Portal-axle of low floor rail vehicles and rail-and-tram vehicles

Abstract

A portal-axle of bogies for light rail vehicles, such as for example trams or light rail metros with street running, is described, the light rail vehicles being characterized by a floor, i.e. a walking surface, lowered with respect to the rails. The portal-axle comprises two shoulders equipped with spindles for mounting wheels and with a central portion for structurally connecting the shoulders. Unlike conventional solutions, the central portion is not made by casting or forging, but advantageously is simply defined by at least two bars coupled thereto during the assembly. The bars are easily available on the market at low cost, have lower weight with respect to a traditional forged/cast component and allow modularity and versatility in dimensioning the portal-axle to be obtained.

Claims

1. A portal-axle (1, 1′, 1″) for low floor light rail vehicles (LRV), comprising two shoulders (5, 6) each provided with a spindle (9, 10) for mounting a wheel (2, 3) and a central portion (4) structurally connecting the shoulders (5, 6), wherein the central portion (4) is defined by at least two bars (7, 8) distinct from the shoulders (5, 6) and are coupled thereto, wherein the at least two bars (7, 8) are keyed and/or screwed to the shoulders (5, 6), the ends of the at least two bars (7, 8) are inserted in corresponding seats of the shoulders (5, 6) and a screw (11) is inserted at least partially in each end of the at least two bars (7, 8) through a corresponding hole obtained in the shoulder (5, 6), to stabilize the coupling and support a load applied to the operating portal-axle (1, 1′, 1″).

2. The portal-axle (1, 1′, 1″) according to claim 1, wherein the shoulders (5, 6) and the central portion (4) define a concave-shaped structure, with the central portion connected to the shoulders at a lower level with respect to the spindles (9, 10).

3. The portal-axle (1, 1′, 1″) according to claim 1, wherein the at least two bars (7, 8) are parallel.

4. The portal-axle (1, 1′, 1″) according to claim 1, wherein the at least two bars (7, 8) are obtained by drawing.

5. The portal-axle (1, 1′, 1″) according to claim 1, wherein the shoulders (5, 6) are obtained by casting or forging.

6. The portal-axle (1, 1′, 1″) according to claim 1, wherein the at least two bars (7, 8) are circular.

7. The portal-axle (1, 1′, 1″) according to claim 6, wherein the at least two bars (7, 8) have diameter in the range 60-120 mm.

8. The portal-axle (1, 1′, 1″) according to claim 1, wherein the spindles (9, 10) have a plurality of longitudinal holes (12) having the function of lightening the spindle (9, 10), allowing the bearings installed on the spindle to be lubricated, and allowing the passage of the electrical connections for grounding the vehicle.

9. The portal-axle (1, 1′, 1″) according to claim 1, wherein the spindles (9, 10) are monobloc with the shoulders (5, 6) or are made separately and coupled to the shoulders (5, 6) during an assembling step and can be made of a material different from the shoulders (5, 6).

10. The portal-axle (1, 1′, 1″) according to claim 1, wherein the at least two bars (7, 8), the shoulders (5, 6) and the spindles (9, 10) are made of the same material or different materials.

11. The portal-axle (1, 1′, 1″) according to claim 1, further comprising wheels (2, 3) mounted on the spindles (9, 10) and comprising corresponding bearings, fittable on the spindles (9, 10).

12. The portal-axle (1, 1′, 1″) according to claim 1, wherein the spindles (9, 10) for mounting the wheels (2, 3) are outward from the respective shoulders (5, 6).

13. The portal-axle (1, 1′, 1″) according to claim 1, wherein the central portion (4) is defined only by bars (7, 8) distinct from the shoulders (5, 6) and coupled thereto.

14. A method for making a portal-axle (1, 1′, 1″) for low floor light rail vehicles (LRV), comprising: providing two shoulders (5, 6) equipped with spindles (9, 10) for the support of wheels (2, 3); providing at least two drawn bars (7, 8), available on the market with size and quality already certified, and coupling the ends of the at least two bars (7, 8) to the shoulders (5, 6) by welding the at least two drawn bars (7, 8) to the shoulders (5, 6) or by keying and/or screwing the at least two drawn bars (7, 8) to the shoulders (5, 6), so that the bars define the low central portion of the portal-axle (1, 1′, 1″); inserting the ends of the at least two bars (7, 8) in corresponding seats of the shoulders (5, 6); and inserting a screw (11) at least partially in each end of the at least two bars (7, 8) through a corresponding hole obtained in the shoulder (5, 6), to stabilize the coupling and support a load applied to the operating portal-axle (1, 1′, 1″).

15. The method according to claim 14, wherein the at least two drawn bars (7, 8) are fastened to the shoulders (5, 6) so that to remain parallel one to another.

16. The method according to claim 14, wherein the at least two bars (7, 8) are fastened to the shoulders (5, 6) underneath the spindles (9, 10).

17. The method according to claim 14, wherein the spindles (9, 10) are monobloc with the shoulders (5, 6) or are made separately and assembled with the shoulders (5, 6) and, if made separately, can be made of a material different from the shoulders (5, 6).

18. The method according to claim 14, further comprising the step of: making holes (12) in the spindles (9, 10), parallel to the rotation axis of the wheels (2, 3) to be mounted on the spindles themselves, in order to lighten the spindles (9, 10), allow the bearings to be lubricated and allow the passage of the electrical connections for grounding the vehicle.

19. The method according to claim 14, further comprising the step of: mounting wheels (2, 3) on the spindles (9, 10) by using cartridge bearings.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the invention will be more evident by the review of the following specification of a preferred, but not exclusive, embodiment, which is depicted for illustration purposes only and without limitation, with the aid of the attached drawings, in which:

(2) FIG. 1 is a perspective view of a first embodiment of a portal-axle according to the present invention and the respective wheels;

(3) FIG. 2 is a perspective view of the only portal-axle shown in FIG. 1, without wheels;

(4) FIG. 3 is a rendering of a second embodiment of a portal-axle according to the present invention;

(5) FIG. 4 is a vertical sectional view of the portal-axle shown in FIG. 1;

(6) FIG. 5 is a bottom plan (horizontal) sectional view of the portal-axle shown in FIG. 1;

(7) FIG. 6 is a perspective view of a detail of a third embodiment of a portal-axle according to the present invention;

(8) FIG. 7 is a perspective and partially sectional view of the portal-axle shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 shows a portal-axle 1 according to a first embodiment of the present invention. The portal-axle 1 is provided with a central portion 4 coupled to two shoulders 5 and 6 having the respective wheels 2 and 3 mounted thereon.

(10) FIG. 2 shows the portal-axle 1 without wheels.

(11) Unlike known solutions, the central portion 4 of the portal axle 1 is not a single monobloc component obtained by casting or forging, but simply consists of two parallel bars 7 and 8, also called “axles” coupled to shoulders 5 and 6. Preferably, the central portion 4 is made only by bars same as the ones shown in figure.

(12) In the examples shown in figures, the portal-axle 1 comprises two bars 7 and 8, but in general the number of bars may be greater depending on the requirements.

(13) As described above the use of the bars 7, 8, in place of a single forged or cast monobloc element, offers many advantages. The bars 7 and 8 can be purchased on the market at very low costs when compared to the production cost of the central portion of a conventional portal-axle; consider for example bars obtained by drawing.

(14) The bars 7, 8 can be purchased already certified by the respective manufacturer, i.e. already inspected to detect possible defects.

(15) The designer can select each time the diameter and length of bars 7, 8 as needed, for example based on vehicle weight and track gauge, thereby obtaining the above described modularity. In practice, it is no longer required to tailor the central portion 4, but only to use the bars 7 and 8 having the suitable length, or to cut to size the bars 7 and 8 starting from bars available in the warehouse, still in a simple, fast and cheap way.

(16) The bars 7 and 8 can be hollow or solid, and in particular completely hollow/solid or one of them hollow and the other solid, etc. In case the bars 7 and 8 are hollow, the minimum thickness of the section of each bar is preferably 2 cm.

(17) The designer can also choose the material of the bars 7 and 8 as needed. For example, if the light rail vehicle is intended to operate in particularly wet or salty climates, the designer is free to select bars 7 and 8 made of moisture-proof steel or alkali-resistant steel, also in order to further simplify the maintenance plan thus reducing the costs thereof and increasing component safety. Among other things, the bars 7 and 8 can be easily painted with protective paints, as happens to the axles of the rail wheel sets.

(18) It should be noted that the bars 7 and 8 may have non-circular cross-section, for example square or rectangular ones, although the one shown in the figures—precisely circular—is the most convenient as regards the coupling of the bars 7 and 8 with the shoulders 5 and 6, as will be explained below. For example, the section of the bars 7, 8 could be square except at the ends, where it may be circular.

(19) Preferably, the diameter of the bars 7, 8 is between 60 mm and 120 mm.

(20) FIGS. 1-2 and 4-5 show a first embodiment of the portal-axle 1, in which the bars 7 and 8 are close to each other. FIG. 3 shows a second embodiment 1′ in which the bars 7 and 8 are spaced apart. The distance between the bars 7 and 8 is one of the parameters the designer can change. Clearly, there is an inverse proportion between the center-to-center distance of the bars 7 and 8 and the extent of deformation in torsion which the portal-axle will be subjected to during use.

(21) As apparent from the foregoing description, the portal-axle 1 according to the present invention can be easily and quickly configured by using bars 7 and 8 easily available on the market. In other words, this is an extremely modular solution that offers great freedom to the designer.

(22) The shoulders 5 and 6 and the bars 7 and 8 can be made either of the same material or different materials. This characteristic, which at first glance appears to be secondary, can not be found in conventional portal-axles because usually different metals can not be easily welded, or anyway the welding must take into account the different nature of the materials.

(23) This problem does not arise in the portal-axle 1 because the bars 7 and 8 can be mechanically coupled to the shoulders 5 and 6 even without welding, for example by keying and/or screwing them on the shoulders 5 and 6.

(24) In the first embodiment 1 shown in FIGS. 1-2 and 4-5, the ends of the bars 7 and 8 are inserted into special holes obtained through the shoulders 5 and 6. They are preferably coupled by an interference fit that can be obtained either in hot or cold condition by using, for example, liquid nitrogen to cool the ends of the bars 7, 8.

(25) Preferably, in order to make the coupling stable and safe, a safety screw 11 is inserted on the opposite side, as best shown in FIGS. 4 and 5. In fact, the designer may dimension the screws 11 so as to support the load on the portal-axle 1 when the rail vehicle is in operation; this makes the system safe even in case the bars 7 and 8 are keyed to the shoulders 5 and 6 in a faulty or ineffective way.

(26) Alternatively or in addition to the above described coupling, the ends of the bars 7 and 8 can be threaded in order to be screwed to the shoulders 5 and 6.

(27) As an alternative to the just described systems, the bars 7 and 8 can be welded to the shoulders 5 and 6.

(28) FIGS. 3 and 6-7 show solutions 1 and 1″ in which the bars 7 and 8 are keyed to the shoulders 5 and 6 without using pins 11. In particular, the third embodiment 1″ shown in FIGS. 6 and 7 is similar to the first embodiment 1, but the bars 7 and 8 are keyed to the shoulders 5 and 6 without the screws 11.

(29) Certainly the field technician will appreciate that the portal-axle 1, 1′ and 1″ can be very easily assembled.

(30) What is needed is to find the bars 7 and 8 having the right length or cut them to size, and then couple them to the shoulders 5 and 6 as previously described.

(31) In turn, the shoulders 5 and 6 can be made of the same material as the bars 7 and 8 or of a different material, by casting or forging techniques.

(32) Advantageously, if one of the components has to be replaced, it will be possible to do so without having to discard the whole portal-axle 1, 1′ or 1″. The only damaged or worn part can be replaced, resulting in evident saving compared to traditional solutions.

(33) So, also for this reason, the management of the spare parts warehouse is extremely simple as compared with traditional solutions.

(34) The spindles 9 and 10 can be integral with the shoulders 5 and 6, for example they can be obtained by machining (for example, turning and/or grinding) the shoulders 5 and 6; alternatively, also the spindles 9 and 10 can be components obtained separately and then secured to the shoulders 5 and 6 (solution not shown in the figures). The advantage obtained by separately making the spindles 9 and 10 is that the finishing can be carried out more easily (for example by turning and/or grinding) even though, as a result, it can be difficult to subsequently obtain the dimensional tolerances of the unit, once the latter is assembled.

(35) Preferably, the spindles 9 and 10 face outward with respect to the respective shoulders 5 and 6.

(36) Preferably, the portal-axle 1, 1′, 1″ according to the present invention is designed to support the wheels 2 and 3 by cartridge bearings, i.e. bearings (not shown in figures) to be inserted like cartridges onto the respective spindle 9 or 10 together with the wheel 2, 3.

(37) By mounting cartridge bearings—each cartridge comprising two bearings for a total of four per each portal-axle—the wheel assembly is greatly simplified, since in the known-in-the-art solutions the shoulders must be suitably machined in order to make the circular seats of the bearings, usually having different diameters, which are keyed. In this sense, cartridge bearings are less expensive and easier to install than traditional bearings.

(38) Preferably, the spindles 9 and 10 have a plurality of lightening holes 12 evenly spaced around the symmetry axis of each spindle 9, 10. These holes 12 provide many benefits: not only they lighten the spindle 9, 10 but also allow the insertion of a lubricant supplying nozzle precisely in order to lubricate the bearings (which must provide this function) when the railway bogie is fully assembled, and they also provide enough space for the passage of electrical connections for grounding the train.