Railway rolling stock – Trucks – Bogie
Reexamination Certificate
1999-11-02
2001-07-03
Morano, S. Joseph (Department: 3617)
Railway rolling stock
Trucks
Bogie
C105S131000, C105S133000, C105S136000, C105S158200
Reexamination Certificate
active
06253686
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a traction unit, particularly a rail vehicle traction unit, comprising at least one chassis bogie in which at least one geared motor unit is arranged, and relates more specifically to a traction unit drive bogie.
The bogie of a railway vehicle executes lateral movements of translation and rotational movements, known by the name of sinusoidal travel, even on a perfectly straight and flat track. The forces exerted by this sinusoidal travel on the bogie chassis and the frequencies of the resulting oscillations increase with the speed of the vehicle.
Added to these forces are the forces which are due to imperfections in the track, to jolts caused by these imperfections, to points and to curves, these forces being the cause of instability phenomena.
Because of these phenomena of instability, the speed of a vehicle fitted with such a bogie has, for safety reasons, not to exceed a speed known as the critical speed.
The speed which is known as the critical speed is the speed at which the natural frequency of the bogie is close to resonance. The frequency at which the bogie vibrates is all the higher, the higher the speed of travel of the vehicle.
It is essential, in vehicles intended to run at high speed, particularly in railway vehicles, for the so-called critical speed to be raised as high as possible by special structural arrangements so as to allow stable running.
For this reason, it is advantageous for a drive bogie to have a very low unsuspended mass so that its moment of inertia is low in comparison with the translational movement perpendicular to the direction of travel and with respect to rotations about its vertical axis.
In known traction units which are in use in very high numbers, the geared motor unit is fixed rigidly in the bogie chassis. A shaft which is preferably hollow in such cases advantageously transmits energy from the reduction gearset to the wheels via the axle.
The instability phenomena are therefore particularly sensitive as the mass of the motor and of the transmission increase the unsuspended mass of the bogie. This assembly cannot therefore be used for vehicles which have to run at high speed.
There are other rail traction units which are intended for high speeds and whose unsuspended bogie mass is reduced by fixing the motor and the transmission not to the bogie but to the chassis of the body of the vehicle.
A cardan shaft transmits energy from the reduction gearset to the wheels driven via a second gearset mounted on the axle. The lengthening and shortening of these telescopic cardan shafts introduce frictional forces which are a function of the torque that is to be transmitted and which retard the movement. Furthermore, the weight of the telescopic shaft is necessarily higher than an undivided cardan shaft.
SUMMARY OF THE INVENTION
The object of the invention is to provide a traction unit drive bogie as specified, but improved in such a way that the lateral displacements of the bogie chassis are limited and that the so-called critical speed is increased.
According to an essential feature of the invention, the geared motor unit is suspended in the bogie chassis from three elastic connecting rods in such a way that it has enough mobility transversely to the longitudinal direction of travel of the vehicle that it can act as an inertia damper. A shock absorber fixed between the bogie chassis and the geared motor unit absorbs the vibrations of the geared motor unit.
The principle of the invention is based on the fact that the lateral displacements of the geared motor unit and the inertias involved act as a damper, particularly during high speed travel or when running over a jolt, such as points for example.
What happens is that the bogie chassis then, as mentioned earlier, experiences lateral jolts likely to cause the vehicle to become unstable and become derailed.
By virtue of the invention, the inertia and the elastic transverse displacement of the geared motor unit in the bogie chassis oppose the displacements of the bogie chassis under the effect of the jolts. Thus, the geared motor unit damps these displacements by virtue of a phase shift between the displacements of the bogie chassis and those of the geared motor unit. The vibration shock absorber lessens the inherent movements of the geared motor unit.
Another advantage of the drive bogie according to the invention is the complete independence of the bogie, both as regards mechanical interfaces and as regards dynamic couplings in alignment and in rotation between the body and the bogie, unlike certain systems in which part of the geared motor unit is suspended beneath the body.
The drive bogie of the invention may also meet at least one of the following characteristics:
the said geared motor unit can move in translation transversely to the longitudinal direction of travel of the said traction unit in order to act as an inertia damper,
the said geared motor unit can move in translation with a lateral travel of at least 30 mm,
the said geared motor unit is suspended from the said bogie chassis by one connecting rod on the axle side, and is suspended from the said bogie chassis by two connecting rods on the motor side,
the said geared motor unit is suspended from the said bogie chassis by two connecting rods on the axle side, and is suspended from the said bogie chassis by one connecting rod on the motor side.
The invention also relates to a traction unit which comprises at least one drive bogie as defined above.
Other objects, features and advantages of the invention will become clear from reading the description of a preferred embodiment of the traction unit drive bogie, the description being made in conjunction with the single figure which is a partial perspective view, partly depicted diagrammatically and partly in section, of a drive bogie for a high speed heavy rail vehicle according to the invention, the geared motor unit being suspended and arranged in the bogie chassis via three connecting rods,
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Alstom Transport SA
Morano S. Joseph
Olson Lars A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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