EP1095838A2

EP1095838A2 - Hinged bogie for rail vehicles

Info

Publication number: EP1095838A2
Application number: EP00830684A
Authority: EP
Inventors: Aldo Frediani
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-10-27
Filing date: 2000-10-19
Publication date: 2001-05-02
Also published as: EP1095838A3; ITFI990224A1; ITFI990224A0; IT1308305B1

Abstract

An hinged bogie for rail vehicles comprising two longitudinal members (1a, 1b) supporting the wheels (2) and two tubular transverse shafts (3,4) each extending from one of the two longitudinal members. Transverse shafts axially and pivotally engage with each other and means for locking (20) the mutual axial sliding thereof are provided.

Description

The present invention relates to an hinged bogie for rail vehicles.
Several types of bogies for rail vehicles exist according to the intended use of the vehicle which can be a railway use, underground railway use or surface tramway use.
The features distinguishing these bogies from one another concern design loads (both static and fatigue loads), gauge, type of rail; furthermore bogie can be of the standard type or of the lowered type. A common feature of all the bogies is the need to ensure stability against derailment, which occurs when the load on one of the four wheels is not sufficient any longer to prevent the wheel rim to go up the rail and jump over it. In order to avoid derailment, it is necessary to design the bogie in such a way that none of the wheels be released of a part of the vertical load in favour of the other three wheels; therefore, an aim of primary importance when designing a bogie is the even distribution of the vertical load over the four wheels of the bogie in every running condition.
Another aim of the bogie manufacturers is the reduction of the production and operation costs, inclusive of the costs for the static and fatigue qualification by means of tests on the bogies at a real scale. The possibility of manufacturing bogies with a standard geometry capable of being easily adapted to various types of gauge, pitch, braking or motor type, is therefore a well felt need in the field.
In the conventional bogies the problem of the derailment is solved by a suitable design of the primary and secondary suspension. However, this solution is not always sufficient, because a low rigidity of the suspensions can be in contrast with the preservation of the vehicle outline and can produce problems of structural dynamics or insufficient values of the critical velocities. A very common type of bogie for underground or surface vehicles, characterized by narrow curvature radiuses and insufficient quality of the rails is that provided with an hinge. The most frequent solution for a hinged bogie consists in the introduction of two ball joints on the crossbar system connecting the two parallel longitudinal beams supporting the wheels axes. The line connecting the centres of the two ball joints constitutes the hinge axis around which a part of the bogie rotates with a rigid rotatory motion with respect to the other part of the bogie. An example of this concept is shown in Figure 1, in which the axis of rotation forms an angle other than 90° with the longitudinal axis of the bogie. As a matter of fact, in the particular case where the ball joints were aligned in the transverse direction the system would be labile. On the other side, with the introduction of the hinge the double symmetry, i.e. with respect to both the longitudinal axis and the transverse one, is lost. This involves a different load distribution over the four wheels and, therefore, a different braking over the wheels and a different rim consumption. Furthermore, the lack of axial symmetry constitutes a significant drawback from the production point of view.
EP-A-0409128 discloses a hinged bogie for rail vehicles comprising two longitudinal members and two cross-members each fixed to one of the longitudinal members and a hinge device enabling each longitudinal member to pitch about a central transverse axis. The hinge device comprises a shaft disposed along a central transverse axis and four bearings supporting the shaft. The cross-members are mounted head-to-tail and each end of the shaft is supported by bearings, one of which belongs to one of the cross-members and the other of which belongs to the other cross member.
In this solution the structure of the longitudinal members is quite complex. They form an assembly with two cross-members, one of which is short and the other one is long, i.e. the, longitudinal member/cross-member assembly extend essentially in two directions, the longitudinal and the transverse one, which are perpendicular to each other. Moreover, the two longitudinal members are connected by a shaft restrained at its ends by a pair of spherical restrains on the inner side, and by a pair of elastic members on the outer side, to eliminate the system lability. The geometry of the bogie depends on the tolerances of the ball joints and the conditions of the elastic means: if before, or when in, operation an elastic member is permanently deformed or if the two members exhibit differences, the bogie geometry changes consequently. Furthermore, restoring the proper geometry appears to be problematic, especially after the bogie has been assembled. It must also be noted that, since the spherical joints are very close to the respective elastic members, the latter are subjected to great forces, and small deviations from the equilibrium position result in significant errors on the bogie attitude.
The object of the present invention is to providee an hinged bogie for rail vehicles which is able to obviate the drawbacks encountered with the above mentioned prior art bogies.
A particular object of the present invention is to provide an hinged bogie for rail vehicles of the above mentioned type with an hinge structure particularly simple from the construction point of view, with an attitude well defined and stable in operation and, furthermore, with such a geometry as to allow for an high standardization degree to be reached.
These objects are achieved with the hinged bogie according to the invention, the essential features of which are set forth in claim 1 and other important features are as set forth in the dependent claims. The features, as well as the advantages of the hinged bogie for rail vehicles according to the present invention will be clearer from the following description of an embodiment thereof made as a nonlimiting example with reference to the attached drawings wherein:

Figure 1 shows a schematic plan view of an hinged bogie for rail vehicles according to the prior art;
Figure 2 shows a schematic, conceptual view of the hinged bogie according to the invention;
Figure 3 is a plan view of a preferred embodiment of the hinged bogie according to the invention;
Figure 4 is a longitudinal sectional view of the hinge cross-member of the hinged bogie of figure 3.

Conceptually the invention can be reduced to the embodiment shown in figure 2. A very diagrammatic view of the hinged bogie is shown therein, all the construction details not essential for the understanding of the invention having been omitted, as will be obvious for a person skilled in the art. The bogie shown in figure 2 comprises a pair of longitudinal memebrs la, lb each of which supports a pair of wheels schematically shown through their rotation axis 2 and arranged near the ends of each longitudinal member. Tubular shafts 3 and 4 extend perpendicularly from the middle point of respective longitudinal members la and lb. The inner diameter of tubular shaft 3 is greater than the outer diameter of tubular shaft 4, whereby shaft 4 can be engaged within shaft 3 in a coaxial relationship and freely rotatable with respect to each other. Though not shown in figure 2, support means between shaft 3 and shaft 4 for allowing their mutual rotation are provided and means for blocking their mutual axial sliding once shaft 4 has been engaged with shaft 3.
In the above described schematic solution the bogie is hinged along the transverse symmetry axis, in such a way that, from the structural point of view, the system is characterized by a double symmetry and the structural members of the bogie consist of two substantially T-shaped members, each of which is formed by a side longitudinal member la and lb and by the respective tubular shafts 3 and 4 perpendicularly extending therefrom.
In the embodiment shown in figure 3 the structure of the bogie comprises three elements: the wheel bearing longitudinal members 1a and 1b, and a hinge cross-member, generally indicated at 5, which is fixed through its flanged ends 6 and 7 to corresponding flanges 8 located at the middle point of longitudinal members 1a and 1b.
Figure 4 is a detailed view of a possible embodiment of the hinge cross-member 5. Cross-member 5 comprises two tubular shafts 9 and 10 coaxially engaged with each other. In particular, a pair of radial bearings 11 pivotally supporting outer tubular shaft 9 is mounted on inner tubular shaft 10. At one end of inner shaft 10 flange 7 is fixed, while at the opposite end of outer shaft 9 flange 6 is fixed. Fixing of flanges 6 and 7 to respective shafts 9 and 10 can be perfomed by welding. A further flange 12 is fixed to the other end of outer shaft 9 and delimits with flange 7 an annular housing 13 within which an axial bearing is mounted. In particular, axial bearing 14 is placed between one end lla of the radial bearing and a washer 15 integral with flange 7. Therefore, axial bearing 14 allows the rotation between flange 7 and radial bearing 11. Annular housing 13 is protected by a circular shell 17 extending from flange 12.
In a structurally similar way, flange 6 delimits with the end of inner shaft 10 an annular housing 18 within which an axial bearing 19 is housed. Axial bearing 19 is placed between one end lla of radial bearing 11 and a tightening ring nut 20 screwed to the end of inner shaft 10. Radial bearing 11, therefore, allows the rotation between radial bearing 11 and ring nut 20, while the latter prevent any axial sliding between shafts 9 and 10.
In the case of embodiment shown in figures 3 and 4, in contrast to conventional bogies, each component member (the two longitudinal members la and lb and the hinge cross-member 5) has a substantially linear shape and no annealing operations or the like are required to avoid distortions due to welding of transverse pieces as provided for in the solutions according to the prior art. In the cross-member 5 shown in figure 4 the interfaces of connection to longitudinal members 1a and 1b are equal, whereby the two longitudinal members 1a and 1b are also identical.
The solution according to the present invention, and in particular the preferred one shown in figures 3 and 4, has several advantages with respect to the conventional solutions. In particular:

the bogie is always formed by the same structural members, i.e. the two longitudinal members and the hinge cross-member; in this way, all the possible values of pitch and gauge are obtained simply by varying the lengths of the longitudinal member and the cross-member, thus attaining a complete standardization of the production; structural calculations as well as tests of static and fatigue qualification for a full scale bogie are simplified;
the monodimensional shape of the member of the bogie makes the performing of stress relieving thermal cycles less important;
the bogie has a double symmetry, thus avoiding the uneven consumption of the wheels due to the braking;
the bogie is featured by a good running dynamics, as shown by simulations performed with suitable calculation codes;
the bogie geometry does not vary in operation and can be set with high precision and reproducibility during the bogie assembling, as only one interface exists between longitudinal member and cross-member, constituted by a flat surface formed on the longitudinal member;
the cross-member provides for an inner passage for torsion bars or wires or tubes without difficulty and is structurally more efficient with respect to the shaft encompassed in EP-A-0409128, which must have a lower diameter to be compatible with the overall dimensions and to mount acceptable ball joints;
the overall dimensions of the structure are lower than those of the solution according to EP-A-0409128, while maintaining a suitable rigidity and leaving more room available for motors and equipment.

It is clear that the hinge cross-member 5 shown in figure 4 is only one of the possible embodiments of the concept which the present invention is based on and several variation, obvious for a person skilled in the art, can be foreseen to allow the mutual rotation of the two coaxial shafts and their axial locking, as well as further variations and/or modifications can be brought to the hinged bogie according to the present invention, without departing from the scope of the invention as set forth in the attached claims.

Claims

Hinged bogie for rail vehicles comprising two longitudinal members (1a, 1b) supporting wheels at their ends and two tubular transverse shafts (3,4; 9,10) each extending from one of said longitudinal members, characterized in that said two shafts are axially and pivotally engaged with one another and means (20) for locking their mutual axial sliding are provided therebetween.
The hinged bogie according to claim 1, wherein each shaft (3,4; 9,10) is equipped at one of its ends, axially opposed to that of the other shaft with a flange (6,7) through which it is fixed to the corresponding longitudinal member.
The hinged bogie according to claim 2, wherein a flattened surface through which each longitudinal member is fixed to the flange of the respective shaft is provided at middle length of each longitudinal member.
The hinged bogie according to anyone of the previous claims, wherein between the two shafts (9,10) there are mounted radial bearings (11) for the mutual rotation of said shafts around their common axis and axial bearings (14) for the relative rotation of the flange (6,7) of a shaft and the end of the same shaft close to said flange.
The hinged shaft according to claim 4, wherein said means for locking the axial sliding of the two shafts comprise a tightening ring nut (20) fixable to the free end of the inner shaft (10) and abutting against the flanged end of the outer shaft (9) through said axial bearings (14).