Method and device for surface-aligning and restoring the profile of two rail portions welded together

Abstract

 A method and device for surface-aligning two rail portions welded together within a weld region, by which the rail portions are milled in said weld region.

Description

[0001] The present invention relates to a method and device for surface-aligning two rail portions welded together.

[0002] As is well known to the expert of the art, the rails used in known railway lines have to be welded together. The common welding operations are carried out using a railway truck presenting at least one pair of grippers to grip the two rail portions to be welded together and press them forcibly against each other. A flash weld is then made in the contact region between the two portions to partially fuse the constituent metal of the rails. The result obtained by this process is a single rail presenting a cusp at the welded portion.

[0003] This cusp must necessarily be removed and the rail surface be levelled and aligned. Said cusp is currently removed by grinding the rail. The grinding operations involve moving a portable grinding wheel from the top of the rail head to its inner side, to obtain a surface in the weld region which corresponds to the standard rail shape. The critical machining operations are those on the top of the rail head and its inner part, on which the train wheels rest.

[0004] The machining of these portions by a grinding wheel is a lengthy procedure with only approximate machining precision.

[0005] The object of the present invention is to provide a method and device which enable the weld region of two rails to be machined with precision, speed and reliability.

[0006] Further characteristics and advantages of the invention will be more apparent from the description of a preferred but non-exclusive embodiment of the method and device for surface-aligning two rail portions welded together in a weld region according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which:

Figure 1 is a section through a rail to be machined by a device of the present invention;

Figure 2 is a view of the milling cutter of a device for surface-aligning two rail portions welded together in a weld region;

Figure 3 is a view of an alternative embodiment of the milling cutter of Figure 2;

Figure 4 is a schematic side view of a device for surface-aligning two rail portions welded together, while machining two rails welded together;

Figure 5 is a simplified section taken on the line A-A of Figure 4;

Figure 6 is a plan view of a detail of the device of Figure 4;

Figure 7 is a side view of the detail of Figure 6; and

Figure 8 is a front view of the detail of Figure 6.

[0007] With reference to said figures, these show a device, indicated overall by the reference numeral 1, for surface-aligning two rail portions welded together in a weld region.

[0008] The device 1 comprises a pair of uprights 2 between which a double-T beam 3 is provided supporting a guide 4 composed of a pair of cylindrical elements 4A, 4B. A plate 5 is slidably mounted on said guide 4. To the plate 5 there are welded two elements 6 for its engagement with the guide 4 and an element 7 with a threaded through hole in which a screw 8 is engaged, rotatably fixed between the two uprights 2 and rotated by a respective motor 9. The screw 8 passes without contact through suitable holes 10 provided in the engagement elements 6.

[0009] On the opposite face to that on which the engagement elements 6 are fixed, the plate 5 presents four guide elements 11 to engage in pairs with a guide formed by a pair of tubular elements 13A, B. On the same face there is also provided, welded in a central position, an element 12 with a threaded through hole engaged by a screw (not shown) rotated by a second motor 15 and rotatably fixed to a frame 21 rigid with the milling head and supporting the motor 15. The tubular elements 13A, 13B are also fixed to said frame 21. The milling head 16 comprises a milling cutter 18 rotated about its axis A by a suitable motor 20, preferably electric.

[0010] To complete the description of the said device it should be noted that a locking gripper is fixed to each of the uprights 2, to grip a rail portion. This locking gripper also presents a wheel for its resting and movement on said rail.

[0011] This described structure is fixed to a conventional railway truck, so that the structure can be raised from or lowered onto the rails, to enable the locking grippers to firmly grip them. The clamping action of the grippers also enables the device to be maintained stable during the milling operation.

[0012] The milling cutter 18 mounted on the milling head 16 is of the type comprising fishbone teeth 19 and is well visible in Figure 3. It presents a first milling surface 30 to machine the upper portion of said rail. This first surface 30 is of shape corresponding to the shape of the top of the head of said rail. Essentially it perfectly reproduces the shape of the top of the rail head in that part where no weld is present, hence where the shape of the rail head is standard. The milling cutter also presents a second surface 31, adjacent to the first, to machine the inner side portion of the rail, and a third surface 32, also adjacent to the first, to machine the outer portion.

[0013] These second and third surfaces also have a shape corresponding to the lateral shape of the head of said rail where it does not comprise the weld and presents its original form.

[0014] The invention operates in the following manner.

[0015] After welding two rails together, the railway truck is driven over the weld region. The wheels of the locking grippers are then rested on the rail, straddling the region comprising the weld. The guide 4 is then substantially parallel to the rail 40. The grippers are clamped and the motor of the milling cutter 18 is started. The motor 15 is operated to lower the milling cutter 18 onto the rail. The position of the milling cutter 18 is controlled by suitable sensors and drives. When the cutter reaches the desired working position, i.e. that of Figure 3, the motor 9 is operated to move the milling head longitudinally along the guide 4 and hence along the length of the rail 40.

[0016] The milling cutter proceeds to skim the rail but without machining it. In this respect the cutter profile coincides with that of the rail, and the cutter rotates without touching it. When the cutter has been advanced by the motor 9 to the deformed weld region, the cutter removes that material excessive to the ideal rail profile. On termination of the operation, the joint region has been perfectly machined and its profile corresponds to that of the rail in any position in which no weld has been made. Consequently the surfaces of the two welded rails are perfectly aligned.

[0017] In an alternative embodiment, a milling cutter is provided of shape substantially similar to that shown in Figure 2. This cutter comprises only the first machining surface 30 and second machining surface 31 (which are identical to those already described), so that it machines the rail only on those surfaces which are essential for correct resting of a railway truck wheel on it. In this embodiment, means must be provided for aligning this milling cutter with the inner side of the rail. In other words, further guides and guide means must be provided to enable the head to move along an axis parallel to the cutter axis A.

[0018] These means can also be suitably provided in the first described embodiment, in particular to make the use of the device more flexible.

[0019] In a further embodiment, means can also be provided to adjust the axis of inclination of the cutting tool, again to obtain improved flexibility.

[0020] The described railway truck can also comprise a device (for example laser) for determining the geometric profile of the rail after milling, and/or a testing device using ultrasound, radiography, penetrating liquids, magnetic resonance, etc. for the welded region. In this manner on termination of machining, a geometrical and siderurgical report can be obtained for the welded and machined portion, to check its characteristics and tolerances. The geometrical report will contain a graph representing differences in tenths of millimetres between the inner surface of the rail head and a perfectly straight line of length one metre and between the upper surface of the rail (rolling plane) and said line.

[0021] The siderurgical report, obtained by a non-destructive method (penetrating liquids, radiography or the like), is intended to verify the weld quality, i.e. whether the material is integral and exactly identical to that of another region of the rail.

[0022] Essentially, the overall objective of the invention is to restore the rail region (relative to its head) neighbouring the weld to the quality standard as supplied, and to demonstrate this fact.

[0023] The invention also relates to a method for surface-aligning two rail portions welded together within a weld region, consisting of milling the top and at least the inner side of said rails in a single pass. In an alternative embodiment, the method also comprises milling the rail outer part.

Claims

1. A method for surface-aligning two rail portions welded together within a weld region, characterised by milling said rail portions in said weld region.

2. A method as claimed in claim 1, characterised by milling the top part and at least the inner side part of said rails.

3. A method as claimed in claim 2, characterised by milling said two parts of said welded rails with the same milling cutter during the same pass.

4. A method as claimed in claim 2, characterised by milling the outer side part of said rails.

5. A method as claimed in claims 3 and 4, characterised by also milling the outer part of said rails with the same milling cutter during the same pass.

6. A device (1) for surface-aligning two rail portions welded together within a weld region, characterised by comprising a milling head (18) supported by a support structure (21), means (13A, 13B, 15) for positioning said milling cutter relative to at least one of said rail portions and means (8, 9, 10) for longitudinally moving said milling cutter along said weld region.

7. A device as claimed in claim 6, characterised in that said milling head (18) comprises at least one milling cutter with a first milling surface (30) for machining the upper portion of said rail, said first surface having a shape corresponding to the upper shape of said rail in at least one portion not involving said weld.

8. A device as claimed in claim 7, characterised in that said milling cutter (18) comprises a second milling surface (31) for machining the inner lateral portion of said rail simultaneously with the upper portion, said second surface presenting a shape corresponding to the inner lateral shape of said rail in at least one portion not involving said weld.

9. A device as claimed in claim 8, characterised in that said milling cutter (18) comprises a third milling surface (32) for machining an outer lateral portion of said rail, said third surface presenting a shape corresponding to the outer lateral shape of said rail in at least one portion not involving said weld.

10. A device as claimed in claim 6, characterised in that said positioning means comprise at least one pair of locking grippers to rest on and grip the rail.

11. A device as claimed in claim 10, characterised in that said locking grippers each comprise at least one wheel.

12. A device as claimed in claim 11, characterised in that said positioning means comprise at least one guide transverse (13A, 13B) to said rail, and a first actuator (15) to drive said milling head along said transverse guide (13A, 13B), such as to regulate the height of said milling cutter (18) over said rail.

13. A device as claimed in claim 6, characterised in that said longitudinal movement means comprise at least one longitudinal guide (4A, 4B) to be brought by said positioning means into a position substantially parallel to said rail, and a second actuator (9) to drive said milling head (18) along said longitudinal guide.

14. A device as claimed in one or more of the preceding claims, characterised in that said first and second actuator (9, 15) comprise at least one motor for rotating at least one screw (8).

15. A device as claimed in claim 6, characterised in that said support structure is a railway truck drivable along a rail track.

16. A railway truck comprising a device as claimed in one or more of the preceding claims.

17. A railway truck as claimed in claim 16, characterised by comprising a device for determining the geometric profile of the rail.

18. A railway truck as claimed in claim 16, characterised by comprising a device for ultrasonic testing of said weld region.

19. A rail formed by the method of claim 1.

Drawing