Axle of wheel sets and respective method for the ultrasound inspection

Abstract

An axle of railway wheel sets and a corresponding method for the ultrasound inspection are described. A blind hole, coaxial to the axle and sized to accommodate an ultrasonic probe, is obtained in each end of the axle. Main holes are intended to accommodate the probe holder containing a plurality of ultrasonic transducers for the inspection of the axle from the inside of the hole. The main advantage is to facilitate the propagation of the ultrasounds without being subjected to the interference caused by the geometric discontinuities normally present at the ends of the axles thereby minimizing false positives in the readings of the echoes.

Claims

1. An axle (100) of railway wheel set extending along a longitudinal axis (X) between two ends (101, 102), the ends (101, 102) each having a journal (107), configured to support a railway wheel and a respective bearing (105) so as to form a wheel set, wherein each end (101, 102) comprises a blind main hole (103), coaxial with the axle (100) and dimensioned to accommodate an ultrasonic probe (200), wherein each blind main hole (103) has a depth within a longitudinal extent of the journal (107) and is dimensioned to receive the ultrasonic probe (200) for inspection of the axle (100) ahead of the probe.

2. The axle (100) according to claim 1, wherein the main holes (103) are accessible from the outside and are circular to allow rotation of the ultrasonic probe (200) inserted therein.

3. The axle (100) according to claim 1 further comprising, in both ends (101, 102), additional longitudinal secondary holes (104), which engage fastening screws of the bearing (105) of the respective wheel, or its bushing, and wherein the secondary holes (104) are arranged around the respective main hole (103), not coaxial with the axle.

4. The axle (100) according to claim 3, wherein the secondary holes (104) have a diameter that is considerably smaller than the diameter of the main holes (103).

5. The axle (100) according to claim 3, wherein the main holes (103) extend longitudinally into the axle (100) for a length that is longer than a length of the secondary holes (104), so that ultrasounds made by the probe (200) are not affected by the presence of the secondary holes (104).

6. The axle (100) according to claim 1, wherein at least one journal (107) of an outer surface of both ends, is configured to allow the bearing (105) of a wheel to be fitted, and wherein the main holes (103) extend into the axle (100) for a length between 50% and 120% of a longitudinal extent of the journal (107), so that ultrasounds generated by the probe (100) are not affected by the presence of the bearings (105) or are affected only partially.

7. A method for the ultrasound inspection of a railway wheel set, the method comprising the steps of: a) providing a wheel set provided with an axle (100) according to claim 1 and an ultrasonic probe (200) provided with one or more transducers (7); b) inserting the ultrasonic probe (200) alternately in the main holes (103), within a longitudinal extent of the journal (107), of the two ends (101, 102) of the axle; c) activating one transducer (7) at a time and rotating the probe in the main hole, within a longitudinal extent of the journal (107), so that the probe performs one or more complete turns; d) detecting echoes propagating in the axle (100) and analyzing the echoes to identify possible defects or discontinuities (B).

8. The method according to claim 7, further comprising one or more of the following additional steps: e) applying a coupling agent between the ultrasonic probe (200) and the bottom of the main holes (103); f) rotating the probe at a speed lower than, or equal to, 30 per second.

9. The method according to the claim 8, wherein step e) provides for: applying one or more outer sealing gaskets (202) to the ultrasonic probe (200), and defining a coupling chamber (300) limited by a bottom of the main hole (103), by a side wall of the main hole (103), by the ultrasonic probe (200) and the respective gaskets (202), and wherein the coupling agent is circulated in the coupling chamber (300).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the invention will be more evident from a review of the following specification of a preferred, but not exclusive, embodiment, shown for illustration purposes only and not limiting, with the aid of the attached drawings, in which:

(2) FIG. 1 is a perspective view of a rotating ultrasonic probe of traditional type;

(3) FIG. 2 is a perspective view of a wheel set traditionally inspected by the probe shown in FIG. 1;

(4) FIG. 3 is a perspective view of an axle of railway wheel sets according to the present invention;

(5) FIG. 4 is a perspective view of an axle and a probe according to the present invention, in use;

(6) FIG. 5 is a schematic sectional view of an axle according to the present invention, during the inspection;

(7) FIG. 6 is a side schematic view of the axle shown in FIG. 5;

(8) FIG. 7 is a diagram of the echoes detected during an inspection of the axle shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIG. 1 shows a rotating ultrasonic probe 1 of traditional type, provided with a body 2 in its turn equipped with a gripping handle 3 and a turning knob 4, the latter being manually operable by the technician in order to rotate the probe 1 during an axle inspection. Ultrasonic transducers 7 are mounted in the head portion of the probe at the front face 5. In the illustrated example four transducers 7 are shown, although they can generally be in different number.

(10) The aligning pin 6 protrudes from the front face 5 of the probe to be inserted in a corresponding countersink formed in the front of the ends of the traditional axles. The pin 6 allows the technician to easily align the probe 1 on the longitudinal axis of the axle to be inspected.

(11) As explained above, the transducers 7 can be converging or diverging or they are mounted on the body 2 of the probe 1 so that the technician can adjust their angle according to the needs.

(12) FIG. 2 shows a portion of a traditional railway wheel set 8 comprising wheels 9 and an axle 10. A technician moved the probe 1 in abutment against the end 11 of the axle 10 so that it is operatively coupled to the axle 10. In order to rotate the probe 1 by at least 360, thereby rotating the ultrasound beam generated by the activated transducer 7, the technician turns the knob 4.

(13) By means of the detecting and analyzing device 12, the technician analyses the echoes generated in the axle 10 by the ultrasounds propagating in the material of the axle itself. Peaks correspond to the detected discontinuities. Also by taking advantage of its experience, the technician has to distinguish the false positives from possible real flaws of the axle 10.

(14) FIG. 3 shows an axle 100 according to the present invention which is different from the prior art because it has two blind holes 103 each formed in one end 101, 102. The outer surface of the ends 101, 102 is at least partially rectified in order to allow the bearings 105 of the wheels to be fitted. The rectified surface 107 is named journal.

(15) FIG. 4 explains the advantage given by the blind holes 103, hereinafter named main holes.

(16) In each end 101, 102, the main holes 103 are coaxial to the axle 100 and are radially internal with respect to the secondary holes 104 for fastening the bushing of the bearing 105 of the wheel (not shown).

(17) An ultrasonic probe 200 according to the present invention can be inserted into the main holes 103 for the axle inspection. As shown in FIG. 4, the probe 200 is not simply in abutment against the end 101, 102, as in the prior art, but is inserted into the axle 100 up to the bottom of the main hole 103 and is rotated therein by the technician.

(18) This solution offers the advantage that the ultrasound generated by the probe 200 does not intercept nor the secondary holes 104 or the bearing 105 (at most the latter, but only partially).

(19) The Applicant carried out tests which showed that, compared to a traditional axle, the proposed solution involves a much smaller number of false positives, which means less peaks in the readings of the echoes.

(20) Preferably, as shown in figure, when the technician inserts the probe, a coupling chamber 300 is formed between the probe 200 and the bottom and the side wall of the main hole 103. In particular, the coupling chamber 300 is delimited by the bottom and the side wall of the hole 103, by the front face 201 of the probe 200 (on which the transducers not shown for the sake of simplicity are provided) and by at least one sealing gasket 202, e.g. an O-ring, which encircles the probe 200 setting it up as a piston with respect to the hole 103.

(21) A coupling agent is circulated inside the coupling chamber 300, as shown by the arrows, by means of feeding ducts 203 and drains 204, connected to an outer recirculation pump (not shown).

(22) The reference 106 indicates a wheel cover that prevents the coupling agents from spilling onto the probe 200.

(23) The bearing 105 is fitted to the journal 107. Preferably, the main hole 103 has a depth at least equal to 50% of the longitudinal extent of the journal 107.

(24) Referring to FIG. 5 showing a partial section of the axle 100 during an inspection, the technician activates one transducer 7 at a time, among those mounted on the probe 200 (not shown in this figure for the sake of simplicity). Each transducer is mounted so as to form a corresponding angle with the longitudinal axis X of the axle 100. In the example shown in figure, the transducer 7 forms a 30 angle with respect to the longitudinal axis X.

(25) The transducer 7 generates an ultrasound beam UT that propagates into the axle 100, starting from the bottom of the main bore 103. By rotating the probe 200, the ultrasonic beam UT is also displaced in order to inspect a corresponding annular portion of the axle 100. The areas indicated as Gate 1 and Gate 2 correspond to two separate areas on the graph shown in FIG. 7.

(26) FIG. 6 shows the same axle 100 of FIG. 5, in a side view rather than in cross section. A notch B, schematically shown as a black rectangle, was made in the axle at a distance of 230 mm from the edge of the end 101.

(27) FIG. 7 shows the diagram corresponding to the readings of the echoes of the ultrasound beam UT. The distance is indicated on the x coordinate and the percentage of reflected ultrasonic energy with respect to a standard quantity on the y coordinate. At the notch B there is a peak showing to the technician that the notch is just 130 mm from zero. The secondary holes 104 and the journal bearing of the axle 100 do not affect the reading.