Conveyors: power-driven – Conveyor section – Endless conveyor
Patent
1996-08-30
1998-07-14
Bidwell, James R.
Conveyors: power-driven
Conveyor section
Endless conveyor
B65G 1534
Patent
active
057790280
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a belt having transverse rigidity.
2. Description of the Prior Art
A belt of this type having transverse rigidity is disclosed in European Patent 0 273 478. In the case of said belt, the layers providing transverse rigidity comprise a number of cables of, for example, four wires each having a diameter of 0.6 mm and a spacing of 2.5 mm, located some distance apart in the horizontal plane. Belts of this type having transverse rigidity are used, for example, as moving pavements in, for example, airports or exhibition areas. The layers providing transverse rigidity are made of a high modulus material, for example a material having a modulus greater than 50 Giga Pascal. Examples thereof are steel wire and aramide threads. This is in contrast to polyester filaments, nylon threads or other relatively weak materials. One example of a high modulus material is Fleximat.RTM., which is marketed by the Bekeart Company. A significant advantage of belts of this type compared with aluminium constructions composed of a large number of parts is the lower maintenance and the lower noise level. A problem, which exists with all installations, is the diameter of the drum around which the belt, or the aluminium pallet system, has to be guided at the end. If this drum is relatively large, this means that the floor of a building in which an installation of this type has to be installed has to be raised or lowered in order to be able to accommodate the installation and the associated parts.
In this context a particular advantage of the belt system compared with the aluminium pallet system is the very small diameter of the drum which can be used.
Long-term trials with drums having an even smaller diameter have shown that no problems occur in the short term but in the long term the outer surfaces of the belt which are subjected to the greatest deformation stress display cracking. Although such cracking has no significant effect on the mechanical characteristics of the belt and the latter can still be used for many years without any problems, a psychological problem with regard to the reliability of the belt certainly arises when said belts are used for transporting people. The aim of the present invention is to prevent said cracking in a belt having transverse rigidity.
SUMMARY OF THE INVENTION
This aim is achieved in the case of a belt having transverse rigidity, described above.
The invention is based on the insight that initiation of the cracks does not occur at the surface but at the wires which form the layers having transverse rigidity. Once the cracks have been initiated there, they are propagated in the direction of the surface of the belt. On the basis of this insight, in contrast to what would appear to be obvious, no attempt has been made to take measures to maintain the surface of the belt undamaged for a longer period, but measures have been taken to prevent initiation of the crack at the cables or wires. If there is no initiation at the cables, the surface of the belt will likewise not crack, so that special measures at the surface are not necessary.
Once the insight had been gained that the cracks start at the cables, the following step was to take measures in order to reduce the tension at the location of the cables. An obvious solution would be simply to increase the distance between the steel cables. However, this gives rise to the problem that the transverse rigidity of the belt concerned is reduced. It would then be possible to use a larger number of wires per cable, but this gives rise to problems because the risk that the cables will work loose from the rubber during operation and come to the surface is appreciably increased. The solution proposed according to the invention, comprising the arranging of at least two layers of cables some distance apart, makes it possible to increase the spacing between the cables in each layer while still using the same amount of cable material in order to provide an adequate transverse rig
REFERENCES:
patent: 2792868 (1957-05-01), Benson
patent: 2850420 (1958-09-01), Hacker
patent: 3900627 (1975-08-01), Angioletti et al.
patent: 4004467 (1977-01-01), Kenney
Bidwell James R.
Dunlop-Enerka B.V.
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