JP5488922B2 - Telescopic ladder - Google Patents

Description

  The present invention is used when, for example, a worker ascends and descends between a high place and a low place in a construction site, or when a passenger moves to the ground from a railway vehicle for a passenger that has unexpectedly stopped in an emergency. In particular, the present invention relates to a telescopic ladder in which a pair of struts that horizontally run across a horizontal rail are configured to have a telescopic structure.

  As this type of telescopic ladder, the present applicant has already proposed a construction as disclosed in, for example, Japanese Patent No. 3594341 and Japanese Patent No. 405263. The telescopic ladder already proposed by the present applicant is composed of a pair of cylindrical struts arranged in parallel to each other at a predetermined interval and between one end of the pair of cylindrical struts in the cylinder axis direction. A plurality of basic members formed in such a manner that the cylindrical strut diameters of the cylindrical struts are sequentially different in a pair of cylindrical struts having a large cylindrical diameter. A shortened state in which the horizontal crosspieces in a plurality of basic members are sequentially contacted by sequentially connecting a pair of cylindrical struts having a smaller cylinder diameter so as to be slidably fitted in the cylinder axis direction. And an extended state in which the horizontal crosspieces of the plurality of basic members are spaced apart at appropriate intervals in the cylinder axis direction, and the end portions of both cylindrical column bodies adjacent in the cylinder axis direction are fitted and held It is configured to have a cylindrical support body with the smallest cylindrical portion among the plurality of basic members. Provided on the horizontal beam of each basic member excluding the basic member, in the extended state by engaging the rod-like member in the engagement holes formed in the end portions of both cylindrical columnar bodies adjacent in the cylindrical axis direction in the extended state And a cylindrical portion at the end portions of the adjacent cylindrical struts that are fitted and held in the extended state, and a locking means that can be unlocked by pulling out the rod-shaped member from the engagement hole. The outward projecting portion projecting outward from the end portion of the cylindrical column body having a small diameter and the inward projecting portion projecting inward from the end portion of the cylindrical column body having a large cylinder portion are in the shortened state. And a retaining means for preventing the adjacent cylindrical struts from coming out by coming into contact with each other when sliding into the extended state.

  The telescopic ladder having the above-described configuration is shortened when not in use, so that the whole is not bulky and can be saved in a compact state, while saving space during storage. By changing the distance between the horizontal crosspieces that become the steps of the ladder to those suitable for ascending and descending and moving stride, and the rod-like members in the locking means are adjacent to each other in the cylinder axis direction. It can be safely used as a state where it is not unexpectedly shortened even when a load is applied to the horizontal crosspiece by engaging with the engaging holes formed at the respective end portions of the frame.

  By the way, in the telescopic ladder having the above-described configuration, both cylinders that are in contact with and adjacent to each other when the cylindrical struts in the basic member are slid in the cylinder axial direction so as to change from the shortened state to the extended state. The outward projecting portion and the inward projecting portion of the retaining means for preventing the column-shaped column body from coming off are locally projected outward from the inner surface of the cylindrical column body and from the outer surface to the inward direction. It was formed by (bulging) processing (for example, refer to Patent Documents 1 and 2).

  FIG. 1 of Japanese Patent No. 3594341   FIG. 4 of Japanese Patent No. 405263263

  However, as shown in Patent Documents 1 and 2, since the protrusion formed by the overhanging process has a semicircular or substantially semicircular cross section, the inner peripheral surface and the outer peripheral surface of the adjacent cylindrical columnar body Because of the small clearance between the two cylindrical struts, the contact point between the outward convex part and the inward convex part is not determined, and the adjacent cylindrical struts in the expanded state are Since the engagement holes of both cylindrical struts are often displaced without being linearly aligned with each other, the engagement work of the rod-shaped members into the engagement holes becomes difficult. Or, when a configuration is adopted in which the rod-shaped member is automatically engaged with the engagement hole by the elastic biasing force, the rod-shaped member may not be correctly engaged normally, or the engagement may be incomplete. Cheap. If it becomes like this, it will become impossible to ensure the safety at the time of use of a ladder, such as a cylindrical support body contracting unexpectedly at the time of use in an extension state.

  Moreover, when the protrusion amount of the convex portion is increased by the overhanging process, the thickness of the convex portion is reduced correspondingly, and a convex portion having a low strength is formed. As described above, the convex portions having a small thickness and weak strength are repeatedly brought into contact with each other, so that the convex portions are easily deformed or damaged in a short period of use. When the convex portion is deformed or damaged in this way, the contact point between the outward convex portion and the inward convex portion is not determined more and more, but the predetermined retaining prevention function is impaired, and the cylindrical support column adjacent at the time of extension There was a problem that it was easy to cause problems such as falling off the body.

  The present invention has been made in view of the above circumstances, and can reliably and properly exert a retaining function during expansion, and can ensure safety during use in an extended state over a long period of time. The aim is to provide a telescopic ladder.

The telescopic ladder according to the present invention devised to achieve the above object includes a pair of cylindrical struts arranged in parallel to each other at a predetermined interval and a cylinder axis direction of the pair of cylindrical struts. A plurality of basic members formed such that the sizes of the cylindrical portion diameters of the pair of cylindrical support columns are sequentially different from each other. In a pair of large cylindrical struts, a pair of cylindrical struts having a smaller cylindrical diameter is a pair of cylindrical struts having a large cylindrical portion diameter and a pair of cylindrical struts having a small cylindrical portion diameter. by sequentially connected as fitted relatively slidably fitted in the cylinder axis line direction in a state having a clearance between the outer peripheral surface of a truncated state lateral桟体abuts sequentially in a plurality of base members, The horizontal crosspieces of the plurality of basic members are spaced apart at an appropriate interval in the cylinder axis direction and are adjacent to each other in the cylinder axis direction. The end portion of the cylindrical strut body is configured to be capable of being changed to an extended state in which it is fitted and held, and among the plurality of basic members, a basic member having a cylindrical strut body having the smallest cylindrical portion diameter is provided. the rod-like member provided laterally桟体in each primary member except, the two engaging holes of formed through the radially each end portion of the adjacent two cylindrical pillar body in the cylinder axis direction in the expanded state the stretched state by causing engageably inserted from the outside in the radial direction can be fixedly held against the fixed releasable locking means by pulling said rod member from said two engaging holes radially outward And an outward projecting portion projecting outward from an end portion of the cylindrical columnar body having a small cylindrical portion diameter at an end portion of both adjacent cylindrical columnar bodies fitted and held in the extended state and a diameter of the cylindrical portion Inward projecting inward from the end of a large cylindrical column And a retaining means for preventing the adjacent cylindrical struts from coming out by abutting each other during sliding from the shortened state to the extended state, thereby preventing the retaining means. The outward convex part and the inward convex part constituting the cylindrical projecting body are press-molded using a pair of male and female dies arranged inside and outside the end part of each cylindrical support body, and both convex parts are respectively in the cylindrical axis direction. It has a contact surface that is orthogonal or substantially orthogonal to it, and is formed in such a shape that the portion immediately below the contact surface is thick, and is formed on each of the end portions of the two cylindrical struts. The two engaging holes are formed at positions that are linearly matched when the contact surfaces of the outward convex portion and the inward convex portion are in surface contact with each other on a surface orthogonal or substantially orthogonal to the cylinder axis direction. It is characterized by being.

According to the present invention having the characteristic configuration as described above, the following effects can be obtained.
(1) A plurality of basic members constituting a ladder are connected to a pair of cylindrical struts having different cylinder diameters so that they can be sequentially slidable in the cylinder axis direction to change between a shortened storage state and an extended use state. Since it is configured to be possible, the entire ladder in the shortened storage state can be significantly reduced in size. Therefore, the storage space in the shortened storage state can be saved, and it can be easily transported to the place of use in the compact shortened storage state.
(2) Further, in the extended state, it is possible to change the cylindrical struts in the plurality of basic members to a shortened state by sliding linearly sequentially by gravity simply by releasing the locking means. Therefore, it is possible to easily and quickly change to the shortened state after use in the extended state.
(3) Moreover, each of the outward convex portion and the inward convex portion constituting the retaining means for preventing the two cylindrical columnar bodies from coming out by contacting each other when sliding from the shortened state to the extended state is provided. It is formed in a form having a contact surface that is orthogonal or substantially orthogonal to the cylinder axis direction on each of both convex portions by press molding using a pair of male and female dies disposed inside and outside the end portion of the cylindrical support column. Therefore, when the outward convex portion and the inward convex portion abut on the abutting surface, it is possible to prevent both cylindrical struts from coming out in the same posture in which their axes coincide. As a result, the engagement holes of both cylindrical struts can be linearly matched in the withdrawal prevention state, and the rod-like member of the locking means can be easily and completely engaged in both engagement holes. There is no inconvenience that the cylindrical support body contracts unexpectedly during use, and safety during use can be ensured.
(4) In addition, since the portion immediately below the contact surface that is orthogonal or substantially orthogonal to the cylindrical axis direction of the outward and inward convex portions is formed thick by press molding, Even if the strength of the contact surface that receives the greatest impact force at times is sufficiently increased and the impact force is repeatedly applied during extension, the contact surface can be prevented from being deformed or damaged. Therefore, even when used for a long period of time, the predetermined retaining function can be reliably and appropriately exhibited.
(5) Further, when the contact surfaces of the outward convex portion and the inward convex portion are in surface contact with each other on a surface orthogonal or substantially orthogonal to the cylinder axis direction, the end portions of both cylindrical support columns Since the two engagement holes formed on each of them are formed at positions that match in a straight line, when they are prevented from coming off, it is confirmed whether the engagement holes of both cylindrical struts are matched. When it is confirmed that there is no problem, the troublesome work of finely adjusting the positions of both cylindrical struts so that both the engagement holes are aligned is unnecessary. By moving from one side to the inside, the rod-like member can be reliably and smoothly engaged in both engagement holes, and the fixing operation in the extended state can be performed easily and quickly.

Due to the synergy of the above (1) to (5) , the present invention can save storage space and facilitate transportation due to remarkable compactness when not in use , and has a reliable , quick and reliable retaining function during expansion. The present inventors have succeeded in providing a telescopic ladder that can be used properly and can ensure safety when used in an extended state over a long period of time.

  In the telescopic ladder according to the present invention, the outward convex portion and the inward convex portion are each formed in an annular shape over the entire circumference of the cylindrical support column (Claim 2), or the cylindrical support column. Any of the above may be formed in pieces along the circumferential direction of the body (Claim 3), but in particular, in the case of forming in pieces along the circumferential direction, the tube at the portion where the convex portion is formed It is possible to provide a ladder that is excellent in strength and durability while reducing the weight of the entire ladder by using a cylindrical support body that is as thin as possible. .

In the telescopic ladder according to the present invention, the locking means is elastically moved and urged toward the direction in which the bar-like member is engaged with the engagement hole, and resists the movement urging force. it is preferable to configure the operation portion for releasing engagement of the rod-like member by pulling operation from said engaging hole is provided (claim 4).
In this case, it is a stretched state, and, when retaining, since the engaging holes of both the tubular support column meets the straight linear, the bar-like member moving with force locking means automatically It is possible to securely and easily lock and fix both cylindrical struts without any trouble by engaging and moving in both engagement holes.

Further, in the high frequency sewing machine, each of the electrodes of the lower a pair on said, it is desirable that the preheating heater is attached (claim 3).
In this case, since it is possible to keep the pair of upper and lower electrodes at a predetermined temperature by preheating when stopping the feeding by the intermittent transfer device, the value of the high-frequency power applied to the electrodes is set as low as possible to generate sparks. While preventing more reliably, predetermined melting strength can be stably obtained by ensuring melting of the resin tape.

<First Embodiment>

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The extendable ladder 1 according to the first embodiment of the present invention includes an extendable ladder main body 2 and a locking means 3 that holds the extended state of the ladder main body 2.

  The telescopic ladder body 2 includes a plurality of basic members 7a, 7b, 7c,... 7m, 7n (hereinafter referred to as the basic member 7 if not specified), retaining means 10, and the like.

  The basic member 7 is a pair of left and right cylindrical columnar bodies 11a, 11b, 11c,... 11m, 11n (hereinafter referred to as the cylindrical columnar body 11 unless otherwise specified) arranged in parallel at a predetermined interval. ) And a plurality of horizontal crosspieces 12a, 12b, 12c,... 12m, 12n (hereinafter, unless otherwise specified) It is described as a horizontal crosspiece 12). As the cylindrical support 11, an aluminum drawing pipe is used.

The cylindrical struts 11 constituting the plurality of basic members 7 are formed so that the diameters of the cylindrical portions are sequentially different, and have the largest cylindrical struts 11a and are located at the bottom. A pair of cylindrical struts 11a, 11c,... 11m, 11n having a diameter smaller than that of the pair of cylindrical struts 11a of the member 7a. The support columns 11b, 11c,... 11m, 11n have a clearance between the inner peripheral surface of the pair of cylindrical support columns having a large cylindrical portion diameter and the outer peripheral surface of the pair of cylindrical support columns having a small cylindrical portion diameter. by sequentially connecting from the bottom toward the top so fitted as to be relatively slidable in the cylinder axis line direction (vertical direction) in a state, as shown in the lower half of FIG. 1, the rungs of the plurality of base members 7 A shortened state in which the body 12 sequentially contacts and overlaps with each other, and FIG. As shown in the half, each of the horizontal crosspieces 12 in the plurality of basic members 7 is vertically separated by an interval corresponding to a step (kick-up) height of one step of the ladder body 2 and is adjacent to the upper and lower sides. The fitting state of the cylindrical struts 11 of the basic member 7 can be changed to an extended state held by a retaining means 10 described later.

  In addition, the cylindrical support | pillar body 11n in the uppermost basic member 7n with the smallest cylinder part diameter is formed longer than the cylindrical support | pillar body 11 in the other basic member 7, and other than the horizontal rail body 12n upwards A horizontal crosspiece 12n ′ is fixed at a step height of one step. In addition, the cylindrical support 11a in the lowermost basic member 7a having the largest diameter of the cylindrical part is also formed slightly longer than the cylindrical support 11 in the other basic members 7, and in addition to the horizontal rail 12a, The horizontal crosspiece 12a 'is fixed at a step height of one step, and a rubber stopper-like anti-slip member 13 is fitted to the lower end thereof.

  For example, as shown in FIGS. 2 and 3, both end portions in the longitudinal direction of the horizontal crosspiece 12 in each basic member 7 except the uppermost basic member 7 n are adjacent in the cylinder axis direction in the extended state, that is, The outer ends in the radial direction with respect to the engagement holes 8 and 8 formed in the end portions 11A and 11A of the cylindrical support bodies 11 and 11 in the two basic members 7 and 7 adjacent to each other in the radial direction. By engaging the rod-shaped member 9 from the side, there is provided a locking means 3 capable of fixing and holding the expanded state of the cylindrical columnar bodies 11, 11 in the two adjacent basic members 7, 7.

  The rod-like member 9 of the locking means 3 is composed of a trunk portion 16, a neck portion 17, and an end portion 18, and the trunk portion 16 slides in a horizontal direction in a through hole 20 formed in a support wall 19 in the horizontal rail body 12. The front end 16a of the body portion 16 is movably supported, and passes through the engagement holes 8 and 8 from the guide hole 22 formed in the side wall 21 of the horizontal crosspiece 12 so that the cylindrical struts 11 and 11 are formed. It is comprised so that it may protrude inside. A coil spring 24 is interposed in a compressed state between the support wall 19 and a spring seat 23 provided on the body portion 16. Due to the elastic force of the coil spring 24, the rod-like member 9 is attached to the body portion 16. The distal end 16a is urged to move so as to protrude into the cylindrical columnar bodies 11 and 11 through the guide hole 22 and the engagement holes 8 and 8.

  The neck 17 of the rod-shaped member 9 has a cylindrical shape formed by the locking means 3 by pulling out the rod-shaped member 9 from the engagement holes 8 and 8 against the elastic biasing force of the coil spring 24. A lever-like operation portion 25 for releasing the locking and fixing of the support columns 11 and 11 is provided on the horizontal beam body 12a through a pin 26 so as to be rotatable.

Next, the structure of the retaining means 10 which is a characteristic part of the present invention will be described in detail.
The retaining means 10 is for preventing the cylindrical struts 11, 11 of the basic members 7, 7 adjacent in the vertical direction from accidentally coming out when the basic member 7 is extended to the use state. . As shown in FIGS. 4 and 5, the retaining means 10 includes a cylindrical support body 11, 11 that is fitted and held over an appropriate length range in the cylinder axis direction in the extended state. An outward projecting portion 27 projecting in an annular shape outwardly from the entire peripheral wall portion of the lower end portion 11A of the cylindrical support 11 made of an aluminum drawing pipe in the upper basic member 7, and an aluminum in the lower basic member 7 An inward convex portion 28 projecting in an annular shape inwardly from the entire peripheral wall portion of the upper end portion 11A of the cylindrical columnar body 11 made of a drawing pipe, and these outward convex portion 27 and inward convex portion By contacting 28, the cylindrical columnar body 11 in the lower basic member 7 is prevented from coming out downward from the cylindrical columnar body 11 in the upper basic member 7.

  Of the outward convex portion 27 and the inward convex portion 28 constituting the retaining means 10, the outward convex portion 27 is a lower end portion of the upper cylindrical column 11 as shown in FIG. As shown in FIG. 6B, the inward convex portion 28 is formed in a lower cylindrical shape by press molding processing using a pair of male and female molds 30A and 30B arranged inside and outside 11A. It is formed by press molding using a pair of male and female molds 31A and 31B arranged inside and outside the upper end portion 11A of the column body 11.

  The outward projection 27 and the inward projection 28 that are press-formed by the pair of male and female dies 30A and 30B and the pair of male and female dies 31A and 31B are the inner peripheries of the respective cylindrical support bodies 11 and 11, respectively. In addition, the outer circumferential side has recesses 27a and 28a having a substantially semicircular arc cross section, while the cylindrical struts 11 and 11 are perpendicular to or substantially perpendicular to the cylinder axis direction o on the outer and inner circumferential sides of the cylindrical support bodies 11 and 11 The annular contact surfaces 27b and 28b are formed, and the portions 27c and 28c directly below the annular contact surfaces 27b and 28b are formed to be thick.

  Further, the outward convex portion 27 and the inward convex portion 28 constituting the retaining means 10 are end portions of the upper and lower cylindrical column bodies 11 and 11 when their contact surfaces 27b and 28b contact each other. Engagement holes 8 and 8 formed in 11A and 11A, respectively, are formed at positions that match linearly.

  In the shortened state, the telescopic ladder body 2 configured as described above is in a state in which the horizontal rails 12 are in contact with each other as seen in the lower half of FIG. When the cylindrical struts 11 and 11 of the basic members 7 and 7 adjacent to each other in the vertical direction are switched relative to each other in the cylinder axis direction in order to switch from the shortened state to the extended state, as shown in FIGS. The abutment surface 27b perpendicular to the cylinder axis direction of the outward convex portion 27 of the lower end portion 11A of the upper cylindrical column 11 and the cylindrical axis of the inward convex portion 28 of the upper end portion 11A of the lower cylindrical column 11 The contact surfaces 28b orthogonal to the direction are in surface contact with each other on a horizontal plane. As a result, it is possible to prevent the cylindrical struts 11 and 11 in the basic members 7 and 7 adjacent in the vertical direction from coming out in the same posture in which their axes coincide with each other, as seen in the upper half of FIG. In addition, each of the crosspieces 12 can be switched to an extended state in which the horizontal crosspieces 12 are vertically separated at an interval corresponding to the step (kickup) height of one step of the ladder body 2.

  In the extended state as described above, the rod-like member 9 of the locking means is formed in the guide hole 22 and the end portions 11A, 11A of the cylindrical columnar bodies 11, 11 in the two upper and lower adjacent basic members 7, 7, respectively. By engaging the engaged holes 8 and 8 from the outside in the radial direction, the cylindrical support bodies 11 and 11 of the two basic members 7 and 7 adjacent to each other in the vertical direction are securely fixed in a predetermined extended state. The telescopic ladder 1 can be safely used for ascending and descending between a high place and a low place.

  Further, the outward projecting portion 27 and the inward projecting portion 28 constituting the retaining means 10 are orthogonally or substantially orthogonal to the cylindrical axis direction o by press molding, and a flat contact surface 27b and Since the portions 27c and 28c directly below 28b are formed thick, the durability of the contact surfaces 27b and 28b that receive the largest impact force when retaining is sufficiently increased, and repeated impact forces are received during extension. However, the contact surfaces 27b and 28b can be prevented from being deformed or damaged. Therefore, even when used for a long period of time, the predetermined retaining function can be reliably and appropriately exhibited.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment will be described mainly with respect to differences from the first embodiment, the same reference numerals are given to the same components as those in the first embodiment, and detailed description thereof will be omitted. In the second embodiment, the description in the first embodiment is applied to points that are not particularly described.

FIG. 7 is an enlarged vertical cross-sectional view of a main part showing an extended state of the telescopic ladder 1 according to the second embodiment, and FIG. 8 is a cross-sectional view taken along line XX of FIG.
As shown in FIGS. 7 and 8, in the telescopic ladder 1 of the second embodiment, the outward projecting portion 27 and the inward projecting portion 28 constituting the retaining means 10 are formed into a cylindrical shape by press molding. A plurality of pieces are formed on the peripheral wall portions of the end portions 11A, 11A of the support bodies 11, 11 along the circumferential direction.

  More specifically, each of the outwardly projecting portions 27 and the inwardly projecting portions 28 is formed in the circumferential direction at intervals of 45 ° at a central angle centered on the tube axis of the cylindrical support 11, and The four outward convex portions 27 and the inward convex portions 28 each have a circumferential length of 45 ° at the central angle.

  The telescopic ladder 1 of the second embodiment configured as described above is used in the same manner as the telescopic ladder 1 of the first embodiment, and can provide the same effects as the telescopic ladder 1 of the first embodiment. In addition to the above, it is possible to suppress a decrease in the strength of the cylindrical support columns 11 and 11 at the formation portions of the convex portions 27 and 28 to be press-formed. Accordingly, while the cylindrical struts 11 and 11 having the thinnest possible thickness are used to reduce the weight of the entire ladder, the cylindrical struts 11 and 11 are bent and deformed at the portions where the convex portions 27 and 28 are formed during use. It is possible to provide the telescopic ladder 1 that is superior in strength and durability without being bent or buckled.

  In the second embodiment, the number of outward projections 27 and inward projections 28 formed in the circumferential direction has been described as four. However, even if two are formed facing each other in the diameter direction, Three or five or more may be formed at equal intervals in the direction.

In the first embodiment, the contact surfaces 27b and 28b of the outward convex portion 27 and the inward convex portion 28 are flat along a plane orthogonal or substantially orthogonal to the cylinder axis direction o. As shown in FIG. 9, the contact surface 27b on the outward convex portion 27 side has an acute angle θ1 with respect to the cylinder axis direction o and the inward convex portion 28 side. The contact surface 28a may be formed as a flat surface having an obtuse angle θ2 with respect to the cylinder axis direction o.
In this case, the end portions (outer end portions) of the contact surfaces 27b on the outward convex portion 27 side come into contact with the contact surfaces 28a on the inward convex portion 28 side, so that the adjacent cylindrical column bodies 11 and 11 are adjacent to each other. Even if it is extended and slid in a state where it is somewhat eccentric, it is possible to exhibit an automatic alignment function that keeps both cylindrical struts 11 and 11 in a concentric state.

DESCRIPTION OF SYMBOLS 1 Telescopic ladder 2 Telescopic ladder main body 3 Locking means 7a, 7b, 7c, ... 7m, 7n Basic member 8 Engagement hole 9 Bar-shaped member 10 Detachment means 11a, 11b, 11c, ... 11m, 11n 11A End portions 12a, 12b, 12c,... 12m, 12n Horizontal beam body 25 Operation part 27 Outward convex part 28 Inward convex part 27b, 28b Abutting surface 27c, 28c Thickness directly below part

Claims (4)

It consists of a transverse桟体being laterally bridged over between the one end portion of the cylindrical axis direction of the predetermined spaced apart pair arranged in parallel with each other in the cylindrical pillar body and the pair of cylindrical pillar body, the pair of the tubular strut plurality of base members the size of the cylindrical portion diameter are formed sequentially different, the pair of cylindrical it smaller cylindrical portion diameter than the pair of cylindrical posts within large cylindrical portion diameter The strut body can slide relative to the cylinder axis in a state where there is a clearance between the inner peripheral surface of the pair of cylindrical strut bodies having a large cylindrical portion diameter and the outer peripheral surface of the pair of cylindrical strut bodies having a small cylindrical portion diameter. Are connected so as to be fitted to each other, the shortened state in which the horizontal bars of the plurality of basic members sequentially contact each other, and the horizontal bars of the plurality of basic members are separated at appropriate intervals in the cylinder axis direction, and The ends of both cylindrical struts that are adjacent in the cylinder axis direction can be changed to the extended state where they are fitted and held. Together are configured, among the plurality of base members, a rod-like member provided laterally桟体in each primary member except the basic member with the most cylindrical portion having a small diameter cylindrical pillar body, cylindrical in the expanded state the stretched state by causing engageably inserted from both tubular strut end portion outwardly of against the two engagement holes radially formed to penetrate radially to the respective adjacent fixable held axially , end portions of the bar-like member and the fixed releasable locking means by the pulling from the two engaging holes radially outward, both tubular strut adjacent the fitted and held in the stretched state And an outward convex portion projecting outward from the end portion of the cylindrical column body having a small cylindrical portion diameter and an inward convex portion projecting inward from the end portion of the cylindrical column body having a large cylindrical portion diameter. Abut each other when sliding from the shortened state to the extended state In telescopic ladder and a, a retaining means for preventing escape of the two tubular struts bodies adjacent by,
The outward projecting portion and the inward projecting portion constituting the retaining means are respectively formed on the both projecting portions by press molding using a pair of male and female dies disposed inside and outside the end portion of each cylindrical support body. It has a contact surface that is orthogonal or substantially orthogonal to the cylinder axis direction, and is formed in such a form that the portion directly below this contact surface is thick ,
The two engaging holes formed in the respective end portions of the cylindrical columnar bodies are mutually connected on the surface where the contact surfaces of the outwardly projecting portion and the inwardly projecting portion are orthogonal or substantially orthogonal to the cylinder axis direction. An extendable ladder that is formed at a position that matches a straight line when the surface abuts .   2. The telescopic ladder according to claim 1, wherein the outward convex portion and the inward convex portion are each formed in an annular shape over the entire circumference of the cylindrical support body.   The telescopic ladder according to claim 1, wherein the outward convex portion and the inward convex portion are each formed in pieces along the circumferential direction of the cylindrical support body. It said locking means, the rod-shaped member is moved biased elastically in a direction that engages said two engaging holes, the rod-like member from said engaging hole against its movement biasing force The telescopic ladder according to any one of claims 1 to 3 , further comprising an operation portion that is pulled out to release the lock.

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