Railways: surface track – Tie-plates
Patent
1988-08-18
1990-05-01
Kashnikow, Andres
Railways: surface track
Tie-plates
238308, E01B 940, E01B 968
Patent
active
049211684
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a support plate, particularly a ribbed plate, for fastening rails of railroad tracks and track switches on wooden sleepers or another inhomogeneous material, which is connected in the vicinity of the ends in each instance with the sleeper by means of screws or the like which engage in the through-holes, whereas the rail flange is supported in the area of the plate between the fastening points on the sleeper side.
The support plates conventionally used during the construction of railroad tracks and track switches are fastened on the wooden sleepers by means of four screws or the like in each instance. In so doing, the aim is a fastening with the most constant possible screwing in forces. These screwing in forces should amount to up to 35 kN for a single screw, but can also reach up to 50 kN. The support plate can therefore be subjected to an area load of approximately 200 kN because of these high screwing in forces.
Since the fastening screws are applied relatively close to the ends of the support plate, a concave longitudinal deformation of the support plate occurs due to the high screwing in forces because these support plates usually only have a thickness which is limited to 16 or 10 mm and therefore only achieve a longitudinal stiffness which is much too low and is not sufficient for a force transmission without deformation.
In order for, e.g. a standard ribbed plate URP 206, as is currently used for fastening rails UIC 60 on wooden sleepers, to achieve a longitudinal stiffness which can enable an introduction of the maximum area load of 200 kN practically without deformation, it would have to obtain a thickness dimensioning of approximately 35 mm, instead of the standard thickness of 20 mm, if a sufficiently uniformly distributed surface pressure on the top of the wooden sleeper is to be achieved.
However, such an increased expenditure in material for the ribbed plates is prohibitive in practical use because of the resulting, considerably higher cost. Also, the reason for the concave curvature already occurring by means of the mounting of the plate has not been understood until now.
Therefore, it was previously taken into account that, in the conventional support plates, constant contact with the wooden sleeper exists only in the engagement area of the sleeper screw, whereas the middle area of each support plate is curved upward in a more or less concave manner, so that a hollow space is formed toward the top of the wooden sleeper where the rail flange has its support surface; the support plate alternately falls and rises--that is, it pumps, so to speak--over this hollow space when traveled over by the railroad car wheels, so that the upper surface of the wooden sleeper is damaged or even destroyed after a certain period of use. A loosening occurs because of the wear of the support plate, so that the track gauge can no longer be maintained, and the spring rings connected between the fastening screws and the support plate break. However, it also happens that the support plates themselves break in the critical area due to constant alternating stresses.
This shortcoming in known support plates causes relatively high maintenance costs because the wooden sleepers must often be removed because of damage to the top of the sleeper and readjusted after the removal of the support plate. However, it is then necessary simultaneously to dowel the holes provided until then for receiving the fastening screws and then to rebore them so that the fastening screws for the support plates can again be fastened in an optimal manner.
Since such recovery work on a wooden sleeper must be carried out approximately two to three times during its entire service life, considerable maintenance costs arise up to the point of its biological decay, that is, until it finally becomes unusable.
Since the spring rings break as a result of the pumping process, a replacement installation of new spring rings is required every 3 to 4 years, which also involves high costs. An elastically pretensioned support plate, whic
REFERENCES:
patent: 1579157 (1926-05-01), Singeltary
patent: 1583774 (1926-05-01), Boyce
patent: 1834256 (1931-12-01), Ruping
patent: 2713975 (1955-07-01), Martin
Kashnikow Andres
Le Mark T.
Schwihag Gesellschaft fur Eisenbahnoberbau mbH
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