JP4245493B2 - Fall prevention ladder for manhole - Google Patents

Description

  The present invention relates to a fall prevention ladder for manholes, and in particular, a fall for manholes that can be forcibly locked when the ladder body is tilted without using an elastic body such as a spring that may break due to corrosion. It relates to prevention ladders.

  An example of a manhole fall prevention ladder is disclosed in Patent Document 1. Hereinafter, this fall prevention ladder for manholes is called a conventional ladder and will be described with reference to the drawings.

  FIG. 15 is a plan view showing a conventional ladder attached to the receiving frame, and FIG. 16 is an exploded perspective view showing a lock mechanism of the conventional ladder.

  As shown in FIGS. 15 and 16, the conventional ladder includes a ladder main body 22, a mounting member 23 provided at a base end portion of the ladder main body 22, and a mounting member 24 provided at a distal end portion of the ladder main body 22. The ladder main body 22 can be tilted up and down about the shaft 26 at the base end portion. The lock mechanism 25 is attached to the mounting member 24.

  The attachment member 23 is detachably attached to a support portion 27A formed in the receiving frame 27, and the mounting member 24 is another support portion 27B that faces the support portion 27A when the ladder body 22 is tilted horizontally. It is placed on and locked by the lock mechanism 25.

  The lock mechanism 25 includes a lock piece 28 that is rotatably mounted in a placement member 24 that is formed in a U-shape, a coil spring 29 that applies a rotational force in the direction of the arrow to the lock piece 28, and a placement A bolt 30 is rotatably mounted in the member 24 via a coil spring 29. The lower end 28A of the one end of the lock piece 28 is formed in a taper shape, and comes into contact with the support portion 27B when the ladder body 22 is tilted horizontally.

  According to the conventional ladder configured as described above, when the ladder body 22 is tilted horizontally, the tapered lower end edge 28A of the lock piece 28 comes into contact with the support portion 27B. As a result, the lock piece 28 rotates about the bolt 30 against the elastic force of the coil spring 29. When the contact with the support portion 27B is completed, the lock piece 28 is rotated to the lower portion of the support portion 27B by the elastic force of the coil spring 29 and is locked.

  On the other hand, when the ladder main body 22 is erected, the other end 28B of the lock piece 28 is rotated by hand to the position where the lower edge 28A is retracted from the lower surface of the support portion 27B against the elastic force of the coil spring 29. To release the lock.

JP-A-11-107303

  According to the above-described conventional ladder, the ladder body 22 is locked when it is tilted horizontally, so that there is no risk of the ladder body 22 being lifted by internal pressure due to overflow from a manhole. Accordingly, it is possible to reliably prevent a person or the like from falling into the manhole in which the iron lid is opened by the internal pressure.

  However, since the rotation of the lock piece 28 is performed by the elastic force of the coil spring 29, if the coil spring 29 breaks due to the corrosion, the lock piece 28 becomes free and cannot be locked. As a result, the ladder body 22 is not locked, causing the serious accident described above.

  Accordingly, an object of the present invention is to provide a manhole fall prevention ladder capable of forcibly locking the ladder body and preventing the ladder body from being lifted when the ladder body is tilted without using a coil spring or the like. is there.

The invention according to claim 1 is a ladder main body that is detachably mounted in a receiving frame of a manhole iron lid, and can be tilted around a base end portion, and the ladder main body and a lock mechanism provided at the tip end portion thereof. in manhole for fall prevention ladder with the locking mechanism, the a tip portion of the ladder body, said mounted on a plane including the ladder body, a rotatable locking shaft axis, is provided on the ladder body And a stopper that prevents rotation of the lock shaft caused by the lifting force of the ladder body, and a ladder floating prevention protrusion and a lock shaft rotation protrusion are respectively provided on the lock shaft on the lock shaft. They are formed so as to be offset from each other in the circumferential direction, and when the ladder body is tilted horizontally, the lock shaft has the protrusion for preventing the ladder from rising. The lock shaft is rotated by the shaft rotation protrusion coming into contact with the inlet of the recess, while being inserted into the recess while releasing the hook formed in the recess formed inside the receiving frame. The ladder levitation preventing projection moves to a position where it engages with the hook in the recess, and thus the ladder body is horizontally supported in a state where the lock shaft is housed in the recess, and the ladder body is supported by the ladder body. When the lifting force is applied, the ladder levitation preventing protrusion comes into contact with the hook, and the stopper prevents rotation of the lock shaft, thereby preventing the ladder body from being lifted. Is.

According to a second aspect of the present invention, in the first aspect of the present invention, at the entrance of the concave portion, a protrusion for preventing the abutment of a side surface of the lock shaft is formed on the opposite side of the hook, and the ladder main body is formed on the ladder main body. It is characterized by preventing the lock shaft from escaping from the recess when a horizontal force is applied.

  An embodiment of a manhole fall prevention ladder according to the present invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing a fall prevention ladder for manholes according to the present invention, FIG. 2 is a plan view showing a receiving frame to which the fall prevention ladder for manholes according to the present invention is attached, and FIG. 3 shows the invention attached to the receiving frame. FIG. 4 is a perspective view showing a locking mechanism of the fall prevention ladder for manholes according to the present invention, FIG. 5 is a perspective view showing the locking mechanism as seen from another direction, and FIG. FIG. 7 is a perspective view showing a lock mechanism that has entered the recess of the receiving frame, FIG. 7 is a plan view showing a lock shaft of the fall prevention ladder for manholes according to the present invention, and FIG. 8 shows a lock for the fall prevention ladder for manholes according to the present invention. FIG. 9 is a front view showing the handle, FIG. 9 is a side view showing the lock handle of the fall prevention ladder for manholes according to the present invention, and FIG. FIG. 11 is a sectional view showing a base end portion of a fall prevention ladder for manholes according to the present invention, which is tilted horizontally, and FIG. 12 is a standup ladder for manhole fall according to the present invention which is erected. FIG. 13 is a process diagram when the manhole fall-preventing ladder according to the present invention is horizontally tilted, and FIG. 14 shows a state in which the ladder lifting prevention protrusion is in contact with the hook of the recess. It is sectional drawing.

  1 to 14, reference numeral 1 denotes a ladder body, which includes a pair of side plates 2 arranged in parallel and a handrail 3 fixed at right angles to the side plates 2. A long hole 4 is formed at the base end of each side plate 2. An interval (L) (see FIG. 11) between the long hole 4 and the outer surface 2A that comes into contact with an inclined surface 5A of the bracket 5 described later (see FIG. 11) continuously extends toward the tip of the side plate 2. The ladder body 1 can be tilted about the shaft 6 in a state where a shaft 6 described later is positioned at an end 4A of the long hole 4 (an end on the base end side of the side plate 2) (see FIG. 12). .

  Reference numeral 5 denotes a bracket attached to the base end portion of each side plate 2 by passing the shaft 6 through the long hole 4. The shaft 6 also functions as a handrail. Each bracket 5 has an inclined surface 5A with which the outer surface 2A of the side plate 2 abuts when the ladder body 1 is erected. The inclined surface 5A is inclined toward the outside of the receiving frame 7 into which a manhole iron lid (not shown) is fitted. Thereby, as shown in FIG. 12, the ladder body 1 has the outer surface 2A of the side plate 2 and the inclined surface 5A of the bracket 5 in close contact with each other, and the shaft 6 is connected to the end 4B of the long hole 4 Stand up while tilting while moving to the end. As described above, the distance (L) between the side plate 2 and the outer surface 2A continuously extends toward the tip of the side plate 2, so that the portion of the distance (L) is inclined with the shaft 6 by the wedge effect. Cut into the gap with 5A. Therefore, after the ladder body 1 is raised, the ladder body 1 does not wobble.

  As shown in FIG. 10, the bracket 5 includes an upper plate 9 and a lower plate that are formed at an interval equal to or longer than the length of a keyhole-shaped fixing hole 8 (see FIG. 2) that is vertically formed inside the receiving frame 7. It consists of a plate 10, a nut fixing plate 11 placed on the lower plate 10, a nut 12 that is non-rotatably fitted in the nut fixing plate 11, and a bolt 13. Note that the receiving frame 7 is an existing one, and the keyhole-shaped fixing hole 8 is formed to insert a lower end of an existing ladder that can be inserted and removed. A groove 11B is formed in the nut fixing plate 11, and the rotation of the nut fixing plate 11 is prevented by fitting the protrusion 10A formed on the lower plate 10 into the groove 11B. The bolt 13 is screwed into the nut 12 through the through hole 9 </ b> A of the upper plate 9 and the through hole 11 </ b> A of the nut fixing plate 11. The bolt 13 is inserted into the parallel part of the keyhole-shaped fixing hole 8, and the hole diameter of the parallel part is substantially the same as the diameter of the bolt 13, so that the play amount of the bracket 5 is very small.

  When the bracket 5 configured as described above is inserted into the fixing hole 8 portion of the receiving frame 7 and the bolt 13 is tightened, the nut 12 rises, and the fixing hole 8 portion is formed by the nut fixing plate 11 and the upper plate 9. It is pinched. Thus, the ladder body 1 is detachably fixed to the receiving frame 7 via the bracket 5.

  Reference numeral 14 denotes a lock mechanism fixed to the tip of one side plate 2 of the pair of side plates 2. As shown in FIGS. 4, 5, and 6, the lock mechanism 14 has a lock shaft 15 that is attached to the distal end portion of one side plate 2 so as to be rotatable about an axis. The tip of the lock shaft 15 enters the recess 7A (see FIG. 6) formed inside the receiving frame 7 when the ladder body 1 is tilted horizontally to support the ladder body 1 horizontally. A ladder levitation preventing protrusion 16 having a lower surface formed in a tapered shape is formed on the tip side portion of the lock shaft 15. A lock shaft rotation protrusion 17 is formed on the top end of the lock shaft.

  When the tip of the lock shaft 15 is tilted horizontally, the lock shaft rotation protrusion 17 contacts the inlet 7B of the recess 7A of the receiving frame 7, and the ladder lifting prevention protrusion 16 is attached to the hook 7C formed in the recess 7A. The lock shaft 15 is forcibly rotated to the engagement position. The ladder floating prevention protrusion 16 abuts against the lower surface of the hook 7C when a force for lifting the ladder main body 1 is applied to the ladder main body 1, thereby preventing the ladder main body 1 from being lifted.

  An escape prevention protrusion 7D is formed on the upper surface of the recess 7A facing the hook 7C, and the tip of the lock shaft 15 is protruded from the protrusion with the ladder floating prevention protrusion 15 in contact with the lower surface of the hook 7C. The lock shaft 15 is prevented from escaping from the recess 7A by coming into contact with 7D.

  As shown in FIG. 7, the rear end portion of the lock shaft 15 is formed in a plate shape, and a lock handle 18 having a shape as shown in FIGS. 8 and 9 is bolted thereto. The lock handle 18 abuts against a stopper 19 provided at the tip of one side plate 2 to prevent further rotation of the lock shaft 15. This is effective when a coil spring 20 described later is provided.

  The operation of forcibly rotating the lock shaft 15 may be more reliably performed by a coil spring 20 wound around the lock shaft 15 as shown by a two-dot chain line in FIGS. 4, 5, and 6.

  Reference numeral 21 denotes a plate-like placement member fixed to the tip of the other side plate 2 of the pair of side plates 2, and is placed on a support portion 7 </ b> E provided in the receiving frame 7.

  In order to attach the fall prevention ladder for manholes of the present invention thus configured to the receiving frame, the bracket 5 is fitted into the fixing hole 8 portion of the receiving frame 7, and the bolt 13 is inserted into the parallel hole of the fixing hole 8. And fix. In this way, the ladder body 1 is fixed to the receiving frame 7 via the bracket 5, but this fixing operation is performed only by tightening the bolt 13 from the outside of the manhole, so that it can be performed easily and in a short time.

  After the ladder main body 1 is fixed to the receiving frame 7 in this way, if the ladder main body 1 is then tilted, the ladder main body 1 is mounted horizontally in the receiving frame 7 and automatically locked. This process will be described with reference to FIG. When the ladder main body 1 is tilted, the ladder main body 1 is lifted and the shaft 6 is moved to the end 4A of the long hole 4 of the side plate 2 and then tilted.

  When the ladder body 1 is tilted horizontally, the tapered lower surface of the ladder levitation preventing protrusion 16 comes into contact with the upper corner portion of the hook 7C of the concave portion 7A. Therefore, as shown in FIGS. 13 (A) to 13 (D), the lock shaft 15 rotates clockwise in the figure. Thereafter, when the distal end of the lock shaft 15 enters the recess 7A, the lock shaft rotation protrusion 17 contacts the inlet of the recess 7A, so that the lock shaft 15 rotates counterclockwise in the figure. Then, after the steps (E) to (H) in the figure, the tip of the lock shaft 15 is finally placed on the bottom of the recess 7A as shown in the figure (I). That is, the ladder levitation preventing protrusion 16 is horizontal, is positioned below the hook 7C of the recess 7A, and is locked. When a force to lift the ladder main body 1 is applied to the ladder main body 1 in the locked state, the ladder main body 1 is slightly lifted until the ladder levitation preventing protrusion 16 comes into contact with the lower surface of the hook 7C as shown in FIG. Does not lift.

  Thus, since the coil spring 20 is not indispensable for rotating the lock shaft 15 counterclockwise, there is no possibility that the lock cannot be locked due to breakage of the coil spring 20 or the like.

In addition, the counterclockwise rotation of the lock shaft 15 is further ensured by attaching the coil spring 20. When the coil spring 20 is provided, a force that further rotates the lock shaft 15 counterclockwise from the locked state acts, but this is prevented by the lock handle 18 coming into contact with the stopper 19. The force that the lock shaft 14 rotates further in the counterclockwise direction from the locked state can occur even when the coil spring 20 is not provided.

  Further, if a horizontal force acts on the ladder body 1, the tip of the lock shaft 15 may escape from the recess 7A and the lock may be released. However, a horizontal force acts on the ladder body 1. However, since the tip of the lock shaft 15 contacts the escape preventing projection 7D, there is no possibility that the lock is released.

  The plate-like placement member 21 fixed to the distal end portion of the other side plate 2 is placed on a support portion 7E provided in the receiving frame 7. Thereby, the ladder body 1 is stably and horizontally attached in the receiving frame 7.

  In order to raise the ladder body 1, the process shown in FIG. 13 may be reversed. That is, when the lock shaft 15 is lifted while rotating the lock handle 18 clockwise by hand, the lock is released and the ladder body 1 can be raised.

It is a top view which shows the fall prevention ladder for manholes of this invention. It is a top view which shows the receiving frame to which the fall prevention ladder for manholes of this invention is attached. It is a top view which shows the fall prevention ladder for manholes of this invention attached to the receiving frame. It is a perspective view which shows the locking mechanism of the fall prevention ladder for manholes of this invention. It is a perspective view which shows the locking mechanism seen from another direction. It is a perspective view which shows the lock mechanism which entered the recessed part of the receiving frame. It is a top view which shows the lock shaft of the fall prevention ladder for manholes of this invention. It is a front view which shows the lock handle of the fall prevention ladder for manholes of this invention. It is a side view which shows the lock handle of the fall prevention ladder for manholes of this invention. It is a disassembled perspective view which shows the bracket which fixes the base end part of the fall prevention ladder for manholes of this invention to a receiving frame. It is sectional drawing which shows the base end part of the fall prevention ladder for manholes of this invention which fell down horizontally. It is sectional drawing which shows the base end part of the fall prevention ladder for manholes of this invention which stood up. It is a process figure at the time of falling down horizontally of the fall prevention ladder for manholes of this invention. It is sectional drawing which shows the state which the protrusion for ladder levitation | floating prevention contact | abutted to the hook of the recessed part. It is a top view which shows the conventional ladder attached to the receiving frame. It is a disassembled perspective view which shows the locking mechanism of the conventional ladder.

Explanation of symbols

1: Ladder body 2: Side plate 2A: Outer plate 3: Handrail 4: Long hole 4A: End portion on the base end side of the side plate 4B: End portion on the front end side of the side plate 5: Bracket 5A: Inclined surface 6: Shaft 7 : Receiving frame 7A: recess 7B: inlet 7C: hook 7D: escape prevention projection 7E: support portion 8: fixing hole 9: upper plate 9A: through hole 10: lower plate 10A: projection 11: nut fixing plate 11A: through hole 11B: Groove 12: Nut 13: Bolt 14: Lock mechanism 15: Lock shaft 16: Ladder levitation prevention protrusion 17: Lock shaft rotation protrusion 18: Lock handle 19: Stopper 20: Coil spring 21: Mounting member 22: Ladder Main body 23: Mounting member 24: Placement member 25: Lock mechanism 26: Shaft 27: Receiving frame 27A: Support portion 27B: Support portion 28: Lock piece 28A: One end lower edge 28B: Other end 29: Coil spring Grayed 30: bolt

Claims (2)

In a manhole fall-preventing ladder having a ladder body that is detachably mounted in a receiving frame of a manhole iron cover and that can be tilted about a base end portion, and the ladder body and a lock mechanism provided at the distal end portion thereof. ,
The lock mechanism is attached to a front end portion of the ladder main body on a plane including the ladder main body, and a lock shaft that can rotate around an axis, and a lifting force of the ladder main body provided in the ladder main body. A stopper that prevents rotation of the lock shaft that occurs,
On the peripheral surface of the lock shaft, a ladder floating prevention protrusion and a lock shaft rotation protrusion are formed so as to be shifted from each other with respect to the circumferential direction of the lock shaft,
When the ladder body is tilted horizontally, the lock shaft begins to be inserted into the recess while the ladder levitation preventing protrusion is released from the hook formed in the recess formed inside the receiving frame. When the shaft rotation protrusion comes into contact with the entrance of the recess, the lock shaft rotates and moves to a position where the ladder levitation prevention protrusion engages with the hook in the recess, and thus the lock shaft. The ladder body is horizontally supported in a state where is housed in the recess,
When a force to lift the ladder main body is applied to the ladder main body, the ladder levitation prevention protrusion comes into contact with the hook, and the stopper prevents rotation of the lock shaft, thereby preventing the ladder main body from being lifted. A fall prevention ladder for manholes. At the entrance of the recess, an escape prevention protrusion is formed on the opposite side of the hook from the hook, and the lock shaft escapes from the recess when a horizontal force is applied to the ladder body. The fall prevention ladder for manholes according to claim 1, wherein the ladder is prevented.

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