Railway switches and signals – Switches
Reexamination Certificate
1999-06-21
2002-04-16
Morano, S. Joseph (Department: 3617)
Railway switches and signals
Switches
C246S382000
Reexamination Certificate
active
06371418
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a curve path of a switch comprising switch tongues, a main track and a branch track, which curve path from the beginning of the curve path to the end of the curve path is comprised of several portions having different curvatures 1/R, R being the radius of curvature.
2. Prior Art
From the article in ETR 39 (1990), H.1/2, January/February, by Reimar Holzinger and Dieter Fritz, “Entwicklung moderner Hochleistungsweichen zur Wahrung der Zukunftschancen der Bahn”, a number of switch geometries have become known for meeting the demands of high-speed traffic, which, as a rule, are characterized by a high degree of symmetry in order to prevent sudden changes in direction or curvature of the track and hence excessive transverse accelerations. The considerations made in that article relate to transition curves of the clothoid and cosine parabola types and sinus transition curves, changes in acceleration (jerks) being contemplated in detail.
From WO 95/31604 a curve path for the course of rails from the main track to a branch track can be taken, in which, likewise departing from a first end portion starting with a radius of curvature towards infinity, the respectively other end of the switch is again configured with a radius ending towards infinity in order to avoid additional vibratory excitations that may have adverse effects on vehicles. In that known configuration, a curve path comprised of three portions has been chosen, three approximately equally long portions being used. Departing from a curvature having a radius of curvature tending towards infinity, a central portion having a constant curvature whose radius constitutes a minimum over the curve path is chosen. In the main, this results in the course of two conventional clothoids having an intermediate portion in the form of a circular arc.
SUMMARY OF THE INVENTION
The invention aims at providing a curve path of the initially defined kind, which entails less wear of the structural components and hence higher service lives as well as lower overall costs, in particular in high-speed operation. At the same time, the invention aims to improve the maintenance expenditures and travelling comfort of such switches, in particular high-speed switches. To solve this object, the curve path of a switch according to the invention essentially consists in that the coefficient of curvature &agr;=1/R/1/R
min
at the beginning of the curve path (&agr;
A
) and at the end of the curve path (&agr;
E
) is selected to be ≧0 and that the point, or a region, in which &agr;=1 is located at a relative distance &ngr;=L/L
ges
≠0.5 from the beginning of the curve path, L being the distance from the beginning of the curve path and L
ges
being the length of the curve path. The curvature 1/R serves to define a dimensionless coefficient of curvature &agr;, which equals the quotient of the instantaneous curvature 1/R and the maximum curvature 1/R
min
, the maximum curvature, in turn, resulting from the quotient of 1 and the minimum radius. &agr;can, thus, assume values of between 0 and 1, hence the radius is tending towards infinity in points in which &agr; equals zero, since the minimum radius has a finite value. In the point of maximum curvature, and hence of minimum radius, this coefficient &agr; assumes the value 1. In addition to defining the value &agr;, also a coefficient &ngr; is defined, which sets the respective distance between the beginning of the curve path and the curve path point considered in relation to the total length of the curve path. The value &ngr;, thus, equals zero at the beginning of the curve path and 1 at the end of the curve path, assuming any values of between 0 and 1 in direct proportion to the distance from the beginning of the curve path. Investigations into vehicle movement dynamics, under consideration of the usual course of cross sectional changes of the structural elements concerned, such as, e.g., tongue and nose of crossing, have now proved that, by turning away from the usual symmetry in the structure of such curve paths, it is feasible to both reduce wear and enhance comfort by the point or region with &agr;=1 being located at a relative distance &ngr;≠0.5 from the beginning of the curve path.
It has now been shown that the curve path geometry may be further optimized to the extent that the moving direction in which the switch is usually travelled over is also taken up into geometry considerations. With a particular advantage, &agr;
A
and &agr;
E
are selected between 0 and 0.5 and &ngr;
max
for &agr;
max
between 0.45 and 0.8 and unequal to 0.5 for a bidirectionally passed switch. A bidirectionally passed switch means that the switch is travelled over both facing and trailing. A switch travelled over primarily in one direction in a particularly advantageous manner is designed such that, for a switch passed facing, &agr;
A
is selected between 0 and 0.5, &agr;
E
is selected between 0.5 and 1 and &ngr; for &agr;
max
is selected between 0.4 and 1 and unequal to 0.5 and that, for a switch passed trailing, &agr;
A
is selected between 0.3 and 0.7, &agr;
E
is selected between 0 and 0.5 and &ngr; for &agr;
max
is selected between 0.3 and <0.5. The values indicated above for the different curve path geometries for different travelling directions have been optimized in terms of minimum lateral accelerations and running-in jerks as well as slight wear phenomena and small wheel-rail forces. A slight lateral acceleration and break-in jerk thereby guarantee a high comfort in passing the switch, little wear and small wheel-rail forces render feasible a long service life of the switch.
In a particularly advantageous manner, the configuration according to the invention is devised such that one, and only one, point of maximum curvature or minimum radius with &ngr;≠0.5 is provided between the beginning of the curve path and the end of the curve path. Here again, the turning away from the hitherto chosen symmetry as suggested, for instance, in WO 95/31604, brings about a substantial improvement in comfort and a reduced wear. If one, and only one, point of maximum curvature is provided, the curve path geometry may have the form of a vertex clothoid in the curved course, wherein &ngr; will assume a value of ≠0.5 in accordance with the definition chosen above, if such a vertex clothoid is used. In the case of cosinoids, it is known to select different values &agr; at the beginning of the curve path and at the end of the curve path, wherein it has hitherto been common also in that case to select the value &agr; at the end of the curve path to be 0 and, thus, progressively merging into the connection rail. If, as in accordance with a preferred further development of the invention, an intermediate region is chosen instead of one, and only one, point of maximum curvature, the configuration advantageously is devised such that a portion of constant maximum curvature is arranged between the beginning of the curve path and the end of the curve path, wherein the radius constitutes a minimum and whose center is arranged outside the center between the beginning of the curve path and the end of the curve path, the symmetry considerations made so far again having been left in the instant case. The central region of such a circular arc portion, like the previously mentioned one, and only one, point of maximum curvature, is not located in the longitudinal center of the curve path, thereby offering improvements in terms of wear and moving comfort.
In a particularly simple manner, the configuration is devised such that the portions differing from the shape of a circular arc are formed by clothoids and/or cosinoids. If, as already pointed out above, the travelling direction is additionally taken up into the switch geometry considerations, the curve path geometry in a particularly advantageous manner is defined such that, with a switch passed facing, the point of maximum curvature is arranged at the end of the curve path. In case of
Gsodam Hannes
Klauser Peter Ernst
Oswald Johannes Rainer
Joyce Kevin E.
Jules Frantz F.
Morano S. Joseph
VAE Aktiengesellschaft
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