A TELESCOPIC LADDER ASSEMBLY

Description

[0001] The present invention relates to a telescopically extendable and collapsible ladder assembly having at least three ladder sections, each of said ladder sections having two tubular stile members arranged parallel to each other and interconnected at one end by a ladder rung to form a U-shaped ladder section; the stile members of each ladder section being telescopically inserted into the stile members of an adjacent ladder section. The ladder assembly further comprises automatic latch mechanisms for locking the telescopically inserted stile members relative to one another when the ladder sections are extended, the latch mechanisms of each ladder section being associated with one or more actuators for unlocking the stile members in order to allow for collapsing of the ladder assembly.

[0002] These ladder assemblies have become quite popular as portable ladders, such as a straight telescopic ladder or a step ladder, but also for stationary mounting, such as a loft ladder providing access to a loft.

[0003] Prior art designs of such ladder assemblies have already been disclosed as early as 1929 in the US patent 1712942 (Smith). More recent designs are disclosed in EP 527 766, EP 1 402 143, GB 2263932 (Telesteps), WO2004/013445 (Core Distribution), US 5743355 (McDonnell), US 5738186 (Foxdale).

[0004] The prior art designs have details that are not satisfactory, either with regard to their construction and/or their practical use. Therefore the present invention aims to propose measures that allow for improvements. These measures can either be applied alone or in combination. In a most preferred embodiment of the invention all measures are applied in a ladder assembly to obtain an optimum result.

[0005] The present invention relates to a ladder assembly according to the preamble of claim 1, which features are disclosed in US 1 712 942.

[0006] In EP 1 402 14a, and EP 1 516 999, it is disclosed to mount the actuators at the front of the rung and in close proximity to the stile members so that each actuator is manually and individually operable by a user holding his hands around the stile members, in particular around the connectors at the upper end of the stile members. This prior art design thus requires the user to hold both his hands around the ladder stiles during the collapse of the ladder. It is alleged that this design increases safety for the user with regard of a user's hand being seized between two rungs upon collapse of a ladder. Whilst that may be correct from said perspective, this arrangement does not take into account the fact that in many situations the user also needs to stabilize the ladder so it does not sway or hit against something during the collapse.

[0007] The present invention aims to provide an improved telescopic ladder assembly that allows the user to employ a single hand for actuating the manually operable actuators and use his other hand for other purposes, e.g. grip the ladder at a higher up position to keep it stable and/or guide a ladder section during its descend.

[0008] The present invention achieves this aim by providing a telescopic ladder assembly according to claim 1.

[0009] Arranging the slidable actuators in the elongated recessed portion has the advantage that the actuators are generally protected from the feet of a person on the ladder, yet can have a suitable thickness to be operated by a single hand, e.g. by thumb and index finger.

[0010] The slots or single contiguous slot in the front wall are preferably located in the recessed portion of the front wall.

[0011] Preferably the actuators are effectively arranged at a mutual distance of less than 10 centimetres to facilitate single handed operation.

[0012] The actuators protrude at the front of the rung between 1 and 4 millimetres. As mentioned above the location of these actuators in the elongated recessed portion of the front wall provides protection for the actuators. Yet it has been found that "some forward protrusion" of these centrally located actuators cause the effect that the actuators provide additional grip for a hand grasping around the central portion of the rung. In practice the actuators will fall in the palm of the hand and so provide additional grip.

[0013] The provision of recessed portions in the front and rear wall give the rung an enhanced stability, allowing in particular the provision of one or more holes or slots in said recessed wall portion in the central region of the rung for the mounting of one or more actuators associated with the latch mechanisms.

[0014] In a preferred embodiment of the rung the top wall is in cross section upwardly convex, and the bottom wall is in cross section upwardly concave, preferably of substantially identical curvature.

[0015] The front wall and the rear wall are symmetrical.

[0016] The invention will now be explained in more detail under referral to the appended drawings. In the drawings:

Fig. 1 shows in side view a straight telescopic ladder according to the invention in collapsed condition,

Fig. 2 shows the ladder of figure 1 in plan view,

Fig. 3a shows in exploded view a stile member and a friction damper of a ladder assembly according to the invention,

Fig. 3b shows the friction damper from a different angle,

Fig. 4 shows in cross-section a rung of a ladder according to the invention,

Fig. 5 shows two rungs stacked against one another,

Fig. 6. shows a perspective view of a portion of a ladder with a rung as in figure 4 and with slidable actuators,

Fig. 7 shows the rung of figures 4 and 6 with the slidable actuator,

Figs. 8a-c show the slidable actuator,

Fig. 9 shows a hand gripping a central portion of the rung of figure 6, and

Figs. 10a-d show a connector of a ladder assembly according to the invention.

[0017] Figures 1 and 2 show an example of a ladder assembly according to the invention, here embodied as a straight telescopic ladder 1. As explained above the ladder assembly may also be part of another "ladder product" such as a stepladder or combination ladder, a work platform with ladder like telescopic legs, etc.

[0018] The ladder 1 includes a lowermost ladder section 2 having two tubular stile members 2a, b which are arranged parallel to each other. Each stile member 2a, b of the lowermost ladder section 2 here is provided with a ground engaging foot member 2c (e.g. of rubber or the like).

[0019] The stile members 2a, b are interconnected at their upper ends by a ladder rung 2d and in this example (as is preferred) also by a lowermost ladder rung 2e.

[0020] The ladder 1 further comprises at least two additional ladder sections; here seven additional ladder sections 3-9. These ladder sections 3-9 each have two tubular stile members arranged parallel to each other and interconnected at the upper end by a ladder rung to form a U-shaped ladder section. The stile members of each ladder section are telescopically inserted into the stile members of a lower and adjacent ladder section.

[0021] The ladder 1 further comprising automatic latch mechanisms (as will be explained by example in more detail below) for locking the telescopically inserted stile members relative to one another when the ladder sections are extended, the latch mechanisms being associated with actuators for unlocking the stile members in order to allow for collapsing or retracting of the ladder assembly.

[0022] As can be seen in figure 1 these actuators are manually operated actuators, indicated with reference numeral 10 in figure 1, The actuators 10 are the slidable actuators and are arranged centrally on the front side of the rung 2d so as to be operable simultaneously with a single hand.

[0023] The rungs 2d-9d are connected to the associated stile members 2a, b via connectors 2f, g of which preferred embodiments will be illustrated with reference to figures 10a-d.

[0024] An issue related to telescopic ladders, such as ladder 1, is the velocity of the telescopic section when the ladder is collapsed (or extended when used as a loft ladder or the like). In order to retard said velocity multiple of the ladder sections are preferably provided with damper members that provide retardation of gravity induced velocity of the ladder section upon collapse and/or extension of the ladder section, each damper member being mounted on a stile member so as to engage on the inside of the stile member of the adjacent ladder section.

[0025] In figure 3 an example is shown of an inventive friction damper member 30 that provides, as only substantial source, the desired retardation on the basis of surface friction with the inside of the stile member of the lower ladder section.

[0026] The effective weight of the ladder sections to be retarded differs from above to below; it effectively increases in said direction in ladder 1, as the release and subsequent collapse of a ladder section such as section 3 towards the lower ladder section, such as section 2, brings in motion all ladder section above said section 3 as well. Therefore it is proposed that the damper members 30 of the respective ladder sections provide a differing surface friction resistance in order to compensate for the total weight of the ladder sections to be retarded, so a greater resistance for a lower section compared to a higher section of the ladder.

[0027] It is preferred that the damper members that provide a differing surface friction resistance are made of materials, preferably plastic materials, most preferably injection-moulded, having a different modulus of elasticity. In a practical solution this can be done by manufacturing the damper members (preferably as unitary components) from a fibre reinforced plastic material, the different modulus of elasticity being obtained by adaptation of the percentage and/or composition of the fibre material.

[0028] For example the plastic material of the damper members 30 is glass-filled, e.g. glass-filled nylon.

[0029] In the example shown in figure 3, as is preferred, the damper member 30 has an annular body having an upper fastening portion 31 which is inserted into the stile member at an end thereof, and having multiple friction tabs that extend below the annular body and are spaced from another in circumferential direction.

[0030] As is further preferred the upper fastening portion 31 includes integral elastic fasteners 33 that are adapted to snap into associated apertures in the stile member for connecting the member 30 to the stile member.

[0031] It is further preferred for the annular body of the damper member 30 to have an annular flange which rests against the stile member end face.

[0032] Referring to figures 4-10 now further aspects and preferred details of the ladder assembly according to the invention will now be explained.

[0033] Figures 4, 5, 7 show a preferred design of a rung for a telescopic ladder, which is incorporated in a ladder according to the invention.

[0034] Here the rung is considered to be any of the rungs of the ladder 1 of figure 1, so that reference numeral 2d is used here.

[0035] The rung 2d is made from an extruded aluminium tubular profile, the profile including a top wall 41, a bottom wall 42, as well as a front wall 43 and a rear wall 44 extending between the top wall and the bottom wall. The front wall 41 here corresponds to the side on which the slidable actuators 10 are mounted. As can be seen in figure 1 the slidable actuators 10 are arranged on the front side of the rung.

[0036] As is preferred the top wall 41 is in cross section upwardly convex, whereas the bottom wall 42 is in cross section upwardly concave. As is preferred the curvature is identical so that in a design of the ladder wherein the rungs contact one another in collapsed state of the ladder (as is preferred) the top wall and bottom wall are in close contact (see figure 5). This provides stability of the ladder in said collapsed condition and avoids items entering in the space between the rungs.

[0037] The front wall has an elongated recessed portion 43a extending over the entire length thereof. This recessed portion is offset inwardly with respect to the above and below located edge portions 43b, c of the front wall 43. The rear wall has a similar recessed portion 44a.

[0038] The front wall and rear wall are symmetrical. These recessed portions extend over a substantial portion of the height of the respective front and rear wall, between 15 and 25 millimetres. The depth may vary, and lies between 3 and 6 millimetres. The rungs have a great stability, even when weakened by one or more holes or slots in a central region of the rung to accommodate one or more actuators for the latch mechanisms.

[0039] The upper surface of the top wall of the rung is preferably provided with a pattern of axial grooves/ribs to avoid slipping of the feet of a person climbing the ladder.

[0040] As can be seen in figures 1, 6, 7 and 9 the slidable actuators 10 are arranged in said recessed portion 43a.

[0041] As shown in figures 1, 6, 9 the slidable actuators 10 here are arranged centrally on the front side of the rung 2d -9d so as to be operable simultaneously with a single hand.

[0042] In this example each rung 2d is provided with two slots in the recessed portion 43a and each actuator 10 has a rear extension portion 11, which extends through a slot into the interior of the rung (see figure 7).

[0043] Each of said rear extension portions 11 is connected to an operating rod (partly shown in figure 10b with reference numeral 60) which extends inside said rung to the latch mechanism (not shown) at the outer end of the rung.

[0044] The slidable actuators 10 are not fully hidden within the recess, but protrude at the front of the rung between 1 and 4 millimetres. This is depicted in figure 7 showing a forward protrusion of 2 mm.

[0045] By being hidden for a major part within the recess it is avoided that the actuators 10 are damaged by the feet of someone climbing or descending the ladder and/or during storage and transportation.

[0046] As is also preferred the manual slide actuators 10 are spaced apart at most 15 centimetres, more preferably at most 10 centimetres. This allows for easy single hand operation of both actuators 10 in a central portion of the rung, so that the operator or ladder user can use his or hers other hand for other purposes, e.g. holding the ladder stable by grabbing the ladder at a higher location than the actuators 10 to be operated for release of a ladder section.

[0047] In combination with some "forward protrusion" these actuators then add to the grip that a person may have on a ladder rung when the person holds a hand centrally around the rung as is shown in figure 9. This is a normal routine for persons climbing and descending a ladder and any additional grip is useful.

[0048] For ergonomic reasons the slidable actuators 10 have a height of between 15 and 25 millimetres.

[0049] As is shown in figures 7, 8a-d the rear extension portions 11 of the actuators 10 preferably include a snap provision adapted to snap around the rod. This facilitates the assembly process of the ladder assembly.

[0050] The figures 10a-d show a connector, here connector 2f, which connects a rung (such as rung 2d) at an end thereof to the upper end of a stile member (here 2a). It is noted that preferably all connectors of a ladder assembly are of generally the same design, albeit with dimensions adapted to the diameter of the stile member (as is shown in figure 1 and common for this field).

[0051] The connector 2f has a body (here of a unitary plastic design) having a rung portion 50, which is here -as is preferred - adapted to be inserted into the end of the rung and be fastened therein (e.g. by press fit or otherwise). The connector body further includes a front collar segment 52 and a rear collar segment 54, these segments 52, 54 each being integral at one end thereof with the rung portion 50.

[0052] The two collar segments 52, 54 substantially encircle the stile member. The collar segments 52, 54 have slightly spaced apart opposed ends and a fastener assembly is provided bridging the opposed ends of the collar segments for rigidly coupling the collar segments around the stile member.

[0053] The front collar segment 52 extends over angle of between 120 and 150 degrees, more preferably between 130 and 140 degrees, with respect to the longitudinal axis 55 of the rung, whereas the rear collar segment 54 extends over a complementary angle. In figures 10a-d the front collar segment extends over 135 degrees which is preferred.

[0054] The opposed ends of the collar segments are provided with a bore 56 through which a screw or bolt is fitted (not shown), the bore e.g. having at one end a recess for a bolt head and a nut being recessed in the opposed collar segment end.

[0055] As is highly preferred the outer face of the collar segments 52, 54 - at the opposed ends thereof - form a substantially triangular protrusion 57 with respect to adjacent portions of the outer face of the collar segments (as can be seen in figures 10a,b). This protrusion 57 provides a body portion for accommodation of a fastener, such as a screw or a bolt, in a manner which is not laterally extending as with the Telesteps ladders. It has been found that this orientation of the split between the collar segments allows easy and accurate tensioning of the collar around the style, better than the known 180 degrees design and better and easier than the mentioned 90 degrees design of Core Distribution.

[0056] The body of the connector preferably is made of plastic material, preferably as a unitary body by injection moulding, preferably of fibre reinforced plastic material.

[0057] The skilled person will appreciate that the body of the connector here includes a passage 58 for a locking pin 60 (which can form an extension of or be connected to the mentioned rod attached to the slide actuators 10) and allows to accommodate a spring 61 for biasing said locking pin 60 towards a locked position (commonly the stile member having an associated locking pin opening to receive said locking pin in extended state of the ladder section).

[0058] As is preferred - and known in the art - the automatic latch mechanisms of the inventive ladder each include a locking pin having a length which is sufficient for extending through a locking hole of the ladder section positioned there above and into the hollow space inside the stile member and the stile member having an extension below the locking hole, so that when an upper ladder section is released and telescopically inserted into an intermediate ladder section, which is locked in relation to a lower ladder section by the locking pin of the lower ladder section engaging the locking hole of the intermediate ladder section, the upper ladder section being stopped in a safety position from being fully inserted in the intermediate ladder section, by a safe distance, e.g. between 3 and 10 cm, by engagement of the extension of the lower ends of the stile members of the upper ladder section with the locking pins of the lower ladder section extending through the locking holes into the hollow space of the stile members of the intermediate ladder section.

Claims

1. A telescopically extendable and collapsible ladder assembly (1) having at least three ladder sections (2-9), each of said ladder sections having two tubular stile members (2a, 2b) arranged parallel to each other and interconnected at one end by a ladder rung (2d-9d) to form a U-shaped ladder section, the stile members of each ladder section being telescopically inserted into the stile members of an adjacent ladder section,
the ladder assembly further comprising automatic latch mechanisms (60,61) at each end of a rung for locking the telescopically inserted stile members relative to one another when the ladder sections are extended, the latch mechanisms each being associated with a slidable actuator (10) for unlocking the stile members in order to allow for collapsing of the ladder assembly,
wherein the ladder rungs (2d-9d) are made from an extruded aluminium tubular profile, the profile including a top wall (41), a bottom wall (42), as well as a front (43) and a rear wall (44) extending between the top wall and the bottom wall, the front and rear wall being symmetrical,
the actuators (10) being arranged on the front side of the rung, wherein the front wall (43) of the rung has an elongated recessed portion (43a) extending over the entire length thereof and located below and inwardly offset from an above located edge portion (43b) of the front wall,
the actuators (10) being arranged in said recessed portion (43a), each actuator (10) extending through a slot in said front wall into the interior of the rung, each of said actuators being connected to a operating rod (60) which extends inside said rung to the latch mechanism (60, 61) at the outer end of the rung,
characterized in that,
the actuators (10) are arranged centrally on the front side of the rung so as to be operable simultaneously with a single hand,
and in that each of the front wall (43) and the rear wall (44) also has an edge portion (43c) below the elongated recessed portions (43a,44a), said recessed portions being also offset inwardly with respect to said below located edge portion (43c) of the respective wall (43,44)
and in that the elongated recessed portions (43a,44a) extend over a substantial portion of the height of the respective front and rear wall which portion is between 15 and 25 millimetres,
and in that the slidable actuators (10) have a height of between 15 and 25 millimetres,
and in that the elongated recessed portions (43a,44a) have a depth which lies between 3 and 6 millimetres,
and in that the slidable actuators (10) protrude at the front of the rung between 1 and 4 millimetres.

2. Ladder assembly according to claim 1, wherein the rung (2d-9d) has a top wall (41) which is in cross section upwardly convex, whereas the bottom wall (42) is in cross section upwardly concave.

3. Ladder assembly according to claim 2, wherein the curvature of the top wall (41) and the bottom wall (42) is identical, and wherein the ladder is designed so that the rungs contact one another in the collapsed state.

Ansprüche

1. Teleskopartig ausziehbare und zusammenklappbare Leiteranordnung (1), mit mindestens drei Leiterabschnitten (2-9), wobei jede der Leiterabschnitte zwei rohrförmige Holmelemente (2a, 2b) umfasst, die parallel zueinander angeordnet und miteinander an einem Ende durch eine Leitersprosse (2d, 9d) verbunden sind, um einen U-förmigen Leiterabschnitt zu bilden, wobei die Holmelemente jedes Leiterabschnitts teleskopartig in die Holmelemente eines benachbarten Leiterabschnitts eingeführt sind,
wobei die Leiteranordnung ferner automatische Riegelmechanismen (60,61) an jedem Ende einer Leitersprosse zum Verriegeln der teleskopartig eingeführten Holmelemente relativ zueinander, wenn die Leiterabschnitte ausgefahren sind, umfasst, wobei die Riegelmechanismen jeweils mit einem verschiebbaren Stellglied (10) zum Entriegeln der Holmelemente ausgestattet sind, um die Holmelemente zu entriegeln, um ein Zusammenschieben der Leiteranordnung zu ermöglichen,
wobei die Leitersprossen (2d-9d) aus einem extrudierten Aluminiumrohrprofil hergestellt sind, wobei das Profil sowohl eine obere Wand (41) und eine untere Wand (42) als auch eine vordere Wand (43) und eine Rückwand (44) aufweist, die sich zwischen der oberen Wand und der unteren Wand erstrecken, wobei die vordere Wand und die Rückwand symmetrisch sind,
wobei die Stellglieder (10) an der vorderen Seite der Sprosse angeordnet sind, wobei die vordere Wand (43) der Sprosse einen länglich vertieften Abschnitt (43a) aufweist, der sich über die gesamte Länge davon erstreckt und unterhalb und nach innen von einem oberhalb befindlichen Kantenabschnitts (43b) der vorderen Wand versetzt angeordnet ist,
wobei die Stellglieder (10) in dem vertieften Abschnitt (43a) angeordnet sind, wobei sich jedes Stellglied (10) durch einen Schlitz in der vorderen Wand in das Innere der Sprosse erstreckt, wobei jedes der Stellglieder mit einer Betätigungsstange (60) verbunden ist, welche sich innerhalb der Sprosse zu dem Riegelmechanismus (60, 61) an dem äußeren Ende der Sprosse erstreckt,
dadurch gekennzeichnet,
dass die Stellglieder (10) zentral an der vorderen Seite der Sprosse angeordnet sind, so dass sie gleichzeitig mit einer Hand bedienbar sind, und
dass jede vordere Wand (43) und jede Rückwand (44) einen Randbereich (43c) unterhalb der länglich vertieften Abschnitte (43a, 44a) aufweist, wobei die vertieften Abschnitte auch in Bezug zu dem unterhalb befindlichen Randbereich (43c) der jeweiligen Wand (43, 44) nach innen versetzt sind, und
dass sich die länglich vertieften Abschnitte (43a, 44a) über einen wesentlichen Teil der Höhe der jeweiligen vorderen Wand und Rückwand erstrecken, wobei der Teil zwischen 15 und 25 Millimeter hoch ist, und
dass die verschiebbaren Stellglieder (10) eine Höhe zwischen 15 und 25 Millimeter haben, und
dass länglich vertiefte Abschnitte (43a, 44a) eine Tiefe haben, die zwischen 3 und 6 Millimetern liegt, und
dass verschiebbare Stellglieder (10) an der Vorderseite der Sprosse zwischen 1 und 4 Millimetern hervorstehen.

2. Leiteranordnung nach Anspruch 1, wobei die Leitersprosse (2d-9d) eine obere Wand (41) aufweist, die im Querschnitt nach oben konvex ist, während die untere Wand (42) im Querschnitt nach oben konkav ist.

3. Leiteranordnung nach Anspruch 2, wobei die Krümmung der oberen Wand (41) und der unteren Wand (42) gleich ist, und wobei die Leiter so ausgebildet ist, dass die Sprossen sich in dem zusammengeschobenen Zustand berühren.

Revendications

1. Ensemble d'échelle extensible et repliable de manière télescopique (1), comportant au moins trois sections d'échelle (2 à 9), chacune desdites sections d'échelle comportant deux éléments de montant tubulaires (2a, 2b) agencés parallèlement l'un à l'autre et interconnectés à une extrémité par un barreau d'échelle (2d à 9d) pour former une section d'échelle en U, les éléments de montant de chaque section d'échelle étant insérés de manière télescopique dans les éléments de montant d'une section d'échelle adjacente,
l'ensemble d'échelle comprenant en outre des mécanismes de verrouillage automatique (60, 61) à chaque extrémité d'un barreau pour verrouiller les éléments de montant insérés de manière télescopique l'un par rapport à l'autre lorsque les sections d'échelle sont étendues, les mécanismes de verrouillage étant associés chacun à un actionneur pouvant coulisser (10) pour déverrouiller les éléments de montant afin de permettre le repliement de l'ensemble d'échelle,
dans lequel les barreaux d'échelle (2d à 9d) sont réalisés à partir d'un profilé tubulaire en aluminium extrudé, le profilé comprenant une paroi supérieure (41), une paroi inférieure (42), ainsi que des parois avant (43) et arrière (44) s'étendant entre la paroi supérieure et la paroi inférieure, les parois avant et arrière étant symétriques,
les actionneurs (10) étant agencés du côté avant du barreau, dans lequel la paroi avant (43) du barreau comporte une partie en retrait allongée (43a) s'étendant sur la longueur entière de celle-ci et située au-dessous d'une partie de bord située au-dessus (43b) de la paroi avant et décalée vers l'intérieur par rapport à celle-ci,
les actionneurs (10) étant agencés dans ladite partie en retrait (43a), chaque actionneur (10) s'étendant à travers une fente dans ladite paroi avant à l'intérieur du barreau, chacun desdits actionneurs étant relié à une tige d'actionnement (60) qui s'étend à l'intérieur dudit barreau vers le mécanisme de verrouillage (60, 61) à l'extrémité extérieure du barreau,
caractérisé en ce que,
les actionneurs (10) sont agencés au centre du côté avant du barreau de manière à pouvoir être utilisés simultanément d'une seule main,
et en ce que chacune de la paroi avant (43) et de la paroi arrière (44) comporte également une partie de bord (43c) au-dessous des parties en retrait allongées (43a, 44a), lesdites parties en retrait étant également décalées vers l'intérieur par rapport à ladite partie de bord (43c) située au-dessous de la paroi (43, 44) respective,
et en ce que les parties en retrait allongées (43a, 44a) s'étendent sur une grande partie de la hauteur des parois avant et arrière respectives, laquelle partie est de 15 à 25 millimètres,
et en ce que les actionneurs pouvant coulisser (10) ont une hauteur entre 15 et 25 millimètres,
et en ce que les parties en retrait allongées (43a, 44a) ont une profondeur qui est entre 3 et 6 millimètres,
et en ce que les actionneurs pouvant coulisser (10) font saillie à l'avant du barreau de 1 à 4 millimètres.

2. Ensemble d'échelle selon la revendication 1, dans lequel le barreau (2d à 9d) a une paroi supérieure (41) qui est convexe vers le haut en coupe, tandis que la paroi inférieure (42) est concave vers le haut en coupe.

3. Ensemble d'échelle selon la revendication 2, dans lequel les courbures de la paroi supérieure (41) et de la paroi inférieure (42) sont identiques, et dans lequel l'échelle est conçue de sorte que les barreaux soient en contact les uns avec les autres dans un état replié.

Drawing