The present invention relates to a magnetically attachable roof rack for a motor vehicle, of the type which comprises a flexible plate which is made of magnetic material and can be fitted on the roof and which can be adapted to the shape of the latter, a flexible base plate connected to the plate made of magnetic material and attached to the latter, and a rack unit supported by the base plate with vibration-damping means interposed, in order to prevent vibrations from being transmitted from the rack unit to the metal plate.
The invention was conceived for application to a ski rack, but this application is not limiting.
Many examples of magnetically attached devices of the type in question are already known, including those known from documents DE-A-2 423 565, DE-A-3 135 649, DE-A-3 221 126, FR-A-2 582 062 and IT-A-90 22271.
The prior art closest to the invention is disclosed in document IT-U-211 951. This document concerns a ski rack in which a rack unit, shaped so as to receive two pairs of skis, is pivotable about a vertical rod which is integral with the centre of a metal base plate, which in turn is integral with the magnetic plate. The rack unit is slidable along the vertical rod and is retained on the latter with the interposition of elastic means in the form of a helical compression spring which enables the rack unit to oscillate vertically and to damp the vertical stresses transmitted to the base plate by the rod.
According to this known solution all the lateral forces applied to the rack unit, such as for example those caused by centrifugal force on bends and by the relative wind, are transmitted in the form of twisting moments, of which the point of application is concentrated at the base of the rod, on the metal base plate and on the underlying magnetic plate.
It will be appreciated that since the rack unit is attached to the metal plate only at a central point of the latter, it is subject to considerable lateral oscillations, which in the long term can give rise to spontaneous detachment of the magnetic plate from the roof. Additionally, when the magnetic plate is being detached from the roof, the metal base plate tends to be deformed by being drawn outwards in the centre, causing it to become detached unintentionally from the magnetic plate.
These disadvantages could be eliminated by the thickness of the base plate being increased, but an increase in the thickness of the base plate stiffens it and impedes adaptation of the flexible magnetic plate to the "convexity" or curvature of the vehicle roof.
In order to prevent these problems, an alternative solution could consist of widening the attachment base, in other words the base plate and the underlying magnetic plate, but even if this is done it detracts from the ability of the magnetic plate to be adapted to the roof and, additionally, from the point of view of vibrations, the opposite result of a very rigid product which does not absorb the vibrations is obtained.
The above-described disadvantages are also encountered in other types of magnetically attached devices, such as for example that according to DE-A-2 423 565.
Another solution aimed at avoiding the aforementioned disadvantage consists in connecting the magnetic supports in pairs by means of crosspieces and/or longitudinal members, as shown for example in documents DE-A-3 221 126 and FR-A-2 582 062.
However this solution has the disadvantage that it makes the operations of fitting and removing the ski rack or general purpose rack unnecessarily complex, and additionally does not permit use for example of two supports alone, aligned in the vicinity of an edge of the roof.