[0001] This invention covers an articulation for simple articulated ladders or for extension
and telescopic articulated ladders.
[0002] This type of ladder generally consists of two or more ladder sections joined by one
or more articulations, so that a long ladder may be folded, transported or stored
in a small space, but also to adapt the ladder to the location and the various work
conditions.
[0003] Currently, articulations for these ladders are generally small, in order not to create
a long interval between the steps at the fastening spots. Generally, they also have
very short arms so that they may be joined and fastened to the ends of the members
comprising the ladder flanges, whereby the articulation arms are joined close to the
first step. After the joint, a variable number of holes are drilled for the rivets
that are placed from the exterior. The rivets cross only the walls that are side by
side - the external wall of the ladder side and the inner wall of the articulation
arm. Since the rivets are of a relatively small diameter, and since the lateral member
commonly applied for these ladders has a wall of about 1.00 mm, it can be easily seen
that the material's resistance to wear and torsion forces is always precarious in
this small joint area, and even if the rivet is made of steel, which is rare, the
safety of persons using this type of ladder is always minimum. Most users agree that
the main problem with these ladders is that they develop loose fittings between the
member and the articulation joint arm due to constant use that causes constant oscillation
and, in time, loosen the rivet holes or shear them.
[0004] The common method of fastening the articulation to the member decreases the ladder's
resistance, particularly when it is totally open, since, if the user is at the top
of the ladder, or on the step next to the articulation, strong pressure is placed
on the member area at the end of the articulation, whereby the rivets are the only
connection parts that disperse the forces between those two elements. When the ladder
is used on a regular basis, there is a constant variation in load direction that eventually
causes play and wear in that area.
[0005] This is a technical problem that has restricted the use of larger ladders equipped
with articulations, and thus most ladders on the market are about 4.5 metres high.
The constant day-to-day bustle and the growing lack of time for performing work generally
leads to a situation in which users, not familiar with the fragility of the fittings,
always overload these types of ladders.
[0006] This invention resolves the problem of the fastening and resistance of ladder articulations
and arises, not only due to a demand for a solution to the problem of safety sought
by most users, but also due to the growing demand for larger articulated ladders by
professional users.
[0007] This innovative articulation for ladders (fig. 1) results from lengthy studies and
a series of drawings taking into account the resistance of the respective materials,
combined with technical know-how on the production of this type of tool, making it
possible to manufacture prototypes of experimental articulations successively submitted
to strict workshop trials.
[0008] The new articulation's main novelty for ladders is the longer arms that, when totally
open, are always longer than the normal distance between the ladder steps. Both articulation
arms have castings (1 and 2) of a square, rectangular, triangular or oval geometric
shape, but always the same as the member's peripheral configuration (3) used on the
ladder steps. These castings make it possible for the articulation arms, after being
deeply inserted into the corresponding ladder flanges (6), that is, the arm and the
flange, to be simultaneously crossed by the ladder step (3), and then the step is
flared outside the flange (4).
[0009] The controlled flared exterior (4), allows for a perfect adjustment and total consolidation
of the respective parts (articulation, flange member and step member): By eliminating
focal load concentration points, the risk of rupture in that ladder area is eliminated
because there are no longer dispersed contact points, which are replaced by a large
contact surface dispersing the forces and thus providing greater robustness along
the whole ladder length, regardless of its number of articulations or of the length
or number of steps of each of its parts, an important user-safety factor.
[0010] With the solid construction provided by this new articulation, at the end of the
ladder's elongation, when the user passes through the centre area, the natural flexing
is distributed along the ladder's whole length. In localised loads, when the user
is at the highest spot of the ladder or when he places his whole weight on the step
closest to the articulation, the pressure loads are absorbed directly by the ladder's
lateral structure and do not create dispersed focal points of rupture forces, neither
on the flange nor on the articulation arm, and this will be the case whatever the
user's position.
[0011] This technical feature called for suitable inlaid saliencies, grooves and external
structural ribs (5 fig.1) to compensate for the elongation of the arms, that is, the
increased distance between the load-supporting point, the fastening step and the articulation
axis.
[0012] It must be noted that in this type of ladder, all the stress loads are generally
supported where the ladder is joined to the articulation, which makes fastenings with
rivets fragile. With this technical solution, the whole area where the articulation
arm and the ladder's flange are joined is reinforced by doubling the structure and,
with this innovation, that area is transformed into a solid and highly resistant structural
area, much contrary to the case of the various articulations fastened with rivets
available on the market.
NOMENCLATURE
[0013]
- 1
- Casting of the articulation arm
- 2
- " " "
- 3
- Ladder step member
- 4
- Exterior flaring of the step member
- 5
- Reinforcement ribs
- 6
- Ladder flange member
1. ARTICULATION FOR LADDERS suitable for application in simple articulated ladders with
two or more step sectors, in articulated extension ladders or telescopic ladders,
characterised by having elongated arms with castings of a varied geometric configuration near the
ends, whereby this geometric configuration is always the same as the periphery of
the member used for the ladder steps, the castings (1 and 2) allow the step closest
to the articulation (3) to be applied by crossing the articulation arm and the flange
where it was inserted, such that it is flared on the outside (4), adjusting and fastening
the articulation.
