US3472340A - Scaling ladder - Google Patents

Description

Od. 14, 1969 E, DAHLQufsT 3,472,340

scALING LADDER Filed sem. 11, 19e? FIGI FIGB FIGA FIGS F|G,6

United States Patent O 3,472,340 SCALING LADDER Evald Dahlquist, 16 Backgatan, Lndvika, Sweden Filed Sept. 11, 1967, Ser. No. 666,598 'Claims priority, application Sweden, Sept. 13, 1966, 12,276/ 66 Int. Cl. E06c 1/52, 1/58 U.S. Cl. 182-207 4 Claims ABSTRACT OF THE DISCLOSURE Scaling ladders and extension ladders are now manufactured to a great extent With sidepieces of tubular steel or light metal sections. Various diiferent constructions have been employed for enabling the ladder sections to be joined together in essentially end-to-end relation but all of them have disadvantages of one kind or another. According to one type of construction the upper end of each ladder section is made slightly narrower than the bottom end so as to enable the sections to be put together. While the ladder sections thus have the advantage of identical construction, there is a disadvantage that in each section, as many diiferent rung lengths are required as there are rungs in the section, and the ladder sections can be joined only by the length of an entire section.

According to another construction, one ladder section has a width slightly smaller than that of another section so that the narrower one can be made to slide along the Wider one with their respective side rails in guiding engagement. The principal disadvantage of this construction is that the ladder sections are not identical.

A good ladder construction must have the properties as follows:

(l) For reasons of rational production and cheapness all ladder units (each one comprising two lsidepieces and a suitable number of rungs) shall be entirely equal, i.e., all ladder units shall have the same width, and all rungs shall have the same length.

(2) A ladder unit shall be extendible by a desired portion of the length of another ladder unit. Therefore, the sidepieces of every ladder unit preferably must be in parallel.

(3) The joining of the different ladder units shall be such, that good strength as Well as good rigidity is obtained.

(4) The sidepieces shall have a simple shape which renders a light, strong and rigid construction, for example a box girder construction in the form of profiled tubes of substantially rectangular shape.

There should further be the possibility of an alternatively simpler construction with sidepieces in the form of a plate girder with a desired section.

Summary of the invention The ladders are constructed in accordance with the aforementioned items 1 to 4, and the essential feature of the present invention is, that the two sidepieces in a ladder unit are arranged symmetrically in relation to the longitudinal central line of the ladder units, so as to form an image of each other, and that the sidepieces are given 3,472,340 Patented Oct. 14, 1969 ICC such a shape and/or inclination in relation to the plane of the ladder unit, that upon placing one displaced ladder unit above another ladder unit of equal shape for joining the same, the two units tend to localize themselves centrally in relation to one another, by cooperation of the two sidepieces in a ladder unit upon their abutment to corresponding sidepieces in another ladder unit of equal shape, said centering effect being obtained in that the contact surfaces are made substantially plane and in parallel and form the same angle, for example 45, with the plane of the ladder.

Various embodiments in accordance with the inventive concept have been illustrated in the accompanying drawings wherein:

FIG. 1 is a schematic illustration of the manner in which two ladder units or sections are placed along each other in accordance with the construction illustrated in FIG. 2;

FIG. 2 is a detailed view of the structure of a rail at one side of a ladder section, the coniiguration of the side rail corresponding to the schematic depicted in FIG. l;

FIGS. 3 to 6 are illustrations of various other configurations for the side rails which are essentially of the plate girder type;

FIG. 7 is a detailed view of the configuration of the side rail depicted to a smaller scale in FIG. 6;

FIGS. 8 to ll are illustrations of still further possibilities for the conguration of the side rails, all having in common the characteristic that the lower outer surface of the side piece or rail of the overlying ladder section abuts the upper inner surface of the side rail of the underlying ladder section; and

FIGS. 12 and 13 are schematic illustrations of ladder sections connected together in accordance with the prior art and with the present invention, respectively.

With reference now to the drawings, FIG. 1 shows in a schematic Way two ladder units placed along each other according to one embodiment of the invention, and FIG. 2 shows in section one side piece. The two sidepieces comprised in one ladder unit are placed symmetrically in relation to the longitudinal central line of the ladder unit, in such a manner, as to form a reflected image of each other.

The side surfaces 1 and 2 (FIG. 2) of the sidepieces may be substantially plane, curving or embossed. The edge surfaces 3 and 4 (FIG. 2 and FIG. l) may be substantially plane and in parallel, and they form an angle, for example of 45 with the plane of the ladder.

In the foregoing embodiment sidepieces of box girder typegin the form of profiled tubes have been used Where the desired centering effect is obtained by the inclination and/ or shape of the edge surface.

The same eifect also is obtained according to another embodiment of the invention by using sidepieces of plate girder type which have the sectional shape, for example, of an open tube or U-beam, FIG. 3, I-beam, FIG. 4, Z-beam, FIG. 5, or Z-beam with an S-shaped central portion, FIG. 6. The upper surface and the lower edge surface are, thus, held together by a central portion which may be a holder for the rungs.

The sidepiece according to the schematic FIG. 6 is shown in section in FIG. 7 wherein 3 and 4 are the edge surfaces.

In the foregong embodiments illustrated respectively in FIGS. 1, 2 and FIGS. 3 to 6. the desired centering effect is achieved by giving the edge surface of the sidepiece a suitable inclination and/ or shape.

The centering eiect also can be obtained by making the lower outer surface of the sidepiece of the overlying ladder unit to abut to the upper inner surface of the sidepiece of the underlying ladder unit. This is possible by giving the sidepieces a suitable inclination, so that the upper surface is slightly wider than the lower surface in a ladder unit, i.e., the width between the sidepieces in a ladder unit is made slightly greater above the plane of the rungs than below said plane.

FIG. 8 shows an example of this embodiment, 5 is a sidepiece in the form of a simple plate girder, 6 is a rung.

In FIG. 9, 7 is a sidepiece in the form of a shaped plate girder, 8 is a rung.

In FIG. 10, 9 is a tube, is a tube, 10 a connecting plate and 11 a rung.

In FIG. 11, 12 is a sidepiece in the form of an oval tube, and 13 is a rung.

Reinforcement When the sidepieces are provided with a reinforcement in the form of a greater material amount, this reinforcement shall be placed in at the edge or edge surface of the sidepiece, irrespective of whether the edge surface (FIG. 2, FIG. 7) of the sidepiece or the side surface (FIG. S-FIG. ll) of the sidepiece is used as a contact surface, and in such a manner, that the contact surface is not disturbed. The reinforcement may, for example, be an outwardly bent plate edge (FIG. 9), a tube or a curved plate edge (FIG.

Material A scaling ladder according to the description above may be made of any material or of any combination of materials which results in a suitable ladder, above all with respect to strength, rigidity, light weight and corrosionresistance, for example, steel, light metal, wood, plastics or wood with metal reinforcement or reinforced plastics.

Endpieces The endpiece for ladder units according to the present invention, which for example is manufactured of wood or rubber, shall have for ladders with sidepieces of profiled tubes at one end the same section as the inner section of the profiled tube, so that the endpiece may be inserted to the desired length into the profiled tube. The portion projecting outside the profiled tube must not have a section exceeding the outer section of the profiled tube, and it shall have a length of about 100 mm. or slightly longer.

By such endpieces the edge of the profiled tube will be located at a safe distance from the wall, even if the angle between the ladder and the Wall is made as small as 10 or smaller. This applies with a good safety margin also to a considerable wear of the endpieces.

Endpieces for ladders with sidepieces of plate or tube girder, are given, for example, rectangular section, and they shall have a length outside the end of the ladder of about 100 mm. or slightly longer. They are secured, for example, by rivets, bolts or fittings to a surface which is not utilized as contact surface for the joining of ladder units.

Joining of ladder units With respect to scaling ladder units with sidepieces of, for example, profiled tubes the connecting means between them are known to be rigidly secured at the uppermost and the next uppermost rung in every ladder unit, as shown with crosses in FIG. l2, seen from one side for two ladder units. This may be accepted in such cases when the ladder units can be joined, i.e., extended only by the length of an entire ladder unit.

With respect to ladders according to the present invention the connecting means shall be rigidly secured at the uppermost and lowermost rung in every ladder unit, as shown with crosses 14 in FIG. 13. Hereby always the greatest possible distance between the connecting points and, thus, also the greatest possible strength and rigidity are obtained, when a ladder unit is being extended by a greater or smaller portion of the length of another ladder unit.

What I claim is:

1. In an extendable ladder construction, the combination comprising a plurality of ladder units of identical construction, each said ladder unit being constituted by parallel spaced sidepieces interconnected by a series of equally spaced rungs of the same length, and the opposite sides of the tWo sidepieces of each ladder unit including single, substantially plane, parallel and equally inclined surfaces located symmetrically to each side of the longitudinal center line of each unit, the single inclined surface at one side of a sidepiece at one side of the ladder unit forming a mirror image of the single inclined surface at the corresponding side of the sidepiece at the other side of the ladder unit, whereby a pair of such ladder units when placed on top of each other in longitudinally extending overlapping relation with the equally inclined surfaces of their respective sidepieces in contact with one another automatically tend to center themselves with respect to the longitudinal center line of the extended ladder so formed.

2. An extendable ladder as dened in claim 1 and which further includes means located at the endmost rungs at each end of each ladder unit for joining the end portions of two ladder units in longitudinally spaced and overlapping relation by connecting said endmost rungs on one ladder unit to correspondingly positioned intermediate rungs of the other ladder unit.

3. An extendable ladder as defined in claim 1 wherein said sidepieces of said ladder units are constituted by tubes which are so profiled as to establish said inclined surfaces each of which is a mirror image of the other.

4. An extendable ladder as defined in claim 1 wherein said sidepieces of said ladder units are constituted by girders of the plate type.

References Cited UNITED STATES PATENTS 5/1914 Graham 182-209 4/ 1929 Lundahl 182-67 REINALDO P. MACHADO, Primary Examiner

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