CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent application claims priority from Italian Patent Application No. 102019000002183 filed on 14/02/2019, the disclosure of which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to a system for balancing railway wheels.

Like automotive wheels, railway wheels need to be balanced so that their rotation in use does not cause vibrations to the structures connected to the railway wheels.

The negative effects of unbalanced railway wheels include a reduction in the comfort of any passenger and an acceleration of the wear of the structures and are all the more evident as the unbalance and the speed increase. Therefore, the problem of the unbalance of the railway wheels has worsened with the progressive spread of high- speed trains.

In general, railway wheels are much heavier than automotive wheels due to their larger size, to their structure and to the used materials.

STATE OF THE ART

The patent literature discloses several documents teaching to balance automotive wheels, among which WO 2005/012,867, EP 607,757, EP 1,203,938 and DE 24,55,279.

However, the above mentioned systems for balancing automotive wheel are not designed to maintain railway wheels .

OBJECT OF THE INVENTION

An object of the present invention is to provide an efficient and practical system for balancing railway wheels .

In accordance with the present invention, it is provided a system for balancing railway wheels, each of which comprises a hub and a rim, the system comprising a measuring device; and a vertical lathe, which includes:

- a base;

- a spindle rotatable about an axis of rotation;

a cylindrical support arranged about the spindle to rotatably support the spindle;

a chuck connected to the spindle and configured to selectively clamp a railway wheel;

- first connection elements, which are arranged between the cylindrical support and the base on opposite sides with respect to the axis of rotation and are configured to allow displacements of the spindle and of the relative cylindrical support in a single direction of oscillation perpendicular to the axis of rotation; - a frame integral with the base and extending over the chuck;

- a plurality of slides coupled together and to the frame;

- a cutting tool supported by said slides; and

- a control device configured to control the movement of the cutting tool based on the entity and the phase of unbalance, in which the measuring device is configured to calculate the entity and the phase of unbalance based on the movements of the cylindrical support with respect to the frame in the direction of oscillation, and the position of the spindle about the axis of rotation with respect to the cylindrical support.

In this way, the first connection elements of the cylindrical support allow small displacements of the cylindrical support with respect to the base in a single direction of oscillation along which the signals related to the unbalance are read. The measuring device is able to calculate the entity of the unbalance based on the small displacements determined by the unbalanced railway wheel. Moreover, the first connection elements are designed to maintain the axis of rotation of the spindle, of the chuck and of the railway wheel in a specific position to allow finishing operations, once the railway wheel has been balanced. In other words, the first connection elements are able to offer adequate resistance to the force transmitted by the tool during the finishing phase.

In particular, the system comprises second connection elements, which are arranged between the cylindrical support and the base, on opposite sides with respect to the axis of rotation, and between the first connection elements about the axis of rotation, and are configured to allow the spindle and the cylindrical support to be moved in the single direction of oscillation.

Thanks to the second connection elements, the cylindrical support is evenly supported with respect to the base.

In particular, the cylindrical support is suspended from the base by means of the first and of the second connection elements, which are compression loaded.

In this way, the cylindrical support is sensitive to the unbalances induced by a railway wheel mounted on the chuck and rotated by the spindle.

In particular, each first connection element comprises a leaf spring with a main face parallel to the axis of rotation and perpendicular to the direction of oscillation. In this way, the first connection elements allow a relative movement between the cylindrical support and the base in the single direction of oscillation.

In particular, the leaf spring has an upper end fixed to the cylindrical support and a lower end fixed to the base. In this way, the leaf spring is subjected to a compression load along its cross section.

In particular, each second connection element comprises a connecting rod with a rectangular cross section and a main face substantially perpendicular to the direction of oscillation.

In this way, the second connection elements allow movements in the single direction of oscillation perpendicular to both the main face of the connecting rod and the main face of the leaf spring.

In particular, the connecting rod comprises an upper end fixed to the cylindrical support and a lower end fixed to the base.

In this way, the connecting rod is subjected to a compression load along its cross section.

In particular, the first and second connection elements are evenly distributed about the axis of rotation.

This configuration allows supporting a relevant mass in an evenly distributed way with respect to the base.

In particular, the measuring device comprises a tie rod, which extends in the direction of oscillation and has a first end connected to the cylindrical support and a second end connected to the base; and a first sensor for acquiring first signals related to the deformation of the tie rod.

In this way, the sensor can be configured as a load cell that detects the deformations of the tie rod for the advantage of the precision and reliability of the measurement .

In particular, the measuring device comprises a second sensor configured to acquire second signals related to the relative position of the spindle with respect to the cylindrical support about the axis of rotation, the measuring device being configured to calculate the entity and phase of the unbalance based on the first and on the second signals.

This allows acquiring the information to correct the unbalance .

In particular, the measuring device is configured to at least partially detect the geometry of the railway wheel clamped on the chuck by means of a third sensor mounted on the slides to acquire third signals related to the geometry of the railway wheel.

This provides both the correct geometry of the railway wheel and the correct assembly of the same on the chuck. Another object of the present invention is to provide a simple and practical method for balancing railway wheels.

The present invention further provides a method for balancing railway wheels by means of a system as claimed in any one of the preceding claims, the method comprising the phase of removing a mass from a railway wheel by means of a turning operation carried out by a cutting tool along an inner face of the rim of the railway wheel.

In this way, no mass is removed from the rolling surface of the railway wheel.

In particular, the method involves acquiring first signals related to the entity of unbalance, second signals related to the phase of unbalance and third signals related to the geometry of the railway wheel; comparing the first and third signals with respective threshold values; and checking the cutting tool during the removal of said mass in correspondence with said phase based on the first, the second and the third signal.

In this way, it is possible to balance railway wheels effectively and precisely while minimizing errors.

BRIEF DESCRIPTION OF THE FIGURES

Further characteristics and advantages of the present invention will become clear from the following description of a non-limiting embodiment thereof, with reference to the Figures, in which:

- Figure 1 is a perspective view, with parts removed for clarity's sake, of a system for balancing railway wheels;

Figure 2 is a section view, with parts removed for clarity' s sake and parts schematically indicated, of the system of Figure 1;

Figure 3 is a section view, with parts removed for clarity's sake and on an enlarged scale, of a detail of Figure 2;

- Figure 4 is a perspective view, with parts removed for clarity's sake and on an enlarged scale, of a detail of the system of Figure 1; and

- Figure 5 is a plan view, with parts removed for clarity' s sake and on an enlarged scale, of a detail of Figure 1. FAVOURITE EMBODIMENT OF THE INVENTION

With reference to Figure 1, 1 indicates as a whole a system for processing railway wheels 2. Each railway wheel 2 is made of iron or steel, extends about an axis A and comprises a hub 3 equipped with a central hole 4, a rim 5 and an intermediate portion 6, which connects the hub 3 to the rim 5.

In the example shown in the attached figures, reference is made to a wheel 2 made of a single or of several pieces, assuming that the present invention extends to any type of railway wheel, made of a single or of several pieces, and to any type of intermediate portion.

With reference to Figure 2, the rim 5 has a rolling surface 7, a flange 8 and two inner faces 9 and 10, which extend on opposite sides with respect to the intermediate portion 6. The system 1 has the function of performing turning operations of the railway wheel 2 limited to the surface finishing and balancing operations of the railway wheel 2. Balancing by turning an unbalanced railway wheel 2 involves removing a mass of material from an area of the railway wheel 2 identified by a phase about the axis A of the railway wheel 2. The removed mass of material has a specific geometry and is removed along the face 9 and/or 10 of the rim 5. The geometry of the mass is connected to the face 9 and/or 10 of the rim 5 so as to avoid discontinuities that could trigger breakages and extends for a determined angle about the phase.

The finishing turning operations mainly concern the rolling surface 7 and the face of the hole 4.

The aforementioned turning operations can be carried out both on new railway wheels and worn railway wheels.

The system 1 comprises a vertical lathe 11 configured to perform finishing chip removal operations.

The vertical lathe 11 comprises a base 12; a spindle 13 rotatable about an axis of rotation A1 ; a cylindrical support 14 arranged about the spindle 13 to rotatably support the spindle 13; a chuck 15 connected to the spindle 13 and configured to selectively clamp a railway wheel 2; two connection elements 16 arranged between the support and the base to allow an oscillation of the spindle 13 and of the relative cylindrical support 14 in a direction of oscillation D1 perpendicular to the axis of rotation A1 ; a frame 17 integral with the base 12 and extending over the chuck 15; a plurality of slides 18 and 19 coupled together and to the frame 18; and a cutting tool 20 supported by the slide 19.

In particular, the vertical lathe 11 comprises a horizontal guide 21 to guide the slide 18, and a vertical guide 22 to guide the slide 19. The horizontal guide 21 is supported by the frame 17, whereas the vertical guide 22 is supported by the slide 18.

The slide 19 supports a tool-holder turret 23, which supports a plurality of cutting tools 20 and is selectively rotatable about the axis A2.

The vertical lathe 11 comprises bearings C arranged inside compartments formed between the spindle 13 and the cylindrical support 14; and an electric motor 24, also housed in a compartment between the spindle 13 and the cylindrical support 14. In the case shown, the electric motor 24 is a permanent magnet electric motor with direct drive to rotate the spindle 13 about the axis A1.

The vertical lathe 11 includes a control unit 25 to control the position of the cutting tool 20 and the rotation of the spindle 13 according to the selected processing parameters.

The system 1 comprises a measuring device 26, which is integrated in the vertical lathe 11 and is configured to detect the extent of the unbalance, the relative phase of the unbalance and the geometry of the railway wheel 2 mounted on the chuck 15. In particular, the measuring device 26 is integrated in the control unit 25 and includes a sensor 27, in this case a load cell, configured to acquire signals related to the displacement of the cylindrical support 14 with respect to the base 12 in a direction of oscillation D1 radial with respect to the axis of rotation A1.

The measuring device 26 includes a sensor 28, in this case an encoder or the like, configured to acquire signals related to the relative position of the spindle 13 with respect to the cylindrical support 14 about the axis of rotation A1.

With reference to Figure 1, the measuring device 26 comprises a sensor 29, in this case a probe, configured to acquire signals related to the coordinates of the railway wheel 2 mounted on the chuck 15.

According to what is better shown in Figure 3, the measuring device 26 comprises a tie rod 30, which has its opposite ends connected to the cylindrical support 14 and to the base 12. The sensor 27 is coupled to a portion between the two ends of the tie rod 30 and is configured to acquire signals related to the deformation of the tie rod 30.

With reference to Figure 2, the measuring device 26 is configured to calculate the entity and the phase of the unbalance based on the signals acquired by the sensors 27 and 28 and the geometry of at least part of the railway wheel 2 based on the signals acquired through the sensor 29, whereas the control unit 25 is configured to control the position of the cutting tool 20 based on the calculated entity and phase of unbalance. The signals related to the geometry of the railway wheel 2 are compared with the expected reference values to verify the correctness of the geometry of the railway wheel and/or its correct assembly. In the presence of an error signal emitted by the measuring device 26, the processing phases of the railway wheel 2 are inhibited .

With reference to Figure 4, the cylindrical support 14 comprises a flange 31, which extends radially at the upper end of the cylindrical support 14 and has a side face.

Each connection element 16 comprises a leaf spring 32 having the shape of a flat plate parallel to the axis of rotation A1 and a bracket 33 for fixing the leaf spring 32 to the base 12. The upper end of the leaf spring 32 is fixed to the side face, whereas the lower end is fixed to the base 12 by means of the bracket 33. In particular, the upper end of the leaf spring 32 is fixed by means of a screw joint and the lower end is fixed to the base 12 by means of the bracket 33, which comprises a wall 34 fixed to the leaf spring 32 by means of a screw joint; and a wall 35 perpendicular to the wall 34 and fixed to the base 12 by means of a screw joint.

Practically, the leaf springs 32 have the function of supporting the cylindrical support 14 with respect to the base 12 and of allowing small displacements of the cylindrical support 14 with respect to the base 12 in the single direction of oscillation D1.

With reference to Figure 5, the vertical lathe 11 comprises two connection elements 36 arranged between the cylindrical support 14 and the base 12 on opposite sides with respect to the axis of rotation A1 and between the connection elements 16. The connection elements 36 have the function of supporting the cylindrical support 14 with respect to the base 12.

With reference to Figure 4, each connection element 36 comprises a connecting rod 37, an upper fixing block 38 for fixing the connecting rod 37 with screws to the side face of the flange 31 and a lower fixing block 39 for fixing the connecting rod 37 to the base 12.

Each connecting rod 37 has a rectangular cross section, whose largest dimension is substantially radial with respect to the axis of rotation A1 and parallel to the flat main faces of the leaf springs 32.

In use, the system is able to detect the extent and the phase of an unbalance induced by an eccentricity in the railway wheel 2 and to control the slides 18 and 19 to remove the mass at the phase calculated by the railway wheel 2 in the absence an error signal determined by the incorrect positioning of the railway wheel 2 and/or by the incorrect dimensions of the railway wheel 2 with respect to the expected dimensions.

In short, the method according to the present invention allows determining the unbalance of the railway wheel 2, measuring the unbalance and verifying the acceptability of the unbalance. If the unbalance does not fall within parameters considered acceptable, then the method calculates the coordinates of a mass to be removed and removes the mass by means of a finishing operation on the vertical lathe 11 along the inner face 9 of the railway wheel, as shown in Figures 1 and 2.

It is clear that the present invention includes further variants not explicitly described, without however departing from the scope of protection of the following claims .