EP1762694A2 - Metal ladder and method of manufacture thereof - Google Patents

Abstract

The ladder (1), made from tubular metal rungs (4) and uprights (2, 3), has the ends of the rungs made with a smaller cross-section than their central sections, with stepped coupling zones between them. The rung ends have oblong cross-sections and are inserted through matching holes in the ladder uprights before being fixed in place by having their outer edges rolled or crimped. In addition, the outer surfaces of the rungs are grooved to make them non-slip.

Description

The invention relates to the rigid assembly of a tubular metal element to a flat metal element.

The present invention finds particular application to the fixing of rungs on rails, for metal ladders.

Metal ladders are here structures with two amounts (the longitudinal members) interconnected by bars (the steps) fixed at predetermined intervals.

By metal ladders, here refers to structures of the general type above, whose bars serve as degrees for going up or down, these structures being called scales in the common language and can be of several varieties, for example sliding ladder, interlocking ladder, crinoline ladder.

By metal ladder, here also refers to cable ladders.

By metal ladder, here also refers scaffolding ladders, that is to say the side scaffolding uprights, these amounts comprising longitudinal members and crosspieces. These lateral amounts allow, if necessary, to go up or down on the scaffolding.

By "scaffolding" is meant here any temporary building or structure, fixed or movable, facilitating access to works and carrying out work.

• les échafaudages de pied, c'est-à-dire les échafaudages sur plans verticaux destinés aux travaux sur façades et parties en élévation ;
• les échafaudages rapides métalliques, en éléments modulaires, parfois appelés échafaudages tubulaires ;
• les échafaudages de plafond ou sur plans horizontaux, c'est-à-dire les échafaudages tubulaires légers, en général mobiles (roulants) et les échafaudages sur tréteaux ;
• les échafaudages en bascule portés par des traverses étrésillonnées contre des encadrements de baies ;
• les échafaudages en éventail portés par des potences ou pointiers inclinés reposant sur les appuis des baies et immobilisés par des entretoises ou des étrésillons.

The following are particularly concerned by the present invention:

• foot scaffolding, ie scaffolding on vertical planes for work on facades and elevations;
• fast metal scaffolding, in elements modular, sometimes called tubular scaffolds;
• ceiling scaffolding or horizontal planes, ie light tubular scaffoldings, generally mobile (rolling) and scaffolding on trestles;
• the scaffolding in tilting carried by braces girderillonnée against frames of berries;
• Fan scaffolding carried by brackets or inclined points resting on the supports of the bays and immobilized by spacers or braces.

The invention more specifically relates to the cold mechanical connection of the ladder ladders ladders scaffolding.

In an old technique, the rungs and spars were welded. Such a method of assembly certainly provides significant safety against the risk of accidental disassembly but may lead to corrosion at welding points, when the longitudinal members and rungs are galvanized steel before welding: a galvanization performed before welding is easily deteriorated during welding. A post-weld galvanization is an operation requiring a great deal of know-how when the rungs and spars have sections to assemble complex shapes.

The assembly by screwing the rungs on the spars is long and expensive. There is a risk of accidental or malicious unscrewing.

The stapling of the rungs to the longitudinal members requires at the ends of the rungs tongues, tenons, pins, or the like may be engaged in slots provided for this purpose in the longitudinal members, and then deformed using a tool of crimping. So, for example, the document FR-2,478,891 proposes that at least a portion of the rungs protrude through an orifice of longitudinal members, the permanent mounting of the rungs on the longitudinal members being ensured by deformation of the projecting parts of the rungs, by means of a crimping tool. The document FR-2 300 887 describes the assembly of rungs provided with lugs penetrating in housings or openings formed on the longitudinal members, a hydraulic device then coming, at the right of each rung, to punch a flat in the spar, the edge of the lower tear of this flat abutting against the upper part of the rung.

The implementation of rungs on the spars by interlocking was considered, this method having the disadvantage of not ensuring a high security dismantling. To overcome this difficulty, the document FR-2 709 528 proposes the establishment of blocking parts, by force, to block the rungs in their nesting position. The process described in the document FR-2 709 528 proves long and expensive.

Various other expensive techniques have been proposed, such as magneto-forming (see document FR 2 561 322 ).

It has long been known to assembly by swaging or crimping the steps to the amounts of tubular metal ladders, particularly a light alloy. For example, one can refer to patents French published under the numbers 1 410 344 , 1,550,157 , 2,100,519 , 2,577,609 , 2,579,965 .

For assembly by crimping, the rungs are conventionally provided, on their two lateral ends, with at least one restraint coming to engage in the bores of the uprights. The end of these retreints protrudes on the outer face of the uprights. It is deformed by crimping, or else by rolling, tulip, or stamping. The simple crimping leads to the deformation of the retreint on the external face of the amount. Double crimping, performed both on the outer face and on the inner face of the upright is naturally stronger than the simple crimping, since it allows clamping on both sides of the wall of the upright.

The dudgeon is conventionally mechanical and comprises a barrel, pebbles or needles and a conical pin. The conical pin (or dudgeon tail) advances inside the profile forming the rung. This spindle is rotated by a machine dégeonneuse, electric or pneumatic. The spindle increases the circumference of the rollers while rotating them. The rollers thus cause the expansion of the profile forming the rung. This expansion is performed while the profile forming the rung has been introduced into an opening in the ladder upright. It is thus possible to form beads on the rung, these beads being placed on either side of at least one of the walls of the ladder upright.

The rotation of the echelon on itself, when using the ladder, is of course to be avoided. The consequences of such a rotation are easy to perceive (injuries, falls). To avoid this rotation, there are known rungs whose ends are flattened, these flattened ends returning into the drill holes of the uprights.

The diversity of the technical solutions presented above shows that to date, no perfectly satisfactory technical solution is known for the cold mechanical connection of steps and amounts of metal ladders.

In particular, the applicant identified the following technical problems.

The flattening of the lateral extremities of the rungs causes a random geometrical shape, since coming from a strike. Thus, the flattened extreme parts a tubular step of circular section have ends whose dimensions are greater than the diameter of said circular section.

The flattening of the lateral ends of the rungs also causes a protuberance between the flattened area and the circular central portion of the rung. This protrusion may interfere or make less secure the assembly of the steps to the amounts.

The random shape of the flattened section of the rungs makes it difficult to control the subsequent play in the link from the rung to the rung.

In an attempt to avoid further game formation between step and amount, the document FR 2,795,127 proposes a metal scaffold ladder in which the flattened end of the rung is pulled into the jamb.

In practice, this method proves to be costly, since it is necessary to draw each of the steps relative to the first amount of the scale and then to the second amount of the scale.

The invention aims to solve the technical problems presented before.

For these purposes, the invention relates, in a first aspect, to a metal ladder, comprising at least one step and two uprights, this step being provided with a central portion and two end portions, at least one of the two parts extremes having, when viewed in cross-section, external dimensions different from the external dimensions of the central portion, also measured in cross-section, said end portion being of substantially reduced geometrical shape in a ratio homothetic to that of the central part, a zone of connection being defined between the central part and said end part, this connection area reproducing the geometry of the intersection between the part central level and at least one amount.

Advantageously, the end portions of the rung and the zones of connection of these end portions with the central part of the rung are provided with ridges extending substantially in the direction of slenderness of the rung. These streaks form a non-slip surface. These grooves reinforce the locking of the step in the mounting holes on the uprights.

Advantageously, the step is provided with two planes of symmetry substantially perpendicular to each other and perpendicular to the cross section of the step.

In some embodiments, said end portion of the rung has external dimensions smaller than those of said central portion, these dimensions being measured in cross-section of the rung.

In some embodiments, said connection zone is at least partly wedged in a hole of the upright, on the internal face of the scale, while said end portion of the step protrudes beyond said upright, this projecting part being plastically deformed. by being pressed against the wall of the upright, on the outer face of the ladder.

In one embodiment, the end portions of the rungs are provided with internal notches.

The amounts are of circular, oval or polygonal cross section, at least said step being of oval, circular or polygonal section.

According to a second aspect, the invention relates to a method of mounting a ladder as presented above, at least one step being fitted into a through-hole of a post, the end portion of this step projecting from external face of the amount, the plastic deformation of this projecting portion from pressing the amount against said connection area.

Plastic deformation is ensured by rolling, interlocking, tilting, crimping, for example in the direction of clockwise.

Said plastic deformation is ensured simultaneously on the two end parts of the rung.

• la figure 1 est une vue partielle en perspective d'une échelle selon un mode de réalisation de l'invention ;
• la figure 2 est une vue de détail de la figure 1 ;
• la figure 3 est une vue de dessus d'une partie extrême latérale d'un échelon de l'échelle représentée en figure 1 ;
• la figure 4 est une vue de côté de la partie extrême latérale de l'échelon représenté en figure 3 ;
• la figure 5 est une vue en perspective de la partie extrême latérale d'échelon représentée en figures 3 et 4 ;
• la figure 6 est une vue d'un échelon pourvu de deux parties extrêmes latérales du type représenté en figures 3 à 5, cet échelon étant représenté avant son montage aux montants d'échelle, les deux montants d'échelles étant partiellement représentés sur cette figure 6 ;
• la figure 7 est une vue de détail en coupe transversale de l'assemblage à froid entre échelon et montant d'échelle, selon l'invention, seule une des deux extrémités d'un échelon étant représentée sur cette figure 7 ;
• la figure 8 est une vue en perspective partielle de l'ensemble formé par un échelon et deux montants, cette figure 8 illustrant le sens de roulage des extrémités de l'échelon ;
• la figure 9 est une vue latérale de détail de la figure 8, le plan de coupe VII-VII de la figure 7 étant reporté sur cette figure 9 ;
• la figure 10 est une vue en coupe selon le plan X-X de la figure 9 ;
• la figure 11 est une vue en coupe transversale d'un échelon, montrant sa surface striée ou crantée ;
• la figure 12 est une vue en coupe de la liaison échelon au montant, avant sertissage.

Other objects and advantages of the invention will become apparent from the following description of embodiments, which description will be made with reference to the accompanying drawings, in which:

• Figure 1 is a partial perspective view of a scale according to one embodiment of the invention;
• Figure 2 is a detail view of Figure 1;
• Figure 3 is a top view of a lateral end portion of a rung of the scale shown in Figure 1;
• Figure 4 is a side view of the lateral end portion of the echelon shown in Figure 3;
• Figure 5 is a perspective view of the lateral end portion shown in Figures 3 and 4;
• FIG. 6 is a view of a rung provided with two lateral end parts of the type shown in FIGS. 3 to 5, this rung being represented before its assembly to the ladder uprights, the two ladder uprights being partially represented in this FIG. 6;
• Figure 7 is a detailed cross-sectional view of the cold assembly between step and scale amount, according to the invention, only one of the two ends of a step being shown in this Figure 7;
• Figure 8 is a partial perspective view of the assembly formed by a rung and two uprights, this figure 8 illustrating the rolling direction of the ends of the rung;
• Figure 9 is a detail side view of Figure 8, the sectional plane VII-VII of Figure 7 being shown in this Figure 9;
• Figure 10 is a sectional view along the plane XX of Figure 9;
• Figure 11 is a cross-sectional view of a rung, showing its striated or notched surface;
• Figure 12 is a sectional view of the step connection to the amount, before crimping.

Referring first to Figures 1 to 5.

Scale 1 as shown in FIG. 1 comprises, in a manner well known per se, two lateral uprights 2,3 and 4 rungs.

In the embodiment shown, the two uprights 2, 3 are substantially identical and parallel to each other. It is understood, however, that the invention also relates to ladders whose amounts are not shaped, in particular of section, identical, and / or which are not parallel over their entire length. For example, the amounts may be further apart from each other at the base of the ladder, especially to stabilize the ladder.

In the embodiment shown, the steps 4 are substantially equidistant. It is understood however that the invention also relates to the scales are the steps are not equidistant.

In the embodiment shown, the posts 2,3 are of circular cross section. In other embodiments, not shown, these amounts are of polygonal section, for example square, or even oval.

The rungs 4 are, in their part 4a located between the uprights 2, 3 of oblong cross-section and are provided with ridges or notches, as will appear more completely later with reference to FIG. 11.

The uprights 2, 3 and steps 4 may be steel, aluminum or aluminum alloy. They can be derived from profiling or bending / welding or rolling / welding.

The two extreme end portions 5 of the rungs 4 are of smaller cross-section than the cross section of the portion 4a of the rungs 4, as it clearly appears in FIGS. 3 to 5.

The connection areas 7 between the central portion 4a of a step 4 and the end portions 5 of this step 4 have a geometry that corresponds to the contact surface intersection between this step 4 and the amounts 2,3.

The echelon 4, as seen in cross section in FIG. 11, is provided with folds or ridges 8. These grooves 8 make it possible in particular to prevent slipping of the user's foot or hand from the ladder. These grooves 8 are corrugations in the thickness of the profile forming the rung, the thickness of this section, measured in cross section of the rung, being substantially constant.

The step 4 is provided with two planes of symmetry, in the embodiment shown, these two planes being substantially perpendicular to each other and perpendicular to the transverse sectional plane of FIG. 11.

When seen in cross section, the rung is of tubular elongated shape, its outer surface being provided with ridges 8, except at its center passing through the axis XX ', where the rung is devoid of streaks over a variable distance.

The connecting zones 7 are provided with ridges 8, as do the lateral end portions 5, as can be seen in FIG. 5.

The amounts 2, 3 are provided with reservation holes 9, these holes passing through the uprights 2, 3 and these holes 9 being of substantially identical geometry to that of the end portions 5 of step 4, but of dimensions slightly greater than those of these end portions 5.

The length L5 of an end portion 5 is a few millimeters larger than the dimension of the upright 2, 3, this dimension being measured in line with the holes 9.

When the end portion 5 of the step 4 is inserted into the holes 9 of an amount 2, 3, this end portion 5 projects in a length E (see FIG. 12). At this moment, the connection zone 7 comes into contact with the wall of the upright 2, 3.

The protruding part, of length E, of the step 4, is then subjected to rolling, forming a collar 10. During this rolling, the collar 10 pushes the upright 2, 3 in B which is applied against the connection area 7.

The connecting zone 7 being provided with the notches or folds 8, the rolling leads to the wedging of the connection zone 7 in the holes 9 of the uprights, eliminating any risk of play between step 4 and upright 2, 3.

The step 4 is blocked by jamming of its connecting zone 7 in the wall of the upright 2, 3, in the internal part of the scale. The step is at the same time rigidly tight against the amount 2, 3, the collar 10 providing a pressure of the step 4 against the amount 2, 3, external side to the scale.

The assembly of the steps to the uprights can be advantageously practiced simultaneously on both sides of the rungs, for example in the same clockwise direction as indicated by the arrows F of FIG. 8.

The extreme parts 5 of a rung, substantially reduced in a ratio homothetic to the central portion 4a of this echelon, are obtained by creep of the material in the longitudinal direction of the echelon 4 and in the direction of the grooves 8.

The collar 10 can be obtained by rolling and pressure under a bouterollage.

The method which has just been described could be adapted to circular, oval or polygonal section steps, with circular, polygonal or oval shaped uprights.

Claims (8)

Metal ladder, comprising at least one step (4) and two uprights (2, 3), this step (4) being provided with a central portion (4a) and two end portions (5), at least one of the two parts extremes (5) having, when viewed in cross section, different external dimensions of the external dimensions of the central portion (4a), also measured in cross-section, characterized in that said end portion (5) is of substantially reduced geometrical shape in a ratio homothetic to that of the central portion (4a), a connection zone (7) being defined between the central portion (4a) and said end portion (5), this connection zone (7) reproducing the geometry of the intersection between the central part (4a) of the step (4) and at least one upright (2, 3), in that the end parts (5) of the step (4) and the connection areas (7) of these end portions (5) with the central portion (4a) of the step (4) are provided streaks (8) extending substantially in the direction of slenderness of the step (4), in that the uprights (2, 3) are of circular or oval cross-section, and in that said at least one step (4) is of oblong cross section. Ladder according to claim 1, characterized in that the step (4) is provided with two planes of symmetry (P1, P2) substantially perpendicular to each other and perpendicular to the cross section of the step (4). Ladder according to any one of the preceding claims, characterized in that said end portion (5) of the step (4) has external dimensions smaller than those of said central portion (4a), these dimensions being measured in section cross-section of the rung (4). Ladder according to any one of the preceding claims, characterized in that said connection zone (7) is at least partially wedged in a hole (9) of the upright (2, 3), on the internal face of the ladder, while that said end portion (5) of the step (4) protrudes beyond said upright, this projecting portion being plastically deformed by being pressed against the wall of the upright, on the outer face of the scale. Metal ladder according to one of the preceding claims, characterized in that the end portions (5) of the rungs (4) are provided with internal notches. A method of mounting a ladder as presented in any one of the preceding claims, characterized in that at least one step (4) is fitted into a through-hole (9) of a post (2, 3), the end portion (5) of this step (4) protruding on the outside face of the upright (2, 3), the plastic deformation of this projecting portion pressing the upright against said connection area. Process according to Claim 6, characterized in that the plastic deformation is ensured by rolling, basting, tilting, crimping, especially in the direction of clockwise. Method according to claim 7, characterized in that said plastic deformation is ensured simultaneously on the two end portions (5) of the step (4).

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