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(11) | EP 2 811 105 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A rigid ladder and a method for manufacturing thereof |
| (57) The invention relates to a rigid ladder 1 comprising a crossbar 2 having a first
end at one end of the crossbar 2 and a second end at the opposite end of the crossbar,
and two longitudinal members 3, each longitudinal member 3 located at each end of
the crossbar 2, wherein the crossbar 2 has been manufactured from a first metal sheet
4 formed to a tubular form, each of the longitudinal members 3 has been manufactured
from a second metal sheet 5 having a first longitudinal edge 6, a second longitudinal
7 edge opposite the first longitudinal edge 6, a first planar surface 8 and a second
planar surface 9 opposite the first planar surface, wherein a hole 10, having an edge,
for the crossbar 2 has been provided in the second metal sheet 5, the edge of the
hole has been bent for providing a rim 11 extending from the second planar surface
9, the crossbar 2 has been attached from an end to the rim 11, the second metal sheet
5 has been bent in the direction of the second planar surface 9, and the first longitudinal
edge 6 has been connected to the second longitudinal edge 7 for a forming tubular
longitudinal member 3.
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FIELD OF THE INVENTION
[0001] The present invention relates to a ladder, and particularly to a rigid ladder. The present invention further concerns a method for manufacturing a rigid ladder.
BACKGROUND OF THE INVENTION
[0002] Normally a ladder is made by providing tubular longitudinal members having oval or some other shaped cross section and making holes for the crossbars through the both walls of the longitudinal members. The crossbars may be connected to the holes in the longitudinal members by welding or by bending the end of the crossbar.
[0003] A problem with this known ladder is that because the crossbars and the longitudinal members are made of a pipe, the inside of the crossbars and longitudinal members cannot be coated, for example galvanized and/or painted. Therefore they are likely to be corroded when exposed to moisture in the air.
[0004] Another problem with the known ladder is that because the crossbars are made of smooth pipe, in wet conditions the crossbar may be slippery.
BRIEF DESCRIPTION OF THE INVENTION
[0005] An object of the present invention is to provide a ladder and a method for manufacturing thereof so as to solve the above problems.
[0006] The objects of the invention are achieved by a ladder and a method, which are characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
[0007] The invention is based on the idea of providing a ladder that is made of sheet metal. More specifically, the crossbar and the longitudinal members are made of sheet metal. The crossbar has been manufactured from a metal sheet formed to a tubular form, and the longitudinal members have been manufactured from a metal sheet, where holes have been provided, by attaching the ends of the crossbar to the holes and bending the metal sheet so that the sides of the metal sheet are connected for forming a tubular longitudinal member. Thus the connection of the crossbar is remained inside the longitudinal member.
[0008] An advantage of the ladder of the invention is that before manufacturing the ladder the sheet metal used can be coated, for example galvanized and/or painted. Therefore a coating can also be obtained on the insides of the crossbar and the longitudinal members. This reduces corrosion of the ladder when exposed to environmental strains.
[0009] Another advantage of the ladder of the invention is that the sheet metal used for manufacturing the ladder can have roughened and/or patterned surface structure for providing a better traction when the ladder is used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which
Figure 1 is a schematic drawing of a ladder;
Figure 2 is a schematic drawing of a cross section a first metal sheet;
Figure 3 is a schematic drawing of a cross section of a second metal sheet;
Figure 4 is a schematic drawing of a cross section of a second metal sheet during the manufacture of the ladder;
Figure 5 is a schematic drawing of a cross section of a second metal sheet during the manufacture of the ladder;
Figure 6 is a schematic drawing of a cross section of a second metal sheet during the manufacture of the ladder;
Figure 7 is a schematic drawing of a cross section of the ladder.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The invention relates to a rigid ladder 1 comprising a crossbar 2 having a first end at one end of the crossbar 2 and a second end at the opposite end of the crossbar, and two longitudinal members 3, each longitudinal member 3 located at each end of the crossbar 2,
wherein
- the crossbar 2 has been manufactured from a first metal sheet 4 formed to a tubular form,
- each of the longitudinal members 3 has been manufactured from a second metal sheet 5 having a first longitudinal edge 6, a second longitudinal 7 edge opposite the first longitudinal edge 6, a first planar surface 8 and a second planar surface 9 opposite the first planar surface, wherein
- a hole 10, having an edge, for the crossbar 2 has been provided in the second metal sheet 5,
- the edge of the hole has been bent for providing a rim 11 extending from the second planar surface 9,
- the crossbar 2 has been attached from an end to the rim 11,
- the second metal sheet 5 has been bent in the direction of the second planar surface 9, and
- the first longitudinal edge 6 has been connected to the second longitudinal edge 7 for a forming tubular longitudinal member 3.
[0012] According to an embodiment the first metal sheet 4 and the second metal sheet 5 are coated. According to an embodiment the first metal sheet 4 and the second metal 5 sheet are galvanized. According to an embodiment the first metal sheet 4 and the second metal sheet 5 are painted.
[0013] According to an embodiment the crossbar 2 has a circular or oval cross section. According to an embodiment the tubular longitudinal member 3 has a circular or oval cross section.
[0014] According to an embodiment the first metal sheet 4 and/or the second metal sheet 5 have/has been provided with a roughened or patterned surface structure. The roughened or patterned surface structure reduces slipperiness of the ladder.
[0015] According to an embodiment the crossbar 2 has been attached from the end to the rim 11 by bending the end over the rim 11. The aim in attaching the crossbar to the rim by bending is to avoid welding because the welded seam may corrode.
[0016] The invention also relates to a method for manufacturing a rigid ladder 1, comprising the steps of
- providing a first metal sheet 4,
- forming the first metal sheet 4 to a tubular form for forming a crossbar 2 having a first end at one end of the crossbar 2 and a second end at the opposite end of the crossbar 2,
- providing a second metal sheet 5 having a first longitudinal edge 6, a second longitudinal edge 7 opposite the first longitudinal edge 6, a first planar surface 8 and a second planar surface 9 opposite the first planar surface 8,
- providing a hole 10, having an edge, for the crossbar 2 in the second metal sheet 5,
- bending the edge of the hole for providing a rim extending from the second planar surface 9,
- attaching the crossbar 2 from an end to the rim 11,
- bending the second metal sheet 5 in the direction of the second planar surface 9, and
- connecting the first longitudinal edge 6 to the second longitudinal edge 7 for forming a tubular longitudinal member 3.
characterized in that
- the crossbar (2) has been manufactured from a first metal sheet (4) formed to a tubular form,
- each of the longitudinal members (3) has been manufactured from a second metal sheet (5) having a first longitudinal edge (6), a second longitudinal (7) edge opposite the first longitudinal edge (6), a first planar surface (8) and a second planar surface (9) opposite the first planar surface, wherein
- a hole (10), having an edge, for the crossbar (2) has been provided in the second metal sheet (5),
- the edge of the hole has been bent for providing a rim (11) extending from the second planar surface (9),
- the crossbar (2) has been attached from an end to the rim (11),
- the second metal sheet (5) has been bent in the direction of the second planar surface (9), and
- the first longitudinal edge (6) has been connected to the second longitudinal edge (7) for a forming tubular longitudinal member (3).
- providing a first metal sheet (4),
- forming the first metal sheet (4) to a tubular form for forming a crossbar (2) having a first end at one end of the crossbar (2) and a second end at the opposite end of the crossbar (2),
- providing a second metal sheet (5) having a first longitudinal edge (6), a second longitudinal edge (7) opposite the first longitudinal edge (6), a first planar surface (8) and a second planar surface (9) opposite the first planar surface (8),
- providing a hole (10), having an edge, for the crossbar (2) in the second metal sheet (5),
- bending the edge of the hole for providing a rim extending from the second planar surface (9),
- attaching the crossbar (2) from an end to the rim (11),
- bending the second metal sheet (5) in the direction of the second planar surface (9), and
- connecting the first longitudinal edge (6) to the second longitudinal edge (7) for forming a tubular longitudinal member (3).