JP4504781B2 - Fire fighting ladder - Google Patents

Description

  The present invention relates to an extensible fire fighting ladder.

  Japanese Examined Patent Publication No. 7-103761 describes an invention relating to a ladder structure welded to each other by a closed body having at least three cavities in a lower parent aggregate of a fire fighting ladder. An object of the present invention is to increase the strength of the ladder.

  Japanese Examined Patent Publication No. 8-26738 describes an invention relating to a ladder structure provided with a new drivable crosspiece for upper parent aggregate that connects the upper parent aggregates of the uppermost ladder of a fire fighting ladder at the shortest distance. ing. An object of the present invention is to reduce the lateral direction and torsional vibration by making the uppermost ladder having the smallest rigidity a closed structure having a square cross section.

Japanese Patent Publication No. 7-103761 Japanese Examined Patent Publication No. 8-26738

  The ladder structure described in Japanese Patent Publication No. 7-103761 has a structure in which a lower parent aggregate is welded with four bent steel plates. It is the number of welds that determines the strength. However, if there are many welding locations, the stress concentration at that location, fatigue strength reduction due to residual stress, difficulty in inspection, and ladder deformation after welding become extremely large. Furthermore, when used for a long time, there is a risk that water or the like may enter from the weld unwelded area and corrosion will occur from the inside. Defect inspection is difficult because the weld is also inside the lower parent aggregate. Even if robot welding is used at the time of manufacture, it is necessary to perform welding at a very large number of points, which causes an increase in manufacturing cost.

  In the ladder structure described in Japanese Patent Publication No. 8-26738, even if the uppermost upper aggregates of the uppermost stage are connected to each other by a detachable horizontal rail, “suppression of vibration” which is an advantage of the ladder structure is realized. For this purpose, micro deformation cannot be suppressed unless the crosspiece is firmly fastened, for example, by welding. Furthermore, suppressing the vibration of the entire ladder is more effective for suppressing the deformation of the lowermost stage than suppressing the deformation of the uppermost stage. Moreover, when the member which connects upper parent aggregates is provided, it will become an obstacle when a ladder goes up and down from the ground for a fire brigade.

  Accordingly, an object of the present invention is to provide a low-cost and lightweight fire fighting ladder that suppresses vibration while ensuring strength.

  (1) In order to achieve the above object, a fire fighting ladder according to the present invention constitutes a multistage knitted telescopic ladder assembly, and includes an upper parent aggregate, a lower parent aggregate, an upper parent aggregate and a lower parent aggregate. In a fire fighting ladder having a diagonal frame to be connected, a horizontal beam spanned by the lower parent aggregate, and a horizontal beam diagonal aggregate connecting the horizontal beam, and these members are connected by welding The lower parent aggregate includes a rectangular tube having at least one polygonal cross section, and a plate member disposed along the rectangular tube to fit and support adjacent ladders, and the plate member is disposed above the rectangular tube. And is connected to the rectangular tube so as not to protrude below the rectangular tube.

  The plate material may be configured by bending a flat plate member. The plate material is preferably welded to the oblique bone material so as to be bent in a rectangular shape and extend along the side rail side.

  It is preferable that the oblique aggregate is welded to the side surface of the plate member and the upper surface of the square tube constituting the lower parent aggregate. Moreover, it is preferable that the said horizontal rail is welded to the side surface of the square pipe which comprises the lower parent aggregate, where the said oblique aggregate is not couple | bonded.

  (2) Since the above object is achieved, the fire fighting ladder according to the present invention constitutes a multistage knitted telescopic ladder assembly, and is composed of an upper parent aggregate, a lower parent aggregate, an upper parent aggregate, and a lower parent aggregate. A ladder for fire fighting, having a cross beam spanning the lower parent aggregate, a cross beam connecting the cross beams, and these members are connected by welding In this, a plate material is provided for connecting the lower parent aggregate and the oblique aggregate arranged at predetermined positions in the longitudinal direction of the intermediate ladder other than the uppermost ladder and the lowermost ladder constituting the telescopic ladder assembly. The predetermined direction portion is a position corresponding to the tip of the lower ladder adjacent to the intermediate ladder when the telescopic ladder assembly is fully extended.

  The said board | plate material consists of a flat member, and it may be bent and formed so that a lower parent aggregate and an oblique aggregate may be connected. The plate member is preferably made of a flat plate member, and is preferably bent to connect the lower parent aggregate and a pair of adjacent oblique aggregates to each other.

  A plate member for connecting the oblique aggregate and the upper parent aggregate arranged at the predetermined portion in the longitudinal direction may be further provided. The plate member is preferably made of a flat plate member, and is preferably bent so as to connect the upper parent aggregate and the oblique aggregate. In addition, the plate material is preferably formed of a flat plate member, and is bent and formed so as to connect the lower parent aggregate and a pair of adjacent oblique aggregates to each other.

  (3) Since the above-described object is achieved, the fire fighting ladder according to the present invention constitutes a multi-stage stretchable ladder assembly, and includes an upper parent aggregate, a lower parent aggregate, an upper parent aggregate, and a lower parent aggregate. A ladder for fire fighting, having a cross beam spanning the lower parent aggregate, a cross beam connecting the cross beams, and these members are connected by welding In the above, in the region where the ladders adjacent to each other overlap when the telescopic ladder assembly is fully extended, the cross beam aggregates are densely arranged.

  The horizontal beam oblique aggregates are arranged symmetrically between adjacent horizontal beams in the area where adjacent ladders overlap, and are arranged symmetrically between every other horizontal beam in areas other than the overlapping areas. It is preferable.

  (4) Since the above object is achieved, the fire fighting ladder according to the present invention constitutes a multi-stage stretchable ladder assembly, and includes an upper parent aggregate, a lower parent aggregate, an upper parent aggregate, and a lower parent aggregate. A ladder for fire fighting, having a cross beam spanning the lower parent aggregate, a cross beam connecting the cross beams, and these members are connected by welding In the above, the oblique aggregate is inclined by an angle θ (0 ° <θ <90 °) with respect to an imaginary line connecting the upper and lower parent aggregates at the shortest distance.

  The cross-sectional shape of the oblique aggregate arranged in the region where the adjacent ladders overlap when the telescopic ladder assembly is fully extended, and the cross-sectional shape of the oblique aggregate arranged in the region other than the overlapping region Are different, and the tensile strength of the oblique aggregates arranged in the overlapping region is preferably set larger than the tensile strength of the oblique aggregates arranged in the region other than the overlapping region. Moreover, it is preferable that the tensile strength of the material which comprises the said cross rail is set smaller than the tensile strength of the material which comprises another member.

  According to the present invention, a light-weight ladder that is easy to manufacture, low-cost, and has high strength reliability is provided.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

<First Embodiment>
FIG. 1 is a cross-sectional view of a fire fighting ladder assembly according to a first embodiment of the present invention.

  This ladder assembly A has four ladders, and ladders of substantially similar shapes (the third, second, and first stage ladders) are sequentially fitted inside the lowermost (fourth) ladder. It is. Generally, among the ladders that make up the ladder assembly, the one that is placed at the top is called the “top ladder,” the one that is placed at the bottom is called the “bottom ladder”, and is placed between them. This ladder is called “intermediate ladder”. The ladder assembly A is connected to a ladder extender (not shown). This ladder extender has a known structure, whereby the third stage ladder slides with respect to the fourth stage ladder (the lowest stage ladder) and the second stage ladder slides with respect to the third stage ladder. The second stage ladder and the first stage ladder (top ladder) slide in the same manner. As a result, the ladder assembly A can be expanded and contracted in the longitudinal direction. Although the number of ladders constituting the ladder assembly A is not limited at all, the ladder assembly A generally includes three to six ladders.

  In the figure, the lowermost ladder includes an upper main aggregate 1 using a square tube, a lower main aggregate 7 composed of a square tube 2, a square tube 3, and a bent plate member 4 sandwiched therebetween, and an upper main aggregate. 1 and a diagonal frame 5 that joins the square tube 2 and a horizontal beam 6 that joins the left and right square tubes 3 to each other. In the present embodiment, the lowermost ladder will be described in order to simplify the description of the structure of each ladder, but the intermediate ladder has the same structure as the lowermost ladder.

  However, in the present embodiment, for the uppermost ladder constituting the ladder assembly A, the lower parent aggregate 8 is constituted by only a single square tube. In the present embodiment, as shown in the figure, the third-stage ladder and the second-stage ladder have cross-sectional shapes similar to the cross-sectional shape of the fourth-stage ladder, and are directed toward the upper stage. Therefore, these cross-sectional shapes are similarly reduced.

  FIG. 2 is a perspective view of the lower parent aggregate 7. In the same figure, the horizontal rail 9 is welded to the inner side surface of the rectangular tube 3 constituting the lower parent aggregate 7. In addition, the horizontal rail 9 in the same figure is the same member as the horizontal rail 6 in FIG. The oblique bone material 5 is welded to the upper surface 2 a of the square tube 2 and the outer side surface 4 a of the bent plate material 4. The position of the lower surface 4 b of the bent plate member 4 is not positioned below the lower surfaces of the rectangular tube 2 and the rectangular tube 3. The lower surfaces of the rectangular tube 2, the rectangular tube 3, and the bent plate member 4 are joined to each other by welding. The square tube 2 and the bent plate material 4 are joined together by welding. The square tube 3 and the bent plate material 4 are joined together by welding.

  The bent plate member 4 is configured by bending a flat plate member. As the flat plate member, high-tensile steel or general structural carbon steel can be adopted. In the present embodiment, the bent plate member 4 has a main body portion 4c and a head portion 4d. The main part 4c is a rectangular flat plate, and is disposed along the longitudinal direction of the ladder and extends upward. The head portion 4d is continuous with the main body portion 4c and is formed in a substantially triangular shape.

  According to the present embodiment, the lower parent aggregate 7 is composed of very inexpensive square tubes 2 and 3 and a plate material (bending plate material 4). And since the three members of the square tubes 2 and 3 and the bent plate material 4 are joined by a single welding operation at the lower part thereof, the lower parent aggregate 7 is manufactured at low cost. Moreover, automatic welding by a robot is easy, and a remarkable cost reduction is possible. Moreover, since the square tube 2 and the square tube 3 are arranged on the left and right, the bending rigidity in the left-right direction of the ladder is increased, and the bent plate 4 is larger than the height of the square tube 2 and the square tube 3. As a result, the bending rigidity in the vertical direction can also be increased.

  By the way, the lower ladder supports the upper ladder, but a tip roller for supporting the upper ladder is generally provided at the tip of the lower ladder. Therefore, when the ladder assembly A is expanded or contracted, the lower surface of the lower parent aggregate of the upper ladder may be strongly pressed by the tip roller. However, as described above, since the bending rigidity in the vertical direction of the ladder is also increased, the lower parent aggregate is difficult to be plastically deformed.

  Further, since all the welded portions are exposed on the outer surface, there is an advantage that defect inspection of the welded portion can be performed very easily.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 3 is a cross-sectional view of the lower parent aggregate of the ladder according to the present embodiment. The ladder according to this embodiment is different from the ladder according to the first embodiment in the structure of the lower parent aggregate. Other configurations are the same as those of the ladder according to the first embodiment.

  The lower parent aggregate of this ladder includes a rectangular tube 30 having a rectangular cross section and a bending member 4. The oblique aggregate 5 is welded to the short side surface 31 of the square tube 30, and the horizontal rail 9 is welded to the long side surface 32 of the square tube 30. The bent plate member 4 is welded so as to be in contact with all of the oblique bone member 5, the square tube 30, and the cross rail 9. In this embodiment, in particular, the bent plate material 4 is L-shaped at a portion in contact with the horizontal rail 9. Therefore, the secondary moment of the cross section in the vertical direction and the horizontal direction of the ladder is increased, and the strength reliability is enhanced.

  FIG. 4 is a cross-sectional view of the lower parent aggregate according to the first modification of the present embodiment. In the ladder according to this modification, the lower parent aggregate includes a rectangular tube 30 having a rectangular cross section and the bending member 4. The oblique aggregate 5 is welded to the long side surface 33 of the rectangular tube 30, and the cross rail 9 is welded to the short side surface 34 of the rectangular tube 30. The bent plate member 4 is welded so as to be in contact with all of the oblique bone member 5, the square tube 30, and the cross rail 9. Also in this modified example, the bent plate member 4 is L-shaped at the portion in contact with the horizontal rail 9, so that the secondary moment in the vertical and horizontal directions of the ladder is increased, and the strength reliability is also improved. Further, since the long side surface 33 of the rectangular tube 30 faces upward and the rectangular tube 30 faces the horizontal direction with respect to the ladder, there is an advantage that the height of the entire ladder can be reduced.

  FIG. 5 is a cross-sectional view of the lower parent aggregate according to the second modification of the present embodiment. In the ladder according to this modification, the lower parent aggregate includes a rectangular tube 30 having a rectangular cross section and a bending member 35. The oblique aggregate 5 is welded to the long side surface 33 of the rectangular tube 30, and the cross rail 9 is welded to the short side surface 34 of the rectangular tube 30. The bent plate material 35 is welded to the side surface 36 of the oblique bone material 5.

  The bent plate member 35 is configured by bending a flat plate member. As the flat plate member, high-tensile steel or general structural carbon steel can be adopted. In the present embodiment, the bent plate member 35 is bent and formed in a “U” shape (rectangular shape). For this reason, the man-hour of the bending process of the bending board | plate material 35 can be reduced rather than the man-hour of the bending process of the bending board | plate material 4 which concerns on the said 1st Embodiment, and manufacturing cost is reduced.

  Further, since the bent plate material 35 is welded to the oblique bone material 5, the distance between the bent plate material 35 and the square tube 30 can be freely determined. Therefore, for example, by setting this distance large, the vertical rigidity of the ladder can be increased without increasing the mass. Needless to say, the bent plate member 35 may be formed of a square tube. Also in this modification, since the long side surface 33 of the rectangular tube 30 faces upward and the rectangular tube 30 faces the horizontal direction with respect to the ladder, there is an advantage that the height of the entire ladder can be reduced.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. FIG. 6 is a perspective view of a fire engine with a ladder.

  In the figure, the ladder (expandable ladder assembly) provided in the fire engine is fully extended. The telescopic ladder assembly has a four-stage knitting, and a basket 10 is attached to the tip of the uppermost ladder (first stage ladder) so as to be driven. The lowermost ladder (fourth ladder) has a lower surface coupled to a ladder frame 11, and the ladder frame 11 is supported by a support frame 12. The ladder frame 11 can stand or fall with respect to the support frame 12, whereby the telescopic ladder assembly can be raised and lowered. The support frame 12 is rotatably attached to the subframe 13. The vertical undulation of the telescopic ladder assembly is performed by the hydraulic cylinder 14.

  When the telescopic ladder assembly is fully extended, the overlapping portion 15 between the lowermost ladder and the third ladder above it, the overlapping portion 16 between the third ladder and the second ladder above it, And the overlapping part 17 of a 2nd step ladder and the uppermost step ladder above it is formed. In these overlapping portions 15 to 17, adjacent ladders are in contact with each other, and a large force is transmitted.

  FIG. 7 is an enlarged perspective view of the rear part of the ladder. In the present embodiment, there is no member that connects the upper and lower parent aggregates at the shortest distance. That is, the upper and lower parent aggregates are connected only by the oblique aggregates, and each of the oblique aggregates 5, 18, and 19, which will be described later, is a virtual that connects the upper and lower parent aggregates at the shortest distance. The line P intersects with the angles θ1 and θ2. These angles θ1 and θ2 may be the same. Each angle θ1 and θ2 is larger than 0 ° (degree) and smaller than 90 °.

  In the present embodiment, the bent plate material 20 is attached to the oblique bone material arranged at a predetermined portion in the longitudinal direction of the intermediate ladder. The bent plate member 20 is attached to the oblique bone member 18 and the oblique bone member 19, and the bent plate member 20 is welded between them. The oblique bone members 18 and 19 are inclined bone materials arranged at positions closest to the leading ends of the lower ladders when the telescopic ladder assembly is fully extended. Further, a bent plate material 21 is welded to a joint portion between the oblique bone 18 and the upper parent aggregate 1. One or a maximum of three folding plate members 21 are attached per place. The oblique bone members 18, 19 and the lower parent bone material 2 are connected to each other by the bent plate material 20, and the oblique bone material 18 and the upper parent material 1 are connected to each other by the bent plate material 21.

  FIG. 8 is a perspective view of the lower parent aggregate. As shown in the figure, bent plate members 20 are welded between the oblique members 18 and 19 and between the oblique members 19 and the square tube 2. By providing these bent plate members 20 and 21, the stress generated in the upper and lower parent materials 1 and 2 is reduced.

  9 is a cross-sectional view taken along the line IX-IX in FIG. The bent plate material 20 is bent in particular in an L shape, and is welded so as to cover the side surface of the bent plate material 4 and the upper surface of the rectangular tube 2. In this case, the folded plate member 20 is configured by bending a flat plate member in the same manner as the folded plate member 4. As the flat plate member, high-tensile steel or general structural carbon steel can be adopted.

  FIG. 10 is a diagram illustrating the relationship between the distance from the rear end of the parent aggregate and the stress of the parent aggregate. In the figure, the solid line indicates the stress distribution when the bending materials 20 and 21 are provided, and the dotted line indicates the stress distribution when the bending materials 20 and 21 are not provided. From this figure, it can be seen that a high stress is generated in the ladder where the tip of the lower ladder of the ladder is located. However, as shown by the solid line in the figure, when the folding members 20 and 21 are present, the stress at this portion is reduced.

  In the telescopic ladder assembly, a tip roller or the like is attached to the tip of the lower ladder to support the upper ladder. When the telescopic ladder assembly is fully extended, the tip roller is strongly pressed upward by the lower parent aggregate of the upper ladder. That is, the lower parent aggregate of the ladder receives a large upward pressure. In general, a reinforcing member for connecting the upper and lower parent aggregates with the shortest distance is attached as a countermeasure. Thereby, the thrust force from the tip roller is transmitted also to the upper parent aggregate, and the deformation of the lower parent aggregate is prevented.

  However, in the present embodiment, since the bent plate members 20 and 21 are provided, a reinforcing member for connecting the upper and lower parent aggregates is not necessary. That is, the stress of the parent material at the time of full extension is suppressed only by the bent plate materials 20 and 21 having an extremely simple structure. That is, in the present embodiment, the use of the bent plate materials 20 and 21 enables effective reinforcement even if no measures for improving the strength such as thickening the entire main bone are taken, and at a low cost. The increase in mass is minimized.

<Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described. FIG. 11 is a side view of a ladder according to the fourth embodiment of the present invention.

  This ladder constitutes a third-stage ladder of a four-stage knitted telescopic ladder assembly. In the drawing, when the telescopic ladder assembly is fully extended, the regions where the intermediate ladder overlaps with other ladders are the region 15 and the region 16 as in FIG. In the present embodiment, the cross-sectional shape of the oblique aggregate 23 arranged in the region 22 that does not overlap any ladder is different from the cross-sectional shape of the oblique aggregate 24 arranged in the regions 15 and 16. The aggregate 23 is smaller than the cross-sectional area of the oblique aggregate 24. In short, the oblique material 23 has a lower mechanical strength than the oblique material 24 and is made of a low-cost material. For example, the oblique aggregate 24 may be composed of high tensile steel having a high tensile strength, and the oblique aggregate 23 may be composed of general structural carbon steel.

  In the present embodiment, the ladder is configured as a third-stage ladder, but is not limited thereto, and may be configured as an intermediate stage ladder that is vertically adjacent. That is, the n-stage knitted ladder assembly may be configured as a second stage ladder or an (n-1) th stage ladder.

  When the telescopic ladder assembly is fully extended, no large shearing force is applied to the oblique bone 23 existing in the region 22, and no large stress is generated in the oblique bone 23. A large shearing force acts on the material 24. Therefore, a large stress is generated in the oblique bone material 24. For this reason, the stress generated in the oblique bone 23 and the stress generated in the oblique bone 24 can be made uniform, for example, by reducing the external dimensions of the oblique bone 23 existing in the region 22. That is, in this embodiment, the cross-sectional secondary moment and the cross-sectional secondary moment of the oblique aggregate 23 existing in the region 22 are set smaller than the cross-sectional secondary moment and the cross-sectional secondary moment of the oblique aggregate 24. Therefore, according to the present embodiment, a lightweight and low-cost ladder can be manufactured without reducing the degree of freedom in designing the strength of the ladder.

<Fifth Embodiment>
Next, a fifth embodiment of the present invention will be described. FIG. 12 is a plan view of a ladder according to the fifth embodiment of the present invention.

  This ladder constitutes a third-stage ladder of a four-stage knitted telescopic ladder assembly. In the drawing, when the telescopic ladder assembly is fully extended, the portions where the ladder overlaps with other ladders are the region 15 and the region 16 as in the fourth embodiment. The region that does not overlap is the region 22.

  In this ladder, a horizontal beam oblique aggregate 25 is provided between the horizontal beams 9. The horizontal beam oblique frame 25 is disposed so as to be inclined along the direction of closing toward the tip end direction (left side in the drawing) of the ladder, and is welded between the horizontal beams 9. And in the said area | regions 15 and 16, the cross beam aggregate 25 is arrange | positioned more densely than the said area | region 22. As shown in FIG. That is, in the regions 15 and 16, the horizontal beam oblique aggregate 25 is disposed between the horizontal beams 9, but in the region 22, the horizontal beam oblique frame 25 is disposed every other horizontal beam. .

  When the ladder vibrates periodically in the left-right direction or the torsional direction, the cross beam aggregate 25 is effective in preventing shear deformation of the entire ladder. In particular, in the regions 15 and 16 where the ladders overlap each other, a large shearing force in the left-right direction may be applied to the overlapping portions. However, since the horizontal beam oblique aggregate 25 is arranged more densely in the regions 15 and 16 than in the region 22, deformation of the ladder in the left-right direction and the twisting direction is suppressed.

  The horizontal beam 9 and the horizontal beam oblique bone 25 are effective members for suppressing the vibration of the ladder in the left-right direction, but do not generate as much stress as the parent material when the ladder is operating or when the extension is stopped. Therefore, a material having a lower cost and a lower mechanical strength than the material constituting the parent aggregate may be employed for the horizontal beam 9 and the horizontal beam oblique bone 25. For example, general structural carbon steel or aluminum alloy material may be employed.

  In the present embodiment, vibrations in the left-right direction and torsional direction of the ladder can be suppressed by applying a minimum necessary number of members. In addition, the cost can be reduced by changing the material.

FIG. 1 is a cross-sectional view of a fire fighting ladder assembly according to a first embodiment of the present invention. FIG. 2 is a perspective view of the lower parent aggregate of the ladder constituting the ladder assembly for fire fighting according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of a lower parent aggregate of a ladder according to the second embodiment of the present invention. FIG. 4 is a cross-sectional view of the lower parent aggregate according to the first modification of the second embodiment of the present invention. FIG. 5 is a cross-sectional view of a lower parent aggregate according to a second modification of the second embodiment of the present invention. FIG. 6 is a perspective view of a fire engine with a ladder according to the third embodiment of the present invention. FIG. 7 is an enlarged perspective view of the rear part of the ladder according to the third embodiment of the present invention. FIG. 8 is a perspective view of a lower parent aggregate of a ladder according to the third embodiment of the present invention. 9 is a cross-sectional view taken along the line IX-IX in FIG. FIG. 10 is a diagram illustrating the relationship between the distance from the rear end of the parent aggregate and the stress of the parent aggregate. FIG. 11 is a side view of a ladder according to the fourth embodiment of the present invention. FIG. 12 is a plan view of a ladder according to the fifth embodiment of the present invention.

Explanation of symbols

A Telescopic ladder assembly 1 Upper parent aggregate 2 Rectangular tube 2a Upper surface 2a of rectangular tube 2
3 Each shape tube 4 Bending plate material 4a Outer side surface 4a
4b Lower surface 4c Main part 4d Head 5 Angled bone 6 Horizontal beam 7 Lower parent material 9 Horizontal beam 15 Region where the 4th ladder and the 3rd ladder overlap 16 The 3rd ladder and the 2nd ladder overlap Matching area 17 Area where the second-stage ladder and the first-stage ladder overlap each other 20 Folding plate material 21 Folding plate material 23 Angled material 24 Angled material 25 Horizontal beam angled aggregate 30 Rectangular pipe 31 Short side surface 32 Long side surface 33 Long side surface 34 Short side surface 35 Bending plate material

Claims (10)

A multi-stage knitted telescopic ladder assembly is constructed, and the upper parent aggregate, the lower parent aggregate, the oblique aggregate that connects the upper parent aggregate and the lower parent aggregate, and a horizontal beam spanned over the lower parent aggregate, In the ladder for fire fighting, which has a horizontal frame oblique aggregate connecting the horizontal beams, and these members are connected by welding,
There is provided a plate material for connecting the lower parent aggregate and the oblique aggregate arranged at predetermined positions in the longitudinal direction of the intermediate ladder other than the uppermost ladder and the lowermost ladder constituting the telescopic ladder assembly,
The predetermined portion in the longitudinal direction is a fire fighting ladder which is a position corresponding to the tip of the lower ladder adjacent to the intermediate ladder when the telescopic ladder assembly is fully extended. 2. The fire fighting ladder according to claim 1 , wherein the plate member is formed of a flat plate member, and is bent to connect the lower parent aggregate and the oblique aggregate. 3. The fire fighting ladder according to claim 1 or 2 , wherein the plate member is made of a flat plate member, and is bent so as to connect the lower parent aggregate and a pair of adjacent oblique aggregates to each other. A multi-stage knitted telescopic ladder assembly is constructed, and the upper parent aggregate, the lower parent aggregate, the oblique aggregate that connects the upper parent aggregate and the lower parent aggregate, and a horizontal beam spanned over the lower parent aggregate, In the ladder for fire fighting, which has a horizontal frame oblique aggregate connecting the horizontal beams, and these members are connected by welding,
A plate member is provided for connecting the upper and lower aggregates arranged at predetermined positions in the longitudinal direction of the intermediate ladder other than the uppermost ladder and the lowermost ladder constituting the telescopic ladder assembly,
The predetermined portion in the longitudinal direction is a fire fighting ladder which is a position corresponding to the tip of the lower ladder adjacent to the intermediate ladder when the telescopic ladder assembly is fully extended. 5. The fire fighting ladder according to claim 4 , wherein the plate member is formed of a flat plate member and is bent so as to connect the upper parent aggregate and the oblique aggregate. The fire fighting ladder according to claim 4 or 5 , wherein the plate member is made of a flat plate member, and is bent so as to connect the upper parent aggregate and a pair of adjacent oblique aggregates to each other. A multi-stage knitted telescopic ladder assembly is constructed, and the upper parent aggregate, the lower parent aggregate, the oblique aggregate that connects the upper parent aggregate and the lower parent aggregate, and a horizontal beam spanned over the lower parent aggregate, In the ladder for fire fighting, which has a horizontal frame oblique aggregate connecting the horizontal beams, and these members are connected by welding,
A fire fighting ladder in which the horizontal beam oblique aggregates are densely arranged in a region where adjacent ladders overlap when the telescopic ladder assembly is fully extended. The horizontal beam oblique aggregates are arranged symmetrically between adjacent horizontal beams in the area where adjacent ladders overlap, and are arranged symmetrically between every other horizontal beam in areas other than the overlapping areas. The ladder for fire fighting as claimed in claim 7 . A multi-stage knitted telescopic ladder assembly is constructed, and the upper parent aggregate, the lower parent aggregate, the oblique aggregate that connects the upper parent aggregate and the lower parent aggregate, and a horizontal beam spanned over the lower parent aggregate, In the ladder for fire fighting, which has a horizontal frame oblique aggregate connecting the horizontal beams, and these members are connected by welding,
The oblique aggregate is inclined by an angle θ (0 ° <θ <90 °) with respect to an imaginary line connecting the upper and lower parent aggregates at the shortest distance ,
The cross-sectional shape of the oblique aggregate arranged in the region where the adjacent ladders overlap when the telescopic ladder assembly is fully extended, and the cross-sectional shape of the oblique aggregate arranged in the region other than the overlapping region The tensile strength of the oblique aggregate disposed in the overlapping region is set to be greater than the tensile strength of the oblique aggregate disposed in the region other than the overlapping region . Fire ladder. The fire fighting ladder according to claim 9 , wherein the tensile strength of the material constituting the cross rail is set smaller than the tensile strength of the material constituting the other member.

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