GB2442419A

GB2442419A - Ramp

Info

Publication number: GB2442419A
Application number: GB0802120A
Authority: GB
Inventors: Tatsuo Ono
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-08-09
Filing date: 2005-08-09
Publication date: 2008-04-02
Anticipated expiration: 2025-08-09
Also published as: WO2007017957A1; GB2442419B; CN101238268B; GB0802120D0; CN101238268A

Abstract

A ramp where footboards are always smoothly and stably held in a horizontal position without being affected by soil, pebbles, and dust, and handrails can be held at a constant height. Footboard (3) are each horizontally supported at both ends between two gliders each composed of an upper chord member (1) and a lower chord member (2) that are arranged in parallel to each other. At either of the upper chord member (1) and the lower chord member (2), there is supported one end of an adjustment link for adjustably supporting the interval between the upper chord member (1) and the lower chord member (2), and at the other end, there is provided a position fixing member (9) for fixing the other end of the adjustment link at a predetermined position. Sockets (3A) for the handrails are installed in a vertical upright orientation, at side end surfaces of the footboards (3). Loosening prevention mechanisms for preventing loosening of supporting columns (23) of the handrails (22) are installed on the sockets (3A).

Description

LADDER DEVICE

FIELD OF ART

The present invention relates to a ladder device for workers going up and down put up askew between, for example, the ground and an elevated work spot at a work site of a construction work, and so forth.

BACKGROUND ART

A ladder device is used to enable workers to go up to, or come down from an elevated work spot at a work site of a construction work. The ladder device is made up of a pair of chord members, arranged side by side, and a plurality of step boards extended between the pair of the chord members, and arranged in the longitudinal direction thereof.

With a conventional ladder device, however, the respective step boards are fixedly attached to the pair of the chord members, so that if the ladder device, that is, the chord members, are put up on an elevated work site at an angle different from a usual angle according to the conditions of the work site, the step boards cannot be kept in a horizontal posture, and come to be inclined at the angle. In such a case, a worker's foot is liable to slip on the step board, thereby raising a possibility of occurrence of an accident, due to a worker making a misstep.

In contrast to the conventional ladder device, there has thus far been proposed a ladder device made up by installing an upper chord member, and a lower chord member, serving as a pair of beams, wherein two pairs of the beams being disposed side by side, and by installing step boards so as to be axially supported between the respective beams such that the respective step boards are held substantially in a horizontal posture regardless of a change in application angles of the respective upper chord members and the :i respective lower chord members, and the horizontal posture is maintained by a stopper member provided on a ground plate at each of lower ends of the respective upper chord members and the respective lower chord members.

With this conventional ladder device, however, the stopper members for keeping the respective step boards in the horizontal posture were provided at the lower ends of the respective beams, so that if, for example, the ground plates were placed on the ground surface, there occurred a problem in that the ground plates were found liable to rust after exposure to moisture, and intrusion of soil and pebbles into the ground plates interfered movements of the stopper members and mutual movements between the respective chord members so the ladder device results in hard-to-use.

Further, as is often the case with the conventional ladder device, handrails are provided, in which case the handrails are directly. fixed to the respective upper chord members, so that a change in angles of the respective upper chord members is accompanied by a change in angles of the handrails, thereby causing a problem in that the handrails cannot always be kept at a constant height from the respective step boards.

DISCLOSURE OF THE INVENTION

The invention has been developed in order to solve the problems described as above, and it is an object of the invention to provide a ladder device that can be used by freely varying angles at which an upper chord member, and a lower chord member are put up, respectively, whereupon horizontal holding of respective step boards can be smoothly and stably executed all the time without being subjected to adverse effects of soil, pebbles, or dust while handrajls can be always held at a given height regardless of respective angles of the upper chord member and the lower chord member. *1

To that end, in accordance with the present invention, there is provided a ladder device comprising two pairs of beams, each beam comprising an upper chord member and a lower chord member, disposed in parallel with each other, a plurality of step boards, each of the step boards having respective ends thereof, axially supported between the two pairs of the beams in such a way as to keep the respective step boards in a horizontal posture, a position fixing member for swingably supporting one end of an adjust link for adjustably holding an interval between the upper chord member and the lower chord member provided on either of the upper chord member and the lower chord member, and a position fixing member for fixing the other end side of the adjust link at a position of a predetermined length, provided on the other of the upper chord member and the lower chord member, wherein a socket of a handrail, for detachably inserting a stanchion of the handrail therein, is attached to a side end face of the step board so as to be erected at right angle with the side end face and the socket is provided with a locking mechanism for preventing the stanchion from being loosened.

With such an embodiment of the invention as described, the respective step boards swingably supported by the upper chord member and the lower chord member, at respective intersection points, can be in mutual relationship forming a parallelogram, thereby enabling the respective step boards to maintain a horizontal posture regardless of an inclination of the beam comprising the upper chord member and the lower chord member, and enabling the horizontal posture to be safely and smoothly maintained with a simple linking makeup, so that the handrail held by inserting a stanchion into a socket of the handrail is held vertically to the step board regardless of an inclination of the beam.

Further, a locking mechanism is provided, so that loosening of the stanchion inserted in the socket can be prevented thereby keeping the

S

stanch ions of the handrail stably erected in the upright position all the time.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view showing one embodiment of a ladder device according to the present invention; Fig. 2 is an enlarged perspective view showing an attachment structure of an adjust link shown in Fig. 1; Fig. 3 is a perspective view showing an attachment structure of another adjust link according to the present invention; Fig. 4 is an enlarged longitudinal sectional view showing a structure for tightening up a lower part of the adjust link in Fig. 2; Fig. 5 is an enlarged longitudinal sectional view showing a structure for tightening up an upper part of the adjust link in Fig. 2; Fig. 6 is a side view showing another embodiment of a ladder device according to the present invention; Fig. 7 is a side view showing a fitting structure for an attachment as a hook member in Fig. 6; Fig. 8 is a side view showing a fitting structure for another attachment according to the present invention; Fig. 9 is an enlarged side view showing a state in which a stanchion of a handrail is inserted into a socket; Fig. 10 is an enlarged plan view of the socket; Fig. 11 is an enlarged plan view the socket in cross-section; Fig. 12 is a schematic rear view of a ladder device according to the present invention; Fig. 13 is an enlarged plan view of a step board according to the present invention; and Fig. 14 is a longitudinal sectional side view taken on line A -A in Fig. 13.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described hereinafter with reference to the accompanying drawings. Fig. 1 is a perspective view showing a basic makeup of a ladder device according to one embodiment of the invention. The ladder device is made up of an upper chord member 1, and a lower chord member 2, in pairs, disposed in parallel with each other, thereby forming a beam, and a pair of the beams disposed on the left and right sides, respectively.

Further, a plurality of step boards 3 are interposed between the respective upper chord members 1, on the left and right sides, as well as between the respective lower chord members 2, on the left and right sides, in such a way as to be arranged at equal intervals in the vertical direction.

Each of the step boards 3 is axially supported rotatably by horizontal spindlles 4 protruding from respective end faces of the step board 3, in the vicinity of four corners thereof, into the respective upper chord members 1, and the respective lower chord members 2. Further, an attachment hole 3h for use in insertion of an attachment bolt for a hook attachment member, which will be described later, is provided at four corners of the topmost step board 3, respectively.

Further, a ground shoe 5 is supported between lower ends of the respective beams made up of each pair of the upper chord member 1 and the lower chord member 2 so as to rotatably reciprocate by use respective horizontal spindles 4, the same as the horizontal spindles 4 described as above. In other words, the respective lower ends of the upper chord member I and the lower chord member 2 are axially supported rotatably by the ground shoe 5 through the intermediary of the horizontal spindles 4.

Accordingly, the upper chord member 1 and the lower chord member 2, in the pair of the beams on the left and the right side, the step board 3, and the ground shoe 5 constitute a plurality of parallelograms as seen from a side of the ladder device.

For this reason, if the upper chord member 1 and the lower chord member 2 are caused to be displaced in the longitudinal direction thereof, and in respective directions opposite from each other, that is, one chord member is caused to be displaced upward, and the other chord member is caused to be displaced downward, this will enable all the step boards 3 to concurrently change angles thereof, against the upper chord member 1 and the lower chord member 2, respectively.

That is, whatever change respective startup angles (that is, an application angle of the ladder device) of the upper chord member 1 and the lower chord member 2 may undergo, it is possible to adjust all the step boards 3 so as to remain in the horizontal posture by executing a displacement operation of the upper chord member 1 and the lower chord member 2, in the respective directions opposite from each other, as described above.

A socket 3A in the shape of a bottomed cylinder, for supporting a stanchion 23 (refer to Fig. 6) of a handrail by inserting the same therein, is fixedly attached to both side faces of, for example, a second step board 3 from the top, and the lowest step boards 3, respectively, among the plurality of the step boards 3, in such a fashion as to be perpendicular to each of those step boards 3 by fastening means such as welding, bolting, and so forth.

Further, as shown in an enlarged view of Fig. 2, a support spindle 6 made up of a bolt, screws, and so forth is provided in such a fashion to be horizontally protruded from external surfaces of the respective upper chord member 1, at a site thereof, excluding the lower ends thereof, for example, at * a a site in the vicinity of the central parts of the respective upper chord members 1, and one end of an adjust link 7 is supported in rotatably reciprocating fashion by each of the support spindles 6. Further, the adjust link 7 is provided with a slender hole 8 extending from the center of the adjust link 7 toward the other end thereof.

Meanwhile, a threaded spindle (not shown) is provided at a position below the support spindle 6, on external surfaces of the respective lower chord members 2, so as to protrude therefrom, the threaded spindle is inserted into the slender hole 8 of the adjust link 7, and further, a thumbscrew 9 is screwed onto an end of the threaded spindle. Accordingly, by screwing the thumbscrew 9 onto the end of the threaded spindle, the adjust link 7 can be clamped between the thumbscrew 9 and the lower chord member 2 so as to be pressed into contact therewith. As a result, an interval between the upper chord member 1 and the lower chord member 2 can be adjusted and maintained with the respective step boards 3 kept in the horizontal posture. The threaded spindle and the thumbscrew 9 are utilized as position fixing members.

Accordingly, when the ladder device made up as above is put up so as to span spacing between buildings, and so forth, differing in height from the ground, the ladder device is handled such that the upper chord members 1 and the lower chord members 2 are caused to slide in respective directions, opposite to each other, to thereby enable the respective step boards 3 to constantly maintain the horizontal posture.

Once the respective step boards 3 are held in the horizontal posture, relative positions of the upper chord members I and the lower chord members 2 or respective intervals therebetween are locked by tightening up the thumbscrew, and such a locked state as described is stably held, so that the ladder device can function as one for use at a construction site, and a worker can safely go up and down the respective step boards 3 thereof.

Fig. 3 shows another adjust link 7A that can be put to use in place of the adjust link 7, and the adjust link 7A is provided with a plurality of small holes 10 in a region thereof, ranging from the center to one end thereof (corresponding to the other end described as above).

Accordingly, when setting the interval between the upper chord member 1, and the lower chord member 2, by inserting the threaded spindle (not shown) provided so as to protrude from the external surface of the lower chord member 2 into any of the small holes 10, and subsequently, by screwing a nut 11 onto the threaded spindle, the upper chord member 1 and the lower chord member 2 can be held by the adjust link 7A such that the interval conforms to a set size, as described with reference to Fig. 2.

There have been described various cases where use is made of the adjust link 7, the slender hole 8, and the thumbscrew 9, or use is made of the adjust link 7A, the small holes 10, and the nut 11, respectively, in order to adjust the upper chord member 1, and the lower chord member 2 such that the interval therebetween conforms to the set size, however, the same object as described above can be achieved by use of adjustment means employing a turnbuckle (not shown) linked with a length of wire or a steel bar having ends thereof, attached to the upper chord member 1 and the lower chord member 2, respectively.

Fig. 4 is a sectional view showing in detail a structure for tightening up a lower part of the adjust link 7 against the lower chord member 2 with the thumbscrew 9 shown in Fig. 2. In the figure, a bolt 12 serving as the threaded spindle, with a part of an outer periphery thereof, covered with a collar 12a, penetrates through a side end face of the step board 3 from the inner side to the outer side thereof through the intermediary of washers 13, 14, made of a nylon material, thereby protruding from the external surface of * the lower chord member 2 after passing through a through-hole 15, and a washer 16.

Then, the washer 16 is held by a nut 17 small in thicknss, screwed onto a protruding part of the bolt 12. Further, a part of the bolt 12, protruding out of the nut 17, penetrates through a pair of toothed lock washers 18, 19, provided on respective sides of the adjust link 7, and the slender hole 8 of the adjust link 7 as shown, and the thumbscrew 9 is screwed onto an external end part of the bolt 12.

With the structure for tightening up as described, due to firm frictional contact of the toothed lock washers 18, 19, with the adjust link 7, occurring upon the thumbscrew 9 being screwed up onto the bolt 12 by manipulation of the worker's finger tips, the adjust link 7 can be reliably, and firmly joined with the external surface of the lower chord member 2 without causing the adjust link 7 to slide thereon.

Fig. 5 is a sectional view showing a structure for tightening up an upper part of the adjust link 7 against the upper chord member 1, and this structure differs from the structure shown in Fig. 4 only in that flat washers 20, 21 are used in place of the toothed lock washers 18, 19, clamping the adjust link 7 therebetween from respective sides, and a nut is screwed onto an external end of the bolt 12 serving as the support spindle penetrating through the flat washers 20, 21, and a small hole 1OA of the adjust link 7.

Since the nut is screwed onto the bolt 12 by use of a tightening tool such as a spanner or the like even with the use of flat washers 20, 21, the adjust link 7 can be firmly joined with the external surface of the lower chord member 2 without causing the adjust link 7 to slide thereon.

Fig. 6 shows an embodiment of the present invention, provided with sockets. With the present embodiment, lower ends of a pair of stanchions 23 for a handrail 22 are inserted in two sockets 3A to be thereby firmly supported by bolts or the like (not shown), respectively, the two sockets 3A being attached erected at right angle with each of the side end faces of the upper and lower step boards 3, as shown in Fig. 1, respectively.

Both ends of an upper crosspiece 24 as well as a lower crosspiece 25 of the handrail are axially supported by the stanchions 23, respectively, so as to be integral therewith by a bolt 26, respectively, or to be rotatable, and both ends of a linkage member 27 as shown in Fig. 6 are axially supported by respective ends of the upper crosspiece 24 as well as the lower crosspiece 25 so as to be rotatable.

Further, with the present embodiment, an adjust link 7 such as the adjust link 7 shown in Fig. 2, with a similar linkage mechanism, is provided between respective parts of an upper chord member 1 and a lower chord member 2, at positions for supporting step boards 3 at the topmost step, and the next step, respectively.

Still further, with the present embodiment, the hook attachment member 28 horizontal in shape is attached to the underside of the step boards 3 at the topmost step with the use of bolts 29, and nuts 30, as shown in Fig. 7. A hook member 31 in a shape resembling an inverted letter J, serving as an attachment protruding upward from a front part of the step boards 3 at the topmost step, is integrally bonded to the hook attachment member 28 by welding and so forth.

The bolts 29 are inserted through the respective attachment holes 3h formed in the topmost step board 3, and respective attachment holes (not shown) formed in the hook attachment member 28, and the nut 30 is screwed onto respective ends of the bolts 29.

The hook member 31 is formed in a shape capable of being engaged with a locked member 32 such as a stopper steel bar, stopper steel pipe, and so forth, installed on an upper floor, when the ladder device is put up to span a spacing between, for example, the ground and the upper floor.

With the present embodiment, for example, while the ground shoe 5 placed on the ground, by engaging the hook member 31 of the ladder device with the stopper steel bar or the stopper steel pipe installed on an upper floor of a building, differing in height from the ladder device, an upper part of the ladder device can be stably held by an upper part of the building without a risk of disengagement easily occurring.

Further, even if the height of a building or a work position varies, for example, when the ladder device is put up on a short building as indicated by two-dot chain lines in Fig. 6, while the threaded spindle is shifted upward along the slender hole 8 by loosening the thumbscrew 9, the upper chord members 1 and the lower chord members 2 are caused to slide in respective directions, opposite to each other, and respective intervals therebetween are narrowed down, thereby enabling the respective step boards 3 to be in the horizontal posture. Thereafter, by tightening up again the thumbscrew 9 on the side of the adjust link 7, kept in this position, the respective step boards 3 can be horizontally maintained, thereby stably holding the upper chord members 1 and the lower chord members 2.

Since the respective step boards 3 are horizontally held at this point, the sockets 3A, attached at right angle with and are erected so as to be in an upright position. As a result, if the bolts 26 attached to the respective stanchjons 23 of the handrail 22, inserted in the sockets 3A, are kept loosened, both the upper crosspiece 24 and the lower crosspiece 25, with the both ends thereof supported by the respective bolts 26, are rendered always parallel with the upper chord members 1 and the lower chord members 2, respectively.

Accordingly, it follows that by tightening the bolts 26 again thereafter, the upper crosspiece 24 and the lower crosspiece 25 of the handrail 22, in a varied inclination state, are stably supported by the ladder device.

Fig. 8 shows a case where a hook attachment member 28A in a shape resembling the letter L in place of the hook attachment member 28 horizontal in shape shown in Fig. 7, is attached to the underside of the step boards 3 at the topmost step with the use of bolts 29 and nuts 30.

A locking member 34 having a flange 33, as an attachment, at the tip thereof is provided in an upper part of the hook attachment member 28A so as to protrude therefrom in the horizontal direction, and a locking piece 35 in a shape resembling the letter L is protruded at the lower part of the hook attachment member 28k When the ladder device is put up to span a spacing between, for example, the ground and a frame 37 supporting stage planks 36 of a work walkway, by inserting the frame 37 within the locking member 34, and the flange 33 as well as the locking piece 35 to thereby cause the hook attachment member 28A to be engaged with the frame 37, it is possible to avoid the risk of the ladder device being accidentally disengaged from the work walkway, as in the case described as above.

Figs. 9 to 11 each show an embodiment of the present invention, wherein the socket 3A is provided with a locking mechanism. The locking mechanism comprises a pin 30 attached to a lower part of the socket 3A so as to be oriented in the direction of a diameter thereof, and a wedge 31 slidably attached to a side of an upper part of the socket 3A, and the stanchions 23 of the handrail 22 are supported at two points by the pin 30 and the wedge 31 respectively, thereby preventing the stanchiorjs 23 from being loosened or tilted.

As shown in Fig. 11, the pin 30 is installed at the center of the socket 3A so as to span across the socket 3A in the direction of the diameter. *

At a side of the upper part of the socket 3A, a reinforced part 32 is jutted out along an axial direction (in the longitudinal direction in Fig. 9) of the socket 3A, and two pin insertion holes 33 are formed in the reinforced part 32 along the axial direction thereof.

Further, in the reinforced part 32, a slit 34 for insertion of the wedge is formed so as to be oriented in the radial direction (the horizontal direction in Fig. 9) in such a way as to open in a hollow part of the socket 3A, and the wedge 31 is inserted in the slit 34 so as to be freely slidable in the radial direction.

The wedge 31 comprises a flat plate body 31A, and a pair of tilted guide holes 35 vertically penetrating through the flat plate body 31A.

When guide pins 36 inserted in the axial direction in the pin insertion holes 33 respectively, are inserted into the guide holes 35 respectively, and the flat plate body 31A is slid, the flat plate body 31A either approaches, or move away from the hollow part of the socket 3A along the guide holes 35, and the guide pins 36, thereby clamping the stanchion 23 between a side face of the flat plate body 3 1A, and an inner periphery of the hollow part of the socket 3A when the flat plate body 31A approaches the hollow part.

A groove 37 in a shape resembling the letter U as inverted is formed at the center in a lower part of the stanchion 23, and the groove 37 fits the pin 30 therein inside the socket 3A when the stanchion 23 is inserted into the socket 3A, thereby preventing deviation of the stanchion 23 in the lateral direction. The stanchion 23 is supported by the wedge 31 in the upper part, and is supported by the pin 30 in the lower part thereof, as described above, that is, the stanchion 23 is prevented from being loosened and tilted by support at two points in the upper and the lower parts thereof, so that the stanchion 23 of the handrail 22 can be stably erected in the upright position * all the time.

Fig. 12 relates to another embodiment of the present invention, in which case a plurality of braces 37, crossing each other in a manner resembling the letter X, are installed between the respective lower chord members 2 of the two pairs of the beams, disposed side by side, thereby preventing distortion of the lower chord members 2 consequently leading to distortion and deformation of the ladder device as a whole even if an external load such as impact, vibration, and so forth acts on the respective beams.

Figs. 13 and 14 show still another embodiment of the invention, wherein a non-slip mechanism is formed on the surface of the step board 3.

This is a case where a non-slip mechanism comprising a plurality of holes 38, 39 is formed on the step board 3.

The step board 3 comprises a board body 3A, and reinforcement frames 3B, 3C provided at both ends of the board body 3A and at the center thereof respectively, and the holes 38, 39 are formed by causing parts of the board body 3A to alternately protrude upward and concave downward along the longitudinal direction and the lateral direction, espective1y.

Accordingly, the rim of the hole 39 protruded upward is utilized as a non-slip part.

The reason why the holes 38, 39 are caused to alternately and symmetrically protrude upward and concave downward in respective directions opposite to each other is that even if the board body 3A is turned upside down after formation of the board body 3A with the holes 38, 39, it may be welded onto the reinforcement frames 3B, 3C, and the board body 3A resulting in the same state can be formed. Accordingly, by simply preparing a multitude of the board bodies 3A, the board body 3A can be attached to the reinforcement frames 3B, 3C regardless of whether or not the board body 3A is turned upside down, thereby accomplishing enhancement in workability, * *o assembly efficiency, and economic efficiency.

With the non-slip mechanism, the respective rims of the holes 38, 39 are utilized, however, ribs, concavity and convexity, or the like may be formed on the surface of the board body 3A to be utilized as the non-slip part.

As described in the foregoing, in the ladder device according to the present invention, the respective ends of the plurality of the step board are axially supported by two pairs of the upper chord members and the lower chord members disposed in parallel with each other on the left and right sides, respectively, in such a way as to keep the respective step boards in a horizontal posture, and a position fixing member for swingably supporting one end of the adjust link for adjustably holding an interval between the upper chord member and the lower chord member is provided on either of the upper chord member and the lower chord member while a position fixing member for fixing the other end side of the adjust link at a position of a predetermined length is provided on the other of the upper chord member and the lower chord member, so it is possible to cause the upper chord members and the lower chord members to be at respective relative positions in such a way as to vary an interval between the upper chord member and the lower chord member according to an application angle of the ladder device, and at the same time, thereby always holding all the step boards in a horizontal posture.

Further, this holding state can be stably held by urging of pressing pressure of the adjust link toward the lower chord member, so that the respective step boards can be easily and reliably secured to the upper chord members and the lower chord members. Accordingly, tilting of the step board does not occur during usage of the ladder device. Further, since the socket of the handrail, for use in detachably inserting the stanchion of the handrail therein is fixedly attached to a side end face of the step board, even * a if respective inclinations of the upper chord member and the lower chord member undergoes a change according to an application state of the ladder device, the stanchion of the handrail canbe erected vertically to the step board all the time, so it is possible to obtain an advantageous effect of keeping the handrails at a given height from the respective stp boards all the time.

Still further, in the ladder device according to the present invention, since attachments for engagement with locked members are provided on the topmost step board so as to be integral therewith) positioning or holding of the upper end of the ladder device to buildings and so forth can be rendered reliable and stable, and consequently, it is possible to avoid the risk of the upper end of the ladder device undergoing displacement or shift due to the upper end slipping from the wall surface of a building, and so forth.

Since the socket is provided with the locking mechanism for the stanchions, loosening or tilting of the stanchion inserted in the socket can be prevented, so that the stanchions of the handrail can be stably erected in the upright position all the time.

Further, since the step board is provided with the non-slip mechanism, it is possible to prevent workers moving up and down the step boards from slipping thereon; whereby achieving stability in up/down movements of the workers.

Furthermore, since the braces, crossing each other in the manner resembling the letter X, are installed between a pair of the lower chord members, it is possible to prevent distortion and deformation of the lower chord members consequently leading to distortion and deformation of the ladder device as a whole even if an external load acts on the lower chord members.

Claims

What is claimed is: 1. A ladder device comprising: two pairs of beams,

each beam comprising an upper chord member and a lower chord member, disposed in parallel with each other; a plurality of step board, each of the step boards having respective ends thereof, axially supported between the two pairs of the beams in such a way as to keep the respective step boards in a horizontal posture; a position fixing member for swingably supporting one end of an adjust link for adjustably holding an interval between the upper chord member and the lower chord member provided on either of the upper chord member and the lower chord member; and a position fixing member for fixing the other end side of the adjust link at a position of a predetermined length, provided on the other of the upper chord member and the lower chord member; wherein a socket of a handrail, for detachably inserting a stanchion of the handrail therein, is attached to a side end face of the step board so as to be erected at right angle with the side end face, and the socket is provided with a locking mechanism for preventing the stanchion from being loosened.
2. A ladder device according to claim 1, wherein attachments for engagement with locked members are provided on the topmost step board so as to be integral therewith.
3. A ladder device according to claims 1 or 2, wherein a non-slip mechanism comprising a multitude of holes, ribs, or concavity and convexity is fOrmed on the surfaces of the respective step boards.
4. A ladder device according to any of claims 1 to 3, wherein one or more braces crossing each other in a manner resembling the letter X are installed between a pair of lower chord members disposed in parallel with each other.
5. A ladder device according to any of claims 1 to 4, wherein a locking mechanism comprises a pin attached to a lower part of the socket so as to be oriented in the direction of a diameter thereof, and a wedge slidably attached to a side of an upper part of the socket) wherein a lower end of the stanchion is supported by the pin, and a side face of the stanchion is tightened up by the wedge in the lateral direction.
6. A ladder device according to claim 5, wherein a groove fitting the pin therein is formed at the lower end of the stanchion.