DK141415B - Ladder or a similar lattice construction. - Google Patents

Description

(11) PUBLICATION 141415 E 04 C 2/42 DENMARK 'n'013 * cs' (21) Application No 5847/72 (22) Filed on 25 · HOV · 1972 (23) Running day 25 · HOV. 1972

(44) The application submitted and Q

the petition for publication published on 10 fflST · 1 980

DIRECTORATE OF

PATENT AND TRADE MARKET (30) Priority requested from it

Nov. 25-Nov. 1971 / 17016/71, CH

(71) AB CARL KEIJSER & CO., Tunbytorpsgatan 1, Yaesterås, SE.

(72) Inventor: Erik Arne Engvall, 95 Kaserngatan, Vaesterås, SE: Thomas Ritscher, Hofackerstrasse 5, Adliswil, CH.

(74) Plenipotentiary in the proceedings:

Plougmann & Vingtoft Patent Office.

(54) Ladder or similar lattice construction.

BACKGROUND OF THE INVENTION The invention relates to a ladder or a similar grid structure with two longitudinal members, each integrally formed and generally parallel beams, preferably of an extrudable light metal alloy, and having between the beams equally spaced and generally perpendicular to these hollow transverse struts, which is preferably also made of an extrudable light metal alloy and has a generally rectangular cross-section, which beams have a body portion located between flanges extending substantially perpendicular to this body portion, holes being formed in the body portion for attaching the cross struts by flanging them to flanges, abutting the body part around the hollow edges on both sides of the body part.

2 141415

The beams of such known lattice structures are usually made of wood, metal or other structural materials and have a generally circular or rectangular cross-section. In the case of metal beams, it is conventional to use profiles or cross-sectional shapes similar to an I, H or double T. In such beam profiles, therefore, the cross-sectional shape has two flanges or tabs interconnected by means of a cross member or A body. Known lattice structures such as ladders made of light metal or metal alloys and whose longitudinal parallel beams have such a profile provide a satisfactory bending stiffness and torsional stability at relatively small cross-sectional areas. However, the side stiffness is usually unsatisfactory. However, the latter requirement is important not only for ladders, especially light ladders of a certain length, but also for other types of grid structures of the above-mentioned type, where the load does not predominantly act in the longitudinal direction of the beams, ie. not perpendicular to the transverse bars or lattice bars, such as the is the case with handrails, railings, etc. In any of these cases, the use of relatively light, high-quality and therefore relatively expensive construction materials, e.g. aluminum alloys, call for the manufacture of structures having the least possible balance between flexural and torsional stability when the structure is subjected to stresses in directions parallel to or perpendicular to the longitudinal direction of the beams.

For example, a ladder of the prior art is disclosed in Swedish Laid-Open Specification No. 308,182, wherein the parallel beams of the ladder have a substantially in-shaped cross-section, while the cross-bars, which are tubular, have a square cross-section. The transverse struts are attached to the beam bodies in that the ends of the transverse struts are inserted into holes in the beam bodies and are plunged so that flanges extending along the hollow edges are formed on both sides of the beam bodies.

In connection with the provision of the present invention, it has been found that a simple increase in the cross-sectional area of the beams in general or in certain areas of stress concentrations usually does not provide an increase in bending and torsional stability sufficient to justify the resulting greater weight and the increased cost of structural material, and that one area of particular importance is the design of the joints between the beams and the cross braces. For example, one approach to improving stability is to weld the cross struts to the beams using inert gas, but such a method is quite expensive for commercial production.

It has been found that with lattice structures of the above known type, surprising improvements in lateral bending and torsional stability can be obtained without a significant increase in the weight of the structure and without the use of expensive manufacturing processes.

Thus, the lattice construction according to the invention is characterized in that the body part consists of a central portion of substantially uniform thickness and extending from this central portion to the flanges of the beam extending gradually from the central portion, and as seen in cross-section together. has a length which constitutes at least 20% of the total length of the body part, and that the flanges of the cross members located along the hollow edges in the direction of the flanges of the beams extend abut the body part at least near the transition between the central body part and the side portions.

Comparative experiments with a construction according to the invention and a known construction of the kind described in the above-mentioned Swedish disclosure show in the construction according to the invention a remarkable increase in the bending stiffness (determined by measuring the deformation of a structure consisting of two generally parallel beams and several at regular intervals arranged cross stiffeners and with a test load applied to both beams), the side bending stiffness (the same construction as mentioned above, but with the load applied to only one beam) and a general improvement of the torsional stiffness. By way of example, the side bending stiffness of the construction according to the invention was found to be about eight times greater than that of the known construction. The test methods used are in accordance with Danish standard (DS 2069.0), which by all official standard regulations for ladders and similar lattice structures is considered to prescribe the most stringent tests.

4 14U15

The thickness of the lateral portions of the body portion may increase in any manner, for example, the lateral portions may have curved or curved lateral surfaces. However, each of the lateral portions of the body portion is preferably wedge-shaped, with generally planar opposite lateral surfaces, enclosing an angle of between approx. 10 ° and approx. 35 °, preferably between 14 ° and 24 °.

In the following, the grid structure according to the invention will be explained in more detail with reference to the drawing, in which fig. 1 is a semi-schematic view of a part of an embodiment of a beam for use in the grating structure according to the invention and seen in perspective; 2 schematically shows a section of a cross-section in an embodiment of a beam for the grating structure according to the invention; FIG. 3 schematically shows a section of a cross-section in another embodiment of a beam for the grating structure according to the invention; FIG. Fig. 4 is a schematic diagram of the general form of an H-beam indicating dimension ratios for preferred embodiments of beams for use in lattice structures according to the invention; 5 is a schematic sectional view illustrating an embodiment of the connection between a beam and a transverse strut in the construction according to the invention; 6 is a schematic partial section showing the connection between a beam and a transverse strut in a preferred embodiment of the lattice construction according to the invention.

In FIG. 1, a beam 11 is shown having a body 12 consisting of a center part or a central part 13 and two side parts or side portions 14 and 15. The center part 13 of the body has a substantially uniform width, while each of the side parts 14 and 15 increases in size. in other words, the side portions 14 and 15 of the body are generally tapered from the region in the vicinity of the flanges 17 and 19 in the direction towards the center portion 13 of the body. 1, the taper for ease of understanding is somewhat exaggerated, as will be described in more detail below, i.e., a taper angle of approx. 40 ° instead of the preferred taper of from approx. 10 ° to approx. 35 °, with 14-24 ° being the preferred range.

5 141415

The center portion 13 of the body is provided with a number of apertures 16, three of which are shown in the drawing, but it is clear that the actual number of apertures, their spacing, shape and size will depend on the required number of transverse struts. length unit in a given structure, of the total length of the structure and of the cross-sectional shape of the cross struts. In a preferred embodiment, the openings are 16 square.

The flanges 17 and 19 adjacent to the side portions 14 and 15 of the body may be shaped as shown, i.e. with flange edges 18 and 20 bent inward toward the center of the body, but other designs, e.g. curved, straightened, etc., will be equally suitable. The exact design of the flanges is in any case not an important feature.

It is to be understood that a grid structure according to the invention will comprise at least two substantially similar beams of this type arranged in the main saw parallel to the above explained. In practice, e.g. in the case of ladders, such a pair of beams will be disposed with the inner side surface of the body portion located adjacent to the corresponding inside of the body portion of the second beam.

Furthermore, the positions, shapes and distances of the openings 16 will be substantially the same in a pair of beams, given that the pair of joists are interconnected by means of transverse struts.

However, more than two beams may be used in a grid structure, e.g. constructions for supporting cables etc.

The beams are preferably made of an extrudable light metal, e.g. an aluminum alloy of the type that will be discussed in more detail below.

In the embodiment shown in FIG. 2 shows the tapered side of the body = part 6 is a non-linear increase in width in the direction from the area designated by dYS. the end of the body portion 2, towards the adjacent flange 3. The surfaces 1a and 1b of the body portion 6 generally follow the shape of logarithmic spirals extending to the "inward" bent ends or edges 5a and 5b of the flange 3 · Although the logarithmic helical shape is suitable for the lateral parts of the beam body, it will be clear to one skilled in the art that various modifications of the "ideal" curvature can be made according to parameters such as beam dimensions, cross-stiffness dimensions and properties of the beam. alloy used. In any case, the curved shape of the side surfaces of the beam in the region of the lateral parts of the body is not essential to the invention.

It should be noted that FIG. 2 shows only half of a beam profile.

FIG. 3 shows half of a beam cross-section which can be considered to be an approximation of that of FIG. 2. This modification may be substantial for the sake of practical requirements in the manufacture of such beams, e.g. by extrusion of light metal alloys through an extruder nozzle. In FIG. 3, the transition from the flange 31 to the side portion 22 of the body begins with a curvature designated 42 and proceeds via a generally planar portion 43 to a transition point 41 'which is the end of the body side portion and the beginning of the body center portion 21 having a length. which is designated by the side portion 22 or 6 of the body may be said to be "wedge shaped" and is peculiar to a wedge angle twice that of FIG. 3 in practical embodiments and in the embodiments which will be explained in detail hereinafter, the wedge angle (2 x a) will generally be between 10 and 35 °, preferably between 15 and 30 ° and best between 14 and 24 °.

Some preferred dimensional conditions for beam profiles which are suitable for use in connection with the lattice construction according to the invention will now be explained by means of the one in FIG. 4 is a schematic drawing.

The ratio of the total length S1 of the body 22 to the length of the center portion SML is generally in the range of 1.0 to 2.5 and preferably in the range of 1.2 to 2.2. The width and thickness of the center portion 21 of the body will be substantially uniform, and the increase of the width of the side portion of the body, designated 7 7141415 SVL ^ or kr ° PPen ^ 2 ~ which as above may be considered wedge-shaped - will begin at a point SD denoted by 50. Generally, both body side portions will have the same length. It is also preferred that the ratio of the total length of the body to the sum of the lengths of the two body side portions, i.e. the ratio of 23, is between 1 and 4 and preferably between 1.9 and 3.4.

The ratio of the total length of the body 22 to the length of the flanges 31, ie. the ratio preferably ranges slightly from 1.0 to 2.0 and even better between 1.4 and 1.9. The ratio of Sq + to the width of the body 22 at the center portion 21, i.e. the ratio is preferably between 15 and 40 and even better between 20 and 37. For practical assessment, the inverse ratio to common characteristic is used, and this ratio is preferably in the range of 0.04 to 0.02.

The ratio between the body width SD and the width Bp of the flanges 31 is preferably between 2.0 and 0.5 and even better between 1.7 and 0.6, with a lower limit of approx. 1 is appropriate for most purposes.

The above in connection with FIG. 4 conditions are particularly advantageous for beams made of extrudable aluminum alloy base, e.g. by extrusion. The cross struts are preferably made of similar materials and may also be extrusions of a type known per se. Typical examples of such alloys are AIHgSi alloys as disclosed in U.S. Pat. standard no. 6351/6 or the corresponding Swedish standard no.

4212-6. Normally, the strength (tensile) of the aluminum alloys used for beams and cross stiffeners shall be at least approx. 25 kp / mm (substantially equivalent to a Webster B hardness of at least about 16). The strength of the alloy should preferably not be more than 10 # below the values immediately above.

The dimensions of the cross braces are, as mentioned above, adjusted to the length of the center part of the body. Generally, the center portion of the body will have substantially the same length as or be somewhat less than the distance between opposing sides of the abutting surface of rect = angular cross stiffeners. The term "abutting surface" refers to the part of the ends of the transverse abutting the side of the body of the beam. Usually, this abutting surface will be one part of a flange portion of the transverse strut, e.g. a knurled bulge or rim formed around the periphery of the transverse strut, and it will usually resemble but be somewhat larger than the transverse strut's cross-section.

Usually, the preferred cross-sectional shape of the transverse struts will be substantially rectangular, and a square cross-sectional shape will constitute the most preferred embodiment. The edges can be rounded if desired.

It is noted that the transverse struts may have a grooved outer surface or be provided with other non-slip means, including coatings, especially if the structure is a ladder.

The interlocking between the transverse struts and the beams will now be explained with reference to fig. 5 and 6. In the semi-schematic cross section shown in FIG. 5, the end portion 60 of the transverse stiffener 6l has an inner flange 62 and an outer flange 63 which abuts the center portion 65 of the body and with their outer edges 621 and 631 abut the body portions 641 and 642.

In practice, for example, as shown in FIG. 6 is obtained by first forming on end cross member 48 an end portion 481 with a knitted or folded collar 49 to serve as the innermost flange.

Thereafter, the remaining free end is inserted into an opening (16 in Fig. 1) in the center portion 52 of the body (13 in Fig. 1) so that it extends through it. Another formed or folded collar 51 is now formed for the end portion 481, e.g. by compression and in accordance with the deformation properties of the material used. By supporting the folded collar 49 against the laterally exerted pressure exerted on the end portion 481 to form the collar 51 and to further press both collars 49 and 51 against the center portion 52 of the body, an extremely strong joint = locking can be produced. connection between the cross stiffener and the body of the beam. It is usually preferred to compress and deform claims 49 and 51 to such an extent that the flanges thus formed will extend to the side portions 46 of the body so that, due to the increasing width of these side portions 46, be formed a wedge line = 9

HUIS

compound. When extrudable light metals of the type mentioned above are used, the interlocking connection thus formed between the cross stiffener and the beam markedly increases the flexural and torsional stability of the grating structure.

It is clear that the embodiment shown in FIG. 5 and 6, the interlocking of the transverse strut and the beam at one side of the structure is repeated or formed simultaneously by the other connection (s). In making ladders, it is preferred to provide the interlock at both ends of each cross brace simultaneously.

Comparative studies of lattice structures according to the invention, e.g. FIG. 6, with grid structures having the same basic structure but a conventional beam, ie. no increase in the width of the side portions of the body, as shown here, shows a remarkable increase in (a) the bending strength (measuring the deformation of a structure consisting of two generally parallel beams and a number of transverse struts connecting the beams to uniform distances, subjecting both beams to a test load), (b) lateral bending strength (the design as above, but with the load acting on only one beam), and (c) general improvements in torsional stability. For example, the side bending strength of the construction according to the invention was approx. 8 times greater than that of the comparative construct.

The test methods used were those described in Danish standard (DS 2069.0) and which must be considered to be the toughest of the official standards for testing of lattice structures.

Although the above description mainly relates to lattice structures for ladders made of extrudable light metal alloys, it will be appreciated that those skilled in the art will be able to make many changes as to the materials used, the specific shapes, dimensions and designs used. Eg. the structure of the invention may have more than two beams, e.g. in that the transverse = struts between two beams are offset relative to the transverse struts for one of these beams and the next beam. Furthermore, other structural materials can be used both for the beams and for the transverse struts including synthetic polymers, e.g. duro = plastics that may be reinforced with fabrics such as glass fibers.