that the second protective plate gradually unfolds, so that the device can adapt to tunnel sections of different shapes and sizes, enhancing the versatility of the device.

[0017] When the second protective plate is fully unfolded, the double-headed motor is started, and the double-headed motor drives the rotating shaft to rotate. The first limit block supports the rotating shaft. When the rotating shaft rotates, it will drive the first connecting rod to rotate with the rotating shaft as the axis, and then drive the first rotating column to move. When the first rotating column moves, the second connecting rod will rotate with the first rotating column as the axis. When the second connecting rod rotates, it will lift the second rotating column to move. When the second rotating column moves, it will drive the first connecting block to move, and then push the first protective plate to move. When the first protective plate moves, it will rotate with the second connecting block as the fulcrum, so that the first connecting block rotates with the second rotating column as the axis, so that the first protective plate gradually stands up. In the process of standing up the first protective plate, it will also drive the second connecting block to rotate with the third rotating column as the axis to ensure that the first protective plate stands up. When the device is in use, the first protective plate can be erected to protect the surrounding area. When it is no longer needed, it can be retracted so that the first protective plate and the supporting platform are in a horizontal state, reducing the occupied space and preventing the measurement path from being blocked.

[0018] When the double-headed motor is started to drive the rotating shaft to rotate, it will also drive the first rotating rod to rotate with the rotating shaft as the axis, so that the first rotating rod presses the second rotating rod downward, and the second rotating rod moves downward to drive the slider to move. The first fixed block ensures that the direction of movement of the slider is certain, and at the same time prevents the slider from detaching and causing the device to fail. When the slider moves downward, it will push the auxiliary plate to move downward, so that the auxiliary plate is completely in contact with the ground and the bottom surface of the auxiliary plate and the bottom surface of the supporting platform are on the same horizontal line, and then two ground nails are nailed into the ground using tools to fix them, so as to increase the contact area with the ground and effectively fix the supporting platform in a certain position, thereby preventing the impact force and vibration generated by the explosion from causing the supporting platform to be displaced, resulting in the effect of protection failure.

[0019] The device can not only adapt to tunnel sections of different shapes and sizes, thus enhancing the versatility of the device, but also can erect the first protective plate to protect the surroundings when in use, and retract it when no longer needed so that the first protective plate and the supporting platform are in a horizontal state, thereby reducing the occupied space, preventing obstruction of the measurement path, and increasing the contact area with the ground while effectively fixing the supporting platform in a certain position, thereby preventing the impact force and vibration generated by the explosion from causing the supporting platform to move and resulting in the failure of the protection.

[0020] The invention provides a tunnel water pressure smooth blasting construction safety protection device, which has the following beneficial effects compared with the prior art: 1. The invention starts a double-headed motor to drive the rotating shaft to rotate, thereby driving the first connecting rod and the second connecting rod to rotate, thereby driving the first connecting block to move, so that the first protection plate stands up with the second connecting block as a fulcrum, and also drives the first rotating rod and the second rotating rod to rotate, thereby pressing down the slider and the auxiliary plate, so that the auxiliary plate fits the ground, and fixes it with ground nails to increase the left and right contact area with the ground, so that the support platform will not shake left and right, and the protection plate can be erected when in use to protect the surroundings. When not in use, it is kept horizontal with the support platform to reduce space occupancy, prevent obstruction of the measurement path, and avoid displacement of the support platform caused by the impact force and vibration of the explosion, thereby preventing protection failure.

[0021] 2. The present invention drives the lead screw to rotate by the worker rotating the turntable, thereby driving the traveling blocks on both sides to move toward the middle. During the movement, the third connecting rod is driven to rotate, thereby pushing the base and the second fixed block to move, so that the second protective plate is expanded outward, thereby achieving the ability to adapt to tunnel sections of different shapes and sizes, greatly enhancing the versatility of the device.

[0022] 3. The present invention rotates the turntable to unfold the second protection plate outward, and then starts the motor to erect the first protection plate, and cooperates with the unfolded second protection plate to provide protection. At the same time, the auxiliary plate will fit the ground and be fixed with ground nails. The operation is simple and convenient to carry, and the time for installation and fixing is effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, so that other features, purposes and advantages of the present invention become more obvious. The accompanying drawings of the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 A perspective view of the present invention;

[0025] Figure 2 It is a schematic diagram of the local structure of the turntable of the present invention;

[0026] Figure 3 It is a schematic diagram of the local structure of the motor of the present invention;

[0027] Figure 4 It is a schematic diagram of the partial structure of the first connecting rod of the present invention;

[0028] Figure 5 It is a schematic diagram of the partial structure of the first rotating rod of the present invention;

[0029] Figure 6 It is a schematic cross-sectional view of the internal structure of the first protection plate of the present invention;

[0030] Figure 7 It is a schematic diagram of the local structure of the traveling block of the present invention.

[0031] Among them, 1. support platform; 2. double-headed motor; 3. rotating shaft; 4. first limit block; 5. first connecting rod; 6. first rotating column; 7. second connecting rod; 8. second rotating column; 9. first connecting block; 10. second limit block; 11. third rotating column; 12. second connecting block; 13. first protective plate; 14. first rotating rod; 15. second rotating rod; 16. slider; 17. first fixed block; 18. auxiliary plate; 19. ground nail; 20. screw; 21. turntable; 22. travel block; 23. limit column; 24. third connecting rod; 25. H-shaped column; 26. base; 27. second fixed block; 28. second protective plate; 29. ​​inner cavity. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the directions or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0035] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0036] In addition, the term "plurality" shall mean two or more.

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] Please see attached Figure 1 -Attached Figure 5The embodiment of the present invention provides a safety protection device for tunnel water pressure smooth blasting construction, including a support platform 1, the outer wall of the support platform 1 is provided with a double-headed motor 2, the output end of the double-headed motor 2 is connected to a rotating shaft 3, the outer wall of the rotating shaft 3 is rotatably connected to a first limit block 4, the lower surface of the first limit block 4 is fixedly connected to the upper surface of the support platform 1, the outer wall of the rotating shaft 3 is fixedly connected to a first connecting rod 5, the inner part of the first connecting rod 5 is rotatably connected to a first rotating column 6, the outer wall of the first rotating column 6 is fixedly connected to a second connecting rod 7, the inner part of the second connecting rod 7 is rotatably connected to a second rotating column 8, the outer wall of the second rotating column 8 is fixedly connected to a first connecting block 9, the upper surface of the support platform 1 is fixedly connected to a second limit block 10, the inner part of the second limit block 10 is rotatably connected to the A third rotating column 11 is rotatably connected to the third rotating column 11, and the outer wall of the third rotating column 11 is fixedly connected to the second connecting block 12, and the outer wall of the second connecting block 12 is fixedly connected to the first protective plate 13, and the outer wall of the first protective plate 13 is fixedly connected to the outer wall of the first connecting block 9, and the outer wall of the rotating shaft 3 is fixedly connected to the first rotating rod 14, and the outer wall of the first rotating rod 14 is rotatably connected to the second rotating rod 15, and the outer wall of the second rotating rod 15 is rotatably connected to the slider 16, and the outer wall of the slider 16 is slidably connected to the first fixed block 17, and the outer wall of the first fixed block 17 is fixedly connected to the outer wall of the supporting platform 1, and the lower surface of the slider 16 is fixedly connected to the auxiliary plate 18, and the interior of the auxiliary plate 18 is slidably connected to a fixing component, and the fixing component is used to fix the auxiliary plate 18.

[0039] Specifically, first start the double-headed motor 2 to drive the shaft 3 to start rotating. At this time, the first limit block 4 can provide effective support for the shaft 3. When the shaft 3 is in a rotating state, it will prompt the first connecting rod 5 to rotate with the shaft 3 as the axis. Driven by this rotation process, the first rotating column 6 will move accordingly. When the first rotating column 6 moves, the second connecting rod 7 will start to rotate with the first rotating column 6 as the axis. At the same time, the rotation action of the second connecting rod 7 will lift the second rotating column 8, thereby moving the second rotating column 8. When the second rotating column 8 moves, the first connecting block 9 will also move under its drive, thereby pushing the first protective plate 13 to move. During the movement of the plate 13, due to the existence of the second connecting block 12, the first protective plate 13 will rotate with the second connecting block 12 as the fulcrum. This rotation process will cause the first connecting block 9 to rotate with the second rotating column 8 as the axis, so that the first protective plate 13 gradually stands up. During the entire process of the first protective plate 13 standing up, it will also drive the second connecting block 12 to rotate with the third rotating column 11 as the axis, ensuring that the first protective plate 13 can stand up smoothly, so that the device can erect the first protective plate 13 to protect the surroundings when in use, and can be retracted when it is no longer needed to make the first protective plate 13 and the support platform 1 in a horizontal state, thereby reducing the occupied space and preventing the measurement path from being blocked.

[0040] When the double-headed motor 2 is started and drives the shaft 3 to start rotating, the first rotating rod 14 will rotate with the shaft 3 as the axis. Due to the rotation of the first rotating rod 14, it will generate a downward pressure on the second rotating rod 15, thereby causing the second rotating rod 15 to move downward, and the downward movement of the second rotating rod 15 will drive the slider 16 to move together. During this process, the first fixed block 17 can not only ensure that the moving direction of the slider 16 always remains fixed, but also effectively prevent the slider 16 from accidentally detaching and causing the entire device to fail. When the slider 16 moves downward, it will apply a downward thrust to the auxiliary plate 18, prompting the auxiliary plate 18 to move downward until the auxiliary plate 18 is completely in contact with the ground, and the bottom surface of the auxiliary plate 18 and the bottom surface of the support platform 1 are on the same horizontal line, increasing the left and right contact area with the ground, so that the support platform 1 will not shake left and right.

[0041] Please see attached Figure 3 -Attached Figure 5 The fixing assembly includes a ground nail 19 , the outer wall of which is slidably connected to the inside of the auxiliary plate 18 , and the ground nail 19 is arranged on both sides of the auxiliary plate 18 .

[0042] Specifically, by using tools to nail two ground nails 19 into the ground and fix them, the support platform 1 can be effectively fixed at a specific position, thereby avoiding the displacement of the support platform 1 caused by the impact force and vibration generated by the explosion, thereby preventing the failure of protection.

[0043] Please see attached Figure 2 , Attachment Figure 6 and attached Figure 7 The first protective plate 13 is internally rotatably connected with a lead screw 20, and the outer wall of the lead screw 20 is fixedly connected with a turntable 21, and an inner cavity 29 is opened inside the first protective plate 13. The outer wall of the lead screw 20 is threadedly connected with a travel block 22, and the inner rotatable connection of the travel block 22 is limited. The outer wall of the limit column 23 is fixedly connected with a third connecting rod 24, and the outer wall of the third connecting rod 24 is fixedly connected with an H-shaped column 25. The outer wall of the H-shaped column 25 is fixedly connected with a base 26, and the outer wall of the base 26 is fixedly connected with a second fixed block 27. The outer wall of the second fixed block 27 is fixedly connected with a second protective plate 28. The outer wall of the second protective plate 28 is slidably connected to the inner wall of the inner cavity 29, and the outer wall of the travel block 22 is slidably connected to the inner wall of the inner cavity 29. The lead screw 20 is set to two sections of reverse threads.

[0044] Specifically, the support platform 1 needs to be placed stably on the ground first, and then the worker manually rotates the turntable 21. The rotation of the turntable 21 will drive the lead screw 20 to rotate accordingly. During the rotation of the lead screw 20, due to the threaded transmission relationship between it and the traveling block 22, and the traveling block 22 is provided with two sections of reverse threads, and at the same time, the outer wall of the traveling block 22 is tightly fitted with the inner wall of the inner cavity 29 opened inside the first protective plate 13 and can slide, which can ensure that the traveling block 22 will only move up and down along the inner wall of the inner cavity 29 without self-rotation, so that the traveling blocks 22 on the upper and lower sides will move to the middle position under the rotation of the lead screw 20. When the traveling block 22 starts to move, it The connected limit column 23 will also move accordingly, thereby driving the third connecting rod 24 to rotate with the H-shaped column 25 as the axis. Since the length of the third connecting rod 24 is fixed, a thrust will be generated on the H-shaped column 25 during its rotation, thereby pushing the H-shaped column 25 to move. The movement of the H-shaped column 25 will in turn drive the upper and lower bases 26 connected thereto to move. When the bases 26 on both sides move, an outward thrust will be applied to the second fixed blocks 27 on both sides at the same time, thereby driving the second protective plate 28 to move outward, allowing the second protective plate 28 to gradually expand, and ultimately enabling the device to have the ability to adapt to tunnel sections of different shapes and sizes, greatly enhancing the versatility of the device.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tunnel hydraulic smooth blasting construction safety protection device, comprising a support platform (1), characterized in that: It also includes a first protective plate (13), a connecting rod mechanism and a driving mechanism for driving the connecting rod mechanism to deform are arranged between the support platform (1) and the first protective plate (13), the first protective plate (13) has a folded position and an unfolded position, when it is in the folded position, the first protective plate (13) is close to the support platform (1) and the two are parallel to each other, when it is in the unfolded position, the first protective plate (13) stands upright on one side of the support platform (1), and at least one side of the support platform (1) is provided with an auxiliary support structure for fixing it to the ground.

2. A tunnel hydraulic smooth blasting construction safety protection device according to claim 1, characterized in that: The connecting rod mechanism comprises a first connecting rod (5) having one end rotatably connected relative to the supporting platform (1), and a second connecting rod (7) having one end rotatably connected to the other end of the first connecting rod (5); the other end of the second connecting rod (7) is rotatably connected to one side of the first protective plate (13); and the other side of the first protective plate (13) is rotatably connected to the supporting platform (1).

3. A tunnel hydraulic smooth blasting construction safety protection device according to claim 1, characterized in that: A first limit block (4) is fixedly arranged on the upper surface of the support platform (1); one end of the first connecting rod (5) is rotatably connected to the first limit block (4) via a rotating shaft (3); the other end of the first connecting rod (5) is rotatably connected to a first rotating column (6); one end of the second connecting rod (7) is fixedly connected to the first rotating column (6); the other end of the second connecting rod (7) is rotatably connected to a second rotating column (8); the second rotating column (8) is fixedly connected to a first connecting block (9); the first connecting block (9) is fixedly connected to the first protective plate (13); a second limit block (10) is also fixedly arranged on the upper surface of the support platform (1); a third rotating column (11) is rotatably arranged on the second limit block (10); a second connecting block (12) is fixedly connected to the third rotating column (11); the second connecting block (12) is fixedly connected to the first protective plate (13).

4. A tunnel hydraulic smooth blasting construction safety protection device according to claim 3, characterized in that: A synchronous driving structure is arranged between the auxiliary supporting structure and the connecting rod mechanism.

5. A tunnel hydraulic smooth blasting construction safety protection device according to claim 4, characterized in that: The synchronous drive structure comprises a first rotating rod (14) fixedly connected to the rotating shaft (3), and a second rotating rod (15) rotatably connected to the first rotating rod (14); a slider (16) is fixedly connected to the second rotating rod (15); the auxiliary support structure is fixedly connected to the slider (16); and a sliding guide structure is provided between the slider (16) and the support platform (1) to limit the slider (16) from sliding in a vertical direction.

6. A tunnel hydraulic smooth blasting construction safety protection device according to claim 5, characterized in that: The sliding guide structure comprises two first fixed blocks (17) fixedly arranged on the side of the support platform (1), and a sliding groove matched with the sliding block (16) is formed between the two first fixed blocks (17).

7. A tunnel hydraulic smooth blasting construction safety protection device according to claim 1, characterized in that: The auxiliary support structure comprises an auxiliary plate (18) and ground nails (19) fixedly arranged on the auxiliary plate (18).

8. The tunnel hydraulic smooth blasting construction safety protection device according to claim 1 is characterized in that: The first protection plate (13) has a cavity opened in a horizontal direction, and a second protection plate (28) is slidably arranged on at least one side of the cavity.

9. A tunnel hydraulic smooth blasting construction safety protection device according to claim 8, characterized in that: A protection plate driving mechanism for driving the second protection plate (28) to fold or unfold is provided between the second protection plate (28) and the first protection plate (13).

10. A tunnel hydraulic smooth blasting construction safety protection device according to claim 9, characterized in that: The protection plate driving mechanism comprises a double-threaded screw (20) rotatably arranged in the cavity, and two screw sleeves (22) matched with the double-threaded screw (20); the second protection plate (28) is rotatably connected to the corresponding screw sleeves (22) through a third connecting rod (24).

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