Railways: surface track – Rail joints – Expansion deflectors
Patent
1995-05-26
1997-06-03
Morano, S. Joseph
Railways: surface track
Rail joints
Expansion deflectors
E01B 1142
Patent
active
056345917
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns suspension bridges comprising an essentially flat main structure, or framework, the top surface of which forms the roadway for the transport means crossing the bridge, and a suspension system formed of catenary cables anchored to end piers of the bridge and of a plurality of vertical stays or hangers to suspend the bridge framework to the catenary cables.
As known, the longer the suspension bridge, the greater the longitudinal excursion it undergoes, mainly due to thermal expansions, live load variations on the bridge, and/or displacements caused by the action of the wind.
The invention thus relates, in particular, to a sliding joint system for railway tracks, allowing a great longitudinal excursion--in theory, unlimited--of one track section in respect of the other.
The problem of longitudinal excursion essentially arises in correspondence of the end piers onto which are anchored the catenary cables to suspend the bridge, whereby sliding joints have to be provided in these areas.
As concerns the sliding joints for roadways, there are already known to be systems allowing considerable excursions. These systems generally consist of parallel intersecting tracks, which are considered to provide a satisfactory solution to the problem.
Whereas, as concerns railways, the only known system allowing a certain reciprocal sliding between the rails--while still ensuring a constant support of the train wheels--consists in tapering the opposed ends of the two railroad sections and placing said tapered ends side by side; the discontinuity between the two rails thus appears in the form of an oblique cut (instead of being perpendicular to the rail axis). The narrower the angle formed between the axis of said cut and the rail axis--i.e. the more marked the tapering--the greater the excursion allowed by such a joint system. In any case, there are no joints of this type allowing an excursion of more than a few decimeters.
From the documents U.S. Pat. No. 2,067,598 and FR-A-2185192, joints are also known in which only one of the adjacent ends of the rails is obliquely cut, while the other end runs close to this oblique surface and along the same. The advantage of this system is provided by the fact that there is always a contact between the two rails, differently from the above cited known technique in which the ends of the rails are separated by an oblique slot and the width of this slot becomes greater as the ends of the rails more apart one from the other due to contraction of the rails, i.e. owing to cooling.
Even if these known systems, as already said, have this advantages to avoid the formation of a more or less wide slot between the ends of the rails, however, they do not allow wide longitudinal excursions between the rails. In U.S. Pat. No. 2,067,598 (page 2, column 2, lines 23, 24) it is said that the longitudinal excursion may be of about 400 mm. and also a less wide longitudinal excursion is foreseen in FR-A-2185192 (see the broken lines a in FIG. 2).
In fact, all the above systems are provided for extensions and contractions of the rails caused in particular by thermal variations. Besides in these conditions--seen from another point of view--the movements of the rails are, as known, extremely slow: normally there is only an extension during the day and a contraction during the night. Therefore the resistance to sliding of the rails, owing to the great friction between them, is practically negligible.
However, in suspension bridges with a very wide span, for instance over 1 Km, one should provide excursions of the order of meters. In the bridge being planned for crossing the Straits of Messina--to which reference is made in EP-A-0.233.528, filed by the same Applicant--having a span greater than 3 Km, the reckoned excursion is of .+-.3.5m in rest conditions, with no traffic on the bridge. But it is perfectly known that, in railway technique, there is no joint system allowing an excursion of 7 m.
Besides, in the case of a joint for a suspension bridge with a very wide span, the sliding
REFERENCES:
patent: 411362 (1889-09-01), Weir
patent: 2067598 (1937-01-01), Clarke
patent: 4171774 (1979-10-01), Deslauriers
patent: 4785994 (1988-11-01), Crone et al.
Morano S. Joseph
Stretto Di Messina S.p.A.
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